JP2012175867A - Direct drive motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a direct drive motor capable of reducing the risk that bearing lifetimes become short.SOLUTION: The direct drive motor includes a cross roller bearing 30 as a first bearing which is provided between a rotor 3 and a stator 2, and supports the rotor 3 rotatably, and bears an axial load and a radial load from the rotor 3; and a plain bearing 31 as a second bearing which is provided between the rotor 3 and stator 2 at a longer distance from one end to which a load of the rotor 3 is coupled than from the cross roller bearing 30, and supports the rotor 3 rotatably and bears a moment load and the radial load from the rotor 3.

Description

  The present invention relates to a direct drive motor.

  Conventionally, a direct drive motor is used to rotate an index table. As a related technique, the applicant of the present invention has a stator that is kept stationary, a rotor that is rotatably arranged with respect to the stator, and a base member that is fixed to the stator and attached to a support member. And an output shaft fixed to the rotor and rotatable with the rotor, and a bearing interposed between the base member and the output shaft to rotatably support the output shaft with respect to the base member A direct drive motor comprising: the base member having at least one continuous surface in contact with the support member in a state of being attached to the support member. Proposed (see Patent Document 1).

JP 2009-303304 A

  In general, it is desired that the direct drive motor has a reduced axial dimension. Therefore, as in the technique described in Patent Document 1, one bearing that can receive both an axial load and a moment load is disposed. However, if the center of gravity of the load attached to the output end of the rotor of the direct drive motor is away from the direct drive motor and the vibration is large, a large moment load acts on the bearing inside the direct drive motor, and the bearing The bearing life may be shortened.

  In addition, when a preload structure using a plurality of bearings is employed, a problem of a change in preload due to the effect of a temperature increase difference between the inside and outside of the direct drive motor occurs, which affects the bearing and shortens the bearing life.

  The present invention has been made in view of the above, and an object of the present invention is to provide a direct drive motor that can reduce the possibility of shortening the bearing life.

  In order to solve the above-described problems and achieve the object, the present invention is a first device that is provided between a rotor and a stator, rotatably supports the rotor, and receives an axial load and a radial load from the rotor. The bearing is provided between the rotor and the stator at a position farther from the first bearing than the first bearing to which the load of the rotor is coupled, and rotatably supports the rotor. And a second bearing that receives a moment load from the rotor as a radial load.

  In the present invention, the second bearing is provided at a position farther from the one end to which the load of the rotor is connected than the first bearing. When the rotor receives a moment load due to an external force, the first bearing receives the axial load and the radial load from the rotor, and the second bearing receives the moment load from the rotor as a radial load. As a result, it is possible to reduce the load applied to the first bearing and suppress the life of the first bearing from being shortened.

  As a desirable mode of the present invention, it is preferable that the first bearing is a cross roller bearing and the second bearing is a slide bearing. As a result, it is possible to receive an axial load and a moment load from the rotor with the first bearing and to receive a radial load from the rotor with the second bearing while suppressing an increase in the size of the direct drive motor.

  As a desirable aspect of the present invention, the electromagnetic brake further provided at the other end of the rotor is further provided, and the second bearing is provided at a position between the first bearing and the electromagnetic brake. Preferably it is. As a result, the radial load can be received by the second bearing while ensuring waterproofness.

  The present invention can provide a direct drive motor capable of reducing the risk of shortening the bearing life.

FIG. 1 is a view showing a cross section of the direct drive motor according to the present embodiment when cut by a plane including a rotation shaft. FIG. 2 is a diagram illustrating a state in which a load is coupled to the output shaft of the direct drive motor according to the present embodiment.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited by the mode for carrying out the invention (hereinafter referred to as an embodiment). In addition, constituent elements in the following description include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range.

  FIG. 1 is a view showing a cross section of the direct drive motor according to the present embodiment when cut by a plane including a rotation shaft. The direct drive motor 1 is an outer rotor type AC motor.

  The direct drive motor 1 has a housing base 21. The housing base 21 has a first cylindrical portion 21Ba that is coaxial with the rotation center axis Zr of the direct drive motor 1. The end of the first cylindrical portion 21Ba of the housing base 21 in the first direction is a motor fixing surface 23. The first direction is a direction parallel to the rotation center axis Zr and a direction opposite to the output shaft 10 described later.

