JP6799426B2 - In-wheel motor drive - Google Patents

Description

The present invention relates to, for example, an in-wheel motor drive device in which an output shaft of an electric motor unit and a wheel bearing unit are connected via a speed reducer unit.

Since the in-wheel motor drive device is housed inside the wheel, it becomes the unsprung weight of the vehicle. Since the increase in unsprung weight deteriorates the riding comfort of the vehicle, it is an important requirement to reduce the size and weight of the in-wheel motor drive device. Since the output torque of the electric motor is proportional to the size and weight of the electric motor, a large motor is required to generate the torque required to drive the vehicle by the motor alone. Therefore, by using the electric motor in combination with the speed reducer, a means for miniaturization is used.

However, if the electric motor, the speed reducer, and the bearing for the wheel are arranged in series, the amount of protrusion of the in-wheel motor drive device from the wheel to the inboard side becomes large. When the space of the wheel housing is the same as that of the vehicle of the internal combustion engine, interference between the vehicle body and the in-wheel motor drive device occurs when the vehicle is steered or moved up and down. Therefore, it is necessary to reduce the tire movable range or modify the vehicle body exclusively for the in-wheel motor drive device.

As a conventional technique, an in-wheel motor drive device has been proposed in which the axial dimension of the in-wheel motor drive device is shortened in order to prevent interference with the suspension device and the brake device and improve the vehicle mountability. (Patent Document 1). In this in-wheel motor drive device, the electric motor and the output shaft to the wheel are arranged on two parallel shafts, and the electric motor and the speed reducer are arranged on different shafts to extend to the inboard side. I'm holding back.

Japanese Unexamined Patent Publication No. 2012-214202

In the in-wheel motor drive device described in Patent Document 1, since the speed reducer, the wheel bearing and the electric motor are not arranged coaxially, the motor can be arranged outside in the radial direction of the speed reducer and the wheel bearing. However, by arranging the wheel bearings outward in the radial direction, the drive and power of the in-wheel motor drive device do not occur when the electric motor, reducer, and wheel bearings are arranged in series (coaxially). The brake disc comes close to the transmission part.

The in-wheel motor drive has a rolling bearing built in to support each rotating shaft, but when the in-wheel motor drive and the brake disc come close to each other, the rolling bearing on the outboard side and the brake disc come close to each other. We paid attention to the concern that the rolling bearings on the outboard side would become hot due to the frictional heat of the brakes.

Rolling bearings subjected to standard heat treatment have little dimensional change up to about 120 ° C., but the dimensional change (expansion) becomes large when used for a long time in a high temperature environment exceeding 120 ° C. In particular, when the expansion of the inner ring becomes large, the internal clearance of the bearing becomes too small, smooth rotation is hindered, and the life is shortened. Therefore, conventionally, it has been found that it is difficult to bring the unit closer to the outboard side by bringing the brake disc, which becomes hot, and the in-wheel motor drive device close to each other, which is a big problem in the vehicle mountability of the in-wheel motor drive device. .. The present invention focuses on this problem.

In view of the above problems, it is an object of the present invention to improve the vehicle mountability of an in-wheel motor drive device in which a braking device is mounted on the outboard side while extending the life of the rotary shaft support bearing. ..

As a technical means for achieving the above-mentioned object, the present invention includes an electric motor unit, a speed reducer unit, and a wheel bearing portion, and includes a casing, and at least the final reduction gear of the speed reducer unit. In an in-wheel motor drive device in which the stage has a reduction structure using parallel shaft gears, the output gear of the final reduction stage has a pitch circle diameter larger than the diameter of the cylindrical portion of the outer ring of the wheel bearing portion, and the reduction is performed. The gear shafts of a plurality of reduction stages of the machine section are supported by rolling bearings , the rolling bearings are lubricated by the lubricating oil supplied to the speed reducer section, and at least the outboard side of the rolling bearings supporting the gear shafts. The rolling bearings arranged in the above are made of high carbon chrome bearing steel and have a heat-treated structure that has been high-temperature tempered after quenching.

With the above configuration, in the in-wheel motor drive device in which the braking device is mounted on the outboard side, it is possible to improve the vehicle mountability while extending the life of the rotary shaft support bearing.

