JPS6262366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure compensation valve that eliminates or reduces the influence of axial thrust of fluid on a spool and improves pressure compensation accuracy.

Conventionally, in general, a pressure compensating valve has a spool slidably fitted into a valve chamber provided in the main body, and a pilot chamber connected to the throttle front end at one end of the spool.
A spring chamber connected to the rear of the throttle and compressed with a spring is formed at the other end, and the spool is operated to open and close between the primary port and the secondary port to reduce the differential pressure before and after the throttle. The pressure is compensated to a constant pressure corresponding to the spring force.

By the way, in a pressure compensating valve having such a structure, it is impossible to avoid the axial thrust that acts on the spool as the momentum of the fluid changes. This axial thrust varies depending on conditions such as the differential pressure before and after the pressure compensating valve and the opening degree of the throttle, and also acts against the spring force of the spring in the spring chamber. Therefore, it is equivalent to the spring force acting on the spool being smaller than the actual setting value.
The differential pressure before and after the throttle that is pressure compensated will be smaller than the set value, and will fluctuate depending on the conditions. As a result, the pressure compensation accuracy deteriorates, and the flow rate control characteristics of the throttle deteriorate.The present invention provides a new pressure compensation valve that eliminates or reduces the influence of the above-mentioned axial thrust and can perform highly accurate pressure compensation. The purpose is to

The pressure compensation valve of the present invention has the following configuration added to the conventional type pressure compensation valve. A pressure chamber is provided adjacent to a spring chamber connected to the rear part of the throttle, and the pressure chamber and the spring chamber are connected to each other. By fitting the sensor pin into the partition so that it can slide freely along the axis of the spool and connecting the primary port to the pressure chamber, the pressure between the pressure in the pressure chamber and the pressure in the spring chamber acting on the sensor pin can be reduced. The sensor pin is differentially pressed toward the spool to balance the pressing force, which is a compensating force, of the sensor pin and the axial thrust force.

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

In FIG. 1, reference numeral 1 denotes a preferential pressure compensation valve, and numeral 2 denotes a variable throttle as a throttle whose pressure is compensated by the preferential pressure compensation valve 1.

The above-mentioned priority type pressure compensation valve 1 has plugs 5 and 6 screwed into both ends of a cylindrical through hole 4 provided in a main body 3.
It is fixed to form a valve chamber 7. A spool 14 having three lands 11, 12, and 13 is slidably fitted into the valve chamber 7, and a pilot chamber 15 is formed at one end of the spool 14, and a spring chamber 16 is formed at the other end. The coil spring 1 is in the spring chamber 16.
7 is reduced.

On the other hand, the valve chamber 7 is provided with annular grooves 21, 22, and 23 sequentially from the left side in the figure, a pressure reducing port 25 as a secondary port is provided in the annular groove 21, and a decompression port 25 as a secondary port is provided in the annular groove 22.
The next port 26 is connected to the annular groove 23 by the bypass port 2.
7 are provided respectively, and the central land 12 can control the opening and closing of the control units 29 and 30 by the operation of the spool 14. In other words, the control unit 29 can control the pressure reduction between the primary port 26 and the decompression port 25, and the primary port 26 and the bypass port 27 can be controlled by the control unit 30. Decompression port 25
is connected to an actuator (not shown) via a line 31 equipped with a variable aperture 2, and is connected to a primary port 26.
is connected to a pressure source 33 via a line 32, the pilot chamber 15 is connected to the front of the variable throttle 2 via a line 34, and the spring chamber 16 is connected to the rear of the variable throttle 2 via a line 35. There is.

