JP2008019781A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the sealing property of a surface to which a front cover covering an endless member is attached, in the front end part of an internal combustion engine to which the endless member connecting a crankshaft with a camshaft is attached. <P>SOLUTION: The front end of a cam carrier 6 is extended forwardly beyond the front end of a cylinder head 4. The upper end of a chain cover 10 attached to the front surface of the cylinder head 4 is sealed with the lower surface of the cam carrier 6. A liquid gasket is used for sealing each of joining surfaces between the chain cover 10 and the cam carrier 6 and between the chain cover and the cylinder head 4. The cam carrier 6 can be made from material having different coefficient of thermal expansion from that of the cylinder head 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an internal combustion engine, and more particularly, to a structure of a front end portion of an internal combustion engine to which an endless member that connects a crankshaft and a camshaft is attached.

  FIG. 2 is a diagram schematically showing an example of the structure of a conventional internal combustion engine. A crankshaft 120 is supported on the cylinder block 102 of the internal combustion engine. A cylinder head 104 is attached to the cylinder block 102, and a cam carrier 106 is attached to the upper part of the cylinder head 104. The cam carrier 106 supports the cam shaft 124. A head cover 108 is attached to the upper portion of the cam carrier 106 so as to cover the cam shaft 124.

  The crankshaft 120 and the camshaft 124 are connected by a chain 128 that is an endless member. The crankshaft 120 extends outward from the front surface of the cylinder block 102, and a sprocket 122 is attached to the tip thereof. The cam shaft 124 extends outward from the front surface of the cam carrier 106, and a sprocket 126 is attached to the tip thereof. The chain 128 is wound around these sprockets 122 and 126.

  The front surfaces of the cylinder block 102, the cylinder head 104, the cam carrier 106, and the head cover 108 are flush with each other. In a conventional internal combustion engine, a chain cover (front cover) 110 is attached to a surface formed on the same plane. The chain 128 is covered with the chain cover 110. The mating surfaces of the chain cover 110, the cylinder block 102, the cylinder head 104, the cam carrier 106, and the head cover 108 are sealed with a liquid gasket (FIPG).

Note that, as an example different from the structure shown in FIG. 2, some conventional internal combustion engines have a head cover directly attached to a cylinder head. In this case, the camshaft is directly supported by the cylinder head or is supported by a cam carrier integrated with the head cover. In any case, the sprocket of the cam shaft is disposed outside the head cover, and a chain cover is attached so as to cover the sprocket and the chain wound around the sprocket.
JP-A-11-280542 JP 2004-124769 A

  By the way, in recent internal combustion engines, various materials have been tried to reduce the weight. For example, aluminum that is lighter than iron is generally used as a material for the cylinder block 102, the cylinder head 104, the cam carrier 106, and the head cover 108. Further, regarding the cam carrier 106 and the head cover 108, use of magnesium or resin that is lighter than aluminum as the material is being studied.

  However, when combining parts of different materials in an internal combustion engine, it is necessary to pay attention to the difference in thermal expansion coefficient between the materials. For example, between aluminum and magnesium, magnesium has a higher coefficient of thermal expansion. For this reason, when aluminum is used for the cylinder block 102 and the cylinder head 104 and magnesium is used for the cam carrier 106 and the head cover 108, the heat during operation between the adjacent cylinder head 104 and the cam carrier 106 is used. A difference occurs in the amount of expansion.

  The difference in the amount of thermal expansion between the cylinder head 104 and the cam carrier 106 is particularly significant at the front end portion in the axial direction. This is because the front end portion of the internal combustion engine is strongly affected by heating and cooling. Since the thermal expansion amount of the cam carrier 106 is larger than that of the cylinder head 104, the chain cover 110 attached to the front surface of the cylinder head 104 and the cam carrier 106 is pushed in the axial direction by the cam carrier 106. If the pressing force at this time is too large, the liquid gasket sealing the mating surface between the chain cover 110 and the cam carrier 106 may be crushed. Once a liquid gasket is crushed, it is difficult to restore its original shape. For this reason, a gap is formed in the mating surface of the chain cover 110 and the cam carrier 106, and the oil in the chain cover 110 may leak out from the gap.

  Note that oil leakage from the mating surface of the chain cover 110 caused by the difference in thermal expansion between the cylinder head 104 and the cam carrier 106 also occurs when a gasket other than a liquid gasket is used to seal the mating surface. It is. For example, even if a metal gasket is used instead of a liquid gasket, a step is formed between the mating surface of the cam carrier 106 and the mating surface of the cylinder head 104 due to the difference in thermal expansion amount. Oil may leak.

