Drive unit

Abstract

To provide an art which can change a torsional resonance frequency of a drive system.SOLUTION: A drive unit mounted on a vehicle includes: a motor; a motor side shaft having a first spline on its outer peripheral surface and configured to rotate by torque from the motor; a gear side shaft having a second spline on its outer peripheral surface and arranged coaxially with the motor side shaft; and a connection sleeve which is disposed ranging from the motor side shaft to the gear side shaft and having a third spline configured to engage with the first spline and the second spline on its inner peripheral surface. The connection sleeve is configured to be movable along an axial direction, and at least one of a first engagement length, in which the third spline and the first spline are engaged, and a second engagement length, in which the third spline and the second spline are engaged, may change according to an axial position of the connection sleeve.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a drive unit mounted on a vehicle. [Background technology]

[0002] A drive unit mounted on a vehicle is disclosed in Patent Document 1. This drive unit includes a motor, a motor-side shaft, and a gear-side shaft arranged coaxially with the motor-side shaft. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-89664 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a vehicle equipped with a drive unit, the torsional resonance frequency of the drive system of the vehicle and the unsprung resonance frequency of the vehicle may be approximately equal. When the vehicle is traveling on an uneven road surface, repeated slips and grips may occur, causing periodic torque fluctuations. If the frequency of this torque fluctuation matches the torsional resonance frequency and the unsprung resonance frequency, excessive torque may be generated in the drive system. It is desirable to suppress the generation of excessive torque in the drive system.

[0005] This specification provides a technique capable of suppressing the generation of excessive torque in a drive system. [Means for solving the problem]

[0006] In a first aspect of the present technology, a drive unit mounted on a vehicle may include a motor, a motor-side shaft having a first spline on an outer circumferential surface and rotating by torque from the motor, a gear-side shaft having a second spline on an outer circumferential surface and arranged coaxially with the motor-side shaft, and a connecting sleeve arranged from the motor-side shaft to the gear-side shaft and having a third spline on an inner circumferential surface that engages with the first spline and the second spline. The connecting sleeve is configured to be movable along the axial direction, and at least one of a first engagement length at which the third spline engages with the first spline and a second engagement length at which the third spline engages with the second spline may change depending on an axial position of the connecting sleeve.

[0007] According to the above configuration, the motor-side shaft and the gear-side shaft are connected by the connecting sleeve. Then, at least one of the first engagement length and the second engagement length changes as the connecting sleeve moves in the axial direction. The torsional rigidity of the drive system changes as at least one of the first engagement length and the second engagement length changes. The torsional resonance frequency of the drive system changes in response to the change in the torsional rigidity of the drive system. Therefore, the torsional resonance frequency of the drive system can be changed by moving the connecting sleeve in the axial direction. By changing the torsional frequency of the drive system, the torsional resonance frequency and the unsprung resonance frequency can be prevented from coinciding. Therefore, it is possible to suppress the generation of excessive torque in the drive system.

[0008] In a second aspect, in the first aspect, the device may further include an actuator that moves the connecting sleeve in the axial direction.

[0009] According to the above configuration, the user does not need to manually move the connecting sleeve, which improves user convenience.

[0010] In a third aspect, in the second aspect, the actuator may move the connecting sleeve at least between a first position and a second position depending on the flatness of a road surface on which the vehicle is traveling.

[0011] The frequency of torque fluctuations generated in a vehicle varies depending on the flatness of the road surface on which the vehicle is traveling. According to the above configuration, the actuator moves the connecting sleeve in accordance with the frequency of the torque fluctuations. Therefore, the torsional resonance frequency of the drive system changes in accordance with the frequency of the torque fluctuations. Therefore, it is possible to prevent the frequency of the torque fluctuations and the torsional resonance frequency from coinciding with each other.

[0012] In a fourth aspect, in the third aspect, when the road surface on which the vehicle is traveling is an undulating road that satisfies a predetermined condition, the actuator may place the connecting sleeve in the first position, and when the road surface on which the vehicle is traveling is not an undulating road, the actuator may place the connecting sleeve in the second position.

[0013] According to the above configuration, even if the torsional resonance frequency of the drive system when the connecting sleeve is located in the first position matches the unsprung resonance frequency and the frequency of torque fluctuations when the vehicle is traveling on an uneven road, it is possible to prevent excessive torque from being generated in the drive system.

[0014] In a fifth aspect, in the third or fourth aspect, the total length of the first engagement length and the second engagement length may be longer when the connecting sleeve is in the second position than when the connecting sleeve is in the first position.

