WO2016043011A1

WO2016043011A1 - In-wheel motor drive device

Info

Publication number: WO2016043011A1
Application number: PCT/JP2015/074241
Authority: WO
Inventors: 鈴木　稔; 朋久魚住
Original assignee: Ntn株式会社; 鈴木　稔; 朋久魚住
Priority date: 2014-09-19
Filing date: 2015-08-27
Publication date: 2016-03-24
Also published as: JP2016061403A

Abstract

An in-wheel motor drive device equipped with a motor unit (A), a decelerator unit (B), and a wheel bearing unit (C). The decelerator unit (B) is equipped with: a decelerator input shaft (25) having eccentric parts (25a, 25b) and connected to a rotary shaft (24) of the motor unit (A); a decelerator output shaft (28) connected to the wheel bearing unit (C); rolling bearings (40) provided on the outer periphery of the eccentric parts (25a, 25b) of the decelerator input shaft (25); and curve plates (26a, 26b), which are rotatably held on the outer peripheries of the eccentric parts (25a, 25b) with the rolling bearings (40) therebetween, and which undergo orbital motion centered around the axis of rotation of decelerator input shaft (25) in conjunction with the rotation thereof. The initial radial internal gap in the rolling bearing (40) is 15-60 μm.

Description

In-wheel motor drive device

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

The size of the in-wheel motor drive device affects the size of the cabin space because the entire device is housed inside the wheel or disposed near the wheel. Moreover, since the in-wheel motor drive device becomes the unsprung weight of the vehicle, the weight affects the riding comfort of the vehicle. For this reason, the in-wheel motor drive device needs to be as light and compact as possible. On the other hand, the in-wheel motor drive device requires a large torque to drive the wheels. In order to satisfy these requirements at the same time, for example, in Patent Document 1 below, a high-rotation type motor that rotates at a rotational speed of, for example, about 15000 min ⁻¹ is adopted as a motor unit that generates a driving force. There has been proposed an in-wheel motor drive device that employs a cycloid reducer that is compact and can provide a high reduction ratio in a reduction part that reduces rotation and transmits it to a wheel bearing part.

The speed reduction part to which the cycloid reduction gear is applied mainly has an eccentric part, and is held rotatably on the outer periphery of the eccentric part via a reduction gear input shaft that rotates by receiving the driving force of the motor part and a rolling bearing. The output of the reducer connected to the wheel bearing section is the curved plate that performs the revolving motion centered on the rotation axis as the reducer input shaft rotates, and the rotational motion that occurred on the curved plate during the revolving motion. A motion conversion mechanism that converts the rotational motion of the shaft.

JP 2012-148725 A

In the reduction part having the above-described configuration, when the motor part is driven, the reduction gear input shaft rotates at a high speed as described above, and accordingly, between the reduction gear input shaft and the curved plate. The provided rolling bearing also rotates at high speed. Further, when the motor unit is driven, a large load (mainly radial load) is repeatedly applied to the above-mentioned rolling bearing through a curved plate or the like. Due to such a harsh usage environment and the load conditions associated with the mechanical special characteristics of the cycloid reducer, there are still points to be improved in the bearing incorporated in the reduction portion.

Specifically, as a result of various studies by the present inventors including a lubrication mechanism and a cooling mechanism inside the in-wheel motor drive device, the following knowledge about the rolling bearing incorporated in the speed reduction unit was obtained.

That is, the reduction gear input shaft of the speed reduction portion is driven to rotate by receiving the output of the motor portion, and if a curved plate or the like rotates accordingly, even if a lubrication mechanism for supplying lubricating oil to the speed reduction portion is provided, the speed reducer In the rolling bearing provided between the input shaft and the curved plate, the temperature rise of the entire bearing and the temperature difference between the inner raceway surface and the outer raceway surface become larger than expected. Under such conditions, not only the radial internal clearance (initial clearance) of the rolling bearing itself decreases due to the engagement with the reducer input shaft (clearance after assembly), but the clearance further increases due to the temperature factors described above. Decrease (driving clearance). When this operating clearance becomes too small, especially when it becomes a negative clearance, an abnormal temperature rise occurs, leading to early peeling and seizure. On the other hand, if the operating clearance is excessive, vibration due to the swirling of the curved plate and sound and vibration due to the contact between the curved plate and the outer pin and the inner pin are generated.

