JPH0919800A - Method of operating hydraulic cylinder and hydraulic circuit thereof - Google Patents

Abstract

(57) [Abstract] [Problem] To prevent the thermal relay from tripping when the hydraulic pump is started, even when the viscosity of the hydraulic oil is low at low temperatures.
Start the pump motor smoothly. SOLUTION: A hydraulic circuit 27 for driving a hydraulic cylinder 17 is used, and a high flow rate pump 3 with a small flow rate is used as a hydraulic pressure generation source.
7 and a low-pressure pump 39 having a large flow rate, a unloading process is performed between the discharge-side pipe line 53 for the pressure oil of the low-pressure pump 39 having a large flow amount and the return pipe line 89 to the tank 29. An unload circuit 87 equipped with a valve 91 was provided. Thus, when the pump motor 35 is started, the unload valve 9
1, the discharge side pipeline 53 and the return pipeline 89 to the tank 29 are opened.
By communicating with and, the pump motor 35 can be smoothly started without tripping the thermal relay even when the viscosity of the hydraulic oil at low temperature is low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating a hydraulic cylinder and a hydraulic circuit thereof, and more particularly, to a method of operating a hydraulic cylinder having two pressures and two volumes for driving the hydraulic cylinder and a hydraulic circuit thereof.

[0002]

2. Description of the Related Art Conventionally, as a hydraulic circuit for driving a large-capacity hydraulic cylinder, for example, in a hydraulic circuit used in a hydraulically driven turret punch press, a large amount of pressure oil is instantaneously flowed to obtain a high hit. I am aiming for a rate. Therefore, the pump for sending the pressure oil also becomes large, and accordingly the pump motor also becomes large.

At present, in order to make the pump motor as small as possible and save energy, a two-pressure / two-flow circuit and a two-pump circuit are assembled.

[0004]

By the way, in the conventional hydraulic circuit described above, the viscosity of the hydraulic oil becomes low when the outside air temperature is low in the winter, and a rotational torque more than necessary when the large capacity pump motor is started. However, there was a problem that the pump motor did not run because the thermal relay tripped due to a large current flowing.

An object of the present invention is to provide a method of operating a hydraulic cylinder and a hydraulic circuit thereof for smoothly starting a pump motor without tripping a thermal relay when the hydraulic pump is driven even when the viscosity of hydraulic oil at a low temperature is low. To provide.

[0006]

In order to achieve the above object, a method of operating a hydraulic cylinder according to the present invention according to claim 1 is a high pressure pump of a small flow rate and a low pressure of a large flow rate provided in a hydraulic circuit for driving the hydraulic cylinder. 2 composed of pump and
Among the continuous pumps, the unload valve provided between the discharge side pipeline of the large flow low pressure pump and the return pipeline to the tank is used to operate the unload valve when the large flow low pressure pump is started. By communicating a line with the return line to the tank and returning a part of the pressure oil to the tank, the low-pressure pump with a low flow rate and a small flow rate is started, and after a short time after startup, It is characterized in that the flow path of the unload valve is switched and the discharge side pipeline and the return pipeline to the tank are closed.

Further, the hydraulic circuit of the present invention according to claim 2 is a hydraulic circuit of two pressures and two flow rates for driving the hydraulic cylinder, and is constituted by a small flow rate high pressure pump and a large flow rate low pressure pump as hydraulic pressure generation sources. And a double pump, and an unload valve capable of switching the flow path is provided between the pressure oil discharge side pipe line of the large flow rate low pressure pump and the return pipe line to the tank. is there.

Further, the hydraulic circuit of the present invention according to claim 3 is characterized in that the hydraulic cylinder is a drive device for reciprocating a punch of a turret punch press.

By adopting the hydraulic cylinder operating method and the hydraulic circuit thereof according to claims 1, 2 and 3 as described above, a dual pump is used to provide a hydraulic circuit with two pressures and two capacities, and the high pressure pump has a small flow rate and low pressure. The pump delivers a large flow rate. Then, an unload circuit incorporating an unload valve was provided between the low pressure and large flow rate pump discharge side pipeline and the return pipeline to the tank.

When the low-pressure pump with a large flow rate is started, the flow path of the unload valve is switched to connect the pump discharge side pipe line and the tank return pipe line to return a part of the pressure oil to the tank. Since the low pressure pump with a large flow rate can be started by the electric current, the thermal relay will not trip even if the viscosity of the hydraulic oil is low.

It should be noted that after the low-pressure pump with a large flow rate is started, the flow path of the unload valve is switched after a while to close the pump discharge side pipe line and the return pipe line to the tank, and the original large flow rate is maintained. It is operated as a circuit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As a machine tool equipped with a large capacity hydraulic cylinder, for example, a turret punch press is adopted in this embodiment, but the machine tool is not limited to this model, and a large capacity hydraulic cylinder used in all machines is targeted. It is what

Referring to FIG. 3, the turret punch press 1 is provided with a gate-shaped frame 3, which is a lower base 5, a side frame 7 standing on the lower base 5, and a side frame 7. And an upper frame 9 provided on the upper part of the.