[0015] The longer the total length of the first engagement length and the second engagement length, the higher the torsional rigidity of the drive system. The vehicle travels on a road surface other than a corrugated road more frequently than the vehicle travels on a corrugated road. In general, the higher the torsional rigidity, the better the ride comfort of the vehicle. According to the above configuration, the torsional rigidity of the drive system when the vehicle travels on a road surface other than a corrugated road is higher than the torsional rigidity when the vehicle travels on a corrugated road. Therefore, the ride comfort of the vehicle can be ensured and the generation of excessive torque in the drive system can be suppressed. [Brief description of the drawings]

[0016] [Figure 1] FIG. [Diagram 2] FIG. 2 is a diagram showing a control configuration of a vehicle 2. [Diagram 3] FIG. 2 is an enlarged view of part III in FIG. [Figure 4] 13 shows a state in which the connection sleeve 70 of the connection unit 36 ​​is in a second position. FIG. [Diagram 5] FIG. 2 is a schematic diagram showing a drive system model. [Figure 6] 1 is a frequency graph. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] (Example) A vehicle 2 of this embodiment will be described with reference to Fig. 1 to Fig. 6. Fig. 1, Fig. 3, and Fig. 4 are schematic cross-sectional views of the vehicle 2 for ease of understanding. In the following, for ease of understanding, the up-down direction and the left-right direction in Fig. 1 will be described as the "up-down direction" and the "left-right direction", respectively, but this does not specify the actual directions.

[0018] 1, the vehicle 2 includes a drive unit 12, a right drive shaft 14, a left drive shaft 16, and a control device 18 (see FIG. 2). The vehicle 2 may be, for example, a battery-powered electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a fuel cell electric vehicle.

[0019] (Configuration of drive unit 12) The drive unit 12 includes a housing 30, a motor 32, a gear unit 34, a coupling unit 36, and a differential mechanism 38. The motor 32, the gear unit 34, the coupling unit 36, and the differential mechanism 38 are accommodated within the housing 30.

[0020] (Configuration of motor 32) The motor 32 includes an output shaft 40, a motor-side shaft 42, a rotor 44, and a stator 46. The output shaft 40 and the motor-side shaft 42 extend along a central axis CA1 extending in the left-right direction. The output shaft 40 is rotatably supported by the housing 30. The left end of the motor-side shaft 42 is attached to the output shaft 40. As shown in FIG. 3, a first spline 42A is formed on the outer circumferential surface of the right end of the motor-side shaft 42. A recessed portion 42B recessed to the left is formed on the right end of the motor-side shaft 42. As shown in FIG. 1, the rotor 44 is fixed to the output shaft 40. The stator 46 is fixed to the inner wall of the housing 30.

[0021] (Configuration of gear unit 34) The gear unit 34 includes a gear-side shaft 50 and an intermediate shaft 52. The gear-side shaft 50 extends along a central axis CA1 extending in the left-right direction. That is, the gear-side shaft 50 is arranged coaxially with the output shaft 40 and the motor-side shaft 42. The right end of the gear-side shaft 50 is rotatably supported by the housing 30. Although not shown, the vicinity of the left end of the gear-side shaft 50 is also rotatably supported by the housing 30. As shown in FIG. 3, a second spline 50A is formed at the left end of the gear-side shaft 50. A protruding portion 50B that protrudes to the left is formed at the left end of the gear-side shaft 50. The protruding portion 50B has a cylindrical shape. The outer diameter of the protruding portion 50B is smaller than the inner diameter of the recessed portion 42B of the motor-side shaft 42. A bearing 54 is provided between the outer circumferential surface of the protruding portion 50B and the inner circumferential surface of the recessed portion 42B. As shown in FIG. 1, the gear-side shaft 50 rotatably supports a first intermediate gear 56 .

[0022] The intermediate shaft 52 extends along a central axis CA2 extending in the left-right direction. The central axis CA2 is located below the central axis CA1. Both left and right ends of the intermediate shaft 52 are rotatably supported by the housing 30. The intermediate shaft 52 rotatably supports a second intermediate gear 58 and a third intermediate gear 60. The second intermediate gear 58 meshes with the first intermediate gear 56 of the gear-side shaft 50. The outer diameter of the second intermediate gear 58 is larger than the outer diameter of the first intermediate gear 56. The outer diameter of the third intermediate gear 60 is smaller than the outer diameter of the second intermediate gear 58.

