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Title:
ENGAGEMENT APPARATUS AND HYBRID VEHICLE DRIVE SYSTEM
Document Type and Number:
WIPO Patent Application WO/2015/071736
Kind Code:
A2
Abstract:
In an engagement apparatus, dog teeth of a piece and a sleeve have a first tooth face and a second tooth face, provided one on each side in a circumferential direction, an end surface provided in an axial direction, a first connecting surface that connects the end surface to the first tooth face, and a second connecting surface that connects the end surface to the second tooth face. The first connecting surface is configured such that an angle between a normal of the first connecting surface and a normal of the first end surface becomes smaller in a stepped or continuous manner as a normal direction of the first connecting surface moves from a connecting portion of the first connecting surface and the first tooth face toward a connecting portion of the first connecting surface and the first end surface.

Inventors:
NAGAI, Hidekazu (of 1 Toyota-cho, Toyota-sh, Aichi-ken ., 471-8571, JP)
FUNAHASHI, Makoto (of 1 Toyota-cho, Toyota-sh, Aichi-ken ., 471-8571, JP)
IWASE, Yuji (of 1 Toyota-cho, Toyota-sh, Aichi-ken ., 471-8571, JP)
EBUCHI, Hiroaki (of 1 Toyota-cho, Toyota-sh, Aichi-ken ., 471-8571, JP)
KATO, Shotaro (of 1 Toyota-cho, Toyota-sh, Aichi-ken ., 471-8571, JP)
HASHIMOTO, Hiroto (of 1 Toyota-cho, Toyota-sh, Aichi-ken ., 471-8571, JP)
Application Number:
IB2014/002422
Publication Date:
May 21, 2015
Filing Date:
November 13, 2014
Export Citation:
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Assignee:
TOYOTA JIDOSHA KABUSHIKI KAISHA (1 Toyota-cho, Toyota-shiAichi-ken, 471-8571, JP)
International Classes:
F16D11/14
Download PDF:
Claims:
CLAIMS:

1. An engagement apparatus comprising:

a first member having a first engaging tooth; and

a second member having a second engaging tooth, an axis of the first member and an axis of the second member being coaxial;

the first member and the second member being configured to rotate relatively around the axis of the first member, and move relatively in an axial direction;

the first engaging tooth being provided in plurality in a circumferential direction around the axis of the first member on a side of the first member that faces the second member;

the second engaging tooth being provided in plurality in a circumferential direction around the axis of the second member on a side of the second member that faces the first member;

the first engaging tooth having a first tooth face, a second tooth face, a first end surface, a first connecting surface, and a second connecting surface;

the first tooth face being a face located on one side of the first engaging tooth in1 the circumferential direction around the axis of the first member;

the second tooth face being a face located on the other side of the first engaging tooth in the circumferential direction around the axis of the first member;

the first end surface being a surface that faces the second member in a position closest to the second member in the axial direction of the first engaging tooth;

the first connecting surface connecting the first end surface to the first tooth face; the second connecting surface connecting the first end surface to the second tooth face; ,

the second engaging tooth having a third tooth face, a fourth tooth face, a second end surface, a third connecting surface, and a fourth connecting surface;

the third tooth face being a face located on the other side of the second engaging tooth in the circumferential direction around the axis of the second member; the fourth tooth face being a face located on. the one side of the second engaging tooth in the circumferential direction around the axis of the second member;

the second end surface being a surface that faces the first member in a position closest to the first member in the axial direction of the second engaging tooth;

the third connecting surface connecting the second end surface to the third tooth face; the fourth connecting surface connecting the second end surface to the fourth tooth face;

a connecting position of the second tooth face and the second connecting surface being closer to the first end surface side than a connecting position of the first tooth face and the first connecting surface;

a connecting position of the fourth tooth face and the fourth connecting surface being closer to the second end surface side than a connecting position of the third tooth face and the third connecting surface;

the first engaging tooth having a width in the circumferential direction around the axis of the first member that becomes smaller toward the first end surface in the axial direction;

the second engaging tooth having a width in the circumferential direction around the axis of the second member that becomes smaller toward the second end surface in the axial direction;

the second tooth face of the first engaging tooth and the fourth tooth face of the second engaging tooth being configured to mesh together in an engaged state in which the first member and the second member are integrated together;

the first connecting surface being configured such that an angle between a normal of the first connecting surface and a normal of the first end surface becomes smaller in a stepped or continuous manner as a normal direction of the first connecting surface moves from a connecting portion of the first connecting surface and the first tooth faqe toward a connecting portion of the first connecting surface and the first end surface; and

the third connecting surface being configured such that an angle between a normal of the third connecting surface and a normal of the second end surface becomes smaller in a stepped or continuous manner as a normal direction of the third connecting surface moves · from a connecting portion of the third connecting surface and the third tooth face toward a connecting portion of the third connecting surface and the second end surface.

2. The engagement apparatus according to claim 1, wherein

the first connecting surface of the first engaging tooth has a plurality of first partial connecting surfaces each with a different angle between the circumferential direction around the axis of the first member and the first connecting surface;

the angle of the plurality of first partial connecting surfaces becomes smaller as the angle of the plurality of first partial connecting surfaces is nearer the first end surface than the first tooth face;

the third connecting surface of the second engaging tooth has a plurality of second partial connecting surfaces each with a different angle between the circumferential direction around the axis of the second member and the third connecting surface; and

the angle of the plurality of second partial connecting surfaces becomes smaller as the angle of the plurality of second partial connecting surfaces is nearer the second end surface than the third tooth face.

3. The engagement apparatus according to claim 2, wherein

the plurality of first partial connecting surfaces includes two first partial connecting surfaces;

the plurality of second partial connecting surfaces includes two second partial connecting surfaces;

an angle between the circumferential direction around the axis of the first member and the second connecting surface is predetermined;

an angle between the circumferential direction around the axis of the second member and the fourth connecting surface is predetermined;

in the axial direction, a distance between the first end surface and a connecting portion of the second connecting surface and the second tooth face is farther away than a distance between a connecting portion of the two first partial connecting surfaces and the first end surface; and

in the axial direction, a distance between the second end surface and a connecting portion of the fourth connecting surface and the fourth tooth face is farther away than a distance between a connecting portion of the two second partial connecting surfaces and the second end surface.

' 4. The engagement apparatus according to claim 3, wherein

a connecting portion of the second connecting surface and the second tooth face, and a connecting portion of the fourth connecting surface and the fourth tooth face have a round shape when viewed from a radial direction.

5. The engagement apparatus according to claim 4, wherein

a connecting portion between the plurality of first partial connecting surfaces has a round shape when viewed from the radial direction; and \ a connecting portion between the plurality of second partial connecting surfaces has a round shape when viewed from the radial direction.

6. The engagement apparatus according to claim 5, wherein

the connecting portion of the first connecting surface and the first tooth face, the connecting portion of the first connecting surface and the first end surface, the connecting portion of the second connecting surface and the first end surface, the connecting portion of the third connecting surface and the third tooth face, the connecting portion of the third connecting surface and the second end surface, and the connecting portion of the fourth connecting surface and the second end surface, have a round shape when viewed from the radial direction.

7. The engagement apparatus according to any one of claims 1 to 6, wherein the second connecting surface has a plurality of third partial connecting surfaces each with a different angle between the circumferential direction and the second connecting surface; and

the fourth connecting surface has a plurality of fourth partial connecting surfaces each with a different angle between the circumferential direction and the fourth connecting surface.

8. An engagement apparatus comprising:

a first member having a first engaging tooth; and

a second member having a second engaging tooth, an axis of the first member and an axis of the second member being coaxial;

the first member and the second member being configured to rotate relatively around the axis of the first member, and move relatively in an axial direction;

the first engaging tooth being provided in plurality in a circumferential direction around the axis of the first member on a side of the first member that faces the second member;

the second engaging tooth being provided in plurality in a circumferential direction around the axis of the second member on a side of the second member that faces the first member;

the first engaging tooth having a first tooth face, a second tooth face, a first end surface, a first connecting surface, and a second connecting surface;

the first tooth face being a face located on one side of the first engaging tooth in the circumferential direction around the axis of the first member;

the second tooth face being a face located on the other side of the first engaging tooth in the circumferential direction around the axis of the first member;

the first end surface being a surface that faces the second member in a position closest to the second member in the axial direction of the first engaging tooth;

the first connecting surface connecting the first end surface to the first tooth face; the second connecting surface connecting the first end surface to the second tooth face; the second engaging tooth having a third tooth face, a fourth tooth face, a second end surface, a third connecting surface, and a fourth connecting surface;

the third tooth face being a face located on the other side of the second engaging tooth in the circumferential direction around the axis of the second member;

the fourth tooth face being a face located on the one side of the second engaging tooth in the circumferential direction around the axis of the second member;

the second end surface being a surface that faces the first member in a position closest to the first member in the axial direction of the second engaging tooth;

the third connecting surface connecting the second end surface to the third tooth face; the fourth connecting surface connecting the second end surface to the fourth tooth face;

a connecting position of the second tooth face and the second connecting surface being closer to the first end surface side than a connecting position of the first tooth face and the first connecting surface;

a connecting position of the fourth tooth face and the fourth connecting surface being closer to the second end surface side than a connecting position of the third tooth face and the third connecting surface;

the first engaging tooth having a width in the circumferential direction around the axis of the first member that becomes smaller toward the first end surface in the axial direction;

the second engaging tooth having a width in the circumferential direction around the axis of the second member that becomes smaller toward the second end surface in the axial direction;

the second tooth face of the first engaging tooth and the fourth tooth face of the second engaging tooth being configured to mesh together in an engaged state in which the first member and the second member are integrated together;

the first connecting surface being configured such that an angle between the circumferential direction and the first connecting surface becomes smaller in a stepped or continuous manner from a connecting portion of the first connecting surface and the first tooth face toward a connecting portion of the first connecting surface and the first end surface; and

the third connecting surface being configured such that an angle between the circumferential direction and the third connecting surface becomes smaller in a stepped or continuous manner from a connecting portion of the third connecting surface and the third tooth face toward a connecting portion of the third connecting surface and the second end surface.

