JPH10287164A - Upper body protection method for vehicular impact absorbing seat and vehicular impact absorbing seat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To much more strengthen the protection of a seated man at the time of rear end collision by approaching a seat attitude to the upper body attitude of the seated man. SOLUTION: Let the revolving arm 36 of a reclining device be inclined afterward around the mounting bolt 3O of a seat back 12 by the actuation of a fuse mechanism 38 accompanied by the input of impact at the time of rear end collision. And the upper half part 12U of the seat back 12 and a head rest 46 located above the upper half part 12U, which are defined to be separated in advance, are integrally inclined forward with respect to the lower half part 12L of the seat back while being accompanied by the afterward inclination of the seat back.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of protecting an upper body of a vehicle shock absorbing sheet which enables the upper body of a seated person including a head to be protected from the impact by absorbing impact energy at the time of a rear collision, and a vehicle. And a shock absorbing sheet.

[0002]

2. Description of the Related Art In a vehicle seat for an automobile or the like, protection of a occupant in a collision from the rear of the automobile or the like, that is, at the time of a so-called rear collision, has been an issue of recent attention. And, for example, a weak part, a so-called weak part, is provided as a fuse mechanism in a part of a seat back frame or a part of a reclining device or the like, and when excessive impact energy such as a rear collision is input to the seat. The so-called shock absorbing sheet, which forcibly tilts the seat back backward by buckling deformation or the like in the fuse mechanism (strength weak portion) and reduces the impact applied to the occupant by absorbing the impact energy due to the backward tilt, is used in automobiles. Etc. are provided as vehicle seats.

[0003] As such an impact absorbing sheet, for example, a configuration disclosed in Japanese Patent Application Laid-Open No. 07-132767 is known. In this known configuration, a meandering reinforcing rib portion is provided as a fuse mechanism on a part of the bracket of the reclining device, and the seatback with buckling deformation at the reinforcing rib portion is tilted backward to prevent a rearward collision. It absorbs impact energy.

[0004]

However, the sitting posture of the occupant does not always correspond to the seat posture. That is, the sitting posture of the occupant may be a round posture (also referred to as a stoop) or a posture in which the head is separated from the headrest when the vehicle is stopped or the like. When a rear-end collision occurs in a posture, especially a posture in which the head of the seated person is far away from the headrest, a sudden backward tilt of the head relative to the upper body in a large space between the headrest and a so-called whiplash movement occurs. It will be easier.

[0005] However, the above-mentioned known Japanese Patent Application Laid-Open No. 07-132767.
In the configuration of the publication, the headrest tilts backward integrally with the seatback while leaving the space between the head and the head intact. Chest by back tilt of back frame,
There may be insufficient protection of the head and neck compared to adequate protection of the waist.

Here, a structure for suppressing the whip movement of the head at the time of a rear collision by filling the space between the head and the headrest is disclosed in, for example, Japanese Patent Application Laid-Open No. 07-2910.
No. 05 discloses this. In this configuration, when the upper body of the seated occupant moves backward excessively under the impact of a rear collision, the space between the headrest and the head is filled by the forward inclination of the headrest with respect to the seatback frame, A sharp backward tilt of the head can be suppressed.

[0007] However, Japanese Patent Application Laid-Open No.
In the known configuration disclosed in Japanese Patent Application Laid-Open Publication No. H11-139, the headrest only tilts forward with respect to the seatback frame, and thus the seat posture does not always match the sitting posture. The head is forcibly supported at the forward position by the headrest that tilts forward while the upper body sinks greatly into the seatback, so damage due to impact energy that cannot be absorbed by the headrest is reduced. There is a possibility that it may be left in the section.

In particular, if the upper body of the occupant sinks significantly into the seat back under the impact of a rear collision, the upper body naturally assumes a round-back posture. It will support the upper body in a seat posture different from the posture,
The head and neck of the seated person are more or less easily damaged.

[0009] In addition, a weak portion of strength such as the above-mentioned reinforcing rib has a characteristic that once it starts to deform under the occurrence of an impact, its deformation resistance becomes small.
That is, when an impact at the time of a rear collision acts, the buckling deformation of the weak portion of the seat back frame is about to be completed immediately from the start thereof, so that the rearward inclination of the seat back frame tends to be high.

