JP2015042425A - Electric gripper device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend a stroke range of a holding member by a simple structure without an increase in a size.SOLUTION: An electric gripper device includes: a top plate 11 where two internal gears 11La, 11Ra are formed; two circle moving gears 9L, 9R which are rotated by a motor 2 and move in a state to mesh the two internal gears 11La, 11Ra on the top plate 11 while rotating without sliding; and holding members 12L, 12R attached to a position which is a point on a pitch circumference of the internal gear 11La, 11Ra and the circle moving gear 9L, 9R and is a pitch radius of the circle moving gear 9L, 9R. In the holding member 12L, 12R, when the circle moving gear 9L, 9R of a pitch radius rm moves with respect to the internal gear 11La, 11Ra of a pitch circle radius rc based on a hypotrochoid theory, the rc, rm, a distance rd are set in such a manner that the holding member 12L, 12R attached to a fixed point P separated from the center of the circle moving gear 9L, 9R by a distance rd is linearly moved.

Description

  The present invention relates to an electric gripper device driven by a motor for gripping a workpiece and performing positioning, length measurement, and the like in automatic product assembly, component conveyance, inspection processes, and the like.

  2. Description of the Related Art Conventionally, an electric gripper device includes a cam member that rotates forward and backward by a motor and a pair of gripping members that slide linearly along a rail, and the cam followers (drive pins) of the pair of gripping members are cam members. A pair of cam grooves that are slidably fitted to the cam member are formed in a spiral shape on the cam member, and the pair of gripping members slide toward and away from each other along the rail by forward and reverse rotation of the cam member by the motor. It has been proposed (see, for example, Patent Document 1).

  The cam groove of the cam member in this type of electric gripper device is formed in a spiral shape along the Archimedes spiral so that the thrust of the gripping member generated by the rotational torque of the motor is constant at any position.

JP 2009-226506 A

  However, in the electric gripper device disclosed in Patent Document 1, the stroke range of the gripping member when the rotational motion of the cam member by the motor is converted into the linear motion in the cam follower (drive pin) of the gripping member is limited to the radius of the cam member. Therefore, in order to increase the stroke range, the radius of the cam member must be increased. In this case, there is a problem that the entire apparatus is increased in size.

  In addition, the electric gripper device of Patent Document 1 requires a guide for linearly sliding the cam member, cam follower, and gripping member, and thus has a problem that the configuration becomes complicated and large.

  The present invention has been made to solve such a problem, and an object of the present invention is to propose an electric gripper device capable of extending the stroke range of a gripping member while having a simple configuration without increasing the size.

ｒｍ＝ｒｄ＝ｒｃ／２……………………………………………………………………（３）
ｒｄ：定点Ｐと動円歯車の中心との距離
θ：動円歯車の回転角 In order to solve this problem, in the invention of claim 1, the top plate on which two internal gears are formed, and the motor rotates by being rotated by a motor without slipping while meshing with the two internal gears of the top plate. Electric wheel comprising two moving circular gears that move while moving, and a gripping member that is a point on the pitch circumference of the internal gear and the moving circular gear, and that is attached to a position that is the pitch circle radius of the moving circular gear In the gripper device, the gripping member moves based on the hypotrochoidal principle when the moving circular gear having the pitch circle radius rm moves while rotating without slipping with respect to the internal gear having the pitch circle radius rc. Parametric variables x and y of the equation of the locus drawn by the gripping member attached to the fixed point P at the position where the pitch circle radius of the circular gear is located are expressed by the following equations (1) and (2), and the following equation (3) )The filling It is so.

rm = rd = rc / 2 …………………………………………………………………… (3)
rd: distance between the fixed point P and the center of the moving circular gear θ: rotation angle of the moving circular gear

  In the invention of claim 2, the two dynamic gears are fixed to the two reduction gears rotated through the motor shaft of the motor, and the two internal gears are rotated together with the rotation of the two reduction gears. Rotate while rotating without slipping in a meshed state.

  According to the first aspect of the present invention, the locus drawn by the gripping member attached to the fixed point P at the position of the moving circular gear pitch circle radius moves linearly on the x-axis, and as a configuration therefor Since a cam member, a cam follower, and a guide are not used, the stroke range of the gripping member can be lengthened with a simple configuration without increasing the size.

