Actuator, manufacturing method of the same, and robot including parallel link

Abstract

To provide an actuator which reduces an error of a moving distance of a screw shaft.SOLUTION: An actuator 1 includes: a housing 11; a nut 13 housed in the housing 11; a screw shaft 14 which is moved relative to the housing 11 by the nut 13 rotating; a slide member 22 having a through hole 22a1 through which the screw shaft 14 penetrates having a gap therebetween and configured to move along a reference axial line SL relative to the housing 11; four set screws 17 which are fitted with the slide member 22 and in each of which a tip 17a contacts with an outer peripheral surface of the screw shaft 14 in the through hole 22a1; and a fixing nut 18 which is fitted with the screw shaft 14 and fixes the screw shaft 14 to the slide member 22. Tips 17a of the four set screws 17 contact with the outer peripheral surface of the screw shaft 14 at positions different from each other in a circumferential direction of the screw shaft 14.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an actuator, a method for manufacturing the actuator, and a robot including a parallel link. [Background technology]

[0002] Patent Document 1 discloses a robot including a parallel link equipped with multiple drive devices. The drive devices include an actuator that drives a rod forward and backward, and a slider to which the tip of the rod is fixed and which guides the rod in one axial direction. The robot of Patent Document 1 can be made smaller by including a parallel link. On the other hand, it is known that in a robot including a parallel link, the positioning accuracy of each axis has a large effect on the positioning accuracy of the entire robot.

[0003] In such a drive device, in order to ensure accuracy in the amount of movement of the rod, an alignment adjustment is performed to make the central axis of the rod parallel to one axial direction, and then the rod is fixed to the slider by, for example, a nut.

[0004] As disclosed in Patent Document 1, the rod may be a screw shaft that moves when a nut rotates. In this case, the screw shaft is fixed to a slider. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7088440 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the screw shaft is fixed to the slider (slide member) by a nut, the central axis of the screw shaft may be tilted with respect to one axial direction (reference axis) due to the torque used to tighten the nut. The greater the inclination angle of the central axis of the screw shaft with respect to the reference axis, the greater the error in the amount of movement of the screw shaft.

[0007] An aspect of the present disclosure aims to provide an actuator that suppresses errors in the amount of movement of a screw shaft, a method for manufacturing the actuator, and a robot that includes a parallel link. [Means for solving the problem]

[0008] In an aspect of the present disclosure, an actuator includes a housing, a nut stored in the housing, a screw shaft that moves relative to the housing as the nut rotates, a slide member having a through hole through which the screw shaft passes with a gap and that moves along a reference axis relative to the housing, three or more set screws that fit with the slide member and have tips that contact the outer circumferential surface of the screw shaft inside the through hole, and a fixing nut that fits with the screw shaft and fixes the screw shaft to the slide member, and tips of the three or more set screws contact the outer circumferential surface of the screw shaft at different positions from one another in the circumferential direction of the screw shaft.

[0009] According to an embodiment of the present disclosure, three or more set screws maintain the position of the screw shaft relative to the slide member. Therefore, the set screws can maintain the central axis of the screw shaft and the reference axis in a state parallel to each other. Therefore, an error in the amount of movement of the screw shaft along the reference axis can be suppressed.

[0010] In addition, in an aspect of the present disclosure, the tips of the three or more set screws are positioned at equal intervals in the circumferential direction of the screw shaft.

[0011] According to an aspect of the present disclosure, the points of application of the tightening force of the set screw are located at equal intervals in the circumferential direction of the screw shaft on the outer circumferential surface of the screw shaft, thereby more reliably maintaining the central axis of the screw shaft parallel to the reference axis.

[0012] In addition, in an aspect of the present disclosure, the slide member has an attachment portion to which a measuring instrument that measures the displacement of the screw shaft when the fixing nut is tightened is attached, and the screw shaft has a measurement portion having a contact surface with which a probe of the measuring instrument comes into contact.

[0013] According to an aspect of the present disclosure, the measuring device can measure the amount of displacement of the screw shaft relative to the slide member. For example, the measuring device measures the amount of displacement of the screw shaft when the fixing nut is tightened in a manufacturing process of the actuator. By tightening the fixing nut so as to suppress the amount of displacement of the screw shaft, the central axis of the screw shaft and the reference axis can be more reliably maintained in a state parallel to each other.

[0014] In an aspect of the present disclosure, the nut is any one of a top-type nut, an end deflector-type nut, and a tube-type nut.

[0015] According to the aspects of the present disclosure, the actuator can be made smaller.

[0016] In addition, in an aspect of the present disclosure, the nut has a plurality of link portions.

[0017] According to an aspect of the present disclosure, the nut is a block type nut, which allows the actuator to be miniaturized and the screw shaft to be positioned precisely.

[0018] In addition, in an aspect of the present disclosure, a manufacturing method of an actuator includes the steps of: passing a screw shaft, which moves relative to a housing as a nut stored in the housing rotates, through a through hole of a slide member that guides the screw shaft along a reference axis line with a gap; performing an alignment adjustment to make a central axis line of the screw shaft parallel to the reference axis line while the screw shaft is passing through the through hole; after the alignment adjustment is completed, fitting three or more set screws into the slide member and contacting tips of the three or more set screws with an outer peripheral surface of the screw shaft inside the through hole at different positions from one another in the circumferential direction of the screw shaft; and fitting a fixing nut onto the screw shaft while tips of the three or more set screws are in contact with the outer peripheral surface of the screw shaft, thereby fixing the screw shaft to the slide member.

