KR20160001284A - A manufacturing method of crankshaft for improving balance - Google Patents

Abstract

The present invention relates to a method to manufacture a crankshaft to improve balance. The method comprises: a modeling step of determining appearance data including a main journal, a pin journal, and a balance weight of a crankshaft to be manufactured; a mold design step of designing a first mold and a second mold using the data determined in the modeling step; a forging step of shaping a material using the molds manufactured through the mold design step; and a finishing step of forming a center hole in a material crankshaft generated through the forging step, and processing a surface thereof wherein in the mold design step, a volume of the balance weight is varied in a direction opposite to a trimming direction at the time of a trimming process included in the forging step. According to the present invention described above, there is an advantage of improving balance of the material crankshaft by complementing unbalance occurring in the trimming process of the forging step.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a crankshaft,

The present invention relates to a method of manufacturing a crankshaft for improving the balance of a crankshaft produced by forging.

Generally, the crankshaft is configured to transfer an explosive force generated in a combustion chamber of a steam engine or an internal combustion engine through a piston and a connecting rod to convert a reciprocating motion into a rotational motion.

To this end, the crankshaft includes a main journal which is a main shaft, a pin journal connected to the connecting rod, and a balance weight for compensating a rotational imbalance caused by the pin journal.

In the crankshaft having the above-described structure, a plurality of pistons are connected to each other through respective connecting rods to provide power at different times, thereby continuously applying loads such as bending, twisting, and rotational vibration, Hereinafter " unbalance value ") is generated.

Therefore, the crankshaft is required to have mechanical strength and abrasion resistance capable of satisfying the above-mentioned load conditions. For this purpose, the crankshaft is mainly manufactured by forging steel material.

On the other hand, in order to manufacture a crankshaft using forging, the following steps are generally performed.

First, the modeling step of the crankshaft to be manufactured is performed.

In the modeling step, the entire shape including the main journal, the pin journal and the balance weight is modeled and stored as data.

When the modeling step is completed, a mold designing step is performed using the obtained data.

In the mold designing step, a mold for forming a crankshaft in a shape corresponding to the modeling data can be manufactured by forming the upper and lower molds using the characteristics of the material and the modeling data.

When the mold designing step is completed, a forging step is performed in which a mold is manufactured with the designed contents and a steel material is formed using the manufactured mold.

In the forging step according to the related art, first, a material distributing step of distributing a billet material to each element part of the crankshaft, a step of applying pressure to the distributed material, A filling material filling process, a final molding process for pressing and molding the filled material into a final shape, and a trimming process for removing the flesh generated between the top and bottom molds after the final molding process.

When the forging step is completed as described above, a finishing process for finishing is performed. For this purpose, a balance center axis of a material crankshaft (hereinafter, referred to as a "material crankshaft") is found, And a finishing process is performed.

Here, when the material crankshaft is manufactured in an ideal shape such as the modeling data, a center hole is formed at the center of the main journal, so that the unbalance value can be easily adjusted to within the permissible value.

However, in actual processing conditions, a thickness deviation occurs in the material crankshaft due to a failure of the mold, an effect of trimming or mold separation, or a case where the center of balance deviates from the allowable value frequently.

Accordingly, in the prior art, in order to adjust the balance center value, a hole is formed in the balance weight at the finishing step to reduce the weight so that the unbalance value can be adjusted within the allowable value.

However, when the unbalance value is adjusted by forming the holes in the balance weight as described above, there is a limit to the number and positions of holes that can be formed. Therefore, if an excessive unbalance value is generated, the crankshaft will eventually become defective.

On the other hand, according to the related art, when the balance center value does not fall within the permissible value and the crankshaft malfunctions, the crankshaft has been manufactured after correcting the center hole machining position through the balance measurement.

For example, in Patent Document 1, as a technique for determining the center hole position of a material crankshaft, a plurality of material crankshafts are sampled and a difference between a shaft center when the center hole is machined and a machined center hole position The influence on the unbalance amount after finishing processing is statistically processed to define a correction amount for determining the center hole position.

In the following Patent Document 2, dynamic balance points at both end faces of a crankshaft are calculated by a dynamic balance test, a shape of a journal portion of a material crankshaft is measured, and then an unbalance amount generated after machining is calculated And a center hole is formed at a corrected position shifted from the dynamic balance point by an unbalance amount.

On the other hand, in Patent Document 3, each piece of shape data of the material crankshaft obtained by molding with the first and second molds is obtained, and after the difference between the design data and the obtained shape data is compared and interpolated, the center hole is machined There is disclosed a technique capable of reproducing an actual shape and determining an appropriate center hole position by using relatively small measurement data as compared with the above-described Patent Documents 1 and 2. [

However, all of the above prior art documents are limited to adjusting the balance center by adjusting the center hole machining position of the processed material crankshaft after machining of the material crankshaft.

That is, in the prior art, after the material crankshaft is produced through the same forging step without correcting the material crankshaft, the position of the center hole for finishing the material crankshaft is adjusted so that the balance center value satisfies the allowable value range do.