  According to the second aspect of the present invention, the gripping member can be moved linearly with a simple configuration using only gears, such as an internal gear, a dynamic gear, and a reduction gear.

It is a basic diagram with which it uses for description of the principle of a hypotrochoid curve. It is a basic diagram which uses for description of conditions when a locus | trajectory becomes a straight line at the fixed point of a hypotrochoid curve. It is a graph showing the relationship between the rotational angle θ of the moving circle and the parameter x in the hypotrochoid curve. It is a graph showing the relationship between parameters x and y in a hypotrochoid curve. It is a graph which shows the locus | trajectory of the fixed point P of a moving circle. It is sectional drawing which shows the whole structure of the electric gripper apparatus using a hypotrochoid mechanism. It is a basic diagram which shows the structure of a hypotrochoid mechanism. It is a basic diagram which shows the locus | trajectory of the movement of the dynamic circle in a hypotrochoid mechanism.

  Next, an embodiment of the present invention will be described with reference to the drawings.

<Hypotrochoid principle>
First, the principle of hypotrochoid for realizing the linear motion of the gripping member in the electric gripper device of the present invention will be described.

  In general, when a circle rolls without sliding on a straight line, the locus drawn by a fixed point on the circumference is called a “cycloid”, and the hypotrochoid obtained when this fixed point is inside the circle instead of on the circumference. A curve or an epitrochoid curve obtained when it is outside a circle is generically called a “trochoid curve”.

  Specifically, as shown in FIG. 1, the hypotrochoid is an arm extending from the center of the moving circle C1 when the moving circle C1 of radius rm rolls without slipping with respect to the outer circle C0 of radius rc. This is a locus drawn by the (fixed) tip point P (fixed point), and the equation of the locus is represented by parameters x and y of the following equations (1) and (2). Here, rd is the distance between the fixed point P and the center of the moving circle C1, and θ is the rotation angle of the moving circle C1.

  As shown in FIG. 2, when the radius rc of the outer circle C0, the radius rm of the moving circle C1, and the distance rd from the center of the moving circle C1 to the fixed point P satisfy the relationship of the following equation (3), the fixed point P is The parametric variables x and y in the drawn locus equation are expressed by the following equations (4) and (5).

rm = rd = rc / 2 ………………………………………………………………… (3)
x = rc · cos θ …………………………………………………………………… (4)
y = 0 …………………………………………………………………………………… (5)

  That is, when the expression (3) is satisfied, for example, when the relationship of rc = 1, rm = 0.5, and rd = 0.5 is established, the relationship between the rotation angle θ of the moving circle C1 and the parameter x is As shown in FIG. 3, the parameter x changes in the range of “−1.0” to “+1.0”, and the relationship between the parameter x and the parameter y is as shown in FIG. On the x-axis, it changes linearly from “−1.0” to “+1.0”, while on the y-axis, it is fixed at “0”. That is, the fixed point P moves linearly on the x axis.

  Therefore, in the hypotrochoid, the moving circle C1 having the radius rm is inscribed and rolls without slipping with respect to the outer circle C0 having the radius rc (when the moving circle C1 moves while rotating), and the arm extending from the center of the moving circle C1. When the equation ((1) and (2)) of the trajectory drawn by the (fixed) fixed point P satisfies the expression (3), as shown in FIG. Since it moves linearly along the axis, it is attached so that one gripping member of the electric gripper device is positioned at the fixed point P.

<Overall configuration of electric gripper device>
The overall configuration of the electric gripper device to which the gripping member is attached based on the principle described above will be described with reference to FIGS.

  The electric gripper device 1 has a stepping motor (hereinafter referred to as a motor) 2, the motor 2 is attached to a motor base plate 3, and a driving gear is provided at the tip of a motor shaft 2 a of the motor 2. 2b is formed, and two reduction gears 4L and 4R are meshed with the drive gear 2b.

  The two reduction gears 4L and 4R have a larger diameter than the drive gear 2b, and are arranged at symmetrical positions 180 degrees apart from each other in the x-axis direction with the drive gear 2b as the center. The reduction gears 4L and 4R are fixed to the reduction gear shafts 4La and 4Ra, and the reduction gear shafts 4La and 4Ra are rotatably supported by the motor base plate 3 via bearings 5L and 5R. Accordingly, the two reduction gears 4L and 4R rotate through the drive gear 2b together with the rotation of the motor shaft 2a of the motor 2 around the reduction gear shafts 4La and 4Ra as the rotation center.

