Vehicle driving force transmission device

Abstract

A transmission device that outputs a power source while allowing differential motion of the output of the power source on a pair of output shafts is provided with: a housing that is drivingly coupled to the power source and rotates about the shaft; a differential gear set which is supported by the housing so as to rotate together around the shaft, and which is provided with a pair of side gears that can differentially move relative to each other; a friction part that is interposed between the housing and the differential gear set, or that is built in the differential gear set, and that frictionally restricts the differential motion; a disconnect device coupled to one of the output shafts to disconnect one of the side gears from one of the output shafts in a coupleable manner; and a cam structure directly or indirectly coupled to the friction part so as to convert torque in the direction in which the rotation is accelerated into thrust in the axial direction and apply the thrust to the friction part.

Description

Technical Field

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

[0002] In an electric vehicle using an electric motor as a power source of the vehicle, in order to compensate for the insufficient torque of the motor, for example, a two-stage or three-stage reduction gear is used in combination with the motor. If the reduction ratio of the reduction gear is increased, a motor with a smaller capacity can be used.

[0003] The motor is used not only for output, but also for energy regeneration by acting as a generator when the vehicle decelerates. If the motor has sufficient capacity, it can absorb the excess energy during deceleration, but small-capacity motors often cause overload. Therefore, a unit that protects the motor, regeneration circuit, or rechargeable battery is required.

[0004] Patent Document 1 discloses a related technology.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-044337 Summary of the invention

[0008] Problems to be solved by the invention

[0009] The device disclosed below can perform differential limitation and regenerate energy with low loss, and can cut off the transmission of torque according to the situation to prevent adverse effects on the electric motor.

[0010] According to one aspect, a power transmission device that allows the output of a power source to be output while allowing differential on a pair of output shafts comprises: a housing that is drivingly coupled to the power source to rotate around an axis; a differential gear set that is supported on the housing in a manner that rotates together around the axis and has a pair of side gears that can be differentially coupled to each other; a friction portion that is interposed between the housing and the differential gear set, or is built into the differential gear set to frictionally limit the differential; a disconnect device that is coupled to one of the output shafts to disconnect one of the side gears from one of the output shafts; and a cam structure that is directly or indirectly coupled to the friction portion to convert torque in a direction that increases the rotation speed into an axial thrust and apply it to the friction portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1A The diagram is a schematic diagram showing a powertrain of an electric vehicle based on an example, and is an example of using a multi-stage parallel gear train as a reduction gear set.

[0012] Figure 1B FIG. 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 coaxially arranged.

[0013] Figure 1C FIG. 1 is a schematic diagram showing a powertrain of an electric vehicle according to still another example, which is an example using a planetary gear.

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

[0015] Figure 3A It is a cross-sectional view of a disconnecting device according to another embodiment.

[0016] Figure 3B It is a cross-sectional view of a disconnecting device according to still another embodiment.

[0017] Figure 4 It is a plan view showing the pinion shaft and the thrust member abutting against each other.

[0018] Figure 5 It is a cross-sectional view of a differential device according to another embodiment.

[0019] Figure 6 This is an exploded perspective view of the side gear consisting of a gear component and an output component.

[0020] Figure 7 It is a partial cross-sectional view of the side gear for particularly illustrating the engagement of the cam surface.

[0021] Figure 8 It is a cross-sectional view of a differential device according to still another embodiment. DETAILED DESCRIPTION

[0022] Hereinafter, several exemplary embodiments will be described with reference to the accompanying drawings. In the following description and technical solutions, unless otherwise specified, the axis means the rotating axis of the differential device, and the axial direction is the direction parallel to it, and the radial direction is the direction orthogonal to it. The distinction between front, rear, right and left is based on the state of the device mounted on the vehicle, and of course, it can also be implemented by reversing the front and rear or the left and right. It should be noted that the drawings may not be shown in an accurate scale, so the mutual dimensional relationship is not limited to the relationship shown in the figure.

[0023] The power transmission device of this embodiment can be used in any type of automobile, and in particular, can be appropriately used in the power transmission system of an electric vehicle and can regenerate energy to a rechargeable battery. Here, the electric vehicle is not limited to a pure electric vehicle, but can also include a so-called (plug-in) hybrid vehicle in which an internal combustion engine is combined with a rechargeable battery, a hybrid fuel cell vehicle in which a fuel cell is combined with a rechargeable battery, and the like.

[0024] 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 entirety of the differential device is housed and supported in a single or divisible housing.

