Robot arm

Abstract

To suppress tangle and breakage of a cable from occurring when expanding and contracting an arm housing, while storing the cable compact.SOLUTION: A robot arm 3 comprises an arm housing 30 that expands and contract in a predetermined longitudinal direction L, a motor 58 that generates driving force for making the arm housing 30 expand and contract, a cable 59 stored in the arm housing 30, and a reel 60, arranged in the arm housing 30, which reels up the cable 59. The reel 60 is driven by driving force of the motor 58 to reel out and reel up the cable 59 in tandem with expansion and contraction of the arm housing 30.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The technology disclosed herein relates to a robot arm. [Background technology]

[0002] For example, Patent Document 1 discloses a robot arm that performs an extending and retracting motion. The robot arm includes an extendable arm housing, a cable housed in the arm housing, and a path extension section for extending the wiring path of the cable. The path extension section has multiple pulleys around which the cable is routed. In this robot arm, the cable itself extends and retracts in response to the extension and retraction of the arm housing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-78160 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a cable is housed inside the arm housing, there is a risk that the cable may become tangled or damaged when the arm housing is extended or retracted. If a mechanism such as a path extension unit is provided as in the robot arm described in Patent Document 1, there is a risk that the robot arm may become large.

[0005] The technology disclosed herein has been made in consideration of these points, and its purpose is to store the cables compactly while preventing the occurrence of tangling and damage to the cables when the arm housing is extended or retracted. [Means for solving the problem]

[0006] The robot arm disclosed herein comprises an arm housing that expands and contracts in a predetermined longitudinal direction, a driver that generates a driving force to expand and contract the arm housing, a cable housed within the arm housing, and a reel that is disposed within the arm housing and winds up the cable, the reel being driven by the driving force of the driver and paying out and winding up the cable in conjunction with the expansion and contraction of the arm housing. Effect of the Invention

[0007] The robot arm can store the cables compactly while preventing the cables from becoming tangled or damaged when the arm housing is extended or retracted. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a robot. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a picking operation. [Diagram 3] FIG. 3 is a perspective view of the robot arm in an extended state. [Figure 4] FIG. 4 is a perspective view of the robot arm in a retracted state. [Diagram 5] FIG. 5 is a perspective view in which a part of the outer wall of the robot arm is cut away. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a front view of the robot arm. [Figure 8] FIG. 8 is an exploded perspective view of the robot arm. [Figure 9] FIG. 9 is a front view for illustrating the connection between the third arm housing and the first pulley holder. [Figure 10] FIG. 10 is a front view for illustrating the connection between the second arm housing and the second pulley holder. [Figure 11] FIG. 11 is a cross-sectional view taken along line XI-XI in FIG. [Figure 12]FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. [Figure 13] FIG. 13 is an enlarged view of the reel portion of FIG. [Figure 14] FIG. 14 is a perspective view of a robot arm according to a modified example. [Figure 15] FIG. 15 is a cross-sectional view taken along line XV-XV in FIG. [Figure 16] FIG. 16 is a cross-sectional view of a robot arm in a contracted state according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An exemplary embodiment will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a robot 1. The robot 1 performs a picking operation. Specifically, the robot 1 picks up a workpiece W from a first container C1 placed on a shelf S, and transfers the workpiece W to a second container C2. The first container C1 is a source container that contains the workpiece W. The second container C2 is a destination container that contains the workpiece W.

[0010] The shelf S has a plurality of shelf boards S1 arranged at intervals in the vertical direction. The first container C1 is placed on the shelf boards S1. On the shelf S, a working space H into which the robot arm 3 can enter is present between the first container C1 and the shelf board S1 located above the first container C1.

[0011] The robot 1 includes a cart 11, an elevator 12 placed on the cart 11, a robot arm 3 attached to the elevator 12, a robot wrist 7 attached to the tip of the robot arm 3, and a hand 8 attached to the robot wrist 7. Hereinafter, the robot wrist 7 will also be referred to simply as "wrist 7".

[0012] The robot 1 moves by traveling on a cart 11. The cart 11 is, for example, an AGV (Automated Guided Vehicle). In this example, the cart 11 carries a second container C2.

[0013] The elevator 12 raises and lowers the robot arm 3 and rotates it. In this example, the elevator 12 has a support 12a. The support 12a has an axis extending in the vertical direction. The axis of the support 12a is also referred to as the lifting axis P. The support 12a is attached to the cart 11 so as to be rotatable around the lifting axis P. The support 12a supports the robot arm 3 so as to be movable along the lifting axis P. The elevator 12 has a linear actuator that moves the robot arm 3 along the lifting axis P, and a rotary actuator that rotates the support 12a around the lifting axis P. That is, the elevator 12 moves the robot arm 3 along the lifting axis P by the linear actuator. The elevator 12 rotates the support 12a, and therefore the robot arm 3, around the lifting axis P by the rotary actuator.

[0014] The robot arm 3 is a linear-acting telescopic arm. The robot arm 3 telescopes in the direction of a predetermined advance / retract axis Q. The robot arm 3 moves the wrist 7 and hand 8 by telescopically extending. Specifically, the robot arm 3 has multiple cylindrical arm housings. The axis of each arm housing coincides with the advance / retract axis Q. The multiple arm housings are nested. The multiple arm housings are capable of moving relative to one another in the direction of the advance / retract axis Q. The robot arm 3 has a linear actuator that moves the multiple arm housings relative to one another. The multiple arm housings move relatively in the direction of the advance / retract axis Q, causing the robot arm 3 to extend and retract in the direction of the advance / retract axis Q.

[0015] The robot arm 3 is supported by the elevator 12 with the advance / retract axis Q intersecting the lift axis P. Specifically, the advance / retract axis Q is perpendicular to the lift axis P. The advance / retract axis Q may be disposed at a skewed position with respect to the lift axis P.

[0016] The wrist 7 moves the hand 8 relative to the robot arm 3. The wrist 7 is attached to the tip of the robot arm 3.

[0017] The hand 8 holds the workpiece W. The form of holding by the hand 8 is arbitrary. For example, holding by the hand 8 may be by gripping or suction. In this example, the hand 8 grips the workpiece W. The hand 8 has a hand body 81 and a plurality of fingers 82 attached to the hand body 81. The hand 8 opens and closes the plurality of fingers 82.

[0018] A picking operation by the robot 1 will be briefly described below. FIG. 2 is a schematic diagram for explaining the movement of the wrist 7 and the hand 8 inside a container during a picking operation. As shown in FIG. 1, the robot 1 moves to a position facing the shelf S by traveling the cart 11. At this time, the elevator 12 moves the robot arm 3 so that the hand 8 is positioned at a predetermined entry start position. The entry start position is a position where the hand 8 faces the working space H between the target first container C1 and the shelf board S1 located above the first container C1.

[0019] Next, the robot 1 extends the robot arm 3, thereby causing the robot arm 3 to enter the workspace H. As a result, the wrist 7 and the hand 8 enter the workspace H. At this time, the hand 8 is positioned above the workpiece W to be picked in the first container C1.

[0020] 2, the robot 1 moves the hand 8 into the first container C1. For example, the robot 1 moves the hand 8 via the wrist 7 in a direction intersecting with the forward / backward axis Q of the robot arm 3, and causes the hand 8 to enter the first container C1. Then, the robot 1 grips the workpiece W to be picked with the fingers 82 of the hand 8.

[0021] When the gripping is completed, the robot 1 moves the hand 8 above the first container C1, i.e., to the working space H. From that state, the robot 1 retracts the robot arm 3 and moves the hand 8 together with the workpiece W back from the working space H.

[0022] Thereafter, the elevator 12 rotates and raises and lowers the robot arm 3 to move the hand 8 above the second container C2. The robot 1 moves the hand 8 into the second container C2. The robot 1 places the workpiece W in the second container C2 by releasing the grip of the workpiece W by the fingers 82 of the hand 8. In this way, the workpiece W to be picked is transferred from the first container C1 to the second container C2.

[0023] Next, the robot arm 3 will be described in detail. Fig. 3 is a perspective view of the robot arm 3 in an extended state. Fig. 4 is a perspective view of the robot arm 3 in a contracted state. Fig. 5 is a perspective view in which a part of the outer wall of the robot arm 3 is cut away. Figs. 3 and 5 depict the robot arm 3 in its most extended state, and Fig. 4 depicts the robot arm 3 in its most contracted state. Hereinafter, the most extended state of the robot arm 3 will be simply referred to as the "longest state", and the most contracted state of the robot arm 3 will be simply referred to as the "shortest state".

[0024] The robot arm 3 is an extendable arm having a telescopic structure. The robot arm 3 changes between a maximum length and a minimum length. The robot arm 3 includes an arm housing 30 that extends and retracts in a predetermined longitudinal direction L, a motor 58 that generates a driving force for extending and retracting the arm housing 30, a cable 59 housed in the arm housing 30, and a reel 60 that is disposed in the arm housing 30 and winds up the cable 59. The motor 58 is an example of a driver. The cable 59 supplies power or transmits and receives signals to at least one of an end effector and a sensor disposed in the robot arm 3. In this example, the cable 59 supplies power to a hand 8 (see FIG. 1) that is an end effector.

