Vehicle seat and head part acceleration control method by headrest of vehicle seat

Abstract

To provide a vehicle seat having a structure capable of reducing weight and reducing an impact to a neck of an occupant at the time of vehicle collision.SOLUTION: A vehicle seat to be installed in a vehicle includes a headrest formed of a resin structure and a backrest part attached with the headrest. The resin structure has a characteristic representing a stress-strain curve SSD including a first region R1 at initial time of compression and a second region R2. In the first region R1, rising of compression stress with respect to compression distortion is relatively large. In the second region R2, a rate of change of a compressive strain with respect to a change in a load in a predetermined compression load region exceeding a compression load in the first region R1 relatively greatly changes.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a vehicle seat and a method for controlling head acceleration using a headrest thereof. [Background technology]

[0002] In order to improve the fuel efficiency of various vehicles, component development has been carried out to further reduce the weight of vehicle bodies, and various studies have been conducted to reduce the weight of vehicle seats, which account for a large proportion of the vehicle's weight. When reducing the weight of vehicle seats, it is not enough to simply aim for weight reduction; various characteristics must also be taken into consideration, such as reduced safety due to reduced strength and increased vibration due to reduced elastic modulus of the components. Of these, the safety of the occupants must be given the utmost consideration. From this perspective, various technologies that take occupant safety into consideration have been proposed (see, for example, Patent Documents 1 to 3).

[0003] Furthermore, in light of the problem that when a vehicle accident occurs, if the impact on the neck of the occupant is large, it can leave after-effects such as whiplash symptoms, it can be said that one of the important issues is how to efficiently mitigate the impact when an accident occurs and reduce the magnitude of the impact on the neck of the occupant. One known solution to this problem is a so-called active headrest, which instantly moves the headrest forward and upward in the event of a rear-end collision, preventing the occupant's head from tilting backward excessively and reducing the strain on the neck (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6266320 [Patent Document 2] Patent No. 3507065 [Patent Document 3] Patent No. 6439724 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-342379 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the active headrest disclosed in Patent Document 4 has the problem of increasing the weight of the vehicle seat, as it requires an additional mechanism to forcibly move the headrest forward. Furthermore, there have been no vehicle seats in the past that are lightweight and have a structure that cushions the impact on the neck of the occupant.

[0006] Therefore, an object of the present invention is to provide a vehicle seat that can be made lighter and has a structure that can reduce the impact on the neck of an occupant in the event of a vehicle collision, and a method for controlling head acceleration using the headrest. [Means for solving the problem]

[0007] To solve this problem, the inventors of the present invention have conducted extensive research into the mechanism by which whiplash occurs, while referring to neck injury values (known as NIC values (Neck Injury Criteria)) in rear-end collisions. It is generally believed that in a rear-end collision, the speed of an occupant's chest is greater than the speed of their head (chest speed > head speed), and whiplash symptoms are caused by a force acting on the neck in accordance with this speed difference. If this is the case, the inventors have come to the realization that if the difference between the speeds of the chest and head during a rear-end collision can be structurally reduced, it may be possible to achieve both weight reduction and improved safety.

[0008] One aspect of the present invention is based on the findings obtained through the above-mentioned investigations, and is a vehicle seat to be installed in a vehicle, comprising: A headrest made of a resin structure; a backrest portion to which the headrest is attached; and Equipped with The resin structure is a vehicle seat having a characteristic that exhibits a stress-strain curve that includes a first region at the beginning of compression where the rise in compressive stress relative to compressive strain is relatively large, and a second region where the rate of change in compressive strain relative to a change in load changes relatively greatly in a predetermined compressive load region that exceeds the compressive load in the first region.

[0009] In a vehicle seat having such a structure, the headrest, which is made of a resin structure having the above-mentioned specific characteristics when compressed, absorbs the impact acting on the occupant's head during a rear-end collision. The characteristics of the headrest and backrest and the actions they achieve can reduce the speed difference between the chest and head, thereby reducing the load acting on the neck in accordance with this speed difference.

[0010] Furthermore, in the vehicle seat described above, it is possible to achieve weight reduction by relying on the structure, without employing a mechanism such as an active headrest, which tends to be heavy.

[0011] In the vehicle seat as described above, the resin structure may have a characteristic of exhibiting a stress-strain curve that further includes a third region in which the compressive stress relative to the compressive strain changes relatively greatly in a predetermined compressive load region that exceeds the compressive load in the second region.

