In-wheel motor

Abstract

To provide an in-wheel motor which enables downsizing of a speed reduction mechanism provided in a wheel.SOLUTION: A speed reduction mechanism 3 includes: a sun gear 15 to which torque is transmitted from a motor 2; a large diameter pinion gear 16 configured to engage with the sun gear 15; a small diameter pinion gear 17 which integrally rotates with the large diameter pinion gear 16; a ring gear 18 configured to engage with the small diameter pinion gear 17 and fixed to a housing 7; and a carrier 19 which holds the large diameter pinion gear 16 and the small diameter pinion gear 17 so that these pinion gears may autorotate and revolve and transmits torque to a wheel 5. The speed reduction mechanism 3 further includes a shaft 20 which connects the large diameter pinion gear 16 with the small diameter pinion gear 17. The carrier 19 is configured to hold the shaft 20 in a rotatable manner between the large diameter pinion gear 16 and the small diameter pinion gear 17.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an in-wheel motor configured to transmit torque of a motor, which is a driving force source, to a wheel via a stepped pinion type planetary gear mechanism having at least two pinion gears with different diameters. [Background technology]

[0002] Patent Document 1 describes an in-wheel motor equipped with a speed reduction mechanism that amplifies the torque output from a motor, which is a driving force source. The speed reduction mechanism is composed of a stepped pinion type planetary gear mechanism. That is, the speed reduction mechanism is composed of a sun gear connected to a motor, a large diameter pinion gear meshed with the sun gear, a small diameter pinion gear formed with a smaller diameter than the large diameter pinion gear, a carrier that holds the large diameter pinion gear and the small diameter pinion gear so that they can rotate and revolve and is connected to a driving wheel, and a ring gear that meshes with the small diameter pinion gear and is connected to a housing. The large diameter pinion gear and the small diameter pinion gear are formed in a hollow shape, and a pinion pin is inserted into the hollow part via a bearing. Both ends of the pinion pin are connected to two carrier plates arranged opposite each other.

[0003] Furthermore, by locating the connection between the ring gear and the housing on the outer periphery of the large diameter pinion gear, space is secured on the outer periphery of the small diameter pinion gear, and part of the rotor and stator that make up the motor are located in that space. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-147177 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the in-wheel motor described in Patent Document 1, a pinion pin is inserted into the hollow portion between the large diameter pinion gear and the small diameter pinion gear, so that the outer diameter of the small diameter pinion gear is determined by the module and the thickness of the tooth bottom determined according to the torque and gear ratio transmitted by the reduction gear mechanism, and the outer diameter of the pinion pin according to the rigidity required for the pinion pin. The rigidity required for the pinion pin is determined based on the bending load (bending moment) acting on the pinion pin from the small diameter pinion gear and the large diameter pinion gear. Therefore, in a configuration in which the small diameter pinion gear is fitted to the pinion pin, there is a limit to how small the small diameter pinion gear can be made in order to ensure the rigidity of the pinion pin.

[0006] The present invention has been made in light of the above technical problems, and has an object to provide an in-wheel motor that can reduce the size of the reduction mechanism provided within the wheel. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides an in-wheel motor including a motor as a driving force source, a wheel on which a tire is mounted, and a reduction mechanism that transmits torque from the motor to the wheel and is provided inside the wheel, the reduction mechanism including a sun gear, a large diameter pinion gear that meshes with the sun gear, a small diameter pinion gear that rotates integrally with the large diameter pinion gear and has a smaller diameter than the large diameter pinion gear, a ring gear that meshes with the small diameter pinion gear, and a reduction gear that reduces the torque of the large diameter pinion gear. the large diameter pinion gear and the small diameter pinion gear are connected to a carrier that holds the small diameter pinion gear so that they can rotate and revolve about their axis, the sun gear is connected to the motor, the ring gear is connected to one of the housing and the wheel, and the carrier is connected to the other of the housing and the wheel, and a shaft is provided that connects the large diameter pinion gear and the small diameter pinion gear, and the carrier is configured to rotatably hold the shaft between the large diameter pinion gear and the small diameter pinion gear. Effect of the Invention

