Rotational Power Transmission Mechanism

Abstract

To provide a rotation power transmission mechanism which can properly impart a preload to a pair of bearings even if a spacer arranged between both the bearings is decentered when imparting the preload to the bearings.SOLUTION: A rotation power transmission mechanism 3 comprises: first and second bearings 41, 42; a pinion gear shaft 30; a spacer 43 arranged between inner rings 411, 421 of the first and second bearings 41, 42; and a nut member 44 screwed to the pinion gear shaft 30, and imparting a preload in an axial direction to the first and second bearings 41, 42. The spacer 43 has a deformation part 433 between a first cylinder part 431 abutting on the inner ring 411 of the first bearing 41 and a second cylinder part 432 abutting on the inner ring 421 of the second bearing 42. In the pinion gear shaft 30, a small-diameter part 312 whose outside diameter is smaller than that of a second fitting face 31b to which the inner ring 421 of the second gear 42 is fit is formed inside the second cylinder part 432.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a rotational power transmission mechanism that transmits rotational power by means of a rotary drive shaft supported by bearings. [Background technology]

[0002] Conventionally, for example, a pinion gear shaft that transmits rotational power from a vehicle's propeller shaft to a differential device is supported on a case member by a pair of bearings that are preloaded in the axial direction in order to suppress the generation of vibration (see, for example, Patent Documents 1 and 2).

[0003] In the pinion gear shaft described in Patent Documents 1 and 2, two axial positions of the pinion gear shaft are supported by bearings (tapered roller bearings), and an annular spacer is disposed between these bearings. The spacer is cylindrical at both ends, and the inner and outer diameters of the central portion are larger than those of the both ends. The pinion gear shaft has a male thread formed on a portion of its outer circumferential surface, and a axial preload is applied to both bearings by tightening a nut that screws onto the male thread. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-194765 A [Patent Document 2] JP 2017-144940 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned configuration, when the spacer is pressed in the axial direction by the axial force generated by tightening the nut, the cylindrical portions at both ends of the spacer may become eccentric and deformed so that they are misaligned with each other. In this case, one of the cylindrical portions may be strongly pressed against the outer circumferential surface of the shaft in a part of the circumferential direction, generating a large frictional force, and there is a risk that an appropriate preload may not be applied to both bearings.

[0006] Therefore, an object of the present invention is to provide a rotational power transmission mechanism that can appropriately apply preload to both bearings even if a spacer arranged between the bearings becomes eccentric and deforms when preload is applied to the pair of bearings. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a rotational power transmission mechanism comprising: first and second bearings each having a plurality of rolling elements disposed between an inner ring and an outer ring; a rotary drive shaft having a shaft portion supported by the first and second bearings; an annular spacer disposed on the outer periphery of the shaft portion between the inner rings of the first and second bearings; and a nut member screwed onto the shaft portion to apply an axial preload to the first and second bearings, the rotational power transmission mechanism transmitting rotational power by the rotary drive shaft, the spacer having a first cylindrical portion abutting against a side surface of the inner ring of the first bearing and a second cylindrical portion abutting against a side surface of the inner ring of the second bearing. the rotation drive shaft has, on an outer periphery of the shaft portion, a first fitting surface into which the inner ring of the first bearing and the first cylindrical portion of the spacer are fitted, and a second fitting surface into which the inner ring of the second bearing is fitted, and a small diameter portion having an outer diameter smaller than that of the second fitting surface is formed inside the second cylindrical portion of the spacer on the shaft portion, and an inner circumferential surface of the second cylindrical portion and an outer circumferential surface of the small diameter portion face each other via a gap, Cage , The axial width of the small diameter portion is greater than the axial width of the second cylindrical portion. A rotary power transmission mechanism is provided. Effect of the Invention

