JPS6124682A - Manufacture of head section of car body of bicycle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a bicycle head section comprising a bicycle head pipe and a pipe (for example, a main pipe) connected thereto.

(Prior Art) Fig. 9 shows a conventional method of manufacturing a head part by butt welding, in which the butt end surface 8 of the main pipe 2 with respect to the head pipe 1 is curved along the side surface of the head pipe l. This is a method of cutting and joining the butted parts by arc welding or brazing.

In addition, FIG. 1θ shows that after the side surface of the head pipe 1 is bulged out by bulge forming or the like, and the bulged portion 4 is perforated,
Insert the tip 2a of the main pipe 2 into the bulge 4,
Brazing is joining by etc.

In addition, FIG. 11 shows that a lid 5 is caulked onto the end surface of the main pipe 2, and the main pipe 2 and the head nozzle 1 are set in a predetermined mold (not shown), and a molten light alloy 6 is placed therein. In this method, the head nozzle l and the main pipe 2 are joined together by pouring the same.

Further, FIG. 12 is disclosed in Japanese Utility Model Publication No. 49-28665, which has a disc-shaped bulge on the side surface of the head nob 1, the outer diameter of which is larger than the outer diameter d of the main pipe 2. 7 is formed, and the end surface of the main pipe 2 is abutted against the end surface of this bulging portion 7 and joined by flash butt welding.

Furthermore, FIG. 13 is disclosed in Japanese Unexamined Patent Publication No. 57-7776, in which the head pipe 1 is provided with a protrusion 8 to be inserted into the main pipe 2, and a step with which the end surface of the pipe 2 comes into contact. A section 9 is provided, and the outer diameter of this stepped section 9 is made the same as the outer diameter of the main pipe 2.

(Problems to be Solved by the Invention) The conventional head manufacturing methods described above each have the following problems.

In other words, the one shown in FIG. 9 requires a long time to cut and join the abutting end surfaces 8 of the main pipes 2, has a poor appearance, and, depending on the butt angle, may have a poor bonding strength at the acute angle portion 2b of the main pipe 2. becomes insufficient. Another problem was that deformation easily occurred during welding.

Next, the one shown in Fig. 10 requires a lot of time for blow molding, drilling, and cutting, requires high processing accuracy, and has to be heated over a wide range of high temperatures during brazing. There were problems in that the strength of the base material deteriorated and post-finishing was required.

In addition, the method shown in Fig. 11 requires large-scale equipment for die casting, has high material costs, and requires post-finishing. The one shown is difficult to process because the top surface of the bulge 7 must be made flat and the radius of curvature of the shoulder 7a must be made as small as possible. In particular, the greater the protrusion height H of the bulge, the more severe the processing conditions.

In addition, since the main pipe 2 is welded against the flat top surface of the bulge 7, accurate positioning is difficult, and
Discrepancies in longitudinal dimensions are likely to occur ◇ Furthermore, when flash butt welding joints, a large amount of flash is generated, which must be removed mechanically, and the joint becomes stepped. , stress is concentrated, which is unfavorable in terms of strength. Furthermore, the stepped joint is not desirable from the viewpoint of appearance.

Furthermore, in the case of Fig. 1 δ, the bulge forming mold becomes complicated and the number of processing steps increases, which increases manufacturing costs, and the cross section and modulus of the joint between the head pipe and the main pipe suddenly Since there are parts where the pressure changes, stress concentration tends to occur easily.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and is provided with a pipe with the same diameter as the connecting pipe on the side surface of the head pipe, which is one member of the bicycle body head. A bulging part is provided at a predetermined angle by bulge forming, and the shoulder part of the bulging part is formed into a uniform curved surface, and the end face of the pipe, which is the other member, is butted against this curved part, and the end face of the pipe is The present invention is characterized by a method of manufacturing a bicycle body head portion, in which a welding groove is formed by the curved surface and the curved surface, and the groove is joined by welding.

(Function) As described above, the method of the present invention forms the shoulder part of the bulge into a uniform curved surface, so the mold is relatively simple and bulge forming is easy. Machining is relatively easy even if the height is larger than that.

Further, since the pipe connected to the head pipe is abutted so as to fit into the curved surface, positioning is easy and dimensional accuracy in the longitudinal direction is improved.

Furthermore, by butting the end surface of the pipe against the curved surface of the bulge, an ideal groove for welding is created, which facilitates welding and provides a smooth joint that does not require post-processing.

Furthermore, the outside diameter of the pipe connected to the bulge is the same, and the joint is smooth, so there is no stress concentration, and the tip of the bulge acts as a reinforcing material, which improves strength and A head portion with excellent appearance can be provided.

(Example) The present invention will be described in detail below with reference to FIGS. 1 to 8.

10 in FIG. 2 is the material for the head pipe, 11 in FIG. is inserted, pressurizing jigs 18 are press-fitted from both sides as shown by arrows A, and high hydraulic pressure is applied to the pipe material 10. As a result, the material 10 goes through the process shown by the two-dot chain line, and then The bulging portion 14 is formed by bulging so as to come into close contact with the jig 12.