[0025] In detail, the arm housing 30 includes a cylindrical third arm housing 33 extending in the longitudinal direction L of the arm housing 30, and a cylindrical second arm housing 32 extending in the longitudinal direction L and accommodated in the third arm housing 33 so as to be movable forward and backward in the longitudinal direction L. The second arm housing 32 holds the reel 60. The second arm housing 32 is an example of a holding arm housing. The third arm housing 33 is an example of a base end arm housing.

[0026] The robot arm 3 further includes an advance / retract actuator (specifically, a linear actuator) that advances and retracts the second arm housing 32. The advance / retract actuator drives the second arm housing 32 by the driving force of a motor 58. The second arm housing 32 advances from the third arm housing 33 in the longitudinal direction L, and retracts into the third arm housing 33 in the longitudinal direction L. As the second arm housing 32 advances from the third arm housing 33, the robot arm 3 extends as a whole. As the second arm housing 32 retracts into the third arm housing 33, the robot arm 3 contracts as a whole.

[0027] In other words, the "longitudinal direction L" is the extension / retraction direction of the robot arm 3 and also the movement direction of the second arm housing 32. In this example, the longitudinal direction L coincides with the direction of the advance / retract axis Q described above. The side in the longitudinal direction L from which the second arm housing 32 advances is simply referred to as the "front side", and the side in the longitudinal direction L from which the second arm housing 32 retreats is simply referred to as the "rear side". In this example, the longitudinal direction L is substantially horizontal. Hereinafter, a direction that is substantially perpendicular to the longitudinal direction L and substantially horizontal is referred to as the "width direction". In addition, movement to the front side in the longitudinal direction L is simply referred to as "advancing", and movement to the rear side in the longitudinal direction L is simply referred to as "retreating".

[0028] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 3. Specifically, FIG. 6 is a cross-sectional view taken along a plane perpendicular to the rotation axis of a first variable speed pulley 63 described later. The forward / backward actuator includes a first pulley holder 41, a pair of first pulleys 45, and a first belt 51. The first pulley holder 41 is disposed in a third arm housing 33. The pair of first pulleys 45 are supported by the first pulley holder 41. The first belt 51 is wound around the pair of first pulleys 45 and is connected to the second arm housing 32 via a second pulley holder 42 described later. A rotational driving force of a motor 58 is applied to one of the first pulleys 45. For example, the motor 58 is a servo motor and disposed in the third arm housing 33. The rotational driving force of the motor 58 is transmitted to one of the first pulleys 45. The rotational driving force of the motor 58 may be transmitted to one of the first pulleys 45 via a belt or a gear train. As one of the first pulleys 45 is driven to rotate, the first belt 51 rotates, and the second arm housing 32 moves forward and backward in conjunction with the first belt 51. In this example, the rotational drive force of the motor 58 is transmitted to the rear first pulley 45. Furthermore, the reel 60 rotates in conjunction with the forward and backward movement of the second arm housing 32, and the cable 59 is unwound and reeled out. For ease of explanation, the motor 58 is depicted in two-dot chain lines in FIG. 6. The same applies to FIGS. 11, 12, 15, and 16, which will be described later.

[0029] In this example, the robot arm 3 further includes a first arm housing 31. The first arm housing 31 is cylindrical and extends in the longitudinal direction L, and is accommodated in the second arm housing 32 so as to be freely movable forward and backward in the longitudinal direction L. The forward and backward actuator advances and retreats the first arm housing 31 in addition to the second arm housing 32. The first arm housing 31 is an example of a distal arm housing. The forward and backward actuator further includes a second pulley holder 42, a pair of second pulleys 46, and a second belt 52. The second pulley holder 42, the second pulley 46, and the second belt 52 are interlocked with the first pulley holder 41, the first pulley 45, and the first belt 51. The first arm housing 31 advances from the second arm housing 32 in the longitudinal direction L, and retreats to the second arm housing 32 in the longitudinal direction L. When the second arm housing 32 advances from the third arm housing 33, the first arm housing 31 advances from the second arm housing 32. This causes the robot arm 3 to extend as a whole. When the second arm housing 32 retracts to the third arm housing 33, the first arm housing 31 retracts to the second arm housing 32. This causes the robot arm 3 to contract as a whole.

[0030] The second pulley holder 42 is disposed in the second arm housing 32. The pair of second pulleys 46 are supported by the second pulley holder 42. The second belt 52 is wound around the pair of second pulleys and is connected to the first arm housing 31. When the second belt 52 rotates, the first arm housing 31 moves forward and backward in conjunction with the second belt 52.

[0031] More specifically, the respective axes of the first arm housing 31, the second arm housing 32, and the third arm housing 33 extend in the longitudinal direction L. The first arm housing 31, the second arm housing 32, and the third arm housing 33 are assembled in a nested manner. The third arm housing 33 has an opening 33b at its rear end. The third arm housing 33 has an opening 33a at its front end. The rear end of the third arm housing 33 is attached to the elevator 2 (see FIG. 1). The second arm housing 32 is accommodated in the third arm housing 33 so as to be able to advance and retreat in the longitudinal direction L via the opening 33a of the third arm housing 33. The second arm housing 32 has an opening 32b at its rear end. The second arm housing 32 has an opening 32a at its front end. The first arm housing 31 is accommodated in the second arm housing 32 so as to be able to advance and retreat in the longitudinal direction L via the opening 32a of the second arm housing 32. The first arm housing 31 has an opening 31b at its rear end and an opening 31a at its front end.

[0032] FIG. 7 is a front view of the robot arm 3. In this example, the front refers to a surface facing the front side. In a cross section perpendicular to the longitudinal direction L, the size of the third arm housing 33 is larger than the size of the second arm housing 32, which is larger than the size of the first arm housing 31. In detail, the cross section perpendicular to the longitudinal direction L of the first arm housing 31 is a closed cross section having a plurality of chamfered first corners 31c. The cross section perpendicular to the longitudinal direction L of the second arm housing 32 is a closed cross section having a plurality of chamfered second corners 32c. The cross section perpendicular to the longitudinal direction L of the third arm housing 33 is a closed cross section having a plurality of chamfered third corners 33c. The second corner 32c of the second arm housing 32 faces the first corner 31c of the first arm housing 31. The third corner 33 c of the third arm housing 33 faces the second corner 32 c of the second arm housing 32 .

[0033] That is, the first arm housing 31, the second arm housing 32, and the third arm housing 33 are each a square tube with chamfered corners. Specifically, the cross-sectional shape of each of the first arm housing 31, the second arm housing 32, and the third arm housing 33 is an octagon. More specifically, the first arm housing 31 includes four first corners 31c and four flat plates 31d. Each two adjacent flat plates 31d are connected by the corresponding first corners 31c. The second arm housing 32 includes four second corners 32c and four flat plates 32d. Each two adjacent flat plates 32d are connected by the corresponding second corners 32c. The third arm housing 33 includes four third corners 33c and four flat plates 33d. Each two adjacent flat plates 33d are connected by the corresponding third corners 33c.

[0034] FIG. 8 is an exploded perspective view of the robot arm 3. For convenience of explanation, the first belt 51, the second belt 52, and the cable 59 are omitted in FIG. 8. The robot arm 3 further includes a first sliding guide 35 arranged inside the third arm housing 33, and a first sliding block 36 arranged on the outer surface of the second arm housing 32. The first sliding guide 35 extends in the longitudinal direction L. The first sliding block 36 slides against the first sliding guide 35 when the second arm housing 32 advances or retreats relative to the third arm housing 33.

[0035] The robot arm 3 further includes a second sliding guide 37 disposed inside the second arm housing 32, and a second sliding block 38 disposed on the outer surface of the first arm housing 31. The second sliding guide 37 extends in the longitudinal direction L. The second sliding block 38 slides relative to the second sliding guide 37 when the first arm housing 31 advances or retreats relative to the second arm housing 32.

[0036] The first sliding block 36 is disposed in a portion of the second arm housing 32 which overlaps with the third arm housing 33 when the second arm housing 32 is in a state where it is maximally extended from the third arm housing 33. The second sliding block 38 is disposed in a portion of the first arm housing 31 which overlaps with the second arm housing 32 when the first arm housing 31 is in a state where it is maximally extended from the second arm housing 32.

[0037] In this example, each of the first sliding block 36 and the second sliding block 38 has a rectangular plate shape in a plan view. Each of the first sliding block 36 and the second sliding block 38 is made of, for example, metal or resin.

[0038] Each of the first sliding guide 35 and the second sliding guide 37 has a rectangular plate shape in a plan view. The first sliding guide 35 and the second sliding guide 37 have a rectangular shape extending in the longitudinal direction L. Each of the first sliding guide 35 and the second sliding guide 37 is made of, for example, metal or resin.

