Gear motor

Abstract

To suitably prevent a shaft from swinging around.SOLUTION: A gearmotor 1 includes a motor 20 having a rotor shaft 21, rotating in unison with a motor rotor 22, a reduction gear 30 having an eccentric body shaft 31 to which rotation of the rotor shaft 21 is transmitted, and a rotation detector 51, which is arranged on an anti-reducer side of the motor rotor 22 and detects the rotation of the rotor shaft 21. The gearmotor 1 further includes a first bearing 36 and a second bearing 48, which support the rotor shaft 21 or the eccentric body shaft 31. The first bearing 36 is a cross roller bearing and is provided on the reduction gear side than the second bearing 48.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gear motor.

Background Art

[0002] Conventionally, a gear motor configured by connecting a speed reducer and a motor is known. For example, in the gear motor described in Patent Document 1, the speed reducer and the motor are connected in the axial direction, and an encoder for detecting rotation is disposed on the side of the motor opposite to the speed reducer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described conventional gear motor, the shaft may wobble due to an eccentric load caused by a driven member connected to the speed reducer. This wobbling of the shaft on the speed reducer side becomes larger at the encoder position on the side opposite to the speed reducer via the motor, which may reduce the rotation detection accuracy of the encoder.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to suitably suppress the wobbling of the shaft.

Means for Solving the Problems

[0006] This The invention is a gear motor including a motor having a rotor shaft that rotates integrally with a motor rotor, a speed reducer having an input shaft to which the rotation of the rotor shaft is transmitted, and a rotation detector that is disposed on the side of the motor rotor opposite to the speed reducer and detects the rotation of the rotor shaft, including a first bearing and a second bearing that support the rotor shaft or the input shaft, The first bearing is a cross roller bearing and is provided on the speed reducer side rather than the second bearing side. The member that supports the outer peripheral side of the first bearing is configured to have a higher Young's modulus than the member that supports the outer peripheral side of the second bearing.

Effect of the Invention

[0007] According to the present invention, the wobbling rotation of the shaft can be suitably suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0010] [Overall Configuration of Gear Motor] FIG. 1 is a cross-sectional view showing a gear motor 1 according to the present embodiment. The gear motor 1 according to the present embodiment is a device that outputs rotational power, and its application is not particularly limited. For example, it can be used as a joint gear motor of a collaborative robot that works in cooperation with a human. Specifically, as shown in FIG. 1, the gear motor 1 includes a motor 20, a speed reducer 30, a brake 40, a rotation detection unit 50, and a circuit unit 60. These speed reducer 30, motor 20, brake 40, rotation detection unit 50, and circuit unit 60 are arranged in this order along the central axis Ax of the gear motor 1. In the following description, the direction along the central axis Ax is referred to as the "axial direction", the direction perpendicular to the central axis Ax is referred to as the "radial direction", and the rotational direction around the central axis Ax is referred to as the "circumferential direction". Also, among the axial directions, the side connected to the driven member E (the left side in the figure) is referred to as the "load side", and the side opposite to the load side (the right side in the figure) is referred to as the "anti-load side". However, due to the positional relationship between the motor 20 and the speed reducer 30, the load side may be referred to as the "anti-motor side" or the "speed reducer side", and the anti-load side may be referred to as the "motor side" or the "anti-speed reducer side".

[0011] [Configuration of the motor] The motor 20 includes a rotor shaft 21 that rotates around the central axis Ax, a motor rotor 22, a motor stator 23, and a motor casing 24. In this embodiment, the rotor shaft 21 penetrates from the speed reducer 30 to the brake 40. As will be described later, the rotor shaft 21 is rotatably supported by a first bearing 36 provided in the speed reducer 30 and a second bearing 48 provided in the brake 40.

[0012] The motor rotor 22 is externally fitted to the rotor shaft 21 and rotates integrally with the rotor shaft 21. The motor rotor 22 has a rotor yoke 22a and rotor magnets 22b. The rotor yoke 22a is made of a non-magnetic material and is fitted and fixed to the outer peripheral surface of the rotor shaft 21. The rotor magnets 22b are permanent magnets such as neodymium magnets, and a plurality of them corresponding to a predetermined number of poles are attached to the outer peripheral surface of the rotor yoke 22a.

