JPH02150910A - Pressure reducing valve with relief - Google Patents

Abstract

PURPOSE:To realize the stable control of the relief pressure despite the increase of a relief flow rate by adding a thrust generating part to a spool to receive the fluid force of the opening direction from a drain flow. CONSTITUTION:A thrust generating part 20 includes a tapered surface 20 formed at the outer circumferential edge of the rear end of a 2nd land 7 of a spool 5 and forming an angle theta to a spool shaft. When the pressure of a secondary port 4 reaches a prescribed upper limit level, a piston 12 presses and slides the spool 5 to the left against a spring 10. Thus a 1st land 6 closes the area between ports 3 and 4, and at the same time the land 7 opens the area between the port 4 and a drain path 14. As a result, the pressure oil of the port 4 is relieved to a tank 17 via a port 9 through the path 14 in the spool 5 and then a spring chamber 8. If the drain flow rate of the pressure oil increases, the surface 20 of the land 7 receives the fluid force which increases gradually to the right side from the drain flow. Then the spool 5 opens the area between ports 3 and 4 and slides in the direction where the area between the port 4 and the path 14 is closed, i.e., in the direction where the increase of the drain flow is suppressed.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention provides a spool that operates to adjust the pressure of a secondary port to a constant low pressure and to open a drain passage at a predetermined upper limit pressure of the secondary port. This invention relates to a pressure reducing valve with a relief type.

<Prior Art> Conventionally, as this type of pressure reducing valve with relief, one shown in FIG. 3, for example, is known. This pressure reducing valve with relief is the main body! A spool 5, which opens and closes a first land 6 between a primary port 3 and a secondary port 4 opening into the valve chamber, is slidably fitted into a valve chamber 2 provided therein. A spring lO is compressed into a spring 8 having a drain port 9 at one end, and a piston 12 is slidably fitted into a piston chamber 11 at the other end of the spool 5. This piston 12 is slid by pressure oil guided from the secondary port 4 through the pilot passage 13 to the piston chamber II, and presses the other end of the spool 5 against the spring IO. The spool 5 has a drain passage I4 that extends through the shaft center from one end to the vicinity of the other end, has both ends open to the outer periphery, and communicates the secondary port 4 with the spring chamber 8, and the other end of this drain passage is connected to the other end of the spool. In addition to providing a passage 15 that communicates with the end chamber I6, when the first land 6 closes between the primary port 3 and the secondary port 4, a second passage that opens between the drain passage 14 and the secondary port 4 is provided. Land 7 is provided.

In the above pressure reducing valve with relief, when the pressure in the secondary port 4 is low, the pressure oil guided from the secondary port 4 to the piston chamber It through the pilot passage 13 causes the piston I2 to move against the spring IO and move the spool 5 as shown in the figure. The first land 6 of the spool, which is pushed to the left and slides to a position where this pushing force and the spring force are balanced, [opens and closes between the next port 3 and the secondary port 4 to reduce the pressure of the Adjust to a constant low pressure. On the other hand, when the secondary port 4 is under high pressure, the spool 5 slides further to the left to the balanced position, the first land 6 closes between both ports 3.4, and the second land 7 connects to the secondary port 4. The drain passage 14 is opened, and the pressure oil of the secondary port 4 is transferred to the drain passage +4. The spring chamber 8 is discharged to the tank 17 via the tren port 9, and the pressure of the secondary port 4 is maintained below a predetermined upper limit pressure.

By the way, when the pressure reducing valve with relief is in relief operation as described above, the force acting on the spool 5 is the pressure 411 of the secondary port 4 (pressure crab P), as shown in FIG.
, ) is the piston 12 (area/A1. See Figure 4(b))
Force pushing leftward through P2A, ■ Force Fs1 pushing rightward by spring lO ■ Drain flow ff1 passing through drain passage 14
Differential pressure caused by q (q/cd”)' (c: constant, d
: Passage diameter) pushes leftward (A2 AIXQ/cd2
)” (Area of the right edge of At Nisbourg, see Figure 4 (a))
, ■ Hydrodynamic force to the right exerted by the drain flow mq on the second land 7 ρq v cos θ (ρ: oil density, ■; drain flow velocity, θ: taper angle of the second land, see Figure 4 (a)) There are four forces, and the following equation (1) holds true between these forces.

