Shaft assembly method

Abstract

This invention provides a technique to prevent the disc spring from shifting from its design-determined position when the shaft is rotatably assembled to the case. [Solution] The assembly method comprises an inner ring press-fitting step in which the shaft is press-fitted into the inner ring of the bearing so that the bearing is spaced a predetermined distance from one end of the shaft; a disc spring placement step in which, after the inner ring press-fitting step, a ring-shaped disc spring is inserted from one end of the shaft and the disc spring is positioned adjacent to the bearing; and an outer ring press-fitting step in which, after the disc spring placement step, the case is brought closer to the bearing from the disc spring side and the outer ring of the bearing is press-fitted into the inner circumferential surface of the bearing holding portion provided on the case. The disc spring placement step and the outer ring press-fitting step are performed with the shaft supported along the vertical direction, with one end of the shaft pointing upward, and the predetermined distance from one end of the shaft to the inner ring is greater than the free height of the disc spring.

Description

Technical Field

[0001] The technology disclosed in this specification relates to an assembly method for rotatably assembling a shaft to a case.

Background Art

[0002] Patent Document 1 describes a shaft rotatably assembled to a case. The shaft is fixed to the inner ring of a bearing. The outer ring of the bearing is fixed to a bearing holder provided in the case. A disc spring is disposed between the bottom surface of the bearing and the bearing holder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] This specification provides a technique for avoiding the displacement of a disc spring from its correct design position when rotatably assembling a shaft to a case.

Means for Solving the Problems

[0005] This specification discloses an assembly method for rotatably assembling a shaft to a case. The assembly method comprises: an inner ring press-fitting step of press-fitting the shaft into the inner ring of the bearing such that the bearing is spaced a predetermined distance from one end of the shaft; a disc spring placement step, after the inner ring press-fitting step, of inserting a ring-shaped disc spring from the one end of the shaft to position the disc spring adjacent to the bearing; and an outer ring press-fitting step, after the disc spring placement step, of bringing the case closer to the bearing from the disc spring side and press-fitting the outer ring of the bearing onto the inner circumferential surface of the bearing retaining portion provided in the case. The disc spring placement step and the outer ring press-fitting step are performed with the shaft supported in the vertical direction, with the one end of the shaft pointing upward, and the predetermined distance from the one end of the shaft to the inner ring is greater than the free height of the disc spring.

[0006] In the assembly method described above, the disc spring placement process and the outer ring press-fitting process are performed with the shaft supported along the vertical direction. Here, a bearing is pre-assembled to the shaft, and the upper end of the shaft protrudes from the bearing. The amount by which the upper end of the shaft protrudes (i.e., the predetermined distance described above) is greater than the free height of the disc spring. This prevents the disc spring from falling off the shaft or from becoming misaligned with the shaft before the outer ring press-fitting process is completed. The shaft can be easily assembled to the case while the disc spring is regulated to the correct position according to the design. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram provides a schematic overview of the vehicle's configuration. [Figure 2] This is a diagram showing the skeleton of the drive system installed in the vehicle. [Figure 3] This is a cross-sectional view of the output shaft and the main parts around the bearing. [Figure 4] This diagram shows an assembly method for rotatably mounting the output shaft to the case. [Figure 5] This diagram shows an assembly method for rotatably mounting the output shaft to the case. [Modes for carrying out the invention]

[0008] The following describes the drive system mounted on the vehicle, referring to the drawings. Here, the directions in some of the drawings correspond to the vehicle's direction. Direction FR indicates the front in the vehicle's longitudinal direction, and direction RR indicates the rear in the vehicle's longitudinal direction. Direction LH indicates the left in the vehicle's lateral direction, and direction RH indicates the right in the vehicle's lateral direction. Direction UP indicates the upward in the vehicle's vertical direction, and direction DW indicates the downward in the vehicle's vertical direction.

[0009] Figure 1 shows the configuration of Vehicle 1. Vehicle 1 is a vehicle that has at least a rotating electric machine as one of its drive sources, and may be, for example, an electric vehicle, a hybrid vehicle, or a fuel cell vehicle.