[0039] The first sliding blocks 36 are disposed on the outer surface of the second corners 32c of the second arm housing 32. In this example, the first sliding blocks 36 are disposed at all four second corners 32c. At each second corner 32c, two first sliding blocks 36 are arranged side by side in the longitudinal direction L. That is, the number of first sliding blocks 36 is eight in total.

[0040] The first sliding guide 35 is disposed on the inner surface of the third corner portion 33c of the third arm housing 33. That is, the number of the first sliding guides 35 is four in total. The first sliding guide 35 has a length sufficient to make contact with the first sliding block 36 when the robot arm 3 transitions between the shortest state and the longest state. In this example, the first sliding guide 35 extends over substantially the entire longitudinal direction L of the third arm housing 33.

[0041] The second sliding blocks 38 are disposed on the outer surface of the first corners 31c of the first arm housing 31. In this example, the second sliding blocks 38 are disposed at all four first corners 31c. At each first corner 31c, two second sliding blocks 38 are arranged side by side in the longitudinal direction L. That is, the number of second sliding blocks 38 is eight in total.

[0042] The second sliding guide 37 is disposed on the inner surface of the second corner portion 32c of the second arm housing 32. That is, the number of the second sliding guides 37 is four in total. The second sliding guide 37 has a length sufficient to make contact with the second sliding block 38 when the robot arm 3 transitions between the shortest state and the longest state. In this example, the second sliding guide 37 extends over substantially the entire longitudinal direction L of the second arm housing 32.

[0043] Next, the configurations of the first pulley holder 41, the first pulley 45, and the first belt 51 will be described in detail. In this example, the first belt 51 is a timing belt, and the first pulley 45 is a timing pulley. As shown in Fig. 6, the first pulley holder 41 supports the pair of first pulleys 45 so that the pair of first pulleys 45 are aligned in the longitudinal direction L. The first pulley holder 41 is attached to the third arm housing 33 so that the front first end 41a is a free end.

[0044] Specifically, the first pulley holder 41 extends in the longitudinal direction L as a whole. The first pulley holder 41 has a first end 41a on the front side and a second end 41b on the rear side. The second end 41b is attached to the inner surface of the third arm housing 33. In other words, the first pulley holder 41 is attached to the third arm housing 33 in a cantilevered manner so as to extend in the longitudinal direction L. The free end of the first pulley holder 41, i.e., the first end 41a, is accommodated in the second arm housing 32 through the opening 32b of the second arm housing 32 at least when the second arm housing 32 is in the most retreated state. In other words, the first end 41a enters the second arm housing 32 beyond the opening 32b at least when the second arm housing 32 is in the most retreated state.

[0045] The first pulley holder 41 supports each of the first pulleys 45 rotatably around an axis extending in the width direction. In detail, as shown in FIG. 7, the first pulley holder 41 has a pair of plates 41p attached to the third arm housing 33 in a state of facing each other. The pair of plates 41p supports the pair of first pulleys 45 in a state of sandwiching them. The pair of plates 41p rotatably support each of the first pulleys 45 via a first shaft 47 extending in the width direction. The first pulleys 45 are attached to the first shaft 47 in a non-rotatable manner. In FIG. 7, for convenience of explanation, the first bracket 55, a second bracket 56 described later, and a third bracket 57 described later are drawn with two-dot chain lines, and the first belt 51, the second belt 52, the cable 59, and a variable speed belt 65 described later are each marked with a dot. As shown in Fig. 6, the first pulleys 45 are disposed at the first end 41a and the second end 41b of the first pulley holder 41. In this example, a motor 58 is attached to the first shaft 47 of the first pulley 45 disposed on the rear side, as shown in Fig. 5. This allows the rotational driving force of the motor 58 to be transmitted to the first pulley 45 on the rear side.

[0046] More specifically, as shown in Fig. 9, the first pulley holder 41 is attached to the third arm housing 33 via a first bracket 55. Fig. 9 is a front view showing the attachment of the first bracket 55 to the third corner portions 33c. Specifically, the first bracket 55 extends in the width direction along the lower flat plate 33d of the third arm housing 33, and is attached to the two lower third corner portions 33c. For ease of explanation, Fig. 9 omits illustrations of components other than the third arm housing 33, the first bracket 55, and the first pulley holder 41.

[0047] As shown in FIG. 6, the first belt 51 is an endless belt. The first belt 51 rotates around the pair of first pulleys 45. A portion of the first belt 51 between the pair of first pulleys 45 extends in the longitudinal direction L and moves in the longitudinal direction L when the first belt 51 rotates. Hereinafter, the portion of the first belt 51 between the pair of first pulleys 45 is referred to as a flat portion. This flat portion extends substantially flat and may include some bending. The first belt 51 has a first flat portion 51A and a second flat portion 51B facing each other. The first flat portion 51A is close to the second belt 52, and the second flat portion 51B is close to the lower flat plate 33d (see FIG. 7) of the third arm housing 33. The first flat portion 51A and the second flat portion 51B move in the longitudinal direction L in opposite directions when the first belt 51 rotates. For example, when the first flat portion 51A advances, the second flat portion 51B retreats.

[0048] The second pulley holder 42 is attached to the first flat portion 51A. In more detail, a second end 42b of the second pulley holder 42, which will be described later, is connected to the first flat portion 51A via a connector 43.

[0049] Next, the configurations of the second pulley holder 42, the second pulley 46, and the second belt 52 will be described in detail. In this example, the second belt 52 is a timing belt, and the second pulley 46 is a timing pulley. The second pulley holder 42 supports the pair of second pulleys 46 so that the pair of second pulleys 46 are aligned in the longitudinal direction L. The second pulley holder 42 is disposed in the second arm housing 32. In terms of the vertical position, the second pulley holder 42 is disposed above the first pulley holder 41.

[0050] Specifically, the second pulley holder 42 extends generally in the longitudinal direction L. The second pulley holder 42 has a first end 42a on the front side and a second end 42b on the rear side. The second end 42b is attached to the inner surface of the second arm housing 32 and is attached to the first belt 51 via a connector 43. In other words, the first belt 51 is connected to the second arm housing 32 via the second pulley holder 42.

[0051] In short, the second pulley holder 42 extends in the longitudinal direction L and is attached to the second arm housing 32 in a cantilevered manner such that the front first end 42a is a free end. The first end 42a, which is the free end, is accommodated in the first arm housing 31 through the opening 31b of the first arm housing 31, at least when the first arm housing 31 is in the most retracted state. In other words, the first end 42a extends beyond the opening 31b and into the first arm housing 31, at least when the first arm housing 31 is in the most retracted state.

[0052] The second pulley holder 42 supports each of the second pulleys 46 rotatably around an axis extending in the width direction. In detail, as shown in FIG. 7, the second pulley holder 42 has a pair of plates 42p attached to the second arm housing 32 in a state facing each other in the width direction. The pair of plates 42p supports the pair of second pulleys 46 in a sandwiched state. The pair of plates 42p rotatably support each of the second pulleys 46 via a second shaft 48 extending in the width direction. The second pulleys 46 are attached to the second shaft 48 in a non-rotatable manner. The second pulleys 46 are disposed at the first end 42a and the second end 42b of the second pulley holder 42, as shown in FIG. 6.

[0053] More specifically, as shown in Fig. 10, the second pulley holder 42 is attached to the second arm housing 32 via a second bracket 56. Fig. 10 is a front view showing the attachment of the second bracket 56 to the second corner portions 32c. Specifically, the second bracket 56 extends in the width direction along the upper flat plate 32d of the second arm housing 32, and is attached to the two upper second corner portions 32c. For the sake of convenience, Fig. 10 omits illustrations of components other than the second arm housing 32, the second bracket 56, and the second pulley holder 42.

[0054] As shown in FIG. 6, the second belt 52 is an endless belt. The second belt 52 rotates around the pair of second pulleys 46. The portion of the second belt 52 between the pair of second pulleys 46 extends in the longitudinal direction L and moves in the longitudinal direction L when the second belt 52 rotates. Hereinafter, the portion of the second belt 52 between the pair of second pulleys 46 is referred to as a flat portion. Note that this flat portion extends substantially flat and may include some bending. The second belt 52 has a first flat portion 52A and a second flat portion 52B facing each other. The first flat portion 52A is close to the upper flat plate 32d (see FIG. 7) of the second arm housing 32, and the second flat portion 52B is close to the first belt 51. The first flat portion 52A and the second flat portion 52B move in the longitudinal direction L in opposite directions when the second belt 52 rotates. For example, when the first flat portion 52A advances, the second flat portion 52B retreats.

[0055] The first pulley holder 41 is attached to the second flat portion 52B. Specifically, a first end 41a of the first pulley holder 41 is connected to the second flat portion 52B via a connector 43, as shown in FIG.

[0056] The second belt 52 is connected to the first arm housing 31 inside the first arm housing 31. More specifically, the second belt 52 is connected to the third arm housing 31 via a third bracket 57. The third bracket 57 extends in the width direction along the upper flat plate 31d of the first arm housing 31, and is attached to the two upper first corner portions 31c.

