JP2002256966A - Cooling structure of cylinder head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling structure of a cylinder head capable of effectively cooling a part positioned in the neighbourhood of a combustion chamber while restraining strength lowering of the cylinder head. SOLUTION: A cooling water passage 12 having a circular (elliptical) diametrical direction cross-section is formed on a part (lower layer deck 11) to the combustion chamber 4 from a water jacket 9 in which cooling water of an engine flows on the cylinder head 2. On the lower layer deck 11 on which such the cooling water passage 12 is formed, stress is hardly concentrated even when force based on combustion pressure at the time when fuel burns in the combustion chamber 4 works, and lowering of fatigue strength of the lower layer deck 11 in accordance with the stress concentration is restrained. The lower layer deck 11 is effectively cooled by the cooling water flowing in the cooling water passage 12 without stagnation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cylinder head cooling structure for an engine.

[0002]

2. Description of the Related Art Generally, in a water-cooled engine, a water jacket is formed inside a cylinder head or a cylinder block, and cooling is performed by cooling water flowing through the water jacket. For example, Japanese Patent Application Laid-Open No. 9-242602
In the publication, the water flow is controlled by devising the shape of the water channel of the water jacket so that the cooling water flows to a portion of the cylinder head that is likely to become hot, such as between engine valves.

In an engine, fuel is supplied into a combustion chamber defined by a cylinder head, a cylinder block, and the like, and is driven by combustion energy generated when the fuel is burned. Therefore, the portion of the cylinder head located near the combustion chamber becomes hot due to the heat generated by the combustion of the fuel. Therefore, it is preferable that the portion be primarily cooled.

[0004] In order to further improve the cooling efficiency of the portion of the cylinder head located in the vicinity of the combustion chamber, the inner shape of the water jacket may be expanded toward the combustion chamber. In this case, the cooling water in the water jacket passes through the portion near the combustion chamber, so that the high-temperature portion is effectively cooled.

[0005]

However, locally expanding the inner shape of the water jacket as described above also leads to a complicated inner shape. And, when the inner shape of the water jacket becomes complicated, the flow rate of the cooling water decreases and stagnation and accumulation of foreign matter occur in the water jacket,
It may be difficult to effectively cool a portion of the cylinder head located near the combustion chamber.

Further, a portion of the cylinder head located near the combustion chamber receives a large force based on the combustion pressure when the fuel burns. Therefore, when the inner shape of the water jacket is complicated, stress is concentrated when receiving a force based on the combustion pressure, which has an adverse effect on the fatigue strength of the cylinder head.

The present invention has been made in view of the above circumstances, and an object of the present invention is to effectively cool a portion located near a combustion chamber while suppressing a decrease in the strength of a cylinder head. It is an object of the present invention to provide a cylinder head cooling structure that can be used.

[0008]

The means for achieving the above object and the effects thereof will be described below. In order to achieve the above object, in the invention according to claim 1, in a cooling structure of a cylinder head including a water jacket through which engine cooling water flows, a portion of the cylinder head closer to a combustion chamber of an engine than the water jacket is provided, A cooling water passage having a circular cross section in the radial direction through which the cooling water of the engine flows was formed.

According to the above-described configuration in which the radial cross section of the cooling water passage is circular, the cooling water flows through the cooling water passage without stagnation, and the combustion pressure is set closer to the combustion chamber than the water jacket of the cylinder head. When a force based on the pressure acts, stress concentration hardly occurs. Therefore, the portion of the cylinder head located in the vicinity of the combustion chamber can be effectively cooled by the cooling water flowing through the cooling water passage while suppressing the deterioration of the fatigue strength of the cylinder head due to the stress concentration.