[0013] The motor stator 23 is configured by winding a coil 23b around a stator core 23a made of laminated steel plates. The motor stator 23 is concentrically arranged on the outer peripheral side of the motor rotor 22. The motor casing 24 covers the outer peripheral sides of the motor rotor 22 and the motor stator 23. The motor stator 23 is held in a state where the stator core 23a of the motor stator 23 is internally fitted. Also, the motor casing 24 is not particularly limited, but is made of aluminum for the purpose of weight reduction and improvement of cooling performance.

[0014] Note that the type of the motor 20 is not particularly limited, and for example, it may be an induction motor instead of a permanent magnet type motor. However, the rated rotational speed of the motor 20 is preferably 1000 rpm or less, more preferably 500 rpm or less.

[0015] [Configuration of the speed reducer] In this embodiment, the speed reducer 30 is an eccentric swing type speed reducer and is disposed on the load side of the motor 20. Specifically, the speed reducer 30 includes an eccentric shaft 31, external gear wheels 32A and 32B, an output shaft 33, and a housing (casing) 34. The reduction ratio of the speed reducer 30 is not particularly limited, but a low reduction ratio is desirable, for example, 50 or less, preferably 30 or less.

[0016] The eccentric shaft 31 is the input shaft of the speed reducer 30 having a hollow structure (hollow structure). In this embodiment, the eccentric shaft 31 is integrally formed of a single material with the rotor shaft 21 of the motor 20. However, the eccentric shaft 31 and the rotor shaft 21 may be separate bodies, and in this case, for example, a configuration in which they are connected by a spline or a key structure and the rotation is transmitted may be sufficient. A plurality (two) of eccentric bodies 311a and 311b are provided on the eccentric shaft 31.

[0017] The external gear wheels 32A and 32B have a plurality of inner pin holes provided circumferentially apart at positions offset from the center and a central through hole through which the eccentric shaft 31 is inserted. The external gear wheels 32A and 32B are rotatably supported with respect to the eccentric bodies 311a and 311b by eccentric bearings 35a and 35b respectively disposed between the external gear wheels 32A and 32B and the eccentric bodies 311a and 311b, and swing by the rotation of the eccentric bodies 311a and 311b.

[0018] The output shaft 33 is disposed on the outer peripheral side of the eccentric shaft 31 and on the load side of the external gear wheels 32A and 32B, and is fixed to the driven member E. The output shaft 33 has a plurality of inner pins 33a formed so as to bulge in a pin shape toward the non-load side. The inner pins 33a are inserted into the inner pin holes of the external gear wheels 32A and 32B. A plate 331 fixed to the housing 34 is disposed on the non-load side of the inner pins 33a. The output shaft 33 rotatably supports the eccentric shaft 31 by a first bearing 36 disposed between the eccentric shaft 31 and the output shaft 33. The first bearing 36 is a cross roller bearing. Also, the output shaft 33 is made of a metal material such as a steel material.

[0019] The housing 34 is disposed on the outer peripheral side of the external gear wheels 32A and 32B and the output shaft 33. The housing 34 is fixed to the motor casing 24 of the motor 20. An internal gear 34g is provided on the inner peripheral portion of the housing 34. The internal gear 34g has a plurality of outer pins that form internal teeth, and is internally meshed with the external gear wheels 32A and 32B. The housing 34 rotatably supports the output shaft 33 by a main bearing 37 disposed between the housing 34 and the output shaft 33. The main bearing 37 is a cross roller bearing. In the present embodiment, the inner ring is provided on the outer peripheral portion of the output shaft 33, and the outer ring is provided on the inner peripheral portion of the housing 34, respectively. The main bearing 37 is disposed at a position overlapping the first bearing 36 when viewed in the radial direction. Specifically, the rolling elements of the main bearing 37 are disposed at positions overlapping the rolling elements of the first bearing 36 when viewed in the radial direction. Also, the housing 34 is made of a metal material such as a steel material, similar to the output shaft 33. However, the housing 34 and the output shaft 33 may have a higher Young's modulus than the frame 47 of the brake 40 that supports the outer peripheral side of the second bearing 48 as a member that supports the outer peripheral side of the first bearing 36.

