Fluid handling – With indicator – register – recorder – alarm or inspection means – Position or extent of motion indicator
Reexamination Certificate
2000-06-09
2001-07-31
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
06267140
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a directional control valve having a position detecting function, capable of detecting operating positions of a valve member such as a spool.
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 arranged 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. Thus, this directional control valve detects that the spool has been changed over by one on/off of the magnetic sensor.
However, since the above-described conventional directional control valve uses the method in which a magnetic sensor outputs the detection signal of “on” or “off” when the spool have arrived at a spool end, this directional control valve can not detect positions of the spool on the way of a stroke, even though it can detect the position of the spool situated at a stroke end. Therefore, even if the spool makes an irregular movement deficient in smoothness due to some abnormality on the way of a stroke, it is impossible to detect this abnormality. This has made it difficult to take suitable precautions against a failure or an accident before they happen, and has thus raised a problem in the maintenance and management.
In addition, the above-described magnetic sensor is generally constituted so as to be turned on when the magnetic flux density is above a fixed value, and to be turned off when it is below another fixed value. Therefore, during the driving stroke of the spool, if the magnetic flux density becomes higher than the fixed value due to the approach of a magnet, the magnetic sensor is turned on even before the spool arrives at a stroke end, and conversely, during the return stroke of the spool, if the magnetic flux density becomes lower than the other fixed value due to the moving-away of the magnet, the magnetic sensor is turned off even before the spool arrives at the return-stroke end. Therefore, even if the magnetic sensor stops on the spot for some reason at the instant when the magnetic sensor is turned on or turned off, the magnetic sensor only outputs an on/off signal noticing that the spool has been completely changed over. Thus, any abnormality can not be detected.
Furthermore, since the above-described conventional directional control valve installs the magnet at a position situated in the fluid passage on the outer periphery of the spool, the magnet directly contacts a hydraulic fluid. Therefore, if the fluid contains water, chemical mist, particulates of magnetic material such as metallic powder, or the like, there would arise 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 a malfunction of the valve member due to adsorbed particulates.
DISCLOSURE OF INVENTION
The main technical problem of the present invention is to provide a directional control valve having a position detecting function capable of detecting the operating positions of the valve member over the le stroke thereof.
The subordinate technical problem of the present invention is to prevent the components constituting the position detecting means in the above-described directional control valve from contacting hydraulic fluid to exclude the influence of the hydraulic fluid, and to maintain an excellent detecting accuracy and operational stability.
In order to solve the above-described problems, the directional control valve of the present invention mounts a magnetic head having a magnetic scale so as to be displaced together with the valve member, and fixedly installs a magnetic sensor for reading the magnetic scale at a portion of the casing
In accordance with the directional control valve of the present invention having above-described features, since pulse-shaped detection signals are outputted from the magnetic sensor by reading the magnetic scale moving together with the valve member, the operating positions of the valve member over the whole stroke thereof can be detected by counting the signals. From the relations between the operating position and the operating time, therefore, it is possible to discriminate whether the valve member has normally operated or not, and to take suitable precautions against a failure or an accident before they happen.
In the present invention, it is preferable that the above-mentioned detection head is disposed at a position shut off from the fluid passages, such as a breathing chamber at an end portion of the valve member.
Thereby the magnetic scale can be prevented from directly contacting the hydraulic fluid. Therefore, even if the hydraulic fluid contains water, chemical mist, particles of magnetic material such as metallic particles, or the like, there is no risk of the magnetic scale rusting, corroding, or adsorbing magnetic particulates. This prevents the occurrence of the reduction in function, or a malfunction of the valve member due to adsorbed particulates.
In accordance with a specific embodiment of the present invention, the above-described detecting head has a construction so that a magnetic scale is affixed on the outer surface of a cylindrical-column shaped substrate, and installed on an end portion of the valve member coaxially with the valve member.
In accordance with another specific embodiment of the present invention, the above-described directional control valve has a piston which is disposed on at least one end side of the valve member and which operates by the action of pilot fluid pressure to change over the valve member, and these proton and valve member are abutted against each other via the detection head.
Moreover, in accordance with the present invention, the above-described sensor is formed of a magnetic resistance element and is constituted so as to output two analog signals different in phase from each other, upon reading the magnetic scale. In addition, the above-mentioned casing is provided with a signal processing circuit, which includes an amplifying circuit for amplifying the read signals from the sensor and a dividing circuit for dividing the amplified signal into a plurality of pulse signals to be outputted.
REFERENCES:
patent: 4953590 (1990-09-01), Kakinuma et al.
patent: 5101856 (1992-04-01), Kakinuma et al.
patent: 5244002 (1993-09-01), Frederick
patent: 5320123 (1994-06-01), Corso et al.
patent: 5623967 (1997-04-01), Hayashi
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
LandOfFree
Directional control valve having position detecting function does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Directional control valve having position detecting function, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Directional control valve having position detecting function will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2522673