JPH09177602A - Manufacture of piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a piston for an internal com bustion engine, which employs a means as a removal support means for a sol uble core for forming a cooling cavity in a piston crown where strength is prevented from being decreased, and no weight saving is impeded at all. SOLUTION: A group of stays equal to or more than two directed inward are formed in a pressure ring to be crowned to the ring groove of a piston crown, let a soluble core 7 be held by the aforesaid group of the stays 6 of the pressure ring, and the pressure ring holding the soluble core 7 is set in a metal mold, so that a piston is thereby casted. The group of stays 6 is fairly extended inward out of the pressure ring, and is light in weight though it remains within a product, it does not affect the weight of the piston. Besides, since no portion of it is protruded out of the piston after it has been formed, no strength is degraded at all.

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 piston for an internal combustion engine in which a cooling cavity is formed near the inside of a ring groove on the top of the piston.

[0002]

2. Description of the Related Art Pistons for internal combustion engines made of aluminum alloys, which have become the mainstream because of their light weight, have overcome the drawbacks of large heat resistance and thermal expansion by devising the substance and structure. That is,
The content of silicon content is adjusted, and metal powder rings are incorporated in a plurality of ring grooves at the top of the piston.

By the way, Japanese Patent Laid-Open No. 63-10043 discloses a piston having an oil cooling cavity formed in the vicinity of the inside of the ring groove. Oil circulates from the fixed oil jet below the piston in the oil cooling cavity to cool the top of the piston to suppress thermal expansion and ensure material strength. According to the above publication, in order to form the cooling cavity, a fixing member that supports a soluble core such as a salt core in the recess of the mold is provided as a mold setting member. A part of the fixing member protruding from the molded piston is cut off at the same position as the outer diameter of the piston, and a part of the fixing member remains in the piston.

Further, Japanese Utility Model Laid-Open No. 1-124058 discloses that a salt strut is supported by extending a projection from a steel strut provided in a piston skirt to prevent thermal deformation of an aluminum alloy piston. ing.

[0005]

However, in the conventional manufacturing method of supporting the salt core by extending the projection from the latter strut, the projection remaining in the molded product extends from the piston skirt portion to the piston top portion. Therefore, the length of the piston must be increased and the weight of the piston must be increased.

Further, in the former method using the fixing member, although the protrusions remaining in the molded product are few, the portion protruding from the molded product causes a local decrease in strength due to poor adhesion with the aluminum alloy. The present invention holds the fusible core by a bearing means that has little influence on the weight of the piston even if it remains inside the piston, and does not create a portion that causes strength reduction on the outer peripheral portion of the piston top, and the ring groove of the piston top is retained. It is an object to be solved to provide a method for manufacturing a piston for an internal combustion engine in which an oil cooling cavity is formed in the vicinity of the inside.

[0007]

The gist of the invention of claim 1 which has solved the above-mentioned problems is as follows: Forming a group of protrusions, (b) sandwiching the soluble core between the bearing protrusions of the metal powder ring, and (c) setting the metal powder ring sandwiching the soluble core in a mold for casting. (D) After casting, water is injected from the piston skirt portion into the oil passage reaching the soluble core to remove the soluble core to form the oil cooling cavity.

The bearing projection group extends slightly inward from the metal powder ring, and even if it remains in the molded product, it is lightweight and does not affect the weight of the piston. Also, since there is no part that protrudes outside the molded piston,
Does not protrude outside when the outer diameter is processed after the molded product is taken out. The gist of the invention of claim 2 is that each of the bearing projection groups is
It is characterized by having a positioning means for positioning the soluble core.

In a preferred aspect, the positioning means for the bearing projection group is an elastic force applied to the bearing projection group. In a preferred aspect, the positioning means for the bearing projection group is formed with a portion where the bearing projection group abuts the outer surface of the soluble core and a portion where the both ends of the soluble core are alternately abutted. Is characterized by.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, the method for manufacturing a piston for an internal combustion engine according to the present invention forms an oil cooling cavity 3 in the piston top 1 in the vicinity of the inside of the ring grooves 2a, 2b, It is intended to manufacture a piston for an internal combustion engine in which oil from the piston skirt portion 4 is supplied to the oil cooling cavity portion 3 to cool the piston top portion 1. In the ring grooves 2a, 2b, a wear-resistant metal powder ring 5 for sealing combustion gas is capped, for example, on the first ring groove 2a adjacent to the cylinder head.

