Shaft arrangement and steering gear with a shaft arrangement

Abstract

Shaft assembly (1) for a steering gear comprising an input shaft (2), an output shaft (3), and a torsion bar (5), wherein the torsion bar (5) is rotationally fixed to the input shaft (2) in an input-side connection area (13) of the shaft assembly (1), wherein the torsion bar (5) is rotationally fixed to the output shaft (3) in an output-side connection area (16) of the shaft assembly (1), and wherein the input-side connection area (13) is spaced apart from the output-side connection area (16), wherein the shaft assembly (1) has an anti-rotation device (18), wherein the anti-rotation device (18) limits the rotation of the input shaft (2) relative to the output shaft (3) to a maximum angle of rotation and, upon reaching the maximum angle of rotation, can transmit a torque from the input shaft (2) to the output shaft (3), wherein the input shaft (2) has a receiving space at its end facing the output shaft (3). (11) exhibitswhich receives at least one end section (9) of the output shaft (3), characterized in that the torsion bar (5) is arranged within the receiving space (11) exclusively within the output shaft (3).

Description

[0001] The invention relates to a shaft arrangement for a steering gear according to the preamble of claim 1. The invention further relates to a steering gear with a shaft arrangement.

[0002] When steering a vehicle, steering forces must be transmitted from the steering wheel to the vehicle's wheels. This is achieved by means of a steering gear. Steering gears typically include a torsion bar, which provides the desired amount of play in the steering mechanism. A torsion bar is a torsionally flexible element. It connects two shafts of the steering gear, such as an input shaft on the steering wheel side and an output shaft on the wheel side. The output shaft can be directly fitted with a thread, pinion, or similar mechanism so that the rotational movement of the output shaft can be converted into a linear movement.

[0003] Steering gears with torsion bars are known from the prior art. For example, DE 10 2011 017 150 A1 describes a steering column with two shaft sections coupled by means of a torsion bar. The torsion bar is torsionally flexible and located within the shaft sections. This arrangement does not provide a safety mechanism in case the torsion bar should break, for example due to material fatigue or overloading. This would result in steering failure.

[0004] DE 10 2014 212 367 A1 describes a steering gear with a steering input shaft and a pinion shaft coupled to the steering input shaft via a torsion bar. The steering input shaft is mounted in a housing. The housing has a locking element. If the steering rod breaks, the locking element limits axial movement of the steering input shaft. This prevents a magnet of the steering gear from colliding with a support bearing in which the steering input shaft is guided.

[0005] Further shaft arrangements for steering gears are known from DE 27 39 406 A1, the generic JP S61-77 659 A, and DE 10 2014 102 807 B3.

[0006] In contrast, the invention is based on the objective of providing a shaft arrangement with a torsion bar that offers greater operational reliability. Furthermore, the invention is based on the objective of providing a steering gear in which reliable steering remains possible even if a torsion bar of the steering gear is damaged.

[0007] The problems are solved by a shaft arrangement according to claim 1 and by a steering gear according to claim 14. The dependent claims relate to various independent, advantageous embodiments of the present invention, the features of which can be freely combined by a person skilled in the art within the bounds of technical practicality.

[0008] According to a first aspect of the invention, a shaft assembly for a steering gear is proposed. The shaft assembly comprises an input shaft, an output shaft, and a torsion bar, wherein the torsion bar is rotationally fixed to the input shaft in an input-side connection area of ​​the shaft assembly. Furthermore, the torsion bar is rotationally fixed to the output shaft in an output-side connection area of ​​the shaft assembly. Finally, the input-side connection area is spaced apart from the output-side connection area. The shaft assembly also includes an anti-rotation device that limits the rotation of the input shaft relative to the output shaft to a maximum angle of rotation and, upon reaching this maximum angle of rotation, can transmit a torque from the input shaft to the output shaft.

[0009] The essential consideration is to design the shaft arrangement by incorporating a rotation lock according to the invention in such a way that the desired rotation of the two elements, input shaft and output shaft, is limited to a maximum. This already advantageously reduces the risk of the torsion bar breaking considerably. Furthermore, the negative consequences for the operational reliability of the overall system are also significantly limited, because even if the torsion bar should fail, the transmission of the rotational movement is still taken over by the rotation lock according to the invention. Thus, it is ensured that steering remains possible even if the torsion bar breaks.

