EP2121378A1

EP2121378A1 - Backrest support mechanism

Info

Publication number: EP2121378A1
Application number: EP07716081A
Authority: EP
Inventors: Lennart Haglund
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2007-03-22
Filing date: 2007-03-22
Publication date: 2009-11-25
Also published as: JP5153794B2; JP2010522111A; CN101641235A; EP2121378A4; CN101641235B; WO2008115103A1

Abstract

The present invention relates to a backrest support mechanism (1) for a motor vehicle seat, comprising a support plate (5) , attached to either of a seat squab (3) and a seat backrest (4) , a first connection (7) between the support plate (5) and either of the squab (3) and the seat backrest (4), a second connection (8) between the support plate (5) and either of the squab (3) and the seat backrest (4) . The support plate (5) is adapted to deform plastically to permit movement of the seat backrest (4) rearwardly relative to the seat squab (3) when subjected to a predetermined force. The present invention aims at providing a space efficient backrest support mechanism not being bulky and complex, which is easy to mount in a seat.

Description

BACKREST SUPPORT MECHANISM

Technical field

The present invention relates to a backrest support mechanism for a motor vehicle seat, comprising a support plate, attached to either of a seat squab and a seat backrest, a first connection between the support plate and either of the squab and the seat backrest, a second connection between the support plate and either of the squab and the seat backrest.

Background of the invention

In a rear impact situation, the occupants in the impacted car are subjected to loads that may lead to neck injuries. The buttocks and the torso of the occupant, which are generally in close contact with the backrest may be given a very rapid acceleration due to the impact. The head of the occupant, which is typically not in contact with any part of the seat initially, experience no acceleration during the first moments. Consequently the buttocks and the torso of a seat occupant will move forwardly, whilst the head due to the inertia remains stationary. This causes the neck of the seat occupant to bend, until the head contacts the headrest, or until the neck itself applies a forward force to the head of the occupant, which may initially tend to rotate the head about a horizontal axis, and flick the head forwardly. Such movement of the neck and head often cause injuries, known as "whiplash" injuries.

Whiplash injuries may be prevented or reduced if the seat is arranged in such a way that the backrest can move and/or tilt under energy absorption causing the buttocks and the torso of the occupant to accelerate more gradually. Such an arrangement is described in GB2316442. The movement of the backrest is provided by a support mechanism mounted between the seat frame and the back of the seat. The support mechanism comprises two pivotal links of which one is connected to a deformable element in a support plate. With respect to previously known solutions, it is desirable to achieve a space efficient backrest support arrangement not being bulky and complex, which is easy to mount in a seat. Furthermore it is desirable to achieve a backrest support arrangement having few parts .

Summary of the invention

An object of the present invention is to provide a seat backrest support mechanism which reduces at least some of the above problems . In one aspect of the present invention, a seat backrest mechanism according to the introduction is further characterised in that at least a part of the support plate is adapted to deform plastically to permit rearward movement of the seat backrest relative the seat squab when subjected to a predetermined force.

Thus a seat backrest support mechanism which may reduce or eliminate the risk for injuries to an occupant involved in a rear impact is provided. A compact seat backrest mechanism that is less complex is achieved. Since the support plate is adapted to deform plastically additional deformation element may not be needed. Thus an arrangement having few parts is provided.

The support plate may have a weakened section where the support plate is deformed when subjected to a predetermined force, in order to adapt the support plate for deformation at a predetermined location. Thus it is possible to control at which location and at which load the support plate is deformed. Such a weakened section may be formed by a notch or aperture in the support plate. Alternatively the weakened section may be defined by a section with thinner material thickness than the rest of the support plate. The support plate may define a force transmitting structure supporting the backrest. That is the backrest may be supported by the deformable support plate itself. Thus a seat backrest mechanism having few parts is achieved.

The first connection may further comprise an engagement element attached to the seat squab and a guiding edge formed in the support plate, wherein relative movement between the seat squab and the support plate is guided along the guiding edge. Thus a controlled movement of the backrest is achieved. The engagement element may be a shaft attached to the squab and received in an aperture formed in the support plate. Alternatively the engagement element may be a pin or a roller. Alternatively the engagement element may be attached to the backrest and the guiding edge may be formed in the seat squab.