[0010] Vehicle 1 comprises a battery pack 2 mounted beneath the floor and a pair of drive units 3. The battery pack 2 supplies power to each of the pair of drive units 3. One of the pair of drive units 3 uses the supplied power to drive the front wheels FW, and the other of the pair of drive units 3 uses the supplied power to drive the rear wheels RW. Although vehicle 1 is exemplified as a four-wheel drive vehicle, it may also be a two-wheel drive vehicle equipped with only one of the pair of drive units 3. The pair of drive units 3 have a common structure. Hereafter, the pair of drive units 3 will be described without distinction.

[0011] The drive unit 3 comprises a rotating electric machine 4, a transmission device 5, a power control unit 6, and a case 7. The rotating electric machine 4, the transmission device 5, and the power control unit 6 are housed within the case 7. The power control unit 6 is positioned adjacent to the rotating electric machine 4 and the transmission device 5 in the longitudinal direction of the vehicle (rear in this example). The power control unit 6 converts the power supplied from the battery pack 2 from direct current to alternating current and supplies it to the rotating electric machine 4. The rotating electric machine 4 generates driving force based on the alternating current power supplied from the power control unit 6. The transmission device 5 amplifies the driving force generated by the rotating electric machine 4 into torque and then distributes it to the left and right wheels.

[0012] The rotating electric machine 4 and the transmission device 5 are arranged coaxially. As a result, the vertical size of the case 7 housing the rotating electric machine 4 and the transmission device 5 is reduced. Consequently, the case 7 is positioned so that, when viewed from the left or right direction of the vehicle, it fits within the range of the corresponding wheels FW and RW. As a result, for example, at the front of the vehicle 1, the degree of freedom in arranging various mechanical components, such as the radiator and the air conditioning control system, is improved, and a larger user space can be secured. Furthermore, at the rear of the vehicle 1, for example, a larger trunk space can be secured, or the range of the rear seat reclining angle can be widened.

[0013] Figure 2 shows a skeleton diagram of the drive unit 3, including the rotating electric machine 4 and the transmission device 5 housed in the case 7. In this example, the rotating electric machine 4 is located on the right side of the case 7, and the transmission device 5 is located on the left side of the case 7. Alternatively, the transmission device 5 may be located on the right side of the case 7, and the rotating electric machine 4 on the left side of the case 7. In the following explanation, for convenience, the names of the components may include left-right directions, but such designations do not limit the position of the components.

[0014] The rotating electric machine 4 comprises a stator core 12, a rotor 14, and an output shaft 16. The stator core 12 is fixed to the case 7. The rotor 14 is supported by the case 7 so as to be rotatable around the rotation axis of the rotating electric machine 4. The output shaft 16 is connected to the rotor 14 and rotates together with the rotor 14. The output shaft 16 is hollow and has a through hole 18 that extends along the rotation axis of the rotating electric machine 10.

[0015] The transmission device 5 comprises a planetary gear section 20 and a differential gear 30. The planetary gear section 20 reduces the rotation of the output shaft 16 of the rotating electric machine 4. The differential gear 30 distributes the driving force of the rotating electric machine 4 transmitted via the planetary gear section 20 to the right wheel 8 and the left wheel 9. The rotating electric machine 4, the planetary gear section 20, and the differential gear 30 are arranged coaxially. Note that the configuration of the transmission device 5 described below is just one example, and other types of configurations can be adopted as appropriate.

[0016] The planetary gear section 20 comprises a sun gear 22, a plurality of stepped pinion gears 24, a ring gear 26, and a carrier 28. The sun gear 22 is connected to the output shaft 16 of the rotating electric machine 4 and rotates together with the output shaft 16. Each of the plurality of stepped pinion gears 24 has a large-diameter pinion gear P1 and a small-diameter pinion gear P2 which is smaller in diameter than the large-diameter pinion gear P1. The large-diameter pinion gear P1 meshes with the sun gear 22. The small-diameter pinion gear P2 meshes with the ring gear 26. The ring gear 26 is fixed to the case 7. The carrier 28 rotatably supports each of the plurality of stepped pinion gears 24. Thus, in the planetary gear section 20, the sun gear 22 is the input element, the ring gear 26 is the reaction element, and the carrier 28 is the output element.