[0008] According to the rotational power transmission mechanism of the present invention, even if the spacer disposed between the pair of bearings is eccentrically deformed, it is possible to appropriately apply preload to both bearings. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an example of the schematic configuration of a four-wheel drive vehicle equipped with a rotational power transmission mechanism according to an embodiment of the present invention; [Diagram 2] 2 is a cross-sectional view showing a driving force transmission device, a rotational power transmission mechanism, a rear differential, and a differential carrier. FIG. [Diagram 3] FIG. 2 is a cross-sectional view showing a part of the driving force transmission device. [Figure 4] FIG. 4 is a configuration diagram showing a support structure for a pinion gear shaft by a first bearing and a second bearing. [Diagram 5] 5(a) to 5(c) are enlarged cross-sectional views showing the spacer together with a part of the inner ring of the first bearing and the inner ring of the second bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Embodiment Mode] An embodiment of the present invention will be described with reference to Figures 1 to 5. Note that the embodiment described below is shown as a preferred specific example for carrying out the present invention, and while there are some parts that specifically exemplify various technical matters that are technically preferable, the technical scope of the present invention is not limited to this specific embodiment.

[0011] (Overall configuration of four-wheel drive vehicle) 1 is a schematic diagram showing an example of the schematic configuration of a four-wheel drive vehicle equipped with a rotational power transmission mechanism according to an embodiment of the present invention. This four-wheel drive vehicle 1 has left and right front wheels 101, 102 as main drive wheels, and left and right rear wheels 103, 104 as auxiliary drive wheels. The driving force (rotational power) of a driving source 11 is changed in speed by a transmission 12 and is constantly transmitted to the front wheels 101, 102, and is also transmitted to the rear wheels 103, 104 depending on the vehicle state. The driving source 11 is, for example, an engine, but may also be an electric motor, or a combination of an engine and an electric motor.

[0012] The four-wheel drive vehicle 1 has a driving force transmission system that transmits the driving force of the drive source 11, which has been changed by the transmission 12, to the left and right front wheels 101, 102 and the left and right rear wheels 103, 104, and includes a front differential 13 and a rear differential 14, left and right drive shafts 151, 152 on the front wheel side arranged between the front differential 13 and the left and right front wheels 101, 102, left and right drive shafts 161, 162 on the rear wheel side arranged between the rear differential 14 and the left and right rear wheels 103, 104, a propeller shaft 17 that transmits driving force in the fore-and-aft direction of the vehicle, a gear mechanism 18 between the front differential 13 and the propeller shaft 17, and a driving force transmission device 19 arranged between the propeller shaft 17 and the rear differential 14. The driving force transmission device 19 has a clutch device 2, a rotational power transmission mechanism 3, and a differential carrier 5 as a housing member that houses the clutch device 2 and the rotational power transmission mechanism 3 together with the rear differential 14.

[0013] The front differential 13 has a front differential case 131, a pinion pin 132 fixed to the front differential case 131, a pair of pinion gears 133 supported by the pinion pins 132, and a pair of side gears 134 meshing with the pair of pinion gears 133, and left and right drive shafts 151, 152 are fixed to the pair of side gears 134, respectively. The driving force of the driving source 11 is transmitted from the transmission 12 to the front differential case 131. The gear mechanism 18 is composed of a ring gear 181 fixed to the front differential case 131, and a pinion gear 182 meshing with the ring gear 181.

[0014] The propeller shaft 17 has a front shaft portion 171 and a rear shaft portion 172, a front universal joint 173 that connects the front shaft portion 171 to a pinion gear 182 of the gear mechanism 18, a rear universal joint 174 that connects the rear shaft portion 172 to a front housing 21 (described later) of the clutch device 2, and a sliding constant velocity joint 175 that connects the front shaft portion 171 to the rear shaft portion 172.

[0015] The rear differential 14 has a rear differential case 141, a pinion pin 142 fixed to the rear differential case 141, a pair of pinion gears 143 supported on the pinion pin 142, a pair of side gears 144 meshing with the pair of pinion gears 143, and a ring gear 145 fastened to the outer periphery of the rear differential case 141, and left and right drive shafts 161, 162 are fixed to the pair of side gears 144, respectively.

