WO2018198829A1

WO2018198829A1 - Retractor for seat belt

Info

Publication number: WO2018198829A1
Application number: PCT/JP2018/015537
Authority: WO
Inventors: 一寛茂呂; 松岡　弘樹
Original assignee: オートリブディベロップメントエービー; 一寛茂呂; 松岡　弘樹
Priority date: 2017-04-27
Filing date: 2018-04-13
Publication date: 2018-11-01
Also published as: JPWO2018198829A1; JP6768149B2

Abstract

[Problem] To provide a retractor for a seat belt, wherein the retractor prevents re-locking by preventing the release of a primary lock, and can provide greater safety to a passenger during a vehicle emergency. [Solution] This retractor 100 is provided with a pre-tensioner 120 that rotates a spindle 122. The pre-tensioner has: a pipe 134 having a curved portion 144; a cylindrical piston 136 which is moved within the pipe by a gas supplied from one end 140 of the pipe; and a plurality of balls 138 which are accommodated in the pipe and pushed out from the other end 152 of the pipe by the moving piston, the plurality of balls 138 rotating the spindle in a webbing winding direction. At least one of the plurality of balls rotates the spindle in the webbing winding direction, and is then pushed back into the pipe by the spindle that rotates in the webbing winding direction as the passenger is restrained. The piston is pushed by the ball and passes through the curved portion while deforming along inner walls 166 and 168 of the curved portion.

Description

Seat belt retractor

The present invention relates to a seat belt retractor for winding and unwinding a webbing for restraining an occupant.

The seat belt device installed in the vehicle includes a retractor that winds and unwinds the webbing for restraining the passenger. 2. Description of the Related Art A retractor is known that includes a spindle that winds and unwinds a webbing by rotating, and a pretensioner that rotates the spindle in a webbing winding direction in a vehicle emergency (for example, Patent Document 1).

In such a retractor, the pretensioner operates in the initial stage of vehicle emergency. The pretensioner includes, for example, a rotating member such as a pinion that rotates integrally with a spindle, a pipe, a gas generator that is attached to one end of the pipe and generates gas in the event of a vehicle emergency, one piston and a plurality of pistons housed in the pipe Ball.

The piston moves in the pipe by the gas supplied from one end of the pipe in the event of a vehicle emergency. The plurality of balls are pushed out one by one from the other end of the pipe by the moving piston, and by rotating the rotating member, a rotational force is applied to the spindle and the spindle is rotated in the webbing take-up direction. Thereby, in the initial stage of the vehicle emergency, it is possible to remove the slack of the webbing and apply tension to the webbing, thereby reliably restraining the occupant.

Patent Document 1 describes a pretensioner in which an expanded portion is formed on the side of a ball that comes into contact with a force transmission member (ball) in a main body of a piston. The expansion portion of the piston expands in the direction of the inner peripheral surface of the pipe when the piston presses the ball. In Patent Document 1, since the outer peripheral surface of the expanded portion of the piston is more closely adhered to the inner peripheral surface of the pipe, the sealing performance between the piston and the inner peripheral surface of the pipe is improved, and the pressure loss of the gas pressure is reduced. The gas pressure can be more effectively applied to the piston.

JP 2010-260426 A

Some retractors are equipped with a so-called load limiter that, after the pretensioner is actuated, when the webbing is pulled due to inertial movement of the occupant and the load exceeds a predetermined value, the webbing is unwound while absorbing energy. . The load limiter includes a twisted member such as a torsion bar. The torsion bar is mounted in the spindle, extends along the axis center of the spindle, and one end portion in the axial direction is coupled to the spindle.

When the load limiter is activated, the tension of the webbing acts not only as a rotational force in the webbing unwinding direction on the torsion bar via the spindle, but also the pinion pushes the ball back into the pipe via the spindle, This also acts as a moving force that moves the piston toward the gas generator. For this reason, the torsion bar not only twists and deforms due to the pulling force of the webbing, but also the piston moves against the resistance force accompanying the movement in the pipe. That is, when the webbing is unwound, in addition to the load associated with the torsional deformation of the torsion bar, the load associated with the movement of the piston acts on the webbing (occupant), and these loads become the load limiter load.

