Rotary Actuator

Abstract

A rotation actuator (1) comprising a hollow motor (2), a strain wave gearing device (4), and an output member (6), wherein an actuator hollow portion (70) is defined by a sleeve (7) extending completely through the rotation actuator (1) in the axial direction, an output-side detector (9) is disposed on the front side of the strain wave gearing device (4), and an input-side detector (8) is disposed on a motor back side. The sleeve (7) has a back end portion (71) fixed on a motor housing (21) side, the motor housing (21) being a fixed-side member, and has a front end portion (72) extending into the center hole of the output member (6). The outer peripheral surface of the front end portion (72) of the sleeve positioned near the rotation center of the output member (6) is set as a mounting portion of a fixed-side detection component of the output-side detector (9), thereby making it possible to reduce deterioration in detection accuracy due to, for example, falling of the output member (6).

Description

[Technical Field]

[0001] The present invention relates to a hollow rotary actuator in which a hollow portion is formed by a cylindrical sleeve that axially passes through a hollow motor and a harmonic gear device that are coaxially arranged. [Background technology]

[0002] In hollow rotary actuators, the hollow portion is used as a space for arranging wiring and other components. In the rotary actuators described in Patent Documents 1 and 2, a cylindrical sleeve is disposed so as to axially penetrate the center of the rotary actuator, and the hollow portion of the actuator is defined by the inner circumferential surface of the sleeve. The sleeve prevents lubricant from leaking into the hollow portion, protecting the wiring and other components disposed within the hollow portion. In addition, hollow rotary actuators are equipped with a motor encoder that detects the rotation of the hollow motor shaft and an output encoder that detects the reduced rotation of the wave gear device, and the drive control of the rotary actuator is based on the information detected by these encoders.

[0003] In a rotary actuator, a load-side component is connected to a reduced-rotation output component (output component of the wave gearing device) located at the front end of the rotary actuator. If an output encoder is mounted on the outside of the output component (on the axial front side), it will be difficult for users to use the rotary actuator and will also cause problems such as an increased axial length. When incorporating an output encoder inside a wave gearing device, it is necessary to prevent the output encoder from being affected by lubricants such as grease that are filled or applied inside, and it is also necessary to devise a way to route the encoder wiring from the inside to the outside.

[0004] Patent Document 3 employs a configuration in which an output-side encoder that detects the rotational state of the output member of the strain wave gearing is located at the rear end of the rotary actuator (rear end of the motor). A cylindrical sleeve is located axially penetrating the center of the rotary actuator, and the inner circumferential surface of the sleeve defines a hollow portion of the actuator. The axial front end of the sleeve is fixed to the output member of the strain wave gearing, and the sleeve rotates integrally with the output member. By detecting the rotation of the sleeve using the output-side encoder located at the rear end of the motor, rotation information such as the rotation angle of the output member located at the front end is detected by the output-side encoder located at the rear end. In this case, a magnetic or optical code wheel of the output-side encoder is attached to the rear end of the sleeve, and this rotation is detected by a magnetic or optical sensor attached to the fixed side of the motor housing.

[0005] The output member of the strain wave gear device, to which the front end of the sleeve is fixed, may tilt due to moment loads acting from the load side, etc. The effects of tilting, etc., are more pronounced on the rear end side of the axially long sleeve, the front end of which is fixed to the output member, and there is a risk that the detection accuracy of the output-side encoder will decrease.

[0006] In the rotary actuator (geared motor assembly) described in Patent Document 4, the front end of the sleeve is fixed to the output member using an adhesive that becomes elastic after hardening, and the rear end of the sleeve is supported by a sliding bearing, thereby suppressing a decrease in detection accuracy due to the sleeve tilting, etc. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-144971 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-243000 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-218422 [Patent Document 4] International Publication No. 2010 / 089796 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a rotary actuator in which a hollow portion of the actuator is defined by a cylindrical sleeve extending axially through the actuator, and an output-side detector for detecting reduced rotation is arranged near the output member so that the rotation state of the output member that outputs reduced rotation can be detected with high accuracy without being affected by tilting of the output member, etc. Another object of the present invention is to provide a rotary actuator in which the hollow portion of the actuator is defined by a cylindrical sleeve that extends axially through the actuator, the output side detector is located near the output member on the front end side of the strain wave gear device, and the input side detector that detects motor rotation is located on the rear end side of the motor, and the wiring for both detectors is gathered in one place and can be pulled out to the outside. [Means for solving the problem]

