Balancers and robotic systems

Abstract

A balancer (1) comprises: a housing (2) mounted on one of a first component or a second component of a robot via a first bearing (21) in a manner rotatable about a first mounting axis (X) parallel to a rotation axis, the robot comprising the first component and a second component rotatably driven relative to the first component about the rotation axis; a rod (3) mounted on the other of the first component or the second component via a second bearing (22) in a manner rotatable about a second mounting axis (Y) parallel to a rotation axis; a force generating unit (5) generating a force in a direction that pulls the rod (3) into the housing (2) or in a direction that pushes the rod (3) out of the housing (2); and a sensor (6) detecting the positional relationship between the housing (2) and the rod (3) in directions orthogonal to the first mounting axis (X) and the second mounting axis (Y).

Description

Technical Field

[0001] This invention relates to balancers and robotic systems. Background Technology

[0002] A balancer is known, which is disposed between the rotating body of a robot and a first arm that is driven to rotate about a horizontal first axis and relative to the rotating body, for compensating for the gravitational load acting on the first arm (for example, see Patent Document 1).

[0003] In a robot equipped with this balancer, the current value of the motor that drives the first arm to rotate relative to the rotating body is monitored to detect a decrease in the force generated by the balancer.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-195849 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The balancers are mounted on the first arm and the rotating body respectively, in a manner that allows them to rotate about an axis parallel to the first axis using bearings. The force generated by the balancers is transmitted to the first arm and the rotating body via the bearings as an auxiliary torque, which is used to compensate for the gravitational load.

[0009] If the robot's operating time increases and the bearings supporting the balancer become damaged or worn, there is a risk of damage to the balancer's mounting parts, rotating body, or first arm. Therefore, it is necessary to detect bearing damage or wear as early as possible. However, even if the bearing is damaged or worn, the motor current value will not change significantly, making it impossible to detect bearing abnormalities by measuring the motor current value.

[0010] Therefore, it is desirable to detect bearing damage or wear as early as possible.

[0011] Solution for solving the problem

[0012] One aspect of the present invention is a balancer comprising: a housing mounted to one of a first component or a second component of a robot, rotatably about a first mounting axis parallel to the rotation axis, the robot comprising the first component and a second component rotatably driven relative to the first component about the rotation axis; a rod mounted to the other of the first component or the second component, one end of which is mounted to the first component or the second component, rotatably about a second mounting axis parallel to the rotation axis, using a second bearing; a force generating unit that generates a force in a direction that pulls the rod into the housing or in a direction that pushes the rod out of the housing; and a sensor that detects at least one of the positional relationship between the first mounting axis and the housing and the positional relationship between the second mounting axis and the rod in a direction orthogonal to the first mounting axis and the second mounting axis. Attached Figure Description

[0013] Figure 1 This is an overall structural diagram of a robot system according to one embodiment of the present invention.

[0014] Figure 2 This is a longitudinal sectional view of a balancer according to one embodiment of the present invention.

[0015] Figure 3 This is a partial longitudinal sectional view illustrating the direction of movement of the housing due to bearing wear, the bearing being rotatably supported. Figure 2 The balancer housing and the first shaft.

[0016] Figure 4 This is a partial longitudinal sectional view illustrating the direction of rod movement caused by bearing wear, the bearing being rotatably supported. Figure 2 The balancer's rod and second shaft.

[0017] Figure 5 This is an explanation Figure 2 A longitudinal cross-sectional view of the difference between the distance detected by the sensor in the balancer and the normal distance.

[0018] Figure 6 It means Figure 2 A longitudinal sectional view of a modified example of a balancer.

[0019] Figure 7 It means Figure 2 A longitudinal sectional view of a modified example of the sensor configuration in a balancer.

[0020] Figure 8 It means Figure 2 A longitudinal sectional view of a modified example of a sensor in a balancer.

[0021] Figure 9 It means Figure 2 A longitudinal sectional view of another variation of the sensor in the balancer.

[0022] Figure 10 It means Figure 2 A longitudinal sectional view of a modified example of the sensor configuration in a balancer.

[0023] Figure 11 It means to substitute Figure 2 A partial longitudinal sectional view of an example configuration of a sensor in a balancer that detects the distance between the housing and the first mounting axis.

[0024] Figure 12 It means to substitute Figure 2 A partial longitudinal sectional view of an example configuration of a sensor in a balancer, which detects the distance between the sensor rod and the second mounting axis. Detailed Implementation

[0025] Hereinafter, a balancer 1 and a robot system 100 according to one embodiment of the present invention will be described with reference to the accompanying drawings.