[0008] In the in-wheel motor of the present invention, the reduction gear mechanism that transmits torque from the motor to the wheel is configured by a so-called stepped pinion type planetary gear mechanism including a large diameter pinion gear and a small diameter pinion gear with different outer diameters. The carrier rotatably holds the shaft between the large diameter pinion gear and the small diameter pinion gear. Therefore, there is no need to provide a pinion pin for rotatably holding the large diameter pinion gear and the small diameter pinion gear. As a result, the outer diameter of the small diameter pinion gear can be reduced by the amount that does not require the insertion of a pinion pin or a bearing. As a result, the outer diameter of the small diameter pinion gear side in the direction of the rotational center axis of the reduction gear mechanism can be reduced. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view illustrating an example of an in-wheel motor according to an embodiment of the present invention. [Diagram 2] 11 is a cross-sectional view for illustrating a configuration in which a motor is disposed in a space on the outer periphery side of a small diameter pinion gear. FIG. [Diagram 3] 11 is a cross-sectional view for illustrating a configuration in which a coil end is disposed in a space on the outer periphery side of a small diameter pinion gear. FIG. [Figure 4] FIG. 11 is a cross-sectional view for illustrating a configuration in which a brake unit is fixed to a housing in a space on the outer periphery side of a small diameter pinion gear. [Diagram 5] 11 is a cross-sectional view for illustrating a configuration in which a motor is fixed to a housing in a space on the outer periphery side of a small diameter pinion gear. FIG. [Figure 6] 1 is a cross-sectional view illustrating a configuration in which a bearing into which a shaft is fitted and a large-diameter pinion gear are arranged to overlap in the central axial direction of the shaft. FIG. [Figure 7] 13 is a cross-sectional view for explaining an example in which the plate portion, the cylindrical portion, and the protrusion portion are made of a resin material. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of the implementation of the present invention, and is not intended to limit the present invention.

[0011] A cross-sectional view for explaining an example of an in-wheel motor according to an embodiment of the present invention is shown typically in Fig. 1. The in-wheel motor 1 shown in Fig. 1 includes a motor 2 as a driving force source, a speed reduction mechanism 3 that amplifies the output torque of the motor 2, and a wheel 5 connected to the speed reduction mechanism 3 and having a tire 4 attached thereto.

[0012] The motor 2 can be configured in the same manner as a conventional in-wheel motor or a motor provided as a driving force source for an electric vehicle or a hybrid vehicle. That is, the motor 2 is electrically connected to an electricity storage device (not shown) and functions as a motor that outputs driving torque when power is supplied from the electricity storage device, and also functions as a generator that converts the power of the output shaft 6 of the motor 2 into electric power and supplies the converted electric power to the electricity storage device when the output shaft 6 of the motor 2 is rotated. A synchronous motor, an induction motor, or the like can be used as the motor 2.

[0013] In the example shown in FIG. 1, an in-wheel motor housing (hereinafter simply referred to as housing) 7 is fixed to a suspension or the like attached to a vehicle body (not shown), and a motor 2 is fixed to the housing 7. The housing 7 is formed in a cylindrical shape, and a flange portion 8 is formed at the end portion on the vehicle body side (the end portion on the right side in FIG. 1). A flange portion 9 facing the flange portion 8 is connected to the motor 2, and the flange portions 8, 9 are fixed by a bolt 10. In the example shown in FIG. 1, an annular stay 11 for reinforcing the flange portion 8 is fixed to the end face of the flange portion 8 by a bolt 12.