[0012] In the vehicle seat described above, the resin structure may have a characteristic that the slope is in a range of 100 kPA or less in a range of nominal strain of 0.2 to 0.5 when compressed.

[0013] In the vehicle seat described above, the resin structure may be a structure made of a metamaterial.

[0014] In the vehicle seat as described above, the resin structure may be configured by joining a plurality of flexible components that deform to different degrees depending on the magnitude of the compressive load.

[0015] In the vehicle seat as described above, the component member may be a rod-shaped member.

[0016] In the vehicle seat as described above, the resin structure may have a polyhedral structure formed by a plurality of constituent members.

[0017] In the vehicle seat as described above, the resin structure may include a first component arranged at an end in the compression direction in which a load acts, a second component joined to the first component so as to be openable and closable in a direction that increases or decreases the opening angle with respect to the compression direction, and a third component arranged in plurality around the periphery of a polyhedron structure to form a polygon joined to the second component, and capable of deforming in a direction that crushes the polygon.

[0018] In the vehicle seat as described above, the magnitude of the load that causes deformation in the second component member and the magnitude of the load that causes deformation in the third component member may be set to different ranges.

[0019] In the vehicle seat as described above, the backrest portion may have a seat frame made of at least one of CFRP, UD material, and composite laminated resin material.

[0020] In the vehicle seat as described above, the backrest may include an upholstery made of a mesh material, and at least the center of the backrest may not be provided with urethane foam.

[0021] In the vehicle seat described above, the mesh material upholstery may be a three-dimensional knitted fabric.

[0022] In the vehicle seat as described above, the backrest portion may be substantially free of a foam shock-absorbing material.

[0023] Another aspect of the present invention is a method for controlling head acceleration of an occupant when an impact is absorbed by a headrest of a vehicle seat, the method comprising: The structure that constitutes the headrest is made of a resin structure, This is a method for controlling head acceleration using a headrest for a vehicle seat, in which the resin structure has characteristics that exhibit a stress-strain curve that includes a first region at the beginning of compression where the rise in compressive stress relative to compressive strain is relatively large, and a second region where the rate of change in compressive strain relative to a change in load changes relatively greatly in a predetermined compressive load region that exceeds the compressive load in the first region. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide a vehicle seat that can be made lighter and has a structure that can reduce the impact on the neck of an occupant in the event of a vehicle collision, and a method for controlling head acceleration using the headrest. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram showing the concept of reducing the impact value on the neck of an occupant during a vehicle collision. [Figure 2] This is a diagram explaining the concept of reducing neck impact value by dividing a vehicle collision into four phases. [Figure 3] FIG. 1 is a diagram explaining the movement of the occupant's head and neck during a vehicle collision, divided into four phases (A) to (D). [Figure 4] These images explain the movement of the occupant's head and neck during a vehicle collision, divided into four phases (A) to (D). [Figure 5] (A) is a graph showing the movement of the occupant's head and neck in phases 2 to 4 during a vehicle collision, and (B) is a graph showing the change in compressive strain-compressive stress, indicating the compressive properties of a resin structure. [Figure 6] 3A to 3C are diagrams showing how the resin structure is deformed in this order. [Figure 7] 1 is an image showing an example of a resin structure. [Figure 8] 1 is a graph showing stress-strain characteristics of a resin structure. [Figure 9]1A is a perspective view showing an example of the configuration of a frame of a vehicle seat, and FIG. 1B is a perspective view of a vehicle seat provided with a mesh upholstery. [Figure 10] 2 is a top view showing the configuration of a joint between a backrest portion and a seat frame of a vehicle seat. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a vehicle seat according to the present invention will now be described in detail with reference to the drawings.

[0027] [Vehicle seats] The vehicle seat 1 is a seat for an occupant installed in a vehicle (not shown) and includes a headrest 10, a seat portion 20, and a backrest portion 30 (see FIG. 9). The vehicle seat 1 is designed to structurally reduce the neck injury criterion (NIC value), also known as the neck impact value, of an occupant P (shown as a model of the occupant P in FIG. 4) in a rear-end collision (rear-end collision) of the vehicle (see FIG. 1). Specifically, based on the notion that, in a rear-end collision, the velocity of the occupant P's chest Pb is generally greater than the velocity of the occupant P's head Ph (chest Pb velocity > head Ph velocity), and a force corresponding to this velocity difference acts as a load on the neck Pn, causing whiplash symptoms, the vehicle seat 1 is designed to structurally reduce the difference between the velocity and acceleration of the occupant Pb and the head Ph in a rear-end collision. The NIC value can be calculated using the following formula:

number

[0028] This concept can be explained in more detail below by dividing the movements of the head Ph and neck Pn of the occupant P during a vehicle collision into four phases (see FIGS. 2 to 4). Note that the four phases referred to in this specification refer to events that occur sequentially in time series or stages at which they occur: (1) "pre-crash," (2) "contact" when the head Ph comes into contact with the headrest 10, (3) "contact-sinking" when the head Ph comes into contact with the headrest 10 and then sinks into it, and (4) "post-rebound" when the head Ph, having sunk into the headrest 10, is rebounded and bounces forward.

