Electricity: motive power systems – Limitation of motor load – current – torque or force
Patent
1988-03-11
1990-07-03
Shoop, Jr., William M.
Electricity: motive power systems
Limitation of motor load, current, torque or force
180 791, 180142, 318446, 318467, 318489, H02K 1732
Patent
active
049394363
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 a rotational force of a motor.
BACKGROUND ART
A conventional power steering device of this type is adapted to transmit drive force of a motor through a reduction mechanism and a transmission mechanism such as gear or belt to a steering shaft or a rack shaft.
The conventional power steering device as mentioned above is of the type in which a vehicle speed is detected by a vehicle speed sensor so that the assist is removed when the detected speed reaches or exceeds a constant value. However, since the speed signal from the speed sensor is supplied as a series of pulses the number of which is proportional to the vehicle speed, a construction of an input circuit and a program for calculating the vehicle speed become complicated, resulting in high costs of a microcomputer and a vehicle speed input circuit to be used in a control unit.
This invention was made in view of such problems as mentioned above and an object thereof is to obtain a motor driven power steering control device which can use an inexpensive microcomputer by simplifying constructions of the input circuit and the control program.
DISCLOSURE OF THE INVENTION
The motor driven power steering control device of this invention comprises a speed change point sensor for sensing a speed change point, a torque sensor for sensing a rotational force of a steering wheel, a control unit to be supplied with signals from these sensors as input signals, a motor driven by a battery through the control unit and an electromagnetic clutch engaged with and disengaged from an output shaft of the motor by means of the control unit.
The motor driven power steering control device of this invention can use an inexpensive microcomputer by simplifying an input circuit and a control program by means of a usage of not a vehicle speed sensor but a speed change point sensor for sensing a speed change point and facilitates a decision of breakage of an input line for a speed change point signal by inputting the speed change point outside a range in which a power assist is to be added, resulting in a highly safe power steering.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a construction of a motor driven power steering control device to an embodiment of this invention,
FIG. 2 is block circuit diagram of a control unit,
FIG. 3 is a steering torque vs. motor current curve showing a control characteristics,
FIG. 4 is a motor current variation curve and a variation curve of voltage applied to an electromagnetic clutch showing a control characteristics when an assist condition is changed and
FIG. 5 is a flow chart of a control program.
PREFERRED EMBODIMENT FOR PRACTICING THE INVENTION
An embodiment of this invention will be described with reference to the drawings. FIG. 1 shows a construction of a motor driven power steering control device with electric portions thereof in block circuit diagram, in which 1 is a steering wheel to be operated by a rotational force given by a driver, 3 a torque sensor for providing an output signal corresponding to the rotational force applied to the steering wheel 1, 4a a first universal joint, 4b a second universal joint, 2a a first steering shaft connecting the steering wheel 1 and the torque sensor 3, 2b a second steering shaft connecting the torque sensor 3 and the first universal joint 4a, 2c a third steering shaft connecting the first universal joint 4a and the second universal joint 4b, 5 a first pinion shaft connected to the second universal joint , 6 a rack shaft having a first rack teeth portion 6a meshed with the pinion shaft 5 and a second rack teeth portion 6b and 7a a ball joint connecting a tie rod 8a and an end of the first rack teeth portion 6a, 7b the other ball joint connecting the other tie rod 8b and the second rack teeth portion 6b. 9 is a control unit, 10 a speed change point sensor for sensing a speed change point, 11 a vehicle mounted battery, 12 a key
REFERENCES:
patent: 4532567 (1985-07-01), Kade
patent: 4580649 (1984-09-01), Ohe et al.
patent: 4582155 (1986-04-01), Ohe
patent: 4591014 (1984-04-01), Yasuda
patent: 4639651 (1987-01-01), Shimizu
patent: 4687976 (1987-08-01), Shimizu
patent: 4789040 (1987-06-01), Morishita et al.
Patent Abstract of Japan, vol. 9, No. 223, 58-189819, Shiraishi.
Kouge Shinichi
Morishita Mitsuharu
Martin David
Mitsubishi Denki & Kabushiki Kaisha
Shoop Jr. William M.
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