LINEAR ACTUATOR FOR REAR AXLE STEERING ON A MOTOR VEHICLE

Abstract

The disclosure relates to a linear actuator, the housing of which encloses a pushrod which is guided displaceably along a longitudinal axis. The linear actuator includes a linear travel sensor intended for determining a position of the pushrod. A housing-side position receiver of the linear travel sensor includes a receiver section extending along the longitudinal axis, and a pushrod-side position transmitter that interacts contactlessly with the position receiver. The position transmitter is made from an electrically conductive material, and a transmitter contour of the linear travel sensor is curved about at least one dimensional axis.

Claims

1. A linear actuator, comprising: a housing enclosing a pushrod, the pushrod guided displaceably along a longitudinal axis, an inductive linear travel sensor configured for determining a position of the pushrod, the inductive linear travel sensor having: a housing-side position receiver comprising a receiver section extending along the longitudinal axis, and a pushrod-side position transmitter configured to interact contactlessly with the housing-side position receiver, the pushrod-side position transmitter constructed from an electrically conductive material and having a transmitter contour curved about at least one dimensional axis.

2. The linear actuator according to claim 1, wherein the transmitter contour is formed by: i) a transmitter surface facing the receiver section, and ii) a peripheral contour delimiting the transmitter surface, and at least one of the transmitter surface or the peripheral contour is curved about the at least one dimensional axis.

3. The linear actuator according to claim 2, wherein the peripheral contour is curved about a dimensional axis arranged transverse to the longitudinal axis.

4. The linear actuator according to claim 3, wherein the transmitter surface is configured to be planar and arranged parallel to the longitudinal axis.

5. The linear actuator according to claim 2, wherein the transmitter surface is curved about a dimensional axis arranged parallel to the longitudinal axis.

6. The linear actuator according to claim 2, wherein the transmitter surface is curved about a dimensional axis arranged transverse to the longitudinal axis.

7. The linear actuator according to claim 2, wherein the transmitter surface convexly crowned.

8. The linear actuator according to claim 2, wherein the pushrod-side position transmitter has a cylindrical pin projecting transversely from the pushrod, and a free front end of with the cylindrical pin has the transmitter contour.

9. The linear actuator according to claim 8, wherein a free end face of the cylindrical pin forms the transmitter surface, and the transmitter surface is delimited by a circular peripheral contour.

10. The linear actuator according to claim 9, wherein the cylindrical pin engages in a housing-side longitudinal groove of the inductive linear travel sensor and is mounted therein via a radial bearing.

11. The linear actuator according to claim 1, further comprising: a screw drive including a threaded spindle coupled to the pushrod, a nut arranged on the threaded spindle, and an electric motor configured to rotate the nut, and when the electric motor rotates the nut, the threaded spindle and pushrod are displaced together along the longitudinal axis.

12. The linear actuator according to claim 11, wherein a displacement of the threaded spindle and pushrod is configured to move a wheel in a motor vehicle.

13. The linear actuator according to claim 1, utilized within a rear axle steering system.

14. A linear actuator, comprising: a housing, a pushrod at least partially enclosed by the housing, a threaded spindle coupled to the pushrod, a nut arranged on the threaded spindle, an electric motor configured to rotate the nut such that rotary motion of the nut is converted to translational movement of the threaded spindle and pushrod along a longitudinal axis, an inductive linear travel sensor having: a position receiver comprising a receiver section extending along the longitudinal axis, and a position transmitter constructed from an electrically conductive material having a transmitter contour curved about at least one dimensional axis, the position transmitter configured to interact contactlessly with the position receiver via the transmitter contour to determine a longitudinal position of the linear actuator.

15. The linear actuator of claim 14, wherein the position transmitter is attached to the pushrod and the inductive linear travel sensor is configured to determine a longitudinal position of the pushrod.

16. The linear actuator according to claim 14, wherein the transmitter contour is formed by: i) a transmitter surface facing the receiver section, and ii) a peripheral contour delimiting the transmitter surface, and at least one of the transmitter surface or the peripheral contour is curved about the at least one dimensional axis.

17. The linear actuator according to claim 16, wherein the peripheral contour is curved about a dimensional axis arranged transverse to the longitudinal axis.

