rotary actuator

Abstract

A rotary actuator (1) is provided with a PWB motor (2) and a wave gear reducer (3). The PWB motor (2) is an axial gap type motor. A motor rotor (24) of the PWB motor (2) is provided with a rotor disc coaxially fixed to a hollow motor shaft (22) and a rotor magnet fixed to the rotor disc. A motor stator (23) is composed of a printed wiring board and is provided with an insulating substrate (26) and a motor coil (27) defined by a printed wiring formed on the insulating substrate (26). Compared with a conventional rotary actuator using an SPM motor or the like, the axial length can be shortened and the hollow diameter can be increased.

Description

TECHNICAL FIELD

[0001] The present application relates to a rotary actuator provided with a wave gear reducer and a motor. BACKGROUND

[0002] As a rotary actuator provided with a wave gear reducer and a motor, a hollow type rotary actuator as disclosed in Patent Documents 1 and 2 is known. With the hollow type rotary actuator as disclosed in the above Patent Documents 1 and 2, a hollow motor is coaxially linked to a hollow wave gear reducer, and a hollow portion extends in such a manner as to pass through a center portion of the actuator in the axial direction. As a motor of the rotary actuator, a SPM motor (Surface Permanent Magnet Motor) is generally used. The SPM motor is a synchronous motor of a rotating magnetic field type in which permanent magnets are attached to an outer periphery of a rotor installed on an outer periphery of a hollow motor shaft.

[0003] Figure 7 is a diagram showing a hollow type rotary actuator provided with a wave gear reducer and a SPM motor. The rotary actuator 400 is provided with a SPM motor 410, and a wave gear reducer 450 coaxially linked to the SPM motor 410. An encoder 460 is attached to the SPM motor 410. The SPM motor 410 is provided with a hollow motor shaft 411, a motor rotor 420 coaxially fixed to an outer periphery of the hollow motor shaft 411, and a motor stator 430 coaxially surrounding the motor rotor 420. Further, a motor wiring substrate 440 is arranged in a side direction of the motor rotor 420 and the motor stator 430.

[0004] The motor rotor 420 is provided with a circular ring-shaped rotor yoke 421 fixed to an outer periphery of the hollow motor shaft 411, and a plurality of magnets 422 attached to an outer peripheral surface of the rotor yoke 421. The motor stator 430 is provided with a circular ring-shaped stator core 431 composed of a laminate of electromagnetic steel sheets, a plurality of salient poles 432 formed at a constant angular interval along an inner peripheral surface of the stator core 431, and a stator coil 433 composed of windings arranged on each salient pole 432. Each stator coil 433 is covered with an insulating member 434. Each phase (for example, three phases of U, V, and W) winding is connected to the motor wiring substrate 440 by welding. Further, a motor power line 413 introduced from the outside is attached to the motor wiring substrate 440 by soldering.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: International Publication No. 2010 / 089796

[0008] Patent Literature 2: Japanese Patent Application Laid-Open (JP A) No. 2001-304382 SUMMARY

[0009] A rotary actuator provided with a wobble gear reducer and a motor is assembled as a power unit, for example, to an apparatus such as an industrial robot. In view of miniaturization and the like of the apparatus, a rotary actuator having a short shaft length, a rotary actuator having a short shaft length and a large hollow diameter, and the like are desired.

[0010] In addition, as described above, an SPM motor for a rotary actuator is provided with a motor stator that forms windings by separately performing winding on a plurality of salient poles formed on an inner peripheral surface of a stator core composed of a laminate of electromagnetic steel sheets and constitutes each winding by performing insulation on the windings, and a motor rotor that is composed by adhering a magnet to an outer peripheral surface of a ring-shaped rotor yoke. The SPM motor has a relatively large number of components, a large number of assembly processes, and a high manufacturing cost. In addition, an insulating member having a complex shape is required to achieve insulation of the windings of each salient pole. Furthermore, since an electromagnetic steel sheet is used for the motor stator, cogging torque is generated.