It is desirable that the tempering temperature of the above-mentioned high-temperature tempering is 200 ° C. or higher. As a result, dimensional changes in a high temperature environment can be suppressed, and the life can be extended. It is also desirable in which the above heat treatment the tissue is further carbonitriding processing is performed. As a result, it is possible to further extend the life of the rotary shaft support bearing and ensure dimensional stability.

Since the wheel bearing portion is of the outer ring rotation type, the vehicle mountability is further improved. In the case of the inner ring rotation type, the structure of the existing hub wheel having a spline hole can be applied while ensuring the vehicle mountability.

According to the present invention, in an in-wheel motor drive device in which a braking device is mounted on the outboard side, it is possible to improve the vehicle mountability while extending the life of the rotary shaft support bearing.

It is a vertical cross-sectional view which shows the in-wheel motor drive device which concerns on 1st Embodiment of this invention, and is seen by the line of line PP of FIG. It is a front view including a part cross section of the in-wheel motor drive device seen by the QG line of FIG. It is a vertical cross-sectional view of a rolling bearing which supports the gear shaft of FIG. It is a vertical sectional view of the in-wheel motor drive device which concerns on 2nd Embodiment of this invention. It is a top view which shows the schematic structure of the electric vehicle equipped with the in-wheel motor drive device. It is a rear sectional view which shows the electric vehicle of FIG.

The in-wheel motor drive device according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 3, 5 and 6. First, an electric vehicle equipped with the in-wheel motor drive device of the present embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 is a schematic plan view of the electric vehicle 11 equipped with the in-wheel motor drive device 21, and FIG. 6 is a schematic cross-sectional view of the electric vehicle 11 as viewed from the rear.

As shown in FIG. 5, the electric vehicle 11 includes a chassis 12, a front wheel 13 as a steering wheel, a rear wheel 14 as a driving wheel, and an in-wheel motor driving device 21 that transmits a driving force to the rear wheel 14. Equip. As shown in FIG. 6, the rear wheel 14 is housed inside the wheel housing 15 of the chassis 12, and is fixed to the lower part of the chassis 12 via a suspension device (suspension) 16.

The suspension device 16 supports the rear wheels 14 by suspension arms extending to the left and right, and absorbs vibrations received by the rear wheels 14 from the ground by struts including a coil spring and a shock absorber to suppress vibrations of the chassis 12. A stabilizer that suppresses the inclination of the vehicle body when turning is provided at the connecting portion of the left and right suspension arms. The suspension device 16 is an independent suspension type in which the left and right wheels are independently raised and lowered in order to improve the followability to the unevenness of the road surface and efficiently transmit the driving force of the rear wheels 14 to the road surface.

The electric vehicle 11 is provided with an in-wheel motor drive device 21 for driving the left and right rear wheels 14 inside the wheel housing 15, so that it is not necessary to provide a motor, a drive shaft, a differential gear mechanism, or the like on the chassis 12. Therefore, there is an advantage that a large cabin space can be secured and the rotations of the left and right rear wheels 14 can be controlled respectively.

Before explaining the characteristic configuration of this embodiment, the overall configuration of the in-wheel motor drive device 21 will be described with reference to FIGS. 1 and 2. In the following description, when the in-wheel motor drive device 21 is mounted on the vehicle, the side closer to the outside of the vehicle is referred to as the outboard side, and the side closer to the center is referred to as the inboard side. The term "outboard side" in the claims is used in the above meaning.

FIG. 1 is a vertical cross-sectional view of the in-wheel motor drive device viewed along the line PP of FIG. 2, and FIG. 2 is a partial cross section of the in-wheel motor drive device viewed along the line QG of FIG. It is a front view including.

As shown in FIGS. 1 and 2, the in-wheel motor drive device 21 includes an electric motor unit A that generates a driving force, a speed reducer unit B that decelerates and outputs the rotation of the electric motor unit A, and a speed reducer unit. It is provided with a wheel bearing portion C that transmits the output from B to the rear wheels as drive wheels. The electric motor portion A, the reduction gear portion B, and the wheel bearing portion C are each housed in the casing 22. The casing 22 has an integral structure as shown in FIG. 2, or may have a divisible structure.

