Control system for hydraulic pumps of a civil machine
AssigneeKabushiki Kaisha Komatsu Seisakusho
InventorsMichiaki Igarashi, Takayasu Inui, Kazuo Otsuka, Saburo Nogami, Satoru Nishimura
Life of this patent
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Abstract
A civil machine having a flow-rate controller which applies a preset signal instead of a normal flow-rate signal to a variable type hydraulic pump when delivery pressure of the hydraulic pump exceeds a preset pressure value. The normal flow-rate signal corresponds to the position of an operating lever. The preset signal has a value of minimum flow rate to hold a working tool in a certain posture. With this control system, pressure loss and temperature rise in hydraulic operating oil as well as fuel consumption of the machine can be reduced and cycle time of the work can be improved.
Claims7
A control system for a plurality of variable type hydraulic pumps driven by an engine of a hydraulic type civil machine which has a plurality of servos, each servo being associated with a pump and responsive to a flow rate signal, for actuating a swash plate of the associated pump, said control system comprising:
- detector means for producing a delivery pressure signal for each of the pumps, each delivery pressure signal being indicative of the delivery pressure of hydraulic fluid from an associated pump;
- an operational circuit responsive to the detector means, for calculating the output torque of the engine on the basis of the pump delivery pressure signals from the detector means, and the flow rate signals applied to the servos;
- a comparing circuit for comparing said output torque with a predetermined torque corresponding to the rated torque of the engine and for producing an output signal when said output torque exceeds said predetermined torque;
- and
- means responsive to the comparing circuit, for applying a predetermined flow-rate command signal to each servo when the comparing circuit provides said output signal so that the hydraulic pumps are driven within the rated torque of the engine.
A control system for a plurality of variable type hydraulic pumps driven by an engine of a hydraulic type civil machine in which a flow-rate signal corresponding to the position of an operating lever controls the flow-rate of a corresponding variable type hydraulic pump, said flow-rate signals being applied to servos, each of which controls an inclination angle of a swash plate of each said hydraulic pump, said control system comprising a first flow-rate controlling device which includes:
- detector means for producing a delivery pressure signal for each of the pumps, each pressure delivery signal being indicative of the delivery pressure of hydraulic fluid from an associated pump;
- an operational circuit responsive to the detector means, for calculating the output torque of the engine on the basis of the pump delivery pressure signals from the detector means, and the flow-rate signals applied to the servos;
- a comparing circuit for comparing said output torque with a predetermined torque corresponding to the rated engine torque and for producing an output signal when said output torque exceeds the predetermined torque, and
- means responsive to the comparing circuit, for applying a predetermined flow-rate command signal to each servo when the comparing circuit provides said output signal, so that the hydraulic pumps are driven within said rated torque of said engine;
- and said control system further comprising a second flow-rate controlling device for at least one of said hydraulic pumps, said second flow-rate controlling device being responsive to the detector means for applying a second predetermined signal having a value of a predetermined minimum flow-rate instead of said lever flow-rate signal to said one hydraulic pump when the delivery pressure signal for said one hydraulic pump exceeds a preset pressure value.
Dependencies are inferred from the claim text.