JP2000320703A - Valve device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a pressure setting spring while maintaining a good override characteristic as a relief valve in a pilot poppet valve. SOLUTION: This device is provided with a flow amplification poppet valve 42 is provided in the out side of a meter of an actuator and a modulation system 54 to control a stroke of the flow amplification poppet valve 42 by controlling a pilot flow amount through the flow amplification poppet valve 42. A pilot poppet valve 57 with a relief valve function is connected to the flow amplification poppet valve 42 in parallel with the modulation system 54. The pilot poppet valve 57 is pressed onto a seat part 62 by a coil spring 61 and a pressure receiving surface 81 of a pilot signal pressure pressing the pilot poppet valve 57 in a direction to open it against the coil spring 61 is formed on a portion between a large diameter part 64 and a small diameter part 82 fitting into a stepped hole. The pressure receiving surface 81 is a donut-shaped pressure receiving surface with an area smaller than that of a circle of a diameter of the valve seat part 62.

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 relief valve function.

[0002]

2. Description of the Related Art FIG. 3 shows a control circuit of a meter-in / meter-out type, and FIG. 3 shows a control circuit of a bridge configuration for controlling a single rod / cylinder type actuator 11.

In this control circuit, a tank 15 is connected via a common bypass valve 14 to a discharge port of a variable displacement pump 13 capable of variably controlling a discharge flow rate by a swash plate 12, and a load hold check valve 16 is connected. Having pump line
A bridge circuit 18 is connected via 17.

The bridge circuit 18 includes two meter-in valves 21 and 22 connected to the pump line 17, respectively.
It is formed by two meter-out valves 23 and 24 connected to these meter-in valves 21 and 22, respectively.

[0005] These meter-out valves 23 and 24 are connected to a tank line 25.
Check valves 26 and 27 for replenishing the working oil as the working fluid from the tank line 25 to the negative pressure generating section in the circuit are connected in parallel to the tanks 23 and 24.

A passage 31 drawn out between the meter-in valve 21 and the meter-out valve 23 shown above the bridge circuit 18 is a chamber (hereinafter, referred to as a chamber) on the side of the piston 32 of the actuator 11 where the rod 33 is located. A passage 35 connected to the “rod side chamber” 34 and drawn out from between the meter-in valve 22 and the meter-out valve 24 illustrated below is located closer to the head than the piston 32 of the actuator 11. A room (hereinafter, referred to as a “head-side room”) 36.

The inlet side of the meter-out valve 23 and the meter-out valve 24 has a return passage from the actuator 11.
37.

[0008] The common bypass valve 14, meter-in valve
The throttle valves 21 and 22 and the meter-out valves 23 and 24 are provided with variable throttle means such as a spool valve or a poppet valve whose opening area can be variably controlled by electromagnetic means or pilot hydraulic means. These variable throttle means are operated by a controller. In the case of electromagnetic means, control is directly performed by an electric signal output from the controller, and in the case of pilot hydraulic means, control is performed by a pilot pressure signal via electro-hydraulic conversion means.

The hydraulic oil supplied from the pump 13 to one of the rod-side chamber 34 and the head-side chamber 36 of the actuator 11 and discharged from the other to the tank 15 is supplied to the second chamber.
It is controlled by a bridge circuit 18 formed by two meter-in valves 21 and 22 and two meter-out valves 23 and 24.

For example, when extending the actuator 11 against the load W, the common bypass valve 14 is closed, the meter-in valve 22 on the head side of the actuator 11 is opened, the meter-out valve 24 is closed, and the rod side is closed. The meter-in valve 21 is closed and the meter-out valve
Open 23.

When the actuator 11 is to be contracted, the common bypass valve 14 is closed, the meter-in valve 21 on the rod side of the actuator 11 is opened and the meter-out valve 23 is closed, and the meter-in valve 22 on the head side is closed. Close and open the meter-side valve 24 on the head side.

