A three-point seatbelt device includes: a webbing configured to function as a shoulder belt and a lap belt; a shoulder-side reeler that includes a pre-tensioner mechanism and a shoulder-side force limiter mechanism, and is configured to reel up an end portion of the webbing on a shoulder belt side so as to allow the webbing to be pulled out; a tongue mounted on the webbing; and an inner belt including a buckle to which the tongue is coupled, the inner belt including, of a pre-tensioner mechanism and a buckle-side force limiter mechanism, only the buckle-side force limiter mechanism. An initial load of the buckle-side force limiter mechanism is set to be larger than an initial load of the shoulder-side force limiter mechanism.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2017-170425 filed on Sep. 5, 2017 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a three-point seatbelt device.

2. Description of Related Art

In the three-point seatbelt device disclosed in Japanese Patent Application Publication No. 11-129864 (JP 11-129864 A), a shoulder belt-side portion of a webbing is fixed to a vehicle body-side member through a retractor including a pre-tensioner mechanism (hereinafter referred to as a PT mechanism) and a force limiter mechanism (hereinafter referred to as an FL mechanism). An inner belt including a buckle, to which a tongue mounted on the webbing is coupled, also includes a PT mechanism and an FL mechanism.

In the three-point seatbelt device disclosed in Japanese Patent Application Publication No. 2016-97869 (JP 2016-97869 A), a shoulder belt-side portion of a webbing is fixed to a vehicle body-side member through a retractor including a PT mechanism and an FL mechanism. A buckle is fixed to a floor through an energy absorbing plate.

SUMMARY

The inner belt including the PT mechanism of JP 11-129864 A causes an increase in the size of the seatbelt device due to the necessity of securing a pull-in stroke etc. Since the PT mechanism of the retractor and the PT mechanism of the inner belt are in such a relationship that they pull each other upon activation, it is necessary to appropriately control the activation timings of these two PT mechanisms so as not to exert an excessive load on the chest of the occupant. Thus, an ECU etc. that controls the activation timings is required, which adds to the cost.

The technique of JP 2016-97869 A does not take into account the relationship between an activation load of the FL mechanism of the retractor and an activation load of the FL mechanism of the inner belt. Here, a load applied to the inner belt during a crash is a load combining a load from the shoulder belt and a load from the lap belt. In the technique of JP 2016-97869 A, therefore, the FL mechanism of the retractor may fail to be effectively activated while the FL mechanism of the inner belt is activated. In particular, in a form of crash in which the occupant moves obliquely toward the vehicle front side and the outer side in the vehicle width direction, the inner belt is more likely to be subjected to a large load than in a form of crash in which the occupant moves toward the vehicle front side. Accordingly, there is a relatively high likelihood that the FL mechanism of the retractor may fail to be effectively activated while the FL mechanism of the inner belt is activated.

The present disclosure provides a compact and inexpensive three-point seatbelt device that can appropriately reduce a load exerted on the chest of an occupant during a crash.

A three-point seatbelt device according to an aspect of the disclosure includes: a webbing configured to function as a shoulder belt and a lap belt; a shoulder-side reeler that includes a pre-tensioner mechanism and a shoulder-side force limiter mechanism, and is configured to reel up an end portion of the webbing on a shoulder belt side so as to allow the webbing to be pulled out; a tongue mounted on the webbing; and an inner belt including a buckle to which the tongue is coupled, the inner belt including, of a pre-tensioner mechanism and a buckle-side force limiter mechanism, only the buckle-side force limiter mechanism. An initial load of the buckle-side force limiter mechanism is set to be larger than an initial load of the shoulder-side force limiter mechanism.

In this aspect of the three-point seatbelt device, the webbing functions as the shoulder belt and the lap belt as the tongue mounted on the webbing is coupled to the buckle. The shoulder-side reeler is provided at the shoulder belt-side end portion of the webbing. The shoulder-side reeler includes the PT mechanism and the FL mechanism (shoulder-side FL mechanism). Thus, as the PT mechanism is activated during a crash, the webbing is pulled in from the shoulder side, so that any slack in the webbing can be removed. Moreover, as the shoulder-side FL mechanism is activated, an excessive load exerted on the chest of the occupant restrained by the shoulder belt can be reduced.