Therefore, in known reinforcing ribs and the like,
There is a possibility that the ability to absorb impact energy during the backward tilting process of the seat back may be reduced, and the occupant may be unexpectedly damaged by residual energy that cannot be absorbed.

According to the present invention, an upper body protection method for a vehicle shock absorbing sheet and a vehicle shock absorbing sheet are provided, in which a seat posture is made closer to a body posture of a seated person to enhance protection of the seated person in a rear collision. It is intended to be provided.

[0012]

In order to achieve this object, according to the method for protecting the upper body of a vehicle shock absorbing sheet of the present invention, the fuse mechanism is operated by the input of a shock at the time of a rear collision. The entire seat back is tilted backward about a predetermined fulcrum with respect to the pivot arm of the reclining device. The upper half of the seat back and the headrest at the upper end thereof, which are separated and defined in advance, follow the backward tilt of the seat back and are integrally tilted forward with respect to the lower half of the seat back, so that the seat is seated. Protects the upper body of the elderly.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIGS. 1 and 2, in a vehicle impact absorbing sheet 10 according to the present invention, a seat back frame 14 forming a skeleton of a seat back 12 is previously provided on an upper frame 14U and a lower frame 14L. Separated and formed,
As a result, the upper half 12U of the seat back and the lower half 12L
Are defined separately in the corresponding ranges.

The lower frame 14L is formed integrally with a pair of left and right side brackets 16 at its side end. Then, the upper frame 14U integrally having the bell crank type bracket 18 at the lower side end rotates with respect to the lower frame 14L with the fulcrum of the bell crank type bracket being attached to the upper part of the side bracket 16. It is connected as possible.

As shown in FIG. 2, the bell crank type bracket 18 is formed integrally with a fixing nut 20 on the inner surface of a portion serving as a fulcrum, and is supported by a support member 22 such as a bush or a washer. The connection nut 24 is connected to and pivotally attached to the side bracket 16 by screwing the connection bolt 24 to the fixing nut. In other words, the upper frame 14U is connected to the side brackets 16,
As a result, it is rotatable in the front-rear direction with respect to the lower frame 14L.

The side bracket 16 is formed integrally with a bracket 26 serving also as a spacer on its inner surface.
The pivotal connection of 18 ensures the rotation of the upper frame 14U without being hindered by the peripheral end 16a of the side bracket.

As shown in FIGS. 1 and 2, for example, a bridge elastic support member 28 made of an S spring or the like is bridged and stretched between the side ends of the lower frame 14L, and the upper frame 14U, A seat pad (not shown) made of a urethane foam material or the like is continuously arranged on the front surface of the lower frame, and the entire body is covered with a trim cover (not shown) made of a skin or the like, so that the upper body of the seated person can be obtained.
In particular, a seat back 12 is formed which can elastically support the chest or waist from behind.

Each end of the S spring or the like (bridged elastic support member) 28 is locked and held on a side end of the lower frame 14L by a locking metal (not shown) called a retainer, for example. .

As shown in FIGS. 1 and 2, in the shock absorbing sheet 10, the side bracket 16
Under the joint bolt 30 screwed to the fixing nut 29 on the inner surface of the side bracket and the connecting bolt 32 screwed down and attached to the fixing bolt 29 at two points (two-point fixing), The rotation arm 36 of the reclining device 34 is integrally connected. In the present invention, the connecting bolt 32 also functions as the fuse mechanism 38 for urging the seat back frame 14, that is, the seat back 12 to tilt backward with respect to the rotating arm 36 by the action of the load equal to or greater than the specified load. By operation, the seat back frame can be tilted rearward with the mounting bolt 30 as a fulcrum.

A detailed description of the fuse mechanism 38 using the connecting bolt 32 will be described later.

As the reclining device 34, a known device can be used, and since the reclining device itself is not the purpose of the present invention, it will not be described in detail here. As this type of reclining device 34, for example,
One disclosed in JP-A-62-026008 can be exemplified.

Here, as shown in FIGS. 1 and 2, in this shock absorbing sheet 10, the upper frame 14U
For example, a pair of left and right stay brackets 40 as a cylindrical body are integrally formed at the upper end, and the headrest 46 is inserted into the stay brackets via the headrest holder 42 and locked, so that the headrest 46 is seat backed. The frame 14, that is, the upper end of the seat back 12 can be mounted. That is, the headrest 46 is rotatable integrally with the upper frame 14U around the fulcrum (connection bolt) 24 of the bell crank type bracket.

