CN1663872A - Hollow crank of bicycle and its cold forging forming method - Google Patents

Abstract

The invention discloses a bicycle hollow crank and the cold-forging method. The method comprise: A. send the solid bar into the rough part with the handle cold-forged by the upper and the lower moulds; B. the said rough part is cold-forged into the hollow tube semifinished product with one open-end; C. the forming cold-forging mould form he semifinished product into the finished product and make its end sealed to form the crank body with socket hole, kick connecting hole and the needed radian. The crank arm and the head and the end of the kick are formed integrate through the solid rough bar cold-forging, and the arm has close hollow slotted eye. The hollow crank of the invention has stronger intensity than the traditional product; the close hollow slotted eye can effectively reduce the weight, save the materials. The cold-forging forming technique does not need jointing assembling, so the following procedures are simple.

Description

Bicycle hollow crank and cold method for forging and molding thereof

Technical field

The present invention relates to bicycle crank and manufacturing process thereof, particularly a kind of bicycle hollow crank and cold method for forging and molding thereof.

Background technology

Bicycle crank is the parts of connection gear dish on the transmission shaft, mostly is iron material impact forging moulding in the past, also have portion of hot forge or die cast after, make the crank of connection gear dish again with welding manner.The aforementioned way not only loaded down with trivial details processing of operation is difficult for, and can't reduce production costs.

Back industry also has and adopts aluminum alloy materials to make crank, aluminum alloy crank light weight and acidproof rain, and ductility is good again is beneficial to forging; But because the aluminum alloy materials cost is higher, the crank material consumption of solid moulding is big, and the advantage of aluminum alloy light weight is also reduced, and intensity is also not as diecasting.

Have with crank separates heads, bar, tail three parts, assembly or welding fabrication in addition again after forge hot or die casting, but not only strength problem still can't solve, the required polishing molding procedure that is connected behind three parts is also quite loaded down with trivial details, and the processing of crank, weight and strength problem can't be taken into account and obtain always actv. and solve.

For solving bicycle crank structural strength and weight issue, industry is actively improved invariably, as No. 500679 " manufacture method of bicycle hollow crank loss of weight " patent scheme of Taiwan notification number, as if it adds at crank end and need inject weighting material man-hour and insert second metal and just can finish, do not show practical for crank intensity and convenient the going up of processing.Check and approve No. 1186750 patent case of bulletin again, though be formed in one, but processing procedure is inserted steps such as taking-up through casting and with the sand material, Casting Parts intensity can't be compared with forging, loaded down with trivial details work programme, repeated steps not only increase manpower and man-hour, productive costs is increased, and it is desirable that its practicality is owed, and is unfavorable for promoting the use of.

In a word, the above-mentioned defective that existing bicycle crank manufacturing process and molding structure exist has research and development to improve necessity of its manufacturing process and structure in fact.

Summary of the invention

For overcoming existing bicycle crank structure and manufacturing process aspect above shortcomings thereof, the invention provides a kind of integrated bicycle hollow crank, and the cold method for forging and molding of this hollow crank, to satisfy market to intensity height, lightweight new construction crank demand.

The present invention realizes according to following technical scheme.Bicycle hollow crank of the present invention is the improvements design of existing bicycle crank, and it is integrated that the end portion that its handle bar, button and connecting pin stepped on is that the solid blank bar of employing is made through cold forging, and the handle bar inside of crank has an osed top hollow slotted eye.

The cold method for forging and molding of above-mentioned bicycle hollow crank comprises the steps:

A, the solid bar of metal is sent into up and down the cold forging die cold forging make and be shaped to the bar-shaped blank that an end is the crank head;

B, described bar-shaped blank cause the hollow tubular half-blank of an end opening by pore-forming cold forging die cold forging; And,

C, by the moulding cold forging die to described hollow tubular half-blank cold-forging forming, make end sealed, form have sleeve joint hole, pin steps on connecting bore and requires the crank main body of radian.

Before step C cold-forging forming, described hollow tubular half-blank is carried out pre-cold forging shaping by the preforming cold forging die.

Hollow crank of the present invention is the one-body molded member through cold forging, the end portion that its handle bar, button and connecting pin stepped on is to adopt solid blank bar to make integrated through the substep cold forging, the handle bar inside of crank has an osed top hollow slotted eye, greatly promotes than the intensity of traditional product.The setting of the handle bar in-to-in sealing hollow slotted eye of crank, effectively expendable weight, saving in material and cost-cutting.

Hollow crank adopts complete cold forging molding process, the one-body molded welding assembly that do not need, and follow-up required processing is simple and direct, is convenient to suitability for industrialized production, reduces manufacturing cost.

Description of drawings

Fig. 1 is solid blank bar scheme drawing for the present invention adopts;

Fig. 2 has the bar-shaped blank cold forging process scheme drawing of crank head for it;

Fig. 3 a.b has the bar-shaped blahk structure scheme drawing of crank head for it;

Fig. 4 is the hollow tubular half-blank cold forging process scheme drawing of one end opening;

Fig. 5 is the hollow tubular half-blank structural representation of one end opening;

Fig. 6 is to the pre-cold forging shaping process of hollow tubular half-blank shown in Figure 5 scheme drawing;

Fig. 7 is for slightly being molded into bending crank half-blank structural representation after the pre-cold forging shaping of Fig. 6;

Fig. 8 is to the bending crank half-blank cold-forging forming process schematic representation that slightly is molded into shown in Figure 7;

Fig. 9 a.b.c is the complete crank agent structure exemplary embodiments scheme drawing behind the last cold-forging forming.