FIG. 4 shows details of a conventional meter-out valve 23 or 24. In a valve chamber 41 formed in a valve body 40, a pilot flow rate amplification type poppet valve (hereinafter referred to as "flow amplification"). A poppet valve 42) is displaceably provided, and a return passage 37 from the actuator 11 is connected to an inlet port 43 opened in the valve chamber 41.

A pilot control unit 44 is formed at one end of the flow amplification poppet valve 42, and a pilot variable slot 45 in which the area of the opening 45a changes depending on the position of the flow amplification poppet valve 42 near the pilot control unit 44. It is formed in the axial direction.

At the opposite end of the flow amplification poppet valve 42, a drain flow controller 47 is formed at the outlet of the valve chamber 41 and is detachably fitted to a valve seat 46 communicated with the tank 15. The main flow rate control slot 48 is formed in the drain flow rate control section 47.

The pilot controller 44 faces a spring chamber 49, and the flow amplifier poppet valve 42 is pressed in a direction of being pressed toward the valve seat 46, that is, in a closing direction by a coil spring 50 built in the spring chamber 49. ing.

An iron core 51 for position detection is integrally provided at a central portion of the pilot control unit 44, and a coil 52 for position detection is disposed on the valve body 40 side, and a flow amplifier poppet valve 42 such as an operation transformer is provided. A displacement detection sensor for detecting the displacement of the sensor is formed.

As means for controlling the opening of the flow amplification poppet valve 42, a passage 53 and a passage 25a are provided from the spring chamber 49 to the tank line 25,
A modulation stem 54 is interposed in 53. The modulation stem 54 controls the drain of the spring chamber 49 in response to an electric signal from a controller (not shown), and is proportionally controlled by a solenoid 55 against a coil spring (not shown). Is done.

The flow amplification poppet valve 42
A pilot poppet valve 57 for preventing overload is interposed in another passage 56a, 56b drawn from the spring chamber 49 toward the tank 15.

The pilot poppet valve 57 is used to open the spring chamber 49 of the flow amplification poppet valve 42 when an excessive load pressure is generated in the return passage 37 from the actuator 11.
The valve seat 46 is opened by drain control of the valve seat. The poppet taper 58 is formed by a coil spring 61 provided in a spring chamber 60 in a pilot cylinder 59.
Pressed to 62.

The poppet taper 58 has a neck 63
The large-diameter portion 64 is formed integrally with the large-diameter portion 64,
The load pressure is guided slidably into a passage 65 communicating with the return passage 37, and is guided to the circular pressure receiving surface 64a of the large-diameter portion 64 via the passage 65. When the force generated by the action is larger than the preload of the coil spring 61, the valve seat portion 62 is opened.

Further, a pilot piston 66 for adjusting the spring force of the coil spring 61 is slidably fitted in the pilot cylinder 59, and an adjusting screw
Locked by 67. The pilot cylinder 59 has
A port 68 for supplying a pilot pressure from the outside to the pilot piston 66 is provided, and an external pilot pressure signal generator is connected to the port 68.

This external pilot pressure signal generating device
Associated piping where the pilot pump 69 has an electromagnetic proportional pressure reducing valve 70
A pilot relief valve 72 for setting a pump discharge pressure is provided in a discharge line of the pilot pump 69, which is connected to a port 68 through a port 71.

Next, the operation of the conventional meter-out valve control device shown in FIG. 4 will be described.

(1) Return flow Q from actuator 11
Is guided to the inlet port 43 of the flow amplification poppet valve 42, and the flow rate q therein flows into the spring chamber 49 through the opening 45a of the pilot variable slot 45.
The stroke control of the flow amplification poppet valve 42 is performed by the modulation stem connected to the spring chamber 49.
Achieved with 54 degree of opening control, the flow through this part is
It is shown in the drawing q _2. Upper pilot poppet valve
Pilot flow rate q ₁ pilot poppet valve toward 57
It is zero when 57 is closed, then q = q ₂ . On the other hand, by controlling the stroke of the flow amplification poppet valve 42, the main flow control slot 48 at the right end in FIG.
There opened, main flow LQ is controlled, shows the main flow LQ is though aspects of the pilot flow rate q ₂ is amplified in the modulation system 54.

