JP4854793B2 - Electric gripper - Google Patents

Description

  The present invention relates to an electric gripping device that is mounted on the tip of a robot arm of an industrial robot that supplies and assembles components and grips a workpiece as a conveyance object.

  In an industrial robot that transports, transfers, and assembles small parts, a device that grips the parts to be transported is required at the tip of the robot arm. As this gripping device, there is known a device that opens and closes a plurality of parallel movable claws using pressurized air and sandwiches a component to be conveyed between the movable claws. However, in recent years, an electric gripping device that opens and closes the movable claw using an electric motor has been widely used in order to save energy and reduce the size of the device.

  This type of electric gripping device converts the rotation of the electric motor into a translational motion of each movable claw, and exhibits the rotational torque of the electric motor as a pressing force of the movable claw, so that an object to be conveyed between the plurality of movable claws. It is comprised so that a loose workpiece may be hold | gripped. As a mechanism for converting the rotation of the electric motor into the translational motion of the movable claw, a cam mechanism, a feed screw mechanism, or a link mechanism is used. The movable claw may be configured as an inner claw that presses the workpiece from the outside to the inside or as an outer claw that presses the workpiece from the inside to the outside.

  In this electric gripping device, for example, when the movable claw is configured as an inner claw, when the electric motor is rotated in one direction, the plurality of movable claws are closed toward the center to sandwich the workpiece from the surroundings. When it is gripped and the electric motor is rotated in the other direction, the plurality of movable claws open radially to release the workpiece. At this time, the movement control of the movable claw is performed by detecting the rotational torque of the electric motor. Since the rotational torque of the electric motor increases when the movable claw grips the workpiece, if the electric motor is energized so that the predetermined rotational torque is exhibited, the gripping force corresponding to the rotational torque exhibited by the electric motor With this, the workpiece is gripped.

  On the other hand, in order for the movable claw to continue to exert a gripping force on the workpiece, the electric motor needs to continue to exhibit a predetermined rotational torque. Accordingly, when the movable claw grips the workpiece, it is necessary to continue energizing the electric motor until the workpiece is released, and the longer the gripping time of the workpiece, the more electric energy is consumed.

  Japanese Patent Application Laid-Open No. 2009-125851 proposes an improvement of an electric gripping device for continuing to hold a workpiece by a movable claw even when energization to an electric motor is stopped. In this improvement, an irreversible feed screw mechanism is adopted as a mechanism for converting the rotation of the electric motor into the translational motion of each movable claw, and the electric motor is energized while the movable claw is pressing the workpiece. Even when stopped, the movable claw is configured not to be retracted by a reaction force from the workpiece. That is, when energization of the electric motor is stopped, each movable claw is locked at the position where the workpiece is gripped.

JP 2009-125851 A

  However, when energization of the electric motor is stopped, each movable claw does not exert any pressing force on the workpiece even if each movable claw is locked at the position where the workpiece is gripped. It is in a state where it is simply in contact with the workpiece. For this reason, the frictional force acting between the movable claw and the workpiece becomes unstable, and the posture of the workpiece is likely to change during the movement of the robot arm. If the workpiece posture changes during the transfer, the robot arm cannot complete the transfer or transfer of the workpiece correctly. In particular, when the contact area between the workpiece and each movable claw is small, a trouble that the workpiece falls out between the plurality of movable claws is also assumed.

  The present invention has been made in view of such problems, and the object of the present invention is to ensure that a gripping force can be reliably exerted on a workpiece even when energization of the electric motor is stopped. Another object of the present invention is to provide an electric gripping apparatus capable of reliably gripping a workpiece in a predetermined posture while saving energy.

  That is, the electric gripping device of the present invention displaces each movable claw in conjunction with a drive member that is given translational motion by an electric motor, a plurality of movable claws that open and close to grip a workpiece, and a displacement of the drive member. And a lock mechanism that restricts displacement of the drive member when the motor is de-energized. The link mechanism includes one or more links. At least one of the one or more links is made of an elastic body, and when the movable claw presses the workpiece, the link is deformed by the reaction force to accumulate elastic force.

