Lightweight cowl crossbar and its manufacturing method

Abstract

To provide a manufacturing method of a lightweight cowl crossbar offering stable rigidity, and a lightweight cowl crossbar.SOLUTION: A manufacturing method of a lightweight cowl crossbar includes the steps of: producing an inner pipe; winding a composite material around the inner pipe so as to accumulate plural winding layers; and pushing an outer pipe to an upper layer of the winding layers. The mutually adjacent composite materials on the plural winding layers are wound in mutually different directions.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a lightweight cowl crossbar and a manufacturing method thereof, and more particularly to a lightweight cowl crossbar made of a plastic material, having reduced weight and a connecting relationship for ensuring sufficient rigidity, and a manufacturing method thereof. [Background technology]

[0002] Generally, the body of an automobile is composed of side frames arranged on both sides and several cross beams that connect the side frames laterally. Among these, the cowl cross beam is a structure that is arranged laterally on the passenger compartment side behind the cowl panel to provide rigidity to the front of the vehicle body. The cowl cross beam supports the steering column and has a rigidity sufficient to absorb engine vibrations transmitted from the steering column. A pair of support legs that support the cowl cross beam are connected to the lower central portion of the cowl cross beam. The support legs serve to disperse vibrations from the steering device to the lower portion of the vehicle body. The support legs are provided with connecting bars to increase the lateral rigidity of the support legs.

[0003] Both sides of the cowl cross beam are provided with side fastening parts for connection to the side frames. In addition, the cowl cross beam is provided with various brackets for mounting an instrument panel, an air conditioning duct, an audio device, a fuse box, an airbag, etc. The support legs, side fastening parts, and various brackets connected to the cowl cross beam are produced by pressing, extrusion, casting, etc., and then connected to the cowl cross beam by welding. However, in response to the supply of autonomous vehicles, the structure of the cowl cross bar is required to be changed according to the shape of the front slim cockpit of the vehicle, and in the case of conventional internal combustion engine vehicles, there was a problem that the weight was increased due to the structure of the aluminum cowl cross bar, which deteriorated the fuel efficiency of the vehicle. Therefore, there has been an increasing demand for lightweight cowl cross bars recently. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Korean Patent Publication No. 10-2006-0005787 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a cowl crossbar made of lightweight plastic and having stable rigidity, and a method for manufacturing a cowl crossbar that includes multiple winding layers, thereby reducing weight. [Means for solving the problem]

[0006] The manufacturing method of the lightweight cowl crossbar according to the present invention includes the steps of manufacturing an inner pipe, winding a composite material on the inner pipe to stack a plurality of winding layers, and extruding an outer pipe onto the upper layer of the winding layers, and is characterized in that adjacent composite materials of the plurality of winding layers are wound in different directions from each other.

[0007] The manufacturing step of the inner pipe may further include the steps of extruding the inner pipe by an extrusion die, and cooling the extruded inner pipe.

[0008] The step of manufacturing the outer pipe further includes the steps of extruding the outer pipe onto the upper surface of the winding layer using an extrusion die, and cooling the extruded outer pipe.

[0009] The winding layer is characterized in that it consists of four different winding layers.

[0010] The winding layer is characterized in that it further includes a step of stacking a first winding layer located on the inner pipe and formed along a first direction, and a step of stacking a second winding layer located on the first winding layer and configured along a second direction having a predetermined angle with the first direction.

[0011] The winding layer is characterized in that it further includes a step of laminating a third winding layer configured to have the same direction as the first direction on the second winding layer, and a step of laminating a fourth winding layer configured to have the same direction as the second direction on the third winding layer.

[0012] The method further includes a step of performing drawing after the multiple winding layers are stacked in the step of winding the composite material on the inner pipe to stack the multiple winding layers.

[0013] In the step of winding a composite material around the inner pipe to form a plurality of winding layers, the composite material constituting the winding layers is characterized by being made of a combination of polypropylene and a single-oriented fiber composite material.

[0014] The lightweight cowl cross bar according to the present invention includes a first cowl cross beam located on a side frame arranged on one side of the vehicle body, and a second cowl cross beam fastened to overlap at least a portion of the first cowl cross beam and fixed to a side frame arranged on the other side of the vehicle body, and is characterized in that it is composed of an inner pipe located inside the first cowl cross beam or the second cowl cross beam, a winding layer formed along the outer surface of the inner pipe, and an outer pipe located on the upper surface of the winding layer.