[0057] Next, the extension and retraction operation of the robot arm 3 will be described. Fig. 11 is a cross-sectional view taken along line XI-XI in Fig. 3. Fig. 12 is a cross-sectional view taken along line XII-XII in Fig. 4. Specifically, Figs. 11 and 12 are cross-sectional views taken along a plane perpendicular to the rotation axis of the reel 60.

[0058] First, the operation when the robot arm 3 changes from the shortest state to the longest state will be described. In the robot arm 3 in the shortest state shown in FIG. 12, the rear first pulley 45 is rotated counterclockwise by the motor 58. Accordingly, the first belt 51 rotates counterclockwise around the pair of first pulleys 45. At this time, the first flat portion 51A of the first belt 51 advances, and the second flat portion 51B retreats. As described above, the second arm housing 32 is connected to the first flat portion 51A via the second pulley holder 42 and the like. In the state in which the second arm housing 32 is most retreated, the connection portion of the first belt 51 to the second pulley holder 42 is located at the end of the first flat portion 51A on the retreat side in the forward and backward direction. Therefore, when the first flat portion 51A advances in conjunction with the rotation of the first belt 51, the second pulley holder 42 and the second arm housing 32 also advance. That is, the second arm housing 32 advances relative to the third arm housing 33.

[0059] At this time, the second pulley holder 42 advances integrally with the second arm housing 32. The second pulley 46 and the second belt 52 supported by the second pulley holder 42 also advance toward the third arm housing 33. The first arm housing 31 connected to the second belt 52 also advances toward the third arm housing 33 together with the second arm housing 32. However, the second belt 52 is connected to the first pulley holder 41. The first pulley holder 41 is fixed to the third arm housing 33. In other words, even if the second pulley holder 42 advances, the connection portion of the second belt 52 to the first pulley holder 41 does not move. Therefore, the second belt 52 advances as a whole while rotating so as to follow the advancement of the second pulley holder 42. More specifically, when the second arm housing 32 is in the most retreated state, the connecting portion of the second belt 52 to the first pulley holder 41 is located at the end of the second flat portion 52B on the advancing side in the longitudinal direction L. The connecting portion of the second belt 52 to the first arm housing 31 is located at the end of the first flat portion 52A on the retreating side in the advancing and retreating direction. When the second belt 52 advances as a whole while rotating, the connecting portion of the second belt 52 to the first pulley holder 41 retreats at the second flat portion 52B, and the connecting portion of the second belt 52 to the first arm housing 31 advances at the first flat portion 52A. As a result, the first arm housing 31 advances relative to the second pulley holder 42, i.e., the second arm housing 32.

[0060] In this way, when the second arm housing 32 advances relative to the third arm housing 33, the first arm housing 31 advances relative to the second arm housing 32. As a result, the robot arm 3 changes from the shortest state to the longest state. At this time, the first sliding block 36 slides relative to the first sliding guide 35. The second sliding block 38 slides relative to the second sliding guide 37.

[0061] When the robot arm 3 changes from the maximum length to the minimum length, the opposite operation to that when changing from the minimum length to the maximum length is performed. That is, in the robot arm 3 in the maximum length shown in FIG. 11, the rear first pulley 45 is rotated clockwise, so that the first flat portion 51A of the first belt 51 retracts, the second flat portion 51B of the first belt 51 advances, the first flat portion 52A of the second belt 52 retracts, and the second flat portion 52B of the second belt 52 advances. As a result, when the second arm housing 32 retracts relative to the third arm housing 33, the first arm housing 31 retracts relative to the second arm housing 32. As a result, the robot arm 3 changes from the maximum length to the minimum length. As in the case of changing from the minimum length to the maximum length, the first sliding block 36 slides relative to the first sliding guide 35, and the second sliding block 38 slides relative to the second sliding guide 37.

[0062] Next, the structure for accommodating the cable 59 in the robot arm 3 configured as above will be described in detail. As shown in FIG. 6, the cable 59 extends over the entire longitudinal direction L of the arm housing 30. In the arm housing 30, a part of the cable 59 is wound around a reel 60. A first end of the cable 59 protrudes to the outside from an opening 31a of the first arm housing 31. The first end of the cable 59 is connected to and fixed to the hand 8 (see FIG. 1). A second end of the cable 59 protrudes to the outside from an opening 33b of the third arm housing 33. The second end of the cable 59 is connected to and fixed to another device such as a power supply or a control device. In this example, the cable 59 is a flat cable.

[0063] The cable 59 includes a first portion P1 extending from the reel 60 to the first arm housing 31. The first portion P1 is a portion of the cable 59 pulled out from the reel 60 to the front side. The first portion P1 is an example of a "portion extending from a reel to the tip arm housing". More specifically, the cable 59 further includes a second portion P2 extending from the reel 60 to the third arm housing 33. The second portion P2 is a portion of the cable 59 pulled out from the reel 60 to the rear side. That is, in this example, the cable 59 extends from the reel 60 to both the front and rear sides.

[0064] The reel 60 is driven by the driving force of the motor 58, and reels out and winds up the cable 59 in conjunction with the extension and contraction of the arm housing 30. In detail, as shown in Fig. 7, the reel 60 is rotatably attached to the arm housing 30. In this example, the reel 60 is attached to the second arm housing 32 via the second pulley holder 42. That is, the reel 60 moves in the longitudinal direction L integrally with the second arm housing 32.

[0065] Specifically, the reel 60 includes a winding core 61 and a flange 62. The cable 59 is wound around the winding core 61. The winding core 61 has an overall cylindrical shape. A shaft 60s extending along the axis of the winding core 61 is attached to the winding core 61 in a non-rotatable manner. One end of the shaft 60s of the reel 60 is attached to the plate 42p of the second pulley holder 42 via a connector 44. The reel 60 is disposed adjacent to the second pulley holder 42 in the width direction. The flange 62 has a substantially disk-like shape. The flange 62 is attached to both ends of the winding core 61 in the axial direction so that the axis of the winding core 61 and the axis of the flange 62 approximately coincide with each other. The axis of the winding core 61 is the rotation axis of the reel 60. The direction of the rotation axis of the reel 60 is substantially parallel to the width direction. When viewed in the direction of the rotation axis of reel 60, the periphery of flange 62 is located radially outward of the periphery of winding core 61. This makes it possible to prevent cable 59 from falling off reel 60 when cable 59 is being unwound and wound up.

[0066] FIG. 13 is an enlarged view of the reel 60 portion of FIG. 11. The reel 60 has a groove 60a extending in a plane intersecting the rotation axis of the reel 60, and two openings 60b arranged on an outer peripheral surface 69 of the reel 60, which are both ends of the groove 60a. The outer peripheral surface of the winding core 61 is the outer peripheral surface 69 of the reel 60. The cable 59 is fixed to the reel 60 in the groove 60a, and is pulled out from each of the two openings 60b to one side in the circumferential direction of the reel 60. In FIG. 13, the cable 59 is pulled out from both one opening 60b and the other opening 60b in the counterclockwise direction in the circumferential direction of the reel 60. For convenience of explanation, the groove 60a is shown by a two-dot chain line in FIG. 13.

[0067] Each of the ends of the groove 60a extends while curving toward the outside in the radial direction of the reel 60 and toward one side in the circumferential direction. More specifically, the inside of the reel 60 has a groove 60a that is substantially S-shaped when viewed in the width direction. This "S-shape" also includes an inverted S-shape. Each of the ends of the groove 60a includes a side wall 68 having a predetermined curvature. In the groove 60a, the cable 59 is wound around the side wall 68 and pulled out from the opening 60b. More specifically, the winding core 61 of the reel 60 includes a first cylinder 61a and a second cylinder 61c arranged with the shaft 60s in between, and a first pillar 61b and a second pillar 61d arranged with the shaft 60s in between. The first cylinder 61a, the first pillar 61b, the second cylinder 61c, and the second pillar 61d are arranged in this order in the circumferential direction of the reel 60. The direction of the axis of each of the first cylinder 61a and the second cylinder 61c is substantially parallel to the direction of the axis of the shaft 60s. Each of the first cylinder 61b and the second cylinder 61d extends in the direction of the axis of the shaft 60s. In this example, the size of the first cylinder 61a is the same as the size of the second cylinder 61c. A part of the outer circumferential surface of the first cylinder 61a and a part of the outer circumferential surface of the second cylinder 61c become the side wall 68 described above.

[0068] Here, the radius of the winding core 61 of the reel 60 and the radius of curvature of the side wall 68 will be described. The radius of the winding core 61 is r1, the radius of curvature of the side wall is r2, and the thickness of the cable 59 is t. The cable 59 is repeatedly wound onto the winding core 61 and unwound from the winding core 61. That is, the cable 59 is subjected to dynamic bending. The minimum bending radius of the cable 59 with respect to dynamic bending substantially coincides with the radius of the winding core 61. Therefore, it is preferable that the radius r1 of the winding core 61 satisfies r1≧8×t. This suppresses deterioration of the cable 59 even if the cable 59 is repeatedly bent and deformed.

