Driving connector for a motor vehicle steering system

Abstract

The invention relates to a driving connector (1) for a motor vehicle steering system, comprising an input steering shaft (3) which is arranged so as to be rotatable about a central longitudinal axis (6), wherein the input steering shaft (3) has a bore (5) for a torsion bar (4), and the input steering shaft (3) comprises a drive profile (11) at one end, and the driving connector (1) further comprises an output steering shaft (2) which is arranged so as to be rotatable about the central longitudinal axis (6), wherein the output steering shaft (2) has an output profile (12) at one end, and the drive profile (11) and the output profile (12) form a stop region (7.2) when rotated.

Description

The invention relates to a driver connector for a motor vehicle steering system, for example an electrically assisted motor vehicle steering system, preferably with a mechanical passage, in particular in a wheel vehicle, such as a passenger vehicle.A motor vehicle steering system of conventional design with a mechanical pass-through establishes a mechanical connection between a steering handle and the steered wheels of a motor vehicle by means of a steering column. The steering torque applied to the steering handle by a motor vehicle driver is transmitted via the steering column to a rack which moves transversely to the direction of travel and is connected to the steered wheels.To assist the steering force, a steering force assistance device can be used, which amplifies the steering force of the vehicle driver. As a result, the vehicle can be safely steered with a lower hand force. In addition, with such a drive, an assistance function for semi-autonomous driving or a lane keeping assist can be implemented. In this case, the steering force of the vehicle driver is superimposed with an assistance force of the assistance device. In order that the auxiliary force is applied as unnoticed as possible by the motor vehicle driver, it is necessary, in particular in the case of an electric steering force assistance, to measure the steering torque applied by the motor vehicle driver. For this purpose, the steering column has an input and an output steering shaft which are connected to one another via a torsion rod. A steering torque is applied by the driver via the input steering shaft, which steering torque is detected via a sensor on the torsion bar. According to the steering torque, an assist force is applied to the output steering shaft.If the steering handle is rotated beyond a permissible range, there is the risk that the torsion rod will be overrotated to an impermissible extent. In order to prevent this, the input steering shaft is connected to the output steering shaft via a stop as soon as an admissible angle of rotation is exceeded. This stop region between the input and output steering shafts also serves to absorb load peaks, such as occur when getting in or out, if the motor vehicle driver is supported on the steering wheel. A rotation of the steering handle in the standstill, i.e. without support device, is also absorbed by the stop device.A plurality of stop devices are known from the prior art. When the input steering shaft is rotated beyond the allowable range, a portion of the input steering shaft comes into contact with and connects the output steering shaft to each other, thereby protecting the torsion bar. DE 10 2015 002 686 discloses an input steering shaft which has a stop device. For the transmission of torque, the input steering shaft has a receiving region with an arcuate toothing in the form of a cloverleaf profile. This profile engages in a complementary-shape recess in the output steering shaft. If the input steering shaft is rotated beyond a permissible range, the four stop points of the cloverleaf profile come into contact with the corresponding cloverleaf profile of the output steering shaft.From KR 20 140 026 927 A an input steering shaft with a rectangular cross-section is known. The rectangular cross section engages in a complementary-shape recess in the output steering shaft, wherein an intermediate sleeve is introduced into the intermediate region.The requirements of enlarging the useful space of a vehicle and consequently of making steering systems more space-saving have the result that individual components of the steering system, such as a driver connector between the input and output steering shafts, must also have smaller dimensions. This leads to a higher surface pressure, with the result that the driver connector is plastically deformed and the function is thereby impaired over the product life cycle and, in the worst case, the driver connector rotates. Thus, there would no longer be any stop for the input steering shaft and the torsion bar would be irreversibly damaged.The reduced geometrical dimensions of the input and output steering shaft and the torsion bar also reduce the stop surface between the input and output steering shaft.It is therefore the object of the present invention to overcome the disadvantages of the prior art, in particular to specify a driver connector with small dimensions and high fatigue strength.This object is achieved by a driver connector of a motor vehicle steering system according to claim 1. according to which the driver connector comprises an input steering shaft which is arranged rotatably about a central longitudinal axis, wherein the input steering shaft has a bore for a torsion bar, and the input steering shaft comprises a drive profile at one end, and the driver connector further comprises an output steering shaft which is arranged rotatably about the central longitudinal axis, wherein the output steering shaft has an output profile at one end, and the drive profile and the output profile form a stop region when rotated. According to the invention, the drive profile of the input steering shaft is designed in the stop region to be opposite in shape to the output profile of the output steering shaft.The shape-opposite configuration of the drive and driven profiles provides an enlarged surface in the stop region, as a result of which the surface pressure is reduced despite a smaller installation space dimension. This allows a longer service life of the components to be ensured. In particular, for this purpose, the output steering shaft has a type of pocket in the stop region, into which a terminal region of the input steering shaft engages, as a result of which the force is transmitted over a larger area than in the prior art.Furthermore, the input steering shaft has a bore in which a torsion rod can be accommodated. This bore extends from the one end, at which the drive profile is formed, in the direction of the steering handle.Following the input steering shaft in the direction of the steered vehicle wheels, an output steering shaft is arranged on the central longitudinal axis. The output steering shaft has an output profile at one end, in particular a depression, which is designed to be opposite in shape to the input profile. If the drive and driven profiles are rotated with respect to one another, i.e. either rotated in different directions or rotated in the same direction at different speeds, a stop region is formed. The stop region can occur in the flat contact region only when the drive profile and the driven profile contact between the input and output steering shafts. If the drive and output profile has a repeating structure in the circumferential direction, correspondingly more stop regions are also produced.The drive profile is designed in the stop region opposite in shape to the driven profile. Accordingly, it is provided that the outer shape of the drive profile differs from that of the driven profile, in particular is not shape-corresponding. Instead, it is provided that the drive profile and the driven profile differ from one another in such a way that a distance between the two profiles is not constant along the circumference. This results in an increased surface contact which can transmit the torque in a more material-saving manner, whereby the service life of the drive connector is increased.According to one embodiment, the driver connector is designed such that the drive profile and the driven profile are spaced apart by means of a radial air clearance, wherein the radial air clearance varies in a state free of steering force following the circumference, in particular the radial air clearance varies in the stop region. The radial air clearance is measured starting from the central longitudinal axis and is the distance which results between the drive profile and the driven profile along the circumference. Depending on the number of stop regions, the radial air clearance varies cyclically. If, for example, the driver connector has four stop regions, the course of the radial air clearance would be repeated four times in the case of a complete rotation about the central longitudinal axis.If the driver connector comprises, for example, four stop regions, it can be provided that the radial air clearance is not present at four points, i.e. has the value zero, in a state in which the input and output steering shafts are rotated with respect to one another. This then corresponds to the four stop regions. In a region of the input steering shaft which is opposite the stop region following the circumference, the radial air clearance can be maximum in this case. If the input steering shaft is rotated in the opposite direction in the preceding example, the stop region also migrates from one side to the other side of the input steering shaft. Here, the radial air clearance is likewise maximum on the side opposite the stop region.If the input and output steering shafts are rotated relative to one another, or if they move in the same direction at different speeds, the radial air clearance changes at all points of the drive and output profile.Due to the in particular pocket-shaped configuration of the output profile, the radial air clearance is maximum in a stop region. In the remaining regions of the drive and output profile, the radial air clearance can be substantially less than in a stop region, since here only a rotation of the input and output steering shaft has to be ensured. In addition, the radial air clearance simplifies mounting, since the two profiles can also be mounted slightly tilted with respect to one another and only position themselves correctly with respect to one another as a result of the mounting.According to a preferred embodiment, the input steering shaft and the output steering shaft are spaced apart by means of a circumferential air clearance, wherein the circumferential air clearance is changed if the input steering shaft and the output steering shaft are rotated relative to one another along the central longitudinal axis. Accordingly, the circumferential air clearance describes a distance between the drive profile and the driven profile along a circumferential direction. The circumferential air clearance describes the distance between the drive profile and the driven profile which occurs if the two profiles are rotated relative to one another. If one of the profiles is now rotated relative to the other, the circumferential air clearance also changes and returns to zero if both profiles touch.A further advantageous embodiment provides that the circumferential air clearance in a state free of steering force is of equal magnitude in both rotational directions. A state free of steering force describes any state in which neither forces are exerted by the steered vehicle wheels on the steering handle nor a steering force is applied by the steering handle to the steered vehicle wheels. A state without steering force also describes a state in which the steering force assistance is inactive. In this state, the circumferential air clearance between the drive profile and the driven profile is of equal magnitude in both rotational directions. As a result, the distance covered for connecting the input steering shaft and the output steering shaft in both rotational directions is of the same size.According to a preferred embodiment, a rotational movement between the input steering shaft and the output steering shaft is made possible as soon as the circumferential air clearance is overcome. If greater torques are transmitted than the torsion bar can absorb, the input steering shaft must be mechanically connected to the output steering shaft. For this purpose, it is provided that the input and output steering shafts are connected as soon as the circumferential air clearance is overcome. As a result, the torque is transmitted via the stop region.According to a further aspect of the invention, the torsion bar is fixed in a rotationally rigid manner to the input steering shaft by a first torsion bar end and the torsion bar is fixed in a rotationally rigid manner to the output steering shaft by a second torsion bar end. In order for the torsion bar to be able to absorb the torques occurring, it must be fastened at one end to the input and output steering shafts. In particular, there must be no play between the torsion bar and the input and output steering shaft. For this purpose, the torsion bar can have a toothing and engage in a corresponding recess in the input and output steering shafts.Furthermore, it is provided that a sensor is arranged on the torsion rod for measuring a torsion torque between the input and output steering shafts. In particular, strain gauges (DMS) are suitable for this purpose, which detect the material deformation on a material surface, wherein a torque can be calculated on the basis of the deformation and the geometric dimension.Preferably, the drive profile and the driven profile have a square basic shape, wherein the drive profile has eight corners and the corners are formed in a bulge-like manner from the driven profile. The square basic shape allows the available installation space to be utilized as effectively as possible. In order to nevertheless save installation space, the square basic shape of the drive profile is changed, in particular the corners have been cut off, resulting in the octagonal shape of the drive profile. The output profile also has a square basic shape, but has curved corners into which the input profile engages. The bulged corners of the output profile form the stop region.A connecting section between the bulge corners of the output profile is defined as a straight section, wherein the radial air clearance in the straight section can be less than at the bulge corners in the stop region.A further advantageous embodiment provides that the drive profile and the driven profile are in direct contact as soon as the circumferential air clearance has been used up. Accordingly, it is provided that no further component is arranged between the output profile and the drive profile. However, it can be provided that lubricant is introduced in the region between the output and drive profiles for noise reduction or for increasing the service life.According to a preferred embodiment, the bulged corners of the output profile are formed in such a way that a contact surface between the input steering shaft and the output steering shaft is enlarged. An increase in the contact area has the result that the surface pressure is reduced, as a result of which the service life of the components is extended.Furthermore, it is provided that the input steering shaft has a drive region, wherein the drive region is arranged at a region opposite the first end and is fastened to the drive region of a steering handle. It can also be provided that the steering handle is not directly connected to the input steering shaft, but rather via a further shaft, such as a articulated shaft. The additional articulated shaft can be used for the individual setting of the steering handle for each driver, thus ensuring a setting for different drivers.A sectional surface of the input and output steering shafts is defined as a surface which describes a cross-sectional surface of the input and output shafts in the region of the driver connector. The ratio of these two cut surfaces is one, preferably 0.75 and in particular 0.5.Further features, advantages and characteristics of the invention will be explained by describing preferred embodiments of the invention with reference to the figures, which show: FIG. 1 shows an embodiment of a steering shaft according to the invention in a sectional illustration; FIG. 2 : the steering shaft according to FIG. 1 in the region of the driver connector in a sectional illustration orthogonal to the central longitudinal axis; and FIG. 3 : shows a driver connector according to FIG. 2 without an input steering shaft and without a torsion rod.FIG. 1 shows a steering shaft 100 comprising an output steering shaft 2 and an input steering shaft 3 and a torsion bar located therebetween. The input steering shaft 3 has a drive region 101 at an end opposite the driver connector 1. The drive region 101 can be used to connect a steering handle (not shown) to the input steering shaft 3. It can also be provided that the steering handle is connected via a articulated shaft to the drive region 101 of the input steering shaft 3.Furthermore, the input steering shaft 3 has a bearing section 106 for mounting in a steering shaft housing. The input steering shaft 3 rotates about its central longitudinal axis 6 and transmits its torque to the torsion bar 4 in a regular operation, which torsion bar is connected to the input steering shaft 3 via a first torsion bar end 103. The first torsion bar end 103 can have a toothing for the rotationally rigid fastening of the torsion bar 4.Along the central longitudinal axis 6, an output steering shaft 2 is furthermore arranged. This has a rack section 105, which can be meshed with a rack in order to actuate the steered vehicle wheels. Further, the output steering shaft 2 has a second torsion bar end 104.The second torsion bar end 104 serves to fix the torsion bar 4 in the output steering shaft 2 in a rotationally rigid manner, wherein a torque applied to the input steering shaft 3 is transmitted to the output steering shaft 2 by the torsion bar 4. If the input steering shaft 3 is rotated beyond a permissible range, the input steering shaft 3 comes into contact with the output steering shaft 2 if the radial air clearance a is used up. For this purpose, an input profile 11 is integrally formed on the input steering shaft 3 and an output profile 12 is integrally formed on the output steering shaft 2.FIG. 2 shows the steering shaft 100 according to FIG. 1 in the output region 102 in a sectional illustration orthogonal to the central longitudinal axis 6. For receiving the torsion bar 4, the input steering shaft 3 has a bore 5.In order that the output steering shaft 2 and the input steering shaft 3 can be rotated relative to one another, a circumferential air clearance α 1, α 2 is provided in the stop region 7.2. If the steering torque is transmitted via the torsion bar 4, the circumferential air clearance α 1, α 2 in the stop region 7.2 varies only to a slight extent. However, if a certain steering force is exceeded, the stop region 7.2 is reduced and the input steering shaft 3 comes into direct contact with the output steering shaft 2. The circumferential air clearance in the clockwise direction α 1 is then, for example, zero and the circumferential air clearance in the counterclockwise direction α 2 is greater than in a rest state.Each of the input steering shaft sections 9 has two stop regions 7.2, one in the clockwise direction and one in the counter-clockwise direction. If the input steering shaft 3 is moved clockwise, for example, circumferential air clearance is reduced clockwise α 1, while the circumferential air clearance is increased counterclockwise α 2.If a stop of the drive profile 11 and the driven profile 12 occurs, there is a surface contact in the stop region 7.2, via which the steering torque is transmitted.A pocket region 10 is provided between the drive profile 11 and the driven profile 12 which has a pocket air clearance 7.3. This region serves to enable the drive profile 11 to perform a rotational movement in a region in which the torsion bar 4 is permitted to be twisted. To reduce the geometric dimensions of the drive profile 11, the square basic shape is modified in such a way that the drive profile 11 has a modified corner section 9. The cut-off corners of the square basic shape result in an octagon.Between two pocket regions 10 there is a passage region 7.1, which facilitates the insertion of the input steering shaft 3 into the output steering shaft 2 and is intended to ensure, in the event of a rotational movement of the two steering shafts relative to one another, that there is contact between the drive profile 11 and the driven profile 12 only in the stop region 7.2.FIG. 3 shows a driver connector according to FIG. 2, but without input steering shaft 3 and without torsion rod 4; in this view, a bore of output steering shaft 13 can be seen, into which torsion rod 4 can be inserted. The production of the bore in the output steering shaft 13, like the bore in the input steering shaft 5, can either be produced by material removal, such as by milling or drilling, or can be formed in an extrusion process. It is provided that the bore 13 and 5 are arranged centered in the center of the input steering shaft 3 and the output steering shaft 2.The bore in the output steering shaft 13 does not pass completely through the output steering shaft 2, but only partially through it and can have a toothing system in order to receive the torsion bar 4 in a rotationally rigid manner. In this illustration, the characteristic stop regions 7.2 are particularly well visible, which offer a larger stop surface compared to the prior art.Isolated features can also be extracted from the combinations of features disclosed here, if necessary, and used in combination with other features to delimit the subject matter of the claim, resolving a structural and / or functional relationship optionally existing between the features. The order and / or number of steps of the methods may be varied. The methods can be combined with one another, for example to form an overall method.Reference numerals denote reference numerals1 Driver connector 2 Output steering shaft 3 Input steering shaft 4 Torsion rod 5 Bore Input steering shaft 6 Central longitudinal axis 7.1 Passage region 7.2 Stop region 7.3 Pocket air clearance 8 Straight section 9 Corner section 10 Pocket region 11 Drive profile 12 Output profile 13 Bore Output steering shaft a Radial air clearance α 1 Circumferential air clearance clockwise α 2 Circumferential air clearance counterclockwise 100 Steering shaft 101 Drive region 102 Output region 103 First torsion rod end 104 Second torsion rod end 105 Rack section 106 Bearing sectionReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2015 002 686

[0005] KR 20 140 026 927 A

[0006]

Claims

Driver connector (1) in a motor vehicle steering system, comprising: - an input steering shaft (3) which is arranged rotatably about a central longitudinal axis (6), wherein the input steering shaft (3) has a bore (5) for a torsion bar (4), and the input steering shaft (3) comprises a drive profile (11) at one end, and - an output steering shaft (2) which is arranged rotatably about the central longitudinal axis (6), wherein the output steering shaft (2) has an output profile (12) at one end, and the drive profile (11) and the output profile (12) form a stop region (7.2) when rotated, characterized in that the drive profile (11) is formed in the stop region (7.2) in a shape-opposite to the output profile (12).Driver connector (1) in a motor vehicle steering system according to Claim 1, characterized in that the drive profile (11) and the driven profile (12) are spaced apart by a radial air clearance (a), wherein the radial air clearance (a) varies in a state free of steering force following the circumference, in particular in the stop region (7.2).Driver connector (1) in a motor vehicle steering system according to Claim 1 or 2, characterized in that the input steering shaft (3) and the output steering shaft (2) are spaced apart by a circumferential air clearance (α 1, α 2) wherein the circumferential air clearance (α 1, α 2) is changed if the input steering shaft (3) and the output steering shaft (2) are rotated relative to one another along the central longitudinal axis (6).Driver connector (1) in a motor vehicle steering system according to one of the preceding claims, characterized in that the circumferential air clearance (α 1, α 2) in a state free from steering force is of the same size in both rotational directions.Driver connector (1) in a motor vehicle steering system according to one of the preceding claims, characterized in that a rotational movement between the input steering shaft (3) and the output steering shaft (2) is made possible as soon as the circumferential air clearance (α 1, α 2) is overcome and in particular the drive profile (11) directly contacts the output profile (12) as soon as the circumferential air clearance (α 1, α 2) is used up.Driver connector (1) in a motor vehicle steering system according to one of the preceding claims, characterized in that the torsion bar (4) is fastened with a first torsion bar end (103) to the input steering shaft (3) in a rotationally rigid manner, and the torsion bar (4) is fastened with a second torsion bar end (104) to the output steering shaft (2) in a rotationally rigid manner.Driver connector (1) in a motor vehicle steering system according to one of the preceding claims, characterized in that a sensor is arranged on the torsion rod (4) in order to measure a torsion torque between the input steering shaft (3) and the output steering shaft (2).Driver connector (1) in a motor vehicle steering system according to one of the preceding claims, characterized in that the drive profile (11) and the output profile (12) have a square basic shape, wherein the drive profile (11) has eight corners and the corners (10) are formed in a bulge-like manner from the output profile (12).Driver connector (1) in a motor vehicle steering system according to one of the preceding claims, characterized in that the bulged corners (10) of the output profile (12) increase a contact surface between the input steering shaft (3) and the output steering shaft (2).Driver connector (1) in a motor vehicle steering system according to one of the preceding claims, characterized in that the input steering shaft (3) has a drive region (101) and an output region (102), wherein the drive region (101) and the output region (102) are arranged at two opposite ends of the input steering shaft (3) and a steering handle is fastened to the drive region (101) and the output region (102) has the drive profile (11).

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