9. A drive system for a hybrid vehicle, the drive system comprising:

a driving wheel;

the engagement apparatus according to any one of claims 1 to 8;

an engine;

an electric motor;

a power split mechanism that splits output of the engine to the electric motor and the driving wheel; - a driving source;

the first member being rotatably supported around a rotating shaft of the electric motor, and rotating around the rotating shaft by motor torque output from the electric motor, the first member being configured such that engine torque output from the engine is transmitted via the power split mechanism;

the second member being movably supported in an axial direction of the rotating shaft, and moving in the axial direction by driving force output from the drive source; and an electronic control unit configured to

(a) control the electric motor to output the motor torque such that the second tooth face of the first engaging tooth and the fourth tooth face of the second engaging tooth bring closer together,

(b) place the engagement apparatus in the engagement state in which the second tooth face is in mesh with the fourth tooth face and limit rotation of the electric motor, by controlling the driving source to output the driving force that brings the second member closer to the first member.

Description:
ENGAGEMENT APPARATUS AND HYBRID VEHICLE DRIVE SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to an engagement apparatus and a hybrid vehicle drive system. 2. Description of Related Art

[0002] A mesh-type engagement apparatus that includes two members coaxially arranged engages both members by meshing rows of teeth on the members together. As one such engagement apparatus, Japanese Patent Application Publication No. 2009-191954 (JP 2009-191954 A) describes a structure of a dog clutch that engages and disengages (releases) dog teeth by driving an actuator.

SUMMARY OF THE INVENTION

[0003] Here, the shape of the teeth that mesh when the engagement apparatus described above is engaged may be an asymmetric shape such as trapezoidal so as to enable the rows of teeth on the members to be able to easily fit together and thus ensure meshing ability. In this case, if faces that have a large taper angle (chamfer angle) engage, the impact load is unable to escape and relatively large input torque is generated in the meshing teeth, which may reduce the durability of the engagement apparatus.

[0004] The invention thus provides an engagement apparatus in which the durability is able to be improved, and a hybrid vehicle drive system provided with this engagement apparatus.

[0005] A first aspect of the invention relates to an engagement apparatus that includes a first member and a second member. The first member has a first engaging tooth. The second member has a second engaging tooth. An axis of the first member and an axis of the second member are coaxial. The first member and the second member are configured to rotate relatively around the axis of the first member, and move relatively in an axial direction. The first engaging tooth is provided in plurality in a circumferential direction around the axis of the first member on a side of the first member that faces the second member. , The second engaging tooth is provided in plurality in a circumferential direction around the axis of the second member on a side of the second member that faces the first member. The first engaging tooth has a first tooth face, a second tooth face, a first end surface, a first connecting surface, and a second connecting surface. The first tooth face is a face located on one side of the first engaging in the circumferential direction. The second tooth face is a face located on the other side of the first engaging in the circumferential direction around the axis of the first member. The first end surface is a surface that faces the second member in a position closest to the second member in the axial direction of the first engaging tooth. The first connecting surface connects the first end surface to the first tooth face. The second connecting surface connects the first end surface to the second tooth face. The second engaging tooth has a third tooth face, a fourth tooth face, a second end surface, a third connecting surface, and a fourth connecting surface. The third tooth face is a face located on the other side of the second engaging tooth in the circumferential direction around the axis of the second member. The fourth tooth face is a face located on the one side of the second engaging tooth in the circumferential direction around the axis of the second member. The second end surface is a surface that faces the first member in a position closest to the first member in the axial direction of the second engaging tooth. The third connecting surface connects the second end surface to the third tooth face. The fourth connecting surface connects the second end surface to the fourth tooth face. A connecting position of the second tooth face and the second connecting surface is closer to the first end surface side than a connecting position of the first tooth face and the first connecting surface. A connecting position of the fourth tooth face and the fourth connecting surface is closer to the second end surface side than a connecting position of the third tooth face and the third connecting surface. The first engaging tooth has a width in the circumferential direction around the axis of the first member that becomes smaller toward the first end surface in the axial direction. The second engaging tooth has a width in the circumferential direction around the axis of the second member that becomes smaller toward the second end surface in the axial direction. The second tooth face of the first engaging tooth and the fourth tooth face of the second engaging tooth are configured to mesh together, in an engaged state in which the first member and the second member are integrated together. The first connecting surface is configured such that an angle between a normal of the first connecting surface and a normal of the first end surface becomes smaller in a stepped or continuous manner as a normal direction of the first connecting surface moves from a connecting portion of the first connecting surface and the first tooth face toward a connecting portion of the first connecting surface and the first end surface. The third connecting surface is configured such that an angle between a normal of the third connecting surface and a normal of the second end surface becomes smaller in a stepped or continuous manner as a normal direction of the third connecting surface moves from a connecting portion of the third connecting surface and the third tooth face toward a connecting portion of the third connecting surface and the second end surface.

[0006] In the engagement apparatus described above, the first connecting surface of the first engaging tooth may have a plurality of first partial connecting surfaces with a different angle between the circumferential direction around the axis of the first member and the first connecting surface. The angle of the plurality of first partial connecting surfaces may become smaller as the angle of the plurality of first partial connecting surfaces is nearer the first end surface than the first tooth face. The third connecting surface of the second engaging tooth may have a plurality of second partial connecting surfaces with a different angle between the circumferential direction around the axis of the second member and the third connecting surface. The angle of the plurality of second partial connecting surfaces may become smaller as the angle of the plurality of second partial connecting surfaces is nearer the second end surface than the third tooth face.

[0007] In the engagement apparatus described above, the plurality of first partial connecting surfaces may include two first partial connecting surfaces. The plurality of second partial connecting surfaces may include two * second partial connecting surfaces. An angle between the circumferential direction around the axis of the first member and the second connecting surface may be predetermined. Ah angle between the circumferential direction around the axis of the second member and the fourth connecting surface may be predetermined. In the axial direction, a distance between the first end surface and a connecting portion of the second connecting surface and the second tooth face may be farther away than a distance between a connecting portion of the two first partial connecting surfaces and the first end surface. In the axial direction, a distance between the second end surface and a connecting portion of the fourth connecting surface and the fourth tooth face may be farther away than a distance between a connecting portion of the two second partial connecting surfaces and the second end surface.

[0008] In the engagement apparatus described above, a connecting portion of the second connecting surface and the second tooth face, and a connecting portion of the fourth connecting surface and the fourth tooth face may have a round shape when viewed from a radial direction.

[0009] In the engagement apparatus described above, a connecting portion between the plurality of first partial connecting surfaces may have a round shape when viewed from the radial direction. A connecting portion between the plurality of second partial connecting surfaces may have a round shape when viewed from the radial direction.

[0010] In the engagement apparatus described above, the connecting portion of the first connecting surface and the first tooth face, the connecting portion of the first connecting surface and the first end surface, the connecting portion of the second connecting surface and the first end surface, the connecting portion of the third connecting surface and the third tooth face, the connecting portion of the third connecting surface and the second end surface, and the connecting portion of the fourth connecting surface and the second end surface, may have a round shape when viewed from the radial direction.

[0011] In the engagement apparatus described above, the second connecting surface may have a plurality of third partial connecting surfaces each with a different angle between the circumferential direction and the second connecting surface. The fourth connecting surface may have a plurality of fourth partial connecting surfaces each with a different angle between the circumferential direction and the fourth connecting surface.

[0012] A second aspect of the invention relates to an engagement apparatus that includes a first member and a second member. The first member has a first engaging tooth. The second member has a second engaging tooth. An axis of the first member and an axis of the second member are coaxial. The first member and the second member are configured to rotate relatively around the axis of the first member, and move relatively in an axial direction. The first engaging tooth is provided in plurality in a circumferential direction around the axis of the first member on a side of the first member that faces the second member. The second engaging tooth is provided in plurality in a circumferential direction around the axis of the second member on a side of the second member that faces the first member. The first engaging tooth has a first tooth face, a second tooth face, a first end surface, a first connecting surface, and a second connecting surface. The first tooth face is a face located on one side of the first engaging in the circumferential direction. The second tooth face is a face located on the other side of the first engaging in the circumferential direction around the axis of the first member. The first end surface is a surface that faces the second member in a position closest to the second member in the axial direction of the first engaging tooth. The first connecting surface connects the first end surface to the first tooth face. The second connecting surface connects the first end surface to the second tooth face. The second engaging tooth has a third tooth face, a fourth tqoth face, a second end surface, a third connecting surface, and a fourth connecting surface. The third tooth face is a face located on the other side of the second engaging tooth in the circumferential direction around the axis of the second member. The fourth tooth face is a face located on the one side of the second engaging tooth in the circumferential direction around the axis of the second member. The second end surface is a surface that faces the first member in a position closest to the first member in the axial direction of the second engaging tooth. The third connecting surface connects the second end surface to the third tooth face. The fourth connecting surface connects the second end surface to the fourth tooth face. A connecting position of the second tooth face and the second connecting surface is closer to the first end surface side than a connecting position of the first tooth face and the first connecting surface. A connecting position of the fourth tooth face and the fourth connecting surface is closer to the second end surface side than a connecting position of the third tooth face and the third connecting surface. The first engaging tooth has a width in the circumferential direction around the axis of the first member that becomes smaller toward the first end surface in the axial direction. The second engaging tooth has a width in the circumferential direction around the axis of the second member that becomes smaller toward the second end surface in the axial direction. The second tooth face of the first engaging tooth and the fourth tooth face of the second engaging tooth are configured to mesh together, in an engaged state in which the first member and the second member are integrated together. The first connecting surface is configured such that an angle between the circumferential direction and the first connecting surface becomes smaller in a stepped or continuous manner from a connecting portion of the first connecting surface and the first tooth face toward a connecting portion of the first connecting surface and the first end surface. The third connecting surface is configured such that an angle between the circumferential direction and the third connecting surface becomes smaller in a stepped or continuous manner from a connecting portion of the third connecting surface and the third tooth face toward a connecting portion of the third connecting surface and the second end surface.

