JPH07139512A - Flow control valve - Google Patents

Abstract

PURPOSE:To improve responsiveness by detecting at all times pressure difference between load pressure to be added to an opening/closing member and atmospheric pressure to be added to a spindle portion and an elastic member to energize the opening/closing member against load pressure, regulating at all times the opening area of a variable throttle according to the load pressure of a control port. CONSTITUTION:A difference between load pressure to be added to a spool 2 and atmospheric pressure to be added to a spindle portion 20 and a spring 3 to energize the spool 2 against load pressure is detected at all times, and the opening area of a control orifice 21 is regulated according to the load pressure of a control port 1A. Accordingly, even in the state of a passing flow quantity not being generated, the opening area of the control orifice 21 is set at a throttle quantity responding to load pressure, and regulation to a predetermined control flow quantity from right after the changeover of a changeover valve 7 becomes possible. Accordingly, a jumping phenomenon occurred at the time of the changeover of the changeover valve 7 is prevented, and at the same time it becomes possible to conduct descent smoothly while the change of the descending speed of load 80 is being restrained, and ascending/descending action can be stabilized by preventing impact and swing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a flow rate control valve which is installed in a hydraulic circuit of a cargo handling machine or the like to adjust the speed.

[0002]

2. Description of the Related Art In a hydraulic circuit of a cargo handling machine such as a forklift that lifts and lowers a load, a flow control valve for suppressing a load descending speed to a predetermined speed is provided. , For example, JP-A-4-316
A flow control valve as disclosed in Japanese Patent No. 782 is known. Explaining this, as shown in FIG. 3, the tubular body 92 is supported on the inner circumference of the flow control valve 9 integrally formed by joining the tubular valve bodies 91A and 91B. Inner circumference of 91A and 91B and body 9
Oil chambers 9A and 9B are defined between the outer periphery of the oil chamber 2 and the outer periphery of the oil chamber 2. The oil chamber 9A communicates with the control port 9C and the oil chamber 9B communicates with the pump port 9P, respectively, while the oil chamber 9A communicates with the inner periphery of the body 92. 94 are defined.

The oil chamber 9A communicates with the cylinder 8 through a cutoff valve 90 connected to the control port 9C, while the oil chamber 9B
Communicates with the pump 31 or the tank 32 via the switching valve 7. The oil chambers 9A and 9B are in communication with the oil chamber 94 via an orifice 92A and a metering orifice 92B that connect the inner circumference and the outer circumference of the body 92, respectively.

A cylindrical spool 93 is provided on the inner circumference of the body 92.
Is slidably accommodated in the axial direction, the spool 93 has a control orifice 93A opening facing the orifice 92A, and a shutoff portion 93B for controlling the opening area of the metering orifice 92B.

The spool 93 is a body 92 on the port 9P side.
It is urged toward the port 9C by a spring 95 interposed between and. The damper 96 restricts the position of the spool 93 at the extended position of the spring 95. At the extended position of the spring 95, the spool 93 moves to the right side in the drawing, and the shutoff portion 93B becomes the metering orifice 92B.
Is the maximum opening position.

The flow rate control in the flow rate control valve 9 is performed by displacing the spool 93 according to the pressure difference between the oil chamber 9A and the oil chamber 94, that is, the flow rate of passage, and when the switching valve 7 is connected to the tank 32. , The oil chamber 9A to the orifice 92A,
Control orifice 93A, metering orifice 92B
The hydraulic oil flows into the oil chamber 9B via the, and the load 80 supported by the cylinder 8 starts to descend. At this time, the spool 93 moves the spring 9 due to the load pressure applied to the oil chamber 9A.
It is displaced to the port 9P side (left side in the drawing) against 3 and the shut-off portion 93B reduces the opening area of the metering orifice 92B to suppress the flow rate passing through the oil chamber 94 and reduce the descent rate of the load 80. It is held at a predetermined value. In addition,
The shutoff valve 90 connected to the control port 9C is the flow control valve 9
Is set so as to operate at a value larger than the maximum flow rate, and the descent rate of the load 80 is suppressed when the pipe between the flow control valve 9 and the valve breaks.

[0007]

At the neutral position of the switching valve 7, the flow rate of the flow rate control valve 9 becomes 0, and the oil chambers 9A and 9B and the oil chamber 94 are balanced with the load pressure applied from the cylinder 8. Then, the spring 95 extends, the spool 93 moves to the right side in the drawing, and the shutoff portion 93B reaches the maximum opening position of the metering orifice 92B.

Therefore, when the switching valve 7 is switched from the neutral position to the tank 32 and the descent of the load 80 is started, after the differential pressure is generated in the oil chambers 9A and 9B, the spool 93 located at the maximum opening position of the metering orifice 92B. Therefore, a response delay occurs in the flow rate control by the metering orifice 92B, and a jumping phenomenon in which the control flow rate transiently exceeds a set value causes a load 80 in a cargo handling machine such as a forklift that raises and lowers a load.
There was a problem that the swaying and the shock might occur.

Therefore, an object of the present invention is to provide a flow control valve which suppresses jumping and has a high responsiveness.

