JP2012139774A - Compliance device and structure of robot arm with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compliance device that is capable of absorbing the positional displacement of a workpiece, while properly pushing out the workpiece (such as a bolt) using the device to the arm of a robot.SOLUTION: The compliance device 7 is intertposed between a holding section (such as a chuck) for holding the workpiece and the arm for supporting the same. The device includes a pair of brackets 70, 71, and a guide shafts 72 for slidably supporting one bracket 70 so as to be brought into close or apart from the other bracket 71. The device further has a biasing means (for example a coil spring 73) applying biasing force to both brackets 70, 71 so as to space apart to each other. Constriction parts 72b are arranged in a guide shaft 72 and the one bracket 70 can displace in a direction perpendicular to the guide shafts 72.

Description

  The present invention relates to a compliance device suitable for use in a robot arm having a chuck for holding a workpiece.

  Conventionally, industrial robots and automatic assembly machines have been used to automate the process of assembling a workpiece into a product at a production site, and various sensors are used to detect the position of the workpiece and the position of the product to be assembled. ing. In addition, in order to omit such a sensor or ease the requirement for detection accuracy, a mechanism that absorbs a positional deviation of a workpiece may be used. Generally, an RCC device (remote center compliance device), a compliance device, etc. being called.

  For example, in the component assembling apparatus described in Patent Document 1, a chuck is suspended from a lower end of a robot arm via a flexible connection member. The connecting member has a structure in which the upper plate and the lower plate are easily relatively displaced in the horizontal direction, and the displacement of the workpiece in the horizontal direction is absorbed by this displacement. Further, the connecting member stays at the reference position by the weight of the chuck and is fixed at the reference position by injecting high-pressure fluid therein.

  Further, in the compliance device described in Patent Document 2, a second base plate is disposed below the first base plate attached to the upper robot hand so as to be movable in the x-axis direction in the horizontal plane, and below the y-axis direction. A third base plate is disposed so as to be movable, a fourth base plate is disposed below the third base plate so as to be rotatable in the θ direction around the vertical axis, and a finger module is disposed below the fourth base plate. Further, a return mechanism to a neutral position and a holding mechanism are provided between the first to fourth base plates, respectively.

  According to these devices, since the relative displacement in an arbitrary direction in the horizontal plane is allowed between the robot arm and the workpiece held thereby, the horizontal displacement of the workpiece is absorbed. It becomes possible to assemble at a predetermined place of the product.

JP 2006-247788 A JP 2007-296587 A

  However, each of the conventional devices has many components, and the mechanism for enabling the chuck, finger unit, and the like holding the workpiece to be displaced in the horizontal direction is complicated. In addition, since a dedicated device for returning the workpiece to the reference position and the neutral position and fixing it is added, the entire apparatus must be increased in size and cost.

  In addition, all of the above devices allow horizontal relative displacement, but do not allow vertical displacement. For this reason, there is a possibility that the peripheral device and the workpiece are subjected to a large load when there is a positional deviation in the vertical direction or during a collision. Also, for example, when a bolt (workpiece) is gripped and screwed into a lower screw hole, for example, in a screw tightening operation, the bolt is synchronized with its rotation and exactly one pitch per rotation. It is necessary to send it out downward, and if this is realized only by the operation of the robot arm, there is a difficulty that the control becomes complicated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to form a compliance device used for a robot or the like with a simple structure so as to reduce costs and appropriately push a workpiece toward an object. It is to be.

  In order to achieve the above object, the present invention is directed to a compliance device that is interposed between a holding portion that holds a workpiece and a support portion that supports the holding portion, and allows positional deviation between the two. To do. A pair of brackets respectively attached to the holding portion and the support portion, and provided between the brackets, can be moved so as to pass through one of the brackets and move the one bracket closer to or away from the other bracket. And a biasing means for applying a biasing force to the two brackets so as to be separated from each other, and a constricted portion is provided on at least a part of the guide shaft, The bracket can be displaced in a direction perpendicular to the axis of the guide shaft.

