JP2812662B2 - Roll forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a cross rolling method for forming a stepped shaft by processing a round bar in a plurality of steps.

[0002]

2. Description of the Related Art Conventionally, when a stepped shaft is machined, a method of continuously performing roll forming with a roller having a plurality of forming sections is disclosed in, for example, Japanese Patent Publication No. 57-133 or Japanese Patent Application Laid-Open No. -107949. That is, a pair of parallel rollers provided with a plurality of stages of forming portions on the outer peripheral surface are opposed to each other, and a heated material round bar is inserted in parallel between the rollers and the roll is rotated in a relative direction. The diameter of the raw material sandwiched between the forming portions is sequentially reduced.

[0003]

By the way, by continuously working in a plurality of forming sections, the reduction rate of the cross-section is gradually increased, and finally the one-step stepped shaft having a fixed working length is enlarged. In the case of molding at a cross-sectional reduction rate, it was necessary to introduce a new technology. That is, the above mentioned Japanese Patent Publication No. 57-1
In the case of No. 33, the purpose is to form two stepped shafts from the beginning, and in the case of Japanese Patent Application Laid-Open No. 49-107949, the outer peripheral portion of the material is axially pressed in the first-stage forming portion. Since the second-stage molding was started during the process of expanding and processing, it was not possible to process with an excessively large cross-sectional reduction rate.

[0004] If the second-stage processing is started after the completion of the processing by the first-stage forming section, processing can be performed with a relatively large cross-section reduction rate. There is a problem that a step is likely to occur at the joint between the second-stage molding and the second-stage molding. That is, as shown in FIG. 8, a medium diameter shaft W1 having forming slopes T1 and T1 at both ends as shown in FIG. After forming, and then processing is started in the second stage forming section as shown in (c), (d)
As shown in (e), the outer peripheral meat is pushed and spread in the axial direction,
Finally, when the small-diameter shaft W2 is formed at the desired length L2 in the intermediate portion, a step d is generated between the forming slope T1 at the end of the middle-diameter shaft W1 and the forming slope T2 at the end of the small-diameter shaft W2, It was necessary to perform processing for removing the step d later. On the other hand, if the forming slope T2 of the small-diameter shaft W2 catches up with the forming slope T1 of the medium-diameter shaft W1 too early in the course of processing, there is a risk that a situation in which processing cannot be performed any more may occur.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a method of forming a stepped shaft by a parallel roller having a plurality of formed processing portions on an outer peripheral surface. In a roll forming method in which a small diameter shaft having a predetermined width and a predetermined diameter is formed while a medium diameter shaft is formed in a processing portion and then the medium diameter shaft is expanded and expanded in a second-stage forming processing portion, the first step The forming width of the radial shaft was such that the molding slope at the end of the medium-diameter shaft coincided with the molding slope at the end of the small-diameter shaft when the molding of the second-stage small-diameter shaft was completed.

[0006]

[Effect] In the case of forming the small-diameter shaft W2 by processing the medium-diameter shaft W1 processed by the first-stage forming processing part in the second-stage forming processing part, the small-diameter shaft W2 of FIG. Assuming that the traveling speed of the forming slope T2 in the axial direction is V2 and the traveling speed of the medium-diameter shaft W1 in the axial direction of the forming slope T1 due to elongation is V1, V2> V1.
Becomes Therefore, when the final length L2 of the small-diameter shaft W2 is determined, the width of the first-stage middle-diameter shaft W1 is processed to a certain length L1, and this L1 is set to the second-stage. At the time when the processing of the length L2 is completed in the forming processing section, just the forming slope T2
Is set to a length that catches up with T1.

[0007]

An embodiment of the present invention will be described with reference to the accompanying drawings. Here, FIG. 1 shows a roll forming die according to the present roll forming method, in which (A) is a front view, (B) is a perspective view, and FIG. 2 is a development view of a forming portion on the outer peripheral surface of the roll and corresponds thereto. FIG. 4 is a processing step diagram showing a shape change of a forming material W. The roll forming method of the present invention is applied, for example, as a forming method for processing a middle portion of a round bar into a small-diameter shaft with a large cross-sectional reduction rate R of 0.8 or more for manufacturing a connecting rod. It is formed using a roll forming die 1 as shown. The cross-sectional reduction rate R is a value calculated by R = (initial cross-sectional area−final cross-sectional area) / initial cross-sectional area × 100 (%).

[0008] The roll forming die 1 includes a pair of rollers 2 and 2 whose roller axes are parallel to each other.
Two wedge-shaped forming sections 3, 4 are provided. The rollers 2 and 2 are arranged to face each other so that the directions of the forming sections 3 and 4 are opposite to each other, and the heated forming material W0 is inserted therebetween so that the rollers 2 and 2 rotate slightly less than one rotation (for example, 3
00 ゜) By rotating the intermediate part of the material W0, the small-diameter shaft W2
Process into At this time, the first-stage forming section 3 performs processing with a cross-sectional reduction rate of, for example, about 55 to 60% to form the medium-diameter shaft W1, and then this middle-axis shaft W1 is formed into the second-stage forming section. In step 4, processing is performed at a cross-sectional reduction rate of about 55-60% to form a small-diameter shaft W2 having a large cross-sectional reduction rate of 80% or more. That is, since it is impossible to obtain a large cross-section reduction rate by one processing, the processing is performed in a plurality of times. In addition, in the figure, 5 and 5 are guides.

