Steering gear for a motor vehicle

Abstract

The invention relates to a steering gear (1) for a motor vehicle, comprising a drive unit (10) comprising an electric machine (12) and a conversion gear (14) for providing power steering assistance, comprising a helical pinion (16) driven by the electric machine (12) which engages with a helical wheel (18), a sleeve (20) arranged on a helical wheel hub (18a), a pinion (22) for driving a rack (24) of the steering gear (1), and a tolerance ring (26) which is arranged between the sleeve (20) arranged on the helical wheel hub (18a) and an outer circumference of the pinion (22), wherein the tolerance ring (26) is designed to transmit a torque generated by the helical wheel (18) to the pinion (22), and wherein the tolerance ring (26) has a division comprising gaps (28, 30) arranged offset from each other in the circumferential direction (U).

Description

[0001] The invention relates to a steering gear for a motor vehicle. State of the art

[0002] Tolerance rings are traditionally used in steering gears as a simple shaft-hub connection for torque and power transmission. Power transmission occurs through elastic deformation of the tolerance ring's beads and a radial force at the interfaces to the shaft or pinion and hub of a helical gear. This results in a frictional force on the shaft, which in turn enables torque and power transmission between the components.

[0003] The tolerance ring acts as a slip clutch, allowing force to be transferred between the components up to a certain limit. Above this limit, the tolerance ring slides on the shaft, resulting in a relative rotational movement between the shaft and hub.

[0004] This makes it possible to protect the components, especially the helical gear in the gearbox, from excessive loads.

[0005] In a single-pinion steering gear, the helical gear is located below the rack. Due to the steering design, the helical gear can only be installed in the steering gear. According to the design, the tolerance ring is then placed on a sleeve and then mounted in the steering gear.

[0006] Due to a slit in the tolerance ring, this sleeve is deformed unevenly across its diameter. This deformation can lead to performance issues with the desired release torque. In addition, this deformation pattern results in a concentricity error in combination with the helical gear.

[0007] It is therefore the object of the invention to provide a steering gear for a motor vehicle which enables a substantially uniform force to be applied to the sleeve.

[0008] This problem is solved by the subject matter of patent claim 1. Disclosure of the invention

[0009] The present invention provides a steering gear for a motor vehicle. The steering gear comprises a drive unit with an electric motor and a converter gear for providing steering force assistance.

[0010] The drive unit comprises a helical pinion driven by the electric machine, which is in engagement with a helical gear, a sleeve arranged on a helical gear hub, a pinion for driving a rack of the steering gear and a tolerance ring which is arranged between the sleeve arranged on the helical gear hub and an outer circumference of the pinion, wherein the tolerance ring is designed to transmit a torque generated by the helical gear to the pinion, and wherein the tolerance ring has a pitch comprising gaps arranged offset from one another in the circumferential direction.

[0011] One idea of ​​the present invention is to apply a more uniform force distribution over the area of ​​the pitch by providing the tolerance ring with the pitch comprising gaps arranged offset from one another in the circumferential direction.

[0012] This can advantageously improve the uneven deformation towards a lower maximum deformation of the sleeve.

[0013] Advantageous embodiments and further developments emerge from the subclaims and from the description with reference to the figures.

[0014] According to a preferred development, it is provided that the division of the tolerance ring extends over an entire axial length of the tolerance ring, wherein the gaps have a first gap formed in the axial direction of the tolerance ring and a second gap formed in the axial direction of the tolerance ring and arranged offset from the first gap.

[0015] The provision of two gaps offset from one another has the advantage of enabling a more uniform application of force from the helical gear to the pinion.

[0016] According to a further preferred development, it is provided that the first gap formed in the axial direction of the tolerance ring and the second gap formed in the axial direction of the tolerance ring are coupled by a connecting gap formed at least partially in the circumferential direction of the tolerance ring.

[0017] The connecting gap results in two overlapping areas of the tolerance ring being created in the connecting gap region, whereby a defined force transmission between the helical gear and the pinion still occurs in the overlapping areas. Conventional tolerance rings with a continuous gap in the axial direction exhibit no force application in the gap region, which leads to maximum deformation of the sleeve. This maximum deformation can be advantageously reduced by offsetting the gaps in the tolerance ring.

[0018] According to a further preferred development, the pitch of the tolerance ring is designed such that the tolerance ring has a first tab formed substantially in the circumferential direction and arranged adjacent to the first gap, and a second tab formed substantially in the circumferential direction and arranged adjacent to the second gap. This advantageously enables a more uniform force transmission in the region of the tabs.

[0019] According to a further preferred development, the first tab and the second tab overlap in the circumferential direction of the tolerance ring in the region of the connecting gap. This advantageously allows for both a division of the tolerance ring and an effective transmission of force between the helical gear and the pinion.

[0020] According to a further preferred development, the tolerance ring is designed to transmit a predetermined force generated by the helical gear to the pinion in the region of the first and second plates. The gaps are designed to reduce radial deformation of the sleeve.

[0021] According to a further preferred development, the connecting gap formed in the circumferential direction has a smaller width than the first gap formed in the axial direction and the second gap formed in the axial direction. Thus, the beads arranged along the circumferential direction of the tolerance ring and adjacent to the connecting gap can advantageously remain intact.

[0022] However, a smaller width is absolutely necessary. The goal in production is to keep the gaps formed in the axial direction as small as possible, taking the tolerance situation into account.

[0023] According to a further preferred development, the tolerance ring has a plurality of wave-shaped beads in the circumferential direction, wherein a width of the first gap and the second gap corresponds at least to the width of one of the plurality of beads. By omitting a corresponding bead, less radial force is generated in this area.

[0024] According to a further preferred development, the width of the overlap between the first tab and the second tab corresponds at least to the width of one of the plurality of beads. Thus, a predetermined number of beads can be omitted in the region of the gap.

[0025] However, it is not absolutely necessary to omit exactly one bead or an integer number of bead sizes. By varying the spacing between the bead sizes / the width of the bead sizes, the number of bead sizes can be increased or decreased.

[0026] According to a further preferred development, it is provided that the tolerance ring transmits a maximum first force from the helical gear to the pinion in the region of the overlap of the first tab and the second tab, and wherein the tolerance ring transmits a maximum second force from the helical gear to the pinion in the region outside the overlap of the first tab and the second tab, wherein the first force is less than the second force.

[0027] Although the first force is lower than the second force, a force transmission still takes place in the area of ​​the overlap of the tabs, so that a maximum deformation of the sleeve can be advantageously reduced.

[0028] 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 exemplary embodiments that are not explicitly mentioned. Short description of the drawings

[0029] 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.

[0030] 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.

[0031] They show: Fig. 1 is a perspective view of a steering gear for a motor vehicle according to a preferred embodiment of the invention; Fig. 2 is a longitudinal sectional view of a detailed portion of a steering gear for a motor vehicle according to the preferred embodiment of the invention; Fig. 3 is a perspective view of a tolerance ring of the steering gear for the motor vehicle according to the preferred embodiment of the invention; Fig. 4 is a perspective view of a waveform of the tolerance ring of the steering gear for the motor vehicle according to the preferred embodiment of the invention; and Fig. 5 a representation of a deformation profile of a sleeve arranged adjacent to the tolerance ring according to the preferred embodiment of the invention.

[0032] In the figures of the drawings, the same reference symbols designate the same or functionally equivalent elements, parts or components, unless otherwise stated.

[0033] Fig. 1 shows a steering gear 1 for a motor vehicle, with a drive unit 10 comprising an electric machine 12 and a conversion gear 14 for providing steering power assistance, comprising a helical pinion 16 driven by the electric machine 12, which is in engagement with a helical gear 18.

[0034] Fig. 2 shows a longitudinal sectional view of a detailed area of ​​a steering gear for a motor vehicle according to the preferred embodiment of the invention.

[0035] The drive unit 10 further comprises a sleeve 20 arranged on a helical gear hub 18a, a pinion 22 for driving a rack 24 of the steering gear 1, and a tolerance ring 26 which is arranged between the sleeve 20 arranged on the helical gear hub 18a and an outer circumference of the pinion 22, wherein the tolerance ring 26 is designed to transmit a torque generated by the helical gear 18 to the pinion 22, and wherein the tolerance ring 26 has a pitch comprising gaps 28, 30 which are arranged offset from one another in the circumferential direction U.

[0036] Fig. 3 shows a perspective view of a tolerance ring of the steering gear for the motor vehicle according to the preferred embodiment of the invention.

[0037] The pitch of the tolerance ring 26 extends over an entire axial length of the tolerance ring 26. The gaps 28, 30 further have a first gap 28 formed in the axial direction of the tolerance ring 26 and a second gap 30 arranged offset from the first gap 28 and formed in the axial direction of the tolerance ring 26.

[0038] The first gap 28 formed in the axial direction of the tolerance ring 26 and the second gap 30 formed in the axial direction of the tolerance ring 26 are coupled by a connecting gap 32 formed at least partially in the circumferential direction U of the tolerance ring 26.

[0039] The pitch of the tolerance ring 26 is designed such that the tolerance ring 26 has a first tab 34 formed substantially in the circumferential direction U and arranged adjacent to the first gap 28 and a second tab 36 formed substantially in the circumferential direction U and arranged adjacent to the second gap 30.

[0040] The tolerance ring 26 further comprises a plurality of wave-shaped beads 38 in the circumferential direction U, wherein a width of the first gap 28 and the second gap 30 corresponds at least to a width of one of the plurality of beads 38. Alternatively, however, a width of the first gap 28 and the second gap 30 can, for example, have a different width therefrom.

[0041] The first tab 34 and the second tab 36 further overlap in the circumferential direction U of the tolerance ring 26 in the region of the connecting gap 32. A width of the overlap of the first tab 34 and the second tab 36 corresponds at least to a width of one of the plurality of beads 38.

[0042] The tolerance ring 26 transmits a maximum first force from the helical gear 18 to the pinion 22 in the region of the overlap of the first tab 34 and the second tab 36. Furthermore, the tolerance ring 26 transmits a maximum second force from the helical gear 18 to the pinion 22 in the region outside the overlap of the first tab 34 and the second tab 36, wherein the first force is less than the second force.

[0043] Furthermore, the tolerance ring 26 is designed to transmit a predetermined force generated by the helical gear 18 to the pinion 22 in the region of the first tab 34 and the second tab 36.

[0044] The connecting gap 32 formed in the circumferential direction U has a smaller width than the first gap 28 formed in the axial direction and the second gap 30 formed in the axial direction.

[0045] Fig. 4 shows a perspective view of a waveform of the tolerance ring of the steering gear for the motor vehicle according to the preferred embodiment of the invention.

[0046] The force is transmitted through elastic deformation of the tolerance ring's grooves or shafts, as well as a radial force at the interfaces to the shaft or pinion 22 and the hub 18a of the helical gear. This results in a frictional force on the shaft, which in turn enables torque and force transmission between the components.

[0047] Fig. 5 shows a representation of a deformation curve of a sleeve arranged adjacent to the tolerance ring according to the preferred embodiment of the invention.

[0048] A conventional tolerance ring with a continuous gap in the axial direction exhibits no force application in the gap region, resulting in a maximum deformation 40 of the sleeve. This maximum deformation can be advantageously reduced by offsetting the gaps in the tolerance ring, so that a correspondingly smaller deformation 42 occurs in the gap region of the tolerance ring of the sleeve.

Claims

[1] Steering gear (1) for a motor vehicle, comprising: a drive unit (10) comprising an electric machine (12) and a conversion gear (14) for providing steering power assistance, comprising: a screw pinion (16) driven by the electric machine (12) which engages with a helical gear (18); a sleeve (20) arranged on a helical gear hub (18a); a pinion (22) for driving a rack (24) of the steering gear (1); and a tolerance ring (26) which is arranged between the sleeve (20) arranged on the helical gear hub (18a) and an outer circumference of the pinion (22), wherein the tolerance ring (26) is designed to transmit a torque generated by the helical gear (18) to the pinion (22), and wherein the tolerance ring (26) has a pitch comprising gaps (28, 30) arranged offset from one another in the circumferential direction (U). [2] Steering gear according to claim 1, wherein the pitch of the tolerance ring (26) extends over an entire axial length of the tolerance ring (26), wherein the gaps (28, 30) have a first gap (28) formed in the axial direction of the tolerance ring (26) and a second gap (30) formed in the axial direction of the tolerance ring (26) and arranged offset from the first gap (28). [3] Steering gear according to claim 2, wherein the first gap (28) formed in the axial direction of the tolerance ring (26) and the second gap (30) formed in the axial direction of the tolerance ring (26) are coupled by a connecting gap (32) formed at least partially in the circumferential direction (U) of the tolerance ring (26). [4] Steering gear according to claim 3, wherein the pitch of the tolerance ring (26) is designed such that the tolerance ring (26) has a first tab (34) formed substantially in the circumferential direction (U) and arranged adjacent to the first gap (28) and a second tab (36) formed substantially in the circumferential direction (U) and arranged adjacent to the second gap (30). [5] Steering gear according to claim 4, wherein the first tab (34) and the second tab (36) overlap in the circumferential direction (U) of the tolerance ring (26) in the region of the connecting gap (32). [6] Steering gear according to claim 4 or 5, wherein the tolerance ring (26) is designed to transmit a predetermined force generated by the helical gear (18) to the pinion (22) in the region of the first tab (34) and the second tab (36). [7] Steering gear according to one of claims 3 to 6, wherein the connecting gap (32) formed in the circumferential direction (U) has a smaller width than the first gap (28) formed in the axial direction and the second gap (30) formed in the axial direction. [8] Steering gear according to one of claims 4 to 7, wherein the tolerance ring (26) has a plurality of wave-shaped beads (38) in the circumferential direction (U), wherein a width of the first gap (28) and the second gap (30) corresponds at least to a width of one of the plurality of beads (38). [9] Steering gear according to claim 8, wherein a width of the overlap of the first tab (34) and the second tab (36) corresponds to at least a width of one of the plurality of beads (38). [10] Steering gear according to claim 8 or 9, wherein the tolerance ring (26) transmits a maximum first force from the helical gear (18) to the pinion (22) in the region of the overlap of the first tab (34) and the second tab (36), and wherein the tolerance ring (26) transmits a maximum second force from the helical gear (18) to the pinion (22) in the region outside the overlap of the first tab (34) and the second tab (36), the first force being less than the second force.

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