1. Field of Invention
The present invention relates to a cooling apparatus of an internal combustion engine, and includes not only the cooling apparatus but also an insert disposed in a water jacket of the engine and a cylinder block of the engine.
2. Description of Related Art
In an internal combustion engine, a water jacket is formed around cylinder bores in a cylinder block, and engine cooling water is caused to flow in the water jacket to cool the engine which is heated due to combustion and sliding of a piston. A temperature of a cylinder bore wall is likely to be higher at an upper portion of the cylinder bore wall than at a lower portion of the cylinder bore wall. Therefore, if the cooling water is caused to flow uniformly at an upper portion and a lower portion of the water jacket for preventing the temperature of the upper portion of the cylinder bore wall from being too high, the lower portion of the cylinder bore will be over-cooled, resulting in an increase in a friction loss generated in the sliding of the piston with the cylinder bore.
In order to improve a temperature distribution in the cylinder bore wall, Japanese Utility Model Publication SHO 57-43338 discloses that an insert is disposed in a water jacket. By providing the insert in the water jacket, a heat removed from the cylinder bore wall can be controlled. More particularly, at a portion where the insert is provided, a flow amount is decreased and the temperature of the cylinder bore wall is maintained high (i.e., less of a cooling effect takes place). By the heat control, the temperature distribution of the cylinder bore wall is improved.
In order to insert the insert into the water jacket, in a cylinder block of a closed deck-type, it is conceivable to insert the insert through a water hole formed in an upper deck of the cylinder block.
However, in the closed deck-type cylinder block, the water hole is small due to a structure of a core used in casting and is discontinuous in an extending direction of the water jacket. As a result, a size of the insert is also small, and a clearance between the insert and the cylinder bore wall is large. The insert also is discontinuous in the extending direction of the water jacket. Therefore, a heat amount removed from the cylinder bore wall is large, and the cylinder bore wall is still over-cooled.