JPH08210550A - Valve device - Google Patents

Abstract

PURPOSE: To provide a valve device in which a predetermined valve travel can be obtained by means of less magnetmotive force by regulating the length of an initialized magnetic gap. CONSTITUTION: A loading means 44 displacing a diaphragm 22 in a valve seat 32 direction is constructed of a thin disk spring 36 and a valve stem 34. The length of an initialized electromagnetic gap between an electromagnetic actuator 38 and the valve stem 34 in initialization is set to be approximately equal to the length Lcs of a reference initialized magnetic gap, by which the valve stem 34 is substantially brought into contact with the magnetic actuator 38 when the maximum permissible magnetmotive force for the electromagnetic actuator 38 is generated and composite restitution force compounded of restitution force of the diaphragm 22 and restitution force of the disk spring 36 is balanced with thrust of the electromagnetic actuator 38, or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve device for precision gas flow rate control for precisely controlling the flow rate of a fluid having a relatively small flow rate such as gas.

[0002]

2. Description of the Related Art Generally, in order to manufacture a semiconductor product or the like, it is necessary to flow a small amount of processing gas while controlling it with high precision. For controlling this flow rate, for example, a precision gas flow rate control device is used. ing.

This type of gas flow rate control device is mainly composed of a sensor unit for detecting the flow rate of a trace amount of gas, a valve unit, and a control circuit unit for controlling this. The sensor portion has a sensor in which an electrothermal coil is wound around a thin tube through which a small proportion of the total gas amount passes, and most of the gas flows through the bypass. Then, the control circuit unit controls the valve opening of the valve device based on the detection value of the sensor unit to control the gas flow rate. In this case, in order to control the valve opening, since the entire gas flow rate itself is very small, it is necessary to control the valve opening accurately against the diaphragm load within a stroke range of several tens of μm, for example. For this reason, a laminated piezoelectric element body is generally used as an actuator because it has a large change in thrust within a small stroke range.

A conventional gas flow rate control device will now be described with reference to FIG. 12. A flow rate of a small ratio of the total gas flow rate is applied to both ends of the bypass 4 of the fluid passage 2, for example, a diameter of 0.5.
A thin tube 6 having a size of about mm is formed, and a pair of electrothermal coils 10 of the sensor unit 8 is wound around the thin tube 6. The pair of electrothermal coils 10 has a high resistance temperature coefficient of, for example, about 5000 PPM / degree, and a bridge is formed by combining this with two resistors to allow current to flow from the constant current circuit 12. Then, in the coil on the upstream side of the gas flow, heat is taken away by the gas flow and the temperature drops, and on the contrary, when the coil on the downstream side tends to heat up and heat transfer occurs, the balanced bridge circuit becomes unbalanced. The potential difference generated at this time becomes the flow rate signal.

This signal is amplified by the amplifier circuit 14 and then input to the comparison control circuit 16, where the input signal is compared with the reference flow rate so as to maintain a predetermined flow rate. The element body 20 is expanded and contracted to expand the valve body,
That is, the diaphragm 22 is moved up and down to have an appropriate valve opening. The reason why the diaphragm 22 made of a thin metal plate is used as the valve body is as follows.

In the past, there was a valve device in which a moving part such as a spring was housed in the gas flow path. However, when a corrosive gas is used, the spring or the like exposed to the gas may cause corrosion or wear. This is because particles are generated and are mixed in the gas flow. That is, in the semiconductor manufacturing process, a high degree of cleanliness is required because fine processing is performed, and when rubber or plastic is used as the valve body, particles such as chips that cause defects in the silicon wafer are generated. With a metal diaphragm, a valve body with a simple structure and high cleanliness can be realized.

[0007]

By using the laminated piezoelectric element body 20 for operating the diaphragm 22 which is the valve body as described above, for example, 30 μm is obtained.
Although it is possible to control the gas flow rate within a minute stroke range, the laminated piezoelectric element 20 of this kind has a minute stroke and is very expensive. There is a problem that the controllable flow rate range is low and is very expensive. Therefore, it is possible to use a solenoid valve having a conventional structure in place of the piezoelectric element 20 and the diaphragm 22, but as described above, in the case of the conventional solenoid valve, particles are generated from a spring exposed to gas. Cannot maintain high cleanliness.

On the other hand, in order to maintain a high degree of cleanliness by using an electromagnetic actuator, it is necessary to increase the thrust of the actuator when using a metal diaphragm as the valve element. This is because the thrust required to displace the diaphragm is several times larger than that of the solenoid valve having the conventional structure. Therefore, the present inventor has earnestly studied to realize an electromagnetic actuator that is cheaper than a piezoelectric element body and can maintain cleanliness. Here, the high thrust of the actuator was solved by devising a magnetic circuit and using a yoke material having a high saturation magnetic flux density. Then, this technique was disclosed in a previous application (Japanese Patent Application No. 5-209868).

