JP4222918B2 - Industrial robot balancer mechanism and industrial robot having the balancer mechanism - Google Patents

Description

  The present invention relates to a balancer mechanism used for an articulated industrial robot, and more particularly, to a balancer mechanism of an industrial robot that has a reduced balancer mechanism and a long life of a coil spring, and an industrial robot having the balancer mechanism. About.

For example, in a vertical articulated industrial robot having an arm 3 tilting in the front-rear direction as shown in FIG. 6, the arm 3 tilting in the front-rear direction receives a load moment due to gravity. Although this load moment varies depending on the posture of the arm 3, particularly in an industrial robot having a load capacity exceeding 100 kg, the load moment becomes remarkably large depending on the posture of the arm 3. For this reason, many robots include a balancer mechanism 9 that cancels the load moment with the force of a spring such as a coil spring (for example, Patent Document 1). In such a conventional balancer mechanism 9, as disclosed in Patent Document 1, the coil spring disposed in the cylinder of the balancer mechanism 9 is moved by the forward / backward tilt of the arm 3 shown in FIG. The stroke will occur over almost the entire area of the cylinder.
JP-A-6-15593

  By the way, in recent years, it is necessary to further increase the spring force and stroke of the coil spring of the balancer mechanism as the industrial robot becomes larger and the operation range is expanded. As a result, the maximum stress, stress amplitude, and average stress generated in the coil spring increase, making it difficult to determine the specifications of the coil spring such as material, wire diameter, center diameter, and pitch so that the coil spring does not undergo fatigue failure. It is coming. This is a factor that reduces the life of the coil spring.

  The present invention has been made to solve the problems of the related art, and an object of the present invention is to provide a balancer mechanism for an industrial robot capable of extending the life of a coil spring used. Another object of the present invention is to provide an industrial robot having a balancer mechanism that can extend the life of a coil spring.

In order to achieve the above-described object, the present invention focuses on the following points. The industrial robot is driven and maintained by an actuator such as a motor as a power source. The balancer mechanism assists the power source when maintaining the posture. However, depending on the posture of the robot, a section where assistance by the balancer mechanism is unnecessary occurs. For example, FIG. 1 shows an example of a vertical articulated robot using a parallelogram link mechanism. However, the load moment becomes small in the vicinity of the arm 3 tilting forward and backward, so that the balancer mechanism does not need to be assisted. Become. On the other hand, the vicinity where the arm 3 is horizontal is a section where the coil spring of the balancer mechanism extends most. The present invention pays attention to this point, and the stopper 13 is provided so that the coil spring does not make a stroke in a section where the assistance of the balancer mechanism is unnecessary (for example, in the vicinity of the arm 3 being vertical).

That is, in the first aspect of the invention, the first end plate is fixed to one end surface of the cylinder portion, and the second end plate having a through hole in the central portion is fixed to the other end surface. Shaped spring case,
A rod having a step projecting in the outer peripheral direction at one end, the step being disposed in the hollow spring case, and a rod that can be inserted into a through hole provided in the second end plate; ,
A compression plate that has a through-hole through which a portion other than the step portion of the rod can be inserted in the center portion, and is movable between the step portion of the rod and the second end plate;
A coil spring interposed between the compression plate and the second end plate;
Have a, and a stopper that is adapted to regulate the operation of the compression plate to the first end plate side, the coil spring, a position where the stepped portion of the rod closest to said first end plate The stopper is located between the second end plate and the coil spring so as to be regulated below the stress amplitude of the coil spring so that the non-operating state is maintained from the first end plate to a position at a predetermined interval. A featured industrial robot balancer mechanism was provided.

