Wheel drive system

Abstract

To provide a wheel drive device of an in-wheel motor structure which is suitably provided with a brake gear.SOLUTION: A wheel unit 10 includes cylindrical wheels 11, rotary electric machines 12 which are stored in the radial inner side of the wheels 11 and rotate the wheels 11, and a brake gear 13 which has a brake disk 61 and a brake caliper 62 and generates a braking force for the wheels 11. The rotary electric machines 12 has a rotor 30 and a stator 40 which are opposite to each other in a radial direction and is provided with a hollow part on the radial inner side of a magnetic circuit part composed of the rotor 30 and the fixer 40. In such a state that the brake caliper 62 is fixed on an axial end surface of the stator 40 and the brake disk 61 is rotated integrally with the rotor 30, the brake gear 13 is provided within the hollow part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The disclosure in this specification relates to a wheel drive device.

Background Art

[0002] Conventionally, as a wheel drive device, a so-called in-wheel motor structure in which a rotating electric machine is housed inside the wheel in the radial direction is known. Also, a technique in which a brake device is integrally incorporated in a wheel drive device having an in-wheel motor has been proposed. For example, in Patent Document 1, in a vehicle wheel drive device, an in-wheel motor includes an outer rotor fixed inside a rim of a wheel and an inner stator disposed inside the outer rotor. Further, a disk brake includes a brake disk attached to an end portion on the outer side in the vehicle width direction of the outer rotor and a caliper attached to an end portion on the outer side in the vehicle width direction of the inner stator.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when a brake device is integrally provided in a wheel drive device having an in-wheel motor structure, it is necessary to appropriately provide the brake device for the rotating electric machine which is the in-wheel motor. In this regard, there is room for improvement over the existing technology.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to suitably provide a brake device in a wheel drive device having an in-wheel motor structure.

Means for Solving the Problems

[0006] The various embodiments disclosed in this specification employ different technical means to achieve their respective purposes. The purposes, features, and effects disclosed in this specification will become clearer by referring to the subsequent detailed description and the accompanying drawings.

[0007] Method 1 is, A rotating electric machine is housed radially inside the cylindrical wheel and rotates the wheel, A wheel drive system comprising a brake device having a brake disc and a brake caliper, which generates a braking force on the wheel, The aforementioned rotating electric machine has a rotor and a stator facing each other in the radial direction, A hollow portion is provided radially inward of the magnetic circuit section consisting of the rotor and the stator. The brake device is provided within the hollow portion, characterized in that the brake caliper is fixed to the axial end face of the stator and the brake disc rotates integrally with the rotor.

[0008] The wheel drive system comprises a rotating electric motor housed radially inside the wheel and a brake device that generates braking force on the wheel. Furthermore, in the rotating electric motor, a hollow section is provided radially inside the magnetic circuit section consisting of a rotor and a stator, and the brake caliper is fixed to the axial end face of the stator, with the brake disc rotating integrally with the rotor, thereby providing the brake device within the hollow section. In this case, by providing the brake device within the hollow section of the magnetic circuit section, the axial length of the wheel drive system can be shortened. In addition, by fixing the brake caliper to the axial end face of the stator, the fixing structure of the brake caliper can be simplified, while allowing the brake device to be suitably housed within the hollow section. As a result, the brake device can be suitably provided in a wheel drive system with an in-wheel motor structure.

[0009] In means 2, the stator has a stator winding and a cylindrical retaining member that holds the stator winding, and the brake caliper has a fixed portion fixed to the axial end face of the stator, and is provided housed within the hollow portion while fixed by the fixed portion.

[0010] The brake caliper is fixed to the axial end face of the stator by a fixed part, and in this fixed state, it is housed within the hollow part of the magnetic circuit. In this configuration, the axle length is shortened by housing the brake caliper within the hollow part, while the fixing work of the fixed part to the axial end face of the stator can be performed from the outside of the wheel, thereby improving the workability of brake caliper installation.

[0011] In means 3, the wheel has a hub that serves as the center of rotation and a cylindrical rim that surrounds the hub, and the rotating electric machine is positioned radially inward of the rim with the rotor fixed to the hub, and has a shaft that is coaxial with the hub, and the brake disc is fixed to the shaft within the hollow portion.

[0012] The rotor is fixed to the wheel hub, and the rotating electric motor is positioned radially inward of the rim. Furthermore, the brake disc is fixed to a shaft coaxial with the hub within the hollow section of the magnetic circuit. In this configuration, when the brake device is operated, the braking torque generated by frictional braking against the brake disc does not directly act on the rotor, thus suppressing deformation of the rotor caused by the braking torque.

[0013] Means 4 is a wheel drive device having a hub bearing fixed to the hub, wherein the rotor comprises a cylindrical rotor carrier and a magnetic flux generating unit fixed to the rotor carrier, the rotor carrier has an end plate portion provided at its axial end, the stationary portion of the hub bearing is coupled to the stator, and the rotating portion of the hub bearing is coupled to the end plate portion of the rotor carrier, and the hub bearing and the shaft are provided on the side of the end plate portion that becomes the hollow portion.

[0014] The stator and rotor are made rotatable relative to each other by a hub bearing. Specifically, the stationary part of the hub bearing is connected to the stator, and the rotating part of the hub bearing is connected to the end plate of the rotor carrier. Furthermore, the hub bearing and shaft are provided on the side of the end plate that becomes the hollow part of the magnetic circuit. In this case, the hollow part of the magnetic circuit can be suitably used as a housing area for the brake device and the hub bearing.

