In-wheel motor

Abstract

To provide an in-wheel motor having a simple structure and free from backlash.SOLUTION: An in-wheel motor 1 comprises: a casing 5 at least partially housed within a wheel; a hub 7 comprising a neck part 21 rotatably supported by the casing and comprising a first face spline 51 in the casing, and a flange part 23 integral with the neck part and extending radially from the neck part outside the casing for connection to the wheel; a stator 9; a rotor 11 comprising a shoulder part 41 coaxial with the hub and comprising a second face spline 53 meshing with the first face spline, and a disk part 43 integral with the shoulder part and extending radially from the shoulder part toward the stator so that a magnetic flux is received and the in-wheel motor is driven around an axis; and a bolt 13 axially passing through the neck part and screwed into the shoulder part to press the first face spline onto the second face spline.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The following disclosure relates to motors for propelling vehicles, and in particular to in-wheel motors that are at least partially contained within a wheel. [Background technology]

[0002] Vehicles using internal combustion engines usually require long drivelines to deliver torque to the wheels. Electric vehicles may also use similar drivelines. Such drivelines contain many gears, couplings, and bearings, which can cause significant energy losses. Gears and couplings also cause backlash, which can also cause ride discomfort or hinder precise power control.

[0003] Since electric motors can be made smaller than internal combustion engines and can be positioned relatively freely, it is possible to arrange one electric motor for each drive wheel to directly drive them. When an electric motor is at least partially housed within a wheel, it is called an in-wheel motor.

[0004] Patent Document 1 discloses a related technique. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2023-34574 A Summary of the Invention [Problem to be solved by the invention]

[0006] Although an in-wheel motor does not require a long power transmission system, backlash between the rotor and the shaft is still unavoidable. In addition, the structure supporting the motor and shaft must be realized in a small space, and must be able to withstand impacts from the road surface. Such a structure makes assembly and maintenance difficult, and also increases costs. The device disclosed below is intended to solve these problems. [Means for solving the problem]

[0007] An in-wheel motor for driving a wheel of a motor vehicle about an axis comprises: a casing sized to be at least partially received within the wheel; a hub supported in the casing for rotation about the axis, the hub having a neck portion with a first face spline within the casing and a flange portion integral with the neck portion and extending radially from the neck portion outside the casing for coupling to the wheel; a stator including an electromagnet generating a magnetic flux and fixedly received in the casing; a rotor supported in the casing coaxially with the hub for rotation, the rotor having a shoulder portion with a second face spline meshing with the first face spline and a disk portion integral with the shoulder portion and extending radially from the shoulder portion towards the stator to receive the magnetic flux and be driven about the axis; and a bolt passing axially through the neck portion and screwing to the shoulder portion and crimping the first face spline to the second face spline.

[0008] Preferably, the first face spline and the second face spline each include a plurality of splines arranged in the circumferential direction and axially opposed to each other in meshing engagement. Alternatively, preferably, the flange portion and the first face spline form both ends of the hub in the axial direction. Also, preferably, the rotor and the stator form an axial gap motor. More preferably, the shoulder portion includes one or more sensors selected from the group consisting of a torque sensor, a rotational speed sensor, and a rotational angle sensor. Effect of the Invention

[0009] To provide an in-wheel motor having a simple structure and free from backlash. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional elevation view of a motor according to the present embodiment. [Figure 2A] FIG. 2A is a schematic partial cross-sectional view showing the relationship between a motor, a tire, and a wheel according to one example. [Figure 2B] FIG. 2B is a schematic partial cross-sectional view showing the relationship between a motor, a tire, and a wheel according to another example. [Diagram 3] FIG. 3 is a cross-sectional elevational view showing the face spline taken out from FIG. [Figure 4] FIG. 4 is a partial cross-sectional elevational view showing an example in which the shoulder portion and the disk portion are separate bodies. [Diagram 5] FIG. 5 is a cross-sectional elevation view of an example motor with sensors around the shoulder. [Figure 6] FIG. 6 is a cross-sectional elevation view of another example motor with sensors around the shoulder. [Figure 7] FIG. 7 is a cross-sectional elevation view of yet another example motor having a sensor around the shoulder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Several exemplary embodiments are described below with reference to the accompanying drawings.

[0012] Referring primarily to Figure 1 in combination with Figure 2A or 2B, a motor 1 according to this embodiment is used to drive a wheel 3 of a motor vehicle about an axis X. Its casing 5 is dimensioned to be at least partially housed within the wheel 3, i.e. the motor 1 is a so-called in-wheel motor. Although not shown in these figures, the casing 5 is connected to the vehicle body, for example via upper and lower arms of a suspension system.

