JP4060693B2 - Motor drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power transmission device for a vehicle, and more particularly to a drive device for an electric vehicle.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a drive device for transmitting the power of a vehicle drive motor to a drive wheel in an electric vehicle generally transmits an input shaft connected to an output shaft that outputs the power of the motor, and the power transmitted to the input shaft. The counter shaft includes an output shaft that transmits power from the counter shaft to the wheels. The shafts provided in these drive devices are connected to other shafts via gears provided around the shafts, thereby transmitting the power of the motor to the wheels. Further, the drive device has bearings arranged on both sides of each shaft in order to rotatably support each shaft.
[0003]
Among these bearings, the second bearing that supports the motor side end of the input shaft also serves as a fulcrum of the output shaft of the motor, and its inner diameter portion is fitted with the output shaft of the motor. The motor output shaft and the input shaft of the drive device are connected by spline fitting in order to reliably transmit power (torque). The fitting of the spline part is a connection method in which key-shaped irregularities extending in the axial direction are provided at equal intervals over the entire circumference of the respective shafts to be connected. In general, the connection state is looser than when fitting with a shaft and a hole, except in the case of so-called serration fittings, etc. where the fitting part accepts movement and there is no play in the fitting part and is joined semipermanently. And the concentricity is low.
[0004]
Therefore, when high-frequency vibration or sound generated in the motor is transmitted from the motor output shaft to the second bearing, the vibration or the like cannot be suppressed, but rather the vibration is amplified. This vibration or the like is transmitted to the motor case, and the motor case causes membrane surface vibration like a speaker.
[0005]
On the other hand, it is possible to press-fit the spline part like a counter shaft to avoid vibration during rotation of the shaft, but the input shaft deteriorates the assembly workability when the drive unit is attached to the motor case. It is difficult to adopt immediately.
[0006]
Also, as a substitute for the single second bearing, the bearing that carries the motor output shaft and the bearing that carries the input shaft are two different bearings, and the two shafts are connected by spline fitting between the two bearings. However, two bearings and a space for receiving them become large, resulting in an increase in size and weight of the driving device, which is not preferable.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-230489
[Problems to be solved by the invention]
In view of the above problems, an object of the present invention is to provide a vibration reduction structure for a drive device that reduces vibration of a motor case in a drive device for a motor and that has good assembly to the motor case. .
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an input shaft connected to a motor shaft of a vehicle drive motor, an output shaft arranged in parallel to the input shaft and connected to a drive wheel, and the input shaft. A motor drive device having at least one set of gears for transmitting power to an output shaft, wherein the output side end of the motor shaft and the input side end of the input shaft are held coaxially to drive the motor And a motor-side bearing (referred to as a second bearing in the embodiment) for rotatably supporting the connection portion with respect to the motor housing, The set of gears is formed of a helical gear configured to generate a thrust force on the motor housing side in the axial direction of the input shaft when a driving force is transmitted to the input shaft. Has a working part that acts on the end face of the thrust force generated on the input shaft inner race of the motor-side bearing (inner ring), the thrust force acting on the end face of the inner race, outer race of the motor-side bearing ( Provided is a motor drive device which acts on the motor housing via an outer ring.
[0010]
In the drive device attached to the motor housing containing the motor, the connecting portion (for example, reference numeral 10a in FIG. 3) between the motor output shaft and the input shaft in the drive device is connected by spline fitting, and the fitting state is loose. Therefore, vibration generated by the motor cannot be suppressed, and vibration is amplified and transmitted to the motor case via a motor side bearing (provided on the motor case to constitute the motor housing) located at the connecting part of both shafts. It is as described above. According to the drive device of the present invention, it is possible to prevent the motor case from causing film surface vibration due to high-frequency vibration and sound generated from the motor. Specifically, to generate a thrust force of the motor housing direction to the input shaft of the drive device, acting portion of the input shaft the thrust force (see, for example, the flange element 11 of FIG. 3) provided on the motor side via the motor Act on the side bearing to hold down the motor housing. Thereby, the film surface vibration which arises in a motor case can be suppressed. Further, in order to make the acting direction of the thrust force generated on the input shaft of the drive device in the direction of the motor housing, a gear that is applied to the input shaft of the drive device and transmits the power of the motor to the counter shaft is a helical gear. Since this helical gear is twisted, the helical gears have a function of improving the meshing rate by applying thrust forces in opposite directions to each other during rotation. Therefore, in the configuration of the input shaft gear and the counter shaft gear meshing with each other, the input shaft gear generates the thrust force of the motor housing, and the counter shaft gear generates the thrust force in the opposite direction to the motor housing. As a result, the thrust force acts only in the motor housing direction on the input shaft. Therefore, according to the present driving device, the original function of the driving device can be achieved, and the membrane vibration of the motor case can be prevented without providing additional means or increasing the weight of the motor case or the like (motor housing). That is, the configuration of the present drive device can function as a motor power transmission device and at the same time have a function as a vibration reduction device.