  According to the compliance device having such a configuration, first, the holding-side bracket that holds the workpiece and the support-side bracket that supports the workpiece can be relatively displaced along the guide shaft. Is protected from overload caused by misalignment or collision. Further, since the holding side bracket and the workpiece are pushed out by the biasing force applied from the support side bracket to the holding side bracket in the displaceable direction, the workpiece such as a bolt is directed toward the screw hole. By simply rotating the workpiece, the workpiece can be sent out by screw pitch every rotation and screwed.

  Further, at least a part of the guide shaft is provided with a constricted portion, and since one bracket can be displaced in a direction perpendicular to the axis of the guide shaft, the one bracket and the other bracket are also provided. Misalignment of the workpiece is allowed and the workpiece misalignment is absorbed. If the range in which the constricted portion is provided is set to be large, one of the brackets is inclined with respect to the guide shaft, and this also absorbs the displacement of the workpiece.

  That is, according to the compliance device of the present invention, it is possible to absorb the displacement of the workpiece with a simple structure, and to push the workpiece toward an object such as a product with an appropriate force. The operation of sending out becomes unnecessary, or the demand for the accuracy of the sending out is eased.

  In the compliance device, a stopper portion may be provided at one end portion of the guide shaft so as to contact the peripheral edge portion of the through hole of one bracket and prevent the one bracket from falling off. On the bracket side in the vicinity of the stopper portion, the guide shaft may be provided with an isomorphous portion having substantially the same outer shape as the through hole. By doing so, the guide shaft and the bracket are positioned by matching the through-hole of one bracket with the same-shaped portion of the guide shaft in contact with the stopper portion.

  The same shape of the guide shaft has the same outer shape as the through hole of the bracket, because the same shape of the guide shaft is similar to and slightly smaller than the through hole, and the guide shaft is smooth when they match. This means that a gap that can slide is formed.

  In this case, the constricted portion of the guide shaft may be provided with a tapered portion so that the outer shape gradually decreases from the same shape portion. In this way, between the state where one bracket abuts against the stopper portion of the guide shaft and is positioned at the same shape portion as described above, and the state where the positional deviation is allowed at the constricted portion, the guide shaft It can move smoothly along. Therefore, the compliance device smoothly switches between the workpiece positioning state and the state of absorbing the displacement. Further, a damping means such as a viscous damper or a friction damper may be provided so as to apply a damping force to the movement of the one bracket.

  As the urging means, an elastic mechanism such as an air cylinder may be used in addition to an elastic body such as a coil spring, a leaf spring, or rubber. In order to reduce the cost, for example, a coil spring may be extrapolated to the guide shaft. In this case, a bush with a flange may be inserted into the through hole of one bracket through which the guide shaft is inserted, and the flange may function as a receiving seat for the coil spring.

  In such a case, the size of the cylindrical hole of the bush is the size of the through hole, and the outer shape of the same shape portion of the guide shaft is substantially the same. If the bush is made of a material having a low friction coefficient, the sliding state of the guide shaft becomes smoother. In addition, sliding with the end of the coil spring that contacts the flange becomes smooth. If the bush is worn out after prolonged use, it is only necessary to replace it.

  Further, the guide shaft may be constituted by a bolt for cost reduction, and a nut screwed to the bolt may be used as the stopper portion. One or two guide shafts may be used, but three guide shafts may be arranged substantially parallel to each other at substantially equal intervals in consideration of the inclination of the bracket at the constricted portion. If a coil spring having the same specifications is extrapolated to each of the three guide shafts, the inclination of the bracket can be suppressed.

  Further, the biasing means is not limited to the configuration in which the coil spring is extrapolated to the guide shaft as described above, and a spring member such as a coil spring, a leaf spring, or a rubber elastic body may be provided separately from the guide shaft. . As the spring member, a spring member whose spring constant increases as the amount of bending increases may be used. In this case, a progressive coil spring in which the thickness or pitch of the winding changes may be used, or a plurality of springs may be used. Progressive characteristics may be obtained by combining members.

