STEERING ACTUATOR FOR A STEERING SYSTEM AND STEERING SYSTEM FOR A MOTOR VEHICLE

Description

State of the art

[0001] The invention relates to a steering actuator for a steering system for a motor vehicle, comprising an actuator rod that is translationally displaceable in its longitudinal direction and a position sensor device designed to detect the linear position of the actuator rod. The position sensor device comprises a rotation sensor having a sensor shaft rotatable about an axis with a wheel that is non-rotatably mounted on the sensor shaft and can roll on a corresponding linear track of the actuator rod in order to convert a translational movement of the actuator rod into a rotation of the sensor shaft. A steering system for a motor vehicle with such a steering actuator is also subject of the invention.

[0002] In a motor vehicle steering system, the mechanical steering angle of the steerable wheels is generated by means of one or more steering actuators.

[0003] A steering actuator of this type has an actuator rod that is movable longitudinally, usually transversely to the direction of travel, relative to the vehicle body. In a conventional steering system, the actuator rod, which is usually arranged transversely to the direction of travel, is connected to the steering knuckles of the two steerable wheels of a vehicle axle. In a single-wheel steering system, it is connected to a single steerable wheel. The steering force of the steering actuator causes the steerable wheels to turn via the translational displacement of the actuator rod.

[0004] A steering command can be mechanically coupled to the steering actuator, for example, via a manual rotation of a steering shaft of a conventional rack-and-pinion steering gear, which engages a rack of the actuator rod via a steering pinion. Alternatively or additionally, a motor drive or auxiliary drive can be provided to amplify or replace the manual steering input. A steering torque can be coupled to the steering shaft via the usually electric motor drive, or alternatively or additionally, the actuator rod can be moved by a motor.

[0005] Steer-by-wire steering systems have no mechanical connection between a manually rotatable steering shaft and the actuator rod. The motor drive can be integrated into the steering actuator or coupled to it to convert an electrical steering command into a corresponding displacement of the actuator rod.

[0006] The steering angle of the steerable wheels can be detected by an electronic position sensor device to monitor and control the steering. This device uses suitable electronic sensors, such as resistive, inductive, optoelectronic, or other measuring methods, to measure the current linear position of the actuator rod, which is clearly correlated with the steering angle. The prior art, for example, proposes applying longitudinally coded position marks directly to the actuator rod, which can be read by a sensor to determine the longitudinal position. However, a disadvantage is that even slight contamination of the rack, such as lubricant or dust, can impair the measurement, making production complex and operation relatively prone to failure.

[0007] A steering actuator of the type described above is known from CN 110 588 765 A. The disadvantage is that transverse forces occurring during operation can impair the function of the rotation sensor.

[0008] In view of the problems explained above, it is an object of the present invention to enable less complex production and greater operational reliability. Description of the invention

[0009] This object is achieved according to the invention by the steering system having the features of claim 1 and a steering system for a motor vehicle according to claim 12. Advantageous further developments emerge from the subclaims.

[0010] In a steering actuator for a steering system for a motor vehicle, comprising an actuator rod which is translationally displaceable in its longitudinal direction and a position sensor device designed to detect the linear position of the actuator rod, wherein the position sensor device comprises a rotation sensor which has a sensor shaft which is rotatable about an axis and has a running wheel which is mounted on the sensor shaft in a rotationally fixed manner and can roll on a corresponding linear track of the actuator rod in order to convert a translational movement of the actuator rod into a rotation of the sensor shaft, it is provided according to the invention that the rotation sensor is arranged or designed to be flexible transversely to the track.

[0011] The linear translational displacement of the actuator rod is converted into a rotation of a wheel, which is rotationally connected to the rotatable axis (also referred to as the sensor axis) of a rotation sensor. The rotation sensor is arranged fixed relative to the actuator rod in the longitudinal direction, which corresponds to the direction of displacement of the actuator rod. For example, the rotation sensor is mounted on an actuator housing in which the actuator rod is displaceably mounted and which is fixed to the body of the motor vehicle. The axis of the sensor shaft is arranged transversely to the longitudinal direction, preferably perpendicular to the longitudinal direction.

[0012] According to the invention, the rotation sensor is arranged or configured to be compliant transverse to the track. If transverse forces acting transversely to the longitudinal direction occur between the actuator rod and the rotation sensor during operation, for example due to thermal effects, load changes, or the like, this could impair the coupling of the rotation sensor, which could lead to excessive material stress, noise generation, and increased wear. Because the rotation sensor is compliantly connected according to the invention, it can deflect laterally in response to transverse forces, thereby avoiding potentially harmful material stresses and increased friction. This can advantageously increase long-term operational reliability and smooth running.

