Pretensioner and seat belt device

A pretensioner and a seat belt device are provided. A pretensioner includes a wire connected to webbing that restrains an occupant, a piston disposed to the wire, a cylinder that slidably accommodates the piston, a gas generator that applies driving force to the piston, and a housing that integrally connects the cylinder and the gas generator. The housing includes an insertion hole that guides the wire, a communication part that is communicated with the cylinder and the insertion hole, and a gas-supply port that supplies gas generated by the gas generator to the communication part. The pretensioner includes a wire guide disposed at a boundary portion of the insertion hole and the communication part, and a holding member that is inserted into the communication part and locked to the gas-supply port, thereby to position the wire guide.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims benefit of priority from the Japanese Patent Application No. 2016-132255, filed on Jul. 4, 2016, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a pretensioner and a seat belt device, and in particular, relates to a pretensioner suitable for a lap belt, and a seat belt device that includes the pretensioner.

BACKGROUND ART

Vehicles, such as automobiles, are generally mounted with seat belt devices that restrain an occupant in a seat that includes a seat portion on which the occupant sits and a backrest portion positioned back of the occupant. Such a seat belt device has webbing that restrains the occupant, a retractor that winds the webbing, a guide anchor that is provided on a vehicle body side and guides the webbing, a belt anchor that fixes the webbing to the vehicle body side, a buckle disposed on a side surface of the seat, and a tongue disposed to the webbing. The tongue is fitted into the buckle, thereby to restrain the occupant in the seat with the webbing.

The webbing in restraining the occupant can be classified into a lap belt that restrains the occupant's waist with the webbing between the belt anchor and the tongue, and a shoulder belt that obliquely restrains the occupant's shoulder with the webbing between the guide anchor and the tongue.

In such a seat belt device, it has been already proposed to arrange a pretensioner capable of retracting the lap belt of the webbing in the belt anchor, in order to improve performance of restraining the occupant in a vehicle collision.

Such a pretensioner includes, for example, as described in Japanese Unexamined Patent Application Laid-open No. 2009-173103, a wire connected to the lap belt, a piston disposed at an end of the wire, a cylinder that slidably accommodates the piston, a gas generator that applies driving force to the piston, and a housing that communicatively connects the cylinder and the gas generator. Additionally, the wire inserted into the housing is inserted into a protection-seal body, which is integrally formed by a protection member and a seal member, and the protection-seal body is fixed inside the housing by a retaining ring.

SUMMARY OF INVENTION

The invention described in Japanese Unexamined Patent Application Laid-open No. 2009-173103 has a problem that manufacturing cost becomes high since the retaining ring is a metal part, and the protection-seal body is a resin part.

The present invention has been made in view of the above-described problem, and an object of the present invention is to provide a pretensioner and a seat belt device that can achieve cost reduction.

According to the present invention, there is provided a pretensioner including a wire connected to webbing that restrains an occupant, a piston disposed to the wire, a cylinder that slidably accommodates the piston, a gas generator that applies driving force to the piston, and a housing that integrally connects the cylinder and the gas generator, in which the housing includes an insertion hole that guides the wire, a communication part that is communicated with the cylinder and the insertion hole, and a gas-supply port that supplies gas generated by the gas generator to the communication part, and the pretensioner includes a wire guide disposed at a boundary portion of the insertion hole and the communication part, and a holding member that is inserted into the communication part and locked to the gas-supply port, thereby to position the wire guide.

Additionally, according to the present invention, there is provided a seat belt device including webbing that restrains an occupant, and a belt anchor that fixes the webbing to a vehicle body side, in which the belt anchor is provided with a pretensioner including a wire connected to the webbing, a piston disposed to the wire, a cylinder that slidably accommodates the piston, a gas generator that applies driving force to the piston, and a housing that integrally connects the cylinder and the gas generator, the housing includes an insertion hole that guides the wire, a communication part that is communicated with the cylinder and the insertion hole, and a gas-supply port that supplies gas generated by the gas generator to the communication part, and the pretensioner includes a wire guide disposed at a boundary portion of the insertion hole and the communication part, and a holding member that is inserted into the communication part and locked to the gas-supply port, thereby to position the wire guide.

