Linear motion mechanism and horizontal articulated robot

Abstract

A linear motion mechanism (100) is provided with an elongate shaft (6) extending along a prescribed axis (C), a drive mechanism (7) which moves the shaft (6) in the axis (C) direction with a prescribed stroke, a housing (4) which accommodates the drive mechanism (7) and which has an opening (42) allowing at least one end portion (61) of the shaft (6) to project to the outside in such a way as to be capable of moving backward and forward, and a tubular protective cover (13) of which the two ends are fixed to the housing (4) and the end portion (61) of the shaft (6), wherein the protective cover (13) encloses the opening (42) and the part of the shaft (6) that projects outward from the opening (42), expands and contracts in the axis (C) direction in accordance with movement of the shaft (6) relative to the housing (4) in the axis (C) direction, and is fixed to the housing (4) in a position in which a part of the drive mechanism (7) including an end surface through which the shaft (6) projects is disposed inside the protective cover (13).

Description

[Technical field]

[0001] The present disclosure relates to a linear motion mechanism and a horizontal articulated robot. [Background technology]

[0002] A SCARA robot is known that includes a cover covering a mechanical section on the top of a horizontally rotatable second arm, and an operating shaft that movably passes through the second arm and the cover in a direction along a vertical axis and is supported rotatably about the vertical axis (see, for example, Patent Document 1). The gap between the operating shaft and an upper insertion hole through which the operating shaft passes through the cover is covered by an upper bellows-shaped member arranged between the upper end of the operating shaft and the upper surface of the cover. Also, the gap between the operating shaft and a lower end opening through which the operating shaft passes through the second arm is covered by a lower bellows-shaped member arranged between the lower end of the operating shaft and the lower surface of the second arm.

[0003] The operating shaft is a splined shaft having a length required to rotate the operating shaft about a vertical axis over a required stroke range, and both ends of the splined shaft are extended by intermediate shafts for mounting bellows-shaped members. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-228733 A Summary of the Invention [Problem to be solved by the invention]

[0005] The intermediate shaft increases the weight of the working shaft and the length of the working shaft in the vertical axis direction, which increases the size of the linear motion mechanism of the SCARA robot. Therefore, it is desirable to provide a protective cover such as a bellows-shaped member without increasing the size of the linear motion mechanism while ensuring the stroke of the working shaft. [Means for solving the problem]

[0006] One aspect of the present disclosure includes a long shaft extending along a predetermined axis, a drive mechanism that moves the shaft in the axial direction by a predetermined stroke, a housing that accommodates the drive mechanism and has an opening through which at least one end of the shaft protrudes outwardly so as to be able to advance and retreat, and a cylindrical protective cover having one end fixed to the housing and the other end fixed to the end of the shaft, the protective cover surrounding the opening and a portion of the shaft protruding outwardly from the opening, expanding and contracting in the axial direction in response to movement of the shaft relative to the housing in the axial direction, and a portion of the drive mechanism including an end face from which the shaft protrudes is disposed radially inward. When the protective cover is most compressed, a position where the distance in the axial direction between the one end and the end face of the drive mechanism is smaller than the distance in the axial direction between the other end and the end face; The one end is fixed to the housing. , a linear motion mechanism. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is an overall configuration diagram showing a horizontal articulated robot according to an embodiment of the present disclosure. [Diagram 2] 2 is a partial vertical cross-sectional view showing a lower linear motion mechanism in the horizontal articulated robot of FIG. 1 when a shaft is located at an upper limit of a stroke. FIG. [Diagram 3] 2 is a partial vertical cross-sectional view showing an upper linear motion mechanism when a shaft is located at the lower limit of the stroke in the horizontal articulated robot of FIG. 1. FIG. [Figure 4] 3 is a partial vertical sectional view showing a modified example of the linear motion mechanism of FIG. 2. [Diagram 5] 4 is a partial vertical sectional view showing a modified example of the linear motion mechanism of FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] A linear motion mechanism 100 and a horizontally articulated robot 1 according to an embodiment of the present disclosure will be described below with reference to the drawings. As shown in FIG. 1, the horizontal articulated robot 1 of this embodiment includes, for example, a base 2 placed on a horizontal floor surface F, a first arm 3 supported by the base 2, and a second arm (housing, arm) 4 supported by the first arm 3.

