JP3625230B2 - Flow control valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow control valve, and more particularly to a flow control valve that is provided in a work machine such as a hydraulic excavator and controls driving of an actuator.
[0002]
[Prior art]
A conventional flow control valve is described in Japanese Utility Model Laid-Open No. 6-25602. This flow control valve is shown in FIGS.
[0003]
7 and 8, this conventional flow control valve is provided in the housing 1 so as to be slidable in the housing 1, and is provided in the housing 1, and is connected to a hydraulic source such as a hydraulic pump 3. The pump port 4, the center bypass passage 11, an actuator, for example, a hydraulic cylinder 5 such as a boom cylinder, and the first and second load ports 6 a and 6 b for supplying and discharging pressure oil to and from the hydraulic cylinder 5, The first and second variable throttles 7a and 7b are provided in the spool valve body 2 corresponding to the first and second load ports 6a and 6b, and change the size of the opening area from the blocking position according to the movement amount. A first feed port 8a that is provided in the housing 1 and supplies the pressure oil of the hydraulic pump 3 to the first load port 6a via the first variable throttle 7a; and the pressure oil of the hydraulic pump 3 And a second feed port 8b to be supplied to the second load port 6b through the second variable throttle 7b.
[0004]
In addition, it is slidably provided between the pump port 4 and the first and second feeder ports 8a and 8b, and the backflow of pressure oil from the first and second feed ports 8a and 8b to the pump port 4 is prevented. A load check valve 10 for blocking is provided. The load check valve 10 includes a poppet 10a, a spring 10b that urges the poppet 10a in a closing direction, a spring chamber 10c that is formed on the back surface of the poppet 10a and accommodates the spring 10b, and the spring chamber 10c and the first spring chamber 10c. It is comprised from the channel | path 10d which connects the 1st and 2nd feeder ports 8a and 8b.
[0005]
In the hydraulic circuit shown in FIG. 8 having the flow control valve configured as described above, for example, when the spool valve body 2 is operated, the center bypass passage 11 is closed and the pressure oil of the pump 3 is loaded from the pump port 4. Further, the first and second feeder ports 8a and 8b, the corresponding ones of the first and second variable throttles 7a and 7b, and the first and second load ports 6a and 6b. The corresponding one is guided to the corresponding one of the first and second load ports 6 a and 6 b and supplied to the pottom side or the rod side of the hydraulic cylinder 5. At this time, since the poppet 10a of the load check valve 10 moves upward, there is no problem in the flow of pressure oil.
[0006]
[Problems to be solved by the invention]
Although the hydraulic circuit shown in FIG. 8 of the prior art described above is shown as having only one flow control valve, the flow control valve provided in the hydraulic excavator is generally a boom cylinder, an arm cylinder, a bucket cylinder, a swing motor, A plurality of actuators such as left and right traveling motors are provided, and the pump port 4 is often connected in parallel to the plurality of flow control valves. In such a configuration, when performing a composite operation of actuators with different load pressures, the flow of pressure oil into the actuator on the lighter load side increases, and the flow of pressure oil into the actuator on the higher load side decreases. Therefore, the operability at the time of the composite operation is deteriorated, so that the maximum opening area of the variable throttle on the light load side is reduced and the pump discharge pressure is increased to supply the pressure oil to the actuator on the high load side.
[0007]
However, when the maximum opening area of the variable throttle provided in the spool valve body is relatively small and the flow rate passing therethrough is large, the fluid force due to the pressure oil passing through the variable throttle greatly acts on the spool valve body. In such a situation, when the spool valve body is driven by a hydraulic pilot operation valve (not shown), the spool valve body does not change smoothly with respect to the pilot pressure that drives the spool valve body. Sudden changes or operability when the actuator is stopped are deteriorated. Further, when the spool valve body is directly driven, the operation force becomes heavy.
[0008]
The objective of this invention is providing the flow control valve which can reduce the fluid force which acts on a spool valve body.