[0025] The motor M includes a stator MS fixed to a motor housing MH and a rotor MR coupled to and rotating with the shaft 11 , but is not limited thereto. The rotor MR generates torque on the stator MS in response to high-frequency current applied from a power source, and the generated torque is output via the shaft 11 .

[0026] The shaft 11 can be led out from the motor housing MH 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 the gear housing 71 of the surrounding chamber different from the motor housing MH. This electrically isolates the motor M from the transmission system, thereby helping to reduce the leakage of high-frequency noise. The gear housing 71 can also be integrally formed with the motor housing MH, which helps to reduce the overall weight of the device, or it can also be a separate body.

[0027] 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 thereof 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 allows differential and outputs the torque to the right axle 5R and the left axle 5L.

[0028] like Figure 1A As shown, the reduction gear set 7 may 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 advantageous in reducing the size of the power transmission system or the transmission system in the axial direction. In addition, the various elements of the power transmission device can be arranged without interfering with the motor M, which provides design freedom.

[0029] but, Figure 1A The illustrated configuration requires considerable dimensions in the radial direction. Figure 1BThe illustrated configuration is effective for reducing the radial dimension. In this example, the motor M and the differential device 1 are adjacent and coaxial in the axial direction, the shaft 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 11. The reduction gear set 7 is composed of only one shaft parallel to them, but even so, it can be connected with Figure 1A The example shown also includes two-stage reduction gears to achieve a sufficient reduction ratio.

[0030] Or, if Figure 1C As shown, a transmission system using a planetary gear 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 housing of the differential device 1, thereby achieving a large reduction ratio in the torque transmission from the input shaft to the differential device 1. Of course, other structures such as using an external gear for input may also be used. Figure 1C It can be easily understood that according to the planetary gear, Figure 1B As shown, the larger diameter gear will not protrude beyond the shaft.

[0031] Combination Figures 1A to 1C , refer to Figure 2 , the differential device 1 includes a disconnect device 3 that can disconnect the output shaft of one of the differential devices 1. The differential device 1 and the disconnect device 3 can also be accommodated and supported in a single gear housing 71. Alternatively, the gear housing 71 can also include a sub-housing 72 that surrounds a chamber different from the main chamber, and the disconnect device 3 can also be accommodated and supported in the sub-housing 72. The sub-housing 72 can be integral with the gear housing 71, or it can be separate. In the case of being formed as an integral body, there is no need for a structure for combining, bolts and other fasteners, so it is advantageous in terms of weight reduction. In the case of being separate, the two can also be connected to each other by bolts, etc. This facilitates the process of assembling the differential part and the disconnect part separately and then combining them.

[0032] For example, the output shaft 5Q is spline-connected to the right gear 45 of the differential device 1, but the axle 5R is coaxial and adjacent to it, but is not always connected. Each adjacent end has a lug 73 and a lug 75, and the coupling sleeve 77 is engaged with these lugs 73 and lugs 75 and can move in the axial direction. Only when the coupling sleeve 77 moves to a position that straddles the lugs 73 and 75, the output shaft 5Q is drivingly connected to the axle 5R. Alternatively, it is also possible to use a dog clutch or other meshing structure without using the lugs 73 and lugs 75, or a friction clutch can be used.

[0033] In order to drive the coupling sleeve 77 axially, for example, a shift fork 79 can be used. The shift fork 79 is slidably engaged with the coupling sleeve 77 at one end and is coupled to the plunger 83 at the other end. For example, a linear actuator 81 fixed to the gear housing 71 causes the plunger 83 to reciprocate in a controllable manner. Alternatively, instead of the combination of the actuator 81 and the plunger 83, a mechanism that converts rotational motion into linear motion, such as a combination of a motor and a ball screw, can be used. In addition, although not shown in the figure, a well-known synchronizer can also be sandwiched between the shafts 5R and 5Q. If the actuator or the motor 81 is operated, the coupling sleeve 77 moves axially via the shift fork 79, and the shafts 5R and 5Q are intermittent.

[0034] In the operation of the disconnecting device 3, as Figure 3A As shown, a coaxial motor can also be used. For example, the coaxial motor has a plurality of iron cores 85 each wound with an electromagnetic coil 87 and arranged around the axis X. The rotor 89 is rotated around the axis X by the generated magnetic flux, and the rotation is converted into axial motion by the cam mechanism 91 to drive the ring 79. A reduction gear set can also be sandwiched between the rotor 89 and the cam mechanism 91 to reduce the rotation (increase the torque). The ring 79 is slidably engaged with the coupling sleeve, so that the coaxial motor can drive the coupling sleeve 77. Alternatively, as Figure 3B As shown, the plunger can be driven in the axial direction by the solenoid 93. In order to prevent leakage of magnetic flux, it is preferable to drive the coupling sleeve 77 via a ring 79 made of a non-magnetic body.