[0009] The rotary actuator of the present invention comprises: a hollow motor having a hollow motor shaft rotatably supported by a motor housing and extending axially therethrough; a wave gear device that is coaxially disposed at a front end of the hollow motor in the axial direction and that reduces the output rotation of the hollow motor; an output member that is arranged coaxially at a front end of the strain wave gear device in the axial direction and that transmits reduced rotation output from the strain wave gear device to a load side; an output side detector that detects a rotation state of the output member; a cylindrical sleeve extending axially through the hollow motor shaft, the strain wave gear device, and the output member; an actuator hollow portion formed by the sleeve and open to both ends in the axial direction; It is equipped with a rear end of the sleeve is fixed to a housing rear end portion that is located at the rear end of the motor housing in the axial direction, The output side detector is a fixed detector component attached to a front end of the sleeve passing through the output member; a rotation-side detector component attached to the output member so as to face the fixed-side detector component; It is characterized by having the following.

[0010] In the rotary actuator of the present invention, the rear end of a cylindrical sleeve extending axially through its center is fixed to the motor housing, which is the stationary member, and the front end of the sleeve extends to the output member. Because the sleeve is the stationary member, the front end of the sleeve, located near the rotation center of the output member, can be used as an attachment portion for the stationary detection component of the output detector. In other words, the output detector is incorporated into the central portion of the output member through which the front end of the sleeve penetrates. As a result, unlike when the output detector is located axially away from the output member at the rear end of the sleeve, the influence of the output member's tilt on the output detector is reduced, thereby preventing a decrease in detection accuracy. Furthermore, because the output detector is located inside the output member, a load member can be easily attached to the output member without being affected by the output detector.

[0011] Furthermore, unlike conventional rotary actuators, the sleeve does not rotate integrally with the output member, so it can be used as a part to fix other components. Also, while it was previously necessary to protect the internal wiring placed inside the sleeve from contact with the rotating sleeve when the sleeve rotates, this is no longer necessary.

[0012] Next, the rotary actuator of the present invention further comprises: an input side detector that detects the rotation state of the hollow motor shaft; a detector circuit board attached to a portion of the motor housing on the side where the rear end of the sleeve is located; a signal transmission line connecting the fixed detector component of the output detector attached to the front end of the sleeve and the detector circuit board; It is equipped with The signal transmission path includes a group of wires arranged in the gap between the hollow motor shaft and the sleeve, a wiring pattern printed on a flexible substrate attached to the outer surface of the sleeve, or a wiring pattern printed directly on the outer surface of the sleeve.

[0013] In a rotary actuator with this configuration, the wiring from the output detector, which is located axially forward of the input detector, can be routed rearward using the gap between the hollow motor shaft and the sleeve and collected on the detector circuit board of the input detector. Alternatively, signals from the output detector can be collected on the detector circuit board via a wiring pattern formed on the outer circumferential surface of the sleeve, which is the fixed member. This allows the outputs of both detectors to be collected in one location and extracted to the outside.

[0014] Next, the rotary actuator of the present invention further comprises: An oil seal provides a seal between the front end of the sleeve and the output member, and the rear end of the sleeve is fixed in a sealed state to the rear end of the housing.

[0015] In the present invention, the sleeve is a fixed member attached to the motor housing, so there is no rotating or sliding part at the rear end of the motor. This provides a reliable seal between the rear end of the sleeve and the rear end of the motor housing. This ensures that the electronic components that make up the input detector located inside the rear end of the motor are protected from the outside. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic vertical cross-sectional view showing a rotary actuator to which the present invention is applied. DETAILED DESCRIPTION OF THE INVENTION

[0017] A rotary actuator according to an embodiment of the present invention will be described below with reference to the drawings. The embodiment described below shows one application example of the present invention, and is not intended to limit the present invention to the embodiment.

