JP3160721B2 - Forming mold for cylinder block of two-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for forming a cylinder block of a two-cycle engine which forms a cylinder block having a scavenging passage.

[0002]

2. Description of the Related Art In a two-stroke engine, for example, a scavenging passage is formed in a cylinder block. By operating a piston, an air-fuel mixture in a crank chamber is guided to a combustion chamber through a scavenging passage, and is compressed and burned in the combustion chamber. ing.

[0003] As described above, the scavenging passage is formed in the cylinder block, so that the cylinder block has a complicated shape.

[0004]

In a two-stroke engine mounted on a motorcycle for racing, for example, three scavenging passages are formed at symmetric positions in a cylinder block, and three scavenging passages are formed at the symmetric positions. In some cases, an intermediate scavenging passage is formed between the scavenging passages and a total of seven scavenging passages are formed.

In such a cylinder block having a large number of scavenging passages, the mold becomes complicated. In particular, the three scavenging passages formed at symmetrical positions are limited by the structural limitations of the scavenging passages.
Three scavenging passages cannot be split into one set,
Inevitably, it is necessary to form a split mold of two scavenging passage sets and a split mold of one scavenging passage set, and a total of five sets of cores are required.

Accordingly, not only is the structure of the mold complicated and the manufacturing cost is increased, but also as the number of split molds in the cylinder block increases, ribs are formed in the connecting portions thereof, and the processing cost for polishing these increases. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a mold for forming a cylinder block of a two-cycle engine in which the number of cores can be reduced and a cylinder block can be easily formed. And

[0008]

In order to solve the above-mentioned problems, the present invention provides a cylinder having three scavenging passages at symmetric positions and an intermediate scavenging passage between the three scavenging passages at the symmetric positions. In a mold for forming a cylinder block of a two-stroke engine forming a block, an inner split mold is provided in which the intermediate scavenging passage and one scavenging passage on the intermediate scavenging passage side among the three scavenging passages at the symmetric position are paired. And the outer split molds, and the inner split mold and the outer split mold are combined with the remaining two scavenging passages of the three scavenging passages at the symmetric position as one set, and scavenging is performed with the three sets of split molds. It is characterized by constituting the core of the passage.

[0009]

According to the present invention, a molding mold having three scavenging passages at symmetrical positions and forming a cylinder block having an intermediate scavenging passage between the three scavenging passages at the symmetrical position is symmetric with the intermediate scavenging passages. The inner split mold and the outer split mold are combined with one scavenging passage on the intermediate scavenging passage side as a set of the three scavenging passages at the position, and the remaining two scavenging passages at the symmetrical position are combined. It has a core consisting of a combination of an inner split mold and an outer split mold with each set of scavenging passages,
By combining one scavenging passage among the three scavenging passages that cannot be combined due to structural restrictions with the intermediate scavenging passage, the number of cores is reduced to three as a whole.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a mold for forming a cylinder block of a two-cycle engine according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is an overall view of a two-stroke engine, and FIG.
FIG. 3 is a view showing a cylinder block of a two-cycle engine and a mold for forming the cylinder block. FIG. 3 is a sectional view taken along the line III-III of FIG. 2, and FIG.

Reference numeral 1 denotes a two-cycle engine. A cylinder block 3 is mounted on a crankcase 2 of the two-cycle engine 1, and a cylinder head 4 is mounted on the cylinder block 3.

A piston 6 is provided on the cylinder 5 of the cylinder block 3 so as to be able to reciprocate. The piston 6 is connected to a crankshaft 8 via a connecting rod 7, and the crankshaft 8 is rotatable with respect to the crankcase 2. It is pivoted on.

A recess 4a is formed in the cylinder head 4 mounted on the cylinder block 3, and a heat-resistant member 9 is provided in the recess 4a. A combustion chamber 10 is formed by the heat-resistant member 9 and the cylinder head 4, and a head of a piston 6 provided in the cylinder 5 of the cylinder block 3.
It is attached to face 0. Further, the combustion chamber 10 and a crank chamber 12 formed in the crankcase 2 are communicated by a scavenging passage 13 formed in the cylinder block 3,
The air-fuel mixture is supplied from the crank chamber 12 to the combustion chamber 10 through the scavenging passage 13 by the operation of the piston 6.