[0009] The first arm 3 is supported by the base 2 so as to be rotatable about a first axis A that extends in the vertical direction. The second arm 4 is supported by the first arm 3 so as to be rotatable about a second axis B parallel to the first axis A. An arm cover (housing) 5 that covers an upper portion of the second arm 4 is attached to the second arm 4, and a space S is defined between the arm cover 5 and the second arm 4.

[0010] The horizontal articulated robot 1 according to this embodiment also includes a linear motion mechanism 100 mounted on the second arm 4. As shown in Fig. 1 to Fig. 3, the linear motion mechanism 100 includes a shaft 6 that passes through the second arm 4 and the arm cover 5 along a third axis (axis) C that extends vertically, and a drive mechanism 7 that drives the shaft 6. The linear motion mechanism 100 also includes cylindrical bellows (protective covers) 13, 23 that are extendable and contractable in the axial direction and positioned to surround the shaft 6 at the portion protruding outward from the second arm 4 and the arm cover 5.

[0011] The shaft 6 is, for example, a ball screw spline shaft. A lower end (end portion) 61 of the shaft 6 protrudes vertically downward from an opening (aperture) 42 provided in the lower surface 41 of the second arm 4, as shown in FIG. Further, at the lower end 61 of the shaft 6, there is provided an attachment portion 63 to which a tool such as a hand (not shown) is attached.

[0012] On the other hand, an upper end (end portion) 62 of the shaft 6 protrudes vertically upward from an opening (opening) 52 provided in an upper surface 51 of the arm cover 5, as shown in FIG. The shaft 6 is provided with a central hole 64 that penetrates along the longitudinal axis from the upper end 62 to the lower end 61. A wire (not shown) such as a cable connected to a control device (not shown) is inserted from the upper end 62 of the shaft 6 into the central hole 64 and wired to a tool attached to the lower end 61 of the shaft 6.

[0013] The drive mechanism 7 includes a ball spline nut 10 and a ball screw nut 20 housed in a space S. The drive mechanism 7 also includes servo motors (not shown) that generate driving force, and pulleys 11, 21 and belts 12, 22 that transmit the driving forces of the servo motors to the ball spline nut 10 and the ball screw nut 20, respectively.

[0014] As shown in FIG. 2, the ball spline nut 10 has a fixed portion 10a fixed to the second arm 4, and a movable portion 10b rotatably supported by a bearing (not shown) around the longitudinal axis of the shaft 6 relative to the fixed portion 10a. The ball spline nut 10 has the movable part 10b meshed with the shaft 6 via balls (not shown). As a result, the ball spline nut 10 supports the shaft 6 so that the shaft 6 can move along the longitudinal axis relative to the movable part 10b, and rotates the shaft 6 about the longitudinal axis by rotation of the movable part 10b.

[0015] As shown in FIG. 3, the ball screw nut 20 has a fixed part 20a fixed to the second arm 4, and a movable part 20b rotatably supported by a bearing (not shown) around the longitudinal axis of the shaft 6 relative to the fixed part 20a. The ball screw nut 20 has a movable part 20b meshed with the shaft 6 via a ball (not shown), and the shaft 6 is moved in the longitudinal direction by the rotation of the movable part 20b relative to the fixed part 20a.