  The compliance device as described above is suitable, for example, for an arm of an industrial robot. When a chuck for holding a workpiece is attached to the tip of this arm, the arm including the chuck is also included. The compliance device may be disposed at least in part.

  In other words, the present invention relates to a structure in which the above-described compliance device is disposed in at least a part of a robot arm to which a chuck for holding a workpiece is attached so as to allow a positional deviation before and after the robot arm.

  As described above, the compliance device according to the present invention has a simple structure including a pair of brackets, a guide shaft, and an urging means, which is advantageous for cost reduction, and can be used for a robot, an automatic assembly machine, or the like. If used, the workpiece can be positioned and held, and the displacement can be absorbed, and it is protected from overload when the workpiece is pressed. Furthermore, since the workpiece can be appropriately pushed out toward the object, the operation of feeding the workpiece by the robot arm or the like becomes unnecessary, or the demand for the accuracy of the feeding is eased. As a result, the control of the robot and the like can be simplified.

It is a perspective view which shows an example of the robot which mounted | wore the wrist of the arm with the compliance apparatus which concerns on this invention. It is the perspective view which expanded the compliance apparatus single-piece | unit and was seen from diagonally upward. (A) is a positioning state, (b) is explanatory drawing which shows a floating state about the compliance apparatus, respectively. It is explanatory drawing which shows operation | movement of the compliance apparatus in the screwing operation | work of a volt | bolt, (a) shows the time of inserting a volt | bolt in a screw hole, (b) shows the time of screwing, respectively. FIG. 5 is a view corresponding to FIG. 4 in the bolt pick-up, in which (a) shows a position immediately before picking up a bolt with misalignment, and (b) shows a misalignment correcting operation. FIG. 3 is a view corresponding to FIG. 2 according to another embodiment using a pair of long and short coil springs.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing an embodiment of a robot to which a compliance device according to the present invention is attached, and FIG. 2 is an enlarged view of the compliance device before being attached to the robot 1. FIG. 3 is an explanatory diagram illustrating the compliance device in a simplified manner in a positioning state and a floating state as viewed from the side.

-Robot configuration example-
The robot 1 shown in FIG. 1 is a so-called multi-joint type, a fixed portion 2 fixed to a floor or the like, a base portion 3 capable of turning (shown by an arrow A) around a vertical axis a at the upper portion thereof, First and second arm portions 4 and 5 are sequentially attached to the upper portion of the base portion 3. A wrist portion 6 is attached to the distal end portion 5 a of the second arm portion 5, and a chuck 8 (holding portion) is attached to the wrist portion 6 via a compliance device 7.

  That is, a pair of left and right support wall portions 3a is provided on the upper portion of the base portion 3, and the base end portion of the first arm portion 4 is supported so as to be rotatable around the horizontal axis b while being sandwiched between them. Has been. Thereby, the first arm portion 4 can be tilted up and down as indicated by an arrow B. The first arm portion 4 is composed of a pair of plate-like members extending from the left and right sides of the base end portion, and supports the base end portion of the second arm portion 5 so as to be rotatable about the axis c therebetween. . As a result, the second arm portion 5 can also be tilted in the vertical direction (arrow C).

  A bifurcated tip portion 5a is provided at the tip of the second arm portion 5 so as to be rotatable (arrow D) around an axis d in the longitudinal direction, and a columnar wrist portion 6 is interposed therebetween. It is supported so as to be rotatable (arrow E) around the axis e. A chuck 8 is attached via a compliance device 7 to the tip of the wrist 6, that is, the end closer to the left front in the figure. The chuck 8 can be rotated (arrow F) around the axis f by the operation of an electric motor built in the wrist 6 together with the compliance device 7, for example.

  In FIG. 1, reference numeral 9 denotes a work gripped (held) by the chuck 8, and a bolt is shown as an example. This bolt 9 is screwed into the screw hole 10a on the upper surface of the product 10 located below. In this example, the taper-shaped enlarged diameter part is formed in the upper end edge of the screw hole 10a.

