Balancer unit and machinery that balances the rotating components of a machine.

Abstract

Throughout history, there has been a search for technologies that reduce stress concentration in the housing of the balancer unit and enable miniaturization and weight reduction of the balancer unit. The balancer unit 50 includes: a potential energy imparting mechanism 54, which generates torque by imparting potential energy to the rotating element 16; and a housing 52, which is rotatably supported on the machine via support shafts 56 and 58 for housing the potential energy imparting mechanism 54. The housing 52 includes: a peripheral wall 66 surrounding and enclosing the potential energy imparting mechanism 54; and hollow shaft receiving portions 68 and 70, which are provided on the peripheral wall 66 in a manner that protrudes inward from the inner peripheral surface of the peripheral wall 66 and rotatably accommodate the support shafts 56 and 58.

Description

[Technical Field]

[0001] Field of Invention

[0002] This disclosure relates to a balancer unit and a mechanism for balancing rotating components of a machine. [Previous Technology]

[0003] Background of the Invention

[0004] A balancing unit for balancing rotating components of a machine is known (e.g., Patent Document 1). Prior Art Documents Patent Documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 11-216697 [Summary of the Invention]

[0006] Summary of the Invention: Problem to be Solved by the Invention

[0007] Previous techniques have sought to reduce stress concentration in the casing of the balancer unit and to achieve miniaturization and weight reduction of the balancer unit. Means used to solve this problem...

[0008] In one embodiment disclosed herein, a balancer unit that applies torque to a rotating element to balance it comprises: a potential energy imparting mechanism that generates torque by imparting potential energy to the rotating element; and a housing rotatably supported on the machine via a support shaft for housing the potential energy imparting mechanism. The housing comprises: a peripheral wall surrounding and enclosing the potential energy imparting mechanism; and a hollow shaft receiving portion disposed on the peripheral wall in a manner protruding inward from the inner peripheral surface of the peripheral wall, rotatably accommodating the support shaft. Effects of the Invention

[0009] According to this disclosure, by providing a shaft receiving portion that protrudes inward toward the peripheral wall to support the rotational movement of the balancer unit, stress concentration in the housing can be suppressed, thereby preventing deformation and damage to the housing. As a result, the housing of the balancer unit can be made thinner, thereby achieving miniaturization and weight reduction of the balancer unit.

Implementation Method

[0011] Form used to implement the invention

[0012] The embodiments disclosed herein will be described in detail below based on the drawings. Furthermore, in the various embodiments described below, the same reference numerals will be used for the same elements, and repeated descriptions will be omitted. First, a machine 10 of one embodiment will be described with reference to FIG1. ​​In this embodiment, the machine 10 is a vertical multi-joint robot, which includes a robot base 12, a rotary body 14, a lower arm 16, an upper arm 18, and a wrist 20.

[0013] The robot base 12 is fixed to the floor of the work cell or to an automated guided vehicle (AGV). The gyro 14 is mounted on the robot base 12 in a manner that allows it to rotate about axis A1. Axis A1 is, for example, parallel to the vertical direction. More specifically, the gyro 14 has: a base portion 14a, and a pair of support walls 14b and 14c that stand opposite each other from the base portion 14a (FIG. 2).

[0014] The lower arm portion 16 is disposed on the rotating body 14 in a manner that allows it to rotate about axis A2. Axis A2 is orthogonal to axis A1 (e.g., parallel to the horizontal direction). More specifically, the lower arm portion 16 has: a base end portion 16a rotatably supported between a pair of support walls 14b and 14c; and a front end portion 16b on the opposite side of the base end portion 16a.

[0015] The upper arm portion 18 has: a base arm portion 18a, which is rotatably disposed at the front end portion 16b of the lower arm portion 16 about an axis A3; and a front arm portion 18b, which is rotatably disposed at the front end portion of the base arm portion 18a about an axis A4. The axis A3 is parallel to the axis A2, and the axis A4 is orthogonal to the axis A3.

[0016] The wrist 20 includes: a wrist base 20a, which is rotatably disposed at the front end of the front arm 18b; and a wrist flange 20b, which is rotatably disposed on the wrist base 20a. The axis A5 is orthogonal to the axis A4, and the axis A6 is orthogonal to the axis A5.

[0017] The mechanism 10 causes the gyropod 14, lower arm 16, base arm 18a, front arm 18b, wrist base 20a, and wrist flange 20b to rotate about axes A1, A2, A3, A4, A5, and A6 respectively, thereby positioning the end connector (not shown) mounted on the wrist flange 20b in any position. Therefore, the gyropod 14, lower arm 16, base arm 18a, front arm 18b, wrist base 20a, and wrist flange 20b each constitute a rotating element of the mechanism 10.

[0018] The machine 10 further includes a balancer unit 50, which applies a torque Mc to the rotating element in order to balance the rotating element of the machine 10. In this embodiment, the balancer unit 50 is provided on the rotating body 14 to balance the lower arm 16. Hereinafter, the balancer unit 50 will be described with reference to FIG2.

