JP2003269409A - Valve device and fluid pressure circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve device which controls pressure-compensated flow rate only in a small flow rate area even when the variation of pressure is generated, and also to provide a fluid pressure circuit having improved fine operability of an actuator by using the valve device. <P>SOLUTION: This valve device V is provided with a main spool 2 displaceable in a body 1, and a flow rate is controlled corresponding to the displacement on the basis of the relative relationship with the body 1. A pressure compensating mechanism 19 is mounted in the main spool 2. The pressure compensating mechanism 19 controls the flow rate in accompany with the compensation of pressure in accordance with the displacement with respect to the displacement smaller than a constant displacement of the main spool 2. The flow rate of the return oil from a hydraulic cylinder 11 is controlled by the valve device V. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve device having a characteristic of a flow rate control characteristic and a fluid pressure circuit using the valve device.

[0002]

2. Description of the Related Art FIG. 4 shows a boom circuit in a hydraulic excavator when a conventional pilot operated spool valve is used.

In FIG. 4, a main spool 2 is slidably fitted in a body 1, and a return spring 5 and a return spring 6 are provided in a cover 3 and a cover 4 at both ends of the main spool 2, respectively. 7
The main spool 2 is supported via the spring receiver 8.

Now, in FIG. 4, when pilot pressure is applied to the pilot port P _P provided on one cover 3, a rightward force is applied to the spool end, and the main spool 2 receives this rightward force. Moves to a position balanced with the resistance of the return spring 6 arranged in the cover 4 on the right side.

When the main spool 2 is displaced rightward, the land portion 9 and the land portion 10 are opened, and the oil flows from the port P to the port A and from the port B to the port T.

The output side ports A and B are connected to the rod side oil chamber 12 and the head side oil chamber of the hydraulic cylinder 11, respectively.
It is connected to 13 via main oil passages 14 and 15, and
The discharge port of the hydraulic pump 16 is connected to the port P, the oil supplied from the port A flows into the rod side oil chamber 12, and the return oil from the head side oil chamber 13 flows into the tank 17 via the port B. As a result, the rod 11r of the hydraulic cylinder 11 moves in the contracting direction, and the boom of the hydraulic excavator lowers.

Notched groove-shaped notches S ₁ , U ₁ and W ₁ are provided on the land portion for controlling the openings S, U and W of the main spool 2 shown in FIG.
_{Due to 1} , ₁ , U ₁ and W ₁ , the openings S, U and W of the main spool 2 have opening characteristics as shown in FIG.

This opening characteristic plays an important role in performing so-called speed control of an actuator represented by a hydraulic cylinder as shown in FIG. 6, and whether it is good or bad depends on the operability of the actuator. It

In particular, the curve of the fine operation range C1 of the actuator at the pilot pressure P _P1 or less in FIG. 6 (hereinafter, this curve is referred to as "fine operation characteristic curve C1") is the spool opening characteristic shown in FIG. It is assumed to be controlled by the minute opening area M1 in the opening U.

[0010] Here, the opening area when opening U of the main spool 2 is opened A _X, the passing oil amount Q, the opening U
If the pressure immediately upstream of the notch U ₁ (that is, the cylinder pressure) is P _C , the pressure immediately after the notch U ₁ (that is, the tank pressure) is P _T , and the differential pressure across these pressures is ΔP, then The following equation (Equation 1) is established from the equation of

(Equation 1) Q = K · A _X · ΔP ^1/2 where ΔP = P _C −P _T , K: constant

[0012]

In the prior art, according to the equation (Formula 1), the amount of oil passing Q changes depending on the magnitude of the differential pressure ΔP across the opening U even if the opening area A _X is the same.
P _C1 notch just before the pressure (cylinder pressure) in FIG. 6, after the pressure (tank pressure) and P _T1, which is an ideal fine operability curve C1 in FIG. 6 at the time of the differential pressure [Delta] P _C Then, the pressure just before the notch is P _C1
When it becomes larger or the pressure immediately after the notch becomes smaller than P _Tl and the differential pressure across it becomes larger than ΔP _C , the amount of oil passing through also increases and the speed curve becomes like C2 and the hydraulic cylinder 11 The speed at which you start moving becomes faster.