However, even if the balance center value is adjusted as described above, if the balance center value of the material crankshaft exceeds a certain value in the forging step, there is a problem that machining of the center hole is difficult.

JP1997-174382A JP1976-76682A KR2011-0008252A

It is an object of the present invention to provide a balance improvement in which the balance of a material crankshaft can be improved by more clearly confirming the occurrence position of an unbalance amount generated in the forging step and designing a mold so as to reduce the unbalance amount of the identified position And to provide a method for manufacturing a forged crankshaft.

The present invention relates to a method of manufacturing a crankshaft comprising a modeling step of determining contour data including a main journal of a crankshaft to be manufactured, a pin journal and a balance weight, a mold designing step of designing a first mold and a second mold using data determined in the modeling step And a finishing step of forming a center hole in a material crankshaft produced through the forging step and machining a surface of the material, wherein the center hole is formed by using a mold manufactured through the mold designing step, And the volume designing step varies the volume of the balance weight in a direction opposite to the trimming direction during a trimming process included in the forging step.

In the mold designing step, when the trimming direction is from the upper side to the lower side, the offset is vertically upward, and the offset range is increased or decreased corresponding to the weight of the crankshaft to be manufactured.

When the portion to be formed by the first mold or the second mold is a lower mold portion of the material crankshaft, the volume of the balance weight included in the first mold or the second mold is reduced, When the portion to be molded is the upper mold portion of the material crankshaft, the volume of the balance weight included in the first mold or the second mold is increased.

According to the present invention, the amount of unbalance generated by the trimming process in the forging step is reflected in the mold design and reflected in the mold for manufacturing the material crankshaft.

Therefore, by reducing the amount of unbalance of the material crankshaft itself, it is possible to increase the probability that the balance center value falls within the allowable range before machining the center hole.

In addition, as described above, since the center value of the balance can be easily entered within an allowable range, the finishing process can be performed more easily and productivity can be improved.

FIGS. 1 to 3 are views for explaining unbalance occurrence areas reflected in a mold design for improving balance. FIG.
4 is a view showing an unbalance amount shown by a balance measuring instrument in a material crankshaft to which the present invention is not applied.
FIG. 5 is a view for illustrating an unbalance amount correction mode applied in a mold designing step in a method of manufacturing a crankshaft for improving balance according to the present invention. FIG.
FIG. 6 is a diagram showing a state in which the unbalance amount is corrected in the state of FIG. 4 through the correction as shown in FIG. 5; FIG.

A method of manufacturing a crankshaft for improving balance according to the present invention includes a modeling step of a crankshaft to be largely manufactured, a mold designing step using modeling data, a forging step of forming a material crankshaft by a designed metal mold, And a finishing step after the center hole is machined.

A feature of the present invention is that the unbalanced portion of the material crankshaft produced in the forging step is supplemented in the mold stage to improve the balance.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. It is to be understood, however, that the spirit of the invention is not limited to the embodiments shown and that those skilled in the art, upon reading and understanding the spirit of the invention, may easily suggest other embodiments within the scope of the same concept.

FIGS. 1 to 3 are diagrams for explaining unbalance occurrence areas reflected in the mold design for improving balance. FIG. 4 is a view showing an unbalance amount shown through a balance meter in a material crankshaft to which the present invention is not applied. ≪ / RTI >

Referring to these drawings, in a forging step which is a constitution of the present invention, a heating step of heating a raw material, a plurality of pressing step of pressing the heated raw material by using a mold, and a trimming step of cutting the flash part after the pressing step .

In detail, the heating process heats the round bar type steel material to a high temperature so that the molding can be easily performed.

Then, the steel material heated through the heating process as described above is transferred to the primary pressurizing process position.

In the primary pressurization process, the heated steel material is primarily pressurized by using the first buster mold 10 and the second buster mold 20 to distribute the volume so as to correspond to the material crankshaft to be manufactured.

The steel material having the volume distributed in the primary pressurizing process is roughly shaped by the first block mold 30 and the second block mold 40 in the secondary pressurizing process, A final material crankshaft molding including a plurality of main journals 120, a pin journal 140 and balance weights 210 to 280 is formed by the first finishing die 50 and the second finishing die 60 Is completed.

After the pressing process is completed as described above, a trimming process is performed. In the trimming process, a cut portion protruding from a gap between the first trimming mold 70 and the second trimming mold 80, As shown in Fig.

2, a load is generated in the moving direction of the cutter 90 while the flash is removed by the cutter 90. The load is " A " .

In addition, the stress concentration generated in the portion " A " causes the balance weights 210 to 280 having a relatively small cross-sectional area to be narrowed along the moving direction of the cutter 90, A change in the weight of the lower mold portion formed by the upper mold portion 60 and the upper mold portion 60 is generated.

Such a change in weight will significantly affect the balance center C of the material crankshaft, and the balance center C will excessively deviate from the target range as shown in FIG.

If the balance center C is excessively deviated from the target range as described above, it is difficult to determine the center hole for finishing machining. If the center hole can not be machined effectively, the crankshaft is defective.