[0029] [Concepts for reducing the impact on the neck of occupants during vehicle collisions] In the "contact" phase, by decreasing chest acceleration and increasing neck acceleration as described above, it is possible to reduce the difference in acceleration (or velocity) between the chest Pb and neck Pn during a rear-end collision (see Figure 2). Also, in the "contact-sinking" phase, the displacement state (front-to-back shift) of the chest Pb and head Ph is suppressed, and the rebound of the head Ph in the subsequent "post-rebound" phase is suppressed as much as possible. In the "post-rebound" phase, by lowering chest acceleration and also lowering neck acceleration, the displacement state (front-to-back shift) of the chest Pb and head Ph is suppressed, while the force acting on the chest Pb and head Ph is reduced. Based on this concept, in this embodiment, as a configuration for structurally reducing the difference between the velocity and acceleration of the chest Pb and the velocity and acceleration of the head Ph during a rear-end collision, first, with regard to neck acceleration, a headrest 10 is adopted that is made of a resin structure 12 that has the characteristic of having a large rate of change in compressive strain in response to changes in the load when compressed in a predetermined compression load range, and with regard to chest acceleration, a backrest portion 30 with a so-called hammock structure that includes upholstery, for example, mesh upholstery (upholstery made of mesh material) 34 is adopted (see Figure 2, etc.).

[0030] [Resin structure] The resin structure (also referred to as foam material) 12 is made of a material having a characteristic that exhibits a stress-strain curve SSD that forms a special SS curve, so to speak, including a first region R1 at the beginning of compression, where the rise in compressive stress relative to compressive strain is relatively large, and a second region R2, where the rate of change in compressive strain relative to a change in compressive load changes relatively rapidly in a predetermined compressive load range that exceeds the compressive load in the first region R1 (see FIG. 5). Furthermore, the resin structure 12 of this embodiment also has a characteristic that exhibits a stress-strain curve that further includes a third region R3, where the compressive stress relative to compressive strain changes relatively rapidly in a predetermined compressive load range that exceeds the compressive load in the second region R2 (see FIG. 5). The characteristic of the second region R2 contributes to absorbing the impact acting on the neck Pn during the "contact" phase and reducing the relative velocity difference between the neck Pn and the chest Pb (see the portion indicated by symbol a in FIG. 5). Furthermore, the characteristics of the second region R2 contribute to increasing the acceleration of the head Ph and reducing the difference with the chest acceleration by causing the resin structure 12 of the headrest 10 to come into contact with the head Ph with a predetermined stress during the "contact-sinking" phase (see the portion indicated by the symbol b in FIG. 5). The resin structure 12 with such a special SS curve controls the acceleration of the head Ph during a vehicle collision, thereby making it possible to reduce the NIC value.

[0031] The specific quantitative characteristics of such resin structure 12 are not particularly limited as long as they can exert the above-mentioned effects. However, as a preferred example, if an NiC value of 5 or less is used as one criterion, the rigidity range is approximately 35 to 75 kPa, or the slope is 100 kPa or less in the nominal strain range of 0.2 to 0.5 during compression.

[0032] [Examples of resin structures] A specific example of the resin structure 12 having the above-described properties is a structure 12 made of a metamaterial. A metamaterial is an artificially designed substance with properties that do not exist in nature (see FIG. 7). A specific example of the structure 12 made of a metamaterial will be described with reference to a diagram (see FIG. 6). The resin structure 12 is formed by joining multiple flexible elements (components) that exhibit different degrees of deformation depending on the magnitude of a compressive load. The components may be, for example, rod-shaped members, and these rod-shaped members may form a structure also known as a Kelvin structure 120. The Kelvin structure 120 of this embodiment that constitutes the resin structure 12 is a polyhedral structure formed by multiple components including a first component 121, a second component 122, and a third component 123 (see FIG. 6).

