WO2016163182A1

WO2016163182A1 - Automotive side sill

Info

Publication number: WO2016163182A1
Application number: PCT/JP2016/056584
Authority: WO
Inventors: 和彦樋貝; 平本　治郎
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2015-04-07
Filing date: 2016-03-03
Publication date: 2016-10-13
Also published as: JP6281522B2; JP2016199055A

Abstract

In the automotive side sill according to the present invention, a side sill 1 disposed at a lower portion of the side surface of a vehicle is equipped with: a side sill outer panel 1a located on the outer side of the vehicle; and a side sill inner panel 1b located on the inner side of the vehicle. The automotive side sill is characterized in that: the side sill outer panel 1a and the side sill inner panel 1b are joined to each other to form a closed cross-section; the side sill outer panel 1a is a steel plate having a tensile strength of 1180-1470 MPa class and a thickness of 0.6-1.6 mm; and the side sill inner panel 1b is a steel plate having a tensile strength of 440 MPa class or more, the steel plate of side sill inner panel 1b being lower in tensile strength than that of the steel plate of the side sill outer panel 1a.

Description

Side sill structure for vehicles

The present invention relates to an automotive side sill structure that extends in the front-rear direction at the lower part of the side of the vehicle.

A hollow long side sill is provided at a lower position in the vehicle longitudinal direction on the side of the vehicle. As shown in FIG. 1, a general side sill 1 includes a side sill outer panel 1a and a side sill inner panel 1b, and, if necessary, between a side sill outer panel 1a and a side sill inner panel 1b. It is composed of a side sill reinforcement (not shown) provided, and is connected via a roof rail 5 and a center pillar 3 provided at an upper position in the vehicle longitudinal direction. Yes. Side sills require weight reduction of automotive bodies due to environmental issues while improving and ensuring collision safety during vehicle side crashes. .

So far, technologies have been proposed and implemented to improve and ensure collision safety in the event of a vehicle-side collision. In Patent Document 1, when an input from the outside in the vehicle width direction to the inside acts on an intermediate portion of the center pillar at the time of a side collision, a locker (side sill) coupled to the center pillar has a torsion input. Compressive stress acts on the outer surfaces of the rocker and the rocker, and it deforms like a wave. Therefore, by providing a bead extending along the direction of compressive stress on the outer surface of the rocker to reinforce the outer surface, the deformation of the rocker is suppressed by suppressing the deformation of the outer surface and the deformation of the rocker in the twisting direction. A vehicle frame structure is disclosed. Patent Document 2 discloses a vehicle body lower structure in which an impact absorbing portion (impact absorpted portion) is provided in the vicinity of a joint end portion of a cross member and a side sill to reduce impact at the time of a side collision. Yes.

JP 2011-143762 A JP 2010-215092 A

The deformation suppression by the bead application shown in the vehicle skeleton structure disclosed in Patent Document 1 is effective for a part having a constant thickness, and suppresses the twist when compared with a member having the same steel plate / thickness. It is possible, but it is difficult to reduce the weight of the vehicle. The vehicle body lower structure disclosed in Patent Document 2 requires a large number of shock absorbing parts, so that the safety at the time of a side collision is improved, but there is a problem that an increase in vehicle weight is unavoidable.

As described above, although a technique for ensuring safety in a side collision is disclosed, it is difficult to significantly reduce the weight of the vehicle. In the future, if the required standards improve due to stricter collision safety performance standards, etc., it will be difficult to prevent weight increase with the above-mentioned conventional technology, which is also disadvantageous to manufacturing costs. It becomes.

Conventionally, it is said that crashworthiness can be improved by improving the tensile strength of the steel sheet of each part (part) used in the car body. There were many cases where the effect of improving the collision performance obtained by the improvement in strength was small. Furthermore, the improvement of the tensile strength of steel sheets will lead to an increase in steel material costs and manufacturing costs, and so-called trial and error is necessary to optimize both component performance and cost balance. Development time and cost were required.

For vehicle side sills, the side sill outer panel and side sill inner panel are thinned using high-strength steel sheets to ensure bending strength and light weight during side impacts. It was compatible. However, the use of high-strength steel sheets hinders the productivity of each part by press forming, and progresses in the direction of increasing the tension of steel sheets even for parts that do not require high-strength steel sheets. In some cases, it was a factor in increasing manufacturing costs.

The present invention has been made in view of the above, and an object thereof is to provide a vehicle side sill structure that has high collision safety at the time of a side collision, achieves weight reduction, and further does not increase manufacturing cost. It is in.