That is, even if the lever operating amount for operating the main spool 2 and the pilot operating pressure associated therewith are the same, if the differential pressure across the opening is high, the hydraulic cylinder suddenly starts to move, and the fine operability deteriorates. There was a problem that it did.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a valve device capable of pressure-compensated flow rate control only in a small flow rate region even when a pressure change occurs.
It is another object of the present invention to provide a fluid pressure circuit that can improve the fine operability of the actuator by using this valve device.

[0015]

According to the invention described in claim 1, the flow rate can be controlled according to the displacement amount by the relative relationship between the valve body and the valve body which is displaceably provided in the valve body. A valve device comprising a flow rate control valve body and a pressure compensation mechanism which is provided in the flow rate control valve body and is capable of performing flow rate control in which the pressure is compensated in accordance with a displacement amount smaller than a constant displacement amount of the flow rate control valve body. Yes, if the displacement amount of the flow control valve element is smaller than the constant displacement amount, the pressure compensating mechanism controls the pressure-compensated flow rate according to the displacement amount, and if the displacement amount is large, the flow control valve element is the valve body. Since the flow rate is controlled according to the amount of displacement based on the relative relationship with, it is possible to control the flow rate according to the amount of displacement without being affected by pressure changes in the small flow rate range, and to reduce the pressure loss in the large flow rate range. Flow rate can be controlled.

According to a second aspect of the present invention, the flow control valve element in the valve device according to the first aspect is a pilot-operated spool, and when the spool is operated by a small amount of displacement by low pilot pressure. The pressure compensating mechanism enables flow rate control according to the displacement amount without being affected by pressure changes such as load. Also, when operating the spool with a large displacement amount by high pilot pressure, this spool can reduce pressure loss. A small flow rate can be controlled.

According to a third aspect of the present invention, in the valve device according to the second aspect, the flow control valve element has a pressure provided in a portion of the land portion of the spool which is opened with a displacement smaller than a predetermined displacement. The compensating mechanism is provided with a flow control hole and a notch-shaped groove provided in a portion of the land portion of the spool that is opened with a displacement amount larger than a certain displacement amount, and in a region where the spool displacement amount is small, The flow rate control hole of the pressure compensating mechanism enables flow rate control according to the displacement amount without being affected by pressure changes, and in the region where the spool displacement amount is large, the flow rate with small pressure loss can be controlled by the notched groove. You can control.

According to a fourth aspect of the invention, there is provided a pressure compensating mechanism in the valve device according to any one of the first to third aspects.
A pressure compensation passage that includes an orifice that is provided in the flow control valve body and whose opening area is controlled in relation to the valve body according to the displacement amount of the flow control valve body, and the differential pressure across the orifice that is provided in the pressure compensation passage A pressure compensation spool that is controlled to be constant,
A pressure compensating spool is provided with a spring for positioning with a biasing force that balances the force generated by the differential pressure across the orifice, and the pressure compensating passage including the orifice provided in the flow control valve body and the pressure compensating passage The pressure compensation mechanism can be compactly incorporated in the flow control valve body by the pressure compensation spool provided in the and the spring for positioning the pressure compensation spool.

According to the invention described in claim 5, the pressure compensating spool in the valve device according to claim 4 has a plurality of land portions formed to have the same diameter. Since it is only necessary to form a straight hole in the flow control valve body, the processing becomes easier.

In a sixth aspect of the present invention, the pressure compensating spool in the valve device according to the fourth aspect has a plurality of land portions having different diameters, and when the land portions having different diameters are used. The spring force for urging the pressure compensating spool is smaller than that in the case of using the land portion having the same diameter, and the spring can be miniaturized.

The invention described in claim 7 is a fluid pressure circuit comprising an actuator operated by fluid pressure and the valve device according to any one of claims 1 to 6 for controlling the flow rate of the return fluid from the actuator. Yes, with a valve device that has a pressure compensation mechanism built into the flow control valve body,
Without being affected by the load pressure from the actuator,
The fine operability of the actuator in the low speed range can be improved, and the high speed operation of the actuator can be controlled in the large flow rate range without receiving an excessive pressure loss.

