Steering system with a steering rod guide system

Abstract

The invention relates to a steering system comprising an axially movably mounted steering rod (16), a linear displacement sensor (28) for determining the steering rod position, and a steering rod guide (10), wherein the steering rod guide (10) comprises a first supporting element (12) and a second supporting element (14), wherein the supporting elements (12, 14) together comprise at least three planar guide surfaces (18, 20, 30, 32), wherein the steering rod (16) comprises at least three planar receiving surfaces (22, 34) for the guide surfaces (18, 20, 30, 32) of the supporting elements (12, 14), wherein the steering rod (16) comprises a signal transmitter (26), wherein the supporting elements (12, 14) are arranged around the steering rod (16) in such a manner that • the supporting elements (12, 14) extend perpendicularly to the axial direction of the steering rod (16), • the supporting elements (12, 14) are arranged on two opposite sides of the steering rod (16) and enclose the steering rod (16); and • the signal transmitter (26) is located between the first supporting element (12) and the steering rod (16).

Description

[0001] Description

[0002] title

[0003] Steering system with a steering rod guidance system

[0004] The invention relates to a steering system, in particular for steer-by-wire steering systems and / or steering systems with electronic control (electronic power steering, EPS).

[0005] State of the art

[0006] Steer-by-wire steering systems are an advanced automotive technology that replaces the traditional mechanical connection between the steering wheel and steering gear with electronic control systems. In a conventional steering system, a steering column transmits the rotational movement of the steering wheel directly to the wheels. In a steer-by-wire system, however, the movements of the steering wheel are detected by linear position sensors and transmitted as electrical signals to a control computer. This computer processes the signals and uses actuators to control the movement of the wheels. This allows for precise adjustments to feedback and steering assistance, resulting in improved vehicle control and individual customization of the steering characteristics.

[0007] The basic structure of a steer-by-wire system comprises several essential components. First, there are linear position sensors on the steering wheel that detect the angle of rotation and torque. This information is transmitted to a central control computer, which calculates the desired driving direction and dynamics. The control commands are then passed on to electric actuators that position the wheels accordingly. Another important component is the feedback system, which provides the driver with realistic feedback about the road conditions by transmitting artificial forces back to the steering wheel.

[0008] A particular problem with steer-by-wire systems is determining the exact position of the steering column after the vehicle has restarted. While in a mechanical system the position of the steering column is physically determined by its connection to the wheels, in a steer-by-wire system the position must be determined electronically after the engine is switched on. This can be challenging because linear position sensors and control units initially lack precise information about the wheel position.

[0009] Sensors that determine position via the rotation of the steering system actuator are not unambiguous. This ambiguity can be solved with a counter system that tracks the number of actuator rotations and uses this data to calculate the exact position of the steering column. However, the counter is inoperative when the vehicle is switched off. If the steering column moves while the vehicle is off—for example, because the wheels are moved during vehicle lift work in a workshop—the stored counter value becomes invalid because it no longer reflects the correct position of the steering column.

[0010] For this reason, it is important to use a steering rod position determination system that enables unambiguous linear travel measurement. In steering systems with ball screws, the steering rod is typically rotaryally fixed via the pinion gear and the thrust piece. In some cases, the support is further enhanced by a non-circular rack back (Y-profile).

[0011] If other measuring methods, such as inductive measuring methods, are used, the steering rod lacks the support provided by the steering pinion and the pressure piece. The steering rod must nevertheless be supported against vertical movement and rotation. The invention therefore aims to propose a steering system with a steering rod guide that supports the steering rod against lateral movements and rotations.

[0012] The problem is solved by the subject matter of the independent claims.

[0013] Disclosure of the invention

[0014] According to a first aspect of the invention, this problem is solved by a steering system comprising an axially movable steering rod, a linear displacement sensor for determining the steering rod position, and a steering rod guide. The steering rod guide comprises a first support element and a second support element.