[0019] The balancer unit 50 includes a housing 52 and a potential energy imparting mechanism 54. The housing 52 is a hollow member with a central axis A7 for accommodating the potential energy imparting mechanism 54. The housing 52 is rotatably supported on the gyro body 14 via a pair of support shafts 56 and 58.

[0020] Furthermore, in the following description, the direction along axis A7 is called the axial direction, the direction of the radius of the circle centered on axis A7 is called the radial direction, and the direction around axis A7 is called the circumferential direction. Also, for convenience, the direction indicated by arrow B in the figure is called the rear axial direction. The outer casing 52 has an outer casing body 60 and a cover 62 fixed to the outer casing body 60.

[0021] Hereinafter, the outer casing body 60 will be described with reference to Figures 3 to 5. The outer casing body 60 has a bottom wall 64, a peripheral wall 66, and a pair of shaft receiving portions 68 and 70. The bottom wall 64 is a flat plate member that defines the rear end of the outer casing body 60 in the axial direction. The peripheral wall 66 is cylindrical and extends forward in the axial direction from the bottom wall 64.

[0022] More specifically, the peripheral wall 66 has a central wall 72 and a pair of bulging walls 74 and 76. In this embodiment, the central wall 72 is a cylindrical member with axis A7 as its central axis, having an inner peripheral surface 72a and an outer peripheral surface 72b. The central wall 72 is divided into two arc-shaped parts by the bulging walls 74 and 76, and the inner peripheral surface 72a of the central wall 72 defines a generally cylindrical internal space S1.

[0023] Each of the bulging walls 74 and 76 is integrally formed on the central wall 72 in such a way that it bulges outward in the radial direction from the outer peripheral surface 72b of the central wall 72. Each of the bulging walls 74 and 76 has a rectangular shape when viewed from the axial direction and extends from the front end of the central wall 72 in the axial direction to the rear end in the axial direction.

[0024] More specifically, the bulging wall 74 has: a pair of sidewall portions 74a and 74b, which face each other and extend radially outward from the outer peripheral surface 72b; and an end wall portion 74c, which extends between the sidewall portions 74a and 74b. The sidewall portions 74a and 74b are substantially orthogonal to the end wall portion 74c. A substantially quadrangular prism-shaped internal space S2 is defined by the inner surface 74d of the sidewall portion 74a, the inner surface 74e of the sidewall portion 74b, and the inner surface 74f of the end wall portion 74c. This internal space S2 is defined as communicating with the internal space S1 and bulging radially outward from the internal space S1.

[0025] Furthermore, the bulging wall 76 has a rotationally symmetrical shape after rotating the bulging wall 74 180° around the axis A7. Specifically, the bulging wall 76 has: a pair of sidewall portions 76a and 76b extending from the outer peripheral surface 72b in the opposite direction to the bulging wall 74; and an end wall portion 76c extending between the sidewall portions 76a and 76b. The inner surface 76d of the sidewall portion 76a, the inner surface 76e of the sidewall portion 76b, and the inner surface 76f of the end wall portion 76c define a generally quadrangular prism-shaped internal space S3. This internal space S3 communicates with the internal space S1 and is defined as bulging outward radially from the internal space S1.

[0026] Furthermore, the inner peripheral surface 66a of the peripheral wall 66 is defined by the inner peripheral surface 72a of the central wall 72 and the inner surfaces (specifically, the inner surfaces 74d, 74e, 74f, 76d, 76e, and 76f) of the bulging walls 74 and 76. The outer peripheral surface 66b of the peripheral wall 66 is defined by the outer peripheral surface 72b of the central wall 72 and the outer surfaces of the bulging walls 74 and 76. In this embodiment, the bulging walls 74 and 76, viewed from the radial direction of the central wall 72, extend from the axial front end of the central wall 72 to the axial rear end with a certain width W (Fig. 5).

[0027] The shaft receiving portions 68 and 70 are hollow and are disposed on the peripheral wall 66 such that they protrude inward from the inner peripheral surface 66a and outward from the outer peripheral surface 66b. Specifically, the shaft receiving portion 68 is integrally disposed on the end wall portion 74c such that it protrudes inward in the radial direction from the inner surface 74f and outward in the radial direction from the outer surface 74g of the end wall portion 74c.

[0028] The shaft receiving portion 68 is a cylindrical component with a central axis A8, which can rotatably accommodate the aforementioned support shaft 56 (Fig. 2). The axis A8 is orthogonal to the axis A7. The radially inner end face 68a of the shaft receiving portion 68 is an arc surface centered on the axis A7. The end face 68a may also have the same radius of curvature as the inner circumferential surface 72a of the central wall 72, or it may have a larger (or smaller) radius of curvature than the inner circumferential surface 72a.

[0029] Furthermore, the shaft receiving portion 70 has a shape that is rotationally symmetrical about the axis A7 after rotating the shaft receiving portion 68 by 180°. Specifically, the shaft receiving portion 70 is a cylindrical member with a central axis A9, which can rotatably accommodate the aforementioned support shaft 58 (FIG. 2). The shaft receiving portion 70 is integrally provided on the end wall portion 76c in such a way that it protrudes radially inward from the inner surface 76f of the end wall portion 76c and radially outward from the outer surface 76g of the end wall portion 76c.

