JPS62171504A - Fluid control device - Google Patents

Abstract

PURPOSE:To perform correct flow regulation by constituting a fluid control device with a main valve and first, second and third pilot valves. CONSTITUTION:A fluid control device is constituted with a main valve 40 consisting of a poppet valve part 42a and a piston part 42c, a first pilot valve 50 consisting of a pressure reducing valve 51, a throttle 52 and a current control relief valve 53, a second pilot valve 60 consisting of first and second switching valves 61, 62 and a third pilot valve 70 consisting of a relief valve 71 and a switching valve 72. Then unless the third pilot valve 70 acts, pressure in the flow path acting on the poppet valve part 42a and the piston part 42c is offset. Therefore, position of the valve body of the main valve 40 can be determined by determining the value of current to be supplied to the first pilot valve 50, and correct flow regulation can be made.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluid control device, and particularly to a fluid control device having a flow rate control function, a pressure holding function, and an IJ-F function.

[Prior art]

A conventional fluid control device of this type is shown in FIG. 6, and the fluid control device shown in FIG.
The main components are a pilot valve 20 and a relief valve 30. The main valve 10 has a large-diameter hole 11a and a small-diameter hole 11b connected to each other, and a valve seat 11C is formed at the step of the connection, and the small-diameter hole side is connected to an actuator (not shown) with the valve seat 11C in between. A valve body 11 that serves as an inflow passage lid and an outflow passage lie whose large diameter hole side is connected to a reservoir;
is slidably inserted into the large diameter hole 11a of the back pressure chamber R via a sealing member 12 such as an O ring or a backup ring.
A poppet valve body 1 that forms an O and seats on or leaves the valve seat 11c to interrupt communication between the inflow path lid and the outflow path lie.
3, a spring 14 that is incorporated in the back pressure chamber RO and urges the poppet valve element 13 toward the valve seat IC, and a valve seat 11c of the poppet valve element 13 that is attached to the valve body 11 so as to be able to be screwed back and forth.
Stopper screw 15 that adjustably defines the amount of lift from
It is made up of. On the other hand, the virofft valve 20 is
This is an electromagnetic switching valve that supplies and discharges pilot pressure to the back pressure chamber RO, and in the non-operating state shown in the figure, the pilot pressure is supplied to and discharged from the back pressure chamber R.
2, and discharges the viroft pressure from the back pressure chamber Ro in the operating state. Further, the relief valve 30 is provided in parallel with the main valve 10, and relieves the oil pressure in the inflow passage lid when the oil pressure reaches a predetermined value.

With the above configuration, in the device shown in FIG. 6, if the pilot valve 20 is in an inoperative state and pilot pressure is supplied to the back pressure chamber RO, the poppet valve body 13 is activated by the pilot pressure and the force of the spring 14. Since the valve seat 11c is seated on the valve seat 11c, communication between the inflow path 11d and the outflow path lie is cut off, and the hydraulic pressure in the inflow path lid is maintained (pressure holding function).

In this state, when the oil pressure in the inflow path lid reaches a predetermined value, the relief valve 30 is activated and the pressure oil in the inflow path lid flows toward the reservoir, suppressing an excessive increase in the oil pressure in the inflow path lid. Actuators etc. are protected (relief function).

Further, when the pilot valve 20 is operated and the pilot pressure is discharged from the back pressure chamber RO, the poppet valve body 13 comes into contact with the stopper screw 15 due to the pressure of the hydraulic oil that is about to flow from the inflow path lid to the outflow path 11e. The stopper screw 1 is inserted from the inflow path lid to the outflow path lie.
Hydraulic oil flows at a flow rate set by 5 (flow rate control function).

Note that there is no flow between the pilot valve 20 and the main valve 10! Since the i amount adjusting valve 1.32 is interposed, the opening/closing speed of the poppet valve body 13 is adjusted.

[Problem that the invention seeks to solve]

By the way, in the conventional fluid control device described above, when adjusting the flow rate, the poppet valve body 13, which has a large pressure receiving area and receives a large force, must be directly moved by the stopper screw 15, and the operation requires a large force. is necessary. Furthermore, the flow rate is adjusted by moving the poppet valve body 13 of the main valve 10 using the stopper screw 15, and since the flow rate changes greatly with a slight movement of the poppet valve body 13, it is important to minimize the pinch of the stopper screw 15. However, it is difficult to set the flow rate (fine adjustment).

