Device for operating a chassis of a two-track vehicle

Abstract

A device for operating a chassis of a two-track vehicle, in which each vehicle wheel is assigned a suspension spring, which carries the static body weight of the vehicle, and a vertical dynamics actuator, which is actuatable by a vertical dynamics control unit, having a tipping detection function which detects a tipping situation with a roll-over risk in which there is a danger that the vehicle will tip sideways on a transversely inclined roadway. When a roll-over risk is detected, the vertical dynamics control unit actuates the vertical dynamics actuators to avoid roll-over.

Claims

1. A device for operating a chassis of a two-track vehicle, in which each vehicle wheel is assigned a suspension spring, which carries the static body weight of the vehicle, and a vertical dynamics actuator, which is actuatable by a vertical dynamics control unit, having a tipping detection function which detects a tipping situation with a roll-over risk in which there is a danger that the vehicle will tip sideways on a transversely inclined roadway, wherein when a roll-over risk is detected, the vertical dynamics control unit actuates the vertical dynamics actuators to lower the vehicle center of gravity and/or to reduce a roll angle on an uphill side until a predetermined body position of the vehicle is reached, wherein if a tipping situation exists, the vertical dynamics control unit automatically actuates the vertical dynamics actuators, and/or the tipping protection function is assigned a display means which triggers a warning message for the user if a critical tipping situation is detected, and/or the device has an input means operable by the user by which the vertical dynamics control device is manually actuatable by the user in order to achieve the predetermined position.

2. The device according to claim 1, wherein the vertical dynamic actuators operate electromechanically or hydraulically.

3. The device according to claim 2, wherein the suspension spring is an air spring, the air chamber of which is integrated together with an air compressor acting as an actuator and with at least one vent valve in a pneumatic circuit, (P) in which the air compressor and the vent valve are actuatable by an air spring control unit.

4. The device according to claim 2, wherein each of the vehicle wheels is assigned a telescopic shock absorber having a damper tube as a damper device, into which a piston rod plunges, and that the hydraulic chambers delimited by the piston rod are integrated together with an oil pump acting as an actuator in a hydraulic circuit (H), in which the oil pump is actuatable as a vertical dynamics actuator by the vertical dynamics control unit.

5. The device according to claim 1, wherein the suspension spring is an air spring, the air chamber of which is integrated together with an air compressor acting as an actuator and with at least one vent valve in a pneumatic circuit, (P) in which the air compressor and the vent valve (are actuatable by an air spring control unit.

6. The device according to claim 5, wherein the air spring can be used as a slow actuator and the vertical dynamics actuator can be used as a fast actuator in comparison.

7. The device according to claim 6, wherein the device has an evaluation unit which has signal connection to the tipping detection function, and/or in the event of a critical tipping situation, the evaluation unit first actuates the vertical dynamics actuators in order to achieve a tipping-stable body position, while the air springs are not actuated by the evaluation unit.

8. The device according to claim 5, wherein the device has an evaluation unit which has signal connection to the tipping detection function, and/or in the event of a critical tipping situation, the evaluation unit first actuates the vertical dynamics actuators in order to achieve a tipping-stable body position, while the air springs are not actuated by the evaluation unit.

9. The device according to claim 5, wherein the vertical dynamics actuators, when actuated by the vertical dynamics control unit, suddenly generate an actuating force (F.sub.Steller), by which the vehicle body can be lowered, counter to a spring force (F.sub.Luftfeder) acting in the opposite direction and generated in the air springs, and the actuating force (F.sub.Steller) generated by the vertical dynamics actuators is only maintained by external energy.

10. The device according to claim 9, wherein until a criterion for the existence of a permanent tipping situation is met, wherein until a predefined holding period (t.sub.o) or other conditions have elapsed, the vertical dynamics actuators hold the vehicle in its tipping-proof body position, and that after the holding period (t.sub.0) has elapsed, the evaluation unit actuates the air spring control unit to start a level control during which the air pressure acting in the respective air spring and thus the spring force generated by the air spring can be dissipated by opening the vent valve, so that the tippping-proof body position is held by the air springs after the holding time (t.sub.0) has elapsed, while the vertical dynamics actuators are relieved.