As shown in FIG. 1, the electric motor unit A is located inside the stator 23 fixed to the casing 22 and the rotor 24 arranged so as to face each other with a gap inside the stator 23 in the radial direction. It is composed of a radial gap type electric motor 26 provided with a motor rotating shaft 25 that is arranged and integrally rotates with the rotor 24. The motor rotation shaft 25 can rotate at high speed at about 10,000 to several thousand rotations per minute. The stator 23 is configured by winding a coil around a magnetic core, and the rotor 24 is composed of a permanent magnet or the like.

The motor rotating shaft 25 has a rolling bearing 40 at one end in the axial direction (left side in FIG. 1) and a rolling bearing 41 at the other end in the axial direction (right side in FIG. 1) with respect to the casing 22. Each is rotatably supported.

The speed reducer unit B includes an input gear 30, a first intermediate gear 31, a second intermediate gear 32, a third intermediate gear 33, a fourth intermediate gear 34, and an output gear 35 as a plurality of intermediate gears. The input gear 30 integrally has an input shaft 30a, and the input shaft 30a is coaxially connected to the motor rotating shaft 25 by spline fitting (including serration fitting; the same applies hereinafter). The first intermediate gear 31 and the second intermediate gear 32 are integrally formed with the first intermediate shaft S1, and the third intermediate gear 33 and the fourth intermediate gear 34 are integrally formed with the second intermediate shaft S2. The output gear 35 is integrally formed with the hollow output gear shaft 36.

The input shaft 30a as the gear shaft, the first intermediate shaft S1, the second intermediate shaft S2, and the output gear shaft 36 are arranged in parallel with each other. The input shaft 30a is provided by rolling bearings 42 and 43, the first intermediate shaft S1 is provided by rolling bearings 44 and 45, the second intermediate shaft S2 is provided by rolling bearings 46 and 47, and the output gear shaft 36 is provided by rolling bearings 48 and 49, respectively. It is rotatably supported with respect to the casing 22. Of the above rolling bearings 42 to 49, the rolling bearings 43, 45, 47, 49 arranged on the outboard side are used in a high temperature environment due to the frictional heat of the brake disc 59. Details will be described later.

As shown in FIG. 2, between the center O1 of the input shaft 30a of the speed reducer portion B (which is also the center of the motor rotating shaft 25) and the center O4 of the wheel bearing portion C, the center O2 of the first intermediate shaft S1. And the center O3 of the second intermediate shaft S2 are bent and arranged to make the outer contour of the in-wheel motor drive device 21 compact. As a result, it can be mounted in the wheel of an existing internal combustion engine vehicle.

As shown in FIG. 1, in the speed reducer unit B, the input gear 30 and the first intermediate gear 31 mesh with each other, the second intermediate gear 32 and the third intermediate gear 33 mesh with each other, and the fourth intermediate gear 34 and the output The gear 35 is in mesh. The number of teeth of the first intermediate gear 31 is larger than the number of teeth of the input gear 30 and the second intermediate gear 32, and the number of teeth of the third intermediate gear 33 is the number of teeth of the second intermediate gear 32 and the fourth intermediate gear 34. The number of teeth of the output gear 35 is larger than the number of teeth of the fourth intermediate gear 34. From the above configuration, a parallel shaft gear reducer 39 that reduces the rotational motion of the motor rotating shaft 25 in three stages is configured.

In the present embodiment, helical gears are used as the input gear 30 constituting the reduction gear 39, the intermediate gears 31, 32, 33, 34 and the output gear 35. Helical gears are effective in that the number of teeth that mesh with each other increases at the same time and the tooth contact is dispersed, so that the sound is quiet and the torque fluctuation is small. It is preferable to set the module of each gear to about 1 to 3 in consideration of the meshing ratio of the gears and the limit rotation speed.

The wheel bearing portion C is composed of an outer ring rotation type wheel bearing 50. The wheel bearing 50 includes an axle 51, a pair of bearing inner rings 52 and 52 fitted and fixed to the outer peripheral surface of the axle 51, a bearing outer ring 53 as an outer member arranged on the outer peripheral side of the axle 51, and a bearing. A double-row inner race 54 formed on the outer peripheral surface of the outer peripheral surface of the inner ring 52, a double-row outer race 55 formed on the inner peripheral surface of the bearing outer ring 53, and a plurality of rows arranged between the inner race 54 and the outer race 55. It is a double-row angular contact ball bearing including a ball 56 as a rolling element and a cage (not shown) for holding each ball 56.