[0016] The clutch device 2 is controlled by a control device 9, and is capable of adjusting the driving force transmitted from the propeller shaft 17 to the rear differential 14 via the rotational power transmission mechanism 3 according to the vehicle state. The control device 9 is capable of acquiring the detection values ​​of rotational speed sensors S1-S4 that detect the rotational speeds of the left and right front wheels 101, 102 and the left and right rear wheels 103, 104, as well as the detection value of an accelerator pedal sensor S5 that detects the depression amount of an accelerator pedal 111, and controls the clutch device 2 based on the detection values ​​of these sensors S1-S5, etc.

[0017] Fig. 2 is a cross-sectional view showing the clutch device 2, the rotational power transmission mechanism 3, the rear differential 14, and the differential carrier 5. Fig. 3 is a cross-sectional view showing a part of the clutch device 2.

[0018] The clutch device 2 includes a cylindrical front housing 21 with a bottom that rotates together with the propeller shaft 17, a rear housing 22 fixed to an end of the front housing 21 on the opening side (rear side of the vehicle), a main clutch 23 accommodated in the front housing 21, a cam mechanism 24 that generates a thrust force for pressing the main clutch 22, a pilot clutch 25 that transmits a torque for operating the cam mechanism 24, an armature 26 arranged in line with the pilot clutch 25 in the axial direction, an electromagnetic coil 27 that generates a magnetic force that attracts the armature 26 toward the pilot clutch 25, a holder 28 provided integrally with the electromagnetic coil 27, and a yoke 29 that supports the electromagnetic coil 27 with respect to the differential carrier 5. An excitation current is supplied to the electromagnetic coil 27 from the control device 9 via a connector pin 281 of a connector portion 280 provided in the holder 28.

[0019] The front housing 21 integrally has a cylindrical portion 211 having a plurality of axially extending spline projections 211a formed on its inner circumference, and a bottom portion 212 having bolt insertion holes 212b formed therein for fastening to the rear universal joint 174 of the propeller shaft 17. The flange yoke 171a of the rear universal joint 174 is fixed to the bottom portion 212 of the front housing 21 by bolts 60 inserted into the bolt insertion holes 212b.

[0020] 3, the rear housing 22 has an outer cylindrical member 221 and an inner cylindrical member 222 made of a magnetic metal that serve as a magnetic path for the magnetic flux generated by the electromagnetic coil 27, and a non-magnetic ring 223 disposed between the outer cylindrical member 221 and the inner cylindrical member 222. The non-magnetic ring 223 is welded to the outer cylindrical member 221 and the inner cylindrical member 222. The outer cylindrical member 221 is screwed and fixed to an end of the cylindrical portion 211 of the front housing 21 on the opposite side to the bottom portion 212 side. The front housing 21 and the rear housing 22 form the clutch housing 20 as a rotating body supported by a support portion 34 of the pinion gear shaft 30 described later.

[0021] The main clutch 23 is a multi-plate clutch formed by alternately arranging a plurality of main outer clutch plates 231 and a plurality of main inner clutch plates 232. The plurality of main outer clutch plates 231 engage with a plurality of spline projections 211a of the front housing 21, and are movable axially relative to the cylindrical portion 211 of the front housing 21 but are unable to rotate relative thereto.

[0022] The cam mechanism 24 has a main cam 241 facing the main clutch 23, a pilot cam 242 aligned with the main cam 241 in the axial direction, and a plurality of cam balls 243 arranged between the main cam 241 and the pilot cam 242. A plurality of arc grooves 241a, 242a whose axial depth becomes deeper toward the center are formed in the main cam 241 and the pilot cam 242, respectively. When the main clutch 23 and the main cam 241 rotate relative to each other and the cam balls 243 roll in the arc grooves 241a, 242a, the main cam 241 approaches and moves away from the pilot cam 242. The axial movement of the pilot cam 242 in the direction away from the main clutch 23 is regulated by a thrust bearing 61 arranged between the pilot cam 242 and the inner cylindrical member 222 of the rear housing 22.

[0023] The pilot clutch 25 has a plurality of pilot outer clutch plates 251 spline-engaged with the front housing 21 and a plurality of pilot inner clutch plates 252 spline-engaged with the pilot cam 242, and the plurality of pilot outer clutch plates 251 and the plurality of pilot inner clutch plates 252 are arranged alternately. The pilot outer clutch plate 251 and the pilot inner clutch plate 252 each have a plurality of arc-shaped slits 251a, 252a formed in the radial center thereof to prevent short-circuiting of magnetic flux between the outer circumferential portion and the inner circumferential portion.