[0011] In addition, with respect to the SPM motor, winding is performed to form windings on the outer periphery of each salient pole of the stator core that is a laminate of electromagnetic steel sheets. The arrangement of the windings for each salient pole is not simple, and it is not simple to increase the winding space factor. Furthermore, after the winding work for each salient pole, wiring work of each phase winding is required. For example, in the wiring work of U, V, and W three-phase windings, there are many manual operations such as wire coating peeling processing and soldering wiring, and skilled experience is required. It is also not simple to ensure the quality of soldering. Furthermore, the power lines are directly connected to the windings, so if the power lines are broken, replacement is required for each motor.

[0012] An object of the present application is to provide a rotary actuator provided with a wobble gear reducer and a motor and having a short shaft length. In addition, an object of the present application is to provide a rotary actuator of a hollow type provided with a wobble gear reducer and a motor and having a short shaft length and a large hollow diameter.

[0013] The present application relates to a rotary actuator provided with a motor and a wobble gear reducer linked to the motor in such a manner that the output rotation of the motor is reduced and output, and an axial gap type motor is used as the motor, the axial gap type motor being provided with a motor shaft and a motor rotor and a motor stator opposed at a constant interval in the direction of the central axis of the motor shaft. The motor rotor is provided with a rotor disc coaxially fixed to the motor shaft and a rotor magnet fixed to the rotor disc. In addition, the motor stator is provided with an insulating substrate and a motor coil defined by a printed wiring formed on the surface or inside of the insulating substrate.

[0014] Further, the hollow type rotary actuator of the present application, on the basis of the above-described structure, uses a hollow motor shaft that extends in a manner that passes through the center portion of the motor in the direction of the center axis. Further, the wave gear reduction device is provided with a reduction device hollow portion that extends in a manner that passes through the wave gear reduction device in the direction of the center axis, and the reduction device hollow portion communicates coaxially with the hollow portion of the hollow motor shaft.

[0015] In the motor of the rotary actuator of the present application, the motor stator is constituted by a printed wiring board (PWB) that is provided with an insulating substrate and a motor coil that is defined by a printed wiring formed on the surface or inside of the insulating substrate. Hereinafter, the motor of this structure will be referred to as a PWB motor. Compared with the conventional rotary actuator that uses a radial gap type SPM motor, the rotary actuator of the present application that uses an axial gap type PWB motor can shorten the shaft length, and also can increase the hollow diameter. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a longitudinal sectional view that shows a hollow type rotary actuator to which Embodiment 1 of the present application is applied.

[0017] Figure 2 is a front view and a perspective view of a PWB motor of Figure 1

[0018] Figure 3 is a perspective view and an exploded perspective view of another example of a PWB motor.

[0019] Figure 4 is a longitudinal sectional view that shows a hollow type rotary actuator to which Embodiment 2 of the present application is applied.

[0020] Figure 5 is a longitudinal sectional view that shows an example of a 2-axis rotary actuator.

[0021] Figure 6 is a longitudinal sectional view that shows another example of a 2-axis rotary actuator.

[0022] Figure 7 is an explanatory view that shows a conventional hollow type rotary actuator. DETAILED DESCRIPTION

[0023] Hereinafter, a rotary actuator according to an embodiment of the present application will be described with reference to the drawings. Note that the following description is not intended to limit the present application to the embodiment.

[0024] (Embodiment 1)

[0025] Figure 1 ​is a schematic longitudinal sectional view showing a hollow type rotary actuator according to Embodiment 1 of the present application. The rotary actuator 1 is provided with a PWB motor 2, a wave gear reducer 3 coupled to the PWB motor 2 in such a manner that the rotation outputted from the PWB motor 2 is reduced and outputted, and a rotary encoder 4 that detects the rotation of the PWB motor 2.