[0014] An input shaft 13 of the reduction gear mechanism 3 is connected to an output shaft 6 of the motor 2. Specifically, a recess 14 is formed in the output shaft 6 along the central axis of rotation, and the tip of the input shaft 13 is fitted into the recess 14. The recess 14 and the input shaft 13 are connected to be able to rotate together by spline engagement or the like.

[0015] 1, a brake unit B for applying a braking torque to the input shaft 13 is provided inside the housing 7. This brake unit B is configured to bring an annular brake disc integrated with the input shaft 13 into frictional contact with a brake plate disposed opposite the brake disc and non-rotatably connected to the housing 7 with a pressing force corresponding to the electromagnetic force of an electromagnetic actuator, the spring force of a spring, etc.

[0016] 1 is configured by a stepped pinion type planetary gear mechanism, that is, includes a sun gear 15, a large diameter pinion gear 16 meshing with the sun gear 15, a small diameter pinion gear 17 that rotates integrally with the large diameter pinion gear 16 and has an outer diameter smaller than that of the large diameter pinion gear 16, a ring gear 18 that meshes with the small diameter pinion gear 17, and a carrier 19 that holds the large diameter pinion gear 16 and the small diameter pinion gear 17 so that they can rotate and revolve about their axes.

[0017] The sun gear 15 is integrally formed with the input shaft 13 by, for example, cutting the end of the input shaft 13. A shaft 20 that connects the large diameter pinion gear 16 and the small diameter pinion gear 17 is connected to the small diameter pinion gear 17. That is, like the sun gear 15, the small diameter pinion gear 17 is also integrally formed by, for example, cutting the end of the shaft 20. The large diameter pinion gear 16 may be integrally formed with the shaft 20, or may be formed separately from the shaft 20 and connected by, for example, spline engagement.

[0018] The end of the housing 7 is formed up to the vicinity of the reduction gear mechanism 3, and an outer circumferential cylindrical portion 21 is formed on the outer circumferential portion of the end so as to surround the outer circumferential side of the small diameter pinion gear 17 in the radial direction of the input shaft 13, and the ring gear 18 is integrated on its inner surface. Furthermore, an inner circumferential cylindrical portion 22 is formed on the inner circumferential portion at the end of the housing 7 so as to surround the input shaft 13, and two ball bearings 23, 24 that hold the input shaft 13 rotatably are fitted into the inner circumferential cylindrical portion 22.

[0019] The carrier 19 is composed of a cylindrical portion 25 that surrounds the central portion of the housing 7 and the large diameter pinion gear 16, and an annular plate portion 26 formed in the central portion in the axial direction of the cylindrical portion 25. A through hole 27 through which the shaft 20 passes is formed in the plate portion 26, and a bearing 28 that holds the shaft 20 rotatably is fitted into the through hole 27. In other words, the shaft 20 is held rotatably in the portion between the large diameter pinion gear 16 and the small diameter pinion gear 17.

[0020] In addition, two ball bearings 29, 30 are fitted to the outer circumferential surface of the housing 7, and the cylindrical portion 25 of the carrier 19 is rotatably held by these ball bearings 29, 30. Specifically, the ball bearing 29 and at least a portion of the small diameter pinion gear 17 are disposed so as to overlap in the direction of the central axis of rotation of the input shaft 13.

[0021] A cylindrically formed wheel 5 is integrated with the outer circumferential surface of the cylindrical portion 25 of the carrier 19, and a tire 4 is attached to the wheel 5. A cover 31 is fixed with a bolt 32 so as to close the open end of the cylindrical portion 25. O-rings 33, 34 are provided at the contact portion between the cylindrical portion 25 and the cover 31 and at the contact portion between the cylindrical portion 25 and the ball bearing 30, respectively, to seal the space in which the reduction gear mechanism 3 is provided in a liquid-tight manner.