[0033] The first component members 121 are members arranged at the ends (top and bottom in this embodiment) of the compression direction CD (vertical direction in FIG. 6) in which the load acts (see FIG. 6(A)). In this embodiment, four first component members 121 are combined to form a rectangular shape such as a square or parallelogram, and are arranged at the top and bottom of the compression direction CD.

[0034] The second component 122 is a component joined to the first component 121 so as to be openable and closable in a direction that increases and decreases the opening angle with respect to the compression direction CD. In this embodiment, one end of the second component 122 is joined to each corner of a rectangular portion formed by combining the first component members 121. A total of eight second component members 122 are provided, four on the upper end side and four on the lower end side, and are arranged so as to form the oblique sides of the polyhedron structure (see FIG. 6(A)).

[0035] A plurality of third components 123 are arranged on the periphery (side) of the Kelvin structure 120, which has a polyhedral structure, to form polygons joined to the second components 122, and the polygons are deformable in the direction of collapse (see FIG. 6(A)). For example, in this embodiment, four third components 123 are combined to form a rectangular shape such as a square or parallelogram, for a total of four sets, and are arranged on all four sides of the side at 90° intervals in the circumferential direction. In addition, one third component 123 is arranged between each adjacent set of rectangular shapes, and another third component 123 is arranged to connect each set of rectangular shapes, for a total of four third components 123 (see FIG. 6(A)).

[0036] Furthermore, in the Kelvin structure 120 described above, the magnitude of the load that causes deformation in the second component 122 and the load that causes deformation in the third component 123 are set to different ranges, so that when a load acts in the compression direction CD, the second component 122 deforms more significantly before the third component 123.

[0037] The deformation of the Kelvin structure 120 will be described below (see FIG. 6). In the initial stage when a load begins to act in the compression direction CD, the portion of the second component 122 joined to the first component 121 is bent and deformed in a direction that increases the angle (the angle representing the degree of opening with respect to the compression direction CD). As a result, the Kelvin structure 120 is crushed in the compression direction CD, and the third component 123 on the periphery (side) protrudes further outward (see FIG. 6(B)). As the load in the compression direction CD increases further, the deformation of the third component 123 becomes significant. The portions of the square-shaped third component 123 joined to the second joining member 122 are deformed so that the angle becomes 90° or more. The square-shaped set of third component 123 is crushed in the compression direction CD and becomes a parallelogram (see FIG. 6(B)). As a larger load acts from this point, the Kelvin structure 120 is further crushed in the compression direction CD (a state of large deformation). An example of such deformation is shown in the graph in Figure 8. By providing a characteristic in which the rate of change of compressive strain relative to a change in load changes relatively significantly in a specific region (for example, a region around a nominal stress of 40 kPa) (in other words, a characteristic in which the region has a plateau stress range), it is possible to prevent abrupt changes in stress on the head Ph and neck Pn (see Figure 8).

[0038] The headrest 10 made of the resin structure 12 having such predetermined properties can absorb the impact acting on the head Ph of the occupant P during a rear-end collision of the vehicle and reduce the relative velocity difference between the head Ph and the chest Pb. Furthermore, by contacting the head Ph with a predetermined stress, the headrest 10 can increase the forward acceleration of the head Ph in the "post-rebound" phase. Such a vehicle seat 1 can achieve weight reduction by relying on the use of the resin structure 12, without employing a mechanism such as an active headrest, which tends to be heavy.

[0039] [Backrest] The seat back 30 of the vehicle seat 1 includes a seat frame 32 and an upholstery such as a mesh upholstery 34 (see FIG. 9).

[0040] The seat frame 32 is made of at least one of CFRP, UD material, and composite laminated resin material (see FIG. 9(A)). By making the seat frame 32 out of these materials instead of metal material (i.e., by using resin), it is possible to reduce the weight of the seat frame 32 and, in turn, the vehicle seat 1 while maintaining the necessary rigidity. Specifically, for example, by using CFRP as the skeleton and arranging UD material as the outer layer, it is possible to use it as a frame instead of metal (see FIG. 10). Alternatively, for example, a combination of UD material and continuous fiber composite material is also suitable.

[0041] The mesh upholstery 34, which is a suitable example of upholstery, is made of mesh material and is supported at its periphery by the seat frame 32, forming a backrest with a hammock structure in the central portion 30C (see FIG. 9(B)). In this embodiment, urethane foam is not provided in at least the central portion 30C or in any portion of the backrest 30. In short, the backrest 30 in the vehicle seat 1 of this embodiment does not substantially contain a foam-like material that absorbs shock, and the function of absorbing shock in the event of a vehicle collision by deforming in the backrest 30 is solely performed by the mesh upholstery 34. The mesh upholstery 34 that performs this function may be a three-dimensional knitted fabric.

