Method and steering system for steering a vehicle

1. A method for steering a vehicle that comprises a steering system with a steering wheel and a front axle as well as a rear axle with wheels, the method comprising:

adjusting a direction of the vehicle is manually by a driver of the vehicle by adjustment of a steering wheel angle of the steering wheel, as a result of which, for the wheels of at least one of the axles, a steering angle is adjusted, which is obtained from the steering wheel angle plus a superposition angle;

setting a ratio of the steering wheel angle to the steering angle for the wheels through an automatically adjustable steering ratio for wheels of at least one of the axles, wherein the vehicle travels at a speed with a first value into a curve on a circular path with a radius;

adjusting a superposition angle that is a function of the first value of the speed automatically by a steering system, taking into consideration a characteristic curve for a relation between the superposition angle and the speed; and

changing the steering ratio automatically by the steering system as a function of the speed, while the radius of the circular path is kept constant.

2. The method according to claim 1 , further comprising:

adjusting the superposition angle automatically while the steering wheel angle is held constant.

3. The method according to claim 1 , further comprising:

altering the steering ratio when the steering wheel angle is altered by the driver, while the radius of the circular path remains constant.

4. The method according to claim 1 , further comprising:

altering the superposition angle for the wheels of the at least one axle in accordance with a change in the steering ratio.

5. The method according to claim 1 , further comprising:

reducing the speed from the first value to a second value.

6. The method according to claim 1 , further comprising:

changing at least one of a steering ratio for the wheels of the front axle and a steering ratio for the wheels of the rear axle depending on a change in the steering wheel angle.

7. The method according to claim 1 , further comprising:

changing the steering ratio in proportion to a change in the speed.

8. A steering system for steering a vehicle comprising:

a steering wheel;

a front axle; and

a rear axle with wheels, wherein a direction of the vehicle can be adjusted manually by a driver of the vehicle by adjusting a steering wheel angle of the steering wheel, the steering system is configured to

adjust a steering angle for the wheels of at least one of the axles depending on the adjusted steering wheel angle, said steering angle being obtained from the steering wheel angle plus a superposition angle,

adjust a steering ratio automatically for the wheels of at least one of the axles to set a ratio of the steering wheel angle to the steering angle for the wheels, wherein, when the vehicle travels into a curve on a circular path with a radius at a speed with a first value and a steering wheel angle is adjusted by the driver, taking into consideration a characteristic curve for a relation between the superposition angle and the speed,

adjust a superposition angle that is a function of the first value of the speed automatically, and

change the steering ratio as a function of the speed automatically, while keeping the radius of the circular path constant.

9. A steering system according to claim 8 , further comprising:

at least one actuator, which is associated with at least one axle and is configured to automatically adjust the steering angle for the wheels of the at least one axle, taking into consideration the manually adjustable steering wheel angle and the automatically adjustable steering ratio.