Actuator

Abstract

To provide an actuator capable of reducing an axial directional length of the actuator and effectively suppressing vibration of a shaft body.SOLUTION: An actuator includes a motor 12 having a motor shaft 20, a crankshaft 40 driven by the motor shaft 20, and an eccentric oscillating reducer 14 having an external gear 44 that oscillates by an eccentric portion 42 of the crankshaft 40, in which the motor 12 has a motor space 82 that accommodates at least one part of the motor shaft 20, the crankshaft 40 has only an eccentric portion 42 of a single eccentric phase as the eccentric portion 42, and a plurality of balance weights 100A and 100B having different eccentric phases is provided integrally and rotatably within the motor space 82 in the axis body 74, which includes the motor shaft 20 and the crankshaft 40.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an actuator.

Background Art

[0002] Patent Document 1 discloses an actuator including a motor and an eccentric swing type speed reducer connected to the motor. The eccentric swing type speed reducer includes a crankshaft rotatable integrally with the motor shaft, and an external gear that swings by an eccentric portion of the crankshaft. The actuator of Patent Document 1 arranges a single balance weight in the motor space of the motor in order to suppress vibration caused by the swing of the external gear in the shaft body composed of the motor shaft and the crankshaft.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the disclosed technology of Patent Document 1, a single balance weight can only cancel out either the centrifugal force acting on the shaft body due to the swing of the external gear or the moment around the bearing. The inventor of the present application has recognized that there is room for improvement in the disclosed technology of Patent Document 1 in order to advantageously suppress the vibration of the shaft body due to the swing of the external gear while miniaturizing the axial length of the actuator.

[0005] One object of the present disclosure is to provide an actuator capable of advantageously suppressing the vibration of the shaft body while miniaturizing the axial length of the actuator.

Means for Solving the Problems

[0006] The actuator of the present disclosure includes an eccentric swing type speed reducer having a motor with a motor shaft, a crankshaft driven by the motor shaft, and an external gear that swings by an eccentric portion of the crankshaft. The motor includes a motor space that houses at least a part of the motor shaft. The crankshaft includes only the eccentric portion of a single eccentric phase as the eccentric portion. A plurality of balance weights having different eccentric phases are provided on the shaft body including the motor shaft and the crankshaft so as to be integrally rotatable within the motor space.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide an actuator that is advantageous for suppressing vibration of the shaft body while reducing the axial length of the actuator.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for implementing the actuator of the present disclosure will be described. The same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted. In each drawing, for convenience of explanation, components are appropriately omitted, enlarged, or reduced. The drawings are to be viewed in accordance with the direction of the reference numerals.

[0010] Refer to FIG. 1. The actuator 10 includes a motor 12 and an eccentric swing type speed reducer 14 (hereinafter also simply referred to as the speed reducer 14) that decelerates the rotation output from the motor 12. In addition to this, the actuator 10 includes, as an optional configuration, a driver unit 16 that drives the motor 12. The actuator 10 has main features in the balance weights 100A and 100B described later, but the peripheral structure will be described first. In this specification, the direction along the rotation center line of the motor shaft 20 of the motor 12 is simply referred to as the axial direction, and the radial direction and the circumferential direction of the circle centered on the rotation center line are also simply referred to as the radial direction and the circumferential direction, respectively. Also, on the axial direction, the side of the speed reducer 14 with respect to the motor 12 is referred to as the load side, and the side opposite to it in the axial direction is referred to as the anti-load side.

[0011] The actuator 10 includes an actuator casing 18 composed of a motor casing 26 (described later) of the motor 12 and a speed reducer casing 50 (described later) of the speed reducer 14. When the actuator 10 includes the driver unit 16, the actuator casing 18 also constitutes the driver casing 88 (described later) of the driver unit 16.

[0012] The motor 12 includes a motor shaft 20, a rotor 22 provided so as to be integrally rotatable with the motor shaft 20, a stator 24 that generates a rotating magnetic field that cooperates with the rotor 22 to rotate the motor shaft 20, and a motor casing 26 that houses the motor shaft 20, the rotor 22, the stator 24, etc.

[0013] The rotor 22 is disposed in a rotor arrangement portion 20a provided on the outer peripheral portion of the motor shaft 20. The rotor 22 is provided so as to be integrally rotatable with the motor shaft 20, for example, by interference fitting, adhesion, etc. The type of the rotor 22 is not particularly limited, and for example, a permanent magnet rotor, a cage type rotor, a wound rotor, a coreless rotor, etc. may be used.

[0014] The stator 24 is disposed on the inner peripheral portion of the motor casing 26 (motor frame 32 described later). The stator 24 is fixed to the motor casing 26 by, for example, interference fitting, adhesion, or the like. The stator 24 of the present embodiment includes a stator core 28 and a coil 30 incorporated in the stator core 28. The coil 30 includes a load-side coil end portion 30a provided on the load side with respect to the stator core 28 and a counter-load-side coil end portion 30b provided on the counter-load side with respect to the stator core 28. The type of the stator 24 is not particularly limited, and a coreless stator in which the stator core is omitted may be used.

[0015] The motor casing 26 of the present embodiment includes a cylindrical motor frame 32 and a load-side cover 34 provided on the axial load side with respect to the motor frame 32. The motor frame 32 and the load-side cover 34 of the present embodiment are provided separately from each other and then integrated by bolts or the like, but they may be integrally provided by the same member. The load-side cover 34 covers the rotor 22 and the stator 24 from the load side. The load-side cover 34 protrudes radially inward from the motor frame 32.

[0016] The speed reducer 14 includes a crankshaft 40, an external gear 44 that swings by an eccentric portion 42 of the crankshaft 40, an internal gear 46 that meshes with the external gear 44, a carrier 48 that can be synchronized with the rotation component of the external gear 44, and a speed reducer casing 50 that houses the external gear 44, the carrier 48, and the like. The speed reducer 14 of the present embodiment is a center crank type eccentric swing type speed reducer in which the crankshaft 40 is located on the swing center C44a of the external gear 44.

