Direct drive device and robot

Abstract

The direct drive device (1) includes: a direct drive mechanism (2) having an elongated shaft member (5) and a connection member (6, 7) attached to the shaft member (5), at least one of the shaft member (5) and the connection member (6, 7) being movable along the length direction of the shaft member (5); and a rustproof member (3, 4) attached to the direct drive mechanism (2), the rustproof member (3, 4) containing a rustproof material having a higher ionization tendency than the material of the direct drive mechanism (2) and being electrically connected to the direct drive mechanism (2).

Description

Technical Field

[0001] This invention relates to a direct-acting device and a robot. Background Technology

[0002] Previously, ball screws were used for the lifting axes of horizontal multi-joint robots (for example, see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-228733 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] When the components of a ball screw rust, the screw shaft cannot move smoothly. This is especially true in the case of horizontal articulated robots, where the screw shaft is located on the outside of the arm cover; therefore, regular maintenance of the ball screw is necessary to prevent rusting. For example, rust inhibitors need to be applied to the ball screw frequently.

[0008] Solution for solving the problem

[0009] One aspect of this disclosure provides a direct-acting device comprising: a direct-acting mechanism having an elongated shaft member and a connecting member mounted on the shaft member, at least one of the shaft member and the connecting member being movable along the length direction of the shaft member; and a rust-preventing member mounted on the direct-acting mechanism, the rust-preventing member comprising a rust-preventing material having a higher ionization tendency than the material of the direct-acting mechanism, and being electrically connected to the direct-acting mechanism. Attached Figure Description

[0010] Figure 1 This is an external view of a robot implemented in one way.

[0011] Figure 2 It is shown Figure 1 A partial longitudinal sectional view of the robot's internal structure. Detailed Implementation

[0012] The following description, with reference to the accompanying drawings, will illustrate a direct-drive device and robot according to one embodiment.

[0013] like Figure 1As shown, robot 10 is a horizontal multi-joint robot, which has a ball screw device 1 with a ball screw shaft 5 serving as a lifting axis, acting as a direct-acting device. Robot 10 includes: a base 11 disposed on the surface to be lifted, a first arm 12 supported on the base 11, a second arm 13 supported on the first arm 12, and the ball screw device 1 disposed on the second arm 13. Reference numerals 18 and 19 are cables or conduits for supplying control signals and power to the servo motors 14, 15, 16, and 17 within robot 10.

[0014] One end of the first arm 12 is supported on the base 11 in a manner that allows it to rotate about a first vertical axis A. The first arm 12 is rotated relative to the base 11 by a servo motor 14 inside the base 11.

[0015] One end of the second arm 13 is supported on the other end of the first arm 12 in a manner that allows it to rotate about a second vertical axis B. The second arm 13 is rotated relative to the first arm 12 by a servo motor 15 inside the second arm 13.

[0016] The ball screw assembly 1 has a screw shaft 5 that extends vertically through the other end of the second arm 13 and is supported on the second arm 13 in a manner that allows it to move linearly along a third axis C in the vertical direction and to rotate about the third axis C. The third axis C is aligned with the major axis of the screw shaft 5.

[0017] The ball screw device 1 includes a ball screw 2 as a direct-acting mechanism and rust-proof components 3 and 4 installed on the ball screw 2.

[0018] like Figure 2 As shown, the ball screw 2 includes a long screw shaft (shaft member) 5, a ball screw nut (connecting member) 6 and a ball spline nut (connecting member) 7 mounted on and supporting the screw shaft 5, and bearings 8 and 9 supporting the nuts 6 and 7. The components 5, 6, 7, 8, and 9 of the ball screw 2 are formed of high-rigidity metal or alloy, and a rust inhibitor is applied to the surface of each component 5, 6, 7, 8, and 9.

[0019] Furthermore, the lead screw shaft 5 is a ball screw spline shaft, with a helical threaded groove (not shown) and a straight spline groove (not shown) extending along the length of the lead screw shaft 5 on its outer circumferential surface. The metal ball of the ball screw nut 6 engages with the helical groove, and the metal ball of the ball spline nut 7 engages with the spline groove. The ball screw nut 6 and the ball spline nut 7 are supported relative to the second arm 13 by bearings 8 and 9 in a manner that allows them to rotate about the third axis C.

[0020] The ball screw nut 6 is connected to the servo motor 16 via the pulley 20 and the belt 21. Rotation of the servo motor 16 is transmitted to the ball screw nut 6 through the belt 21 and the pulley 20, and the ball screw nut 6 rotates around the third axis C, so that the screw shaft 5 moves in the vertical direction along the third axis C.