The inner belt including the buckle also includes the FL mechanism (buckle-side FL mechanism). Thus, as the buckle-side FL mechanism is activated, an excessive load exerted on the waist or the chest of the occupant can be reduced.

Here, including no PT mechanism, the inner belt of the three-point seatbelt device can be manufactured in a compact size. Moreover, electrical control such as ignition to activate the PT mechanism is not required, which can eliminate the need for an ECU etc. to keep costs down.

The initial load of the buckle-side FL mechanism is set to be larger than the initial load of the shoulder-side FL mechanism. This setting allows the shoulder-side FL mechanism to be effectively activated compared with if the initial load of the buckle-side FL mechanism is set to be about equal to or smaller than the initial load of the shoulder-side FL mechanism. As a result, both the shoulder-side FL mechanism and the buckle-side FL mechanism can be effectively activated to appropriately reduce the load exerted on the chest of the occupant. In particular, even during a crash such as an oblique crash in which the occupant moves toward an obliquely front side of the reeler, both the shoulder-side FL mechanism and the buckle-side FL mechanism can be effectively activated to appropriately protect the occupant.

In the above aspect, the initial load of the buckle-side force limiter mechanism may be set to be within a range of 1.3 to 2.2 times the initial load of the shoulder-side force limiter mechanism.

In this configuration, the initial load of the buckle-side FL mechanism is set to be within a range of 1.3 to 2.2 times the initial load of the shoulder-side FL mechanism. With the initial load of the buckle-side FL mechanism thus set to be within an appropriate range with respect to the initial load of the shoulder-side FL mechanism, both the shoulder-side FL mechanism and the buckle-side FL mechanism can be effectively activated.

In the above aspect, a load of the buckle-side force limiter mechanism may be set to become smaller in a latter half of an action of the buckle-side force limiter mechanism than in an early stage of the action.

In this configuration, the load of the buckle-side FL mechanism is set to become smaller in a latter half of an action thereof than in an early stage of the action. Thus, in an early stage of a crash when a load exerted on the shoulder belt starts to increase, the load (initial load) of the buckle-side FL mechanism becomes large, so that the chest of the occupant is securely restrained in the early stage of the crash. Then, in the latter half of the crash when the load exerted by the shoulder belt on the chest of the occupant becomes large as the occupant moves forward, the load of the buckle-side FL mechanism decreases so as to appropriately reduce the load exerted on the chest of the occupant.

In the above aspect, a load of the buckle-side force limiter mechanism may be set to become smaller in a latter half of an action of the buckle-side force limiter mechanism than in an early stage of the action.

In this configuration, the buckle-side FL mechanism is disposed between the buckle and the anchorage position of the inner belt. Thus, the buckle-side FL mechanism is so compact that it can be appropriately applied even to a structure in which a center console is provided on a lateral side of a seat to which the three-point seatbelt device is applied.

In the above aspect, the buckle-side force limiter mechanism may include: a case; a deformable tube disposed inside the case; a wire coupled to the buckle, and extending into the case and passing through the deformable tube; and a squeeze member coupled to the wire at a lower end of the wire. The buckle-side force limiter mechanism may be configured such that, as the buckle is pulled by the tongue, the squeeze member moves upward while deforming the deformable tube and causes the buckle to be pulled out, and a lower part of the deformable tube may have a larger plate thickness than a plate thickness of the remaining part of the deformable tube or has a smaller inside diameter than an inside diameter of the remaining part of the deformable tube.

In this configuration, the buckle-side FL mechanism can have a simple configuration and yet only the initial load thereof can be set to be large.

