Normally closed solenoid-operated valve

A normally closed solenoid-operated valve is composed of a stationary element provided at one end of a stationary sleeve, a movable element slidably inserted in the sleeve to face the stationary element and provided at an external surface thereof with a communication groove which axially extends between the opposite ends thereof for permitting the flow of the operating fluid, and an electromagnetic coil for exciting the stationary element and the movable element. A damper chamber is defined by an annular shim provided between the lower end surface of the stationary element and the top surface of the movable element. When the damper chamber is closed by the lower end surface of the stationary element and the top surface of the movable element, a dent groove makes the damper chamber communicate with the communication groove.

INCORPORATION BY REFERENCE

This application is based on and claims priority under 35 U.S.C. sctn. 119 with respect to Japanese Application No. 2002-347509 filed on Nov. 29, 2002, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a normally closed solenoid-operated valve for controlling the flow of fluid such as hydraulic oil or the like in response to an electric command applied to an electromagnetic coil which excites the solenoid-operated valve.

2. Discussion of the Related Art

Heretofore, as normally closed solenoid-operated valves of this type, there has been known one described in the U.S. Pat. No. 5,601,275 to the inventor of the present application. The known valve is provided with a cylindrical sleeve, a stationary element provided at one end of the cylindrical sleeve, a movable element inserted slidably within the sleeve to move relative to the stationary element, and an electromagnetic coil for exciting the stationary element and the movable element. On the external surface of the movable element, there are formed communication grooves, which axially extend between the both ends of the movable element for permitting the flow of operating fluid therethrough.

Further, in the known solenoid-operated valve, a damper chamber and a valve chamber are formed at the axial opposite ends of the movable element, and a sealing member is provided on the external wall surface. At a part of the circumferential surface of the sealing member, a V-groove is formed, by which a throttle passage is constituted to make the valve chamber and the damper chamber communicate with each other.

In the aforementioned solenoid-operated valve, the valve chamber and the damper chamber are in communication only through the fixed throttle passage. Thus, as shown by the broken line inFIG. 4, the throttle area remains invariable or constant regardless of the movement of the movable element, i.e., regardless of whether the movable element comes close to the stationary element or goes away therefrom. This causes a damping effect to act over the entire area in which the movable element (valve member) moves. As a result, a delay takes place in the operation response of the solenoid-operated valve. On the contrary, if preference is taken to the operation responsiveness of the solenoid-operated valve, a problem would arise in that a sufficient damping effect cannot be obtained so that the operation noise cannot be diminished satisfactorily. Further, the use of the sealing member raises another problem in respect of increasing the manufacturing cost.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to provide an improved solenoid-operated valve which is inexpensive and capable of effectively restraining the operation noise accompanying the open/close operation thereof and of preventing the operation delay.

Briefly, in a normally closed solenoid-operated valve according to the present invention, a stationary element is provided at one end of a stationary sleeve, a movable element is slidably inserted in the sleeve to face the stationary element and is provided at an external surface thereof with a communication groove which axially extends between axial opposite ends thereof for permitting the flow of operating fluid, and an electromagnetic coil is provided for exciting the stationary element and the movable element. A closed wall is provided on at least one of a stationary element end surface facing the movable element of the stationary element and a movable element end surface facing the stationary element of the movable element for defining a damper chamber therein. A fixed throttle is formed for making the damper chamber to communicate with the communication groove when the stationary element end surface and the movable element end surface closes the damper chamber as a result of the movable element excited by the electromagnetic coil being moved toward the stationary element.

With this configuration, when the movable element excited by the electromagnetic coil is moved to come close to the stationary element, the operating fluid within the damper chamber is discharged into the communication groove by way of a clearance between the stationary element end surface or the movable element end surface and the closed wall as well as by way of the fixed throttle. When the movable element is brought into contact with the stationary element, the damper chamber is closed by the stationary element end surface and the movable element end surface, in which state the damper chamber remains to communicate with the communication groove through the fixed throttle. In this way, when the movable element is coming close to the stationary element, the path area which makes the damper chamber communicate with the communication groove is decreased thereby to increase the throttle resistance and to decrease the moving speed of the movable element as the same comes close to the stationary element. Thus, the operation noise which is generated when the movable element is brought into contact with the stationary element can be sufficiently diminished. Further, when the movable element is far from the stationary element, the clearance is kept large between the stationary element end surface or the movable element end surface and the closed wall. Thus the operating fluid within the damper chamber is able to be discharged therefrom and charged thereinto through the clearance without being substantially throttled, so that the movable element can move at a high responsiveness. Accordingly, it can be realized to provide a solenoid-operated valve which is inexpensive and which is capable of effectively restraining the operation noise brought about by the open/close operation thereof without the addition of any sealing member as used in the prior art solenoid-operated valve, and also capable of preventing the occurrence of the delay in response.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a normally closed solenoid-operated valve in the first embodiment according to the present invention will be described with reference toFIGS. 1 to 4.FIG. 1is a longitudinal section showing the normally closed solenoid-operated valve.

