JPS5919364B2 - Pressure compensated flow control valve with check valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-compensated flow control valve with a check valve that controls the operation of a hydraulic cylinder used in a dump truck or the like.

For example, if the telescoping speed of a hydraulic cylinder used in a dump truck or the like is accelerated more than necessary under a large load, the hydraulic cylinder or its built-in (
- A large impact load is generated on the mechanical system, and there is a high risk of damage to the hydraulic cylinder and the mechanical system.

In order to eliminate the above-mentioned drawbacks, the present invention provides a highly compact check valve that is installed in the hydraulic piping system of a dump truck, for example, and integrates a flow control valve and a check valve into the mounting part of the check valve. The present invention provides a pressure-compensated flow control valve.

Embodiments of the present invention will be described below with reference to the drawings. Reference numeral 1 denotes a cylindrical valve cylinder, at one end of which a first flow port 3 through which hydraulic oil from a pump 2 flows into the valve cylinder 1, and at the other end. A second flow port 5 is provided on the side of the valve cylinder 1 to allow the hydraulic oil that has flowed into the valve cylinder 1 to flow out to the hydraulic cylinder 4, and a second flow port 5 is provided on the side of the valve cylinder 1 to flow the hydraulic oil from the hydraulic cylinder 4 to the oil tank 1 via a switching valve 6. The third flow ports 8 for the outflow are respectively opened.

Reference numeral 9 denotes a hollow balance piston that is slidably fitted on the side of the second flow port 5 in the valve cylinder 1, and the balance piston 9 has an orifice 10 formed therein facing the second flow port 5. By sliding the balance piston 9 left and right, the opening area of the third flow port 8 is variably controlled.

Reference numeral 11 denotes a check valve body that is slidably fitted on the first flow port 3 side in the valve cylinder 1 and prevents backflow from the second flow port 5 to the first flow port 3. The part becomes a small diameter part, and a space part 12 is formed between the outer surface of this small diameter part and the inner face of the valve cylinder 1. It communicates with mouth 5.

A compression spring 14 is interposed between the check valve body 11 and the balance piston 9 and presses the check valve body 11 and the balance piston 9 away from each other.

The present invention has the above configuration, and when the switching valve 6 is now switched to the left position, the hydraulic oil discharged from the pump 2 flows into the first flow port 3 of the valve cylinder 1 and resists the force of the compression spring 14. Push open the check valve body 11, open the space 12, and open the through hole 13.
It flows into the hydraulic cylinder 4 through the orifice 10 and the second flow port 5 and causes the hydraulic cylinder 4 to expand.

Next, when contracting the hydraulic cylinder 4, when the switching valve 6 is switched to the right position, the discharged oil from the hydraulic cylinder 4 passes through the second flow port 5, the orifice 10, and the third flow port 8, and reaches the oil tank. However, when passing through the orifice 10, a pressure difference occurs between the pressures acting on the front and rear surfaces of the balance piston 9, and this pressure difference causes the balance piston 9 to move in the direction of compressing the compression spring 14. By this, the opening area of the third flow port 8 is variably controlled, and the flow rate flowing out from the third flow port 8 is controlled to be constant regardless of fluctuations in the load acting on the hydraulic cylinder 4.

As described above, the present invention can control the discharged oil from the hydraulic cylinder at a constant level, thereby eliminating the risk of damaging the mechanical system in which the hydraulic cylinder is installed.

In particular, the check valve and the flow rate control valve are integrated into a structure, and the compression spring that makes up the check valve and the compression spring that makes up the flow rate control valve are combined into one compression spring, so the overall structure is It has a very compact structure and can be built into the case of the hydraulic pump and switching valve, simplifying the piping system.

Furthermore, a space is formed between the outer surface of the tip of the check valve body and the inner surface of the valve cylinder, and this space is communicated with the hydraulic cylinder side through a hole drilled in the side of the check valve body. When the hydraulic oil flows into the hydraulic cylinder side, it does not pass through the third flow port whose opening area is variably controlled. Therefore, the hydraulic oil can flow smoothly without any resistance.

[Brief explanation of drawings]

The figure is a sectional view showing the flow control valve of the present invention.

Claims (1)

[Claims] 1. A valve cylinder having a first flow port communicating with the pump side at one end, a second flow port communicating with the hydraulic cylinder side at the other end, and a third flow port communicating with the oil tank side on the side. a hollow balance piston that is slidably fitted on the second flow port side in the valve cylinder and controls the flow of flow from the second flow port to the third flow port; is slidably fitted on the first flow port side of the
A check valve body that prevents backflow from the second flow port to the first flow port, and a check valve body that is interposed between the balance piston and the check valve body and presses the balance piston and the check valve body in a direction away from each other. A compression spring is formed between the inner surface of the valve cylinder and the tip of the outer surface of the check valve body to form a space that communicates with the first flow port when the first flow port is opened. A pressure-compensated flow control valve with a check valve, which communicates with the second flow port through a through hole formed in a side surface.