The first weakened section may be adapted to deform plastically when the support plate being in a second displacement position. Thus energy is absorbed during a subsequent rearward pivotal action of the support plate. The deformation of said first weakened section may be possible when the engagement element has performed a relative movement along the guiding edge to a second displacement position. Thus a first parallel movement of the backrest due to relative movement of the engagement element along the guiding edge from a initial position to a second position may be possible without deformation of the support plate. Subsequent rearward pivotal movement under energy absorbing deformation of the support plate is then possible. The first weakened section may be formed adjacent to the guiding edge.

The mechanism may further comprise an element to prevent relative movement of the support plate in ordinary use. The element may for instance be a breakable pin attached to the seat squab and received in a recess formed in the support plate. Alternatively a breakable pin may be attached to the support plate and received in a recess formed in the squab. Thus a robust support of the seat backrest in ordinary use is provided. Furthermore undesired relative movement and play between the support plate and the seat squab are avoided.

The mechanism may further comprise a retaining element to retain the engagement element in its initial position relative the guiding edge until a first threshold force is excessed. Thus a robust support of the seat backrest in ordinary use is provided. Furthermore undesired relative movement and play between the support plate and the seat squab are avoided. Such a first threshold force will be excessed when the car is involved in a rear impact situation where there is a risk of injuries to the occupant.

The retaining element may be deformable in order to permit relative movement between the support plate and the seat squab when subjected to a first threshold force. Thus when a first threshold force is excessed the retaining element is gradually deformed during the generally parallel movement of the backrest. The retaining element may be resilient in order to deform elastically .

The retaining element may be releasable. Thus the retaining element can be released during the subsequent rearward pivotal action. That is the retaining element is active during the first generally parallel movement of the backrest.

The support plate may have a second weakened section where the support plate is deformed when subjected to a predetermined force. Thus it is possible to adapt the support plate for deformation at different locations, different predetermined forces and different stages of an impact . The support mechanism may be deformed at the second weakened section to permit a parallel movement of the backrest in a first phase of a rear impact and the support plate may be deformed at the first weakened section to permit a tilting movement of the backrest in a second phase of a rear impact. Thus a controlled movement of the seat backrest during a rear impact is achieved. The second connection may be a link arm having a first and a second pivoting joint. Thus the rearward parallel part of the movement may be possible without deformation of the support plate.

Contact may be established between a part of the support plate and a part of the second pivoting joint after a first parallel movement of the backrest in order to stop further parallel movement of the backrest.

A locking means may be provided in order to prevent the support plate from returning to its initial position from a first deformation position.

Brief description of the drawings

The present invention will now be described in more detail with the reference to the accompanying schematic drawings which show preferred embodiments of the invention and in which:

Fig. 1 shows a side view of selected parts of a vehicle seat in which a backrest support mechanism according to an embodiment of the present invention is mounted.

Fig. 2a shows a side view of the back rest support mechanism in fig. 1 in a first and initial retained condition.

Fig. 2b shows a side view of the mechanism in fig. 1 in a second condition.

Fig. 2c shows a side view of the mechanism in fig. 1 in a third and final condition.

Fig. 3 shows a side view of selected parts of a vehicle seat in which a backrest support mechanism according to another embodiment of the present invention is mounted. Detailed description of preferred embodiments

Fig. 1 shows a backrest support mechanism 1 according to an embodiment of the present invention. The mechanism 1 is mounted in a vehicle seat 2 between a seat squab 3 and a seat backrest 4 to support the seat backrest 4. The backrest support mechanism 1 comprises a support plate 5 attached to the backrest 4, by suitable attachment means 6, and connected to the seat squab 3 by means of a first mechanical connection 7 and a second mechanical connection 8.

In this embodiment the support plate 5 has two weakened sections 9 and 10 where the support plate 5 is deformed plastically at different stages of a rear impact. The support plate 5 is deformed at the first 9 and the second 10 weakened sections respectively due to forces on the seat when the vehicle is involved in a rear impact situation. The weakened sections 9 and 10 are formed in the support plate 5 by a first recess 11 and a second recess 12 respectively. The function of the mechanism including deformation of the support plate in a rear impact situation will be described.

In this embodiment the first mechanical connection 7 is formed by an aperture 13 in the support plate 5 receiving an engagement element 14, in this case a shaft, attached to the seat squab 3. The aperture 13 forms an open guiding edge 15. Alternatively a guiding edge may be formed by a closed aperture. During relative movement between the backrest 4 and the seat squab 3 the engagement element 14 is guided along the guiding edge 15.

The second mechanical connection 8 is in this embodiment formed by a pivotal joint 16. The joint 16 is formed by a recess in the support plate 5 receiving a shaft attached to the squab 3. Thus the shaft defines an axis for pivotal action of the support plate 5.