Here, it is preferable that the load acting on the webbing (occupant) is stable after the pretensioner operation until the load limiter operation is completed, but a state of “re-lock” may occur. Hereinafter, “re-lock” will be described. When the pretensioner is activated, the piston is pushed by the gas pressure generated by the gas generator and the spindle is rotated by a ball or the like in contact with the piston. (Primary lock) It is preferable that the load limiter operates while the webbing is retracted (winded). However, when the load limiter is activated and a load greater than the gas internal pressure at which the piston is pushed is applied to the load limiter, a phenomenon occurs in which the piston is returned. When this phenomenon occurs, the load on the webbing is momentarily removed, and the restraining force of the occupant is reduced. For this reason, immediately after the load on the webbing is removed, the lock mechanism is actuated to stop the rotation of the spindle. “Re-lock” refers to a phenomenon in which the spindle is locked by the lock mechanism after the load on the webbing is once released after the primary lock (that is, after the primary lock is released). When re-locking occurs, as an example, the load change rate (N / ms) after the pretensioner operation is the difference between the maximum load change rate and the minimum change rate within 5 ms (the load on the webbing is momentarily lost) In this case, the difference between the first and second locks is 1000 N / ms or more. That is, when re-locking occurs, the passenger is not restrained by webbing after the piston starts to move after the primary lock until re-locking, and the passenger restraining performance at the time of collision is reduced.

The technology described in Patent Document 1 merely improves the sealing performance of the piston to the pipe and suppresses the pressure loss of the gas pressure, increases the load accompanying the movement of the piston, maintains the load limiter load, and re-locks. There is room for improvement in terms of preventing the occurrence of

In view of such problems, the present invention provides a seatbelt retractor that prevents the occurrence of re-locking by preventing the phenomenon of the primary lock being released, and that can ensure higher safety for passengers in the event of a vehicle emergency. The purpose is to do.

In order to solve the above problems, a typical configuration of a seatbelt retractor according to the present invention includes a spindle that rotates and unwinds a webbing by rotating, and a pretensioner that rotates the spindle in the webbing winding direction. The pretensioner includes a pipe that includes a curved portion that extends along a predetermined path and is curved in the middle, and a predetermined gas that is accommodated in the pipe and supplied from one end of the pipe. A cylindrical piston that moves in the pipe and a plurality of balls housed in the pipe, which are pushed out one by one from the other end of the pipe by the moving piston to give rotational force to the spindle, and the spindle is wound by webbing A plurality of balls rotating in a direction, at least one of the plurality of balls having a spindle After rotating in the webbing winding direction, the occupant is restrained by the webbing and pushed back into the pipe by the spindle rotating in the webbing unwinding direction. The piston is pushed by at least one ball and hits the inner wall of the curved portion. It passes through the curved portion while being deformed along.

When the seat belt retractor pretensioner is activated in the early stage of the vehicle emergency, the piston moves in the pipe by the gas pressure generated from the gas generator attached to one end of the pipe, for example, and a plurality of balls are moved to the other end of the pipe. Extrude from. The plurality of extruded balls rotate a rotating member (such as a pinion) that rotates integrally with the spindle to rotate the spindle in the webbing take-up direction. Thereby, in the initial stage of the vehicle emergency, it is possible to remove the slack of the webbing and apply tension to the webbing, thereby reliably restraining the occupant.

After the pretensioner is activated, the load limiter is activated when the webbing is pulled due to the inertial movement of the occupant and the load exceeds a predetermined value. That is, the tensile force of the webbing acts as a rotational force in the webbing unwinding direction on a twisted member (such as a torsion bar) via the spindle. Also, the pinion pushes the ball back into the pipe via the spindle, and acts as a moving force that moves the piston toward the gas generator by the pushed back ball.

For this reason, the torsion bar not only twists and deforms due to the tensile force of the webbing, but also the piston moves against the resistance force accompanying the movement in the pipe. That is, when the webbing is unwound, in addition to the load associated with the torsional deformation of the torsion bar, the load associated with the movement of the piston acts on the webbing (occupant), and these loads become the load limiter load.

Here, it is preferable that the load acting on the webbing (occupant) after the pretensioner operation is completed and the gas pressure for the first pretensioner operation is maintained and stable (primary). Lock). However, if the load limiter load becomes greater than the gas holding pressure after the primary lock, the primary lock is released, and immediately after that, the lock mechanism is activated and the spindle is locked (relock). If this re-lock occurs, the load acting on the webbing will fluctuate greatly between the time of the primary lock and the time of re-lock, and the occupant may move inadvertently, and the webbing will not be restrained. As a result, the occupant restraint performance at the time of collision is reduced.

