Steering gear for a motor vehicle steering system with marked timing belt

Abstract

The invention relates to a steering gear for a steering system of a motor vehicle, comprising a housing and a steering rod arranged at least partially in an interior of the housing, which is mounted via a conversion gear and can be connected to a tie rod at each axial end section; a drive unit comprising an electric machine and the conversion gear coupled to the electric machine via a toothed belt (10), wherein the toothed belt (10) has at least one marking (12), wherein the at least one marking (12) is formed from at least one metal fiber, and wherein the steering gear further comprises a sensor (14) for detecting the marking (12).

Description

[0001] The invention relates to an electronically assisted steering gear and lies in the field of vehicle construction, in particular steering systems for motor vehicles.

[0002] Electronically assisted steering systems and steering gears for motor vehicles are well known. In such vehicles, an EPS (electric power steering) system controls and assists the steering with the help of an electric motor. This improves steering feel for the driver and provides additional safety in the event of a fault. In advanced versions, an EPS can take over the steering control of autonomous vehicles.

[0003] There are many options available for transferring the torque of an EPS electric motor to the steering gear of the steering system. One option is to couple the electric motor to the steering gear with a toothed belt. A ball screw drive can be an essential component of a steering system.

[0004] The electric motor serves to assist the steering movements and provide the required power. The steering system's control unit generates a control signal based on the torque detected by a sensor on the steering shaft. This control signal is sent to the electric motor to generate the appropriate power for the steering movement.

[0005] A timing belt serves as the connecting element between the electric motor and the ball screw. The timing belt is tightly stretched around a pulley on the electric motor and a pulley on the ball screw. When the electric motor is activated, it exerts torque on the pulley, causing the timing belt to rotate.

[0006] The ball screw consists of a lead screw and a nut connected to the steering gear. The lead screw has a spiral thread on which balls are located. The nut contains a matching thread that corresponds to the lead screw. When the lead screw rotates, the balls move forward or backward in the nut, depending on the direction of rotation of the screw.

[0007] The torque transmitted from the electric motor to the ball screw via the timing belt causes the lead screw to rotate. This rotation causes the balls in the nut to move forward or backward. Since the nut is connected to the steering gear, this movement results in a corresponding steering movement of the vehicle.

[0008] Timing belt tension can decrease over time. If the tension is insufficient, slippage may occur between the belt and the pulleys, resulting in poor steering performance. It is therefore beneficial to know the condition of the timing belt and monitor it. The timing belt may have a marking to help monitor the condition.

[0009] From the document DE 10 2020 128 355 A1, a belt tension monitoring device for monitoring the belt tension of a belt of a belt drive system is known. The belt drive system comprises a drive pulley and a driven pulley, which is rotated by the drive pulley thanks to the belt. The belt tension monitoring device is designed to determine the belt slippage effect using at least one marker provided on the belt and a sensor. The sensor is designed to detect the marker and send a signal to an electronic control unit. The marker consists of a magnetized area, such as a magnet or magnetized rubber, attached to a surface of the belt, or a magnetic powder embedded in or on the belt.

[0010] The invention is therefore based on the object of proposing a steering gear with an alternative marking option.

[0011] The problem is solved by the subject matter of the independent claims. Disclosure of the invention

[0012] According to a first aspect of the invention, this object is achieved by a steering gear for a steering system of a motor vehicle, having a housing and a steering rod which is arranged at least in sections in a housing interior, which steering rod is mounted via a conversion gear and can be connected to a tie rod at each of its axial end sections, a drive unit having an electric machine and the conversion gear which is coupled to the electric machine via a toothed belt, wherein the toothed belt has at least one marking, wherein the at least one marking is formed from at least one metal fiber, and wherein the steering gear further comprises a sensor for detecting the marking.

[0013] In order to meet the requirements of strength, durability and performance of a timing belt in a steering system, metal fibers are used as a marker according to the invention.

