Belt retractor and method for tightening an unused vehicle belt

Abstract

In a belt retractor (10) for a seat belt comprising a belt reel (12) onto which webbing (14) can be wound while being spring-loaded and comprising a tensioning device (16) which is adapted to act on the belt reel (12) in a winding direction (A), a control (18) is provided which is adapted to activate the tensioning device (16) when the seat belt is unloaded and not fastened.

Claims

1. A method of tensioning a non-used vehicle seat belt by acting on a belt reel (12) in the winding direction, wherein a control (18) detects that the seat belt is unfastened and that subsequently the belt reel (12) is rotated in the winding direction, and wherein the control (18) determines whether the vehicle has been parked and locked up, the control being configured so that it activates the tensioning so as to rotate the belt reel in the winding direction only when the vehicle is parked and locked up.

2. The method according to claim 1, wherein the tensioning is activated delayed in time vis--vis the determination of whether the vehicle has been parked and locked up.

3. The method according to claim 1, wherein the control (18) checks whether a vehicle occupant is present in the vehicle, by passenger compartment monitoring or a motion sensor, and the tensioning is activated only when no person is present in the vehicle.

4. The method according to claim 1, wherein a sensor determines a position of the vehicle and the belt reel is rotated in the winding direction only when the position of the vehicle is one wherein a vehicle-sensitive belt reel locking device is inactive.

5. The method according to claim 1, wherein the control (18) detects a position of a seat belt webbing (14) and the belt reel is rotated in the winding direction only when the seat belt is unfastened and wound onto the belt reel.

6. The method according to claim 5, wherein the control detects the position of the webbing by means of a pull-out sensor.

7. The method according to claim 1, wherein the control (18) checks a charge condition of a vehicle battery and the belt reel is rotated in the winding direction only above a defined charge condition of the vehicle battery.

8. The method according to claim 1, wherein the control (18) counts a number of times the belt is wound and unwound from the belt reel and the belt reel is rotated in the winding direction only after the belt has been wound and unwound from the belt reel a defined number of times.

9. A method of tensioning an unused vehicle seat belt, comprising: detecting if the seat belt is unfastened; determining if the vehicle is parked and locked up; and rotating a belt reel in a winding direction by a motor configured to tension the seat belt only when it is determined that the vehicle is parked and locked and the seat belt is unfastened.

10. The method of claim 9, wherein rotating the belt reel in the winding direction is delayed for a specified amount of time after it is determined that the vehicle is parked and locked.

11. The method of claim 9 further comprising determining if an occupant is present in the vehicle and rotating the belt reel in the winding direction when it is determined that no occupant is present in the vehicle.

12. The method of claim 9 further comprising sensing the position of the vehicle and rotating the belt reel in the winding direction only when the position of the vehicle is one wherein a vehicle-sensitive belt reel locking device is inactive.

13. The method of claim 9 further comprising detecting a position of a seat belt webbing and rotating the belt reel in the winding direction only when it is detected that the seat belt is unfastened and wound onto the belt reel.

14. The method according to claim 9 further comprising determining a charge condition of a battery of the vehicle and rotating the belt reel in the winding direction only when it is determined that the battery is above a defined charge condition.

15. The method according to claim 9 further comprising counting a number of times the belt is wound and unwound from the belt reel and rotating the belt reel in the winding direction only after the belt has been wound and unwound from the belt reel a defined number of times.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and features will be evident from the following description in connection with the enclosed drawings in which:

(2) FIG. 1 shows a schematic of a belt retractor according to the invention before the tensioning device is activated, and

(3) FIG. 2 shows a schematic of a belt retractor according to the invention after activation of the tensioning device.

DESCRIPTION

(4) FIG. 1 illustrates a belt retractor 10 comprising a belt reel 12 which is rotatably supported in the belt retractor 10 and onto which webbing 14 can be wound. A winding mechanism known per se and not shown here in detail acts on the belt reel 12 and applies a spring force directed in the winding direction A to the belt reel 12 so that the webbing 14 is wound onto the belt reel 12 while being spring-loaded.

(5) The belt retractor 10 further includes a tensioning device 16 comprising a motor adapted to act on the belt reel 12 additionally in the winding direction A, a control 18 for activating the tensioning device 16 and a locking device not shown here.

(6) As is evident from FIGS. 1 and 2, furthermore sensors adapted to measure different conditions of the vehicle are provided. The sensors are coupled to the control 18 and can transmit the measured vehicle conditions to the control 18.

(7) A first sensor provided on the belt retractor is an inclinometer 20 measuring the inclination of the vehicle relative to the horizontal. Said sensor usually controls a vehicle-sensitive locking of the belt reel 12. For this purpose the inclinometer 20 is additionally coupled to the locking device.

(8) A second sensor is a webbing extension sensor 22 for detecting the position of the webbing 14 and, resp., how far the webbing is extended.

(9) Additionally, a passenger compartment sensor 24 is provided for detecting the movements in the passenger compartment.

(10) In conventional belt retractors 10 the tensioning device 16 serves for tensioning the webbing 14 in the restraining case of the belt retractor 10 by reducing a belt slack and pulling the vehicle occupant into the seat. For this, the belt reel 12 is loaded in the winding direction A so that webbing 14 which is not required is wound onto the belt reel 12. Thus the webbing 14 of the seat belt is in tight contact with the vehicle occupant and the latter can be involved more quickly in the overall deceleration of the vehicle.

