Pretensioner, seat belt retractor with pretensioner, and seat belt unit including seat belt retractor

There is provided a pretensioner. The pretensioner includes: a pipe; a gas generator that generates a gas in the pipe in an emergency case; a gas generator mount on which the gas generator is mounted; a spool driving mechanism that rotates a spool in a direction to retract a seatbelt by the gas generated by the gas generator in the emergency case; a discharge hole formed in the pipe so as to allow communication between inside and outside of the pipe; and a blocking member configured to block the discharge hole from inside of the pipe, the blocking member being configured to open the discharge hole when the blocking member is pressed from outside of the pipe with a pressing force equal to or greater than a given pressing force.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2011-034179, filed on Feb. 21, 2011, the entire contents of which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

Embodiments described herein relate to a pretensioner, a seatbelt retractor, and a seatbelt unit that activates the seatbelt retractor.

2. Related Art

Various seatbelt retractors that include a pretensioner have thus far been developed for use in a seatbelt unit provided in a vehicle such as an automobile. The pretensioner is configured so as to rotate a spool of the seatbelt retractor in a direction to retract the seatbelt with a gas generated by a gas generator at an initial stage of an emergency case, to thereby take up the seatbelt around the spool. This action quickly removes slack of the seatbelt and gives higher tension to the seatbelt, thus increasing the restraining force of the seatbelt with respect to the occupant.

An example of conventional pretensioners includes a plurality of force transmission members composed of balls accommodated in a pipe, and the force transmission members are made to move by the pressure of the gas generated by the gas generator inside of the pipe, so as to be pressed against a plurality of pressure-receiving portions formed of a lever of a link gear, so that the spool is made to rotate in the direction to retract the seatbelt by the rotation of the link gear (for example, see JP-A-2001-63520).

In the pretensioner according to JP-A-2001-63520, the pipe includes an hole that allows communication between outside and inside of the pipe, and the hole is blocked by a blocking member. In the case where the gas pressure inside of the pipe excessively increases so as to exceed a predetermined pressure during the operation of the pretensioner, the excessive gas pressure acts to remove the blocking member so as to open the hole, thereby discharging the gas out of the pipe.

Recently, usable parts of vehicles that include a pretensioner that has been activated in an emergency case are required to be recycled. However, in general, a considerable gas pressure resides in the pipe after the pretensioner is activated. Such a residual gas pressure in the pipe makes it difficult to demolish the vehicle to recycle the usable parts. Accordingly, it is necessary to discharge the gas inside of the pipe before demolishing the vehicle.

A technique of discharging the gas out of the pipe is disclosed in JP-A-2001-63520. However, the technique of discharging the gas according to JP-A-2001-63520 is only intended to discharge the gas utilizing the gas pressure when the gas pressure inside of the pipe excessively increases so as to exceed the predetermined pressure. Accordingly, in the case where the gas pressure inside of the pipe has not increased beyond the predetermined pressure during the operation of the pretensioner, the gas pressure resides in the pipe after the operation of the pretensioner is finished, unless a piston is removed from the pipe. Therefore, the technique of discharging the gas according to JP-A-2001-63520 is unsuitable for solving the foregoing problem. When the pretensioner is activated, actually the gas pressure inside of the pipe often remains below the predetermined pressure during the operation of the pretensioner.

SUMMARY OF THE INVENTION

One of illustrative aspects of the present invention is to provide a pretensioner from which a gas residing in a pipe can be easily discharged out of the pipe after the operation of the pretensioner is finished, a seatbelt retractor with the pretensioner, and a seatbelt unit including the seatbelt retractor.

According to one or more illustrative aspects of the present invention, there is provided a pretensioner. The pretensioner includes: a pipe; a gas generator that generates a gas in the pipe in an emergency case; a gas generator mount on which the gas generator is mounted; a spool driving mechanism that rotates a spool in a direction to retract a seatbelt by the gas generated by the gas generator in the emergency case; a discharge hole formed in the pipe so as to allow communication between inside and outside of the pipe; and a blocking member configured to block the discharge hole from inside of the pipe, the blocking member being configured to open the discharge hole when the blocking member is pressed from outside of the pipe with a pressing force equal to or greater than a given pressing force.

Other aspects and advantages of the present invention will be apparent from the following description, the drawings and the claims.

The pretensioner configured as above according to the present invention includes the blocking member that blocks the discharge hole of the pipe from inside thereof and opens the discharge hole upon being moved by a pressing force greater than the predetermined pressing force from outside of the pipe. Such a configuration allows, the gas inside of the pipe to be easily discharged outwardly, simply by pressing the blocking member thereby opening the discharge hole, after the operation of the pretensioner.

In particular, the generated gas serves to press the blocking member in the direction to more air-tightly block the discharge hole, and hence the blocking member can more effectively block the discharge hole during the operation of the pretensioner. Such an arrangement suppresses the pressure loss of the generated gas and allows the occupants to be more effectively restrained.

Providing the fitting portion and the blocking portion on the blocking member separately from each other enables the fitting portion to more effectively support the blocking member, and allows the blocking portion to more effectively block the discharge hole. In addition, forming the blocking projection that intrudes into the discharge hole on the blocking portion allows the discharge hole to be more air-tightly blocked.

