Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
1999-11-03
2001-09-18
Jillions, John M. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
C280S805000
Reexamination Certificate
active
06290159
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a seat belt retractor.
DISCUSSION OF THE PRIOR ART
DE 196 04 483 C1 teaches a seat belt retractor provided with a load limiter which allows limited extraction of belt webbing with absorption of energy when the belt reel is blocked. The absorption of energy can be adjusted as a function of crash-related data detected by sensors. This crash-related data can be data about the vehicle occupant's body, seat position data, crash condition data such as severity of the crash and the like. This data is determined by sensors arranged outside the seat belt retractor and is evaluated for adjusting the energy absorption of the load limiter. This should allow the restraint characteristic of the seat belt to be influenced in a controlled manner when the seat belt is blocked, in particular after the tightening of the seat belt, optionally in conjunction with the restraint function of an airbag.
SUMMARY OF THE INVENTION
There is provided in accordance with the present invention a seat belt retractor wherein limited extraction of belt webbing with crash-related energy absorption is achieved at reduced cost when the belt reel is blocked. The rotating movement of the belt reel is scanned to yield a measurement signal, or signals for the extracted length of belt webbing and/or the velocity of extraction of belt webbing by differentiation over time and/or the acceleration of extraction of belt webbing by further differentiation over time. An actuating signal with which the load limiter is adjusted is derived from this measurement signal, or signals. The time beginning with the extraction of belt webbing with blocked belt reel is used for differentiation over time. The extracted length of belt webbing is determined by scanning of components that rotate with the belt reel and comprise markings, teeth of the set of blocking teeth or other elements that represent rotational angle increments. The measurement signal or the measurement signals and, here in particular, the signal corresponding to the acceleration of belt webbing extraction is compared with a belt force characteristic field. This belt force characteristic field reproduces the desired characteristic of the limited extraction of belt webbing. The load limiter is adjusted as a function of the comparison.
The load limiter can be an energy absorber with variable absorption of energy. For example, adjustable braking devices with which the limited extraction of belt webbing is decelerated with the desired belt force characteristic field are suitable for this purpose. Preferably an energy absorber with variable energy absorption operates by the principle of a hydraulic pump in which the rotor of the hydraulic pump is coupled to the belt reel, for example by actuation of a coupling, and the rotor conveys a hydraulic medium through a throttle device adjusted as a function of the measurement signal or the measurement signals. The hydraulic pump alone can form the adjustable load limiter. However, it is also possible to combine the hydraulic pump with an energy absorber having a predetermined energy absorption characteristic, for example with a torsion bar. The hydraulic pump then forms the variable part of the load limiter.
Instead of a hydraulic pump, an electric motor can connected to the winding shaft, for example by a coupling, in order to achieve the desired absorption of energy when the extraction of belt webbing is limited. A corresponding counter electromotive force can be generated in the electric motor for this purpose in order to achieve the necessary braking force. The electric motor can also be coupled to an energy absorber with fixed predetermined energy absorption, for example a torsion bar. It is preferable to use an electric motor of flat construction of the type known, for example, from DE 43 02 042 A1.
DE 44 26 621 A1 discloses a hydraulic pump as tightener drive for tightening a seat belt. With the present invention, however, the hydraulic pump is used for the consumption of energy, hydraulic medium being conveyed through a butterfly valve controlled by the measurement signal or the measurement signals by the rotation caused by the winding shaft. The hydraulic pump can therefore be used if limited extraction of belt webbing with energy absorption that can be adjusted to the respective incidence of a crash is to be achieved when the belt reel is blocked.
The energy absorption of the load limiter can also be adjustable in design if a plurality of cumulatively switchable energy absorbers having a predetermined energy absorption characteristic can be switched selectively cumulatively in order to achieve the desired restraint characteristic during decelerated extraction of belt webbing.
With the present invention, in contrast to the above discussed prior art, the information required for obtaining the restraint characteristic required for decelerated extraction of belt webbing is obtained from the behavior, in particular rotating behavior, of the belt reel. The severity of the crash, the weight and the size of the vehicle occupant are indicated directly by the rotating movement of the belt shaft. A direct relationship between the crash sequence and the adjustment of load limitation is therefore obtained.
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Kilian Thomas
Krauss Walter
Specht Martin
Breed Automotive Technology Inc.
Drayer Lonnie
Jillions John M.
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