[0024] The armature 26 is spline-engaged with the front housing 21 and is movable in the axial direction but not rotatable relative to the cylindrical portion 211 of the front housing 21. The pilot clutch 25 is disposed between the armature 26 and the rear housing 22, and when an electric current is applied to the electromagnetic coil 27, the armature 26 presses the pilot clutch 25 toward the rear housing 22.

[0025] The rotational power transmission mechanism 3 has a pinion gear shaft 30 as a rotational drive shaft, and a bearing unit 4 that rotatably supports the pinion gear shaft 30 with respect to the differential carrier 5. The bearing unit 4 has a first bearing 41 and a second bearing 42 aligned in the axial direction, an annular spacer 43 disposed between the first bearing 41 and the second bearing 42, and a nut member 44 screwed onto the pinion gear shaft 30. The nut member 44 applies an axial preload to the first bearing 41 and the second bearing 42.

[0026] The pinion gear shaft 30 integrally includes a shaft portion 31 supported by a first bearing 41 and a second bearing 42, a gear portion 32 having a diameter larger than that of the shaft portion 31, a spline engagement portion 33 having a plurality of spline projections 33a formed on its outer periphery, and a support portion 34 for supporting the clutch housing 20 of the clutch device 2. The gear portion 32 is provided at one end of the pinion gear shaft 30 in the axial direction, which corresponds to the rear side of the vehicle, and meshes with a ring gear 145 of the rear differential 14. The support portion 34 is provided at the other end of the pinion gear shaft 30 in the axial direction, which corresponds to the front side of the vehicle. The spline engagement portion 33 is provided between the shaft portion 31 and the support portion 34, and a main cam 241 and a plurality of main inner clutch plates 232 are engaged with the plurality of spline projections 33a. The configurations of the pinion gear shaft 30 and the bearing portion 4 will be described in detail later.

[0027] The differential carrier 5 is supported by the body 100 of the four-wheel drive vehicle 1, with a main body 51 on the vehicle front side and a cover body 52 on the vehicle rear side fastened by a plurality of bolts 53. The rear differential case 141 is supported rotatably relative to the differential carrier 5 by a pair of tapered roller bearings 62, 63 disposed between the main body 51 and the cover body 52.

[0028] The main body 51 of the differential carrier 5 integrally includes a support cylinder portion 511 that houses the bearing portion 4 and the shaft portion 31 of the pinion gear shaft 30, and an annular protrusion 512 that protrudes inward from the support cylinder portion 511. A ball bearing 64 is disposed between the end of the support cylinder portion 511 on the vehicle front side and the inner cylindrical member 222 of the rear housing 22. The ball bearing 64 includes an inner ring 641, an outer ring 642, a plurality of rolling elements 643, and a retainer 644. The outer ring 642 is fitted inside the support cylinder portion 511 and the yoke 29. The inner ring 641 is fitted outside the inner cylindrical member 222, and the rear housing 22 is supported by the support cylinder portion 511 via the ball bearing 64.

[0029] An axial through hole 210 is formed in the bottom 212 of the front housing 21, and a ball bearing 65 is disposed between an inner surface 210a of the through hole 210 and an outer peripheral surface 34a of the support portion 34 of the pinion gear shaft 30. The ball bearing 65 has an inner ring 651, an outer ring 652, a plurality of rolling elements 653, and a cage 654, and the inner ring 651 is prevented from coming off the support portion 34 by a retaining ring 66.

[0030] A pair of disc springs 671, 672 and a washer 68 are arranged inside the through hole 210 in the axial direction alongside the outer ring 652, and the washer 68 is engaged with a flange 212a provided on the bottom 212 of the front housing 21. The outer ring 652 is biased in the axial direction by the restoring forces of the disc springs 671, 672. The opening of the through hole 210 is closed by a disk-shaped cap 69.