[0014] The metal fiber can, for example, consist of a combination of different metals, particularly an alloy. The metals can be selected to achieve optimal properties for the respective steering system. For example, trucks may have different requirements for the timing belt than cars.

[0015] For example, steel alloys with special additives such as chromium, nickel, and molybdenum can be used to ensure high strength, corrosion resistance, and temperature resistance. The alloy composition is precisely controlled to achieve the desired mechanical properties, including the required elasticity, tensile strength, and wear resistance.

[0016] The metal fiber can be produced through a complex manufacturing process. First, the selected metals are alloyed together in a melt and then drawn into a strand to form a continuous fiber. This fiber is then shaped through several stages of cold working and heat treatment to achieve the desired mechanical properties. These process steps make the fiber particularly resistant to mechanical stress and exhibit high rigidity, ensuring efficient torque transmission.

[0017] The surface of the metal fiber can be further improved with special coatings or finishes. A thin layer of a wear-resistant material such as tungsten carbide can be applied to increase the durability and service life of the fiber. This is especially important because timing belts in steering systems are subject to high loads and friction.

[0018] The use of metal fibers as markers in timing belts for steering systems can be less susceptible to wear and prevent breakage of the timing belt due to their high strength and durability. Furthermore, the properties of the marker can be adjusted by selecting the metal of the metal fiber. The proposed steering gear thus achieves the objective of the invention.

[0019] In one embodiment, the sensor is a magnetic, inductive or capacitive sensor.

[0020] A magnetic sensor is an electronic device capable of detecting magnetic fields and converting them into electrical signals. The operation of a magnetic sensor is based on the principle of magnetoresistive or Hall-effect sensors. In magnetoresistive sensors, the electrical resistance of a magnetoresistive element changes depending on the strength and direction of the magnetic field. This change in resistance is measured and converted into an electrical signal. Hall-effect sensors, on the other hand, utilize the Hall effect, in which an electrical voltage is generated perpendicular to a current flowing in a magnetic field. The strength of the generated voltage is proportional to the strength of the magnetic field and is detected by the Hall sensor. In both cases, these sensors enable the precise detection of magnetic fields.

[0021] An inductive sensor is an electronic device based on the principle of electromagnetic induction to detect the presence or absence of a metallic object. The operation of an inductive sensor relies on an oscillator that generates a high-frequency alternating voltage. This voltage is passed through a coil placed near the object to be detected. When a metallic object approaches the sensor, the magnetic field of the coil is influenced by the metallic object, thereby changing the coil's inductance. This change is detected by the sensor, and an electrical signal is generated indicating the presence of the metallic object.

[0022] A capacitive sensor is based on the principle of capacitance change to detect the presence or approach of an object. The operation of a capacitive sensor is based on an electric field generated between the sensor and the object to be detected. The sensor consists of one or more electrodes supplied with an electrical voltage. When an object moves close to the sensor, it changes the electric field and thus the capacitance between the electrodes. This capacitance change is detected by the sensor, and an electrical signal is generated that indicates the presence or approach of the object. Capacitive sensors are characterized by high sensitivity and precision.

[0023] The sensor types mentioned are advantageously particularly well-suited for detecting metal fibers in an otherwise non-metallic object. For example, the sensors can be designed to detect the presence of a metallic object within a certain radius. This radius can be a few centimeters, for example.

[0024] In embodiments, the sensor can be configured to detect the position or distance of a marker from the sensor. The position or distance can, for example, be associated with different values ​​of the monitored variable.

[0025] In one embodiment, the metal fiber is formed of ferromagnetic metal.

[0026] Ferromagnetic metal fibers are special metal fibers made from materials that exhibit a strong magnetic response. Ferromagnetic metal fibers can be made from alloys containing iron, nickel, or cobalt, for example, because these metals have high magnetic permeability. The ferromagnetic nature of these metals allows the fibers to attract or repel magnetic fields, making them suitable for use in magnetic applications.