Further, the seatbelt retractor and the seatbelt unit according to the present invention include the pretensioner according to the present invention. Accordingly, the gas inside of the gas generator mount and the pipe can be easily discharged outwardly after the operation of the pretensioner. Consequently, the vehicle such as an automobile including the pretensioner that has been activated can be easily demolished to recycle the parts used in the vehicle.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereafter, exemplary embodiments of the present invention will be now described with reference to the drawings.

FIG. 1is a schematic perspective view showing a seatbelt unit including a seatbelt retractor with a pretensioner according to a first example of the embodiment of the present invention.

As shown inFIG. 1, the seatbelt unit1according to the first example is basically the same as a conventionally known three-point seatbelt unit. InFIG. 1, a reference numeral1designates the seatbelt unit,2designates a vehicle seat,3designates a seatbelt retractor located close to the vehicle seat2,4designates a seatbelt that can be withdrawably retracted in the seatbelt retractor3and including a belt anchor4aattached to a leading end thereof via which the seatbelt4is fixed to the vehicle floor or the vehicle seat2,5designates a guide anchor that guides the seatbelt4withdrawn from the seatbelt retractor3to a shoulder of the occupant,6designates a tongue slideably supported by the seatbelt4extending from the guide anchor5, and7designates a buckle fixed to the vehicle floor or the vehicle seat2and in which the tongue6is to be removably inserted for connection.

The fastening and releasing operation of the seatbelt4of the seatbelt unit1is also the same as that of the conventionally known seatbelt unit.

The seatbelt retractor3according to the first example may be either a conventionally known emergency locking seatbelt retractor (ELR) or a conventionally known automatic locking seatbelt retractor (ALR). The seatbelt retractor3includes a pretensioner. The pretensioner is activated, as a conventionally known pretensioner is, in an emergency case such as collision in which a deceleration far greater than that experienced during a normal driving has been applied to a vehicle, so as to rotate a spool (not shown) of the seatbelt retractor3in a direction to retract the seatbelt (hereinafter, seatbelt retracting direction) to thereby take up the seatbelt4by a predetermined length thus increasing the restraining force of the seatbelt with respect to the occupant.

FIG. 2is a partially cut away side view of the seatbelt retractor including the pretensioner according to the first example shown inFIG. 1.

As shown inFIG. 2, the pretensioner8according to the first example is supported by a frame9of the seatbelt retractor3. The frame9includes a base portion9alocated on the side of the vehicle chamber (left side inFIG. 2) so as to be attached to the vehicle body, and a pair of side walls9b,9cformed by bending a portion of the base portion9a.

The pretensioner8includes a pipe10, and a guide member11is provided at a leading end portion10aof the pipe10. The leading end portion10aof the pipe10and the guide member11are attached to a pipe mount23fixed to the side wall9bwith a fixture such as a bolt. A cutaway portion10cis formed on the leading end portion10aof the pipe10, so as to allow communication between inside and outside of the pipe10and extending in a longitudinal direction of the pipe10.

The pipe10stores therein a plurality of balls12amade of a metal such as iron or aluminum, and a plurality of force transmission members12constituted of a piston (not shown) that presses the balls12awith a gas pressure, the balls12aand the force transmission members12being movable and disposed in contact with each other. A base end portion10bof the pipe10is formed in a larger diameter than the force transmission member storage portion of the pipe10, and constitutes a gas generator mount13. A gas generator14is mounted on the gas generator mount13.

The pretensioner8includes a case body (not shown) attached to the side wall9bof the frame9. The case body includes a link gear15mounted so as to rotate and to move to the right inFIG. 2. The link gear15includes a plurality of inner teeth15aformed on an inner circumferential surface thereof. The link gear15is formed so as to partially intrude into the pipe10through the cutaway portion10cof the pipe10.

The link gear15includes a generally arcuate stopper16disposed in contact with a first (leading) one of the balls12ain a normal state (while the pretensioner8is not activated) and having an outer peripheral edge of a predetermined circumferential length (corresponding to the pressure-receiving portion according to the present invention), and a plurality (in the first example, six) of generally triangular levers17(corresponding to the pressure-receiving portion according to the present invention), the stopper16and the levers17being formed so as to project from an outer circumferential surface of the link gear15. The stopper16and all of the levers17can intrude into the pipe10through the cutaway portion10c.

A pinion19is attached to a rotary shaft18of a locking base (not shown) of the seatbelt retractor3, so as to rotate interlocked with the rotary shaft18(here, the pinion19may be attached to a rotary shaft of the spool (not shown) of the seatbelt retractor3, so as to rotate interlocked with the rotary shaft). The locking base is employed in the conventionally known ELR and ALR. The locking base rotates, in the normal state, interlocked with the spool of the seatbelt retractor3that takes up the seatbelt4, and is locked by a lock mechanism to be activated in the emergency case to thereby inhibit the rotation of the spool in the direction to withdraw the seatbelt. The ELR that employs the pretensioner including the plurality of balls and the locking base can be found, for example, in Japanese Unexamined Patent Application Publication No. 2001-233172, and hence detailed description of the locking base will not be made herein since the operation thereof can be understood from Japanese Unexamined Patent Application Publication No. 2001-233172 (incorporated by reference).

The pinion19includes a plurality of outer teeth19a. The outer teeth19aof the pinion19are to be engaged with the inner teeth15aof the link gear15. Once the pretensioner8is activated, the balls12apress from above the stopper16and the levers17intruding in the pipe10through the cutaway portion10cthereof, to thereby apply to the link gear15a rotational driving force in the seatbelt retracting direction (counterclockwise inFIG. 2) as well as a linear displacement force toward the pinion19.

