JP2003301803A - Fluid pressure circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid pressure circuit capable of easily preventing or eliminating a fault in reduction of signal pressure by a leak. <P>SOLUTION: In load pressure signal passages 23a and 23b in a load sensing circuit 30 to feed back load pressure signals of actuators 13 and 14 to a variable displacement pump 11, shut-off valves 41 and 42 to disconnect the load pressure signal passages 23a and 23b by detecting the leak quantity of a prescribed value or more are provided. The shut-off valves 41 and 42 are provided for compensator valves 21 and 22 for regulating an opening area by differential pressure between pump pressure and actuator load pressure. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid pressure circuit having a shutoff valve.

[0002]

2. Description of the Related Art Conventional hydraulic circuits such as hydraulic excavators are
As shown in FIG. 3, between the discharge line 12 of the variable displacement pump 11 and the actuators 13 and 14, the main spools 16 and 17 of the control valve 15 and the pump pressure and the actuator load pressure are provided. Compensator valves 21 and 22 whose opening area is adjusted by differential pressure are provided, and the maximum load pressure of actuators 13 and 14 taken out via shuttle valve 20 and the like is used as a load pressure signal for pump flow rate control and a variable capacity. A load pressure signal passage 23 leading to the capacity varying means 11a of the die pump 11 is provided.

The discharge line 12 of the variable displacement pump 11
Is provided so as to be able to communicate with the tank 25 via the differential pressure relief valve 24, and the load pressure signal passage 23 of the actuators 13 and 14 is guided to the external pilot pressure acting portion of the differential pressure relief valve 24.

A load sensing circuit that uses the maximum load pressure of the system as a load pressure signal for controlling the pump flow rate is used to measure the pump pressure discharged from the variable displacement pump 11 and the maximum load pressure of the actuators 13 and 14. The differential pressure is
The variable pressure pump 11 is controlled to have a constant pressure set by the variable volume means 11a.

FIG. 4 shows the structure of the compensator valves 21 and 22. A plurality of holes 32 are formed in a part of the valve body 31 of the control valve 15, and each of the holes 32 has a cylindrical movable valve body.
33 is slidably fitted.

A passage 34 from the main spools 16 and 17 is communicated with the lower side of the movable valve bodies 33, and a spring chamber 35 is provided on the upper side of each movable valve body 33.
These spring chambers 35 have compensator valves 21, 22
A spring 36 for urging the load pressure signal passage 23 is provided, and the load pressure signal passage 23 is communicated via an orifice 37.

A number of holes 38 for controlling the flow rate are formed below the partition wall portion 33a provided in the middle portion of the compensator valves 21 and 22, so that the compensator valves 21 and 22 can be moved upward. Thus, the opening area that connects the passage 34 from the main spools 16 and 17 and the chamber 39 to the actuators 13 and 14 via these holes 38 changes.

As described above, the load pressure signal acts on the compensator valves 21 and 22 from the upper side, and the pump pressure can act from the lower side via the main spools 16 and 17.

One compensator valve 21, 22 is prepared for each actuator, and the compensator valve 21, 22 corresponding to the actuator being operated is provided.
The pump pressure is applied to the lower side of 22, but the pump pressure is not applied to the lower side of the compensator valves 21 and 22 corresponding to the inactive actuators.

For example, as shown in FIG. 3, one actuator 13 is operating and the other actuator 13 is operating.
Compensator valve 21 corresponding to actuator 13 that is operating when 14 is in the main spool state that is not operating
In Fig. 4, high voltage is introduced above and below the
Due to the small pressure difference between the upper and lower parts, this compensator valve 21
The amount of leakage from the clearance between the sliding surfaces of the movable valve body 33 and the valve body 31 is very small.

[0011]

However, in the compensator valve 22 corresponding to the actuator 14 which is not operating as shown in FIG. 3, the pump pressure is not guided to the lower side in FIG. On the other hand, since the load pressure from the load pressure signal passage 23 is guided to the upper side and the differential pressure between the upper and lower parts is large, the movable valve element 33 of the compensator valve 22 and the valve are connected from the load pressure signal passage 23. The leak amount that leaks through the clearance between the sliding surface with the main body 31 increases, and the load pressure signal decreases due to the leak.

