Hollow rotary actuator

Abstract

To provide a hollow rotary actuator with a relatively large reduction ratio while keeping costs down. [Solution] The hollow rotary actuator 100 comprises a rotating shaft 18 having an internal gear 15 that meshes with a drive pinion 17 and an output stage pinion 9, and a ring-shaped external gear 4 that meshes with the output stage pinion. The internal gear and the output stage pinion are positioned at an interval in the axial direction of the rotating shaft, and the meshing direction between the internal gear and the drive pinion as seen from the drive pinion and the meshing direction between the external gear and the output stage pinion as seen from the external gear may be the same.

Description

Technical Field

[0001] The present invention relates to a hollow rotary actuator.

Background Art

[0002] The following Patent Documents 1 and 2 are cited as documents related to hollow rotary actuators.

[0003] Patent Document 1 describes an electric motor with a speed reducer formed by assembling a speed reducer to an electric motor. This electric motor with a speed reducer is provided with a hollow portion for accommodating an air tube, an electric wire, etc. A gear formed at the end of the output shaft of the electric motor meshes with the gear portion of a spur gear incorporated in the gear case of the speed reducer, and the driven member rotates by the rotation of the spur gear. In this electric motor with a speed reducer, in order to eliminate the backlash between the gear formed on the output shaft of the electric motor and the gear portion of the spur gear, a change in the axial distance between the gear and the gear portion of the spur gear is absorbed by the deflection of the output shaft of the electric motor.

[0004] Patent Document 2 cites Patent Document 1 as prior art. The hollow speed reducer described in Patent Document 2 includes a sun gear that rotates in response to the driving force of a drive source, an internal gear coaxially arranged with respect to the sun gear with an air gap between them, planetary gears that mesh with the sun gear and the internal gear and revolve around the sun gear while rotating on their own axis, a planetary speed reducer output shaft that rotatably supports the planetary gears and rotates on its own axis around the rotation axis of the sun gear due to the revolution of the planetary gears, an input gear that rotates around the rotation axis of the planetary speed reducer output shaft, an output gear that meshes with the input gear, and an output shaft that has a hollow portion formed on its inner circumference and rotates as the output gear rotates. Furthermore, Patent Document 2 also describes how this hollow reducer includes a case that internally supports the output shaft, a planetary reducer case that houses the sun gear, the internal gear, and the planetary gears, and connecting bolts that connect the planetary reducer case and the case via a reducer mounting flange, the reducer mounting flange is provided with connecting bolt insertion holes into which the connecting bolts are inserted, and a clearance is provided between the connecting bolt insertion holes and the connecting bolts to eliminate backlash caused by variations in machining accuracy due to machining errors and assembly errors. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-235207 [Patent Document 2] Japanese Patent Publication No. 2011-38573 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In Patent Document 1, backlash can be eliminated by pressing a cantilevered pinion (small gear) against a large gear, but it may be difficult to achieve a relatively large reduction ratio. In Patent Document 2, it is thought that a relatively large reduction ratio can be achieved with a planetary gear reduction mechanism, but planetary gear reduction mechanisms generally have a large number of parts and tend to be expensive.

[0007] In view of these circumstances, the present invention aims to provide a hollow rotary actuator with a relatively large reduction ratio while keeping costs down. [Means for solving the problem]

[0008] The hollow rotary actuator according to the present invention comprises a rotating shaft having an internal gear that meshes with a drive pinion and an output stage pinion, and a ring-shaped external gear that meshes with the output stage pinion.

[0009] According to the present invention, it is possible to provide a hollow rotary actuator with a relatively large reduction ratio while keeping costs down. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view of a hollow rotary actuator. [Figure 2] This is a cross-sectional view of the motor section. [Figure 3] This is a cross-sectional view of the first stage deceleration section. [Figure 4] This is a cross-sectional view of the output stage reduction section. [Figure 5] This is a bottom view of the output stage reduction gear. [Figure 6] This is a bottom view of the first stage deceleration unit. [Figure 7] This is a cross-sectional view of the first-stage reduction gear unit assembled with the motor unit. [Figure 8] This is an explanatory diagram of a double-sided cantilevered beam. [Figure 9] This is a perspective view showing an example of tooth contact. [Figure 10]It is a perspective view showing another example of the tooth contact state. [Figure 11] It is a perspective view showing the tooth contact state in one embodiment of the present invention.

