Robot arm and robot

Abstract

To provide a robot arm and a robot capable of suppressing deformation in a longitudinal direction.SOLUTION: A robot arm has a longitudinal shape and includes a first member having a positive linear expansion coefficient and a second member having a negative linear expansion coefficient, and the first member and the second member are arranged side by side in a longitudinal direction. The first member may be made of a metal material, and the second member may be made of carbon fiber reinforced plastic. When a length of the first member along the longitudinal direction is L1, a length of the second member along the longitudinal direction is L2, a linear expansion coefficient of the first member is C1, a linear expansion coefficient of the second member is C2, and a temperature change amount of the robot arm is Δ T, a relation of 0. 05mm ≥ (L1 * C1) Δ T + (L2 * C2) Δ T is satisfied.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a robot arm and a robot. [Background technology]

[0002] Patent Document 1 describes that the shape of the closed link mechanism of a robot arm is deformed due to thermal expansion, causing a change in the position of the hand connected to the tip of the robot arm (robot tip position), resulting in a decrease in the accuracy of the robot. Furthermore, in Patent Document 1, in order to solve the above problem, that is, to suppress positional deviation of the hand, the material of each link constituting the closed link mechanism is selected so that the closed link mechanism is deformed by thermal expansion while maintaining a similar shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2008 / 136292 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with the configuration of Patent Document 1, it is not possible to sufficiently prevent the position of the robot tip from shifting due to thermal expansion, and this is disadvantageous in situations where high-precision work is required. [Means for solving the problem]

[0005] The robot arm of the present invention has an elongated shape, a first member having a positive linear expansion coefficient; a second member having a negative linear expansion coefficient; The first member and the second member are arranged side by side in the longitudinal direction.

[0006] The robot of the present invention is a robot including a robot arm, The robot arm It has a longitudinal shape, a first member having a positive linear expansion coefficient; a second member having a negative linear expansion coefficient; The first member and the second member are arranged side by side in the longitudinal direction.

[0007] The robot of the present invention comprises: an object to be connected; an arm having a longitudinal shape and rotating about a rotation axis perpendicular to the longitudinal direction of the object to be connected; a connection portion located between the object to be connected and the arm, connecting the object to be connected and the arm, the connecting portion has a first member having a positive linear expansion coefficient, the arm has a second member having a negative linear expansion coefficient; The first member and the second member are arranged side by side in a direction along the rotation axis. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a robot according to a first embodiment. [Figure 2] FIG. 4 is a cross-sectional view of a connecting portion between the base and the first arm. [Figure 3] FIG. 4 is a cross-sectional view of a connecting portion between a first arm and a second arm. [Figure 4] FIG. 2 is a top view of the first arm. [Figure 5] FIG. 10 is a top view showing a modified example of the first arm. [Figure 6] FIG. 10 is a top view of a first arm of a robot according to a second embodiment. [Figure 7] FIG. 10 is a top view showing a modified example of the first arm. [Figure 8] FIG. 10 is a top view showing a modified example of the first arm. [Figure 9] FIG. 10 is a cross-sectional view of a connecting portion between a first arm and a second arm of a robot according to a third embodiment. [Figure 10] FIG. 2 is a cross-sectional view of a connecting portion between the base and the first arm of the robot. [Figure 11] FIG. 1 is a diagram showing a six-axis articulated robot. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A robot arm and a robot according to the present invention will be described in detail below based on the embodiments shown in the accompanying drawings.

[0010] FIG. 1 is a diagram showing a robot according to a first embodiment. FIG. 2 is a cross-sectional view of a connecting portion between a base and a first arm. FIG. 3 is a cross-sectional view of a connecting portion between a first arm and a second arm. FIG. 4 is a top view of the first arm. FIG. 5 is a top view showing a modified example of the first arm. Note that the up-down direction in FIG. 1 coincides with the vertical direction, and the upper side in FIG. 1 is also referred to as "upper" and the lower side as "lower."

[0011] 1 is a horizontally articulated robot, i.e., a SCARA robot. The robot 1 has a base 2 fixed to the floor or the like, a first arm 3 which is a robot arm rotatably connected to the base 2, a second arm 4 rotatably connected to the first arm 3, a work head 5 disposed on the second arm 4, and a duct 6 which connects the base 2 and the second arm 4.

[0012] The first arm 3 is connected at its base end to the base 2 and rotates around a first rotation axis J1 that is vertical to the base 2. The second arm 4 is connected at its base end to the first arm 3 and rotates around a second rotation axis J2 that is parallel to the first rotation axis J1 and relative to the first arm 3.

