Vehicle driving force transmission device

Abstract

A power transmission device is provided with: a differential case provided with an outer case that receives torque and rotates about an axis, and an inner case that is coaxial with the outer case and is rotatable relative to the outer case; a clutch member which is fixed to or engaged with the outer housing, forms a dog clutch with the inner housing, and transmits the torque from the outer housing to the inner housing when the clutch member is engaged with the inner housing; and a differential gear set that is provided with a pair of side gears that are respectively rotatable about the shaft and are capable of differential motion with each other, and a pinion gear that constitutes a friction clutch that restricts the differential motion in combination with the differential case, the side gears being a pair of side gears that are respectively rotatable about the shaft and are capable of differential motion with each other. And a pinion gear that is supported by the inner housing so as to be able to transmit the torque to the side gear, and that meshes with the side gear so as to allow the differential motion.

Description

Technical Field

[0001] The present invention relates to a power transmission device which can be applied to a powertrain of an electric vehicle. Background Art

[0002] In a car, the left and right axles do not necessarily rotate at the same speed, so it is necessary to allow for differential movement between them. In order to allow for differential movement between the two axles, a differential device is used. When the two wheels ensure traction, the differential device can effectively transmit torque to the two axles, but when one wheel loses traction and the other wheel's differential remains possible, torque will not be transmitted to either axle. One means to avoid this situation is the so-called limited slip differential (LSD). The LSD, for example, has a friction clutch that works by inducing torque, and the friction clutch works in a manner that limits differential movement (torque-sensing LSD).

[0003] There are various types of torque-sensitive LSDs. For example, the cone clutch type disclosed in Patent Document 1 cannot expect a large differential limiting force, but can realize the LSD with a simple structure.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-49345 Summary of the invention

[0007] LSD can potentially provide the above advantages to electric vehicles, but it is usually not used. This is because, in electric vehicles, the motor is operated as a generator during deceleration to regenerate excess energy, but the LSD installed without special design also works during deceleration, thereby consuming energy. The inventors have thought of applying LSD to the power transmission device of electric vehicles.

[0008] According to one scheme, the power transmission device comprises: a differential case, which comprises an outer case that receives torque and rotates around an axis, and an inner case that is coaxial with the outer case and can rotate relative to the outer case; a clutch component that is fixed or engaged with the outer case and forms a dog-type clutch with the inner case, and the clutch component transmits the torque from the outer case to the inner case when meshing with the inner case; and a differential gear set, which comprises side gears and pinion gears, the side gears being a pair of side gears that can rotate respectively around the axis and can be differentially moved with each other, and each of which is combined with the differential case to form a friction clutch that limits the differential, and the pinion gear is supported on the inner case in a manner that can transmit the torque to the side gears, and meshes with the side gears in a manner that allows the differential. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A This is a schematic diagram showing a powertrain of an electric vehicle according to an example, in which an electromagnetic solenoid is used to drive a clutch.

[0010] Figure 1B This is a schematic diagram showing a powertrain, in which a combination of a motor, a gear mechanism, and a cam mechanism is used to drive the clutch.

[0011] Figure 1C 1 is a schematic diagram showing a powertrain of an electric vehicle according to another example, in which a power source and a differential are arranged coaxially.

[0012] Figure 1D It is a schematic diagram showing the powertrain, the clutch configuration and Figure 1C on the contrary.

[0013] Figure 1E is a schematic diagram showing a powertrain of an electric vehicle according to yet another example, Figure 1B In the example shown, a planetary gear is used to reduce the speed (increase the power) of the output of the power source.

[0014] Figure 2 It is a cross-sectional view of a differential device included in the power transmission device according to one embodiment.

[0015] Figure 3 This is a cross-sectional view of a differential device in the case where a combination of a motor, a gear mechanism, and a cam mechanism is used to drive the clutch.

[0016] Figure 4 This is an exploded perspective view of the side gear consisting of a gear component and an output component.

