JP4893670B2 - Forging die and piston forging die - Google Patents

Description

  The present invention relates to a forging die for hot forging various products from a blank made of an aluminum alloy with good shape and dimensional accuracy, and further includes a piston for an internal combustion engine having portions with different thicknesses and lengths. The present invention also relates to a piston forging die suitable for forging.

Generally, a piston used in various internal combustion engines has a disk-shaped head facing the innermost part of the cylinder, and a thick-walled pair of pin bosses formed on the opposite side of the head and pin-coupled to a connecting rod. And a pair of convex walls extending radially in parallel from both sides of the pin boss part, and a pair of thin and long skirt parts extending from both ends of the pair of convex walls to the connecting rod side. It has a complicated shape.
When a piston having a complicated overall shape as described above and having a certain difference in the thickness of each part is made of an aluminum alloy and is manufactured by hot forging from a flat cylindrical blank, it is generated from the blank. It is necessary to adapt the metal flow to the shape and thickness of each part in the piston.

For example, when the piston is forged, metal flow is excessively generated, and therefore, on the inner surface of the mold that comes into contact with the surface of the blank, which is prone to defects such as piping, Alternatively, a forging die in which irregularities are provided or the die inner surface is roughened has been proposed (see, for example, Patent Document 1).
JP 2000-218336 A (pages 1 to 4, FIGS. 1 to 6)

By the way, the pair of skirt portions provided on the piston are thin and long along the axial direction. Therefore, as in Patent Document 1, when the metal flow is suppressed, a chipped portion (defect) is generated at the tip portion on the connecting rod side. It becomes easy. On the other hand, since the pair of pin boss portions provided on the piston is thick and relatively short along the axial direction, for example, when lubricating oil is applied to the entire surface of the blank including the portions to be the pair of pin boss portions, the metal flow Is easily promoted excessively. As a result, a thin peeled portion (defect) called “fogging” is easily formed along the tip of the pin boss.
As described above, the skirt portion and the pin boss portion to be formed on the piston show behaviors in which the metal flows generated from the aluminum alloy of the same blank in the hot forging process are opposite to each other. A forging method or a forging die that solves the “fogging” of the pin boss at the same time has not been found.

  The present invention solves the problems described in the background art, and by hot forging, easily prevents the above-mentioned chipping and “covering” defects, etc., and a product such as a piston having a good shape and dimensional accuracy, It is an object of the present invention to provide a forging die and a piston forging die that can surely be hot forged.

Means for Solving the Problems and Effects of the Invention

In order to solve the above-mentioned problems, the present invention has been compared with the results of intensive studies and trials by the inventors to promote metal flow in the vicinity of the mold cavity for hot forging, for example, the piston skirt. A heater is placed at the site where it is desired to maintain a high forging temperature, and cooling water is circulated and supplied to the site where it is desired to maintain a relatively low forging temperature so as to suppress metal flow such as the pin boss part of the piston. Invented.
That is, in the forging die of the present invention (Claim 1), the cooling hole for cooling water circulation where the tip is located and the heater hole into which the heater is inserted are arranged in the vicinity of the cavity of the die. It is characterized by.

  According to this, for example, a heater hole for inserting a heater is arranged in the vicinity of a cavity to be kept at a relatively high forging temperature so as to promote a metal flow that later becomes a skirt portion of the piston. Cooling holes for cooling water circulation are arranged in the vicinity of the cavity to be kept at a relatively low forging temperature so as to suppress the metal flow that becomes the pin boss portion of the steel plate. As a result, at the tip of the skirt that requires a thin and relatively long distance metal flow, it is difficult for the chipping to occur, and at the tip of the pin boss that should be a thick and relatively short distance metal flow, “Cover” due to excessive metal flow is less likely to occur. Therefore, a product such as a piston having a good shape and dimensional accuracy can be efficiently and reliably manufactured by hot forging.

In the present specification, “aluminum alloy” which is a blank material includes aluminum.
The piston forging die according to the present invention is a female die having a cavity for piston forging, and is used together with a male die having a recess on the bottom surface side, which is pushed into the cavity and forges each part of the piston. It is done. Or the recessed part which forge-molds each part of a piston is provided in the bottom face of the cavity in the die for piston forging of this invention, and it is good also as a form used with the male mold | die with a flat bottom face in this cavity.
Further, on the surface of the blank made of an aluminum alloy as a raw material, various lubricants are applied to the entire surface or a part of the surface where the metal flow such as the skirt of Pinton is to be promoted, and then the gold is applied. Hot forging may be performed using a mold or a male mold.