[0026] The PWB motor 2 is an axial gap type motor provided with a cylindrical housing 21, a hollow motor shaft 22, a motor stator 23, and a motor rotor 24 arranged inside the housing 21. The hollow motor shaft 22 is coaxially arranged inside the housing 21 in a rotatable state by means of a bearing. The hollow motor shaft 22 extends in such a manner that the central portion of the PWB motor 2 is penetrated in the direction of the central axis la. The motor stator 23 and the motor rotor 24 are arranged in parallel in constant intervals in the direction of the central axis la of the hollow motor shaft 22 in a state of coaxially surrounding the hollow motor shaft 22.

[0027] The rotary encoder 4 is arranged at the rear side axial end portion 22a of the hollow motor shaft 22. The rotary encoder 4 is covered by an encoder cover 41 installed at the rear side open end of the housing 21. The rear end of the hollow motor shaft 22 penetrates the central portion of the encoder cover 41, and the hollow portion 22b of the hollow motor shaft 22 is open to the rear. The front side axial end portion 22c of the other side of the hollow motor shaft 22 penetrates the housing partition wall 25 between the hollow motor shaft 22 and the wave gear reducer 3 in a rotatable state, and extends to the side of the wave gear reducer 3.

[0028] The wave gear reducer 3 is provided with a rigid internal gear 31, a flexible external gear 32, and a wave generator 33. In this example, the external gear 32 is a top hat shaped external gear, and is fixed to the housing 21. The external gear 32 and the internal gear 31 are held in a state of being relatively rotatable by means of a bearing 34. The wave generator 33 is a rotational input element, and is provided with a rigid plug 33a coaxially fixed to the outer peripheral surface of the front side axial end portion 22c of the hollow motor shaft 22, and a wave bearing 33b fitted to the elliptical outer peripheral surface of the above-mentioned rigid plug 33a. The portion of the external gear 32 in which the external teeth 32a are formed is flexed into an elliptical shape by the wave generator 33. Thus, at the positions of both ends of the major axis of the elliptical shape, the external teeth 32a engage with the internal teeth 31a of the internal gear 31.

[0029] The internal gear 31 is a reduction rotation output element, and a disc-shaped output shaft 35 is fixed coaxially to the internal gear 31. A central hole 35a of the output shaft 35 communicates coaxially with the hollow portion 22b of the hollow motor shaft 22. A reduction gear hollow portion extending in a manner that passes through the center portion of the reduction gear 3 is formed by the hollow portion of the shaft end portion 22c of the hollow motor shaft 22 and the central hole 35a. That is, the hollow portion extending in a manner that passes through the center portion of the rotation actuator 1 in the direction of the center axis 1a and opens at both ends is formed in the rotation actuator 1.

[0030] Figure 2 (a) is a schematic front view showing the PWB motor 2, Figure 2 (b) is a schematic perspective view showing the PWB motor 2. Reference Figure 1 、 Figure 2 is made, the motor stator 23 of the PWB motor 2 is provided with an insulating substrate 26 having a central hole through which the hollow motor shaft 22 passes in a rotatable state, and a motor coil 27 (a coreless coil) defined by a coil winding pattern formed of a copper foil formed in the insulating substrate 26. The insulating substrate 26 is fixed to the housing 21. In this example, the motor coils 27 are arranged at equal angle intervals around the center axis 1a on the surface of the insulating substrate 26. For example, 12 motor coils 27 of U, V, and W phases are arranged in the circumferential direction. The arrangement form, the number of arrangements, the shape, and the like of the motor coils 27 are not limited to the example shown in the drawing.