[0017] The speed reducer 14 includes a fixed body 52 fixed to an external member and an output body 54 that outputs rotation to an external driven member. Here, an example will be described in which the speed reducer casing 50 constitutes the fixed body 52 and the carrier 48 constitutes the output body 54. The driven member is driven by the output of the output body 54. The driven member is, for example, (1) a robot such as an industrial robot or a service robot, (2) an industrial machine such as a machine tool or a construction machine, (3) a conveying machine such as a conveyor or a film conveying device, or (4) a part of various machines such as a vehicle.

[0018] In addition to the eccentric portion 42, the crankshaft 40 includes shaft portions 56 provided on both axial sides of the eccentric portion 42. In this embodiment, the eccentric portion 42 is integrally provided by the same member as the shaft portions 56, but may be separately provided by a member different from the shaft portions 56.

[0019] The crankshaft 40 is driven by the motor shaft 20. In this embodiment, the crankshaft 40 is provided so as to be integrally rotatable with the motor shaft 20. To achieve this, the motor shaft 20 and the crankshaft 40 in this embodiment are constituted by separate members and are provided so as to be integrally rotatable by interference fitting, screws, splines, keys, etc. In this embodiment, with the shaft portion 56 of the crankshaft 40 inserted into the interior of the motor shaft 20 from the opening 20b provided on the load side of the motor shaft 20, the motor shaft 20 and the crankshaft 40 are provided so as to be integrally rotatable. In addition to this, the motor shaft 20 and the crankshaft 40 may be provided so as to be integrally rotatable by constituting them with the same member.

[0020] The center of gravity C42 of the eccentric portion 42 is eccentric with respect to the rotation center line C40 of the crankshaft 40. The eccentric portion 42 can swing the external gear 44 by rotating around its rotation center line C40. Here, "swing" means that the gear center C44b of the external gear 44 rotates around the swing center C44a. The eccentric portion 42 has a circular shape centered on its center of gravity C42.

[0021] The crankshaft 40 includes, as the eccentric portion 42, only the eccentric portion 42 with a single eccentric phase. This means that it does not include a plurality of eccentric portions 42 with different eccentric phases. To satisfy this condition, it may include only a single eccentric portion 42, or may include a plurality of eccentric portions 42 with the same eccentric phase. Here, the "eccentric phase" refers to the phase around the rotation center line C40 in the eccentric direction D1 from the rotation center line C40 of the crankshaft 40 to the center of gravity C42 of the eccentric portion 42.

[0022] The external gear 44 is rotatably supported on the eccentric portion 42 of the crankshaft 40 via an eccentric bearing 64. The internal gear 46 of the present embodiment is integrated with the speed reducer casing 50.

[0023] The carrier 48 is disposed on the axial load side with respect to the external gear 44. The carrier 48 of the present embodiment is configured by combining a plurality (here, two) of carrier members 66. A pin 68 projects axially from the carrier 48, and the pin 68 penetrates the external gear 44. As a result, the carrier 48 can be synchronized with the rotation component of the external gear 44. Here, "synchronizing with the rotation component" means maintaining the rotation component of the carrier 48 at the same magnitude as the rotation component of the external gear 44 within a numerical range including zero. For example, when the carrier 48 serves as the output body 54, the external gear 44 rotates, and its rotation component is transmitted to the carrier 48 via the pin 68, causing the carrier 48 to rotate. As a result, the carrier 48 is synchronized with the rotation component of the external gear 44. On the other hand, when the carrier 48 serves as the fixed body 52, the rotation component of the carrier 48 is maintained at zero, and the rotation of the external gear 44 is restricted by the carrier 48 and the pin 68, so that the rotation component of the external gear 44 is also maintained at zero. As a result, the carrier 48 is synchronized with the rotation component of the external gear 44.

[0024] The speed reducer casing 50 is connected to the motor casing 26 by bolts or the like. The speed reducer casing 50 of the present embodiment is configured by combining a plurality (here, two) of speed reducer casing members 70. A main bearing 72 is disposed between the speed reducer casing 50 and the carrier 48.

[0025] The actuator 10 includes a shaft body 74 including a motor shaft 20 and a crankshaft 40. The shaft body 74 of the present embodiment consists of a motor shaft 20 and a crankshaft 40 that are integrally rotatable. The shaft body 74 of the present embodiment includes a hollow portion 74a that penetrates the shaft body 74 in the axial direction. A center pipe 76 is disposed in the hollow portion 74a of the shaft body 74. The load-side portion of the center pipe 76 is fixed to the carrier 48 by bolts, interference fitting, or the like. An anti-load-side member 78 is fixed to the anti-load-side portion of the center pipe 76.

[0026] The actuator 10 includes bearings 80A and 80B that support the shaft body 74. The bearings 80A and 80B include a load-side bearing 80A disposed on the load side and a counter-load-side bearing 80B disposed on the counter-load side. The load-side bearing 80A of this embodiment is disposed between the shaft portion 56 of the crankshaft 40 of the shaft body 74 and the carrier 48. Further, the counter-load-side bearing 80B of this embodiment is disposed between the shaft portion 56 of the crankshaft 40 of the shaft body 74 and the actuator casing 18. Specifically, the counter-load-side bearing 80B is disposed between the inner peripheral portion of the load-side cover 34 of the motor casing 26 and the shaft body 74. In addition to this, the counter-load-side bearing 80B may be provided on the counter-load side of the stator 24 and the rotor 22 and disposed between the counter-load-side cover that forms a part of the motor casing 26 and the shaft body 74. The bearings 80A and 80B are constituted by various bearings such as ball bearings and roller bearings.

[0027] The motor 12 includes a motor space 82 that houses at least a part of the motor shaft 20. In addition to the motor shaft 20, the stator 24 and the rotor 22 are housed in the motor space 82. The motor space 82 is provided in the motor casing 26 on the load side of the counter-load-side end portion 26a of the motor casing 26.

[0028] The speed reducer 14 includes a speed reducer space 84 that houses at least the external gear 44. In addition to the external gear 44, the carrier 48 and the like are housed in the speed reducer space 84. The speed reducer space 84 is provided in the speed reducer casing 50 on the load side of the motor casing 26.