  On the opposite side of the motor base plate 3 to the motor 2, a top plate 11 formed with internal gears 11 La and 11 Ra meshing with two circular gears 9 L and 9 R of external gear structure is formed at the end of the motor base plate 3. It is fixed. Two reduction gears 4L and 4R are arranged between the motor base plate 3 and the top plate 11. The moving circular gears 9L and 9R are fixed to the outer peripheral surface of the end of the holding member holders 7L and 7R on the speed reduction gears 4L and 4R side.

  The gripping member holders 7L and 7R have holder shafts 7La and 7Ra. The gripping member holders 7L and 7R are rotatably supported by the holder shafts 7La and 7Ra via bearings 8L and 8R. The shafts 7La and 7Ra are fixed integrally with the reduction gears 4L and 4R.

  Here, the gripping member holder is located at the position where the pitch circle radius rc / 2 in the x-axis direction from the center 11Lb, 11Rb of the internal gear 11La, 11Ra of the top plate 11 is the same as the center shaft 4Lb, 4Rb of the reduction gear 4L, 4R. The holder shafts 7La and 7Ra of 7L and 7R are fixed, and the internal gears 11La and 11Ra of the top plate 11 and the moving circular gears 9L and 9R are meshed on the pitch circumference.

  Furthermore, the gripping members 12L and 12R are located with respect to the gripping member holders 7L and 7R at a position away from the centers 7Lb and 7Rb of the holder shafts 7La and 7Ra of the gripping member holders 7L and 7R by the distance rd toward the motor shaft 2a. It is supported so that it can rotate and slide. That is, the gripping members 12L and 12R are supported at the position of the fixed point P separated from the center of the moving circular gears 9L and 9R by the same distance rd as the pitch circle radius rm, and the above-described expression (3) is satisfied. .

  In this case, the internal gears 11La and 11Ra with the pitch circle radius rc in the top plate 11 correspond to the outer circle C0 in the hypotrochoid, the dynamic gears 9L and 9R with the pitch circle radius rm correspond to the dynamic circle C1, and the dynamic gears. Since the position on the pitch circumference away from the centers of 9L and 9R by the distance rd corresponds to the fixed point P of the moving circle C1 and satisfies the relationship of the above-described equation (3), the position of the fixed point P of the moving circle C1 The movement trajectory of the gripping members 12L and 12R attached to is a straight line on the x axis.

<Operation of electric gripper device>
Opening and closing operations for holding or releasing the workpiece by the gripping members 12L and 12R of the electric gripper device 1 having such a configuration will be described with reference to FIGS. 7 and 8, but only the gripping member 12L will be described here for convenience. . The operations of the gripping members 12L and 12R are common except in the opposite directions.

  When the motor shaft 2a of the motor 2 in the electric gripper device 1 is rotated in the clockwise direction in the figure, the reduction gear 4L is rotated in the counterclockwise direction in the figure via the drive gear 2b of the motor shaft 2a. At this time, the rotating circular gear 9L integrated with the reduction gear 4L rotates in the clockwise direction in the figure without slipping in a state of meshing with the internal gear 11La of the top plate 11 as shown in FIG. It is moved in the counterclockwise direction toward the outer side (left side in the figure) in the x-axis direction that is farthest from the axially centered motor shaft 2a.

  At this time, the gripping member 12L attached to the position of the fixed point P of the moving circular gear 9L is similar to the trajectory in which the fixed point P of the moving circular gear 9L moves linearly on the X axis. It moves linearly outward (left side in the figure) in the x-axis direction that is farthest from the center.

  At the same time, the gripping member 12R attached to the position of the fixed point P of the moving circular gear 9R also has a motor shaft 2a of the electric gripper device 1 in the same manner as a locus in which the fixed point P of the moving circular gear 9R moves linearly on the X axis. It moves linearly outward (right side in the figure) in the x-axis direction that is farthest from the center. Thereby, the gripping members 12L and 12R are positioned outward in the x-axis direction farthest from the motor shaft 2a, that is, preparations for gripping the workpiece are completed.

