JP2001124006A - Hydraulic drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low cost hydraulic drive system capable of high speed and highly accurate machining, conserving energy, using a low capacity motor and minimizing degrees of temperature rise. SOLUTION: A basic circuit 2 and a power assist circuit 3 are connected to a hydraulic cylinder 1. While the basic circuit 2 dives the hydraulic cylinder 1 with no-load, the power assist circuit 3 accumulates oil to supply to the hydraulic cylinder 1 only when the hydraulic cylinder 1 is loaded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydraulic drive system,
In particular, the present invention relates to a hydraulic drive system applied to a press device such as a punch press, a press brake, and a shearing machine.

[0002]

2. Description of the Related Art Conventionally, as a punch press as an example of a press device, there is, for example, a crank type punch press shown in FIG.

In FIG. 7, when a motor 46 is driven,
The rotational motion of the motor 46 is converted into linear motion by the crankshaft 40 via the pinion gear 38 and the main gear 39, and the slide 42 moves up and down as the connecting rod 41 moves up and down.

Thus, a predetermined punching process is performed on the workpiece by cooperation of the die P and the punch P attached to the lower surface of the slide 42.

[0005]

[Problems to be solved by the invention]

However, the punch press shown in FIG. 7 has a fixed bottom dead center and a fixed moving speed pattern of the slide 42 due to its structure.

Therefore, it is difficult to process the workpiece W with high accuracy and at high speed.

A hydraulic punch press shown in FIG. 8 has been proposed to solve this problem.

In FIG. 8, when a hydraulic control valve 31 is operated, oil in an oil tank 32 circulates between the hydraulic cylinder 30 and a pump 33 driven by a motor 34.

As a result, the hydraulic cylinder 30 moves up and down, presses the punch P and cooperates with the die D to perform predetermined punching on the work W.

According to this hydraulic punch press, the speed of the hydraulic cylinder 30 can be freely changed by operating the hydraulic control valve 31, and the bottom dead center thereof can be arbitrarily selected. High-speed and high-precision machining of the work W becomes possible.

However, in FIG. 8, a large amount of oil must be circulated between the oil tank 32 and the hydraulic cylinder 30 by constantly rotating the motor 34 to operate the pump 33. Is wastefully consumed, so that energy waste is large and the degree of increase in oil temperature is large.

A ball screw type punch press shown in FIG. 9 has been proposed to solve this problem.

In FIG. 9, when the motor 47 is driven,
Since the rotational motion of the motor 47 is transmitted to the ball screw 43 via the pinion gear 38 and the main gear 39,
The slide 42 connected to the ball screw 43 moves up and down.

As a result, a predetermined punching process is performed on the work in cooperation with the die P and the punch P attached to the lower surface of the slide 42.

According to this ball screw type punch press,
The power of the motor 47 is controlled by the pinion gear 38 and the main gear 3.
9 and the ball screw 43 efficiently transmit the energy, the waste of energy is relatively small, and no oil is used, so there is no problem such as an increase in oil temperature.

However, in FIG. 9, there are problems that the capacity of the motor 47 increases, the cost increases accordingly, and the life of the ball screw 43 is shortened due to wear.

An object of the present invention is to provide a low-cost hydraulic drive system that enables high-speed and high-precision machining, eliminates waste of energy, can use a low-capacity motor, reduces the degree of rise in oil temperature, and reduces the cost. I do.

[0019]

According to the present invention, a basic circuit 2 and a power assist circuit 3 are connected to a hydraulic cylinder 1 as shown in FIG. A hydraulic drive system characterized in that the power assist circuit 3 accumulates oil while operating the hydraulic cylinder 1 under load and supplies the oil to the hydraulic cylinder 1 only when there is a load to operate the hydraulic cylinder 1. Is provided.

According to the configuration of the present invention, since the hydraulic cylinder 1 is used, the speed and the position can be set arbitrarily, so that high-speed and high-precision machining can be performed. Large energy is released only when a load is applied to punch W (t4 to t5 in FIG. 6), and the release time is extremely short. Therefore, energy is not wasted, and the basic circuit 2 operates the hydraulic cylinder 1 when there is no load. Therefore, the capacity can be reduced, so that a motor with a low capacity can be used, the degree of increase in the oil temperature can be reduced, and the cost can be reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings according to embodiments. FIG. 1 is an overall view showing an embodiment of the present invention.

