Electric vehicle

Abstract

To provide an electric vehicle suppressing NV.SOLUTION: A motor-side end surface of a large diameter part formed between a spline-fitting part at a gear shaft, and a first gear, comes in contact with a first-gear-side end surface of an inner race of a second bearing. In addition, a clearance between a third-bearing-side end surface of a step part formed so as to be adjacent to an end part on a side of a third bearing at a rotor shaft and a motor-side end surface of the third bearing is made larger than an inside clearance of the second bearing. Thereby, when thrust force acting in a direction of the motor is generated on the gear shaft, the internal clearance of the second bearing is reduced prior to the clearance between the third-bearing side end surface of the step part and the motor-side end surface of the third bearing. Accordingly, the thrust force is transmitted to a second case via the second bearing and sound radiation is suppressed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an electric vehicle having an electric motor and one of a set of helical gears disposed on the same rotation axis. [Background technology]

[0002] There is a well-known electric vehicle including an electric motor, a helical gear in which a first gear arranged on the rotation axis of the electric motor and a second gear arranged on another rotation axis parallel to the rotation axis of the electric motor are meshed, a gear shaft in which the first gear is fixed so as not to rotate relative to the rotor shaft of the electric motor, the outer peripheral surface of which is connected to the inner peripheral surface of the rotor shaft of the electric motor by spline fitting, a case having a first case and a second case, the first case and the second case being joined to form a gear chamber in which the helical gear is accommodated, and the second case being formed as a motor chamber in which the electric motor is accommodated, a first bearing rotatably supporting the gear shaft on the first case at an end of the gear shaft opposite to the motor side, and a second bearing rotatably supporting the rotor shaft on the second case at an end of the rotor shaft on the first gear side. For example, a motor drive device described in Patent Document 1 is such an example. Patent document 1 discloses that a thrust force acting toward the electric motor, which is generated on the gear shaft by the gear meshing reaction force of the helical gear, is applied to the inner race of the second bearing, and the thrust force acting on the inner race is then applied to the second case via the outer race of the second bearing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-175261 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, there is a case where a third case is provided that forms a motor chamber by joining with the second case, and the rotor shaft is rotatably supported on the third case via a third bearing at the end of the rotor shaft opposite to the first gear side. In this case, for example, a thrust force transmitted to the rotor shaft directly from the gear shaft or indirectly via the second bearing may be transmitted to the third case via the third bearing. If this occurs, the thrust force may cause the rotor shaft to strike the third case via the third bearing, which may worsen the NV. "NV" is a general term for noise and vibration generated in a vehicle, and refers to at least one of the noise and vibration in a vehicle.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide an electric vehicle capable of suppressing NV. [Means for solving the problem]

[0006] The gist of a first invention is that a motor having a helical gear in which a first gear arranged on a rotation axis of the motor and a second gear arranged on another rotation axis parallel to the rotation axis of the motor are meshed, a gear shaft in which the first gear is fixedly mounted so as not to rotate relative to the motor, the gear shaft having an inner peripheral surface on the motor side connected by spline fitting to an inner peripheral surface on the first gear side of a rotor shaft of the motor, the outer peripheral surface on the motor side being spline-fitted, the gear shaft having a first case, a second case, and a third case, the first case and the second case being joined to form a gear chamber in which the helical gear is accommodated, and the second case and the third case being joined to form a motor chamber in which the motor is accommodated, the first case and the second case being joined to form a motor chamber, An electric vehicle comprising a second bearing supported by the second case, and a third bearing supporting the rotor shaft on the third case at an end of the rotor shaft opposite the first gear side, wherein (b) the gear shaft has a large diameter portion formed between the splined engagement portion and the first gear, the large diameter portion having a larger diameter than the splined engagement portion, (c) the rotor shaft has a stepped portion formed adjacent to the end of the rotor shaft on the third bearing side, the stepped portion having a larger diameter than the end of the third bearing side, (d) an end face of the large diameter portion on the electric motor side is abutted against an end face of an inner race of the second bearing on the first gear side, and (e) a clearance between the end face of the stepped portion on the third bearing side and an end face of the third bearing on the electric motor side is larger than an internal clearance of the second bearing. Effect of the Invention