[0017] Figure 5 It is a partial top cross-sectional view for particularly illustrating the side gear engaging with the cam surface. DETAILED DESCRIPTION

[0018] Hereinafter, several exemplary embodiments will be described with reference to the accompanying drawings. In the following description and claims, unless otherwise specified, an axis is a rotation axis of a differential device, and an axial direction is a direction parallel thereto, and a radial direction is a direction orthogonal thereto. The distinction between front, rear, right, and left is based on the state of the device mounted on the vehicle, and of course, the front and rear directions can also be reversed or the left and right directions can be reversed. It should be noted that the accompanying drawings may not be shown to an accurate scale, so the mutual dimensional relationship is not limited to the relationship shown in the figure.

[0019] The power transmission device of this embodiment can be used in any type of automobile, and in particular can be applied to the powertrain of an electric vehicle and can regenerate energy into a rechargeable battery. Here, the electric vehicle is not limited to a pure electric vehicle, but can be a so-called (plug-in) hybrid vehicle that combines an internal combustion engine with a rechargeable battery, a hybrid fuel cell vehicle that combines a fuel cell with a rechargeable battery, etc.

[0020] For example, refer to Figure 1A The powertrain of an electric vehicle includes, for example, an electric motor M as a power source, a reduction gear set 7 for reducing rotation (ie, multiplying torque), and a differential device 1 for outputting torque while allowing differential motion. The whole is accommodated and supported in a single or divisible housing.

[0021] The motor M includes a stator MS fixed to a motor housing and a rotor MR coupled to the shaft 11 to rotate together, but is not limited thereto. The rotor MR generates torque with respect to the stator MS according to high-frequency current applied from a power source, and the generated torque is output via the shaft 11 .

[0022] The shaft 11 can be led out from the motor housing and directly serve as the input shaft of the reduction gear set 7, but a coupling 15 can also be sandwiched between the input shaft 13. The transmission system including the reduction gear set 7 and the differential device 1 is accommodated and supported in a gear housing that surrounds a chamber different from the motor housing. This electrically isolates the motor M from the transmission system, thereby helping to reduce the leakage of high-frequency noise. The gear housing can also be integrally formed with the motor housing, which helps to reduce the overall weight of the device, or it can be separate.

[0023] In any case, the reduction gear group 7 includes a group of reduction gears of one or more stages, and reduces the speed of the input rotation while multiplying the torque and transmitting it to the differential device 1. The differential device 1 receives the torque by meshing with the reduction gear group 7 via the ring gear 9, for example, and outputs the torque to the right axle 5R and the left axle 5L while allowing differential motion.

[0024] like Figure 1A , 1B As shown, the reduction gear set 7 can also be composed of two or more parallel shafts. In this case, the differential device 1 belongs to the third to fourth shafts in the transmission system. This structure is conducive to reducing the size of the powertrain to the transmission system in the axial direction. In addition, the various elements of the power transmission device can be arranged without being interfered by the motor M, which provides design freedom.

[0025] but, Figure 1A , 1B The illustrated configuration requires considerable dimensions in the longitudinal direction. Figure 1C , 1DThe illustrated configuration is effective for reducing the radial dimension. In these examples, the motor M and the differential device 1 are adjacent and coaxial in the axial direction, the shaft body 11 of the motor M is hollow, and the left axle 5L (or the right axle 5R) is led out to the outside through the shaft body 11. The reduction gear set 7 is composed of only one shaft parallel to them, but even so, it can be connected with the differential device 1. Figure 1A , 1B The example shown also has two stages of reduction gears to achieve a sufficient reduction ratio. Figure 1C In the example shown, the actuator 3 can be arranged in the space between the motor M and the differential device 1 which is usually prone to become a dead zone, which is advantageous in terms of space saving. Figure 1D In the example shown, the motor M whose magnetic flux is easily disturbed is arranged away from the actuator 3, so a more stable operation can be expected.

