JP2020152141A - In-wheel motor driving device - Google Patents

Abstract

To improve durability and quietness of an in-wheel motor driving device that uses a parallel shaft reduction gear.SOLUTION: An in-wheel motor driving device 21 uses a parallel shaft reduction gear 30 with respective gears composed of helical gears in a reduction gear part B which reduces rotation of an electric motor unit A and outputs the rotation to a wheel bearing part C. One or both of two gears 31, 32 forming a meshing part M1 is/are different in tooth thickness at one end and the other end in a tooth-trace direction from each other due to application of tooth surface amending. One of the one end and the other end that has a relatively smaller tooth thickness is positioned on a side of a decreasing distance between the meshing surfaces of the two gears 31 and 32 in response to occurrence of an inclination in an intermediate gear shaft 36 with a moment of an axial load occurring in the meshing part M1 in driving of the electric motor unit A.SELECTED DRAWING: Figure 5

Description

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

Since the in-wheel motor drive device is used with the entire device housed inside the wheel, its weight and size affect the unsprung weight (running performance) of the vehicle and the size of the cabin space. It is desirable to be as lightweight and compact as possible. On the other hand, the in-wheel motor drive device requires a large torque to drive the wheels. Therefore, in the in-wheel motor drive device, the rotation of the electric motor is decelerated between the electric motor that generates the driving force and the wheel bearing that rotatably supports the wheel, and the deceleration is output to the wheel bearing. It is common to install a machine. For example, in the in-wheel motor drive device described in Patent Documents 1 to 3 below, a multi-stage reduction gear reduction gear (parallel) having an input gear shaft, an intermediate gear shaft, and an output gear shaft arranged in parallel with each other. Axis reducer) is adopted.

In Patent Document 3, a helical gear having tooth streaks in the shape of a spiral line is adopted as the gear provided on each gear shaft. In this case, the number of teeth that mesh with each other increases at the same time, and the tooth contact is dispersed, which is advantageous in realizing a speed reducer that is quiet and has a small torque fluctuation. However, when helical gears are used, not only radial load but also axial load (moment load due to axial load) acts on each gear shaft due to the meshing of the gears, so the gear shaft (especially the intermediate gear shaft) Tilt is likely to occur. When the intermediate gear shaft is tilted and one-sided contact of the gear as schematically shown in FIG. 11A occurs due to this tilt (in the same figure, the input gear and the input side intermediate gear that mesh with each other are out. (Example is the case where one-sided contact occurs at the end on the board side), tooth wear and breakage are likely to occur, which adversely affects the durability and sound vibration performance of the reducer. One-sided contact between gears can be achieved by applying crowning (tooth streak crowning) to the tooth surface of the gear as a tooth surface modification, for example, as described in FIG. 6 (b) of Patent Document 4 below. It can be prevented.

JP-A-2017-65306 JP-A-2017-160961 JP-A-2018-53927 Japanese Unexamined Patent Publication No. 2013-72528

By the way, in the multi-stage speed reduction type parallel shaft speed reducer incorporated in the in-wheel motor drive device, the layout of the gear shaft is adjusted in order to make it compact. For example, in Patent Documents 1 to 3, a narrowing angle formed by a straight line connecting the rotation centers of two gear shafts forming a meshing portion between gears (in the case of a two-stage reduction type parallel shaft speed reducer, an input gear). The angle formed by the straight line connecting the shaft and the center of rotation of the intermediate gear shaft and the straight line connecting the center of rotation of the intermediate gear shaft and the output gear shaft. In the present specification, this is hereinafter referred to as "the arrangement angle of the gear shaft". ) Is approximately 60 ° to 110 °, and each gear shaft is arranged.

However, as verified by the present inventors, when the arrangement angle of the gear shaft is set within the above angle range, the forces that tilt the gear shaft generated at each meshing portion influence each other, and the gear shaft Since a large misalignment occurs due to the inclination becoming a staggered error as a component perpendicular to the gear axis, a single arc tooth streak crowning (in the tooth streak direction) as shown in Patent Document 4 occurs. It has been found that it is not possible to appropriately prevent the occurrence of one-sided contact, as schematically shown in FIG. 11 (b), only by performing crowning) in which the amount of drops at one end and the other end is the same. For example, it is considered that the occurrence of one-sided contact can be prevented as much as possible by increasing the curvature of crowning in accordance with the condition where the inclination (misalignment) of the gear shaft is maximized. However, if the curvature of the crowning is increased, the tooth contact is reduced and the actual meshing rate is lowered under the condition that the misalignment is small, so that problems such as tooth breakage and generation of abnormal noise / vibration are likely to occur.

