Joint mechanism and robot arm mechanism

Abstract

The aim is to reduce the load on the support members of the arm in an industrial robot equipped with a balancer mechanism. The joint mechanism 1 includes a balancer mechanism 5 that generates an auxiliary torque that resists the load torque applied to the support member 45 about the rotational centerline of the arm due to the weight of the arm 3. The balancer mechanism has a balancer body 50 and a transmission member 55. The balancer body 50 has a rotatable housing 51 supported by a base, a piston rod 53 inserted into the housing, and a traction device 52 that pulls the piston rod. The transmission member 55 converts the traction force generated by the traction device into an auxiliary torque and transmits it to the arm. The transmission member is separate from the support member, rotatable by a base shaft, with one end engaging with the front end of the piston rod and the other end engaging with the arm.

Description

Technical Field

[0001] This invention relates to a joint mechanism and a robotic arm mechanism. Background Technology

[0002] Among multi-jointed industrial robots, industrial robots equipped with a balancer mechanism are known. This balancer mechanism generates a force in the opposite direction to the load caused by gravity to assist the power of the drive arm mechanism (e.g., Patent Document 1). For example, the balancer mechanism consists of a housing that is tiltably connected to a base and a piston rod that is slidably disposed inside the housing. The front end of the piston rod is rotatably connected to the arm and is pulled into the housing. As the arm rotates, the piston rod is pulled out of the housing, thereby pulling the arm in the opposite direction to the load caused by gravity, thus assisting the power of the drive arm mechanism.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent document 1: Japanese Patent No. 2543539. Summary of the Invention

[0006] The problem the invention aims to solve

[0007] In conventional designs, the arm's support structure must withstand two types of loads: the load caused by the arm's weight and the load caused by the traction force generated by the balancer mechanism. Therefore, in industrial robots equipped with a balancer mechanism, it is desirable to reduce the load acting on the arm's support structure.

[0008] means for solving problems

[0009] One aspect of the disclosed joint mechanism includes a base, an arm, a support member that rotatably supports the arm on the base, and a balancer mechanism that generates an auxiliary torque that resists a load torque applied about the arm's rotational centerline due to the arm's weight. The balancer mechanism has a balancer body and a transmission member. The balancer body has a housing supported by the base for rotatability, a piston rod inserted into the housing, and a traction device for pulling the piston rod. The transmission member converts the traction force generated by the traction device into an auxiliary torque and transmits it to the arm. The transmission member is separate from the support member and is rotatably supported by a base shaft. The transmission member engages with the front end of the piston rod at a first position spaced a first distance from the centerline of the shaft and with the arm at a second position spaced a second distance from the centerline of the shaft.

[0010] Invention Effects

[0011] According to one method, in an industrial robot equipped with a balancer mechanism, the load acting on the arm support components can be reduced. Attached Figure Description

[0012] Figure 1 This is a perspective view of the joint mechanism of one embodiment.

[0013] Figure 2 yes Figure 1 An exploded three-dimensional view of the joint mechanism.

[0014] Figure 3 yes Figure 1 Top view of the joint mechanism.

[0015] Figure 4 It is shown Figure 1 A side view of the reference pose of the arm of the articulated mechanism.

[0016] Figure 5 It is shown Figure 1 A side view of the tilting posture of the arm of the joint mechanism.

[0017] Figure 6 This is a side view showing the reference posture of the arm of the joint mechanism of a first variant of an embodiment.

[0018] Figure 7 This is a side view showing the reference posture of the arm of the joint mechanism in a second variation of an embodiment.

[0019] Explanation of reference numerals in the attached figures

[0020] 1: Joint mechanism; 2: Base; 21: Base plate; 23, 25: Side plates; 3: Arm; 4: Arm drive mechanism; 41: Motor; 43: Reducer; 45: Output shaft; 47: Bearing; 5: Balancer mechanism; 50: Balancer body; 51: Housing; 52: Traction device (compression coil spring); 53: Piston rod; 54, 57: Shaft; 55: Transmission component; 56: Fixing component; RA1: Rotation shaft of the arm; RA2: Rotation shaft of the transmission component. Detailed Implementation

[0021] Hereinafter, the joint mechanism of this embodiment will be described with reference to the accompanying drawings. In the following description, the same reference numerals are used to denote components that have approximately the same function and structure, and descriptions will be repeated only where necessary.