  In addition, the configuration of the electric gripping device is not limited to gripping the workpiece by the movable claw, but can also be used as a device that continues to exert a predetermined pressing force on the workpiece.

  In the electric gripping device of the present invention configured as described above, for example, when the electric motor is a rotary motor, when the electric motor rotates, a translational motion corresponding to the rotation angle is given to the drive member, and this drive The displacement of the member is transmitted to each movable claw by the link mechanism, and these movable claws open and close according to the rotation angle of the electric motor. Since at least one of the links constituting the link mechanism is an elastic body, when the movable claw grips a workpiece, the link made of the elastic body accumulates and deforms an elastic force corresponding to the rotational torque exerted by the electric motor. become. When the energization of the electric motor is stopped from this state, the locking mechanism restricts the displacement of the driving member. Therefore, even if the electric motor does not exert any holding force, the link mechanism exerts an elastic force in the direction of pressing the movable claw against the workpiece. The accumulated state is maintained.

  That is, in the electric gripping device of the present invention, even if the electric power to the electric motor is stopped while the movable claw is holding the workpiece, the movable claw continues to exert the same pressing force on the workpiece as before the electric power supply to the electric motor is stopped. Thus, it is possible to reliably hold the workpiece in a predetermined posture while saving energy.

  In addition, since at least one of the one or more links constituting the link mechanism is an elastic body, and the link is configured to exert an elastic force only when the movable claw is in contact with the workpiece, In a state where the movable claw is separated from the workpiece, no urging force is applied to the movable claw. For this reason, when the electric motor opens and closes the movable claw, it is not necessary to exert an extra force. In this respect as well, the electric gripping device of the present invention can achieve energy saving.

It is a perspective view showing an example of an electric gripping device to which the present invention is applied. FIG. 2 is a front view of the electric gripping device shown in FIG. It is a left view of the electric holding apparatus shown in FIG. It is a right view of the electric holding apparatus shown in FIG. FIG. 3 is a front view showing an example in which the movable member is displaced in the electric gripping device shown in FIG. 2. It is the schematic which shows the state of the moment when the nail | claw member hold | grip the workpiece | work. It is the schematic which shows the state which the nail | claw member is holding | grip continuously, exerting pressing force with respect to a workpiece | work.

  Hereinafter, the electric gripping device of the present invention will be described in detail with reference to the accompanying drawings.

  1 to 5 show an example of an electric gripping device to which the present invention is applied. The electric gripping device 1 is roughly divided into a base plate 2, a pair of movable members 3 provided on the front surface side of the base plate 2, an electric motor 4 attached to the back surface side of the base plate 2, and the electric motor 4 And a transmission mechanism 5 that converts the rotation of the movable member 3 into a translational motion of the movable member 3.

  A single track rail 6 is disposed on the base plate 2, and two moving blocks 7 are assembled to the track rail 6. These moving blocks 7 are assembled to the track rail 6 via a large number of balls, and can move freely along the track rail 6. As a combination of the track rail 6 and the moving block 7, a known linear guide can be used. The movable member 3 is fixed to each moving block 7 and moves on the base plate 2 along the arrow X direction in FIG. That is, the movement of the movable member 3 is constrained by the track rail 6 and only translational motion along the axial direction of the track rail 6 is allowed.

  As indicated by a one-dot chain line in FIG. 2, a claw member 8 is fixed to each movable member 3, and a pair of claw members 8 grip a workpiece (not shown) between them according to the translational movement of the movable member 3. Is configured to do. Therefore, the movable claw of the present invention is constituted by the movable member 3 and the claw member 8. The movable member 3 and the claw member 8 may be integrally formed as a movable claw, and the movable claw may be configured to be fixed to the moving block 7, but the shape of the claw member 8 is an object to be grasped. It is preferable to optimize according to the shape of the workpiece. From this viewpoint, the movable member 3 is fixed to the moving block 7 as a mounting plate for the claw member 8.