[0031] The differential carrier 5 contains differential oil (not shown), and the front housing 21 contains clutch oil, which has a lower viscosity than the differential oil. The leakage of the differential oil is prevented by the seal members 71 and 72 arranged between the main body 51 and the cover body 52 of the differential carrier 5 and the drive shafts 161 and 162, and by the seal member 73 arranged inside the support cylinder portion 511. The leakage of the clutch oil is prevented by the seal member 74 arranged between the inner cylindrical member 222 of the rear housing 22 and the shaft portion 31 of the pinion gear shaft 30, and by the cap 69. In addition, the deflector 75, the seal member 76, and the slinger 77 prevent foreign matter from entering through the gap between the differential carrier 5 and the front housing 21.

[0032] In the clutch device 2 and the rotational power transmission mechanism 3 configured as described above, when an electric current is supplied from the control device 9 to the electromagnetic coil 27 during acceleration of the four-wheel drive vehicle 1, the armature 26 attracted to the rear housing 22 side by the magnetic force presses the pilot clutch 25, and the rotational torque of the front housing 21 is transmitted to the pilot cam 242 by the pilot clutch 25. As a result, the pilot cam 242 rotates relative to the main cam 241, and the main cam 241 presses the main clutch 23, and the driving force is transmitted from the front housing 21 to the pinion gear shaft 30 by the main clutch 23. The driving force transmitted to the pinion gear shaft 30 is transmitted from the gear portion 32 to the rear differential 14 and distributed to the left and right rear wheels 103.

[0033] 4 is a configuration diagram showing a support structure for the pinion gear shaft 30 by the first bearing 41 and the second bearing 42. The first bearing 41 and the second bearing 42 each have an inner ring 411, 421 fitted onto the shaft portion 31 of the pinion gear shaft 30, an outer ring 412, 422 arranged on the outside of the inner ring 411, 421, a plurality of rolling elements 413, 423 arranged between the inner ring 411, 421 and the outer ring 412, 422, and a cage 414, 424 that holds the plurality of rolling elements 413, 423.

[0034] In this embodiment, as an example, the first bearing 41 is a tapered roller bearing and the second bearing 42 is an angular ball bearing, but this is not limited to this, and the first bearing 41 may be an angular ball bearing and the second bearing 42 may be a tapered roller bearing.

[0035] The first bearing 41 is disposed closer to the gear portion 32 (toward the rear of the vehicle) than the second bearing 42. An outer ring 412 of the first bearing 41 and an outer ring 422 of the second bearing 42 sandwich an annular protrusion 512 provided on the main body 51 of the differential carrier 5 in the axial direction. The annular protrusion 512 protrudes inward from the support cylinder portion 511 toward the shaft portion 31 of the pinion gear shaft 30. The nut member 44 is disposed closer to the support portion 34 (toward the front of the vehicle) than the second bearing 42. The spacer 43 is disposed on the outer periphery of the shaft portion 31 of the pinion gear shaft 30 between the inner rings 411, 421 of the first and second bearings 41, 42, respectively.

[0036] Hereinafter, of both side surfaces of the inner ring 411 of the first bearing 41, the side surface on the vehicle front side is referred to as the first front inner ring side surface 411a, and the side surface on the vehicle rear side is referred to as the first rear inner ring side surface 411b. Also, of both side surfaces of the inner ring 421 of the second bearing 42, the side surface on the vehicle front side is referred to as the second front inner ring side surface 421a, and the side surface on the vehicle rear side is referred to as the second rear inner ring side surface 421b. A washer 45 is disposed between the first rear inner ring side surface 411b and the back surface 32a of the gear portion 32. A nut member 44 abuts against the second front inner ring side surface 421a.

[0037] The spacer 43 is made of metal and has a first cylindrical portion 431 that abuts against the first front inner race side surface 411a, a second cylindrical portion 432 that abuts against the second rear inner race side surface 421b, and a deformation portion 433 that is provided between the first cylindrical portion 431 and the second cylindrical portion 432 and deforms so as to be compressed in the axial direction by a preload applied by the nut member 44. The deformation portion 433 protrudes radially outward in a mountain shape in a cross section along the axial direction, and is formed with inner and outer diameters larger than those of the first and second cylindrical portions 431, 432. The deformation of the deformation portion 433 due to the preload may be elastic deformation or plastic deformation.

