FIELD OF THE INVENTION

[0001] The invention relates to a rotary expansible chamber device in which a working chamber part is provide with a movable means mounted on the working member having at least substantial engagement with another working chamber part to oppose the passage of working fluid therepast to constrain the working fluid to move in a prescribed path of flow, and more particularly to an assembly of a cam phaser and concentric rotary camshafts for operating at least one poppet-type intake or exhaust valve of an internal combustion engine of a motor vehicle.

BACKGROUND

[0002] Variable valve-timing mechanisms for internal combustion engines are generally known in the art. For example, see U.S. Patent No. 4,494,495; U.S. Patent No. 4,770,060; U.S. Patent No. 4,771,772; U.S. Patent No. 5,417,186; and U.S. Patent No. 6,257, 186. Internal combustion engines are generally known to include single overhead camshaft (SOHC) arrangements, dual overhead camshaft (DOHC) arrangements, and other multiple camshaft arrangements, each of which can be a two- valve or a multi-valve configuration. Camshaft arrangements are typically used to control intake valve and/or exhaust valve operation associated with combustion cylinder chambers of the internal combustion engine. In some configurations, a concentric camshaft is driven by a crankshaft through a timing belt, chain, or gear to provide synchronization between a piston connected to the crankshaft within a particular combustion cylinder chamber and the desired intake valve and/or exhaust valve operating characteristic with respect to that particular combustion cylinder chamber. To obtain optimum values for fuel consumption and exhaust emissions under different operating conditions of an internal combustion engine, the valve timing can be varied in dependence on different operating parameters.

[0003] A concentric camshaft includes an inner camshaft and an outer camshaft. The two camshafts can be phased relative to each other using a mechanical device, such as a cam phaser, to vary the valve timing. Cam phasers require precise tolerances and alignment to function properly. Misalignment between the inner camshaft and the outer camshaft of the concentric camshaft can create problems preventing proper function of the cam phaser. It would be desirable to provide an assembly capable of adapting to misalignment between inner and outer camshafts of a concentric camshaft and a cam phaser. It would be desirable to provide an assembly capable of accommodating tolerance stack up and thereby resolving binding issues that adversely affect concentric camshaft and phaser system assemblies.

SUMMARY

[0004] A concentric camshaft includes two shafts; an inner shaft and an outer shaft. The two shafts are phased relative to each other using a mechanical device such as a cam phaser. Cam phasers require precise tolerances and alignment to function properly. A problem can exist with respect to the alignment of the inner shaft to the outer shaft of the concentric camshaft. An axial seal on a cam face of the cam phaser can correct this problem when mounted between the phaser rotor and an axial wall portion of the phaser rotor housing. The axial rotor seal allows for the phaser to adjust for perpendicularity, and axial misalignment, while permitting a torsionally stiff coupling.

[0005] It would be desirable to eliminate the need for parts that are precision ground to tight tolerances to reduce perpendicularity issues. The axial rotor seal is intended to solve a tolerance stack-up binding problem that can exist when a cam phaser is attached to both parts of a concentric camshaft. To account for

misalignment of the shafts and perpendicularity tolerances of the phaser parts as the parts are mounted to the inner and outer shafts of the concentric cam, an axially compliant seal between the rotor and housing is required.

[0006] The rotor includes face seals added to the rotor face to reduce oil flow across the rotor face. Grooves in the rotor surface receive a seal to reduce the oil flow across the face. The seal in the groove of the rotor face is biased into contact with the end plate using a spring or biasing material, by way of example and not limitation, such as a compliant or elastomeric material which could be squeezed by the end plate. The seal can be formed of rigid or elastomeric material. Seals with low friction coefficient would be preferred. Seal materials for internal combustion engines must be able to withstand a hot engine oil environment. The rotor face seal configuration can be used in any fixed vane hydraulic actuator, or any cam phaser for an internal combustion engine. The use of a rotor face seal can reduce the cost of precision grinding parts down to precise tolerances.

[0007] The axial rotor seal can include a compliant surface formed between an axial wall portion of the phaser housing and a rotor of the phaser permitting torsionally rigid connection of the phaser to a concentric camshaft. The axial rotor seal allows for misalignment of the rotor with respect to the housing. If the misalignment of the rotor with respect to the housing was not corrected, the rotor could bind within the housing portion of the cam phaser assembly.