According to an eighth aspect of the present invention, the actuator in the fluid pressure circuit according to the seventh aspect is a hydraulic actuator that operates a movable portion of a hydraulic excavator, and the hydraulic actuator is in a high load state. However, the fine operability of the hydraulic actuator in the low speed range can be improved, excellent inching operation can be performed, and the operating speed of the hydraulic actuator in the high speed range can be reduced from the conventional technology without receiving excessive pressure loss. You can do the same.

[0023]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to one embodiment shown in FIG. 1 and another embodiment shown in FIG. The same parts as those of the conventional technique shown in FIG. 4 may be denoted by the same reference numerals and the description thereof may be omitted.

First, one embodiment of the pilot operated spool type valve device V shown in FIG. 1 and a fluid pressure circuit using the valve device V for controlling a boom cylinder of a hydraulic excavator will be described.

In the valve device V, a main spool 2 as a flow rate control valve body is slidably fitted in a body 1 as a valve body so as to be displaceable. The main spool 2 is displaced with respect to the body 1 by a pilot pressure introduced at one end and the other end of the main spool 2, and the relative relationship with the body 1 makes it possible to control the flow direction according to the direction control and the displacement amount. It is an operation type spool.

Pilot ports P are provided at both ends of the body 1.
Covers 3 and 4 for receiving pilot pressure oil from _P are integrally provided, and return springs 5 and 6 are provided in these covers 3 and 4, respectively. The spring receivers 7 and 8 fitted to both ends of the main spool 2 are biased inwardly, respectively, and the main spool 2 is returned to the neutral position when the pilot pressure oil is not introduced into the covers 3 and 4. .

The main spool 2 is provided with lands 9 and 10 for direction control and flow rate control. The body 1 is provided with a relative positional relationship between the lands 9 and 10 displaced by pilot pressure and the body 1. Switching of the passages connecting the provided ports P and T with the ports A and B and control of the opening area in the passages are performed.

Ports A and B are provided in a rod-side oil chamber 12 and a head-side oil chamber 13 of a hydraulic actuator (hereinafter, this hydraulic actuator will be referred to as a "hydraulic cylinder") 11 that operates by hydraulic pressure as a fluid pressure. , The main oil passages 14 and 15, and the port P is connected to the discharge port of the hydraulic pump 16 and the port T.
Is connected to tank 17. The hydraulic cylinder 11 is, for example, a boom cylinder for vertically moving a boom that constitutes a front working machine of a hydraulic excavator.

Further, in the main spool 2 of the valve device V, there is provided a pressure compensating mechanism 19 capable of performing flow rate control in which the pressure is compensated in accordance with the amount of displacement of the main spool 2 at a displacement amount smaller than a constant displacement amount. Has been.

The pressure compensating mechanism 19 controls the flow rate of the return oil as the return fluid from the hydraulic cylinder 11, and the pressure compensating passage is formed in the end of the main spool 2 on the opening U side.
An axial hole forming 20 is provided, and a small spool 21 as a pressure compensating spool is slidably fitted in the axial hole. This small spool 21 has an end face 23 on the opposite side, due to the urging force of a spring 22 provided at one end,
It is in contact with the end face 20E of the axial hole.

A plurality of orifices 24 serving as flow rate control holes are opened in the tank side region of the land portion 10 of the main spool 2, the opening characteristic curve is V1, and the total opening area is the minute opening area M1 in FIG. It has become equivalent.

An opening hole 25 having a total cross-sectional area sufficiently larger than the total cross-sectional area of the orifice 24 is formed in the port B-side land drop portion 2B located on the cylinder side of the opening U of the main spool 2. Orifice 24 through this opening hole 25
Is connected to port B. The opening area of the opening hole 25 is controlled by the small spool 21 according to the displacement amount thereof.

The pressure compensating passage 20, together with the axial hole, has a radial orifice 24 whose opening area is controlled in relation to the body 1 in accordance with the displacement of the main spool 2.
Also, it includes a radial opening hole 25 whose opening area is controlled according to the amount of displacement of the small spool 21.

