Fluid handling – With indicator – register – recorder – alarm or inspection means – Position or extent of motion indicator
Reexamination Certificate
2000-06-14
2001-09-04
Chambers, A. Michael (Department: 3753)
Fluid handling
With indicator, register, recorder, alarm or inspection means
Position or extent of motion indicator
C137S625640, C137S625650, C137S884000
Reexamination Certificate
active
06283149
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a directional control valve having a position detecting function, improved by permitting the detection of operating positions of a valve member such as a spool, through the use of a magnet.
BACKGROUND ART
The directional control valve capable of detecting the changeover operation of a spool utilizing a magnet is well known as disclosed in, for example, Japanese Unexamined Utility Model Publication No. 2-66784. This known directional control valve is provided with a magnet on the outer periphery of a spool and provided with a magnet sensor on a casing. This directional control valve is constituted so that, when the spool moves to one changeover position, the magnet approaches the magnetic sensor, and the magnetic sensor is turned on, and that, when the spool moves to the other changeover position, the magnet moves away from the magnetic sensor, and the magnetic sensor is turned off. This directional control valve is thus adapted to detect that the spool has been changed over by the on/off of the magnetic sensor.
However, since the above-described conventional directional control valve installs the magnet at a position situated in a fluid passage on the outer periphery of the spool, the magnet directly contacts the hydraulic fluid. Therefore, when the fluid contains water, chemical mist, particulates of magnetic material such as metallic powder, or the like, there has often arisen the problem that the contact of the magnet with these substances makes the magnet rust, corrode, or adsorb the particulates, thereby causing the reduction in detection accuracy due to the decrease in magnetic force, or incurring poor sliding conditions.
Furthermore, since the above-described conventional directional control valve uses the method in which the changeover of the spool is detected by the turning on/off of the magnetic sensor, any position on the way of a stroke can not be known, even if that the spool has reached each of the two stroke ends can be known. It is, therefore, substantially impossible to know whether the spool has normally operated during the whole stroke and reached a stroke end or not. This has created a problem in the reliability or the maintenance in executing automatization.
DISCLOSURE OF INVENTION
The main technical problem of the present invention is to provide a directional control valve excellent in the detecting accuracy and the operational stability and having a position detecting function, wherein the magnet is prevented from directly contacting a hydraulic fluid so as not to be affected by the hydraulic fluid.
The other technical problem of the present invention is to permit the above-described directional control valve having a position detecting function to detect the operating positions of the valve member over the whole stroke thereof.
In order to solve the above-described problems, the directional control valve of the present invention mounts the magnet for position detecting at a position, shut off from the flow passage of hydraulic fluid, at the end portion of the valve member received in a valve hole, and also installs the magnetic sensor for detecting the magnetism from the magnet at a portion opposite to the magnet, in the casing.
In accordance with the present invention having above-described features, since the magnet for position detecting is disposed at a position shut off from the flow passages of a hydraulic fluid, the magnet is prevented from directly contacting the hydraulic fluid. Therefore, even if the pilot fluid contains water chemical mist, particles of magnetic material such as metallic particles, or the like, there is no risk of the magnet rusting, corroding, or adsorbing particulates. This prevents the reduction in function, or the occurrence of a malfunction of the valve member due to adsorbed particulates.
In accordance with a specific embodiment of the present invention, the above-described directional control valve comprises breathing chambers which are opened to the outside, and which are situated at positions facing the ends of the valve member and end sealing members which are disposed on the outer peripheries and which shut off the breathing chambers from the fluid passages in the valve hole, and the above-described magnet is installed at a position which is adjacent to the breathing chamber and which is more exterior than the end sealing member disposed on an end portion of the valve member.
In the present invention, the magnet may be directly installed on the outer periphery of the valve member, or may be installed on the end portion of the valve member via a holder.
Also, the present invention may be provided with one magnet and one magnetic sensor, or may be provided with one magnet and a plurality of magnetic sensors.
In accordance with another specific embodiment of the present invention, the above-described magnetic sensor is installed so as to be able to detect the magnetism from the magnet over the whole stroke of the valve member, and is constituted so as to be able to detect all operating positions of the valve member, from the change in magnetic flux density with the displacement of the magnet.
Thereby, not only the stroke end positions of the piston, but also any position on the way of a stroke can be known. It is therefore possible to easily discriminate, by means of a discrimination circuit, whether the valve member has normally operated or not, from the relations between the position and the operating time of the valve member from the initiation to the termination of a stroke thereof. This permits taking precautionary measures against a failure before it happens, and preventing the occurrence of a long downtime of a working system due to a failure or an accident.
REFERENCES:
patent: 5244002 (1993-09-01), Frederick
patent: 5623967 (1997-04-01), Hayashi
patent: 5829481 (1998-11-01), Tajima et al.
patent: 2-66784 (1990-05-01), None
patent: 2-66785 (1990-05-01), None
patent: 2-88079 (1990-07-01), None
Hayashi Bunya
Ishikawa Makoto
Chambers A. Michael
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
SMC Corporation
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