A flange portion 101 that is attached and fixed to the knuckle 100 is formed at the inboard side end portion of the axle 51. Further, a male screw portion 51c is formed at the shaft end on the outboard side of the axle 51. By screwing the nut 58 into the male threaded portion 51c and tightening the nut 58, the wheel bearing 50 is prevented from being separated and a preload is applied to the inside of the bearing.

A flange portion 53a for mounting a wheel is formed at the outboard side end portion of the bearing outer ring 53. A brake disc 59 and a rear wheel wheel 102 are attached to the flange portion 53a using a hub bolt 103. A cylindrical portion 53b arranged on the inner circumference of the output gear shaft 36 of the speed reducer 39 is formed on the inboard side of the flange portion 53a of the bearing outer ring 53. A male spline formed on the outer peripheral surface of the cylindrical portion 53b and a female spline formed on the inner peripheral surface of the output shaft 36 are fitted, and the bearing outer ring 53 and the output gear shaft 36 are connected so as to be able to transmit torque. As a result, the output of the speed reducer unit B is transmitted to the rear wheels. The output gear 35 has a pitch circle diameter PCD (see FIG. 2) larger than the diameter of the cylindrical portion 53b of the outer ring 53 of the wheel bearing portion C.

In the in-wheel motor drive device 21, lubricating oil is supplied to each part by a rotary pump (not shown) for cooling the electric motor 26 and lubricating and cooling the speed reducer 39. The inside of the wheel bearing 50 is lubricated with grease.

Since the in-wheel motor drive device 21 is housed inside the wheel housing 15 (see FIG. 6) and has an unsprung load, it is essential to reduce the size and weight. By combining the parallel shaft gear reducer 39 having the above-described configuration with the electric motor 26, it is possible to use a small electric motor 26 having a low torque and a high rotation speed. For example, when a parallel shaft gear reducer 39 having a reduction ratio of 11 is used, the electric motor 26 can be miniaturized by using an electric motor 26 that rotates at a high speed of about 10,000 and several thousand rotations per minute. As a result, a compact in-wheel motor drive device 21 can be realized, and an electric vehicle 11 having excellent running stability and NVH characteristics can be obtained by suppressing the unsprung weight.

The overall configuration of the in-wheel motor drive device 21 of the present embodiment is as described above. Next, a characteristic configuration will be described.

As shown in FIG. 1, in the in-wheel motor drive device 21 of the present embodiment, in order to shorten the axial dimension of the device as much as possible, rolling bearings 42, 43, which support the input shaft 30a of the speed reducer unit B, Rolling bearings 44 and 45 that support the first intermediate shaft S1, rolling bearings 46 and 47 that support the second intermediate shaft S2, and rolling bearings 48 and 49 that support the output gear shaft 36 are arranged in axial positions. doing. In particular, the rolling bearings 43, 45, 47, and 49 on the outboard side facing the brake disc 59 are aligned in the axial direction to unify the end faces of the casing 22 on the outboard side, and the in-board from the structural aspect. It makes it possible to bring the wheel motor drive device 21 closer to the brake disc 59.

The in-wheel motor drive device 21 of the present embodiment corresponds to the close arrangement of the end faces of the brake disc 59 and the casing 22 on the outboard side, and rolls on the outboard side where there is a concern about a high temperature environment due to frictional heat of the brake. Bearings 43, 45, 47 and 49 have a characteristic configuration. As an example, FIG. 3 shows a single view of the rolling bearing 47 that supports the outboard side of the second intermediate shaft S2.

As shown in FIG. 3, the rolling bearing 47 is a deep groove ball bearing including an inner ring 105, an outer ring 106, a ball 107 as a rolling element, and a cage 108. The inner ring 105, the outer ring 106 and the ball 107 are made of high carbon chromium bearing steel (for example, SUJ2), and are tempered at a high temperature of 200 ° C. or higher after quenching. Therefore, the inner ring 105, the outer ring 106, and the ball 107 have a heat-treated structure that has been tempered at a high temperature.