[0030] Furthermore, the inner end face 70a of the shaft receiving portion 70 in the radial direction is an arc surface centered on axis A7. The end face 70a may also have the same radius of curvature as the inner circumferential surface 72a of the central wall 72, or it may have a larger (or smaller) radius of curvature than the inner circumferential surface 72a. In this embodiment, axes A8 and A9 are aligned with each other (i.e., aligned on the same straight line), and the shaft receiving portions 68 and 70 are concentrically arranged with reference to axes A8 and A9.

[0031] Referring again to FIG. 2, the cover 62 has a body portion 62a and a guide portion 62b. The body portion 62a is a flat plate-shaped component, which is fixed to the front end of the peripheral wall 66 in the axial direction by fasteners such as bolts (not shown) to close the opening defined on the front side of the outer casing body 60 in the axial direction. A through hole 62c is formed in the center of the body portion 62a.

[0032] The guide portion 62b is cylindrical and integrally formed on the body portion 62a, extending rearward in the axial direction from the body portion 62a. Alternatively, the guide portion 62b may also extend forward in the axial direction from the body portion 62a. The inner circumferential surface 62d of the guide portion 62b is a through hole 62c that connects to the body portion 62a in the axial direction. As shown in FIG2, when the cover 62 is fixed to the outer shell body 60, the central axis of the guide portion 62b is approximately aligned with axis A7. Furthermore, in this embodiment, the inner circumferential surface 62d is constructed of a sliding bearing.

[0033] The outer casing 52 is disposed between the support walls 14b and 14c of the rotating body 14 in a manner that allows it to rotate about the support shaft 56 disposed on the support wall 14b and the support shaft 58 disposed on the support wall 14c. As shown in FIG2, when the outer casing 52 is supported by the support shafts 56 and 58, the central axis of the support shaft 56 is aligned with the axis A8, and the central axis of the support shaft 58 is aligned with the axis A9.

[0034] That is, the shaft receiving portions 68 and 70 and the support shafts 56 and 58 are arranged concentrically with reference to axes A8 and A9, and extend in a direction orthogonal to the axial direction (i.e., the radial direction). Furthermore, axes A8 and A9 are substantially parallel to axis A2 (in other words, the axial direction of the housing 52 is substantially orthogonal to axis A2).

[0035] The potential energy imparting mechanism 54 imparts potential energy to the lower arm portion 16, thereby generating a torque Mc in the lower arm portion 16. The potential energy imparting mechanism 54 has a rod 80 and a potential energy imparting element 82. The rod 80 is arranged approximately concentrically with the housing 52 with reference to the axis A7, and is retractably accommodated in the guide portion 62b of the cover 62.

[0036] Specifically, the rod 80 has: a cylindrical shaft portion 80a that extends straight in the axial direction; a circular flange portion 80b that protrudes outward from the rear end of the shaft portion 80a in the axial direction; and a cylindrical portion 80c that is fixedly disposed at the front end of the shaft portion 80a in the axial direction. The shaft portion 80a is inserted into the guide portion 62b and the through hole 62c in a manner that allows it to move forward and backward in the axial direction.

[0037] The flange portion 80b is housed within the internal space S1, while the cylindrical portion 80c protrudes from the exterior of the outer casing 52. The shaft portion 80a and the flange portion 80b are surrounded and enclosed by the peripheral wall 66 of the outer casing body 60, and are arranged concentrically with the central wall 72 of the peripheral wall 66 with reference to the axis A7.

[0038] Furthermore, in this embodiment, the outer peripheral surface 80d of the flange portion 80b is disposed at a slight distance from the inner peripheral surface 72a of the central wall 72 in the radial direction. The outer peripheral surface 80d of the flange portion 80b is substantially parallel to the inner peripheral surface 72a of the central wall 72 and the end faces 68a and 70a of the shaft receiving portions 68 and 70.

[0039] As an alternative, the outer peripheral surface 80d of the flange portion 80b and the inner peripheral surface 72a of the central wall 72 may also abut against each other. In this case, the inner peripheral surface 72a may also be constructed of a sliding bearing, or lubricating oil may be applied to the inner peripheral surface 72a. The cylindrical portion 80c has a central axis A10, in which the connecting shaft 84 is rotatably accommodated. The axis A10 is orthogonal to the axis A7 (or parallel to the axis A2).

[0040] A potential energy imparting element 82 is housed within the internal space S1 to impart potential energy to the rod 80. In this embodiment, the potential energy imparting element 82 is an elastic member (more specifically, a compression coil spring) inserted between the flange portion 80b of the rod 80 and the body portion 62a of the cover 62. The potential energy imparting element 82 applies a spring force to the flange portion 80b, causing the flange portion 80b to move away from the body portion 62a, thereby imparting potential energy to the rod 80 in the axial rearward direction.