The inventors of the present invention diligently studied the influence of the tensile strength and thickness of the steel sheet used in the vehicle side sill structure on the bending strength at the time of vehicle side collision, satisfying sufficient bending strength and being reduced in weight. The knowledge about the vehicle side sill structure was obtained. The present invention has been made based on the above findings, and specifically comprises the following configuration.

A vehicle side sill structure according to the present invention is a vehicle side sill structure including a side sill outer panel positioned on the vehicle outer side and a side sill inner panel positioned on the vehicle inner side, wherein the side sill outer panel and the side sill inner panel are mutually connected. The side sill outer panel is formed of a steel plate having a tensile strength of 1180 MPa class (1180 MPa-class) or more and 1470 MPa class or less and a thickness of 0.6 mm or more and 1.6 mm or less. The panel is formed of a steel plate having a tensile strength of 440 MPa or higher and a tensile strength of a steel plate forming the side sill outer panel.

According to the present invention, it is possible to provide a vehicle side sill structure that has high collision safety at the time of a side collision, achieves weight reduction, and does not increase manufacturing cost.

FIG. 1 is a perspective view of a vehicle side part structure including a vehicle side sill according to an embodiment of the present invention, and shows a state seen from the outside of the vehicle in a state where each part is disassembled. FIG. 2 is an explanatory diagram of an analysis model of FEM (Finite Element Method) analysis that simulates a side collision in the vehicle body side structure provided with the vehicle side sill according to the embodiment of the present invention. FIG. 3 shows an example of an analysis result of a load due to an underpunch stroke in an FEM analysis simulating a side collision of a vehicle side structure having a vehicle side sill according to an embodiment of the present invention. FIG. FIG. 4 shows a vehicle side part structure provided with a vehicle side sill according to an embodiment of the present invention. The maximum value at the time of a side collision of the vehicle side part structure when the tensile strength and thickness of the steel plate of the side sill outer panel is changed. It is a graph which shows the relationship between a load and a weight change rate. FIG. 5 is a side view of a vehicle having a side sill for a vehicle according to an embodiment of the present invention. The maximum of a side collision of the vehicle side structure when the tensile strength and thickness of the steel plate of the side sill inner panel are changed. It is a graph which shows the relationship between a load and a weight change rate.

As shown in FIG. 1, the vehicle side sill structure according to the embodiment of the present invention is a structure of the side sill 1 disposed in the lower part of the side surface of the vehicle, and includes a side sill outer panel 1a located outside the vehicle, And a side sill inner panel 1b located inside the vehicle. The side sill outer panel 1a and the side sill inner panel 1b are joined together to form a closed cross section. The side sill outer panel 1a is formed of a steel plate having a tensile strength of 1180 MPa class or more and a plate thickness of 0.6 mm or more and 1.6 mm or less. The side sill inner panel 1b is formed of a steel plate having a tensile strength of 440 MPa or higher and not higher than the tensile strength of the steel plate forming the side sill outer panel 1a.

As shown in FIG. 1, the lower end of the center pillar 3 where the center pillar outer panel 3a and the center pillar inner panel 3b are joined is joined to the side sill 1, and the upper end of the center pillar 3 is the roof rail 5 (the roof rail outer panel 5a). , The roof rail inner panel 5b) is joined to form the vehicle side structure 11.

The tensile strength and thickness of the steel plate of the side sill outer panel 1a and the tensile strength and thickness of the steel plate of the side sill inner panel 1b were determined based on the following examination results. First, the tensile strength and thickness of the steel plate of the side sill outer panel 1a were determined from the maximum load at the time of a side collision in the vehicle side part structure 11 formed by the side sill 1, the center pillar 3, and the roof rail 5 as shown in FIG. .

Specifically, using the analysis model shown in FIG. 2, FEM analysis of a three-point bending test in which the center pillar outer panel 3a is pushed by an under punch is performed, and the load for pushing the under punch is calculated. The relationship between the under punch strokes was determined, and the maximum load within the range of 0-100 mm under punch strokes was defined as the maximum load. The boundary conditions in the FEM analysis include the full constraint condition at the upper end of the center pillar 3 joined to the roof rail 5, the rotation and the vehicle width direction (downward direction in FIG. 2) at the lower end of the center pillar 3 joined to the side sill 1. ) Was given a constraint that only freed deformation.

FIG. 3 shows an example of the analysis result of the relationship between the under punch stroke and the load obtained by the FEM analysis. The analysis results are obtained when a steel plate having a 1470 MPa class and a thickness of 1.2 mm is used for the side sill outer panel 1 a and a steel plate having a thickness of 590 MPa and a thickness of 1.0 mm is used for the side sill inner panel 1 b.