[0015] In means 5, the stator has stator windings, the axial end of the stator windings is bent radially inward at the first coil end on one axial side, and the axial end of the stator windings is bent radially outward at the second coil end on the other axial side, the stator is assembled with the first coil end on the side closer to the hub and the second coil end on the side further from the hub in the axial direction, the rotor is positioned radially outside the stator, and the brake device is fixed radially inside the stator, inserted from the side of the second coil end.

[0016] In the stator winding, the axial end of the stator winding at the first coil end is bent radially inward, and the axial end of the stator winding at the second coil end is bent radially outward. The stator is assembled with the first coil end closer to the hub and the second coil end further away from the hub in the axial direction. The rotor is positioned radially outside the stator, and the brake device is fixed radially inside the stator, inserted from the side of the second coil end. In this case, the radial bending of the axial end of the stator winding allows for a suitable arrangement of the stator winding while suppressing interference between the phase windings of each phase. Furthermore, the rotor can be assembled to the stator from one side in the axial direction, and the brake device can be assembled from the other side in the axial direction.

[0017] In means 6, the brake caliper has a first part and a second part that are on one side and the other side of the brake disc in the axial direction, and the first part and the second part are connected by a connecting part on the radially outer side of the brake disc, and when the wheel drive device is mounted on the vehicle, the connecting part is configured to be above a horizontal line passing through the wheel rotation center, or at least a part of the connecting part is configured to be below the horizontal line, in which case the connecting part does not intersect a vertical line passing through the wheel rotation center.

[0018] In a brake caliper, a configuration is conceivable in which a first part and a second part, which are on either side of the brake disc, are connected by a connecting part on the radially outer side of the brake disc. In this case, when the wheel drive system is mounted on a vehicle, there is a concern that brake dust may remain on the inner circumferential surface of the connecting part on the brake disc side. In this regard, when the wheel drive system is mounted on a vehicle, the connecting part can be configured to be above a horizontal line passing through the wheel's rotation center, or, if at least a part of the connecting part is located below a horizontal line, the connecting part can be configured not to intersect a vertical line passing through the wheel's rotation center, thereby suppressing the accumulation of brake dust on the inner circumferential surface of the connecting part on the brake disc side.

[0019] In means 7, the stator has a stator winding and a cylindrical holding member that holds the stator winding. On both axial sides of the stator winding, on the side opposite to the fixed side of the brake caliper, each phase winding of the stator winding has a winding connection member electrically connected thereto, and a relay wiring extending from the winding connection member is provided so as to extend axially along the inner peripheral surface of the holding member, and the relay wiring is passed through at a position circumferentially away from the brake caliper in the hollow portion.

[0020] In a configuration in which a winding connection member is provided on both axial sides of the stator winding on the side opposite to the fixed side of the brake caliper, it is conceivable to draw out the relay wiring extending from the winding connection member through the hollow portion of the magnetic circuit portion. And in such a configuration, the relay wiring is passed through at a position circumferentially away from the brake caliper in the hollow portion of the magnetic circuit portion. In this case, in the hollow portion of the magnetic circuit portion, since the brake caliper and the relay wiring are provided at a separated position, the heat source is dispersed, and the cooling performance can be improved.

[0021] In means 8, a recess for passing the relay wiring is formed on the inner peripheral surface of the holding member.

[0022] Since a recess for passing the relay wiring is formed on the inner peripheral surface of the holding member, the relay wiring can be drawn out of the wheel drive device without reducing the braking force by securing the brake disc diameter, that is, by reducing the brake disc diameter.

[0023] In means 9, the brake caliper has a first part and a second part that can be divided in the axial direction, and the first part and the second part are each fixed to the stator.

[0024] In the brake caliper, a configuration is adopted in which a first part and a second part that can be divided in the axial direction are each fixed to the stator. In this case, since each part on the back side and the front side of the brake disc can be divided in the hollow portion of the magnetic circuit portion, the assembly work can be facilitated.

Brief Description of the Drawings

[0025] [Figure 1] Perspective view showing the whole wheel unit. [Figure 2] Longitudinal sectional view of the wheel unit. [Figure 3] Exploded perspective view of the wheel unit. [Figure 4] Longitudinal sectional view of the rotating electric machine. [Figure 5] Perspective view of the stator. [Figure 6] Longitudinal sectional view of the wheel unit. [Figure 7] Front view showing the mounting state of the wheel unit on the vehicle. [Figure 8] Perspective view of the wheel unit. [Figure 9] Cross-sectional view of the stator holder. [Figure 10] Longitudinal sectional view of the wheel unit.

Mode for Carrying Out the Invention

[0026] Hereinafter, an embodiment in which the wheel drive device according to the present invention is embodied as a wheel unit will be described with reference to the drawings. The wheel unit is used as a drive wheel in a vehicle such as a four-wheeled vehicle or a two-wheeled vehicle, and includes a wheel to which a tire is attached and a rotating electric machine (in-wheel motor) housed in the inner space of the wheel.

[0027] Figure 1 is a perspective view showing the entire wheel unit 10, Figure 2 is a longitudinal cross-sectional view of the wheel unit 10, and Figure 3 is an exploded perspective view of the wheel unit 10. As shown in Figures 1 to 3, the wheel unit 10 is broadly composed of a cylindrical wheel 11, a rotating electric machine 12 that rotates the wheel 11, and a brake device 13 that brakes the wheel 11. The rotating electric machine 12 is fixed to the inner circumference of the wheel 11. The rotating electric machine 12 has a fixed part which includes the stator and a rotating part which includes the rotor. The fixed part is fixed to the vehicle body (not shown), and the rotating part is fixed to the wheel 11, and the wheel 11 rotates due to the rotation of the rotating part. In the following description, the direction in which the rotation axis of the rotating electric machine 12 (wheel 11) extends is called the axial direction, the direction extending radially from the center of the rotation axis is called the radial direction, and the direction extending circumferentially with respect to the rotation axis is called the circumferential direction. The detailed configuration of the rotating electric machine 12, including the fixed and rotating parts, will be described later. In this embodiment, the rotating electric machine 12 and the brake device 13 correspond to the "wheel drive device".