A rotatable lower turret 11 is supported on the lower base 3, and a plurality of dies D are mounted on the circumference of the lower turret 11 at appropriate intervals. A rotatable upper turret 13 is supported on the upper frame 9 corresponding to the lower turret 11, and a plurality of punches P are mounted on the upper turret 13 at a position corresponding to the die D.

FIG. 3 of the lower and upper turrets 11 and 13.
, The position of the die D and the punch P mounted on the right side is the processing position.
A striker 15 is provided on the upper frame 9 above and below so as to be vertically movable. The striker 15 is connected to a hydraulic cylinder 17 provided in the upper frame 9 via a ram 19, for example.

At the right end in FIG. 3 on the lower base 5, there is provided a carriage base 21 which is movable in the Y-axis direction (left-right direction in FIG. 3), and this carriage base 21 is in the X-axis direction. A carriage 23 that is movable in the direction (perpendicular to the paper surface in FIG. 3) is provided. The carriage 23 is provided with a plurality of work clamps 25 that clamp the work W at appropriate intervals in the X-axis direction.

With the above structure, by moving the carriage base 21 in the Y-axis direction and the carriage 23 in the X-axis direction, the work W clamped by the work clamp 25 provided in the carriage 23 is moved in the X-axis and Y-axis directions. The workpiece W is moved in the direction, and the desired position of the work W is positioned at the processing position.

With the desired position of the work W positioned at this machining position, the upper and lower turrets 13, 11 are placed.
Is rotated to index and position the desired punch P and die D at the processing position. Next, by driving the hydraulic cylinder 17 to move the striker 15 up and down via the ram 19, normal punching is performed at a desired position of the work W by cooperation of the punch P and the die D. .

Next, the hydraulic circuit 27 for driving the hydraulic cylinder 17, which is a main part of the embodiment, will be described in detail.

Referring to FIGS. 1 and 2, the hydraulic circuit 2
7 is a dual pump 41 in which a small flow high pressure pump 37 and a large flow low pressure pump 39, which are driven by a pump motor 35 from a tank 29 via filters 31 and 33, are connected.
Is provided.

The discharge side conduit 43 of the small flow high-pressure pump 37 is connected to the P port of the servo valve 49 via a filter 45 and a check valve 47 (see FIG. 2). Then, the servo valve 49 and the check valve 4 in the discharge side pipe line 43
A high pressure line accumulator 51 is provided between the high pressure line accumulator and the high pressure line 7. The discharge side conduit 43 is connected with the A symbol shown in FIG. 1 and the A symbol shown in FIG.

The discharge side conduit 53 of the large flow low-pressure pump 39 is connected to the T port of the servo valve 49 via a filter 55 and a check valve 57 (see FIG. 2). Then, the servo valve 49 and the check valve 5 in the discharge side conduit 53 are
A low-voltage line accumulator 59 is provided between the low-voltage line accumulator and the low-voltage line 7. The discharge side conduit 53 is connected to the B symbol shown in FIG. 1 and the B symbol shown in FIG.

In the servo valve 49, as shown in FIG. 2, the conduit 61 connected to the A and B ports on the outlet side of the servo valve 49 is unified to the P port of the three-position switching valve 63. It is connected. The outlet A port of the three-position switching valve 63 is connected to the upper oil chamber 65 of the hydraulic cylinder 17, and the pressure oil discharged from the lower oil chamber 67 of the hydraulic cylinder 17 is three.
The oil enters the B port of the position switching valve 63, returns from the T port to the tank 29, returns through the pipe line 69, and returns the pressure oil. Further, a pulsation prevention damper 71 for preventing pulsation is provided in the middle of the return pipe 69.
Is provided.

A stop valve 75 is provided on the pressure switch 73 for detecting the pressure supplied to the upper oil chamber 65 of the hydraulic cylinder 17 and a pipe connecting the upper and lower oil chambers 65 and 67. Further, a cooler 77 is provided at the end of the return line 69.
Are provided (see FIG. 1).

Check valve 4 provided in the discharge side conduit 43 of the high pressure pump 37 and the discharge side conduit 53 of the low pressure pump 39.
Branch to the outlet side of 7, 57 and check valves 79, 8 respectively
1, a return line 83 is provided.
Is provided with a two-position solenoid-operated switching valve 85.

Further, an unload circuit 87, which is the main part of this embodiment, is provided, and this unload circuit 87 is branched from the discharge side pipe line 53 of the large capacity low pressure pump 39. An unload valve 91 is provided in the middle of the return pipe line 89 provided and branched, and the unload valve 91 is a two-position electromagnetic switching valve. The return pipe 89 is integrated with the return pipe 83, and the pressure oil is returned to the tank 29. Reference numeral 93 is a pressure gauge, and 95 is a pressure alarm. Further, the return line 69 is formed by connecting the C symbol shown in FIG. 1 and the C symbol shown in FIG.