Further, according to the present invention, the position of the tip of the cooling hole is for forging where the distance of the metal flow extending from the blank to be forged is relatively short and the thickness of the metal flow is a relatively thick portion. A mold (Claim 2) is also included.
According to this, for example, the tip of the cooling water circulation hole is disposed in the vicinity of the cavity to be kept at a relatively low forging temperature so as to suppress the metal flow that becomes a pin boss portion of the piston later. As a result, products such as pistons having pin boss portions that are less prone to defects such as “fogging” due to excessive metal flow can be reliably forged by the cooling action by the cooling water that is circulated and taught in the cooling holes.

Further, in the present invention, the position of the tip of the heater hole is a forging portion in which the distance of the metal flow extending from the blank to be forged is relatively long and the thickness of the metal flow is a relatively thin portion. A mold (Claim 3) is also included.
According to this, for example, the tip of the heater hole for inserting the heater is arranged in the vicinity of the cavity to be kept at a relatively high forging temperature so as to promote the metal flow that becomes a piston skirt portion later. . As a result, the heating action of the heater makes it easy to promote a thin and long-distance metal flow, and can reliably forge a product such as a piston having a skirt that is less likely to cause defects such as chipping at the tip. .

In addition, according to the present invention, in the forging die, the tip of the cooling hole is disposed in the vicinity of the cavity portion that will be the piston pin boss, and the cavity portion that is to be the piston skirt portion is disposed in the vicinity of the cavity portion. A piston forging die (Claim 4) in which the tip of the heater hole is disposed is also included.
According to this, the tip of the cooling hole is disposed in the vicinity of the cavity portion that will be the pin boss portion later, and the tip of the heater hole is disposed in the vicinity of the cavity portion that will be the skirt portion. Therefore, since there is no defect such as “cover” or lack of meat, or it is possible to suppress the defect to an extremely fine level that can be repaired, a piston with excellent shape and dimensional accuracy can be reliably and efficiently It can be manufactured.

In the following, the best mode for carrying out the present invention will be described.
FIG. 1 is a horizontal sectional view showing a piston forging die 1 according to one embodiment of the forging die of the present invention, and FIG. 2 is a partial vertical sectional view taken along the line XX in FIG. It is.
As shown in FIGS. 1 and 2, a piston forging die (hereinafter simply referred to as a die) 1 is a substantially quadrangular prism-shaped main body 2 including a pair of opposing side surfaces 3 and 5 and a bottom surface 7. And a cylindrical cavity C that is formed so as to penetrate the central portion in a vertical (axial) direction in a plan view of the main body 2 and that has a vertical central axis.
The main body 2 is made of, for example, SKD steel grade or SKT steel grade hot tool steel. An upper part of a knockout pin (rod) 9 having a cross section similar to that of the cavity C is inserted in the lower part of the cavity C opened to the bottom surface 7 of the main body 2 so as to be movable up and down.

As shown in FIGS. 1 and 2, in the main body 2, a cooling hole in which a tip is disposed in the vicinity of the cavity C on the back surface of each concave portion 4 formed in the middle of a pair of opposing side surfaces 3. The end of 6 is open in the center. Further, on both sides of the cooling hole 6, end portions of the pair of heater holes 8 are opened, and their tips are also arranged in the vicinity of the cavity C.
In the cooling hole 6, a small-diameter water supply pipe p is inserted substantially concentrically at the center thereof, and the cooling water w fed through the pipe p by a pump from a water storage tank (not shown) is supplied to the tip of the cooling hole 6. After discharging toward the surface, the cooling water w can be circulated so as to circulate to the tank along the outer peripheral surface of the pipe p.
Furthermore, a U-shaped heater H that is substantially elongated in plan view is inserted into the heat hole 8 so that the front end of the heater H is located on the front end side of the heat hole 8. The vicinity of the tip of the heating hole 8 can be heated by being energized by the power source, the wiring, and the switch that are not.

As shown in FIGS. 1 and 2, the pair of cooling holes 6 facing each other with the cavity C in plan view approach the pair of pin boss portions b in the piston P that is formed by following the tip of the cavity C in the cavity C. It arrange | positions in the vicinity of the inner wall face of the said cavity C to do. That is, the tip of the cooling hole 6 is positioned at a portion that becomes a pin boss portion b where the distance of the metal flow extending along the axial direction from a blank to be described later is relatively short and the thickness of the metal flow is relatively thick. is doing.
Further, the pair of heat holes 8 facing each other with the cavity C sandwiched therebetween in a plan view approaches the vicinity of both ends of the pair of skirt portions s of the piston P formed in the cavity C. It is arranged near the inner wall surface of the cavity C. That is, the tip of the heater hole 8 is positioned at a portion that becomes a skirt portion s in which the distance of the metal flow extending along the axial direction from a blank described later is relatively long and the thickness of the metal flow is relatively thin. is doing.
As shown in FIG. 2, the cooling hole 6 is located in a lower position in the cavity C near the knockout pin 9 than the pair of heating holes 8.

