Drive system for electric vehicles

Abstract

To provide a drive device for an electric vehicle capable of suppressing resonance of motor noise generated from a pair of electric motors without complicating the structure.SOLUTION: A first reduction gear 20 and a second reduction gear 24 stored in a case 26 of a drive device 12 have mutually different characteristic frequencies so as to suppress the mutual excitation caused by the transmission of the vibration (motor noise) generated from a first electric motor MG1 and the vibration (motor noise) from a second electric motor MG2 through the first reduction gear 20 and the second reduction gear 24. Since the noise characteristics of the first reduction gear 20 and the second reduction gear 24 differ from each other, a peak of the combined noise level is reduced. Therefore, the vibration level of the drive device 12 is suppressed without complicating the structure of the drive device 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a drive device for an electric vehicle in which a first electric motor rotationally drives a first drive wheel via a second speed reducer, and a second electric motor rotationally drives a second drive wheel via the second speed reducer. In particular, the present invention relates to a technique for suppressing the generation of vibration and noise from a drive unit while avoiding an increase in the size of the drive device.

Background Art

[0002] A drive device for an electric vehicle in which a first electric motor rotationally drives a first drive wheel via a first speed reducer, and a second electric motor rotationally drives a second drive wheel via a second speed reducer is known. For example, the drive device for an electric vehicle described in Patent Document 1 is such a device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] When the first speed reducer and the second speed reducer are speed reduction mechanisms of the same principle, and the first electric motor and the second electric motor have the same rotational speed, vibrations generated from the first electric motor, known as motor noise, and vibrations from the second electric motor are transmitted through the first speed reducer and the second speed reducer, causing them to vibrate against each other and potentially increasing the vibration due to resonance. On the other hand, according to the drive device for an electric vehicle described in the above-cited Document 1, the first speed reducer and the second speed reducer are composed of one of different types of speed reduction mechanisms, such as a gear type speed reduction mechanism, a belt type speed reduction mechanism, or a reduction chain type speed reduction mechanism, and another one. Therefore, since the vibration characteristics of the first electric motor and the first speed reducer and the second electric motor and the second speed reducer are different, the vibrations generated from the first electric motor and the vibrations from the second electric motor do not vibrate against each other, suppressing an increase in the vibration of the drive device.

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, in the electric vehicle drive system described in Reference 1, the first and second reduction gears are composed of reduction mechanisms using different reduction principles. For example, if the first reduction gear is composed of a reduction gear mechanism, the second reduction gear will be composed of a belt-type reduction mechanism or a chain-type reduction mechanism. Thus, when the first and second reduction gears are composed of reduction mechanisms using different reduction principles, there is a drawback in that the number of parts increases, making the structure of the electric vehicle drive system more complex.

[0006] The present invention was made against the background described above. The object of the present invention is to provide a drive system for electric vehicles that can suppress the resonance of motor noise generated from a pair of electric motors without complicating the structure. [Means for solving the problem]

[0007] 1 The gist of the invention is a drive system for an electric vehicle in which (a) a first electric motor drives a first drive wheel via a first reduction gear and a second electric motor drives a second drive wheel via a second reduction gear, (b) the first reduction gear and the second reduction gear are composed of the same type of reduction mechanism, and (c) the first reduction gear and the second reduction gear have different natural frequencies (d) The first reduction gear and the second reduction gear are each composed of the same number of power transmission components, (e) at least one of the multiple power transmission components of the first reduction gear and at least one of the multiple power transmission components of the second reduction gear that corresponds to at least one of the multiple power transmission components of the first reduction gear have different masses, and (f) a parking lock gear constituting part of the parking lock mechanism is provided on either at least one of the multiple power transmission components of the first reduction gear or at least one of the multiple power transmission components of the second reduction gear that corresponds to at least one of the multiple power transmission components of the first reduction gear. It is the matter. The gist of the second invention is a drive system for an electric vehicle of the type in which (a) a first electric motor drives a first drive wheel via a first reduction gear and a second electric motor drives a second drive wheel via a second reduction gear, (b) the first reduction gear and the second reduction gear are composed of the same type of reduction mechanism, (c) the first reduction gear and the second reduction gear have different natural frequencies, (d) the first reduction gear and the second reduction gear are each composed of the same number of multiple power transmission components, (e) at least one of the multiple power transmission components of the first reduction gear and at least one of the multiple power transmission components of the second reduction gear that corresponds to at least one of the multiple power transmission components of the first reduction gear have different masses, and (f) an oil pump is provided in either at least one of the multiple power transmission components of the first reduction gear or at least one of the multiple power transmission components of the second reduction gear that corresponds to at least one of the multiple power transmission components of the first reduction gear. The gist of the third invention is that, in the first or second invention, (g) at least one of the plurality of power transmission components of the first reduction gear and at least one of the plurality of power transmission components of the second reduction gear that corresponds to the plurality of power transmission components of the first reduction gear have different rigidities from each other. [Effects of the Invention]