[0021] The ball spline nut 7 is connected to the servo motor 17 via the pulley 22 and the belt 23. Rotation of the servo motor 17 is transmitted to the ball spline nut 7 through the belt 23 and the pulley 22, and the ball spline nut 7 rotates around the third axis C, so that the screw shaft 5 rotates around the third axis C. In Figure 2 In the example, the illustration of the servo motor 17 is omitted.

[0022] In addition, the ball screw 2 is provided with a stopper 3 fixed to the upper end portion of the screw shaft 5, and a stopper 4 fixed to the lower end portion of the screw shaft 5. The stoppers 3, 4 are members in a circular ring shape or a cylindrical shape fixed to the outer circumferential surface of the screw shaft 5. With the two stoppers 3, 4, the vertical direction movement of the screw shaft 5 with respect to the second arm 13 is mechanically limited within a predetermined movable range. Specifically, the upper stopper 3 abuts against a member provided to the arm cover 13a of the second arm 13 or the second arm 13, thereby limiting further lowering of the screw shaft 5. By making the lower stopper 4 abut against a member provided to the arm cover 13a or the second arm 13, further raising of the screw shaft 5 is limited. In Figure 2 In the example, the stopper 3 is configured to abut against the ball screw nut 6, and the stopper 4 is configured to abut against the ball spline nut 7.

[0023] The rust-preventing members are the stoppers 3, 4. The stoppers 3, 4 are formed of a metal or an alloy having high rigidity, directly contact the screw shaft 5, and are electrically connected to the respective members 5, 6, 7, 8, 9 of the ball screw 2. In addition, the stoppers 3, 4 contain a rust-preventing material having a higher ionization tendency than the material of the ball screw 2. The rust-preventing material is preferably a metal or an alloy having high strength in addition to a high ionization tendency. For example, the main material of the respective members 5, 6, 7, 8 of the ball screw 2 is iron, and the rust-preventing material of the stoppers 3, 4 is zinc or magnesium. The material of the stoppers 3, 4 is selected in accordance with the material of the ball screw 2.

[0024] In one example, the entire body of each of the stoppers 3, 4 is formed of the rust-preventing material.

[0025] In another example, each of the stoppers 3, 4 has a coating film of the rust-preventing material covering the surface of the stopper 3 or 4. The coating film is formed by surface treatment of the stopper 3, 4. When the stoppers 3, 4 have the coating film of the rust-preventing material, the material of the main body of the stopper 3, 4 can be any material normally used as a material of a stopper, such as aluminum or iron, etc.

[0026] Next, the functions of the ball screw device 1 and the robot 10 will be explained.

[0027] Robot 10 is sometimes configured in environments where cleaning fluid is splashed or exposed to water or water vapor. In particular, the lead screw 5 exposed on the outside of the arm cover 13a is easily exposed to water or water vapor.

[0028] According to this embodiment, the stoppers 3 and 4, which are fixed to the end of the lead screw shaft 5, contain rust-preventive materials with a higher ionization tendency than the material of the ball screw 2, and are electrically connected to the ball screw 2. Therefore, the stoppers 3 and 4 act as sacrificial anodes relative to the ball screw 2, preferentially oxidizing and rusting compared to the ball screw 2. This prevents rusting of the ball screw 2, especially the lead screw shaft 5, and maintains the effect of the rust inhibitor for a long time. Therefore, the application cycle of the rust inhibitor can be extended, and the time required to maintain the robot 10 can be reduced.

[0029] The lead screw shaft 5 is the exposed part outside the robot 10, and the stops 3 and 4 are installed on the exposed part. Thus, the stops 3 and 4 can effectively act as sacrificial anodes for the lead screw shaft 5, effectively preventing the lead screw shaft 5 from rusting.

[0030] Furthermore, the stoppers 3 and 4, located on the outer side of the arm cover 13a, are easier to replace and maintain compared to the components 6, 7, 8, and 9 of the ball screw 2 located on the inner side of the arm cover 13a. Therefore, by using the stoppers 3 and 4 as rust-preventing components, the maintenance required to maintain the rust-preventing effect can be made easier.

[0031] In this embodiment, the stoppers 3 and 4 also serve as rust-proof components, but instead, other components besides the stoppers 3 and 4 can also be rust-proof components.

[0032] In a variant, a rust-proof component, different from the stops 3 and 4, may be installed on the ball screw 2. To achieve a high rust-proof effect, the rust-proof component is preferably installed on the screw shaft 5 or the stops 3 and 4 that are exposed outside the robot 10.

