In-wheel motor system

Abstract

The present application relates to an in-wheel motor system (1), comprising: a tire (10) having a rotation axis (X); a wheel hub (12) supporting and driving the tire (10) to rotate synchronously; a motor assembly (30) having an output shaft (35) for outputting rotational motion; a transmission assembly (50), comprising a planetary carrier (60) non-rotatably connected to the output shaft (35) to rotate synchronously therewith, a first planetary gear (74) supported by the planetary carrier (60) and capable of rotating about its own central axis while revolving around the rotation axis (X) with the planetary carrier (60), a fixed first inner gear (72) meshed with the first planetary gear (74), a second planetary gear (84) revolving and rotating synchronously with the first planetary gear (74), a second inner gear (82) meshed with the second planetary gear (84), the second inner gear (82) being engaged to the wheel hub (12) to drive the wheel hub (12) and the tire (10) to rotate synchronously about the rotation axis (X).

Description

Technical Field

[0001] The present application relates to an in-wheel motor system (also referred to as a "hub motor"). Background Art

[0002] The in-wheel motor system effectively utilizes the wheel hub space by arranging a motor assembly that drives the wheel hub in rotation and a transmission assembly that transmits the motor assembly's driving force to the wheel hub within the wheel hub's housing space. By improving the structure of the in-wheel motor system, the in-wheel motor system can effectively utilize the wheel hub space. Generally speaking, the in-wheel motor system includes a wheel hub, a motor assembly, and a transmission assembly disposed within the wheel hub's housing space. The motor assembly has a rotor and a stator and outputs rotational power for driving the wheel hub. The transmission assembly receives the high-speed rotational motion output from the motor assembly's rotor, performs a deceleration and torque-increasing transmission, and ultimately outputs a low-speed, high-torque rotational motion to the wheel hub around the same rotation axis as the rotational motion output by the motor assembly.

[0003] Transmission components, commonly referred to as reduction gears, are typically used for low-speed, high-torque transmissions, reducing speed and increasing torque in response to the high-speed rotational motion of the motor assembly. Planetary gear trains, due to their coaxial transmission and compact structure, are often used as transmission components in in-wheel motor systems. However, due to the limited space within the wheel hub, achieving a simplified structure and a wide range of transmission ratios is challenging.

[0004] Hopefully, the in-wheel motor system can be improved. Summary of the Invention

[0005] The purpose of the present application is to further simplify the in-wheel motor system, especially the structure of its transmission assembly, which is arranged in the limited accommodation space of the wheel hub, and to provide a wider range of transmission ratios.

[0006] To this end, the present application provides an in-wheel motor system, comprising:

[0007] a tire having an axis of rotation;

[0008] The wheel hub that supports and drives the tires to rotate synchronously;

[0009] a motor assembly having an output shaft for outputting rotational motion about a rotational axis;

[0010] A transmission assembly includes a planetary carrier non-rotatably connected to the output shaft for synchronous rotation therewith, a first planetary gear supported by the planetary carrier and capable of rotating about its own central axis while revolving around the rotation axis with the planetary carrier, a fixed first inner ring gear meshed with the first planetary gear, a second planetary gear revolving and rotating synchronously with the first planetary gear, a second inner ring gear meshed with the second planetary gear, the second inner ring gear being engaged to the wheel hub to drive the wheel hub and the tire to rotate synchronously about the rotation axis.

[0011] In one embodiment, the first planetary gear and the corresponding second planetary gear are both mounted on the same planetary gear shaft, so that the three can revolve and rotate synchronously.

[0012] In one embodiment, the planetary carrier includes a planetary carrier active half body connected to the output shaft of the motor assembly in a non-rotatable manner, and includes a planetary carrier driven half body, and the planetary gear shaft is rotatably supported in the planetary carrier active half body and the planetary carrier driven half body by bearings at both ends, so that the planetary carrier active half body drives the planetary carrier driven half body to rotate synchronously through the planetary gear shaft when rotating.

[0013] In one embodiment, the planet carrier driven half is rotationally supported in the wheel hub via bearings so that the two can rotate independently of each other.

[0014] In one embodiment, the wheel hub includes a generally plate-shaped body and a driving protrusion extending from the generally plate-shaped body, and the second internal gear is attached to the driving protrusion to drive the wheel hub and the tire to rotate synchronously.

[0015] In one embodiment, the tire has a first axial end along the axial direction of the rotation axis, and the roughly plate-shaped body of the hub is located at the first axial end of the tire, so that the tire and the hub define a receiving space, and the motor assembly and the transmission assembly are accommodated in the receiving space.