(2) Next, this modulation stem
When 54 is closed and both q ₂ and LQ are zero,
When the return pressure of the return passage 37 from the actuator 11 rises and the force acting on the tip circular pressure receiving surface 64a of the large diameter portion 64 provided at the tip of the pilot poppet valve 57 overcomes the repulsive force of the coil spring 61, poppet tapered portion 58 is opened from the valve seat 62, the pilot flow rate q ₁ starts to flow (in this case becomes q = q _1), the opening 45a of the pilot variable slot 45 of the flow amplifier Reference Ipoh pets valve 42
, A flow amplification poppet valve 42 moves to the left in the figure, a main flow control slot 48 is opened, and a main flow LQ is generated, so that the return pressure of the return passage 37 from the actuator 11 is abnormal. The rise is suppressed, and the pressing force of the spring 61 acting on the pilot poppet valve 57 is almost settled by a pressure value obtained by dividing the pressing force by the pressure receiving area of the circular pressure receiving surface 64a. That is, it also has a relief valve function.

(3) The pilot poppet valve 57 having the above-described relief valve function requires the opening gain thereof not to be increased.
The lift amount of the flow amplification poppet valve 42 does not increase. That is, the flow amplification poppet valve
The opening of the pilot variable slot 45 of 42 becomes large, and q
That is, when q ₁ is not properly large, personality that override characteristics as a relief valve (that override pressure is the differential pressure between the cracking pressure when the total amount pressure during the valve fully open and the valve opening is small is desirable) is not improved Yes, the diameter of the valve seat portion 62 with respect to the pilot poppet valve 57 and the large-diameter portion at the tip to improve the override characteristics
It is necessary to increase the diameter of 64. And since the pressure receiving area of the large diameter portion 64 has to be large in this way,
In order to set a high-pressure relief valve, the spring force of the coil spring 61 must necessarily be increased.

For this reason, as shown in FIG. 4, in a structure having a variable set pressure, a coil spring
Because the spring force of 61 is strong, it is difficult to control the spring force of the coil spring 61 with a normal small thrust electromagnetic actuator. As shown in FIG. An external pilot pressure is applied from a pilot oil pressure source including a valve 70 and a pilot relief valve 72 via a related pipe 71 to control the thrust of the pilot piston 66 and control the compression amount of the coil spring 61. Therefore, there are many related parts, and there is a disadvantage that the cost is high.

[0028]

As described above, conventionally,
In order to improve the override characteristics of the relief valve, the pressure setting spring must be increased in size, and the setting pressure of the powerful large spring cannot be variably controlled by a small thrust electromagnetic actuator, resulting in expensive electromagnetic Since the amount of spring compression is controlled by an external pilot pressure signal generator using a proportional pressure reducing valve or the like, there is a problem that the cost is increased.

The present invention has been made in view of the above points, and by improving the shape of the pilot poppet valve, it is possible to reduce the size of the pressure setting spring while ensuring good override characteristics as a relief valve. The purpose is to be able to variably control the relief valve set pressure with an inexpensive electromagnetic actuator,
The purpose is to reduce costs.

[0030]

According to the first aspect of the present invention, there is provided a valve seat portion, a pilot poppet valve having a relief valve function which is provided on the valve seat portion so as to be capable of coming and going.
A spring for pressing the pilot poppet valve against the valve seat portion, and a pressure receiving surface having an area smaller than the area of the valve seat portion for receiving a pilot signal pressure for pressing the pilot poppet valve in the opening direction against the spring. A valve device comprising:

Since the pressure receiving surface of the pilot signal pressure has an area smaller than the area of the valve seat portion of the pilot poppet valve, a sufficient opening gain can be secured in the valve seat portion, and a good override characteristic as a relief valve is secured. While the pilot signal pressure receiving area is small,
The pressure setting spring can be downsized.

