Actuator

Abstract

To provide an actuator whose shaft has higher propulsive force and whose motor has higher reverse actuation.SOLUTION: An actuator includes a first motor having a first stator and a first rotor, a second motor that is spaced apart from the first motor in the axial direction of the central axis and includes a second stator and a second rotor, a shaft member that axially passes through the first rotor and the second rotor and has a first portion, a second portion, and a third portion, a spline outer cylinder, a nut member, and a mounting member that is attached to the outer circumferential side of the second portion via a bearing and that blocks transmission of rotational force of the second portion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an actuator.

Background Art

[0002] Actuators including a ball screw and a ball spline are known (see, for example, Patent Document 1). The actuator described in Patent Document 1 includes a ball screw nut, a ball spline outer cylinder, a single motor, a composite shaft (shaft) in which both a ball screw groove and a ball spline groove are formed on an outer periphery thereof, and a mounting member fixed to an end of the composite shaft. With this configuration, the ball screw nut rotates when driven by the motor, and the composite shaft and the mounting member fixed to the composite shaft linearly move in the axial direction along the ball spline groove.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] There is a demand for an actuator that has higher propulsive force when the composite shaft (shaft) performs linear motion, and has higher reverse operability of the motor when an external force is applied to the composite shaft (shaft).

[0005] The present disclosure has been made in view of the above, and an object thereof is to provide an actuator in which the propulsive force of the shaft is higher and the reverse operability of the motor is higher.

Means for Solving the Problem

[0006] An actuator according to one aspect of the present disclosure includes: a first motor having a first stator and a first rotor rotatable around the axis of the central axis relative to the first stator; a second motor disposed spaced apart from the first motor in the axial direction of the central axis and having a second stator and a second rotor rotatable with respect to the second stator and coaxial with the central axis of the first rotor; a first portion having a spline groove on its outer circumference that penetrates the first rotor and the second rotor in the axial direction, protruding from the first rotor toward the opposite side of the second rotor toward the opposite side of the second rotor and extending in the axial direction; a second portion provided on one side of the first portion in the axial direction and extending in the axial direction; and a portion extending from the second rotor toward the front The device comprises: a shaft member having a third portion that protrudes to the other side in the axial direction toward the opposite side of the first rotor and has a male threaded portion on its outer circumference; a spline outer cylinder that guides the shaft member in the axial direction along the spline groove of the first portion of the shaft member and rotates together with the first rotor to rotate the shaft member in the direction of the axis of the central axis; a nut member having a female threaded portion that engages with the male threaded portion of the third portion of the shaft member via a plurality of balls and rotates together with the second rotor to move the shaft member in the axial direction; a bearing; and a mounting member attached to the outer circumference of the second portion via the bearing, and the transmission of rotational force to the second portion is blocked by the bearing.

[0007] The actuator described in Patent Document 1, mentioned above, has only one motor, and the thrust force when the composite shaft moves linearly is also driven by the driving force of that single motor. In contrast, this disclosure has two motors, a first motor and a second motor. Therefore, by rotationally driving both the first motor and the second motor, the axial thrust force of the shaft member can be increased.

[0008] Furthermore, in the actuator of Patent Document 1, it is conceivable to arrange two motors side by side in order to obtain a high thrust force. However, when two motors are arranged side by side and subjected to reverse operation, the torque generated by the back electromotive force in the two motors becomes greater than the torque generated by the back electromotive force in one motor of the actuator of Patent Document 1. Therefore, when two motors are arranged in Patent Document 1, the reverse operation capability of the motors becomes low. In contrast, in this disclosure, as described above, when an axial external force is input to the mounting member, only the second motor is rotated, and the first motor does not output torque due to the back electromotive force. Therefore, the actuator according to one aspect of this disclosure has higher motor reverse operation capability.

[0009] Furthermore, since the transmission of rotational force from the second part is blocked at the mounting member, it is possible to accommodate a free mode of motion independent of the second part.

[0010] In a desirable configuration, the rotational axis of the bearing is coaxial with the central axis of the first rotor. This suppresses radial oscillation of the mounting member due to rotation when the mounting member is rotated relative to the second part.

[0011] A desirable configuration includes a cylindrical motor housing that extends along the circumferential direction around the central axis and houses the first and second motors. In this configuration, the motor housing is cylindrical and has higher rigidity. Therefore, even if an external force causing radial oscillation is applied to the motor housing via the mounting member, the motor housing can support this external force.

[0012] In a desirable configuration, the shaft member is divided into a first shaft including the first portion and a second shaft including the second portion, and the first shaft and the second shaft are connected by screw fastening. This allows for a reduction in parts costs, as only the worn portion needs to be replaced if wear occurs in the first shaft or the second shaft.

