WO2015137085A1

WO2015137085A1 - In-wheel motor drive device

Info

Publication number: WO2015137085A1
Application number: PCT/JP2015/054733
Authority: WO
Inventors: 雪島　良; 鈴木　稔; 朋久魚住
Original assignee: Ntn株式会社; 雪島　良; 鈴木　稔; 朋久魚住
Priority date: 2014-03-13
Filing date: 2015-02-20
Publication date: 2015-09-17
Also published as: JP2015175391A

Abstract

An in-wheel motor drive device (21) is configured in such a manner that a speed reduction section (B) comprises a cycloidal speed reduction mechanism having: a speed reducer input shaft (25) having eccentric sections (25a, 25b); and curved plates (26a, 26b) rotatably held on the outer peripheries of the eccentric sections (25a, 25b) of the speed reducer input shaft (25) and revolving. The curved plates (26a, 26b) are formed from case hardening steel and have hardened layers(H) formed by carburizing, quenching, and tempering.

Description

In-wheel motor drive device

The present invention relates to an in-wheel motor drive device.

A conventional in-wheel motor drive device is disclosed in, for example, Patent Document 1 below. The in-wheel motor drive device is housed inside the wheel or placed near the wheel, so its weight and size affect the unsprung weight (running performance) of the vehicle and the size of the passenger compartment. Effect. For this reason, the in-wheel motor drive device needs to be as light and compact as possible. Therefore, in the in-wheel motor drive device of Patent Document 1, by providing a speed reduction unit between the motor unit that generates the driving force and the wheel bearing unit to which the wheels are connected, the motor unit, and thus the overall size of the device is reduced. It tries to make it. The motor part, the wheel bearing part and the speed reduction part are held in a casing, and the casing is attached to the vehicle body via a suspension device (not shown).

Furthermore, in the in-wheel motor drive device of Patent Document 1, in order to obtain a large torque required for the wheel bearing portion while promoting weight reduction and compactness, the motor portion has a low torque and a high rotation type (for example, 15000 min). ^-1 ) and a cycloid reducer (cycloid reduction mechanism) that is compact and can provide a high reduction ratio.

The speed reducer to which the cycloid speed reducer is applied is mainly a speed reducer input shaft having an eccentric portion, and is rotatably held on the outer periphery of the eccentric portion, with the rotation axis centering on the rotation of the speed reducer input shaft. A curved plate as a revolving member that performs the revolving motion, a plurality of outer pins that engage with the outer peripheral portion of the curved plate (curved plate during the revolving motion) and cause the revolving motion to the curved plate, and a curved plate during the revolving motion And an inner pin that takes out the rotational motion of the curved plate by sliding contact with the shaft and converts it into rotational motion of the output shaft of the speed reducer connected to the wheel bearing portion.

JP 2012-148725 A

As described above, in the in-wheel motor drive device in which the cycloid speed reduction mechanism is applied to the speed reduction portion, when the motor portion is driven (when the speed reducer input shaft is rotated), the curved plate revolves while being in sliding contact with various members. Rotate. For this reason, the curved plate has not only strength sufficient to withstand loads applied from various members, but also wear resistance (surface hardness) that does not wear when sliding with various members. There is a need. In addition, when driving a vehicle equipped with an in-wheel motor drive device, the momentary impact load may be input to the speed reduction part via the wheel bearing part. It is also necessary to have toughness that does not cause deformation or breakage even when a load is applied.

On the other hand, in order to popularize the in-wheel motor drive device, it is necessary to promote cost reduction of the in-wheel motor drive device. For this reason, it is desired that the curved plate constituting the speed reducing portion can be manufactured (processed) as simply as possible.

As described above, the curved plate, which is a component part of the deceleration unit, must satisfy various required characteristics at the same time. However, in the in-wheel motor drive device disclosed in Patent Document 1, no technical means for satisfying the above various required characteristics at the same time has been studied. Therefore, there is room for improvement in the in-wheel motor drive device of Patent Document 1.

The present invention was devised in view of the above circumstances, and the object of the present invention is to provide a curved plate that can be easily produced, has excellent strength and wear resistance, and has the required toughness. The object is to provide an in-wheel motor drive device that is realized at low cost and excellent in durability.

In order to achieve the above object, the present invention is based on the following knowledge found as a result of examining the material surface of the curved plate, which is a component part of the reduction part.

Materials that can satisfy the strength and wear resistance at a high level include, for example, carburized and tempered low-carbon steels such as case-hardened steel, bearing steels that have been subjected to continuous quenching, and high-carbon steels. The thing which gave induction hardening can be mentioned. However, when quenching is performed, the hardness of the core portion as well as the surface layer portion is increased. Therefore, there is a problem that it is difficult to ensure the toughness required for the curved plate when the bearing steel is subjected to continuous quenching. High-carbon steel has a higher material cost than low-carbon steel and is inferior in workability before heat treatment. In addition, when high-frequency steel is induction-hardened, a special coil is used according to the shape of the workpiece. Because of the need to design and prepare the plate, it lacks flexibility in changing the shape of the curved plate.

Therefore, in the present invention, the motor portion, the speed reduction portion, and the wheel bearing portion are held in the casing, the speed reduction portion has an eccentric portion, and the speed reducer input shaft that is rotationally driven by the motor portion, and the speed reducer input shaft In an in-wheel motor drive device comprising a cycloid reduction mechanism having a curved plate that performs a revolving motion around its rotational axis as it rotates, the curved plate is formed of case-hardened steel and carburized and quenched and tempered. An in-wheel motor drive device is provided.