The specific embodiment

Below in conjunction with the embodiment accompanying drawing hollow crank structure of the present invention and manufacturing process are described in detail.

Fig. 1～each several part shown in Figure 9 is:

Solid blank bar 1, an end are the bar-shaped blank 2 of crank head, crank half-blank 3, summary bending crank half-blank 4 and the complete hollow crank 6 that an end seals an end opening.

A～I is the various cold forging dies that adopt in the cold-forging technique process, and wherein, A and B are cold forging die up and down, and C, D and E are the pore-forming cold forging die, and F and G are the preforming cold forging die, and H and I are the moulding cold forging die.

Bicycle hollow crank exemplary embodiments of the present invention as shown in Figure 9.This hollow crank 6 has handle bar 63, handle bar 63 two are the end portion 65 that button 61 and connecting pin are stepped on, the end portion 65 that handle bar 63, button 61 and connecting pin are stepped on is to adopt solid blank bar to make integrated through cold forging, handle bar 63 inside of crank have an osed top hollow slotted eye 64, at the negative winding stem 61 of described crank the sleeve joint hole 62 of connection gear dish is arranged, part 65 has pin to step on connecting bore 66 endways.The sleeve joint hole 62 that is used for the connection gear dish can be square hole, tri-angle-holed and polygonal hole etc.Pin is stepped on connecting bore 66 and be can be unthreaded hole, tapped bore etc.

With reference to Fig. 1～Fig. 9, the cold method for forging and molding of above-mentioned bicycle hollow crank is described, mainly comprise the steps:

A, solid blank bar 1 is put into as shown in Figure 2 A.B cold forging die up and down, implement cold forging and make and make it to be shaped to bar-shaped blank 2 shown in Figure 3, these bar-shaped blank 2 one ends are the crank head, and Fig. 3 a, b are respectively the front view and the birds-eye vieies of this bar-shaped blank 2.

B, more described bar-shaped blank 2 is put into C.D.E pore-forming cold forging die as shown in Figure 4, impose cold forging equally, cold forging causes end one of shown in Figure 5 to be the hollow tubular half-blank 3 of crank head other end opening.

After the hollow tubular half-blank 3 of C ', end sealing other end opening takes out, put into preforming cold-forging forming mould F.G shown in Figure 6 again and carry out pre-cold forging shaping, be shaped to slightly forniciform crank half-blank 4 shown in Figure 7.

C, by moulding cold forging die H shown in Figure 8, I to described slightly forniciform crank half-blank 4 cold-forging formings, make end sealed, form have sleeve joint hole, pin steps on connecting bore and requires the crank main body 6 (Fig. 9) of radian.

In the above-mentioned cold method for forging and molding, C ' the step of hollow tubular half-blank 3 being carried out pre-cold forging shaping is omissible, after step B causes an end to be the hollow tubular half-blank 3 of crank head other end opening bar-shaped blank 2 cold forgings, directly carry out follow-up processing.

This cold forging causes the type technological process to comprise:

A, solid blank bar 1 is put into as shown in Figure 2 A.B cold forging die up and down, implement cold forging and make and make it to be shaped to bar-shaped blank 2 shown in Figure 3, these bar-shaped blank 2 one ends are the crank head.

B, more described bar-shaped blank 2 is put into C.D.E pore-forming cold forging die as shown in Figure 4, impose cold forging equally, cold forging causes end one of shown in Figure 5 to be the hollow tubular half-blank 3 of crank head other end opening.

C, by moulding cold forging die shown in Figure 8 to described hollow tubular half-blank 3 direct cold-forging formings, make end sealed, form have sleeve joint hole, pin steps on connecting bore and requires the crank main body 6 (Fig. 9) of radian.

Above-mentioned hollow crank manufacture method adopts full cold forging integral forming process, the one-body molded welding assembly that do not need, and following process is simple and direct, is convenient to suitability for industrialized production, reduces manufacturing cost.

The above only is the narration of the present invention program's exemplary embodiments, and any simple modification and equivalent variations that any foundation technical spirit of the present invention is done the foregoing description all still belong to the scope of technical solution of the present invention.

Claims (4)

1. bicycle hollow crank, it is characterized in that: the end portion that handle bar, button and the connecting pin of crank stepped on is made through cold forging and is shaped to one, and the handle body inside of crank has an osed top hollow slotted eye.

2, bicycle hollow crank as claimed in claim 1 is characterized in that: the sleeve joint hole that is used for the connection gear dish that is positioned at negative winding stem is square hole or tri-angle-holed or polygonal hole.

3, a kind of cold method for forging and molding of bicycle hollow crank is characterized in that comprising:

A, the solid bar of metal is sent into up and down the cold forging die cold forging make and be shaped to the bar-shaped blank that an end is the crank head;

B, described bar-shaped blank cause the hollow tubular half-blank of an end opening by pore-forming cold forging die cold forging; And,

C, by the moulding cold forging die to described hollow tubular half-blank cold-forging forming, make end sealed, form have sleeve joint hole, pin steps on connecting bore and requires the crank main body of radian.

4, the cold method for forging and molding of bicycle hollow crank as claimed in claim 1 is characterized in that: before step C cold-forging forming, by the preforming cold forging die described hollow tubular half-blank is carried out pre-cold forging shaping.

Images