Patent Application
20200254964
The disclosures herein relate to a pretensioner and a seat belt apparatus.
A pretensioner provided in a seat belt apparatus for a vehicle has been proposed. The pretensioner retracts webbing at the time of a vehicle collision so as to improve performance of restraining an occupant by the webbing. For example, Patent Document 1 discloses a pretensioner including a wire having one end connected to webbing, a piston connected to the other end of the wire, a cylinder that slidably accommodates the piston, and a gas generator that supplies gas, for operating the piston in a retraction direction of the wire, through a gas chamber within a housing to the piston.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2013-163502
The retraction speed of the webbing by the pretensioner is determined by the pressure of the gas supplied from the gas generator to the piston. However, in the conventional pretensioner, because the gas generator mainly uses an explosive to generate the gas, the pressure of the gas is adjusted by adjusting the type and amount of the explosive. However, adjusting the type and amount of the explosive requires time and cost.
It is an object of the present disclosure to provide a pretensioner and a seat belt apparatus, in which the pressure of gas can be readily adjusted.
According to an aspect of an embodiment of the present invention, a pretensioner includes a wire having one end connectable to webbing that restrains an occupant of a vehicle; a piston connected to another end of the wire; a cylinder that slidably accommodates the piston; a housing through which the wire passes and that holds the cylinder; and a gas generator that supplies gas to the piston through a gas chamber within the housing, the gas being for operating the piston in a retraction direction of the wire. The piston includes, at one end of a gas chamber side, a cylindrical portion that extends in an axial direction of the piston, and an initial volume of the gas chamber is adjusted by adjusting a volume of an inner space of the cylindrical portion.
Similarly, according to an aspect of an embodiment of the present invention, a seat belt apparatus includes webbing that restrains an occupant of a vehicle; and the above-described pretensioner connected to the webbing and retracting the webbing at a time of a vehicle collision so as to improve performance of restraining the occupant by the webbing.
According to the present invention, it is possible to provide a pretensioner and a seat belt apparatus, in which the pressure of gas can be readily adjusted.
In the following, embodiments of the present invention will be described with reference to the accompanying drawings. For convenience of explanation, the same elements are denoted by the same reference numerals in the drawings, and a duplicate description thereof will be omitted. In the following description, an x-direction, a y-direction, and a z-direction are perpendicular to each other, the x-direction and the y-direction are horizontal directions, and the z-direction is a vertical direction. The x-direction is a sliding direction of a piston 3, and a retraction direction of webbing 101 is a positive x-direction.
The webbing 101 is a strip-shaped member for restraining an occupant in a seat. One end 103 of the webbing 101 is connected to the retractor 102, and the other end 106 of the webbing 101 is connected to the pretensioner 1.
The retractor 102 is a device that allows the webbing 101 to be retracted or extracted. When deceleration equal to or exceeding a predetermined value is detected at the time of a vehicle collision or the like, the retractor 102 restricts the webbing 101 from being pulled out of the retractor 102. The retractor 102 is fixedly mounted on the vehicle body at the side of a back 109 of the seat 108 (for example, mounted on a lower portion of a pillar on which a shoulder anchor 104 is fixedly mounted).
The tongue 105 is a plate-shaped member slidably attached to the webbing 101 between the pretensioner 1 and the shoulder anchor 104.
The buckle 107 is a member to which the tongue 105 is removably attached. The buckle 107 is fixedly mounted on the seat body on the opposite side of a seat bottom 110 of the seat 108 from the retractor 102.
With the tongue 105 attached to the buckle 107, a shoulder belt portion 101b of the webbing 101 restrains the chest of an occupant in the seat 108, and a lap belt portion 101a of the webbing 101 restrains the waist of the occupant. The shoulder belt portion 101b is a portion of the webbing 101 located between the shoulder anchor 104 and the tongue 105. The lap belt portion 101a is a portion of the webbing 101 located between the tongue 105 and the pretensioner 1.
The pretensioner 1 is a lap pretensioner that promptly retracts the lap belt portion 101a of the webbing 101 when deceleration equal to or exceeding a predetermined value is detected at the time of a vehicle collision or the like, thereby tightening up any slack in the lap belt portion 101a relative to the occupant's waist. The pretensioner 1 is typically mounted on the vehicle body towards the door with respect to a vehicle exterior side-side portion of the seat bottom 110.
As illustrated in
The pretensioner 1 functions as a belt anchor, and is fixed to the vehicle body by inserting a bolt 9 into a fixing hole 7a formed in the bracket 7 and into a fixing hole 6a formed in the housing 6. The bracket 7 includes a guide portion 7b. The bracket 7 retains the bending angle of the wire 2 by inserting the wire 2 along the guide portion 7b, with the bracket 7 being integrally assembled to the housing 6.
A holder 21 and a ferrule 22 are connected to one end of the wire 2. The ferrule 22 is connected to the end of the lap belt 101a of the webbing 101.