[0013] In a preferred configuration, the first and second motors are direct-drive motors. Direct-drive motors transmit the generated driving force directly to the object without the need for a reduction mechanism. That is, the shaft member can be rotated by directly rotating the spline outer cylinder with the driving force of the first motor. Similarly, the shaft member can be moved in a straight line by directly rotating the nut member with the driving force of the second motor. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an actuator that has a higher thrust force from the shaft and a higher reverse action capability from the motor. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a cross-sectional view of the actuator according to the embodiment. [Figure 2] Figure 2 is an enlarged cross-sectional view of a portion of Figure 1. [Figure 3] Figure 3 is a cross-sectional view of the actuator according to the embodiment, showing the state where the stroke of the shaft member is at its upper limit. [Figure 4] Figure 4 is an enlarged cross-sectional view of a portion of Figure 3. [Modes for carrying out the invention]

[0016] Embodiments for carrying out the invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below. Furthermore, the components described below include those that can be easily imagined by those skilled in the art, and those that are substantially the same. Moreover, the components described below can be combined as appropriate.

[0017] Figure 1 is a cross-sectional view of the actuator according to the embodiment. Figure 2 is an enlarged cross-sectional view of a portion of Figure 1. Figure 3 is a cross-sectional view of the actuator according to the embodiment, showing the state where the stroke of the shaft member is at its upper limit. Figure 4 is an enlarged cross-sectional view of a portion of Figure 3.

[0018] As shown in FIG. 1, the actuator 1 is used as, for example, a pick-and-place apparatus. The actuator 1 includes a first motor M1, a second motor M2, a shaft member SF, an outer spline cylinder 61, a nut member 51, a mounting member 70, a first motor housing 40, and a second motor housing 40A. Hereinafter, the central axis of the first motor M1 and the second motor M2 is referred to as a central axis AX, and the axial direction of the central axis AX is defined as the Z direction. One side in the axial direction (Z direction) is defined as the Z1 side, and the other side in the axial direction (Z direction) is defined as the Z2 side.

[0019] The first motor M1 includes a first stator 10, a first rotor 20, and a first rotation detection unit 101.

[0020] A first stator holder 11 is arranged radially inward of the first stator 10. The first stator 10 is fixed to the first stator holder 11. The first rotor 20 is arranged on an outer peripheral side of the first stator 10. The first rotor 20 rotates about the central axis AX. The first rotor 20 includes a first rotor bracket 21 and a first rotor core 22. The first rotor core 22 is fixed radially inward of the first rotor bracket 21. The first rotor core 22 has a permanent magnet. The first rotor bracket 21 has a cylindrical shape centered on the central axis AX. Further, the first rotor bracket 21 has an outer ring retainer 21a that supports the outer ring of the first bearing 31.

[0021] The first stator 10 and the first rotor 20 are arranged coaxially around the central axis AX. The first rotor 20 is arranged radially outward of the first stator 10 and the first stator holder 11, and rotates relative to the first stator 10. In other words, the first rotor 20 is rotatably supported by the first stator 10 and the first stator holder 11 via the first bearing 31. The first stator holder 11 is fixed to the first motor housing 40 via bolts. The first stator 10 is provided in a cylindrical shape around the central axis AX.

[0022] The first motor housing 40 is formed, for example, in a cylindrical shape and accommodates the first motor M1. The upper end of the first motor housing 40 is open, and the opening is covered by a spline outer cylinder housing 43. The spline outer cylinder housing 43 includes a housing main body portion 43a and a cylindrical portion 43b. The cylindrical portion 43b is provided in a cylindrical shape along the direction around the central axis AX. A spline outer cylinder 61 is disposed inside the cylindrical portion 43b. The housing main body portion 43a is attached to the upper bottom portion 40a of the first motor housing 40 via bolts. A first lid member 111 is provided on the Z2 side of the housing main body portion 43a. The first lid member 111 is fixed to an outer ring retainer 21a of a first rotor bracket 21 via bolts. A through hole is provided in a radially central portion of the first lid member 111, and the spline outer cylinder 61 penetrates the through hole. A downwardly facing recess 112 that is recessed upward is provided on a lower surface of the first lid member 111.

[0023] Although not shown in the drawings, a spline portion is provided on an inner periphery of the spline outer cylinder 61. The spline portion meshes with a spline groove 633 provided on an outer periphery of a shaft member SF to be described later via a plurality of balls. The spline portion has a plurality of protrusions protruding toward the inner peripheral side and extending in the axial direction (Z direction). The plurality of protrusions are arranged at equal intervals in the circumferential direction on the inner periphery of the spline outer cylinder 61. A flange 62 spreading radially outward is provided at a lower end portion of the spline outer cylinder 61. The flange 62 is inserted into the recess 112. The flange 62 is fixed to the first lid member 111 via bolts.

