JP6922771B2 - How to design the front bumper up absorber - Google Patents

Description

The present invention relates to a method for designing a front bumper up absorber having a notch in the upper part on the front side of the vehicle.

Vehicle bumpers have a requirement for pedestrian leg protection in the event of a collision. For this purpose, a resin absorber is arranged inside the bumper, and the absorber absorbs the impact at the time of a collision.

In addition, the pedestrian leg protection performance has been tested using a hinge type impactor. This hinge type impactor has a structure in which a member on the tibial side and a member on the thigh side are connected by a hinge portion simulating a knee. Then, this hinge type impactor is made to collide with the bumper of the vehicle, and the medial collateral ligament (MCL), the anterior cruciate ligament (ACL), and the posterior cruciate ligament (PCL) of the knee are determined from the load received by the hinge type impactor at this time. ) Is measured as the pedestrian leg protection performance. In the following, the amount of extension of the medial collateral ligament, the anterior cruciate ligament, and the posterior cruciate ligament of the knee will be appropriately referred to as MCL, ACL, and PCL.

Here, Patent Document 1 indicates that a collision detection sensor is arranged between the absorber of the bumper and the bumper infoce that supports the bumper behind the absorber, and the upper part of the absorber on the front side of the collision detection sensor is cut off. It has been shown to be lacking.

Japanese Unexamined Patent Publication No. 2009-40423

The absorber can soften the impact at the time of a collision, but the pedestrian leg protection performance such as MCL may not be sufficient. When the hinge type impactor extending in the vertical direction collides with the bumper, the lower part (tibial side) is pushed back by the drag force of the bumper, a rotational force is applied around the hinge part, and the amount of extension of the MCL etc. cannot be sufficiently reduced. it is conceivable that. In the prior art, there is no proposal as to how to reduce the amount of elongation of MCL or the like.

The present invention is a method for designing a front bumper up absorber having a notch in the upper part on the front side of the vehicle, based on the target elongation amount of the hinge portion when colliding with a hinge type impactor having the hinge portion. The target angle of the hinge portion is set, the amount of penetration of the hinge type impactor into the front bumper up absorber is set based on the set target angle, and the amount of penetration into the hinge type impactor is set based on the set penetration amount. A target load is set, and the size of the notch is determined based on the set target load.

In addition, the required angle reduction amount of the hinge portion is calculated based on the comparison between the elongation amount and the target elongation amount when the front bumper up absorber of a predetermined shape collides with the hinge type impactor, and the calculated required angle reduction amount is supported. It is preferable to calculate the required load reduction amount to the hinge type impactor and determine the size of the notch based on the calculated required load reduction amount.

Further, the area reduction rate in the cross section of the front bumper up absorber in the front-rear direction of the vehicle may be determined according to the ratio of the required load reduction amount.

Further, the length of the notch portion in the vehicle front-rear direction may be determined by the deformation stroke of the front bumper up absorber, which is the target at the time of the collision test.

Further, in the method of manufacturing a front bumper up absorber having a notch in the upper part on the front side of the vehicle, a bumper having a predetermined front bumper up absorber is subjected to a collision test with a hinge type impactor having a hinge portion, and a collision test is performed based on the result of the collision test. , The required load reduction amount for the hinge type impactor may be calculated, and the notch amount for the front bumper up absorber used in the collision test may be determined based on the calculated required load reduction amount.

According to the present invention, it is possible to easily obtain a front bumper up absorber having appropriate pedestrian leg protection performance.

It is sectional drawing which shows the structure of a bumper and a hinge type impactor. It is a figure explaining the movement of a hinge type impactor, (a) is a figure which shows the spacing of the hinge part of a hinge type impactor, (b) is a figure which shows the rotation angle after a test. It is a figure which shows the bending degree of the hinge type impactor after a collision test. It is a figure which shows the relationship (FS curve) of a load F [N] of a front bumper up absorber, and a stroke. It is a figure which shows the size of the notch part to form. It is a figure which shows the time-dependent change of the ligament elongation amount (MCL) at the time of a collision experiment. It is a flowchart about the design method which concerns on embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described herein.

"overall structure"
FIG. 1 is a cross-sectional view (cross-sectional view taken along the front-rear direction of the vehicle) showing the structure of the bumper and the hinge type impactor used in the collision test with respect to the bumper.

The bumper 10 is a member extending in the vehicle width direction at the lower front portion of the vehicle, and has a plate-shaped front bumper cover 12 extending over the entire width in the vehicle width direction on the front side thereof. The front bumper cover 12 has a horizontally long rectangular shape, and the upper, lower, left, and right ends extend rearward by a predetermined length, forming a box shape with a shallow rear opening as a whole. The front bumper cover 12 is a member that constitutes a design surface at the front portion of the vehicle, and in this example, the front bumper cover 12 has a grill portion 12a slightly below the center in the vertical direction.