[0069] On the other hand, the portion of the cable 59 wound around the side wall 68 continues to be wound around the side wall 68 even if the cable 59 is repeatedly wound around and unwound from the winding core 61. That is, this portion of the cable 59 is subjected to continuous, i.e., static bending. The minimum bending radius of the cable 59 with respect to static bending substantially coincides with the radius of curvature of the side wall 68. Therefore, it is preferable that the radius of curvature r2 of the side wall 68 satisfies r2≧4×t. This suppresses deterioration of the cable 59 even if the cable 59 is continuously bent.

[0070] As shown in Fig. 6, the robot arm 3 further includes a transmission T that transmits a driving force to the reel 60. That is, the driving force of the motor 58 is transmitted to the reel 60 via the transmission T. The transmission T has a first variable speed pulley 63, a second variable speed pulley 64, and a variable speed belt 65. The first variable speed pulley 63 and the second variable speed pulley 64 are examples of timing pulleys. The variable speed belt 65 is an example of a timing belt.

[0071] The first variable speed pulley 63 is connected to the second pulley 46. More specifically, as shown in FIG. 7, the second shaft 48 of the rear second pulley 46 extends toward the outside of the plate 42p in the direction of its axis. The first variable speed pulley 63 is attached to a portion of the second shaft 48 that is outside the plate 42p (see FIG. 5). The first variable speed pulley 63 is attached so as not to rotate relative to the second shaft 48. The rotation axis of the first variable speed pulley 63 and the rotation axis of the rear second pulley 46 approximately coincide with each other. The first variable speed pulley 63 rotates integrally with the rear second pulley 46. In this example, the first variable speed pulley 63 is a timing pulley.

[0072] The second variable speed pulley 64 is connected to the reel 60. Specifically, the second variable speed pulley 64 is disposed alongside the reel 60 in the direction of the rotation axis of the reel 60. The second variable speed pulley 64 is attached so as to be unable to rotate with respect to the reel 60. The rotation axis of the second variable speed pulley 64 and the rotation axis of the reel 60 approximately coincide with each other. In this example, the second variable speed pulley 64 is a timing pulley.

[0073] 6, the transmission belt 65 is wound around the first speed-changing pulley 63 and the second speed-changing pulley 64. As a result, the second speed-changing pulley 64 rotates in conjunction with the rotation of the first speed-changing pulley 63. That is, the reel 60 rotates in conjunction with the rotation of the rear second pulley 46 via the first speed-changing pulley 63, the second speed-changing pulley 64, and the transmission belt 65. In this example, the transmission belt 65 is a timing belt.

[0074] Here, the pitch diameter of the second variable speed pulley 64 is different from the pitch diameter of the first variable speed pulley 63. That is, the rotation speed of the reel 60 is different from the rotation speed of the second pulley 46. In this example, the pitch diameter of the second variable speed pulley 64 is larger than the pitch diameter of the first variable speed pulley 63. That is, the rotation speed of the reel 60 is slower than the rotation speed of the second pulley 46. That is, by adjusting the ratio of the pitch diameter of the second variable speed pulley 64 to the pitch diameter of the first variable speed pulley 63, the amount of the cable 59 that is let out and the amount of the cable 59 that is taken up in response to the extension and retraction of the robot arm 3 are adjusted. Furthermore, the ratio of the outer diameter of the winding core 61 of the reel 60 to the pitch diameter of the second pulley 46 also affects the amount of the cable 59 that is let out and the amount of the cable 59 that is taken up in response to the extension and retraction of the robot arm 3.

[0075] Next, the operation of the reel 60 to pay out and take up the cable 59 will be described. The reel 60 pays out or takes up the cable 59 in response to the extension and contraction of the arm housing 30. Specifically, the reel 60 pays out the cable 59 when the first arm housing 31 advances relative to the second arm housing 32, and takes up the cable 59 when the first arm housing 31 retreats relative to the second arm housing 32. More specifically, the reel 60 pays out both the first portion P1 and the second portion P2 of the cable 59 when the second arm housing 32 advances relative to the third arm housing 33 and the first arm housing 31 advances relative to the second arm housing 32. Similarly, the reel 60 takes up both the first portion P1 and the second portion P2 of the cable 59 when the second arm housing 32 retreats relative to the third arm housing 33 and the first arm housing 31 retreats relative to the second arm housing 32.

[0076] The operation when the cable 59 is unwound from the reel 60 will be described in detail. As described above, when the robot arm 3 changes from the shortest state to the longest state, the second arm housing 32 advances relative to the third arm housing 33, and the first arm housing 31 advances relative to the second arm housing 32. As shown in Figs. 6, 11 and 12, the second belt 52 advances overall while rotating counterclockwise in response to the advancement of the first arm housing 31 and the second arm housing 32. At this time, the reel 60 also advances integrally with the second arm housing 32. In conjunction with the rotation of the second belt, each of the pair of second pulleys 46 rotates counterclockwise. The first variable speed pulley 63 also rotates counterclockwise integrally with the rear second pulley 46. The first variable speed pulley 63 rotates the second variable speed pulley 64 counterclockwise via the variable speed belt 65. The reel 60 also rotates counterclockwise integrally with the second variable speed pulley 64. Due to the counterclockwise rotation of the reel 60, the first portion P1 of the cable 59 is unwound from the reel 60 toward the first arm housing 31. At this time, the first arm housing 31 advances relative to the second arm housing 32, so the first portion P1 of the cable 59 is unwound corresponding to the advancement of the first arm housing 31. Furthermore, due to the counterclockwise rotation of the reel 60, the second portion P2 of the cable 59 is unwound from the reel 60 toward the third arm housing 33. At this time, the second arm housing 32 advances relative to the third arm housing 33, so the second portion P2 of the cable 59 is unwound corresponding to the advancement of the second arm housing 32. That is, in this example, both the first portion P1 and the second portion P2 of the cable 59 are unwound from the reel 60.

[0077] When the cable 59 is wound around the reel 60, the opposite operation to the operation when the cable 59 is unwound from the reel 60 is performed. That is, as described above, when the robot arm 3 changes from the maximum length state to the minimum length state, the second arm housing 32 retracts relative to the third arm housing 33, and the first arm housing 31 retracts relative to the second arm housing 32. In response to the retraction of the first arm housing 31 and the second arm housing 32, the second belt 52 rotates clockwise and retracts as a whole. At this time, the reel 60 also retracts integrally with the second arm housing 32. In conjunction with the rotation of the second belt, each of the pair of second pulleys 46 rotates clockwise. The first variable speed pulley 63 also rotates clockwise integrally with the rear second pulley 46. The first variable speed pulley 63 rotates the second variable speed pulley 64 clockwise via the variable speed belt 65. The reel 60 also rotates clockwise integrally with the second variable speed pulley 64. Due to the clockwise rotation of the reel 60, the first portion P1 of the cable 59 is wound onto the reel 60. At this time, since the first arm housing 31 retracts relative to the second arm housing 31, the first portion P1 of the cable 59 is wound up corresponding to the retraction of the first arm housing 31. Furthermore, due to the clockwise rotation of the reel 60, the second portion P2 of the cable 59 is wound onto the reel 60. At this time, since the second arm housing 32 retracts relative to the third arm housing 33, the second portion P2 of the cable 59 is wound up corresponding to the retraction of the second arm housing 32. That is, in this example, both the first portion P1 and the second portion P2 of the cable 59 are wound onto the reel 60.

[0078] In such an operation of unwinding and winding the cable 59, a part of the driving force of the motor 58 is transmitted to the reel 60 via the transmission device T. That is, the driving force of the motor 58 is used for extending and retracting the arm housing 30, and is also used for unwinding or winding the cable 59.

[0079] Next, the relationship between the amount of cable 59 let out and taken up by the reel 60 and the stroke amount of the arm housing 30 will be described. The amount of cable 59 let out and taken up by the reel 60 corresponds to a stroke amount, which is the amount of movement of the first arm housing 31 relative to the second arm housing 32 in the longitudinal direction L when advancing or retreating. In this example, the stroke amount of the first arm housing 31 relative to the second arm housing 32 is greater by a predetermined amount than the amount of cable 59 let out and taken up by the reel 60. Note that the correspondence relationship between the amount of cable 59 let out and taken up by the reel 60 and the stroke amount of the arm housing 30 described in this specification is established at least when the robot arm 3 changes from the shortest state to the longest state and when the robot arm 3 changes from the longest state to the shortest state.

[0080] 6, in a first portion P1 of the cable 59, the amount of cable 59 let out and taken up by the reel 60 corresponds to a first stroke amount L1 which is the amount of movement of the first arm housing 31 relative to the second arm housing 32 in the longitudinal direction L when advancing or retreating. In this example, in the first portion P1, the first stroke amount L1 of the first arm housing 31 relative to the second arm housing 32 is larger by a predetermined amount than the amount of cable 59 let out and taken up by the reel 60.

