ROTOR HUB

[0001] The present disclosure relates generally to electric motor rotors and more specifically to electric motor rotors in hybrid modules.

BACKGROUND

[0002] Hybrid motor vehicle drive trains include a hybrid module having an electric motor rotor carrier hub that is typically a forged material with higher ductility allowing the staking process to work. Other methods of clamping the rotor are use of threads and a nut such as in Ford’s HF35 transmission. Aisin uses another method where they deform the hub up around the rotor end ring.

[0003] U.S. Pub. No. 2016/0105060A1 shows a method of staking the hub to retain the end ring.

SUMMARY OF THE INVENTION

[0004] An electric motor includes a rotor, a stator for rotationally driving the rotor and a rotor carrier hub for supporting the rotor on an outer circumferential surface thereof. The rotor carrier hub includes a groove on the outer circumferential surface. The electric motor also includes a clamping ring configured for holding the rotor axially in place on the rotor carrier hub. The clamping ring being fixed on the outer circumferential surface of the rotor carrier hub by at least one inner radial protrusion of the clamping ring extending into contact with the rotor carrier hub in the groove.

[0005] Embodiments of the electric motor may include one or more of the following features:

the clamping ring includes at least one staked indentation formed in an axially facing radially extending surface thereof; a non-ferrous plate axially between the clamping ring and the rotor, the clamping ring axially pressing the non-ferrous plate against the rotor to hold the rotor axially in place;

the rotor carrier hub includes an axially extending section and a radially extending section extending radially outward from the axially extending section, the rotor being sandwiched between the clamping ring and the radially extending section;

the rotor is non-rotatably connected to the outer circumferential surface of the rotor carrier hub by a plurality of splines, the splines including a first section having a first outer diameter for supporting the rotor and a second section having a second outer diameter for supporting the clamping ring, the first outer diameter being greater than the second outer diameter;

the groove is formed in sections of each of the splines;

the clamping ring is a non-ferrous metal; or

the non-ferrous metal is bronze or a high strength low alloy.

[0006] A hybrid module configured for arrangement in the torque path upstream from a transmission and downstream from an internal combustion engine is also provided. The hybrid module includes a hybrid drive unit including an input shaft configured for connecting to the internal combustion engine, the electric motor and a clutch. The hybrid module also includes a torque converter fixed to the electric motor. The clutch is configured for selectively connecting torque converter to the input shaft or disconnecting the torque converter from the input shaft.

[0007] A method of forming an electric motor is also provided. The method includes providing a clamping ring onto a rotor carrier hub such that the clamping ring covers a groove formed in an outer circumferential surface of the rotor carrier hub; and staking the clamping ring such that material of the clamping ring protrudes into the groove so as to axially fix the clamping ring in place on the rotor carrier hub.

[0008] Embodiments of the method may include one or more of the following features: forming the groove into splines formed the outer circumferential surface of the rotor carrier hub; non-rotatably fixing a rotor onto the outer circumferential surface of the rotor carrier hub, the clamping ring fixing the rotor axially in place on the rotor carrier hub; the material protrudes radially into the groove upon axially staking of an axially facing radially extending surface of the clamping ring;

the staking includes contacting the axially facing radially extending surface of the clamping ring with an inclined surface of a staking tool;

the clamping ring is a non-ferrous metal;

the non-ferrous metal is bronze or a high strength low alloy;

heating the clamping ring before placing the clamping ring onto the rotor carrier hub, the clamping ring fixing rotor axially in place on the rotor carrier hub after the cooling of the clamping ring.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention is described below by reference to the following drawings, in which:

[0010] Fig. 1 shows a hybrid module in accordance with an embodiment of the present invention;

[0011] Figs. 2a to 2c illustrate the fixing of a rotor clamping ring of the hybrid module onto a rotor carrier hub in accordance with an embodiment of the present invention;

[0012] Fig. 3a to 3c illustrate enlarged views of the views shown in Figs. 2a to 2c, respectively; and

[0013] Fig. 4 shows an exploded view illustrating a rotor, a clamping ring, plates, a hub and a front cover of the hybrid module of Fig. 1.

