GB2107432A

GB2107432A - Electromagnetic switching valve

Info

Publication number: GB2107432A
Application number: GB08128742A
Authority: GB
Inventors: Seiji Kosugi
Original assignee: Shoketsu Kinzoku Kogyo KK
Current assignee: Shoketsu Kinzoku Kogyo KK
Priority date: 1981-09-23
Filing date: 1981-09-23
Publication date: 1983-04-27
Also published as: GB2107432B

Abstract

An electromagnetic switching valve wherein an appropriate relation is set for the resilient forces between a spring for actuating a valve body that closes or releases the passage of fluid and a spring for actuating a movable core that is incorporated with the valve body and moved by electromagnetic operation force, thereby enabling to provide a power saving structure with no additional components and increase fluid discharging capacity. <IMAGE>

Description

SPECIFICATION Electromagnetic switching valve This invention relates to an electromagnetic switching valve for switching the direction of flow of fluid.

Prior art electromagnetic switching valves have generally been constructed as shown in the crosssectional view of Figure 1 of the accompanying drawings, wherein a movable core 102 having a feed valve body 103 and a discharge valve body 104 is driven by the ON/OFF switching of a coil 101 in a solenoid operation section on a valve main body 100, to thereby open and close a feed valve seat 105 and a discharge valve seat 106 alternately. Upon energizing, the discharge valve seat 106 communicating with a discharge port 107 is closed to establish a fluid channel from an input port 108 to an outport port 109 and, upon deenergizing, the feed valve seat 105 is closed to establish a fluid channel from the output port 109 to the discharge port 107.

In electromagnetic switching valves of this general type, since the resilient force of a spring 110 for actuating the feed valve body 103 is set greater than that of a return spring 111, and the movable core 102 has to be attracted, upon energizing, against a relatively large resilient force exerted by the return spring 111, it is necessary that the solenoid be operated in a range where the electromagnetic attraction force is relatively strong, that is, the movable core can only have a relatively small stroke.

Thus, the stroke of the movable core is greatly restrained and the fluid discharge performance in the discharge valve seat 106 is limited significantly.

Alternatively, if the stroke of the movable core is extended in order to increase the fluid discharge performance, since the movable core has to overcome the resilient force of the return spring in the weak range of the electromagnetic attraction force, various disadvantages are incurred such as an increase in the size of the solenoid coil 101 or an increase in the electric power consumed therein.

Further, in order to provide the feed valve seat 105 and the discharge valve seat 106 with sufficient fluid passing performance, the stroke between the feed valve body 103 and the feed valve seat 105 having a bore diameter d1 is typically set to 1/4d1 and, accordingly, the stroke between the discharge valve body 104 and the discharge valve seat 106 having a bore diameter d2 has to be set to 1/4d2. Therefore, if it is desired to set the bore diameter d2 greater than the bore diameter d1, for increasing the discharge performance, the stroke of the movable core has to be set corresponding to the bore diameter d2.

Accordingly, for enlarging the bore diameter d2 from the state shown in Figure 1 in order to improve the discharge performance, the stroke of the movable core 102 has necessarily to be extended. However, the valves heretofore in use are disadvantageous in such a case, in that the distance between the two valve seats 105 and 106 has to be increased and in that such extension of the stroke, although impor tantforthe discharge valve seat 106, is contrary to the requirements of the feed valve seat 105 of a smaller bore diameter.

The present invention has been made from a consideration of the foregoing problems and it provides an electromagnetic switching valve having movable and stationary cores, in which the resilient force of a return spring for the movable core is reduced by means of a spring for actuating a feed valve body in the range where the movable core is relatively remote from the stationary core, and thus the attraction force of the solenoid operation section is weak, thereby ensuring satisfactory attraction of the movable core even though a small attracting force is acting upon it. Thus, it becomes possible to reduce the size of the solenoid coil and thus reduce the power consumption.

The present electromagnetic switching valve may advantageously permit an increase in the fluid discharging performance by lengthening the stroke of the movable core, thereby enabling the bore diameter in the discharge valve seat to be increased.

Preferably, the present electromagnetic switching valve is constructed so that a large resilient force is exerted by the return spring on the movable core at the attraction end of the movable core, thereby ensuring a satisfactory return of the movable core upon deenergizing even with a discharge valve seat having a relatively large bore diameter.

In the illustrated embodiment of the present invention, there is provided an effective electromagnetic switching valve having no useless stroke of the movable core, in which the stroke of the movable core for closing the feed valve seat is set longer than the stroke required for closing the feed valve seat by the feed valve body, thereby enabling the stroke of the movable core to be increased without enlarging the distance between the two valve seats and the stroke for the opening and closing of the feed valve seat and for the opening and closing of the discharge valve seat to be distributed in accordance with the bore diameter in each of the valve seats.

