JPH0621680B2 - Pilot type relief valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a relief valve generally used in hydraulic devices, equipment and the like, and more particularly to a pilot type relief valve.

[Conventional technology]

The relief valves can be roughly classified into a direct acting type and a pilot type, but the pilot type is generally used for large capacity due to its good performance.

A typical pilot type structure is shown in FIG. This relief valve operates as follows. When the inlet pressure becomes higher than a predetermined pressure, the pilot poppet 4 opens and oil flows. Due to this flow, a differential pressure is generated between the upstream side and the downstream side of the orifice 3a attached to the main poppet 3. Due to the pressure difference, the main poppet 3 is in the cartridge 2
Lifts from the valve seat 2a and stops at a position balanced with the spring 5. Then, a large amount of oil is stored in the valve seat 2a and the main poppet 3
It flows from the annular gap between and, and functions as a relief valve.

[Problems to be solved by the invention]

In the conventional pilot type relief valve, the main poppet 3 is configured to slide on the inner diameter portion of the cartridge 2, and the annular gap of the sliding portion allows the chamber A for entering high pressure and the outlet B for low pressure to communicate with each other. It has a possible structure. For this reason, when pressure is applied to the inlet E, leakage that always passes through the annular gap described above occurs, and there is a problem that the relief valve cannot be used in applications where such leakage is not allowed. The characteristics at this time are shown in FIG.

In the above pilot type relief valve, as shown in FIG. 7, it is possible to use an O-ring 6 for the above-mentioned sliding portion in order to prevent leakage, but if such an O-ring 6 is used, The frictional force causes hysteresis, which causes problems such as variations in set pressure. Therefore, in general, the O-ring 6 is not used.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a pilot type relief valve capable of sufficiently preventing leakage at a set pressure or less.

[Means for solving problems]

Therefore, according to the present invention, in a relief valve having a pilot poppet for a small flow rate and a main poppet for a large flow rate inside the valve body, the relief valve is arranged coaxially with the main poppet on the downstream side of the main poppet. A movable seat is provided, and the main poppet 13 and the movable seat are slidably fitted into the cartridge of the valve body, and the movable seat has a large diameter portion on the upstream side and a step portion on the downstream side of the large diameter portion. The movable seat is formed with a small-diameter portion, and a seal portion that can be in line contact with the downstream end surface of the main poppet is formed on the upstream-side end surface of the large-diameter portion of the movable seat. O-rings are respectively provided along the inner peripheral surface of the cartridge that slides with the outer peripheral surfaces of the small diameter portion and the large diameter portion, and the outer peripheral portion of the movable seat and the car An annular chamber formed by the inner peripheral portion of the ridge is communicated with the low pressure outlet of the relief valve through a small hole penetrating the cartridge and a gap between the cartridge and the valve body. It has a feature.

[Work]

In the above-described pilot type relief valve of the present invention, the main poppet and the large diameter portion of the movable seat come into line contact with each other in a sealed state when the pressure is not higher than a normal set pressure, and an O-ring is arranged on the outer periphery of the movable seat. Therefore, there is no leakage as in the conventional case. Further, when the set pressure is exceeded, the above-mentioned line contact portion opens to operate as a normal pilot type relief valve.

〔Example〕

A pilot type relief valve as one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view thereof, and FIGS. 2 and 3 are vertical sectional views showing its operating state.

As shown in FIG. 1, a large flow rate main poppet 13 having an orifice 13a inside a valve body 10.
And a pilot poppet 14 for small flow rate are arranged so as to be loaded with springs 15 and 17, respectively, and a cartridge 12a is arranged on the outer periphery of the main poppet 13.

In this way, the main poppet portion 11a and the pilot poppet portion 11b are formed as in the conventional pilot type relief valve.

In the relief valve of the present invention, the cylindrical movable seat 16 is arranged coaxially with the main poppet 13 particularly in the main poppet portion 11a, and the end surface of the large diameter portion of the movable seat 16 at the step outer diameter portion and the main poppet portion The end surface of the poppet 13 is always in line contact with the end surface of the poppet 13 to form the seal portion 21.

O-rings 19 and 20 are provided along the inner peripheral surface of the cartridge 12b that slides on the outer peripheral surfaces of the large diameter portion and the small diameter portion of the step outer diameter portion of the movable sheet 16, respectively.

The annular chamber C formed by the step outer diameter portion of the movable seat 16 and the cartridge 12b has a small hole 25 penetrating the cartridge 12b, the cartridge 12b and the valve body 10.
Is communicated with the low-pressure outlet B via a gap 26 between.

When the pressure at the inlet E is equal to or lower than the set pressure, the movable seat 16 is pushed leftward in the drawing by the spring 18, and the seal portion 21 is formed by the line contact between the end surface of the large diameter portion and the main poppet 13. The relationship between the diameter D ₁ of the seal portion 21 and the diameter D ₂ of the large diameter portion and the diameter D _{3 of the} small diameter portion in the step outer diameter portion of the movable sheet is as follows.

D ₁ > D ₃ , D ₁ D ₂ Therefore, the pressure at the inlet E or the orifice at the inlet E
When the pressure in the chamber A in the main poppet 13 that communicates via the 13a is less than or equal to a set pressure, the fluid that tries to leak from the chamber A to the outlet B through the gap between the sliding portions of the cartridge 12a and the main poppet 13. Will be blocked by the line contact seal portion 21. In this state, the line-contacting seal portion 2 is located at a portion where leakage is attempted from the high pressure side to the low pressure side.
Since there is only the 1 and the O-rings 19 and 20 and there is no face seal portion, the amount of leakage can be almost zero.

