JP2008057406A - Camshaft support structure for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently inhibit noise and vibration of a head cover part while using a structure integrating an upper bearing with a head cover, without increasing the number of components in relation to a camshaft support structure for an internal combustion engine. <P>SOLUTION: This structure is provided with a lower bearing 34 supporting camshafts 26, 28 from a cylinder head 10 side. The structure is provided with a head cover 30 provided with the upper bearing 32 supporting the cam shafts 26, 28 from a side opposite to the lower bearing 34 as a one body. The head cover 30 is provided with an intake water supply channel 58, an intake water supply groove 60, an intake water drain channel 62, a cover side intake water supply groove 64, an exhaust water supply channel 66, an exhaust water supply groove 68, an exhaust water drain channel 70, and a cover side water drain groove 72 as a structure for supplying cooling water for cooling an internal combustion engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a camshaft support structure for an internal combustion engine, and more particularly to a camshaft support structure suitable as a structure for supporting a camshaft inside an internal combustion engine mounted on a vehicle.

  Conventionally, for example, Patent Document 1 discloses a camshaft support structure in which an upper bearing is integrated with a head cover. The conventional support structure includes a lower bearing that is paired with an upper bearing. The upper bearing and the lower bearing are both formed in a semicircular shape, and the camshaft can be supported by being fixed in a state where both face each other.

Japanese Patent Laid-Open No. 7-166756 No. 7-29217 Japanese Patent No. 2532277 Japanese Patent Laid-Open No. 1-130043 Japanese Utility Model Publication No. 6-47609

  The vibration accompanying the movement of each member of the valve system (rotating movement of the camshaft, reciprocating movement of the valve, etc.) propagates to the head cover of the internal combustion engine. Such vibration is amplified by the head cover and causes noise.

  In the conventional camshaft support structure, as described above, the upper bearing is integrated with the head cover. For this reason, vibration is directly transmitted to the head cover via the upper bearing. Therefore, the head cover using the above-described conventional support structure is likely to generate vibration and noise more easily than a general head cover not using such a structure.

  The present invention has been made in order to solve the above-described problems. The camshaft of an internal combustion engine that can efficiently suppress vibration and noise of the head cover while using a structure in which the upper bearing is integrated with the head cover. The object is to provide a support structure.

A first invention is a cylinder head of an internal combustion engine;
A camshaft comprising a cam for driving a valve of an internal combustion engine;
A lower bearing that supports the camshaft from the cylinder head side;
A head cover integrally provided with an upper bearing that supports the camshaft from the side opposite to the lower bearing;
A liquid passage provided in the head cover for supplying liquid to the head cover;
It is characterized by providing.

  According to a second aspect of the present invention, in the first aspect, the liquid passage is disposed close to the upper bearing.

The third invention further comprises an auxiliary machine disposed on the head cover in the first or second invention,
The liquid passage is connected to a passage that passes through the auxiliary machine.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the head cover allows the rocker arm to be visually observed in a state where the head cover is assembled on the cylinder head. A viewing window that enables viewing of the cam while being held by the upper bearing;
The head cover includes a plurality of upper bearings arranged in the axial direction of the camshaft,
The upper bearing has a semicircular portion that holds the journal portion of the camshaft,
The head cover includes a connecting portion that connects at least a part of the plurality of upper bearings with at least the most convex portions of the semicircular portion between adjacent upper bearings,
The liquid passage is provided in the connecting portion.

  According to a fifth invention, in any one of the first to fourth inventions, the head cover is made of magnesium, a magnesium alloy, or a resin composite material.

In a sixth aspect based on any one of the first to fifth aspects, the liquid passage includes an intake side liquid passage that passes through an intake side of the head cover, and an exhaust side liquid passage that passes through an exhaust side of the head cover. With
The exhaust side liquid passage is formed to have a passage cross-sectional area larger than that of the intake side liquid passage.

  According to the first aspect of the invention, the vibration propagated to the head cover with the movement of each member of the valve system can be damped by causing the liquid to flow through the head cover. For this reason, by using a structure in which the upper bearing is integrated with the head cover, the camshaft of the internal combustion engine that can efficiently suppress vibration and noise of the head cover portion while imparting sufficiently high rigidity to the upper bearing. A support structure can be obtained.

  According to the second invention, it is possible to efficiently suppress vibration and noise of the valve train transmitted from the camshaft to the upper bearing.

  According to the third invention, the auxiliary machine mounted on the head cover can also be cooled.