[0008] 1 According to the electric vehicle drive system of the invention, the first reduction gear and the second reduction gear have different natural frequencies. As a result, the noise characteristics of the first reduction gear and the second reduction gear differ from each other, and the combined noise Z The peak level is reduced. Therefore, the vibration level of the drive unit is suppressed without complicating the structure of the drive unit. Furthermore, since at least one of the multiple power transmission components of the first reduction gear and at least one of the multiple power transmission components of the second reduction gear that corresponds to the multiple power transmission components of the first reduction gear have different rotational inertia, a difference in dynamic stiffness is formed between the first and second reduction gears, resulting in different natural frequencies. This reduces the peak of the combined noise level and suppresses the vibration level of the drive system. In addition, since the mass of the power transmission component on which the parking lock gear is installed is substantially larger than the mass of the other power transmission component, the first and second reduction gears have different inertial masses, forming a difference in dynamic stiffness. This reduces the peak of the combined noise level and suppresses the vibration level of the drive system. According to the electric vehicle drive system of the second invention, the first reduction gear and the second reduction gear have different natural frequencies. As a result, the noise characteristics of the first reduction gear and the second reduction gear are different, so the peak of the combined noise level is reduced. Therefore, the vibration level of the drive system is suppressed without complicating the structure of the drive system. Furthermore, at least one of the multiple power transmission components of the first reduction gear and at least one of the multiple power transmission components of the second reduction gear that corresponds to at least one of the multiple power transmission components of the first reduction gear have different rotational inertia. As a result, a difference in dynamic stiffness is formed between the first reduction gear and the second reduction gear, resulting in different natural frequencies, which reduces the peak of the combined noise level and suppresses the vibration level of the drive system. Moreover, since the mass of the power transmission component on which the oil pump is installed is substantially larger than the mass of the other power transmission component, the first reduction gear and the second reduction gear have different inertial masses, forming a difference in dynamic stiffness, which reduces the peak of the combined noise level and suppresses the vibration level of the drive system. According to the electric vehicle drive system of the third invention, a state in which the components have different rigidities is achieved, for example, by having different outer diameters, different hole shapes, or different materials. As a result, the first and second reduction gears have different dynamic rigidities, which reduces the peak of the combined noise level and suppresses the vibration level of the drive system.

[0013] Preferably, the first reduction gear and the second reduction gear are configured to have the same reduction ratio from a gear-type reduction mechanism, and the first motor and the first reduction gear and the second motor and the second reduction gear are arranged symmetrically with respect to the center line of the drive unit. This maintains the center of gravity of the drive unit in the center of the width direction of the electric vehicle.