In the present invention, the upper end of the link arm 48 is, for example, connected to the movable end 18a of the bell crank type bracket 18 extending forward (to the left in FIG. 1).
The pivot arm is pivotally connected via a combination of a pivot pin 50 and a corresponding latch 52, and the lower end of the link arm is pivotally connected to a connection pin 54 of the rotating arm 36.

The connection pin 54 is formed, for example, as a stepped pin, and is located at a position forward (leftward in FIG. 1) of an imaginary line 56 connecting the mounting bolt 30 and the connection bolt 32 and between these bolts. On a possible arc, it protrudes inward from the rotating arm 36 and is fixed. Then, for example, a connection pin 54 extends inward of the side bracket through an arc-shaped long hole 58 centered on the mounting bolt 30 pre-drilled in the side bracket 16, and The lower end of the link arm 48 is pivotally connected with a fitting 60.

That is, in the shock absorbing sheet 10 of the present invention, the movable end 18a of the bell crank type bracket is connected to the rotating arm 36.

As shown in FIG. 1, this shock absorbing sheet 10
In the upper frame of the seat back frame
The lower frame 14L and the lower frame 14L are arranged and set on a straight line in the vertical direction under the support of the upper frame by the link arm 48. In this configuration, since the lower end of the link arm 48 is pivotally connected to the connecting pin 54 of the rotating arm, the operation of the reclining device 34 causes the upper frame 14L to be lower than the lower frame 14L.
The entire seat back frame 14, that is, the seat back 12, is swung without the rotation of U.

In the shock absorbing sheet 10 having such a structure, when a rear collision of the automobile occurs, the load from the upper body of the occupant who has moved backward due to the impact is firstly changed to the initial state shown in FIG. Received by the seat back frame 14. When the load exceeds the specified load of the fuse mechanism 38,
By the operation of this fuse mechanism, the seat back frame
14 is tilted rearward with respect to the rotating arm 36 with the mounting bolt 30 as a fulcrum.

In the present invention, since the movable end 18a of the bell crank type bracket is connected to the rotating arm 36 via the link arm 48, the mounting bolt
When the entire back tilt of the seat back frame 14 with the fulcrum 30 as a fulcrum occurs, the upper frame 14U moves around the fulcrum 24 and the lower headrest 46 around the fulcrum 24 as shown in FIG. It is inclined forward with respect to the frame 14L. That is, following the backward inclination of the seat back 12 with respect to the rotating arm 36, the upper half 12U of the seat back and the headrest 46 are integrally inclined forward with respect to the lower half 12U, thereby including the headrest. The side surface shape of the seat back 12 has a substantially inverted shape in the figure.

Since the seat posture of the seat back 12 bent in a substantially inverted letter shape in the drawing approaches such an extent that the seat back posture or the sitting posture in which the head is separated from the headrest is almost the same, The upper body of the occupant in a round-back posture including the head can be entirely supported by the seating surfaces of the upper half 12U and the lower half 12L of the seat back and the headrest 46.

That is, according to the method for protecting the upper body of the vehicle shock absorbing sheet of the present invention, the upper half 12U and the headrest 46 are integrally formed with the lower half 12L following the rearward tilt due to the impact at the time of a rear collision. By the forward leaning, the side shape of the seat back including the headrest, that is, the seat posture, approaches the body posture of the occupant deeply sunk in the seat back. Therefore, the upper body of the occupant can be entirely supported by the seat back 12 and the headrest 46, and the upper body of the occupant is protected over the entire area without the support of the upper body of the occupant being concentrated locally.

Accordingly, the protection effect of the seat back 12 and the headrest 46 is improved, so that the occupant's damage is further reduced.

Since the headrest 46 leans forward integrally with the upper half 12U of the seat back, the space between the headrest and the head is naturally filled by the forward lean of the headrest. Therefore, whiplash movement caused by a sharp backward inclination of the head with respect to the upper body can be reliably suppressed, and damage to the head and neck can be reliably reduced.

