Wheel hub motor

Abstract

The invention relates to a wheel hub motor comprising: a housing that is at least partially enclosed in a wheel; a hub that is rotatable about an axis and has a neck section with a first spur gear arranged in the housing and a flange section radially extended outside the housing for connection with the wheel; a stator with an electromagnet for generating a magnetic flux, which is rigidly connected to the housing; a rotor that is rotatably mounted in the housing and has a shoulder section with a second spur gear that engages with the first spur gear, and a disk section that is integral with the shoulder section and extends radially from it to the stator in order to receive magnetic flux and be driven about the axis; and a bolt that is screwed into the shoulder section to connect the first spur gear to the second spur gear.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a motor for propelling a vehicle and in particular to a wheel hub motor which is at least partially installed in a wheel hub. BACKGROUND

[0002] A vehicle with an internal combustion engine typically requires a long and heavy power transmission system (drivetrain) to transfer torque to the wheels. Electric vehicles occasionally use a similar power transmission system. Because such a system includes many gears, joints, and bearings, it results in a significant increase in weight. Furthermore, these gears and joints introduce play, which can negatively impact ride quality or prevent precise control of power delivery.

[0003] Since electric motors can be smaller and designed with greater freedom compared to combustion engines, a fundamental change in design or layout would be possible. For example, each drive wheel could be equipped with an electric motor and thus driven directly. If an electric motor is partially integrated into a wheel hub, the motor is also referred to as a wheel hub motor or in-wheel motor. Japanese patent application JP 2023-34 574 A discloses a related prior art.

[0004] From US patent 2016 / 0 121 709 A1, a wheel hub drive device is known that comprises a motor housing, a rotor, a rotor shaft, and a hub. The motor housing is mounted in a wheel of the wheel hub drive device, and the rotor is rotatably mounted in the motor housing. The rotor shaft projects from the rotor and is designed to rotate with the rotor. The hub connected to the rotor shaft is rotatably connected to the motor housing.

[0005] From CN 1 02 673 380 B, an electric bicycle with a hub motor drive is known. The electric bicycle comprises a hub motor, a brake, a wheel, a damping mechanism, and a speed reduction mechanism.

[0006] From DE 10 2006 002 421 A1, a front wheel is known which is rotatably attached to a joint of a suspension by means of a hub unit. A stator carrier, which is attached to an outer hub of the hub unit, supports an annular stator. A rotor carrier, which is attached to an inner hub of the hub unit, supports an annular rotor outside the stator. The rotation of the rotor is guided by a bearing of the hub unit.

[0007] US Patent 1,660,792 A discloses a shaft coupling with a pair of shaft sections. The shaft sections are connected to each other at their facing ends by means of a face gear, preventing rotation.

[0008] In the 2022 press release “Compact and lighter for the modern premium powertrain” by GKN Automotive, a joint technology with face spline joint technology is described. SUMMARY OF THE INVENTION

[0009] A wheel hub motor doesn't require a long and heavy power transmission system; however, some play between the rotor and shaft is unavoidable. Furthermore, a support structure for the motor and shaft must be accommodated in a very small space and must also be sufficiently resistant to road impacts. Such a structure can complicate installation and maintenance, further increasing costs.

[0010] The present invention is based on the objective of proposing a wheel hub motor that solves the aforementioned problems, in particular having a simple design or enabling simple assembly or maintenance.

[0011] This problem is solved according to the invention by the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

[0012] A wheel hub motor for driving a vehicle wheel about an axle is proposed, comprising: a housing dimensioned to be at least partially housed or received in the wheel; a hub rotatably mounted about the axle in or by the housing, the hub having a neck section with a first face toothing arranged in the housing and a flange section formed integrally with the neck section and radially extended outside the housing to allow connection with the wheel; and a stator comprising an electromagnet for generating a magnetic flux and fixedly connected to the housing.supported in the housing; a rotor rotatably mounted in the housing and arranged coaxially to the hub, the rotor having a shoulder section with a second face toothing engaging with the first face toothing, and a disk section formed integrally with the shoulder section and extending radially from the shoulder section towards the stator to accommodate the magnetic flux and be driven about the axis; and a bolt extending axially through the neck section and screwed into the shoulder section to clamp the first face toothing to the second face toothing, forcing them into tight contact or connecting them in a rotationally fixed manner. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a sectional view of a motor according to the present embodiment. Fig. 2A is a schematic partial sectional view showing the relationship between the motor and wheel with a tire according to an example. Fig. 2B is a schematic partial sectional view showing the relationship between the motor and a wheel with a tire according to another example. Fig. Figure 3 is a sectional view showing a face gear made of Fig. 1 shows. Fig. Figure 4 is a partial sectional view showing an example where a shoulder section and a disc section are separated. Fig. Figure 5 is a sectional view of a motor according to an example where the motor has sensors around its shoulder area. Fig. Figure 6 is a sectional view of a motor according to another example, where the motor has sensors around its shoulder area. Fig. Figure 7 is a sectional view of a motor according to another example, where the motor has sensors around its shoulder area. DESCRIPTION OF THE EXECUTION FORMS