[0015] The support elements together comprise at least three flat guide surfaces, wherein the steering rod comprises at least three flat receiving surfaces for the guide surfaces of the support elements. The steering rod includes a signal transmitter extending in the axial direction of the steering rod.

[0016] The linear position sensor integrated into the steering housing detects the position from the signal transmitter. This can be done, for example, inductively, magnetically, capacitively, optically, or in another way.

[0017] The support elements are arranged around the steering rod such that they extend perpendicular to the axial direction of the steering rod. Furthermore, the support elements are positioned on two opposite sides of the steering rod, thus enclosing it. The signal transmitter is located between the first support element and the steering rod.

[0018] The movement of the wheels can be transmitted to the steering column to a certain extent. This applies particularly to vertical movements. Consequently, the steering column would also move vertically. However, with inductive and other non-contact measurement methods for determining the steering column's position, which rely on the interaction between a linear displacement sensor module and a signal transmitter mounted on the steering column, it is crucial that the distance between the linear displacement sensor module and the signal transmitter remains as constant as possible. Vertical movements can distort the result or even make position determination impossible. In the worst-case scenario, excessive movement can cause the signal transmitter to collide with the linear displacement sensor module, potentially damaging both, or at least one of them.

[0019] The support elements brace the steering rod so that it cannot move, or can only move within a very limited range. For this purpose, the support elements together comprise at least three flat guide surfaces. The number three is necessary to limit the movement of the steering rod in two spatial directions. These spatial directions are perpendicular to the axial direction of the steering rod. The axial movement of the steering rod is already limited by the steering system's drive mechanism and therefore requires no additional support.

[0020] For optimal support of the steering column, the support elements are arranged on opposite sides of the steering column. For example, one support element can be positioned above the steering column and the other below it. The three guide surfaces essentially prevent movement of the steering column in all directions. However, the force transmission to the support elements is particularly effectively compensated when the support elements are arranged vertically.

[0021] The flatness of the guide surfaces also has the advantage of preventing rotation of the steering rod. The guide surfaces engage the equally flat receiving surfaces of the steering rod from several sides. Similar to a pair of pliers, they positively prevent the steering rod from rotating around its own longitudinal axis.

[0022] The first support element refers to the support element that, together with the steering rod, encloses the signal transmitter. In principle, it would also be possible to position the signal transmitter between the support elements, for example, laterally on the steering rod in a vertical support element arrangement. However, positioning the signal transmitter between the steering rod and the first support element results in a particular effect: the air gap between the signal transmitter and the linear position sensor is kept more constant due to the optimized force transmission from the steering rod to the support elements.

[0023] Overall, the arrangement of the support elements and their guide surfaces prevents the steering rod from moving perpendicular to its axis and from rotating around its axis. This keeps the air gap between the signal transmitter and the linear position sensor constant, or at least largely constant, thereby improving position determination. The invention thus achieves its objective.

[0024] In one embodiment, the second support element is mounted perpendicular to the direction of movement of the steering rod and comprises a return element, wherein the return element presses the second support element against the steering rod.

[0025] The return element can, in particular, comprise a spring that presses the second support element against the steering rod. Advantageously, the return element ensures that the pressure on the steering rod is variable within a defined range and increases as the external force on the steering rod increases.

[0026] A fixed second support element would also be possible in principle. However, the embodiment with the spring-loaded return element offers the advantage that wear on the guide or receiving surfaces can be compensated for by the readjustment. Furthermore, the steering system has the ability to yield under excessive forces, thus preventing breakage of the steering rod or other damage to the steering system. An unacceptably large increase in friction due to clamping effects can also be prevented. The integrated spring also ensures that the system remains backlash-free, preventing unwanted acoustic effects. In one embodiment, the second support element includes an adjusting screw for the return element, whereby the adjustment screw (38) allows for setting the play between the return element and the steering rod (16).

[0027] The adjusting screw allows the return element, or the force exerted by the return element, to be adjusted and adapted to different situations.

[0028] In one embodiment, the first support element is structurally connected to the linear displacement sensor.