In the technique of this application, a disc spring is provided so that the diaphragm, which is the valve body, is always biased in the closing direction, and the actuator and the force obtained by subtracting the reaction force of the diaphragm from the force of the disc spring. The valve opening is set at the place where the thrust force due to is balanced. In other words, the disc spring is adapted to match the magnetomotive force characteristic of the electromagnetic actuator by utilizing the characteristic that a large amount of change in elastic force is exhibited within a minute stroke. Also enables highly precise minute stroke control of the diaphragm.

However, when the temperature of the electric circuit system of the electromagnetic actuator is low, good flow rate control is performed, but the temperature of the electromagnetic actuator is high due to high duty cycle and high ambient environment temperature. When it rises, the magnetomotive force generated when the same voltage is applied becomes low, which causes a new problem that the responsiveness during control deteriorates. This will be described with reference to FIG. 13. FIG. 13 shows an electric equivalent circuit of the electromagnetic actuator, and the electromagnetic actuator 24 is shown by a series circuit of a resistance component 26 and an inductance component 28. This circuit is configured as a constant voltage circuit because of the simplification of the circuit, but in order to generate a magnetomotive force in the actuator, it is generally in the range of 0 to 15 V by applying a voltage according to the valve opening degree. , A predetermined valve opening is obtained.

However, when the resistance value of the inductance component 28 increases due to the temperature rise of the circuit system, the current decreases,
The magnetomotive force when the same voltage is applied becomes low. Therefore, in order to obtain the same magnetomotive force, the applied voltage must be increased, and as a result of the PID control calculation, the output command signal for valve control reaches the applied voltage for obtaining the required magnetomotive force. The time became longer and the response of the flow rate control deteriorated. At present, it is required to have responsiveness such that a predetermined flow rate must be reached within 2 seconds after input of a flow rate setting command from the outside, but due to the temperature rise as described above,
The responsiveness had been extended to about 2.4 to 3 seconds. In addition, in this valve device, when the electromagnetic actuator and the valve rod partially or wholly contact with each other to cause residual magnetism, the valve opening characteristic is affected thereby. In order to prevent this from occurring, the magnetic gap between them is made relatively large at the time of initial setting. Therefore, a large current is required for driving, and problems such as heat have occurred. The present invention has been made to pay attention to the above problems and to solve them effectively. An object of the present invention is to provide a valve device capable of obtaining a predetermined valve displacement amount with a small magnetomotive force by adjusting the length of the initially set magnetic gap.

[0012]

As a result of intensive studies on a valve device using an electromagnetic actuator, the present inventor has found that there are two different initial magnetic gap lengths for a certain valve displacement amount. The present invention has been achieved by finding out that. That is, in order to solve the above-mentioned problems, a valve main body having a fluid inlet, a fluid outlet, and a valve seat between them, and a diaphragm having a fixed peripheral edge arranged facing the valve seat. , A load means provided on the side opposite to the valve seat with respect to the diaphragm for displacing the diaphragm in the valve seat direction, and acting to separate the diaphragm from the valve seat against the load means. An electromagnetic actuator, the load means is composed of a thin disk spring fixed at the periphery, and a valve rod fixed to the center of the thin disk spring, the electromagnetic actuator and the valve rod initial stage When the maximum allowable magnetomotive force of the electromagnetic actuator is generated, the valve rod is substantially in contact with the electromagnetic actuator when the maximum electromagnetic force of the electromagnetic actuator is generated. The length of the reference initial magnetic gap is set to be substantially equal to or smaller than the length of the reference initial magnetic gap such that the combined elastic force obtained by combining the elastic force of the disc spring and the thrust of the electromagnetic actuator is substantially balanced. It is configured as follows.

[0013]

Since the present invention is constructed as described above, the diaphragm as the valve body is always urged by the elastic force of the thin disc of the load means so as to close the valve toward the valve seat of the valve body. ing. When adjusting the valve opening, for example, a predetermined current is passed through the electromagnetic coil 46 to attract the valve rod and move the diaphragm away from the valve seat to adjust the valve opening. In this case, the suction force of the electromagnetic actuator increases in inverse proportion to the square of the gap, but the elastic force of the thin disk spring acts so as to properly oppose the suction force of the electromagnetic actuator, and the smoothness of the valve opening is ensured. This enables substantially linear control.

