JPH0814201A - Hydraulic circuit of cargo vehicle - Google Patents

Abstract

PURPOSE:To reduce load of a pump by supplying to a cylinder oil pressure stored by utilizing return oil from the cylinder. CONSTITUTION:An accumulator turbine 12 is driven by return oil from a boom hydraulic cylinder 1, oil pressure is generated and stored in an accumulator 13. When oil pressure from the accumulator 13 exceeds a set value, a pressure supply valve 4 is switched, the oil pressure from the accumulator 13 is supplied to the cylinder 1 to extend the cylinder 1. When oil pressure of the accumulator 13 is decreased to less than a set value, the pressure supply valve 4 is switched, oil pressure from a main pump 2 is supplied to the cylinder 1, and the cylinder 1 is continuously extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for supplying hydraulic pressure to a cylinder for cargo handling or braking in a cargo handling vehicle such as a wheel loader.

[0002]

2. Description of the Related Art In a conventional hydraulic circuit for cargo handling such as a wheel loader, a boom cylinder for raising and lowering a boom is supplied with hydraulic pressure generated by driving a gear pump to extend the boom cylinder. The returned oil was drained to the oil tank as it was. This is done not only in the cargo handling hydraulic circuit, but also in the brake hydraulic circuit, for example.

[0003]

In the above prior art, since the hydraulic pressure generated by the drive of the gear pump is always supplied when the hydraulic pressure is supplied to the cylinders for cargo handling and braking, the load applied to the gear pump, that is, the gear pump is The load of the driving engine was large, the amount of energy consumption was large, and the fuel efficiency was poor.

In view of the above, the present invention utilizes a flow of return oil from a cylinder for cargo handling, braking, etc. to store hydraulic pressure and supplies the stored hydraulic pressure to the cylinder to reduce the load on the pump. The purpose is to provide a hydraulic circuit of.

[0005]

The means for solving the problems according to the present invention is, as shown in FIGS. 1 and 2, a pump 2 for supplying a hydraulic pressure to a cylinder 1 for cargo handling or a brake, and a flow of return oil from the cylinder 1. Accumulation means 3 for accumulating hydraulic pressure by utilizing
And a switching means 4 for stopping the supply of the hydraulic pressure from the pump 2 to the cylinder 1 and switching to the supply of the hydraulic pressure from the pressure storage means 3 to the cylinder 1 when the hydraulic pressure stored in the pressure storage means 3 exceeds a certain value, The pressure accumulating means 3 includes a pressure accumulating turbine 12 that is driven by the flow of return oil from the cylinder 1 to generate hydraulic pressure, an accumulator 13 that stores the generated hydraulic pressure,
A check valve 14 for blocking the flow of oil from the accumulator 13 to the pressure accumulating turbine 12 is provided.

[0006]

In the above means for solving the problems, when the cylinder 1 contracts, the return oil discharged from the cylinder 1 drives the accumulator turbine 12 to generate hydraulic pressure, and the generated hydraulic pressure passes through the check valve 14 and the accumulator 13. Stored in. When the hydraulic pressure stored in the accumulator 13 becomes a certain value or more, the switching means 4 makes it impossible to supply the hydraulic pressure from the pump 2 to the cylinder 1. At this time, hydraulic pressure can be supplied from the accumulator 13 to the cylinder 1. When the accumulator 13 reaches the upper limit pressure, the hydraulic pressure is not supplied from the pressure accumulating turbine 12 to the accumulator 13, and the check valve 14 causes the accumulator 13 to operate.
The flow of oil from the accumulator to the accumulator turbine 12 is blocked, and the hydraulic pressure stored in the accumulator 13 is trapped.