[0035] In short, when the shafts 5R and 5Q are drivingly connected by the disconnect device 3, the torque can be differentially output to the axles 5R and 5L via the differential device 1. On the other hand, when the shafts 5R and 5Q are disconnected, of course, no torque is output to the right axle 5R, and no torque is output to the left axle 5L due to idling by the differential device 1. In addition, even when the vehicle is decelerating, the torque does not flow back to the power source via the differential device 1.

[0036] The structure of the disconnecting device 3 is not limited to the structure described above, and may be various structures. For example, the disconnecting device 3 can be separated into the shaft 5R side and the shaft 5Q side. In addition, the disconnecting device 3 can also be stored in the housing 21 to disconnect the side gear on one side from the shaft 5R. This can concentrate the related components in the housing 21, thus helping to miniaturize the device as a whole.

[0037] Return to reference Figure 2 The differential device 1 generally includes: a housing 21, which is drivingly coupled to a power source to receive torque and rotate around an axis X; a differential gear set 25, which outputs torque while allowing differential motion; and a friction clutch 27, which frictionally limits differential motion. The friction clutch 27 is, for example, interposed between the housing 21 and the differential gear set 25, or built into the differential gear set 25.

[0038] The housing 21, for example, has bosses 32 at both ends thereof, and the gear housing 71 has bearings 34 corresponding thereto, whereby the housing 21 can be rotatably supported on the gear housing 71. As described above, the housing 21, for example, meshes with the reduction gear set 7 via the ring gear 9 to receive torque. In order to be combined with the ring gear 9, the housing 21 can, for example, have a flange 21F, but is not necessarily limited thereto. The outer periphery of the housing 21 can be directly provided with a gear, or a separate gear can be integrated with the housing 21 by welding or the like. Furthermore, or the transmission of torque can be performed by a belt or other transmission means.

[0039] The housing 21 can directly support the differential gear set 25, but can also support the differential gear set 25 via a pair of thrust members 23. The thrust member 23 is engaged with the housing 21 and can transmit torque. The thrust member 23 also has the function of applying thrust to the friction clutch 27 described later. For engagement, the housing 21 and the thrust member 23 can respectively have lugs and grooves extending in the axial direction and engaging with each other, thereby, the thrust member 23 can transmit torque, but can move in the axial direction.

[0040] The differential gear set 25 includes, for example, a plurality of pinions 43 rotatably supported on a pinion shaft 41, and right and left gears 45 respectively meshing with the pinions 43. When torque is input to the pinion shaft 41, torque is output to the gears 45 on both sides through meshing of the gears, but differentials between the side gears 45 are allowed. The illustrated example and the following description mainly involve bevel gear types, but of course, a plane gear type may be used instead of the bevel gear type, and other appropriate forms may also be used.

[0041] The housing 21 is supported by engaging with the plurality of outer plates 29 through the above-mentioned grooves, for example. The bosses of the side gears 45 are provided with lugs, for example, respectively, and are engaged with the plurality of inner plates 31. The outer plates 29 and the inner plates 31 are alternately stacked to form a multi-plate clutch 27 as a friction clutch. The multi-plate clutch 27 is sandwiched between the end surface of the housing 21 and the thrust member 23, and when the thrust member 23 receives the thrust, the differential between the side gears 45 is frictionally restricted.

[0042] Combination Figure 2 Reference Figure 4 The thrust member 23 preferably includes a groove 51 for supporting the pinion shaft 41, and the end of the pinion shaft 41 is supported by being clamped by the groove 51. The groove 51 is not symmetrical in shape, and the surface that contacts the pinion shaft 41 in the positive direction with respect to the rotation of the differential device 1 is a cam surface 51A that is inclined relative to the circumferential direction, and the surface 51B that contacts in the reverse direction is substantially orthogonal to the circumferential direction.

[0043] When torque is applied in the direction of increasing the rotation speed (driving direction) in order to contact the cam surface 51A, a part of it is converted into an axial thrust f1 to press the multi-disc clutch 27, thereby limiting the differential by the differential gear set 25. Since the thrust increases as the applied torque increases, the differential limitation by the multi-disc clutch 27 is a torque-sensitive type.