A small spool provided in the pressure compensation passage 20
Reference numeral 21 controls the differential pressure across the orifice 24 to be constant, and the spring 22 positions the small spool 21 with an urging force that balances the force generated by the differential pressure across the orifice 24.

Further, an opening hole 26 is opened in the land drop portion 2T on the port Т side of the main spool 2, and the opening hole 26 allows the spring chamber 27 in which the spring 22 for the small spool is housed and the port Т. And are conducted.

Further, the opening area portion larger than the minute opening area M1 in FIG. 5 is constituted by the total opening area of the notch U ₁ as a notched groove provided on the outer peripheral surface of the opening U of the main spool 2. Be present.

On the other hand, the small spool 21 has a radial conduction hole 2
8, the axial conduction hole 29 and the radial conduction hole 30 are opened, and the pressure of the oil chamber 31 located in the center is transferred to the oil chamber 32 located on the left side by these conduction holes 28, 29, 30. There is continuity.

A plug 33 is screwed into the end of the main spool 2, and the spring 22 is supported by the end face 20F of the spring fitting hole provided in the plug 33, and the small spool 21. Is designed to hit this end face 20F during full stroke.

[0039] Here, the opening area when the orifice 24 of the opening U of the main spool 2 is opened A _X1, the passing amount of oil at the orifice 24 Q _C, the pressure immediately before the orifice 24 (i.e. the oil chamber 31 when the pressure) P _C1, the tank pressure after the orifice 24 and P _T1, as the ideal fine operability curve C1 in FIG. 6 when the differential pressure [Delta] P _C of the orifice 24, the following equation ( Equation 2) holds.

[0040] (number _{2) Q C = K · A} X1 · ΔP C 1/2 _{However, ΔP C = P C1 -P T1} , K: constant

In addition, the outer diameters of the two land portions 34 and 35 that define the three chambers in the small spool 21 are formed to have the same diameter.

Further, the cross-sectional area of the land portion of the small spool 21 is U _S , and the opening area of the opening portion 36 of the opening hole 25 opened by the land portion 34 of the small spool 21 is A _X2 , A _X1 = A
If the urging force of the spring 22 when the _X2 was F _C, F _C is assumed to be set as the following equation (Equation 3) is satisfied.

(Equation 3) F _C = U _S · (P _C1 −P _T1 ) = U _S · ΔP _C

When the small spool 21 is in the position shown in FIG. 1, since the opening area of the opening hole 25 is sufficiently large, the pressure immediately before the opening hole 25 (that is, the port B
Pressure P _B is equal to the pressure P _C1 immediately before the orifice 24, and P _B = P _C1 .

Next, the function and effect of the embodiment shown in FIG. 1 will be described.

When pilot pressure is applied to the pilot port P _P provided on one cover 3, a rightward force is applied to the spool end, and the main spool 2 receives this rightward force inside the right cover 4. It moves to a position where it balances the drag force of the return spring 6 arranged at.

When the main spool 2 is displaced rightward, the land portion 9 and the land portion 10 eventually open, and the oil discharged from the hydraulic pump 16 flows from the port P to the port A, and from the port A. The oil supplied to the main oil passage 14 flows into the rod-side oil chamber 12 of the hydraulic cylinder 11. On the other hand, the return oil from the head side oil chamber 13 of the hydraulic cylinder 11 flows through the main oil passage 15 from the port B to the port Т, and the tank
Returned to 17. As a result, the rod 11 of the hydraulic cylinder 11
r moves in the direction of contraction, and in a hydraulic excavator using this hydraulic cylinder 11 as a boom cylinder, the boom lowers.

In a work machine such as a hydraulic excavator, the load is likely to change, and the return hydraulic pressure from the hydraulic cylinder 11 is also likely to change. Therefore, the oil chamber 31 located immediately before the orifice 24
Consider a case where the internal pressure becomes P _C1L (= P _B1L ) which is larger than P _C1 and the front-back differential pressure becomes ΔP _{CL which} is larger than ΔP _C.

At this time, from the formula (Equation 2), the orifice 24
Although the passing oil amount becomes likely larger than Q _C, from equation (3), since the _{F C <U S · ΔP CL} , a small spool 21 is moved rightward against the spring 22 When the opening hole 25 is narrowed by the land portion 34 and becomes A _X2S smaller than the opening area A _X2 of the opening portion 36, a differential pressure is generated before and after the opening portion 36, and the pressure in the oil chamber 31 is _changed from P _C1L. , This P
It becomes P _C2 smaller than _C1L .