In the above aspect, the buckle-side force limiter mechanism may include: a deformable plate in which a long hole is formed; a tubular member coupled to the buckle; and a squeeze pin supported at both ends on the tubular member. The long hole may include a fitting part in which the squeeze pin is fitted and a deformable part having a smaller width than the fitting part, the buckle-side force limiter mechanism may be configured such that, as the buckle is pulled by the tongue, the squeeze pin moves in a longitudinal direction of the long hole while deforming the deformable part and causes the buckle to be pulled out, and a width of a portion of the deformable part adjacent to the fitting part may be smaller than a width of the remaining portion of the deformable part, or a plate thickness of the deformable plate at the portion of the deformable part adjacent to the fitting part is larger than a plate thickness of the deformable plate at the remaining portion of the deformable part.

In this configuration, the buckle-side FL mechanism can have a simple configuration and yet only the initial load thereof can be set to be large.

In the above aspect, the buckle-side force limiter mechanism may include: a deformable plate in which a long hole is formed; a tubular member coupled to the buckle; and a squeeze pin supported at both ends on the tubular member. The long hole may include a fitting part in which the squeeze pin is fitted and a deformable part having a smaller width than the fitting part, the buckle-side force limiter mechanism may be configured such that, as the buckle is pulled by the tongue, the squeeze pin moves in a longitudinal direction of the long hole while deforming the deformable part and causes the buckle to be pulled out, and the deformable plate may include a main plate and an additional plate laid on a portion of the main plate such that a plate thickness of the deformable plate at a portion of the deformable part adjacent to the fitting part is larger than a plate thickness of the deformable plate at the remaining portion of the deformable part.

Thus, a simple configuration can be realized in which the initial load of the FL mechanism is set to be large by forming the deformable plate with a partially increased plate thickness.

DETAILED DESCRIPTION OF EMBODIMENTS

First Embodiment

A three-point seatbelt device S according to a first embodiment will be described below usingFIG. 1toFIG. 6.

The arrows FR, UP, W1, and W2in the drawings respectively indicate a front side in a seat front-rear direction, an upper side in a seat up-down direction, one side in a seat width direction (buckle side), and the other side in the seat width direction (retractor side). Unless otherwise specified, the words front and rear sides, upper and lower sides, and one and the other sides in the width direction used in the following description respectively mean front and rear sides in the seat front-rear direction, upper and lower sides in the seat up-down direction, and one and the other sides in the seat width direction.

As shown inFIG. 1, the three-point seatbelt device S according to this embodiment is applied to a vehicle seat10that is a right-side seat in a first row (the driver's seat in a right-hand drive vehicle). Thus, in this embodiment, a vehicle front side, a vehicle upper side, an inner side in a vehicle width direction, and an outer side in the vehicle width direction respectively coincide with the seat front side, the seat upper side, the one side in the seat width direction, and the other side in the seat width direction.

Basic Configuration of Three-Point Seatbelt Device

The three-point seatbelt device S includes a webbing20that restrains an occupant. The webbing20is made of a material such as chemical fiber and formed as a flexible elongated belt. An end portion of the webbing20on one side in a longitudinal direction thereof (on the side of a shoulder belt20S) is engaged on a spool (not shown) of a retractor32serving as a “shoulder-side reeler” provided at a lower end of a B-pillar16. An intermediate portion of the webbing20in the longitudinal direction is passed through a shoulder anchor34(a slip guide or a slip joint), provided at an upper part of the B-pillar16, so as to be folded back. An end portion of the webbing20on the other side in the longitudinal direction thereof (on the side of a lap belt20L) is engaged on an anchor member36fixed at the lower end of the B-pillar16.

A tongue40is mounted on a portion of the webbing20between the shoulder anchor34and the anchor member36so as to be movable in the longitudinal direction of the webbing20.

An inner belt50is provided on one side of the vehicle seat10in the seat width direction (the inner side in the vehicle width direction). The inner belt50includes a buckle52. When the tongue40is coupled to the buckle52, the occupant seated in the vehicle seat10is fastened with the seatbelt (this state will be hereinafter referred to as a fastened state). In the fastened state, a portion of the webbing20between the tongue40and the shoulder anchor34functions as the shoulder belt20S that restrains the chest and the shoulder of the occupant, while a portion of the webbing20between the tongue40and the anchor member36functions as the lap belt20L that restrains the waist of the occupant.

