Motor unit

Abstract

To provide a technique capable of improving a degree of freedom for layout of a bearing and a casing in an in-wheel-type motor unit.SOLUTION: A motor unit comprises: a first rotating shaft that is driven by a motor and has a first gear; a pair of first bearings positioned at both sides of the first gear, and rotatably supporting the first rotating shaft with respect to a casing; a second rotating shaft parallel to the first rotating shaft and having a second gear that engages with the first gear; and a pair of second bearings positioned at both sides of the second gear, and rotatably supporting the second rotating shaft with respect to the casing. With respect to an axis direction parallel to the first rotating shaft and to the second rotating shaft, the pair of second bearings are positioned between the pair of first bearings. Each of the pair of second bearings has an outer ring fixed to the second gear from inside in a radial direction thereof, an inner ring fixed to the casing from outside in the radial direction thereof, and a rolling body positioned between the outer ring and the inner ring.SELECTED DRAWING: Figure 3

Description

Technical Field

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[0001] The technology disclosed in this specification relates to a motor unit. In particular, it relates to an in-wheel type motor unit for driving the wheels of a vehicle.

Background Art

[0002] The in-wheel motor drive device disclosed in Patent Document 1 includes a casing, an input shaft driven by an electric motor and having an input gear, and an intermediate shaft parallel to the input shaft and having an input intermediate gear meshing with the input gear. Between the input shaft and the intermediate shaft, a bearing for supporting the input shaft in the casing and a bearing for supporting the intermediate shaft in the casing are provided.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The bearings rotatably support the outer surface of the rotating shafts relative to the casing. Furthermore, the two rotating shafts, each having meshing gears, are offset radially from one another. Between these two shafts, two bearings, each rotatably supporting its respective shaft relative to the casing, and the casing supporting these bearings are arranged superimposed radially. Additionally, the casing supporting the bearings is subjected to loads resulting from the rotation of the shafts. Therefore, the casing requires sufficient rigidity to withstand these loads. This makes it difficult to make the radial height of the casing extremely thin. Thus, in in-wheel motor units with two offset rotating shafts, the layout of the bearings and casings is complex, and depending on these layouts, the size of the casing can become large. This specification provides a technology that can improve the degree of freedom in the layout of the bearings and casings. [Means for solving the problem]

[0005] This specification discloses an in-wheel type motor unit for driving the wheels of a vehicle. The motor unit comprises a motor, a casing housing the motor, a first rotating shaft driven by the motor and having a first gear, a pair of first bearings located on both sides of the first gear and rotatably supporting the first rotating shaft relative to the casing, a second rotating shaft parallel to the first rotating shaft and having a second gear meshing with the first gear, and a pair of second bearings located on both sides of the second gear and rotatably supporting the second rotating shaft relative to the casing. With respect to the axial direction parallel to the first and second rotating shafts, the pair of second bearings are located between the pair of first bearings, and each of the pair of second bearings has an outer ring fixed radially inward to the second gear, an inner ring fixed radially outward to the casing, and rolling elements located between the outer ring and the inner ring.

[0006] In the motor unit described above, each of the pair of second bearings rotatably supports the second gear from the radially inward direction relative to the casing. Therefore, compared to a configuration in which, for example, the casing is interposed between the second gear and the pair of second bearings, the degree of freedom in the layout of the pair of second bearings can be improved.

[0007] Details of the technology disclosed herein and further improvements are described in the following "Modes for Carrying Out the Invention". [Brief explanation of the drawing]

[0008] [Figure 1] A side view of the motor unit 10 of the embodiment is shown. [Figure 2] Figure 1 shows a cross-sectional view along line II-II. [Figure 3] This shows an enlarged view of the area enclosed by line III in Figure 2. [Figure 4] This shows an enlarged view of the area enclosed by line IV in Figure 3. [Modes for carrying out the invention]

[0009] In one embodiment of this technology, grooves for accommodating the pair of second bearings may be provided on both axial end faces of the second gear. In this case, the outer ring of the second bearing may be fixed to the inner circumferential surface of the groove from the radially inward side. With this configuration, the axial size of the casing can be reduced by housing the second bearing at least partially in the groove.