Therefore, the present invention employs a piston that moves while deforming along the inner wall of the bending portion when passing through the bending portion of the pipe. According to such a piston, the frictional force between the pipe inner wall and the piston can be increased, and the resistance force accompanying the movement in the pipe can be increased. In this way, by increasing the friction force between the piston and the inner wall of the pipe, the movement of the piston after the pretensioner operation is limited, and the load acting on the webbing after the pretensioner operation is maintained in an increased state. Can do. As a result, the load limiter load is maintained to prevent the load from being released after the primary lock (ie, the release of the primary lock), thereby preventing the occurrence of re-locking and increasing the safety of passengers in the event of a vehicle emergency. It can be secured.

The length of the piston in the moving direction is preferably 1.4 times or more the inner diameter of the pipe. In this way, since the length of the piston in the moving direction is sufficiently longer than the inner diameter of the pipe, the bending resistance of the piston itself increases when passing through the curved portion of the pipe, and the contact area with the inner wall of the curved portion also increases. The friction force also increases because it becomes larger. For this reason, the load accompanying the movement of the piston can be reliably increased, the load limiter load can be maintained, and the occurrence of re-locking can be prevented.

The durometer hardness of the piston is preferably D scale 63 or higher. With such durometer hardness, the deformation of the piston during movement in the pipe is limited, the frictional force between the piston and the inner wall of the pipe can be increased, the load accompanying the movement of the piston is increased, The occurrence of re-locking can be prevented.

The bending strength of the above piston is preferably 350 MPa or more. With such bending strength, the deformation of the piston during movement in the pipe is limited, the frictional force between the piston and the inner wall of the pipe can be increased, the load accompanying the movement of the piston is increased, and the primary lock It is possible to prevent the subsequent load from coming off and prevent relocking.

The piston should have a breaking strength value in an Izod impact strength test at 23 ° C or -20 ° C. If the fracture strength value is measured in such an Izod impact strength test, the deformation of the piston during movement in the pipe is limited, and the frictional force between the piston and the pipe inner wall can be increased, By increasing the load accompanying the movement of the piston, it is possible to prevent the load from being lost after the primary lock, thereby preventing relocking.

The above piston includes a cylindrical main body, a through-hole penetrating the main body in the moving direction of the piston, a concave recess formed on the ball side of the main body, and a groove formed by cutting out the edge of the recess. It is good to have. Thus, since the recessed part is formed in the side which contacts a ball among the main bodies of a piston, a recessed part and a ball can contact reliably. Further, the gas on the gas generator side generated by the gas generator can move to the ball side through the through hole of the piston and further through the groove of the recess. For this reason, it can avoid that the gas pressure between a gas generator and a piston becomes high too much, and can prevent destruction of a pipe.

According to the present invention, it is possible to provide a seatbelt retractor that prevents the occurrence of re-locking by preventing the phenomenon that the primary lock is released, and that can ensure higher safety for the passenger in the event of a vehicle emergency.

It is a figure which illustrates the seatbelt apparatus provided with the retractor for seatbelts in embodiment of this invention. It is a figure which illustrates the cross section of the retractor for seatbelts of FIG. FIG. 3 is an AA cross-sectional view of the seat belt retractor of FIG. 2. It is a figure which illustrates the piston of the pretensioner of FIG. It is a figure which illustrates the state of the pretensioner after the load limiter operation | movement following FIG.3 (b). It is a figure which illustrates the other example of the piston of FIG. It is the graph which compared the webbing load of the embodiment of the present invention, and the change rate of webbing load. It is a graph which illustrates the relationship between the piston of an embodiment of the present invention, and re-locking.

