Motor vehicles – Compensating devices
Patent
1988-09-23
1990-01-16
Hill, Mitchell J.
Motor vehicles
Compensating devices
180140, 192 002R, 192 84R, 280 91, B62D 504, B62D 602, B62D 714
Patent
active
048936880
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to an electric rear wheel steering apparatus which operates in cooperation with front wheel steering of a vehicle, and steers the rear wheels by a motor.
DESCRIPTION OF THE PRIOR ART
Hitherto, in this type of electric rear wheel steering apparatus, the steering angle of rear wheels has been indicated in response to a signal from the steering wheel state sensor or a vehicle speed sensor, a feedback signal has been obtained to see whether the rear wheels are at a predetermined steering speed and angle, and an error of the predetermined steering angle of the rear wheels and the actual steering angle of the rear wheels has been detected, and a voltage to be applied to the motor for steering the rear wheels has been calculated in the closed loop control.
In the actual vehicles, however, since the sensors are installed over a wide range in parts of the vehicle, they must be connected by wiring. Accordingly, if a trouble should occur in these sensors or wiring, the rear wheels were steered without control even if it was not necessary to steer the rear wheels, or, to the contrary, the motor could not be driven due to breakage of power supply line or the like, and the positions of the rear wheels could not be determined, and other dangerous state might occur.
This invention is intended to solve these problems, and it is hence a primary object of this invention to present an electric rear wheel steering apparatus capable of preventing occurrence of an incontrollable state even in the event of abnormality such as trouble of sensors, interruption of power supply to the motor or the like.
SUMMARY OF THE INVENTION
The electric rear wheel steering apparatus of this invention comprises an electromagnetic clutch disposed between a motor for steering the rear wheels and a worm reduction gear having a reversion efficiency of zero or lower, and a control unit designed to cut off an electric current flowing to the motor and disengage the electromagnetic clutch when an abnormal operation other than a predetermined operation is ascertained.
Accordingly, when a trouble of sensors or disconnection of power supply line or other abnormality is detected, the control unit stops the motor and disengages the electromagnetic clutch at the same time. As a result, the rear wheel steering is fixed at that position, so that the rear wheels are prevented from becoming incontrollable.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural drawing of an electric rear wheel steering apparatus according to one of the embodiments of this invention, and FIG. 2 is a block diagram showing essential parts of the same electric rear wheel steering apparatus.
MOST PREFERRED EMBODIMENTS FOR ENFORCING INVENTION
Referring now to the drawings, this invention is described below in further details.
FIG. 1 is a drawing showing the structure of an electric rear wheel steering apparatus according to one of the embodiments of this invention. In the drawing, reference numeral 1 denotes a steering wheel, 2 is a steering shaft for transmitting a steering torque to the wheel 1, 3 is a gear box for steering the front wheels incorporating therein a motion direction changing mechanism such as rack and pinion, 4 is a tie rod for steering the front wheels connected to the gear box 3 for steering the front wheels, 5 represents front wheels, and 6 is a knuckle arm which is coupled to the tie rod 4 to turn the front wheels 5.
Numeral 7 is a gear box for steering the rear wheels incorporating therein a motion direction changing mechanism such as a rack and pinion, 8 is a tie rod for steering the rear wheels, 9 represents rear wheels, and 10 is a knuckle arm which is coupled to the tie rod 8 to turn the rear wheels 9.
Numeral 11 is a DC motor which is a driving source for steering the rear wheels 9, 12 is an electromagnetic clutch for mechanically engaging or disengaging the output of the motor 11, 13 is a reduction gear having a motion direction changing mechanism by a worm and worm wheel for feeding the output of th
REFERENCES:
patent: 4762194 (1988-08-01), Morishita et al.
patent: 4779693 (1988-10-01), Takahashi et al.
patent: 4782907 (1988-11-01), Morishita et al.
patent: 4789040 (1988-12-01), Morishita et al.
Hill Mitchell J.
Mitsubishi Denki & Kabushiki Kaisha
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