The load increased with the increase of the under punch stroke, the load showed a maximum value when the under punch stroke was about 50 mm, and the load decreased within the range of about 50 mm to 110 mm. When the under punch stroke was about 110 mm or more, the load increased again. From the above, the maximum load at the time of a side collision in the vehicle side part structure 11 was determined as 27.9 kN from the maximum value in the range where the under punch stroke was 0 to 100 mm.

In FIG. 4, a steel plate having a tensile strength of 440 MPa and a plate thickness of 1.4 mm is used for the side sill inner panel 1 b, a tensile strength of the steel plate used for the side sill outer panel 1 a is 590 MPa to 1470 MPa, and a plate thickness is 0.4 mm to 1. The maximum load at the time of a side collision when changing within the range of 6 mm is shown. The center pillar outer panel 3a was a steel plate having a tensile strength of 1470 MPa and a thickness of 1.8 mm, and the center pillar inner panel 3b was a steel plate having a tensile strength of 440 MPa and a thickness of 1.0 mm. With the increase in the tensile strength of the steel plate used for the side sill outer panel 1a, the maximum load at the time of a side collision improved with the same plate thickness. Moreover, with the steel plates having the same tensile strength, the maximum load at the time of side impact was improved as the plate thickness increased. Therefore, it can be seen that weight reduction can be achieved while ensuring the side impact performance by improving the tensile strength of the steel plate used for the side sill outer panel 1a and reducing the plate thickness.

As an example of a vehicle side sill structure used in commercially available cars, a steel plate having a tensile strength of 590 MPa and a thickness of 1.6 mm is used for the side sill outer panel. Based on the maximum load (62.6 kN) at the time of a side collision in a vehicle side part structure equipped with a side sill using the steel plate, the result shown in FIG. The side sill 1 using a .6 mm steel plate for the side sill outer panel 1a shows that the maximum load at the time of side collision satisfies the above-mentioned standard.

Furthermore, from the result of FIG. 4, since the plate thickness of the side sill outer panel 1a having a tensile strength of 590 MPa used for the vehicle side sill structure as a reference is 1.6 mm, the plate of the side sill outer panel 1a having a tensile strength of 1180 MPa or more is used. If the thickness is 0.6mm or more, it will be more than the maximum load at the time of side impact of the side sill as a standard, and it will be lighter than the standard vehicle side sill structure by using a steel plate with a thickness of 1.6mm or less It was suggested that From the above, it is preferable to use a steel plate having a tensile strength of 1180 MPa class or more and a thickness of 0.6 mm or more and 1.6 mm or less for the side sill outer panel 1a.

Next, the examination result about the tensile strength of the steel plate of the side sill inner panel 1b will be described. The tensile strength of the steel plate of the side sill inner panel 1b is based on the FEM analysis result of the maximum load in the three-point bending test of the vehicle side structure 11 that simulates the side collision, similarly to the tensile strength of the steel plate of the side sill outer panel 1a. Were determined. The analysis model and boundary conditions of the FEM analysis are the same as those of the side sill outer panel 1a described above.

In FIG. 5, the side sill outer panel 1a is a steel plate having a tensile strength of 780 MPa class and a plate thickness of 1.3 mm or a steel plate having a tensile strength of 1470 MPa class and a plate thickness of 1.0 mm, and the tensile strength of the steel plate used for the side sill inner panel 1b is 440 MPa class to The maximum load at the time of a side collision when the plate thickness is changed from 0.6 mm to 1.6 mm is shown. Although the maximum load of the panel in which the tensile strength of the steel plate used for the side sill inner panel 1b was changed slightly increased with the increase in the plate thickness, the effect on the maximum load was slight at any plate thickness.

From the above, from the viewpoint of side impact performance, increasing the strength of the steel plate used for the side sill inner panel 1b hardly contributes to the improvement of the maximum load during side impact, but is disadvantageous in terms of manufacturing cost. It has been found that even when a steel plate having a tensile strength of 440 MPa is used as the inner panel 1b, sufficient side collision performance can be obtained.

From the viewpoint of weight reduction, the steel plate used for the side sill inner panel 1b is preferably thin. However, as a vehicle crash safety performance standard, strength (rear-crash safety performance) at the time of a collision from the rear of the vehicle is required, so the thickness of the side sill inner panel 1b is set to the side sill outer panel 1a. The thinnest plate that satisfies the rear impact performance by comparing the amount and state of deformation when a load is applied perpendicularly to the closed cross section where the side sill inner panel 1b is joined to the conventional plate thickness Thickness is sufficient.

