Robot hand

Abstract

To enable gripping force to be adjusted efficiently according to an object to be held by a robot hand.SOLUTION: A robot hand includes: a movable arm 50A which is assembled to a shaft 3 of a motor; an elastic body 70A which has one end fixed to the movable arm and biases the movable arm in a circumferential direction of the shaft; and a ring-shaped component 60 into which the shaft penetrates and which has the other end of the elastic body fixed thereto. A fixing position of the ring-shaped component can be adjusted relative to an exterior part of the motor.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present invention relates to a robot hand. [Background technology]

[0002] The sample holder described in Patent Document 1 comprises a grip, a fixed arm integrally provided with the grip, a movable arm rotatably attached to the grip, a biasing member for biasing the movable arm toward the fixed arm, a fixed arm side holder attached to the fixed arm and holding the peripheral edge of the sample, and a biasing member for biasing the movable arm against the fixed arm side holder. and a movable arm side holding portion for holding the peripheral portion of the sample.

[0003] The object gripping device described in Patent Document 2 comprises a gripping device main body for gripping an object, a plurality of gripping arms rotatably suspended from the gripping device main body, a torsion spring that imparts a gripping force to the gripping arms to grip the object, and a gripping force adjustment mechanism that adjusts the gripping force of the gripping arms applied by the torsion spring.

[0004] The finger mechanism of a robot hand described in Patent Document 3 includes a base side finger link and a tip side finger link which configure the fingers of the robot hand, a finger joint shaft which connects the tip side finger link to the base side finger link so as to be rotatable in the gripping direction and the opening direction of the robot hand, a biasing member which constantly biases the tip side finger link in the gripping direction with a predetermined force, and a motor which rotates the tip side finger link about the finger joint shaft in the gripping direction and the opening direction.

[0005] Patent Document 4 describes a system including a hip joint. The hip joint includes a rotation axis, a first member rotatable about the rotation axis and having a lower body joining position configured to be joined to a lower body link, a second member rotatable about the rotation axis and having an upper body joining position configured to be joined to an upper body link, and a force adjustable mechanism connected to at least one of the first member and the second member and configured to apply an adjustable force to the at least one member to prevent rotation in a rotational direction of the upper body joining position relative to the lower body joining position. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-80792 [Patent Document 2] JP 2006-346247 A [Patent Document 3] International Publication No. 2009 / 107164 [Patent Document 4] Special Publication No. 2018-522747 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the prior art, an object of the present invention is to make it possible to efficiently adjust the gripping force of a robot hand in accordance with an object to be gripped. [Means for solving the problem]

[0008] The robot hand of the present invention comprises a movable arm attached to the shaft of a motor, an elastic body having one end fixed to the movable arm and biasing the movable arm in a circumferential direction of the shaft, and a ring-shaped part through which the shaft passes and to which the other end of the elastic body is fixed, and the fixing position of the ring-shaped part relative to the exterior part of the motor is adjustable. Effect of the Invention

