JPS6125512B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic circuit that prevents abnormal operations during teaching in an industrial robot.

An example of a hydraulic circuit for enabling automatic operation of a hydraulic industrial robot is the one shown in FIG.

Briefly, hydraulic oil supplied from a hydraulic pump 1 via a check valve 2 is supplied to several electro-hydraulic servo valves 3 (one shown in the figure) that operate in response to signals from a separately provided electric control system. The automatic switching causes each actuator 4 to operate, allowing the main body of the industrial robot, its wrist, etc. to perform desired movements.

In the hydraulic circuit of such an industrial robot, the required amount of hydraulic fluid fluctuates because the robot operates intermittently. For this purpose, an accumulator 5 is provided in the pipeline between the hydraulic pump 1 and the electro-hydraulic servo valve 3, and by storing hydraulic oil therein and compensating for a part of the fluctuation amount, the hydraulic pump 1 can be made smaller. It is planned.

Incidentally, during teaching work for teaching the movement of an industrial robot before it is operated automatically, a worker often enters the working area of the industrial robot.
For this reason, means is used to limit the current value acting on the electro-hydraulic servo valve 3 in advance so that the actuator for driving each axis operates slowly.

However, if only the speed limit means based on signals from the electrical control system are used, short-circuit accidents may occur in the electrical control system, or dust may adhere between the nozzle and the flapper, reducing the nozzle opening area and reducing the pilot pressure. When a problem occurs such as an abnormal rise in the electrohydraulic servo valve, the opening degree of the electrohydraulic servo valve increases, causing the robot to operate at high speed and contacting workers in the work area, potentially causing an unexpected accident.

In addition, when a situation arises in which the speed cannot be controlled by the electro-hydraulic servo valve as described above, even if the operator presses the full stop button to stop the hydraulic pump, the residual pressure in the accumulator will cause the hydraulic pump to operate. The disadvantage is that the actuator cannot be stopped immediately, since oil is still supplied to the electrohydraulic servovalve.

By the way, Japanese Patent Application Laid-Open No. 12496/1983 states that when the flow rate control valve setting exceeds or falls short of the input setting, the flow rate fluctuation is supplemented or absorbed by the servo flow rate, and the actuator is set to the input setting for the servo valve. A control device is described that performs follow-up control according to setting input of a device. If the circuit including the servo valve and the flow rate adjustment valve is switched in this way to form a compensation circuit, the servo valve can compensate for the excess or deficiency of the flow rate relative to the input setting, and the large Flow rate control can be performed using a small capacity servo valve. However, as mentioned above, it is difficult to solve problems such as short-circuit accidents in the electrical control system, or dirt adhering between the nozzle and the flapper, which reduces the nozzle opening area and causes the pilot pressure to rise abnormally. or,
It is not possible to prevent the actuator from running out of control due to residual pressure in the accumulator. As described above, it is desired that the troubles caused by the presence of servo valves and accumulators, which are essential to the hydraulic circuit of industrial robots but cause the above-mentioned problems, can be eliminated and work safety can be ensured.

The present invention has been made in order to solve the above-mentioned problems, and the first object of the present invention is to prevent short-circuit accidents in the electrical control system during teaching, or the adhesion of dust between the nozzle and the flapper. To provide a hydraulic circuit for an industrial robot in which an actuator can continue to operate at a slow speed even when an electrohydraulic servo valve becomes fully open and flow control by the servo valve becomes impossible.

The second object of the present invention is to provide an industrial system in which the operation of each axis is stopped immediately when the operator performs an operation to stop the hydraulic pump when speed control by the electro-hydraulic servo valve becomes impossible. Our goal is to provide hydraulic circuits for robots.

The first invention is characterized by an industrial robot equipped with an accumulator in the discharge pipe of a hydraulic pump, and in which hydraulic oil is guided to an actuator for driving each axis via an electro-hydraulic servo valve. In a hydraulic circuit, a switching valve is provided in the supply line between the accumulator and the electro-hydraulic servo valve, and a branch line is connected in parallel to this supply line and has a flow control valve interposed in the middle. The second invention is characterized in that, in addition to the above configuration, the hydraulic fluid is guided to the electrohydraulic servo valve through this branch pipe during teaching. The downstream pipeline of the valve and the oil tank are connected by a pipeline equipped with an on-off valve, and this on-off valve operates in a closed position when the hydraulic pump is driven and in an open position when the hydraulic pump is stopped.