[0031] The motor rotor 24 is provided with a rotor disc 28 of constant thickness fixed coaxially to the hollow motor shaft 22, and a rotor magnet 29 mounted to the rotor disc 28. The rotor magnet 29 is arranged at equal angle intervals around the center axis 1a. In this example, eight circular magnet insertion holes 28a are formed at equal angle intervals in the circumferential direction in the rotor disc 28. A rotor magnet 29 of disc shape having a thickness greater than that of the rotor disc 28 is inserted in each of the magnet insertion holes 28a. Further, the arrangement form, the number of arrangements of the rotor magnet 29 are not limited to the example shown in the drawing. In addition, the shape of the rotor magnet 29 is not limited to the disc shape, and can be a quadrangular shape or the like. Further, the mounting method can employ various methods such as adhesion, press-fitting, and the like.

[0032] The motor coil 27 of the motor stator 23 and the rotor magnet 29 of the motor rotor 24 are opposed at a constant gap in the direction of the center axis 1a. Thereby, a motor magnetic circuit is constituted. Further, a motor power line 5 is disposed through a wiring hole formed in the housing 21. The motor power line 5 is connected to the connector 6 mounted to the insulating substrate 26, and is connected to a wiring pattern (not shown) formed in the insulating substrate 26 via the connector 6.

[0033] As explained above, the rotary actuator 1 of the present embodiment employs the PWB motor 2 of the axial gap type. The PWB motor 2 is configured to include a motor stator 23 configured to have an insulating substrate 26 formed with a coil winding pattern, and a motor rotor 24 configured to have a rotor disc 28 to which a rotor magnet 29 is attached. Compared with the conventional rotary actuator employing the SPM motor of the radial gap type, it is possible to shorten the shaft length, and in addition, it is also possible to increase the hollow diameter.

[0034] In addition, compared with the SPM motor generally used, the number of parts and the number of assembly processes are small, so that it is also possible to reduce the manufacturing cost. In order to achieve the insulation of the winding of each salient pole, it is not necessary to use a complicatedly shaped insulating member. Further, since an electromagnetic steel sheet is not used for the motor stator, there is also no concern about the generation of cogging torque.

[0035] Further, with regard to the PWB motor 2, as long as the winding pattern composed of a copper foil is formed on the surface or inside of the insulating substrate, it is possible to simply form a high-precision winding pattern, and it is also possible to improve the winding space factor. In addition, it is not necessary to perform a manual work such as soldering work of the winding. Further, the connection of the power line and the winding pattern can be formed by means of a connector mounted on the insulating substrate. Thus, it is possible to avoid the influence of the breakage of the power line on the insulating substrate and the winding pattern.

[0036] Figure 3 is a schematic perspective view and a schematic exploded perspective view showing another example of the PWB motor 2. With regard to the PWB motor 2A shown in these drawings, the motor stators 23A, 23B are arranged on both sides in the direction of the central axis la with the motor rotor 24A interposed, coaxially attached to the hollow motor shaft 22. The configurations of the motor stators 23A, 23B are the same as those of the above-described motor stator 23, and are symmetrically arranged with the motor rotor 24A interposed. In addition, the configuration of the motor rotor 24A is also the same as that of the above-described motor rotor 24. By using two motor stators 23A, 23B, it is possible to improve the motor output.

[0037] (Embodiment 2)

[0038] Figure 4is a schematic longitudinal sectional view of a flat / hollow type rotary actuator according to Embodiment 2. The rotary actuator 100 is provided with a PWB motor 120, a cup-shaped wave gear reducer 130, a circular ring-shaped output shaft 140, and a rotary encoder 150 that detects the rotation of the PWB motor 120. The rotary encoder 150 is disposed at the end (rear end) of the side of the cylindrical housing 160 on the side of the rear of the actuator (one side in the direction of the central axis 100a). The PWB motor 120 and the wave gear reducer 130 are assembled inside the housing 160 from the rear end of the housing 160 toward the front of the actuator, and the output shaft 140 is disposed at the front end of the housing 160. The output shaft 140 is supported in a rotatable state by a cross roller bearing 170 and the housing 160.