[0028] The wheel 11 has a tire 21 and a wheel 22 fixed to the inner circumference of the tire 21. The wheel 22 has a hub 23 which is the rotation center of the wheel 11, a cylindrical rim 24 provided so as to surround the hub 23, and spokes 25 which connect the hub 23 and the rim 24. The tire 21 is attached to the outer circumference of the rim 24. The hub 23 and spokes 25 are provided on one axial end of the rim 24, and a rotating electric machine 12 is housed in the inner space of the rim 24 (the inner space of the wheel 22). The rotating electric machine 12 is provided in a state fixed to the hub 23 of the wheel 22.

[0029] The configuration of the rotating electric machine 12 is described below. Figure 4 is a longitudinal cross-sectional view of the rotating electric machine 12.

[0030] The rotating electric machine 12 is an outer rotor type surface magnet motor and comprises a rotor 30 and a stator 40 positioned radially inward of the rotor 30. The rotor 30 and stator 40 are each cylindrical in shape and are positioned opposite each other with an annular air gap in between.

[0031] The rotor 30 comprises a substantially cylindrical rotor carrier 31 and an annular magnet unit 32 fixed to the rotor carrier 31. The magnet unit 32 corresponds to the "magnetic flux generating section". The rotor carrier 31 has a cylindrical portion 33 and an end plate portion 34 provided on one axial end of the cylindrical portion 33. The magnet unit 32 is fixed to the inner circumferential surface of the cylindrical portion 33. The other axial end of the rotor carrier 31 is open. The rotor carrier 31 functions as a magnet holding member.

[0032] The magnet unit 32 has a plurality of magnets fixed to the inner circumferential surface of the cylindrical portion 33 of the rotor carrier 31. In the magnet unit 32, the magnets are arranged so that their polarity alternates along the circumferential direction of the rotor 30. As a result, the magnet unit 32 has a plurality of magnetic poles in the circumferential direction. The magnets are, for example, anisotropic permanent magnets, sintered neodymium magnets with an intrinsic coercivity of 400 [kA / m] or more and a residual magnetic flux density Br of 1.0 [T] or more. Incidentally, the rotating electric machine 12 may also be an embedded magnet type synchronous machine (IPMSM).

[0033] In the rotor carrier 31, a hub bearing 35 is fixed to the inner surface of the end plate portion 34, which is on the side of the cylindrical portion 33, at the radial center of the rotor 30, and a shaft 36 extending in the axial direction is fixed to the hub bearing 35. The hub bearing 35 comprises an outer ring 35a which is a stationary part, an inner ring 35b which is a rotating part, and a plurality of rolling elements 35c (for example, balls) provided between the outer ring 35a and the inner ring 35b. The inner ring 35b of the hub bearing 35 is fixed to the end plate portion 34. The shaft 36 is also fixed to the inner ring 35b in a manner that allows it to rotate integrally with it. The shaft 36 is provided at the radial center of the rotating electric machine 12 and has a disc portion 36a at its tip.

[0034] As shown in Figure 2, the rotor 30 is assembled to the wheel 11 by fixing the end plate portion 34 of the rotor carrier 31 to the hub 23 of the wheel 22 with fasteners such as bolts. When the rotor 30 is assembled to the wheel 11, the shaft 36 is coaxial with the hub 23.

[0035] The stator 40 includes a stator winding 41, a stator core 42, and a stator holder 43. The stator core 42 and the stator holder 43 are integrated with the stator core 42 facing radially outward, and the stator winding 41 is assembled to its radially outward side. The stator holder 43 corresponds to the "holding member." However, the assembly of the stator core 42 and the stator holder 43 may also correspond to the holding member.

[0036] The stator winding 41 has multiple phase windings, and is formed in a cylindrical shape by arranging the phase windings of each phase in a predetermined order in the circumferential direction. In this embodiment, the stator winding 41 is composed of three phase windings of U, V, and W phases. The stator core 42 is cylindrical and is provided as a back yoke.

[0037] In this embodiment, the stator 40 has a teethless structure that does not have teeth for forming slots. This structure may be any of the following (A) to (C). (A) In the stator 40, interconductor members are provided between each conductor section (intermediate conductor section 52 described later) in the circumferential direction, and the interconductor members are made of a magnetic material such that Wt × Bs ≤ Wm × Br, where Wt is the circumferential width dimension of the interconductor member at one magnetic pole, Bs is the saturation magnetic flux density of the interconductor member, Wm is the circumferential width dimension of the magnet at one magnetic pole, and Br is the residual magnetic flux density of the magnet constituting the magnet unit 32. (B) A structure in which, in the stator 40, interconductor members are provided between each conductor portion in the circumferential direction, and a non-magnetic material is used as the interconductor member. (C) In the stator 40, there is no structure in which inter-conductor members are provided between each conductor portion in the circumferential direction.

[0038] Next, the configuration of the stator winding 41 in this embodiment will be described with reference to Figure 5.

