Steering system for non track-bound motor vehicles

The invention relates to a steering system for non-track-bound Motor vehicles with a driver-operated steering handle, eg steering wheel, a steering actuator for steering adjustment steerable vehicle wheels, a steering handle operable with the Steering angle setpoint generator, a dirigible with the vehicle wheels actuated steering angle actual value, a the Steering actuator in dependence on a comparison of the Setpoints and actual values ​​of the steering angle controlling and and interacting with it Sensors constantly malfunction checked control arrangement and a between the steering handle and the steerable vehicle wheels arranged mechanical or hydraulic forced coupling which when correctly operating control arrangement is opened and remains open (Ineffective normal state) and in case of faulty control arrangement is automatically closed (effective special state), wherein the effective geschalteke forced coupling having a predetermined elasticity and effectively forced coupling between the steering handle and steered vehicle wheels transferable forces and moments a relative adjustment between should and is cause value encoder.

Such steering systems, according to the concept "steer by wire" work, are generally known (for example from the DE19540956C) and for future Motor vehicles developed. These systems provide the basic Advantage that it at least in terms of the control arrangement and the associated sensor without constructive Amendments for different vehicles are suitable. With suitable programming, on the one hand practically each gear ratio between the actuating stroke of the steering handle and the change in steering angle of the steered vehicle wheels, be realized. In addition, there is the possibility to connect the control arrangement with additional sensors, to be predetermined parameters, eg side wind influences, automatically to take account or auszuregeln.

To ensure the requisite level of protection system errors can, is provided upon the occurrence of a Error in the control arrangement and the failure of signals, to be evaluated by the control arrangement automatically an operation for abnormal operation or emergency operation turn. In this operating mode is a Forced coupling between the steering handle and steered vehicle wheels provided so that the steering system principle by Type of conventional steering works, although the usual conventional steering mechanical steering column possibly by other mechanical system or by hydraulic systems, especially hydrostatic systems, may be replaced.

The object of the invention is thus, in a steering system of the type described above with regard to safety the system show advantageous measures.

This object is achieved by that the steering system in the special state (effective connected Forced coupling) with sufficient residual function of regulating arrangement and sensor as power steering, by the Control arrangement the steering actuator analogous to amount and Direction of from the signals of the steering angle setpoint generator and steering angle actual value detectable relative adjustment to Generating a servo motor with a the transmitted forces or moments controls diminishing direction.

The invention is based on the general idea, with activated Forced coupling the applied by the driver to reduce manual force on the steering handle as far as possible and to the steering system similar to a conventional power steering to operate. In this context, the control arrangement the steering actuator to generate a the Hand forces diminishing servo motor control. Here uses Invention consisting fact that the activated in an emergency Forced coupling between the steering handle and steered Fahrzeuggrädern due to elastic compliances of the coupling elements or media an appropriate elastic may have resilience, with the result that between the steering handle end or input and the steered Vehicle wheels associated end or exit the Forced coupling between the transmission of forces and moments more or less large relative movements occur, to appropriate Relative adjustments between the steering angle setpoint generator and steering angle value encoder lead. In the invention, are now in the special condition of the steering system, the aforementioned Setpoint and actual value to measure these relative adjustments and thus for detecting the transmitted forces and Moments used.

So while nominal and actual value in the normal state of Steering system for determining the target actual value deviation of the Steering angle are used, they are in the special condition for determining between the steering handle and steered vehicle wheels transmitted forces and moments exploited. Based on these Dual function of desired and actual value can be used without additional Sensors in the special operation of the convenience of a conventional Power Steering are made possible.

It is only necessary to design the control arrangement so, that it immediately when switching the forced coupling present relative positions of set and actual value detected. Since immediately at the time of turning on the Forced coupling no forces or moments between steered Vehicle wheels and steering handle is transmitted, is the aforementioned relative position characteristic of an unstrained Forced coupling.

A particular advantage of the invention is that the technical training of the forced coupling can be arbitrary. Because of the feasibility of the invention it is of minor Meaning, if a forced coupling on mechanical Elements or hydraulically done. In the former case, the exploited elastic deformability of the mechanical elements. In the second case, the elastic resilience the walls of the hydraulic lines and the compressibility of the hydraulic medium used.

Incidentally, with regard to preferred features of the invention to the claims and the following explanation of referenced drawings, with reference to the particularly preferred embodiments to be discribed.

It shows<dl tsize="6" compact="compact"><dt>Fig. 1</dt><dd>a circuit diagram-like representation of a first embodiment,</dd><dt>FIG. 2</dt><dd>a corresponding view of a second embodiment and</dd><dt>Fig. 3</dt><dd>a corresponding view of another embodiment the invention.</dd></dl>

In the example shown in Fig. 1 has a not specifically illustrated motor vehicle steerable front wheels 1, steering adjustable via tie rods 2 and a rod 3 together are coupled.

