Speed reducer and electric vehicle drive device

Abstract

To provide a speed reducer which can inhibit increase of the size of the device due to a higher speed reduction ratio, and to provide an electric vehicle drive device.SOLUTION: A planetary gear part 101 includes: planetary gears 7 which are disposed at intervals in a circumferential direction at the radial outer side of a sun gear 6; carriers 8 each of which holds the planetary gear 7 and may rotate coaxially with the sun gear 6; a first ring gear 9 located at the radial outer side of the respective planetary gears 7 and fixed to an inner wall of a housing 100; and a second ring gear 10 which is located at the radial outer side of the respective planetary gears 7 and may rotate coaxially with the sun gear 6. The planetary gear part 101 outputs a speed ratio of the sun gear 6 and the second ring gear 10. A differential part 12 is installed coupled to the second ring gear 10. In the carrier 8, a position in an axial direction Y is restricted such that an other end side Y2 in the axial direction Y is restricted by a first restriction part 13 installed at the housing 100 and one end side Y1 in the axial direction Y is restricted by a second restriction part 14 installed at the differential part 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a speed reducer and an electric vehicle drive device. [Background technology]

[0002] Conventional electric vehicle drive devices are composed of a motor unit, a reduction gear mechanism with two output shafts that can be driven differentially using a gear mechanism, and an inverter. The motor unit accounts for a relatively large proportion of the overall weight and size. For this reason, the reduction gear ratio on the reduction gear mechanism side is often increased and combined with a motor unit that enables high-speed rotation, thereby reducing the torque required for the motor unit and making the motor unit smaller and lighter. However, this comes at the expense of making the reduction gear mechanism larger, so there is a demand for a reduction gear mechanism that is compact yet capable of achieving a high reduction gear ratio.

[0003] For example, Patent Document 1 discloses a planetary reduction mechanism that uses stepped planetary gears, fixes the ring gear, and derives the speed ratio between the sun gear and the carrier, and achieves miniaturization by making the motor shaft and the reducer shaft coaxial and passing the drive shaft through the motor shaft of the motor section.

[0004] Also, for example, Patent Document 2 discloses a mechanism that uses two stages of planetary gears and two separate stages of ring gears, with the output being the second stage ring gear. In such a mechanism, it is possible to obtain a reduction ratio based on the difference in the number of teeth of the front and rear gear sets, and by selecting a number of teeth that minimizes the difference, it is possible to obtain a very high reduction ratio without increasing the diameter of the entire planetary gear mechanism. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-142774 A [Patent Document 2] Patent No. 6782494 Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional planetary gear mechanisms such as that in Patent Document 1, the ratio of the number of teeth to the number of teeth is the reduction ratio, so increasing the reduction ratio is a dilemma that requires increasing the diameter of the entire planetary gear mechanism. One way to make the sun gear as small as possible is to make it as small as possible, but since the differential mechanism is provided coaxially with the input and output shafts, one of the drive shafts passes through the inside of the sun gear, and therefore the minimum diameter of the sun gear must necessarily be larger than the drive shaft, which means there is little room for innovation.

[0007] Furthermore, in conventional reduction gear mechanisms and electric vehicle drive devices such as those disclosed in Patent Document 2, the number of parts in the planetary gear mechanism is increased, which poses a problem that including a differential mechanism results in an increase in the axial size of the entire reduction gear mechanism.

[0008] The present disclosure discloses a technique for solving the above problems, An object of the present invention is to provide a reducer and an electric vehicle drive device in which an increase in size of the device due to a high reduction ratio is suppressed. [Means for solving the problem]

