Vehicle steering system and coupling-mechanism switching method

A vehicle steering system provided for a vehicle whose driving state is switchable between a manual driving state and an automatic driving state, the vehicle steering system including a coupling mechanism configured to couple a steering operation member operated by a driver and at least one steerable wheel of the vehicle,

• wherein, when the driving state of the vehicle is switched from the manual driving state to the automatic driving state, the coupling mechanism is switched from a mechanically coupling state in which the coupling mechanism mechanically couples the steering operation member and the at least one steerable wheel to each other to a mechanically decoupling state in which the coupling mechanism mechanically decouples the steering operation member and the at least one steerable wheel from each other,
• wherein the vehicle steering system includes:
• a neutral position guide configured to guide, in the mechanically decoupling state of the coupling mechanism, rotation of the steering operation member toward a neutral position in accordance with a change of a position of the steering operation member toward a forward direction of the vehicle;
• a steering shaft coupled to the steering operation member such that the steering shaft is rotatable about an axis thereof integrally with the steering operation member;
• and
• a column holding the steering shaft such that the steering shaft is rotatable about the axis, the column being held by a body of the vehicle so as to be unrotatable about the axis relative to the body of the vehicle,
• wherein a second protrusion is provided for one of an inside portion of the column and an outer circumferential portion of the steering shaft,
• wherein the neutral position guide is provided for the other of the inside portion of the column and the outer circumferential portion of the steering shaft, and
• wherein the steering shaft is moved relative to the column in the forward direction of the vehicle in a state in which the second protrusion is in contact with the neutral position guide, so that the neutral position guide guides rotation of the steering shaft about the axis toward a phase corresponding to the neutral position of the steering operation member.