[0027] Ferromagnetic metal fibers are manufactured using various processes, such as melt spinning. In this process, the alloy is melted in liquid form and then drawn into a fiber. The fiber can have various diameters and lengths, depending on the specific requirements of the application.

[0028] Due to their magnetic properties, ferromagnetic metal fibers enable precise detection by a magnetic sensor. In a further development, this can be enhanced by external fields.

[0029] In one embodiment, the metal fiber is embedded in the material of the timing belt and the material of the timing belt completely or partially encloses the metal fiber.

[0030] Partially or completely enclosing the metal fiber advantageously improves the integrity of the timing belt. For example, the metal fiber can be completely enclosed in a flexible material, reducing the likelihood of the metal fiber becoming detached from the timing belt and damaging the timing belt or steering gear.

[0031] In a further embodiment, the toothed belt comprises a base body formed from fibers and the metal fiber is woven or braided into the base body of the toothed belt.

[0032] Timing belts with a fiber core are often more stable than those cast, sintered, or vulcanized from plastic. A metal fiber can be advantageously woven or braided into a fibrous core, further increasing the durability of the marking.

[0033] In one embodiment, the fibers of the base body are made of a paramagnetic material.

[0034] The base body of the timing belt should preferably be made of a different material than the metal fibers, otherwise the metal fibers will not form a marking against the background of the timing belt. The base body should preferably be made of a paramagnetic material if a magnetic or inductive sensor is used. A paramagnetic base body provides a good sensory contrast to a metal fiber serving as a marking. The use of metal fibers in a paramagnetic base body advantageously improves the detection of the marking.

[0035] In one embodiment, the metal fiber is introduced into the timing belt transversely to the direction of rotation.

[0036] By inserting the metal fiber perpendicular to the direction of rotation, the marking can easily extend across the entire width of the timing belt or just a portion of it. The timing belt moves in the direction of rotation, so a marking running perpendicular to the direction of rotation is particularly suitable for indicating a specific position or setting of the timing belt.

[0037] In one embodiment, the at least one marking comprises a first and a second marking. The markings are arranged at a defined distance from one another in the circumferential direction of the toothed belt.

[0038] On a new timing belt, the markings are spaced at a fixed distance from each other. Since the timing belt rests on the drive and driven pulleys with a certain amount of tension, it will sag and wear out over time. As this happens, the distance between the markings also increases.

[0039] Furthermore, the timing belt can also expand in hot conditions, especially on hot summer days, so that the tension may not be sufficient to ensure the operation of the drive unit.

[0040] Advantageously, the two markings spaced apart in the direction of rotation can be used to indicate the age of the timing belt and / or the expansion under heat.

[0041] In one embodiment, the toothed belt has a defined width and a plurality of markings are arranged in the circumferential direction in tracks, each extending over a part of the width of the toothed belt.

[0042] Advantageously, this arrangement of the markings allows multiple pieces of information to be marked in the timing belt, which can improve the precision of the position determination on the timing belt.

[0043] In a further aspect, the invention relates to a toothed belt, in particular for a steering gear as described above, wherein the toothed belt has at least one marking which is formed from at least one metal fiber.

[0044] Timing belts with metal fiber markings can also be used advantageously in applications other than steering gears. For example, timing belts can be used as conveyor belts, V-belts, drive belts in motor vehicles, or generally as timing belts.

[0045] In a further aspect, the invention relates to a computer-implemented method for determining a state of a steering gear, as described above, using two or more markings. The steering gear is further configured to determine a steering position using a control unit, the method comprising the following steps: - Detecting a first mark; - Detecting a second mark; - Determining a distance between the first mark and the second mark by the control unit; - Comparing the determined distance with the defined distance between the first mark and the second mark and determining a difference between the determined distance and a defined distance between the marks; - Determining the condition of the steering gear from the difference determined.

