JP2011194522A - Gravity compensation mechanism of robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a movable space for a pneumatic cylinder that compensates gravity.SOLUTION: A gravity compensation mechanism includes a sealed cylindrical body 13 housing a shaft 5 provided movably in the vertical direction. The sealed cylindrical body 13 is equipped with an air supply and exhaust part 28 supplying/exhausting air to/from the inside of the sealed cylindrical body 13. Accordingly, the shaft 5 and the sealed cylindrical body (cylinder body) 13 are integrated, obviating the need for movable space for the pneumatic cylinder that has been separately provided to compensate gravity, which reduces the movable space for the pneumatic cylinder.

Description

  The present invention relates to a gravity compensation mechanism for a robot that performs gravity compensation of a shaft provided at the tip of an arm so as to be movable in the vertical direction.

  In a SCARA robot (horizontal 4-axis robot), a shaft is provided at the tip of an arm so as to be movable in the vertical direction and to be rotatable. In the vicinity of the shaft on the upper surface of the tip of the arm, an air cylinder is provided upwardly to perform gravity compensation for the vertical movement of the shaft. An example of a robot provided with an air cylinder for gravity compensation is described in Patent Document 1.

Japanese Patent Laid-Open No. 7-60663

  In the case of the above conventional configuration, since the air cylinder protrudes upward from the upper surface of the arm, an air cylinder movable space is required separately from the arm movable space. Since the shaft can move in the vertical direction, the shaft movable space can be reduced if the shaft is used in a state of being moved downward.

  In recent years, robots have been required to be miniaturized, which is not only to reduce the robot body size, but also to reduce the movable space for extra members that are not directly involved in work as much as possible.

  Accordingly, an object of the present invention is to provide a gravity compensation mechanism for a robot that can reduce the movable space for an air cylinder that performs gravity compensation.

  According to the first aspect of the present invention, the airtight exhaust cylinder for supplying and exhausting air into the airtight cylinder is provided in the airtight cylinder, which includes the airtight cylinder that houses the shaft that is movable in the vertical direction. The shaft is provided at the end opposite to the end of the shaft to which the hand is attached, and is formed so as to follow an outer diameter smaller than the outer diameter of the shaft, followed by the outer diameter of the joint. Since the shaft end portion is composed of a disk-shaped portion having an outer diameter equal to or larger than the dimensions, the shaft and the sealed cylinder (air cylinder) are integrated, and gravity compensation that has been provided separately is provided. Since the air cylinder movable space to be performed can be eliminated, the air cylinder movable space can be reduced.

  According to the invention of claim 2, the sliding resistance when the seal member at the lower part of the disk-shaped portion of the shaft end portion slides with respect to the inner peripheral portion of the innermost tube is adjacent to the plurality of tubes. Since it is configured to be smaller than the sliding resistance of the seal member at the point of engagement with the cylinder, when the shaft rises, only the shaft rises at first and the plurality of cylinders do not move. Then, when the shaft rises to a position where the sealing member for contact with the disk-shaped portion of the shaft end portion comes into contact with the upper end side where the inner diameter of the inner peripheral portion of the innermost cylinder is small, the shaft rises thereafter. Along with this, the innermost cylinder starts to rise, and then the outer cylinder of the innermost cylinder also rises sequentially.

  On the other hand, when the shaft is lowered, the sliding resistance between the seal member for contact with the disk-shaped portion of the shaft end portion and the upper end side where the inner diameter of the innermost cylinder is small is the resistance of each cylinder. Since it is configured to be larger than the sliding resistance of the seal member, each cylinder first descends, and the relative position between the shaft and the innermost cylinder does not change. Then, after the plurality of cylinders descend to the limit, the shaft begins to descend so as to change the relative position with the innermost cylinder for the first time.