[0039] The PWB motor 120 is a hollow motor of the axial gap type, and is provided with a hollow motor shaft 122, a motor rotor 124 assembled to the hollow motor shaft 122, and a motor stator 123 assembled to the housing 160. With respect to the hollow motor shaft 122, the front side portion in the direction of the central axis 100a is a small-diameter shaft portion 122a, and the rear side portion is a large-diameter shaft portion 122b. A rotor disc 122c that expands to the outside in the radial direction is integrally formed at the rear end of the small-diameter shaft portion 122a, and the front end of the large-diameter shaft portion 122b is coaxially joined and fixed to the rotor disc 122c. The motor rotor 124 is provided with a rotor magnet 124a that is installed at a position on the outer peripheral side of the large-diameter shaft portion 122b of the rotor disc 122c. The motor stator 123 opposes the rotor magnet 124a with a slight gap from the rear side in the direction of the central axis 100a.

[0040] The rotary encoder 150 is assembled at the shaft end portion on the rear side of the large-diameter shaft portion 122b of the hollow motor shaft 122. The rotary encoder 150 is covered by an encoder cover 151 that is installed at the open end on the rear side of the housing 160. A motor hollow portion 125 that is the hollow portion of the hollow motor shaft 122 is open to the rear from a central opening portion 152 of the encoder cover 151. An oil seal 153 is installed at the central opening rim of the encoder cover 151. With respect to the motor hollow portion 125, the rear side in the direction of the central axis 100a is a large-diameter hollow portion, and the front side is a small-diameter hollow portion.

[0041] The wave gear reducer 130 has a hollow input shaft 131 which is formed integrally with the small diameter shaft portion 122a of the hollow motor shaft 122 on the front side, a wave generator 132 which is assembled to the outer peripheral surface of the hollow input shaft 131, a flexible outer tooth gear 133 which is formed in a cup shape, and a circular ring-shaped rigid inner tooth gear 134 which is formed integrally with the inner peripheral surface of the housing 160. A disc-shaped partition plate portion 161 is formed on the end surface of the inner tooth gear 134 on the motor side. The PWB motor 120 and the wave gear reducer 130 are partitioned by the partition plate portion 161. The portion of the hollow input shaft 131 which is connected to the hollow motor shaft 122 is supported in a rotatable state by a bearing 162 which is mounted to the inner peripheral edge portion of the partition plate portion 161.

[0042] The outer tooth gear 133 has a cylindrical main body portion 133a which is flexible in the radial direction, a disc-shaped diaphragm 133b which extends to the inner side in the radial direction from the rear end of the cylindrical main body portion 133a, a rigid circular ring-shaped protrusion 133c which is continuously formed integrally with the inner peripheral edge of the diaphragm, and outer teeth 133d which are formed on the outer peripheral surface portion of the open end side of the cylindrical main body portion 133a. The outer tooth gear 133 is a deceleration rotation output element, and the rigid protrusion 133c of the outer tooth gear 133 is coaxially connected and fixed to the output shaft 140. In this example, the output shaft 140 is formed integrally with the inner race 171 of the cross roller bearing 170. The outer race 172 of the cross roller bearing 170 is connected and fixed to the housing 160.

[0043] The wave generator 132 is arranged on the inner side of the portion of the outer tooth gear 133 in which the outer teeth 133d are formed. The wave generator 132 has an elliptical profile plug portion 132a which is formed integrally with the outer peripheral surface of the hollow input shaft 131, and a wave bearing 132b which is mounted to the elliptical outer peripheral surface of the plug portion 132a. The portion of the outer tooth gear 133 in which the outer teeth 133d are formed is flexed into an elliptical shape by the wave generator 132. Thus, the outer teeth 133d are engaged with the inner teeth 134a of the inner tooth gear 134 at the positions of both ends of the major axis of the elliptical shape.