[0009] According to the present invention, it is possible to efficiently adjust the gripping force of the robot hand in accordance with the object to be gripped. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 2 is a perspective view of the robot hand before the fixed arm and the second movable arm are attached. [Figure 1B] FIG. 2 is a perspective view of the robot hand before the fixed arm and the second movable arm are attached. [Figure 2A] FIG. 2 is a perspective view of the robot hand after the fixed arm and the second movable arm are attached. [Figure 2B] FIG. 2 is a perspective view of the robot hand after the fixed arm and the second movable arm are attached. [Figure 3A] FIG. [Figure 3B] FIG. [Figure 4A] FIG. 4 is a perspective view showing how the case is assembled to the motor. [Figure 4B] FIG. 2 is a perspective view showing a state in which a case is assembled to a motor. [Diagram 5] 1A to 1C are explanatory diagrams showing examples of combinations of various motors and cases. [Figure 6A] FIG. 4 is a perspective view of a holding torque adjustment ring. [Figure 6B] FIG. 4 is a perspective view of a holding torque adjustment ring. [Figure 7A] 13 is a perspective view showing how a torsion coil spring is attached to a holding torque adjustment ring. FIG. [Figure 7B] 13 is a perspective view showing a state in which a torsion coil spring is assembled to a holding torque adjustment ring. FIG. [Figure 8A] 13 is a perspective view showing how the holding torque adjustment ring and the torsion spring are assembled to the case. FIG. [Figure 8B]13 is a perspective view showing a state in which a holding torque adjustment ring and a torsion spring are assembled to a case. FIG. [Figure 9A] FIG. 11 is a perspective view showing how the pressing plate is attached to the case. [Figure 9B] FIG. 4 is a perspective view showing a state in which a pressing plate is attached to a case. [Figure 9C] FIG. 4 is a perspective view showing a state in which a pressing plate is attached to a case. [Figure 10A] FIG. 4 is a perspective view showing how a coupling is assembled to a motor shaft. [Figure 10B] FIG. 2 is a perspective view showing a state in which a coupling is assembled to a motor shaft. [Figure 11A] FIG. 11 is a perspective view showing how a first movable arm is assembled to a coupling. [Figure 11B] FIG. 4 is a perspective view showing a state in which a first movable arm is assembled to a coupling. [Figure 12A] FIG. 4 is a perspective view of a first movable arm and a coupling. [Figure 12B] FIG. 11 is a perspective view of a first movable arm and a coupling according to another example. [Figure 13] 4 is an explanatory diagram of an opening angle and a deflection angle α of a torsion coil spring in its natural state. FIG. [Figure 14] 13 is a front view of the robot hand when a torsion coil spring 70A is fitted into a groove A2 of the holding torque adjustment ring and the holding torque adjustment ring is fixed in the center of the adjustment range. FIG. [Figure 15] 13 is a graph showing the relationship between the angle θ of the first movable arm and the deflection angle α of the torsion coil spring when the torsion coil spring 70A is fitted into the groove A2 of the holding torque adjustment ring and the holding torque adjustment ring is fixed in the center of the adjustment range. [Figure 16] 13 is a graph showing the relationship between the angle θ and the holding torque when a torsion coil spring 70A is fitted into a groove A2 of a holding torque adjustment ring and the holding torque adjustment ring is fixed at the center of the adjustment range. [Figure 17A] 13 is a front view showing a state after the fixing position of the holding torque adjustment ring has been changed. FIG. [Figure 17B] 13 is another front view showing the state after the fixing position of the holding torque adjustment ring has been changed. FIG. [Figure 18] 13 is a graph showing the adjustable range when a torsion coil spring 70A is fitted into a groove A2 of a holding torque adjustment ring and the holding torque adjustment ring is rotatable within a range of 120°. [Figure 19A] FIG. 1 is a perspective view of a robot hand capable of adjusting the holding torque in stages. [Figure 19B] FIG. 13 is a perspective view of a pressing plate capable of adjusting the holding torque in stages. [Figure 20] 11 is a graph showing the relationship between the angle θ and the holding torque when the holding torque is adjusted in stages. [Figure 21] 13 is a graph showing the relationship between the angle θ and the holding torque when the fixing position of the leg of a torsion coil spring 70A is changed. [Figure 22A] FIG. 2 is a perspective view of a right-handed torsion coil spring. [Figure 22B] FIG. 2 is a perspective view of a left-handed torsion coil spring. [Diagram 23] 1 is a perspective view of a robot hand that grips a hollow portion of a workpiece from the inside. [Figure 24A] FIG. 2 is a front view of the robot hand (spring 70A, fixed position A1). [Figure 24B] FIG. 1 is a front view of the robot hand (spring 70A, fixed position A2). [Figure 24C] FIG. 13 is a front view of the robot hand (spring 70A, fixed position A3). [Figure 25A] FIG. 13 is a front view of the robot hand (spring 70B, fixed position B1). [Figure 25B] FIG. 13 is a front view of the robot hand (spring 70B, fixed position B2). [Figure 25C] FIG. 13 is a front view of the robot hand (spring 70B, fixed position B3). [Figure 26A] FIG. 13 is a front view of the robot hand (spring 71C, fixed position C1). [Figure 26B] FIG. 13 is a front view of the robot hand (spring 71C, fixed position C2). [Figure 26C] FIG. 13 is a front view of the robot hand (spring 71C, fixed position C3). [Figure 27A] FIG. 13 is a front view of the robot hand (spring 71D, fixed position D1). [Figure 27B] FIG. 13 is a front view of the robot hand (spring 71D, fixed position D2). [Figure 27C] FIG. 13 is a front view of the robot hand (spring 71D, fixed position D3). [Figure 28] 11 is a graph showing adjustable ranges of holding torque for torsion coil springs 70A and 70B having different spring constants. [Figure 29] FIG. 15 is a perspective view showing a modified example of the robot hand shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0012] 1A and 1B show a robot hand 100. The robot hand 100 includes a motor 1, a case 20, a presser plate 30, a coupling 40, a first movable arm 50, a holding torque adjustment ring 60, and screw parts for fixing them in place. The robot hand 100 also includes a torsion coil spring 70, which will be described later.

[0013] The motor 1 has a rectangular parallelepiped exterior. One of the two longitudinal sides of the exterior of the motor 1 is called the front or mounting side (FF in Fig. 4A), and the other is called the rear side. Of the two widthwise sides of the exterior of the motor 1, the widthwise side on the right side from the rear side to the front side is called the right side side (RF in Fig. 4A), and the widthwise side on the left side is called the left side side. The exterior of the motor 1 further has an upper surface (UF in Fig. 4A) and a lower surface that face each other in the height direction. The shaft 3 of the motor 1 protrudes outward from the front side of the exterior of the motor 1 along the longitudinal direction of the exterior.

[0014] The protruding direction of shaft 3 is the positive x-axis direction, the left direction from the positive x-axis direction is the positive y-axis direction, and the direction from the bottom to the top of the exterior of motor 1 is the positive z-axis direction.