According to a second aspect of the present invention, a pilot flow amplification type poppet is provided on the meter-out side of the actuator, and the pilot flow amplification type poppet is controlled by controlling the pilot flow of the pilot flow amplification type poppet valve. A pilot modulation valve for controlling a valve stroke, and a pilot flow amplification type poppet valve, which is connected in parallel with the pilot modulation valve and has an area smaller than an area of a circle having the same diameter as the diameter of the valve seat portion according to claim 1. And a pilot poppet valve having a pilot signal pressure receiving surface.

When the pilot poppet valve functions as a relief valve with respect to the pilot flow amplification type poppet valve in which the pilot flow is controlled by the pilot modulation valve, the pilot signal pressure having a smaller area than the valve seat area is received. A pilot poppet valve having a surface can increase its opening gain, secure a large lift amount of a pilot flow amplification type poppet valve, and maintain a good override characteristic as a relief valve, while the pressure receiving surface of the pilot signal pressure is Since it is small, the pressure setting spring can be downsized.

According to a third aspect of the present invention, there is provided a donut-shaped pressure receiving surface formed between the large-diameter portion and the small-diameter portion fitted in the stepped hole. Surface.

By reducing the difference in diameter between the large diameter portion and the small diameter portion, the area of the pressure receiving surface in the form of a donut area can be made sufficiently small. The thrust of the valve can be made sufficiently small, the spring force for setting the relief valve pressure can be made sufficiently small, and the spring can be made sufficiently small.

According to a fourth aspect of the present invention, in the valve device according to the first or second aspect, the diameter of the valve seat portion of the pilot poppet valve is smaller than that of the valve seat portion and is abutted on the end face of the poppet valve opposite to the spring. It has a separate small-diameter piston, a pressure-receiving surface provided on the end face opposite to the contact side of the small-diameter piston, and a pressure chamber for applying a pilot signal pressure to the pressure-receiving surface.

Since the pilot signal pressure is transmitted to the pilot poppet valve via the small-diameter piston received on the pressure receiving surface having a smaller diameter than the valve seat portion, the thrust of the pilot poppet valve can be reduced even if the pilot signal pressure becomes high. The spring force for setting the pressure of the relief valve can be reduced, and the size of the spring can be reduced, and the pilot poppet valve and the separate small-diameter piston can be easily machined.

According to a fifth aspect of the present invention, there is provided the valve device according to any one of the first to fourth aspects, wherein the pilot poppet valve is provided in parallel with the spring to variably control the set pressure of the relief valve function. It is a valve device provided with a pressure varying means.

Since the set pressure varying means installed in parallel with the spring acts directly on the pilot poppet valve without any intervening spring, there is no need to adjust the expansion and contraction of the spring, and the space of the spring can be saved.

According to a sixth aspect of the present invention, there is provided a valve device according to the fifth aspect, wherein the set pressure varying means is an electromagnetic actuator.

In the valve device according to any one of the first to fourth aspects, the spring for setting the pressure can be reduced in size, so that a small spring force can be obtained without using a conventional expensive external pilot pressure signal generator. Even with an inexpensive electromagnetic actuator with a small thrust that is almost compatible, the pressure setting of the relief valve can be variably controlled, and costs can be reduced.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. 1, and another embodiment will be described with reference to FIG. FIG. 3 is also used in the embodiment according to the present invention.

FIG. 1 shows the internal structure of the meter-out valve 23 and the meter-out valve 24. In a valve chamber 41 formed in a valve body 40, a pilot flow rate amplification type poppet valve (hereinafter referred to as a poppet valve). A “flow amplification poppet valve” 42) is provided so as to be displaceable, and the actuator is connected to an inlet port 43 opened in the valve chamber 41.
A return passage 37 from 11 (FIG. 3) communicates.

A pilot control section 44 is formed at one end of the flow amplification poppet valve 42, and a pilot variable slot 45 in which the area of the opening 45a changes depending on the position of the flow amplification poppet valve 42 near the pilot control section 44. It is formed in the axial direction.