As shown inFIG. 1, the solenoid-operated valve V of an open/close type is provided with a sleeve11formed cylindrically. The lower end portion of the sleeve11is inserted into an installation hole12aprovided in a valve body12and is fluid-tightly secured thereto by caulking. The upper portion of the sleeve11is protruded from the valve body12and is provided at its upper end portion with a stationary element13of a cylindrical shape. The stationary element13is provided coaxially and bodily with the sleeve11and has the same diameter as the upper portion of the sleeve11. A non-magnetic material11ais interposed at the boundary portion between the stationary element13and the sleeve11. An axial hole13ais formed in the center of the stationary element13from the lower end thereof and contains a compression spring14therein.

An almost cylindrical yoke15is secured to the circumferential surface of the stationary element13and covers the stationary element13and the protruding portion of the sleeve11(i.e., the upper portion of the sleeve11). The upper end portion of the stationary element13is fixedly fit in the upper opening portion of the yoke15. The lower end of the yoke15extends down to the installation hole12a, and a ring16is tightly fit between the internal wall of the lower opening end of the yoke15and the external surface of the sleeve11. An electromagnetic coil17is provided inside the yoke15in coaxial alignment with the sleeve11for covering the upper portion of the sleeve11. The electromagnetic coil17is secured to the yoke15.

The sleeve11, the stationary element13, the yoke.15, the ring16and a movable element18referred to later are made of magnetic materials. When electric current is applied to the electromagnetic coil17, a magnetic path is formed around the electromagnetic coil17to go through the stationary element13, the yoke15, the ring16and the sleeve11, whereby the stationary element13and the movable element18are excited.

A valve seat member19is tightly fit in the lower end portion of an axial hole11cof the sleeve11, and the movable element18is slidably inserted in the axial hole11cbetween the valve seat member19and the stationary element13with itself facing the stationary element13. The valve seat member19is formed with a valve hole19ain coaxial alignment therewith. The valve hole19ais formed with a valve seat19bat its upper opening edge. The lower end opening of the valve hole19afaces onto an outlet passage P2which opens to the bottom of the installation hole12a.

The movable element18is formed with a large diameter portion18aand a small diameter portion18b, which is formed at the lower portion of the large diameter portion18abodily and coaxially with the same. The large diameter portion18ais in abutting engagement at its upper surface with the lower end of the compression spring14, so that the movable element18is urged by the compression spring14downward as viewed inFIG. 1, i.e., in the direction of closing the valve. A valve member21in the form of a ball is provided bodily on the lower end of the small diameter portion18band is movable together with the movable element18. That is, when no electric current is being applied to the electromagnetic coil17, the movable element18is kept urged by the compression spring14downward, so that the valve member21remains in abutment with the valve seat19bthereby to close the valve hole19a, When electric current is applied to the electromagnetic coil17, on the contrary, the movable member18is moved toward the stationary element13against the compression spring14, so that the valve member21departs from the valve seat19bto open the valve hole19a.

When no electric current is being applied to the electromagnetic coil17, as shown inFIGS. 1 and 2, a predetermined clearance is provided between the upper end surface of the large diameter portion18aof the movable element18and the lower end surface of the stationary element13. A fluid chamber R1is defined by the clearance, the axial hole11cof the sleeve11and an annular shim24referred to later. It is to be noted that the clearance corresponds to the operating stroke length of the movable element18.

A valve chamber R2is defined by the small diameter portion18bof the movable element18, the internal wall of the sleeve11and the valve member19. A pair of diametrically opposite communication grooves22,22are provided on the external wall surface of the large diameter portion18aof the movable element18to extend in the axial direction for permitting the operating fluid to flow between the fluid chamber R1and the valve chamber R2.