[0010] In one embodiment of this technology, the casing may be provided with a pair of bosses protruding toward each groove of the second gear. In this case, the inner ring of the second bearing may be fixed to the outer circumferential surface of the bosses from the radially outer side. With this configuration, the portion of the second bearing that is housed in the groove can be stably supported by the bosses of the casing.

[0011] In one embodiment of this technology, the pair of first bearings and the pair of second bearings may overlap at least partially when viewed along the axial direction. This configuration allows for a reduction in the distance between the first and second rotation axes.

[0012] In one embodiment of this technology, the first rotating shaft may be coaxially connected to the motor, and the second rotating shaft may be coaxially connected to the wheel. However, in another embodiment, for example, the second rotating shaft may be radially offset from the wheel. In that case, the second gear may mesh with a third gear provided on a third rotating shaft that is coaxially positioned with respect to the wheel.

[0013] (Examples) Figure 1 shows a side view of the motor unit 10 of the embodiment. The motor unit 10 is installed on the rear wheel 6R of the electric vehicle 100. The electric vehicle 100 drives the rear wheel 6R by supplying power from a battery (not shown) to the in-wheel type motor unit 10 installed on the rear wheel 6R. In this specification, the electric vehicle 100 includes not only electric vehicles but also fuel cell vehicles. In the coordinate system in the figure, FR indicates the front of the electric vehicle 100, UP indicates the top of the electric vehicle 100, and LH indicates the left of the electric vehicle 100. Hereafter, "up", "down", "left", "right", "front", and "rear" will be described based on the coordinate system in the figure.

[0014] Although not shown in the diagram, the motor unit 10 is connected to the body 2 of the electric vehicle 100 by a trailing arm without going through the rear suspension. Furthermore, as will be described later with reference to Figure 2, the motor unit 10 is directly connected to the rear wheel 6R without going through the rear suspension. The rear wheel 6R comprises a wheel 8 and a tire 9. The wheel 8 covers the motor unit 10 from the outside of the vehicle (i.e., the front side of the page in Figure 1).

[0015] As shown in Figure 2, the motor unit 10 comprises a motor 21, an input shaft 20, an output shaft 30, and a casing 12. The motor 21 is a so-called radial gap motor and comprises a rotor 24, a rotor core 25, a stator coil 26, and a stator core 27. The rotor core 25 is provided on the outer circumferential surface of the rotor 24. The stator coil 26 is wound around the outer circumferential surface of the stator core 27. The stator coil 26 and the stator core 27 face the rotor core 25 from the radial direction (i.e., the vertical direction in the plane of Figure 2) of the rotor core 25. Both the rotor core 25 and the stator core 27 are made of magnetic material. When current flows through the stator coil 26, a magnetic force is generated between the rotor core 25 and the stator coil 26, causing the rotor 24 to rotate.

[0016] An input shaft 20 is inserted into the radial center of the rotor 24. The input shaft 20 has a cylindrical shape that extends along the left-right direction. The input shaft 20 is positioned coaxially with the central axis A1 of the rotor 24. That is, the input shaft 20 is provided coaxially with the motor 21. The rotational motion of the rotor 24 from the motor 21 is transmitted to the input shaft 20. That is, the input shaft 20 is driven by the motor 21.

[0017] An input gear 22 is provided at the left end of the input shaft 20 (i.e., the right end of the paper in Figure 2). The input gear 22 rotates together with the input shaft 20. An output gear 32 is located in front of the input gear 22 (i.e., below the paper in Figure 2). The input gear 22 and the output gear 32 mesh with each other.

[0018] The output gear 32 is fixed to the outer surface of the output shaft 30. This allows the rotation of the rotor 24 of the motor 21 to be transmitted to the output shaft 30 via the input shaft 20. The output shaft 30 has a cylindrical shape extending along the left-right direction; that is, the output shaft 30 extends parallel to the input shaft 20. The central axis A1 of the rotor 24 and the central axis A2 of the output shaft 30 extend parallel to each other; that is, the input shaft 20 and the output shaft 30 extend in axial directions AD parallel to both shafts 20 and 30.