At the opposite end of the flow amplification poppet valve 42, a drain flow control unit 47 is formed at the outlet of the valve chamber 41 and is detachable from a valve seat 46 communicated with the tank 15. The main flow rate control slot 48 is formed in the drain flow rate control section 47.

The pilot controller 44 faces the spring chamber 49, and the flow amplifier poppet valve 42 is pressed toward the valve seat 46, that is, in the closing direction by the coil spring 50 built in the spring chamber 49.

An iron core 51 for position detection is integrally provided at the center of the pilot control unit 44, and a coil 52 for position detection is arranged on the valve body 40 side, and a flow amplifier poppet valve 42 such as an operation transformer is provided. A displacement detection sensor for detecting the displacement of the sensor is formed. This displacement detection sensor is used for feedback control of the flow amplification poppet valve 42, monitoring of the valve operation, and the like. However, this displacement detection sensor is not essential and may be omitted in some cases.

As means for controlling the opening of the flow amplification poppet valve 42, a passage 49a, a passage 53a, a passage 53b and a passage 25a are provided from the spring chamber 49 to the tank line 25, and pilot modulation is provided in the passages 53a, 53b. Modulation stem 54 as a valve
Is interposed.

The modulation stem 54 controls the flow rate of the drain from the spring chamber 49 of the flow amplification poppet valve 42 according to an electric signal from a controller (not shown), that is, controls the pilot flow rate of the flow amplification poppet valve 42. By doing so, the stroke of the flow amplification poppet valve 42 is pilot-controlled, and the control valve portion 54a provided at one end of the modulation stem 54 is connected to the spring receiving plate 54b locked at the other end. Push type solenoid that is pressed in the closing direction by the provided coil spring 54c and receives an electric signal from the controller
When the push rod 55b pushes the push rod 55b in response to the electric signal, the control valve portion 54a is proportionally controlled to the opening corresponding to the electric signal (the amount of electricity).

The flow amplifier poppet valve 42
The passages 56a, 56b and 25 branch from the passage 49a over the spring chamber 49 of the tank line 25.
The pilot poppet valve 57 having a relief valve function for preventing overload is interposed in the passages 56a and 56b.

That is, a pilot poppet valve 57 is connected to the spring chamber 49 of the flow amplification poppet valve 42 in parallel with the modulation stem 54.

The pilot poppet valve 57 is used to open the spring chamber 49 of the flow amplification poppet valve 42 when an excessive load pressure is generated in the return passage 37 from the actuator 11.
The valve seat portion 46 is opened by drain control, and a poppet taper portion 58 has a spring chamber formed in the valve body 40.
Coil spring 61 as a spring provided in 60
Is pressed by the valve seat portion 62 which can be freely contacted and separated.

The poppet taper 58 has a neck 63
A large-diameter portion 64 is formed integrally with the small-diameter portion 82 via a pressure receiving surface 81 in the form of a donut area. The large diameter portion 64 and the small diameter portion 82 are slidably fitted in the stepped holes.

The diameter of the valve seat portion 62 and the large diameter portion 64 is
In order to improve the override characteristics of the pilot poppet valve 57 as a relief valve (the override pressure, which is the differential pressure between the total pressure when the valve is fully opened and the cracking pressure when the valve is opened, is desirably small), Although formed in a diameter, the pressure receiving surface 81 in the shape of a donut area has a smaller area than the conventional circular pressure receiving surface 64a (FIG. 4) and has an area smaller than the area of the valve seat portion 62. The area of the valve seat portion 62 is the area of a circle having the same diameter as the diameter of the inner space of the valve seat portion 62.

The pressure receiving surface 81 in the form of a donut area faces a pressure chamber 83 formed in the valve body 40 for applying a pilot signal pressure.
The valve 41 communicates with a return passage 37 from the actuator via the valve chamber 41.

Therefore, the load pressure from the actuator 11 is guided to the donut area-shaped pressure receiving surface 81 via the passage 65, and the pilot pressure is applied to the pilot poppet valve against the coil spring 61.
It becomes the pilot signal pressure to press 57 in the opening direction.