Since case-hardened steel, which is a kind of low-carbon steel, is relatively soft and excellent in workability before heat treatment, a predetermined shape can be obtained easily and with high accuracy. On the other hand, if carburizing quenching and tempering is performed as a heat treatment on the workpiece made of case-hardened steel, a hardened layer can be formed only on the surface layer portion, so that the strength and surface are ensured while ensuring the toughness required for the core portion. Hardness (abrasion resistance) can be effectively increased. In addition, since carburizing, quenching and tempering have flexibility with respect to shape change, the cost required for new workpiece fabrication and design change can be reduced. From the above, by adopting the above configuration, it is possible to obtain a curved plate that is excellent in strength and wear resistance and that has the required toughness of the core portion, while being able to be manufactured at low cost. Therefore, cost reduction and durability improvement of the in-wheel motor drive device can be realized at the same time.

As the cycloid speed reducing mechanism, for example, a plurality of outer pins that engage with the outer peripheral portion of the curved plate during the revolution motion and cause the curved plate to rotate, and the curved plate by sliding contact with the curved plate during the rotation motion. It is possible to employ one provided with an inner pin that converts the rotational motion of the plate into the rotational motion of the output shaft of the reduction gear connected to the wheel bearing portion.

The curved plate can be rotatably held on the outer periphery of the eccentric part via the rolling bearing. In this way, since the contact resistance between the curved plate and the eccentric portion (reduction gear input shaft) can be reduced, the life of the curved plate and the eccentric portion (reduction gear input shaft) can be extended. . In this case, of the outer raceway surface and the inner raceway surface on which the rolling elements of the rolling bearing roll, the outer raceway surface can be provided on the curved plate. In this case, as the above-described rolling bearing, it is possible to use a bearing in which a separate outer ring having an outer raceway surface is omitted, so that the speed reduction portion can be reduced in weight and size. In the configuration of the present invention, the curved plate has a hardened layer (surface hardened layer) formed with carburizing and quenching, and its surface hardness is sufficiently increased, so that the rolling element of the rolling bearing rolls. As a result, the situation where the outer raceway surface provided on the curved plate is worn and deformed is prevented as much as possible.

Eccentric parts holding curved plates on the outer periphery can be provided at a plurality of locations in the axial direction. In this case, it is preferable that the eccentric portions are provided with phases different from each other so as to cancel the centrifugal force generated with the rotation of the speed reducer input shaft. Further, in this case, the first spacer that holds the curved plates adjacent in the axial direction in a separated state (in the axial direction), and the first spacer that holds each curved plate in the separated state from other members adjacent in the axial direction. Two spacers are preferably provided. This is because any one or both of the curved plates adjacent in the axial direction are tilted and the curved plates are prevented from slidingly contacting each other as much as possible, and power is appropriately transmitted in the speed reduction portion. At this time, there is a concern about the wear and deformation of the curved plate due to the sliding contact between the curved plate and the spacer. As described above, the curved plate has a hardened layer formed by carburizing and quenching, and its surface. Since the hardness is sufficiently increased, it is possible to prevent as much as possible the situation where the curved plate is worn and deformed due to the sliding contact with the spacer.

As described above, according to the present invention, it is possible to realize a curved plate that can be easily manufactured, has excellent strength and wear resistance, and ensures required toughness. The in-wheel motor drive device excellent in (1) can be provided at low cost.

It is a figure which shows the in-wheel motor drive device which concerns on one Embodiment of this invention. FIG. 2 is a cross-sectional view taken along line ZZ in FIG. 1. It is explanatory drawing which shows the load which acts on a curve board. It is a cross-sectional view of a rotary pump. FIG. 3 is a cross-sectional view taken along the line Z ₁ -Z ₁ shown in FIG. 2 of a curved plate. It is a schematic plan view of an electric vehicle. It is the schematic sectional drawing which looked at the electric vehicle of Drawing 6 from back.

An outline of the electric vehicle 11 equipped with the in-wheel motor drive device will be described with reference to FIGS. As shown in FIG. 6, the electric vehicle 11 is configured to drive an chassis 12, a pair of front wheels 13 that function as steering wheels, a pair of rear wheels 14 that function as drive wheels, and a left and right rear wheel 14. A wheel motor drive device 21. As shown in FIG. 7, the rear wheel 14 is accommodated in the wheel housing 12a of the chassis 12, and is fixed to the lower portion of the chassis 12 via a suspension device (suspension) 12b.

The suspension device 12b supports the rear wheel 14 by a suspension arm extending left and right, and suppresses vibration of the chassis 12 by absorbing vibration received by the rear wheel 14 from the road surface by a strut including a coil spring and a shock absorber. Furthermore, a stabilizer that suppresses the inclination of the vehicle body during turning or the like is provided at a connecting portion of the left and right suspension arms. The suspension device 12b is an independent suspension type in which the left and right wheels can be moved up and down independently in order to improve the followability to the road surface unevenness and efficiently transmit the driving force of the rear wheel 14 to the road surface. desirable.

In this electric vehicle 11, an in-wheel motor drive device 21 that rotates each of the left and right rear wheels 14 is incorporated in the left and right wheel housings 12 a, so that a motor, a drive shaft, a differential gear mechanism, and the like are mounted on the chassis 12. There is no need to provide it. Therefore, the electric vehicle 11 has an advantage that a large cabin space can be secured and the rotation of the left and right rear wheels 14 can be controlled.

In order to improve the running stability and NVH characteristics of the electric vehicle 11, it is necessary to suppress the unsprung weight. Moreover, in order to expand the cabin space of the electric vehicle 11, it is necessary to reduce the size of the in-wheel motor drive device 21. Therefore, as shown in FIG. 1, an in-wheel motor drive device 21 according to an embodiment of the present invention is employed.

An in-wheel motor drive device 21 according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the in-wheel motor drive device 21 includes a motor unit A that generates a driving force, a deceleration unit B that decelerates and outputs the rotation of the motor unit A, and outputs from the deceleration unit B to the rear wheels. 14 (see FIGS. 6 and 7), and a wheel bearing portion C that is transmitted to 14 (see FIGS. 6 and 7). Although the details will be described later, the in-wheel motor drive device 21 has a lubrication mechanism that supplies lubricating oil to the motor part A and the speed reduction part B. The motor part A and the speed reduction part B are mounted in the wheel housing 12a (see FIG. 7) of the electric vehicle 11 while being housed in the casing 22. The casing 22 of the present embodiment is configured by fastening a portion that houses (holds) the motor portion A and a portion that houses (holds) the speed reduction portion B and holds the wheel bearing portion C with bolts. ing.