  In addition, each movable member 3 is provided with a connection arm 9, and each connection arm 9 passes through a long hole 10 provided in the base plate 2 and projects to the back side of the base plate 2. The connection arm 9 protruding to the back side of the base plate 2 is connected to the transmission mechanism 5. Connection arms 9 extending from each of the pair of movable members 3 are positioned on opposite sides of the track rail 6, and a pair of long holes 10 formed in the base plate 2 are also provided with the track rail 6 in between. ing.

  On the other hand, the electric motor 4 is fixed to the back side of the base plate 2 via a support bracket 11. The support bracket 11 is formed in a rectangular shape having a space inside, and the electric motor 4 is fixed to the support bracket 11 so that its output shaft is inserted into the support bracket 11. A drive pulley 12 is provided inside the sahort bracket 11 coaxially with the output shaft of the electric motor 4, and the rotation of the electric motor 4 is transmitted to the drive pulley 12.

  The electric motor 4 is a servo motor, and has a built-in sensor for detecting the rotation angle of the output shaft, and the rotation angle of the output shaft is feedback-controlled by sending the sensor output to a control unit (not shown). The control unit detects a current value supplied to the electric motor 4 and controls the rotational torque generated by the electric motor 4 based on the detected value.

  In the electric gripping device 1 shown in FIGS. 1 to 5, the transmission mechanism 5 disposed on the back side of the base plate 2 is exposed to the outside. However, in actual use, the cover is fixed around the base plate 2. Thus, the transmission mechanism 5 is protected from the outside. However, in order to promote heat dissipation of the electric motor 4, the electric motor is fixed to the support bracket 11 outside the cover.

  The transmission mechanism 5 converts the rotation of the electric motor 4 into a translational motion that matches the axial direction of the electric motor 4, and the translational motion obtained by the feed screw mechanism 50 in the movable member 3. It is comprised from a pair of link mechanism 51 which converts into the translational motion of this and transmits.

  The feed screw mechanism 50 includes a screw shaft 13 rotatably supported by the support bracket 11 and a rectangular drive member 14 that performs translational movement in the axial direction of the screw shaft 13 in accordance with the rotation of the screw shaft 13. It consists of and. The screw shaft 13 is disposed in the vicinity of the center of the back side of the base plate 2 in parallel with the output shaft of the electric motor 4, and one end thereof is coupled to the driven pulley 15 inside the support bracket 11. The driven pulley 15 is adjacent to the drive pulley 12 inside the support bracket 11, and a timing belt is stretched between the pulleys 12 and 15. Therefore, when the electric motor 4 rotates, the rotation is transmitted from the drive pulley 12 to the driven pulley 15 via the timing belt, and the screw shaft 13 is rotated according to the rotation angle of the electric motor 4. 2 to 5 are drawn with the timing belt omitted.

  A through hole through which the screw shaft 13 is inserted is formed in the center of the drive member 14, and a nut member that is screwed into the screw shaft 13 is fixed inside the through hole. A pair of guide shafts 16 are fixed to the support bracket 11 that rotatably supports the screw shaft 13 in parallel with the screw shaft 13, while the drive member 14 has a cylindrical shape through which the guide shaft 16 passes. The ball bush is fixed, and the drive member 14 is guided along the axial direction of the screw shaft 13 by a linear guide constituted by the guide shaft 16 and the ball bush.

  Therefore, when the electric motor 4 is rotated, the screw shaft 13 disposed in parallel with the output shaft of the electric motor 4 is rotated, and the drive member 14 of the screw shaft 13 is rotated according to the rotation angle of the electric motor 4. Translational movement is performed along the axial direction, that is, the direction of the arrow Y in FIG. At this time, the guide shaft 16 prevents the drive member 14 from being rotated around the screw shaft 13.

  In this embodiment, the rotation of the electric motor 4 is transmitted to the screw shaft 13 using a pair of pulleys 12 and 15 and a timing belt. However, it is also possible to transmit the rotation using a steel belt or a plurality of gears. It is. Moreover, the electric motor 4 may be arrange | positioned on the same axial center as this screw shaft 13, and the output shaft of the electric motor 4 and the screw shaft 13 may be directly couple | bonded through a coupling.

