JP2017196681A - Industrial robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce energy for holding the posture of a multi-joint arm.SOLUTION: An industrial robot includes: a base; a multi-joint arm which is connected to the base; a joint drive motor which operates the joint of the multi-joint arm; a hydraulic cylinder which assists at least one driving force of the joint drive motor and is provided with two ports to/from which hydraulic fluid flows on both sides of a piston; a hydraulic circuit which connects the two ports of the hydraulic cylinder; and at least one selector valve which switches a state for allowing the flow of the hydraulic fluid in the two ports and a state for blocking the flow of the hydraulic fluid in the two ports.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an industrial robot including a hydraulic cylinder that assists the driving force of a joint of a multi-joint arm.

  Conventionally, in an industrial robot having an articulated arm in which a plurality of links are connected, in order to reduce the load applied to the shaft that drives the link, a force that balances the gravitational moment acting on the link or the link or A balancer is known to be applied to the shaft. Patent Document 1 discloses an industrial robot provided with this type of balancer.

  The industrial robot described in Patent Document 1 includes an abutment, a first arm connected to the abutment via a vertical axis so as to be rotatable, one end connected to the first arm, and the other end supported. And a balancer connected to the table. The balancer includes an air cylinder, an air supply unit that supplies compressed air to the air cylinder, and a controller that controls the air supply unit. The controller stores the air pressure of compressed air for balancing the arm to the posture corresponding to the position and posture of the first arm, and the controller is based on the current posture of the first arm. Operate the air supply unit to supply the corresponding air pressure.

  The industrial robot described in Patent Document 2 includes an arm rotatably supported by a base part, and a balance mechanism having one end connected to the base part and the other end connected to the arm. . This balance mechanism has a drive mechanism including a speed reduction mechanism and a servo motor. The servo motor generates drive torque in a direction that cancels out the gravitational moment around the center of rotation of the base of the arm.

JP-A-6-262561 JP 2009-505951 A

  However, the industrial robots of Patent Documents 1 and 2 have room for improvement in terms of reducing energy for maintaining the posture of the arm. In particular, in the industrial robot of Patent Document 1, when the first arm is in a certain position and posture, compressed air must be constantly supplied to the balancer in order to maintain the posture.

  The present invention has been made in view of the above circumstances, and an object thereof is to reduce energy for maintaining the posture of an arm in an industrial robot.

An industrial robot according to one embodiment of the present invention is
Base and
An articulated arm connected to the base;
A joint drive motor for operating the joint of the articulated arm;
A hydraulic cylinder provided with two ports through which hydraulic oil enters and exits on both sides of the piston for assisting at least one driving force of the joint drive motor;
A hydraulic circuit connecting the two ports of the hydraulic cylinder;
It is characterized by comprising at least one switching valve for switching between a state allowing the flow of hydraulic oil in the two ports and a state blocking the flow of hydraulic oil in the two ports.

  According to the industrial robot having the above-described configuration, the flow of hydraulic oil in the two ports is blocked by switching the switching valve to a state in which the flow of hydraulic oil in the two ports is blocked, and the position and thrust of the hydraulic cylinder are maintained. The As a result, the assist force by the hydraulic cylinder continues and the posture of the arm is maintained. In this way, since the posture of the arm is maintained by preventing the flow of hydraulic oil, the posture of the arm is maintained as compared with the case where the torque for maintaining the posture is applied to the arm only by the joint drive motor. Energy to be reduced.

The industrial robot above
A bidirectional hydraulic pump provided in the hydraulic circuit;
Forward and reverse electric motors for driving the hydraulic pump;
A controller,
The hydraulic cylinder assists at least one driving force of the joint driving motor by the bidirectional hydraulic pump,
The controller may be configured to control the operation of the electric motor and the switching valve so as to generate the position and thrust of the hydraulic cylinder according to the position and posture of the articulated arm.

  In the industrial robot, the position and thrust (ie, assist force) of the cylinder piston are controlled by controlling the rotation direction, rotation torque, and rotation speed of the electric motor. As a result, the direction and magnitude of the assist force when operating the joint can be changed according to the position and posture of the articulated arm, and the effective assist force can be applied to the hydraulic cylinder at any position and posture of the articulated arm. Can be generated.

  In the industrial robot, the position and thrust of the cylinder are maintained by setting the switching valve in a state in which the flow of hydraulic oil in the two ports is blocked, and the assist force by the hydraulic cylinder is continued. Therefore, by switching the switching valve according to the operation of the articulated arm, it is possible to realize energy saving of assisting the joint driving force.

  In the industrial robot, the controller is configured to set the switching valve in a state of blocking the flow of hydraulic oil in the two ports when the movement of the joint assisted by the hydraulic cylinder stops for a predetermined time or more. May have been.

  Thereby, when the joint assisted by the hydraulic cylinder is stationary, the position and thrust of the piston of the cylinder are maintained, so that the state where the assist force is applied to the joint is maintained while suppressing the use of energy.