Retractor with PT Mechanism and FL Mechanism

The retractor32is a reeler that reels up the webbing20on the spool and houses the webbing20so as to allow the webbing20to be pulled out. The retractor32has a locking mechanism that locks the spool so as not to rotate and restricts pulling out of the webbing20, when it is detected that an acceleration rate of the vehicle is not lower than a predetermined value or that a pull-out acceleration rate of the webbing20is not lower than a predetermined value.

The retractor32has a PT mechanism (not shown). The PT mechanism may be a publicly known one, and for example, is of a pyrotechnic type. When a frontal crash is detected, an explosive is ignited, which causes the spool to rotate and forcibly reel up the webbing20. The retractor32further has a pre-crash seatbelt mechanism. When a frontal crash or a lateral crash is predicted, the pre-crash seatbelt mechanism rotates the spool by the driving force of a motor to forcibly reel up the webbing20.

The retractor32further has an FL mechanism (not shown; hereinafter referred to as a shoulder-side FL mechanism). The shoulder-side FL mechanism may be a publicly known one. In this embodiment, for example, the initial load of the shoulder-side FL mechanism is set to about 4 kN. The initial load of the FL mechanism means a load (a load in a direction in which the webbing is pulled out) required for the FL mechanism to start an action from an inactive state.

Inner Belt

FIG. 2Ashows the inner belt50with a longitudinal direction thereof oriented in the up-down direction. The inner belt50is coupled to the tongue40at the buckle52on one side in the longitudinal direction (upper side), and is rotatably coupled to a vehicle body-side member such as a vehicle body or the vehicle seat10on the other end side (lower side). The inner belt50includes an FL mechanism54as a “buckle-side FL mechanism.” As can be understood from the other part of the description of this embodiment, in this specification, a member that includes the buckle and is coupled to a vehicle body-side member is referred to as an inner belt. Therefore, a member that does not include an elongated belt-shaped member like a webbing as in this embodiment also corresponds to the inner belt.

The FL mechanism54includes a case56. The case56includes a housing part58in which a deformable tube62and a squeeze member66to be described later are disposed, and an anchor60coupled to the vehicle body-side member. The anchor60has a shaft insertion hole60A. The inner belt50is rotatably coupled to the vehicle body-side member by using the shaft insertion hole60A.

The housing part58is formed integrally with the anchor60. The housing part58is formed so as to protrude toward the one side in the seat width direction (the inner side in the vehicle width direction) relative to the flat plate-shaped anchor60. In other words, the housing part58is located on the outer side in the seat width direction relative to an imaginary plane defined by the plate-shaped anchor60. The housing part58has a substantially rectangular parallelepiped shape.

The FL mechanism54includes the deformable tube62. The deformable tube62is provided inside the case56. The deformable tube62extends in the longitudinal direction of the inner belt50and has a tube shape with a quadrangular cross-section, and is formed so as to have a constant plate thickness from an upper end to a lower end. The upper end of the deformable tube62is joined to an upper wall58T of the case56, and the lower end of the deformable tube62is disposed with a clearance to a lower wall58B of the case56.

The FL mechanism54includes a wire64coupled to the buckle52. One end (upper end) of the wire64is coupled to the buckle52, while the other end is inserted into the case56through a through-hole58A formed in the upper wall58T of the case56. The through-hole58A of the upper wall58T communicates with an inside of the deformable tube62, and the wire64passes through the inside of the deformable tube62. The squeeze member66is mounted at the other end (lower end) of the wire64.

Specifically, the squeeze member66has an insertion hole66A for the wire64to pass through. The wire64is passed through the insertion hole66A of the squeeze member66, and an engaging member68is fixed at the other end (lower end) of the wire64. Thus, the squeeze member66is prevented from coming off from the other end side of the wire64.

