JPS59215939A - Piston for internal-combustion engine and its production method - Google Patents

Abstract

PURPOSE:To efficiently produce a lightweight piston excellent in heat resistance, abrasion resistance, etc. by internally casting a reinforcing member having characteristics, e.g., heat resistance, abrasion resistance, etc., in necessary portions of a piston and forming a piston head section to be hollow. CONSTITUTION:A piston proper 1 is formed of an aluminum alloy, and a spherical graphite cast iron member is internally cast as a reinforcing member 2 in part of its top section and the first piston ring groove section. A hollow section 3 is provided on the piston head section, and a bridge section 4 of the reinforcing member 2 is suspended across this hollow section 3. When producing the piston, after a core 5 is fitted in one body with the reinforcing member 2 via the bridge section 4 by molding the reinforcing member 2 by a core molding machine, this combined body is placed in a metal mold and the melted aluminum alloy is poured to produce the piston. A projection 6 is provided on the core 5 in advance, and the piston can be obtained by removing the core 5 through this projection 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston for an internal combustion engine and a method for manufacturing the same.

BACKGROUND ART Conventionally, light alloys such as aluminum alloys or magnet alloys have been used for pistons for internal combustion engines (hereinafter simply referred to as pistons) for the purpose of reducing weight and improving the performance of internal combustion engines. In this case, light alloys do not have sufficient heat resistance to withstand the high heat generated in the combustion chamber of an internal combustion engine, and furthermore, they do not have sufficient wear resistance on the cylinder bore or the sliding surface with the cylinder bore. A reinforcing member such as a metal material such as iron or a ceramic material with excellent durability is cast, and furthermore, a reinforcing member such as a material with excellent heat resistance and wear resistance, such as a Niresist ring or ceramic fiber, is used in the piston ring groove. It had been molded into something.

However, these reinforcing members are generally heavier than the material of the piston body, so when looking at the piston as a whole, it increases the weight and prevents the piston from fully demonstrating its original function. Efforts have been made to improve the situation, but it has not yet reached a satisfactory state. Reducing the weight of screws has become a major issue, particularly in order to save resources and reduce fuel consumption.

On the other hand, in order to reduce the weight of the piston, it has been proposed to make the head portion of the piston hollow.

One of these is a type in which the head part of the piston is formed by pressing a plate material, but since a considerable amount of plate material is used, it is particularly large-scale compared to a model in which reinforcing members are cast only in necessary parts such as the piston ring groove. No weight reduction could be expected.

Additionally, when manufacturing pistons by casting, it is necessary to use a core to make the head of the piston hollow, but special design considerations are required to secure the core in the mold. . In particular, when reinforcing members are cast together with the core, it takes time to install them and the accuracy is not necessarily sufficient, so the current situation is that they have not yet reached the practical stage.

The present invention has been made in order to solve the problems of the prior art described in 2.It is an object of the present invention to provide a piston that has excellent heat resistance and wear resistance, and is significantly lighter in weight. The purpose is to provide a method for manufacturing with good workability.

According to the piston according to the present invention, this purpose is to achieve heat resistance,
This is achieved by casting reinforcing members with such properties in areas where properties such as wear resistance are required, and by making the head of the piston hollow.

Further, this object is achieved by integrating a reinforcing member having properties such as heat resistance and wear resistance with a core forming the hollow part of the piston head, according to the piston manufacturing method according to the present invention,
This is achieved by placing the mold in a piston casting mold, pouring the molten light alloy into it, and removing the spores after solidification.

According to the piston of the present invention, reinforcing members having properties such as heat resistance and/or wear resistance are cast into the head portion of the piston and the piston ring groove portion, so that the piston as a whole has sufficient heat resistance and wear resistance. In addition to being resistant to wear, the head of the piston is hollow, resulting in a significant weight reduction, resulting in resource savings, low fuel consumption, and improved engine performance.

Furthermore, according to the piston manufacturing method of the present invention, since the reinforcing member and the core are integrated, there is no need for special measures to support the core in the mold, and furthermore, installation in the mold is easy. Since it only needs to be done once, it has the effect of significantly improving work efficiency. Furthermore, since the shape of the core can be changed freely,
This has the additional effect of increasing the degree of freedom in design and, in turn, improving cooling performance.

Next, the present invention will be explained in detail.

First, the piston of the present invention will be explained.

Any reinforcing member may be used as long as it has excellent heat resistance and wear resistance. Generally, metal materials, ceramics, etc. can be used.

The reinforcing member is attached to the top of the piston head, which is subject to high heat loads, and to the piston ring groove, which requires heat resistance and wear resistance.

The portion reinforced with the reinforcing member does not have to be the entire top of the piston or the piston ring groove, and in particular,
It may be necessary to only apply a portion of the load. Moreover, conversely, the entire head portion of the piston can be made of a reinforcing member.

The reinforcing member attached to the top of the piston and the reinforcing member attached to the piston ring groove are integrally formed with each other. That is, if they are made of the same material, they are manufactured integrally by casting, and if the top of the piston and the piston ring groove are made of different materials, they are partially joined by appropriate means such as welding. Thereby, the rigidity of the entire piston can be improved.

The piston of the present invention has a hollow head. The size of this hollow portion is appropriately determined within a range that can maintain the strength of the entire piston to a level that does not pose a practical problem. Further, the shape of the hollow portion can be determined as appropriate in consideration of cooling performance and the like.

Next, a method for manufacturing a piston according to the present invention will be explained.

The present invention is characterized in that the reinforcing member and the core are integrated and cast in a light alloy, and other steps are not particularly different from conventional casting methods.