-Composition of compliance device-
In this embodiment, the compliance device 7 is interposed between the chuck 8 of the robot 1 and the wrist portion 6 (support portion), and is held by the chuck 8 by allowing a positional shift therebetween. Absorbs misalignment of the workpiece (bolt 9). The structure will be described in detail below.

  As shown in an enlarged view in FIG. 2, the compliance device 7 of this embodiment includes one bracket 70 to which the chuck 8 is attached (positioned downward in the drawing, hereinafter referred to as a lower bracket), and the wrist 6 of the robot arm. The other bracket 71 (located in the upper part in the figure, hereinafter referred to as the upper bracket) is attached. In the illustrated example, both brackets 70 and 71 are substantially triangular plate members, and round holes 70a and 71a are opened in the center. A cable or the like for supplying electric power to the motor of the chuck 8 is inserted into the round holes 70a and 71a.

  In the illustrated example, the central circular hole 70a of the lower bracket 70 has a larger diameter than the circular hole 71a of the upper bracket 71, and a plurality of bolt holes 70b (four in the illustrated example) surround the same. Is formed. Although not shown, the chuck 8 is fastened to the lower portion of the lower bracket 70 by bolts inserted into these bolt holes 70b. Similarly, a plurality of bolt holes 71b are formed in the upper bracket 71 so as to surround the central circular hole 71a. In the example shown in the figure, eight bolt holes 71b are shown, but in six of them, bolts for fastening the upper bracket 71 to the wrist 6 of the robot 1 are inserted, and in the remaining two, A pin for positioning is inserted.

  The brackets 70 and 71 are connected to each other by three guide shafts 72 provided therebetween. Each guide shaft 72 has an upper end fixed to the upper bracket 71, and a lower end penetrating the lower bracket 70 to support the lower bracket 70 so as to be slidable up and down. In addition, a coil spring 73 (biasing means) is externally attached to each guide shaft 72, and a pressing force is applied to both the brackets 70 and 71 so as to be separated vertically.

  In FIG. 2, only two of the three guide shafts 72 and the coil springs 73 in the front of the figure are shown, and one guide shaft 72 and the coil springs 73 at the back of the figure are Hidden in the upper bracket 71. Further, for the convenience of explanation, the hidden portion of the guide shaft 72 on the right side in the figure is also indicated by a broken line, and the coil spring 73 externally attached to the guide shaft 72 is notched in the middle.

  Specifically, as shown in cross section in FIG. 3 (a), the brackets 70 and 71 are formed with through holes 70c and 71c, respectively, at three locations corresponding to the tops of the approximately triangular shapes. The end of the guide shaft 72 is inserted. In each of the upper and lower brackets 71 and 70, the three through holes 71c and 70c are formed at intervals of 120 degrees in the circumferential direction so as to surround the central circular holes 71a and 70a, and the three guide shafts 72 are mutually connected. They are arranged substantially in parallel and at equal intervals. In FIG. 3, only two guide shafts 72 appearing in the cross section of the lower bracket 70 are shown for convenience of explanation.

  As an example, the guide shaft 72 is a reamer bolt, and its shaft portion is press-fitted into the through hole 71 c of the upper bracket 71 to the root. The head of the reamer bolt located on the upper surface of the upper bracket 71 is pressed by a pressing plate 74 from above. The presser plate 74 has an approximately triangular outer shape that is the same as that of the upper bracket 71, and has a deformed ring shape by opening a large round hole 74a therein. The holding plate 74 is fastened to the upper bracket 71 by bolts 75 on both sides of the guide shaft 72.

  On the other hand, in this example, a flanged bush 76 is inserted into the through hole 70c of the lower bracket 70 from above, and the guide shaft 72 is slidably inserted into the cylindrical hole. The bush 76 is formed of a resin material in which lubricating oil is dispersed as an example, and has high slidability. The flange portion 76a of the bush 76 functions as a receiving seat that covers the peripheral edge of the through hole on the upper surface of the lower bracket 70 and receives the lower end of the coil spring 73 that contacts the upper surface.