[0010] The anti-rotation device allows the input shaft to rotate relative to the output shaft up to the maximum angle of rotation. According to the invention, this rotation of the input shaft relative to the output shaft can involve rotation about a longitudinal axis of the shaft assembly. If the torsion bar is damaged, it may no longer be able to transmit torque from the input shaft to the output shaft. In this case, the anti-rotation device ensures that the maximum angle of rotation between the input and output shafts is not exceeded. Furthermore, the anti-rotation device prevents the torsion bar from being rotated too far, which could damage it. According to the invention, the torsion bar can be a rod-shaped, torsionally elastic spring element.When the input shaft is rotated relative to the output shaft, it is torsionally deformed along its length between the input-side connection area and the output-side connection area.

[0011] Advantageously, the anti-rotation device can be designed in such a way that the torque to be transmitted from the input shaft to the output shaft is transmitted exclusively via the anti-rotation device.

[0012] The anti-rotation device is preferably formed by a safety pin that is fixedly connected to the input shaft and by a recess in the output shaft, wherein a section of the safety pin projects into the recess, and wherein the recess is dimensioned such that there is clearance between a wall of the recess and the safety pin, allowing rotation of the input shaft relative to the output shaft. Thus, a gap or clearance exists between the safety pin and the wall of the recess, permitting rotation of the input shaft relative to the output shaft. Rotation is only prevented when the safety pin abuts the wall. Various geometric shapes are possible for the safety pin, but it preferably has a cylindrical shape. Similarly, various geometric shapes are possible for the recess, which, however, should be adapted to the shape of the safety pin.The recess can, for example, extend completely through the output shaft in a direction transverse to the axis of the output shaft and preferably centrally, for example as a through-hole, and the safety pin can pass completely through the recess. If the output shaft is hollow inside in the area of ​​the recess, for example, then the recess can be formed on both opposite sections of the hollow shaft's outer surface.

[0013] It is advantageous if the recess has opposing safety surfaces against which the safety pin can come into contact when the input shaft is rotated relative to the output shaft, the distance and / or angular position of the safety surfaces relative to each other defining the maximum angle of rotation. For example, the recess can have a wedge-shaped cross-section in sections, which allows rotation of the input shaft relative to the output shaft within certain limits. The recess can advantageously be wedge-shaped when viewed from the outer circumferential surface of the output shaft towards its axis. The recess can then have a larger opening width on the respective outer surface of the output shaft than on the respective inner surface of the section of the output shaft's circumferential surface facing the axis.

[0014] Preferably, the input shaft has an input-side bore in which a section of the safety pin is received without play. In the context of the present invention, a bore is to be understood as any cavity formed in an element, regardless of how it was created. The input-side bore is particularly preferably arranged transversely to the axis of the input shaft and centrally, and preferably extends completely through the input shaft. According to the invention, it is possible for the input-side bore to have a circular cross-section, with the safety pin being cylindrical. The safety pin can be inserted into the input-side bore and removed from it as needed.Preferably, the center of the input shaft bore on the input side and the previously described recess in the output shaft are aligned in accordance with each other.

[0015] Preferably, the safety pin connects the torsion bar to the input shaft in the input-side connection area in a rotationally fixed manner. The safety pin thus not only secures the input shaft against the output shaft, but also establishes the rotationally fixed connection between the input shaft and the torsion bar. This is preferably implemented such that the torsion bar has an input-side torsion bar bore in which a section of the safety pin is received without play. The safety pin can therefore be arranged section by section in the input-side input shaft bore and in the input-side torsion bar bore, with a further section of the safety pin being arranged in the recess.Preferably, the input shaft bore and the input torsion bar bore are aligned with each other. According to other embodiments of the invention, it is also possible that the safety pin is not used to connect the input shaft to the torsion bar. In that case, for example, another connecting element such as a connecting pin or the like can be inserted into the input shaft and the torsion bar.

[0016] According to the invention, the output shaft may have an output shaft bore in the output-side connection area, and the torsion bar may have an output torsion bar bore in the output-side connection area, wherein a connecting pin is received section by section in the output shaft bore and the output torsion bar bore, respectively, without play. In this way, the torsion bar can be connected to the output shaft in a rotationally fixed manner. However, other possibilities for connecting the torsion bar to the output shaft are also conceivable within the scope of the present invention.