[0046] The proposed computer-implemented method can advantageously be used to detect or monitor an aging process of the steering gear, in particular of the toothed belt. This can prevent misuse of a toothed belt, for example, beyond a permissible age.

[0047] In one embodiment, the determination of the condition of the toothed belt for the steering gear from the determined difference is carried out using a threshold value, wherein the condition of the toothed belt lies within a normal range if the determined difference is below the predetermined threshold value, and wherein the condition of the toothed belt lies outside the normal range if the determined difference exceeds the predetermined threshold value.

[0048] Advantageously, the threshold value can be used to adjust how sensitively the status detection reacts to fluctuations. Fluctuations can arise, for example, from temperature differences. At high temperatures, the timing belt material expands, so the difference tends to be larger. At low temperatures, the timing belt material contracts, so the difference is smaller or even negative.

[0049] In a further aspect, the invention relates to a method for producing a toothed belt with the properties described above. The method comprises the steps: - Creating a base body made of fibers; - Inserting, braiding or weaving a metal fibre as a marker into the base body; - Casting the base body with a flexible material; and - Vulcanizing the flexible material.

[0050] Preferably, the flexible material completely encloses the base body with the metal fiber markings. This can increase the service life of the timing belt.

[0051] Overall, a steering gear with a toothed belt, a toothed belt, a computer-implemented method for detecting markings and a method for producing a toothed belt with markings made of metal fibers are specified.

[0052] The described designs and further training courses can be combined as desired.

[0053] Further possible embodiments, further developments and implementations of the invention also include combinations of features of the invention described previously or below with regard to the embodiments that are not explicitly mentioned. Short description of the drawings

[0054] The accompanying drawings are intended to provide a further understanding of embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention.

[0055] Other embodiments and many of the aforementioned advantages will become apparent upon review of the drawings. The elements illustrated in the drawings are not necessarily drawn to scale.

[0056] They show: Fig. 1 shows a perspective schematic representation of a toothed belt for a steering gear according to an embodiment; Fig. 2 shows a perspective schematic representation of a toothed belt for a steering gear with two markings; Fig. 3 shows a perspective schematic representation of a toothed belt for a steering gear with a base body formed from fibers; Fig. 4 shows a perspective schematic representation of a toothed belt with several markings arranged in several rows across the width of the toothed belt; and Fig. 5 schematically shows the sequence of a method for determining a condition of a toothed belt.

[0057] In the figures of the drawings, the same reference symbols designate the same or functionally equivalent elements, parts or components, unless otherwise stated.

[0058] Fig. Figure 1 shows a schematic representation of a toothed belt 10 according to one embodiment. The toothed belt 10 includes a marking 12 made of metal fibers. In this embodiment, the marking 12 extends across the entire width B of the toothed belt 10. The width B extends transversely to the direction of rotation U.

[0059] The toothed belt 10 is designed to move in or against the direction of rotation U over a drive pulley and a driven pulley (both not shown). With the movement of the toothed belt 10, the marking 12 also moves relative to the steering gear in which the toothed belt 10 is used.

[0060] A sensor 14 is designed to detect the position of the toothed belt 10. The sensor 14 can, for example, be a capacitive sensor that examines the electric field in its surroundings. If the marking 12, consisting of metal fibers, is moved toward the sensor 14, the electrical capacitance measured by the sensor 14 increases. If the marking 12 is moved away from the sensor 14 due to the movement of the toothed belt 10, the measured capacitance decreases. Each position of the marking 12 can be assigned a specific capacitive value so that the sensor 14 can determine the position of the marking 12. Alternatively, the sensor 14 or a computing unit (not shown) communicatively connected thereto can be designed to calculate a position of the marking from the determined value. From the position of the marking, a position of the toothed belt can be derived, which corresponds to a specific angle of rotation in the direction of rotation U.