[0009]
[Means for Solving the Problems]
(1) In order to solve the above problem, the present invention provides a pump port connected to a hydraulic pressure source, a load port connected to an actuator, and between the pump port and the load port. comprising a load check valve for preventing backflow of hydraulic oil into the pump port, and a spool valve body provided with a variable throttle for controlling the flow rate of the hydraulic fluid supplied from the pump port to the load port, defined the hydraulic actuator at the maximum flow rate control valve which enables supply of a passage leading to the load port from the pump port, the upstream position of the sheet portion of the load check valve has a constant flow area, said pump When pressure oil from the port opens the seat portion of the load check valve and flows into the load port via the variable throttle Provided a resistance generating means for providing a resistance to the flow of the hydraulic fluid, and so that the maximum flow rate of the prescribed in the actuator to compensate for pressure drop caused by the resistance generating means can be supplied, the maximum opening area of the variable throttle It is set larger than the case where the prescribed maximum flow rate can be supplied without providing the resistance generating means.
[0010]
In the flow control valve configured as described above, when the spool valve body is operated, the pressure oil from the hydraulic pressure source is supplied from the pump port to the load port via the resistance generating means and the variable throttle. At this time, the resistance generating means Since the pump discharge pressure increases, pressure oil can be supplied to the actuator on the higher load side, and the specified maximum flow rate can be supplied to the actuator by compensating for the pressure drop caused by the resistance generating means. so that, since the maximum opening area of the variable throttle are set, the actuator maximum flow provisions can be supplied. In addition, since the maximum opening area of the variable throttle is set larger than the case where the specified maximum flow rate can be supplied without providing the resistance generating means, the flow acting on the spool valve body even if the specified maximum flow rate flows. Physical strength does not increase.
[0013]
(2) In order to solve the above problems, the present invention provides at least one spool valve body slidably provided in the housing, a pump port provided in the housing and connected to a hydraulic power source, The first and second load ports connected to the actuator and the spool valve body corresponding to the first and second load ports, and the size of the opening area from the blocking position according to the amount of movement thereof A first feeder port that is provided in the housing and supplies the hydraulic pressure of the hydraulic source to the first load port via the first variable throttle, A second feeder port that supplies pressure oil from the hydraulic source to the second load port via the second variable throttle, and is provided between the pump port and the first feeder port, First And a load check valve for preventing backflow of hydraulic oil from the feeder port to the pump port, the in the hydraulic actuator a flow control valve which enables supplying a maximum flow rate of provisions, the first feeder port from said pump port In the passage leading to the upstream side of the seat portion of the load check valve and having a constant flow area, and the pressure oil from the pump port opens the seat portion of the load check valve to open the seat portion. There is provided resistance generating means for imparting resistance to the flow of pressure oil when flowing into the first load port via the first feeder port and the first variable throttle , and the pressure drop caused by the resistance generating means is reduced. as maximum flow rate compensation to the specified to the actuator can be supplied, the resistance generating the maximum opening area of the first variable throttle It is obtained by greater than would be capable of delivering up to the flow rate of the prescribed without providing the step.
[0014]
Also in the flow rate control valve configured as described above, similarly to the above (1), a resistance generating means is provided, and a specified maximum flow rate can be supplied to the actuator. Even if the specified maximum flow rate flows, the spool valve The fluid force acting on the body does not increase.
[0015]
( 3 ) In the above ( 2 ), preferably, the relationship between the resistance generating means and the maximum opening area of the first variable throttle so that the pressure drop by the resistance generating means is larger than the pressure drop by the first variable throttle. Set.
[0016]
Thus, by setting the relationship between the resistance generating means and the maximum opening area of the first variable throttle, the fluid force acting on the spool valve body can be sufficiently reduced even when the specified maximum flow rate flows.
[0017]
( 4 ) In the above (1) or (2 ), preferably, the resistance generating means is provided in the load check valve.
