Abstract: A four-wheel steering mechanism comprising a front steering disposed outside of a passenger compartment for steering front wheels in accordance with a steering wheel, rear steering mechanism disposed outside of the passenger compartment for steering rear wheels in accordance with the steering amount of the front wheels, and connecting members connected with both the front and rear steering mechanisms and extended longitudinally for transmitting the steering in the front wheels to the rear steering mechanism characterized by the connecting member being provided in the passenger compartment. The steering mechanism can be protected from rusting.

Abstract: In a four-wheel steering system for a vehicle, a rear wheel turning mechanism for turning the rear wheels is controlled so that the ratio of the rear wheel turning angle to the front wheel turning angle changes with change in the vehicle speed. The ratio of the rear wheel turning angle to the front wheel turning angle is set so that the vehicle lateral acceleration response characteristics and the vehicle heading response characteristics generated by operation of the steering wheel approximate each other as far as possible.

Abstract: A four-wheel steering system for a vehicle comprises a steering wheel, a front wheel turning mechanism for turning the front wheels in response to operation of the steering wheel, a rear wheel turning mechanism including a rear wheel steering ratio determining circuit for determining the rear wheel steering ratio and an actuator for turning the rear wheels according to the rear wheel steering ratio determined by the rear wheel steering ratio determining circuit. The four-wheel steering system is provided with a road condition sensor for detecting road surface conditions which can weaken the road gripping force of the wheels and a rear wheel steering ratio controller for changing the rear wheel steering ratio determined by the rear wheel steering ratio determining circuit so that the rear wheel steering ratio is increased when the road condition is such that the road gripping force of the wheels can be weakened.

Abstract: A vehicle four wheel steering system including a rear wheel steering mechanism with a power assist device. The rear wheel steering mechanism includes a steering rod extending transversely of the vehicle and having the opposite ends connected with tie rods which are in turn connected with knuckle arms of the rear wheels. The steering rod is provided with a power cylinder in which a piston is slidably disposed. The piston is provided on the steering rod and defines hydraulic chambers in the cylinder. A control valve is provided to control hydraulic oil supply to the power cylinder. The control valve has a casing which is connected with the steering rod through an interconnecting section and hydraulic oil passages are formed in the interconnecting section for passing hydraulic oil to and from the power cylinder.

Abstract: In a four-wheeled vehicle, the rear wheels are turned as well as the front wheels in response to operation of the steering wheel. The rear wheel turning angle characteristics relative to the front wheel turning angle is changed according to the vehicle speed. In the low to high vehicle speed region, the rear wheel turning angle is increased with increase of the front wheel turning angle and the increasing rate is increased as the vehicle speed increases. In the very low vehicle speed region, the rear wheels are not turned until the front wheels are turned at least by a predetermined angle, and are turned in the direction opposite to the front wheels when the front wheels are turned by an angle larger than the predetermined angle. The rear wheel turning angle in the opposite direction is changed in proportion to the front wheel turning angle.

Abstract: A four-wheel steering system comprises a steering wheel; a steering shaft which is connected to the steering wheel to be rotated in response to operation of the steering wheel and is provided with a first pinion fixedly mounted thereon; a rack bar which is supported for sliding motion in the transverse direction of the vehicle body, is provided with a first rack gear in mesh with the first pinion and a second rack gear, and is connected to the right and left front wheels by way of tie rods, a rear wheel turning force taking-out mechanism which includes a second pinion in mesh with the second rack gear on the rack bar and a rod member connected to the second pinion, and which converts the sliding motion of the rack bar into rotation of the rod member; and a rear wheel turning mechanism which is arranged to turn the rear wheels in response to rotation of the rod member.

Abstract: In a four-wheel steering apparatus of a vehicle for steering also the rear wheels in conformity with the steering of the front wheels by a steering wheel, a control force for a rear wheel steering device is mechanically taken out from a front wheel steering device and is suitably controlled in the intermediate portion and is transmitted as a steering control force to the rear wheel steering device, whereby the front wheels and the rear wheels are steered in the same direction when the absolute value of the steering angle of the front wheels is less than a predetermined value, and the rear wheels are steered in the direction reverse to the front wheels when the absolute value is greater than the predetermined value.

Abstract: The rear wheels of a vehicle are turned in response to the turning of the front wheels upon operation of the steering wheel. A rack member is provided to be operatively connected with a movable member of the front wheel steering system which is moved right and left in response to operation of the steering wheel so that the rack member is moved together with the movable member. The rack member is in mesh with a pinion fixed to an end of an output shaft whose rotation is transmitted to the rear wheel steering system as steering force for moving it by way of a transmission shaft.

Abstract: In the four-wheeled vehicle, both the front and rear wheels are turned in response to operation of the steering wheel. The turning angle of the rear wheels is controlled in accordance with a turning angle ratio characteristic curve defined on a .theta.F-.theta.R plane wherein .theta.F and .theta.R respectively represent the turning angles of the front and rear wheels. The turning angle ratio characteristic curve is substantially a broken line having a positive inclination in the region where the value of the front wheel turning angle .theta.F is smaller than a predetermined value and having a smaller inclination in the region where the value of the front wheel turning angle .theta.F is larger than the predetermined value. The turning angle ratio characteristic curve is changed according to the vehicle speed so that the turning angle ratio .theta.R/.theta.F is increased as the vehicle speed increases.