[0023] (Configuration of connecting unit 36) As shown in FIG. 3, the connecting unit 36 ​​includes a connecting sleeve 70, a fork 72, and an actuator 74. The connecting sleeve 70 is disposed from the right end of the motor-side shaft 42 to the left end of the gear-side shaft 50. A third spline 70A is formed on the inner circumferential surface of the connecting sleeve 70, which engages with the first spline 42A of the motor-side shaft 42 and the second spline 50A of the gear-side shaft 50. A recessed portion 70B is formed on the outer circumferential surface of the connecting sleeve 70, which is recessed radially inward. The fork 72 has a semicircular arc shape when viewed from the left and right. A radially inner end 72A of the fork 72 fits into the recessed portion 70B of the connecting sleeve 70. An actuator 74 is connected to a radially outer end of the fork 72. The actuator 74 moves the connecting sleeve 70 in the left and right direction via the fork 72. That is, the actuator 74 moves the connecting sleeve 70 along the axial direction of the motor-side shaft 42 and the gear-side shaft 50. The connecting sleeve 70 is movable between a first position (see FIG. 3) and a second position (see FIG. 4). At the first position, a first engagement length where the third spline 70A engages with the first spline 42A is length L1, and a second engagement length where the third spline 70A engages with the second spline 50A is length L2. At the second position in FIG. 4, the first engagement length is length L3, and the second engagement length is length L4. The length L1 is longer than the length L3. The lengths L2 and L4 are the same. That is, the total length of the first engagement length and the second engagement length is shorter when the connecting sleeve 70 is at the second position (see FIG. 4) than when the connecting sleeve 70 is at the first position (see FIG. 3).

[0024] (Configuration of differential mechanism 38) As shown in FIG. 1, the differential mechanism 38 includes a ring gear 80, a differential case 82, a pinion shaft 84, a pinion gear 86, a right drive gear 88, and a left drive gear 90. The ring gear 80 meshes with the third intermediate gear 60 of the intermediate shaft 52. The differential case 82 is fixed to the ring gear 80 by screws. The differential case 82 rotates integrally with the ring gear 80. The differential case 82 is rotatably supported by the housing 30. The pinion shaft 84 is rotatably supported by the differential case 82. The pinion gear 86 is fixed to the pinion shaft 84. The right drive gear 88 meshes with the pinion gear 86. The right drive shaft 14 is connected to the right drive gear 88. The left drive gear 90 meshes with the pinion gear 86. The left drive gear 90 is connected to the left drive shaft 16. The right drive shaft 14 and the left drive shaft 16 extend along a central axis CA3 that extends in the left-right direction. The central axis CA3 is located below the central axis CA2.

[0025] The motor-side shaft 42, the gear unit 34, the differential mechanism 38, the right drive shaft 14, and the left drive shaft 16 function as a so-called "drive system" that transmits the driving force of the motor 32 to the wheels.

[0026] (Configuration of control device 18) 2 includes a CPU, a ROM, a RAM, etc. As an example, the control device 18 is an electronic control unit (ECU) mounted on the vehicle 2. The control device 18 controls the operations of the motor 32, the actuator 74, etc.

[0027] The control device 18 is configured to be able to detect whether the road surface on which the vehicle 2 is traveling is a wavy road (hereinafter, referred to as a "specific wavy road") that satisfies a predetermined condition. Hereinafter, the road surface on which the vehicle 2 is traveling is referred to as a "traveling road surface." As an example, the control device 18 detects whether the traveling road surface is a specific wavy road based on whether the change amount of the wheel speed of the wheels connected to the right drive shaft 14 and the left drive shaft 16 is equal to or greater than a first predetermined value. As an example, the predetermined condition is satisfied when the absolute difference between the frequency of the torque fluctuation generated when traveling on a wavy road and the unsprung resonance frequency of the vehicle 2 described later is within a second predetermined value. When the traveling road surface is not a specific wavy road, the control device 18 moves the connecting sleeve 70 to a first position (see FIG. 3). On the other hand, when the traveling road surface is a specific wavy road, the control device 18 moves the connecting sleeve 70 to a second position (see FIG. 4). Note that a wavy road is a road on which unevenness of the road surface is repeated.

[0028] 5 and 6, the reason for moving the connecting sleeve 70 to the second position when the traveling road surface is a specific wavy road will be described. The vertical axis of Fig. 6 indicates the amplitude ratio, and the horizontal axis indicates the frequency [Hz].

