Coaxial driving device

Abstract

A coaxial drive device for driving a pair of axles capable of rotating around a first shaft is provided with: a motor coaxial with the first shaft; a differential which is coaxial with the first shaft, can rotate around the first shaft, and is provided with a differential gear set which outputs received torque to the pair of axles in a differential manner; an output shaft that passes through the motor, is driven by the motor to rotate around the first shaft, and has a through hole sized to allow one of the pair of axles to reach the differential from the outside; a transmission shaft that is rotatable about a second axis parallel to the first axis, meshes with both the output shaft and the differential, and transmits the torque from the motor to the differential; a clutch disposed between the motor and the differential gear set to restrict differential motion of the differential gear set, or disposed on the transmission shaft to detachably connect the output shaft and the differential; and an actuator that is disposed above the first shaft and that drives the clutch.

Description

Technical Field

[0001] The following disclosure relates to a coaxial drive device mainly used for driving wheels of electric vehicles, which can be coaxial with the axle of the driving wheel and is not easily affected by stones, mud or water flying from the road surface. Background Art

[0002] The technology of driving a vehicle only by an electric motor instead of an internal combustion engine is being studied intensively. Although it is possible to drive a vehicle by directly combining a motor with an axle, a motor with a large output that satisfies this situation needs to be adopted. If its weight and cost are considered, it cannot be said to be a realistic solution. Usually, a moderate output (i.e. small) motor is used, and the torque of the motor is multiplied by a multi-stage reduction gear set to drive the vehicle.

[0003] The drive device composed of a combination of a gear box including a reduction gear set and a motor usually protrudes significantly outward from the axle as exemplified in Patent Document 1. Such a size reduces the advantage of intentionally using a small motor. Patent Document 2 proposes a drive device that can be coaxial with the axle.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Patent Application Publication WO2013 / 076878A1

[0007] Patent document 2: International patent application publication WO2021 / 004780A1 Summary of the invention

[0008] The drive device protruding outward from the axle is convenient for protecting the electrical components from stones, mud or water flying from the road surface due to its size. This is because, as long as the lower side facing the road surface is avoided, no matter where the electrical components are arranged, they can be hidden behind the device when viewed from the road surface. In a coaxial drive device such as Patent Document 2, there is a lack of space to hide the electrical components, and it is not necessarily convenient to arrange the electrical components in such a place. For example, the figure in Patent Document 2 shows a situation where the actuator driving the decoupling device 7 is located below the oil level 11. Obviously, the actuator is close to the road surface. Even if it is assumed that the device is turned upside down, since the decoupling device 7 is located at the left end of the device, it is impossible to avoid the actuator from being exposed axially outward from the drive device. Obviously, the actuator cannot avoid flying objects from the road surface.

[0009] The device disclosed below changes the arrangement of a plurality of components to provide a coaxial drive device capable of causing an actuator to avoid flying objects from a road surface.

[0010] A coaxial drive device for driving a pair of axles rotatable about a first axis comprises: a motor coaxial with the first axis; a differential coaxial with the first axis and rotatable about the first axis and comprising a differential gear set for differentially outputting received torque to the pair of axles; an output shaft penetrating the motor and driven by the motor to rotate about the first axis and having a through hole sized to allow one of the pair of axles to reach the differential from the outside; a transmission shaft rotatable about a second axis parallel to the first axis and meshing with both the output shaft and the differential to transmit the torque from the motor to the differential; a clutch disposed between the motor and the differential gear set and limiting the differential of the differential gear set, or disposed on the transmission shaft and connecting the output shaft and the differential so as to be releasable; and an actuator disposed above the first axis and driving the clutch. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view of the coaxial drive device according to one embodiment, and is a cross-sectional view obtained by cutting along a plane passing through each axis.

[0012] Figure 2 is used in Figure 1 The device mainly shows an enlarged cross-sectional view of the clutch and the actuator.

[0013] Figure 3 This is a schematic side view for showing the positional relationship of three axes in the coaxial drive device.

[0014] Figure 4 It is a cross-sectional view of a coaxial drive device according to another embodiment, and is a cross-sectional view obtained by cutting along a plane passing through each axis.