DESCRIPTION OF SYMBOLS 100 ... Retractor for seat belts, 102 ... Seat belt device, 104 ... Vehicle seat, 106 ... Webbing, 108 ... Seat back, 110 ... Through anchor, 112 ... Tip of webbing, 114 ... Anchor plate, 116 ... Tongue plate, 118 ... Buckle, 120 ... Pretensioner, 122 ... Spindle, 124 ... Retractor frame, 126, 128 ... A pair of side plates of the retractor frame, 130 ... Torsion bar, 132 ... Tread head, 134 ... Pipe, 136, 136A ... Piston, 138 138a to 138i ... ball, 140 ... one end of pipe, 142 ... gas generator, 144 ... curved portion, 146 ... pinion, 148 ... cover member, 150 ... pocket, 152 ... other end of pipe, 154, 154A ... main body, 156 ... concave 158 ... edge, 160 ... groove portion, 162,162A ... end surface, 164,164A ... through hole, 166, 168 ... inner wall of the pipe, 170 ... recessed portion

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

FIG. 1 is a diagram illustrating a seat belt device 102 including a seat belt retractor (hereinafter referred to as a retractor 100) according to an embodiment of the present invention. In the drawing, the retractor 100 is schematically illustrated.

The seat belt device 102 is a safety device installed on a vehicle seat 104 which is a left front seat (for example, a passenger seat) of the vehicle. The seat belt device 102 restrains an occupant (not shown) to the vehicle seat 104 by using an occupant restraining webbing 106.

The retractor 100 is a device that winds and unwinds the webbing 106 by a rotational force, and is disposed in a center pillar that is not shown here. In the drawing, however, the retractor 100 is not limited to the center pillar, and may be disposed behind or inside the seat back 108 of the vehicle seat 104.

The webbing 106 is unwound from the retractor 100, inserted through a through anchor 110 attached to the upper part of the side of the passenger compartment, such as above the center pillar, and folded downward. An anchor plate 114 attached to the lower side of the vehicle body is stitched to the front end portion 112 of the webbing 106 folded back by the through anchor 110. The folded webbing 106 is inserted into the tongue plate 116. Further, a buckle 118 is disposed on the vehicle seat center side of the vehicle seat 104.

In such a seat belt device 102, the occupant seated on the vehicle seat 104 grips the tongue plate 116 and attaches the tongue plate 116 to the buckle 118, whereby the body of the occupant is restrained by the webbing 106.

FIG. 2 is a diagram illustrating a cross section of the retractor 100 of FIG. FIG. 3 is a cross-sectional view taken along the line AA of the retractor 100 of FIG. FIGS. 3A and 3B illustrate the states before and after the operation of the pretensioner 120 of the retractor 100 in the event of a vehicle emergency.

2, the retractor 100 includes a spindle 122 that rotates and unwinds the webbing by rotating, and a pretensioner 120 that rotates the spindle 122 in the webbing winding direction in the event of a vehicle emergency. The spindle 122 is rotatably supported by a pair of

side plates

126 and 128 of the retractor frame 124.

In the spindle 122, a torsion bar 130 that is a torsion member is mounted. As shown in FIG. 2, the torsion bar 130 extends along the axis of the spindle 122, one end in the axial direction is coupled to the spindle 122, and the other end is coupled to the tread head 132. The torsion bar 130 is included in a load limiter mechanism (described later) that draws out the webbing while absorbing energy when a load greater than the setting is applied to the webbing.

The pretensioner 120 and a winding spring device (not shown) are attached to the side plate 126 of the retractor frame 124. The side plate 128 of the retractor frame 124 is provided with sensors such as vehicle acceleration detecting means and webbing unwinding acceleration detecting means (not shown) and locking means. The lock means prevents the rotation of the webbing in the unwinding direction by engaging the tread head 132 with the retractor frame 124 in the event of a vehicle emergency.

As shown in FIG. 3, the pretensioner 120 includes a pipe 134 that extends along a predetermined path, a cylindrical piston 136 that is accommodated in the pipe 134, and a plurality of balls 138 made of metal. The pipe 134 is attached with a gas generator 142 that generates gas at the time of vehicle emergency at one end 140 thereof, and includes a curved portion 144 that is curved in the middle.

The piston 136 is disposed in the vicinity of the gas generator 142 attached to one end 140 of the pipe 134 before the operation of the pretensioner 120 shown in FIG. Of the plurality of balls 138, the ball 138 a is disposed at a position closest to the piston 136.

The pretension 120 further includes a pinion 146 as a rotating member and a cover member 148 (see FIG. 2) that covers the pipe 134. The pinion 146 is always coupled to the spindle 122 by spline fitting, and rotates together with the spindle 122. A plurality of hemispherical pockets 150 for accommodating the balls 138 are provided on the outer periphery of the pinion 146 in the circumferential direction. The cover member 148 restricts the shape of the pipe 134 by covering the pipe 134.

