LINEAR ACTUATOR COMPRISING A MEASURING DEVICE FOR DETERMINING A POSITION OF A LINEARLY MOVEABLE COMPONENT

Abstract

A linear actuator for a steer-by-wire system including a component, in particular an axle or a shaft, that can be moved along a linear trajectory, and including a measuring device for determining a position of the component. The measuring device has a coil for inductively determining the position of the component, and the coil is arranged coaxially relative to the linear trajectory of the component.

Claims

1. A linear actuator for a steer-by-wire system, the linear actuator comprising: a component that is movable along a linear trajectory; a measuring device configured for determining a position of the component; wherein the measuring device has a coil for inductively determining the position of the component, and the coil is arranged coaxially relative to the linear trajectory of the component.

2. The linear actuator according to claim 1, wherein the coil is arranged on a coil carrier.

3. The linear actuator according to claim 2, wherein the coil carrier has a receiving region for the coil and a fastening region for fastening the coil carrier in a recess of a housing which encloses the trajectory of the component.

4. The linear actuator according to claim 2, further comprising a cover which is arranged in a recess of a housing enclosing the trajectory of the component, and the coil carrier is connected to the cover.

5. The linear actuator according to claim 1, further comprising evaluation electronics connected to the coil.

6. The linear actuator according to claim 1, wherein the measuring device further comprises a second coil such that there are two of the coils for inductively determining the position of the component, and the coils are arranged coaxially relative to the linear trajectory of the component.

7. The linear actuator according to claim 1, further comprising a target made of a ferromagnetic material arranged on the component.

8. The linear actuator according to claim 1, wherein the component comprises a material transition or target contour detectable by the coil.

9. The linear actuator according to claim 1, wherein the component is formed from a ferromagnetic material and a target made of duplex steel is arranged on the component.

10. A method for determining a position of a component of a linear actuator for a steer-by-wire system, the method comprising: moving the component along a linear trajectory, and determining the position of the component by a measuring device which comprises a coil for inductively determining the position of the component that is arranged coaxially relative to the linear trajectory of the component.

11. A linear actuator, comprising: a component that is movable along a linear trajectory; a measuring device configured for determining a position of the component; wherein the measuring device has a coil for inductively determining the position of the component, and the coil is arranged coaxially relative to the linear trajectory of the component about the component.

12. The linear actuator according to claim 1, wherein the coil is arranged on a coil carrier.

13. The linear actuator according to claim 12, wherein the coil carrier has a receiving region for the coil and a fastening region for fastening the coil carrier in a recess of a housing which encloses the trajectory of the component.

14. The linear actuator according to claim 13, further comprising a cover arranged in the recess of the housing, and the coil carrier is connected to the cover.

15. The linear actuator according to claim 11, further comprising evaluation electronics connected to the coil.

16. The linear actuator according to claim 11, wherein the measuring device further comprises a second coil such that there are two of the coils for inductively determining the position of the component, and the coils are arranged coaxially relative to the linear trajectory of the component about the component.

17. The linear actuator according to claim 11, further comprising a target made of a ferromagnetic material arranged on the component.

18. The linear actuator according to claim 11, wherein the component comprises a material transition or target contour detectable by the coil.

19. The linear actuator according to claim 11, wherein the component is formed from a ferromagnetic material and a target made of duplex steel is arranged on the component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Further details and advantages of the disclosure will be explained below with reference to the exemplary embodiment shown in the drawings. In the figures:

[0020] FIG. 1 shows a first exemplary embodiment of a linear actuator in a schematic sectional view;

[0021] FIG. 2 shows a second exemplary embodiment of a linear actuator in a schematic sectional view; and

[0022] FIG. 3 shows a first exemplary embodiment of a measuring device that can be used with a linear actuator according to FIG. 1 or FIG. 2; and

[0023] FIG. 4 shows a second exemplary embodiment of a measuring device that can be used with a linear actuator according to FIG. 1 or FIG. 2.

DETAILED DESCRIPTION

[0024] FIG. 1 shows a first exemplary embodiment of a linear actuator 1 designed according to the disclosure. The linear actuator 1 is suitable for use as part of a rear-axle steering system of a motor vehicle and can deflect a wheel of the motor vehicle. The linear actuator 1 comprises a drive 3, which can be designed as an electric motor, for example. The drive 3 is coupled via a transmission 4 to a linearly movable component 2, which is designed in the manner of an axle. The transmission 4 is configured to convert a rotary motion of the drive 3 into a linear motion of the component 2. The component 2 is movable along a trajectory T that is linear and extends within a housing 5 of the linear actuator 1. On a side of the component 2 opposite the transmission 4, the component 2 is connected to a wheel carrier connecting element 7, to which a wheel carrier can be connected, which carries the wheel of the motor vehicle to be steered. In the exemplary embodiment, the wheel carrier connecting element 7 is designed as an eyelet. The housing 5 of the linear actuator 1 further comprises a fastening element 6, by means of which the linear actuator 1 can be fastened to a chassis element or a body part of a motor vehicle.