Further, even if the clearance between the movable valve body 33 of the compensator valves 21 and 22 and the valve body 31 is small at the time of a new vehicle, it may increase due to wear due to long-term operation, and the load pressure signal may be reduced due to leakage. is there.

As described above, the load sensing circuit uses the maximum load pressure of the system as a load pressure signal for controlling the pump flow rate. When the load pressure signal causes a pressure drop due to leakage, the variable displacement pump is used. 11 capacity changing means
There is also a problem that the pump pressure set by 11a will also drop, resulting in poor performance.

Originally, even if the wear is within the normal range, if the user desires to use the machine further, the control valve 15 is conventionally entirely replaced, but the control valve 15 is replaced. Causes machine down due to the great cost and replacement time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a fluid pressure circuit capable of easily preventing or eliminating the problem that the signal pressure is lowered due to a leak.

[0016]

According to a first aspect of the present invention, there is provided a signal pressure circuit for transmitting a signal pressure through a signal pressure passage, and a signal leak amount provided in the signal pressure passage for detecting a signal leak amount above a certain level. A fluid pressure circuit having a shut-off valve that shuts off the signal pressure passage.By providing a shut-off valve that shuts off the signal pressure passage by detecting a signal leak amount above a certain level in the signal pressure passage. The problem that the pressure drops can be easily prevented or eliminated.

According to a second aspect of the present invention, a load sensing circuit that feeds back a load pressure signal of an actuator to a variable displacement pump, and a leak amount above a certain level provided in a load pressure signal passage of the load sensing circuit are detected. And a shutoff valve for shutting off the load pressure signal passage, and a shutoff valve for shutting off the load pressure signal passage for a certain amount or more of leakage in the load pressure signal passage of the load sensing circuit. By providing it, it is possible to easily prevent problems due to a drop in the load pressure signal of the load sensing circuit due to leakage, or to recover at low cost and in a short time. Can also handle.

According to a third aspect of the present invention, in the fluid pressure circuit according to the second aspect, a plurality of compensator valves whose opening area is adjusted by the differential pressure between the pump pressure and the load pressure of the actuator are provided, and the shutoff valve is provided. Is provided for the leaking compensator valve, and a shutoff valve can be provided only for the leaking compensator valve to take measures against a drop in the load pressure signal due to abrasion of the compensator valve. .

According to a fourth aspect of the present invention, a plurality of compensator valves in the fluid pressure circuit according to the third aspect have a valve body common to the control valve, and a plurality of holes formed in one surface of the valve body. And a plurality of movable valve bodies slidably fitted in these holes, and a cover body provided on the surface of the valve body in which the plurality of holes are opened and closing each hole, and a plurality of cutoffs. The valve is provided on the cover body of multiple compensator valves, and the valve body of the compensator valve is the same as the valve body of the control valve, but at least the cover body is detached to shut off this cover body. It is possible to easily install additional valves, and it is possible to take countermeasures against malfunctions without replacing the control valve or making major modifications as in the past.

According to a fifth aspect of the invention, in the fluid pressure circuit according to the fourth aspect, a plug having a shut-off valve built therein and screwed to the cover body, and a plug screwed to the cover body without incorporating the shut-off valve. It is equipped with a dummy plug that has been installed. By disconnecting the plug, the shut-off valve can be easily installed and removed, and for actuators that do not cause malfunctions, use a dummy plug that does not have a built-in shut-off valve to reduce costs. Can be achieved. Further, it is possible to deal with an increase in the leak amount by replacing the minimum necessary parts.