The present invention has been proposed in view of the above points, and it is an object of the present invention to improve the durability of an in-wheel motor drive device and prevent the occurrence of vibration and abnormal noise.

The present invention proposed to achieve the above-described object includes a motor unit, a reduction unit, and a wheel bearing unit, and the rotational driving force of the motor unit is decelerated by the reduction unit and the wheel bearing unit is provided. An in-wheel motor drive device for transmitting to the motor, wherein the speed reduction part has an eccentric part, a speed reducer input shaft connected to the rotating shaft of the motor part, and a speed reducer connected to the wheel bearing part An output shaft, a rolling bearing provided on the outer periphery of the eccentric portion of the speed reducer input shaft, and rotatably held on the outer periphery of the eccentric portion via the rolling bearing, with the rotation of the speed reducer input shaft A revolving member that performs a revolving motion around the rotation axis; an outer peripheral engagement member that engages with an outer peripheral portion of the revolving member to cause the revolving member to rotate; and Motion conversion to convert to rotational motion of reducer output shaft And a structure, characterized in that the initial radial internal clearance of the rolling bearing and 15 ~ 60 [mu] m.

Thus, in the rolling bearing arranged between the eccentric part of the reduction gear output shaft and the revolution member, the initial radial internal clearance is set to 15 μm or more, so that the temperature rise of the entire bearing and the inner raceway surface of the bearing Even considering the temperature difference on the outer raceway surface, the radial internal clearance (operational clearance) during operation does not become negative, and early peeling and seizure can be prevented. Further, in the above-described rolling bearing, the initial radial internal clearance is set to 60 μm or less, so that the generation of sound and vibration due to an excessive positive clearance can be suppressed. The initial radial internal clearance of the rolling bearing means the radial internal clearance (diameter clearance) of the rolling bearing alone before assembling other members at room temperature.

The bearing ring (member having a raceway surface) constituting the rolling bearing is made of bearing steel or carburized steel, is subjected to carbonitriding, has a surface austenite of 25 to 50%, and has a core. The residual austenite in the part is preferably 15 to 20%. In this way, it is possible to improve the rolling fatigue life and to suppress the generation and development of cracks due to retained austenite, thereby improving the durability (longer life) of the in-wheel motor drive device. be able to. Further, in order to ensure the same life, it is possible to reduce the thickness of the bearing ring as compared to the case where the bearing ring not having the above configuration is employed. Therefore, the in-wheel motor drive device can be reduced in size and weight through, for example, downsizing the rolling bearing in the radial direction. The surface layer is a region obtained by nitriding to the depth affected by the surface pressure of the rolling element on the surface of the race (the raceway surface), and the core portion is formed with a nitride layer deeper than the surface layer. Say no area.

Moreover, it is preferable that the bearing ring constituting the rolling bearing is made of bearing steel containing Si of 0.35 wt% or more and Mn of 0.50 wt% or more. Si contributes to the improvement of the amount of retained austenite in the surface layer part by increasing the stability of austenite and Mn ensuring the hardenability.

In addition, for the same reason as described above, the rolling elements constituting the rolling bearing are preferably made of bearing steel, subjected to carbonitriding, and the amount of retained austenite in the surface layer portion is preferably 20 to 35%.

As described above, according to the present invention, it is possible to improve the durability of the in-wheel motor drive device and to prevent the occurrence of vibration and abnormal noise.

It is sectional drawing which shows the in-wheel motor drive device which concerns on one Embodiment of this invention. It is an enlarged view of the deceleration part of the in-wheel motor drive device shown in FIG. 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 sectional drawing of a rotary pump. 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 riding comfort 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. In addition, the casing 22 of this embodiment is comprised by fastening the part which accommodated the motor part A, and the part which accommodated the deceleration part B with the volt | bolt.

