JP3928786B2 - Counter balance valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a counterbalance valve provided in a hydraulic cylinder for expansion and contraction of 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, the conventional counterbalance valve A includes an expansion side supply port A1 and a reduction side supply port A2 connected to the switching control valve B side, a hydraulic cylinder, and a valve body A0. 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 forward flow path A9 that communicates with the exhaust port A3, and a spool A6 is provided in the reverse flow path that communicates between the extended supply port A1 and the extended supply / discharge port A3. Is provided so as to be slidable in the left-right direction, and an orifice A7 is provided on the front end 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, the hydraulic oil enters from the hydraulic pump via the switching control valve B into the supply port A1 on the extension side, and the check valve A5 is pushed to the left to move. The hydraulic oil flows into the extension side oil chamber C ₁ of the hydraulic cylinder C via the extension side supply / discharge port A 3, and the oil in the reduction side oil chamber C ₂ flows into the reduction side supply / discharge port A 4 and the reduction side oil chamber C ₁ . 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 is reduced, the hydraulic oil passes from the hydraulic pump through the switching control valve B and flows into the supply port A2 on the reduction side, and passes through the orifice A7 and pushes the spool A6 to move rightward. As a result, the return-side channel A10 is opened. At the same time, the hydraulic oil flows into the reduction-side oil chamber C ₂ of the hydraulic cylinder C via the reduction-side supply / discharge port A4. At the same time, the pressure oil in the extension-side oil chamber C ₁ passes through the extension-side supply / discharge port A3, fixed throttle A8, return-side flow path A10, extension-side supply port A1, and switching control valve B to the tank E in sequence. with flowing, rod C ₃ of the hydraulic cylinder is reduced. In this case, the flow rate of the pressure oil from the extension side oil chamber C ₁ is limited by the opening degree of the fixed throttle A8, so that the reduction speed of the rod C ₃ is slowed down.
[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 It will be the same.
For this reason, in the case of heavy boom lifting or work with a long boom with a large lifting moment, the speed is as fast as when the load is small, despite the fact that the load acting on the hydraulic cylinder is large. It is possible to perform a reduction operation of the hydraulic cylinder at a speed. If the operator performs an operation suddenly accidentally, the reduction speed of the hydraulic cylinder C is too high, causing a load swing, making the crane unstable and falling over. Therefore, it was necessary to operate at a safe speed according to the will of the operator.
[0006]
In addition, if the throttle opening is determined so that the crane does not become unstable even if a sudden sudden operation is performed with a large load acting on the hydraulic cylinder, it will act on the hydraulic cylinder. When the load to be applied is small, the reduction speed becomes too slow, the operation feels stressed, the working efficiency is deteriorated, and the pressure oil temperature is likely to rise.
[0007]
Therefore, the present invention solves such a problem in the counter balance valve, and an object of the present invention is to provide a counter balance valve capable of changing the reduction speed in accordance with the load acting on the hydraulic cylinder. To do.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, a counterbalance valve according to the present invention includes an extension-side supply port, a reduction-side supply port connected to a hydraulic oil supply side, and an extension-side oil chamber and a reduction-side oil chamber of a hydraulic cylinder. In the valve body provided with the expansion side supply / exhaust port and the reduction side supply / exhaust port respectively connected to each other, the reverse side is in the forward flow path that connects the expansion side supply port and the expansion side supply / exhaust port. A counter balance valve provided with a stop valve and having a main spool in a reverse flow path between the extension-side supply port and the extension-side supply / exhaust port, wherein the hydraulic pressure depends on the load acting on the hydraulic cylinder at the time of reduction A variable throttle valve is provided in the reverse flow path to reduce the flow rate discharged from the extension side oil chamber of the cylinder, and the variable throttle valve has a sub spool, and both ends of the sub spool are connected to the extension side supply / discharge ports. In contact with the pilot oil passage An expansion side spool chamber and a reduction side spool chamber connected to a pilot oil passage from the reduction side supply port, and when a pilot pressure is generated, the reduction side spool chamber and the extension side spool chamber of the variable throttle valve The sub-spool is moved and the throttle opening of the variable throttle valve is changed in accordance with the thrust difference generated in step 1. The pressure-receiving area ratio between the reduction-side spool chamber and the extension-side spool chamber of the variable throttle valve is determined by the hydraulic cylinder. The pressure-receiving area ratio of the reduction-side oil chamber and the expansion-side oil chamber is the same .