[0014] Preferably, the first rotor shaft of the first electric motor and the second rotor shaft of the second electric motor are arranged concentrically in a direction perpendicular to the center line. The first reduction gear includes a first input shaft concentrically connected to the first rotor shaft, a first counter shaft arranged parallel to the first input shaft and having outer teeth that mesh with the outer teeth of the first input shaft, a first reduction gear shaft arranged parallel to the first counter shaft and having large-diameter teeth that mesh with the outer teeth of the first counter shaft and small-diameter teeth smaller in diameter than the large-diameter teeth, and a first output shaft arranged parallel to the first reduction gear shaft and having a first ring gear that meshes with the small-diameter teeth. The second reduction gear comprises a second input shaft concentrically connected to the second rotor shaft, a second counter shaft having outer teeth that mesh with the outer teeth of the second input shaft and arranged parallel to the second input shaft and concentrically with the first counter shaft, a second reduction gear shaft having large-diameter teeth that mesh with the outer teeth of the second counter shaft and small-diameter teeth smaller in diameter than the large-diameter teeth and arranged parallel to the second counter shaft and concentrically with the reduction gear shaft, and a second output shaft having a second ring gear that meshes with the small-diameter teeth and arranged parallel to the second reduction gear shaft and concentrically with the first output shaft. As a result, the first reduction gear and the second reduction gear are composed of the same type of reduction mechanism, i.e., a gear-type reduction mechanism, so common parts can be used with each other, and the structure of the drive unit is not complicated. [Brief explanation of the drawing]

[0015] [Figure 1] This is a diagram illustrating a drive system for an electric vehicle, which is one embodiment of the present invention. [Modes for carrying out the invention]

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Examples]

[0017] Figure 1 is an exploded view showing a cross-section of the power transmission components described later, passing through the rotation axes C1, C2, C3, and C4, in order to explain the drive unit 12 of an electric vehicle 10 according to one embodiment of the present invention. In Figure 1, the drive unit 12 comprises a first electric motor MG1 and a second electric motor MG2, which are independent power sources for driving the electric vehicle 10; a first reduction gear 20 that reduces the rotation of the first electric motor MG1 and outputs it to one of the first drive wheels 18 located on the left side in Figure 1; a second reduction gear 24 that reduces the rotation of the second electric motor MG2 and outputs it to the other second drive wheel 22 located on the right side in Figure 1; and a case 26 that houses the first electric motor MG1 and the first reduction gear 20, and the second electric motor MG2 and the second reduction gear 24.

[0018] The case 26 preferably includes a central bulkhead 28 along a centerline CL passing through the center of the width direction of the electric vehicle 10. The inside of the case 26 is divided symmetrically with respect to the centerline CL by the central bulkhead 28 into a first motor room 30 housing the first motor MG1 and a first reduction gear room 31 housing the first reduction gear 20, and a second motor room 32 housing the second motor MG2 and a second reduction gear room 33 housing the second reduction gear 24. The first motor MG1 and the second motor MG2, and the first reduction gear 20 and the second reduction gear 24 are arranged symmetrically with respect to the centerline CL. The power transmission components constituting the first reduction gear 20 and the power transmission components constituting the second reduction gear 24 are also configured symmetrically with respect to the centerline CL and are arranged symmetrically with respect to the centerline CL.

[0019] The first electric motor MG1 has a cylindrical first stator 34 fixed in position and a first rotor 38 rotatably supported on the inner circumferential side thereof by a first rotor shaft 36. The second electric motor MG2 has a cylindrical second stator 40 fixed in position and a second rotor 44 rotatably supported on the inner circumferential side thereof by a second rotor shaft 42. The first rotor shaft 36 and the second rotor shaft 42 are provided concentrically in a direction orthogonal to the center line CL in FIG. 1. That is, the first rotor shaft 36 and the second rotor shaft 42 are rotatably supported by the case 26 via a pair of bearings 45 and a pair of bearings 46, respectively, around a rotation axis C1 orthogonal to the center line CL in FIG. 1.