[0022] The joint mechanism of this embodiment can be used independently or as a joint mechanism such as a robot arm mechanism.

[0023] like Figures 1-4 As shown, the joint mechanism 1 has a base 2, a rod-shaped arm 3 supported by the base 2 and rotatable, an arm drive mechanism 4 that drives the arm 3, and a balancer mechanism 5 that functions as a balancer to reduce the load on the bearings of the support arm 3, etc.

[0024] The base 2 has a rectangular base plate 21 and a pair of side plates 23, 25 arranged parallel to each other on both edges of the base plate 21. In the following description, the axis parallel to the thickness direction of the base plate 21 is designated as the Z-axis, the axis parallel to the thickness direction of the side plates 23, 25 (the direction in which the pair of side plates 23, 25 are separated) is designated as the X-axis, and the axis orthogonal to the X-axis and Z-axis is designated as the Y-axis, as appropriate.

[0025] The arm drive mechanism 4 is supported by one of the side plates 23 of a pair of side plates 23 and 25. The arm drive mechanism 4 includes a motor 41 that generates power to rotate the arm 3 and a reducer 43 that slows down the rotation of the motor 41. The arm drive mechanism 4 is configured such that the center line RA1 (rotation axis RA1) of the output shaft 45 of the reducer 43 is parallel to the X-axis. The arm 3 is mounted to the housing of the reducer 43 via bearings 47 and fastened to the output shaft 45 of the reducer 43 using bolts or other fasteners. Thus, as the output shaft 45 of the reducer 43 rotates, the arm 3 can rotate about the rotation axis RA1, which is parallel to the X-axis.

[0026] The balancer mechanism 5 has a balancer body 50 and a transmission component 55.

[0027] The balancer body 50 includes a housing 51, a piston rod 53 inserted into the housing 51, and a traction device 52 for pulling the piston rod 53 into the housing 51. Typically, as the traction device 52, a compression coil spring 52 is housed inside the housing 51 in a compressed state. One end of the piston rod 53 is connected to the compression coil spring 52. Thus, the piston rod 53, pulled out from the inside of the housing 51, can be pulled into the housing 51 by the compression coil spring 52. The housing 51 is rotatably mounted on the base 2 about the X-axis. Typically, a shaft 54 ​​is fixed between a pair of side plates 23, 25, with its center line RA3 (rotation axis RA3) parallel to the X-axis. The housing 51 is mounted to this shaft 54 ​​via bearings or the like. Thus, the housing 51 can rotate about the rotation axis RA3 parallel to the X-axis.

[0028] The transmission member 55 is configured as an L-shaped plate. One end of the transmission member 55 is rotatably connected to the other end of the piston rod 53 about an axis RA4 parallel to the X-axis. The other end of the transmission member 55 is fixed to the front end of the arm 3 via a fixing member 56. The transmission member 55 is rotatably mounted on the base 2 about the X-axis. Typically, a shaft 57 is fixed to the other side plate 25 of a pair of side plates 23, 25, with its center line RA2 aligned with the rotation axis RA1 of the arm 3. The transmission member 55 is mounted to this shaft 57 via a bearing or the like. Thus, the transmission member 55 can rotate about the center line RA2 (rotation axis RA2) aligned with the rotation axis of the arm 3. The shaft 57 supporting the transmission member 55 is separate from the shaft 57 supporting the arm 3 and the bearing 47, and is detached from the shaft 57 and the bearing 47. Thus, the arm 3 and the transmission member 55 are fixed at their respective ends, but the support structure of the transmission member 55 relative to the base 2 and the support structure of the arm 3 relative to the base 2 are separate components, which is a feature.