The motor part A includes a stator 23a fixed to the casing 22, a rotor 23b disposed opposite to the inside of the stator 23a via a radial gap, and a hollow rotating shaft (motor) mounted with a rotor 23b on the outer periphery. The rotary shaft 24 is configured to be rotatable at a rotational speed of about 15000 min ⁻¹ .

The motor rotating shaft 24 has ends on one side in the axial direction (right side in FIG. 1, hereinafter also referred to as “inboard side”) and the other side (left side in FIG. 1 and hereinafter also referred to as “outboard side”). It is rotatably supported with respect to the casing 22 by rolling

bearings

36, 36 respectively disposed in the section. The rolling bearing 36 includes an outer ring that is fitted and fixed to the inner diameter surface of the casing 22, an inner ring that is fitted and fixed to the outer diameter surface of the motor rotation shaft 24, and a plurality of balls disposed between the outer ring and the inner ring. A deep groove ball bearing comprising a cage that holds a plurality of balls in a circumferentially spaced state.

The speed reduction unit B decelerates the rotation of the speed reducer input shaft 25 rotated by the motor part A, the speed reducer output shaft 28 arranged coaxially with the speed reducer input shaft 25, and the speed reducer input shaft 25. And a cycloid reduction mechanism serving as a reduction mechanism for transmitting to the reduction gear output shaft 28. The reduction gear output shaft 28 transmits the rotation of the reduction gear input shaft 25 that has been reduced by the reduction mechanism to the wheel bearing portion C.

The speed reducer input shaft 25 is rotatably supported with respect to the speed reducer output shaft 28 by rolling

bearings

37a and 37b that are spaced apart from each other in two axial directions.

Eccentric portions

25a and 25b whose shaft centers are eccentric with respect to the rotational axis of the speed reducer input shaft 25 are provided at two locations in the axial direction of the speed reducer input shaft 25. These two

eccentric portions

25a and 25b are In order to cancel out centrifugal forces due to the eccentric motion (to prevent the speed reducer input shaft 25 from swinging), the phases are different by 180 °.

The speed reducer input shaft 25 is fitted with a spline formed on the outer periphery of the end portion on the inboard side (including serrations, the same applies hereinafter) to a spline formed on the inner periphery of the end portion on the outboard side of the motor rotation shaft 24. The motor rotating shaft 24 is connected by so-called spline fitting. Thus, since the reduction gear input shaft 25 is connected to the motor rotation shaft 24 by spline fitting, the reduction gear input shaft 25 is also about 15000 min ^{−1 in the same} manner as the motor rotation shaft 24 when the motor unit A is driven. Rotate at high speed. At this time, if the fit between the speed reducer input shaft 25 and the inner rings of the rolling

bearings

37a and 37b is a clearance fit, an abnormal noise / vibration that cannot be ignored when the motor rotating shaft 24 rotates is generated. This adversely affects the NVH characteristics. For this reason, the fit between the reduction gear input shaft 25 and the inner rings of the rolling

bearings

37a and 37b is preferably an interference fit.

As shown in FIG. 1, the speed reducer output shaft 28 has a shaft portion 28b and a flange portion 28a extending radially outward from an end portion of the shaft portion 28b on the inboard side. The flange portion 28a has a plurality of holes (through holes in the illustrated example) formed at equal intervals on the circumference centered on the rotational axis of the reduction gear output shaft 28. The end portion on the outboard side of the inner pin 31 to be engaged is fixedly fitted. The shaft portion 28b is connected by spline fitting to a hollow hub wheel 32 that constitutes the wheel bearing portion C.

The speed reduction mechanism (cycloid speed reduction mechanism) is rotatably held by the

eccentric portions

25a and 25b of the speed reducer input shaft 25, and performs a revolving motion centering on the rotational axis as the speed reducer input shaft 25 rotates. A plurality of outer pins which are held at fixed positions on the

plates

26a and 26b and the casing 22 and engage with the outer peripheral portions of the

curved plates

26a and 26b (during revolving motion) to cause the

curved plates

26a and 26b to rotate. 27 and a motion conversion mechanism that converts the rotational motion of the

curved plates

26a and 26b into the rotational motion of the speed reducer output shaft 28.

As shown in FIG. 2, the curved plate 26 a has a plurality of corrugations composed of trochoidal curves such as epitrochoids on its outer peripheral portion, and has axial through

holes

30 a and 30 b that open at both end faces thereof. . A plurality of through-holes 30a are provided at equal intervals on the circumference centered on the rotation axis of the curved plate 26a, and receive one inner pin 31 to be described later. The through hole 30 b is provided at the center of the curved plate 26 a and receives the eccentric portion 25 a of the reduction gear input shaft 25.

