Hub motor

Abstract

The invention provides an in-wheel motor. The in-wheel motor is provided with a housing which is at least partially accommodated in a wheel; a hub rotatable about an axis, the hub having a neck disposed in the housing and having a first face spline and a flange portion radially expanding to an exterior of the housing to engage with a wheel; comprising electromagnets for generating a magnetic flux, the stator being fixedly supported by the housing; a rotor rotatably supported by the housing, the rotor including a shoulder having a second face spline engaged with the first face spline, and a disk portion integral with the shoulder and radially expanding from the shoulder toward the stator to receive magnetic flux to be driven about the axis; and a bolt screwed into the shoulder to force the first face spline into close contact with the second face spline.

Description

Technical Field

[0001] The disclosure herein relates to a motor for propelling a vehicle, and more particularly to a hub motor at least partially incorporated into a hub of a wheel. Background Art

[0002] Vehicles using internal combustion engines usually require a long and heavy power transmission system (drivetrain) to transmit torque to the wheels. Even electric vehicles sometimes use a similar power transmission system. Such a power transmission system results in a significant increase in weight because it includes many gears, joints, and bearings. In addition, these gears and joints cause play, which in turn may deteriorate ride quality or prevent precise control of power output.

[0003] Since the size of electric motors can be reduced compared to internal combustion engines and their layout can be relatively free, some fundamental changes in design can be made. For example, each drive wheel can be given an electric motor and driven directly by the electric motor. If the electric motor part is incorporated into the hub of the wheel, the motor is sometimes called a "hub motor". Japanese patent application No. 2023-34574 discloses a related technology. Summary of the invention

[0004] The hub motor does not require a long and heavy power transmission system, but the gap between the rotor and the shaft is still inevitable. In addition, the structure for supporting the motor and the shaft must be enclosed in a limited space and must also be strong enough to resist impact from the road. Such a structure may complicate its assembly and maintenance, and may also lead to increased costs. The device disclosed below is intended to solve these problems.

[0005] A wheel hub motor for driving a wheel of a vehicle around an axis comprises: a housing sized to be at least partially accommodated in the wheel; a wheel hub supported by the housing to be rotatable around the axis, the wheel hub comprising a neck disposed in the housing and having a first face spline and a flange portion, the flange portion being integrally formed with the neck and radially extending to the outside of the housing to engage with the wheel; a stator comprising an electromagnet for generating a magnetic flux and fixedly supported by the housing; a rotor rotatably supported by the housing and coaxially disposed with the wheel hub, the rotor comprising a shoulder portion and a disk portion, the shoulder portion having a second face spline meshing with the first face spline, the disk portion being integrally formed with the shoulder and radially extending from the shoulder toward the stator to receive the magnetic flux so as to be driven around the axis; and a bolt axially passing through the neck portion and being screwed into the shoulder to force the first face spline into close contact with the second face spline. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a front cross-sectional view of the motor according to the present embodiment.

[0007] Figure 2A is a schematic partial cross-sectional view showing the relationship of a motor to a tire and a wheel according to one example.

[0008] Figure 2B is a schematic partial cross-sectional view showing the relationship of a motor to a tire and a wheel according to another example.

[0009] Figure 3 It is shown from Figure 1 Front view of the cross section of the face spline taken in .

[0010] Figure 4 is a partial cross-sectional view showing an example in which the shoulder portion and the disc portion are separated.

[0011] Figure 5 is a cross-sectional elevation view of a motor including a sensor around a shoulder thereof according to one example.

[0012] Figure 6 is a cross-sectional elevation view of a motor according to another example, wherein the motor includes a sensor around a shoulder thereof.

[0013] Figure 7 is a cross-sectional elevation view of a motor according to yet another example, wherein the motor includes a sensor around a shoulder thereof. DETAILED DESCRIPTION

[0014] Exemplary embodiments will be described below with reference to the accompanying drawings.

[0015] Main reference Figure 1 Combined with Figure 2A or Figure 2B The motor 1 according to this embodiment is used to drive a wheel 3 of a vehicle about an axis X. Its housing 5 is dimensioned to be at least partially accommodated in the wheel 3, so that the motor 1 is a so-called "wheel hub motor". Although not shown in these figures, the housing 5 is connected to the vehicle body via, for example, upper and lower arms of a suspension device.

