JP2002089362A - Structure of cylinder block - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the durability of a cylinder block having a reinforcing cast material and to improve the productivity. SOLUTION: The structure of a cylinder block 1 in which a reinforcing cast material 6 is cast-in with a metal base material 5 having a lower melting point than the reinforcing cast material 6, and a main bearing portion 2 is divided into a reinforcing cast material 6 and a cap portion 4. The cap portion 4 and the reinforcing cast material 6 to which the cap portion 4 is attached are formed of the same metal, and after the cap portion 4 and the reinforcing cast material 6 are integrally cast, they are divided by cracking. It is the structure which was done.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a cylinder block of an internal combustion engine.

[0002]

2. Description of the Related Art As is well known, a cylinder block of an internal combustion engine includes a cylinder for accommodating a piston and a bearing for supporting a crankshaft rotated by reciprocating motion of the piston. The main bearing portion generally has a divided structure, and as a structure for positioning the main bearing cap, a method is known in which an inlay is formed on the main body side and the main bearing cap is fitted thereto.

[0003] Even with this kind of cylinder block having a divided structure, it is necessary to firmly integrate the main bearing cap and the main body side. At the same time, they are reassembled and integrated. One example is described in JP-A-10-225747. The structure described in this publication, by so-called cracking,
This is a method for manufacturing the main body portion of the cylinder block and the main bearing cap. More specifically, the main bearing cap is connected to the main body portion by arranging the mesh member in advance at the cracking site, performing casting, and breaking (cracking) the casting at the cracking site where the mesh member is arranged. The structure is manufactured at the same time, and the unevenness generated on the fractured surface is positively used for the alignment between the spindle cap and the main body.

On the other hand, when a light alloy material such as aluminum or magnesium is used as the structure of the cylinder block for weight reduction, the strength becomes insufficient particularly when the combustion pressure is increased as in a diesel engine. In order to compensate for this, a structure in which a cast iron reinforcing material is cast around with a light alloy material has been studied.

[0005]

The above-described method of manufacturing a cylinder block by cracking is a method that is established on the assumption that the manufacturing conditions of the main body portion of the cylinder block and the main bearing cap are the same. Therefore, in the above-described structure in which the reinforcing material made of cast iron is cast, the main bearing cap has a single structure made of cast iron, while the main body portion is a composite structure and requires at least two castings. ,
Furthermore, since the mating surface between the main bearing cap and the main body part may hang not only on the reinforcing material on the main body side but also on the light alloy material part, the main bearing cap is cast in a separate process from the main body part, and the predetermined After cutting or grinding, it is assembled to the main body. In this case, a spigot that is conventionally generally used is used for positioning the main bearing cap. In such a case, the main bearing cap made of cast iron and having high rigidity is replaced with a low-rigidity light alloy spigot portion. Therefore, there is a possibility that a crack may be generated in the spigot portion and durability may be reduced. Further, since the main bearing cap is manufactured in a separate process, productivity may be impaired.

The present invention has been made in view of the above technical problem, and has as its object to provide a structure of a cylinder block having high strength and excellent productivity.

[0007]

According to the present invention, in order to achieve the above object, a reinforcing cast material is cast in a metal base material having a melting point lower than that of the reinforcing cast material, and the main bearing is reinforced. In a cylinder block structure divided into a casting material and a cap portion, the cap portion and the reinforcing casting material to which the cap portion is attached are formed of the same metal, and these cap portions and the reinforcing casting material are integrally cast. And then divided by cracking.

Therefore, in the cylinder block structure of the present invention, the main bearing portion is divided by the reinforcing cast material and the cap portion. The reinforcing cast material is made of a metal having a relatively high melting point with respect to the metal base material, and the cap portion attached to the metal is made of the same metal as the reinforcing cast material. In other words, these reinforcing cast material and the cap attached to it are
It is cast integrally and then divided by cracking. Therefore, the positioning (positioning) of the cap portion with respect to the reinforcing cast material is performed using a fractured surface having irregularities caused by cracking. Therefore, there is no need to machine a special portion for positioning the cap portion on the main body side, resulting in a cylinder block having good productivity, and a load is applied to the low melting point metal base material from the cap portion. Therefore, it is possible to prevent a decrease in durability due to cracks or breaks of the metal base material.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described based on a specific example shown in the drawings. FIG. 1 is a schematic vertical cross-sectional view of a cylinder block 1 according to the present invention, and is a cross-sectional view of a main bearing 2 supporting a crankshaft (not shown). The cylinder block 1 includes a main body 3 and a bearing cap 4, and the main body 3 is constituted by a metal base material 5 and a reinforcing cast material 6.

The metal base material 5 forms a main part of the cylinder block 1 and is made of a light alloy such as an aluminum alloy or a magnesium alloy.
A cylinder (not shown) that slidably accommodates the piston, an upper surface 7 to which the cylinder is opened and a cylinder head (not shown) is attached, and a crankcase (each shown in FIG. ) Is formed.

The reinforcing cast material 6 is integrally provided inside the metal base material 5 in order to increase the strength of the cylinder block 1, and has a higher melting point than the metal base material 5, for example, It is formed by cast iron. The shape of the reinforcing cast material 6 is arbitrary provided that it does not interfere with the cylinder and the water jacket 9 surrounding the cylinder. In the example shown in FIG. 8 and the lower surface 8
And is exposed so as to be flush with the metal base material 5. The main bearing 2 is located at the center of the lower end of the reinforcing cast material 6.
A semi-circular portion 10 which is the upper half of is formed.