DETAILED DESCRIPTION

[0014] The present disclosure provides a method of fixing a rotor clamp ring to a rotor carrier hub. The present disclosure involves plastically deforming the rotor clamp ring into a machined groove in the cast rotor carrier hub. In some embodiments, the rotor clamp ring is heated before installation, causing it to expand, the rotor clamp ring shrinks after installation. In other embodiments, the rotor clamp ring is not heated for installation. In preferred embodimments, the rotor clamp ring is made of a material with sufficient ductility such that it can be staked axially to be deformed radially inwardly and with sufficient strength that it can be staked with sufficient force - i.e., to deform the material elastically a sufficient amount - to clamp the rotor and form a spring element that continues maintain a residual clamp load on the rotor after the staking. In preferred embodiments, the clamp ring is formed of a non-ferrous metal, which may be bronze or HSLA (high strength low alloy) steel. In one preferred embodimment, the rotor clamp ring is made of 060XLF, which has higher strength than for example a AISI 1020 steel. AISI 1020 steel would not allow such a residual clamping load as it would plastically axially deform under the same geometry constaints and would not be able to clamp the rotor axially in place with a preload.

[0015] Fig. 1 shows hybrid module 10 in accordance with an embodiment of the present invention. Module 10 includes a hybrid drive unit 12 configured for attachment to an internal combustion engine and a torque converter 14 configured for attachment to a transmission input shaft. In a known manner, hybrid drive unit 12 is selectively operable to transmit torque from the internal combustion engine to torque converter 14 or directly drive torque converter 14 via an electric motor 16 of drive unit 12. Along these lines, hybrid drive unit 12 includes an engine connect/disconnect clutch 18 for selectively connecting torque converter 14 to an input shaft 20, which is configured for non-rotatably connecting for example via a flywheel to a crankshaft of the internal combustion engine, or disconnecting torque converter 14 from input shaft 20 such that torque converter can be driven solely by electric motor 16.

[0016] Electric motor 16 includes a stator 22 and a rotor 24, with stator 22 being fixed to a housing 26 of hybrid drive unit 12. Upon current being provided to coils of stator 22, rotor 24 is rotated about a center axis CA of hybrid module 10 in a known manner, due to rotor 24 including a plurality of permanent magnet segments 24a that are energized by the current in the coils. The terms axially, radially and circumferentially as used herein are used with respect to center axis CA. Magnet segments 24a are supported at their inner circumferences by a rotor carrier hub 28. Rotor carrier hub 28 includes a cylindrical axially extending section 28a supporting the inner circumferences of magnet segments 24a and a radially extending section 28b protruding radially outward from an end of axially extending section 28a. Torque converter 14 is fixed to hybrid drive unit 12 at radially extending section 28b of rotor carrier hub 28 by a plurality of fasteners 29 passing through a cover 31 of torque converter 14.

[0017] Clutch 18 includes a plurality of clutch plates 30, at least some of which are supported in an axially slidable manner at outer diameter ends thereof by splines 32 formed on an inner circumferential surface of axially extending section 28a. At least one of clutch plates 30 are supported in an axially slidable manner at inner diameter ends thereof by an inner support 34 that is fixed to a counter pressure plate 36, which is nonrotatably fixed to shaft 20. Clutch 18 further includes a piston 38 that is axially slidable along an outer circumference of shaft 20 to engage and disengage clutch 18 based on fluid pressure differences on front and rear sides of piston 38. When piston 38 forces clutch plates 30 against counter pressure plate 36, clutch 18 is engaged and torque from shaft 20 is transmitted through clutch plates 30 into rotor carrier hub 28, which then transmits the received torque to damper assembly 14. Piston 38 is held axially away from clutch plates 30 by a spring 40 supported by a support plate 42. Piston 38 is also resiliently connected to a liftoff control plate 43 that limits the liftoff of piston 38 with respect to clutch plates 30.

[0018] Housing 26 includes an axially extending protrusion 44 provided on an engine side of clutch 18 radially outside of shaft 20. Protrusion 44 supports a ball bearing 46, which rotatably supports a rotor flange 48 on protrusion 44. An inner race of ball bearing 46 sits on an outer circumferential surface of protrusion 44 and rotor flange 48 extends from an outer circumferential surface of the outer race of ball bearing 46 to axially extending section 28a of rotor carrier hub 28.

[0019] Torque converter 14 includes a front cover 3 la and a rear cover 3 lb together forming cover 31, with fasteners 29 passing axially through a radially extending section of front cover 3 la, which extends radially inward to intersect center axis CA. Rear cover 3 lb includes forms an impeller shell 50 of an impeller 52 that includes a plurality of impeller blades 54, which are supported by a rounded blade supporting portion 50a of impeller shell 50, which is shaped as an annular bowl and contacts rear edges of impeller blades 54.