  According to the fourth aspect of the present invention, the rigidity of the upper bearing can be efficiently increased while providing a visual window on the head cover, and vibration and noise of the valve train transmitted from the camshaft to the upper bearing can be efficiently suppressed. Can be suppressed.

  According to the fifth aspect of the present invention, it is possible to efficiently suppress the expansion of the head cover made of a material having a high coefficient of thermal expansion, and it is possible to prevent an increase in the friction of the valve operating system due to the thermal expansion.

  According to the sixth aspect of the invention, the cooling performance of the portion on the exhaust side of the head cover that becomes higher than the intake side by the transmission of exhaust heat can be enhanced. Thereby, the thermal expansion which arises in a head cover can be suppressed efficiently.

Embodiment 1 FIG.
[Structure of Embodiment 1]
(Basic structure)
FIG. 1 is a diagram for explaining a camshaft support structure according to Embodiment 1 of the present invention. The support structure of this embodiment includes a cylinder head 10 of an internal combustion engine. The cylinder head 10 is made of aluminum or cast iron and includes an intake port 12 and an exhaust port 14.

  The internal combustion engine shown in FIG. 1 is a multi-cylinder engine having a plurality of cylinders, and includes two intake ports 12 and exhaust ports 14 for each cylinder. FIG. 1 is a cross-sectional view obtained by cutting an internal combustion engine so that one of them is illustrated. The internal combustion engine shown in FIG. 1 is provided with a plurality of cylinders and a plurality of intake ports 12 and exhaust ports 14 in a state of being arranged in series in a direction perpendicular to the paper surface.

  As shown in FIG. 1, the cylinder head 10 incorporates an intake valve 16 for opening and closing the intake port 12 and an exhaust valve 18 for opening and closing the exhaust port 14. The intake valve 16 and the exhaust valve 18 are both opened by moving downward in FIG. And they are urged | biased by the valve spring which is not illustrated in the valve closing direction, ie, the upward direction in FIG.

  The upper end portion of the intake valve 16 is in contact with one end of the intake rocker arm 20. The other end of the intake rocker arm 20 is in contact with the upper end of the lash adjuster 22. That is, the intake rocker arm 20 is placed on the intake valve 16 and the lash adjuster 22. Similarly, the upper end of the exhaust valve 18 is in contact with one end of the exhaust rocker arm 24. The other end of the exhaust rocker arm 24 is placed on an exhaust side lash adjuster (not shown). That is, the exhaust rocker arm 24 is placed on the exhaust side lash adjuster and the exhaust valve 18.

  The internal combustion engine shown in FIG. 1 includes an intake camshaft 26 for driving the intake valve 16 and an exhaust camshaft 28 for driving the exhaust valve 18. The intake camshaft 26 is provided so as to extend above all cylinders arranged in series, and more specifically, an intake cam corresponding to each intake valve 16, more specifically, each intake valve 16. An intake cam (not shown) is provided in contact with each intake rocker arm 20 mounted thereon. Similarly, the exhaust camshaft 28 includes an exhaust cam (not shown) that contacts the individual exhaust rocker arms 24.

  A head cover 30 is assembled on the cylinder head 10. The head cover 30 is made of magnesium that is lighter than aluminum or cast iron. The head cover 30 is integrally provided with an upper bearing 32. More specifically, a plurality of upper bearings 32 are provided in the head cover 30 so as to be located at the boundary portions of the individual cylinders.

  Each of the upper bearings 32 is assembled with a lower bearing 34. The lower bearing 34 is made of magnesium in the same manner as the head cover 30 (and thus also in the upper bearing 32). The upper bearing 32 and the lower bearing 34 are provided with semicircular portions 36 and 38 that are paired with each other. The journal portions of the intake camshaft 26 and the exhaust camshaft 28 are rotatably held between their semicircular portions 36 and 38.

(Head cover structure)
FIG. 2 is a perspective view of the head cover 30 shown in FIG. The support structure of this embodiment has a part in the structure of the head cover 30. The head cover 30 includes a seal portion for separating the internal space of the internal combustion engine from the external space over the entire circumference. That is, the head cover 30 includes the flange portion 40 over the entire circumference. A plurality of bolt fastening holes 42 are provided in the flange portion 40. The head cover 30 is fastened to the cylinder head 10 by bolts (not shown) inserted into the bolt fastening holes 42. A seal member is incorporated in the flange portion 40. For this reason, when the head cover 30 is fastened to the cylinder head 10, a sufficient seal can be obtained between the flange portion 40 and the cylinder head 10.