[0019] According to an embodiment of the present disclosure, when the fixing nut is tightened, three or more set screws maintain the position of the screw shaft relative to the slide member. Therefore, the set screws can maintain the central axis of the screw shaft and the reference axis in a state parallel to each other. Therefore, an error in the amount of movement of the screw shaft along the reference axis can be suppressed.

[0020] In addition, in an aspect of the present disclosure, a robot including a parallel link includes a plurality of the above-mentioned actuators, and one of the plurality of actuators and another of the actuators are arranged with their respective reference axes parallel to each other.

[0021] According to the aspects of the present disclosure, in a robot including a parallel link, similar to the actuator described above, errors in the amount of movement of the screw shaft can be suppressed. Effect of the Invention

[0022] According to an aspect of the present disclosure, the actuator can suppress an error in the amount of movement of the screw shaft. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a perspective view of an actuator according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a cross-sectional view of the actuator taken along a reference axis. [Diagram 3] FIG. 3 is a diagram showing a cross-sectional shape of the nut taken along the central axis of the nut. [Figure 4] FIG. 4 is a diagram showing a cross-sectional shape of the nut perpendicular to the central axis of the nut. [Diagram 5] FIG. 5 is a cross-sectional view of the actuator taken along line VV shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view of the nut and the screw shaft when the central axis of the screw shaft is inclined with respect to the reference axis, showing a state in which there is no groove in the first link portion on the side where the screw shaft is inclined. [Figure 7] FIG. 7 is a cross-sectional view of the nut and the screw shaft when the central axis of the screw shaft is inclined with respect to the reference axis, and shows a state in which the groove of the first link portion is on the side where the screw shaft is inclined. [Figure 8] FIG. 8 is a diagram showing a state in which the amount of displacement of the screw shaft is measured by using a measuring device when the screw shaft is fixed to a slide member. [Figure 9] FIG. 9 is a perspective view of a robot including a parallel link according to an embodiment of the present disclosure. [Figure 10] FIG. 10 is a plan view of the robot including the parallel link shown in FIG. 9 as viewed from the +Z side. [Figure 11] FIG. 11 is a side view of the robot including the parallel link shown in FIG. 9 as viewed from the -X side. [Figure 12] FIG. 12 is a diagram showing a state in which the second arm unit is inclined with respect to the first arm unit from the reference state of the robot including the parallel link shown in FIG. [Figure 13] FIG. 13 is a side view of the robot including the parallel link shown in FIG. 9 as viewed from the -Y side. [Figure 14]FIG. 14 is a diagram showing a state in which the medical instrument has been moved by the third arm unit being driven from the reference state of the robot including the parallel link shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited thereto. The components of each embodiment and each modified example described below can be appropriately combined. In addition, some components may not be used.

[0025] <Actuator 1> An actuator 1 according to an embodiment of the present disclosure will be described with reference to the drawings.

[0026] Fig. 1 is a perspective view of an actuator 1 according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view of the actuator 1 along a reference axis line SL. The reference axis line SL is a reference axis line that the actuator 1 has.

[0027] The actuator 1 includes a drive unit 10 and a guide unit 20 .

[0028] The driving unit 10 includes a housing 11, a motor 12, a nut 13, and a screw shaft 14. The housing 11 has a hollow rectangular parallelepiped shape extending along a reference axis line SL.

[0029] The motor 12 is a stepping motor and includes a stator 12a and a rotor 12b. The stator 12a is fixed inside the housing 11. The rotor 12b passes through the stator 12a and is disposed in the housing 11 via a first bearing 15 so as to be rotatable relative to the housing 11.

[0030] The nut 13 is accommodated in the housing 11 via a second bearing 16 so as to be rotatable relative to the housing 11. The nut 13 is fixed to the rotor 12b and rotates integrally with the rotor 12b.

[0031] Fig. 3 is a diagram showing a cross-sectional shape of the nut 13 along the central axis CL1 of the nut 13. Fig. 4 is a diagram showing a cross-sectional shape of the nut 13 perpendicular to the central axis CL1 of the nut 13. The nut 13 is a top-type nut. The nut 13 has a nut body 13a and four top portions 13b.

[0032] 3 and 4 show a first frame portion 13b1, a second frame portion 13b2, a third frame portion 13b3, and a fourth frame portion 13b4. When the first frame portion 13b1, the second frame portion 13b2, the third frame portion 13b3, and the fourth frame portion 13b4 are described without distinction, they are simply referred to as "frame portions 13b".

[0033] The nut body 13a has a cylindrical shape through which the screw shaft 14 passes, and has a spiral groove 13a1 on its inner circumferential surface in which a plurality of balls B can roll.

[0034] The first, second, third, and fourth link portions 13b1, 13b2, 13b3, and 13b4 are located at different positions on the central axis CL1 corresponding to each other in the radial direction, and are arranged in this order on the nut body 13a along the central axis CL1. The first, second, third, and fourth link portions 13b1, 13b2, 13b3, and 13b4 are positioned at equal intervals around the central axis CL1.

[0035] The link portion 13b faces the screw shaft 14 and has a link groove D that allows the ball B to ride up the threads of the screw shaft 14. The link grooves D of the first link portion 13b1, the second link portion 13b2, the third link portion 13b3 and the fourth link portion 13b4 are each positioned at equal intervals in the circumferential direction of the screw shaft 14.

[0036] The balls B rolling in the screw groove 14a of the screw shaft 14 move via the pair grooves D to the adjacent screw groove 14a in the direction along the central axis CL1, whereby the balls B circulate within the nut 13.

[0037] The nut 13 may be an end deflector type nut or a tube type nut. When the nut 13 is any of a top type nut, an end deflector type nut, and a tube type nut, the axial length of the actuator 1 can be made smaller than when the nut 13 is an end cap type nut. The structures of the end deflector type nut, the tube type nut, and the end cap type nut are well known, and a description thereof will be omitted.