The present invention may provide an electromagnetic switching valve which can apply also to a pilot valve which can increase the response speed of the switching valve and improve the fluid discharging performance.

In one embodiment the electromagnetic switching valve of this invention comprises a valve main body having an input port and an output port for fluid, a valve chamber defined, on said valve main body with a guide cylinder of a solenoid operation section having a stationary core fitted thereto, a feed valve seat between the input port and the output port, a discharge valve seat on the stationary core communicating with a fluid discharge port provided opposing to each other in the valve chamber, a feed valve body for opening and closing the feed valve seat and a discharge valve body for opening and closing the discharge valve seat each provided to the inside of the movable core contained movably in the valve chamber, a spring disposed to the inside of the movable core for actuating the feed valve body toward the feed valve seat, and a return spring mounted in the valve chamber for actuating the movable core in the direction of closing the feed valve seat with a resilient force greater than that of said spring, with the stroke of the movable core for closing the feed valve seat being set greater than the stroke required for closing the feed valve seat by the feed valve body.

A preferred embodiment of an electromagnetic switching valve of this invention will now be described with reference to Figures 2-5 of the accompanying drawings, in which: Figure 2 is a cross-sectional view of the electromagnetic switching valve; Figure 3 and Figure 4 are cross-sectional views of a part of the valve showing the position of movable parts in different switching states; and Figure 5 is a chart illustrating the operational characteristics of a preferred embodiment of the valve according to the present invention.

Referring first to Figure 2, a valve main body 200 has an input port 201 and an output port 202 for fluid. Avalve chamber 207 is defined, on the valve main body 200, by a guide cylinder 205 which is provided therearound with a coil 204 of a solenoid operation section 203, and a stationary core 206 is fitted to the upper end of the valve chamber 207. A feed valve seat 208 is formed, on the valve main body 200, between the input port 201 and the output port 202, and a discharge valve seat 210 communicating with a fluid discharge port 209 thereabove is formed on the stationary core 206 and opposite to the feed valve seat 208. A feed valve body 212 and a discharge valve body 213 are disposed within a core 211 movable within the valve chamber 207 for opening and closing the feed valve seat 208 and the discharge valve seat 210, respectively.As will be described in more detail below, both valve bodies 212 and 213 are movable relatively to the movable core 211 but are restricted from moving outwardly of the core 211 by a stopper 214 and an engaging step 215, respectively, formed on the core 211. An inter-valve spring 216 is resiliently mounted between the valve body 212 and the valve body 213 for urging them outwardly from each other. An auxiliary spring 218 is mounted between the feed valve body 212 and the spring seat 217 of the movable core 211 for urging the feed valve body 212 in the same direction as it is urged by the inter-valve spring 216.

A return spring 219 is mounted between the movable core 211 and the guide cylinder 205 for urging the movable core 211 in the direction closing the feed valve seat 208.

The resilient force of the return spring 219 is set greater than the synthetic resilient force of the inter-valve spring 216 and the auxiliary spring 218, and the stroke of the movable core 211 is set greater than the closing stroke of the valve seats 208 and 210 by the two valve bodies 212 and 213, respectively. By thus setting the resilative spring forces and strokes, where the two valve bodies 212 and 213 close the feed valve seat 208 and the discharge valve seat 210, respectively, at the stroke ends of the movable core 211, the valve bodies 212 and 213 are somewhat compressed and retracted inwardly to keep the resilient force of the inter-valve spring 216 and of the auxiliary spring 218 exerted on the movable core 211.

The solenoid operation section 203 also includes a magnetic frame 220 and a magnetic flux plate 221.

In the condition of the switching valve shown in Figure 2 wherein the solenoid coil 204 is not energized, the movable core 211 keeps its lowermost position in which its lower end abuts against the bottom surface of the valve chamber 207 under the urging of the return spring 219, the feed valve body 212 is urged to contact and close the feed valve seat 208, and the discharge valve body 213 is spaced from the discharge valve seat 210 which therefore is open. Accordingly, fluid flow from the input port 201 is interrupted, while fluid from the output port 202 is discharged out of the valve chamber 207 by way of the discharge valve seat 210 to the discharge port 109.

In the switching state referred to above, the feed valve body 212 keeps a somewhat retracted position against the resilient force of the inter-valve spring 216 and of the auxiliary spring 218 while being urged to the feed valve seat 208, whereby an upward resilient force resulting from the compression in the two springs is exerted on the movable core 211.

Consequently, the resultant resilient force exerted downwardly on the movable core 211 is the force of the return spring 219 minus the force of the two springs 216 and 217, and this net downward force f1 is shown by the reference I in Figure 5.

