Seat-belt retractor with determination of angle of rotation

Abstract

A belt retractor (10) is provided with a retractor shaft (12) and a device (26) for determining the rotational speed and/or the angle of rotation of the retractor shaft (12), with a rotating magnetic element (18), a stationary magnetic field sensor (24) and a stationary element guiding the magnetic flux (20) arranged between the rotating magnetic element (18) and the magnetic field sensor (24).

Claims

1. A belt retractor (10) comprising a retractor shaft (12) and a device (26) for determining the rotational speed and/or the angle of rotation of the retractor shaft (12), comprising a rotating magnetic element (18), a stationary magnetic field sensor (24) and a stationary element (20) guiding the magnetic flux between the rotating magnetic element (18) and the magnetic field sensor (24).

2. The belt retractor according to claim 1, wherein the element (20) guiding the magnetic flux is made of magnetically soft material.

3. The belt retractor according to claim 1, wherein the element (20) guiding the magnetic flux is curved and/or bent.

4. The belt retractor according to claim 1, wherein the dimensions of the end face of the element (20) guiding the magnetic flux facing the magnetic field sensor (24) substantially correspond to the dimensions of the magnetic field sensor (24).

5. The belt retractor according to claim 4, wherein the end face of the element (20) guiding the magnetic flux facing the magnetic field sensor (24) is aligned substantially in parallel to the opposite surface of the magnetic field sensor (24).

6. The belt retractor according to claim 1, wherein the magnetic field sensor (24) is a Hall sensor.

7. The belt retractor according to claim 6, wherein the element guiding the magnetic flux is fastened to an ECU board (22) supporting the Hall sensor.

8. The belt retractor according to claim 1, wherein the rotating magnetic element (18) is connected indirectly or directly to the retractor shaft (12) or is driven by the same.

9. The belt retractor according to claim 1, wherein the rotating magnetic element (18) includes more than one pair of magnetic poles.

10. The belt retractor according to claim 1, wherein the rotating magnetic element (18) is arranged on a drive motor (16), the retractor shaft (12) and/or a gearwheel (28) of the belt retractor (10).

11. The belt retractor according to claim 1, wherein the belt retractor (10) is a retracting tensioner.

12. The belt retractor according to claim 1, wherein the magnetic field sensor is an SMD-Hall sensor.

13. The belt retractor according to claim 1, wherein the rotating magnetic element is configured as a magnetic wheel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention will result from the following description and from the enclosed drawings which are referred to In the drawings:

(2) FIG. 1 shows a belt retractor according to the invention in a front view,

(3) FIG. 2 shows the retractor shaft of the belt retractor according to FIG. 1 and a device for determining the rotational speed and/or the angle of rotation according to FIG. 1,

(4) FIG. 3 a view of a further embodiment of the belt retractor according to the invention including two alternative embodiments of the device for determining the rotational speed and/or the angle of rotation, and

(5) FIG. 4 a view of a partly cut belt retractor according to the invention including a further embodiment of the device for determining the rotational speed and/or the angle of rotation.

DESCRIPTION

(6) In FIG. 1 a belt retractor 10 is illustrated in the form of a retracting tensioner. The belt retractor 10 includes a retractor shaft 12 for receiving the seat belt (not shown) which is connected to a drive motor 16 for tensioning or pre-tensioning via a drive unit 14. A magnetic element 18, preferably a magnetic wheel, is connected to the drive motor, more exactly its drive shaft, in a rotationally fixed manner.

(7) An element 20 guiding the magnetic flux which is fastened to an ECU board 22 is arranged in the direct vicinity of the magnetic element 18 (cf. FIG. 2).

(8) On the ECU board 22 moreover a magnetic field sensor 24 is arranged. The magnetic element 18, the element 20 guiding the magnetic flux and the magnetic field sensor 24 in this case form a device for determining the rotational speed and/or the angle of rotation of the retractor shaft 12.

(9) In the illustration of FIG. 1 the element 20 guiding the magnetic flux and the magnetic field sensor 24 are covered by the magnetic element 18, therefore it is referred to FIG. 2 which separately illustrates the device 26 for determining the rotational speed and/or the angle of rotation of the retractor shaft 12. It is evident that the magnetic field sensor 24, preferably an SMD-Hall sensor, is directly fastened to the ECU board 22. The element 20 guiding the magnetic flux is arranged between the magnetic field sensor 24 and the magnetic element 18.

(10) The element 20 guiding the magnetic flux is made of magnetically soft material, for example of electric sheets.

(11) Moreover, the side of the element 20 guiding the magnetic flux facing the magnetic field sensor 24 is tapered so that its cross-section approximately corresponds to the surface of the magnetic field sensor 24 sensitive to the magnetic field at its end face facing the magnetic field sensor 24, the end face further being aligned in parallel to the opposite surface at the sensor 24.

(12) In order to determine the rotational speed and/or the angle of rotation of the drive motor 16 a magnetic field varying corresponding to the angle of rotation is generated by the magnetic element 18 connected to the shaft of the drive motor 16 in a rotationally fixed manner. The magnetic field then causes a corresponding variation of its magnetization in the element 20 guiding the magnetic flux which is arranged in direct vicinity of the magnetic element 18.

(13) On the side of the element 20 guiding the magnetic flux facing the magnetic field sensor 24 in turn a varying magnetic field is induced due to the alternating magnetization of the element 20 guiding the magnetic flux. The variation of the magnetic field always corresponds to the rotational speed and/or the angle of rotation of the rotating magnetic element 18 and can be detected by the magnetic field sensor 24. Now the speed and/or the angle of rotation of the drive motor 16 and thus the speed and/or the angle of rotation of the drive shaft 12 can be concluded from the signal of the magnetic field sensor 24, in particular because the transmission ratio of the drive unit 14 is known.

(14) The embodiments according to FIGS. 3 and 4 correspond to the embodiment according to FIGS. 1 and 2, wherein hereinafter only the differences shall be discussed and parts that are equal or equal in function are provided with the afore-introduced reference numerals.

(15) FIG. 3 illustrates two embodiments of the device for determining the speed or the angle of rotation. The magnetic field sensor 24 is arranged on the ECU board 22 in the area of the retractor shaft 12 and the magnetic element is provided directly on the retractor shaft 12 or on a gearwheel 28 of the drive unit 14 meshing with the retractor shaft 12.

(16) For each of the two alternatives an element 20 guiding the magnetic flux is shown in FIG. 3, namely between the retractor shaft 12 and the magnetic field sensor 24 or the gearwheel 28 and the magnetic field sensor 24. The element 20 guiding the magnetic flux is bent or curved once or several times m different planes This does not influence the action of the element 20 guiding the magnetic flux so that the determination of the rotational speed and/or the angle of rotation of the retractor shaft 12 or the gearwheel 28 operates as illustrated in the first embodiment.

(17) FIG. 4 illustrates another embodiment of the device according to the invention. In contrast to the previous embodiments, the magnetic element 18 is supported on a separate axle. The magnetic element 18 is in frictional closure or in form closure with the retractor shaft 12 so that rotation of the retractor shaft 12 entails rotation of the magnetic element 18. In this way the rotational speed and/or the angle of relation of the retractor shaft 12 can be concluded from determining the rotational speed of the magnetic element 18.