[0041] The rod 80 is rotatably connected to the lower arm 16 via the connecting shaft 84, with its cylindrical portion 80c rotatably connected to it. More specifically, the cylindrical portion 16c is fixedly provided at the base end 16a of the lower arm 16, protruding outward from the base end 16a. The cylindrical portion 16c is arranged concentrically with the cylindrical portion of the rod 80 with reference to the axis A10, and is used to accommodate the connecting shaft 84. Thus, the rod 80 is rotatably connected to the cylindrical portion 16c of the lower arm 16 via the connecting shaft 84, with its cylindrical portion 80c rotatably connected to it.

[0042] When the lower arm 16 rotates from an upright position roughly parallel to the vertical direction around axis A2 and tilts towards a horizontal position roughly parallel to the horizontal direction, a gravitational torque Mg (Fig. 1) will act on the lower arm 16 due to gravity. In order to counteract this gravitational torque Mg, the potential energy imparting mechanism 54 imparts potential energy to the lower arm 16, thereby applying a torque Mc to the lower arm 16 in the opposite direction to the gravitational torque Mg.

[0043] More specifically, when the lower arm 16 tilts towards a horizontal position, the rod 80 is pulled forward in the axial direction by the cylindrical portion 16c, which rotates around the axis A2, through the connecting shaft 84, thereby being pulled out of the outer casing 52 and moving forward in the axial direction. In this way, the potential energy element 82 is compressed in the axial direction, and as its reaction force, it applies a rearward elastic force in the axial direction to the rod 80 (specifically the flange portion 80b), thereby imparting potential energy to the rod 80 in the axial direction.

[0044] As a result, the rod 80 applies a force to the cylindrical portion 16c through the connecting rod 84, thereby imparting potential energy to the lower arm portion 16 in the opposite direction to the gravitational torque Mg, thereby generating a torque Mc in the lower arm portion 16. In this way, the balancer unit 50 balances the lower arm portion 16 relative to gravity.

[0045] Furthermore, as the lower arm 16 rises in the vertical direction, the rod 80 retracts axially and is pushed into the interior of the housing 52. This axial retraction of the rod 80 is guided by the guide portion 62b of the cover 62. Then, the balancer unit 50 rotates about the support shafts 56 and 58 (i.e., axes A8 and A9) as the rod 80 retracts. The shaft receiving portions 68 and 70 of the housing body 60 support this retraction of the rod 80 and the rotation of the balancer unit 50 about axes A8 and A9.

[0046] As described above, in this embodiment, the outer casing 52 has: a peripheral wall 66 that surrounds and encloses the potential energy imparting mechanism 54 (specifically, the shaft portion 80a and the flange portion 80b); and shaft receiving portions 68 and 70 that are provided on the peripheral wall 66 in such a way that they protrude inward from the inner peripheral surface 66a of the peripheral wall 66.

[0047] Here, the inventors performed a simulation analysis of the stress generated in the housing 52 during the operation of the balancer unit 50, and found that by forming the shaft receiving portions 68 and 70 to protrude inward toward the peripheral wall 66, the stress concentration generated in the housing 52 can be reduced.

[0048] According to this embodiment, since the forward and backward movement of the rod 80 and the rotation of the balancer unit 50 are supported by the shaft receiving portions 68 and 70 that protrude into the inner side of the peripheral wall 66, stress concentration in the outer shell 52 (specifically the outer shell body 60) can be suppressed, thereby preventing deformation and damage to the outer shell 52.

[0049] As a result, since stress concentration can be suppressed without increasing the thickness of the outer shell body 60, air bubbles (i.e., pores) can be prevented from forming in the material during the molding of the outer shell body 60. Furthermore, the outer shell body 60 can be made thinner, avoiding its large size and increased weight. Therefore, miniaturization and weight reduction of the balancer unit 50 can be achieved. Moreover, by suppressing stress concentration to avoid off-center loading on the outer shell body 60, the service life of the balancer unit 50 can be extended.

[0050] Furthermore, in this embodiment, the shaft receiving portions 68 and 70 further protrude outward from the outer peripheral surface 66b of the peripheral wall 66. This configuration allows for a shorter protrusion length of the shaft receiving portions 68 and 70 from the outer peripheral surface 66b in the radial direction, and allows for a larger length in the directions of the axes A8 and A9 of the shaft receiving portions 68 and 70. This effectively suppresses stress concentration in the outer casing body 60 and improves the strength of the shaft receiving portions 68 and 70.

[0051] Furthermore, in this embodiment, the peripheral wall 66 has: a central wall 72, which is concentrically arranged with the potential energy imparting mechanism 54 (specifically, the shaft portion 80a and the flange portion 80b); and bulging walls 74 and 76, which bulge outward from the outer peripheral surface 72b of the central wall 72; and shaft receiving portions 68 and 70 are provided on the bulging walls 74 and 76 in such a way that they protrude inward from the inner peripheral surfaces (specifically, the inner surfaces 74f and 76f) of the bulging walls 74 and 76.

[0052] Based on this configuration, the size (i.e., radius) of the central wall 72 can be minimized. On the other hand, the strength of the bulging walls 74 and 76, which are provided with shaft receiving portions 68 and 70, can be increased by bulging them to the sides. In this way, the increase in the total weight of the outer casing 60 can be suppressed.