The curved plate 26a is rotatably supported with respect to the eccentric portion 25a via the rolling bearing 41. The rolling bearing 41 is fitted and fixed to the outer diameter surface of the eccentric portion 25a, and is directly formed on the inner ring 42 having the inner raceway surface 42a on the outer diameter surface and the inner diameter surface (inner wall surface) of the through hole 30b of the curved plate 26a. A cylinder provided with the outer raceway surface 43, a plurality of cylindrical rollers 44 as rolling elements disposed between the inner raceway surface 42 a and the outer raceway surface 43, and a cage (not shown) that holds the cylindrical rollers 44. It is a roller bearing. The inner ring 42 has flange portions 42b that protrude radially outward from both axial end portions of the inner raceway surface 42a, and restricts axial movement of the cylindrical rollers 44. In the rolling bearing 41 of the present embodiment, the inner raceway surface 42a is formed on the inner ring 42 provided separately from the eccentric portion 25a. However, the inner raceway surface is formed directly on the outer diameter surface of the eccentric portion 25a. The inner ring 42 may be omitted. In addition, although detailed illustration is abbreviate | omitted, the curved plate 26b has the same structure as the curved plate 26a, and is arrange | positioned in the outer periphery of the eccentric part 25b, The structure similar to the rolling bearing 41 which supports the curved plate 26a It is supported so as to be rotatable with respect to the eccentric part 25b through a rolling bearing having

As shown in FIGS. 1 and 2, a plurality of outer pins 27 are provided at equal intervals on the circumference centered on the rotational axis of the speed reducer input shaft 25, so that the speed reducer input shaft 25 rotates. Accordingly, when the

curved plates

26a and 26b revolve, the

curved plates

26a and 26b are engaged with the outer peripheral portions of the

curved plates

26a and 26b (concave portions 34 provided on the outer peripheral portion) in the circumferential direction to cause the

curved plates

26a and 26b to rotate. Each outer pin 27 is freely rotatable with respect to the casing 22 via a pair of rolling

bearings

61 and 61 disposed at both ends in the axial direction and an outer pin housing 60 holding the rolling

bearings

61 and 61 on the inner periphery. It is supported by. Thereby, the contact resistance between the outer pin 27 and the

curved plates

26a and 26b is reduced. Each rolling bearing 61 includes an inner raceway surface formed directly on the outer diameter surface of the outer pin 27, an outer ring fitted and fixed to the inner periphery of the outer pin housing 60, and having an outer raceway surface on the inner diameter surface, and an inner raceway surface. A needle roller bearing including a plurality of needle rollers disposed between outer raceway surfaces.

As shown in FIG. 1,

annular restraining members

62 and 62 are fixed to one end surface and the other end surface of the outer pin housing 60, respectively. Thereby, the outer pin 27 is restrained in the axial direction, and the axial movement of the outer pin 27 is restricted.

Although not shown in detail, the outer pin housing 60 and the restraining

members

62 and 62 are supported in a floating state with respect to the casing 22 by a detent means (not shown) having an elastic support function. This is a component of the motion conversion mechanism that absorbs a large radial load or moment load generated by turning or sudden acceleration / deceleration of the vehicle, and converts the rotational motion of the

curved plates

26a and 26b into the rotational motion of the reducer output shaft 28. This is to prevent damage.

The deceleration part B further includes counterweights 29 arranged adjacent to each other on the outer side in the axial direction of the

eccentric parts

25a and 25b. The counterweight 29 has a substantially fan shape, for example, and is fitted and fixed to the outer periphery of the speed reducer input shaft 25. Each counterweight 29 is arranged with a 180 ° phase shift from the axially adjacent eccentric portion 25a (25b) in order to cancel out the unbalanced inertia couple generated by the rotation of the

curved plates

26a, 26b.

As shown in FIGS. 1 and 2, the motion conversion mechanism mainly includes a plurality of through holes 30a provided in the

curved plates

26a and 26b, and a plurality of inner pins 31 inserted into the through holes 30a one by one. The motion conversion mechanism of the present embodiment is further configured to include a needle roller bearing 31a disposed on the inner periphery of each through hole 30a. By providing the needle roller bearing 31a in this manner, the frictional resistance between the inner pin 31 and the inner wall surface of the through hole 30a is reduced. The inner pins 31 are arranged at equal intervals on the circumference centering on the rotational axis of the reduction gear output shaft 28, and the end portion on the outboard side is provided on the flange portion 28 a of the reduction gear output shaft 28. It is fitted and fixed in a hole (through hole in the illustrated example). The inner diameter dimension of the through hole 30a is set larger than the outer diameter dimension of the inner pin 31 (referred to as “maximum outer diameter including the needle roller bearing 31a”; the same applies hereinafter).

As shown in FIG. 1, the deceleration unit B further includes a stabilizer 31 b. The stabilizer 31b integrally includes an annular portion 31c and a cylindrical portion 31d extending in the axial direction from the inner diameter surface of the annular portion 31c, and the end portion on the inboard side of each inner pin 31 is connected to the annular portion 31c. It is fixed. As a result, the load applied to some of the inner pins 31 from the

curved plates

26a and 26b when the motor part A is driven is supported by all of the inner pins 31 via the stabilizer 31b, and therefore the stress acting on the inner pins 31. Is reduced and durability is improved.

In addition, as shown in FIG. 1, between the two opposing surfaces of the

curved plates

26a and 26b, a circle that holds the

curved plates

26a and 26b adjacent in the axial direction in a state of being separated in the axial direction (non-contact state). An annular first spacer 70a is arranged. Further, the other member (in this embodiment, the annular portion 31c of the stabilizer 31b) adjacent to the curved plate 26a in the axial direction, and the other member (in this embodiment, the reduction gear output) adjacent to the curved plate 26b in the axial direction. Between the flange portions 28a) of the shaft 28, second spacers 70b are disposed to hold them in a state of being separated from each other in the axial direction. Accordingly, it is possible to prevent as much as possible that one or both of the

curved plates

26a and 26b are inclined with respect to the radial direction and the

curved plates

26a and 26b come into sliding contact with each other. It is possible to transmit power appropriately inside.

Here, the state of the load acting on the curved plate 26a and further on the reduction gear input shaft 25 when the motor part A is driven will be described with reference to FIG. When the motor unit A is driven, a load acts on the curved plate 26b in the same manner as described below.

The axis O ₂ of the eccentric portion 25 a provided on the speed reducer input shaft 25 is eccentric from the axis (rotational axis) O of the speed reducer input shaft 25 by the amount of eccentricity e. The outer periphery of the eccentric portion 25a is held curved plate 26a via a rolling bearing 41, since the eccentric portion 25a (the rolling bearing 41) rotatably supports the curve plate 26a, the axial center _{O 2} is the curved plates 26a Axis It is also a heart. The outer peripheral portion of the curved plate 26a is formed by a waveform curve, and has concave portions 34 that are recessed in the radial direction at equal intervals in the circumferential direction. Around the curved plate 26a, a plurality of outer pins 27 that engage with the recesses 34 are arranged in the circumferential direction with the axis O as the center.