[0026] Or, if Figure 1E As shown, a transmission system using planetary gears 7P may also be used. In the example shown in the figure, the external gear is fixed to the gear housing, the sun gear is fixed to the input shaft, and the planetary carrier is combined with the differential case of the differential device 1, thereby achieving a larger reduction ratio in the torque transmission from the input shaft to the differential device 1. Of course, other structures such as using external gears for input may also be used. Figure 1E It can be easily understood that according to the planetary gear, Figure 1C , 1D As shown, the larger diameter gear will not protrude beyond the shaft.

[0027] and Figures 1A to 1E Combined with reference Figure 2 In the differential device 1, the differential case 21 is composed of an outer case 31 that receives torque and rotates around the axis X, and an inner case 33 that is coaxially fitted with the outer case 31. For example, the outer case 31 has bosses 32 at both ends, and the gear housing has bearings 34 corresponding thereto, so that the outer case 31 is rotatably supported by the gear housing. The inner case 33 can rotate relative to the outer case 31, but when the clutch 23 is engaged, the two are drivingly connected, and the input torque is transmitted to the differential gear set 25. That is, only when the clutch 23 is engaged, the torque based on the motor M is output to the axles 5R and 5L via the differential gear set 25 and used for the travel of the vehicle, but when the clutch 23 is disengaged, the torque is not output to any axle 5R or 5L. On the other hand, when the vehicle is decelerated, if the clutch 23 is engaged, the motor M exerts a braking force and can regenerate excess energy, but energy regeneration is not performed when it is disengaged.

[0028] The clutch 23 can be composed of, for example, clutch teeth engraved on the edge of the inner housing 33 and a clutch member 29 having clutch teeth corresponding thereto. The clutch member 29 is roughly annular, and the clutch teeth can be engraved on one surface thereof, and one or more legs protrude from the other surface. Corresponding to the legs, the outer housing 31 has one or more openings 39 that penetrate the outer housing 31 at least in the axial direction. The opening 39 can also be opened in the radial direction, which is conducive to the circulation of lubricating oil. The legs of the clutch member 29 are exposed to the outside of the outer housing 31 through the openings 39 respectively. In addition, in order to facilitate operation from the outside, the legs exposed to the outside can be combined with components such as the ring plate 55. The legs of the clutch member 29 are respectively engaged with the openings 39, whereby the clutch member 29 is immovable in the circumferential direction relative to the outer housing 31 and receives torque, but is movable in the axial direction.

[0029] Regarding the operation of the clutch 23, the clutch 23 can be operated from the outside of the transmission system by the actuator 3. Figure 2 As shown in the example, the actuator 3 can utilize an electromagnetic solenoid 61 that electromagnetically drives the plunger. The electromagnetic solenoid 61 is, for example, annular, and is slidably fitted around the boss portion 32 of one side of the differential case 21, and is prevented from rotating. The plunger is, for example, fitted with the inner circumference of the electromagnetic solenoid so as to be movable in the axial direction, and abuts, engages, or is fixed to the clutch component 29 or the ring plate 55 connected to the clutch component 29. A cable C is electrically connected to the electromagnetic solenoid 61, such as Figure 1A , 1C As shown in FIG. 1D , the cable C is led out of the gear housing. When current is applied to the electromagnetic solenoid 61 from the outside through the cable C, the plunger is driven in the axial direction, and the clutch 23 can be operated via the ring plate 55 .

[0030] Alternatively, instead of driving the movable plunger by the stationary electromagnetic solenoid 61 , the electromagnetic solenoid 61 itself may be made movable and driven relative to a fixed member, thereby operating the clutch 23 .

[0031] In addition, the actuator 3 is not limited to the electromagnetic solenoid, and any driving device such as a hydraulic device, a pneumatic device, an electric motor, etc. can be used. Figure 3 As shown Figure 1B , 1ESchematically shown is an example thereof, in which the actuator 3 is roughly composed of an electric motor 63, a gear mechanism 65, 67 and a cam structure 69. The gear mechanism is composed of, for example, a pinion 65 rotated by the electric motor 63 and a gear ring 67 having an axis parallel to the pinion 65 and meshing with the pinion 65. The diameter of the gear ring 67 is larger than the diameter of the pinion 65, forming a reduction gear mechanism. In order to increase the reduction ratio, other gears may be further interposed. The cam structure 69 is a mechanism that converts the rotational motion achieved by the gear ring 67 into a linear motion, and is, for example, provided with a cam ball formed by a cam protrusion that abuts against or is formed on the gear ring 67 or rolls on the gear ring 67. When current is applied through the cable C, the gear ring 67 rotates, and the cam structure 69 presses the ring plate 55, so that the actuator 3 can engage or disengage the clutch 23.