[0018] 1, the rotary actuator 1 according to this embodiment includes a hollow motor 2, a harmonic drive gear 4 that is coaxially disposed at the axial front end of the hollow motor 2 and reduces the speed of the hollow motor 2, an output member 6 that is coaxially disposed at the axial front end of the harmonic drive gear 4 and transmits the reduced rotation output from the harmonic drive gear 4 to a load (not shown), and a cylindrical sleeve 7 that extends axially through the center of the hollow motor 2, the harmonic drive gear 4, and the output member 6. The sleeve 7 defines a hollow actuator portion 70 that is open at both axial ends. The rotary actuator 1 also includes an input-side detector 8 disposed at the rear end of the hollow motor 2 to detect the rotational state (rotational position, speed) of the hollow motor 2, and an output-side detector 9 disposed near the output member 6 to detect the rotational position of the output member 6.

[0019] The hollow motor 2 comprises a motor housing 21, a motor stator 22 attached to the motor housing 21, a hollow motor shaft 23 rotatably supported by the motor housing 21, and a motor rotor 24 attached to the outer periphery of the hollow motor shaft 23. The motor housing 21 is composed of a cylindrical housing main body with a disk-shaped mounting flange 25 formed at its front end and a disk-shaped end plate 26 formed at its rear end, and a cup-shaped detector cover 27 attached coaxially to the rear end of the end plate 26. The hollow motor shaft 23 is supported by motor bearings 28 and 29 attached to the mounting flange 25 and the end plate 26, respectively. A front end 231 of the hollow motor shaft 23 protrudes forward from the mounting flange 25, and a rear end 232 of the hollow motor shaft 23 protrudes rearward from the rear motor bearing 29.

[0020] The strain wave gearing 4 includes a rigid internal gear 41, a cup-shaped flexible external gear 42 coaxially disposed inside the rigid internal gear 41, and a wave generator 43 coaxially fitted inside the external gear 42. The strain wave gearing 4 also includes a reducer bearing 44 that supports the internal gear 41 and the external gear 42 so that they can rotate freely relative to each other. The internal gear 41 is sandwiched from both axial sides between the mounting flange 25 of the hollow motor 2 and an outer ring 441 of the reducer bearing 44, and the three components are fastened together in this state by fastening bolts. The external gear 42 includes a cylindrical portion 421 that is flexible in the radial direction, external teeth 422 formed on the outer peripheral surface portion on one open end side of the cylindrical portion 421, a diaphragm 423 that extends radially inward from the other end of the cylindrical portion 421, and a rigid cylindrical boss 424 that is integrally formed on the inner peripheral edge of the diaphragm 423. The external gear 42 is arranged with its open end facing the mounting flange 25 of the hollow motor 2, and a boss 424 located on the axial front side is coaxially fitted into and fixed to the center hole of an inner ring 442 of the reducer bearing 44. The wave generator 43 includes an annular rigid plug 431 coaxially fitted into and fixed to the outer circumferential surface of the front end 231 of the hollow motor shaft 23, and a wave generator bearing 432 attached to the non-circular outer circumferential surface of the rigid plug 431, which in this example is an elliptical outer circumferential surface. The wave generator 43 bends the portion of the external gear 42 where the external teeth 422 are formed into an elliptical shape, and the external teeth 422 located at both ends of the major axis of the ellipse mesh with the internal teeth 411 of the internal gear 41.

[0021] In this example, the output member 6 is formed integrally with the inner ring 442 of the reducer bearing 44 fixed to the external gear 42. That is, the inner ring 442 has an annular convex portion that protrudes forward from its end face facing forward in the axial direction, and this annular convex portion functions as the output member 6. The output member 6 may also be manufactured as a separate member and fastened to the front end face of the inner ring 442.

[0022] The cylindrical sleeve 7 extends from the rear end surface of the detector cover 27, which defines the axial rear end of the rotary actuator 1, to the front end surface of the output member 6, which defines the axial front end of the rotary actuator 1. The sleeve 7 is a fixed member fixed to the motor housing 21. That is, a rear end portion 71 of the sleeve 7 is fixed to a circular inner peripheral edge portion 271 of the detector cover 27. The rear end surface of this rear end portion 71 is exposed rearward from the detector cover 27. The sleeve 7 penetrates the hollow motor shaft 23 of the hollow motor 2 and the central holes of the rigid plug 431 and boss 424 of the strain wave gear device 4, with its front end portion 72 extending into the central hole 61 of the output member 6 and its front end surface exposed forward.

