INERTIA SENSOR AND METHOD FOR REDUCING THE FRICTION BETWEEN TWO COMPONENTS OF AN INERTIA SENSOR

Abstract

An inertia sensor (10), in particular provided on a belt retractor (12), includes at least two components which are reversibly movable relative to each other and each of which includes at least one contact surface (20, 22, 34, 36) on which the components are in contact with each other, wherein at least one of the contact surfaces (20, 22, 34, 36) is coated with graphite powder (38).

Claims

1-10. (canceled)

11. An inertia sensor (10) provided on a belt retractor (12), comprising at least two components which are reversibly movable relative to each other and each of which includes at least one contact surface (20, 22, 34, 36) on which the components are in contact with each other, wherein at least one of the contact surfaces (20, 22, 34, 36) is coated with graphite powder (38).

12. The inertia sensor (10) according to claim 11, wherein at least the contact surface (22, 34, 36) of one of the components is made from plastic.

13. The inertia sensor (10) according to claim 11, wherein the components are arranged so that the contact surfaces (20, 22, 34, 36) are shifted against each other.

14. The inertia sensor (10) according to claim 11, wherein an average grain size of the graphite particles of the graphite powder (38) ranges from 2 μm and 15 μm.

15. The inertia sensor (10) according to claim 11, wherein an inertia element (16), a deflection element (18) in direct contact with the inertia element (16) and a sensor element (32) in direct contact with the deflection element (18) are provided, the deflection element (18) including a contact surface (22, 34) on each of opposite outer faces and both contact surfaces (22, 34) being coated with graphite powder (38).

16. The inertia sensor (10) according to claim 15, wherein the deflection element (18) has a shell-type portion (26), wherein a contact surface (22) is provided on a concave side (28) of the shell-type portion (26) facing the inertia element (16), and a contact surface (34) is provided on a convex side (30) of the shell-type portion (26) facing the sensor element (32).

17. A method for reducing the friction between at least two components of an inertia sensor (10) according to claim 11, the components including contact surfaces (20, 22, 34, 36) reversibly movable relative to each other, wherein a coating of graphite powder (38) is applied to at least one of the contact surfaces (20, 22, 34, 36).

18. The method according to claim 17, wherein at least one of the components is completely coated with graphite powder (38).

19. The method according to claim 17, wherein the components comprise an inertia element (16), a deflection element (18) in direct contact with the inertia element (16) and a sensor element (32) in direct contact with the deflection element (18), the deflection element (18) including a contact surface (22, 34) on each of opposite outer faces, and only the deflection element (18) being coated with graphite powder (38).

20. The method according to claim 17, wherein the graphite powder (38) reduces the electrostatic charge between the components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Hereinafter, the invention shall be described in detail by way of an embodiment with reference to the attached drawings, wherein:

[0027] FIG. 1 shows a schematic side view of a cutout of a belt retractor comprising an inertia sensor according to the invention;

[0028] FIG. 2 shows a top view onto the end face of the belt retractor from FIG. 1; and

[0029] FIG. 3 shows a schematic sectional view of the inertia sensor according to the invention along a line III-III in FIG. 1.

DETAILED DESCRIPTION

[0030] The Figures illustrate an inertia sensor 10 which in this example is part of a belt retractor 12 shown in portion only.

[0031] The Figures illustrate the belt retractor 12 in the final vehicle-mounted alignment. The inertia sensor 10 in the shown embodiment is arranged, in the installed state, at a lower end of the belt retractor 12.

[0032] A sensor housing 14 is usually integrally connected to a housing of the belt retractor 12.

[0033] The inertia sensor 10 in this example includes three components movable relative to each other. In the sensor housing 14, an inertia element 16, here in the form of a metal ball, is accommodated as a first component so that it can move freely within the sensor housing 14. In the normal case, the ball rolls off an inner face of the sensor housing 14.

[0034] On the side of the inertia element 16 opposite to the contact area of the inertia element 16 with the sensor housing 14, a deflection element 18 is disposed as a second component such that contact surfaces 20, 22 constantly contact each other at the inertia element 16 and at the deflection element 18.

[0035] The deflection element 18 is movably connected to the sensor housing 14. In this example, on one side of the deflection element 18 a pivot axis 24 is provided which is firmly supported within the sensor housing 14 and about which the deflection element 18 can pivot.

[0036] The deflection element 18 in this case includes a shell-type portion 26 (see FIG. 3) whose concave side 28 faces the inertia element 16 and forms the contact surface 22, whereas the opposite convex side 30 thereof faces away from the inertia element 16.

[0037] Above the deflection element 18, a sensor element 32 including a contact surface 34 which constantly abuts on a contact surface 36 on the convex side 30 of the deflection element 18 is arranged as a third component. The sensor element 32 is fixed to be deflectable on the sensor housing 14, for example.

[0038] When the vehicle in which the belt retractor 12 is mounted experiences positive or negative acceleration, the inertia element 16 is moved relative to the sensor housing 14 out of its home position shown in FIG. 3. In so doing, the ball of the inertia element 16 in this case rolls off the inner face of the sensor housing 14. Accordingly, the inertia element 16 moves also relative to the deflection element 18, with the two contact surfaces 20, 22 being shifted against each other, hence the deflection element 18 slides along the surface of the inertia element 16. This movement of the inertia element 16 relative to the deflection element 18 causes the deflection element 18 to be pivoted about the pivot axis 24, and, in so doing, to deflect the sensor element 32 from the home position thereof (see FIG. 3) into a deflected position (not shown). The two contact surfaces 34, 36 of the deflection element 18 and the sensor element 32 are shifted against each other and slide along each other. The movement of the sensor element 32 ensures a ratchet which blocks a belt reel of the belt retractor 12 (not shown) to be pivoted.

[0039] Whereas the inertia element 16 frequently is made from metal, both of the deflection element 18 and the sensor element 32 are usually plastic parts. A suitable plastic material is POM (polyoxymethylene), for example.

[0040] In the embodiment shown here, the deflection element 18 is completely coated with a graphite powder 38. In this case, for example a graphite powder 38 having an average grain size ranging from 2 μm to 15 μm is used.

[0041] For this purpose, prior to assembling the inertia sensor 10, the entire deflection element 18 is immersed, for example, into graphite powder 38 or is sprayed with graphite powder 38. The graphite powder 38 then adheres to the contact surfaces without any further aids.

[0042] Consequently, a thin permanent layer of graphite powder 38 is formed along the contact surfaces 20, 22 of the deflection element 18 and the inertia element 16 as well as along the contact surfaces 34, 36 of the deflection element 18 and the sensor element 32. The layer thickness may range from about 2 μm and 200 μm, for example. Due to the small layer thickness, the layer is not explicitly illustrated in the Figures.

[0043] The graphite coating reduces the friction on the contact surfaces 20, 22 and 34, 36. Moreover, it ensures permanent charge exchange between the inertia element 16, the deflection element 18 and the sensor element 32.