Further, under the operation of the fuse mechanism 38, the seat back 12 is tilted rearward with respect to the rotating arm 34.
The impact energy at the time of a rear collision is reliably absorbed. Therefore, the entire protection of the upper body of the occupant including the head and neck can be easily secured without impairing the protection effect on the chest and waist.

The impact absorbing sheet for a vehicle according to the present invention.
According to 10, the above upper body protection method can be properly performed, not only filling the space between the head and the headrest 46,
The change in the shape of the seat back frame 14 corresponding to the posture of the seated body improves the overall protection ability of the body of the seated person, thereby further reducing the damage to the seated person.

Here, in the embodiment of the present invention, the connecting bolt 32 is arranged below the mounting bolt 30, but on the contrary, the connecting bolt may be arranged above the mounting bolt. . However, mounting bolts
Considering that 30 serves as a fulcrum when the seat back frame 14 is tilted backward with respect to the pivot arm 36, the pivot bolt can be easily miniaturized by disposing the connecting bolt 32 below the mounting bolt. Peel off.

The mounting bolt 30 and the connecting bolt 32
If the connecting pin 54 is provided on an arc that can be positioned between
Since the space between the bolts can be used, the size of the rotating arm 36 can be reduced from this point as well.

The connecting pin 54 is protruded from the rotating arm 36,
Although it is embodied as a fixed configuration, the present invention is not limited to this, and a configuration in which the connecting pin is rotatably inserted into the rotating arm may be adopted.

Here, in the embodiment of the present invention, the fuse mechanism 38 is formed as an impact absorbing element whose generated resistance decreases as the rearward tilt angle of the seat back frame 14 with respect to the rotating arm 36 increases. . And
As shown in FIGS. 1 and 2, in this embodiment,
On an arc centered on the mounting bolt 30, the connecting bolt 32
Provided in the through hole 62 of the side bracket of the
Fuse mechanism (shock absorbing element) by combining tapered shock absorbing groove 64, which is continuously widened from the small diameter end smaller than the diameter of the connection bolt to the large diameter end which is almost the same diameter as the connection bolt, with the connection bolt 32 38.

After the connection bolt 32 is inserted through the insertion hole 62, the nut 66 is disposed inside the side bracket 16.
Is screwed on.

The insertion hole 62 and the tapered shock absorbing groove 64 are
For example, a curling hole is formed on the inner surface side of the side bracket 16 as a so-called curling hole, and at the small-diameter end side narrower than the diameter of the connection bolt 32, the tapered shock absorbing groove is continuous with the insertion hole. Have been.

In the shock absorbing sheet 10 having such a configuration, when the seat back frame 14 is inclined backward with the mounting bolt 30 as a fulcrum at the time of an impact at the time of a rear collision, the connecting bolt 32 is inserted into the insertion hole 62. Moves to the small-diameter end side of the tapered shock absorbing groove 64 with the expansion deformation. Since the tapered shock absorbing groove 64 is formed in a tapered shape having a groove width substantially the same as the diameter of the connecting bolt 32 at the large diameter end, the connecting bolt moved to the small diameter end of the tapered shock absorbing groove is When the seat back frame 14 is tilted backward with the mounting bolt 30 as a fulcrum due to the impact, the tapered shock absorbing groove is moved to the large diameter end while widening and deforming (see FIG. 3).

As described above, when the impact at the time of a rear collision is input to the seat back frame 14, the connecting bolt is tilted backward with the mounting bolt 30 as a fulcrum.
32 moves while enlarging and deforming the insertion hole 62 and enlarging and deforming the tapered shock absorbing groove 64. Then, since the resistance force at the time of movement of the connecting bolt 32 with respect to the insertion hole 62 and the tapered shock absorbing groove 64 is applied to the seat back frame 14 as a regulating force against the backward inclination, the shock energy at the time of the rear collision is reduced. ,
It is absorbed gradually and steplessly under the backward inclination of the seat back frame.

That is, according to the shock absorbing sheet 10 of this embodiment, the seat back frame is provided by applying the resistance force by the fuse mechanism 38 serving as the shock absorbing element.
Since the tire 14 is tilted backward while being restricted by the resistance, the seat back frame is prevented from being sharply tilted backward.
Then, the seat back frame 14 by the fuse mechanism 38
The shock energy at the time of a rear collision is gradually and steplessly absorbed by the resistance force when the vehicle leans backward. With the improvement of the protection effect accompanying this, reduction of the damage of the occupant,
I can get it more reliably.