[0018]
Thereby, the resistance generating means can be easily and inexpensively incorporated using the existing load check valve.
[0019]
( 5 ) In that case, the resistance generating means is preferably an aperture stop provided in the valve body of the load check valve.
[0021]
( 6 ) Further, in order to solve the above-described problem, the present invention includes at least one spool valve body slidably provided in the housing, and a first and a first valve valve provided in the housing and connected to a hydraulic pressure source. A second pump port, first and second load ports connected to the actuator, and the spool valve body corresponding to the first and second load ports; The first and second variable throttles that change the size of the opening area and the housing are provided in the housing, and the hydraulic pressure of the hydraulic source is supplied to the first load port via the first variable throttle. A first feeder port; a second feeder port for supplying pressure oil from the hydraulic source to the second load port via the second variable throttle; the first pump port; and the first feeder. With port A first load check valve that prevents backflow of pressure oil to the first pump port, and is slidably provided between the second pump port and the second feeder port, A flow control valve comprising a second load check valve for preventing backflow of pressure oil from the second feeder port to the second pump port, and capable of supplying a prescribed maximum flow rate to the hydraulic actuator ; Only in the passage from the first pump port to the first feeder port, and at a position upstream of the seat portion of the first load check valve, has a constant flow area , When pressure oil from the pump port opens the seat portion of the load check valve and flows into the first load port via the first feeder port and the first variable throttle. Kino provided a resistance generating means for providing resistance to the flow of the hydraulic fluid, and so that the maximum flow rate of the prescribed to compensate for the pressure drop due to the resistance generating means to said actuator can be supplied, the first variable The maximum opening area of the throttle is set larger than the case where the prescribed maximum flow rate can be supplied without providing the resistance generating means.
[0022]
Also in the flow rate control valve configured as described above, similarly to the above (1), a resistance generating means is provided, and a specified maximum flow rate can be supplied to the actuator. Even if the specified maximum flow rate flows, the spool valve The fluid force acting on the body does not increase. In addition, since the resistance generating means is not provided in the passage from the pump port to the second feeder port, it is suitable for drive control of an actuator such as a boom cylinder in a hydraulic excavator having a different load pressure depending on the operation direction.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the flow control valve of the present invention will be described with reference to the drawings.
[0024]
First, a first embodiment of the present invention will be described with reference to FIGS.
[0025]
In FIG. 1, the flow control valve of the present embodiment is connected to a spool valve body 2 slidably provided in the housing 1 and a hydraulic source such as a hydraulic pump 3 (see FIG. 3). A pump port 4, a center bypass passage 11, and first and second load ports 6 a and 6 b which are connected to a hydraulic cylinder 5 such as a boom cylinder and supply and discharge pressure oil to and from the hydraulic cylinder 5. The first and second variables are provided in the spool valve body 2 corresponding to the first and second load ports 6a, 6b, and change the size of the opening area from the blocking position according to the amount of movement. A throttle 20a, 20b, a first feeder port 8a provided in the housing 1 for supplying the hydraulic oil of the hydraulic pump 3 to the first load port 6a via the first variable throttle 20a, a hydraulic pump 3 of the pressure oil and a first feeder port 8b to be supplied to the second load port 6b through the second variable throttle 20b.
[0026]
Further, it is slidably provided in a passage between the pump port 4 and the first and second feeder ports 8a and 8b, and the pressure oil from the first and second feeder ports 8a and 8b to the pump port 4 is slidable. And a load check valve 30 for preventing backflow. The load check valve 30 includes a poppet 30a, a spring 30b that urges the poppet 30a in a closing direction, a spring chamber 30c that is formed on the back surface of the poppet 30a and accommodates the spring 30b, and the spring chamber 30c and the second spring chamber 30c. It comprises a passage 30d for communicating the first and second feeder ports 8a and 8b.