[0015] The winding layer is characterized by being made of a single-oriented fiber composite material.

[0016] The winding layer is characterized by being made of at least two or more unidirectional fibers having different angles from each other.

[0017] The outer pipe of the second cowl cross beam is configured to have a sawtooth shape, and the inner circumferential surface of the first cowl cross beam includes a shape corresponding to the sawtooth shape.

[0018] At least a portion of the outer surface of the first cowl cross beam is characterized by including a flat area. Effect of the Invention

[0019] According to the present invention, the following effects can be obtained from the embodiments. Since the cowl crossbar is made of a plastic material, it can be made lighter. In addition, since the cowl crossbar is made of a plastic material and has a winding layer made of multiple layers to increase its rigidity, it can provide sufficient rigidity performance. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a configuration diagram of a lightweight cowl cross bar according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of a first cowl cross beam according to the present invention. [Diagram 3] FIG. 4 is an explanatory diagram showing a method of forming a winding layer of the first cowl cross beam according to the present invention. [Figure 4] FIG. 2 is a side cross-sectional view of a second cowl cross beam according to the present invention. [Diagram 5] FIG. 2 is a side cross-sectional view of a pull block portion according to the present invention. [Figure 6] FIG. 2 is a configuration diagram of a manufacturing device for a lightweight cowl cross bar according to the present invention. [Figure 7] 4 is a flow chart of a method for manufacturing a lightweight cowl cross bar in accordance with the present invention. [Figure 8] 4 is a flow chart of a method for manufacturing a four-layer winding according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The embodiment may be modified in various forms and is not limited to the following embodiment. In addition, terms such as "... part" and "... beam" described in the specification indicate a unit that processes one function or operation. Components are classified as "first", "second", etc., based on the front of the vehicle when the components have the same configuration, and the order is not necessarily limited to that. In addition, this embodiment does not limit the number of cowl cross beams.

[0022] The cowl crossbar 100 of the present invention is made by combining polypropylene and glass fiber (GF), includes at least two or more mold frames, and is integrally formed into the cowl crossbar 100 by plastic injection molding. The winding layer 112 surrounding the outside of the inner pipe 111 is made by combining polypropylene (PP) and a single-oriented fiber composite material (glass fiber), is configured to form at least two or more layers, and is configured to be surrounded by the outer pipe 113. Hereinafter, the composite material means the continuous fiber that constitutes the winding layer of the winding layer.

[0023] In FIG. 1, the cowl cross bar 100 includes a first cowl cross beam 110a and a second cowl cross beam 110b that cross both sides of the vehicle body and have both ends connected to the side frame 300, and includes a side fastening portion 150 configured to be coupled to the first cowl cross beam 110a, the second cowl cross beam 110b, and the side frame 300. The first cowl cross beam 110a and the second cowl cross beam 110b include support legs 120 at their central portions that are configured to be supported by the vehicle body. More preferably, the support legs 120 are located on the second cowl cross beam 110b, and the support legs 120 are configured to be fastened to the first cowl cross beam 110a integrally with the second cowl cross beam 110b. The shape of the support legs 120 can be changed according to the shape of the vehicle cockpit.

[0024] In one embodiment of the present invention, as the cowl cross bar 100 applied to a vehicle using a slim cockpit, the support leg 120 located at the center of the cowl cross beam is configured to have a certain curvature and to be fixed to the body of the vehicle. The shape of the support leg 120 including the curvature can be applied to a vehicle including a cockpit applied to the vehicle or a walk-through shape between the driver's seat and the passenger seat. The cowl cross bar 100 of the present invention is configured by integral injection molding of a plastic material, and is manufactured by dividing into a first cowl cross beam 110a and a second cowl cross beam 110b, and the second cowl cross beam 110b is fastened and fixed so as to overlap at least a part of the first cowl cross beam 110a. More preferably, the cowl cross bar 100 is configured by molding a resin in which polypropylene and glass fiber are mixed.

[0025] The first cowl cross beam 110a is composed of an inner pipe 111, a winding layer 112, and an outer pipe 113, and is configured so that a single-oriented fiber composite material forms at least one layer on the upper part of the inner pipe 111. At least a part of the surface of the outer pipe 113 is configured in a flat state, but is configured so that a side fastening part 150 and a steering column fastening part 140, which are fastened to the first cowl cross beam 110a made of polypropylene (PP), can be bolted and fixed.