In addition, in the above-described conventional fluid control device, although the opening and closing speed of the poppet valve body 13 can be adjusted by both the flow rate adjustment valves 31 and 32, the poppet valve body 13 moves due to the difference in the pressing force acting on both sides thereof. Since it is a back pressure chamber R
The opening/closing speed of the poppet valve body 13 fluctuates due to fluctuations in the pilot pressure supplied to O and fluctuations in the internal pressures of the inflow passage lid and the outflow passage lie.

Furthermore, in the conventional fluid control device described above, the main valve 10 and the relief valve 30, which are its constituent members, control a large flow rate and are large. There is a problem.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a fluid control device in which small diameter holes of the same diameter are connected to both ends of a large diameter hole, and a valve seat is formed in one of the connected steps. a valve body, and a poppet valve part that is fitted into the large diameter hole and forms a first oil chamber on one side that constantly communicates with the inflow passage, and that is seated on the valve seat and opens and closes the valve seat when separated. and a second oil chamber connected to one example of the poppet valve portion, extending into the one small diameter hole, and constantly communicating with the outflow passage between the small diameter hole and communicating with the first oil chamber through the valve seat. and a third connecting portion connected to the connecting portion and slidably inserted into the one small diameter hole and at the end of the small diameter hole.
A piston part that forms an oil chamber is integrally provided, and the piston part is connected to the other side of the poppet valve part, and is slidably inserted into the other small diameter hole, and a throttle is provided at the end of the small diameter hole on the inflow path side. A fifth oil chamber is formed at the end of the large diameter hole and communicates with the inflow passage through a second throttle.
a main valve provided with a valve body integrally having a small diameter portion forming an oil chamber, and a spring that urges the valve body toward the third oil chamber; a first pilot valve that proportionally controls pilot pressure according to a current applied value; and a first pilot valve whose operation is controlled by the pilot pressure to cut off communication between the fourth oil chamber and the return path when the pilot pressure is less than a set value. a second pilot valve that communicates the fourth oil chamber with the return passage when the pilot pressure is equal to or higher than a set value; The third pilot valve is configured to operate when the oil pressure in the oil chamber reaches a predetermined value to relieve the oil pressure and also to relieve the oil pressure in the fourth oil chamber.

[Action of the invention]

In the fluid control device according to the present invention, unless the third pilot valve operates, the inflow passage side hydraulic pressure is applied to the first oil chamber and the fifth oil chamber, and the pressing force acting on the poppet valve portion is canceled out. The valve body of the main valve is not pushed by fluctuations in the inflow passage side oil pressure applied to the first oil chamber and the fifth oil chamber. On the other hand, the oil pressure on the outflow side acts on the poppet valve part and the piston part of the valve body of the main valve in the second oil chamber, and the pressing force is canceled out, so the fluctuation in the oil pressure on the outflow side causes the valve body of the main valve to You will not be pushed.

Furthermore, when the current applied to the first pilot valve is less than the set value and the pilot pressure applied to the third oil chamber is less than the set value, the second pilot valve closes the communication between the fourth oil chamber and the return path. It's blocked. For this reason, the valve body of the main valve is pressed against the pilot pressure in the third oil chamber by the hydraulic pressure applied to the fourth oil chamber from the inflow path side through the throttle and the action of the spring, and the poppet valve part is pressed against the valve seat. is seated, communication between the inflow and outflow channels is cut off, and the hydraulic pressure on the inflow channel is maintained (
pressure holding function). When the inflow passage side oil pressure reaches a predetermined value in such a state, the third pilot valve is activated and the fourth oil chamber and the fifth oil chamber are activated.
In order to relieve the hydraulic pressure in the oil chamber, the valve body of the main valve is operated by the differential pressure between the first oil chamber hydraulic pressure and the fifth oil chamber hydraulic pressure, and the differential pressure between the third oil chamber hydraulic pressure and the fourth oil chamber hydraulic pressure (mainly the former). differential pressure) causes it to slide against the action of the spring. Therefore, the poppet valve portion of the valve body separates from the valve seat, and pressure oil flows from the inflow path to the outflow path, suppressing an excessive increase in the oil pressure on the inflow path side (relief function).

However, when the current applied to the first pilot valve is equal to or higher than the set value and the pilot pressure applied to the third oil chamber is equal to or higher than the set value, the second pilot valve operates and the fourth oil chamber is directed to the return path. communicate. Therefore, the oil pressure in the fourth oil chamber decreases, and the valve body of the main valve is pressed by the pilot pressure in the third oil chamber (which is set to a value higher than the set value by the first pilot valve) and the spring pressure. The acting force (specifically, the resultant force of the acting force and the pressing force due to the hydraulic pressure remaining in the fourth oil chamber) is maintained at a balanced position, and the flow rate from the inflow path to the outflow path is regulated. Therefore, by changing the current applied to the first pilot valve and the pilot pressure applied to the third oil chamber, the position of the valve body of the main valve can be adjusted, and the flow rate flowing from the inflow path to the outflow path can be adjusted. can do(
flow control function).