[0008] As the outer and inner end plates of the phaser housing are bolted together through the phaser housing side wall portion, the end plates can align to the rotor. The sprocket ring gear is affixed rigidly to the outer shaft of the camshaft assembly. The orientation of the inner to outer shaft, and subsequently the rotor, along with housing portion and end plates assembly, to the cam drive sprocket ring gear is provided by the cam lobes. Since the end plate of the assembly is held in close proximity to the rotor, an axial rotor seal can be used between the two components to provide for slight differences in parallelism between the two.

[0009] Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:

[0011] Figure 1 is a cross sectional view of a cam phaser assembly;

[0012] Figure 2 is a perspective view of an axial face seal for a rotor of a cam phaser assembly, where the rotor has separate vane tip seals;

[0013] Figure 3 is a perspective view of a combined axial face and vane tip seal with butt joint for a rotor of a cam phaser assembly;

[0014] Figure 4 is a cross sectional perspective view of a combined axial face and vane tip seal with overlapping joint; and [0015] Figure 5 is a schematic view of a prior known phaser assembly for floating a rotor and housing of a cam phaser with respect to one another.

DETAILED DESCRIPTION

[0016] A working member is defined herein as a movable member in a rotary expansible chamber device having a surface portion disposed to either receive the energy of a working fluid directed there against for moving the member to thereby produce a mechanical force output, or which, may move a working fluid by the application of a mechanical force to the movable member whereby fluid is admitted into and exhausted from the expansible chamber. A working chamber is defined as the space in an expansible chamber device which includes the working member and which is adapted to receive working fluid for acting upon the working member or for being acted upon by the working member, the chamber expanding and contracting incident to movement of the working member. The working member may include a movable vane thereon having a surface portion for either receiving energy from or energizing a working fluid passing through the expansible chamber. A working fluid is defined as the fluid (expansible or inexpansible) which is introduced into and withdrawn from the working chamber of the rotary expansible chamber device either to act upon or be acted upon by the working member. Fluid which is withdrawn from the working fluid supply for perfecting the operation of the device is considered to be working fluid even though it never enters the working chamber of the device. A fluid combined with working fluid introduced into and exhausted with the working fluid from the working chamber of the device used merely to perfect the operation of the device (i.e., cooling, sealing, lubricating, etc.), is considered to be a nonworking fluid. A cylinder is defined as an external member having wall or surface portions forming part of the working chamber of the rotary expansible chamber device, the member being either fixed or movable and may surround a fixed reaction member to move or be moved by the working fluid and may also include an abutment or reaction surface against which working fluid acts. However, the abutment or reaction surface for the rotary expansible chamber device need not necessarily be formed by the cylinder but may be formed by relatively movable opposed rotating members within the cylinder at least one of which is a working member. An abutment is defined as a partition member having relative movement with a cylinder or reaction member of which it is a part and moving incident to the expansion and contraction of the working chamber, the cylinder or reaction member not constituting the working member in this case. A partition member is defined as a member either fixed or movable on either the cylinder working member or other reaction member having a surface portion fomiing part of the working chamber to either (1) separate the working chamber into a plurality of working fluid compartments or (2) separate the inlet from the outlet of the rotary expansible chamber device. A vane is defined as a partition member that generally moves with the working member but also has movement relative to the working member incident to the expansion and contraction of the chamber. The vane may be on the cylinder if the cylinder is the working member.

[0017] Referring now briefly to Figure 5, a known cam phaser assembly configuration provides a concentric camshaft 112 defined by an inner shaft 112a and an outer shaft 112b. The rotor 136 is connected for rotation with the outer shaft 112b by a hollow outer threaded fastener 114. The inner shaft 112a is connected to the housing 122 by an inner threaded fastener 116 passing through the cover 126. A hollow shaft 124 supports the inner shaft bolt clamp load and has a slotted coupling joint 140 to the inner shaft 112a. The cover 126 is connected to the outer end plate 130, the housing side wall 132, and inner end plate 128 by fasteners to allow these components to rotate with the inner shaft 112a, while the rotor 136 rotates with the outer shaft 112b. The slotted coupled joint 140 allows the rotor 136 and housing 122 to float with respect to one another preventing the rotor 136 from binding with the inner or outer end plates 128, 130.

