Lightweight rear bumper beam

Abstract

The present invention relates to a bumper beam, which comprises: a first end portion and a second end portion; a center beam, which is adjacent to the first end portion and the second end portion and is oriented between the first end portion and the second end portion, wherein the center beam comprises a front face and a back face; wherein the center beam has a center section and end sections at opposite ends of the center section, the end sections are respectively adjacent to the end portions, the center beam comprises horizontal and vertical ribs, the horizontal and vertical ribs extend from the front face and the back face and / or extend between the front face and the back face, and the bumper beam is made of a plastic material.

Description

Technical Field

[0001] The present invention relates to a lightweight rear bumper beam and a vehicle comprising such a lightweight rear bumper beam. Background Art

[0002] Bumper beams, especially rear bumper beams, are part of every automobile that protects against low-speed vehicle collisions. Such bumper beam assemblies are designed so that they absorb most of the energy during a collision. The rear bumper beam typically extends transversely across the rear end of a motor vehicle.

[0003] Conventional bumpers are made of metal due to the high rigidity of metal. These bumpers are typically manufactured by assembling multiple metal parts to form a bumper beam. However, due to recent regulations and increased fuel efficiency, there has been a recent focus on reducing the weight of vehicles while maintaining reduced damage to the vehicle in low-speed collisions. In the event of a low-speed collision, an energy absorbing assembly can be used in the bumper and can absorb the collision energy so as to reduce vehicle damage. Injection molded thermoplastic beams both reduce weight and reduce the number of parts. Thermoplastic beam solutions are already available for rear beams, as described in international patent documents WO2018 / 109211 and WO2017 / 021856, but the novel features proposed in this application will likely make the beam 25% lighter than existing thermoplastic beams and 40% lighter than steel beams while meeting performance requirements. Summary of the invention

[0004] According to the present invention, there is provided a bumper beam, comprising:

[0005] - a first end portion and a second end portion;

[0006] - a central beam adjacent to the first end portion and the second end portion and oriented between the first end portion and the second end portion, wherein the central beam comprises a front face and a back face;

[0007] wherein the center beam has a center section and end sections at opposite ends of the center section, the end sections being adjacent to the end portions, respectively,

[0008] The central beam includes horizontal and vertical ribs extending from and / or between the front and rear faces,

[0009] The bumper beam is manufactured from a plastic material.

[0010] Different performance requirements for vehicles are set by organizations including the U.S. Department of Transportation's National Highway Traffic Safety Administration (NHTSA), the Insurance Institute for Highway Safety (IIHS), the Research Council for Vehicle Repair (R-CAR), and the Economic Commission for Europe (ECE). Regulations governing low-speed damage requirements for vehicles vary around the world. For example, in Europe and the Pacific, a vehicle must meet ECE-R42 and R-CAR standards on both its front and rear. In the United States, vehicles must pass other deformable barrier impact tests, such as those set by NHTSA and IIHS.

[0011] To verify the structural performance of any rear bumper beam, a test is performed in which the rear of the vehicle impacts a fixed 7-inch diameter upright at its mid-axis at a speed of 4 km / h (kilometers per hour). The bumper beam is designed so that the penetration of the impactor is limited to a minimum of 10-15 mm that the bumper beam remains spaced from the rear panel of the body-in-white (BIW) after the impact, but at the same time absorbs the maximum amount of energy.

[0012] Multiple testing agencies and associations in Europe, Asia, and South America use the Research Council for Repair of Automobiles ("R-CAR" herein) test procedure, which specifies that the front and rear bumper systems of a vehicle meet specific criteria under standard test conditions. The purpose of R-CAR's evaluation of bumper performance is to encourage manufacturers to design bumper systems that meet various goals, including systems that protect vehicle corners and have appropriate energy absorption under low-speed impacts. The R-CAR test causes the bumper components to impact a solid obstacle at a specified speed and seeks non-destructive bending of the bumper beam while preventing damage to the lower side of the vehicle. In addition, the bumper system may be subject to Economic Commission for Europe Regulation No. 42 ("ECE-R42"), which stipulates that the safety system of the vehicle should continue to operate normally after the vehicle is hit by a pendulum or moving obstacle at a specific speed at a specific location of the bumper assembly under simulated collisions. It has been found that in order to meet the R-CAR and ECE-R42 standards, it may be desirable for the rear beam to have high rigidity at the corners and high rigidity at the center.