  The screw shaft 13 and the nut member constitute a slide screw, and in this embodiment, the shape of the thread is a trapezoidal screw. The shape of the thread is not limited to a trapezoidal screw, and may be a square screw or a triangular screw. This sliding screw functions as the locking mechanism of the present invention. That is, this is the case where a force along the axial direction of the screw shaft 13 is applied to the drive member 14 with the energization of the electric motor 4 stopped and the holding force of the electric motor 4 disappeared. However, the driving member 14 can be locked at a fixed position on the screw shaft 13 without rotating the screw shaft 13 due to the frictional force acting between the screw shaft 13 and the nut member. ing.

  On the other hand, the pair of link mechanisms 51 described above are provided between the connecting arm 9 of each movable member 3 protruding through the base plate 2 and projecting to the back side thereof, and the driving member 14, as shown in FIGS. As shown, a pair is provided so as to sandwich the screw shaft 13 from the front and the back. Each link mechanism 51 is rotatably coupled to the first link 17 that is rotatably coupled to the drive member 14 that translates in the Y direction, and to the connection arm 9 that translates in the X direction. And the elastic link 19 that couples the first link 17 and the second link 18 to each other. Further, the drive member 14 and the connection arm 9 can be recognized as a slip pair at the end of the link mechanism, and can be regarded as constituting a part of the link mechanism 5.

  The first link 17 and the second link 18 are plate-like members having rotary bearings at both ends, and are rotatably coupled to the drive member 14, the connection arm 9, or the elastic body link 19 through these rotary bearings. Yes.

  The elastic body link 19 has two rod-shaped spring members 20 and 21 orthogonal to each other, and is formed in a substantially L shape. A joint portion 22 for connecting the spring members 20 and 21 is formed on the base plate 2. The side plate 23 is fixed to the side plate 23 so as to be rotatable. In other words, the elastic body link 19 rotates about the reference pin 24 provided on the side plate 23. The tip of the spring member 20 is rotatably connected to the first link 17, while the tip of the spring member 21 is rotatably connected to the second link 18. The two spring members do not necessarily intersect at 90 °, and the intersecting angle may be freely changed in consideration of the power transmission path in the link mechanism.

  The spring members 20 and 21 are rod-shaped members having a circular cross section, and are configured to accumulate an elastic force with a bending deformation when a load in a direction perpendicular to the longitudinal direction is applied to the tip thereof. In other words, the spring members 20 and 21 function as elastic bodies, and in this embodiment, the spring members 20 and 21 are formed from oil temper wires for valve springs. As will be described later, each time the claw member 8 grips the workpiece, the spring members 20 and 21 are repeatedly bent and deformed. Therefore, the spring members 20 and 21 are required to have high strength and toughness, and are excellent. It is necessary to have high fatigue resistance. Accordingly, the spring members 20 and 21 may be formed of a material other than the valve spring oil temper wire as long as the material satisfies such requirements. However, if the amount of deformation when the load is applied is large, the rotation angle of the electric motor increases when the workpiece is gripped or released, so that the spring member can accumulate a large elastic force with a small displacement. Is preferably made of spring steel.

  The spring members 20 and 21 may have any shape as long as they accumulate elastic force with deformation such as bending or bending when a load in a direction orthogonal to the longitudinal direction is applied to the tip. Yes, it is not limited to a rod-shaped member having a circular cross section, that is, a rod-shaped spring. For example, a leaf spring or a torsion spring may be used.

  Next, the operation of the electric gripping device 1 will be specifically described.

  FIG. 5 shows a state where the electric motor 4 is rotated from the state shown in FIG. 2 and the drive member 14 is moved in the Y direction along the screw shaft 13. More specifically, a state in which the driving member 14 is moved downward in FIG. 2 is shown. When the drive member 14 is moved in the Y direction in this way, the first link 17 coupled to the drive member 14 moves in the Y direction together with the drive member 14, and the elasticity coupled to the first link 17. Since the spring member 20 of the body link 19 is swung, the elastic body link 19 rotates around the reference pin 24. Further, when the elastic body link 19 rotates around the reference pin 24, the spring member 21 swings, so that the connecting arm 9 of the movable member 3 is pushed through the second link 18 coupled to the spring member 21. Will be pulled. As a result, the movable member 3 performs translational movement in the X direction.