The piston for internal combustion engine is of a type without a strut, but since the strut is not directly related to the present invention, the present invention can be applied to a piston of a type with a strut. . First, as shown in FIG. 2, the manufacturing method according to the first embodiment of such a piston for an internal combustion engine is preferably made of a steel plate, and is generally a metal plate harder than an aluminum alloy, or the same material as the metal powder ring 5. The stay 6 made of metal is attached to the coarse material 5a of the metal powder ring 5 by fastening means such as a child screw or caulking.
Multiple (3 in the figure)
Pieces) Stick in equal directions. The ring rough material 5a is a cold pressed material made of a sintered body of powder such as iron-based particles or a powder compact.

The group of stays 6 corresponds to a bearing projection of the present invention, and as shown in FIG. 3, along the leg portion 6a overlapping the end surface of the ring rough material 5a and the inner side surface of the ring rough material 5a, That is, it is a substantially L-shaped member consisting of an elastic portion 6b extending in the axial direction and protruding to a position higher than the opposite end surface, and a circle connecting the elastic portions 6b (the portion along the inner surface of the metal powder ring 5) Is slightly smaller than the outer circle of the soluble core 7 such as a salt core, and the elastic core holds the soluble core 7. The tip of the elastic portion 6b is curled slightly inward so that the axial position of the soluble core 7 can be regulated.

Next, the ring rough material 5a holding the soluble core 7 is, as shown in FIG. 4, a recessed portion 11a of the upper mold 11.
The lower mold (not shown) that is fixed between the left and right intermediate molds 12 and 13 and the upper mold 11 in a state of being fitted to the upper mold 11 and that molds the piston boss portion and the piston skirt portion 4 is provided on the intermediate molds 12 and 13. set. In this way, the soluble core 7 held by the ring rough material 5a is assembled at a prescribed position in the mold.

Next, after casting, a molded product 9 (hereinafter referred to as a piston rough material) is taken out. Here, the oil passage 8 (plurality) reaching the soluble core 7 is drilled from inside the piston skirt portion 4 of the piston rough material 9 by drilling, and after drilling, water is injected from the oil passage 8 to be soluble. The cooling cavity 3 is formed by melting the core 7. Furthermore, ring rough material 5
A is processed into a U-shaped cross section as shown in FIG.

As described above, in this embodiment, the stay 6 group is fixed to the originally required metal powder ring 5 to hold the fusible core 7, so that the stay 6 group projects from the outside of the piston rough material 9. It does not require a cutting step after taking out the molded product. Further, the stay 6 group only needs to have elasticity for holding the soluble core 7, and although it remains in the molded product, it is only a slight amount from the weight of the entire piston, and the influence on the weight of the piston is affected. It can be avoided.

Further, since the stay 6 group elastically holds the soluble core 7, the soluble core 7 can be easily positioned, and the oil cooling cavity 3 can be formed at an accurate position on the top of the piston. it can. Next, in the manufacturing method according to the second embodiment, the ring rough material 14a as shown in FIG. 6 is replaced by two plate-shaped rings 15, 16 as shown in FIG. (Cold pressed material) Produced by stacking them on top of each other, and each plate-shaped ring 15, 16 has projecting pieces 15a, 15a and 16a, 16 which perform the same function as the stay 6 group.
and a are provided at 180 ° opposite positions. Therefore, the distance between the protrusions 15a and 16a is 90 °. The protruding piece 15a provided on the upper plate-shaped ring 15 stands up in a substantially L-shape upward, and the protruding piece 16a provided on the lower plate-shaped ring 16 is provided.
Hangs downward in a substantially L shape.

The soluble core 7 is interposed between the protruding piece 15a standing up and the protruding piece 16a hanging downward, that is, sandwiched between the L-shaped lateral portions of the protruding pieces 15a, 16a. , L-shaped vertical part. As a result, the soluble core 7 is held by the ring rough material 14a in a state in which the axial position and the central position with respect to the ring rough material 14a are restricted.