[0024] The first rotation detection unit 101 is, for example, a resolver. The first rotation detection unit 101 detects the rotation state of the first motor M1. The first rotation detection unit 101 is disposed above the first bearing 31.

[0025] The second motor M2 is located on the Z2 side with respect to the first motor M1. The second motor M2 is arranged side by side with respect to the first motor M1 in the axial direction of the central axis AX. The second motor M2 includes a second stator 10A, a second rotor 20A, and a second rotation detection unit 101A. The first motor M1 and the second motor M2 are cylindrical direct drive motors.

[0026] The second rotor 20A is positioned on the outer circumference of the second stator 10A. The second rotor 20A rotates about a central axis AX. That is, the central axis of the second rotor 20A is coaxial with the central axis AX of the first rotor 20. The second rotor 20A has a second rotor bracket 21A and a second rotor core 22A. The second rotor core 22A is fixed radially inward of the second rotor bracket 21A. The second rotor core 22A has permanent magnets. The second rotor bracket 21A is formed in a cylindrical shape with a central axis AX as its center. The second stator 10A and the second rotor 20A are positioned coaxially with respect to the central axis AX.

[0027] The second rotor 20A is positioned radially outward of the second stator 10A and the second stator holder 11A, and rotates relative to the second stator 10A and the second stator holder 11A. In other words, the second rotor 20A is rotatably supported by the second stator 10A and the second stator holder 11A via the second bearing 32. The second stator 10A is fixed to the second stator holder 11A. The second stator holder 11A is positioned radially inward of the second stator 10A. The second stator holder 11A is fixed to the second motor housing 40A via bolts. The second stator 10A is cylindrical around a central axis AX.

[0028] Here, the shaft member SF will be described. The shaft member SF is positioned coaxially with the central axis AX. The shaft member SF extends in the axial direction of the central axis AX. The shaft member SF has a first shaft 63 and a second shaft 53.

[0029] The first shaft 63 extends from the connecting portion 100 to the narrow-diameter portion 635. The connecting portion 100 is positioned to be aligned with the second rotation detection portion 101A in the Z direction. The first shaft 63 comprises a small-diameter portion 632, a large-diameter portion (first portion S1) 631, a medium-diameter portion 634, and a narrow-diameter portion 635. The small-diameter portion 632, large-diameter portion 631, medium-diameter portion 634, and narrow-diameter portion (second portion S2) 635 are arranged in order from the Z2 side to the Z1 side.

[0030] A second motor M2 is positioned on the outer circumference of the small-diameter section 632. A first motor M1 is positioned on the outer circumference of the large-diameter section 631. The Z2 end of the large-diameter section 631 is aligned with the lower bottom portion 40b of the first motor housing 40 in the Z direction. The large-diameter section 631 is also referred to as the first portion S1. A spline groove 633 is provided on the outer circumference of the large-diameter section 631. The spline groove 633 has a diameter D1. The diameter D1 of the spline groove 633 is the larger of the large and small diameters. That is, the diameter D1 of the spline groove 633 is larger than the outer diameter of the small-diameter section 632, the outer diameter of the medium-diameter section 634, and the outer diameter of the small-diameter section 635. The spline groove 633 extends in the Z direction (axial direction). Multiple spline grooves 633 are provided on the outer circumference of the large-diameter section 631 at equal intervals in the circumferential direction. As described above, the spline groove 633 engages with the spline portion provided on the inner circumference side of the spline outer cylinder 61 via a plurality of balls. Therefore, the shaft member SF is movable in the Z direction (axial direction) relative to the spline outer cylinder 61, but cannot rotate in the circumferential direction about the axis of the central axis AX.

[0031] The medium-diameter portion 634 protrudes toward Z1 from the Z1-side end of the large-diameter portion 631. The outer diameter of the medium-diameter portion 634 is larger than the outer diameter of the small-diameter portion 632. The thin-diameter portion 635 protrudes toward Z1 from the Z1-side end of the medium-diameter portion 634. The thin-diameter portion 635 is also referred to as the second portion S2. The outer diameter of the thin-diameter portion 635 is smaller than the outer diameter of the small-diameter portion 632, the outer diameter of the large-diameter portion 631, and the outer diameter of the medium-diameter portion 634.