[0013] Duct 6 is a tubular member that directly connects base 2 and second arm 4 without passing through first arm 3. Although not shown, signal wiring, compressed air piping, and the like are drawn from base 2 into second arm 4 via duct 6. With this configuration, wiring and piping can be drawn from base 2 to second arm 4 without passing through first arm 3, making it easier to route wiring and piping. However, this is not limiting, and duct 6 may be omitted and wiring and piping may be drawn from base 2 to second arm 4 via first arm 3.

[0014] The work head 5 is disposed at the tip of the second arm 4. The work head 5 has a spline nut 51 and a ball screw nut 52 arranged coaxially in the vertical direction, and a spline shaft 53 inserted through the spline nut 51 and the ball screw nut 52. Although not shown, an end effector appropriate for the intended work is attached to the lower end of the spline shaft 53. In this work head 5, rotation of the spline nut 51 causes the spline shaft 53 to rotate about the third rotation axis J3 and move linearly (up and down) along the third rotation axis, rotation of the ball screw nut 52 causes the spline shaft 53 to move linearly along the third rotation axis J3, and rotation of both the spline nut 51 and the ball screw nut 52 causes the spline shaft 53 to rotate about the third rotation axis J3.

[0015] In the robot 1, a TCP (Tool Center Point) that serves as a reference point for position control of the robot 1 is set at the lower end of the spline shaft 53.

[0016] As shown in FIG. 2, the robot 1 includes a first arm drive mechanism 71 that connects the base 2 and the first arm 3 and rotates the first arm 3 about a first rotation axis J1 relative to the base 2. The first arm drive mechanism 71 includes a reducer 711 that connects the base 2 and the first arm 3 and a motor 712 connected to the input side of the reducer 711. The reducer 711 is a harmonic gear device, and a circular spline 711a is fixed to the base 2 and a flexspline 711b is fixed to the first arm 3. The output shaft of the motor 712 is fixed to a wave generator 711c. The motor 712 is located below the reducer 711 (inside the base 2) and is fixed to the base 2. The motor 712 is, for example, a servo motor, particularly a three-phase motor driven by three-phase AC.

[0017] In the first arm drive mechanism 71 configured as above, the wave generator 711c rotates together with the rotation of the motor 712, and further, the flexspline 711b rotates at a predetermined reduction ratio relative to the rotation of the wave generator 711c. As a result, the first arm 3 rotates about the first rotation axis J1 relative to the base 2. However, the configuration of the first arm drive mechanism 71 is not particularly limited.

[0018] As shown in FIG. 3 , the robot 1 also includes a second-arm drive mechanism 72 that connects the first arm 3 and the second arm 4 and rotates the second arm 4 about a second rotation axis J2 relative to the first arm 3. The second-arm drive mechanism 72 has a configuration similar to that of the first arm drive mechanism 71 and includes a reducer 721 that connects the first arm 3 and the second arm 4 and a motor 722 connected to the input side of the reducer 721. The reducer 721 is a harmonic gear device, and a circular spline 721a is fixed to the second arm 4 and a flexspline 721b is fixed to the first arm 3. The output shaft of the motor 722 is fixed to a wave generator 721c. The motor 722 is located above the reducer 721 (inside the second arm 4) and is fixed to the second arm 4. The motor 722 is, for example, a servomotor, particularly a three-phase motor driven by three-phase AC.

[0019] In the second arm drive mechanism 72 configured as above, the wave generator 721c rotates together with the rotation of the motor 722, and the flexspline 721b rotates at a predetermined reduction ratio relative to the rotation of the wave generator 721c. As a result, the second arm 4 rotates about the second rotation axis J2 relative to the first arm 3. However, the configuration of the second arm drive mechanism 72 is not particularly limited.

[0020] As shown in FIG. 3, the robot 1 also has a first spline shaft drive mechanism 73 that rotates the spline nut 51 to rotate and linearly move the spline shaft 53, and a second spline shaft drive mechanism 74 that rotates the ball screw nut 52 to linearly move the spline shaft 53.

[0021] The first spline shaft drive mechanism 73 has a motor 732 arranged inside the second arm 4 and a speed reduction mechanism 731 that transmits the rotation of the motor 732 to the spline nut 51. The speed reduction mechanism 731 has a first pulley 731a fixed to the output shaft of the motor 732, a second pulley 731b fixed to the spline nut 51, and a belt 731c that is wound around the first pulley 731a and the second pulley 731b. The motor 732 is a servo motor, particularly a three-phase motor that is driven by three-phase AC, and is fixed to the second arm 4.

[0022] In the first spline shaft drive mechanism 73 configured as described above, the rotation of the motor 732 is transmitted to the second pulley 731b via the first pulley 731a and the belt 731c, and the second pulley 731b rotates around the third rotation axis J3 together with the spline nut 51 at a predetermined reduction ratio. This causes the spline shaft 53 to rotate and translate.