[0026] like Figure 1 As shown, the robot system 100 of this embodiment includes a robot 110 and a control device 120 for controlling the robot 110.

[0027] Robot 110 is, for example, a vertical six-axis articulated robot. Robot 110 includes: a base 111 disposed on the ground F; a rotating body (first component) 112 capable of rotating about a first axis A extending in the vertical direction and relative to the base 111; a first arm (second component) 113 capable of rotating about a second horizontal axis (rotation axis) B and relative to the rotating body 112; and a balancer 1.

[0028] like Figure 2 As shown, the balancer 1 includes a housing 2, a rod 3, a movable plate (movable part) 4, a compression coil spring (force generating unit) 5, and a sensor 6.

[0029] The housing 2 includes: a cylindrical main body 7; a flat front end plate (end plate) 8 and a rear end plate (end plate) 9, which close the two ends of the main body 7 in the axial direction; and a bearing 12, which is disposed on the front end plate 8 and supports the rod 3 in a manner that allows it to move in the longitudinal direction.

[0030] On the outer peripheral surface of the main body 7, a pair of mounting portions 10 are provided at the midpoint of the axial direction, arranged opposite to each other across the axis. Each mounting portion 10 has an inner hole 11 with a circular cross-section, and the inner hole 11 is formed into a cylinder extending in opposite directions along the same straight line from the outer peripheral surface of the main body 7 toward the radially outward direction.

[0031] The front end plate 8 has a through hole 13 extending through the plate thickness in the center. A bearing 12 is disposed in the through hole 13, and the rod 3 is movably supported axially on the main body 7 by means of the inserted bearing 12. A mounting bracket 14 is fixed to one end of the rod 3, which is disposed outside the housing 2. The mounting bracket 14 has a through hole 15 extending through the rod 3 in a direction orthogonal to the length axis C of the rod 3.

[0032] At the other end of the rod 3, which is disposed within the housing 2, a movable plate 4 is fixed by fastening the external thread 3a formed on the rod 3 to the nut 16. The movable plate 4 is formed into a circular plate with an outer diameter slightly smaller than the inner diameter of the main body 7.

[0033] In this embodiment, a compression coil spring 5 is arranged in a compressed state between the front end plate 8 through which the rod 3 passes and the movable plate 4. Therefore, the rod 3 is always subjected to the force generated by the compression coil spring 5 in the direction of being pulled into the housing 2. Furthermore, when the rod 3 is moved in the direction of being pulled out of the housing 2, the compression of the compression coil spring 5 increases, and the force pulling the rod 3 into the housing 2 increases.

[0034] Sensor 6 is a non-contact distance sensor, such as a laser displacement meter, which is fixed to the outside of the rear end plate 9 of the housing 2. It shines a laser beam through the through hole 17 provided in the rear end plate 9 onto the end of the rod 3 and detects the reflected light from the end of the rod 3. In the figure, reference numeral 18 is a bracket for mounting sensor 6 to the rear end plate 9 of the housing 2.

[0035] Therefore, it is possible to measure the distance from the front end of sensor 6 to the end of rod 3. Measuring the distance from the front end of sensor 6, which is fixed to housing 2, to the end of rod 3 refers to detecting the positional relationship between rod 3 and housing 2.

[0036] The balancer 1 thus constructed is mounted between the rotating body 112 and the first arm 113 using a pair of first shafts 19 fixed to the rotating body 112 and a second shaft 20 fixed to the first arm 113. The first shafts 19 and the second shaft 20 are configured to be parallel to the second axis B and spaced apart from each other.

[0037] The first shaft 19, fixed to the rotating body 112, is inserted into the inner hole 11 of the mounting part 10 of the housing 2 of the balancer 1, and the housing 2 is supported by a bearing, such as a sliding bearing (first bearing) 21, disposed between the outer surface of the first shaft 19 and the inner surface of the inner hole 11, so that it can rotate around the first mounting axis X.

[0038] The second shaft 20, which is fixed to the first arm 113, is inserted into the through hole 15 of the mounting bracket 14 of the rod 3, and the rod 3 is supported by a bearing, such as a rolling bearing (second bearing) 22, which is disposed between the outer surface of the second shaft 20 and the inner surface of the through hole 15, in a manner that allows it to rotate about the second mounting axis Y.