  A male screw is formed at the lower end portion of the guide shaft 72 that protrudes downward through the bush 76, and a nut 77 is screwed into the male screw. The nut 77 is in contact with the peripheral edge of the through hole 70 c on the lower surface of the lower bracket 70 from below, and functions as a stopper that prevents the lower bracket 70 from falling off the guide shaft 72. That is, the lower bracket 70 is supported by the guide shaft 72 so as to be slidable (movable) up and down (approaching / separating from the upper bracket 71) as indicated by white arrows in FIG. The coil spring 73 is biased downward by a pressing force and is pressed against the nut 77.

  In this state, the shaft portion of the reamer bolt that constitutes the guide shaft 72 is located in the through hole 70c (cylinder hole of the bush 76) of the lower bracket 70. The diameter of this part is the same as the cylinder diameter of the bush 76. It is almost the same. There is no backlash between the two, and a gap is formed so that it can slide smoothly. In other words, in the vicinity of the lower end of the guide shaft 72 to which the nut 77 is screwed, for example, in the range of the thickness of the lower bracket 70, it is substantially the same as the through hole 70c of the lower bracket 70 (in this example, the cylindrical hole of the bush 76). The same diameter part 72a (same shape part) of the same diameter is provided.

  Therefore, the lower bracket 70 that is pressed against the lower nut 77 under the pressing force of the coil spring 73 as described above has a through hole 70c that matches the same diameter portion 72a of the guide shaft 72 via the bush 76. By doing so, it is positioned (positioning state). That is, the lower bracket 70 is positioned with respect to the upper bracket 71 via the guide shaft 72 and, consequently, with respect to the second arm portion 5 of the robot 1. Thereby, the bolt 9 held by the chuck 8 is positioned.

  The positioning accuracy is determined by the gap between the cylindrical hole of the bush 76 inserted into the through hole 70c of the lower bracket 70 and the same diameter portion 72a of the guide shaft 72. In this embodiment, the bush 76 has a high slidability. Therefore, the gap between the two can be set small. For example, the gap may be set to several millimeters at most from several hundred microns.

  Further, the guide shaft 72 of this embodiment is formed with a constricted portion 72b which is continuous with the upper portion of the same diameter portion 72a so as to have a relatively small diameter. Here, the lower bracket 70 is disposed in the horizontal direction ( It can also be displaced in the direction perpendicular to the guide shaft 72. That is, in the state where the lower bracket 70 is displaced upward as shown in FIG. 3B and the through hole 70c (bush 76) includes the constricted portion 72b of the guide shaft 72, for example, several millimeters therebetween. A gap of a certain degree is formed. At this time, the lower bracket 70 is in a floating state where it floats from the guide shaft 72.

  In the floating state, the lower bracket 70 can be displaced in the horizontal direction with respect to the guide shaft 72 as indicated by an arrow S in the drawing within the range of the gap between the constricted portion 72b and the through hole 70c (bush 76). Similarly, as shown by the arrow R, it can swing and be displaced obliquely. That is, a positional deviation between the upper and lower brackets 70 and 71 of the compliance device 7 in the horizontal direction and the horizontal axis is allowed, and thereby the positional deviation of the bolt 9 held by the chuck 8 is absorbed.

  In this embodiment, as an example, a predetermined range from the center to the tip side of the shaft portion of the reamer bolt is cut, and the outer diameter gradually changes in this range, and the constricted portion 72b is formed so that the diameter is reduced most in the center. Forming. In the example shown in the figure, the constricted portion 72b of the guide shaft 72 is substantially constant over the length of the tapered bracket portion where the outer diameter gradually decreases from the same diameter portion 72a upward and the thickness of the lower bracket 70. It consists of a portion that is kept at the minimum diameter, and a taper-shaped portion that gradually increases the outer diameter toward the top. Note that the length of the minimum diameter portion may be larger than the thickness of the lower bracket 70.

