JP2020153265A - Cylinder block for multicylinder internal combustion engine and its manufacturing method - Google Patents

Abstract

To bring about a form that the high roundness of an internal periphery of a liner layer is maintained, and an energy loss is not generated, in a cylinder block in which a liner layer is formed by spray coating.SOLUTION: A cylinder bore 3 is formed into an elliptical circular shape which is short in a crank axial line direction, and on the other hand, an internal periphery of a liner layer 8 is formed into true roundness. Therefore, a thickness of the liner layer 8 is the thinnest in a point in an inter-bore part 5, and becomes the thickest in a fore-and-aft intermediate position 10. Since the thickness becomes thin and the heat dissipation is high in the point of the inter-bore part 5 which is large in the muffling of heat, even if a temperature is raised by an operation, an internal periphery of the liner layer 8 is maintained high in true roundness. As a result, friction with a piston can be reduced, and the blowout of a combustion gas can be remarkably suppressed, thus contributing to an improvement of an output and fuel economy.SELECTED DRAWING: Figure 4

Description

The present invention relates to a cylinder block of a multi-cylinder internal combustion engine and a method for manufacturing the same.

Cylinder bores are formed side by side in the crank axis direction in the cylinder block of a multi-cylinder internal combustion engine, and a piston is fitted inside the cylinder bore. Since the cylinder block is generally made of aluminum, a steel cylinder liner is cast to ensure strength and heat resistance, reduce friction, etc., but both aluminum and steel have a coefficient of thermal transfer. Therefore, the thermal expansion becomes large especially in the inter-bore portion, and the roundness of the cylinder bore tends to decrease.

Furthermore, since the aluminum cylinder block has a large residual stress during casting, when the temperature rises due to the operation of the engine, the area between the bores tends to extend in the width direction of the cylinder block (direction orthogonal to the crank axis). As the height increases, the cylinder bore tends to deform into an elliptical shape that is long in the width direction of the cylinder block.

On the other hand, for example, as disclosed in Patent Document 1, a liner layer made of an iron-based material is formed on the inner surface of the cylinder bore by thermal spraying, and when this thermal spray liner layer is adopted, wear resistance is reduced. There are advantages such as improvement of properties and corrosion resistance, improvement of fuel efficiency by weight reduction, and an advantage of being effective in preventing knocking because the temperature rise of the inner surface of the cylinder bore can be suppressed by high heat dissipation.

Japanese Unexamined Patent Publication No. 2008-240029

The liner layer by thermal spraying has excellent advantages as described above, but the liner layer has a uniform thickness over the entire circumference, while the cooling effect by the cooling water is low between the bores, so that the area between the bores is In, the ratio of heat dissipation from the liner layer becomes relatively low, and as a result, the cylinder bore tends to have an elliptical shape that is long in the width direction of the cylinder block, and as with the steel liner, the blow-by of combustion gas increases. Problems such as a decrease in output due to an increase in friction with the piston and an increase in blow-by gas have appeared.

Regarding this point, it is conceivable that the thermal spray liner layer is not formed in the inter-bore portion of the inner circumference of the cylinder bore, but the thermal spray liner layer is formed in the portion where the amount of heat radiated to the water jacket is large. In the part where the aluminum background is exposed, the friction with the piston becomes large, so the effect of eliminating energy loss is reduced, the problem that it takes a lot of time and effort to process, or the aluminum is partially exposed. Therefore, there are concerns about problems such as insufficient wear resistance and corrosion resistance.

The present invention has been made in the wake of such a situation, and is intended to solve the problem of thermal deformation caused by the difference in the amount of heat received while maximizing the advantages of the liner layer by thermal spraying.

The present invention includes a cylinder block and a method for producing the same, and the configuration of the cylinder block is specified in claim 1.

That is, the cylinder block
"A plurality of cylinder bores are formed side by side in the direction of the crank axis, and a liner layer having excellent heat dissipation is formed by thermal spraying on the inner peripheral surface of each cylinder bore."
In the basic configuration
"The distance from the center of the cylinder bore to the inner circumference with the space between the adjacent cylinder bores in the inner circumference of the cylinder bore as the intermediate position and the front-rear middle portion of the inner circumference of the cylinder bore facing the crank axis direction as the intermediate position. However, while gradually shrinking from the intermediate position to the position between the bores,
The inner circumference of the liner layer is a perfect circle, so that the thickness of the liner layer gradually decreases from the intermediate position toward the space between the bores. "
It has the feature.

The manufacturing method is specified in claim 2. That is, this manufacturing method
"A plurality of cylinder bores are formed side by side in the direction of the crank axis, and a liner layer having excellent heat dissipation is formed by thermal spraying on the inner peripheral surface of each cylinder bore."
This is a cylinder block manufacturing method.
"It includes a step of manufacturing the main body without the liner layer by casting or die casting, and a step of forming the liner layer by thermal spraying.
In the manufacturing process by casting or die casting, the space between adjacent cylinder bores in the inner circumference of the cylinder bore is set as the intermediate position, and the front and rear middle parts of the inner circumference of the cylinder bore facing the crank axis direction are set as intermediate positions. Manufactured so that the distance from the center of the cylinder bore to the inner circumference gradually decreases from the intermediate position to the position between the bores.
Next, the liner layer is formed to have substantially the same thickness by thermal spraying.
Then, by processing the inner circumference of the liner layer into a perfect circle, the thickness of the liner layer is formed so as to gradually decrease from the intermediate position toward the space between the bores. "
It has the feature.

In the present invention, since the thermal spray liner layer is formed on the entire circumference of the cylinder bore, friction with the piston can be uniformly maintained over the entire circumference, and wear resistance and corrosion resistance can be ensured. Since the thermal spray liner layer is thin in the inter-bore portion, the heat dissipation property in the inter-bore portion is improved, and the amount of heat radiation can be made uniform over the entire circumference. As a result, it is possible to prevent or significantly suppress the liner layer and the cylinder bore from forming an elliptical shape due to thermal expansion, and maintain high roundness.

Therefore, in the present invention, while enjoying the advantages of the thermal spray liner layer such as abrasion resistance, corrosion resistance, and low friction, the cylinder bore is maintained at high roundness to reduce mechanical loss and blow-by gas. The effect can be improved.

Further, in claim 2, it is difficult to manufacture because it is possible to easily realize different thicknesses of the thermal spray liner layers by forming the thermal spray liner layers to the same thickness and then cutting them into a perfect circle. There is no. Therefore, it is also excellent in reality.

It is a top view of the embodiment. It is a partially enlarged plan view. It is a partial plan view in the middle stage of a manufacturing process. It is a partially enlarged plan view after processing.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following, the front-back and left-right terms are used to specify the direction, but the front-back direction is the crank axis direction, and the left-right direction is the direction orthogonal to the crank axis and the cylinder bore axis. In an internal combustion engine, the side on which the timing chain is arranged is generally called the front, and the side on which the mission is arranged is called the back. Therefore, this method is also followed in this embodiment. The directions are clearly shown in FIGS. 1 and 2.

(1). Description of structure This embodiment is applied to the cylinder block of a 3-cylinder internal combustion engine for automobiles. Therefore, the cylinder block 1 is formed with three cylinder bores 2, 3 and 4 arranged side by side in the front-rear direction. When the three cylinder bores are individually specified, they are referred to as the first cylinder bore 2, the second cylinder bore 3, and the third cylinder bore 4 in order from the front.

Since the cylinder block 1 has three cylinders, an inter-bore portion 5 exists between the first cylinder bore 2 and the second cylinder bore 3 and between the second cylinder bore 3 and the third cylinder bore 4. Further, the cylinder block 1 is formed with an annular water jacket 6 that surrounds a group of cylinder bores 2, 3, and 4, and the water jacket 6 includes a recessed portion 6a that is inserted toward the bore-between portion 5. ..

The cylinder block 1 is a cast product or a die-cast product made of aluminum, and liner layers 7, 8 and 9 made of an iron-based composite material are formed by thermal spraying on the inner circumferences of the cylinder bores 2, 3 and 4. ing. The liner layers 7, 8 and 9 have a higher hardness than aluminum and are excellent in abrasion resistance and corrosion resistance, and are also excellent in heat dissipation as compared with a steel cylinder liner.

Since each of the cylinder bores 2, 3 and 4 is circular, the left-right width is the largest at the intermediate position 10 in the front-rear direction. The inner circumference of each liner layer 7, 8 and 9 is a perfect circle, but the thickness of each liner layer 7, 8 and 9 will be described first. First, the first liner layer 7 and the third liner layer 9 Then, as shown in FIG. 2, the intermediate position 10 is the thickest, and the thickness gradually decreases from the intermediate position 10 toward the bore 5 and the half region on the opposite side of the bore 5 is formed. Then, it has the same thickness as the intermediate position 10.

Therefore, the outer shape of the first liner layer 7 and the third liner layer 9 has a shape in which a half region close to the bore portion 5 is a left-right ellipse divided into left and right halves, and is on the opposite side of the bore interval 5. The half area of is shaped like a perfect circle divided into left and right halves.

On the other hand, in the second cylinder bore 3, since it is sandwiched between the front and rear bores 5, the front and rear bores 5 are the thinnest and the intermediate position 10 is the thickest, as shown in FIG. The thickness gradually decreases from 10 toward the front and rear bores 5. Therefore, the outer shape of the second liner layer 8 has an elliptical shape that is long in the left-right direction.

The liner layers 7, 8 and 9 are iron-based composite materials, and the friction with the piston is very small. Since the liner layers 7, 8 and 9 are formed over the entire circumference of the cylinder bores 2, 3 and 4, the movement of the piston is smooth, and there is a problem of deterioration in wear resistance and corrosion resistance. There is no.

The amount of heat radiated from the liner layers 7, 8 and 9 is inversely proportional to the thickness, but it is the thinnest at the portion 5 between the bores where the heat retention is large, and the portion where the amount of heat radiated to the water jacket 6 is large becomes thick. Therefore, it is possible to remarkably suppress the uneven thermal deformation of the liner layers 7, 8 and 9 due to the difference in the amount of heat radiation. As a result, the inner circumferences of the liner layers 7, 8 and 9 can be maintained at a high roundness in the operating state of the engine.

In this way, the inner circumferences of the liner layers 7, 8 and 9 can be maintained at a high roundness while the liner layers 7, 8 and 9 by thermal spraying are formed over the entire circumference of the cylinder bores 2, 3 and 4. It is possible to remarkably suppress the blow-by of combustion gas while reducing the friction with the piston, and as a result, it is possible to eliminate energy loss and contribute to the improvement of output and fuel consumption.

(2). Manufacturing method Next, the manufacturing method of the cylinder block 1 will be described. To explain the second cylinder bore 3 by taking up, when the main body of the cylinder block 1 is manufactured by casting or die casting, the second cylinder bore 3 is manufactured into an elliptical shape long in the left-right direction, and then the second liner layer 8 is formed by thermal spraying. It is formed to be approximately equal in thickness over the entire circumference. Next, as shown in FIG. 4, the inner circumference of the second liner layer 8 is cut into a perfect circle.

At the time of thermal spraying, it is conceivable that the liner layer 8 is formed to have an unequal thickness so that the portion between the bores 5 becomes thin, but it is assumed that it is difficult to control the injection amount of the material. In this respect, as in the present embodiment, when the liner layer 8 is formed by thermal spraying to a substantially equal thickness and then cut into a perfect circle, the inner peripheral surface of the perfect circle can be formed while easily forming the liner layer 8 with the conventional apparatus. ..

After the main body of the cylinder block 1 is manufactured by casting or die casting, the cylinder bore 3 can be precision machined by honing or the like before the thermal spraying process of the liner layer 8, or it can be directly machined without processing. It is also possible to spray. Further, the second cylinder bore 3 can be formed into a perfect circle by casting or die casting and then formed into an ellipse by cutting, but if it is formed into an ellipse at the time of casting or die casting, it is processed. You can save the trouble of.

The same applies to the first cylinder bore 2 and the third cylinder bore 4, and when manufacturing by casting or die casting, a half region close to the bore portion 5 is formed into an elliptical shape, and then the liner layers 7 and 9 are formed by thermal spraying. , The process of rounding the inner peripheral surface of the liner layer by cutting is performed. In either case, the rounding step of the inner peripheral surface of the liner layer can be completed by one process, or can be performed by a two-step process of rough cutting and finishing step.

Although the embodiments of the present invention have been described above, the present invention can be variously embodied.

The invention of the present application can be embodied in a cylinder block and a method for producing the same. Therefore, it can be used industrially.

1 Cylinder block 2-4 Cylinder bore 5 Between bores 6 Water jacket 7-9 Liner layer 10 Intermediate position

Claims (2)

A plurality of cylinder bores are formed side by side in the direction of the crank axis, and a liner layer having excellent heat dissipation is formed by thermal spraying on the inner peripheral surface of each cylinder bore.
The distance from the center of the cylinder bore to the inner circumference is the distance between the adjacent cylinder bores in the inner circumference of the cylinder bore, and the front-rear middle portion of the inner circumference of the cylinder bore facing the crank axis direction as the intermediate position. , While gradually shrinking from the intermediate position to the position between the bores,
The inner circumference of the liner layer is a perfect circle, so that the thickness of the liner layer gradually decreases from the intermediate position toward the inter-bore portion.
Cylinder block for multi-cylinder internal combustion engine. A cylinder block manufacturing method in which a plurality of cylinder bores are formed side by side in the direction of the crank axis, and a liner layer having excellent heat dissipation is formed on the inner peripheral surface of each cylinder bore by thermal spraying.
It includes a step of manufacturing the main body without the liner layer by casting or die casting, and a step of forming the liner layer by thermal spraying.
In the manufacturing process by casting or die casting, the space between adjacent cylinder bores in the inner circumference of the cylinder bore is set as the intermediate position, and the front and rear middle parts of the inner circumference of the cylinder bore facing the crank axis direction are set as intermediate positions. Manufactured so that the distance from the center of the cylinder bore to the inner circumference gradually decreases from the intermediate position to the position between the bores.
Next, the liner layer is formed to have substantially the same thickness by thermal spraying.
Then, by processing the inner circumference of the liner layer into a perfect circle, the thickness of the liner layer is formed so as to gradually decrease from the intermediate position toward the inter-bore portion.
A method for manufacturing a cylinder block for a multi-cylinder internal combustion engine.

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