In addition, in the fluid control device according to the present invention, if the value of current applied to the first pilot valve is appropriately time constant controlled to appropriately adjust the rate of increase or decrease of the pilot pressure applied to the third oil chamber, The opening speed and closing speed of the valve body of the main valve can be adjusted as appropriate.

〔Effect of the invention〕

As is clear from the above explanation of the operation, in the fluid control device according to the present invention, unless the third pilot valve is operated, the pressing force due to the inflow passage side hydraulic pressure acting on the poppet valve portion of the valve body of the main valve is canceled out. At the same time, the pressing force due to the oil pressure on the outflow passage side acting on the poppet valve part and the piston part is canceled out, and by determining the value of the current applied to the first pilot valve, regardless of fluctuations in the oil pressure on the inflow passage side and the oil pressure on the outflow passage side, Since the position of the valve body of the main valve can be set, the operation is not only extremely easy, but also the position of the valve body can be set accurately, allowing accurate flow rate adjustment.

In addition, in the fluid control device according to the present invention, unless the third pilot valve operates, the pressing force due to the inflow passage side hydraulic pressure acting on the poppet valve portion of the valve body of the main valve is canceled out, and the poppet valve portion and the piston portion are If the pressing force due to the acting oil pressure on the outflow path side is canceled out and the fourth oil chamber is communicated with the return path due to the operation of the second pilot valve,
Since the valve body of the main valve is not pushed due to fluctuations in the inflow passage side oil pressure or the outflow passage side oil pressure, the valve body of the main valve is set by appropriately controlling the time constant of the current applied to the first pilot valve. The opening/closing speed is not affected by fluctuations in the inflow passage side oil pressure or the outflow passage side oil pressure, and can always be obtained stably.

Furthermore, the fluid control device according to the present invention includes a single main valve that controls a large flow rate, and a first valve that controls a small flow rate. Since it uses the second and third pilot valves as its constituent members, it can be made smaller compared to the conventional fluid control device shown in Figure 6, reducing installation space and cost. .

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows a fluid control device according to the present invention, which includes a main valve 40. 1st pilot valve 50° 2nd. It is composed of a pilot valve 60 and a third pilot valve 70.

As shown in FIGS. 1 and 2, the main valve 40 has a first
The valve body 41 is made up of a member 41A, a second member 41B, and a third member 41C, and the valve body 41 is fitted into the valve body 41 so as to be slidable in the vertical direction. It is composed of a valve body 42 and a spring 43 that urges the valve body 42 downward. The valve body 41 is
Small diameter holes 41b and 41 with the same diameter are provided at both upper and lower ends of the large diameter hole 41a.
The valve seats 41d are connected to each other and the valve seats 41d are connected to each other.
It has a stepped inner hole formed by forming an inflow path P1.
It has an annular groove 41e that communicates with the annular groove 41e and an annular groove 41f that communicates with the outflow path P2.

The valve body 42 is slidably inserted into the large-diameter hole 41a, forms a first oil chamber R1 that is always in communication with an inflow path PL connected to an actuator (not shown), and is seated on a valve seat 41d. A poppet valve section 42 that opens and closes communication between the inflow path P1 and the outflow path 22 connected to the reservoir 80.
an outflow path P that is connected to the lower side of the poppet valve part 42a and extends into the lower small diameter hole 41b;
2 is connected to the connecting portion 42b forming a second oil chamber R2 that is always in communication and communicates with the first oil chamber R1 through the valve seat 41d, and the connecting portion 42b is connected to the connecting portion 42b and is slidably fitted into the small diameter hole 41b below. A piston part 42c is integrally inserted into the small diameter hole 41b and forms a third oil chamber R3 at the end of the small diameter hole 41b, and the small diameter hole 41C is slidably inserted into the upper small diameter hole 41c above the poppet valve part 42a. A small diameter cylindrical portion 42 that forms a fourth oil chamber R4 at the end and a fifth oil chamber R5 at the end of the large diameter hole 41a.
d is integrally provided. Thus, the third oil chamber R3 is connected to the first pilot valve 50 and the first switching valve 61 of the second pilot valve 60, and the fourth oil chamber R4 is connected to the inflow path P1 via the throttle 44. The second
It is connected to the second switching valve 62 of the pilot valve 60, and the fifth oil chamber R5 communicates with the inflow path P1 via the second throttle 45, and is also connected to the third viroft valve 70.