When high carbon chromium bearing steel is hardened by quenching and subjected to normal tempering treatment (temperature of 150 to 180 ° C.), retained austenite is present in the microstructure, and retained austenite is decomposed by the high temperature state during use. Dimensional changes occur with the phase transformation. Therefore, the rolling bearing 47 on the outboard side used in a high temperature environment is tempered and then tempered at a high temperature of 200 ° C. or higher, and heat-treated to decompose retained austenite, which is unstable to heat, in advance. There is. As a result, dimensional change (expansion) is suppressed even when the bearing is used for a long time in a high temperature environment, smooth rotation can be maintained without the internal clearance of the bearing becoming excessive, and the life can be extended.

Further, the inner ring 105, the outer ring 106 and the ball 107 of the rolling bearing 47 are tempered at a high temperature of 200 ° C. or higher after quenching to ensure dimensional stability and to compensate for the decrease in life due to the decrease in hardness. Therefore, it is subjected to carburizing and nitriding treatment. As a result, a long life and high dimensional stability can be maintained in a high temperature environment. The carburizing nitriding treatment is a treatment in which nitrogen is simultaneously permeated and diffused mainly of carbon.

In the above description, the rolling bearing 47 that supports the outboard side of the second intermediate shaft S2 is taken as an example, but the same applies to the other rolling bearings 43, 45, 49.

In addition to SUJ2, the high carbon chrome bearing steel may be SUJ3, SUJ5, or, for example, an ASTM A295 standard 52100 material, an ASTM A485 standard Grade 1 material, a Grade 2 material, or the like.

As described above, in the in-wheel motor drive device 21 of the present embodiment, heat is transferred from the brake disc 59, and even if the rolling bearings 43, 45, 47, 49 are exposed to an environment of 120 ° C. or higher, residual austenite remains. Since it is possible to suppress the formation of martensite, it is difficult for the dimensions to change, and it is possible to prevent the life of the bearing from being shortened. Therefore, the in-wheel motor drive device 21 can be brought closer to the disc brake 59 (closer to the outboard side), and by reducing the amount of protrusion of the in-wheel motor drive device 21 from the wheel 102 to the inboard side, the vehicle body and the vehicle body and Clearance with suspension parts can be secured, and vehicle mountability is improved.

When the outer ring rotation type wheel bearing 50 is used for the in-wheel motor drive device 21, the output gear 35 of the final reduction stage can be arranged on the outer periphery of the wheel bearing 50, so that the output gear 35 is moved toward the outboard side. Is possible. Along with this, the support bearing 49 of the output gear 35 and the support bearing 47 of the intermediate gear 34 that meshes with the output gear 35 are also brought closer to the outboard side and approach the brake disc 59. Therefore, the in-wheel motor drive device 21 according to the present embodiment is particularly effective when the outer ring rotation type wheel bearing 50 is used.

Next, the in-wheel motor drive device 21 according to the second embodiment of the present invention will be described with reference to FIG. The in-wheel motor drive device of the present embodiment is different from the in-wheel motor drive device of the first embodiment in the configurations of the output gear of the speed reducer portion and the wheel bearing portion. Since the other configurations are the same as those in the first embodiment, the parts having the same function are designated by the same reference numerals, and only the main points are omitted.

In the in-wheel motor drive device 21 of the present embodiment, as shown in FIG. 4, the wheel bearing 50'of the wheel bearing portion C is an inner ring rotation type. In this case, the existing hub wheel structure having spline holes can be applied while ensuring vehicle mountability. The wheel bearing 50'mainly includes an inner member 61 composed of a hub ring 60 and an inner ring 52, an outer ring 53', a ball 56, and a cage (not shown). A flange portion 60a for mounting a wheel is formed on the outer periphery of the hub wheel 60 on the outboard side, and an inner ring 52 is fitted and crimped and fixed to a small diameter step portion on the inboard side. The inner raceway surface 54 "on the outboard side is formed on the outer circumference of the hub wheel 60, and the inner raceway surface 54' on the inboard side is formed on the outer circumference of the inner ring 52. Although not shown, the flange portion for mounting the wheel A brake disc and wheels are attached to the 60a.