[0081] In the second portion P2 of the cable 59, the amount of cable 59 let out and taken up by the reel 60 corresponds to a second stroke amount L2, which is the amount of movement of the second arm housing 32 relative to the third arm housing 33 in the longitudinal direction L when advancing or retreating. In this example, in the second portion P2, the second stroke amount L2 of the second arm housing 32 relative to the third arm housing 33 is larger by a predetermined amount than the amount of cable 59 let out and taken up by the reel 60.

[0082] Here, the pitch diameters of the first speed-changing pulley 63 and the second speed-changing pulley 64 will be described. As shown in FIG. 6, the pitch diameter of the first speed-changing pulley 63 is d3, the pitch diameter of the second speed-changing pulley 64 is d4, and the pitch diameter of the second pulley 46 is d5. As shown in FIG. 11, the diameter of the winding core 61 of the reel 60 is d1. In the following, for the sake of simplicity, the first stroke amount L1 and the second stroke amount L2 are set to the same value L (i.e., L1=L2=L). That is, the second arm housing 32 and the first arm housing 31 advance or retreat with respect to the third arm housing 33 at a stroke amount of 2L. Also, the amount of the cable 59 that is unwound and wound from the reel 60 is set to be equal to the stroke amount 2L. The reel 60 winds up the maximum stroke amount of 2L when the arm housing 30 is fully contracted. The reel 60 can take up the maximum stroke amount of 2L by rotating Nr (=L / (d1×π)). When the arm housing 30 contracts at the maximum stroke amount of 2L, the second pulley 46 rotates Np (=L / (d5×π)). The pitch diameter d3 and the pitch diameter d4 may be determined so as to satisfy Np / Nr=d1 / d5=d4 / d3.

[0083] In the robot arm 3 configured as described above, the second portion P2 of the cable 59 is unwound from or wound around the reel 60 in response to the advancement and retreat of the second arm housing 32 relative to the third arm housing 33. The first portion P1 of the cable 59 is unwound from or wound around the reel 60 in response to the advancement and retreat of the first arm housing 31 relative to the second arm housing 32. That is, the cable 59 is unwound from or wound around the reel 60 in response to the extension and contraction of the arm housing 30. This can prevent the cable 59 from becoming tangled when the arm housing 30 contracts, or from being damaged due to excessive tension or the like being applied to the cable 59 when the arm housing 30 expands. Furthermore, the reel 60 rotates by using a part of the driving force of the motor 58. That is, in the robot arm 3, it is not necessary to separately prepare a driver for rotating the reel 60. This can prevent the arm housing 30 from becoming large even when the reel 60 is disposed inside the arm housing 30. As a result, the cable 59 can be accommodated compactly within the arm housing 30.

[0084] In this example, the reel 60 is held in the second arm housing 32, and the second arm housing 32 advances or retreats relative to the third arm housing 33. That is, the reel 60 moves integrally with the second arm housing 32 in the longitudinal direction L. In the robot arm 3, in addition to the first portion P1, the second portion P2 is also unwound from or wound onto the reel 60 in response to the advancement or retreat of the second arm housing 32. Therefore, even when the reel 60 moves in the longitudinal direction L, tangling and damage to the cable 59 can be suppressed.

[0085] Moreover, the transmission T has a first variable speed pulley 63, a second variable speed pulley 64, and a variable speed belt 65. Each of the first variable speed pulley 63 and the second variable speed pulley 64 is a timing pulley, and the variable speed belt 65 is a timing belt. Therefore, a part of the driving force of the motor 58 can be efficiently transmitted to the reel 60. Also, the stroke amount of the arm housing 30 and the payout amount and winding amount of the cable 59 can be synchronized.

[0086] 13, both ends of groove 60a are curved, so that the load on the portion of cable 59 that is pulled out from opening 60b is reduced. In particular, by satisfying r1≧8×t and r2≧4×t as described above, excessive bending does not occur in cable 59 when it is being paid out and taken up. As a result, deterioration of cable 59 is suppressed.

[0087] Furthermore, in the robot arm 3, in the first portion P1 of the cable 59, the amount of the cable 59 let out and taken up by the reel 60 corresponds to the first stroke amount L1. As a result, the length of the first portion P1 is appropriately adjusted in accordance with the advancement and retreat of the first arm housing 31 relative to the second arm housing 32, so that tangling and damage of the first portion P1 can be effectively suppressed. Similarly, in the second portion P2 of the cable 59, the amount of the cable 59 let out and taken up by the reel 60 corresponds to the second stroke amount L2. As a result, the length of the second portion P2 is appropriately adjusted in accordance with the advancement and retreat of the second arm housing 32 relative to the third arm housing 33, so that tangling and damage of the second portion P2 can be effectively suppressed.

[0088] Next, a robot arm 300 according to a modified example will be described. The robot arm 300 differs mainly from the robot arm 3 in the number of arm housings and pulley holders. The following description will focus on the differences from the robot arm 3.

[0089] Fig. 14 is a perspective view of the robot arm 300. Fig. 14 shows the robot arm 300 in its maximum length. Fig. 15 is a cross-sectional view taken along line XV-XV in Fig. 14. Specifically, Fig. 15 is a cross-sectional view taken along a plane perpendicular to the rotation axis of a first variable speed pulley 363, which will be described later.

[0090] The robot arm 300 includes an arm housing 330, a pair of first pulleys 345 arranged in the arm housing 330, a first pulley holder 341 that supports the pair of first pulleys 345, a first belt 351 that is wound around the pair of first pulleys 345, and a reel 360 that winds up a cable 359. The arm housing 330 includes a first arm housing 331 and a second arm housing 332. That is, in this example, the robot arm 300 has two arm housings and one pulley holder.

[0091] The second arm housing 332 holds the reel 360 and incorporates the first arm housing 331 so as to be movable forward and backward in the longitudinal direction L. The first arm housing 331 is an example of a tip arm housing. The second arm housing 332 is an example of a holding arm housing. The configurations of the first arm housing 331, the second arm housing 332, the first pulley holder 341, the pair of first pulleys 345, and the first belt 351 are generally the same as the configurations of the first arm housing 31, the third arm housing 33, the first pulley holder 41, the pair of first pulleys 45, and the first belt 51 of the robot arm 3, respectively. Therefore, detailed explanations of each of these configurations will be omitted.

[0092] The first belt 351 is connected to the first arm housing 331 inside the first arm housing 331. More specifically, a first flat portion 351A of the first belt 351 is connected to the first arm housing 331 via a third bracket 357. The manner in which the first belt 351 is connected to the first arm housing 331 is generally the same as the manner in which the second belt 52 is connected to the first arm housing 31 in the robot arm 3, and therefore a detailed description thereof will be omitted.

[0093] The reel 360 is rotatably attached to the first pulley holder 341. The reel 360 winds the cable 359. In this example, the cable 359 is not continuous within the reel 360. Specifically, the portion of the cable 359 wound around the reel 60 and the second portion P2 are electrically connected so that the second portion P2 of the cable 359 is not unwound or reeled out from the reel 360 even when the reel 360 rotates. For example, the portion of the cable 359 wound around the reel 60 and the second portion P2 are connected via an electrical contact.

[0094] The rotational driving force of the motor 58 is transmitted to a first pulley 345 on the rear side. The robot arm 300 further includes a transmission T. The transmission T has a first variable speed pulley 363, a second variable speed pulley 364, and a variable speed belt 365. The first variable speed pulley 363 and the second variable speed pulley 364 are examples of timing pulleys. The variable speed belt 365 is an example of a timing belt.

[0095] The first variable speed pulley 363 is connected to the first pulley 345. More specifically, the first shaft 347 of the rear first pulley 345 extends toward the outside of the first pulley 345 in the direction of its axis. The first variable speed pulley 363 is attached to a portion of the first shaft 347 that is outside the first pulley 345. The first variable speed pulley 363 is attached to the first shaft 347 so as not to rotate. The rotation axis of the first variable speed pulley 363 and the rotation axis of the rear first pulley 345 approximately coincide with each other. The first variable speed pulley 363 rotates integrally with the rear first pulley 345. In this example, the first variable speed pulley 363 is a timing pulley.

[0096] The second variable speed pulley 364 is connected to the reel 360. Specifically, the second variable speed pulley 364 is attached to a flange 362 of the reel 360. The second variable speed pulley 364 is attached so as to be non-rotatable with respect to the reel 360. The rotation axis of the second variable speed pulley 364 and the rotation axis of the reel 360 approximately coincide with each other. In this example, the second variable speed pulley 364 is a timing pulley.

[0097] The transmission belt 365 is wound around the first variable speed pulley 363 and the second variable speed pulley 364. As a result, the second variable speed pulley 364 rotates in conjunction with the rotation of the first variable speed pulley 363. That is, the reel 360 rotates in conjunction with the rotation of the rear first pulley 345 via the first variable speed pulley 363, the second variable speed pulley 364, and the transmission belt 365. That is, a part of the driving force of the motor 58 is transmitted to the reel 360 via the transmission T. In this example, the transmission belt 365 is a timing belt.

[0098] Next, a description will be given of the operation of the robot arm 300. Fig. 16 is a cross-sectional view of the robot arm 300 in the shortest state. Specifically, Fig. 16 is a cross-sectional view in a plane perpendicular to the rotation axis of the first variable speed pulley 363.