The annular shim24constituting a closed wall is attached to the top surface of the large diameter portion18aof the movable member18. As best shown inFIG. 3, the annular shim24takes the form of generally oval and is placed thereon not to overlap the upper end openings of the communication grooves22,22provided on the movable element18. The annular shim24is provided with a pair of engaging claws25,25, which are engaged respectively with the communication grooves22,22to hold the annular shim24on the movable element18. The annular shim24defines a damper chamber R3between the lower end surface of the stationary element13and the movable element18. Thus, at the upper and lower portions in the axial hole11cof the sleeve11, the damper chamber R3and the valve chamber R2are defined with the movable element18therebetween.

When the electromagnetic coil17is brought into the state of excitation, the movable element18is moved upward to come close to the stationary element13. Thus; the operating fluid within the damper chamber R3is discharged into the valve chamber R2through the fluid chamber R1and then, the pair of communication grooves22,22; When the electromagnetic coil17is brought into the state of non-excitation, on the other hand, the movable element18is moved downward to depart from the stationary element13, whereby that the operating fluid within the valve chamber R2is charged into the damper chamber R3through the pair of communication grooves22,22and then the fluid chamber R1.

The sleeve11is provided with communication holes11bto extend radially and is also provided with a filter attached to the circumferential wall surface of its lower portion. An inlet passage P1is formed in the valve body12to extend toward the lower portion of the sleeve11in the radial direction of the sleeve11. The valve chamber R2is in communication with the inlet passage P1through the communication holes11band the filter23on one hand and with the outlet passage P2through the valve hole19aon the other hand.

As shown inFIG. 3, a dent groove26serving as a fixed throttle is formed to radially extend to the circumferential end wall at a portion which is of the, top circumferential edge portion and at which the communication grooves22are not formed. Thus, when the movable element18is excited by the electromagnetic coil17thereby to move toward the stationary element13, the damper chamber R3is closed by the lower end surface of the stationary element13and the annular shim24attached to the top surface of the movable element18, in which state the damper chamber R3remains in communication with the communication grooves22through the dent groove26and the clearance of the fluid chamber R1which remains formed around the top circumferential portion of the movable element18at that time.

The radial length of the dent groove26is set longer than the radial width of the annular shim24, and the inner end of the dent groove26extends inside beyond the internal surface of the annular shim24. Further, the dent groove26is triangle in cross-section, whose area is set favorably to that corresponding to φ0.4 mm (i.e., a hole of 0.4 millimeters in diameter). The cross-section of the dent groove26is not limited to triangle, but it may be rectangular, semicircular or the like.

In the normally closed solenoid-operated valve as constructed above, when the movable element18excited by the electromagnetic coil17is moved to come close to the stationary element13, the operating fluid within the damper chamber R3is discharged into the communication grooves22by way of an annular variable throttle and the dent groove26as fixed throttle. The annular variable throttle defined at this time has a path area of (h×l) which is made by multiplying the circumferential length (l) of the internal wall surface24aof the annular shim24with the clearance (h) between the lower end surface of the stationary element13and the annular shim24as closed wall. As understood from the graph shown inFIG. 4, as the movable element18comes close to the stationary element13, the variable throttle decreases its path area thereby to increase its throttle resistance. Further, when the annular shim24provided on the movable element18is brought into contact with the stationary element13, the damper chamber R3is closed by the lower end surface of the stationary element13and the top surface of the movable element18, in which state the damper chamber R3remains to communicate with the communication grooves22only through the dent groove26.

As understood from the foregoing description, in this particular first embodiment, as the movable element18comes close to the stationary element13, the path area which makes the axial opposite ends of the movable element18communicate with each other is decreased to increase the throttle resistance and the moving speed of the movable element18is reduced. Thus, the operation noise which is generated when the movable element18is brought into contact with the stationary element13can be sufficiently diminished. Further, when the movable element18is far from the stationary element13, the clearance (h) between the lower end surface of the stationary element13and the annular shim24is large, which enables the operating fluid within the damper chamber R3to be discharged therefrom and charged thereinto without being substantially throttled, so that the movable element18can move at a high responsiveness. Accordingly, it can be realized to provide a solenoid-operated valve which is inexpensive and which is capable of, without any sealing member to be added as used in the prior art solenoid-operated valve, effectively restraining the operation noise accompanying the open/shut operation thereof and preventing the delay in response from occurring.

