JP3302291B2 - Method for manufacturing composite piston and tool for forming main part thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a composite piston for reinforcing a portion of an internal combustion engine where durability is required with a metal other than aluminum, and to a main part forming tool therefor.

[0002]

2. Description of the Related Art In a piston used for an internal combustion engine, various reinforcement measures have been taken at a main portion thereof in order to enhance durability. As a part of this, cast iron, iron, or other heat-resistant materials with higher heat resistance than the main aluminum alloy are cast into the lip of the piston crown combustion chamber as heat-resistant reinforcement treatment (for example, see Japanese Patent Application Laid-Open No. 64-7).
It is known to improve the durability by adopting a method of performing physical or chemical treatment such as a combination of anodizing treatment and molybdenum disulfide impregnation treatment.

[0003]

However, the conventional heat-resistant reinforcement processing generally requires a large number of work steps, and in particular, the heat-resistant reinforcement processing by surface treatment is performed through complicated work steps. Nevertheless, at present, they do not function sufficiently, such as cracking due to thermal stress during use.

[0004] Further, the top ring groove and the top land portion of the piston are exposed to high temperatures during operation of the internal combustion engine and are softened by the aluminum alloy, and are hit by the vertical movement of the piston ring to cause stepped wear, Topland is struggling to solve problems such as scuffing.

[0005] Further, heat resistance is insufficient during operation of the internal combustion engine above the piston pin hole, and a galling phenomenon may occur on a contact surface with the pin, thereby impairing the function. As a countermeasure, a surface treatment is performed to create a porous state on the surface of the pin hole, and a heat-resistant chemical such as molybdenum disulfide is impregnated into the surface to solve the heat-resistant lubrication of the surface. ing. However, even in this method, a measure in terms of heat resistance due to stress concentration has not been sufficiently solved.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a composite material piston capable of improving workability by a simple operation which can suppress thermal expansion deformation in addition to a heat resistance function. An object of the present invention is to provide a manufacturing method and a main part forming tool thereof.

[0007]

In order to achieve the above-mentioned object, a method of manufacturing a composite material piston according to the first invention is to provide a method for manufacturing a composite material piston, comprising: The main part forming tool of the piston, which is made of iron and has high heat resistance and covers the upper part of the formation part of the top ring groove and the formation part of the piston pin hole, is positioned and inserted, and the main part of the piston is formed. The tool is stuffed with molten aluminum alloy, and the resulting casting intermediate product is machined and finished to form the crown surface and top land portion of the piston and the top ring groove, and the upper surface side of the piston pin hole with the iron. It is characterized by being performed.

[0008] According to the present invention, there is a problem in that a main part forming tool of a piston preliminarily formed of an iron material having excellent heat resistance is positioned in a mold, charged from above, and then cast with a molten metal. It is possible to reinforce all the important points at once, and then finish it to the specified size and shape by machining, exposing the high-strength iron material to the main parts, preventing the occurrence of cracks and local deformation, A product that can achieve the intended purpose by eliminating galling on the sliding surface can be obtained. In addition, there is an effect that productivity is improved and product cost can be easily reduced.

In the present invention, when the main part forming tool of the piston is positioned and charged into the mold, the upper surface of the opening of the mold is covered by the main part forming tool of the piston, and the positioning member is previously attached to the main part forming tool of the piston. The mold is provided with a fitting portion with which a part of the positioning member engages, and the positioning member is engaged with the fitting portion on the mold side, so that the main part of the piston is provided. The forming tool may be charged into the mold. In this case, there is an effect that the main part forming tool of the piston is correctly cast at the time of casting and a product can be obtained reliably.

Next, a main part forming tool of a piston according to a second aspect of the present invention is a disk-shaped main body having a flange portion supported on an upper surface of a mold with a thickness from a head portion of the piston to at least a position where a top ring groove is formed. And a pair of legs made of cast iron having a length vertically reaching the upper surface of the piston pin hole from the main body, and a positioning piece protruding in the radial direction is detachably attached to the upper surface of the main body. It is characterized by the following.