[0022] As described above, by holding the central portion of the shaft 20 connecting the small diameter pinion gear 17 and the large diameter pinion gear 16 by the plate portion 26, there is no need to provide a pinion pin for rotatably holding the large diameter pinion gear 16 and the small diameter pinion gear 17. Therefore, since there is no need to insert a pinion pin or a bearing, the outer diameter of the small diameter pinion gear 17 can be reduced in size. As a result, the outer diameter of the small diameter pinion gear 17 side in the direction of the rotation center axis of the reduction mechanism 3 can be reduced, so that the ball bearing 29 can be provided on the outer periphery side of the small diameter pinion gear 17 without increasing the size of the wheel 5. In other words, there is no need to dispose the small diameter pinion gear 17 and the ball bearing 29 offset from each other in the direction of the center axis of the wheel 5, so the axial length of the in-wheel motor 1 can be shortened.

[0023] Also, there is no need to reduce the outer diameter of the shaft 20 in order to reduce the size of the small-diameter pinion gear 17. Therefore, an increase in the amount of deflection of the shaft 20 can be suppressed, and the shaft 20 can be supported at its central portion. In other words, there is no need to support the shaft 20 at both ends. As a result, the axial length of the reduction gear mechanism 3 can be shortened. Furthermore, when the shaft 20 is supported at both ends, co-machining is required to satisfy the coaxiality of the fitting hole into which the shaft 20 is fitted, which tends to increase production costs, but by adopting a configuration in which the shaft 20 is supported at its central portion, such an increase in production costs can be suppressed.

[0024] Furthermore, by making small diameter pinion gear 17 smaller, the diameters of ball bearings 29, 30 can be reduced, and mass-produced ball bearings can be reused, thereby reducing the production costs of in-wheel motor 1.

[0025] In addition, by making the small-diameter pinion gear 17 smaller, the reduction ratio of the reduction mechanism 3 can be increased. In other words, when the reduction ratio of the reduction mechanism 3 is set to the same reduction ratio as in the past, the large-diameter pinion gear 16 can be made smaller, and the outer diameter of the wheel 5 can be made smaller. That is, the diameter of the part where the tire 4 is attached to the wheel 5 can be made smaller. As a result, the freedom of selection of the type of tire 4 that can be attached to the wheel 5 can be improved, such as a pneumatic tire in which air is sealed between the wheel 5 and the outer circumferential surface of the tire 4, or a tire in which rubber is filled between the wheel 5 and the outer circumferential surface of the tire 4. That is, since a space for a valve attachment part for putting air into the tire can be secured, the in-wheel motor 1 can be adopted as a driving force source even for a relatively small-diameter pneumatic tire.

[0026] 2 to 5 show an example in which the space on the outer periphery side of the small diameter pinion gear 17 is used for another purpose. In the following explanation, the same reference numerals are used for the same configurations as in Fig. 1, and the explanation thereof will be omitted.

[0027] In the example shown in Fig. 2, rotor 35 is disposed on the outer periphery of small diameter pinion gear 17. In the example shown in Fig. 2, a hub 36 is connected to input shaft 13, and rotor 35 is connected to a cylindrical portion on the outer periphery of hub 36. Rotor 35 shown here is configured by laminating steel plates formed into an annular shape, and its tip portion extends to the outer periphery of small diameter pinion gear 17. Note that a permanent magnet penetrating in the axial direction is provided on the outer periphery of rotor 35.

[0028] A stator 37 made of laminated annular steel plates is provided so as to surround the rotor 35 , and the stator 37 is fixed to the housing 7 .

[0029] 2, a cylindrical portion 39 protrudes in the axial direction from a rear cover 38 that closes one open end of the housing 7, and a rotation speed sensor 40 is provided on the inner peripheral side of the rotor 35 so as to detect the difference in rotation speed between the cylindrical portion and the rotor 35 as the rotation speed of the motor 2. The input shaft 13 is rotatably held by ball bearings 41, 42 provided in the cover 31 and the rear cover 38. The carrier 19 is fixed to the cover 31 by bolts, and the cylindrical portion connected to the outer periphery of the cover 31 is held by ball bearings 29, 30. In other words, the cover 31 constitutes a part of the carrier 19.