[0007] According to the first aspect of the present invention, the electric motor side end face of the large diameter portion formed between the splined portion of the gear shaft and the first gear and having a larger diameter than the splined portion is abutted against the first gear side end face of the inner race of the second bearing. In addition, the clearance between the third bearing side end face of the stepped portion formed adjacent to the third bearing side end face of the rotor shaft and the electric motor side end face of the third bearing is made larger than the internal clearance of the second bearing. As a result, when a thrust force acting on the gear shaft toward the electric motor is generated by the gear meshing reaction force of the helical gear, the thrust force is applied to the inner race of the second bearing. At this time, the internal clearance of the second bearing, i.e., the backlash between the inner race and the outer race, is eliminated before the clearance between the third bearing side end face of the stepped portion and the electric motor side end face of the third bearing is eliminated. Therefore, the thrust force acting on the gear shaft in the direction of the motor is transmitted to the second case via the second bearing and received by the second case, and is not easily transmitted to the third case, making it difficult for the third case to become a sound-generating part. Because the second case is located between the gear chamber and the motor chamber, sound radiation to the outside of the case is suppressed even if the thrust force is transmitted to the second case. This makes it possible to suppress NV. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of an electric vehicle to which the present invention is applied; [Diagram 2] FIG. 2 is a diagram illustrating an example of a schematic configuration of a drive device. [Diagram 3] 5A to 5C are diagrams illustrating an example of a structure for supporting a rotor shaft and a reduction shaft on a case. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. EXAMPLES

[0010] Fig. 1 is a diagram illustrating an example of a schematic configuration of an electric vehicle 10 to which the present invention is applied. In Fig. 1, the electric vehicle 10 is a hybrid vehicle equipped with an engine 12, a first electric motor MG1, and a second electric motor MG2. The electric vehicle 10 also includes drive wheels 14 and a power transmission device 16. The power transmission device 16 is provided in a power transmission path between the engine 12 and the drive wheels 14, and in a power transmission path between the second electric motor MG2 and the drive wheels 14.

[0011] The first electric motor MG1 and the second electric motor MG2 are each a known rotating electric machine, a so-called motor generator, and are provided in a non-rotatable case 18 that is a non-rotating member attached to the vehicle body.

[0012] The power transmission device 16 includes, within a case 18, a damper 20, an input shaft 22, a transmission section 24, a compound gear 26, a driven gear 28, a driven shaft 30, a final gear 32, a differential gear 34, a reduction gear 36, a reduction shaft 37, etc. The power transmission device 16 also includes a pair of drive shafts 38 connected to the differential gear 34, etc.

[0013] The damper 20 is connected to the crankshaft 12a of the engine 12. The input shaft 22 functions as an input rotating member of the transmission unit 24. The input shaft 22 is connected to the damper 20, and is connected to the crankshaft 12a via the damper 20. The transmission unit 24 is connected to the input shaft 22. The compound gear 26 is a rotating body on the output side of the transmission unit 24. The compound gear 26 has a drive gear 26a formed on a part of its outer circumferential surface. The drive gear 26a is an output rotating member of the transmission unit 24. The driven gear 28 is meshed with the drive gear 26a. The driven shaft 30 fixes the driven gear 28 and the final gear 32 so that they cannot rotate relative to each other. The final gear 32 has a smaller diameter than the driven gear 28, and meshes with the differential ring gear 34a. The reduction gear 36 has a smaller diameter than the driven gear 28 and is in mesh with the driven gear 28. The reduction shaft 37 is a gear shaft on which the reduction gear 36 is fixed so as not to rotate relative to the driven gear 28.