[0029] At least a part of the motor space 82 is provided on the counter-load side with respect to the load-side cover 34 of the motor casing 26, and at least a part of the speed reducer space 84 is provided on the load side with respect to the load-side cover 34. The load-side cover 34 functions as a partition wall that axially separates the speed reducer space 84 and the motor space 82.

[0030] The speed reducer 14 includes sealing members 86A and 86B that seal the speed reducer space 84. The sealing members 86A and 86B of this embodiment include a counter-load side sealing member 86A disposed between the motor casing 26 and the shaft body 74, and a load side sealing member 86B disposed between the speed reducer casing 50 and the carrier 48. The counter-load side sealing member 86A of this embodiment is incorporated between the outer ring and the inner ring of the counter-load side bearing 80B, and the counter-load side bearing 80B constitutes a seal bearing. In addition to this, the counter-load side sealing member 86A may also be an oil seal or the like disposed between the inner peripheral portion of the load side cover 34 of the motor casing 26 and the shaft body 74. The counter-load side sealing member 86A separates the counter-load side motor space 82 and the load side speed reducer space 84.

[0031] The driver unit 16 is disposed on the counter-load side with respect to the motor 12. The driver unit 16 includes a driver casing 88 and at least one circuit board 90A, 90B accommodated in the driver casing 88.

[0032] The driver casing 88 is fixed to the motor casing 26. The driver casing 88 is configured by combining a plurality (here, three) of driver casing members 92. A bearing 98 for supporting the center pipe 76 is disposed between the driver casing 88 and the center pipe 76. The bearing 98 of this embodiment is disposed on the counter-load side member 78 and supports the center pipe 76 via the counter-load side member 78.

[0033] The circuit boards 90A and 90B of this embodiment include a load side circuit board 90A and a counter-load side circuit board 90B fixed to the driver casing 88. A driver circuit for driving the motor 12 is incorporated in either of the circuit boards 90A and 90B.

[0034] The actuator 10 includes a first rotation detector 94 that detects the rotation of the shaft body 74, and a second rotation detector 96 that detects the relative rotation between the actuator casing 18 and the carrier 48. The first rotation detector 94 includes a first detected portion 94a fixed to the shaft body 74, and a first detection portion 94b mounted on the load-side circuit board 90A. The second rotation detector 96 includes a second detected portion 96a fixed to the anti-load-side member 78, and a second detection portion 96b mounted on the anti-load-side circuit board 90B. For example, the detected portions 94a and 96a are scales such as an optical scale or a magnetic scale, and the detection portions 94b and 96b are sensors such as an optical sensor or a magnetic sensor.

[0035] The operation of the actuator 10 described above will be explained. When the stator 24 and the rotor 22 generate a rotating magnetic field, the motor shaft 20 rotates, and the crankshaft 40 is driven by the motor shaft 20, so the crankshaft 40 rotates. When the crankshaft 40 rotates, the external gear 44 swings. When the external gear 44 swings, the meshing position between the external gear 44 and the internal gear 46 changes in the circumferential direction. Accordingly, every time the crankshaft 40 makes one rotation, one of the gears (here, the external gear 44) of the external gear 44 and the internal gear 46 rotates, and the rotation component is taken out by the output body 54 and then output to the driven member. At this time, a rotation decelerated compared to the rotation of the crankshaft 40 is output to the driven member.

[0036] Move on to the description of the balance weights 100A and 100B. A plurality of balance weights 100A and 100B with different eccentric phases are provided on the shaft body 74 so as to be integrally rotatable within the motor space 82. The plurality of balance weights 100A and 100B in this embodiment consist of a total of two balance weights, namely a load-side balance weight 100A (first balance weight) and a counter-load-side balance weight 100B (second balance weight). The counter-load-side balance weight 100B is provided on the counter-load side with respect to the load-side balance weight 100A. The balance weights 100A and 100B are provided on the shaft body 74 so as to be rotatable around the rotation center line C20 of the motor shaft 20. The directions from the rotation center line C20 of the motor shaft 20 to the center of gravity C100A and C100B of each balance weight 100A and 100B are referred to as the eccentric directions D2 and D3. The eccentric direction of the load-side balance weight 100A is D2, and the eccentric direction of the counter-load-side balance weight 100B is D3. At this time, the eccentric phases of the balance weights 100A and 100B refer to the phases around the rotation center line C20 of the eccentric directions D2 and D3 of each balance weight 100A and 100B.

[0037] In order to satisfy the condition of "a plurality of balance weights with different eccentric phases", it is only necessary that the eccentric phases of at least two balance weights 100A and 100B are different. Therefore, in order to satisfy this condition, when there are three or more balance weights, the eccentric phases of the third and subsequent balance weights and the two balance weights with different eccentric phases from each other may be the same. In this embodiment, the eccentric phases of the load-side balance weight 100A and the counter-load-side balance weight 100B are different. It can also be said that as long as there exist a first balance weight (load-side balance weight 100A) and a second balance weight (counter-load-side balance weight 100B) with different eccentric phases, the condition of "a plurality of balance weights with different eccentric phases" is satisfied.

[0038] The plurality of balance weights 100A and 100B are integrally provided by the same member in this embodiment, but may be separately provided by different members. When the plurality of balance weights 100A and 100B are integrally provided by the same member, a plurality of portions with different eccentric phases that become the balance weights 100A and 100B are provided at different portions in the axial direction of the same member. The balance weights 100A and 100B have the same cross-sectional shape in the axial direction in this embodiment, but in addition, the cross-sectional shape may change in the axial direction so as to change the amount of eccentricity while maintaining the same eccentric phase. The latter cross-sectional shape assumes, for example, a case where the outer shape of the balance weight gradually becomes smaller or gradually becomes larger in the axial direction.