The hydraulic drive system shown in FIG. 1 includes a hydraulic cylinder 1, a basic circuit 2, a power assist circuit 3, a pilot circuit 4, and an NC 5.

The hydraulic cylinder 1 is, for example, a single-rod double-acting cylinder having a double structure on the head side, and includes a head-side large-diameter chamber 1A, a head-side small-diameter chamber 1B, and a rod-side chamber 1C.
And the head side small diameter chamber 1B and the rod side chamber 1C.
Are formed substantially equal in area.

The head-side small-diameter chamber 1B and the rod-side chamber 1C of the hydraulic cylinder 1 are connected to the basic circuit 2, and the head-side large-diameter chamber 1A is connected to the power assist circuit 3.

The NC 5 compares the target value by feeding back a signal from the piston position sensor 8 of the hydraulic cylinder 1, and controls the basic circuit 2 via the servo amplifier 6 to thereby control the hydraulic cylinder 1. Position H
The entire apparatus shown in FIG. 1 is controlled, for example, by accurately controlling (FIG. 6).

As described above, in the present invention, the hydraulic cylinder 1 is used, and the position H of the hydraulic cylinder 1 (FIG. 6)
Since the speed H / t can be freely controlled, high-speed and high-precision machining can be performed according to the size and the thickness τ of the work W.

The basic circuit 2 has a servomotor 2C and a bidirectional pump 2B driven by the servomotor 2C, and operates the hydraulic cylinder 1 under no load (FIGS. 3 and 4). .

That is, the basic circuit 2 operates the bidirectional pump 2B so that when the hydraulic cylinder 1 in a no-load state is lowered (FIG. 3), the rod side chamber 1C
Is moved to the head-side small-diameter chamber 1B, and when ascending (FIG. 4), the oil in the head-side small-diameter chamber 1B is moved to the rod-side chamber 1C.

As described above, since the basic circuit 2 operates the hydraulic cylinder 1 when no load is applied, the capacity can be extremely reduced.

Therefore, according to the present invention, it is possible to use the servomotor 2C having a low capacity, to reduce the degree of increase in the oil temperature, and to further reduce the cost.

The bidirectional pump 2 constituting the basic circuit 2
B (FIG. 2) is connected to a relief valve 18 via check valves 12 and 13.

As a result, the pressure of the bidirectional pump 2B is maintained at the set value, and the hydraulic cylinder 1 when no load is applied (FIG. 3,
(FIG. 4) It can operate smoothly.

The shuttle valve 2A of the basic circuit 2 (FIG. 2) has two inlets connected to the head side small diameter chamber 1B and the rod side chamber 1C of the hydraulic cylinder 1 and an outlet connected to the relief valve 15. Have been.

Thus, the high pressure of the rod side chamber 1C when the hydraulic cylinder 1 is not loaded (FIG. 4) or the high pressure of the head side small diameter chamber 1B when the loaded cylinder is dropped (FIG. 5) is selected and set to a set value. By being held, the pilot line L3, L1 (FIG. 4) or L2 (FIG. 5) in each case works effectively.

The power assist circuit 3 includes a servo motor 3
C, a variable displacement piston pump 3B driven by the servomotor 3C, and an accumulator 3A, and emits large energy only when a load is applied (t4 to t5 in FIGS. 5 and 6).

That is, the power assist circuit 3 discharges oil from the oil tank 3G by the variable displacement piston pump 3B and stores it in the accumulator 3A when there is no load, and stores the stored oil in the hydraulic cylinder only when there is a load. Supply to the head side large diameter chamber.

As a result, the power assist circuit 3 emits a large amount of energy only when a load is applied, such as when the workpiece W is punched (FIG. 6) (t4 to t5), and the release time is extremely short in view of the entire operation time. .