The rod 3 forms the piston rod of two parallel arranged piston-cylinder units 4 and 5, are each designed as double-acting units.

The piston-cylinder unit 4 is connected via two hydraulic lines 6 and 7 with the two piston working spaces of a double-acting Piston-cylinder unit 8 coupled whose piston are mechanically positively coupled to a steering wheel. 9 The piston of the unit 8 to move to the right or left when the steering wheel clockwise or counter -clockwise direction. For displacement of the pistons the piston-cylinder unit 8, the steering wheel accordingly turned.

Moreover, the manual steering wheel 9 is provided with a self-locking free Electric motor 10 drivingly connected, which at a fixed Motor shaft to operate as a pure power generator can and whose purpose will be explained further below.

Between the hydraulic pipes 6 and 7 is a normally closed Shut-off valve 11 is arranged, which by itself Energization to its operating magnet against the force of a restoring spring from the illustrated closed position to its open position can switch and shutdown of the Solenoid electric current acting automatically brought by the return spring in the illustrated closed position or is held in this position.

The piston-cylinder unit 5 is connected via hydraulic lines 12 and 13 connected to two terminals of a control valve 14, which has two additional ports with a relatively pressureless hydraulic reservoir 15 and a hydraulic Pressure source, in the example shown a hydraulic Pressure reservoir 16 and pumps 17 and 18, respectively. Of the Pressure accumulator 16, by means of the pump 17 or another Pump be recharged 18th Both pumps 17 and 18 are through check valves 19 to check the pressure to secured its suction side and suction side of the reservoir 15 connected. The pump 17 is of an electric motor 20 driven. The pump 18 is via a clutch 21 with the motor 22 of the motor vehicle connectable.

Between the hydraulic lines 12 and 13 is a normally open Shut-off valve 23 is arranged, which by electrical Energization to its operating magnet against the force of a restoring spring from the position shown in his Offfenlage are brought closed position or held in this closed position can.

An electronic regulating and control system 24 has an input side a timer 25 for the actual value of the steering angle of the front wheels 1 are connected. This encoder 25, for example, cooperate with the rod 3 in steering adjustment the wheels 1 to a steering angle analog control stroke performs.

In addition, the input side of the regulating and control system 24 with a steering wheel operated by the 9 encoder 26 for the Target value of the steering angle, respectively.

In addition, the input side of the regulating and control system connected to a torque sensor 27, which the transmitted between the steering wheel 9 and electric motor 10 Forces or moments captured.

Finally, to the input side of the regulating and control system 24, a plurality of pressure sensors 28, 29 and 30 connected, which signals the hydraulic pressures in the Hydraulic lines 6 and 7 or 12 and 13 or the pressure at reflect pressure inlet of the control valve 14th

On the output side, the regulating and control system 24 with the Actuating magnet of the shutoff valves 11 and 23 and the control valve 14. Moreover, the outcome of the Regulating and control system, the electric motors 10 and 20, and the clutch 21 is controlled.

. The steering system of Figure 1 functions as follows:

In normal operation, the switching valves 11 and 23 of the regulating and control system 24 by energization of the aforementioned valves 11 and 23 associated parking refrigerator brought the documents and not shown in these documents kept. Accordingly, the piston-cylinder unit 4 the piston-cylinder unit 8 and the manual steering wheel 9 hydraulically decoupled.

On the other hand, the pressure difference between the two piston working spaces the piston-cylinder unit 5 by operating of the control valve 14 is controlled, in the following Manner indicated:

The regulating and control system 24 detected by the encoder 25 the actual value of the steering angle of the front wheels 1. Above the Steering wheel operated timer 26 receives the regulating and control system 24 shows the target value of the steering angle. According to a performed by regulating and control system 24 target actual value comparison then the operating magnets of the control valve 14 controlled. If no target actual value deviation is present, remains, the control valve 14 in the illustrated central position, in which the piston-cylinder unit 5 hydraulic freewheel is switched and connected to the reservoir 15, while the pressure accumulator 16, which from a function signal the pressure sensor 30 via the pump 17 or 18, as necessary, is continuously recharged, opposite the piston-cylinder assembly 5 is blocked. If a target-actual value deviation occurs, the control valve 14 from the position shown is Central position depending on the direction sense of the target actual value deviation shifted to the right or left, so that in each case a piston working chamber of the piston-cylinder unit 5 with the pressure connection of the control valve 14 and the other piston working space the unit 5 with the reservoir 15 controllable connected and the piston-cylinder unit 5 a controllable Pressure differential is effective, with the result that the piston-cylinder assembly 5 is a force in one of the predetermined direction of the target actual value deviation of the steering angle produced direction. In this way, a target-actual value deviation the steering angle corrected shortly, and the front wheels 1 follow the steering movement of the steering handwheel . 9

