KR960006359B1 - Pilot check valve having low-velocity-return function - Google Patents

Abstract

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Description

Pilot check valve with low speed return function

1 is a cross-sectional view showing an embodiment of a pilot valve with a low speed regeneration function according to the present invention.

2 is a system diagram showing an embodiment of a hydraulic circuit to which a conventional low speed return valve mechanism is applied.

* Explanation of symbols for main parts of the drawings

14,22: cylinder 14a, 22a: control valve

26: signal line 30: low speed return pilot valve

32: pilot poppet valve 34: main valve

35: spring 36: hydraulic chamber

38,44,49: Euro 40: Piston

42: projection 46: hydraulic drawing hole

48: cylindrical member 50: adjusting screw

51: exhaust chamber 52: check valve

54: control valve cylinder port shaft chamber 56: passage

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slow return valve mechanism for preventing a natural drop of a boom or the like driven by a hydraulic actuator in a construction machine (particularly a hydraulic excavator).

In general, in the shovel, it is necessary to prevent the natural drop of the boom or the arm in terms of the stability of the work and the stability of the vehicle body. Therefore, the boom or the arm actuator is used to regulate the return flow rate. Low speed return valve mechanism is installed.

The low speed return valve mechanism is composed of a throttle installed in a spool (spoo1) of a control valve for driving an actuator, or a low speed return valve and a pilot valve provided between the actuator and the throttle.

However, in the valve mechanism of the former configuration, since a gap for sliding between the valve body and the spool is interposed, a minimum leakage is inevitable and a defect occurs that the shutoff of the return oil from the actuator cannot be reliably achieved.

For this reason, in particular, as the pressure of the hydraulic circuit is increased, the valve mechanism (hereinafter, referred to as the `` valve valve method) having the latter configuration in which the return oil from the actuator is reliably achieved has been preferred. However, since the check valve method is composed of two types of check valves, a low speed return check valve and a pilot valve as described above, there is a basic difficulty in that the structure becomes complicated.

That is, when the two check valves are provided in the valve body, the entire control valve is extremely large, including the control valve portion that does not require the low speed return valve mechanism.

On the other hand, in the case where both check valves are installed outside the valve body, the actuator relief valves and the new tank passages need to be installed outside the valve body in addition to the two check valves, and the manufacturing cost greatly increases.

For this reason, the present applicant has developed and applied for a patent for a hydraulic circuit that can be easily installed outside the valve only in a location where only a low speed return valve mechanism is required to solve the above-mentioned difficulties (Japanese Patent Application No. 63-123338).

Hereinafter, the hydraulic circuit according to the above patent application will be briefly described.

The patent application hydraulic circuit has control valves l4a, 16a and 18a in two composite control valves 12a and 12b to which discharge oil from two pumps 10a and l0b is supplied as shown in FIG. 20a) (22a) and (24a), respectively, a cylinder 14 for a swing, a swing motor 16, a left driving motor 18, a space travel motor 20, a boom cylinder 22, a bucket cylinder 24, respectively. In the hydraulic circuit driven by the pilot valve, between the female cylinder 14 and its control valve l4a and between the auxiliary cylinder 22 and its control valve 22a, respectively, the pilot check valves l4b and 22b and low speed return. The check valves 14c and 22c are provided, and the switching valves 14d, 22d and 24d are provided in the respective control valves 14a, 22a and 24a, respectively. 22c), the valve opening and closing signal of the pilot pump is supplied through the signal line 26.

In such a configuration, when each of the control valves 14a, 22a and 24a is in a neutral state, each of the pilot valves 14b and 22b is closed through the reactivation valves 14d, 22d and 24d. The return from the female cylinder 14, the boom cylinder 22, and the bucket cylinder 24 is blocked reliably.

On the other hand, each pilot check valve 14b or 22b is opened at a predetermined timing when the control valves 14a, 22a and 24a are operated. Therefore, when an abnormal high pressure in the hydraulic circuit occurs due to sudden stop of an actuator, The operation of the relief valves 14e, 22e and 24e is not disturbed.