[0010] The cooling water passage is preferably provided in a portion of the cylinder head where the force acting on the basis of the combustion pressure becomes larger than the other. By providing the cooling water passage as described above, the above-described portion is efficiently cooled by the cooling water flowing through the passage, and the fatigue strength is increased as compared with a high temperature, so that a decrease in the strength of the cylinder head can be accurately suppressed. Become like

According to a second aspect of the present invention, in the first aspect of the invention, the cooling water passage is formed such that a distance between the cooling water passage and the combustion chamber is smaller than a distance between the cooling water passage and the water jacket. The gist is that it has been done.

Although the temperature of a portion of the cylinder head closer to the combustion chamber is likely to be high, the above configuration makes it possible to effectively cool the portion of the cylinder head which is easily heated by the cooling water in the cooling water passage.

According to the third aspect of the present invention, the first or second aspect is provided.
In the present invention, the gist is that the cooling water passage passes near an engine valve. The temperature near the engine valve in the cylinder head is likely to be high, but according to the above configuration, that portion can be effectively cooled by the cooling water flowing through the cooling water passage.

The cooling water passage is preferably formed so as to pass not only near the engine valve but also around the engine valve. According to a fourth aspect of the present invention, in the third aspect of the present invention, the engine includes two intake valves and two exhaust valves as engine valves for each cylinder, and the cooling water passage includes It passes between two exhaust valves and branches into two, each passing between the intake valve and the exhaust valve.

Although the temperature between the engine valves such as the intake valve and the exhaust valve in the cylinder head tends to be high, according to the above configuration, that portion can be effectively cooled by the cooling water flowing through the cooling water passage.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the cooling water passage has an oblong cross-section in a radial direction having a major axis in a direction in which a force based on the combustion pressure acts. It was made.

By making the radial cross section of the cooling water passage oval as described above, it is possible to increase the rigidity of the cylinder head when a force based on the combustion pressure acts. Here, the term “elliptical shape” includes not only a so-called oval shape in which the width in a direction perpendicular to the major axis is constant for a predetermined length in the major axis direction, but also other shapes such as an elliptical shape. Shall be considered.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, the cooling water passage includes a passage formed in an engine cylinder block for flowing cooling water and the water. It was connected to the jacket.

According to the above construction, the cooling water passage is used to connect the passage of the cylinder block to the water jacket, and it is not necessary to provide a separate passage for the connection, so that the structure of the cooling water passage in the engine can be simplified. It can be.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects of the present invention, the engine includes a plurality of cylinders, and the cooling water passage is independently provided for each of the cylinders. The gist is that it is provided.

If the cooling water after cooling in a given cylinder is also used for cooling in other cylinders, a difference in cooling performance occurs between the cylinders because the temperature of the cooling water gradually increases. In addition, it becomes difficult to perform uniform cooling for each cylinder. According to the above configuration, since the cooling water after cooling in the predetermined cylinder is not used for cooling in other cylinders, it is possible to suppress a difference in cooling performance between the cylinders as described above. be able to. In addition, the degree of cooling can be adjusted for each cylinder by changing the diameter of the cooling water passage for each cylinder.

In the invention described in claim 8, in the invention described in any one of claims 1 to 7, the cylinder head is formed by casting, and the cooling water passage is formed when the cylinder head is cast. It was formed by disposing a core in a mold.

According to the above configuration, since the cooling water passage is formed by the core at the time of casting the cylinder head, the cooling water passage can have a complicated shape such as a curved shape in the direction in which the cooling water passage extends. The degree of freedom in forming the water passage can be increased.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a cast aluminum cylinder head of a water-cooled multi-cylinder diesel engine will be described below with reference to FIGS.

FIG. 1 is an enlarged sectional view showing the vicinity of the combustion chamber of one cylinder in the engine. The engine includes a cylinder head 2 mounted on an upper side of a cylinder block 1 and a piston 3 provided in the cylinder block 1 so as to be able to reciprocate. Fuel is supplied from a fuel injection nozzle 10 into a combustion chamber 4 defined between the cylinder head 2 and the piston 3. When the fuel supplied to the combustion chamber 4 burns, the piston 3 reciprocates with the combustion energy at that time, and the engine is driven.

