| 摘要 |
A four-wheel steering system comprises a steering handle (2), a steering gear system (1), a couple of hydraulic pumps (4, 4a) for front and rear wheels (3, 7), a first solenoid valve (5), an ON-OFF valve (51), a control part operating the valves and an actuator (8) controlling the rear wheel steering via the ON-OFF valve. The actuator comprises a cylinder (81), a piston (82), a couple of piston rods (71) linked to the rear wheel, a couple of springs (83), a stopper means (9) and a second solenoid valve (10) operating the stopper means. It is characterized that the stopper means may set the piston to be locked in a neutral position when the steering system is out of order. Releasing the locked piston is achieved by transferring a high pressure from the hydraulic pump for the rear wheel to the stopper means.
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