[0013] The first end portion and the second end portion may each include a crash can. To understand the features of the beam, the design of the beam can be broken down into two main features, the crash boxes at the ends for corner impact and R-CAR bumper testing and the beam connecting the crash boxes for center impact in ECE-R42. A bumper system including the beam of the present invention can conform to desired space constraints while meeting ECE-R42 and / or R-CAR standards and specifications.

[0014] Bumper systems including the beam of the present invention can meet R-CAR, including, for example, low speed damage insurance tests, such as R-CAR Section 0031 and / or ECE-R42 standards, such as low speed damage regulations ECE-R42 Section 0031. In an embodiment, a bumper system including a beam of the present invention can absorb a corner impact of 2.5 kilometers per hour (kph) when connected to a vehicle weighing 500 to 2000 kilograms (kg), such as 900 to 1600 kg, and an inward bulge of less than or equal to 140 millimeters (mm), wherein inward bulge refers to the amount of the beam protruding into the passenger compartment of the vehicle. The beam of the present invention can have higher rigidity than conventional beams and can have lower inward bulge levels. In an embodiment, a bumper system including a beam of the present invention can absorb a 4 kph center pendulum impact when connected to a vehicle weighing 500 to 2000 kg, such as 900 to 1600 kg, and an inward bulge of less than or equal to 140 mm. In an embodiment, a bumper system including the beam of the present invention is capable of absorbing a 4 kph outboard impact when connected to a vehicle weighing 500 to 2000 kg (eg, 900 to 1600 kg) and having an inward bulge of less than or equal to 140 mm.

[0015] The present invention introduces novel design features for rear bumper beams (also called cross members) for automobiles and their manufacture. Lightweight automotive components are a major requirement of automobile manufacturers, who are constantly pushing the limits in design and engineering to obtain the lightest possible design without compromising performance and style. The main function of the rear bumper beam is to reduce the low-speed damageability of the automobile. Traditional steel solutions are not only bulky, but also consist of multiple parts, thereby increasing the number of parts and installation complexity. Several injection moldable thermoplastic material solutions can also be used for the rear bumper beam. In the present invention, we propose three unique design features for the rear beam, thereby obtaining design freedom for the injection molding process to obtain a lighter beam with the same or better performance.

[0016] In the present invention, we have addressed the requirements of the ECE-R42 pendulum impact on beams. One of the most critical requirements for the ECE-R42 (or GB17354) standard is the center pendulum impact. In a center pendulum impact, the beam is struck at the center by a relatively rigid pendulum at a speed of 4km / hr. For the ECE-R42 standard, the center of the pendulum bumper should be at a height of 458mm (or 18 inches) from the ground, and for GB 17354, it should be at a height of 445mm from the ground. The height of the center of the pendulum relative to the ground is called the ground clearance.

[0017] The first idea is to improve the bumper beam design to improve the crash performance. For a center pendulum impact, the beam area is the key area responsible for transferring the load to the fixed position. For a center pendulum impact, the area on the beam that contributes to the rigidity is the center section of the center beam. A center pendulum impact forms a load path from the front of the center section of the center beam to the back of the end section of the center beam, such as Figure 1 For a beam design of constant cross-section, there is sufficient material in the center of the beam, but relatively little material is available at the ends.

[0018] Variable cross-section of beam: used to place the maximum amount of material in the load transfer area. This can be improved by flipping the sections at the ends so that the cross section of the beam at the ends is a mirror image of the cross section of the beam at the center. The cross section of the center section can be reversed relative to the cross section of the corresponding end section so that a load transfer path is created along the center beam from the center section through the end section to the end section.

