Servo drive and steering system for a motor vehicle

Abstract

The invention relates to a servo drive (10) for a steering system (1) of a motor vehicle, comprising a worm shaft (12); a rolling bearing (14) for supporting the worm shaft (12), wherein the worm shaft (12) is inserted into a bearing inner ring (14a) of the rolling bearing (14) with a transition fit; a hub (16) pressed onto the worm shaft (12), the hub (16) being designed to transmit a torque generated by an electric motor (18) of the servo drive (10) to the worm shaft (12), wherein the bearing inner ring (14a) of the rolling bearing (14) can be clamped between the worm shaft (12) and the hub (16) with a predetermined preload force (F) by at least one deformation element (20a, 20b) arranged on the bearing inner ring (14a) and / or on a component of the servo drive (10) arranged axially adjacent to the bearing inner ring (14a). The invention also relates to a steering system (1) for a motor vehicle.

Description

Technical Field

[0001] The present invention relates to a servo drive mechanism for a steering system of a motor vehicle. In addition, the present invention also relates to a steering system for a motor vehicle. Background Art

[0002] A conventional servo drive mechanism for a steering system has an electric motor, which transmits the generated torque to a worm shaft via a wheel hub. Usually, a bearing, such as a rolling bearing, is arranged between the wheel hub and the worm shaft for axially supporting the worm shaft.

[0003] In this case, the hub is pressed onto the outer circumference of the worm shaft in the region of an axial end section of the worm shaft, wherein the torque transmission from the electric motor to the worm shaft takes place via a serration connection of the hub to the worm shaft.

[0004] Furthermore, in order to fix the bearing axially between the worm shaft and the hub, a certain preload must be generated in order to prevent the inner ring of the bearing from rotating on the bearing support during operation, which could lead to functional and / or acoustic problems.

[0005] DE 10161715 A1 describes a bearing seat for use in a helical gear mechanism in an electric power steering. The worm gear mechanism is constructed with a housing in which a worm and a worm wheel are arranged, wherein the worm is connected to a drive shaft of an electric drive motor supported in a bearing by means of a coupling. Summary of the invention

[0006] It is therefore desirable to provide a structurally simplified press fit for a servo drive of a steering system, which press fit has simplified manufacturability and an optimized functionality.

[0007] The object is to achieve a servo transmission for a steering system of a motor vehicle, the servo transmission for a steering system of a motor vehicle comprising: a worm shaft; a rolling bearing for supporting the worm shaft, wherein the worm shaft is inserted into a bearing inner ring of the rolling bearing, in particular with a transition fit; a hub pressed onto the worm shaft, the hub being constructed for transmitting a torque generated by an electric motor of the servo transmission to the worm shaft, wherein the bearing inner ring of the rolling bearing can be clamped between the worm shaft and the hub with a predetermined preload force by means of at least one deforming element arranged on the bearing inner ring and / or on a component of the servo transmission arranged axially adjacent to the bearing inner ring.

[0008] The object is also achieved with a steering system for a motor vehicle having a steering shaft, a steering gear and a servo drive according to the invention, which is operatively connected to the steering shaft or to the steering gear and is used to generate steering force support.

[0009] The invention provides a servo drive for a steering system of a motor vehicle, the servo drive having a worm shaft and a rolling bearing for supporting the worm shaft, wherein the worm shaft is inserted into a bearing inner ring of the rolling bearing, in particular with a transition fit.

[0010] In addition, the servo transmission mechanism also includes a hub pressed onto the worm shaft, and the hub is constructed to transmit the torque generated by the motor of the servo transmission mechanism to the worm shaft, wherein the bearing inner ring of the rolling bearing can be clamped between the worm shaft and the hub with a predetermined preload force by at least one deformation element, and the at least one deformation element is arranged on the bearing inner ring and / or on a component of the servo transmission mechanism that is arranged axially adjacent to the bearing inner ring.

[0011] Furthermore, the present invention provides a steering system for a motor vehicle having a steering shaft, a steering gear and a servo drive according to the present invention operatively connected to the steering shaft or the steering gear for generating steering force assistance.

[0012] The idea of ​​the present invention is to generate a preload that is increased in an advantageous manner relative to the surface pressure between the bearing inner ring of the rolling bearing and the component axially adjacent to the bearing ring by providing at least one deforming element arranged on the bearing inner ring and / or on a component of the servo transmission mechanism arranged axially adjacent to the bearing inner ring when a predetermined or specified axial force is applied.

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

[0014] According to a preferred improvement, the cross-sectional area of ​​at least one deformation element is smaller than 10%, preferably 5%, of the cross-sectional area of ​​the end surface of the bearing inner ring on which the at least one deformation element is arranged and / or a component of the servo transmission mechanism arranged axially adjacent to the bearing inner ring.