As shown by the one-dot chain line in FIGS. 1 and 2, the piston P to be hot forged is a disk-shaped head h formed on the knockout pin 9 that has entered the lower part of the cavity C, and the radial direction of the head h. A pair of thin skirt portions s extending in the axial direction from both ends of the pair, a pair of thick pin boss portions b standing short between the pair of skirt portions s and near the center of the piston P, and a pair of skirts It has a pair of thin convex wall t which connects between the part s and each pin boss | hub part b.
That is, the tip of each cooling hole 6 is disposed in the vicinity of the inner wall surface of the cavity C in which the tip side of the pin boss portion b that is thick and short in the axial direction is formed, and the tip of each heater hole 8 is forged later. In the piston P, the tip side of the skirt portion s which is thin and long in the axial direction is disposed in the vicinity of the inner wall surface of the cavity C formed.

Next, a piston forging method using the mold 1 will be described.
First, as shown in FIG. 3, with the upper end portion of the knockout pin 9 inserted into the lower part of the cubity C of the mold 1, it is made of, for example, an Al—Si aluminum alloy and exhibits a flat cylindrical shape as a whole. Blank B is inserted into cavity C and placed on the upper end surface of knockout pin 9. The blank B is heated to about 420 to 500 ° C. in advance, and graphite-based water-soluble lubricating oil is preliminarily formed on the entire upper surface (surface) or a pair of partial surfaces that later become a pair of skirt portions b. It has been applied. The mold 1 is heated to about 300 to 400 ° C. in advance, and a release agent made of, for example, graphite-containing oil is applied to the inner peripheral surface of the cavity C and the upper end surface of the knockout pin 9. .

Next, as indicated by a one-dot chain line in FIG. 3, a male mold 10 having an outer shape substantially similar to that of the cavity C enters the cavity C of the mold 1 vertically from above along the arrow in the figure. And hot forging the blank B.
The male mold 10 is made of the same hot tool steel as described above. As shown in FIG. 3, the male mold 10 extends from the vicinity of both ends in the radial direction of the cylindrical body and its bottom surface 11 along the axial direction and has a width. A pair of recesses 12 for forming a narrow skirt portion (s), a pin boss portion (b) for forming a wide pin boss portion (b) that extends short from the symmetrical position in the middle of the horizontal direction in FIG. A pair of concave portions 14 and a pair of front and rear concave grooves 16 for forming a convex wall (t) in a groove shape communicating between the concave portion 14 and the concave portion 12 are provided.
The male mold 10 is heated to about 240 to 300 ° C. in advance, and the same release agent as that described above is applied to the bottom surface 11 and the recess 12.

When the bottom surface 11 of the male mold 10 presses the upper surface of the blank B downward with high pressure and reaches the vicinity of the bottom dead center approaching the knockout pin 9 side of the cavity C, the aluminum alloy forming the blank B is The plastic flow causes a metal flow f indicated by an arrow in FIG.
At this time, as shown in FIG. 4, upward metal flows f are generated in the respective recesses 12 of the male mold 10 from the aluminum alloy in the vicinity of the upper surface of the blank B. Since the metal flow f is heated to about 300 to 400 ° C. by the heater H of the heater hole 8 whose tip is located in the vicinity of each recess 12, the metal flow f is promoted and the recess 12 It flows to the upper end. As a result, as shown in the perspective view of the piston P in FIG. 5, a pair of skirt portions s having no chipped portions (defects) at the upper (front) end portions are formed in a predetermined shape and size.

On the other hand, an upward metal flow f (not shown) is generated from the aluminum alloy in the vicinity of the upper surface of the blank B in the pair of concave portions 14 for forming pin bosses in the male mold 10. Since the metal flow f is cooled to about 200 to 300 ° C. by the cooling water w circulating in the cooling hole 6 whose tip is located in the vicinity immediately above each recess 14, the metal flow f is suppressed. .
As a result, due to not having an excessive metal flow f, along the both sides of the upper (front) end, as shown in the partial cross-sectional view Y along the arrow line YY in FIG. A pair of pin boss portions b without a thin “fog k” (defect) is formed.
Furthermore, the upward metal flow f generated from the aluminum alloy in the vicinity of the upper surface of the blank B with respect to the pair of concave portions 16 for forming the convex wall in the male mold 10 also has the pin boss portions b cooled as described above. Therefore, as shown in FIG. 5, a pair of convex walls t having no defect is formed as described above.