Specific experiments were conducted to confirm the effects of the present invention, which will be described below. In this embodiment, the side collision performance and weight change rate of the side sill 1 including the side sill outer panel 1a and the side sill inner panel 1b, the vehicle side structure 11 (see FIG. 1), which includes the center pillar 3 and the roof rail 5. And about the manufacturing cost, it evaluated about the case where the tensile strength and board thickness of the steel plate used for the side sill outer panel 1a and the side sill inner panel 1b were changed. The center pillar outer panel 3a was a steel plate having a tensile strength of 1470 MPa and a thickness of 1.8 mm, and the center pillar inner panel 3b was a steel plate having a tensile strength of 780 MPa and a thickness of 1.0 mm.

Table 1 shows the conditions (Invention Examples 1 to 6) in which the tensile strength and thickness of the steel plates used in the side sill outer panel 1a and the side sill inner panel 1b in the side sill 1 were changed, and the side collisions obtained under each condition. The evaluation results of performance (side-crash safety performance), weight change rate and manufacturing cost are shown.

As in the embodiment, the side impact performance, which is an evaluation item, was subjected to FEM analysis of a three-point bending test with the vehicle side structure 11 shown in FIG. 2 as an analysis target, and the under punch stroke was 0 in the three-point bending test. The maximum value of the load within a range of ˜100 mm is evaluated as the maximum load at the time of a side collision.

The side impact performance was evaluated based on the FEM analysis result (63.6 kN) of the maximum load at the time of side impact in the vehicle side part structure of the conventional example. . The weight change was evaluated based on the weight change rate based on the weight (12817 g) of the conventional vehicle side structure. The production cost is based on the raw material (steel plate) cost in the conventional example as long as it is cheaper than this.

In Table 2, as a comparative example, the tensile strength or thickness of the steel plate used for the side sill outer panel 1a and the side sill inner panel 1b is outside the range of the tensile strength and thickness of the steel plate in the vehicle side sill structure according to the present invention. The evaluation results of the side impact performance, weight change rate and manufacturing cost of the vehicle side sill structure are shown. Side impact performance, weight change rate, and manufacturing cost were evaluated according to the same evaluation criteria as in Table 1.

In Comparative Example 1, the side sill outer panel 1a had a steel plate with a tensile strength of less than 1180 MPa and a thickness of 0.6 mm, and the side sill inner panel 1b had a tensile strength of less than 440 MPa with a 390 MPa grade. The crash performance was below the evaluation standard.

In Comparative Example 2, the tensile strength of the steel plate of the side sill outer panel 1a was set to 780 MPa class, but since the plate thickness was increased to 1.6 mm, the side impact performance satisfied the evaluation standard, but the manufacturing cost exceeded.

In Comparative Example 3, since the tensile strength of the steel plate of the side sill inner panel 1b was set to 1470 MPa class, the side impact performance and the weight change satisfied the evaluation criteria, but the manufacturing cost exceeded.

In Comparative Example 4, the steel plate of the side sill outer panel 1a has a tensile strength of 1470 MPa, a plate thickness of 0.4 mm, and a significant weight reduction (weight change rate: -25%) is obtained, and the manufacturing cost is also evaluated. Although it was below the standard, the side impact performance was below the evaluation standard.

As described above, in the vehicle side sill structure according to the present invention, the side sill outer panel is a steel plate having a tensile strength of 1180 MPa class or more, the thickness of the steel plate is 0.6 mm or more and 1.6 mm or less, and the side sill inner panel is By using a steel plate with a tensile strength of 440 MPa or higher and a lower tensile strength than the steel plate of the side sill outer panel, a vehicle side sill structure that satisfies the necessary and sufficient side impact performance and can be reduced in weight without increasing manufacturing costs. It has been demonstrated that it can be realized.

DESCRIPTION OF SYMBOLS 1 Side sill 1a Side sill outer panel 1b Side sill inner panel 3 Center pillar 3a Center pillar outer panel 3b Center pillar inner panel 5 Roof rail 5a Roof rail outer panel 5b Roof rail inner panel 11 Vehicle side part structure

Claims

A vehicle side sill structure comprising a side sill outer panel located outside the vehicle and a side sill inner panel located inside the vehicle,
The side sill outer panel and the side sill inner panel are joined together to form a closed cross section,
The side sill outer panel is formed of a steel plate having a tensile strength of 1180 MPa class or more and 1470 MPa class or less and a plate thickness of 0.6 mm or more and 1.6 mm or less,
The side sill inner panel is formed of a steel plate having a tensile strength of 440 MPa or higher and a tensile strength lower than that of the steel plate forming the side sill outer panel.