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 capable of rotating 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”). The bearings are rotatably supported with respect to the casing 22 by rolling bearings (deep groove ball bearings in the illustrated example) 36, 36 disposed in the respective portions.

The wheel bearing portion C includes a hub ring 32 having a hollow structure and a wheel bearing 33 that rotatably supports the hub ring 32 with respect to the casing 22. The hub wheel 32 extends radially outward from the cylindrical hollow portion 32a connected to the shaft portion 28b of the reduction gear output shaft 28 constituting the speed reduction portion B, and the end portion on the outboard side of the hollow portion 32a. The flange portion 32b is integrally provided. The rear wheel 14 (see FIGS. 6 and 7) is connected and fixed to the flange portion 32b by a bolt 32c. Accordingly, when the hub wheel 32 rotates, the rear wheel 14 rotates integrally with the hub wheel 32.

The wheel bearing 33 is a double row angular contact ball bearing. Specifically, one inner raceway surface 33 f is directly formed on the outer peripheral surface of the hub wheel 32, and the other inner side is formed on the outer peripheral surface of the inner ring 33 a fitted to the small diameter step portion of the outer peripheral surface of the hub wheel 32. A raceway surface is formed. A double-row outer raceway surface is formed on the inner peripheral surface of the outer ring 33 b fitted and fixed to the inner peripheral surface of the casing 22. A plurality of balls 33c are arranged between the double row inner raceway surface and the double row outer raceway surface. The balls 33c in each row are held in a state of being separated in the circumferential direction by a holder 33d. Both end portions in the axial direction of the wheel bearing 33 are sealed with seal members 33e.

As shown in an enlarged view in FIG. 2, the speed reduction unit B is decelerated by the speed reducer input shaft 25 that is rotationally driven by the motor unit A, a speed reduction mechanism that decelerates the rotation of the speed reducer input shaft 25, and a speed reduction mechanism. A reduction gear output shaft 28 for transmitting the rotation of the reduction gear input shaft 25 to the hub wheel 32 of the wheel bearing portion C. The reduction gear input shaft 25 and the reduction gear output shaft 28 are arranged coaxially.

The reduction gear input shaft 25 has a spline 25g (including serrations; the same applies hereinafter) formed on the outer periphery of the end portion on the inboard side. By fitting the spline 25g of the speed reducer input shaft 25 to a spline formed on the inner periphery of the end portion on the outboard side of the motor rotational shaft 24, the speed reducer input shaft 25 and the motor rotational shaft 24 are connected.

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. One rolling bearing 37a supports a substantially central portion of the reduction gear input shaft 25 in the axial direction, and the other rolling bearing 37b supports an end portion of the reduction gear input shaft 25 on the outboard side.

Eccentric portions

25 a and 25 b 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. In the present embodiment, the

eccentric portions

25a and 25b are formed in a disc shape whose center is offset from the rotation center of the speed reducer input shaft 25 (see FIG. 3). In the present embodiment, the

eccentric portions

25 a and 25 b are provided integrally with the speed reducer input shaft 25. The

eccentric portions

25a and 25b are provided with a phase difference of 180 ° in order to cancel the centrifugal force due to the eccentric motion.

The counterweight 29 is fixed to the speed reducer input shaft 25 (see FIG. 2). The counterweight 29 has a substantially fan shape and is fixed to the outer peripheral surface of the speed reducer input shaft 25. The counterweight 29 changes the phase of the

eccentric portions

25a, 25b and 180 ° to positions adjacent to the

eccentric portions

25a, 25b in order to cancel out the unbalanced inertial couple (unbalance) caused by the rotation of the

curved plates

26a, 26b. Arranged.

The reduction gear output shaft 28 has a shaft portion 28b and a flange portion 28a. The flange portion 28a has a hole portion (through hole in the illustrated example) in which an end portion on the outboard side of the inner pin 31 described later is fitted and fixed. The hole portion serves as a rotational axis of the speed reducer output shaft 28. A plurality are formed at equal intervals on the circumference of the center. The shaft portion 28b is connected to the hub wheel 32 constituting the wheel bearing portion C by spline fitting. The reduction gear output shaft 28 is rotatably supported by the outer pin housing 60 via rolling

bearings

48 and 48 that are spaced apart from each other in two axial directions.