  In this case, the holding member 12L has a stroke range St (FIG. 8) that moves linearly over the diameter of the internal gear 11La of the top plate 11. Therefore, compared with the case where the stroke range of the conventional gripping member is limited to the radius of the cam member, the gripping member 12L moves linearly in the stroke range St that is sufficiently long near the diameter of the internal gear 11La. be able to.

  Thereafter, in a state where the gripping member 12L is moved outward (left side in the drawing) in the x-axis direction farthest from the motor shaft 2a (position where the gripping members 12L and 12R are farthest from each other), the motor of the motor 2 When the shaft 2a is rotated in the counterclockwise direction in the figure, the reduction gear 4L is rotated in the clockwise direction via the drive gear 2b of the motor shaft 2a. At this time, as shown in FIG. 8 as a whole, the moving circular gear 9L integrated with the reduction gear 4L rotates in the counterclockwise direction in the figure without slipping while meshing with the internal gear 11La of the top plate 11. It is moved clockwise toward the motor shaft 2a.

  At this time, the gripping member 12L attached to the position of the fixed point P of the moving circular gear 9L is similar to the trajectory in which the fixed point P of the moving circular gear 9L moves linearly on the X axis. It moves linearly from the outermost part in the x-axis direction toward the motor shaft 2a at the center in the x-axis direction.

  At the same time, the gripping member 12R attached to the position of the fixed point P of the moving circular gear 9R also has a motor shaft 2a of the electric gripper device 1 in the same manner as a locus in which the fixed point P of the moving circular gear 9R moves linearly on the X axis. It moves linearly from the outermost part in the x-axis direction toward the motor shaft 2a at the center in the x-axis direction. As a result, the gripping members 12L and 12R can be positioned in the state closest to the motor shaft 2a.

  As described above, the electric gripper device 1 has a simple and small configuration that does not require a guide or the like for linearly sliding the cam member, the cam follower, and the gripping member as in the related art, but has a longer stroke than the conventional one. The gripping members 12L and 12R can be moved linearly within the range St.

<Other embodiments>
In the embodiment described above, the circular gears 7L and 7R are meshed with the internal gears 11La and 11Rb of the top plate 11 via the reduction gears 4L and 4R meshed with the drive gear 2b of the motor shaft 2a of the motor 2. In the above description, the case of moving while rotating without slipping is described. However, the present invention is not limited to this, and the moving circular gears 7L and 7R are moved by the motor without using the reduction gears 4L and 4R. The gears 7L and 7R may be moved while rotating without slipping in a state where the gears 7L and 7R are engaged with the internal gears 11La and 11Rb of the top plate 11.

  DESCRIPTION OF SYMBOLS 1 ... Electric gripper apparatus, 2 ... Motor, 2a ... Motor shaft, 2b ... Drive gear, 3 ... Motor base plate, 4L, 4R ... Reduction gear, 4La, 4Ra ... Reduction gear shaft, 5L, 5R ... Bearing, 7L, 7R ... Holding member holder, 7La, 7Ra ... Holder shaft, 8L, 8R ... Bearing, 9L, 9R ... Dynamic gear, 11 ... Top plate, 12L, 12R ... Holding member.

Claims (2)

A top plate on which two internal gears are formed;
Two rotating gears that rotate by a motor and rotate while rotating without slipping in a state of meshing with the two internal gears of the top plate;
An electric gripper device comprising: a gripping member attached at a position that is a point on the pitch circumference of the internal gear and the dynamic circular gear and that is a pitch circle radius of the dynamic circular gear;
The gripping member is
Based on the hypotrochoidal principle, the position of the circular gear having the pitch circle radius when the dynamic gear having the pitch circle radius rm moves while rotating without slipping with respect to the internal gear having the pitch circle radius rc. The parameters x and y of the equation of the trajectory drawn by the gripping member attached to the fixed point P are expressed by the following equations (1) and (2) and satisfy the following equation (3): Electric gripper device.

rm = rd = rc / 2 ………………………………………………………………… (3)
rd: distance between the fixed point P and the center of the moving circular gear θ: rotation angle of the moving circular gear The two moving circular gears are fixed to two reduction gears rotated via the motor shaft of the motor, and do not slip in a state of meshing with the two internal gears as the two reduction gears rotate. The electric gripper according to claim 1, wherein the electric gripper rotates while rotating.

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