The first viroft valve 50 includes a pressure reducing valve 51 that reduces the pressure of pressure oil introduced through the supply path P3 to a predetermined value, and this pressure reducing valve 5.
The current control relief valve 53 proportionally controls the pilot pressure applied from 1 to the third oil chamber R3 through the throttle 52 in accordance with the current applied value. The second pilot, If-60, as shown in Figures 1 and 3,
It is comprised of a first switching valve 61 whose operation is controlled by the pilot pressure applied to the third oil chamber R3, and a second switching valve 62 whose operation is controlled by the first switching valve 61. The first switching valve 61 includes a spool valve body 61a and a spring 61b, and is inoperative as shown in the figure when the pilot pressure applied from the third oil chamber R3 to the oil chamber R6 through the passage P5 is less than a set value. In this state, the connection between the supply path P3 and the second switching valve 62 is cut off, and when the pilot pressure is equal to or higher than the set value, the operation state is established and the supply path P3 is connected to the second switching valve 62. The second switching valve 62 includes a piston 62a that integrally has a protrusion, a poppet valve body 62b, and a spring 6.
2c, which operates when the oil chamber R7 is connected to the supply path P3 by the first switching valve 61, and connects the passage P6 communicating with the fourth oil chamber R4 and the return path P4 communicating with the reservoir 80, Further, when the oil chamber R7 is disconnected from the supply path P3 and connected to the return path P4 by the first switching valve 61, it becomes inactive as shown in the figure, and the passage P6 communicating with the fourth oil chamber R4 and the return path P4 become inactive as shown in the figure. The communication of path P4 is cut off.

The third pilot valve 70 operates when the oil pressure in the fifth oil chamber R5, which is applied from the inflow path P1 through the throttle 45, reaches a predetermined value, and causes the hydraulic oil in the fifth oil chamber R5 to flow into the return path P4. It is composed of a relief valve 71 and a switching valve 72 that operates in response to the operation of the relief valve 71. As shown in FIGS. 1 and 4, the switching valve 72 has a valve body 72.
a and a spring 72b, and the oil pressure in the fifth oil chamber R5, which is applied to the oil chamber R8 through the passage P7, is applied to the relief valve 71.
When it is not relieved by the relief valve 71, it is in an inactive state as shown in the figure, and the connection between the oil chamber R9 communicating with the fourth oil chamber R4 and the return path P4 is cut off, and the oil pressure applied to the oil chamber R8 is controlled by the relief valve 71. When relieved, the valve body 72a slides against the spring 72b by the hydraulic pressure in the inflow path Pl applied to the oil chamber RIO through the path P8, thereby connecting the oil chamber R9 to the return path P4.

In this embodiment configured as described above, unless the third pilot valve 70 is operated, the inflow passage Pl side hydraulic pressure is applied to the first oil chamber R1 and the fifth oil chamber R5 and acts on the poppet valve portion 42a. Since the pressing forces are offset, the valve body 42 of the main valve 40 is not pushed by fluctuations in the inflow path Pl side oil pressure applied to the first oil sac R1 and the fifth oil sac R5.

On the other hand, the oil pressure on the outflow path P2 side acts on the poppet valve part 42a and the piston part 42c of the valve body 42 in the second oil chamber R2, and the pressing force thereof is canceled out. The valve body 42 of the valve 40 is not pushed.

Further, when the current applied to the relief valve 53 in the first pilot valve 50 is less than the set value and the pilot pressure applied to the third oil chamber R3 is less than the set value, as shown in the figure, the second pilot First switching valve 61 in valve 60
is in an inoperative state, cutting off the connection between the supply path P3 and the second switching valve 62, and the second switching valve 62 is in an inactive state, cutting off communication between the fourth oil chamber R4 and the return path P4. There is. Therefore, the valve body 42 of the main valve 40 is connected from the inflow path -P1 to the throttle 4.
Hydraulic pressure applied to the fourth oil chamber R4 through 4 and the spring 43
The poppet valve portion 42a is seated on the valve seat 41d, and communication between the inflow path P1 and the outflow path P2 is blocked. Therefore, the oil pressure in the circuit including the inflow path P1 from the main valve 40 to the actuator (not shown) is maintained, and the actuator is maintained in its stopped state (pressure holding function).

