KR20150061048A - Titanium bicycle frame, method of fabricating the titanium bicycle frame - Google Patents

Abstract

The present invention relates to a titanium bicycle frame which ensures rigidity using a light structure and a method for fabricating the same. The titanium bicycle frame includes a titanium tube, a stay, and a titanium lug integrated with a plurality of connection tubes to be connected to the titanium tube and the stay. Filler metal shaped into an amorphous foil is inserted into and brazed to a contact surface where the titanium tube or the stay is connected to the titanium lug.

Description

Title: METHOD OF MANUFACTURING TITANIUM BICYCLE FRAME, METHOD OF MANUFACTURING THE TITANIUM BICYCLE FRAME

The present invention relates to a method of manufacturing a titanium bicycle frame and a titanium bicycle frame, and more particularly to a titanium bicycle frame and a method of manufacturing a titanium bicycle frame implemented by diffusion brazing members.

A bicycle frame is an important component of a bicycle, placing the relative positions of wheels and handles appropriately while supporting the user's weight. Generally, the bicycle frame is formed in a diamond shape in which two triangular structures are combined as viewed from the side, and its shape can be changed by a design element or a functional element.

Fig. 1 is a side view illustrating a configuration of a general bicycle frame 1. Fig.

1, a triangular frame of a front half portion provided on a front wheel portion around a seat portion is composed of a seat tube 11, a top tube 12, and a down tube 13, The head tube 14 is seated so that the steering apparatus fog can be installed at a portion where the steering shaft 13 meets. In the rear half portion where the rear wheel portion is provided, the seat stay 15 and the chain stay 16 are connected to each other around the seat tube 11 to form a triangle shape. The vertex portion where the seat stay 15, the down tube 13, and the chain stay 16 meet is called a bottom bracket 17, and a pedal for driving is provided at this portion.

The tubes 11, 12 and 13, the stays 15 and 16, the brackets 17 and the like, which are members of the bicycle frame 1, are assembled according to their respective positions, By welding the surfaces, one body, i.e., the bicycle frame 1, is formed. Since the welding method adopts the local heating method for bonding the members constituting the bicycle frame 1, defects such as welding impurities are introduced into the joint parts, defects such as welding defects remain in the joint parts, And the stiffness of the stiffener is deteriorated. Therefore, the manufacture of the bicycle frame 1 by such a coupling technique requires considerable technical know-how and excellent functionality, making it difficult to ensure uniformity in quality. In addition, since the conventional joining technique is a joining technique in which the base material and the filler material are melted by the local heating and then they are solidified and joined to the base material, thermal stress is inevitably generated to cause deformation such as twisting of the bicycle frame 1, Thereby forming a residual stress in the form of tensile stress at each of the engaging portions of the bicycle frame 1. Therefore, in the case of the bicycle frame (1) combined with the local heating method such as welding, the joint portion and its neighboring portions are frequently damaged due to the vibration and repeated load of the bicycle generated during the actual operation.

Particularly, when the bicycle frame 1 is formed using a titanium alloy material, since the titanium alloys react with oxygen and the like in the atmosphere very easily at high temperature to easily form impurities, it is not easy to form the bonding by a general welding method, Gas and shielding tools are required, and many technical efforts and functions are required to prevent defects in the welds.

In addition, welding must be performed in a state in which the various tubes 11, 12 and 13, the stays 15 and 16, the bracket 17 and the like are formed with a special angle formed by design. In particular, the bottom bracket 17, Part 4 shows a configuration in which one tube is concentrated, so that overlapping of the joints occurs, so that a process sequence for preventing welding defects must be established and welding is intermittently made, thereby forming a form of mass production Is difficult.

Since a great load is applied to the parts of the bicycle frame 1 to which the various tubes 11, 12 and 13, the stays 15 and 16 and the bracket 17 are interconnected when viewed from a functional standpoint, These parts must be constructed to withstand high loads. In the case of a general bicycle frame (1), since one tube must be formed with the same thickness, the center portion of the tube with relatively low load is often made unnecessarily thick for the purpose of maintaining the rigidity of the joint portion. The lightweight and high-strength materials such as the above-described lightweight materials are difficult to achieve.