  In the example shown in FIG. 5, when the drive member 14 moves downward in the drawing along the Y direction, the pair of movable members 3 moves along the X direction in directions approaching each other. Conversely, when the drive member 14 moves upward in the drawing along the Y direction, the pair of movable members 3 move away from each other along the X direction. That is, when the electric motor 4 is rotated and a translational movement along the axial direction of the screw shaft 13 is given to the drive member 14, the link mechanism 51 that couples the drive member 14 and the connection arm 9 of the movable member 3. As a result, the pair of movable members 3 provided on the base plate 2 perform a translational motion in a direction approaching or separating from each other. By this, it becomes possible to grip the workpiece between the claw members 8 and to release the gripped workpiece.

  6 and 7 illustrate the action of the elastic body link 19 when the claw member 8 grips the workpiece 100. FIG. 6 shows a state at the moment when the claw member 8 contacts the workpiece 100. FIG. On the other hand, FIG. 7 shows a state where the electric motor 4 is further rotated from the state shown in FIG. 6 and the claw member 8 exerts a pressing force F on the workpiece 100.

  When the workpiece 100 is gripped by the pair of claw members 8, the claw member 8 moves in conjunction with the rotation of the electric motor 4 until both of the claw members 8 come into contact with the workpiece 100. Generates only a small rotational torque necessary for the movement of the claw member 8. However, as shown in FIG. 6, when both the claw members 8 come into contact with the workpiece 100, the movement of the claw members 8 is locked by the workpiece 100. The rotational torque exerted will increase.

  In this state, when energization of the electric motor 4 is continued until the rotational torque exerted by the electric motor 4 reaches a predetermined value, the force resulting from the rotational torque of the electric motor 4 is transmitted via the drive member 14 and the first link 17. This acts on the elastic body link 19, and this force tries to forcibly rotate the elastic body link 19 in the direction of arrow A. On the other hand, since the workpiece 100 exerts a reaction force that tries to hold down the rotation of the elastic body link 19, the two spring members 20 and 21 are expanded to the elastic body link 19. Force is applied.

  As a result, as shown in FIG. 7, each spring member 20, 21 is bent and deformed, and these spring members accumulate elastic force themselves. At this time, since the claw member 8 applies a pressing force F corresponding to the rotational torque exerted by the electric motor 4 to the workpiece 100, the elastic body link 19 generates an elastic force corresponding to the pressing force F. Accumulated.

  Then, when energization to the electric motor 4 is stopped from the state shown in FIG. 7 and the holding force of the electric motor 4 is lost, the sliding screw by the screw shaft 13 and the nut member acts as a lock mechanism as described above. The movement of the drive member 14 with respect to the screw shaft 13 in the Y direction is locked. In other words, even when the electric motor 4 is de-energized, the drive member 14 that forms the slip pair of the link mechanism 5 is fixed at a fixed position on the screw shaft 13, so that the spring member 20 in the elastic link 19, The state of bending deformation 21 is maintained.

  For this reason, in the electric gripping apparatus 1 of the present embodiment, the elastic body link 19 is accumulated even when the claw member 8 stops energizing the electric motor 4 from the state where the claw member 8 grips the workpiece 100 with the pressing force F. Since the connecting arm 9 is urged by the elastic force, the claw member 8 continues to grip the workpiece 100 with the pressing force F.

  Therefore, in this electric gripping device 1, even when the energization to the electric motor 4 is interrupted while the claw member 8 grips the work 100, the claw member 8 continues to exert a gripping force on the work 100 reliably. It is possible to reliably hold 100 in a predetermined posture. As a result, it is possible to stop energization of the electric motor 4 while gripping the workpiece 100 and to achieve energy saving.

  Further, since the elastic body link 19 accumulates an elastic force only when the claw member 8 is pressed against the work 100, the electric motor 4 is rotated by a small amount when the claw member 8 is not in contact with the work 100. It is possible to drive with torque. Also in this respect, the electric gripping device of the present invention contributes to energy saving.