[0015] Due to the significantly smaller cross-sectional area of ​​the at least one deforming element relative to the end surface of the associated bearing inner ring or a component of the servo drive mechanism arranged adjacent to the bearing inner ring, the necessary preload force for clamping the bearing inner ring of the rolling bearing between the worm shaft and the hub can be generated in an advantageous manner with relatively small axial forces.

[0016] According to another preferred improvement, the at least one deformation element has a first deformation element and a second deformation element which are arranged on the end surface of the hub or the worm shaft facing the bearing inner ring of the rolling bearing, and the first deformation element and the second deformation element are arranged offset to each other by essentially 180°.

[0017] By such an arrangement of the first and second deformation elements, a uniform compression of the component of the servomechanism on which the at least one deformation element is arranged and of components adjacent thereto can thus be achieved in an advantageous manner.

[0018] According to another preferred improvement, it is provided that the at least one deformation element has a first deformation element arranged on the end side surface of the hub or the worm shaft facing the bearing inner ring of the rolling bearing, and wherein the at least one deformation element has a second deformation element on the end side surface of the bearing inner ring of the bearing facing the hub or the worm shaft, wherein the first deformation element and the second deformation element are arranged substantially 180° offset from each other.

[0019] The first deformation element and the second deformation element can thus be advantageously assigned to different components of the actuating drive.

[0020] According to another preferred improvement, the at least one deformation element has a cylindrical, hemispherical, conical and / or square geometry, or extends annularly around an annular end surface of a bearing inner ring of a rolling bearing and / or an annular end surface of a component of a servo drive mechanism arranged axially adjacent to the bearing inner ring.

[0021] The at least one deformation element can thus advantageously have a geometry that is suitable for the prestressing force to be achieved.

[0022] According to another preferred development, it is provided that the component of the servo drive on which the at least one deformation element is arranged has a lower hardness than the component of the servo drive against which the at least one deformation element is pressed. This advantageously enables an optimal deformation of the at least one deformation element and a resulting improved surface pressure on the component of the servo drive against which the at least one deformation element is pressed.

[0023] According to another preferred development, it is provided that the torque generated by the electric motor of the servo drive can be transmitted to the worm shaft via surface pressure of the inner circumference of the hub and surface pressure of the outer circumference of the worm shaft.

[0024] The fine-toothed connection conventionally used for transmitting the torque from the electric motor via the hub to the worm shaft and formed in the region of the worm shaft and the hub can thereby advantageously be omitted.

[0025] According to another preferred improvement, the worm shaft, the inner ring of the rolling bearing and the wheel hub form a press fit, which is configured to clamp the inner ring of the rolling bearing between the worm shaft and the wheel hub with a predetermined preload force. This advantageously enables an improved solution for axially fixing and clamping the inner ring of the rolling bearing.

[0026] According to another preferred development, the at least one deformation element is plastically deformed in the assembled state of the servo drive by an axial preload acting on the at least one deformation element. Due to the plastic deformation of the at least one deformation element, an optimal adhesion or fixation between the relevant components of the servo drive can be achieved, so that no relative rotational movement can occur between the relevant components, that is, no rotation of the bearing inner ring on the bearing support can occur.

[0027] The described embodiments and developments can be combined with one another as desired.

[0028] Further possible embodiments, improvements and implementations of the invention also include combinations of features of the invention described above or below with respect to the exemplary embodiments that are not explicitly mentioned. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are intended to help further understanding of the embodiments of the present invention. The accompanying drawings illustrate embodiments and together with the description serve to explain the principles and concepts of the present invention.

[0030] Further embodiments and many of the advantages mentioned can be seen with reference to the drawings. The elements shown in the drawings are not necessarily shown true to scale with respect to one another.

[0031] in:

[0032] Figure 1 A longitudinal sectional view of a partial section of a servo drive for a steering system of a motor vehicle according to a preferred embodiment of the present invention is shown;

[0033] Figure 2 shows a perspective view of a wheel hub of a servo drive mechanism for a steering system of a motor vehicle according to the preferred embodiment of the present invention; and

[0034] Figure 3 A schematic diagram of a steering system for a motor vehicle according to this preferred embodiment of the present invention is shown.

[0035] In the figures of the drawings, identical reference signs denote identical or functionally identical elements, components or assemblies, unless otherwise indicated. DETAILED DESCRIPTION

[0036] Figure 1 A longitudinal section through a partial section of a servo drive for a steering system of a motor vehicle is shown according to a preferred specific embodiment of the present invention.

[0037] A servo drive 10 for a steering system 1 of a motor vehicle comprises a worm shaft 12, a roller bearing 14, a hub 16 and an electric motor 18 operatively connected to the hub 16. Other components of the servo drive 10 that are not essential to the invention are therefore not shown.

