JPH04219502A - Driving circuit for hydraulic cylinder - Google Patents

Abstract

PURPOSE:To obtain a driving circuit with a good efficiency by utilizing pressure energy of working oil, which flows out from a hydraulic cylinder in accordance with a load, to drive the hydraulic cylinder. CONSTITUTION:A passage 15, which supplies discharging oil coming from a reversible hydraulic pump 7 in order to operate a hydraulic cylinder 1, resisting a load 2, and a means 32, which rotates the hydraulic pump 7 in the reverse direction in order to make the working oil flow out from the hydraulic cylinder 1 following the load 2, are provided. In addition, an accumulator 18, which accumulates the discharging oil from the hydraulic pump 7 rotated in the reverse direction, and a switching means 20, which supplies the working oil accumulated in the accumulator 18 to the hydraulic cylinder 1 when the hydraulic cylinder 1 is driven against the load 2, are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in drive circuits for hydraulic actuators and the like for raising and lowering heavy objects.

0002

2. Description of the Related Art A hydraulic actuator for raising and lowering a heavy object is constructed as shown in FIG. 2, for example.

In this figure, the hydraulic actuator supports a load 2 at the tip of a piston rod 13 that freely slides upward from a hydraulic cylinder 1.
A piston 12 coupled to the piston 12 and housed inside the hydraulic cylinder 1 moves the load 2 up and down by sliding up and down in accordance with the inflow and outflow of hydraulic oil in an oil chamber 3 defined below. It has become.

Hydraulic oil is supplied to the oil chamber 3 by a hydraulic pump 40.
This is done through the passage 41. A pilot check valve 4, a switching valve 5, and a check valve 6 are provided in the middle of the passage 41. The pilot check valve 4 is a hydraulic pump 40
The switching valve 5 is switched based on an operator's operation to selectively connect the oil chamber 3 to the hydraulic pump 40 and the tank 14.

[0005] Also, the switching valve 5 and the check valve 6 in the passage 41
An accumulator 8 is connected between the hydraulic pump 40 and
An unload valve 9 and a relief valve 10 are connected to the discharge port 40A. The unload valve 9 is switched when the pressure of the pressure switch 11 attached to the accumulator 8 rises to a set value, and the oil discharged from the hydraulic pump 40 flows out into the tank 14 through the orifice 42 to unload the hydraulic pump 40. . Further, when the discharge pressure further increases, the relief valve 10 opens and the discharge oil flows directly into the tank 14. Thereby, the discharge pressure of the hydraulic pump 40 is maintained within a certain range.

When increasing the load 2, the hydraulic pump 40
and switch the switching valve 5 to switch the oil chamber 3 to the hydraulic pump 4.
When connected to the discharge port 40A of the hydraulic pump 40, the piston 12 moves upward as the oil discharged from the hydraulic pump 40 is sent into the oil chamber 3, and the piston rod 13 extends to increase the load 2.

On the other hand, when lowering the load 2, the switching valve 5
When the passage 41 is connected to the tank 14 by switching the
4, the piston 12 moves downward, and the piston rod 13 contracts to lower the load 2.

Note that the hydraulic pump 40 also
The operation continues, and the pilot check valve 4 is held open by the discharge pressure. This discharged oil flows into the accumulator 8 and accumulates pressure in the accumulator 8. This accumulated pressure is used when increasing the load 2 again.

Furthermore, in order to stop the lifting and lowering of the load 2, the switching valve 5 is operated to shut off the flow of hydraulic oil into and out of the oil chamber 3. Note that when the hydraulic pump 40 is stopped, the pilot check valve 4 is closed to prevent the load 2 from falling due to its own weight.

0010

[Problems to be Solved by the Invention] By the way, the hydraulic oil flowing out from the oil chamber 3 when the load 2 is lowered has a large pressure energy based on the weight of the load 2. Since the spilled hydraulic oil flows back into the tank 14, the pressure energy of the spilled hydraulic oil cannot be used to raise the load 2 again, and in this respect, it cannot be said that the energy efficiency is sufficiently high.

The present invention has been made to solve the above problems, and its purpose is to realize a drive circuit that can reuse the pressure energy of hydraulic oil flowing out from a hydraulic cylinder depending on the load. do.

0012

[Means for Solving the Problems] The present invention provides a passage for supplying discharge oil of a reversible hydraulic pump to operate a hydraulic cylinder against a load, and a passage for discharging hydraulic oil from a hydraulic cylinder that follows a load. A means for reversing the hydraulic pump, an accumulator for storing hydraulic oil discharged from the reversing hydraulic pump, and a switching means for supplying the hydraulic oil accumulated in the accumulator to the hydraulic cylinder when the hydraulic cylinder is driven against a load. It is equipped with

[0013]

[Operation] By reversing the hydraulic pump and storing the outflowing hydraulic oil from the hydraulic cylinder driven by the load in the accumulator, the pressure energy of the outflowing hydraulic oil is accumulated in the accumulator. Furthermore, when the hydraulic cylinder is driven against a load, the accumulated hydraulic fluid is supplied to the hydraulic cylinder via the switching means, thereby utilizing the pressure energy recovered when the hydraulic cylinder is driven.