[0009] The reducer according to the present disclosure comprises: a planetary gear unit that reduces the speed of rotation of a motor shaft of the motor unit to increase torque; a differential unit that absorbs a relative rotation difference between left and right wheels of a vehicle and transmits the power after reduction in speed by the planetary gear unit to the left and right wheels of the vehicle, the differential unit being installed inside a housing, The planetary gear portion is a sun gear that is coupled to one axial end of the motor shaft and rotates on its axis; a plurality of planetary gears arranged at intervals in a circumferential direction and meshing with the radially outer side of the sun gear; a carrier that holds each of the planetary gears and is rotatable coaxially with the sun gear; a first ring gear that meshes with the radially outer side of each of the planetary gears and is fixed to an inner wall of the housing; a second ring gear that meshes with the radially outer side of each of the planetary gears and is rotatable coaxially with the sun gear, the planetary gear unit outputs a speed ratio between the sun gear and the second ring gear, The differential portion is The second ring gear is coupled and installed; The carrier is The other end of the axial direction is regulated by a first regulating portion installed on the housing, and one end of the axial direction is regulated by a second regulating portion installed on the differential portion. It is something. In addition, the electric vehicle drive device according to the present disclosure includes: An electric vehicle drive device including the motor unit and the above-described reduction gear, A drive shaft for rotating left and right wheels of the vehicle is provided, The drive shaft is assembled and installed in the differential portion. It is something. Effect of the Invention

[0010] According to the reduction gear and electric vehicle drive device of the present disclosure, It is possible to suppress the increase in size of the device due to the high reduction ratio. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing the configuration of an electric vehicle driving device using a reduction gear and a motor unit according to a first embodiment. [Diagram 2] 2 is a cross-sectional view showing a cross section of the reduction gear of the electric vehicle driving device shown in FIG. 1 along line HH. [Diagram 3] 2 is a cross-sectional view showing a cross section of the reduction gear of the electric vehicle driving device shown in FIG. 1 along line TT. [Figure 4] 4 is a cross-sectional view showing the configuration of another reducer according to embodiment 1. FIG. [Diagram 5]FIG. 5A is a cross-sectional view showing the configuration of another bearing at one axial end according to embodiment 1, and FIG. 5B is a cross-sectional view showing the configuration of another bearing at the other axial end according to embodiment 1. [Figure 6] FIG. 6A is a cross-sectional view showing the configuration of another bearing at one axial end according to embodiment 1, and FIG. 6B is a cross-sectional view showing the configuration of another bearing at the other axial end according to embodiment 1. [Figure 7] 6 is a cross-sectional view showing the configuration of another bearing at one end in the axial direction according to embodiment 1. FIG. [Figure 8] FIG. 8A is a cross-sectional view showing the configuration of a motor shaft and a sun gear of a motor section of an electric vehicle driving device according to embodiment 2, and FIG. 8B is a cross-sectional view showing the configuration of the motor shaft shown in FIG. 8A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Preferred embodiments of an electric drive device according to this disclosure will be described below with reference to the drawings, and the same or corresponding parts in each drawing will be described with the same reference numerals. Note that the size and scale of each corresponding component part in each drawing are independent. Furthermore, within the scope of this disclosure, each embodiment can be freely combined, modified, or omitted as appropriate.

[0013] Embodiment 1 Fig. 1 is a cross-sectional view showing the configuration of an electric vehicle driving device including a reducer and a motor unit according to embodiment 1. Fig. 2 is a cross-sectional view showing a cross section of the reducer of the electric vehicle driving device shown in Fig. 1, taken along line HH. Fig. 3 is a cross-sectional view showing a cross section of the reducer of the electric vehicle driving device shown in Fig. 1, taken along line TT. Fig. 4 is a cross-sectional view showing the configuration of another reducer according to embodiment 1.

[0014] Fig. 5A is a cross-sectional view showing the configuration of another bearing at one axial end according to embodiment 1. Fig. 5B is a cross-sectional view showing the configuration of another bearing at the other axial end according to embodiment 1. Fig. 6A is a cross-sectional view showing the configuration of another bearing at one axial end according to embodiment 1. Fig. 6B is a cross-sectional view showing the configuration of another bearing at the other axial end according to embodiment 1. Fig. 7 is a cross-sectional view showing the configuration of another bearing at one axial end according to embodiment 1.