  In the industrial robot, the controller stores a motion pattern of the hydraulic cylinder including a position and thrust of the hydraulic cylinder corresponding to a motion pattern of the articulated arm, and based on the motion pattern of the hydraulic cylinder. The operation of the electric motor and the switching valve may be controlled.

Alternatively, the industrial robot further includes a load detector that detects a load applied to a joint assisted by the hydraulic cylinder,
The controller obtains the position and orientation of the articulated arm based on the rotation angle of the joint drive motor, and determines the position of the hydraulic cylinder based on the load detected by the load detector and the position and orientation of the articulated arm. A target position and a target thrust may be obtained, and operations of the electric motor and the switching valve may be controlled based on the target position and the target thrust of the hydraulic cylinder.

  By controlling the switching valve as described above, the switching valve can be switched so that energy saving is realized according to the operation of the articulated arm.

  In the industrial robot, a relief valve that releases hydraulic oil from the hydraulic circuit to the oil tank is provided in the hydraulic circuit, and the switching valve is provided between the port of the hydraulic circuit and the relief valve. It may be.

  Thereby, since the flow of hydraulic fluid is blocked at a position closer to the cylinder in the hydraulic circuit, the position and thrust of the cylinder while the switching valve is off can be efficiently maintained.

  In the industrial robot, the hydraulic cylinder is provided in the articulated arm, the electric motor is installed apart from the articulated arm, and a hydraulic pipe forming the hydraulic circuit is connected to the articulated arm and / or the base. It may be inserted inside.

  Thereby, the centrifugal force which acts on the articulated arm by the drive mechanism of the hydraulic cylinder can be reduced.

  The industrial robot may further include a spring balancer provided in parallel with the hydraulic cylinder.

  Thereby, the assist force of the driving force of the joint can be increased.

  In the industrial robot, the controller may be configured to control the operation of the joint drive motor.

  Thus, the number of controllers can be reduced by controlling the operation of the joint drive motor and the operation of the hydraulic cylinder by the controller. In addition, it is possible to easily construct a configuration in which the hydraulic cylinder performs an operation associated with the operation or posture of the articulated arm.

  ADVANTAGE OF THE INVENTION According to this invention, in the robot provided with the hydraulic cylinder which assists the driving force of the joint of a multi joint arm, the energy for hold | maintaining the attitude | position of an arm can be reduced.

It is a mimetic diagram showing a schematic structure of an industrial robot concerning a 1st embodiment of the present invention. It is a block diagram which shows the structure of the drive system of an industrial robot. It is a hydraulic circuit diagram which shows the structure of the drive system of a balancer apparatus. It is a hydraulic circuit diagram which shows the modification of the structure of the drive system of a balancer apparatus. It is a hydraulic circuit diagram which shows the structure of the drive system of the balancer apparatus of the industrial robot which concerns on 2nd Embodiment. It is a schematic diagram which shows the modification of schematic structure of an industrial robot.

[First Embodiment]
Next, embodiments of the present invention will be described with reference to the drawings. First, the schematic configuration of the robot 1 will be described. FIG. 1 is a schematic diagram showing a schematic configuration of an industrial robot (hereinafter simply referred to as “robot 1”) according to an embodiment of the present invention. As shown in FIG. 1, a robot 1 according to this embodiment is a 6-axis vertical articulated robot. However, the present invention is not limited to the above, and can be widely applied to robots having a multi-joint arm regardless of the number of axes regardless of whether they are a horizontal multi-joint type or a vertical multi-joint type.

  The robot 1 includes a base 2, an articulated arm (hereinafter simply referred to as “arm”) 10 supported by the base 2, an end effector 5 attached to the tip of the arm 10, and the arm 10 and the end effector 5. And a controller 6 for controlling the operation.

  The arm 10 is formed by connecting a plurality of links in series. Specifically, the arm 10 has a pivot shaft 21, a first link 11, a second link 12, a third link 13, a fourth link 14, and a fifth link 15 that are directed from the proximal end to the distal end. Concatenated in this order. The turning shaft 21 is connected to the base 2 through a turning joint JT1 so as to be turnable around a vertical axis. The base end portion of the first link 11 is connected to the turning shaft 21 via the rotary joint JT2. The distal end portion of the first link 11 and the proximal end portion of the second link 12 are connected via a rotary joint JT3. The rotary joints JT2 and JT3 are joints that link the links so as to rotate vertically around the horizontal axis. The distal end portion of the second link 12 and the proximal end portion of the third link 13 are connected via a twisted joint JT4.

  The distal end portion of the third link 13 and the proximal end portion of the fourth link 14 are connected via a rotary joint JT5. The distal end portion of the fourth link 14 and the proximal end portion of the fifth link 15 are connected via a twisted joint JT6. The connecting body of the third link 13, the fourth link 14, and the fifth link 15 including the rotary joint JT5 and the twist joint JT6 constitutes the wrist portion of the arm 10. A mechanical interface is provided at the tip of the fifth link 15, and an end effector 5 corresponding to the work performed by the robot 1 is connected to the mechanical interface.