[0013] Exemplary embodiments are described below with reference to the attached drawings.

[0014] Mainly on Fig. 1 in combination with Fig. 2A or Fig. Referring to Figure 2B, a motor 1 according to the present embodiment is used to drive a wheel 3 of a vehicle about an axis X. The housing 5 of the motor is dimensioned to be at least partially housed or received within the wheel 3, and the motor 1 is thus a so-called wheel hub motor or "in-wheel motor". Although not shown in these drawings, the housing 5 is connected to a vehicle body, for example, via an upper and a lower arm of a suspension or support device.

[0015] The motor 1 is generally provided with a hub 7 for connecting to the wheel 3, a stator 9, a rotor 11, and a bolt 13 to bring the hub 7 into fixed contact with the rotor 11, or to clamp the hub 7 to the rotor 11. The hub 7 and the rotor 11 are arranged coaxially with each other, meaning they share the axis X. The stator 9 is fixedly mounted in the housing 5, in particular supported against rotation, but the hub 7 and the rotor 11 are rotatably mounted in the housing 5 so that the hub 7 rotates about the axis X when the stator 9 electromagnetically drives or impinges on the rotor 11.

[0016] The housing 5 is generally flat and cylindrical and encloses a chamber for receiving the hub 7, the stator 9, and the rotor 11. To facilitate assembly, the housing 5 is preferably divisible into a part 5A on the hub 7 side and a part 5B on the rotor 11 side, and these parts are in turn connectable to each other. This connection can be achieved, for example, by screws, although other methods such as snap-fit, bonding, or welding can also be used.

[0017] The hub 7 comprises a relatively thin, cylindrical neck section 21, a flange section 23 which forms a single body with the neck section 21 and is radially expanded or has a larger diameter relative to it, and a foot 25 at an end of the neck section 21 opposite the flange section 23. The neck section 21 is preferably sleeve-shaped and transmits torque from the foot 25 to the flange section 23; it can also be referred to as the sleeve or shaft section. The foot 25, the neck section 21, and / or the flange section 23 are preferably integrally designed, that is, in particular formed as one part. The flange section 23 extends out of the housing 5 to serve for coupling with the wheel 3, while the foot 25 is arranged inside the housing 5 to serve for coupling with the rotor 11. The hub 7 is, particularly in the area of ​​the shaft orNeck section 21 is rotatably mounted in housing 5 by means of a bearing about the axis of rotation X.

[0018] The flange section 23 is disc-shaped to form a sufficiently large contact surface for connection with the wheel 3 and has a plurality of studs firmly embedded or integrally formed within it (e.g., for the Japanese market) or a plurality of bolt holes (e.g., for the European market) into which wheel bolts can be screwed. Between the flange section 23 and the wheel 3, as shown in Fig. As shown in 2A, any intermediate element, such as a brake rotor 15, can be inserted, or the flange section 23 and the wheel 3 can be, as in Fig. As shown in Figure 2B, the rotors 11 and 15 can be in direct contact with each other or directly connected. In the latter case, the rotor 11 can be partially extended out of the housing 5, as shown, and the brake rotor 15 can be coupled or connected to the rotor 11. Alternatively, the rotor 11 can not be extended outwards, but a brake can be integrated into the motor 1, in contrast to the examples shown in the drawings.