[0019] The casing 12 houses the motor 21, the input gear 22, and the output gear 32. The casing 12 includes a first casing 14, a second casing 16, and a third casing 18. Each of the casings 14, 16, 18 overlaps in the left - right direction. The first casing 14 located closest to the inside of the vehicle (i.e., the left side of the paper in FIG. 2) supports the motor 21 from the inside of the vehicle. A bearing 11R is provided between the rotor 24 of the motor 21 and the first casing 14.

[0020] The second casing 16 covers the motor 21 from the outside of the vehicle (i.e., the right side of the paper in FIG. 2). The first casing 14 and the second casing 16 are fastened by a plurality of bolts B1. A bearing 11L is provided between the input shaft 20 and the second casing 16. Thus, the first casing 14 and the second casing 16 of the casing 12 support the motor 21 rotatably by a pair of bearings 11R, 11L provided on both sides in the axial direction AD of the rotor 24.

[0021] The input shaft 20 extends outside the vehicle through the outer wall of the second casing 16. The tip of the input shaft 20 and the input gear 22 are covered by the third casing 18 from the outside of the vehicle. The second casing 16 and the third casing 18 are fastened by a plurality of bolts B1. A bearing 13L is provided between the tip of the input shaft 20 and the third casing 18. Similarly, a bearing 13R is provided between the input shaft 20 and the second casing 16 on the right side (i.e., the left side of the paper in FIG. 2) of the input gear 22 of the input shaft 20. Thus, the second casing 16 and the third casing 18 of the casing 12 support the input shaft 20 rotatably by a pair of bearings 13R, 13L provided on both sides in the axial direction AD of the input gear 22.

[0022] The output gear 32 is positioned between the second casing 16 and the third casing 18. A pair of bearings 15R and 15L are provided on both sides of the output gear 32 in the axial direction AD. The output shaft 30 extends outside the vehicle through the outer wall of the third casing 18. A disk rotor 34 is provided at the tip of the output shaft 30. The disk rotor 34 has a disk shape and rotates together with the output shaft 30. A brake piston 36 is provided behind the disk rotor 34 (i.e., above the paper surface of FIG. 2). The brake piston 36 stops the rotation of the output shaft 30 by sandwiching the disk rotor 34.

[0023] The tip of the output shaft 30 is covered by the wheel 5 from the outside of the vehicle. Thus, the output shaft 30 is coaxially connected to the rear wheel 6R. Thus, the second casing 16 and the third casing 18 support the output shaft 30. In a modified example, the structure of the casing 12 is not limited to a structure divided into the respective casings 14, 16, and 18, and an integral structure may be adopted.

[0024] Referring to FIG. 3, the positional relationship between the pair of bearings 13R and 13L and the pair of bearings 15R and 15L in the motor unit 10 of the present embodiment will be described. In the axial direction AD, the distance between both ends of the pair of bearings 15R and 15L is shorter than the distance D1 between the pair of bearings 13R and 13L. In other words, in the axial direction AD, the pair of bearings 15R and 15L are positioned between the pair of bearings 13R and 13L. For example, in a configuration where a part of the pair of bearings 13R and 13L and the pair of bearings 15R and 15L overlap when viewed along the radial direction RD of the output shaft 30, it is necessary for the casing 12 to interpose a boss that supports both between the pair of bearings 13R and 13L and the pair of bearings 15R and 15L. In such a configuration, the distance D2 between the central axis A1 of the input shaft 20 and the central axis A2 of the output shaft 30 becomes longer.

[0025] <0000Furthermore, in this case, the boss of the casing 12 that supports both casings 12 is subjected to loads from both sides of the radial RD via a pair of bearings 13R, 13L and a pair of bearings 15R, 15L as the input shaft 20 and output shaft 30 rotate. For this reason, the boss of the casing 12 is required to have higher rigidity compared to a configuration where the load is applied from only one side of the radial RD. As a result, the boss is higher in the radial RD with respect to the radial RD compared to the boss of the casing 12 that does not support a pair of bearings 13R, 13L and a pair of bearings 15R, 15L. For this reason, the distance D2 between the central axis A1 of the input shaft 20 and the central axis A2 of the output shaft 30 tends to be longer.