[0013] A third aspect of the invention relates to a drive system for a hybrid vehicle. This drive system includes a driving wheel, the engagement apparatus described above, an engine, an electric motor, a power split mechanism, a driving source and an electronic control unit. The power split mechanism splits output of the engine to the electric motor and the driving wheel. The first member is rotatably supported around a rotating shaft of the electric motor, and rotates around the rotating shaft by motor torque output from the electric motor. The first member is configured such that engine torque output from the engine is transmitted via the power split mechanism. The second member is movably supported in an axial direction of the rotating shaft, and moves in the axial direction by driving force output from the drive source. The electronic control unit is configured to control the electric motor to output the motor torque such that the second tooth face of the first engaging tooth and the fourth tooth face of the second engaging tooth bring closer together. The electronic control unit is configured to place the engagement apparatus in the engagement state in which the second tooth face is in mesh with the fourth tooth face and limit rotation of the electric motor, by controlling the driving source to output the driving force that brings the second member closer to the first member.

[0014] According to the first, second and third aspects of the invention, the first connecting surfaces with a relatively small angle between the circumferential direction and the first connecting surface tend to strike each other more easily as the rotational difference between the first member and the second member increases, and the incident angle in the direction in which the second engaging tooth and the first engaging tooth approach each other becomes smaller, so the impact force at the time of impact is able to suitably escape in the disengaging direction. As a result, impact torque received by the second engaging tooth and the first engaging tooth can be reduced, thereby enabling durability to be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a skeleton view of a power transmitting apparatus of a hybrid vehicle to which an engagement apparatus according to one example embodiment of the invention is applied;

FIG. 2 is an enlarged longitudinal sectional view of the main portions of the engagement apparatus in the power transmitting apparatus shown in FIG. 1;

FIG. 3 is an alignment graph according to a MG1 lock in the hybrid vehicle drive system shown in FIG. 1;

FIG. 4 is a sectional view taken along line IV - IV in FIG. 2, showing the shape of dog teeth of a piece and dog teeth of a sleeve in a radial view; FIG. 5 is an enlarged view showing a frame format of the shape of the dog teeth in FIG. 4;

FIG. 6 is a view showing a frame format of a change in the positional relationship between the sleeve and the piece when the dog teeth of the sleeve enter the spaces between the dog teeth of the piece when engagement control is being performed;

FIG. 7 is a view showing a frame format of a change in the positional relationship between the sleeve and the piece when a second connecting surface of a dog tooth of the sleeve strikes a second connecting surface of a dog tooth of the piece; and

FIG. 8 is a view showing a frame format of a change in the positional relationship between the sleeve and the piece when engagement control is performed while the piece is negatively rotating, and a first connecting surface of the dog tooth of the sleeve strikes a first connecting surface of the dog tooth of the piece.

DETAILED DESCRIPTION OF EMBODIMENTS

[0016] Hereinafter, example embodiments of the engagement apparatus according to the invention will be described with reference to the accompanying drawings. Like or corresponding portions in the drawings described below will be denoted by like reference characters, and descriptions of these portions will not be repeated.

[0017] First, the structure of an engagement apparatus 10 according to one example embodiment of the invention, and a hybrid vehicle drive system (hereinafter, referred to as a "power transmitting apparatus 1 of a hybrid vehicle 100") that includes this engagement apparatus 10, will be described with reference to FIGS. 1 and 2.

[0018] As shown in FIG. 1, in this example embodiment, the engagement apparatus 10 is applied to the power transmitting apparatus 1 (i.e., the hybrid vehicle drive system) mounted in the hybrid vehicle 100. The hybrid vehicle 100 (hereinafter, also simply referred to as the "vehicle 100") has an engine 2, a first rotary electric machine MG1, and a second rotary electric machine MG2, as power sources.

[0019] The power transmitting apparatus 1 includes the engine 2, a planetary gear set 3 (i.e., a power split mechanism), the first rotary electric machine MG1, the second rotary electric machine MG2, and the engagement apparatus 10. The power transmitting apparatus 1 may be applied to a FF (front engine, front wheel drive) vehicle or a RR (rear engine, rear wheel drive) vehicle or the like. The power transmitting apparatus 1 is mounted in the hybrid vehicle 100 such that the axial direction is in the vehicle width direction, for example.

[0020] The engine 2 provides output by converting combustion energy of fuel into rotational movement of a rotating shaft 2a according to a control command from an ECU 50. The rotating shaft 2a of the engine 2 is connected to an input shaft 4 via a damper 23. The rotating shaft 2a of the engine 2 and the input shaft 4 are coaxially arranged. The input shaft 4 is connected to a carrier 3d of the planetary gear set 3.

[0021] The planetary gear set 3 functions as a power split mechanism that split the power from the engine 2 to the output side and to the first rotary electric machine MG1. The planetary gear set 3 has a sun gear 3a, pinion gears 3b, a ring gear 3c, and the carrier 3d. The sun gear 3a is arranged to the radial outside of the input shaft 4. This sun gear 3a is arranged so as to be able to rotate about the same axis as the input shaft 4. The ring gear 3c is arranged to the radial outside of the sun gear 3a, and so as to be able to rotate about the same axis as the sun gear 3a. The pinion gears 3b are arranged between the sun gear 3a and the ring gear 3c, and are engaged with both the sun gear 3a and the ring gear 3c. The pinion gears 3b are rotatably supported by the carrier 3d that arranged on the same axis as the input shaft 4.

[0022] The carrier 3d is connected to the input shaft 4 and rotates together with the input shaft 4. Therefore, the pinion gears 3b are able to rotate (revolve) with the center line of the input shaft 4 as the rotational center, and are supported by the carrier 3d, and able to rotate (spin) with the center line of the pinion gears 3b as the rotational center.

[0023] The first rotary electric machine MG1 is connected to the sun gear 3a. A rotating shaft 30 of the first rotary electric machine MG1 is coaxially arranged with the input shaft 4, and is connected to the sun gear 3a. Therefore, a rotor of the first rotary electric machine MG1 rotates together with the sun gear 3a. Also, the rotating shaft 30 of the first rotary electric machine MG1 is supported by a housing 32 that houses the power transmitting apparatus 1.

[0024] A counter drive gear 5 is connected to the ring gear 3c. The counter drive gear 5 is an output gear that rotates together with the ring gear 3c. The counter drive gear 5 is arranged closer to the engine 2 side than the ring gear 3c is in the axial direction. The ring gear 3c is also an output element capable of outputting rotation input from either the first rotary electric machine MGl or the engine 2 to a driving wheel 22 side.

[0025] The counter drive gear 5 is in mesh with a counter driven gear 6. A reduction gear 7 of the second rotary electric machine MG2 is in mesh with the counter driven gear 6. The reduction gear 7 is arranged on a rotating shaft 31 of the second rotary electric machine MG2, and rotates together with the rotating shaft 31. That is, torque output from the second rotary electric machine MG2 is transmitted to the counter driven gear 6 via the reduction gear 7. The reduction gear 7 has a smaller diameter than the counter driven gear 6, and reduces the speed of rotation of the second rotary electric machine MG2, and then transmits the rotation at this reduced speed to the counter driven gear 6.

[0026] The first rotary electric machine MGl and the second rotary electric machine MG2 are connected to a battery, not shown, via an inverter. The first rotary electric machine MGl and the second rotary electric machine MG2 are each able to function as a rotary electric machine that converts electric power supplied from the battery into mechanical power and outputs this power according to a control command from the ECU 50. Electric power generated by the first rotary electric machine MGl and the second rotary electric machine MG2 is able to be charged to the battery. An AC synchronous motor- generator, for example is able to be used for both the first rotary electric machine MGl and the second rotary electric machine MG2.

[0027] A drive pinion gear 8 is connected to the counter driven gear 6. This drive pinion gear 8 is coaxially arranged with the counter driven gear 6, and rotates together with the counter driven gear 6. The drive pinion gear 8 is in mesh with a differential ring gear 9 of a differential gear unit 20. The differential gear unit 20 is connected to the driving wheels 22 via left and right drive shafts 21. That is, the ring gear 3c is connected to the driving wheels 22 via the counter drive gear 5, the counter driven gear 6, the drive pinion gear 8, the differential gear unit 20, and the drive shafts 21. Also, the second rotary electric machine MG2 is arranged closer to the driving wheel 22 side than the ring gear 3c is, and is connected to the power transmission path between the ring gear 3c and the driving wheels 22, so as to be able to transmit power to both the ring gear 3c and the driving wheels 22.