[0032] In the example shown in the figure, the clutch member 29 itself has clutch teeth and meshes with the inner housing 33, but the clutch member 29 and the clutch teeth may be separate bodies. For example, a movable member that is movable in the axial direction but fixed in the circumferential direction relative to the outer housing 31 may have clutch teeth, so that it is driven by the clutch member 29. Alternatively, the outer housing 31 itself or a member fixed to the outer housing 31 may have clutch teeth, and the clutch member 29 drives the inner housing 33 to mesh with it. In addition, the clutch 23 may not rely on the meshing of the clutch teeth, and may be composed of an appropriate meshing structure such as a combination of a protrusion and a groove extending in the axial direction.

[0033] Main reference Figure 2 , Figure 3 The inner housing 33 is coupled to the differential gear set 25. For example, the pinion shaft 41 is coupled to the inner housing 33 by a pin, and a plurality of pinions 43 are rotatably supported on the pinion shaft 41. The pinion gears 43 also mesh with the right and left side gears 45, and the side gears 45 can be coupled to each axle. For the convenience of coupling, for example, a structure such as a spline can be provided on the inner circumference thereof.

[0034] The combination of the outer surface of the side gear 45 in the axial direction and the inner surface of the outer housing 31 constitutes the friction clutch 27, which works in a manner of limiting the differential between the side gears 45. The illustrated example and the following description mainly relate to a bevel gear type and a cone clutch type LSD, but of course, a plane gear type may be used instead of the bevel gear type, a multi-plate clutch type may be used instead of the cone clutch type, and other appropriate forms may be used. In addition, in the illustrated example, the inner surface of the outer housing 31 constitutes the friction clutch 27, but if possible, the inner surface of the inner housing 33 may constitute the friction clutch 27 instead of the outer housing 31 or on the basis of the outer housing 31. In any case, the friction clutch 27 is located radially inside relative to the clutch member 29, and is configured so as not to directly interfere with each other. Even if the clutch member 29 is driven in the axial direction, it will not affect the operation of the friction clutch 27, and even if the friction clutch 27 is operated, it will not affect the fastening of the clutch member 29. This structure effectively utilizes the limited configuration space in the differential device.

[0035] The meshing reaction force between the gear teeth of the pinion 43 and the gear teeth of the side gear 45 presses the side gear 45 outward in the axial direction, thereby enabling the friction clutch 27 to operate. The larger the applied torque, the greater the thrust, so the differential limit achieved by the friction clutch 27 is a torque-sensitive type. In order to further enhance the effect, the friction surface 35 of the outer housing 31 and the friction surface 51 of the side gear 45 can also be conical surfaces (i.e., cone clutches), and a friction ring 37 can also be interposed between the friction surfaces 35 and 51.

[0036] and Figure 2 , Figure 3 Combined with reference Figure 4 The side gears 45 may not be integral, and may be composed of, for example, a gear member 49 meshing with the pinion 43 and an output member 47 engaged therewith and rotating integrally therewith. The output member 47 can be used for coupling with the axle, and has a flange portion 47F extending radially outward to accommodate the gear member 49. The friction surface 51 may be formed on the outer edge of the flange portion 47F in the radial direction.

[0037] The gear member 49 is provided with a sleeve 53, which is a recessed portion open outward in the axial direction, in order to engage with the output member 47, and the output member 47 is provided with a corresponding projection. The relationship between the sleeve and the projection may be reversed, but in any case, the engagement structure transmits torque between the gear member 49 and the output member 47 in both the forward rotation R1 and the reverse rotation R2.