The insertion hole66A of the squeeze member66extends through the squeeze member66in the up-down direction. The cross-section of the squeeze member66orthogonal to the up-down direction has a quadrangular shape similar to the cross-sectional shape of the deformable tube62. The squeeze member66is shaped so as to expand gradually from an upper end toward a lower end. Thus, a side surface66S of the squeeze member66is a flat surface inclined in a direction away from a central axis of the squeeze member (in this embodiment, from a portion thereof where the wire64is passed) while extending from the upper end toward the lower end of the squeeze member66.

A portion of the squeeze member66on the upper side is disposed inside the deformable tube62. On the other hand, a portion of the squeeze member66on the lower side is disposed outside the deformable tube62(on the lower side of the deformable tube62). The side surface66S of the squeeze member66is in contact with the lower end of the deformable tube62. Specifically, the entire circumference of the deformable tube62at the lower end is in contact with the inclined side surface66S of the squeeze member66.

Description of Action of FL Mechanism

Next, an action of the FL mechanism54will be described.

For example, when a form of crash such as a frontal crash in which the occupant moves toward the seat front side occurs, the buckle52is subjected to a large load acting in the direction of separating the buckle52from the case56. This load is transmitted to the squeeze member66through the wire64coupled to the buckle52, causing the squeeze member66to move upward while deforming the deformable tube62(FIG. 2B). Thus, energy is absorbed by deformation of the deformable tube62, and the buckle52is pulled out upward.

Specifically, the deformable tube62deforms along the inclined side surface66S of the squeeze member66. As the squeeze member66comes in contact with the upper wall58T of the case56, the amount of the buckle52pulled out is limited. The dimension of the cross-section of the squeeze member66at the lower end is set such that the deformed deformable tube62comes in contact with or closer to the case56from the inner side.

The load characteristics of the FL mechanism54, i.e., the relationship between the amount of movement of the occupant during a crash and a load exerted on the inner belt50(the load on the inner belt) is represented by the solid line inFIG. 6. The dashed line inFIG. 6represents the relationship in a case where the inner belt50does not include an FL mechanism.

As shown inFIG. 6, the load exerted on the inner belt in an early stage of a crash increases as the amount of movement of the occupant increases. However, after hitting an upper limit, for example, about 5.5 kN, the load on the inner belt does not increase further and remains substantially constant even when the amount of movement of the occupant increases. A time point at which the load on the inner belt reaches about 5.5 kN is a time point at which the FL mechanism54starts an action. Thus, in the FL mechanism54of this embodiment, when a load acting in the direction of pulling out the buckle52(the upward direction inFIG. 2AandFIG. 2B) reaches about 5.5 kN, the deformable tube62starts to be deformed by the squeeze member66. Thereafter, the buckle52is pulled out while the load remains substantially constant (at about 5.5 kN).

Operational Effects

Next, operational effects of this embodiment will be described.

The three-point seatbelt device S of this embodiment is a three-point seatbelt device in which the webbing20functions as the shoulder belt20S and the lap belt20L as the tongue40mounted on the webbing20is coupled to the buckle52. The retractor32is provided at the end portion of the webbing20on the side of the shoulder belt20S. The retractor32includes the PT mechanism and the FL mechanism (shoulder-side FL mechanism). Thus, as the PT mechanism is activated during a crash, the webbing20is pulled in and any slack in the webbing20can be removed. Moreover, as the shoulder-side FL mechanism is activated, an excessive load exerted on the chest of the occupant restrained by the shoulder belt20S can be reduced. The inner belt50including the buckle52also includes the FL mechanism54(buckle-side FL mechanism). Thus, as the buckle-side FL mechanism54is activated, an excessive load exerted on the waist or the chest of the occupant can be reduced.

Here, including no PT mechanism, the inner belt50of the three-point seatbelt device S can be manufactured in a compact size. Moreover, electrical control such as ignition to activate the PT mechanism is not required, which can eliminate the need for an ECU etc. to keep costs down.