The speed reduction mechanism (cycloid speed reducer) rotates on the outer periphery of the

eccentric portions

25a and 25b via the rolling

bearings

40 and 40 disposed on the outer periphery of the

eccentric portions

25a and 25b of the speed reducer input shaft 25.

Curved plates

26a and 26b that are freely held, a plurality of outer pins 27 fixed to the outer pin housing 60, and a motion conversion mechanism that converts the rotational motion of the

curved plates

26a and 26b to the rotational motion of the reducer output shaft 28. With.

As shown in FIG. 3, the outer peripheral surface of the curved plate 26a has a corrugated shape composed of a trochoidal curve such as an epitrochoid. A plurality of axial through holes 30a are formed in the curved plate 26a. The plurality of through holes 30a are provided at equal intervals on a circumference centered on the rotation axis of the curved plate 26a (centers of the

eccentric portions

25a and 25b). One inner pin 31 is inserted into each through-hole 30a. An axial through hole 30b is formed in the axial center of the curved plate 26a. A rolling bearing 40 and an eccentric portion 25a are disposed on the inner periphery of the through hole 30b.

As shown in the enlarged view of FIG. 2 and FIG. 3, the rolling bearing 40 includes an inner raceway surface 42, an outer raceway surface 43, and a plurality of cylindrical rollers as rolling elements disposed between the raceway surfaces 42 and 43. 44 and a cylindrical roller bearing provided with a retainer 45 for holding a plurality of cylindrical rollers 44. In the illustrated example, the inner raceway surface 42 is formed on the outer circumference surface of the inner ring 41 fitted and fixed to the outer circumference surface of the eccentric portion 25a, and the outer raceway surface 43 is directly on the inner circumference surface of the through hole 30b of the curved plate 26a. It is formed. The inner ring 41 has

flange portions

46 and 46 that protrude from the both end portions in the axial direction of the inner raceway surface 42 toward the outer diameter side.

Although the detailed description is omitted, the curved plate 26b has a structure similar to that of the curved plate 26a, and an eccentric portion via a rolling bearing 40 similar to the rolling bearing 40 that supports the curved plate 26a. 25b is rotatably held.

As shown in FIG. 3, 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. When the

curved plates

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

curved plates

26a and 26b engage with the outer pins 27, and the

curved plates

26a and 26b are caused to rotate. Let As shown in FIG. 2, each outer pin 27 is rotatably held by an outer pin housing 60 fixed to the casing 22 via a pair of

needle roller bearings

61, 61 disposed at both ends in the axial direction. Has been.

2 and 3, the motion conversion mechanism includes a plurality of inner pins 31 fixed to the flange portion 28a of the reduction gear output shaft 28, and a plurality of through holes 30a provided in the

curved plates

26a and 26b. Consists of. 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 fixed to the hole. When the through holes 30a of the

curved plates

26a and 26b and the inner pin 31 are engaged in the circumferential direction, the rotational motion of the

curved plates

26a and 26b is converted into the rotational motion of the speed reducer output shaft 28. In order to reduce the frictional resistance between the inner pin 31 and the

curved plates

26a, 26b at this time, a needle roller bearing 31a is provided on the outer periphery of the inner pin 31. The inner diameter dimension of the through hole 30a refers to the outer diameter dimension of the inner pin 31 ("maximum outer diameter including the needle roller bearing 31a") so that the revolving motion of the

curved plates

26a and 26b is not hindered by the inner pin 31. It is set larger than the same).

As shown in FIG. 2, the deceleration unit B further includes a stabilizer 31 b. The stabilizer 31b integrally includes an annular ring portion 31c and a cylindrical portion 31d extending from the inner peripheral end of the annular portion 31c to the inboard side. The end portion on the inboard side of each inner pin 31 is fixed to the annular portion 31c. As a result, when the motor part A is driven (when the speed reducer input shaft 25 is rotated), all the loads applied to some of the inner pins 31 from the

curved plates

26a, 26b are transmitted via the stabilizer 31b and the flange part 28a. The inner pin 31 is supported.