[0016] The bellows 13 has an upper end 13 a fixed to the lower surface 41 of the second arm 4 , and a lower end 13 b attached to the lower end 61 of the shaft 6 by an attachment mechanism 8 . The mounting mechanism 8 comprises a circular inner ring member 81 fixed to the lower end 61 of the shaft 6, a circular outer ring member 82 to which the lower end 13b of the bellows 13 is fixed, and a bearing 83 that supports the outer ring member 82 rotatably around the third axis C relative to the inner ring member 81.

[0017] The bellows 23 has a lower end 23 b fixed to the upper surface 51 of the arm cover 5 and an upper end 23 a attached to the upper end 62 of the shaft 6 by an attachment mechanism 9 . The mounting mechanism 9 comprises an annular inner ring member 91 fixed to the outer peripheral surface of the upper end 62 of the shaft 6, an annular outer ring member 92 to which the upper end 23a of the bellows 23 is fixed, and a bearing 93 that supports the outer ring member 92 rotatably relative to the inner ring member 91 around the third axis C.

[0018] As a result, when the shaft 6 moves in the direction of the third axis C, the bellows 13, 23 are expanded and contracted in response to the up and down movement of the mounting mechanisms 8, 9 fixed to the shaft 6. The bellows 13, 23 have dimensions that enable them to maintain a state in which they cover the openings 42, 52 and the outer surface of the shaft 6 protruding from the openings 42, 52 over the entire stroke of the shaft 6. In addition, when the shaft 6 rotates around the third axis C, the inner ring members 81, 91 are rotated relative to the outer ring members 82, 92, thereby preventing the bellows 13, 23 from twisting.

[0019] In this case, a cylindrical recess 43 recessed upward is provided on the lower surface 41 of the second arm 4 at a position surrounding the outer periphery of the ball spline nut 10 housed in the space S. A seat surface for fixing the upper end 13a of the bellows 13 is provided on a bottom surface 43a of the recess 43. An opening 42 provided in the second arm 4 is disposed at a position substantially equivalent to the lower surface (end surface) of the movable part 10b of the ball spline nut 10.

[0020] 2, the depth from the opening 42 to the bottom surface 43a of the recess 43 is set to a dimension capable of accommodating the bellows 13 in the most compressed state at the upper limit of the stroke of the shaft 6. At this position, the attachment mechanism 8 is closest to the lower surface 41 of the second arm 4 with a small gap therebetween.

[0021] Moreover, a cylindrical recess 53 recessed downward is provided on the upper surface 51 of the arm cover 5 at a position surrounding the outer periphery of the ball screw nut 20 housed in the space S. A seat surface for fixing the lower end 23b of the bellows 23 is provided on a bottom surface 53a of the recess 53. Moreover, an opening 52 provided in the arm cover 5 is disposed at a position substantially equivalent to the upper surface (end surface) of the movable part 20b of the ball screw nut 20.

[0022] 3, the depth from the opening 52 to the bottom surface 53a of the recess 53 is set to a dimension capable of accommodating the bellows 23 in the most compressed state at the lower limit of the stroke of the shaft 6. At this position, the attachment mechanism 9 is closest to the upper surface 51 of the arm cover 5 with a small gap therebetween.

[0023] The operation of the linear motion mechanism 100 and the horizontal articulated robot 1 thus configured will be described below. According to the horizontal articulated robot 1 of this embodiment, the shaft 6 can be positioned two-dimensionally at a desired horizontal position by rotating the first arm 3 about the first axis A relative to the base 2 and rotating the second arm 4 about the second axis B relative to the first arm 3.

[0024] Then, by rotating the ball spline nut 10 about the third axis C through operation of the servo motor, the shaft 6 can be rotated about the third axis C relative to the second arm 4. Also, by rotating the ball screw nut 20 about the third axis C through operation of the servo motor, the shaft 6 can be moved linearly along the third axis C relative to the second arm 4. In this way, the shaft 6 positioned at a desired horizontal position can be rotated and moved up and down, and the vertical position and the angle about the third axis C of the tool attached to the attachment portion 63 at the lower end 61 of the shaft 6 can be adjusted.

