JP2009197725A - Cylinder head of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a cylinder head in which any stress is not concentrated in an intake port branch point part in order to improve the stress concentration in the cylinder head. <P>SOLUTION: The cylinder head includes an intake port 6 branched in a fork shape, a bolt hole formed aside the intake port to allow a head bolt 8 to pass therethrough, a bolt seating face provided around the bolt hole in an upper surface of a cylinder head to allow a head part 8a of the head bolt to be seated, a cooling water passage 10 which extends to a bolt seating face corresponding area Y connecting two bolt seating faces on both sides of the intake port 6 and has an extension portion 11a reducing the material of a portion between branches of the branched intake port 6, and a branch point part Z of the intake port located in the bolt seating face corresponding area Y. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cylinder head of an internal combustion engine, and more particularly to a structure for reducing stress concentration in the cylinder head.

  A cooling water passage (water jacket) disposed in a cylinder head of a water-cooled internal combustion engine is generally provided so as to intensively cool the vicinity of a spark plug insertion hole called a plug tower, and is provided at an intake port. It is widely provided on the exhaust port side where the temperature is higher than that (see Patent Document 1). Examples of the structure are shown in FIGS.

FIG. 5 is a plan view of the cylinder head as viewed from above, and shows an in-line four-cylinder internal combustion engine.
A plug tower 1 is drilled at a substantially top portion of each cylinder, and on both sides thereof, two valve accommodating holes 2 and 3 for intake valves and exhaust valves are provided. The camshaft bearings 4 and 5 in the valve mechanism of the intake and exhaust valves are recessed in the upper surface of the cylinder head. Further, the intake port 6 schematically shown by a dotted line in the figure corresponds to the two intake valves of each cylinder, and for each cylinder, branches from an oval shape to a fork in the middle and opens into the cylinder.

  Such a cylinder head is attached to the cylinder block by a head bolt 8 (FIG. 6) through a bolt hole 7 drilled on the side of the port so as to sandwich the intake port 6 and an exhaust port (not shown). A bolt seat surface 7a is provided around the bolt hole 7 on the upper surface of the cylinder head, and the head 8a of the head bolt 8 is seated on the seat surface 7a and tightened with a predetermined torque. The bolt holes 7 of this example are arranged in a straight line in the cylinder series direction on both the exhaust side and the intake side so that the force for tightening the cylinder head is not offset.

FIG. 6 shows a cross section of the main part on the intake side in the cross-sectional view taken along the line AA in FIG.
The cooling water passage 9 in the cylinder head is formed so as to surround the plug tower 1 so as to cool the periphery of the plug tower 1 in a concentrated manner. Then, the cooling water passage 9a passing through the intake port side is narrow and the cooling water passage 9a passing through the exhaust port side is widened so that the higher temperature side can be efficiently cooled. It has a structure that can reduce water and focus on the exhaust port side. The opening above the cooling water passage 9 is a lightening portion for weight reduction.
JP 2002-213298 A

  As described above, in the cylinder head, the cooling water flowing to the intake port side is suppressed and the cooling water is concentrated on the periphery of the plug tower 1 and the exhaust port side, so that the cooling efficiency is excellent. 9a is formed narrowly. Therefore, the portion corresponding to the portion between the intake ports 6 branched into two branches, that is, the portion X between the branches is relatively thick. The inter-branch portion X is a portion located below the bearing 4 in the plan view of FIG.

  As is well known, a force for lifting the lower surface by the combustion pressure acts on the cylinder head during operation of the internal combustion engine. At this time, the cylinder head is tightened by the head bolts 8 on both sides of the intake port 6 and the portion X between the branches is thick and has high rigidity. Therefore, the stress is concentrated on the branch point portion Z of the intake port 6. Happens.

  The present invention is intended to improve the stress concentration, and proposes a cylinder head structure in which stress is not concentrated at the intake port branch point.