Here, as a result of the length of the initial setting gap being set as described above, a predetermined valve displacement amount can be obtained with a small magnetomotive force as compared with the valve device previously proposed by the present inventor. Therefore, the drive voltage or drive current can be suppressed to that low. Also, by interposing a spacer member made of a non-magnetic material in the magnetic gap between the electromagnetic actuator and the valve rod, contact between the two is prevented even if the magnetic gap at the time of initial setting is made small, and therefore the residual magnetic flux causes It is possible to prevent the deterioration of the responsiveness.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the valve device according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a configuration diagram showing a valve device according to the present invention, FIG. 2 is a component diagram of a dynamic system of the valve device of the present invention, FIG. 3 is an enlarged view of a main part showing a state when the valve is fully closed, and FIG. FIG. 5 is an enlarged view of a main part showing an open state of the valve, and FIG. 5 is a plan view showing a thin disk spring used in the apparatus shown in FIG. First, before describing the specific configuration of the valve device of the present invention, the basic configuration thereof will be described based on FIG.

In the figure, reference numeral 2 is a fluid passage, and a valve body 30 having a fluid inlet and a fluid outlet is provided in the middle of the passage.
The diaphragm 22 can be bent and deformed to be seated on the valve seat 32 at the fluid inlet. The diaphragm 22 is pressed by directly or indirectly contacting the valve rod 34, and the pressing force is generated by the biasing spring 36. The biasing spring 36 corresponds to a thin disk spring described later. Valve stem 34
The electromagnetic actuator 38 is disposed above the valve, and an attractive force is applied to the valve rod 34 so that the valve rod 34 is pulled upward. Figure 2 shows the valve fully closed and the diaphragm 2
2 is always set to generate a reaction force F _D. Then, the sum of the diaphragm reaction force F _D and the thrust force (electromagnetic force) F _A by the electromagnetic actuator 38 is balanced at a position equal to the elastic force F _S of the biasing spring 36, and the valve opening is set there. From this value, the relation can be expressed as follows. F _S = F _A + F _{D In the} figure, the wavy line shows the state where the diaphragm 22 gradually returns to its original shape due to the increase in the thrust of the electromagnetic actuator, and the valve gradually opens.

The above is the basic configuration of the present invention, but the feature of the present invention is that a thin disk spring having a spring characteristic similar to the thrust characteristic of an electromagnetic actuator is used as the biasing spring and the magnetic force at the time of initial setting is set. The point is that the gap length is set within an appropriate range. Next, the valve device of the present invention will be specifically described.

As shown in FIG. 12, the valve device 40 of the present invention is configured as a part of a gas flow rate control device provided in a fluid passage through which a fluid such as gas flows, and is detachably attached to, for example, a pipe 42 as a whole. To be This valve device 4
0 is a valve body 30 having a valve seat 32 and the valve seat 3
2 is a thin plate-shaped diaphragm 22 which is arranged so as to be opposed to 2 and has a fixed peripheral edge portion and which is provided so as to be seated on the valve seat 32; The load means 44 provided on the side, and the diaphragm 2 against the load means.
An electromagnetic actuator 38 including, for example, an electromagnetic coil 46 and a yoke 48, which acts to separate the valve seat 32 from the valve seat 32.
It is mainly composed of and. And this load means 4
4 is a thin disk spring 36 whose peripheral edge is fixed to the valve body side, and a pressing member 50 and a connecting member 9 to the spring 36.
It is mainly configured by a valve stem 34 having a function as a plunger which is integrally connected via 0.

Specifically, the valve body 30 is removably provided in the middle of the pipe 42 serving as the fluid passage, and a fluid which is circularly opened and connected to the fluid inflow passage 52 is provided inside the valve body 30. An inflow port 54 and a fluid outflow port 58, which is connected to the fluid outflow passage 56 and has a circular opening, are arranged in parallel. The fluid inlet 54 is formed so as to project slightly above the bottom of the valve body, and the opening edge of the inlet 54 serves as the valve seat 32. Above the valve seat 32, a diaphragm 22 as a valve body, which is a circular plate made of, for example, stainless steel and having a diameter of about 22 mm, is separated from the valve seat 32 by a distance of, for example, about 100 μm in a flat state. It is fixed by a fixing member 60 and is provided in a substantially horizontal direction in the figure, that is, in a direction orthogonal to the axial direction of the valve rod 34. A ring-shaped corrugation 62 is provided on the diaphragm 22 to allow the bending. In the illustrated example, the diaphragm 22 is bent downward and is fully closed.

The diaphragm 22 can be deformed with a force sufficiently smaller than the thrust of the electromagnetic actuator. The center of the diaphragm 22 is set so as to correspond to the center of the valve seat 32, and the diaphragm 22 is bent downward to completely close the fluid inlet 54. The thin disk springs 36 are arranged in parallel with the diaphragm 22 with a predetermined space between them, and the peripheral edge thereof is between the upper end of the diaphragm fixing member 60 and the protrusion of the ring-shaped outer casing 64. It is sandwiched and fixed.
The lower end of the outer casing 64 is fixed to the valve body 30 side. As shown in FIG. 5, the disc spring 36 has an insertion hole 66 in the center thereof, and is set to have a diameter of, for example, about 5 mm, and the pressing member 50 is sandwiched and fixed. Therefore, the disc spring 36 is elastically displaceable in the vertical direction in the figure integrally with the valve rod 34 through the connecting member 90 in a state where the peripheral edge portion is fixed. The disc spring 36 is made of, for example, a nickel alloy having a thickness of about 0.25 mm.