[0026] The first cowl cross beam 110a includes a side fastening portion 150 to be fastened to the side frame 300 of the vehicle body. The side fastening portion 150 is configured to be fastened to one end of the first cowl cross beam 110a, and is fastened and fixed to an insert cap formed inside the hollow when the first cowl cross beam 110a is extruded. The first cowl cross beam 110a includes a steering column fastening portion 140 fastened to a flat surface of the first cowl cross beam 110a. The steering column fastening portion 140 is fixed to a flat surface located on the upper surface of the first cowl cross beam 110a, and the outermost corner is composed of a steel bracket 141. The second cowl cross beam 110b is configured to have an outer diameter smaller than the outer diameter of the inner pipe 111 of the first cowl cross beam 110a, and is configured so that at least a portion of the second cowl cross beam 110b can be retracted and fixed inside the first cowl cross beam 110a based on the drawing block portion 130.

[0027] More preferably, at least a portion of the support leg 120 located at one end of the second cowl cross beam 110b is configured to be retracted and fixed to the first cowl cross beam 110a simultaneously with the second cowl cross beam 110b. One end of the second cowl cross beam 110b retracted into the inside of the first cowl cross beam 110a is configured with a gear structure 114 and can be inserted into the inside of the first cowl cross beam 110a, and more preferably, at least a portion of the support leg 120 is formed by the gear structure 114 of the second cowl cross beam 110b and configured to be retracted into the inside of the first cowl cross beam 110a.

[0028] One surface of the support leg 120 includes a hollow portion 121, which is configured to absorb the impact when an occupant comes into contact with the hollow portion 121 due to an impact generated on the vehicle. Furthermore, the pull-out block portion 130 located adjacent to the support leg 120 includes an absorbing member 131 capable of absorbing an impact, which is made of foam (Expanded Polypropylene: EPP) and is configured to absorb an impact applied to the cowl cross bar 100. The support leg 120 includes an upper end portion fastened to the second cowl cross beam 110b and a lower end portion fastened to the underside of the vehicle body. The lower end portion is fixed via at least one fastening groove located at the upper end portion.

[0029] In one embodiment of the present invention, the fastening groove is composed of an upper end fastening groove and a lower end fastening groove, and is configured so that the support rigidity of the lower end fastening groove is lower than that of the upper end fastening groove in response to a vertical impact. Therefore, in response to a vertical impact applied to the cowl crossbar 100 and the support leg 120, the lower end fastening groove breaks first, and then the upper end fastening groove breaks, releasing the fastening between the upper end and the lower end. In this way, the support leg 120 is configured to absorb the impact applied in the vertical direction of the cowl crossbar 100.

[0030] In addition, in one embodiment of the present invention, the support leg 120, the steering column fastening part 140, and the side fastening part 150, which can be formed by insert injection molding, can be formed on the outer pipe 113. Also, the support leg 120, the steering column fastening part 140, and the side fastening part 150 can include a steel bracket as a reinforcing member, which is configured to perform the functions of absorbing impact and preventing breakage. That is, in one embodiment of the present invention, the outer pipe 113 is configured so that at least a portion of the lower structure of the cowl crossbar can be molded by insert injection molding.

[0031] Fig. 2 shows a cross-sectional view of a first cowl cross beam 110a as an embodiment of the present invention, and Fig. 3 shows a manufacturing method of the first cowl cross beam 110a, which is constructed by a winding layer made of three composite materials forming a winding layer 112. The first cowl cross beam 110a is constructed by sequentially stacking an inner pipe 111, a winding layer 112, and an outer pipe 113 to be hollow. That is, the inner pipe 111 is constructed to have a hollow circular cross section, and includes at least one winding layer 112 made of a single-oriented fiber composite material wound around the outer side of the inner pipe 111. More preferably, the single-oriented fiber composite material of the present invention is made of a thermoplastic composite material (Continuous fiber thermoplastic, CFT).

[0032] In one embodiment of the present invention, the winding layer 112 is made of three composite materials, with the first winding layer 112a wound at a 45 degree angle with respect to the initial inner pipe 111. The first winding layer 112a is made of two layers of single-oriented fibers. After this, the second winding layer 112b is configured to be positioned at a 90 degree angle with the first winding layer wound first, and the second winding layer 112b is made of two layers of single-oriented fibers. The third winding layer 112c is wound on the top surface of the second winding layer 112b at the same angle as the first winding layer 112a. The composite materials are configured to have a thickness of 0.25T each. In another embodiment of the present invention, the winding layer 112 can be configured to include six composite material layers.