  The arm 10 having the above-described configuration includes a joint driving unit corresponding to each of the joints JT1 to JT6 (axis). FIG. 2 is a block diagram showing the configuration of the drive system of the robot 1. As shown in FIG. 2, each joint drive unit includes servo drivers D1 to D6, joint drive motors M1 to M6, a speed reducer (not shown), and the like. Each of the joint drive motors M1 to M6 is a servomotor, and rotation angle detectors E1 to E6 for detecting the rotation angles of the joints JT1 to JT6 are attached. The rotation angle detectors E1 to E6 may be any devices that can detect the rotation angles of the joints JT1 to JT6, such as a rotary encoder, a resolver, and a pulse generator.

  Returning to FIG. 1, the arm 10 is provided with a balancer device 7 that applies an assist force Ta to the first link 11 in a direction that cancels the gravitational moment around the joint JT2 of the arm 10 (that is, a direction that balances the gravitational moment). Yes. In the present embodiment, the assist force Ta is an assist torque, and the assist torque Ta applied to the first link 11 by the balancer device 7 assists the drive torque Tm of the joint drive motor M2 that drives the joint JT2.

  The balancer device 7 includes a hydraulic cylinder 71 having one end connected to the turning shaft 21 and the other end connected to the first link 11. The balancer device 7 may be installed between the links of the arm 10 or between any link of the arm 10 and the base 2 according to the joint to be assisted. The cylinder 71 is provided on the back side of the arm 10 in the same manner as a conventional spring balancer or the like. That is, when the tip end side of the first link 11 is rotated upward around the joint JT2, the cylinder 71 contracts, and when the tip end side of the first link 11 is rotated downward around the joint JT2, the cylinder 71 extends. As described above, the cylinder 71 is attached to the arm 10.

  FIG. 3 is a hydraulic circuit diagram showing the configuration of the drive system of the balancer device 7. As shown in FIG. 3, the cylinder 71 of the balancer device 7 is a so-called closed circuit type actuator, and includes a hydraulic pump 72 in the drive mechanism of the cylinder 71 and an electric motor 73 directly connected to the hydraulic pump 72. Yes. In the closed circuit type actuator, by controlling the rotation direction, rotation speed, and rotation torque of the electric motor 73, the discharge direction, discharge amount, and discharge pressure of the pressure oil discharged from the hydraulic pump 72 are adjusted. Thereby, the position (speed) and thrust of the piston 711 of the cylinder 71 are controlled.

  The balancer device 7 may be of a package type in which a cylinder 71, a hydraulic pump 72, an electric motor 73, and hydraulic piping that connects the cylinder 71 and the hydraulic pump 72 are integrally provided. Alternatively, the balancer device 7 may be a split type in which the cylinder 71 is attached to the arm 10 and the base 2, and the hydraulic pump 72 and the electric motor 73 are separated from the cylinder 71 apart from the arm 10. In addition, the hydraulic piping connecting the cylinder 71 and the hydraulic pump 72 may be inserted into the arm 10 and / or the base 2. If the split-type balancer device 7 is employed in this way, the influence of the centrifugal force of the balancer device 7 on the movement of the arm 10 can be reduced. In addition, the balancer device 7 that does not interfere with the movement of the arm 10 can be easily arranged.

  The cylinder 71 includes a rod 710, a piston 711 connected to the rod 710, and a sleeve 712 in which the piston 711 reciprocates. The inside of the sleeve 712 is divided into a forward movement chamber 71a and a backward movement chamber 71b by a piston 711. The rod 710 extends when the hydraulic oil flows into the forward movement chamber 71a of the cylinder 71, and the rod 710 contracts when the hydraulic oil flows into the backward movement chamber 71b of the cylinder 71. The pressure receiving area of the piston 711 in the backward movement chamber 71b is smaller than the pressure receiving area of the piston 711 in the forward movement chamber 71a.

  The sleeve 712 is a double-acting type that has ports on both sides of the piston 711 through which hydraulic oil enters and exits. Two ports of the cylinder 71 are connected by oil passages 81 and 82 with a hydraulic pump 72 interposed therebetween, and a hydraulic circuit closed by the cylinder 71 and the hydraulic pump 72 is formed. This hydraulic circuit is defined by the aforementioned hydraulic piping or the like.

  The return chamber 71 b of the cylinder 71 and the hydraulic pump 72 are connected by a first oil passage 81. The forward movement chamber 71 a of the cylinder 71 and the hydraulic pump 72 are connected by a second oil passage 82. The second oil passage 82 is connected to the hydraulic oil tank 86 via the supply / discharge oil passage 85.