[0029] A structural connection can be achieved, for example, via a shared supporting element or through a direct connection between the support element and the linear position sensor. The support elements limit the movement of the steering rod, particularly where they directly engage with it. The structural connection also restricts the relative movement of the linear position sensor to the first support element. As a result, the structural connection limits the relative movement between the linear position sensor and the steering rod with the signal transmitter perpendicular to the steering rod's axis.

[0030] In principle, the smaller the distance between the linear displacement sensor and the second support element, the better the air gap between the signal transmitter and the linear displacement sensor can be kept constant.

[0031] Although the movement of the steering rod perpendicular to the axial direction is limited by the support elements, the steering rod can also deform, so that the distance between the signal transmitter and the linear position sensor increases the further the linear position sensor is located from the first support element.

[0032] In one embodiment, the steering system comprises a steering rod housing, and the support elements and the linear position sensor are rigidly connected to the steering rod housing. Many steering systems have a housing that protects the steering system from dirt, moisture, etc. In this embodiment of the invention, the housing can perform an additional function, namely to structurally connect the first support element to the linear position sensor and to protect both against relative movement.

[0033] The housing can preferably be made entirely or partially of a metal, in particular steel or aluminium, in order to create particularly high stability and thus a good structural connection between the first support element and the linear displacement sensor.

[0034] In one embodiment, the first support element and the second support element each comprise two guide surfaces.

[0035] In this embodiment, the support elements can preferably be designed such that the guide surfaces in each support element form a "V" or a "Y", with the guide surfaces limiting the movement of the steering rod in four directions. In this embodiment, the steering rod has four flat receiving surfaces corresponding to the number of guide surfaces.

[0036] The use of four guide and mounting surfaces increases the stability of the steering rod perpendicular to its axial direction of movement, as the forces from the steering rod to the support elements are distributed over two guide surfaces in almost all directions.

[0037] In one embodiment, the guide surfaces of the first support element and the second support element are arranged symmetrically to each other.

[0038] With a V- or Y-shaped arrangement of the guide surfaces, a symmetrical arrangement of the guide surfaces is advantageous, as this allows the forces to be distributed evenly across the support elements. The even distribution of force transmission also ensures that wear due to friction is evenly distributed, thereby increasing the service life of the individual components. In one embodiment, the first support element has a recess for the signal transmitter, creating an air gap between the first support element and the signal transmitter.

[0039] Preferably, the signal transmitter lies in section on a line with the first support element and the steering rod, in particular the bracket of the first support element and the center of the steering rod.

[0040] To prevent the signal transmitter from being damaged by friction with the first support element, an air gap is provided between the signal transmitter and the support element. In this embodiment, support is provided by the "V" or "Y" arrangement of the guide surfaces, with the recess for the signal transmitter preferably located at the apex of the support element.

[0041] In one embodiment, one of the support elements comprises a flat guide surface and two support surfaces flanking the flat guide surface.

[0042] As an alternative to a "V" or "Y" arrangement of two flat guide surfaces, one of the support elements can comprise a flat guide surface and two support surfaces that preferably guide the steering rod laterally. The support surfaces and the guide surface can be arranged together in a "U" shape, such that the flat guide surface is located at the apex of the U.

[0043] The support surfaces are preferably arranged symmetrically around the guide surface and support the guidance of the steering rod.

[0044] In one embodiment, the support surfaces are adapted to the cross-sectional profile of the steering rod.

[0045] The steering rod can have different profiles. Preferably, steering rods with round or circular cross-sectional profiles are used. In some embodiments, however, the steering rod can also be elliptical or oval, which can provide additional protection against rotation of the steering rod around its longitudinal axis. The support surfaces are adapted to the cross-sectional area and shape of the steering rod so that, in addition to the guide surfaces, they also provide support to the steering rod. Advantageously, by using the adapted support surfaces, the guide surface of the corresponding support element and the receiving surface on the steering rod can be made smaller, which simplifies the manufacture of the steering system and, in particular, the steering rod. The support surfaces prevent the steering rod from shifting transversely to the orientation of the guide surface and thus stabilize the steering rod.