[0016] The motor 1 generally has a hub 7 for coupling with a wheel 3, a stator 9, a rotor 11, and bolts 13 for forcing the hub 7 to be in close contact with the rotor 11, wherein these elements jointly possess an axis X and are coaxial with each other. The stator 9 is fixedly supported by the housing 5, while the hub 7 and the rotor 11 are rotatably supported by the housing 5, so that when the stator 9 electromagnetically pushes the rotor 11, the hub 7 rotates around the axis X.

[0017] The housing 5 is generally flat and cylindrical, and surrounds a chamber for accommodating the hub 7, the stator 9, and the rotor 11. For ease of assembly, the housing 5 is preferably divided into a portion 5A located on the hub 7 side and a portion 5B located on the rotor 11 side, which can be combined together again. For example, bolt fastening is suitable for mutual combination, and any other means such as bonding, bonding, or fusion may be applied instead.

[0018] The hub 7 has a relatively narrow and cylindrical neck 21, a flange portion 23 formed integrally with the neck 21 and radially expanded to have a larger diameter, and a root portion 25 which is an end portion of the neck 21 opposite to the flange portion 23. The flange portion 23 is led out of the housing 5 for coupling with the wheel 3, while the root portion 25 is provided in the housing 5 for coupling with the rotor 11, and is supported by the housing 5 at the neck 21.

[0019] The flange portion 23 is disc-shaped, forms a sufficiently wide contact area for coupling with the wheel 3, and has a plurality of stud bolts (for example, designed for the Japanese market) fixedly embedded therein or a plurality of bolt holes (for example, designed for the European market) for fastening wheel bolts. Figure 2A As shown, between the flange portion 23 and the wheel 3, any intermediate object such as a brake rotor 15 may be inserted, or Figure 2B As shown, the flange portion 23 and the wheel 3 may be in direct contact with each other. In the latter case, as shown in the figure, the rotor 11 may be partially led out of the housing 5, and the brake rotor 15 may be combined therewith, or unlike the example in the drawings, the rotor 11 may not be led out to the outside, but a brake may be built into the motor 1.

[0020] As described above, the root 25 is a structure for coupling with the rotor 11, and has a face spline 51 on its end facing the rotor 11, such as Figure 3 As shown in the example in . The face spline 51 is formed by a plurality of splines, which are radially elongated and erected in the direction of the axis X, respectively, and which are arranged circumferentially around the axis X. Therefore, each spline does not necessarily take the form of a rectangular parallelepiped or any equivalent shape, but may take the form of a truncated cone tapering toward the axis X or any equivalent shape as in the example shown. The splines may be arranged on a plane perpendicular to the axis X, but may also be arranged on a slightly inclined conical surface as shown. Specifically, the top surface 51T and the bottom surface 51B may each be arranged on a conical surface having a vertex at any point on the axis X, and further, the conical surface may have a common vertex. Its side surface 51S may stand upright on the bottom surface 51B, but may be inclined so that each spline tapers toward the rotor 11.

[0021] Similar face splines 53 are engraved on the edge portion 45 of the rotor 11 described later, and the splines 51, 53 may also be complementary to each other. When this combination of face splines 51, 53 is forced into close contact with each other, the pressure generates a force in the direction in which these elements are directed along the axis X, thereby generating a self-aligning function. The hub 7 and the rotor 11 are thereby prevented from being eccentric. In addition, due to the mutual engagement through close contact, the face splines 51, 53 can transmit torque without clearance.

[0022] Refer again Figure 1 The following description relates to an axial gap motor in which the stator 9 and the rotor 11 are arranged in the direction of the axis X as a preferred example, but the description is for illustrative purposes only and the present embodiment is not necessarily limited to the axial gap motor.

[0023] The stator 9 includes a plurality of cores made of, for example, a soft magnetic material, which are arranged circumferentially at uniform intervals around the axis X and can be connected together to form the entirety of the stator 9. Each core has a coil 31 wound around itself to form an electromagnet, and the magnetic flux generated thereby is conducted axially through each core. In order to effectively utilize the magnetic flux, pairs of stators 9 facing each other in the axial direction can be arranged, and the rotor 11 is placed between them. These stators 9 can be fixedly accommodated in the housing 5.

[0024] The rotor 11 has a shoulder portion 41 which is, for example, a substantially cylindrical body, a disk portion 43 which is integrally formed with the shoulder portion 41 and radially expanded, and an edge portion 45 corresponding to the root portion 25. At any one of the shoulders 41, the rotor 11 is rotatably supported by the housing 5, thereby being rotatable about the axis X. The disk portion 43 takes the form of a disk symmetrical about the axis X, and is elongated toward the stator 9, thus being close to the stator 9, so as to receive the magnetic flux generated by the coil 31. In the case where the stators 9 are paired as shown in the figure, the disk portion 43 is placed between the paired stators 9, but does not contact the paired stators 9, thereby sufficiently receiving the magnetic flux.