[0032] The second shaft 53 extends from the connecting portion 100 to the stopper 55. The second shaft 53 has a large diameter portion (third portion S3) 531, a small diameter portion 532, and a thin diameter portion 531a. The thin diameter portion 531a, the large diameter portion 531, and the small diameter portion 532 are arranged in order from the Z1 side to the Z2 side. A male thread is provided on the outer circumference of the thin diameter portion 531a. A recess 632a is provided at the end of the small diameter portion 632 of the first shaft 63. A female thread is provided on the inner circumference of the recess 632a that engages with the male thread of the thin diameter portion 531a. The female thread on the inner circumference of the recess 632a engages with the male thread of the thin diameter portion 531a. As a result, the small diameter portion 632 of the first shaft 63 and the large diameter portion 531 of the second shaft 53 are integrally connected. In other words, the first shaft 63 and the second shaft 53 are connected by screw fastening to form a connecting portion 100.

[0033] Furthermore, a male threaded portion 533 is formed on the outer circumference of the large-diameter portion 531. The large-diameter portion 531 is also referred to as the third portion S3. In addition, the diameter D1 of the spline groove portion 633 in the shaft member SF is larger than the diameter D2 of the male threaded portion 533. Note that the diameter D1 of the spline groove portion 633 is the larger diameter of the large and small diameters. The diameter D2 of the male threaded portion 533 is the outer diameter of the inner diameter (root diameter) of the outer diameter and inner diameter.

[0034] Furthermore, a small-diameter portion 532 is provided on the Z2 side of the large-diameter portion 531. The outer diameter of the small-diameter portion 532 is smaller than the diameter D2 of the large-diameter portion 531. A stopper 55 is attached to the Z2 end of the small-diameter portion 532 by a nut 56. The stopper 55 is an annular-shaped member. An annular-shaped cushioning member 55a is provided on the Z1 side of the stopper 55. The cushioning member 55a is, for example, an elastic urethane rubber. When the shaft member SF rises, the rise of the shaft member SF can be restricted by the stopper 55 hitting the bottom 42c of the nut housing 42 via the cushioning member 55a.

[0035] The second motor housing 40A is formed, for example, in a cylindrical shape and houses the second motor M2. The Z1 end of the second motor housing 40A is open, and a shaft member SF is provided passing through this opening. An upper bottom portion 40Aa is provided on the outer circumference of the opening, extending in an annular manner around the axis of the central axis AX. The upper bottom portion 40Aa abuts against the lower bottom portion 40b of the first motor housing 40 and is fixed to the lower bottom portion 40b via bolts. The lower bottom portion 40Ab of the second motor housing 40A is also open, and this opening is covered by a nut housing 42 and a stopper cover 44. In this way, the first motor housing 40 and the second motor housing 40A have a cylindrical shape that extends along the circumferential direction around the axis of the central axis AX.

[0036] The nut housing 42 has an upper flange 42a, a cylindrical portion 42b extending downward from the inner circumference end of the upper flange 42a, and a bottom portion 42c extending inward from the lower end of the cylindrical portion 42b. The upper flange 42a is fixed to the lower bottom portion 40Ab of the second motor housing 40A via bolts. The stopper cover 44 is fixed to the bottom portion 42c of the nut housing 42 via bolts. A groove 42d is provided on the Z1 side surface of the bottom portion 42c, recessed toward the Z2 side. The diameter of the groove 42d is larger than the outer diameter of the large diameter portion 531 of the second shaft 53. Therefore, the Z2 side end of the large diameter portion 531 fits into the groove 42d. The groove 42d also has a through hole, through which the small diameter portion 532 of the second shaft 53 passes.

[0037] The stopper cover 44 has an upper flange 44a, a cylindrical portion 44b, and a bottom portion 44c. The upper flange 44a is fixed to the bottom portion 42c via bolts. The cylindrical portion 44b has a cylindrical shape extending from the upper flange 44a toward the Z2 side. The bottom portion 44c seals the opening on the Z2 side of the cylindrical portion 44b. A mounting portion 57 protruding toward the Z2 side is attached to the bottom portion 44c. The mounting portion 57 is provided with a through hole 57a. The through hole 57a is, for example, circular. The mounting portion 57 is fixed to, for example, a mechanical device to which the actuator 1 is attached. That is, for example, a protruding portion of the mechanical device is inserted into the through hole 57a and fixed to the mechanical device.

[0038] The nut member 51 and the second connecting bracket 45 are housed inside the nut housing 42.

