DE10015922A1 - Automobile steer-by-wire steering system has mechanical steering mechanism brought into operation upon failure of steer-by-wire system - Google Patents

Abstract

The steering system has an electronic regulator (23) for regulation of a steering setting drive (5) for the steered wheels (1) in dependence on the position of a manual steering wheel (11), together with a resistance force device (12) coupled to the steering wheel, for simulating mechanical steering. The correct function of the steer-by-wire system is monitored for switching to mechanical steering by closing a normally open coupling (6) between the steering wheel and a mechanical steering mechanism (3,4,10). A sleeve is positioned coaxial to the coupling and displaced helically for transmission of the closure force by a spring bias, with an electric motor holding the sleeve in the open coupling position during normal function of the steer-by-wire system.

Description

The invention relates to a steering system for a track-bound motor vehicle, the steered vehicle wheels in normal operation with a steering handle, especially one Steering handwheel, on a constantly correct function Checking electronic control system effective are connected, which one with the steered vehicle wheels controls the steering actuator connected to their steering adjustment and with a steering angle operated by the steering handle Setpoint generator and one with the steered vehicle wheels actuated steering angle actual value sensor is connected, the Control arrangement preferably also one with the steering handle connected to the simulation of a steering resistance Manual power controller regulates and with a transferred power between steering actuator and steered vehicle wheels manual force setpoint sensor and a transmitted one Detect the forces between the manual power actuator and the steering handle Hand force actual value sensor is connected. During abnormal operation or emergency operation, the steered vehicle wheels become Mechanical steering adjustment with the steering handle positively coupled by a clutch open during normal operation in a between the steering handle and steered vehicle wheels arranged mechanical steering gear assembly closes.

Steering systems of this type, which are based on the "steer by wire" concept work, are from DE 195 46 733 C1 and the DE 690 22 848 T2 basically known. This for future ones Systems provided for motor vehicles offer the basic ones Advantage that at least with regard to the control arrangement as well as the associated sensors without any design changes  are suitable for different vehicles. By Appropriate programming can be practical in normal operation any gear ratio between the stroke of the Steering handle and the steering angle change of the steered Vehicle wheels are realized. In addition, there is Possibility of adding additional sensors to the control arrangement connect in order to specify parameters, e.g. B. Cross wind influences, to be taken into account automatically or to settle.

The necessary security in the event of system errors To be able to guarantee, it is provided that when it occurs an error in the control arrangement or in the event of failure of Signals that are evaluated by the control system automatically have an abnormal operation mode or emergency operation is switched on. At this Operating mode is specified in the case of the input Steering system a mechanical positive coupling between Steering handle and steered vehicle wheels effective, so that Steering system basically like a conventional one mechanical steering works, although the conventional steering conventional mechanical steering column may be replaced by other mechanical systems can.

That which becomes effective during abnormal operation or emergency operation mechanical system has a clutch, which at Normal operation is kept open and thus the mechanical System ineffective during normal operation.

In normal operation, the appropriate sensors should be used continuously be monitored whether the clutch is open. This can to be avoided by incorrectly closing the Clutch critical operating states are able to occur: At A steering of the type specified is between the Stroke of the steering handle and the change in steering angle  steered vehicle wheels during abnormal operation or Emergency operation and accordingly closed clutch a different transmission ratio is given than with Normal operation with the clutch open. Should be with this Normal operation of the clutch completely or partially unnoticed could close, movements of the steered vehicle wheels to an undesirable effect on the steering handle and thus lead to the steering angle setpoint device. Then this would have as a result that the electronic control arrangement one of the Setpoint change corresponding adjustment of the steered Tried to make vehicle wheels, which then again Adjustment of the steering angle setpoint generator would be caused. This could "build up" considerable misregistration, if the clutch closes unnoticed during normal operation should stay.

The object of the invention is now a particularly advantageous Possibility to operate and keep the clutch open to accomplish.

