Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Patent
1999-04-13
2000-11-07
Zanelli, Michael J.
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
180443, B62D 507, B62D 600
Patent
active
061449091
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a power steering apparatus which applies a steering assist force to a steering mechanism by a hydraulic pressure generated by a pump driven by an electric motor.
BACKGROUND ART
Power steering apparatuses are known which assist operation of a steering wheel by supplying a working oil from an oil pump to a power cylinder coupled to a steering mechanism. The oil pump is driven by an electric motor, and a steering assist force is generated by the power cylinder in accordance with the speed of the electric motor.
Drive control of the electric motor is performed, for example, on the basis of the steering angular speed of the steering wheel. That is, the steering angular speed which corresponds to the time-related change rate of the steering angle of the steering wheel is determined on the basis of an output of a steering angle sensor provided in association with the steering mechanism, and the speed of the electric motor is controlled on the basis of the steering angular speed thus determined.
FIG. 7 is a diagram for explaining the drive control of the electric motor in greater detail, wherein the abscissa and the ordinate represent the steering angular speed V.theta. of the steering wheel and the motor speed R, respectively. Where the steering angular speed V.theta. is not greater than a predetermined first threshold VT1, the motor speed R is kept at the first speed R1. Where the steering angular speed V.theta. is not smaller than a second threshold VT2 which is greater than the first threshold VT1, the motor speed R is kept at a second speed R2 which is greater than the first speed R1. Where the steering angular speed is in a range between the first threshold VT1 and the second threshold VT2, the motor speed R is varied generally linearly with the steering angular speed V.theta. between the first speed R1 and the second speed R2.
Through this control, a greater steering assist force is generated as the steering wheel is more quickly turned and, hence, the steering assist can properly be provided.
When a motor vehicle travels straight, the steering wheel is virtually unoperated. In this case, therefore, virtually no steering assist force is required. In the aforesaid electric motor drive control, however, the electric motor is driven at the first speed R1 even if the steering angular speed V.theta. is at a value close to zero. Accordingly, the electric motor is kept driven even though no steering assist is required. This makes impossible to avoid wasteful energy consumption.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a power steering apparatus which ensures energy saving.
The power steering apparatus of the present invention, which is adapted to generate a steering assist force by a hydraulic pressure generated by a pump driven by an electric motor, comprises: steering angular speed detecting means (steering angle sensor 11, CPU 31, and Step S1 in FIG. 2) for detecting a steering angular speed; first control means (CPU 31 and Steps S7, S8 in FIG. 2) for variably setting the speed of the electric motor in accordance with the steering angular speed detected by the steering angular speed detecting means if the steering angular speed is greater than a first predetermined value (VT1); second control means (CPU 31 and Steps S5, S6 in FIG. 2) for setting the speed of the electric motor at a predetermined constant speed if the steering angular speed detected by the steering angular speed detecting means is between the first predetermined value and a second predetermined value (Vb) which is smaller than the first predetermined value; and third control means (CPU 31 and Steps S10 to S14 in FIG. 2) for stopping the electric motor on a predetermined condition if the steering angular speed detected by the steering angular speed detecting means is not greater than the second predetermined value.
In accordance with the present invention, the driving of the electric motor is controlled in accordance with the steering angular speed, whereb
REFERENCES:
patent: 4549627 (1985-10-01), Takeshima et al.
patent: 4552240 (1985-11-01), Takeshima et al.
patent: 5372214 (1994-12-01), Haga et al.
patent: 5761627 (1998-06-01), Seidel et al.
Kaji Hiroaki
Sakamaki Masahiko
Koyo Seiko Co. Ltd.
Zanelli Michael J.
LandOfFree
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