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 Art

[0002] Patent Document 1 discloses a drive unit mounted on a vehicle. 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

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a vehicle on which a drive unit is mounted, the torsional resonance frequency of the vehicle's drive system may be substantially the same as the unsprung resonance frequency of the vehicle. When the vehicle is traveling on a road surface with irregularities, slip and grip may repeatedly occur, resulting in periodic torque fluctuations. If the frequency of this torque fluctuation coincides with the torsional resonance frequency and the unsprung resonance frequency, excessive torque may be generated in the drive system. It is desired to suppress the generation of excessive torque in the drive system.

[0005] This specification provides a technology capable of suppressing the generation of excessive torque in the drive system.

Means for Solving the Problems

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

[0007] In the above configuration, the motor-side shaft and the gear-side shaft are connected by a connecting sleeve. When the connecting sleeve moves axially, at least one of the first engagement length and the second engagement length changes. This change in at least one of the first and second engagement lengths changes the torsional rigidity of the drive system. As the torsional rigidity of the drive system changes, the torsional resonance frequency of the drive system changes. Therefore, by moving the connecting sleeve axially, the torsional resonance frequency of the drive system can be changed. By changing the torsional frequency of the drive system, the torsional resonance frequency and the unsprung resonance frequency can be made to not coincide. Consequently, it is possible to suppress the generation of excessive torque in the drive system.

[0008] In a second embodiment, the first embodiment may further include an actuator for moving the connecting sleeve in the axial direction.

[0009] With the above configuration, the user does not need to manually move the connecting sleeve. Therefore, user convenience can be improved.

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

[0011] The frequency of torque fluctuations generated by the 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 fluctuation. Therefore, the torsional resonance frequency of the drive system changes according to the frequency of the torque fluctuation. Consequently, it is possible to suppress the coincidence between the torque fluctuation frequency and the torsional resonance frequency.

[0012] In a fourth embodiment, in the third embodiment, when the road surface on which the vehicle is traveling is a wavy road that satisfies predetermined conditions, the actuator may position the connecting sleeve in the first position, and when the road surface on which the vehicle is traveling is not a wavy road, the actuator may position 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 in the first position matches the unsprung resonance frequency and the frequency of torque fluctuations when the vehicle is traveling on a wavy road, it is possible to suppress the generation of excessive torque in the drive system.

[0014] In the fifth embodiment, in the third or fourth embodiment, the sum 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 sum of the first engagement length and the second engagement length, the higher the torsional rigidity of the drivetrain. The frequency with which a vehicle travels on road surfaces other than wavy roads is higher than the frequency with which it travels on wavy roads. Generally, higher torsional rigidity results in a more comfortable ride. With the above configuration, the torsional rigidity of the drivetrain when the vehicle travels on road surfaces other than wavy roads is higher than the torsional rigidity when the vehicle travels on wavy roads. Therefore, it is possible to ensure a comfortable ride while suppressing the generation of excessive torque in the drivetrain. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram of vehicle 2. [Figure 2] This diagram shows the control configuration of vehicle 2. [Figure 3] This is an enlarged view of part III in Figure 1. [Figure 4] This diagram shows the state where the connecting sleeve 70 of the connecting unit 36 ​​is in the second position. [Figure 5] This is a schematic diagram showing the drivetrain model. [Figure 6] This is a frequency graph. [Modes for carrying out the invention]

[0017] (Examples) Vehicle 2 of this embodiment will be described with reference to Figures 1 to 6. Figures 1, 3, and 4 are schematic cross-sectional views of Vehicle 2 for the purpose of making the explanation easier to understand. In the following, for the sake of clarity, the vertical and horizontal directions in Figure 1 will be described as "vertical direction" and "horizontal direction," respectively, but this does not define the actual directions.

[0018] As shown in Figure 1, the vehicle 2 comprises a drive unit 12, a right drive shaft 14, a left drive shaft 16, and a control device 18 (see Figure 2). The vehicle 2 is, 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 the 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 housed in the housing 30.