[0029] like Figure 4 As shown, the rotation angle of arm 3 when its centerline is parallel to the Z-axis (vertical axis) is set to 0 degrees. This posture is taken as the reference posture of arm 3. When arm 3 is in the reference posture, no load torque F1 caused by the weight of arm 3 around the rotation axis RA1 is generated in the bearing 47 supporting arm 3. On the other hand, as Figure 5As shown, when arm 3 tilts (rotates) from its reference position, a load torque F1 is generated around the rotation axis RA1 by the weight of arm 3 at the bearing 47 supporting arm 3. At this time, the balancer mechanism 5 functions as follows: The transmission member 55 rotates around the rotation axis RA2 in tandem with the rotation of arm 3. As the transmission member 55 rotates, the distance between the rotation axis RA4 at the connection point of the transmission member 55 and piston rod 53 and the rotation axis RA3 of the housing 51, and the angle around the X-axis change. The housing 51 rotates around the rotation axis RA3, causing the piston rod 53 to be arranged along a straight line passing through the rotation axes RA3 and RA4. The piston rod 53 is pulled out of the housing 51 against the traction force of the compression coil spring 52. The length of the piston rod 53 pulled out of the housing 51 corresponds to the difference in distances between the distance from rotation axis RA3 to rotation axis RA4 when arm 3 is in a tilted position and the distance from rotation axis RA3 to rotation axis RA4 when arm 3 is in a reference position. The piston rod 53, pulled out from the housing 51, is pulled into the housing 51 by the compression coil spring 52. The traction force F2 generated by the compression coil spring 52 is converted into an auxiliary torque F2′ around the rotation axis RA2 (rotation axis RA1) by means of the transmission member 55 and is transmitted to the arm 3. The auxiliary torque F2′ acts in the opposite direction to the load torque F1 around the rotation axis RA1 caused by the weight of the arm 3. Therefore, a torque corresponding to the combined torque (F1-F2′) of the load torque F1 and the auxiliary torque F2′ is applied to the bearing 47 of the support arm 3. On the other hand, in the joint mechanism without the balancer mechanism 5, the above-mentioned auxiliary torque F2′ is not generated. Therefore, a torque corresponding to the load torque F1 is applied to the bearing 47 of the support arm 3. That is, according to the joint mechanism 1 of this embodiment, the load applied to the bearing 47 of the support arm 3 can be reduced to the torque corresponding to the auxiliary torque F2′.

[0030] By configuring the structure so that it is connected to the front end of the arm 3 via the transmission member 55, instead of directly connecting the balancer mechanism 5 to the arm 3, the following effect is achieved. That is, in the structure where the piston rod 53 of the balancer mechanism 5 is directly connected to the arm 3, the traction force generated by the compression coil spring 52 also acts as a load on the bearing 47 of the supporting arm 3. Therefore, the bearing 47 of the supporting arm 3 must bear two loads, namely, the load caused by the traction force generated by the compression coil spring 52 and the load caused by the weight of the arm 3. According to the joint mechanism 1 of this embodiment, the traction force generated by the compression coil spring 52 is transmitted to the front end of the arm 3 via the transmission member 55. Furthermore, the shaft 57 of the supporting transmission member 55 is separate from the bearing 47 of the supporting arm 3. Thus, the traction force generated by the compression coil spring 52 acts directly as a load on the shaft 57 of the supporting transmission member 55, but does not act directly as a load on the bearing 47 of the supporting arm 3.

[0031] According to the joint mechanism 1 of this embodiment described above, the torque caused by the combined torque (F1-F2′) applied to the bearing 47 of the support arm 3 by the balancer mechanism 5 is only the torque caused by the combined torque described above, thereby reducing the load on the bearing 47 of the support arm 3. This reduces the risk of failure of the bearing 47 of the support arm 3 and the reducer 43 (motor 41) of the drive arm 3, achieving a longer lifespan. Furthermore, since the load applied to the bearing 47 of the support arm 3 is small, the size of the bearing 47 can be reduced. This helps to reduce component costs. Furthermore, by increasing the auxiliary torque, the static torque generated by the motor 41 can be reduced. This helps to reduce the power consumption of the joint mechanism 1 and the robot including the joint mechanism 1.