[0061] Fig. Figure 2 schematically shows another embodiment of a toothed belt 10. In this embodiment, the toothed belt 10 has two markings 12, each extending across the entire width B of the toothed belt 10. The distance L between the markings 12 is fixed for new toothed belts 10.

[0062] Over time, a timing belt 10 can wear out, with the material of the timing belt 10 expanding. This means that the circumference of the timing belt 10 increases and the distance L becomes larger. One or more sensors 14 can detect the markings 12.

[0063] If the embodiment has only one sensor 14, the sensor 14 can detect the markings 12 one after the other when the toothed belt 10 is moved, particularly during a steering movement. The detection can be used, together with the setting angle set by the toothed belt drive during the steering movement, to calculate the distance between the markings 12.

[0064] For example, if the drive rotates the drive pulley 360°, i.e., once completely, the timing belt 10 travels the same distance as the circumference of the drive pulley. If the sensor 14 detects both markings 12 during this movement, it can be checked whether the markings 12 are still spaced apart by a length L. If the distance between the markings 12 is greater than the distance L, this is a sign of aging of the timing belt 10 and an indicator that it needs to be replaced.

[0065] Fig. 3 shows a further embodiment of a toothed belt 10 with a marking 12. In this embodiment, the toothed belt 10 comprises a base body 16 formed from fibers. The metal fibers that form the marking 12 are incorporated, in particular woven, into the base body 16.

[0066] In embodiments, the structure comprising the base body 16 and the metal fiber can additionally be coated with a vulcanized material that protects the base body 16 and the metal fibers.

[0067] Fig. 4 schematically shows a further embodiment of a toothed belt 10. This toothed belt 10 comprises, as the embodiment of Fig. 3, a base body 14 formed of fibers. The metal fibers forming the markings 12 are incorporated into the base body 14.

[0068] In this embodiment, the markings 12 do not extend across the entire width B of the toothed belt 10. Instead, they are distributed in two tracks arranged in the circumferential direction across the width B of the toothed belt 10. In further embodiments, multiple tracks of markings 12 can also be incorporated into the toothed belt 10. Furthermore, it is also possible for a toothed belt 10 with a base body 14 that is not made of fibers to have markings 12 arranged in multiple tracks.

[0069] The markings 12 can be spaced at different distances from one another. Preferably, the spacing between the markings 12 is configured such that no distance between two markings 12 is identical to any other distance. By arranging the markings 12 in multiple tracks, and in particular at different spacings, the toothed belt 10 is given a magnetic, inductive, and / or capacitive pattern that appears different at each position in the direction of rotation. A magnetic, inductive, or capacitive sensor 14 can be configured to detect the pattern and thus identify the position of the toothed belt 10. In other words, by incorporating multiple markings 12 into two or more tracks, the toothed belt 10 can be coded so that its position can be clearly determined.

[0070] Fig.Figure 5 schematically shows the sequence of one aspect of the invention. In a first step S10, a sensor detects a first marking. In a second step S12, a sensor detects a second marking. The same sensor can be used to detect the markings. Alternatively, different sensors can be used.

[0071] Using the sensor(s), a distance between the markings is determined in step S14. Additional factors, such as a positioning angle or a torque of the drive unit, can be used to determine the distance. Furthermore, the distance between the markings can be determined, for example, from the temporal evolution of the magnetic, inductive, and / or capacitive pattern of the timing belt during its movement.

[0072] The determined distance between the markings is compared in step S16 with a defined distance between the markings. The defined distance can, in particular, be the distance between the markings of a new, i.e., non-aged, timing belt.

[0073] Comparing involves calculating the difference between the measured and the defined distance. If the difference is significantly greater than 0, this indicates that the timing belt has aged and worn out, or has expanded due to heat.

[0074] In the last step S18, a condition of the timing belt is determined or derived from the difference.

[0075] In one embodiment, the aforementioned difference can be determined and examined over a longer period of time. If the difference is consistently increasing or an upward trend is evident, the cause of the increasing distance between the marks may be the aging of the timing belt. However, if the difference is only occasionally excessive, this may indicate that the timing belt is overheating and therefore expanding.