11. The device according to claim 10, wherein the vent valve is electrically actuatable by the air spring control unit, and the vent valve is closed when de-energized, so that the tipping-proof body position is maintained without external energy.

12. The device according to claim 1, wherein each of the vehicle wheels is assigned a telescopic shock absorber having a damper tube as a damper device, into which a piston rod plunges, and that the hydraulic chambers delimited by the piston rod are integrated together with an oil pump acting as an actuator in a hydraulic circuit (H), in which the oil pump is actuatable as a vertical dynamics actuator by the vertical dynamics control unit.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) An exemplary embodiment of the invention is described below on the basis of the appended figures.

(2) In the figures:

(3) FIG. 1 shows a view describing the structure and the mode of operation of the active chassis according to the invention.

(4) FIG. 2 shows another view describing the structure and the mode of operation of the active chassis according to the invention.

(5) FIG. 3 shows another view describing the structure and the mode of operation of the active chassis according to the invention.

(6) FIG. 4 shows another view describing the structure and the mode of operation of the active chassis according to the invention.

DETAILED DESCRIPTION

(7) In FIG. 1, an equivalent circuit diagram of an active chassis of a two-track vehicle is indicated to the extent that it is necessary for understanding the invention. Accordingly, each of the vehicle wheels HL, HR, VL, VR is assigned a vibration/damping device, each of which is formed from a suspension spring 3, a telescopic shock absorber 5, and a vertical dynamics actuator 7. In the present exemplary embodiment, the suspension spring 3 is an air spring having an air bellows, as shown in the equivalent circuit diagram in FIG. 2. Accordingly, the air spring 3 delimits an air chamber 9, which is integrated together with an air compressor 11 and a vent valve 13 in a pneumatic circuit P, which is only indicated in FIG. 2. In the pneumatic circuit P, the air compressor 11 and the vent valve 13 are actuated by an air spring control unit 15 to perform a level control or height adjustment of the vehicle body 17. Both the vent valve 13 and the air compressor 11 are electrically actuated by the air spring control unit 13. The vent valve 13 is closed when de-energized.

(8) As can also be seen from FIG. 2, the telescopic shock absorber 5 has a damper tube 19 into which a piston rod 21 plunges. The piston rod 21 delimits two hydraulic chambers in the damper tube 19. These, together with an oil pump 7, are part of a hydraulic circuit H. In the hydraulic circuit H, the oil pump 7 acts as a vertical dynamics actuator, which is actuatable by a vertical dynamics control unit 21.

(9) According to FIGS. 1 and 2, both the vertical dynamics control unit 21 and the air spring control unit 13 have a signal connection to an evaluation unit 23. The evaluation unit 23 is assigned a tipping detection function 25. With the aid of the tipping detection function 25, a roll-over risk is monitored during off-road driving, as indicated in FIG. 3. Accordingly, the vehicle is on a transversely inclined roadway 27, on which the vehicle wheels on the downhill side are retracted, while the vehicle wheels on the uphill side are extended. In a critical body position A1 indicated in FIG. 3, the normal force F.sub.N passing through the vehicle center of gravity SP is close to a contact point K of the vehicle wheel on the downhill side with the roadway 27. In this case, the tipping detection function 25 detects a high roll-over risk, which poses the danger that the vehicle will tip sideways on the transversely inclined roadway 27. If such a roll-over risk exists, the evaluation unit 23 first actuates the vertical dynamics control unit 21 so that the vertical dynamics actuators 7 immediately, i.e. in real time, bring the vehicle into a tipping-proof body position A2 by generating active actuating forces F.sub.Steller. This is achieved by lowering the vehicle center of gravity SP with the aid of wheel-attracting active actuating forces F.sub.Steller and by reducing the roll angle by stronger deflection on the uphill side. The air spring control unit 13, however, is not yet actuated by the evaluation unit 23. In the tipping-proof body position A2 (indicated by dashed lines in FIG. 3), the center of gravity SP and the normal force F.sub.N passing through the center of gravity SP are spaced apart from the contact point K in the direction of the uphill side.