[0038] In this embodiment, the inner and outer diameters of the first cylindrical portion 431 are equal to the inner and outer diameters of the second cylindrical portion 432. In addition, the axial length of the first cylindrical portion 431 is equal to the axial length of the second cylindrical portion 432. This allows the spacer 43 to be assembled to the pinion gear shaft 30 from either direction, preventing the occurrence of incorrect assembly. That is, of the two cylindrical portions at both axial ends of the spacer 43, the cylindrical portion arranged on the first bearing 41 side is the first cylindrical portion 431, and the cylindrical portion arranged on the second bearing 42 side is the second cylindrical portion 432.

[0039] The pinion gear shaft 30 has a first fitting surface 31a on the outer periphery of the shaft portion 31, into which the inner ring 411 of the first bearing 41 and the first cylindrical portion 431 of the spacer 43 are fitted, and a second fitting surface 31b on which the inner ring 421 of the second bearing 42 is fitted. The inner ring 411 of the first bearing 41 is press-fitted into the first fitting surface 31a. In addition, the shaft portion 31 is formed with a male thread portion 311 into which a nut member 44 is screwed, on the support portion 34 side of the second fitting surface 31b, and an axial preload is applied to the first and second bearings 41, 42 by tightening the nut member 44 screwed into the male thread portion 311.

[0040] In this embodiment, the outer diameter D1 of the first fitting surface 31a and the outer diameter D2 of the second fitting surface 31b are equal. Here, "equal" means that the difference in diameter between the outer diameter D1 of the first fitting surface 31a and the outer diameter D2 of the second fitting surface 31b is 0.5 mm or less. In addition, as described in Patent Documents 1 and 2, for example, the outer diameter of the pinion gear shaft of a typical differential device is formed so that the outer diameter of the portion where the inner ring of one of the pair of bearings on the gear side is fitted is larger than the outer diameter of the portion where the inner ring of the other bearing is fitted. This is in consideration of the fact that the load on the gear side is large when transmitting the driving force. However, in this embodiment, the support portion 34, which is the end portion opposite to the gear portion 32, supports the clutch housing 20 of the clutch device 2, so that the load received by the support portion 34 is larger than that of the pinion gear shaft of a typical differential device. For this reason, in this embodiment, the outer diameter D1 of the first fitting surface 31a and the outer diameter D2 of the second fitting surface 31b are made equal to each other.

[0041] In this embodiment, since the gear portion 32 has a larger diameter than the shaft portion 31, the first bearing 41, the spacer 43, the second bearing 42, and the nut member 44 are arranged in this order on the outer periphery of the shaft portion 31 from the support portion 34 side. Therefore, the outer diameter D2 of the second fitting surface 31b is set to be equal to or smaller than the outer diameter D1 of the first fitting surface 31a in consideration of ease of assembly. That is, the inner ring 411 of the first bearing 41 easily passes through the second fitting surface 31b in the axial direction.

[0042] In this embodiment, since the inner ring 411 of the first bearing 41 is press-fitted into the first fitting surface 31a as described above, it is desirable that the diameter difference between the first fitting surface 31a and the second fitting surface 31b is equal to or larger than the press-fit allowance (tightening allowance) of the inner ring 411 of the first bearing 41. If this diameter difference is equal to or larger than the press-fit allowance of the inner ring 411 of the first bearing 41, the load pressing the first bearing 41 when the inner ring 411 of the first bearing 41 passes through the second fitting surface 31b can be small, improving the ease of assembly. The press-fit allowance of the inner ring 411 is, for example, 0.03 mm in diameter.