When the cylinder 1 is extended,
The hydraulic pressure stored in the accumulator 13 is supplied to the cylinder 1. Accumulator 1 as cylinder 1 extends
When the oil pressure from 3 drops to a predetermined value or less, the switching means 4 supplies the oil pressure from the pump 2 to the cylinder 1, and the cylinder 1 continues to expand.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic circuit for cargo handling such as a wheel loader according to an embodiment of the present invention, as shown in FIG. 1, is a single-acting boom cylinder 1 for raising and lowering a boom, and a hydraulic pressure is supplied to the boom cylinder 1 driven by a motor. Main pump 2 and a main valve 10 for controlling the drive of the boom cylinder 1
And a pressure accumulating means 3 for accumulating hydraulic pressure using the flow of return oil from the boom cylinder 1, and either the hydraulic pressure from the main pump 2 or the hydraulic pressure from the pressure accumulating means 3 are switched to be supplied to the boom cylinder 1. And a pressure supply valve 4 which is a switching means.

On the tail side of the boom cylinder 1, a main valve 10 which is switched by operating a lever or a switch is connected. The main valve 10 is a two-position switching valve, and a main pump is provided via a pressure supply valve 4. Boom cylinder 1 by connecting 2 and boom cylinder 1
It is possible to switch between a position where the boom cylinder 1 is extended by supplying hydraulic pressure to the boom cylinder 1 and a position where the boom cylinder 1 is contracted by connecting the boom cylinder 1 and the oil tank 11 and discharging the oil from the boom cylinder 1. Has been done.

The pressure accumulating means 3 is discharged from the boom cylinder 1 when the boom cylinder 1 is contracted, and the oil tank 1 is discharged.
1, a pressure accumulating turbine 12 that is driven by return oil guided to generate hydraulic pressure, an accumulator 13 that stores the generated hydraulic pressure, a pressure accumulating turbine 12, and an accumulator 13
And a check valve 14 which is disposed between the accumulator 13 and the accumulator 13 and blocks the flow of oil from the accumulator turbine 12 toward the accumulator turbine 12.

The pressure-accumulation turbine 12 is rotated by the flow of return oil from the boom cylinder 1 to the first turbine 1.
5 and the second turbine 1 that is connected to the first turbine 15 via gears and rotates following the rotation of the first turbine 15.
It consists of 6 and 6. The second turbine 16 includes the oil tank 11
It has a function of forcibly sending the oil from the direction of the accumulator 13 to generate the hydraulic pressure.

The pressure supply valve 4 is composed of an offset type two-position switching valve. The main pump 2 and the main valve 10 are connected to each other so that a hydraulic pressure can be supplied from the main pump 2 to the boom cylinder 1. Pump 2
Is connected to the oil tank 11, and the accumulator 13 and the main valve 10 are connected to each other so that the hydraulic pressure can be switched from the accumulator 13 to the boom cylinder 1 in an emergency position.

Pilot pressure from the accumulator 13 is supplied to the spool of the pressure supply valve 4, and when the hydraulic pressure stored in the accumulator 13 exceeds a certain value larger than the biasing force of the spring 20 of the pressure supply valve 4, The pressure supply valve 4 is configured to switch from the normal position to the emergency position against the biasing force of the spring 20.

In the above structure, when a lever or a switch is operated to lower the raised boom,
As shown in FIG. 2, the main valve 10 is switched to a position connecting the boom cylinder 1 and the oil tank 11,
Return oil from the boom cylinder 1 is discharged toward the oil tank 11, the boom cylinder 1 contracts, and the boom descends.

At this time, the first turbine 15 is rotated by the return oil from the boom cylinder 1, and the second turbine 16 is rotated following this rotation. Then, the oil tank 1
Oil from 1 is forcibly sent in the direction of the accumulator 13 to generate hydraulic pressure, which is stored in the accumulator 13 through the check valve 14.

When the hydraulic pressure stored in the accumulator 13 exceeds a certain value, the pressure supply valve 4 switches from the constant position to the emergency position against the urging force of the spring 20 of the pressure supply valve 4, and the main pump 2 operates. It is connected to the oil tank 11 via the pressure supply valve 4. Further, when the accumulator 13 reaches the upper limit pressure, hydraulic pressure is not supplied from the pressure accumulating turbine 12 to the accumulator 13, and the check valve 14 causes the accumulator 13 to move to the accumulating turbine 12.
The flow of oil to the is blocked and the hydraulic pressure stored in the accumulator 13 is trapped.