In order to keep the engagement element 14 in its initial retained position in the guiding aperture 13 in ordinary use, a retaining element 17 is arranged between the engagement element 14 and a pin 18 attached to the support plate 5. The retaining element 17 is in this case a resilient pawl provided with a first recess for receiving the engagement element 14 and a second recess 19 partly enclosing the pin 18, see fig 1.

With reference to fig. 2a, 2b and 2c the function of the backrest support mechanism will be described in the following, in a rear impact situation. Fig. 2a shows parts of a seat 2 in ordinary use. In ordinary use the support plate 5 is kept in a first position, see fig. 2a. The engagement element 14 is retained in the guiding aperture 13 due to forces from the retaining element 17. That is the retaining element 17 is acting to keep the engagement element 14 in its initial position in the aperture 13. The seat 2 and consequently the backrest 4 remain in a first position until the backrest 4 is subjected to a first threshold force. Such a first threshold force is excessed in case the car is involved in a rear impact situation where there is a risk of injuries to the occupant. On the other hand this first threshold force will not be excessed during ordinary use such as adjustment of the seat by a occupant sitting in the seat using the seat length-, height- and angle adjustment, under normal driving conditions, or in a rear impact situation at very low speed. That is a certain crash severity is needed to initiate the rearward movement of the backrest relative the seat squab. Thus a robust connection between the seat and the seat backrest is provided in ordinary use.

In case the vehicle is involved in a rear impact, whilst the seat is occupied by an occupant, the inertia will cause the buttocks of the occupant to apply a substantial generally rearwardly directed force to the lower part of the seat back. As soon as this force exceeds a first threshold force the resilient retaining element 17 will start to deform and/or deflect, which permit the support plate 5 to move towards a second position, see fig. 2b. During this movement the support plate 5 is deformed at the second weakened section 10. Furthermore sliding movement takes places between the pin 18 and the retaining element 17 during the deformation and/or deflection of the retaining element 17. Due to the shape of the guiding aperture 13 tilting of the backrest 4 is not possible in this first phase of the backrest movement. Thus the movement in this first phase is essentially a parallel displacement of the backrest 4 under preservation of the seat backrest angle. The support plate 5 is deformed at the second weakened section 10 until contact between the upper and the lower part of the recess 12 is established, see fig. 2b. Thus after this first generally parallel movement of the seat back 4 relative the squab 3 the support plate 5 has been deformed in such a way that a stop that prevents further parallel movement of the backrest 4 has been formed in the support plate adjacent to the second weakened section 10, see fig. 2b. It should be noted that the position of the engagement element 14 in the guiding aperture 13 is changed during this first essentially parallel movement of the backrest, see fig. 2b. In the enlargement of fig. 2b the retaining element is not shown to clearly illustrate the position of the engagement element 14. The guiding aperture is formed to allow a essentially parallel movement of the seat backrest under preservation of the seat angle in the first phase of the backrest movement. Thus in this first phase of the backrest movement the support plate is moved from a first position, shown in fig. 2a, to a second deformation position, shown in fig. 2b.

The back rest may then, in response to a continuing force applied by the torso of the occupant, pivot around the joint 16 toward a third displacement position, see fig. 2c. As a first part of the pivotal action the shaft performs a relative movement along the guiding edge 15 until the engagement element 14 is stopped by the guiding edge 15 in the guiding aperture 13. That is when contact is established between the engagement element 14 and the part of the guiding edge 15 that forms a stop, see fig. 2c. Subsequent tilting is then possible since the support plate 5 is deformable at the first weakened section 9. The force that is needed to deform the support plate 5 at the first weakened section 9 may correspond to a second threshold force. As the backrest executes subsequent tilting the support plate is deformed at the first weakened section. Thus rearward tilting movement of the seat back is possible due to the pivotal function of the second mechanical connection 8 and since the support plate 5 is deformable. During the deformation of the support plate due to the pivotal action energy is absorbed by the support plate. Thus the inertial energy of the occupant is gradually absorbed, minimising the risk of injury. The support mechanism provides a controlled backward movement of the backrest in a rear impact situation. During the tilting the retaining element 17 is released from the pin 18. During this second phase of the backrest movement a pivotal action around the joint 16 is provided.

It should be noted that a substantially greater amount of energy is absorbed during the subsequent rearward pivotal action of the backrest than during the first essentially rearward parallel movement of the backrest .