Ps-+-pq v cosθ=(A2-AIXq/C
d2)'+PtA <Problem to be solved by the invention> During the relief operation of the pressure reducing valve with relief, the above (1)
Fs in the formula, pq v cosθ, (At-AIXQ
/cd2)2 changes as the drain flow ff1q increases, so the pressure at the secondary port 4, that is, the set pressure P
, also changes. However, the second part of the conventional spool 5 mentioned above
As shown in FIG. 4(a), the outer periphery of the land 7 has no taper angle at all (θ-〇), so the drain flow f
The change in the set pressure P as f1q increases is as shown by the broken line in FIG. That is, the secondary port pressure is 250 kg/
At C12, relief begins and the set pressure P2 gradually increases as the drain flow ff1q increases, but when the drain flow q reaches only 5σ/+nin, the spool 5 moves extremely to the left and the drain passage 14 closes. The problem is that the set pressure is drastically reduced or fluctuates greatly and becomes unstable, and the upper limit pressure can no longer be controlled and the relief function cannot be exerted.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pressure reducing valve with a relief that can stably control the relief pressure even when the relief flow rate increases by providing a thrust generating part on the spool that receives fluid force in the opening direction from the drain flow. That's true.

Means for Solving the Problems> In order to achieve the above object, the pressure reducing valve with relief of the present invention has primary ports 3 and 2, as illustrated in FIGS. 1 and 3.
A spool 5 that is slidably fitted into a valve chamber 2 provided in the main body 1 having a next port 4 and opens and closes between the two ports 3 and 4 with a land 6, and a drain port on one end side of the spool 5. A spring lO compressed in a spring chamber 8 having a spring 9 is slidably fitted into a piston chamber 11 provided at the other end of the spool 5, and is connected to the piston from the secondary port 4 through a pilot passage 13. A piston 12 that presses the other end of the spool 5 with pressure oil guided into the chamber 11, and a piston 12 that is provided on the spool 5 and that is connected to the piston 12 with the land 6 closing between the primary port 3 and the secondary port 4. In a device equipped with a drain passage 14 communicating from the next port 4 to the spring chamber 8, a passage 15 is provided that communicates the chamber 16 at the other end of the spool 5 with the drain passage 14, and the land 6 of the spool 5 connects both the ports. When closing between 3 and 4, the above secondary port 4
The spool 5 is characterized in that the spool 5 is provided with a thrust generating section 20 that applies a fluid force in the opening direction to the spool 5 by the drain flow flowing from the drain flow into the drain passage 14.

When the pressure P of the secondary port 4 reaches a predetermined upper limit pressure, the piston 12 is spooled against the spring 10 by pressure oil guided from the secondary port 4 to the piston chamber 2 via the pilot passage 13. Suppress 5.

By sliding, the land 6 of the spool 5 closes the space between the primary port 3 and the secondary port 4, and opens the space between the secondary port 4 and the drain passage 14. Then, the pressure oil at secondary port 4 is
The above drain passage provided in spool 5! 4, and is relieved from the drain port 9 to the tank 17 via the spring chamber 8. At this time, the drain flow ff of the pressure oil to be relieved
1q increases, the thrust generating section 20 provided on the spool 5 receives a fluid force that gradually increases in the opening direction from the drain flow, and the spool 5 opens between the primary port 3 and the secondary port 4, and the It slides in the direction of closing the gap between the port 4 and the drain passage 14, that is, in the direction of suppressing an increase in the drain flow ff1q. Therefore, unlike the conventional system, the relief pressure does not become uncontrollable due to the drain passage 14 being opened all the time, and the relief pressure can be stably controlled even if the relief flow rate (drain flow ff1q) increases.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

Figure 1 shows an example of a thrust generating part provided on the spool of a pressure reducing valve with a relief, and this pressure reducing valve with a relief has the following characteristics:
The configuration is the same as that of the conventional example described in FIG. 3 except for the thrust generating section, and the same members are given the same numbers and their explanations will be omitted.

The thrust generating portion is constituted by a tapered surface 20 formed on the outer peripheral edge of the rear end side of the second land 7 provided on the spool 5 and forming an angle θ with the spool shaft. And the above angle θ is
For example, it is 15°.

The operation of the pressure reducing valve with relief constructed as described above will be described next.

When the pressure at the secondary port 4 is low, the spool 5 slides to a position where the pressing force of the piston 12 and the spring force of the spring 10 are balanced, as described in the conventional example, and the first land 6 moves toward the primary port 3. and the secondary port 4 to adjust the pressure P of the secondary port 4 to a constant low pressure. On the other hand, secondary port 4
pressure is a predetermined upper limit pressure (e.g. 250 &9/cff”
)l Then, from this secondary port 4 to the pilot passage 1
3 and into the piston chamber 11, the piston 12 presses the spool 5 to the left against the spring 10.

The first land 6 of the spool 5 closes the gap between the primary port 3 and the secondary port 4, and the second land 7 closes the gap between the primary port 3 and the secondary port 4.
Open between the next port 4 and the drain passage 14. Then, the pressure oil in the secondary port 4 passes through the drain passage 14 in the spool 5, passes through the spring chamber 8, and is leaked from the drain port 9 to the tank 17.