[0025] The rotor 11 is formed of magnetic material at the disk 43 or at least at some parts facing the core. Such a structure can be easily produced by a method such as sintering. Alternatively, the production of the entire structure can be carried out by independently producing any magnetic part and the main part of the disk, and then matching, joining or fusing them together. The above structure enables the disk 43 to convert the received magnetic flux into a torque around the axis X.

[0026] The edge portion 45 is preferably formed integrally with at least the disc portion 43, and may slightly protrude from the disc portion 43 toward the hub 7. As described above, the edge portion 45 has the face splines 53, which have a shape complementary to the splines 51. Since the face splines 51, 53 are meshed with each other, the torque generated in the disc portion 43 is transmitted to the hub 7 through the face splines 51 and 53, and rotates the wheel 3 combined with this portion about the axis X there.

[0027] In order to press-fit the face spline 51 onto the face spline 53, the bolt 13 passes through the neck 21 and is screwed into the rotor 11. For this purpose, the disk 43 is provided with a bolt hole 47 at its center, and the bolt 13 is provided with a corresponding thread 49. However, instead of or in addition to the combination of the bolt hole 47 and the thread 49, any suitable fastening means that generates pressure in the axial direction may be used.

[0028] In the rotor 11, although the shoulder 41 may be integral with the disk 43, the shoulder 41 and the disk 43 may be formed as separate bodies and coupled together, as shown in FIG. Figure 4 As shown. The connection can be established by the mutually meshing face splines 61, 63 shown herein. In order to apply a press-fit force on the face splines 61, 63, any fastening device such as a bolt can be used. Alternatively, the bolt 13 as described above can be further passed through the disk 43 and then fastened in the shoulder 41, so that a single bolt 13 can combine the hub 7, the disk 43 and the shoulder 41 together. Of course, instead of a spline connection, the shoulder 41 and the disk 43 can be combined by brazing, welding, friction welding, etc. after being produced as separate bodies. In any case, the possibility of production as separate bodies is conducive to the application of separate materials that are respectively optimal for the separate bodies, and is conducive to any surface treatment such as shot peening or hardening on a limited area such as the periphery of the shoulder 41.

[0029] In order to support the hub 7 and the rotor 11 as a whole in a rotatable manner about the axis X, ball bearings 55, 57 may be used, for example. One or more of them may be a bearing unit in which a plurality of rows of bearings are combined, but this is not critical.

[0030] Reference Figure 1 , Figure 4 Regardless of whether the shoulder 41 and the disc 43 are integral or separate, a certain amount of available space is still left around the shoulder 41. This is particularly applicable when the wheel hub motor 1 is an axial gap motor. The wheel hub motor 1 can also be provided with other elements using this space. Figure 5 , Figure 6 , Figure 7 An example is shown in which the hub motor 1 is provided with one or more sensors 65 , 67 , 69 around the shoulder 41 .

[0031] One example of the sensor 65 is a torque sensor. According to the example of the magnetostrictive torque sensor, the sensor 65, for example, generates a magnetic flux, and the magnetic flux at least partially passes through the adjacent shoulder 41 and then forms a loop. When torque is applied to the shoulder 41, a potential change is generated in the sensor 65, which can be taken out to monitor the torque generated in the rotor 11. In order to enhance the sensor output, any surface treatment such as shot peening can be applied to the shoulder 41. Of course, any torque sensor based on any other principle is applicable. The output of the torque sensor is input to the electronic control unit (ECU) built into the vehicle and can be used to control the motor output.

[0032] An example of the sensor 67 is a rotation speed sensor. For example, a magnetic encoder is attached to the shoulder 41 in advance, and then the rotation speed of the rotor 11 can be detected by reading the fluctuation of the magnetic field generated thereby in the sensor 67. Of course, any rotation speed sensor based on any other principle is applicable. The output of the rotation speed sensor is input to the ECU and can be used for vehicle control and can replace the detection of the vehicle speed by any other means.

