Valves and valve actuation – Fluid actuated or retarded – Dashpot or fluid controlled retarder or timer
Reexamination Certificate
1999-10-07
2001-04-10
Shaver, Kevin (Department: 3754)
Valves and valve actuation
Fluid actuated or retarded
Dashpot or fluid controlled retarder or timer
C251S065000, C251S129070, C251S129150, C137S909000
Reexamination Certificate
active
06213445
ABSTRACT:
INDUSTRIAL FIELD
The present invention relates to a solenoid valve to open/close a valve member by a solenoid.
DESCRIPTION OF THE RELATED ART
In a solenoid valve to open/close a valve member by a solenoid, the valve member is generally mounted on a moving core, and when a coil is energized, the moving core is attracted to a fixed core to drive the valve member, and when the coil is de-energized, the moving core is separated from the fixed core by the force of a return spring to return the valve member, and a flow passage is opened/closed thereby.
In such a solenoid valve, when the moving core is attracted to the fixed core, both cores are strongly collided with each other at high speed to generate large collision noise. There is another problem that attraction surfaces are easily worn by repeating the collision of both cores. In particular, the solenoid valve with large collision noise can not be used in an equipment to be used in a silent environment such as medical facilities.
The above-described moving core is generally inserted in a core holes provided in a coil of the solenoid in a slidable manner, and is magnetically coupled with a magnetic frame by piercing a center hole in a metallic magnetic plate forming a part of the magnetic frame arranged to surround the coil at a tip part of the core hole. Because the moving core pierces the center hole keeping a small gap therebetween, the gap becomes the gap of the magnetic passage to increase the magnetic resistance, the efficiency of the solenoid is degraded, and the power consumption is increased. Thus, to increase the efficiency of the solenoid and to save the power, it is effective to reduce the magnetic resistance. In addition, when the moving core pierces the center hole in an eccentric condition, the moving core is attracted by the magnetic plate and brought into contact therewith, and may cause the sliding, and in such a case, the moving core is subjected to the interference at a contact part with the magnetic plate to make its operation unstable.
DISCLOSURE OF THE INVENTION
A main technical problem of the present invention is to reduce the collision noise in the attraction, and to prevent the wear of an attraction surface of both cores by suppressing the speed at which a moving core is attracted by a fixed core in a solenoid valve to open/close a valve member by a solenoid.
Another technical problem of the present invention is to increase the efficiency of the solenoid and to save the power by reducing the magnetic resistance caused by the gap between the moving core and a magnetic plate in the solenoid valve.
Still another technical problem of the present invention is to prevent the mutual friction, and to stabilize the operation of the moving core by eliminating a contact part of the moving core with the magnetic plate in the solenoid valve.
In order to solve the above-described problems, the solenoid valve of the present invention is characterized in that a gap part is formed between a core hole in the solenoid part and the moving core, and a magnetic fluid whose viscosity is increased when the magnetic force is applied is accommodated in the gap part so that the magnetic fluid is subjected to the influence of the magnetic force when the moving core is attracted to the fixed core by the energization to a coil.
In the solenoid valve of the above-described construction, when the coil is energized, the moving core is attracted to the fixed core to drive the valve member, and when the coil is de-energized, the moving core is separated from the fixed core to return the valve member, and because the viscosity of the magnetic fluid is rapidly increased by the magnetic field excited by the coil during the energization, the attraction speed of the moving core to the fixed core is reduced. Thus, the strong collision with the fixed core is prevented, the collision noise is reduced, and the wear of both attraction surfaces is prevented.
In the present invention, the gap part is preferably formed between the magnetic plate forming a part of a magnetic frame and the moving core, and the magnetic fluid is filled in the gap space.
No magnetic gap is thus present between the moving core and the magnetic plate, and the magnetic resistance can be reduced. Further, by substantially and uniformly surrounding the whole periphery of the moving core with the magnetic fluid, the moving core is prevented from sliding with the magnetic plate through the partial contact with each other, and the operation of the moving core can be stabilized.
In the present invention, a magnetic unit to maintain the magnetic fluid in the gap part by the magnetic force can be provided. The magnetic unit includes a permanent magnet as an example, and the permanent magnet is provided on each end of the magnetic plate across moving core. As another example of the magnetic unit, the remanent magnetism of the magnetic plate and/or the moving core can be used. In such a case, at least one of the magnetic plate and the moving core is formed of a hard or semi-hard ferromagnetic material. The permanent magnet can be used together with the remanent magnetism.
In one specific embodiment of the present invention, a communication hole to balance the air pressure to be applied to each end of the moving core by communicating both end parts of the moving core with each other, is provided at the position not to be directly intersected with the gap part in which the magnetic fluid is accommodated.
REFERENCES:
patent: 4852853 (1989-08-01), Toshio et al.
patent: 5452745 (1995-09-01), Kordonsky et al.
patent: 5517096 (1996-05-01), Shtarkman et al.
patent: 5955934 (1999-09-01), Raj
patent: 6019201 (2000-02-01), Gordaninejad et al.
patent: 6095486 (2000-08-01), Ivers et al.
Hangai Masayuki
Sato Hideharu
Keasel Eric
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Shaver Kevin
SMC Corporation
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