[0019] The foot 25, as described above, is a structure for connecting to the rotor 11 and has a face toothing 51 at its end facing the rotor 11, as shown in Fig. Figure 3 is shown as an example. The foot 25 is thus a torque-introducing section of the hub and can also be referred to as the foot section or connecting section of the hub 7. The face gear 51 comprises a plurality of radially extending teeth or splines projecting in the direction of the axis X, which are arranged circumferentially around the axis X, i.e., distributed around the axis X. Each tooth or spline therefore does not necessarily assume the form of a rectangular parallelepiped or an equivalent shape, but can, as in the example shown, have the form of a truncated pyramid tapering towards the axis X or an equivalent shape. The teeth or splines can be arranged on or in planes perpendicular to the axis X, but they can also be arranged on slightly inclined, conical surfaces, as shown in the figure. In particular, the upper surfaces 51T or head surfaces and the lower surfaces 51B orFoot surfaces are arranged on the conical surfaces whose vertices are located at arbitrary points on the X-axis, and furthermore, the conical surfaces can, in particular, have a common vertex. The side surfaces 51S can stand upright on the base surfaces 51B, but can also be inclined, so that each tooth or spline tapers towards the rotor 11.

[0020] A similar spur gear 53 is formed or provided on an edge section 45 of the rotor 11, as described later. In particular, the gears 51 and 53 can be designed to be complementary to each other. When this combination or pairing of spur gears 51 and 53 is subjected to mutual contact or engagement, the pressure generates a force in the direction in which these elements or gears are oriented along the X-axis, thus creating a self-aligning function. This prevents the hub 7 and the rotor 11 from being eccentric to each other. Furthermore, due to the close or tight engagement, the spur gears 51 and 53 can transmit a torque without backlash.

[0021] Referring again to Fig. 1 The following descriptions refer to an axial gap motor in which the stator 9 and the rotor 11 are arranged adjacent to each other with respect to the axis X as a preferred example, but the descriptions serve only for illustration and the present embodiments are not necessarily limited to the axial gap motor, but other electric motors can also be used, such as radial gap motors.

[0022] The stator 9 comprises several cores, for example made of a soft magnetic material, arranged at uniform intervals circumferentially around the axis X and which can be connected to one another to form a single body of the stator 9. Each core includes a winding 31, or coil, wound around it to form an electromagnet, and the magnetic flux generated thereby is guided axially through each core. To utilize the magnetic flux efficiently, pairs of stators 9 can be arranged so that they face each other axially, with the rotor 11 positioned between them. These stators 9 can be rigidly housed or mounted in the casing 5.

[0023] The rotor 11 is provided with a shoulder section 41, which is, for example, a substantially cylindrical or sleeve-shaped body, a disk section 43, which is integrally formed with the shoulder section 41 or forms a single body and extends radially from it or extends in a radial direction, and an edge section 45 corresponding to the base section 25 of the hub 7. The rotor 11 is rotatably mounted in the housing 5 about the axis X at a suitable section, in particular in some region of the shoulder section 41. The disk section 43 has the form of a disk symmetrical about the axis X and is elongated towards or near the stators 9 in order to receive the magnetic flux generated by the windings 31.In a case where the stators 9 are configured as a pair, as shown in the drawing, the disk section 43 is arranged between the pair of stators 9, but not in contact with them, thus adequately absorbing the magnetic flux. Radial gaps are formed between the two stators 9 and the disk section 43 arranged axially between them, which are bridged by the magnetic field generated when the stators 9 are energized.

[0024] The rotor 11 is made of a magnetic material in the area of ​​the disk 43, or at least in certain areas facing the cores. This structure can be easily manufactured, for example, by a sintering process. Alternatively, the entire structure can be manufactured by independently producing magnetic sections and a main section of the disk segment, and then fitting, joining, or fusing them together. The structure described above causes the disk segment 43 to convert the received magnetic flux into a torque about the X-axis.

[0025] The edge section 45 is preferably integrally formed, or formed in a single body, at least with the disc section 43 and may project slightly from the disc section 43 in the direction of the hub 7. The edge section 45 may, in particular, have a ring shape and may therefore also be referred to as the ring section 45. As already described, the edge section 45 is provided with the face teeth 53, which have a shape complementary to the teeth 51 of the hub 7. Since the face teeth 51 and 53 are in mesh with each other, the torque generated in the disc section 43 is transmitted via the face teeth 51 and 53 to the hub 7 and rotates the wheel 3 connected to the flange section 23 about the axis X.