[0019] The front face of the center section may include a first base from which a plurality of horizontal ribs extend toward the back face of the center section, thereby forming one or more cavities at the back face of the center section, wherein the back face of each end section includes a second base from which a plurality of horizontal ribs extend toward the front face of the end section, thereby forming one or more cavities at the front face of the end section, and the first base and the second base are connected by diagonally oriented ribs. Moreover, the cross-section of the center beam is formed into two U-shapes connected with vertical flanges at adjacent legs.

[0020] Variable height of the beam: used to maintain a thicker section with a lower height in the center, thereby avoiding local bending and thus optimizing the use of material for maximum rigidity of the beam. The height of the center section can be smaller relative to the height of the end sections and / or end portions, so that the first side edge of the center portion is offset relative to the second side edge of the adjacent end section and / or end portion, thereby generating an offset distance between the respective side edges. The first side edge of the center portion and the second side edge of the end section and / or end portion form a pair of side edges, and the offset distances between the opposite pair of side edges are equal or different. In other words, the distance between the opposite second side edges of the center section at the center axis of the bumper beam is smaller than the distance between the opposite first side edges of the end sections and / or end portions. The first and second side edges can form a single smooth side edge of the center beam and / or bumper beam.

[0021] The height of the beam will be greatest near the ends, while in the center it should have maximum overlap with the pendulum. The height of the beam in the center does not need to be greater than the height of the striker. However, we also need to consider the manufacturability of the beam when determining the height of the beam. The height of the beam can be varied gradually from a maximum at the ends to an optimum value in the center (for maximum overlap) to maintain tangency to the horizontal plane for smooth stress flow. This also allows us to move material out of the load transfer path without complicating the injection molding tool. Figure 3 and 4 shows an example of how the beam height should vary. When the beam is centered on the impactor, Figure 4 As shown in , the beam will be primarily in bending mode and the rectangular ribs will be sufficient for good bending stiffness. However, when the beam is not centered on the impactor, as in Figure 5 As shown in , due to the offset (eccentricity), the beam will also experience a torsional moment, and the regular rectangular ribs have very low stiffness for carrying the torsional moment. Figure 5 The same result can be observed in the deformed shape of the center beam.

[0022] Adding cross (slanted or diagonal) ribs: Used to increase the torsional rigidity of the beam in situations where the overlap between the impactor and the beam is small (due to the aggressive styling of the bumper fascia). For this situation, the slanted or cross ribs towards the ends of the beam can significantly increase the torsional rigidity.

[0023] Diagonally oriented ribs or cross ribs may be provided in at least a portion of the center beam, with the diagonally oriented ribs extending between the vertical and / or horizontal ribs. The angle between the longitudinal axis of the bumper beam and the diagonally oriented ribs may be greater than 0 degrees and less than 90 degrees, preferably between 20 degrees and 70 degrees, more preferably between 30 degrees and 60 degrees, most preferably between 40 degrees and 50 degrees, or any combination thereof. Preferably, the diagonally oriented ribs are provided at least in the end sections of the center beam.

[0024] The above-mentioned measures of changing the cross section of the central beam, changing the height of the central beam in the longitudinal direction and adding cross ribs to a portion of the central beam have been used to design an embodiment of the beam according to the present invention. For a central pendulum impact, the design and deformation of the beam are as follows Figure 6 as shown in .

[0025] In addition to the above embodiments, we also propose novel techniques for solving potential problems of manufacturability of such beams using an injection molding process. These techniques include efficient design of injection molding tools and minor changes in part geometry to improve manufacturability. A lightweight rear beam (or cross member) for an automobile is designed to meet low speed damage standards (European ECE-R42 and Chinese GB17354).