Hereinafter, the present invention will be explained in detail based on examples thereof.

FIG. 2 shows one embodiment of the present invention, showing an accumulator 5 and an electro-hydraulic servo valve 3.
refers to a supply pipe 10 equipped with a switching valve, for example, a two-position, two-port type on-off valve 12, and this pipe 1.
0 and is connected by a branch pipe 11 which is provided in parallel with the flow control valve 13 and has a flow control valve 13 interposed therebetween.

The on-off valve 12 is in the closed position when the industrial robot is being taught and not in use, and is switched to the open position during automatic operation.

Further, the flow rate control valve 13 is adjusted so that a flow rate corresponding to the maximum speed of the actuator in the normal state at the time of teaching can pass therethrough.

FIG. 3 shows another embodiment of the present invention, in which an accumulator 5 and an electro-hydraulic servo valve 3 are shown.
A supply pipe 15 is provided with a switching valve, for example, a two-position, three-port type directional switching valve 14, and a branch pipe 17 is provided in parallel with this pipe 15 and has a flow rate control valve 16 interposed therebetween. connected by.
The directional control valve 14 is in the A position when the industrial robot is being taught or not in use, and guides the hydraulic oil from the accumulator 5 to the electrohydraulic servo valve 3 via the branch pipe 17, and is in the B position during automatic operation. Switch to . Further, the flow rate control valve 16 is adjusted so that a flow rate corresponding to the maximum speed of the actuator in the normal state at the time of teaching can pass therethrough.

Since the present invention has the circuit configuration as described above, during teaching, the hydraulic fluid of the hydraulic pump 1 or the accumulator 5 is transferred to the electro-hydraulic system via the branch pipe 11 or 17 with the flow control valve 13 or 16 interposed. type servo valve 3. Therefore, even if an unexpected accident occurs in the electro-hydraulic servo valve 3 and the opening becomes abnormally large, the maximum speed of the actuator during teaching will be regulated by the flow rate control valve 13 or 16, so it will not reach high speed. This allows the worker time to evacuate out of the robot's work area or perform an operation to stop the industrial robot.

Next, FIGS. 4 and 5 show other embodiments of the invention, and the embodiment of FIG. 4 shows the flow control valve 13 in the hydraulic circuit of the embodiment shown in FIG.
The downstream pipe line and an oil tank (not shown) are connected via a pipe line 23 provided with an on-off valve 21 and a return pipe line 25. The embodiment shown in FIG. 5 is the hydraulic circuit of the embodiment shown in FIG. and are connected via a return pipe line 25. The on-off valves 21 and 22 are in the closed position when the hydraulic pump 1 is driving, and are switched to the open position when the hydraulic pump 1 is stopped.

With the above configuration, when driving the industrial robot, the on-off valve 21 or 22 is switched to the closed position at the same time as the hydraulic pump is started, cutting off communication with the oil tank, so the oil pressure in the supply path increases. As a result, the pressure of hydraulic oil is accumulated in the accumulator 5.

When performing the teaching operation, the hydraulic fluid is guided to the actuator 4 via the branch pipes 11 and 17 and the electro-hydraulic servo valve 3 as described above, and even if an unexpected accident occurs to the electro-hydraulic servo valve 3, Even if this occurs and flow control becomes impossible, the speed of the actuator is regulated by the flow control valve 13 or 16, so the low speed state is maintained.

Furthermore, when the operator notices an abnormality and stops the hydraulic pump 1, at the same time the on-off valve 21 or 22
operates to the open position, the hydraulic fluid accumulated in the accumulator flows through the branch pipe 11 or 17, the flow control valve 13 or 16, the pipe 23 or 24, the on-off valve 21 or 22, and the return pipe 25. reflux to the oil tank via Therefore, the actuator can be stopped immediately.

Furthermore, when the on-off valve 21 or 22 is switched to the open position, the hydraulic oil accumulated in the accumulator is returned to the oil tank via the flow rate control valve 13 or 16. The pressure drop is gradual and can prevent shock from occurring.

