Four-wheel steering apparatus

A four-wheel steering apparatus for a vehicle having a rotatable steering wheel, front wheels, and rear wheels, the steering wheel when rotated having a rotational torque, said apparatus comprising:

• (a) a front-wheel steering device including a hydraulic power steering mechanism for steering the front wheels in response to the rotation of the steering wheel and oil pressure in proportion to the rotational torque of the steering wheel, said power steering mechanism including a hydraulic circuit and a movable front-wheel steering bar;
• and
• (b) a rear-wheel steering device including:
• (i) a rear-wheel steering ar mechanically separated from said front-wheel steering device and movable for steering the rear wheels;
• (ii) a rear-wheel steering bar drive assembly for moving said rear-wheel steering bar;
• (iii) a maximum steering amount regulating assembly having a variably regulating member for mechanically restricting the maximum amount of movement of said rear-wheel steering bar to decrease as the vehicle speed increases and for adjusting the maximum amount of movement of said rearwheel steering bar, said maximum steering amount regulating assembly being connected to said hydraulic circuit of said power steering mechanism to decrease the maximum amount of movement of said rear-wheel steering bar which is mechanically restricted by said variably regulating member in response to a decrease in the front wheel steering oil pressure;
• and
• (iv) a rear-wheel steering control system for controlling said rear-wheel steering bar drive assembly in accordance with the steering amount of the front wheels to thereby control the amount of movement of said rear-wheel steering bar and control the steering amount of the rear wheels.

A four-wheel steering apparatus for a vehicle having a rotatable steering wheel, front wheels, and rear wheels, the steering wheel when rotated having a rotational torque, said apparatus comprising:

• (a) a front-wheel steering device having a front-wheel steering bar movable for steering the front wheels;
• (b) a rear-wheel steering device including:
• (i) a rear-wheel steering bar mechanically separated from said front-wheel steering device and movable for steering the rear wheels;
• (ii) a rear-wheel steering bar drive assembly for moving said rear-wheel steering bar;
• (iii) a maximum steering amount regulating assembly comprising a variably regulating member for mechanically restricting the maximum amount of movement of said rear-wheel steering bar to decrease as the vehicle speed increases and for adjusting the maximum amount of movement of said rear-wheel steering bar, said variably regulating member having a groove perpendicular to said rear-wheel steering bar and an amount-of-movement regulating member fitted in said groove, said groove extending in one direction with its width gradually decreasing, and said variably regulating member being fixed to said rear-wheel steering bar, wherein movement of said variably regulating member in a direction perpendicular to said rear-wheel steering bar changes the position of said amount-of-movement regulating member in said groove to decrease the maximum amount of movement of said rear-wheel steering bar to be mechanically restricted by said variably regulating member, as the vehicle speed increases;
• and
• (iv) a rear-wheel steering control system for controlling the rear-wheel steering bar drive assembly in accordance with the steering amount of the front wheels to thereby control the amount of movement of the rear-wheel steering bar and control the steering amount of the rear wheels.

A four-wheel steering apparatus for a vehicle having a rotatable steering wheel, front wheels, and rear wheels, the steering wheel when rotated having a rotational torque, said apparatus comprising:

• (a) a front-wheel steering device comprising a hydraulic power steering mechanism for steering the front wheels in response to the rotation of the steering wheel and oil pressure in proportion to the rotational torque of the steering wheel, said power steering mechanism including a movable front-wheel steering bar and a hydraulic circuit;
• and
• (b) a rear-wheel steering device including:
• (i) a rear-wheel steering bar mechanically separated from said front-wheel steering device and movable for steering the rear wheels;
• (ii) a rear-wheel steering bar drive assembly for moving said rear-wheel steering bar;
• and
• (iii) a maximum steering amount regulating assembly comprising a variably regulating member for mechanically restricting the maximum amount of movement of said rear-wheel steering bar and for adjusting the maximum amount of movement of said rear-wheel steering bar, said variably regulating member having a groove perpendicular to said rear-wheel steering bar and an amount-of-movement regulating member fitted in said groove, said groove extending in one direction with its width gradually decreasing, and said regulating member being fixed to said rear-wheel steering bar, said maximum steering amount regulating assembly being connected to said oil pressure circuit of said hydraulic power steering mechanism, whereby movement of said variably regulating member in a direction perpendicular to said rear-wheel steering bar changes the position of said amount-of-movement regulating member in said groove to decrease the maximum amount of movement of said rear-wheel steering bar to be mechanically restricted by said variably regulating member, as the front-wheel steering oil pressure decreases;
• and
• (c) a rear-wheel steering control system for controlling said rear-wheel steering bar drive assembly in accordance with the steering amount of the front wheels to thereby control the amount of movement of said rear-wheel steering bar and control the steering amount of the rear wheels.