The initial load of the buckle-side FL mechanism54is set to be larger than the initial load of the shoulder-side FL mechanism. This setting allows the shoulder-side FL mechanism to be effectively activated compared with if the initial load of the buckle-side FL mechanism is set to be about equal to or smaller than the initial load of the shoulder-side FL mechanism. As a result, both the shoulder-side FL mechanism and the buckle-side FL mechanism54can be effectively activated to appropriately reduce the load exerted on the chest of the occupant. In particular, even during a crash such as an oblique crash in which the occupant moves toward an obliquely front side of the reeler (in this embodiment, provided on the outer side in the vehicle width direction), both the shoulder-side FL mechanism and the buckle-side FL mechanism54can be effectively activated to appropriately protect the occupant.

The initial load of the buckle-side FL mechanism is set to be within a range of preferably 1.3 to 2.2 times, and more preferably 1.5 to 2.0 times, the initial load of the shoulder-side FL mechanism. With the initial load of the buckle-side FL mechanism54thus set to be within an appropriate range with respect to the initial load of the shoulder-side FL mechanism, both the shoulder-side FL mechanism and the buckle-side FL mechanism54can be effectively activated.

In this embodiment, the buckle-side FL mechanism54is disposed between the buckle52and the anchorage position of the inner belt50(the shaft insertion hole60A of the anchor60). Thus, the buckle-side FL mechanism54is so compact that it can be appropriately applied even to a structure in which a center console is provided on a lateral side of the seat (vehicle seat10) to which the three-point seatbelt device S is applied.

Second Embodiment

Next, a three-point seatbelt device according to a second embodiment will be described. In the second embodiment, the configuration of an inner belt150is different from the configuration of the inner belt50of the first embodiment.

FIG. 4AandFIG. 4Bshow the inner belt150of the second embodiment. An FL mechanism154of the inner belt150of the second embodiment includes an anchor bracket70as a “deformable plate.” The anchor bracket70is made of metal and has a plate shape. A shaft insertion hole70A is formed at a lower end of the anchor bracket70. A shaft (not shown) is passed through the shaft insertion hole70A, and the anchor bracket70is coupled to a vehicle body-side member so as to be rotatable around the shaft extending substantially in the seat width direction.

A long hole72in which a squeeze pin76to be described later is fitted and of which a longitudinal direction is oriented in the up-down direction is formed in a region of the anchor bracket70above the shaft insertion hole70A. The specific configuration of the long hole72will be described later.

The FL mechanism154includes a buckle bracket74as a “tubular member” that is coupled to the buckle52. The buckle bracket74has a tubular shape with a rectangular cross-section. A portion of the anchor bracket70is disposed inside the buckle bracket74.

A pin support hole74A is formed in the buckle bracket74. The pin support hole74A extends through a pair of opposite side walls74S of the buckle bracket74. The squeeze pin76is passed through the pin support hole74A, and both side portions of the squeeze pin76in an axial direction thereof are respectively supported on the side walls74S of the buckle bracket74. An intermediate portion of the squeeze pin76in the axial direction is fitted in a portion of the long hole72of the anchor bracket70.

FIG. 5Ashows the anchor bracket70as a single component. The long hole72includes a fitting part72A in which the squeeze pin76is fitted, and a deformable part72B. The fitting part72A is formed in a size corresponding to the size of the intermediate portion of the squeeze pin76in the axial direction. On the other hand, the deformable part72B is formed so as to have a width dimension (in the right-left direction inFIG. 5A) smaller than the diameter of the intermediate portion of the squeeze pin76in the axial direction. Thus, the squeeze pin76is normally fitted in the fitting part72A of the long hole72so as not to move.

Description of Action of FL Mechanism

Next, an action of the FL mechanism154will be described.

For example, when a form of crash such as a frontal crash in which the occupant moves toward the seat front side occurs, first, the PT mechanism of the retractor32is activated, so that the webbing20is pulled in from the shoulder side and any slack in the webbing20is removed. Next, as the occupant tries to move toward the seat front side by inertia, a high tension is applied to the shoulder belt20S and the lap belt20L restraining this occupant. Then, the buckle52is subjected to a load combining a load from the shoulder belt20S and a load from the lap belt20L, i.e., a large load acting in the direction of separating the buckle52from the anchor bracket70(see the arrow F inFIG. 4A). This load is transmitted to the squeeze pin76through the buckle bracket74coupled to the buckle52, causing the squeeze pin76to move upward while deforming the deformable part72B of the long hole72. Thus, energy is absorbed by deformation of the long hole72(anchor bracket70), and the buckle52is pulled out upward. The FL mechanism154can also realize the load characteristics shown inFIG. 6.