[0039] A female thread is provided on the inner circumference of the nut member 51. The female thread engages with the male thread 533 of the large diameter portion 531 of the shaft member SF via a number of balls. A second connecting bracket 45 is positioned radially outward of the nut member 51. A flange portion 51a that extends radially outward is formed at the Z2 end of the nut member 51. The flange portion 51a is fixed to the second connecting bracket 45 via bolts. A flange 45a that extends radially outward is provided at the Z1 end of the second connecting bracket 45, and the flange 45a is fixed to the first connecting bracket 46 via bolts.

[0040] The first connecting bracket 46 is fixed to the second rotor bracket 21A via bolts. In this way, the nut member 51, the second connecting bracket 45, the first connecting bracket 46, and the second rotor bracket 21A are rotatable as a single unit. More specifically, the nut member 51, the second connecting bracket 45, the first connecting bracket 46, and the second rotor bracket 21A are rotatably supported with respect to the second stator 10A and the second stator holder 11A via the second bearing 32.

[0041] The second rotation detection unit 101A is, for example, a resolver. The second rotation detection unit 101A detects the rotation state of the second motor M2. The second rotation detection unit 101A is positioned in the axial direction, aligned with the connecting portion 100.

[0042] Next, the mounting member 70 will be described. As shown in Figure 2, the mounting member 70 includes a housing 71, a bearing 72, a cover 73, and a mounting portion 75. The mounting member 70 and the small-diameter portion 635 of the shaft member SF are rotatable relative to each other in the circumferential direction about the axis of the central axis AX. In other words, the mounting member 70 is attached to the outer circumference of the small-diameter portion 635 (second portion S2) via the bearing 72, and this bearing 72 prevents the transmission of rotational force from the small-diameter portion 635 to the mounting member 70. The small-diameter portion 635 and the bearing 72 are housed inside the housing 71. The bearing 72 is provided between the housing 71 and the small-diameter portion 635. The bearing 72 has an inner ring 72a, an outer ring 72b, and rolling elements 72c. The inner ring 72a is attached to the small-diameter portion 635 by being sandwiched in the Z direction between the bearing retaining member 74B and the medium-diameter portion 634. The bearing retaining member 74B extends in the circumferential direction about the axis of the central axis AX. The bearing retaining member 74B comprises a fixed portion 74Ba and a retaining portion 74Bb. The bearing retaining member 74B has a U-shape in cross-section including the central axis AX. The retaining portion 74Bb is provided on the outer circumference side of the fixed portion 74Ba. The thickness of the retaining portion 74Bb in the Z direction is greater than the thickness of the fixed portion 74Ba in the Z direction. The fixed portion 74Ba is fixed to the Z1 side end face of the small diameter portion 635 via bolts BL1 and BL2. The retaining portion 74Bb presses against the inner ring 72a.

[0043] The bearing retaining member 74A extends in the circumferential direction about the axis of the central axis AX. The bearing retaining member 74A comprises a fixed portion 74Aa and a retaining portion 74Ab. The bearing retaining member 74A has an L-shape in cross-section including the central axis AX. The retaining portion 74Ab is provided on the inner circumference side of the fixed portion 74Aa. The thickness of the retaining portion 74Ab in the Z direction is greater than the thickness of the fixed portion 74Aa in the Z direction. The fixed portion 74Aa is fixed to the bottom surface of the recess 71b of the housing 71 via bolts BL3 and BL4. The retaining portion 74Ab presses against the outer ring 72b. That is, the outer ring 72b is attached to the housing 71 by being sandwiched in the Z direction between the bearing retaining member 74A and the bottom portion 71a of the housing 71.

[0044] On the Z1 side of the housing 71, an annular portion 71c protrudes toward the Z1 side along the circumferential direction around the axis of the central axis AX. A recess 71b is located radially inward of the annular portion 71c. The opening on the Z1 side of the housing 71 is sealed with a cover 73. The cover 73 is fixed to the Z1 side end face 71d of the annular portion 71c via bolts BL5 and BL6. A mounting portion 75 protrudes toward the Z1 side from the Z1 side end face of the cover 73. A through hole 75a is provided in the mounting portion 75. The through hole 75a is, for example, circular. An arm, for example, can be attached to the mounting portion 75, and a workpiece can be attached to the arm. For example, the protruding portion of the arm is inserted into the through hole 75a and the arm is fixed to the mounting portion 75.

[0045] Next, we will explain the movement of actuator 1.

[0046] (First aspect) First, we will describe a first mode in which the shaft member SF moves up and down (linearly). In this first mode, only the second motor M2 operates, and the first motor M1 does not operate.

[0047] As shown in Figure 1, when the second motor M2 is activated, the second rotor 20A rotates around the axis of the central axis AX. More specifically, the second rotor 20A rotates around the axis of the central axis AX relative to the second stator 10A and the second stator holder 11A via the second bearing 32. The first rotor 20 does not rotate.