According to the main part forming tool of the piston configured as described above, the main body of the main part forming tool of the piston is supported by the opening of the mold, and the flange on the outer periphery of the main body is supported by the periphery of the opening. It can be inserted and held in a mold.
Then, the positioning pieces attached to the upper surface of the main body are engaged (fitted) in advance with positioning locking grooves or the like provided on the upper part of the mold, so that a pair of the main body is suspended below the main body. The leg piece can be correctly set in the mold corresponding to the position of the piston pin hole, and each part having a problem as a piston for an internal combustion engine can be reinforced at once with a material having high heat and wear resistance.

In the main part forming tool of the piston, it is preferable to provide a cylindrical feeder protruding upward by a required length at a center position of the main body. With such a configuration, it is possible to cope with shrinkage at the time of solidification without separately providing a feeder, and thus it is possible to prevent the product from shrinking. Of course, if the feed gate is cut off during machining, there is no problem in obtaining a finished piston product.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a specific embodiment of a method for manufacturing a piston according to the present invention will be described with reference to the drawings of a specific example of a main part forming tool of a piston.

FIG. 1 is a longitudinal sectional view showing an embodiment of a main part forming device of a piston (hereinafter, referred to as a main part forming device of a piston). In this embodiment, the piston main part forming tool 1 has a diameter slightly smaller than the required finished outer diameter of the piston and at least the crown surface (top surface) of the product piston.
A main body 2 having a height dimension from the position where the processing dimension is added to slightly lower than the position of the top ring groove and having a flange 2a of a required length formed on an upper peripheral portion, and a lower surface of the main body 2 And a pair of leg pieces 3 extending vertically to the upper surface of the piston pin hole of the product piston, and a cylindrical feeder port 4 (feeder portion) projecting at a required height from the center of the upper surface of the main body 2. And are integrally formed. A positioning piece 5 (positioning member) is provided on the upper surface of the main body 2 so as to extend in the radial direction and be detachable.

As shown in FIG. 2, the leg 3 of the piston main part forming tool 1 is suspended from the lower surface of the main body 2 with a width wider than the diameter of the piston pin hole 24 in the product piston. The intermediate portion of the leg piece 3 is formed such that aluminum is sufficiently covered when the hollow is cast by providing the recessed portions 3a, 3a on both front and rear surfaces. The lower end 3b of the leg piece 3 is formed in an arc shape occupying approximately 1/4 of the peripheral surface of the piston pin hole. Such a leg piece 3 is formed symmetrically.

As shown in FIG. 3, the positioning piece 5 is a rectangular member and has a required dimension outside the outer periphery of the flange 2a of the main body 2 (in a locking groove for positioning on the mold side, which will be described later). When the tip of the positioning piece 5 comes into contact with the bottom of the groove, the projecting dimension is set so that the center of the piston main part forming tool 1 coincides with the center of the mold). Attached to the top of Since the positioning piece 5 is necessary only at the time of casting and is not cast, it is preferable to form the positioning piece 5 from carbon steel for machine structure.

Next, in order to cast a piston using the piston main part forming tool 1, as shown in FIG.
In a piston mold (die) 10 having a well-known structure into which the piston 2 is inserted from below, a part (a part) of the mold 10 is previously set so that the piston main part forming tool 1 is mounted in a cavity 11 having an open upper surface. In this specific example, the pouring port forming section 14
The projection end 5 ′ of the positioning piece 5 is engaged with a vertical locking groove 15 (fitting portion) provided on the
The flange 2 a of the main body 2 is supported on the upper surface of the mold 10. In this way, the center of the piston main part forming tool 1 coincides with the center line of the mold 10, and the two leg pieces 3, 3
Is correctly received on the upper surface of the mold 10 by the flange 2a of the main body 2 corresponding to the upper position of the piston pin hole (pin core) 16.

When the preparation is completed, the molten aluminum alloy is poured from the pouring port 13 into the cavity 11 of the mold 10.
If it is poured into the cavity, the upper surface of the cavity 11 of the mold 10 is covered with the main body 2 of the piston main part forming tool 1 having a larger mass than the molten aluminum alloy, so that it does not float up. The part below the inserted part is wrapped in a molten aluminum alloy and cast. In addition, the feeder flows into the feeder port 4 formed integrally with the piston main part forming tool 1, and exhibits the same function as in the conventional mold.

After the casting is completed, the core 12 and the pin core 16 of the mold 10 are removed by a known means, and the cast intermediate product 20a of the piston is removed from the mold 10, and FIGS. 5 (a) and 5 (b). As shown by, the upper part of the main body 2 of the piston main part forming tool 1 and the gate 4 are exposed at the head part of the piston.