On the other hand, a chamber 84 facing the front end surface of the small diameter portion 82
Communicates with the passage 56b through the passage 85,
a, and communicates with the tank line 25.

The coil spring 61 for pressing the pilot poppet valve 57 in the closing direction is locked at a fixed position by a solenoid mounting portion 86 fixed to the valve body 40. Further, the solenoid mounting portion 86 is provided with an electromagnetic actuator 87 as means for varying the set pressure of the pilot poppet valve 57.

In this electromagnetic actuator 87, a small push type solenoid 88 is provided in a solenoid mounting portion 86, and the tip of a push rod 89 operated by the push type solenoid 88 abuts on the end face of the pilot poppet valve 57. Have been.

That is, the push rod 89 of the electromagnetic actuator 87 is directly in contact with the pilot poppet valve 57 similarly to the coil spring 61, and
61 and electromagnetic actuator 87 are pilot poppet valve 57
Are configured to act in parallel with respect to each other.

As described above, (1) The opening control mechanism by the modulation stem 54 for controlling the stroke of the flow amplification poppet valve 42 is almost the same as the conventional one shown in FIG. 4, but functions as a relief valve. The structure of the pilot poppet valve 57 for determining the set pressure is different.

[0062] (2) The pilot poppet valve 57 to the override characteristic as a relief valve with favorable, for flowing without resistance the pilot flow rate q _1, has a larger valve seat diameter considerably. However, the pressure receiving area for sensing the return pressure of the return passage 37 from the actuator 11 is defined as a donut area shaped pressure receiving surface 81 between the large diameter portion 64 and the small diameter portion 82 fitted in the stepped hole, and the large diameter portion The area of the pressure receiving surface 81 is made sufficiently small by reducing the difference in diameter between the small diameter portion 64 and the small diameter portion 82.

(3) With the above structure, the actuator
Even if the return pressure in the return passage 37 from 11 becomes high, the thrust given to the pilot poppet valve 57 can be small. Therefore, the size of the coil spring 61 can be reduced, and the coil spring 61
In parallel with 61, a small electromagnetic actuator 87 having a level comparable to the spring force and its maximum thrust can be installed.

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

(1) By increasing the diameter of the valve seat portion 62 of the pilot poppet valve 57, the opening gain of the pilot poppet valve 57 can be increased, and a good override characteristic of the flow amplification poppet valve 42 as a relief valve can be secured. it can.

(2) A stepped large-diameter portion 64 and a small-diameter portion 82 are formed at the tip of the pilot poppet valve 57, and the large-diameter portion is formed.
Since the area of the pressure receiving surface 81 is reduced by forming a difference in the cross-sectional area between the small diameter portion 64 and the small diameter portion 82, that is, by forming a donut area, the spring force for setting the relief valve pressure can be reduced, and the coil spring 61 can be reduced in size.

(3) In order to variably control the set pressure of the relief valve, a small and inexpensive electromagnetic actuator 87 having a level where the spring force of the coil spring 61 and its maximum thrust are comparable is used. It can be incorporated in parallel with the coil spring 61 for space saving.

(4) As in the conventional case, parts such as the pilot piston 66 for the relief valve setting pressure variable control, the external pilot pump 69, the electromagnetic proportional pressure reducing valve 70, the pilot relief valve 72, and the related piping 71 are required. Cost can be reduced.

In the embodiment shown in FIG. 1 described above, the donut area-shaped pressure receiving surface 81 is formed with respect to the pilot poppet valve 57, but the present invention is not limited to this structure.

Next, FIG. 2 shows an embodiment in which a small-diameter piston is used instead of the donut-area-shaped pressure receiving surface 81 in the pilot poppet valve 57 shown in FIG. 1 are given the same reference numerals as those shown in FIG. 1 and the description thereof will be omitted.