[0013] The motor 1 generally includes a hub 7 for coupling to the wheel 3, a stator 9, a rotor 11, and bolts 13 for pressing the hub 7 against the rotor 11, which are coaxial and share an axis X. The stator 9 is fixedly supported by the casing 5, while the hub 7 and the rotor 11 are rotatably supported by the casing 5. The stator 9 electromagnetically drives the rotor 11, causing the hub 7 to rotate about the axis X.

[0014] The casing 5 is generally in the shape of a flattened cylinder, and the inside thereof is a chamber for accommodating the hub 7, the stator 9, and the rotor 11. For ease of assembly, the casing 5 is preferably separable into a portion 5A on the hub 7 side and a portion 5B on the rotor 11 side, which can be joined together. The joining together can be achieved, for example, by bolts, or by other means such as engagement, adhesion, or fusion.

[0015] The hub 7 comprises a relatively thin cylindrical neck portion 21, a flange portion 23 which is integral with the neck portion 21 and extends radially and has a larger diameter, and a root 25 which is the end of the neck portion 21 opposite the flange portion 23. The flange portion 23 is drawn out of the casing 5 to be used for connection with the wheel 3, while the root 25 is inside the casing 5 to be used for connection with the rotor 11, and is supported by the casing 5 at the neck portion 21.

[0016] The flange portion 23 is disk-shaped to ensure a sufficient contact surface for connection to the wheel 3, and has a plurality of stud bolts fixed thereto for connection (for example, in Japanese specification vehicles) or has a plurality of bolt holes for screwing in wheel bolts (for example, in European specification vehicles). Between the flange portion 23 and the wheel 3, there may be an intermediate object such as a brake rotor 15 as shown in Fig. 2A, or the flange portion 23 and the wheel 3 may be in direct contact with each other as shown in Fig. 2B. In the latter example, the rotor 11 may be partially drawn out to the outside of the casing 5 as shown in the figure, and the brake rotor 15 may be coupled thereto, or, unlike the illustration, the rotor 11 may not be drawn out to the outside and the motor 1 may have a built-in brake.

[0017] As already described, the root 25 is a structure for coupling with the rotor 11, and has a face spline 51, as shown in FIG. 3, on its end surface facing the rotor 11. The face spline 51 is made up of a plurality of splines each extending radially with respect to the axis X and standing in the direction of the axis X, and these splines are arranged in the circumferential direction around the axis X. Therefore, each spline does not necessarily have to be a rectangular parallelepiped or a similar shape, and can be a truncated pyramid or a similar shape tapering toward the axis X as shown in the example. The splines may be arranged on a plane perpendicular to the axis X, or on a slightly inclined conical surface as shown in the example. That is, the top surface 51T and the bottom surface 51B may each be along a conical surface having a vertex on the axis X, and the vertex may be common to both. The side surface 51S may be perpendicular to the bottom surface 51B, but may be inclined so that each spline tapers toward the rotor 11.

[0018] As will be described later, a similar face spline 53 is also engraved on the rim portion 45 of the rotor 11, and the splines 51, 53 may have complementary shapes. When such a combination of face splines 51, 53 are pressed against each other, they generate a force that directs them toward the axis X, i.e., they automatically align with each other. This prevents eccentricity of the hub 7 and the rotor 11. Furthermore, by meshing with each other and coming into close contact, the face splines 51, 53 can transmit torque without backlash.

[0019] Referring back to FIG. 1, the following description relates to an axial gap motor in which the stator 9 and rotor 11 are aligned in the axial direction, and while this is a preferred example, it is for convenience of explanation only and the present embodiment is not necessarily limited to axial gap motors.

[0020] The stator 9 may include a plurality of cores made of, for example, a soft magnetic material, which may be arranged at equal intervals in the circumferential direction around the axis X and coupled to each other to form the stator 9. A coil 31 is wound around each core to form an electromagnet, and the generated magnetic flux is guided in the axial direction by each core. To efficiently utilize the magnetic flux, a pair of stators 9 may be disposed axially opposite each other, sandwiching the rotor 11. Each of these stators 9 is fixedly housed in the casing 5.

[0021] The rotor 11 includes a shoulder portion 41, which is, for example, a substantially cylindrical body, a disk portion 43 which is integral with the shoulder portion 41 and extends in the radial direction, and a rim portion 45 which corresponds to the root 25. Either of the shoulder portions 41 is rotatably supported by the casing 5, so that the entire rotor 11 can rotate about the axis X. The disk portion 43 is a circular plate symmetrical with respect to the axis X, and extends toward and is close to the stator 9, so as to receive the magnetic flux generated by the coil 31. When the stators 9 are paired as in the illustrated example, the disk portion 43 is sandwiched between the pair of stators 9 without contacting each other, so as to fully receive the magnetic flux.