[0053] Furthermore, in this embodiment, the bulging walls 74 and 76 extend from the front end of the central wall 72 in the axial direction to the rear end in the axial direction, and extend with a certain width W when viewed from the radial direction of the central wall 72. With this configuration, the strength of the bulging walls 74 and 76 can be effectively improved. Also, in this embodiment, the bulging walls 74 and 76 have a rectangular shape when viewed from the axial direction of the central wall 72. With this configuration, the strength of the bulging walls 74 and 76 can be improved even more effectively.

[0054] Furthermore, in this embodiment, the potential energy imparting mechanism 54 includes: a rod 80 connected to a rotating element (specifically, a lower arm) 16 and retractably housed in a housing 52; and a potential energy imparting element 82 housed inside the housing 52 for imparting potential energy to the rod 80; and support shafts 56 and 58 extending in a direction orthogonal to the retraction direction (i.e., the axial direction) of the rod 80 (i.e., the radial direction).

[0055] Based on this configuration, since the potential energy generated by the potential energy element 82 can be efficiently applied to the rotating element 16 via the rod 80, and the housing 52 can rotate around the support shafts 56 and 58 (specifically axes A7 and A8) according to the forward and backward movement of the rod 80, the forward and backward movement of the rod 80 can be effectively supported. In this way, the rotating element 16 can effectively generate torque Mc.

[0056] Furthermore, in this embodiment, the potential energy imparting element 82 includes an elastic member (compression coil spring), which is inserted between the rod 80 (specifically, the flange portion 80b) and the outer casing 52 (specifically, the body portion 62a of the cover 62), thereby imparting potential energy to the rod 80 by applying an elastic force to it. With this configuration, a relatively simple elastic member, such as a compression coil spring, can be used to effectively impart potential energy to the rod 80.

[0057] Furthermore, in this embodiment, the connection between the central wall 72 and the side wall portion 74a or 74b, the central wall 72 and the side wall portion 76a or 76b, the side wall portion 74a or 74b and the end wall portion 74c, the side wall portion 76a or 76b and the end wall portion 76c, the shaft receiving portion 68 and the end wall portion 74c, or the shaft receiving portion 70 and the end wall portion 76c, can be formed into a rounded corner (so-called a rounded corner). In this way, stress concentration generated in the outer shell body 60 can be more effectively avoided.

[0058] Furthermore, the protruding length L1 (Fig. 5) of the shaft receiving portion 68 protruding radially inward from the inner surface 74f of the end wall portion 74c, and the protruding length L2 of the shaft receiving portion 68 protruding radially outward from the outer surface 74g of the end wall portion 74c, can also be: L1=L2, L1>L2, or L1<L2. Similarly, the protruding length L1 of the shaft receiving portion 70 protruding radially inward from the inner surface 76f of the end wall portion 76c, and the protruding length L2 of the shaft receiving portion 70 protruding radially outward from the outer surface 76g of the end wall portion 76c, can also be: L1=L2, L1>L2, or L1<L2.

[0059] Furthermore, the aforementioned potential energy imparting element 82 may also be constituted by a tension coil spring inserted between the flange portion 80b and the body portion 62a. In this case, the potential energy imparting element 82 applies a spring force to the flange portion 80b in such a way that the flange portion 80b approaches the cover body 62, thereby imparting potential energy to the rod 80 in the axial direction forward.

[0060] Furthermore, various modifications of the outer shell body 60 are conceivable. Hereinafter, modifications of the outer shell body 60 will be described with reference to Figures 6 to 11. The outer shell body 90 shown in Figure 6 differs from the outer shell body 60 in terms of the peripheral wall 92. The peripheral wall 92 has: the aforementioned central wall 72; and a pair of bulging walls 94 and 96, which are integrally formed on the central wall 72 in such a way that they bulge outward in the radial direction from the outer peripheral surface 72b of the central wall 72.

[0061] Each of the bulging walls 94 and 96 extends in such a way that the width W decreases from the front end in the axial direction to the rear end in the axial direction of the central wall 72. More specifically, the bulging wall 94 has: a pair of side wall portions 94a and 94b that face each other and extend radially outward from the outer peripheral surface 72b; and an end wall portion 94c that is orthogonal to the side wall portions 94a and 94b.

[0062] An internal space S2 that bulges outward radially from the internal space S1 is defined by the inner surface 94d of the side wall portion 94a, the inner surface 94e of the side wall portion 94b, and the inner surface 94f of the end wall portion 94c. The side walls 94a and 94b extend in such a manner that they become closer to each other as they move from the axial front end of the central wall 72 toward the axial rear end, and connect to each other at the axial rear end. Therefore, the width W of the bulging wall 94 decreases towards the axial rear end.

[0063] Furthermore, the bulging wall 96 has a rotationally symmetrical shape after rotating the bulging wall 94 180° around the axis A7. Specifically, the bulging wall 96 has sidewall portions 96a, 96b, and 96c corresponding to the sidewall portions 94a, 94b, and 94c, respectively. The inner surface 96d of the sidewall portion 96a, the inner surface 96e of the sidewall portion 96b, and the inner surface 96f of the end wall portion 96c define the inner space S3 that bulges outward radially from the inner space S1.