[0011]
In the motor drive device having the above-described configuration, the input shaft is rotatably supported by an opposite side bearing (referred to as a first bearing in the embodiment) at an opposite end opposite to the input side end. The gear arranged on the input shaft of the at least one set of gears is preferably arranged in the vicinity of the opposite bearing. Further, in the motor drive device having the above-described configuration, a contact surface that contacts the end surface of the inner race of the motor-side bearing is formed on the action portion, and the contact surface has a groove on the surface. The configuration is preferable.
[0012]
As described above, when a thrust force in the direction of the motor housing is applied to the input shaft of the drive device, vibration of the motor case (and the drive device attached thereto) can be prevented, but the input shaft is supported in the drive device. Therefore , a large force acts on the motor-side bearing and the opposite-side bearing provided at both ends of the shaft. Specifically, a thrust force is applied to these bearings as described above in addition to the radial force acting on the input shaft when power is transmitted to the counter shaft via the helical gear. In particular, as described above, it is necessary to apply as much thrust force as possible to the motor-side bearing provided on the motor side . As a result, if a large thrust force is applied to the motor-side bearing, the durability of the motor-side bearing is increased. In order to improve, it is necessary to provide a large one. However, an increase in the size of the motor-side bearing is undesirable because it results in an increase in the size and weight of the entire drive device in association with other essential component placement spaces in the drive device. In order to solve this problem, as a preferred driving device, a motor side bearing is provided with a means for accepting all thrust force while minimizing radial force. Specifically, a gear that is applied to the input shaft and transmits power to the counter shaft is disposed near the input shaft end opposite to the motor, that is, near the opposite bearing, and further to the opposite bearing from the input shaft. The input shaft is made free in the axial direction with respect to the opposite bearing so that the thrust force does not act. With this configuration, a large radial force acts on the opposite bearing located on the opposite side of the motor, but no thrust force acts, and a small radial force and a large thrust force appear on the motor side bearing located on the motor side. Will act. This is because, as shown in FIG. 4 showing the relationship between the position of the gear and the radial force, the radial force acting on the bearing has a property of acting more when close to the gear and acting small when moving away from the gear. In other words, in the case of the preferred drive device referred to herein, the opposite bearing carries most of the radial force, and the motor side bearing carries all of the thrust force, and both bearings have radial force and thrust force respectively. And approximately one of them. As a result, either the opposite side bearing or the motor side bearing becomes excessively large, and the opposite side (or motor side) bearing is configured by combining a bearing capable of carrying radial force and a bearing capable of carrying thrust force. It is possible to avoid the necessity of making it happen. Therefore, it is possible to prevent the motor case and the drive device attached to the motor case from increasing in size and weight.
[0013]
As described above, in the drive device of the present invention, the thrust force acting on the input shaft is pressed against the motor-side bearing located on the motor side to prevent membrane vibration and the like. In order to achieve this easily, a contact surface having a groove portion that contacts the end surface of the inner race of the motor-side bearing is formed in the action portion of the input shaft here, and the thrust force acting on the input shaft is reduced. Means for pressing the end surface of the inner race of the motor-side bearing through the contact surface is provided.
[0014]
Although the contents of the present invention have been described above, specific embodiments of the present invention will be described with reference to the accompanying drawings in order to facilitate understanding.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
First, as a premise of the description of the drive device of the present invention, a skeleton showing the configuration of the drive device for an electric vehicle will be described with reference to FIG. As shown in this figure, a vehicle drive device (hereinafter simply referred to as a “drive device”) 1 of the present embodiment receives a power supply from a battery B mounted on the vehicle and supplies rotational power to an output shaft S. The electric motor M to be applied is a prime mover, and is a type of vehicle drive device mounted on a so-called electric vehicle .
[0016]
The input shaft 10 in the drive device 1 is supported in a freely rotating manner around the shaft by a first bearing 51 and a second bearing 52 (the second bearing 52 is attached to a motor case 5a described later) inside the drive device case 5. And is directly coupled to the output shaft S of the electric motor M. The counter shaft 20 is supported by a third bearing 53 and a fourth bearing 54 at a position parallel to the input shaft 10 so as to be rotatable about the axis.