(11) The seat belt is usually wound comparatively loosely on the belt reel 12 by the repeated winding and unwinding operations. This has the effect that the windings 26 of the webbing 14 are tightened on the belt reel 12 upon locking of the belt reel 12 and a forward movement of the vehicle occupant, thereby additional webbing extension taking place although the belt reel 12 is locked. In general, this effect is referred to as film reel effect.

(12) A belt slack can be eliminated by the tensioning device 16 and in the case of tensioning a defined length of the webbing 14 can be drawn in even after the belt reel 12 has been locked.

(13) However, according to the invention it is provided that the control 18 activates the tensioning device 16 when the seat belt is not fastened so that upon activation of the locking device the webbing 14 is wound more tightly onto the belt reel 12.

(14) As is evident from FIG. 1, in the unloaded state the webbing 14 is tensioned between a fitting 28 fixed to the vehicle and the belt retractor 10, with deflection via deflection fittings 30 being possible. Hence the webbing 14 is completely stretched so that loading the belt reel 12 in the winding direction A results in the windings 28 of the webbing 14 being tightened on the belt reel 12, as is evident from FIG. 2.

(15) This results in the fact that the film reel effect is prevented or at least reduced during or after locking of the belt retractor 10. Exactly speaking, the belt reel 12 is loaded in the unloaded state of the seat belt so that said effect occurs, other than in prior art, already before fastening the seat belt and hence the webbing 14 is wound most tightly onto the belt reel 12 already before the seat belt is fastened.

(16) As the tensioning device 16 may cause very high tensioning forces to act on the belt reel 12 and thus on the webbing 14, however, this operation has to take place when the seat belt is not fastened and not in use so that the vehicle occupant is not confused, distracted or impaired by the sudden tensioning of the webbing 14.

(17) The passenger compartment sensor 24 detects, for example, whether a person is present in the passenger compartment. The tensioning device 16 is activated by the control 18 exclusively when no person is present in the passenger compartment.

(18) It can be detected by additional sensors, for instance, that the vehicle is parked and locked up. In this case it is assumed that no person is present inside the locked and parked vehicle. For detecting this state, additional sensors of tie locking system or a parking brake may be coupled to the control 18, for example.

(19) In addition, it can be detected by the webbing extension sensor 22 whether the webbing 14 is completely wound on the belt reel 12, hence there is no waiting person buckled or the seat belt is not fastened around an object inside the parked vehicle.

(20) The inclinometer 20 additionally ensures that the vehicle is parked in a horizontal position. Regular belt retractors include a locking function which locks the belt reel 12 and thus the seat belt when the vehicle is inclined. Such locking can be released only by slackening the webbing 14 or by rotating the belt reel 12 in the winding direction A. If the tensioning device 16 is activated when the vehicle is not parked horizontally, there is a risk that the webbing 14 will be additionally tensioned and the vehicle-sensitive lock function will be triggered. As the webbing 14 is completely wound up and additionally tensioned in thus state, relief of the webbing 14 required to release the locking is not possible. For this reason, the tensioning device 16 is activated only when a response of the vehicle-sensitive locking is excluded, i.e. when the vehicle is horizontally positioned.

(21) Alternatively, it is also possible that, after detecting that the vehicle has been parked and the doors have been locked, tensioning is not activated before a defined period of time has lapsed so as to make sure that no person is present inside the vehicle. Moreover, in this way any confusion of the persons possibly still standing next to the vehicle by the noise in the vehicle will be avoided.

(22) Furthermore, the webbing extension sensor 22 can measure the number of unwinding operations and winding operations of the webbing 14 or can detect how far the webbing 14 is extended.

(23) Tensioning is not necessary after each unwinding operation of the webbing 14, to be sure, as only the windings 26 which have been unwound before are loosely wound up. Thus the effect of the tighter winding is maintained longer for the windings 26 which are not unwound.

(24) Thus it is only after a defined number of unwinding operations that a repeated tensioning of the windings 26 may occur, i.e. when it has to be assumed that the entire webbing 14 has slackened again on the belt reel 12. This offers the advantage that the tensioning device 16 as well as the entire mechanism of the belt retractor 10 is preserved. Moreover, also the battery of the vehicle supplying the energy required for tensioning is spared.

(25) Optionally, the control 18 can also check the charge condition of the vehicle battery so as to prevent the vehicle battery from being discharged by the tensioning device 16.

(26) If any hazard to vehicle occupants or objects in the vehicle is excluded and it is thus detected by the sensors that the seat belt is unloaded and not in use, tensioning can be carried out by the tensioning device 16 by applying very high force so that the webbing 14 is wound as tightly as possible on the belt reel 12.

(27) Tensioning is performed, for example, by a force of 100 N, whereas during regular operation of the winding mechanism usually merely a winding force of about 10 N is attained.

(28) For this purpose, a slowly increasing tensioning force can be applied, for example. In this way the mechanism of the tensioning device 16 is preserved and high noise emission is prevented which might occur e.g. by sudden tensioning of the webbing 14 and might confuse persons inside and outside of the vehicle. For instance, the tensioning device 16 may be controlled via the current intensity so that the tensioning force can be gradually increased.