[0017] According to a particular embodiment of the invention, the output shaft has a passage extending longitudinally along the output shaft, in which the torsion bar is arranged, at least to a large extent. Within the passage, the torsion bar is elastically deformed when the input shaft is rotated relative to the output shaft. Since the torsion bar is arranged within the output shaft, the shaft assembly can have a comparatively short design, as no additional space needs to be provided for the torsion bar, for example, between the input and output shafts. According to the invention, it is possible for the torsion bar to be arranged within the passage of the output shaft, at least with the portion extending from the input-side connection area to the output-side connection area. However, according to the invention, the torsion bar can also extend into other areas of the output shaft.According to a variant of the invention, the torsion bar can further protrude from one end of the output shaft. Preferably, at least 70%, more preferably at least 80%, and more preferably at least 90%, and particularly at least 95% of the torsion bar's length along its axis, are arranged within the passage of the output shaft.

[0018] The input shaft has a receiving chamber at its end facing the output shaft, which accommodates at least one end section of the output shaft. To connect the input shaft to the output shaft, the output shaft can thus be inserted into the receiving chamber of the input shaft. The receiving chamber can, for example, be cylindrical. The receiving chamber can also advantageously be configured as a blind hole. According to an advantageous embodiment of the invention, the anti-rotation device is arranged at the level of the receiving chamber. For example, the safety pin described above can be inserted into both the input shaft and the output shaft at the level of the receiving chamber.

[0019] According to the invention, not only is the end section of the output shaft received by the input shaft, but the torsion bar is also arranged within the receiving space, exclusively within the output shaft. This means that one end of the torsion bar is located at the level of the receiving space within the end section of the output shaft. A rotationally fixed connection between the torsion bar and the input shaft at the level of the receiving space is particularly preferred. For this purpose, the safety pin can be inserted into bores in both the input shaft and the torsion bar at the level of the receiving space, according to the invention.

[0020] According to an advantageous embodiment of the invention, the component of the shaft assembly that forms the rotationally fixed connection in the input-side connection area between the torsion bar and the input shaft also forms part of the anti-rotation device. This component can be the safety pin described above or a comparable locking element. However, the precise design of the anti-rotation device is freely selectable in this embodiment and is not limited to the previously described variant in which the output shaft has a recess in which a section of the safety pin is arranged.

[0021] The output shaft is preferably a threaded spindle. A threaded spindle is provided with an external thread. In the present invention, the external thread preferably extends at least over a section of the threaded spindle between the input-side connection area and the output-side connection area. In a steering gear, a nut (also called a ball screw nut) is usually fitted onto the external thread of the threaded spindle. This nut is enclosed in the steering gear in such a way that it is not rotatable. When the threaded spindle rotates, the nut is therefore displaced axially along the threaded spindle. The nut can, for example, be coupled to a steering column lever, via which steering forces are transmitted to the wheels of a vehicle. In principle, however, the shaft arrangement according to the invention can also be used in other areas of application.

[0022] According to a further aspect of the invention, a steering gear is described which is equipped with the shaft arrangement described above. This steering gear is preferably designed such that forces from a steering wheel can be transmitted to the input shaft of the shaft arrangement. The input shaft is elastically coupled to the output shaft of the shaft arrangement by means of the torsion bar. If the torsion bar breaks or can no longer fulfill its coupling function for any other reason, steering is still possible via the steering gear. This is made possible by the anti-rotation device of the shaft arrangement, which limits the rotation of the input shaft relative to the output shaft to a maximum angle of rotation and, upon reaching this maximum angle of rotation, can transmit a torque from the input shaft to the output shaft.

[0023] The drawings depict an advantageous embodiment of the invention. They show: Fig. 1 a schematic representation of a shaft arrangement according to the invention for a steering gear in a side view, Fig. 2 a schematic representation of an output wave of the wave arrangement in a side view, Fig. 3 a schematic representation of the wave arrangement in a sectional view, Fig. 4 a schematic representation of a rotation lock of the shaft arrangement in a sectional view and Fig. 5 a schematic representation of the rotational safety device of the shaft arrangement in a further sectional view.

[0024] Fig. Figure 1 shows a schematic side view of a shaft arrangement 1 according to the invention for a steering gear. The shaft arrangement 1 has an input shaft 2 and an output shaft 3, the output shaft 3 being a threaded spindle. The output shaft 3 is provided with an external thread 4. When the shaft arrangement 1 is used in a steering gear, a nut (also called a ball screw nut) can, for example, be fitted onto the external thread 4. This nut moves axially along the output shaft 3 as it rotates and can be coupled to a steering column lever of the steering gear. The shaft arrangement 1 also has a torsion bar 5. The torsion bar 5 is arranged mostly inside the output shaft 3 and the input shaft 2, respectively, and projects into Fig. 1 from the output wave 3 only with a small section.