[0016] In one embodiment, the driving protrusion is an annular projection that protrudes from a substantially plate-shaped body toward the motor assembly.

[0017] In one embodiment, the motor assembly includes a motor inner end cover close to the wheel hub and a motor outer end cover away from the wheel hub, and the motor stator and motor rotor of the motor assembly are accommodated in the motor internal space defined by the motor inner end cover, the motor outer end cover and the cylindrical motor housing therebetween.

[0018] In one embodiment, the first inner ring gear is fixedly connected to the motor inner end cover.

[0019] In one embodiment, at least one of the first inner gear ring and the second inner gear ring has an annular oil drain groove formed on its outer circumferential surface, and an oil drain hole is formed at each tooth root and is in fluid communication with the annular oil drain groove.

[0020] The in-wheel motor system of this application utilizes a two-stage planetary gearset consisting solely of intermeshing planetary gears and an internal gear ring, without a sun gear, as its transmission assembly, achieving both structural simplicity and a higher transmission ratio. By rationally configuring the number of teeth on the planetary gears and internal gear rings in the two-stage internally meshing planetary gearset, transmission ratios ranging from tens to thousands can be achieved. The structure of this transmission assembly, particularly the use of a common planetary gear axle in the two-stage internally meshing planetary gearset, minimizes the required axial space along the longitudinal direction of the rotational axis, thus minimizing the axial dimensions of the in-wheel motor system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other features and advantages of the present application will be reflected in the detailed description given below with reference to the accompanying drawings. The accompanying drawings are part of the specification and only show an exemplary embodiment for explaining the principles of the present application. The accompanying drawings are not drawn to scale. In the drawings:

[0022] Figure 1 is a cross-sectional view of the in-wheel motor system according to the present application, the cross-sectional view being taken along a longitudinal section passing through the rotation axis of the in-wheel motor system;

[0023] Figure 2 yes Figure 1 Schematic diagram after rotation by an angle;

[0024] Figure 3 yes Figure 2 Another view of the in-wheel motor system, with some components not cut away to more clearly illustrate the structure;

[0025] Figure 4a and Figure 4b A comparison diagram showing the transmission ratios achievable by a transmission assembly consisting of a conventional internal meshing planetary gear set and an external meshing stage planetary gear set and a transmission assembly consisting of a double internal meshing planetary gear set of the present application;

[0026] Figure 5 A schematic diagram of a transmission assembly is illustrated, particularly showing the lubricating oil drain grooves on each inner gear ring;

[0027] Figure 6 A schematic diagram of a first internal gear ring with an oil drain groove and an oil drain hole is shown. DETAILED DESCRIPTION

[0028] Please refer to the following Figure 1-5 The in-wheel motor system of the present application is described.

[0029] Figure 1Figure 1 is a cross-sectional view of an in-wheel motor system 1. In-wheel motor system 1 includes an outermost tire 10 and a wheel hub 12 that supports and rotates tire 10 together. In-wheel motor system 1 has a rotation axis X about which tire 10 and wheel hub 12 rotate. For ease of description, this application defines the direction in which rotation axis X extends as the axial direction, with the radial direction extending perpendicular to the axial direction.

[0030] The wheel hub 12 includes a generally plate-shaped body 14 and a driving protrusion 16 that protrudes generally axially from the generally plate-shaped body 14 toward the motor assembly 30 and the transmission assembly 50 of the in-wheel motor system 1. The generally plate-shaped body 14 extends radially inward from or near the first axial end 10a of the tire 10, so that the tire 10 and the wheel hub 12 jointly define an open receiving space for accommodating other components of the in-wheel motor system 1, particularly the motor assembly 30 and the transmission assembly 50.

[0031] The motor assembly 30 of the in-wheel motor system 1 is mounted within the aforementioned housing and includes an output shaft 35 that also rotates about the rotation axis X. Specifically, the motor assembly 30 includes an inner motor end cap 32 axially proximal to the wheel hub 12 and an outer motor end cap 34 distal to the wheel hub 12. The inner and outer motor end caps 32 and 34, along with a cylindrical motor housing 36 axially disposed therebetween, constitute the motor housing of the motor assembly 30 and define an internal motor space. Within the internal motor space, a motor stator 42 located radially outward and a motor rotor 44 disposed radially inward are concentrically arranged about the rotation axis X. The motor stator 42 is fixed to the motor housing, such as any of the inner motor end cap 32, the outer motor end cap 34, and the cylindrical motor housing 36. The motor rotor 44 is connected to a rotor support 46, which is fixedly connected to the output shaft 35 via a fixed connection method such as a spline fit or an interference fit, and is capable of driving the output shaft 35 in rotation. In this manner, the output shaft 35 of the motor assembly 30 outputs rotational motion. The output shaft 35 , which rotates about the axis of rotation X, is mechanically connected to and drives an input member of the transmission assembly 50 .

