JP2004011822A - Counter balance valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a counter balance valve capable of changing the reduction speed in accordance with load acting on a hydraulic cylinder. <P>SOLUTION: This counter balance valve is provided with a supply port 111 on an elongation side, a supply port 112 on a reduction side, a supply and discharge port 113 on the elongation side, a supply and discharge port 114 on the reduction side, a check valve 115 on a forward flow passage 111a side, and a main spool 116 on a reverse flow passage 111b side. A variable throttle valve is provided on the reverse flow passage side and has a subspool 121. A spool chamber X on the reduction side connected with a pilot oil passage from the supply port on the reduction side and a spool chamber Y on the elongation side connected with a pilot oil passage from the supply and discharge port on the elongation side are provided on both end sides of the variable throttle valve. When pilot pressure is generated, the subspool 121 is moved and the degree of throttle opening of the variable throttle valve is changed by the difference in thrust generated in the spool chamber X on the reduction side and the spool chamber Y on the elongation side. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a counterbalance valve mounted on a hydraulic cylinder for extending and retracting a crane.
[0002]
[Prior art]
Conventionally, in a crane, a hydraulic actuator such as a hydraulic cylinder is used to operate the boom up and down, and hydraulic oil is supplied to the hydraulic actuator via a counter balance valve.
As shown in FIGS. 5 and 6, a conventional counterbalance valve A includes a supply port A1 on the extension side and a supply port A2 on the reduction side connected to the switching control valve B side in a valve body A0, and a hydraulic cylinder. C and extension-side oil chamber C ₁ and the reduced side oil chamber supply and discharge port A3 extension side connected to the C ₂ and supply and discharge port A4 of the reduction side are provided in a sheet extension side and the supply port A1 of the extension side A check valve A5 is fitted in a normal flow path A9 that communicates with the discharge port A3, and a spool A6 is mounted in a reverse flow path that communicates between the supply port A1 on the extension side and the supply / discharge port A3 on the extension side. Are provided so as to be slidable left and right, an orifice A7 is provided at the tip side of the spool A6, and a fixed throttle A8 is provided between the spool A6 and the check valve A5. ing.
[0003]
When the hydraulic cylinder C extends, hydraulic oil from the hydraulic pump enters the supply port A1 on the extension side via the switching control valve B, and the check valve A5 is pushed leftward to move. hydraulic oil through the supply and discharge port A3 of the extension side flow into the extension-side oil chamber C ₁ of the hydraulic cylinder C, the oil in the contraction side oil chamber C ₂ is the reduction side supply and discharge port A4, the reduction side supply port A2, with flow to the tank E are sequentially passed through the switching control valve B, the rod C ₃ of the hydraulic cylinder C is extended.
[0004]
On the other hand, when the hydraulic cylinder C contracts, the hydraulic oil from the hydraulic pump passes through the switching control valve B and flows into the supply port A2 on the contraction side, and also passes through the orifice A7 and pushes the spool A6 to move rightward. By doing so, the return channel A10 is opened. At the same time via the supply and discharge port A4 on the reduction side, hydraulic oil flows to the reduction side oil chamber C ₂ of the hydraulic cylinder C. At the same time, extension-side oil chamber supply and discharge port of the pressure oil in the C ₁ is extended side A3, fixed throttle A8, the return-side passage A10, through the supply port A1 and the switching control valve B of the extension-side sequentially to the tank E with flowing, rod C ₃ of the hydraulic cylinder is reduced. In this case, the throttle opening of the fixed throttle A8, the flow rate of the pressure oil from the extension-side oil chamber C ₁ is restricted, reduced speed of the rod C ₃ is slow.
[0005]
[Problems to be solved by the invention]
However, in the conventional counterbalance valve A, the diaphragm opening of the fixed throttle A8 in advance because it is fixedly set, regardless of the magnitude of load acting on the rod C ₃ of the hydraulic cylinder C during reduction, the reduction rate Will be the same.
For this reason, in the case of lifting a heavy load or working with a long boom in which the lifting moment is large, despite the state in which the load acting on the hydraulic cylinder is large, it is as fast as when the load is small. The reduction operation of the hydraulic cylinder can be performed at the speed. Then, if the operator accidentally performs an abrupt operation, the reduction speed of the hydraulic cylinder C is too fast, which causes a load swing, and the crane becomes unstable and may fall down. Therefore, it was necessary to operate at a safe speed according to the operator's will.
[0006]
In addition, when the throttle opening is determined so that the crane does not become unstable even if a sudden operation is mistakenly performed suddenly with a large load acting on the hydraulic cylinder, the throttle cylinder is actuated. When the load to be applied is small, there is a problem that the reduction speed becomes too slow, the operation is stressed, the working efficiency is deteriorated, and the temperature of the pressure oil tends to increase.