[0042] The backrest 30 of this embodiment, including the mesh upholstery 34 as described above, can exhibit greater strain during compression than conventional backrests made of urethane foam or the like, thereby allowing the chest Pb of the occupant P to sink more during a rear-end collision and thereby reducing the difference in displacement between the chest Pb and head Ph. The backrest 30 having such characteristics, in combination with the characteristics of the headrest 10 described above, reduces the difference in speed between the chest Pb and head Ph of the occupant P during a vehicle collision, thereby reducing the load acting on the neck Pn in accordance with this difference in speed. [Industrial Applicability]

[0043] The present invention is suitable for application to vehicle seats. [Explanation of symbols]

[0044] 1...Vehicle seat 10...Headrest 12...Resin structure 20... Seat area 30...Backrest 30C…Central part 32...Seat frame 34...Mesh upholstery (mesh material upholstery) 120...Kelvin structure 121...First component 122...Second component 123...Third component CD: Compression direction (direction in which the compressive load acts) P...Crew member Pb…Chest Ph…Head Pn...cervix R1…first area R2…Second area R3...Third area SSD: Stress-strain curve

Claims

1. A vehicle seat to be installed in a vehicle, A headrest made of a resin structure; a backrest portion to which the headrest is attached; and Equipped with The resin structure has a characteristic of exhibiting a stress-strain curve that includes a first region at the beginning of compression where the rise in compressive stress with respect to compressive strain is relatively large, and a second region where the rate of change in compressive strain with respect to a change in compressive load changes relatively greatly in a predetermined compressive load region that exceeds the compressive load in the first region.

2. 2. The vehicle seat according to claim 1, wherein the resin structure has a characteristic of exhibiting a stress-strain curve that further includes a third region in which the compressive stress relative to the compressive strain changes relatively greatly in a predetermined compressive load region that exceeds the compressive load in the second region.

3. 3. The vehicle seat according to claim 2, wherein the resin structure has a characteristic of having a region in which the slope is 100 kPA or less in a region in which the nominal strain during compression is 0.2 to 0.

5.

4. The vehicle seat according to claim 2 , wherein the resin structure is a structure made of a metamaterial.

5. 5. The vehicle seat according to claim 4, wherein the resin structure is formed by joining a plurality of flexible structural members that deform to different degrees depending on the magnitude of a compressive load.

6. 6. The vehicle seat according to claim 5, wherein the component member is a rod-shaped member.

7. The vehicle seat according to claim 7 , wherein the resin structure has a polyhedron structure formed by the plurality of constituent members.

8. 8. The vehicle seat according to claim 7, wherein the resin structure includes: a first component arranged at an end portion in a compression direction in which a load acts; a second component joined to the first component so as to be openable and closable in a direction that increases or decreases an opening angle with respect to the compression direction; and a third component arranged in plurality around the periphery of the polyhedron structure and joined to the second component, forming a polygon and deformable in a direction that crushes the polygon.

9. 9. The vehicle seat according to claim 8, wherein a magnitude of the load that causes deformation of the second component member and a magnitude of the load that causes deformation of the third component member are set to different ranges.

10. 10. The vehicle seat according to claim 1, wherein the backrest portion has a seat frame made of at least one of CFRP, UD material, and composite laminated resin material.

11. 11. The vehicle seat according to claim 10, wherein the backrest includes an upholstery made of a mesh material, and at least a central portion of the backrest is free from urethane foam.

12. The vehicle seat according to claim 11, wherein the mesh material upholstery is a three-dimensional knitted fabric.

13. 13. The vehicle seat of claim 12, wherein the backrest portion is substantially free of foam shock absorbing material.

14. A method for controlling head acceleration of an occupant when absorbing an impact by a headrest of a vehicle seat, comprising: The structure constituting the headrest is made of a resin structure, A method for controlling head acceleration using a headrest for a vehicle seat, wherein the resin structure has characteristics that exhibit a stress-strain curve that includes a first region at the beginning of compression where the rise in compressive stress relative to compressive strain is relatively large, and a second region where the rate of change in compressive strain relative to a change in load changes relatively greatly in a predetermined compressive load region that exceeds the compressive load in the first region.

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