JP4200580B2 - Light alloy seat back frame - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a seat back frame for a vehicle seat, which is integrally formed of a light alloy.
[0002]
[Prior art]
As this kind of light alloy seat back frame, there is a structure as shown in FIG. 7, for example. This is formed by integrally molding a pair of left and right side members 2 and an upper member 3 and a lower member 4 respectively connecting the upper and lower portions of both side members with a light alloy having a considerable elongation at break. It has a structure in which the elements are connected. The side member 2 has a substantially L-shaped cross section, and a plurality of reinforcing ribs 2a that connect both sides are formed inside. The seat back frame 1 is attached so as to rise from the rear part of the seat cushion frame through an attachment hole 5 formed in the lower part of the left and right side members 2.
[0003]
[Problems to be solved by the invention]
When a rear-end collision is received during operation of the vehicle, a backward load F (see an arrow in FIG. 7) due to the inertial force of the seated person's weight is applied to the upper portion of the seat back frame 1. The seat back frame 1 constituted by the plate-like elements as shown in FIG. 7 can be expected to have considerable rigidity, but when subjected to the load F, the tensile stress generated at the lower front edge of the side member 2 increases. Fracture due to local breakage begins, and this progresses and breaks up and down as shown in FIG. In this case, the load F applied to the upper portion of the seat back frame 1 rises sharply with respect to the deformation near the point of action of the load F as shown by the characteristic curve A in FIG. Reaches the maximum load Aa, and then suddenly decreases as the breakage progresses and breaks up and down at point Ab. Accordingly, since the amount of deformation until breaking is not large, there is a problem that the amount of energy absorbed due to the breakage of the seat back frame 1 does not increase and the impact given to the seated person increases. The present invention aims to solve such problems.
[0004]
[Means for Solving the Problems]
A light alloy seat back frame according to the present invention is a seat back frame formed by integrally forming a pair of left and right side members, and an upper member and a lower member respectively connecting the upper and lower portions of both side members with a light alloy. The side member has a pair of cross-sectional shapes extending in the longitudinal direction with a front-rear interval, and is composed of a circular front side and rear bar element, and the cross-sectional area of the rear bar element is smaller than the cross-sectional area of the front bar element, When a rearward load is applied to the upper part of the seat back frame, a compression force is applied to the rear bar element to cause buckling, and the front bar element is bent without breaking. . If rearward load to the top of the seat back frame due collision is applied, since the side bar element After side members Rutotomoni front side rod element caused buckling applied compressive force bends without breaking, the sheet The back frame is greatly deformed without breaking. Moreover, since each bar element has a circular cross-sectional shape, local cracks do not occur due to stress concentration.
[0006]
The pair of bar elements according to the invention of the preceding paragraph is preferably connected by a plurality of connecting bar elements thinner than that.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
First, the first embodiment of the present invention will be described with reference to FIGS. In the seat back frame 10 according to this embodiment, upper and lower ends of a pair of left and right elongated side members 11 extending in parallel to each other are connected by an upper member 12 and a lower member 13. Each side member 11 is configured by a pair of rod elements 11a and 11b extending in the vertical direction in use and extending in the longitudinal direction with the front and the back except for the upper and lower ends. Each bar element 11a, 11b has a substantially constant circular cross-sectional shape over its entire length, and the cross-sectional area of the rear bar element 11b is smaller than the cross-sectional area of the front bar element 11a. The seat back frame 10 is bolted and fixed to the left and right seat support members, which are attached to the vehicle body of the automobile and support the seat cushion, by means of attachment holes 14 formed at the lower end of the side member 11 via a reclining mechanism. Yes.
[0008]
The seat back frame 10 is integrally formed by a die casting method using a light alloy (magnesium alloy, aluminum alloy, etc.) having high ductility as a raw material. As the die casting method, a thixo molding method in which a material is injection-molded in a semi-molten state is suitable, but a normal die casting method may be used.
[0009]
When a rear-end collision is received during driving of the vehicle, a backward load F (see the arrow in FIG. 1) due to the inertial force of the seated person's weight is applied to the upper portion of the seat back frame 1, thereby increasing the cross-sectional area. Tensile force is applied to the front bar element 11a, and compressive force is applied to the rear bar element 11b, which has a smaller cross-sectional area . This load F rises rapidly with respect to the deformation near the point of action of the load F, as shown by the characteristic curve B in FIG. 4 until the compressive force applied to the rear bar element 11b reaches the buckling load. When the above-described compressive force reaches the buckling load, the maximum load Ba is obtained. Thereafter, the rear bar element 11b buckles due to the applied compressive force, so that the tensile force applied to the front bar element 11a is reduced to mainly bending force without breaking as shown in FIG. The seatback frame 10 is bent and greatly deformed without breaking. The load F decreases from the maximum load Ba, but the degree of the load F does not decrease much from a value that gradually decreases.