[0017] The differential gear 30 includes a differential case 31 and a differential gear mechanism 32. The differential case 31 is supported by the case 7 so as to be rotatable around the rotation axis of the rotating electric machine 4. The differential case 31 is connected to the carrier 28 of the planetary gear unit 20 and rotates integrally with the carrier 28. The differential gear mechanism 32 is housed in the differential case 31.

[0018] The differential gear mechanism 32 includes a pinion shaft 33, a pair of differential pinion gears 34, 35, a right side gear 36, and a left side gear 37.

[0019] The pinion shaft 33 is connected to the differential case 31 and rotates integrally with the differential case 31. The pinion shaft 33 extends in the differential case 31 along a direction orthogonal to the rotation axis direction of the rotating electric machine 4. Each of the pair of differential pinion gears 34, 35 is supported by the pinion shaft 33 so as to be rotatable around the axis of the pinion shaft 33. The right side gear 36 is a member that outputs driving force to the right wheel 8 and meshes with each of the pair of differential pinion gears 34, 35. The left side gear 37 is a member that outputs driving force to the left wheel 9 and meshes with each of the pair of differential pinion gears 34, 35.

[0020] The drive device 3 further includes an intermediate shaft 40, a right drive shaft 50 connected to the right wheel 8, and a left drive shaft 60 connected to the left wheel 9.

[0021] The intermediate shaft 40 extends in the through hole 18 of the output shaft 16 along the rotation axis direction of the rotating electric machine 4. The left end portion of the intermediate shaft 40 is connected to the right side gear 36 of the differential gear 30, and the right end portion of the intermediate shaft 40 is connected to the right drive shaft 50. That is, the intermediate shaft 40 transmits the torque of the rotating electric machine 4 transmitted through the output shaft 16, the planetary gear unit 20, and the differential gear mechanism 32 to the right wheel 8.

[0022] The right drive shaft 50 has a drive shaft inboard 52, an intermediate drive shaft 54, and a drive shaft outboard 56. The drive shaft inboard 52 is the left end portion on the side inserted into the case 7 among both end portions in the axial direction of the right drive shaft 50, and refers to the portion from the constant velocity joint to the left end face. The drive shaft outboard 56 is the right end portion on the side connected to the right wheel 8 among both end portions in the axial direction of the right drive shaft 50, and refers to the portion from the constant velocity joint to the right end face. The drive shaft inboard 52 of the right drive shaft 50 is connected to the right side gear 36 of the differential gear 30 via the intermediate shaft 40. The driving force output by the right side gear 36 is transmitted to the right drive shaft 50 via the intermediate shaft 40.

[0023] The left drive shaft 60 has a drive shaft inboard 62, an intermediate drive shaft 64, and a drive shaft outboard 66. The drive shaft inboard 62 is the right end portion on the side inserted into the case 7 among both end portions in the axial direction of the left drive shaft 60, and refers to the portion from the constant velocity joint to the right end face. The drive shaft outboard 66 is the left end portion on the side connected to the left wheel 9 among both end portions in the axial direction of the left drive shaft 60, and refers to the portion from the constant velocity joint to the left end face. The drive shaft inboard 62 of the left drive shaft 60 is connected to the left side gear 37 of the differential gear 30. The driving force output by the left side gear 37 is directly transmitted to the left drive shaft 60.

[0024] Figure 3 shows a cross-sectional view in the vicinity of the intermediate shaft 40 passing through the case 7. The case 7 is provided with a passage port 78 through which the intermediate shaft 40 passes.

[0025] The case 7 is further provided with a bearing retaining section 70. The bearing retaining section 70 is arranged coaxially with the through opening 78. The outer ring 76B of the bearing 76 is fixed to the inner circumferential surface 72 of the bearing retaining section 70. The outer circumferential surface 16A of the right end of the output shaft 16 is fixed to the inner ring 76A of the bearing 76. The bearing 76 rotatably supports the output shaft 16 relative to the case 7.

[0026] A ring-shaped disc spring 80 is positioned between the axial end face of the outer ring 76B of the bearing 76 and the bottom surface 74 of the bearing retaining portion 70 that faces the end face. The disc spring 80 is compressed and deformed between the end face of the outer ring 76B and the bottom surface 74. The restoring force of the disc spring 80 acts on the outer ring 76B, suppressing the formation of a gap between the outer ring 76B and the inner circumferential surface 72 of the bearing retaining portion 70.