In a normal state, the link gear15is retained by shear pins20at a standby position shown inFIG. 2. While the link gear15is at the standby position the inner teeth15aare not engaged with the outer teeth19a, but spaced therefrom. In an emergency case, the pretensioner8is activated so that a pressing force originating from the pressure of the gas generated by the gas generator14is applied to the force transmission members12, and the force transmission members12apply a rotational driving force and a linear displacement force to the link gear15. Resultantly the shear pins20undergo a shear failure and the link gear15is moved to an operational position shown inFIG. 3(a). When the link gear15comes to the operational position, the inner teeth15aare engaged with the outer teeth19a. Accordingly, the link gear15and the pinion19(in other words, spool) are rotationally coupled, such that the rotary shaft18, hence the spool, is caused to rotate in the seatbelt retracting direction through the plurality of force transmission members12, the link gear15, and the pinion19by the pressing force originating from the pressure of the gas generated by the gas generator14. Thus, the plurality of force transmission members12, the link gear15, and the pinion19constitute the spool driving mechanism according to the present invention.

The gas generator14includes a case14aof a stepped cylindrical shape, as shown inFIG. 4(a). A planar surface14bis formed on an outer circumferential surface of an end portion of the case14aon a gas-injecting side (lower end portion inFIG. 4(a)). An inner circumferential surface of the case14aopposite the planar surface14bmay be similarly formed in a planar surface, or in a cylindrical shape.

As shown inFIG. 4(b), the gas generator mount13includes a planar portion13a. An outer surface13a1and an inner surface13a2of the planar portion10are both formed in a planar surface as shown inFIGS. 4(c) and4(d). The planar portion13aincludes a discharge hole13bthat allows communication between outside and inside of the gas generator mount13(in other words, pipe10). When the gas generator14is fitted in the gas generator mount13, at least a part of the planar surface14bof the case14aof the gas generator14and at least a part of the planar inner surface13a2of the gas generator mount13including the discharge hole13bare disposed so as to oppose each other, as indicated by dash-dot-dot lines inFIG. 4(b).

As shown inFIGS. 4(a) to4(d), a blocking member25formed of a metal such as iron or a resin in a thin flat plate of a predetermined shape (in this example, rectangular) is joined to the planar surface14bof the case14aof the gas generator14, via an adhesive or the like (indicated by dash-dot-dot lines inFIGS. 4(a) and4(b)). The blocking member25is located so as to oppose the entirety of the discharge hole13bwhen the gas generator14is fitted in the gas generator mount13. Accordingly, when the gas generator14is fitted in the gas generator mount13as shown inFIGS. 4(b) and4(c), the outer surface of the blocking member25is brought into contact with the inner surface13a2of the gas generator mount13of the pipe10, so as to block the discharge hole13bfrom inside of the gas generator mount13(in other words, from inside of the pipe10). Thus, the outer surface of the blocking member25constitutes a blocking surface25b1that blocks the discharge hole13b.

On the other hand, when the blocking member25is pressed, while being disposed so as to block the discharge hole13b, by a pressing device (not shown) such as a tool from outside of the gas generator mount13(outside of the pipe10) through the discharge hole13b, with a pressing force F equal to or greater than a predetermined pressing force as shown inFIG. 4(d), the discharge hole13bis opened. To be more detailed, a predetermined region of the case14aof the gas generator14including the portion where the blocking member25is attached is concavely deformed upon being pressed with the pressing force F equal to or greater than the predetermined pressing force, and the blocking member25is displaced while being deformed, so that the blocking surface25b1is separated from the inner surface13a2of the gas generator mount13. Thus, the discharge hole13bis opened so as to allow communication between outside and inside of the discharge hole13b.

An operation of the pretensioner8configured as above according to the first example will now be described.

The operation of the pretensioner8according to the first example is basically the same as that of the conventional pretensioner that employs the plurality of ball, up to the stage where the spool of the seatbelt retractor3is caused to rotate in the seatbelt retracting direction in an emergency case.

While the pretensioner8remains unactivated, the link gear15is retained at the standby position as shown inFIG. 2. Accordingly, the inner teeth15aof the link gear15are kept from being engaged with the outer teeth19aof the pinion19. Also, the first ball12ais retained in contact with a lateral face16aof the stopper16on an upstream side in the rotating direction of the link gear15(counterclockwise inFIG. 2, i.e., the seatbelt retracting direction). The subsequent balls12aare sequentially in contact with the adjacent ones. In such a state, the gas generator14does not generate the gas and the balls12aare substantially kept from applying a pressing force to the stopper16on the link gear15. In addition, the discharge hole13bis air-tightly blocked by the blocking member25.

Once an emergency case has occurred, the pretensioner8is activated. More specifically, the gas generator14is activated so as to generate the gas, and the case14aof the gas generator14expands outwardly owing to the pressure of the generated gas. The expansion of the case14abrings the blocking surface25b1of the blocking member25into firm and close contact with the inner surface13a2of the gas generator mount13. Accordingly, the discharge hole13bbecomes more air-tightly blocked by the blocking member25.

The gas generated by the gas generator14opens up the gas injecting end face14dof the case14aand intrudes into the gas generator mount13. At this stage, since the discharge hole13bis air-tightly blocked by the blocking member25, the gas inside of the gas generator mount13and the pipe10is inhibited from leaking out of the gas generator mount13and the pipe10, and hence gas pressure loss is barely incurred.