[0015] As shown in Figs. 10A, 10B, 11A and 11B, a first movable arm 50 is fixed to the shaft 3 of the motor 1 via a coupling 40. The first movable arm 50 includes a first portion 50A and a second portion 50B, both of which are elongated plate-like bodies, and is generally L-shaped when viewed in the width direction. The first portion 50A is perpendicular to the shaft 3, and the longitudinal direction from the base portion to which the coupling 40 is attached to the tip portion is parallel to the radially outward direction of the shaft 3. The second portion 50B extends in the longitudinal direction from the base portion in contact with the tip portion of the first portion 50A to the tip portion in the opposite direction to the protruding direction of the shaft 3. The second portion 50B is perpendicular to the first portion 50A. When the shaft 3 rotates, the first movable arm 50 rotates accordingly.

[0016] 2A and 2B show a robot hand 200. This robot hand 200 is configured by attaching a fixed arm 80 and a second movable arm 90 for gripping a workpiece to a basic robot hand 100. The fixed arm 80 is a long and thin plate-like body, and the longitudinal direction from the base part attached to the right side part 20B (details will be described later) of the case 20 facing the right side of the exterior part of the motor 1 to the tip part is parallel to the downward direction.

[0017] The second movable arm 90 includes a first portion 90A and a second portion 90B, both of which are elongated plate-like bodies, and is generally V-shaped when viewed in the width direction. The direction of the first portion 90A from the base portion attached to the outer surface of the second portion 50B of the first movable arm 50 toward the tip portion is parallel to the width direction of the second portion 50B. If the first portion 50A of the first movable arm 50 is likened to the hands of a clock, when the first portion 50A is in the approximately 4 o'clock position when viewed from the front (the state shown in FIGS. 2A and 2B), the tip portion of the first portion 90A of the second movable arm 90 is lower than the base portion. When the second portion 90B of the second movable arm 90 is in the 4 o'clock position described above, the direction from the base end portion in contact with the tip portion of the first portion 90A toward the tip portion is the negative z-axis direction.

[0018] Both the fixed arm 80 and the second movable arm 90 are removably fixed by screws so that they can be replaced according to the shape of the workpiece to be gripped.

[0019] 3A, 3B, 4A, and 4B, the case 20 has a plate-shaped front portion 20A in contact with the front surface FF of the motor 1, a plate-shaped right side portion 20B facing the right side surface RF of the motor 1, and a plate-shaped top portion 20C facing the top surface UF of the motor 1. In other words, when viewed along the arrow B, the case 20 has a shape that resembles a substantially rectangular parallelepiped with the front surface, right side surface, and top surface hollowed out so that the motor 1 can be inserted from side B.

[0020] Additionally, the top surface 20C of the case 20 is provided with tapped holes 22 (four locations) and positioning pin holes 24 (round hole and elongated hole) for fixing the robot hand 100 to another device. The right side surface 20B is provided with tapped holes 23 (four locations) and positioning pin holes 25 (round hole and elongated hole) for fixing the fixed arm 80 to the case 20. A spigot hole 21 with a spigot joint formed therein is formed in the center of the front surface 20A.

[0021] Fig. 4A shows how the spigot joint 2 of the motor 1 is inserted into the spigot hole 21 of the case 20 along the arrow B (Fig. 3A). Fig. 4B shows the state in which the case 20 is attached to the motor 1. The shaft 3 protrudes forward through the spigot hole 21.

[0022] FIG. 5 shows an example of a combination of motors 1a, 1b and motors with rotation angle detectors 1c, 1d, which have the same mounting dimensions (width and height dimensions at the front) but different overall lengths (different output torque), and a case 20. In this way, the case 20 and the flange 4, which forms part of the exterior of the motor 1, are separate parts so that the motor incorporated in the robot hand can be easily changed. The exterior of the motor 1 may be composed of the flange 4, end bracket 5, and motor stator, or may be a motor housing. Furthermore, the exterior of the motor 1 is not limited to being rectangular and may be cylindrical, for example. The flange 4 and the case 20 may be integrated together.

[0023] 6A and 6B show the holding torque adjustment ring 60 attached to the front portion 20A of the case 20. The holding torque adjustment ring 60 has a ring-shaped main body and ears 62 provided so as to protrude radially outward from the main body. An axial tapped hole 63 is machined in the center of the ears 62.

[0024] A plurality of grooves (12 locations, designated by symbols A1, A2, A3, B1, B2, B3, C1, C2, C3, D1, D2, and D3 in FIG. 6A) are provided on the rear surface of the main body of the holding torque adjustment ring 60. The holding torque adjustment ring 60 also has axial through holes (12 locations, designated by symbols A1', A2', A3', B1', B2', B3', C1', C2', C3', D1', D2', and D3' in the drawing). The grooves A1 to D3 all extend generally in the radial direction, with their base ends communicating with the inner circumferential surface 64 of the main body and their tip ends communicating with the through holes A1' to D3', respectively. On the back surface of the main body of the holding torque adjustment ring 60, grooves A1, B1, A2, B2, A3, and B3 are located in this order along the counterclockwise direction from a position close to the ear 62. In addition, grooves C1, D1, C2, D2, C3, and D3 are located in this order along the clockwise direction from a position close to the ear 62.