18. The linear actuator of claim 16, wherein the transmitter surface is convexly crowned.

19. The linear actuator according to claim 16, wherein the transmitter surface is curved about a dimensional axis arranged parallel to the longitudinal axis.

20. The linear actuator according to claim 16, wherein the transmitter surface is curved about a dimensional axis arranged transverse to the longitudinal axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The disclosure is explained in more detail below with reference to seven figures of a total of 22 figures. In the figures:

[0025] FIG. 1 shows a longitudinal section through a linear actuator of a rear axle steering on a motor vehicle,

[0026] FIG. 2 shows an enlargement of the section of FIG. 1,

[0027] FIG. 3 shows the enlargement of the section of FIG. 2 in cross-section through the linear actuator,

[0028] FIG. 4 shows a position transmitter of a linear travel sensor of the linear actuator as a single part in a perspective view,

[0029] FIG. 5 shows the linear travel sensor of the linear actuator with an alternative position transmitter,

[0030] FIG. 6 shows another view of the linear travel sensor of FIG. 5,

[0031] FIG. 7 shows the linear travel sensor in a perspective with an alternative position transmitter,

[0032] FIG. 8 shows the position transmitter of FIG. 7 as a single part,

[0033] FIG. 9 shows another alternative position transmitter in a perspective view,

[0034] FIG. 10 shows the linear travel sensor with the position transmitter of FIG. 9,

[0035] FIG. 11 shows another view of the linear travel sensor of FIG. 10,

[0036] FIG. 12 shows another alternative position transmitter in a perspective view,

[0037] FIG. 13 shows the linear travel sensor with the position transmitter of FIG. 12,

[0038] FIG. 14 shows another view of the linear travel sensor of FIG. 13,

[0039] FIG. 15 shows another alternative position transmitter in a perspective view,

[0040] FIG. 16 shows the linear travel sensor with the position transmitter of FIG. 15,

[0041] FIG. 17 shows another view of the linear travel sensor of FIG. 16,

[0042] FIG. 18 shows another alternative position transmitter in a perspective view,

[0043] FIG. 19 shows the linear travel sensor with the position transmitter of FIG. 18,

[0044] FIG. 20 shows another view of the linear travel sensor of FIG. 19,

[0045] FIG. 21 shows an enlargement of a section as in FIG. 2 with an alternative position transmitter, and

[0046] FIG. 22 shows the position transmitter of FIG. 21 in a perspective view.

DETAILED DESCRIPTION

[0047] FIG. 1 shows a longitudinal section through a linear actuator of a rear axle steering on a motor vehicle. The linear actuator has a housing 1 in which a pushrod 2 is guided displaceably along a longitudinal axis. The pushrod 2 penetrates the housing 1 at its ends, onto which heads or fork heads 7 are screwed to accommodate wheel control arms, which are not shown.

[0048] An electric motor 3 drives a screw drive 4 by means of a toothed belt not shown in more detail here, the nut 5 of which is driven in rotation by the toothed belt. The nut 5 engages with a threaded spindle 6, which is part of the pushrod 2. When the nut 5 rotates, the threaded spindle 6, i.e., the pushrod 2, is displaced along its longitudinal axis relative to the housing 1.

[0049] An inductive linear travel sensor 8 is provided for determining a position of the pushrod 2 (FIGS. 2 and 3). A housing-side position receiver 9 is provided with a receiver section 10 along the longitudinal axis. A pushrod-side position transmitter 11 interacts with the position receiver 9. The position transmitter 11 fixed to the pushrod 2 moves along a longitudinal axis while the pushrod 2 is displaced and sweeps over the receiver section 10 of the position receiver 9. A plurality of coils are accommodated in the region of the receiver section 10. The receiver section 10 generates a magnetic field. The position transmitter 11 is formed of metal and is electrically conductive. When the position transmitter 11 passes through the receiver section 10, the amplitude and frequency of the oscillating circuit are changed. Based on these changes, a proper position detection of the pushrod 2 can be performed. This position detection is performed contactlessly.

[0050] FIGS. 4 to 6 show the linear travel sensor 8 with the position transmitter 11, which in this exemplary embodiment has an approximately ring-shaped securing section 12, which is pushed onto the pushrod 2 and fixed with lock nuts 13. On the outer circumference of the securing section 12, a pin 14 extends in the radial direction and projects into a longitudinal groove 15 of the linear travel sensor 8 in which the receiver section 10 of the position receiver 9 is accommodated. FIGS. 5 and 6 clearly show that the pin 14 has its free end facing the receiver section 10.

[0051] The pin 14 is designed to be curved at its free end with a transmitter contour 16 around a dimensional axis. The transmitter contour 16 is formed here by the peripheral contour of the pin 14 and a transmitter surface 17 at the free front end of the pin 14. In this example, the dimensional axis coincides with the longitudinal axis of the pushrod 2. The curvature of the transmitter surface 17 is partially cylindrical. Under a rotation of the position transmitter 11 around the longitudinal axis, the measurement result is not or only insignificantly influenced, because this curvature is at least approximately parallel to the direction of movement under this rotation.

[0052] The shape of the transmitter contour 16 varies in the other exemplary embodiments.

[0053] FIGS. 7 and 8 show a variant with a position transmitter 18 formed as a ring 19. The ring 19 is fixed to the pushrod 2 in the same way as the ring-shaped securing section. The cylindrical lateral surface forms a transmitter surface 20 that is curved like the transmitter surface of the previously described exemplary embodiment.

[0054] FIGS. 9 to 11 show the linear travel sensor 8 with a further variant of a position transmitter 21, which differs from the position transmitter of the first exemplary embodiment only in that the transmitter surface 22 is curved about a dimensional axis arranged transverse to the longitudinal axis and transverse to the pin axis of the pin 14. This curvature is partially cylindrical. If the pushrod 2 tilts around this dimensional axis, the measurement result is not or only insignificantly influenced, because this curvature is at least approximately parallel to the direction of movement under this tilting.

[0055] The exemplary embodiment according to FIGS. 12 to 14 shows the linear travel sensor with a further alternative position transmitter 23, the crowned transmitter surface 24 of which combines the curvatures of the two transmitter surfaces 17 and 22 from the exemplary embodiments described above and in this way compensates for a tilt and a rotation of the pushrod 2 with regard to the measurement result.

[0056] The exemplary embodiment according to FIGS. 15 to 17 shows a position transmitter 25 that differs from all previously described exemplary embodiments in that the pin 14 is cylindrical and its transmitter contour 16 is formed by the planar transmitter surface 26 at the front end of the pin and the circularly curved peripheral contour 27 of the transmitter surface 26. The peripheral contour 27 is arranged around a dimensional axis that coincides with a pin axis. This variant is advantageous if tilting of the pushrod 2 is expected about an axis that roughly coincides with the pin axis.

[0057] The exemplary embodiment according to FIGS. 18 to 20 shows a position transmitter 28 that differs from the previously described exemplary embodiments in that the transmitter surface 29 is convexly crowned. The transmitter contour 16 is formed by the circular peripheral contour 27 and the crowned transmitter surface 29.

[0058] The exemplary embodiment according to FIGS. 21 and 22 differs from the exemplary embodiment according to FIGS. 15 to 17 in that the cylindrical pin 14 is supported by means of a radial bearing 31 designed as a rolling bearing 30 and is guided along a longitudinal wall of the longitudinal groove 15.

LIST OF REFERENCE SYMBOLS

[0059] 1 Housing [0060] 2 Pushrod [0061] 3 Electric motor [0062] 4 Screw drive [0063] 5 Nut [0064] 6 Threaded spindle [0065] 7 Fork head [0066] 8 Linear travel sensor [0067] 9 Position receiver [0068] 10 Receiver section [0069] 11 Position transmitter [0070] 12 Securing section [0071] 13 Lock nut [0072] 14 Pin [0073] 15 Longitudinal groove [0074] 16 Transmitter contour [0075] 17 Transmitter surface [0076] 18 Position transmitter [0077] 19 Ring [0078] 20 Transmitter surface [0079] 21 Position transmitter [0080] 22 Transmitter surface [0081] 23 Position transmitter [0082] 24 Transmitter surface [0083] 25 Position transmitter [0084] 26 Transmitter surface [0085] 27 Peripheral contour [0086] 28 Position transmitter [0087] 29 Transmitter surface [0088] 30 Rolling bearing [0089] 31 Radial bearing