JPH05123826A - Mold forming cylinder block of two-cycle engine - Google Patents

Abstract

PURPOSE:To provide a forming mold for cylinder block in a twocycle engine, in which the cylinder block can simply be formed by reducing the number of cores. CONSTITUTION:The forming mold for cylinder block 3 having three pieces of scavenge air passages 131, 132. 133 at symmetrical positions and an intermediate scavenge air passage 134 among three pieces of the scavenge air passages 131, 132, 133 at this symmetrical positions, combines an inside split mold 50 and an outside split mold 51 as one set of the scavenge air passage 133 at the intermediate scavenge air passage side in three pieces of the scavenge air passages 131, 132, 135 at the symmetrical positions with the intermediate scavenge air passage 134 and combines an inside split mold 60 and an outside split mold 61 as one set of the remained two pieces of the scavenge air passages 131, 132 in three pieces of the scavenge air passages 131, 132, 135 at the symmetrical positions to constitute the core for scavenge air passage with three sets of the split molds.

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-stroke engine which forms a cylinder block having a scavenging passage.

[0002]

2. Description of the Related Art For example, in a two-cycle engine, a scavenging passage is formed in a cylinder block, and an air-fuel mixture in a crank chamber is introduced into a combustion chamber through a scavenging passage by the operation of a piston, and is compressed and burned in the combustion chamber. ing.

As described above, the scavenging passage is formed in the cylinder block, and since the cylinder block has a complicated shape by this, it is formed by the mold.

[0004]

By the way, for example, in a two-cycle engine mounted on a motorcycle for racing or the like, three scavenging passages are formed at symmetrical positions in a cylinder block, and three scavenging passages at these symmetrical positions are formed. In some cases, an intermediate scavenging passage is formed between the individual scavenging passages, and a total of seven scavenging passages are formed.

As described above, in the cylinder block having a large number of scavenging passages, the mold becomes complicated, and in particular, the three scavenging passages formed at symmetrical positions are restricted by the structure of the scavenging passages.
It is not possible to make a split type with three scavenging passages as one set,
Inevitably, it was necessary to make a split mold for two scavenging passage groups and a split mold for one scavenging passage group, and a total of five cores were required.

Therefore, the structure of the mold is complicated, the manufacturing cost must be increased, and the increased number of split molds in the cylinder block causes ribs to be formed in the connection portion, which increases the processing cost for polishing the same. There is a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a mold for forming a cylinder block of a two-cycle engine which can easily form a cylinder block by reducing the number of cores. I am trying.

[0008]

In order to solve the above problems, the present invention is a cylinder having three scavenging passages at symmetrical positions and an intermediate scavenging passage between the three scavenging passages at the symmetrical positions. In a mold for forming a cylinder block of a two-cycle engine forming a block, an inner split mold is formed by combining the intermediate scavenging passage and one scavenging passage on the intermediate scavenging passage side among the three scavenging passages at the symmetrical positions. And the outer split mold are combined, the remaining two scavenging passages of the three scavenging passages at the symmetrical positions are respectively set as one set, and the inner split mold and the outer split mold are combined, and scavenging is performed by the three split molds. The feature is that it constitutes the core of the passage.

[0009]

According to the present invention, the molding mold having the three scavenging passages at the symmetrical positions and forming the cylinder block having the intermediate scavenging passages between the three scavenging passages at the symmetrical positions is symmetrical to the intermediate scavenging passages. Of the three scavenging passages at the positions, one scavenging passage on the side of the intermediate scavenging passage is used as a set to combine the inner split type and the outer split type, and the remaining two scavenging passages of the three scavenging passages at the symmetrical positions are combined. It has a core consisting of a combination of an inner split mold and an outer split mold with each scavenging passage as one set,
By combining one scavenging passage out of three scavenging passages, which cannot be made into one set due to structural restrictions, with the intermediate scavenging passage, the total number of cores is reduced to three.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a mold for forming a cylinder block of a two-cycle engine of the present invention will be described in detail below with reference to 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 its forming mold, FIG. 3 is a sectional view taken along line III-III of FIG. 2, and FIG. 4 is a development view of a part of the cylinder block.

Reference numeral 1 is 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 attached to the cylinder block 3.

A piston 6 is provided in the cylinder 5 of the cylinder block 3 so as to be capable of reciprocating. The piston 6 is connected to a crankshaft 8 via a connecting rod 7, and the crankshaft 8 is rotatable around a crankcase 2. Is supported by.