(10) When setting the tipping-proof body position A2, the vertical dynamics adjuster 7 works against the spring forces F.sub.Luftfeder generated by the air springs 3. The vertical dynamic actuators 7 can only keep the vehicle in its tipping-proof body position with an external energy supply, during which the oil pump 7 has to be permanently supplied with electrical energy.

(11) According to the invention, the following control strategy is generally used to permanently maintain the tipping-proof body position A2: First, the evaluation unit 23 actuates the vertical dynamics control unit 21 alone. As soon as a criterion for the existence of a permanent tipping situation is met, a transfer phase t.sub.U follows, in which the evaluation unit 23 actuates both the air spring control unit 15 and the vertical dynamics control unit 21. During the transfer phase t.sub.U, the actuating forces F.sub.Steller generated by the vertical dynamic actuators 7 are continuously reduced to zero; synchronously thereto, the air spring control unit 13 starts a level control in which the vent valve 13 is opened, by which the air pressure acting in the respective air spring 3 and thus the spring force F.sub.Luftfeder generated by the air spring 3 are dissipated to a value at which the air springs 3 maintain the tipping-proof body position A2, while at the same time the vertical dynamics actuators 7 are completely relieved of load, i.e. are switched to non-functional at the end of the transfer phase t.sub.U.

(12) In the present exemplary embodiment, the criterion for the existence of a permanent tipping situation is specifically a time criterion, i.e. the holding period t.sub.0. This results in the following control strategy, which is illustrated by the diagrams in FIG. 4: The evaluation unit 23 actuates the vertical dynamics control unit 21 alone until the predefined holding period t.sub.0 elapses. This means that until the holding period to elapses, the negatively oriented actuating forces F.sub.Steller are introduced into the telescopic shock absorbers 5. Until the holding period to elapses, only the vertical dynamics actuators 7 (i.e. the oil pumps) therefore hold the vehicle in its tipping-proof body position A2.

(13) After the holding time to has elapsed, the transfer phase t.sub.U described above follows, in which the evaluation unit 23 actuates both the air spring control unit 15 and the vertical dynamics control unit 21.

(14) It should be emphasized that the criterion for the existence of a permanent tipping situation can also comprise other conditions alternatively and/or additionally to the time criterion, such as applying the parking brake, the parking mode, the status of the operational readiness of the vehicle (such as ignition off), and operation of the central locking system.

(15) As can also be seen from FIGS. 1 and 2, the anti-tipping function 25 has a display means 29 which triggers a warning message for the vehicle user if a critical tipping situation A1 is detected. In addition, the evaluation unit 23 is assigned an input means 31 which is operable by the vehicle user. By operating the input means 31, the vehicle user can manually actuate the vertical dynamics control unit 21 so that the vertical dynamics actuators 7 set a tipping-proof body position A2.

LIST OF REFERENCE SIGNS

(16) 3 suspension spring or air spring 5 telescopic shock absorber 7 vertical dynamics actuator 9 air chamber 11 air compressor 13 vent valve 15 air spring control unit 17 vehicle body 19 damper tube 20 piston rod 21 vertical dynamics control unit 23 evaluation unit 25 tipping detection function 27 roadway 29 display means 31 input means A1 tipping-critical body position A2 tipping-proof body position SP, SP center of gravity K contact point F.sub.N, F.sub.N normal force F.sub.Luftfeder spring force of the air spring F.sub.Steller actuating force of the vertical dynamics actuator HL, HR, VL, VR vehicle wheels t.sub.U transition phase H hydraulic circuit P pneumatic circuit