# US 2019/0315399 A1 · Four-wheel steering system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0315399 A1 - Document ID: US20190315399A1 - Status: Published application - Kind: A1 - Application number: 16/376,048 - Filed: 2019-04-05 - Published: 2019-10-17 - Earliest claimed: 2018-04-11 - Assignees: Jtekt Corporation - Applicants: Jtekt Corporation - Inventors: Yasuharu YAMAMOTO - Web page: https://patentgrep.com/patent/US20190315399A1 ## CPC - B62D 7/1509: {with different steering modes, e.g. crab-steering, or steering specially adapted for reversing of the vehicle} - B62D 6/002: {computing target steering angles for front or rear wheels (B62D7/159 takes precedence)} - B62D 6/02: responsive only to vehicle speed - B62D 7/026: {characterised by comprising more than one bogie, e.g. situated in more than one plane transversal to the longitudinal centre line of the vehicle} - B62D 7/159: {characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition} - B62D 15/0265: {Automatic obstacle avoidance by steering} - B62D 15/027: {Parking aids, e.g. instruction means} - B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M) ## Abstract The four-wheel steering system includes a front-wheel steering system that steers front wheels of a vehicle and a rear-wheel steering system that steers rear wheels of the vehicle in accordance with a steering angle that is a rotation angle of a steering wheel. The rear-wheel steering system includes a second ECU that, when the vehicle speed is equal to or lower than a vehicle speed threshold, performs antiphase control in which the rear wheels are steered in the opposite direction to that in which the front wheels are steered. When the vehicle speed is equal to or lower than the vehicle speed threshold, the second ECU performs in-phase control in which the rear wheels are steered in the same direction as that in which the front wheels are steered, in response to a specific trigger operation that is performed via the steering wheel. ## Claims ### Claim 1 A four-wheel steering system, comprising: a front-wheel steering system that steers front wheels of a vehicle; and a rear-wheel steering system that steers rear wheels of the vehicle in accordance with a steering angle that is a rotation angle of a steering wheel, wherein, the rear-wheel steering system includes a control device that, when a vehicle speed is equal to or lower than a vehicle speed threshold, performs antiphase control in which the rear wheels are steered in an opposite direction to that in which the front wheels are steered, and when the vehicle speed is equal to or lower than the vehicle speed threshold, the control device performs in-phase control in which the rear wheels are steered in the same direction as that in which the front wheels are steered, in response to a specific trigger operation that is performed via the steering wheel. ### Claim 2 (depends on 1) The four-wheel steering system according to claim 1, wherein, when the vehicle speed is equal to or lower than the vehicle speed threshold, the control device determines that the specific trigger operation has been performed, if at least an absolute value of steering torque is equal to or larger than a torque threshold, and the torque threshold is set based on steering torque that is applied to the steering wheel when the steering wheel turned to a limit position in its physical operation range is further turned in such a direction that an absolute value of the steering angle increases. ### Claim 3 (depends on 2) The four-wheel steering system according to claim 2, wherein, when the vehicle speed is equal to or lower than the vehicle speed threshold, the control device determines that the specific trigger operation has been performed, if the absolute value of the steering torque has been equal to or larger than the torque threshold for a first set time or longer. ### Claim 4 (depends on 2) The four-wheel steering system according to claim 2, wherein, when the vehicle speed is equal to or lower than the vehicle speed threshold, the control device determines that the specific trigger operation has been performed, if the steering torque equal to or larger than the torque threshold is detected a set number of times within a second set time. ### Claim 5 (depends on 1) The four-wheel steering system according to claim 1, wherein, when the in-phase control is being performed in response to the specific trigger operation, the control device switches a steering control mode for the rear wheels from the in-phase control to the antiphase control if it is determined that a distance by which the vehicle has moved in a lateral direction of the vehicle is equal to or larger than a distance threshold, and the distance threshold is set based on a maximum amount by which a corner of a rear end of the vehicle moves outward of a turn when the antiphase control is performed.