[0015] Figure 5 is used in Figure 4 The device mainly shows an enlarged cross-sectional view of the clutch. DETAILED DESCRIPTION

[0016] Hereinafter, several exemplary embodiments will be described with reference to the accompanying drawings. In the following description and the appended claims, the term "parallel" refers to the usual geometric parallelism, that is, the meaning of being located in the same plane but not intersecting each other, and does not include the meaning of being necessarily identical to each other. In addition, the distinction between the front, rear, top and bottom is based on the state of the device being mounted on the vehicle. It should be noted that the drawings may not be shown with an accurate scale, so the mutual dimensional relationship is not limited to the relationship shown in the figure.

[0017] The coaxial drive device of the present embodiment described below is generally used to drive a pair of axles extending left and right. Of course, the use is not limited to this, and it can be used to drive any device that operates by supplying torque via an axle.

[0018] Reference Figure 1 , arrow F indicates the front of the vehicle, and arrow R indicates the rear. The first axis, the second axis, and the third axis X1, X2, and X3 are parallel to each other and are orthogonal to the longitudinal direction of the vehicle. A pair of axles are not shown, but extend to the right and left directions respectively along the first axis X1.

[0019] The coaxial drive device generally includes a motor 1 that generates torque, an output shaft 3 that outputs the torque, a differential 5 that differentially outputs the received torque to a pair of axles, a transmission shaft 7 that mediates between the output shaft 3 and the differential 5, a clutch 9 that limits the differential of the differential 5, and an actuator 11 that operates the clutch 9. The motor 1 and the differential 5 are coaxially arranged adjacent to each other, but they are not directly connected, and the transmission shaft 7 that is not coaxial with them is responsible for torque transmission. Such an arrangement of the elements is conducive to making the overall drive device compact both in the longitudinal and lateral directions.

[0020] These elements are contained and supported as a whole in the housings 21 and 23, but the housing 23 containing the motor 1 and the housing 21 mainly containing the differential 5 and the transmission shaft 7 may be separate and can be combined with each other. In this way, the motor 1 and the other elements can be assembled independently, and finally the two can be combined to assemble the whole device, thus facilitating the production of the device. The housings 21 and 23 may also be decomposed into a plurality of elements, respectively. For example, the housing 21 may be divided into a main body 25 and covers 27 and 29, and the housing 23 may be divided into a main body 23B and a cover 23C. These will be described later.

[0021] According to the example shown in the figure, the motor 1 is arranged on the right side in the coaxial drive device. Of course, the motor 1 can also be arranged on the left side opposite to the example shown in the figure. In short, the motor 1 is coaxial with the first axis X1, and has a stator composed of, for example, an electromagnet and a rotor that receives its magnetic flux and rotates around the axis in order to generate a rotational force around it. In addition, the electromagnet is connected to the battery of the vehicle via a controller, so that the rotor can rotate in a controllable manner.

[0022] The output shaft 3 passes through the motor 1, is drivingly coupled to the rotor in the motor 1, and rotates around the first axis X1 by the received rotational force. One end of the output shaft 3 faces the end of the housing 23, and the other end is exposed in the housing 21 and has gear teeth 33. The gear teeth 33 output the rotational force of the motor 1 to the transmission shaft 7 by meshing with the gear 71 described later. The output shaft 3 can be supported by the cover 23C near one end, and the other end can be supported by the cover 29.

[0023] The output shaft 3 is hollow as a whole, that is, it has a through hole 31 extending from one end to the other end along the first axis X1. The size of the through hole 31 is designed so that one axle of the pair of axles, in the example shown in the figure, the right axle can pass through the through hole 31 from the outside of the device to reach the differential 5 and connect with it.

[0024] The transmission shaft 7 is a shaft different from the output shaft 3 and is supported by the housing 21 in a manner that rotates around the second axis X2. For example, one end of the transmission shaft 7 may protrude beyond the cover 27 and be supported by the cover 29. If one end of the transmission shaft 7 and the other end of the output shaft 3 are supported by the cover 29 in common, it is advantageous to stabilize the positional relationship between them and stabilize the meshing. The other end of the transmission shaft 7 may be supported by the main body 25.

[0025] The transmission shaft 7 has a gear 71 near one end thereof to mesh with the gear teeth 33, and has a gear portion 73 near the other end thereof to mesh with the ring gear 53 described later. The diameter of the gear portion 73 is smaller than that of the gear 71, and therefore, the combination of these gears constitutes a reduction gear set that reduces the rotation of the motor 1 (multiplies the torque) and outputs it to the differential 5. In addition, although not necessarily, for ease of assembly, the gear portion 73 may be integrated with the transmission shaft 7 as in the example shown in the figure, or the gear 71 may be separated and coupled to the transmission shaft 7 by press-fitting, welding, spline coupling, or the like.

