JP4343588B2 - Door beam - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a door beam that is mounted inside a door of a vehicle such as an automobile to reinforce the door and protects an occupant in the event of a collision from the side.
[0002]
[Prior art]
In a vehicle such as an automobile, a door beam that reinforces the door itself is generally installed inside the door in order to prevent the intrusion of the door into the passenger compartment caused by a collision from the side and protect the passenger. Yes. The door beam as the vehicle reinforcing member is required to satisfy a desired quality standard, that is, strength and durability, and to be lightweight and low cost from the viewpoint of improving fuel efficiency.
[0003]
FIG. 6 is a view showing a door beam mounting state. A door beam 51 is mounted in a substantially central portion of the inside of the door 50 in parallel with the ground, and the door 50 enters the inside of the vehicle in response to a collision from the side of the vehicle. Is preventing. For example, as shown in FIG. 7, the door beam 51 has a beam portion 52 having a circular cross section using a flat strip made of a high-strength steel plate in order to reduce weight and cost. At the same time, mounting bracket portions 53 and 54 for the doors 50 at both ends of the beam portion 52 are press-molded integrally with the beam portion 52.
[0004]
The beam portion 52 is press-formed with a circular cross section, and the abutting portion 55 is not welded and is mounted toward the indoor side. Here, when the beam portion 52 is formed, the outer edge portions of the arm portions 56 and 57 are also in a state of being abutted with each other in the same manner as the abutting portion 55 of the beam portion 52. It is growing. The inner edge 59 of the notch 58 in the unfolded state gradually opens outward from the end of the beam section 52 having a circular cross section in the molded state to form a cross-sectional shape transition portion 60. The end portions of both arms 56 and 57 are mounting bracket portions 53 and 54 extending on the same plane.
[0005]
In this door beam 51, since the beam portion 52 is formed in a circular cross section, a compressive force is applied in the circumferential direction, and plastic deformation occurs due to the compressive force over the entire plate thickness, and the plate surface portion and the plate inner surface portion. The difference in tensile residual stress generated between and the absolute value decreases. Thereby, the occurrence of delayed fracture due to the tensile residual stress of the beam portion 52 can be prevented.
[0006]
On the other hand, the cross-sectional shape transition portion 60 between the beam portion 52 and the mounting bracket portion 53 has a flange shape in which the inner edge 59 of the notch 58 rises toward the outside of the passenger compartment, so that the load is actually applied from outside the passenger compartment. , A compressive load is applied in the vicinity of the inner edge 59, and no load in the direction of tearing the inner edge 59 is received. Therefore, the notch 58 can be enlarged, processing becomes easy, and complicated tensile residual stress is not generated, so that delayed fracture can be prevented and the length of the cross-sectional shape transition portion 60 can be reduced. Since the beam portion 52 can be lengthened as much as possible, the reliability is further improved (see, for example, Patent Document 1).
[0007]
[Patent Document 1]
JP-A-10-109537 (3rd and 4th pages, FIGS. 1 to 4)
[0008]
[Problems to be solved by the invention]
However, in order to form the beam section 52 having a circular cross section from the band plate, as shown in FIG. 8, the preliminary bending step (a) for the next step of bending the band plate into a U-shaped cross section, the diameter of the beam portion 52 is set. Molding step (b) with a mold 61 composed of the formed upper mold 62 and lower mold 63, and then molding into a substantially circular cross section with a gap S formed between the upper mold 62 and the lower mold 63. The molding step (c) and the molding step (d) for compressing the gap S and closing the upper die 62 and the lower die 63 are required.
[0009]
As is well known, not only high-tensile steel, but also when pressing a steel sheet, the surface hardness of the material increases due to work hardening as the number of forming steps increases. Therefore, an excessive stress may be generated on the surface of the material to induce micro cracks. In this case, it is difficult from the viewpoint of moldability to use a strip having a tensile strength of 100 MPa or more, that is, a so-called super high tensile material. Under such circumstances, not only in terms of quality, but also in combination with an increase in the number of processes, the mold life also decreases, leading to an increase in cost, which is not preferable.
[0010]
In addition, the beam section 52 having a circular cross section has a high section modulus and is advantageous to bending load, but stress concentration may occur at the joint between the beam section 52 and the mounting bracket section 53, particularly at the notch 58. This is not preferable from the viewpoint of the balance of the strength of the door beam 51 as a whole. Furthermore, since the beam portion 52 has a circular cross section, it is difficult to appropriately respond to a predetermined specification, and the die must be changed greatly for each specification. Therefore, although there is little impact in small-variety and mass-production, a large variety of small-volume production requires preparation of many molds, and the number of setup changes increases the cost of the product, greatly reducing costs. It became a factor to inhibit.