In FIG. 3, when the motor part A is driven and the speed reducer input shaft 25 rotates counterclockwise on the paper surface, the eccentric part 25a and the curved plate 26a held on the outer periphery thereof revolve around the axis O. Therefore, the concave portion 34 formed on the outer peripheral portion of the curved plate 26a sequentially contacts the outer pin 27 in the circumferential direction. As a result, the curved plate 26a rotates clockwise in response to a load Fi as indicated by an arrow in the drawing from the plurality of outer pins 27.

Further, the curve plates 26a and a plurality of circumferentially disposed around the the axis O ₂ through-holes 30a, each through-hole 30a, which is arranged coaxially with the axis O (reduction gear input shaft 25) An inner pin 31 that is fixedly provided to the reduction gear output shaft 28 is inserted. Since the inner diameter of the through hole 30a is larger than the outer diameter of the inner pin 31, the inner pin 31 does not hinder the revolving motion of the curved plate 26a, and the inner diameter of the through hole 30a of the rotating curved plate 26a is not reduced. The rotational movement of the curved plate 26a is taken out by sliding contact with the wall surface, and the reduction gear output shaft 28 is rotated (converted into the rotational movement of the reduction gear output shaft 28). At this time, the speed reducer output shaft 28 has a higher torque and a lower rotational speed than the speed reducer input shaft 25, and the curved plate 26a receives a load Fj as indicated by arrows in the figure from the plurality of inner pins 31. A resultant force Fs of the plurality of loads Fi and Fj is applied to the reduction gear input shaft 25 (the eccentric portion 25a thereof).

The direction of the resultant force Fs changes due to the influence of centrifugal force in addition to geometric conditions such as the shape of the outer peripheral portion of the curved plate 26a and the number of concave portions 34. Specifically, the angle α between the reference line X perpendicular to the straight line Y connecting the rotation axis O ₂ and the axis O and passing through the rotation axis O ₂ and the resultant force Fs is approximately 30 ° to 60 °. Fluctuates. The plurality of loads Fi and Fj change in the direction and magnitude of the load while the speed reducer input shaft 25 rotates once. As a result, the resultant force Fs acting on the speed reducer input shaft 25 is also in the direction and magnitude of the load. Fluctuates. Then, when the speed reducer input shaft 25 rotates once, the concave portion 34 of the curved plate 26a is decelerated and rotates clockwise by one pitch, resulting in the state of FIG. 3, and this is repeated.

As shown in FIG. 1, the wheel bearing portion C includes a hub wheel 32 and a wheel bearing 33 that rotatably supports the hub wheel 32 with respect to the casing 22. The hub wheel 32 integrally includes a cylindrical hollow portion 32a connected to the shaft portion 28b of the reduction gear output shaft 28 and a flange portion 32b extending radially outward from the end portion on the outboard side of the hollow portion 32a. Have. Since the rear wheel 14 (see FIGS. 6 and 7) is connected and fixed to the flange portion 32b by the bolt 32c, the rear wheel 14 rotates integrally with the hub wheel 32 when the hub wheel 32 rotates.

The wheel bearing 33 has an inner member having an inner raceway surface 33 f formed directly on the outer diameter surface of the hub wheel 32 and an inner ring 33 a fitted to a small diameter step portion of the outer diameter surface, and an inner diameter surface of the casing 22. The outer ring 33b fitted and fixed, a plurality of rolling elements (balls) 33c arranged between the inner member and the outer ring 33b, a retainer 33d that holds the balls 33c in a circumferentially spaced state, and a wheel It is a double row angular contact ball bearing provided with a seal member 33e that seals both axial ends of the bearing 33.

Next, the lubrication mechanism will be explained. The lubrication mechanism supplies lubricating oil to various parts of the motor part A and the speed reducing part B. As shown in FIG. 1, the lubricating

oil paths

24a and 24b provided on the motor rotating shaft 24 and the speed reducer input shaft are provided. 25, lubricating

oil passages

25c, 25d, 25e, 25f, a lubricating oil passage 31e provided in the stabilizer 31b, a lubricating oil passage 31f provided in the inner pin 31, a lubricating oil discharge port 22b provided in the casing 22, The main components are a lubricating oil reservoir 22d, a lubricating oil passage 22e, a lubricating oil passage 45 (45a to 45c), and a rotary pump 51 that is disposed in the casing 22 and that pumps the lubricating oil to the circulating oil passage 45 of the casing 22. And The white arrow shown in FIG. 1 indicates the direction in which the lubricating oil flows.

The lubricating oil passage 24a extends along the axial direction inside the motor rotating shaft 24, and the lubricating oil passage 24a includes a lubricating oil passage 25c extending along the axial direction inside the reduction gear input shaft 25. It is connected. The lubricating oil passage 25d extends in the radial direction from the lubricating oil passage 25c toward the outer diameter surface of the speed reducer input shaft 25, and the outer diameter end portion opens to the outer diameter surfaces of the

eccentric portions

25a and 25b. . The lubricating oil passage 25e extends in the axial direction from the end portion on the outboard side of the lubricating oil passage 25c, and opens to the outer end surface of the reduction gear input shaft 25 on the outboard side. The lubricating oil passage 25f extends in the radial direction from the lubricating oil passage 25c toward the outer diameter surface of the speed reducer input shaft 25 in the same manner as the lubricating oil path 25d. It opens in the area | region of the inboard side rather than the to-be-fixed part of the rolling bearing 37a among outer diameter surfaces. In particular, the formation positions of the lubricating

oil passages

25d and 25f extending in the radial direction are not limited to this, and can be provided at any position in the axial direction of the reduction gear input shaft 25.