The other end of the wire 2 is inserted through the bracket 7 into the housing 6, and is connected to a wire end 23 within the cylinder 4. The piston 3 is slidably provided in the cylinder 4, and the wire 2 is connected to the wire end 23 after being inserted into the piston 3. An O-ring 31 for improving airtightness is provided on the outer circumference of the piston 3. Further, balls 32 and a ball ring 33 for preventing reverse movement of the piston 3 are provided in the middle portion of the piston 3.
As illustrated in
Further, the gas generator 5 is, for example, connected to a deceleration sensor (not illustrated) that detects vehicle collisions. The gas generator 5 operates upon a vehicle collision to inject high-pressure gas into the housing 6. For example, the gas generator 5 uses an explosive included in the gas generator 5 to generate gas. The high-pressure gas injected into the housing 6 presses the piston 3, and moves the piston 3 in a direction (positive x-direction) away from the housing 6. Along with the movement of the piston 3, the wire 2 is retracted into the housing 6 and the cylinder 4, and tightens the webbing 101 (lap belt 101a).
The housing 6 is, for example, formed of a material with a specific gravity lower than that of iron (such as aluminum or an aluminum alloy). Specifically, the housing 6 may be manufactured by aluminum die casting. By employing a material with a specific gravity lower than that of iron, the weight of the housing 6 can be reduced.
Further, the housing 6 includes, on one end side (negative x-side), the insertion hole 61 that guides the wire 2 from the bracket 7 to the cylinder 4, and includes, on the other end side (positive x-side), a connecting portion 65 that connects with the cylinder 4. The wire 2 is inserted into the insertion hole 61, and the connecting portion 65 is screwed with a screw portion of the cylinder 4. The communication portion 62 that communicates with the insertion hole 61 and the connecting portion 65 is formed between the insertion hole 61 and the connecting portion 65.
The inner diameter of the connecting portion 65 is larger than that of the communication portion 62. Therefore, a step is formed between the connecting portion 65 and the communication portion 62. In addition, the inner diameter of cylinder 4 is larger than that of the communication portion 62. Therefore, when the piston 3 is positioned on the negative x-side of the cylinder 4, an end face 37 on the negative x-side of the piston 3 abuts the step. As a result, further movement of the piston 3 toward the negative x-side is restricted. As illustrated in
The inner circumferential surface on the insertion hole 61 side of the communication portion is a conical surface whose diameter decreases toward the insertion hole 61, and forms the boundary portion 66 between the insertion hole 61 and the communication portion 62. The wire guide 8 made of a resin is inserted into the boundary portion 66. The wire guide 8 has an approximately truncated cone shape, and a hole into which to insert the wire 2 is formed at the center of the wire guide 8. The wire guide 8 guides the wire 2 to the communication portion 62, and also functions to seal the boundary portion 66. An opening for communicating with the gas supply port 63 is formed on a portion of the inner circumferential surface of the communication portion 62.
As illustrated in
Particularly in the present embodiment, as illustrated in
The cylindrical portion 36 has an inner space 38, and the inner circumferential surface of the inner space 38 extends in the axial direction of the piston 3. The cylindrical portion 36 has, at the base of the inner space 38, a hole into which the wire 2 is inserted. The inner space 38 of the cylindrical portion 36 is exposed to the communication portion 62 of the housing 6.
Accordingly, as indicated by a dotted line in
The volume of the inner space 38 of the cylindrical portion 36 can be adjusted by adjusting the inner diameter ϕ of the inner space 38 and the depth D from the end face 37 of the piston 3 to the base of the inner space 38. Accordingly, the initial volume of the gas chamber C can be adjusted.
The inner diameter ϕ of the inner space 38 is preferably smaller than the inner diameter of the stopper portion 67 of the housing 6. Accordingly, the contact area between the piston 3 and the stopper portion 67 can be maximized, thereby securely restricting movement of the piston 3 to the negative x-side.
An effect of the pretensioner 1 according to the present embodiment will be described. The retraction speed of the webbing 101 by the pretensioner 1 is determined by the pressure of gas supplied from the gas generator 5 to the piston 3. In the conventional pretensioner, the pressure of gas is adjusted mainly by adjusting the type and amount of an explosive. However, adjusting the type and amount of an explosive requires time and cost.
The pressure of gas may also be adjusted by adjusting the volume of the gas chamber C at the time of gas generation, namely by adjusting the initial volume of the gas chamber C. However, in order to adjust the pressure of gas, if the internal shape of the housing 6 were to be changed, a variety of internal shapes would need to be produced, which would require considerable time and cost, and thus would be unrealistic.