In the embodiment shown in FIG. 2, a large-diameter portion 64 is formed integrally with the poppet taper portion 58 via a neck portion 63, and a distal end surface of the large-diameter portion 64, that is, a coil spring 61 is formed. A separate small-diameter piston 91 formed in a circular cross section having a diameter smaller than the inner diameter of the valve seat portion 62 and having the same diameter over the entire length is in contact with the end face of the poppet valve on the opposite side.

The small-diameter piston 91 is slidably fitted in a small hole 92 between the pressure chamber 83 and the pressure chamber 83 which is functionally opposite to the pressure chamber 83 and the chamber 84 shown in FIG. Have been combined.

A pressure receiving surface 93 for receiving a return pressure from the actuator 11 is provided on an end surface of the small-diameter piston 91 opposite to a side contacting the large-diameter portion 64. The pressure receiving surface 93 is provided between the valve chamber 41 and the passage 65 in the return passage 37.
The pressure chamber 83, which acts on the pilot signal pressure and communicates via
It faces the chamber 84 which communicates with the tank 15 by 85 or the like. Therefore, the return pressure from the actuator does not act on the distal end surface 94 of the large diameter portion 64.

Further, for the pilot poppet valve 57,
An electromagnetic actuator 87 as a set pressure varying means for variably controlling a set pressure of a relief valve function is provided in parallel with the coil spring 61, as in the embodiment shown in FIG.

In the pilot poppet valve 57 shown in FIG. 2, the diameter of the valve seat portion 62 and the diameter of the large diameter portion 64 are also increased in order to improve the override characteristics as a relief valve. The pressure receiving surface 93 at the tip of the small-diameter piston 91 is formed to have a diameter smaller than the diameter of the valve seat portion 62 and the large-diameter portion 64.

Therefore, also in the embodiment having the small-diameter piston 91, the pressure receiving surface 93 has a smaller area than the conventional circular pressure receiving surface 64a (FIG. 4), and the area of the valve seat portion 62, that is, the valve seat. Since it has an area smaller than the area of a circle having the same diameter as the diameter of the inner space of the portion 62, the same operation and effect as the donut area-shaped pressure receiving surface 81 can be achieved.

As described above, the cracking pressure set in the pilot poppet valve 57 having the relief valve function provided for the spring chamber 49 of the pilot flow amplification type poppet valve provided in the return passage 37 from the actuator 11. The structure of the pilot poppet valve 57 for determining the set pressure having a relief valve function is changed so that the pressure receiving surface of the return pressure from the actuator 11 is changed to a small step-shaped donut area. By reducing the pressure receiving surface 81 in the shape of a circle or replacing the pressure receiving surface 81 in the shape of a donut area with the pressure receiving surface 93 of the small piston 91, the size of the coil spring 61 can be reduced.

Further, as a means for varying the set pressure of the pilot poppet valve 57, only a small and inexpensive push-type electromagnetic actuator 87 need be installed, and the conventional pilot piston 66, pilot pump 69, electromagnetic proportional pressure reducing valve, etc. Expensive equipment such as 70, pilot relief valve 72 and related piping 71 is not required, and cost can be reduced.

The valve device of the present invention is particularly suitable as a relief valve for a pilot flow amplification type poppet valve used for actuator meter-out control of construction equipment.
It is widely applicable to other parts.

[0080]

According to the first aspect of the present invention, the pressure receiving surface for receiving the pilot signal pressure for pressing the pilot poppet valve in the opening direction against the spring has an area smaller than the area of the valve seat portion. Since a sufficient opening gain can be ensured in the valve seat portion of the pilot poppet valve, and a good override characteristic as the relief valve is secured, the pressure receiving area of the pilot signal pressure is small, so that the pressure setting spring can be downsized.

According to the second aspect of the present invention, when the pilot poppet valve functions as a relief valve with respect to the pilot flow amplification type poppet valve whose pilot flow is controlled by the pilot modulation valve, the area is smaller than the area of the valve seat portion. A pilot poppet valve having a pilot signal pressure receiving surface with a large area can increase its opening gain, ensure a large lift of a pilot flow amplification type poppet valve, and ensure good override characteristics as a relief valve. Since the pressure receiving surface of the pilot signal pressure is small, the pressure setting spring can be downsized.