The lubricating oil discharge port 22b provided in the casing 22 discharges the lubricating oil inside the speed reduction part B (speed reduction mechanism), and is provided in at least one position of the casing 22 at the position of the speed reduction part B. The lubricating oil discharge port 22b and the lubricating oil path 24a of the motor rotating shaft 24 are connected via a lubricating oil reservoir 22d, a lubricating oil path 22e, and a lubricating oil path 45. Therefore, the lubricating oil discharged from the lubricating oil discharge port 22b returns to the lubricating oil path 24a of the motor rotating shaft 24 through the lubricating oil path 22e, the circulating oil path 45, and the like. The lubricating oil reservoir 22d has a function of temporarily storing the lubricating oil.

As shown in FIG. 1, the circulating oil passage 45 provided in the casing 22 includes an axial oil passage 45a extending in the axial direction inside the casing 22, and end portions on the outboard side and the inboard side of the axial oil passage 45a. Are connected to each other, and are constituted by

radial oil passages

45b and 45c extending in the radial direction. The radial oil passage 45b supplies the lubricating oil pumped from the rotary pump 51 to the axial oil passage 45a, and the lubricating oil supplied to the axial oil passage 45a passes through the radial oil passage 45c to the motor rotating shaft 24. Is supplied to the lubricating oil passage 24a of the speed reducer and the lubricating oil passage 25c of the reduction gear input shaft 25.

The rotary pump 51 is provided between the lubricating oil passage 22e connected to the lubricating oil reservoir 22d and the circulating oil passage 45. By disposing the rotary pump 51 in the casing 22, it is possible to prevent the in-wheel motor drive device 21 from being enlarged as a whole.

As shown in FIG. 4, the rotary pump 51 includes an inner rotor 52 that rotates using the rotation of the reduction gear output shaft 28, an outer rotor 53 that rotates following the rotation of the inner rotor 52, both

rotors

52, 53 is a cycloid pump including a plurality of pump chambers 54 provided in a space between 53, a suction port 55 communicating with the lubricating oil passage 22e, and a discharge port 56 communicating with the radial oil passage 45b of the circulating oil passage 45. .

The inner rotor 52 rotates around the rotation center c ₁ , and the outer rotor 53 rotates around a rotation center c ₂ different from the rotation center c ₁ of the inner rotor 52. Thus, since the inner rotor 52 and the outer rotor 53 rotate about different rotation centers c ₁ and c ₂ , the volume of the pump chamber 54 changes continuously. Thereby, the lubricating oil flowing into the pump chamber 54 from the suction port 55 is pumped from the discharge port 56 to the radial oil passage 45 b of the circulating oil passage 45.

The lubrication mechanism mainly has the above configuration, and lubricates and cools each part of the motor part A and the reduction part B as follows.

First, referring to FIG. 1, in the motor portion A, the supply of lubricating oil to the rotor 23b and the stator 23a is mainly performed via the circulating oil passage 45 of the casing 22, as shown in FIG. A part of the lubricating oil supplied to the lubricating oil passage 24 a of the motor rotating shaft 24 is affected by the centrifugal force generated by the rotation of the motor rotating shaft 24 and the pressure of the rotary pump 51, and the outer diameter of the lubricating oil passage 24 b. This is done by discharging from the side opening. That is, the lubricating oil discharged from the outer diameter side opening of the lubricating oil passage 24b is supplied to the rotor 23b and then supplied to the stator 23a. Further, the rolling bearing 36 that supports the end portion of the motor rotating shaft 24 on the inboard side mainly oozes out part of the lubricating oil flowing through the circulating oil passage 45 from between the casing 22 and the motor rotating shaft 24. It is lubricated by. Further, the rolling bearing 36 that supports the end portion on the outboard side of the motor rotating shaft 24 is mainly discharged from the lubricating oil passage 24b, and the inner portion on the outboard side of the portion of the casing 22 in which the motor portion A is accommodated. It is lubricated by the lubricating oil that has fallen along the wall.

Next, the lubricating oil that has flowed into the lubricating oil passage 25c of the reduction gear input shaft 25 via the lubricating oil passage 24a of the motor rotation shaft 24 is subjected to centrifugal force and pressure of the rotary pump 51 accompanying the rotation of the reduction gear input shaft 25. The oil is discharged from the openings of the lubricating

oil passages

25d, 25e, and 25f toward the inside of the deceleration unit B (deceleration mechanism). The discharged lubricating oil is supplied to various locations in the speed reduction portion B mainly by centrifugal force, and lubricates and cools the various locations in the speed reduction portion B. Then, as shown in FIG. 1, the lubricating oil that has reached the inner wall surface of the casing 22 is discharged from the lubricating oil discharge port 22b and stored in the lubricating oil storage portion 22d. As described above, since the lubricating oil reservoir 22d is provided between the lubricating oil discharge port 22b and the lubricating oil passage 22e connected to the rotary pump 51, it can be completely discharged by the rotary pump 51 especially during high-speed rotation. Even if no lubricating oil is temporarily generated, the lubricating oil can be stored in the lubricating oil storage unit 22d. As a result, it is possible to prevent an increase in heat generation and torque loss at various portions of the deceleration portion B. On the other hand, the amount of lubricating oil reaching the lubricating oil discharge port 22b decreases particularly during low-speed rotation. Even in such a case, the lubricating oil stored in the lubricating oil reservoir 22d is used as the lubricating oil. Since it can recirculate | reflux to the path |

routes

24a and 25c, lubricating oil can be supplied to the motor part A and the deceleration part B stably.

In addition, the lubricating oil inside the deceleration part B moves to the outside by gravity in addition to the centrifugal force. Therefore, it is desirable that the in-wheel motor drive device 21 is attached to the electric vehicle 11 so that the lubricating oil reservoir 22d is positioned below the in-wheel motor drive device 21.