The gas in the gas generator mount13further proceeds into the pipe10. The gas that has intruded into the pipe10applies a great pressing force to the balls12athrough a piston24(seeFIG. 3(a)). Then the stopper16of the link gear15is pressed by the balls12a, so that the shear pins20undergo a shear failure. Accordingly, the link gear15is displaced to the right inFIG. 2and caused to rotate counterclockwise, by the pressing force applied through the balls12a. The inner teeth15aof the link gear15are then engaged with the outer teeth19aof the pinion19as shown inFIG. 3(a), so that the pinion19starts to rotate in the same direction as the link gear15. Thus, the rotary shaft18hence the spool starts to rotate in the seatbelt retracting direction, so that the seatbelt4worn by the occupant starts to be retracted.

Thereafter, the subsequent balls12asequentially press the levers17as shown inFIG. 3(a), which makes the link gear15and the pinion19rotate together in the seatbelt retracting direction (counterclockwise inFIG. 3(a)). Accordingly, the seatbelt4is taken up around the spool by a longer distance.

When a subsequent ball12astarts to press the lever17, the pressing force of the preceding ball12that pressed the lever17earlier becomes substantially ineffective. The balls12that have lost the pressing force move with the rotation of the link gear15along a guide groove21. Then the first ball12acomes into contact with a stopper22of the case body as shown inFIG. 3(a). At this stage, a lateral face16bof the stopper16of the link gear15on a downstream side in the rotating direction of the link gear is not in contact with any of the opposing balls12a.

When the first ball12acomes into contact with the stopper22, the stopper22is deformed by the pressing force of the first ball12aas shown inFIG. 3(b), and the link gear15further rotates counterclockwise. Such deformation of the stopper22absorbs a part of the kinetic energy of the respective balls12a. The additional counterclockwise rotation of the link gear15brings the outer peripheral edge16cof the stopper16of the link gear15into contact with the opposing ball12aas shown inFIG. 3(b), so that the ball12ais detained between the outer peripheral edge16cof the stopper16and the inner circumferential surface10dof the pipe10opposite the cutaway portion10c. Accordingly the link gear15stops rotating. Therefore the pinion19and the spool also stop rotating and the spool finishes taking up the seatbelt, and thus the operation of the pretensioner8is finished. The retracting action of the seatbelt4by the pretensioner8increases the restraining force of the seatbelt4with respect to the occupant.

At this stage, the volume of the space inside of the pipe10directly communicating with the inside of the gas generator mount13(space unoccupied with the balls12a) is increased, and hence a residual gas pressure is present in the gas generator mount13and the pipe10, although the residual gas pressure is somewhat lower than the peak pressure of the generated gas. Also, the discharge hole13bremains air-tightly blocked by the blocking member25even after the operation of the pretensioner8is finished.

To discharge the gas from the gas generator mount13and the pipe10at a certain timing after the pretensioner8finishes the operation, the blocking member25is pressed with the pressing force F equal to or greater than the predetermined pressing force, as shown inFIG. 4(d). Then the blocking member25is deformed and displaced while causing deformation of the predetermined region of the gas generator mount13including the portion where the blocking member25is attached, thus to be separated from the inner surface13a2of the gas generator mount13. Accordingly, the discharge hole13bis opened and the gas inside of the pipe10flows out through the discharge hole13bas indicated by an arrow a inFIG. 4(d), and the pressure in the gas generator mount13and the pipe10substantially returns to the atmospheric pressure. Here, althoughFIG. 4(d) illustrates such that the gas flows through the gap between the planar surface14b, which is the outer surface of the case14aon which the blocking member25is provided, and the inner surface13a2of the gas generator mount13, actually the gas is discharged also through a gap between another portion of the outer surface of the case14aand another portion of the inner surface of the gas generator mount13.

The configuration of the remaining portions of the pretensioner8according to the first example, as well as the operation thereof, is substantially the same as those of the conventional pretensioner including the plurality of balls. Likewise, the configuration of the remaining portions of the seatbelt retractor3according to the first example, as well as the operation thereof, is substantially the same as those of the conventional ELR or ALR.

In the pretensioner8according to the first example, the gas generator mount13includes the discharge hole13b, which is normally blocked by the blocking member25from inside of the gas generator mount13. The discharge hole13bcan be opened after the operation of the pretensioner8is finished, by pressing the blocking member25from outside of the gas generator mount13through the discharge hole13bwith the pressing force F equal to or greater than the predetermined pressing force. Accordingly, the gas in the gas generator mount13and the pipe10can be easily discharged after the operation of the pretensioner8is finished, simply by pressing the blocking member25thereby opening the discharge hole13b.

In particular, the generated gas serves to press the blocking member25in the direction to more firmly block the discharge hole13b, and hence the blocking member25can more effectively block the discharge hole13bduring the operation of the pretensioner8. Such an arrangement suppresses the pressure loss of the generated gas and allows the occupants to be more effectively restrained.

The seatbelt retractor3and the seatbelt unit1according to the first example allow the gas inside of the gas generator mount13and the pipe10to be easily discharged after the operation of the pretensioner8, thereby enabling the vehicle such as an automobile including the pretensioner8that has been activated to be easily demolished so as to recycle the parts used in the vehicle.