[0023] Next, the input-side detector 8 is a magnetic or optical encoder and includes a code wheel 81 on which magnetically or optically detectable detection codes are arranged in the circumferential direction, and a detector 82 that can magnetically or optically read the code wheel 81. The code wheel 81 is attached to the outer peripheral surface of the rear end 232 of the hollow motor shaft 23, which protrudes rearward from the rear motor bearing 29. The detector 82 is attached to the inner peripheral surface of the end plate 26 that surrounds the outer peripheral surface of the rear end 232 of the shaft, facing the code wheel 81 at a fixed distance. In addition, a detector circuit board 83 is disposed between the end plate 26 and the detector cover 27, on which a signal processing circuit for the detection signal from the detector 82 is mounted. The detector circuit board 83 is attached to the end plate 26 or the detector cover 27.

[0024] The output-side detector 9 is incorporated inside the central hole 61 of the output member 6, through which the front end 72 of the sleeve 7 passes. The output-side detector 9 includes a code wheel 91 (rotation-side detector component) that is a rotation-side detector component attached to the output member 6 side, and a circuit board 93 (fixed-side detector component) on which a detector 92 is mounted, which is attached to the front end 72 of the sleeve 7. In this example, an annular pedestal 94 is coaxially fixed to the inner circumferential surface of the central hole 61 of the output member 6, and the code wheel 91 is attached to the annular end surface of the pedestal 94 facing the axial rear. A cylindrical pedestal 95 is coaxially fixed to the outer circumferential surface of the sleeve 7 that extends through the central hole of the boss 424 of the external gear 42. The front end of the pedestal 95 has an annular end surface that faces the annular end surface of the pedestal 94 on the output member 6 side. A circuit board 93 with a detector mounted thereon is attached here, and the detector faces the code wheel 91 from the rear at a fixed distance. The sleeve 7 is supported via a pedestal 95 by a bearing 10 attached to the inner peripheral surface of the center hole of a rigid plug 431 of the wave generator 43 .

[0025] The outer peripheral surface of the front end 72 of the sleeve 7 and the inner peripheral surface of an annular base 94 attached to the output member 6 are sealed by an oil seal 11 placed between them. In addition, the rear end 71 of the sleeve 7 and the inner peripheral edge 271 of the detector cover 27 are fixed in a sealed state. This prevents lubricant from leaking from the inside to the outside along the outer peripheral surface of the sleeve 7, and also prevents foreign matter such as dust from entering the inside of the detector cover 27 from the outside.

[0026] Next, the wiring (signal transmission path) drawn from the output detector 9 arranged on the front side of the strain wave gear device 4 is collected on a detector circuit board 83 arranged on the rear side of the hollow motor 2, and is drawn from there to the outside. The wiring drawn from the circuit board 93 of the output detector 9 passes through a wiring hole or wiring groove formed in the base 94, as shown by the imaginary line 12, and is drawn to the rear side in the axial direction. The wiring drawn to the rear from the base 94 is connected to the outer surface of the sleeve 7 and the hollow motor shaft 23. Inner surfaceThe wiring is led out to the rear of the hollow motor shaft 23 through a gap 13 formed between the sleeve 7 and the hollow motor shaft 23, and connected to the detector circuit board 83. The wiring portion led out along the outer circumferential surface of the sleeve 7 may be a wiring pattern printed on a flexible substrate attached to the outer circumferential surface of the sleeve 7, or a wiring pattern printed directly on the outer circumferential surface of the sleeve 7.

[0027] In the rotary actuator 1 configured in this manner, when the wave generator 43 of the wave gearing 4 is rotated by the hollow motor shaft 23, a relative rotation occurs between the internal gear 41 and the external gear 42 according to the difference in the number of teeth therebetween. Because the internal gear 41 is the fixed member, the external gear 42 rotates. The rotation of the external gear 42 is output as reduced rotation from the output member 6 attached thereto to the load side (not shown). The rotational position of the hollow motor shaft 23 is detected by the input-side detector 8, and the rotational position of the output member 6 is detected by the output-side detector 9. Based on these detection results, the rotational position of the output member 6 is controlled with high precision.