[0038] Furthermore, when the nut 13 is a top-type nut, the outer diameter of the nut 13 can be made small, and the nut 13 can be made compact in the radial direction, and can also be used with a screw shaft 14 having a relatively small lead. Therefore, in this case, the positioning of the screw shaft 14 can be made more precise than with end deflector-type, tube-type, and end cap-type nuts.

[0039] The nut 13 may not have the link portion 13b, and the link groove D may be formed in the nut body portion 13a of the nut 13. The nut 13 may not have the link portion 13b, and the link groove D may be formed in the screw shaft 14. When the link groove D is formed in the screw shaft 14, the ball B circulates by moving to the groove 13a1 of the adjacent nut 13 in the direction along the central axis CL1 via the link groove D. In this way, when the nut 13 does not have the link portion 13b, the number of parts of the nut 13 is reduced, thereby making it possible to reduce the cost and compactness of the nut 13.

[0040] 1 and 2, a first end of the screw shaft 14 is disposed within the housing 11, and a second end of the screw shaft 14 is disposed in a state where it is exposed from the housing 11. A central axis CL2 of the screw shaft 14 is aligned so as to be parallel to a reference axis SL.

[0041] The screw shaft 14 passes through the rotor 12b and the nut 13. The outer circumferential surface of the screw shaft 14 has a helical screw groove 14a (see FIG. 3) into which a plurality of balls B are rollably fitted. The screw shaft 14 moves relative to the housing 11 as the nut 13 rotates. The screw shaft 14 has a flange portion 14b as shown in FIG. 2.

[0042] The screw shaft 14 is fitted with a rectangular parallelepiped measurement target portion 14c having a contact surface 14d that comes into contact with a probe Mc of a measuring instrument M, which will be described later. The contact surface 14d is polished. As a result, the surface roughness of the contact surface 14d is lower than the surface roughness of the other surfaces of the measurement target portion 14c. The measurement target portion 14c may be cylindrical.

[0043] The guide unit 20 guides the screw shaft 14 along a reference axis SL. The guide unit 20 includes a support 21, a slide member 22, two guide rails 23a and 23b, four linear guides 24a, 24b, 24c and 24d, and a linear encoder 25.

[0044] The support body 21 has a cylindrical shape that is rectangular in cross section and extends along the reference axis line SL, and is fixed to the housing 11.

[0045] The slide member 22 is L-shaped and integrally includes a fixed portion 22a and a rectangular parallelepiped portion 22b. A second end of the screw shaft 14 is fixed to the fixed portion 22a. Thus, the slide member 22 moves integrally with the screw shaft 14 relative to the housing 11. The rectangular parallelepiped portion 22b penetrates the support body 21 along the reference axis SL.

[0046] The fixed portion 22a has a through hole 22a1 through which the screw shaft 14 passes. The inner diameter of the through hole 22a1 is larger than the outer diameter of the screw shaft 14. In other words, the screw shaft 14 passes through the through hole 22a1 with a gap therebetween.

[0047] The slide member 22 also has an attachment portion 22a2 to which a measuring device M (described later) is attached. The attachment portion 22a2 is a part of the outer surface of the fixed portion 22a. The slide member 22 has an attachment hole 22a3 that opens at the attachment portion 22a2 and to which the measuring device M is attached.

[0048] The two guide rails 23a, 23b extend along the reference axis SL, and are fixed to the rectangular parallelepiped portion 22b of the slide member 22 at positions opposite to each other.

[0049] The four linear guides 24a, 24b, 24c, and 24d are fixed inside the support 21 and guide the two guide rails 23a and 23b along the reference axis SL. Specifically, the two linear guides 24a and 24b are disposed apart from each other in the direction along the reference axis SL and guide the guide rail 23a. The two linear guides 24c and 24d are disposed apart from each other in the direction along the reference axis SL and guide the guide rail 23b.

[0050] As described above, the support 21 is fixed to the housing 11, and the guide rails 23a, 23b are disposed on the slide member 22. Therefore, the slide member 22 is movable along the reference axis SL relative to the housing 11 by the linear guides 24a, 24b, 24c, 24d. As described above, the slide member 22 moves integrally with the screw shaft 14. Therefore, the guide portion 20 guides the screw shaft 14 along the reference axis SL.

[0051] The linear encoder 25 includes a scale 25a and a head 25b. The scale 25a is disposed on the slide member 22 along the reference axis SL. Therefore, the scale 25a moves integrally with the screw shaft 14 relative to the housing 11. The head 25b is disposed on the support 21 fixed to the housing 11. In other words, the linear encoder 25 detects the amount of movement of the screw shaft 14 relative to the housing 11.

[0052] Fig. 5 is a cross-sectional view of the actuator 1 taken along line VV shown in Fig. 2. As shown in Figs. 2 and 5, the actuator 1 further includes a set screw 17 and a fixing nut 18.

[0053] In this embodiment, the actuator 1 includes four set screws 17. The set screws 17 fit into the slide member 22. Specifically, the fixed portion 22a of the slide member 22 is formed with threaded holes 22a4 into which the set screws 17 fit. That is, the fixed portion 22a has four threaded holes 22a4.

[0054] When a set screw 17 is attached to each of the four screw holes 22a4, the central axes CL3 of the four set screws 17 are located on the same plane perpendicular to the reference axis SL. The central axes CL3 of the four set screws 17 are located at different positions in the circumferential direction of the screw shaft 14. Specifically, the central axes CL3 of two adjacent set screws 17 are perpendicular to each other in the circumferential direction of the screw shaft 14. The tip 17a of the set screw 17 is flat. The tip 17a of the set screw 17 may be pointed.