An intake passage 5 and an exhaust passage 6 of the engine are connected to the combustion chamber 4 in a state of being branched into two (FIG. 1).
Shows only one of the intake passage 5 and the exhaust passage 6). The intake valve 5 shown in FIG. 2 is opened and closed by the operation of the engine to open and close the communication between the intake passage 5 and the combustion chamber 4, and the connection between the exhaust passage 6 and the combustion chamber 4 is the same. 2
Are opened / closed based on the driving of the engine to communicate or shut off.

A water jacket 9 through which engine cooling water flows is formed in the cylinder head 2 (FIG. 1). The water jacket 9 has an intake passage 5 and an exhaust passage 6 and a hole 10 for accommodating a fuel injection nozzle 10.
It has a complicated and complicated shape in order to avoid interference with a. Then, the cylinder head 2 is cooled by the cooling water flowing in the water jacket 9.

In the cylinder head 2, a portion (hereinafter referred to as a lower deck 11) indicated by a dashed line in FIG.
It is preferable to focus the cooling because the temperature rises due to the heat accompanying the combustion of the fuel in the inside. In this embodiment, a cooling water passage 12 having a circular cross-section in the radial direction is formed in the lower deck 11 in order to mainly perform cooling of the lower deck 11.

This cooling water passage 12 is provided independently for each cylinder, and is located closer to the combustion chamber 4 than the water jacket 9. The cooling water passage 12
Is formed so that the distance (interval) between the combustion chamber 4 and the water jacket 9 is smaller. The cooling water passage 12 is provided in the block-side passage 1 for cooling water formed for each cylinder of the cylinder block 1.
3 and the water jacket 9 of the cylinder head 2 to connect the two.

After the cooling water of the engine is discharged from a water pump (not shown), it passes through the block side passage 13, the cooling water passage 12, and the water jacket 9 in this order, and the cylinder block 1, the lower deck 11, and the cylinder Each part of the engine such as the upper part of the head 2 is cooled. Since the cooling water passages 12 are provided independently for each cylinder, the lower deck 11 corresponding to each cylinder is cooled by cooling water passing through a separate cooling water passage 12 for each cylinder. .

The cooling water passage 12 is formed by disposing a core in a mold when the cylinder head 2 is cast. As the material of the core, a spherical artificial sand having a small coefficient of thermal expansion is used for the purpose of increasing the strength of the core, or water such as calcium oxide is used for easily removing the core after casting with water. It is conceivable to use a substance that has the property of reacting with and disintegrating.

Next, the shape of the cooling water passage 12 formed corresponding to one cylinder in the extending direction and the cross section in the radial direction will be described with reference to FIGS. FIG. 2 is a perspective view showing a positional relationship among the cooling water passage 12, the intake valve 7, the exhaust valve 8, and the fuel injection nozzle 10.

As shown in this figure, the cooling water passage 12
Is provided with an introduction portion 12a into which cooling water is introduced from the block side passage 13 and extends so as to pass between the two exhaust valves 8. The introduction portion 12a is connected to an annular portion 12b extending annularly around the fuel injection nozzle 10. Further, from the annular portion 12b, the intake valve 7
Between the water jacket 9 and the exhaust valve 8
Two outgoing portions 12c for outgoing cooling water extend.

Therefore, the cooling water flowing in the cooling water passage 12 passes through a portion between the two exhaust valves 8 in the lower deck 11 (FIG. 1) and is cooled.
Cooling after passing around 0, then branching in two directions, and then cooling through a portion between the intake valve 7 and the exhaust valve 8. In the lower deck 11, the temperature between the intake valve 7, the exhaust valve 8, and the fuel injection nozzle 10 tends to be high due to the heat generated by the combustion of the fuel in the combustion chamber 4. It is cooled effectively by the cooling water flowing through.