As mentioned above, the reinforcing member is an integral part of the top part of the piston and the piston ring groove part, and if the reinforcing member is applied only to a part of the piston head, the part of the reinforcing member is a bridge between the top part of the piston and the piston ring groove part. It can be attached to a hanging part, and if the entire head part of the piston is made of a reinforcing member, it can be integrated by inserting a core inside.

The method of joining the reinforcing member and the core depends on the shape of the reinforcing member and the core, but the reinforcing member can be installed in a core molding machine and integrated at the stage of molding the core. Also,
Both may be joined by adhesion.

In the present invention, in addition to the gravity casting method using a general sand mold, a mold casting method, a low pressure casting method, a pressure casting method, etc. can be used.

Moreover, as the material of the core, a water-soluble core can be used in addition to a general sand core. Here, the water-soluble core is a core that has the property of dissolving in water, such as gypsum, NaC1
, KCj, Na2CO3, etc. In the case of a water-soluble core, workability is improved because the core can be easily removed.

Next, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view of a piston according to a first embodiment of the present invention, the right half is a sectional view of the piston pin hole seen from the front, and the left half is a sectional view of the right half viewed from the right angle FIG.

The piston body 1 is made of aluminum alloy (JIS AC8A
), and a spheroidal graphite cast iron member (
JIS FCD4.5) is molded. Also,
A hollow portion 3 is provided in the head portion of the piston, and a bridging portion 4 of a reinforcing member crosses this hollow portion 3.

Next, a method of manufacturing this piston will be explained. FIG. 2 is a plan view of the reinforcing member 2 used in the first embodiment, and FIG. 3 is a sectional view taken from the line Tll7-TIT in FIG. 2.

The reinforcing member 2 having the shape shown in FIGS. 2 and 3 was integrally cast using a spheroidal graphite cast iron member (JIS FCD45). Next, this reinforcing member 2 is installed in a core molding machine and molded to form the bridging portion 4 of the reinforcing member 2.
The core 5 was integrally attached to the reinforcing member 2 via. This integrated core 5 and reinforcing member 2 was placed in a mold having a piston-shaped space, and molten aluminum alloy (JIS AC8A) was poured into the mold by gravity casting to produce a screw tube. .

Figure 4 shows the state in which the casting plan part has been removed after the molten metal has solidified. A protrusion 6 for removing the core is integrally formed in advance on the core 5. By removing the core 5 from the protrusion 6, the piston shown in FIG. 1 was obtained. Note that the hole 7 from which the core 5 has been removed may be plugged with a blind plug.

The weight of the piston obtained in this example could be reduced by about 20% compared to a conventional piston having a solid piston head.

Embodiment 2 FIG. 5 is a sectional view of a piston according to a second embodiment of the present invention. FIG.

The piston body 1 is made of aluminum alloy (JIS AC8A), and a part of the top of the piston and the outer circumference of the head are made of spheroidal graphite cast iron (JIS FCD), which has excellent heat resistance and wear resistance.
The reinforcing member 2 is integrally cast from 45). Further, a hollow portion 3 is provided in the head portion of the piston.

Next, a method of manufacturing this piston will be explained. 61st! ′
1 shows the cross section of the core '5. It was molded using NaCl.

Next, this core 5 is placed in a mold, and the head portion of the piston consisting of the reinforcing member 2 is made of spheroidal graphite cast iron (JIS FCD4
5) When casting with molten metal, it is integrally cast. after that,
The integrated reinforcing member 2 and core 5 were placed in a piston mold, and a piston was manufactured at low pressure using aluminum alloy (JIS AC8A) hot water.

FIG. 6 shows the state in which the casting plan part is removed after the molten metal solidifies. The core 5 is provided with a protrusion 6 for core removal in advance. The entire piston is immersed in water, and from the protrusion 6 to the core 5.
By removing , the piston shown in FIG. 5 was obtained.

Note that the hole 7 from which the core 5 has been removed may be plugged with a blind plug.

The weight of the bis-1 cylinder obtained in this example could be reduced by about 30 to 40% compared to the conventional piston head having a solid piston head.

Furthermore, since the core was formed of NaCl, it was extremely easy to remove the core.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a piston according to a first embodiment of the present invention, Fig. 2 is a plan view of a reinforcing member used in the first embodiment, and Fig. 3 is a view taken from the line m-'m in Fig. 2. 4 is a sectional view showing one step of the manufacturing process in the first embodiment of the present invention, FIG. 5 is a sectional view of a piston according to the second embodiment of the present invention, and FIG. 6 is a sectional view of the piston according to the second embodiment of the present invention. 1, 4, 5, and 6, the right half is a sectional view showing the hole of the piston pin from the front, The left half is a sectional view seen from a direction perpendicular to the right half. 1------ Piston body 2------ Reinforcing member 3----Hollow part 4------Bridge part 5---One core 6---One bump Part 7 ---- Applicant Anabe I. Kokuji 5! A'4 Zhu Shiki Company 1] Figure 1 Figure 4 2 Sentry 2

Claims (3)

[Claims] (1) A reinforcing member with properties such as heat resistance or abrasion resistance is cast in parts that require properties such as heat resistance or abrasion resistance, and
A piston for an internal combustion engine, characterized in that the screws 1 to 1 are hollow. (2) A reinforcing member with such properties is cast in parts that require properties such as heat resistance or abrasion resistance, and
A method of manufacturing a piston for an internal combustion engine having a hollow piston head, the step of integrating the reinforcing member with a core forming a hollow part of the piston head, the integrated reinforcing member and the core forming a hollow part of the piston head. A method for manufacturing a piston for an internal combustion engine, comprising the following steps: placing a core in a piston casting mold, pouring a molten light alloy into the mold, and removing the core after solidification. One A (3) A method for manufacturing a piston for an internal combustion engine according to claim 2, wherein the core is made of a water-soluble substance.