[0007]
Therefore, the present invention is to solve such a problem in the counterbalance valve, and has an object to provide a counterbalance valve capable of changing a reduction speed in accordance with a magnitude of a load acting on a hydraulic cylinder. I do.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, a counterbalance valve according to the present invention includes an extension supply port, a reduction supply port connected to a supply side of hydraulic oil, an extension oil chamber and a reduction oil chamber of a hydraulic cylinder. The valve body is provided with a supply / discharge port on the extension side and a supply / discharge port on the contraction side, respectively, which are respectively connected to the normal flow path communicating the supply port on the extension side and the supply / discharge port on the extension side. A counterbalance valve provided with a stop valve, and provided with a main spool in a reverse flow path between a supply port on the extension side and a supply / discharge port on the extension side, wherein the hydraulic pressure is adjusted according to a load acting on a hydraulic cylinder when the hydraulic cylinder is contracted. A variable throttle valve for reducing the flow rate discharged from the oil chamber on the extension side of the cylinder is provided in the reverse flow path.
[0009]
Here, the variable throttle valve has a sub-spool, and at both ends of the sub-spool, an expansion-side spool chamber connected to a pilot oil passage from an expansion-side supply / discharge port, and a supply port from a reduction-side supply port. A reducing spool chamber connected to the pilot oil passage is provided, and when a pilot pressure is generated, the sub-spool is moved by the thrust difference generated between the reducing spool chamber and the extension spool chamber of the variable throttle valve, and the variable spool valve is moved. The throttle opening of the throttle valve is changed.
[0010]
Further, the pressure receiving area ratio between the reduction side spool chamber and the expansion side spool chamber of the variable throttle valve is the same as the pressure receiving area ratio between the expansion side oil chamber and the reduction side oil chamber of the hydraulic cylinder.
Further, the variable throttle valve is provided with adjusting means for adjusting the initial value of the operating pressure of the sub-spool.
[0011]
The counterbalance valve of the present invention is provided with a variable throttle valve that reduces the flow rate discharged from the expansion-side oil chamber of the hydraulic cylinder as the load acting on the hydraulic cylinder at the time of reduction increases. Can be changed. Therefore, when the load acting on the hydraulic cylinder is large, the boom lowering operation can be performed at a slow and safe reduction speed, and when the load acting on the hydraulic cylinder is small, the boom lowering operation can be performed efficiently at a high reduction speed. It can be performed.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a right side view of a counterbalance valve according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the counterbalance valve of FIG. 1 taken along the line II, and FIG. 3 is a line II-II of FIG. FIG. 4 is a hydraulic circuit diagram of a hydraulic cylinder for raising and lowering a boom of a crane provided with a counterbalance.
[0013]
As shown in FIG. 4, a switching control valve B is connected to a discharge path from the hydraulic pump D, and a counter balance valve 1 is connected to a pair of secondary ports of the switching control valve B. An oil passage from the hydraulic pump D and a return oil passage to the tank E are connected to a pair of primary ports of the switching control valve B, respectively.
Then, the switching control valve B performs an operation of expanding and contracting a hydraulic cylinder C for boom raising and lowering as a hydraulic actuator by switching an operation lever. That is, the switching control valve B is a four-port, three-position switching control valve configured so that two positions can be selected manually and returned to the neutral position by a spring. When the switching control valve B is at the neutral position, the hydraulic pump D An oil passage is set so that the pressure oil from the tank returns to the tank E.
[0014]
As shown in FIG. 2, the valve body 11 of the counterbalance valve 1 has a supply port 111 on the expansion side, a supply port 112 on the reduction side, and a hydraulic port connected to the supply side (switching control valve B side) of hydraulic oil. cylinder C extension-side oil chamber C ₁ and the reduced side oil chamber C ₂ to extension-side supply-discharge port 113 connected respectively, and supply and discharge port 114 of the reduction side. In the valve body 11, a check valve 115 is fitted in a forward flow path 111a that connects the extension-side supply port 111 and the extension-side supply / discharge port 113. The main spool 116 is slidably fitted in the axial direction in the reverse flow passage 111b between the supply and discharge ports 113 on the extension side.
[0015]
The check valve 115 allows the flow from the supply port 111 on the extension side to the supply / discharge port 113 on the extension side, and shuts off the inflow oil from the supply / discharge port 113 on the extension side. The inflow path from the supply / discharge port 112 on the reduction side is branched, one of which flows out to the supply / discharge port 114 on the reduction side, and the other communicates with an internal pilot oil path 112 a for switching the main spool 116. A fixed throttle 117 is provided in the internal pilot oil passage 112a.