According to the third aspect of the present invention, by reducing the difference in diameter between the large-diameter portion and the small-diameter portion, the area of the donut area-shaped pressure receiving surface can be sufficiently reduced. Even when the pressure becomes high, the thrust of the pilot poppet valve can be made sufficiently small, the spring force for setting the relief valve pressure can be made sufficiently small, and the spring can be made sufficiently small.

According to the fourth aspect of the present invention, since the pilot signal pressure is transmitted to the pilot poppet valve via the small-diameter piston received on the pressure receiving surface having a smaller diameter than the valve seat, even if the pilot signal pressure becomes high, The thrust of the pilot poppet valve can be reduced, the spring force for setting the pressure of the relief valve can be reduced, the size of the spring can be reduced, and the pilot poppet valve and the separate small-diameter piston can be easily machined.

According to the fifth aspect of the present invention, the set pressure variable means for variably controlling the set pressure of the relief valve function provided in parallel with the spring acts directly on the pilot poppet valve without the intervention of the spring. It is not necessary to adjust the expansion and contraction of the spring, and the space of the spring can be saved.

According to the sixth aspect of the invention, in the valve device according to any one of the first to fourth aspects, the pressure setting spring is an electromagnetic actuator. Without using an expensive external pilot pressure signal generator, even a small and inexpensive electromagnetic actuator, which is almost compatible with a small spring force, can variably control the set pressure of the relief valve, thereby reducing costs.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a valve device according to the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the valve device according to the present invention.

FIG. 3 is a circuit diagram showing a meter-in / meter-out separated control circuit.

FIG. 4 is a sectional view showing a conventional valve device.

[Explanation of symbols]

11 Actuator 42 Pilot flow amplification type poppet valve (flow amplifier poppet valve) 54 Modulation stem as pilot modulation valve 57 Pilot poppet valve 61 Spring 62 Valve seat 64 Large diameter section 81 Donut area pressure receiving surface 82 Small diameter section 83 Pressure Chamber 87 Electromagnetic actuator as variable set pressure means 91 Small diameter piston 93 Pressure receiving surface

Claims (6)

[Claims] 1. A valve seat portion, a pilot poppet valve having a relief valve function provided so as to be able to contact and separate from the valve seat portion, a spring pressing the pilot poppet valve against the valve seat portion, and a spring against the spring. A pressure receiving surface having an area smaller than an area of the valve seat portion for receiving a pilot signal pressure for pressing a pilot poppet valve in an opening direction. 2. A pilot flow amplification type poppet valve provided on a meter-out side of an actuator, and a pilot modulation for controlling a stroke of the pilot flow amplification type poppet valve by controlling a pilot flow of the pilot flow amplification type poppet valve. And a pilot poppet valve having a pilot signal pressure receiving surface having an area smaller than an area of the valve seat portion according to claim 1 and connected to the pilot flow amplification type poppet valve in parallel with the pilot modulation valve. A valve device comprising: 3. The pressure receiving surface according to claim 1, wherein the pressure receiving surface is a donut area shaped pressure receiving surface formed between the large diameter portion and the small diameter portion fitted into the stepped hole. Valve device. 4. A separate small-diameter piston which is smaller in diameter than the valve seat portion of the pilot poppet valve and which is in contact with the end face of the poppet valve opposite to the spring, and which is opposite to the contact side of the small-diameter piston. 3. The valve device according to claim 1, further comprising a pressure receiving surface provided on the end face, and a pressure chamber for applying a pilot signal pressure to the pressure receiving surface. 5. The valve according to claim 1, further comprising a set pressure varying means installed in parallel with the spring with respect to the pilot poppet valve to variably control a set pressure of the relief valve function. apparatus. 6. The valve device according to claim 5, wherein the set pressure varying means is an electromagnetic actuator.