[0017]
Rotational power first gear (main gear) 12 is inputted constant-mesh with the second gear (counter gear) 22 fixed on the counter shaft 20, the input shaft 10 from an electric motor M which is fixed on the input shaft 10 Is transmitted to the counter shaft 20 through the first gear 12 and the second gear 22. A third gear (final drive gear ) 24 is provided to the right of the second gear 22 on the counter shaft 20. The third gear 24 is a fourth gear (final driven) fixed to the differential case 30. Gear ) 32 is always meshed.
[0018]
Inside the differential case 30 two pinions 34 and two side gears 36a, left and right output shafts 42a, 42b is fixed to 36b. The central axes of the left and right output shafts 42a and 42b are arranged in parallel with the rotation shafts of the input shaft 10 and the counter shaft 20, and the differential case 30 rotates about the central axes of the left and right output shafts 42a and 42b. It is supported by a fifth bearing 55 and a sixth bearing 56 so as to be able to do so. Further, driving wheels (not shown) are attached to the ends of the left and right output shafts 42a and 42b.
[0019]
As shown in FIG. 2, the drive device case 5 of the drive device 1 is composed of a right case 5a and a left case 5b, and each case 5a, 5b is joined by a plurality of joining bolts. An electric motor M is attached to the right side of the right case 5a with a plurality of motor mounting bolts.
[0020]
Here, as shown in FIG. 2, a parking gear 26 is fixed to the left position of the second gear 22 on the counter shaft 20, but the description is omitted because it is not directly related to the contents of the present invention.
[0021]
Next, the force which acts on the input shaft 10 in the drive device 1 of the present invention will be described with reference to FIGS. FIG. 1 is an actual partial cross-sectional view of the drive unit 1 of FIG. 2 described above.
[0022]
First, as shown in FIG. 1, the first gear 12 for transmitting the rotational power of the input shaft 10 to the counter shaft 20 is a helical gear that cooperates with the second gear 22 that is applied to the counter shaft 20 and meshes with the first gear 12. Consists of. As described above, the first gear 12 that is a helical gear has a characteristic that a thrust force acts in the axial direction opposite to each other. Specifically, as shown in FIG. 3, the first gear 12 has twisted teeth, and when the input shaft 10 rotates, each tooth contacts the teeth of the second gear 22 and the axis of the input shaft. Since the tooth surfaces inclined with respect to each other press each other to improve the meshing rate, a force, that is, a thrust force acts not only in the rotational direction but also in the axial direction. For example, when the input shaft 10 rotates in the arrow X direction (the normal rotation direction of the motor M), a thrust force acts in the arrow Y direction.
[0023]
Next, means for transmitting the thrust force to the motor housing, that is, the motor case 5a will be described. Referring again to FIG. 1, the motor side end of the input shaft 10 is supported by the second bearing 52. The second bearing 52 is formed integrally with the motor case 5 a, and the motor output shaft S rotates in contact with the inner race 52 b of the bearing 52. The input shaft 10 is connected to the motor output shaft S by spline fitting with the former as a male part and the latter as a female part. If the thrust force acting on the input shaft 10 is applied to the inner end face of the second bearing end face 52a (acting on the inner race 52b of the second bearing 52), the motor case 5a can be pressed in the motor direction. That is, the thrust force applied to the inner side of the second bearing end surface 52a is transmitted from the outer race 52c of the second bearing 52 (not shown) to the motor case 5a via the second bearing carrying portion 5c, and as a result, the motor case 5a. Is pressed in the motor direction (right direction in FIG. 1). The pressing using such a thrust force is performed by a brim portion (brief element) 11 provided integrally with the output shaft 10. Specifically, the contact surface 11b of the flange portion 11 as shown in FIG. 3 is formed to contact the inner end surface of the second bearing end surface 52a (see also FIG. 1). In the present embodiment, as shown in FIG. 3, a groove 11a through which lubricating oil flows is provided in the contact surface 11b, particularly in a portion that contacts the second bearing end surface 52a.