[0025] 7A and 7B respectively show how a right-handed torsion coil spring 70 is inserted into the holding torque adjustment ring 60 and how it is inserted after insertion. Also, FIG. 22A shows only the right-handed torsion coil spring 70. In the torsion coil spring 70, a leg 70a at the start of winding extends in a tangential direction of the coil part, and a leg 70c at the end of winding extends in another tangential direction of the coil part. The tips of both the legs 70a and 70c are bent and extend in the positive direction of the x-axis (the direction in which the shaft 3 protrudes). In the illustrated example, the leg 70a is inserted into the groove A2 and the through hole A2', the coil part having the hollow part 70b is located in the hollow part of the holding torque adjustment ring 60, and the tip of the leg 70c protrudes forward from the hollow part of the holding torque adjustment ring 60.

[0026] 8A and 8B show how the holding torque adjustment ring 60 with the torsion coil spring 70 inserted therein is assembled to the case 20, and the state after assembly. By fitting the spigot joint portion 2 of the motor 1 with the recess 61 (FIG. 6A) on the back surface of the holding torque adjustment ring 60, the holding torque adjustment ring 60 can rotate while maintaining its coaxiality around the spigot portion 2. In addition, the shaft 3 of the motor 1 is passed through the hollow portion 70b of the torsion spring 70.

[0027] A recess 20a is formed in the front surface 20A of the case 20 to accommodate the holding torque adjustment ring 60. In addition, an ear accommodating portion 20b is formed to communicate with the recess 20a, which limits the movable range of the ear 62 to within a range of approximately 120 degrees counterclockwise from the 1 o'clock position on the front surface of the case.

[0028] 9A and 9B show the state in which the holding torque adjustment ring 60 is stored in the recess of the case 20 and then fixed with the pressing plate 30. Since the thickness of the holding torque adjustment ring 60 is slightly smaller than the depth of the recess in the front of the case 20, in FIG. 9C, the ear 62 can rotate coaxially with the shaft 3 of the motor 1, but the range of rotation is limited to a range of about 120 degrees by the ear receiving portion 20b of the case 20.

[0029] A hole through which the shaft 3 passes is formed in the center of the pressing plate 30, and an arc-shaped slit 30a is formed near the hole so as to face the lug receiving portion 20b in the axial direction. The retainer plate 30 is fixed by screws 31 and 32. The three screws 32 are used to fasten the case 20 and the motor 1 together, and the single screw 31 is used to fasten only the case 20. The holding torque adjustment ring 60 can be fixed so as not to rotate by fastening a washer 33 and a screw 34 through a slit 30a of the pressing plate 30 to a screw hole 63 provided in an ear 62 of the holding torque adjustment ring 60. To change the position of the ear 62 of the holding torque adjustment ring 60, the screw 34 is slightly loosened to release the fixation, and the ear 62 of the holding torque adjustment ring 60 is manually moved together with the screw 34 to the desired position, and then the screw 34 is retightened to fix it.

[0030] 10A and 10B respectively show how the coupling 40 is inserted onto the shaft 3 of the motor 1 and fixed with a setscrew 41, and how it appears after fixing. Figures 11A and 11B respectively show how the first movable arm 50 is assembled to the coupling 40, and how it appears after assembly. The first movable arm 50 is joined to the coupling 40 by press-fitting, gluing, crimping, welding, or a combination thereof. 12A, the first portion 50A of the first movable arm 50 has a plurality of holes a-d along the shaft direction provided around the mounting portion of the coupling 40 for passing one leg 70c of the torsion coil spring 70 therethrough. The holes d, c, a, and b are positioned in this order counterclockwise in the shaft direction. In the illustrated example, the one leg 70c of the torsion coil spring 70 passes through the hole a.

[0031] 12B, holes a-d in the shaft direction can be provided on the end face of the coupling 40', and one leg 70c of the torsion spring 70 can be fixed thereto. The coupling 40' can be attached to a first movable arm 50' that does not have a hole for fixing one leg.

[0032] With the above steps, the robot hand 100 as a basic form shown in FIGS. 1A and 1B is completed.

[0033] Next, the operation of the robot hand 200 will be described. The motor 1 that drives the robot hand 200 generates a torque in the first movable arm 50 that is approximately proportional to the set winding current. This torque grips the workpiece (object to be gripped). Alternatively, if the motor 1 is a stepping motor, it is positioned according to the size of the workpiece, and is controlled to grip the workpiece within the maximum excitation static torque.

[0034] When the motor 1 is de-energized due to an emergency stop or power outage while the robot hand 200 is gripping a workpiece, it is desirable to prevent the workpiece from falling. To achieve this, it is possible to combine an electromagnetic brake with the motor 1, or to use a mechanical element with low reverse drive efficiency, such as a worm gear or a sliding screw, or a spring, but in this embodiment, as described above, the lightweight and inexpensive torsion coil spring 70 is used.