[0015] In FIG. 1, the electric vehicle drive device 1 includes a motor section 2 having a hollow motor shaft 11, and a reduction gear 3. The axial direction of the motor shaft 11 is the axial direction Y, the side opposite to the motor section 2 in the axial direction Y is the one end side Y1, and the motor section 2 side is the other end side Y2. The reduction gear 3 includes a planetary gear section 101 that reduces the rotation of the motor shaft 11 to increase the torque, and a differential section 12 that transmits the power after reduction by the planetary gear section 101 to the left and right wheels of the vehicle by absorbing the relative rotation difference between the left and right wheels of the vehicle, inside a housing 100. The housing 100 includes a housing section 4 having an opening 40 at one end side Y1 in the axial direction Y, and a cover section 5 that closes the opening 40 of the housing section 4 to form a sealed structure. The housing 100 is formed of, for example, an aluminum material.

[0016] The motor shaft 11 is supported by the housing 100 via a third bearing 15. The planetary gear unit 101 includes a sun gear 6, a plurality of planetary gears 7 and a carrier 8, a first ring gear 9, and a second ring gear 10. The sun gear 6 is coupled to one end side Y1 of the motor shaft 11 in the axial direction Y, and rotates by receiving power from the motor shaft 11. Here, the sun gear 6 is formed integrally with the motor shaft 11. The planetary gear 7 meshes with the radial outside of the sun gear 6, and a plurality of planetary gears 7, three in this example, are arranged at intervals in the circumferential direction (see Figs. 2 and 3). The number of planetary gears 7 is not limited to three.

[0017] The carrier 8 holds each planetary gear 7 and is formed to be rotatable coaxially with the sun gear 6. A first bearing 13 as a first regulating part installed in the housing part 4 of the housing 100 is installed on the other end side Y2 of the carrier 8 in the axial direction Y, and a second bearing 14 as a second regulating part installed in the differential part 12 is installed on one end side Y1 of the carrier 8 in the axial direction Y, thereby regulating the position of the carrier 8 in the axial direction Y. Note that the fact that the position of the carrier 8 in the axial direction Y is regulated means that the position of each planetary gear 7 in the axial direction Y is also regulated in the same way. The first bearing 13 and the second bearing 14 are formed of, for example, thrust bearings of balls, cylindrical rollers, or needle rollers.

[0018] The first ring gear 9 meshes with the radially outer sides of each planetary gear 7 and is fixed to the inner wall of the housing 100. The first ring gear 9 is installed by press-fitting into the housing part 4, or fixed by screwing or shrink fitting. The second ring gear 10 meshes with the radially outer sides of each planetary gear 7 and is formed to be rotatable coaxially with the sun gear 6. The second ring gear 10 is installed by being integrally connected to the differential part 12 by, for example, screwing or welding.

[0019] Here, the planetary gear 7 has a single tooth type and is formed to mesh with the sun gear 6 as well as with both the first ring gear 9 and the second ring gear 10. Because of this configuration, the planetary gear 7 and the carrier 8 are positioned in the axial direction Y in a relatively rotatable state. The planetary gear unit 101 outputs the speed ratio between the sun gear 6 and the second ring gear 10.

[0020] One end side Y1 of the differential part 12 in the axial direction Y is rotatably installed on the cover part 5 of the housing 100 via a fifth bearing 17. At least a part of the differential part 12 is disposed in an inner space S surrounded by the planetary gears 7. Furthermore, a part of the differential part 12 is disposed inside one end side Y1 of the motor shaft 11 in the axial direction Y, and a fourth bearing 16 is disposed between the inner wall of the motor shaft 11 and the differential part 12. The drive shaft 18 is assembled to the differential part 12 and is disposed so as to penetrate the motor shaft 11 and the cover part 5. The drive shaft 18 rotates the left and right wheels of the vehicle.

[0021] According to the electric vehicle driving device 1 of the first embodiment configured as described above, a high reduction ratio can be achieved by using the first ring gear 9 and the second ring gear 10. Furthermore, by disposing a part of the differential part 12 in the inner space S surrounded by the planetary gears 7, the speed reducer 3 and therefore the electric vehicle driving device 1 can be made compact without increasing in size in the axial direction Y. Furthermore, by providing the second ring gear 10 and the second bearing 14 in the differential part 12, the number of parts can be reduced.