[0028] Engine torque output from the engine 2 is transmitted to the pair of driving wheels 22 via the planetary gear set 3 that serves as the power split mechanism, and the differential gear unit 20. Also, when functioning as a generator, the first rotary electric machine MG1 regenerates power using the supplied engine torque distributed by the planetary gear set 3. The planetary gear set 3 is able to be used as a continuously variable transmission by causing the first rotary electric machine MG1 to function as a generator and performing regenerative control. That is, the output of the engine 2 is transmitted to the driving wheels 22 after the rotation speed of the output is changed by the planetary gear set 3. Control of the engine speed of the engine 2 and output control to the driving wheels 22 can be performed by controlling the driving of the second rotary electric machine MG2 or controlling the rotation speed of the first rotary electric machine MG1 or the second rotary electric machine MG2.

[0029] In the hybrid vehicle 100 in this example embodiment, as shown in FIG. 1, the first rotary electric machine MG1 is concentrically arranged with the rotating shaft 2a of the engine 2. The second rotary electric machine MG2 is arranged on the rotating shaft 31 that is different from the rotating shaft 2a of the engine 2. That is, the power transmitting apparatus 1 in this example embodiment is a multiple shaft-type power transmitting apparatus in which the input shaft 4, and the rotating shaft 31 of the second rotary electric machine MG2 are arranged on different axes.

[0030] With the power transmitting apparatus 1 in this example embodiment, the planetary gear set 3 is coaxially arranged with the rotating shaft 2a of the engine 2, between the engine 2 and the first rotary electric machine MG1. Also, the engagement apparatus 10 is arranged on the opposite of the first rotary electric machine MGl from the engine 2. That is, with the power transmitting apparatus 1 in this example embodiment, the counter drive gear 5, the planetary gear set 3, the first rotary electric machine MGl, and the engagement apparatus 10 are arranged, in order from the side nearest to the engine 2, on the same axis as the rotating shaft 2a of the engine 2.

[0031] The engagement apparatus 10 is connected to the first rotary electric machine MGl, as shown in FIG. 1. In this example embodiment, the engagement apparatus 10 is configured so as to be able to restrict the rotation of the first rotary electric machine MGl, and is used as a MGl locking mechanism that mechanically locks the rotation of the first rotary electric machine MGl. When executing output control to the driving wheels or engine speed control by the power transmitting apparatus 1, the rotation of the first rotary electric machine MGl is mechanically locked by the engagement apparatus 10 when it is necessary to control the rotation speed of the first rotary electric machine MGl to 0. Therefore, there is no longer a need to electrically control the rotation speed of the first rotary electric machine MGl, so electricity does not need to be supplied to the first rotary electric machine MGl, which enables fuel efficiency to be improved. The engagement apparatus 10 mechanically locks the rotation of the first rotary electric machine MGl, so the planetary gear set 3 no longer functions as a continuously variable transmission and instead operates at a fixed gear speed.

[0032] Here, the role of the engagement apparatus 10 as a MGl locking mechanism will be further described with reference to FIG. 3. FIG. 3 is an alignment graph related to the MGl lock in the hybrid vehicle drive system shown in FIG. 1.

[0033] With the power transmitting apparatus 1 of the hybrid vehicle 100 shown in FIG. 1, the relationships between the rotating speeds of the engine 2, the first rotary electric machine MGl, and the second rotary electric machine MG2 are illustrated by the alignment graph shown in FIG. 3. In the alignment graph in FIG 3, the vertical axis represents the rotation speeds of the first rotary electric machine MGl, the engine 2, and the second rotary electric machine MG2 in order from the left. The region above the horizontal axis represents positive rotation and the region below the horizontal axis represents negative rotation. The rotation speeds of the first rotary electric machine MGl, the engine 2, and the second rotary electric machine MG2 change in tandem so that they are always lined up in a straight line in the alignment graph. Also, the alignment graph in FIG. 3 also shows a dog clutch (i.e., the engagement apparatus 10) connected to the left side of the vertical axis that represents the rotation speed of the first rotary electric machine MGl. As shown in FIG. 1, the second rotary electric machine MG2 is connected to the output shaft, so the vertical axis on the right end in FIG. 3 represents the rotation speed of both the second rotary electric machine MG2 and the output shaft.

[0034] The output shaft rotation speed is able to be controlled by outputting reaction torque (MGl torque and MG2 torque) with respect to engine torque to the first rotary electric machine MGl and the second rotary electric machine MG2 so as to create the alignment graph shown by the solid line in FIG. 3, while the hybrid vehicle 100 is running. Furthermore, there are cases in which the first rotary electric machine MGl is electrically stopped by outputting negative torque to the first rotary electric machine MGl such that the rotation speed of the first rotary electric machine MGl is 0. The engagement apparatus 10 serving as the MGl locking mechanism mechanically stops the first rotary electric machine MGl from rotating, instead of electrically stopping the first rotary electric machine MGl from rotating in this way. When the engagement apparatus 10 is engaged and the first rotary electric machine MGl is locked against rotation, the reaction force of the engine torque is received by the dog clutch instead of the first rotary electric machine MGl.

[0035] When the engagement apparatus 10 is used as the MGl locking mechanism in this way, the engagement apparatus 10 may have a structure such as that shown in FIG. 2, for example. As shown in FIG. 2, the engagement apparatus 10 includes a piece 11 (a first member), a sleeve 12 (a second member), a hub bracket 15, an electromagnetic actuator 40 (a drive source), and the ECU 50 (Electronic Control Unit).

[0036] The piece 11 and the sleeve 12 are arranged around the rotating shaft 30 of the first rotary electric machine MGl. This rotating shaft 30 rotates about an axis C illustrated by the alternate long and short dash line in the left-right direction at the bottom of FIG. 2. In the description below, the left-right (lateral) direction in FIG. 2 will be referred to as the "axial direction" of the rotating shaft 30, and the up-down (vertical) direction in FIG. 2 will be referred to as the "radial direction" of the rotating shaft 30, unless otherwise noted. Also, the direction around the axis C will be referred to as the "circumferential direction" of the rotating shaft 30.

[0037] The piece 11 rotates together in conjunction with the rotating shaft 30 about the axis C. This piece 11 is restricted from moving in the axial and radial directions. In the description below, the circumferential direction will also be referred to as the "rotational direction" of the piece 11.

[0038] The sleeve 12 is arranged to the radial outside of the piece 11. This sleeve 12 is spline- engaged with the hub bracket 15. The hub bracket 15 is fixed to the housing 32 that houses the constituent elements of the power transmitting apparatus 1. That is, the sleeve 12 is configured to be able to move in the axial direction, while being restricted from moving in the radial direction and rotating around the axis C, by being spline-engaged with the hub bracket 15. Also, the sleeve 12 has a sandwiched portion 12a that extends toward the radial outside.

[0039] The inner peripheral surface of the sleeve 12 is able to be engaged / disengaged with the outer peripheral surface of the piece 11 by the sleeve 12 moving in the axial direction. A plurality of dog teeth 13 (external teeth, first engaging teeth) are arranged along in the circumferential direction around the axis C pointing radially outward, on the outer peripheral surface of the piece 11. A plurality of dog teeth 14 (internal teeth, second engaging teeth) are arranged along in the circumferential direction around the axis C pointing radially inward, on the inner peripheral surface of the sleeve 12. These dog teeth 13 and 14 form an engaging dog clutch. The piece 11 and the sleeve 12 are able to be engaged by the sleeve 12 moving towards the piece 11 (i.e., in the engaging direction) and the dog teeth 14 of the sleeve 12 precisely fitting together and engaging with the dog teeth 13 of the piece 11. Rotation of the rotating shaft 30 is able to be restricted by fixing the rotating shaft 30 of the first rotary electric machine MG1 that operates in tandem with the piece 11, by spline-engaging the sleeve 12 to the piece 11. Also, the sleeve 12 and the piece 11 are able to be disengaged by moving the sleeve 12 away from the piece 11 (in a disengaging direction) to separate the dog teeth 14 of the sleeve 12 from the dog teeth 13 of the piece 11.

[0040] In FIG. 2, the sleeve 12 is arranged on the left side of the piece 11, and is configured to engage with the piece 11 when the sleeve 12 moves to the right, and disengage from the piece 11 when the sleeve 12 moves to the left. In the description below, the direction toward the right in FIG. 2 may also be referred to as the "engaging direction", and the direction toward the left may also be referred to as the "disengaging direction". Also, the moving direction of the piece 11 including the engaging direction and the disengaging direction may also be referred to as the "stroke direction".

[0041] The electromagnetic actuator 40 is a drive source that generates driving force in the axial direction and moves the sleeve 12 in the axial direction. As shown in FIG. 2, the electromagnetic actuator 40 in this example embodiment is more specifically an electromagnetic solenoid type actuator. The electromagnetic actuator 40 is arranged around the rotating shaft 30 and to the radial outside of the piece 11 and the sleeve 12.

[0042] The electromagnetic actuator 40 includes an electromagnetic coil 41, an inner yoke 42, an outer yoke 43, an armature 44, a return spring 45, and a spring 48.

[0043] The inner yoke 42 is arranged around the electromagnetic coil 41 from the engaging direction side, and the outer yoke 43 is arranged around the electromagnetic coil 41 from the disengaging direction side. The inner yoke 42 and the outer yoke 43 are connected to the radially outer side of the electromagnetic coil 41 and fixed to the housing 32. That is, the inner yoke 42 and the outer yoke 43 function as fixed portions that are arranged fixed around the electromagnetic coil 41 so as to sandwich the electromagnetic coil 41 from both sides in the axial direction. Also, the inner yoke 42 and the outer yoke 43 are not connected together on the radially inner side of the electromagnetic coil 41, but instead form an opening 46 at a portion on the radially inner side of the electromagnetic coil 41. The inner yoke 42 and the outer yoke 43 are both formed by magnetic bodies.

