Drive unit

Abstract

The invention relates to a drive unit. A drive unit mounted on a vehicle is provided with: a motor; a motor-side shaft having a first spline on the outer peripheral surface thereof, the motor-side shaft being rotated by the torque from the motor; a gear-side shaft having a second spline on the outer peripheral surface thereof, the gear-side shaft being disposed coaxially with the motor-side shaft; and a connection sleeve disposed from the motor-side shaft to the gear-side shaft, the connection sleeve having a third spline that engages with the first spline and the second spline on the inner peripheral surface thereof. The connecting sleeve is configured so as to be movable in 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 in accordance with the position of the connecting sleeve in the axial direction.

Description

Technical Field

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

[0002] Japanese Patent Application Laid-Open No. 2002-89664 discloses a drive unit mounted on a vehicle, which includes a motor, a motor-side shaft, and a gear-side shaft disposed coaxially with the motor-side shaft.

[0003] In a vehicle equipped with a drive unit, the torsional resonance frequency of the vehicle's drive system is sometimes roughly consistent with the unsprung resonance frequency of the vehicle. When the vehicle is traveling on a bumpy road, periodic torque fluctuations may occur due to repeated slipping and gripping. If the frequency of the torque fluctuations is consistent with 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. Summary of the invention

[0004] This specification provides a technique capable of suppressing the generation of excessive torque in a drive system.

[0005] In a first aspect of the present technology, a drive unit mounted on a vehicle may include:

[0006] Motor;

[0007] A motor-side shaft having a first spline on an outer peripheral surface thereof and being rotated by a torque from the motor;

[0008] a gear side shaft, the gear side shaft having a second spline on an outer peripheral surface and being coaxially arranged with the motor side shaft; and

[0009] A connecting sleeve is arranged from the motor-side shaft to the gear-side shaft and has a third spline on an inner peripheral surface thereof that engages with the first spline and the second spline.

[0010] The connecting sleeve may be configured to be movable in the axial direction, and at least one of a first engagement length of the third spline with the first spline and a second engagement length of the third spline with the second spline may change according to an axial position of the connecting sleeve.

[0011] According to the above structure, the motor side shaft and the gear side shaft are connected by a connecting sleeve. Moreover, by moving the connecting sleeve in the axial direction, at least one of the first engagement length and the second engagement length changes. By changing at least one of the first engagement length and the second engagement length, the torsional rigidity of the drive system changes. As the torsional rigidity of the drive system changes, the torsional resonance frequency of the drive system changes. Therefore, by moving the connecting sleeve in the axial direction, the torsional resonance frequency of the drive system can be changed. By changing the torsional frequency of the drive system, the torsional resonance frequency can be made inconsistent with the unsprung resonance frequency. Therefore, it is possible to suppress the generation of excessive torque in the drive system.

[0012] In a second aspect, in the above-mentioned first aspect, an actuator may be further provided to move the connecting sleeve in the axial direction.

[0013] According to the above structure, the user does not need to manually move the connecting sleeve. Therefore, the convenience of the user can be improved.

[0014] In a third aspect, in the second aspect, the actuator may move the connecting bushing between at least a first position and a second position according to the flatness of a road surface on which the vehicle is traveling.

[0015] The frequency of the torque variation generated in the vehicle is different depending on the flatness of the road surface on which the vehicle is traveling. According to the above structure, the actuator moves the connecting sleeve according to the frequency of the torque variation. Therefore, the torsional resonance frequency of the drive system changes according to the frequency of the torque variation. Therefore, it is possible to suppress the frequency of the torque variation from being consistent with the torsional resonance frequency.

[0016] In a fourth embodiment, in the above-mentioned third embodiment, when the road surface on which the vehicle is traveling is a wavy road that meets specified conditions, the actuator configures the connecting sleeve in the second position, and when the road surface on which the vehicle is traveling is not the wavy road, the actuator configures the connecting sleeve in the first position.

[0017] According to the above configuration, even when the torsional resonance frequency of the drive system when the connecting sleeve is in the first position coincides with the unsprung resonance frequency and the frequency of torque fluctuation when the vehicle travels on a wavy road, generation of excessive torque in the drive system can be suppressed.

[0018] In a fifth aspect, in the third or fourth aspect, the total length of the first engagement length and the second engagement length when the connecting sleeve is in the second position may be shorter than the total length when the connecting sleeve is in the first position.