[0064] Furthermore, the inner peripheral surface 92a of the central wall 72 is defined by the inner peripheral surface 72a and the inner surfaces (inner surfaces 94d, 94e, 94f, 96d, 96e, and 96f) of the bulging walls 94 and 96. Additionally, the outer peripheral surface 92b of the peripheral wall 92 is defined by the outer peripheral surface 72b of the central wall 72 and the outer surfaces of the bulging walls 94 and 96.

[0065] The shaft receiving portion 68 is integrally provided on the end wall portion 94c such that it protrudes radially inward from the inner surface 94f of the end wall portion 94c and radially outward from the outer surface 94g of the end wall portion 94c. Similarly, the shaft receiving portion 70 is integrally provided on the end wall portion 96c such that it protrudes radially inward from the inner surface 96f of the end wall portion 96c and radially outward from the outer surface 96g of the end wall portion 96c.

[0066] Furthermore, the bulging walls 94 and 96 can also be formed to have a generally elliptical shape when viewed from the direction of axes A8 and A9 (i.e., radially outward). This configuration improves the aesthetics of the outer shell body 90. Additionally, the bulging walls 94 and 96 can extend axially from the front end of the central wall 72 and terminate at a position closer to the front axial direction than the bottom wall 64. In this case, the rear end of the central wall 72 becomes annular, and the bottom wall 64 has the same shape as the central wall 72 and is integrally formed at the rear end of the central wall 72.

[0067] Furthermore, the connection between the central wall 72 and the side wall portion 94a or 94b, the central wall 72 and the side wall portion 96a or 96b, the side wall portion 94a or 94b and the end wall portion 94c, the side wall portion 96a or 96b and the end wall portion 96c, the shaft receiving portion 68 and the end wall portion 94c, or the shaft receiving portion 70 and the end wall portion 96c can be formed into a corner with a rounded arc.

[0068] The outer shell body 100 shown in Figures 7 and 8 differs from the outer shell body 60 in terms of the peripheral wall 102. The peripheral wall 102 has: the aforementioned central wall 72; and a pair of bulging walls 104 and 106, which are integrally formed on the central wall 72 in such a way that they bulge outward in the radial direction from the outer peripheral surface 72b of the central wall 72.

[0069] Each of the bulging walls 104 and 106 has a circular shape when viewed from the axial direction. More specifically, the bulging wall 104 extends in an arc shape from one end edge 104a in the circumferential direction to the other end edge 104b in the circumferential direction, and extends from the front end in the axial direction of the central wall 72 to the rear end in the axial direction with a certain width W (Fig. 8). The arc-shaped inner circumferential surface 104c of the bulging wall 104 defines the inner space S2 that bulges outward from the inner space S1 in the radial direction.

[0070] Similarly, the bulging wall 106 extends in an arc shape from one end edge 106a in the circumferential direction to the other end edge 106b in the circumferential direction, bulging outward in the radial direction, and extends from the front end in the axial direction of the central wall 72 to the rear end in the axial direction with a certain width W. The arc-shaped inner circumferential surface 106c of the bulging wall 106 defines the inner space S3 that bulges outward in the radial direction from the inner space S1. Each of the bulging walls 104 and 106 has a smaller radius of curvature than the central wall 72, end surfaces 68a and 70a.

[0071] The inner peripheral surface 102a of the peripheral wall 102 is defined by the inner peripheral surface 72a of the central wall 72 and the inner peripheral surfaces 104c and 106c of the bulging walls 104 and 106. The outer peripheral surface 102b of the peripheral wall 102 is defined by the outer peripheral surface 72b of the central wall 72 and the outer peripheral surfaces 104d and 106d of the bulging walls 104 and 106d.

[0072] The shaft receiving portion 68 is integrally provided on the bulging wall 104 in such a way that it protrudes radially inward from the inner peripheral surface 104c of the bulging wall 104 and radially outward from the outer peripheral surface 104d of the bulging wall 104. Similarly, the shaft receiving portion 70 is integrally provided on the bulging wall 106 in such a way that it protrudes radially inward from the inner peripheral surface 106c of the bulging wall 106 and radially outward from the outer peripheral surface 106d of the bulging wall 106.

[0073] In this embodiment, since the bulging walls 104 and 106 have a circular shape when viewed from the axial direction, stress concentration in the bulging walls 104 and 106 can be effectively suppressed. Therefore, the strength of the bulging walls 104 and 106 can be improved. Furthermore, the connection between the central wall 72 and the bulging wall 104 or 106, the shaft receiving portion 68 and the end wall portion 94c, or the shaft receiving portion 70 and the end wall portion 96c can be formed into a rounded corner.

[0074] The outer casing 110 shown in Figures 9 and 10 differs from the outer casing 60 in terms of its peripheral wall 112. The peripheral wall 112 has an elliptical shape, and the aforementioned ellipse has a major axis parallel to the extending directions of the support axes 56 and 58. More specifically, the peripheral wall 112 has an elliptical shape, and the aforementioned ellipse has a major axis aligned with axes A8 and A9, and a minor axis orthogonal to axes A7, A8, and A9.