The scavenging passage 13 formed in the cylinder block 3 is configured as shown in FIGS.
That is, three scavenging passages 131, 132 and 133 are formed at symmetric positions of the cylinder block 3, and the three scavenging passages 131, 132 and 133 are formed at the symmetric positions.
An intermediate transfer passage 134 is formed between the transfer passages 131, 132, 133. These three scavenging passages 13
Openings 131a, 132a, 133a, 132a,
133a, and the intermediate scavenging passage 134 also has an opening 134a that opens inside the cylinder block 3 similarly.

Further, a main exhaust passage 14 is formed at a position opposed to the intermediate scavenging passage 134, and sub exhaust passages 15 are formed on both sides of the main exhaust passage 14, respectively. It branches from 14 and opens above the opening 131 a of the scavenging passage 131.

The cylinder block 3 is formed by a mold, and a pair of the intermediate scavenging passage 134 and one scavenging passage 133 on the side of the intermediate scavenging passage 134 among the three scavenging passages 131, 132, 133 symmetrically positioned. The inner split mold 50 and the outer split mold 51 are combined, and the remaining two scavenging passages 131, 132 among the three scavenging passages 131, 132, 133 at the symmetrical position are each set as one set, and the inner split mold 60 and the outer split mold are combined. Combined with the split mold 61, the core of the scavenging passage is constituted by three sets of split molds.

As described above, the three scavenging passages 1 are located at symmetric positions.
The core forming the cylinder block 3 having the scavenging passages 131, 132, and 133 at the symmetrical positions and having the scavenging passages 131, 132, and 133 has a symmetrical position with the intermediate scavenging passages 134. The inner split mold 50 and the outer split mold 51 are combined as one set of the scavenging passages 133, and the inner split mold 60 and the outer split mold 61 are formed as two sets of symmetrically positioned scavenging passages 131 and 132, respectively. Even if three scavenging passages 131, 132, and 133 cannot be divided into one set due to structural restrictions of the scavenging passage, one scavenging passage 133 of each of them can be used. By combining with the intermediate scavenging passage 134, 3
The number of cores has been reduced.

[0018]

As described above, the present invention has three scavenging passages at symmetric positions,
A core forming a cylinder block having an intermediate scavenging passage between the two scavenging passages forms a pair of the intermediate scavenging passage and one scavenging passage on the intermediate scavenging passage side among the three scavenging passages at symmetric positions. The inner split mold and the outer split mold are combined, and the inner split mold and the outer split mold are combined to form a pair of the remaining two scavenging passages of the three scavenging passages at the symmetric positions. Even if there are three scavenging passages which have structural limitations, it is possible to reduce the number of cores by combining the one scavenging passage with the intermediate scavenging passage, thereby simplifying the mold and reducing the manufacturing cost. be able to.

[Brief description of the drawings]

FIG. 1 is an overall view of a two-cycle engine.

FIG. 2 is a view showing a cylinder block of a two-cycle engine and a mold for forming the cylinder block.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a development view of a part of the cylinder block.

[Explanation of symbols]

 3 Cylinder block 50, 60 Inner split mold 51, 61 Outer split mold 13, 131, 132, 133 Scavenging passage 134 Intermediate scavenging passage

Claims (1)

(57) [Claims] 1. A mold for forming a cylinder block of a two-cycle engine having three scavenging passages at symmetrical positions and forming a cylinder block having an intermediate scavenging passage between the three scavenging passages at the symmetrical position. The intermediate scavenging passage and one scavenging passage on the side of the intermediate scavenging passage among the three scavenging passages at the symmetric position are paired to form an inner split mold and an outer split mold. A two-stroke engine characterized in that the remaining two scavenging passages of the scavenging passages are respectively set as a set and an inner split mold and an outer split mold are combined to form a core of the scavenging passage with the three sets of split molds. Forming cylinder block mold.