[0020] [Configuration of Brake] The brake 40 brakes the rotation of the rotor shaft 21 (eccentric shaft 31), and is disposed on the non-load side of the motor 20. The brake 40 includes a hub member 41 fixed so as to restrict relative rotation with respect to the rotor shaft 21, a disk-shaped rotor 42 spline-fitted to the hub member 41, an armature 43 displaceable toward the rotor 42, an electromagnetic coil 44 for driving the armature 43, a spring member 45 for returning the armature 43 to its original position, a plate 46 facing the rotor 42 on the opposite side of the armature 43, and a frame 47 for holding the electromagnetic coil 44, the plate 46, etc. Linings (abrasive materials) are fixed to both surfaces of the rotor 42 facing the plate 46 and the armature 43, respectively.

[0021] The frame 47 is fixed to the motor casing 24 of the motor 20. In the present embodiment, the housing 34 of the speed reducer 30, the motor casing 24 of the motor 20, and the frame 47 are fastened together with fixing screws 71. The frame 47 rotatably supports the rotor shaft 21 by a second bearing 48 disposed between the frame 47 and the rotor shaft 21. The second bearing 48 is provided between the motor rotor 22 and the rotation detector 51, and more specifically, between the hub member 41 of the brake 40 and the rotation detector 51. The second bearing 48 is a ball bearing in the present embodiment. However, the type of the second bearing 48 is not particularly limited, and it may be a roller bearing such as a cross roller bearing, for example. Also, the second bearing 48 is preferably disposed near the rotating portion 51a of the rotation detection portion 50 described later in terms of improving the detection accuracy of the rotation detection portion 50. Also, the frame 47 is made of aluminum or resin, although not particularly limited, solely for the purpose of weight reduction.

[0022] In the brake 40, due to the action of the electromagnetic coil 44 or the spring member 45, the rotor 42 is sandwiched between the armature 43 and the plate 46 via the lining, whereby a braking force is applied to the rotor shaft 21 (eccentric body shaft 31). Also, due to the action of the spring member 45 or the electromagnetic coil 44, the force for sandwiching the rotor 42 between the armature 43 and the plate 46 is released, whereby the braking force applied to the rotor shaft 21 (eccentric body shaft 31) is released.

[0023] [Configuration of Rotation Detection Unit and Circuit Unit] The rotation detection unit 50 is arranged on the counter load side of the brake 40. The rotation detection unit 50 includes a rotation detector 51 that detects the rotation of the rotor shaft 21 (eccentric body shaft 31), and an encoder board 52 on which its detection circuit is mounted. The rotation detector 51 has a rotating part 51a that rotates integrally with the rotor shaft 21, and a sensor 51b that is arranged opposite to the counter load side of the rotating part 51a and detects the rotation amount of the rotating part 51a. The rotation detector 51 is, for example, a rotary encoder that outputs the displacement of the rotation of the rotating part as a digital signal, but it may also be a resolver that outputs as an analog signal, or other rotation detectors. The rotary encoder may have an optical detection part or a magnetic detection part. The encoder board 52 mounts the sensor 51b, detects the rotation of the rotor shaft 21 (eccentric body shaft 31), and outputs it to the circuit unit 60.

[0024] The circuit unit 60 is arranged on the counter load side of the rotation detection unit 50. On the circuit unit 60, a motor driver board or the like on which the drive circuit of the motor 20 is mounted is arranged. Note that the circuit unit 60 may be configured to include the rotation detection unit 50.

[0025] [Operation of Gear Motor] In the gear motor 1 of this embodiment, when the motor 20 is driven by the circuit unit 60 and the rotor shaft 21 rotates, the rotation output is input to the eccentric body shaft 31 of the speed reducer 30 that is integral with the rotor shaft 21.