[0035] Fig. 13 shows a torsion spring 70 with an opening angle of 135° in its natural state (i.e., a state in which a deflection angle α=0°, which will be described later). One leg 70a of the torsion spring 70 is fixed to the holding torque adjustment ring 60, as shown in Figs. 7A, 7B, 8A, and 8B. The other leg 70c is fixed to the first movable arm 50 or the coupling 40, as shown in Figs. 11A, 11B, 12A, and 12B.

[0036] As described above, the holding torque adjustment ring 60 can be rotated within a range of 120 degrees. In addition, the first movable arm 50 (and the coupling 40) is fastened to the shaft 3 of the motor 1. Therefore, when the shaft 3 rotates in a direction to grip the workpiece (clockwise in FIG. 14 described later), the deflection angle α of the torsion coil spring 70 decreases within a range of positive values. The deflection angle α is the angle of change from the natural state of the opening angle of both legs, and when α>0, a restoring torque acts on the torsion coil spring 70 to return it to its natural state. In this embodiment, this restoring torque is used as a gripping torque for the workpiece when not excited, thereby preventing the workpiece from falling when not excited. The gripping torque of the workpiece when the motor is excited is the total torque of the motor torque and the restoring torque of the torsion coil spring 70.

[0037] 2A and 2B, when a workpiece is grasped by sandwiching it between the second movable arm 90 and the fixed arm 80, a restoring torque of the torsion coil spring 70 is generated in the direction in which the second movable arm 90 closes (the direction in which the second movable arm 90 approaches the fixed arm 80). Even if the motor 1 is in a de-excited state, the restoring torque of the torsion coil spring 70 makes it possible to continue holding the workpiece. For the purpose of saving energy and suppressing heat generation of the motor, the motor may be intentionally de-energized while gripping the workpiece, and the workpiece may be gripped using only the restoring torque of the torsion coil spring. Alternatively, the current value flowing through the motor when gripping the workpiece may be reduced from the rated value, and the ratio of the motor torque and the restoring torque of the torsion coil spring may be changed to grip the workpiece. Furthermore, if motor 1 is a stepping motor with a rotation angle detector, for example, the stepping motor can be de-energized when second movable arm 90 is located near the workpiece or before loss of step-out after contacting the workpiece, and the workpiece can be gripped using only the holding torque of torsion coil spring 70, thereby enabling the workpiece to be gripped stably and also resulting in energy savings.

[0038] The holding torque (restoring torque) Tc of the torsion coil spring 70 is simply expressed by the following formula. Tc = kc × α (1) Here, kc is the spring constant, and α is the deflection angle of the torsion coil spring 70. The spring constant kc of the torsion coil spring 70 is determined by the wire diameter of the spring wire, the inner diameter of the spring, the number of turns, the length of the legs, the material, etc., but if a torsion coil spring with a different spring constant kc can be selected according to the output torque of the motor, as shown in Figure 5, the variations will be expanded. Furthermore, if a right-handed or left-handed torsion coil spring can also be assembled, the direction in which the holding torque Tc is applied to the first movable arm 50 can be changed, which is even more convenient. 6A and 6B, a plurality of grooves and through holes are provided on the back surface of the holding torque adjustment ring 60, so that the grooves and through holes can be appropriately selected according to the torsion coil spring to be used. The details of the selection will be described later.

[0039] As described above, the holding torque adjustment ring 60 is coaxial with the shaft 3 of the motor 1 and is rotatable within a range of 120 degrees. The effect of this will be described. As an example of the torsion coil spring 70, a right-handed torsion coil spring 70A with a wire diameter of φ0.5 mm, an inner diameter of 5 mm, 5 turns, and a spring constant kc=0.112 Nmm / deg is selected. A case in which one leg 70Aa of the torsion coil spring 70A is inserted into the groove A2 and through-hole A2' of the holding torque adjustment ring 60, and the other leg 70Ac of the torsion spring 70A is inserted into the hole a of the first movable arm 50 will be described below.

[0040] In order to explain the effect of holding torque adjustment ring 60, it is first assumed that screw hole 63 in ear 62 of holding torque adjustment ring 60 is fastened and fixed from above presser plate 30 by screw 34 at the center of a rotation range of 120°, as shown in Fig. 14. In other words, it is assumed that one leg 70Aa of torsion spring 70A is in a state where it does not move relative to case 20.

[0041] When the first movable arm 50 is open to grip the workpiece W1, the angle θ between the longitudinal direction of the first portion 50A and the negative direction of the z axis (-z direction) varies depending on the size of the workpiece W1. When the first portion 50A of the first movable arm 50 faces downward (-z direction), θ=0°, and when the first movable arm 50 moves to open from the state of θ=0°, the angle θ is θ>0°.

[0042] The relationship between the angle θ of the first movable arm 50 and the deflection angle α of the torsion coil spring 70A is expressed as shown in Fig. 15. Therefore, from equation (1), the relationship between the angle θ of the first movable arm 50 and the holding torque Tc is expressed as shown in Fig. 16. There is a proportional relationship between the angle θ of the first movable arm 50 and the deflection angle α of the torsion coil spring 70A. For example, when the angle θ = 45°, the holding torque Tc = 7.28 N mm and is fixed. In other words, the holding torque Tc changes linearly with the angle θ of the first movable arm 50.