[0043] Furthermore, in this embodiment, a small diameter portion 312 having an outer diameter smaller than that of the second fitting surface 31b is formed inside the second cylindrical portion 432 of the spacer 43 in the shaft portion 31 of the pinion gear shaft 30. The inner peripheral surface 432a of the second cylindrical portion 432 and the outer peripheral surface 312a of the small diameter portion 312 face each other via a gap. This small diameter portion 312 is for preventing the second cylindrical portion 432 from being strongly pressed against the outer peripheral surface of the shaft portion 31 even if the first cylindrical portion 431 and the second cylindrical portion 432 are deformed eccentrically so as to be misaligned with each other when the spacer 43 is pressed in the axial direction by the axial force generated by fastening the nut member 44.

[0044] 5(a) to 5(c) are enlarged cross-sectional views showing the spacer 43 together with a part of the inner ring 411 of the first bearing 41 and the inner ring 421 of the second bearing 42. FIG. 5(a) shows a state before the nut member 44 is fastened. FIG. 5(b) shows a state in which the spacer 43 is deformed without the first cylindrical portion 431 and the second cylindrical portion 432 becoming misaligned when the nut member 44 is fastened. FIG. 5(c) shows an example of a state in which the spacer 43 is deformed due to the first cylindrical portion 431 and the second cylindrical portion 432 becoming misaligned when the nut member 44 is fastened.

[0045] The first bearing 41, the spacer 43, the second bearing 42, and the nut member 44 are attached to the pinion gear shaft 30 by positioning the pinion gear shaft 30 in the vertical direction so that the gear portion 32 faces downward. The spacer 43 is positioned coaxially with the pinion gear shaft 30 by fitting the first cylindrical portion 431 into the first fitting surface 31a.

[0046] As shown in FIG. 5(a), the axial width W1 of the small diameter portion 312 is wider than the axial width W2 of the second cylindrical portion 432. Here, the axial width W1 of the small diameter portion 312 is the overall width of a portion having an outer diameter smaller than that of the second fitting surface 31b. The axial width W2 of the second cylindrical portion 432 is the width of a portion where the inner circumferential surface 432a of the second cylindrical portion 432 is formed linearly in a cross section of the spacer 43 along the axial direction. The small diameter portion 312 is formed such that the entire range of the width W2 of the second cylindrical portion 432 is included within the range of the width W1 both before and after the deformation of the spacer 43 by tightening the nut member 44.

[0047] 5(a), the axial end face 431b of the first cylindrical portion 431 contacts the first front inner race side surface 411a, and the axial end face 432b of the second cylindrical portion 432 contacts the second rear inner race side surface 421b, but no axial force is generated by fastening the nut member 44, and the spacer 43 is not deformed. When the nut member 44 is fastened from this state, the deformed portion 433 of the spacer 43 deforms so as to be compressed in the axial direction, and the second cylindrical portion 432 moves toward the first cylindrical portion 431, as shown in FIG. 5(b) and FIG. 5(c).

[0048] When the spacer 43 deforms in this manner, it is ideal for the first cylindrical portion 431 and the second cylindrical portion 432 to deform while maintaining coaxiality, as shown in Figure 5(b). However, in this embodiment, even if the second cylindrical portion 432 deforms eccentrically relative to the first cylindrical portion 431, as shown in Figure 5(c), a small diameter portion 312 is formed at a portion corresponding to the inside of the second cylindrical portion 432, so that, for example, the corner between the inner surface 432a and the axial end face 432b of the second cylindrical portion 432 is prevented from being pressed strongly against the shaft portion 31, thereby preventing friction from occurring.

[0049] In addition, the depth D of small diameter portion 312 in shaft portion 31 (the depth of the annular groove formed by the difference between the outer diameter D2 of the second fitting surface 31b and the outer diameter of small diameter portion 312) may be set to a dimension deep enough that the second cylindrical portion 432 does not contact the outer peripheral surface 312a of the small diameter portion 312 even if the second cylindrical portion 432 is significantly displaced radially. However, even if the second cylindrical portion 432 contacts the outer peripheral surface 312a of the small diameter portion 312, friction when the second cylindrical portion 432 is pressed against shaft portion 31 can be reduced compared to the case where the small diameter portion 312 is not formed.

