JPH0537103Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to improvements in valves for controlling fluid pressure.

(Prior Art) As a valve for controlling fluid pressure, there is a conventional valve as shown in FIG.

This control valve 5 is connected to the supply circuit 2 from the pump 1.
Interposed in a passage 4 branching from the tank 3 and returning to the tank 3,
The pressure in the supply circuit 2 is controlled according to its opening degree.

In the control valve 5, a spool 8 is driven against a spring 7 by excitation of a solenoid 6. The spool 8 is slidably inserted into the valve body 9,
Its tip is a plug 10 that fits into the valve body 9.
is in contact with. At the center of the plug 10 is the inlet port 1.
1 is formed in the valve body 9, while a discharge port 12 is formed in the valve body 9, which communicates with the inlet port 11 when the spool 8 retreats.
An inlet 11 is connected to the branch passage 4, and an outlet 12 is connected to the tank 3. A recess 13 is formed at the tip of the spool 8,
As shown in FIGS. 5A and 5B, this recess 1
A plurality of control holes (windows) 14 are formed around the valve body 3, and when the spool 8 moves (gets out) from a seat portion 15 formed on the inner periphery of the valve body 9, the control holes 14 are formed in accordance with the amount of movement. A variable opening is formed through which the inlet 11 and the outlet 12 communicate with each other.

When the solenoid 6 is energized with a certain set current, the spool 8 moves back by a certain amount against the spring 7, thereby opening the control hole 14. When the current value is decreased from this state, the spool 8 moves to the left in the figure due to the acting force of the spring 7, and the opening area of the control hole 14 decreases.

Figure 6A shows the relationship between the stroke of the spool 8 and the valve opening area. In this case, the valve stroke is set to zero at the maximum current value, and as the current value decreases, the stroke amount increases. It is set to .

According to the conventional rectangular shape of the control hole 14,
The relationship between stroke and opening area is a linear characteristic, and the opening area decreases proportionally as the current value decreases. The pressure ΔP controlled by this control valve has the following relationship: ΔP = C・Q ² /A 2, where A is the valve opening area and Q is the flow rate at that time. The control pressure ΔP is ² times the opening area A.
It changes inversely proportional to the power of

(Problem to be solved by the invention) Therefore, when the valve opening area decreases as the stroke amount increases, the controlled pressure increases secondarily, but as mentioned above, the stroke amount and If the relationship between the opening areas is linearly proportional, even a slight change in the stroke amount in the small valve opening range will cause a large change in the control pressure (see FIG. 6B).

Therefore, in a region where the valve opening is small and the control pressure is high, the rate of change in pressure with respect to the valve stroke becomes too large, in other words, the valve sensitivity becomes too high, making it difficult to control the pressure with high precision.

The present invention aims to solve these problems by improving the shape of the control hole of the spool.

(Means for Solving the Problems) The present invention provides a method for forming a control hole in a valve spool that is in sliding contact with a seat part, and allowing fluid to flow through a variable opening formed by the control hole and the seat part. In the control valve, the control hole is formed from a first control section and a second control section connected to the first control section, and the control hole is formed from a first control section and a second control section connected thereto.
The control part is formed so that the groove width gradually changes with respect to the valve stroke, and the second control part is formed so that the change in the groove width becomes small with respect to the valve stroke.

(Function) In the region where the opening area decreases and the control pressure increases secondarily, the change in the control hole area with respect to the stroke slows down, which means that the valve sensitivity is appropriately suppressed and the pressure control accuracy in the high pressure region is improved. will improve.

(Example) Embodiments of the present invention are shown in FIGS. 1 and 2.

As shown in the figure, in the present invention, the control hole 14 formed in the spool 8 has a first control part 20 having a substantially triangular shape whose groove width gradually narrows as it advances in the axial direction, and a first control part 20 connected to the tip of the first control part 20 and connected to the shaft. The second control portion 21 is formed from a second control portion 21 in which the groove width changes little in the direction.

The shape of the second control part 21 may be, for example, a single substantially circular groove 21A as shown in FIG.
As shown in Figure B, a groove 21B in which two circles are connected in parallel.
or, as shown in Figure 2C, the first
There is a rectangular groove 21C wider than the tip of the control section 20.

Further, the shape of the first control section 20 is as shown in FIG.
As shown in F, it may be semicircular. Furthermore, the first control section 20 may have a closed circular shape or a closed triangular shape, as shown in FIGS. 2G and 2H.

The structure is as described above, and the same reference numerals will be used for the other parts that are the same as those of the conventional system, and a detailed description thereof will be omitted.

The operation will be explained with reference to FIGS. 3A and 3B.

When a set current is supplied to the solenoid 6 and the current value is decreased from the state where the valve is opened to the maximum, the opening area of the spool 8 gradually decreases as the spool 8 strokes. 20
When the opening area overlaps the seat portion 15, the amount of change in the opening area with respect to the stroke amount is relatively large, and the area decreases in approximately linear proportion. Since the absolute value of the opening area in this region is large, the control pressure, which is inversely proportional to the square of the opening area, is gradually increased.

When the absolute value of the opening area becomes smaller in the latter half of the valve stroke, the control pressure tends to rise rapidly in response to the stroke change, but after the second control section 21 starts to overlap with the seat section 15, the opening area relative to the stroke changes. The rate of change in the stroke becomes smaller, and the opening area gradually decreases compared to the same stroke up to that point, so that the increase in control pressure with respect to the change in stroke follows a gentle curve. Since the second control section 21 has a small change in groove width with respect to the valve stroke, the first control section 21
The rate of change in the opening area in the small opening area is smaller than in the large opening area where the opening area is superimposed on the sheet portion 15,
Sudden changes in control pressure due to movement of the spool 8 can be avoided.

In other words, the valve sensitivity in the high pressure region is reduced, suppressing a sudden increase in pressure with respect to the valve stroke, and improving pressure control accuracy.

(Effects of the invention) As described above, according to the invention, the shape of the valve control hole can be changed between the first control part in which the groove width gradually changes with respect to the valve stroke, and the first control part in which the groove width changes little with respect to the valve stroke. Since it is formed from the second control part, it is possible to reduce the area change rate with respect to the valve stroke in the region where the valve opening is small, and the control pressure, which is inversely proportional to the square of the opening area, changes suddenly (suddenly) in the high pressure region. This makes it possible to control pressure with high precision from the low pressure region to the high pressure region.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the main parts of the present invention, Figure 2 A, B, C, D, E, F, G, and H are explanatory diagrams showing the shape of the control hole, and Figure 3 A is the valve stroke. FIG. 3B is a characteristic diagram showing the relationship between the opening area and the opening area, and FIG. 3B is a characteristic diagram showing the relationship between the valve stroke control pressure. Figure 4 is a sectional view of the conventional example, Figure 5A
is a sectional view of the main part, Figure 5B is a front view, and Figure 6 is a front view.
Figure A is a characteristic diagram showing the relationship between valve stroke and opening area, and Figure 6B is a characteristic diagram showing the relationship between valve stroke and control pressure. 6... Solenoid, 7... Spring, 8...
Spool, 14...control hole, 15...seat part,
20...first control section, 21...second control section.

Claims (1)

[Scope of utility model registration request] In a fluid control valve in which a control hole is formed in a valve spool that is in sliding contact with a seat part, and fluid flows through a variable opening formed by the control hole and the seat part, the control hole is connected to the first control part and the first control part. The groove width of the first control part changes gradually with respect to the valve stroke, and the second control part is formed with a groove width that changes little with respect to the valve stroke. Features a fluid control valve.