[0013] One possible way to implement a compliant arrangement is for the rotation sensor to be mounted so that it can move relative to the actuator rod. For example, a bearing arrangement that can be moved or pivoted transversely to the longitudinal direction can be mounted between the rotation sensor and the actuator housing. This allows the rotation sensor as a whole to move transversely to the actuator rod. One advantage of this is that a complete sensor assembly of the rotation sensor, which can be provided as a vendor part, for example, can be easily mounted on a compliant bearing. It is also conceivable for at least the sensor shaft in the rotation sensor to be mounted so that it can move translationally transversely to the axis.

[0014] In principle, any bearing arrangement can be used that allows a relative deflection movement of the functional elements of the position sensor device, which are arranged in a resilient manner according to the invention, in response to transverse forces acting transversely to the sensor shaft. A structurally simple and operationally reliable resilient bearing can be realized, for example, by a translational or pivot bearing, which can comprise a plain or rolling bearing, or a deformable bearing element.

[0015] A further advantageous implementation of a compliant arrangement can be achieved by providing the impeller and / or the raceway with at least one compliantly configured compensating element. The compensating element is arranged between two functional elements of the position sensor device, between which the said transverse forces can occur and which, according to the invention, are arranged so as to be compliantly movable relative to one another. For example, the impeller can be held so as to be compliantly movable relative to the sensor shaft via a compensating element, or alternatively or additionally, the raceway can be held so as to be compliantly movable relative to the actuator rod via a compensating element. It is also conceivable and possible to additionally or alternatively arrange or form a compensating element between the impeller and the raceway, for example on the outside of the impeller or on the raceway, which can, for example, comprise a compliantly deformable layer.Such a compliant layer may consist of a deformable material or have a deformable structure and may be arranged, for example, between the teeth of the gear and the rack, between the gear and the sensor shaft, or between the rack and the actuator rod.

[0016] The outer circumference of the idler wheel mounted on the axle contacts the raceway arranged longitudinally on the actuator rod, which extends in the direction of displacement. As a result, the outer circumference rolls along the raceway when the steering wheel is turned, and the idler wheel is rotated by the amount of the linear displacement of the actuator rod. As long as the idler wheel rolls without slippage, which can be ensured by appropriate measures, the rotation of the axle is clearly correlated with the displacement of the actuator rod. Accordingly, the rotational or rotary position of the axle indicates the linear position of the actuator rod.

[0017] An electronic angle sensor can be used as a rotation sensor. It has the angular resolution required for the desired measurement accuracy and is suitable for use in motor vehicles in terms of its dimensions and operating characteristics. For example, optoelectronic, inductive, capacitive, or other electronic sensors operating according to measuring methods are known. These sensors are accurate, robust, and insensitive to the mechanical and thermal stresses that occur during operation, for example, due to vibrations and temperature fluctuations. Because such a sensor is mechanically coupled to the actuator rod only via the rotatable sensor shaft, the actual measuring sensor technology can be housed safely protected against external interference with little effort.For example, rotation sensors in an encapsulated design can be used, in which the sensor shaft is sealed and guided to the outside through a closed sensor housing. This largely protects the sensor against interference from lubricants, dust, or similar substances that may occur in the area of ​​the actuator rod. This ensures high measurement accuracy and operational reliability.

[0018] Commercially available rotation sensors can be used, requiring only the provision and installation of a wheel adapted to the respective actuator rod design. This allows for flexible and cost-effective design and production with relatively little effort.

[0019] Preferably, the actuator rod is displaceably mounted in an actuator housing, as is generally known from the generic design of a steering actuator. The rotation sensor can preferably be attached to the actuator housing or integrated therein. The sensor shaft can also be mounted in the actuator housing, which has the advantage that the impeller is clearly positioned with respect to the track. For installation in the motor vehicle, the actuator housing can have connecting or fastening means, as is known in principle from the prior art.

[0020] The actuator rod can be designed as a rack or have one, as is known in principle from steering gears of rack and pinion steering systems in the prior art.

[0021] It can be provided that a motor drive is provided for the translational displacement of the actuator rod. The motor drive is preferably an electric motor drive, which is also synonymously referred to as a steering drive. This comprises an electric motor coupled to gear means for converting the rotation of the motor shaft into a longitudinal displacement of the actuator rod. For example, the motor drive can have a spindle drive with a threaded spindle arranged coaxially on the actuator rod, which engages in a spindle nut supported longitudinally in the actuator housing and rotatably driven by the motor. The spindle drive can preferably be designed as a smooth-running and easy-running ball screw drive.