[0020] The first speed reducer 20 has four power transmission components involved in power transmission. The four power transmission components include a first input shaft 48, a first reduction gear shaft 52, and a first output shaft 54 that are parallel to each other. Similarly, the second speed reducer 24 is composed of four power transmission components involved in power transmission, the same as those of the first speed reducer 20, and has the same reduction ratio as the first speed reducer 20. The four power transmission components include a second input shaft 56, a second reduction gear shaft 60, and a second output shaft 62 that are parallel to each other. The first input shaft 48 and the second input shaft 56, the first reduction gear shaft 52 and the second reduction gear shaft 60, and the first output shaft 54 and the second output shaft 62 are configured similarly to each other except for the differences described later.

[0021] The first input shaft 48 is supported via a pair of bearings 64 so as to be rotatable around a rotation axis C1 orthogonal to the center line CL while being connected to the first rotor shaft 36 by spline fitting. The first input shaft 48 has external teeth 48a. The second input shaft 56 is supported via a pair of bearings 66 so as to be rotatable around the rotation axis C1 while being connected to the second rotor shaft 42 by spline fitting. The second input shaft 56 has external teeth 56a. The first input shaft 48 and the second input shaft 56 are concentric.

[0022] The first reduction gear shaft 52 includes a large-diameter gear 52a that meshes with the outer peripheral teeth 48a, and a small-diameter gear 52b that is smaller in diameter than the large-diameter gear 52a. The first reduction gear shaft 52 is supported via a pair of bearings 72 so as to be rotatable about a rotation axis C2 parallel to the rotation axis C1. The second reduction gear shaft 60 includes a large-diameter gear 60a that meshes with the outer peripheral teeth 56a, and a small-diameter gear 60b that is smaller in diameter than the large-diameter gear 60a. The second reduction gear shaft 60 is supported via a pair of bearings 74 so as to be rotatable about a rotation axis C2 parallel to the rotation axis C1. The second reduction gear shaft 60 is concentric with the first reduction gear shaft 52.

[0023] The first output shaft 54 includes an outer peripheral tooth 54a that meshes with the small-diameter gear 52b. The first output shaft 54 is supported via a pair of bearings 76 so as to be rotatable about a rotation axis C3 parallel to the rotation axis C1. The second output shaft 62 includes an outer peripheral tooth 62a that meshes with the small-diameter gear 52b. The second output shaft 62 is supported via a pair of bearings 78 so as to be rotatable about a rotation axis C3 parallel to the rotation axis C1. The second output shaft 62 is concentric with the first output shaft 54.

[0024] The pair of left and right first drive wheels 18 and second drive wheels 22 of the electric vehicle 10 are respectively connected to the first output shaft 54 and the second output shaft 62 via the first drive shaft 80 and the second drive shaft 82. The rotation of the first electric motor MG1 is decelerated by the first reduction gear 20 and transmitted to the first drive wheel 18. Independently thereof, the rotation of the second electric motor MG2 is decelerated by the second reduction gear 24 and transmitted to the second drive wheel 22.

[0025] At least one of the power transmission components of the first reduction gear 20, namely the first input shaft 48, the first reduction gear shaft 52, and the first output shaft 54, and at least one of the power transmission components of the second reduction gear 24, namely the second input shaft 56, the second reduction gear shaft 60, and the second output shaft 62, have different masses or rigidities from one another. As a result, the first reduction gear 20 and the second reduction gear 24 have different natural frequencies from one another. In this embodiment, as will be explained below, the first input shaft 48 and the second input shaft 56, the first reduction gear shaft 52 and the second reduction gear shaft 60, and the first output shaft 54 ​​and the second output shaft 62 have different masses or rigidities from one another.

[0026] The basic shapes of the first input shaft 48 and the second input shaft 56, as well as the outer diameters of the outer teeth 48a and outer teeth 56a, are common to each other. However, the shaft portion of the second input shaft 56 from the outer teeth 56a toward the second motor MG2 is longer than the shaft portion of the first input shaft 48 from the outer teeth 48a toward the first motor MG1. A parking lock gear 88 is fitted to the shaft portion of the second input shaft 56 from the outer teeth 56a toward the second motor MG2. The parking lock gear 88 is part of a parking lock mechanism (not shown) and engages with a parking lock pawl (not shown) when the electric vehicle 10 is stopped. Comparing the first input shaft 48 with the second input shaft 56 to which the parking lock gear 88 is fitted, the second input shaft 56 has a larger rotational mass and greater rotational inertia relative to the first input shaft 48.