[0011]
The present invention has been made in view of such circumstances, and substantially reduces the work hardening of the material by making the molding process substantially a single process, and appropriately responds to various specifications without significant changes in the molding die. The purpose of the present invention is to provide a door beam that can be reduced in weight and cost.
[0012]
[Means for Solving the Problems]
In order to achieve such an object, the invention according to claim 1 of the present invention is a door beam that is mounted inside a door of a vehicle to reinforce the door and protects an occupant in the event of a collision from the side. , A beam portion formed integrally by pressing a steel plate and having a substantially U-shaped cross section, and flat mounting bracket portions extending at both ends in the longitudinal direction of the beam portion. The rib portion is formed on both sides of the beam portion in the width direction, and the central portion in the longitudinal direction of the rib portion is capable of plate thickness in a single molding step than the flat surface of the mounting bracket portion via the connecting portion. Rutotomoni formed into a flat surface having a slightly higher level difference degree, the connecting portion is formed with a large radius of curvature connecting the step.
[0013]
In this way, a beam portion formed integrally by pressing a steel plate and having a substantially U-shaped cross section, and a flat mounting bracket portion extending at both ends in the longitudinal direction of the beam portion, The rib portion is formed on both sides of the beam portion in the width direction, and the central portion of the rib portion in the longitudinal direction is capable of being formed in a single molding step than the flat surface of the mounting bracket portion via the connecting portion. it is formed into a flat surface having a slightly high step with a thickness of about Rutotomoni, since the connecting portion is formed with a large radius of curvature connecting step, can be set to a simple shape, substantially the molding process A single process can be achieved, and work hardening of the material can be suppressed. Therefore, it is possible to minimize the surface cracks by minimizing the load on the strip material due to press working, and the reliability is improved by improving the quality, and the predetermined cross-sectional height is increased. Within this range, the height of the beam portion can be set to the maximum, the section modulus can be increased, and the strength can be effectively increased against bending loads. In addition, along with the improvement of formability, high-tensile steel such as super high-tensile material can be used without difficulty, and coupled with the reduction in the number of processes, the mold life is improved, contributing to further cost reduction. be able to.
[0015]
In the invention according to claim 2 , since the concave groove extending in the longitudinal direction is formed in the mounting bracket portion, the strength of the mounting bracket portion can be increased with a simple configuration.
[0016]
According to a third aspect of the present invention, the cross section of the beam portion is composed of an arc portion having a predetermined radius of curvature and a tapered portion that gradually expands from the arc portion to the skirt portion. The stress can be easily set by adjusting the height of the beam portion. Therefore, it is possible to appropriately cope with various specifications without significant change of the molding die.
[0017]
In the invention according to claim 4 , since the cross section of the beam portion is formed with a flat portion at the bottom thereof, the height of the cross section can be suppressed while maintaining the section modulus.
[0018]
Further, as in the invention described in claim 5 , if the cross section of the beam portion is formed with a ridge at the center portion in the width direction of the bottom portion, the height of the cross section can be suppressed without reducing the strength. Can do.
[0019]
In the invention described in claim 6 , since the slightly bent portion is formed at the edge of the rib portion, it is possible to improve the bending strength and torsion strength of the beam portion with a simple configuration. it can.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a front view showing an embodiment of a door beam according to the present invention, FIG. 2 is a plan view, and FIG. 3 is a side view of FIG.
[0021]
The door beam 1 is made of a high-strength steel plate (JIS standard, SAPH1180), and the beam portion 2 at the center in the longitudinal direction and the mounting bracket portions 3 and 3 at both ends of the beam portion 2 are integrated. The mounting bracket portions 3 and 3 are fixed to the front end portion and the rear end portion of the door, respectively, in parallel with the ground at a substantially central portion inside the door (not shown).
[0022]
The beam portion 2 has a substantially U-shape including a circular arc portion 2a whose cross-sectional shape has a predetermined radius of curvature and a tapered portion 2b that spreads from the circular arc portion 2a to the skirt, and is formed in the width direction. The rib parts 4 and 4 are provided on both sides. The width dimension of the beam part 2 including these rib parts 4 and 4 is smaller than the width dimension of the mounting bracket parts 3 and 3 and is set in a range of 50 to 70% (see FIG. 3). Here, since the beam part 2 is provided with the rib parts 4 and 4, it can raise not only bending strength but torsional strength with respect to the collision from the side surface of a vehicle. Further, as shown in FIG. 2, the rib portions 4, 4 are slightly higher than the flat surfaces of the mounting bracket portions 3, 3 through the connecting portions 5, 5 having a large curvature radius R. A step (e) is formed. Therefore, the substantially U-shaped beam portion 2 is deepest at the center portion, gradually becomes shallower from the connecting portions 5 and 5, and converges to the flat mounting bracket portions 3 and 3. By forming into such a shape, the height h of the beam part 2 can be set to the maximum (H≈h) within the range of the predetermined cross-sectional height H, and the cross-section coefficient is increased, and the bending load is increased. Strength can be increased effectively.