[0039] The centers of gravity C100A and C100B of the balance weights 100A and 100B are provided at positions eccentric in the radial direction from the rotation center line C20 of the motor shaft 20. The specific shape for realizing this is not particularly limited. For example, the balance weights 100A and 100B may have a circular shape centered on the centers of gravity C100A and C100B similar to the eccentric portion 42, or may have other shapes. The balance weights 100A and 100B of this embodiment are provided integrally with the motor shaft 20 by the same member as the motor shaft 20, but may be provided separately from the motor shaft 20. In this embodiment, the load-side balance weight 100A has an eccentric phase opposite to that of the eccentric portion 42, that is, the eccentric phase is shifted by 180° from the eccentric portion 42. This means that the eccentric direction D2 of the load-side balance weight 100A is opposite to the eccentric direction D1 of the eccentric portion 42. To satisfy the condition of "opposite" here, the eccentric phase of the load-side balance weight 100A and the eccentric phase of the eccentric portion 42 may be shifted by 180° ± several degrees. Also, in this embodiment, the counter-load-side balance weight 100B has the same eccentric phase as the eccentric portion 42. This means that the eccentric direction D3 of the counter-load-side balance weight 100B is the same as the eccentric direction D1 of the eccentric portion 42. To satisfy the condition of "same" here, the eccentric phase of the counter-load-side balance weight 100B and the eccentric phase of the eccentric portion 42 may be shifted by several degrees.

[0040] The plurality of balance weights 100A and 100B are provided on both axial sides of the rotor 22. In this embodiment, the load-side balance weight 100A is provided on the axial load side of the rotor 22, and the anti-load-side balance weight 100B is provided on the axial anti-load side of the rotor 22.

[0041] At least one of the plurality of balance weights 100A and 100B is provided at a position radially overlapping with the stator 24. In this embodiment, each of the load-side balance weight 100A and the anti-load-side balance weight 100B satisfies this condition. Specifically, the load-side balance weight 100A is provided at a position radially overlapping with the load-side portion of the stator 24. To achieve this, the load-side balance weight 100A of this embodiment is provided at a position radially overlapping with the load-side coil end portion 30a of the stator 24. Also, the anti-load-side balance weight 100B is provided at a position radially overlapping with the anti-load-side portion of the stator 24. To achieve this, the anti-load-side balance weight 100B of this embodiment is provided at a position radially overlapping with the anti-load-side coil end portion 30b of the stator 24.

[0042] Refer to FIGS. 1 and 2. FIG. 2 schematically shows a swing body 102 including an external gear 44, a shaft body 74, bearings 80A and 80B, and balance weights 100A and 100B. The swing body 102 here refers to an object that swings integrally with the eccentric portion 42 and the external gear 44, and includes an eccentric bearing 64 and the like in addition to the external gear 44 and the eccentric portion 42.

[0043] Refer to Fig. 2(A). When the external gear 44 swings due to the rotation of the shaft body 74, a centrifugal force F1 acts on the shaft body 74 due to the swing of the external gear 44. This centrifugal force F1 acts along the eccentric direction D1 of the eccentric part 42. Also, due to this centrifugal force F1, a moment M1 around the bearings 80A and 80B acts on the shaft body 74. That is, due to the swing of the external gear 44, a centrifugal force F1 and a moment M1 act on the shaft body 74. Due to this centrifugal force F1 and moment M1, vibration occurs in the shaft body 74. Here, for the convenience of explanation, only the moment M1 around the counterloading-side bearing 80B is shown in the figure.

[0044] Refer to Fig. 2(B). The plurality of balance weights 100A and 100B are configured to cancel out the centrifugal force F1 acting on the shaft body 74 and the moment M1 around the bearings 80A and 80B respectively due to the swing of the external gear 44. It can also be said that the plurality of balance weights 100A and 100B are configured to act on the shaft body 74 with centrifugal forces F2 and F3 that cancel out the centrifugal force F1, and moments M2 and M3 that cancel out the moment M1. It can also be said that the plurality of balance weights 100A and 100B are configured to suppress the vibration of the shaft body 74 caused by the centrifugal force F1 and the moment M1 respectively.

[0045] First, the conditions for canceling out the centrifugal force F1 will be explained. When the shaft body 74 rotates, centrifugal forces F2 and F3 act on the shaft body 74 due to the rotation of the plurality of balance weights 100A and 100B respectively. Here, the centrifugal force acting due to the rotation of the load-side balance weight 100A is taken as F2, and the centrifugal force acting due to the rotation of the counterloading-side balance weight 100B is taken as F3. These centrifugal forces F2 and F3 act along the eccentric directions D2 and D3 of the respective balance weights 100A and 100B.

[0046] The centrifugal force F1 is represented by the product of the eccentricity (mm) of the eccentric portion 42 and the total weight (N) of the swing body 102, as shown in the following formula (1). The eccentricity of the eccentric portion 42 refers to the displacement amount from the rotation center line C40 of the crankshaft 40 to the centroid C42 of the eccentric portion 42. When considering the total weight of the swing body 102, the weight of the entire portion that overlaps with the eccentric portion 42 in the radial direction on the crankshaft 40 is regarded as the weight of the eccentric portion 42. Centrifugal force F1 = Eccentricity of eccentric portion 42 × Total weight of swing body 102 ··· (1)

[0047] The centrifugal forces F2 and F3 are represented by the product of the eccentricities (mm) of the balance weights 100A and 100B and the weights (N) of the balance weights 100A and 100B, as shown in the following formula (2). The eccentricities of the balance weights 100A and 100B refer to the displacement amounts from the rotation center line C20 of the motor shaft 20 to the centroids C100A and C100B of the balance weights 100A and 100B. When considering the weights of the balance weights 100A and 100B, the weight of the entire portion that overlaps with the balance weights 100A and 100B in the radial direction on the shaft body 74 is regarded as the weight of the balance weights 100A and 100B. For example, when considering the weight of the load-side balance weight 100A, the total weight of the portions of the motor shaft 20 and the crankshaft 40 located at the positions that overlap with the load-side balance weight 100A in the radial direction is regarded as the weight of the load-side balance weight 100A. Centrifugal forces F2, F3 = Eccentricities of balance weights 100A, 100B × Weights of balance weights 100A, 100B ··· (2)

[0048] The direction in which the centrifugal force F1 acts is referred to as the X direction (the vertical direction on the paper surface of FIG. 2), and the direction orthogonal to the axial direction and the X direction is referred to as the Y direction (the depth direction on the paper surface of FIG. 2). The X direction is parallel to the eccentric direction D1 of the eccentric portion 42.

