Abstract: A rear wheel turning system for a four-wheel steered vehicle includes a rear wheel turning mechanism for turning the rear wheels of the vehicle, a front wheel turning angle sensor which detects a turning angle of front wheels .theta..sub.F, a vehicle speed sensor which detects a vehicle speed V, a yaw rate detector which detects a yaw rate .PSI. of the vehicle, a yaw acceleration detector which detects a yaw acceleration .PSI. of the vehicle, and a control unit which causes the rear wheel turning mechanism to turn the rear wheels by a target rear wheel turning angle TG.theta..sub.R which is defined by formulaTG.theta..sub.R =-K.sub.1 .theta..sub.F +K.sub.2 .multidot.V.multidot..PSI.+K.sub.3 .multidot.V.multidot..PSI.wherein K.sub.1, K.sub.2 and K.sub.3 respectively represent positive coefficients. The coefficient K.sub.3 is increased with increase in the vehicle speed V over a predetermined range of vehicle speed where the coefficient K.sub.2 is constant.

Abstract: A rear wheel steering device for a vehicle has a steering control mechanism which steers rear wheels of the vehicle on the following formula:TG.theta..sub.R =-K.sub.F .multidot..theta..sub.F +K.sub.R .multidot.V.multidot..psi.whereTG.theta..sub.R : target steering angle of rear wheels.theta..sub.F : steering angle of front wheelsV: vehicle speed.theta.: yaw rateK.sub.F, K.sub.R : coefficients determined by the properties of vehicle.To achieve slip angle .beta.=0, the device further includes a vehicle condition detecting mechanism which detects various conditions of the vehicle, and a changing mechanism being connected with the steering control mechanism and the vehicle condition detecting mechanism for changing at least one of the coefficients K.sub.F, K.sub.R based on the conditions of the vehicle.

Abstract: An automotive vehicle having a fluid-operated, four wheel steering system for steering not only the front wheel pair, but also the rear wheel pair as a function of the amount of turn of the front wheel pair with respect to the direction of straightforward run of the vehicle. The system makes use of a front cylinder operatively associated with a steering gear assembly and a rear cylinder operated by a fluid medium supplied from the front cylinder for steering the rear wheel pair. In order for the steering system to be responsive to the vehicle running speed thereby to control the amount of turn of the rear wheel pair appropriate for a particular range of vehicle running speed, a device is provided for accommodating a portion of the fluid medium to be supplied to the rear cylinder when the pressure of the fluid medium increases to a value higher than a predetermined pressure.

Abstract: In an automotive vehicle having front and rear wheel pairs and a steering wheel drivingly coupled with the front wheel pair for steering the vehicle with respect to the direction of run of the vehicle, said steering wheel being rotatable in any one of the opposite directions from a neutral position at which the vehicle can run straightforward, an automotive four wheel steering system is provided with a right-hand rear wheel turning structure for turning the right-hand rear wheel in a direction in which the toe-in takes place, a left-hand rear wheel turning structure for turning the left-hand rear wheel in a direction in which the toe-in takes place, a right-hand rear wheel toe-out stopper for mechanically preventing the right-hand rear wheel from turning in a direction in which the toe-out takes place, a left-hand rear wheel toe-out stopper for mechanically preventing the left-hand rear wheel from turning in a direction in which the toe-out takes place, and a rear wheel operating structure for operating eithe