[0032] In the joint mechanism 1 of this embodiment, the transmission member 55 is also externally separate from the arm 3. However, since the rotation axis RA2 of the transmission member 55 is aligned with the rotation axis RA1 of the arm 3, the transmission member 55 can be easily housed inside the arm 3. By housing the transmission member 55 inside the arm 3, not only is the joint mechanism 1 miniaturized, but it also simplifies the appearance, improves aesthetics, and avoids the possibility of cables or other wires with external wiring of the joint mechanism 1 entering between the arm 3 and the transmission member 55 and breaking.

[0033] In the joint mechanism 1 of this embodiment, the balancer body 50 is configured to have a helical spring type in which a compression helical spring 52 is used as the traction device 52. As long as a traction force can be generated to pull the piston rod 53 back into the housing 51, the structure of the balancer body 50 is not limited to this. For example, the balancer body 50 can adopt known methods such as a gas spring type, a cylinder type, or a hydraulic type, where the compressible gas sealed in the housing 51 is compressed when the piston rod 53 is pulled out of the housing 51, and the piston rod 53 is pulled back into the housing 51 by its reaction force.

[0034] The shape of the transmission member 55 is not limited to this embodiment. As long as the transmission member 55 can be fixed at the front end of the arm 3, can be rotatably supported coaxially with the rotation axis RA1 of the arm 3, and can be rotatably connected to the piston rod 53, it can be, for example, a plate with a U-shape or an arch shape.

[0035] Furthermore, when the distance from the centerline of shaft 54 ​​to the position where the transmission member 55 connects to the piston rod 53 is defined as the first distance L1, and the distance from the centerline of shaft 54 ​​to the position where the transmission member 55 is fixed to the arm 3 is defined as the second distance L2, the transmission member 55 is typically configured such that the second distance L2 is longer than the first distance L1. However, it is not precluded that the second distance L2 is less than or equal to the first distance L1, and these parameters L1 and L2 of the transmission member 55 can be determined from the perspectives of the magnitude of the traction force, the magnitude of the required auxiliary torque, and the installation space of the balancer mechanism 5.

[0036] The support structure of arm 3 relative to base 2 is not limited to this embodiment. For example, arm 3 may be configured to be connected to base 2 via bearing 47, or arm 3 may be configured to be directly connected to output shaft 45 of reducer 43. In this case, balancer mechanism 5 serves to reduce the load applied to output shaft 45 of reducer 43 supporting arm 3.

[0037] The support structure of the transfer member 55 relative to the base 2 is not limited to this embodiment. The support structure of the transfer member 55 can be separate from the support structure of the arm 3. For example, the shaft 57 on which the transfer member 55 is fixed can be rotatably mounted on the base 2. Alternatively, the transfer member 55 can be rotatably supported on another member fixed in position relative to the base 2 about the X-axis. Similarly, the support structure of the housing 51 relative to the base 2 is not limited to this embodiment.

[0038] In the joint mechanism 1 of this embodiment, one end of the transmission member 55 is rotatably connected to the piston rod 53 of the balancer mechanism 5, and the other end is fixed to the front end of the arm 3. Therefore, the balancer mechanism 5 can function even by tilting the arm 3 from the reference posture by a small angle. However, when the arm 3 is tilted slightly from the reference posture, the load torque around the rotation axis RA1 caused by the weight of the arm 3 is small, and it may not always be necessary for the balancer mechanism 5 to function. In this case, the balancer mechanism 5 can be configured to function when the arm 3 rotates more than a predetermined angle from the reference posture. Hereinafter, a first and a second modification will be described regarding the structure that limits the angle range in which the balancer mechanism 5 functions. The first modification shows a structure that changes the engagement configuration between the other end of the transmission member 55 and the arm 3, and the second modification shows a structure that changes the engagement configuration between the piston rod 53 and one end of the transmission member 55.