FIG. 5shows a pretensioner according to a second example of the embodiment of the present invention,FIG. 5(a) being a schematic perspective view showing a gas generator and a blocking member,FIG. 5(b) being a perspective view showing a gas generator mount, andFIG. 5(c) being a cross-sectional view taken along a line VC-VC inFIG. 5(b). In the subsequent description of examples of the embodiment, the same constituents will be given the same numeral, and detailed description thereof will not be repeated.

While the case14aof the gas generator14includes a single planar surface14bformed on the outer surface thereof in the pretensioner8according to the first example, a pair of planar surfaces14b,14care provided in the pretensioner8according to the second example, as shown inFIGS. 5(a) to5(c). In this case, the pair of planar surfaces14b,14care symmetrically located with respect to the axial center of the cylindrical case14a. In addition, the region of the case14awhere the pair of planar surfaces14b,14care formed such that the outer surface and the inner surface thereof are parallel to each other.

Although the blocking member25of the pretensioner8according to the first example is formed of a thin plate, the blocking member25of the pretensioner8according to the second example is formed of a flat and thin strip-shaped plate as shown inFIGS. 5(a) and5(c). In this case, the blocking member25is formed by bending the respective end portions of the strip-shaped plate, generally into a C-shape or U-shape in a side view, and includes a bottom portion25aat the central portion and a pair of side walls25b,25cerected on the respective end portions of the bottom portion25a. The pair of side walls25b,25care elastic, and hence the blocking member25has a clipping function. The blocking member25is disposed such that the bottom portion25ais in contact with the gas injecting end face14d(lower end face inFIG. 4(a)) of the case14a, and the side walls25b,25care elastically in contact with the planar surfaces14b,14cof the case14arespectively, because of the clipping function. Thus, the blocking member25is removably fitted to the case14a. Accordingly, the respective outer surfaces of the side walls25b,25c(opposite the mutually opposing surfaces) constitute blocking surfaces25b1,25c1that can block the discharge hole13b. The respective inner surfaces of the side walls25b,25c(mutually opposing surfaces) constitute fitting surfaces25b2,25c2to be brought into contact with the planar surfaces14b,14cof the case14a. Although the blocking surface25b1of the side wall25bblocks the discharge hole13bin the second example, the blocking surface25c1of the opposing side wall25cmay be disposed so as to block the discharge hole13b.

When the gas generator14is fitted in the gas generator mount13with the blocking member25fitted to the case14a, one of the side walls25b,25c(side wall25bin this example) of the blocking member25is disposed in contact with the planner inner surface13a2of the gas generator mount13, so as to block the discharge hole13b. In this case, since the side walls25b,25cof the blocking member25have the clipping function and are held between the outer surface of the case14aof the gas generator14and the inner surface13a2of the gas generator mount13, the blocking member25can be kept from coming off from the case14aof the gas generator14in a normal state.

The configuration of the remaining portions of the pretensioner8according to the second example is the same as that of the first example.

In the pretensioner8configured as above according to the second example, the case14aof the gas generator14expands outwardly owing to the pressure of the gas generated by the gas generator14once the pretensioner8is activated, so that the side wall25beffectively comes into close contact with the inner surface13a2of the gas generator mount13. Accordingly, the discharge hole13bbecomes more air-tightly blocked by the side wall25b, and the gas is suppressed from leaking through the discharge hole13b, resulting in reduced gas pressure loss.

Upon pressing the side wall25bthrough the discharge hole13b, as in the first example, with the pressing force F equal to or greater than the predetermined pressing force after the operation of the pretensioner8to thereby discharge the gas from the pipe10and the gas generator mount13, the case14ais concavely deformed and the side wall25bis flexurally deformed, so that the side wall25bis separated from the inner surface13a2of the gas generator mount13. Accordingly, the discharge hole13bis opened and the gas inside of the pipe10is outwardly discharged, and the pressure in the gas generator mount13and the pipe10returns to the atmospheric pressure.

The operations of other aspects of the pretensioner8according to the second example are the same as those of the first example. The second example offers substantially the same advantageous effects as those offered by the first example.

Further, the configuration of the remaining portions of the seatbelt retractor3including the pretensioner8according to the second example and the advantageous effects thereof, as well as the configuration of the remaining portions of the seatbelt unit1including the seatbelt retractor3according to the second example and the operation thereof, are substantially the same as those of the seatbelt retractor3and the seatbelt unit1according to the first example.

FIG. 6shows a pretensioner according to a third example of the embodiment of the present invention,FIG. 6(a) being a schematic perspective view showing a gas generator and a blocking member,FIG. 6(b) being a perspective view showing a gas generator mount, andFIG. 6(c) being a cross-sectional view taken along a line VIC-VIC inFIG. 6(b).

While the blocking member25of the pretensioner8according to the second example is formed by bending the respective end portions of the strip-shaped plate, generally into a C-shape or U-shape in a side view, the blocking member25of the pretensioner8according to the third example is formed by bending the central bottom portion25aof the blocking member25in a curved shape, generally into a C-shape (or U-shape) in a side view as shown inFIGS. 6(a) to6(c). The respective side walls25b,25cof the blocking member25according to the third example also have the clipping function. As shown inFIG. 6(a), the blocking member25is removably and elastically fitted to the case14afrom a lateral direction. In this state, the inner surface of the curved bottom portion25acomes into contract with the arcuate outer circumferential surface of the case14a.

The operation and the advantageous effects of the pretensioner8according to the third example are substantially the same as those of the second example.