Therefore, the present invention is an in-wheel motor drive in which a multi-stage speed reduction type parallel shaft speed reducer in which each gear is composed of helical gears is used for the speed reducer unit that decelerates the rotation of the electric motor unit and outputs the speed. It is an object of the present invention to provide an in-wheel motor drive device which can prevent one-sided contact at a meshing portion between gears and has excellent durability and sound vibration performance.

The present invention, which was devised to achieve the above object, has an electric motor unit for generating a driving force, and an input gear shaft, an intermediate gear shaft, and an output gear shaft arranged in parallel with each other, and the input gear shaft has an input gear shaft. In a vehicle drive device that includes a speed reducer unit that decelerates the input rotation of the electric motor unit in two or more stages and outputs it, and the gears provided on each gear shaft are helical gears. One or both of the two gears that mesh with each other in the portion have different tooth thicknesses at one end and the other end in the tooth streak direction due to the tooth surface modification, and the one end and the other Of the ends, the one with a relatively small tooth thickness has the above two gears as the intermediate gear shaft is tilted due to the moment of the axial load generated in the meshing portion between the gears when the electric motor portion is driven. It is characterized in that it is arranged on the side where the distance between the meshing tooth surfaces is shortened.

In a multi-stage reduction type parallel shaft reducer in which each gear is composed of helical gears, one-sided contact occurs in the meshing part between the gears because of the moment of the axial load generated in the meshing part between the gears. This is the side where the distance between the meshing tooth surfaces of the two gears that mesh with each other decreases as the tilt (misalignment) occurs. In addition, the degree of misalignment can be estimated with relatively high accuracy at the design stage based on the twisting direction of the gear teeth and the specifications of the gear. Therefore, for either or both of the two gears that mesh with each other, the tooth thickness is made different from each other at one end and the other end in the tooth streak direction by modifying the tooth surface based on the above estimation result. If the one end and the other end having a relatively small tooth thickness are arranged on the side where the distance between the tooth surfaces that mesh with each other decreases as the intermediate gear shaft tilts, the intermediate gear shaft Regardless of the amount of inclination (misalignment), it is possible to realize an appropriate meshing state at the meshing portion between the gears. As a result, it is possible to realize a high-quality parallel-axis speed reducer having excellent durability, quietness (sound vibration performance), and torque transmission performance, and by extension, an in-wheel motor drive device.

In order to reduce the labor and cost required for tooth surface modification, tooth surface modification is performed only on one of the two gears that mesh with each other (the tooth thickness is mutually adjusted at one end and the other end in the tooth streak direction). It is preferable that the tooth surface is modified only on the gear having the smaller number of teeth (the one having the smaller diameter) among the two gears that mesh with each other.

In order to prevent the occurrence of one-sided contact as much as possible, first, as a tooth surface modification for one or both of the two gears that mesh with each other, a tapered thinning along the tooth streak direction is performed. It is preferable to adopt it. One or both of the two gears that mesh with each other are further subjected to either one or both of the crowning along the tooth streak direction (tooth streak crowning) and the tooth profile direction crowning (tooth profile crowning) as the tooth surface modification. You may do so.

From the above, according to the present invention, in the in-wheel motor drive device in which each gear employs a multi-stage speed reduction type parallel shaft speed reducer in which each gear is composed of helical gears, the gears mesh with each other. It is possible to effectively prevent one-sided contact from occurring in the portion. This makes it possible to provide an in-wheel motor drive device having excellent durability and sound vibration performance.