The front bumper up absorber 14 is arranged in an area slightly above the center in the vertical direction on the rear side of the front bumper cover 12. The front bumper up absorber 14 has a substantially rectangular cross section and extends laterally on the rear side of the front bumper cover 12. The front bumper up absorber 14 is a shock absorbing member made of a resin such as urethane foam. In the present embodiment, a notch portion 14a having a rectangular cross section is formed in the upper part on the front side of the front bumper up absorber 14.

After the front bumper up absorber 14, a bumper infoce 16 extending in the vehicle width direction is provided. The bumper infoce 16 is a hollow square lumber made of a high-strength material such as a steel material, and supports the front bumper up absorber 14 from the rear. The bumper infoce 16 is fixed to side members which are vehicle body structural members extending on both sides of the vehicle on both sides in the vehicle width direction.

A front bumper lower absorber 18 extending in the vehicle width direction is arranged behind the lower portion (below the grille) of the front bumper cover 12. The front bumper lower absorber 18 is composed of a shock absorbing member and a hollow lumber-shaped reinforce that supports the shock absorbing member from behind.

The hinge type impactor 20 used for the collision test is shown in front of the bumper 10. The hinge type impactor 20 has an upper member 22 that simulates the thigh, a lower member 24 that simulates the shin, and a hinge portion 26 that simulates the knee that rotatably connects the two. Various sensors such as an accelerometer are built in each part of the hinge type impactor 20, and the load applied to each part is measured in the collision test. In the figure, the lower member 24 of the hinge type impactor 20 is arranged in front of the front bumper up absorber 14 of the bumper 10.

"Crash test-> Notch setting"
In the collision test, the vehicle and the hinge type impactor 20 are made to collide with each other at a predetermined relative speed. For example, when the lower member 24 of the hinge type impactor 20 collides with the bumper 10, the lower member 24 is hindered from advancing and the upper member 22 advances by inertia, so that the rear side (opposite side to the bumper 10) of the hinge portion 26 is moved. spread.

For example, in the case of the hinge type impactor 20 as shown in FIG. 2A, the length (gap) of the hinge portion 26 extends from the initial value to the length after the test as shown in FIG. 2B. The length after this test corresponds to the MCL.

In this example, in the test in which the notch portion 14a is not provided for the front bumper up absorber 14, the upper member 22 rotates clockwise with respect to the lower member 24 by the rotation angle θ, and the rotation angle θ is increased from the initial angle of the hinge portion 26. Only the angle of the hinge portion 26 is increased.

Here, the difference between the measured MCL after the test and the target MCL is obtained. In the collision test, basic conditions are defined, and there is a certain relationship between the size of the MCL and the angle of the hinge portion 26. In the collision test using the current hinge type impactor 20, reducing the MCL by 1 mm corresponds to reducing the angle of rotation by 1 °.

Therefore, with the upper member 22 and the lower member 24 as the target state, the angle θ1 of the hinge portion 26 required to achieve the target MCL is calculated.

FIG. 3 is a diagram showing how the hinge type impactor 20 is bent after the collision test. The state of the upper member 22 and the lower member 24 after the test is shown by a broken line, and the target state is shown by a solid line. In the present embodiment, the notch 14a is set so as to be the target when the MCL is larger than the target by not providing or making the notch 14a small. It should be noted that even if the notch portion 14a is too large, it can be dealt with in the same manner.

Based on the state after the test shown by the broken line, the states of the upper member 22 and the lower member 24 after the test in which the angle of the hinge portion 26 is set to the target angle θ1 are calculated, and the front of the hinge type impactor 20 in the target state is calculated. The amount of penetration (stroke) into the bumper-up absorber 14 is calculated. In this case, the target value of the stroke is L1, and the stroke needs to be increased by L2.

FIG. 4 shows the relationship between the load F [N] of the front bumper up absorber 14 and the stroke (FS curve). In the present embodiment, based on this relationship, the reduction rate of the reaction force of the front bumper up absorber 14 when the penetration amount of the hinge type impactor 20 is increased by L2 is calculated.

First, the relationship between the stroke and the load (initial FS curve) in the case of the front bumper up absorber 14 without the notch portion 14a is drawn. On the other hand, the target FS curve (target FS curve) is determined by changing the final load on the line in which the stroke is increased by L2. That is, with respect to the area (torque: F × S) defined by the initial F-S curve in the initial stroke, the area that decreases when the load F decreases and the stroke is increased by L2 to decrease the load. The target FS curve is defined as the FS curve in which the area (torque: F × S) increased by the FS curve is the same area J. That is, the stroke is changed while maintaining the torque applied to the front bumper up absorber 14 at a constant level.