[0044] The front end of the hollow input shaft 131 extends to near the boss 133c of the external gear 133. An annular bearing support 135 is coaxially fixed to the boss 133c. The front end of the hollow input shaft 131 is rotatably supported by a bearing 136 mounted on the bearing support 135. The hollow portion of the boss 133c, the hollow portion of the bearing support 135, and the hollow portion of the hollow input shaft 131 form a reducer hollow portion 137 that penetrates the center of the wave gear reducer 130. The reducer hollow portion 137 is coaxially connected to the motor hollow portion 125. The motor hollow portion 125 and the reducer hollow portion 137 form an actuator hollow portion that extends in the direction of the central axis 100a and penetrates the rotary actuator 100.

[0045] In this structure of the rotary actuator 100, the rotation of the hollow motor shaft 122 of the PWB motor 120 is transmitted to the wave generator 132 via the hollow input shaft 131. Rotation of the wave generator 132 causes the meshing position of the external gear 133 with the internal gear 134 to move circumferentially. This generates relative rotation between the two gears 133 and 134, corresponding to the difference in the number of teeth between the two gears. Because the internal gear 134 is a fixed-side component integrally formed with the housing 160, the external gear 133 rotates. The rotation of the external gear 133 is then output via the output shaft 140.

[0046] The PWB motor 120 is configured as Figure 2 The motor stator 123 of the PWB motor 120 is the same as the PWB motor 2 shown. The motor stator 123 of the PWB motor 120 includes: an insulating substrate 123a having a center hole, and the large diameter shaft portion 122b of the hollow motor shaft 122 rotatably passes through the center hole; and a motor coil (not shown) defined by a coil winding pattern composed of copper foil formed on the insulating substrate 123a. The insulating substrate 123a is fixed to the housing 160. The motor coils are arranged on the surface of the insulating substrate 123a with the center axis 100a as the center and at equal angular intervals. For example, 12 motor coils forming the U, V, and W phases are arranged in the circumferential direction. The arrangement form, number of arranged coils, shape, etc. of the motor coils are not limited to the example shown in the figure.

[0047] The motor rotor 124 has rotor magnets 124a installed to a rotor disc 122c of constant thickness, which is integrally formed to the small diameter shaft portion 122a of the hollow motor shaft 122. The rotor magnets 124a are arranged at equal angular intervals about the center axis 100a. For example, eight circular magnet insertion holes 122d are formed at equal angular intervals in the circumferential direction of the rotor disc 122c. A disc-shaped rotor magnet 124a having a thickness greater than that of the rotor disc 122c is inserted into each of the magnet insertion holes 122d. The arrangement form and number of the rotor magnets 124a are not limited to the example shown in the drawing. In addition, the shape of the rotor magnets 124a is not limited to a disc shape, but can be a quadrangular shape or the like. Furthermore, various methods such as adhesion or press-fitting can be used for the installation method.

[0048] The motor coil (not shown) of the motor stator 123 opposes the rotor magnets 124a of the motor rotor 124 in the direction of the center axis 100a with a constant gap therebetween. This forms a motor magnetic circuit. In addition, a motor power line 180 is routed through a wiring hole formed in the housing 160. The motor power line 180 is connected to a connector 190 mounted to the insulating substrate 123a, and is connected to a wiring pattern (not shown) formed in the insulating substrate 123a via the connector 190. Furthermore, as the PWB motor 120, a motor of the structure shown in FIG. 2 can also be used. Figure 3

[0049] As described above, the rotary actuator 100 uses the PWB motor 120 of the axial gap type. Compared to a conventional rotary actuator using an SPM motor of the radial gap type, the shaft length can be shortened, and in addition, the hollow diameter can be increased. In particular, the motor hollow portion 125 can be formed to have a large diameter. In addition, compared to a generally used SPM motor, the number of parts and the number of assembly processes are small, so that the manufacturing cost can also be reduced. In order to achieve insulation of the windings of each salient pole, a complicatedly shaped insulating member need not be used. Furthermore, since an electromagnetic steel sheet is not used for the motor stator, there is also no concern about generation of cogging torque.