According to a sixth aspect of the present invention, the shutoff valve in the fluid pressure circuit according to any one of the first to fifth aspects is a valve seat body and a check valve that is opposed to the valve seat body so as to be separable from the valve seat body. A valve body, an orifice provided in the check valve body, and a spring for urging the check valve body in a direction against a pressure difference generated by a flow rate through the orifice, and the shutoff valve is Since the valve seat body, the check valve body having the orifice, and the spring have a simple structure, the valve seat body can be installed in a limited space and the interference with the pipes arranged in the periphery can be prevented.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to the embodiment shown in FIGS.

FIG. 1 shows a fluid pressure circuit used in a hydraulic circuit such as a hydraulic excavator. Between a discharge line 12 of a variable displacement pump 11 and a plurality of actuators 13 and 14,
A control valve 15 is installed.

The control valve 15 includes a plurality of main spools 16 and 17, and a compensator valve 2 whose opening area is adjusted by the pressure difference between the pump pressure and the actuator load pressure.
1, 22 and are provided.

Further, the maximum load pressure of the actuators 13 and 14 taken out via the shuttle valve 20 and the like is guided to the displacement varying means 11a of the variable displacement pump 11 as a load pressure signal as a signal pressure for controlling the pump flow rate. A load pressure signal passage 23 is provided as a signal pressure passage.

The discharge line 12 of the variable displacement pump 11
Is provided so as to be able to communicate with the tank 25 via the differential pressure relief valve 24, and the load pressure signal passage 23 is guided to the external pilot pressure acting portion of the differential pressure relief valve 24.

As described above, in order to use the maximum load pressure of the hydraulic system as a load pressure signal for controlling the pump flow rate, a signal pressure circuit for feeding back the load pressure signals of the actuators 13 and 14 to the variable displacement pump 11 is used. Load sensing circuit 30 is configured, and by the load sensing circuit 30, the differential pressure between the pump pressure discharged from the variable displacement pump 11 and the maximum load pressure of the actuators 13 and 14 is
The variable pressure pump 11 is controlled to have a constant pressure set by the variable volume means 11a.

FIG. 2 shows the structure of the compensator valves 21 and 22. A plurality of holes 32 formed in a part of the valve body 31 common to the control valve 15 are opened in one surface of the valve body 31. A cylindrical movable valve element 33 is slidably fitted in each of the holes 32.

The passages 34 from the main spools 16 and 17 are connected to the lower sides of the compensator valves 21 and 22, and the spring chambers 35 are provided above the compensator valves 21 and 22, respectively. A spring 36 for urging the compensator valves 21, 22 downward is provided in these spring chambers 35.

A partition wall 33a is provided in the middle of the compensator valves 21 and 22, and a number of flow control holes 38 are formed below the partition wall 33a.
Depending on the amount of upward movement of 22, the passage 34 from the main spools 16 and 17 through these holes 38 and the actuators 13 and
The opening area communicating with the chamber 39 to 14 changes.

Further, as shown in FIG. 1, a leak amount above a certain level is detected in the load pressure signal passages 23a and 23b as signal pressure passages for the compensator valves 21 and 22 of the actuators 13 and 14, respectively. Shut-off valves 41 and 42 for shutting off the load pressure signal passages 23a and 23b are provided, respectively.

These shut-off valves 41, 42 are provided for the compensator valves 21, 22 that have leaked, and need not necessarily be provided for new compensator valves that do not leak.

As shown in FIG. 2, the holes 32 of the compensator valves 21, 22 are formed in the surface of the valve body 31 in which the holes 32 are formed.
A cover body 43 for closing the above is integrally provided via a seal member 44, and the cover body 43 is provided with respective shutoff valves 41, 42.

That is, the plug 45 is screwed to the cover body 43, the seal members 46 and 47 are fitted to the plug 45, and the load pressure signal passage 48 in the radial direction communicating the load pressure signal passage 23 with the plug 45. And axial load pressure signal passages 23a and 23b which communicate the load pressure signal passage 48 with the shutoff valves 41 and 42,
Shut-off valves 41 and 42 are built in below the plug 45. The upper end of the spring 36 is locked by a spring receiving body 49 fitted to the cover body 43.