The overall structure of the in-wheel motor drive device 21 is as described above, and the in-wheel motor drive device 21 of the present embodiment has a characteristic configuration as described below.

FIG. 5 shows a cross-sectional view of the curved plate 26a along the line Z1-Z1 in FIG. The curved plate 26a is made of case-hardened steel such as SCM415, SCM420, and SCr420, and has a hardened layer H (indicated by cross-hatching in FIG. 5) formed by performing carburizing, quenching, and tempering as heat treatment. In the present embodiment, the hardened layer H is formed over the entire surface layer portion of the curved plate 26a including the inner wall surfaces of the through

holes

30a and 30b. The hardness of the hardened layer H is 62 to 66.5 on the Vickers hardness C scale (HRC), while the hardness of the core (the portion where the hardened layer H is not formed) is about HRC29 to 38. In addition, although illustration is abbreviate | omitted, the curve board 26b is also formed with case hardening steel like the curve board 26a, and has the hardened layer H formed by performing carburizing quenching tempering.

As described above, when the

curved plates

26a and 26b revolve with the rotation of the speed reducer input shaft 25, the outer peripheral portions of the

curved plates

26a and 26b during the revolving motion are engaged with the outer pin 27 in the circumferential direction. Autorotation occurs in the

curved plates

26a and 26b. This rotation motion is decelerated by the inner pin 31 inserted through the through holes 30a of the

curved plates

26a and 26b slidingly contacting the inner wall surfaces of the through holes 30a provided in the

curved plates

26a and 26b during the rotation motion. It is converted into a rotary motion of the machine output shaft 28. In short, the

curved plates

26a and 26b revolve and rotate while slidingly contacting the outer pin 27 and the inner pin 31 when the speed reducer input shaft 25 rotates. Therefore, the

curved plates

26a and 26b are not only strong enough to withstand the load applied from the outer pin 27 and the inner pin 31, but also resistant to wear due to sliding with the outer pin 27 and the inner pin 31. It is necessary to have wearability (surface hardness).

In response to such a request, the

curved plates

26a and 26b have a hardened layer H by carburizing, quenching and tempering over the entire surface layer portion, and the strength and surface hardness thereof are increased, so that the outer peripheral portion is outside. The inner wall surface of the through hole 30a is deformed by the load applied from the inner pin 31, and the inner wall surface of the through hole 30a is deformed by the load applied from the pin 27 or worn with the sliding with the outer pin 27. Or wear due to sliding with the inner pin 31 (needle roller bearing 31a) can be effectively prevented. Furthermore, since the hardened layer H is formed over the entire surface layer portion of the

curved plates

26a and 26b, the rolling elements (cylindrical rollers 44) of the rolling bearing 41 roll on the inner wall surface (outer raceway surface 43) of the through hole 30b. In addition to wear / deformation of the inner wall surface of the through-hole 30b, the wear of the end faces caused by the

curved plates

26a, 26b slidingly contacting the spacers 70a, 70b can be effectively prevented.

On the other hand, since the hardened layer H is not formed on the cores of the

curved plates

26a and 26b, the

curved plates

26a and 26b have toughness. Thereby, for example, even when an instantaneous impact load is input to the deceleration portion B via the wheel bearing portion C during driving of the vehicle, the

curved plates

26a and 26b may be deformed or damaged by the impact load. Can be effectively reduced.

Further, as the material for forming the

curved plates

26a and 26b, the case-hardened steel having a relatively soft and rich workability is selected before the heat treatment (carburizing quenching and tempering). It can be manufactured well. Moreover, since the carburizing and quenching tempering selected as the heat treatment method has flexibility in changing the shape, the cost required for newly producing and changing the design of the

curved plates

26a and 26b can be reduced.

As described above, according to the present invention, the curved plate 26a, which has excellent workability and can be easily manufactured, has high strength and wear resistance, and has toughness capable of withstanding an instantaneous impact load. 26b can be obtained. Thereby, the in-wheel motor drive device 21 with low cost and excellent durability can be realized.

The overall operation principle of the in-wheel motor drive device 21 having the above configuration will be described with reference to FIGS.

In the motor part A, for example, the rotor 23b made of a permanent magnet or a magnetic material rotates by receiving an electromagnetic force generated by supplying an alternating current to the coil of the stator 23a. Accordingly, when the speed reducer input shaft 25 connected to the motor rotating shaft 24 rotates, the

curved plates

26 a and 26 b revolve around the rotational axis of the speed reducer input shaft 25. At this time, the outer pin 27 engages with the curved waveform provided on the outer periphery of the

curved plates

26a and 26b in the circumferential direction, and the

curved plates

26a and 26b are opposite to the rotation direction of the speed reducer input shaft 25. To rotate around.

The inner pin 31 inserted through the through hole 30a comes into contact with the inner wall surface of the through hole 30a as the

curved plates

26a and 26b rotate. As a result, the revolving motion of the

curved plates

26 a and 26 b is not transmitted to the inner pin 31, and only the rotational motion of the

curved plates

26 a and 26 b is transmitted to the wheel bearing portion C via the reduction gear output shaft 28. At this time, since the rotation of the speed reducer input shaft 25 is decelerated by the speed reducing portion B and then transmitted to the speed reducer output shaft 28, even when the low torque, high speed type motor portion A is employed, the drive wheels ( The required torque can be transmitted to the (rear wheel) 14.

The speed reduction ratio of the speed reduction portion B having the above-described configuration is (Z _A −Z _B ), where Z _{A is} the number of outer pins 27 and Z _B is the number of waveforms (concave portions 34) provided on the outer peripheral portions of the curved plates 26a and 26b. ) / is calculated by _{Z B.} In the embodiment shown in FIG. 2, since Z _A = 12 and Z _B = 11, a very large reduction ratio of 1/11 can be obtained.

