JPS5933805A - Proportional electromagnetic actuator - Google Patents

Abstract

PURPOSE:To permit a variable-gap type elecromagnetic actuator to have a large stroke and reduce its power consumption, by allowing a return spring against an electromagnetic attraction force to have such a non-linear characteristic that its stiffness becomes larger as the gap decreases. CONSTITUTION:A fluid flows as shown by an arrow 13. In the state where no current flows through a coil 8, a poppet valve 11 is pressed on a nozzle 12 by the force F0 of a return spring 9. The magnitude of the force F0 is determined so that if a predetermined differential pressure is applied the fluid is not allowed to flow. When current flows through the coil 8, a plunger 4 is attracted by the force F of a core 3. As a result, the return spring 9 is slightly deflected to produce a gap between the nozzle 12 and the poppet valve 11, thereby allowing the fluid to flow. As the current increases, the gap increases correspondingly, so that the fluid flows at a higher flow rate. When deflected, the spring 9 is simultaneously brought into close contact with a pipe holder 7 by l1 and with a valve holder 10 by l2. In consequence, the effective span of the return spring 9 is reduced, and the spring 9 strongly resists, so that a non-linear characteristic can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Description of the technical field to which the invention pertains The present invention relates to a proportional electromagnetic actuator that utilizes electromagnetic force. There are various types of electromagnetic actuators, such as a movable iron piece type, a moving coil type, and a rotating magnetic field type, and the present invention belongs to the movable iron piece type, and more specifically to the variable gap type. The main purpose is to control the pulp by making the deflection of the movable iron piece proportional to the input signal and controlling the flow rate of fluids such as water, oil, and gas.

(2) Description of the prior art A plunger-type proportional electromagnetic actuator is a typical example of this type of electromagnetic actuator, and has been put into practical use, but it has the disadvantage of not being able to take a large stroke. Ta. If you try to force the stroke to be larger, a large amount of power will be consumed, which poses a practical problem.

For this reason, it has been limited to special applications where minute strokes are acceptable. If proportional control is absolutely desired, a diamond ram valve that uses nitrogen pressure or a motor pulp that uses a motor has been used. Plunger type solenoid valves are used because 0N-OF”F does not require proportionality.
Most of the areas involve movement.

(3) Detailed Description of the Invention The present invention has been made by focusing on the above-mentioned conventional actuator 1°δ. Therefore, an object of the present invention is to provide a proportional electromagnetic actuator with a large stroke and low power consumption. It's about getting.

(4) Structure of the Invention In order to achieve the above object, the present invention provides a variable gap electromagnetic actuator in which a return spring that opposes electromagnetic attractive force has a nonlinear structure in which stiffness increases as the gap becomes smaller. Constructed with characteristics.

(5) Detailed Description of the Invention Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention when used as a proportional electromagnetic valve. It goes without saying that the use of this actuator is limited to electromagnetic valves. As shown in FIG. 1, the proportional IR valve according to the present invention is almost the same as the conventional one except for the return spring section.

In FIG. 1, reference number 1 is a base for mounting a solenoid valve, and a case yoke 2, which serves as a case and a magnetic path for the solenoid valve, is screwed into the base. 3 is a core, 4 is a plunger, and 5 is a yoke. The yoke 5 and the plunger 4 are separated by a non-magnetic vibro. The upper end of the vibro is welded to the core 3 and the lower end to the pipe holder 7 to prevent fluid from leaking to the coil 8 side.

9 is a return spring according to the present invention, 1o is a valve holder, 11 is a poppet valve, and 12 is a nozzle screwed into the base. The periphery of the flat thin plate return spring 9 is sandwiched and fixed between the base 1 and the pipe holder 7. The center portion of the return spring 9 is fixed between the plunger 4 and the valve holder 1o, and generates a force that counters the suction force of the plunger 4, while at the same time preventing eccentricity of the plunger 4. Further, in order to equalize the pressure in the space above and below the return spring 9, a hole is provided in the return spring 9.

The fluid flows from left to right or vice versa, as shown by arrow 13. When no current flows through the coil 8, the poppet valve 11 is pressed against the nozzle 12 by the force FO of the return spring 9. The magnitude of the FO force is determined so that the fluid will not flow even if a specified differential pressure is generated. When a current is applied to the coil 8, the plunger 4 is attracted to the core 3 with a force of F. As a result, the return spring 9 is slightly bent, creating a gap between the nozzle 12 and the poppet valve 11, allowing fluid to flow.

The larger the current, the larger the gap, allowing more fluid to flow. When the gap between the plunger 4 and the core 3 is g, the suction force F is expressed by the following formula.