[0050] (Effects of the embodiment) According to the embodiment of the present invention described above, when the nut member 44 is fastened to apply a preload to the first and second bearings 41, 42, even if the spacer 43 is eccentrically deformed, the preload can be appropriately applied to the first and second bearings 41, 42. In addition, in this embodiment, the inner diameter of the first cylindrical portion 431 of the spacer 43 is equal to the inner diameter of the second cylindrical portion 432, so that there is no restriction on the assembling direction of the spacer 43, and assembling performance is improved. In addition, in this embodiment, the outer diameter D1 of the first fitting surface 31a of the pinion gear shaft 30 is equal to the outer diameter D2 of the second fitting surface 31b, so that the clutch housing 20 can be supported by the support portion 34 with high rigidity. Furthermore, according to this embodiment, the axial width W1 of the small diameter portion 312 is wider than the axial width W2 of the second cylindrical portion 432 of the spacer 43, so that interference between the second cylindrical portion 432 and the pinion gear shaft 30 can be easily avoided.

[0051] (Additional Note) Although the present invention has been described above based on the embodiment, the invention according to the claims is not limited to the embodiment. It should be noted that not all of the combinations of features described in the embodiment are necessarily essential to the means for solving the problems of the invention. The present invention can be appropriately modified and implemented by omitting some configurations or adding or replacing configurations within the scope of the gist of the invention. For example, in the above embodiment, the rotational power transmission mechanism of the present invention is described as being used to transmit the driving force of a vehicle, but the present invention is not limited to this, and can also be applied to a rotational power transmission mechanism used in, for example, industrial machinery. [Explanation of symbols]

[0052] 3... Rotational power transmission mechanism 30... Pinion gear shaft (rotational drive shaft) 31...Shaft part 312...Small diameter part 312a...Outer peripheral surface 314...Support part 31a: first mating surface 31b: second mating surface 32 ... gear portion 34 ... support portion 41...first bearing 42...second bearing 411,421…inner wheel 412,422…outer wheel 413,423...Rolling element 414,424...Cage 43...Spacer 431...First cylindrical portion 432: second cylindrical portion; 433: deformation portion 44…Nut member

Claims

1. A rotational power transmission mechanism comprising: first and second bearings each having a plurality of rolling elements disposed between an inner ring and an outer ring; a rotational drive shaft having a shaft portion supported by the first and second bearings; an annular spacer disposed on an outer periphery of the shaft portion between the inner rings of the first and second bearings; and a nut member screwed onto the shaft portion to apply an axial preload to the first and second bearings, the rotational power transmission mechanism transmitting rotational power by the rotational drive shaft, the spacer has a first cylindrical portion in contact with a side surface of the inner ring of the first bearing, a second cylindrical portion in contact with a side surface of the inner ring of the second bearing, and a deformation portion provided between the first cylindrical portion and the second cylindrical portion and deformed so as to be compressed in the axial direction by the preload, the rotation drive shaft has, on an outer periphery of the shaft portion, a first fitting surface into which the inner ring of the first bearing and the first cylindrical portion of the spacer are fitted, and a second fitting surface into which the inner ring of the second bearing is fitted, a small diameter portion having an outer diameter smaller than that of the second fitting surface is formed inside the second cylindrical portion of the spacer in the shaft portion, an inner circumferential surface of the second cylindrical portion and an outer circumferential surface of the small diameter portion face each other via a gap, The axial width of the small diameter portion is greater than the axial width of the second cylindrical portion. Rotational power transmission mechanism.

2. The spacer has an equal first cylindrical portion and an equal second cylindrical portion, and an outer diameter of the first fitting surface of the rotary drive shaft is equal to an outer diameter of the second fitting surface.

2. The rotary power transmission mechanism of claim 1.

3. The rotary drive shaft has a gear portion at one end in the axial direction, the gear portion having a larger diameter than the shaft portion, and a support portion at the other end in the axial direction, the support portion supporting a rotor.

3. The rotational power transmission mechanism according to claim 1 or 2.

4. the first bearing is disposed closer to the gear portion than the second bearing, and the inner ring of the first bearing is press-fitted into the first fitting surface, The outer diameter of the second mating surface is equal to or smaller than the outer diameter of the first mating surface.

4. The rotary power transmission mechanism according to claim 3.

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