  The first oil passage 81 is connected to the hydraulic oil tank 86 via the supply / discharge oil passage 85. Between the first oil passage 81 and the supply / discharge oil passage 85, the flow of hydraulic oil from the first oil passage 81 to the supply / discharge oil passage 85 is prohibited, and from the supply / discharge oil passage 85 to the first oil passage 81. A check valve 83 is provided to allow the flow of hydraulic oil. Further, between the first oil passage 81 and the supply / discharge oil passage 85, when the oil pressure of the first oil passage 81 exceeds a predetermined pressure, the supply / discharge from the cylinder 71 side than the check valve 83 of the first oil passage 81 is performed. A relief valve 87 for releasing hydraulic oil to the oil passage 85 is provided.

  Between the second oil passage 82 and the supply / discharge oil passage 85, the flow of hydraulic oil from the second oil passage 82 to the supply / discharge oil passage 85 is prohibited, and from the supply / discharge oil passage 85 to the second oil passage 82. A check valve 88 is provided to allow the flow of hydraulic oil. Also, between the second oil passage 82 and the supply / discharge oil passage 85, if the oil pressure of the second oil passage 82 exceeds a predetermined pressure, the supply / discharge from the cylinder 71 side rather than the check valve 88 of the second oil passage 82. A relief valve 89 that releases hydraulic oil to the oil passage 85 is provided. Further, between the second oil passage 82 and the supply / discharge oil passage 85, the flow of hydraulic oil from the supply / discharge oil passage 85 to the check valve 88 and the relief valve 89 of the second oil passage 82 is allowed. A pilot check valve 93 that prohibits reverse flow is provided. The pilot check valve 93 operates using the oil pressure of the first oil passage 81 as a pilot signal, and is released when the oil pressure of the second oil passage 82 becomes lower than the oil pressure of the first oil passage 81, and moves backward with the forward movement chamber 71 a. The difference in flow rate due to the difference in pressure receiving area of the chamber 71b is absorbed.

  In the first oil passage 81 and the second oil passage 82, a switching valve 80 is provided in the vicinity of each port of the cylinder 71. The switching valve 80 is a normally closed on-off valve. The operation of the switching valve 80 is controlled by the controller 6. If the switching valve 80 is on, the flow of hydraulic oil at the two ports of the cylinder 71 is allowed, and the rod 710 can move. If the switching valve 80 is off, the flow of hydraulic oil at the two ports of the cylinder 71 is blocked, and the rod 710 stops.

  The first oil passage 81 and the second oil passage 82 are provided with pressure sensors 90 and 91 for detecting the pressure of the hydraulic oil, respectively. Further, the cylinder 71 is provided with a position sensor 92 for detecting the position of the piston 711 (or rod 710). Detection signals from the position sensor 92 and the pressure sensors 90 and 91 are transmitted to the controller 6.

  The hydraulic pump 72 is a bidirectional hydraulic pump, and can selectively send hydraulic oil to the return chamber 71b and the forward chamber 71a of the cylinder 71. The hydraulic pump 72 is rotationally driven by an electric motor 73 that can rotate both forward and reverse. The electric motor 73 is a servo motor, and the rotation direction, rotation speed (rotation angle), and rotation torque of the electric motor 73 are servo-controlled by the controller 6 and the servo driver 75.

  Next, the controller 6 will be described. The controller 6 is a so-called computer, and includes an arithmetic processing device such as a CPU and a storage device such as a ROM and a RAM (none of which are shown). The storage device stores a program executed by the arithmetic processing unit, various fixed data, and the like. The arithmetic processing device transmits / receives data to / from an input device such as a teaching pendant or an operation panel or an external device. Further, the arithmetic processing unit inputs detection signals from various sensors and outputs control signals to each control target. In the controller 6, processing for controlling various operations of the robot 1 is performed by the arithmetic processing device reading and executing software such as a program stored in the storage device. The controller 6 may execute each process by centralized control by a single computer, or may execute each process by distributed control by cooperation of a plurality of computers. Moreover, the controller 6 may be comprised from the microcontroller, the programmable logic controller (PLC), etc.

  The controller 6 stores the motion patterns of the arm 10 and the end effector 5 that are taught in advance or programmed. Based on the motion pattern and the rotation angles detected by the rotation angle detectors E1 to E6, the controller 6 generates a drive command including a position command and a torque command for each joint drive unit, and the corresponding servo driver D1. To D6. The servo drivers D1 to D6 calculate a drive current value based on the drive command and the rotation angles detected by the rotation angle detectors E1 to E6, and supply the drive current to the joint drive motors M1 to M6.

  The controller 6 stores a motion pattern of the cylinder 71. The motion pattern of the cylinder 71 includes the position and thrust of the piston 711 of the cylinder 71 corresponding to the motion (position, posture, etc.) of the arm 10, on / off of the switching valve 80, and the like. The thrust of the piston 711 corresponds to the assist force Ta generated at the joint JT2 by the action of the cylinder 71. The controller 6 generates a drive command based on the position and thrust included in the motion pattern of the cylinder 71, detection values of the position sensor 92 and the pressure sensors 90 and 91, and the like. The generated drive command is output to the servo driver 75. The servo driver 75 calculates a drive current value based on the drive command, the rotation angle detected by the rotation angle detector 74, and supplies the drive current to the electric motor 73.