With the above-described structure, when the piston 97 provided on the hydraulic cylinder 17 is lowered to punch a work, the three-position switching valve 6 is used.
The flow channel 3 is switched to the right flow channel shown in FIG. Then, the low-pressure pump 39 having a large flow rate (for example, 65 L / min) is driven to supply the low-pressure, large-flow pressure oil into the upper oil chamber 65 of the hydraulic cylinder 17 to lower the piston 97.

Immediately before the piston 97 descends and the workpiece is machined, the servo valve 49 is switched and the high pressure pump 37 of a small flow rate (for example, 20 L / min) sends high pressure oil to the upper oil chamber 65 of the cylinder 17. , The work is punched.

After the processing is completed, the flow paths of the servo valve 49 and the three-position switching valve 63 are switched to change a small flow rate (for example, 20 L /
min) high pressure pump 37 and a large flow rate (eg 65 L / m
In driving the low pressure pump 39, a large amount of pressure oil is supplied into the lower oil chamber 67 of the hydraulic cylinder 17 to raise the piston 97. The oil discharged when the piston 97 provided in the hydraulic cylinder 17 rises and falls is returned to the tank 29 through the return pipe 69 from the T port of the three-position switching valve 63, but the pulsation provided in the middle of the return pipe 69. The oil damper can be reduced by the prevention damper 69.

Next, the operation of the unload circuit 87, which is the main part of this embodiment, will be described.

The unload circuit 87 includes a discharge side conduit 53 and a return conduit 8 of low pressure and large flow rate in which an overcurrent flows when the pump is started.
An unloading valve 91 is provided between the unloading valve 9 and the unloading valve 9. Since the high-pressure, small-flow-rate discharge-side pipe line 43 is used only during high-pressure processing, it is not used when the pump is started, and thus an unload circuit is unnecessary.

The pump motor 35 can be started with a small starting current because the unload valve 91 provided in the unload circuit 87 starts the pump motor 35 at a low pressure and a small flow rate. Therefore, since the pump motor 35 can be started with a low pressure and a small flow rate, the pump motor 35 can be started without overloading even when the viscosity of the hydraulic oil is low at low temperatures, and the thermal relay does not trip.

After the pump motor 35 is started, the flow path of the unload valve 91 is switched after a few seconds by, for example, a timer, and the return conduit 89 is closed to be used as an original large flow circuit.

The present invention is not limited to the above-described embodiments, but can be implemented in other modes by making appropriate changes.

[0035]

As will be understood from the above description of the embodiments, the present invention according to claims 1, 2 and 3 makes it possible to provide a low pressure in a hydraulic circuit for driving a hydraulic cylinder. An unload circuit provided with an unload valve that opened and closed the discharge side pipeline of the pump and the return pipeline to the tank was provided.

By opening the unload valve at the time of starting the pump and connecting the discharge side pipe and the return pipe, the pump motor is not overloaded even when the viscosity of the hydraulic oil is low at low temperatures. It can be started, and the pump motor can be smoothly started without tripping the thermal relay.

[Brief description of the drawings]

FIG. 1 shows a main part of the present invention and is a hydraulic circuit for driving a hydraulic cylinder.

FIG. 2 shows a main part of the present invention, and is a hydraulic circuit for driving a hydraulic cylinder.

FIG. 3 is a front explanatory view showing a schematic configuration of a hydraulic turret punch press according to an embodiment of the present invention.

[Explanation of symbols]

 1 Turret Punch Press 17 Hydraulic Cylinder 27 Hydraulic Circuit 29 Tank 37 High Flow Pump with Small Flow Rate 39 Low Pressure Pump with Large Flow Rate 41 Double Pump 53 Discharge Side Pipeline 87 Unload Circuit 89 Return Pipeline 91 Unload Valve P Punch

Claims (3)

[Claims] 1. To a discharge side pipe line and a tank of a low flow pump of a large flow rate, of a double pump composed of a high pressure pump of a small flow rate and a low pressure pump of a large flow rate provided in a hydraulic circuit for driving a hydraulic cylinder. The unloading valve provided between the return line and the unloading valve activates the unload valve when the low-pressure pump with a large flow rate is started, and connects the discharge side line and the return line to the tank with a part of hydraulic pressure. By returning to the tank, start the low-pressure pump of low flow rate and low flow rate of large flow rate, switch the flow path of the unload valve after a short time after startup, and then return to the discharge side pipe line and the return pipe to the tank. A method for operating a hydraulic cylinder, characterized by closing a passage. 2. A two-pressure, two-flow rate hydraulic circuit for driving a hydraulic cylinder is provided, and a dual pump composed of a high-pressure pump with a small flow rate and a low-pressure pump with a large flow rate is provided as a hydraulic pressure source, A hydraulic circuit for a hydraulic cylinder, characterized in that an unload valve, which is capable of flow path switching, is provided in an unload circuit that connects a pressure oil discharge side pipeline of a low pressure pump and a return pipeline to a tank. 3. A hydraulic circuit for a hydraulic cylinder according to claim 2, wherein the hydraulic cylinder is a drive device for reciprocating a punch of a turret punch press.