  The housing base 21 has an annular portion 21R extending from the end portion in the second direction of the first cylindrical portion 21Ba toward the rotation center axis Zr. The second direction is a direction parallel to the rotation center axis Zr and a direction on the output shaft 10 side described later. Furthermore, the housing base 21 has a second cylindrical portion 21Bb extending in the second direction from the central portion including the axis of the annular portion 21R.

  In the present embodiment, the first cylindrical portion 21a and the annular portion 21R are coupled by fastening means such as a bolt. Further, the second cylindrical portion 21b and the annular portion 21R are coupled by fastening means such as a bolt. With such a structure, the first cylindrical portion 21 a and the second cylindrical portion 21 b are coupled via the annular portion 21 </ b> R, and these three members form the housing base 21.

  The space on the inner peripheral side of the housing base 21, that is, the space surrounded by the first cylindrical portion 21Ba, the annular portion 21R, and the mounting target of the direct drive motor 1 is the housing inner 22. An electromagnetic brake 25 is disposed on the housing inner 22. A motor core 24 </ b> A and a winding 24 </ b> B are disposed on the outer peripheral surface of the second cylindrical portion 21 </ b> Bb of the housing base 21. These members constitute the stator 2. Note that the direct drive motor 1 does not necessarily have the electromagnetic brake 25.

  The direct drive motor 1 has an output shaft 10 to which a load (a driving target of the direct drive motor 1) is coupled. The output shaft 10 includes an annular portion 10R in which the center axis of the annular ring is formed coaxially with the rotation center axis Zr of the direct drive motor 1, and a second axis coaxially with the central axis of the annular portion 10R from the annular portion 10R. A cylindrical portion 21B extending in the direction. A load is coupled to the end portion 10BT of the cylindrical portion 10B of the output shaft 10 on the second direction side.

  A cylindrical rotor flange 12 is coupled to the edge portion 10RC of the annular portion 10R of the output shaft 10 so as to extend in the first direction. The rotor flange 12 is a structure in which two cylindrical first flanges 12A and a second flange 12B are coupled with bolts or the like.

  A permanent magnet is disposed on the inner peripheral surface of the rotor flange 12 on the first direction side, more specifically on the inner peripheral surface of the second flange 12B so as to face the motor core 24A and the winding 24B of the stator 2. 13 is attached. The output shaft 10, the rotor flange 12, and the permanent magnet 13 constitute the rotor 3 of the direct drive motor 1.

  A hollow shaft 11 coaxial with the output shaft 10 is coupled to a central portion including the central axis of the annular portion 10R of the output shaft 10 so as to extend in the first direction. The hollow shaft 11 passes through the annular portion 21 </ b> R of the housing base 21 and extends to the position of the electromagnetic brake 25. A brake flange 14, which is an annular member, is attached to the end of the hollow shaft 11 opposite to the output shaft 10. The brake flange 14 is made of a magnetic material and has a brake ring 15 that is attracted to the electromagnetic brake 25 by a magnetic force when the electromagnetic brake 25 is operated. The brake flange 14 and the brake ring 15 serve as a rotor for the electromagnetic brake 25.

  When the electromagnetic brake 25 is activated, the brake ring 15 is attracted and fixed to the electromagnetic brake 25. Since the electromagnetic brake 25 is attached to the annular portion 21R of the housing base 21 that is a stationary system, the rotor 3 that is a rotating system is connected to the electromagnetic brake 25 via the hollow shaft 11, the brake flange 14, and the brake ring 15. Fixed to. With such a structure, the electromagnetic brake 25 can apply a braking force to the rotor 3.

  A cross roller bearing 30 serving as a first bearing is disposed between the rotor flange 12 and the second cylindrical portion 21Bb of the housing base 21. The position where the cross roller bearing 30 is disposed is the second circumferential surface of the second flange 12B of the rotor flange 12 and a portion on the second direction side of the portion where the permanent magnet 13 is disposed, and the housing base 21. The outer peripheral surface of the second cylindrical portion 21Bb is between the motor core 24A and the winding 24, that is, the portion on the second direction side of the portion where the stator 2 is disposed.