[0014]

Embodiment FIG. 1 shows an embodiment of the present invention.

As shown in the figure, a hydraulic cylinder 1 has a load 2
is supported upward by the piston rod 13, and the piston 12
It expands and contracts in accordance with the expansion and contraction of the oil chamber 3 defined below. A passage 15 in which a pilot check valve 4 is provided in the middle serves as a passage for supplying oil discharged from the hydraulic pump 7 to the hydraulic cylinder 1.
connects one port 7A of the hydraulic pump 7 and the oil chamber 3. A low pressure accumulator 22 is connected to the other port 7B of the hydraulic pump 7 via a passage 16 and a check valve 26. Further, a pilot circuit 4A of the pilot check valve 4 is connected to the passage 16.

The hydraulic pump 7 is of a double discharge type and a variable capacity type, and the suction direction and discharge direction are reversed by adjusting the tilt angle via the tilt angle adjustment cylinder 32. Incidentally, the tilt angle adjusting cylinder 32 constitutes means for reversing the suction and discharge directions, and by reversing the direction, the hydraulic fluid flowing out from the hydraulic cylinder 1 is guided to the port 7A which becomes a suction port.

A boost pump 30 that rotates integrally with the hydraulic pump 7 is attached. The boost pump 30 is connected to the solenoid valve 31 via a filter 34 and a check valve 35 arranged in parallel. The solenoid valve 31 selectively connects the boost pump 30 and the tank 14 to the tilt angle adjustment cylinder 32.
position A, which drives the tilt angle adjustment cylinder 32 in the direction of increasing the discharge amount of the port 7A, position C, which drives the tilt angle adjustment cylinder 32 in the opposite direction, and a position C, which controls the driving direction of the tilt angle adjustment cylinder 32. Position B that blocks entry and exit
Consisting of

The solenoid valve 31 includes a pilot circuit 31A that switches positions A and C to position B depending on the pressure at port 7A.

The oil discharged from the boost pump 30 is also supplied to the low pressure accumulator 22 via a check valve 33. This low pressure accumulator 22 is connected to passages 15 and 16 via check valves 25 and 26, respectively.

A high pressure accumulator 18 is also connected to the passages 15 and 16 via check valves 17 and 24. The high-pressure accumulator 18 stores the discharge pressure when the hydraulic pump 7 reverses the suction direction and the discharge direction to suck in and pressurize the hydraulic oil flowing out from the hydraulic cylinder 1. High pressure accumulator 18 and low pressure accumulator 22 are connected to solenoid valve 20 via variable orifices 19 and 23, respectively.

The solenoid valve 20 is the accumulator 18
and 22 are selectively connected to the passage 15 according to the operator's operation, and the low pressure accumulator 22 is connected to the passage 15.
and position E to connect the high pressure accumulator 18.
and a position F that disconnects both of these connections, and serves as a switching means for supplying the accumulated pressure of the high pressure accumulator 18 to the hydraulic cylinder 1 when the hydraulic cylinder 1 is extended against the load 2. Function.

A high pressure relief valve 21 is attached to the high pressure accumulator 18 for releasing high pressure above a certain level to the low pressure accumulator 22. In addition, the low pressure accumulator 18
Also, when the pressure rises above a certain level, it opens and drains the hydraulic oil into the tank 14.
A low pressure relief valve 27 is attached to allow the water to flow back. 28 is a variable orifice that communicates the passage 15 and the tank 14;
Reference numeral 9 denotes an oil cooler that cools the hydraulic oil flowing back into the tank 14 from the variable orifice 28 and the low pressure relief valve 27.

Next, the operation will be explained. When using a hydraulic actuator, first operate the hydraulic pump 7 with the solenoid valve 20 in position B and the solenoid valve 31 in position F. It is assumed that at the start of operation, all the hydraulic pressure in the circuit is released to the tank 14, the hydraulic cylinder 1 is in the most contracted state, and the hydraulic pump 7 is in an unloaded state.

When the hydraulic pump 7 rotates, the oil discharged from the boost pump 30 is supplied to the passages 15 and 16 via the check valves 33, 25, and 26, filling the entire circuit with hydraulic oil and accumulating pressure in the low pressure accumulator 22. Also, aisle 1
6, the pilot check valve 4 opens as the pressure rises.

Next, when the solenoid valve 31 is switched to the A position, the tilt angle adjusting cylinder 32 is operated by the oil discharged from the boost pump 30, and the tilt angle of the hydraulic pump 7 is increased. As a result, the hydraulic pump 7 sucks the hydraulic oil in the passage 16 from the port 7B, pressurizes it, and discharges it to the port 7A. The discharged oil is supplied to the oil chamber 3 of the hydraulic cylinder 1 through the passage 15, drives the piston 12 upward, extends the piston rod 13, and increases the load 2.

The solenoid valve 31 is automatically switched to position B by the pilot circuit 31A when the pressure in the port 7A reaches the set pressure. As a result, the tilting angle of the hydraulic pump 7 remains constant until the solenoid valve 31 is operated again, and the load 2 increases at a constant speed.