[0026] In the above description, the reduction gear set is a two-stage gear set, but it can also be a gear set with more stages. In addition, instead of reducing speed by combining a small-diameter gear and a large-diameter gear, any gear set capable of reducing speed, such as an external meshing gear set, an internal meshing gear set, a planetary gear set, or a harmonic drive gear set, can be used, or a gear set composed of a combination of these can also be used.

[0027] The differential 5 is coaxial with the output shaft 3 and supported by the housing 21 in a manner that rotates around the first axis X1. For example, one end of the differential 5 is supported by the first cover 27 and faces the other end of the output shaft 3, and the other end of the differential 5 is supported by the main body 25. If the other end of the differential 5 and the other end of the transmission shaft 7 are commonly supported by the main body 25, it is advantageous to stabilize the positional relationship between them and stabilize the meshing.

[0028] The differential 5 includes a differential case 51 supporting a differential gear set, and a ring gear 53 is fixed to the circumference of the differential case 51 , for example, so that the differential case 51 and the ring gear 53 rotate integrally by receiving torque. Alternatively, the ring gear 53 may be integral with the differential case 51 .

[0029] In the example shown in the figure, the differential gear set is a bevel gear type, but it can also be replaced by a face gear type, a planetary gear type or other appropriate forms. In short, the differential gear set is configured to transmit the torque received by the differential case 51 to the gears 55R and 55L on both sides, but allow the differential between the side gears 55R and 55L. The gears 55R and 55L on both sides are respectively configured to be combined with two axles, and for example, they can each have a spline structure on the inner surface. The left axle connected to the left side gear 55L extends to the outside through the opening of the differential case 51 and the housing 21, and the right axle connected to the right side gear 55R extends to the outside through the through hole 31 and the opening of the housing 23, thereby respectively connecting to the two wheels. As described above, the left and right can also be opposite to the example shown in the figure.

[0030] The clutch 9 is a device having a driving member and a driven member and capable of transmitting power between them. Usually, the driving member and the driven member are annular and coaxially arranged. In the present embodiment, the clutch 9 is arranged between the motor 1 and the differential gear set, and is configured to limit the differential of the differential gear set when viewed in the direction of the first axis X1. The clutch 9 is, for example, a multi-plate clutch, one of the clutch plates of which is coupled to the right gear 55R, and the other clutch plate is coupled to the differential case 51. When the alternately stacked clutch plates are subjected to a pressing force, the right gear 55R is braked relative to the differential case 51, thereby limiting the differential between the side gears 55R and 55L. Of course, other forms of friction clutches such as cone clutches may be used instead of the multi-plate clutch. Alternatively, the friction clutch may be replaced, or a claw clutch, for example, may be used on this basis. This will give the differential 5 a so-called differential locking function.

[0031] In order to apply a pressing force to the clutch 9 , the coaxial drive device includes, for example, a combination of an actuator 11 and a cam mechanism 13 . The actuator 11 is disposed on a third axis X3 different from the axes X1 and X2 . The cam mechanism 13 is disposed between the motor 1 and the clutch 9 .

[0032] Combination Figure 1 Reference Figure 2 The actuator 11 is, for example, a small motor and includes a gear shaft 15 for output. The gear shaft 15 rotates around the third axis X3. The gear shaft 15 meshes with the gear plate 41 of the cam mechanism 13 directly or via the reduction gear 17 to drive the cam mechanism 13.

[0033] The cam mechanism 13 includes a pressure plate 45 in a manner opposed to the gear plate 41, and includes a cam structure for converting rotational motion into axial motion between the gear plate 41 and the pressure plate 45. The cam structure is, for example, an inclined surface provided on one or both of the plates 41 and 45 and a cam ball 43 that can roll on the inclined surface. A roller may be used instead of the cam ball, or a combination of an inclined surface on one side and a protrusion on the other side that slide directly may be used. In short, the gear plate 41 can rotate around the first axis X1 but is fixed in the axial direction, while the pressure plate 45 is stopped from rotating around the first axis X1 but is movable in the axial direction. Therefore, when the gear plate 41 is rotated by the actuator 11, the pressure plate 45 is driven in the axial direction by the interposed cam structure, thereby applying a pressing force to the clutch 9.