  The head cover 30 is provided with an intake visual window 44 and an exhaust visual window 46. The intake visual window 44 is provided so as to extend along the longitudinal direction of the intake camshaft 26 shown in FIG. Further, the exhaust viewing window 46 is provided so as to extend along the longitudinal direction of the exhaust camshaft 28 shown in FIG.

  The intake viewing window 44 allows the intake rocker arm 20 (see FIG. 1) and all intake cams included in the intake camshaft 26 to be viewed through the intake viewing window 44 in a state where the head cover 30 is assembled to the cylinder head 10. It is provided so that it can. Further, the exhaust visual window 46 has all the exhaust cams included in the exhaust rocker arm 24 (see FIG. 1) and the exhaust cam shaft 28 through the exhaust visual window 46 in a state where the head cover 30 is assembled to the cylinder head 10. Each is provided so as to be visible.

  Further, both the intake visual window 44 and the exhaust visual window 46 are opened only in a region where the rigidity of the upper bearing 32 is not greatly reduced. That is, when the intake cam pushes down the intake valve 16, a large force directed to the upper bearing 32 acts on the intake cam shaft 26 as a reaction force. Similarly, when the exhaust cam pushes down the exhaust valve 18, a large force directed to the upper bearing 32 acts on the exhaust cam shaft 28 as a reaction force.

  These reaction forces toward the upper bearing 32 mainly act on the central portion of the semicircular portion 36 (see FIG. 1), that is, in the vicinity of the most convex portion of the semicircular portion 36. To do. Therefore, the head cover 30 of the present embodiment is provided with a connecting portion 48 for connecting adjacent upper bearings 32 at least at the most convex portions of the semicircular portion 36. In other words, the intake visual window 44 and the exhaust visual window 46 are not interposed between the most convex portions of the semicircular portion 36.

  According to the visual windows 44 and 46 described above, in the process of assembling the head cover 30, the operator can secure the rigidity of the upper bearing 32 and the rocker arms 20 and 24 and the intake air through the visual windows 44 and 46. The operation can be carried out while visually checking the cam and the exhaust cam. Further, after the operation of placing the head cover 30 is completed, the operator can check whether all the rocker arms 20, 24 and all the intake cams and the exhaust cams are in an appropriate state by checking their viewing windows 44, It can be easily confirmed via 46.

  FIG. 3 is a view for showing the overall shapes of the intake visual window cover 50 and the exhaust visual window cover 52. The head cover 30 includes an intake visual window cover 50 and an exhaust visual window cover 52 assembled on the head cover 30. The intake visual window cover 50 is a member for covering the intake visual window 44. On the other hand, the exhaust viewing window cover 52 is a member for covering the exhaust viewing window 46. Both the intake visual window cover 50 and the exhaust visual window cover 52 are made of magnesium.

  The intake visual window cover 50 and the exhaust visual window cover 52 are respectively provided with flange portions 54 and 56 over the entire circumference thereof. These visual window covers 50 and 52 are fastened to the head cover 30 as shown in FIG. 1 by fastening bolts (not shown) penetrating the flange portions 54 and 56, respectively.

(Characteristics of this embodiment)
Hereinafter, the most characteristic part of the present embodiment will be described with reference to FIGS. 1 and 4.
FIG. 4 is a view of the head cover 30 as viewed from above the internal combustion engine. Cooling water is supplied to predetermined portions of the cylinder block (not shown) and the cylinder head 10 of the internal combustion engine. The cooling water is cooled by a radiator (not shown) provided separately in the vehicle. The head cover 30 of the present embodiment has a configuration for circulating the cooling water provided in the internal combustion engine for such use through the head cover 30.

  Specifically, as shown in FIG. 4, in the vicinity of the upper bearing 32 of the first cylinder (# 1 cylinder) on the intake side, an intake water supply path 58 for guiding cooling water from the cylinder head 10 connects the head cover 30. It is formed through. An intake water supply groove 60 is formed on the top surface of the head cover 30 so as to intersect with the intake water supply path 58. The intake water supply groove 60 is provided on the mating surface of the head cover 30 and the intake viewing window cover 50 so as to extend above all the cylinders in parallel with the intake camshaft 26. In other words, the intake water supply groove 60 is disposed close to the upper bearing 32 provided in each cylinder in order to hold the journal portions of the camshafts 26 and 28. In addition, the intake water supply groove 60 is provided in the connecting portion 48 for ensuring the rigidity of a portion in the vicinity of the upper bearing 32.