  In the present invention, at least a bifurcated intake port, a bolt hole that is perforated on the side of the intake port and through which a head bolt is passed, and provided around the bolt hole on the upper surface of the cylinder head, the head bolt head is seated. An extended portion that extends until reaching a bolt seat surface equivalent region connecting the bolt seat surface and the two bolt seat surfaces on both sides of the intake port, and the portion between the branches of the branched intake port is thinned A cylinder head of an internal combustion engine is proposed that includes a cooling water passage that forms a stub and a branch point portion of the intake port located in the bolt seating surface equivalent region.

  According to the cylinder head according to this proposal, the portion between the branches is thinned by the extended portion of the cooling water passage. By removing the thickness, the rigidity of the portion between the branches is lowered, and the rigidity balance of the portion where the intake port branches is improved. In other words, the entire port portion receives the input due to the combustion pressure, and the stress concentration at the port branch point portion is alleviated.

  Rather than increasing the thickness to increase the rigidity, the object is achieved without increasing the weight of the cylinder head by removing the thickness, and the degree of freedom in designing the port shape can also be improved.

A preferred embodiment is illustrated in FIGS.
FIG. 1 is a cross-sectional view of the main part of the intake side in the cross-sectional view taken along the line AA in FIG. Although an in-line 4-cylinder, 4-valve internal combustion engine will be described as an example, the number of cylinders and the number of valves are not limited thereto. The present invention can be applied to any cylinder head having a structure in which the intake port for one cylinder branches into two or more branches.

  As described above with reference to FIG. 5, the valve accommodating holes 2 and 3 for the two intake valves and the two exhaust valves are provided on both sides of the plug tower 1 drilled in the approximate top portion of each cylinder. Is provided. The camshaft bearings 4 and 5 in these valve operating mechanisms are recessed on the upper surface of the cylinder head. In addition, the intake port 6 schematically shown by a dotted line in FIG. 5 corresponds to the two intake valves of each cylinder, and is branched into a bifurcated shape from an ellipse to a halfway for each cylinder and opens into the cylinder. In the cylinder head, a bolt hole 7 is formed on the side of the port so as to sandwich an intake port 6 and an exhaust port (not shown), and a head bolt 8 is inserted into the bolt hole 7. A bolt seat surface 7a is provided around the bolt hole 7 on the upper surface of the cylinder head, and a head 8a of a head bolt 8 having substantially the same diameter is seated on the bolt seat surface 7a and tightened with a predetermined torque. It is done. The bolt holes 7 of this example are arranged in a straight line in the cylinder series direction on both the exhaust side and the intake side so that the force for tightening the cylinder head is not offset.

  As shown in FIG. 1, the cooling water passage 10 in the cylinder head of this example includes a cooling water passage 11 passing through the intake port side so as to surround the plug tower 1 in order to intensively cool the periphery of the plug tower 1 and A cooling water passage 12 passing through the exhaust port side is formed. Also in the case of this example, the cooling water passage 12 passing through the exhaust port side is made wider so that the higher temperature side can be efficiently cooled. The opening above the cooling water passage 10 is a lightening portion for weight reduction.

  The cooling water passage 11 on the intake port side is extended with an extension portion 11a for thinning out an inter-branch portion X (see FIG. 6) of the branched intake port 6. The extension portion 11a is extended at the inter-branch portion X until at least the tip reaches the bolt seat surface equivalent region Y (see FIG. 2) connecting the two bolt seat surfaces 7a on both sides of the intake port 6. ing.

  By removing the thickness due to the presence of the extended portion 11a, the rigidity of the inter-branch portion X is reduced, and the rigidity balance around the port is improved. As a result, stress concentration at the branch point portion Z of the intake port 6 is reduced. It is difficult to deteriorate over time. In particular, in the case of the configuration shown in FIG. 1, in addition to the branch point portion Z being located in the bolt seating surface equivalent region Y, the extension portion 11a and the branch point portion Z are in the vertical direction (that is, the axial direction of the cylinder). It overlaps. That is, they are formed in a state where their tips overlap each other when viewed in plan. As a result, the branch point portion Z and the upper deck are separated from each other, and the stress concentration is greatly improved.

FIG. 2 to FIG. 4 are cross-sectional views of the main part seen from the BB cross section in FIG. 1, showing an example of a plan view shape (transverse cross-sectional shape) of the extended portion 11a.
The example of FIG. 2 is an example of the extension portion 11a formed so that the shape in plan view is a slit shape (elongated notch). The width of the slit is equal to or greater than the diameter of the tip R (roundness) of the branch point portion Z. In the case of this slit shape, it is difficult for the cooling water to flow from the cooling water passage 11 to the extension portion 11a, and it is difficult for the cooling water to flow from the extension portion 11a to the cooling water passage 11. Therefore, the influence on the water flow of the cooling water passage 10 is small. . In addition, although it is preferable that the slit is easy to form a straight shape as shown in the drawing, the slit is not limited to this and may be meandering.

  The example of FIG. 3 is an example of the extended portion 11a formed so that the shape in plan view is a mountain shape (a rounded triangle). In the case of the mountain shape, the amount of lightening of the portion X between the branches increases, which is preferable in terms of balancing rigidity. However, since the cooling water easily enters and exits compared to the slit shape of FIG. 2, the influence on the water flow in the cooling water passage 10 is larger than that of the slit shape. Therefore, it is preferable to determine the width of the bottom of the mountain that is the base end in consideration of both the amount of meat removal and the water flow. The hypotenuse of the mountain shape is not limited to a straight line shape, and may be curved along the port shape.

  The example of FIG. 4 is an example of a shape like a pen tip of a fountain pen in which a middle portion swells more than an end portion (tip and base end portions) in a plan view shape. This shape example incorporates the advantages of the slit shape of FIG. 2 and the mountain shape of FIG. 3, and is a shape that makes it difficult for cooling water to enter and exit and to increase the amount of meat removal.

The principal part longitudinal cross-sectional view which showed embodiment of the cylinder head which concerns on this invention. The principal part cross-sectional view which showed the planar shape example of the cooling water channel extension part. The principal part cross-sectional view which showed the planar shape example of the cooling water channel extension part. The principal part cross-sectional view which showed the planar shape example of the cooling water channel extension part. The top view of a cylinder head. The principal part longitudinal cross-sectional view equivalent to the AA cross section of FIG. 5 which showed the cylinder head which concerns on related technology.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plug tower 2, 3 Valve accommodation hole 4, 5 Bearing 6 Intake port 7 Bolt hole 7a Bolt seat surface 8 Head bolt 8a Head 10 Cooling water passage 11 Intake port side cooling water passage 11a Extension part 12 Exhaust port side cooling water passage X Inter-branch part Y Bolt seat equivalent area Z Branch point part

Claims (5)

An intake port that branches into at least two branches,
A bolt hole drilled on the side of the intake port, through which a head bolt is passed;
A bolt seat surface provided around the bolt hole on the upper surface of the cylinder head and seating the head of the head bolt;
Cooling water that is extended to reach a bolt seating surface equivalent region that connects the two bolt seating surfaces on both sides of the intake port, and that forms an extended portion that removes a portion between the branches of the branched intake port A passage,
A branch point portion of the intake port located in the bolt seating surface equivalent region;
A cylinder head for an internal combustion engine, comprising:   The cylinder head of the internal combustion engine according to claim 1, wherein an extension portion of the cooling water passage and a branch point portion of the intake port overlap in the vertical direction.   The cylinder head of the internal combustion engine according to claim 1 or 2, wherein the extended portion of the cooling water passage has a slit shape in plan view.   The cylinder head of the internal combustion engine according to claim 1 or 2, wherein the extended portion of the cooling water passage has a mountain shape in plan view.   The cylinder head of the internal combustion engine according to claim 1 or 2, wherein the extended portion of the cooling water passage has a middle portion that is larger than an end portion in a plan view.