JP7384381B2 - electric gripper - Google Patents

Description

The present invention relates to an electric gripper that grips a member such as a workpiece, and particularly to an electric gripper that can detect the position of a gripped member.

Conventionally, the rotation of a motor is transmitted to a threaded shaft having left and right threaded parts, left and right nut parts are screwed into the left and right threaded parts of the threaded shaft, respectively, and a grip part connected to these nut members can be freely moved in a linear direction. There is an electric gripper that is supported by a conventional electric gripper (Patent Document 1). The electric gripper can grip different workpieces at the same axial position by moving a pair of gripping parts closer to each other by rotation of a motor.

Further, similarly to the above, a module for a robot device has been proposed in which gripping portions are slidably supported on the left and right threaded portions of a screw shaft rotated by a motor (Patent Document 2). This module for robot equipment uses a servo motor as a motor, and can stop the left and right gripping parts (jaws) at any position, drive the left and right gripping parts at high speed, and stop the gripping parts just before gripping the workpiece. By slowing down the movement of the workpiece, it becomes possible to grip the workpiece without applying any impact to it.

Further, the robot device module is provided with an encoder for position detection in conjunction with the servo motor for driving, and can detect the position of the gripping part when the gripping part grips a workpiece. .

Japanese Unexamined Patent Publication No. 56-134192 Japanese Patent Application Publication No. 6-114760

In the electric gripper of Patent Document 1, a buffer spring is interposed between the nut portion and the gripping portion, and when the gripping portion grips a workpiece, each of the buffer springs disposed on the left and right nut portions is compressed. , it is possible to reduce the gripping impact, but when the gripping part grips the workpiece, the degree of compression of the buffer springs between the left and right nuts and each gripping part is different, causing the workpiece to be transferred to the machine tool. The accuracy of the supply or removal position is not sufficient.

In addition, the robot device module of Patent Document 2 can reduce the impact on the workpiece by controlling the servo motor, but the setting of the servo motor, especially when working with different sizes or the gripping position and release position, is difficult. If it is not constant, the control operation is troublesome, and it is difficult to use it as a normal electric gripper for feeding or taking out a workpiece to a machine tool.

In addition, since the position detection encoder is directly connected to the servo motor, the encoder can prevent transmission errors between the motor and the grip, such as gear backlash between the motor and the screw shaft, left and right screw Due to the influence of the threaded gap between the gripping part and the nut part, detection cannot be performed with high accuracy, and highly accurate positioning control of the gripping part is difficult.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electric gripper that has a relatively simple configuration, reduces impact load, enables highly accurate gripping of the gripping portion, and thereby solves the above-mentioned problems.

The present invention transmits the rotation of a motor (10) to a screw shaft (12) having a left-hand threaded portion (12a) and a right-handed threaded portion (12b), and is linearly guided by the left-hand threaded portion and right-handed threaded portion. In an electric gripper (1) in which a left nut part (14a) and a right nut part (14b) are screwed together and grip parts (7, 7) are provided on the left nut part and the right nut part, respectively,
The motor (10) and the screw shaft (12) are arranged in parallel in a case (2),
The output shaft (10a) of the motor (10) and the screw shaft (12) are interlocked by a transmission path (D) arranged on one side of the case (2),
Two members (25) and (26) supported in a relatively rotatable manner are arranged adjacent to each other in the transmission path (D), and pin holes (25a) and (26a) are formed in the two members . Connect by inserting the pin (27) into the
The two members include a gear coupling (25) fixed to the output shaft (10a) of the motor (10) and a gear (26) that meshes with the gear (18) provided on the screw shaft. ,
A buffer member (29) is interposed at the connecting portion between the pin (27) and the pin hole (26a) to absorb an impact load (K) larger than the gripping force with which the gripping portion (7, 7) grips the gripped member. It is characterized by doing.

An annular rubber buffer member (29) (29 ₂ ) is fitted into one pin hole (26a) of the pin (27), and the impact load causes the buffer member to connect with the pin (27). It deforms between the pin hole (26a) and absorbs the impact load.

The annular rubber buffer member is an O-ring (29).

A scale (20) is fixed to either the left nut part (14a) or the right nut part (14b), and the scale (20) is placed in a case (2) that houses the motor (10) and screw shaft (12). 20) is arranged.

The motor (10) is arranged above the case (2), the screw shaft (12) is arranged below the case (2),
installing the motor (10) placed above the case (2) so as to sandwich it between the upper case (3);
A rail (16) is arranged below the screw shaft (12) of the case (2), and the left nut part (14a) and the right nut part (14b) are respectively engaged with the rail (16). It is formed by fixing linear guides (17a) (17b) that perform linear motion guidance.

Note that the above reference numerals in parentheses are for contrast with the drawings, but do not affect the description of the claims in any way.