Mode for Carrying Out the Invention

[0011] Embodiments of the present invention will be described below. However, the present invention is not limited to the embodiments described below. In the figures referred to below, the x-axis, y-axis, and z-axis may be shown. The orthogonal coordinate system of the three-dimensional space is a right-handed system, the xy plane is the horizontal plane, and the z-axis is vertically upward with respect to the xy plane.

[0012] As shown in FIG. 1, a hollow rotary actuator 100 according to one embodiment has an output stage reduction unit 110, a first stage reduction unit 120, and a motor unit 130.

[0013] As shown in FIGS. 1 and 2, the motor unit 130 has a flange surface 132 which is an attachment surface to which the first stage reduction unit 120 is attached. The output shaft 131 of the motor unit 130 projects from the flange surface 132 along the positive z-axis direction. The positive z-axis direction can also be called the output direction, and the negative z-axis direction can also be called the reverse output direction. A motor pinion 17 is formed at the tip of the output shaft 131. The motor pinion 17 meshes with the internal teeth 15a of an internal gear 15 in the first stage reduction unit 120 described later.

[0014] The motor pinion 17 may be directly gear-cut on the output shaft 131, or a pinion as another member may be press-fitted to the tip of the output shaft 131. Alternatively, the motor pinion 17 can also be constituted by fastening a pinion as another member to the output shaft 131 by means of a coupling or the like.

[0015] An example of the motor unit 130 is a stepping motor, and it may be provided with a rotation detector. Further, the motor unit 130 is not limited to a stepping motor, and may be other types of motors such as a servo motor, a brushless DC motor, or an induction motor.

[0016] As shown in FIGS. 1 and 3, the first-stage reduction unit 120 has a first case 10a and a second case 10b, and both cases together form the case 10 of the first-stage reduction unit 120 as a whole. Both cases are cylindrical members extending in the z-axis direction. The end face of the first case 10a on the positive z-axis side is substantially closed, and the end face of the second case 10b on the negative z-axis side is substantially closed.

[0017] The first-stage reduction unit 120 further has a rotating shaft 18 extending in the z-axis direction. A part of the rotating shaft 18 is accommodated in the case 10, and the other part protrudes from the first case 10a. The rotating shaft 18 is rotatably supported by a first bearing 11 fixed to the first case 10a and a second bearing 12 sandwiched between the first case 10a and the second case 10b.

[0018] The rotating shaft 18 has a large-diameter portion 18a, an internal gear 15 provided on the negative z-axis side of the large-diameter portion 18a, a small-diameter portion 18b provided on the positive z-axis side of the large-diameter portion 18 and having a smaller diameter than the large-diameter portion 18, and a shaft portion 18c provided on the positive z-axis side of the small-diameter portion 18b and having a smaller diameter than the small-diameter portion 18b. The internal gear 15, the large-diameter portion 18a, the small-diameter portion 18b, and the shaft portion 18c are on the same axis. An output-stage pinion 9 is formed at the tip of the shaft portion 18c protruding from the first case 10a. The small-diameter portion 18b is supported by the first bearing 11, and the large-diameter portion 18a is supported by the second bearing 12.

[0019] The outer circumferential surface of the large-diameter portion 18a is stepped, forming a stepped surface that extends radially inward and a stepped portion 18a2 that extends from the stepped surface in the negative z-axis direction and has a slightly smaller diameter due to the stepped surface. The diameter of this stepped portion 18a2 is the same as the diameter of the internal gear 15. The stepped portion 18a2 is press-fitted into the inner ring 12b of the second bearing 12 in the negative z-axis direction so that the stepped surface and the end face of the inner ring 12b of the second bearing 12 abut against each other. The internal gear 15 is further fitted into the inner ring 12b in the positive z-axis direction. This fit is a clearance fit. The positioning of the internal gear 15 is determined using the inner ring 12b of the second bearing 12 as the fitting reference.