[0026] To engage and create a positive connection between the face teeth 51 and the face teeth 53, the bolt 13 is guided through the neck section 21 and screwed into the rotor 11. For this purpose, the disk section 43 is provided with a bolt hole 47 in its center, and the bolt 13 is provided with a corresponding thread 49. However, instead of or in addition to the combination of bolt hole 47 and thread 49, any suitable fastener that generates a compressive force or clamping force in the axial direction can be used.

[0027] In rotor 11, the shoulder section 41 and the disc section 43 can be a single body, as in Fig. 1 shown. However, it is also possible that the shoulder section 41 and the disc section 43 are designed as separate bodies and are coupled together, as in the embodiment according to Fig. Figure 4 shows that the coupling can be produced or realized using face gears 61, 63, which interlock axially, as shown, forming a positive locking connection. Any fasteners, such as bolts, can be used to apply a pressing, connecting, or preloading force to the face gears 61, 63. Alternatively, as already described, the bolt 13 can extend through the disc section 43 and then be fastened or clamped in the shoulder section 41. In this way, a single bolt 13 can connect the hub 7, the disc section 43, and the shoulder section 41. Instead of the gear or spline coupling, the shoulder section 41 and the disc section 43 can also be joined together after manufacturing as separate bodies by brazing, welding, friction welding, or similar processes.In any case, the possibility of manufacturing as separate bodies is advantageous when using separate materials that are each optimal or suitable for the requirements of the respective bodies, and when carrying out a surface treatment such as shot peening or hardening on a limited area such as the circumference of the shoulder section 41.

[0028] To mount the entire assembly of hub 7 and rotor 11 rotatably about axis X, ball bearings 55, 57, for example, can be used. One or more of them can form a bearing unit in which several rows of bearings may be provided, this being immaterial and not limiting.

[0029] Referring to Fig. 1 and Fig. 4. Regardless of whether the shoulder section 41 and the disc section 43 are manufactured as a single piece or separately, a certain amount of available space always remains around the shoulder section 41. This is particularly true if the wheel hub motor 1 is an axial gap motor. Using this space, the wheel hub motor 1 can be fitted with additional elements. Fig. 5, Fig. 6 and Fig. Figure 7 shows examples in which the wheel hub motor 1 is each equipped with one or more sensors 65, 67, 69 around the shoulder section 41.

[0030] An example of a sensor 65 is a torque sensor. In the case of a magnetostrictive torque sensor, the sensor 65 generates a magnetic flux that flows, at least partially, through the adjacent shoulder section 41 and then forms a loop. When a torque is applied to the shoulder section 41, a potential change is generated in the sensor 65, which can be detected or extracted to monitor the torque generated in the rotor 11. To enhance the sensor output, any surface treatment, such as shot peening, can be applied to the shoulder section 41. Of course, any torque sensor based on a different principle can be used. The torque sensor output is transmitted to an electronic control unit (ECU) installed in the vehicle and can be used to control the engine power.

[0031] An example of a sensor 67 is a rotational speed sensor. A magnetic encoder is attached, for example, to the shoulder section 41, and then the rotational speed of the rotor 11 can be detected by reading fluctuations or variations in a magnetic field generated by the sensor 67. Of course, any speed sensor based on a different principle can be used. The output signal of the speed sensor is transmitted to a control unit (ECU) and can be used for vehicle control, replacing the need to measure vehicle speed using another method.

[0032] An example of the sensor 69 is a rotary angle sensor, or so-called resolver. If, for example, a non-circular rotor 59 is pre-attached to the shoulder section 41 so that they rotate together, and the sensor 69, which comprises a plurality of electromagnetic coils arranged at regular intervals around its circumference, is positioned near the non-circular rotor 59, the inductance would change depending on the rotation angle of the non-circular rotor 59 and can be output as a signal. The non-circular rotor can also be referred to as a sensor disk. Of course, any rotary angle sensor based on a different principle is also applicable. The output of the rotary angle sensor is transmitted, for example, to a control unit (ECU) and can thus be used to control the rotational movement of the motor.

[0033] The wheel hub motor 1 can be equipped with one of these sensors 65, 67, 69, or of course with two, more, or all of them. The outputs of the sensors 65, 67, 69 are routed via internal wiring 71 or electrical lines and led together to the outside, out of the housing or wheel hub motor. Naturally, the outputs can be routed independently of each other. Alternatively, one or more of the outputs can be routed to the motor via an input terminal or connector.