[0055] Further, the tips 17a of the four set screws 17 each come into contact with the outer circumferential surface of the screw shaft 14 inside the through hole 22a1. Due to the positional relationship of the four set screws 17, the tips 17a of the four set screws 17 come into contact with the outer circumferential surface of the screw shaft 14 at different positions from one another in the circumferential direction of the screw shaft 14. Further, the tips 17a of the four set screws 17 are positioned at equal intervals in the circumferential direction of the screw shaft 14.

[0056] In this embodiment, the actuator 1 includes one fixing nut 18. The fixing nut 18 fits onto the screw shaft 14, and the fixing nut 18 and the flange portion 14b sandwich the fixed portion 22a. This causes the slide member 22 to be fixed to the screw shaft 14, and the screw shaft 14 and the slide member 22 move together.

[0057] Next, the operation of the actuator 1 will be described.

[0058] When a voltage is applied to the motor 12, the rotor 12b rotates, which in turn rotates the nut 13. As a result, the screw shaft 14 moves relative to the housing 11. In addition, the screw shaft 14 moves along the reference axis SL by being guided by the guide portion 20.

[0059] As described above, the alignment is adjusted so that the central axis CL2 of the screw shaft 14 and the reference axis SL are parallel to each other. As a result, the amount of movement of the screw shaft 14 along the reference axis SL when the nut 13 rotates once is equal to the lead of the screw shaft 14.

[0060] In other words, when the central axis CL2 of the nut 13 is inclined with respect to the reference axis SL, a so-called lead error occurs in which the amount of movement of the screw shaft 14 along the reference axis SL when the nut 13 rotates once is shorter than the lead of the screw shaft 14. The larger the inclination angle of the central axis CL2 of the nut 13 with respect to the reference axis SL, the smaller the amount of movement of the screw shaft 14 along the reference axis SL when the nut 13 rotates once, and the larger the lead error becomes.

[0061] Furthermore, when the nut 13 is a top-type nut 13, the lead error may become large, as will be described next.

[0062] Fig. 6 is a cross-sectional view of the nut 13 and the screw shaft 14 when the central axis CL2 of the screw shaft 14 is inclined relative to the reference axis SL, showing a state in which the groove D of the first block portion 13b1 is not present on the side to which the screw shaft 14 is inclined. Fig. 7 is a cross-sectional view of the nut 13 and the screw shaft 14 when the central axis CL2 of the screw shaft 14 is inclined relative to the reference axis SL, showing a state in which the groove D of the first block portion 13b1 is present on the side to which the screw shaft 14 is inclined.

[0063] As described above, the four block portions 13b of the nut 13 are arranged in line along the central axis CL1 of the nut 13. The positions on the central axis CL1 corresponding to the radial direction are different, and the block portions 13b are arranged in order on the nut body 13a along the central axis CL1. The block grooves D of the block portions 13b are located at equal intervals in the circumferential direction of the screw shaft 14. When the nut 13 rotates and the block groove D of the first block portion 13b1 is on the side to which the screw shaft 14 is inclined as shown in FIG. 7, the screw shaft 14 is further inclined toward the block groove D. That is, in this case, the inclination angle of the screw shaft 14 is larger than the state in which the block groove D of the first block portion 13b1 is not on the side to which the screw shaft 14 is inclined as shown in FIG. 6. As described above, the larger the inclination angle of the screw shaft 14, the larger the lead error.

[0064] That is, when the nut 13 is a top-type nut 13, a particularly high degree of accuracy is required for the parallelism of the central axis CL2 of the screw shaft 14 with respect to the reference axis SL.

[0065] As described above, the screw shaft 14 is fixed to the slide member 22 by the fixing nut 18. When the fixing nut 18 is tightened to fix the screw shaft 14 to the slide member 22, the screw shaft 14 may tilt, and the central axis CL2 of the screw shaft 14 may tilt with respect to the reference axis SL. When the central axis CL2 of the screw shaft 14 tilts with respect to the reference axis SL, a lead error occurs as described above.

[0066] In order to suppress such a lead error, as will be described below, in the manufacturing process of the actuator 1, the position of the aligned screw shaft 14 is held by the set screw 17, and the fixing nut 18 is tightened.

[0067] Next, a manufacturing process for the actuator 1 when fixing the screw shaft 14 to the slide member 22 will be described.

[0068] First, a process is performed in which the screw shaft 14 is inserted through the through hole 22a1 of the slide member 22 with a gap therebetween. Then, a process is performed in which an alignment adjustment is performed to make the central axis CL2 of the screw shaft 14 parallel to the reference axis SL in a state in which the screw shaft 14 is inserted through the through hole 22a1.

[0069] Furthermore, after the alignment adjustment is completed, a process is performed in which the four set screws 17 are fitted into the slide member 22 and the tips 17a of the four set screws 17 are brought into contact with the outer circumferential surface of the screw shaft 14. At this time, the tips 17a of the set screws 17 are brought into contact with the screw shaft 14 so as to maintain the posture of the screw shaft 14 after the alignment adjustment. This fixes the radial position of the screw shaft 14.

[0070] Next, a process is performed in which the fixing nut 18 is fitted onto the screw shaft 14 to fix the screw shaft 14 to the slide member 22. The screw shaft 14 is fixed to the slide member 22 by tightening the fixing nut 18.