[0039] The stator winding 41 has a plurality of partial windings 51, which are unit coils, and these partial windings 51 are arranged in a circumferential direction. Each partial winding 51 is made by winding a conductor material in multiple layers and has a pair of intermediate conductor sections 52 that are parallel to each other and extend in the axial direction, and a pair of connecting sections 53, 54 that connect the pair of intermediate conductor sections 52 at their respective axial ends. These pair of intermediate conductor sections 52 and the pair of connecting sections 53, 54 form an annular shape.

[0040] Each of the connecting portions 53 and 54 on both sides of the axial direction is provided as a portion corresponding to the coil end, and of the connecting portions 53 and 54, one connecting portion 53 is formed by bending in the radial direction, while the other connecting portion 54 is formed without bending in the radial direction. Each partial winding 51 includes a partial winding 51 in which the connecting portion 53 is bent radially inward, and a partial winding 51 in which the connecting portion 53 is bent radially outward. In the stator 40, at the coil end CE1 on one axial end side (upper side of Figure 5), the connecting portion 53 of the partial winding 51 is bent radially inward, and at the coil end CE2 on the other axial end side (lower side of Figure 5), the connecting portion 53 of the partial winding 51 is bent radially outward.

[0041] Returning to the explanation of Figure 4, the stator holder 43 has a cylindrical portion 44 assembled radially inward of the stator core 42, an end plate portion 45 provided radially inward of the cylindrical portion 44 at one axial end of the cylindrical portion 44, and a protruding portion 46 provided radially outward from the cylindrical portion 44 at the other axial end. In the axial direction, the stator holder 43 has the end plate portion 45 on the same side as the end plate portion 34 of the rotor carrier 31. As a result, the rotor carrier 31 and the stator holder 43 have the end plate portions 34 and 45 facing each other on one side of the axial direction, and are open on the other side.

[0042] A refrigerant passage 47 is formed in the cylindrical portion 44 for circulating a refrigerant such as cooling water. The refrigerant passage 47 extends in a flattened shape in the axial direction and is provided in an annular shape along the cylindrical portion 44, and circulates the refrigerant in the circumferential direction between an inlet and an outlet (not shown).

[0043] The end plate portion 45 has a hole 45a in its center, into which the hub bearing 35 (more specifically, the outer ring 35a of the hub bearing 35) is assembled. As a result, the rotor carrier 31 (rotor 30) and the shaft 36 are rotatably supported by the stator holder 43 (stator 40).

[0044] The overhang portion 46 is provided so as to be outside the stator winding 41 in the axial direction, that is, outside the connecting portions 53 and 54. The overhang portion 46 is preferably provided with a position regulating function that restricts the position of each connecting portion 53 and 54. Specifically, the overhang portion 46 is preferably provided with engaging portions that engage with 53 and 54 of each section winding 51, and the engaging portions are configured to restrict the position of each section winding 51 in the axial direction, radial direction, and at least one of the axial directions.

[0045] In the stator 40, the inner circumference of the cylindrical portion 44 of the stator holder 43 is a hollow portion 48. This hollow portion 48 corresponds to the hollow space inside the magnetic circuit section consisting of the rotor 30 and the stator 40. In this embodiment, because the stator 40 has a teethless structure, the radial thickness of the stator 40 can be reduced, and the radial hollow portion 48 can be expanded.

[0046] In the stator 40, at the open end of the rotor carrier 31, the rotor carrier 31 and the stator holder 43 are double-layered, with an annular end ring 49 fitted into the gap between these components.

[0047] Furthermore, as shown in Figure 4, the stator 40 is provided with a wiring module 55 as a winding connection member that is electrically connected to each partial winding 51 of the stator winding 41. The wiring module 55 is formed in an annular shape and has wiring members such as busbars for each phase. The wiring module 55 connects the partial windings 51 of each phase in parallel or in series for each phase, and the phase windings of each phase are connected at their neutral points. The wiring module 55 is provided on the coil end CE1 side of the coil ends CE1 and CE2 on both axial sides of the stator 40, which is the side opposite to the open side of the stator holder 43. Note that coil end CE1 is the coil end on the side where the connecting portion 53 of the partial winding 51 is bent radially inward.

[0048] The wiring module 55 is connected to power wiring 56 for each phase. The power wiring 56 is provided so as to extend axially through the stator holder 43, with one end of each power wiring 56 connected to the wiring module 55. The power wiring 56 is provided so as to extend from coil end CE1 to coil end CE2. The power wiring 56 corresponds to "relay wiring". The power wiring 56 for each phase is connected to an inverter (not shown) so that power is input and output. The wiring module 55 may also be provided with a current sensor to detect the phase current of each phase. In addition, the power wiring 56 may include sensor signal lines.

[0049] Next, the brake device 13 will be explained using Figures 2 and 3.

[0050] The brake system 13 is a disc-type friction brake system and includes a disc-shaped brake disc 61 and a brake caliper 62. Since the configuration of the brake system 13 itself is well known, a detailed diagrammatic explanation will be omitted. However, the brake disc 61 consists of a solid disc made of a single disc, or a ventilated disc with a cavity for ventilation inside. The brake caliper 62 is operated by hydraulic pressure or electrical signals and includes a pair of brake pads that contact the brake disc 61 to generate braking force, a piston that presses the brake pads against the brake disc 61, and a caliper body that supports these brake pads and piston.

[0051] The brake disc 61 is fixed to the tip (disc portion 36a) of the shaft 36, which rotates integrally with the rotor 30, by fasteners 63 such as bolts. In this case, the brake disc 61 is coupled to the rotor carrier 31 via the shaft 36 and the hub bearing 35. Therefore, compared to a configuration in which the brake disc 61 is directly coupled to the rotor carrier 31, the effect of braking torque on the rotor 30 can be reduced. In other words, deformation of the rotor carrier 31 due to braking torque is suppressed. Also, compared to a configuration in which the brake disc 61 is directly coupled to the rotor carrier 31, heat generated when the brake device 13 is in operation is less likely to be transmitted to the rotor 30.