In the embodiment of the present invention,
Although the combination of the connecting bolt 32 and the tapered shock absorbing groove 64 is embodied as a shock absorbing element, it is sufficient that the generated resistance decreases as the rearward tilt angle of the seat back frame 14 increases. The shock absorbing element 38 is not limited to the combination of the connecting bolt and the tapered shock absorbing groove, and the shock absorbing element may be formed from other combinations.

As can be seen from FIG. 3, at the large-diameter end of the tapered shock absorbing groove 64, the connecting bolt 32 is locked and held on the peripheral edge thereof. The backward tilt is prevented. Therefore, an increase in damage to the occupant due to excessive backward leaning of the seat back frame 14, jumping out of the seat, and the like are reliably prevented, and in this respect also, occupant safety is improved.

Further, the forward lean of the upper frame 14U and the headrest 46 with respect to the lower frame 14L is simultaneously regulated by the regulation of the amount of backward lean of the seat back frame 14, which results from excessive forward lean of the upper frame and the headrest. Damage to the occupant can be reliably prevented.

In the embodiment of the invention, a shock absorbing sheet to be mounted on an automobile is exemplified. However, the present invention is not limited to this, although it is suitable for an automobile. The present invention may be applied to a sheet.

The embodiments of the present invention described above are intended to explain the present invention, and do not limit the present invention in any way. Modifications, alterations, etc., within the technical scope of the present invention may be made. It goes without saying that all are included in the present invention.

[0050]

As described above, according to the method for protecting the upper body of the vehicle shock absorbing sheet according to the present invention, the upper half and the headrest with respect to the lower half follow the rearward tilt due to the impact at the time of a rear collision. The forward leaning of the seat back allows the side shape of the seat back including the headrest, that is, the seat posture, to approach the body posture of the occupant deeply sunk in the seat back, so that the posture of the occupant's upper body is Even if it deviates from the seat posture, the upper body of the seated person can be supported on the entire surface of the seat back.

Therefore, the protection effect of the seat back and the headrest is improved, so that the damage to the occupant is further reduced.

Further, since the headrest is inclined forward with the upper half of the seat back, the space between the headrest and the head is naturally filled by the inclination of the headrest. Therefore, whiplash movement caused by a sharp backward inclination of the head with respect to the upper body can be reliably suppressed, and damage to the head and neck can be reliably reduced.

Further, under the operation of the fuse mechanism, the seat back is tilted rearward with respect to the rotary arm, so that the impact energy at the time of a rear collision is reliably absorbed. Therefore, the entire protection of the upper body of the occupant including the head and neck can be easily secured without impairing the protection effect on the chest and waist.

According to the impact absorbing sheet for a vehicle of the present invention, the above-mentioned method of protecting the upper body can be appropriately performed, and not only can the space between the head and the headrest be filled, but also the posture of the seated upper body can be adjusted. The corresponding change in the shape of the seat back frame improves the overall protection ability of the occupant's upper body, thereby further reducing the occupant's damage.

Further, if the impact absorbing element is a fuse mechanism, the impact energy at the time of a rear collision is gradually absorbed over the rearward tilt range of the seat back frame, so that the ability to absorb the impact energy is enhanced and the occupant is protected. The improvement of the effect further reduces the damage of the occupant.

Since the shock absorbing element reduces the generated resistance as the rearward tilt angle of the seat back frame increases, it is possible to appropriately secure the resistance corresponding to the shock energy that is gradually absorbed and becomes smaller. . Therefore,
Effective absorption of impact energy is easily possible.

If the connecting bolt is provided below the mounting bolt and the connecting pin is projected from the rotating arm on an arc that can be positioned between the bolts, the size of the rotating arm can be easily reduced. Get off.

[Brief description of the drawings]

FIG. 1 is a schematic side view of an impact absorbing sheet for a vehicle according to the present invention in an initial state, partially broken.

FIG. 2 is a schematic exploded perspective view showing a partially broken portion of the vehicle impact absorbing sheet.

FIG. 3 is an operation diagram of a vehicle impact absorbing sheet when an impact due to a rear collision occurs.