[0027]
Further, as shown in FIG. 2, the poppet 30a has an axially extending portion 30g in the direction of the pump port 4, an annular chamber 30e is formed outside the axially extending portion 30g, and the axially extending portion 30g. An aperture stop 30f that communicates the annular chamber 30e and the pump port 4 is provided. When the poppet 30a moves in the opening direction, the seat portion 31 between the poppet 30a and the housing 1 is opened, and the first and second feeder ports 8a and 8b communicate with the pump port 4 via the annular chamber 30e and the aperture stop 30f. To do.
[0028]
An opening throttle 30f provided in the poppet 30a of the load check valve 30 functions as a resistance generating means for giving resistance to the flow of pressure oil in a passage from the pump port 4 to the load ports 6a and 6b. As shown in FIG. 3, the throttles 20a and 20b are larger than the variable throttles 7a and 7b of the conventional flow control valve shown in FIGS. 7 and 8 so as to compensate for the pressure drop caused by the aperture throttle 30f (resistance generating means). The opening area is set large. Further, the relationship between the opening area of the aperture stop 30f and the maximum opening area of the variable throttles 20a and 20b is set so that the pressure drop due to the first and second variable throttles 20a and 20b is smaller than the pressure drop due to the aperture stop 30f. Has been.
[0029]
In the flow control valve 100 of the present embodiment configured as described above, when the spool valve body 2 is moved by operating an operating device (not shown), the center bypass passage 11 is closed and the hydraulic source, that is, the discharge oil of the pump 3 is discharged. The poppet 30 a of the load check valve 30 is opened by the pressure oil supplied to the pump port 4 and the pressure oil supplied to the pump port 4. As a result, the pressure oil flows into the first and second feeder ports 8a and 8b via the opening throttle 30f and the annular chamber 30e provided in the poppet 30a, and further the first or second variable throttles 20a and 20b. Then, it flows into the first or second load port 6a, 6b via the, and is supplied to the hydraulic cylinder 5. At this time, the pressure oil is supplied to the load port via the aperture stop 30f and the first or second variable throttle 20a, 20b and receives resistance by the aperture stop 30f, but the first and second variable throttles 20a, 20b. Since the maximum opening area is set large so as to compensate for the pressure drop due to the resistance of the aperture stop 30f as described above, a prescribed maximum flow rate can be supplied to the hydraulic cylinder 5. In addition, since the maximum opening areas of the first and second variable throttles 20a and 20b are set large, the fluid force acting on the spool valve body 2 does not increase even when a specified maximum flow rate flows.
[0030]
FIG. 4 shows an example of a hydraulic circuit configured using the flow control valve of the present embodiment. This hydraulic circuit is provided, for example, in a hydraulic excavator, and 100 is a flow control valve of the present embodiment, and is provided as one that controls the hydraulic cylinder 5 such as a boom cylinder as described above. The flow rate control valve is the same as that shown in FIG. 1 and is provided to drive and control a hydraulic cylinder 102 such as an arm cylinder. Pump ports 4, 4 of the flow control valves 100, 101 are connected in parallel to the hydraulic pump 3 by a pipe line 103. The operation in the contraction direction of the hydraulic cylinder 5 corresponds to, for example, boom lowering of the hydraulic excavator, the operation in the contraction direction of the hydraulic cylinder 102 corresponds to, for example, arm dumping of the hydraulic excavator, and the hydraulic cylinder 5 is combined in the combined operation of boom lowering and arm dumping. The hydraulic cylinder 102 has a different load pressure, and the hydraulic cylinder 5 has a lower load pressure.