[0010]
As described above, when a rearward load F is applied to the upper portion of the seat back frame 10 due to a rear-end collision or the like, the seat back frame 10 is greatly deformed without breaking, so that the amount of energy absorption is increased and the weight of the seat back frame is increased. If the same level, maximum load Ba in the case of this embodiment is smaller than the maximum load Aa in the prior art shown in FIG. 7, therefore the shock applied to the seat occupant decrease.
[0011]
In the first embodiment, the cross-sectional area of the rear bar element 11b is smaller than the cross-sectional area of the front bar element 11a. Therefore, the buckling load of the rear bar element 11b is reduced. The maximum value of the applied load F is further reduced to increase the deformation, and the impact given to the seated person is further reduced. The buckling direction of the rear bar element 11b is not limited to the forward direction as shown in FIG. 3, but may occur laterally or rearward.
[0012]
Further, each bar element 11a, 11b has a circular cross-sectional shape. In this way, there is no corner portion where stress concentration occurs, and therefore, breakage due to a local crack occurring in such a case does not occur .
[0013]
5 and 6 show a second embodiment of the present invention. In the second embodiment, the front bar element 11a and the rear bar element 11b of the first embodiment are arranged in a zigzag manner, and a plurality of connecting bar elements 11c that are thinner than both the bar elements 11a and 11b. It is connected by. Since other configurations are the same as those of the first embodiment, detailed description thereof is omitted.
[0014]
According to this second embodiment, the rear bar element 11b because it is connected to the front bar element 11 a by a connecting rod element 11c, the maximum load Ba when load F in the first embodiment It does not buckle when it reaches it. If the load F further increases, the connecting rod element 11c is deformed or broken, and the rear rod element 11b buckles, and the seat back frame 10 is greatly deformed without breaking as in the case of the first embodiment. Therefore, when the maximum load Ba that the seat back frame 10 can withstand is the same, the cross-sectional area of the rear bar element 11b can be reduced, and the weight of the seat back frame 10 is reduced.
[0015]
【The invention's effect】
According to the present invention, when a rearward load is applied to the upper portion of the seat back frame due to a rear-end collision or the like, the seat back frame is greatly deformed without breaking, so that the amount of energy absorption is increased, and the impact given to the seated person is thereby increased. Can be reduced. In addition, the cross-sectional area of the rear bar element is smaller than the cross-sectional area of the front bar element, which reduces the buckling load of the rear bar element, so that the maximum value of the load applied to the seat back frame is reduced and deformed. And the impact on the seated person can be further reduced. Furthermore, each bar element has a circular cross-sectional shape, and there are no corners where stress concentration occurs. Therefore, breakage caused by local cracks occurring at such corners does not occur, and the effect of reducing the impact is not lost. .
[0017]
In the invention of the preceding paragraph , when a pair of bar elements are connected by a plurality of connecting bar elements thinner than that, the cross-sectional area of the rear bar element when the maximum load that the seat back frame can withstand is the same. Since the size can be reduced, the weight of the seat back frame can be reduced.
[Brief description of the drawings]
FIG. 1 is an overall perspective view showing a light alloy seat back frame according to a first embodiment of the present invention.
2 is a cross-sectional view taken along the line 2-2 in FIG.
FIG. 3 is an overall perspective view showing a state after deformation of the seat back frame according to the first embodiment.
FIG. 4 is a diagram comparing deformation of a seat back frame according to the present invention and the prior art with respect to load.
FIG. 5 is an overall perspective view showing a second embodiment of a light alloy seat back frame according to the present invention.
6 is a cross-sectional view taken along the line 6-6 in FIG.
FIG. 7 is an overall perspective view showing an example of a light alloy seat back frame according to the prior art.
8 is an overall perspective view showing a state in which the seat back frame shown in FIG. 7 is broken by a load. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Seat back frame, 11 ... Side member, 11a ... Front side bar element, 11b ... Rear side bar element, 11c ... Connecting bar element, 12 ... Upper member, 13 ... Lower member

Claims (2)

In a seat back frame formed by integrally forming a pair of left and right side members and an upper member and a lower member respectively connecting the upper and lower portions of both side members with a light alloy, the side members are spaced apart from each other A pair of cross-sectional shapes extending in the longitudinal direction are circular front and rear bar elements, and the rear bar element has a cross-sectional area smaller than the cross-sectional area of the front bar element, and faces rearward to the upper part of the seat back frame. A light alloy seat back frame characterized in that when the load is applied, a compressive force is applied to the rear bar element to cause buckling, and the front bar element bends without breaking . The light alloy seat back frame according to claim 1, wherein the pair of bar elements are connected by a plurality of connecting bar elements thinner than the pair of bar elements.

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