[0020] Torque converter 14 also includes a turbine 56 configured to define a piston that is axially moveable toward and away from impeller shell 50 such that an engagement section of turbine 56 engages an engagement section of impeller shell 50 so as to form a lockup clutch. Turbine 56 includes a turbine shell 58 supporting a plurality of turbine blades 60. Torque converter 14 also includes a stator 62 axially between turbine 56 and impeller 52 to redirect fluid flowing from the turbine blades 60 before the fluid reaches impeller blades 54 to increase the efficiency of torque converter 14. Torque converter 14 further includes a damper assembly 64 fixed to turbine shell 58. Damper assembly 64 is configured for receiving torque from turbine shell 58 and transferring torque to the transmission input shaft. For transferring torque to the transmission input shaft, damper assembly 64 includes a support hub 66, which includes a splined inner circumferential surface for non-rotatably connecting to an outer circumferential surface of the

transmission input shaft.

[0021] A friction material 68 is bonded onto a radially extending impeller facing surface of an outer radial extension 70 of turbine shell 58, which is radially outside of blades 60 and forms the engagement section of turbine 56, for engaging a radially extending wall 72 of impeller shell 50, which is radially outside of blades 54 and forms the engagement section of impeller shell 50. In other embodiments, instead of or in addition to being bonded to outer radial extension 70, friction material 68 may be bonded to radially extending turbine facing surface of radially extending wall 72 or to one or more additional discs between radially extension 70 and wall 72. Regardless of whether friction material 68 is bonded to outer radial extension 70, radially extending wall 72 or one or more additional discs, friction material 68 is provided axially between extension 70 and wall 72 to selectively rotationally engage the engagement section of turbine piston 56 with the engagement section of impeller shell 50. Torque converter 14 receives torque input from hybrid drive unit 12 through fasteners 29 at front cover 3 la, which is transmitted to impeller 52. Impeller 52 drives turbine 56 via fluid flow from impeller blades 54 to turbine blades 60, when the lockup clutch is disengaged, or via friction material 68, when the lockup clutch is engaged. Turbine 56 then drives damper assembly 64, which in turn drives the transmission input shaft.

[0022] Referring back to electric motor 16, it further includes a rotor clamping ring 74 fixed to axially extending section 28a for axially retaining rotor 24 on rotor carrier hub 28. Rotor clamping ring 74 is provided at a first axial end 28c of rotor carrier hub 28 that is opposite to a second axial 28d of rotor carrier hub 28 at which radially extending section 28b is provided, such that magnets 24a are clamped axially between section 28b and ring 74. A first non-ferrous plate 75a is provided axially between rotor 24 and ring 74 and a second non-ferrous plate 75b is provided axially between rotor 24 and section 28b. Plates 75a, 75b may be formed of aluminum and contact the rotor magnets to block eddy currents, which are essentially short circuits of the magnetic flux field and lead to low e-motor efficiency. As noted above, rotor clamping ring 74 is formed of a HSLA material such as 060XLF. Fig. 4 shows an exploded view illustrating rotor 24, clamping ring 74, plates 75a, 75b, hub 28 and front cover 3 la.

[0023] Figs. 2a to 2c illustrate the fixing of rotor clamping ring 74 onto rotor carrier hub 28 in accordance with an embodiment of the present invention, while Fig. 3a to 3c illustrate enlarged view of the view shown in Figs. 2a to 2c, respectively. Rotor clamping ring 74 is first heated to a predetermined temperature of for example at least 325°C. The ring 74 is heated such that an inner diameter IDR of ring 74 expands enough to slip onto hub 28. Next, as shown in Figs. 2a, 3a, clamping ring 74 is slid axially via an axial force Fl onto axially extending section 28a of rotor carrier hub 28 at axial end 28c to axially press against non-ferrous plate 75a positioned axially between rotor 24 and clamping ring 74. Section 28a of rotor carrier hub 28 is provided with a plurality of circumferentially spaced axially extending splines 76 at the outer circumferential surface thereof. Splines 76 each include a first section 76a having a first outer diameter OD1 and a second section 76b having a second outer diameter OD2, with outer diameter OD1 being greater than outer diameter OD2. Both sections 76a, 76b of splines 76 have an inner diameter IDS. Rotor 24 is non-rotatably fixed in place on rotor carrier hub 28 via first sections 76a of splines 76. Clamping ring 74, which upon heating has an inner diameter IDR that is smaller than outer diameter OD2, is slid on rotor carrier hub 28 onto sections 76b of splines 76. As shown in Fig. 3a, axially extending section 28a of hub 28 is provided with a circumferentially extending groove 78 on the outer circumferential surface thereof. More specifically, each of splines 76 is provided with a section of groove 78 at spline section 76b. Each section of groove 78 extends radially inward from outer diameter OD2 in to the respective spline 76 at section 76b. Clamping ring 74 is provided in axial alignment with groove 78 directly radially outside or groove 78 such that the sections of groove 78 are covered by the inner circumferential surface 74a of clamping ring 74. Clamping ring 74 includes an annular protrusion 77 at a front side thereof, an arc portion of which is machined after clamping ring 74 is installed for proper balancing.