In this way, the low-speed return valve mechanism capable of reliably blocking the return oil from the required actuator by the hydraulic circuit of the prior application can be easily installed outside the valve body only where necessary. However, although the hydraulic circuit of the above-mentioned prior application may be provided only where necessary, there is room for further improvement in that the low speed return valve mechanism is constituted by a separate double check valve.

Therefore, an object of the present invention is to provide a composite valve type low speed return valve mechanism provided outside the valve body that regulates the return flow rate from an actuator that preserves a load such as a hydraulic excavator. By providing an assembly in the valve, it is possible to provide a pilot check valve with a low speed return function that enables the low speed return valve mechanism to be manufactured more simply and inexpensively.

In order to achieve the above object, the pilot check valve to which the low-speed return mechanism according to the present invention is added has a pilot valve 32 operated by a release signal 26 and a check valve function released by the operation of the pilot valve. A pilot valve 30 having a valve 34, the main valve 34 having a spring 35 portion hydraulic chamber 36 which elastically presses and seats it against the valve seat. An axially adjustable cylindrical member 48 for retaining one end of the spring 35 in the 36 and preserving the other end of the spring 35 to partition the exhaust chamber for the main check valve 34. And the exhaust chamber 51 and the hydraulic chamber 36 are communicated with each other by the flow paths 49 and 44 with respect to the secondary side of the valve, and the pilot valve 32 is the main valve. Passage opening / closing by a predetermined stroke amount of 34 (46) (38) has a bypass passage (56) which communicates with the hydraulic chamber and opens its internal pressure to the primary side of the low-pressure valve, and the primary side of the primary valve (34) When the pressure is high, the hydraulic oil in the exhaust chamber 51 and the hydraulic chamber 36 flows to the secondary side of the check valve so that the rear end of the check valve is opposed to the elasticity of the spring 35 so that the exhaust chamber 51 ends. The maximum stroke until contact with the valve is set to move to achieve free flow as the secondary side of the primary side hydraulic oil, and the pressure at which the secondary side of the main valve 34 becomes high pressure by switching the control valve 14a. When the return oil flows, the pilot valve 32 is opened by the release signal 26, the hydraulic oil in the hydraulic chamber 36 flows to the primary side of the check valve, the lift valve is lifted, and the passage 46 Check valve at the set position in which 38 is closed. By regulating the opening of the protruding portion 42 it is characterized in that is configured to regulate the return amount.

In this case, the means 50 for adjusting the stroke amount can be provided as a means for opening and closing the passages 46 and 38 by the predetermined stroke amount of the main check valve 34.

According to the pilot valve with the low speed return function of the present invention, when the primary side of the main valve is high pressure and the secondary side is low pressure, the secondary side, the exhaust chamber and the hydraulic chamber are at the same pressure and communicate with each other. The rear end is set to move the maximum stroke until it comes in contact with the end face of the exhaust chamber against the spring's elasticity to achieve free flow from the primary side to the secondary side of the hydraulic oil.

Subsequently, when the return oil of the hydraulic oil in which the secondary side of the main valve becomes high pressure flows by switching the control valve, the pilot valve is opened by the release signal, and the hydraulic oil in the hydraulic chamber flows to the primary side of the valve and lifts the valve. This stops at the set position where the passage is closed. For this reason, the opening degree of the projection part of a check valve is regulated, Therefore, the said return flow volume is regulated and the low speed return function is exhibited.

Next, an embodiment of a pilot check valve (hereinafter abbreviated as a low speed return pilot check valve) to which a low speed return mechanism according to the present invention is added will be described in detail with reference to the accompanying drawings.

First, the low-speed return pilot valve 30 of the present invention has a cylinder (actuator) 14 (22) (secondary side) and control valves 14a (22a) (primary side) as shown in FIG. It is installed between each.