Before the pretensioner 120 shown in FIG. 3A is operated, the

balls

138b and 138c among the plurality of balls 138 are stored in the pockets 150 of the pinion 146 in advance. The ball 138c is in contact with a ball 138d located near the other end 152 of the pipe 134. Further, the balls 138e to 138a following the ball 138d are accommodated in the pipe 134 in a state of being in contact with each other as shown in FIG.

When the gas generator 142 is activated and gas is supplied into the pipe 134 in the event of a vehicle emergency, the piston 136 is pressed by the pressure of the generated gas and moves in the pipe 134 as shown in FIG. To do. The piston 136 shown in FIG. 3B moves to a position where the plurality of balls 138 are pushed out toward the other end 152 of the piston 136 while being in contact with the ball 138 a and passes through the curved portion 144 of the pipe 134.

As the piston 136 moves in the hype 134, the plurality of balls 138 are pushed out one by one from the other end 152 of the pipe 134 by the piston 136. The pushed ball 138 rotates the pinion 146, thereby applying a rotational force to the spindle 122 and rotating the spindle 122 in the webbing take-up direction (arrow B in the figure). The ball 138 after rotating the pinion 136 is detached from the pocket 150 of the pinion 136 and accumulated in a predetermined ball accumulation area (not shown). In this manner, in the retractor 100, the pretensioner 120 operates in the initial stage of the vehicle emergency, thereby removing the slack of the webbing and applying tension to the webbing so that the occupant can be reliably restrained.

FIG. 4 is a diagram illustrating the piston 136 of the pretensioner 120 of FIG. FIG. 4A is a perspective view of the piston 136. 4 (b) and 4 (c) are enlarged views of the piston 136 in the state shown in FIGS. 3 (a) and 3 (b).

The piston 136 has a cylindrical main body 154 as shown in FIG. A recessed portion 156 is formed on the side of the main body 154 that is in contact with the ball 138a. The recess 156 has a groove 160 formed by cutting out the edge 158. As shown in FIG. 4B, the gas generator side facing the gas generator 142 in the main body 154 has a flat end surface 162.

Furthermore, the piston 136 has a through hole 164 through which the main body 154 passes. As shown in FIG. 4B, the through-hole 164 penetrates the main body 154 along the direction from the gas generator side of the main body 154 to the ball side or from the ball side to the gas generator side, that is, the moving direction of the piston 136. Yes.

As an example, the length La of the piston 136 in the moving direction is 14 mm, and the inner diameter Lb of the pipe 134 is 10 mm. That is, the length La of the piston 136 in the moving direction is 1.4 times the inner diameter Lb of the pipe 134 and is sufficiently longer than the inner diameter Lb of the pipe 134. Further, as shown in FIG. 4B, the inner diameter of the piston 136 is slightly larger than the inner diameter Lb of the pipe 134.

The position of the piston 136 shown in FIG. 4 (c) is the position after the pretensioner operation shown in FIG. 3 (b). After the pretensioner 120 is actuated, as shown in FIG. 3B, the

balls

138 f and 138 g among the plurality of balls 138 pushed out by the piston 136 are accommodated in the pocket 150 of the pinion 146. The ball 138g is in contact with the ball 138h located near the other end 152 of the pipe 134. The ball 138h is in contact with the subsequent ball 138i. Further, the ball 138 i is in contact with the ball 138 a that is in direct contact with the piston 136.

Thus, after the pretensioner is activated, the

balls

138a, 138f to 138i remain in the pretensioner 120. In the retractor 100, when the webbing is pulled due to inertia movement of the occupant and the load (tensile force) exceeds a predetermined value after the pretensioner 120 shown in FIG. 3B is activated, the load limiter is activated.

FIG. 5 is a diagram illustrating the state of the pretensioner 120 after the load limiter operation subsequent to FIG. 3B. In this state, the piston 136 is pushed (held) by the internal pressure of the gas generated by the gas generator 142. In the pretensioner 120, the ball 138 is not easily returned to the gas generator 142 side by the gas pressure that presses the piston 136 and the frictional force between the piston 136 and the pipe 134, that is, “primary lock”. "" When the load limiter is activated, the webbing tensile force acts on the torsion bar 130 (see FIG. 2) via the spindle 122 as a rotational force in the webbing unwinding direction (arrow C in the figure). Further, the tension of the webbing is such that the pinion 146 pushes the ball 138 (here,

balls

138a, 138f to 138i) back into the pipe 134 via the spindle 122, and the piston 136 is moved to the gas generator side by the pushed back ball 138. Also acts as a moving force to move to.