In this state, an excessive load is applied to the actuator, and the oil pressure in the hydraulic circuit including the above-mentioned inflow path P1 increases, and the oil pressure in the fifth oil chamber R5 is set by the relief valve 71 of the third pilot valve 70. When the predetermined value is reached, the oil passage P7
Pressure oil in the fourth oil chamber R4 of the main valve 40 flows to the return path P4 through the changeover valve 72 and operates the switching valve 72. Therefore, in such a case, the main valve 4
The valve body 42 of No. 0 has a pressure difference between the hydraulic pressure in the first oil chamber R1 and the hydraulic pressure in the fifth oil chamber R5, and the differential pressure between the hydraulic pressure in the third oil chamber R3 and the hydraulic pressure in the fourth oil chamber R4 (mainly the difference in the former). pressure), it slides against the action of the spring 43. Therefore, the poppet valve portion 42a of the valve body 42 separates from the valve seat 41d, and pressure oil flows from the actuator to the reservoir 80, suppressing an excessive increase in the oil pressure in the hydraulic circuit between the main valve 40 and the actuator, and causing the actuator, etc. protected.

Therefore, the relief valve 5 in the first pilot valve 50
When the pilot pressure applied to the third oil chamber R3 is made equal to or higher than the set value by setting the current applied to P3 to the set value or more, the first switching valve 61 in the second pilot valve 60 operates to switch the supply path P3 to the second oil chamber R3. In order to connect to the switching valve 62, the second switching valve 62
operates to communicate the fourth oil chamber R4 with the return path P4. For this reason, the oil pressure in the fourth oil chamber R4 decreases, and the valve body 42 of the main valve 40 releases the pilot pressure in the third oil chamber R3 (which is set to a value equal to or higher than the set value by the first viroft valve 50). ) and the acting force of the spring 43 (more specifically, the resultant force of the acting force and the pressing force due to the hydraulic pressure remaining in the fourth oil chamber R4) are maintained at a position where the pressure is balanced, and the flow from the inflow path P1 to the outflow path is maintained. The flow rate flowing to P2 is defined. Therefore, the first
By changing the value of current applied to the relief valve 53 in the pilot valve 50 and changing the pilot pressure applied to the third oil chamber R3, the position of the valve body 42 of the main valve 40 can be adjusted, and the position of the valve body 42 from the inflow path P1 to the outflow path can be adjusted. The flow rate flowing to P2 can be adjusted (flow rate control function).

In addition, in the fluid control device of the present embodiment, the value of current applied to the relief valve 53 in the first pilot valve 50 is appropriately time constant controlled to increase or decrease the rate of increase or decrease of the biloft pressure applied to the third oil chamber R3. If the main valve 40 is adjusted appropriately, the main valve 40
The opening speed and closing speed of the valve body 42 can be adjusted as appropriate.

As is clear from the above explanation of the operation, in the fluid control device of the present embodiment, unless the third pilot valve 70 is operated, the pressing force due to the hydraulic pressure on the inflow path Pl side acting on the poppet valve portion 42a of the valve body 42 is The outflow path P acts on the poppet valve part 42a and the piston part 42c while canceling each other out.
The pressing force due to the 2 side oil pressure is canceled out, and regardless of the fluctuations in the inflow path Pl side oil pressure and the outflow path P 2 (i13 oil pressure,
By determining the value of current applied to the relief valve 53 in the first pilot valve 50, the position of the valve body 42 of the main valve 40 can be set. Settings can be made accurately and flow rates can be adjusted accurately.

In addition, in the fluid control device of this embodiment, as long as the third pilot valve 70 is not operated, the poppet 7) of the valve body 42 is offset by the pressing force due to the hydraulic pressure on the inflow path Pl side acting on the valve portion 42a, and the poppet Valve part 42a and piston part 42
The pressing force due to the oil pressure on the outflow path P2 side acting on the outflow path P2 side is canceled out, and the operation of the second pilot valve 60 causes the fourth oil chamber R
4 communicates with the return path P4, the valve body 42 of the main valve 40 is not pushed due to fluctuations in the inflow path Pl side oil pressure or the outflow path P2 side oil pressure, so the first pilot valve 5
The opening/closing speed of the valve body 42 of the main valve 40, which is set by appropriately controlling the current applied to the relief valve 53 at 0, is not affected by fluctuations in the oil pressure on the inflow path P1 side or the oil pressure on the outflow path P2 side. , always obtained stably.