Modified Example of Load Characteristics of FL Mechanism54

The load characteristics of the FL mechanism (the relationship between the amount of movement of the occupant and the load exerted on the inner belt during a crash) may be changed to the load characteristics as shown inFIG. 7.

As shown inFIG. 7, in the modified example of the load characteristics, the load exerted on the inner belt increases as the amount of movement of the occupant increases in an early stage of a crash. At a time point when the load exerted on the inner belt reaches about 7 kN, for example, the load exerted on the inner belt stops increasing. The time point at which the load exerted on the inner belt reaches about 7 kN is a time point at which the FL mechanism54starts an action. When the amount of forward movement of the occupant further increases, the load exerted on the inner belt decreases to about 5.5 kN, for example. Thereafter, the load remains at about 5.5 kN even when the amount of movement of the occupant increases.

As has been described above, in the modified example of the load characteristics, the initial load is set to be large (about 7 kN), and the load thereafter in the latter half of the action is set to be small (about 5.5 kN). Thus, the load of the buckle-side FL mechanism is set to become smaller in the latter half of the action thereof than in an early stage of the action. As a result, in an early stage of a crash when the load exerted on the shoulder belt20S starts to increase, the load of the buckle-side FL mechanism54becomes large (initial load: about 7 kN), so that the chest of the occupant is securely restrained in the early stage of the crash. Then, in the latter half of the crash when the load exerted by the shoulder belt20S on the chest of the occupant becomes large as the occupant moves, the load of the buckle-side FL mechanism54decreases (to about 5.5 kN) to appropriately reduce the load exerted on the chest of the occupant.

For example, the FL mechanism having such load characteristics can be realized by changing the structure of the deformable tube62of the FL mechanism54of the first embodiment to the structures shown inFIG. 3AandFIG. 3B, or by changing the structure of the anchor bracket70of the FL mechanism154of the second embodiment to the structures shown inFIG. 5BandFIG. 5C.

Modified Examples of First Embodiment

FIG. 3Ashows a deformable tube162of an FL mechanism according to Modified Example 1 of the first embodiment. The plate thickness of the deformable tube162changes at the border between an inlet part162A on the lower side and a general part162B which is a part of the deformable tube162other than the inlet part162A. Specifically, the deformable tube162has the inlet part162A on the lower side with a large plate thickness (thick part) and the general part162B with a comparatively small plate thickness (thin part). The internal shapes of the inlet part162A and the general part162B are the same. On the other hand, the external shape of the inlet part162A is larger than the external shape of the general part162B. The length of the inlet part162A in an axial direction of the deformable tube162is smaller than the length of the general part162B in the axial direction.

FIG. 3Bshows a deformable tube262of an FL mechanism according to Modified Example 2 of the first embodiment. Unlike the deformable tube162of Modified Example 1, the deformable tube262of Modified Example 2 is formed so as to have a constant plate thickness along the entire length in an axial direction thereof. On the other hand, the cross-sectional shape of the deformable tube262of Modified Example 2 changes at the border between an inlet part262A and a general part262B. Thus, the inlet part262A of the deformable tube262is formed so as to have a smaller cross-sectional shape (smaller inside diameter and outside diameter) than the general part262B.

Also with either of the deformable tubes162,262of Modified Example 1 and Modified Example 2, in an early stage of deformation when the squeeze member66(seeFIG. 2AandFIG. 2B) deforms the inlet parts162A,262A of the deformable tubes162,262, a larger amount of energy is required for the deformation, while in the latter half of deformation when the general parts162B,262B of the deformable tubes162,262are deformed, a smaller amount of energy is required for the deformation. Thus, the load characteristics shown inFIG. 7can be realized.