  Therefore, when the shaft moves up, the plurality of tubes do not move up to the above position. Also, when the shaft descends, multiple cylinders will descend from the beginning, so the height of the sealed cylinder will always be the minimum required, and the extra movable space can be further reduced. it can.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention, in which (a) is a perspective view of a SCARA robot showing a state where an air cylinder is most extended, and (B) is a perspective view of a SCARA robot showing a state where an air cylinder is most contracted. Longitudinal section with the air cylinder retracted most and the shaft lowered most Longitudinal cross-sectional view of the air cylinder when it is most contracted and the shaft is raised to the upper limit where only the shaft is raised Longitudinal sectional view showing a state where the shaft and the innermost cylinder rise integrally Longitudinal section with the air cylinder extended the most and the shaft raised the most A longitudinal sectional view showing a state in which the shaft and the innermost peripheral cylinder are integrally lowered and a plurality of cylinders start to descend. A longitudinal sectional view showing a state where the shaft and the innermost cylinder are integrally lowered and the plurality of cylinders are being lowered.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. First, FIG. 1 is a diagram showing an external configuration of the SCARA robot of the present embodiment. As shown in FIG. 1, a main body 1 of a SCARA robot includes a base 2 fixed to an installation surface, a first arm 3 connected to an upper portion of the base 2 so as to be pivotable about a vertical axis J1, The second arm 4 is connected to the tip of the first arm 3 so as to be pivotable about the vertical axis J2, and the shaft 5 is provided at the tip of the second arm 4 so as to be vertically movable and rotatable. It is configured. A hand such as a clamp for gripping a workpiece (not shown) is detachably attached to the lower end of the shaft 5.

  A rack 6 for driving and moving the shaft 5 is provided at a portion adjacent to the shaft 5 at the tip of the second arm 4 so as to be movable in the vertical direction integrally with the shaft 5. The rack 6 is configured to be driven to move in the vertical direction by meshing with a pinion gear (not shown) that is rotationally driven by a motor (not shown) disposed inside the second arm 4.

  An air cylinder 7 that performs gravity compensation of the vertical movement of the shaft 5 is disposed at a portion corresponding to the shaft 5 in the upper surface portion of the distal end portion of the second arm 4. As shown in FIGS. 1A and 1B, the air cylinder 7 is a telescopic air cylinder having a structure that expands and contracts in the vertical direction, that is, a telescopic structure. Hereinafter, specific configurations of the air cylinder 7 and the shaft 5 will be described with reference to FIGS.

  First, the arrangement structure of the shaft 5 will be described. As shown in FIG. 2, two upper and lower annular shaft housings 8 (only one shaft housing 8 on the upper side is shown) are screwed to the upper and lower surfaces of the second arm 4. A shaft support cylinder 9 is rotatably supported by these shaft housings 8 via bearings 10. The shaft support cylinder 9 is rotationally driven by a motor (not shown) disposed in the second arm 4.

  The shaft 5 is supported in the shaft support cylinder 9 so as to be movable in the up-down direction in a non-rotating state. The shaft 5 is provided so as to move up and down integrally with the rack 6 (see FIG. 1), and is driven to move up and down via the pinion gear and the rack 6 by a motor inside the second arm 4. .

  The upper end, which is one end of the shaft 5, has a coupling part 11a whose outer dimension is smaller than the main body part of the shaft 5, and a disc provided so as to follow the coupling part 11a and whose outer dimension is slightly larger than the main body part. A shaft end portion 11 composed of the shape portion 11b is formed.

  A cylinder body (sealed container) 13 is fixed to the upper portion of the shaft housing 8 on the upper side by, for example, screwing so as to cover the upper end portion of the shaft support tube 9. The cylinder body 13 is composed of a telescopic telescopic cylinder that can be expanded and contracted in the vertical direction, and has a function of accommodating the rising shaft 5 (see FIG. 5).