  The effect | action by having set it as such a structure is as follows. A stopper that restricts the movement of the compression plate toward the first end plate is a predetermined distance between the position when the rod step is closest to the first end plate and the second end plate when the arm is tilted. It is provided in the position. On the other hand, since the coil spring is interposed between the compression plate and the second end plate, the compression plate always receives the spring force of the coil spring. The through hole provided in the compression plate is larger than the portion other than the step portion of the rod, but smaller than the step portion. Therefore, when the tilt of the arm is large, that is, when the position of the rod step is closer to the second end plate than the position of the stopper, the rod receives the spring force of the coil spring via the compression plate. The arm connected to the balancer mechanism is assisted by the balancer mechanism. On the other hand, when the tilt of the arm is small (near the arm is vertical), that is, when the position of the rod step is closer to the first end plate than the stopper, the compression plate is moved by the stopper to the first end plate. Since the movement to the side is restricted, the spring force of the coil spring is not biased to the rod, and as a result, the arm connected to the balancer mechanism is not assisted by the balancer mechanism. In such a balancer mechanism, the stroke of the coil spring is reduced due to the movement of the compression plate toward the first end plate side being restricted by the stopper, so that the stress amplitude of the coil spring is reduced. The life of the coil spring will be extended.

  By the way, the stopper described above may be provided in the spring case as long as it can stably regulate the movement of the compression plate toward the first end plate (Claim 2). It may be provided on the end plate (claim 4). In addition, when providing a stopper in a spring case, the stroke of a coil spring can be made variable according to a use form etc. by making the attachment position changeable (Claim 3).

  As the robot using the balancer mechanism described above, for example, as in the invention according to claim 5, a turning base placed so as to be turnable with respect to the base and an arm capable of being tilted with respect to the turning base And a balancer mechanism according to any one of claims 1 to 4, wherein one end of the spring case or the rod opposite to the stepped portion is connected to the turning base and the other Is connected to the arm. In the industrial robot having such a configuration, when the arm is tilted with respect to the turning base, if the arm needs to be assisted by the balancer mechanism, the arm is assisted by the balancer mechanism. If the tilt of the arm that does not need to be supported by the balancer mechanism is small, the arm is not supported by the balancer mechanism.

  According to the balancer mechanism of the industrial robot and the industrial robot having the balancer mechanism according to the present invention, the coil spring does not make a stroke in a section that does not require assistance by the balancer mechanism. As a result, the life of the coil spring was extended. In addition, by increasing the initial tension of the coil spring as much as the margin for the life of the coil spring, it becomes possible to further increase the balance force in the section where the balance force is required. The number of choices in increased.

  Furthermore, according to the balancer mechanism of the present invention, with respect to the spring case, the inner diameter of the spring case is larger than the stepped portion of the rod in the spring case where the coil spring does not stroke, that is, between the stopper and the first end plate. The balancer mechanism as a whole can be reduced in size and weight because it only needs to be slightly larger.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial view showing a vertical articulated industrial robot to which a balancer mechanism 9 according to an embodiment of the present invention is applied. In FIG. 1, a cross section of the balancer mechanism 9 is shown. Reference numeral 1 denotes a base fixedly mounted on the installation surface 0. Reference numeral 2 denotes a turning base supported on the base 1 so as to be turnable about an axis perpendicular to the installation surface 0. An arm 3 is pivotally supported so as to be tiltable forward and backward with respect to the turning base 2. The end 4 of the swivel base 2 is connected to one end of a rod 8 included in the balancer mechanism 9 on a shaft 5. The arm 3 is connected to a first end plate 17 of the balancer mechanism 9 on the shaft 15. Here, the shaft 5 and the shaft 15 described above are provided such that the distance between the two shafts is the shortest when the arm 3 is in a vertical posture as shown in FIG. Therefore, the assistance that the arm 3 receives by the balancer mechanism 9 is the smallest in the vertical posture of the arm 3, while it increases as the tilting of the arm 3 back and forth increases.