[0032] In the illustrated embodiment, the transmission assembly 50 is in the form of an internally meshing planetary gear set, including a common planet carrier 60 , and a first-stage planetary gear set and a second-stage planetary gear set driven by the common planet carrier 60 .

[0033] In the illustrated embodiment, along the axial direction, the first axial end of the common planetary carrier 60 is connected to the output shaft 35 of the motor assembly 30 by a fixed connection method such as a spline, so that the output shaft 35 of the motor assembly 30 can drive the common planetary carrier 60 to rotate synchronously, and the second axial end of the common planetary carrier 60 is supported in the wheel hub by a bearing.

[0034] Specifically, in one exemplary embodiment shown, the common planet carrier 60 includes a planet carrier driving half 60a defining a first axial end and a planet carrier driven half 60b defining a second axial end. The planet carrier driving half 60a is connected to and driven by the output shaft 35, while the planet carrier driven half 60b is supported in the wheel hub 12 via bearings 61 such that the planet carrier driven half 60b and the wheel hub 12 can rotate independently of each other about the rotation axis X.

[0035] The planetary gear shaft 75 is rotatably supported in the planetary carrier driving half 60a and the planetary carrier driven half 60b via bearings disposed at opposite ends. When the output shaft 35 of the motor assembly 30 drives the planetary carrier driving half 60a to rotate about the rotation axis X, the planetary carrier driven half 60b is driven by the planetary gear shaft 75 to rotate synchronously with the planetary carrier driving half 60a about the rotation axis X. Furthermore, due to the arrangement of the bearings, the planetary gear shaft 75 can simultaneously rotate about its own central axis while orbiting with the common planetary carrier 60 about the central axis X.

[0036] The first-stage planetary gear set and the second-stage planetary gear set driven by the common planet carrier 60 are provided between the planet carrier driving half 60 a and the planet carrier driven half 60 b .

[0037] The first-stage planetary gearset includes a first internal ring gear 72, which is held stationary, and one or more (e.g., three in the illustration) first planet gears 74 meshing with the first internal ring gear 72. The first internal ring gear 72 can be held stationary by being fixed to the motor housing of the motor assembly 30, such as the motor inner end cap 32, which is relatively close to the motor. Alternatively, the first internal ring gear 72 can be fixed by other means. Each first planet gear 74 is mounted or supported on a planetary gear shaft 75 in a manner that prevents relative rotation.

[0038] The second-stage planetary gearset includes a second inner ring gear 82 and second planetary gears 84 meshing with the second inner ring gear 82. In addition to the first planetary gears 74, each planetary shaft 75 also mounts or supports a second planetary gear 84 in the same manner. Specifically, the second planetary gears 84 and the planetary shaft 75 are non-rotatable relative to each other, meaning that the first planetary gears 74, the planetary shaft 75, and the second planetary gears 84 rotate synchronously. The second inner ring gear 82 is connected to the driving protrusion 16 of the wheel hub 12, enabling synchronous rotation with the wheel hub 12. The connection between the second inner ring gear 82 and the driving protrusion 16 of the wheel hub 12 can be achieved by any suitable mechanical connection method known in the art, including, but not limited to, one or a combination of the following: interference fit, bolting, welding, riveting, press-fitting, and form-fitting. The driving protrusion 16 of the wheel hub 12 can be an annular protrusion, as shown, or any other structure capable of engaging with and being driven by the second inner ring gear 82.

[0039] On the one hand, the in-wheel motor system 1 of the present application is capable of driving the tire 10 in rotation via the motor assembly 30. To this end, when the output shaft 35 of the motor assembly 30 generates rotational motion, the active planetary carrier half 60a of the common planetary carrier 60 of the planetary assembly 50 rotates synchronously with the output shaft 35 about the rotation axis X. Consequently, the active planetary carrier half 60a, the planetary shaft 75, the first and second planetary gears 74, 84 mounted on the planetary shaft 75, and the driven planetary carrier half 60b all rotate synchronously with the output shaft 35 about the rotation axis X. Because the first inner ring gear 72 is stationary, the first planetary gear 74 meshed with the first inner ring gear 72 simultaneously revolves and rotates about the central axis of the planetary shaft 75. Simultaneously, the first planetary gear 74 drives the planetary shaft 75 and the second planetary gear 84 mounted on the planetary shaft 75 in a manner that prevents relative rotation, thereby rotating about the central axis of the planetary shaft 75. Due to the meshing with the second inner ring gear 82, the orbiting and rotating second planetary gears 84 drive the second inner ring gear 82 and, thereby, the wheel hub 12 (and the tire 10) fixedly engaged with the second inner ring gear 82 to rotate about the rotation axis X. In this way, the rotational speed and torque output by the output shaft 35 of the motor assembly 30 are transmitted to the wheel hub 12 and the tire 10 after being subjected to the torque increase and speed reduction of the planetary gear train constituting the transmission assembly 50.