The intermediate product 20 of the piston thus obtained is
a, the positioning piece 5 is removed by removing its mounting bolt 6, and then the main body 2 and the feeder 4 are machined.
, The combustion chamber 22 on the piston crown, the ring groove 23
(See FIG. 6) and finishing of the outer peripheral surface and processing of the piston pin hole 24 are performed. As a result, FIGS. 6A and 6B
The product piston 20 is completed as shown by.
The obtained piston 20 is mounted on the lip portion 2 of the crown combustion chamber 22.
2 ′, top ring groove 23a and top land portion 2
3b and the upper surface portion 24 'of the piston pin hole 24 are reinforced by exposing a metal (cast iron) having a high heat-resistant strength and high durability. By solving the problem, a product with high durability as a whole can be obtained.

As described above, the composite piston obtained in this manner is cast and manufactured with cast iron as a piston main part forming tool 1 in which main parts requiring reinforcement are integrated in advance. By incorporating the piston main part forming tool 1 into the mold 10 at the time of piston casting, the main parts can be reinforced by compounding without the need for complicated means, and if the resulting intermediate product is machined, A piston that can achieve the purpose of the period will be obtained. Also, by attaching the positioning piece 5 to the piston main part forming tool 1, the work of assembling the piston main part forming tool 1 into the mold 10 can be simplified and the workability can be further improved, which is advantageous. Further, by providing the feeder gate 4 directly on the piston main part forming tool 1, it is convenient to separately attach the feeder gate.

According to the present invention, the above-described piston main part forming tool 1 is formed of cast iron, but may be formed of another steel material having high heat resistance.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a piston main part forming tool according to the present invention.

FIG. 2 is a side view of the piston main part forming tool of FIG. 1;

FIG. 3 is an overall perspective view of the main part forming device of the piston shown in FIG. 1;

FIG. 4 is a view showing an embodiment of casting a piston according to the present invention.

5A and 5B are views showing an intermediate product of a piston obtained by casting, wherein FIG. 5A is an external perspective view, and FIG. 5B is a partially cutaway view showing a main part.

FIGS. 6A and 6B are views showing a piston obtained by the present invention, in which FIG. 6A is an external perspective view, and FIG.

[Description of Signs] 1 Piston main part forming tool 2 Main body 2a Flange 3 Leg piece 4 Feeder 5 Positioning piece 10 Mold 11 Mold cavity 13 Pouring port 14 Mold pouring port forming section 15 Locking groove 16 Piston pin hole (pin) Core) 20 Piston (product) 20a Intermediate product of piston 22 Combustion chamber of piston 23a Top ring groove 23b Top land portion 24 Piston pin hole

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) B22D 19/08 F02F 3/00 F02F 3/00 301 F02F 3/26 F16J 1/00

Claims (4)

(57) [Claims] 1. A piston made of iron having high heat resistance and having a high heat resistance covering an upper portion of a crown combustion chamber, a top land portion, a formation portion of a top ring groove, and a formation portion of a piston pin hole. The main part forming tool of the piston is positioned and charged, the main part forming tool of the piston is cast with a molten aluminum alloy, and the obtained cast intermediate product is machined and finished, so that the crown surface of the piston and A method of manufacturing a composite piston, wherein a top land portion, a top ring groove, and an upper surface side of a piston pin hole are formed of the iron. 2. A positioning device for positioning the main part forming tool of the piston in the mold, the upper part of the opening of the mold is covered by the main part forming tool of the piston, and the positioning member is previously removed from the main part forming tool of the piston. The main part of the piston is formed by providing a fitting part on the mold side with which a part of the positioning member is engaged, and engaging the positioning member with the fitting part on the mold side. 2. The method according to claim 1, wherein the mold is charged into a mold. 3. A disk-shaped main body having a flange portion supported on an upper surface of a mold with a thickness from a head portion of a piston to at least a position where a top ring groove is formed, and an upper surface portion of a piston pin hole vertically from the main body. A main part forming tool for a composite piston, comprising: a cast iron provided with a pair of leg pieces having a length reaching the main body, wherein a positioning piece projecting in a radial direction is detachably attached to an upper surface of the main body. . 4. The main part forming tool for a composite piston according to claim 3, wherein a cylindrical feeder portion protruding upward by a required length is provided at a center position of the main body.