Then, the differential pressure across the orifice 24 ΔP _CL
And the small spool 21 is pushed back by the spring 22 to the left from the formula (Equation 3).
Move to the position kept at P _C.

That is, even if the pressure difference between the port B and the port T becomes large, the small spool 21 operates so that the differential pressure before and after the orifice 24 is always ΔP _C. Therefore, from the formula (Equation 2), passing oil amount is kept at Q _C, it has a so-called pressure compensation circuit, ideal fine operability curve C1 is maintained in FIG. 6, the fine operability as in the prior art does not deteriorate.

Next, referring to FIG. 2, another embodiment of the pilot operated spool type valve device V will be described together with a fluid pressure circuit using this valve device V for controlling a boom cylinder of a hydraulic excavator. To do. The same parts as those of the embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

Similar to the valve device V shown in FIG. 1, in the main spool 2, it is possible to perform flow rate control in which the pressure is compensated in accordance with the displacement in the displacement smaller than the constant displacement of the main spool 2. A pressure compensating mechanism 19 is provided.

On the small spool 21 of this pressure compensation mechanism 19,
The radial conduction hole 28a, the axial conduction hole 29, and the radial conduction hole 30 are opened, and the pressure in the spring chamber 27 is changed to the oil chamber 32.
To the same pressure.

[0055] Here, the equation (Equation 2) as well as, the opening area A _X1, the passing amount of oil at the orifice 24 Q _C when the orifice 24 of the opening U of the main spool 2 is opened,
P _C1 immediately before the pressure (i.e., pressure of the oil chamber 31) of the orifice _24, when the tank pressure immediately after the orifice 24 and P _T1, the ideal fine operation in FIG. 6 when the differential pressure [Delta] P _C of the orifice 24 The following equation (Equation 4) is established as the characteristic curve C1.

[0056] (number _{4) Q C = K · A} X1 · ΔP C 1/2 _{However, ΔP C = P C1 -P T1} , K: constant

In the small spool 21, the outer diameter of the land portion 34 on the left side of FIG. 2 is D ₁ and the outer diameter of the land portion 35 on the right side of FIG. 2 is D ₂
Then, it is a so-called different diameter spool in which D ₁ <D _2, and the cross-sectional area of the land portion 34 is S ₁ , the cross-sectional area of the land portion 35 is S ₂ , and the area difference is ΔS.

Further, the small spool of the opening hole 25 provided in the land drop portion 2B on the port B side of the main spool 2
The opening area of the opening 36 opened at the land 34 of 21 is A
_{When the urging} force of the spring 22 when _X2 and A _X1 = A _X2 is F _C, it is assumed that F _C is set so that the following equation (Equation 5) holds.

(Equation 5) F _C = (S ₂ −S ₁ ) · (P _C1 −P _T1 ) = ΔS · Δ
P _C

When the small spool 21 is at the position shown in FIG. 2, P _B = P _C1 because the opening area of the opening hole 25 is sufficiently large.

Next, the function and effect of the embodiment shown in FIG. 2 will be described.

The return hydraulic pressure from the hydraulic cylinder 11 changes so that the pressure immediately before the orifice 24 is P greater than P _{C 1.
C1L (= P B1L)} next, the case where the differential pressure becomes [Delta] P _C is greater than [Delta] P _{C L.}

At this time, from the formula (Equation 4), the orifice 24
The pass oil amount becomes likely be larger than Q _C, from equation (5), since the F C _<ΔS · ΔP _CL, a small spool 21 is moved rightward against the spring 22, When the opening hole 25 is narrowed by the land portion 34 and becomes A _X2S smaller than the opening area A _X2 of the opening portion 36, a differential pressure is generated before and after the opening portion 36, and the pressure in the oil chamber 31 is _changed from P _C1L to This P
It becomes P _C2 smaller than _C1L .