Further, the configuration of the remaining portions of the seatbelt retractor3including the pretensioner8according to the third example and the advantageous effects thereof, as well as the configuration of the remaining portions of the seatbelt unit1including the seatbelt retractor3according to the third example and the operation thereof, are substantially the same as those of the seatbelt retractor3and the seatbelt unit1according to the first example.

FIG. 7shows a pretensioner according to a fourth example of the embodiment of the present invention,FIG. 7(a) being a schematic perspective view showing a blocking member used in the pretensioner according to the fourth example,FIG. 7(b) being an enlarged fragmentary cross-sectional view similar to a part ofFIG. 5(c) partially showing a state where the gas generator is mounted, andFIG. 7(c) being an enlarged fragmentary cross-sectional view of a portion VIIC inFIG. 7(b).

While the side walls25b,25cof the blocking member25respectively include the blocking surfaces25b1,25c1on the outer side and the fitting surfaces25b2,25c2(see FIG.5(a)) on the inner side in the pretensioner8according to the second example, the side walls25b,25crespectively include only the fitting surfaces25b2,25c2on the inner side in the pretensioner8according to the fourth example, as shown inFIGS. 7(a) to7(c). In other words, the side walls25b,25cserve as fitting portions via which the blocking member25is to be supported by the case14a.

Further, in the pretensioner8according to the fourth example, the side walls25b,25care partially cut and the cut portion is outwardly bent so as to form blocking portions25d,25e. The blocking portions25d,25eare formed parallel or substantially parallel to the respectively corresponding side walls25b,25c. The respective outer surfaces of the blocking portions25d,25eserve as blocking surfaces25d1,25e1. In the blocking member25according to the fourth example also, the side walls25b,25cand the blocking portions25d,25ehave the clipping function.

The configuration of the remaining portions of the pretensioner8according to the fourth example is substantially the same as that of the second example.

The blocking member25is removably fitted to the case14aof the gas generator14such that the fitting surfaces25b2,25c2of the side walls25b,25care elastically in contact with the planar surfaces14b,14cof the case14a. When the gas generator14is fitted in the gas generator mount13, the blocking surface25d1of one of the blocking portions25d,25e(blocking portion25din this example) is separably disposed in contact with the planner inner surface13a2of the gas generator mount13, so as to block the discharge hole13b.

When the gas generator14generates the gas in an emergency case, the case14aexpands owing to the pressure of the gas, so that the blocking surface25d1of the blocking portion25dis pressed against the inner surface13a2of the gas generator mount13. Accordingly, the blocking portion25deffectively comes into close contact with the inner surface13a2, so that the discharge hole13bbecomes more air-tightly blocked.

Upon pressing the blocking surface25d1through the discharge hole13b, as in the foregoing examples, with the pressing force F equal to or greater than the predetermined pressing force after the operation of the pretensioner8to thereby discharge the gas from the pipe10, the blocking portion25dis flexurally deformed so that the blocking surface25d, is separated from the inner surface13a2of the gas generator mount13, as indicated by dash-dot-dot lines inFIG. 7(c). Accordingly, the discharge hole13bis opened and the gas inside of the pipe10and the gas generator mount13is outwardly discharged, and the pressure in the gas generator mount13and the pipe10returns to the atmospheric pressure. Here, the blocking portion25dmay be flexurally deformed while causing the case14aof the gas generator14to be concavely deformed.

Providing the fitting portions25b,25cand the blocking portions25d,25eseparately from each other as in the pretensioner8according to the fourth example enables the fitting portions to more effectively retain the blocking member25, and allows the blocking portions25d,25eto more effectively block the discharge hole13b.

The operation and the advantageous effects of the pretensioner8according to the fourth example are substantially the same as those of the second example.

Further, the configuration of the remaining portions of the seatbelt retractor3including the pretensioner8according to the fourth example and the advantageous effects thereof, as well as the configuration of the remaining portions of the seatbelt unit1including the seatbelt retractor3according to the fourth example and the operation thereof, are substantially the same as those of the seatbelt retractor3and the seatbelt unit1according to the first example.

FIG. 8shows a pretensioner according to a fifth example of the embodiment of the present invention,FIG. 8(a) being a schematic perspective view showing a blocking member used in the pretensioner according to the fifth example,FIG. 8(b) being an enlarged fragmentary cross-sectional view similar toFIG. 7(b) partially showing a state where the gas generator is mounted, andFIG. 8(c) being an enlarged fragmentary cross-sectional view of a portion VIIIC inFIG. 8(b).

In the pretensioner8according to the fifth example, as shown inFIGS. 8(a) to8(c), one of the blocking portions25d,25eaccording to the fourth example that is disposed so as to block the discharge hole13bincludes a blocking projection25fformed so as to outwardly protrude, such that a portion thereof can intrude into the discharge hole13b. The blocking projection25fis formed in a semispherical or substantially semispherical shape.

The configuration of the remaining portions of the pretensioner8according to the fifth example is substantially the same as that of the fourth example.

When the gas generator14is fitted in the gas generator mount13, the blocking projection25fformed on one of the blocking portions (blocking portion25din this example) intrudes into the discharge hole13band a portion of the blocking surface25d1peripheral to the base portion of the blocking projection25fcomes into contact with the planner inner surface13a2of the gas generator mount13, so as to block the discharge hole13b. Once the gas generator14generates the gas, the blocking surface25d1of the blocking portion25dis effectively brought into close contact with the inner surface13a2by the gas pressure, so that the discharge hole13bis more air-tightly blocked, as in the foregoing examples. Here, the blocking projection25fintruding into the discharge hole13bfurther ensures the air-tight blocking effect of the discharge hole13b.