[0040] Transmission assembly 50 is constructed as a planetary gear train transmission assembly consisting of a two-stage planetary gear set. Both stages consist solely of planetary gears and an internal gear ring, with no sun gear present. This internally meshing planetary gear set offers the advantage of a large speed ratio when performing the aforementioned drive functions. For example, if the number of teeth on the first planetary gear 74, the first internal gear ring 72, the second planetary gear 84, and the second internal gear ring 82 are set to Zp1, Zr1, Zp2, and Zr2, respectively, the speed ratio achieved by this structure can be written as: Zp1*Zr2 / (Zp1*Zr2-Zr1*Zp2). Thus, by appropriately matching the number of teeth on each planetary gear and internal gear ring, transmission ratios ranging from tens to thousands can be achieved.

[0041] Figure 4a and 4b This diagram compares the transmission ratios of a conventional transmission assembly composed of an internally meshing planetary gear set and an externally meshing planetary gear set, and a transmission assembly 50 composed of a dual internally meshing planetary gear set according to the present invention. In the diagram, "H" represents the planet carrier; Zf, Zb, Ze, and Zg represent the number of teeth on gears f, b, e, and g, respectively.

[0042] Figure 4a It is a traditional transmission component, and the transmission ratio of the transmission component is: 1+Zf*Zb / Ze*Zg. Figure 4b In the transmission assembly of the present application shown, Figure 4aThe external meshing planetary gear set consisting of the sun gear and planet gears is replaced with an internal meshing planetary gear set consisting of the ring gear and planet gears, forming a double internal meshing planetary gear set transmission assembly 50. In this case, the transmission ratio of the transmission assembly 50 is: ZgZe / (ZgZe-ZbZf). By properly matching the number of teeth, the difference ZgZe-ZbZf can be made as small as possible, thus obtaining a relatively large transmission ratio. Figure 4b In the schematic diagram, gears g, b, e and f are equivalent to Figure 1-3 The first planetary gear 74 , the first inner ring gear 72 , the second inner ring gear 82 and the second planetary gear 84 .

[0043] On the other hand, by appropriately matching the number of teeth of each planetary gear and the inner ring gear, the above-mentioned in-wheel motor system 1 of the present application can also achieve a self-locking feature. For example, when the vehicle is on a slope and the power is interrupted, the tire 10 has a tendency to slide down the slope. When the vehicle has a tendency to slide, that is, power is input from the wheel hub 12 and transmitted to the second inner ring gear 82 of the transmission assembly 50, the power is transmitted from the second inner ring gear 82 to the output shaft 35 of the motor assembly 30 via the second planetary gear 84, the planetary gear shaft 75, the first planetary gear 74, and the first inner ring gear 72. The transmission assembly 50 self-locks and cannot rotate, thereby avoiding the phenomenon of the vehicle sliding when the power is interrupted on the slope.

[0044] Further references Figure 5 and Figure 6 To enhance lubrication and reduce hydraulic resistance during meshing, the outer circumferences of each of the first and second inner ring gears 72 and 82 are formed with annular drain grooves 76 and 86 recessed therein, and drain holes 78 and 88 located at the roots of at least some, and preferably every, of the teeth 79 and 89. Drain holes 78 and 88 are in fluid communication with annular drain grooves 76 and 86, respectively. This allows the planetary gears 74 and 84 to quickly squeeze lubricating oil from the roots of the inner ring gears 72 and 82 when the internal gears rotate at high speed. The provision of drain grooves and drain holes facilitates the flow of lubricating oil and reduces the hydraulic resistance caused by the lubricating oil during meshing of the internal gears.