[0034] According to the above configuration, from Figure 1 It can be easily understood that the cam mechanism 13, which is the object driven by the actuator 11, is close to the center of the device and is arranged to overlap with the clutch 9 in the axial direction. Therefore, the actuator 11 will not necessarily protrude outward from the housing 21, 23 in the axial direction. Figure 3 As shown, the third axis X3 is radially inward of the outer periphery of the motor 1, so the actuator 11 can also be roughly arranged inward of the outer periphery of the motor 1. The transmission shaft 7 and the actuator 11 can be located at any position around the first axis X1, but if the actuator 11 is located below D relative to the housing 21, it is easily affected by flying objects from the road surface, and it is preferably arranged above U relative to the first axis X1 in the vehicle. In addition, relative to the transmission shaft 7, the actuator 11 is preferably located at the rear R rather than the front F. The actuator 11 can be hidden behind the housing 21 relative to the ground G, thereby avoiding flying objects from the road surface.

[0035] Based on the same configuration, such as Figure 4 As shown, an embodiment using the clutch 9 for the purpose of intermittently transmitting the torque from the motor 1 to the differential 5 may be implemented.

[0036] Combination Figure 4 Reference Figure 5 The gear portion 73 is coaxial with the transmission shaft 7 but is separate and can rotate freely with respect to each other. Lubrication between them can be only through lubricating oil, or a bearing element such as a needle bearing can be interposed. The clutch 9 is arranged on the transmission shaft 7 and, for example, between the gear 71 and the gear portion 73.

[0037] The transmission shaft 7 is provided with a hub 75 integrally adjacent to the gear portion 73, and a sleeve 63 is spline-coupled to the outer circumference thereof. The sleeve 63 rotates together with the hub 75, but is movable relative to the hub 75 in the axial direction.

[0038] The gear portion 73 is coupled with a cone 67. The cone 67 faces the sleeve 63 and has claws 69 meshing therewith. When the sleeve 63 moves in the axial direction and meshes with the claws 69, the rotation of the transmission shaft 7 is transmitted to the gear portion 73 via the sleeve 63 and the cone 67. In order to eliminate the speed difference between the two before meshing, a synchronizer ring 65 may be interposed. Through meshing, torque is transmitted from the motor 1 to the differential 5. When the sleeve 63 is disengaged from the claws 69, the rotation is not transmitted, and thus the torque transmission is cut off.

[0039] Although not shown again, the actuator 11 drives the sleeve 63 in the axial direction via the shift fork 61. In order to convert the rotational motion of the actuator 11 into the axial motion, a cam mechanism 13 having the same structure as that described above can be used, or a simpler ball screw mechanism can also be used. Alternatively, the actuator 11 may not be a motor that generates rotation, but a linear motor, a hydraulic mechanism, etc. that directly generates axial motion.

[0040] In short, the actuator 11 can be arranged close to the transmission shaft 7, and can also be arranged close to the transmission shaft 7. Figure 1 The example also relies on the central configuration of the device, and can also use Figure 3 Therefore, the actuator 11 can be hidden behind the housing 21, thereby avoiding flying objects from the road surface.

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

Claims

1. A coaxial drive device that drives a pair of axles that are rotatable about a first axis, The coaxial drive device is characterized by comprising: a motor coaxial with the first shaft; a differential coaxial with the first shaft and rotatable about the first shaft, and including a differential gear set for differentially outputting received torque to the pair of axles; an output shaft that passes through the motor and is driven by the motor to rotate about the first axis, and has a through hole whose size is set to allow one of the pair of axles to reach the differential from the outside; a transmission shaft rotatable about a second axis parallel to the first axis and meshing with both the output shaft and the differential to transmit the torque from the motor to the differential; a clutch disposed between the motor and the differential gear set to limit the differential of the differential gear set, or disposed on the transmission shaft to releasably couple the output shaft and the differential; and The actuator is disposed above the first shaft and drives the clutch.

2. The coaxial drive device according to claim 1, characterized in that: The actuator is arranged along a third axis that is different from the first axis and the second axis and is located inward of an outer circumference of the motor in a radial direction of the first axis.

3. The coaxial drive device according to claim 2, characterized in that: It also has a cam mechanism for converting rotational motion into axial motion to drive the above clutch, The actuator includes: a second motor that generates rotation about the third axis; and a gear train that meshes with the second motor to impart the rotational motion to the cam mechanism.

4. The coaxial drive device according to claim 1, characterized in that: The actuator is arranged to overlap with the clutch in the axial direction.

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