In the case of the fifth example, the blocking projection25fis pressed through the discharge hole13bwith the pressing force F equal to or greater than the predetermined pressing force after the operation of the pretensioner8to thereby discharge the gas from the pipe10, instead of the blocking surface25d1as in the foregoing examples. As a result, the blocking portion25dis flexurally deformed and the discharge hole13bis opened.

The operation and the advantageous effects of the pretensioner8according to the fifth example are substantially the same as those of the fourth example.

Further, the configuration of the remaining portions of the seatbelt retractor3including the pretensioner8according to the fifth example and the advantageous effects thereof, as well as the configuration of the remaining portions of the seatbelt unit1including the seatbelt retractor3according to the fifth example and the operation thereof, are substantially the same as those of the seatbelt retractor3and the seatbelt unit1according to the first example.

FIG. 9shows a pretensioner according to a sixth example of the embodiment of the present invention,FIG. 9(a) being a schematic perspective view showing a blocking member used in the pretensioner according to the sixth example,FIG. 9(b) being an enlarged fragmentary cross-sectional view similar toFIG. 7(b) partially showing a state where the gas generator is mounted, andFIG. 9(c) being an enlarged fragmentary cross-sectional view of a portion IXC inFIG. 9(b).

As shown inFIGS. 9(a) to9(c), in the pretensioner8according to the sixth example the blocking member25includes the pair of side walls25b,25cserving as the fitting portion, and the blocking portion25d, as in the pretensioner8according to the fifth example. While the pair of blocking portions25d,25eare provided in the fifth example, just the single blocking portion25dis provided in the sixth example. However, the pair of blocking portions25d,25emay be provided in the sixth example. The following description is based on the assumption that only the blocking portion25dis provided.

In this case, in the pretensioner8according to the sixth example the pair of side walls25b,25care connected via the bottom portion25aformed in a curved shape as in the third example shown inFIG. 6, and have the clipping function. Now, in the fifth example the pair of blocking portions25d,25eare formed so as to outwardly protrude from the respectively corresponding side walls25b,25c; in other words the pair of blocking portions25d,25eand the respectively corresponding side walls25b,25care formed in different planes. In contrast, in the pretensioner8according to the sixth example the blocking portion25dis formed on the same or substantially the same plane as the side wall25b, in a direction orthogonal or substantially orthogonal to the curving direction of the blocking member25.

The blocking member25is removably fitted to the case14afrom a lateral direction as the blocking member of the third example, such that the pair of side walls25b,25care oriented orthogonal to the longitudinal direction of the gas generator14. When the gas generator14is fitted in the gas generator mount13, the blocking projection25fof the blocking portions25dintrudes into the discharge hole13band a portion of the blocking surface25d1peripheral to the base portion of the blocking projection25fcomes into contact with the planner inner surface13a2of the gas generator mount13, so as to block the discharge hole13b. In this case, the respective outer surfaces of the side walls25b,25calso come into contact with the planar inner surface13a2of the gas generator mount13, in the sixth example. Alternatively, the respective outer surfaces of the side walls25b,25cmay be formed so as to be spaced from the inner surface13a2of the gas generator mount13.

The configuration of the remaining portions of the pretensioner8according to the sixth example is substantially the same as that of the fifth example.

In the case of the sixth example, the blocking projection25fis pressed through the discharge hole13bwith the pressing force F equal to or greater than the predetermined pressing force after the operation of the pretensioner8to thereby discharge the gas from the pipe10, instead of the blocking surface25d1as in the foregoing examples. As a result, the blocking portion25dis flexurally deformed and the discharge hole13bis opened. In this case in the sixth example, although the blocking portion25dis flexurally deformed the side wall25bis barely deformed.

The operation and the advantageous effects of the pretensioner8according to the sixth example are substantially the same as those of the fifth example.

Further, the configuration of the remaining portions of the seatbelt retractor3including the pretensioner8according to the sixth example and the advantageous effects thereof, as well as the configuration of the remaining portions of the seatbelt unit1including the seatbelt retractor3according to the sixth example and the operation thereof, are substantially the same as those of the seatbelt retractor3and the seatbelt unit1according to the first example.

FIG. 10shows a pretensioner according to a seventh example of the embodiment of the present invention,FIG. 10(a) being a cross-sectional view similar toFIG. 4(c),FIG. 10(b) being a front view of a blocking member,FIG. 10(c) being a cross-sectional view taken along a line XC-XC inFIG. 10(b) for explaining an operation,FIG. 10(d) being an enlarged fragmentary cross-sectional view of a portion XD inFIG. 10(a),FIG. 10(e) being a front view showing a variation of the seventh example, andFIG. 10(f) being a right side view ofFIG. 10(e).

While the blocking member25according to the first example is formed of the thin plate attached to the case14a, the blocking member25of the pretensioner8according to the seventh example is formed in a pin shape including a disk-shaped head portion25gand a shaft portion25hformed projecting from the center of the head portion25gso as to be fitted in the discharge hole13b, as shown inFIGS. 10(a) and10(b). The shaft portion25hhas a diameter substantially the same as that of the discharge hole13b. The head portion25ghas an outer diameter larger than the diameter of the discharge hole13b. When the blocking member25is fitted in the gas generator mount13, the surface of the head portion25gfrom which the shaft portion25his projecting serves as a blocking surface25g1disposed in close contact with the inner surface13a2of the gas generator mount13so as to block the discharge hole13b.