Here, F; Attraction force (N) 11o; Vacuum permeability = 4πX 10 (Wb /Am
) d; plunger diameter tn) NI; coil ampere turns (A) The above equation is an approximate equation that ignores the magnetic resistance of the core, yoke, etc., and also ignores the magnetic resistance between the yoke 5 and the plunger 4. (NI)'' is proportional to the power consumption W of the coil 8, so if the diameter d of the plunger 4 is constant, the power consumption W' is kept constant, and if the gap g is decreased, the suction force F increases rapidly.g= At o, F becomes infinite, but in other cases it does not become infinite due to ignored magnetic resistance and saturation of the magnetic material, but it is a fact that we often experience that it becomes an extremely large force.

FIG. 2 illustrates the relationship between the gap g and the suction force W using the power W as a parameter. When the coil power W is increased from zero to WIXWg, W3, and W4, the attraction force F also increases. In the vicinity of g=o, the suction force 11M rapidly increases. W4 is the maximum power that can be produced by electrolytic erosion1
Once the plunger is attracted in the vicinity of g-0, it cannot be separated due to residual magnetism and loses its proportional operation function, so a non-magnetic material with a thickness of g8 is inserted as a spacer. Prevent the gap from becoming less than gs.

The spring line Pgo crosses a load line representing the characteristics of a conventional linear return spring. The relationship between the return spring's load and deflection is called linear because it is linear.

When the pressing force FO of the poppet valve 11 is 0, the gap between the core 3 and the plunger 4 is g in FIG. 2 when the coil is powered off. It has become. When the feeling of maximum power W is applied, it moves to the intersection point I of the W4 curve and the load line, and the gap becomes g
The maximum flow is reduced to l. The stroke of the plunger 4, that is, the gap between the poppet valve 11 and the nozzle 12 is (
go-g4). This is the maximum stroke. In order to increase the maximum stroke, it would seem that it would be better to make the slope of the load line gentler, but this is not possible due to the stability according to equation (3) below.

As is clear from FIG. 2, dF/dg is negative everywhere on the characteristic curve, so it is said to have negative stiffness. This is because the gap g is in the denominator in equations (1) and (2). The stability of equation (3) must be 1 or more. The stability level is usually selected to be 3 or above based on the comfort. If the stability is set to 1 or less, an adsorption phenomenon will occur and subsequent proportional operation will not occur. It will not operate stably unless the negative stiffness caused by the electromagnetic force is canceled out by the positive stiffness of the return spring, resulting in a positive stiffness as a whole.

In FIG. 2, the absolute value of dF/dg is maximum when the gap is g8 on the W4 curve. In order to achieve a stability level of 3, the slope of the load line, that is, the stiffness of the return spring, must be three times this value.

In Figure 2, it is written roughly like that. In the end, a strong return spring is needed. As a result, the stroke is reduced, making it fundamentally unsuitable for applications requiring a large stroke. If you use it forcibly, it will consume a lot of power.

The dotted curve Pg'o in FIG. 2 is the load line of the return spring according to the present invention. It is a nonlinear return spring in which there is no proportional relationship between deflection and force, and the smaller the gap, the stronger the repulsive force. In this case, the power is zero and the gap is g′o1 power W direct and g4
, and the maximum stroke is (glo-g4), which is much larger than the conventional (go-g,).

Although FIG. 2 shows the case where the pressing force Fo=0, it is clear that even when Fo is finite, a large maximum stroke can be obtained by using the nonlinear return spring of the present invention. Conversely, the maximum power required to produce a given stroke decreases.

FIG. 3 shows an enlarged view of the return spring section.

Figure 1 shows a state in which the power is OFF, but Figure 3 shows a state in which current is applied to the coil 8, the plunger 4 is lifted, a gap is created between the poppet valve 11 and the nozzle 12, and fluid is flowing. . At the same time as the return spring 9 is bent,
The pipe holder 7 is in close contact with the pipe holder 7, and the valve holder 10 is also in close contact with the valve holder 10 by a distance of 12. As a result, the effective span of the return spring 9 decreases (7) and becomes strongly resistant, resulting in the nonlinear curve Pg'o shown in FIG.

Another embodiment of the nonlinear return spring 9 is shown in FIG. The return spring 9' is manufactured in advance into a dish shape. When the suction force of plunger 4 increases,
The adhesion length 11.111 increases and nonlinear characteristics are obtained.

FIGS. 5, 6, and 7 show other embodiments of the history of return springs, and show only a nonlinear return spring.

The winding pitch of the helical coil 190 constituting the return spring shown in FIG. 5 is narrower at the bottom. When the plunger 40 force is applied to the wire, close contact starts from the bottom and nonlinear characteristics are obtained.

The return spring shown in Fig. 6 has an equal pinch coil 2.
9, but when compressive force is applied, it starts to adhere from the lower part and non-linear characteristics are obtained. Even better effects can be obtained by reducing the pinch at the bottom.