  In the above description, the case where there is a difference in the coefficient of thermal expansion between the cylinder head 104 and the cam carrier 106 is taken as an example, but the cam carrier 106 is made of aluminum like the cylinder head 104 and the head cover 108 is used. In some cases, magnesium may be used. In that case, there is a difference in the amount of thermal expansion during operation between the head cover 108 and the cam carrier 106, and there is a possibility that the sealing performance between the chain cover 110 and the head cover 108 may be reduced due to this.

  The present invention has been made to solve the above-described problems, and is a surface to which a front cover of an internal combustion engine to which an endless member that connects a crankshaft and a camshaft is attached is attached with a front cover that covers the endless member. The purpose is to improve the sealing performance.

In order to achieve the above object, a first invention covers a front cover that covers an endless member that connects a crankshaft and a camshaft, a camshaft housing that is mounted on a cylinder head and houses the camshaft, An internal combustion engine comprising:
The front end of the cam shaft housing extends forward from the front end of the cylinder head, the front cover is attached to the front surface of the cylinder head, and the upper end thereof is sealed by the lower surface of the cam shaft housing. It is said.

According to a second invention, in the first invention,
The camshaft housing body includes a cam carrier attached on the cylinder head and supporting the camshaft, and a head cover attached on the cam carrier and covering the camshaft.

According to a third invention, in the second invention,
The head cover constitutes a bearing of the cam shaft together with the cam carrier.

According to a fourth invention, in the first invention,
The cam shaft housing is a head cover that is mounted on the cylinder head and covers the cam shaft.

A fifth invention is the fourth invention,
The head cover is integrated with a cam carrier that supports the cam shaft.

A sixth invention is any one of the first to fifth inventions,
The front cover is characterized in that the mating surfaces of the cylinder head and the cam shaft housing are sealed with a liquid gasket.

A seventh invention is the invention according to any one of the first to sixth inventions,
The cam shaft housing is formed of a material having a coefficient of thermal expansion different from that of the cylinder head.

According to an eighth aspect of the invention, in order to achieve the above object, a front cover that covers an endless member that connects the crankshaft and the camshaft, a cam carrier that is mounted on a cylinder head and supports the camshaft, An internal combustion engine comprising: a head cover mounted on the cam carrier and covering the cam shaft;
The front end of the head cover extends forward from the front end of the cam carrier, the front cover is attached to the front surface of the cylinder head and the cam carrier, and the upper end thereof is sealed by the lower surface of the head cover. .

  According to the first invention, the front cover is attached to the front surface of the cylinder head, and is attached to the lower surface of the cam shaft housing, so that the front cover is disposed between the cam shaft housing and the cylinder head. Even if the position of the front end of the cam shaft housing changes with respect to the front end of the cylinder head due to the difference in thermal expansion amount between the front cover and the cam shaft housing, and between the front cover and the cylinder head Will not be affected.

  In particular, according to the second invention, since there is no mating surface between the head cover and the front cover, the thermal expansion of the head cover does not affect the sealing performance of the front cover. Further, since the attachment / detachment of the head cover does not affect the sealing performance of the front cover, maintenance around the cam shaft after the head cover is removed from the cam carrier is easy. Furthermore, in this case, the front end of the cam carrier is inevitably closed, which has the advantage of increasing the rigidity of the cam carrier.

  According to the third aspect of the invention, the head cover can be made thinner and the maintainability around the camshaft is further improved.

  According to the fourth aspect of the invention, the front end of the head cover is inevitably closed, which has the advantage of increasing the rigidity of the head cover.

  According to the fifth invention, there is an advantage that the rigidity of the head cover is further increased by integrating the cam carrier with the head cover.

  According to the sixth aspect, the surface to which the Freon cover is attached can be easily and reliably sealed by using the liquid gasket. Even if the position of the front end of the camshaft housing body with respect to the front end of the cylinder head changes due to the difference in thermal expansion between the camshaft housing body and the cylinder head, each alignment of the front cover with the cylinder head and the camshaft housing body Since no force acts on the surfaces, there is no fear that the liquid gasket sealing the mating surfaces will be crushed.

  According to the seventh aspect, the material corresponding to the required performance can be selected for each part without being restricted by the thermal expansion coefficient. Even if the difference in thermal expansion between the camshaft housing body and the cylinder head increases due to the use of materials having different thermal expansion coefficients, the front cover and the camshaft housing body, and the front cover The sealing performance with the cylinder head is not affected.