[0033] In another variation, components of the ball screw 2 other than the stoppers 3 and 4 can also be rust-proof components. For example, a rust-proof coating can be used to cover the outer surface of a portion of the screw shaft 5 that is not inserted into the ball screw nut (connecting member) 6 and the ball spline nut (connecting member) 7, thereby enabling a portion of the screw shaft 5 to function as a rust-proof component.

[0034] In this embodiment, the lead screw shaft 5 is a ball screw spline shaft with both threaded grooves and spline grooves. However, it can also be a ball screw shaft with threaded grooves but without spline grooves. When the lead screw shaft 5 is a ball screw shaft, the ball spline nut 7 is not required.

[0035] In this embodiment, the robot 10 may also have a direct-acting mechanism other than the ball screw 2, and the shaft member having the direct-acting mechanism serves as a lifting shaft. In this case, rust-proof members 3 and 4 can be installed on the lifting shaft. Furthermore, an actuator for moving the lifting shaft up and down can also be connected to a connecting member. For example, it can be configured such that the actuator is the ball screw 2, the ball screw nut 6 is fixed to the lifting shaft via the connecting member, and the ball screw nut 6 and the lifting shaft move up and down together by rotating the screw shaft 5.

[0036] In this embodiment, robot 10 is a horizontal joint robot, but instead, robot 10 can be any other type of robot with a linear axis, and the axis member of the linear mechanism can be used as the linear axis.

[0037] In this embodiment, the ball screw assembly 1 is disposed on the robot 10, but the ball screw assembly 1 can also be disposed on any machine or device other than the robot. In particular, the ball screw assembly 1 is suitable for machine or device used in humid environments, and is even more suitable when at least a portion of the ball screw 2 is exposed outside the machine or device. For example, the ball screw assembly 1 can be used as a moving mechanism to move the worktable of a machine tool.

[0038] Depending on the machine or device using the ball screw device 1, the specific structure of the ball screw device 1 can be changed. For example, the screw shaft 5 can be a ball screw shaft, and the bearings 8 and 9 can directly support the screw shaft 5 instead of the nuts 6 and 7.

[0039] In this embodiment, the direct-acting device is the ball screw device 1, but it can also be any direct-acting device that includes a direct-acting mechanism other than the ball screw 2. For example, the direct-acting mechanism and device can be configured such that one of the shaft member and the connecting member is connected to a motor, and the shaft member and the connecting member move relative to each other in the longitudinal direction by the power of the motor. Alternatively, the direct-acting mechanism and device can also be configured such that the connecting member is fixed to the shaft member and connected to the motor, and the connecting member and the shaft member move integrally in the longitudinal direction by the power of the motor.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1. Ball screw assembly (direct-acting assembly)

[0042] 2. Ball screw (direct-acting mechanism)

[0043] 3, 4 Stopping parts, rust-proof components

[0044] 5. Lead screw shaft (shaft component)

[0045] 6. Ball screw nut (connecting component)

[0046] 7. Ball spline shaft nut (connecting component)

[0047] 8 and 9 bearings

[0048] 10. Robots (machinery, devices)

Claims

1. A direct acting device characterized by, Possessing: a linear motion mechanism having a long shaft member and a connecting member attached to the shaft member, at least one of the shaft member and the connecting member moving in a length direction of the shaft member; and a rust-preventing member attached to an end portion of the shaft member, the rust-preventing member containing a rust-preventing material having a higher ionization tendency than a material of the linear motion mechanism, and being electrically connected to the linear motion mechanism.

2. The linear motion device according to claim 1, wherein the linear motion mechanism has a lead screw shaft as the shaft member and a ball screw nut as the connecting member, the shaft member and the ball screw nut being a ball screw in which the shaft member and the ball screw nut relatively move in the length direction.

3. The linear motion device according to claim 1 or 2, wherein the rust-preventing member is formed of the rust-preventing material.

4. The linear motion device according to claim 1 or 2, wherein the rust-preventing member has a film of the rust-preventing material covering a surface of the rust-preventing member.

5. The linear motion device according to claim 1 or 2, wherein the rust-preventing member is a stopper fixed to an end portion of the shaft member.

6. The linear motion device according to claim 1 or 2, wherein at least a portion of the linear motion mechanism is an exposed portion exposed to an outside of a machine or a device in which the linear motion mechanism is mounted, the rust-preventing member is attached to the exposed portion.

7. A robot, comprising: the robot comprising the linear motion device according to any one of claims 1 to 6.

8. The robot according to claim 7, wherein the robot is a horizontal multi-joint robot comprising the shaft member as a lifting shaft. ​

Images