JPH08303297A - Internal combustion engine piston and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [Object] To provide an FRM piston with a cooling channel for cooling an internal combustion engine having suitable characteristics and a method for manufacturing the same. [Structure] An FRM strengthened portion was manufactured in advance in a shape of a portion to be strengthened by a molten metal casting method, and thereafter, a core for a cooling channel was set in a mold together with the FRM strengthened portion and cast by an aluminum alloy melt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston for an internal combustion engine and a method for manufacturing the piston, and more particularly, to an FRM piston with a cooling channel for cooling and a method for manufacturing the FRM piston.

[0002]

2. Description of the Related Art The pistons of internal combustion engines, especially automobile engines, are exposed to unprecedentedly high temperature combustion gas in accordance with the recent high performance, and the usage situation is becoming more and more severe. In fact, the temperature around the piston head and the 1st ring groove was sometimes as high as 300 ° C or higher. Conventionally, the following measures have been taken as measures against heat. (1) As shown in FIG. 4, the piston head 41 and the ring groove 42 are made of ceramic fibers having excellent high-temperature strength, heat resistance, and wear resistance, or an FRM piston in which whiskers and aluminum alloys are combined to improve heat resistance of the piston itself. Improve. (2) As shown in FIG. 5, when a piston is cast, a cooling channel 51 is provided by using a core behind the ring groove directly below the piston head, and an oil jet nozzle 52 is provided there.
Cooling is done by flowing engine oil from.

[0003]

When ceramics and aluminum alloy are compounded, for example, as shown in Table 1, when JIS whisker is compounded with JIS AC8A alloy in a volume ratio of 20%, the original AC8A alloy is obtained. The thermal conductivity is reduced by about 20%. Therefore, although the heat resistance of the piston itself is improved, the ability to release the heat generated by the combustion through the piston ring is rather decreased. As a result, the composite reinforced portion became a hot spot and knocking was likely to occur, and the original heat resistance of the FRM piston was not utilized.

[0004]

[Table 1]

However, in order to form a composite of ceramics and aluminum alloy, it must be manufactured by a molten metal casting method in which a pressure is applied to the molten metal by a plunger, and the core is destroyed by the pressure of the molten metal, so that cooling is performed. It is not possible to manufacture FRM pistons with channels. In addition, the cooling channel alone has a limited cooling capacity, so it was not possible to cope with higher engine performance. Therefore, an object of the present invention is to provide an FRM piston with a cooling channel for cooling and a method for manufacturing the same, which solves the above-mentioned drawbacks.

[0006]

In order to solve the above-mentioned problems, an invention according to claim 1 is a FRM piston with a cooling channel, wherein an FRM strengthening portion is formed in advance in a shape of a portion to be strengthened by a molten metal casting method. It is characterized in that it is manufactured, and then, the core for the cooling channel is set in the mold together with the FRM strengthening portion, and the core is cast and wrapped in the molten aluminum alloy.

According to a second aspect of the present invention, in the FRM piston with a cooling channel according to the first aspect, the weight of the casting material is set when the core for the cooling channel is set in the mold together with the FRM strengthening portion and cast in the molten aluminum alloy. On the other hand, it is characterized in that the molten aluminum is poured so that the weight of the feeder becomes 2 to 7 times.

According to a third aspect of the present invention, there is provided a method of manufacturing an FRM piston with a cooling channel, wherein the FRM strengthened portion is manufactured in a shape of a portion to be strengthened in advance by a molten metal casting method, and thereafter, the cooling channel together with the FRM strengthened portion is manufactured. It is characterized in that the inner core is set in a mold and cast in a molten aluminum alloy.

According to a fourth aspect of the present invention, in the method for manufacturing an FRM piston with a cooling channel according to the third aspect, when the cooling channel core is set in the mold together with the FRM strengthening portion and cast with the molten aluminum alloy, It is characterized in that molten aluminum is poured so that the weight of the molten metal is 2 to 7 times the weight of the casting material.

An outline of the process of the present invention will be described with reference to FIG. (1) Manufacture of preform Suitable whiskers, for example, whisker diameter 0.3-
A Tokai Carbon SiC whisker having a size of 1.4 μm, a whisker length of 5 to 30 μm and an aspect ratio of 10 to 40 is put into a mold and press-molded by a dry press to obtain a preform of an FRM-reinforced portion.