[0011]
The counter balance valve of the present invention is provided with a variable throttle valve that reduces the flow rate discharged from the extension side oil chamber of the hydraulic cylinder as the load acting on the hydraulic cylinder increases during reduction, thereby reducing the reduction speed of the hydraulic cylinder. Can be changed. Therefore, when the load acting on the hydraulic cylinder is large, the boom can be operated at a slow and safe reduction speed, and when the load acting on the hydraulic cylinder is small, the boom can be operated efficiently at a high reduction speed. It can be performed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
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 the counterbalance valve of FIG. 1, and FIG. 3 is a line II-II of FIG. FIG. 4 is a hydraulic circuit diagram of a crane boom raising and lowering hydraulic cylinder provided with a counterbalance.
[0013]
As shown in FIG. 4, a switching control valve B is connected to the 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 expansion / contraction operation of the boom hoisting hydraulic cylinder C as a hydraulic actuator by switching the operation lever. That is, the switching control valve B is a four-port three-position switching control valve that can be selected by manual operation and can be returned to the neutral position by a spring. When the switching control valve B is in the neutral position, the hydraulic pump D The 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 includes an extension side supply port 111 connected to the hydraulic oil supply side (switching control valve B side), a reduction side supply port 112, and a hydraulic pressure. An extension-side supply / discharge port 113 and a reduction-side supply / discharge port 114 connected to the extension-side oil chamber C ₁ and the reduction-side oil chamber C ₂ of the cylinder C are provided. In the valve body 11, a check valve 115 is fitted in a forward flow path 111a that communicates the extension-side supply port 111 and the extension-side supply / discharge port 113, and the extension-side supply port 111 is inserted. The main spool 116 is fitted in the reverse flow path 111b between the extension side supply / discharge port 113 and slidable in the axial direction.
[0015]
The check valve 115 allows a flow from the supply port 111 on the extension side to the supply / discharge port 113 on the extension side and blocks inflow oil from the supply / discharge port 113 on the extension side. The inflow path from the reduced-side supply / discharge port 112 branches, one flows out to the reduced-side supply / discharge port 114, and the other communicates with the internal pilot oil path 112 a that switches 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 counter balance valve 1 includes a sub-spool 121 fitted in the valve body in parallel with the main spool 116 and the both ends of the sub-spool 121 separated from each other. The reduction-side spool chamber X and the expansion-side spool chamber Y that are arranged in this manner constitute a main part. 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. Via a fixed throttle T and an internal pilot oil passage Z, it is connected to a pilot oil passage (hereinafter referred to as an extension-side branch passage HH ′) from the extension-side supply / discharge port 113. 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 are adapted to throttle the flow rate of the pressure oil while the sub spool 121 moves to the left. Further, the notch β serves as a stopper for the leftward movement of the sub spool 121. Furthermore, 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 123a having a female screw on the inside and a box body 123b having a male screw on the outside. 123 is attached. Since the compression amount of the spring 122 changes according to the tightening condition of the box 123b, 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 configuration as described above, 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 when the boom hoisting hydraulic cylinder C is reduced is reduced. Create big and small. This pressure difference acts on the spring 122 that urges the sub spool 121 in the right direction, and becomes a thrust for moving the sub spool 121 in the left direction. This thrust determines the throttle opening of the variable throttles S ₁ and S ₂ . That is, as the load applied to the boom raising and lowering hydraulic cylinder C increases, the sub spool 121 moves to the left and the variable throttles S ₁ and S ₂ are throttled to slow down the reduction speed. Finally, the pressure oil outflow from the internal pilot oil passage Z is prevented by the notch β of the sub spool 121.
[0019]
Further, in the present embodiment, the pressure receiving area x on the reduction side spool chamber X, the area ratio of the pressure receiving area y extension side spool chamber Y is of the hydraulic cylinder C on the reduction side oil chamber C ₂ and the pressure receiving area c ₂ extension The ratio x / y = c ₂ / c ₁ is the same as the pressure receiving area c ₁ of the side oil chamber C ₁ . When the hydraulic cylinder C is reduced, the pressure of the pressure oil flowing into the reduction side oil chamber C ₂ of the hydraulic cylinder C and the pressure oil discharged from the extension side oil chamber C _{1 of the} hydraulic cylinder C are since the area c ₂ rod C ₃ by the area fraction receiving surface product of the hydraulic cylinder C is smaller than the pressure receiving area c _1, the pressure of the hydraulic fluid discharged from the expansion side oil chamber C1 in proportion to the ratio of the pressure receiving areas is low.