In recent years, there have been known techniques for realizing weight reduction of a bicycle frame by intensively reinforcing a high-load portion by reinforcing the cross-sectional thickness and shape of a bicycle tube by developing process technologies such as hydroforming, hot bulge forming, and butt processing However, it is very difficult to produce tubes for bicycle frames by using the above-described processes in the case of materials having such a high-cost process technology as titanium and having poor plastic-forming performance such as titanium. Therefore, It is technically very difficult to realize the weight reduction of the bicycle frame by the optimum design construction.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of manufacturing a titanium bicycle frame and a titanium bicycle frame, which are designed to solve the above-mentioned problems and which realize weight reduction of a structure while maintaining rigidity and suppress thermal deformation and thermal stress due to local heating of a joint portion to provide. These and other objects of the present invention are presented by way of example, and the present invention is not limited thereto.

In the titanium bicycle frame proposed in the present invention, a seat lug, a head lug, a bottom bracket lug, a dropout lug, or the like having a connecting tube that can be connected to tubes and stays, respectively, When assembling the bicycle frame assembly with the top tube, the seat tube, the down tube, the seat stay, and the chain stays together, the amorphous brazing filler metal in the form of a foil is preliminarily inserted into the coupling surface thereof, And is then integrated by diffusion brazing.

Titanium bike frame assembly for diffusion brazing The rigidity of the titanium bicycle frame assembly is realized by selecting the material of the lug part which should endure under the higher load than the material of the tubes and stays as the high strength titanium alloy material.

The step of integrating by diffusion brazing involves placing the bicycle frame assembly in a furnace under an inert atmosphere such as vacuum or Ar and brazing it under the same temperature conditions to complete the bicycle frame.

According to the embodiment of the present invention as described above, the local deformation of the joined body due to the local thermal stress is suppressed, and the tensile residual stress is not generated in the coupled portion, thereby suppressing the promotion of fatigue fracture. Further, titanium alloy lugs of high strength material having appropriate thickness are provided in the lug portion constituting the high-load portion to secure the rigidity corresponding to the high-load portion, and the tubes and stays as the middle portion are made of a titanium alloy material having a small thickness, The rigidity of the bicycle frame structure can be ensured and the weight of the structure can be realized.

1 is a side view illustrating a configuration of a general bicycle frame.
2 is a flowchart illustrating a method of manufacturing a titanium bicycle frame according to an embodiment of the present invention.
3 is an exploded perspective view of an assembly of a titanium bicycle frame according to an embodiment of the present invention.
4 is an assembled perspective view of a completed body of a titanium bicycle frame according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user.

2 is a flowchart illustrating a method of manufacturing a bicycle frame according to an embodiment of the present invention. Referring to FIG. 2, a method of manufacturing a bicycle frame according to an exemplary embodiment of the present invention includes providing tubes, stays, and lugs (S10), supplying amorphous foil filler metal to a connection portion of the assembly of the bicycle frame (S30) of inserting an amorphous foil filler metal between the tubes and / or stays and the lug flow and connecting them together to form a bicycle frame assembly (S30) A step (S40) of charging the furnace after being mounted on a jig system (S40), and a step (S50) of forming a finished body of a bicycle frame by heating the assembly of the bicycle frame to a brazing junction temperature. These steps are described in detail below.

FIG. 3 is an exploded perspective view of an assembly 100 of a bicycle frame according to an embodiment of the present invention, and FIG. 4 is an assembled perspective view of a finished body 100a of a bicycle frame according to an embodiment of the present invention.

Referring to FIGS. 3 and 4, the bicycle frame according to the embodiment of the present invention may have, for example, a diamond-shaped frame. Specifically, the triangular frame of the front half portion provided on the front wheel portion around the seat portion is constituted by the seat tube 111, the top tube 112, and the down tube 113, and the rear half, And the chain stay 116 is connected to the seat stay 115 to form a triangle shape.