[0071] As described above, the tips 17a of the four set screws 17 are in contact with the outer circumferential surface of the screw shaft 14 and are positioned at equal intervals in the circumferential direction of the screw shaft 14. This prevents the screw shaft 14 from tilting due to the tightening of the fixing nuts 18, and makes it possible to maintain the posture of the screw shaft 14 after the alignment adjustment.

[0072] The amount of displacement of the screw shaft 14 may be measured when the fixing nut 18 is tightened.

[0073] FIG. 8 is a diagram showing a state in which the amount of displacement of the screw shaft 14 is measured by using a measuring device M when the screw shaft 14 is fixed to the slide member 22. As shown in FIG.

[0074] The measuring instrument M is capable of measuring the amount of displacement of the screw shaft 14 when the fixing nut 18 is tightened. The measuring instrument M is, for example, an electric micrometer. The measuring instrument M includes a detection unit Ma, an arm Mb, and a measuring element Mc.

[0075] The detection unit Ma is attached to a mounted portion 22a2 having a mounting hole 22a3 in the slide member 22. The detection unit Ma has a differential transformer inside. The arm Mb connects the detection unit Ma and the probe Mc. The arm Mb has a plurality of links and a joint that connects the plurality of links, and is configured to be bendable. The probe Mc comes into contact with a contact surface 14d of a measured portion 14c attached to the screw shaft 14.

[0076] The detection portion Ma is attached to the attachment portion 22a2, and the probe Mc is in contact with the contact surface 14d. Thus, the measuring device M detects the amount of displacement of the screw shaft 14 relative to the slide member 22.

[0077] By tightening the fixing nut 18 so as to suppress the amount of displacement of the screw shaft 14 relative to the slide member 22, the posture of the screw shaft 14 after the alignment adjustment can be maintained.

[0078] As described above, according to this embodiment, the actuator 1 includes the housing 11, the nut 13 housed in the housing 11, the screw shaft 14 that moves relative to the housing 11 as the nut 13 rotates, the slide member 22 that has a through hole 22a1 through which the screw shaft 14 passes with a gap and moves along a reference axis SL relative to the housing 11, four set screws 17 that fit with the slide member 22 and whose tips 17a contact the outer circumferential surface of the screw shaft 14 inside the through hole 22a1, and a fixing nut 18 that fits with the screw shaft 14 and fixes the screw shaft 14 to the slide member 22. The tips 17a of the four set screws 17 contact the outer circumferential surface of the screw shaft 14 at different positions in the circumferential direction of the screw shaft 14. According to this, the four set screws 17 maintain the attitude of the screw shaft 14 relative to the slide member 22. Therefore, the set screws 17 can maintain the central axis CL2 of the screw shaft 14 and the reference axis SL in a state parallel to each other. Therefore, an error in the amount of movement of the screw shaft 14 along the reference axis SL can be suppressed.

[0079] Further, the tips 17a of the four set screws 17 are positioned at equal intervals in the circumferential direction of the screw shaft . According to this, on the outer circumferential surface of the screw shaft 14, the points of application of the tightening force of the set screws 17 are positioned at equal intervals in the circumferential direction of the screw shaft 14. Therefore, the set screws 17 can more reliably maintain the central axis CL2 of the screw shaft 14 and the reference axis SL in a state parallel to each other.

[0080] The slide member 22 also has an attachment portion 22a2 to which a measuring device M is attached for measuring the amount of displacement of the screw shaft 14 when the fixing nut 18 is tightened. The screw shaft 14 has a measurement portion 14c having a contact surface 14d with which a probe Mc of the measuring device M comes into contact. According to this, the measuring device M can measure the amount of displacement of the screw shaft 14 relative to the slide member 22. For example, the measuring device M measures the amount of displacement of the screw shaft 14 when the fixing nut 18 is tightened in the manufacturing process of the actuator 1. By tightening the fixing nut 18 so as to suppress the amount of displacement of the screw shaft 14, the central axis CL2 of the screw shaft 14 and the reference axis SL can be more reliably maintained in a state where they are parallel to each other.

[0081] The nut 13 is any one of a top-type nut, an end deflector-type nut, and a tube-type nut. This allows the actuator 1 to be made smaller.

[0082] The nut 13 also has a plurality of link portions 13b. According to this, the nut 13 is a locking nut, which allows the actuator 1 to be made smaller and the screw shaft 14 to be positioned more precisely.

[0083] In addition, the manufacturing method of the actuator 1 includes the steps of: inserting the screw shaft 14, which moves relative to the housing 11 as a nut 13 stored in the housing 11 rotates, with a gap between the screw shaft 14 and the through hole 22a1 of the slide member 22 that guides the screw shaft 14 along a reference axis SL; performing an alignment adjustment to make the central axis CL2 of the screw shaft 14 parallel to the reference axis SL while the screw shaft 14 is inserted through the through hole 22a1; after the alignment adjustment is completed, fitting the four set screws 17 into the slide member 22 and bringing the tips 17a of the four set screws 17 into contact with the outer peripheral surface of the screw shaft 14 inside the through hole 22a1 at different positions in the circumferential direction of the screw shaft 14; and fitting a fixing nut 18 onto the screw shaft 14 while the tips 17a of the four set screws 17 are in contact with the outer peripheral surface of the screw shaft 14, thereby fixing the screw shaft 14 to the slide member 22. According to this, when the fixing nut 18 is tightened, the four set screws 17 maintain the position of the screw shaft 14 relative to the slide member 22. Therefore, the set screws 17 can maintain the central axis CL2 of the screw shaft 14 and the reference axis SL in a state parallel to each other. Therefore, an error in the amount of movement of the screw shaft 14 along the reference axis SL can be suppressed.