[0034] At least one of the sensors 65, 67, 69 can be arranged inside the housing 5. As in Fig. As shown in Figure 5, the sensor 65 can be arranged as a torque sensor inside the housing 5 and attached to an inner surface of a side wall SW of the housing 5 by screws or the like. At least one cable of the internal wiring 71 can be connected to the sensor 65 and led to the outside through a through-hole in the side wall SW. This through-hole can be arranged radially inside relative to the stator 9. The remaining sensors 67, 69 can be located outside the housing 5, but they may be covered.

[0035] Alternatively, as in Fig. As shown in Figure 6, the sensor 67, acting as a speed sensor, is arranged together with the sensor 65 inside the housing 5 and attached together to the side wall SW. Of course, the sensor 69, together with the non-circular rotor 59, can also be arranged inside the housing 5, as shown in Figure 6. Fig.Figure 7 shows that, as illustrated in the drawing, sensor 69 can be arranged internally relative to sensor 67, or, contrary to the drawing, externally relative to sensor 67. While the order of sensors 65, 67, 69 can be arbitrary, these sensors are preferably arranged so that they are adjacent to each other, making the device compact in its axial direction.

[0036] According to the present embodiment, the wheel hub motor can accommodate sensors, thus eliminating the need for external sensors to control the vehicle or reducing their number. Furthermore, since the measured objects are backlash-free, the measurement results are not affected by play.

[0037] It goes without saying that the wheel hub motor 1 can be equipped with any other sensors or other elements instead of one of the sensors, or in addition to the torque sensor, speed sensor and rotation angle sensor.

[0038] It is understood that the torque transmission path from the disc section 43 of the rotor 11 to the flange section 23 of the hub 7 is a single, continuous body, with the exception of the spur gears 51 and 53, and the connection formed by the interlocking spur gears 51 and 53 is backlash-free, as already described. The wheel hub motor 1 therefore enables backlash-free torque output and transmission, despite its simple design. Furthermore, the wheel hub motor 1 can be easily assembled by installing the hub 7 and associated components into the housing part 5A, then installing the rotor 11 and associated components into the housing part 5B, and finally screwing in the bolt 13. Disassembly of the motor is equally simple, requiring only the reverse of this process. In fact, both assembly and maintenance are straightforward.

Claims

[1] Wheel hub motor (1) for driving a vehicle wheel (3) about an axis (X), comprising: a housing (5) dimensioned so that it can be at least partially accommodated in the wheel (3); a hub (7) which is rotatably mounted in the housing (5) about the axis (X), the hub (7) having a neck portion (21) with a first spur gear (51) arranged in the housing (5), and a flange portion (23) which is formed integrally with the neck portion (21) and is radially expanded outside the housing (5) in order to be connected to the wheel (3); a stator (9) with an electromagnet for generating a magnetic flux, wherein the stator (9) is fixedly connected to the housing (5); a rotor (11) which is rotatably mounted in the housing (5) and arranged coaxially with the hub (7), wherein the rotor (11) has a shoulder portion (41) with a second spur toothing (53) which engages in the first spur toothing (51), and a disc portion (43) which is formed integrally with the shoulder portion (41) and extends radially from the shoulder portion (41) towards the stator (9) to receive the magnetic flux and thus be driven about the axis (X); and a bolt (13) extending axially through the neck portion (21) and screwed into the shoulder portion (41) to non-rotatably connect the first spur gear (51) to the second spur gear (53). [2] Wheel hub motor (1) according to claim 1, wherein the first spur gear (51) and the second spur gear (53) each comprise a plurality of axially projecting and circumferentially arranged gears, wherein the first spur gear (51) and the second spur gear (53) face each other axially and are in engagement with each other. [3] Wheel hub motor (1) according to claim 1, wherein the flange portion (23) and the first spur gear teeth (51) form the two axial ends of the hub (7). [4] Wheel hub motor (1) according to claim 1, wherein the rotor (11) and the stator (9) form an axial gap motor. [5] A wheel hub motor (1) according to claim 4, wherein the shoulder portion (41) comprises one or more sensors (65, 67, 69) selected from the group consisting of a torque sensor, a rotational speed sensor and a rotational angle sensor.

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