[0023]
On the other hand, as shown in FIG. 1, the mounting bracket portions 3 and 3 extend in the longitudinal direction from the rib portion 4 of the beam portion 2 via the connecting portions 5 and 5 and extend on the same plane. Further, the edge portions 3a, 3a in the width direction are smoothly formed with a plurality of arcs having a predetermined radius of curvature so as to gradually increase from the edge portions 4a, 4a of the rib portions 4 , 4 . The mounting bracket portions 3 and 3 are integrally formed with concave grooves 6 and 6 extending in the longitudinal direction in order to increase the section modulus and increase the strength against bending load. Thereby, the intensity | strength of the attachment bracket parts 3 and 3 can be raised with a simple structure. The outer surfaces of the bottoms of the concave grooves 6 and 6 are set to be substantially flush with the rib parts 4 and 4.
[0024]
In this embodiment, the strip material made of high-strength steel plate is set to a simple shape that minimizes the load caused by pressing, so it can be set to a simple shape, and the forming process is substantially single. It can be processed and the work hardening of a raw material can be suppressed. Therefore, it is possible to minimize the load on the strip material due to the press work and suppress the micro cracks on the surface due to the press process as much as possible, and the reliability is further improved by improving the quality. In addition, along with the improvement of formability, high-tensile steel such as super high-tensile material can be used without difficulty, and coupled with the reduction in the number of processes, the mold life is improved, contributing to further cost reduction. be able to.
[0025]
FIG. 4 is a cross-sectional view showing another embodiment of the beam portion of the door beam according to the present invention. In addition, the same code | symbol is attached | subjected to the same site | part as embodiment mentioned above, and the duplicate description is abbreviate | omitted.
[0026]
FIG. 4A shows a flat bottom portion 7a of the beam portion 7 having a U-shaped cross section, in which the cross section height is suppressed while maintaining the cross section coefficient. (B) is a modification of (a), in which the bottom 8a of the beam portion 8 having a U-shaped cross section is formed flat, and the protrusion 9 is formed at the center in the width direction to maintain the section modulus. Thus, the height of the cross section is suppressed. (C) forms the beam part 10 in the U shape close | similar to a cross-sectional rectangle, and improves the manufacturability of a metal mold | die. The beam portion 11 shown in (d) is basically the same as that of the above-described embodiment, but the bent portions 12a and 12a are formed by slightly projecting the edges of the rib portions 12 and 12, and bending is performed. Strength and torsional strength are improved. The edges 12a and 12a may be bent in the opposite direction.
[0027]
As a result of the FEM analysis of the door beam carried out by the present applicant, it is possible to obtain a bending load / displacement curve equivalent to that of a conventional door beam having a circular beam section as shown in the bending load / displacement curve shown in FIG. understood. Here, as the setting conditions of the FEM analysis, the yield point of the material strip is 1180 MPa, the cross section is symmetrical in the width direction, and a predetermined bending load is applied to the beam portion with the back surface of the mounting bracket portion restrained. did.
[0028]
The door beam 1 according to the present invention is mounted such that the convex portion of the beam portion 2 is on the outside of the vehicle, so that the central portion in the longitudinal direction of the beam portion 2 is compressive stress and the back surface of the mounting bracket portion 3 is tensile stress. However, as a result of FEM analysis, it was found that the stress of the beam portion 2 and the mounting bracket portion 3 is reduced by increasing the height h of the beam portion 2. Further, in the embodiment described above, the stress of the beam portion 2 is reduced by about 32% in the embodiment shown in FIG. 4B compared to the embodiment shown in FIGS. In the embodiment shown, equivalent results were obtained. On the other hand, the stress of the mounting bracket portion 3 is increased by approximately 28% in the embodiment shown in FIG. 4B compared to the embodiment shown in FIGS. 1 to 3, and is substantially reduced in the embodiment shown in FIG. Decreased by 45%. Moreover, it turned out that forming a bending part in the edge part 3a of the attachment bracket part 3 will increase a tensile stress on the contrary, and is unpreferable.
