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US 4,657,102 AGranted
Four-wheel steering device for vehicle
AssigneeToyo Kogyo Co., Ltd.
InventorsHirotaka Kanazawa, Teruhiko Takatani, Naoto Takata
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AssigneeToyo Kogyo Co., Ltd.
InventorsHirotaka Kanazawa, Teruhiko Takatani, Naoto Takata
Estimating the term…
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.
A four-wheel steering device for a vehicle comprising a front wheel steering mechanism for turning the front wheels, a rear wheel steering mechanism for turning the rear wheels, a vehicle speed sensor for detecting the vehicle speed, and a controller for controlling the rear wheel steering mechanism, characterized in that said controller controls the rear wheel steering mechanism so that the rear wheel turning angle is changed in accordance with a turning angle ratio characteristic curve which is defined on a .theta.F-.theta.R cartesian coordinate system wherein .theta.F and .theta.R respectively represent the front wheel turning angle and the rear wheel turning angle, said cartesian coordinate system including an origin, a positive .theta.F axis, a negative .theta.R axis and a positive .theta.R axis, said .theta.F axis and said positive .theta.R axis defining a quadrant I and said .theta.F axis and said negative .theta.R axis defining a quadrant IV, a positive .theta.R value denoting turning of the rear wheels in equal phase with the front wheels and a negative .theta.R value denoting turning of the rear wheels in reverse phase to the front wheels, and which is changed according to the vehicle speed, the turning angle ratio characteristic curve for very low vehicle speeds not higher than a first predetermined speed including a first portion extending on said .theta.F axis in the region in which the value of .theta.F is smaller than a first predetermined value and a second portion having a negative inclination to extend into quadrant IV so that the rear wheels are turned in the reverse phase when the front wheel turning angle exceeds the predetermined value, the first and second portions being connected with each other at a reverse phase starting point having values of .theta.F and .theta.R respectively equal to the first predetermined value and zero, and the turning angle ratio characteristic curve for vehicle speeds higher than said first predetermined speed having a positive inclination to extend into quadrant I so that the front wheels and rear wheels are turned in the equal phase, said turning angle ratio characteristic curve for vehicle speeds higher than said first predetermined speed comprising a plurality of lines with different positive inclinations extending from the origin of the .theta.F and .theta.R axes, increasing inclination of the line corresponding to increasing vehicle speed;
A four wheel steering device for a vehicle comprising a front wheel steering mechanism for turning the front wheels, a rear wheel steering mechanism for turning the rear wheels, a vehicle speed sensor for detecting the vehicle speed, and a controller for controlling the rear wheel steering mechanism, characterized in that said controller controls the rear wheel steering mechanism so that the rear wheel turning angle is changed in accordance with a turning angle ratio characteristic curve which is defined on a .theta.F-.theta.R cartesian coordinate system wherein .theta.F and .theta.R respectively represent the front wheel turning angle and the rear wheel turning angle, said cartesian coordinate system including an origin, a positive .theta.F axis, a negative .theta.R axis and a positive .theta.R axis, said .theta.F axis and said positive .theta.R axis defining a quadrant I and said .theta.F axis and said negative .theta.R axis defining a quadrant IV, a positive .theta.R value denoting turning of the rear wheels in equal phase with the front wheels and a negative .theta.R value denoting turning of the rear wheels in reverse phase to the front wheels, and which is changed according to the vehicle speed, the turning angle ratio characteristic curve for very low vehicle speeds not higher than a first predetermined speed including a first portion extending on the .theta.F axis in the region in which the value of .theta.F is smaller than a first predetermined value and a second portion having a negative inclination to extend into quadrant IV so that the rear wheels are turned in the reverse phase when the front wheel turning angle exceeds the predetermined value, the first and second portions being connected with each other at a reverse phase starting point having the values of .theta.F and .theta.R respectively equal to the first predetermined value and zero, the absolute value of the inclination of the second portion being increased with reduction of the vehicle speed and the turning angle ratio characteristic curve for the vehicle speeds higher than said first predetermined speed being substantially a broken line having an inflection point at which the inclination thereof is changed and having a positive first inclination in the region where the value of .theta.F is smaller than the value of .theta.F at the inflection point and a second inclinatgion smaller than the first inclination in the region where the value of .theta.F is not smaller than the value of .theta.F at the inflection point;