In this way, by adopting the reduction part B that can obtain a large reduction ratio without using a multistage configuration, the in-wheel motor drive device 21 having a compact and high reduction ratio can be obtained. Further, by providing rolling bearings (needle roller bearings) 61 and 31a that rotatably support the outer pin 27 and the inner pin 31, friction between the

curved plates

26a and 26b and the outer pin 27 and the inner pin 31 is achieved. Since resistance is reduced, the power transmission efficiency in the deceleration part B improves.

As described above, the in-wheel motor drive device 21 of the present embodiment is lightweight and compact as a whole device. Therefore, if the in-wheel motor drive device 21 is mounted on the electric vehicle 11, the unsprung weight can be suppressed, so that the electric vehicle 11 excellent in running stability and NVH characteristics can be realized.

As described above, the in-wheel motor driving device 21 according to the embodiment of the present invention has been described. However, the in-wheel motor driving device 21 can be variously modified without departing from the gist of the present invention. is there.

For example, in the above description, the cycloid pump is adopted as the rotary pump 51. However, the present invention is not limited to this, and any rotary pump driven by using the rotation of the reduction gear output shaft 28 can be adopted. Furthermore, the rotary pump 51 may be omitted, and the lubricating oil may be circulated only by centrifugal force.

In the above description, the

eccentric portions

25a and 25b are provided at two locations in the axial direction of the speed reducer input shaft 25. However, the number of installed eccentric portions can be arbitrarily set. For example, the eccentric portions can be provided at three positions in the axial direction of the speed reducer input shaft 25. In this case, each eccentric portion is 120 ° so as to cancel out the centrifugal force generated by the rotation of the speed reducer input shaft 25. It is preferable to change the phase.

In the above, mainly, the through hole 30a provided in the

curved plates

26a and 26b and the inner pin 31 fixed to the flange portion 28a of the reduction gear output shaft 28 so as to be slidable with the inner wall surface of the through hole 30a. Although the motion conversion mechanism is configured, the motion conversion mechanism is not limited to this, and any configuration that can transmit the rotational motion of the

curved plates

26a and 26b to the hub wheel 32 of the wheel bearing portion C can be used.

The description of the operation in the present embodiment has been made by paying attention to the rotation of each member, but in reality, power including torque is transmitted from the motor part A to the rear wheel 14. Therefore, the power decelerated as described above is converted into high torque.

Also, the case where power is supplied to the motor unit A to drive the motor unit and the power from the motor unit A is transmitted to the rear wheels 14 is shown. On the contrary, the vehicle decelerates or goes down the hill. In such a case, the power from the rear wheel 14 side can be converted to rotation of high rotation and low torque by the speed reduction unit B and transmitted to the motor unit A, and the motor unit A can generate power. Furthermore, the electric power generated here can be stored in a battery and used as electric power for driving the motor unit A and electric power for operating other electric devices provided in the vehicle.

In the above description, the present invention is applied to a configuration in which a radial gap motor is used for the motor part A. However, the present invention is an axial gap motor in which the stator and the rotor are opposed to the motor part A via an axial gap. It is preferably applicable also when adopting.

Further, the in-wheel motor drive device 21 according to the present invention is not limited to the rear wheel drive type electric vehicle 11 having the rear wheel 14 as the drive wheel, but also the front wheel drive type electric vehicle having the front wheel 13 as the drive wheel, The present invention can also be applied to a four-wheel drive type electric vehicle having 13 and rear wheels 14 as drive wheels. In the present specification, “electric vehicle” is a concept including all vehicles that obtain driving force from electric power, and includes, for example, a hybrid vehicle.

The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the scope of the present invention. The scope of the present invention is not limited to patents. It includes the equivalent meanings recited in the claims and the equivalents recited in the claims, and all modifications within the scope.

DESCRIPTION OF SYMBOLS 11 Electric vehicle 21 In-wheel motor drive device 22 Casing 25 Reduction

gear input shaft

25a, 25b

Eccentric part

26a, 26b Curve board 27 Outer pin 28 Reduction gear output shaft 30a Through-hole 30b Through-hole 31 Inner pin 41 Rolling bearing 43 Outer raceway surface 70a 1st spacer 70b 2nd spacer A Motor part B Deceleration part C Wheel bearing part H Hardened layer

Claims

The motor part, the reduction part and the wheel bearing part are held in the casing,
The speed reducer has an eccentric part, and is connected to a speed reducer input shaft that is rotationally driven by the motor part, and is rotatably held on the outer periphery of the eccentric part. In an in-wheel motor drive device comprising a cycloid reduction mechanism having a curved plate that performs a revolving motion centered on the heart,
An in-wheel motor drive device, wherein the curved plate is made of case-hardened steel and carburized, quenched and tempered.
The cycloid reduction mechanism is configured to slide and contact the curved plate during the rotational movement, and a plurality of outer pins that engage with the outer peripheral portion of the curved plate to cause the curved plate to rotate. The in-wheel motor drive device of Claim 1 provided with the inner pin which converts a rotational motion into the rotational motion of the reduction gear output shaft connected with the said bearing part for wheels.
The in-wheel motor drive device according to claim 1 or 2, wherein the curved plate is rotatably held on an outer periphery of the eccentric portion via a rolling bearing.
The in-wheel motor drive device according to claim 3, wherein an outer raceway surface is formed on the curved plate among an outer raceway surface and an inner raceway surface on which rolling elements of the rolling bearing roll.
The eccentric portions holding the curved plate on the outer periphery are provided at a plurality of positions in the axial direction, and the respective eccentric portions have phases different from each other so as to cancel the centrifugal force generated by the rotation of the speed reducer input shaft. The in-wheel motor drive device according to any one of claims 1 to 4, wherein the in-wheel motor drive device is provided.
6. The apparatus according to claim 5, further comprising: a first spacer that holds the curved plates adjacent in the axial direction apart from each other, and a second spacer that holds the curved plate and other members adjacent in the axial direction apart from each other. The in-wheel motor drive device of description.