[0029]
Therefore, in the door beam according to the present invention, the stress can be easily set by adjusting the height of the beam portion 2, and the shapes of the stresses of the beam portion 2 and the mounting bracket portion 3 are crafted. By doing so, it is possible to easily set a predetermined stress, and it is possible to cope with various specifications by a simple shape change. In other words, it is possible to appropriately cope with various specifications without significant change of the molding die, and it is possible to provide a door beam that is reduced in weight and cost.
[0030]
The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.
[0031]
【The invention's effect】
As described above in detail, the door beam according to the present invention reinforces the door by being mounted inside the door of the vehicle, and presses the steel plate in the door beam for protecting the occupant in the event of a collision from the side. A beam portion that is integrally formed by processing and has a substantially U-shaped cross section, and flat mounting bracket portions that extend at both ends in the longitudinal direction of the beam portion, the width of the beam portion A rib portion is formed on both sides in the direction, and the central portion in the longitudinal direction of the rib portion is slightly higher than the flat surface of the mounting bracket portion through the connecting portion, which is slightly higher than the plate thickness that is possible in a single molding process. is formed into a flat surface having a Rutotomoni, since the connecting portion is formed with a large radius of curvature connecting the step can be set to a simple shape, substantially single step the molding process Can suppress the work hardening of the material It is possible. Therefore, it is possible to minimize the load on the strip material due to the press work and suppress the micro cracks on the surface due to the press work as much as possible. Within the range of the section height, the height of the beam portion can be set to the maximum, the section modulus can be increased, and the strength can be effectively increased against the bending load. In addition, along with the improvement of formability, high-tensile steel such as super high-tensile material can be used without difficulty, and coupled with the reduction in the number of processes, the mold life is improved, contributing to further cost reduction. be able to.
[Brief description of the drawings]
FIG. 1 is a front view showing an embodiment of a door beam according to the present invention.
FIG. 2 is a plan view of the above.
FIG. 3 is a side view of FIG.
FIG. 4A is a cross-sectional view showing another embodiment of the beam portion of the door beam according to the present invention.
(B) is a cross-sectional view showing a modification as above.
(C) is a cross-sectional view showing still another embodiment.
(D) is a cross-sectional view showing still another embodiment.
FIG. 5 is a bending load / displacement diagram of the door beam according to the present invention and a conventional product by FEM analysis.
FIG. 6 is a view showing a door beam attached state.
FIG. 7 is an external perspective view showing a conventional door beam.
FIG. 8 is an explanatory view showing a forming process of a beam portion in a conventional door beam.
[Explanation of symbols]
1 ···················· Door beam 2, 7, 8, 10, 11 ·············· Beam portion 2a ...・ ・ ・ ・ Arc part 2b ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Tapered part 3 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Mounting bracket parts 3a, 4a ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Ring 4, 12 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Rib 5 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ Connecting part 6 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Concave groove 6 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Concave groove 7a, 8a ・ ・ ・ ・········· Bottom 9 ·······································································・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Door 51 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Door Beams 52, 52 ′ ・ ・ ・ ・ ・ ・ ・ ・··········································································.・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Arm 58 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Notch 59 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Inner edge Section 60 ··········· Cross-sectional shape transition portion 61 ························································· ············ Upper die 63, 63 '············· Lower die F ·········· cross section height R ····················· curvature radius e・ ・ ・ ・ ・ Step h ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Beam height δ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Displacement

Claims (6)

In the door beam that is installed inside the door of the vehicle to reinforce the door and protect the occupant in the event of a collision from the side,
A beam portion formed integrally by pressing a steel plate and having a substantially U-shaped cross section; and a flat mounting bracket portion extending at both ends in the longitudinal direction of the beam portion, Rib portions are formed on both sides in the width direction of the beam portion, and the central portion in the longitudinal direction of the rib portion is about a plate thickness that is possible in a single molding process than the flat surface of the mounting bracket portion via the connecting portion . Rutotomoni formed into a flat surface having a slightly high step, door beam, wherein the connecting portion is characterized in that it consists of a large radius of curvature connecting said step.   The door beam according to claim 1, wherein a concave groove extending in a longitudinal direction is formed in the mounting bracket portion.   The door beam according to claim 1 or 2, wherein a cross section of the beam portion includes an arc portion having a predetermined radius of curvature and a tapered portion that gradually expands from the arc portion toward the skirt portion.   The door beam according to claim 1 or 2, wherein a cross section of the beam portion is formed with a flat portion at a bottom thereof.   3. The door beam according to claim 1, wherein a cross section of the beam portion is formed with a ridge at a center portion in a width direction of a bottom portion thereof.   The door beam according to any one of claims 1 to 5, wherein a bent portion that slightly protrudes is formed at an edge of the rib portion.

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