According to the present invention according to claim 1, since a buffer member that absorbs an impact load larger than the gripping force is interposed in the transmission path from the electric motor to the screw shaft, the structure is relatively simple, and the gripping portion is not covered. The shock-absorbing member deforms to absorb an instantaneous impact load that occurs when the gripping member is gripped or when the gripping portion collides with the end member. As a result, the impact load acting on the gripping part is eased, the object to be gripped can be gripped smoothly, and since it absorbs the impact of the rotational transmission force in the transmission path, advanced control of servo motors etc. is not required. By using a normal motor such as a DC motor, the gripping position of the gripping section can be maintained with high precision, and the gripping member can act on the gripped member such as a workpiece and the transmission member such as a gear, without using a complicated and expensive motor. The impact load caused by this is reduced, and the highly accurate gripping part can be maintained for a long period of time.

Furthermore , since two adjacent members are connected by a pin and the buffer member is interposed at the connection between the pin and the pin hole, the buffer member can be arranged compactly and the electric gripper can be made smaller. .
Furthermore, since the motor and the screw shaft are arranged in parallel, and the motor output shaft and the screw shaft are interlocked through the transmission path, the overall structure is compact and approximately rectangular, and the two members with the above-mentioned buffer member interposed therebetween. Since the gear is adjacent to the gear coupling fixed to the motor output shaft, the length of the screw shaft can be secured.

According to the present invention according to claim 2 , with a simple structure in which an annular rubber cushioning member is fitted into the pin and one pin hole portion, the impact load can be absorbed by elastic deformation of the annular rubber cushioning member. Can be done.

According to the present invention according to claim 3 , since the buffer member is an O-ring, a general O-ring as a sealing member is applied to the buffer member, and the O-ring can be attached to the pin and inserted into the pin hole. Combined with the fact that it is easy to assemble, it is possible to significantly reduce costs and improve ease of assembly, and the O-ring has a considerable thickness and can absorb a high percentage of impact load. .

According to the present invention according to claim 4 , a scale is fixed to one of the left and right nut parts, and the scale is detected by an encoder disposed in the case, so that the linear movement position of one nut part can be directly monitored by the encoder. The gripping member position can be accurately detected without being affected by backlash or hysteresis in the transmission path, and by detecting one nut part, the other nut part that is integrated with the screw shaft can be detected. The position of the electric gripper can also be recognized, and with a relatively simple configuration, highly accurate positioning control of the electric gripper is possible.

According to the present invention according to claim 5 , the motor is mounted on the upper side of the case and installed so as to be sandwiched between the case and the upper case, so that the motor can be easily assembled and replaced. In addition, a screw shaft is arranged on the lower side of the case, a rail is arranged on the lower side of the screw shaft, and a linear guide integrated with the nut part is engaged with the rail to linearly guide the left and right nut parts. Therefore, in addition to the above-mentioned linear motion guide, the rail can also be used as a cover for storing the grease of the screw shaft.

FIGS. 1A and 2B are diagrams showing the entire electric gripper according to the present invention, in which (A) and (B) are perspective views seen from different directions. A central sectional view of the electric gripper. FIG. 2 is an exploded perspective view of the entire electric gripper. FIG. 3 is a diagram showing the main parts of the electric gripper, in which (A) is a perspective view, (B) is a front view, (C) is a plan view, and (D) is a side view. The motor of an electric gripper and the output part from the motor are shown, (A) is a front view, (B) is a side view, and (C) is an exploded perspective view. FIG. 2 is a diagram showing the gripping force when the gripping portion grips the workpiece, in which (A) shows the case without a buffer member, and (B) shows the case with the buffer member. FIG. 3 is a perspective view showing an output part of a motor with a modified buffer member.

Embodiments of the present invention will be described below along with the drawings. As shown in FIG. 1, the electric gripper 1 has an upper case 3 fixed to a case 2, a cover 5 and a side cover 6 fixed to it, and has a generally rectangular shape as a whole, and has two gripping parts at the bottom. 7,7 stands out.

As shown in FIGS. 2 and 3, the electric gripper 1 has flexible sheets 9, 9 interposed between a motor storage section 2a on the upper surface of the case 2 and a motor storage section 3a on the lower surface of the upper case 3, and the gear A motor 10, which is a DC motor with a motor, is housed in a sandwiched manner, and the motor 10 is arranged by fixing the upper case 3 to the case 2 with bolts. A screw shaft 12 is rotatably supported via bearings 11 and 13 on support parts 2b and 2c extending on both sides of the lower part of the case 2. The screw shaft 12 has a left-hand threaded part (or right-hand threaded part) 12a and a right-hand threaded part (or left-hand threaded part) 12b on the left and right sides, which have different winding directions. The nut portion 14a and the right nut portion 14b are screwed together. Further, a gear 18 is integrally fixed to the outside of the support portion 2b at one end of the screw shaft 12.