[0025] 2, when the shaft 6 is moved vertically upward relative to the second arm 4, the amount of protrusion of the shaft 6 from the opening 42 decreases by the amount of movement of the shaft 6, and the amount of protrusion of the shaft 6 from the opening 52 increases by the amount of movement of the shaft 6. At this time, the bellows 13 is compressed in response to the decrease in the amount of protrusion of the shaft 6 from the opening 42, and the bellows 23 is expanded in response to the increase in the amount of protrusion of the shaft 6 from the opening 52.

[0026] 3, when the shaft 6 is moved vertically downward relative to the second arm 4, the amount of protrusion of the shaft 6 from the opening 52 decreases by the amount of movement of the shaft 6, and the amount of protrusion of the shaft 6 from the opening 42 increases by the amount of movement of the shaft 6. In this case, the bellows 23 is compressed, and the bellows 13 is extended.

[0027] That is, even if the shaft 6 is moved up and down relative to the second arm 4, the openings 42, 52 and the shaft 6 protruding from the openings 42, 52 are maintained in a state of being covered by the bellows 13, 23, respectively. This protects the shaft 6 and the inside of the space S from moisture, dust, and the like from the outside.

[0028] 2 and 3, the bellows 13, 23 have a predetermined length in the axial direction even in the most compressed state. According to this embodiment, the seating surface for mounting the bellows 13, 23 is disposed on the bottom surface 43a, 53a of the recess 43, 53, so that the bellows 13, 23 can be accommodated in the recess 43, 53 in the most compressed state.

[0029] That is, even if the bellows 13, 23 are attached to the shaft 6, the end of the shaft 6 can be brought sufficiently close to the end face of the ball spline nut 10 or the ball screw nut 20 at the stroke end. As a result, there is no need to extend both ends of the shaft 6 by intermediate shafts in order to attach the bellows 13, 23 to the shaft 6, which has the advantage of preventing the horizontal articulated robot 1 from becoming larger.

[0030] In the conventional case where both ends of the shaft 6 are extended by intermediate shafts to attach the bellows 13, 23, the position of the tool mounting portion 63 at the end of the shaft 6 varies depending on whether or not the bellows 13, 23 are present. However, this embodiment eliminates such a disadvantage.

[0031] In this embodiment, as shown in FIG. 4, the gap between the lower end 13b of the bellows 13 and the outer ring member 82, and the gap between the upper end 13a of the bellows 13 and the bottom surface 43a of the recess 43 may be sealed by a ring-shaped sealing member 15 such as a gasket. Furthermore, the gap between the outer circumferential surface of the shaft 6 and the inner ring member 81 may be sealed with a seal member 16 such as an O-ring, and a sealed bearing may be used as the bearing 83.

[0032] Similarly, as shown in FIG. 5, the gap between the upper end 23a of the bellows 23 and the outer ring member 92, and the gap between the lower end 23b of the bellows 23 and the bottom surface 53a of the recess 53 may be sealed with an annular sealing member 25 such as a gasket. Furthermore, the gap between the outer circumferential surface of the shaft 6 and the inner ring member 91 may be sealed with a seal member 26 such as an O-ring, and a sealed bearing may be used as the bearing 93.

[0033] This makes it possible to more reliably prevent moisture, dust, and the like from entering the shaft 6 and the space S from the outside. Furthermore, a labyrinth structure may be formed between the shaft 6 and the inner ring members 81, 91.

[0034] In addition, in this embodiment, a case has been illustrated in which the shaft 6 passes vertically through both the second arm 4 and the arm cover 5, but instead, the shaft 6 may pass vertically through only one of the second arm 4 or the arm cover 5. In this case, there is no need to provide a bellows at the end of the shaft 6 that does not pass through the second arm 4 or the arm cover 5, and the linear motion mechanism 100 can have a simpler configuration.