[0033] An example of the sensor 69 is a rotation angle sensor or a so-called resolver. If, for example, the non-circular rotor 59 is pre-fixed to the shoulder 41 so as to rotate together, and the sensor 69 including a plurality of electromagnetic coils arranged circumferentially at uniform intervals is arranged close to the non-circular rotor 59, the inductance will vary according to the rotation angle of the non-circular rotor 11, and can be taken out as its output. Of course, any rotation angle sensor based on any other principle is applicable. The output of the rotation angle sensor is input to the ECU, for example, and is used to control the rotation of the motor.

[0034] The wheel hub motor 1 may be provided with one of these sensors 65, 67, 69, and of course, two or more or all of them may be provided. The outputs of the sensors 65, 67, 69 are led out through the internal wiring 71 and taken out to the outside together. Of course, the outputs may not be gathered together, but taken out independently. Alternatively, one or more outputs may be taken out through the input connector of the motor.

[0035] At least one of the sensors 65, 67, 69 may be disposed inside the housing 5. For example, Figure 5As shown, the sensor 65 as a torque sensor can be arranged in the housing 5 and fixed to the inner surface of the side wall SW of the housing 5 by bolts or the like. At least one cable in the internal wiring 71 can be connected to the sensor 65 and led out to the outside through the through hole on the side wall SW. The through hole can be arranged radially inside with respect to the stator 9. The rest of the sensors 67, 69 can be outside the housing 5, and they can still be covered with a cover.

[0036] Alternatively, if Figure 6 As shown, the sensor 67 as the rotation speed sensor can be arranged inside the housing 5 together with the sensor 65 and fixed to the side wall SW together. Needless to say, the sensor 69 and the non-circular rotor 59 can also be as shown. Figure 7 As shown, the sensor 69 is arranged inside the housing 5. As in the figure, the sensor 69 can be arranged inside relative to the sensor 67, or it can be arranged outside opposite to the figure. Although the order of the sensors 65, 67, 69 can be arbitrary, these sensors are preferably arranged adjacent to each other, so that the device is compact in its axial direction.

[0037] According to the present embodiment, the in-wheel motor 1 can accommodate the sensor, so external sensors for controlling the vehicle become unnecessary or can be reduced. In addition, since the measurement object is a member without a gap, the measurement result is not disturbed by the gap.

[0038] It goes without saying that the hub motor 1 may be provided with any other sensors, or other elements instead of any sensors, instead of or in addition to the torque sensor, the rotation speed sensor and the rotation angle sensor.

[0039] It will be easily understood that the torque transmission path from the disc portion 43 to the flange portion 23 is an integral body except for the face splines 51, 53, and as described above, there is no gap between the face splines 51 and 53. Therefore, even with a simple structure, the hub motor 1 is able to output torque without a gap. In addition, the hub motor 1 can be easily assembled by combining the hub 7 and related components into the part 5A, then combining the rotor 11 and related components into the part 5B, and further screwing the bolts 13 therein, and the disassembly of the motor can also be achieved only by the reverse process. More specifically, its assembly and maintenance are easy.

[0040] While certain exemplary embodiments have been described above, modifications and variations of the embodiments will occur to those skilled in the art in light of the above teachings.

Claims

1. A wheel hub motor for driving a wheel of a vehicle about an axis, comprising: a housing sized to be at least partially received within the wheel; a wheel hub supported by the housing so as to be rotatable about the axis, the wheel hub including a neck portion disposed in the housing and having a first face spline and a flange portion, the flange portion being integrally formed with the neck portion and radially extending to the outside of the housing to be coupled with the wheel; a stator including an electromagnet for generating magnetic flux and fixedly supported by the housing; a rotor rotatably supported by the housing and disposed coaxially with the hub, the rotor comprising a shoulder portion and a disk portion, the shoulder portion having a second face spline meshing with the first face spline, the disk portion being integrally formed with the shoulder and radially extending from the shoulder toward the stator to receive the magnetic flux, thereby being driven about the axis; as well as A bolt is axially passed through the neck and screwed into the shoulder to force the first face spline to be in close contact with the second face spline.

2. The wheel hub motor according to claim 1, wherein: The first face spline and the second face spline each include a plurality of splines that are axially erected and circumferentially arranged, whereby the first face spline and the second face spline axially face each other and mesh with each other.

3. The wheel hub motor according to claim 1, wherein: The flange portion and the first surface spline form both axial ends of the hub.

4. The wheel hub motor according to claim 1, wherein: The rotor and the stator constitute an axial gap motor.

5. The wheel hub motor according to claim 4, wherein: The shoulder includes one or more selected from the group consisting of a torque sensor, a rotation speed sensor, and a rotation angle sensor.

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