STEERING GEAR APPARATUS FOR A MOTOR VEHICLE

Abstract

A steering gear apparatus (2) for a motor vehicle (1), comprising a hydraulic steering gear (11) and an electromechanical actuator (7) which is configured to actuate a working valve (10) of the hydraulic steering gear, it being possible for hydraulic fluid to be conducted out of a fluid reservoir (14) selectively into one of at least two working spaces (12) of the hydraulic steering gear (11) in a manner which is dependent on a position of the working valve (10), the steering gear apparatus (1) having a fallback device (16) which is configured, in particular in emergency operation of the steering gear apparatus (2), to selectively conduct hydraulic fluid into one of the at least two working spaces (12) independently of the position of the working valve (10).

Claims

1. A steering gear apparatus (2) for a motor vehicle (1), comprising a hydraulic steering gear (11) and an electromechanical actuator (7) which is configured to actuate a working valve (10) of the hydraulic steering gear, it being possible for hydraulic fluid to be conducted out of a fluid reservoir (14) selectively into one of at least two working spaces (12) of the hydraulic steering gear (11) in a manner which is dependent on a position of the working valve (10), distinguished by a fallback device (16) which is configured, in particular in emergency operation of the steering gear apparatus (2), to selectively conduct hydraulic fluid into one of the at least two working spaces (12) independently of the position of the working valve (10).

2. The steering gear apparatus (2) as claimed in claim 1, wherein the fallback device has a switchover valve (17) which is configured to establish a fluidic connection between the fluid reservoir (14) and the working valve (10) in normal operation, and to establish a fluidic connection between the fluid reservoir (14) and the working spaces (12) in emergency operation.

3. The steering gear apparatus (2) as claimed in claim 1, wherein the switchover valve (17) or an additional regulating valve (19) is configured to regulate, in particular in an infinitely variable manner, the pressure of the hydraulic fluid which prevails in the working spaces (12) from the fluid reservoir (14).

4. The steering gear apparatus (2) as claimed in claim 1, wherein the steering gear apparatus (2) has a fallback control device (18) or is coupled to a fallback unit of a control device which is configured to generate a control signal for an actuation of the switchover valve (17) and/or the regulating valve (19) in emergency operation.

5. The steering gear apparatus (2) as claimed in claim 1, wherein the fallback device (16) is configured by way of a first and/or a second pressure generation device (15) for conveying hydraulic fluid, a first pressure generation device (15) being engine-operated and a second pressure generation device (15) being passively operated, in particular being gear-operated or by means of an electric energy store.

6. The steering gear apparatus (2) as claimed in claim 1, distinguished by a detection device (5, 20) which is configured to transmit a steering angle signal, in particular from a steering angle sensor, to a control device (18) which is assigned to the fallback device (16), the fallback device (16) being configured to load the working spaces (12) with hydraulic fluid in a manner which is based on the steering angle signal.

7. The steering gear apparatus (2) as claimed in claim 6, wherein the detection device (5, 20) is assigned at least one steering angle sensor which is arranged on a steering element (3) and/or a detection element which is coupled to the steering element (3), and/or the detection device (5, 20) is assigned at least one steering angle sensor which is arranged at an output of the steering gear (11).

8. The steering gear apparatus (2) as claimed in claim 1, wherein the steering gear apparatus (2) has at least one monitoring device which is configured to monitor the functional capability of at least one component of the steering gear apparatus (2).

9. The steering gear apparatus (2) as claimed in claim 1, wherein the fallback device (16) is configured to carry out emergency operation in an autonomous driving mode of the steering gear apparatus (2).

10. A motor vehicle (1), comprising a steering gear apparatus (2) as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will be described in the following text on the basis of one exemplary embodiment with reference to the FIGURE. The FIGURE is a diagrammatic illustration and shows a detail of a motor vehicle with a steering gear apparatus.