[0022] Furthermore, the housing 100 that houses the reducer 3 has an opening 40 of the housing section 4 on the side of the differential section 12 opposite the motor section 2, and the opening 40 is sealed with the lid section 5. As a result, when assembling the reducer 3, the lid section 5 is removed, the first ring gear 9 is inserted through the opening 40, and the first ring gear 9 is fixed to the inner wall of the housing section 4 for assembly. Thereafter, the freely rotatable planetary gear 7 and carrier 8, the second ring gear 10, and the differential section 12 can be assembled while rotating. This improves ease of assembly.

[0023] In the above embodiment 1, an example is shown in which the motor unit 2 is installed in one housing 100 in the electric vehicle driving device 1, but the electric vehicle driving device 1 may also be formed by forming the housing 100 that houses the motor unit 2 and the reducer 3 and the housing that houses the motor unit 2 separately and fastening these housings together by screws or the like.

[0024] In addition, in the above embodiment 1, an example was shown in which the planetary gear 7 is formed with a single tooth type so as to mesh with the sun gear 6 and also with both the first ring gear 9 and the second ring gear 10, but this is not limited to this, and as shown in Figure 4, the same can be done using a planetary gear 7 in which the first gear portion 70 that meshes with the first ring gear 9 and the second gear portion 71 that meshes with the second ring gear 10 are formed with gears of different tooth types, and the same effect can be achieved.

[0025] In the above-mentioned first embodiment, the first bearing 13 and the second bearing 14 are formed by thrust bearings, but the present invention is not limited to this, and the shapes may be appropriately changed. For example, the first bearing 13 and the second bearing 14 may be formed by radial bearings with balls, cylindrical rollers, or needle rollers as shown in Figures 5A and 5B, or may be formed by radial bearings with tapered rollers as shown in Figures 6A and 6B. In addition, in Figures 1, 5, and 6, the first bearing 13 is supported by the housing 4, but the shape of the first ring gear 9 may be changed and the first bearing 13 may be supported by the housing 4 via the first ring gear 9 as shown in Figure 7.

[0026] Moreover, the planetary gear portion 101 may be configured with a helical gear. If a helical gear is used, it is possible to increase the meshing ratio compared to a spur gear, which is advantageous for strength design and improves noise and vibration performance when the gears mesh.

[0027] According to the reducer of the first embodiment configured as described above, a planetary gear unit that reduces the speed of rotation of a motor shaft of the motor unit to increase torque; a differential unit that absorbs a relative rotation difference between left and right wheels of a vehicle and transmits the power after reduction in speed by the planetary gear unit to the left and right wheels of the vehicle, the differential unit being installed inside a housing, The planetary gear portion is a sun gear that is coupled to one axial end of the motor shaft and rotates on its axis; a plurality of planetary gears arranged at intervals in a circumferential direction and meshing with the radially outer side of the sun gear; a carrier that holds each of the planetary gears and is rotatable coaxially with the sun gear; a first ring gear that meshes with the radially outer side of each of the planetary gears and is fixed to an inner wall of the housing; a second ring gear that meshes with the radially outer side of each of the planetary gears and is rotatable coaxially with the sun gear, the planetary gear unit outputs a speed ratio between the sun gear and the second ring gear, The differential portion is The second ring gear is coupled and installed; The carrier is Since the axial position is restricted by a first restricting portion whose other axial end is installed on the housing and a second restricting portion whose one axial end is installed on the differential portion, By using the first ring gear and the second ring gear, a high reduction ratio can be achieved, which allows the size of the device to be made smaller. Furthermore, by integrating the second ring gear with the differential section, the axial size can be shortened, resulting in a reduction in the number of parts. Furthermore, by providing the first and second regulating sections to the differential section, the axial positions of the planetary gear and the carrier can be regulated.

[0028] Furthermore, according to the reducer of the first embodiment configured as described above, At least a portion of the differential portion is disposed in an inner space surrounded by each of the planetary gears, This enables the axial size of the reducer to be shortened, resulting in a reduction in the number of parts.