[0027] The first reduction gear shaft 52 and the second reduction gear shaft 60 have a common shape and are therefore composed of common parts. However, the rotor shaft 92 of the oil pump 90 is connected to the shaft end of the first reduction gear shaft 52 on the side of the first electric motor MG1. The oil pump 90 supplies lubricating oil to various parts of the drive unit 12 and has a pump rotor (not shown) inside the pump housing 94 that is rotationally driven by the rotor shaft 92. When comparing the first reduction gear shaft 52 and the second reduction gear shaft 60 with the rotor shaft 92 connected, the first reduction gear shaft 52 has a relatively larger rotational mass and rotational inertia, as well as greater rotational resistance, compared to the second reduction gear shaft 60.

[0028] The basic shapes of the first output shaft 54 ​​and the second output shaft 62, as well as the outer diameters of the outer teeth 54a and 62a, are common to each other. However, the shaft diameter D1 of the first output shaft 54 ​​is relatively larger than the shaft diameter D2 of the second output shaft 62. The first output shaft 54, with its relatively larger shaft diameter, has a relatively larger rotational mass and rotational inertia compared to the second output shaft 62.

[0029] In this embodiment of the drive unit 12, the first reduction gear 20 and the second reduction gear 24 housed in the case 26 of the drive unit 12 have different natural frequencies to suppress the excitation of vibrations (motor noise) generated from the first motor MG1 and vibrations (motor noise) from the second motor MG2 as they are transmitted through the first reduction gear 20 and the second reduction gear 24. As a result, the noise characteristics of the first reduction gear 20 and the second reduction gear 24 are different, which lowers the peak of the combined noise level. Therefore, the vibration level of the drive unit 12 is suppressed without complicating the structure of the drive unit 12.

[0030] In the drive unit 12 of this embodiment, the first reduction gear 20 and the second reduction gear 24 are each composed of the same number of power transmission components. At least one of the power transmission components of the first reduction gear 20, for example, the first output shaft 54, and the second output shaft 62 of the second reduction gear 24, which corresponds to at least one of the power transmission components of the first reduction gear, have different masses. As a result, the first output shaft 54 ​​of the first reduction gear 20 and the second output shaft 62 of the first reduction gear 24 have different rotational inertia. Therefore, a difference in dynamic stiffness is formed between the first reduction gear 20 and the second reduction gear 24, resulting in different natural frequencies. Consequently, the peak of the combined noise level is reduced, and the vibration level of the drive unit 12 is suppressed.

[0031] In the drive unit 12 of this embodiment, a parking lock gear 88, which constitutes part of the parking lock mechanism, is provided on one of the following: at least one of the multiple power transmission components of the first reduction gear 20, for example, the first input shaft 48, and the second input shaft 56 of the second reduction gear 24, which corresponds to at least one of the multiple power transmission components of the first reduction gear (in this embodiment, the second input shaft 56). As a result, the mass of the second input shaft 56, on which the parking lock gear 88 is provided, is substantially greater than the mass of the other power transmission component. Therefore, the power transmission components of the first reduction gear 20 and the power transmission components of the second reduction gear 24 have different inertial masses, creating a difference in dynamic stiffness, which lowers the peak of the combined noise level and suppresses the vibration level of the drive unit 12.

[0032] In the drive unit 12 of this embodiment, an oil pump 90 is provided on one of the following: at least one of the multiple power transmission components of the first reduction gear 20, for example, the first reduction gear shaft 52, and the second reduction gear shaft 60, which corresponds to at least one of the multiple power transmission components of the first reduction gear 20 among the multiple power transmission components of the second reduction gear 24 (in this embodiment, the first reduction gear shaft 52). As a result, the mass of the first reduction gear shaft 52 on which the oil pump 90 is provided is substantially greater than the mass of the other second reduction gear shaft 60. Therefore, the power transmission components of the first reduction gear 20 and the power transmission components of the second reduction gear 24 have different inertial masses, creating a difference in dynamic stiffness, which lowers the peak of the combined noise level and suppresses the vibration level of the drive unit 12.