Although in the foregoing embodiment, the dent groove26is provided on the top surface of the movable element18, it may be provided on each of the top surface of the movable element18and the lower end surface of the stationary element13. Further, although in the foregoing embodiment, the annular shim24is attached to the movable element18, it may be attached to the stationary element13. In this modified case, the operating fluid within the damper chamber R3is discharged into the communication grooves22through a so-called annular variable throttle which is defined by the top surface of the movable element18and the annular shim24as a closed wall as well as through the dent groove26.

Next, the second embodiment according to the present invention will be described with reference toFIGS. 5 and 6. The same elements as those in the first embodiment are given the same reference numerals and therefore, are omitted from further description for the sake of brevity.

In the foregoing first embodiment, the annular shim24is interposed between the lower end surface of the stationary element13and the top surface of the movable element18, and the dent groove26is provided on the top surface of the movable element18. Further, the damper chamber R3is defined using the annular shim24between the lower end surface of the stationary element13and the top surface of the movable element18, and the fixed throttle is constituted in the form of the dent groove26. In place of these configurations, in the second embodiment, as shown inFIGS. 5 and 6, an annular shim124is interposed between the lower end surface of the stationary element13and the top surface of the movable element18, a damper chamber R13is formed using the annular shim124between the lower end surface of the stationary element13and the top surface of the movable element18, and the fixed throttle may be formed as one or two portions where the annular shim124does not overlap the communication grooves22. That is, the fixed throttle may be formed by making one or two parts of the upper end openings of the communication grooves22to open within the internal wall surface124aof the annular shim124. For example, the fixed throttles are formed by providing apertures S, S between the lower end edge of the internal wall surface124aof the annular shim124and the upper end openings of the communication grooves22of the movable element18.

In this case, when the movable element18excited by the electromagnetic coil17is moved to come close to the stationary element13, the operating fluid within the damper chamber R13is discharged through the clearance between the lower end surface of the stationary element13or the top surface of the movable element18and the annular shim124and through the portions where the annular shim124does not overlap the communication grooves22, namely, the apertures S, S. With this configuration, the same functions and advantages as those in the foregoing embodiment can be achieved, and in addition, the configuration can be simplified thereby to reduce the manufacturing cost because there can be saved time and labor in implementing the machining such as forming the dent groove26on the movable element18, providing the engaging claws25on the annular shim24or the like.

Further, in the foregoing second embodiment, instead of providing the annular shim124, an annular convex portion corresponding to the shim124may be provided on the lower surface of the stationary element13. In this modified case, when the movable element18is brought into contact with the stationary element13, the damper chamber R13is closed by the lower end surface of the stationary element13and the top surface of the movable element18, in which state the fixed throttle is defined by the lower end edge of the internal wall surface of the annular convex portion and the upper end openings of the communication grooves22, i.e., by the apertures S, S.

Next, the third embodiment according to the present invention will be described with reference toFIGS. 7 and 8. The same elements as those in the first embodiment are given the same reference numerals and therefore, are omitted from further description for the sake of brevity.

In the foregoing first embodiment, the annular shim24is interposed between the lower end surface of the stationary element13and the top surface of the movable element18, and the dent groove26is provided on the top surface of the movable element18. Further, the damper chamber R3is defined using the annular shim24between the lower end surface of the stationary element13and the top surface of the movable element18, and the fixed throttle is constituted in the form of the dent groove26. In place of these configurations, in the second embodiment, as shown inFIGS. 7 and 8, an annular convex portion224is provided to define a closed wall at the top surface circumferential edge portion of the movable element18, and a dent groove224ais formed at a part in the circumferential direction on the annular convex portion224. The dent groove224aradially extends across the annular convex portion224and makes a dent portion or space, encircled by the annular convex portion224, communicate with one of the communication grooves22,22. Thus, a damper chamber R23is defined as the dent portion or space encircled by the annular convex portion224, and a fixed throttle is defined by the dent groove224a. In this case, the dent groove224amay be provided to open directly to one of the communication grooves22, as shown inFIG. 8, or it may be provided at a portion which is any place in the circumferential direction on the annular convex portion224and to which it does not open.

