JPS58152987A - Electromagnetic proportional control valve - Google Patents

Abstract

PURPOSE:To obtain a small-sized electromagnetic proportional control valve stably operated with a small power by constucting a magnetic circuit with a core and a yoke, fixing one end of the core to a sealed diaphragm, and opening and closing the valve in response to an excitation current by means of a lever extended to the opposite side of the sealed diaphragm. CONSTITUTION:The lower end of a core 10 is magnetically connected to a yoke 9 via a gap (g) and the core 10 is , although capable of inclining, restricted so as not to move in the vertical direction by a means not illustrated. Accordingly, the gap (g) is approximately unchangeable even if the core 10 inclines. When a current of NI ampere-turn is applied to a coil 11, the tip of core 10 turns anticlockwise taking the seal diaphragm 21 as a rotary center while the tip of the core 10 is pulled in toward the left yoke side. Consequently, a lever 20 overcomes the thrusting force of a spring 8, allowing a poppet valve 4 to be opened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control valve for fluids such as water and gas, and more particularly to an electromagnetic proportional control valve that controls a fluid flow rate in proportion to an input signal.

Conventionally, the most widely used electromagnetic control valve of this type is an electromagnetic valve that operates 0N-01FF, but it is not possible to proportionally control the flow rate of fluid using an input signal.

If proportional control is absolutely desired, a diaphragm valve using air pressure, a motor valve using a motor, etc. are used.

The present invention is a stuttering device made in view of the above-mentioned conventional situation,
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a novel proportional control valve that can be constructed electromagnetically in a compact and inexpensive manner without using a pneumatic source or an expensive motor.

Common applications include city gas flow control and thermal mass flow needle flow control. 41, the latter thermal mass flowmeter is widely used in the semiconductor industry to control the doping concentration of impurities. In such applications, fluctuations in flow rate can be extreme. If there is a change in flow rate due to disturbance, the automatic control system immediately operates the proportional control valve to cancel out the fluctuation.

What is important about such a valve is that the valve movement is smooth and there is no step-like movement such as stick slip. The allowed stepwise movement is approximately 7 of the total stroke.
It is necessary to be less than 1/10,000th. Diaphragm valves that use air pressure cannot be used because of the friction between the stem foot and the gland packing, which causes stick-slip motion.

Similarly, motorized valves cannot be used for the same reason.

In short, mechanisms involving frictional elements are not available.

An example of a known electromagnetic proportional control valve developed for this purpose is shown in FIG. In the figure, the fluid of the ninth/next pressure P is applied from the input hole of the case L to the valve seat 3. The pressure is reduced at the poppet valve and the output hole! It becomes the primary pressure P2 and is discharged. The poppet valve is connected to an armature 7 via a stem 6.

The poppet valve holder is pressed against the valve seat 3 by a pressing spring t to prevent the valve from opening by itself.

d is a yoke, 10 is a core, // is a drive coil, and l is a thin shield plate for preventing gas leakage. Armature? , the yoke, and the core IO are made of a ferromagnetic material such as electromagnetic mild steel.

The operation when the differential pressure (P knee P2) is zero is as follows. When the ampere turn NI of the drive coil // is increased, the ampere turn NI overcomes the pressing force of the pressing spring l and the poppet valve starts moving upward. Furthermore, the ampere turns are increased and the valve is fully open at NI2.

If the stiffness of the pressing spring j is small (9 f/m for the force required to compress the spring by a unit length), the valve will start with an ampere turn of N, and the valve will be fully open at the ninth moment. That is, it becomes an ON-OFF solenoid valve. In order to prevent this and create a proportional control valve with good positioning, the stiffness 8□ of the pressing spring t must be extremely strong. The power of the round drive coil that overcomes this strong pressing spring and proportionally controls the valve becomes extremely large as will be described later.

As shown in FIG. 1, a system in which the gap g of the magnetic circuit changes depending on the operation is called a gear 4 type magnetic circuit. The gap variant is essentially O from the salt mountain as follows.
It tends to become N-OFν type.

That is, core 10. Assuming that the opposing areas of the B-wheels to the armature 7 are each equal to 8 (-), and ignoring the magnetic resistance of the magnetic circuit, the attractive force F (N) of the armature 7 is expressed by the following equation.

Here, Mo has a vacuum permeability of about 8 power = daπx10'
(wb/Am). (In equation 4, the gap g is squared in the denominator, so when the gap g becomes smaller, the suction force increases rapidly. This is something we often experience in everyday life. The suction force F is expressed as the square of the denominator. The differentiated value is especially called magnetic stiffness S2, and is expressed as
It is expressed by the formula.