[0049] Consider the case where the centrifugal forces F2 and F3, which contain only the X-direction components, act on the shaft body 74. This refers to the case where only the balance weights 100A and 100B with an eccentric phase opposite to or the same as that of the eccentric part 42 exist as in this embodiment. In this case, in order to satisfy the condition of canceling out the centrifugal force F1, it is only necessary that the magnitude of the resultant force F(sum) of the centrifugal force F1 and the centrifugal forces F2 and F3 corresponding to the respective balance weights 100A and 100B is smaller than the magnitude of the centrifugal force F1. That is, in order to satisfy this condition, at least a part of the centrifugal force F1 acting on the external gear 44 may be canceled out by the respective centrifugal forces F2 and F3 acting on the respective balance weights 100A and 100B.

[0050] Next, the conditions for canceling out the moment M1 will be described. When the shaft body 74 rotates, moments M2 and M3 around the bearings 80A and 80B act on the shaft body 74 due to the centrifugal forces F2 and F3 corresponding to the respective balance weights 100A and 100B. Here, the moment acting due to the centrifugal force F2 corresponding to the load-side balance weight 100A is referred to as M2, and the moment acting due to the centrifugal force F3 corresponding to the counter-load-side balance weight 100B is referred to as M3. Also, let the distances from the fulcrum, which is the axial position overlapping the counter-load-side bearing 80B and is the rotation center of the moment, to the force application points of the respective centrifugal forces F1 to F3 be L1 to L3. Here, the axial center position of the counter-load-side bearing 80B is used as the fulcrum, and the axial center positions of the eccentric part 42 and the respective balance weights 100A and 100B are used as the force application points of the respective centrifugal forces F1 to F3. Each of the moments M1 to M3 is represented by the product of the centrifugal forces F1 to F3 and the distances L1 to L3. For example, the moment M1 is represented by the product of the centrifugal force F1 and the distance L1 (= F1 × L1), the moment M2 is represented by the product of the centrifugal force F2 and the distance L2 (= F2 × L2), and the moment M3 is represented by the product of the centrifugal force F3 and the distance L3 (= F3 × L3).

[0051] Consider the case where centrifugal forces F2 and F3, which include only the X-direction components, act on the shaft body 74 as in this embodiment. In this case, in order to satisfy the condition of canceling out the moment M1, the sum M(sum) of the moment M1 corresponding to the swing body 102 and the moments M2 and M3 corresponding to the plurality of balance weights 100A and 100B may be smaller than the moment M1 corresponding to the swing body 102. That is, in order to satisfy this condition, at least a part of the moment M1 acting on the bearings 80A and 80B may be canceled out by the moments M2 and M3 acting by the respective balance weights 100A and 100B.

[0052] For example, in this embodiment, the resultant force F(sum) of the aforementioned centrifugal forces F1 to F3 is expressed as F1 + F3 - F2. Also, in this embodiment, the sum M(sum) of the moments M1 to M3 is expressed as M1 + M2 - M3. In this embodiment, the resultant force F(sum) of the centrifugal forces F1 to F3 becomes zero, satisfies the following formula (3), and the centrifugal force F1 is completely canceled out. Also, in this embodiment, the sum M(sum) of the aforementioned moments M1 to M3 becomes zero, satisfies the following formula (4), and the moment M1 is completely canceled out. F1 + F3 - F2 = 0 ···(3) M1 + M2 - M3 = 0 ···(4)

[0053] Since the formula (4) represents the moments M1 to M3 as the products of the centrifugal forces F1 to F3 and the distances L1 to L3, it can be represented by the following formula (4)'. F1×L1 + F2×L2 - F3×L3 = 0 ···(4)'

[0054] In order to cancel out the centrifugal force F1 and the moment M1 respectively in this way, it is only necessary to set F2, F3, L2, and L3 so as to satisfy equations (3) and (4)'. In this case, since there are two equations and four unknowns, by determining appropriate values for two of the four unknowns, the magnitudes of the remaining unknowns can be obtained from equations (3) and (4)'. For example, when assuming F1 = F3 and L2 = L1 × 2, from equations (3) and (4)', F2 = F1 × 2 is obtained, and L3 = L1 × 5 is derived. That is, when F3 = F1, F2 = F1 × 2, L2 = L1 × 2, and L3 = L1 × 5, the centrifugal force F1 and the moment M1 can be completely canceled out.

[0055] In this way, due to the existence of a plurality of balance weights 100A and 100B with different eccentric phases, the centrifugal force F1 and the moment M1 corresponding to the oscillating body 102 can be canceled out respectively. As described above, this is achieved by changing the centrifugal forces F2 and F3 corresponding to the balance weights 100A and 100B by adjusting the eccentric amounts and weights of the balance weights 100A and 100B, and changing the distances L2 and L3 from the bearings 80A and 80B to the balance weights 100A and 100B by adjusting the axial positions of the balance weights 100A and 100B. The specific examples of F2, F3, L2, and L3 described above are merely examples given for the purpose of explanation, and it goes without saying that they may be set to various magnitudes. Not only the conditions for completely canceling out the centrifugal force F1 and the moment M1, but also the conditions for the centrifugal forces F2 and F3 and the distances L2 and L3 for canceling out at least a part of them can be set by those skilled in the art without excessive trial and error by using experiments, simulations, etc.

[0056] Note that the condition of configuring so as to cancel each of the centrifugal force F1 and the moment M1 corresponding to the swinging body 102 only needs to be realized by using a plurality of balance weights 100A and 100B. When focusing on any one of the balance weights 100A and 100B, the centrifugal force and moment corresponding to that one balance weight 100A or 100B may amplify without canceling the centrifugal force F1 and the moment M1. For example, in the illustrated example, when focusing on the moment M2 corresponding to the load-side balance weight 100A, the moment M2 amplifies the moment M1, but it suffices that the moment M1 is canceled by the moments M2 and M3 corresponding to the two balance weights 100A and 100B.