[0044] The armature 44 is arranged to the radially inner side of the inner yoke 42 and the outer yoke 43, and to the radially outer side of the sleeve 12. This armature 44 is arranged so as to be able to move in the axial direction, and is able to apply thrust to the sleeve 12 through axial motion.

[0045] The armature 44 is formed by two members, i.e., a third member- 44a and a fourth member 44b. The third member 44a of the armature 44 is arranged able to be operatively linked to the sandwiched portion 12a of the sleeve 12 via the spring 48 from the disengaging direction side in the axial direction, and the fourth member 44b is arranged able to abut against the sandwiched portion 12a of the sleeve 12 from the engaging direction side. This structure makes it possible to ensure the assemblability of the sleeve 12 that is arranged between the third member 44a and the fourth member 44b.

[0046] The third member 44a of the armature 44 is supported via a supporting member 47 such as a plate or bush, on the radially inner side of the outer yoke 43. The fourth member 44b is supported via the supporting member 47 on the radially inner side of the inner yoke 42. That is, the third member 44a and the fourth member 44b are supported individually by the fixed portions (i.e., the inner yoke 42 and the outer yoke 43). That is, the armature 44 is configured having two support points according to the fixed portions in the axial direction and is supported at both ends (two-point support), which enables the stability of axial movement to be improved, thus enabling thrust to be efficiently transmitted to the sleeve 12.

[0047] Also, the armature 44 is formed as an integrated member by the fourth member 44b being press-fit into the third member 44a. As a result, even if the armature 44 is formed by a plurality of members, integrated operation is possible while realizing improved performance due a reduction in inertia, improved assemblability, and a reduction in size with regards to the dimensions in the radial and axial directions. The third member 44a and the fourth member 44b of the armature 44 may also be fastened together by fastening means such as a bolt.

[0048] Also, the third member 44a of the armature 44 has a protruding portion 44c that protrudes toward the radial outside and extends in the axial direction. The protruding portion 44c is inserted into the opening 46 between the inner yoke 42 and the outer yoke 43. A stopper surface 44d that is orthogonal to the operating direction of the armature 44 is provided on an end surface on the engaging direction side of the protruding portion 44c. Meanwhile a stopper surface 42a is provided in a position facing the stopper surface 44d of the armature 44, on an end surface on the disengaging direction side of the inner yoke 42. When the armature 44 moves in the engaging direction, the stopper surface 44d of the armature 44 abuts against the stopper surface 42a of the inner yoke 42, thus enabling the movement of the armature 44 in the engaging direction to be stopped.

[0049] The third member 44a of the armature 44 is formed by a magnetic body, and the fourth member 44b is formed by a nonmagnetic body. As a result, magnetic paths to all but the necessary portions are able to be cut off even without providing an air gap or the like in a supporting portion (i.e., the supporting member 47) of the fixed portions (i.e., the inner yoke 42 and the outer yoke 43) and the third member 44a and the fourth member 44b.

[0050] Also, each supporting portion of the two-point supports of the armature 44 and the fixed portions are set matching the radial dimensions. That is, the supporting portion of the outer yoke 43 and the third member 44a of the armature 44, and the supporting portion of the inner yoke 42 and the fourth member 44b of the armature 44 are arranged in the same radial position. Here, when the radial position of both supporting portions is the same, it means that a difference in the radial dimensions of the supporting portions is within a predetermined range (such as ± 0.2 mm or less). As a result, the " machining accuracy is able to be improved, and the supporting accuracy is able to be improved.

[0051] The return spring 45 is arranged between the inner yoke 42 and the fourth member 44b of the armature 44. The return spring 45 is a compression spring, for example, and is retained in an appropriately compressed state, urging the armature 44 in the disengaging direction. The return spring 45 generates more urging force in the disengaging direction as the armature 44 moves, i.e., advances, in the engaging direction, i.e., as the degree of meshing between the sleeve 12 and the piece 11 deepens.

[0052] The spring 48 is arranged between the third member 44a of the armature 44 and the sandwiched portion 12a of the sleeve 12. The spring 48 is arranged so as to be able to expand and contract in the axial direction according to the relative positional relationship in the axial direction between the armature 44 and the sandwiched portion 12a of the sleeve 12.

[0053] The hub bracket 15 has an inner cylindrical portion 15a that extends adjacent to the piece 11 and is spline-engaged with the sleeve 12, around the rotating shaft 30. The hub bracket 15 has a shape that extends radially outward while covering the sleeve 12 and the electromagnetic actuator 40, following the shape of the electromagnetic actuator 40 from this inner cylindrical portion 15a, and is bolted (fixed) to the housing 32 at an outer edge end portion 15b. The inner cylindrical portion 15a of the hub bracket 15 is arranged to the radial inside of the sleeve 12, and a plurality of spline teeth 15c are arranged along in the circumferential direction pointing radially outward, on the outer peripheral surface of the inner cylindrical portion 15a. The sleeve 12 is spline-engaged with the hub bracket 15 by the dog teeth 14 being inserted between the spline teeth 15c, and is thus supported so as to be able to move in the axial direction.

[0054] The ECU 50 is a controller that controls portions of the hybrid vehicle 100 based on information from various sensors in the hybrid vehicle 100. The ECU 50 is connected to the engine 2, the first rotary electric machine MG1, and the second rotary electric machine MG2, and is able to control the running of the hybrid vehicle 100 by controlling the operation of these. Also, in this example embodiment, the ECU 50 is connected to the electromagnetic actuator 40 of the engagement apparatus 10, and is able to control the movement of the sleeve 12 in the axial direction by controlling the operation of the electromagnetic actuator 40. Also, the ECU 50 is able to control the rotation in the circumferential direction (i.e., the rotational direction) of the piece 11, by controlling the operation of the first rotary electric machine MG1. The ECU 50 is able to control the engagement / disengagement of the engagement apparatus 10 by this kind of control of the electromagnetic actuator 40 and the first rotary electric machine MG1.

[0055] When the electromagnetic coil 41 of the electromagnetic actuator 40 is in a de-energized state, the electromagnetic actuator 40 is stopped and the sandwiched portion 12a of the sleeve 12 receives the urging force of the return spring 45 in the disengaging direction via the fourth member 44b of the armature 44. As a result of this urging force, the sleeve 12 is retained in a position on the inner cylindrical portion 15a of the hub bracket 15 away from the piece 11, in a state out of mesh with the piece 11, as shown in FIG. 2. That is, when the electromagnetic actuator 40 is in a de-energized state, the engagement apparatus 10 is in a disengaged state so the piece 11 is able to rotate in conjunction with the rotating element.

[0056] When the electromagnetic coil 41 is energized in response to a control command from the ECU 50, a magnetic circuit M is formed around the third member 44a of the armature 44, and the inner yoke 42 and the outer yoke 43 that are magnetic bodies arranged around the electromagnetic coil 41. This magnetic circuit M is formed cutting across a gap between the stopper surface 42a of the inner yoke 42 and the stopper surface 44d of the protruding portion 44c of the armature 44, as shown by the dash arrow in FIG. 2. Therefore, the armature 44 is magnetically attracted to the inner yoke 42 while being guided by the inner peripheral surfaces of the inner yoke 42 and the outer yoke 43. The armature 44 moves in the engaging direction against the return spring 45 by this magnetic attractive force (electromagnetic force). As the armature 44 operates, the spring 48 transmits pressure received from the armature 44 to the sandwiched portion 12a of the sleeve 12, such that the sleeve 12 also moves in the same direction in conjunction with the armature 44, and the dog teeth 14 of the sleeve 12 consequently meth with the dog teeth 13 of the piece 11. That is, when the electromagnetic actuator 40 is in an energized state, the engagement apparatus 10 is in an engaged state so rotation of the rotating element that is connected to the piece 11 is able to be stopped.

[0057] Here, although the sleeve 12 starts to engage with the piece 11 by the sleeve 12 moving in the engaging direction, the phases of the piece 11 and the sleeve 12 are offset, so the dog teeth 14 of the sleeve 12 may not be able to mesh well with the dog teeth 13 of the piece 11. In this situation, further advancement of the sleeve 12 in the engaging direction is impeded by the piece 11, so engagement of the piece 11 and the sleeve 12 is incomplete. With the electromagnetic actuator 40 of this example embodiment, even in this kind of situation, the armature 44 is able to continue to move in the engaging direction while pushing and contracting the spring 48. Also, after the armature 44 has transitioned to a state in which the phases of the piece 11 and the sleeve 12 are aligned, the sleeve 12 is pushed out in the engaging direction by the urging force of the spring 48 and moves to a position where the dog teeth 14 of the sleeve 12 is sufficiently meshed with the dog teeth 13 of the piece 11.

[0058] In this way, with the electromagnetic actuator 40 of this example embodiment, when the phases of the piece 11 and the sleeve 12 are off and the sleeve 12 receives equal to or more than a predetermined reaction force in the disengaging direction from the piece 11, movement of the sleeve 12 in the engaging direction is stopped by the action of the spring 48, and thrust transmitted from the armature 44 is able to be accumulated. Then when the phases of the piece 11 and the sleeve 12 become aligned and the reaction force received by the sleeve 12 is reduced, the sleeve 12 is able to be quickly moved in the engaging direction using the accumulated thrust. As a result, the electromagnetic actuator 40 of this example embodiment is able to even more reliably perform the engaging operation of the piece 11 and the sleeve 12 that is the operated member.