[0022] At least the portions of the disk portion 43 facing the core, the rotor 11 is made of a magnetic material. Such a structure can be easily manufactured by, for example, a sintering method. Alternatively, the magnetic material portions and the main body of the disk portion may be manufactured separately and then fitted, bonded, or fused together to manufacture the entire structure. With such a structure, the disk portion 43 generates a torque about the axis X due to the magnetic flux received.

[0023] The rim portion 45 is preferably integral with at least the disk portion 43, and may protrude slightly from the disk portion 43 toward the hub 7. As already described, the rim portion 45 is provided with the face spline 53 having a shape complementary to the spline 51. As the face splines 51, 53 mesh with each other, torque generated in the disk portion 43 is transmitted to the hub 7 via the face splines 51, 53, causing the wheel 3 coupled thereto to rotate about the axis X.

[0024] The bolt 13 passes through the neck portion 21 and threads into the rotor 11 to press the face spline 51 against the face spline 53. To this end, the disk portion 43 has a bolt hole 47 at its center and the bolt 13 has a corresponding thread 49. However, any other suitable fastening means that provides an axial pressing force may be used instead of or in addition to the bolt hole 47 / thread 49 combination.

[0025] In the rotor 11, the shoulder portion 41 may be integral with the disk portion 43, or as shown in FIG. 4, the shoulder portion 41 and the disk portion 43 may be separate bodies and connected to each other. The connection may be, for example, by face splines 61, 63 that mesh with each other as shown in the figure. A fastening means such as a bolt may be used to apply a pressure force to the face splines 61, 63. Alternatively, the already-mentioned bolt 13 may further penetrate the disk portion 43 and be screwed into the shoulder portion 41, that is, one bolt 13 may connect the hub 7, the disk portion 43, and the shoulder portion 41. Of course, instead of the spline connection, the shoulder portion 41 and the disk portion 43 may be manufactured as separate bodies and then integrated by brazing, welding, friction welding, or the like. In any case, the ability to manufacture them as separate bodies makes it convenient to use the most suitable material for each, and also makes it convenient to apply surface treatments such as hardening and shot peening only to limited areas such as the peripheral surface of the shoulder portion 41.

[0026] Ball bearings 55, 57, for example, may be used to support the entire hub 7 and rotor 11 for rotation about axis X. One or more of these may be, but need not be, a bearing unit incorporating multiple rows of bearings.

[0027] 1 and 4, there is still usable space around the shoulder portion 41, regardless of whether the shoulder portion 41 is integral with the disk portion 43 or separate from it. This is particularly characteristic when the in-wheel motor 1 is an axial gap motor. By utilizing such space, the in-wheel motor 1 can further include other components. For example, FIGS. 5, 6 and 7 show an example in which the in-wheel motor 1 includes one or more sensors 65, 67, 69 around the shoulder portion 41.

[0028] An example of the sensor 65 is a torque sensor. In the case of a magnetostrictive torque sensor, for example, the sensor 65 generates a magnetic flux that circulates at least partially through the adjacent shoulder portion 41. When torque is applied to the shoulder portion 41, a voltage change occurs in the sensor 65, and by extracting this voltage to the outside, the torque generated in the rotor 11 can be read. To strengthen the sensor output, the shoulder portion 41 may be subjected to a surface treatment such as shot peening. Of course, torque sensors based on other principles can be used. The output of the torque sensor is input to an electronic control unit (ECU) equipped in the vehicle and can be used to control the output of the motor, for example.

[0029] An example of the sensor 67 is a rotation speed sensor. For example, a magnetic encoder is attached to the shoulder portion 41 in advance, and the rotation speed of the rotor 11 can be read by reading the magnetic field fluctuations generated in the sensor 67. Of course, a rotation speed sensor based on another principle can be used. Also, instead of or in addition to the sensor 67, the bearing 55 or the bearing 57 may be provided with a rotation speed sensor. The output of the rotation speed sensor can be input to the ECU and used for controlling the vehicle, and can also be used to detect the vehicle speed by other means.

[0030] An example of the sensor 69 is a rotation angle sensor or a so-called resolver. For example, if the non-circular rotor 59 is fixed to the shoulder portion 41 in advance so as to rotate together with the non-circular rotor 59, and a sensor 69 including electromagnetic coils arranged at equal intervals in the circumferential direction is installed close to the non-circular rotor 59, the inductance changes according to the rotation angle of the non-circular rotor 59, and this can be taken out as an output. Of course, a rotation angle sensor based on another principle can be used. The output of the rotation angle sensor is input to, for example, an ECU and used for inverter control, and thus for controlling the rotation of the motor.