[0043] Next, as shown in Figs. 17A and 17B, the ears 62 of the holding torque adjustment ring 60 are released from the center of the rotation range, and are allowed to rotate and be fixed freely within a range of 120° in a stepless (or continuous) manner. In other words, the position of the torsion spring 70Aa relative to the case 20 can be changed, and even if the angle θ of the first movable arm 50 is the same, the deflection angle α, i.e., the holding torque Tc, can be changed. At this time, the relationship between the angle θ of the first movable arm 50 and the holding torque Tc is as shown in Fig. 18. For example, the holding torque Tc when the angle θ of the first movable arm 50 is 45° can be adjusted in the range of 0.56 to 14 N mm. In this way, the adjustment range is expanded.

[0044] The holding torque Tc can be adjusted by fastening a washer 33 and a screw 34 from above the holding plate 30 to a screw hole 63 machined in an ear 62 of the holding torque adjustment ring 60 in Fig. 9A to fix the rotation of the holding torque adjustment ring 60. An arc-shaped slit 30a is formed in the holding plate 30, and fine adjustment is possible because it can be adjusted and fixed in a stepless manner. However, when using multiple robot hands while suppressing the variation in the adjustment torque, the labor can be reduced if the adjustment can be made in steps (or discretely) so that all the robot hands can be stably adjusted in the same way.

[0045] The holding plate 35 shown in Figs. 19A and 19B is used instead of the holding plate 30, and has a total of seven circular portions at 20° intervals in the slit portion 35a through which the head of the screw 34 passes (the diameter of which is larger than the slit width), allowing adjustment in stages (seven stages in this embodiment). The screw 34 is directly fastened to the ear portion 62 of the holding torque adjustment ring 60. When changing the holding torque Tc, the screw 34 is loosened until the bottom of the head of the screw 34 slightly protrudes from the holding plate 35, and the holding torque adjustment ring 60 is rotated. Then, the screw 34 is tightened at a position where the head of the screw 34 can pass through the slit portion 35a of the holding plate 35. The holding torque adjustment ring 60 is fixed because the side of the head of the screw 34 hits the side of the slit portion 35a of the holding plate 35 and acts as a stopper.

[0046] 20 shows the relationship of the holding torque Tc to the angle θ of the first movable arm 50 during stepped adjustment. In this example, the holding torque Tc can be set in seven steps at intervals of 2.24 N mm for the angle θ of the first movable arm 50.

[0047] The adjustment range of the holding torque Tc is expanded by adjusting the fixed position of the holding torque adjustment ring 60 within the rotation range of 120° as described above. As shown in Fig. 18, when the angle θ of the first movable arm 50 is 15°, the holding torque Tc is a maximum of 10.64 N mm. When the angle θ of the first movable arm 50 is 75°, the holding torque Tc is a minimum of 3.92 N mm.

[0048] If the size of the workpiece to be gripped is more or less fixed (i.e., if the range of angle θ of first movable arm 50 is more or less fixed), it is convenient to be able to shift the adjustment range of holding torque Tc accordingly. For the grooves and through-holes of holding torque adjustment ring 60 shown in Figures 6A and 6B, the adjustment range of holding torque Tc can be shifted by changing the insertion position of one leg 70Aa of torsion coil spring 70A from groove A2 to groove A1 or groove A3.

[0049] 21 is a graph showing the relationship between the angle θ of the first movable arm 50 and the holding torque Tc when one leg 70Aa of the torsion coil spring 70A is inserted into the groove A3 or the groove A1. The case where the one leg 70Aa is inserted into the groove A3 is shown as region RA3, and the case where the one leg 70Aa is inserted into the groove A1 is shown as region RA1. Region RA13 is a common region between region RA1 and region RA3. When the one leg 70Aa is inserted into the groove A3, the adjustment range of the holding torque Tc can be relatively large when the angle θ of the first movable arm 50 is relatively small. Also, when the leg 70Aa is inserted into the groove A1, the adjustment range of the holding torque Tc can be relatively large when the angle θ of the first movable arm 50 is relatively large, and it is also possible to set the holding torque Tc to a considerably small value.

[0050] <Other embodiments> So far, we have described the case where a holding torque is generated in the direction in which the first movable arm 50 closes. In order to generate a holding torque in the direction in which the first movable arm 50 closes, this can be achieved by incorporating a right-handed torsion coil spring 70 (FIG. 22A) into the holding torque adjustment ring 60. On the other hand, a left-handed torsion coil spring 71 shown in Fig. 22B can also be attached to the holding torque adjustment ring 60. Then, as shown in Fig. 23, the fixed arm 80 is replaced with another fixed arm 81, and the second movable arm 90 is replaced with another second movable arm 91, so that a workpiece W2 having a hollow portion is gripped from the inside. A holding torque in the direction in which the second movable arm 91 moves away from the fixed arm 81 (i.e., in the opening direction) can be generated by the torsion coil spring 71. A right-handed or left-handed torsion coil spring can be used depending on the workpiece so that the deflection angle α of the torsion coil spring is always a positive value.