[0029] Furthermore, according to the reducer of the first embodiment configured as described above, The motor shaft is formed as a hollow shaft, a portion of the differential portion is disposed inside one end side of the motor shaft in the axial direction, Since a bearing is provided between the inner wall of the motor shaft and the differential portion, This enables the axial size of the reducer to be reduced.

[0030] Furthermore, according to the reducer of the first embodiment configured as described above, The housing includes: an opening on a side opposite to the motor unit in the axial direction; a lid portion that closes the opening, The differential portion is mounted on the cover portion via a bearing, The ease of assembling the reducer can be improved.

[0031] Furthermore, according to the reducer of the first embodiment configured as described above, Since the planetary gear portion is formed of a helical gear, This provides an advantage in the strength design of the reducer, improving noise and vibration performance when the gears mesh.

[0032] Furthermore, according to the electric vehicle driving device of the first embodiment configured as described above, An electric vehicle drive device including the motor unit and the above-described reduction gear, A drive shaft for rotating left and right wheels of the vehicle is provided, The drive shaft is assembled and installed in the differential portion, It is possible to suppress the increase in size of the device due to the high reduction ratio.

[0033] Embodiment 2 In the above-mentioned first embodiment, an example was shown in which the motor shaft 11 of the motor section 2 and the sun gear 6 were formed integrally, but in the present second embodiment, a case will be described in which the motor shaft 11 of the motor section 2 and the sun gear 6 are formed separately and then assembled. FIG. 8A is a cross-sectional view showing the configuration of the motor shaft and sun gear of the motor section of an electric vehicle driving device according to the second embodiment. FIG. 8B is a cross-sectional view showing the configuration of the motor shaft shown in FIG. 8A. In the figure, the same parts as those in the above-mentioned first embodiment are given the same reference numerals and the description thereof will be omitted.

[0034] In the figure, a male spline portion 261 is formed on the motor shaft 11, and a female spline portion 262 is formed on the sun gear 6. The sun gear 6 is inserted into the motor shaft 11, and the male spline portion 261 of the motor shaft 11 and the female spline portion 262 of the sun gear 6 are engaged to form the spline portion 26. This allows the motor shaft 11 and the sun gear 6 to be engaged. Then, the torque generated by the motor section 2 is transmitted to the reducer 3. Furthermore, after the sun gear 6 is inserted into the motor shaft 11, a stopper 25 may be provided and fixed on the motor shaft 11 to regulate the position of one end side Y1 in the axial direction Y.

[0035] In this way, since the sun gear 6 and the motor shaft 11 are formed separately, the motor shaft 11 can be processed easily, the third bearing 15 that supports the motor shaft 11 can be pressed in easily, and the assembly of the motor section 2 is improved.

[0036] According to the reducer of the second embodiment configured as described above, the same effects as those of the first embodiment can be obtained, and in addition, Since the sun gear is formed separately from the motor shaft, The assembly of the reducer is improved.

[0037] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless modifications not exemplified are assumed within the scope of the technology disclosed in this specification, including, for example, modifying, adding, or omitting at least one component, and further, extracting at least one component and combining it with a component of another embodiment.

[0038] Various aspects of the present disclosure are summarized below as appendices.