This object is achieved in that coaxially a sleeve part to the input or output shaft of the clutch is arranged, which for transmitting the closing force the clutch in a clutch or gearbox screw-mounted, arranged without self-locking, and that the sleeve part rotatably with a coaxial to the sleeve part Rotor of an electric motor is connected, which at Current turns the rotor in a direction in which the Sleeve part is advanced axially against the closing force.

The invention is based on the general idea that a Closing force as part of the coupling Form rotor carrier of an electric motor, which the aforementioned part when energized with screw adjustment against the closing force is adjusted and thus the coupling is secure opens or keeps open.  

According to a particularly preferred embodiment of the Invention can screw mobility by means of storage Ball circulations must be extremely low-friction.

Otherwise, the preferred features of the Invention on the claims and the following explanation referred to the drawing, based on a particularly preferred Embodiment is described.

It shows

Fig. 1 is a circuit diagram representation of the entire steering system and

Fig. 2 is a sectional view of a steering gear with a clutch for interrupting a through drive between steered vehicle wheels and steering handle.

In the example in FIG. 1, a motor vehicle (not shown in more detail) has steerable front wheels 1 which are coupled to one another in an adjustable manner by means of tie rods 2 and a rod 3 . The rod 3 has a part 3 ′ designed as a toothed rack, which meshes with a pinion 4 , and a part 3 ″ designed as a piston rod of a double-acting hydraulic piston-cylinder unit 5 .

The pinion 4 is connected to one side of a non-positive and / or positive clutch 6 , which is constantly loaded in the closing direction by a spring unit 7 and opened in the manner shown below by means of an actuating unit 8 and can be held in the open position by a lock 9 . The other side of the coupling 6 is connected to a steering handwheel 11 via a preferably articulated shaft 10 .

Arranged parallel to the steering handwheel 11 is a self-locking electric motor 12 which is mechanically positively coupled to the shaft 10 and which can work as a pure force generator when the motor shaft is held and the purpose of which is explained below.

A torsion bar 13 is arranged between the drive connection between the electric motor 12 and the shaft 10 on the one hand and the steering handwheel 11 on the other hand, so that the steering handwheel 11 is connected to the shaft 10 with a certain torsional elasticity. Angle sensors 14 and 15 are arranged on both sides of the torsion bar 13 , the purpose of which is explained below.

Another angle sensor 16 is provided on the pinion 4 .

The two sides of the piston-cylinder unit 5 can be connected to one another via a normally open shut-off valve 17 in such a way that the piston-cylinder unit 5 is switched to freewheel under all circumstances. By energizing its steep magnet, the shut-off valve 17 is brought into its closed position.

Otherwise, the piston-cylinder unit 5 is connected to two connections of a control valve 18 , which is connected via two further connections to a reservoir 19 or to the pressure side of a hydraulic pump 20 . In the position normally assumed by the control valve 18 , the piston-cylinder unit 5 is switched to freewheeling. By energizing one of its solenoids, the control valve 18 can be controlled in such a way that when the pump 20 is working, a more or less large pressure difference occurs between the two sides of the piston-cylinder unit 5 and the piston-cylinder unit 5 has a corresponding actuating force in one or other direction. The pressure difference and thus the actuating force can be detected with pressure sensors 21 and 22 on the two sides of the unit 5 .

An electronic regulating or control arrangement 23 is connected on the input side to the angle sensors 14 to 16 and the pressure sensors 21 and 22 . On the output side, the regulating or control arrangement 23 controls the actuating unit 8 , the locking device 9 , the electric motor 12 , the actuating magnets of the valves 17 and 18 and, if appropriate, the hydraulic pump 20 .