  In the motion pattern of the cylinder 71, the switching valve 80 is in principle on when the arm 10 is operating, but the switching valve 80 is off when the position of the piston 711 is held at a constant value for a predetermined time or more. Can be switched to. In other words, the switching valve 80 is turned off when the movement of the joint JT2 assisted by the cylinder 71 is stationary for a predetermined time or more. For example, when the swing joint JT1 is operated without operating the joint JT2, that is, when the arm 10 rotates horizontally as a whole, the switching valve 80 is turned off. Further, for example, when only the joints JT3 to JT5 on the distal end side relative to the joint JT2 of the arm 10 are operated, the switching valve 80 is turned off. If the switching valve 80 is off, the flow of hydraulic oil in the cylinder 71 is blocked, so that the position and thrust of the piston 711 of the cylinder 71 are generally maintained. Thus, the assist force Ta of the cylinder 71 is maintained while suppressing the use of energy of the balancer device 7.

  An example of the operation of the balancer device 7 in the robot 1 having the above configuration will be described.

  When the distal end side of the first link 11 is rotated upward, the joint drive motor M2 of the joint drive unit of the joint JT2 rotates in the rotational direction to rotate the first link 11 around the joint JT2. Is generated. Here, in the balancer device 7, the switching valve 80 is turned on, the hydraulic pump 72 is operated so that the cylinder 71 is contracted, and an assist force Ta in the same rotational direction as the drive torque Tm is generated. As a result, the sum of the drive torque Tm and the assist force Ta acts on the first link 11, and the drive torque Tm of the joint drive motor M2 is assisted by the assist force Ta.

  Further, when the distal end side of the first link 11 is rotated downward, the joint drive motor M2 of the joint drive unit of the joint JT2 is driven in the direction of rotating the first link 11 downward around the joint JT2. Tm is generated. Here, in the balancer device 7, the switching valve 80 is turned on, the hydraulic pump 72 is operated so that the cylinder 71 extends, and an assist force Ta in the same rotational direction as the drive torque Tm is generated. As a result, the sum of the drive torque Tm and the assist force Ta acts on the first link 11, and the drive torque Tm of the joint drive motor M2 is assisted by the assist force Ta. However, the balancer device 7 may generate an assist force Ta in the rotation direction opposite to the drive torque Tm. In this case, the rotational speed of the first link 11 can be suppressed and the braking force can be increased.

  Further, when rotating the turning joint JT1 and the joints JT3 and JT4 with the angle of the joint JT2 kept constant, the switching valve 80 of the balancer device 7 is turned off, and the flow of the hydraulic oil in the hydraulic cylinder 71 is reduced. By setting the state to be blocked, the length of the cylinder 71 (that is, the position of the piston 711) is kept constant. The balancer device 7 tries to maintain the position of the first link 11 against the gravitational moment acting on the first link 11. Here, when the holding force of the balancer device 7 cannot sufficiently counter the gravitational moment, the drive torque Tm in the same rotational direction as the assist force Ta is generated in the servo-controlled joint drive motor M2 to generate the first link 11. The position of is kept constant.

  As described above, the robot 1 according to this embodiment includes the balancer device 7 that assists the driving force of at least one of the joint drive motors M1 to M6 (here, the joint drive motor M2). This balancer device 7 includes a cylinder 71 provided with ports through which hydraulic oil enters and exits on both sides of a piston 711, a hydraulic circuit connecting the two ports of the cylinder 71, and a bidirectional hydraulic pump 72 provided in the hydraulic circuit. , A forward / reverse rotating electric motor 73 for driving the hydraulic pump 72, and at least one switching valve 80 for switching between a state allowing the flow of hydraulic oil in the two ports and a state blocking the flow of hydraulic oil in the two ports. And have. The switching valve 80 may operate so as to allow the flow of hydraulic oil in the two ports when turned on and prevent the flow of hydraulic oil in the two ports when turned off. The controller 6 controls the operation of the electric motor 73 and the switching valve 80 so as to generate the position and thrust of the cylinder 71 according to the position and posture of the arm 10. The controller 6 that controls the operation of the balancer device 7 may be a component of the balancer device 7, or a controller (robot controller) that is a component of the robot 1 may be provided with the function. .

  In the robot 1, the position and thrust (ie, assist force Ta) of the piston 711 of the cylinder 71 are controlled by controlling the rotation direction, rotation torque, and rotation speed of the electric motor 73. As a result, the direction and magnitude of the assist force Ta when operating the joint JT2 can be changed according to the position and posture of the arm 10, and the assist device effective for the balancer device 7 at any position and posture of the arm 10 can be obtained. Can generate power. That is, the assist force Ta generated by the balancer device 7 allows the arm 10 to perform an operation with little energy loss in any posture.