  Thus, since the outer diameter gradually changes from the same diameter portion 72a of the guide shaft 72 to the smallest diameter portion of the constricted portion 72b, the lower bracket between the positioning state in the same diameter portion 72a and the floating state in the constricted portion 72b. 70 can slide smoothly. That is, the compliance device 7 smoothly switches between the positioning state of the bolt 9 that is the workpiece and the state that absorbs the displacement.

  Note that the guide shaft 72 is formed by an original shaft portion of a reamer bolt above the constricted portion 72b. The original thickness of the shaft portion is set so that the gap between the coil spring 73 and the inner periphery of the winding is not so large that the coil spring 73 can be smoothly expanded and contracted. The shaft diameter of the reamer bolt and the inner diameter of the coil spring 73 may be set to be approximately the same so that the gap is further smaller than in the illustrated example.

-Operation of the compliance device-
Next, the operation of the compliance device 7 when the bolt 9 held by the chuck 8 of the robot 1 is screwed into the screw hole 10a of the product 10 will be described with reference to FIG. FIG. 4A schematically shows a case where the bolt is inserted into the screw hole, and FIG. 5B schematically shows a case where the bolt is screwed.

  First, as shown in FIG. 1, the bolt 9 gripped by the chuck 8 is positioned above the screw hole 10a of the product 10 by the arm of the robot 1. Thereafter, the chuck 8 is lowered by the operation of the arm of the robot 1. At this time, for example, the installation location of the product 10 is slightly shifted, and the position of the bolt 9 is shifted with respect to the screw hole 10 a opened on the upper surface. As schematically shown in FIG. 4 (a), the bolt 9 is displaced from the screw hole 10a in the horizontal direction (to the right in the example in the figure).

  Thus, the tip of the bolt 9 that is lowered while being displaced is brought into contact with the enlarged diameter portion at the upper end of the screw hole 10a and is guided closer to the axis of the screw hole 10a (left side in the figure). . At this time, as the robot arm descends, the bolt 9 receives an upward reaction force, so that the lower bracket 70 is pressed upward in the compliance device 7 and is displaced upward as shown in FIG. become. As a result, the displacement of the lower bracket 70 to the left side of the figure relative to the upper bracket 71 and the swinging to the left side are allowed.

  That is, the displacement of the bolt 9 with respect to the screw hole 10a is absorbed by the compliance device 7, and the bolt 9 is inserted into the screw hole 10a as shown in FIG. In this state, while lowering the arm of the robot 1 little by little, the compliance device 7 and the chuck 8 are rotated by the electric motor of the wrist portion 6 to screw the bolt 9 into the screw hole 10a. At this time, the bolt 9 receives a pressing force from the compliance device 7 and is appropriately pushed out and descends by a screw pitch every rotation. Therefore, it is not necessary to accurately correspond the speed at which the chuck 8 is lowered with the rotational speed of the bolt 9 only by the operation of the robot arm, and the robot arm may not be lowered in some cases.

  Next, the operation of the compliance device 7 when picking up the bolt 9 prior to screwing in the bolt 9 will be described with reference to FIG. FIG. 4A shows a state immediately before gripping (pickup) a bolt whose position is shifted, and FIG. 5B shows correction of the position shift due to a gripping operation.

  First, in order to pick up the bolt 9 placed at a predetermined position, the chuck 8 is moved closer to the bolt 9 from above by the operation of the arm of the robot 1. At this time, as shown in FIG. 5A, the chuck 8 is opened, and the bolt 9 is included in the range of the claw, but the position is shifted from the center of the chuck 8. Further, no external force is applied to the compliance device 7 in the vertical direction, and the compliance device 7 is in the positioning state shown in FIG.

  When the claw is moved to the center by the closing operation of the chuck 8 from here, the bolt 9 in contact therewith moves to the right side of the drawing as shown in FIG. 5B and is positioned at the center of the chuck 8. At this time, the compliance device 7 is in a positioning state, and a positional shift between the upper bracket 71 and the lower bracket 70 is not allowed. Therefore, the bolt 9 positioned at the center of the chuck 8 is attached to the wrist 6 of the robot 1. Located on the center line. That is, the displacement of the bolt 9 can be corrected and held at an appropriate position.