[0050] Furthermore, with the PWB motor 120, as long as a winding pattern composed of a copper foil is formed on the surface or inside of the insulating substrate 123a, a high-precision winding pattern can be easily formed, and the winding space factor can also be improved. In addition, manual work such as soldering of the winding is not necessary. Furthermore, connection of the power line to the winding pattern can be formed via the connector 190 mounted to the insulating substrate 123a. Thus, damage to the power line can be prevented from affecting the insulating substrate 123a and the winding pattern.

[0051] (Multi-axis rotary actuator)

[0052] ​As described above, in the rotary actuator 100, the PWB motor 120 is an axial gap type motor, and there is no need to arrange the constituent parts in the radial direction, so it is easy to increase the hollow diameter of the motor hollow portion 125. For example, it is easy to set the hollow diameter of the large-diameter hollow portion of the motor hollow portion 125, which is open at the rear end, to a size larger than the outer diameter dimension of the front end portion of the output shaft 140 arranged at the front end. If the dimensions are thus set, it is possible to coaxially connect the rotary actuators 100 in the axial direction to constitute a multi-axle rotary actuator.

[0053] Figure 5 is a schematic longitudinal sectional view showing the structure of a 2-axle rotary actuator 200 in which rotary actuators 100(1), 100(2) of the same size and the same structure are connected in the axial direction. The front rotary actuator 100(1) and the rear rotary actuator 100(2) are formed in the same size and the same structure as the above-described rotary actuator 100, so the explanation of the structure thereof is omitted. The front end portion of the output shaft 140(2) of the rear rotary actuator 100(2) is coaxially inserted in the motor hollow portion 125(1) open at the rear end of the front rotary actuator 100(1) in a rotatable state. In this state, the two rotary actuators 100(1), 100(2) are connected and fixed. The inner peripheral portion of the center opening portion 152(1) of the encoder cover 151(1) defining the rear end portion of the motor hollow portion 125(1) and the outer peripheral surface of the rear output shaft 140(2) are sealed by the oil seal 153(1) attached to the encoder cover 151.

[0054] By coaxially connecting the rotary actuators 100(1), 100(2) of the same size, it is possible to arrange the output shaft 140(1) of the front rotary actuator and the output shaft 140(2) of the rear rotary actuator on the same axis. Similarly, by coaxially connecting three or more rotary actuators 100 of the same size, it is possible to constitute a multi-axle rotary actuator.

[0055] With respect to the 2-axle rotary actuator 200 or the multi-axle rotary actuator, a hollow portion having a large inner diameter extending in a manner that the center thereof is penetrated is formed. This hollow portion can be used as a space through which a plurality of wires, pipes pass. In addition, it can be used as a space in which a ball screw or the like power transmission member is arranged. Furthermore, it can also be used as an optical path of laser light or the like.

[0056] Figure 6is a schematic longitudinal sectional view of a 2-axis rotary actuator 300 in which rotary actuators 100(1), 100(3) of different sizes and the same structure are coupled in the axial direction. The rotary actuator 100(1) is formed in the same size and the same structure as the rotary actuator 100 described above. The rotary actuator 100(3) is formed in the same structure as the rotary actuator 100, but is one size smaller than the rotary actuator 100. In this example, the outer diameter dimension of the housing 160(3) of the rotary actuator 100(3) is set to a dimension smaller than the inner diameter dimension of the large-diameter hollow portion on the rear side of the motor hollow portion 125(1) of the rotary actuator 100(1). In addition, the outer diameter dimension of the front end portion of the output shaft 140(3) of the rotary actuator 100(3) is set to a dimension smaller than the inner diameter dimension of the small-diameter hollow portion on the front side of the motor hollow portion 125(1) of the rotary actuator 100(1).