  Further, in the robot 1, the position and thrust of the cylinder 71 are maintained by turning off the switching valve 80. Therefore, by switching the switching valve 80 according to the operation of the arm 10, it is possible to continue the assist force Ta by the cylinder 71 while suppressing the use of energy. In this way, energy saving in assisting the joint driving force can be realized.

  In principle, the switching valve 80 is turned off when the joint motion assisted by the cylinder 71 is stationary for a predetermined time or more. Here, the controller 6 stores the motion pattern of the cylinder 71 including the position and thrust of the cylinder 71 corresponding to the motion pattern of the arm 10. Based on the motion pattern of the cylinder 71, the controller 6 It is configured to control the operation. By controlling the switching valve 80 in this way, the switching valve 80 is switched so that energy saving is realized according to the operation of the arm 10.

  Further, in the robot 1, the control unit that controls the operation of the electric motor 73 included in the balancer device 7 can be shared with the controller 6 that controls the operation of the arm 10. In this way, the controller 6 controls the electric motor 73 of the balancer device 7 and the joint drive motors M1 to M6 of the arm 10 to operate the balancer device 7 (cylinder 71) in relation to the operation of the arm 10. The structure can be easily realized. Then, by combining the joint drive motors M1 to M6 and the balancer device 7 including the electrohydraulic actuator, the arm 10 is positioned by the joint drive motors M1 to M6 at a high position regardless of the accuracy of the assist force Ta generated by the balancer device 7. Accuracy is ensured.

[Modification 1]
Next, the modification 1 of the said embodiment is demonstrated. In the above, the switching valve 80 is provided in the vicinity of the port of the cylinder 71 in the hydraulic circuit. According to this, since the flow of hydraulic oil is blocked at a position closer to the cylinder 71 of the hydraulic circuit, the position and thrust of the cylinder 71 while the switching valve 80 is off can be efficiently maintained. However, the arrangement of the switching valve 80 on the hydraulic circuit is not limited to this. In Modification 1, an example in which the arrangement of the switching valve 80 is modified in the above embodiment will be described.

  FIG. 4 is a hydraulic circuit diagram showing a modification of the configuration of the drive system of the balancer device 7. In the balancer device 7A according to Modification 1 shown in FIG. 4, switching valves 80A and 80B are provided between the relief valves 87 and 89 and the hydraulic pump 72 in the oil passages 81 and 82, respectively. Further, when the switching valves 80A and 80B are provided between the relief valves 87 and 89 and the hydraulic pump 72, one of the switching valves 80A and 80B may be omitted. As described above, if the switching valves 80A and 80B can be separated from the cylinder 71 or the number of the switching valves 80A and 80B can be reduced, the degree of freedom in the layout of the hydraulic circuit can be increased.

[Modification 2]
Then, the modification 2 of the said embodiment is demonstrated. In the above, the operation of the cylinder 71, that is, the operation of the electric motor 73 is controlled based on the motion pattern of the cylinder 71 stored in advance. According to this, the control of the balancer device 7 becomes relatively simple. However, the operation control of the balancer device 7 is not limited to the above. In Modification 2, Examples 2 (i) and 2 (ii) in which the operation of the cylinder 71 is controlled based on detection values of various sensors in the above embodiment will be described.

  Example 2 (i): The controller 6 obtains the position and orientation of the arm 10 based on the detection values of the rotation angle detectors E1 to E6, and detects a load applied to the assisted joint JT2 (not shown). ) And the position and posture of the arm 10, the target position and target thrust of the piston 711 of the cylinder 71 are obtained. Then, the controller 6 controls the operation of the electric motor 73 and the switching valve 80 based on the obtained target position and target thrust of the piston 711 of the cylinder 71. Here, the load detector is, for example, a deflection detector that detects the deflection of the first link 11, an ammeter that detects the current of the joint drive motor M2 of the joint JT2, a torque detector applied to the speed reducer of the joint JT2, and the like. Any device that can directly or indirectly detect the load applied to the joint drive section of the first link 11 or the joint JT2 is acceptable.

  Example 2 (ii): The controller 6 stores a calculation model for obtaining the position and thrust of the cylinder 71 suitable for the position and posture of the arm 10. The controller 6 obtains the position and orientation of the arm 10 based on the detection values of the rotation angle detectors E1 to E6, and obtains the target position and target thrust of the cylinder 71 from the position and orientation of the arm 10 and the calculation model. The operation of the electric motor 73 and the switching valve 80 is controlled based on the target position and target thrust of the cylinder 71.

[Second Embodiment]
Next, a second embodiment will be described. The balancer device 7 included in the robot 1 according to the first embodiment is configured to realize an operation with little energy loss even in any posture of the arm 10. However, the balancer device mounted on the robot 1 to which the present invention is applied may be configured to assist the joint drive motor only when the posture of the arm 10 is maintained. Therefore, in the second embodiment, a robot 1 including a balancer device 7B configured to assist the joint drive motor M2 only when holding the posture of the arm 10 will be described.