[0010]

SUMMARY OF THE INVENTION The present invention comprises a control port to which a load is connected, a pump port for receiving pressure oil supply,
A valve hole formed in the valve body, an opening / closing member that forms a shaft portion with a predetermined outer diameter at one end and a tubular portion from the other end, and a tubular portion at a predetermined position facing the pump port. A variable throttle that communicates an inner circumference and an outer circumference is provided, and the opening / closing member is axially slidably accommodated in a valve hole so that the inner circumference of the tubular portion communicates with a control port, and the shaft portion is provided. An elastic member is provided which penetrates the valve body at the end portion thereof and biases the opening / closing member toward the opening direction of the variable diaphragm.

[0011]

[Function] The opening / closing member slidably accommodated in the valve hole receives axial pressure in the direction of closing the variable throttle according to the load pressure applied to the inner circumference of the tubular portion, while the valve body is opened. Atmospheric pressure is applied to the end of the penetrating shaft, and pressure is applied in the direction of opening the variable diaphragm together with the urging force of the elastic member.
Even if the flow rate passing through the valve is 0, the opening / closing member displaces the valve hole according to the difference between the load pressure and the pressure due to the elastic member and the atmospheric pressure, and the variable throttle opening in the tubular portion is relatively located with the pump port. The displacement can be changed to change the opening area and the flow rate can be set according to the load pressure, and the jumping phenomenon can be suppressed to perform accurate flow rate control.

[0012]

EXAMPLE FIG. 1 shows an example of the present invention.

The valve body 1 is formed with a control port 1A which communicates with a cylinder 8 which drives a load 80 up and down, and a pump port 1B which communicates with a pump 31 or a tank 32 via a switching valve 7. The spool 2 as an opening / closing member is housed in the valve hole 10 formed in the above.

The spool 2 has a cylindrical portion 2A formed of a cylindrical member having a predetermined inner diameter at one end, while having a predetermined outer diameter protruding to the outside from a through hole 12 formed in the valve body 1 at the other end. The shaft portion 20 is provided, and the tubular portion 2A and the shaft portion 20 are coaxially formed via the partition portion 2B. A cover 6 for protecting the end portion 20A of the protruding shaft portion 20 is fixedly provided at the end portion of the valve body 1 having the through hole 12 formed therein.

The cylindrical portion 2A is in sliding contact with the lands 13 and 14 formed in the valve hole 10 and the shaft portion 20 in the through hole 12, whereby the spool 2 is axially moved in the valve hole 10 (left and right in the drawing). Slidably supported. In addition, land 14
Defines a control port 1A and a pump port 1B, and the land 13 defines a pump port 1B and an oil chamber 1C.

At a predetermined position of the cylindrical portion 2A facing the pump port 1B, a control orifice 21 is formed as a variable throttle which connects the inner circumference and the outer circumference, and is controlled in accordance with the axial displacement of the spool 2. The orifice 21 is displaced relative to the land 13 to change the opening area. That is, the control orifice 21 reduces its opening area by the displacement of the spool 2 in the direction of the shaft portion 20 (rightward in the figure), while the control orifice 21 opens by the displacement in the direction of the tubular portion 2A (leftward in the figure). Increase the area. It should be noted that an orifice 22 that is always fixed with a constant opening area is formed in the cylindrical portion 2A so as to face the pump port 1B.

A spring 3 as an elastic member is provided between the partition 2B and the end of the oil chamber 1C defined by the land 13.
Are accommodated, and the spool 2 is biased toward the opening direction of the control orifice 21 (direction of the cylindrical portion 2A).

Displacement of the spool 2 in the opening direction is restricted by contacting the end of the cylindrical portion 2A with a plug 4 screwed into the valve body 1 on the cylindrical portion 2A side. The position where the tubular portion 2A abuts on the plug 4 is preset to be the maximum opening position of the control orifice 21, and the notch 40 is formed at the end of the plug 4 so that the tubular portion 2A When in contact with the plug 4, the inner periphery of the control port 1A and the cylindrical portion 2A communicate with each other through the cutout portion 40.

On the other hand, the maximum throttle position of the control orifice 21 is restricted by the step portion 11 formed in the oil chamber 1C, and the spool 2 resists the spring 3 by the load pressure and the shaft portion 2 is prevented.
The position where the partition 2B comes into contact with the step 11 after being displaced in the 0 direction is the maximum throttle position of the control orifice 21.

A hydraulic oil passage 15 is formed between the pump port 1B and the oil chamber 1C. The hydraulic oil passage 15 allows the flow from the pump port 1B to the oil chamber 1C, while flowing in the opposite direction. A check valve 5 that regulates the

A working oil passage 16 is formed in the center hole 23 formed in the partition 2B so as to extend from the outer circumference of the shaft portion 20 in the radial direction. The working oil passage 16 is provided at the inner circumference of the oil chamber 1C and the cylindrical portion 2A of the spool 2. The spool 2 can be smoothly displaced by communicating with the passage 16.

With the above construction, the operation will be described.