Further, a long adjusting hole 68 penetrating through the valve rod 34 and the connecting member 90 and coming out in the vertical direction is formed, and a screw thread is cut on the lower inner wall of the adjusting hole 68, and the diaphragm adjusting means is formed therein. The adjusting screw 70 is screwed so as to be capable of projecting and retracting downward. And this adjustment screw 7
0 and a cylindrical receiving member 72 provided at the center of the upper surface of the diaphragm 22, a steel ball 74 is interposed, and a conical recess formed on the upper surface of the receiving member 72 forms a lower portion of the steel ball 74. By receiving the force, even if the biasing force against the steel ball 74 is uneven, a uniform force can be applied to the diaphragm 22. The adjusting screw 70 can be adjusted to associate the displacement relationship between the diaphragm 22 and the disc spring 36, and the reaction force of the diaphragm 22 and the elastic force of the disc spring 36 facing the diaphragm 22 will be described later. It can be treated as a synthetic spring property.

On the other hand, a cylindrical ring-shaped long sleeve 76 is fixed to the upper end of the ring-shaped outer casing 64, and a thread is formed on the inner wall surface thereof. And
A cylindrical actuator holding cylinder 78 that holds the outside of the electromagnetic actuator 38 has a thread 80 formed on the outer periphery thereof, and this thread is detachably engaged with the screw on the inner wall of the sleeve 76. Therefore, the gap adjusting means 84 is formed by screwing the screw thread 80 of the actuator holding cylinder 78 with the screw on the inner wall surface of the sleeve 76, and by rotating the holding cylinder 78, the length of the magnetic gap MG is adjusted. can do.

A magnetic gap MG is formed between the lower end of the electromagnetic actuator 38 and the upper end of the valve rod 34. When the maximum allowable magnetomotive force of the electromagnetic actuator 38 is generated, the valve rod 34 is substantially in contact with the lower surface of the actuator 38 so that the length of the magnetic gap MG at the time of initial setting is substantially in contact with the elastic force of the diaphragm 22 and the disc spring 36. The length of the reference initial magnetic gap is set to be equal to or smaller than the length of the reference initial magnetic gap such that the combined elastic force obtained by combining the elastic forces and the attraction force (thrust) of the electromagnetic actuator 38 are substantially balanced. As a result, the desired valve displacement amount can be obtained with a small magnetomotive force, which is a very excellent effect. Further, on the upper surface of the valve rod 34, the valve rod 3
4 and the actuator 38 are prevented from directly contacting each other,
Further, the spacer member 82 made of a thin non-magnetic material is provided to prevent the adverse effect on the characteristics due to the residual magnetic flux. As this material, for example, polyester resin or the like can be used. Since the spacer member 82 is provided in the magnetic gap MG, it may be provided not on the valve rod 34 side but on the lower end surface side of the electromagnetic actuator 38.

Next, the operation of the valve device constructed as described above will be described. First, most of the fluid such as gas flowing through the fluid passage 2 passes through the bypass 4, and the fluid having a constant diversion ratio passes through the thin tube 6 (see FIG. 12). Then, the fluid passing therethrough reaches the fluid inlet 54 through the fluid inflow path 52 of the valve device 40 of the present invention, and the valve body 3
After passing through 0, the fluid outlet 58 is connected to the fluid outlet 56.
It flows to the side (see Fig. 1). The sensor unit 8 is the thin tube 6 described above.
The total flow rate is detected by the fluid flowing inside, and the result is input to the comparison control circuit 16 and compared with the set flow rate input from outside here (see FIG. 12). Then, the control circuit 16 applies a drive current to the electromagnetic coil of the electromagnetic actuator 38 of the valve device 40 to control the valve opening so that the overall flow rate maintains the set flow rate (see FIG. 1).

Next, the control of the valve opening of the valve device will be described. First, FIG. 3 shows the state when the valve is fully closed, and no drive current is applied to the electromagnetic actuator 38. In this state, the elastic force F _S of the disc spring 36 pushes the diaphragm 22 downward in the drawing to seat it, thereby closing the valve port. At this time, the diaphragm 22 produces a reaction force F _D (see also FIG. 2). In order to completely stop the flow of the fluid, it is not enough that the diaphragm 22 is seated, and it is known that a certain amount of preload is applied. In this case, the amount of preload varies from the elastic force (F _S ) to the reaction force (F _S
D ) will be subtracted. In the adjustment of the preload, in the state shown in FIG. 1, the electromagnetic actuator 38 screwed into the sleeve 76 is rotated and removed from the sleeve 76, and a driver or the like is inserted into the sleeve from above and the connecting member 90 of the valve rod 34 is inserted. This is done by rotating the adjusting screw 70 provided at the position and retracting it.