Then, the male mold 10 is raised and extracted from the cavity C of the mold 1, and further, the knockout pin 9 is raised and the piston P formed by the hot forging is taken out from the mold 1.
According to the forging method using the mold 1 as described above, as shown in FIG. 5, a pair of thin skirt portions s which are long in the axial direction, a pair of pin boss portions b which are thick and short in the axial direction, The piston P has the convex wall t and the head h, and these have a predetermined shape and size, and the piston P having no defect can be reliably and efficiently hot forged.

FIG. 6 is a horizontal sectional view similar to FIG. 1 showing a mold 1 a which is a modification of the mold 1.
As shown in FIG. 6, the mold 1 a includes a pair of cooling holes 6 whose front ends extend in the vicinity of the cavity C from the central portion of the back surface of the concave portion 4 for each of the main body 2, the cavity C, and the side surface 3. ing. The metal mold 1a is different from the metal mold 1 in that a pair of left and right heater holes 8 are arranged in total between the pair of side surfaces 5 and the vicinity of the cavity C in the main body 2. It is. The tip of each heater hole 8 is disposed in the vicinity of both ends of the pair of skirt portions s in the piston P that is molded in the cavity C.

FIG. 7 is a partial horizontal sectional view showing a mold 1 b which is a different modification of the mold 1. The mold 1b is also provided with a pair of cooling holes 6 whose tips extend from the center of the back surface of the recess 4 for each of the main body 2, the cavity C, and the side surface 3 in the vicinity of the cavity C.
The mold 1b is different from the mold 1 in that a pair of left and right heater holes 8 is disposed between a pair of side surfaces 5 opposed to each other in the body 2 and the vicinity of the cavity C. The tip of each heater hole 8 is disposed in the vicinity of the center of each skirt portion s in the piston P that is molded in the cavity C.
Even with the molds 1a and 1b as described above, the same operation as that of the mold 1 can be achieved and the same effect can be obtained.

The present invention is not limited to the embodiments described above.
For example, the tip of the cooling hole may be disposed in the vicinity of the cavity where the pin boss portion of the piston will be formed later, and in the vicinity of the right side of the upper end portion of the pin boss portion.
Further, the tip of the heater hole may be disposed in the vicinity of the cavity where the skirt portion of the piston is formed and in the vicinity of the side of the upper end portion of the skirt portion.
Further, the cooling holes may be formed in a pair in parallel on the same side surface of the mold, and the tips thereof are arranged in the vicinity of the cavity where the pin boss portion of the piston is formed.
The cooling hole and the heater hole may have a central axis drilled along an oblique direction with respect to the side surface of the mold body.
In addition, the forging die of the present invention can be applied to heat-sensitive forging of products other than pistons.

The horizontal sectional view which shows the metal mold | die for piston forging of one form by this invention. FIG. 2 is a partial vertical sectional view taken along line XX in FIG. 1. Schematic which shows the forge process by the said metal mold | die. Schematic which shows the forge process following FIG. The perspective view which shows the piston forged by said each forge process. The horizontal sectional view which shows the deformation | transformation form of the said metal mold | die. The partial horizontal sectional view which shows the different deformation | transformation form of the said metal mold | die.

Explanation of symbols

1, 1a, 1b ... Die for piston forging 6 .......... Cooling hole 8 .......... Heater hole C ........... Cavity P ........... Piston H .......... ……… Heater w ……………… Cooling water B ……………… Blank b ……………… Pin boss part s ……………… Skirt part f ……………… Metal flow

Claims (4)

In the vicinity of the cavity of the mold, a cooling hole for cooling water circulation where the tip is located and a heater hole into which the heater is inserted are arranged.
A forging die characterized by that. The position of the tip of the cooling hole is a portion where the distance of the metal flow extending from the blank to be forged is relatively short, and the thickness of the metal flow is relatively thick.
The forging die according to claim 1. The position of the tip of the hole for the heater is a portion where the distance of the metal flow extending from the blank to be forged is relatively long, and the thickness of the metal flow is relatively thin.
The forging die according to claim 1 or 2, wherein the forging die is provided. The forging die according to any one of claims 1 to 3,
The tip of the cooling hole is disposed in the vicinity of the cavity portion to be the pin boss of the piston, and the tip of the heater hole is disposed in the vicinity of the cavity portion to be the skirt portion of the piston.
A piston forging die characterized by that.

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