JPS62242116A - Connecting rod for internal combustion engine - Google Patents

Abstract

PURPOSE:To form a connecting rod main unit in light weight while to hold its predetermined strength, by forming the connecting rod main unit of box- shaped section by sheet metal working to be constituted of the first cylindrical member and the second cylindrical members which are integrally formed in end parts of the connecting rod main unit. CONSTITUTION:A connecting rod 8 is constituted of a big-end part 18, small-end part 19 and a connecting rod main unit 20. The big-end part 18 is constituted of the first cylindrical member 18a, mounted to one end of the connecting rod main unit 20, and the second cylindrical member 18b, internally fitted to the first cylindrical member 18a, while the small-end part 19 is constituted of the first cylindrical member 19a, mounted to one end of the connecting rod main unit 20, and the second cylindrical member 19b internally fitted to the first cylindrical member 19a. The first cylindrical members 18a, 19a, which are made of high carbon steel with a good rolling fatigue characteristic, are directly mounted to the rod main unit 20 by brazing. The connecting rod main unit 20, which is manufactured by pressurizing a round pipe of low carbon steel with good toughness to be deformed, promotes the lightness of weight.

Description

[Detailed description of the invention] (Industrial application field) This invention relates to a connecting rod for an internal combustion engine.

(Prior Art) In an internal combustion engine, a connecting rod is provided to connect a crankshaft and a piston in order to interlock the two. This connecting rod normally has a large end that is rotatably fitted onto the crankshaft, a small end that is rotatably fitted onto the piston pin, and connects these large and small ends. The main body of the connecting rod 'a' is conventionally made of a forged piece and is therefore a solid member.

(3? The problem that Akira tries to solve) By the way, when an internal combustion engine is driven, the connecting rod is repeatedly subjected to an impactful axial force, so the connecting rod must have sufficient strength. required. In this case, the above requirements can be met by making the connecting rod thicker. However, if the connecting rod is made thicker, firstly, the weight of the connecting rod increases, and the inertia force becomes too large during high-speed operation, resulting in This has the disadvantage that the loss becomes excessive. Secondly, since the connecting rod is solid, @
The surface stress that occurs when bending occurs under a compressive load is large, and therefore, even if the thickness is increased as described above, the fatigue strength cannot be improved.

Moreover, when an internal combustion engine is used to drive the connecting rod, rolling fatigue occurs at the large end and the small end, and an impactful axial force is repeatedly applied to the connecting rod body. Therefore, the large end and small end are required to have improved transfer fatigue properties, while the connecting rod body is required to have improved toughness. However, in the conventional configuration described above, since the connecting rod is integrally formed with a forged product, it is difficult to satisfy the above-mentioned plurality of requirements at the same time. Therefore, it is conceivable to construct the large end, the small end, and the connecting rod body individually from different materials and to connect them to each other. However, in this case, in order to ensure sufficient strength at the connection between the two,
The configuration of the connecting rod may become complicated.

(Object of the Invention) This invention was made in view of the above-mentioned circumstances, and aims to maintain a predetermined strength in a connecting rod, make it lightweight, and improve fatigue strength. In addition, it satisfies the multiple requirements of improving transfer fatigue properties at the large end and small end, and improving toughness in the connecting rod body, and the large end, small end, and connecting rod body It is an object of the present invention to ensure a predetermined strength at a connecting portion of the holder with a simple structure.

(Structure of the Invention) A feature of the present invention for achieving the above object is that the connecting rod body is formed into a box-shaped cross section using a sheet metal mold, and each of the large end and small end is formed at the end of the connecting rod main body. The structure consists of an MS1 cylindrical body that is integrally molded with the part, and a second cylindrical body that is fitted inside the first cylindrical body.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, reference numeral 1 denotes a two-stroke engine that is an internal combustion engine, and although this engine 1 is not shown, it is mounted on a motorcycle.