[0076] The timing belt can become hot, for example, due to heavy stress and the resulting movement of the timing belt. However, other effects that don't directly affect the timing belt can also cause heating.

[0077] In any case, an overstretched timing belt may eventually lose its grip on the drive pulley and / or the driven pulley due to a loss of belt tension. In the worst case, the performance of the timing belt may be compromised, resulting in slippage between the timing belt and the drive pulley and / or the driven pulley.

[0078] In one embodiment, the steering gear may include a control unit that generates a signal indicating the condition of the timing belt.

[0079] This can advantageously prompt a driver or mechanic to service and / or replace the steering gear and in particular the timing belt. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 128 355 A1

[0009]

Claims

[1] Steering gear for a steering system of a motor vehicle, comprising: - a housing and - a steering rod arranged at least in sections in a housing interior, which is mounted via a conversion gear and can be connected to a tie rod at each of its axial end sections; - a drive unit comprising an electric machine and the conversion gear coupled to the electric machine via a toothed belt (10), wherein the toothed belt (10) has at least one marking (12), wherein the at least one marking (12) is formed from at least one metal fiber, and wherein the steering gear further comprises a sensor (14) for detecting the marking (12). [2] Steering gear according to claim 1, wherein the sensor (14) is a magnetic, inductive or capacitive sensor (14). [3] Steering gear according to one of the preceding claims, wherein the metal fiber is formed from a ferromagnetic metal. [4] Steering gear according to one of the preceding claims, wherein the metal fiber is inserted into the material of the toothed belt (10) and the material of the toothed belt (10) completely or partially encloses the metal fiber. [5] Steering gear according to one of the preceding claims, wherein the toothed belt (10) comprises a base body (16) formed from fibers and wherein the metal fiber is woven or braided into the base body (16) of the toothed belt (10). [6] Steering gear according to claim 5, wherein the fibers of the base body (16) are formed from a paramagnetic material. [7] Steering gear according to one of the preceding claims, wherein the metal fiber is introduced into the toothed belt (10) transversely to the direction of rotation (U). [8] Steering gear according to one of the preceding claims, wherein the at least one marking (12) comprises a first marking (12) and a second marking (12), wherein the markings (12) are arranged at a defined distance (L) from one another in the circumferential direction (U) of the toothed belt. [9] Steering gear according to one of the preceding claims, wherein the toothed belt (10) has a defined width (B) and wherein a plurality of markings (12) are arranged in the circumferential direction (U) in tracks which each extend over a part of the width (B) of the toothed belt (10). [10] Toothed belt (10), in particular for a steering gear according to one of the preceding claims, wherein the toothed belt (10) has at least one marking (12), wherein the at least one marking (12) is formed from at least one metal fiber. [11] A computer-implemented method for determining a condition of a toothed belt for a steering gear according to claim 10, comprising the steps: - detecting the first mark (12); - detecting the second marking (12); - Determining a distance between the first marking (12) and the second marking (12) by the control unit; - comparing the determined distance with the defined distance (L) between the first marking (12) and the second marking (12) and determining a difference between the determined distance and the defined distance (L); - Determine the condition of the steering gear timing belt from the difference determined. [12] Computer-implemented method according to claim 11, wherein the determination of the condition of the toothed belt for the steering gear from the determined difference is carried out using a threshold value, wherein the condition of the toothed belt is within a normal range if the determined difference is below the predetermined threshold value, and wherein the condition of the toothed belt is outside the normal range if the determined difference exceeds the predetermined threshold value. [13] A method for manufacturing a toothed belt (10) according to claim 10, the method comprising the steps of: - creating a base body (16) made of fibres; - inserting, braiding or weaving a metal fibre as a marker (12) into the base body (16); - Casting the base body (16) with a flexible material; and - Vulcanizing the flexible material.

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