Further, the bearing cap 4 is made of the same metal material as the above-mentioned reinforcing cast material 6, that is, cast iron. The bearing cap 4 is formed integrally with the reinforcing cast material 6 to form the main bearing portion 2. Therefore, the joint surface to the main body portion 3 is the same as the exposed surface of the reinforcing cast material 6 to the lower surface portion 8. It has a shape. In other words, mutual positioning is performed only by both the reinforcing cast material 6 and the bearing cap 4, and the metal base material 5 made of the light alloy material is not provided with a portion that engages with the bearing cap 4. . In addition, it has a semicircular portion 11 that is the lower half of the main bearing portion 2, and thus is joined to the reinforcing cast material 6 to form a circular bearing portion by the upper and lower semicircular portions 10, 11. ing.

The reinforcing cast material 6 and the bearing cap 4 are made of the same metal, and have the same joint surfaces. This is because they are manufactured by the following method. That is, the reinforcing cast material 6 and the bearing cap 4 are integrally cast as shown in FIG. In that case, a cracking inducing portion 13 is provided at a position corresponding to these division surfaces 12. The cracking inducing portion 13 may be a notch having an acute angle for causing stress concentration,
It may be a mesh member described in Japanese Patent No. 747. As shown in FIG. 2B, a shearing load or a bending load is applied to the reinforcing cast material 6 and the bearing cap 4 integrally cast in this way to cause the cracking inducing portion 13.
Then, at the division surface 12, the reinforcing cast material 6 and the bearing cap 4 are divided into two.

Since the divided surface 12 is a surface formed by the progress of cracks, it is a surface having irregularities randomly.
Therefore, unless the reinforcing cast material 6 and the bearing cap 4 are located at the relative positions at the time of breakage, the engagement of the unevenness does not match, and the surfaces cannot be brought into close contact with each other.
That is, since the unevenness generated on the fractured surface functions to determine the relative position between the two, the above bearing cap 4
Are positioned with respect to the reinforcing cast material 6 using the fractured surface generated by cracking in the manufacturing process as it is. The reinforcing cast material 6 is set in the mold beforehand when the main body 3 is cast, and in this state, the light alloy is poured into the mold to be cast into the main body 3.

A crankshaft is penetrated by the main bearing portion 2 of the cylinder block 1 so as to be rotatably supported. That is, in a state where the bearing cap 4 is removed, a plate-shaped plain bearing (not shown) having a semicircular arc is attached to each of the semicircular portion 10 of the reinforcing cast material 6 and the semicircular portion 11 of the bearing cap 4. In this state, the bearing cap 4 is joined to the lower surface of the reinforcing cast material 6 so as to sandwich the journal of the crankshaft between the semicircular portions 10 and 11.

In this case, since the bearing cap 4 and the reinforcing cast material 6 are integrally cast and then fractured and divided by cracking, the bearing cap 4 is separated from the reinforcing cast material 6 by its dividing surface ( Fracture surface) 12
Is accurately positioned. In this state, a bolt (not shown) is passed through from below the bearing cap 4 and screwed into the reinforcing cast material 6, whereby the bearing cap 4 is fixed to the reinforcing cast material 6, that is, the main body portion 3, and the crankshaft is rotated. Are rotatably supported.

[0017] Even in an engine using the above-described cylinder block, a load acts on the bearing cap 4 in multiple directions through the crankshaft due to the reciprocating motion of the piston. It also acts to shift in a direction parallel to the division surface 12. In the above-described structure, even if such a so-called lateral load is applied, the unevenness at the time of cracking on the dividing surface 12 is engaged with the bearing cap 4.
Does not occur. Also, such a reaction force,
Since it occurs between the reinforcing cast material 6 made of cast iron and the bearing cap 4, in other words, a load for positioning the bearing cap 4 does not act on the low-strength metal base material 5, damage such as cracks or breakage occurs. In addition, it is possible to prevent the durability from being lowered.

It should be noted that the present invention is not limited to the above specific example, and the reinforcing cast material and the cap portion in the present invention may be made of metal other than cast iron.
It may be made of a metal having a higher melting point than the metal base material.

[0019]

As described above, according to the present invention, the reinforcing cast material forming the main body portion and the cap portion integrally formed with the reinforcing cast material and divided by cracking are formed. Therefore, the positioning (positioning) of the cap portion with respect to the main body portion can be performed using the uneven fracture surface generated by cracking, and therefore, a special portion for positioning the cap portion on the main body side. It is possible to produce a cylinder block with good productivity in combination with the fact that there is no need to process the metal base material, and since a load is not applied to the low melting point metal base material from the cap portion, cracking of the metal base material and A decrease in durability due to breakage or the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a cylinder block according to the present invention.

FIG. 2 is a diagram for explaining a process of manufacturing a reinforcing cast material and a bearing cap by cracking.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder block, 2 ... Main bearing part, 3 ... Body part, 4 ... Bearing cap, 5 ... Metal base material, 6
... reinforcement casting material, 12 ... partition surface, 13 ... cracking inducing part.

Claims (1)

[Claims] 1. A cylinder block structure in which a reinforced cast material is cast with a metal base material having a lower melting point than the reinforced cast material, and a main bearing portion is divided into a reinforced cast material and a cap portion. A cylinder block structure, wherein the reinforcing casting material to which the cap portion is attached is formed of the same metal, and the cap portion and the reinforcing casting material are integrally cast and then divided by cracking.