From this fully closed state, the electromagnetic actuator 38
When a drive current is applied to the valve rod 34, an upward thrust (electromagnetic force) acts on the valve rod 34 as shown in FIG. 4, and the valve rod 34 is pulled up to return the diaphragm 22 to its original state. When the forces, F _A , F _S , and F _D are balanced, the pulling is stopped, and the flow rate according to the pulling amount flows. With the pulling up of the valve rod 34, the deformation of the disc spring 36 increases, so that the elastic force F _S increases.
The reaction force F _D of the diaphragm 22 becomes smaller. Now, the magnetic gap MG between the electromagnetic actuator 38 and the valve rod 34 will be examined.

In general, the thrust force (electromagnetic force) P generated by the electromagnetic actuator has a relationship inversely proportional to the square of the magnetic gap (air gap) as shown in the following equation using the magnetomotive force as a parameter. P = U ² · μ ₀ · S / (4 · δ ² ) where P: thrust (electromagnetic force) (N), U: magnetomotive force (A
T), μ ₀ : permeability of the air gap, S: magnetic path cross-sectional area (m ² ),
δ: Length of magnetic gap That is, the smaller the length δ of the magnetic gap, the larger the thrust P, and the larger the length of the magnetic gap, the smaller the thrust. If the drive coil current is increased and the magnetomotive force U is increased, the thrust P also increases. Here, in the valve device of the present invention, when the disc spring 36 and the diaphragm 22 having a spring property are combined into one and are regarded as a synthetic spring, this synthetic spring characteristic has the elastic force F _S of the disc spring 36. from a value obtained by subtracting the reaction force F _D of the diaphragm 22 (F _S -F _D), its orientation is the direction opposite to the thrust force F _a by the electromagnetic actuator 38.

Therefore, the valve rod 3 having the function of the plunger.
4 receives a force in the direction away from the electromagnetic actuator 38 by the force of the synthetic spring. When the length L of the magnetic gap MG is large, the amount of bending of the disc spring 36 is small, so that the combined spring force is small, and conversely, when the length L of the magnetic gap is small, the bending of the disc spring 36 is small. Since the amount is large, the synthetic spring force is large. FIG. 6 is a graph showing the relationship between the length L of the magnetic gap, the thrust (electromagnetic force) of the electromagnetic actuator 38, and the composite spring characteristic line. The magnetomotive force of the actuator 38 is 100 AT (ampere turn)
To 300 AT. When the length of the magnetic gap changes, the thrust of the actuator increases or decreases in a quadratic curve.

In the structure shown in FIG. 1, when the actuator holding cylinder 78, which is a part of the gap adjusting means 84, is rotated to adjust the vertical position of the actuator, the force of the composite spring does not change, but the length of the magnetic gap increases. Since the length L changes, the magnetic gap characteristic lines A1 to A3 in FIG.
Translates. That is, when the actuator is moved upward, the length of the magnetic gap increases, so that the composite spring characteristic line A1 moves to the right side in the graph to become a characteristic line A2 shown by a wavy line. When moved to, the length of the magnetic gap becomes smaller, so that the composite spring characteristic line A1 moves to the left side in the graph and becomes a characteristic line A3 shown by a wavy line. Then, this composite spring characteristic line A1
The point at which points A3 to A3 intersect the thrust curves B1 to B4 is the point at which the thrust and the synthetic spring force are balanced, and the valve opening of the valve (diaphragm) is defined at this point.

Therefore, when the composite spring characteristic line is fixed,
When the magnetic gap length when the actuator is not operating is fixed and the characteristic line A1 is selected, for example, the valve when the magnetomotive force of the actuator is changed from 100 AT to 300 AT, that is, the diaphragm is the intersection with the curve B1. The length changes from the point P1 to the point P2, which is the intersection with the curve B4, corresponding to the length of the horizontal axis. That is, assuming that the characteristic line A1 is selected and set for the magnetic gap, when the current flowing through the electromagnetic coil is gradually increased, when the current is small, there is no point (intersection) that balances with the composite spring characteristic line A. However, the magnetomotive force is 10
When reaching 0AT, the thrust and the composite spring force balance at point P1 only when the preload is applied.