[0039] Therefore, when the first arm 113 rotates relative to the rotating body 112 about the second axis B, the second axis 20 fixed to the first arm 113 moves about the second axis B. As a result, the distance between the first mounting axis X and the second mounting axis Y changes, and the compression of the compression coil spring 5 inside the housing 2 changes. When the first arm 113 is positioned in the vertical direction... Figure 1 In this state, the gravitational load torque acting on the first arm 113 is minimal. The first arm 113 tilts forward or backward. The greater the tilt angle relative to the vertical direction, the greater the gravitational load torque acting on the first arm 113 becomes.

[0040] On the other hand, in the balancer 1, the compression of the coil spring 5 increases when the first arm 113 is tilted forward or backward relative to the vertical direction compared to when it is positioned vertically. Furthermore, the distance between the plane including the first mounting axis X and the second mounting axis Y and the second axis B increases when the first arm 113 is tilted forward or backward relative to the vertical direction compared to when it is positioned vertically.

[0041] As a result, the auxiliary torque generated by the balancer 1 can be varied in a pattern that increases when the gravitational load torque acting on the first arm 113 is large and decreases when it is small, thereby reducing the load on the motor throughout the entire range of motion of the first arm 113.

[0042] The control device 120 includes at least one processor, at least one memory, and a display (notification unit) 121.

[0043] Under normal conditions, when the first arm 113 is configured at a predetermined angle relative to the rotating body 112, for example, 0°, i.e., as Figure 1 As shown, when the first arm 113 is configured in the vertical direction, the control device 120 stores the distance detected by the sensor 6.

[0044] "Normal time" refers to the moment when robot 110 leaves the factory, or the moment immediately after the first and second bearings 21 and 22 of the support balancer 1 have been replaced, or the moment when the sliding bearing 21 and rolling bearing 22 of the support balancer 1 have not deteriorated. The stored distance can be the actual distance detected by sensor 6, or it can be a stored design value.

[0045] Additionally, the processor of the control device 120 calculates, as needed, manually, periodically, or when the first arm 113 of the robot 110 is positioned vertically, the difference between the distance detected by the sensor 6 and the normal distance stored in the memory. Then, the processor of the control device 120 determines whether the absolute value Δ of the calculated difference exceeds a predetermined threshold. If the absolute value Δ exceeds the threshold, it notifies the display 121 that the balancer 1 has an abnormal state.

[0046] The function of the balancer 1 and the robot system 100 configured as described in this embodiment will be explained below.

[0047] According to the balancer 1 of this embodiment, the rebound force of the compression coil spring 5 always acts in the direction that pulls the rod 3 into the housing 2. Therefore, in the sliding bearing 21 provided on the first shaft 19 side, in order to support the housing 2 stretched forward by the compression coil spring 5, the load generated by the rebound force of the compression coil spring 5 only acts on the rear side of the first shaft 19. In addition, in the rolling bearing 22 provided on the second shaft 20 side, in order to support the rod 3 stretched backward by the compression coil spring 5, the load generated by the rebound force of the compression coil spring 5 only acts on the front side of the second shaft 20.

[0048] Furthermore, under the condition that the offset load described above is always applied, due to the long-term operation of robot 110, if the sliding bearing 21 wears, such as... Figure 3 As indicated by arrow P, housing 2 moves forward relative to the first shaft 19. Additionally, in the event of wear of the rolling bearing 22, as... Figure 4 As shown, rod 3 moves rearward relative to the second axis 20, as indicated by arrow Q. Figure 3 as well as Figure 4 In the diagram, it is assumed that wear occurred on bearings 21 and 22, which are shown in the shaded area.

[0049] As a result, in either the case of wear of the sliding bearing 21 or the case of wear of the rolling bearing 22, such as Figure 5 As shown by the dotted line, the distances detected by sensor 6 all become smaller than the stored normal distances.

[0050] According to the robot system 100 of this embodiment, if the absolute value Δ of the difference between the distance detected by the sensor 6 and the normal distance exceeds a predetermined threshold, the system notifies the display 121 of an abnormal state. This provides the advantage that measures such as replacing bearings 21 and 22 can be implemented before the wear of the sliding bearing 21 and rolling bearing 22 supporting the balancer 1 further develops and adversely affects other parts.

[0051] That is, although it is difficult to detect the initial wear of bearings 21 and 22 by measuring the motor current value, abnormal conditions can be detected and addressed by detecting the positional relationship between rod 3 and housing 2, which changes due to wear. In particular, when bearings 21 and 22, which support rod 3 and housing 2 respectively, wear simultaneously, abnormal conditions can be detected earlier based on the total wear of the two bearings 21 and 22.