[0044] When torque is applied in the direction of decelerating the rotation (sliding direction), the orthogonal surface 51B does not generate thrust. Therefore, the differential device 1 of this embodiment is a one-way LSD that mainly exerts differential limiting ability in the direction of increasing speed. In the deceleration direction, the torque is not consumed and flows back to the power source through the housing 21. The reverse flow torque can be used for energy regeneration.

[0045] The above description relates to an example based on a multi-plate clutch, but Figure 5 The pinion shaft 41 is connected to the housing 21 by a pin or the like, a plurality of pinions 43 are rotatably supported on the pinion shaft 41 , and a right gear 45 and a left gear 45 are respectively meshed with the pinion shaft 41 .

[0046] The combination of the axially outer surface of the side gear 45 and the inner surface of the housing 21 constitutes a friction clutch 27 , which functions to limit the differential between the side gears 45 .

[0047] 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 operating the friction clutch 27. The greater the applied torque, the greater the thrust, and therefore the differential limit of the friction clutch 27 is a torque-sensitive type. In order to further enhance the effect, the friction surface 35 of the housing 21 and the friction surface 53 of the side gear 45 can also be conical surfaces (i.e., cone clutches), and in addition, a friction ring 37 can be interposed between the friction surfaces 35 and 53.

[0048] Combination Figure 5 Reference Figure 6 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 53 may be formed on the outer edge of the flange portion 47F in the radial direction.

[0049] The gear member 49 has a recessed socket 55 that is open toward the outside in the axial direction in order to engage with the output member 47, and the output member 47 has a lug corresponding thereto. The relationship between the socket and the lug may be reversed, but in short, this engagement structure transmits torque between the gear member 49 and the output member 47 for both the forward rotation R1 and the reverse rotation R2.

[0050] combination Figure 5 , Figure 6 And refer to Figure 7 , the surface 55A of the side surfaces 55A and 55B of the socket 55 that abuts against the direction (driving direction) R1 that increases the rotation speed may also be inclined relative to the circumferential direction. Of course, correspondingly, the side surfaces of the lugs may also be inclined. The inclined and mutually abutting side surfaces act as a cam that partially converts the torque acting on the gear member 49 into a thrust f1. The thrust f1 presses the output member 47 outward in the axial direction to operate the friction clutch 27. These inclination angles θ1 can be appropriately set, but generally, the larger the inclination angle, the greater the thrust generated, thereby being able to exert a greater differential limiting capability.

[0051] On the other hand, the opposing side surface 55B can be set as a plane substantially orthogonal to the circumferential direction. When torque is applied to the direction (sliding direction) R2 that decelerates the rotation, no thrust is generated. Therefore, the differential device 1 of this embodiment is a unidirectional LSD that mainly exerts differential limiting capability in the direction of speed increase. In the deceleration direction, the torque is not consumed and flows back to the power source via the housing 21. The reverse flow torque can be used for energy regeneration.

[0052] In addition, instead of a multi-plate or cone clutch type, e.g. Figure 8 As shown, a helical gear type can be used in which pinions 57, 59 and a pair of side gears 45, 46 are arranged parallel to the axis. The housing 21 has a long hole and a short hole respectively parallel to the axis X, which respectively accommodate the long pinion 57 and the short pinion 59 and support them so that they can rotate. The pinions 57 and 59 have helical gear teeth 57H and 59H respectively, and the right gear 45 and the left gear 46 have helical gear teeth 45H and 46H respectively, which mesh with each other. In addition, the long pinion 57 has helical gear teeth 57G for meshing with the short pinion 59, and they mesh with each other. That is, the side gears 45 and the side gears 46 allow differential motion to each other via the pinions 57 and the pinion 59.

[0053] When torque is applied to the housing 21, it is differentially distributed to the side gears 45 and 46 via the pinions 57 and 59. At this time, the gear teeth that mesh with each other generate thrust in the axial direction, and this thrust acts on the helical gear teeth 45H, 46H, 57G, 57H, and 59H from the pinions 57 and 59 supported on the end wall of the housing 21. When torque is applied in the direction of increasing the rotation speed (driving direction), the thrust increases the sliding of the side gears 45 and 46 relative to the housing 21, thereby operating the friction clutch 27. As a result, the differential between the side gears 45 and 46 is limited. The larger the applied torque, the larger the thrust, so the helical gear type differential limitation is a torque-sensitive type.