Here, the state of the load acting on the curved plate 26a, the rolling bearing 40, and the speed reducer 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 similar to that described below also acts on the curved plate 26b.

The axis O ₂ of the eccentric portion 25 a provided on the speed reducer input shaft 25 is eccentric from the axis O of the speed reducer input shaft 25 by the amount of eccentricity e. Eccentric portion 25a, so that rotatably holds the curved plate 26a via a rolling bearing 40, the axis _{O 2} is also the axis of the curved plate 26a. The outer periphery of the curved plate 26a is formed in a corrugated curve, and has corrugated recesses 34 that are recessed toward the inner diameter side 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. 4, 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 are counterclockwise centered on the axis O. Do the revolving movement around. Thereby, the recessed part 34 of the outer periphery of the curve board 26a is sequentially engaged with the outer pin 27 in the circumferential direction. As a result, the curved plate 26a receives a load Fi as indicated by an arrow in the drawing from the plurality of outer pins 27, and rotates clockwise. At this time, as the speed reducer input shaft 25 rotates once, the curved plate 26a revolves once and rotates clockwise by one pitch of the recess 34.

Then, when the through hole 30a of the curved plate 26a and the inner pin 31 are engaged in the circumferential direction, the rotational motion of the curved plate 26a is transmitted to the reduction gear output shaft 28, and the reduction gear output shaft 28 rotates clockwise. To do. 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 direction of the resultant force Fs varies depending on geometrical conditions such as the waveform shape of the outer peripheral portion of the curved plate 26a, the number of the concave portions 34, and the influence of centrifugal force. 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 axis O ₂ and the resultant force Fs varies in a range of approximately 30 ° to 60 °. . The directions and magnitudes of the loads Fi and Fj fluctuate while the reduction gear input shaft 25 makes one rotation (360 °), and as a result, the direction and magnitude of the resultant force Fs acting on the reduction gear input shaft 25 also fluctuates. To do.

For this reason, when the motor unit A is driven, the rolling bearing (cylindrical roller bearing) 40 that supports the

curved plates

26a and 26b receives a radial load and a moment load that vary in the direction and size of the load in addition to the high-speed rotation. Will be loaded. As a result, in addition to the temperature of the rolling bearing 40 significantly increasing, the temperature difference between the inner and outer rings of the rolling bearing 40 (in this embodiment, the inner ring 41 and the

curved plates

26a and 26b) may become larger than expected. found. To cope with this, even when the initial clearance δ0 of the rolling bearing 40 is set, if the amount of the initial clearance δ0 is as small as possible, the operating clearance becomes negative and heat is generated, resulting in early separation and seizure. There was found.

In order to avoid such a problem, the value of the initial clearance δ0 of the rolling bearing 40 may be increased. However, if the value of the initial clearance δ0 is excessive, various values arranged in the speed reduction portion B are used. Vibration due to the rotation of the rotating body may occur, or abnormal noise or vibration may occur due to the contact between the

curved plates

26a and 26b and the outer pin 27 and the inner pin 31. It has been found that the in-wheel motor drive device 21 equipped with the cycloid reduction gear is sensitive to these abnormal sounds and vibrations. In addition, since the special condition of the in-wheel motor drive device 21 that is the unsprung weight is superimposed, it is difficult to attenuate the abnormal noise and vibration, which adversely affects the NVH (Noise, Vibration, Harshness) characteristics, and driving. It has also been found to cause discomfort to passengers and passengers.