For this reason, when the load limiter is operated, the torsion bar 130 is twisted and deformed due to the tensile force of the webbing, and the piston 136 moves against the resistance force accompanying the movement in the pipe 134. That is, when the webbing is unwound, in addition to the load associated with the torsional deformation of the torsion bar 130, the load associated with the movement of the piston 136 also acts on the webbing (occupant), and these loads become load limiter loads.

Here, it is preferable that the load acting on the webbing (occupant) is stable (primary lock) from after the pretensioner operation until after the load limiter operation is completed. However, if the load limiter load becomes greater than the gas holding pressure after the primary lock, the primary lock is released, and immediately after that, the lock mechanism is activated and the spindle is locked. This is called “re-lock”. When this re-lock occurs, for example, in the load change speed (N / ms) after the pretensioner operation, the difference between the maximum change speed and the minimum change speed in 5 ms is 1000 N / ms or more. May be. In other words, when re-locking occurs, the load acting on the webbing fluctuates greatly between the time after the primary lock and the time when re-locking is completed, and the occupant may move inadvertently and is not restrained by the webbing. It will be in a state and the passenger | crew restraint performance at the time of a collision will fall.

Therefore, in the present embodiment, a configuration is adopted in which the load associated with the movement of the piston 136 is increased and the load limiter load is maintained to prevent the phenomenon that the primary lock is released, thereby preventing the occurrence of re-locking. That is, the length 136 of the piston 136 in the moving direction is sufficiently longer than the inner diameter Lb of the pipe 134 as shown in FIG. 4B, and the inner diameter is slightly larger than the inner diameter Lb of the pipe.

Therefore, immediately after the start of the load limiter operation, the piston 136 receives a moving force by the pushed-back ball 138a and makes a large contact with the

inner walls

166, 168 of the curved portion 144 of the pipe 134, as shown in FIG. While maintaining the area, it deforms in a state of being in close contact with the

inner walls

166 and 168. Further, the piston 136 moves while being bent along the

inner walls

166 and 168, passes through the curved portion 144 of the pipe 134, and is pushed back to the position shown in FIG. 5. Thereby, when the piston 136 moves through the pipe 134 from the position shown in FIG. 4C to the position shown in FIG. 5 and passes through the bending portion 144 when the load limiter is operated, the

inner walls

166 and 168 of the bending portion 144 are passed. The frictional force between the

inner walls

166 and 168 increases, and the bending resistances Fc and Fd also increase.

Therefore, according to the retractor 100, the load accompanying the movement of the piston 136 in the pipe 134 can be increased, and the occurrence of re-locking can be achieved by holding the load limiter load and preventing the phenomenon that the primary lock is released. Can be prevented, and higher safety of the passengers in the event of a vehicle emergency can be ensured. Since the length of the piston 136 in the moving direction is long, the number of balls 138 is reduced to match the initial volume of the combustion chamber of the gas generator 142. Therefore, the cost is reduced by reducing the number of balls 138. You can also. Further, since the piston 136 can be changed in length with respect to the existing piston, no additional parts are required, and the piston 136 can be applied to various retractors. Further, since the length of the piston 136 is changed, it is easy to distinguish from the existing piston.

Further, in the retractor 100, since the concave portion 156 is formed on the ball side of the main body 154 of the piston 136, the concave portion 156 and the ball 138 can be reliably in contact with each other. Therefore, the ball 138 can prevent a large amount of gas from moving into the pipe 134 on the side where the ball 138 is present in a state where the piston 136 is pushed by the gas. On the other hand, part of the gas generated by the gas generator 142 can move to the ball side through the through hole 164 of the piston 136 and further through the groove 160 of the recess 156. Therefore, in the retractor 100, the gas pressure between the gas generator 142 and the piston 136 can be prevented from becoming too high, and the pipe 134 can be prevented from being broken.