[0057] The effects of the actuator 10 described above will be explained.

[0058] The plurality of balance weights 100A and 100B are provided in the motor space 82. When providing the balance weights 100A and 100B on the shaft body 74, it is easier to secure a free space around the shaft body 74 in the motor space 82 than in the speed reducer space 84. This free space can be secured, for example, at a position that overlaps the stator 24 in the radial direction. By providing the plurality of balance weights 100A and 100B in such a motor space 82, it is advantageous for miniaturizing the axial length of the actuator 10 as compared with the case of providing the balance weights 100A and 100B in the speed reducer space 84.

[0059] If only a single balance weight 100A, 100B is provided in the motor space 82, it can only be configured to cancel out either the centrifugal force F1 acting on the shaft body 74 or the moment M1 around the bearings 80A, 80B due to the swinging of the external gear 44. On the other hand, when a plurality of balance weights 100A, 100B with different eccentric phases are provided, by adjusting their weights, eccentric amounts, axial positions, eccentric phases, etc., it is possible to configure them to cancel out the centrifugal force F1 and the moment M1 acting on the shaft body 74 respectively. Therefore, compared with the case where only either the centrifugal force F1 or the moment M1 acting on the shaft body 74 can be canceled out, it is advantageous for suppressing the vibration generated in the shaft body 74. Since it is advantageous to suppress the vibration generated in such a shaft body 74, it is also advantageous for suppressing the noise associated with that vibration.

[0060] If the crankshaft 40 has eccentric portions 42 with different eccentric phases, by adjusting the eccentric phases of the individual eccentric portions 42, it is possible to balance the centrifugal force and moment acting on the shaft body 74. For example, when the crankshaft 40 has two eccentric portions 42, by shifting the eccentric phases of the individual eccentric portions 42 by 180°, such a balance of centrifugal force and moment can be achieved. On the other hand, when the crankshaft 40, as in this embodiment, has only an eccentric portion 42 with a single eccentric phase, it is not possible to adjust the eccentric phases of the individual eccentric portions 42 in this way. Therefore, in the case of a structure like this embodiment, an imbalance of the centrifugal force and moment acting on the shaft body 74 occurs, and as a result, the aforementioned vibration becomes a problem. According to this embodiment, even under a structure where the vibration of the shaft body 74 becomes a problem in this way, it is particularly effective in that the use of a plurality of balance weights 100A, 100B as described above can advantageously suppress the vibration.

[0061] In order to solve the problem of "advantageously suppressing vibration" generated in the shaft body 74 in this way, it is sufficient that a plurality of balance weights 100A and 100B with different eccentric phases are provided on the shaft body 74 so as to be integrally rotatable. In order to solve this problem, it is not essential that the plurality of balance weights 100A and 100B are configured to cancel out the centrifugal force F1 and the moment M1 respectively. That is, in order to solve the problem of "advantageously suppressing vibration", it is sufficient that the difficulty of realizing the suppression of the vibration can be reduced, and the realization itself is not essential. In order to obtain the effect of "··· advantageously", it is sufficient that the difficulty of realizing the effect can be reduced, and it can be said that the realization itself is not essential.

[0062] The plurality of balance weights 100A and 100B are provided on both axial sides with respect to the rotor 22. Therefore, the individual balance weights 100A and 100B can be provided in the empty spaces on both axial sides with respect to the rotor 22. For this reason, the empty spaces on both axial sides with respect to the rotor 22 can be effectively utilized, which is more advantageous for reducing the axial length of the actuator 10.

[0063] At least one of the plurality of balance weights 100A and 100B is provided at a position radially overlapping with the stator 24. Therefore, the balance weights 100A and 100B are provided in the empty space radially overlapping with the stator 24, which is more advantageous for reducing the axial length of the actuator 10 compared with the case where the balance weights 100A and 100B are provided in the speed reducer space 84.

[0064] The load-side balance weight 100A has an eccentric phase opposite to that of the eccentric portion 42, and the counter-load-side balance weight 100B has the same eccentric phase as the eccentric portion 42. Thereby, the eccentric phases of the eccentric portion 42, the balance weights 100A and 100B can be simplified compared with the case where the eccentric phases of the respective balance weights 100A and 100B are not opposite to or the same as the eccentric phase of the eccentric portion 42.

[0065] Next, other features of the actuator 10 will be described. In this embodiment, as described above, in order to cancel out the centrifugal force F1 and satisfy the condition of formula (3), F2 and F3 are set. As can be understood from this formula (3), the centrifugal force F2 corresponding to the load-side balance weight 100A is larger than the centrifugal force F3 corresponding to the anti-load-side balance weight 100B. Let the eccentric amounts of the load-side balance weight 100A and the anti-load-side balance weight 100B be e2 and e3. Also, let the weights of the load-side balance weight 100A and the anti-load-side balance weight 100B be m2 and m3. At this time, in order to make the centrifugal force F2 > the centrifugal force F3, as can be understood from formula (2), the eccentric amount e2 is made larger than the eccentric amount e3, or the weight m2 is made larger than the weight m3.

[0066] In order to achieve this, in this embodiment, the weight m2 is made larger than the weight m3. As a result, it becomes easier to make the centrifugal force F2 larger than the centrifugal force F3 without making the eccentric amount e2 larger than the eccentric amount e3. Consequently, it becomes easier to reduce the radial length of the load-side balance weight 100A, which is advantageous for reducing the radial length of the actuator 10.

[0067] In order to make the weight m2 larger than the weight m3 in this way, in this embodiment, the axial length L100A of the load-side balance weight 100A is made longer than the axial length L100B of the anti-load-side balance weight 100B (see also FIG. 1). The longer the length L100A is than the length L100B, the more advantageous it is to make the weight m2 larger than the weight m3. As a result, the weight m2 of the load-side balance weight 100A can be made larger than the weight m3 of the anti-load-side balance weight 100B with a simple configuration.