In the pretensioner and the seat belt device described above, the holding member may also include a main body that is made of resin and in a cylindrical shape, and a projection lockable to the gas-supply port. Further, the holding member may also include a rib formed axially on a surface of the main body.

Moreover, the housing may include a key groove formed axially on the holding member, and the holding member may have a protrusion that can be inserted into the key groove.

Moreover, the housing may include a key groove formed axially on the holding member, and the holding member may include a main body that is made of resin and in a cylindrical shape, a protrusion that is formed on the main body and can be inserted into the key groove, a projection that is formed on the protrusion and lockable to the gas-supply port, and a rib formed axially on a surface of the main body.

According to the pretensioner and the seat belt device of the present invention described above, since the holding member is made to be locked to the gas-supply port formed in the housing, the holding member can be easily disposed in the housing, and product cost can be reduced, even when a material of the holding member is changed from metal to resin.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention is now described below with reference toFIGS. 1 to 5. Here,FIG. 1is a developed view of parts, showing a pretensioner according to an embodiment of the present invention.FIGS. 2(A) and 2(B)are enlarged views illustrating a housing shown inFIG. 1, in whichFIG. 2(A)illustrates a cross-sectional view, andFIG. 2(B)illustrates a front view.FIGS. 3(A) and 3(B)are enlarged views illustrating a holding member shown inFIG. 1, in whichFIG. 3(A)illustrates a side view, andFIG. 3(B)illustrates a front view.

A pretensioner1according to an embodiment of the present invention includes, for example, as shown inFIGS. 1 to 3(B), a wire2connected to webbing that restrains an occupant, a piston3disposed to the wire2, a cylinder4that slidably accommodates the piston3, a gas generator5that applies driving force to the piston3, a housing6that integrally connects the cylinder4and the gas generator5, and a bracket7that is connected to the housing6and positions wire2. The housing6includes an insertion hole61that guides the wire2, a communication part62that is communicated with the cylinder4and the insertion hole61, and a gas-supply port63that supplies gas generated by the gas generator5to the communication part62. The pretensioner1includes a wire guide8disposed at a boundary portion66of the insertion hole61and the communication part62, and a holding member9that is inserted into the communication part62and locked to the gas-supply port63, thereby to position the wire guide8.

The pretensioner1has a function as a belt anchor, and is fixed to a vehicle body by inserting a bolt into a securing hole7aformed on the bracket7, and a securing hole6aformed on the housing6. The bracket7includes an opening7cfor securing a rivet7b, and a bending angle of the wire2is maintained by securing the rivet7bto the bracket7.

A first end of the wire2is connected with a holder21, and the holder21is connected to a ferrule22. The ferrule22is connected to an end of the webbing. The webbing connected with the wire2via the ferrule22forms a lap belt that restrains occupant's waist in restraining the occupant.

A second end of the wire2is inserted into the housing6via the bracket7, and connected to a wire end23in the cylinder4. The piston3is slidably arranged in the cylinder4, and the wire2is inserted into the piston3and then connected to the wire end23. An outer circumference of the piston3is disposed with an O-ring31that improves airtightness. An intermediate portion of the piston3is disposed with a ball and a ball ring32for preventing reversing.

The gas generator5is, as illustrated inFIG. 2(A), disposed in an opening (gas-generator mounting portion64) formed in the housing6, and fixed to the housing6by a keeper51. A passage connecting this gas-generator mounting portion64with the communication part62forms the gas-supply port63.

Moreover, the gas generator5is, for example, connected to an acceleration sensor that detects a vehicle collision, and the gas generator5operates upon a vehicle collision to inject high pressure gas into the housing6. The high pressure gas injected into the housing6presses the piston3, and moves the piston3in a direction away from the housing6. Along with the movement of the piston3, the wire2is retracted in the housing6and the cylinder4, and fastens the webbing (lap belt).

The housing6is, for example, formed of a material with a lower specific gravity than iron (e.g., aluminum, aluminum alloy, or the like). In particular, the housing6may be manufactured by aluminum die cast. Adopting a material with a lower specific gravity than iron enables weight reduction of the housing6.