[0039] (First variation)

[0040] like Figure 6As shown, in the joint mechanism 7 of the first modified example, the other end of the transmission member 55 is set as a free end. The arm 3 is provided with protrusions 31 and 33 that engage with the transmission member 55 when the arm 3 tilts from a reference posture to a predetermined angle. Since the position of the other end of the transmission member 55 on the front end side of the arm 3 is not fixed, the rotation axis RA2 of the transmission member 55 does not need to be aligned with the rotation axis RA1 of the arm 3. According to the joint mechanism 7 of the first modified example, the balancer mechanism 5 can function when the end of the transmission member 55 contacts the protrusions 31 and 33 provided on the arm 3, i.e., when the arm 3 tilts from the reference posture to a predetermined angle or more. On the other hand, the balancer mechanism 5 does not function before the end of the transmission member 55 contacts the protrusions 31 and 33 provided on the arm 3, i.e., during the period when the arm 3 tilts from the reference posture to the predetermined angle. Since the range of rotation angles in which the balancer mechanism 5 functions can be narrowed, the required stroke length of the piston rod 53 can be shortened, thereby enabling miniaturization of the balancer mechanism 5.

[0041] (Second variation)

[0042] like Figure 7 As shown, in the joint mechanism 8 of the second modification, an arc-shaped slit 59 centered on the rotation axis RA2 is formed at one end of the transmission member 55, and the front end of the piston rod 53 slides freely into the slit 59. The arc length of the slit 59 corresponds to the tilting angle of the arm 3, which prevents the balancer mechanism 5 from functioning. According to the joint mechanism 8 of the second modification, the balancer mechanism 5 can function when the piston rod 53 is in contact with the end of the slit 59, that is, when the arm 3 is tilted at a predetermined angle or more from the reference posture. On the other hand, the balancer mechanism 5 does not function during the period when the piston rod 53 slides along the slit 59 of the transmission member 55, that is, when the arm 3 is tilted from the reference posture to a predetermined angle. Since the range of rotation angles in which the balancer mechanism 5 functions can be narrowed, the required stroke length of the piston rod 53 can be shortened, thereby enabling the miniaturization of the balancer mechanism 5.

[0043] While several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope of the invention as described in the claims and its equivalents, just as they are included within the scope or spirit of the invention.

Claims

1. A joint mechanism of a robot, wherein, Possessing: a base, an arm, a support member that rotatably supports the arm to the base, and a balancer mechanism that generates an assistive torque that counteracts a load torque around a rotational center line of the arm that is applied to the support member due to the weight of the arm; the balancer mechanism has a balancer main body and a transmission member, the balancer main body has a housing that is rotatably supported by the base, a piston rod that is inserted into the housing, and a traction device that pulls the piston rod, the transmission member converts a traction force generated by the traction device into the assistive torque and transmits it to the arm, the transmission member is rotatably supported by the base shaft separately from the support member, engages with a front end of the piston rod at a first position that is separated from a rotational center line of the transmission member by a first distance, and engages with the arm at a second position that is separated from the rotational center line of the transmission member by a second distance.

2. The joint mechanism of the robot according to claim 1, wherein The second distance is longer than the first distance.

3. The joint mechanism of the robot according to claim 1 or 2, wherein The transmission member has an L shape, a k shape, or an arch shape.

4. The joint mechanism of the robot according to any one of claims 1 to 3, wherein The rotational center line of the transmission member coincides with the rotational center line of the arm.

5. The joint mechanism of the robot according to any one of claims 1 to 4, wherein The transmission member is rotatably connected to the front end of the piston rod at the first position and is fixed to the arm at the second position.

6. The joint mechanism of the robot according to any one of claims 1 to 4, wherein A member that comes into contact with the transmission member as the arm tilts is provided at a position of the arm that corresponds to the second position.

7. The joint mechanism of the robot according to any one of claims 1 to 4, wherein A slit in the shape of a circular arc centered on the rotational center line of the transmission member is formed in the transmission member, and the front end of the piston rod is slidably engaged with the slit.

8. A robot arm mechanism, wherein, A joint mechanism of a robot according to any one of claims 1 to 7.

Images