[0052] Furthermore, in this embodiment, an example is given of a balancer 1 that utilizes a compression coil spring 5 to generate a force in the direction that pulls the rod 3 into the housing 2. Instead, as... Figure 6 As shown, the following balancer 1 can also be used: a compression helical spring 5 is placed between the movable plate 4 and the rear end plate 9, and the compression helical spring 5 generates force in the direction of pushing the rod 3 out of the housing 2.

[0053] In this case, a through hole 23 is provided in the front plate 8, and the distance of the movable plate 4 can be detected by a sensor 6 such as a laser displacement meter fixed to the front plate 8. Furthermore, the distance detected by the sensor 6 under normal conditions or the design value is pre-stored, and the absolute value Δ of the difference between the distance detected by the sensor and the distance under normal conditions is determined as needed or periodically to see if it exceeds a threshold.

[0054] Furthermore, in this embodiment, a laser displacement meter fixed to the rear end plate 9 is used as sensor 6 to detect the reflected light of the laser from the end face of the rod 3. Instead, as... Figure 7 As shown, the distance to the movable plate 4 (or nut 16) fixed to the rod 3 can also be detected.

[0055] Furthermore, in this embodiment, the distance under normal conditions is stored, and it is determined whether the absolute value Δ of the difference between the normal distance and the detected distance exceeds a threshold. Therefore, the angle of the first arm 113 relative to the rotating body 112 when the detection distance is arbitrarily set can be arbitrarily set.

[0056] Instead, when detecting the distance at the end of the stroke of lever 3, the new threshold can be stored as the distance obtained by subtracting the threshold from the normal distance, and it can be determined whether the detected distance is below the new threshold. The distance corresponding to the new threshold is usually outside the end of the stroke and is a distance that cannot be reached in the normal operation state of robot 110. Thus, even without setting the angle of the first arm 113 relative to the rotating body 112, an abnormal state can be detected when the detected distance is below the threshold.

[0057] Additionally, as a sensor, it can replace the laser displacement meter and other distance sensors 6, such as... Figure 8As shown, a contact switch such as limit switch 24 or a non-contact switch such as a proximity sensor can also be used. In this case, by configuring limit switch 24 to operate when lever 3 is in a position beyond the end of its travel, an abnormal state can also be detected when limit switch 24 is operating.

[0058] Additionally, as a sensor, it can replace the laser displacement meter and other distance sensors 6, such as... Figure 9 As shown, an optical sensor can also be used: the emitter 25 and the receiver 26 are arranged opposite each other on the main body 7 of the housing 2, and the optical axis L of the light emitted from the emitter 25 is positioned beyond the end of the stroke of the rod 3. When the positional relationship between the housing 2 and the rod 3 changes due to wear of the bearings 21 and 22, the absolute value Δ of the difference can be detected by blocking the optical axis L with the rod 3 (or the movable plate 4 or the nut 16).

[0059] Alternatively, instead of using sensor 6 to detect the distance between the rear end plate 9 and the rod 3, such as... Figure 10 As shown, the distance between the front end plate 8 and the mounting bracket 14 can also be detected using the sensor 6. Since there is no need to configure the sensor 6 inside the housing 2, the balancer 1 can be used not only as a spring balancer with a built-in compression coil spring 5, but also as a gas balancer with sealed gas.

[0060] In addition, in this embodiment, since the positional relationship between the housing 2 and the rod 3 is detected by the sensor 6, the displacement obtained by adding the displacement of the housing 2 relative to the first axis 19 and the displacement of the rod 3 relative to the second axis 20 is used to determine whether it is in an abnormal state.

[0061] Instead, such as Figure 11 As shown, the distance between the first mounting axis X (orthogonal to both the first mounting axis X and the second mounting axis Y) of the housing 2 and the outer surface (housing 2) of the mounting portion 10 can also be detected using sensor 6. Additionally, as... Figure 12 As shown, the distance between the second mounting axis Y (orthogonal to both the first mounting axis X and the second mounting axis Y) of the rod 3 and the end face (rod 3) of the mounting bracket 14 can also be detected using sensor 6. Alternatively, the distance can be detected separately. Figure 11 as well as Figure 12 The distance.

[0062] Since the wear degree of bearings 21 and 22 varies depending on the type of bearings 21 and 22 they support or the load applied to each bearing 21 and 22, each bearing 21 and 22 can be inspected separately, and different threshold values ​​can be used to determine whether an abnormal condition exists. For example, the wear of rolling bearing 22 is more likely to be greater than that of sliding bearing 21. Figure 1 In the example, the wear of the two sliding bearings 21 is significantly less than that of the single rolling bearing 22. Therefore, by detecting the distance variation of each bearing 21 and 22 separately and using different thresholds to determine whether it is an abnormal state, the wear of bearings 21 and 22 can be detected individually, and countermeasures can be taken as early as possible.