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 the head of the piston 6 provided in the cylinder 5 of the cylinder block 3, and an ignition plug 11 is provided in the center of the cylinder head 4 to form the combustion chamber 1.
It is attached so as to face 0. Further, the combustion chamber 10 and the crank chamber 12 formed in the crankcase 2 are communicated with each other by a scavenging passage 13 formed in the cylinder block 3,
By the operation of the piston 6, the air-fuel mixture is supplied from the crank chamber 12 to the combustion chamber 10 through the scavenging passage 13.

The scavenging passage 13 formed in the cylinder block 3 is constructed as shown in FIGS.
That is, three scavenging passages 131, 132, 133 are formed at symmetrical positions of the cylinder block 3, and the three scavenging passages 131, 132, 133 are formed at the symmetrical positions.
An intermediate scavenging passage 134 is formed between the individual scavenging passages 131, 132, 133. These three scavenging passages 13
1, 132, 133 communicate with each other on the crank chamber side, and on the other hand, on the way to the combustion chamber side, branch portions 131a, 132a, which branch off to open inside the cylinder block 3, respectively.
133a, and the intermediate scavenging passage 134 also has an opening 134a that opens to the inside of the cylinder block 3.

Further, a main exhaust passage 14 is formed at a position facing the intermediate scavenging passage 134, and a sub exhaust passage 15 is formed on each side of the main exhaust passage 14. The sub exhaust passage 15 is a main exhaust passage. It branches from 14 and opens at a position above the opening 131 a of the scavenging passage 131.

The cylinder block 3 is formed by a mold, and one of the three scavenging passages 131, 132, 133 symmetrical to the intermediate scavenging passage 134 and one scavenging passage 133 on the side of the intermediate scavenging passage 134 are set as a set. 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 symmetrical positions are respectively set as one set, and the inner split mold 60 and the outside are formed. In combination with the split mold 61, three sets of split molds constitute the core of the scavenging passage.

In this way, the three scavenging passages 1 are symmetrically arranged.
The core forming the cylinder block 3 having 31, 132, 133 and having the intermediate scavenging passages 134 between the three scavenging passages 131, 132, 133 at the symmetrical positions has a core symmetric to the intermediate scavenging passages 134. The inner split mold 50 and the outer split mold 51 are combined with one scavenging passage 133 as one set, and the two split scavenging passages 131 and 132 at symmetrical positions are respectively set as one set, and the inner split mold 60 and the outer split mold 61 are combined. Even if it is not possible to form the three scavenging passages 131, 132, 133 into a set of split molds due to the structural limitation of the scavenging passage, one of the scavenging passages 133 is included in each scavenging passage 133. 3 in combination with the intermediate scavenging passage 134
The number of cores is reduced.

[0018]

As described above, according to the present invention, the three scavenging passages are provided at the symmetrical positions, and the three scavenging passages are provided at the symmetrical positions.
A core that forms a cylinder block having an intermediate scavenging passage between the scavenging passages and one scavenging passage on the intermediate scavenging passage side of the three scavenging passages symmetrical to the intermediate scavenging passage as a set. The inner split mold and the outer split mold are combined, and the remaining two scavenging passages out of the three symmetrical scavenging passages are set as one set, respectively, and the inner split mold and the outer split mold are combined to form a scavenging passage. Even if there are three scavenging passages that have structural restrictions, the one scavenging passage can be combined with the intermediate scavenging passage to reduce the number of cores, which simplifies the mold and reduces manufacturing costs. be able to.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a cylinder block of a two-cycle engine and its forming mold.

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

FIG. 4 is a development view of a part of a 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)

[Claims] 1. A mold for forming a cylinder block of a two-cycle engine, which has three scavenging passages at symmetrical positions and forms a cylinder block having an intermediate scavenging passage between the three scavenging passages at the symmetrical positions, The intermediate scavenging passage and one scavenging passage on the side of the intermediate scavenging passage out of the three scavenging passages at the symmetrical position are combined as a set to combine an inner split mold and an outer split mold, and A two-cycle engine characterized in that the remaining two scavenging passages of the scavenging passages are respectively set as one set, and an inner split mold and an outer split mold are combined, and the core of the scavenging passage is constituted by the three split dies. Cylinder block forming mold.