Abstract A pressure regulated variable delivery hydraulic pump includes a control for varying the pump displacement which responds not only to outlet pressure of the pump, but also to the rate of change of pressure and to the rate of change of pump delivery. Regulation is by outlet pressure opposed by two springs in back-to-back relation with a dashpot intermediate the two springs which retards rapid movements of one spring in backing up the other. The dashpot action is further modified by a feedback responsive to the rate of change of pump displacement. This is derived from pressure differentials generated by flow in the displacement varying servomotor system. The result is a servocontrol system which has high gain characteristics for small transients and lower gain for large transients and an increased damping ratio with a reduction in overshoots of pressure transients.
In a pressure regulated variable delivery pump having an inlet and an outlet, expansible chamber means for pumping fluid therebetween, a shiftable member connected with the expansible chamber means and effective to vary the volumetric pumping capacity, hydraulic regulating means responsive to outlet pressure for shifting the member the regulating means including a differential area servomotor connected to and controlled by a valve responsive pump outlet pressure that improvement which comprises a multiple spring system opposing outlet pressure at the valve of the regulating means, including a first spring acting directly on the valve, a second spring backing up the first spring, dashpot means intermediate the two springs effective to retard rapid movements of the second spring in backing up the first spring, and a fluid connection between the differential area servomotor and the dashpot for sensing flow rate changes in the servomotor.
Claim 2
Dependent Claim
143 words
In a pressure regulated variable delivery pump having an inlet and an outlet, expansible chamber means for pumping fluid therebetween, a shiftable member connected with the expansible chamber means and effective to vary the volumetric pumping capacity, hydraulic regulating means responsive to outlet pressure for shifting the member the regulating means including a differential area servomotor connected to and controlled by a valve responsive pump outlet pressure that improvement which comprises a multiple spring system opposing outlet pressure at the valve of the regulating means, including a first spring acting directly on the valve, a second spring backing up the first spring, dashpot means intermediate the two springs effective to retard rapid movements of the second spring in backing up the first spring, and a fluid connection between the differential area servomotor and the dashpot for sensing flow rate changes in the servomotor.
Claim 3
Dependent Claim
45 words
A pump as defined in claim 1 wherein the dashpot means includes a first chamber surrounding the first spring, a second chamber surrounding the second spring and connected to the outlet, a floating piston sepArating the chambers, and a restricted connection between the two chambers.
Claim 4
Dependent Claim
17 words
A pump as defined in claim 1 wherein the first and second springs have equal force-displacement rates.
Claim 5
Dependent Claim
46 words
A pump as defined in claim 2 wherein a pilot relief valve is provided to regulate the pressure in the first spring chamber and govern the flow through the restricted connection between the two spring chambers to thereby vary the pressure differential between the two chambers.