[0033] After each composite material is wound, a heat flattening operation is performed on the wound winding layer 112, and more preferably, after at least two composite materials are wound, the heat flattening operation is performed. The outer pipe 113 is extruded after the winding layer 112 is formed, and is made of a polypropylene and glass fiber composite. More preferably, the inner pipe 111 and the outer pipe 113 are extruded from the same material.

[0034] 2, at least a portion of the outer pipe 113 is configured to include a flat surface, and more preferably, the cross-sectional area of ​​the outer pipe 113 may be located including a protruding region having vertices of different thicknesses. Therefore, the support legs 120, the steering column fastening portion 140, the side fastening portion 150, etc. are bolted to the flat surface of the first cowl cross beam 110a located between the different vertices.

[0035] 4 shows a cross section of the second cowl cross beam 110b as an embodiment of the present invention, which includes four winding layers on the upper surface of the inner pipe 111, and is formed by injection molding the outer pipe 113 on the upper surface of the winding layer 112. Furthermore, when the outer cover material is injected by the extrusion die 610 to form the outer pipe 113, the shape of the outer pipe 113 is determined by the extrusion die 610. In one embodiment of the present invention, the outer pipe 113 is extruded to form a gear structure including a plurality of protrusions on the outer side of the second cowl cross beam 110b, which is extruded on the inner peripheral surface of the inner pipe 111 of the first cowl cross beam 110a so as to be drawn into and fixed inside the first cowl cross beam 110a. That is, the shape of the inner surface of the inner pipe 111 of the first cowl cross beam 110a is determined according to the shape of the extrusion die, and the shape of the outer surface of the outer pipe 113 of the second cowl cross beam 110b is determined, but the first cowl cross beam 110a and the second cowl cross beam 110b can be fastened together and fixed so that they do not rotate relative to each other.

[0036] 5, the first cowl cross beam 110a and the second cowl cross beam 110b are configured to be at least partially overlapped. More preferably, the gear structure 114 located at the outermost corner of the second cowl cross beam 110b is configured integrally with the support leg 120, and the second cowl cross beam 110b including the gear structure 114 and a portion of the support leg 120 are configured to be inserted and fixed inside the first cowl cross beam 110a.

[0037] More preferably, the outer pipe of the second cowl cross beam 110b is configured to have a sawtooth shape, and the inner peripheral surface of the first cowl cross beam 110a is configured to include a shape corresponding to the sawtooth shape, but the outer pipe of the second cowl cross beam 110b is configured to be inserted and fixed onto the inner peripheral surface of the first cowl cross beam 110a. Furthermore, the outer pipe of the cowl cross beam is configured to have a sawtooth shape, but the structure fastened to the outer surface of the outer pipe by insert injection molding is located in the sawtooth shape. Therefore, the structure fastened to the cowl cross beam by insert injection molding can be prevented from rotating due to impact.

[0038] The pull-out block unit 130 is configured to surround the outer pipe 113 of the first cowl cross beam 110a in an area where the first cowl cross beam 110a and the second cowl cross beam 110b overlap. The pull-out block unit 130 is configured to surround the first cowl cross beam 110a and the second cowl cross beam 110b, and is configured to simultaneously surround at least a portion of the support leg 120 located on the second cowl cross beam 110b. One side of the support leg 120 may include a hollow portion 121, and may include a hollow shape located on the pull-out block unit 130 corresponding to the hollow portion 121, and one side of the pull-out block unit 130 includes an absorbing member 131 configured to cushion an impact.

[0039] The absorbing member 131 may be located at one end of the pull-out block 130 facing the inside of the vehicle, and functions to absorb an impact applied in the vehicle cabin through the absorbing member 131 together with the hollow portion 121 and a hollow shape corresponding to the hollow portion 121 for impact absorption. More preferably, the pull-out block 130 is configured to surround at least a part of the upper end of the support leg 120, and the lower end of the support leg 120 facing the pull-out block 130 may include an ejection break portion, and the first applied impact is absorbed through the hollow portion 121, and when a predetermined amount of impact or more is applied to the cowl cross bar 100, the ejection break portion of the support leg 120 breaks. As described above, the present invention includes a plurality of impact absorbing structures and configurations to absorb an impact applied to a position where the first cowl cross beam 110a and the second cowl cross beam 110b face each other.