Further, when the magnetomotive force is increased by increasing the current, the valve rod gradually rises, the valve opens, and the maximum magnetomotive force 30
Point P2 of intersection of thrust curve B4 of 0AT and composite spring characteristic line A1
Until the valve will move. Here, the valve displacement will also be considered. The present inventor considered the valve displacement, and as a result, the valve displacement amount (corresponding to the flow rate).
Has a region determined by the length of the magnetic gap at the time of initialization and a region determined by the maximum magnetomotive force of the actuator. If the region is determined by the region determined by the length of the magnetic gap at the time of initialization, it will be small. The present invention has been accomplished based on the finding that an equivalent amount of displacement can be obtained with a magnetomotive force. In the previous application (Japanese Patent Application No. 5-209868), a large magnetomotive force is required because the default magnetic gap length is defined in the region determined by the maximum magnetomotive force of the actuator. There were various problems associated with fever.

When the thrust of the actuator is zero and the diaphragm 22 is in the fully closed state, a downward force (preload) is exerted on the diaphragm by a synthetic spring so as to maintain this fully closed state.
As given above. When a driving current is applied to the electromagnetic coil 46 from the state where the thrust of the actuator is zero and the driving current is increased, the actuator causes the valve rod 3 to move.
4 thrust force is applied to the valve rod,
Moves until it contacts the underside of the actuator. The amount of movement at this time is the valve displacement. However, the current passed through the electromagnetic coil 46 of the actuator 38 has a maximum value determined by a certain input voltage, and the maximum magnetomotive force is also determined thereby. This is defined as the maximum allowable magnetomotive force.

Now, assuming that the maximum allowable magnetomotive force is 300 AT, the relationship between the length of the initially set magnetic gap and the valve displacement will be considered as shown in FIG. The actuator 38 and the valve rod 34 are shown in FIG. 7, and the amount of movement of the valve rod 34 (shown by the alternate long and short dash line) is the amount of valve displacement. The position of the valve rod 34 when the thrust of the actuator is zero is shown, and the position of the valve rod 34 when the maximum allowable magnetomotive force of 300 AT is applied to the actuator is shown by a chain line. Therefore, the distance L _G between the actuator 38 and the valve rod 34 shown by the solid line is
This is the default magnetic gap length in this model. As shown in FIGS. 7A to 7G, the actuator is gradually moved upward to gradually increase the length L _G of the initially set magnetic gap.

Now, when the maximum allowable magnetomotive force 300AT is applied to each actuator in the length of the initial setting magnetic gap as shown in FIGS. 7 (A) to 7 (G), FIG. In FIG. 7 (C), the length of the magnetic gap is too small as compared with the thrust force generated at that time, so the valve rod 34 abuts the actuator 38 and the further valve displacement is mechanically limited, Although not obtained, if the length L _G of the magnetic gap is further increased from the state shown in FIG. 7 (C), the lower surface of the actuator and the upper surface of the valve rod 34 come into close contact with each other and are almost pressed between them. The thrust of the actuator and the combined elastic force of the combined spring are in balance with each other in the state where no pressure is generated. The state at this time is shown in FIG. The length of the magnetic gap at this time is defined as a reference initial magnetic gap L _GS .

Then, as shown in FIGS. 7 (E) to 7 (G), when the length of the initial setting magnetic gap is further increased from the state shown in FIG. 7 (D), the actuator and the valve rod are separated from each other. Do not come into contact with each other, and the displacement amount of the valve rod, that is, the valve displacement, gradually decreases. Therefore, FIG.
The region on the left side of (D) is the region where the valve displacement is determined by the length of the initially set magnetic gap,
On the other hand, in the area on the right side of FIG. 7D, the valve displacement is an area determined by the maximum allowable magnetomotive force.

FIG. 8 shows the results of plotting the valve displacement amounts shown in FIG. In the figure, point Q1 corresponds to the state shown in FIG. That is, when the length L _G of the initial setting magnetic gap is gradually increased from zero, the valve displacement amount is gradually increased while being mechanically restricted by the valve rod contacting the actuator, but at a point Q1 (Fig. (Corresponding to 7 (D)), the further valve displacement becomes maximum,
This state is maintained for a short time. Then, when the length L _{G of the} magnetic gap further increases, the valve displacement amount gradually decreases this time. That is, the meaning of the graph shown in FIG. 8 is that in order to obtain the same valve displacement amount, rather than setting the magnetic gap in the region on the right side of the point Q1, it is set at the point Q1 or on the left side of the point Q1. It is shown that the magnetomotive force (AT) can be reduced by setting the magnetic gap in the region.