From the signals of the pressure sensors 29 and / or from the electrical Voltages and currents to the actuator magnet Control valve 14, the controller and control arrangement 24 the the piston-cylinder unit 5 effective pressure difference directly or indirectly determine their degree with the between the steering wheels 1 and the piston-cylinder unit 5 transferred is correlated forces or torques. In correlation with this Forces is from the regulating and control system 24 a determined setpoint for the manual steering wheel 9 tactile hand force and by corresponding control of the electric motor 10 set, the torque sensor 27 between the Electric motor 10 and the steering wheel 9 effective forces or moments and thus the value of the manual force is detected. As a result, is therefore the motor 10 in dependence on a desired-actual value comparison regulated for the manual forces. In this way the driver is at the steering wheel 9 haptic feedback between the vehicle steering wheel 1 and the piston-cylinder assembly 5 effective forces.

The regulating and control system 24 monitors to constantly correct function. In addition, the signals are coupled connected to the input side of the regulating and control system 24 Encoders and sensors 25 and 30 continuously for plausibility checked. If a system error is detected, switched the solenoid shut-off valve 11 of the normally that the shut-off valve 11 shown with the result in shown in Fig. 1 Closed position switches and the piston-cylinder units 4 and 8, and thus the steerable front wheels 1 and the manual steering wheel 9 positively coupled to each other hydraulically are.

Unless a sufficient residual function of regulating and control system 24 and, of cooperating sensors is steering system of the invention works with activated Forced coupling manner of a conventional power steering. This means that the regulating and control system 24 the control valve 14 as a function of the steering wheel between 9 and steered vehicle wheels 1 transmitted forces and moments controls, such that the piston-cylinder assembly 5 a to be applied at the steering wheel 9 Hand force produces diminishing self-energizing.

To capture the between manual steering wheel 9 and the steered vehicle wheels 1 transmitted forces and moments in the example of FIG. 1, the elasticity of the hydraulic coupling between the piston-cylinder units 4 and 8 exploited. by virtue of the compressibility of the hydraulic medium and the elastic flexibility of the walls of the hydraulic lines 6 and 7 and the cylinder of the piston-cylinder units 4 and 8 occurs between the manual steering wheel 9 and the steered Vehicle wheels 1 is a more or less large elastic Resilience on, with the result that between the manual steering wheel 9 and steered vehicle wheels 1 relative movements occur can, by the gear ratio of the drive connection between the manual steering wheel 9 and the steered vehicle wheels 1 differs.

These relative movements can be made of the signals of the target and be determined actual value sensor 25 and 26, when the regulating and Control assembly 24, the relative positions of the two sensors 25 and 26 when switching on the hydraulic forced coupling between Manual steering wheel 9 and the steered vehicle wheels 1 "knows"; at the time of turning on the Zangskopplung is a practically force-free state before the forced coupling. by virtue of the structurally predetermined ratio between rotational movements of the steering handwheel 9 and steering movements of the wheels 1 can then the regulating and control system for each detected from the signals of the sensor 26 of the rotational position Manual steering wheel 9, an expected position of the steered steering Vehicle wheels 1 and a correspondingly to be expected Signal of the sensor 25 determined. Then, when the actual signal of the sensor 25 in the one or other direction of the expected signal differs, this is tantamount so that between the manual steering wheel 9 and the steered vehicle wheels 1 a corresponding force or a special moment is transmitted in the one or other direction. Thus then the regulating and control system 24 by appropriate Adjustment of the control valve 14, the piston-cylinder assembly 5 hydraulic drive such that this Unit 5 a the driver's respective steering maneuver supportive generates servo motor.

The embodiment shown in Fig. 2 differs of the arrangement of FIG. 1 essentially in that the piston-cylinder unit 6 by a hydrostatic, reversible Pump is replaced 31, the hydraulic medium be exchanged between the hydraulic lines 6 and 7 can. This pump 31 is on the one hand to the electric motor 10 and on the other hand forced drivingly coupled to the steering wheel. 9

In addition, a further reversible and preferably also hydrostatic pump 32, the hydraulic lines 12 and 13 connect. To drive this pump is an electric motor 33, which is operated by the regulating and control system 24 becomes.

The operation of the embodiment of FIG. 2 corresponds with the operation of the embodiment of Fig. 1 as far as possible agreement.

When the changeover valve 11 is in its closed position, are the hydrostatic pump 31 and the piston-cylinder assembly 4 and hence the steerable vehicle wheels 1 and the steering handwheel 9 together positively coupled.