[0019] 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 frequency of a vehicle traveling on a road surface different from a wavy road is higher than the frequency of a vehicle traveling on a wavy road. Generally speaking, the higher the torsional rigidity, the better the ride comfort of the vehicle. According to the above structure, the torsional rigidity of the drive system when the vehicle is traveling on a road surface different from a wavy road is higher than the torsional rigidity when the vehicle is traveling on a wavy 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

[0020] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like symbols represent like elements, and in which:

[0021] Figure 1 is a schematic diagram of vehicle 2.

[0022] Figure 2 2 is a diagram showing a control structure of the vehicle 2 .

[0023] Figure 3 yes Figure 1 An enlarged view of Part III.

[0024] Figure 4 This is a diagram showing a state in which the connection sleeve 70 of the connection unit 36 ​​is located at the second position.

[0025] Figure 5 is a schematic diagram showing the drive system model.

[0026] Figure 6 It is a frequency graph. DETAILED DESCRIPTION

[0027] Reference Figures 1 to 6 , the vehicle 2 of this embodiment is described. Figure 1 , Figure 3 , Figure 4 2 is a schematic cross-sectional view of the vehicle 2 for easy understanding of the description. Figure 1 The up-down direction and the left-right direction are respectively described as the “up-down direction” and the “left-right direction”, but the actual directions are not specified.

[0028] like Figure 1 As shown, the vehicle 2 includes 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 electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or a fuel cell electric vehicle.

[0029] (Structure of drive unit 12)

[0030] 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 in the housing 30 .

[0031] (Structure of Motor 32)

[0032] 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. Figure 3 As shown, 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 recessed to the left is formed on the right end portion of the motor side shaft 42. Figure 1 As shown, the rotor 44 is fixed to the output shaft 40 , and the stator 46 is fixed to the inner wall of the housing 30 .

[0033] (Structure of gear unit 34)

[0034] 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 coaxially arranged 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 in the figure, the vicinity of the left end of the gear side shaft 50 is also rotatably supported by the housing 30. Figure 3 As shown, a second spline 50A is formed at the left end of the gear side shaft 50. A protrusion 50B protruding to the left is formed at the left end of the gear side shaft 50. The protrusion 50B has a cylindrical shape. The outer diameter of the protrusion 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 protrusion 50B and the inner circumferential surface of the recessed portion 42B. Figure 1 As shown, the gear-side shaft 50 rotatably supports the first intermediate gear 56 .

[0035] The intermediate shaft 52 extends along the center axis CA2 extending in the left-right direction. The center axis CA2 is located below the center axis CA1. The left and right ends of the intermediate shaft 52 are rotatably supported by the housing 30. The intermediate shaft 52 supports the second intermediate gear 58 and the third intermediate gear 60 so that they can rotate. 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.

[0036] (Structure of the connecting unit 36)

[0037] like Figure 3 As shown, the connection unit 36 ​​includes a connection sleeve 70, a fork 72 and an actuator 74. The connection sleeve 70 is configured 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 connection 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 recessed radially inward is formed on the outer circumferential surface of the connection sleeve 70. The fork 72 has a semicircular arc shape when the fork 72 is observed from the left and right directions. The radially inner end 72A of the fork 72 is engaged with the recessed portion 70B of the connection sleeve 70. The actuator 74 is connected to the radially outer end of the fork 72. The actuator 74 moves the connection sleeve 70 in the left and right directions 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 can be in the first position (see Figure 3 ) and the second position (ref. Figure 4 ). At the first position, the first engagement length of the third spline 70A and the first spline 42A is L1, and the second engagement length of the third spline 70A and the second spline 50A is L2. Figure 4 At the second position, the first engagement length is length L3, and the second engagement length is length L4. Length L1 is longer than length L3. Length L2 and length L4 are the same. That is, for the total length of the first engagement length and the second engagement length, the connecting sleeve 70 is located at the second position (refer to Figure 4 ) when the total length is greater than the connecting sleeve 70 is located in the first position (refer to Figure 3 ) is shorter than the above total length.

[0038] (Structure of Differential Mechanism 38)

[0039] like Figure 1 As shown, 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 screwed and fixed 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 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 gear 90. The right drive shaft 14 and the left drive shaft 16 extend along the central axis CA3 extending in the left-right direction. The central axis CA3 is located below the central axis CA2.

[0040] 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 drive force of the motor 32 to the wheels.

[0041] (Structure of Control Device 18)

[0042] Figure 2 The control device 18 includes a CPU, a ROM, a RAM, and the like. As an 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, the actuator 74, and the like.