Stiffness 82 represents the slope of the gap g and attraction force F characteristic curve. Because it has a negative sign, it is called negative stiffness. This negative stiffness is the main reason why 0N-OF]F tends to occur. In order to stabilize and provide localization, a large positive stiffness S (pressing spring) must be added to make the overall stiffness positive. As is clear from equation (C), the gap g is included in the denominator, so the smaller g is, the stiffness 6
The absolute value of 2 becomes large and therefore requires the use of strong springs for stabilization. As a result, a large ampere turn NI, or power, is required.

Nevertheless, the gap variant shown in FIG. 1 is put into practical use because of rounding for which there is no other better method. Although the proportional control valve shown in FIG. 7 requires a large amount of power, it is important to note that there are no friction parts anywhere and the movement is smooth.

As another proportional control valve for such applications, one that utilizes thermal linear expansion of metal wire is commercially available (for example, U.S. Percent Pestle No.
No. 7). It operates smoothly by controlling the temperature of the metal wire. The disadvantages of this method are that because it uses linear expansion, the valve stroke cannot be large, making it unsuitable for large-capacity valves, and that the response is slow because it uses heat.

The present invention has also been made to obviate the above-mentioned drawbacks and it is therefore another object of the invention to provide an essentially stable electromagnetic proportional control valve.

The object of the chain of the present invention is to configure a magnetic circuit with a core and a yoke, fix one end of the core with a seal diaphragm, and change the area of the other end of the core with respect to the yoke depending on the inclination of the core. This is achieved by an electromagnetic proportional control valve that opens and closes the valve in accordance with the excitation current using a lever extended to the opposite side of the seal diaphragm.

Next, the present invention will be described with reference to a preferred embodiment thereof in Figures C and 3.
Let me explain in detail with reference to the diagram.

FIG. 1 is a plan view showing an embodiment of a proportional control valve according to the present invention, and FIG. 3 is a sectional view thereof.

In Figures 1 and 93, the fluid at the primary pressure P applied from the input hole of case L is reduced in pressure at the valve seat 3 and the poppet valve, and becomes the primary pressure P from the output hole S. The point of discharge is exactly the same as in the case of FIG. It is also the same that the poppet valve da is pressed by the pressing spring g. The lever is connected to the core 10 via a seal diaphragm 21. The core 10 has a round bar shape, and only the upper end is crushed into a rectangular shape with a thickness of a% and a width of 10%. In the case of FIG. 1, the area of the upper end of the core 10 facing the yoke at the gap g is bx. The lower end of the core 10 is connected to the yoke 9 at a gap g. are connected magnetically. Although the core 10 can be tilted by means not shown, it is possible to tilt the core 10 in the vertical direction (
It is restrained so that it cannot move in the longitudinal direction. Due to this rounding, the gap g remains approximately unchanged even if the core IO is tilted. When a NI ampere turn is applied to the coil l/, the tip of the core 10 is pulled toward the left yoke,
The core 10 rotates counterclockwise around the seal diaphragmco/, and as a result, the lever 〃 is rotated by the spring t.
overcoming the pressing force and opening the poppet valve.

The pulling force 1 of the upper end of the core to the left is the gap g. If the magnetic resistance of is ignored, it is given by the following equation (3).

“0b(N1)” ・・・・・・・・・・・・
(3) 1g Since the core tip gap g does not change, the retraction force F is only directly proportional to (NI), that is, the power W, as is clear from the above equation (3). Since the amount X related to the inclination of the core 10 is not included, the phase IAfb is
Negative stiffness8. is also zero. In other words, even if X changes, the retraction lever does not change. For this purpose, the stiffness S of the stabilizing spring I is required to ensure the localization of the entire system.
The construction is extremely small and torturous compared to the case shown in Figure 7. As a result, the driving force (W) can be small.Instrument and Automatic Control Engineers, Automatic Control Handbook, p. 993-
According to 10/3, a method in which the opposing area of the magnetic poles changes without changing the gap, as shown in FIGS. 1 and 3, is classified as a variable area type.

Prototypes of both the gap variable type proportional control valve and the area variable type proportional control valve according to the present invention shown in Fig. 1 were fabricated and compared.
Shown in the table. This solenoid valve has a differential pressure of 0.7 to 9 f/d and a maximum flow rate of 008 bM (8 standard Liter).
perMinute). Secondary pressure P
2 is a case close to vacuum. In this case, the flow becomes a critical flow, the flow rate converted to 8bMK becomes small, and the conditions are the most severe.

Table 1 shows that the power consumption of the gap variable type is approximately 10-X) times greater than that of the area variable proportional control valve according to the present invention. Therefore, as a practical matter.

The coil of the gap-variable control valve overheats, making it unusable. In other words, the gap variation type cannot be put to practical use as a 8LM proportional control valve.