At this time, when the drain flow rate q of the pressure oil to be relieved increases, the tapered surface 20 formed on the second land 7 receives a gradually increasing fluid force from the drain flow in the opening direction, that is, to the right, and the spool 5 It slides in the direction of opening the space between the primary port 3 and the secondary port 4 and closing the space between the secondary port 4 and the drain passage 14, that is, in the direction of suppressing an increase in the drain flow rate.

Therefore, unlike in the conventional case, the relief pressure does not become uncontrollable due to the drain passage 14 opening, and the relationship between the drain flow rate q and the set pressure P changes as shown by the solid line in FIG. The drain flow ff1q is 1512/3 times that of the conventional one.
Set pressure P until min.

is controlled stably while gradually increasing from 250 kg/cx''. This means that when the pressure reducing valve with relief of the above embodiment performs relief operation, as the drain flow ff1q increases, the above equation (1) This means that the set pressure P, which is determined, increases steadily and gradually until a large drain flow rate is reached by setting the angle θ of the taber surface 20 to 15 degrees.In other words, the spool slides in the direction of opening the drain passage. By effectively utilizing the reverse axial thrust from the drain flow that increases due to the above taper surface 20, the relief-equipped pressure reducing valve was able to operate stably in relief up to a large drain flow rate.

In the above embodiment, the angle θ of the tapered surface 20, which is the thrust generating part provided on the second runt 7, is set to 15 degrees, but this angle varies depending on the structure and dimensions of the pressure reducing valve with relief, so All you have to do is find the optimal value. Also,
The thrust generating portion does not necessarily need to be formed on the entire outer peripheral edge of the rear end side of the second land 7 as in the embodiment, and the second land 7 having a tapered surface at the rear end may be formed continuously and integrally with the first land 6. It can also be formed.

Furthermore, it goes without saying that the present invention is not limited to the illustrated embodiment.

<Effects of the Invention> As is clear from the above description, the pressure reducing valve with relief of the present invention has one end of the spool slidably fitted in the valve chamber in the main body compressed into a spring chamber having a drain port. The other end of the spool is pressed by a piston that is fitted into the piston chamber and receives pilot pressure led from the secondary port, and the land of the spool opens and closes between the primary port and the secondary port. In a device in which the secondary port is communicated with the spring chamber by the drain passage of the spool when both ports are closed, the chamber at the other end of the spool is communicated with the drain passage by the passage, and both ports are connected by the land. Since the spool is provided with a thrust generating part that receives fluid force in the opening direction due to the drain flow flowing into the drain passage from the secondary port when the drain passage is closed, as the drain flow rate increases, the spool moves in the direction of suppressing this increase. Because it slides, the relief pressure does not become uncontrollable when the drain passage opens like in the past, and the relief pressure can be stably controlled even at large drain flow rates, providing stable relief over a wide area. operation can be realized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a thrust generating part provided on the spool of the pressure reducing valve with relief of the present invention, and FIG. 2 is a diagram showing the relief operation characteristics of the pressure reducing valve with relief in comparison with a conventional example. FIG. 3 is a sectional view of a conventional pressure reducing valve with relief, FIG. 4 is a detailed view of a portion of FIG. 3, and FIG. 5 is a diagram showing the force acting on the spool during relief operation. 1. Main body, 2. Valve chamber, 3. Primary port, 4.
Secondary port, 5... Spool, 6... 1st land,
7...Second land, 8...Spring chamber, 9...Drain port, 10...Spring, 11...Piston chamber, 12...
...Piston, I3...Pilot passage, 14...
Drain passage, 15... passage, 16... chamber at the other end, 2
0... Tapered surface, θ... Taper angle. Figure 1 Zero 2s Patent Applicant Agent: Daikin Industries, Ltd.
Person Patent attorney Previously mentioned 葆 Haka 1 person drain style view q (Q/
m1n)→

Claims (1)

[Claims] (1) It is slidably fitted into the valve chamber (2) provided in the main body (1) which has a primary port (3) and a secondary port (4), and the land (6) connects both the ports ( 3, 4); a spring (10) compressed into a spring chamber (8) having a drain port (9) on one end of the spool (5); It is slidably fitted into the piston chamber (11) provided on the other end side, and the above-mentioned 2
Pressure oil is guided from the next port (4) to the piston chamber (11) via the pilot passage (13) to the spool (5).
) is provided on the spool (5), and the land (6) is connected to the primary port (3).
) and the secondary port (4) in a closed state and a drain passage (14) communicating from the secondary port (4) to the spring chamber (8). A passage (15) is provided that communicates the chamber (16) at the other end with the drain passage (14), and both the ports (3, 4) are connected to the land (6) of the spool (5).
), a thrust generating part (20) is attached to the spool (5) that applies a fluid force in the opening direction to the spool (5) by the drain flow flowing from the secondary port (4) into the drain passage (14). A pressure reducing valve with a relief feature.