CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Application No. 2018-159027 filed on Aug. 28, 2018, disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a turning control device.

BACKGROUND

There is a vehicle control device for controlling vehicle steering. For example, the vehicle control device performs such control that when a driver performs a steering operation for tighter turning in an end contact state of a steering wheel, the vehicle control device adjusts distribution of driving forces and braking forces to left and right tire wheels to turn the vehicle with a small turning radius. In the above, the end contact state of the steering wheel is the state where the steering wheel is at a maximum angle.

Discussion on the above background art will be given below, which is not necessarily prior art.

In the above electric power steering device, when the steering wheel becomes the end contact state, steering torque of the steering wheel may increase drastically. Specifically, because the control is performed responsive to the driver's force applied to the steering wheel in a steering-wheel hard-to-move state, a vehicle turning state may be changed even though rotation of the steering wheel is absent. This may disadvantageously provide an uncomfortable feeling to the driver.

SUMMARY

The present disclosure provides a turning control device for use in a vehicle control system that includes a steer-by-wire system and a brake system. The steer-by-wire system is such a system where a steering member and a steered wheel are mechanically separated from each other. The steer-by-wire system includes: a turning device configured to generate torque for turning the steered wheel in accordance with a steering state of the steering member; and a reaction force device configured to apply a reaction force to the steering member. The brake system is capable of controlling braking forces of left and right tire wheels independently from each other.

The turning control device comprises one or more microcomputers configured to act as a braking difference calculation unit that calculates a braking force difference, which is a difference in braking force between the left and right tire wheels. The one or more microcomputers is further configured to perform a high turning control that provides the braking force difference to the left and right tire wheels to cause a smaller turning radius of the vehicle when a steering angle corresponding value is larger than a judgment threshold, wherein the steering angle corresponding value is a steering angle or an absolute value of a value convertible into the steering angle. With the above turning control device, it is possible to make the turning radius of the vehicle smaller than a turning radius realized by the turning device only.

