JPH0326287Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a piston for internal combustion engines, and in particular to a piston that is pressure cast from a light alloy such as an aluminum alloy, and is made from a steel plate that produces a bimetallic effect. This invention relates to a piston for an internal combustion engine in which a strut is cast into a skirt portion.

〓Background technology and its problems〓 In order to reduce the weight of pistons for internal combustion engines, pistons are cast using aluminum alloy. However, aluminum alloy has a large coefficient of thermal expansion, and in order to allow it to slide without seizing inside the cylinder bore made of cast iron, which has a small coefficient of thermal expansion, the clearance when cold is large, and the piston does not move during engine operation. This prevents interference with the cylinder bore even at high temperatures.
Therefore, the clearance becomes larger during partial load operation or low speed rotation when the piston does not get very hot.
The slap noise when the piston collides with the cylinder bore becomes louder. Therefore, it is common practice to cast a steel strut into the piston in order to suppress thermal expansion and to prevent the cold time clearance from becoming too large.

Such a conventional piston is shown in FIGS. 8 and 9, for example, in which a steel plate strut 3 is cast into the pin boss 2 of the piston 1, and the central curved The portion is cast into the pin boss 2, and both ends in the circumferential direction are exposed to the inner surface of the piston 1. Exposing both ends of the steel strut 4 inside the piston 1 in this way maximizes the bimetallic effect, and also allows the strut 4 to be brought into close contact with the mold during casting so that the strut 4 is held in the correct position. This is for casting into the piston 1.

Note that the bimetal effect here refers to the bimetal action of the steel strut 3 and the skirt portion of the aluminum alloy piston 1, which causes the piston to intentionally curve in the Y direction as shown by the dotted line in FIG. This refers to preventing deformation in the X direction indicated by the chain line in the same figure by deforming.

By the way, when pistons are cast from aluminum alloy, conventionally they have generally been manufactured by die casting. In order to improve the quality of the cast piston and to modify the material, pistons have been manufactured by molten metal forging or pressure casting. When casting by molten metal forging, the molten metal contains 70~
Since a pressure of 2000 kg/cm ² is applied, the molten metal can enter even very narrow gaps.

Therefore, if the strut 3 made of steel plate is cast into a piston formed by such molten metal forging or pressure casting method, the molten metal will enter between the mold and the strut, resulting in the problem shown in FIGS. 8 and 8. Burrs as shown by 4 in FIG. 9 occur. Since this burr 4 is very thin, with a thickness of 0.5 mm or less, there is a possibility that the piston may come off while the piston is operating in the engine. Therefore, it is necessary to remove such burrs 4 before installing the engine.
However, since the burr 4 comes into close contact with the strut 3, it is very difficult to remove it, and removing the burr 4 requires a large number of man-hours, causing an increase in the cost of the piston 1.

〓Purpose of the invention〓 The present invention was made in view of the above problems, and even if burrs are generated due to molten metal entering between the mold and the steel plate strut,
It is an object of the present invention to provide a piston for an internal combustion engine that prevents the burrs from falling off during operation of the piston and eliminates the need for a step of removing the burrs.

〓Summary of the invention〓 The present invention is a piston formed by pressure casting from a light alloy, in which a strut made of a steel plate is cast into the skirt portion, and the circumferential end of the strut is attached to the piston. In a piston that is exposed on the inner surface of the piston, a rib is formed from the piston base material so as to cover at least a part of the surface of the strut, and a rib is formed in the piston base material to prevent the strut from entering between the mold and the strut during pressure casting. This invention relates to a piston for an internal combustion engine, characterized in that burrs generated by molten metal are connected to the ribs, and the ribs prevent burrs generated on the surface of the strut from falling off. be.

〓Example〓 The present invention will be described below with reference to an illustrated example.
FIGS. 1 and 2 show a mold 10 for casting a piston according to an embodiment of the present invention. 11. A punch die 12 used together with the die 11 has a recess 13 formed on its side surface to form a pin boss.
A strut 14 made of a steel plate is held so as to cross this recess 13. The punch die 12 holding the strut 14 is inserted into a cylindrical mold 10 into which a molten metal 15 made of aluminum alloy has been poured, and the molten metal 15 is pressurized. At this time, the molten metal 15 has
Depending on the punch die, a pressure of 700 to 2000 kg/cm ² can be applied.

Steel plate strut 1 formed by the punch die 12
4 is achieved by a retaining magnet 16. Magnet 16 is the second
As shown in the figure, the punch die 12 is embedded within the punch die 12, and a stepped portion 17 consisting of a notch is formed on both sides of the tip end thereof. This stepped portion 17 allows a rib, which will be described later, to be formed on the inner circumferential surface of the piston.

Next, we will explain about a piston that is pressure cast using such a mold. As shown in Figures 3 to 5, it is a piston that is molded from an aluminum alloy by pressure casting or molten metal forging. In this piston, a strut 14 made of a steel plate that produces a bimetallic effect is cast into the pin boss 19, and both sides of the strut 14 in the circumferential direction are exposed to the inner surface of the piston 18. .

A rib 20 is integrally formed with the piston 18 so as to cross the exposed portion of the strut 14 in the width direction. That is, the ribs 20 are formed integrally with the piston 18 on the surface of the strut 14 by the molten metal flowing into the stepped portion 17 formed by the notch on the distal end side of the magnet 16. Therefore, the burr 21 produced by the molten metal 15 entering between the strut 14 and the punch die 12 when casting the piston 18 becomes connected to the rib 20. Since the burr 21 is connected to the rib 20 in this manner, the burr 21 is prevented from falling off when the piston 18 is installed in the engine and operated.

Moreover, in this piston 18, the piston 1
Rib 20 made of base material forming 8
extends in the height direction of the piston 18, so after the piston 18 solidifies, the mold 1
0 and 12 can be easily separated. Also, regarding the number of ribs 20, burr 2
It can be changed as appropriate depending on the occurrence tendency of 1. Further, since the entire surface of the strut 14 is not covered with the rib 20 but only partially, the bimetal effect of the strut 14 is not impaired. Furthermore, when holding the strut 14 in the punch die 12, no gap is formed between the magnet 16 and the strut 14, and the strut 14
can be held securely.

As described above, the piston 18 pressure-cast from the aluminum alloy according to the present embodiment has a structure in which the portion of the strut 14 exposed to the inner surface of the piston 18 is locally covered with the rib 20. The ribs 20 connect and hold the burrs 21. Therefore, with such a piston, the burr 21 is prevented from falling off during operation, and there is no need to remove the burr 21 in advance. Therefore, the number of man-hours for deburring is not required, and the cost of the piston 18 can be reduced.

Next, a modification of the above embodiment will be explained with reference to FIG. In this modification and subsequent modifications, parts corresponding to those in the above embodiment are given the same reference numerals, and descriptions of parts having the same configuration will be omitted. The feature of this modification is that the rib 20
The struts 14 extend only to approximately the center in the width direction, and the ribs 20 are not formed in the lower portions. This is because the tendency of the burrs 21 to appear changes depending on the casting method of the piston 18. For example, when the piston 18 is cast with its head facing down, the burrs 21
tends to occur only on the upper side of the piston 18. Therefore, in such a case, strut 14
By simply forming the rib 20 only on the upper part in the width direction, it becomes possible to connect and hold the burr 21.

Next, another modification will be explained with reference to FIG. The feature of this modification is that the rib 20 has a width approximately one-half that of the strut 14, and is formed continuously on the circumferential side of the strut 14.
This is because the ribs 20 may be formed continuously as long as there remains a sufficient portion of the struts 14 in direct contact with the mold.
It is also possible to completely cover a portion of the width in the length direction, and in this case, almost the same purpose as in the above embodiment can be achieved.

Effects of the invention As described above, the present invention forms ribs using the piston base material so as to cover at least a portion of the surface of the strut, and prevents molten metal from entering between the mold and the strut during pressure casting. The burrs caused by this are connected to the ribs. Therefore, according to the present invention, when a piston is cast by pressure casting, it is possible to connect and support the burr caused by the molten metal that has entered between the strut and the mold by means of the rib, and the engine It is possible to prevent this burr from falling off during operation. Therefore, the step of removing the burr after casting the piston is not necessary.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an apparatus for pressure casting of a piston for an internal combustion engine according to an embodiment of the present invention;
Figure 2 is a cross-sectional view taken along the line ~ in Figure 1, Figure 3 is a longitudinal cross-sectional view showing a piston cast by this device, Figure 4 is a cross-sectional view taken along the ~ line in Figure 3, and Figure 5 is a cross-sectional view taken along the line ~ in Figure 3. 3 is a sectional view taken along the line ˜, FIG. 6 is a longitudinal sectional view of a piston according to a modified example, FIG. 7 is a longitudinal sectional view of a piston according to another modified example, and FIG. 8 is a vertical sectional view showing a conventional piston. , Figure 9 is the 8th
It is a sectional view taken along the line ˜ in the figure. In addition, in the symbols used in the drawings, 10... cylindrical mold, 12... punch die, 14... steel plate strut, 15... molten metal (aluminum alloy),
16... Holding magnet, 17... Step part (cut), 18... Piston, 19... Pin boss, 2
0...rib, 21...burr.

Claims (1)

[Scope of utility model registration request] It is a piston formed by pressure casting from a light alloy, in which a strut made of a steel plate is cast in the skirt part, and the circumferential end of the strut is exposed on the inner surface of the piston. In the piston, ribs are formed from the piston base material so as to cover at least a portion of the surface of the strut, and the ribs are formed to remove burrs caused by molten metal that has entered between the mold and the strut during pressure casting. A piston for an internal combustion engine, characterized in that the piston is connected to the piston.