  An intake water drainage passage 62 for returning the cooling water to the cylinder head 10 is formed at the end of the intake water supply groove 60 on the # 4 cylinder side so as to penetrate the head cover 30. Above the intake water supply path 58, the intake water supply groove 60, and the intake drainage path 62, the flange portion 54 of the intake visual observation window 44 is located. A cover-side intake water supply groove 64 corresponding to the intake water supply groove 60 of the head cover 30 is formed in the flange portion 54 (see FIG. 1). According to the above configuration, the cooling water can be supplied to the periphery of the intake side upper bearing 32 in the head cover 30.

  As shown in FIG. 4, the head cover 30 is provided with an exhaust water supply channel 66, an exhaust water supply groove 68, and an exhaust drainage channel 70 as a configuration for circulating cooling water through the exhaust side head cover 30. The exhaust visual window cover 52 is provided with a cover-side exhaust water supply groove 72. Since the detailed configuration of each of these components is the same as that on the intake side described above, detailed description thereof will be omitted here.

[Effect of Embodiment 1]
In general, vibrations associated with the movement of each member of the valve system (rotational movement of the camshaft, reciprocating movement of the valve, etc.) propagate to the head cover of the internal combustion engine. Such vibration is amplified by the head cover and causes noise. When the upper bearing is integrated with the head cover as in the present embodiment, vibration is directly transmitted to the head cover via the upper bearing. Therefore, a head cover using a structure in which upper bearings are integrated is likely to generate vibration and noise more easily than a general head cover that does not use such a structure.

  As described above, the head cover 30 of the present embodiment includes a configuration for supplying cooling water to the periphery of the upper bearing 32 that directly receives input from the camshafts 26 and 28. For this reason, by using a structure in which the upper bearing 32 is integrated with the head cover 30, vibration generated in the upper bearing 32 can be efficiently damped by the cooling water while giving the upper bearing sufficiently high rigidity. Thus, the generation of noise from the head cover 30 can be efficiently reduced. Furthermore, the head cover is formed so as to be as thin as possible in order to reduce the weight. For this reason, the said connection part 48 receives the same request | requirement. If it is thin, vibrations are easily propagated. According to the configuration of the present embodiment, the vibration can be efficiently damped by the circulation of the cooling water in the connecting portion 48 that is close to the upper bearing 32 and is formed thin.

  And according to said structure, such a vibration and noise suppression effect can be implement | achieved, without requiring the separate water supply pipe etc. for supplying cooling water to the head cover 30. FIG. That is, it is possible to efficiently suppress vibration and noise of the head cover portion while suppressing an increase in cost and weight and without deteriorating the assemblability and the appearance of the head cover 30 that is touched by human eyes.

  Further, according to the configuration of the present embodiment, the head cover 30 can be cooled by supplying cooling water to the head cover 30. The exhaust heat of the internal combustion engine is transmitted from the cylinder head 10 to the head cover 30. As described above, the material of the head cover 30 is magnesium. Magnesium has a higher coefficient of thermal expansion than aluminum and iron used in the cylinder head 10. The camshafts 26 and 28 are also made of iron. According to the configuration of the present embodiment, the expansion of the head cover 30 having a larger thermal expansion rate than the peripheral parts such as the camshafts 26 and 28 can be prevented, and the friction of the valve operating system due to the dimensional change with the peripheral parts. Can be prevented from increasing.

  Further, if the plastic deformation (high temperature creep phenomenon) of the head cover 30 due to the heat transfer of the exhaust heat occurs, for example, in the fastening portion of the lower bearing 34 in the head cover 30, the axial force of the fastening bolt is reduced, and the internal combustion engine Reliability will be reduced. On the other hand, according to the configuration of the present embodiment, such an adverse effect can be avoided by cooling the head cover 30 with the cooling water.

  By the way, in Embodiment 1 mentioned above, although the water supply groove | channel 60 etc. which were provided in both the head cover 30 and the viewing window covers 50 and 52 are formed, the channel | path for supplying cooling water to the head cover 30 is formed. In addition to such a groove, for example, a water supply conduit that extends over all the cylinders in parallel with the camshafts 26 and 28 may be provided near the upper bearing 32. Good.

  In the first embodiment described above, the head cover 30, the lower bearing 34, and the viewing window covers 50 and 52 are made of magnesium. However, the material thereof is not limited to magnesium. That is, they may be made of a magnesium alloy or a resin composite that is lighter than aluminum or cast iron. Furthermore, as with the cylinder head 10, they may be made of aluminum or cast iron.