[0029] The drive system model of the vehicle 2 is as shown in FIG. 5. The spring constants k0, k1, k2, and k3 in FIG. 5 are the spring constants of the wheels, the drive shaft, the part connected by the connecting unit 36, and the mount (not shown), respectively. The inertia moments I0, I1, and I2 are the torsional inertia moments of the wheels, the rotor 44 of the motor 32, and the drive unit 12, respectively. The torsional resonance frequency of the drive system is determined by the torsional inertia moment and the torsional rigidity. The torsional rigidity is equivalent to the spring constant. Therefore, the torsional resonance frequency of the drive system can be changed by changing the spring constant. Since the spring constants k0, k1, and k2 are the spring constants of the springs connected in series, the composite spring constant of these is "(k0*k1*k2) / (k0+k1+k2)". The torsional rigidity (i.e., spring constant k2) changes between when the connecting unit 36 ​​is located at the first position (see FIG. 3) and when it is located at the second position (see FIG. 3). This changes the spring constant of the drive train, and as a result, the torsional resonance frequency of the drive train changes.

[0030] As shown in FIG. 6, the first torsional resonance frequency F1 of the drive system when the connecting unit 36 ​​is disposed at the first position is approximately equal to the unsprung resonance frequency of the vehicle 2. When the road surface is a specific wavy road, slip and grip occur repeatedly, causing periodic torque fluctuations. The frequency of the torque fluctuations is equal to the unsprung resonance frequency and the first torsional resonance frequency F1. In this case, excessive torque is generated in the drive system. In order to suppress the generation of excessive torque in the drive system, a means for limiting the output torque of the motor 32 is considered. However, limiting the output torque of the motor 32 reduces the acceleration performance of the vehicle 2. Therefore, when the control device 18 detects that the road surface is a specific wavy road, it moves the connecting sleeve 70 from the first position to the second position. The movement of the connecting sleeve 70 to the second position changes the spring constant k2 in FIG. 5, and as a result, the torsional resonance frequency of the drive system changes from the first torsional resonance frequency F1 to the second torsional resonance frequency F2. As a result, the torsional resonance frequency of the drive system does not coincide with the frequency of torque fluctuation and the unsprung resonance frequency. Therefore, excessive torque is not generated in the drive system even if the output torque of the motor 32 is not limited. For this reason, when the road surface is a specific wavy road, the connecting sleeve 70 is moved to the second position.

[0031] (Effects of this embodiment) As described above, the drive unit 12 mounted on the vehicle 2 may include the motor 32, the motor-side shaft 42 having the first spline 42A on its outer circumferential surface and rotated by the torque from the motor 32, the gear-side shaft 50 having the second spline 50A on its outer circumferential surface and arranged coaxially with the motor-side shaft 42, and the connecting sleeve 70 arranged from the motor-side shaft 42 to the gear-side shaft 50 and having the third spline 70A on its inner circumferential surface that engages with the first spline 42A and the second spline 50A. The connecting sleeve 70 is configured to be movable along the axial direction, and at least one of the first engagement length at which the third spline 70A engages with the first spline 42A and the second engagement length at which the third spline 70A engages with the second spline 50A may change depending on the axial position of the connecting sleeve 70.

[0032] According to the above configuration, the motor-side shaft 42 and the gear-side shaft 50 are connected by the connecting sleeve 70. Then, at least one of the first engagement length and the second engagement length changes as the connecting sleeve 70 moves in the axial direction. At least one of the first engagement length and the second engagement length changes, so that the torsional rigidity of the drive system changes. The torsional resonance frequency of the drive system changes in response to the change in the torsional rigidity of the drive system. Therefore, the torsional resonance frequency of the drive system can be changed by moving the connecting sleeve 70 in the axial direction. By changing the torsional frequency of the drive system, it is possible to prevent the torsional resonance frequency from coinciding with the unsprung resonance frequency. Therefore, it is possible to suppress the generation of excessive torque in the drive system.

[0033] In addition, the vehicle 2 further includes an actuator 74 that moves the connecting sleeve 70 in the axial direction.

[0034] According to the above configuration, the user does not need to manually move the connecting sleeve 70. This improves user convenience.

[0035] Furthermore, the actuator 74 moves the connecting sleeve 70 at least between the first position and the second position depending on the flatness of the road surface on which the vehicle 2 is traveling.

[0036] The frequency of torque fluctuations generated in the vehicle 2 varies depending on the flatness of the road surface on which the vehicle 2 is traveling. According to the above configuration, the actuator 74 moves the connecting sleeve 70 in accordance with the frequency of the torque fluctuations. Therefore, the torsional resonance frequency of the drive system changes in accordance with the frequency of the torque fluctuations. Therefore, it is possible to prevent the frequency of the torque fluctuations and the torsional resonance frequency from coinciding with each other.