[0026] In the speed reducer 30, as the eccentric shaft 31 rotates, the eccentric members 311a and 311b rotate inside the external gear wheels 32A and 32B, causing the external gear wheels 32A and 32B to oscillate in different phases relative to each other. The external gear wheels 32A and 32B oscillate such that the external teeth farthest from the central axis Ax mesh with the internal gear wheel 34g, and this meshing position changes circumferentially with the oscillation. Specifically, each time the eccentric shaft 31 makes one full rotation, the meshing position between the internal gear wheel 34g and the external gear wheels 32A and 32B makes one full circle circumferentially. There is a difference in the number of teeth between the external gear wheels 32A and 32B and the internal gear wheel 34g, and each time the meshing position with the internal gear wheel 34g makes one full circle, the external gear wheels 32A and 32B rotate by the difference in the number of teeth described above. This rotation is transmitted to the output shaft 33 via the inner pin 33a. As a result, the rotational motion of the eccentric shaft 31 is decelerated and taken out from the driven member E connected to the output shaft 33. During the transmission of this rotational motion, the rotation of the rotor shaft 21 (eccentric shaft 31) is detected by the rotation detector 51.

[0027] When the drive of the motor 20 stops and the brake 40 is activated, the armature 43 is driven, the rotor 42 is sandwiched between the plate 46 and the armature 43, and a braking force acts on the rotor shaft 21 (eccentric shaft 31). When the motor 20 is driven, the armature 43 is separated from the rotor 42 and the braking force is released.

[0028] Here, among the first bearing 36 and the second bearing 48 that support the rotor shaft 21 (eccentric shaft 31), the first bearing 36 provided on the load side (speed reducer side) relative to the second bearing 48 is a cross roller bearing. Therefore, during the transmission of the rotational motion, although an eccentric load caused by the driven member E connected to the output shaft 33 acts on the load side end of the rotor shaft 21 (eccentric shaft 31), the cross roller bearing's first bearing 36, which can support loads in complex directions with high rigidity, can preferably suppress the wobbling of the rotor shaft 21 (eccentric shaft 31) on the load side. Consequently, the wobbling of the rotor shaft 21 (eccentric shaft 31) at the second bearing 48 located on the anti-load side relative to the first bearing 36 can also be preferably suppressed, ensuring the detection accuracy of the rotation detector 51.

[0029] In this embodiment, the first bearing 36 is provided on the load side with respect to the motor rotor 22, and the second bearing 48 is provided on the non-load side with respect to the motor rotor 22. However, for the first bearing 36 and the second bearing 48, it is sufficient that the first bearing 36 of the cross roller bearing is provided on the load side (reduction gear side) with respect to the second bearing 48. For example, the first bearing 36 may be provided on the further load side (opposite motor side) with respect to the reduction mechanism of the reduction gear 30 (in this embodiment, the meshing portion of the external gear 32 and the internal gear 34). Also, the second bearing 48 may be provided on the load side with respect to the motor rotor 22 and on the non-load side with respect to the reduction mechanism of the reduction gear 30 (in this embodiment, the meshing portion of the external gear 32 and the internal gear 34). In this case, the second bearing 48 may be attached to the non-load side of the housing 34 and supported by providing a carrier member that holds the non-load side of the inner pin 33a, or the non-load side portion of the housing 34 may be formed as a disc portion whose inner circumference is narrowed to the inner circumference side and supported at the inner circumference portion.

[0030] [Technical Effects of this Embodiment] As described above, according to the gear motor 1 of this embodiment, it includes a motor 20, a reduction gear 30, and a rotation detector 51 disposed on the non-load side (opposite reduction gear side) with respect to the motor rotor 22. Among the first bearing 36 and the second bearing 48 that support the rotor shaft 21 (eccentric body shaft 31), the first bearing 36 provided on the load side (reduction gear side) with respect to the second bearing 48 is a cross roller bearing. Thereby, the eccentric load caused by the driven member E connected to the reduction gear 30 can be preferably suppressed by the high-rigidity cross roller bearing. Therefore, the wobbling of the rotor shaft 21 (eccentric body shaft 31) can be preferably suppressed. Furthermore, since the rotor shaft 21 is supported by the second bearing 48, more specifically, the vicinity of the rotation detector 51 on the opposite reduction gear side with respect to the motor rotor 22 is supported, the detection accuracy of the rotation detector 51 can also be maintained high.