  In the first embodiment described above, the intake water supply path 58, the intake water supply groove 60, the intake water discharge path 62, the cover-side intake water supply groove 64, the exhaust water supply path 66, the exhaust water supply groove 68, the exhaust drainage path 70, and the cover The side exhaust water supply groove 72 corresponds to the “liquid passage” in the first aspect of the present invention.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
The camshaft support structure of the present embodiment is basically configured similarly to the support structure of the first embodiment described above. FIG. 5 is a view for explaining a characteristic portion of the camshaft support structure according to the second embodiment of the present invention, and is a view of the head cover 80 as viewed from the side of the internal combustion engine. Hereinafter, in FIG. 5, the same reference numerals are used for the same elements as those shown in FIG. 1 and FIG.

  As shown in FIG. 5, an auxiliary machine 82 for the internal combustion engine may be mounted on the head cover 80 of the present embodiment. Here, it is assumed that the auxiliary machine 82 generates heat during operation, and specifically a motor. Further, it is assumed that the auxiliary machine 82 is disposed above the intake side upper bearing 32 for convenience of explanation. And in the site | part in which the auxiliary machine 82 is not provided, as shown in FIG. 5, the visual window cover 84 shall be provided.

  Also in the present embodiment, the cooling water is supplied to the head cover 80 as in the first embodiment. Further, the present embodiment is characterized in that the cooling water supplied to the head cover 80 is guided to the auxiliary machine 82 for the purpose of cooling. More specifically, as shown in FIG. 5, the head cover 80 has an intake water supply path 86 for supplying cooling water from the cylinder head 10 to the head cover 80, and an intake air for returning the cooling water from the head cover 80 to the cylinder head 10. A drainage channel 88 is provided. An intake water supply pipe 90 is formed in the vicinity of the intake side upper bearing 32 in the head cover 80 in parallel with the intake camshaft 26 so as to connect the intake water supply path 86 and the intake drainage path 88. The intake water supply pipe 90 is formed as a pipe line inside the head cover 80, and the auxiliary water supply pipe 92 passing through the inside of the auxiliary machine 82 is connected to the intake water supply pipe 90.

  According to the configuration of the present embodiment described above, the vibration and noise of the head cover portion can be efficiently suppressed without increasing the number of parts while using the structure in which the upper bearing 32 is integrated with the head cover 80. In addition, the auxiliary machine 82 mounted on the head cover 80 can be cooled.

  In the second embodiment described above, the auxiliary machine water supply pipe 92 corresponds to the “passage through the auxiliary machine” in the third aspect of the invention.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The camshaft support structure of the present embodiment is basically configured similarly to the support structure of the first embodiment described above. FIG. 6 is a view for explaining a characteristic part in the camshaft support structure according to the third embodiment of the present invention, and is a view of the head cover 100 as viewed from above the internal combustion engine. Hereinafter, in FIG. 6, the same reference numerals are used for the same elements as those shown in FIGS. 1 and 2, and the detailed description thereof is omitted or simplified.

  As shown in FIG. 6, in the head cover 100 according to the present embodiment, passages for supplying cooling water to the exhaust-side upper bearing 32 (exhaust water supply channel 102, exhaust water supply groove 104, exhaust drainage channel 106, and cover-side exhaust gas). The passage diameter (passage cross-sectional area) of the water supply groove 108 is a passage for supplying cooling water to the intake side upper bearing 32 (intake water supply path 58, intake water supply groove 60, intake drainage path 62, and cover side intake water supply). It is characterized in that it is formed larger than the passage diameter of the groove 64).

  The exhaust side is directly subjected to the transmission of exhaust heat from the cylinder head 10, and therefore tends to be hotter than the intake side. As a result, the relative displacement between the head cover 100 and the cylinder head 10 due to the performance degradation of the sealant itself and the difference in thermal expansion caused by the difference in material between the head cover 100 and the cylinder head 10. It is conceivable that the sealing performance between the two deteriorates due to the increase in.

  According to the configuration of the present embodiment described above, a large amount of cooling water is supplied to the exhaust side portion of the head cover 100 as compared to the intake side. For this reason, the occurrence of the above problems can be avoided in advance. Further, as described above, the method of making the coolant water passage diameter different between the intake side and the exhaust side is different from that of the cylinder head 10 as in the head cover 100 of the present embodiment in which magnesium or a resin composite material is used. This is particularly effective when the head cover 100 having a high coefficient of thermal expansion is used.