A four-wheel steering device for a vehicle comprising a front wheel steering mechanism for turning the front wheels, a rear wheel steering mechanism for turning the rear wheels, a vehicle speed sensor for detecting the vehicle speed, and a controller for controlling the rear wheel steering mechanism, characterized in that said controller controls the rear wheel steering mechanism so that the rear wheel turning angle is changed in accordance with a turning angle ratio characteristic curve which is defined on a .theta.F-.theta.R cartesian coordinate system wherein .theta.F and .theta.R respectively represent the front wheel turning angle and the rear wheel turning angle, said cartesian coordinate system including an origin, a positive .theta.F axis, a negative .theta.R axis, and a positive .theta.R axis, said .theta.F axis and said .theta.R axis defining a quadrant I and said .theta.F axis and said negative .theta.R axis defining a quadrant II, a positive .theta.R value denoting turning of the rear wheels in equal phase with the front wheels and a negative .theta.R value denoting turning of the rear wheels in reverse phase to the front wheels, and which is changed according to the vehicle speed, the turning angle ratio characteristic curve for very low vehicle speeds not higher than a first predetermined speed including a first portion extending on said .theta.F axis in the region in which the value of .theta.F is smaller than a first predetermined value and a second portion having a negative inclination to extend into quadrant IV so that the rear wheels are turned in the reverse phase when the front wheel turning angle exceeds the predetermined value, the first and second portions being connected with each other at a reverse phase starting point having the values of .theta.F and .theta.R respectively equal to a first predetermined value and zero, and the turning angle ratio characteristic curve for vehicle speeds higher than said first predetermined speed is substantially a broken line having an inflection point at which the inclination thereof is changed and has a positive first inclination in the region where the value of .theta.F is smaller than the value of .theta.F at the inflection point and a second inclination smaller than the first inclination in the region where the value of .theta.F is not smaller than the value of .theta.F at the inflection point, the second inclination of the turning angle ratio characteristic curve for vehicle speeds higher than said first predetermined speed and lower than a second predetermined speed being negative so that the turning angle ratio characteristic curve intersects the .theta.F axis, whereby the rear wheels are turned in the reverse phase when the front wheel turning angle exceeds the value of .theta.F at the intersection of the turning angle ratio characteristic curve and the .theta.F axis, the turning angle ratio characteristic curve for vehicle speeds higher than the second predetermined speed being held above the .theta.F axis, wherein for the vehicle speeds higher than said first predetermined speed and lower than the second predetermined speed, said intersection of the turning angle ratio characteristic curve and said .theta.F axis is shifted in the direction of increasing .theta.F as the vehicle speed increases;
A four-wheel steering device for a vehicle comprising a front wheel steering mechanism for turning the front wheels, a rear wheel steering mechanism for turning the rear wheels, a vehicle speed sensor for detecting the vehicle speed, and a controller for controlling the rear wheel steering mechanism, characterized in that said controller controls the rear wheel steering mechanism so that the rear wheel turning angle is changed in accordance with a turning angle ratio characteristic curve which is defined on a .theta.F-.theta.R cartesian coordinate system wherein .theta.F and .theta.R respectively represent the front wheel turning angle and the rear wheel turning angle, said cartesian coordinate system including an origin, a positive .theta.F axis, a negative .theta.R axis and a positive .theta.R axis, said .theta.F axis and said positive .theta.R axis defining a quadrant I and said .theta.F axis and said negative .theta.R axis defining a quadrant II, a positive .theta.R value denoting turning of the rear wheels in equal phase with the front wheels and a negative .theta.R value denoting turning of the rear wheels in reverse phase to the front wheels, and which is changed according to the vehicle speed, the turning angle ratio characteristic curve for very low vehicle speeds not higher than a first predetermined speed including a first portion extending on the .theta.F axis in the region in which the value of .theta.F is smaller than a first predetermined value and a second portion having a negative inclination to extend into quadrant IV so that the rear wheels are turned in the reverse phase when the front wheel turning angle exceeds the predetermined value, the first and second portions being connected with each other at a reverse phase starting point having the values of .theta.F and .theta.R respectively equal to the first predetermined value and zero, and the turning angle ratio characteristic curve for vehicle speeds higher than said first predetermined speed is substantially a broken line having an inflection point at which the inclination thereof is changed and has a positive first inclination in the region where the value of .theta.F is smaller than the value of .theta.F at the inflection point and a second inclination smaller than the first inclination in the region where the value of .theta.F is not smaller than the value of .theta.F at the inflection point, said turning angle ratio characteristic curve for vehicle speeds higher than said first predetermined speed being changed according to the vehicle speed so that the inflection point is continuously shifted to converge on said reverse phase starting point as the vehicle speed is reduced;
Dependencies are inferred from the claim text.