[0027] (Assembly method; Figures 4 and 5) Figures 4 and 5 show an assembly method for rotatably mounting the output shaft 16 to the case 7. As shown in Figures 2 and 3, when the drive unit 3 is mounted on the vehicle 1, the output shaft 16 extends along the left-right direction. On the other hand, the assembly method of this embodiment is performed with the output shaft 16 supported along the vertical direction, with one end 16B of the output shaft 16 pointing upward. That is, the orientation of the output shaft 16 during assembly is different from the orientation when it is mounted on the vehicle 1.

[0028] The assembly method comprises an inner ring press-fitting step, a disc spring arrangement step, and an outer ring press-fitting step. Figure 4(1) shows the inner ring press-fitting step and the disc spring arrangement step. In the inner ring press-fitting step, the output shaft 16 is press-fitted into the inner ring 76A of the bearing 76 such that the bearing 76 is separated from one end 16B of the output shaft 16 by a predetermined distance D2.

[0029] The disc spring placement process is performed after the inner ring press-fitting process. In the disc spring placement process, the inner circumferential surface 82 of the disc spring 80 is inserted from one end 16B of the output shaft 16, and the disc spring 80 is positioned adjacent to the bearing 76.

[0030] Figure 4(2) shows the configuration after the disc spring placement process and the outer ring press-fitting process. The disc spring 80 has a free height D1. The predetermined distance D2 is greater than the free height D1. Therefore, even if the output shaft 16 is tilted slightly from the state in which it is supported along the vertical direction, the disc spring 80 is prevented from falling off the output shaft 16.

[0031] The outer ring press-fitting process is performed after the disc spring placement process. In the outer ring press-fitting process, the case 7 approaches the bearing 76 from the disc spring 80 side. Then, the outer ring 76B of the bearing 76 is press-fitted onto the inner circumferential surface 72 of the bearing retaining portion 70.

[0032] Here, the inner circumferential surface 72 of the bearing retaining portion 70 has a chamfered end 72A on the side into which the outer ring 76B is press-fitted. Even if the disc spring 80 deviates from the position determined by the design, and the outer circumferential surface 84 of the disc spring 80 interferes with the end 72A of the bearing retaining portion 70, the chamfered end 72A can guide the disc spring 80 to the position determined by the design.

[0033] Figure 5 shows the state after the outer ring press-fitting process. As described above, the disc spring 80 is compressed and deformed between the outer ring 76B of the bearing 76 and the bottom surface 74 of the bearing retaining portion 70. In this state, a gap exists between the inner circumferential surface 82 of the disc spring 80 and the outer circumferential surface 16A of the output shaft 16. The output shaft 16 is a rotating body that rotates as part of the rotating electric machine 4, while the disc spring 80 is a stationary body that remains stationary within the bearing retaining portion 70. Contact between the stationary disc spring 80 and the rotating output shaft 16 can be avoided.

[0034] (Effects of this embodiment) In the assembly method of this embodiment, the disc spring placement process is performed with the output shaft 16 supported along the vertical direction (see Figure 4(1)). In this state, the disc spring 80 is constrained to the correct design position. Also, the predetermined distance D2 is greater than the free height D1 of the disc spring 80. This prevents the disc spring 80 from falling off the output shaft 16 or becoming misaligned with the output shaft 16 before the outer ring press-fitting process is performed. Furthermore, the outer ring press-fitting process is also performed with the output shaft 16 supported along the vertical direction. This allows the outer ring 76B of the bearing 76 to be press-fitted onto the inner circumferential surface 72 of the bearing retaining portion 70 while the disc spring 80 is constrained to the correct design position. Thus, according to the assembly direction of this embodiment, the output shaft 16 can be easily assembled to the case 7 while the disc spring 80 is constrained to the correct design position.

[0035] (Correspondence) The rotating electric machine 4, through hole 18, and intermediate shaft 40 are examples of "rotating electric machine," "through hole," and "intermediate shaft," respectively. The case 7 and output shaft 16 are examples of "case" and "shaft," respectively. The bearing 76, inner ring 76A, and outer ring 76B are examples of "bearing," "inner ring," and "outer ring," respectively. The bearing holder 70, inner circumferential surface 72, and end portion 72A are examples of "bearing holder," "inner circumferential surface," and "end portion," respectively. The disc spring 80 is an example of a "disc spring." The free height D1 and predetermined distance D2 are examples of "predetermined distance" and "free height," respectively.