It is sectional drawing of the in-wheel motor drive device which concerns on 1st Embodiment of this invention. It is the schematic when the in-wheel motor drive device of FIG. 1 is seen from the outboard side. It is a figure for demonstrating the twisting direction of a gear (the helical gear) provided in the reduction gear part shown in FIG. 1 and the directionality of an axial load generated by meshing of gears. It is the schematic perspective view when the reduction gear part shown in FIG. 1 is seen from the outboard side. FIGS. (A) to (d) are schematic views of the meshing portion between the input gear and the input side intermediate gear in the in-wheel motor drive device of FIG. It is a schematic perspective view which shows an example of tooth profile crowning. FIGS. (A) to (d) are schematic views of the meshing portion between the output side intermediate gear and the output gear in the in-wheel motor drive device of FIG. It is a figure for demonstrating the direction | direction of the axial load generated by the twisting direction of the helical gear provided in the reduction gear part, and the meshing of gears in the in-wheel motor drive device which concerns on 2nd Embodiment of this invention. .. It is a schematic plan view of an electric vehicle equipped with an in-wheel motor drive device. It is a rear sectional view of the electric vehicle shown in FIG. (A) and (b) are schematic views for explaining the problems of the prior art.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, an outline of the electric vehicle 11 equipped with an in-wheel motor drive device, which is a kind of vehicle drive device, will be described with reference to FIGS. 9 and 10. As shown in FIG. 9, the electric vehicle 11 drives the chassis 12, the pair of front wheels 13 that function as steering wheels, the pair of rear wheels 14 that function as driving wheels, and the left and right rear wheels 14, respectively. A wheel motor drive device 21 is provided. As shown in FIG. 10, 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 the suspension device 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 road surface by struts including a coil spring and a shock absorber to suppress vibrations of the chassis 12. The suspension device 16 is preferably 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, but other suspensions. The method may be adopted.

In the electric vehicle 11, an in-wheel motor drive device 21 for rotationally driving each of the left and right rear wheels 14 is incorporated inside the left and right wheel housings 15, so that a motor, a drive shaft, a differential device, 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 rotations of the left and right rear wheels 14 can be controlled respectively.

As described above, the in-wheel motor drive device 21 includes not only a rear-wheel drive type electric vehicle 11 having a rear wheel 14 as a drive wheel, but also a front-wheel drive type electric vehicle 11 having a front wheel 13 as a drive wheel. It can also be applied to a four-wheel drive type electric vehicle in which both the front wheels 13 and the rear wheels 14 are drive wheels.

In order to improve the running stability and NVH characteristics of the electric vehicle 11, it is necessary to suppress the unsprung weight. Further, in order to expand the cabin space of the electric vehicle 11, it is necessary to make the in-wheel motor drive device 21 as compact as possible. Therefore, the in-wheel motor drive device 21 as described below is adopted.

FIG. 1 shows a cross section of an in-wheel motor drive device 21 according to the first embodiment of the present invention, more specifically, an in-wheel motor drive device 21 that rotationally drives the left drive wheel of an electric vehicle 11 (see FIG. 9). The figure is shown. The in-wheel motor drive device 21 has an electric motor unit A that generates a driving force for driving the wheels, a speed reducer unit B that decelerates and outputs the rotation of the electric motor unit A, and outputs of the speed reducer unit B. Is provided with a wheel bearing portion C that transmits the above to the drive wheels. The electric motor portion A and the speed reducer portion B are housed in the casing 22, and the wheel bearing portion C is attached to the casing 22. In the following description, the in-wheel motor drive device 21 is mounted in the wheel housing 15 (see FIG. 10), and the outer side in the vehicle width direction and the inner side in the vehicle width direction are the outboard side and the inboard side, respectively. Called the side. In FIG. 1, the left side of the paper surface is the outboard side, and the right side of the paper surface is the inboard side.

The electric motor unit A includes a tubular stator 23 fixed to the casing 22, a rotor 24 arranged on the inner circumference of the stator 23 via a radial gap (not shown), and a motor rotation in which the rotor 24 is mounted on the outer circumference. A radial gap type electric motor 26 having a shaft 25 is provided. The motor rotating shaft 25 is rotatably supported with respect to the casing 22 by rolling bearings 40 and 41 arranged at two positions apart from each other in the axial direction, and at a rotation speed of about 10,000 times per minute. It is rotatable. An axial gap type electric motor may be used for the electric motor unit A instead of the radial gap type.

As shown in FIG. 1, the speed reducer unit B includes an input gear shaft 35 having an input gear 31, an intermediate gear shaft 36 having an input side intermediate gear 32 and an output side intermediate gear 33, and an output gear having an output gear 34. A parallel shaft gear reducer (parallel shaft reducer) 30 is provided with a shaft 37 and the gear shafts 35 to 37 are arranged in parallel with each other. As shown in FIG. 2, in the parallel shaft speed reducer 30, the input gear 31 and the input side intermediate gear 32 mesh with each other, and the output side intermediate gear 33 and the output gear 34 mesh with each other. The number of teeth of the input side intermediate gear 32 is larger than the number of teeth of the input gear 31 and the output side intermediate gear 33, and the number of teeth of the output gear 34 is larger than the number of teeth of the output side intermediate gear 33. From this configuration, the parallel shaft speed reducer 30 reduces the rotation of the motor rotation shaft 25 in two stages and outputs the speed.