[0068] In this embodiment, the load-side balance weight 100A and the counter-load-side balance weight 100B are made of the same material. This material is composed of, for example, a metal material such as a steel-based material. In addition to this, in order to make the weight m2 larger than the weight m3, the specific gravity of the load-side balance weight 100A may be made larger than the specific gravity of the counter-load-side balance weight 100B. In this case, for example, the magnitude relationship between the axial length L100A of the load-side balance weight 100A and the axial length L100B of the counter-load-side balance weight 100B is not particularly limited, and they may be the same.

[0069] Next, a modified form of each component described so far will be described.

[0070] So far, an example has been described in which the eccentric phases of the balance weights 100A and 100B are only either opposite to or the same as the eccentric phase of the eccentric portion 42. As will be described next, the eccentric phases of the balance weights 100A and 100B are not limited to this.

[0071] Refer to FIGS. 3(A) and (B). FIGS. 3(A) and (B) show an example in which three balance weights 100A, 100B, and 100C are provided on the shaft body 74. Each of the balance weights 100A to 100C is provided in the motor space 82. A configuration similar to that of the actuator 10 of the embodiment may be applied except for the number of the balance weights 100A to 100C. FIG. 3(A) is a view of the centrifugal forces F1, F2x to F4x and the moments M1, M2x to M4x acting on the shaft body 74 by the rocking body 102 and each of the balance weights 100A to 100C in the modified form as viewed from the Y direction, and FIG. 3(B) is a view of the centrifugal forces F1 to F4 as viewed from the axial direction.

[0072] The eccentric phases of the balance weights 100A, 100B, and 100C in this embodiment are offset by (180° + θ2), (180° - θ3), and θ4, respectively, from the eccentric phase of the eccentric portion 42 (not shown) of the oscillating body 102. On the shaft body 74, centrifugal forces F2 to F4 act along the directions forming angles of θ2, θ3, and θ4 with respect to the X direction due to the balance weights 100A, 100B, and 100C. In this embodiment, θ2, θ3, and θ4 are angles greater than 0° and less than 90°. In addition to the X-direction components, centrifugal forces F2 to F4 having Y-direction components act on the shaft body 74 due to the respective balance weights 100A to 100C. Let the distances from the fulcrum, which is the center of rotation of the moment and is in the axial position overlapping the anti-load side bearing 80B, to the force application points of the respective centrifugal forces F2 to F4 be L2 to L4. The definition of the distances L2 to L4 is the same as described above.

[0073] Let the X-direction components of the respective centrifugal forces F2, F3, and F4 be F2x, F3x, and F4x, and the Y-direction components be F2y, F3y, and F4y. Also, let the moments acting on the shaft body 74 due to the X-direction components F2x, F3x, and F4x of these respective centrifugal forces be M2x, M3x, and M4x, and the moments acting on the shaft body 74 due to the Y-direction components F2y, F3y, and F4y of the respective centrifugal forces be M2y, M3y, and M4y. The moments M2x to M4x are moments around the Y-direction axis passing through the bearings 80A and 80B, and the moments M2y to M4y are moments around the X-direction axis passing through the bearings 80A and 80B. Here, only the moment around the anti-load side bearing 80B is considered.

[0074] In this case, on the premise of satisfying the condition of canceling out the centrifugal force X1 by the respective balance weights 100A to 100C, it is sufficient to cancel out at least a part of the centrifugal force F1 by the resultant force of the X-direction components F2x to F4x of the centrifugal forces F2 to F4 and maintain the balance of the Y-direction components F2y to F4y of the centrifugal forces F2 to F4. Here, "maintaining the balance of the Y-direction components F2y to F4y of the centrifugal forces F2 to F4" means making the resultant force of the Y-direction components F2y to F4y of the centrifugal forces F2 to F4 zero.

[0075] Also, as long as the condition that the moment M1 is canceled out by each of the balance weights 100A to 100C is satisfied, at least a part of the moment M1 is canceled out by the sum of the moments M2x to M4x corresponding to the X-direction components F2x to F4x of the centrifugal forces F2 to F4, and it is only necessary to be able to maintain the balance of the moments M2y to M4y corresponding to the Y-direction components F2y to F4y of the centrifugal forces F2 to F4. Here, "maintaining the balance of the moments M2y to M4y" means making the sum of the moments M2y to M4y corresponding to the Y-direction components zero.

[0076] Note that on the drawing, the magnitudes of θ2, θ3, θ4, F1 to F4, L1 to L4 are only shown schematically and do not indicate the exact magnitudes for balancing the centrifugal forces F1 to F4 and the moments M1 to M4. Also, as described above, in order to make the resultant force of the Y-direction components F2y to F4y of the centrifugal forces F2 to F4 and the sum of the moments M2y to M4y corresponding to the Y-direction components F2y to F4y zero, in addition to the case of making it exactly zero mathematically, the case of making it approximately zero is also included.

[0077] For example, in this embodiment, the balance of the X-direction components of the aforementioned centrifugal forces F1 to F4 is represented by the following formula (5), and the balance of the Y-direction components is represented by the following formula (6). F1 + F4×cosθ4 = F2×cosθ2 + F3×cosθ3 ··· (5) F2×sinθ2 = F3×sinθ3 + F4×sinθ4 ··· (6)

[0078] Also, in this embodiment, the balance of the moments M1, M2x to M4x around the Y-direction axis is represented by the following formula (7), and the balance of the moments M2y to My4 around the X-direction axis is represented by the following formula (8). M1 + M2x + M3x = M4x ···(7) M2y = M3y + M4y ···(8)

[0079] When each of the moments M1, M2x to M4x, M2y to M4y in formulas (7) and (8) is expressed as the product of the centrifugal forces F1, F2x to F4x, F2y to F4y and the distances L1 to L4, they can be expressed by the following formulas (7)' and (8)'. F1×L1 + F2×cosθ2×L2 + F3×cosθ3×L3 = F4×cosθ4×L4 ··· (7)' F2×sinθ2×L2 = F3×sinθ3×L3 + F4×sinθ4×L4 ··· (8)'