[0084] In the above embodiment, the number of set screws 17 is four, but it may be three, five or more. Furthermore, the tips 17a of the three, five or more set screws 17 do not have to be positioned at equal intervals in the circumferential direction of the screw shaft 14. For example, when the fixing nut 18 is tightened, if the moving direction of the screw shaft 14 can be known in advance, the tips 17a of the set screws 17 may be positioned so that the direction of the force acting from the set screws 17 on the outer circumferential surface of the screw shaft 14 is opposite to the moving direction of the screw shaft 14.

[0085] Furthermore, at least one of the central axes of the four set screws 17 may be located at a position different from the other set screws 17 in the direction along the reference axis SL.

[0086] Furthermore, when the tip 17a of the set screw 17 comes into contact with the outer circumferential surface of the screw shaft 14, the amount of displacement of the screw shaft 14 may be measured by a measuring device M. In this case, the tip 17a of the set screw 17 comes into contact with the outer circumferential surface of the screw shaft 14 so as to suppress the amount of displacement of the screw shaft 14 relative to the slide member 22, thereby making it possible to maintain the posture of the screw shaft 14 after the alignment adjustment.

[0087] Furthermore, the actuator 1 may include two fixing nuts 18. In this case, the sliding member 22 is fixed to the screw shaft 14 by sandwiching the fixing portion 22a between the two fixing nuts 18.

[0088] <Robot with parallel link 2> A robot 2 including a parallel link according to an embodiment of the present disclosure will be described with reference to the drawings.

[0089] In the following description, the Z direction is the up-down direction, the direction perpendicular to the Z direction is the X direction, and the direction perpendicular to the Z direction and the X direction is the Y direction. Note that the X, Y, and Z directions are merely examples, and the present disclosure is not limited to these directions. Also, viewing the robot 2 including the parallel links along the Z direction from the +Z side or -Z side is referred to as a "planar view."

[0090] FIG. 9 is a perspective view of a robot 2 including a parallel link according to an embodiment of the present disclosure. The robot 2 including a parallel link is a medical robot arm used during surgery performed by a doctor. The robot 2 including a parallel link may be an industrial robot arm used in the production of industrial products. The robot 2 including a parallel link is electrically connected to a control device (not shown) by wire or wirelessly. A doctor operates the control device to operate the robot 2 including a parallel link.

[0091] The robot 2 including a parallel link includes a first arm unit 110, a first joint portion 120a, a second arm unit 130, a second joint portion 120b, and a third arm unit 140. A medical instrument 3 is fixed to the third arm unit 140 in a replaceable manner.

[0092] The medical instrument 3 is an instrument used for treatment. The medical instrument 3 of this embodiment has a needle-shaped needle portion 3a. A doctor performs treatment by, for example, inserting the needle portion 3a from the tip of the needle portion 3a into an affected area of ​​a patient. Note that FIG. 9 shows the robot 2 including the parallel link in a reference state H in which the tip of the needle portion 3a faces the -Z side and the needle portion 3a of the medical instrument 3 extends along the Z direction.

[0093] Fig. 10 is a plan view of the robot 2 including the parallel link shown in Fig. 9 as seen from the +Z side. Fig. 11 is a side view of the robot 2 including the parallel link shown in Fig. 9 as seen from the -X side. Note that Fig. 11 omits the illustration of a counterweight 113, which will be described later.

[0094] 9, 10, and 11 includes a first arm 111, a second arm 112, and a counterweight 113. In a reference state H of the robot 2 including a parallel link, the first arm 111 and the second arm 112 are arranged in parallel along the Z direction in a posture extending along the Y direction.

[0095] The first arm 111 and the second arm 112 are each the above-mentioned actuator 1. The first arm 111 and the second arm 112 are arranged with their respective reference axes SL parallel to each other. In the reference state H of the robot 2 including the parallel link, the reference axes SL of the first arm 111 and the second arm 112 are parallel to the Y direction. The counterweight 113 is attached to the slide member 22 of the first arm 111 (see FIG. 10).

[0096] The first joint portion 120a connects the first arm unit 110 and the second arm unit 130 so that the second arm unit 130 can be inclined relative to the first arm unit 110. As shown in Figures 10 and 11, the first joint portion 120a includes a first link 121a, a second link 122a, a cylindrical first shaft member 123a, a third link 124a, a fourth link 125a, and a cylindrical second shaft member 126a.

[0097] The first link 121a is fixed to the slide member 22 of the first arm portion 111. The second link 122a is connected to a planar first mounting surface 130b of the first mounting portion 130a of the second arm unit 130 via a linear guide 127a and a guide rail 130c. As a result, the second link 122a is connected to the first mounting surface 130b so as to be movable along the first mounting surface 130b.

[0098] The first link 121a and the second link 122a are connected via a first shaft member 123a so as to be relatively tiltable around a central axis CL4a of the first shaft member 123a. In a reference state H of the robot 2 including the parallel links, the central axis CL4a of the first shaft member 123a is aligned along the X direction.

[0099] A first end of the third link 124a is fixed to the slide member 22 of the second arm portion 112. The fourth link 125a is fixed to the first mounting surface 130b.

[0100] The third link 124a and the fourth link 125a are connected via a second shaft member 126a so as to be relatively tiltable about a central axis CL5a of the second shaft member 126a. The central axis CL5a of the second shaft member 126a is parallel to the central axis CL4a of the first shaft member 123a.

[0101] In this manner, by connecting the first attachment portion 130a of the second arm unit 130 and the first arm unit 110 via the first joint portion 120a, the first arm unit 110, the first joint portion 120a, and the first attachment portion 130a configure a so-called parallel link mechanism. As a result, the second arm unit 130 inclines and moves in translation relative to the first arm unit 110, as will be described next.