[0054] On the other hand, when torque is applied in the direction of decelerating the rotation (sliding direction), thrust is generated in the opposite direction to the above, and the friction of the side gears 45 and 46 with respect to the housing 21 is reduced, so the differential limiting capacity is significantly reduced. Friction is generated between the side gears 45 and 46, but in order to reduce the friction, a low friction member, such as a thrust bearing, may be interposed between the side gears 45 and 46.

[0055] The direction of rotation may be opposite to the above description. In this case, the low friction member may be arranged between the side gears 45, 46 and the housing 21 instead of between the side gears 45, 46. Of course, the direction of the spiral of the helical gear teeth 45H, 46H, 57G, 57H, 59H can be appropriately changed according to the direction of rotation. That is, the direction of rotation, the direction of the spiral, and the arrangement of the low friction member can be appropriately selected, and thereby, the differential limiting capability in the driving direction and the sliding direction can be respectively enhanced or weakened.

[0056] In addition, the helical gear set described above can also be used in combination with the reference Figure 6 , Figure 7 The gear component and the cam structure of the output component described above can respectively enhance or weaken the differential limiting capability in the driving direction and the sliding direction.

[0057] Figure 8 In the example of , when torque is applied in the direction of accelerating the rotation (driving direction), a greater differential limiting capacity is generated compared to the case of decelerating the rotation (sliding direction). Therefore, the differential device 1 is a semi-unidirectional LSD that exerts a greater differential limiting capacity in the direction of accelerating. In the direction of decelerating, the energy consumed for differential limiting is smaller, so the reverse torque can be effectively used for energy regeneration.

[0058] According to the above-described embodiments, the differential device has a differential limiting capability, so the power transmission device having the differential limiting capability can transmit torque to the other drive wheel even when one drive wheel loses traction. On the other hand, during deceleration, the electric motor regenerates the remaining energy of the vehicle, but at this time, due to the differential limiting, no energy is lost or the loss is extremely small, so energy regeneration can be performed with low loss. In addition, when the inflow of energy through the transmission device is too large compared to the capacity of the electric motor, the power transmission can be cut off by the disconnection device, so that overload to the electric motor, the regeneration circuit or the rechargeable battery can be prevented.

[0059] Although several embodiments have been described, corrections or modifications of the embodiments can be made based on the above disclosure.

Claims

1. A power transmission device that outputs an output of a power source while allowing a differential on a pair of output shafts, the power transmission device comprising: a housing drivingly coupled to the power source to rotate about an axis; a differential gear set supported by the housing so as to rotate together about the shaft and including a pair of side gears capable of being differentially moved with each other; a friction portion, which is interposed between the housing and the differential gear set, or is built into the differential gear set to frictionally restrict the differential; a disconnecting device coupled to one of the output shafts to disconnect one of the side gears from the output shaft; and A cam structure is directly or indirectly coupled to the friction portion to convert the torque in the direction of increasing the rotation speed into an axial thrust and apply the thrust to the friction portion.

2. The power transmission device according to claim 1, characterized in that: The differential gear set includes: a pinion gear meshing with the side gear in a manner allowing the differential; and a pinion shaft supporting the pinion gear in a manner rotatable around an axis orthogonal to the shaft. The cam structure generates the thrust force by including a thrust member, wherein the thrust member includes a cam surface that abuts against the pinion shaft at an angle in the circumferential direction.

3. The power transmission device according to claim 2, characterized in that: The thrust member is engaged with the housing in a torque-transmittable manner and is movable in the axial direction.

4. The power transmission device according to claim 2, characterized in that: The thrust member is in contact with the pinion shaft so as not to generate force in the axial direction with respect to a torque in a direction that decelerates the rotation.

5. The power transmission device according to claim 1, characterized in that: The differential gear set includes a pinion gear meshing with the side gear in a manner allowing the differential. The side gears include: gear members meshing with the pinion gears, respectively; and output members including friction surfaces that directly or indirectly contact with the inner surface of the housing to form the friction clutch. The gear member and the output member engage with each other on a cam surface that is inclined with respect to the circumferential direction, and the cam surfaces that abut against each other generate the thrust force.

6. The power transmission device according to claim 5, characterized in that: The gear member and the output member are engaged with each other so as not to generate force in the axial direction with respect to torque in a direction to decelerate the rotation.

7. The power transmission device according to claim 1, characterized in that: The differential gear set includes a pinion gear meshing with the side gear to allow the differential, and the pinion gear and the side gear each include helical gear teeth that generate a tooth pressure that generates the thrust force.

8. The power transmission device according to claim 7, characterized in that: A low friction member is interposed between the pair of side gears or between the side gear and the housing.

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