As shown in FIGS. 3 and 4, a lower plate 15 is fixed to the lower ends of the left and right support parts 2b and 2c of the case 2, and a rail 16 is integrally fixed to the upper surface of the lower plate. Linear guides 17a and 17b are fixed to the lower surfaces of the left nut part 14a and right nut part 14b, respectively. It is supported so as to be movable in the linear motion direction. Plate portions 7a, 7a of the gripping portions 7, 7 are integrally fixed to both side surfaces of the left and right nut portions 14a, 14b with pan head machine screws, and these gripping portions 7, 7 extend downward and It is possible to grip or release a gripped member such as the like.

A scale 20 is integrally fixed to the upper part of one side of the one (left) nut part 14b via a scale holder 19. Further, a linear encoder 21 is arranged on the side of the case 2 where the scale 20 is located, and the linear encoder 21 detects the scale 20 and moves the position of one nut portion 14b, thus symmetrically. It is possible to detect the position and distance between the two gripping parts 7, 7 that can be used.

As shown in FIG. 5, a gear coupling 25 is supported non-rotatably on the output shaft 10a of the motor 10, and a gear 26 is rotatably supported on a sleeve 25c extending outside the gear coupling 25. The gear coupling 25 and the gear 26 are supported by a snap ring 28 to prevent them from coming off on the output shaft 10a. Pin holes 25a, 25a are formed in the disk-shaped gear coupling 25 at equal intervals, for example, 180 degrees, and similar pin holes 26a, 26a are formed in the gear 26. Pins 27, 27 penetrate and are supported by aligned pin holes 25a, 26a of the gear coupling 25 and gear 26. The pin 27 is a stepped pin with different diameters, and its large diameter portion fits into the pin holes 26a, 26a of the gear 26. An annular groove 27a is formed in the large diameter portion, and an O-ring 29 constituting an annular rubber cushioning member is fitted into the groove 27a.

Therefore, the rotation of the motor 10 is transmitted from the gear coupling 25, which is the transmission path D, to the gear 26 via the pin 27 and the O-ring 29, and when an impact load from the grip part 7 acts on the gear 26, the O-ring 29 is compressively deformed and temporarily absorbs the impact load. The gear 26 meshes with a gear 18 connected to the screw shaft 12, and the rotation of the motor 10 is transmitted to the screw shaft 12 via the gears 26 and 18. The encoder 21 and the motor 10 are connected to the relay base material 30 via lead wires, and connected to a cable together in one connector.

Note that the buffer member made of an O-ring or the like is not limited to the one that is fitted onto and arranged on the pin 27 that connects the gear coupling 25 and the gear 26, and is not limited to the one that is placed on the pin 27 that connects the gear coupling 25 and the gear 26. They may be placed anywhere on the transmission path, such as between the motor output shaft 10a and the gear (transmission member) 26, between the gear (transmission member) 18 and the screw shaft 12, etc.

In the electric gripper 1, based on the above-described configuration, the rotation of the DC motor 10 is transmitted to the gear 26 via the gear coupling 25, the pin 27, and the O-ring 29, and further transmitted to the screw shaft 12 via the gear 18. to rotate the screw shaft 12. The left and right nut parts 14a and 14b screwed into the left threaded part 12a and right threaded part 12b of the screw shaft 12 move linearly in different directions as the linear guides 17a and 17b are guided by the rail 16. . For example, the gripping parts 7, 7 grip the workpiece by moving the left and right nut parts 14a, 14b in a direction toward each other.

When the gripping parts 7, 7 grip a workpiece, as shown in FIG. 6(A), the transmission from the motor 10 to the gripping part 7 occurs until the gripping parts come into contact with the workpiece and stop moving. Due to this inertial force, an impact load K that is larger than the actual gripping force acts instantaneously. In the absence of the O-ring 29 constituting the buffer member, the impact load K acts on the grips 7, 7, the motor 10, and the transmission path D from the motor. In this embodiment, when torque is transmitted from the motor 10 to the gear 26 via the pin 27 and the O-ring 29, the O-ring 29 is elastically deformed, so that the impact load K is absorbed and alleviated. , as shown in FIG. 6(B), the gripping force smoothly transitions from the gripping position to the gripping state.

When releasing the grip of the workpiece by the grippers 7, 7, the motor 10 is rotated in the opposite direction. As a result, the left and right nut portions 14a, 14b and the gripping portions 7, 7 move in a direction away from each other, and the gripping portions release the grip on the workpiece. Furthermore, the left and right nut parts 14a, 14b move in the direction of separation, and the nut parts abut against the support parts 2b, 2c (case 2). At this time, as in the case of gripping the workpiece, an impact load K is applied, but the impact load is absorbed and relaxed by the buffer member (O-ring) 29, and the nut portions 14a and 14b stop smoothly.