[0048] The nut member 51 is integrated with the second rotor 20A. Therefore, the nut member 51 also rotates integrally with the second rotor 20A in the direction of the axis of the central axis AX. The female thread portion of the nut member 51 engages with the male thread portion 533 of the shaft member SF, so the rotation of the nut member 51 causes the shaft member SF to move linearly along the axial direction. In detail, as shown in Figure 3, the shaft member SF rises along the axial direction. As the shaft member SF rises, the stopper 55 contacts the bottom portion 42c of the nut housing 42 via the buffer member 55a, thereby restricting the upward movement of the shaft member SF. Here, as mentioned above, the mounting member 70 is attached to the outer circumference of the small diameter portion 635 (second portion S2) via a bearing 72, and the transmission of rotational force from the small diameter portion 635 is blocked. Therefore, as shown in Figures 3 and 4, the mounting member 70 rises together with the small diameter portion 635 without rotating. Furthermore, since it is also possible to rotate only the mounting member 70, the mounting member 70 may be rotated while being raised.

[0049] Next, a description will be given of the mode in which the shaft member SF rotates. In this mode, depending on how the shaft member SF moves in the Z direction, a second mode, a third mode, and a fourth mode are included.

[0050] (Second aspect) In the second embodiment, the first motor M1 operates, but the second motor M2 does not. As described above, the spline groove 633 and the spline portion engage. As a result, the shaft member SF is guided axially along the spline portion of the spline outer cylinder 61. Furthermore, the shaft member SF rotates together with the first rotor 20 via the spline outer cylinder 61, allowing the shaft member SF to rotate around the axis of the central axis AX. In addition, since the second motor M2 does not operate, the nut member 51 also does not rotate. Therefore, as shown in Figures 3 and 4, when the shaft member SF rotates due to the spline outer cylinder 61, the shaft member SF rises along the axial direction due to the nut member 51. Thus, in the second embodiment, the shaft member SF rotates together with the spline outer cylinder 61 and rises (linearly) by rotating relative to the stationary nut member 51. The mounting member 70 can rise together with the small diameter portion 635 without rotating. However, it is also possible to rotate the mounting member 70.

[0051] (Third aspect) In the third embodiment, the shaft member SF rotates integrally with the spline outer cylinder 61, while the nut member 51 rotates so that the position of the shaft member SF in the Z direction does not change. Therefore, in the third embodiment, both the first motor M1 and the second motor M2 are operated. That is, the rotation by the first motor M1 is the same as in the first embodiment, and the shaft member SF rotates together with the first rotor 20 via the spline outer cylinder 61, thereby enabling the shaft member SF to rotate in the direction of the central axis AX. The second motor M2, which was not operated in the second embodiment, rotates the nut member 51 in the opposite direction to the linear motion of the shaft member SF. Thus, in the third embodiment, the shaft member SF rotates integrally with the spline outer cylinder 61 without changing its position in the Z direction. The mounting member 70 neither rotates nor rises. However, it is also possible to rotate only the mounting member 70.

[0052] (Fourth aspect) In the fourth embodiment, the shaft member SF rotates integrally with the spline outer cylinder 61, and the rotational speed of the nut member 51 is appropriately adjusted to vary the linear motion speed (movement speed in the Z direction) of the shaft member SF. Therefore, in the fourth embodiment, both the first motor M1 and the second motor M2 are operated. That is, the rotation by the first motor M1 is the same as in the first and second embodiments, and the shaft member SF rotates together with the first rotor 20 via the spline outer cylinder 61, thereby enabling the shaft member SF to rotate in the direction of the central axis AX. The rotational speed of the second motor M2 is set to match the desired linear motion speed of the shaft member SF. Thus, in the fourth embodiment, the shaft member SF rotates integrally with the spline outer cylinder 61 while appropriately adjusting the movement speed of the shaft member SF in the Z direction. The mounting member 70 can be moved linearly together with the small diameter portion 635 without rotating. However, it is also possible to rotate the mounting member 70.

[0053] Next, we will explain the thrust force of the shaft member SF and the reverse operation properties of the motor.

[0054] (Propulsion force of shaft member SF) To achieve a small thrust, for example, only one of the two motors M1 and M2 needs to be driven. Specifically, this is the first and second embodiments described above.

[0055] To generate greater thrust, for example, both motors M1 and M2 can be driven. Specifically, this corresponds to the third and fourth embodiments described above.