[0052] The tip of the shaft 36 extends to an intermediate axial position within the cylindrical portion 44 of the stator holder 43, and with the brake disc 61 fixed to its tip, the entire brake disc 61 is housed within the cavity 48. In this case, the brake disc 61 is housed within the cavity 48 at a position where at least a portion is closer to the axial center (to the left in the figure) with respect to the axial position X which is the axial end face of the magnet unit 32 of the rotor 30. Furthermore, in terms of its positional relationship with the wheel 22, it is preferable that the entire brake disc 61 is housed on the inner circumference side of the rim 24. However, it is also acceptable to have a configuration in which only a portion of the brake disc 61 is housed within the cavity 48, or a configuration in which only a portion of the brake disc 61 is housed on the inner circumference side of the rim 24.

[0053] As shown in Figure 6, the brake caliper 62 has a fixed portion 64 that is fixed to the stator holder 43 while in contact with the axial end face of the stator holder 43, and is fixed to the stator holder 43 at the fixed portion 64 by fasteners 65 such as bolts. In other words, at least the portion of the brake caliper 62 excluding the fixed portion 64 is housed within the cylindrical portion 44, i.e., the hollow portion 48, of the stator holder 43. In this case, the fixed portion 64 can be fixed to the axial end face of the stator holder 43 from the outside of the wheel. Furthermore, when the brake device 13 is operated, the heat generated in the brake caliper 62 is directly transferred to the stator holder 43 via the fixed portion 64. This makes it possible to cool the brake device 13 with the stator holder 43.

[0054] During normal vehicle operation, the heat generated by the stator 40 and the heat dissipated by the brake caliper 62 are balanced. However, during emergency braking, the rotating electric motor 12 stops. Therefore, the cooling capacity of the stator 40 is entirely used for brake cooling.

[0055] The brake caliper 62 is provided so as to straddle both sides of the brake disc 61, and has an inner portion 62a facing the first surface near the center of the cavity 48 of the brake disc 61, and an outer portion 62b facing the second surface near the outside of the cavity 48. Brake pads are provided on the inner portion 62a and the outer portion 62b, and a piston is provided on the inner portion 62a. The inner portion 62a and the outer portion 62b are connected by a connecting portion 62c of the caliper body on the radially outer side of the brake disc 61. The brake caliper 62 has an external mounting structure in which the caliper body is stretched across the radially outer side of the brake disc 61. The inner portion 62a corresponds to the "first part," and the outer portion 62b corresponds to the "second part."

[0056] Although not shown in the diagram, the brake caliper 62 is connected, for example, to a hydraulic pipe to actuate the piston. This hydraulic pipe is preferably routed radially outward from the brake disc 61.

[0057] When assembling the brake device 13 to the rotating electric machine 12, it is preferable to assemble the brake disc 61 in a state where it is set in the brake caliper 62, that is, with the brake disc 61 and brake caliper 62 integrated together as shown in Figure 3.

[0058] Here, Figure 7 is a front view showing the state in which the wheel unit 10 is mounted on the vehicle. In the state shown in Figure 7, the brake device 13 is mounted in a position where the brake caliper 62 is vertically upward. More specifically, the brake device 13 is mounted in a position where the connecting portion 62c of the brake caliper 62 is above the horizontal line H passing through the wheel's rotation center. Note that if at least a part of the connecting portion 62c of the brake caliper 62 is located below the horizontal line H, as shown by the dashed line in Figure 7, it is preferable that the connecting portion 62c does not intersect the vertical line V passing through the wheel's rotation center. In this case, even if wear particles are generated by the frictional braking of the brake caliper 62 (brake pad) against the brake disc 61, the wear particles are more easily discharged from the inside of the connecting portion 62c (the inner circumferential surface on the brake disc 61 side), and the retention of wear particles on the brake caliper 62 is suppressed.

[0059] The brake device 13 is installed in a state where it is housed in the hollow part 48 of the rotating electric machine 12, that is, in the hollow part within the magnetic circuit section of the rotating electric machine 12. In this case, when the brake device 13 is assembled to the rotating electric machine 12, the radial arrangement, viewed from the central axis side, is in the order of brake caliper 62, stator 40, air gap, and rotor 30. In this configuration, the heat dissipation section (coolant passage 47) of the stator holder 43 and the air gap exist between the heat-generating brake caliper 62 and the rotor 30 (magnet), making it difficult for heat from the brake caliper 62 to be transferred to the rotor 30 (magnet), thus suppressing demagnetization of the magnet.

[0060] As shown in Figure 2, the stator 40 is assembled with the coil end CE1 closer to the hub 23 and the coil end CE2 further away from the hub 23 in the axial direction. In this configuration, the rotor 30 is positioned radially outward of the stator 40, and the brake device 13 is fixed radially inward of the stator 40, inserted from the coil end CE2 side. In this case, the brake device 13 can be assembled to the stator 40 from the coil end CE2 side.

[0061] On the side of the end plate portion 34 that forms the hollow portion 48, the hub bearing 35 and the shaft 36 are attached. In this case, the brake caliper 62 is positioned to overlap radially with the hub bearing 35, and the hollow portion 48 serves as a housing area for the brake device 13 and the hub bearing 35.