  According to the eighth invention, the front cover is attached to the front surface of the cylinder head and the cam carrier, and is attached to the lower surface of the head cover. Even if the position of the front end of the head cover with respect to the front end of the cylinder head and cam carrier changes due to the difference in thermal expansion amount between the front cover and the head cover, and between the front cover and the cylinder head and cam carrier, Sealability is not affected.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Description of structure of internal combustion engine]
FIG. 1 is a diagram schematically showing the structure of an internal combustion engine as an embodiment of the present invention. As shown in this figure, a crankshaft 20 is supported on the cylinder block 2 of the internal combustion engine. A cylinder head 4 is attached to the cylinder block 2, and a cam carrier 6 is attached to the top of the cylinder head 4. The cam carrier 6 supports the cam shaft 24. A head cover 8 is attached to the upper portion of the cam carrier 6 so as to cover the cam shaft 24. The head cover 8 and the cam carrier 6 constitute a bearing for the cam shaft 24. The cylinder block 2 and the cylinder head 4 are made of aluminum as the material, whereas the cam carrier 6 and the head cover 8 are made of magnesium as the material.

  The cam carrier 6 extends forward from the front end of the cylinder head 4 and its front surface is completely closed. That is, the cam carrier 6 has a structure in which only the lower surface and the upper surface are opened. The head cover 8 has a structure in which only the lower surface is opened. By mounting the head cover 8 on the upper surface of the cam carrier 6, the cam shaft 24 is completely accommodated in the cam shaft accommodating body including the cam carrier 6 and the head cover 8. A sprocket 26 attached to the tip of the cam shaft 24 is also accommodated in the cam shaft housing.

  The crankshaft 20 extends outward from the front surface of the cylinder block 102, and a sprocket 22 is attached to the tip thereof. When the chain 28, which is an endless member, is wound around the sprockets 22 and 26, the camshaft 24 is connected to the crankshaft 20 and rotates in synchronization with the crankshaft 20.

  The front surfaces of the cylinder block 2 and the cylinder head 4 are flush with each other. A chain cover (front cover) 10 is attached to the flush surface. The chain cover 10 has a structure in which the upper end is opened, and the opening is sealed by the lower surface of the cam carrier 6. It can be said that the opening on the lower surface of the cam carrier 6 is sealed by the cylinder head 4 and the chain cover 10. The chain 28 is covered with the chain cover 10. The mating surfaces of the chain cover 10, the cylinder block 2, the cylinder head 4, and the cam carrier 6 are sealed with a liquid gasket (FIPG).

[Explanation of the effects of the above structure]
Magnesium used as the material of the cam carrier 6 is lighter than aluminum used as the material of the cylinder head 4, but has a feature of a large thermal expansion coefficient. For this reason, when the internal combustion engine is operated, the cam carrier 6 is more thermally expanded than the cylinder head 4. However, according to the structure shown in FIG. 1, the chain cover 10 is attached to the front surface of the cylinder head 4, but is attached to the lower surface of the cam carrier 6. For this reason, even if the position of the front end of the cam carrier 6 with respect to the front end of the cylinder head 4 changes due to the difference in thermal expansion between the cam carrier 6 and the cylinder head 4, the chain cover 10, the cylinder head 4, and the cam carrier 6. Since no force is applied to each mating surface, there is no concern that the liquid gasket sealing the mating surface will be crushed. That is, the sealing performance between the chain cover 10 and the cam carrier 6 and between the chain cover 10 and the cylinder head 4 is not affected.

  In the structure shown in FIG. 1, the cam carrier 6 has a structure in which the front end is closed. Magnesium is a low-rigidity material compared to aluminum, but by using a structure with the front end closed, magnesium can be used as the material for the cam carrier 6 without causing a reduction in rigidity. Similarly, since the head cover 8 also has a structure in which the front end is closed, high rigidity can be ensured while using magnesium as the material.

  Further, according to the structure shown in FIG. 1, since there is no mating surface between the head cover 8 and the chain cover 10, thermal expansion of the head cover 8 does not affect the sealing performance of the chain cover 10. Further, since the attachment / detachment of the head cover 8 does not affect the sealing performance of the front cover 10, maintenance around the cam shaft 24 by removing the head cover 8 from the cam carrier 6 is easy. The fact that the head cover 8 constitutes a bearing for the cam shaft 24 is also effective in improving the maintainability around the cam shaft 24.

[Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made.