As described in detail above, the present invention provides an industrial robot which is equipped with an accumulator in the discharge pipe of a hydraulic pump and which guides hydraulic oil to actuators for driving each axis via an electro-hydraulic servo valve. In a hydraulic circuit, a switching valve is provided in the supply line between the accumulator and the electro-hydraulic servo valve, and a branch line is connected in parallel to this supply line and has a flow control valve interposed in the middle. Since the hydraulic oil is guided to the electro-hydraulic servo valve through this branch pipe during teaching, there is no possibility of an accident occurring in the electric control system during teaching or the inability to adjust the flow rate with the electro-hydraulic servo valve. Even if the actuator is moved at a slow speed, the actuator can still operate at a slow speed, and dangerous abnormal movements of the robot, such as when the robot body or arm collide with the worker being taught at high speed, can be prevented.

Furthermore, in addition to the structure of the invention described above, a pipe line is provided for returning the hydraulic fluid from the switching valve and the flow control valve to the hydraulic tank via the on-off valve, so the actuator can be stopped immediately and the robot body and arm can be stopped. This has the effect of preventing the worker from colliding with the worker being taught.

[Brief explanation of the drawing]

Figure 1 is a hydraulic circuit diagram of a conventional industrial robot.
2 and 3 are main part diagrams of a hydraulic circuit of an industrial robot according to the present invention, and FIGS. 4 and 5 are main part diagrams of a hydraulic circuit of an industrial robot according to a different invention. 1... Hydraulic pump, 3... Electro-hydraulic servo valve, 5... Accumulator, 10, 15... Supply pipe line, 12, 14... Switching valve, 13, 16...
Flow rate control valve, 11, 17...branch pipe, 21, 2
2...Opening/closing valve, 23, 24...Pipe line.

Claims (1)

[Scope of Claims] 1. A hydraulic circuit for an industrial robot, which includes an accumulator in the discharge pipe of a hydraulic pump and guides hydraulic fluid to an actuator for driving each axis via an electro-hydraulic servo valve, A switching valve is provided in the supply line between the accumulator and the electro-hydraulic servo valve, and a branch line is connected in parallel to this supply line and a flow rate control valve is interposed in the middle. A hydraulic circuit for an industrial robot characterized in that hydraulic fluid is sometimes guided to an electro-hydraulic servo valve via this branch pipe. 2. The hydraulic circuit for an industrial robot according to claim 1, wherein the switching valve is an on-off valve, and the on-off valve is arranged in parallel with the flow rate control valve. 3. The switching valve is a directional switching valve, and includes a pipe line that directly leads hydraulic oil to the electrohydraulic servo valve and a pipe line that supplies hydraulic oil whose flow rate has been adjusted via the flow rate control valve. A hydraulic circuit for an industrial robot according to claim 1, wherein the hydraulic circuit is connected to an outlet of a directional control valve. 4. In the hydraulic circuit of an industrial robot, which is equipped with an accumulator in the discharge pipe of the hydraulic pump and guides hydraulic fluid to the actuator for driving each axis via an electro-hydraulic servo valve, the accumulator and the electro-hydraulic A switching valve is provided in the supply line between the type servo valve and a branch line connected in parallel to this supply line with a flow control valve interposed in the middle, and a branch line is provided downstream of the flow rate control valve. The side pipe and the oil tank are connected by a pipe provided with an on-off valve, and during teaching, hydraulic oil is guided to the electro-hydraulic servo valve via the branch pipe, and when the hydraulic pump is driven, the on-off valve is connected. A hydraulic circuit for an industrial robot, characterized in that it operates in a closed position and in an open position when stopped. 5. The hydraulic circuit for an industrial robot according to claim 4, wherein the switching valve is an on-off valve, and the on-off valve is arranged in parallel with the flow control valve. 6. The switching valve is a directional switching valve, and includes a pipe line that directly leads hydraulic oil to the electrohydraulic servo valve and a pipe line that supplies hydraulic oil whose flow rate has been adjusted via the flow rate control valve. 5. The hydraulic circuit for an industrial robot according to claim 4, wherein the hydraulic circuit is connected to an outlet of a directional control valve.