Here, the forming sections 3, 4 will be described with reference to FIG. The first-stage forming section 3 includes a biting portion A1 that first bites into the forming material W0, an expanding portion B1 that expands the outer peripheral meat of the forming material W0 in the axial direction, and a pressing portion having a predetermined length. Parallel part C1 which flattens both ends in the axial direction after spreading
In the first-stage forming section 3, the intermediate portion of the forming material W0 is processed into a medium-diameter shaft W1, and forming slopes T1, T1 are formed at both ends of the medium-diameter shaft W1. . In addition, the second-stage forming section 4 axially pushes the engaging portion A2 which bites into the medium-diameter shaft W1 from the start position of the first-stage parallel portion C1 and the outer peripheral wall of the medium-diameter shaft W1. It is provided with an expanding portion B2 and a final shape portion D2 for forming a final shape. The second-stage forming portion 4 further processes the medium-diameter shaft W1 into a small-diameter shaft W2, and also has both ends of the small-diameter shaft W2. The forming slopes T2 and T2 'are formed.

The advance angle α of the first-stage biting portion A1 and the second-stage biting portion A2 is the same, and each of the biting portions A1,
A2 and left and right slope forming portions a1, a2 of the expanding portions B1, B2,
In b1 and b2, a plurality of slip prevention grooves m (...) indicate a plurality.
The same applies hereinafter. ) Is formed. The slip prevention grooves m are formed in a round shape as shown in the sectional view of FIG. As shown in FIG. 4, which is a cross-sectional view taken along line XX of FIG. 2, FIG. 5, which is a cross-sectional view taken along line YY of FIG. 2, and FIG. 6, which is a cross-sectional view taken along line ZZ of FIG. Slope forming parts b1, c1,
The angles β of b2 are all the same, and the left and right slope forming portions d2 and d2 'of the final shape portion D2 are configured to be asymmetric in order to form an unequal angle. That is, the unequal angle slope forming part d on the wide side
2 'forms a slope (T2') with a shallow angle β '.

By the way, the molding material W0 is processed into a final product shape Ws through such a shape change as shown in FIG.
It is necessary to set the length L2 of the small-diameter shaft W2 to a predetermined standard value. Also, the formed slope T2 of the final product shape Ws,
Care must be taken so that a step or the like does not occur between T2 'and the molding slopes T1, T1 at both ends of the medium diameter shaft W1. For that purpose, if the length L1 of the medium-diameter shaft W1 by the first-stage forming section 3 is processed with a certain value, finally the forming slope T
1, T2 can be matched. Therefore, the length of the middle diameter axis L1 satisfying this is obtained.

Now, as shown in FIG.
The cross-sectional area of 0 is S0, the cross-sectional area of the medium-diameter shaft W1 is S1, and the small-diameter shaft W2 is
After forming the medium-diameter shaft W1 in the first-stage forming section 3 (solid line) as shown in FIG.
At the expanding portion B2 (FIG. 2) of the step forming portion 4, the portion is expanded by an axial length Δq (broken line) (broken line), and accordingly, the end e of the forming slope T1 and the end f of the material W are set to Δq ′. Assuming that the object has moved (broken line) (this assumption is not precisely correct as described later), the following equation holds between Δq and Δq ′, and Δq> Δq ′. . .DELTA.q '=. DELTA.q.times. (S1-S2) / S1 ...

The reason is that the amount of meat removed (hatched portion) when the medium diameter shaft W1 is processed by Δq is approximately Δq × (S1
-S2), which is the amount of increase Δq '× S0 due to the movement of the material end f by Δq', and the forming slope T1.
Is approximately the same as the subtraction amount of Δq ′ × (S0−S1) due to the movement of the end e of Δq ′ by Δq ′. That is, Δq × (S1−S2) = Δq ′ × S0−Δq ′ × (S0
−S1) = S1 × Δq ′, and the above equation is obtained. Then, (S1−S2) / S1 is smaller than 1, and if Δq is further advanced, the forming slope T2 should catch up with the forming slope T1, and if the forming is completed at that point, (Δ
q = L2 / 2), and simultaneously with the completion of the molding of the small-diameter shaft W2, the molding slopes T1 and T2 coincide with each other, so that no step is formed.