[0014] The second electric motor MG2 is an electric motor having a stator STmg2, a rotor core RCmg2, and a rotor shaft RSmg2. The rotor shaft RSmg2 is a rotor shaft of the second electric motor MG2. The rotor shaft RSmg2 is a hollow shaft connected to the rotor core RCmg2 on the radially inner side of the rotor core RCmg2 so as not to rotate relative to the rotor core RCmg2, and is connected to a reduction shaft 37 by spline fitting. The reduction shaft 37 has an inner circumferential surface on the reduction gear 36 side of the rotor shaft RSmg2 connected to an outer circumferential surface on the second electric motor MG2 side by spline fitting (see FIG. 3). The second electric motor MG2 is connected to the reduction gear 36 so as to be capable of transmitting power.

[0015] The transmission unit 24 includes a first electric motor MG1 and a differential mechanism 40. The differential mechanism 40 is a known single-pinion type planetary gear device including a sun gear S, a carrier CA, and a ring gear R. The sun gear S is connected to the first electric motor MG1 so as to be capable of transmitting power. The carrier CA is connected to the engine 12 via the input shaft 22 or the like so as to be capable of transmitting power. The ring gear R is formed on a part of the inner peripheral surface of the compound gear 26, and is connected integrally to the drive gear 26a. The differential mechanism 40 is a power split mechanism that mechanically splits the power of the engine 12 input to the carrier CA to the first electric motor MG1 and the drive gear 26a. The transmission unit 24 is a known electric transmission mechanism.

[0016] The power transmission device 16 has a first axis CL1, a second axis CL2, a third axis CL3, and a fourth axis CL4. These four axes CL1, CL2, CL3, and CL4 are parallel to one another. The first axis CL1 is a rotation axis of the input shaft 22, the transmission unit 24, and the first electric motor MG1. The second axis CL2 is a rotation axis of the driven gear 28, the driven shaft 30, and the final gear 32. The third axis CL3 is a rotation axis of the reduction gear 36 and the second electric motor MG2. The fourth axis CL4 is a rotation axis of the differential gear 34 and the drive shaft 38.

[0017] The case 18 includes a housing 18a as a first case, a case body 18b as a second case, and a cover 18c as a third case. An engine block 12b of the engine 12 is connected to an open portion of the housing 18a on the engine 12 side. The housing 18a and the case body 18b are connected together by fasteners such as bolts so that an open portion of the housing 18a on the opposite side to the engine 12 and an open portion of the case body 18b on the engine 12 side are aligned. The case body 18b and the cover 18c are connected together by fasteners so that the open portion of the case body 18b on the opposite side to the engine 12 is closed by the cover 18c.

[0018] The case body 18b includes a partition wall 18b1 that separates a gear chamber Rg that houses the differential gear 34, the helical gear 39, the differential mechanism 40, etc., from a motor chamber Rm that houses the first electric motor MG1 and the second electric motor MG2. The helical gear 39 is a gear pair that meshes with a reduction gear 36 as a first gear arranged on the third axis CL3 and a driven gear 28 as a second gear arranged on a second axis CL2 that is another rotation axis parallel to the third axis CL3. In the case 18, the gear chamber Rg is formed by joining the housing 18a and the case body 18b, and the motor chamber Rm is formed by joining the case body 18b and the cover 18c.

[0019] The electric vehicle 10 includes a power control unit (not shown), and the first electric motor MG1, the second electric motor MG2, and the like are controlled by the power control unit.

[0020] FIG. 2 is a diagram illustrating an example of a schematic configuration of the transaxle 50. FIG. 2(a) is a perspective view of the electric vehicle 10 from the front and left side. FIG. 2(b) is a side view of the electric vehicle 10 from the left side. In FIG. 2, the transaxle 50 is housed in a case 18. The transaxle 50 is a drive device including a power transmission device 16 (26a, 28, 32, 34a, 36, etc.) and a first electric motor MG1 and a second electric motor MG2. Note that the vertical direction, forward / reverse direction, and vehicle width direction in the figure indicate directions in a mounted state in the electric vehicle 10. The vehicle width direction is a horizontal direction perpendicular to the forward / reverse direction of the electric vehicle 10 and is parallel to the axial directions of each of the four axes CL1, CL2, CL3, and CL4.

