Hydraulic servo control particularly hydraulic power steering system for motor vehicles
First Claim
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1. A hydraulic servo control for a hydraulic power steering system of a vehicle, comprising:
- a hydraulic servo motor;
a hydraulic pump having a delivery side and a suction side;
an electric motor for driving said hydraulic pump;
a servo valve having an open center position, said servo valve controllably connecting said hydraulic servo motor to said delivery side of said pump as well as to one of the suction side of said pump and an unpressurized reservoir; and
an electric speed control unit for controlling rotational speed of said electric motor as a function of one of electric current and electric power consumption of said motor, which speed control unit changes automatically between standby operation at an approximately low rotational speed, and load operation at an approximately constant high rotational speed, whereinsaid electric speed control unit switches to the high rotational speed when said one of electric current and power consumption of the electric motor exceeds a lower threshold value at the low rotational speed, which threshold value is slightly above a first minimum value of said one of current and power consumption of the electric motor at the low rotational speed; and
said electric speed control unit switches to the low rotational speed when said one of electric current and power consumption of the electric motor at the high rotational speed has fluctuated minimally for a predeterminable time period and has remained below an upper threshold value which is slightly above a second minimal value of the current or power consumption of the electric motor at the high rotational speed.
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Abstract
A hydraulic servo control, particularly a hydraulic power steering system for motor vehicles, has hydraulic pressure pump which is driven by an electric motor. The rotational speed of the electric motor is controlled as a function of the load, so that a high rotational speed occurs only when there is a corresponding demand.
18 Citations
16 Claims
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1. A hydraulic servo control for a hydraulic power steering system of a vehicle, comprising:
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a hydraulic servo motor; a hydraulic pump having a delivery side and a suction side; an electric motor for driving said hydraulic pump; a servo valve having an open center position, said servo valve controllably connecting said hydraulic servo motor to said delivery side of said pump as well as to one of the suction side of said pump and an unpressurized reservoir; and an electric speed control unit for controlling rotational speed of said electric motor as a function of one of electric current and electric power consumption of said motor, which speed control unit changes automatically between standby operation at an approximately low rotational speed, and load operation at an approximately constant high rotational speed, wherein said electric speed control unit switches to the high rotational speed when said one of electric current and power consumption of the electric motor exceeds a lower threshold value at the low rotational speed, which threshold value is slightly above a first minimum value of said one of current and power consumption of the electric motor at the low rotational speed; and said electric speed control unit switches to the low rotational speed when said one of electric current and power consumption of the electric motor at the high rotational speed has fluctuated minimally for a predeterminable time period and has remained below an upper threshold value which is slightly above a second minimal value of the current or power consumption of the electric motor at the high rotational speed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification