JPS6221974B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a noise reduction device for a reciprocating internal combustion engine.

In a conventional reciprocating internal combustion engine, a cylinder liner B is press-fitted into a cylinder block A, as shown in FIG. Further, the cylinder niner B and a piston (not shown) are fitted with a required clearance, and the clearance is large because the amount of thermal expansion of the piston is small during starting and idling when the cylinder temperature is low. Therefore, especially when the compression stroke shifts to the combustion stroke, the piston collides with the cylinder liner B, and the impact energy is transmitted to the cylinder block A via the cylinder liner B and is emitted as a slap sound. In this way, slapping noise, which is one of the engine noises, can be reduced by reducing the fitting clearance between the piston and cylinder liner, which reduces the energy at the time of collision and reduces the sound pressure level. Considering the thermal expansion of the piston and cylinder liner, the slapping sound at low temperatures was considered unavoidable.

The present invention has been made in view of the above, and reduces the collision energy transmitted to the cylinder block without changing the fitting clearance between the piston and the cylinder liner, thereby reducing the slapping sound, which is one type of engine noise. The aim is to reduce

The present invention will be explained in detail below based on an embodiment shown in FIGS. 2 to 4.

In the figure, cooling water jacket 1
A liner insertion hole 3 is provided in the cylinder block 2 formed with a liner. A first elliptical liner 4 as a buffer is press-fitted into the liner insertion hole 3, and
A second elliptical liner 5, which also serves as a buffer, is press-fitted into the first elliptical liner 4 and fixed therein. Further, inside the second elliptical liner 5, a cylinder liner 6 formed into a perfect circle is press-fitted and fixed as in the conventional case. Here, the first elliptical liner 4 is formed in an elliptical shape with its major axis in the axial direction of a piston pin (not shown), and the second elliptical liner 5 has a minor axis in the axial direction of the piston pin. .

Therefore, a clearance α is formed between the inner wall surface of the liner insertion hole 3 formed in the cylinder block 2 and the first elliptical liner 4, and a clearance α is formed between the second elliptical liner 5 and the cylinder liner 6. Clearance γ is in the same direction, but both elliptical liners 4 and 5
The clearance β between them is shifted by 90°.
Note that the widths of the clearances α, β, and γ are, for example,
It is preferable to set the clearance to about 100 to 500 μ so that when the cylinder temperature rises and each liner thermally expands, the clearances α, β, and γ are closed and come into close contact with each other.

In the internal combustion engine configured as described above, the collision energy given to the cylinder liner 6 due to the collision of the pistons is transmitted through the liner 6 in a direction perpendicular to the axis of the piston pin, and is transmitted to the short axis of the second elliptical liner 5. This will be communicated to the department. In addition, the collision energy transmitted to the short axis of the second elliptical liner 5 is transmitted from its long axis to the short axis of the first elliptical liner 4, and further from the long axis of the first elliptical liner 4. It is transmitted to cylinder block 2. Here, the collision between the piston and the cylinder liner occurs only in the direction perpendicular to the piston pin axis due to the action of the connecting rod. An elliptical liner (second elliptical liner in this example) whose short axis side abuts and whose long axis side contacts the liner mounting hole or a buffer (first ellipse liner in this example) mounted in contact with the liner mounting hole. By providing this, the impact energy in the direction perpendicular to the piston pin axis can be effectively absorbed by the elliptical liner, which is elastically deformed in the same direction and is inexpensively arranged.

Since each liner that transmits collision energy in this way is only partially in contact with other parts, the cylinder as a whole acts like a spring to reduce the transmitted energy. The impact energy transmitted to block 2 is significantly reduced. Therefore, it is possible to reduce the piston slap noise that becomes noticeable during starting and idling.

Furthermore, when the temperature inside the cylinder increases, the liner thermally expands and the clearances α, β, and γ are closed. For this purpose, the cylinder liner 6 is connected to both oval liners 4 and 5.
Since the heat transfer area (heat radiation area) to the cylinder block 2 formed through the cylinder block 2 increases, the cylinder liner 6 can be sufficiently cooled. Furthermore, when the temperature inside the cylinder increases, the piston thermally expands beyond the cylinder liner 6 and the fitting clearance between the two decreases.
There is no particularly problematic slapping sound.

On the other hand, since the cylinder block and cylinder liner are attached via an elliptical liner, it is considered that the heat transfer coefficient between them deteriorates and the cylinder liner is not cooled sufficiently. In this case, the cylinder liner 6 may be cooled with oil by injecting engine oil or the like into the clearance α.

In the example, two elliptical liners are used as buffers, but the inner wall surface on the short axis side of the ellipse is in contact with the outer wall surface of the cylinder liner in the direction perpendicular to the piston pin, and the outer wall surface on the long axis side of the ellipse is attached to the liner. It is also possible to provide only one elliptical liner in direct contact with the hole, and even in this case a considerable buffering function can be obtained.

As explained above, the present invention has an extremely simple structure in which an elliptical liner with the long and short axes appropriately arranged is interposed between the cylinder block and the cylinder liner, but the piston collisions transmitted to the cylinder block can be prevented. By reducing the energy, the piston slap noise radiated from the cylinder block can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing how a conventional cylinder liner is installed, FIG. 2 is a top view of a cylinder block equipped with the present invention, and FIG. 3 is a cross-sectional view taken along line AA in FIG.
FIG. 4 is a sectional view taken along line BB in FIG. 3. 2...Cylinder block, 3...Liner insertion hole,
4, 5...Oval liner, 6...Cylinder liner.

Claims (1)

[Claims] 1. Between the inner wall surface of the liner mounting hole formed in the cylinder block and the outer wall surface of the cylinder liner, the inner wall surface on the short axis side of the ellipse is brought into contact with the outer wall surface of the cylinder liner in the direction perpendicular to the piston pin, and 1. A noise reduction device for a reciprocating internal combustion engine, comprising an elliptical liner whose wall surface is in contact with a liner mounting hole or an inner wall surface of a buffer mounted in contact with the liner mounting hole.