[0026] The beam should be rigid enough to transfer the load from the impactor in the limited design space (inward bulge) and at the same time it should have minimum mass in order to keep the vehicle lightweight. These two requirements are inherently contradictory and present a significant challenge in designing the beam. On the other hand, the injection molding process offers design freedom superior to conventional metal forming. The proposed unique and novel design features (material independent) not only make the beam lighter than existing designs but also reduce the low speed damage of the vehicle. The load versus inward bulge performance of the new design is compared with a baseline design and it shows that ( Figure 7 The load bearing capacity is increased by 20%, the inward bulge level is reduced by 10%, and / or the mass is reduced by 10%. The present invention enables the design of a rear beam design with high crashworthiness for vehicles with limited design space.

[0027] The invention also relates to a vehicle comprising a bumper beam according to any one of the preceding claims.

[0028] Furthermore, the present invention also relates to a method for manufacturing a bumper beam as described above, the method comprising:

[0029] - injection molding the plastic material into the mold;

[0030] - Use baffles and coolant to provide local cooling of the injection molded material.

[0031] The method may further include adding one or more mold inserts to the mold prior to injecting the plastic material, wherein the mold insert has a higher thermal conductivity than the mold.

[0032] The beam or part may include multiple ribs and deep pockets or cavities on both sides. However, the beam does not require slides or lifters. Therefore, in order to determine the most logical orientation of the part (determine the fixed side and the movable side of the part in the mold), the geometric surface area that shrinks into the mold is calculated to determine which side will shrink more strongly on the mold. This side is set as the movable side. A sequential gating method is proposed to ensure that no critical weld lines appear inside the beam portion of the part. Starting from the center will ensure that the center beam portion is properly filled, even with a reduced beam height.

[0033] The beam or part may include many deep and narrow pockets or cavities. The material around such deep and narrow pockets is generally difficult to cool inside the injection molded part. This is especially true when dealing with relatively large and thick walls that are connected together or intersect, which is the case with the beam of the present invention. The time taken to produce a single part (cycle time) will generally depend on the cooling time of the single part. Therefore, when producing large quantities of such parts, efficient cooling will play a big role. Taking away heat from the depths of the pockets will be a major consideration in reducing cycle time. Longer cooling times increase the risk of longer cycle times, thereby increasing the manufacturing cost of the part and / or reducing product quality (due to the introduction of uncontrolled shrinkage, voids, uncontrolled warping and / or larger sink marks).

[0034] The following adjustments can be used to address potential manufacturing issues with bumper beams according to the present invention.

[0035] Local strong cooling

[0036] By using protruding cooling channels and equipping them with baffles and coolant, the heat removal efficiency of the cooling system can be improved in pockets that are difficult to cool. This solution can be applied to every pocket along the height, where the pockets alternate along the length. It can also be used in critical areas. The principle is Figure 8 This approach can set a lower limit on the cavity size so that standard mold components can still be used and there is enough molding material "skin" around the cooling channels.

[0037] Offset of the center base plane

[0038] By moving the central base plane or base towards the inside of the U-shape (i.e. the U-shape can be offset to form an H-shape or similar), the cross-section of the central beam can be cooled more efficiently. This reduces the depth of the pocket or cavity, thereby reducing the amount of heat that needs to be removed from the pocket. This Fig. 9 Indicated in.

[0039] Reduce the transverse rib height

[0040] The top edge of the transverse or vertical ribs inside the U-shape may not be mechanically loaded. Forming a cutout at the top of the rib, i.e. at the edge of the rib opposite the base, such as a semicircular cutout extending from the edge towards the base, will effectively reduce the depth of the pocket or cavity, thereby bringing the greater cooling capacity closer to the deepest part of the pocket. This is Fig.10 Indicated in.

[0041] High thermal conductivity mold inserts

[0042] While standard injection molding molds can be made of steel or other suitable materials, mold inserts with high thermal conductivity can be used in certain strategic locations. Higher thermal conductivity will effectively carry away heat faster. This strategy can also be applied to manufacturing the bumper beam of the present application, especially when there is no room for strong local cooling, such as due to hot runner drops or ejectors blocking potential cooling channels from entering the cavity.