  The cross roller bearing 30 is sandwiched between the first flange 12A and the second flange 12B of the rotor flange 12, is fixed to the rotor flange 12, and is fitted into the second cylindrical portion 21Bb of the housing base 21. . With such a structure, the housing base 21 rotatably supports the rotor 3 via the cross roller bearing 30.

  The cross roller bearing 30 is a bearing in which rollers are arranged orthogonally between an inner ring and an outer ring. In the cross roller bearing 30, the rolling surfaces of the rollers, the inner ring, and the outer ring are in line contact. The cross roller bearing 30 can receive both an axial load and a moment load. As described above, the cross roller bearing 30 is provided between the rotor 3 and the stator 2, rotatably supports the rotor 3, and receives an axial load and a radial load from the rotor 3.

  In the direct drive motor 1, a slide bearing 31 as a second bearing is disposed between the inner peripheral surface of the annular portion 21 </ b> R of the housing base 21 and the outer peripheral surface of the hollow shaft 11. The slide bearing 31 is a radial bearing with a high load capacity. The slide bearing 31 as the second bearing is a cross roller bearing in which the distance from one end to which the load of the rotor 3 is coupled, that is, the end of the cylindrical portion 10B of the output shaft 10 is the first bearing. It is provided between the rotor 3 and the stator 2 at a position farther than 30, and supports the rotor 3 in a rotatable manner.

  Further, the outer peripheral surface of the housing base 21 and the portion on the second direction side of the portion where the cross roller bearing 30 is disposed, and the inner peripheral surface of the rotor flange 12 and the cross roller bearing 30 are disposed. A rotation detector (resolver) 26 that detects the rotation of the rotor 3 is disposed in a portion on the second direction side of the portion that is present. More specifically, the resolver 26 is disposed between the second direction side of the second cylindrical portion 21Bb of the housing base 21 and the first flange 12A of the rotor flange 12.

  In the direct drive motor 1, a bottom plate 27 as a sealing member for sealing the housing base 21 is attached to the motor fixing surface 23 side of the housing base 21. In the direct drive motor 1, a cylindrical housing 28 extending in the second direction is attached to the outer periphery of the annular portion 21 </ b> R of the housing base 21. The casing 28 is disposed on the outer peripheral side of the rotor 3 so as to face the rotor 3.

  Between the bottom plate 27 and the brake flange 14, an attachment-side seal 5 is provided as a sealing member for suppressing intrusion of moisture from between the rotary brake flange 14 and the stationary bottom plate 27. Similarly, between the casing 28 and the cylindrical portion 10B of the output shaft 10 of the rotor 3, it is possible to prevent moisture from entering between the rotor 3 of the rotating system and the casing 28 of the stationary system. A rotor-side seal 7 is provided as a sealing member. The direct drive motor 1 may not include the attachment side seal 5 and the rotor side seal 7, and may include at least one of the attachment side seal 5 and the rotor side seal 7.

  FIG. 2 is a diagram illustrating a state in which a load is coupled to the output shaft of the direct drive motor according to the present embodiment. The direct drive motor 1 is characterized by including a slide bearing 31 as a second bearing in addition to a cross roller bearing 30 as a first bearing.

  For example, in the case where only the cross roller bearing 30 is provided as a bearing and the slide bearing 31 is not provided, when the load 40 coupled to the output shaft 10 vibrates, the cross roller bearing 30 is caused to have a moment load (M × g via the hollow shaft 11. × L). Here, M is the mass of the load 40, g is the acceleration of vibration, and L is the distance between the center of gravity 40a of the load 40 and the roller portion of the cross roller bearing 30.

  When the mass of the load 40 is large, the acceleration of vibration is large, or the distance L between the center of gravity 40a of the load 40 and the roller portion of the cross roller bearing 30 is long, the cross roller bearing 30 is caused by vibration of the load 40 or the like. It receives a very large moment load. The moment load cannot be borne by the cross roller bearing 30 alone, and the cross roller bearing 30 may be affected, leading to a reduction in the life of the cross roller bearing 30.