[0020] Multiple through holes 18a1 extending in the z-axis direction are formed in the large-diameter portion 18a at circumferential intervals. Multiple internal gear fixing female screws 14 are formed in the internal gear 15 so as to overlap with the multiple through holes 18a1 in the z-axis direction. Internal gear fixing screws 13 are inserted into the through holes 18a1 and fastened to the internal gear fixing female screws 14, thereby fixing the internal gear 15 to the large-diameter portion 18a.

[0021] Although the structure shown involves fastening the internal gear 15 to the large-diameter portion 18a with internal gear fixing screws 13, the structure is not limited to this, and the rotating shaft 18 may be made as a single molded part.

[0022] The inner circumferential surface of the first case 10a is stepped, forming a stepped surface extending radially outward and a stepped portion 10a2 extending from the stepped surface in the negative z-axis direction, with the inner diameter slightly increased by the stepped surface. The inner circumferential surface of the second case 10b is also stepped, forming a stepped surface extending radially outward and a stepped portion 10b2 extending from the stepped surface in the positive z-axis direction, with the inner diameter slightly increased by the stepped surface. Both stepped portions are fitted with the outer ring 12a of the second bearing 12 in a clearance fit along the z-axis direction. The positioning of the first case 10a and the second case 10b is determined using the outer ring 12a as the fitting reference. Furthermore, a bearing spring 16 is provided between the z-axis negative end face of the outer ring 12a and the stepped surface related to the stepped portion 10b2 of the second case 10b. The preload from this bearing spring 16 suppresses the internal gap between the first bearing 11 and the second bearing 12.

[0023] As shown in Figures 1 and 4, the inner ring 1b of the cross roller bearing 1 is fastened to the generally ring-shaped case 3 of the output stage reduction unit 110 by multiple cross roller bearing fixing screws 7. The outer ring 1a of the cross roller bearing 1 is rotatably supported. A relatively large external gear, the output stage gear 4, is fastened to the outer ring 1a by multiple output stage gear fixing screws 5.

[0024] In this embodiment, the outer ring 1a of the cross roller bearing 1 itself serves as the output section (hollow output table) of the hollow rotary actuator 100. However, the embodiment is not limited to this, and the output section (hollow output table) may be separately fastened to the outer ring 1a. Alternatively, the outer ring 1a may be fixed to the case 3, and the inner ring 1b may be used as the output section. Furthermore, two deep groove ball bearings may be used in combination instead of the cross roller bearing 1.

[0025] In such a hollow rotary actuator 100, when the rotating shaft 131 and motor pinion 17 of the motor unit 130 rotate, the internal gear 15 that meshes with the motor pinion 17 rotates. As a result, the rotating shaft 18 and output stage pinion 9 of the first stage reduction unit 120 rotate. The rotation of the output stage pinion 9 causes the output stage gear 4 that meshes with the output stage pinion to rotate. Consequently, the outer ring 1a of the cross roller bearing 1 to which the output stage gear 4 is fastened (i.e., the output shaft (hollow output table) of the hollow rotary actuator) rotates.

[0026] As mentioned above, in the hollow rotary actuator 100, the first-stage reduction unit 120 is assembled to the output stage reduction unit 110. Therefore, a larger reduction ratio can be obtained compared to conventional hollow rotary actuators that do not have a component equivalent to the first-stage reduction unit 120, making it applicable to applications requiring high torque or load inertia moment. In addition, the first-stage reduction unit 120 has fewer parts than a planetary gear reduction mechanism, which helps to reduce costs.

[0027] <Assembly> The case 3 of the output stage reduction unit 110 and the first case 10a of the first stage reduction unit 120 are assembled so that the output stage pinion 9 meshes with the output stage gear 4. Also, the flange surface 132 of the motor unit 130 is joined to the second case 10b of the first stage reduction unit 120 so that the internal teeth 15a of the internal gear 15 mesh with the motor pinion 17. The meshing direction between the motor pinion (drive pinion) 17 and the internal gear 15 as seen from the output stage gear (external gear) 4 and the meshing direction between the output stage pinion 9 as seen from the output stage gear (external gear) 4 are the same direction (positive x-axis direction).

[0028] The output stage pinion 9 is pressed against the output stage gear 4 to eliminate backlash between the output stage gear 4 and the output stage pinion 9, but without causing the output stage pinion 9 to tilt. As a result, the reduction in the tooth contact area in the gear tooth width is suppressed, and the transmission of torque is less likely to be limited. In addition, backlash at the point where the internal teeth 15a of the internal gear 15 of the first stage reduction unit 120 mesh with the motor pinion 17 can also be eliminated. Details are described below.