In this third embodiment, when the movable element18excited by the electromagnetic coil17is moved to come close to the stationary element13, the operating fluid within the damper chamber R23is discharged into the communication grooves22through the clearance between the lower end surface of the stationary element13and the annular convex portion224and through the dent groove224a. In this manner, the same functions and advantages as those in the foregoing embodiment can be achieved only by providing the annular convex portion224with the dent groove224a, and in addition, the number of the parts and hence, the manufacturing cost can be reduced since a discrete annular shim is no longer required. In a modification, the annular convex portion224may be provided at the lower surface of the stationary element13instead of being provided on the top surface of the movable element18, or two annular convex portions224may be provided at both of the top surface of the movable element18and the lower end surface of the stationary element13.

Moreover, the shim24(124) used in the foregoing embodiments may be a thin spacer or may be substituted by a gasket or the like as the case may be, and therefore, the term “shim” used herein encompasses these equivalents in the meaning thereof. Further, the dent groove26,224amay be a dent, depression, cutout or the like defined by casting, press forming, machining or any other forming measures.

Finally, various features and the attendant advantages of the foregoing embodiments will be summarized as follows:

In a first aspect of the foregoing embodiments as shown inFIGS. 1 to 4for example, a closed wall24(124,224) is provided on at least one of the a stationary element end surface of the stationary element13facing the movable element18and a movable element end surface of the movable element18facing the stationary element13for defining a damper chamber R3(R13, R23) therein. A fixed throttle26(S,224a) is formed for making the damper chamber R3(R13, R23) to communicate with the communication groove22when the stationary element end surface and the movable element end surface close the damper chamber R3(R13, R23) as a result of the movable element18excited by the electromagnetic coil17being moved toward the stationary element13.

Therefore, when the movable element18is coming close to the stationary element13, the path area which makes the damper chamber R3communicate with the communication groove22is decreased thereby to increase the throttle resistance and to decrease the moving speed of the movable element18as the same comes close to the stationary element13. Thus, the operation noise which is generated when the movable element18is brought into contact with the stationary element13can be sufficiently diminished. Further, when the movable element18is far from the stationary element13, the clearance is kept large between the stationary element13end surface or the movable element18end surface and the closed wall (e.g., annular shim24). Thus, the operating fluid within the damper chamber R3(R13, R23) is able to be discharged therefrom and charged thereinto without being substantially throttled, so that the movable element18can move at a high responsiveness.

In a second aspect of the foregoing embodiment as shown inFIGS. 2 and 3for example, an annular shim24is interposed between the stationary element13end surface and the movable element18end surface for defining the damper chamber R3in an internal surface thereof. Further, the fixed throttle26is constituted by a dent groove provided at least one of the stationary element13end surface and the movable: element18end surface for communication with the communication groove22. When the movable element18excited by the electromagnetic coil17comes close to the stationary element13, the operating fluid within the damper chamber R3is discharged into the communication groove22through the clearance between the stationary element13end surface or the movable element18end surface and the annular shim24. Thus, the same functions and advantages as those in the aforementioned first aspect can be attained with a simple construction which employs the annular shim24and the dent groove26.

In a third aspect of the foregoing embodiment as shown inFIGS. 5 and 6for example, an annular shim124is interposed between the stationary element13end surface and the movable element11end surface for defining the damper chamber R13in an internal surface thereof. The fixed throttle is constituted by the portion S where the annular shim124does not overlap at least one of the communication grooves22. When the movable element18excited by the electromagnetic coil17comes close to the stationary element13, the operating fluid within the damper chamber R13is discharged into the communication groove22through the clearance between the stationary element13end surface or the movable element18end surface and the annular shim24and through the portion S where the annular shim124does not overlap at least one of the communication grooves22or where the upper end openings of the communication grooves22partly open to the space inside the annular shim24. Therefore, the same functions and advantages as mentioned earlier can be attained by the provision of the annular shim124only.

In a fourth aspect of the foregoing embodiment as shown inFIGS. 7 and 8for example, an annular convex portion224is formed on at least one of the stationary element13end surface and the movable element18end surface for defining the closed wall encircled by the annular convex portion224with the damper chamber R23therein, and the fixed throttle is formed by a dent groove224aprovided on the annular convex portion224radially across the same to communicate with the communication groove22. When the movable element18excited by the electromagnetic coil17comes close to the stationary element13, the operating fluid within the damper chamber R23is discharged into the communication groove22through the clearance between the stationary element13end surface or the movable element18end surface and the annular convex portion224. Therefore, the same functions and advantages as mentioned earlier can be attained by the provision of the annular convex portion224only.