[0020] (Configuration of the 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 portion 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 peripheral surface of the right end portion of the motor-side shaft 42. A recessed portion 42B that recesses to the left is formed at the right end portion 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 the 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 portion of the gear-side shaft 50 is rotatably supported by the housing 30. Although not shown, the vicinity of the left end portion 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 portion of the gear-side shaft 50. A protruding portion 50B that protrudes to the left is formed at the left end portion 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 peripheral surface of the protruding portion 50B and the inner peripheral 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 that extends in the left-right direction. The central axis CA2 is located below the central axis CA1. Both ends of the intermediate shaft 52 are rotatably supported by the housing 30. The intermediate shaft 52 rotatably supports the second intermediate gear 58 and the third intermediate gear 60. The second intermediate gear 58 meshes with the first intermediate gear 56 on 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 the connecting unit 36) As shown in Figure 3, the connecting unit 36 ​​comprises a connecting sleeve 70, a fork 72, and an actuator 74. The connecting sleeve 70 is positioned 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 area 70B is formed on the outer circumferential surface of the connecting sleeve 70, which is recessed radially inward. The fork 72 has a semi-circular shape when viewed from the left or right direction. The radially inward end 72A of the fork 72 fits into the recessed area 70B of the connecting sleeve 70. An actuator 74 is connected to the radially outward end of the fork 72. The actuator 74 moves the connecting sleeve 70 along the left-right direction via the fork 72. In other words, the actuator 74 moves the connecting sleeve 70 along the axial directions of the motor-side shaft 42 and the gear-side shaft 50. The connecting sleeve 70 is movable between a first position (see Figure 3) and a second position (see Figure 4). In the first position, the first engagement length in which the third spline 70A engages with the first spline 42A is length L1, and the second engagement length in which the third spline 70A engages with the second spline 50A is length L2. In the second position in Figure 4, the first engagement length is length L3, and the second engagement length is length L4. Length L1 is longer than length L3. Lengths L2 and L4 are the same. In other words, the sum of the first engagement length and the second engagement length is shorter when the connecting sleeve 70 is in the second position (see Figure 4) than when the connecting sleeve 70 is in the first position (see Figure 3).

[0024] (Configuration of differential mechanism 38) As shown in Figure 1, the differential mechanism 38 comprises a ring gear 80, a differential case 82, a pinion shaft 84, a pinion gear 86, a right-side drive gear 88, and a left-side drive gear 90. The ring gear 80 meshes with the third intermediate gear 60 of the intermediate shaft 52. The differential case 82 is screw-fastened to the ring gear 80. 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-side drive gear 88 meshes with the pinion gear 86. The right-side drive shaft 14 is connected to the right-side drive gear 88. The left-side 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 the central axis CA3, which extends in the left-right direction. The central axis CA3 is located below the central axis CA2.

[0025] The motor-side shaft 42, gear unit 34, differential mechanism 38, right-side drive shaft 14, and left-side 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) The control device 18 in Figure 2 includes a CPU, ROM, RAM, etc. For example, the control device 18 is an electronic control unit (ECU) mounted on the vehicle 2. The control device 18 controls the operation of the motor 32, actuator 74, etc.

[0027] The control device 18 is configured to detect whether the road surface on which the vehicle 2 is traveling is a wavy road that satisfies predetermined conditions (hereinafter referred to as a "specific wavy road"). Hereinafter, the road surface on which the vehicle 2 is traveling will be referred to as the "traveling road surface". For example, the control device 18 detects whether the traveling road surface is a specific wavy road based on whether the amount of change in the wheel speed of the wheels connected to the right drive shaft 14 and the left drive shaft 16 is greater than or equal to a first predetermined value. For example, the predetermined conditions are met when the absolute difference between the frequency of torque fluctuations that occur when traveling on a wavy road and the unsprung resonance frequency of the vehicle 2, which will be described later, is within a second predetermined value. If the traveling road surface is not a specific wavy road, the control device 18 moves the connecting sleeve 70 to the first position (see Figure 3). On the other hand, if the traveling road surface is a specific wavy road, the control device 18 moves the connecting sleeve 70 to the second position (see Figure 4). A wavy road is a road in which the surface is uneven.

[0028] Referring to Figures 5 and 6, the reason for moving the connecting sleeve 70 to the second position when the road surface is a specific type of wavy road will be explained. In Figure 6, the vertical axis shows the amplitude ratio, and the horizontal axis shows the frequency [Hz].

[0029] The drivetrain model of vehicle 2 is as shown in Figure 5. The spring constants k0, k1, k2, and k3 in Figure 5 are the spring constants of the wheel, drive shaft, the part connected by the coupling unit 36, and the mount (not shown), respectively. The moments of inertia I0, I1, and I2 are the torsional moments of inertia of the wheel, the rotor 44 of the motor 32, and the drivetrain 12, respectively. The torsional resonance frequency of the drivetrain is determined by the torsional moment of inertia and torsional stiffness. Torsional stiffness is equivalent to the spring constant. Therefore, the torsional resonance frequency of the drivetrain can be changed by changing the spring constant. Since the spring constants k0, k1, and k2 are the spring constants of springs connected in series, their combined spring constant is "(k0*k1*k2) / (k0+k1+k2)". Furthermore, the torsional rigidity (i.e., spring constant k2) changes depending on whether the connecting unit 36 ​​is positioned in the first position (see Figure 3) or the second position (see Figure 3). This changes the spring constant of the drive system, and consequently, the torsional resonance frequency of the drive system changes.

[0030] As shown in Figure 6, when the coupling unit 36 ​​is positioned in the first position, the first torsional resonance frequency F1 of the drive system approximately coincides with the unsprung resonance frequency of the vehicle 2. When the road surface is a specific wavy road, repeated slips and grips occur, causing periodic torque fluctuations. The frequency of these torque fluctuations coincides with the unsprung resonance frequency and the first torsional resonance frequency F1. In this case, excessive torque is generated in the drive system. To suppress the generation of excessive torque in the drive system, a means of limiting the output torque of the motor 32 can be 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 coupling sleeve 70 from the first position to the second position. As the coupling sleeve 70 moves to the second position, the spring constant k2 in Figure 5 changes, 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 no longer coincides with the torque fluctuation frequency and the unsprung resonance frequency. Therefore, excessive torque is not generated in the drive system even without limiting the output torque of the motor 32. For this reason, the connecting sleeve 70 is moved to the second position when the road surface is a specific type of wavy road.