[0029] <Backlash adjustment between the output stage gear 4 of the output stage reduction unit 110 and the output stage pinion 9 of the first stage reduction unit 120> Figure 5 shows the case 3 of the output stage reduction unit 110 as viewed along the positive z-axis, and Figure 6 shows the first stage reduction unit 120 as viewed along the positive z-axis. A horizontal mounting surface 3a is formed on the negative z-axis side of case 3 to which the first stage reduction unit 120 is attached, and a hole 3c is formed in this mounting surface 3a into which the shaft portion 18c of the rotating shaft 18 is inserted (Figure 5). On the horizontal mounting surface of the first case 10a of the first stage reduction unit 120 to which the output stage reduction unit 110 is attached, a flange portion 10a1 is formed that protrudes in both directions along the y-axis (Figure 6). An x-axis oriented guide groove 3b is formed on the mounting surface 3a to guide the flange portion 10a1 (Figure 5). The mounting surface of the first case 10a, including the guide groove 3b and the flange portion 10a1, has the same dimension along the y-axis. By fitting the flange portion 10a1 into the guide groove 3b, the first case 10a and case 3 can be moved relative to each other along the x-axis direction in which the output stage gear 4 and output stage pinion 9 mesh, thereby adjusting the backlash.

[0030] After adjusting the backlash, the output stage reduction unit 110 and the first stage reduction unit 120 are assembled by fastening the first case 10a of the first stage reduction unit 120 to the mounting surface 3a of case 3 with bolts (not shown). At this time, let P2 be the load in the negative x-axis direction applied to the output stage gear 4 (Figure 1). The output stage pinion 9 is subjected to a load P2' in the positive x-axis direction, which is the reaction force to the load P2 (Figure 7).

[0031] <Backlash adjustment between the motor pinion 17 of the motor section 130 and the internal gear 15 of the first stage reduction section 120> In the second case 10b of the first stage reduction unit 120, an elongated hole 10b1 into which the motor pinion 17 is inserted is formed on the mounting surface where the motor is attached (Figures 3 and 6). A spigot portion (circular projection) 132a is formed on the motor flange 132 (Figure 2). The elongated hole 10b1 is elongated in the direction of meshing between the motor pinion 17 and the internal teeth 15a of the internal gear 15 (x-axis direction). The y-axis dimension of the elongated hole 10b1 is the same as the diameter of the spigot portion 132a.

[0032] The motor unit 130 is assembled to the first stage reduction unit 120 by fitting the spigot portion 132a of the motor flange 132 into the elongated hole 10b1 of the first stage reduction unit 120 so that the motor pinion 17 meshes with the internal teeth 15a of the internal gear 15. As mentioned above, since the elongated hole 10b1 is long in the x-axis direction, the motor pinion 17 can be moved in a direction that presses it against the internal teeth 15a. Backlash can be adjusted by adjusting the load that presses the motor pinion 17 against the internal teeth 15a of the internal gear 15.

[0033] The rotating shaft 18 is supported by two bearings, the first bearing 11 and the second bearing 12. As described above, when the output stage gear 4 of the output stage reduction unit 110 and the output stage pinion 9 of the first stage reduction unit 120 are assembled while adjusting the backlash, a load of P2' is applied to the output stage pinion 9 as a reaction force.

[0034] The rotating shaft 18 (material: steel) is designed with a large shaft diameter and high rigidity. Therefore, when a load P2' is applied to the output stage pinion 9, the rotating shaft 18 will tilt in the direction of the load P2' due to the internal gaps between the first bearing 11 and the second bearing 12, as well as the gaps between the outer rings of the two bearings and the mounting parts (housing parts) of the two bearings, unless there is any other particular load besides the load P2'. In that case, the tooth contact of the output stage pinion 9 with respect to the output stage gear 4 will be uneven (see Figure 9 described later), which may shorten the lifespan of the two bearings.