[0037] In addition, when the road surface on which the vehicle 2 is traveling is an undulating road that satisfies predetermined conditions, the actuator 74 places the connecting sleeve 70 in a first position, and when the road surface on which the vehicle 2 is traveling is not an undulating road, the actuator 74 places the connecting sleeve 70 in a second position.

[0038] According to the above configuration, even if the torsional resonance frequency of the drive system when the connecting sleeve 70 is located in the first position matches the unsprung resonance frequency and the frequency of torque fluctuation when the vehicle 2 is traveling on an undulating road, it is possible to prevent excessive torque from being generated in the drive system.

[0039] Furthermore, the total length of the first engagement length and the second engagement length is longer when the connecting sleeve 70 is in the second position than when the connecting sleeve 70 is in the first position.

[0040] The longer the total length of the first engagement length and the second engagement length, the higher the torsional rigidity of the drive system. The vehicle 2 travels on road surfaces other than an undulating road more frequently than the vehicle 2 travels on an undulating road. In general, the higher the torsional rigidity, the better the ride comfort of the vehicle 2. According to the above configuration, the torsional rigidity of the drive system when the vehicle 2 travels on a road surface other than an undulating road is higher than the torsional rigidity when the vehicle 2 travels on an undulating road. Therefore, the ride comfort of the vehicle 2 can be ensured and the generation of excessive torque in the drive system can be suppressed.

[0041] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

[0042] (First Modification) The drive unit 12 may include a mechanism for manually switching the position of the connecting sleeve 70. In this modification, the drive unit 12 does not need to include the actuator 74.

[0043] (Second Modification) The actuator 74 may move the connecting sleeve 70 in accordance with conditions other than the flatness of the road surface.

[0044] (Third Modification) The actuator 74 may continuously move the connecting sleeve 70 in accordance with the flatness of the road surface on which the vehicle is traveling.

[0045] (Fourth Modification) The total length of the first engagement length and the second engagement length may be longer when the connecting sleeve 70 is in the second position than when the connecting sleeve 70 is in the first position. In other words, the torsional rigidity when the connecting sleeve 70 is in the first position may be greater than the torsional rigidity when the connecting sleeve 70 is in the second position.

[0046] In addition, the technical elements described in this specification or drawings have technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of those objectives is itself technically useful. [Explanation of symbols]

[0047] 2: vehicle, 10: housing, 12: drive unit, 14: right drive shaft, 16: left drive shaft, 18: control device, 30: housing, 32: motor, 34: gear unit, 36: coupling unit, 38: differential mechanism, 40: output shaft, 42: motor side shaft, 42A: first spline, 42B: recess, 44: rotor, 46: stator, 50: gear side shaft, 50A: second spline, 50 B: protrusion, 52: intermediate shaft, 54: bearing, 56: first intermediate gear, 58: second intermediate gear, 60: third intermediate gear, 70: connecting sleeve, 70A: third spline, 70B: recess, 72: fork, 72A: end, 74: actuator, 80: ring gear, 82: differential case, 84: pinion shaft, 86: pinion gear, 88: right drive gear, 90: left drive gear, CA1, CA2, CA3: central axis

Claims

1. A drive unit mounted on a vehicle, A motor; a motor-side shaft having a first spline on an outer circumferential surface thereof and rotated by torque from the motor; a gear-side shaft having a second spline on an outer peripheral surface thereof and arranged coaxially with the motor-side shaft; a connecting sleeve disposed across the motor-side shaft and the gear-side shaft, the connecting sleeve having a third spline on an inner circumferential surface thereof, the third spline engaging with the first spline and the second spline, The connecting sleeve is configured to be movable along the axial direction, and at least one of a first engagement length at which the third spline engages with the first spline and a second engagement length at which the third spline engages with the second spline changes depending on the axial position of the connecting sleeve. Drive unit.

2. The drive unit of claim 1 , further comprising an actuator for axially moving the coupling sleeve.

3. The drive unit according to claim 2 , wherein the actuator moves the coupling sleeve between at least a first position and a second position depending on the flatness of a road surface on which the vehicle is traveling.

4. When the road surface on which the vehicle is traveling is an undulating road that satisfies a predetermined condition, the actuator places the connecting sleeve at the first position, The drive unit according to claim 3 , wherein the actuator places the coupling sleeve in the second position when the road surface on which the vehicle is traveling is not the undulating road.

5. The drive unit of claim 4 , wherein a sum of the first engagement length and the second engagement length is shorter when the connecting sleeve is in the second position than when the connecting sleeve is in the first position.

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