At the time of filing the previous application (Japanese Patent Application No. 5-209868), the existence of a region determined by the length of the initial setting magnetic gap in FIG. In consideration of a problem caused by a mounting error when mounting the actuator, a point Q1 in FIG.
The area on the right side of, ie, the actuator is located above the position defined by the point Q1,
In 2, the length L _G of the initial setting magnetic gap was set. On the other hand, in the valve device of the present invention,
In FIG. 8, the length L _G of the initial setting magnetic gap is set at the position of the point Q1 or the area on the left side of this, for example, the point S1. That is, the length L _G of the initial setting magnetic gap of the device of the present invention is set to be substantially the same as or smaller than the length L _GS of the reference initial magnetic gap shown at the point Q1. The length L _GS of this reference initial magnetic gap
Needless to say, when the maximum allowable magnetomotive force changes due to improvements in the electromagnetic coil and its control circuit, the maximum allowable magnetomotive force changes accordingly.

As described above, the maximum allowable magnetomotive force is 300 AT
Assuming that, when the length of the initially set magnetic gap (which is equal to the length of the reference initial magnetic gap in this case) is set at the point Q1 in FIG. 8, the combined spring characteristic at that time is as shown in FIG. It will be represented as a characteristic line A1 in the inside. In an actual valve device, as shown by a point S1 in FIG. 8, the length of the initial setting magnetic gap is set at a position slightly shifted to the left of the point Q1.
The maximum allowable magnetomotive force is not exhibited, and control is performed with a margin, and a non-magnetic spacer member 82 is provided in order to prevent the actuator and the valve rod from coming into contact with each other to generate residual magnetism.

Now, as described above, point Q1 in FIG.
At the position of or at a point on the left side of this, the length of the magnetic gap is initialized so that the magnetomotive force (driving current) is the same as that of the device disclosed by the inventor in the previous application. It is possible to generate the valve displacement amount of

Therefore, since the amount of heat generated in the electromagnetic actuator and this control circuit system is reduced accordingly, the amount of heat generated in FIG.
In the circuit as shown in FIG. 3, the resistance value of the resistance component 26 hardly increases, and it is possible to improve control responsiveness by eliminating various problems caused by heat generation. In an actual valve device, the length of the initial magnetic gap is set to, for example, about 100 μm, and the thickness of the magnetic gap is set to 8 μm.
When a spacer member made of a polyester film of 0 μm is interposed, a maximum valve displacement amount of 20 μm is obtained, and the maximum flow rate at this time is 200 cc / min, and this valve device can adjust the flow rate in the range of 0 to 200 cc / min. Become. When a spacer member having a thickness of 25 μm is interposed, a maximum valve displacement of 75 μm is obtained, and the maximum flow rate at this time is 10 liters / min. This valve device can adjust the flow rate in the range of 0-10 liters / min. Becomes The responsiveness of the device of the present invention will now be compared with that of the device of the previous application.

FIG. 9 (A) shows the responsiveness of the flow control in the device of the previous application, and FIG. 9 (B) shows the flow control of the device of the present invention with the same PID control constant as in FIG. 9 (A). Responsive. In FIGS. 9A and 9B, the inclination angle θ of the characteristic indicating the actuator drive voltage is the same. In the case of the device of the previous application shown in FIG. 9 (A), even if the command signal SP indicating the set flow rate is input, the heat generation amount is large, and therefore the circuit resistance value is correspondingly large. The actuator drive voltage for obtaining a large magnetomotive force (current) becomes large, and as a result, the actual flow rate increases slowly and the reactivity is poor. The time t1 from the input of the command signal SP to the reaching of the set flow rate takes, for example, about 3 seconds and exceeds the allowable limit.

On the other hand, in the case of the apparatus of the present invention shown in FIG. 9B, the command signal SP
When is input, the actuator drive voltage for obtaining the required magnetomotive force is small and the desired magnetomotive force can be quickly obtained, so the actual flow rate reached the prescribed flow rate in a short time.
In this case, the time t2 from the input of the command signal SP to the reaching of the set flow rate is within 2 seconds, for example, about 1.5 seconds, which shows a very excellent responsiveness. In this case,
In the case of the device of the previous application shown in (A), a driving voltage of 13 to 14 V was required to flow the maximum set flow rate, but in the case of the device of the present invention shown in FIG. 9B, The driving voltage was about 9 to 10 V in order to flow the same maximum set flow rate as above. This means that even if the actuator temperature rises excessively, the drive voltage can be raised to about 14 V to increase the flow rate, and the margin of device design can be improved.

FIG. 10 shows the actual flow rate measurement result of the device of the previous application, and FIG. 11 shows the actual flow rate measurement result of the device of the present invention. FIG. 10 (A) shows the characteristics at the time of hot start at a fluid differential pressure of 0.5 kg and a temperature of 15 ° C., and FIG. 10 (B) shows a fluid differential pressure of 0.5 kg.
The characteristics at the time of hot start at a temperature of 40 ° C. are shown. When the temperature is 15 ° C, the set flow rate flows in about 2 seconds after the command signal is input, indicating a good result, but when the temperature is 40 ° C, it takes about 3 seconds until the set flow rate is reached after the command signal is input. It took a long time, and the responsiveness has deteriorated considerably.