[0028] In the rotary actuator 1, a cylindrical sleeve 7 extends axially through its center. The rear end 71 is fixed to the detector cover 27, which is the rear end of the motor housing 21, which is the stationary member, and the front end 72 of the sleeve 7 extends to the output member 6. The sleeve 7 is the stationary member, and the front end 72 of the sleeve 7, located near the rotation center of the output member 6, is used as an attachment portion for the stationary detection component of the output detector 9. The sleeve 7 is supported by a bearing 10 at a midpoint in the axial direction, making it easy to align the rotation center with the output member 6. This structure prevents a decrease in the detection accuracy of the output detector 9 due to, for example, tilting of the output member 6. Furthermore, because the output detector 9 is incorporated into the center hole of the output member 6, attachment of load members to the output member 6 can be easily performed from the axial front side without being affected by the output detector 9.

[0029] Furthermore, unlike conventional rotary actuators, the sleeve 7 does not rotate integrally with the output member 6, so the sleeve 7 can be used as a part for fixing other components. In addition, the sleeve 7, which is a fixing member, forms the actuator hollow portion 70. When members or components such as wiring groups are placed in the actuator hollow portion 70, there is no need to take measures to prevent them from coming into contact with and being damaged by the sleeve 7, so wiring, etc. can be easily performed using the actuator hollow portion 70.

[0030] Furthermore, the wiring drawn from the output detector 9, which is located axially forward of the input detector 8, is drawn rearward using the gap between the hollow motor shaft 23 and the sleeve 7 and is gathered at the detector circuit board 83 of the input detector 8. This allows the outputs of both detectors 8, 9 to be gathered in one place and drawn to the outside.

[0031] Next, in the rotary actuator 1, the sleeve 7 extending to the rear end of the motor is a fixed member, so there is no rotating sliding part at the rear end of the motor. A seal can be reliably formed between the rear end 71 of the sleeve 7 and the detector cover 27 at the rear end of the motor housing 21. This ensures that the electronic components and other components that make up the input-side detector 8, which are located in the space surrounded by the detector cover at the rear end of the motor, are protected from the outside.

Claims

1. a hollow motor having a hollow motor shaft rotatably supported by a motor housing and extending axially therethrough; a wave gear device that is coaxially disposed at a front end of the hollow motor in the axial direction and that reduces the output rotation of the hollow motor; an output member that is arranged coaxially at a front end of the strain wave gear device in the axial direction and that transmits reduced rotation output from the strain wave gear device to a load side; an output side detector that detects a rotation state of the output member; a cylindrical sleeve extending axially through the hollow motor shaft, the strain wave gear device, and the output member; an actuator hollow portion formed by the sleeve and open to both ends in the axial direction; A rotary actuator comprising: the sleeve is a fixed member having a rear end portion fixed to a housing rear end portion located at a rear end of the motor housing in the axial direction, The output side detector is a fixed detector component attached to a front end of the sleeve passing through the output member; a rotation-side detector component attached to the output member so as to face the fixed-side detector component; A rotary actuator comprising:

2. In claim 1, an input side detector that detects the rotation state of the hollow motor shaft; a detector circuit board attached to a portion of the motor housing on the side where the rear end of the sleeve is located; a signal transmission line connecting the fixed detector component of the output detector attached to the front end of the sleeve and the detector circuit board; It is equipped with The signal transmission path is a group of wires arranged in the gap between the hollow motor shaft and the sleeve, a wiring pattern printed on a flexible substrate attached to the outer peripheral surface of the sleeve, or a wiring pattern printed directly on the outer peripheral surface of the sleeve.

3. In claim 1, The space between the front end of the sleeve and the output member is sealed by an oil seal, The rear end of the sleeve is fixed in a sealing state to the rear end of the housing.

4. In claim 1, The strain wave gear device is a rigid internal gear fixed to the motor housing; a cup-shaped flexible external gear that is coaxially disposed inside the internal gear and coaxially fixed to the output member; a wave generator that is coaxially fitted inside the external gear and coaxially fixed to the hollow motor shaft; a reducer bearing that supports the internal gear and the external gear so that they can rotate relative to each other; It is equipped with The reducer bearing is a rotary actuator including an outer ring attached to the internal gear and an inner ring attached to the output member or formed integrally with the output member.

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