[0063] Furthermore, while this embodiment exemplifies a vertical six-axis articulated robot, the form of the robot 110 can be arbitrary. Additionally, the housing 2 is rotatably supported on the rotating body 112, and the rod 3 is rotatably supported on the first arm 113, but the reverse is also possible. Furthermore, although the support position of the housing 2 in the rotating body 112 is set at the midpoint of the housing 2's axial direction, a balancer 1 that provides support further rearward than the rear end plate 9 could also be applied.

[0064] Explanation of reference numerals in the attached figures:

[0065] 1: Balancer

[0066] 2: Shell

[0067] 3: Rod

[0068] 4: Movable plate (movable part)

[0069] 5: Compression coil spring (force generating unit)

[0070] 6: Distance sensor (sensor)

[0071] 7: Main body

[0072] 8: Front-end board (end board)

[0073] 9: Rear end board (end board)

[0074] 21: Sliding bearing (first bearing)

[0075] 22: Rolling bearing (second bearing)

[0076] 24: Limit switch (switch, sensor)

[0077] 25: Light emitter (sensor)

[0078] 26: Light receiver (sensor)

[0079] 100: Robotic Systems

[0080] 110: Robot

[0081] 112: Rotating body (first component)

[0082] 113: First arm (second component)

[0083] 121: Display (Notification Department)

[0084] B: Second axis (axis of rotation)

[0085] X: First mounting axis

[0086] Y: Second mounting axis

Claims

1. A balancer characterized by, Possessing: a housing mounted to one of a first member or a second member of a robot in a manner rotatable about a first mounting axis parallel to a rotation axis, the robot possessing the first member and the second member rotationally driven about the rotation axis relative to the first member, by a first bearing; a rod mounted to the other of the first member or the second member in a manner rotatable about a second mounting axis parallel to the rotation axis by a second bearing; a force generating unit generating a force in a direction to draw the rod into the housing or in a direction to push the rod out of the housing; and a sensor detecting at least one of a positional relationship of the first mounting axis to the housing and a positional relationship of the second mounting axis to the rod in a direction orthogonal to the first mounting axis and the second mounting axis.

2. The balancer according to claim 1, wherein the housing possesses a cylindrical main body and an end plate closing an axial one end of the main body, the balancer possesses a movable member disposed at the other end of the rod disposed in the main body, the force generating unit is a compression coil spring disposed between the end plate and the movable member.

3. The balancer according to claim 1, wherein the sensor is a distance sensor detecting a distance.

4. The balancer according to claim 1, wherein the sensor is a switch detecting that the positional relationship becomes a prescribed state. Possessing:

5. A robot system, characterized by a robot possessing the balancer according to any one of claims 1 to 4; and a notification unit notifying that an abnormal state has occurred in a case where a difference between the positional relationship detected by the sensor in a state where the first member and the second member are disposed at a prescribed relative position and the positional relationship at normal times exceeds a prescribed threshold value.

6. A robot system characterized by: possessing a balancer and a detection unit, the balancer possessing: a housing mounted to one of a first member or a second member of a robot in a manner rotatable about a first mounting axis parallel to a rotation axis, the robot possessing the first member and the second member rotationally driven about the rotation axis relative to the first member, by a first bearing; a rod mounted to the other of the first member or the second member in a manner rotatable about a second mounting axis parallel to the rotation axis by a second bearing; a force generating unit generating a force in a direction to draw the rod into the housing or in a direction to push the rod out of the housing; and a sensor detecting a positional relationship of the housing to the rod in a direction orthogonal to the first mounting axis and the second mounting axis, the detection unit detecting damage and wear of the first bearing and the second bearing according to the positional relationship.

7. The robot system according to claim 6, wherein the housing possesses a cylindrical main body and an end plate closing an axial one end of the main body, the detection unit possesses a sensor detecting a positional relationship of the first mounting axis to the housing and a positional relationship of the second mounting axis to the rod in a direction orthogonal to the first mounting axis and the second mounting axis. ​ The balancing device is provided with a movable member which is arranged at the other end of the lever, the other end of the lever being arranged in the main body portion, The force generating unit is a compression coil spring arranged between the end plate and the movable member.

8. The robot system according to claim 6 or 7, characterized in that, The sensor is a distance sensor which detects a distance.

9. The robot system according to claim 6 or 7, characterized in that, The sensor is a switch which detects that the positional relationship becomes a prescribed state.

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