Similar to the previous embodiment, the ring rough material 14a in this state is fitted to the recessed portions 11a of the upper mold 11 as shown in FIG. 5, and the left and right intermediate molds 12 and 13 and the upper mold. 11
While being fixed in between, the lower mold is set in the intermediate molds 12 and 13 and pressure-cast to form a reinforcing ring which is a composite of the ring rough material 14a and the aluminum alloy. According to such an embodiment as well, similarly to the previous embodiment, while the soluble core 7 is positioned, the processing after taking out the molded product is unnecessary and the influence on the piston weight can be avoided. In addition, in this second embodiment, each protrusion 15a,
Since the position of the soluble core 7 is uniquely determined by 16a, there is an advantage that the position of the injection port of the molten aluminum filled by pressurization is not limited. That is, it is possible to cast the upper mold 11 and the intermediate (lower) molds 12, 13 described above upside down.

Further, the projection piece 1 in the case of the second embodiment
Since 5a and 16a do not position the fusible core 7 by elastic force, it is possible to position the fusible core 7 to the true center more accurately than in the previous embodiment. Therefore, each protrusion 15
The protruding pieces 15a and 16a are arranged so that the a and 16a alternately come into contact with both end surfaces and the outer surface of the soluble core 7.
Processing is performed so that the circle connecting the formation base points of (1) and (3) are made to coincide with the center of the ring rough material 14a and substantially coincide with the outer circle of the soluble core 7.

The above-described embodiments are merely examples, and various modifications can be made without departing from the spirit of the claims. For example, the ring rough material 14a in the second embodiment is
It may be an integrated product without stacking two plate-shaped rings.
A structure in which the soluble cores are alternately sandwiched like the protrusion pieces of the second embodiment can be applied to the stay of the first embodiment. According to this, the above-mentioned upper mold and middle (lower)
The molds can be turned upside down and cast.

Further, in each of the above-mentioned embodiments, the stay or the protruding piece is provided on the metal powder ring which is impregnated in the first ring groove 2a, but the stay or projection piece is provided in the metal powder ring which is impregnated in the second ring groove 2b. It may be provided.

[0022]

As described above, according to the present invention, the soluble core is sandwiched by the group of bearing projections provided inward from the metal powder ring, so that the soluble core is secured by the bearing projections of a small length. It can be held and has no effect on the weight of the piston even if it remains in the molding, and since it has no part protruding outside the piston body, it contributes to the production of a lightweight piston without a strength reduction part in the outer peripheral direction. .

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a piston for an internal combustion engine molded according to the present invention, in which a right side of a dashed-dotted line is shown in a cross section.

FIG. 2 is a plan view of a coarse material of a metal powder ring having a bearing protrusion according to the first embodiment of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

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

FIG. 5 is an explanatory diagram showing a state of casting according to a second embodiment of the present invention.

FIG. 6 is a plan view of a rough material of a metal powder ring having a bearing protrusion according to a second embodiment of the present invention.

FIG. 7 is a sectional view taken along the line BB of FIG. 6;

[Explanation of symbols]

Reference numeral 1 is a piston top portion, 2a and 2b are ring grooves, 3 is an oil cooling cavity, 4 is a piston skirt portion, 5 is a metal powder ring,
5a (14a) is a ring rough material, 6 is a stay (supporting protrusion), 7 is a soluble core, 8 is an oil passage, 9 is a piston rough material, 11, 12 and 13 are molds, and 15 and 16 are plate rings. 1
Reference numerals 5a and 16a denote projection pieces (supporting projections), and the same or the same members in each drawing are denoted by common reference numerals.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohiro Sawada 2-1-1 Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd.

Claims (2)

[Claims] 1. A method of manufacturing a piston for an internal combustion engine, wherein a cooling cavity provided near the inside of the ring groove at the top of the piston is formed by using a fusible core. A group of two or more inwardly-directed bearing projections is formed on the metal powder ring to be held, the soluble core is sandwiched between the bearing projections of the metal powder ring, and the metal powder ring sandwiching the soluble core is made of gold. The casting is performed by setting in a mold, and after casting, water is injected from the piston skirt portion into the oil passage reaching the soluble core to remove the soluble core to form the cooling cavity. And a method for manufacturing a piston for an internal combustion engine. 2. The method for manufacturing a piston for an internal combustion engine according to claim 1, wherein the bearing projection group has a positioning means for positioning the soluble core.