  The robot 1 according to the second embodiment has substantially the same configuration as the robot 1 according to the first embodiment described above, except for the balancer device 7B. Therefore, in the description of the robot 1 according to the present embodiment, the balancer device 7B will be described in detail, and description overlapping with the first embodiment will be omitted.

  FIG. 5 is a hydraulic circuit diagram showing the configuration of the drive system of the balancer device 7B of the robot 1 according to the second embodiment. In addition, description of a structure and an effect | action is abbreviate | omitted by attaching | subjecting the same code | symbol to a member the same as that of above-mentioned 1st Embodiment, or a similar.

  The balancer device 7B according to the present embodiment includes a hydraulic cylinder 71 having one end connected to the turning shaft 21 and the other end connected to the first link 11 (see FIG. 1). As shown in FIG. 5, the balancer device 7B includes a hydraulic cylinder 71 provided with two ports through which hydraulic oil enters and exits on both sides of a piston 711, an oil passage circuit 81A connecting the two ports of the cylinder 71, And at least one switching valve 80 provided in the path circuit 81A. The operation of the switching valve 80 is controlled by the controller 6, and the switching valve 80 causes the oil passage circuit 81A to permit the flow of hydraulic oil in the two ports and to block the flow of hydraulic oil in the two ports. Can be switched. The oil passage circuit 81A is defined by hydraulic piping or the like. In addition, a hydraulic oil tank 86 is connected to the oil passage circuit 81A through a supply / discharge oil passage 97. The hydraulic oil in the hydraulic oil tank 86 covers the difference in the amount of hydraulic oil flowing in and out between the forward movement chamber 71a and the backward movement chamber 71b of the cylinder 71.

  In the robot 1 including the balancer device 7B having the above-described configuration, the controller 6 prevents the flow of hydraulic oil in the two ports when the joint motion assisted by the hydraulic cylinder 71 is stationary for a predetermined time or longer. State As a result, the flow of hydraulic oil in the two ports of the hydraulic cylinder 71 is blocked, and the position and thrust of the hydraulic cylinder 71 are maintained. As a result, the assist force by the hydraulic cylinder 71 continues and the posture of the arm 10 is maintained. In this way, since the posture of the arm is maintained by preventing the flow of hydraulic oil, the posture of the arm is maintained as compared with the case where the torque for maintaining the posture is applied to the arm only by the joint drive motor. Energy to be reduced.

  In addition to the above, the controller 6 sets the switching valve 80 in a state that allows the flow of hydraulic oil in the two ports.

  As in the first embodiment, the controller 6 stores the motion pattern of the hydraulic cylinder 71 including the position and thrust of the hydraulic cylinder 71 corresponding to the motion pattern of the arm 10. Based on the above, the operation of the switching valve 80 is controlled.

  The preferred embodiments of the present invention (the first embodiment and its modifications, and the second embodiment) have been described above, but the above configuration can be modified as follows, for example.

  For example, in the above embodiment, the arm 10 and the balancer device 7 are controlled by a single controller 6. Thereby, the number of controllers 6 can be reduced. In addition, it is possible to easily construct a configuration that causes the balancer device 7 to perform an operation associated with the operation or posture of the arm 10. However, the arm 10 and the balancer device 7 may be controlled by different controllers.

  Further, for example, in the above embodiment, the cylinder 71 of the balancer device 7 is a closed circuit type actuator. However, the configuration of the cylinder 71 of the balancer device 7 is not limited to this. For example, the cylinder 71 may be an open circuit type actuator. In this case, a control valve for controlling the position of the piston 711 may be provided in a hydraulic circuit that connects the cylinder 71 and the hydraulic pump 72, and an electric motor that supplies the hydraulic pump 72 with constant power may be provided.

  Further, for example, in the above embodiment, the balancer device 7 is provided in the joint JT2, but a balancer device (not shown) having substantially the same configuration as the balancer device 7 may be provided in the joint JT3. Alternatively, a conventional spring balancer (not shown) may be juxtaposed in addition to the balancer device 7 at the joint JT2. As described above, when the robot 1 includes a plurality of assisting means, the assisting force of the joint driving force can be increased.

  Further, for example, in the above embodiment, the balancer device 7 includes a hydraulic cylinder 71 that is a closed circuit type actuator. Then, by combining the joint drive motor M2 of the joint drive unit of the joint JT2 and the balancer device 7, the positioning accuracy of the arm 10 is ensured by the operation of the joint drive motor M2 that is servo-controlled, and in any posture of the arm 10 Can realize operation with less energy loss.

