JPH0114541Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow control valve device with a built-in pressure relief valve that is integrated with a hydraulic pump as a hydraulic unit of a power steering device or the like.

Generally, a hydraulic unit that drives hydraulically operated equipment is equipped with a pressure relief valve that maintains the pressure of the hydraulic circuit below a certain value in order to prevent the hydraulic circuit from being overloaded. Such pressure relief valves have a relatively small footprint and can be mounted inside the spool of the flow control valve.

However, in the case of a flow control valve device with a built-in pressure relief valve, dust and foreign matter tend to accumulate inside the passage and pressure chamber, and if foreign matter adheres to the inside of the pressure relief valve, the pressure relief valve remains open. As a result, it becomes impossible to supply pressure fluid at the desired pressure to the hydraulic circuit.

Therefore, conventionally, as shown in Fig. 1, a filter 2 was installed on the upstream side of the passage closest to the pressure relief valve.
9 is placed. FIG. 1 shows a flow control valve device with a built-in pressure relief valve installed in a conventional hydraulic pump 3 for a power steering device, in which a cylindrical valve chamber 30 is configured in the casing of the hydraulic pump 3. It is sealed by a screw plug 5. A spool valve 24 is fitted inside the valve chamber 30 to partition the pressure chambers 23 and 25, and the spool valve 24 is abutted against a stopper 22 of the screw plug 5 by a spring 16. Pressure liquid from the discharge port of the hydraulic pump is directly introduced into the pressure chamber 23, and pressure liquid from the discharge port is introduced into the pressure chamber 25 through an orifice (not shown). An annular groove 2 is provided on the outer periphery of the spool valve 24.
1 and 10 are provided, and the annular groove 21 communicates with the liquid tank.

In the pressure relief valve, a valve seat 12 having a passage connecting the hollow part and the pressure chamber 25 is screwed onto one end side of a hollow part provided inside the spool valve 24, and a valve body 18 consisting of a pole is screwed onto one end side of a hollow part provided inside the spool valve 24. The valve seat 12 is biased and engaged with the valve seat 12 by the force of a spring 20 via the valve seat 12 . The other end of the hollow portion is connected to the annular groove 21 via the passage 9.

When the discharge flow rate increases with the rotation of the hydraulic pump 3, the pressure difference between the pressure chambers 23 and 25 increases, the spool valve 24 moves to the right against the spring 16, and the excess flow rate increases. returned to the tank.

Further, when the output hydraulic pressure exceeds a predetermined pressure due to load fluctuation, the valve body 18 is pushed open to the left against the spring 20, and a portion of the flow rate from the hydraulic pump is transferred to the pressure chamber 23. Orifice, pressure chamber 25 and passage 9
It overflows into the liquid tank 4 through the flow, creating a pressure difference between the pressure chambers 23 and 25. Furthermore, due to the pressure difference, the spool valve 24 moves to the right against the spring 16, and the pressure chamber 2
3 is directly returned to the liquid tank 4.

In this way, the pressure relief valve maintains the pressure of the pressure fluid supplied to the power steering device below a certain value and plays the role of protecting the power steering device 2. If the pressure relief valve remains slightly open due to the stagnation of the valve seat 12 and the valve body 18, the hydraulic pressure supplied to the power steering system will decrease, and the predetermined steering output will be reduced. You will not be able to obtain

Therefore, in the past, a filter 29 was installed at the end of the valve seat 12.
is installed to prevent foreign matter from flowing into the valve body 18. However, in such a conventional configuration, the dimensions of the filter are limited and the filtration area is small, so there are drawbacks such as a short life due to clogging. Another problem is that when the filter becomes clogged, the relief pressure increases, leading to damage to the power steering device. Particularly in the case of industrial vehicles such as forklift trucks, other hydraulically operated equipment in addition to the power steering system is driven by the same hydraulic fluid, so the capacity of the liquid tank that stores the hydraulic fluid is large. , the degree of contamination of the working fluid is high, and filter 2
9 becomes clogged, the relief pressure only increases, and the driver often does not notice this.

In view of these problems, the purpose of the present invention is to install a pressure relief valve near the pressure relief valve.
If the filtration area is larger and clogging occurs, the filter moves back against the spring, allowing the pressure liquid to bypass the gap in the filter support and flow toward the pressure relief valve. The object of the present invention is to provide a flow control valve device with a built-in pressure relief valve, which prevents damage to hydraulically operated equipment due to an increase in relief pressure.

For this reason, the configuration of the present invention is equipped with a movable spool valve that is communicated with the pump discharge port and bypasses the excess flow of the pump discharge liquid to the pump suction port side so as to keep the pressure difference before and after the orifice constant. A pressure chamber is formed at one end of the spool valve and has an inlet in the end wall through which the pressure liquid after passing through the orifice is introduced, and a spring is interposed between the end wall and the spool valve. In the flow control valve device with a built-in pressure relief valve, the spool valve includes a pressure relief valve that maintains the liquid pressure below a set value, the pressure liquid inlet is covered with the end wall of the pressure chamber, and the pressure The reason is that a filter having a smaller diameter than the inner diameter of the chamber is pressed against the filter by the spring.