  The direct drive motor 1 according to the present embodiment includes a slide bearing 31 as a second bearing in addition to a cross roller bearing 30 as a first bearing. Therefore, even if the load 40 vibrates, the impact moment load acting on the rotor 3 of the direct drive motor 1 is supported by the slide bearing 31 which is a high load capacity radial bearing via the hollow shaft 11. With such a structure, when a moment load acts on the rotor 3, the cross roller bearing 30 bears an axial load and a radial load, and the load ratio of the moment load is reduced. Further, the sliding bearing 31 receives the moment load from the rotor 3 as a radial load. Thereby, the possibility that the life of the cross roller bearing 30 may be shortened can be reduced. When the moment load does not act on the rotor 3, the load does not act on the slide bearing 31. Furthermore, since the load is distributed to both the cross roller bearing 30 and the slide bearing 31, both load carrying capacities can be afforded. As a result, the allowable load of the direct drive motor 1 can be increased.

  In the present embodiment, the slide bearing 31 is disposed on the inner circumferential surface of the annular portion of the housing base 21 and on the second direction side of the portion where the electromagnetic brake 25 is disposed. From the viewpoint of reducing the load, the slide bearing 31 is disposed so as to be in contact with the end portion on the first direction side of the portion where the electromagnetic brake 25 is disposed, that is, on the first direction side of the hollow shaft 11. Also good.

  When the direct drive motor 1 is used for applications such as for turning on-vehicle cameras, waterproofing may be required. When used for such an application, as described above, the direct drive motor 1 includes the attachment-side seal 5 and the rotor-side seal 7. When the direct drive motor 1 has the attachment-side seal 5, the slide bearing 31 is preferably arranged on the first direction side with respect to the electromagnetic brake 25 shown in FIG. 1. That is, the sliding bearing 31 is preferably provided at a position between the cross roller bearing 30 as the first bearing and the electromagnetic brake 25. This is preferable because even if the direct drive motor 1 has the attachment-side seal 5 and the slide bearing 31, an increase in the dimension of the direct drive motor 1 in the direction parallel to the rotation center axis Zr can be suppressed. Moreover, since the waterproof of the slide bearing 31 can also be ensured, it is preferable.

  Moreover, although this embodiment demonstrated the case where the cross roller bearing 30 was used as a 1st bearing and the sliding bearing 31 was used as a 2nd bearing, it is not limited to this. The first bearing may be a bearing that can receive an axial load and a radial load, and the second bearing may be a bearing that can receive a radial load. For example, a four-point contact ball bearing may be used as the first bearing.

  As described above, the direct drive motor 1 is more resistant to moment load and load vibration than the conventional direct drive motor. For this reason, it is suitable for an application that is susceptible to many vibrations, for example, an application mounted on a vehicle. As such an application, for example, the direct drive motor 1 is mounted on a vehicle and used to rotate an in-vehicle camera. The direct drive motor 1 is also suitable for applications in which high acceleration acts other than the vehicle. Furthermore, the direct drive motor 1 is also suitable for applications in which a high moment load acts on the rotor 3, such as an application in which the direct drive motor 1 directly drives an index table of a machine tool.

DESCRIPTION OF SYMBOLS 1 Direct drive motor 2 Stator 3 Rotor 5 Mounting side seal 7 Rotor side seal 10 Output shaft 11 Hollow shaft 12 Rotor flange 13 Permanent magnet 14 Brake flange 15 Brake ring 21 Housing base 22 Housing inner 23 Motor fixing surface 24A Motor core 24B Winding 25 Electromagnetic brake 26 Rotation detector (resolver)
27 Bottom plate 28 Case 30 Crossed roller bearing 31 Slide bearing

Claims (3)

A first bearing provided between the rotor and the stator, rotatably supporting the rotor, and receiving an axial load and a radial load from the rotor;
A distance from one end to which the load of the rotor is coupled is provided at a position farther than the first bearing between the rotor and the stator, and rotatably supports the rotor. A second bearing that receives the moment load as a radial load;
Direct drive motor characterized by including. The first bearing is a cross roller bearing;
The direct drive motor according to claim 1, wherein the second bearing is a slide bearing. An electromagnetic brake provided at the other end of the rotor;
The direct drive motor according to claim 1, wherein the second bearing is provided at a position between the first bearing and the electromagnetic brake.

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