[0024]
If it demonstrates in detail, the input shaft 10 has comprised the hollow structure which provided the through-hole 10b for letting lubricating oil pass. Lubricating oil is supplied into the input shaft 10 from the left direction in FIG. 3 and supplied to a spline portion 10 a that is a connection portion with the motor output shaft S. The lubricating oil that has passed through the spline portion 10 a flows into the groove portion 11 a provided in the flange portion 11 and is blown to the outside by the rotational centrifugal force of the input shaft 10. This allows the lubricating oil to prevent wear of the contact surface 11a and the inner end surface of the second bearing end surface 52a abutting thereto flange 11 at the same time can prevent wear of the spline portion.
[0026]
Next, the relationship between the arrangement position of the first gears 12 applied to the input shaft 10 and the radial force acting on the input shaft 10 (force acting in the direction around the radius of the input shaft) will be described.
FIG. 4 is a schematic diagram showing the positional relationship between the gears 12, 22, 24, 32 disposed inside the driving device 1 and the bearings 51-56 provided to the shafts 10, 20, 42. In this figure, the input shaft 10 will be described. For example, when the first gear 12 is located at a distance b from the first bearing 51 and a distance a from the second bearing 52, the first gear acting on the first and second bearings. The radial forces F1 and F2 at
F1: F2 = b: a
It will have the relationship.
Accordingly, the transmission distribution of the radial force to the first and second bearings 51 and 52 that support both ends of the input shaft 10 increases as the first gear 12 approaches, and decreases as the distance increases. This relationship is the same for the fifth and sixth bearings 55 and 56 that support the output shaft 42. However, with respect to the third and fourth bearings 53 and 54 that support the counter shaft 20, since the radial force in the reverse direction acts from the second and third gears 22 and 24, the radial force in the reverse direction distributed from each gear. Are offset by the respective bearings 53 and 54, and the differential radial force of the difference acts. Therefore, if attention is paid to the first and second bearings 51 and 52, since the first gear 12 is disposed in the vicinity of the first bearing 51 in this embodiment, most of the radial force is distributed to the first bearing 51, It can be seen that the distribution to the two bearings 52 is small.
[0027]
Here, the force acting on the first and second bearings 51 and 52 will be considered based on the correlation between the radial force and the thrust force described above. A large radial force acts on the first bearing 51, but no thrust force. On the other hand, all the thrust force acts on the second bearing 52, but only a small radial force acts. Generally speaking, the radial force is mainly received by the first bearing 51, and the thrust force is received by the second bearing 52. Therefore, if the configuration of the present embodiment is adopted, a large thrust force can be applied to the second bearing 52 to prevent film vibration of the motor case 5a. An excessive force is not applied, and the force can be appropriately distributed to the first and second bearings 51 and 52, and an increase in size and an increase in weight due to an improvement in durability of the second bearing 52 can be avoided.
[0028]
Further, if the configuration of the present embodiment is adopted, the first and second bearings 51 and 52 can be reduced in size, so that the distance between the axes in the drive device 1 can be shortened. As a result, the drive device 1 can be reduced in size. Can be Moreover, in this embodiment, the force distribution which acts on the 1st and 2nd bearings 51 and 52 can be optimized.
[0029]
As mentioned above, mainly focusing on the force acting on the first and second bearings 51 and 52, the means for preventing the vibration of the film surface of the motor case has been described. Optimizing the relationship between the radial force acting on the bearing and the thrust force is important for downsizing the drive device. Hereinafter, the configuration of each gear conceivable in the electric vehicle drive device will be specifically verified.
[0030]
Referring to FIGS. 5 to 7, a schematic diagram of the configuration of each possible gear and shaft of the driving device 1 is possible. In FIG. 5 (a), elements with reference numbers are also present and referred to in other drawings in which numbers are omitted. Moreover, in the example shown in FIGS. 5-7, the case where the thrust force which acts on an output shaft is on the opposite side to an output is excluded. As described above, when the gear is disposed in the vicinity of the bearing, a large radial force is distributed, and a thrust force and a large radial force are applied to the sixth bearing 56. However, since the drive device amplifies the rotational power while decelerating the rotational speed of the motor, an excessive force acts on the sixth bearing with such a gear arrangement. Therefore, since it is not necessary to examine the configuration of each gear and shaft here, it is omitted from FIGS.