[0023] The second spline shaft drive mechanism 74 has a configuration similar to that of the first spline shaft drive mechanism 73, and includes a motor 742 disposed within the second arm 4 and a speed reduction mechanism 741 that transmits the rotation of the motor 742 to the ball screw nut 52. The speed reduction mechanism 741 includes a first pulley 741a fixed to the output shaft of the motor 742, a second pulley 741b fixed to the ball screw nut 52, and a belt 741c that is wound around the first pulley 741a and the second pulley 741b. The motor 742 is a servo motor, particularly a three-phase motor driven by three-phase AC, and is fixed to the second arm 4.

[0024] In the second spline shaft drive mechanism 74 configured as described above, the rotation of the motor 742 is transmitted to the second pulley 741b via the first pulley 741a and the belt 741c, and the second pulley 741b rotates around the third rotation axis J3 together with the ball screw nut 52 at a predetermined reduction ratio. This causes the spline shaft 53 to move linearly.

[0025] The above is a brief description of the overall configuration of the robot 1. Next, the first arm 3, which is a robot arm, will be described in detail.

[0026] 4, the first arm 3 has a longitudinal shape extending in a direction perpendicular to the first rotation axis J1, which is the rotation axis. The first arm 3 has a first member 31 located at the base end (the end on the base 10 side), a third member 33 located at the tip end (the end on the second arm 4 side), and a second member 32 located between the first member 31 and the third member 33. In other words, from the base end side, the first member 31, the second member 32, and the third member 33 are arranged side by side along the longitudinal direction.

[0027] Of these first, second, and third members 31, 32, and 33, the first member 31 and the third member 33 located at both ends of the first arm 3 each have a positive linear expansion coefficient in the longitudinal direction of the first arm 3, and the second member 32 located in the center of the first arm 3 has a negative linear expansion coefficient in the longitudinal direction of the first arm 3. In other words, the first member 31 and the third member 33 each expand in the longitudinal direction of the first arm 3 due to an increase in temperature. In contrast, the second member 32 contracts in the longitudinal direction of the first arm 3 due to an increase in temperature.

[0028] In this way, the first arm 3, which combines the first and third members 31 and 33 having a positive linear expansion coefficient and the second member 32 having a negative linear expansion coefficient, can at least partially offset the expansion of the first and third members 31 and 33 due to temperature rise and the contraction of the second member 32 due to temperature rise. This effectively suppresses deformation of the first arm 3 due to temperature changes, particularly changes in the length of the first arm 3 along its longitudinal direction. This effectively suppresses deviations in the position of the TCP due to the temperature of the robot 1. This results in a robot 1 that can perform tasks with high precision. The "TCP position deviation" refers to the deviation between the calculated position of the TCP, which is determined from the rotation angles of the motors 712, 722, 732, and 742, the dimensions of the first arm 3, the second arm 4, and the spline shaft 53, and the like, and the actual position of the TCP.

[0029] Here, let L1 be the length of the first member 31 along the longitudinal direction of the first arm 3, L2 be the length of the second member 32 along the longitudinal direction of the first arm 3, L3 be the length of the third member 33 along the longitudinal direction of the first arm 3, C1 be the linear expansion coefficient of the first member 31 along the longitudinal direction of the first arm 3, C2 be the linear expansion coefficient of the second member 32 along the longitudinal direction of the first arm 3, C3 be the linear expansion coefficient of the third member 33 along the longitudinal direction of the first arm 3, and ΔT be the temperature change amount of the robot arm. It is preferable to satisfy the relationship of the following formula (1), more preferably to satisfy the relationship of the following formula (2), and even more preferably to satisfy the relationship of the following formula (3). As shown in FIG. 4, length L1 means the distance between the tip end surface of the first member 31 and the first rotation axis J1, and length L3 means the distance between the base end surface of the third member 33 and the second rotation axis J2.

[0030] 0.05mm≧|(L1×C1)ΔT+(L2×C2)ΔT+(L3×C3)ΔT|…(1)

[0031] 0.02mm≧|(L1×C1)ΔT+(L2×C2)ΔT+(L3×C3)ΔT|…(2)

[0032] 0=|(L1×C1)ΔT+(L2×C2)ΔT+(L3×C3)ΔT|…(3)

[0033] By satisfying the relationships of the above formulas (1), (2), and (3), deformation of the first arm 3 due to temperature changes, particularly changes in the length of the first arm 3 along its longitudinal direction, can be more effectively suppressed. Therefore, positional deviation of the TCP due to the temperature of the robot 1 can be more effectively suppressed. Here, in the field of industrial robots, the absolute position accuracy required of a robot is generally 0.05 mm or less, and the repeatable position accuracy required of a robot is generally 0.02 mm or less. Therefore, the threshold value of the above formula (1) is set to 0.05 mm, which is the standard for absolute position accuracy, and the threshold value of the above formula (2) is set to 0.02 mm, which is the repeatable position accuracy.