[0051] 24A to 27C show a further embodiment in which only the torsion coil spring is replaced and other parts are not changed. A total of four types of torsion coil springs are used: two types of right-handed torsion coil springs with different spring constants kc (different dimensions), and two types of left-handed torsion coil springs with similarly different spring constants.

[0052] As shown in Figures 6A and 6B, twelve grooves (A1 to D3) and twelve through holes (A1' to D3') are provided in the holding torque adjustment ring 60. Furthermore, as shown in Figures 12A and 12B, four holes are provided in the first movable arm 50 or the coupling 40'.

[0053] 24A to 24C show the case where a right-handed torsion coil spring 70A with a wire diameter of φ0.5 mm, an inner diameter of 5 mm, 5 turns, and a spring constant kc=0.112 Nmm / deg is used. One leg 70Aa is inserted into one of the grooves A1 to A3 of the holding torque adjustment ring 60. The other leg 70Ac is inserted into the hole a of the first movable arm 50 or the coupling 40'.

[0054] 25A to 25C show the case where a right-handed torsion coil spring 70B with a wire diameter of φ0.6 mm, an inner diameter of 6 mm, 5 turns, and a spring constant kc=0.194 Nmm / deg is used. One leg 70Ba is inserted into one of the grooves B1 to B3 of the holding torque adjustment ring 60. The other leg 70Bc is inserted into the hole b of the first movable arm 50 or the coupling 40'.

[0055] 26A to 26C show the use of a left-handed torsion coil spring 71C having a wire diameter of φ0.5 mm, an inner diameter of 5 mm, 5 turns, and a spring constant kc=0.112 Nmm / deg. One leg 71Ca is inserted into one of the grooves C1 to C3 of the holding torque adjustment ring 60. The other leg 71Cc is inserted into the hole c of the first movable arm 50 or the coupling 40'.

[0056] 27A to 27C show the use of a left-handed torsion coil spring 71D with a wire diameter of φ0.6 mm, an inner diameter of 6 mm, 5 turns, and a spring constant kc=0.194 Nmm / deg. One leg 71Da is inserted into one of the grooves D1 to D3 of the holding torque adjustment ring 60. The other leg 71Dc is inserted into the hole d of the first movable arm 50 or the coupling 40'.

[0057] 24A to 27C, the angle θ of the first movable arm 50 when gripping a workpiece is 45°. For each torsion coil spring, by changing the selection of the groove and through hole of the holding torque adjustment ring 60 to which one leg is fixed, the deflection angle α can be changed, and the holding torque Tc can be varied. This is also as described with reference to FIGS. 6A and 6B and FIG. 21.

[0058] 28, the adjustable range of holding torque Tc when one leg 70Aa of right-handed torsion coil spring 70A is inserted into groove A2 of holding torque adjustment ring 60 is shown as region R70A. Moreover, the adjustable range of holding torque Tc when one leg 70Ba of right-handed torsion coil spring 70B is inserted into groove B2 of holding torque adjustment ring 60 is shown as region R70B. Region R70AB is a common region of regions R70A and R70B. Compared to when torsion coil spring 70A is used, when torsion coil spring 70B is used, holding torque Tc is about 1.8 times higher. In other words, a holding torque that can be used with a high torque motor can be obtained using the same parts except for the torsion coil spring.

[0059] As shown in Figure 5, the motor can be changed if the mounting angle is the same. The same concept can also be applied to a geared motor. In that case, the case 20 can be designed to match the mounting part of the geared motor, and a robot hand with a different reduction ratio, i.e., different gripping force, can be obtained. Also, it is of course possible to combine it with a motor with an electromagnetic brake and a geared motor.

[0060] A modified example of the robot hand shown in Fig. 14 is shown in Fig. 29. The procedure for modification is to first remove the fixed arm 80 and the second movable arm 90 from the robot hand shown in Fig. 14. Next, the mounting position of the case 20 relative to the motor 1 is changed so that the plate-shaped portion 20B and the plate-shaped portion 20C of the case 20 face the upper surface UF and the left side surface of the motor 1, respectively. Next, the fixed arm 80 or 81 is attached to the plate-shaped portion 20C of the case 20, and the second movable arm 90 or 91 is attached to the first movable arm 50. In the illustrated example, the fixed arm 81 and the second movable arm 91 are attached. This makes it possible to change an outer gripping type robot hand (FIG. 14) that grips a workpiece from the outside to an inner gripping type robot hand (FIG. 29) that grips a workpiece from the inside, without needing to replace torsion coil spring 70A with a different torsion coil spring. Furthermore, since the movable arm and the fixed arm are attached by screw fastening, this is easy for both the manufacturer of the robot hand and the user.