What should be noted here is that the seal between the main poppet 13 and the movable seat 16 is performed by the seal portion 21 which brings the end surface of the large diameter portion of the stepped outer diameter portion of the movable seat 16 into line contact with the end surface of the main poppet 13. That's what it means.

With this configuration, special consideration is given to the sitting of the main poppet 13 with respect to the cartridge 12a and the movable seat 16, that is, in order to cause the main poppet 13 to perform both members at appropriate timing.
For example, it is not necessary to make a special design such as providing play, the original performance of the relief valve is not impaired, and the structure can be simplified.

Next, when the pressure at the inlet E increases, the movable sheet 16 first moves to the right against the spring 18, and the line contact seal portion 21 is released.

Therefore, as shown in FIG. 2, the main poppet 13
The fluid begins to leak through the gap between the sliding portion of the cartridge and the cartridge 12a. Reference numeral q _{1 in} FIG. 2 indicates the leak amount.

Then, when the pressure at the inlet E becomes higher, the pilot poppet 14 is opened, and then the main poppet 13 is opened, as shown in FIG. 3, similarly to the case of the conventional pilot type relief valve. The fluid directly flows out to the relief valve, and thus the function as the relief valve is fulfilled. In FIG. 3, the symbol Qp indicates the flow rate through the pilot poppet portion 11b, and Qr indicates the flow rate through the main poppet portion 11a.

The characteristics of the relief valve based on the above operation are shown in FIG. There is no leakage when the area (I) seal portion 21 is formed.

 Flow rate Q = 0 Area (II) Leakage occurs when the seal part 21 is released.

Q = q ₁ Area (III) When the pilot poppet 14 is lifted.

Q = q ₁ + Qp Area (IV) When the main poppet 13 is lifted.

Q = q ₁ + Qp + Qr. Since the sliding portion between the movable sheet 16 and the cartridge 12b is sealed by the O-rings 19 and 20, hysteresis is generated by frictional force, and the sections (I) and (II) in FIG.
However, there is no variation in the set pressure, and the original performance of the relief valve is not hindered.

Further, in order to prevent fluid from leaking through the gap between the sliding parts of the main poppet 13 and the cartridge 12a,
Since the O-ring is not used, there is no performance deterioration due to hysteresis that occurs when the O-ring is used (it does not close completely even if the pressure drops once the main poppet 13 opens), and a relief valve with good operating characteristics is provided. can get.

〔The invention's effect〕

As described above in detail, according to the pilot type relief valve of the present invention, in the relief valve having the pilot poppet for a small flow rate and the main poppet for a large flow rate inside the valve body, the downstream side of the main poppet. The main poppet and the movable seat are arranged coaxially with each other, and the main poppet and the movable seat are slidably fitted in the cartridge of the valve body, and the movable seat is the same as the large diameter portion on the upstream side. A seal portion that is configured with a small diameter portion that is continuously provided via a step portion on the downstream side of the large diameter portion, and that can make line contact with the downstream end surface of the main poppet on the upstream end surface of the large diameter portion of the movable seat. And O-rings are respectively formed along the inner peripheral surface of the cartridge that slides with the outer peripheral surfaces of the small diameter portion and the large diameter portion of the movable sheet. The annular chamber formed by the outer peripheral portion of the movable seat and the inner peripheral portion of the cartridge is provided with the relief through the small hole penetrating the cartridge and the gap between the cartridge and the valve body. With the simple structure of communicating with the low pressure outlet of the valve, there is an advantage that the leakage phenomenon in the pilot type relief valve, which has been a problem in the past, can be sufficiently prevented without impairing the performance of the relief valve body. .

[Brief description of drawings]

1 to 3 show a pilot type relief valve as an embodiment of the present invention. FIG. 1 is a longitudinal sectional view thereof, and FIGS. 2 and 3 are longitudinal sectional views showing its operating state. FIG. 4 is a graph showing the characteristics of the pilot type relief valve of the present invention, FIG. 5 is a longitudinal sectional view showing a conventional pilot type relief valve, and FIG. 6 is the conventional pilot type relief valve. FIG. 7 is a graph showing the characteristics of the relief valve, and FIG. 7 is a vertical sectional view showing a case where an O-ring is added to the conventional pilot type relief valve. 10 ... Valve body, 11a ... Main poppet part, 1
1b …… Pilot poppet part, 12a, 12b …… Cartridge, 13 …… Main poppet, 13a …… Olihuis, 1
4 ... Pilot poppet, 15 ... Spring, 16 ... Movable seat, 17,18 ... Spring, 19,20 ... O-ring, 21 ... Line contact seal part, 25 ... Small hole, 26 ...
… Gap, A …… Room inside the main poppet, B …… Exit, C
…… Annular room, E …… Entrance.

Claims (1)

[Claims] 1. A relief valve having a pilot poppet for a small flow rate and a main poppet for a large flow rate inside a valve body, and a movable seat disposed coaxially with the main poppet on the downstream side of the main poppet. The main poppet and the movable seat are slidably inserted into the cartridge of the valve body, and the movable seat is connected to the large diameter portion on the upstream side and the downstream side of the large diameter portion via a step portion. It is composed of a small diameter part to be installed,
A seal portion that can be in line contact with the downstream end surface of the main poppet is formed on the upstream end surface of the large diameter portion of the movable seat, and also slides on the outer peripheral surfaces of the small diameter portion and the large diameter portion of the movable seat. O-rings are respectively provided along the inner peripheral surface of the cartridge, and an annular chamber formed by the outer peripheral portion of the movable sheet and the inner peripheral portion of the cartridge has a small hole penetrating the cartridge and the cartridge. A pilot-type relief valve, which is communicated with a low-pressure outlet of the relief valve through a gap between the relief valve and the valve body.