The engine 1 has a crankcase 3, within which a crankshaft 4 is supported. This crankshaft 4 is interlocked and connected to a rear wheel, which is a driving wheel, via a power transmission means 5. A cylinder 6 is provided on the crankcase 3, and a piston 7 is fitted into the cylinder 6 so as to be vertically slidable. The axes of the crank pin 4a of the crankshaft 4 and the piston pin 7a of the piston 7 are parallel to each other, and a connecting rod 8 is provided to link these together.

The upper part of the cylinder 6 partitioned by the piston 7 is a combustion chamber 9, and a spark plug 10 is provided for this combustion chamber 9. -012 is an intake port;
A carburetor 14 is attached to 2 via a reed valve 13. This reed valve 13 only allows the air-fuel mixture to flow into the crankcase 3. 15 is an exhaust boat, and 16 is a scavenging port.

Then, if the piston 7 rises (arrow A in Fig. 2),
), since the inside of the crankcase 3 becomes negative pressure, the carburetor 14
The air-fuel mixture from the engine passes through the reed valve 13 to the crankcase 3
(arrow B in the figure) Next, when the piston 7 descends, the air-fuel mixture that has been drawn into the crankcase 3 is pressurized as described above, and this air-fuel mixture flows into the scavenging boat 1.
6 into the combustion chamber 9 (arrow c in the figure).

When the piston 7 rises again, the air-fuel mixture that has entered the combustion chamber 9 is compressed and ignited by the spark plug 10 to be combusted. At this time, as the piston 7 rises, the air-fuel mixture is sucked into the crankcase 3 as described above. When the piston 7 descends during the above combustion, the air-fuel mixture in the crankcase 3 flows into the combustion chamber 9 as described above, and at this time,
The gas that was combusted first is discharged from the exhaust boat 15 with this air-fuel mixture (arrow D in the figure). From then on, this process is repeated to drive the engine l.

The connecting rod 8 will be explained in more detail with reference to FIGS. 1 and 3.

The connecting rod 8 has a large end 18 externally fitted around the crank pin 4a so as to be freely rotatable around its axis, and a small end 19 externally fitted around the piston pin 7a so as to be freely rotatable around its axis. , a connecting rod main body 20 connecting these large end portions 18 and small end portions 19.
A large number of needles 21 are inserted between the large end 18 and the crank pin 4a, and between the small end tA19 and the piston pin 7a.

The connecting rod main body 20 is made of sheet metal and has a box-shaped cross section. Further, the large end portion 18 includes a first cylindrical body 18a that is integrally molded on one end of this 11 contact rod main body 20, and a first cylindrical body 18a that is integrally formed with one end of this 11 contact rod main body 20.
8a and a second cylindrical body 18b that is fitted inside. On the other hand, the small end portion 19 is composed of a first cylindrical body 19a that is integrally formed with the other end of the connecting rod main body 20, and a second cylindrical body 19b that is fitted inside the first cylindrical body 19a. The fitted parts 1 and the second cylindrical body are connected to each other by welding or brazing. The connecting rod main body 20 and each of the first cylindrical bodies 18a, 19a are formed by pressurizing and plastically deforming a circular pipe, and are therefore integrally molded.

Each of the second cylindrical bodies 18b and 19b is made of high carbon steel with good transfer fatigue properties, for example, the carbon content is 0.8% or more by weight. (SUJ) etc.

On the other hand, the connecting rod main body 20 and each first cylindrical body 18a, 19
a is made of low carbon steel with good toughness, which is, for example,
The carbon content is 0.8% or less by weight.

In addition, each of the first cylindrical bodies 18a and 19a and the second cylindrical body 1
A case where 8b and 19b are connected by brazing using copper will be explained.