[0059] This kind of function of the electromagnetic actuator 40 by the spring 48 may also be said to have a so-called ratchet function in which the position of the sleeve 12 in the stroke direction is maintained or retracted such that the piece 11 rotates idly when reaction force is received. The spring 48 need simply be configured to be able to accumulate thrust while stopping the movement of the sleeve 12, when thrust is being transmitted from the armature 44 to the sleeve 12, and may be replaced with a stopping mechanism that is realized by an element other than a spring.

[0060] Next, the shapes of the dog teeth 13 and 14 of the engagement apparatus 10 of this example embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a sectional view taken along line IV - IV in FIG. 2, and shows the shapes of the dog teeth of the piece and the dog teeth of the sleeve in a radial view. FIG. 5 is an enlarged view showing a frame format of the shapes of the dog teeth in FIG. 4. FIG 5 basically shows the reference characters related to the dog teeth 13 of the piece 11. The reference characters related to the dog teeth 14 of the sleeve 12 are shown in parentheses.

[0061] As shown in FIG. 4, each dog tooth 13 of the piece 11 has a first tooth face 51 being a face located on one side of the dog tooth 13 in the circumferential direction, a second tooth face 52 being a face located on the other side in the circumferential direction; a planar end surface (a first end surface) 53 being a surface that faces the sleeve 12 in a position closest to the sleeve 12 in the axial direction, a first connecting surface 54 that connects the end surface 53 with the first tooth face 51, and a second connecting surface 55 that connects the end surface 53 with the second tooth face 52. Similarly, each dog tooth 14 of the sleeve 12 has a first tooth face (a third tooth face) 61 being a face located on the other side in the circumferential direction, a second tooth face (a fourth tooth face) 62 being a face located on the one side in the circumferential direction, a planar end surface (a second end surface) 63 being a surface that faces the piece 11 in a position closest to the piece 11 in the axial direction, a first connecting surface (a third connecting surface) 64 that connects the end surface 63 with the first tooth face 61, and a second connecting surface (a fourth connecting surface) 65 that connects the end surface 63 with the second tooth face 62.

[0062] The first tooth face 51 of the dog teeth 13 of the piece 11, and the first tooth face 61 of the dog teeth 14 of the sleeve 12 are arranged so as to approach each other opposing each other when the piece 11 rotates in one direction with respect to the sleeve 12. Also, the second tooth face 52 of the dog teeth 13 of the piece 11, and the second tooth face 62 of the dog teeth 14 of the sleeve 12 are arranged so as to approach each other opposing each other when the piece 11 rotates in the opposite direction of the one direction with respect to the sleeve 12. In this example embodiment, regarding the rotational direction of the sleeve 12, the direction in which the first tooth face 51 of the dog teeth 13 of the piece 11 and the first tooth face 61 of the dog teeth 14 of the sleeve 12 approach each other will also be referred to as the "negative rotational direction". Meanwhile, the direction in which the second tooth face 52 of the dog teeth 13 of the piece 11 and the second tooth face 62 of the dog teeth 14 of the sleeve 12 approach each other will also be referred to as the "positive rotational direction". In FIG. 2, the direction toward the left in the drawing is the positive rotational direction of the piece 11 and the direction toward the right in the drawing is the negative rotational direction of the piece 11 (the same also applies to FIGS. 6 to 8). The positive rotational direction and the negative rotational direction correspond to the rotational directions of the first rotary electric machine MGl to which the piece 11 is connected.

, [0063] When the dog teeth 13 of the piece 11 are viewed from the sleeve 12 side, a front edge end portion 56 (i.e., a connecting portion between the first tooth face 51 and the first connecting surface 54) of the first tooth face 51 is arranged farther back in the axial direction than a front edge end portion 57 (i.e., a connecting portion between the second tooth face 52 and the second connecting surface 55) Of the second tooth face 52 on the dog teeth 13 of the piece 11 is. Similarly, when the dog teeth 14 of the sleeve 12 are viewed from the piece 11 side, a front edge end portion 66 (i.e., a connecting portion between the first tooth face 61 and the first connecting surface 64) of the first tooth face 61 of the dog teeth 14 of the sleeve 12 is arranged farther back in the axial direction than a front edge end portion 67 (i.e., a connecting portion between the second tooth face 62 and the second connecting surface 65) of the second tooth face 62 is. In other words, with the dog teeth 13 of the piece 11, the axial position of the connecting portion 57 between the second tooth face 52 and the second connecting surface 55 is arranged closer to the end surface 53 side than the axial position of the connecting portion 56 between the first tooth face 51 of the first connecting surface 54, and with the dog teeth 14 of the sleeve 12, the axial position of the connecting portion 67 between the second tooth face 62 and the second connecting surface 65 is arranged closer to the end surface 63 side than the axial position of the connecting portion 66 between the first tooth face 61 and the first connecting surface 64.

[0064] Also, the first connecting surface 54 of the piece 11 is formed such that the normal direction thereof is a direction between the circumferential direction and the axial direction, and changes in a stepped manner from the circumferential direction side toward the axial direction side, from the connecting portion 56 of the first tooth face 51 toward a connecting portion 59 of the end surface 53. More specifically, the first connecting surface 54 has two tapered surfaces (first partial connecting surfaces) 54a and 54b with different chamfer angles (taper angles). The chamfer angles of the tapered surfaces 54a and 54b are formed so as to become smaller from the. first tooth face 51 side toward the end surface 53 side. The tapered surface 54a is connected to the end surface 53, and the tapered surface 54b is connected to the first tooth face 51. As shown in FIG. 5, the tapered surface 54a is formed at a predetermined chamfer angle Θ1 and chamfer width XI, and the tapered surface 54b is formed at a predetermined chamfer angle Θ2 and chamfer width X2. Here, the chamfer angle is the inclination angle in the axial direction with respect to the circumferential direction, i.e., the extending direction of the end surface 53. The chamfer width is the distance from the position of the end surface 53 in the axial direction to the end portion of the tapered surface. The chamfer angle Θ1 of the tapered surface 54a on the end surface 53 side is smaller than the chamfer angle Θ2 of the tapered surface 54b on the first tooth face 51 side, so the tapered surface 54a has a shallower chamfer angle than the tapered surface 54b does.

[0065] Similarly, the first connecting surface 64 of the sleeve 12 also has two tapered surfaces (second partial connecting surfaces) 64a and 64b with different chamfer angles. The chamfer angles of the tapered surfaces 64a and 64b are formed so as to become smaller from the first tooth face 61 side toward the end surface 63 side. The chamfer angles and chamfer widths of the tapered surfaces 64a and 64b are Θ1 and Θ2, and XI and X2, respectively, just like the tapered surfaces 54a and 54b of the piece 11.

[0066] The second connecting surface 55 of the piece 11 is a single tapered surface formed at a predetermined chamfer angle Θ3 and chamfer width X3, as shown in FIG. 5. The chamfer width X3 of the second connecting surface 55 is set to be larger than the chamfer width XI of the tapered surface 54a of the first connecting surface 54, and smaller than the chamfer width X2 of the tapered surface 54b. That is, when viewed from the sleeve 12 side, the axial position of the connecting portion 57 between the second connecting surface 55 and the second tooth face 52 is arranged farther back in the axial direction (i.e., in a position away from the end surface 53) than the axial position of the connecting portion 58 between the two tapered surfaces 54a and 54b of the first connecting surface 54 is. The second connecting surface 65 of the sleeve 12 is also a single tapered surface formed at the predetermined chamfer angle Θ3 and chamfer width X3, just like the second connecting surface 55.

[0067] In this way, the dog teeth 13 of the piece 11 and the dog teeth 14 of the sleeve 12 have laterally asymmetrical shapes in the axial direction in a view of the sectional shape in the circumferential direction (i.e., the shape shown in FIGS. 4 and 5). Also, the dog teeth 13 and 14 are formed such that the widths (tooth thickness) in the circumferential direction become smaller toward the sides where they face each other in the axial direction. That is, the widths in the circumferential direction of the end surfaces 53 and 63 of the dog teeth 13 and 14 are smallest in a view of the sectional shape along the circumferential direction.

[0068] With the dog teeth 13 of the piece 11 and the dog teeth 14 of the sleeve 12, the connecting portions 57 and 67 between the second tooth faces 52 and 62 and the second connecting surfaces 55 and 65 have a round shape in which the angle formed by both surfaces is rounded. Also, the connecting portion 58 between the tapered surfaces 54a and 54b of the first connecting surface 54 of the piece 11, and a connecting portion 68 between the tapered surfaces 64a and 64b of the first connecting surface 64 of the sleeve 12 are also preferably round shaped. Moreover, the connecting portions 56 and 66 between the first tooth faces 51 and 61 and the first connecting surfaces 54 and 64, connecting portions 59 and 69 between the end surfaces 53 and 63 and the first connecting surfaces 54 and 64, and connecting portions 60 and 70 between the end surfaces 53 and 63 and the second connecting surfaces 55 and 65 are also preferably round shaped.

[0069] The ECU 50 appropriately changes the relative positions of the piece 11 and the sleeve 12 of the engagement apparatus 10 by driving the first rotary electric machine MG1 and the actuator 40, to perform engagement control that engages the sleeve 12 with the piece 11, and disengagement control that disengages the sleeve 12 from the piece 11. In the engagement control, the ECU 50 establishes an engaged state in which the second tooth face 52 of the dog teeth 13 of the piece 11 is engaged with the second tooth face 62 of the dog teeth 14 of the sleeve 12 by controlling the first rotary electric machine MGl to rotate in the positive rotational direction such that the second tooth face 52 of the dog teeth 13 of the piece 11 and the second tooth face 62 of the dog teeth 14 of the sleeve 12 both rotate toward each other, and controlling the actuator 40 to move the sleeve 12 in the engaging direction toward the piece 11. Here, the "engaged state" may also be said to be a state in which the piece 11 and the sleeve 12 are connected together as a single integrated unit. Also, in disengagement control, the ECU 50 disestablishes the engaged state described above by controlling the first rotary electric machine MGl to rotate in the negative rotational direction such that the first tooth face 51 of the dog teeth 13 of the piece 11 and the first tooth face 61 of the dog teeth 14 of the sleeve 12 both rotate toward each other, and controlling the electromagnetic actuator 40 to move the sleeve 12 in the disengaging direction away from the piece 11.