On the other hand, a cylindrical through hole 40 is provided in the axial center of the plug 6 on the side of the spring chamber 16.
While screwing and fixing the small diameter plug 41 to one end of the
A sensor pin 42 is slidably fitted into the other end to form a pressure chamber 43 between the small diameter plug 41 and the sensor pin 42. That is, the sensor pin 42 is fitted into the partition wall 45 between the pressure chamber 43 and the spring chamber 16 so as to be slidable along the axis of the spool 14. Both tips of the sensor pin 42 are spherical, so that even if the tip of the sensor pin 42 comes into contact with the spool 14, fluid pressure is applied to the tip. Further, the pressure chamber 43 is connected to the primary port 26 via a radial hole 46 provided in the plug 6, an annular groove 47, and a line 48. A portion 50 of the partition wall 45 on the spring chamber side projects inside the coil spring 17 and serves as a guide for the coil spring 17.

Note that 51, 52, and 53 are seal members that seal each part.

The priority type pressure compensating valve 1 having the above structure is currently in the state shown in FIG. 1, with the bypass port 27
It is assumed that the valve is operated as a pressure reducing type pressure compensating valve by blocking.

At this time, if the flow rate flowing through the control section 29 of the priority type pressure compensation valve 1 is Q, an axial thrust F ₁ acts on the spool 14 in the direction of the spring chamber 16 .

F ₁ = αQ√ _P −′ ... Here, P _P : Pressure at the primary port 26. P′: Pressure behind the control unit 29, that is, in front of the variable throttle 2, α: Coefficient This axial thrust F ₁ acts in a direction that cancels out the spring force of the coil spring 17, so the sensor pin 4 If it were not provided, it would be the same as if the spring force of the coil spring 17 was smaller than the actual value, and therefore the differential pressure before and after the variable throttle 2 would be smaller than the expected value. . Since the magnitude of this axial thrust _F1 increases as the pressure difference (P _P - P') and the flow rate Q increase, the control flow rate that should originally be determined and constant only by the opening degree of the variable throttle 2 However, as shown in the curves Q' ₁ , Q' ₀ , Q' ₂ in Fig. 3, the pressure difference (P _P -
P') and the set opening degree of the variable throttle 2, that is, the set flow rate (Q ₁ , Q ₀ , Q ₂ ) increase, the deviation tends to decrease from the desired value and become larger.

However, in this priority type pressure compensation valve 1, the sensor pin 42 is provided, and the pressure of the pressure chamber 43 is applied to one end of the sensor pin 42, and the pressure of the spring chamber 16 is applied to the other end. A compensating force F ₂ acts in a direction that presses the axial thrust F ₁ , that is, in a direction that cancels out the axial thrust F 1 , and the sensor pin 42 presses the spool 14 with the compensating force F ₂ . This compensation force F ₂ is F ₂ = (P _P - P _L ) a. ... Here, P _P : Pressure in the pressure chamber 43, that is, the pressure at the primary port 26 P _L : Pressure in the spring chamber 16, that is, the variable throttle 2 Rear pressure a: pressure receiving area of sensor pin 42 Therefore, axial thrust force acting on spool 14 F ₁
The resultant force F of this and the compensation force F ₂ is F = F ₁ - F ₂ = αQ√ _P -'- (P _P - P _L ) a...The influence of the axial thrust F ₁ is alleviated and the pressure Compensation accuracy is improved.

Now, let P _L = P′−△P ……. Then, ΔP is assumed to be a constant value approximately equal to the surface pressure of the spring force of the coil spring 17 acting on the end surface of the spool 14. By substituting the expression into the expression, the following expression is derived.

F=F ₁ −F ₂ =αQ√ _P −′ −{(P _P −P′)a+ΔP・a}... The formula is shown in FIG. As you can see from this,
When the differential pressure (P _P - P') before and after the control section 29 is wide, the compensation force _F2 cancels out the axial thrust _F1 , and the resultant force F becomes a value close to zero, resulting in highly accurate pressure. Compensation control, that is, the differential pressure before and after the variable throttle 2 can be controlled to a constant value corresponding to the spring force of the coil spring 17. This means that the axial thrust F ₁ and the compensation force F ₂ are both expressed as the pressure difference (P _P - P')
It is clear from the fact that as the axial thrust F ₁ becomes larger, the compensation force F ₂ becomes larger.