[0062] As described above, if a wiring module 55 is provided at the coil end CE1 on the side opposite to the open side of the stator holder 43, the power wiring 56 connected to the wiring module 55 is routed through the radially inner side of the stator holder 43 to the open side of the stator holder 43. This configuration is shown in Figure 8.

[0063] As shown in Figure 8, in the stator holder 43, a recess 44a extending in the axial direction is formed on the inner circumferential surface of the cylindrical portion 44 on the radially inner side, and the power wiring 56 is pulled out so that it fits into this recess 44a. In this configuration, the power wiring 56 is pulled out outside the wheel while maintaining the brake disc diameter, that is, without causing a reduction in braking force due to a reduction in the brake disc diameter.

[0064] Furthermore, the circumferential position where the recess 44a is provided in the stator holder 43, that is, the insertion position of the power wiring 56 within the cavity 48, is located circumferentially away from the brake caliper 62. This allows the heat source to be dispersed within the cavity 48, improving cooling performance.

[0065] Considering that the stator holder 43 is provided with an annular refrigerant passage 47, it is preferable that a recess 44a be provided at a position that does not overlap with the refrigerant passage 47 in the circumferential direction. This configuration will be explained using Figure 9, which shows a cross-section of the stator holder 43. In Figure 9, the cylindrical portion 44 of the stator holder 43 is provided with an annular refrigerant passage 47, with one end of the refrigerant passage 47 being the passage inlet and the other end being the passage outlet. In this case, the cylindrical portion 44 is locally thicker in the radial direction between the passage inlet and the passage outlet of the refrigerant passage 47, and the recess 44a is provided in this thickened portion, allowing for the routing of suitable power wiring 56 without affecting the refrigerant passage 47.

[0066] The shaft 36 may be provided with a rotation detection device 37, such as a resolver. In this embodiment, the brake device 13 is located within the cavity 48, which limits the installation space for the rotation detection device 37. Therefore, an SRX (Semiconductor Resolver) sensor may be used as the rotation detection device 37. This allows for a compact wheel unit 10 while also enabling the proper placement of the rotation detection device 37.

[0067] According to the embodiment described in detail above, the following excellent effects can be obtained.

[0068] By providing the brake device 13 within the hollow section (cavity 48) of the magnetic circuit in the rotating electric machine 12, the axial length of the wheel unit 10 can be shortened. Furthermore, by fixing the brake caliper 62 to the axial end face of the stator 40, the fixing structure of the brake caliper 62 can be simplified while accommodating the brake device 13 within the hollow section. As a result, the brake device 13 can be suitably provided in the wheel unit 10 with an in-wheel motor structure.

[0069] The brake caliper 62 is fixed to the axial end face of the stator 40 by a fixed part 64, and in this fixed state, it is housed within the hollow part of the magnetic circuit. In this configuration, the axle length is shortened by housing the brake caliper 62 within the hollow part, while the fixing work of the fixed part 64 to the axial end face of the stator 40 can be performed from the outside of the wheel, thereby improving the workability of installing the brake caliper 62.

[0070] The rotor 30 is fixed to the hub 23 of the wheel 22, and the rotating electric motor 12 is positioned radially inward of the rim 24. In addition, the brake disc 61 is fixed to a shaft 36 that is provided coaxially with the hub 23 within the hollow portion of the magnetic circuit. In this configuration, when the brake device 13 is operated, the braking torque generated by frictional braking against the brake disc 61 does not directly act on the rotor 30, thus suppressing deformation of the rotor 30 caused by the braking torque.

[0071] The stator 40 and rotor 30 are made rotatable relative to each other by a hub bearing 35. Specifically, the outer ring 35a (stationary part) of the hub bearing 35 is connected to the stator 40, and the inner ring 35b (rotating part) of the hub bearing 35 is connected to the end plate portion 34 of the rotor carrier 31. Furthermore, the hub bearing 35 and shaft 36 are provided on the side of the end plate portion 34 that will be the hollow portion of the magnetic circuit. In this case, the hollow portion of the magnetic circuit can be suitably used as a housing area for the brake device 13 and the hub bearing 35.

[0072] In the stator winding 41, the axial end of the stator winding 41 (partial winding 51) at coil end CE1 is bent radially inward, and the axial end of the stator winding 41 (partial winding 51) at coil end CE2 is bent radially outward. The stator 40 is assembled with coil end CE1 closer to the hub 23 and coil end CE2 further away from the hub 23 in the axial direction. The rotor 30 is positioned radially outward of the stator 40, and the brake device 13 is fixed radially inward of the stator 40, inserted from the coil end CE2 side. In this configuration, the radial bending of the axial end of the stator winding 41 allows for a suitable arrangement of the stator winding 41 while suppressing interference between the phase windings of each phase. Furthermore, the rotor 30 can be assembled to the stator 40 from one axial side, and the brake device 13 can be assembled from the other axial side.

[0073] When the wheel unit 10 is mounted on the vehicle, the connecting portion 62c of the brake caliper 62 is configured to be above the horizontal line H passing through the wheel's rotation center, or, if at least a part of the connecting portion 62c is configured to be below the horizontal line H, the connecting portion 62c is configured not to intersect the vertical line V passing through the wheel's rotation center, thereby suppressing the accumulation of wear particles on the brake device 13.

[0074] The power wiring 56 is routed within the hollow portion of the magnetic circuit at a position circumferentially away from the brake caliper 62. In this case, the heat source is dispersed because the brake caliper 62 and the power wiring 56 are located at separate positions within the hollow portion of the magnetic circuit, thereby improving cooling performance.