[0034] The first and third members 31 and 33, each having a positive linear expansion coefficient, are made of a metal material, while the second member 32, having a negative linear expansion coefficient, is made of carbon fiber reinforced plastic (CFRP). By using metal materials for the first and third members 31 and 33 and carbon fiber reinforced plastic for the second member 32, the materials for these components can be easily selected. This also results in a lightweight and strong first arm 3, which effectively suppresses deformation (flexure, bending, etc.) and vibration of the first arm 3. This increases the movement speed of the first arm 3 and quickly converges residual vibration after reaching the target position. This improves the cycle time of the robot 1.

[0035] In particular, in this embodiment, the first and third members 31 and 33 are each made of aluminum (Al), and the second member 32 is made of pitch-based carbon fiber reinforced plastic. Note that "pitch-based carbon fiber reinforced plastic" refers to carbon fiber reinforced plastic manufactured using pitch, a by-product of coal, petroleum, coal tar, etc., as a raw material. This makes the above-mentioned effects more pronounced. However, the materials for the first and third members 31 and 33 are not particularly limited as long as they have a positive linear expansion coefficient. Furthermore, the materials for the second member 32 are not particularly limited as long as they have a negative linear expansion coefficient. Furthermore, for example, the materials for the first and third members 31 and 33 may be the same or different from each other.

[0036] Note that, because the second member 32 is made of carbon fiber reinforced plastic, there are significant restrictions on the method for joining the second member 32 to the first and third members 31 and 33. In this embodiment, as shown in Fig. 4, flanges 321 having a plurality of screw insertion holes 322 formed therein are disposed on both ends of the second member 32, and screws N1 inserted into the screw insertion holes 322 are threaded into screw holes 311 and 331 formed in the end faces of the first and third members 31 and 33, thereby joining them together. This method makes it possible to easily and firmly join the second member 32 to the first and third members 31 and 33 without damaging the second member 32.

[0037] However, the method of joining the second member 32 to the first and third members 31 and 33 is not limited to the above-mentioned method. For example, as shown in Fig. 5, the first member 31 may be inserted into an opening on the base end side of the tubular second member 32 and joined to the inner circumferential surface of the second member 32 with adhesive B1, and the third member 33 may be inserted into an opening on the tip end side of the second member 32 and joined to the inner circumferential surface of the second member 32 with adhesive B2. Even with this method, the second member 32 and the first and third members 31 and 33 can be easily and firmly joined together without damaging the second member 32.

[0038] As shown in FIG. 4 , in this embodiment, a heat-conducting member 34 is disposed between the second member 32 and the first member 31. The heat-conducting member 34 tightly contacts the end faces of the second member 32 and the first member 31, thereby efficiently transferring heat between them. Similarly, a heat-conducting member 35 is disposed between the second member 32 and the third member 33. The heat-conducting member 35 tightly contacts the end faces of the second member 32 and the third member 33, thereby efficiently transferring heat between them. This configuration minimizes the temperature gradient within the first arm 3. This makes it easier to balance the expansion of the first and third members 31 and 33 with the contraction of the second member 32, effectively preventing misalignment of the TCP. The heat-conducting members 34 and 35 can be disposed in a similar manner even when using the joining method shown in FIG. 5 .

[0039] The thermally conductive members 34, 35 are not particularly limited, but may be, for example, a thermally conductive sheet, thermally conductive grease, or the like having high thermal conductivity. A thermally conductive sheet is, for example, a flexible resin sheet whose main component is acrylic resin, silicone resin, or the like, containing a highly thermally conductive filler such as metal or ceramic. On the other hand, a thermally conductive grease is, for example, a grease whose main component is acrylic resin, silicone resin, or the like, containing a highly thermally conductive filler such as metal or ceramic.

[0040] However, at least one of the heat conducting members 34 and 35 may be omitted.

[0041] As described above, the first arm 3 has the first member 31 and the third member 33 located at both ends thereof. That is, the second member 32 is located between the first member 31 and the third member 33. With this configuration, as shown in FIG. 4 , the reducer 711 serving as a connecting portion can be fixed to the metal first member 31. Similarly, the reducer 721 can be fixed to the metal third member 33. Therefore, compared to, for example, a case in which the reducers 711 and 721 are fixed to the carbon fiber reinforced plastic second member 32, the first arm 3 and the reducers 711 and 721 can be fixed more easily and firmly. Note that the connecting portion is not limited to the reducer 711 and may be, for example, various bearings such as a cross roller bearing that rotatably connects the base 2 and the first arm 3.