Then, in order to raise the boom again,
When the lever or switch is operated, the main valve 10 is switched to a position connecting the boom cylinder 1 and the pressure supply valve 4 as shown in FIG.
The hydraulic pressure stored in 3 is supplied to the boom cylinder 1 via the pressure supply valve 4, the boom cylinder 1 extends, and the boom starts to rise. At this time, the hydraulic pressure from the main pump 2 is guided to the oil tank 11 without being used to extend the boom cylinder 1, and the load on the main pump 2 is reduced.

When the hydraulic pressure from the accumulator 13 decreases with the extension of the boom cylinder 1 and falls below a certain value, the biasing force of the spring 20 of the pressure supply valve 4 exceeds the hydraulic pressure from the accumulator 13, and as shown in FIG. The pressure supply valve 4 is switched from the emergency position to the constant position. Then, the hydraulic pressure from the main pump 2 is supplied to the boom cylinder 1 via the pressure supply valve 4, and the boom cylinder 1
Continues to grow and the boom rises. Hereinafter, the above operation is repeated every time the boom cylinder 1 is expanded and contracted.

As described above, when the boom cylinder 1 contracts, the flow of return oil from the boom cylinder 1 is used to drive the pressure accumulating turbine 12 to store the hydraulic pressure in the accumulator 13 to extend the boom cylinder 1. It is possible to assist the load of the main pump 2 at the time of starting the boom cylinder 1 having a particularly large load by using the hydraulic pressure stored at that time. Therefore, the load applied to the main pump 2, that is, the load of the engine driving the main pump 2, is reduced compared to when the boom cylinder 1 is extended only by the hydraulic pressure generated by driving the main pump 2, and the energy of the engine is reduced. The fuel consumption can be improved by reducing the consumption, and an energy saving hydraulic circuit can be realized.

The present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention. For example, the hydraulic circuit of the present invention may be applied not only for cargo handling but also for braking. The switching means 4 may be composed of a sensor that detects the hydraulic pressure from the accumulator 13 and a solenoid valve that switches the oil passage according to the output signal of the sensor.

[0021]

As is apparent from the above description, according to the present invention, it is possible to generate a hydraulic pressure by utilizing the flow of the return oil from the cylinder, store the hydraulic pressure, and supply the hydraulic pressure to the cylinder. It is possible to reduce the load on the pump when driving it, that is, the load of the engine etc. for driving the pump, reduce the energy consumption of the engine etc. and improve fuel consumption, and realize an energy-saving hydraulic circuit. .

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a cargo handling vehicle according to an embodiment of the present invention.

[Fig. 2] Hydraulic circuit diagram during boom lowering

FIG. 3 is a hydraulic circuit diagram when the hydraulic pressure from the accumulator is being supplied to the boom cylinder when the boom is raised.

FIG. 4 is a hydraulic circuit diagram when the hydraulic pressure from the main pump is being supplied to the boom cylinder when the boom is raised.

[Explanation of symbols]

 1 Cylinder 2 Pump 3 Pressure Accumulation Means 4 Switching Means 12 Accumulation Turbine 13 Accumulator 14 Check Valve

Claims (2)

[Claims] 1. A pump for supplying a hydraulic pressure to a cylinder for cargo handling or a brake, a pressure accumulating means for accumulating the hydraulic pressure by utilizing a flow of return oil from the cylinder, and a constant hydraulic pressure accumulated by the accumulating means. A hydraulic circuit for a cargo handling vehicle, comprising: switching means for stopping the supply of the hydraulic pressure from the pump to the cylinder and switching the hydraulic pressure from the pressure accumulating means to the cylinder when the value exceeds a value. 2. A pressure accumulating means, which is driven by a flow of return oil from a cylinder to generate an oil pressure,
The hydraulic circuit for a cargo handling vehicle according to claim 1, further comprising an accumulator that stores the generated hydraulic pressure, and a check valve that blocks the flow of oil from the accumulator to the pressure accumulating turbine.