[0035] Taking this concern into consideration, the position where the motor pinion 17 of the motor unit 130 and the internal teeth 15a of the internal gear 15 of the first stage reduction unit 120 mesh is on the opposite side of the rotation axis 18 from the output stage gear 4. In other words, on the rotation axis 18 extending in the z-axis direction, the output stage pinion 9 on the positive z-axis side meshes with the output stage gear 4, and the internal gear 15 on the negative z-axis side meshes with the motor pinion 17.

[0036] The motor pinion 17 is pressed against the internal teeth 15a of the internal gear 15 in the same direction (positive x-axis direction) as the load P2' applied to the output stage pinion 9, thereby suppressing the tilt of the rotation axis 18. In other words, by adjusting the load that presses the motor pinion 17 against the internal teeth 15a of the internal gear 15, it is possible to adjust the backlash and prevent the rotation axis 18 from tilting. Let the adjusted load be P1 (Figures 1 and 7). Both load P1 and load P2' are in the positive x-axis direction.

[0037] To adjust the backlash and prevent the first-stage reduction gear rotating shaft 18 from tilting, the flange 132 of the motor unit 130 is fastened to the second case 10b of the first-stage reduction gear 120 with bolts (not shown) while a load P1 is applied. This assembles the first-stage reduction gear 120 and the motor unit 130.

[0038] As described above, the backlash between the output stage gear 4 of the output stage reduction unit 110 and the output stage pinion 9 of the first stage reduction unit 120 is adjusted, and the output stage reduction unit 110 and the first stage reduction unit 120 are assembled. Next, the backlash between the motor pinion 17 of the motor unit 130 and the internal gear 15 of the first stage reduction unit 120 is adjusted, and the motor unit 130 is assembled to the first stage reduction unit 120. In this way, the hollow rotary actuator 100 is completed.

[0039] In the above description, the output stage reduction unit 110 and the first stage reduction unit 120 were assembled, and then the motor unit 130 was assembled to the first stage reduction unit 120 to complete the hollow rotary actuator 100. However, this is not the only way; the backlash between the motor pinion 17 of the motor unit 130 and the internal gear 15 of the first stage reduction unit 120 may be adjusted, and then the motor unit 130 may be assembled to the first stage reduction unit 120. After that, the backlash between the output stage gear 4 of the output stage reduction unit 110 and the output stage pinion 9 of the first stage reduction unit 120 may be adjusted, and then the output stage reduction unit 110 and the first stage reduction unit 120 may be assembled.

[0040] <Load calculation> As the basic principle of this embodiment, the load calculation for a double-sided cantilever beam is applied, as shown in Figures 7 and 8. Figure 7 is an enlarged view of the first-stage reduction unit 120, and Figure 8 is a diagram illustrating the basic principle of load calculation for a double-sided cantilever beam. As shown in both figures, the rotating shaft 18 can be likened to a double-sided cantilever beam. Load P2' is the load applied to the output stage pinion 9 when the output stage pinion 9 is pressed against the output stage gear 4 to eliminate backlash. Load P1 is the load applied to the internal gear 15 when the motor pinion 17 is pressed against the internal gear 15 of the first stage reduction unit to eliminate backlash.

[0041] The symbol b represents the z-axis distance between the center of the output stage pinion 9 and the center of the first bearing 11. The symbol L represents the distance in the z-axis direction between the center of the first bearing 11 and the center of the second bearing 12. The symbol 'a' represents the distance in the z-axis direction between the center of the second bearing 12 and the center of the motor pinion 17. R AThis is the negative x-axis load applied to the second bearing 12. R B This is the negative x-axis load applied to the first bearing 11.

[0042] Load P1 is in the same direction as load P2', and the position where the motor pinion 17 meshes with the internal teeth 15a of the internal gear 15 is on the opposite side of the output stage gear 4 with respect to the rotation axis 18.