Further, the seat lug 132 has the shape of a structure in which a plurality of connecting pipes each connected to the seat tube 111, the top tube 112, and the seat stay 115 are integrated. The seat lug 132 may further include a connection pipe formed so that the seat portion can be installed. The head lug 134 has the shape of a structure in which a plurality of connection tubes each connected to the top tube 112 and the down tube 113 are integrated. The head lug 134 may further include a connection pipe formed at a portion where the top tube 112 and the down tube 113 meet so that the steering fog can be installed. The bottom bracket lug 136 has the shape of a structure in which a plurality of connecting pipes each connected to the seat tube 111, the down tube 113, and the chain stay 116 are integrated. The dropout lug 138 has the shape of a structure in which a plurality of connecting pipes respectively connected to the seat stay 115 and the chain stay 116 are integrated.

In order to construct the bicycle frame according to the present invention, the lugs 132, 134, 136, 138 including two or more assembling parts and the tubes 111, 112, 113 or stays Currents 115 and 116 are prepared in the form of respective parts.

In this embodiment, the lugs 132, 134, 136 and 138 are formed by precisely casting a Ti-6Al-4V titanium alloy and then the inner diameters of the lugs 132, 134, 136, The tubes 111, 112 and 113 and the stays 115 and 116 were prepared by extruding Ti-3Al-2.5 V seamless pipes were prepared by plastic working such as cutting and banding according to the length and shape. However, unlike the present embodiment, the outer diameter of the lugs 132, 134, 136, and 138 can be designed to be coupled with the inner diameters of the tubes 111, 112, and 113 and / or the stays 115 and 116, It can be utilized without any problem in continuing the steps of the invention. In another modified embodiment, the inner and outer diameters of the lugs 132, 134, 136, and 138 are equal to the inner and outer diameters of the tubes 111, 112, 113 and the stays 115, May be designed.

The prepared parts are assembled to each position after being cleaned. At this time, an amorphous brazing foil having a thickness of 40 to 80 mu m is inserted into the yarn of the assembly overlapping portion. In this embodiment, the assembled ply chip was assembled so that it could be maintained at 15 mm.

In addition to the amorphous foil as the brazing filler metal, powder, paste, or crystalline ribbon may be used. However, in the case of powder or paste filler metal, excessive filler supply may cause degradation of strength due to erosion of the brazing joint portion and removal of residual filler metal It gives difficulties. In addition, in the case of the filler metal of the crystalline foil, problems such as deformation or breakage during assembly often occur, which tends to make the structure of a smooth assembly difficult, which limits its use in the present invention.

The titanium diffusion brazing filler metal is selected from the group consisting of Zr-17.2Ti-24Ni, Zr-14.2Ti-12.6Ni-6.8Cu, Ti-37.5Zr-15Cu-10Ni, Ti-37.5Zr-25Cu, Ti-20Zr-20Cu- -25Zr-50Cu, Ti-15Cu-25Ni, and the like. However, the material constituting the titanium brazing filler metal is not limited thereto and may be composed of various other materials capable of diffusion brazing of titanium.

In order to form the bicycle frame assembly 100a according to the present invention, the bicycle frame assembly 100a is heated to a brazing joint temperature under a vacuum or an inert atmosphere, and is then cooled to room temperature.

When the bike frame assembly 100 is put in a vacuum furnace (300 in FIG. 7) and then heated to a brazing joint temperature in a vacuum or an inert atmosphere and maintained for a predetermined period of time, the material 130 constituting the lug flow, The brazing filler metal 120 interposed between the materials 110 constituting the flow is diffused in both directions and the material 130 constituting the lug flow is bonded to the material 110 constituting the tubes and the stays . The brazing junction temperature is higher than the liquidus temperature of the filler metal 120 but lower than the beta transus temperature of the parent material 110,

In order to optimize the rigidity of the titanium bicycle frame according to the present invention, the high-load parts are reinforced with lugs and joined together by a pipe-like structure commonly referred to as a tube and a stay, and their joint surfaces are joined by a brazing method It is a different part from the general titanium bike frame produced by the welding process.

Titanium and its alloys undergo a phase transformation process called high-temperature transformation accompanied by rapid microstructure change at high temperature and rapid volume change due to change of crystal structure. If the brazing process is performed at a temperature higher than the transformation temperature, a sudden volume change due to the two rounds of transformation occurring in the heating process and the cooling process is applied to the bicycle frame, so that the bike frame is easily deformed. Changes in microstructure will be induced. Generally, Ti-3Al-2.5V titanium alloys used in bicycle frames are formed at 935 ℃ and it is very important to perform brazing before this temperature. If the brazing is performed at a high temperature even at the temperature before the transformation, the softening of the material may be intensified to cause the deformation of the bicycle frame during brazing. To prevent this, the shape of the brazing jig becomes complicated, .