Then, the differential pressure across the orifice 24, ΔP _CL
And the small spool 21 is pushed back to the left by the spring 22 according to the formula (Equation 5), and eventually moves to a position where the front-to-back differential pressure is maintained at ΔP _C.

That is, even if the pressure difference between the port B and the port T becomes large, the small spool 21 operates so that the differential pressure before and after the orifice 24 is always ΔP _C. Therefore, from the equation (Equation 4), passing oil amount is kept at Q _C, have a so-called pressure compensation circuit, ideal fine operability curve C1 is maintained in FIG. 6, never fine operability as in the prior art may deteriorate .

Next, in order to solve the problem relating to the deterioration of the fine operability, for example, as shown in FIG. 3, a case where an existing pressure-compensated flow control valve 41 is simply incorporated in the main oil passage 15 on the return side will be described. Consider.

In the flow control valve 41 with pressure compensation, the pressure compensating portion 44 is constituted by the stepped spool 43 incorporated in the body 42 on the upstream side of the opening U, and the stepped spool 43 is provided.
Then, the set load K of the spring 45 and the differential pressure across the opening U are made to act, and the opening of the pressure compensator 44 is increased or decreased by the movement of the stepped spool 43, and the flow rate passing through this pressure compensator 44 is Control.

The differential pressure across the opening U is caused by the stepped spool 43.
When acting, the inlet pressure P of the opening U ₁Is the right end small diameter part 46
(Pressure receiving area a₁) And annular portion 47 (pressure receiving area a_Two) To
And outlet pressure P_TwoIs the left large diameter portion 48 (pressure receiving area a_Three) To
To work.

Since the stepped spool 43 is in the equilibrium state, (a ₁ + a ₂ ) · P ₁ = K + a ₃ · P ₂ holds, and a ₁ + a ₂ = a ₃ holds, so P ₁ -P ₂ = It becomes K / a ₃ , and the differential pressure across the opening U is kept constant.

As described above, even when the existing flow control valve with pressure compensation 41 is incorporated in the main oil passage 15 on the return side, it is true that the inching operation range does not depend on the magnitude of the differential pressure across the opening U. Although the fine operability curve C1 is guaranteed and good fine operability can be obtained, when the flow control valve 41 with pressure compensation is incorporated in the main oil passage 15, it is possible to operate in the medium and high speed range other than the fine control range in FIG. That is, when a large flow rate flows, another problem arises in that an excessive pressure loss occurs in the pressure compensating section 44 of the flow control valve with pressure compensation 41 and a large energy loss occurs.

On the other hand, in each of the embodiments shown in FIGS. 1 and 2, the pressure compensating circuit is configured only when controlling the small flow rate in the fine operation region, and the medium and high speed regions other than the fine operation region, that is, When a large amount of oil flows, most of the oil passes through the notch U ₁ on the outer peripheral surface of the main spool 2 as in the prior art, so that an excessive pressure loss does not occur and therefore a large amount of energy is consumed. There is no loss.

As described above, the spool displacement amount of the main spool 2 is determined by the pilot pressure P _P1 shown in FIGS. 5 and 6.
Orifice 24
The opening area of is controlled by the relative relationship with the body 1,
The pressure compensating mechanism 19 built in the main spool 2 controls the flow rate that is pressure-compensated according to the spool displacement amount, and when the spool displacement amount is large, the notch U of the main spool 2
₁ opening area is controlled by the relative relationship between the body 1, the notch U ₁ is a flow control according to the spool displacement. Therefore, in the small flow rate range, the flow rate control according to the spool displacement amount can be performed without being affected by the pressure change, and in the large flow rate range, the flow rate control with a small pressure loss can be performed.

That is, when the main spool 2 is operated by a small displacement amount with a low pilot pressure, the pressure compensating mechanism 19 controls the flow rate according to the displacement amount without being affected by the pressure change such as the load of the hydraulic cylinder 11. Further, when the main spool 2 is operated by a large amount of displacement by the high pilot pressure, the flow rate control with a small pressure loss can be performed by the notch U ₁ of the main spool 2.

In other words, in the region where the spool displacement amount of the main spool 2 is small, the orifice 24 of the pressure compensating mechanism 19 can control the flow rate according to the displacement amount without being affected by the pressure change, and In a region where the spool displacement amount is large, the notch U ₁ capable of controlling a large flow rate enables flow rate control with a small pressure loss.