[0080] In order to cancel out the centrifugal force F1 and the moment M1 respectively, F2 to F4 and L2 to L4 may be set so as to satisfy formulas (5), (6), (7)' and (8)'. In this case, since the number of formulas is 4 and the number of unknowns is 6 (the number of unknowns becomes 9 when θ2 to θ4 are added), for example, after determining appropriate values for two of the unknowns of F2 to F4 and L2 to L4, and then determining appropriate values for θ2 to θ4, the magnitudes of the remaining unknowns can be obtained from formulas (5), (6), (7)' and (8)'. In this case, the centrifugal force F1 can be completely canceled out by the resultant force of the X - direction components F2x to F4x of the centrifugal forces F2 to F4, and the balance of the Y - direction components F2y to F4y of the centrifugal forces F2 to F4 can be maintained. Also, the moment M1 can be completely canceled out by the sum of the moments M2x to M4x corresponding to the X - direction components F2x to F4x of the centrifugal forces F2 to F4, and the balance of the moments M2y to M4y corresponding to the Y - direction components F2y to F4y of the centrifugal forces F2 to F4 can be maintained.

[0081] In addition to the angles of the eccentric phases of the balance weights 100A to 100C with respect to the eccentric phase of the eccentric portion 42 listed here, the above-mentioned F2 to F4 and L2 to L4 are merely examples cited for the purpose of explanation, and it goes without saying that they may be set to various sizes. Also, the number of the balance weights 100A to 100C may be four or more. Further, when the centrifugal forces F2 to F4 of the balance weights 100A to 100C include Y-direction components, in addition to the condition of completely canceling out the centrifugal forces F1 and M1 as described above, the conditions of the centrifugal forces F2 to F4, the distances L2 to L4, and the angles θ2 to θ4 of the respective balance weights for canceling out a part of them can be set by those skilled in the art without excessive trial and error by using experiments, simulations, etc.

[0082] The plurality of balance weights 100A and 100B may be provided only on one axial side with respect to the rotor 22. At least one of the plurality of balance weights 100A and 100B may be provided at a position radially overlapping with the stator 24. For example, either one of the load-side balance weight 100A and the counter-load-side balance weight 100B may be provided at a position radially overlapping with the stator 24, and the other of them may be provided at a position not radially overlapping with the stator 24.

[0083] The speed reducer 14 may be a distribution type eccentric swing type speed reducer in which a plurality of crank shafts 40 are provided at positions radially offset with respect to the swing center C44a of the external gear 44. In this case, the speed reducer 14 includes a distribution gear integrally rotatable with the motor shaft 20, a crank shaft gear meshing with the distribution gear and integrally rotatable with the crank shaft 40, and a plurality of crank shafts 40. In this case, the crank shaft 40 is driven by the motor shaft 20 when the rotation of the motor shaft 20 is transmitted via the distribution gear and the crank shaft gear. In this case, the shaft body 74 is regarded as being constituted by a combination of the motor shaft 20, the distribution gear, the crank shaft gear, and the plurality of crank shafts 40. In this case, the number of teeth of the distribution gear and the crank shaft gear may be the same so as to transmit constant-speed rotation.

[0084] The above embodiments and modified forms are illustrative. The technical ideas abstracted from these should not be construed as being limited to the content of the embodiments and modified forms. Many design changes such as component changes, additions, deletions, etc. are possible for the content of the embodiments and modified forms. In the foregoing embodiments, with respect to the content for which such design changes are possible, the notation "embodiment" is attached and emphasized. However, design changes are also permitted for content without such notation. The hatching applied to the cross-section of the drawing does not limit the material of the object to which the hatching is applied.

[0085] In the embodiments and modified forms, structures and numerical values mentioned should naturally include those that can be regarded as the same considering errors such as manufacturing errors and dimensional errors. A component configured by a single member in an embodiment may be configured by a plurality of members. Similarly, a component configured by a plurality of members in an embodiment may be configured by a single member.

Description of Reference Numerals

[0086] 10... Actuator, 12... Motor, 14... Eccentric swing type speed reducer, 20... Motor shaft, 22... Rotor, 24... Stator, 40... Crankshaft, 42... Eccentric portion, 44... External gear, 74... Shaft body, 80A, 80B... Bearings, 82... Motor space, 100A... Load side balance weight, 100B... Counter load side balance weight.

Claims

1. A motor having a motor shaft, An eccentric swing type speed reducer having a crankshaft driven by the motor shaft and an external gear that swings by an eccentric portion of the crankshaft, and an actuator comprising: The motor includes a motor space that houses at least a part of the motor shaft. The crankshaft includes, as the eccentric portion, only the eccentric portion having a single eccentric phase. An actuator in which a plurality of balance weights having different eccentric phases are provided on a shaft body including the motor shaft and the crankshaft so as to be integrally rotatable within the motor space.

2. Comprising a bearing for supporting the shaft body, The actuator according to claim 1, wherein the plurality of balance weights are configured to cancel out, respectively, a centrifugal force acting on the shaft body due to the swing of the external gear and a moment around the bearing.

3. The motor includes a rotor provided so as to be integrally rotatable with the motor shaft. The actuator according to claim 1, wherein the plurality of balance weights are provided on both axial sides with respect to the rotor.

4. The motor includes a stator. The actuator according to claim 1, wherein at least one of the plurality of balance weights is provided at a position radially overlapping the stator.

5. The plurality of balance weights include a load-side balance weight and a counter-load-side balance weight. The load-side balance weight has an eccentric phase opposite to that of the eccentric portion. The actuator according to claim 1, wherein the counter-load-side balance weight has the same eccentric phase as the eccentric portion.

6. The actuator according to claim 5, wherein a centrifugal force acting on the shaft body due to the rotation of the load-side balance weight is greater than a centrifugal force acting on the shaft body due to the rotation of the counter-load-side balance weight.

7. The actuator according to claim 6, wherein the weight of the load-side balance weight is greater than the weight of the counter-load-side balance weight.

8. The actuator according to claim 6, wherein an axial length of the load-side balance weight is greater than an axial length of the counter-load-side balance weight.

Images