[0102] Fig. 12 is a diagram showing a state in which the second arm unit 130 is inclined with respect to the first arm unit 110 from the reference state H of the robot 2 including the parallel link shown in Fig. 11. When the screw shaft 14 in the first arm 111 moves from the reference state H of the robot 2 including the parallel link shown in Fig. 11 to the side where it protrudes from the housing 11, as shown in Fig. 12, the second link 122a inclines with respect to the first link 121a and the fourth link 125a inclines with respect to the third link 124a in the counterclockwise direction in Fig. 12, so that the second arm unit 130 inclines with respect to the first arm unit 110.

[0103] In addition, when the screw shaft 14 in the second arm 112 moves from the reference state H of the robot 2 including the parallel link shown in Figure 11 toward the side where it protrudes from the housing 11, the second link 122a tilts clockwise in Figure 12 relative to the first link 121a, and the fourth link 125a tilts relative to the third link 124a, causing the second arm unit 130 to tilt relative to the first arm unit 110.

[0104] Furthermore, from the reference state H of the robot 2 including the parallel link shown in Figure 11, when the screw shafts 14 in the first arm unit 111 and the second arm unit 112 move at equal speeds toward the side protruding from the housing 11, the second arm unit 130 moves translationally toward the +Y side relative to the first arm unit 110.

[0105] As shown in FIGS. 9, 10, and 11, the second arm unit 130 includes a first attachment portion 130a, a third arm portion 131, and a fourth arm portion 132.

[0106] As described above, the first attachment portion 130a has a first attachment surface 130b to which the second link 122a and the fourth link 125a of the first joint portion 120a are connected.

[0107] The third arm 131 and the fourth arm 132 are arranged in parallel along the Z direction in a posture extending along the X direction in a reference state H of the robot 2 including a parallel link.

[0108] The third arm 131 and the fourth arm 132 are each the above-mentioned actuator 1. The third arm 131 and the fourth arm 132 are disposed with their respective reference axes SL parallel to each other. In the reference state H of the robot 2 including the parallel link, the reference axes SL of the first arm 111 and the second arm 112 are each parallel to the X direction.

[0109] The second joint portion 120b connects the second arm unit 130 and the third arm unit 140 so that the third arm unit 140 can be tilted relative to the second arm unit 130. The second joint portion 120b has the same configuration as the first joint portion 120a, and therefore a description of the second joint portion 120b will be omitted. However, the reference numerals of the components of the second joint portion 120b are the same as those of the components of the first joint portion 120a that correspond to the components of the second joint portion 120b, except that the suffix "a" is changed to "b".

[0110] As shown in FIG. 10, in the second joint portion 120b, the second link 122b is connected to a planar second mounting surface 140b of the second mounting portion 140a of the third arm unit 140 via a linear guide 127b and a guide rail 140c. As a result, the second link 122b is connected to the second mounting surface 140b so as to be movable along the second mounting surface 140b. In addition, in the reference state H of the robot 2 including the parallel link, the first shaft member 123b is disposed so that the central axis CL4b of the first shaft member 123b is aligned along the Y direction. The fourth link 125b shown in FIG. 9 is fixed to the second mounting surface 140b.

[0111] In this way, the second attachment portion 140a of the third arm unit 140 and the second arm unit 130 are connected via the second joint portion 120b, so that the second arm unit 130, the second joint portion 120b, and the second attachment portion 140a configure a so-called parallel link mechanism. Therefore, the third arm unit 140 inclines clockwise and counterclockwise relative to the second arm unit 130 in FIG. 13 (described later) and translates along the X direction, similar to the inclination and translation of the second arm unit 130 relative to the first arm unit 110 described above.

[0112] Fig. 13 is a side view of the robot 2 including the parallel link shown in Fig. 9 when viewed from the -Y side. As shown in Figs. 10 and 13, in the reference state H of the robot 2 including the parallel link, the reference axis SLa of the third arm unit 140 extends along the Z direction. The third arm unit 140 includes a drive unit 141 and an instrument guide unit 142.

[0113] The driving section 141 has the same configuration as the driving section 10 of the above-described actuator 1. The central axis CL2 of the screw shaft 14 of the driving section 141 is aligned so as to be parallel to the reference axis SLa.

[0114] The instrument guide portion 142 guides the medical instrument 3. The instrument guide portion 142 includes the above-mentioned second attachment portion 140a and a slide member 142a.

[0115] 10, the drive unit 141 is fixed to the second attachment portion 140a. The second attachment portion 140a has a second attachment surface 140b to which the second joint portion 120b is connected, and a guide surface 140d. As described above, the second link 122b and the fourth link 125b of the second joint portion 120b are connected to the second attachment surface 140b.

[0116] The guide surface 140d is a plane parallel to the second mounting surface 140b. A slide member 142a is attached to the guide surface 140d so as to be movable relative to the second mounting portion 140a. Specifically, a linear guide 142b is fixed to the slide member 142a, and a guide rail 140e that fits with the linear guide 142b is fixed to the guide surface 140d. The guide rail 140e extends along the reference axis SLa. Therefore, the slide member 142a moves along the reference axis SLa relative to the second mounting portion 140a.

[0117] 13, the slide member 142a is fixed to the second end of the screw shaft 14 of the drive unit 141 by a fixing nut 18. As described above, the central axis CL2 of the screw shaft 14 of the drive unit 141 is aligned with respect to the reference axis SLa. In addition, the medical instrument 3 is fixed to the slide member 142a. In other words, when the screw shaft 14 of the drive unit 141 moves, the slide member 142a and the medical instrument 3 move together along the reference axis SLa relative to the second attachment portion 140a.