DESCRIPTION

[0033] The FIGURE shows a motor vehicle 1 in a diagrammatic detail, in particular in the region of a steering gear apparatus 2. In this exemplary embodiment, the steering gear apparatus 2 has a steering element 3, for example a steering wheel, and a steering column 4, on which a detection device 5 is arranged which has, for example, a torque sensor and an angle sensor, which angle sensor is configured to detect a steering angle by which the steering element 3 is deflected. The torque sensor can detect a torque which is brought about on the steering element 3 by way of the user. The motor vehicle 1 can fundamentally also be configured for autonomous steering or lateral control, with the result that the steering element 3, the steering column 4 and the detection device 5 are considered optional and can be dispensed with if the motor vehicle 1 is steered in a purely autonomous manner.

[0034] Furthermore, the steering gear apparatus 2 has an electromechanical system 6 which has an electromechanical actuator 7, a control device 8 and a transmission gear 9. The actuator 7 can fundamentally be of electromechanical configuration, in order to transmit or to generate a torque. The control device 8 can be connected to a bus of the motor vehicle 1, for example of a central control unit which is not shown in greater detail. Furthermore, the control device 8 can receive the signals of the detection device 5 or can request them.

[0035] The actuator 7 is connected via the transmission gear 9 to a working valve 10, for example via a torsion bar. The working valve 10 is in turn connected to a hydraulic steering gear 11, and can selectively fill working spaces 12 (not shown in greater detail) of the hydraulic steering gear 11. The hydraulic steering gear 11 subsequently brings about the setting of a wheel angle at the steerable wheels 13 of the motor vehicle 1.

[0036] The actuator 7 can therefore generate a torque, in particular in a manner which is based on an actuation by way of the control device 8 which in turn receives the steering angle, set at the steering element 3 by way of the user, from the detection device 5. The torque from the actuator 7 can therefore be transmitted via the transmission gear 9 to the working valve 10, with the result that the working spaces 12 can be filled with hydraulic fluid from the fluid reservoir 14 in accordance with the steering angle. To this end, a pressure generation device 15 can be actuated, in order to convey hydraulic fluid under pressure into one of at least two working spaces 12, depending on how the working valve 10 is actuated. Here, hydraulic fluid can escape from the respective other working space 12 back into the fluid reservoir 14.

[0037] As has been described, the motor vehicle 1 can have autonomous lateral control, with the result that the steering element 3, the steering column 4 and the detection device 5 are dispensed with or are without function in the autonomous operating mode. The description is otherwise transferable, the required steering angle or wheel angle being fed from the bus of the motor vehicle 1, in particular from a control unit, to the control device 6.

[0038] If a fault occurs in the electromechanical system 6, for example in the control device 8, the actuator 7, the transmission gear 9 or the working valve 10, emergency operation is triggered, for which purpose the steering gear apparatus 2 has a fallback device 16.

[0039] The fallback device 16 has a switchover valve 17 which is fundamentally configured to conduct the fluid flow or fluid path from the fluid reservoir directly to the at least two working spaces 12. In other words, the switchover valve 17 represents a “bypass”, since the hydraulic fluid is no longer conducted from the fluid reservoir 14 to the working valve 10, but rather the working valve 10 is bypassed. In the exemplary embodiment which is shown, the fallback device 16 has, furthermore, a fallback control device 18 which is configured to actuate the switchover valve 17. If, for example, a fault is detected in the electromechanical system 6, either the control device 8 or a central control unit of the motor vehicle 1 of the fallback control device 18 can announce the fault. In this case, the electromechanical system 6 can be switched off. The control devices 8, 18 might also fundamentally be dispensed with, and the corresponding control signals might be generated directly at a central control unit of the motor vehicle 1.