Modified Examples of Second Embodiment

FIG. 5Bshows an anchor bracket170of an FL mechanism according to Modified Example 3 of the second embodiment. In the anchor bracket170of Modified Example 3, the shape of the deformable part72B of the long hole72is different from the shape of the deformable part72B of the second embodiment. The deformable part72B of the long hole72includes a narrow portion72BA and a wide portion72BB. The width dimensions of the narrow portion72BA and the wide portion72BB are both set to be smaller than the diameter of the intermediate portion of the squeeze pin76in the axial direction. The width dimension of the narrow portion72BA is set to be smaller than that of the wide portion72BB. The narrow portion72BA is formed at a portion of the deformable part72B adjacent to the fitting part72A, and the wide portion72BB is formed at a portion (general portion) of the deformable part72B other than the narrow portion72BA.

In Modified Example 3, the width dimension of the portion (narrow portion72BA) of the deformable part72B adjacent to the fitting part72A, i.e., the portion that is deformed in an early stage of the action of the FL mechanism, is smaller than the width dimension of a general portion (wide portion72BB) which is a portion of the deformable part72B other than the portion adjacent to the fitting part72A. Thus, in the early stage of the action of the FL mechanism, a larger load is required to deform the narrow portion72BA. On the other hand, in the latter half of the action, the load required to deform the wide portion72BB is smaller than the load required to deform the narrow portion72BA. Thus, the load characteristics of the FL mechanism can be set such that the initial load is larger and the load in the latter half of the action is smaller.

FIG. 5Cshows an anchor bracket270of an FL mechanism according to Modified Example 4 of the second embodiment. In the anchor bracket270of Modified Example 4, the shape of the long hole72is the same as the shape of the long hole72of the second embodiment (seeFIG. 5A). On the other hand, the plate thickness of the anchor bracket270changes at a portion of a part where the long hole72is formed. Specifically, the anchor bracket270includes a main plate270H having the same configuration as the anchor bracket70of the second embodiment, and an additional plate270T that is laid on an intermediate portion of the main plate270H in a longitudinal direction thereof. The long hole72is formed so as to extend through both the main plate270H and the additional plate270T. The portion of the long hole72at which the plate thickness is increased by the additional plate270T corresponds to the fitting part72A of the long hole72and a portion of the deformable part72B (a portion thereof adjacent to the fitting part72A).

In Modified Example 4, the plate thickness of the anchor bracket270at the portion of the deformable part72B adjacent to the fitting part72A, i.e., the portion that is deformed in an early stage of the action of the FL mechanism, is larger than the plate thickness of the anchor bracket270at a general portion (the portion of the deformable part72B not corresponding to the additional plate270T). Thus, the load characteristics of the FL mechanism can be set such that the initial load is larger and the load in the latter half of the action is smaller.

Supplementary Description of Above Embodiments

In the above embodiments, the example in which the three-point seatbelt device is applied to the driver's seat has been described, but the present disclosure is not limited to this example. The three-point seatbelt device of the present disclosure may also be applied to a front passenger's seat or a rear seat, or to a vehicle seat that is disposed at the center in the vehicle width direction.

In the above embodiments, the example in which the retractor32(shoulder-side reeler) is provided at the lower end of the B-pillar16has been described, but the present disclosure is not limited to this example. The shoulder-side reeler may instead be provided inside a vehicle seat.

In the above embodiments, the example has been described in which the end portion of the webbing20on the other side in the longitudinal direction (the side of the lap belt20L) is engaged on the anchor member36fixed at the lower end of the B-pillar16. However, the present disclosure is not limited to this example. For example, the end portion of the webbing20on the lap outer side may instead be fixed to the vehicle seat. Moreover, the end portion may be connected to a retractor (lap-side reeler) with a PT mechanism and be reeled up during a crash etc.

In the above embodiments, the example in which the tongue40is mounted so as to be movable in the longitudinal direction of the webbing20(continuous three-point seatbelt device) has been described, but the present disclosure is not limited to this example. The three-point seatbelt device of the present disclosure may instead be a separate three-point seatbelt device in which a lap belt and a shoulder belt are formed by separate webbings.