[0118] Moreover, the third arm unit 140 further includes a linear encoder 143. The linear encoder 143 includes a scale 143a and a head 143b.

[0119] The scale 143a is disposed on the second attachment portion 140a so as to be aligned with the reference axis line SLa. The housing 11 of the driving portion 141 is fixed to the second attachment portion 140a. The head 143b is disposed on a slide member 142a that moves integrally with the screw shaft 14. In other words, the linear encoder 143 detects the amount of movement of the screw shaft 14 relative to the housing 11 of the driving portion 141.

[0120] Fig. 14 is a diagram showing a state in which the medical instrument 3 has been moved by driving the third arm unit 140 from the reference state H of the robot 2 including the parallel link shown in Fig. 13. When the screw shaft 14 of the drive unit 141 moves from the reference state H of the robot 2 including the parallel link shown in Fig. 13 to the side where it protrudes from the housing 11, the medical instrument 3 moves to the -Z side along the reference axis line SLa as shown in Fig. 14. On the other hand, when the screw shaft 14 of the drive unit 141 moves from the state of the robot 2 including the parallel link shown in Fig. 14 toward the side where it fits into the housing 11, the medical instrument 3 moves to the +Z side along the reference axis line SLa as shown in Fig. 13.

[0121] In the robot 2 including the parallel link configured as described above, a doctor inputs an operation amount to the control device. The control device adjusts the movement amount of each screw shaft 14 corresponding to the input operation amount based on the detection results of each linear encoder 25, 143. As described above, each screw shaft 14 is guided by the slide members 22, 142a and moves with high precision along the reference axes SL, SLa.

[0122] This allows for precise adjustment of the attitude and position of second arm unit 130 and third arm unit 140 relative to first arm unit 110. Furthermore, the attitude and position of medical instrument 3 is precisely adjusted, and medical instrument 3 moves precisely.

[0123] As described above, according to this embodiment, the robot 2 including a parallel link is provided with a plurality of actuators 1. Of the plurality of actuators 1, the actuator 1 constituting the first arm 111 and the actuator 1 constituting the second arm 112 are arranged with their respective reference axes SL parallel to each other. Also, of the plurality of actuators 1, the actuator 1 constituting the third arm 131 and the actuator 1 constituting the fourth arm 132 are arranged with their respective reference axes SL parallel to each other. According to this, in the robot 2 including the parallel link, as in the actuator 1 described above, the error in the amount of movement of the screw shaft 14 can be suppressed.

[0124] Next, a robot 2 including a parallel link according to a modified example of the embodiment of the present disclosure will be described.

[0125] For example, the third arm unit 140 may further include three or more set screws 17, similar to the above-described actuator 1. Specifically, the slide member 142a has a through hole through which the screw shaft 14 passes, and tips 17a of, for example, four set screws 17 contact the outer circumferential surface of the screw shaft 14 inside the through hole. This prevents the screw shaft 14 from tilting when the fixing nut 18 is tightened, similar to the above-described actuator 1, and the posture of the screw shaft 14 after alignment adjustment can be maintained. [Explanation of symbols]

[0126] 1 Actuator 2 Robots with parallel links 10 Drive unit 11. Housing 13 Nut 13b Frame 14 Screw shaft 14c Part to be measured 14d Contacted surface 17 Setscrew 17a Setscrew tip 18 Fixing nut 20 Guide section 22 Slide member 22a1 through hole 22a2 Mounted part CL2 Central axis of the screw shaft M Measuring Instrument Mc measuring head SL reference axis

Claims

1. Housing and A nut housed in the housing; A screw shaft that moves relative to the housing as the nut rotates; a slide member having a through hole through which the screw shaft passes with a gap therebetween and moving along a reference axis line relative to the housing; Three or more set screws that fit with the slide member and have tips that contact the outer circumferential surface of the screw shaft inside the through hole; A fixing nut that fits onto the screw shaft and fixes the screw shaft to the slide member, The tips of the three or more set screws contact the outer circumferential surface of the screw shaft at different positions in the circumferential direction of the screw shaft. Actuator.

2. The three or more tips of the set screws are positioned at equal intervals in the circumferential direction of the screw shaft. The actuator of claim 1 .

3. The slide member has an attachment portion to which a measuring device that measures a displacement amount of the screw shaft when the fixing nut is tightened is attached, The screw shaft has a measured portion having a contact surface with which the measuring device comes into contact, The actuator of claim 1 .

4. The nut is any one of a top-type nut, an end deflector-type nut, and a tube-type nut. The actuator of claim 1 .

5. The nut has a plurality of link portions. The actuator of claim 1 .

6. A step of passing a screw shaft, which moves relative to the housing as a nut housed in the housing rotates, through a through hole of a slide member that guides the screw shaft along a reference axis line with a gap; A step of performing an alignment adjustment to make a central axis line of the screw shaft parallel to the reference axis line in a state in which the screw shaft penetrates the through hole; After the alignment adjustment is completed, three or more set screws are fitted into the slide member, and tips of the three or more set screws are brought into contact with the outer circumferential surface of the screw shaft inside the through hole at different positions in the circumferential direction of the screw shaft; The step of fitting a fixing nut to the screw shaft with the tip of each of the three or more set screws in contact with the outer circumferential surface of the screw shaft to fix the screw shaft to the slide member. A method for manufacturing an actuator.

7. A plurality of actuators according to any one of claims 1 to 5 are provided, one of the actuators and the other of the actuators are arranged in a state in which the reference axes of the actuators are parallel to each other; A robot that includes a parallel link.

Images