  As described above, in the robot 1 of this embodiment, the compliance device 7 is interposed between the wrist portion 6 of the arm and the chuck 8, and if it is in a positioning state, the workpiece (bolt 9) is appropriately attached. It can be positioned and held. On the other hand, when an external force is received due to the positional deviation of the workpiece, the compliance device 7 smoothly switches to the floating state and absorbs the positional deviation.

  Further, since the compliance device 7 can appropriately push the workpiece toward the object by the pressing force of the coil spring 73, for example, when the bolt 9 is screwed into the screw hole 10a, the operation of the arm of the robot 1 is as follows. It is only necessary to rotate the screw toward the screw hole 10a, or in addition to this, it is only necessary to roughly send it out, and it is not necessary to perform high-accuracy control that sends the bolt 9 accurately in synchronism with the rotation. That is, the control can be simplified.

  Further, the pressing force of the coil spring 73 for feeding out the workpiece can be easily changed simply by changing the specification of the coil spring 73. For example, the size and weight of the workpiece, the mutual relationship with the object, etc. By selecting the preferable specifications of the coil spring 73 according to the purpose and conditions of the work, such as the positional relationship and the required pressing force, the above-described effects can be obtained to the maximum.

  The compliance device 7 having such excellent performance and function has a simple structure including a pair of upper and lower brackets 70 and 71, a guide shaft 72, and a coil spring 73, and is advantageous for cost reduction. In particular, in this embodiment, the guide shaft 72 is constituted by a general-purpose reamer bolt, thereby further reducing the cost.

-Other embodiments-
The description of the above-described embodiment is merely an example, and does not limit the present invention, its application, or its use. For example, in the above-described embodiment, the compliance device 7 constitutes an urging unit that extrapolates the coil springs 73 to the three guide shafts 72 and applies a pressing force between the upper and lower brackets 70, 71. This is not a limitation.

  That is, the number of guide shafts 72 is not limited to three, and may be one or two. However, from the viewpoint of suppressing the inclination of the lower bracket 70 and the upper bracket, it is preferable to use three or more. If the three guide shafts 72 are arranged substantially in parallel with each other at regular intervals as in the above embodiment and the coil springs 73 having the same specifications are extrapolated to each of the three guide shafts 72, the lower bracket 70 is kept parallel to the upper bracket 71. Is advantageous.

  On the other hand, anisotropy may be given to the urging force, which is the sum of those spring forces, by using a coil spring having a different specification. For example, if the spring constant of one coil spring is made lower than that of the other coil springs, the lower bracket 70 tends to tilt toward the coil spring having a lower spring constant. You may adjust to the direction where the requirement of positioning accuracy of a work is loose.

  Alternatively, while the specifications of the plurality of coil springs are the same, the guide shaft layout for extrapolating them may be devised to obtain the same effect as described above. For example, the interval between the guide shafts may be widened in a direction where the positioning accuracy is strict and the interval may be narrowed in a direction where the requirement is loose.

  In the above-described embodiment, the guide shaft 72 is constituted by a general-purpose reamer bolt, and the stopper of the lower bracket 70 is constituted by a nut 77 screwed to this, but the guide shaft 72 is not limited to the reamer bolt, and its shape Also, the shape is not limited to a round bar shape, and may be, for example, a prism. In this case, the through hole 70c of the lower bracket 70 also has a cross-sectional shape corresponding to the outer shape of the guide shaft 72 instead of a circular cross section. In addition, although the external shape of the same shape part of the guide shaft 72 becomes the same as the through-hole 70c, the external shape of a constriction part may differ.

  Further, as a biasing means, for example, a large-diameter coil spring may be interposed between the brackets 70 and 71 concentrically with the round holes 70a and 70b, or between the upper and lower brackets 70 and 71. A leaf spring may be interposed. Alternatively, a rubber elastic body may be interposed between the brackets 70 and 71, or an air cylinder may be used.