When the load 2 reaches the desired height, the operator switches the solenoid valve 31 to the C position. As a result, when the pressure in the port 7A decreases to the set value, the pilot circuit 31A switches the solenoid valve 31 from the C position to the B position. As a result, the hydraulic cylinder 1 stops the extension of the piston rod 13, and the load 2
stops in the raised position. Note that the operating pressure of the pilot circuit 31A is set so that the discharge amount of the hydraulic pump 7 at this time substantially matches the amount of hydraulic oil leaking from the variable orifice 28 and the like.

When lowering the load 2 at the raised position,
The operator switches the solenoid valve 31 to the C position again. As a result, the hydraulic pump 7 changes its tilt angle in the negative direction and reverses the suction direction and discharge direction, and the port 7A
It sucks hydraulic oil from the port and discharges it to port 7B. Pilot check valve 4 opens due to the pressure generated in port 7B,
Outflow hydraulic oil from the hydraulic cylinder 1 is sent into the passage 15.

At this time, the hydraulic oil supplied from the passage 15 to the port 7A is a hydraulic oil with high pressure energy that flows out from the oil chamber 3 of the hydraulic cylinder 1 according to the weight of the load 2, and the hydraulic pump 7 This hydraulic oil is further pressurized and discharged to port 7B. This high-pressure discharge oil flows from the passage 16 through the check valve 17 into the high-pressure accumulator 18 and is accumulated in the high-pressure accumulator 18 . The pilot circuit 31A is connected to port 7 due to an increase in the suction amount of the hydraulic pump.
When the pressure at A decreases to the set pressure, the solenoid valve 31 is switched to the B position, and the tilting angle of the hydraulic pump 7 thereafter is maintained at a predetermined angle.

To stop the lowering of the load 2, the solenoid valve 31 is set to the A position. As a result, the tilting angle adjusting cylinder 32 decreases the negative tilting angle and further increases in the positive direction, and when the pressure in the port 7A reaches the same value as when the rise is stopped, the pilot circuit 31A turns the solenoid valve 31 to A. Switch from position to B position.

Now, in order to raise the load 2 from the lowered position again, first switch the solenoid valve 20 to the G position,
Subsequently, the solenoid valve 31 is switched to the A position. As a result, high-pressure hydraulic oil from the high-pressure accumulator 18 is first supplied to the oil chamber 3, and this hydraulic oil pressure causes the hydraulic cylinder 1
expands. Then, the oil discharged from the hydraulic pump 7 causes the hydraulic cylinder 1 to further extend. Load 2 from hydraulic pump 7
The amount of hydraulic oil required to raise the high pressure accumulator 18
Only an amount of hydraulic oil is supplied that is equal to the difference between the amount of oil supplied to the oil chamber 3 and the amount of oil supplied to the oil chamber 3.

In this way, when the load 2 is lowered, the oil chamber 3
Since the pressure energy of the hydraulic oil flowing out from the hydraulic oil is stored in the high pressure accumulator 18 and used to raise the load 2 again, the power burden of the hydraulic pump 7 is first applied to the load 2.
It will be much smaller than when it was raised. Thereafter, the load 2 is raised and lowered only by receiving energy supply little by little from the hydraulic pump 7. Note that if the solenoid valve 31 and the solenoid valve 20 are switched at the same time, the flow rate of the hydraulic oil flowing into the oil chamber 3 increases, so that the rising speed of the load 2 can be increased. Also, when lowering the load 2, the solenoid valve 2
0 to the E position, the hydraulic oil in the oil chamber 3 will flow back to the tank 14 through the low pressure relief valve 27.
Load 2 can be dropped rapidly.

[0033]

[Effects of the Invention] As described above, the present invention stores the pressure energy of the hydraulic oil flowing out from a hydraulic cylinder that follows a load in an accumulator, and uses this energy when restarting the hydraulic cylinder against the load. This reduces wasted energy, resulting in favorable effects in downsizing the hydraulic pump that drives the hydraulic cylinder and reducing power costs.

[Brief explanation of the drawing]

FIG. 1 is a drive circuit diagram of a hydraulic cylinder showing an embodiment of the present invention.

FIG. 2 is a drive circuit diagram of a hydraulic cylinder showing a conventional example.

[Explanation of symbols] 1 Hydraulic cylinder 2 Load 7 Hydraulic pump 15 Passage 18 High pressure accumulator 20 Solenoid valve 32　Tilt angle adjustment cylinder

Claims (1)

[Claims] 1. A passageway for supplying discharge oil of a reversible hydraulic pump to operate a hydraulic cylinder against a load; and means for reversing the hydraulic pump to cause hydraulic oil to flow out of a hydraulic cylinder that follows a load; The present invention is characterized by comprising an accumulator that stores hydraulic oil discharged from the hydraulic pump that rotates in reverse, and a switching means that supplies the hydraulic oil accumulated in the accumulator to the hydraulic cylinder when the hydraulic cylinder is driven against a load. Hydraulic cylinder drive circuit.