[0099] First, an operation will be described when the robot arm 300 changes from the shortest state to the longest state and the cable 359 is unwound from the reel 360. In the robot arm 300 in the shortest state shown in FIG. 16, the rear first pulley 345 is rotated counterclockwise by the motor 58. Accordingly, the first belt 351 rotates counterclockwise around the pair of first pulleys 345. At this time, the first flat portion 351A of the first belt 351 advances and the second flat portion 351B retreats. As described above, the first arm housing 331 is connected to the first flat portion 351A via the third bracket 357. When the first arm housing 331 is in the most retreated state, the connection portion of the first belt 351 to the first arm housing 331 is located at the rear end of the first flat portion 351A in the forward and backward direction. Therefore, when the first flat portion 351A advances in conjunction with the rotation of the first belt 351, the first arm housing 331 also advances.

[0100] Furthermore, the first variable speed pulley 363 also rotates counterclockwise integrally with the rear first pulley 345. The first variable speed pulley 363 rotates the second variable speed pulley 364 and the reel 360 to which the second variable speed pulley 364 is attached counterclockwise via the variable speed belt 365. Due to the counterclockwise rotation of the reel 360, the first portion P1 of the cable 359 is unwound from the reel 360 in response to the advancement of the first arm housing 331 relative to the second arm housing 332. On the other hand, in this example, the second portion P2 of the cable 359 is not unwound from the reel 360. In this way, the robot arm 300 changes from the shortest state to the longest state, and the cable 359 is unwound from the reel 360.

[0101] When the robot arm 300 changes from the maximum length state to the minimum length state and the cable 359 is wound around the reel 360, the opposite operation to the operation when the robot arm 300 changes from the minimum length state to the maximum length state and the cable 359 is unwound from the reel 360 is performed. That is, in the robot arm 300 in the maximum length state shown in FIG. 15, the rear first pulley 345 is rotated clockwise by the motor 58, so that the first flat portion 351A of the first belt 351 retreats and the second flat portion 351B advances. In conjunction with the retreat of the first flat portion 351A, the first arm housing 331 also retreats. Furthermore, in conjunction with the rotation of the rear first pulley 345, the reel 360 rotates clockwise via the first variable speed pulley 363, the variable speed belt 365, and the second variable speed pulley 364. As a result, the first portion P1 of the cable 359 is wound around the reel 60 in response to the retreat of the first arm housing 331. On the other hand, the second portion P2 of the cable 359 is not wound onto the reel 360. As a result, the robot arm 300 changes from the maximum length state to the minimum length state, and the cable 59 is wound onto the reel 60.

[0102] In such an operation of the robot arm 300, the first pulley 345 rotates by the driving force of the motor 58, and the first belt 351 is rotationally driven in conjunction with this rotation. This causes the arm housing 330 to extend and retract. Furthermore, the reel 360 rotates in conjunction with the rotation of the rear first pulley 345. This causes the cable 359 to be unwound from or wound onto the reel 360. That is, the driving force of the motor 58 is used to unwound and retract the arm housing 330, and is also used to unwound and wind the cable 359. In this way, the reel 360 rotates by using a part of the driving force of the motor 58.

[0103] In the robot arm 300 configured as described above, the first portion P1 of the cable 359 is unwound from the reel 360 or wound around the reel 60 in response to the advancement and retreat of the first arm housing 331 relative to the second arm housing 332. That is, the cable 359 is unwound from the reel 360 or wound around the reel 60 in response to the extension and contraction of the arm housing 330. This can prevent the cable 359 from becoming tangled when the arm housing 330 contracts, or from being damaged due to excessive tension or the like being applied to the cable 359 when the arm housing 330 extends. Furthermore, the reel 360 that winds up the cable 359 rotates by using a part of the driving force of the motor 58. That is, in the robot arm 300, it is not necessary to separately prepare a driver that rotates the reel 360. This can prevent the arm housing 330 from becoming large even when the reel 360 is disposed inside the arm housing 330. As a result, the cable 359 can be accommodated compactly within the arm housing 330.

[0104] In this example, the reel 360 is held by the second arm housing 332. The second arm housing 332 does not move in the longitudinal direction L when the arm housing 330 is extended or retracted. That is, unlike the robot arm 3, the reel 360 does not move in the longitudinal direction L. In the robot arm 300, the first portion P1 is unwound from or wound onto the reel 360 in response to the advancement or retreat of the first arm housing 331, and the second portion P2 is not unwound from or wound onto the reel 360. Therefore, even when the reel 360 does not move in the longitudinal direction L, tangling and damage of the cable 359 can be effectively suppressed.

[0105] Other Embodiments As described above, the above embodiment has been described as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this, and can be applied to embodiments in which modifications, replacements, additions, omissions, etc. are appropriately performed. In addition, it is also possible to combine the components described in the above embodiment to form a new embodiment. In addition, among the components described in the attached drawings and detailed description, not only components essential for solving the problem but also components that are not essential for solving the problem in order to exemplify the technology may be included. Therefore, the fact that these non-essential components are described in the attached drawings and detailed description should not immediately be taken to mean that these non-essential components are essential.

[0106] For example, if the reel 60 is driven by the driving force of the motor 58 and reels out and winds the cable 59 in conjunction with the extension and contraction of the arm housing 30, the advance / retract actuator is not limited to the configuration shown in FIG. 6 and the like.

[0107] In the above example, the arm housing 30 includes the first arm housing 31, the second arm housing 32, and the third arm housing 33, but the number of arm housings is not limited.

[0108] There are no limitations on the cross-sectional shape of each of the first arm housing 31, the second arm housing 32, and the third arm housing 33. For example, the cross-sectional shape may be a simple rectangle with no chamfered corners.

[0109] The robot arm 3 does not necessarily have to have the first sliding guide 35, the first sliding block 36, the second sliding guide 37 and the second sliding block 38.

[0110] The actuator is not limited to the motor 58. For example, the actuator may be an air cylinder. When the actuator is an air cylinder, the air cylinder may be attached to the inner surface of the third arm housing 33 so that the direction in which the air cylinder expands and contracts is approximately parallel to the longitudinal direction L. The tip of the air cylinder may be connected to the rear end of the second arm housing 32. In this way, the second arm housing 32 and the first arm housing 31 may advance and retreat in response to the expansion and contraction of the air cylinder.

[0111] The cable 59 is not limited to a flat cable. For example, the cable 59 may be a linear cable. In this case, the thickness t of the cable 59 used in calculating the radius of the winding core 61 and the like described above may be the diameter of the cable 59.

[0112] The mounting position of the reel 60 relative to the arm housing 30 is not limited. For example, in the robot arm 3, the reel 60 may be held by the third arm housing 33. That is, the reel 60 may be attached to the first pulley holder 41. In this case, the reel 60 does not move in the longitudinal direction L when the arm housing 30 is extended or contracted. Therefore, the part of the cable 59 wound around the reel 60 and the second part P2 may be electrically connected so that the second part P2 of the cable 59 is not unwound from or wound around the reel 60 even when the reel 60 rotates. The first part P1 of the cable 59 is unwound from or wound around the reel 60 according to the advancement and retreat of the second arm housing 32 and the first arm housing 31 relative to the third arm housing 33. On the other hand, the second part P2 of the cable 59 is neither unwound from nor wound around the reel 60.

[0113] In the first portion P1, the first stroke amount L1 may be approximately the same as the amount of cable 59 paid out and taken up by the reel 60. In the second portion P2, the second stroke amount L2 may be approximately the same as the amount of cable 59 paid out and taken up by the reel 60.

[0114] Each of the two ends of the groove 60a of the reel 60 does not have to extend while curving toward one side in the circumferential direction on the radially outer side of the reel 60. For example, the groove 60a may extend in a straight line. The shape of the winding core 61 of the reel 60 is not limited. For example, the first cylindrical body 61a and the first columnar body 61b may be integral with each other. Similarly, the second cylindrical body 61c and the second columnar body 61d may be integral with each other.

[0115] The technology disclosed herein can be summarized as follows.

[0116] [1] The robot arm 3,300 comprises an arm housing 30,330 which extends and retracts in a predetermined longitudinal direction L, a motor 58 (driver) which generates a driving force to extend and retract the arm housing 30,330, a cable 59,359 housed within the arm housing 30,330, and a reel 60,360 which is disposed within the arm housing 30,330 and winds up the cable 59,359. The reel 60,360 is driven by the driving force of the motor 58 and reels out and winds up the cable 59,359 in conjunction with the extension and retraction of the arm housing 30,330.