At the neutral position of the switching valve 7, the control port 1A
The load pressure corresponding to the load 80 is applied from the cylinder 8 connected to the inner peripheral bottom portion of the spool 2, that is, the partition portion 2B facing the plug 4 to apply the spool 2 to the control orifice 2
A pressure for driving in the throttle direction of 1 is generated.

On the other hand, the opening area of the control orifice 21 of the spool 2 is controlled by the urging force of the spring 3 from the oil chamber 1C side of the spool 2 and the atmospheric pressure applied to the end 20A protruding from the through hole 12 to the outside of the valve body 1. Is applied to the spool 2, and the spool 2 is displaced to a position where the load pressure and the spring 3 and the atmospheric pressure are in equilibrium, and the control orifice 21 is displaced relative to the land 13 according to the load pressure of the control port 1A. Set to the opening area.

Control orifice 2 by displacement of spool 2
The opening area of 1 is preset to the characteristics shown in FIG.
In this figure, the position where the stroke of the spool 2 is 0 indicates the maximum opening position where the tubular portion 2A contacts the plug 4.

When the switching valve 7 is connected to the tank 32 from the neutral position, hydraulic oil flows from the control port 1A to the pump port 1B via the orifice 22 and the control orifice 21,
The load 80 supported by the cylinder 8 starts to fall.

At this time, the spool 2 is preset at the neutral position of the switching valve 7 where the flow rate is 0, and the throttle amount corresponding to the load pressure applied to the control port 1A is preset by the opening area of the control orifice 21. Therefore, the spool 2 can be adjusted to a predetermined control flow rate immediately after the switching valve 7 is switched without displacing, preventing a jumping phenomenon and suppressing fluctuation of the descending speed of the load 80. It is possible to smoothly descend.

On the other hand, when the switching valve 7 is switched to the pump 31 to increase the load 80, the hydraulic pressure applied to the pump port 1B flows to the control port 1A via the orifice 22 and the control orifice 21 of the tubular portion 2A, and Check valve 5 interposed between pump port 1B and oil chamber 1C
Is opened and the oil pressure of the pump 32 is applied to the oil chamber 1C, and the spool 2 is displaced in the direction of the plug 4 against the load pressure by the oil pressure of the pump 31 in addition to the atmospheric pressure of the spring 3 and the shaft portion 20. The opening area of the control orifice 21 can be increased so that the pressure oil can be smoothly supplied to the cylinder 8.

In this way, the differential pressure between the load pressure applied to the spool 2 and the atmospheric pressure applied to the spring 3 and the shaft portion 20 for biasing the spool 2 against the load pressure is constantly detected,
Control orifice 21 according to the load pressure of control port 1A
The opening area of the control orifice 21 is set to a throttle amount according to the load pressure even when the passing flow rate is not generated, and the predetermined control flow rate is set immediately after the switching valve 7 is switched. It becomes possible to prevent the jumping phenomenon that occurs when the switching valve 7 is switched, and to smoothly lower the load 80 while suppressing the fluctuation of the lowering speed of the load 80. If applied to a cargo handling machine that elevates and lowers the load, it is possible to prevent shock and sway due to its high responsiveness to stabilize the elevating operation, and because the jumping phenomenon is suppressed, the control port 1A and the cylinder 8 If a shut-off valve (not shown) is provided between them, it is possible to set the operating region without considering the transient increase in flow rate, and it is possible to design by itself. It is possible to expand the degree.

Although the spool 2 is used as the opening / closing member in the above embodiment, it may be formed of a piston or a slide although not shown.

[0031]

As described above, according to the present invention, the pressure difference between the load pressure applied to the opening / closing member and the atmospheric pressure applied to the shaft and the elastic member for urging the opening / closing member against the load pressure is constantly maintained. By detecting and adjusting the opening area of the variable throttle according to the load pressure of the control port at all times, it is possible to control to a predetermined flow rate immediately after the passage flow rate is generated, and the responsiveness is better than before. It is possible to prevent the jumping phenomenon that occurs at the time of switching the switching valve and to smoothly lower the load while suppressing the fluctuation of the load lowering speed.

[Brief description of drawings]

FIG. 1 is a sectional view of a flow control valve showing an embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a stroke of a spool and an opening area of a control orifice.

FIG. 3 is a sectional view of a flow control valve showing a conventional example.

[Explanation of symbols]

 1 Valve body 1A Control port 1B Pump port 2 Spool 2A Cylindrical part 3 Spring 10 Valve hole 12 Through hole 20 Shaft part 21 Control orifice

Claims (1)

[Claims] 1. A control port to which a load is connected, a pump port for receiving pressure oil supply, a valve hole formed in a valve body, and a shaft portion having a predetermined outer diameter at one end, and a cylinder from the other end. An opening / closing member having a cylindrical portion and a variable throttle that communicates the inner circumference and the outer circumference of the tubular portion at a predetermined position facing the pump port are provided, and the inner circumference of the tubular portion communicates with the control port. As described above, the opening / closing member is axially slidably accommodated in the valve hole, and the valve body is penetrated at the end of the shaft portion to provide an elastic member for urging the opening / closing member in the opening direction of the variable throttle. A flow control valve characterized in that