The experimental results shown in Table 1 do not indicate that the stiffness 81 was intentionally increased. Absolute value 1807 of the ratio of spring stiffness S1 to negative stiffness day 2 caused by the magnetic circuit
Day, 1 is called cheap mt. When the stability is /, it is just fON-
This is the limit for transitioning from an OFF type to a proportional control valve. In the above experiment, the stability is 1. This is the case of S. Since it is desirable for the stability to be 1 or more, doing so will require more power.

In the configurations shown in FIGS. 1 and 3, the tip width of the core 10 is directly proportional to the retraction force IK as shown in equation (3), so the larger the width, the better. On the other hand, if the coil 1/ is round, the winding speed will be higher and productivity will be better. As a compromise, the core IO should crush only the tip of the round rod. A flat core may be used if space for the coil, etc. permits.

The seal diaphragm column 1 is pushed upward by the primary pressure. Since the seal diaphragm column 1 has a weak resistance force in the axial direction, it is necessary to prevent the core 10 from popping out by a method not shown. Since the tip of the core io is always magnetically pulled upward, it is necessary to prevent the core 10 from popping out in order to counter this.

In the nine embodiments described above, for convenience of explanation, the fluid is made to flow from left to right, but it goes without saying that there is no problem even if the fluid flows in the opposite direction.

Furthermore, it is clear that the same effect can be obtained even if the upper end of the core 10 is pulled to the right by a spring without directly pressing the poppet valve trough with the pressing spring t.

Moreover, it is practically advantageous to use a mild steel l11i0 cylinder instead of the stiff U-shaped yoke shown in FIG. 3, and to serve as both a magnetic path and a protective case.

Furthermore, as shown in FIG. 3, it is clear that the same effect can be obtained by attaching a coil only to the yoke 9 side or both, instead of having the core IO pass through the coil /l.

Further, the same effect can be achieved even if a ball or other shaped valve is used instead of the triangular poppet valve.

The present invention is constructed and operates as described above.According to the present invention, four major effects are that a relatively small and stable proportional control valve can be obtained with low power, but there are also secondary effects. Another great advantage is that by changing the lever ratio, it can accommodate various strokes and valve seat diameters. Additionally, it becomes easier to deal with changes in the maximum rated flow rate.

In addition, there are cases where it is desired to accurately deflect the valve using a signal current or voltage from the outside, but in this case, a deflection conversion element such as a Hall element is attached to the tip of the core to generate a feedback position signal. , accurate deflection control can be achieved by controlling the coil current using an amplifier so that it is equal to the set signal. A displacement conversion element used for such purposes is called a positioner. Another great advantage of the present invention is that the positioner can be easily installed. In the configuration shown in FIG. 1, it is structurally impossible to attach a positioner.

Generally, in the case of impurity doping of a semiconductor, gas contamination is extremely removed, so the armature 7 cannot be exposed to the atmosphere as shown in FIG. Cladding with a material such as stainless steel is essential. This is also necessary when using water or other corrosive fluids.

On the other hand, the present invention has the great advantage that it does not require the use of materials that cause such problems in the lower part of the seal diaphragm.

As is clear from the above description, according to the present invention, a small electromagnetic proportional control valve that operates stably with low electric power can be easily obtained, and its practical effects are very large.

[Brief explanation of the drawing]

FIG. 7 is a sectional view of a conventional electromagnetic proportional control valve, and FIG. 2 is a plan view showing an embodiment of the electromagnetic proportional control valve according to the present invention.
Figure 3 is a sectional view of one embodiment of the present invention shown in Figure 7. L...Case, C...Input hole, J...Valve seat, D...
...Bopets 1? ,! ...Output hole, 6...Stem, 7
... Armature, l... Pressing spring, de...
・Yoke%10... Core, //... Drive coil, /
Co...shield plate, J...lever, top...seal diaphragm. Patent applicant: Okura Electric Co., Ltd. Agent: Yutabe Kumagai, patent attorney Figure 2 1 Figure 3

Claims (1)

[Scope of Claims] (C. A magnetic circuit is formed by the core and the l-ring, one end of the core is fixed with a seal diaphragm, and the area of the other end of the core relative to the yoke changes depending on the inclination of the core. An electromagnetic proportional control valve configured to open and close the valve in accordance with an excitation current by a lever extending to the opposite side of the seal diaphragm. The electromagnetic proportional control valve according to claim 1, which further prevents mold from being pressed. (3) A spring is attached to both the core side and the expansion side. Claim No. 3 further characterized in that the electromagnetic proportional control valve described in Clause C. The electromagnetic proportional control valve described in paragraph (1).