JP2852885B2 - Bleed-off type compensator valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bleed-off type compensator valve provided for compensating a pressure difference between a primary side and a secondary side of a flow control throttle constituting a flow control valve.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 1, an operation circuit a such as a pump discharge circuit is provided with a flow control throttle b to control a flow from a hydraulic pump c flowing therethrough. In this case, when the load pressure of the operation circuit a changes, the pressure difference before and after the flow control throttle b fluctuates and the flow rate flowing therethrough also changes, and the flow control becomes inaccurate. A bleed-off type compensator valve d is provided together with the control restrictor b, and the pressure difference is constantly compensated. The compensator valve d has a plunger f slidably in a valve housing e, and a pressure receiving surface g in front of the plunger f.
The pressure of the operation circuit in front of the flow control throttle b is applied to the pressure control surface b, and the pressure and control spring of the operation circuit behind the flow control throttle b introduced through the orifice j on the pressure receiving surface i behind the plunger. When the pressure difference before and after the flow control throttle b increases by applying a spring force of k, the plunger f slides and a part of the flow rate of the operation circuit a in front of the flow control throttle b is changed to the valve housing e. The pressure difference is constantly compensated by bleeding off to a tank circuit n via a tank port m provided at a position corresponding to the sliding portion of the plunger.
The upper limit of the pressure acting on the rear pressure receiving surface i is controlled by a relief valve l.

[0003]

The orifice j is for preventing the occurrence of vibration phenomena such as hunting in the plunger f. To improve the effect, the area of the orifice j should be as small as possible. Need to be smaller. However, from the spring chamber o provided with the control spring k facing the pressure receiving surface i behind the plunger f, the plunger f
When the area of the orifice j is reduced, the pressure in the chamber o is reduced by the leak, and the leak does not increase to the maximum pressure of the operation circuit. occured. This is likely to occur when the temperature of the working circuit fluid is high and its viscosity is low.

The present invention prevents the pressure in the operation circuit behind the flow control throttle from leaking from the sliding portion of the plunger to the tank port, and reduces the area of the orifice to improve the vibration phenomenon of the plunger. It is an object of the present invention to provide a bleed-off type compensator valve which can be prevented.

[0005]

According to the present invention, a plunger is slidably provided in a valve housing, and a pressure in front of a flow control throttle provided in an operation circuit is applied to a pressure receiving surface in front of the plunger. The pressure and spring force of the operating circuit behind the flow control throttle introduced through the orifice to the pressure receiving surface behind the plunger act on the plunger, and when the pressure difference before and after the flow control throttle increases, the plunger slides. The pressure difference is kept constant by bleeding off a part of the flow rate of the operating circuit in front of the flow rate control throttle to the tank circuit via a tank port provided in the valve housing at a position corresponding to the sliding portion of the plunger. In the plunger, one end is opened in the front pressure receiving surface, and the other end is opened in the plunger sliding portion between the pressure receiving surface behind the plunger and the tank port. Introduction By providing the road, and so as to achieve the above object. The plunger is formed to have a larger diameter behind the position corresponding to the tank port to form a buffer chamber by the step portion of the plunger and the valve housing, and the other end of the high-pressure introduction passage is opened to the buffer chamber. Preferably, a throttle is interposed in the high-pressure introduction passage.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 2. In FIG. 2, reference numeral 1 denotes a hydraulic pump, 2 denotes an operation circuit extending from the hydraulic pump 1 to an actuator such as a hydraulic motor, Denotes a flow control throttle for controlling the flow rate of the operation circuit 2. Reference numeral 4 denotes a bleed-off type compensator valve for compensating a pressure difference between the front and rear of the flow control throttle 3 of the operation circuit 2 to a constant value. The valve 4 includes a slidable plunger 6 in a valve housing 5. The pressure in front of the flow control restrictor 3 acts on a pressure receiving surface 7 in front of the plunger 6 via a branch circuit 16, and an orifice 1 provided in a load pressure introducing line 9 in a pressure receiving surface 8 behind the plunger 6.
The pressure of the operating circuit 2 behind the flow control throttle 3 and the spring force of the control spring 11 introduced through the pressure control valve 11 are applied. The valve housing 5 is provided with a spring chamber 13 in which the rear pressure receiving surface 8 faces and the control spring 11 is accommodated. A tank port 15 having a tank circuit 14 connected to a position corresponding to the sliding portion of the plunger 6 is provided. The upper limit of the pressure acting on the rear pressure receiving surface 8 is controlled by the relief valve 12.

Such a configuration is the same as the conventional one, and the pressure difference before and after the flow control throttle 3 is reduced by the control spring 11.
, The plunger 6 slides by bending the control spring 11, and a part of the flow rate of the operating circuit 2 in front of the flow rate control throttle 3 is transferred from the branch circuit 16 to the valve housing 5. Bleed-off to the tank circuit 14 via the tank port 15 provided at the same time does not differ from the conventional one in that the pressure difference is constantly compensated, but in the present invention, the plunger 6 has One end is open to the front pressure receiving surface 7, and the other end is connected to the pressure receiving surface 8 behind the plunger and the tank port 1.
High pressure introduction passage 1 opening to the plunger sliding portion between
7 to prevent the pressure of the operating circuit 2 introduced into the spring chamber 13 from the sliding portion of the plunger 6 from leaking to the tank port 15.