[0021] The transaxle 50 is disposed such that each of the four axes CL1, CL2, CL3, and CL4 is parallel to the vehicle width direction when the transaxle 50 is mounted on the electric vehicle 10. When the transaxle 50 is mounted on the electric vehicle 10, the positions of the four axes CL1, CL2, CL3, and CL4 of the transaxle 50 are arranged in the following order in the vertical direction from top to bottom: second electric motor MG2, driven shaft 30, first electric motor MG1, and differential gear 34, and also in the following order from front to rear in the forward and reverse travel direction: first electric motor MG1, driven shaft 30, differential gear 34, and second electric motor MG2.

[0022] Fig. 3 is a diagram for explaining an example of a structure for supporting the rotor shaft RSmg2 and the reduction shaft 37 on the case 18. Fig. 3(a) and (b) are diagrams for explaining a support structure of a comparative example, and Fig. 3(c), (d), and (e) are diagrams for explaining the support structure of this embodiment. Fig. 3(d) is a partially enlarged view of the periphery of the second bearing BR2 and the periphery of the third bearing BR3 in Fig. 3(c). Fig. 3(a), (c), and (d) are cross-sectional views.

[0023] In Fig. 3, the electric vehicle 10 includes a first bearing BR1, a second bearing BR2, and a third bearing BR3 in the case 18. The first bearing BR1 is a ball bearing that rotatably supports the reduction shaft 37 in the housing 18a at an end of the reduction shaft 37 opposite to the second electric motor MG2 side. The second bearing BR2 is a ball bearing that rotatably supports the rotor shaft RSmg2 in the case main body 18b, particularly the partition wall 18b1, at an end of the rotor shaft RSmg2 on the reduction gear 36 side. The third bearing BR3 is a ball bearing that rotatably supports the rotor shaft RSmg2 in the cover 18c at an end of the rotor shaft RSmg2 opposite to the reduction gear 36 side.

[0024] 3A and 3B, in a structure in which the rotor shaft RSmg2 and the reduction shaft 37 are supported by bearings at three locations, a thrust load (also synonymous with thrust force) caused by the gear meshing reaction force of the helical gear 39 is transmitted to the rotor shaft RSmg2, and the rotor shaft RSmg2 may strike the cover 18c via the third bearing BR3. In this case, since the cover 18c is the outermost surface of the case 18 and has a large surface area, it is likely to become a sound-generating part, and the radiated sound caused by being struck may increase, which may deteriorate the NV.

[0025] 3(c), (d), and (e), the reduction shaft 37 has a large diameter portion 37a formed between the spline-fitted portion and the reduction gear 36, the large diameter portion 37a having a larger diameter than the spline-fitted portion. In addition, the rotor shaft RSmg2 has a stepped portion RSa formed adjacent to the end portion on the third bearing BR3 side, the stepped portion having a larger diameter than the end portion on the third bearing BR3 side.

[0026] The end face of the large diameter portion 37a on the second electric motor MG2 side is abutted against the end face of the inner race BR2i of the second bearing BR2 on the reduction gear 36 side. In addition, the side clearance, which is the clearance (also synonymous with gap) between the end face of the stepped portion RSa on the third bearing BR3 side and the end face of the third bearing BR3 on the second electric motor MG2 side, is made larger than the internal clearance of the second bearing BR2. The internal clearance of the second bearing BR2 is the backlash (also synonymous with gap) between the inner race BR2i and the outer race BR2o of the second bearing BR2 in the direction of the third axis CL3. When a thrust load is generated by the gear meshing reaction force of the helical gear 39, the backlash of the second bearing BR2 is filled before the side clearance. As a result, the thrust load is transmitted from the reduction shaft 37 to the case body 18b (partition wall 18b1), and the thrust load is received by the case body 18b. Since the partition wall 18b1 is located between the gear chamber Rg and the motor chamber Rm, it is possible to suppress radiated noise. Since the outermost cover 18c is not directly struck, radiated noise is less likely to be transmitted.