As shown in FIG. 1, the input gear shaft 35 is arranged coaxially with the motor rotating shaft 25, and is integrally rotatably connected to the motor rotating shaft 25 by spline fitting. The input gear shaft 35 is rotatably supported by rolling bearings 42 and 43, the intermediate gear shaft 36 is rotatably supported by rolling bearings 44 and 45, and the output gear shaft 37 is rotatably supported by rolling bearings 46 and 47 with respect to the casing 22. ..

As shown in FIGS. 3 and 4, the input gear 31, the intermediate gears 32, 33, and the output gear 34 all have tooth streaks of teeth 31a to 34a formed in a spiral line shape (tooth streaks). A helical gear (inclined with respect to the axial direction) is used. The helical gear has an advantage that the number of teeth meshed at the same time is large and the tooth contact is dispersed, so that the sound at the time of meshing is quiet and the torque fluctuation is small. Therefore, the use of helical gears is advantageous in realizing a parallel shaft reducer 30 that is quiet and has excellent torque transmission efficiency.

Since each of the gears 31 to 34 is composed of helical gears, the meshing portion M1 of the input gear 31 and the input side intermediate gear 32 and the output side intermediate gear 33 and the output while the in-wheel motor drive device 21 is being driven. Both a radial load and an axial load act on the meshing portion M2 of the gear 34. These radial and axial loads are mainly supported by rolling bearings 42-47 that support gear shafts 35-37. Therefore, for the rolling bearings 42 to 47, bearings capable of receiving both radial load and axial load, for example, deep groove ball bearings are used.

As shown in FIG. 1, in the present embodiment, the rolling bearing 44 that supports the end of the intermediate gear shaft 36 on the inboard side is more than the rolling bearing 45 that supports the end of the intermediate gear shaft 36 on the outboard side. A rolling bearing 47 having a large diameter, that is, having a large load capacity, and a rolling bearing 47 supporting the vicinity of the central portion in the axial direction of the output gear shaft 37, and a rolling bearing 46 supporting the end portion on the inboard side of the output gear shaft 37. The one with a larger diameter is used. In addition to this configuration, the input side intermediate gear 32 is partially lightened, and a rolling bearing 44 that supports the inboard side end of the intermediate gear shaft 36 is arranged on the inner circumference of the input side intermediate gear 32, and the output is output. The gear 34 is partially lightened, and a rolling bearing 47 that supports the vicinity of the central portion of the output gear shaft 37 in the axial direction is arranged on the inner circumference of the output gear 34. With this configuration, the reduction gear unit B (in-wheel motor drive device 21) is made compact in the axial direction while ensuring a high reduction ratio for the reduction gear 30.

From the viewpoint of making the speed reducer portion B compact in the radial direction, in the present embodiment, the gear shaft arrangement angle (the straight line connecting the input gear shaft 35 and the rotation centers O1 and O2 of the intermediate gear shaft 36, and the intermediate gear shaft 36 The gear shafts 35 to 37 are arranged so that the angle formed by the straight lines connecting the rotation centers O2 and O3 of the output gear shafts 37) is about 65 °. It should be noted that FIGS. 2 and 4 show the rotation directions of the gear shafts 35 to 37 when the electric vehicle 11 moves forward by receiving the driving force of the in-wheel motor drive device 21 (when the electric motor 26 runs in the forward rotation force). Are indicated by black arrows, and the rotation directions of the gear shafts 35 to 37 when the electric vehicle 11 receives the driving force of the in-wheel motor drive device 21 and moves backward (when the electric motor 26 is running the reverse force) are shown by white arrows. It is shown by.

In the present embodiment, the axial load input to the intermediate gear shaft 36 (the axial load acting on the input side intermediate gear 32 and the output side intermediate gear 33 act on the intermediate gear 33 when the electric motor 26 operates most frequently. The resultant force of the axial load acts on the rolling bearing 44 having a relatively large load capacity among the two rolling bearings 44 and 45 that support the intermediate gear shaft 36, and the axial load (output gear) input to the output gear shaft 37. The teeth 31a to 34a of the gears 31 to 34 so that the axial load acting on the 34) acts on the rolling bearing 47 having a relatively large load capacity among the two rolling bearings 46 and 47 supporting the output gear shaft 37. The twist direction of is set. Specifically, as shown in FIGS. 3 and 4, the twisting directions of the teeth 31a and 34a of the input gear 31 and the output gear 34 are so-called left-handed twists, and the twisting directions of the teeth 32a and 33a of the intermediate gears 32 and 33. Is a so-called right-handed twist.