  Resin may be used as the material of the cam carrier 6 and the head cover 8. Resin, like magnesium, is lightweight but has a large thermal expansion coefficient and low rigidity. Either the cam carrier 6 or the head cover 8 may be formed of resin. Of course, materials other than magnesium and resin can be used. According to the structure shown in FIG. 1, it is possible to select a material corresponding to the required performance for each of the parts 4, 6, and 8 without being restricted by the difference in thermal expansion coefficient between the parts 4, 6, and 8. it can. That is, there is no limitation on the material used for each component 4, 6, 8.

  In addition, a metal gasket can be used instead of a liquid gasket for sealing the mating surfaces. According to the structure shown in FIG. 1, even when a metal gasket is used, the sealability between the chain cover 10 and the cam carrier 6 and between the chain cover 10 and the cylinder head 4 is affected by thermal expansion. There is nothing.

  The cam carrier may be integrated with the head cover. That is, the head cover may be directly attached to the cylinder head, and the cam shaft may be supported by the cylinder head. In this case, the head cover serves as the cam shaft housing according to the present invention. The front end of the head cover extends further forward than the front end of the cylinder head, and the upper end of the chain cover is sealed by the lower surface of the head cover. According to this structure, since the front end of the head cover is necessarily closed, high rigidity can be ensured even when a low-rigidity material such as magnesium is used.

  In the structure in which the head cover is mounted on the cam carrier, the cam carrier is formed of the same material as the cylinder head (for example, aluminum), and the head cover may be formed of a material (for example, magnesium or resin) having a larger thermal expansion coefficient than the cam carrier. it can. In this case, in addition to the structure shown in FIG. 1, the front surface of the cam carrier may be flush with the front surface of the cylinder head, and the front end of the head cover may be extended to the front of the front end of the cam carrier. That is, the cam carrier has a conventional structure as shown in FIG. 2, and the head cover has a structure as shown in FIG. In this case, the front cover is attached to the front surfaces of the cylinder head and the cam carrier, and the upper ends thereof are sealed by the lower surface of the head cover. According to this structure, the sealability between the chain cover and the head cover and between the chain cover, the cylinder head, and the cam carrier can be kept high without being affected by the thermal expansion of the head cover.

  As an endless member for connecting the camshaft and the crankshaft, a timing belt can be used in addition to the chain. In this case, the belt cover that houses the timing belt is the front cover according to the present invention. The belt cover is attached to the front surface of the cylinder head, and the upper end of the belt cover is sealed by the cam shaft housing.

It is a figure showing typically the structure of the internal-combustion engine as an embodiment of the invention. It is a figure which shows the structure of the conventional internal combustion engine typically.

Explanation of symbols

2,102 Cylinder block 4, 104 Cylinder head 6, 106 Cam carrier 8, 108 Head cover 10, 110 Chain cover 20, 120 Crankshaft 22, 122 Sprocket 24, 124 Camshaft 26, 126 Sprocket 28, 128 Chain

Claims (8)

In an internal combustion engine comprising: a front cover that covers an endless member that connects a crankshaft and a camshaft; and a camshaft housing body that is mounted on a cylinder head and houses the camshaft.
The front end of the cam shaft housing extends forward from the front end of the cylinder head, the front cover is attached to the front surface of the cylinder head, and the upper end thereof is sealed by the lower surface of the cam shaft housing. An internal combustion engine.   2. The camshaft housing body includes a cam carrier that is mounted on the cylinder head and supports the camshaft, and a head cover that is mounted on the cam carrier and covers the camshaft. The internal combustion engine described.   The internal combustion engine according to claim 2, wherein the head cover constitutes a bearing of the cam shaft together with the cam carrier.   The internal combustion engine according to claim 1, wherein the cam shaft housing is a head cover that is mounted on the cylinder head and covers the cam shaft.   The internal combustion engine according to claim 4, wherein a cam carrier that supports the cam shaft is integrated with the head cover.   The internal combustion engine according to any one of claims 1 to 5, wherein the front cover has a mating surface between the cylinder head and the cam shaft housing sealed with a liquid gasket.   The internal combustion engine according to any one of claims 1 to 6, wherein the camshaft housing is formed of a material having a coefficient of thermal expansion different from that of the cylinder head. A front cover that covers an endless member that connects the crankshaft and the camshaft; a cam carrier that is mounted on a cylinder head to support the camshaft; and a head cover that is mounted on the cam carrier and covers the camshaft; An internal combustion engine comprising:
The front end of the head cover extends forward from the front end of the cam carrier, the front cover is attached to the front surface of the cylinder head and the cam carrier, and the upper end thereof is sealed by the lower surface of the head cover. Internal combustion engine.

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