[0036] The following points should be noted regarding the technology shown in the embodiment. At least the disc spring placement process and the outer ring press-fitting process should be performed with the output shaft 16 supported along the vertical direction. The inner ring press-fitting process may be performed with the output shaft 16 supported along a direction other than the vertical direction, for example, along the left-right direction.

[0037] The end portion 72A of the inner circumferential surface 72 of the bearing retaining portion 70 does not need to be chamfered.

[0038] The assembly method of this embodiment may also be used to assemble devices other than the rotating electric machine 4, which has a hollow output shaft 16 through which the intermediate shaft 40 passes. For example, the assembly method of this embodiment may be used to assemble a rotating electric machine which has a solid output shaft that does not have a through hole 18. Furthermore, the assembly method of this embodiment may also be used to assemble rotating devices other than rotating electric machines which have a stator and a rotor. [Explanation of symbols]

[0039] 1: Vehicle, 2: Battery pack, 3: Drive unit, 4: Rotating electric machine, 5: Transmission device, 6: Power control unit, 7: Case, 8: Right wheel, 9: Left wheel, 10: Rotating electric machine, 12: Stator core, 14: Rotor, 16: Output shaft, 16A: Outer surface, 16B: One end, 18: Through hole, 20: Planetary gear section, 22: Sun gear, 24: Stepped pinion gear, 26: Ring gear, 28: Carrier, 30: Differential gear, 31: Differential case, 32: Differential gear mechanism, 33: Pinion shaft, 34: Differential pinion gear, 35: Differential pinion gear, 36: Right side gear, 37: Left side gear, 40: Intermediate shaft, 50: Right drive shaft, 52: Drive shaft inboard, 54: Intermediate drive shaft, 56: Drive shaft outboard, 60: Left drive shaft, 62: Drive shaft inboard, 64: Intermediate drive shaft, 66: Drive shaft outboard, 70: Bearing holder, 72: Inner circumferential surface, 72A: End, 74: Bottom, 76: Bearing, 76A: Inner ring, 76B: Outer ring, 78: Through opening, 80: Disc spring, 82: Inner circumferential surface, 84: Outer circumferential surface, D1: Free height, D2: Determined distance, FW: Front wheel, RW: Rear wheel, P1: Large diameter pinion gear, P2: Small diameter pinion gear

Claims

1. An assembly method for rotatably mounting a shaft to a case, An inner ring press-fitting step in which the shaft is pressed into the inner ring of the bearing so that the bearing is spaced a predetermined distance from one end of the shaft, After the inner ring press-fitting step, a disc spring arrangement step is performed in which a ring-shaped disc spring is inserted from one end of the shaft and the disc spring is positioned adjacent to the bearing, After the disc spring arrangement step, the case is brought closer to the bearing from the disc spring side, and the outer ring of the bearing is pressed into the inner circumferential surface of the bearing retaining portion provided in the case in an outer ring press-fitting step. Equipped with, The disc spring arrangement step and the outer ring press-fitting step are performed with the shaft supported in the vertical direction, with one end of the shaft facing upward. An assembly method wherein the predetermined distance from one end of the shaft to the inner ring is greater than the free height of the disc spring.

2. The assembly method according to claim 1, wherein the inner circumferential surface of the bearing retaining portion is chamfered at the end on the side into which the outer ring is press-fitted.

3. The assembly method according to claim 1, wherein, when the outer ring of the bearing is press-fitted to the inner circumferential surface of the bearing retaining portion, a gap exists between the inner circumferential surface of the disc spring and the outer circumferential surface of the shaft.

4. The aforementioned shaft is the rotor shaft of a rotating electric machine. The assembly method according to claim 1, wherein the case is a motor case for housing the rotating electric machine.

5. The shaft has a through hole extending along the axial direction, The assembly method according to claim 4, wherein an intermediate shaft extending along the axial direction and transmitting the torque of the rotating electric machine toward the wheels of the vehicle is inserted into the through hole.

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