In FIG. 3, for reference, the directions of the axial loads acting on the intermediate gears 32 and 33 when the electric motor 26 is driven in the forward direction are indicated by black arrows F1 and F2, respectively. The directions of the axial loads acting on the intermediate gears 32 and 33 are indicated by the white arrows F1'and F2', respectively. In FIG. 3, the lengths of the arrows F1 and F2 are different from each other. This is because the output side intermediate gear 33 is located on the rear stage side in the power transmission direction with respect to the input side intermediate gear 32 and exerts a large rotational torque. It means that the axial load acting on the output side intermediate gear 33 is larger than the axial load acting on the input side intermediate gear 32 because it is transmitted. The same applies to the arrows F1'and F2'.

As shown in FIG. 1, the wheel bearing portion C includes a so-called inner ring rotation type wheel bearing 50. The wheel bearing 50 is composed of a double row angular contact ball bearing including an inner member 53 including a hub ring 51 and an inner ring 52, an outer ring 54, a ball 57, and a cage (not shown). The wheel bearing 50 is formed on a ball track formed by an inner raceway surface 55 formed on the outer periphery of the hub ring 51 and the inner ring 52, and a double row outer raceway surface 56 formed on the inner circumference of the outer ring 54. A plurality of balls 57 are incorporated. Although detailed illustration is omitted, the internal space of the wheel bearing 50 is filled with grease as a lubricant. Seal members are provided at both ends of the wheel bearing 50 in the axial direction in order to prevent foreign matter from entering the bearing internal space and grease from leaking to the outside of the bearing.

The hub wheel 51 is rotatably connected to the output gear shaft 37 constituting the parallel shaft speed reducer 30 by spline fitting. A flange portion 51a extending outward in the radial direction is provided at the end of the hub wheel 51 on the outboard side, and wheels (driving wheels) are attached to the flange portion 51a. Further, a crimping portion 51b formed by crimping and fixing the inner ring 52 in order to apply a preload to the wheel bearing 50 is formed at the end portion of the hub wheel 51 on the inboard side.

A flange portion extending outward in the radial direction is provided at the end of the outer ring 54 on the outboard side, and the attachment 58 is bolted to the flange portion. The wheel bearing portion C is bolted to the casing 22 via the attachment 58.

The overall operation mode of the in-wheel motor drive device 21 having the above configuration will be briefly described. First, in the electric motor unit A, when an alternating current is supplied to the stator 23 of the electric motor 26, the rotor 24 and the motor rotating shaft 25 are integrally rotated by the electromagnetic force generated by the alternating current. The rotation of the motor rotating shaft 25 is decelerated by the parallel shaft speed reducer 30 in the speed reducer unit B and then transmitted to the wheel bearing 50. Therefore, even when a low torque and high rotation type electric motor (small electric motor) 26 is adopted, the required torque can be transmitted to the drive wheels.

Although not shown, the in-wheel motor drive device 21 has a lubrication mechanism for supplying lubricating oil to each of the electric motor unit A and the speed reducer unit B. Then, while the in-wheel motor drive device 21 is being driven, each part of the electric motor part A is cooled and each part of the speed reducer part B is lubricated and cooled by the lubricating oil supplied from the lubrication mechanism. It has become.

The basic configuration of the in-wheel motor drive device 21 of the present embodiment is as described above, but the in-wheel motor drive device 21 of the present embodiment has an intermediate gear shaft 36 constituting the parallel shaft speed reducer 30 at the time of driving the in-wheel motor drive device 21. The main feature is that it is possible to prevent the gears from hitting each other as much as possible due to the tilting of the wheels. Hereinafter, the main reason why the intermediate gear shaft 36 is tilted will be described first, and then the characteristic configuration adopted in the present invention will be described.

As described above, in the present embodiment, the torsional directions of the teeth 31a to 34a of each of the gears 31 to 34 are the axial loads (both intermediate gears 32, 33) input to the intermediate gear shaft 36 when the electric motor 26 runs in the forward rotation force. The axial load applied to the rolling bearing 44 of the two rolling bearings 44 and 45 supporting the intermediate gear shaft 36, and the axial load input to the output gear shaft 37 supports the output gear shaft 37. It is set to act on the rolling bearing 47 of the two rolling bearings 46 and 47.