[0117] According to this configuration, the cable 59, 359 is unwound from or wound around the reel 60, 360 in conjunction with the extension and contraction of the arm housing 30, 330, so that the cable 59 can be prevented from becoming tangled when the arm housing 30 is contracted, and from being damaged when the arm housing 30 is extended. Furthermore, the reel 60, 360 is driven by the driving force of the motor 58 that extends and contracts the arm housing 30, 330. That is, the reel 60, 360 rotates by using a part of the driving force of the motor 58. Therefore, in the robot arm 3, 300, it is not necessary to separately prepare a driver that rotates the reel 60, 360. This makes it possible to prevent the arm housing 30, 330 from becoming large even when the reel 60, 360 is disposed in the arm housing 30, 330. As a result, the cable 59, 359 can be accommodated compactly in the arm housing 30, 330.

[0118] [2] In the robot arm 3,300 described in [1], the arm housing 30,330 has a first arm housing 31,331 (tip arm housing) which is cylindrical and extends in the longitudinal direction L, and a second arm housing 32,332 (holding arm housing) which is cylindrical and extends in the longitudinal direction L, holds the reel 60,360, and incorporates the first arm housing 31,331 so that it can be moved forward and backward in the longitudinal direction L, and the cable 59,359 includes a portion P1 extending from the reel 60,360 to the first arm housing 31,331, and the reel 60,360 pays out the cable 59,359 when the first arm housing 31,331 advances relative to the second arm housing 32,332, and takes up the cable 59,359 when the first arm housing 31,331 retreats relative to the second arm housing 32,332.

[0119] According to this configuration, the cable 59, 359 is unwound from or wound around the reel 60, 360 in response to the movement of the first arm housing 31, 331 forward and backward relative to the second arm housing 32, 332, thereby effectively preventing tangling and damage to the cable 59.

[0120] [3] In the robot arm 3,300 described in [1] or [2], the amount of the cable 59,359 that is paid out and wound by the reel 60,360 corresponds to a stroke amount, which is the amount of movement of the first arm housing 31,331 relative to the second arm housing 32,332 in the longitudinal direction L when advancing or retreating.

[0121] According to this configuration, the amount by which the cables 59, 359 are paid out and taken up is appropriately adjusted according to the amount of stroke, so that tangling and damage to the cables 59, 359 can be effectively prevented.

[0122] [4] The robot arm 3,300 described in any one of [1] to [3] further includes a transmitter T that transmits driving force from the motor 58 to the reel 60,360, the transmitter T having a timing pulley and a timing belt.

[0123] According to this configuration, a part of the driving force of the motor 58 can be efficiently transmitted to the reels 60, 360. Also, the stroke amount of the arm housings 30, 330 and the payout and winding amounts of the cables 59, 359 can be synchronized.

[0124] [5] In the robot arm 3 described in any one of [1] to [4], the arm housing 30 has a first arm housing 31 (tip arm housing) which is cylindrical and extends in the longitudinal direction L, a second arm housing 32 (holding arm housing) which is cylindrical and extends in the longitudinal direction L, holds the reel 60, and incorporates the first arm housing 31 so as to be movable forward and backward in the longitudinal direction L, and a third arm housing 33 (base arm housing) which is cylindrical and extends in the longitudinal direction L, and incorporates the second arm housing 32 so as to be movable forward and backward in the longitudinal direction L, and the cable 59 is connected from the reel 60 to the first arm housing 31. and a second portion P2 extending from the reel 60 to the third arm housing 33, and the reel 60 pays out both the first portion P1 and the second portion P2 of the cable 59 when the second arm housing 32 advances relative to the third arm housing 33 and the first arm housing 31 advances relative to the second arm housing 32, and winds up both the first portion P1 and the second portion P2 of the cable 59 when the second arm housing 32 retracts relative to the third arm housing 33 and the first arm housing 31 retracts relative to the second arm housing 32.

[0125] According to this configuration, the reel 60 is held in the second arm housing 32, and the second arm housing 32 advances or retreats relative to the first arm housing 31. That is, the reel 60 moves in the longitudinal direction L in conjunction with the advancement and retreat of the second arm housing 32. In this configuration, both the first portion P1 and the second portion P2 are unwound from or wound onto the reel 60 in response to the advancement and retreat of the second arm housing 32. Therefore, even when the reel 60 moves in the longitudinal direction L, tangling and damage to the cable 59 can be suppressed.

[0126] [6] In the robot arm 3 described in any one of [1] to [5], in the first portion P1 of the cable 59, the amount of the cable 59 let out and taken up by the reel 60 corresponds to a first stroke amount L1 which is the amount of movement of the first arm housing 31 relative to the second arm housing 32 in the longitudinal direction L when advancing or retreating, and in the second portion P2 of the cable 59, the amount of the cable 59 let out and taken up by the reel 60 corresponds to a second stroke amount L2 which is the amount of movement of the second arm housing 32 relative to the third arm housing 33 in the longitudinal direction L when advancing or retreating.

[0127] According to this configuration, in the first portion P1, the amount of cable 59 paid out and taken up by the reel 60 corresponds to the first stroke amount L1, so tangling and damage in the first portion P1 can be effectively suppressed. Similarly, in the second portion P2, the amount of cable 59 paid out and taken up by the reel 60 corresponds to the second stroke amount L2, so tangling and damage in the second portion P2 can be effectively suppressed.

[0128] [7] In a robot arm according to any one of [1] to [6], the reel 60 has a groove 60a extending in a plane intersecting a rotation axis of the reel 60, and two openings 60b arranged on an outer peripheral surface 69 of the reel 60, which are both ends of the groove 60a, the cable 59 is fixed to the reel 60 in the groove 60a, and is pulled out from each of the two openings 60b to one circumferential side of the reel 60, and each of the both ends of the groove 60a extends radially outside the reel 60 while curving toward the one circumferential side.

[0129] According to this configuration, since both ends of groove 60a are curved, the load on the portion of cable 59 that is pulled out from opening 60b is reduced. [Explanation of symbols]

[0130] 3,300 Robot Arms 30,330 Arm housing 31,331 First arm housing (tip arm housing) 32,332 Second arm housing (retaining arm housing) 33,333 3rd arm housing (base end arm housing) 58 Motor (driver) 59,359 Cable 60,360 reels 60a Groove 60b aperture 69 Outer surface T transmitter L1 First stroke amount L2 Second stroke amount P1 Part 1 P2 2nd part

Claims

1. an arm housing that extends and contracts in a predetermined longitudinal direction; a driver that generates a driving force for extending and retracting the arm housing; A cable housed within the arm housing; a reel disposed within the arm housing for winding up the cable; The reel is driven by the driving force of the driver, and pays out and winds up the cable in conjunction with the extension and contraction of the arm housing.

2. 2. The robot arm of claim 1, the arm housing includes a cylindrical tip arm housing extending in the longitudinal direction, and a holding arm housing also extending in the longitudinal direction, holding the reel, and incorporating the tip arm housing so as to be freely movable forward and backward in the longitudinal direction, the cable includes a portion extending from the reel to the distal arm housing, The reel reels out the cable when the tip arm housing advances relative to the holding arm housing, and reels in the cable when the tip arm housing retreats relative to the holding arm housing.

3. 3. The robot arm of claim 2, A robot arm in which the amount of cable that is paid out and wound up by the reel corresponds to a stroke amount, which is the amount of movement of the tip arm housing relative to the holding arm housing in the longitudinal direction when advancing or retreating.

4. A robot arm according to any one of claims 1 to 3, a transmission unit that transmits a driving force from the driver to the reel, The transmitter is a robot arm having a timing pulley and a timing belt.

5. A robot arm according to any one of claims 1 to 3, the arm housing includes a tip arm housing which is cylindrical and extends in the longitudinal direction, a holding arm housing which is cylindrical and extends in the longitudinal direction, holds the reel, and incorporates the tip arm housing so as to be movable forward and backward in the longitudinal direction, and a base arm housing which is cylindrical and extends in the longitudinal direction, and incorporates the holding arm housing so as to be movable forward and backward in the longitudinal direction, the cable includes a first portion extending from the reel to the distal arm housing and a second portion extending from the reel to the proximal arm housing, The reel reels out both the first and second portions of the cable when the holding arm housing advances relative to the base arm housing and the tip arm housing advances relative to the holding arm housing, and winds up both the first and second portions of the cable when the holding arm housing retracts relative to the base arm housing and the tip arm housing retracts relative to the holding arm housing.

6. 6. The robot arm of claim 5, in the first portion of the cable, an amount of the cable that is let out and an amount of the cable that is taken up by the reel correspond to a first stroke amount that is an amount of movement of the tip arm housing relative to the holding arm housing in the longitudinal direction when the tip arm housing is advanced or retreated, A robot arm in which, in the second portion of the cable, the amount of the cable that is paid out and wound up by the reel corresponds to a second stroke amount, which is the amount of movement of the holding arm housing relative to the base end arm housing in the longitudinal direction when advancing or retreating.

7. A robot arm according to any one of claims 1 to 3, the reel has a groove extending in a plane intersecting a rotation axis of the reel, and two openings disposed on an outer peripheral surface of the reel and serving as both ends of the groove; The cable is fixed to the reel in the groove, and is pulled out from each of the two openings to one side in the circumferential direction of the reel, A robot arm in which each of both ends of the groove extends while curving toward the one side in the circumferential direction on the radially outer side of the reel.

Images