[0025] The output wave 3 is in a (in Fig. The input shaft 2 is inserted into a receiving space (not visible) in the input shaft 2. A safety pin 6 is also inserted into a section of the input shaft 2 that contains the receiving space. The safety pin 6 connects the input shaft 2 to the torsion bar 5 in a rotationally fixed manner. Furthermore, the safety pin 6 limits the rotation of the input shaft 2 relative to the output shaft 3 to a maximum angle of rotation. The shaft assembly 1 also includes a connecting pin 7. This connecting pin 7 is inserted into an end of the output shaft 3 opposite the input shaft 2. The connecting pin 7 connects the torsion bar 5 to the output shaft 3 in a rotationally fixed manner.

[0026] Fig. Figure 2 shows a schematic representation of the output shaft 3 of the shaft assembly. The output shaft 3 has an output shaft bore 8 on the output side for receiving the connecting pin 7 (not shown here). An end section 9 of the output shaft 3 is slightly narrower than other sections of the output shaft 3. The end section 9 of the output shaft 3 can be inserted into the input shaft. A recess 10 is located in the end section 9. The connecting pin 7 (not shown here) passes through this recess. Fig. 2 safety pins 6, which are also not shown, were passed through them.

[0027] Fig. Figure 3 shows a schematic representation of the wave arrangement 1 in a sectional view. The section runs along the section line AA according to Fig. 1. The operation of the shaft assembly 1 is explained in more detail below. The input shaft 2 has a receiving chamber 11. The end section 9 of the output shaft 3 is inserted into the receiving chamber 11 of the input shaft 2. The output shaft 3 has a passage 12 in which the torsion bar 5 is located. The torsion bar 5 is connected to the input shaft 2 in an input-side connection area 13 of the shaft assembly 1 in a rotationally fixed manner by means of the safety pin 6. The safety pin 6 sits without play in an input-side input shaft bore 14 of the input shaft 2 and in an input-side torsion bar bore 15 of the torsion bar 5. The torsion bar 5 is also connected to the output shaft 3 in an output-side connection area 16 of the shaft assembly 1 in a rotationally fixed manner by means of the connecting pin 7.The connecting pin 7 sits without play in the output shaft bore 8 of the output shaft 3 and in an output torsion bar bore 17 of the torsion bar 5. The input shaft 2 is thus connected to the output shaft 3 via the torsion bar 5. Since the torsion bar 5 is torsionally elastic, rotational movement of the input shaft 2 relative to the output shaft 3 is possible.

[0028] The input shaft 2 should not be able to rotate too far relative to the output shaft 3. In particular, if the torsion bar 5 is damaged, it must be ensured that torque can still be transmitted from the input shaft 2 to the output shaft 3. This is guaranteed by the safety pin 6. The safety pin 6 passes through the recess 10 of the output shaft 3. The recess 10 is dimensioned such that there is clearance between the safety pin 6 and a wall of the recess 10, allowing the input shaft 2 to rotate relative to the output shaft 3 up to a maximum angle of rotation. This is evident from the Fig. 4 and Fig. 5. The recess 10 and the safety pin 6 together form a rotation lock for the shaft assembly 1.

[0029] Fig. Figure 4 shows a schematic representation of the rotation lock 18 of the shaft assembly in a sectional view. The section runs along the section line CC. Fig. 3. The anti-rotation device 18 is formed by the recess 10 and the safety pin 6. The recess 10 is located in the end section 9 of the output shaft 3. The safety pin 6 passes through the recess 10. Between the safety pin 6 and a wall of the recess 10, there are clearances 19 that allow movement of the safety pin 6 within the recess 10. Thus, it is possible to rotate the input shaft 2 relative to the output shaft 3 until a maximum angle of rotation is reached, at which point the safety pin 6 engages safety surfaces 20 ( Fig. 5) the recess 10 comes to the request.

[0030] Fig. Figure 5 shows a schematic representation of the rotation lock 18 of the shaft assembly in a further sectional view. This section runs along the section line BB. Fig. 1. The safety pin 6 sits without play in the input-side input shaft bore 14 of the input shaft 2 and in the input-side torsion bar bore 15 of the torsion bar 5. The safety pin 6 also passes through the recess 10 of the output shaft 3. Between the safety surfaces 20 of the recess 10 and the safety pin 6 are clearances 19. This allows the input shaft 2 to be rotated relative to the output shaft 3 until the safety pin 6 comes to rest against the safety surfaces 20. This prevents the torsion bar 5 from being rotated too far, and, should the torsion bar 5 fail, torque can be transmitted from the input shaft 2 to the output shaft 3 via the safety pin 6. REFERENCE MARK LIST 1 Wave arrangement 2 Input wave 3 Output wave 4 external threads 5 Torsion bar 6 safety pin 7 Connecting pin 8 Output-side output shaft bore 9 Final Section 10 recesses 11 Recording Room 12 rounds 13 Entrance-side connection area 14 Input-side input shaft bore 15 Input-side torsion bar bore 16 Output side connection area 17 Output-side torsion bar bore 18 Rotation lock 19 Free space 20 safety area

Claims

[1] Shaft assembly (1) for a steering gear comprising an input shaft (2), an output shaft (3) and a torsion bar (5), wherein the torsion bar (5) is non-rotatably connected to the input shaft (2) in an input-side connection area (13) of the shaft assembly (1), wherein the torsion bar (5) is non-rotatably connected to the output shaft (3) in an output-side connection area (16) of the shaft assembly (1), and wherein the input-side connection area (13) is spaced apart from the output-side connection area (16), wherein the shaft assembly (1) has an anti-rotation device (18), wherein the anti-rotation device (18) limits the rotation of the input shaft (2) relative to the output shaft (3) to a maximum angle of rotation and, upon reaching the maximum angle of rotation, can transmit a torque from the input shaft (2) to the output shaft (3),wherein the input wave (2) has a receiving space (11) at its end facing the output wave (3), which receives at least one end section (9) of the output wave (3), characterized by , that the torsion bar (5) is arranged within the receiving space (11) exclusively within the output shaft (3). [2] Shaft arrangement (1) according to claim 1, characterized by , that the anti-rotation device (18) is formed by a safety pin (6) which is connected to the input shaft (2) in a rotationally fixed manner and by a recess (10) in the output shaft (3), wherein a section of the safety pin (6) is arranged to project into the recess (10), and wherein the recess (10) is dimensioned such that there is a clearance between a wall of the recess (10) and the safety pin (6) which allows the rotation of the input shaft (2) relative to the output shaft (3). [3] Shaft arrangement (1) according to claim 2, characterized by, that the recess (10) has mutually opposing safety surfaces (20) against which the safety pin (6) can come into contact when the input shaft (2) is rotated relative to the output shaft (3), wherein the distance and / or the angular position of the safety surfaces (20) to each other determines / determine the maximum angle of rotation. [4] Shaft arrangement (1) according to claim 2 or 3, characterized by , that the input shaft (2) has an input-side input shaft bore (14) in which a section of the safety pin (6) is received without play. [5] Shaft arrangement (1) according to any one of claims 2 to 4, characterized by , that the safety pin (6) connects the torsion bar (5) to the input shaft (2) in the input-side connection area (13) in a rotationally fixed manner. [6] Shaft arrangement (1) according to any one of claims 2 to 5, characterized by, that the torsion bar (5) has an input-side torsion bar bore (15) in which a section of the safety pin (6) is received without play. [7] Shaft arrangement (1) according to one of the preceding claims, characterized by , that the output shaft (3) has an output shaft bore (8) in the output-side connection area (16) and the torsion bar (5) has an output torsion bar bore (17) in the output-side connection area (16), wherein a connecting pin (7) is received section by section in the output shaft bore (8) and the output torsion bar bore (17) respectively without play. [8] Shaft arrangement (1) according to one of the preceding claims, characterized by , that the output shaft (3) has a passage (12) extending in the longitudinal direction of the output shaft (3) in which the torsion bar (5) is arranged at least to a large extent. [9] Shaft arrangement (1) according to claim 8, characterized by , that the torsion bar (5) is arranged at least with the part which extends from the input-side connection area (13) to the output-side connection area (16) in the passage (12) of the output shaft (3). [10] Shaft arrangement (1) according to any of the preceding claims, characterized by , that the rotation lock (18) is arranged at the level of the receiving space (11). [11] Shaft arrangement (1) according to any of the preceding claims, characterized by , that the rotationally fixed connection between the torsion bar (5) and the input shaft (2) is formed at the level of the receiving space (11). [12] Shaft arrangement (1) according to any of the preceding claims, characterized by, that the component of the shaft arrangement (1) forming the rotationally fixed connection in the input-side connection area (13) between the torsion bar (5) and the input shaft (2) also forms part of the rotation protection (18). [13] Shaft arrangement (1) according to one of the preceding claims, characterized by , that the output shaft (3) is designed as a threaded spindle. [14] Steering gear with a shaft arrangement (1) according to any one of claims 1 to 13.

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