Then, from the ratio of the final load of the initial FS curve to the final load of the target FS curve, the load reduction rate X% is calculated in order to set the load as the target value.

In this way, the load reduction rate X% required to obtain the target MCL is calculated. Then, the required reduction rate of the load is obtained by removing the area of X% from the cross-sectional area of the front bumper up absorber 14. That is, as shown in FIG. 5, when the required stroke L1 is set in the depth direction and the height direction is set to H, the cross-sectional area of the front bumper up absorber 14 included here is divided by the cross-sectional area before the notch. The size of the notch portion 14a is determined by setting the result to be X%.

FIG. 6 shows the change over time in the amount of ligament elongation (MCL) during the collision experiment. The one shown as an actual machine without a cut does not form the notch 14a of the front bumper up absorber 14, the one shown as an actual machine with a cut has a notch 14a with a cross-sectional area of X%, as a CAE prediction. What is shown is the calculated value of MCL using the model.

Table 1 shows the measured values of MCL, ACL, and PCL.

According to the present embodiment, by providing the notch portion 14a in the anterior upper part of the front bumper up absorber 14, not only the extension amount of the medial collateral ligament (MCL) of the knee portion can be improved, but also the anterior cruciate ligament can be improved. The amount of elongation of (ACL) and posterior cruciate ligament (PCL) can also be improved.

The front bumper up absorber 14 may not have the same thickness over the entire width of the vehicle, and may not be provided over the entire width (the length is limited). In such a case, the size of the notch portion 14a may be determined so that the repulsive force of the front bumper up absorber 14 in a collision becomes appropriate.

"Processing flow"
The design method in this embodiment will be described with reference to the flowchart of FIG. First, a test is conducted by colliding the hinge type impactor 20 with a vehicle equipped with a bumper 10 that employs a front bumper up absorber 14 having a predetermined shape (for example, one without a notch 14a or a small one) (S11). Thereby, the penetration amount (stroke) of the hinge type impactor 20 after the test, the rotation angle θ of the hinge portion 26, the MCL, and the like are detected.

Then, these test results are taken into a computer (S12). In the computer, the cross-sectional area of the notch portion 14a is determined by calculation from the angle of the hinge portion 26 after the test and the angle θ1 of the target hinge portion 26.

First, the difference between the MCL after the test and the target MCL is converted into the angle at which the hinge portion 26 is reduced (S13). Based on the obtained reduction angle, the target state of the hinge type impactor 20 is estimated, and in the case of the target, the amount of penetration of the hinge type impactor 20 into the front bumper up absorber 14 (target stroke L1) and the target. The stroke increase amount L2 required to obtain the stroke L1 to be obtained is obtained (S14).

The rate of change in the load of the hinge type impactor 20 required to obtain the obtained increase amount L2 is obtained (S15). At this time, the torque is kept constant.

The rate of change of the notch portion 14a is determined by the obtained rate of change of the load, and the size of the notch is determined (S16).

In this way, the size of the notch portion 14a is determined, and the front bumper up absorber 14 is designed based on this.

"Effect of embodiment"
According to this embodiment, the size of the notch of the front bumper up absorber 14 is determined based on the result of the collision test. Therefore, trial and error experiments can be significantly reduced. In particular, the target angle of the hinge portion is set based on the target elongation amount of the hinge portion when colliding with the hinge type impactor having the hinge portion, and the hinge type impactor of the hinge type impactor is set based on the set target angle. The amount of penetration into the front bumper up absorber is set, the target load to the hinge type impactor is set based on the set amount of penetration, and the size of the notch is determined based on the set target load. The technique can determine the size of the notch relatively accurately.

10 bumper, 12 front bumper cover, 12a grille, 14 front bumper up absorber, 14a notch, 16 bumper infoce, 18 front bumper lower absorber, 20 hinge type impactor, 22 upper member, 24 lower member, 26 hinge part.

Claims (1)

It is a design method of the front bumper up absorber that has a notch in the upper part on the front side of the vehicle.
The target angle of the hinge portion is set based on the target elongation amount of the hinge portion when colliding with the hinge type impactor having the hinge portion.
Based on the set target angle, the amount of penetration of the hinge type impactor into the front bumper up absorber is set.
A target load on the hinge type impactor is set based on the set intrusion amount, and the target load is set.
The size of the notch is determined based on the set target load.
How to design the front bumper up absorber.

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