Motor vehicles – Compensating devices
Patent
1988-03-07
1989-06-27
Pekar, John A.
Motor vehicles
Compensating devices
36442401, B62D 504
Patent
active
048420875
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
This invention relates to a motor driven type power steering control device for assisting an operation of a steering device of an automobile with rotational force of a motor.
BACKGROUND OF TECHNOLOGY
A conventional power steering device of this type assists an operation of a steering shaft or a rack shaft with driving force of a motor through a reduction mechanism and a transmission mechanism such as gears or belts.
Since, in such a conventional power steering device, it is impossible to distinguish between a malfunction of the motor or other mechanical systems, such as locking thereof, and a locking of a steering wheel, there may be a case where a current supply to the motor is continued for long enough to heat power elements for controlling the motor to high temperature, causing them to be damaged and/or making steering impossible by such mechanical locking, causing a severe accident to occur.
This invention was made in view of such problems, and an object of this invention is to obtain a motor driven power steering control device capable of preventing a motor and power elements from being damaged by excessive temperature and of making steering wheel operation possible when mechanical locking occurs to thereby assure safe operation of an automobile.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a construction of a motor driven power steering control device according to an embodiment of this invention,
FIG. 2 is a block circuit diagram of a control unit,
FIG. 3 is a steering torque vs. motor current curve showing control characteristics,
FIG. 4 shows a vehicle speed vs. motor current curve and a vehicle speed vs. voltage applied to an electromagnetic clutch curve showing control characteristics,
FIG. 5 is a flow chart of a control program,
FIG. 6 is a construction of a motor driven power steering control device according to a second embodiment of this invention,
FIG. 7 is a block circuit diagram of a control unit in the second embodiment,
FIG. 8 is a flow chart of a control program for the second embodiment,
FIG. 9 is a motor current vs. time curve showing a current reducing control characteristics when a supply of current exceeding a predetermined value to the motor is continued for a predetermined time period or longer,
FIG. 10 is a motor current vs. time curve showing current reducing characteristics in another embodiment and
FIG. 11 is a flow chart of a control program for another embodiment.
DISCLOSURE OF THE INVENTION
In this invention, when a steering wheel becomes heavy due to a motor locking or a locking of a mechanical system, a discrimination means distinguishes the locking of the motor or the mechanical system from a steering around wheel locking positions to reduce a motor current to zero and disengage an electromagnetic clutch, so that damage to the motor and power elements are prevented and steering operation becomes possible even if mechanical locking occurs.
Further, in this invention, motor current is made zero and, simultaneously, the electromagnetic clutch is disengaged. Then, when the steering is performed around the wheel locking positions, motor current is made zero within a predetermined time, so that the power steering can be performed with minimized abnormal feeling of steering.
PREFERRED EMBODIMENTS FOR PRACTICING THE INVENTION
The present invention now will be described in detail, with reference to the accompanying drawings.
FIG. 1 shows a construction of a motor driven power steering control device according to this invention, together with a block circuit diagram, in which 1 is a steering wheel to be operated by rotational steering force given by a driver, 3 is a torque sensor for providing a signal corresponding to the rotational force applied to the steering wheel 1, 4a is a first universal joint, 4b is a second universal joint, 2a is a first steering shaft connecting the steering wheel 1 and the torque sensor 3, 2b is a second steering shaft connecting the torque sensor 3 and the first universal joint 4a, 2c is a third steering shaft conne
REFERENCES:
patent: 4621327 (1986-11-01), Dolph et al.
patent: 4715461 (1987-12-01), Shimizu
patent: 4715463 (1987-12-01), Shimizu
Kouge Shinichi
Morishita Mitsuharu
Mitsubishi Denki & Kabushiki Kaisha
Pekar John A.
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