. The steering system of Figure 1 functions as follows, first of all the normal operation is shown:

In normal operation, the shut-off valve 17 is closed and the clutch 6 is held in the open position. The steering actuation of the front wheels 1 takes place in that the steering sensor 11 actuates the angle sensor 14 , which forwards a signal representing the steering angle setpoint to the control arrangement 23 . The control arrangement 23 receives from the angle sensor 16 a signal representing the actual steering angle value. The control arrangement 23 carries out a target / actual value comparison and controls the control valve 18 as a function thereof. Because the shut-off valve 17 is closed, the actuation of the control valve 18 generates a more or less large actuating force with a controllable direction by the piston-cylinder unit 5 such that the setpoint-actual value deviation is corrected and the actual value of the steering angle on the front wheels 1 corresponds to the steering angle setpoint specified by the steering handwheel 11 via the rotation angle sensor 14 .

The signals from the pressure sensors 21 and 22 assigned to the two sides of the piston-cylinder unit 5 indicate the pressure difference between the two sides, in terms of amount and direction. This pressure difference is analogous to the steering and interference forces acting on the front wheels 1 . In correlation to this steering and interference forces, the control arrangement 23 now specifies a target value for the manual force felt on the steering handwheel 11 , which is simulated by the electric motor 12 : the actual value of the manual force is determined by the control arrangement 23 from the signals of the angle sensors 14 and 15 determined. Because, depending on the degree of manual force, the torsion bar 13 is twisted more or less, with the result that the signals from the angle sensors 14 and 15 indicate a corresponding angle difference in one direction or the other. Thus, the control arrangement 23 can control the electric motor 12 as a function of a setpoint / actual value comparison so that the hand force that can be felt on the steering handwheel 11 is varied as a result in accordance with the steering and interference forces effective on the steered front wheels 1 .

The control arrangement 23 constantly checks itself and the system parts interacting with it for correct function, the plausibility of the signals from the various sensors also being monitored.

If the safety of the steering system can no longer be guaranteed with certainty in the normal operation described above, the actuating magnets of the valves 17 and 18 are de-energized so that the piston-cylinder unit 5 is hydraulically switched to freewheeling under all circumstances. At the same time, the lock 9 for the open position of the clutch 6 is also deactivated (this is shown in more detail below). The clutch 6 is thus closed by the spring unit 7 . Thus, the steering handwheel 11 and the steerable front wheels 1 are mechanically positively coupled to one another for the steering adjustment. The vehicle can now be mechanically steered in a conventional manner.

If sufficient residual functions of the control arrangement 23 are still available at the end of normal operation, the electric motor 12 can be used as a servo motor. For this purpose, those supplied by the angle sensors 14 and 15 . Signals evaluated, which reflect the manual force exerted on the steering handwheel 11 . Depending on this manual force, the electric motor 12 is now controlled by the control arrangement 23 in such a way that a more or less strong reduction in the manual forces exerted during the respective steering maneuvers is achieved.

In principle, it is also possible to operate the piston-cylinder unit 5 as a servo motor when the clutch 6 is closed and the mechanical forced coupling of the steering handwheel 11 and the steered front wheels 1 is effected. For this purpose, the solenoid of the shut-off valve 17 must be energized while this valve is closed, and the control valve 18 , depending on the signals of the angle sensors 14 and 15 which reproduce the manual forces, must be actuated by means of the control 23 in such a way that the piston-cylinder unit 5 is one each on the steering wheel 11 tactile hand power reducing power.

Fig. 2 shows an advantageous embodiment of the clutch 6 , which is housed together with the pinion 4 and the meshing part 3 'of the rack in a common housing arrangement 24 .

The clutch input is formed by an input shaft 25 which can be connected to the shaft 10 (cf. FIG. 1) and the clutch output is formed by a pinion shaft 26 which is integrally connected to the pinion 4 . Both shafts 25 and 26 are rotatably supported on the one hand in the housing 24 and on the other hand by the end of the input shaft 25 facing the pinion shaft 26 having a stepped blind bore which receives a ball bearing for an axial extension of the pinion shaft 26 on the end face.