FIG. 6 is a diagram illustrating another example of the piston 136 in FIG. In the drawing, another example of the piston 136A is shown corresponding to the piston 136 shown in FIG. The piston 136A has a length Lc in the moving direction (see FIG. 6B) shorter than the length La in the moving direction of the piston 136, and further changes the material. The end face of the main body 154A on the gas generator side It differs from the piston 136 in that a recess 170 is formed in 162A. As shown in FIG. 6B, the inner diameter of the piston 136A is slightly larger than the inner diameter Lb of the pipe 134.

The material of the piston 136A is selected based on the durometer hardness, bending strength, and isod impact strength from the viewpoint of preventing the occurrence of re-locking by increasing the load accompanying the movement of the piston 136A during the load limiter operation. ing. Here, the durometer hardness is the surface hardness when the measurement condition is durometer, the test method is JIS K7125, and the unit is D scale. The isod impact strength is obtained by an isod impact strength test when the measurement condition is 23 ° C. or −20 ° C., the test method is ASTM D256, and the unit is J / m notch.

Immediately after the start of the load limiter operation, the piston 136A receives a moving force by the pushed back ball 138a and deforms in a state of being in close contact with the

inner walls

166, 168 of the bending portion 144 of the pipe 134, as shown in FIG. While moving along the

inner walls

166, 168, it moves through the curved portion 144 of the pipe 134.

Therefore, when the load limiter is operated, the piston 136A moves from the position shown in FIG. 6C through the pipe 134 and passes through the bending portion 144. Thus, the piston 136A moves from the

inner walls

166, 168 of the bending portion 144 with a large vertical drag Fa, In addition to Fb, bending resistances Fc and Fd are also received. Therefore, by selecting a material that increases the bending resistances Fc and Fd as the material of the piston 136A, it is possible to increase the load accompanying the movement of the piston 136A when the load limiter is activated.

If the material of the piston 136A has a durometer hardness of D scale 63 or more (see FIG. 8B) or a bending strength of 350 MPa or more, the load accompanying the movement of the piston 136A can be increased. The occurrence of re-locking can be prevented.

Further, the material of the piston 136A may be any material as long as the fracture strength value is measured by an Izod impact strength test at 23 ° C. or −20 ° C. The material of the piston 136A is not limited to the breaking strength value, and any appropriate material may be selected as long as the measured value is observed (however, the material from which the measured value cannot be obtained is included in the present invention). Absent). As an example, by selecting a material called Hytrel (registered trademark) that is a block copolymer of a crystalline layer (hard segment) and an amorphous layer (soft segment), the load accompanying the movement of the piston 136A is increased, The occurrence of locks can be prevented.

Therefore, according to the piston 136A, the load accompanying the movement in the pipe 134 can be increased, the load limiter load can be maintained, the occurrence of re-locking can be prevented, and the safety of the occupant in the event of a vehicle emergency can be ensured. . Further, since the piston 136A is formed with the recess 170 on the gas generator side of the main body 154A, the gas pressure by the gas generator 142 can sufficiently act on the piston 136A. Since the through-hole 164A is formed in the main body 154A, it is possible to avoid the gas pressure between the gas generator 142 and the piston 136A from becoming too high (similar to the case of FIG. 5). Furthermore, since the piston 136A can be realized by changing the material with respect to the existing piston, an additional part or the like is not necessary and can be applied to various retractors.

FIG. 7 is a graph comparing the webbing load and the change rate of the webbing load between the embodiment of the present invention and the comparative example. In FIG. 7A, the horizontal axis is time (ms) and the vertical axis is webbing load (N). In FIG. 7B, the horizontal axis is time (ms), and the vertical axis is the webbing load change rate (N / ms). In each graph, this embodiment is indicated by a solid line and a comparative example is indicated by a dotted line. In this embodiment,

pistons

136 and 136A are used. As a comparative example, a piston made of an existing material whose length in the moving direction of the piston is not increased is used.

Each graph shown in FIGS. 7A and 7B shows the change in webbing load and the change in change rate of the webbing load after the pretensioner operation in the vehicle emergency and after the load limiter operation is completed. Show.

As shown in the graph of FIG. 7A, in this embodiment, the webbing load is stable between 5000 and 6000 (N) between 80 and 100 (ms). On the other hand, in the comparative example, the webbing load greatly changes from 4000 to 7000 (N). Further, the change rate of the webbing load in the comparative example exceeds 1000 (N / ms) and is lower than −1000 (N / ms) as shown in the graph of FIG.