Further, the pressure compensating passage 20 including the orifice 24 provided in the main spool 2, the small spool 21 provided in the pressure compensating passage 20, and the small spool 21.
The pressure compensating mechanism 19 can be compactly assembled in the main spool 2 by means of the spring 22 for positioning.

Further, the small spool 21 shown in FIG. 1 has a plurality of land portions 34 and 35 formed to have the same diameter, and the main spool 2 is made to correspond to the land portions 34 and 35 having the same diameter. Since it is only necessary to make a straight hole, it is easy to process.

On the other hand, when a plurality of lands 34 and 35 having different diameters are used like the small spool 21 shown in FIG. 2, it is clear from the formula (formula 5) to the formula (formula 3). In this way, the urging force of the spring 22 that urges the small spool 21,
It is smaller than when using land parts 34 and 35 of the same diameter,
The spring 22 can be miniaturized.

Further, the main spool 2 has a pressure compensation mechanism.
The valve device V having the built-in 19 can improve the fine operability in the low speed range of the hydraulic cylinder 11 without being affected by the load pressure from the hydraulic cylinder 11 in the small flow rate range, and can increase the excessive flow rate in the large flow rate range. The high speed operation of the hydraulic cylinder 11 can be controlled by the notch U ₁ without receiving any pressure loss.

When the hydraulic cylinder 11 is a boom cylinder that moves the boom of the hydraulic excavator up and down, the fine operability in the low speed range of the boom cylinder can be improved even if the boom cylinder is under a high load condition. The inching operation is possible, and the operating speed of the boom cylinder in the high speed range can be improved without receiving an excessive pressure loss, so that the workability of the hydraulic excavator can be improved.

The valve device and fluid pressure circuit of the present invention include a hydraulic actuator that operates the movable part of a hydraulic excavator, that is, a boom cylinder that moves a boom up and down, an arm cylinder, a bucket cylinder, a traveling motor, and a swing motor. Not only can it be applied to the hydraulic circuits of all hydraulic actuators such as motors and attachments, but it can also be applied to the hydraulic circuits of hydraulic actuators that operate the movable parts of work machines other than hydraulic excavators.

[0081]

According to the first aspect of the invention, when the displacement amount of the flow control valve element is smaller than the constant displacement amount, the pressure compensating mechanism performs the flow rate control in which the pressure is compensated according to the displacement amount, and When the flow rate is large, the flow control valve disc controls the flow rate according to the displacement amount based on the relative relationship with the valve body, so in the small flow rate range, the flow rate control according to the displacement amount is not affected by the pressure change. In addition, the flow rate can be controlled with a small pressure loss in the large flow rate range.

According to the second aspect of the present invention, when the pilot operated spool is operated by a small displacement amount with a low pilot pressure, the displacement amount is adjusted by the pressure compensating mechanism without being affected by a pressure change such as a load. The flow rate can be controlled accordingly, and when the spool is operated by a large amount of displacement by high pilot pressure, the flow rate can be controlled with a small pressure loss by this spool.

According to the third aspect of the invention, in the region where the spool displacement amount is small, the flow rate control hole of the pressure compensation mechanism can control the flow rate according to the displacement amount without being affected by the pressure change, and the spool displacement amount can be controlled. In a large volume region, the flow rate can be controlled with a small pressure loss due to the notch-shaped groove that can control a large flow rate.

According to the fourth aspect of the present invention, the pressure compensation passage including the orifice provided in the flow control valve body, the pressure compensation spool provided in the pressure compensation passage, and the spring for positioning the pressure compensation spool. As a result, the pressure compensation mechanism can be compactly incorporated in the flow control valve body.

According to the fifth aspect of the present invention, the flow control valve body may be formed with a straight hole corresponding to the land portion having the same diameter of the pressure compensating spool, which facilitates the processing.

According to the sixth aspect of the present invention, when the pressure compensating spool is a land portion having a different diameter, the urging force of the spring for urging the pressure compensating spool is smaller than that when a land portion having the same diameter is used. The spring can be downsized.