[0031]
When the hydraulic cylinders 5 and 102 are combined and operated in the contraction direction in such a hydraulic circuit, the opening check 30f provided in the load check valve 30 against the flow of pressure oil to the hydraulic cylinder 5 having a low load pressure. Since resistance is given, the discharge pressure of the hydraulic pump 3 rises, and pressure oil can be supplied to the hydraulic cylinder 102 with high load pressure, so that operability is good. In addition, since the first and second variable throttles 20a and 20b have a large maximum opening area, a prescribed maximum flow rate can be supplied to the hydraulic cylinder 5, and the driving speed of the hydraulic cylinder 5 can be reduced. Nor. Further, when the spool valve body 2 is driven by a hydraulic pilot operation valve (not shown), the maximum opening areas of the first and second variable throttles 20a and 20b are set large, and the flow acting on the spool valve body 2 is set. Since the physical strength does not increase, the position of the spool valve body 2 smoothly changes due to the pilot pressure that drives the spool valve body 2, so that the speed of the actuator does not change suddenly, and the operability when the actuator is stopped is good, Further, the operating force for directly driving the spool valve body 2 does not increase.
[0032]
As described above, according to the present embodiment, the opening throttle 30f provided in the load check valve 30 provides resistance to the flow of pressure oil, so that the pump discharge pressure rises and pressure is applied to the hydraulic cylinder 102 with high load pressure. Oil can be supplied, and the maximum opening area of the first and second variable throttles 20a and 20b is set large, so that the fluid force acting on the spool valve body 2 can be reduced, and therefore the spool valve body 2 The position of the spool valve body 2 smoothly changes due to the pilot pressure that drives the hydraulic cylinder 5, the speed of the hydraulic cylinder 5 does not change suddenly, and the operability when the hydraulic cylinder 5 is stopped is improved. The operating force does not increase even when driving directly. Further, since the prescribed maximum flow rate can be supplied to the hydraulic cylinder 5, the hydraulic cylinder 5 can be driven at a necessary maximum speed.
[0033]
Further, since the aperture stop 30f as the resistance generating means is provided by using the poppet 30a of the load check valve 30, it can be incorporated very easily and inexpensively.
[0034]
A second embodiment of the present invention will be described with reference to FIG. In the figure, members equivalent to those shown in FIG.
[0035]
The second embodiment also includes a boom cylinder in which the hydraulic cylinder 5 is provided in a hydraulic excavator. Two pump ports 4 a and 4 b are provided in the housing 1. Between the pump port 4a and the first feeder port 8a, the load check valve 10 which has been conventionally provided is disposed. The load check valve 10 includes a poppet 10a, a spring 10b, and a spring chamber 10c. In the load check valve 10, when the poppet 10a performs an opening operation, the pressure oil flowing from the pump port 4a to the first feeder port 8a is not subject to any restriction. The first variable diaphragm 7a also has an opening area similar to that of the prior art, that is, an opening area indicated by a broken line in FIG.
[0036]
On the other hand, the load check valve 30 provided in the first embodiment shown in FIG. 1 is disposed between the pump port 4b and the second feeder port 8b. That is, the poppet 30a has an axially extending portion 30g in the direction of the pump port 4 as shown in FIG. 2, an annular chamber 30e is formed outside the axially extending portion, and the axially extending portion 30g An aperture stop 30f that communicates the annular chamber 30e and the pump port 4a is provided. When the poppet 30a moves in the opening direction, the seat portion 31 between the poppet 30a and the housing 1 is opened, and the first and second feeder ports 8a and 8b communicate with the pump port 4a via the annular chamber 30e and the opening throttle 30f. . Further, as in the first embodiment, the second variable throttle 20b has a large maximum opening area as shown by a solid line in FIG. 3 so as to compensate for the pressure drop caused by the aperture throttle 30f.
[0037]
The second embodiment is suitable for drive control of a hydraulic cylinder 5 including a boom cylinder that performs a boom lowering operation with a low load pressure and a boom raising operation with a high load pressure.
[0038]
That is, in the second embodiment, the poppet 10 is opened by the pressure oil guided to the pump port 4a in accordance with the rightward movement of the spool valve body 2 that is the boom raising direction where the load pressure is high. Since the pressure oil is supplied to the bottom side of the hydraulic cylinder 5 through the feeder port 8a and the variable throttle 7a and the load port 6a, it is not subjected to resistance by the opening throttle 30f of the load check valve 30.