  Specifically, the cylinder body 13 includes a plurality of, for example, three cylinders, specifically, a cylindrical fixed cylinder 14, and is provided in the fixed cylinder 14 so as to be movable in the vertical direction. The intermediate cylinder 15 includes a small-diameter intermediate cylinder 15, and an innermost cylinder 16 provided in the intermediate cylinder 15 so as to be movable in the vertical direction and having a slightly smaller diameter than the intermediate cylinder 15. A large-diameter housing portion 17 is formed at the lower end portion of the fixed cylinder 14, and the housing portion 17 is fixed to the upper portion of the shaft housing 8. A space between the inner peripheral portion of the housing portion 17 and the outer peripheral portion of the shaft support tube 9 is sealed (sealed) by a sealing member 18 made of an elastic member.

  Between the inner peripheral part of the fixed cylinder 14 and the outer peripheral part of the intermediate cylinder 15, seal members 19 and 20 made of an elastic member are disposed, and the intermediate cylinder 15 can be moved up and down by these seal members 19 and 20. Is sealed. The seal member 19 is provided at the upper end portion of the inner peripheral portion of the fixed cylinder 14. The seal member 20 is provided at the lower end portion of the outer peripheral portion of the intermediate cylinder 15. When the intermediate cylinder 15 moves up and down, the seal member 19 slides on the outer periphery of the intermediate cylinder 15, and the seal member 20 slides on the inner periphery of the fixed cylinder 14.

  Seal members 21 and 22 made of an elastic member are disposed between the inner peripheral part of the intermediate cylinder 15 and the outer peripheral part of the innermost peripheral cylinder 16, and the innermost peripheral cylinder 16 is provided by these seal members 21 and 22. Is sealed so that it can move up and down. The seal member 21 is provided at the upper end portion of the inner peripheral portion of the intermediate cylinder 15. The seal member 22 is provided at the lower end of the outer peripheral portion of the innermost peripheral cylinder 16. When the innermost peripheral cylinder 16 moves up and down, the seal member 21 slides on the outer peripheral part of the innermost peripheral cylinder 16, and the seal member 22 slides on the inner peripheral part of the intermediate cylinder 15.

  A seal member 23 made of an elastic member is disposed between the inner peripheral portion of the innermost peripheral cylinder 16 and the outer peripheral portion of the disc-like portion 11 b of the shaft end portion 11 of the shaft 5. Thus, the shaft end portion 11 is sealed so as to be movable up and down. The seal member 23 is provided at the lower end portion of the outer peripheral portion of the disc-like portion 11 b of the shaft end portion 11. When the shaft 5 (shaft end portion 11) moves up and down, the seal member 23 slides on the inner peripheral portion of the innermost peripheral cylinder 16.

  At the upper end portion of the inner peripheral portion of the innermost peripheral cylinder 16, an inclined surface portion 24 whose inner diameter dimension is gradually reduced is formed. A seal member 25 made of an elastic member that comes into contact with the inclined surface portion 24 is provided at the upper end portion of the outer peripheral portion of the disc-like portion 11b of the shaft end portion 11 (see FIG. 3). In this case, when the shaft 5 is raised, as shown in FIG. 3, the seal member 25 comes into contact with and comes into close contact with the inclined surface portion 24 at the upper end portion of the inner peripheral portion of the innermost peripheral tube 16.

  Further, the upper end portion of the innermost peripheral cylinder 16 is closed by a closing portion 26. For example, four vent holes 16a are formed at the upper end portion of the innermost peripheral cylinder 16, and a filter 27 for removing dust, oil and the like is provided in each vent hole 16a.

  Further, an air supply / exhaust connection pipe (air supply / exhaust section) 28 is connected to the housing portion 17 at the lower end of the fixed cylinder 14, and an air hose or air pipe (not shown) is connected to the air supply / exhaust connection pipe 28. Is connected. In this case, the air supply device (not shown) is configured to be able to supply air into the fixed cylinder 14 (and thus into the cylinder body 13) via the air hose and the air supply / exhaust connection pipe 28. Further, an air exhaust device (not shown) is configured to be able to exhaust the air in the fixed cylinder 14 (and thus in the cylinder body 13) through the air hose and the air supply / exhaust connecting pipe 28. Note that the air supply amount (supply pressure) and the air exhaust amount (exhaust pressure) can be controlled by a control device (not shown).