[0030] By making the small diameter pinion gear 17 smaller as described above, the ring gear 18 can be made smaller. Therefore, as shown in FIG. 2, the rotor 35 and the stator 37 can be disposed in the space on the outer periphery side of the small diameter pinion gear 17. As a result, the components of the motor 2 can be accommodated inside the housing 7. In other words, the motor 2 can be made smaller. Therefore, the production cost as a whole, including the motor 2 and the reduction mechanism 3, can be reduced.

[0031] In the example shown in Fig. 3, coil ends 43 are disposed on the outer periphery of small diameter pinion gear 17. In the example shown in Fig. 3, rotor 35 is connected to input shaft 13 without a hub, and stator 37 is provided on the outer periphery thereof. That is, rotor 35 is disposed such that small diameter pinion gear 17 and rotor 35 are aligned in the direction of the rotation center axis.

[0032] Furthermore, one of the coil ends 43 of the coil wound around the stator 37 protruding in the axial direction of the stator 37 is disposed on the outer periphery of the ring gear 18. In other words, the coil end 43 is disposed in the space on the outer periphery of the small diameter pinion gear 17 that meshes with the ring gear 18.

[0033] In the example shown in Figure 3, a rotation speed sensor 40 is provided on the outer peripheral surface of the input shaft 13 to detect the difference in rotation speed with a cylindrical portion 39 protruding from the rear cover 38 in the axial direction as the rotation speed of the motor 2.

[0034] With the above configuration, the motor 2 can be made smaller than the in-wheel motor 1 shown in Fig. 2 in which a hub 36 is provided on the input shaft 13. Even if the motor 2 is made smaller as shown in Fig. 2 and Fig. 3, the reduction ratio of the reduction mechanism 3 can be increased by making the small diameter pinion gear 17 smaller, so that it is possible to transmit torque to the tire 4 at the same level as in a conventional in-wheel motor.

[0035] In addition, as shown in FIG. 4, the brake unit B may be fixed to the housing 7 in the space on the outer periphery of the small diameter pinion gear 17, or as shown in FIG. 5, the motor 2 may be fixed to the housing 7 in the space on the outer periphery of the small diameter pinion gear 17.

[0036] In the in-wheel motor according to the embodiment of the present invention, the bearing 28 into which the shaft 20 is fitted and the large diameter pinion gear 16 may be arranged to overlap in the central axial direction of the shaft 20. An example of such a configuration is shown in Fig. 6. Note that the same components as those in the example shown in Fig. 1 are given the same reference numerals and their description will be omitted.

[0037] The large diameter pinion gear 16 shown in FIG. 6 is composed of a plate portion 16a formed in an annular shape and a cylindrical portion 16b extending from the outer circumferential end of the plate portion 16a toward the small diameter pinion gear 17 and having external teeth formed on its outer circumferential surface.

[0038] The inner peripheral end of the plate portion 26 is located inside the cylindrical portion 16b in the radial direction of the input shaft 13, and a cylindrical portion 26a is formed extending from the inner peripheral end toward the plate portion 16a. That is, the cylindrical portion 16b and the cylindrical portion 26a are arranged on the same axis. A bearing 28 is inserted into the cylindrical portion 26a, and the shaft 20 is fitted into the bearing 28.

[0039] By arranging the bearing 28 into which the shaft 20 is fitted and the large diameter pinion gear 16 in this manner so as to be overlapped in the central axial direction of the shaft 20, the axial length of the large diameter pinion gear 16, the shaft 20, and the small diameter pinion gear 17 can be shortened, and therefore the axial length of the reduction mechanism 3 and, ultimately, the axial length of the in-wheel motor 1 can be shortened.