[0045] The in-wheel motor system of the present application utilizes a two-stage planetary gearset consisting solely of intermeshing planetary gears and an internal gear ring, without a sun gear, as a transmission assembly. This achieves the dual goals of simplifying the transmission system structure and increasing the transmission ratio. By rationally configuring the number of teeth on each of the planetary gears and the internal gear ring within the two-stage internally meshing planetary gearset, transmission ratios ranging from tens to thousands can be achieved. The two-stage internally meshing planetary gearset utilizes a common planetary gear shaft, minimizing the required axial space along the longitudinal direction of the rotation axis and thus minimizing the axial dimensions of the in-wheel motor system. By appropriately matching the number of teeth on each planetary gear and the internal gear ring, the high speed ratio characteristics of this planetary transmission assembly enable the electromagnetic resistance torque of the motor in generator mode to offset the considerable wheel-end back-drag torque, enabling the in-wheel motor system to achieve self-locking characteristics, thereby preventing the vehicle from rolling when power is interrupted on a slope.

[0046] The present application has been described above with reference to the specific embodiments shown in the drawings. Those skilled in the art will appreciate that the present application is not limited to the specific details described above and shown in the drawings. Those skilled in the art may make various modifications or substitutions to the details without departing from the basic principles of the present application and the scope of protection defined by the claims.

Claims

1. An in-wheel motor system (1), comprising: a tire (10) having an axis of rotation (X); A wheel hub (12) that supports and drives the tire (10) to rotate synchronously; a motor assembly (30) having an output shaft (35) for outputting rotational motion about an axis of rotation (X); A transmission assembly (50) not including a sun gear, comprising a planetary carrier (60) non-rotatably connected to the output shaft (35) for synchronous rotation therewith, a first planetary gear (74) supported by the planetary carrier (60) and capable of rotating about its own central axis while revolving about the rotation axis (X) with the planetary carrier (60), a first fixed inner ring gear (72) meshed with the first planetary gear (74), a second planetary gear (84) revolving and rotating synchronously with the first planetary gear (74), a second inner ring gear (82) meshed with the second planetary gear (84), the second inner ring gear (82) being engaged to the wheel hub (12) to drive the wheel hub (12) and the tire (10) to rotate synchronously about the rotation axis (X).

2. The in-wheel motor system (1) according to claim 1, wherein: The first planetary gear (74) and the corresponding second planetary gear (84) are both mounted on the same planetary gear shaft (75), so that the three of them revolve and rotate synchronously.

3. The in-wheel motor system (1) according to claim 2, wherein: The planetary carrier (60) includes a planetary carrier active half (60a) that is non-rotatably connected to the output shaft (35) of the motor assembly (30), and includes a planetary carrier driven half (60b), and the planetary gear shaft (75) is rotatably supported in the planetary carrier active half (60a) and the planetary carrier driven half (60b) through bearings at both ends, so that when the planetary carrier active half (60a) rotates, it drives the planetary carrier driven half (60b) to rotate synchronously through the planetary gear shaft (75).

4. The in-wheel motor system (1) according to claim 3, wherein: The planet carrier driven half (60b) is rotatably supported in the wheel hub (12) via a bearing so that the two can rotate independently of each other.

5. The in-wheel motor system (1) according to any one of claims 1 to 4, wherein: The wheel hub (12) includes a plate-shaped body (14) and a driving protrusion (16) extending from the plate-shaped body (14), and the second inner gear ring (82) is attached to the driving protrusion (16) to drive the wheel hub (12) and the tire (10) to rotate synchronously.

6. The in-wheel motor system (1) according to claim 5, wherein: The tire (10) has a first axial end along the axial direction of the rotation axis (X), and the plate-shaped body (14) of the wheel hub (12) is located at the first axial end of the tire (10), so that the tire (10) and the wheel hub (12) define a receiving space, and the motor assembly (30) and the transmission assembly (50) are accommodated in the receiving space.

7. The in-wheel motor system (1) according to claim 5, wherein: The driving protrusion (16) is an annular protrusion that protrudes from the plate-shaped body (14) toward the motor assembly (30).

8. The in-wheel motor system (1) according to any one of claims 1 to 4, wherein: The motor assembly (30) comprises a motor inner end cover (32) close to the wheel hub (12) and a motor outer end cover (34) away from the wheel hub (12); the motor stator (42) and the motor rotor (44) of the motor assembly are accommodated in a motor internal space defined by the motor inner end cover (32), the motor outer end cover (34) and a cylindrical motor housing (36) therebetween.

9. The in-wheel motor system (1) according to claim 8, wherein: The first inner gear ring (72) is fixedly connected to the motor inner end cover (32).

10. The in-wheel motor system (1) according to any one of claims 1 to 4, wherein: At least one of the first inner gear ring (72) and the second inner gear ring (82) has an annular oil drain groove (76, 86) recessed into the outer circumferential surface formed on its outer circumferential surface, and an oil drain hole (78, 88) is formed at the root of each tooth (79, 89) and is in fluid communication with the annular oil drain groove (76, 86).

Images