  Next, operations of the shaft 5 and the air cylinder 7 configured as described above will be described with reference to FIGS. First, the state shown in FIG. 2 is a state where the shaft 5 is lowered to the lower limit position. In this state, the rack 6 is raised, and the shaft 5 is raised by supplying air into the cylinder body 13 via the air supply / exhaust connection pipe 28. In this case, since the sliding resistance between the seal member 23 and the inner peripheral portion of the innermost peripheral cylinder 16 is set to be small, the innermost peripheral cylinder 16 does not rise, and only the shaft 5 rises.

  Thereafter, as shown in FIG. 3, when the shaft end portion 12 (the seal member 25) of the shaft 5 comes into contact with the inclined surface portion 24 at the upper end portion of the inner peripheral portion of the innermost peripheral cylinder 16, thereafter, As shown in FIG. 4, the shaft 5 and the innermost cylinder 16 are integrally raised by the lifting force of the rack 6 and the pressure of the air supplied from the air supply / exhaust pipe 28. In this case, the sliding resistance between the seal member 22 and the inner peripheral part of the intermediate cylinder 15 and the sliding resistance between the seal member 21 and the outer peripheral part of the innermost peripheral cylinder 16 are set small, and the intermediate cylinder 15 is raised. Without doing so, the shaft 5 and the innermost cylinder 16 are raised.

  When the shaft 5 and the innermost peripheral cylinder 16 are moved up to a position where the seal member 22 at the lower end of the innermost peripheral cylinder 16 comes into contact with the seal member 21 at the upper end of the intermediate cylinder 15, thereafter, the rack 6 Due to the ascending force and the pressure of the air supplied from the air supply exhaust pipe 28, the shaft 5, the innermost peripheral cylinder 16 and the intermediate cylinder 15 are integrally raised. In this case, the sliding resistance between the seal member 20 and the inner peripheral part of the fixed cylinder 14 and the sliding resistance between the seal member 19 and the outer peripheral part of the intermediate cylinder 15 are set to be small. 16 and the intermediate cylinder 15 rise. Then, the shaft 5 (as a result, the innermost cylinder 16 and the intermediate cylinder 15) can be raised to the upper limit position shown in FIG.

  Next, the operation of lowering the shaft 5 from the upper limit position shown in FIG. 5 will be described. In the state shown in FIG. 5, the shaft 5 and the innermost peripheral cylinder 16 are integrally lowered by the descending force of the rack 6 and the exhaust pressure of the air exhausted through the air supply exhaust pipe 28. In this case, the sliding resistance between the seal member 22 and the inner peripheral portion of the intermediate cylinder 15 and the sliding resistance between the seal member 21 and the outer peripheral portion of the innermost peripheral cylinder 16 are set small, and the shaft 5 When the seal member 25 of the shaft end portion 11 comes into contact with and presses the inclined surface portion 24 at the upper end portion of the inner peripheral portion of the innermost peripheral cylinder 16, the adhesion force that the seal member 25 is in close contact with the inclined surface portion 24 is It is set stronger than the sliding resistance. For this reason, as shown in FIG. 6, the seal member 25 of the shaft end portion 11 of the shaft 5 is lowered while being in close contact with the inclined surface portion 24 at the upper end portion of the inner peripheral portion of the innermost peripheral cylinder 16, that is, the shaft 5 and the innermost peripheral cylinder 16 are integrally lowered, and the innermost peripheral cylinder 16 (and the shaft 5) is lowered in the intermediate cylinder 15. At this time, the intermediate cylinder 15 is also slightly lowered in the fixed cylinder 14.