In addition, when the brazing temperature is low, the change in the length of the bicycle frame due to the thermal expansion and heat shrinkage accompanying the brazing cycle is small, and the rigidity of the material is relatively high, so that a high quality bicycle frame can be manufactured by the brazing method without using a complicated form jig .

However, the brazing method proposed in the present invention is basically a method in which the brazing filler metal supplied for brazing is melted and supplied to the brazing joint surface, and finally the mutual bonding between the parts is progressed by the melt diffusion bonding, Should be carried out at a temperature sufficiently high to permit melting.

Therefore, in view of the process flow of the present invention, the brazing should be performed at a temperature not lower than the melting point of the filler metal and below the temperature of the biaxial frame material, and may be performed at 800 ° C to 950 ° C, Preferably 800 [deg.] C to 870 [deg.] C. In addition, considering the fluidity of the brazing filler metal and the high temperature stiffness of the bicycle frame material, it is most preferable to braze at 800 ° C to 830 ° C.

According to the present invention, the assembly 100 of the bicycle frame comprises a combined titanium bike frame finished body 100a (see FIG. 1) which is formed by lapping lugs supporting the high-load region, tubes and stays connecting the lugs, Is formed. By supplying the joints of different materials and thickness to the high-load area and the low-load area through the above-described joint construction method, a lightweight titanium bicycle frame can be provided even under the same rigidity structure compared to a frame manufactured by welding a single- .

In the present invention, since the entire bicycle frame is heated up to the same temperature, it is applied to the brazing method in which cooling is performed. Therefore, the tensile residual stress of the joint portion, which may appear in the frame manufactured by the local heating method such as welding, The possibility of occurrence of fatigue fracture due to cyclic loading is significantly reduced.

In addition, according to the present invention, the brazing preparation process such as assembling the bicycle frame, supplying the filler metal, assembling the brazing jig and the bicycle frame can be carried out very simply, and the quality of the final product can be improved by designing the bicycle frame, The quality of the welded joint frame is reduced compared with the welded joint frame in which the quality varies due to the skill of the welding technique and the degree of functioning and the plurality of bicycle frame assemblies 100 are charged at a time It can be said that it is advantageous for mass production because it can be brazed.

Further, in the present invention, since the brazing filler metal is inserted into all the joint portions of the lug, the tube, and the stator, or the brazing filler metal is applied to the bracket filler metal, the entire assembly is inserted into the furnace, The bicycle frame thus completed can be provided.

100: Assembly of the bicycle frame 100a: Finished body of the bicycle frame
111: sheet tube 112: top tube
113: down tube 115: seat stay
116: chain stay 132: seat lug
134: head lug 136: bottom bracket lug
138: Dropout lug 200: Brazing jig

Claims (4)

And a titanium alloy lug having a titanium alloy tube and a stay and a plurality of connecting tubes connected to the tube or stay, wherein the titanium alloy tube or the stay has a brazing filler metal on a contact surface to which the titanium alloy lug is connected, Bonded brazed, titanium bike frame by inserting. The titanium bicycle frame according to claim 1, wherein the titanium lug is made of a titanium alloy material having a higher strength than the titanium tube and the stay. Providing a titanium tube and a stay; providing a titanium lug having a structure in which a plurality of connection tubes are integrated to be connected to the titanium tube or the stay; providing a brazing filler metal to the connection portion of the titanium lug, Connecting the titanium lug to the titanium tube and the stay to form a titanium bicycle frame assembly; charging the titanium electric frame assembly into a furnace; and placing the titanium bicycle frame assembly in a vacuum Or heating the brazing metal under an inert atmosphere to diffuse the filler metal so that the titanium lug and the titanium tube and stay are joined to form a titanium bicycle frame finished body. 4. The method of claim 3, wherein the step of supplying the filler metal to the connecting portion of the titanium lug and the titanium tube and the stay is performed by supplying filler metal in the form of amorphous foil having a thickness of 40 to 80 占 퐉.

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