[0038] The rolling bearing 14 serves to support the worm shaft 12 , wherein the worm shaft 12 is inserted into an inner bearing ring 14 a of the rolling bearing 14 , in particular with a transition fit.

[0039] Furthermore, the hub 16 is pressed onto the worm shaft 12 . The hub 16 is designed to transmit a torque generated by an electric motor 18 of a servo drive to the worm shaft 12 .

[0040] In this embodiment, inner bearing ring 14 a of rolling bearing 14 can be clamped between worm shaft 12 and hub 16 with a predefined preload force F by means of first deformation element 20 a and second deformation element 20 b arranged on hub 16 .

[0041] As an alternative, the first deformation element 20 a and the second deformation element 20 b may be arranged, for example, not on the hub 16 but on the end surface 12 a of the worm shaft 12 .

[0042] In addition, as an alternative, the first deformation element 20a can, for example, be arranged at the end side surface 12a, 16a of the worm shaft 12 or the hub 16 facing the bearing inner ring 14a of the rolling bearing 14, and the second deformation element 20b can be arranged at the end side surface 14a1, 14a2 of the bearing inner ring 14a of the rolling bearing 14 facing the hub 16 or the worm shaft 12.

[0043] It is also advantageous for this configuration if first deformation element 20 a and second deformation element 20 b are arranged offset from one another by substantially 180°.

[0044] It is also conceivable that a different number of deformation elements may be provided.

[0045] In this preferred embodiment, the first deformation element 20a and the second deformation element 20b are pressed onto the end side surfaces 14a1 and 14a2 of the bearing inner ring 14a, and the first deformation element 20a and the second deformation element 20b have a cross-sectional area that is smaller than 10%, in particular 5%, of the cross-sectional area of ​​the end side surfaces 14a1 and 14a2 of the bearing inner ring 14a.

[0046] If the first deformation element 20a and the second deformation element 20b are alternatively arranged at other suitable components, such as, for example, at the bearing inner ring 14a of the rolling bearing 14 or at the end side surface 12a of the worm shaft 12, then the first deformation element 20a and the second deformation element 20b also have a cross-sectional area that is smaller than 10%, in particular 5%, of the cross-sectional area of ​​the adjacently arranged surface of the correspondingly adjacently arranged component of the servo transmission mechanism 10.

[0047] According to this preferred embodiment, the component of servo drive 10 , in the present exemplary embodiment, hub 16 on which deformation elements 20 a , 20 b are arranged, has a lower hardness than the component of servo drive 10 arranged adjacent thereto and against which deformation elements 20 a , 20 b are pressed.

[0048] The torque generated by the motor 18 of the servo transmission mechanism 10 can be transmitted to the worm shaft 12 through the surface pressure of the inner circumference 16b of the hub 16 and the surface pressure of the outer circumference 12b of the worm shaft 12, that is, through the surface pressure of the corresponding surface of the inner circumference 16b of the hub 16 and the surface pressure of the corresponding surface of the outer circumference 12b of the worm shaft 12.

[0049] The worm shaft 12 , the bearing inner ring 14 a of the rolling bearing 14 , and the hub 16 thus form a press fit which is designed to clamp the bearing inner ring 14 a of the rolling bearing 14 with a predetermined preload force F between the worm shaft 12 and the hub 16 .

[0050] The first deformation element 20a and the second deformation element 20b are Figure 1 In the assembled state of the illustrated servo drive 10 , plastic deformation occurs due to an axial preload force F or an axial force acting on the deformation elements 20 a , 20 b .

[0051] Figure 2 A perspective view of a wheel hub of a servo drive for a steering system of a motor vehicle is shown according to the preferred embodiment of the present invention.

[0052] In this embodiment, first deformation element 20a and second deformation element 20b are arranged at end surface 16a of hub 16. Furthermore, first deformation element 20a and second deformation element 20b are arranged substantially 180° offset from each other.

[0053] In this embodiment, the first deformation element 20a and the second deformation element 20b have a cylindrical geometry. Alternatively, the first deformation element 20a and the second deformation element 20b can have, for example, a hemispherical, conical and / or square geometry.

[0054] Furthermore, as an alternative, only a single deformation element may be provided, which extends around an annular end surface of the bearing inner ring 14a of the rolling bearing 14 and / or around an annular end surface of a component of the servo drive 10 arranged adjacent to the bearing inner ring 14a.

[0055] Figure 3 A schematic diagram of a steering system for a motor vehicle according to this preferred embodiment of the present invention is shown.