The low-speed return pilot valve 30 includes a pilot valve (pilot poppet valve) 32 which is operated by a release signal from the signal line 26 as shown in an enlarged view in FIG. 1, and the pilot poppet valve. Flow path from the hydraulic chamber 36 with pilot valve 34 to which pilot valve function is released by operation of the valve 32 and having spring 35 of the pilot valve 34; 38 is configured to close by the lift of the main valve 34 (the direction indicated by the arrow in FIG. 1), that is, by the movement of a predetermined stroke amount.

In FIG. 1, 40 denotes a piston for driving the pilot poppet valve 32. As shown in FIG.

In addition, 42, 44, 46, and 48 represent the projection part, the flow path, the hydraulic extraction hole, and the cylindrical member of the main valve 340, respectively.

In addition, 50 is an adjustment screw for positioning the cylindrical member 48 forward and backward, 56 is a bypass passage communicating with the pilot poppet valve 32 and the cylinder port side chamber 54 (the 1st side) of the control valve 14a. And 52 denotes a check valve installed in the passage 56.

In addition, the spring 35 is retained by a main valve 34 whose one end forms a hydraulic chamber 36, and the other end thereof is a lateral direction that divides the exhaust chamber 51 with respect to the main valve 34. It is preserved by the cylindrical member 48 which is adjustable.

In general, when the cylinder port side chamber (primary side) of the control valve 14a of the main valve 34 becomes high pressure, the pressure in the exhaust chamber 51 and the hydraulic chamber 36 is changed to the actuator of the main valve 34. 14) (secondary side) and the maximum stroke until the rear end of the main valve 34 contacts the end surface of the exhaust chamber 51 against the elasticity of the spring 35 can be moved. By setting so that free flow of the primary side hydraulic oil to the secondary side can be achieved.

The sustained return pilot valve 30 of the present invention configured as described above has a high release signal pressure (relief set pressure 30 to 40 kgf / cm 2), pressurizing the piston 40 to bypass it, and then catching the pilot. The poppet valve 32 is pressurized to bypass this.

In this case, if the piston cross-sectional area is set at about 10 times (about 3 times the diameter) of the pilot poppet seat hydraulic area, it can be released by the cylinder load pressure of 300 to 400 kgf / cm2 (approximately the maximum circuit pressure used). When the pilot poppet valve 32 is released, the hydraulic oil in the hydraulic chamber 36 of the main valve 34 passes through the hydraulic outlet hole 46, the flow path 38, the passage 56, and the check valve 52. Opened in the port side chamber 54, the main valve 34 becomes shiftable.

In this case, the discharge oil from the pilot poppet valve 32 is discharged to the cylinder port side chamber 54 of the control valve 14a, and at this time, the passage from the cylinder port of the control valve 14a to the tank is in a closed state, and the actuator The instantaneous drop of 14 does not occur.

However, the flow path 44 provided in the main valve 34 flows freely from the main valve 34 flowing from the cylinder port side chamber 54 (primary side) of the control valve 14a to the actuator 14 (secondary side). It is necessary to set so that the pressure of the hydraulic chamber 36 may fully decrease at the time of opening of the pilot poppet valve 32 without delay of a test answer.

In addition, in the free flow of the injection valve 34, the pressure of the cylinder port side chamber 54 acts on the spring 35 in the hydraulic chamber 36 of the injection valve 34 so that the injection valve 34 lifts. The check valve 52 is set in the bypass passage 56 to the pilot poppet valve 32 so as not to open.

In this way, operation as a pilot valve is achieved.

The following describes the low speed return function.

In FIG. 1, the oil passage 38 connecting the hydraulic chamber 36 of the main check valve 34 and the pilot poppet valve 32 is directed in the outer circumferential direction of the main check valve 34, and the migration check valve 34 is provided. The hydraulic outlet port 46 provided at the outer periphery of the valve is configured to be closed by a slidable cylindrical member 48 installed inside the main valve 34 when the lift valve 34 is lifted (in the direction indicated by the arrow in FIG. 1). And the position of the cylindrical member 48 is determined by the adjustment screw (50).