Then, while the in-wheel motor drive device 21 (electric motor 26) is being driven, in addition to the axial load acting on the input side intermediate gear 32 and the output side intermediate gear 33, the intermediate gear shaft 36 receives a moment load due to this axial load. Since it always acts, the intermediate gear shaft 36 rotates in an inclined state inclined with respect to the axial direction.

More specifically, when the electric motor 26 is running in the forward rotation force, the axial load (axial load directed to the outboard side) indicated by the arrow F1 in FIG. 3 acts on the input side intermediate gear 32, and is in the middle of the output side. Since the axial load indicated by the arrow F2 in FIG. 3 (an axial load directed toward the inboard side and larger than the axial load acting on the input side intermediate gear 32) acts on the gear 33, the intermediate gear shaft 36 is affected. Is acted on by a moment load that causes the intermediate gear shaft 36 to rotate in the counterclockwise direction in FIG. When the intermediate gear shaft 36 is tilted due to the action of such a moment load, in the meshing portion M1 between the input gear 31 and the input side intermediate gear 32, the both gears 31 and 32 are at the end on the outboard side. The distance between the meshing tooth surfaces is shortened (see, for example, the front tooth surface T'of the input gear 31 and the tooth surface T of the input side intermediate gear 32 shown in FIG. 5A), and the output side intermediate gear 33. In the meshing portion M2 of the output gear 34, the distance between the meshing tooth surfaces of the gears 33 and 34 is shortened at the end on the inboard side thereof (for example, the front tooth surface of the output gear 34 shown in FIG. 7A). See T'and the tooth surface T of the output side intermediate gear 33).

Further, when the electric motor 26 runs in reverse force, the axial load (axial load directed toward the inboard side) indicated by the arrow F1'in FIG. 3 acts on the input side intermediate gear 32, and the output side intermediate gear 33 is shown in FIG. Since the axial load indicated by the arrow F2'(axial load directed toward the outboard side) acts on the intermediate gear shaft 36, the intermediate gear shaft 36 is rotated in the clockwise direction in FIG. Moment load acts. When the intermediate gear shaft 36 is tilted due to the action of such a moment load, both gears 31 and 32 at the end of the meshing portion M1 on the outboard side, as in the case of the forward rolling force of the electric motor 26. The distance between the meshing tooth surfaces of the gears is shortened, and the distance between the meshing tooth surfaces of the gears 33 and 34 is shortened at the end of the meshing portion M2 on the inboard side.

In short, when the twisting directions of the teeth 31a to 34a of the gears 31 to 34 are set as shown in FIGS. 3 and 4, when the electric motor 26 is driven, the meshing portion M1 has an end portion on the outboard side. The distance between the meshing tooth surfaces of the gears 31 and 32 is shortened to cause one-sided contact, and at the meshing portion M2, the distance between the meshing tooth surfaces of the gears 33 and 34 is shortened at the end on the inboard side. One-sided hit occurs. In this case, if no measures are taken, the parallel shaft reducer 30 is continuously driven in the state where the above-mentioned one-sided contact occurs, so that each gear 31 to 34 may be broken at an early stage. Increase. However, as shown in FIG. 11B, it is not possible to realize an appropriate meshing state only by applying general single arc tooth streak crowning.

Therefore, in the in-wheel motor drive device 21 according to the present invention, one or both of the two gears that mesh with each other are subjected to tooth surface modification at one end and the other end in the tooth streak direction (axial direction). Two gears that have different tooth thicknesses and mesh with each other as the intermediate gear shaft 36 is tilted as described above, with the one end and the other end having a relatively smaller tooth thickness. We are trying to take measures to place it on the side where the distance between our meshing tooth surfaces is shortened.

Hereinafter, specific examples of the above measures will be described with reference to the drawings.

First, as described above, as a result of the intermediate gear shaft 36 being tilted by the moment of the axial load generated in the meshing portions M1 and M2, one of the gears 31 and 32 is formed at the end of the meshing portion M1 on the outboard side. When a hit occurs, for example, as shown in FIG. 5A, the tooth surface of the input gear 31 (each of a large number of teeth constituting the input gear 31) is tapered along the tooth trace direction (meat removal). The tooth thickness x1 at the end of the input gear 31 on the outboard side is made smaller than the tooth thickness x2 at the end on the inboard side by modifying the tooth surface such as (the portion indicated by reference numeral 60). x2). The tooth surface modification may be applied to the input side intermediate gear 32 instead of the input gear 31 [see FIG. 5B], or may be applied to both the input gear 31 and the input side intermediate gear 32. Good [see Figure 5 (c)]. However, considering the labor and cost required for tooth surface modification, it is preferable to perform tooth surface modification on only one of the input gear 31 and the input side intermediate gear 32 as shown in FIGS. 5A and 5B. Further, as shown in FIG. 5A, it is preferable to modify the tooth surface only on the input gear 31 having a smaller number of teeth than the input side intermediate gear 32.

