JPS6021344Y2 - bicycle frame - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a bicycle frame, and is particularly characterized by the joints of the members constituting the frame.

FIG. 1 shows the general structure of a conventional bicycle frame.

In the figure, 1 is the upper pipe, 2 is the lower pipe, 3 is the vertical pipe, 4 is the chainstay, 5 is the hanger lug, 6 is the head pipe,
7 is a seat lug.

In other words, in a conventional bicycle frame, each pipe member such as the upper pipe 1, lower pipe 2, vertical pipe 3, and chain stay 4 is inserted into the hole of each lug member and joined by welding. The protruding parts of the parts had to be drilled, and the lug ends of the joints had to be finished so that the wall thickness remained as they were, which required a lot of work and was not very productive. .

The present invention was devised to eliminate these drawbacks, and aims to simplify the processing process for bicycle frames and increase productivity, as well as to increase the bending strength of the pipe material.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 6.

In the figure, the same reference numerals as in FIG. 1 indicate equivalent members.

In the present invention, at a component joint of a bicycle frame, for example, a hollow cylindrical protrusion with a closed tip inserted into the upper pipe 1 and lower pipe 2 connected to the head vibro is attached to one member, the head vibro. 8, and a stepped portion 9 on which the end surfaces of each pipe 1 and 2 come into contact.
, and the joint portion is formed so that the outer diameter of the stepped portion 9 is approximately the same as the outer diameter of the pipes 1 and 2 to which they are connected.

If necessary, as shown in FIG. 2, the protrusion 8 and step 9 are similarly provided on the upper end of the vertical pipe 3, which is another joint, and on the bunker lug 5, respectively.
．． 2.3. 4 and fix it.

In order to form the above-mentioned protruding portion 8 and step portion 9, a bulging process using internal pressure, that is, a bulge forming method is used.

4 to 6 show an example of a bulge forming method for forming the protruding portion 8 and step portion 9 on the head vibro.

That is, in the figure, 10 is a pair of split molds, 11 is a fitting groove for a material pipe, and the cross-sectional shape thereof is semicircular.

Further, 12 is a bulging cavity for forming a stepped portion, and 13 is a bulging cavity for forming a protrusion.

As shown in FIG. 5, the material Vibro' is inserted into the mold 40, and from both sides of the fitting groove 11 of the material pipe,
Insert the punch shafts 14.15, each with a step 14av 15a.

Note that this punch shaft 15 has a hole 15b for supplying internal pressure.
is the provision.

As shown in FIG. 6, both punch shafts 14.1
5 by compressing the material Vibro' to a predetermined length, and applying high hydraulic pressure to the inside of the material pipe through the hole 15b, the material pipe is expanded into the bulging cavity 12, 13 to form a stepped portion 9 and a protruding portion 8 integrally with the head vibro.

As described above, the frame joints to be barked according to the present invention are formed by integrally molding the protruding part 8 and the step part 9 on the lug or pipe using the bulge forming method, and inserting the protruding part 8 into each pipe. This eliminates the need for drilling holes in protrusions and finishing work on cut surfaces, which were previously required.

Further, the joint part of the step part of the joint part according to the present invention in which the end surfaces of the pipes come into contact has a smooth appearance because the outside diameter of the step part and the outside diameter of the pipe are approximately the same.

Further, since the tip of the inserted protrusion 8 is located at an inner position away from the end surface of the pipe, as if it were a bamboo node, the bending strength of the pipe can be increased.

That is, in order to obtain a conventional lug as shown in FIG. 1, it is essential to cut the bulging end after basil processing.

Cutting here does not just mean cutting, but also includes the steps of cutting, shaping the cut surface, chamfering, and inner diameter, which requires more man-hours than basil processing itself. This will greatly undermine the advantage of bulge processing as a high value-added process.

As mentioned above, the reason why it is necessary to cut the bulging end after bulging is due to the fixed idea that frame pipes are to be joined by fitting into lugs.