That is, in the operating circuit 2, the pressure in front of the flow control throttle 3 is higher than the pressure behind it.
The high pressure is introduced into the sliding portion between the rear pressure receiving surface 8 and the tank port 15 through the branch circuit 16 and the high pressure introducing passage 17, so that the pressure fluid of the operating circuit 2 introduced into the pressure receiving surface 8 is applied to the spring. Leakage from the chamber 13 to the tank port 15 does not occur. Therefore, even if the area of the orifice 10 of the load pressure introducing line 9 is reduced, and even if the temperature of the fluid is high, the pressure acting on the rear pressure receiving surface 8 is not reduced, and the plunger 6 Of the plunger 6 can be effectively prevented by reducing the area of the orifice 10.

A high pressure introducing passage 1 is provided in the sliding portion of the plunger 6.
Although the high pressure introduced from 7 leaks to the spring chamber 13 to some extent, the pressure difference between the high pressure and the pressure in the spring chamber 13 is a slight pressure difference corresponding to the spring force of the control spring 11. Therefore, the leakage amount is very small, and there is almost no influence on the performance as a flow control valve. Also, when the working fluid is at a high temperature and the leak amount slightly increases, and thus the pressure (load pressure) of the spring chamber 13 rises, the plunger 6 operates in the valve closing direction, and the flow rate flowing through the flow control throttle 3 decreases. However, in the machine, various hydraulic devices are provided in the operation circuit 2 behind the flow control throttle 3, and the amount of leakage from the devices increases with the increase of the load pressure. Has the advantage that the required flow rate can be ensured.

As shown in FIG. 3, the diameter 18 of the plunger 6 behind the position corresponding to the tank port 15 is formed larger to form a buffer chamber 19 by the step 6a of the plunger and the valve housing 5. The other end of the high-pressure introduction passage 17 may be opened, and a throttle 20 may be interposed in the high-pressure introduction passage 17. In this case, the high pressure supplied to the sliding portion of the plunger 6 may be used. The high pressure from the introduction passage 17 is confined in the buffer chamber 19 due to the throttle 20, and the vibration phenomenon such as hunting of the plunger 6 is reduced by the load pressure introduction line 9.
Can be prevented in cooperation with the orifice 10, and the operation of the plunger 6 can be further stabilized.

[0011]

As described above, according to the present invention, a plunger of a bleed-off type compensator valve for compensating for a pressure difference before and after a flow control throttle constituting a flow control valve is provided from a pressure receiving surface in front of the plunger. Since the high pressure introduction passage opening to the plunger sliding portion between the pressure receiving surface behind the plunger and the tank port is provided, even if the pressure fluid acting on the rear pressure receiving surface is high temperature, the sliding portion is And the pressure fluid can be introduced through an orifice having a small area to improve the effect of preventing the vibration phenomenon of the plunger with a simple structure. Thereby, the prevention effect is further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a conventional example.

FIG. 2 is an explanatory view of an embodiment of the present invention.

FIG. 3 is a sectional view of a main part of another embodiment of the present invention.

[Explanation of symbols]

2 Operating circuit 3 Flow control throttle 4 Bleed-off type compensator valve
5 Valve housing 6 Plunger 6a Step
7 Front pressure receiving surface 8 Rear pressure receiving surface 10 Orifice
11 control spring 14 tank circuit 15 tank port
17 High pressure introduction circuit 18 Diameter 19 Buffer room
20 aperture

Claims (2)

(57) [Claims] A plunger is slidably provided in a valve housing,
A pressure in front of the flow control restrictor provided in the operation circuit is applied to a pressure receiving surface in front of the plunger, and a pressure in an operation circuit behind the flow control restrictor introduced through an orifice to the pressure receiving surface in the rear of the plunger. When the spring force is applied and the pressure difference before and after the flow control throttle increases, the plunger slides and a part of the flow rate of the operation circuit in front of the flow control throttle is changed to a position corresponding to the sliding portion of the plunger. A valve that bleeds off to a tank circuit through a tank port provided in the valve housing to constantly compensate for the pressure difference. In the plunger, one end is opened on the front pressure receiving surface, and A bleed-off type compensator valve, the end of which is provided with a high-pressure introduction passage that opens to a plunger sliding portion between the pressure receiving surface behind the plunger and the tank port. 2. A stepped portion of the plunger and a valve housing are formed to have a larger diameter at a rear side than a position corresponding to the tank port of the plunger, and the other end of the high-pressure introduction passage is connected to the other end of the high-pressure introduction passage. 2. The bleed-off type compensator valve according to claim 1, wherein the valve is opened to the buffer chamber, and a throttle is interposed in the high pressure introduction passage.