[0033] In the drive unit 12 of this embodiment, the first reduction gear 20 and the second reduction gear 24 are each composed of the same number of multiple power transmission components. The first output shaft 54, which is at least one of the multiple power transmission components of the first reduction gear 20, and the second output shaft 62, which is at least one of the multiple power transmission components of the second reduction gear 24 that corresponds to at least one of the multiple power transmission components of the first reduction gear 20, have different rigidities due to the difference in shaft diameter D1 of the first output shaft 54 ​​and shaft diameter D2 of the second output shaft 62 (D1 > D2). As a result, the power transmission components of the first reduction gear 20 and the power transmission components of the second reduction gear 24 have different dynamic rigidities, which lowers the peak of the combined noise level and suppresses the vibration level of the drive unit 12.

[0034] In this embodiment of the drive unit 12, the first reduction gear 20 and the second reduction gear 24 are composed of the same type of reduction mechanism, i.e., a gear-type reduction mechanism. Therefore, they can use common parts with each other, thus avoiding complicating the structure of the drive unit 12.

[0035] Although one embodiment of the present invention has been described above with reference to the drawings, the present invention can also be implemented in other embodiments.

[0036] For example, the first reduction gear 20 and the second reduction gear 24 described above are configured such that their natural frequencies are different from each other. Different natural frequencies mean that a difference in natural frequencies is formed that suppresses the excitation of vibrations (motor noise) generated from the first motor MG1 and vibrations (motor noise) from the second motor MG2 as they are transmitted through the first reduction gear 20 and the second reduction gear 24. For example, the natural frequencies of the first reduction gear 20 and the second reduction gear 24 are made different so that the peak of the combined noise level is lower than the peak of the resonance point of each first reduction gear 20 and the second reduction gear 24, and so that the half-width of the vibration intensity at the resonance point of each first reduction gear 20 and the second reduction gear 24 is greater than the half-width of the vibration intensity at the resonance point of each first reduction gear 20 and the second reduction gear 24.

[0037] Furthermore, in the embodiment shown in Figure 1, a parking lock gear 88 is fitted to the shaft portion of the second input shaft 56, the rotor shaft 92 of the oil pump 90 is connected to the shaft end of the first reduction gear shaft 52, and the shaft diameter D1 of the first output shaft 54 ​​is larger than the shaft diameter D2 of the second output shaft 62. However, at least one of these may be adopted. In addition, the parking lock gear 88 may be fitted to one of the first output shaft 54 ​​and the second output shaft 62, the rotor shaft 92 of the oil pump 90 may be connected, or the shaft diameter may be larger than the other.

[0038] Furthermore, the parking lock gear 88 may be fitted onto the first input shaft 48 which is symmetrically positioned to the second input shaft 56, the rotor shaft 92 of the oil pump 90 may be connected to the shaft end of the second reduction gear shaft 60 which is symmetrically positioned to the first reduction gear shaft 52, and the shaft diameter D1 of the first output shaft 54 ​​may be smaller than the shaft diameter D2 of the second output shaft 62.

[0039] Furthermore, in the above-described embodiment, the shaft diameter D1 of the first output shaft 54 ​​was made larger than the shaft diameter D2 of the second output shaft 62 in order to make them different in mass or composition. However, the material of one of the first output shaft 54 ​​and the second output shaft 62 may be changed or a hole may be formed. In short, it is sufficient that at least one of the power transmission components of the first reduction gear 20 and the power transmission component of the second reduction gear 24 that corresponds to at least one of the power transmission components of the first reduction gear 20 have different masses or compositions from each other.