[0056] (Motor reverse action capability) For example, when an external force directed toward the Z2 side is applied to the mounting member 70, that is, when the motor is subjected to reverse operation, a back electromotive force is generated in the motor, and torque is output in the direction opposite to the reverse operation. In this embodiment, when an external force from the Z2 side is applied to the mounting member 70 and the shaft member SF is pushed toward the Z2 side, only the second motor M2 is rotated, and the first motor M1 does not output torque due to the back electromotive force. Therefore, compared to the case where both the first motor M1 and the second motor M2 output torque in the direction opposite to the reverse operation, the motor's ability to reverse operation is higher in this embodiment.

[0057] Next, the procedure for transmitting force when an external force directed toward the Z2 side is applied to the mounting member 70 will be briefly explained. As shown in Figure 2, first, the end face 71d of the annular portion 71c is pushed toward the Z2 side from the mounting portion 75 via the cover 73. Next, the bearing retaining member 74A pushes the outer ring 72b of the bearing 72, and the inner ring 72a of the bearing 72 pushes the middle diameter portion 634 toward the Z2 side. As a result, the shaft member SF is pushed toward the Z2 side, and a back electromotive force is generated in the second motor M2.

[0058] As described above, the actuator 1 comprises a first motor M1 having a first stator 10 and a first rotor 20, a second motor M2 having a second stator and a second rotor 20A and being spaced apart from the first motor M1 in the axial direction of the central axis AX, a shaft member SF having a first part S1, a second part S2 and a third part S3 and passing through the first rotor 20 and the second rotor 20A in the axial direction, a spline outer cylinder 61, a nut member 51, and a mounting member 70 attached to the outer circumference of the second part S2 via a bearing 72 and blocking the transmission of rotational force of the second part S2.

[0059] The actuator described in Patent Document 1, mentioned above, has only one motor, and the thrust force when the composite shaft moves in a linear motion is also driven by the driving force of that single motor. In contrast, this embodiment has two motors, a first motor M1 and a second motor M2. Therefore, by rotating both the first motor M1 and the second motor M2, the axial thrust force of the shaft member SF can be increased.

[0060] Furthermore, in the actuator described in Patent Document 1, if two motors are arranged side by side to obtain high thrust, when the motors are subjected to reverse operation, a back electromotive force is generated in both motors, outputting a high torque in the direction opposite to the reverse operation. Therefore, when two motors are arranged in Patent Document 1, the reverse operation capability of the motors is reduced. In contrast, in this embodiment, as described above, when an external force from the Z2 side is input to the mounting member 70, only the second motor M2 is rotated, and the first motor M1 does not output torque due to the back electromotive force. Therefore, the reverse operation capability of the motors is higher in this embodiment.

[0061] Furthermore, since the transmission of rotational force from the second part S2 is blocked to the mounting member 70, it is possible to accommodate free motion modes independent of the second part S2. It is conceivable that a small amount of rotational force due to static friction may be transmitted to the mounting member 70 in the initial stages of rotation of the second part S2, but the "blocking" of the present invention includes this small transmission of rotational force in the initial stages.

[0062] The rotational axis of the bearing 72 is coaxial with the central axis AX of the first rotor 20. This suppresses radial oscillation of the mounting member 70 due to rotation when the mounting member 70 is rotated relative to the small diameter portion 635 (second portion S2).

[0063] The system includes a cylindrical first motor housing 40 and a second motor housing 40A (motor housing) that extend along the circumferential direction around the central axis AX and house the first motor M1 and the second motor M2. Thus, the motor housing is cylindrical and has high rigidity. Therefore, even if an external force causing radial oscillation is applied to the motor housing via the mounting member 70, the motor housing can support this external force.

[0064] The shaft member SF is divided into a first shaft 63 including a first portion S1 and a second shaft 53 including a second portion S2, and the first shaft 63 and the second shaft 53 are connected by screw fastening. With this configuration, if wear or other damage occurs to the first shaft 63 or the second shaft 53, only the worn or damaged portion needs to be replaced, thereby reducing parts costs.

[0065] The first motor M1 and the second motor M2 are direct-drive motors. Direct-drive motors transmit the generated driving force directly to the object without going through a reduction mechanism. That is, the shaft member SF can be rotated by directly rotating the spline outer cylinder 61 with the driving force of the first motor M1. Also, the shaft member SF can be moved in a straight line by directly rotating the nut member 51 with the driving force of the second motor M2.

