Machine element or mechanism – Gearing – Directly cooperating gears
Reexamination Certificate
1999-03-03
2002-02-05
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Gearing
Directly cooperating gears
C242S374000
Reexamination Certificate
active
06343522
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gear mechanism having a pinion and a rack, a large diameter gear meshing therewith and a webbing retractor for use in a seat belt system of a vehicle for taking out and taking up a webbing.
2. Description of the Related Art
Some types of the webbing retractor for use in the seat belt system contain a mechanism (pretensioner) for cancelling a slack of the webbing by taking up the webbing to tension it at the time of an emergent deceleration like a collision of the vehicle. Webbing retractors apparatus having such a pretensioner have been disclosed in for example, Japanese Utility Model Application Publication (JP-Y) No. 55-21696 and Japanese Patent No. 2500192.
The webbing retractor described in Japanese Utility Model Application Publication (JP-Y) No. 55-21696 comprises a drum to which an end portion of a seat belt (webbing) is fixed, a pinion fixed to a rotation shaft of this drum coaxially therewith, a piston supported slidably in a cylinder and a rack connected to a piston rod of this piston. Before the piston is actuated, the rack is held at a position in which it does not mesh with the pinion. Upon an emergency like a collision of a vehicle, gas is supplied into the cylinder by a gas generator and the piston is moved in a predetermined direction by this gas pressure. At the same time, the rack meshes with the pinion so as to rotate the pinion in a direction for taking up the seat belt. Therefore, according to the seat belt retractor described in Japanese Utility Model Application Publication (JP-Y) No. 55-21696, because the rack is held at a position in which it is not in mesh with the pinion before the piston is actuated, the pinion and the drum are capable of rotating without being interfered by the rack. Further, because the rack meshes with the pinion upon an emergency so as to rotate the pinion in the direction for drawing in the seat belt, the seat belt is wound up by the drum fixed to the pinion to cancel a slack of the seat belt.
The webbing retractor disclosed in Japanese Patent No. 2500192 comprises a belt drum for winding up a belt web (webbing), a pinion linked with this belt drum through a flywheel linking device and gear transmission means for transmitting only a rotation of a single direction, a rack meshing with this pinion and a piston cylinder driving unit in which a piston thereof is connected to the rack. Upon a collision of a vehicle, the piston cylinder driving unit is actuated by gas generated by a gas generator so as to move the rack. As a result, the pinion is rotated in the direction for taking up the belt web and the gear transmission means increases an angular velocity of the pinion and transmits the rotation of the pinion to the belt drum. Therefore, according to the belt retractor disclosed in Japanese Patent No. 2500192, because the gear transmission means increases the angular velocity of the pinion and transmits the rotation of the pinion to the belt drum, a taking-up amount for the belt web by the belt drum relative to a traveling amount of the rack can be made large.
However, in the webbing retractor described in Japanese Utility Model Application Publication (JP-Y) No. 55-21696, because upon an emergency, after the rack is moved from a position in which it is not in mesh with the pinion to a position in which it comes in mesh with the pinion, it rotates the pinion, when the rack meshes with the pinion, a large impact load is applied to the teeth of the pinion as an initial driving force. Therefore, in the webbing retrator having such a structure, the strength of the pinion teeth needs to be very high and therefore, it is difficult to reduce the size of the pinion. As a result, to secure a taking-up amount of the webbing necessary for an emergency time, the length of the rack and traveling range thereof need to be large, so that the retractor must be large-sized.
In the webbing retractor described in Japanese Patent No. 2500192, because the gear transmission means increases the angular velocity of the pinion, the traveling range of the rack can be reduced without reducing the number of the teeth of the pinion. However, since in the webbing retractor having such a structure, its gear transmission means is structured with at least two gears, the number of parts increases thereby leading to increases in production costs and weight.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been achieved in views of the above described problems and therefore, an object of the invention is to provide a gear mechanism in which, even if a large initial driving force is applied from a gear to a pinion, teeth of the pinion are prevented from being damaged and a small-sized webbing retractor having the same gear mechanism.
According to a first aspect of the present invention, there is provided a gear mechanism comprising: a pinion; a gear meshing with said pinion; and an initial driving member provided on the pinion for receiving an initial driving force from the gear to rotate the pinion.
According to the gear mechanism having the above structure, at the same time when the gear in a stop state starts to drive the initial driving member, the initial driving member receives an initial driving force from the gear so as to rotate the pinion. As a result, the initial driving force is not applied from the gear directly to the teeth of the pinion or the initial driving force is applied indirectly to the teeth of the pinion. Thus, even when the initial driving force from the gear is large, the teeth of the pinion can be prevented from being damaged by the initial driving force.
The gear mentioned here refers to a gear having a larger diameter than the pinion, including a rack and a sector gear. In some case, the initial driving force is applied to the initial driving member in a condition that this gear is in mesh with the pinion, and in some case, the initial driving force is applied to the initial driving member from a position far from the pinion. The initial driving force mentioned here refers to a force which the gear applies to the pinion until the pinion is rotated by a predetermined rotation amount after the rotation of the pinion is started by the gear, and this initial driving force includes an impact force from the gear.
According to a second aspect of the present invention, there is provided a gear mechanism according to the first aspect, wherein the initial driving member is provided on the pinion coaxially therewith.
In the above described gear mechanism, the initial driving member can be supported by a shaft common to the pinion. Thus, any supporting shaft or bearing for supporting the initial driving member does not need to be added, thereby suppressing an increase of the number of parts.
According to a third aspect. of the present invention, there is provided a gear mechanism according to the first aspect, wherein the initial driving member supports a pressure receiving portion for receiving the initial driving force outwardly in a radius direction relative to the pinion.
In the gear mechanism having such a structure, in case where the direction of the initial driving force to be applied to the pressure receiving portion of the initial driving member by the gear is substantially parallel to a tangent line (pitch line) of a pitch circle on the pinion, the driving torque and angular velocity of the pinion can be changed by changing a distance from the pinion axis to the pressure receiving portion. Therefore, the driving torque and angular velocity of the pinion can be adjusted depending on the characteristic of the rotation load to be applied to the pinion at the initial phase of drive start.
According to a fourth aspect of the present invention, there is provided a gear mechanism according to the second and third aspects, wherein the gear or its supporting portion includes a recess for avoiding an interference with the initial driving member which rotates the pinion by receiving the initial driving force.
In the gear mechanism having the above d
Hori Seiji
Imai Keisuke
Kato Keiichi
Nagata Tomonori
Nishide Seiji
Cole Thomas W.
Fenstermacher David
Kabushiki Kaisha Tokai-Rika-Denki-Seisakusho
Nixon & Peabody LLP
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