[0043] Unless otherwise stated herein, any reference to a standard, regulation, test method, etc. (eg, RCAR and ECE-R42) refers to the standard, regulation, guide, or method in effect at the time this application was filed.

Claims

1. A bumper beam, comprising: - a first end portion and a second end portion; - a central beam adjacent to the first end portion and the second end portion and oriented between the first end portion and the second end portion, wherein the central beam comprises a front face and a back face; wherein the central beam has a central section and end sections at opposite ends of the central section, the end sections being adjacent to the first end portion and the second end portion, respectively, The central beam includes horizontal ribs and vertical ribs extending from and / or between the front and rear faces, The bumper beam is made of plastic material, The cross section of the center beam is formed into two U-shaped shapes connected with vertical flanges at adjacent legs. the cross section of the central beam at the end sections being a mirror image of the cross section of the central beam at the central section, the cross section of the central section being inverted relative to the cross section of the corresponding end section so that a load transfer path is created along the central beam from the central section through the end sections to the first end portion and the second end portion, A distance between opposite side edges of the U-shape of the center section at a center axis of the bumper beam is smaller than a distance between opposite side edges of the U-shape of the end sections.

2. The bumper beam according to claim 1, wherein: The height of the center segment is smaller relative to the height of the end segments such that a first side edge of the center segment is offset relative to a second side edge of an adjacent end segment, thereby creating an offset distance between the respective side edges.

3. The bumper beam according to claim 2, wherein: The first side edge of the central section and the second side edge of the end section form a pair of side edges, and the offset distances between the opposite pair of side edges are equal or different.

4. The bumper beam according to any one of claims 1 to 3, wherein: A distance between opposing first side edges of the center section at a center axis of the bumper beam is smaller than a distance between opposing second side edges of the end sections.

5. The bumper beam according to claim 4, wherein: The first side edge and the second side edge form a single smooth side edge of the center beam.

6. The bumper beam according to any one of claims 1 to 3, wherein: The first end portion and the second end portion each include a crash can.

7. The bumper beam according to claim 1, wherein: Diagonally oriented ribs are provided in at least a portion of the central beam, the diagonally oriented ribs extending between the vertical ribs and / or the horizontal ribs.

8. The bumper beam according to claim 7, wherein: An angle between the longitudinal axis of the bumper beam and the diagonally oriented rib is greater than 0 degrees and less than 90 degrees.

9. The bumper beam according to claim 7 or 8, wherein: The diagonally oriented ribs are provided at least in the end sections of the central beam.

10. The bumper beam according to any one of claims 1 to 3, wherein: The front face of the center segment includes a first base, and a plurality of horizontal ribs extend from the first base toward the back face of the center segment to form one or more cavities at the back face of the center segment, wherein the back face of each end segment includes a second base, and a plurality of horizontal ribs extend from the second base toward the front face of the end segment to form one or more cavities at the front face of the end segment, and the first base and the second base are connected by diagonally oriented ribs.

11. The bumper beam according to claim 8, wherein: The angle between the longitudinal axis of the bumper beam and the diagonally oriented rib is between 20 degrees and 70 degrees.

12. The bumper beam according to claim 8, wherein: The angle between the longitudinal axis of the bumper beam and the diagonally oriented rib is between 30 degrees and 60 degrees.

13. The bumper beam according to claim 8, wherein: The angle between the longitudinal axis of the bumper beam and the diagonally oriented rib is between 40 degrees and 50 degrees.

14. A vehicle comprising a bumper beam according to any one of claims 1-13.

15. A method of manufacturing a bumper beam according to any one of claims 1 to 13, the method comprising: - injection molding the plastic material into the mold; - Use baffles and coolant to provide local cooling of the injection molded material.

16. The method according to claim 15, further comprising: One or more mold inserts are added to the mold prior to injecting the plastic material, wherein the mold insert has a higher thermal conductivity than the mold.

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