Then, upon energizing the coil 204, the movable core 211 is attracted toward the stationary core 206 by the magnetic flux passing through the magnetic circuit comprising magnetic frame 220, stationary core 206, movable core 211 and magnetic flux plate 221. Referring specifically to this state, the movable core 211 is attracted towards core 206 against the force f1, and first moves by the distance a to arrive at the position shown in Figure 3, where the stopper 214 abuts against the feed valve body 212. In this case, the attraction characteristic of the solenoid operation section 203 is as shown by the curve A in Figure 5.Although only the low attraction portion of curve A can be used at the start of the attraction, since only a relatively small downward resistive force f1 is exerted on the movable core 211 (due to the relation for the resilient forces between each of the springs as described above), the movable core 211 can be actuated surely even with a small attraction force and thus the length of the stroke for the movable core can be extended. The downward resistive force exerted on the movable core 211 is gradually increased as each of the springs 216,218 and 219 is compressed and this force is represented by the reference II in Figure 5 at the instance the stopper 214 abuts against the feed valve body 212.

Then, immediately before the opening of the feed valve seat 208 when the resilient force of the inter-valve spring 216 and the auxiliary spring 218 is now received on the stopper 214, the downward force acting on core 211 is increased rapidly as represented by the reference Ill in Figure 5, since that force now comprises only that exerted by the return spring 219.

In the succeeding stage during which the movable core 211 moves by the distance b to bring the discharge valve body 213 into abutment against the discharge valve seat 210, the resistive force acting on the core 211 still comprises only the resilient force of the return spring 219, but increases as the compression in the return spring 219 increases, as represented by the reference IV in Figure 5.

Then, when the movable core 211 is further attracted and the compression in the inter-valve spring 216 begins to act on the discharge valve body 213 as shown in Figure 4, the combined resilient force of the inter-valve spring 216 and the return spring 219 is now exerted as the resistive force acting downwardly on the movable core 211, and this downward resistive force changes as represented by the references V - VI in Figure 5. Since a great attraction force is exerted on the movable core 211 at a point where the movable core is attracted to some extent as apparent from the attraction characteristics shown in Figure 5, the movable core 211 can surely be attracted while overcoming the resistive force if the latter is increased.

Then, at the end of the stroke of the movable core 211, which is reached when it has moved further by the distance c, the upper end of the core abuts against the lower surface of the stationary core 206, and the discharge valve body 213 is urged to close discharge valve seat 210 and the feed valve body 212 opens the feed valve seat 208. Thus, fluid from the input port 210 flows by way of the feed valve seat 208 and the valve chamber 207 to the output port 202.

Then, upon deenergizing of the coil 204 again, the movable core 211 starts to return with a great force, being actuated by both the return spring 219 and the inter-valve spring 216, both of which have stored considerable resilient force during compression.

Accordingly, the return of the movable core to position I is ensured even when the discharge valve 210 has a large diameter bore.

The feed valve body 212 may alternatively be actuated by either one of the inter-valve spring 216 and the auxiliary spring 218.

Claims

1. An electromagnetic switching valve comprising a valve main body, an input port and an output port for fluid, a valve chamber defined on said main body, with a guide cylinder of a solenoid operation section and a stationary core fitted thereto, a feed valve seat between said input port and said output port and a discharge valve seat on said stationary core communicating with a fluid discharge port provided opposing to each other in said valve chamber, a feed valve body for opening and closing said feed valve seat and a discharge valve body for opening and closing said discharge valve seat each provided to said movable core contained movably in said valve chamber, a spring disposed to the inside of said movable core for actuating said feed valve toward said feed valve seat, and a return spring mounted in said valve chamber for actuating said movable core in the direction of closing said feed valve seat with a resilient force greater than that of the spring referred to above.

2. The electromagnetic switching valve according to Claim 1, in which the stroke of the movable core is set greater by keeping said movable core at a lowermost position where the lower end thereof is abutted against the bottom surface of the valve chamber by the resilient force of the return spring.

3. The electromagnetic switching valve according to Claim 1, in which the stroke of the movable core for closing the feed valve seat is set greater than the stroke required for closing the feed valve seat by the feed valve body.

4. The electromagnetic switching valve according to Claim 1, in which an auxiliary spring is disposed between the spring seat of the movable core and the feed valve body for actuating said feed valve body in the same direction as the spring for actuating said feed valve body toward the feed valve seat.

5. An electromagnetic switching valve for controlling the flow of a fluid, comprising a movable core carrying therewith in spring-loaded first and second valve members for seating against first and second valve seats, respectively, and being movable upon energising of a solenoid towards a stationary core from a first position in which said first valve member is seated on said first valve seat and said second valve member is spaced from said second valve seat, to a second position in which said second valve member is seated on said second valve seat and said first valve member is spaced from said first valve seat, and a return spring which is mounted around said movable core for returning said core from said second to said first positions upon deenergising of said solenoid, characterised in that the spring-loading means for said valve members is arranged so as to reduce the force required to initiate movement of said movable core from said first to said second positions thereof against the action of said return spring.