[0075] Since a recess 44a for passing the power wiring 56 is formed on the inner circumferential surface of the stator holder 43, the power wiring 56 can be routed outside the wheel while maintaining the brake disc diameter, that is, without reducing the braking force caused by reducing the brake disc diameter.

[0076] (modified version) In the brake caliper 62, the inner portion 62a and the outer portion 62b may be axially separable and fixed individually to the stator holder 43. Specifically, as shown in Figure 10, the inner portion 62a of the brake caliper 62 is fixed to the inner circumferential surface of the stator holder 43, then the brake disc 61 is fixed to the shaft 36, and then the outer portion 62b of the brake caliper 62 is fixed to the axial end face of the stator holder 43. In this case, since the portions on the rear and front sides of the brake disc 61 are separable, the assembly work can be made easier.

[0077] The brake system 13 may have multiple brake calipers 62 provided for a single brake disc 61. Alternatively, multiple brake discs 61 may be provided on the shaft 36. By using multiple brake discs 61 or brake calipers 62 in the brake system 13, the braking force in the in-wheel motor can be increased.

[0078] In the above embodiment, the piston is provided in the inner portion 62a of the brake caliper 62, but this can be changed to a configuration where the piston is provided in the outer portion 62b.

[0079] The stator winding 41 is not limited to one using multiple partial windings 51, but may also be a configuration in which a conductor is wound by wave winding. In this case, it is preferable that the stator winding 41, which is formed into a cylindrical shape by wave winding, is assembled to the cylindrical stator core 42.

[0080] In the embodiments described above, a surface-mounted magnet type rotor was used as the rotor 30, but instead, a recessed magnet type rotor or a field coil type rotor may be used.

[0081] In the embodiments described above, the rotating electric machine is of an outer rotor structure, but this may be changed to a rotating electric machine of an inner rotor structure. In a rotating electric machine of an inner rotor structure, the stator is provided on the radially outer side, and the rotor is provided on the radially inner side.

[0082] The disclosures in this specification are not limited to the exemplary embodiments. The disclosures encompass the exemplary embodiments and variations thereof by those skilled in the art. For example, the disclosures are not limited to combinations of parts and / or elements shown in the embodiments. The disclosures are implementable in a variety of combinations. The disclosures may have additional parts that can be added to the embodiments. The disclosures encompass embodiments in which parts and / or elements are omitted. The disclosures encompass substitutions or combinations of parts and / or elements between one embodiment and another. The scope of the disclosed technical areas is not limited to the descriptions of the embodiments. Some of the scope of the disclosed technical areas are indicated by the claims and should be understood to include all modifications within the meaning and scope equivalent to the claims.

[0083] The technical concepts extracted from the above-described embodiments are described below. [Configuration 1] A rotating electric machine (12) is housed radially inside the cylindrical wheel (11) and rotates the wheel, A wheel drive system comprising a brake device (13) having a brake disc (61) and a brake caliper (62) that generates a braking force on the wheel, The aforementioned rotating electric machine has a rotor (30) and a stator (40) facing each other in the radial direction. A hollow portion (48) is provided radially inward of the magnetic circuit section consisting of the rotor and the stator. A wheel drive system in which the brake caliper is fixed to the axial end face of the stator, and the brake disc rotates integrally with the rotor, and the brake device is provided within the hollow portion. [Configuration 2] The stator has a stator winding (41) and cylindrical holding members (42, 43) that hold the stator winding. The wheel drive device according to configuration 1, wherein the brake caliper has a fixed portion (64) fixed to the axial end face of the stator, and is provided in a state where it is fixed by the fixed portion and housed within the hollow portion. [Configuration 3] The wheel has a wheel (22) which includes a hub (23) that serves as the center of rotation and a cylindrical rim (24) that surrounds the hub. The aforementioned rotating electric machine is configured such that the rotor is fixed to the hub and positioned radially inward of the rim. The hub has a shaft (36) that is provided coaxially with the hub, The wheel drive device according to configuration 1 or 2, wherein the brake disc is fixed to the shaft within the hollow portion. [Structure 4] A wheel drive device having a hub bearing (35) fixed to the hub, The rotor comprises a cylindrical rotor carrier (31) and a magnetic flux generating unit (32) fixed to the rotor carrier. The rotor carrier has an end plate portion (34) provided at its axial end, The stationary portion (35a) of the hub bearing is coupled to the stator. The rotating portion (35b) of the hub bearing is connected to the end plate portion of the rotor carrier. The wheel drive device according to configuration 3, wherein the hub bearing and the shaft are provided on the side of the end plate portion that forms the hollow portion. [Composition 5] The stator has a stator winding (41), The stator winding is such that at the first coil end (CE1) on one axial side, the axial end of the stator winding is bent radially inward, and at the second coil end (CE2) on the other axial side, the axial end of the stator winding is bent radially outward. The stator is assembled such that the first coil end is closer to the hub in the axial direction and the second coil end is further away from the hub. The wheel drive device according to configuration 3 or 4, wherein the rotor is positioned radially outward of the stator, and the brake device is fixed radially inward of the stator, inserted from the side of the second coil end. [Composition 6] The brake caliper has a first portion (62a) and a second portion (62b) that are on one side and the other side of the brake disc in the axial direction, The first and second portions are connected by a connecting portion (62c) on the radially outer side of the brake disc. A wheel drive device according to any one of configurations 1 to 5, wherein, when the wheel drive device is mounted on a vehicle, the connecting portion is configured to be above a horizontal line passing through the wheel's rotation center, or, if at least a part of the connecting portion is provided below the horizontal line, the connecting portion does not intersect a vertical line passing through the wheel's rotation center. [Composition 7] The stator has a stator winding (41) and cylindrical holding members (42, 43) that hold the stator winding. In the stator winding, on both sides of the axial direction, the side opposite to the fixed side of the brake caliper, there is a winding connecting member (55) that is electrically connected to each phase winding of the stator winding, The relay wiring (56) extending from the winding connection member is provided so as to extend axially along the inner circumferential surface of the holding member. A wheel drive device according to any one of configurations 1 to 6, wherein the relay wiring is routed within the hollow portion at a position circumferentially away from the brake caliper. [Structure 8] The wheel drive device according to configuration 7, wherein a recess (44a) for passing the relay wiring is formed on the inner circumferential surface of the holding member. [Composition 9] The brake caliper has a first part (62a) and a second part (62b) that are axially separable, A wheel drive device according to any one of configurations 1 to 8, wherein the first part and the second part are respectively fixed to the stator. [Explanation of symbols]