According to the seventh aspect of the invention, the valve device having the pressure compensating mechanism built in the flow control valve body is used in the low flow rate range of the actuator without being affected by the load pressure from the actuator in the small flow rate range. It is possible to improve the fine controllability and to control the high-speed operation of the actuator in the large flow rate range without receiving an excessive pressure loss.

According to the invention described in claim 8, even if the hydraulic actuator of the hydraulic excavator is in a high load state, the fine operability of the hydraulic actuator in the low speed range can be improved.
An excellent inching operation is possible, and the operation speed of the hydraulic actuator in the high speed range can be improved without receiving an excessive pressure loss, and thus the workability of the hydraulic excavator can be improved.

[Brief description of drawings]

FIG. 1A is a cross-sectional view showing an embodiment of a valve device and a fluid pressure circuit according to the present invention, and FIG. 1B is an enlarged cross-sectional view of a main part thereof.

FIG. 2A is a cross-sectional view showing another embodiment of the valve device and the fluid pressure circuit according to the present invention, and FIG. 2B is an enlarged cross-sectional view of a main part thereof.

FIG. 3 is a cross-sectional view when a conventional flow control valve with pressure compensation is attached to a main oil passage.

4A is a sectional view showing a state in which a conventional spool valve is incorporated in a hydraulic circuit, and FIG. 4B is an enlarged sectional view of a notch forming portion thereof.

FIG. 5 is a characteristic diagram showing an opening characteristic of a spool valve.

FIG. 6 is a characteristic diagram showing a speed curve of a hydraulic cylinder controlled by a spool valve.

[Explanation of symbols]

V valve device 1 Body as valve body 2 Main spool (pilot operated spool) as flow control valve body 10 Land portion 11 Hydraulic actuator (hydraulic cylinder) as actuator 19 Pressure compensation mechanism 20 Pressure compensation passage 21 Pressure compensation spool Small spool 22 Spring 24 Orifice U ₁ as flow control hole Notch 34 and 35 land as cutout groove

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2D003 AA01 AB03 BA01 BA05 CA02                       DB02                 3H002 BA01 BB02 BC01 BC02 BD04                       BE02                 3H053 AA03 BA02 BA13 BC03 CA06                       DA11                 3H089 AA44 BB15 CC01 DA02 DB23                       DB63 DB75 DB78 GG02 JJ02

Claims (8)

[Claims] 1. A flow control valve body, which is provided in the valve body so as to be displaceable in the valve body and capable of controlling a flow rate according to a displacement amount by a relative relationship between the valve body and a flow rate control valve body. A valve device comprising: a pressure compensating mechanism capable of pressure-compensated flow rate control in accordance with a displacement amount smaller than a constant displacement amount of a control valve body. 2. The valve device according to claim 1, wherein the flow control valve element is a pilot operated spool. 3. The flow control valve body comprises a flow control hole of a pressure compensating mechanism provided in a portion of the land portion of the spool which is opened with a displacement amount smaller than a constant displacement amount, and a constant displacement at the land portion of the spool. 3. The valve device according to claim 2, further comprising a notch-shaped groove provided in a portion opened with a displacement amount larger than the displacement amount. 4. The pressure compensating mechanism includes a pressure compensating passage including an orifice provided in the flow control valve body and having an opening area controlled in relation to the valve body in accordance with a displacement amount of the flow control valve body, and a pressure compensating passage. It is characterized by comprising a pressure compensating spool provided therein for controlling the differential pressure across the orifice to be constant, and a spring for positioning the pressure compensating spool with a biasing force that balances the force generated by the differential pressure across the orifice. The valve device according to any one of claims 1 to 3. 5. The valve device according to claim 4, wherein the pressure compensation spool has a plurality of lands formed to have the same diameter. 6. The valve device according to claim 4, wherein the pressure compensating spool has a plurality of lands having different diameters. 7. An actuator operated by fluid pressure, and a flow rate control of a return fluid from the actuator.
7. A fluid pressure circuit comprising the valve device according to any one of items 1 to 6. 8. The fluid pressure circuit according to claim 7, wherein the actuator is a hydraulic actuator that operates a movable portion of the hydraulic excavator.