  In the third embodiment described above, the intake water supply passage 58, the intake water supply groove 60, the intake water discharge passage 62, and the cover side intake water supply groove 64 are provided in the “intake side liquid passage” in the sixth aspect of the invention. The passage 102, the exhaust water supply groove 104, the exhaust drainage passage 106, and the cover side exhaust water supply groove 108 respectively correspond to the “exhaust side liquid passage” in the sixth aspect of the invention.

  By the way, in the first to third embodiments described above, the cooling water for cooling the internal combustion engine is guided to the head cover 30, but in the present invention, the internal combustion engine is used for other purposes such as cooling and lubrication. The liquid to be mounted and supplied to the head cover 30 and the like is not limited to the cooling water of the internal combustion engine, but may be oil for lubricating the internal combustion engine, for example. The liquid supplied to the head cover 30 or the like is such a liquid that is mounted on the internal combustion engine for other uses, thereby effectively suppressing vibration and noise of the head cover 30 or the like without increasing the number of parts. It becomes possible.

  Further, in the first to third embodiments described above, a configuration for supplying a liquid such as cooling water to the top surface of the head cover 30 or the like is provided. You may make it provide the structure which supplies such a liquid.

It is a figure for demonstrating the camshaft support structure of Embodiment 1 of this invention. It is a perspective view of the head cover shown in FIG. It is a figure for showing the whole shape of an intake visual window cover and an exhaust visual window cover. It is the figure which looked down at the head cover from the upper direction of the internal combustion engine. It is a figure for demonstrating the characteristic part in the camshaft support structure of Embodiment 2 of this invention. It is a figure for demonstrating the characteristic part in the camshaft support structure of Embodiment 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cylinder head 16 Intake valve 18 Exhaust valve 20 Intake rocker arm 24 Exhaust rocker arm 26 Intake camshaft 28 Exhaust camshaft 30,80,100 Head cover 32 Upper bearing 34 Lower bearing 36,38 Semicircular part 44 Intake viewing window 46 Exhaust Visual window 48 Connecting portion 50, 84 Intake visual window cover 52 Exhaust visual window cover 54, 56 Flange 58, 86 of visual window cover Intake water supply path 60 Intake water supply groove 62, 88 Intake water discharge path 64 Cover side intake water supply groove 66, 102 Exhaust water supply path 68, 104 Exhaust water supply groove 70, 106 Exhaust water discharge path 72, 108 Cover side exhaust water supply groove 82 Auxiliary machine 90 Intake water supply pipe 92 Auxiliary machine water supply pipe

Claims (6)

A cylinder head of an internal combustion engine;
A camshaft comprising a cam for driving a valve of an internal combustion engine;
A lower bearing that supports the camshaft from the cylinder head side;
A head cover integrally provided with an upper bearing that supports the camshaft from the side opposite to the lower bearing;
A liquid passage provided in the head cover for supplying liquid to the head cover;
A camshaft support structure for an internal combustion engine, comprising:   2. The camshaft support structure for an internal combustion engine according to claim 1, wherein the liquid passage is disposed in proximity to the upper bearing. An auxiliary machine disposed on the head cover;
3. The camshaft support structure for an internal combustion engine according to claim 1, wherein a passage that passes through the auxiliary machine is connected to the liquid passage. The head cover is provided with a viewing window that allows the rocker arm to be viewed when assembled on the cylinder head and / or allows the cam to be viewed while the cam shaft is held by the upper bearing. Prepared,
The head cover includes a plurality of upper bearings arranged in the axial direction of the camshaft,
The upper bearing has a semicircular portion that holds the journal portion of the camshaft,
The head cover includes a connecting portion that connects at least a part of the plurality of upper bearings with at least the most convex portions of the semicircular portion between adjacent upper bearings,
The camshaft support structure for an internal combustion engine according to any one of claims 1 to 3, wherein the liquid passage is provided in the connecting portion.   The camshaft support structure for an internal combustion engine according to any one of claims 1 to 4, wherein the head cover is made of magnesium, a magnesium alloy, or a resin composite material. The liquid passage includes an intake side liquid passage that passes through an intake side of the head cover, and an exhaust side liquid passage that passes through an exhaust side of the head cover,
6. The camshaft of an internal combustion engine according to claim 1, wherein the exhaust side liquid passage is formed to have a passage cross-sectional area larger than that of the intake side liquid passage. Support structure.

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