[0042] 2, the reducer 711 is fixed to the first member 31 with a screw N2. This facilitates fixing of the reducer 711. Specifically, the screw N2 is inserted into a screw insertion hole 312 formed in the first member 31 and threadedly engages with the screw hole 711d of the circular spline 711a, thereby fixing the reducer 711 to the first member 31.

[0043] The robot 1 has been described above. As described above, the first arm 3, which is a robot arm of the robot 1, has a longitudinal shape and includes a first member 31 having a positive linear expansion coefficient and a second member 32 having a negative linear expansion coefficient. The first member 31 and the second member 32 are arranged side by side in the longitudinal direction of the first arm 3. This configuration can at least partially cancel out the expansion of the first member 31 due to a temperature rise and the contraction of the second member 32 due to a temperature rise. This effectively suppresses deformation of the first arm 3 due to temperature changes, particularly changes in the length of the first arm 3 along the longitudinal direction. This effectively suppresses misalignment of the TCP due to the temperature of the robot 1.

[0044] As described above, the first member 31 is made of a metal material, and the second member 32 is made of carbon fiber reinforced plastic. This configuration makes it easy to select the materials for each part. The first arm 3 is also lightweight and has high strength. This makes it possible to effectively suppress deformation (flexure, bending, etc.) and vibration of the first arm 3. This makes it possible to increase the movement speed of the first arm 3 and quickly converge residual vibrations after reaching the target position. This improves the cycle time of the robot 1.

[0045] As described above, the third member 33 is made of a metal material and has a positive linear expansion coefficient, and the second member 32 is disposed between the first member 31 and the third member 33. With this configuration, the reducer 711 can be fixed to the first member 31 made of metal. Similarly, the reducer 721 can be fixed to the third member 33 made of metal. Therefore, the reducers 711 and 721 can be fixed more easily and firmly to the first arm 3 than in the case where the reducers 711 and 721 are fixed to the second member 32 made of carbon fiber reinforced plastic, for example.

[0046] As described above, the first arm 3 has the reducer 711 as a connection part fixed to the first member 31. With this configuration, the first arm 3 and the reducer 711 can be fixed more easily and firmly than when the reducer 711 is fixed to the second member 32 made of carbon fiber reinforced plastic, for example.

[0047] As described above, the reducer 711 is fixed to the first member 31 with the screw N2. With this configuration, the reducer 711 can be easily fixed to the first member 31.

[0048] Furthermore, as described above, the first arm 3 has the heat conduction member 34 disposed between the first member 31 and the second member 32. This configuration makes it possible to reduce the temperature gradient within the first arm 3. This makes it easier to maintain a balance between the amount of expansion of the first member 31 and the amount of contraction of the second member 32, effectively suppressing misalignment of the TCP.

[0049] As described above, the robot 1 includes a first arm 3, which is a robot arm. The first arm 3 has a longitudinal shape and includes a first member 31 having a positive linear expansion coefficient and a second member 32 having a negative linear expansion coefficient. The first member 31 and the second member 32 are arranged side by side in the longitudinal direction of the first arm 3. This configuration can at least partially cancel out the expansion of the first member 31 due to a temperature rise and the contraction of the second member 32 due to a temperature rise. This effectively suppresses deformation of the first arm 3 due to temperature changes, particularly changes in the length of the first arm 3 along the longitudinal direction. This effectively suppresses misalignment of the TCP due to the temperature of the robot 1.

[0050] Second Embodiment Fig. 6 is a top view of a first arm of a robot according to a second embodiment, Fig. 7 and Fig. 8 are top views showing modified examples of the first arm.

[0051] The robot 1 according to this embodiment is similar to the robot 1 of the first embodiment described above, except for the configuration of the first arm 3. Therefore, in the following description, differences between the robot 1 of this embodiment and the first embodiment described above will be mainly described, and descriptions of similar points will be omitted. Furthermore, in each drawing of this embodiment, the same reference numerals are used to designate the same components as those in the previously described embodiment.

[0052] 6, the first arm 3 of this embodiment has a second member 32 arranged separately at a base end (the end on the base 2 side) and a tip end (the end on the second arm 4 side), and a first member 31 arranged between these two second members 32. That is, from the base end side, the second member 32, the first member 31, and the second member 32 are arranged side by side along the longitudinal direction. A reducer 711 is fixed to the second member 32 on the base end side, and a reducer 721 is fixed to the second member 32 on the tip end side.