  Moreover, you may use the spring member of a progressive characteristic from which a spring constant becomes high as an amount of bending increases as an urging | biasing means. For example, as shown in FIG. 6, when the long and short coil springs 78 and 79 are used as a set, the spring constant when only the longer coil spring 78 is compressed becomes lower, and the shorter coil spring is reduced. When 79 is compressed, the spring constant rises stepwise.

  Or although illustration is abbreviate | omitted, you may use the coil spring (progressive coil spring) of what is called uneven pitch in which the thickness and pitch of a winding change. In this case, the thickness of the winding of the coil spring may be made different, for example, by reducing the thickness at a narrow winding pitch.

  Further, although not shown, a damping means such as a viscous damper or a friction damper may be provided between the upper and lower brackets 70 and 71 so as to apply a damping force to the relative movement of both. Good. In this way, for example, even if the external force applied to the workpiece is suddenly reduced and the lower bracket 70 is pushed downward and collides with the nut 77, the impact is alleviated and does not become too great.

  Furthermore, the compliance device according to the present invention is not only interposed between the wrist 6 of the robot arm and the chuck 8 as in the above-described embodiment, but the robot 1 shown in FIG. You may interpose between the part 5 and the front-end | tip part 5a. Furthermore, the compliance device according to the present invention can be applied to various automatic assembly machines other than the robot arm.

  As described above, the compliance device according to the present invention can be reduced in cost with a simple structure, and can compensate for displacement while appropriately pushing a workpiece toward an object. It is suitable for use.

1 Robot 6 Arm wrist (support)
7 Compliance device 70 Lower bracket (one bracket)
71 Upper bracket (the other bracket)
72 Guide shaft (Reamer bolt)
72a Same diameter part (same shape part)
72b Constricted part 73 Coil spring (biasing means)
76 Bushing with flange 76a Flange 77 Nut (stopper)
8 Chuck (holding part)
9 bolts (work)

Claims (10)

A compliance device that is interposed between a holding portion that holds a workpiece and a support portion that supports the holding portion, and allows positional deviation between the two,
A pair of brackets respectively attached to the holding part and the support part;
A guide shaft that is provided between the brackets, pierced through one of the brackets, and movably supports the one bracket so as to approach / separate from the other bracket;
Biasing means for applying a biasing force to the brackets so as to be separated from each other,
A compliance device, wherein a constricted portion is provided on at least a part of the guide shaft, and the one bracket can be displaced in a direction perpendicular to the axis of the guide shaft in the constricted portion. One end of the guide shaft is provided with a stopper that abuts against the peripheral edge of the through hole of the one bracket and prevents the one bracket from falling off,
The compliance device according to claim 1, wherein the guide shaft is provided with an isomorphous portion having substantially the same outer shape as the through hole on the bracket side in the vicinity of the stopper portion.   The compliance device according to claim 2, wherein the constricted portion of the guide shaft is provided with a tapered portion whose outer shape gradually decreases from the same shape portion.   The compliance device according to any one of claims 1 to 3, further comprising a damping unit that applies a damping force to the movement of the one bracket. A coil spring is externally attached as an urging means to the guide shaft,
The bushing with a flange is inserted in the through hole of the one bracket, and one end of the coil spring is in contact with the flange. Compliance device.   The compliance device according to any one of claims 2 to 5, wherein the guide shaft is constituted by a bolt, and the stopper portion is constituted by a nut screwed to the bolt.   The compliance device according to claim 1, wherein the number of the guide shafts is three, and the guide shafts are arranged substantially in parallel with each other at substantially equal intervals.   The compliance device according to any one of claims 1 to 7, wherein the urging means includes a spring member, and the spring member has a spring constant that increases as the amount of bending thereof increases.   The compliance device according to claim 1, wherein the holding unit includes a chuck attached to a robot arm, and is disposed on at least a part of the robot arm.   The compliance device according to any one of claims 1 to 9 is disposed in at least a part of a robot arm to which a chuck for holding a workpiece is attached in order to allow a positional deviation in the front and rear thereof. The structure of a robot arm characterized by

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