Therefore, according to the present invention, waste of energy can be eliminated, and the energy can be effectively utilized.

Although the energy release time is short in this way, as is apparent from FIG.
That is, a long time for accumulating oil in the accumulator 3A (ACC1) can be ensured long.

Therefore, the variable displacement piston pump 3
By adjusting and reducing the capacity of B, almost no time (FIG. 6) can be used as energy securing time when there is no load (FIGS. 3 and 4), and the oil in the oil tank 3G is filtered by the filter 3F. And accumulates in the accumulator 3A.

The operation of the present invention having the above configuration will be described below.

(1) No load (FIGS. 3 and 4).

Lowering operation (FIG. 3).

For example, at time t2 (FIG. 6), assuming that the position H of the hydraulic cylinder 1 is h, the bi-directional pump 2B of the basic circuit 2 (FIG. 3) is operated, whereby the rod side chamber of the hydraulic cylinder 1 is operated. 1C oil on head side small diameter chamber 1
Move to B.

As a result, the hydraulic cylinder 1 is pulled down, the pressure on the head-side large-diameter chamber 1A decreases, and oil flows from the oil tank 7 to the head-side large-diameter chamber 1A via the prefill valve 9. Supplied.

As a result, the hydraulic cylinder 1 is lowered, and t
The position after 2 (FIG. 6) becomes lower.

On the other hand, the operation of the hydraulic cylinder 1 at the time of no load is irrelevant to the power assist circuit 3, so that the power assist circuit 3 drives the variable displacement piston pump 3B to 3G oil is discharged through the filter 3F and accumulated in the accumulator 3A.

Ascending operation (FIG. 4).

For example, at time t7 (FIG. 6), assuming that the position H of the hydraulic cylinder 1 is at the lowest position, the bidirectional pump 2B of the basic circuit 2 (FIG. 3) is operated, whereby the hydraulic cylinder 1 The oil in the head side small diameter chamber 1B is moved to the rod side chamber 1C.

As a result, the hydraulic cylinder 1 is pulled upward, but the oil in the head-side large-diameter chamber 1A cannot escape, so that the hydraulic cylinder 1 does not rise any more and the pressure in the rod-side chamber 1C increases. I do.

When the pressure in the rod side chamber 1C rises, first, the oil in the rod side chamber 1C flows in from the pilot pressure inlet of the pilot check valve 11 through the pilot line L3 and opens () to open the head side. Large diameter room 1
The oil of A is accumulated in the accumulator 17.

Next, when the pressure on the rod side chamber 1C further rises, the oil in the rod side chamber 1C is released via the pilot line L1 by the relief valve 4A of the counter balance valve 4A.
Pass 1

The oil that has passed through the relief valve 4A1 flows into the pilot pressure inlet of the prefill valve 9 and opens it.

Accordingly, the oil in the large-diameter chamber 1A on the head side of the hydraulic cylinder 1 returns to the oil tank 7 via the opened prefill valve 9.

As a result, the hydraulic cylinder 1 is raised, and the position after time t7 (FIG. 6) is raised.

In this case as well, the operation of the hydraulic cylinder 1 when there is no load is irrelevant to the power assist circuit 3, so that the power assist circuit 3 drives the variable displacement piston pump 3B to 3G oil is discharged through the filter 3F and accumulated in the accumulator 3A.

(2) When there is a load (FIG. 5).

In this case, first, the basic circuit 2 (FIG. 5)
By operating the bidirectional pump 2B, the oil in the rod side chamber 1C of the hydraulic cylinder 1 is moved to the head side small diameter chamber 1B.

As a result, the hydraulic cylinder 1 attempts to pull down, but there is a work W having a plate thickness τ (FIG. 6), and due to the load, the hydraulic cylinder 1 does not drop below that, and The pressure on the small diameter chamber 1B side increases.

When the pressure in the head-side small-diameter chamber 1B rises, the oil in the head-side small-diameter chamber 1B flows in through the pilot pressure inlet of the pilot check valve 10 via the pilot line L2 and opens it.