[0016]
Further, as shown in FIG. 3, the variable throttle valve of the counterbalance valve 1 includes a sub-spool 121 inserted in the valve main body in parallel with the main spool 116, and a separate sub-spool 121 at both ends of the sub-spool 121. The main part is constituted by the reduction-side spool chamber X and the extension-side spool chamber Y which are arranged in the horizontal direction. The reduction-side spool chamber X is connected to a pilot oil passage (hereinafter, referred to as a reduction-side branch flow path GG ′) from the reduction-side supply port 112 via a fixed throttle W. Through a fixed throttle T and an internal pilot oil passage Z, it is connected to a pilot oil passage from the supply / discharge port 113 on the extension side (hereinafter, referred to as an extension side branch passage HH ′). Further, notches α and β are provided on the side surface of the sub spool 121 on the extension side spool chamber Y side, and variable throttles S ₁ and S ₂ are formed. The variable throttles S ₁ and S ₂ move the sub-spool 121 to the left and reduce the flow rate of the pressure oil. The notch β serves as a stopper for the left movement of the sub spool 121. Further, the pressure oil passing through the variable throttles S ₁ and S ₂ flows into the reverse flow path 111b via the return-side branch flow path II ′.
[0017]
On the other hand, a spring 122 is urged to the left end of the sub-spool 121, and the spring 122 is formed by screwing a box body 123 a provided with a female screw on the inside and a box body 123 b provided with a male screw on the outside. 123. The amount of compression of the spring 122 changes according to the state of the tightening of the box 123b, so that a predetermined spring force can be obtained. Therefore, the initial value of the operating pressure of the sub spool 121 can be changed.
[0018]
According to the above configuration, the pressure difference between the reduction side spool chamber X provided on both sides of the sub-spool 121 and the extension side spool chamber Y due to the magnitude of the load during the reduction operation of the boom raising / lowering hydraulic cylinder C is also reduced. Causes big and small. This pressure difference acts as a thrust for moving the sub-spool 121 to the left by acting on the spring 122 biasing the sub-spool 121 to the right. This thrust determines the throttle opening of the variable throttles S ₁ and S ₂ . That is, as the load on the hydraulic cylinder C for boom hoisting increases, the sub-spool 121 is greatly moved in the left direction, the variable throttle reduction rate by S ₁ and S ₂ is throttled is slow. Ultimately, the cutout β of the sub-spool 121 prevents outflow of pressurized oil from the internal pilot oil passage Z.
[0019]
In the present embodiment, the area ratio between the pressure receiving area x of the reduction side spool chamber X and the pressure receiving area y of the expansion side spool chamber Y is smaller than the pressure receiving area c ₁ of the expansion side oil chamber C ₁ of the hydraulic cylinder C. The same ratio x / y = c ₂ / c ₁ as the area of the pressure receiving area c ₂ of the side oil chamber C ₂ is set. The time of reduction of the hydraulic cylinder C, and the pressure of the pressure oil flowing into the reduction side oil chamber C ₂ of the hydraulic cylinder C, a pressure of the hydraulic fluid discharged from the extension-side oil chamber C ₁ of the hydraulic cylinder C is receiving the cylinder C since the area c ₂ is the pressure receiving area c ₂ by rods C ₃ surface integral of the hydraulic cylinder C is smaller than the pressure receiving area c _1, the pressure of the hydraulic fluid discharged from proportional to the ratio extension-side oil chamber C ₁ of the pressure receiving area Low.
[0020]
Therefore, the ratio of the pressure receiving area x of the reduction side spool chamber X in which the sub spool 121 slides and the pressure receiving area y of the expansion side spool chamber Y is reduced to the pressure receiving area c ₁ of the expansion side oil chamber C ₁ of the hydraulic cylinder C. If the same ratio as the area ratio of the pressure receiving area c ₂ side oil chamber C _2, when the load of the hydraulic cylinder C is zero, the extension-side oil chamber C _1, has a pressure generated in the reduction side oil chamber C ₂ and Also, the thrust generated on the sub spool 121 becomes zero.
[0021]
Next, the operation procedure of the counterbalance valve of the present invention will be described.
First, when the hydraulic cylinder extends, oil from the pump D passes through the switching control valve B and enters the supply port 111 on the extension side of the counterbalance valve 1. Then outflow from the sheet discharge port 113 of the extension-side press the check valve 115 and into the extension-side oil chamber C ₁ of the hydraulic cylinder C. Further together with the oil from the contraction side oil chamber C ₂ of the hydraulic cylinder C flows out, the reduction side of the supply and discharge port 114, supply ports 112, switching control valve B, the oil flows in the order of the tank E, the hydraulic cylinder C is extended .