Therefore, it can be confirmed that re-locking occurs when the piston of the comparative example is used, and re-locking does not occur when the

pistons

136 and 136A of the present embodiment are used.

FIG. 8 is a graph illustrating the relationship between the

pistons

136 and 136A and the relock according to the embodiment of this invention. In FIG. 8A, the horizontal axis is the length (mm) in the moving direction of the piston 136, and the vertical axis is the webbing load change rate (N / ms). The inner diameter of the pipe 134 through which the piston 136 moves is 10 mm. In FIG. 8B, the horizontal axis is durometer hardness (D scale), and the vertical axis is the webbing load change rate (N / ms). Each graph shows a change in the change rate of the webbing load between the time after the pretensioner operation in the vehicle emergency and the time after the load limiter operation is completed.

As shown in the graph of FIG. 8A, when the length of the piston in the moving direction is 14 mm, 16 mm, and 18 mm, the change rate of the webbing load is less than 1000 (N). On the other hand, when the length in the moving direction of the piston is less than 14 mm, here, 8 mm, 10 mm, and 12 mm, the change rate of the webbing load is around 3500 (N / ms), and exceeds 1000 (N / ms). .

Therefore, as shown in the graph of FIG. 8A, when the inner diameter of the pipe 134 is 10 mm, the length in the moving direction of the piston 136 is 14 mm or more, that is, 1.4 times the inner diameter of the pipe 134. If it is above, it can confirm that a re-lock does not generate | occur | produce.

As shown in the graph of FIG. 8B, if the durometer hardness of the piston 136A is 63, 72, the change rate of the webbing load is less than 1000 (N). On the other hand, when the durometer hardness of the piston is less than 63 mm, here 47, 55, the change rate of the webbing load is around 3000 (N / ms) and exceeds 1000 (N / ms).

Therefore, as shown in the graph of FIG. 8B, even if the length of the piston in the moving direction is not increased, if the durometer hardness of the piston 136A is greater than or equal to the D scale 63, the re-locking is performed. It can be confirmed that it does not occur.

As described above, in the retractor 100 according to this embodiment, the length in the moving direction of the piston 136 is increased from the viewpoint of increasing the load accompanying the movement of the

pistons

136 and 136A when the load limiter is operated, or the material of the piston 136A is increased. By selecting the, the occurrence of re-locking can be prevented, and the safety of passengers in the event of a vehicle emergency can be ensured.

The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

Moreover, although the example which applied the seatbelt retractor concerning this invention to the motor vehicle was demonstrated in the said embodiment, it is also possible to apply to an aircraft, a ship, etc. besides a motor vehicle, and obtains the same effect. Can do.

The present invention can be used for a seat belt retractor for winding and unwinding a webbing for restraining an occupant.

Claims

In a retractor for a seat belt comprising a spindle that rotates and rotates the webbing by rotating, and a pretensioner that rotates the spindle in the webbing winding direction.
The pretensioner is
A pipe including a curved portion extending along a predetermined path and curved in the middle;
A cylindrical piston which is accommodated in the pipe and moves in the pipe by a predetermined gas supplied from one end of the pipe;
A plurality of balls housed in the pipe, each of which is pushed out from the other end of the pipe by the moving piston one by one to give a rotational force to the spindle and to rotate the spindle in the webbing take-up direction; And a ball
At least one of the plurality of balls is pushed back into the pipe by the spindle that rotates in the webbing unwinding direction when the spindle is rotated in the webbing winding direction and an occupant is restrained by the webbing. ,
The retractor for a seat belt, wherein the piston is pushed by the at least one ball and passes through the curved portion while being deformed along an inner wall of the curved portion.
The seatbelt retractor according to claim 1, wherein the length of the piston in the moving direction is 1.4 times or more the inner diameter of the pipe.
The seat belt retractor according to claim 1 or 2, wherein the durometer hardness of the piston is D scale 63 or more.
The seat belt retractor according to claim 1 or 2, wherein the bending strength of the piston is 350 MPa or more.
The seat belt retractor according to claim 1 or 2, wherein the piston has a breaking strength value in an Izod impact strength test at 23 ° C or -20 ° C.
The piston is
A cylindrical body;
A through-hole penetrating the main body in the moving direction of the piston;
A recessed recess formed on the ball side of the body;
The seatbelt retractor according to any one of claims 1 to 5, further comprising a groove formed by cutting out an edge of the recess.