[0040] 6 shows a schematic diagram of a manufacturing apparatus for forming a lightweight cowl crossbar 100 as one embodiment of the present invention. As shown in the figure, the apparatus includes an inner pipe extrusion die 410 for injection molding an initial inner pipe 111. A resin in which polypropylene and 50% glass fiber are mixed as the physical properties constituting the inner pipe 111 is injected into one end of the inner pipe extrusion die 410. The extruded inner pipe 111 undergoes a step of cooling by a cooling die 420, and then moves to a take-up machine 510 so that the glass fiber is wound around the inner pipe 111.

[0041] In the take-off machine 510, the first winding layer 112a is wound on the inner pipe 111 so as to have a 45 degree inclination (first direction) with respect to the initial inner pipe 111. The first winding layer 112a is made of two layers of single-oriented fibers. After this, the second winding layer 112b is configured to be positioned so as to form a 90 degree angle (second direction) with the first wound first winding layer 112a, and the second winding layer 112b is made of two layers of single-oriented fibers. The third winding layer 112c is wound on the top surface of the second winding layer 112b so as to have the same angle as the first winding layer 112a. Additionally, the fourth winding layer 112d is wound so as to have the same angle as the second winding layer 112a.

[0042] As described above, in one embodiment of the present invention, the winding layer 112 is formed by stacking four layers of composite material using the puller 510, and after each winding layer (a layer in which each composite material is stacked), the puller 520 is configured to flatten the uneven sections of the winding layer 112 and increase the adhesive strength. More preferably, at least one puller 510 is configured so that the composite material is stacked in a direction (first direction or second direction) corresponding to each layer. In this way, the present invention makes it possible to set the angle at which each winding layer is formed depending on the position and angle of the puller 510.

[0043] After the winding layer 112 is laminated on the upper surface of the inner pipe 111, it is moved to an extrusion die 610 for the outer pipe 113 so that the outer pipe 113 is extruded onto the upper surface of the winding layer 112, and then moved to a cooling die 620 for the outer pipe 113 to cool the extruded outer pipe 113.

[0044] In this way, the first cowl cross beam 110a and the second cowl cross beam 110b of the present invention are composed of the inner pipe 111, the winding layer 112 and the outer pipe 113, and are configured so that the outer peripheral surface of the extruded outer pipe 113 can be changed by varying the shape of the extrusion die 610 for the outer pipe 113. More preferably, in one embodiment of the present invention, the outer peripheral surface of the second cowl cross beam 110b is configured so that the outer pipe 113 is extruded to have a gear structure 114.

[0045] FIG. 7 shows a flow chart of a method for manufacturing the lightweight cowl crossbar 100 as an embodiment of the present invention. According to the method for manufacturing the lightweight cowl crossbar 100 as an embodiment of the present invention, a step of injecting a resin into the inner pipe extrusion die 410 so as to extrude the inner pipe is included (S100). The inner pipe 111 thus extruded is cooled by the cooling die 420 (S200). To form the winding layer 112 on the cooled inner pipe 111, glass fiber is wound as a composite material by the take-up machine 510 (S300). In one embodiment of the present invention, four winding layers are formed, and the formed winding layer 112 includes first to fourth winding layers.

[0046] Furthermore, after each winding layer is laminated, the surface of the layer is flattened by the drawing machine 520 (S400). After the winding layer 112 is laminated, the outer pipe 113 is configured to surround the upper surface of the winding layer 112 by the extrusion die 610 of the outer pipe 113 (S500). Then, a step of cooling the outer pipe is performed (S600), and the outer pipe 113 is post-processed so that the support leg 120, the drawing block portion 130, the steering column fastening portion 140, etc. are fastened to the cowl cross beam (S700).

[0047] More preferably, the outer pipe 113 can be processed so that the surface facing the support leg 120, the pull-out block portion 130 and the steering column fastening portion 140 forms a parallel surface, and is configured to include bolt holes etc. so that the support leg 120, the pull-out block portion 130 and the steering column fastening portion 140 are fixed to the cowl cross beam.