[0022] Alternatively, it is conceivable and possible that the motor drive rotates a steering pinion which is attached to a steering shaft or a drive shaft of the motor drive or an auxiliary drive, which engages with a longitudinally extending rack of the actuator rod.

[0023] It can preferably be provided that the impeller is designed as a gear and the raceway as a rack. The toothed engagement ensures a substantially slip-free and virtually backlash-free, positive conversion of the linear displacement of the actuator rod into a corresponding rotation of the sensor shaft connected to the gear. This ensures precise, robust, and reliable position measurement. The rack can be formed directly on the actuator rod or attached to it as a separate component.

[0024] It is possible for the impeller to mesh with the rack, which also engages the steering pinion of a drive to move the actuator rod. This allows for a compact design.

[0025] According to an advantageous development of the invention, the impeller can be elastically preloaded against the raceway. By elastically resiliently pressing the impeller against the raceway, optimized rolling with virtually no play or slippage can be ensured under all operating conditions. At the same time, the elastic deformability allows the flexible bearing arrangement according to the invention to be realized.

[0026] The elastic force, such as the spring force, of the preload is preferably specified at a value that is less than the maximum permissible transverse force that can act on the position sensor device without impairing its function. This effectively prevents wear and damage in the long term, thus increasing operational reliability.

[0027] To generate the aforementioned preload, the rotation sensor can be elastically preloaded against the actuator rod. The rotation sensor as a whole can be spring-loaded transversely against the actuator rod, for example, by spring elements supported against the actuator housing, which can be metallic or rubber-like. At least the sensor shaft can be pressed resiliently against the actuator rod in the area of ​​the raceway. Such spring elements are known and generally available in the required dimensions and elastic properties. Their design and manufacture can be carried out with little effort.

[0028] In an advantageous embodiment, it can be provided that the impeller and / or the raceway have at least one elastic spring element. The spring element ensures that the impeller and the raceway are resiliently pressed against each other in the area of ​​rolling contact. By means of the spring element, the impeller can be designed to be elastic in itself or can be held relative to the sensor shaft, for example by a hub arrangement that is elastically deformable in the radial direction or the like. It is also possible to attach a spring element between the raceway, for example a toothed rack, and the actuator rod, for example in the form of a rubber-elastic layer or another flat spring arrangement, for example with leaf or wave springs.Alternatively or additionally, a spring element can be arranged or formed on the outside of the impeller or on the raceway, for example, as an elastic, rubber-like layer between the teeth of the gear and the rack, which can be attached to the gear or rack. For example, the teeth of the gear and / or the rack can be completely or partially rubber-elastic, for example, by being coated with an elastic material.

[0029] Preferably, a compensating element can be designed as a spring element. In its function as a compensating element, its deformability enables flexible mobility, and, due to its elastic design, it can also provide elastic preload. This integration of functions in one component allows for the realization of a particularly advantageous, compact, lightweight, and functionally reliable position sensor device that requires relatively low design and manufacturing effort.

[0030] Such a combined compensation and spring element can be realized, for example, by a layer or other structure made of a rubber-elastic material, which can be injection-molded, for example, which enables efficient production.

[0031] In a steering system for a motor vehicle, comprising a steering actuator operatively connected to at least one steerable wheel, the invention provides that the steering actuator is designed according to one of the previously described embodiments. All combinations of the described features can be implemented.

[0032] Preferably, the steering system can be designed as a steer-by-wire steering system. In this case, the steering actuator has no mechanical connection to the manual steering input, and the translational displacement of the actuator rod is exclusively provided by a motor drive, which is controlled by a control unit using electrical control signals to generate a steering angle.

[0033] The rotation sensor can be connected to an electrical control unit to detect and evaluate the electrical position signals. This is preferably the control unit of a steer-by-wire steering system, whereby, thanks to the position sensor device according to the invention, reliable monitoring of the actual value of the steering angle of a steerable wheel is enabled. Description of the drawings

[0034] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail: Figure 1 shows a schematic representation of a steer-by-wire steering system according to the invention. Figure 2 shows a steering actuator according to the invention of the steering system according to Figure 1 in a perspective view, Figure 3 a cross section through a steering actuator according to Figure 2 in a first embodiment, Figure 4 shows a cross section through a steering actuator according to Figure 2in a second embodiment, Figure 5 shows a cross section through a steering actuator according to Figure 2 in a third embodiment, Figure 6 shows a schematic perspective partial view of the steering actuator according to Figure 2 with the actuator rod and a position sensor device according to the invention according to one of the Figures 3, 4 , or 5 . Embodiments of the invention

[0035] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0036] Figure 1shows a schematic diagram of a steer-by-wire steering system 1 comprising a steering column 2. This has a support unit 21 mountable on a vehicle body (not shown), of which a steering spindle 22 is rotatably mounted about its longitudinal axis L. At its rear, driver-side end with respect to the direction of travel, a steering wheel 23 is non-rotatably mounted on the steering spindle 22 for inputting manual steering commands.