[0046] In one embodiment, the edges of the guide surfaces are rounded in the axial direction of the steering rod.

[0047] The steering rod must move axially to perform its function. The guide surfaces positively limit the lateral movement of the steering rod.

[0048] In one embodiment, the guide surfaces are made of a friction- and wear-resistant material, e.g. ceramic, sinter, bronze, brass or a plastic.

[0049] In another aspect, the invention relates to a steering rod guide with a first support element and a second support element, as described above.

[0050] In summary, the present invention provides a steering system with a steering rod guide and a steering rod guide.

[0051] The described configurations and training programs can be combined in any way desired.

[0052] Further possible embodiments, developments, and implementations of the invention also include combinations of features of the invention described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. Brief description of the drawings

[0053] The accompanying drawings are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain the principles and concepts of the invention.

[0054] Other embodiments and many of the aforementioned advantages become apparent with reference to the drawings. The elements depicted in the drawings are not necessarily shown to scale.

[0055] They show:

[0056] Figs. 1a and 1b show a first embodiment for a steering rod guide with four

[0057] Guide surfaces;

[0058] Figs. 2a and 2b show a second embodiment for a steering rod guide with three guide surfaces, wherein one guide surface is located directly on the signal transmitter; and

[0059] Figs. 3a and 3b show a third embodiment for a steering rod guide with three flat support surfaces and an additional round support area.

[0060] In the figures of the drawings, identical reference symbols denote identical or functionally equivalent elements, parts or components, unless otherwise stated.

[0061] Fig. 1a shows a section of a steering rod guide 10 in a steering system. Fig. 1b shows the same section of the steering rod guide 10 from a different perspective.

[0062] The steering rod guide 10 has a first support element 12 and a second support element 14 for stabilizing a steering rod 16. The support elements 12 and 14 enclose the steering rod 16 in such a way that it cannot move in a direction perpendicular to its extension. The first support element 12 is the upper support element in Figures 1a and 1b. It has two flat guide surfaces 18 and 20 to limit the movement of the steering rod. The guide surfaces 18 and 20 are in contact with receiving surfaces 22 of the steering rod 16, which are milled out of the steering rod 16.

[0063] A signal transmitter 26 is arranged on the steering rod 16, which a linear displacement sensor 28 uses to determine the position of the steering rod 16. The steering rod 16 moves axially through the steering rod guide 10, so that the signal transmitter 26 moves beneath the linear displacement sensor 28. Depending on the response of the signal transmitter 26 to a measurement signal, the position of the steering rod 16 can be determined from the linear displacement sensor data.

[0064] When using, for example, an inductive linear displacement sensor, the amplitude or voltage is measured. However, these measured values ​​depend not only on the position of the signal transmitter 26 under the linear displacement sensor 28. The distance between the linear displacement sensor 28 and the signal transmitter 26 also plays a role. Therefore, it is important to keep this distance as constant as possible.

[0065] The first support element 12 also has a recess 24. In order to allow the signal transmitter 26 to move freely and without damage through the steering rod guide 10 with the steering rod 16, the recess 24 creates an air gap between the signal transmitter 26 and the first support element 12.

[0066] The first support element 12 is preferably arranged close to the linear displacement sensor 28 and structurally connected to it, for example by a steering system housing. Although the steering rod 16 should be made of a rigid material, it can deform under sufficient forces, so that the distance between the signal transmitter 26 and the linear displacement sensor 28 may be smaller or larger than a target value. The closer the linear displacement sensor 28 is arranged to the steering rod guide 10, the smaller this deviation will be.