[0038] and Figures 2 to 4 Combined with reference Figure 5, the side surfaces 53A and 53B of the sleeve 53 may also be inclined relative to the axial direction. Of course, correspondingly, the side surfaces of the projection may also be inclined. The side surfaces that are inclined and abut against each other function as cams that partially convert the torque acting on the gear member 49 into thrusts f1 and f2. The thrusts f1 and f2 press the output member 47 outward in the axial direction to operate the friction clutch 27.

[0039] The inclination angles θ1 and θ2 of the side surfaces 53A and 53B relative to the axis X direction can be appropriately set independently, thereby independently increasing or decreasing the thrusts f1 and f2. This thrust can be greater than the thrust based on the meshing reaction force of the differential gear, so this structure can enhance the differential limiting capacity based on the friction clutch 27. By increasing the inclination angle θ1 of the side surface 53A on which the torque in the positive direction R1 acts, a greater thrust f1 is generated relative to the torque applied in the direction of accelerating the vehicle (driving direction), thereby exerting a greater differential limiting capacity. By reducing the inclination angle θ2 of the side surface 53B on which the torque in the reverse direction R2 acts or making it zero, the thrust f2 can be weakened or made zero relative to the torque applied in the direction of decelerating the vehicle (sliding direction), thereby reducing the differential limiting capacity.

[0040] According to the present embodiment, in order to make the differential device have a differential limiting capability, the transmission device equipped with the differential device can also transmit torque to the other side when one of the driving wheels loses traction. On the other hand, the electric motor regenerates the residual energy of the vehicle during deceleration, but the differential limiting capability is small at this time, so the energy loss accompanying the differential limiting is also small, so energy regeneration can be performed with low loss. In addition, in the case where the inflow of energy through the transmission system is too large compared to the capacity of the electric motor, the power transmission can be cut off by clutch operation, so that overload to the electric motor or the regeneration circuit or the rechargeable battery can be prevented. In addition, before and after the clutch operation, the speed difference between the clutch teeth is extremely small, so the abnormal sound accompanying its operation and the impact on the vehicle body are extremely small, for example, compared with the disconnection device on the shaft body, it can be extremely small.

[0041] Several embodiments have been described, but corrections or modifications of the embodiments can be made based on the above disclosure.

Claims

1. A power transmission device, characterized in that: have: A differential case including an outer case that receives torque and rotates about an axis, and an inner case that is coaxial with the outer case and can rotate relative to the outer case; a clutch member fixed or engaged with the outer housing and constituting a dog clutch with the inner housing, wherein the clutch member transmits the torque from the outer housing to the inner housing when meshing with the inner housing; as well as A differential gear set, comprising side gears and pinion gears, wherein the side gears are a pair of side gears that can rotate around the shafts respectively and can be differentially moved with each other, and each of the side gears is combined with the differential case to form a friction clutch that limits the differential, and the pinion gear is supported on the inner case in a manner that can transmit the torque to the side gears, and meshes with the side gears in a manner that allows the differential.

2. The power transmission device according to claim 1, characterized in that: The friction clutch is composed of the side gear and the outer housing.

3. The power transmission device according to claim 2, characterized in that: The friction clutch includes friction surfaces provided on the side gears and inner surfaces of the outer housing corresponding to the friction surfaces.

4. The power transmission device according to claim 3, characterized in that: The side gears respectively include: a gear component that meshes with the pinion gear; and an output component that includes the friction surface, and the gear component and the output component engage with each other on a cam surface that is inclined relative to the circumferential direction, whereby the cam surface converts a portion of the torque into an axial thrust and presses the friction surface toward the differential case.

5. The power transmission device according to claim 1, characterized in that: The clutch member is configured to move in the axial direction to engage with and disengage from the inner housing.

6. The power transmission device according to claim 1, characterized in that: An opening is further provided, the opening penetrating the outer housing in the axial direction, engaging with the clutch member and exposing the clutch member at least partially to the outside of the outer housing.

7. The power transmission device according to claim 1, characterized in that: The friction clutch is arranged radially inward of the clutch member.

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