[0035] In addition, in this embodiment, the horizontally articulated robot 1 is illustrated in which the bellows 13, 23 are attached to the lower end 61 and the upper end 62 of the shaft 6, but instead, the bellows may be attached to only one of them.

[0036] In addition, in this embodiment, the vertical axis mounted on the second arm 4 of the horizontal articulated robot 1 is exemplified as the linear motion mechanism 100, but instead, any other linear motion mechanism having a similar structure may be adopted.

[0037] In addition, in this embodiment, the shaft 6 is a ball screw spline shaft, but instead, the shaft 6 may be a ball spline shaft. In this case, the drive mechanism 7 may include a mechanism for rotationally driving the ball spline shaft about its longitudinal axis, and a mechanism for linearly moving the ball spline shaft in its longitudinal axis direction. As a mechanism for linearly moving the ball spline shaft in the direction along the longitudinal axis, a ball screw or a known linear motion mechanism such as a cylinder may be used.

[0038] In this embodiment, the shaft 6 may be formed of a ball screw shaft, and a ball screw nut 20 may be provided as the drive mechanism 7. In this case, the ball screw shaft is movable only in the direction along its longitudinal axis, so that the mounting mechanisms 8 and 9 can be omitted from having a rotation function about the third axis C. In addition, although a bellows is given as an example of the protective cover, the present invention is not limited thereto, and a protective cover of any structure that is axially expandable and contractible may be adopted. For example, a telescopically expandable protective cover or a spirally expandable protective cover may be adopted. [Explanation of symbols]

[0039] 1. Horizontal articulated robot 4 Second arm (housing, arm) 5 Arm cover (housing) 6 Shaft 7 Driving mechanism 10 Ball spline nut 13 Bellows (protective cover) 20 Ball screw nut 23 Bellows (protective cover) 41 Bottom surface 42 Opening (Aperture) 51 Top side 52 Opening (Aperture) 61 Lower end (end) 62 Upper end (end) 100 Linear motion mechanism C 3rd axis (axis) S space

Claims

1. An elongated shaft extending along a predetermined axis; a drive mechanism for moving the shaft in the axial direction by a predetermined stroke; a housing that houses the drive mechanism and has an opening through which at least one end of the shaft can protrude to the outside in a retractable manner; a cylindrical protective cover having one end fixed to the housing and the other end fixed to the end of the shaft; the protective cover surrounds the opening and a portion of the shaft protruding outward from the opening, expands and contracts in the axial direction in response to movement of the shaft relative to the housing in the axial direction, and a portion including an end surface from which the shaft of the drive mechanism protrudes is disposed radially inward; a linear motion mechanism, wherein the one end is fixed to the housing at a position where, when the protective cover is most compressed, the axial distance between the other end and the end face is smaller than the axial distance between the one end and the end face of the drive mechanism.

2. the shaft is a splined shaft, the drive mechanism includes a ball spline nut that rotates the shaft about the axis by rotating the ball spline nut about the axis, 2. The linear motion mechanism according to claim 1, wherein the protective cover is fixed to the housing at a position where at least a portion of the ball spline nut is disposed inside.

3. the shaft is a ball screw spline shaft, the drive mechanism includes a ball screw nut that moves the shaft in a direction along the axis by rotating about the axis, 3. The linear motion mechanism according to claim 1, wherein the protective cover is fixed to the housing at a position where at least a portion of the ball screw nut is disposed inside.

4. A linear motion mechanism according to any one of claims 1 to 3, An arm is supported so as to be horizontally rotatable, the arm mounts the drive mechanism and supports the shaft so as to be movable in a vertical direction; the housing includes the arm and an arm cover that houses the drive mechanism in a space between the arm and the arm cover, A horizontal articulated robot in which the protective cover is positioned in a position to surround at least one of the end of the shaft that protrudes vertically downward from the opening in the underside of the arm and the end of the shaft that protrudes vertically upward from the opening in the upper surface of the arm cover.

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