[0056] In this Figure 3 The steering system 1 shown only symbolically in the figure has a steering wheel 2a connected to a steering shaft 2, a steering gear 3 and a servo gear 10 operatively connected to the steering gear 3 for generating steering force support. In addition, the steering gear 3 is also connected to the corresponding wheels 4, 5 to be steered.

Claims

1. A servo drive mechanism (10) for a steering system (1) of a motor vehicle, comprising: Worm shaft (12); A rolling bearing (14) for supporting the worm shaft (12), wherein the worm shaft (12) is inserted into the bearing inner ring (14a) of the rolling bearing (14) with a transition fit; A hub (16) pressed onto the worm shaft (12), the hub (16) being designed to transmit a torque generated by an electric motor (18) of the servo drive (10) to the worm shaft (12), wherein the bearing inner ring (14a) of the rolling bearing (14) can be clamped between the worm shaft (12) and the hub (16) with a predetermined preload force (F) by at least one deformation element (20a, 20b) arranged on the bearing inner ring (14a) and / or on a component of the servo drive (10) arranged axially adjacent to the bearing inner ring (14a). , the component (12, 14, 16) on which the at least one deformation element (20a, 20b) is arranged has a lower hardness than the component (12, 14, 16) of the servo transmission mechanism (10) against which the at least one deformation element (20a, 20b) is pressed, wherein the value of the cross-sectional area of ​​the at least one deformation element (20a, 20b) is less than 10% of the value of the cross-sectional area of ​​the end side surface (14a1, 14a2) of the bearing inner ring (14a) on which the at least one deformation element (20a, 20b) is arranged and / or the component of the servo transmission mechanism (10) arranged axially adjacent to the bearing inner ring (14a).

2. The servo drive mechanism (10) according to claim 1, characterized in that The value of the cross-sectional area of ​​the at least one deformation element (20a, 20b) is less than 5% of the value of the cross-sectional area of ​​the end surface (14a1, 14a2) of the component of the bearing inner ring (14a) and / or the servo transmission mechanism (10) arranged axially adjacent to the bearing inner ring (14a) on which the at least one deformation element (20a, 20b) is arranged.

3. The servo drive mechanism (10) according to claim 1 or 2, characterized in that: The at least one deformation element (20a, 20b) comprises a first deformation element (20a) and a second deformation element (20b) arranged on the end side surface (12a, 16a) of the worm shaft (12) or the hub (16) facing the bearing inner ring (14a) of the rolling bearing (14), wherein the first deformation element (20a) and the second deformation element (20b) are arranged substantially 180° offset from each other.

4. The servo drive mechanism (10) according to claim 1 or 2, characterized in that: The at least one deformation element (20a, 20b) has a first deformation element (20a) arranged at an end surface (12a, 16a) of the worm shaft (12) or the hub (16) facing the bearing inner ring (14a) of the rolling bearing (14), and the at least one deformation element (20a, 20b) has a second deformation element (20b) at an end surface (14a1, 14a2) of the bearing inner ring (14a) of the rolling bearing (14) facing the hub (16) or the worm shaft (12), wherein the first deformation element (20a) and the second deformation element (20b) are arranged substantially 180° offset from each other.

5. The servo drive mechanism (10) according to claim 1 or 2, characterized in that: The at least one deformation element (20a, 20b) has a cylindrical, hemispherical, conical and / or square geometry, or extends annularly around an annular end surface of the bearing inner ring (14a) of the rolling bearing (14) and / or an annular end surface of a component of the servo drive (10) arranged axially adjacent to the bearing inner ring (14a).

6. The servo drive mechanism (10) according to claim 1 or 2, characterized in that: The torque generated by the motor (18) of the servo drive mechanism (10) can be transmitted to the worm shaft (12) through the surface pressure of the inner circumference (16b) of the hub (16) and the surface pressure of the outer circumference (12b) of the worm shaft (12).

7. The servo drive mechanism (10) according to claim 1 or 2, characterized in that: The worm shaft (12), the bearing inner ring (14a) of the rolling bearing (14) and the wheel hub (16) form a press fit, which is configured to clamp the bearing inner ring (14a) of the rolling bearing (14) between the worm shaft (12) and the wheel hub (16) with a predetermined preload force (F).

8. The servo drive mechanism (10) according to claim 1 or 2, characterized in that: The at least one deformation element (20a, 20b) is plastically deformed in the assembled state of the servo drive (10) by an axial preload (F) acting on the at least one deformation element (20a, 20b).

9. A steering system (1) for a motor vehicle, comprising a steering shaft (2), a steering transmission (3) and a servo transmission (10) according to any one of claims 1 to 8, wherein the servo transmission (10) is operatively connected to the steering shaft (2) or to the steering transmission (3), and the servo transmission (10) is used to generate steering force support.

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