Fluid handling – Self-proportioning or correlating systems – Supply and exhaust type
Patent
1990-12-20
1992-05-19
Michalsky, Gerald A.
Fluid handling
Self-proportioning or correlating systems
Supply and exhaust type
91420, F15B 1302
Patent
active
051138948
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a counterbalance valve provided for drive oil hydraulic circuitry of an oil hydraulic motor used in travel equipment or the like for construction machinery.
BACKGROUND ART
Conventional drive oil hydraulic circuitry of an oil hydraulic motor, for example, as shown in FIG. 7, is known.
In other words, more specifically, an operation valve 2 connects a delivery path 1a of an oil hydraulic pump 1 to a first main circuit 3 and a second main circuit 4, or the operation valve 2 disconnects the delivery path 1a from the first and second main circuits 3, 4. The first and second main circuits 3, 4 are respectively connected to a first port 6.sub.1 and a second port 6.sub.2 of an oil hydraulic motor 5. A counterbalance valve 7 is arranged between the first and second main circuits 3, 4. When the operation valve 2 is moved to a neutral position "N", because of non-return valves 8 placed in the first and second main circuits 3, 4, the side of the oil hydraulic motor 5 is disconnected from the counterbalance valve 7. Thus, the oil hydraulic motor 5 is not caused to rotate by an external force. When the operation valve 2 is moved to either a first position "I" or a second position "II", the counterbalance valve 7 is switched over to either the first position "I" or the second position "II", this switching being caused by highly pressurized oil in either the first main circuit 3 or the second main circuit 4.
The counterbalance valve 7 for use in such oil hydraulic circuitry is switched over to the first and second positions by highly pressurized oil in the first and second main circuits 3, 4. The counterbalance valve 7 returns to the neutral position "N" when the highly pressurized oil runs out.
When the oil hydraulic motor 5 is not driven by the first main circuit 3 or the second main circuit 4, it can be caused to rotate by an external load, thereby acting as a pump.
For this reason, if the counterbalance valve 7 is in the neutral position "N" when the oil hydraulic motor 5 is first rotated by an external load while the operation valve 2 is in the neutral position, either the first main circuit 3 or the second main circuit 4 becomes a high pressure circuit, thereby causing a great shock.
To moderate such a shock during cessation, the speed for the counterbalance valve 7 to return to the neutral position "N" from the first position and the second position is rendered slow. The counterbalance valve 7 throttles the pressurized oil in the first and second positions, thus causing it to flow to the tank 9.
For example, throttles 11, 11 are arranged in circuits 10, 10 which connect the first and second main circuits 3, 4 to the counterbalance valve 7. The speed for the counterbalance valve 7 to return to the neutral position "N" from the first and second positions is made slow by increasing the throttle amounts of these throttles 11, 11. In such an arrangement, however, the time required for the counterbalance 7 to return to the neutral position "N" is delayed. This causes cavitation and the oil hydraulic motor to stop for long periods.
An object of the present invention is therefore to provide a counterbalance valve in which an oil hydraulic motor can slow down without shock, while cavitation is prevented, thus coming to rest in a short period time.
DISCLOSURE OF THE INVENTION
A counterbalance valve of the present invention is constructed in such a manner that a right pressure receiving chamber and a left pressure receiving chamber are connected, through throttle apertures, to ports on a first pump side and a second pump side. These pressure receiving chambers move rightward or leftward along a spool. The connection areas of the throttle apertures, through which the pressure receiving chambers and the ports are connected to each other, are increased or decreased by the movement of the spool. At the beginning of a spool stroke when the spool moves to a neutral position from a first position or a second position, the connection areas become large; in the middle of t
REFERENCES:
patent: 2837106 (1958-06-01), Bauer
Kabushiki Kaisha Komatsu Seisakusho
Michalsky Gerald A.
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