[0027] As described above, according to this embodiment, the end face of the large diameter portion 37a on the second electric motor MG2 side is abutted against the end face of the inner race BR2i of the second bearing BR2 on the reduction gear 36 side. In addition, the side clearance between the end face of the stepped portion RSa on the third bearing BR3 side and the end face of the third bearing BR3 on the second electric motor MG2 side is made larger than the internal clearance of the second bearing BR2. As a result, when a thrust force acting toward the second electric motor MG2 is generated on the reduction shaft 37 due to the gear meshing reaction force of the helical gear 39, the thrust force is applied to the inner race BR2i of the second bearing BR2. At this time, the backlash of the second bearing BR2 is eliminated before the side clearance. Therefore, the thrust force is transmitted to the partition wall 18b1 via the second bearing BR2 and received by the partition wall 18b1, and is difficult to be transmitted to the cover 18c, so that the cover 18c is difficult to become a sound-generating part. Since the partition wall 18b1 is located between the gear chamber Rg and the motor chamber Rm, even if a thrust force is transmitted to the partition wall 18b1, noise radiation to the outside of the case 18 is suppressed. Therefore, NV can be suppressed.

[0028] The above describes in detail an embodiment of the present invention based on the drawings, but what has been described above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0029] 10: Electric vehicle 18: Case 18a: Housing (first case) 18b: Case body (second case) 18b1: Partition (second case) 18c: Cover (third case) 28: Driven gear (second gear) 36: Reduction gear (first gear) 37: Reduction shaft (gear shaft) 37a: Large diameter section 39: Helical gear BR1: First bearing BR2: Second bearing BR2i: Inner race BR3: Third bearing CL2: Second axis (another axis of rotation parallel to the axis of rotation of the motor) CL3: Third axis (axis of rotation of the motor) MG2: Second motor (motor) RSmg2: Rotor shaft (rotor shaft of the motor) RSa: Step section Rg: Gear chamber Rm: Motor chamber

Claims

[Claim 1] An electric motor; a helical gear in which a first gear arranged on a rotation axis of the electric motor and a second gear arranged on another rotation axis parallel to the rotation axis of the electric motor are meshed with each other; a gear shaft, the first gear being fixed so as not to rotate relative to the rotor shaft of the electric motor, the outer circumferential surface of which is connected to an inner circumferential surface of the rotor shaft of the electric motor on the first gear side by spline fitting; a case having a first case, a second case, and a third case, the first case and the second case being joined together to form a gear chamber that houses the helical gear, and the second case being joined together to form a motor chamber that houses the electric motor; a first bearing that rotatably supports the gear shaft on the first case at an end of the gear shaft opposite to the electric motor side; a second bearing that rotatably supports the rotor shaft on the second case at an end of the rotor shaft on the first gear side; a third bearing that rotatably supports the rotor shaft on the third case at an end of the rotor shaft opposite to the first gear side; An electric vehicle comprising: the gear shaft has a large diameter portion formed between the spline-fitted portion and the first gear, the large diameter portion having a diameter larger than that of the spline-fitted portion, the rotor shaft has a stepped portion formed adjacent to an end portion of the rotor shaft on the third bearing side and having a diameter larger than that of the end portion of the rotor shaft on the third bearing side, an end surface of the large diameter portion on the electric motor side is brought into contact with an end surface of an inner race of the second bearing on the first gear side, an end face of the step portion facing the third bearing and an end face of the third bearing facing the electric motor, the end face being larger than an internal clearance of the second bearing;

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