[0024] Next, as shown in Figs. 2b, 3b, while the rotor clamping ring 74 is being held on axially extending section 28a and against plate 75a via force Fl over groove 78, an axially facing radially extending surface 74b of clamping ring 74 is staked with an axial force F2 via a staking tool 80, with force F2 being applied in the same direction as force Fl, to form at least one indentation 74d in surface 74b. The staking of clamping ring 74 displaces material 74c of clamping ring 74 radially inward into groove 78. Material 74c protrudes radially inward from inner circumferential surface 74a of clamping ring 74 to contact axially extending section 28a in groove 78 and generate a form-fitting connecting between ring 74 and rotor carrier hub 28 that holds ring 74 axially place on axially extending section 28a. In the embodiment shown in Figs. 2a to 2c and 3a to 3c, staking tool 80 includes an inclined contact surface 80a for contacting surface 74b of ring 74. Surface 80a is configured such that when tool 80 is moved axially parallel to center axis CA (Fig. 1), surface 80a forms a non-perpendicular angle with respect to center axis CA and provides a radially inward force component on ring 74 to help generate the movement of material 74c radially inward into groove 78. In one preferred embodiment, staking tool 80 includes a plurality of circumferentially spaced surfaces 80a for generating a plurality of circumferentially spaced indentations 74d and the same number of material protrusions 74c as indentations 74d.

[0025] As shown in Figs. 2c, 3c, after indentations 74d and material protrusions 74c are formed and ring 74 sufficiently cools, ring 74 is held by force Fl until ring 74 cools. In some preferred embodiments, ring 74 is held by force Fl until ring 74 is at ambient temperature or approximately 20°C. Staking force F2 can be removed prior to force Fl . Ring 74 is held axially in place on rotor carrier hub 28 by protrusions 74c being fixed in groove 78 after staking tool 80 is moved back axially away from ring 74 and ring 74 is no longer held by force Fl against plate 75a. In other words, after ring 74 cools, protrusions 74c permanently fixes ring 74 axially in place on axially extending section 28a of hub 28 by the interlocking fit of protrusions 74c in groove 78 such that ring 74 elastically presses rotor 24 against carrier hub section 28b. Ring 74 axially forces plate 75a against rotor 24 to clamp rotor 24 in place on hub 28. Figs. 3c illustrates that inclined surface 80a of staking tool 80 creates indentation 74d such that indentation 74d includes a radially extending surface 74e that is axially tapered such that surface 74e forms a non perpendicular angle with respect to center axis CA (Fig. 1).

[0026] In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.

[0027] List of Reference Numerals

CA center axis

Fl first axial force

F2 second axial force

OD1 first outer diameter

OD2 second outer diameter

IDR ring inner diameter

IDS spline inner diameter

10 hybrid module

12 hybrid drive unit

14 torque converter

16 electric motor engine connect/disconnect clutch input shaft

stator

a outer circumferential surface

rotor

a magnet segments

housing

8 rotor carrier hub

8a cylindrical axially extending section8b radially extending section

8c first axial end

8d second axial end

9 fasteners

0 clutch plates

1 cover

la front cover

lb rear cover

2 splines

4 inner support

6 counter pressure plate

8 piston

0 spring

2 support plate

3 liftoff control plate

4 housing protrusion

6 ball bearing

8 rotor flange

0 impeller shell

0a rounded blade supporting portion2 impeller

4 impeller blades turbine

turbine shell

turbine blades

stator

damper assembly

support hub

friction material

outer radial extension

radially extending wall

rotor clamping ring

a inner circumferential surfaceb axially facing radially extending surfacec radially inner material protrusiond indentation

e inclined indentation surface

a non-ferrous plate

b non-ferrous plate

axially extending splines

a first spline section

b second spline section

protrusion

circumferentially extending groove staking tool

a inclined staking tool surface