In order to effectively cool the lower deck 11, it is preferable to increase the cross-sectional area of the cooling water passage 12 in the radial direction as much as possible. However, the cooling water passage 12 has the intake valve 7, the exhaust valve 8, and the fuel injection nozzle 10
In order to allow the cooling water passage 12 to pass through, there is a limit even if the cross-sectional area of the cooling water passage 12 is increased. In particular,
When the valve seats of the intake valve 7 and the exhaust valve 8 are assembled to the connection between the intake passage 5 and the exhaust passage 6 with respect to the combustion chamber 4, the cross-sectional area is made smaller so that the cooling water passage 12 does not interfere with the valve seat. Must be set.

Therefore, instead of providing such a valve seat, a build-up layer having excellent wear resistance is formed by a so-called laser cladding method in a portion where the intake valve 7 and the exhaust valve 8 of the cylinder head 2 come into contact when the valve is closed. It can be used as a valve seat. If this build-up layer is used as a valve seat, the radial cross-sectional area of the cooling water passage can be increased, and the lower-layer deck 11 can be made more effective by setting the cross-sectional area to an allowable maximum value.
Can be cooled.

Here, the shape of the radial cross section of the cooling water passage 12 will be described with reference to FIG. FIG. 3 is an enlarged sectional view showing a radial section of the cooling water passage 12.
The cooling water passage 12 has an elliptical cross section in a radial direction (an oval).
And the direction in which the force based on the combustion pressure when the fuel burns in the combustion chamber 4 (the vertical direction in FIGS. 1 and 3) is formed so as to be the major axis of the elliptical cross section. . Therefore, the rigidity of the cylinder head 2 (lower deck 11) when the force based on the combustion pressure acts on the lower deck 11 is increased. Further, by making the radial cross section of the cooling water passage 12 circular (elliptical), stress concentration is less likely to occur when the above-mentioned force acts on the lower deck 11, and the cylinder head 2 (lower deck) The deterioration of the fatigue strength of 11) is suppressed.

According to the embodiment described in detail above, the following effects can be obtained. (1) Since the cooling water passage 12 having a circular cross section (elliptical shape) in the radial direction is formed in the lower deck 11, the inside of the cooling water passage 12 is suppressed while suppressing the deterioration of the fatigue strength of the lower deck 11 due to the stress concentration described above. The lower deck 11 can be effectively cooled by the cooling water flowing without stagnation.

(2) The temperature of the lower deck 11 is likely to be higher as it is closer to the combustion chamber 4. However, since the cooling water passage 12 is formed so that the distance from the combustion chamber 4 is smaller than the distance from the water jacket 9 closest to the combustion chamber 4,
It is possible to effectively cool a portion of the lower deck 11 that is likely to be high in temperature (a portion near the combustion chamber 4).

(3) In the lower deck 11, the portion between the intake valve 7, the exhaust valve 8, and the fuel injection nozzle 10 is located at a position close to the intake valve 7 and the exhaust valve 8. Although the temperature tends to be high due to the heat generated by the combustion of the fuel, that portion can be effectively cooled by the cooling water passage 12.

(4) The radial cross section of the cooling water passage 12 has an elliptical shape (elliptical shape) whose major axis is the direction in which the force based on the combustion pressure acts on the lower deck 11 (vertical direction in FIG. 1). The rigidity of the lower deck 11 (cylinder head 2) when the above-mentioned force is applied can be increased.

(5) The cooling water passage 12 is used to connect the block-side passage 13 and the water jacket 9, and it is not necessary to provide a separate passage for the connection, so that the cooling water passage structure in the engine can be simplified. Things.

(6) Since the cooling water passage 12 is provided independently for each cylinder, the cooling water after cooling the lower deck 11 of a predetermined cylinder cools the lower deck 11 of another cylinder. It is possible to suppress a difference in cooling performance of the lower deck 11 from occurring. Further, the cooling performance (cooling degree) of the lower deck 11 can be adjusted for each cylinder by changing the diameter of the cooling water passage 12 for each cylinder.

(7) Since the cooling water passage 12 is formed by a core disposed in a mold when the cylinder head 2 is cast, the degree of freedom in determining the shape in the extending direction is increased. 2 can be formed into a complicated shape as shown in FIG.