[0031] Further, according to the gear motor 1 of the present embodiment, since the speed reducer 30 is an eccentric swing type speed reducer that receives the shaft with an offset, the rotor shaft 21 (eccentric body shaft 31) is more likely to wobble compared to other types of speed reducers. However, this wobbling can be preferably suppressed by the first bearing 36 of the cross roller bearing. Furthermore, by applying the eccentric swing type speed reducer, it is possible to preferably cope with a low reduction ratio. By applying the speed reducer 30 with a low reduction ratio, the sensitivity (back drivability) to impacts from the load side can be improved.

[0032] Also, according to the gear motor 1 of the present embodiment, since the rated rotational speed of the motor 20 is relatively low at 1000 rpm or less, a cross roller bearing in which the rolling elements are in line contact can be preferably applied as the first bearing 36. That is, since heat generation becomes a problem when a cross roller bearing is used to support a high-speed rotating shaft, it has been conventionally considered unsuitable for supporting a rotor shaft. In the present embodiment, by adopting an eccentric swing type speed reducer with a low reduction ratio and a low-speed motor, heat generation of the cross roller bearing is suppressed, and it can be used to support the rotor shaft 21.

[0033] Also, according to the gear motor 1 of the present embodiment, the members (output shaft 33, housing 34) that support the outer peripheral side of the first bearing 36 have a higher Young's modulus than the frame 47 of the brake 40 that supports the outer peripheral side of the second bearing 48. Thereby, the first bearing 36, which has a greater load than the second bearing 48, can be supported with high rigidity, and thus, the wobbling of the rotor shaft 21 (eccentric body shaft 31) can be more preferably suppressed.

[0034] [Others] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments. For example, in the above embodiment, an eccentric swing type speed reducer was described as an example. However, the speed reducer according to the present invention is not limited to the eccentric swing type speed reducer and can be applied to various speed reduction mechanisms such as a flexure engagement type speed reduction device and a simple planetary speed reduction device. Further, even in the case of an eccentric swing type speed reducer, it can also be applied to a type in which a plurality of eccentric body shafts are arranged at positions offset from the center of the internal gear. In addition, the details shown in the above embodiment can be appropriately changed without departing from the gist of the invention.

Explanation of Reference Numerals

[0035] 1 Gear motor 20 Motor 21 Rotor shaft 22 Motor rotor 24 Motor casing 30 Speed reducer 31 Eccentric body shaft (input shaft) 33 Output shaft 34 Housing 36 First bearing 37 Main bearing 40 Brake 47 Frame 48 Second bearing 50 Rotation detection unit 51 Rotation detector 52 Encoder board Ax Central axis E Driven member

Claims

1. A gear motor comprising: a motor having a rotor shaft that rotates integrally with a motor rotor; a speed reducer having an input shaft to which the rotation of the rotor shaft is transmitted; and a rotation detector disposed on the side of the speed reducer opposite to the motor rotor to detect the rotation of the rotor shaft, comprising a first bearing and a second bearing that support the rotor shaft or the input shaft, wherein the first bearing is a cross roller bearing and is provided on the side of the speed reducer relative to the second bearing, and a member that supports the outer peripheral side of the first bearing has a higher Young's modulus than a member that supports the outer peripheral side of the second bearing. Gear motor.

2. The motor has a rated rotational speed of 1000 rpm or less. The gear motor according to claim 1.

3. The first bearing is provided on the side of the speed reducer relative to the motor rotor, and the second bearing is provided on the side of the motor rotor opposite to the speed reducer. The gear motor according to claim 1 or claim 2.

4. The first bearing is provided on the side of the speed reducer mechanism opposite to the motor. The gear motor according to any one of claims 1 to 3.

5. The second bearing is provided between the motor rotor and the rotation detector. The gear motor according to any one of claims 1 to 4.

6. The second bearing is a ball bearing. The gear motor according to any one of claims 1 to 5.

7. The speed reducer is an eccentric swing type speed reducer. The gear motor according to any one of claims 1 to 6.

8. The rotor shaft and the input shaft are integrally formed of a single material. The gear motor according to any one of claims 1 to 7.

9. Comprising a brake for braking the rotation of the rotor shaft, wherein the brake is provided between the motor rotor and the rotation detector, and the second bearing is provided between the brake and the rotation detector. The gear motor according to claim 5.

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