Land vehicles – Wheeled – Attachment
Reexamination Certificate
2001-06-07
2003-06-10
Morris, Lesley D. (Department: 3619)
Land vehicles
Wheeled
Attachment
C242S374000, C297S480000
Reexamination Certificate
active
06575498
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a webbing retractor which has a pretensioner mechanism for eliminating slackness of a webbing when a vehicle is in an emergency and a force limiter mechanism for limiting an amount of load applied to a vehicle occupant by the webbing to a fixed amount or less when a vehicle is in an emergency.
2. Description of the Related Art
There are webbing retractors with which a pretensioner mechanism, which eliminates slackness of a webbing when a vehicle is in an emergency, e.g., a collision, is provided.
In a webbing retractor having, among such a pretensioner mechanism, for example a so-called rack and pinion type pretensioner mechanism, a pinion is connected to a shaft for taking up the webbing. The pinion always rotates integrally with the take-up shaft. A substantially hollow cylinder is provided in the vicinity of the pinion. When a vehicle is in an emergency, gas is supplied to the cylinder.
A piston is movably provided within the cylinder. A fitting portion is formed at the lower portion of the piston. The fitting portion substantially fits into an inner wall of the cylinder. When a vehicle is in an emergency, the piston receives the gas pressure from below the fitting portion so as to be moved upward within the cylinder. A rack is provided at the upper portion of the piston. Due to moving upward of the piston, the rack meshes with the pinion such that the pinion is rotated in the direction in which the webbing is taken up. Thus, the webbing is taken up onto the take-up shaft when a vehicle is in an emergency to eliminate slackness of the webbing.
Further, the above-described webbing retractor is provided with a force limiter mechanism which limits an amount of load exerted upon a vehicle occupant by the webbing to a fixed amount or less when a vehicle is in an emergency.
Such a force limiter mechanism is provided with, for example, an energy absorbing member. The energy absorbing member is deformed by a load of a vehicle occupant onto the webbing when a vehicle is in an emergency, so that the take-up shaft is rotated in the direction in which the webbing is pulled out. Thus, when a vehicle is in an emergency, the webbing is pulled out from the take-up shaft, so that a load exerted upon a vehicle occupant by the webbing is limited to a fixed amount or less.
However, in such a webbing retractor, when the force limiter mechanism is operated, the take-up shaft is rotated in the direction in which the webbing is pulled out. Accordingly, the pinion is rotated in the direction in which the webbing is pulled out such that the piston is moved downward via the rack within the cylinder. The gas pressure within the cylinder (below the fitting portion) is increased to inhibit moving downward of the piston. Rotation of the take-up shaft via the rack and the pinion in the direction in which the webbing is pulled out is thereby inhibited, so that pulling out of the webbing is inhibited.
As illustrated in
FIG. 12
, a so-called force limiter load (which is equal to a load required for the webbing to be pulled out when a vehicle is in an emergency) is a load (a load shown by the portion A in
FIG. 12
) that a load by the gas pressure within the cylinder (the pressure which is increased due to moving downward of the piston) is added to a load required for the energy absorbing member to be deformed. Thus, there arises a problem that the degree of freedom of the setting of the force limiter load is narrowed.
SUMMARY OF THE INVENTION
In view of the aforementioned facts, an object of the present invention is to obtain a webbing retractor which can broaden the degree of freedom of the setting of a force limiter load.
A first aspect of the present invention is a webbing retractor which comprises a take-up shaft for taking up a webbing, a pretensioner mechanism which has a substantially hollow cylinder and a piston which is provided within the cylinder and with which a fitting portion which substantially fits into the inner wall of the cylinder is provided, and in which when a vehicle is in an emergency, gas is supplied within the cylinder and below said fitting portion such that the piston is moved upward due to the gas pressure to rotate the take-up shaft in the direction in which said webbing is taken up, and a force limiter mechanism having a deformable energy absorbing member in which when a vehicle is in an emergency, the energy absorbing member is deformed due to a load of a vehicle occupant upon the webbing such that the take-up shaft is rotated in the direction in which the webbing is pulled out to move the piston downward, and the webbing retractor comprising a gas passing portion which is provided at the piston and from which the gas can be discharged from below to above the fitting portion, and a closing device which is provided so as to correspond to a hole portion of the gas passing portion, substantially closes the gas passing portion under normal circumstances, maintains the state in which the gas passing portion is substantially closed when the piston is moved upward by the pretensioner mechanism, and which opens the gas passing portion when the piston is moved downward by the force limiter mechanism.
The webbing retractor of a first aspect of the present invention is provided with the pretensioner mechanism. When a vehicle is in an emergency, gas is supplied within the cylinder (below the fitting portion of the piston). As the gas passing portion of the piston is generally substantially closed by the closing device, gas within the cylinder is not discharged from the gas passing portion. Thus, the piston starts to be moved upward due to the gas pressure. When the piston is moved upward, the state in which the gas passing portion is substantially closed by the closing device is maintained. Thus, the piston continues to be moved upward such that the take-up shaft is rotated in the direction in which the webbing is taken up. Accordingly, when a vehicle is in an emergency, the webbing is taken up onto the take-up shaft such that slackness of the webbing is eliminated.
The webbing retractor of the first aspect of the present invention is provided with the force limiter mechanism. When a vehicle is in an emergency, the energy absorbing member is deformed by a load of a vehicle occupant upon the webbing such that the take-up shaft is rotated in the direction in which the webbing is pulled out. Accordingly, when a vehicle is in an emergency, the webbing is pulled out from the take-up shaft such that an amount of a load exerted on a vehicle occupant by the webbing is limited to a fixed amount or less.
In the force limiter mechanism, the take-up shaft is rotated in the direction in which the webbing is pulled out such that the piston is moved downward. When the piston is moved downward, the gas passing portion of the piston is opened by the closing device. Then, gas within the cylinder (below the fitting portion) is discharged from the gas passing portion. It is possible to prevent that moving downward of the piston is inhibited due to gas within the cylinder such that pull-out of the webbing is also inhibited.
A force limiter load (i.e., a load required for the webbing to be pulled out when a vehicle is in an emergency) can be determined by only a load required for the energy absorbing member to be deformed. Accordingly, the degree of freedom of the setting of the force limiter load can be broadened.
In the webbing retractor of the first aspect of the present invention, preferably the closing device is disposed on the fitting portion to substantially close the gas passing portion under normal circumstances. When the piston is moved upward by the pretensioner mechanism, the closing device is pushed upward by the fitting portion such that the state in which the gas passing portion is substantially closed is maintained. Further, when the piston is moved downward by the force limiter mechanism, the closing device is remained further upward than the gas passing portion, and the gas passing portion is thereby open
Mori Shinji
Nagata Tomonori
Cole Thomas W.
Kabushiki Kaisha Tokai-Rika-Denki-Seisakusho
Morris Lesley D.
Nixon & Peabody LLP
Royal, Jr. Paul
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