Further, in the fluid control device of this embodiment, there is a single main valve 40 that controls a large flow rate, and a single main valve 40 that controls a small flow rate. Second
and third pilot valves 50, 60, and 70 as its constituent members, it can be made smaller compared to the conventional fluid control device shown in Fig. 6, reducing installation space and cost. be able to.

FIG. 5 shows another embodiment of the present invention, and in the fluid control device shown in the same figure, a current-controlled pressure reducing valve 51 is used instead of the first viroft valve 50 consisting of a throttle 52 and a relief valve 53. A first pilot valve 50A consisting of a valve is adopted, and is operated directly by pilot pressure in place of the second pilot valve 60 consisting of a first switching valve 61 and a second switching valve 62 to connect the fourth oil chamber R4 and the return path P4. A second pilot valve 60A is employed, which is a switching valve that communicates with and disconnects from the flow. Similarly to the first pilot valve 50 of the above embodiment, the first pilot valve 50A converts the pilot pressure applied to the third oil chamber R3 into a current. Proportional control is performed according to the applied value, and the operation of the second pilot valve 60A is controlled by the pilot pressure similarly to the second pilot valve 60 of the above embodiment, and when the pilot pressure is less than the set value, the operation is controlled in the fourth oil chamber R4. and return path P4, and when the pilot pressure is above the set value, the fourth
The oil chamber R4 and the return path P4 are communicated with each other.

The functions and effects of the embodiment shown in FIG. 5 are substantially the same as those of the embodiments shown in FIGS. 1 to 4 described above, and are easily understood from the above explanation. In order to
The explanation will be omitted.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a fluid control device according to the present invention, FIG. 2 is a detailed enlarged sectional view of the main valve portion of the device shown in FIG. 1, and FIG. Detailed enlarged cross-sectional view of the second pilot valve section in the illustrated device, No. 4
The figure is a detailed enlarged sectional view of the third pilot valve part in the device shown in Figure 1, Figure 5 is an overall configuration diagram showing another embodiment of the present invention, and Figure 6 is an overall configuration diagram showing a conventional example. It is. Explanation of symbols 40...Main valve, 4■...Valve body, 41a...Large diameter hole, 41b, 41C...Small diameter hole, 41d...Valve seat,
42... Valve body, 42a... Poppet valve part, 42b.
...Connection part, 42G... Piston part, 42d... Small diameter part, 43... Spring, 44... Throttle, 45... Second throttle, 50° 50A... First pilot valve , 60
．． 60Δ...Second viroft valve, 70...Third pilot valve, Pl...Inflow path, R2...Outflow path, R3
... Supply path, R4... Return path, R1... First oil chamber, R2... Second oil chamber, R3... Third oil chamber, R4...
・4th oil chamber, R5...5th oil chamber.

Claims (1)

[Scope of Claims] A valve body comprising a large-diameter hole and small-diameter holes of the same diameter connected to each other at both ends thereof, and a valve seat formed in one of the continuous steps, and a valve body that is fitted into the large-diameter hole. A first oil chamber is formed on one side of the poppet valve, and the poppet valve portion is connected to one side of the poppet valve portion to open and close the valve seat by seating on or leaving the valve seat. A connecting portion that extends into the one small diameter hole and forms a second oil chamber that is in constant communication with the outflow passage and communicates with the first oil chamber through the valve seat, and is connected to the same connecting portion. and integrally includes a piston portion that is slidably inserted into the one small diameter hole and forms a third oil chamber at the end of the small diameter hole, and is connected to the other side of the poppet valve portion and is connected to the other side of the poppet valve portion. A fourth oil chamber is formed which is slidably inserted into the small diameter hole and connected to the inlet passage side at the end of the small diameter hole via a throttle, and is connected to the inflow passage side at the end of the large diameter hole through a second throttle. a main valve comprising: a valve body integrally provided with a small diameter portion forming a fifth oil chamber communicating with the third oil chamber; and a main valve comprising a spring that urges the valve body toward the third oil chamber; a first pilot valve that proportionally controls the pilot pressure applied to the chamber according to the current applied value; and a return path to the fourth oil chamber whose operation is controlled by the pilot pressure and when the pilot pressure is less than a set value. a second pilot valve that interrupts communication between the fourth oil chamber and the return passage when the pilot pressure is equal to or higher than a set value; and a third pilot valve that operates when the fifth oil chamber hydraulic pressure reaches a predetermined value to relieve the same hydraulic pressure and also relieve the fourth oil chamber hydraulic pressure.