On the other hand, FIG. 11 (A) and FIG.
(B) shows fluid differential pressures of 0.5 kg and 3.0 kg, respectively.
Shows the characteristics of the device of the present invention when the temperature is both 15 ° C., and both reach a predetermined flow rate within 1.0 to 2.0 seconds after the input of the command signal, and show good results. It turned out that In addition, FIG. 11C and FIG.
Shows the characteristics of the device of the present invention when the fluid pressure difference is 0.5 kg and 3.0 kg and the temperature is 40 ° C., respectively.
After inputting the command signal as in the case of 1 (A) and FIG. 11 (B), both have reached the predetermined flow rate within the range of 1.0 to 2.0 seconds and exhibit good responsiveness. There was found. It should be noted that the respective dimensions shown in the above embodiment are merely examples and are not limited to these.

[0045]

As described above, according to the valve device of the present invention, the following excellent operational effects can be exhibited. By setting the length of the initially set magnetic gap to be smaller than that of the prior application device by the present applicant, the driving voltage for obtaining the same valve displacement amount can be significantly reduced. Therefore, since the magnetomotive force (driving current) of the electromagnetic actuator can be suppressed to a low level, the amount of heat generation can be reduced and the temperature rise can be suppressed to a low level. It can be improved and kept good. Further, by interposing a spacer member made of a non-magnetic material between the electromagnetic actuator and the valve rod, as described above, even if the length of the magnetic gap at the time of initial setting is reduced, the two directly contact each other or the valve rod is contacted. It is possible to prevent the residual magnetism from being generated and adversely affecting the controllability.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a valve device according to the present invention.

FIG. 2 is a structural element diagram of a dynamic system of a valve device according to the present invention.

FIG. 3 is an enlarged view of an essential part showing a state when the valve is fully closed.

FIG. 4 is an enlarged view of a main part showing an open state of a valve.

5 is a plan view showing a thin disk spring used in the apparatus shown in FIG. 1. FIG.

FIG. 6 is a graph showing the relationship between the length of the magnetic gap and the thrust of the electromagnetic actuator and the synthetic spring characteristic line.

FIG. 7 is a diagram showing the relationship between the length of the initially set magnetic gap and the valve displacement amount.

FIG. 8 is a graph showing the relationship between the length of the initially set magnetic gap and the valve displacement amount.

FIG. 9 is a schematic diagram showing the response of the flow rate to a command signal.

FIG. 10 is a graph showing the flow rate response of the valve device previously proposed by the applicant.

FIG. 11 is a graph showing the flow rate response of the valve device of the present invention.

FIG. 12 is a configuration diagram showing a conventional gas flow rate control device.

FIG. 13 is an equivalent circuit diagram of an electromagnetic actuator.

[Explanation of symbols]

8 sensor part 10 electric heating coil 12 constant current circuit 14 amplification circuit 16 comparison judgment circuit 22 diaphragm 30 valve body 33 valve body 36 thin film disc spring (biasing spring) 38 electromagnetic actuator 40 valve device 44 load means 46 electromagnetic coil 50 pressing member 54 fluid inlet 58 fluid outlet 70 adjusting screw (diaphragm adjusting means) 82 length M _G magnetic gap length L _GS reference initial magnetic gap of the spacer member 84 gap adjusting unit L _G initialization magnetic gap

Claims (4)

[Claims] 1. A valve body having a fluid inlet, a fluid outlet, and a valve seat therebetween, a diaphragm having a peripheral edge fixed to face the valve seat, and the diaphragm having the valve seat. Load means provided on the opposite side of the diaphragm with respect to the diaphragm for displacing in a direction,
And an electromagnetic actuator that acts to separate the diaphragm from the valve seat against the load means,
The load means is composed of a thin disk spring fixed at the periphery and a valve rod fixed to the center of the thin disk spring, and an initial setting electromagnetic gap at the time of initial setting of the electromagnetic actuator and the valve rod. Is the combined elastic force obtained by combining the elastic force of the diaphragm and the elastic force of the disc spring when the valve rod is substantially in contact with the electromagnetic actuator when the maximum allowable magnetomotive force of the electromagnetic actuator is generated. And a length of the reference initial magnetic gap such that the thrust of the electromagnetic actuator is substantially balanced, or is set to be smaller than the reference initial magnetic gap. 2. The valve device according to claim 1, wherein the load means has a diaphragm adjusting means for allowing the diaphragm to be seated on the valve seat. 3. The valve device according to claim 1, wherein the electromagnetic actuator has gap adjusting means for adjusting an initial setting magnetic gap between the actuator and the valve rod. 4. The valve device according to claim 1, wherein a spacer member made of a non-magnetic material is interposed between the electromagnetic actuator and the valve rod.