[Explanation of symbols]

 10 Shock absorbing seat for vehicle 12 Seat back 12U, 12L Upper and lower half of seat back 14 Seat back frame 14U Upper frame 14L Lower frame 16 Side bracket 18 Bell crank type bracket 30 Mounting bolt 32 Connecting bolt 36 For reclining device Rotating arm 38 Fuse mechanism (shock absorbing element) 46 Headrest 48 Link arm 62 Insertion hole 64 Tapered shock absorbing groove

Claims (5)

[Claims] 1. A seat back connected to a rotation arm of a reclining device is tilted rearward with respect to the rotation arm by the operation of a predetermined fuse mechanism. In a vehicle shock absorbing sheet capable of protecting against impact in the event of a collision, the seat back is separated into an upper half portion and a lower half portion in advance, and the operation of the fuse mechanism in response to the input of a rear impact impact is performed. Thereby, the entire seat back is tilted rearward with respect to the rotation arm around a predetermined fulcrum, and following the rearward tilt, the upper half of the seat back and the headrest at the upper end thereof are moved to the seat back. An upper body protection method for a vehicle shock absorbing sheet, wherein the upper body is inclined forward with respect to the lower half. 2. A fuse mechanism, wherein a predetermined shock absorbing element whose generated resistance decreases with an increase in the rearward tilt angle of the seat back with respect to the rotating arm is used as a fuse mechanism.
2. The method for protecting an upper body of a vehicle impact absorbing sheet according to claim 1, wherein the impact energy at the time of a rear collision is absorbed over a rearward tilt range of the seat back. 3. The seat back frame connected to the pivot arm of the reclining device is tilted rearward with respect to the pivot arm under the operation of a predetermined fuse mechanism provided at a side end of the seat back frame. An impact absorbing seat for a vehicle which can protect a seated person from an impact at the time of a rear collision by absorbing an impact due to inclination, wherein the seat back frame includes an upper frame having a headrest connected to an upper end thereof; A lower frame integrally having a bracket at a side end; and a mounting bolt serving as a fulcrum when the side bracket of the lower frame is tilted backward with respect to the rotating arm; The upper arm is integrally connected to the rotating arm under two-point fixing with a connecting bolt also serving as the fuse mechanism; -The frame is pivotally attached to the side bracket of the lower frame via the fulcrum of the bell crank type bracket provided at the lower end thereof, and the link arm at the upper end pivotally attached to the movable end of the bell crank type bracket. When the lower end is pivotally attached to the pivot arm at a position in front of the mounting bolt, and the fuse mechanism is actuated due to the input of an excessive impact at the time of a rear collision, the seat back frame is tilted backward about the mounting bolt as a fulcrum. And an upper frame and a headrest which can be integrally tilted forward with respect to the lower frame. 4. A connecting bolt continuously inserted through the rotating arm and the side bracket; and a connection provided on an arc of a circle centered on the mounting bolt and being continuously provided in an insertion hole of the side bracket of the connecting bolt. A fuse mechanism is formed as a shock-absorbing element having a combination of a tapered shock-absorbing groove continuously widened from a small-diameter end smaller than the diameter of the bolt to a large-diameter end having at most the same diameter as the connecting bolt. Due to the input of an excessive impact at the time of collision, the seat back frame is tilted backward with the mounting bolt as a fulcrum, so that the connecting bolt is moved from the insertion hole to the tapered impact absorbing groove under the expansion deformation of the peripheral edge. By moving the connecting bolt to the small-diameter end and moving the connecting bolt with widening deformation of the periphery from the small-diameter end to the large-diameter end, it is possible to continuously absorb the impact energy at the time of a rear collision. In both cases, the locking and holding of the connecting bolt at the large diameter end of the tapered shock absorbing groove makes it possible to regulate the rearward tilting of the seat back frame afterward and the forward tilting of the upper frame and the headrest with respect to the lower frame. 3. The shock absorbing sheet for vehicles according to 3. 5. A connecting pin serving as a stepped pin is provided below the mounting bolt, and a connecting pin serving as a stepped pin projects from an inner side of the rotating arm on an arc that can be positioned between the connecting bolts. 5. The impact absorbing sheet for a vehicle according to claim 3, wherein a lower end of a link arm is pivotally attached to an extension end of a connection pin extending through an arc-shaped long hole formed in the bracket.