  Thereafter, as shown in FIG. 7, when the shaft 5 and the innermost peripheral cylinder 16 are further lowered integrally, and the flange portion at the upper end of the innermost peripheral cylinder 16 contacts the upper end of the intermediate cylinder 15, the shaft 5 The innermost cylinder 16 and the intermediate cylinder 15 begin to descend integrally. In this case, the sliding resistance between the seal member 20 and the inner peripheral part of the fixed cylinder 14 and the sliding resistance between the seal member 19 and the outer peripheral part of the intermediate cylinder 15 are set small, and the shaft end of the shaft 5 is also set. The contact force at which the seal member 25 of the portion 11 is in close contact with the inclined surface portion 24 at the upper end of the inner peripheral portion of the innermost peripheral cylinder 16 is set to be stronger than the above sliding resistances. For this reason, as shown in FIG. 7, the seal member 25 of the shaft end portion 11 of the shaft 5 is lowered while being in close contact with the inclined surface portion 24 at the upper end portion of the inner peripheral portion of the innermost peripheral cylinder 16, that is, the shaft 5. The innermost cylinder 16 and the intermediate cylinder 15 are integrally lowered in the fixed cylinder 14.

  When the shaft 5, the innermost peripheral cylinder 16 and the intermediate cylinder 15 are further lowered, the lower end of the intermediate cylinder 15 comes into contact with the ring portion 14a projecting from the lower portion of the fixed cylinder 14 (see FIG. 3). The shaft 5 starts to descend in the innermost cylinder 16. Thereafter, when the shaft 5 is lowered to the lower limit position, the state shown in FIG. 2 is obtained.

  According to the present embodiment having such a configuration, the shaft 5 is accommodated in the cylinder body 13 of the air cylinder 7 so that the shaft 5 can be moved in the vertical direction. The moving space can be made unnecessary, and the moving space can be made smaller accordingly. In this embodiment, since the cylinder body 13 has a telescopic structure, that is, a structure that can be expanded and contracted, when the cylinder body 13 is contracted, the projecting dimension of the cylinder body 13 is reduced to about 1/3. Therefore, the moving space for the air cylinder 7 can be further reduced in size.

  In the above embodiment, the sliding resistance when the seal member 23 below the disc-like portion 11b of the shaft end portion 11 slides with respect to the inner peripheral portion of the innermost peripheral tube 16 is a plurality of tubes. 14, 15, 16 is configured to be smaller than the sliding resistance of the seal members 19, 20, 21, 22 at the point of engagement with the adjacent cylinder, so when the shaft 5 rises, the shaft 5 is initially Only the cylinders 15 and 16 do not move. Then, the shaft 5 rises to a position where the seal member 25 at the upper part of the disk-like portion 11b of the shaft end portion 11 comes into contact with the inclined surface portion 24 on the upper end side where the inner diameter of the innermost peripheral tube 16 is small. Then, as the shaft 5 is raised thereafter, the innermost cylinder 16 starts to rise, and thereafter, the intermediate cylinder 15 outside the innermost cylinder 16 also rises sequentially.

  On the contrary, in the above embodiment, when the shaft 5 is lowered, the seal member 25 at the upper part of the disk-like part 11b of the shaft end part 11 and the inner diameter dimension of the inner peripheral part of the innermost peripheral cylinder 16 are small. Since the contact force (sliding resistance) with the inclined surface portion 24 is configured to be larger than the sliding resistance of the seal members 19, 20, 21, and 22 of the respective cylinders 14, 15, and 16, initially, The cylinders 15 and 16 are lowered, and the relative positions of the shaft 5 and the innermost cylinder 16 are not changed. Then, after the plurality of cylinders 1516 are lowered to the limit, the shaft 5 starts to descend so as to change the relative position with respect to the innermost circumferential cylinder 16 for the first time.