For either one or both of the gears 31 and 32, in addition to the tapered lightening 60 described above, as shown in FIG. 5 (d), tooth streak crowning (along the tooth streak direction) as tooth surface modification is performed. A crowning) may be additionally provided. Note that FIG. 5D is an example in which tooth streak crowning 61 is additionally provided for both the input gear 31 and the input side intermediate gear 32. Further, in addition to the tapered lightening 60 described above, one or both of the gears 31 and 32 is additionally provided with a tooth profile crowning 62 as a tooth surface modification as schematically shown in FIG. You can do it. Note that FIG. 6 is an example of the case where the input gear 31 is provided with the tooth profile crowning 62 in addition to the tapered lightening 60 and the tooth streak crowning 61.

Further, as a result of the intermediate gear shaft 36 being tilted due to the moment of the axial load generated in the meshing portions M1 and M2, the output side intermediate gear 33 and the output gear 34 come into contact with each other at the end of the meshing portion M2 on the inboard side. When, for example, as schematically shown in FIG. 7A, the tooth surface of the output gear 34 is tapered along the tooth trace direction (the portion to be thinned is the portion indicated by reference numeral 60). ) To make the tooth thickness x2 at the end on the inboard side of the output gear 34 smaller than the tooth thickness x1 at the end on the outboard side (x2 <x1). The tooth surface modification may be applied to the output side intermediate gear 33 instead of the output gear 34 [see FIG. 7B], or may be applied to both the output side intermediate gear 33 and the output gear 34. Good [see Figure 7 (c)]. However, even in this case, from the viewpoint of reducing the labor and cost required for tooth surface repair, as shown in FIGS. 7A and 7B, only one of the output side intermediate gear 33 and the output gear 34 is used. It is preferable to perform tooth surface modification on the tooth surface, and further, as shown in FIG. 7B, it is preferable to perform tooth surface modification only on the output side intermediate gear 33 having a smaller number of teeth than the output gear 34.

Further, in addition to the tapered lightening 60 described above, tooth streak crowning and / or tooth profile crowning (see FIG. 6) as tooth surface modification is additionally applied to either one or both of the gears 33 and 34. You may do so. FIG. 7D is an example in which tooth streak crowning 61 is additionally provided for both the output side intermediate gear 33 and the output gear 34.

If the measures shown above are taken, even if the parallel shaft reducer 30 is operated with the intermediate gear shaft 36 tilted, the meshing positions and meshing positions and meshing of the gears 31 and 32 in the meshing portion M1. The amount (actual meshing ratio), and the meshing positions and meshing amounts of the gears 33 and 34 in the meshing portion M2 can be optimized. Therefore, it is possible to effectively prevent breakage of the gears 31 to 34 and generation of abnormal noise / vibration at the meshing portions M1 and M2.

Combined with the effects described above, according to the present invention, according to the present invention, a high-quality parallel shaft speed reducer 30 having excellent durability, quietness (sound vibration performance), and torque transmission efficiency, and by extension, an in-wheel The wheel motor drive device 21 can be realized.

The in-wheel motor drive device 21 according to the first embodiment of the present invention has been described above, but the in-wheel motor drive device 21 can be appropriately modified without departing from the gist of the present invention. ..

For example, as shown in FIG. 8, the twisting directions of the teeth 31a to 34a of the gears 31 to 34 may be opposite to those of the first embodiment shown in FIG. In this case, the direction of the axial load generated in the meshing portions M1 and M2 of the gears when the electric motor 26 is driven is opposite to the case where the gears 31 to 34 as shown in FIG. 3 are adopted. Therefore, the direction of inclination of the intermediate gear shaft 36 caused by the moment due to the axial load acting on the intermediate gear shaft 36 is also reversed. Therefore, when the intermediate gear shaft 36 is tilted when the electric motor 26 is driven (when the forward rotation force is applied and when the reverse rotation force is applied), the meshing portion M1 between the input gear 31 and the input side intermediate gear 32 is on the inboard side. The distance between the meshing tooth surfaces of the gears 31 and 32 is shortened at the end, and the meshing portion M2 of the output side intermediate gear 33 and the output gear 34 is engaged with the gears 33 and 34 at the end on the outboard side. The distance between the matching tooth surfaces will be shortened. In short, when the twisting directions of the teeth 31a to 34a of the gears 31 to 34 are set as shown in FIG. 8, when the electric motor 26 is driven, the meshing portion M1 has both gears at the end on the inboard side. The distance between the meshing tooth surfaces of 31 and 32 is shortened to cause one-sided contact, and at the end of the meshing portion M2, the distance between the meshing tooth surfaces of both gears 33 and 34 is reduced to one-sided contact. Occurs.