[0061] According to the embodiment described above, the following effects can be obtained. (1) The holding torque can be adjusted by rotating the holding torque adjustment ring within a certain angle range (for example, within a range of 120 degrees) relative to the case. The adjustment range of the holding torque can be easily expanded without the need to disassemble and reassemble any major mechanisms. (2) When the range of sizes of workpieces to be gripped is limited (when the angle range of the first movable arm is limited), the adjustment range of the holding torque can be shifted by inserting the legs of the torsion coil spring into one of the multiple grooves provided in the holding torque adjustment ring, without the need to change or add new parts. (3) Even if the motor torque is different, the limit holding torque can be increased by changing only the spring with a different spring constant kc and leaving the other components unchanged. (4) By simply changing the winding direction of the torsion coil spring, a holding torque can be applied to the first movable arm in both the closing and opening directions.

[0062] The above advantages (1) to (3) can be obtained without changing the external dimensions of the robot hand (although when the motor is changed, only the length of the motor changes).

[0063] In addition, when adjusting the holding torque, as many parts as possible can be used in common. Furthermore, because the holding torque adjustment ring is attached to the motor shaft, it is possible to prevent the robot hand from becoming larger due to the addition of a holding torque adjustment function.

[0064] In order to enable the first movable arm to move in the direction opposite to the biasing direction of the torsion coil spring, it is necessary to use a motor capable of generating a torque greater than the restoring torque of the torsion coil spring. When using a motor with a relatively small motor torque, it is necessary to use a torsion coil spring with a relatively small spring constant to match the motor. In some cases, the motor used in a robot hand is changed from one with a relatively small motor torque to one with a relatively large motor torque so that it can grip a relatively heavy workpiece. In this case, if a torsion coil spring that is compatible with a motor with a relatively small motor torque is used without being changed, the restoring torque is relatively small, so there is a possibility that the workpiece will fall when the motor is de-excited. In the above-described embodiment, a torsion coil spring with a spring constant suited to the motor torque can be selected, and the torsion coil spring can be easily replaced when the motor is replaced. Therefore, the torsion coil spring can be used to hold a variety of workpieces.

[0065] Regarding the embodiments described above, the following supplementary notes are disclosed. <Appendix 1> A movable arm attached to the motor shaft; an elastic body having one end fixed to the movable arm and biasing the movable arm in a circumferential direction of the shaft; a ring-shaped part through which the shaft passes and to which the other end of the elastic body is fixed; Equipped with The fixed position of the ring-shaped part relative to the exterior part of the motor is adjustable. Robot hand. <Appendix 2> The robot hand described in Appendix 1, wherein the other end of the elastic body is fixed to one of multiple fixing portions provided on the ring-shaped part. <Appendix 3> 3. The robot hand described in claim 1 or 2, wherein the elastic body is replaceable. <Appendix 4> 3. The robot hand described in claim 1 or 2, wherein one end of the elastic body is fixed to one of a plurality of fixing portions provided on the movable arm. <Appendix 5> 3. The robot hand according to claim 1, further comprising a case attached to an exterior portion of the motor and to which the ring-shaped part is fixed. <Appendix 6> The motor further includes a fixed arm that is detachable from an exterior of the motor. Depending on the mounting position of the fixed arm relative to the exterior part of the motor, the robot hand becomes an outer holding type that holds an object to be held from the outside or an inner holding type that holds an object to be held from the inside. 3. The robot hand according to claim 1 or 2.

[0066] Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and various modifications and changes can be made based on the technical concept of the present invention. [Explanation of symbols]

[0067] 100, 200 Robot Hand 1 Motor 3 Shaft 20 cases 30, 35 Retaining plate 40 Coupling 50 First Movable Arm 60 Holding torque adjustment ring 70, 71 Torsion coil spring 80 Fixed Arm 90 Second movable arm A1~D3 Grooves A1'~D3' through holes a~d Hole of first movable arm or coupling W1, W2 Workpiece (object to be grasped)

Claims

1. A movable arm attached to the motor shaft; an elastic body having one end fixed to the movable arm and biasing the movable arm in a circumferential direction of the shaft; a ring-shaped part through which the shaft passes and to which the other end of the elastic body is fixed; Equipped with The fixed position of the ring-shaped part relative to the exterior part of the motor is adjustable. Robot hand.

2. The robot hand according to claim 1 , wherein the other end of the elastic body is fixed to one of a plurality of fixing portions provided on the ring-shaped part.

3. The robot hand according to claim 1 or 2, wherein the elastic body is replaceable.

4. The robot hand according to claim 1 or 2, wherein one end of the elastic body is fixed to one of a plurality of fixing portions provided on the movable arm.

5. The robot hand according to claim 1 or 2, further comprising a case attached to an exterior of the motor and to which the ring-shaped part is fixed.

6. The motor further includes a fixed arm that is detachable from an exterior of the motor. Depending on the mounting position of the fixed arm relative to the exterior part of the motor, the robot hand becomes an outer holding type that holds an object to be held from the outside or an inner holding type that holds an object to be held from the inside. The robot hand according to claim 1 or 2.

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