[0057] As shown in Figure 6 , the rotary actuator 100(3) of the smaller size on the rear side is inserted from the rear end opening portion side of the motor hollow portion 125(1) of the rotary actuator 100(1) of the larger size on the front side in a coaxial state. In this state, the housings of the two rotary actuators 100(1), 100(3) are coupled to each other. In addition, the space between the two rotary actuators 100(1), 100(3) is sealed by the oil seal 153(1). Thus, the 2-axis rotary actuator 300 of a short axial length can be configured.

Claims

1. A rotary actuator comprising: a motor; and a wave gear reducer connected to the motor so as to reduce the output rotation of the motor and output the output rotation; It is characterized by: The motor is an axial gap type motor and includes: a motor shaft; and a motor rotor and a motor stator, which are opposed to each other at a constant interval in the direction of the central axis of the motor shaft. The motor rotor includes: a rotor disk coaxially fixed to the motor shaft; and a rotor magnet fixed to the rotor disk. The motor stator includes: an insulating substrate; and a motor coil defined by printed wiring formed on the surface or inside of the insulating substrate. The motor shaft is a hollow motor shaft extending in the direction of the central axis so as to penetrate the central portion of the motor. The hollow portion of the hollow motor shaft forms a motor hollow portion. The wave gear reducer includes a reducer hollow portion extending in the direction of the central axis so as to penetrate the wave gear reducer. The hollow portion of the reducer is coaxially connected to the hollow portion of the motor. The hollow portion of the reducer opens on one side in the direction of the central axis, that is, in front of the actuator. The motor hollow portion opens on the other side of the central axis, that is, behind the actuator. Regarding the hollow motor shaft, the front portion in the direction of the central axis is a small-diameter shaft portion, and the rear portion is a large-diameter shaft portion. The rotor disk extending radially outward is formed at the rear end of the small-diameter shaft portion in the direction of the central axis. The front end of the large-diameter shaft portion in the direction of the central axis is coaxially connected and fixed to the rotor disk. The rotor magnet is mounted on a portion on the outer peripheral side of the large-diameter shaft portion of the rotor disk. The motor hollow portion includes: a large-diameter hollow portion defined by the large-diameter shaft portion and opening at the rear of the actuator; and a small-diameter hollow portion defined by the small-diameter shaft portion. The wave gear reducer includes a hollow output shaft for outputting reduced rotation, and the hollow output shaft is arranged at an end portion in front of the actuator. The hollow diameter of the large-diameter hollow portion is set to be larger than the outer diameter of a front end portion of the hollow output shaft of the wave gear reducer in the direction of the central axis.

2. The rotary actuator according to claim 1, wherein: The rotary actuator includes a cylindrical housing. The motor and the wave gear reducer are assembled inside the housing from the rear end of the housing on the rear side of the actuator toward the front of the actuator, and the hollow output shaft is arranged at the front end of the housing on the front side of the actuator. An internal gear is formed on the inner circumferential surface of the housing, and a disc-shaped partition plate portion is formed on the end surface of the internal gear facing the rotor disc side of the motor. The small diameter shaft portion of the hollow motor shaft is supported by a bearing installed between the inner circumferential edge portion of the partition plate portion and the outer circumferential surface of the small diameter shaft portion of the hollow motor shaft in a freely rotatable state.

3. A multi-axis rotary actuator, characterized in that: It has a front rotary actuator and a rear rotary actuator. The front-stage rotary actuator and the rear-stage rotary actuator are respectively the rotary actuators according to claim 1 or claim 2, The front end portion of the hollow output shaft of the rear-stage rotary actuator is coaxially inserted into the large-diameter hollow portion of the motor hollow portion with a rear end opening in the direction of the central axis of the front-stage rotary actuator in a freely rotatable state. In this state, the respective shells of the front-stage rotary actuator and the rear-stage rotary actuator are connected and fixed to each other.

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