  3 is a cross-sectional view showing the internal structure of the balancer mechanism 9 according to an embodiment of the present invention. FIG. 3 (a) is a view from the front of the industrial robot shown in FIG. FIG. 2B is a cross-sectional view when viewing from the right side of the industrial robot shown in FIG. 1 (when viewing the paper in FIG. 1).

  The hollow cylindrical spring case 16 has a first end plate 17 fixed to one end surface of a cylinder portion and a second end plate 18 fixed to the other end surface. Among these, the second end plate 18 is provided with a through hole through which the rod 8 can be inserted at the center thereof. The first end plate 17 is pivotally supported by a shaft 15 fastened to a part of the arm 3 via a bearing 14. As a result, the balancer mechanism 9 including the first end plate 17 is rotatably connected to the arm 3. The first end plate 17 is detachably attached to the spring case 16 with a bolt or the like in order to perform maintenance work such as replacement of the coil spring 12.

  The rod 8 has a rod-like shape as a whole, and has a step portion 10 projecting in the outer peripheral direction at one end. The step portion 10 is disposed in a hollow cylindrical spring case 16 and other than the step portion 10. The portion can be inserted into the through hole provided in the central portion of the second end plate 18 described above. A knuckle 7 is fastened to an end portion of the rod-shaped rod 8 opposite to the step portion 10 described above. The knuckle 7 is pivotally supported on the shaft 5 provided at the end 4 of the turning base 2 via a bearing 6. Thereby, the balancer mechanism 9 including the rod 8 is connected to the turning base 2 so as to be rotatable.

  The compression plate 11 is provided in a hollow cylindrical spring case 16. The compression plate 11 has a substantially disk shape as a whole, and has a through hole through which a portion other than the step portion 10 of the rod 8 can be inserted. The through hole is sized such that the step portion 10 of the rod 8 cannot be inserted, and the compression plate 11 has a substantially disk-shaped outer diameter slightly smaller than the inner diameter of the hollow cylindrical spring case 16. Therefore, the compression plate 11 is movable between the step portion 10 of the rod 8 and the second end plate 18.

  The coil spring 12 is a spring having a coil shape, and is interposed between the compression plate 11 and the second end plate 18 in the spring case 16. The coil spring 12 urges the rod 8 to be pulled back to the spring case 16 when the rod 8 inserted through the through hole of the second end plate 18 is pulled out from the spring case 16.

  The stopper 13 is provided on the inner wall of the spring case 16, and the above-described compression plate 11 is interposed between the stopper 13 and the second end plate 18. The function of the stopper 13 is to stably regulate the movement of the compression plate 11 toward the first end plate 17 side. Therefore, as a form of the stopper 13, for example, any form such as a plurality of block-like members provided at the inner wall position that restricts the movement of the compression plate 11 in the spring case 16 may be used. The stopper 13 is provided at a predetermined position between the position when the step portion 10 of the rod 8 comes closest to the first end plate 17 side and the second end plate 18 when the arm 3 is tilted. Therefore, even if the compression plate 11 is moved to the first end plate 17 side in the spring case 16 by the urging of the coil spring 12, the compression plate 11 is further moved to the first end plate 17 side by the stopper 13. Movement to is restricted.

  Next, the operation of the balancer mechanism 9 when the arm 3 tilts will be described. Here, a case will be described in which the arm 3 tilts forward from the vertical posture shown in FIG. 1 (the arm 3 tilts to the left in FIG. 1) and then returns to the vertical position shown in FIG. The same applies to the case where the arm 3 tilts backward from the vertical posture shown in FIG. 1 (the arm 3 tilts to the right in FIG. 1) and then returns to the vertical position shown in FIG.