The configuration of the present invention will be explained based on an example.
FIG. 2 shows an embodiment of a flow control valve device with a built-in hydraulic pressure relief valve for a power steering device. The power steering device 2 is integrally equipped with a servo control valve operated by the handle 1 and a power cylinder, and a hydraulic pump 3 supplies pressure fluid to one of the liquid chambers of the power cylinder via the servo control valve. and transfer the liquid from the other liquid chamber to liquid tank 4.
It's starting to go back to .

The flow rate control valve that controls the flow rate of the pressure fluid supplied to the power steering device 2 is the same as in the conventional example. That is, the pressure liquid from the hydraulic pump 3 is introduced into the pressure chamber 23 of the housing 6 through the passage 7, and into the chamber 25 through the passage 7, the passage 13, the orifices 32, 14, and the inlet 27. It's getting old. The chambers 23 and 25 are separated by a spool valve 24 fitted into a valve chamber 30.

A relief valve integrally provided inside the spool valve 24 is located on the right end side of the hollow part of the spool valve 24.
A valve seat 12 having a passage 17 is screwed into the valve seat 12, and the left end portion is connected to an annular groove 21 via a passage 9. This annular groove 21 is connected to the liquid tank 4 via a passage 8. The spherical valve body 18 is biased and engaged with the valve seat 12 via the spring seat 19 by a spring 20 housed in the hollow portion, so that the passage 17 is opened and closed.

An important feature of the present invention is that the filter 15 is disposed between the pressure chamber 25 and the inlet 27 to prevent foreign matter from flowing toward the valve body 18. As shown in an enlarged view in FIG.
The frame 31 is supported by an elastic frame 31 made of rubber or the like and has an outer diameter slightly smaller than the inner diameter of the pressure chamber 25 . It's getting old. The spring 16 is originally a resistance member for causing the spool valve 24 to generate an actuation amount proportional to the hydraulic pressure difference between the pressure chambers 23 and 25 connected before and after the orifice 14, and also serves to support the filter 15. Therefore, no special snap springs or other parts are required to support the filter 15. Since the filter 15 is placed inside the pressure chamber 25, it is possible to have a larger filtration area than a conventional filter installed inside the valve seat 12.

By configuring the present invention in this way, the passages 7, 13 and the orifices 32, 1 are connected from the hydraulic pump 3.
4. The pressure liquid flowing into the inlet 27 passes through the filter 15
Since dust and foreign matter are filtered out and introduced into the pressure chamber 25, the pressure relief valve composed of the valve seat 12 and the valve body 18 is maintained in a normal operation.

When the filter 15 becomes clogged, the pressure at the inlet 27 gradually increases, causing the filter 15 to retreat to the left against the force of the spring 16. Therefore, as shown by the arrow in FIG. 3, the pressure liquid in the inlet 27 flows into the pressure chamber 25 through the gap between the outer circumferential side of the filter 15 and the inner circumferential surface of the valve chamber 30, and the pressure relief valve normally It works like. Therefore, an abnormal increase in the output hydraulic pressure applied from the hydraulic pump 3 to the power steering device 2 can be prevented, and damage to the power steering device can be prevented.

As described above, in the present invention, the filter 15 is engaged with and supported by the housing end wall 26 by the return spring 16 of the spool valve of the flow rate control valve, so that when the filter 15 becomes clogged, it acts as a safety valve. The filter 15 moves in the axial direction against the spring 16 to form a bypass passage passing through the outer periphery of the filter 15, thereby preventing an increase in relief pressure and preventing damage to hydraulically operated equipment. , compared to the conventional example, the following advantages can be obtained.

(1) Compared to conventional pressure relief valves in which the filter is attached directly, since it is attached to the housing of the flow control valve, the filtration area of the filter can be increased, and the life of the filter can be extended accordingly. .

(2) Compared to a conventional pressure relief valve in which a filter is directly attached, the filter is easier to replace, and since the filter is large, it is also easier to clean.

(3) Conventional systems use a snap spring or caulk to fix the relief valve to the cylindrical part, but according to the present invention, it is sufficient to simply press the filter against the end wall of the flow control valve housing with a spring. Reducing parts such as snap springs,
The effort required for installation can be saved.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a conventional flow control valve device with a built-in pressure relief valve provided in the housing of a hydraulic pump, and Fig. 2 is a longitudinal cross-section of a flow control valve device with a built-in pressure relief valve according to the present invention. 3 and 3 are enlarged views of the same essential parts. 2... Power steering device, 3... Hydraulic pump, 4...
...Liquid tank, 6...Housing, 7, 8, 9, 13,
17... Passage, 12... Valve seat, 14, 32... Orifice, 15... Filter, 16, 20... Spring, 18... Valve body of pressure relief valve, 24... Spool valve, 25... Pressure Room, 26... End wall, 27
...Introduction port, 31...frame.

Claims (1)

[Scope of utility model registration request] A movable spool valve is provided which is communicated with the pump discharge port and bypasses the excess flow of the pump discharge liquid to the pump suction port side so as to keep the pressure difference before and after the orifice constant, and the orifice is connected to one end of the spool valve. A pressure chamber is formed having an inlet in an end wall into which the pressure fluid is introduced after passing through, a spring is interposed between the end wall and the spool valve, and the fluid pressure in the pressure chamber is lowered to a set value or less. In the flow control valve device with built-in pressure relief valve, the pressure relief valve is provided inside the spool valve. A flow control valve device with a built-in pressure relief valve, characterized in that a filter is pressed by the spring.