The head portion25gincludes a chamfered portion25g2formed along the peripheral edge of the surface thereof opposite the blocking surface25g1. The shaft portion25hincludes a predetermined number (in this example, four) of discharge grooves25h1formed on the outer circumferential surface thereof so as to extend in an axial direction.

When the gas generator14is to be fitted in the gas generator mount13, the blocking member25is first attached to the gas generator mount13as shown inFIG. 10(a). More specifically, the shaft portion25hof the blocking member25is fitted in the discharge hole13band the blocking surface25g1is brought into contact with the inner surface13a2of the gas generator mount13. With the blocking member25thus fitted, the gas generator14is then inserted in the gas generator mount13from the left inFIG. 10(a) to be fitted therein. In this case, despite the blocking member25having been attached in advance, the gas generator14can be relatively smoothly fitted because of an interaction between a rounded portion14eformed on the gas injecting end portion of the case14aof the gas generator14and the chamfered portion25g2of the head portion25g.

The configuration of the remaining portions of the pretensioner8according to the seventh example is substantially the same as that of the first example.

When the gas generator14is fitted in the gas generator mount13, the blocking surface25g1of the blocking member25is brought into contact with the planar inner surface13a2of the gas generator mount13, so as to block the discharge hole13b. As in the foregoing examples, when the case14aexpands owing to the pressure of the gas generated by the gas generator14, the blocking surface25g1of the blocking member25is effectively brought into close contact with the inner surface13a2of the gas generator mount13, so that the blocking member25more air-tightly blocks the discharge hole13b.

To discharge the gas from the pipe10after the operation of the pretensioner8, the shaft portion25his pressed through the discharge hole13bwith the pressing force F equal to or greater than the predetermined pressing force, as shown inFIG. 10(d). As a result, the blocking member25is displaced while concavely deforming the case14aso as to separate the blocking surface25g1from the inner surface13a2, and the discharge hole13bis opened through the discharge grooves25h1.

The operation and the advantageous effects of the pretensioner8according to the seventh example are substantially the same as those of the first example.

Further, the configuration of the remaining portions of the seatbelt retractor3including the pretensioner8according to the seventh example and the advantageous effects thereof, as well as the configuration of the remaining portions of the seatbelt unit1including the seatbelt retractor3according to the seventh example and the operation thereof, are substantially the same as those of the seatbelt retractor3and the seatbelt unit1according to the first example.

Alternatively, as shown inFIGS. 10(e) and10(f), the shaft portion25hmay be formed in a stepped shape including a major diameter portion25h2having an outer diameter substantially the same as the diameter of the discharge hole13band a minor diameter portion25h3smaller in diameter than the major diameter portion25h2. In a normal state both the major diameter portion25h2and the minor diameter portion25h3are fitted in the discharge hole13b, so that the blocking member25is stably attached to the gas generator mount13. When the gas is to be discharged, the blocking member25is pressed with the pressing force F equal to or greater than the predetermined pressing force until at least the major diameter portion25h2becomes disengaged from the discharge hole13b, so that the gas can flow out through the gap between the outer circumferential surface of the minor diameter portion25h3and the inner circumferential surface of the discharge hole13b. In this case, therefore, it is not necessary to form the discharge groove25h1on the shaft portion25h.

Alternatively, the shaft portion25hmay be solely formed of the major diameter portion25h2, in other words in a shorter axial length than the shaft portion25hshown inFIGS. 10(a) to10(d). In this case, when the blocking member25is pressed with the pressing force F equal to or greater than the predetermined pressing force the shaft portion25his entirely removed from the discharge hole13bso as to open the discharge hole13b. Further, the shaft portion25hmay be solely formed of the minor diameter portion25h3, instead of the stepped shape.

It is to be understood that the pretensioner and the seatbelt retractor according to the present invention are in no way limited to the foregoing examples, but various modifications may be made. For example, although the pipe10and the gas generator mount13are formed of a single material such that the base end portion10bof the pipe10is formed as the gas generator mount13in the foregoing examples, the pipe10and the gas generator mount13may be separately formed and then air-tightly and integrally coupled.

The spool driving mechanism is not limited to the combination of the plurality of force transmission members12, the link gear15, and the pinion19according to the foregoing examples, but any mechanisms including a rack and pinion mechanism may be employed, as long as the mechanism allows the spool to rotate in the seatbelt retracting direction with the pressure of the gas generated in the pipe10by the gas generator14.

Further, the discharge hole13bmay be located in the pipe10at a position between the gas generator14and the force transmission member12, instead of in the gas generator mount13.

Further, it is not mandatory to provide the arcuate stopper16on the link gear15, and the pretensioner according to JP-A-2001-63520 or the pretensioner according to JP-A-2001-233172 may instead be employed.

To summarize, the present invention is applicable to any pretensioner within the scope defined in the appended claims, provided that the pretensioner includes a gas generator that generates a gas in an emergency case.

The pretensioner, the seatbelt retractor, and the seatbelt unit according to the present invention are suitably applicable to a pretensioner that includes a gas generator to be activated so as to generates a gas at an initial stage of an emergency case, a seatbelt retractor configured to retract the seatbelt in cooperation with the pretensioner, and a seatbelt unit configured to restrain an occupant by using the seatbelt retractor in the emergency case.

While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention.