JPH021468Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to an improvement in engine structure, and particularly to an improvement in the cylinder head gasket mounting portion of a multi-cylinder engine.

(Prior Art) Conventionally, in multi-cylinder engines, in order to reduce the length of the crankcase in the crankshaft direction in order to reduce the weight of the engine, the distance between adjacent cylinders has been shortened. However, with this type of structure, in engines where the cylinder liner is a separate member from the crankcase, the cylinder liner must be locked to the crankcase in order to maintain the strength of the crankcase with the cylinder spacing shortened. In order to do this, a shelf is formed on the crankcase to protrude in a direction perpendicular to the piston sliding direction, and the protruding length of the shelf is shorter in the crankshaft direction than in the direction perpendicular to the crankshaft. The cylinder head is tightened to the crankcase having such a shelf portion with uniform tightening force through a gasket having a substantially circular bore hole shape.

(Problems to be Solved by the Invention) In such a conventional structure, the moment applied to the shelf portion of the crankcase is different in the direction of the crankshaft and in the direction perpendicular to the crankshaft. For this reason, the amount of shelving on the shelf of the crankcase is not equalized, and large shelving tends to occur in some areas.The fallen shelf presses against the outer peripheral wall of the cylinder liner, deforming the cylinder liner and causing deformation of the bore hole. As a result, a gap or a pressurized portion was created between the outer peripheral wall of the piston and the inner peripheral wall of the cylinder liner, resulting in problems such as combustion gas leaking from inside the cylinder and damage to the inner peripheral wall of the cylinder liner.

(Means for solving the problem) The present invention was devised for the purpose of solving the above-mentioned problem, and in order to lock the cylinder liner to the crankcase, the piston slide direction is set on the crankcase. In an engine structure in which a shelf is formed to protrude in the vertical direction, and the protrusion length of the shelf is short in the direction of the crankshaft and long in the direction perpendicular to the crankshaft, the shape of the bore hole of the cylinder head gasket of the engine is The bore hole is formed in an elliptical shape with the short axis in the direction of the crankshaft and the long axis in the direction perpendicular to the crankshaft, and the edge in the short axis direction of the bore hole having the same elliptical shape is located approximately at the tip of the shelf. The longitudinal edge of the bore hole is located slightly closer to the base than the tip of the shelf, and the base of each shelf is caused by the cylinder head tightening force acting through the edge of the bore hole. This cylinder head gasket is characterized in that it is constructed so that the moments acting on the cylinder head gaskets are approximately equal.

(Operation and Effect of the Invention) According to the configuration of the invention, when the cylinder head is tightened to the crankcase via the gasket with a uniform tightening force, the protruding length of the crankcase shelf in the direction of the crankshaft is short. In,
The shape of the bore hole of the gasket is in the direction of the short axis, and the edge of the bore hole in the direction of the short axis is located approximately at the tip of the shelf formed with a short protruding length. The part where the tightening force is applied is approximately at the tip of the above-mentioned shelf, and in the part where the crankcase shelf protrudes in the direction perpendicular to the crankshaft is long, the bore hole shape of the gasket is in the long axis direction. Since the edge of the bore hole in the long axis direction is located slightly closer to the base than the tip of the shelf formed with a long protruding length, the part on which the tightening force is applied via the edge of the bore hole of the gasket is attached to the shelf. It is slightly closer to the base of the shelf than the tip of the shelf. Therefore, the moment applied to the shelf of the crankcase is approximately equal in the direction of the crankshaft and in the direction perpendicular to the crankshaft,
The moment acting on the base of the shelf is made uniform. As a result, the deformation of the shelf portion is made uniform, so that there is no large drop off of the shelf portion, and the shelf portion of the crankcase is significantly prevented from falling off.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3. In FIG. 1, 2 is a crankcase, and 4 is a cylinder head gasket. In the figure, the direction of arrow A is the direction of the crankshaft, and the direction of arrow B is the direction perpendicular to the crankshaft. The shape of the bore hole 6 of the gasket 4 is formed into an ellipse whose short axis is in the direction of the crankshaft (direction A) and whose long axis is in the direction perpendicular to the crankshaft (direction B).

FIG. 2 shows a partial sectional view of the cylinder opening edge in the crankshaft direction (direction A), in which 2 is a crankcase, 8 is a cylinder liner, and 4 is a cylinder head gasket. An annular flange 12 is formed at the upper edge of the cylinder liner 8 and projects radially outward. Also, the flange 1 of the liner 8 is attached to the crankcase 2.
A shelf portion 14 is formed at a position where it locks with 2.
A communication hole 16 is provided below the shelf 14 to circulate cooling water to cool the engine. However, in an engine configured to shorten the length in the crankshaft direction (A direction) in order to reduce the weight of the engine, in order to maintain the strength of the cylinder case, the cooling water communication hole in the crankshaft direction is 16 is formed narrowly, and this shelf 1
The protrusion length a of No. 4 is formed to be short. On the other hand, as shown in FIG. 3, the opening of the cooling water communication hole 18 in the direction perpendicular to the crankshaft (direction B) is formed wider than in the direction of the crankshaft in order to increase the cooling capacity. Projection length of portion 20
The length a' is longer than the protrusion length a in the crankshaft direction.

(Operation and effect of the embodiment) The shape of the bore hole 6 of the cylinder head gasket 4 is an ellipse with the short axis c in the direction of the crankshaft (direction A) and the long axis c' in the direction perpendicular to the crankshaft (direction B). The edge of the bore hole 6 in the direction of the short axis c is located approximately at the tip of the shelf 14, and the edge of the bore hole 6 in the long axis c' portion is located closer to the tip of the shelf 20. Since it is located slightly closer to the base, the distances b and b' from the base of the shelves 14 and 20 to the position where the tightening force is applied are approximately equal, and the moment applied to the base of the shelves 14 and 20 is approximately equal. be equal. As a result, the moment acting on the root portion of the shelf is made uniform, eliminating the possibility of a large drop of the shelf, resulting in the effect that the shelf of the crankcase is significantly prevented from falling.

Further, by preventing the shelf portion from falling off, deformation of the cylinder liner 8, leakage of combustion gas from the cylinder caused by the deformation, damage to the inner wall surface of the liner, etc. can be avoided.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one embodiment of the present invention;
The figure is an enlarged partial cross-sectional view corresponding to the line indicated by the arrow in FIG. 1, and FIG. 3 is an enlarged partial cross-sectional view corresponding to the line indicated by the arrow in FIG. 2... Crank case, 4... Cylinder head gasket, 6... Bore hole, 8... Cylinder liner, 14, 20... Shelf.

Claims (1)

[Scope of utility model registration request] In order to lock the cylinder liner to the crankcase, a shelf is formed on the crankcase to protrude in a direction perpendicular to the piston sliding direction, and the protruding length of the shelf is shortened in the crankshaft direction, so that the shelf extends in the direction perpendicular to the crankshaft. In the long engine structure, the bore hole shape of the cylinder head gasket of the engine is formed in an elliptical shape with the short axis in the direction of the crankshaft and the long axis in the direction perpendicular to the crankshaft, and The edge in the short axis direction of the bore hole is located approximately at the tip of the shelf, the edge in the long axis direction of the bore hole is located slightly closer to the base than the tip of the shelf, and the edge of the bore hole is located at approximately the tip of the shelf. An engine structure characterized in that the moment acting on the root portion of each shelf portion due to the cylinder head clamping force acting through the edge portion is approximately equal.