[0031] (Effects of this embodiment) As described above, the drive unit 12 mounted on the vehicle 2 may include a motor 32, a motor-side shaft 42 having a first spline 42A on its outer circumference and rotating by torque from the motor 32, a gear-side shaft 50 having a second spline 50A on its outer circumference and arranged coaxially with the motor-side shaft 42, and a connecting sleeve 70 arranged from the motor-side shaft 42 to the gear-side shaft 50 and having a third spline 70A on its inner circumference 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 in which the third spline 70A engages with the first spline 42A and the second engagement length in 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. When the connecting sleeve 70 moves axially, at least one of the first engagement length and the second engagement length changes. This change in at least one of the first engagement length and the second engagement length changes the torsional rigidity of the drive system. In response to the change in the torsional rigidity of the drive system, the torsional resonance frequency of the drive system changes. Therefore, by moving the connecting sleeve 70 axially, the torsional resonance frequency of the drive system can be changed. By changing the torsional frequency of the drive system, the torsional resonance frequency and the unsprung resonance frequency can be made to not coincide. Consequently, it is possible to suppress the generation of excessive torque in the drive system.

[0033] Vehicle 2 is further equipped with an actuator 74 that moves the connecting sleeve 70 in the axial direction.

[0034] With the above configuration, the user does not need to manually move the connecting sleeve 70. Therefore, user convenience can be improved.

[0035] Furthermore, the actuator 74 moves the connecting sleeve 70 between at least a first position and a 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 vehicle 2 differs depending on the flatness of the road surface on which 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 fluctuation. Therefore, the torsional resonance frequency of the drive system changes in accordance with the frequency of the torque fluctuation. Consequently, it is possible to suppress the coincidence of the torque fluctuation frequency and the torsional resonance frequency.

[0037] Furthermore, when the road surface on which vehicle 2 is traveling is a wavy road that meets predetermined conditions, the actuator 74 positions the connecting sleeve 70 in the first position, and when the road surface on which vehicle 2 is traveling is not a wavy road, the actuator 74 positions the connecting sleeve 70 in the second position.

[0038] According to the above configuration, even if the torsional resonance frequency of the drive system when the connecting sleeve 70 is in the first position matches the unsprung resonance frequency and the frequency of torque fluctuations when the vehicle 2 is traveling on a wavy road, it is possible to suppress the generation of excessive torque in the drive system.

[0039] Furthermore, the sum 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 sum of the first engagement length and the second engagement length, the higher the torsional rigidity of the drivetrain. The frequency with which vehicle 2 travels on road surfaces other than wavy roads is higher than the frequency with which vehicle 2 travels on wavy roads. Generally, higher torsional rigidity results in a better ride for vehicle 2. According to the above configuration, the torsional rigidity of the drivetrain when vehicle 2 travels on road surfaces other than wavy roads is higher than the torsional rigidity when vehicle 2 travels on wavy roads. Therefore, it is possible to ensure a comfortable ride for vehicle 2 while suppressing the generation of excessive torque in the drivetrain.

[0041] The specific examples of the technology disclosed herein have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described 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 modified example) The actuator 74 may move the connecting sleeve 70 according to conditions other than the flatness of the road surface.

[0044] (Third Modification) The actuator 74 may continuously move the connecting sleeve 70 according to the flatness of the road surface.

[0045] (Fourth modified example) The sum 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. That is, 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] Furthermore, the technical elements described herein or in the drawings demonstrate technical usefulness individually 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 herein or in the drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself. [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: Recessed part, 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: Center axis

Claims

1. A drive unit mounted on a vehicle, Motor and, The motor-side shaft has a first spline on its outer surface and rotates due to the torque from the motor, It has a second spline on its outer circumference and is arranged coaxially with the motor-side shaft, The device comprises a connecting sleeve that is arranged from the motor-side shaft to the gear-side shaft and has a third spline on its inner 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 the first engagement length in which the third spline engages with the first spline and the second engagement length in which the third spline engages with the second spline changes depending on the axial position of the connecting sleeve. The aforementioned drive unit is The device further comprises an actuator for moving the connecting sleeve in the axial direction, The actuator moves the connecting sleeve between at least a first position and a second position according to the flatness of the road surface on which the vehicle is traveling. Drive unit.

2. When the road surface on which the vehicle is traveling is a wavy road that satisfies predetermined conditions, the actuator positions the connecting sleeve in the first position. The drive unit according to claim 1, wherein when the road surface on which the vehicle is traveling is not a wavy road, the actuator positions the connecting sleeve in the second position.

3. The drive unit according to claim 2, wherein the 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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