[0066] Furthermore, the first motor housing 40, the second motor housing 40A, the second connecting bracket 45, the nut member 51, the spline outer cylinder 61, the first motor M1, the second motor M2, etc., are all separate. Therefore, when assembling them in order, the positional relationship between predetermined parts and other parts can be assembled with high precision, making it easy to perform high-precision centering of the motors. [Explanation of Symbols]

[0067] 1 Actuator 10 First Status 10A Second Stator 11 First stator holder 11A Second stator holder 20 Rotor 1 20A Second Rotor 21. First rotor bracket 21a Outer ring retainer 21A Second rotor bracket 22 First rotor core 22A Second Rotor Core 31 First bearing 32 Second bearing 40. First motor housing (motor housing) 40a top bottom 40b bottom bottom 40A Second motor housing (motor housing) 40Aa top bottom 40Ab lower bottom 42 Nut housing 42a Upper flange 42b Cylindrical part 42c bottom 42d groove 43 Spline outer cylinder housing 43a Housing main body 43b Cylinder part 44 Stopper cover 44a Upper flange 44b Cylindrical part 44c bottom 45. Second connecting bracket 46. ​​First connecting bracket 51 Nut component 51a Flange section 53. Second shaft 55 Stopper 55a Buffer material 56 nuts 57 Mounted part 57a Through hole 61 Splined outer cylinder 62 Flange 63. First shaft 70 Mounting components 71 cabinets 71a bottom 71b recess 71c Ring section 71d End face 72 Bearings 72a Inner ring 72b Outer ring 72c rolling element 73 Lid 74A Bearing retaining member 74B Bearing retaining member 75 Mounting part 75a through hole 100 Connection part 101 First rotation detection unit 101A Second rotation detection unit 111 First lid member 112 recess 531 Large diameter section 531a Narrow diameter part 532 Small diameter section 533 Male threaded section 631 Large diameter section 632 Small diameter section 632a Recess 633 Spline groove 634 Medium diameter section 635 Thin section D1 diameter D2 diameter M1 First Motor M2 Second motor S1 Part 1 S2 2nd part S3 3rd part SF shaft member

Claims

1. A first motor having a first stator and a first rotor rotatable around the central axis relative to the first stator, A second motor is provided, which is positioned at a distance from the first motor in the axial direction of the central axis and has a second stator and a second rotor that is rotatable relative to the second stator and is positioned coaxially with the central axis of the first rotor. The first rotor and the second rotor are penetrated in the axial direction, A shaft member having: a first portion having a spline groove on its outer circumference that protrudes from the first rotor toward the opposite side of the second rotor in the axial direction and extends in the axial direction; a second portion having an axial extension and provided on the same side as the first portion; a medium diameter portion having an axial extension and provided between the first portion and the second portion; and a third portion having a male thread on its outer circumference that protrudes from the second rotor toward the opposite side of the first rotor in the axial direction. A spline outer cylinder is provided which the shaft member is guided in the axial direction along the spline groove of the first portion of the shaft member, and which rotates together with the first rotor to rotate the shaft member in the direction of the axis of the central axis, A nut member is provided which has a female thread that engages with the male thread of the third portion of the shaft member, and which rotates together with the second rotor to move the shaft member in the axial direction, A bearing having an outer ring, an inner ring, and rolling elements, A mounting member is attached to the outer circumference of the second portion via the bearing, and the transmission of rotational force to the second portion is interrupted by the bearing. Equipped with, The outer diameter of the middle diameter portion is smaller than the larger diameter of the first portion, and the outer diameter of the second portion is smaller than the outer diameter of the middle diameter portion. The aforementioned mounting member is A housing having a bottom portion positioned on the outer circumference of the second portion and projecting radially inward from the other end in the axial direction, The second portion comprises a first bearing retainer member fixed to one end face in the axial direction, a second bearing retainer member positioned on the outer circumference of the first bearing retainer member and fixed to the upper surface of the housing, a cover fixed to one end face in the axial direction of the housing, and a mounting portion provided on the cover. The inner ring of the bearing is clamped in the axial direction by the aforementioned middle diameter portion and the first bearing retaining member. The bottom of the housing and the second bearing retaining member clamp the outer ring of the bearing in the axial direction. The outer diameter of the housing is larger than the outer diameter of the spline outer cylinder. Actuator.

2. The rotational axis of the bearing is coaxial with the central axis of the first rotor. The actuator according to claim 1.

3. It comprises a cylindrical motor housing that extends along the circumferential direction about the axis of the central shaft and houses the first motor and the second motor, The actuator according to claim 1 or 2.

4. The shaft member is divided into a first shaft including the first portion and a second shaft including the second portion, and the first shaft and the second shaft are connected by screw fastening. The actuator according to claim 1 or 2.

5. The first motor and the second motor are direct drive motors. The actuator according to claim 1 or 2.

Images