The present invention has been able to achieve various effects by discarding this fixed idea and fitting the bulge of the lug or frame pipe into the frame pipe.

The details are as follows.

In other words, bulge processing is a process in which the outer diameter of the material pipe is constrained by a mold and high pressure is applied inside the material pipe to form the material, so while the accuracy of the outer diameter is good, it is also possible to prevent variations in the wall thickness of the material pipe. The inner diameter varies due to differences in lubrication conditions, etc.

Therefore, when fitting a frame pipe into a lug as in the conventional lug shown in FIG. 1, it is essential to process the inner diameter to ensure accuracy.

In contrast, in the present invention, sufficient accuracy can be obtained because the outer diameter of the bulge-processed portion can be used as is as the joint portion of the frame.

Furthermore, the accuracy of the lugs greatly affects the assembly accuracy of the entire frame.

For example, if the upper pipe length is 50 ha with a 2-mark diamond frame, ±0.1° of the inner diameter at the head lug.
The wobbling appears as a deviation of ±0.87 mm at the seat lug.

When machining the inner diameter by cutting after bulge machining, as in the case of the lug in Figure 1, in order to keep this deviation within ±0.177+771, the cutting jig must be set within an error range of approximately ±0.01°. Therefore, strict management is necessary.

On the other hand, according to the method of the present invention that utilizes the mold accuracy as is, the current mold machining accuracy is 0.0036°.
Since it is possible to process with an accuracy of less than or equal to 1, it is possible to obtain high reliability with a deviation of approximately ±0.003 wIt or less for 500 mm.

In addition, the one shown in Utility Model Publication No. 32-10613 connects the left and right back pipes 5 by means of a connecting fitting in which a connecting part 2, a stepped part 3, and a fitting part 4 are integrally molded by pressing a flat plate, and a pipe 1. However, this connecting fitting is not formed integrally with the material pipe by bulge processing as in the present invention, but is instead formed by pressing a flat plate, which is a major difference from the present invention.

Even if the two frame members and the connecting member are set with great care, this method of using connecting metal fittings will not satisfy the required precision of the bicycle frame, leading to a decline in quality. Become.

Moreover, it is difficult to create a jig that can accurately fix such small joint members, and even if they are successfully fixed, there will be a lot of loss during heating, raising questions about the reliability of welding.

Further, in such stepped drawing processing, the height of the fitting portion 4 is at most 10 to 20% of the inner diameter of the pipe to which it is joined.

For example, since the inner diameter of the upper pipe of the diamond frame is about 22 cm, the height of the fitting part 4 is about 4 cm, which cannot guarantee the strength of the joint.

On the other hand, in the case of the present invention, which utilizes the bulging part of the bulge process, the height of the joint part is set to 70 to 8 of the outer diameter of the joint part.
Since it can be reduced to 0%, the inner diameter is 22rIr! This results in a joint of approximately 15 mm for n pipes.

Therefore, the present invention has many excellent effects, such as reducing costs by improving the joints of the frame, improving the appearance by reducing complexity, and increasing the strength of the pipe.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional side view of a conventional bicycle frame.
Fig. 2 is a side view showing a part of the bicycle frame of the present invention in cross section, Fig. 3 is a detailed sectional view of its main parts, and Figs. 4 to 6
The figure is an explanatory diagram showing a bulge forming method. 1...Top pipe, 2...Bottom pipe, 3
・・・・・・Vertical pipe, 4・・・・・・Chain stay,
5...Hanger lug, 6...Head pipe, 8...Protrusion, 9...Step.

Claims (1)

[Scope of utility model registration request] At a component joint of a bicycle frame, a hollow cylindrical protrusion 8 with a closed tip is provided by bulge processing on one member, a lug or a pipe, and connected to the base of the protrusion 8. A step 9 is provided with which the end surface of the pipe comes into contact, and the joint is shaped so that the outside diameter of the step 9 is approximately the same as the outside diameter of the connecting pipe, and the protrusion 8 of this member is A bicycle frame that is inserted and fixed into another pipe that is connected to the other pipe.