[0039] (Appendix 1) a planetary gear unit that reduces the speed of rotation of a motor shaft of the motor unit to increase torque; a differential unit that absorbs a relative rotation difference between left and right wheels of a vehicle and transmits the power after reduction in speed by the planetary gear unit to the left and right wheels of the vehicle, the differential unit being installed inside a housing, The planetary gear portion is a sun gear that is coupled to one axial end of the motor shaft and rotates on its axis; a plurality of planetary gears arranged at intervals in a circumferential direction and meshing with the radially outer side of the sun gear; a carrier that holds each of the planetary gears and is rotatable coaxially with the sun gear; a first ring gear that meshes with the radially outer side of each of the planetary gears and is fixed to an inner wall of the housing; a second ring gear that meshes with the radially outer side of each of the planetary gears and is rotatable coaxially with the sun gear, the planetary gear unit outputs a speed ratio between the sun gear and the second ring gear, The differential portion is The second ring gear is coupled and installed; The carrier is A reducer whose axial position is regulated by a first regulating section whose other axial end side is installed on the housing and a second regulating section whose one axial end side is installed on the differential section. (Appendix 2) 2. The reducer according to claim 1, wherein at least a portion of the differential portion is disposed in an inner space surrounded by each of the planetary gears. (Appendix 3) The motor shaft is formed as a hollow shaft, a portion of the differential portion is disposed inside one end side of the motor shaft in the axial direction, 3. The reducer according to claim 1 or 2, further comprising a bearing between an inner wall of the motor shaft and the differential portion. (Appendix 4) The housing includes: an opening on a side opposite to the motor unit in the axial direction; a lid portion that closes the opening, The reducer according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the differential portion is mounted on the cover portion via a bearing. (Supplementary Note 5) The reducer according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the planetary gear portion is formed of a helical gear. (Supplementary Note 6) The reducer according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the sun gear is formed separately from the motor shaft. (Supplementary Note 7) An electric vehicle drive device including the motor unit and the reduction gear according to any one of Supplementary Note 1 to Supplementary Note 6, A drive shaft for rotating left and right wheels of the vehicle is provided, The drive shaft is assembled to the differential portion and installed in the electric vehicle drive device. [Explanation of symbols]

[0040] 1 Electric vehicle drive device, 2 Motor unit, 3 Speed ​​reducer, 4 Housing unit, 5 Cover unit, 6 sun gear, 7 planetary gear, 70 first gear section, 71 second gear section, 8 carrier, 9 first ring gear, 10 second ring gear, 100 housing, 11 motor shaft, 12 differential portion, 13 first bearing, 14 second bearing, 15 third bearing, 16 fourth bearing, 17 fifth bearing, 18 drive shaft, 25 stopper, 26 spline portion, 261 male spline portion, 262 female spline portion, S Inner space, Y axis direction, Y1 one end side, Y2 other end side.

Claims

1. a planetary gear unit that reduces the speed of rotation of a motor shaft of the motor unit to increase torque; a differential unit that absorbs a relative rotation difference between left and right wheels of a vehicle and transmits the power after reduction in speed by the planetary gear unit to the left and right wheels of the vehicle, the differential unit being installed inside a housing, The planetary gear portion is a sun gear that is coupled to one axial end of the motor shaft and rotates on its axis; a plurality of planetary gears arranged at intervals in a circumferential direction and meshing with the radially outer side of the sun gear; a carrier that holds each of the planetary gears and is rotatable coaxially with the sun gear; a first ring gear that meshes with the radially outer side of each of the planetary gears and is fixed to an inner wall of the housing; a second ring gear that meshes with the radially outer side of each of the planetary gears and is rotatable coaxially with the sun gear, the planetary gear unit outputs a speed ratio between the sun gear and the second ring gear, The differential portion is The second ring gear is coupled and installed; The carrier is A reducer whose axial position is regulated by a first regulating portion whose other axial end side is installed on the housing and a second regulating portion whose one axial end side is installed on the differential portion.

2. The reducer according to claim 1 , wherein at least a portion of the differential portion is disposed in an inner space surrounded by each of the planetary gears.

3. The motor shaft is formed as a hollow shaft, a portion of the differential portion is disposed inside one end side of the motor shaft in the axial direction, 3. The reducer according to claim 1, further comprising a bearing provided between an inner wall of the motor shaft and the differential portion.

4. The housing includes: an opening on a side opposite to the motor unit in the axial direction; a lid portion that closes the opening, The reducer according to claim 1 or 2, wherein the differential portion is mounted on the cover portion via a bearing.

5. 3. The reducer according to claim 1, wherein the planetary gear portion is formed of a helical gear.

6. The reducer according to claim 1 or 2, wherein the sun gear is formed separately from the motor shaft.

7. An electric vehicle drive device including the motor unit and the reduction gear according to claim 1 or 2, A drive shaft for rotating left and right wheels of the vehicle is provided, The drive shaft is assembled to the differential portion and installed in the electric vehicle drive device.

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