[0039]
On the other hand, when the spool valve body 2 moves in the left direction, which is the boom lowering direction where the load pressure is low, the flow of pressure oil is resisted by the opening throttle 30f of the load check valve 30, and the discharge pressure of the hydraulic pump 3 increases. Pressure oil can be supplied to a hydraulic cylinder with high load pressure, and operability is good. In addition, since the maximum opening area of the second variable throttle 20b is set large, the prescribed maximum flow rate can be supplied to the hydraulic cylinder 5, and the fluid force acting on the spool valve body 2 can be reduced. The same effect as in the embodiment can be obtained.
[0041]
In the above embodiment, the resistance generating means is provided in the load check valve. However, a normal throttle made of a ring-shaped metal fitting may be installed in the passage downstream of the pump port 4 or 4b. An effect is obtained.
[0042]
Furthermore, in the above embodiment, the variable throttle 20a or 7a, 20b is located adjacent to the passage leading to the load ports 6a, 6b, and the variable throttle 20a, 7a, 20b also serves as a pressure oil supply direction switching portion. Although the present invention is applied to the flow control valve, the present invention may be applied to other types of flow control valves. For example, the present invention may be applied to a flow control valve of a type in which a separate switching unit is provided on the downstream side of the variable throttle and a load check valve is provided on the upstream side of the switching unit. It is obtained.
[0043]
【The invention's effect】
According to the present invention, the resistance generating means provides resistance to the flow of the pressure oil, so that the pressure oil can be supplied to the actuator having a high load pressure and the maximum opening area of the variable throttle is set large. The fluid force acting on the spool valve body can be reduced. For this reason, the position of the spool valve body smoothly changes due to the pilot pressure that drives the spool valve body, the actuator speed does not change suddenly, the operability when the actuator is stopped is improved, and the spool valve body is further improved. The operating force does not increase even when driving directly. In addition, since the specified maximum flow rate can be supplied to the actuator, the actuator can be driven at a required maximum speed.
[0044]
In addition, according to the present invention, since the load check valve is provided with the resistance generating means, the resistance generating means can be easily and inexpensively incorporated using the load check valve.
[0045]
Further, according to the present invention, it is possible to provide a structure suitable for drive control of an actuator such as a boom cylinder in a hydraulic excavator having a different load pressure depending on the operation direction.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a main part of a flow control valve according to a first embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a load check valve portion of the flow control valve shown in FIG.
FIG. 3 is a diagram showing an opening area characteristic of a variable throttle of the flow rate control valve shown in FIG. 1 in comparison with the prior art.
4 is a diagram showing an example of a hydraulic circuit incorporating the flow control valve shown in FIG. 1. FIG.
FIG. 5 is a longitudinal sectional view showing a main part of a flow control valve according to a second embodiment of the present invention.
FIG. 6 is a longitudinal sectional view showing a main part of a conventional flow control valve.