[0053] In this way, by disposing the first member 31, which has a positive linear expansion coefficient, in the center of the first arm 3, the first member 31 can be disposed as far away as possible from the heat source, that is, the motor 712 of the first arm drive mechanism 71 and the motor 722 of the second arm drive mechanism 72. This makes it difficult for the first member 31 to heat up, thereby suppressing thermal expansion of the first member 31. The absolute value of the linear expansion coefficient of the carbon fiber reinforced plastic constituting the second member 32 is significantly smaller than the linear expansion coefficient of the metal material (aluminum) constituting the first member 31. For example, the linear expansion coefficient of pitch-based carbon fiber reinforced plastic is -0.8 to -1.2 × 10 -6 / K, and the linear expansion coefficient of aluminum is 24.0×10 -6 / K, which is a difference of more than 10 times in absolute value. Therefore, by suppressing the temperature rise of the first member 31 and suppressing its thermal expansion, it becomes easier to design a configuration in which the expansion of the first member 31 due to the temperature rise and the contraction of the second member 32 due to the temperature rise can be offset. Furthermore, it is also possible to keep the temperature gradient occurring in the first arm 3 small. Therefore, it becomes easier to maintain a balance between the amount of expansion of the first member 31 and the amount of contraction of the second member 32, and it is possible to effectively suppress misalignment of the TCP.

[0054] In this embodiment, the first member 31 is disposed in the center of the first arm 3, but this is not limiting. For example, as shown in Fig. 7, the first member 31 may be disposed offset toward the tip end of the first arm 3, or conversely, offset toward the base end. Furthermore, as shown in Fig. 8, the first member 31 may be divided into two or more parts and disposed.

[0055] The position of the first member 31 can be determined, for example, according to the outputs of the motors 712 and 722 located on both sides of the first arm 3. For example, if the output of the motor 712 is A1 [W], the output of the motor 722 is A2 [W], and the distance between the first rotation axis J1 and the first member 31 is L4 and the distance between the second rotation axis J2 and the first member 31 is L5 as shown in FIG. 7 , the position of the first member 31 may be determined so that the relationship A1:A2 = L4:L5 is satisfied. For example, if the output of the motor 712 is 400 W and the output of the motor 722 is 200 W, the position of the first member 31 within the first arm 3 may be determined so that the ratio L4:L5 is 2:1. This configuration makes it more difficult for heat from the motors 712 and 722 to be transferred to the first member 31, thereby minimizing the temperature gradient occurring in the first arm 3.

[0056] 6, when the length of the first member 31 along the longitudinal direction of the first arm 3 is L1, the length of the second member 32 along the longitudinal direction of the first arm 3 is L2, the linear expansion coefficient of the first member 31 along the longitudinal direction of the first arm 3 is C1, the linear expansion coefficient of the second member 32 along the longitudinal direction of the first arm 3 is C2, and the temperature change amount of the robot arm is ΔT, it is preferable to satisfy the relationship of the following formula (4A), more preferably to satisfy the relationship of the following formula (5A), and even more preferably to satisfy the relationship of the following formula (6A). Note that the length L2 means the sum of the distance L21 between the tip end surface of the second member 32 on the base end side and the first rotation axis J1 and the distance L22 between the base end surface of the second member 32 on the tip end side and the second rotation axis J2.

[0057] 0.05mm≧|(L1×C1)ΔT+(L2×C2)ΔT|…(4A)

[0058] 0.02mm≧|(L1×C1)ΔT+(L2×C2)ΔT|…(5A)

[0059] 0=|(L1×C1)ΔT+(L2×C2)ΔT|…(6A)

[0060] By satisfying the relationships of the above formulas (4A), (5A), and (6A), deformation of the first arm 3 due to temperature changes, particularly changes in the length of the first arm 3 along its longitudinal direction, can be more effectively suppressed. Therefore, positional deviation of the TCP due to the temperature of the robot 1 can be more effectively suppressed. In the field of industrial robots, the absolute position accuracy required of a robot is generally 0.05 mm or less, and the repeatable position accuracy required of a robot is generally 0.02 mm or less. Therefore, the threshold value of the above formula (4A) is set to 0.05 mm, which is the standard for absolute position accuracy, and the threshold value of the above formula (5A) is set to 0.02 mm, which is the repeatable position accuracy.

[0061] Here, the length of the entire first arm 3 along the longitudinal direction is defined as L0. L0 is the sum of L1 and L2. In this case, by respectively transforming the above formulas (4A), (5A), and (6A), we obtain the following formulas (4B), (5B), and (6B).

[0062] 0.05mm≧|(L0×C1)ΔT+{L2×(C2-C1)}ΔT|…(4B)

[0063] 0.02mm≧|(L0×C1)ΔT+{L2×(C2-C1)}ΔT|…(5B)

[0064] 0=(L0×C1)ΔT+{L2×(C2-C1)}ΔT…(6B)

[0065] Furthermore, if we assume that the temperature change ΔT is 1° for the above equations (4B), (5B), and (6B), we can transform the above equations (4B), (5B), and (6B) into the following equations (4C), (5C), and (6C), respectively, making it possible to more easily calculate the length L2.