[0043] From the load calculation of the double-sided cantilevered beam, the R due to the loads of P1 and P2' A and R B The load will be as follows:

number

[0044] In principle, the rotating shaft 18 (material: steel) is designed with a large shaft diameter and high rigidity, so even when a load of P2' is applied to the output stage pinion 9, the amount of distortion of the output stage pinion 9 is minimal. However, as explained above, the rotating shaft 18 itself becomes tilted due to the gaps between the first bearing 11 and the second bearing 12 and their bearing housings, as well as the internal gaps in the bearings. In this embodiment, since loads P1 and P2' are in the same direction, the tilt of the rotating shaft 18 can be suppressed even if there is a gap between the first bearing 11 and the second bearing 12 and their bearing housings, as well as an internal gap in the bearings. The condition for suppressing this tilt is the load R applied to the second bearing 12. A is 0 or greater (R A The result is ≥0). From equation (1),

number

[0045] Since a+L>b is basically the case in the above embodiment, P2' is obtained from equation (5). <P1となる。

[0046] As described above, the tilt of the rotating shaft 18 can be suppressed by applying a load P1 to the internal teeth 15a of the internal gear 15 using the motor pinion 17 in accordance with the load P2'. In addition, the load (backlash adjustment force) P2' applied to the output stage pinion 9 can be reduced by assembling the first stage reduction unit and applying a load P1, which widens the tooth contact area in the tooth width of the gear and allows it to be allocated to amplifying the output torque, thereby increasing the power transmission torque output.

[0047] Next, we will explain tooth contact in output stage gears. Figure 9 shows the teeth Ta of an output stage gear meshing with a cantilevered pinion (not shown). The contact area where the pinion makes contact is indicated by light gray. When the pinion is pressed against the output stage gear to eliminate backlash, the pinion tilts, causing the contact area to be biased towards the edge in the tooth width direction, as shown in Figure 9. Because the load is concentrated on the edge, the strength of the gear is significantly reduced. The tooth contact (the ratio of the length of the contact area along the tooth width direction to the tooth width) is approximately 1 / 3.

[0048] Figure 10 shows the contact area of ​​a cantilevered pinion (not shown) in a tooth Tb formed by crowning the tooth Ta of the output stage gear shown in Figure 9. Because the contact area is located in the center of the tooth width direction of tooth Tb rather than on the edge side due to the crowning process, the strength is higher than in the case of Figure 9. However, crowning generally reduces the area of ​​tooth contact in the tooth width of the gear, and the tooth contact remains about 1 / 3 of that in the case of Figure 9, so there is a limitation on the torque that can be transmitted.

[0049] Figure 11 shows the contact area where the output stage pinion 9 contacts the teeth 4a of the output stage gear 4 according to the above embodiment. The rotating shaft 18 having the output stage pinion 9 is subjected to loads of similar size and orientation at two locations spaced apart in the axial direction. Therefore, it is not in a cantilevered state but closer to a double-sided overhanging beam, which suppresses the tilt of the gear shaft and eliminates the need for crowning. As a result, as shown in the figure, the contact area is located in the center in the tooth width direction and the tooth contact is approximately 80%, which is a significant increase compared to the case in Figure 10, and the strength is also improved.

[0050] <Effects> As described above, the above embodiment provides the following effects. • In the first stage, the reduction mechanism consists of internal gears and pinion gears, which have fewer parts than a planetary gear reducer, resulting in a hollow rotary actuator with a relatively large reduction ratio at a low cost. In a two-stage hollow rotary actuator, even when a force is applied to press the gears to eliminate backlash in each reduction stage, the tilt of the first stage gear rotation axis can be suppressed depending on the direction of the adjustment force. By making the adjustment force P2' of the output stage smaller than the adjustment force P1 of the first stage, it can be allocated to amplifying the output torque, thus enabling a mechanism that allows for high-torque, high-precision positioning operation.

[0051] In the above embodiment, the meshing direction between the motor pinion (drive pinion) 17 and the internal gear 15 as seen from the motor pinion (drive pinion) 17 and the meshing direction between the output stage pinion 9 as seen from the output stage gear (external gear) 4 do not have to be the same. For example, the motor pinion 17 may mesh with the region of the internal gear 15 on the negative x-axis side as shown in Figure 1.