[0026] In this embodiment, the motor unit 10 has a pair of bearings 15R and 15L positioned between a pair of bearings 13R and 13L with respect to the axial direction AD. Therefore, there is no need to interpose a boss of the casing 12 between them. As a result, the degree of freedom in the layout of the pair of bearings 15R and 15L relative to the pair of bearings 13R and 13L can be improved.

[0027] Referring to Figure 4, the detailed structure of the pair of bearings 15R and 15L will be described. In this specification, the structure of bearing 15R, located on the right side (i.e., the left side of Figure 2), will be mainly described. However, bearings 11R, 11L, 13R, 13L, and 15L have a similar configuration.

[0028] The bearing 15R is a so-called radial ball bearing. The bearing 15R extends in an annular shape along the circumferential direction of the output gear 32. The bearing 15R comprises an outer ring 52, an inner ring 54, and rolling elements 56. The outer ring 52 is located outside the radial RD of the rolling elements 56. The inner ring 54 is located inside the radial RD of the rolling elements 56. The outer ring 52 and the inner ring 54 support the rolling elements 56 so that they can slide along the circumferential direction of the output gear 32.

[0029] A groove 40 is provided on the right end face of the output gear 32. The groove 40 is a recess that extends in an annular shape along the circumferential direction of the output gear 32. The groove 40 houses the bearing 15R and the boss 60 of the second casing 16. The boss 60 is a projection that extends in an annular shape along the circumferential direction of the output gear 32. The boss 60 has a rectangular cross-section and faces the inner surface of the inner circumferential surface 42 of the groove 40 in the radial direction RD (i.e., the lower side of the paper in Figure 2) with a gap between them.

[0030] As shown in Figure 4, the bearing 15R is located between the outer surface of the radial RD of the inner circumferential surface 42 of the groove 40 and the outer circumferential surface 62 of the boss 60. That is, the bearing 15R is housed in the groove 40. More specifically, the outer ring 52 of the bearing 15R is fixed to the inner circumferential surface 42 of the groove 40 from the inside of the radial RD (i.e., the bottom side of the paper in Figure 4), and the inner ring 54 of the bearing 15R is fixed to the outer circumferential surface 62 of the boss 60 from the outside of the radial RD. Similarly, the outer ring 52 of the left-hand bearing 15L of the pair of bearings 15R, 15L is also fixed to the inner circumferential surface 42 of the groove 40 from the inside of the radial RD, and the inner ring 54 of the bearing 15L is fixed to the boss 80 of the third casing 18 (see Figure 3) from the outside of the radial RD. In this way, the output gear 32 is rotatably supported relative to the casing 12. By housing the bearing 15R in the groove 40, the distance between the pair of bearings 15R and 15L can be shortened. As a result, the size of the casing 12 can be reduced with respect to the axial AD.

[0031] Thus, in the motor unit 10 of this embodiment, the bosses 60 and 80 of the casing 12 are not interposed between the pair of bearings 15R and 15L and the outer surface of the inner circumferential surface 42 of the output gear 32 in the radial direction RD. Therefore, the pair of bearings 15R and 15L can be brought closer to the input shaft 20. Furthermore, as shown in Figure 3, in the motor unit 10, the rear ends of the pair of bearings 15R and 15L (i.e., the upper ends of the paper in Figure 3) are positioned behind the front ends of the pair of bearings 13R and 13L. That is, when viewed along the axial direction AD, the rear ends of the pair of bearings 15R and 15L overlap with the front ends of the pair of bearings 13R and 13L by a distance D3. In other words, the distance D2 between the central axis A1 of the input shaft 20 and the central axis A2 of the output shaft 30 is shorter by a distance D3 than the sum of the distance between the front ends of the central axis A1 and the pair of bearings 13R and 13L, and the distance between the central axis A2 and the rear ends of the pair of bearings 15R and 15L. In this way, the motor unit 10 of this embodiment can reduce the size of the casing 12, particularly with respect to the radial direction RD, by improving the degree of freedom in the layout of the pair of bearings 15R and 15L.