[0070] Physically, the ECU 50 is an electronic circuit that has as its main component a well-known micro-computer that includes Central Processing Unit (CPU), Random Access Memory (RAM), Read Only Memory (ROM), and an interface and the like. The functions of the ECU 50 are realized by operating various devices in the hybrid vehicle 100 under the control of the CPU by loading application programs stored in the ROM into the RAM and executing these programs with the CPU, and reading and writing data in the RAM and ROM.

[0071] Next, the operations of the sleeve and the piece at the time of engagement control of the engagement apparatus 10 according to this example embodiment will be described by pattern with reference to FIGS. 6 to 8. FIG. 6 is a view showing a frame format of a change in the positional relationship between the sleeve and the piece when the dog teeth of the sleeve enter the spaces between the dog teeth of the piece in engagement control. FIG. 7 is a view showing a frame format of a change in the positional relationship between the sleeve and the piece when the second connecting surface of a dog tooth of the sleeve strikes the second connecting surface of a dog tooth of the piece in the engagement control. FIG. 8 is a view showing a frame format of a change in the positional relationship between the sleeve and the piece when engagement control is performed while the piece is negatively rotating, and the first connecting surface of the dog tooth of the sleeve strikes a first connecting surface of the dog tooth of the piece.

[0072] With the power transmitting apparatus 1 in this example embodiment, when the vehicle is traveling at a high speed, the rotation speed of the second rotary electric machine MG2 on the output side increases in the positive direction, while the first rotary electric machine MGl negatively rotates, as shown in the alignment graph indicated by the alternate long and short dash line in FIG 3, for example. When an attempt is made to perform MGl lock in this kind of high speed running state, engagement control is performed after the rotation speed of the first rotary electric machine MGl first temporarily changes to near 0 in the positive rotational direction, as shown in the alignment graph indicated by the dotted line in FIG. 3.

[0073] FIG. 6 is a view showing the change in the position of a dog tooth 14 of the sleeve 12, with respect to the piece 11, when the dog tooth 14 of the sleeve 12 is fitting nicely between the dog teeth 13 of the piece 11, in three stages represented by reference characters 14-1, 14-2, and 14-3, in this kind of engagement control. The dog tooth 14 of the sleeve 12 that is in a position away from the piece 11 as shown by reference character 14-1 in FIG. 6 approaches the piece 11 while moving in a direction (toward the right in FIG. 6) in which the second tooth face 62 comes relatively closer to the piece 11, as shown by reference character 14-2 in FIG. 6, as a result of positive rotation of the piece 11 and thrust in the engaging direction of the sleeve 12. Then the dog tooth 14 of the sleeve 12 enters the space between two dog teeth 13 of the piece 11 without contacting the dog teeth 13 of the piece 11, as shown by reference character 14-3. The dog tooth 14 of the sleeve 12 is such that the width of the first tooth face 61 in the axial direction is shorter due to the provision of the first connecting surface 64 (in particular, the tapered surface 64b with a large chamfer angle that is arranged on the first tooth face 61 side). The dog teeth 13 of the piece 11 are also similarly shaped. Therefore, there is some allowance in the space between the dog tooth 14 of the sleeve 12 and the dog teeth 13 of the piece 11, so the dog tooth 14 of the sleeve 12 is able to easily enter between the dog teeth 13 of the piece 11, and can thus he guided smoothly in. Then, the second tooth face 62 of the dog tooth 14 of the sleeve 12 meshes with the second tooth face 52 of the dog tooth 13 of the piece 11, such that the sleeve 12 engages with the piece 11.

[0074] FIG. 7 is a view showing the change in the positional relationship of the piece 11 and the sleeve 12 when the dog tooth 14 of the sleeve 12 does not enter the space between the dog teeth 13 of the piece 11, but instead the second connecting surface 65 of the dog tooth 14 of the sleeve 12 strikes the second connecting surface 55 of the dog teeth 13 of the piece 11, in three stages represented by reference characters 14-4, 14-5, and 14-6, in engagement control. The dog tooth 14 of the sleeve 12 that is in a position away from the piece 11 as shown by reference character 14-4 in FIG. 7 approaches the piece 11 while moving in a direction (toward the right in FIG. 7) in which the second tooth face 62 comes relatively closer to the piece 11, as shown by reference character 14-5 in FIG. 7, as a result of positive rotation of the piece 11 and thrust in the engaging direction of the sleeve 12. Then, the second connecting surface 65 of the dog tooth 14 of the sleeve 12 is unable to enter the space between the two dog teeth 13 of the piece 11, and instead strikes the second connecting surface 55 of the dog tooth 13 of the piece 11.

[0075] The sleeve 12 continues to generate thrust in the engaging direction even after striking the second connecting surface 55 of the piece 11. Also, the sleeve 12 receives pressure from the piece 11 via the second connecting surface 65 due to the positive rotation of the piece 11. When the pressure received from the piece 11 is greater than the thrust of the sleeve 12 and the friction force between the second connecting surfaces 55 and 65 that are contacting each other is less than the pressure, the dog tooth 14 of the sleeve 12 displays a so-called ratchet function in which it is pushed back in the disengaging direction along the second connecting surface 55 of the piece 11, as shown by reference character 14-6 in FIG. 7. If the second connecting surface 65 of the sleeve 12 passes by the second connecting surface 55 of the piece 11, the dog tooth 14 of the sleeve 12 skips the dog teeth 13 of the piece 11 that it was contacting and moves in the direction of the next dog teeth 13. Then the dog tooth 14 of the sleeve 12 starts to move in the engaging direction again by the thrust. In this way, even if the dog tooth 14 is unable to fit nicely between the dog teeth 13, the dog tooth 14 of the sleeve 12 returns in the disengaging direction by contact between the second connecting surfaces 55 and 65, and the engaging operation is able to be performed again so that the dog tooth 14 engages with the next dog teeth 13.

[0076] With the power transmitting apparatus 1 of this example embodiment, when engagement control of the engagement apparatus 10 is executed to perform MG1 lock as described above, the rotation speed of the first rotary electric machine MG1 temporarily changes to near 0 in the positive rotational direction. However, a situation is conceivable in which the MG1 lock function operates and engagement control ends up being executed due to a malfunction of the engagement apparatus 10 or the like while the hybrid vehicle 100 is traveling at a high speed and the rotation speed of the first rotary electric machine MG1 is large in the negative rotational direction, as shown by the alignment graph of the alternate long and short dash line in FIG. 3. FIG. 8 is a , view showing the change in the positional relationship of the sleeve 12 and the piece 11 in this kind of situation, in three stages represented by reference characters 14-7, 14-8, and 14-9.

[0077] In this case, as shown in FIG. 8, unlike normal engagement control described with reference to FIGS. 6 and 7, the piece 11 is rotating at a high speed in the negative rotational direction. Therefore, the dog tooth 14 of the sleeve 12 that is in a position away from the piece 11 as shown by reference character 14-7 in FIG. 8 approaches the piece 11 while moving in the direction in which the first tooth face 61 comes relatively closer to the piece 11 (toward the left in FIG. 8), as shown by reference character 14-8 in FIG. 8, as a result of the negative rotation of the piece 11 and the thrust of the sleeve 12 in the engagement direction. If the dog tooth 14 of the sleeve 12 is unable to enter the space between the two dog teeth 13 of the piece 11 at this time, the first connecting surface 64 of the dog tooth 14 of the sleeve 12 will strike the first connecting surface 54 of the dog teeth 13 of the piece 11.

[0078] At this time, the hybrid vehicle 100 is traveling at a high speed, the first rotary electric machine MG1 is rotating, at a high rotation speed in the negative rotational direction, and the rotational difference between the piece 11 that is connected to the first rotary electric machine MG1 and the sleeve 12 that is engaged with this piece 11 is large, so if the dog teeth 13 and 14 strike one another, the impact force received by the dog teeth 13 and 14 will be large. Also, if the tapered surface 64b of the first connecting surface 64 of the sleeve 12 that is arranged on the first tooth face 61 side and has a large chamfer angle strikes the tapered surface 54b of the piece 11, the impact force will not be able to escape easily in the axial direction, so excessive impact force may be input to the dog teeth 13 and 14.

[0079] In contrast, with this example embodiment, the tapered surfaces 54a and 64a that have a smaller chamfer angle than the tapered surfaces 54b and 64b do are provided between the tapered surfaces 54b and 64b and the end surfaces 53 and 63, so the end portions of the tapered surfaces 54b and 64b in the axial direction are able to move toward the dedendum side (i.e., in the direction in which the piece 11 and the sleeve 12 separate), thus creating extra space between the tapered surfaces 54b and 64b, which makes it possible to reduce the striking frequency of the tapered surfaces 54b and 64b. Also, when the rotation speed of the first rotary electric machine MG1 is high, the rotational difference between the piece 11 and the sleeve 12 is large, so the incident angle in the direction in which the sleeve 12 approaches the piece 11 during engagement control becomes shallow. In this example embodiment, the first connecting surfaces 54 and 64 are formed such that the chamfer angle becomes smaller closer to the end surfaces 53 and 63, so the tapered surfaces 54a and 64a that have a smaller chamfer angle than the tapered surfaces 54b and 64b do will tend to strike each other as the rotation speed of the piece 11 increases. In this way, the reaction force is able to escape more easily to the disengaging direction side in the axial direction by striking the tapered surfaces 54a and 64a that have a smaller chamfer angle than the tapered surfaces 54b and 64b do. As a result, even if engagement control is performed when the piece 11 is rotating at a high speed, it is possible to avoid excessive impact torque from being input to the dog teeth 13 and 14.