[0066] {-0.05mm-(L0×C1)} / (C2-C1)≦L2≦{0.05mm-(L0×C1)} / (C2-C1)…(4C)

[0067] {-0.02mm-(L0×C1)} / (C2-C1)≦L2≦{0.02mm-(L0×C1)} / (C2-C1)…(5C)

[0068] L2=-(L0×C1) / (C2-C1)…(6C)

[0069] In the first embodiment described above, if the constituent materials of the first and third members 31 and 33 are the same, the sum of the lengths of the first arm 3 of the first and third members 31 and 33 along the longitudinal direction is defined as L1, and the linear expansion coefficient of the first arm 3 of the first and third members 31 and 33 along the longitudinal direction is defined as C1, and the design may be such that any of the relationships in the above formulas (4A), (5A), (6A), (4B), (5B), (6B), (4C), (5C), or (6C) is satisfied.

[0070] As described above, in the first arm 3 described above, when the length of the first member 31 along the longitudinal direction is L1, the length of the second member 32 along the longitudinal direction is L2, the linear expansion coefficient of the first member 31 is C1, the linear expansion coefficient of the second member 32 is C2, and the temperature change amount of the robot arm is ΔT, the relationship 0.05 mm ≥ |(L1 × C1) ΔT + (L2 × C2) ΔT| is satisfied. With this configuration, deformation of the first arm 3 due to temperature change, in particular change in the length of the first arm 3 along the longitudinal direction, can be more effectively suppressed.

[0071] The second embodiment can also achieve the same effects as the first embodiment. The second members 32 may be made of the same or different materials, as long as they each have a negative linear expansion coefficient.

[0072] Third Embodiment Fig. 9 is a cross-sectional view of a connecting portion between a first arm and a second arm of a robot according to a third embodiment, and Fig. 10 is a cross-sectional view of a connecting portion between a base of the robot and the first arm.

[0073] The robot 1 according to this embodiment is similar to the robot 1 of the first embodiment described above, except for the configuration of the first arm 3. Therefore, in the following description, differences between the robot 1 of this embodiment and the first embodiment described above will be mainly described, and descriptions of similar points will be omitted. Furthermore, in the drawings of this embodiment, the same reference numerals are used to designate similar components to those of the previously described embodiment.

[0074] 9, the first arm 3 of this embodiment has a second member 32 arranged at least at the tip end (the end on the second arm 4 side). The second member 32 is connected to the second arm 4, which is the object to be connected, via a reducer 721, which is a connecting part. Therefore, the second member 32 of the first arm 3 and the reducer 721 are arranged side by side in a direction along the second rotation axis J2 (a direction perpendicular to the longitudinal direction of the first arm 3).

[0075] The reducer 721 is also made of a first member 721d that has a positive coefficient of linear expansion in the direction along the second rotation axis J2. Specifically, the circular spline 721a, the flexspline 721b, and the wave generator 721c, which are the main components that make up the reducer 721, are each made of the first member 721d. In this embodiment, the first member 721d is made of a metal material. The metal materials that make up the circular spline 721a, the flexspline 721b, and the wave generator 721c may be the same or different from one another.

[0076] In contrast, the second member 32 constituting the tip end of the first arm 3 has a negative coefficient of linear expansion in the direction along the second rotation axis J2. This makes it possible to at least partially cancel out the expansion of the reducer 721 due to temperature rise and the contraction of the second member 32 due to temperature rise. This makes it possible to effectively suppress deviation of the TCP in the direction along the second rotation axis J2.

[0077] As described above, the robot 1 includes the second arm 4 as a connection target, the longitudinal first arm 3 that rotates around the second rotation axis J2, which is a rotation axis perpendicular to the longitudinal direction of the second arm 4, and the reducer 721 that is located between the second arm 4 and the first arm 3 and serves as a connector connecting the second arm 4 and the first arm 3. The reducer 721 includes a first member 721d that has a positive linear expansion coefficient, and the first arm 3 includes a second member 32 that has a negative linear expansion coefficient. The first member 721d and the second member 32 are arranged side by side along the second rotation axis J2. This configuration allows at least a portion of the expansion of the reducer 721 due to temperature rise and the contraction of the second member 32 due to temperature rise to be offset. As a result, misalignment of the TCP along the second rotation axis J2 can be effectively suppressed.

[0078] The third embodiment can also achieve the same effects as the first embodiment. In this embodiment, the object to be connected is the second arm 4. However, the object to be connected is not limited to this and may be, for example, the base 2. In this case, as shown in FIG. 10 , the base end (the end on the base 2 side) of the first arm 3 is made up of the second member 32, and the circular spline 711a, flexspline 711b, and wave generator 711c of the reducer 711, which are the connecting part, are each made up of the first member 711e, and the first member 711e and the second member 32 are arranged side by side in the direction along the first rotation axis J1. Even with this configuration, the same effects as the present embodiment can be achieved.

