Power plants – Pressure fluid source and motor – Condition responsive control of pump or motor displacement
Patent
1990-12-18
1992-09-15
Look, Edward K.
Power plants
Pressure fluid source and motor
Condition responsive control of pump or motor displacement
60450, 91446, 91468, F16D 3102, F15B 1108
Patent
active
051467470
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a valve apparatus for use in hydraulic circuit systems for civil engineering and construction machines such as hydraulic excavators or cranes, and a hydraulic circuit system including the valve apparatus, and more particularly to a valve apparatus and a hydraulic circuit system in which pressure regulating means is provided for holding a differential pressure across a variable restricting section at a predetermined value, and a hydraulic fluid is distributed and supplied from a hydraulic pump to a plurality of actuators.
2. Background Art
A hydraulic excavator typical of an example of civil engineering and construction machines each equipped with a plurality of working members. The hydraulic excavator is constituted by a lower travel body, an upper swing, and a front mechanism provided on the upper swing and comprising a boom, an arm as well as a bucket. A hydraulic circuit system is also provided for driving these components. This hydraulic circuit system comprises a hydraulic pump, a plurality of actuators driven by a hydraulic fluid delivered from the hydraulic pump for operating the plurality of working members, and a valve apparatus for controlling to flow of the hydraulic fluid supplied to the plurality of actuators. The valve apparatus incorporates therein a plurality of directional control valves each equipped with a pair of variable restricting sections.
Some of this type of hydraulic circuit system includes means for controlling a pump delivery pressure, e.g., a pump regulator for controlling a pump delivery rate, so that the pump delivery pressure is held higher a fixed value than a maximum load pressure among the plurality of actuators. This is generally called a load sensing system.
Recently, various types of load sensing systems have been proposed. For example, GB 2195745A proposes a valve apparatus having a pressure controller disposed downstream of the paired variable restricting sections of each directional control valve to introduce the maximum load pressure among the plurality of actuators, as a control pressure, for holding a differential pressure across the variable restricting sections at a predetermined value. Also, JP, A, 60-11706 proposes a valve apparatus having a pressure compensating valve disposed upstream of the paired variable restricting sections of each directional control valve to introduce the maximum load pressure, as a control pressure, for holding a differential pressure across the variable restricting sections at a predetermined value. By thus holding the differential pressures across the variable restricting sections at a predetermined value, the flow rates of the hydraulic fluid passing through the respective directional control valves when the plural actuators are simultaneously driven, i.e., the flow rates supplied to the respective actuators, can be distributed at the ratios corresponding to relative proportions of input amounts (demanded flow rates) of associated operating levers, thereby permitting smooth combined operation.
However, the above conventional valve apparatus has following problems.
In the conventional valve apparatus, a detection line is branched from a line communicating with a load passage downstream of the paired variable restricting sections in order to communicate a load pressure of each actuator to the associated directional control valve. A maximum load pressure among the load pressures communicated by this and other detection lines is selected through a plurality of shuttle valves and introduced to a control line. The maximum load pressure introduced to the control line is in turn introduced, as a control pressure, to the aforesaid pressure controller or pressure compensating valve for controlling the differential pressure across the variable restricting section. Concurrently, the maximum load pressure is also introduced to the aforesaid pump regulator for controlling the pump delivery pressure so that the pump delivery pressure is held higher by a fixed value than the maximu
REFERENCES:
patent: 2892312 (1959-06-01), Allen et al.
patent: 2971536 (1961-02-01), Junck et al.
patent: 3884123 (1975-05-01), De Vita et al.
patent: 3911942 (1975-10-01), Becker
patent: 3914939 (1975-10-01), Purdy
patent: 4037410 (1977-07-01), Jackson et al.
patent: 4145958 (1979-03-01), Ille
patent: 4184410 (1980-01-01), Johnson
patent: 4343152 (1982-08-01), Habiger
patent: 4510751 (1985-04-01), Jackson
patent: 4617798 (1986-10-01), Krusche et al.
patent: 4617854 (1986-10-01), Kropp
patent: 5067389 (1991-11-01), St. Germain
patent: 5083430 (1992-01-01), Hirata et al.
Hirata Toichi
Sugiyama Genroku
Hitachi Construction Machinery Co. Ltd.
Look Edward K.
Ryznic John
LandOfFree
Valve apparatus and hydraulic circuit system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Valve apparatus and hydraulic circuit system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Valve apparatus and hydraulic circuit system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-729637