[0031]
The configuration shown in FIG. 5A is the same as the above-described embodiment of the present invention. In the case of this configuration, as described above, the membrane vibration of the motor case can be prevented, and the output shaft 42 extends opposite to the input side (motor side), so that a space for arranging a large motor M can be secured. . In the case of FIG. 5B, since large radial force and thrust force act on the first bearing 51 and the third bearing 53, that is, the load acting on them is large, the first and second bearings 51 and 53 are enlarged. It is necessary to do this, or a motor with a high output cannot be provided. In the case of FIG. 5C as well, the load on the first bearing 51 is similarly large, leading to an increase in size. Further, in this case, since the output shaft 42 extends to the motor side (right direction in the figure), it is necessary to separate the output shaft 42 and the lower part of the motor M by a predetermined distance d or more, and the motor M is increased in size (increased output). )Can not do it. In the case of FIG. 6D, the thrust force acting on the counter shaft 20 is in the same direction and is not canceled out, and the load on the third bearing 53 is large. Also in this case, the motor M cannot be increased in output as in the case of FIG. In the case of FIG. 6E, the force balance is good, but there is a problem that a large radial force is applied to the second bearing 52 and the drive device is enlarged. Also in the case of FIG. 6 (f), a large radial force and thrust force are applied to the second bearing 52, leading to an increase in the size of the driving device, and at the same time, the thrust force acting on the counter shaft 20 is not canceled out and applied to the fourth bearing 54. The load becomes excessive. In the case of FIG. 7G as well, as in FIG. 6E, a large radial force is received by the second bearing 52, which causes an increase in size and weight, and at the same time a thrust force acting on the counter shaft 20. Is not offset. Further, also in the case of FIG. 7H, the second bearing 52 receives a thrust force and a large radial force, resulting in an increase in size and weight. Therefore, it will be understood that a preferable configuration in the configurations shown in FIGS. 5 to 7 is the configuration (a) which is the same as the case of the driving apparatus exemplified as the embodiment of the present invention.
[0032]
【The invention's effect】
According to the driving apparatus of the present invention, the thrust force of the input shaft is applied to the motor-side second bearing, so that the film vibration of the motor case caused by the relatively high frequency vibration generated by the motor can be prevented and driven. Amplified vibration and sound transmitted to the outside of the apparatus can be suppressed. Further, according to the present drive device, an appropriate force can be distributed to the first and second bearings that support the input shaft, so that it is possible to prevent an increase in the size and weight of the bearing that acts when the force is biased. As a result, it is possible to achieve a reduction in size and weight of the entire drive device.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a drive device of the present invention.
FIG. 2 is a skeleton diagram showing a configuration of a driving apparatus of the present invention.
FIG. 3 is a perspective view showing an input shaft of the driving apparatus of the present invention.
FIG. 4 is a schematic diagram showing the relationship between the position of each gear and each bearing in the driving device and the radial force acting on each bearing.
FIG. 5 is a schematic diagram of a configuration of each gear and shaft that can be considered in the driving device.
FIG. 6 is a schematic diagram of a configuration of each gear and shaft that can be considered in the driving device.
FIG. 7 is a schematic diagram of a configuration of each gear and shaft that can be considered in the driving device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Drive device 5 ... Case 10 ... Input shaft 12 ... 1st gear 20 ... Counter shaft 22 ... 2nd gear 24 ... 3rd gear 32 ... 4th gear 42 ... Output shaft 51 ... 1st bearing 52 ... 2nd bearing 53 ... Third bearing 54 ... Fourth bearing 55 ... Fifth bearing 56 ... Sixth bearing S ... Motor output shaft M ... Motor

Claims (3)

An input shaft coupled to the motor shaft of the vehicle drive motor;
An output shaft arranged in parallel to the input shaft and connected to the drive wheel side;
A motor drive device comprising at least one set of gears for transmitting power from the input shaft to the output shaft,
A connecting portion that coaxially holds the output side end of the motor shaft and the input side end of the input shaft so as to transmit the driving force of the motor to the input shaft;
A motor-side bearing that rotatably supports the connecting portion with respect to the motor housing;
Furthermore, the at least one set of gears is formed of a helical gear configured to generate a thrust force on the motor housing side in the axial direction of the input shaft when a driving force is transmitted to the input shaft.
The input shaft has an action portion that causes a thrust force generated on the input shaft to act on an end surface of the inner race of the motor side bearing, and the thrust force acting on the inner race causes the outer race of the motor side bearing to And a motor drive device that acts on the motor housing. The input shaft is rotatably supported at its opposite end opposite to the input end by an opposite bearing,
The gear disposed on the input shaft of the at least one pair of gears, characterized in that it is disposed near the opposite bearing, the motor driving apparatus according to claim 1. A contact surface that contacts the end surface of the inner race of the motor-side bearing is formed in the action portion,
The motor driving device according to claim 1, wherein the contact surface has a groove on a surface thereof.

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