In the other 26 end facing the input shaft 25 is a pinion shaft 26 opens toward the ring gear 27 is arranged or formed on the pinion shaft which is rotatably supported with its in Fig. 2 to the left end face facing axially on the housing 24. Inside of the ring gear 27, first clutch plates 28 'axially slidably but non-rotatably supported relative to the ring gear 27th Further clutch plates 28 "are axially displaceable at the end of the pinion shaft 26 protruding into the ring gear 27 , but are non-rotatably arranged relative to the pinion shaft 26. The plates 28 'and 28 " follow one another alternately in the axial direction, with a pressure plate 29 which closes off the plate pack like the other slats. 28 "on the pinion shaft 26 is axially displaceable and non-rotatable, one of the first disks 28 'is provided, while one of the further disks 28 " is arranged in front of the disk-shaped part of the ring gear 27 .

Coaxial to the pinion shaft 26 is a clamping sleeve 30 which is axially displaceable relative to the pinion shaft 26 and which is screw-guided in a housing-fixed sleeve 60 by means of bearing balls 61 , ie the clamping sleeve 30 performs an axial stroke with respect to the sleeve 60 and the pinion shaft 26 when rotating relative to the sleeve 60 out.

The clamping sleeve 30 is tensioned by a plate spring assembly 33 , which is supported on a housing-side abutment ring 34 , against the plates 28 'and 28 ". The abutment ring 34 also serves to hold a bearing shell of a ball bearing 35 axially on the housing side under the action of the force of the plate spring assembly 33 This bearing 35 , which is designed as a grooved ball bearing and the inner bearing shell of which is firmly held axially on the pinion shaft 26 , serves for the radial and axial bearing of the pinion shaft 26 .

The clamping sleeve-side abutment of the cup spring package 33 is formed by an annular disk-shaped pressure plate 62 axially, the clamping sleeve opposite an annular step of a 30 in Fig. 2 to the right continuing, screwed to the clamping sleeve 30 sleeve member 31. Between the sleeve part. 31 and the pressure plate 62 , an axial bearing 63 is arranged. Another axial bearing 32 is located between the pressure plate 29 of the coupling 6 and the end of the clamping sleeve 30 facing the coupling 6 . A radial bearing 64 is arranged between the sleeve part 31 and the sleeve 60 , which permits axial displacement of the sleeve part 31 and thus the clamping sleeve 30 .

Thus, the clamping sleeve 30 with the sleeve part 31 can rotate relative to the spring assembly 33 and relative to the pressure plate 29 , the clamping sleeve 30 and the sleeve part 31 simultaneously executing an axial movement according to the screw guide through the balls 61 .

The rotor 65 of an electric motor 66 , whose stator is fastened to the sleeve 60 and is encased by the latter, is arranged in a rotationally fixed manner on a central section of the clamping sleeve 30 . The rotor 65 is axially displaceable to the stator of the electric motor 66 .

For normal operation of the steering system, the clutch 6 is opened in that the electric motor 66 is supplied with electrical current and rotates the rotor 65 , taking the clamping sleeve 30 with it, in such a way that the clamping sleeve 30 with the sleeve part 31 counteracts the force of the plate spring assembly 33 in a position shown in FIG . 2 right end position is axially displaced.

In this end position, a sensor 67 is preferably actuated, ie a signal assigned to the end position is generated in this end position.

If a fault occurs in the steering system, the electrical supply current for the electric motor 66 is switched off. Thus, the plate spring assembly 33 can axially move the clamping sleeve 30 against the pressure plate 29 into the end position on the left in FIG. 2, in which the clutch 6 is closed.

In the embodiment described above, it is provided that during normal operation of the steering system the electric motor 66 is constantly energized and holds the clamping sleeve 30 in the right end position.

Instead, it can also be provided that the electric motor 66 is energized only to open the clutch 6 , ie to adjust the clamping sleeve 30 in its right end position. As soon as this end position is reached, the clamping sleeve 30 can be held in the aforementioned end position by a non-self-locking locking element (not shown) against the force of the plate spring assembly 33 . For this purpose, an actuating magnet (not shown) or other actuating element for the locking element must then be energized or supplied with energy. As soon as this electrical current or the energy supply is switched off, the locking element falls back into its unlocked position, and the plate spring assembly can in turn move the clamping sleeve 30 to the left while the clutch 6 is closed.