[0080] The sleeve 12 continues to generate thrust in the engaging direction even after striking the tapered surface 54b of the first connecting surface 54 of the piece 11. Also, the sleeve 12 receives pressure from the piece 11 via the tapered surface 64b by the negative rotation of the piece 11. If the pressure received from the piece 11 is greater than the thrust of the sleeve 12 and the friction force between the tapered surfaces 54b and 64b that are contacting each other is less than the pressure, the dog tooth 14 of the sleeve 12 displays a so-called ratchet function in which it is pushed back in the disengaging direction along the tapered surface 54b of the piece 11, as shown by reference character 14-9 in FIG. 8. As a result, the sleeve 12 and the piece 11 that are engaged are able to be suitably disengaged.

[0081] Next, the effects of the engagement apparatus 10 according to this example embodiment will be described.

[0082] In the engagement apparatus 10 of this example embodiment, the dog teeth 13 and 14 of the piece 11 and the sleeve 12 each have a first tooth face 51 and 61 and a second tooth face 52 and 62, one on each side in the circumferential direction, ' an end surface 53 and 63 provided in the axial direction, a first connecting surface 54 and 64 that connects the end surface 53 and 63 to the first tooth face 51 and 61, and a second connecting surface 55 and 65 that connects the end surface 53 and 63 to the second tooth face 52 and 62. The first connecting surface 54 and 64 is configured such that an angle between a normal of the first connecting surface 54 and 64 and a normal of the end surface 53 and 63 becomes smaller in a stepped or continuous manner as a normal direction of the first connecting surface 54 and 64 moves from a connecting portion of the first connecting surface 54 and 64 and the first tooth face 51 and 61 toward a connecting portion of the first connecting surface 56 and 66 and the end surface 53 and 63. (The first connecting surface 54 and 64 is configured such that an angle between the circumferential direction and the first connecting surface 54 and 64 becomes smaller in a stepped or continuous manner from a connecting portion of the first connecting surface 54 and 64 and the first tooth face 51 and 61 toward a connecting portion of the first connecting surface 54 and 64 and the end surface 53 and 63). More specifically, the first connecting surface 54 of the piece 11 has two tapered surfaces 54a and 54b with different chamfer angles. These tapered surfaces 54a and 54b are formed such that the chamfer angle becomes smaller closer toward the end surface 53. Similarly, the first connecting surface 64 of the sleeve 12 has two tapered surfaces 64a and 64b with different chamfer angles. These tapered surfaces 64a and 64b are formed such that the chamfer angle becomes smaller closer toward the end surface 63.

[0083] According to this structure, the tapered surfaces 54a and 64a with relatively small chamfer angles tend to strike each other more easily as the rotation speed of the first rotary electric machine MGl and the piece 11 in the negative rotation direction increases, the rotational difference between the piece 11 and the sleeve 12 increases, and the incident angle in the direction in which the piece 11 and the sleeve 12 approach each other becomes smaller. As a result, impact force at the time of impact between the piece 11 and the sleeve 12 is able to suitably escape in the disengaging direction, so impact torque received by the dog teeth 13 and 14 of the piece 11 and the sleeve 12 can be reduced, thereby enabling durability to be improved.

[0084] Also, the dog teeth 13 and 14 of the piece 11 and the sleeve 12 each have the first connecting surface 54 and the second connecting surface 55 on opposite sides in the circumferential direction, so even if the differential rotational direction is the positive rotational direction, impact between the second tooth faces 52 and 62 can be avoided by having the second connecting surfaces 55 and 65 strike each other, so the impact torque received by the dbg teeth 13 and 14 of the piece 11 and the sleeve 12 can be reduced.

[0085] Also, in the engagement apparatus 10, the second connecting surfaces 55 and 65 of the dog teeth 13 and 14 of the piece 11 and the sleeve 12 are tapered surfaces formed with a predetermined chamfer angle (an angle between the second connecting surfaces 55 and 65 and the circumferential direction around the axis of the first member is predetermined). The axial positions of the connecting portions 57 and 67 of the second connecting surfaces 55 and 65 and the second tooth faces 52 and 62 are positions that are farther away from the end surfaces 53 and 63 than the axial positions of the connecting portions 58 and 68 of the two tapered surfaces of the first connecting surfaces 54 and 64 are. That is, the chamfer width X3 of the second connecting surfaces 55 and 65 is greater than the chamfer width XI of the tapered surface 54a of the first connecting surface 54, and smaller than the chamfer width X2 of the tapered surface 54b. This structure makes it possible to shorten the width of the second tooth faces 52 and 62 in the axial direction, and thus inhibit improper engagement of the second tooth faces 52 and 62 during high speed rotation.

[0086] Also, impact surface pressure is able to be reduced, thereby enabling durability to be improved, by making the connecting portions 56, 57, 58, 59, and 60 between tooth faces of the piece 11, and the connecting portions 66, 67, 68, 69, and 70 between tooth faces of the sleeve 12 in the engagement apparatus 10 round shaped.

[0087] Hereinafter, example embodiments of the invention have been described, but the example embodiments are merely examples and are in no way intended to limit the scope of the invention. The example embodiments described above may also be carried out in various other modes. Various omissions, substitutions, and modifications are possible without departing from the scope of the invention. The example embodiments described above and modifications thereof are included in the scope of the invention and the scope equivalent to the invention described in the claims.

[0088] In the example embodiment described above, an example is given in which the engagement apparatus 10 according to the invention is applied as the first rotary electric machine MG1 lock mechanism that mechanically locks the rotation of the first rotary electric machine MG1. The engagement apparatus 10 according to the example embodiment may also be applied as an engagement element relating to another element within a drive system, such as overdrive lock, engine direct shaft speed change, and engine shaft disconnect, for example. The engine direct shaft speed change is a system that provides a transmission arranged between the ring gear 3c of planetary gear and the second rotary electric machine MG2. Also, the engagement apparatus 10 according to the invention may also be replaced by a related engagement element such as an AT internal wet type multiple disc clutch.

[0089] In the example embodiment described above, the dog teeth 13 of the piece 11 protrude radially outward, and the dog teeth 14 of the sleeve 12 protrude inward from the radial outside of the piece 11, but the positions of the dog teeth 13 and 14 of the piece 11 and the sleeve 12 may also be different. For example, the dog teeth 13 of the piece 11 and the dog teeth 14 of the sleeve 12 may both protrude toward each, other.

[0090] Also, in the example embodiment described above, the piece 11 rotates and the sleeve 12 moves linearly in one direction, but another mode may also be used as long as the relative positional relationship in the rotational direction and the stroke direction between the piece 11 and the sleeve 12 is able to change. For example, one of the piece 11 and the sleeve 12 may be configured so as to be able to move in both the rotational direction and the stroke direction, or the piece 11 may move in the stroke direction and the sleeve 12 may move in the rotational direction, opposite from the example embodiment.

[0091] Further, the first connecting surfaces 54 and 64 of the piece 11 and the sleeve 12 need only be formed such that the normal direction thereof be a direction between the circumferential direction and the axial direction, and change in a stepped or continuous manner from the circumferential direction side toward the axial direction side, from the connecting portions 56 and 66 of the first tooth faces 51 and 61 toward the connecting portions 59 and 69 of the end surfaces 53 and 63. In the example embodiment described above, the first connecting surface 54 of the piece 11 has two tapered surfaces 54a and 54b with different chamfer angles, and similarly, the first connecting surface 64 of the sleeve 12 has two tapered surfaces 64a and 64b, but they may also have a plurality of three or more tapered surfaces as long as the chamfer angle is the smallest on the end surface 53 and 63 side. Also, the first connecting surfaces 54 and 64 may have another shape such as that of a convex curve, for example, aside from having a plurality of tapered surfaces.

[0092] Moreover, in the example embodiment described above, the connecting portions 56, 57, 58, 59, and 60 between tooth faces of the piece 11, and the connecting portions 66, 67, 68, 69, and 70 between tooth faces of the sleeve 12 are all round shaped, but only a portion may be round shaped. For example, the connecting portions 57 and 67 of the second tooth faces 52 and 62 and the second connecting surfaces 55 and 65 have the highest impact frequency and thus need to be wear resistant, so only these connecting portions 56 and 67 may be round shaped. Also, the connecting portion 58 between the tapered surfaces 54a and 54b of the first connecting surface 54 of the piece 11, and the connecting portion 68 between the tapered surfaces 64a and 64b of the first connecting surface 64 of the sleeve 12 also have a relatively high impact frequency, so these connecting portions 58 and 68 may also be round shaped in addition to the connecting portions 57 and 67.

[0093] Also, in the example embodiment described above, the second connecting surfaces 55 and 65 of the piece 11 and the sleeve 12 are single tapered surfaces, but there may also be a plurality of tapered surfaces, similar to the first connecting surfaces 54 and 64. Also, the second connecting surfaces 55 and 65 may also have another shape such as that of a convex curve, for example, aside from the tapered surfaces.