[0031] The in-wheel motor 1 may include one of these sensors 65, 67, 69, and may of course include two or more, or all of them. The outputs of the sensors 65, 67, 69 are drawn to a connector 73 via internal wiring 71, and can be taken out in a concentrated manner to the outside. Of course, the outputs do not have to be concentrated in one connector, and may be taken out individually. Alternatively, one or more of the outputs may be taken out via an input connector to the motor.

[0032] At least one of the sensors 65, 67, 69 may be located inside the casing 5. For example, as shown in Fig. 5, the sensor 65, which is a torque sensor, may be located inside the casing 5 and fixed to the inner surface of the side wall SW of the casing 5 with bolts or the like. At least one cable of the internal wiring 71 may be connected to the sensor 65 and may be drawn out to the outside through a through hole opened in the side wall SW. Such a through hole may be located radially inward from the stator 9. The other sensors 67, 69 may be located outside the casing 5, and in that case may be covered by a cover or the like.

[0033] Alternatively, as shown in Fig. 6, a sensor 67, e.g. a rotational speed sensor, may also be arranged in the casing 5 together with the sensor 65, and both are fixed to the side wall SW. Needless to say, as shown in Fig. 7, a sensor 69 may also be arranged in the casing 5 together with the non-circular rotor 59. As shown in the figure, the sensor 69 may be located inside the sensor 67, or, unlike the figure, it may be located outside. The sensors 65, 67, 69 may be arranged in any order, but are preferably arranged adjacent to each other, so that the device can be made axially compact.

[0034] According to this embodiment, the in-wheel motor 1 can have a built-in sensor, eliminating the need to attach external sensors for controlling the motor or the vehicle, or reducing the number of external sensors. In addition, since the measurement targets of these sensors are all members without backlash, the measurement results are not disturbed by backlash.

[0035] Needless to say, instead of or in addition to the torque sensor, the rotational speed sensor and the rotational angle sensor, the in-wheel motor 1 may be provided with other sensors, and other components may be provided instead of the sensors.

[0036] As can be easily understood, the torque transmission path from the disk portion 43 to the flange portion 23 is integrated except for the face splines 51, 53, and there is no backlash between the face splines 51, 53 as already described. Therefore, the in-wheel motor 1 is capable of outputting torque without backlash, despite its simple structure. Also, the in-wheel motor 1 can be assembled by incorporating the hub 7 and related parts into section 5A, incorporating the rotor 11 and related parts into section 5B, fastening sections 5A and 5B together, and tightening the bolts 13, and can be disassembled by performing the reverse procedure. In other words, assembly and maintenance are easy.

[0037] Although several embodiments have been described, the embodiments can be modified or altered based on the above disclosure. [Industrial Applicability]

[0038] To provide an in-wheel motor having a simple structure and free from backlash. [Explanation of symbols]

[0039] 1 In-wheel motor 3 Wheels 5 Casing 7. Hub 9 Stator 11 Rotor 13 Volts 15 Brake rotor 21 Neck 23 Flange 25 routes 31 Coil 41 Shoulder 43 Disk section 45 Rim section 47 Bolt Holes 49 Threads 51 1st Face Spline 53 Second Face Spline 55,57 Bearings 59 Non-circular rotor 61,63 Face spline 65 Torque Sensor 67 Rotational Speed ​​Sensor 69 Rotational Angle Sensor 71 Internal wiring 73 Connector X-axis

Claims

1. An in-wheel motor that drives a wheel of an automobile around an axis, a casing sized to be at least partially received within the wheel; a hub supported in the casing for rotation about the axis, the hub including a neck portion with a first face spline in the casing, and a flange portion integral with the neck portion and extending radially from the neck portion outside the casing for coupling to the wheel; a stator including an electromagnet that generates a magnetic flux and fixedly accommodated in the casing; a rotor coaxial with the hub and rotatably supported in the casing, the rotor comprising: a shoulder portion having a second face spline meshing with the first face spline; and a disk portion integral with the shoulder portion and extending radially from the shoulder portion towards the stator for receiving the magnetic flux and being driven about the axis; a bolt that passes through the neck portion in the axial direction and screws into the shoulder portion to press the first face spline onto the second face spline; An in-wheel motor equipped with

2. The in-wheel motor according to claim 1 , wherein the first face spline and the second face spline each include a plurality of splines extending in an axial direction and arranged in a circumferential direction, so as to face and mesh with each other in the axial direction.

3. The in-wheel motor according to claim 1 , wherein the flange portion and the first face spline form opposite ends of the hub in the axial direction.

4. The in-wheel motor according to claim 1 , wherein the rotor and the stator form an axial gap motor.

5. The in-wheel motor according to claim 4 , wherein the shoulder portion is provided with at least one sensor selected from the group consisting of a torque sensor, a rotational speed sensor, and a rotational angle sensor.

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