As described above, the rolling bearing 40 of the in-wheel motor drive device 21 of the present embodiment is used in a special environment involving various factors. Therefore, in the present embodiment, the initial radial internal clearance (initial clearance δ0) of the rolling bearing 40 is set to 15 to 60 μm, preferably 15 to 45 μm, in the speed reduction portion B of the in-wheel motor drive device 21. As a result, heat generation and seizure of the rolling bearing 40 can be prevented even under conditions such as fitting (press fitting) with the speed reducer input shaft 25, temperature rise, and temperature difference between the inner and outer rings, and noise and vibration can be prevented. It is possible to minimize the degradation of the NVH characteristics due to the influence of the effect within the processable range. Thereby, in spite of special conditions such as an in-wheel motor drive device and a cycloid reducer that are unsprung weights, it is possible to realize an in-wheel motor drive device that suppresses abnormal noise and vibration and has excellent NVH characteristics. . In the present embodiment, the rolling bearing 40 includes an outer ring (

curved plates

26 a and 26 b), an inner ring 41, a cylindrical roller 44, and a cage 45, and the speed reducer input shaft 25 is inserted into the inner periphery of the inner ring 41. The radial internal clearance of the previous rolling bearing 40 alone at room temperature is the initial clearance δ0.

Further, in this embodiment, the bearing rings (inner ring 41 and

curved plates

26a and 26b) of the rolling bearing 40 are made of bearing steel or carburized steel. As the bearing steel, for example, a high carbon chromium bearing steel specified in JIS G 4805 can be used, and in particular, SUJ3 and SUJ5 containing 0.35 wt% or more of Si and 0.50 wt% or more of Mn are preferable. Can be used. Moreover, as carburized steel, SCM415, SCM420, SCr420 etc. can be used, for example. In this embodiment, the inner ring 41 and the

curved plates

26a and 26b are made of SUJ3.

After carbonitriding the bearing ring formed of the above materials, a quenching and tempering treatment is performed, so that nitrogen is diffused into the surface layer portion (especially the raceway surface) of the bearing ring and 25 to 50% residual Austenite was kept stable. At this time, the retained austenite at the core of the raceway is 15 to 20%.

Further, in this embodiment, the cylindrical roller 44 of the rolling bearing 40 is made of bearing steel and subjected to carbonitriding treatment, and nitrogen is diffused in these surface layers to stably retain the retained austenite. Specific examples of the bearing steel that can be used as the material of the cylindrical roller 44 are the same as those described above, and thus a duplicate description is omitted. In the present embodiment, the cylindrical roller 44 is made of SUJ3. Further, by making the heat treatment condition after the carbonitriding treatment of the cylindrical roller 44 different from the heat treatment condition after the carbonitriding treatment of the raceway ring, the ratio of retained austenite in the surface layer portion of the cylindrical roller 44 is slightly lowered (20 to 35%). ).

Because of the above materials and heat treatment, the retained austenite reduces crack sensitivity, so the corrected rated life (ISO 281) can be improved, and the rolling bearing 40 has a long life. In other words, in order to ensure the equivalent life, the bearing ring (inner ring 41) is made thinner and the rolling bearing 40 has a diameter compared to the case where a rolling bearing (race ring or rolling element) not having the above-described configuration is employed. It can be downsized in the direction. In this way, through the improvement and miniaturization of the rolling bearing 40, the in-wheel motor drive device 21 that is rich in durability and that is small and light can be realized. In particular, by forming the bearing ring with a high carbon chromium bearing steel containing 0.35 wt% or more of Si and 0.50 wt% or more of Mn, the hardenability is improved, so that retained austenite is easily obtained.

In addition, the material and heat treatment method of the inner ring 41, the

curved plates

26a and 26b, and the cylindrical roller 44 constituting the rolling bearing 40 are not limited to the above. For example, the cylindrical roller 44 may be heat-treated under the same conditions as the race. Further, some members of the inner ring 41, the

curved plates

26a and 26b, and the cylindrical roller 44 constituting the rolling bearing 40 are made of bearing steel, and the amount of retained austenite in the surface layer portion is set in the above range by carbonitriding. It is good also as a structure.