  In addition, the rotation control of the electric motor 4 in the electric gripping device 1 is not different from that of the conventional electric gripping device, and can be performed by torque control using the rotational torque exhibited by the electric motor 4 as an index. is there. For example, if the rotation torque of the electric motor 4 is controlled so that the claw member 8 grips the workpiece 100 with a force of 10 N, the elastic force corresponding to this is accumulated in the elastic body link 19, and If the energization of the electric motor 4 is stopped after detecting that the rotational torque of the motor 4 has reached a predetermined value, the claw member 8 continues to grip the workpiece with a force of 10N.

  The electric gripping device 1 described with reference to the drawings is a so-called inner claw type that grips the workpiece 100 between a pair of claw members 8. In addition, even a so-called outer claw type that grips a workpiece is applicable. In that case, when the electric motor 4 exerts a predetermined rotational torque while the claw member is in contact with the workpiece, the pair of spring members 20 and 21 of the elastic body link 19 are elastically deformed in a closing direction, The elastic force corresponding to the pressing force F is accumulated.

  The link mechanism 5 for interlocking the drive member 14 and the movable member 3 is not limited to the example described with reference to the drawings as long as the link mechanism 5 is composed of one or more links. Further, if at least one link is configured to elastically deform due to the rotational torque of the electric motor 4 to accumulate elastic force as the workpiece is gripped, a specific link that accumulates the elastic force is specified. The shape and arrangement in the link mechanism may be changed as appropriate.

  For example, the connection arm 9 may be formed of the same material as the spring member, and one end of the connection arm 9 may be fixedly supported on the movable member 3 and the other end may be rotatably supported on another link.

  Furthermore, in the above-described embodiment, the two movable members 3 are opened and closed, and the workpiece is gripped by the claw members 8 fixed to these movable members 3. However, the movable members include three or four movable members. There is no problem. In that case, the movable member is arranged on the base plate 2 so as to open and close radially, and the link mechanism 5 is provided for each movable member.

  Furthermore, in the above-described embodiment, a slide screw that gives translational motion to the drive member 14 is used as a lock mechanism that locks the drive member 14 when energization to the electric motor 4 is stopped. However, the present invention is not limited to this. For example, a brake device for locking the rotation of the screw shaft 13 due to the stop of energization of the electric motor 4 may be provided separately. However, the configuration shown in the embodiment is useful in terms of simplification of the configuration.

  In the above-described embodiment, the rotary motor is used as the electric motor. However, the present invention is not limited to this as long as the drive member can be translated. For example, a linear motor may be used. .

  DESCRIPTION OF SYMBOLS 1 ... Electric gripping device, 3 ... Movable member, 4 ... Electric motor, 5 ... Transmission mechanism, 50 ... Feed screw mechanism, 51 ... Link mechanism, 8 ... Claw member, 9 ... Connection arm, 13 ... Screw shaft, 14 ... Drive Member, 19 ... elastic body link, 20, 21 ... spring member

Claims (4)

A drive member to which translational motion is given by a motor; a plurality of movable claws that open and close to grip a workpiece; a link mechanism that displaces each movable claw in conjunction with displacement of the drive member; and when energization of the motor stops A lock mechanism for limiting the displacement of the drive member,
The link mechanism includes one or more links, and at least one of the one or more links is made of an elastic body. When the movable claw grips a workpiece, the link is deformed by the reaction force and accumulates elastic force. An electric gripping device characterized by that. 2. The electric gripping device according to claim 1, wherein the motor is a rotary motor, and the lock mechanism is a slide screw that converts rotation of the motor into translational motion of the drive member. The electric gripping device according to claim 1, wherein at least a part of the link made of the elastic body is formed of spring steel. A drive member that is given translational motion by a motor, a movable member that is guided by a linear guide and presses an object, a link mechanism that displaces the movable member in conjunction with the displacement of the drive member, and energization of the motor A locking mechanism that restricts the displacement of the drive member when stopped,
The link mechanism includes one or more links, and at least one of the one or more links is an elastic member. When the movable member presses an object, the link member is deformed by a reaction force and accumulates an elastic force. A press drive device characterized by:

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