[0037] In the steering column 2, a rotation angle and torque detection sensor system (not shown in detail) is accommodated, which converts a steering command introduced into the steering spindle 22 as a rotation of the steering wheel 23 into an electrical control signal, namely a steering signal.

[0038] The control signal is transmitted via an electrical control line 3 to an electrical steering actuator 4 according to the invention.

[0039] The steering actuator 4 - which is shown in detail in the Figures 2 to 6shown - has an actuator housing 41 which has connecting elements 410 for attaching the steering actuator 4 to a vehicle body, not shown.

[0040] In the actuator housing 41, an actuator rod 42, which extends along an axis A, the so-called actuator axis A, transversely to the direction of travel of the vehicle, is displaceably mounted in its longitudinal direction predetermined by this axis A, as indicated by the double arrow.

[0041] The two outer ends of the actuator rod 42 are each connected to a steerable wheel 5 via a tie rod 43, so that a displacement of the actuator rod 42 causes a steering angle of the steered wheel 5 relative to the roadway 50.

[0042] To generate a steering angle, the steering actuator 4 has an electric motor drive 44, which can be electrically controlled via the control line 3 and which comprises an electric motor (not specifically designated) attached to the actuator housing 41. The motor can drive a spindle nut, which is rotatably mounted in the actuator housing 41 and supported in the longitudinal direction of the axis A, into which a spindle thread 45 formed on the actuator rod 42 engages. In this way, a linear spindle drive is formed in a manner known per se, in which the actuator rod 42 can be moved longitudinally relative to the actuator housing 41 by rotating the motor in the appropriate direction.

[0043] The steering actuator 4 has a position sensor device 6 according to the invention, which is shown in detail in the sectional views of Figures 3, 4 and 5 which each have a cross section BB of Figure 2In the schematic overview of Figure 6 the actuator housing 41 is omitted and provides a view of the actuator rod 42 and the position sensor device 6.

[0044] The position sensor device 6 has an electrical rotation sensor 62, which can operate according to a measuring method known per se, for example inductively, capacitively, optically or the like, and detects a rotation of a sensor shaft 62 rotatably mounted about a sensor axis S as an electrical measured value.

[0045] The sensor shaft 62 is rotatably mounted in the actuator housing 41 in a bearing 63, which can be designed, for example, as a needle bearing.

[0046] The sensor axis S of the sensor shaft 62 is arranged transversely to the axis A of the actuator rod 42.

[0047] A gear 64 is mounted on the sensor shaft 62 in a rotationally fixed manner, forming a running wheel according to the invention, and meshing with a rack 46 which is mounted on the actuator rod 42 extending in the longitudinal direction of the axis A and which forms a raceway according to the invention. This arrangement is shown in the schematic perspective view of Figure 6 clearly visible.

[0048] A linear displacement of the actuator rod 42 is converted into a rotation of the sensor shaft 62 with virtually no slippage due to the toothed engagement. As a result, a linear position of the actuator rod 42 relative to the actuator housing 41 is clearly correlated with an angular position of the sensor shaft 62, which is detected and output as an electrical measured value by the rotation sensor 61.

[0049] The actual electrical sensor system for detecting the angular movement of the sensor shaft 62 can be housed in the rotation sensor 61, protected against external influences, which can be provided and mounted as a commercially available, externally sealed sensor unit.

[0050] Figures 3, 4 and 5 show various embodiments of the invention in the same view, using the same reference numerals. The different features can be implemented according to each individual embodiment, as shown in the figures, or in combination with one another.

[0051] In the first version according to Figure 3A rubber-elastic compensating element 65 is arranged between the teeth of the gear 64 and the rack 46. This can, for example, comprise a rubber-elastic coating on the teeth of the gear 64 and / or the rack 46, wherein the gear 64 and the rack 46 are resiliently preloaded against one another. The compensating element 65 can resiliently compensate for fluctuations in the distance between the actuator rod 42 and the sensor shaft 62, i.e. between the corresponding axes A and S, and at the same time serve as a spring element that ensures an elastically springy preload of the gear 64 against the rack 46, which is advantageous with regard to slip- and backlash-free gear engagement. An advantage of this arrangement is that potentially adverse transverse forces on the sensor shaft 62 are elastically absorbed and limited.