When a workpiece is gripped by the gripping parts 7, 7, the position of one gripping part 7 is directly detected by the encoder 21 detecting the scale 20 of one of the nut parts 14b. The position of the other gripping part is also recognized by the position of the one gripping part 7, and the gripping position of the gripping parts 7, 7 can be detected. Since the position detection by the encoder 21 directly detects the nut portion 14b that is integrated with the grip portion 7, accurate position detection is possible without being influenced by mechanical backlash or hysteresis of a transmission member or the like. The electric gripper 1 can perform highly accurate positioning control by detecting the position using the encoder 21.

The motor 10 is held by being sandwiched between a motor storage section 2a of the case 2 and a motor storage section 3a of the upper case 3. Therefore, the motor can be easily assembled and replaced. Further, the nut portions 14a and 14b are linearly guided by a rail 16 provided on a lower plate 15 attached below the screw shaft 12. Therefore, the lower plate 15 and the rail 16 function as a grease cover for receiving the grease on the screw shaft 12 portion.

FIG. 7 shows an embodiment in which the buffer member is changed. A cylindrical rubber bushing ₂₉₂ is fitted onto the pin 27 attached to the gear coupling 25 instead of an O-ring. The rubber bush ₂₉₂ is fitted into the pin hole 26a of the gear 26, and the gear 26 and gear coupling 25 are supported by the snap ring 28 to prevent them from coming off.

Therefore, even in this embodiment, the rubber bushing ₂₉₂ elastically deforms to absorb and relieve the impact load, and the gripping parts 7 smoothly grip the workpiece and abut against the case 2. and stop.

Note that the cushioning material is not limited to the O-ring 29 or the rubber bushing ₂₉₂ , but the pin itself may have elasticity, and an elastic member such as a rubber bushing may be fitted and fixed in the pin hole. Furthermore, the buffer member may be of another type, such as one in which the gear coupling 25 or the like is provided with a relatively rotating portion with a spring interposed therebetween, and the buffer member may be placed anywhere along the transmission path D from the motor 10 to the screw shaft 12. Furthermore, a buffer member may be arranged at a transmission member such as a gear, or at a connection portion between a gear (transmission member) and a shaft, without providing a gear coupling.

The threaded portions 12a, 12b and the nut portions 14a, 14b are not limited to ordinary feed screws, but may also be ball screws, and the gears 18, 26 are not limited to gears, but may be other transmission devices such as chains or sprockets. But that's fine.

1 Electric gripper 2 Case 3 Upper case 7 Gripping part 10 (DC with gear) Motor 10a Output shaft 12 Screw shaft 12a Left thread part 12b Right thread part 14a Left nut part 14b Right nut part 16 Rails 17a, 17b Linear guide 18 Gear 20 Scale 21 Encoder 25, 26 2 parts (gear coupling, gear)
25a, 26a Pin hole 27 Pin 29, 29 ₂ Buffer member (O ring, rubber bush)
D Transmission path K Impact load

Claims (5)

Rotation of the motor is transmitted to a threaded shaft having a left threaded portion and a right threaded portion, and a left nut portion and a right nut portion linearly guided by the left threaded portion and right threaded portion are screwed together to form the left nut. In the electric gripper, which has a gripping part on the right nut part and the right nut part,
disposing the motor and the screw shaft in parallel in a case;
The output shaft of the motor and the screw shaft are interlocked by a transmission path arranged on one side of the case,
two members supported in a relatively rotatable manner are disposed adjacent to each other in the transmission path, and the two members are connected by fitting a pin into a pin hole formed in the two members ;
The two members include a gear coupling fixed to the output shaft of the motor and a gear meshing with a gear provided on the screw shaft,
A buffer member is interposed at a connecting portion between the pin and the pin hole to absorb a shock load larger than the gripping force with which the gripping portion grips the gripped member.
An electric gripper characterized by: An annular rubber buffer member is fitted into one pin hole of the pin, and the shock load deforms the buffer member between the pin and the one pin hole to absorb the shock load. Become,
The electric gripper according to claim 1 . The annular rubber buffer member is an O-ring.
The electric gripper according to claim 2 . A scale is fixed to either the left nut part or the right nut part, and an encoder capable of detecting the scale is arranged in a case that houses the motor and screw shaft.
The electric gripper according to any one of claims 1 to 3 . the motor is arranged above the case, the screw shaft is arranged below the case,
installing the motor disposed above the case so as to sandwich it between the upper case;
A rail is disposed below the screw shaft of the case, and linear guides are fixed to the left nut portion and the right nut portion, respectively, to engage with the rail and provide linear motion guidance.
The electric gripper according to any one of claims 1 to 4 .

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