  As described above, the distance between the shaft 5 and the shaft 15 is the shortest when the arm 3 is in a vertical posture. When the arm 3 tilts forward from the vertical posture, the distance between the shaft 5 and the shaft 15 gradually increases, so that the step portion 10 of the rod 8 moves toward the second end plate 18 side, The compression plate 11 is gradually approached. When the arm 3 further tilts forward, the step portion 10 of the rod 8 comes into pressure contact with the compression plate 11. When the arm 3 is further tilted forward, the step portion 10 of the rod 8 and the compression plate 11 are integrally moved toward the second end plate 18, whereby the coil spring 12 is moved. Compress. The spring force that the rod 8 receives from the coil spring 12 at this time is the force that returns the arm 3 to the rear, that is, the vertical posture.

  On the other hand, when the arm 3 returns to the rear, that is, the vertical posture from the state where the arm 3 is largely inclined, the distance between the shaft 5 and the shaft 15 gradually decreases, so that the step portion 10 of the rod 8 and the compression plate 11 are The coil spring 12 is integrally moved toward the first end plate 17, and the coil spring 12 is thereby extended. Further, when the arm 3 returns to the rear, that is, the vertical posture, the compression plate 11 comes into pressure contact with the stopper 13. Then, when the arm 3 further returns to the rear, that is, vertical posture, the step portion 10 of the rod 8 moves toward the first end plate 17 side, but the compression plate 11 is operated by the stopper 13. Is blocked from moving to the first end plate 17 side, and therefore the coil spring 12 cannot extend any further.

Next, assistance that the arm 3 receives from the balancer mechanism 9 in this embodiment will be described. The stopper 13 for restricting the operation of the compression plate 11 toward the first end plate 17 is located at the position when the step portion 10 of the rod 8 comes closest to the first end plate 17 by the tilting of the arm 3 and the second end plate 17. It is provided at a predetermined position between the end plate 18. That is, the coil spring 12 has the stopper 13 so as to keep the inoperative state from the position where the step 10 of the rod 8 is closest to the first end plate 17 to the predetermined position between the second end plate 18 and the coil spring 12. Is provided so that the compression plate 11 is positioned between the second end plate 18 and below the stress amplitude of the coil spring. On the other hand, since the coil spring 12 is interposed between the compression plate 11 and the second end plate 18, the compression plate 11 always receives the spring force of the coil spring 12. The through hole provided in the compression plate 11 is larger than the portion other than the step portion 10 of the rod 8 but smaller than the step portion 10.

  Therefore, when the tilt of the arm 3 is large, that is, when the position of the step portion 10 of the rod 8 is closer to the second end plate 18 than the position of the stopper 13, the rod 8 is connected to the coil spring 12 via the compression plate 11. Since the spring force is received, the arm 3 connected to the balancer mechanism 9 receives the assistance of the balancer mechanism 9. On the other hand, when the tilt of the arm 3 is small (near the arm 3 becomes vertical), that is, when the position of the step portion 10 of the rod 8 is closer to the first end plate 17 than the position of the stopper 13, the compression plate 11 is Since the movement toward the first end plate 17 side is restricted by the stopper 13, the spring force of the coil spring 12 is not biased to the rod 8, and as a result, the arm 3 connected to the balancer mechanism 9 is moved to the balancer mechanism 9. Will not receive any assistance.

  In the balancer mechanism 9 having the above-described configuration and function, the stroke of the coil spring 12 is reduced because the stopper 13 restricts the operation of the compression plate 11 toward the first end plate 17. Therefore, the stress amplitude of the coil spring 12 is reduced, and as a result, the life of the coil spring 12 is extended. This point will be described in detail below.

  FIG. 6 is a partial view showing a vertical articulated industrial robot to which a balancer mechanism according to the prior art is applied. Since such a conventional balancer mechanism does not include a stopper like the balancer mechanism of the present embodiment, the coil spring 12 expands and contracts in accordance with the operation of the step portion 10 of the rod 8 for the entire stroke of the rod 8. . Here, the life of the coil spring will be considered for each balancer mechanism according to the related art and the present embodiment. FIG. 5 is a graph showing a life line of a coil spring (balancer spring). In FIG. 5, the horizontal axis represents the average stress, the vertical axis represents the stress amplitude, and the solid line represents the life line. Here, in a certain coil spring (spring), if the stress amplitude corresponding to the average stress in use is lower than the life line, there is a high possibility that the life defined by the specification of the coil spring can be achieved. On the other hand, if the stress amplitude corresponding to the average stress in use of a certain coil spring (spring) is above the life line, the life specified by the specification of the coil spring will not be completed and the life shorter than specified Is likely to be.