[0048] FIG. 8 is a flow chart showing steps of forming a winding layer 112 as an embodiment of the present invention. In an embodiment of the present invention, when stacking four winding layers, the first winding layer is configured to be wound around the inner pipe 111 at a predetermined angle in a first direction based on the width of the cowl crossbar 100 (S310). More preferably, in an embodiment of the present invention, the first direction is configured at an angle of 45 degrees based on the width direction of the cowl crossbar 100. After the first winding layer is wound, the first winding layer is flattened by a drawing machine 520, and a winding layer is laminated on the flattened first winding layer in a second direction. More preferably, the second direction can be set at an angle of -90 degrees based on the first direction (S320).

[0049] After the second winding layer is laminated, the upper surface of the second winding layer is flattened by the drawing machine 520, and the third winding layer is laminated on the upper surface of the second winding layer in the same direction as the first direction (S330). After the third winding layer is laminated, a drawing operation is performed, and the fourth winding layer is laminated on the upper surface of the third winding layer (S340).

[0050] In another embodiment of the present invention, the directions of the composite materials forming the first winding layer to the fourth winding layer may all be different, and in yet another embodiment of the present invention, at least two winding layers may be wound in the same direction.

[0051] The above detailed description is illustrative of the present invention. Moreover, the above description is a preferred embodiment of the present invention, and the present invention can be used in various other combinations, modifications, and environments. The examples are intended to explain the best mode for realizing the technical idea of ​​the present invention, and various modifications required for specific application fields and uses are possible. Therefore, the detailed description of the present invention does not limit the present invention. [Explanation of symbols]

[0052] 100 Cowl crossbar 110a First cowl cross beam 111 Inner pipe 112 Winding layer 112a 1st winding layer 112b 2nd Winding Layer 112c 3rd winding layer 113 Outer Pipe 114 Gear Structure 110b 2nd cowl cross beam 120 Support Leg 121 Hollow part 130 Pull-out block part 131 Absorbing material 140 Steering column fastening 141 Steel bracket 150 Side fastening section 300 Side Frame 410 Inner Pipe Extrusion Die 420 Inner pipe cooling mould 510 Pick-up Machine 520 Puller 610 Outer pipe extrusion die 620 Outer pipe cooling mold

Claims

1. Fabricating an inner pipe; A step of stacking a winding layer consisting of a plurality of winding layers in which a composite material is wound on the inner pipe; and extruding an outer pipe having a sawtooth shape on the upper layer of the winding layer. A method for manufacturing a lightweight cowl crossbar, characterized in that adjacent composite materials of the winding layers are wound in different directions.

2. In the step of manufacturing the inner pipe, extruding the inner pipe through an extrusion die; The method of claim 1, further comprising the step of: cooling the extruded inner pipe.

3. In the step of manufacturing the outer pipe, extruding the outer pipe onto the upper surface of the winding layer by an extrusion die; The method of claim 1, further comprising the step of: cooling the extruded outer pipe.

4. The method of claim 1, wherein the winding layer comprises two or more different winding layers.

5. The winding layer is laminating a first winding layer located on the inner pipe and formed along a first direction; 5. The method of claim 4, further comprising the step of laminating a second winding layer on the first winding layer, the second winding layer being configured along a second direction having a predetermined angle with the first direction.

6. The winding layer is laminating a third winding layer on the second winding layer; The method of claim 5, further comprising the step of: laminating a fourth winding layer on the third winding layer.

7. In a step of stacking a winding layer consisting of a plurality of winding layers in which a composite material is wound around the inner pipe, The method of claim 1, further comprising the step of: drawing after the plurality of winding layers are laminated.

8. In a step of stacking a winding layer consisting of a plurality of winding layers in which a composite material is wound around the inner pipe, 2. The method of claim 1, wherein the composite material constituting the winding layer is a combination of polypropylene and a single-oriented fiber composite material.

9. An inner pipe located inside the cowl cross beam; A winding layer formed along an outer surface of the inner pipe; and an outer pipe located on the upper surface of the winding layer, 1. A lightweight cowl crossbar, wherein the outer pipe is configured to have a sawtooth shape.

10. 10. The lightweight cowl crossbar of claim 9, wherein said winding layer is made of a uni-oriented fiber composite material.

11. 10. The lightweight cowl crossbar of claim 9, wherein the winding layer is made of at least two or more uni-oriented fibers having different angles from each other.

Images