In another embodiment the second mechanical connection 8 is formed by a link arm 20 having a first pivoting joint 21 and a second pivoting joint 22 as shown in fig. 3. The support plate 5 has a first weakened section 9. A retaining element 17 that prevents movement of the support plate 5 in ordinary use is provided. In case the vehicle is involved in a rear impact, whilst the seat is occupied by an occupant, the inertia will cause the buttocks of the occupant to apply a substantial generally rearwardly directed force to the lower part of the seat back. If the force acting on the seat excess a first threshold value the retaining element 17 will start to deform and/or deflect and consequently the seat backrest 4 is moved generally rearwardly relative to the seat squab 3. The guiding aperture 13 and the pivotal link arm 20 permit the support plate 5 to perform a parallel movement a certain distance without being deformed. Thus in this first phase of the movement the seat backrest 4 is moved relative the seat squab 3 generally without changing the angle of the backrest 4 and without deformation of the support plate 5. The second mechanical connection 8, which in this case is a pivotal link arm 20 having a first pivoting joint 21 and a second pivotal joint 22, permits a parallel movement of the support plate 5 until contact is established between a part of the support plate 5 and a part of the second joint 22.

In response to a continuing force applied by the torso of the occupant subsequent tilting of the backrest

4 around the joint 22 is then possible in a similar way as described for the previous embodiment. Due to deformation at a weakened section 9 of the support plate

5 energy is absorbed during this pivotal action. The force that is needed to deform the support plate at the first weakened section may correspond to a second threshold force.

It will be appreciated that the described embodiment of the invention can be modified and varied by a person skilled in the art without departing from the inventive concept defined in the claims.

For instance the retaining function in ordinary use could be provided by adapting the pivotal joints with a predetermined resistance to rotation.

Claims

1. A backrest support mechanism (1) for a motor vehicle seat, comprising a support plate (5), attached to either of a seat squab (3) and a seat backrest (4), a first connection (7) between the support plate (5) and either of the squab (3) and the seat backrest (4), a second connection (8) between the support plate (5) and either of the squab (3) and the seat backrest (4) c h a r a c t e r i s e d i n that at least a part of the support plate (5) is adapted to deform plastically to permit movement of the seat backrest (4) rearwardly relative to the seat squab (3) when subjected to a predetermined force.

2. A mechanism according to claim 1, wherein the support plate (5) has a first weakened section (9) where the support plate (5) is deformed when subjected to a predetermined force.

3. A mechanism according to claim 1-2, wherein the support plate (5) defines a force transmitting structure supporting the backrest (4) .

4. A mechanism according to claim 1-3, wherein said first connection (7) comprises an engagement element (14) attached to the seat squab (3) and a guiding edge (15) formed in the support plate (5) , wherein relative movement between the seat squab (3) and the support plate (5) is guided along the guiding edge (15).

5. A mechanism according to claim 1-4, wherein the first weakened section (9) is adapted to deform plastically when the support plate (5) being in a second displacement position.

6. A mechanism according to claim 4-5, wherein deformation of said first weakened section (9) is possible when the engagement element (14) has performed a relative movement along the guiding edge (15) to a second displacement position.

7. A mechanism according to claim A-6, wherein the first weakened section (9) is formed adjacent to the guiding edge (15) .

8. A mechanism according to claim 1-7, wherein the mechanism further comprises an element to prevent relative movement of the support plate in ordinary use.

9. A mechanism according to claim 4-8, wherein the mechanism further comprises a retaining element (17) to retain the engagement element (14) in its initial position relative the guiding edge (15) until a predetermined force is excessed.

10. A mechanism according to claim 9, wherein the retaining element (17) is deformable.

11. A mechanism according to claim 9-10, wherein the retaining element (17) is releasable.

12. A mechanism according to claim 2-11, wherein the support plate (5) has a second weakening section (10) where the support plate (5) is deformed when subjected to a predetermined force.

13. A mechanism according to claim 12, wherein the support plate (5) is deformed adjacent to the second weakened section (10) to permit a parallel movement of the backrest (4) in a first phase of a rear impact and the support plate (5) is deformed adjacent to the first weakened section (9) to permit a tilting movement of the backrest (4) in a second phase of a rear impact.

14. A mechanism according to claim 1-11, wherein said second connection (8) is a link arm (20) having a first (21) and a second (22) pivoting joint.

15. A mechanism according to claim 14 where contact is established between a part of the support plate (5) and a part of the second pivoting joint (22) after a first parallel movement of the backrest (4) .

16. Seat support mechanism according to claim 14-15, wherein a locking means is provided.