[0052] The compensating element 65 may, for example, comprise a thermoplastic elastomer which may be injection-molded onto at least one of the toothings or connected thereto in some other way.

[0053] The Figure 4 in the same view as in Figure 3 The second embodiment shown has a compensating element 66, which is inserted between the bearing 63 and the actuator housing 41. This can also preferably be made of a rubber-elastic material, for example as a bushing receiving the bearing 63, so that a resiliently yielding movement of the sensor axis 62 relative to the actuator rod 42 is enabled, as indicated by the double arrow on the sensor axis S. As a result, the gear 64 is resiliently pressed against the rack 46 into toothed engagement, and it can yieldably deflect relative to the axis A.

[0054] The Figure 5 in the same view as in the Figures 3 and 4The third embodiment shown has a compensating element 67, which is arranged between the rack 46 and the actuator rod 42. This can also preferably be made of a rubber-elastic material, so that a resiliently yielding movement of the rack 46 relative to the actuator rod 42 is enabled. As a result, the rack 46 is pressed radially outwardly with respect to the axis A in a resilient manner against the gear 64 into toothing engagement, and can thereby yieldably deflect relative to the axis A.

[0055] In all embodiments shown, the rotation sensor 61 is better protected against potentially harmful influences from lubricants, dust, and the like than in the prior art, and the compensating element 65, 66, 67 deflects transverse forces occurring between the axes A and S during operation from the rotation sensor 61. The arrangements of the compensating elements 65, 66, 67 can be combined with one another if necessary. List of reference symbols

[0056] 1Steering system 2Steering column 21Support unit 22Steering spindle 3Control line 4Steering actuator 41Actuator housing 410Connecting element 42Actuator rod 43Tie rod 44Drive 45Spindle thread 46Rack (raceway) 5Vehicle wheel 50Road surface 6Position sensor device 61Rotation sensor 62Sensor shaft 63Bearing 64Gear (impeller) 65Compensating element (spring element) 66Compensating element (spring element) 67Compensating element (spring element) LLongitudinal axis AAxis (actuator axis) SSensor axis

Claims

1. Steering actuator (4) for a steering system (1) for a motor vehicle, comprising an actuator rod (42) which can be displaced in translation in the longitudinal direction thereof and a position sensor apparatus (6) which is constructed to detect the linear position of the actuator rod (42), wherein the position sensor apparatus (6) comprises a rotation sensor (61) which has a sensor shaft (62) which can be rotated about an axis (S) and which has a running wheel (64) which is fitted in a rotationally secure manner to the sensor shaft (62) and which can roll on a corresponding linear track (46) of the actuator rod (42) in order to convert a translational movement of the actuator rod (42) into a rotation of the sensor shaft (62), characterised in that the rotation sensor (61) is arranged or configured so as to be flexible transversely relative to the track (46).

2. Steering actuator according to Claim 1, characterised in that the actuator rod (42) is displaceably supported in an actuator housing (41).

3. Steering actuator according to either of the preceding claims, characterised in that the running wheel is constructed as a gear (64) and the track is constructed as a toothed rack (46).

4. Steering actuator according to any one of the preceding claims, characterised in that the rotation sensor (61) is movably supported relative to the actuator rod (42).

5. Steering actuator according to any one of the preceding claims, characterised in that the running wheel (64) and / or the track (46) has at least one compensation element (65, 67) which is configured in a flexible manner.

6. Steering actuator according to any one of the preceding claims, characterised in that the running wheel (64) is resiliently pretensioned against the track (46).

7. Steering actuator according to any one of the preceding claims, characterised in that the rotation sensor (61) is resiliently pretensioned against the actuator rod (42).

8. Steering actuator according to any one of the preceding claims, characterised in that the running wheel (64) and / or the track (46) has at least one resilient spring element (65, 67).

9. Steering actuator according to Claim 8, characterised in that the resilient element is constructed as a compensation element (65, 66, 67).

10. Steering actuator according to any one of the preceding claims, characterised in that a motorised drive for translational displacement of the actuator rod (42) is provided.

11. Steering actuator according to any one of the preceding claims, characterised in that there is provided a rack and pinion steering gear mechanism having a rotatably drivable steering pinion which engages in a tooth arrangement of the actuator rod (42).

12. Steering system (1) for a motor vehicle, comprising a steering actuator (4) which is operationally connected to at least one steerable wheel (5), characterised in that the steering actuator (4) is constructed according to any one of Claims 1 to 11.

13. Steering system according to Claim 12, characterised in that it is constructed as a steer-by-wire steering system (1).

14. Steering system according to any one of Claims 12 to 13, characterised in that the rotation sensor (61) is connected to an electrical control unit.