For this reason, the oil stored in the accumulator 3A of the power assist circuit 3 when there is no load flows into the head-side large-diameter chamber 1A of the hydraulic cylinder 1 through the opened pilot check valve 10.

Therefore, even if there is a load, the hydraulic cylinder 1
Is lowered, the punch P is pressed (FIG. 5), and the work W having the thickness τ can be punched in cooperation with the die D (t4 in FIG. 6).
To t5).

In the above embodiment, the case where the present invention is applied to a punch press has been described in detail. However, the present invention is not limited to this, and is applicable to other press devices such as a press brake and a shearing machine. It is possible, and in this case, it is needless to say that the same effect is obtained.

[0064]

As described above, according to the present invention, the basic circuit and the power assist circuit are connected to the hydraulic cylinder, and while the basic circuit operates the hydraulic cylinder when there is no load,
Technical measures have been taken in which the power assist circuit accumulates oil and supplies it to the hydraulic cylinder only when it has a load to operate it.

According to the configuration of the present invention, since the hydraulic cylinder is used, the speed and the position can be set arbitrarily, so that high-speed and high-precision machining can be performed. Large energy is released only when a load is applied during punching, and the release time is extremely short. Therefore, energy is not wasted, and the basic circuit operates the hydraulic cylinder when no load is applied. It is possible to use a motor having a large capacity, to reduce the degree of increase in the oil temperature, and to achieve the technical effect of realizing it at low cost.

[0066]

[Brief description of the drawings]

FIG. 1 is an overall view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a hydraulic circuit constituting the present invention.

FIG. 3 is a diagram showing a flow of oil when the hydraulic cylinder 1 at the time of no load according to the present invention descends.

FIG. 4 is a diagram showing a flow of oil when the hydraulic cylinder 1 at the time of no load according to the present invention rises.

FIG. 5 is a diagram showing a flow of oil when the hydraulic cylinder 1 under load according to the present invention descends.

FIG. 6 is a diagram illustrating the operation of the present invention.

FIG. 7 is an explanatory diagram of a first related art.

FIG. 8 is an explanatory diagram of a second conventional technique.

FIG. 9 is an explanatory diagram of a third conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic cylinder 1A Head side large diameter chamber 1B Head side small diameter chamber 1C Rod side chamber 2 Basic circuit 2A Shuttle valve 2B Bidirectional pump 2C Servo motor 3 Power assist circuit 3A Accumulator 3B Variable capacity piston pump 3C Servo motor 4 Pilot circuit 5 NC 6 Servo amplifier 7, 16, 19 Oil tank 8 Piston position sensor 9, 10, 11 Pilot check valve 12, 13, 14 Check valve 15, 18 Relief valve 17 Accumulator

Claims (5)

[Claims] A basic circuit and a power assist circuit are connected to a hydraulic cylinder, and the power assist circuit stores oil while the basic circuit operates the hydraulic cylinder when there is no load, and only when a load is applied. A hydraulic drive system wherein the oil is supplied to a hydraulic cylinder for operation. 2. The hydraulic cylinder comprises a head-side large-diameter chamber, a head-side small-diameter chamber, and a rod-side chamber. The head-side small-diameter chamber and the rod-side chamber are connected to a basic circuit, and the head-side large-diameter chamber is connected to a power assist circuit. The hydraulic drive system according to claim 1, wherein: 3. A prefill valve is provided between the hydraulic cylinder and the oil tank, and a pilot check valve is provided between the hydraulic cylinder and the power assist circuit. The prefill valve and the pilot check valve are connected to the pilot circuit. The hydraulic drive system according to claim 1, which is connected. 4. The basic circuit includes a bidirectional pump driven by a servomotor, and the bidirectional pump moves oil between the head side small diameter chamber and the rod side chamber of the hydraulic cylinder when no load is applied. The hydraulic drive system as described. 5. The power assist circuit has a variable displacement piston pump driven by a servomotor. Oil is accumulated in the accumulator by the variable displacement piston pump when there is no load, and is accumulated in the accumulator only when there is a load. 2. The hydraulic drive system according to claim 1, wherein oil is supplied to a head-side large-diameter chamber of the hydraulic cylinder.