(2) The FRM manufacturing preform is preheated to 700 to 750 ° C. in an electric furnace and then placed in a mold heated to 200 to 400 ° C.
Aluminum alloy melt at 0 to 780 ° C, for example JIS A
Pour molten C8A into the mold and use a plunger to make 50-20
The fiber-reinforced metal (FRM) that becomes the piston-reinforced portion is obtained by solidifying while applying a pressure of 0 MPa. This is machined to form a piston 1st ring groove reinforcing material.

(3) Installation of the core and the strengthening part in the mold A cooling channel core molded with sand or salt and a 1st ring groove strengthening part manufactured by FRM are used for 100 to 100%.
After preheating to 400 ° C, the core and the strengthening part are placed in the piston die heated to 100 to 400 ° C.

(4) Casting , then the weight of the riser is 2 to 7 relative to the weight of the piston material.
An aluminum alloy melt of 700 to 780 ° C., for example, JIS AC8A melt was poured into the mold by gravity casting so as to be doubled, and then cooled and solidified as it was. At this time, by continuously supplying a sufficient amount of the molten aluminum alloy into the mold so that the weight of the pressed metal is twice the weight of the piston material, thermal energy is supplied from the molten aluminum alloy to generate the composite material. The surface is heated and melted, the oxide film on the surface is destroyed, and the liquid phase of the reinforcing material matrix and the liquid phase of the aluminum molten metal are diffused with each other to form a strong joint interface. Further, when the amount of molten metal is more than 7 times the weight of the casting material, the melting loss of the material to be cast is severe, which is not preferable. Therefore, it is preferable to control the molten metal amount within the above range. The casting material is a casting product before machining, and the casting material weight refers to the weight of the casting product.
In addition, the hot water is generally used to replenish the molten metal to the portion that contracts due to solidification and shrinkage to prevent shrinkage cavities.
In the present proposal, it is used for the purpose of supplying heat energy from the molten metal to the surface of the material to be cast, and the weight of the molten metal refers to the weight of the entire molten metal.

(5) Taking out the core After casting, the core for the cooling channel is taken out. (6) Heat treatment / machining After the solution heat treatment and aging heat treatment are applied to the piston casting material, the outer circumference of the piston, ring groove, oil groove, piston pin hole, etc. are machined and the FRM has a cooling channel. The piston was molded.

A sectional view of the piston obtained as described above is shown in FIG. In FIG. 2, reference numeral 1 shows a portion using the FRM reinforcing member, and 2 is a cooling channel. Oil is supplied to the cooling channel 2 from an oil jet nozzle 3. Thus, the piston of FIG.
The RM reinforcing member 1 and the cooling channel 2 are both provided.

[0016]

Embodiments of the present invention will be described below. (1) Manufacture of preform Whisker diameter 0.3 to 1.4 μm, whisker length 5
After the Tokai Carbon SiC whiskers with a thickness of -30 μm and an aspect ratio of 10-40 were put into the mold, the volume ratio was 20.
Press molding was carried out with a dry press so that the content of the disc was 0.5% to obtain a disc-shaped preform. (2) After preheating the FRM manufacturing preform to 750 ° C in an electric furnace, 250
Placed in a mold heated to ℃ 750 ℃ JIS AC
Pour 8A molten metal into the mold and use a plunger to 100MPa
Solidification was carried out while applying the pressure of 1. to obtain a fiber-reinforced metal (FRM) which becomes a ring-shaped piston-reinforced portion. This is machined to form a piston 1 with an outer diameter of 65 mm and a thickness of 9 mm.
The st-ring groove reinforcing material was used. (3) The cooling channel core molded with cast-in sand or salt and the 1st ring groove reinforced part manufactured by FRM are heated to 200 ° C.
After preheating, the core and the reinforcement are placed in a piston die heated to 200 ° C. Next, the piston material weight 25
JIS AC8A alloy at 750 ° C. was poured into a mold by gravity casting so that the weight of the molten metal was 500 g, which was twice the weight of 0 g, and then cooled and solidified. At this time, by continuously supplying a sufficient amount of the molten aluminum alloy into the mold so that the weight of the pressed metal is twice the weight of the piston material, thermal energy is supplied from the molten aluminum alloy to generate the composite material. The surface is heated and melted, the oxide film on the surface is destroyed, and the liquid phase of the reinforcing material matrix and the liquid phase of the aluminum molten metal are diffused with each other to form a strong joint interface. (4) Heat treatment / machining After the solution heat treatment and aging heat treatment are applied to the piston casting material, the outer circumference of the piston, ring groove, oil groove, piston pin hole, etc. are machined and the FRM has a cooling channel. The piston was molded. (5) Product The product obtained is an F with a cooling channel in which the 1st ring groove is reinforced with FRM as described in FIG.
It is an RM piston.

