Method for steering a vehicle and steering system therefore

#The invention concerns a method for steering a vehicle, which is steered via a steering unit by a first steering arrangement, particularly a wheel steering, and a second steering, particularly an articulated steering, and a steering deflection means for detecting the second steering arrangements, with the steering unit operatively connected to both steering arrangements.

#A method and a steering system is shown in U.S. Pat. No. 4,565,257. The vehicle described therein can be steered in two ways: firstly by means of a wheel steering, which turns steered wheels in relation to a chassis. Secondly, the vehicle can also be steered by means of an articulated steering. This steering turns two vehicle parts, which are connected via a converting kit, in relation to each other.

#Another vehicle, which is equipped with wheel and articulated steering, is shown in U.S. Pat. No. 4,802,545. Also DE 35 43 054 A1 shows a vehicle of this kind. With this vehicle, a steering occurs in that firstly the wheel steering is taken to the end stop, before a working cylinder for the articulated steering is activated.

#FIG. 1 is a schematic view of the steering system of this invention.

#A steering system 1 has a steering unit 2, which is connected with a pump 4 via a priority valve 3. Therefore, hydraulic fluid under a pressure is available at a pressure inlet P. When the steering unit 2 is activated via a schematically shown steering hand wheel 5, an amount of this pressurised fluid will be passed on to one of two directional connections L, R, which amount is determined by the deflection of the steering hand wheel 5. The amount is measured by a measuring motor arrangement, which is formed by two measuring motors 6, 7, of which the first measuring motor 6 is permanently active, whereas the second measuring motor 7 can be connected in parallel with the first measuring motor 6 via a hydraulically operated change-over valve 8, to increase the displacement of the steering unit 2.

#The steering unit 2, or rather, its two directional connections L, R, is connected with a valve block 9, which again is connected with a first steering motor arrangement 10 and a second steering motor arrangement 11. In the present case, the first steering motor arrangement 10 acts upon steered wheels, that is, it can turn the wheels (not shown) in relation to the chassis of a vehicle. The second steering motor arrangement 11, however, acts upon a converting kit, that is, it can change the angle position of two vehicle parts, which are connected with each other by means of a connecting kit, in relation to each other. Wheels are arranged on both vehicle parts, so that a change of the angle position of the two vehicle parts enables a steering, that is, a directional change, of the vehicle. The first steering motor arrangement 10 is provided with a sensor 12. The second steering motor arrangement is provided with a second sensor 13. Both sensors are connected with a control device 14, which does accordingly receive current information about the position and the state of the two steering motor arrangements 10, 11. Each steering motor arrangement 10, 11 is shown with two piston-cylinder units. However, it is obvious that both steering motor arrangements 10, 11 can also be equipped with only one piston-cylinder unit.

#In the valve block 9 a selection valve 15 is arranged, by means of which the driver of the vehicle can select the steering motor arrangement 10, 11, that is, the steering mode, with which he wants to steer the vehicle. In the position of the selection valve 15 shown in the Figure, the vehicle is steered by means of a wheel steering, that is, via the first steering motor arrangement 10. When the selection valve 15 is displaced, the vehicle is steered by means of an articulated steering, that is, via the second steering motor arrangement 11. The selection valve is controlled by a pressure in a control line 16, which is connected with a priority valve 17, which again is activated by the control device 14, for example when the driver activates a switch 18. Further to the switch 18, a large number of additional switches and other control devices can be connected with the control device 14 via control inlets, which switches and devices are not described in detail in the present case.