The present embodiment can be modified, for example, as follows. The cooling water passage 12 is formed by a core. Alternatively, the cooling water passage 12 may be formed by casting a pipe-shaped material different from the material of the cylinder head 2 at the time of casting. You may.

It is not always necessary to provide the cooling water passage 12 for each cylinder. The cooling water passage 12 may pass between the two intake valves 7. The cooling water passage 12 not only passes between the engine valves such as the intake valve 7 and the exhaust valve 8, but also, for example, as shown in FIG.
May be passed around each engine valve as shown in FIG.

Although the cooling water passage 12 having the introduction portion 12a, the annular portion 12b, and the lead-out portion 12c has been exemplified, the shape of the cooling water passage 12 in the extending direction may be appropriately changed. For example, instead of using the annular portion 12b for connection between the introduction portion 12a and the lead-out portion 12c, a cooling water passage in which the connection is made by a semicircular passage portion may be adopted.

A separate passage other than the cooling water passage 12 may be provided as a passage connecting the block side passage 13 and the water jacket 9. -Instead of making the radial cross section of the cooling water passage 12 an elliptical shape, for example, a circular shape close to a perfect circle, or a width in a direction orthogonal to the major axis is constant by a predetermined length in the major axis direction,
A so-called oval shape may be used. If the oval shape is adopted as the radial cross section of the cooling water passage 12, the stress concentration when the force due to the combustion pressure acts on the lower deck 11 can be more suitably suppressed.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view showing the vicinity of a combustion chamber of an engine to which a cylinder head cooling structure according to an embodiment is applied.

FIG. 2 is a perspective view showing a positional relationship among an intake valve, an exhaust valve, a fuel injection nozzle, and a cooling water passage.

FIG. 3 is an enlarged sectional view showing a radial section of a cooling water passage.

FIG. 4 is a schematic view showing another example of the shape of the cooling water passage in the extending direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder block, 2 ... Cylinder head, 3 ... Piston, 4 ... Combustion chamber, 5 ... Intake passage, 6 ... Exhaust passage, 7 ...
Intake valve, 8: exhaust valve, 9: water jacket, 11: lower deck, 12: cooling water passage, 12a: introduction part, 12b: annular part, 12c: outlet part, 13: block side passage.

Claims (8)

[Claims] 1. A cooling structure for a cylinder head having a water jacket through which engine cooling water flows, wherein a radial cross section of the cylinder head at a portion of the cylinder head closer to a combustion chamber of the engine than the water jacket. A cooling structure for a cylinder head, wherein a cooling water passage having a shape is formed. 2. The cooling structure for a cylinder head according to claim 1, wherein said cooling water passage is formed such that a distance between said cooling water passage and said combustion chamber is smaller than a distance between said cooling water passage and said water jacket. 3. The cooling structure for a cylinder head according to claim 1, wherein the cooling water passage passes near an engine valve. 4. The engine has two intake valves and two exhaust valves as engine valves for one cylinder, and the cooling water passage passes between the two exhaust valves and is provided with two cooling valves. 4. The cooling structure for a cylinder head according to claim 3, wherein the cylinder head branches off and passes between the intake valve and the exhaust valve. 5. The cylinder head cooling according to claim 1, wherein said cooling water passage has a radial cross-sectional elliptical shape whose major axis is a direction in which a force based on said combustion pressure acts. Construction. 6. The cylinder head according to claim 1, wherein the cooling water passage connects the cooling water passage formed in the cylinder block of the engine to the water jacket. Cooling structure. 7. The cylinder head cooling system according to claim 1, wherein said engine has a plurality of cylinders, and said cooling water passage is provided independently for each of said cylinders. Construction. 8. The cylinder head is formed by casting, and the cooling water passage is formed by arranging a core in a mold at the time of casting the cylinder head. 8. The cooling structure for a cylinder head according to any one of claims 7 to 7.