[0040] Even if the bearing 28 into which the shaft 20 is fitted and the large diameter pinion gear 16 are arranged overlapping in the central axial direction of the shaft 20 as shown in Figure 6, the motor 2, the coil end 43, the fixed portion of the brake unit B, or the fixed portion of the motor 2 may be arranged in the space on the outer circumferential side of the small diameter pinion gear 17 as shown in Figures 2 to 5.

[0041] The large diameter pinion gear 16 shown in Fig. 6 may be made of a resin material. Specifically, as shown in Fig. 7, the plate portion 16a, the cylindrical portion 16b, and the protrusion portion 16c protruding from the plate portion 16a toward the cover 31 side may be made of a resin material. In that case, the large diameter pinion gear 16 and the shaft 20 may be molded separately and then integrated in the rotational direction by spline engagement or the large diameter pinion gear 16 and the shaft 20 may be molded integrally by integrating the tip portion of the shaft 20 with the large diameter pinion gear 16 by insert molding.

[0042] By constructing the large diameter pinion gear 16 from a resin material in this manner, the molding cost of the large diameter pinion gear 16, which has a relatively complicated shape, can be reduced. In addition, by using a resin material with a smaller Young's modulus than a metal material, the meshing between the large diameter pinion gear 16 and the sun gear 15 becomes meshing between a metal material and a resin material, and the meshing surface becomes a relatively large ellipse shape. As a result, the actual meshing ratio can be increased. Furthermore, by constructing the large diameter pinion gear 16 from a resin material, the moment of inertia can be reduced. As a result, the generation of abnormal noise during the torque transmission of the reduction mechanism 3 can be suppressed.

[0043] Furthermore, each gear is usually configured with a gear having a twist angle, such as a helical gear, to suppress the generation of abnormal noise, and a thrust load is generated when transmitting torque. Therefore, by configuring the protrusion 16c with a resin material as shown in FIG. 7, it is possible to reduce the friction resistance at the contact surface when the protrusion 16c comes into contact with the cover 31. As a result, it is possible to improve the torque transmission efficiency of the in-wheel motor 1 and the durability of the reduction gear mechanism 3.

[0044] Note that even if large diameter pinion gear 16 is made of a resin material as shown in Fig. 7, motor 2, coil end 43, a fixed portion of brake unit B, or a fixed portion of motor 2 may be disposed in the space on the outer periphery side of small diameter pinion gear 17 as shown in Fig. 2 to Fig. 5. In addition, in the example shown in Fig. 1 to Fig. 7, carrier 19 is configured to function as an output element connected to wheel 5, and ring gear 18 is configured to function as a reaction element connected to housing 7, but carrier 19 may be connected to housing 7 and provided as a reaction element, and ring gear 18 may be connected to wheel 5 and provided as an output element. [Explanation of symbols]

[0045] 1 In-wheel motor 2 Motors 3 Reduction mechanism 5 Wheels 7. Housing 15 Sun gear 16 Large diameter pinion gear 17 Small diameter pinion gear 18 Ring gear 19 Carrier 20 Shaft 27 Through hole 28 Bearings

Claims

[Claim 1] An in-wheel motor including a motor as a driving force source, a wheel to which a tire is attached, and a reduction mechanism that transmits torque from the motor to the wheel and is provided inside the wheel, the reduction mechanism includes a sun gear, a large diameter pinion gear meshing with the sun gear, a small diameter pinion gear rotating integrally with the large diameter pinion gear and formed with a diameter smaller than that of the large diameter pinion gear, a ring gear meshing with the small diameter pinion gear, and a carrier that holds the large diameter pinion gear and the small diameter pinion gear so that they can rotate and revolve about their own axis, the sun gear is connected to the motor, the ring gear is connected to one of the housing and the wheel, and the carrier is connected to the other of the housing and the wheel, a shaft connecting the large diameter pinion gear and the small diameter pinion gear, The carrier is configured to rotatably hold the shaft between the large pinion gear and the small pinion gear. An in-wheel motor comprising:

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