[0067] The second support element 14 also has two guide surfaces 30 and 32, which are in contact with corresponding receiving surfaces 34 of the steering rod 16. Together with the guide surfaces 18 and 20, the guide surfaces 30 and 32 form a prism in cross-section that encloses the steering rod 16. The geometry of the guide surfaces ensures that the steering rod can only move in the axial direction, but not perpendicular to it. Rotation about the longitudinal axis is also prevented by the guide surfaces 18, 20, 30, and 32.

[0068] The second support element 14 has a return element, which in the illustrated embodiment is designed as a spring 36. The spring 36 presses the second support element 14 against the steering rod, so that it is fixed perpendicular to its axis with a certain amount of pressure, yet remains flexible. If the force exerted by the steering rod 16 on the steering rod guide 10 becomes too great, the spring 36 can yield and the second support element 14 moves. This protects the steering rod 16 and / or the steering system from damage.

[0069] The use of a spring in the first support element 12 would be unsuitable, however, since the air gap between the signal transmitter 26 and the linear displacement sensor 28 is already quite small. If the steering rod 16 were able to move upwards, or in the direction of the first support element 12, the linear displacement sensor 28 and / or the signal transmitter 26 could be damaged by a collision.

[0070] In the illustrated embodiment, the spring 36 has an adjusting screw 38 with which the force of the spring 36 can be adjusted. This allows the play and, depending on the spring rate, the desired preload force to be adjusted.

[0071] Fig. 2a shows a section of an alternative embodiment of a steering rod guide 10. Fig. 2b shows the same section from a different perspective. In this embodiment, the steering rod guide 10 has a first support element 12 which rests directly on the signal transmitter 26 with its guide surface 18. This embodiment has the advantage that less material needs to be removed from the steering rod 16 to form at least three flat receiving surfaces 34 for the guide surfaces 18, 30, and 32. In this embodiment, the steering rod 16 comprises two receiving surfaces 34 and the signal transmitter 26, which is flat anyway.

[0072] Since the signal transmitter 26 is in direct contact with the first support element 12, this arrangement is only suitable for steering systems in which the signal transmitter 26 is made of a sufficiently strong and resistant material.

[0073] A further advantage arises from the geometry of the first support element 12. This can be significantly less complex than the corresponding counterpart from Figures 1 a and 1 b.

[0074] Fig. 3a shows a section of another embodiment of a steering guide 10. Fig. 3b shows the same section from a different perspective.

[0075] The embodiment shown in Figures 3a and 3b shares the first support element 12 with the embodiment shown in Figures 1a and 1b. This first support element 12 also includes a recess 24 for the signal transmitter 26 and two guide surfaces 18 and 20.

[0076] However, the second support element 14 differs from the second support element 14 shown in Figures 1a and 1b.

[0077] In this embodiment, the second support element 14 has a flat guide surface 40 which, under light load, is not in contact with the steering rod 16. This reduces the frictional area, thereby reducing friction and the sliding force. The guide surface 40 is, however, flanked by two support surfaces 42 and 44. In the context of the invention, "flanked" means that the support surfaces 42 and 44 extend on both sides of the guide surface 40 and within the plane perpendicular to the direction of movement of the steering rod 16. The support surfaces 42 and 44 assist in guiding the steering rod 16 by preventing lateral movement of the steering rod 16.

[0078] Under high load and the resulting slight tilting of the steering rod, the guide surface 40 also comes into contact and limits the tilting of the steering rod. This distributes the torsional moment evenly across three contact surfaces (18, 20, and 40). Reducing the tilting is necessary to prevent the air gap between the signal transmitter and the linear displacement sensor from changing excessively. Otherwise, the quality of the linear displacement sensor signal would deteriorate, or contact between the two components could occur.

[0079] In contrast to the embodiment shown in Figures 1a and 1b, the steering rod needs to have fewer receiving surfaces, which makes its manufacture less complex and therefore cheaper.

[0080] All embodiments have in common that the guide and support layers can be provided with rounded edges. Rounded edges on these surfaces have the advantage of reducing the friction of the steering rod 16 against the corresponding surfaces and improving the sliding of the steering rod 16 through the steering rod guide 10. This advantage is particularly relevant when lateral forces act on the steering rod, which would be especially large at the edges of the guide surfaces 18, 20, 30, and 32.