[0052] The following additional information is disclosed regarding the embodiments described above. <Note 1> A rotating shaft having an internal gear that meshes with a drive pinion and an output stage pinion, A ring-shaped external gear that meshes with the output stage pinion and A hollow rotary actuator equipped with [a specific feature / feature]. <Effects of Appendix 1> A hollow rotary actuator with a relatively large reduction ratio can be obtained at a low cost. <Note 2> The hollow rotary actuator as described in Appendix 1, wherein the internal gear and the output stage pinion are positioned at an interval in the axial direction of the rotation shaft, and the meshing direction between the drive pinion and the internal gear as seen from the drive pinion is the same as the meshing direction between the external gear and the output stage pinion as seen from the external gear. <Effects of Appendix 2> This allows for the elimination of backlash while suppressing the tilt of the rotation axis. <Note 3> The rotating shaft has a large-diameter portion to which the internal gear is attached, and a small-diameter portion located between the large-diameter portion and the output stage pinion. Bearings supporting the rotating shaft are provided in the large-diameter portion and the small-diameter portion. A hollow rotary actuator as described in Appendix 1 or 2. <Effects of Appendix 3> The aforementioned rotating shaft can be efficiently supported. <Note 4> A first-stage reduction gear case that houses a part of the aforementioned rotating shaft, An output unit case housing the aforementioned external gear, Furthermore, The output unit case has a guide groove formed therein for assembling the first stage reduction unit case. The hollow rotary actuator described in Appendix 2. <Effects of Appendix 4> The assembly of the first-stage reduction unit and the output unit can be easily performed. <Note 5> The hollow rotary actuator as described in Appendix 4, wherein the guide groove extends in the meshing direction. <Effects of Appendix 5> The backlash between the output stage pinion of the rotating shaft and the external gear can be easily adjusted. <Note 6> The hollow rotary actuator according to Appendix 4 or 5, wherein the first-stage reduction gear case has a hole formed therein that engages with a spigot projection provided in the case of the drive unit equipped with the drive pinion. <Effects of Appendix 6> The drive unit and the first-stage reduction unit can be easily assembled. <Note 7> The hollow rotary actuator as described in Appendix 6, wherein the aforementioned hole is an elongated hole that is longer in the direction of engagement. <Effects of Appendix 7> The backlash between the drive pinion and the internal gear can be easily adjusted.

[0053] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and changes are possible based on the technical concept of the present invention. [Explanation of symbols]

[0054] 100: Hollow Rotary Actuator 110: Output stage reduction section 120: First stage reduction section 130: Motor section 1: Cross roller bearing 1a: Outer ring of cross roller bearing (hollow output table) 1b: Inner ring of cross roller bearing 3: Output stage case 3a: Mounting surface 4: Output stage gear (external gear) 5: Screw for fixing the output stage gear 7: Screws for fixing the cross roller bearings 9: Output stage pinion 10: Case 10a: Case 1 10b: Case 2 11: First bearing 12: Second bearing 13: Screw for fixing internal gear 14: Female thread for fixing internal gears 15: Internal gear 16: Bearing spring 17: Motor pinion 18: Rotation axis 18a: Large diameter section 18b: Small diameter part 18c: Shaft 18a1: Screw hole (through hole) 131: Motor output shaft 132: Flange surface

Claims

1. A rotating shaft having an internal gear that meshes with a drive pinion and an output stage pinion, A ring-shaped external gear that meshes with the output stage pinion and A hollow rotary actuator equipped with [a specific feature / feature].

2. The hollow rotary actuator according to claim 1, wherein the internal gear and the output stage pinion are positioned at an interval in the axial direction of the rotation shaft, and the meshing direction with the internal gear as seen from the drive pinion and the meshing direction with the output stage pinion as seen from the external gear are the same.

3. The rotating shaft has a large-diameter portion to which the internal gear is attached, and a small-diameter portion located between the large-diameter portion and the output step pinion. Bearings supporting the rotating shaft are provided in the large-diameter portion and the small-diameter portion. The hollow rotary actuator according to claim 1 or 2.

4. A first-stage reduction gear case that houses a part of the aforementioned rotating shaft, An output unit case housing the aforementioned external gear, Furthermore, The output unit case has a guide groove formed therein for assembling the first stage reduction unit case. The hollow rotary actuator according to claim 2.

5. The hollow rotary actuator according to claim 4, wherein the guide groove extends in the meshing direction.

6. The hollow rotary actuator according to claim 4 or 5, wherein the first-stage reduction gear case has a hole formed therein that fits with a spigot projection provided in the case of the drive unit equipped with the drive pinion.

7. The hollow rotary actuator according to claim 6, wherein the hole is an elongated hole that is long in the meshing direction.

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