Next, the lubrication mechanism will be explained. The lubricating mechanism supplies lubricating oil to various parts of the motor part A and the speed reducing part B. As shown in FIGS. 1 and 2, the lubricating

oil paths

24a and 24b provided on the motor rotating shaft 24, and the speed reducing part are provided. Lubricating

oil passages

25c, 25d, 25e provided on the machine input shaft 25, a lubricating oil passage (not shown) provided on the stabilizer 31b, a lubricating oil passage (not shown) provided on the inner pin 31, and the casing 22 A lubricating oil discharge port 22b, a lubricating oil reservoir 22d, a lubricating oil passage 22e, a lubricating oil passage 49, and a rotary pump 51 disposed in the casing 22 for pumping the lubricating oil to the lubricating oil passage 49 of the casing 22. Is mainly provided. 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. A lubricating oil passage 25c extending in the axial direction inside the reduction gear input shaft 25 is connected to the lubricating oil passage 24a. The lubricating oil passage 25d extends radially from the lubricating oil passage 25c toward the outer peripheral surface of the speed reducer input shaft 25, and the outer diameter end of the lubricating oil passage 25d in the illustrated example is the outer peripheral surface of the

eccentric portions

25a and 25b. Is open. 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 end face on the outboard side of the reduction gear input shaft 25. The formation position of the lubricating oil passage 25d extending in the radial direction is 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 in the speed reduction part B, and is provided in at least one location 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 49. 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 lubricating oil path 49, and the like. The lubricating oil reservoir 22d has a function of temporarily storing the lubricating oil. The lubricating oil passage 49 is connected to the axial oil passage 49a extending in the axial direction inside the casing 22 and the end portions on the outboard side and the inboard side of the axial oil passage 49a and extends in the radial direction. It is composed of

paths

49b and 49c.

The rotary pump 51 is provided between the lubricating oil passage 22e and the lubricating oil passage 49 connected to the lubricating oil reservoir 22d. 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. 5, the rotary pump 51 includes an inner rotor 52 that rotates using the rotation of the reducer 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 49b of the lubricating oil passage 49. . 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. Therefore, the volume of the pump chamber 54 changes continuously. As a result, 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 49 b of the lubricating oil passage 49.

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, as shown in FIG. 1, a part of the lubricating oil flowing through 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. It is discharged from the outer diameter side opening of the lubricating oil passage 24b. This lubricating oil is supplied to the rotor 23b and the stator 23a in the motor part A. Further, a part of the lubricating oil flowing through the lubricating oil passage 49 oozes out from between the casing 22 and the motor rotating shaft 24, and this lubricating oil supports the inboard side end of the motor rotating shaft 24. 36. Further, a part of the lubricating oil discharged from the lubricating oil passage 24 b travels down the inner wall surface on the outboard side of the portion of the casing 22 in which the motor part A is accommodated, and this lubricating oil passes through the motor rotating shaft 24. It is supplied to a rolling bearing 36 that supports the end on the outboard side.

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 and 25e (see FIG. 2) and is supplied to various places in the speed reduction portion B mainly by centrifugal force. And the lubricating oil which reached | attained the inner wall surface of the casing 22 is discharged | emitted from the lubricating oil discharge port 22b, and is stored by the lubricating oil storage part 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 operating 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. Rotate to

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 periphery 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 the resistance is reduced, the power transmission efficiency in the speed reduction portion B is also improved from this point.

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 embodiment, the inner race surface 42 of the rolling bearing (cylindrical roller bearing) 40 that rotatably holds the

curved plates

26 a and 26 b is fixed to the

eccentric portions

25 a and 25 b of the speed reducer input shaft 25. Although the case where it provided in the outer peripheral surface of 41 was shown, it does not restrict to this, For example, you may abbreviate | omit the inner ring | wheel 41 by forming the inner track surface 42 directly in the outer peripheral surface of the eccentric part 25a. If it does in this way, the rolling bearing 40 and by extension, the deceleration part B can be further reduced in weight and compactness.

Further, in the above embodiment, the outer raceway surface 43 of the rolling bearing 40 is directly provided on the inner peripheral surface of the through hole 30b of the

curved plates

26a and 26b. May be provided separately, and the outer peripheral surface of the outer ring may be fixed to the inner peripheral surface of the through hole 30b of the

curved plates

26a, 26b.