Accordingly, the present invention provides a method of manufacturing a crankshaft that grasps the cause of the above-described problem and complements the above-described problems in the mold designing step.

FIG. 5 is a view for showing an unbalance amount correction mode applied in a mold designing step in a method of manufacturing a crankshaft for improving balance according to the present invention.

Referring to the drawings, in order to compensate for the unbalance amount generated in the trimming process, the volume of the balance weight portion is designed to vary at least in designing the molds of the first finishing die 50 and the second finishing die 60.

In detail, in the mold designing step according to the present invention, when designing the balance weight portion of the lower mold portion formed by the upper mold half formed by the first finishing mold 50 and the lower mold half 60 by the second finishing mold 60, To a predetermined amount.

That is, when the trimming process is performed while the cutter 90 is moved from the upper side to the lower side, the lower side is compacted, whereby the volume of the upper portion of the balance weight is decreased and the volume of the lower portion is increased.

Therefore, in the present invention, the volume of the balance weight included in the lower portion is reduced in advance in the mold design step, and the volume of the balance weight corresponding to the upper portion is increased, thereby compensating for the unbalance amount generated in the trimming process.

The mold design may be applied to the first block mold 30 and the second block mold 40 as well.

FIG. 6 is a diagram showing a state in which the unbalance amount is corrected through the correction as shown in FIG.

6, when a crankshaft in which eight balance weights 210 to 280 are formed is manufactured, in the present embodiment, the eight balance weights corresponding to the eight balance weights When designing the part mold, the lower part is vertically moved to the upper side by 0.4 mm.

The amount of change in the balance of the balance weights 210 to 280 after the completion of the forging step using the offset mold was confirmed as shown in Table 1 below.

division Before improvement After improvement Remarks
Balancing data
1) Angle: Average 23.5 °
(Distributed between 350 ° and 63 °)
2) Weight: Average 390g.cm
(Distribution of 166 ~ 555)

1) Angle: Average 252 °
(Distributed between 178 ° and 360 °)
2) Weight: Average 224g.cm
(120 to 370 distribution)

Target
1) Angle: 180 ± 45 °
2) Weight: 200g.cm or less

That is, in the present invention, by offsetting the entirety of the balance weights 210 to 280 included in the lower die portion in the mold design, the height of the balance weights 210 to 280 after the improvement (the balance (b) The center (C) position is very close to the target range, and the weight is close to the target value.

When the center hole is determined using the balancing data of the improved material crankshaft as described above, the crankshaft can be manufactured more easily by performing the finishing step after forming the center hole more easily.

On the other hand, the volume of the balance weight can be increased or decreased corresponding to the size of the crankshaft to be manufactured.

In the present invention, the offset range can be limited as shown in Table 2 according to the size of the crankshaft through a plurality of experimental results.

Size of crankshaft
small
medium
versus
Weight range of crankshaft
Less than 10kg and less than 20kg
20kg or more and less than 30kg
30kg or more and less than 40kg
Offset range

0.2mm or more and less than 0.3mm
0.3mm or more and less than 0.4mm
0.4mm or more and less than 0.5mm

As shown in the above table, in the present invention, the sizes of the crankshaft are classified into small, medium, and large based on the weight range of the crankshaft. The range in which balancing improvement effect can be confirmed while adjusting is confirmed as described above.

That is, when the crankshaft is small, if the offset is less than 0.2 mm, the balancing effect is insufficient, and when the crankshaft is formed over 0.3 mm, a larger eccentricity is generated.

When the size of the crankshaft is medium (small), satisfactory balancing improvement effect is confirmed when the offset range is 0.3 mm or more and less than 0.4 mm. When the crankshaft size is large, the offset range is 0.4 mm and 0.5mm, respectively.

10 ...... First buster mold 20 ...... Second buster mold
30 ... first block mold 40 ... second block mold
50 ...... first finishing die 60 ...... second finishing die
70 ...... First trimming mold 80 ...... Second trimming mold
90 ...... cutter
210-280. Balance weight

Claims (3)

A modeling step of determining outer shape data including a plurality of main journals constituting a crankshaft to be manufactured, a pin journal and a balance weight;
A mold designing step of designing the first mold and the second mold by using the data determined in the modeling step;
A forging step of forming a material using a mold manufactured through the mold designing step;
And a finishing step of forming a center hole in the material crankshaft produced through the forging step and machining the surface,
In the mold designing step,
Wherein the volume of the balance weight in the first mold and the second mold is varied in a direction opposite to the trimming direction during a trimming process included in the forging step.
2. The method according to claim 1,
Wherein the offset is vertically upward when the trimming direction is from the upper side to the lower side and the offset range is increased or decreased corresponding to the volume of the crankshaft to be manufactured.
3. The method according to claim 2,
Wherein when the portion to be formed by the first mold or the second mold is a lower mold portion of the material crankshaft, the volume of the balance weight included in the first mold or the second mold is reduced,
And the volume of the balance weight included in the first mold or the second mold is increased when the portion to be formed by the first mold or the second mold is the upper mold portion of the crankshaft of the material. Gt;

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