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US 7,730,993 B2Granted
Power steering device
AssigneeHitachi, Ltd.
InventorMasaki Watanabe
Life of this patent
Estimating the term…
Abstract
In a power steering device, a hydraulic power cylinder is configured to assist a steering force of a steering mechanism linked to steerable road wheels, a pump is configured to supply a hydraulic pressure to respective pressure chambers of the hydraulic power cylinder, an electric motor is configured to drive the pump, a torque sensor is configured to detect a steering torque of the steering mechanism, an operating load state detecting circuit is configured to detect an operating load state of the pump based on a viscosity resistance characteristic of a working oil, and an electric motor control circuit is configured to output a drive signal to the motor on the basis of a torque signal from the torque sensor and the operating load state of the pump.
Claims21
A power steering device comprising:
- a hydraulic power cylinder configured to assist a steering force of a steering mechanism linked to steerable road wheels;
- a pump configured to supply a hydraulic pressure to respective pressure chambers of the hydraulic power cylinder;
- an electric motor configured to drive the pump;
- a torque sensor configured to detect a steering torque of the steering mechanism;
- an operating load state detecting circuit configured to detect an operating load state of the pump based on a viscosity resistance characteristic of a working oil;
- and
- an electric motor control circuit configured to output a drive signal to the motor on the basis of a torque signal from the torque sensor and the operating load state of the pump, wherein the operating load state detecting circuit detects the operating load state of the pump on a basis of an actual number of revolutions per unit time of the electric motor,
- wherein the operating load state detecting circuit comprises a revolution state detecting circuit configured to detect a revolution state of the electric motor and the operating load of the pump is estimated on the basis of the revolution state of the electric motor, and
- wherein the revolution state detecting circuit detects the revolution state of the electric motor by detecting a number of revolutions per unit time of the electric motor when a constant voltage is caused to flow into the electric motor, and
- wherein the operating load state detecting circuit estimates a temperature of the working oil on the basis of the revolution state of the electric motor and the electric motor control circuit outputs the drive signal to the electric motor on the basis of the temperature of the working oil and the steering torque.
7 more elements
A power steering device comprising:
- a hydraulic power cylinder configured to assist a steering force of a steering mechanism linked to steerable road wheels;
- a pump configured to supply a hydraulic pressure to respective pressure chambers of the hydraulic power cylinder;
- an electric motor configured to drive the pump;
- a torque sensor configured to detect a steering torque of the steering mechanism;
- an operating load state detecting circuit configured to detect an operating load state of the pump based on a viscosity resistance characteristic of a working oil;
- and
- an electric motor control circuit configured to output a drive signal to the motor on the basis of a torque signal from the torque sensor and the operating load state of the pump, wherein the operating load state detecting circuit comprises a revolution state detecting circuit configured to detect a revolution state of the electric motor and the operating load of the pump is estimated on the basis of the revolution state of the electric motor and wherein the power steering device further comprises:
- first and second passages through which the hydraulic pressure is supplied to the respective pressure chambers of the hydraulic power cylinder;
- a communication passage communicating between the first passage and the second passage;
- and a switching valve configured to switch between a communication of the communication passage and an interruption thereof;
- and a switching valve control circuit configured to output a control signal to the switching valve, wherein the switching valve is turned in a valve open state when the revolution state of the electric motor is detected by the revolution state detecting circuit.
8 more elements
A power steering device comprising:
- a hydraulic power cylinder configured to assist a steering force of a steering mechanism linked to steerable road wheels;
- a pump configured to supply a hydraulic pressure to respective pressure chambers of the hydraulic power cylinder;
- an electric motor configured to drive the pump;
- a torque sensor configured to detect a steering torque of the steering mechanism;
- an operating load state detecting circuit configured to detect an operating load state of the pump based on a viscosity resistance characteristic of a working oil;
- and
- an electric motor control circuit configured to output a drive signal to the motor on the basis of a torque signal from the torque sensor and the operating load state of the pump, wherein the power steering device further comprises a voltage value detecting circuit configured to detect a voltage value applied across the electric motor and the operating load of the pump is estimated on the basis of the voltage value and wherein the power steering device further comprises:
- first and second passages through which the hydraulic pressure is supplied to the respective pressure chambers of the hydraulic power cylinder;
- a communication passage to communicate between the first passage and the second passage;
- a switching valve configured to switch between a communication of the communication passage and an interruption thereof, and a switching valve control circuit configured to output a control signal to the switching valve and wherein the switching valve control circuit outputs the control signal to the switching valve to turn a valve open state when the revolution state of the electric motor is detected.
7 more elements
A power steering device comprising:
- a hydraulic power cylinder configured to assist a steering force of a steering mechanism linked to steerable road wheels;
- a pump configured to supply a hydraulic pressure to respective pressure chambers of the hydraulic power cylinder;
- an electric motor configured to drive the pump;
- a torque sensor configured to detect a steering torque of the steering mechanism;
- an operating load state detecting circuit configured to detect an operating load state of the pump;
- a viscosity resistance characteristic estimation circuit configured to estimate a viscosity resistance characteristic of a working oil on the basis of the operating load state of the pump based on an actual number of revolutions per unit time of the electric motor;
- and
- an electric motor control circuit configured to output a drive signal to the electric motor on the basis of a torque signal from the torque sensor and a viscosity resistance characteristic indicative signal from the viscosity resistance characteristic estimation circuit,
- wherein the power steering device further comprises a voltage value detecting circuit configured to detect a voltage value applied across the electric motor and the operating load of the pump is estimated on the basis of the voltage value.
6 more elements
A power steering device comprising:
- a hydraulic power cylinder configured to assist a steering force of a steering mechanism linked to steerable road wheels;
- a pump configured to supply a hydraulic pressure to respective pressure chambers of the hydraulic power cylinder;
- an electric motor configured to drive the pump;
- a torque sensor configured to detect a steering torque of the steering mechanism;
- a revolution state detecting circuit configured to detect a revolution state of the electric motor;
- a viscosity resistance estimation circuit configured to estimate a viscosity resistance characteristic of a working oil on a basis of the revolution state of the electric motor;
- a basic controlled variable calculating circuit configured to calculate a basic controlled variable of the electric motor on the basis of a torque signal from the torque sensor;
- a correction circuit configured to correct the basic controlled variable on the basis of a viscosity resistance characteristic indicative signal from the viscosity resistance estimation circuit and based on an actual number of revolutions per unit time of the motor;
- and
- an electric motor control circuit configured to output the basic controlled variable corrected by means of the correction circuit as an electric motor control signal to the electric motor.
7 more elements
Dependencies are inferred from the claim text.