As described above, after the FRM strengthened portion is manufactured by the molten metal casting method in advance, the cooling channel core, which has been impossible to manufacture by the conventional method, is used by casting and encapsulating the FRM strengthened portion. FRM piston manufacturing is now possible. As for the cast-in interface, as shown in FIG. 3, by casting using a sufficient amount of molten aluminum, thermal energy is supplied from the molten aluminum, the oxide film on the surface of the reinforcing material is destroyed, and a strong bonded interface is obtained. Can be formed. By using the FRM piston with the cooling channel, the FRM reinforced portion having a low thermal conductivity is positively cooled by the engine oil, and the heat resistance and wear resistance inherent to FRM are utilized. Therefore, it is possible to achieve higher compression ratio and leaner combustion, in which the combustion gas temperature becomes higher, which was not possible with the conventional FRM piston, and as a result, to achieve higher engine performance such as higher output and lower combustion cost. You can In addition, since only the strengthened part is manufactured by molten metal forging and then compounded by casting encapsulation, it is possible to greatly simplify the mold and equipment compared with the FRM piston integrally manufactured by conventional molten metal forging. Therefore, the FRM piston can be manufactured at a lower cost than before.

[0018]

As is apparent from the above description, according to the present invention, there is provided an FRM piston with a cooling channel for cooling an internal combustion engine, which has suitable characteristics, and a manufacturing method thereof.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a method of manufacturing an FRM piston with a cooling channel for cooling an internal combustion engine according to the present invention.

FIG. 2 is a sectional view illustrating an FRM piston with a cooling channel for cooling an internal combustion engine manufactured according to the present invention.

FIG. 3 is a 100 × optical micrograph of a cast-in interface of an FRM piston with a cooling channel for cooling an internal combustion engine manufactured according to the present invention.

FIG. 4 is a sectional view illustrating a conventional piston.

FIG. 5 is a sectional view illustrating a conventional piston.

[Explanation of symbols]

 1 Parts using FRM strengthening member 2 Cooling channel 3 Oil jet nozzle

Claims (4)

[Claims] 1. A FRM-reinforced portion is manufactured in advance in a shape of a portion to be strengthened by a molten metal casting method, and thereafter, a core for a cooling channel is set in a mold together with the FRM-reinforced portion, and the FRM-reinforced core is cast and wrapped in molten aluminum alloy. An FRM piston with a cooling channel for an internal combustion engine, which is manufactured. 2. An F with a cooling channel according to claim 1.
In the RM piston, when the core for the cooling channel is set in the mold together with the FRM strengthening part and is cast and wrapped with the molten aluminum alloy, the weight of the molten aluminum should be 2 to 7 times the weight of the casting material. F with cooling channel for internal combustion engine characterized by pouring hot water
RM piston. 3. An FRM-reinforced portion is manufactured in advance in a shape of a portion to be strengthened by a molten metal casting method, and thereafter, a core for a cooling channel is set in a mold together with the FRM-reinforced portion and cast by an aluminum alloy melt. A method for manufacturing an FRM piston with a cooling channel for an internal combustion engine, which is characterized. 4. The method of manufacturing an FRM piston with a cooling channel for an internal combustion engine according to claim 3, wherein the weight of the casting material is set when the core for the cooling channel is set in the mold together with the FRM strengthening portion and cast with the molten aluminum alloy. On the other hand, a method for manufacturing an FRM piston with a cooling channel for an internal combustion engine, which comprises pouring the molten aluminum so that the weight of the riser becomes 2 to 7 times.