[0018] Referring now to Figure 1, a portion of a variable cam timing (VCT) assembly 10 is illustrated including a concentric camshaft 12 having an inner camshaft 12a and an outer camshaft 12b. Primary rotary motion can be transferred to the concentric camshaft 12, while secondary rotary motion, or phased relative rotary motion between inner camshaft 12a and outer camshaft 12b, can be provided by a rotary expansible chamber device, sometimes referred to herein as a mechanical or hydraulic actuator assembly or cam phaser 22. The mechanical hydraulic actuator assembly or cam phaser 22 can be operably associated with an inner camshaft 12a. A moveable working member, sometimes referred to herein as a rotor 36, can be pressed onto the inner camshaft 12a and secured with a pin 38. The rotor 36 can be enclosed within a cylinder, sometimes referred to herein as an external member or housing 26 defined by an outer end plate 30, a side wall portion 32, and an inner end plate 28 of the cam phaser 22. The housing 26 can include at least one partition member 26a. The inner end plate 28 can be defined by a flange 16 supporting a sprocket ring gear 52 connected to the outer camshaft 12b. The rotor 36 and housing 26 define a working chamber or at least one expansible chamber on each side of at least one vane 42 associated with the rotor 36. Cam phasers 22 require precise tolerances and alignment to function properly. Misalignment between the inner camshaft 12a and the outer camshaft 12b of the concentric camshaft 12 can create problems preventing proper function of the cam phaser 22. The partition member 26a defines at least a portion of the expansible chamber and can also function as an abutment surface to define a rotational end limit of movement for a corresponding vane 42 located within the working chamber.

[0019] Referring now to Figures 1 - 4, a rotor face seal 14 can be provided to compensate for misalignment between inner camshaft 12a and outer camshaft 12b of the concentric camshaft 12 and cam phaser 22. The rotor face seal 14 can be assembled within a groove 36b formed in a face 36a of the rotor 36. The rotor face seal 14 permits adjustment for perpendicularity and axial misalignment of the inner and outer camshafts 12a, 12b, while allowing a torsionally stiff coupling between a cam phaser 22 and one of the inner and outer camshafts 12a, 12b of the concentric camshaft 12. The rotor face seal 14 can include separate, or an integral, vane tip seal portions 40 and separate, or integral, partition member seals 44.

[0020] The rotor face seal 14 is meant as a means of allowing assembly of a concentric cam based camshaft phaser 22 while allowing misalignment of components as caused by manufacturing tolerances. In this case, the misalignment is meant to be taken up by the rotor face seal 14 located between the rotor 36 and the outer end plate 30 of the phaser 22, and between the rotor 36 and the inner end plate 28 as defined by the flange 16 supporting the cam drive sprocket ring gear 52. By locating rotor face seals 14 between the rotor and the inner and outer end plates 28, 30, the rotor face seal 14 can conform to the angular inclination of the rotor 36 with respect to the end plates 28, 30. As the inner and outer end plates 28, 30 are bolted together through the phaser housing side wall portion 32, the end plates 28, 30 can seal with respect to the rotor 36 to reduce or eliminate fluid flow across the face 36a of the 5 rotor 36. The sprocket ring gear 52 can be affixed rigidly to the outer shaft 12b of the camshaft assembly. The orientation of the inner to outer shaft 12a, 12b, and subsequently the rotor 36, along with side wall portion 32 and end plates 28, 30 assembly, to the cam driving sprocket ring gear 52 is provided by the cam lobes. Since the inner and outer end plates 28, 30 of the assembly are held in close proximity i o to the rotor 36, a rotor face seal 14 can be used between the components to provide a means of sealing against excessive fluid flow while also allowing for slight differences in parallelism between the components.

[0021] A variable cam timing assembly 10 for operating at least one poppet- type valve of an internal combustion engine of a motor vehicle can include a cam

15 phaser 22 having a housing 26 enclosing a rotor 36 with an axis of rotation connected to a concentric camshaft 12 including an inner rotary camshaft 12a and an outer rotary camshaft 12b. A rotor face seal 14 can be located between the inner and outer end plates 28, 30 of the cam phaser 22 and the rotor 36 for sealing against excessive fluid flow therebetween. The rotor face seal 14 can permit adjustment for perpendicularity

20 and axial misalignment of the inner and outer camshafts 12a, 12b with respect to one another and/or with respect to the inner and outer end plates 28, 30 of the cam phaser 22, while allowing a torsionally stiff coupling between the cam phaser 22 and the concentric camshaft 12. The rotor face seal 14 can be formed from one of separate face seals 14a, 14b and separate vane tip seals 40 and partition member seals 42

25 (Figure 2), separate face seals 14a, 14b having abutting ends 14c 14d defining integral vane tip seal portions 40a, 40b (Figure 3), and separate face seals 14a, 14b having overlapping ends 14e, 14f defining integral vane tip seal portions 40a, 40b (Figure 4).