Additionally, the housing6has, as shown inFIG. 2(A), an insertion hole61that guides the wire2from the bracket7to the cylinder4, on a first-end side, and has a connecting part65connected with the cylinder4, on a second-end side. The insertion hole61is inserted with the wire2, and the connecting part65is screwed with a screw portion of the cylinder4. Between the insertion hole61and the connecting part65, there is formed the communication part62that is communicated with the insertion hole61and the connecting part65.

An inner circumferential surface of the communication part62on a side of the insertion hole61forms a conical surface reduced in diameter toward the insertion hole61, and forms the boundary portion66of the insertion hole61and the communication part62. The boundary portion66is inserted with the wire guide8made of resin. The wire guide8has a substantially truncated cone shape, and has a hole that can be inserted with the wire2in a center. The wire guide8guides the wire2to the communication part62, and has a function of sealing the boundary portion66.

Additionally, the communication part62may have a stepped portion67that regulates an axial position of the holding member9when the holding member9is inserted, and may have a key groove68that regulates rotation (circumferential position) of the holding member9. The key groove68is, for example, as shown inFIG. 2(B), formed by cutting a part of the inner circumferential surface of the communication part62. It should be noted the front view illustrated inFIG. 2(B)is equivalent to a view as viewed from the direction of the arrow B inFIG. 2(A). Moreover, for convenience of description, a drawing of the gas generator5and the holding member9is omitted inFIG. 2(B).

Further, the inner circumferential surface of the communication part62may be formed such that a diameter is slightly reduced toward the boundary portion66from the connecting part65, in order to improve holding performance of the holding member9. As shown inFIG. 2(A), on a part of the inner circumferential surface of the communication part62, an opening communicated with the gas-supply port63is formed. Consequently, a branch portion69is formed between the communication part62and the gas-supply port63.

The holding member9includes, for example, as shown inFIGS. 3(A) and 3(B), a main body91that is made of resin and in a cylindrical shape, a protrusion92that is formed on the main body91and can be inserted into the key groove68, a projection93that is formed on the protrusion92and lockable to the gas-supply port63, and a plurality of ribs94formed axially on a surface of the main body91. It should be noted the front view illustrated inFIG. 3(B)is equivalent to a view as viewed from the direction of the arrow B inFIG. 3(A).

The holding member9is a resin part, and the main body91, the protrusion92, the projection93, and the ribs94are integrally formed by injection molding or the like. The main body91may have, on a part of an outer circumference, a diameter-expanded portion95that abuts against the stepped portion67of the communication part62. The protrusion92is formed such that a part of the diameter-expanded portion95projects radially outward, and the protrusion92has a shape that can be inserted into the key groove68of the communication part62formed axially.

The projection93has a lever shape that is formed so as to axially project from the protrusion92. The projection93is formed such that a tip portion is slightly separated from the outer circumference of the main body91with respect to a root portion, and the projection93is structured to be flexible radially of the main body91. Additionally, the tip of the projection93may be formed with a locking portion96lockable to the branch portion69of the housing6. The locking portion96is, for example, a stepped portion formed at the tip of the projection93.

The ribs94are formed along an axial direction as shown inFIG. 3(A), and the seven ribs94are uniformly arranged at an interval of 22.5° with respect to the projection93as a reference, as shown inFIG. 3(B). The ribs94have a function of preventing an axial center of the main body91from moving away due to deviation or inclination when the holding member9is inserted into the communication part62, and the projection93is locked to the gas-supply port63(branch portion69in this embodiment). Therefore, the ribs94are, for example, preferably arranged at a position to regulate a movement in a direction opposite to the projection93(vertical direction) and a horizontal direction.

The number and arrangement of the ribs94are, however, not limited to the illustrated arrangement. For example, the ribs94may be arranged at two positions of a range between 45° to 90° and a range between 90° to 135°, and there may be arranged a rib94formed with a wider width than the illustrated ribs94. Further, depending on a shape of the communication part62formed in the housing6, the ribs94may be omitted.

After the wire guide8is inserted into the boundary portion66from the communication part62of the housing6, for example, as shown inFIG. 2(B), the above-described holding member9is inserted and pushed into the communication part62, with the protrusion92positioned to the key groove68. At this time, the projection93is pressed in while abutting and being bent on an inner surface of the communication part62. Then, when the diameter-expanded portion95of the holding member9abuts against the stepped portion67of the communication part62, and the projection93reaches the gas-supply port63, the locking portion96of the projection93is locked to the branch portion69of the housing6.