In the shut-off valves 41, 42, a check valve body 51 is slidably fitted in a mounting hole formed in the axial direction from the lower surface of the plug 45, and a small diameter portion below the check valve body 51. A coil-shaped spring 53 is fitted in 52, and a valve seat body 54 is screwed into a screw hole opened at the lower end of the plug 45 via a seal member 55, and the spring compressed by the valve seat body 54. By 53, a preset load in the direction of separating from the valve seat body 54 is applied to the check valve body 51 that is opposed to the valve seat body 54 so as to be able to come into contact with and separate from (movably move up and down).

As described above, the check valve body 51 is provided with the spring 53 provided in a compressed state between the check valve body 51 and the valve seat body 54.
While being urged in an upward direction away from 54,
Since the orifice 56 is provided in the check valve body 51,
Due to the flow rate through the orifice 56, a downward pressure difference is generated between the upper side and the lower side of the check valve body 51. spring
53 urges the check valve body 51 in an upward direction against the direction in which this differential pressure acts.

In the check valve body 51, an axial through hole 57 is formed above the orifice 56, and a radial through hole 58 is formed below the orifice 56, and a small diameter portion of the check valve body 51 is formed. A spring chamber 59 is formed around 52, a through hole 60 is formed in the valve seat 54, and a load pressure signal passage is formed by these through hole 57, orifice 56, through hole 58, spring chamber 59 and through hole 60. Has been done.

Further, for compensator valves (not shown) in which leakage due to wear does not occur, shutoff valves 41, 42 are provided.
The dummy plug (not shown) that does not have a built-in
Is screwed to.

This dummy plug has the same outer shape as the plug 45, but instead of the shut-off valves 41 and 42, a fixed orifice (not shown) is provided inside.

Next, the function and effect of this embodiment will be described.

As shown in FIG. 1, one of the main spools 16 is pilot-operated to operate one of the actuators.
When 13 is activated, the corresponding compensator valve
Pump pressure is applied to the main spool 16 side of 21 and load pressure is applied to the actuator 13 side.

In the compensator valve 21 corresponding to the actuator 13 in operation as described above, high pressure is introduced to the upper side and the lower side of the movable valve body 33 in FIG. 2, and the differential pressure between the upper and lower parts is small. Even if the clearance between the sliding surface of the movable valve body 33 of the compensator valve 21 and the valve body 31 becomes large due to wear, the amount of leak generated in this clearance is very small.

On the other hand, as shown in FIG. 1, when the other main spool 17 is in the neutral position and the other actuator 14 is stopped, the corresponding compensator valve 22 is placed on the main spool 17 side. Is not applied with a pump pressure, but a load pressure such as a load is applied to the actuator 14 side.

The actuator 14 in such a deactivated state
The pump pressure is not guided to the lower side of the movable valve element 33 in FIG. 2 and drains to the compensator valve 22 corresponding to the load pressure signal on the upper side of the movable valve element 33. The load pressure due to the load applied to the actuator 14 is guided from the passage 23 through the load pressure signal passage formed by the through hole 57, the orifice 56, the through hole 58, the spring chamber 59 and the through hole 60, and the movable valve body When the clearance between the movable valve body 33 of the compensator valve 22 and the valve body 31 becomes large due to wear or the like because the differential pressure between the upper and lower portions of the 33 is large, the check valve body 51, etc. Load pressure signal path,
And, a flow rate that leaks through the clearance of the compensator valve 22 is generated.

Since the check valve body 51 is provided with the orifice 56, depending on the flow rate of the oil flowing through the orifice 56, the check valve body 51 faces downward between the upper side and the lower side of the orifice 56. A differential pressure acting in the direction is generated.

Due to this pressure difference, the check valve body 51 moves downward against the spring 53, and is brought into close contact with the valve seat body 54 so that the through hole is formed.
Close 60.

Therefore, the amount of leak through the clearance of the compensator valve 22 can be suppressed to a minimum, the drop of the load pressure signal in the load pressure signal passage 23 due to the leak can be prevented, and the function of the load sensing circuit 30 can be normally operated. Can be maintained.

The load sensing circuit 30 can variably control the pump discharge flow rate by the pump flow rate control signal sent to the displacement varying means 11a of the variable displacement pump 11 via the load pressure signal passage 23, and the differential pressure relief valve 24 can be controlled. By the pressure setting signal sent, the pump pressure discharged from the variable displacement pump 11 can be controlled to be higher than the load pressure by a constant pressure.

As described above, in the load pressure signal passages 23a and 23b of the load sensing circuit 30, the shut-off valves 41, which inline detect a leak amount above a certain level and shut off these load pressure signal passages 23a and 23b. By providing 42, it is possible to prevent a decrease in the load pressure signal of the load sensing circuit 30 due to a leak, and it is possible to recover a defect due to a decrease in the load pressure signal at low cost and in a short time.

In particular, a compensator valve that has leaked
If necessary, shut-off valves 41 and 42 are provided only on 21 and 22, and measures can be taken promptly against a drop in the load pressure signal due to wear of the compensator valves 21 and 22. We can also respond when it occurs.

At this time, by processing the cover body 43 of the compensator valves 21 and 22 and adding the shutoff valves 41 and 42, or by mounting the plug 45 on the cover body 43,
The shutoff valves 41, 42 can be easily added to the compensator valves 21, 22, and trouble countermeasures can be taken without replacement or major modification of the control valve 15 as in the related art.

That is, even if the clearance between the sliding surfaces of the movable valve bodies 33 of the compensator valves 21 and 22 and the valve body 31 is increased due to wear, some users still want to use the machine body. It is not necessary to replace the entire valve 15, and at least only the cover body 43 may be detached and the shutoff valves 41 and 42 may be additionally installed in the cover body 43.

Alternatively, when the cover body 43 is fitted with a dummy plug (not shown) having the same shape as the plug 45 but not including the shut-off valves 41 and 42, the cover body 43
The inexpensive shut-off valves 41, 42 can be easily attached only by removing the mounted dummy plug and screwing the plug 45 having the shut-off valves 41, 42 into the cover body 43. .

In other words, before the clearance between the sliding surfaces of the movable valve bodies 33 of the compensator valves 21 and 22 and the valve body 31 increases due to wear, that is, for the actuator in which no malfunction occurs, the shutoff valve 41 Cost reduction can be achieved by using a dummy plug that does not have the built-in capacitors 42 and 42. Further, it is possible to deal with an increase in the leak amount by replacing the minimum necessary parts.

As described above, compared with the case where the control valve 15 is replaced, the cost can be reduced, the replacement time can be shortened, and the decrease in the operating rate of the construction machine can be minimized.

Further, since the shutoff valves 41, 42 have a simple structure composed of the valve seat body 54, the check valve body 51 having the orifice 56, and the spring 53, they are almost the same as the conventional control valve. It can be installed in a space, and it can also prevent interference with pipes and the like arranged around it.

As described above, the movable valve element 33 of the compensator valve 21 and the valve body are replaced without replacing the control valve 15.
It is possible to easily install the shutoff valves 41 and 42 that cut the load pressure signals on the compensator valves 21 and 22 only when the amount of leakage increases due to the abrasion of the sliding surface with 31. It is possible to prevent problems that occur when the amount becomes large, or it is possible to solve the problems that occur when the amount of leakage becomes large by replacing the minimum necessary number of parts, and it is possible to recover at low cost and in a short time.

The fluid pressure circuit can be applied to another signal pressure circuit other than the load sensing circuit 30, and the shut-off valve 41 is provided in the signal pressure passage where there is a risk of leakage or in the signal pressure passage where leakage has occurred. , 42, it is possible to detect a signal leak amount above a certain level and shut off the signal pressure passage.

[0059]

According to the first aspect of the present invention, by providing a shutoff valve in the signal pressure passage for detecting a signal leak amount above a certain level and shutting off the signal pressure passage, the signal pressure is reduced by the leak. It is possible to easily prevent or eliminate problems that occur.

According to the second aspect of the present invention, the load pressure signal passage of the load sensing circuit is provided with a shut-off valve that shuts off the load pressure signal passage for a certain amount of leakage or more. Problems due to a decrease in the load pressure signal of the circuit can be easily prevented or can be recovered at a low cost in a short time, and such a problem can be dealt with in the field.

According to the third aspect of the present invention, the shutoff valve is provided only in the compensator valve that has leaked, and it is possible to take measures against the drop in the load pressure signal due to wear of the compensator valve.

According to the invention described in claim 4, the valve body of the compensator valve is common to the valve body of the control valve, but at least the cover body is detached, so that the shut-off valve can be easily added to the cover body. It can be installed without changing the control valve or major modification as in the past.
It becomes possible to take countermeasures against defects.

According to the fifth aspect of the present invention, the shut-off valve can be easily attached / detached by detaching / attaching the plug, and for the actuator in which no malfunction occurs, the dummy plug having no built-in shut-off valve is used, and the cost is reduced. Can be reduced. Further, it is possible to deal with an increase in the leak amount by replacing the minimum necessary parts.

According to the invention described in claim 6, the shutoff valve is
Since the valve seat body, the check valve body having the orifice, and the spring have a simple structure, the valve seat body can be installed in a limited space and the interference with the pipes arranged in the periphery can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a fluid pressure circuit according to the present invention.

FIG. 2 is a sectional view of a compensator valve in which a shutoff valve in the same circuit is incorporated.

FIG. 3 is a circuit diagram showing a conventional fluid pressure circuit.

FIG. 4 is a sectional view of a conventional compensator valve.

[Explanation of symbols]

11 Variable displacement pump 13, 14 Actuator 15 Control valve 21, 22 Compensator valve 23, 23a, 23b Load pressure signal passage as signal pressure passage 30 Load sensing circuit as signal pressure circuit 31 valve body 32 holes 33 Movable valve body 41, 42 Shut-off valve 43 cover body 45 plug 51 Check valve body 53 spring 54 valve seat 56 orifice

Continued front page    F-term (reference) 2D003 AA01 AB05 BB02 CA02 DA03                       DB02                 3H082 AA02 AA18 BB01 BB26 CC02                       DA06 DA18 DA37 EE02                 3H089 AA27 BB16 BB17 CC01 CC11                       DA03 DB03 DB47 DB49 EE07                       EE14 EE16 GG02 JJ02

Claims (6)

[Claims] 1. A signal pressure circuit for transmitting a signal pressure through a signal pressure passage, and a shut-off valve provided in the signal pressure passage for shutting off the signal pressure passage by detecting a signal leak amount above a certain level. Characteristic fluid pressure circuit. 2. A load sensing circuit for feeding back a load pressure signal of an actuator to a variable displacement pump, and a load pressure signal passage of the load sensing circuit, which detects a leak amount above a certain level and shuts off the load pressure signal passage. And a shut-off valve for controlling the fluid pressure circuit. 3. A compensator valve, the opening area of which is adjusted by a pressure difference between a pump pressure and a load pressure of an actuator, the shutoff valve being provided for the leaked compensator valve. The fluid pressure circuit according to claim 2. 4. A plurality of compensator valves comprises a valve body common to a control valve, a plurality of holes opened in one surface of the valve body, and a plurality of slidably fitted in these holes. A movable valve body and a cover body that is provided on the surface of the valve main body in which a plurality of holes are opened and closes each hole, and the plurality of shutoff valves are provided in the cover bodies of the plurality of compensator valves. The fluid pressure circuit according to claim 3. 5. The plug according to claim 4, further comprising a plug having a shutoff valve built therein and screwed to the cover body, and a dummy plug screwed to the cover body without incorporating the shutoff valve. Fluid pressure circuit. 6. The shut-off valve is generated by a valve seat body, a check valve body facing the valve seat body so as to freely come into contact with and away from the valve seat body, an orifice provided in the check valve body, and a flow rate through the orifice. The fluid pressure circuit according to any one of claims 1 to 5, further comprising a spring that biases the check valve body in a direction against the differential pressure.