[0079] While the robot arm and robot of the present invention have been described above based on the illustrated embodiments, the present invention is not limited to these, and the configuration of each part can be replaced with any configuration having a similar function. Furthermore, any other components may be added to the present invention. Furthermore, the above-described embodiments may be combined as appropriate.

[0080] Furthermore, in the above-described embodiment, the robot arm is the first arm 3, but this is not limiting, and the robot arm may be the second arm 4. Furthermore, both the first arm 3 and the second arm 4 may be robot arms. In other words, any arm of the robot 1 may be the robot arm.

[0081] In the above-described embodiment, the robot 1 is a SCARA robot. However, the present invention is not limited to this. For example, the robot 1 may be a vertically articulated robot such as a six-axis articulated robot or a dual-arm robot, or may be any other robot. As shown in Fig. 11, the six-axis articulated robot 9 includes a base 90, a first arm 91 rotatably connected to the base 90, a second arm 92 rotatably connected to the first arm 91, a third arm 93 rotatably connected to the second arm 92, a fourth arm 94 rotatably connected to the third arm 93, a fifth arm 95 rotatably connected to the fourth arm 94, and a sixth arm 96 rotatably connected to the fifth arm 95. At least one of the first to sixth arms 91 to 96 may be a robot arm. [Explanation of symbols]

[0082] 1...robot, 10...base, 2...base, 3...first arm, 31...first member, 311...screw hole, 312...screw insertion hole, 32...second member, 321...flange, 322...screw insertion hole, 33...third member, 331...screw hole, 34...heat conduction member, 35...heat conduction member, 4...second arm, 5...work head, 51...spline nut, 52...ball screw nut, 53...spline shaft, 6...da 71...first arm drive mechanism, 711...reduction gear, 711a...circular spline, 711b...flex spline, 711c...wave generator, 711d...screw hole, 711e...first member, 712...motor, 72...second arm drive mechanism, 721...reduction gear, 721a...circular spline, 721b...flex spline, 721c...wave generator, 721d...first member, 722...motor, 73...spline shaft first drive mechanism, 731...reduction gear, 731a...first pulley, 731b...second pulley, 731c...belt, 732...motor, 74...spline shaft second drive mechanism, 741...reduction gear, 741a...first pulley, 741b...second pulley, 741c...belt, 742...motor, 9...6-axis articulated robot, 90...base, 91...first arm, 92...second arm, 93...third arm, 94...fourth arm, 95...fifth arm, 96...sixth arm, B1...adhesive, B2...adhesive, J1...first rotating shaft, J2...second rotating shaft, J3...third rotating shaft, L1...separation distance, L2...separation distance, L21...separation distance, L22...separation distance, L3...separation distance, L4...separation distance, L5...separation distance, N1...screw, N2...screw

Claims

1. It has a longitudinal shape, a first member having a positive linear expansion coefficient; a second member having a negative linear expansion coefficient; A robot arm, characterized in that the first member and the second member are arranged side by side in the longitudinal direction.

2. A robot having a robot arm, The robot arm It has a longitudinal shape, a first member having a positive linear expansion coefficient; a second member having a negative linear expansion coefficient; A robot characterized in that the first member and the second member are arranged side by side in a longitudinal direction.

3. A linked object; an arm having a longitudinal shape and rotating about a rotation axis perpendicular to the longitudinal direction of the object to be connected; a connection portion located between the object to be connected and the arm, and connecting the object to be connected and the arm, the connecting portion has a first member having a positive linear expansion coefficient, the arm has a second member having a negative coefficient of linear expansion; A robot characterized in that the first member and the second member are arranged side by side in a direction along the rotation axis.

4. the first member is made of a metal material, The robot arm according to claim 1 , wherein the second member is made of carbon fiber reinforced plastic.

5. a third member made of a metal material and having a positive coefficient of linear expansion; The robot arm according to claim 4 , wherein the second member is disposed between the first member and the third member.

6. 5. The robot arm of claim 4, further comprising a connection portion fixed to the first member.

7. The robot arm according to claim 6 , wherein the connection portion is fixed to the first member with a screw.

8. 5. The robot arm of claim 4, further comprising a heat conducting member disposed between the first member and the second member.

9. The length of the first member along the longitudinal direction is defined as L1, The length of the second member along the longitudinal direction is L2, The linear expansion coefficient of the first member is C1, The linear expansion coefficient of the second member is C2, When the temperature change amount of the robot arm is ΔT, 2. The robot arm according to claim 1, wherein the relationship 0.05 mm ≥ |(L1×C1)ΔT+(L2×C2)ΔT| is satisfied.

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