[0040] The first electric motor MG1 and the second electric motor MG2, and the first reduction gear 20 and the second reduction gear 24 are arranged symmetrically with respect to the center line CL. The power transmission components constituting the first reduction gear 20 and the power transmission components constituting the second reduction gear 24 are also configured symmetrically with respect to the center line CL and are arranged symmetrically. However, they do not necessarily have to be in symmetrical positions.

[0041] In the above-described embodiment, the first rotor shaft 36 of the first electric motor MG1 and the second rotor shaft 42 of the second electric motor MG2 were arranged in a position perpendicular to the center line CL. However, the first electric motor MG1 and the second electric motor MG2 may be arranged parallel to each other along the center line CL.

[0042] It should be noted that the above is merely one example of the present invention, and various modifications can be made to the present invention without departing from its spirit. [Explanation of symbols]

[0043] 10: Electric vehicle, 12: Drive unit, 18: First drive wheel, 20: First reduction gear, 22: Second drive wheel, 24: Second reduction gear, 26: Case, 28: Central bulkhead, 30: First motor room, 31: First reduction gear room, 32: Second motor room, 33: Second reduction gear room, 34: First stator, 36: First rotor shaft, 38: First rotor, 40: Second stator, 42: Second rotor shaft, 44: Second rotor, 45: Bearing, 46: Bearing, 48: First input shaft, 48a: Outer teeth, 52: First reduction teeth Axle, 52a: large diameter teeth, 52b: small diameter teeth, 54: first output shaft, 54a: outer diameter teeth, 56: second input shaft, 56a: outer diameter teeth, 60: second reduction gear shaft, 60a: large diameter teeth, 60b: small diameter teeth, 62: second output shaft, 62a: outer diameter teeth, 64: bearing, 66: bearing, 72: bearing, 74: bearing, 76: bearing, 78: bearing, 80: first drive shaft, 82: second drive shaft, 88: parking lock gear, 90: oil pump, 92: rotor shaft, MG1: first motor, MG2: second motor

Claims

1. A drive system for an electric vehicle in which a first electric motor drives a first drive wheel via a first reduction gear, and a second electric motor drives a second drive wheel via a second reduction gear, The first reduction gear and the second reduction gear are each composed of the same type of reduction mechanism. The first reduction gear and the second reduction gear have different natural frequencies. The first reduction gear and the second reduction gear are each composed of the same number of power transmission components. At least one of the multiple power transmission components of the first reduction gear and at least one of the multiple power transmission components of the second reduction gear that corresponds to the multiple power transmission components of the first reduction gear have different masses from each other. A parking lock gear, which constitutes part of the parking lock mechanism, is provided on at least one of the multiple power transmission components of the first reduction gear, and on at least one of the multiple power transmission components of the second reduction gear that corresponds to at least one of the multiple power transmission components of the first reduction gear. A drive system for an electric vehicle characterized by the following features.

2. A drive system for an electric vehicle, wherein a first electric motor drives a first drive wheel via a first reduction gear, and a second electric motor drives a second drive wheel via a second reduction gear, The first reduction gear and the second reduction gear are each composed of the same type of reduction mechanism. The first reduction gear and the second reduction gear have different natural frequencies. The first reduction gear and the second reduction gear are each composed of the same number of power transmission components. At least one of the multiple power transmission components of the first reduction gear and at least one of the multiple power transmission components of the second reduction gear that corresponds to the multiple power transmission components of the first reduction gear have different masses from each other. An oil pump is provided in at least one of the multiple power transmission components of the first reduction gear, and in at least one of the multiple power transmission components of the second reduction gear that corresponds to at least one of the multiple power transmission components of the first reduction gear. A drive system for an electric vehicle characterized by the following features.

3. At least one of the plurality of power transmission components of the first reduction gear and at least one of the plurality of power transmission components of the second reduction gear that corresponds to the plurality of power transmission components of the first reduction gear have different rigidities from each other. A drive system for an electric vehicle according to claim 1 or 2, characterized by the above.

Images