In addition, it is easy to regulate the flow rate when the main valve 34 stops at the set position where the projection 42 is provided at the tip of the main valve 34.

For example, when returning from the actuator 14 (secondary side), i.e., detained by switching of the control valve 14a, the pilot poppet valve 32 is opened by the release signal, and the hydraulic oil in the hydraulic chamber 36 is controlled. It flows into the cylinder port side chamber 54 of the valve 14a. Due to this, the main valve 34 lifts, and when the main valve 34 lifts up to a position where the hydraulic outlet hole 46 is closed, the hydraulic chamber 36 and the pilot poppet valve 32 of the main valve 34 are closed. Since the connecting flow path 38 is closed, the pressure of the hydraulic chamber 36 cannot continue to fall, and the lift of the main valve 34 stops at that position.

At this time, since the opening area of the tip of the main valve 34 is restricted by the projection 42, the flow rate regulation is achieved.

The cylindrical member 48 can be positioned freely by the adjustment screw 50, and can adjust the positioning which regulates the stroke of the main valve 34, and can obtain arbitrary specified flow volume.

In this embodiment, the cylindrical member 48 for closing the hydraulic outlet hole 46 provided to communicate with the oil passage 38 connecting the hydraulic chamber 36 and the pilot poppet valve 32 of the main valve 34 is closed. Although the case where the inner diameter part of the thermostat valve 34 was comprised was shown, the outer peripheral part of the thermostat valve 34 may slide as an alternative.

Instead of the adjustment screw 50, a configuration of adjusting the positioning of the cylindrical member 48 by a shim may be employed.

As is apparent from the above-described embodiment, in the present invention, a continuous return valve mechanism is provided for preventing the natural fall of the actuator in the neutral position (when the actuator stops) of the actuator control valve which preserves the actuator load such as a boom. With respect to the pilot check valve to be installed, the low speed return function can be easily added to the pilot check valve at about the same cost as the pilot check valve by assembling a few additional parts into the pilot check valve.

Claims (2)

The pilot valve 30 which has the pilot valve 32 operated by the release signal 26, and the main valve 34 by which the valve | bulb valve function is canceled by operation | operation of this pilot valve 32 is comprised. The valve 34 has an oil pressure chamber 36 with a spring 35 for elastically pressing and seating it on the valve seat, and at the same time, the one end of the spring 35 is retained in the oil pressure chamber 36. On the other hand, by installing the axially adjustable cylindrical member 48 for preserving the other end of the spring (35) to partition the exhaust chamber (51) for the main valve 34, these exhaust chamber (51) and The hydraulic chamber 36 is configured to communicate with the flow paths 49 and 44 with respect to the secondary side of the check valve, respectively, and the pilot valve 32 is a passage opened and closed by a predetermined stroke amount of the check valve 34. A check valve which communicates with the hydraulic chamber 36 through the 46 and 38 and at the same time makes its internal pressure low. Has a bypass passage 56 which opens to the primary side of the valve, and when the primary side of the main valve 34 becomes high pressure, the hydraulic oil in the exhaust chamber 5l and the hydraulic chamber 36 flows to the secondary side of the valve. , So as to move the maximum stroke until the rear end of the shock valve is connected to the end surface of the exhaust chamber 51 against the elasticity of the spring 35, the free flow to the secondary side of the primary pressure oil When the return oil of the hydraulic oil in which the secondary side of the main valve 34 becomes high pressure flows by switching of the control valve 14a, the pilot valve 32 is opened by the release signal 26, The hydraulic oil in the hydraulic chamber 36 flows to the primary side of the check valve, lifts the check valve, stops it at the set position at which the passages 46 and 38 are closed, and regulates the opening degree of the protrusion 42 of the check valve. Thereby regulating the return flow rate. Pilot check valve with low speed return function. The means for opening / closing the passages 46 and 38 by the predetermined stroke amount of the main valve 34 is provided with a low speed return function by providing a means 50 for adjusting the stroke amount. One pilot valve.

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