7 is a diagram showing a hydraulic circuit including the flow control valve shown in FIG. 6. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 2 Spool valve body 4 Pump port 5 Hydraulic cylinder 6a 1st load port 6b 2nd load port 7a 1st variable throttle 7b 2nd variable throttle 8a 1st feeder port 8b 2nd feeder port 20a 1st 1 of the variable throttle 20b second variable throttle 30 load check valve 30a poppet 30b spring 30c spring chamber 30d passage 30e annular chamber 30f aperture stop 30g axial extending portion
1 00 Flow control valve 101 Flow control valve 102 Hydraulic cylinder 103 Pipe line

Claims (6)

A pump port connected to a hydraulic pressure source, a load port connected to an actuator, and a load check valve provided between the pump port and the load port, which prevents backflow of pressure oil from the load port to the pump port; A spool valve body provided with a variable throttle for controlling the flow rate of pressure oil supplied from the pump port to the load port, and a flow rate control valve capable of supplying a specified maximum flow rate to the hydraulic actuator ,
In the passage from the pump port to the load port, at a position upstream of the seat portion of the load check valve, the passage portion has a constant flow area, and the pressure oil from the pump port is seated on the load check valve. Is provided with resistance generating means for giving resistance to the flow of the pressure oil when flowing into the load port through the variable throttle , and compensating for the pressure drop by the resistance generating means to the actuator so that the maximum flow rate of the prescribed can be supplied, characterized by being larger than would be the maximum opening area of the variable throttle can supply a maximum flow rate of the prescribed without providing the resistance generating means Flow control valve. At least one spool valve body slidably provided in the housing, a pump port provided in the housing and connected to a hydraulic pressure source, first and second load ports connected to an actuator, and First and second variable throttles which are provided in the spool valve body corresponding to the first and second load ports and change the size of the opening area from the blocking position according to the movement amount; A first feeder port for supplying the hydraulic pressure of the hydraulic source to the first load port via the first variable throttle, and the pressure oil of the hydraulic source via the second variable throttle. A second feeder port for supplying to the second load port; and provided between the pump port and the first feeder port, for supplying pressure oil from the first feeder port to the pump port. And a load check valve to prevent flow, the flow control valve which enables supplying a maximum flow rate specified in the hydraulic actuator,
In the passage from the pump port to the first feeder port, at a position upstream of the seat portion of the load check valve, a constant flow passage area is provided, and pressure oil from the pump port receives the load check. There is provided resistance generating means for opening the valve seat portion to give resistance to the flow of the pressure oil when flowing into the first load port via the first feeder port and the first variable throttle. and so that the maximum flow rate of the prescribed in the actuator to compensate for pressure drop caused by the resistance generating means can be supplied, the prescribed maximum opening area of the first variable throttle without providing the resistance generating means A flow rate control valve characterized in that it is set larger than the maximum flow rate that can be supplied . 3. The flow rate control valve according to claim 2, wherein the relationship between the resistance generating means and the maximum opening area of the first variable throttle is set so that the pressure drop due to the resistance generating means is larger than the pressure drop due to the first variable throttle. A flow control valve characterized by that. 3. The flow control valve according to claim 1, wherein the resistance generating means is provided in the load check valve. 5. The flow rate control valve according to claim 4, wherein the resistance generating means is an opening throttle provided in a valve body of the load check valve. At least one spool valve body slidably provided in the housing, first and second pump ports provided in the housing and connected to a hydraulic pressure source, and first and second connected to an actuator The first and second variable ports are provided in the spool valve body corresponding to the first load port and the first and second load ports, and change the size of the opening area from the blocking position according to the amount of movement. A throttle, a first feeder port that is provided in the housing and supplies the hydraulic pressure of the hydraulic source to the first load port via the first variable throttle, and the hydraulic oil of the hydraulic source is the second A second feeder port that supplies the second load port via the variable throttle, and is provided between the first pump port and the first feeder port, and is connected to the first pump port. Reverse of pressure oil A first load check valve for blocking the pressure, and is slidably provided between the second pump port and the second feeder port, and pressure from the second feeder port to the second pump port A flow control valve comprising a second load check valve for preventing back flow of oil and capable of supplying a prescribed maximum flow rate to the hydraulic actuator ;
Only in the passage from the first pump port to the first feeder port, and at a position upstream of the seat portion of the first load check valve, has a constant flow area , When the pressure oil from the pump port opens the seat portion of the load check valve and flows into the first load port via the first feeder port and the first variable throttle , It provided a resistance generating means for providing a resistance to the flow, and the maximum opening area of the resistance generating means to compensate for the pressure drop due to the maximum flow rate of the prescribed can be supplied to the actuator, the first variable throttle A flow rate control valve, wherein the flow rate control valve is set larger than the case where the specified maximum flow rate can be supplied without providing the resistance generating means.

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