[0022] Referring now to Figure 2, the rotor face seal 14 can be formed from longitudinally separated, inner and outer face seals 14a, 14b, and at least one separate

30 seal, such as a separate vane tip seal 40, and/or a separate partition member seal 44.

Each face seal 14a, 14b can include a radially inner ring 14g, and radially outwardly located outer ends 18, where some of the radially outwardly located outer ends 18a are located adjacent vanes 42 and other of the radially outwardly located outer ends 18b are located adjacent partition members 26a. The radially outwardly located outer ends 18a are in abutting relationship with separate vane tip seals 40, while the radially outwardly located outer ends 18b are in abutting relationship with separate partition member seals 44. The combination of rotor face seals 14, separate vane tip seals 40, and separate partition member seals 44 constrain the working fluid to move in a prescribed path of flow and accounts for misalignment of the concentric camshafts 12a, 12b and perpendicularity tolerances of the phaser parts as the parts are mounted to the inner and outer camshafts 12a, 12b of the concentric camshaft 12, while permitting a torsionally stiff coupling to be used between the cam phaser 22 and the inner and outer camshafts 12a, 12b of the concentric camshaft 12.

[0023] Referring now to Figure 3, the rotor face seal 14 can be formed from longitudinally separated, inner and outer face seals 14a, 14b having abutting ends 14c, 14d defining integral vane tip seal portions 40a, 40b and integral partition member seal portions 44a, 44b. Each face seal 14a, 14b can include a radially inner ring 14g and radially outwardly located longitudinally inwardly extending outer ends 18, where some longitudinally inwardly extending outer ends 18c are located adjacent vanes 42 and other longitudinally inwardly extending outer ends 18d are located adjacent partition members 26a. The longitudinally inwardly extending outer ends 18c of each separate face seal 14a, 14b are in abutting relationship with one another to define integral vane tip seal portions 40a, 40b, while longitudinally inwardly extending outer ends 18d of each separate face seal 14a, 14b are in abutting relationship with one another to define integral partition member seal portions 44a, 44b. The combination of rotor face seals 14a, 14b, integral vane tip seal portions 40a, 40b, and integral partition member seal portions 44a, 44b constrain the working fluid to move in a prescribed path of flow and account for misalignment of the concentric camshafts 12a, 12b and perpendicularity tolerances of the phaser parts as the parts are mounted to the inner and outer camshafts 12a, 12b of the concentric camshaft 12, while permitting a torsionally stiff coupling to be used between the cam phaser 22 and the inner and outer camshafts 12a, 12b of the concentric camshaft 12. [0024] Referring now to Figure 4, the rotor face seal 14 can be formed from longitudinally separated, inner and outer face seals 14a, 14b having overlapping ends 14e, 14f defining integral vane seal tip portions 40a, 40b and defining integral partition member seal portions 44a, 44b . Each face seal 14a, 14b can include a radially inner ring 14g, and radially outwardly located, longitudinally inwardly extending outer ends 18, where some longitudinally inwardly extending outer ends 18e are located adjacent vanes 42 and other longitudinally inwardly extending outer ends 18f are located adjacent partition members 26a. The longitudinally inwardly extending outer ends 18e of each separate face seal 14a ,14b are in overlapping relationship with one another to define integral vane tip seal portions 40a, 40b, while longitudinally inwardly extending outer ends 18f of each separate face seal 14a, 14b are in overlapping relationship with one another to define integral partition member seal portions 44a, 44b. The overlapping relationship can be identical for outer ends 18e, 18f and can be defined by at least one complementary interface 46 including at least one radially extending surface 46a and at least one longitudinally extending surface 46b, wherein the at least one complementary interface 46 includes first and second radially extending surfaces 46a, 46c spaced longitudinally from one another, and a longitudinally extending surface 46b interposed between the first and second radially extending surfaces 46a, 46a, wherein a length of the longitudinally extending surface 46b is greater than a length of the first radially extending surface 46a and is greater than a length of the second radially extending surface 46c. The combination of rotor face seals 14a, 14b, integral vane tip seal portions 40a, 40b, and integral partition member seal portions 44a, 44b constrain the working fluid to move in a prescribed path of flow and account for misalignment of the concentric camshafts 12a, 12b and perpendicularity tolerances of the phaser parts as the parts are mounted to the inner and outer camshafts 12a, 12b of the concentric camshaft 12, while permitting a torsionally stiff coupling to be used between the cam phaser 22 and the inner and outer camshafts 12a, 12b of the concentric camshaft 12.