In the state where the formed slope T2 finally catches up with T1, the length L1, Δq, Δq
′, A relationship of L1 / 2 + Δq ′ = Δq holds,
At this time, considering the equation and Δq = L2 / 2, L1 + L2 × (S1-S2) / S1 = L2, and the following equation holds. L1 = L2 × (1- (S1-S2) / S1) = L2 × S2 / S1

By the way, the calculation result based on the above-mentioned assumption is more simply expressed as follows.
The volume of one portion and the volume of the small-diameter shaft W2 portion after processing can be rephrased as being invariable (that is, L1 × S1 = L2 × S2). It is specified that the volume is unchanged.) However, actual testing has shown that the above assumptions are not precisely correct. That is, as a conclusion, it is necessary to multiply the above equation by a coefficient K (usually larger than 1), and the following equation is established.・ L1 = K × L2 × S2 / S1 ...

The reason for this is that the amount of movement between the end e of the forming slope T1 and the end f of the material W assumed in FIG.
It is considered that there is a problem when q 'is assumed, and it is considered that the amount of movement of the end e of the forming slope T1 is smaller than the amount of movement of the end f of the material W. In other words, in other words, it is considered that not all of the volume of the medium-diameter shaft W1 is converted to the volume of the small-diameter shaft W2, but some portions are buried so as to rise on the molding slope T1. Therefore, in the present invention, the coefficient K is obtained by an experiment, and L1 is obtained from the above equation.

Incidentally, a specific example of this embodiment is as follows. From a molding material W0 having a cross-sectional area S0 of 780 mm ² , a small-diameter shaft W2 having a cross-sectional area S2 of about 140 mm ² finally (cross-sectional reduction rate 82%)
Is formed with a length L2 = 70 mm, and the medium-diameter shaft W1
The coefficient K when the cross-sectional area S1 and 340 mm ² approximately 1.2
The length L1 is set to about 36 mm.

The main forming method using the above-mentioned roll forming die 1 will be described. First, the molding material W0 is heated and inserted between the rollers 2 and 2, and the rollers 2 and 2 are rotated in relative directions. Then, a medium-diameter shaft W1 of a predetermined length L1 is formed at the intermediate portion in the first-stage forming section 3. Then
Processing is started from the center of the medium-diameter shaft W1 in the second-stage forming section 4, and a small-diameter shaft W2 having a length L2 is formed. Then, the shaping surface T2 at the end of the small-diameter shaft W2 becomes the medium-diameter shaft W
It merges with the forming slope T1 at one end and is made the same slope, and then, by further rotation of the rollers 2, 2, the slope on one side is made a shallow angle by the non-conformal slope forming part d2 '. . In the embodiment, the slope forming portions d2 and d2 'are made non-conformal.

[0019]

As described above, in the roll forming method of the present invention, a medium-diameter shaft having a predetermined length is formed in the first-stage forming portion, and then a small-diameter shaft is formed in the second-stage forming portion. In a molding method in which a stepped shaft of a total of one step having a large cross-section reduction rate is formed, the working length of the first-stage forming part is set to a predetermined value, thereby completing the forming of the second-step forming part. At the same time, the molding slope at the end of the medium-diameter shaft and the molding slope at the end of the small-diameter shaft are made to coincide with each other.

[Brief description of the drawings]

FIG. 1 is a roll forming die according to the present roll forming method,
(A) is a front view, (B) is a perspective view.

FIG. 2 is a development view of a forming portion on the outer peripheral surface of the roll and a processing step diagram showing a corresponding change in the shape of the forming material W;

FIG. 3 is a sectional view of a slip stopper groove.

FIG. 4 is a sectional view taken along line XX of FIG. 2;

FIG. 5 is a sectional view taken along line YY of FIG. 2;

FIG. 6 is a sectional view taken along line ZZ of FIG. 2;

FIG. 7 is an explanatory view in the middle of molding, (A) is an explanatory view of a processing process in an axial direction, and (B) is an explanatory view of a cross-sectional area.

FIG. 8 is an explanatory view of a conventional molding process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Roll forming die, 2 ... Roller, 3 ... First stage forming part, 4 ... Second stage forming part, W0 ... Forming material, W1 ... Medium diameter shaft, W2 ... Small diameter shaft, T1 ... Medium diameter Shaping end of shaft end, T
2, T2 ': Molded slope at the end of the small diameter shaft.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takashi Kihara 1-10-1 Shinsayama, Sayama City, Saitama Prefecture Inside Honda Engineering Co., Ltd. (72) Ryuji Soga 1-10-1 Shinsayama, Sayama City, Saitama Prefecture (58) Field surveyed (Int.Cl. ⁶ , DB name) B21H 1/22

Claims (1)

(57) [Claims] 1. A method for forming a stepped shaft by a parallel roller having a plurality of forming portions on an outer peripheral surface, wherein a medium diameter shaft is formed by a first forming portion and then a second step. In a roll forming method in which a small-diameter shaft having a predetermined width and a predetermined diameter is formed while expanding and expanding the medium-diameter shaft in a forming section, the forming width of the first-stage medium-diameter shaft is reduced to a second-stage small-diameter shaft. Wherein the forming slope at the end of the medium-diameter shaft is formed with a length corresponding to the forming slope at the end of the small-diameter shaft when the forming is completed.