[0022]
On the other hand, when the hydraulic cylinder is reduced, the oil from the pump D passes through the switching control valve B and enters the supply port 112 on the reduction side of the counterbalance valve 1. Then the pressure oil passes through the fixed throttle 117, press the main spool 116, to open the reverse flow path 111b, flows out of the supply and discharge port 114 of the reduction side at the same time, entering the reduction side oil chamber C ₂ of the hydraulic cylinder C. At the same time, it passes through the reduction side branch flow path GG ′ and enters the reduction side spool chamber X of the sub spool 121 via the fixed throttle W. At this time, pressure oil extension-side oil chamber C ₁ of the hydraulic cylinder C is branched from the expansion side branch channel H-H 'from the sheet discharge port 113 of the extension side, passes through the fixed throttle T, sub-spool 121 It enters the extension side spool chamber Y.
[0023]
Here, the thrust generated by the pressure of the extension-side spool Y Entered extension-side oil chamber C _1, the thrust generated by the pressure of the reduction side spool chamber contraction side oil chamber C ₂ entering the X is a sub-spool 121 The sub-spools 121 are pressed against each other in opposite directions and move by pushing the spring 122 by an amount corresponding to the thrust of the extension-side spool Y exceeding the thrust of the reduction-side spool chamber X, and the apertures of the apertures S ₁ and S ₂ are determined. . Then, the oil passes through the throttles S ₁ and S ₂ of the determined sub spool 121 and returns in the order of the return side branch flow path II ′, the main spool 116, the supply port 111 on the extension side, the switching control valve B, and the tank E. flow, rod C ₃ of the hydraulic cylinder C is reduced.
[0024]
【The invention's effect】
As described above, the counterbalance valve of the present invention can change the reduction speed by changing the throttle opening of the variable throttle valve when the hydraulic cylinder is reduced. Therefore, even when abrupt operation is performed in a state where the load acting upon reduction of the hydraulic cylinder is large, the reduction operation can be performed at a safe operation speed at which the crane does not become unstable. In addition, when the load acting when the hydraulic cylinder is reduced is small, the operating speed does not become too slow, and the operation does not feel stress. Therefore, the working efficiency is good and the temperature of the hydraulic oil is hard to rise.
[Brief description of the drawings]
FIG. 1 is a right side view of a counterbalance valve according to an embodiment of the present invention.
FIG. 2 is a sectional view taken along line II of FIG. 1;
FIG. 3 is a sectional view taken along line II-II of FIG.
FIG. 4 is a hydraulic circuit diagram of a hydraulic cylinder for raising and lowering a boom of a crane provided with a counterbalance according to the present invention.
FIG. 5 is a sectional view of a conventional counterbalance valve.
FIG. 6 is a hydraulic circuit diagram of a hydraulic cylinder for raising and lowering a boom of a crane provided with a conventional counterbalance valve.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 counter balance valve 11 valve body 111 extension-side supply port 112 contraction-side supply port 113 extension-side supply / discharge port 114 contraction-side supply / discharge port 115 check valve 116 main spool 117 fixed throttle 111a forward flow path 111b reverse flow path 121 Sub spool 122 Spring 123 Spring housing 123a Box 123b Box X Reduction side spool chamber Y Extension side spool chamber W Fixed throttle T Fixed throttle S ₁ Variable throttle S ₂ Variable throttle GG ′ Reduction side branch flow path HH 'Extension side branch flow path II' Return side branch flow path

Claims (4)

The supply port on the extension side and the supply port on the reduction side connected to the supply side of the hydraulic oil, and the supply and discharge ports on the extension side connected to the extension side oil chamber and the reduction side oil chamber of the hydraulic cylinder, respectively, A check valve is provided within a valve body provided with a supply / discharge port in a forward flow path communicating the supply port on the extension side and the supply / discharge port on the extension side, and the supply port on the extension side and the supply port on the extension side are provided. A counterbalance valve provided with a main spool in a reverse flow path between the discharge ports,
A counterbalance valve, wherein a variable throttle valve for reducing a flow rate discharged from an extension-side oil chamber of the hydraulic cylinder according to a load acting on the hydraulic cylinder at the time of contraction is provided in a reverse flow path. The variable throttle valve has a sub-spool, and at both ends of the sub-spool, an expansion-side spool chamber connected to a pilot oil path from an expansion-side supply / discharge port, and a pilot oil path from a reduction-side supply port. The sub-spool is moved by the thrust difference generated between the reduction side spool chamber and the expansion side spool chamber of the variable throttle valve when pilot pressure is generated, and the variable spool valve is connected to the variable throttle valve. 2. The counterbalance valve according to claim 1, wherein the throttle opening is changed. The pressure receiving area ratio between the reduction side spool chamber and the expansion side spool chamber of the variable throttle valve is equal to the pressure receiving area ratio between the expansion side oil chamber and the reduction side oil chamber of the hydraulic cylinder. 3. The counterbalance valve according to 2. The counterbalance valve according to claim 1, wherein the variable throttle valve is provided with adjusting means for adjusting an initial value of the operating pressure of the sub-spool.

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