[0075] The shaft receiving portions 68 and 70 are each integrally formed on the peripheral wall 112 in such a way that they protrude radially inward from the inner peripheral surface 112a and radially outward from the outer peripheral surface 112b of the peripheral wall 112. In this embodiment, since the peripheral wall 112 has an elliptical shape, stress concentration in the peripheral wall 112 can be effectively suppressed. Therefore, the strength of the peripheral wall 112 can be improved.

[0076] Furthermore, the connection between the peripheral wall 112 and the shaft receiving portion 68 or 70 may be formed as a corner with a rounded arc. Also, the peripheral wall 112 is not limited to an ellipse, and may have any shape (such as a rectangle, rhombus or hexagon, etc.) in the direction of the long side when viewed from the axial direction along the axes A8 and A9.

[0077] The outer casing 120 shown in FIG11 differs from the outer casing 60 in terms of the shaft receiving portions 68' and 70'. In this embodiment, the shaft receiving portion 68' protrudes radially inward from the inner surface 74f of the end wall portion 74c, but does not protrude outward from the outer surface 74g of the end wall portion 74c.

[0078] Similarly, the shaft receiving portion 70' protrudes radially inward from the inner surface 76f of the end wall portion 76c, but does not protrude outward from the outer surface 76g of the end wall portion 76c. Furthermore, the connection between the end wall portion 74c and the shaft receiving portion 68', or between the end wall portion 76c and the shaft receiving portion 70', can be formed into a rounded corner. In this embodiment, since stress concentration in the outer casing body 120 can also be suppressed, the outer casing body 120 can be made thinner, thereby achieving miniaturization and weight reduction of the balancer unit 50.

[0079] Furthermore, shaft receiving portions 68' and 70' may also be applied to the aforementioned outer casing body 90, 100 or 110. In this case, shaft receiving portions 68' and 70' protrude inward from the inner peripheral surface of the peripheral wall 92, 102 or 112, but do not protrude outward from the outer peripheral surface of the peripheral wall 92, 102 or 112.

[0080] Furthermore, in the above embodiment, the potential energy imparting mechanism 54 is described as having a potential energy imparting element 82 as an elastic member. However, the potential energy imparting element can also be made of fluid. This type of embodiment is shown in FIG12. The balancer unit 50' shown in FIG12 has a housing 52 and a potential energy imparting mechanism 54', which has a rod 80' and a potential energy imparting element 82'. The rod 80' has: the aforementioned shaft portion 80a and cylindrical portion 80c, and a flange portion 80b' protruding outward from the rear end of the shaft portion 80a in the axial direction. The flange portion 80b' has the same shape as the peripheral wall 66 and is slidably in close contact with the inner peripheral surface 66a of the peripheral wall 66.

[0081] In this embodiment, the potential energy element 82' is a fluid sealed in the spaces S1, S2, and S3 between the rod 80' and the outer casing 52. More specifically, the potential energy element 82' is, for example, gas or oil, sealed in the space between the flange 80b' of the rod 80' and the bottom wall 64 of the outer casing body 60 within the internal spaces S1, S2, and S3 of the outer casing 52.

[0082] For example, when a negative pressure is applied to the potential energy element 82', the potential energy element 82' will act in the same way as the potential energy element 82 composed of a compression coil spring, and apply pressure to the flange portion 80b' in such a way that the flange portion 80b' moves away from the cover body 62, thereby applying potential energy to the rod 80' in the axial direction rearward.

[0083] Furthermore, when a positive pressure is applied to the potential energy element 82', the potential energy element 82' will act in the same way as the potential energy element 82 composed of a tension coil spring, and apply pressure to the flange portion 80b' in such a way that the flange portion 80b' approaches the cover body 62, thereby applying potential energy to the rod 80' in the axial direction forward.

[0084] A fluid inlet 64a may also be formed on the bottom wall 64 of the outer casing 60, through which the potential energy element 82' is introduced into the internal spaces S1, S2, and S3 of the outer casing 52. After the potential energy element 82' is introduced, the fluid inlet 64a can also be tightly sealed by the plug 114.

[0085] Furthermore, at least one of the aforementioned axes A8 and A9 may be inclined relative to axis A7 (or axis A2). Also, the shaft receiving portion 68 or 70 is not limited to a cylindrical shape; for example, it may have a polygonal shape, or any hollow shape. Also, the aforementioned central wall 72 is not limited to a cylindrical shape; for example, it may be an ellipse with a major axis aligned with axes A8 and A9, or any other shape. Also, the bulging walls 74, 76, 94, 96, 104, or 106 are not limited to being rectangular or circular when viewed from the axial direction; they may have any shape.

[0086] Furthermore, in the above embodiments, a pair of shaft receiving portions 68 and 70 are described as being provided on the outer casing bodies 60, 90, 100, and 110. However, this is not a limitation, and one of the shaft receiving portions 68 and 70 may be omitted. For example, in the outer casing bodies 60, 90, 100, or 110, instead of the shaft receiving portion 70, a support shaft 58' protruding radially outward from the peripheral wall 66, 92, 102, or 112 may be integrally formed on the peripheral wall 66, and the outer casing body 60 may be rotatably supported on the rotating body 14 through the support shaft 58' and the support shaft 56. Similarly, one of the pair of shaft receiving portions 68' and 70' may also be omitted from the outer casing body 120.