[0040] Furthermore, it is apparent from the FIGURE that the fallback device 16 has a regulating valve 19 which is configured to regulate the pressure of the hydraulic fluid in the at least two working spaces 12 in an infinitely variable manner, that is to say to load at least one working space 12 with hydraulic fluid in a targeted manner, with the result that a defined pressure is generated therein, and to discharge hydraulic fluid in a defined manner from the at least one further working space 12 and to feed it to the reservoir 14 again. A corresponding control of the pressure generation device 15 is likewise possible here, it also being possible as an alternative for it to generate a pressure which is subsequently distributed through the regulating valve 19. The regulating valve 19 and the switchover valve 17 can fundamentally also be integrated into a single valve unit. The switchover valve 17 can otherwise be configured, for example, as a 4/2-way valve and the regulating valve 19 can be configured as a 4/3-way valve. In general, any desired combination of a plurality of valves can be used.

[0041] In the described emergency operation, the required wheel angle is therefore set at the wheels 13 by virtue of the fact that the control signal (for example, generated by way of the fallback control device 18) is routed to the switchover valve 17 which feeds the hydraulic fluid, which can be conveyed out of the reservoir 14, via the regulating valve 19 to the working spaces 12. As has been described above, the hydraulic steering gear 11 can actuate the wheels 13 by the defined wheel angle by way of the corresponding setting of the necessary pressure in the working spaces 12. Furthermore, the fallback device 16 is assigned a detection device 20, for example an angle sensor. The latter can access a gear output 21 of the hydraulic steering gear 11 or can tap off a steering angle there or can detect the wheel angle directly. As a result, in particular, it can be determined whether the desired steering angle or wheel angle is actually being implemented. If a steering element 3 is used to fix the steering angle or a user carries out the steering operation via the steering element 3, the steering angle or wheel angle determined on the part of the detection device 5 and the steering angle/wheel angle determined on the part of the fallback detection device 20 can be compared with one another and it can be determined whether the desired wheel angle is actually being generated.

[0042] The fallback device 16 advantageously achieves a situation where the steering gear apparatus 2 remains completely usable and the motor vehicle 1 maintains its steering capability. Here, the fallback device 16 does not make recourse to components of the electromechanical system 6, but rather brings about a direct actuation of the working spaces 12 of the hydraulic steering gear 11. In this way, a fault can occur in any arbitrary components of the electromechanical system 6, with the result that the steering capability of the motor vehicle 1 is maintained completely even in the case of a complete malfunction of the control device 8, the electromechanical actuator 7, the transmission gear 9 or the working valve 10.

[0043] A first pressure generation device which is driven, for example, in an engine-operated manner can be used, in particular, as pressure generation device 15. Here, the engine of the motor vehicle 1, that is to say the drive device, can be used via a corresponding gear unit to operate the first pressure generation device, with the result that hydraulic fluid can be conveyed from the fluid reservoir 14 and can be fed to the corresponding working spaces 12. As an alternative or in addition, it is likewise possible that the fallback device 16 has an additional pressure generation device, as second pressure generation device, for example a passively operated pressure generation device. The second pressure generation device can be operated, for example, via a gear of the motor vehicle 1, with the result that, as long as the motor vehicle 1 is in movement, driving the second pressure generation device is possible. The second pressure generation device can likewise be assigned a separate, in particular electric, energy store which can drive the second pressure generation device at least until the motor vehicle 1 can be moved into a safe state.

LIST OF DESIGNATIONS

[0044] 1 Motor vehicle

[0045] 2 Steering gear apparatus

[0046] 3 Steering element

[0047] 4 Steering column

[0048] 5 Detection device

[0049] 6 Electromechanical system

[0050] 7 Actuator

[0051] 8 Control device

[0052] 9 Transmission gear

[0053] 10 Working valve

[0054] 11 Hydraulic steering gear

[0055] 12 Working space

[0056] 13 Wheel

[0057] 14 Fluid reservoir

[0058] 15 Pressure generation device

[0059] 16 Fallback device

[0060] 17 Switchover valve

[0061] 18 Fallback control device

[0062] 19 Regulating valve

[0063] 20 Detection device

[0064] 21 Gear output