Moreover, in said embodiment, although the example of the cycloid pump was shown as the rotary pump 51, not only this but the rotary pump driven using the rotation of the reduction gear output shaft 28 is employable. . Furthermore, the rotary pump 51 may be omitted, and the lubricating oil may be circulated only by centrifugal force.

In the above-described embodiment, an example in which two

curved plates

26a and 26b of the deceleration unit B are provided with a 180 ° phase change is shown. However, the number of curved plates can be arbitrarily set, for example, When three curved plates are provided, it is preferable to change the phase by 120 °.

In the above embodiment, the motion conversion mechanism is configured by the inner pin 31 fixed to the reduction gear output shaft 28 and the through hole 30a provided in the

curved plates

26a and 26b. Without being limited thereto, any configuration capable of transmitting the rotation of the speed reduction portion B to the hub wheel 32 can be employed. For example, it may be a motion conversion mechanism composed of an inner pin fixed to a curved plate and a hole formed in a reduction gear output shaft.

In the above embodiment, a case has been described in which electric power is supplied to the motor unit A to drive the motor unit, and power from the motor unit A is transmitted to the drive wheels 14. When decelerating or going down a hill, the power from the drive wheel 14 side is converted into high-rotation low-torque rotation by the deceleration unit B and transmitted to the motor unit A. Good. Furthermore, the electric power generated here may be stored in a battery, and the motor unit A may be driven later, or used for the operation of other electric devices provided in the vehicle.

In the present embodiment, an example in which a radial gap motor is adopted as the motor unit A has been shown, but the present invention is not limited to this, and a motor having an arbitrary configuration can be applied. For example, an axial gap motor in which a stator and a rotor are opposed to each other via an axial gap may be employed.

Furthermore, although the electric vehicle 11 shown in FIG. 6 showed the example which used the rear wheel 14 as the driving wheel, it is not restricted to this, The front wheel 13 may be used as a driving wheel and may be a four-wheel driving vehicle. . In the present specification, “electric vehicle” is a concept including all vehicles that obtain driving force from electric power, and should be understood as including, 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.

21 In-wheel motor drive device 22 Casing 24 Motor rotating shaft 25

Reducer input shaft

25a, 25b

Eccentric part

26a, 26b Curved plate (revolving member)
27 Outer pin (outer peripheral engagement member)
28 Reduction gear output shaft 31 Inner pin 33 Wheel bearing 40 Rolling bearing A Motor part B Reduction part C Wheel bearing part

Claims

An in-wheel motor drive device comprising a motor part, a speed reduction part, and a wheel bearing part, wherein the rotational driving force of the motor part is decelerated by the speed reduction part and transmitted to the wheel bearing part,
The speed reduction part has an eccentric part, a speed reducer input shaft connected to the rotating shaft of the motor part, a speed reducer output shaft connected to the wheel bearing part, and an eccentric part of the speed reducer input shaft A rolling bearing provided on the outer periphery of the shaft, and is rotatably held on the outer periphery of the eccentric portion via the rolling bearing, and performs a revolving motion centering on the rotating shaft as the speed reducer input shaft rotates. A revolving member, an outer peripheral engaging member that engages with an outer peripheral portion of the revolving member and causes the revolving member to generate a revolving motion, and a motion conversion that converts the revolving motion of the revolving member into a rotational motion of the reducer output shaft. With a mechanism,
An in-wheel motor drive device characterized in that an initial radial internal clearance of the rolling bearing is 15 to 60 μm.
The rolling bearing raceway ring is made of bearing steel or carburized steel, carbonitrided, surface austenite is 25 to 50%, and core austenite is 15 to 20%. Item 2. The in-wheel motor drive device according to Item 1.
The in-wheel motor drive device according to claim 1 or 2, wherein the race is made of bearing steel containing Si of 0.35 wt% or more and Mn of 0.50 wt% or more.
The in-wheel motor drive device according to any one of claims 1 to 3, wherein the rolling elements of the rolling bearing are made of bearing steel, are subjected to carbonitriding, and the residual austenite of the surface layer is 20 to 35%.