The curve Q _{0 ″} in Fig. 3 shows the variable flow rate when the pressure receiving area a of the sensor pin 42 is determined so that the compensation force F ₂ cancels the axial thrust F ₁ when the set flow rate of the variable throttle 2 is Q 0. The flow rate control characteristics of the throttle 2 are shown. In this case, it can be seen that the controlled flow rate is approximately constant regardless of the pressure difference (P _P - P'). The curve Q ₂ '' is the flow rate control characteristic of the variable throttle 2.
Increase the opening degree to change the set flow rate Q ₂ to the above flow rate Q ₀
This shows the characteristics when the value is larger than . At this time, as the pressure difference (P _P - P') increases, the compensation force
Since F ₂ cannot fully cancel out the axial thrust F ₁ , as the pressure difference (P _P −P′) increases, the controlled flow rate Q ₂ ″ decreases from the set flow rate Q ₂ .However, the sensor pin 42 is not provided. The controlled flow rate characteristics are much better than the conventional curve Q ₂ ′.In addition, the curve Q ₁ ″ is a curve in which the opening degree of the variable throttle 2 is made smaller so that the set flow rate Q ₁ is lower than the above flow rate Q ₀ . The characteristics when made smaller are shown. At this time, the compensation force _F2 becomes larger than the axial thrust _F1 , which is equivalent to the spring force of the coil spring 17 becoming stronger, and the pressure difference (P
As _P − P′) increases, the controlled flow rate Q ₁ ″ increases more than the set flow rate. Therefore, the pressure receiving area of the sensor pin 42 must be determined according to the opening range of the variable throttle 2, that is, the control flow range. Must be.

In the above embodiment, the bypass port 27 of the priority type pressure compensation valve 1 is blocked and used as a pressure reduction type pressure compensation valve, but the bypass port 27 can also be connected to an actuator and used as the original priority type pressure compensation valve. It performs exactly the same function of eliminating thrust. In other words, the present invention is not limited to a reduced pressure type or a priority type.

As is clear from the above description, according to the present invention, a pressure chamber is provided adjacent to a spring chamber connected to the rear of the throttle, and a sensor pin is slidably fitted into a partition wall between the pressure chamber and the spring chamber. At the same time, since the primary port is connected to the pressure chamber, the sensor pin is pushed toward the spool with a compensation force determined by the pressure difference between the pressure chamber and the spring chamber, and the compensation force and axial thrust are balanced. Therefore, the influence of the axial thrust can be eliminated or reduced, and highly accurate pressure compensation can be performed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a pressure compensation valve according to an embodiment of the present invention, FIG. 2 is a graph showing the axial thrust and compensation force characteristics of the pressure compensation valve shown in FIG. 1, and FIG. 3 is a graph showing pressure difference flow rate characteristics of the pressure compensation valve shown in FIG. 1...Priority type pressure compensation valve, 2...Variable throttle, 3
...Body, 7...Valve chamber, 14...Spool, 15
...Pilot chamber, 16...Spring chamber, 17...Spring, 25...Secondary port, 26...Primary port,
42...sensor pin, 43...pressure chamber, 45...
...bulkhead.

Claims (1)

[Claims] 1. A spool 14 is slidably fitted into a valve chamber 7 provided in the main body 3, and a pilot chamber 15 connected to the front side of the throttle 2 is formed at one end of the spool 14. At the other end of the spool 14 is a spring chamber 16 connected to the rear of the throttle 2 and housing a spring 17.
and a primary port 26 connected to a pressure source by actuation of the spool 14, and a 2 connected to the throttle 2.
In the pressure compensation valve that opens and closes between the next port 25 and the pressure difference before and after the throttle 2 constant, a pressure chamber 43 adjacent to the spring chamber 16 is provided,
The sensor pin 42 is slidably fitted into the partition wall 45 between the pressure chamber 43 and the spring chamber 16 along the axis of the spool 14, and the primary port 26 is connected to the pressure chamber 43. A pressure compensating valve characterized in that 42 presses a spool 14.