# US 5,346,030 A · Rear-wheel steering apparatus for vehicles > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,346,030 A - Document ID: US5346030A - Status: Granted - Kind: A - Application number: 08/010,992 - Filed: 1993-01-29 - Granted: 1994-09-13 - Earliest claimed: 1992-01-31 - Assignees: Mazda Motor Corporation - Inventors: Hiroshi Ohmura; Masanobu Kosaka; Koji Hosoda - Web page: https://patentgrep.com/patent/US5346030A ## CPC - B62D 7/159: {characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition} - B62D 7/148: {provided with safety devices} - 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 A rear-wheel steering apparatus having a high-speed step motor revolving in accordance with a target steering angle ratio and a power cylinder for converting a change of the revolved angle of the motor to an amount of steering angle of rear wheels with a power assist by a hydraulic power. When a failure is detected in the rear-wheel steering system when the steering angle ratio is changed from in-phase to opposite phase, an oil pressure is released out of the power cylinder simultaneously with an interruption of current supply to the motor. ## Claims ### Claim 1 A rear-wheel steering apparatus which controls a phase inversion of a steering angle ratio of rear wheels when a vehicle is turned, comprising: electric motor means for setting the steering angle ratio of the rear wheels adjustably with respect to the steering angle of front wheels; hydraulic driving means for driving the rear wheels with an oil pressure in accordance with the steering angle ratio set by said electric motor means; detection means for detecting a failed state in a rear-wheel steering control system; a fail-safe valve for releasing the oil pressure from said hydraulic driving means in order to force to return the steering angle of the rear wheels to a neutral position; and control means for controlling to stop said electric motor means and controlling said fail-safe valve to release the oil pressure from said hydraulic driving means in response to a detection of the failed state. ### Claim 2 (depends on 1) The apparatus according to claim 1, wherein said electric motor means is a high-speed step motor. ### Claim 3 (depends on 1) The apparatus according to claim 1, wherein the phase inversion control of steering angle ratio is performed in a case where the speed of the vehicle is at an intermediate speed or high speed region. ### Claim 4 (depends on 1) The apparatus according to claim 1, wherein said control means controls simultaneously to perform an energizing operation of the fail-safe valve and to stop said electric motor means. ### Claim 5 (depends on 1) The apparatus according to claim 1, wherein said hydraulic driving means further comprises: a cylinder to which an oil pressure is supplied; a rod provided in the cylinder for steering a left rear wheel and right rear wheel; and a spring for setting the rod, when the oil pressure is released via the fail-safe valve, so that the left rear wheel and right rear wheel are returned to the neutral position. ### Claim 6 (depends on 5) The apparatus according to claim 5, further comprising an orifice in a release circuit in order to control an amount of oil to be released when said fail-save valve is operated. ### Claim 7 (depends on 6) The apparatus according to claim 6, wherein said control means controls to stop the motor means before said fail-safe valve is operated and then controls to return the rear wheels to the neutral position. ### Claim 8 (depends on 1) The apparatus according to claim 1, wherein said detection means comprises means for detecting the direction of revolution on the basis of phases of driving currents applied to the electric motor means. ### Claim 9 A rear-wheel steering apparatus which controls a phase inversion of a steering angle ratio of rear wheels when a vehicle is turned, the apparatus comprising: electric motor means for setting the steering angle ratio of the rear wheels adjustably with respect to the steering angle of front wheels; hydraulic driving means for driving the rear wheels with an oil pressure in accordance with the steering angle ratio set by said electric motor means; detection means for detecting a failed state in a rear-wheel steering control system; a fail-safe valve for releasing the oil pressure from said hydraulic driving means in order to force to return the steering angle of the rear wheels to a neutral position; and control means for controlling to interrupt a current to the electric motor means and for controlling said fail-safe valve to release the oil pressure from said hydraulic driving means in response to a detection of the failed state. ### Claim 10 (depends on 9) The apparatus according to claim 9 wherein said electric motor means is a high-speed step motor. ### Claim 11 (depends on 9) The apparatus according to claim 9 wherein the phase inversion control of steering angle ratio is performed in a case where the speed of the vehicle is at an intermediate speed or high speed region. ### Claim 12 (depends on 9) The apparatus according to claim 9 wherein said control means controls simultaneously to perform an energizing operation of the fail-safe valve and to stop said electric motor means. ### Claim 13 (depends on 9) The apparatus according to claim 9 wherein said hydraulic driving means further comprises: a cylinder to which an oil pressure is supplied; a rod provided in the cylinder for steering a left rear wheel and right rear wheel; and a spring for setting the rod, when the oil pressure is released via the fail-safe valve, so that the left rear wheel and right rear wheel are returned to the neutral position. ### Claim 14 (depends on 13) The apparatus according to claim 13 further comprising an orifice in a release circuit in order to control an amount of oil to be released when said fail-safe valve is operated. ### Claim 15 (depends on 14) The apparatus according to claim 14 wherein said control means controls to stop the motor means before said fail-safe valve is operated and then controls to return the rear wheels to the neutral position. ### Claim 16 (depends on 9) The apparatus according to claim 9 wherein said detection means comprises a means for detecting the direction of revolution on the basis of phases of the driving currents applied to the electric motor means.