[0084] 10...wheel unit, 11...wheel, 12...rotating electric machine, 13...brake device, 30...rotor, 40...stator, 48...cavity, 61...brake disc, 62...brake caliper.

Claims

1. A rotating electric machine (12) is housed radially inside the cylindrical wheel (11) and rotates the wheel, The vehicle comprises a brake device (13) having a brake disc (61) and a brake caliper (62) that generates a braking force on the wheel, The wheel drive device has a wheel (22) that includes a hub (23) which is the center of rotation and a cylindrical rim (24) which is provided so as to surround the hub, The aforementioned rotating electric machine has a rotor (30) and a stator (40) facing each other in the radial direction, and the rotor is fixed to the hub and positioned radially inward of the rim. A hollow portion (48) is provided radially inward of the magnetic circuit section consisting of the rotor and the stator. The brake caliper is fixed to the axial end face of the stator, and the brake disc rotates integrally with the rotor, and the brake device is provided within the hollow portion. The stator has a stator winding (41), The stator winding is such that at the first coil end (CE1) on one axial side, the axial end of the stator winding is bent radially inward, and at the second coil end (CE2) on the other axial side, the axial end of the stator winding is bent radially outward. The stator is assembled such that the first coil end is closer to the hub and the second coil end is further away from the hub in the axial direction. A wheel drive system in which the rotor is positioned radially outward of the stator, and the brake device is fixed radially inward of the stator, inserted from the side of the second coil end.

2. A wheel drive device having a hub bearing (35) fixed to the hub, The rotor comprises a cylindrical rotor carrier (31) and a magnetic flux generating unit (32) fixed to the rotor carrier. The rotor carrier has an end plate portion (34) provided at its axial end, The stationary portion (35a) of the hub bearing is coupled to the stator. The rotating portion (35b) of the hub bearing is connected to the end plate portion of the rotor carrier. The wheel drive device according to claim 1, wherein the hub bearing is provided on the side of the end plate portion that forms the hollow portion.

3. A rotating electric machine (12) is housed radially inside the cylindrical wheel (11) and rotates the wheel, A wheel drive system comprising a brake device (13) having a brake disc (61) and a brake caliper (62) that generates a braking force on the wheel, The aforementioned rotating electric machine has a rotor (30) and a stator (40) facing each other in the radial direction. A hollow portion (48) is provided radially inward of the magnetic circuit section consisting of the rotor and the stator. The brake caliper is fixed to the axial end face of the stator, and the brake disc rotates integrally with the rotor, and the brake device is provided within the hollow portion. The stator has a stator winding (41) and cylindrical holding members (42, 43) that hold the stator winding. In the stator winding, on both sides of the axial direction, opposite to the fixed side of the brake caliper, there is a winding connecting member (55) electrically connected to each phase winding of the stator winding. The relay wiring (56) extending from the winding connecting member is provided to extend axially along the inner circumferential surface of the holding member, A wheel drive device in which the relay wiring is routed within the hollow portion at a position circumferentially away from the brake caliper.

4. The wheel drive device according to claim 3, wherein a recess (44a) for passing the relay wiring is formed on the inner circumferential surface of the holding member.

5. A rotating electric machine (12) is housed radially inside the cylindrical wheel (11) and rotates the wheel, A wheel drive system comprising a brake device (13) having a brake disc (61) and a brake caliper (62) that generates a braking force on the wheel, The aforementioned rotating electric machine has a rotor (30) and a stator (40) facing each other in the radial direction. A hollow portion (48) is provided radially inward of the magnetic circuit section consisting of the rotor and the stator. The brake caliper is fixed to the axial end face of the stator, and the brake disc rotates integrally with the rotor, and the brake device is provided within the hollow portion. The brake caliper has a first part (62a) and a second part (62b) that are axially separable, A wheel drive device in which the first part and the second part are respectively fixed to the stator.

6. The stator has a stator winding (41) and cylindrical holding members (42, 43) that hold the stator winding. The wheel drive device according to any one of claims 1 to 5, wherein the brake caliper has a fixed portion (64) fixed to the axial end face of the stator, and is provided in a state where it is fixed by the fixed portion and housed within the hollow portion.

7. The brake caliper has a first portion (62a) and a second portion (62b) that are on one side and the other side of the brake disc in the axial direction, The first and second portions are connected by a connecting portion (62c) on the radially outer side of the brake disc. The wheel drive device according to any one of claims 1 to 5, wherein, when the wheel drive device is mounted on a vehicle, the connecting portion is configured to be above a horizontal line passing through the wheel's rotation center, or, if at least a part of the connecting portion is provided below the horizontal line, the connecting portion is configured not to intersect a vertical line passing through the wheel's rotation center.

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