  In FIG. 5, springs 1 and 2 are obtained by plotting the stress amplitude corresponding to the average stress of the coil spring in the conventional balancer mechanism. On the other hand, the springs 3 and 4 are obtained by plotting the stress amplitude corresponding to the average stress of the coil spring in the balancer mechanism of the present embodiment. According to FIG. 5, it can be seen that the springs 1 and 2 according to the prior art are plotted almost on the life line, but the springs 3 and 4 according to the present embodiment are plotted below the life line. As described above, in the balancer mechanism according to the present embodiment, the average stress increases as compared with the prior art, but the stress amplitude decreases, and there is a margin for the life line. Accordingly, the life of the coil spring is longer in the balancer mechanism of the present embodiment than in the prior art.

  The embodiment of the present invention has been described above. In the embodiment described above, the balancer mechanism 9 interposed between the turning base 2 and the arm 3 is arranged on the side surface of the arm 3. However, the arrangement of the balancer mechanism 9 in the present invention is not limited to the above-described form. If the balancer mechanism 9 is interposed between the swivel base 2 and the arm 3, for example, the balancer mechanism 9 is placed on the swivel base as shown in FIG. 2 may be arranged. In FIG. 2, the balancer mechanism 9 is disposed on the turning base 2, and another balancer mechanism 9 ′ is disposed on the side surface of the arm 3. By arranging a plurality of balancer mechanisms in this way, it is possible to reduce the size of each balancer mechanism.

  FIG. 4 is a cross-sectional view showing the internal structure of the balancer mechanism 9 according to an embodiment of the present invention when the balancer mechanism 9 shown in FIG. 2 is arranged on the turning base 2. The rod 8 is connected to the swivel base 2 in the above-described embodiment, but is connected to the arm 3 in the form shown in FIGS. 2 and 4, and the two forms are different in this respect. However, since both forms are substantially the same in the configuration other than the above point, detailed description of the forms shown in FIGS. 2 and 4 is omitted.

  The embodiment of the present invention has been described above. Incidentally, as described above, the function of the stopper 13 in the present invention is to stably regulate the movement of the compression plate 11 toward the first end plate 17. Therefore, as long as it has this function, the form of the stopper 13 in the present invention is not limited to the plurality of block-like members provided on the inner wall of the spring case 16 described above.

  That is, as a form of the stopper 13 in the present invention, for example, an annular member provided so as to go around the inner wall at this position at the inner wall position that restricts the movement of the compression plate 11 in the spring case 16. Good. In these forms in which the stopper 13 is provided on the inner wall of the spring case 16, the mounting position thereof may be changeable. Specifically, the stopper 13 having the block shape or the annular shape described above is configured to be detachable from the spring case 16 by a fastening member such as a bolt. Then, holes (bolt holes or the like) in which the fastening members such as bolts described above can be attached are provided at several positions in the stroke direction of the rod 8 on the cylindrical side surface of the spring case 16. By adopting such a configuration, the stroke of the coil spring 12 interposed between the stopper 13 and the second end plate 18 can be made variable according to the usage pattern and the like.

  Further, the stopper 13 may not be provided on the inner wall of the spring case 16 but may be provided inside the first end plate 17. Specifically, for example, a plurality of projecting members having the same projecting length may be provided inside the first end plate 17 and the operation of the compression plate 11 may be regulated at the tip portions of these projecting members. In the case of such a configuration, a plurality of sets of projecting members having different projecting lengths are prepared, or a plurality of sets of first end plates 17 having projecting members are prepared, and the projecting members protrude for each set. By making the lengths different, the stroke of the coil spring 12 can be made variable as in the case of the above-described embodiment.