  Therefore, in the said embodiment, when the shaft 5 raises, the some cylinders 15 and 16 do not raise to the said position (refer FIG. 3). Further, when the shaft 5 is lowered, the plurality of cylinders 15 and 16 are lowered from the beginning, so that the height of the cylinder body (sealed cylinder) 13 is always the minimum necessary, and extra movable. The space for use can be further reduced.

  The cylinder body 13 is composed of the three-stage cylinders 14, 15, and 16. However, the present invention is not limited to this, and the cylinder body 13 may be composed of one-stage cylinder, two-stage cylinders, or four-stage cylinders or more. good. In addition, when the cylinder body 13 is configured with a single-stage cylinder, the cylinder body does not expand and contract, but since the shaft 5 is accommodated in the cylinder body, a separate movable space dedicated to the cylinder body is not required. Compared to the conventional configuration, the movable space for the air cylinder can be reduced.

  In the drawings, 1 is a main body, 3 is a first arm, 4 is a second arm, 5 is a shaft, 7 is an air cylinder, 8 is a shaft housing, 9 is a shaft support tube, 11a is a coupling portion, and 11b is a disk-shaped portion. , 11 is a shaft end portion, 13 is a cylinder body (sealed cylinder), 14 is a fixed cylinder, 15 is an intermediate cylinder, 16 is an innermost cylinder, 18 is a seal member, 19 is a seal member, 20 is a seal member, 21 Is a seal member, 22 is a seal member, 23 is a seal member, 24 is an inclined surface portion, 25 is a seal member, and 28 is an air supply / exhaust connection pipe.

Claims (2)

A SCARA robot arm,
A shaft provided at the tip of the arm so as to be movable in the vertical direction;
A sealed cylinder that is provided on the top surface of the tip of the arm and houses the shaft;
An air supply / exhaust unit provided in the sealed cylinder, for supplying and exhausting air into the sealed cylinder;
Of the shaft, provided at the end opposite to the end to which the hand is attached, an outer diameter coupling portion smaller than the outer diameter size of the shaft, followed by an outer diameter size of the coupling portion. A gravity compensation mechanism for a robot, comprising: a shaft end portion composed of a disk-like portion having an outer diameter equal to or larger than the outer diameter. The inner diameter dimension of the uppermost side of the innermost cylinder among the plurality of cylinders is configured to be smaller than the inner diameter dimension of the lower end side of the cylinder,
The plurality of cylinders have a sealing member made of an elastic member at an engagement point with an adjacent cylinder, and are configured to be movable by sliding the sealing member,
A seal member made of an elastic member is provided at an engagement point with an inner peripheral portion of the innermost cylinder at a lower portion of the outer peripheral portion of the disc-shaped portion of the shaft end portion, and the shaft slides when the seal member slides. The disc-shaped part of the end part is configured to be movable with respect to the innermost cylinder,
A contact sealing member made of an elastic member is provided at a contact point with an upper end side having a small inner diameter of the inner peripheral portion of the innermost cylinder in an upper portion of an outer peripheral portion of the disc-shaped portion of the shaft end portion; When the shaft is moved upward and the sealing member for contact comes into contact with the upper end side of the inner peripheral portion of the innermost cylinder, it is configured to always be in a close contact state,
The sliding resistance when the seal member at the lower part of the disk-shaped part of the shaft end part slides with respect to the inner peripheral part of the innermost cylinder is at an engagement point with an adjacent cylinder in the plurality of cylinders. It is configured to be smaller than the sliding resistance of a certain seal member,
The sliding resistance between the contact sealing member of the disk-shaped portion of the shaft end portion and the upper end side where the inner diameter of the innermost peripheral portion of the innermost cylinder is small is more than the sliding resistance of the sealing member of each cylinder. 2. The gravity compensation mechanism for a robot according to claim 1, wherein the gravity compensation mechanism is configured to be larger.

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