[0081] Furthermore, the guide and / or support surfaces can be made of a material that offers good sliding properties but also high robustness. For example, low-wear ceramics, metals, or plastics can be used for this purpose.

[0082] Alternatively, the guide and / or support surfaces can be provided with a coating that promotes sliding.

[0083] Furthermore, the embodiments shown here can include a steering system housing (not shown here) through which the individual components, in particular the first support element 12, the linear displacement sensor 28 and a holder for the return element of the second support element 14, are structurally connected to each other.

[0084] Alternatively, the components can be connected via other structural measures, for example, beams joined to form a framework or the body of a vehicle.

[0085] vehicle. It is particularly important that the first support element 12 and the linear displacement sensor 28 do not move relative to each other. However, it is generally advantageous to limit the movement of the steering rod 16 in directions perpendicular to its axis of extension.

Claims

Claims 1. Steering system comprising an axially movable steering rod (16), a linear displacement sensor (28) for determining the steering rod position, and a steering rod guide (10), wherein the steering rod guide (10) comprises a first support element (12) and a second support element (14), wherein the support elements (12, 14) together comprise at least three planar guide surfaces (18, 20, 30, 32), wherein the steering rod (16) comprises at least three planar receiving surfaces (22, 34) for the guide surfaces (18, 20, 30, 32) of the support elements (12, 14), wherein the steering rod (16) comprises a signal transmitter (26) extending in the axial direction of the steering rod (16), and wherein the support elements (12, 14) are arranged around the steering rod (16) such that • the support elements (12, 14) extend perpendicular to the axial direction of the steering rod (16), • the support elements (12, 14) are arranged on two opposite sides of the steering rod (16) and enclose the steering rod (16); and • the signal transmitter (26) is located between the first support element (12) and the steering rod (16).

2. Steering system according to claim 1, wherein the second support element (14) is movably mounted perpendicular to the direction of movement of the steering rod (16) and comprises a return element, wherein the return element presses the second support element (14) against the steering rod (16).

3. Steering system according to claim 2, wherein the second support element (14) comprises an adjusting screw (38) for the return element, wherein with the The adjusting screw (38) allows for adjustment of the play between the return element and the steering rod (16).

4. Steering system according to one of the preceding claims, wherein the first support element (12) is structurally connected to the linear displacement sensor (28).

5. Steering system according to one of the preceding claims, wherein the steering system comprises a steering rod housing and wherein the support elements (12, 14) and the linear displacement sensor (28) are rigidly connected to the steering rod housing.

6. Steering system according to one of the preceding claims, wherein the first support element (12) and the second support element (14) each comprise two guide surfaces (18, 20, 30, 32).

7. Steering system according to claim 6, wherein the guide surfaces (18, 20, 30, 32) of the first support element (12) and the second support element (14) are arranged symmetrically to each other.

8. Steering system according to claim 7, wherein the first support element (12) has a recess (24) for the signal transmitter (26), such that an air gap is located between the first support element (12) and the signal transmitter (26).

9. Steering system according to one of claims 1 to 6, wherein one of the support elements (12, 14) comprises a flat guide surface (40) and two support surfaces (42, 44) flanking the flat guide surface (40).

10. Steering system according to claim 9, wherein the shape of the support surfaces (42, 44) is adapted to the cross-sectional profile of the steering rod (16).

11. Steering system according to one of the preceding claims, wherein the edges of the guide surfaces (18, 20, 30, 32) are rounded in the axial direction of the steering rod (16).

12. Steering system according to one of the preceding claims, wherein the guide surfaces (18, 20, 30, 32) are made of a friction- and wear-resistant material are made of a material, in particular ceramic, sinter, bronze, brass or a plastic.

13. Steering rod guide (10) with a first support element (12) and a second support element (14) according to one of the preceding claims.

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