[0043] 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 specified conditions (hereinafter, referred to as a "specific wavy road"). Hereinafter, the road surface on which the vehicle 2 is traveling is referred to as a "driving road surface." As an example, the control device 18 detects whether the traveling road surface is a specific wavy road based on whether the amount of change in wheel speed of the wheels connected to the right drive shaft 14 and the left drive shaft 16 is greater than a first specified value. As an example, the specified conditions are satisfied when the absolute difference between the frequency of torque fluctuations generated when traveling on a wavy road and the unsprung resonance frequency of the vehicle 2 described later is within a second specified value. When the traveling road surface is not a specific wavy road, the control device 18 moves the connecting sleeve 70 to the first position (refer to Figure 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 the second position (refer to Figure 4 ). It should be noted that a wavy road refers to a road with repeated bumps and depressions on the road surface.

[0044] Reference Figure 5 , Figure 6 The reason why the connecting sleeve 70 is moved to the second position when the traveling road surface is a specific wavy road will be described. Figure 6 The vertical axis represents the amplitude ratio, and the horizontal axis represents the frequency [Hz].

[0045] The drive system model of vehicle 2 becomes Figure 5 Model shown. Figure 5The spring constants k0, k1, k2, and k3 are respectively the spring constants of the wheel, the drive shaft, the portion connected by the connecting unit 36, and the bracket (mount) (not shown). The moments of inertia I0, I1, and I2 are respectively the torsional moments of inertia of the wheel, the rotor 44 of the motor 32, and the drive unit 12. The torsional resonance frequency of the drive system is determined by the torsional moment of inertia and the torsional rigidity. The torsional rigidity is equivalent to the spring constant. Therefore, by changing the spring constant, the torsional resonance frequency of the drive system can be changed. Since the spring constants k0, k1, and k2 are the spring constants of the springs connected in series, their combined spring constant is "(k0*k1*k2) / (k0+k1+k2)". Moreover, when the connecting unit 36 ​​is configured in the first position (refer to Figure 3 ) and the configuration in the second position (refer to Figure 4 ), the torsional rigidity (ie, the spring constant k2) changes. As a result, the spring constant of the drive system changes, and as a result, the torsional resonance frequency of the drive system changes.

[0046] like Figure 6 As shown, the first torsional resonance frequency F1 of the drive system when the connecting unit 36 ​​is configured in the first position is roughly consistent with the unsprung resonance frequency of the vehicle 2. When the driving surface is a specific wavy road, periodic torque fluctuations will occur due to repeated slipping and gripping. Moreover, the frequency of the torque fluctuations is consistent with the unsprung resonance frequency and the first torsional resonance frequency F1. In this case, excessive torque is generated in the drive system. It should be noted that in order to suppress the generation of excessive torque in the drive system, a method of limiting the output torque of the motor 32 can be considered. However, if the output torque of the motor 32 is limited, the acceleration performance of the vehicle 2 will be reduced. Therefore, when the control device 18 detects that the driving surface is a specific wavy road, the connecting sleeve 70 moves from the first position to the second position. By moving the connecting sleeve 70 to the second position, Figure 5 The spring constant k2 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 is inconsistent with the frequency of the torque variation and the unsprung resonance frequency. Therefore, even if the output torque of the motor 32 is not limited, an excessive torque will not be generated in the drive system. For this reason, when the driving road surface is a specific wavy road, the connecting sleeve 70 moves to the second position.

[0047] (Effects of this embodiment)

[0048] As described above, the drive unit 12 mounted on the vehicle 2 may include: the motor 32; the motor side shaft 42, which has the first spline 42A on the outer circumference and rotates by the torque from the motor 32; the gear side shaft 50, which has the second spline 50A on the outer circumference and is coaxially arranged with the motor side shaft 42; and the connecting sleeve 70, which is arranged from the motor side shaft 42 to the gear side shaft 50 and has the third spline 70A engaged with the first spline 42A and the second spline 50A on the inner circumference. Alternatively, the connecting sleeve 70 may be configured to be movable in the axial direction, and at least one of the first engagement length of the third spline 70A engaged with the first spline 42A and the second engagement length of the third spline 70A engaged with the second spline 50A changes according to the axial position of the connecting sleeve 70.

[0049] According to the above structure, the motor side shaft 42 and the gear side shaft 50 are connected by the connecting sleeve 70. Moreover, by moving the connecting sleeve 70 in the axial direction, at least one of the first engagement length and the second engagement length changes. By changing at least one of the first engagement length and the second engagement length, the torsional rigidity of the drive system changes. As the torsional rigidity of the drive system changes, the torsional resonance frequency of the drive system changes. Therefore, by moving the connecting sleeve 70 in the axial direction, the torsional resonance frequency of the drive system can be changed. By changing the torsional frequency of the drive system, the torsional resonance frequency can be made inconsistent with the unsprung resonance frequency. Therefore, it is possible to suppress the generation of excessive torque in the drive system.