[0020]
Therefore, a pressure receiving area x on the reduction side spool chamber X by sliding the sub-spool 121, the ratio of the pressure receiving area y extension side spool chamber Y includes a pressure receiving area c ₂ on the reduction side oil chamber C ₂ of the hydraulic cylinder C extension If the same ratio as the area ratio of the pressure receiving area c ₁ of the side oil chamber C _1, 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 However, the thrust generated in the sub spool 121 becomes zero.
[0021]
Next, the operation procedure of the counter balance valve of the present invention will be described.
First, when the hydraulic cylinder extends, the oil from the pump D passes through the switching control valve B and enters the supply port 111 on the extension side of the counter balance valve 1. Next, the check valve 115 is pushed to flow out from the supply / discharge port 113 on the extension side, and enters 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, in the case of hydraulic cylinder reduction, oil from the pump D passes through the switching control valve B and enters the supply port 112 on the reduction side of the counter balance 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, the pressure oil in the extension side oil chamber C ₁ of the hydraulic cylinder C is branched from the extension side supply / discharge port 113 through the extension side branch flow path HH ′, passes through the fixed throttle T, Enters the expansion side spool chamber Y.
[0023]
Here, the thrust generated by the pressure of the extension side oil chamber C ₁ entering the extension side spool Y and the thrust generated by the pressure of the reduction side oil chamber C ₂ entering the reduction side spool chamber X cause the sub spool 121 to move. The sub-spool 121 pushes the spring 122 and moves by the amount that the thrust of the extension side spool Y exceeds the thrust of the reduction side spool chamber X by pushing in opposite directions, and the throttle openings of the throttles 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 to the return side branch flow path II ′, the main spool 116, the extension side supply port 111, the switching control valve B, and the tank E in this order. flow, rod C ₃ of the hydraulic cylinder C is reduced.
[0024]
【The invention's effect】
As described above, the counter balance 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 an abrupt operation is performed in a state where the load acting when the hydraulic cylinder is reduced, the crane can be reduced at a safe operating 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 is not stressed, so that the working efficiency is good and the temperature of the pressure oil is hardly increased.
[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 cross-sectional view taken along the line II of FIG.
3 is a cross-sectional view taken along line II-II in FIG.
FIG. 4 is a hydraulic circuit diagram of a hydraulic cylinder for lifting a boom of a crane provided with a counterbalance according to the present invention.
FIG. 5 is a sectional view of a conventional counter balance valve.
FIG. 6 is a hydraulic circuit diagram of a crane boom raising and lowering hydraulic cylinder provided with a conventional counterbalance valve.
[Explanation of symbols]
1 Counterbalance valve 11 Valve body 111 Expansion side supply port 112 Reduction side supply port 113 Extension side supply / discharge port 114 Reduction 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 H-H 'Extension side branch flow path II' Return side branch flow path

Claims (1)

Extension side supply port connected to hydraulic oil supply side, reduction side supply port, extension side supply / discharge port connected to extension side oil chamber and reduction side oil chamber of the hydraulic cylinder, reduction side supply port A check valve is provided in a forward flow path that connects the extension-side supply port and the extension-side supply / discharge port in the valve body in which the supply-discharge port is provided, and the extension-side supply port and the extension-side supply port are connected. A counter balance valve in which a main spool is provided in a reverse flow path between exhaust ports,
According to the load acting on the hydraulic cylinder at the time of reduction, a variable throttle valve for reducing the flow rate discharged from the extension side oil chamber of the hydraulic cylinder is provided in the reverse flow path ,
The variable throttle valve has a sub-spool, and at both ends of the sub-spool, an extension-side spool chamber connected to a pilot oil passage from an extension-side supply / discharge port, and a pilot oil passage from a reduction-side supply port When the pilot pressure is generated, the sub spool is moved by the thrust difference generated between the reduction side spool chamber and the extension side spool chamber of the variable throttle valve, and the variable throttle valve It is a configuration that changes the throttle opening,
A counter balance valve characterized in that the pressure receiving area ratio between the reduction side spool chamber and the extension side spool chamber of the variable throttle valve is the same as the pressure receiving area ratio between the reduction side oil chamber and the extension side oil chamber of the hydraulic cylinder .

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