The return spring shown in FIG. 7 is a combination of a thick disc spring 20 and a thin disc spring 21. When a compressive load is applied, the disc spring 21 first bends, and when it becomes almost flat, the disc spring 20 begins to bend. The overall relationship between load and deflection can be approximately approximated by a bifold line. If three types of disc springs are stacked together, a three-fold line characteristic will be obtained. Similar characteristics can be obtained by stacking wave washers with different thicknesses.

Generally speaking, Figures 3, 4 and 7 are suitable for relatively short stroke applications, while Figures 5 and 6 are suitable for long stroke applications. Since the return springs shown in FIGS. 5 and 6 have poor positioning ability for the core 3, an element for preventing eccentricity of the core 3 is required.

Generally, when a flat diaphragm is used with a small deflection, the in-plane stress is only the bending moment, but when the diaphragm is used with a large deflection, the diaphragm also stretches and generates tensile stress (balloon stress), and the relationship between load and deflection is becomes slightly non-linear. Even if we try to obtain a large nonlinear effect,
The stress in the diaphragm exceeds its elastic limit. On the other hand, in the case of FIG. 3, since no bending greater than the curvature of the curved surface of the pipe holder 7 is applied, the stress in the diaphragm is automatically kept within the elastic limit. The present invention does not include non-linear effects such as those exhibited by ordinary flat diamond slams at large deflections.

In FIG. 1, the core 3 and the plunger 4 face each other on a plane-to-plane plane, but there is also a known type in which the upper end of the plunger 4 protrudes in a conical shape and the core 3 is recessed in a conical shape.
Used when a relatively long stroke is required. The suction force in this case is slightly different from the formula (1), but the fact remains that the gap g is in the denominator of the formula (1), resulting in a characteristic curve as shown in Figure 2. A type in which the gap changes with the stroke in this manner is classified as a variable gap type electromagnetic actuator. Another type of variable gap type is one in which a disc-shaped armature faces the end surfaces of the core 3 and the case yoke 2. In this case, the gap between the armature and the core and the pitch between the armature and the case yoke change simultaneously.

For convenience of explanation, the return spring in FIGS. 1, 3, and 4 is a diaphragm, but it may be in the form of a strip. t', it is effective to stack thin plates to reduce the stress on the return spring. It is convenient for production to adjust the stiffness of the return spring by the number of stacked plates to accommodate changes in the model. Although it has been explained that the return spring 9 is clamped at the periphery and the center, the core positioning function and nonlinear characteristics can be provided even if the return spring 9 is not clamped.

(6) Detailed Description of the Invention As is clear from the above description, the present invention has greatly improved the disadvantage of variable gap electromagnetic actuators, which is the inability to obtain a large stroke. Furthermore, in the case of the same stroke, the same stroke can be obtained with approximately % less power consumption, which expands the applications of variable gap type actuators and has great practical effects. The number of parts that need to be improved is almost the same as the conventional one, and it is also advantageous that it does not cause an increase in costs.

By changing the characteristics of the nonlinear return spring,
Coil current and stroke or fluid flow rate can be made proportional. Very advantageous as an automatic control valve. Conventional linear return springs cannot provide proportional control in principle and have poor controllability.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the proportional electromagnetic actuator according to the present invention used as a proportional control valve, FIG. 2 is an explanatory diagram of the operation, and FIG. FIG. 4 is an enlarged sectional view of a main part of another embodiment of the present invention, and FIGS. 5, 6, and 7 are views of other nonlinear return springs used in the present invention. It is a figure showing an example. 1. Fist - solenoid valve mounting pace, 2II.. case yoke, 3.-Φ core, 4.. plunger, 5.. yoke, 6.. non-11゛a pipe, 7.. pipe Holder, 8...-Coil, 9.9'...Return spring, 10...Valve holder, 11...Boven 1-f-P,
12・Balance・Nozzle, 19・・・−・Lican coil, 2
0.21---Disc spring 29 g m m Coil Patent applicant Okura Electric Co., Ltd. Representative Patent attorney Yutabe Kumagai 15 - Figure 1 Figure 2 Figure 4

Claims (4)

[Claims] (1) A variable gap electromagnetic actuator characterized in that a return spring that opposes electromagnetic attractive force has a nonlinear characteristic such that stiffness increases as the gap becomes smaller. (2) The proportional type according to claim (1), further characterized in that a flat plate or a pre-formed spring material is used as the return spring, and the contact length increases as the stroke increases. electromagnetic actuator. (3) The proportional electromagnetic actuator according to claim (1), further characterized in that the return spring is a disc spring having a polygonal relationship between load and deflection. (4) The proportional electromagnetic actuator according to claim (1), further characterized in that a coil spring having nonlinear characteristics is used as the return spring.