Thus, simply pushing the holding member9into the communication part62allows the holding member9to be locked to the housing6, enabling easy positioning of the wire guide8. It should be noted that, the wire guide8and the holding member9are preferably inserted into the communication part62, with the wire2inserted into the wire guide8and the holding member9.

Since the holding member9is a resin part, the holding member9can be crushed by high pressure gas generated from the gas generator5upon operation of the pretensioner1, and the crushed holding member9is contained in the communication part62. Therefore, until the pretensioner1operates, the wire guide8can be easily positioned.

According to the pretensioner1of the embodiment described above, since the holding member9is made to be locked to the gas-supply port63formed in the housing6, the holding member9can be easily disposed in the housing6, and cost for the pretensioner1can be reduced, even when a material of the holding member9is changed from metal to resin.

Here,FIGS. 4(A) and 4(B)are views illustrating modifications of the holding member, in whichFIG. 4(A)illustrates a first modification, andFIG. 4(B)illustrates a second modification. It should be noted that like reference numerals are given to components that are identical to those of the holding member9illustrated inFIGS. 3(A) and 3(B), to omit a repeated description.

The first modification illustrated inFIG. 4(A)is made by omitting the locking portion96formed at the tip of the projection93. Such a configuration also allows the tip of the projection93to be locked to the gas-supply port63, and the wire guide8to be positioned.

The second modification illustrated inFIG. 4(B)is made by forming the protrusion92and the projection93at different positions. In the illustrated second modification, the protrusion92is arranged at a position opposite to the projection93. In such a modification, the key groove68is also formed at a position opposite to the gas-supply port63in the communication part62of the housing6. In such a way, the protrusion92and the key groove68can be formed at any positions, and the projection93may be formed at a position different from that of the protrusion92.

Next, a seat belt device according to an embodiment of the present invention is described with reference toFIG. 5. Here,FIG. 5is a view illustrating an overall structure of the seat belt device according to an embodiment of the present invention. It should be noted that, for convenience of description, parts other than the seat belt device are indicated by dotted-chain lines inFIG. 5.

A seat belt device100according to the embodiment illustrated inFIG. 5includes webbing W that restrains an occupant, a retractor101that winds the webbing W, a guide anchor102that is provided on a vehicle body side and guides the webbing W, a belt anchor103that fixes the webbing W to the vehicle body side, a buckle104that is disposed on a side surface of a seat S on which the occupant sits, and a tongue105that is disposed to the webbing W. The belt anchor103includes, for example, a pretensioner1illustrated inFIG. 1.

The seat belt device100illustrated inFIG. 5is a seat belt device disposed at a passenger seat. A first end of the webbing W is connected to the retractor101, and a second end of the webbing W is connected to the belt anchor103. An intermediate portion of the webbing W is inserted into the belt anchor103and the tongue105. Fitting the tongue105into the buckle104enables restraint of the occupant sitting on the seat S by the webbing W.

In restraining the occupant, the webbing W can be classified into a lap belt that restrains the occupant's waist with the webbing W between the belt anchor103and the tongue105, and a shoulder belt that restrains the occupant's shoulder with the webbing W between the guide anchor102and the tongue105.

The belt anchor103is configured by the pretensioner1illustrated inFIG. 1. In particular, the pretensioner1is fixed to a vehicle body by inserting a bolt into a securing hole7aof the bracket7and a securing hole6aof the housing6, and securing the bolt to the vehicle body side. Thus, performance of restraining an occupant in a vehicle collision can be improved by disposing the pretensioner1to the belt anchor103.

Thus, by using the pretensioner1according to the embodiment (including modifications) described above, since the holding member9is made to be locked to the gas-supply port63formed in the housing6, the holding member9can be easily disposed in the housing6, and cost for the seat belt device100can be reduced, even when a material of the holding member9is changed from metal to resin.

The present invention is not limited to the above-described embodiment. Of course, the present invention can be changed in various manners without departing from the gist of the invention. For example, the seat belt device100may be a seat belt device used for a driver's seat or a rear seat of a vehicle, and may be a seat belt device used for a conveyance other than the vehicle.