[0025] Another component of the linear actuator 1 is a measuring device 10 by means of which the position of the component 2 along its trajectory T can be determined. The measuring device 10 enables a compact design of the linear actuator 1 and will be described in more detail in connection with FIGS. 3 and 4.

[0026] The illustration in FIG. 2 shows a second exemplary embodiment of a linear actuator 1 according to the disclosure, in which such elements that exercise an identical function as in the linear actuator 1 according to the first exemplary embodiment are also denoted by identical reference signs. In contrast to the first exemplary embodiment, the linear actuator 1 according to the second exemplary embodiment is provided with a movable component 2, which is connected at two ends in each case to a wheel carrier connecting element 7, 8. Therefore, two wheels of a common axle can be deflected with the linear actuator 1 according to the second exemplary embodiment.

[0027] In FIG. 2, a region in which the measuring device 10 can be arranged to determine the position of the component 2 is indicated by dashed lines. Suitable measuring devices 10 are explained in connection with FIG. 3 and FIG. 4.

[0028] FIG. 3 shows a schematic representation of a measuring device 10 that can be used with a linear actuator according to the disclosure, for example as shown in FIG. 1 or FIG. 2. The measuring device 10 comprises a coil 11, by means of which the position of the component 2 can be inductively determined. According to the disclosure, the coil 11 is arranged coaxially relative to the linear trajectory T of the component 2 and can therefore be arranged completely inside the housing 5 of the linear actuator 1. This enables a compact design.

[0029] The coil 11 is arranged on a coil carrier 12, which is designed as an injection-molded part, for example as a plastic injection-molded part. The coil carrier 12 comprises a hollow cylindrical receiving region 12.1 for the coil 11 and a fastening region 12.2 for fastening the coil carrier 12 in a recess 5.1 of the housing 5. The fastening region 12.2 is connected to a cover 13. The cover 13 is arranged in a recess 5.1 of the housing 5 enclosing the trajectory of the component 2. Evaluation electronics 14 connected to the coil 11 are arranged inside the cover 13 and are used to evaluate the signals measured by the coil 11.

[0030] The component 2 according to FIG. 3 comprises a target contour 9 which is detectable by the coil 11. In the present case, the target contour 9 has a larger cross-section perpendicular to the trajectory T of the component 2. As soon as the target contour 9 moves with respect to the coil 11, it changes the inductance of the coil 11. The evaluation unit evaluates the signals measured by the coil 11 and uses the inductance or the change in inductance to determine the position of the target contour 9 and thus also the position of the component 2.

[0031] According to a variation of the exemplary embodiment shown in FIG. 3, the component 2 can have a material transition instead of or in addition to a target contour, which material transition can be detected by the coil 11. In such a material transition, the magnetic properties of the material of the component 2 change, for example because two sub-elements of the component 2 with different magnetic properties are adjacent to one another.

[0032] A further variation of the exemplary embodiment shown in FIG. 3 provides that a target made of a ferromagnetic material is formed on the component 2, or that the component 2 is formed from a ferromagnetic material and a target made of duplex steel is formed on the component 2.

[0033] FIG. 4 shows another variant of a measuring device 1 for a linear actuator 1 according to the disclosure. This measuring device 1 is basically the same as the measuring device 1 according to FIG. 3, except that it comprises exactly two coils 11 for inductively determining the position of the component 2. Both coils 11 are mirror-symmetrical, arranged coaxially relative to the linear trajectory T of the component and are identical in design. Both coils 11 are connected to the evaluation electronics 14 and are configured in such a way that they can determine the difference between the signals measured by the two coils 11 and can use this to determine the position of the component 2.

[0034] The linear actuators 1 described above can be used to carry out a method for determining the position of a component 2 of the linear actuator 1 for a steer-by-wire system, wherein the component 2, in particular an axle or a shaft, is moved along the linear trajectory T, and wherein the measuring device 10 is used to determine the position of the component 2. The measuring device 10 comprises a coil 11 for inductively determining the position of the component 2 and is arranged coaxially relative to the linear trajectory T of the component 2.

LIST OF REFERENCE SIGNS

[0035] 1 Linear actuator [0036] 2 Component [0037] 3 Drive [0038] 4 Transmission [0039] 5 Housing [0040] 5.1 Recess [0041] 6 Fastening element [0042] 7 Wheel carrier connecting element [0043] 8 Wheel carrier connecting element [0044] 9 Target contour [0045] 10 Measuring device [0046] 11 Coil [0047] 12 Coil carrier [0048] 12.1 Receiving region [0049] 12.2 Fastening region [0050] 13 Cover [0051] 14 Evaluation electronics [0052] T Trajectory