The emergency state, ie the closed state of the clutch 6 , is in principle also automatically set by switching off the current or energy supply to the electric motor 66 or to the actuating member of the aforementioned locking member if no signals from the sensor 67 for the right end position of the clamping sleeve 30 and thus for the open state of the clutch 6 .

If necessary, the electric motor 66 can be electrically energized in an emergency, ie when the clutch 6 is to be closed, also in the opposite direction to normal operation (open clutch 6 ), so that the closed state of the clutch 6 is reached particularly quickly since the clutch is closed Coupling 6 cooperating electric motor 66 compensates for the inertia of the system.

Claims (7)

1. Steering system for a non-track-bound motor vehicle, the steered vehicle wheels ( 1 ) are connected in normal operation with a steering handle, in particular a steering handwheel ( 11 ), via an electronic control arrangement ( 23 ) constantly checking for correct function, which one with the steered Controls vehicle wheels ( 1 ) connected to their steering adjustment steering actuator ( 5 ) and is connected to a steering angle setpoint sensor ( 14 ) operated by the steering handle and a steering angle actual value transmitter ( 16 ) operated by the steered vehicle wheels, the control arrangement ( 23 ) preferably also controls a manual power actuator ( 12 ) connected to the steering handle to simulate a steering resistance and for this purpose with a manual force setpoint generator ( 21 , 22 ) which records forces transmitted between the steering actuator ( 5 ) and the steered vehicle wheels ( 1 ) and a transferred forces between the manual power actuator and the steering hand Have manual force sensor ( 13 , 14 , 15 ) is connected, with the abnormal vehicle or emergency operation, the steered vehicle wheels ( 1 ) are mechanically positively coupled to the steering adjustment with the steering handle by a clutch ( 6 ) open during normal operation in a between steering handle and steered vehicle wheels arranged mechanical steering gear arrangement ( 3 , 4 , 10 ) closes, characterized in that
that a sleeve part ( 30 ) is arranged coaxially to the input or output shaft ( 25 , 26 ) of the clutch ( 6 ) and can be screwed axially in a clutch or transmission housing ( 24 ) to transmit the closing force ( 33 ) to the clutch, is arranged without self-locking, and
that the sleeve part ( 30 ) is connected in a rotationally fixed manner to a rotor ( 65 ) of an electric motor ( 66 ) which is coaxial with the sleeve part and which, when energized, rotates the rotor in a direction in which the sleeve part is axially displaced against the closing force. 2. Steering system according to claim 1, characterized in that the sleeve part ( 30 ) within the clutch or gear housing ( 24 ) by means of balls or a ball screw arrangement ( 61 ) is guided so as to be screwable. 3. Steering system according to claim 1 or 2, characterized in that a housing-fixed sleeve ( 60 ) is arranged coaxially to the sleeve part ( 30 ), which on the one hand encases the stator of the electric motor ( 66 ) and on the other hand the screw guide or screw guide elements for the sleeve part ( 30 ) records. 4. Steering system according to one of claims 1 to 3, characterized in that a sensor ( 67 ) is arranged which generates signals when the clutch ( 6 ) is open or when the sleeve part ( 30 ) is pushed into its end position against the closing force. 5. Steering system according to one of claims 1 to 4, characterized in that a sensor is arranged which generates signals when the clutch ( 6 ) and / or when the clutch ( 6 ) is not fully open. 6. Steering system according to one of claims 1 to 5, characterized in that the sleeve part ( 30 ) or a part firmly connected to it ( 31 ) can be locked in its advanced position against the closing force by means of a non-latching latch arrangement, which only their latching state can take or hold when receiving energy. 7. Steering system according to one of claims 1 to 6, characterized in that the electric motor ( 66 ) is also energized according to a direction of rotation supporting the closing force and is energized in abnormal operation or emergency operation for a quick closing of the clutch ( 6 ).