A double-row outer raceway surface 55 is formed on the inner circumference of the outer ring 53'corresponding to the inner raceway surface 54 "of the hub ring 60 and the inner raceway surface 54' of the inner ring 52. On the outer circumference of the outer ring 53'. A flange portion is formed, and the casing 22 is fastened and fixed with bolts.

The output gear 35'of the final reduction stage is formed integrally with the output shaft 51'(which is also the output gear shaft 36'), and the output shaft 51'is rotatably supported by the casing 22 by rolling bearings 48' and 49'. ing. The output shaft 51'is spline-fitted to the hub wheel 60 and is connected so that torque can be transmitted. Also in this embodiment, the output gear 35'has a pitch circle diameter PCD (see FIG. 2) larger than the diameter of the cylindrical portion 53b'of the outer ring 53'of the wheel bearing portion C.

Also in the present embodiment, the rolling bearings 42 and 43 supporting the input shaft 30a as the gear shaft, the rolling bearings 44 and 45 supporting the first intermediate shaft S1, the rolling bearings 46 and 47 supporting the second intermediate shaft S2, and the rolling bearings 46 and 47. Of the rolling bearings 48'and 49'that support the output gear shaft 36', the supporting bearings of the rolling bearings 43, 45, 47, 49'arranged on the outboard side are 200 after quenching the high carbon chrome bearing steel. It is tempered at a high temperature of ℃ or higher, and further subjected to carburizing and nitriding treatment. Therefore, the same effect as that of the first embodiment is obtained.

Since the other configurations are the same as those in the first embodiment, all the contents described in the first embodiment shall be applied mutatis mutandis, and the description thereof will be omitted.

The speed reducer unit B of the in-wheel motor drive device 21 of the above embodiment exemplifies the one using the parallel shaft gear speed reducer 39 for 3-step deceleration, but the present invention is not limited to this, and 2-step deceleration or It may be four-step deceleration or more. Further, the final reduction gear may have a parallel shaft gear reduction structure and may be combined with a planetary gear reduction gear.

The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be carried out in various forms without departing from the gist of the present invention. Indicated by the scope of claims and further includes the equal meanings set forth in the claims, and all modifications within the scope.

21 In-wheel motor drive device 22 Casing 25 Motor rotating shaft 26 Electric motor 30 Input gear 30a Input gear Axle 31 First intermediate gear 32 Second intermediate gear 33 Third intermediate gear 34 Fourth intermediate gear 35 Output gear 35'Output gear 36 Output Gear Shaft 36'Output Gear Shaft 39 Reducer 42 Rolling Bearing 43 Rolling Bearing 44 Rolling Bearing 45 Rolling Bearing 46 Rolling Bearing 47 Rolling Bearing 48 Rolling Bearing 49 Rolling Bearing 50 Wheel Bearing 53 Outer Ring 53b Cylindrical Part 53'Outer Ring 53b' Cylindrical Part A Electric motor part B Reducer part C Wheel bearing part S1 First intermediate shaft S2 Second intermediate shaft

Claims (5)

In an in-wheel motor drive device that is composed of an electric motor unit, a speed reducer unit, and a wheel bearing unit, includes a casing, and has a reduction structure in which at least the final reduction stage of the reduction gear unit is a parallel shaft gear. ,
The output gear of the final reduction stage has a pitch circle diameter larger than the diameter of the cylindrical portion of the outer ring of the wheel bearing portion.
The gear shafts of the plurality of reduction stages of the speed reducer section are supported by rolling bearings , and the rolling bearings are lubricated with the lubricating oil supplied to the speed reducer section.
Among the rolling bearings that support the gear shaft, at least the rolling bearings arranged on the outboard side are made of high carbon chrome bearing steel and have a heat-treated structure that has been tempered at a high temperature after quenching. Drive device. The in-wheel motor drive device according to claim 1, wherein the tempering temperature of the high-temperature tempering is 200 ° C. or higher. The in-wheel motor drive device according to claim 1 or 2 , wherein the heat-treated structure is further carburized and nitrided. The in-wheel motor drive device according to any one of claims 1 to 3, wherein the wheel bearing portion is of an outer ring rotation type. The in-wheel motor drive device according to any one of claims 1 to 3, wherein the wheel bearing portion is an inner ring rotation type.

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