Motor vehicles – Including one or more ski-like or runner members – With at least one surface-engaging propulsion element
Patent
1990-11-02
1992-01-14
Rice, Kenneth R.
Motor vehicles
Including one or more ski-like or runner members
With at least one surface-engaging propulsion element
180 791, 180133, 74388PS, B62D 506
Patent
active
050801864
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The conventional steering system is disclosed in DE 3714833A.
A steering wheel shaft is connected via a rotary slide valve with an input member such as a steering worm gear or a bevel gear of a servo assisted steering gear. A working piston of a hydraulic servomotor or boost device is arranged within the steering gear housing. In case of a relative rotation of the steering wheel shaft with respect to the input member, the rotary slide valve operates to apply pressure generated by a hydraulic servopump to assist the steering effort. At a power takeoff shaft an electric motor is connected with the input member of the steering gear. The electric motor is controlled by a signal from a sensor which is generated in response to rotation of the steering wheel. In the conventional servo assisted power steering system, a signal from a sensor such as a torque sensor, provides the electric motor power assist in case of hydraulic power boost failure such as low oil pressure. A torque rod arranged between the steering wheel shaft and the input memeber, supplies a relatively minor but vehicle operator noticeable reaction torque to the steering wheel. By means of the torque rod, the rotary slide valve is also turned toward its neutral position. Precise mid-point centering of the rotary slide valve and influencing the manual force or torque required by the operator by the presence of parameters such as vehicle load or speed in not possible in the conventional power assisted steering system.
THE PRESENT INVENTION
The purpose of the invention is to improve on a servo assisted steering system so that the exact rotary slide valve midpoint centering is made possible. Further, the reaction torque to be noticed by the vehicle operator when turning the steering wheel, is influenced in a simple manner by various parameters, such as, the vehicle speed, the cargo weight or both.
According to the invention, an electric motor is connected to the rotary slide of a rotary valve and thus with the steering wheel shaft. A sensor responsive to the turning of the steering wheel generates a signal to cause the motor to provide a slight opposing torgue to the manual turning of the steering wheel. After termination of the rotary motion of the steering wheel, as the steering wheel is released, the rotary valve is moved back into its neutral position by the electric motor. The signal for operating the electric motor can be controlled by sensor signals which are a function of the vehicle speed, the vehicle load or both. By means of a second sensor arranged on an output member of the steering gear the electric motor is so controlled that it will move the rotary slide beyond its neutral position into a control position which corresponds to a steering direction reversal. The rotary slide is thus kept in this steering position until such time as the output member (worm gear) returns to its neutral position by responding to the hydraulic power boost means. This results in power assisted steering return to neutral position of the steering shaft.
A further object of the invention, in case of failure of the hydraulic power assist, such as low oil pressure is made possible by the addition of a pressure sensor in the oil pressure line leading from the servopump to the rotary slide valve. Upon detection of low oil pressure, the electric motor is operated to turn the steering wheel shaft in the same direction as the direction of the steering wheel so as to provide an electrical assist function, The location of the sensor is optional. If arranged on the side of the electric motor instead of near the steering wheel, the installation conditions will be identical to the conventional system.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a longitudinal section of the main components of the invention with the electric motor connected to the power takeoff shaft.
FIG. 2 shows a second arrangement but including a torsion spring or torque rod.
FIG. 3 shows a further arrangement with the motor connected via bevel gear.
DESCRIPTION OF
REFERENCES:
patent: 3939938 (1976-02-01), Inoue
patent: 4368794 (1983-01-01), Elser et al.
patent: 4686433 (1987-08-01), Shimuzu
patent: 4800975 (1989-01-01), Oshita et al.
patent: 4886138 (1989-12-01), Graber et al.
Elser Dieter
Holub Heinrich
Schurr Rudolf
Hurley Kevin
Rice Kenneth R.
Zahnradfabrik Friedrichshafen AG.
Zalkind Albert M.
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