[0032] (Correspondence) Input gear 22 is an example of a "first gear," and output gear 32 is an example of a "second gear." Input shaft 20 is an example of a "first rotation shaft," and output shaft 30 is an example of a "second gear." A pair of bearings 13R and 13L are an example of a "pair of first bearings," and a pair of bearings 15R and 15L are an example of a "pair of second bearings."

[0033] The specific examples of the technology disclosed herein have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above. Modifications of the above embodiments are listed below.

[0034] (Modification 1) In the motor unit 10 of this embodiment, the entire range of the bearing 15R is housed in the groove 40 of the output gear 32 with respect to the axial direction AD. However, in the modification, for example, half of the bearing 15R may be housed in the groove 40 with respect to the axial direction AD. Generally speaking, it is sufficient for the bearing 15R to be partially housed in the groove 40.

[0035] (Modification 2) The output gear 32 does not need to have a groove 40. In that case, the outer ring 52 of the bearing 15R may be fixed from the inside in the radial direction RD to a projection provided on the right end face of the output gear 32 in the axial direction AD.

[0036] (Modification 3) The casing 12 does not need to have bosses 60 and 80. In that case, for example, the inner ring 54 of the bearing 15R may be fixed to the casing 12 in the axial direction AD.

[0037] (Modification 4) An intermediate gear may be provided between the input gear 22 and the output gear 32. In this case, for example, a pair of intermediate bearings that rotatably support the intermediate gear in the casing 12 may be located between a pair of bearings 13R and 13L with respect to the axial direction AD. Furthermore, each of the pair of intermediate bearings may have an outer ring 52 fixed radially inward to the first intermediate gear, an inner ring 54 fixed radially outward to the casing 12, and rolling elements 56. In this modification, the intermediate gear is an example of a "second gear," and the intermediate bearing is an example of a "second bearing."

[0038] The technical elements described herein or in the drawings demonstrate technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated herein or in the drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself. [Explanation of Symbols]

[0039] 2: Body, 5: Wheel, 6R: Rear wheel, 8: Wheel, 9: Tire, 10: Motor unit, 11L, 11R, 13L, 13R, 15L, 15R: Bearings, 14: First casing, 16: Second casing, 18: Third casing. 20: Input shaft, 21: Motor, 22: Input gear, 24: Rotor, 25: Rotor core, 26: Stator coil, 27: Stator core, 30: Output shaft, 32: Output gear, 34: Disc rotor, 36: Brake piston, 40: Groove, 42: Inner surface, 52: Outer ring, 54: Inner ring, 56: Rolling element, 60: Boss, 62: Outer surface, 80: Boss, 100: Electric vehicle, A1, A2: Center axis, AD: Axial direction, B1, RD: Radial direction

Claims

1. An in-wheel type motor unit that drives the wheels of a vehicle, Motor and, A casing for housing the motor, Driven by the motor, and comprising a first rotating shaft having a first gear, A pair of first bearings are located on both sides of the first gear and rotatably support the first rotating shaft relative to the casing, A second rotating shaft is parallel to the first rotating shaft and has a second gear that meshes with the first gear, A pair of second bearings are located on both sides of the second gear and rotatably support the second rotating shaft relative to the casing, Equipped with, With respect to the axial direction parallel to the first and second rotation axes, the pair of second bearings are located between the pair of first bearings. Each of the pair of second bearings has an outer ring fixed radially inward to the second gear, an inner ring fixed radially outward to the casing, and rolling elements located between the outer ring and the inner ring. When viewed along the axial direction, the pair of first bearings and the pair of second bearings overlap at least partially. Motor unit.

2. The axial ends of the second gear are provided with grooves for housing the pair of second bearings, The motor unit according to claim 1, wherein the outer ring of the second bearing is fixed to the inner circumferential surface of the groove from the radially inner side.

3. The casing is provided with a pair of bosses that protrude toward each groove of the second gear, The motor unit according to claim 2, wherein the inner ring of the second bearing is fixed to the outer circumferential surface of the boss from the radially outer side.

4. The first rotating shaft is coaxially connected to the motor, The motor unit according to any one of claims 1 to 3, wherein the second rotating shaft is connected coaxially with respect to the wheel.

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