Toyota Jidosha Kabushiki Kaisha

Hitoshi Iwata

Hiroaki Tanaka

Kaoru Ohashi

Mizuho Sugiyama

Osamu Takeda

Shin Koike

Masaru Ishikawa

Hideki Kusunoki

In an electric control apparatus for a four-wheel steering system including an electric motor the rotary angle of which is electrically controlled in accordance with a target steering angle of rear road wheels, and a hydro-mechanical tracer mechanism having a fluid control valve the valve element of which is drivingly connected to the electric motor to be displaced in proportion to the rotary angle of the electric motor, the tracer mechanism being arranged to steer the rear road wheels in proportion to a displacement amount of the valve element, the target steering angle is converted into a control value for rotation of the electric motor, and a drive signal indicative of the control value is applied to the electric motor. The electric control apparatus is designed to greatly change the control value to and from zero when the target steering angle is less than a predetermined small angle and to change the control value in proportion to the target steering angle when the target steering angle is more than the predetermined small angle.

Electric control apparatus for four-wheel steering system

An electric control apparatus for a four-wheel steering system is designed to calculate a rear wheel steering angle on a basis of a control rule corresponding with a steering mode selected from a plurality of rear wheel steering modes thereby to steer a set of dirigible rear road wheels at the calculated steering angle. The electric control apparatus is further designed to calculate a difference between new and old steering angles calculated when the selected steering mode has been changed to another one of the steering modes and immediately after change of the selected steering mode, to gradually decreasing an absolute value of the calculated difference at a predetermined time interval, to correct the new steering angle in accordance with the absolute value of the calculated difference until the absolute value becomes zero after change of the selected steering mode and to control an actual steering angle of the rear road wheels in accordance with the corrected new steering angle.

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Okazaki, Japan

Hitoshi Iwata