[0050] In addition, the vehicle 2 further includes an actuator 74 that moves the connecting sleeve 70 in the axial direction.

[0051] According to the above configuration, the user does not need to manually move the coupling sleeve 70. Therefore, the convenience of the user can be improved.

[0052] In addition, the actuator 74 moves the connecting sleeve 70 between at least the first position and the second position according to the flatness of the road surface on which the vehicle 2 travels.

[0053] The frequency of the torque variation generated in the vehicle 2 is different depending on the flatness of the road surface on which the vehicle 2 is traveling. According to the above structure, the actuator 74 moves the connecting sleeve 70 according to the frequency of the torque variation. Therefore, the torsional resonance frequency of the drive system changes according to the frequency of the torque variation. Therefore, it is possible to suppress the frequency of the torque variation from being consistent with the torsional resonance frequency.

[0054] When the road surface on which the vehicle 2 is traveling is a corrugated road satisfying a predetermined condition, the actuator 74 places the connecting sleeve 70 in the second position, and when the road surface on which the vehicle 2 is traveling is not a corrugated road, the actuator 74 places the connecting sleeve 70 in the first position.

[0055] According to the above configuration, even when the torsional resonance frequency of the drive system when the connecting sleeve 70 is in the first position coincides with the unsprung resonance frequency and the frequency of torque fluctuation when the vehicle 2 travels on a wavy road, generation of excessive torque in the drive system can be suppressed.

[0056] Furthermore, the total length of the first engagement length and the second engagement length when the connecting sleeve 70 is located at the second position is shorter than the total length when the connecting sleeve 70 is located at the first position.

[0057] 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 frequency of vehicle 2 traveling on a road surface different from the wavy road is higher than the frequency of vehicle 2 traveling on the wavy road. Generally speaking, the higher the torsional rigidity, the better the ride comfort of vehicle 2. According to the above structure, the torsional rigidity of the drive system when vehicle 2 travels on a road surface different from the wavy road is higher than the torsional rigidity when vehicle 2 travels on the wavy road. Therefore, the ride comfort of vehicle 2 can be ensured, and the generation of excessive torque in the drive system can be suppressed.

[0058] The above detailed description of the specific examples of the technology disclosed in this specification is only for illustration and does not limit the scope of protection of the claims. The technology described in the scope of protection of the claims includes various modifications and changes to the specific examples exemplified above.

[0059] (First Modification)

[0060] The drive unit 12 may include a mechanism for manually switching the position of the connection sleeve 70. In the present modification, the drive unit 12 may not include the actuator 74.

[0061] (Second Modification)

[0062] The actuator 74 may move the connecting sleeve 70 according to conditions other than the flatness of the travel road surface.

[0063] (Third Modification)

[0064] The actuator 74 may continuously move the coupling sleeve 70 according to the flatness of the travel road surface.

[0065] (Fourth Modification)

[0066] 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. That is, the torsional rigidity when the connecting sleeve 70 is in the second position may be greater than when the connecting sleeve 70 is in the first position.

[0067] In addition, the technical elements described in this specification or drawings can be used alone or in various combinations to achieve technical practicality, and are not limited to the combinations recorded in the claims at the time of application. In addition, the technology exemplified in this specification or drawings can achieve multiple purposes at the same time, and achieving one of the purposes itself has technical practicality.

Claims

1. A drive unit mounted on a vehicle, wherein: The drive unit comprises: Motor; A motor-side shaft having a first spline on an outer peripheral surface thereof and being rotated by a torque from the motor; a gear side shaft, the gear side shaft having a second spline on an outer peripheral surface and being coaxially arranged with the motor side shaft; and a connecting sleeve, the connecting sleeve being arranged from the motor side shaft to the gear side shaft and having a third spline on an inner peripheral surface thereof that engages with the first spline and the second spline, The connecting sleeve is configured to be movable in the axial direction, and at least one of a first engagement length of the third spline engaging with the first spline and a second engagement length of the third spline engaging with the second spline changes according to the axial position of the connecting sleeve.

2. The drive unit according to claim 1, wherein: The driving unit further includes an actuator that moves the connecting sleeve in the axial direction.

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

4. The drive unit according to claim 3, wherein: When the road surface on which the vehicle is traveling is a corrugated road that satisfies a predetermined condition, the actuator disposes the connecting sleeve at the second position. When the road surface on which the vehicle is traveling is not the corrugated road, the actuator arranges the connecting sleeve at the first position.

5. The drive unit according to claim 4, wherein: The total length of the first engagement length and the second engagement length when the connecting sleeve is located at the second position is shorter than the total length when the connecting sleeve is located at the first position.

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