In view of the above-described problem, in the pretensioner 1 according to the present embodiment, the piston 3 includes the cylindrical portion 36 that is formed at one end of the gas chamber C side of the piston 3 along the outer circumferential surface, and that extends in the axial direction of the piston 3. By adjusting the volume of the inner space 38 of the cylindrical portion 36, it is possible to adjust the initial volume of the gas chamber C, with the shape of the housing 6 remaining the same. Further, because the volume of the inner space 38 of the cylindrical portion 36 of the piston 3 is adjusted, the outer diameter of the piston 3 does not change. Therefore, the shape of the cylinder 4 that accommodates the piston 3 is not required to change. In order to adjust the pressure of gas, a plurality of pistons 3, whose cylindrical portions 36 have different volumes of inner spaces 38, may be applied to the existing pretensioner 1, and actual gas pressures may be checked in the plurality of pistons 3. Accordingly, in the pretensioner 1 according to the present embodiment, the pressure of gas can be readily adjusted by adjusting the volume of the inner space of the cylindrical portion 36 of the piston 3, instead of adjusting the type and amount of an explosive.
Further, in the present embodiment, the cylindrical portion 36 is formed at one end of the piston 3. Therefore, the cylindrical portion 36 can serve as a chuck margin in lathe machining. In the case of the conventional piston having no cylinder portion 36, in order to form a groove 34 and a tapered surface 35 by cutting, the conventional piston needs to be re-chucked because there is no sufficient chuck margin at the end of the groove 34 side of the conventional piston. Conversely, in the present embodiment, the cylindrical portion 36 is formed at the end of the groove 34 side of the piston 3, thereby providing a sufficient chuck margin. Accordingly, with the cylindrical portion 36 being chucked, both the groove 34 and the tapered surface 35 can be formed by cutting. As a result, re-chucking of the piston 3 is not required during machining, thus reducing machining costs.
Further, in the present embodiment, the volume of the inner space 38 of the cylindrical portion 36 is adjusted by adjusting the inner diameter (I), the depth d, or the taper angle α of the inner circumferential surface of the inner space 38. Therefore, the pressure of gas can be more readily adjusted by adjusting the size of the inner space 38 of the cylindrical portion 36 without changing the outer diameter of the piston 3.
Further, in the present embodiment, the annular end face 37 of the cylindrical portion 36 of the piston 3 is formed in a plane perpendicular to the axial direction of the piston 3. The housing 6 includes the stopper portion 67 that projects toward the center from the inner circumferential surface of the cylinder 4. In an initial state, the end face 37 of the cylindrical portion 36 of the piston 3 is disposed facing the stopper portion 67. When the wire 2 is pulled toward the webbing 101 side, the end face 37 abuts the stopper portion 67, thereby restricting movement of the piston 3 toward the housing 6 side.
In the conventional pretensioner, the end face of the gas chamber C side of the piston is a flat face, thereby increasing the contact area between the end face and a stopper portion of a housing. With the above configuration, the conventional pretensioner securely restricts movement of the piston to the negative x-side. In the piston 3 according to the present embodiment, the inside of the center of the cylindrical portion 36 is cut, while the end face 37 is left on the outer edge, thus allowing the contact area between the piston 3 and the stopper portion 67 to remain the same as that of the conventional pretensioner. Therefore, in the piston 3 according to the present embodiment, it is possible to adjust the pressure of gas and restrict movement of the piston 3 to the negative x-side, while also securing the contact area between the piston 3 and the stopper portion 67 as in the conventional pretensioner.
Referring to
As illustrated in
The relationship of forces exerted on the ball 32 will be further described with reference to
The above-described forces can be expressed as N=F cos θ, F2=F sin θ, and F3=μN=μF cos θ, where μ is a friction coefficient and θ is the inclined angle of the tapered surface 35. When the condition F3>F2 is satisfied, the ball 32 is locked without sliding on the inner circumferential surface of the cylinder 4 and the tapered surface 35 of the piston 3.
As described above, with the configuration in which the tapered surface 35 is formed on the outer circumference of the piston 3, and the balls are provided on the tapered surface 35, it is possible to restrict movement of the piston 3 to the negative x-side, while allowing movement of the piston 3 to the positive x-side. As a result, once the pretensioner 1 is operated and the webbing 101 is retracted, the wire 2 does not return to the webbing 101 side even if a force is applied in the direction of loosening the webbing 101. Accordingly, the webbing 101 can be securely fixed.
Although specific embodiments have been described above, the present disclosure is not limited to the above-described embodiments. These described embodiments may be modified by a person skilled in the art as long as the features of the present disclosure are included. The arrangement, conditions, and shapes of the structural elements as described in the embodiments are not limited to the arrangement, conditions, and shapes as described, and may be modified as necessary. It should be noted that combination of the elements of the above-described embodiments may be changed as long as no technical contradiction occurs.
For example, unlike the above-described embodiments, the pretensioner 1 may be coupled to the buckle 107, and the buckle 107 may be instantly retracted when deceleration equal to or exceeding a predetermined value is detected at the time of a vehicle collision or the like, such that the performance of restraining an occupant by the webbing 101 can be improved.
The present application is based on and claims priority to Japanese patent application No. 2017-177982 filed on Sep. 15, 2017, with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-177982 | Sep 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/032901 | 9/5/2018 | WO | 00 |
