초록 ▼

An apparatus for use in controlling a variable displacement pump in a hydrostatic transmission comprises servo-positioning means for varying the displacement of the variable displacement pump, signal producing means for producing a first signal dependent on the rotational speed of the input shaft of

An apparatus for use in controlling a variable displacement pump in a hydrostatic transmission comprises servo-positioning means for varying the displacement of the variable displacement pump, signal producing means for producing a first signal dependent on the rotational speed of the input shaft of the variable displacement pump and means communicating the first signal dependent on the rotational speed of the input shaft to the servo-positioning means to increase or decrease the displacement of the variable displacement pump as the rotational speed of the input shaft increases or decreases. A second signal dependent on the output pressure of the variable displacement pump is communicated to the servo-positioning means to act in opposition to the first signal to tend to reduce or increase the displacement of the variable displacement pump.

대표청구항 ▼

1. An apparatus in combination with a hydrostatic transmission including a variable displacement pump and a motor, said variable displacement pump having an input shaft driven by an engine, said apparatus comprising servo-positioning means for varying the displacement of said variable displacement p

1. An apparatus in combination with a hydrostatic transmission including a variable displacement pump and a motor, said variable displacement pump having an input shaft driven by an engine, said apparatus comprising servo-positioning means for varying the displacement of said variable displacement pump, signal producing means for producing a first signal dependent upon the rotational speed of said input shaft, means for communicating said first signal dependent on the rotational speed of said input shaft to said servo-positioning means, means for communicating a second signal dependent upon the output pressure of said variable displacement pump to said servo-positioning means, said servo-positioning means including means responsive to the difference between said first signal dependent on the rotational speed of said input shaft and said second signal dependent on said variable displacement pump output pressure, said means for producing said first signal dependent on the rotational speed of said input shaft for said pump including a constant displacement pump connected with said input shaft of said variable displacement pump, said means for communicating said first signal to said servo-positioning means including an output line from said constant displacement pump, a restrictor in said output line, said conduit means for conducting the pressure upstream of said restrictor to said servo-positioning means, said variable displacement pump being adapted to provide a reversible flow of fluid, said servo-positioning means includes a piston having two piston faces and axially slidable in a bore and a pressure chamber at each end of said bore, and a pair of opposed auxiliary pistons axially slidable in an auxiliary bore under the influence of said second signal dependent on the output pressure of said variable displacement pump, said auxiliary pistons abuttingly engaging said piston to thereby influence the axial position of said piston in said bore, said conduit means for conducting the pressure upstream of said restrictor to said servo-positioning means includes conduits connected with each of said pressure chambers and individually actuable solenoid valves controlling the flow of fluid in said conduits. 2. An apparatus as set forth in claim 1 wherein said solenoid valves include means for biasing said solenoid valves to a closed position and pressure responsive means for moving said solenoid valves to an open position. 3. An apparatus as set forth in claim 2 wherein the constant displacement pump as said means for producing a signal dependent on the rotational speed of said input shaft to said variable displacement pump is replaced by means for producing an electrical signal dependent on the rotational speed of said input shaft and circuit means conducting the electrical signal so produced to said solenoid valves, said solenoid valves being electrically controlled. 4. An apparatus for use in controlling a variable displacement pump in combination with a hydrostatic transmission including a variable displacement pump and motor, said variable displacement pump having an input shaft driven by an engine, said apparatus comprising servo-positioning means for varying the displacement of said variable displacement pump, signal producing means for producing a first signal dependent upon the rotational speed of said input shaft, means for communicating said first signal dependent on the rotational speed of said input shaft to said servo-positioning means to increase or decrease the displacement of said variable displacement pump as the rotational speed of said input shaft increases or decreases, respectively, and means for communicating a second signal dependent on the output pressure of said variable displacement pump to said servo-positioning means to act in opposition to said first signal to tend to decrease or increase the displacement of said variable displacement pump, said servo-positioning means including means responsive to the difference between said first signal dependent on the rotational speed of said input shaft and said second signal dependent on said variable displacement pump output pressure, said means responsive to the difference between said first signal dependent on the rotational speed of said input shaft and said second signal dependent on said variable displacement pump output pressure including a piston having two piston faces, said piston being axially slidable in a bore, and a pressure chamber located at each end of said bore, said means for communicating said first signal to said servo-positioning means comprising an output line from a source of fluid, a restrictor in said output line, and conduit means for conducting the pressure upstream of said restrictor to said servo-positioning means, said conduit means for conducting the pressure upstream of said restrictor to said servo-positioning means including conduits connected with each of said pressure chambers, and individually actuatable regulating solenoid valves regulating the flow of fluid in said conduits, said signal producing means for producing said first signal dependent on the rotational speed of said input shaft including sensing means for sensing the rotational speed of said input shaft and generating an electrical signal to control said regulating solenoid valves to thereby regulate the flow of fluid therethrough. 5. An apparatus as set forth in claim 4, wherein said speed sensing means is a generator connected to said input shaft.