Therefore, in the meshing portion M1, the tooth thickness x2 of the end on the inboard side is adjusted to the end on the outboard side by modifying the tooth surface on either or both of the input gear 31 and the intermediate gear 32 on the input side. The tooth thickness of the portion is made smaller than x1 (x2 <x1), and in the meshing portion M2, one or both of the output side intermediate gear 33 and the output gear 34 are subjected to tooth surface modification to be out. The tooth thickness x1 at the end on the board side is made smaller than the tooth thickness x2 at the end on the inboard side (x1 <x2). As a result, the same effect as that of the in-wheel motor drive device 21 of the first embodiment can be obtained.

In the above, the in-wheel motor drive device 21 adopting a two-stage reduction type (three-axis type) parallel shaft reduction gear 30 in which a single intermediate gear shaft 36 is arranged between the input gear shaft 35 and the output gear shaft 37. Although the case where the present invention is applied to is described above, the scope of application of the present invention is not limited to this. That is, the problem that "the moment of the axial load generated in the meshing portion between the helical gears causes the intermediate gear shaft to tilt, and the meshing portion between the gears causes one-sided contact" is solved. The same occurs in a parallel shaft reducer in which the layout of each gear shaft is adjusted so that the arrangement angle of the gear shafts is approximately 60 ° to 110 °. Therefore, the present invention employs, for example, a three-stage reduction type (four-axis type) parallel shaft reduction gear 30 in which a two-axis intermediate gear shaft 36 is arranged between the input gear shaft 35 and the output gear shaft 37. The same can be applied to the in-wheel motor drive device 21 ((not shown)).

The present invention is not limited to the above-described embodiments, and can be further implemented in various forms without departing from the gist of the present invention. That is, the scope of the present invention is indicated by the scope of claims, and further includes the equal meaning described in the scope of claims, and all modifications within the scope.

11 Electric vehicle (vehicle)
21 In-wheel motor drive device 26 Electric motor 30 Parallel shaft reducer 31 Input gear 32 Input side intermediate gear (large diameter gear)
33 Output side intermediate gear (small diameter gear)
34 Output gear 35 Input gear shaft 36 Intermediate gear shaft 37 Output gear shaft 50 Wheel bearing 60 Weeping 61 Tooth streak crowning A Electric motor part B Reducer part C Wheel bearing part M1, M2 Mating part T Tooth surface T' Pre-repair tooth surface x1 Outboard side end tooth thickness x2 Inboard side end tooth thickness

Claims (5)

It has an electric motor unit that generates driving force, a wheel bearing unit that rotatably supports the wheels, and an input gear shaft, an intermediate gear shaft, and an output gear shaft arranged in parallel with each other, and inputs to the input gear shaft. A speed reducer unit that decelerates the rotation of the electric motor unit in two or more stages and outputs the speed to the wheel bearing unit, and gears provided on each gear shaft are made of helical gears. In the wheel motor drive unit
One or both of the two gears that mesh with each other in the speed reducer portion have different tooth thicknesses at one end and the other end in the tooth streak direction due to the tooth surface modification.
Of the one end and the other end, the one having a relatively small tooth thickness causes the intermediate gear shaft to tilt due to the moment of the axial load generated in the meshing portion between the gears when the electric motor portion is driven. An in-wheel motor drive device characterized in that it is arranged on a side where the distance between the tooth surfaces where the two gears mesh with each other is shortened. The in-wheel motor drive device according to claim 1, wherein only the gear having the smaller number of teeth among the two gears has different tooth thicknesses at the one end portion and the other end portion. The in-wheel motor drive device according to claim 1 or 2, wherein the tooth surface modification is a tapered thinning provided along the tooth streak direction. The in-wheel motor drive device according to claim 3, wherein either one or both of the two gears is further crowned in the tooth streak direction as the tooth surface modification. The in-wheel motor drive device according to claim 3 or 4, wherein either one or both of the two gears is further crowned in the tooth profile direction as the tooth surface modification.

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