[0087] Furthermore, in the above embodiment, it is described that the balancer units 50 and 50' are provided on the rotating body 14 to balance the lower arm portion 16. However, it is not limited to this. For example, the balancer unit 50 or 50' may also be provided at the front end 16b of the lower arm portion 16 to balance the upper arm portion 18, or it may be configured to balance any of the rotating elements 14, 16, 18a, 18b, 20a, 20b of the machine 10.

[0088] Furthermore, the machine 10 is not limited to a vertical multi-joint robot, but can be any type of machine with rotating elements, such as a horizontal multi-joint robot, a parallel-link robot, or a rotary positioner that rotates a workpiece. The present disclosure has been described above by way of embodiments, but the above embodiments do not limit the invention related to the scope of the claims. [Simplified Explanation of the Diagram]

[0010] Figure 1 is a schematic diagram of one embodiment of the machine. Figure 2 is a cross-sectional view of the balancer unit shown in Figure 1. Figure 3 is a perspective view of the housing body shown in Figure 2. Figure 4 is a front view of the housing body shown in Figure 3 viewed from the axial direction (arrow IV in Figure 3). Figure 5 is a cross-sectional view of the housing body shown in Figure 3 cut by a plane orthogonal to the axial direction. Figure 6 is a perspective view of the housing body in another embodiment. Figure 7 is a perspective view of the housing body in yet another embodiment. Figure 8 is a front view of the housing body shown in Figure 7 viewed from the axial direction. Figure 9 is a perspective view of the housing body in yet another embodiment. Figure 10 is a front view of the housing body shown in Figure 9 viewed from the axial direction. Figure 11 is a front view of the housing body in yet another embodiment viewed from the axial direction. Figure 12 is a cross-sectional view of the balancer unit in another embodiment.

Claims

1. A balancer unit that applies torque to a rotating element of a machine in order to balance the rotating element, the balancer unit comprising: a potential energy imparting mechanism that generates the torque by imparting potential energy to the rotating element; and a housing rotatably supported on the machine via a support shaft for accommodating the potential energy imparting mechanism, the housing comprising: a peripheral wall surrounding and enclosing the potential energy imparting mechanism; and a hollow shaft receiving portion disposed on the peripheral wall in a manner protruding inward from the inner peripheral surface of the peripheral wall, rotatably accommodating the support shaft.

2. The balancer unit of claim 1, wherein the aforementioned shaft receiving portion further protrudes outward from the outer peripheral surface of the aforementioned peripheral wall.

3. The balancer unit of claim 1 or 2, wherein the aforementioned peripheral wall has: a central wall, which is concentrically arranged with the aforementioned potential energy imparting mechanism; and a bulging wall, which bulges outward from the outer peripheral surface of the aforementioned central wall, wherein the aforementioned shaft receiving portion is provided on the bulging wall in such a way that it protrudes inward from the aforementioned inner peripheral surface of the aforementioned bulging wall.

4. The balancer unit as claimed in claim 3, wherein the aforementioned bulging wall extends from one end of the aforementioned central wall in the axial direction to the other end.

5. The balancer unit of claim 4, wherein the aforementioned bulging wall, viewed from the radial direction of the aforementioned central wall, extends from the aforementioned one end to the aforementioned other end with a certain width, or extends in a manner in which the aforementioned width decreases as it extends from the aforementioned one end to the aforementioned other end.

6. The balancer unit of claim 3, wherein the aforementioned bulging wall has a rectangular or circular shape when viewed from the axial direction of the aforementioned central wall.

7. The balancer unit of claim 1 or 2, wherein the aforementioned peripheral wall has an elliptical shape, and the aforementioned ellipse has a major axis parallel to the extension direction of the aforementioned support shaft.

8. The balancer unit of claim 1 or 2, wherein the aforementioned potential energy imparting mechanism comprises: a rod connected to the aforementioned rotating element and retractably housed in the aforementioned housing; and a potential energy imparting element housed inside the aforementioned housing for imparting potential energy to the aforementioned rod, wherein the aforementioned support shaft extends in a direction orthogonal to the retraction direction of the aforementioned rod.

9. The balancer unit of claim 8, wherein the aforementioned potential energy-granting element comprises: an elastic member inserted between the aforementioned rod and the aforementioned housing, which imparts potential energy to the rod by applying an elastic force to the rod; or a fluid sealed in the space between the aforementioned rod and the aforementioned housing, which imparts potential energy to the rod by applying pressure to the rod.

10. A machine having a balancer unit as claimed in any one of claims 1 to 9.

11. The machine of claim 10, wherein the machine is a multi-joint robot having an arm as the aforementioned rotating element, the aforementioned balancer unit is provided with potential energy by the aforementioned potential energy imparting mechanism to the aforementioned arm, thereby imparting the aforementioned torque in the opposite direction to the gravitational torque acting on the arm due to gravity, so as to make the arm balanced relative to the aforementioned gravity.

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