Here, the above-mentioned brazing is performed, for example, at a temperature of 1125° C., a holding time of 18 minutes, and a gap of 50 l between each of the first cylindrical bodies 18a, 19a and the second cylindrical bodies 18b, 19b. When brazing is performed under these conditions, the second
Columnar crystals grow from the cylindrical bodies 18b and 19b toward the first cylindrical bodies 18a and 19a, which are the low carbon steel sides, and the first cylindrical bodies 18a and L9a are eroded by the molten copper. Therefore, the first cylindrical bodies 18a, 19a and the second cylindrical bodies 18b, 19b are extremely strongly connected to each other. Therefore, the desired strength of the connecting rod 8 can be ensured. The growth of the above-mentioned columnar crystals is more remarkable as the difference in carbon content between the first cylindrical bodies 18a, 19a and the second cylindrical bodies 18b, 19b is larger, which is preferable in terms of strength.

Although the above is based on the illustrated example, the space inside the connecting rod body 20 may be filled with lightweight resin, cement, etc. to improve the strength especially against compressive loads. It may also be an engine.

(Effect of the invention) According to the invention, since the connecting rod body has a box-shaped cross section,
It has the following effects.

That is, firstly, if the external dimensions of the connecting rod body are increased to a certain extent, the moment of inertia of area can be made sufficiently large, and thereby the connecting rod body can maintain a predetermined strength. Moreover, in this case, the moment of inertia of area can be made sufficiently large even if the connecting rod body has a thin wall, so that the connecting rod body can be made lightweight while maintaining sufficient strength. , the power loss of the internal combustion engine can be kept small.

Furthermore, secondly, since the connecting rod body has a box-shaped cross section,
Compared to the case where this is solid, surface stress is reduced, and fatigue strength can also be improved.

Thirdly, the connecting rod body is box-shaped in cross section.

Therefore, as the external dimensions of the crankcase increase, the volume within the crankcase decreases accordingly. In this case, the internal combustion engine
In a cycle engine, when the air-fuel mixture is compressed within the crankcase due to the downward movement of the piston, the compression ratio increases by the amount that the volume within the crankcase decreases as described above. This also has the advantage of improving the scavenging efficiency of the internal combustion engine.

Further, in the present invention, the connecting rod body is made of sheet metal and formed into a box-shaped cross section, and the first cylindrical body is integrally formed with the large end and the small end of the connecting rod body, and Since the second cylindrical body is fitted inside the cylindrical body, the second cylindrical body at the large end and the small end and the connecting rod body are separate bodies, so the characteristics required for these parts are determined. The material can be made to match. Therefore, multiple requirements for the connecting rod can be satisfied.

Moreover, in this invention, since the second cylindrical body is fitted into the first cylindrical body that is integrally molded with the connecting rod main body, that is, firmly connected to the connecting rod main body, the connecting rod main body and each second cylindrical body are They are firmly connected, and a predetermined strength is ensured at this connecting portion. Since this connection is achieved by fitting each of the second cylindrical bodies into the first cylindrical body integrally molded into the connecting rod main body, the predetermined strength in the above-mentioned connection part can be achieved with a simple structure. .

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which FIG. 1 is an overall side view of the connecting rod, FIG. 2 is a side sectional view of the engine, and FIG. 3 is a sectional view taken along the line -■ in FIG. 1φ Engine (internal combustion engine), 4 Crankshaft, 7a Piston pin, 8 Connecting rod, 18 Large end, 18a First cylindrical body, 18b Second cylindrical body, 1
9--Small end, 19a*・first cylindrical body, 19b・◆second
Cylindrical body, 20... Connecting rod body. Fig. 2

Claims (1)

[Claims] 1. A large end that is rotatably fitted on the crankshaft, a small end that is rotatably fitted on the piston pin, and a connecting rod body that connects these large and small ends. In the connecting rod for an internal combustion engine, the connecting rod body is made of sheet metal and formed into a box-shaped cross section, and a first cylindrical body and a first cylindrical body are formed integrally with the ends of the connecting rod body, respectively. A connecting rod for an internal combustion engine, comprising: a second cylindrical body fitted inside the first cylindrical body;