[0025] It should be recognized that the rotor face seals 14 can be formed with any combination of outer ends selected from a group including radially outwardly located, longitudinally inwardly extending abutting outer ends 18c, 18d and/or radially outwardly located, longitudinally inwardly extending overlapping outer ends 18e, 18f to define at least one integral seal portion 40a, 40b, 44a, 44b, such as at least one integral vane tip seal 40 defined by portions 40a, 40b and/or to define at least one integral partition member seal 44 defined by portions 44a, 44b, and in any

combination of outer ends 18, 18a, 18b, 18c, 18d, 18e, 18f desired. It should also be recognized that the rotor face seals 14 can be formed with any combination of outer ends 18 suitable for engagement with separate vane tip seals 40 and/or partition member seals 44, and/or with at least one radially outwardly located, longitudinally inwardly extending outer end 18c, 18d, 18e, 18f of each inner and outer face seal 14a, 14b suitable for engagement with each other in either abutting or overlapping relationship to define at least one integral vane tip seals 40 and/or at least one integral partition member seals 44, and in any combination of outer ends 18 desired.

[0026] A method of assembling a variable cam timing assembly 10 for an internal combustion engine of a motor vehicle having a cam phaser 22 to be connected between an inner camshaft 12a and an outer camshaft 12b of a concentric camshaft 12 can include connecting a rotor face seal 14 between the rotor 36 of the cam phaser 22 and the inner and outer end plates 28, 30 of the housing 26 for constraining the working fluid to move in a prescribed path of flow. The rotor face seal 14 accounts for misalignment of the concentric camshafts 12a, 12b and perpendicularity tolerances of the phaser parts as the parts are mounted to the inner and outer camshafts 12a, 12b of the concentric camshaft 12, while permitting a torsionally stiff coupling to be used between the cam phaser 22 and the inner and outer camshafts 12a, 12b of the concentric camshaft 12. The rotor face seal 14 can permit adjustment for

perpendicularity and axial misalignment of the inner and outer camshafts 12a, 12b with respect to one another and/or with respect to the cam phaser 22, while permitting use of a torsionally stiff coupling between the cam phaser 22 and the inner and outer camshafts 12a, 12b of the concentric camshaft 12. The method can also include assembling a rotor face seal 14 having outer ends selected from a group including radially extending outer ends 18 a, 18b suitable for abutting engagement with separate vane tip seals 40 and/or partition member seals 44, and/or radially outward, longitudinally inwardly extending outer abutting ends 18c, 18d and/or overlapping ends 18e, 18f to define integral vane tip seal portions 40a, 40b and/or to define integral partition member seal portions 44a, 44b, in any combination desired.

[0027] In operation, the rotor face seal 14 is located between rotor 36 and the inner and outer end plates 28, 30 of the phaser 22. The rotor face seal 14

accommodates misalignment of the inner and outer camshafts 12a, 12b with respect to one another and/or with respect to a joint with the rotor 36 or housing 26 of the cam phaser 22, which if uncorrected could cause the rotor 36 to bind within the housing 26 of the cam phaser 22. The rotor face seal 14 adjusts for perpendicularity and axial misalignment between the inner and outer camshafts 12a, 12b and the phaser 22 assembly, while permitting the use of a torsionally stiff coupling between the inner and outer camshafts 12a, 12b and the rotor 36 or housing 26 of the phaser 22. The rotor face seal 14 permits limited perpendicularity and axial realignment of the rotor 36 or housing 26 of the phaser 22 with respect to one of the inner and outer camshafts 12a, 12b. The inner camshaft 12a remains free to rotate relative to the outer camshaft 12b in response to actuation of phaser 22, as both inner and outer camshafts 12a, 12b of the concentric camshaft 12 are driven in rotation.

[0028] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent

arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.