  For the above reason, the cylinder 71 of the balancer device 7 is a closed circuit type actuator. However, the configuration of the cylinder 71 of the balancer device 7 is not limited to this. For example, the cylinder 71 may be an open circuit type actuator. In this case, a control valve for controlling the position of the piston 711 may be provided in a hydraulic circuit that connects the cylinder 71 and the hydraulic pump 72, and an electric motor that supplies the hydraulic pump 72 with constant power may be provided.

  Further, for example, in the above embodiment, the switching valve 80 is a normally closed on-off valve, but the switching valve 80 may be a normally-open on-off valve. The operation of the switching valve 80 in this case is the same as that described in the description of the operation of the switching valve 80 in the above embodiment with the on / off reversed.

Further, for example, in the above embodiment, the arm 10 of the robot 1 is a vertical articulated type. However, as shown in FIG. 6, the present invention can also be applied to a robot 1A including a horizontal articulated arm 10A. The robot 1A includes a base 2, a horizontal articulated arm 10A connected to the base 2, and an end effector 5 connected to the tip of the arm 10A. The arm 10A includes a lifting shaft 22 connected to the base 2 via a lifting joint JT11, a first link 11A connected to the lifting shaft 22 via a horizontal rotary joint JT12, a first link 11A and a horizontal rotary joint JT13. The second link 12A connected via the third link 13A connected via the second link 12A via the lifting joint JT14, and the fourth link connected via the third link 13A via the horizontal rotary joint JT15. 14A. Here, the balancer device 7 includes a cylinder 71 attached across the arm 10A and the base 2 so as to expand and contract in parallel with the lifting direction of the lifting shaft 22 so as to assist the joint driving force of the lifting joint JT11. Yes. And the balancer apparatus 7 produces the assist force Ta of an up-down direction according to the position and attitude | position of arm 10A similarly to the said embodiment.

  From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

1: Industrial robot 2: Base 6: Controller 7, 7A, 7B: Balancer device 10: Articulated arm 71: Hydraulic cylinder 72: Hydraulic pump 73: Electric motor 74: Rotation angle detector 75: Servo driver 80: Switching valve 81: First oil passage (hydraulic circuit)
82: Second oil passage (hydraulic circuit)
83, 88: Check valve 85: Supply / discharge oil passage 86: Hydraulic oil tank 87, 89: Relief valve 90, 91: Pressure sensor 92: Position sensor JT1 to JT6: Joint M1-M6: Joint drive motor Ta: Assist force Tm : Driving torque

Claims (9)

Base and
An articulated arm connected to the base;
A joint drive motor for operating the joint of the articulated arm;
A hydraulic cylinder provided with two ports through which hydraulic oil enters and exits on both sides of the piston for assisting at least one driving force of the joint drive motor;
A hydraulic circuit connecting the two ports of the hydraulic cylinder;
At least one switching valve that switches between a state that allows the flow of hydraulic oil in the two ports and a state that blocks the flow of hydraulic oil in the two ports.
Industrial robot. A bidirectional hydraulic pump provided in the hydraulic circuit;
Forward and reverse electric motors for driving the hydraulic pump;
A controller,
The hydraulic cylinder assists at least one driving force of the joint driving motor by the bidirectional hydraulic pump,
The controller controls the operation of the electric motor and the switching valve so as to generate the position and thrust of the hydraulic cylinder according to the position and posture of the articulated arm;
The industrial robot according to claim 1. The controller sets the switching valve in a state of preventing the flow of hydraulic oil in the two ports when the movement of the joint assisted by the hydraulic cylinder is stationary for a predetermined time or more;
The industrial robot according to claim 2. The controller stores a motion pattern of the hydraulic cylinder including a position and thrust of the hydraulic cylinder corresponding to a motion pattern of the articulated arm, and the electric motor and the switching are based on the motion pattern of the hydraulic cylinder. Control the operation of the valve,
The industrial robot according to claim 2 or 3. A load detector for detecting a load applied to the assisted joint;
The controller obtains the position and posture of the articulated arm based on the rotation angle of each joint of the articulated arm, and based on the load detected by the load detector and the position and posture of the articulated arm. Obtaining a target position and a target thrust of the hydraulic cylinder, and controlling operations of the electric motor and the switching valve based on the target position and the target thrust of the hydraulic cylinder;
The industrial robot according to claim 2 or 3. The hydraulic circuit is provided with a relief valve that releases hydraulic oil from the hydraulic circuit to the oil tank, and the switching valve is provided between the port of the hydraulic circuit and the relief valve.
The industrial robot according to any one of claims 2 to 5. The hydraulic cylinder is provided in the articulated arm;
The electric motor is installed away from the articulated arm;
Hydraulic piping forming the hydraulic circuit is inserted into the articulated arm and / or the base;
The industrial robot according to any one of claims 2 to 6. A spring balancer arranged in parallel with the hydraulic cylinder;
The industrial robot as described in any one of Claims 1-7. The controller controls the operation of the joint drive motor;
The industrial robot according to any one of claims 2 to 7.

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