This forced coupling is carried out when the regulating and establish control arrangement 24 a malfunction in the steering system should. As far as in such a case, a malfunction on parts of the hydraulic system of the piston-cylinder assembly 5 is present or appears as possible, is automatically the power supply of the magnet of the reversing valve 23 is deenergized, so that the changeover valve 23 to the in Fig. 2 open position illustrated switches and the piston-cylinder assembly 5 connected in all circumstances hydraulic freewheel is.

In normal operation, ie when the regulating and control system 24 no malfunction detects the change-over valves 11 and 23 of the regulating and control system 23 each in their not shown in Fig. 2 positions held. Of the Electric motor 33 is then of the regulating and control system in dependence on a desired-actual value comparison of the steering angle, ie, depending on the difference between the Signals of the encoders 25 and 26, in one direction or the other operated with more or less force, so that the piston-cylinder unit 5 a corresponding force transmits on the steered wheels of the first

Also in the embodiment of FIG. 2, the control and Control arrangement 24 in turn from the signals of sensors 25 and 26 with activated forced coupling of the steering wheel 9 and steered vehicle wheels between the manual steering wheel 9 and steered vehicle wheels 1 transmitted forces and moments and determine, depending on the electric motor 33 in such a way driving, that he above-mentioned one to the forces and Moments generates analog force which then hydraulically via the driven by the electric motor 33 and the pump 32 Hydraulic lines 12 and 13 on the piston-cylinder assembly 5 transferred and thus is effective as a steering assistance force.

The embodiment shown in Fig. 3 differs of the previously described embodiments initially in that between the emergency, a mechanical drive-through provided manual steering wheel 9 and the steered vehicle wheels 1 is.

In the example shown to the rod 3 of a rack arranged which meshes with a pinion 40 which in turn acted upon by a spring in the closing direction Clutch 41 and a subsequent wave 42 with the Manual steering wheel 9 is mechanically connected. The clutch 41 can by an actuator 43 against the force of its closing spring be opened to the mechanical drive-through between steered vehicle wheels and steering wheel 9 unravel. The Shaft 42 is also provided with the self-locking-free electric motor 10 drivingly (-self-locking) connected. Between the manual steering wheel 9 and the shaft 42 and the electric motor 10 and the shaft 42 are torque sensors 44 and 45 are arranged.

The pinion 40 is connected to the angle sensor designed as a donor 25 connected for determining the steering angle actual value. The Shaft 42 is at the steering wheel 9 with the also as an angle sensor trained encoder 26 connected, the during normal operation serves as a steering angle setpoint generator.

Moreover, the rod 3 again forms the piston rod of Piston-cylinder unit 5, which in turn according to the arrangement according to Fig. 1 or 2 can be operated.

In normal operation, the servomotor 43 of the clutch 41 is of the regulating and control system 24 continuously energized, so that He holds open the clutch 41 against the force of its closing spring. Moreover actuates the regulating and control system 24 the piston-cylinder unit 5 or this aggregate 5 controlling elements such that the aggregate of 5 generated actuating forces any difference between the supplied from the encoder 26 steering angle command value and the Encoder 25 supplied steering angle actual value is corrected. Reference is made to the description for FIGS. 1 and 2.

In case of any system malfunctions, the servomotor 43 is of off of the regulating and control system 24, so that the Clutch 41 closes and manual steering wheel 9 and steered vehicle wheels are 1 forcibly coupled together.

In the example of FIG. 3 occurs between the manual steering wheel 9 and steered vehicle wheels 1 with switched positive coupling a more or less elastic resilience to, particularly on the torsional elasticity of the shaft parts based between the pinion 40 and the steering wheel. 9 Thus, the Control and regulating arrangement 24 in turn from the signals of Sensors 25 and 26 between the manual steering wheel 9 and the steered Vehicle wheels 1 transmitted forces and moments determine and depending on the force of the steering actuator, in the case of Fig. 3, a piston-cylinder unit 5, control.

Notwithstanding the embodiments illustrated in the drawings can the torque sensors 27 and 44 also lenkhandradseitig the unit 8 and the pump 31 and the drive connection arranged between the motor 10 and shaft 42 be.

If when turning the Nofallbetriebes, ie the effective date the forced coupling between the steering wheel and steered 9 Vehicle wheels 1 of the electric motor 10 or a torque generate, its effect on the signal difference can between the signals of the angle sensors 25 and 26 computer ischl be compensated for, as a result, only the by manual forces caused signal difference between the sensors 25 and 26 for controlling the unit 5 and / or used with the electric motor 10 generated servo motor becomes. For these mathematical compensation can eg stored Empirical values ​​for the function of the aforementioned Signal difference between the manual steering wheel 9 and the steered Vehicle wheels 1 considered effective forces and moments will.