  According to the balancer mechanism of the industrial robot and the industrial robot having the balancer mechanism according to the present embodiment, the coil spring 12 does not stroke in a section where the balancer mechanism 9 does not require assistance. As a result, the life of the coil spring 12 is extended. Further, by increasing the initial tension of the coil spring 12 as much as the margin for the life of the coil spring 12, the balancer mechanism 9 can further increase the balance force in the section where the balance force is required. Options for designing the mechanism 9 were increased. Further, with respect to the spring case 16, the inner diameter of the spring case 16 is slightly larger than that of the step portion 10 of the rod 8 at a portion where the coil spring 12 does not stroke in the spring case 16, that is, between the stopper 13 and the first end plate 17. The balancer mechanism 9 can be reduced in size and weight because it only needs to be larger.

1 is a partial view showing a vertical articulated industrial robot to which a balancer mechanism 9 according to an embodiment of the present invention is applied. FIG. It is a block diagram of the industrial robot shown about the application example different from FIG. 1 in the balancer mechanism 9 which concerns on one Embodiment of this invention. It is sectional drawing which shows the internal structure of the balancer mechanism 9 which concerns on one Embodiment of this invention, (a) A figure is sectional drawing when it sees from the front of the industrial robot shown in FIG. 1, (b) The figure is a figure It is sectional drawing when it sees from the right side of the industrial robot shown in FIG. FIG. 3 is a cross-sectional view showing the internal structure of the balancer mechanism 9 according to an embodiment of the present invention when the balancer mechanism 9 shown in FIG. 2 is disposed on a turning base 2. It is a graph which shows the life line of a coil spring. FIG. 10 is a partial view showing a vertical articulated industrial robot to which a balancer mechanism according to the related art is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 0 Installation surface 1 Base 2 Turning base 3 Arm 4 End of turning base 5 Shaft 6 Bearing 7 Knuckle 8 Rod 9 Balancer mechanism 10 Rod 8 step 11 Compression plate 12 Coil spring 13 Stopper 14 Bearing 15 Shaft 16 Spring case 17 First end plate 18 Second end plate

Claims (5)

A hollow spring case in which a first end plate is fixed to one end surface of the cylinder portion and a second end plate having a through hole provided in the center portion is fixed to the other end surface;
A rod having a step projecting in the outer peripheral direction at one end, the step being disposed in the hollow spring case, and a rod that can be inserted into a through hole provided in the second end plate; ,
A compression plate that has a through-hole through which a portion other than the step portion of the rod can be inserted in the center portion, and is movable between the step portion of the rod and the second end plate;
A coil spring interposed between the compression plate and the second end plate;
Have a, and a stopper that is adapted to regulate the operation of the compression plate to the first end plate side, the coil spring, a position where the stepped portion of the rod closest to said first end plate The stopper is located between the second end plate and the coil spring so as to be regulated below the stress amplitude of the coil spring so that the non-operating state is maintained from the first end plate to a position at a predetermined interval. A featured industrial robot balancer mechanism.   The balancer mechanism for an industrial robot according to claim 1, wherein the stopper is provided on the spring case.   The balancer mechanism for an industrial robot according to claim 2, wherein the mounting position of the stopper according to claim 2 can be changed.   The balancer mechanism for an industrial robot according to claim 1, wherein the stopper according to claim 1 is provided on the first end plate. A swing base placed so as to be turnable with respect to a base, an arm made tiltable with respect to the turn base, and a balancer mechanism according to any one of claims 1 to 4,
An industrial robot having a balancer mechanism, wherein one end of the spring case or the rod opposite to the stepped portion is connected to the turning base and the other is connected to the arm. .

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