Note that the outer diameter of the bulging portion 14 is set to be equal to the outer diameter of the pipe to which it is connected.

FIG. 4 shows the head pipe 15 formed as described above, and the shoulder ↓4a of this bulging portion 14 is formed into a uniform curved surface (partial spherical surface). In this case, the distal end surface 14 of the bulge 14
Although b may have any shape, it is usually preferable that the end of the bulging portion 14 be hemispherical.

Note that the tip of the bulging portion 14 does not need to be perpendicular to the axial direction, but the shoulder portion 14a, which is the butt portion with the pipe to be joined, has a uniform curved surface over the entire circumference of the contact surface, as described above. (partial sphere). Therefore, normally, in order to mold the tip of the bulging part 14, it is sufficient to shape the end face of the jig 12 into an appropriate shape. If so, then
The jig 12 may be pushed in in the direction of arrow B, and the tip may be pressure-formed as a post-processing process. As shown in FIG. 6, the end surfaces 16a of the pipes to be connected, for example, the main pipe 16, are butted against each other, and the welding groove 17 is formed by the pipe end surfaces 16a and the curved surface (shoulder portion of the bulging portion 14) 14a.
This groove 17 is welded as shown in FIG. 7, and the head pipe 15 and main pipe 16 are joined by welding 18 as shown in FIG. 1 to form the head section of the bicycle body. .

As shown in FIG. 6, it is preferable to add a chamfer 16b to the inner circumferential edge of the abutting end surface 16a of the main pipe 16, which is approximately equal to the thickness of the pipe 16. If this is done, the groove 17 becomes narrower, and As a result of narrowing the welding range, a stable arc can be maintained, making it possible to perform plasma welding with good welding performance.

Reference numeral 19 in Fig. 7 shows a welding torch.Of course, general arc welding can be used for this welding, but if plasma welding is used as described above, there is no need for post-processing such as finishing. A good appearance and high joint strength can be obtained. FIG. 8 shows an overall view of a bicycle having a head part manufactured by the method of the present invention, in which 20 is a front wheel and 21 is a rear wheel.

(Effects of the Invention) Since the present invention is as described above, the following effects can be obtained. Since bulge molding is sufficient, the mold is relatively simple and bulge molding is also easy. The base material obtained through plastic processing by bulge forming is homogeneous, and the constraints on the bulge are that the shoulder should be a uniformly curved surface (partially spherical).
・There is a large degree of freedom in the protrusion length and protrusion angle, so it has a wide range of applications and is suitable for mass production. Since it abuts against the partial spherical surface of the shoulder of the part, positioning is easy, and
Dimensional accuracy in the longitudinal direction also improves (0). Furthermore, by butting the end surface of the pipe against the shoulder of the bulge, an ideal groove for welding is created, making welding easier.

In particular, by chamfering the inner circumference of the end face of the pipe, the welding range becomes narrower and a stable arc can be maintained, making plasma welding possible. At the same time, a smooth joint surface that requires no post-treatment can be obtained.

(a) Furthermore, according to the present invention, since the outer diameter of the pipe connected to the bulge is the same and the joint is smooth, there is no stress concentration and the tip of the bulge is reinforced. Since it serves as a material, it is possible to provide a head portion with excellent strength and appearance.

(e) Overall, according to the present invention, it is possible to produce a relatively lightweight and inexpensive bicycle body head portion of good quality with high efficiency.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a bicycle body head manufactured according to the present invention, Fig. 2 is a side view of the head pipe material, Fig. 8 is an explanatory view of the bulge forming mold and jig, and Fig. 4 is an explanatory view of the bulge forming mold and jig. A side view of the head pipe after bulge forming. Figure 6 is a partially cutaway side view showing the butt of the head pipe and main pipe. Figure 6 is a partially enlarged sectional view. Figure 7 is a welded groove. FIG. 8 is an overall view of a bicycle having a head section manufactured according to the present invention, and FIGS. 9 to 13 are explanatory diagrams showing various conventional methods of manufacturing the head section. 10... Head pipe material 11... Mold for bulge forming 12... Jig for forming the tip of the bulge 18... Pressure jig 14... Bulging part 14a
...Shoulder (uniform curved surface, partially spherical surface) 14b...Tip surface 15...Head pipe 16...Main pipe 16a...End surface 16b...Chamfer
17...Welding groove 18...Welding
19...Welding torch. Patent applicant Brideston Cycle Co., Ltd. Figure 1 Figure 4 Figure 5 f Figure 6 Figure 7 Figure 8 Figure 9 Figure 1O Figure 11

Claims (1)

[Claims] 1. On the side surface of the head pipe, which is one of the members of the bicycle head section, a bulge with the same diameter as the connecting pipe is provided at a predetermined angle by bulge forming, and the shoulders of the bulge are made uniform. The pipe is formed into a curved surface, and the end surface of the pipe, which is the other member, is butted against this curved surface portion, a welding groove is formed by the pipe end surface and the curved surface, and this groove is joined by welding. A method for manufacturing a bicycle body head section.