JP2008248897A - Cam shaft supporting structure of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable visual check of rocker arms positioned in a head cover while using structure in which an upper bearing is integrated with the head cover, concerning the camshaft support structure of an internal combustion engine. <P>SOLUTION: The rocker arms 20, 24 are incorporated in a cylinder head 10 of the internal combustion engine. Camshafts 26, 28 are arranged so that the rocker arms 20, 24 are abutted on cams. The camshafts 26, 28 are turnably supported by a lower bearing 34 supporting them from below and the upper bearing 32 integrated with the head cover 30. View windows are disposed in the head cover 30 so as to visually check the rocker arms 20, 24 through the head cover. View window covers 54, 56 covering the view windows are attached to the head cover 30. <P>COPYRIGHT: (C)2009,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, a camshaft support structure in which an upper bearing is integrated with a head cover is known, as disclosed in, for example, Japanese Patent Laid-Open No. 7-166958. 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 support the camshaft by being fixed in a state where both face each other.

  A cam for opening the intake valve or the exhaust valve is fixed to the camshaft. The intake valve and the exhaust valve are opened by being pushed by the cam nose as the camshaft rotates. The reaction force acts on the camshaft when the cam nose pushes open the intake valve and the exhaust valve. This reaction force acts in the direction of pressing the camshaft against the upper bearing. For this reason, the upper bearing is required to have higher rigidity than the lower bearing.

  According to the conventional support structure, high rigidity can be imparted to the upper bearing by being integrated with the head cover. For this reason, according to this rigidity, it is possible to support the camshaft with sufficiently high rigidity and high accuracy.

Japanese Patent Laid-Open No. 7-166756 JP 11-173210 A Japanese Utility Model Publication 4-95643

  When realizing the above conventional support structure, the following assembly procedure is inevitably taken. That is, in order to realize this structure, first, an intake valve and an exhaust valve are incorporated in the cylinder head. Next, a rocker arm is placed on the intake valve or the exhaust valve. The rocker arm is a member for transmitting the pressing force of the cam to the valve body.

  Apart from the above steps, the camshaft is assembled to the head cover. That is, the lower bearing is fixed to the upper bearing while the camshaft is placed on the upper bearing of the head cover. As a result, the cam shaft is held by the head cover in a rotatable state.

  Following the above steps, the head cover is fixed to the cylinder head while holding the camshaft. At this time, the camshaft needs to be assembled so that the rocker arm is properly sandwiched between the cam and the valve body.

  However, the rocker arm is usually only placed on the valve body until it is pressed by the camshaft. For this reason, when the head cover supporting the camshaft is assembled to the cylinder head, the rocker arm is likely to drop off. In order to prevent such dropout, it is desirable that the rocker arm can be visually observed when the head cover is assembled. Further, in order to confirm the state of the valve operating mechanism even after the internal combustion engine is properly assembled, it is desirable that the state of the rocker arm can be easily observed.

  However, in the above-described conventional support structure, it is extremely difficult to visually observe the rocker arm that is positioned inside the head cover when the head cover is assembled. Further, in order to visually check the state of the rocker arm, it is necessary to remove the head cover, and it is impossible to visually observe the rocker arm in a state where the assembly is completed. In this respect, the conventional support structure is not necessarily preferable from the viewpoint of productivity and ease of maintenance and inspection.

  The present invention has been made in order to solve the above-described problems, and is an internal combustion engine cam that allows a rocker arm located inside the head cover to be viewed while using a structure in which the upper bearing is integrated with the head cover. An object is to provide a shaft support structure.

In order to achieve the above object, the present invention provides a camshaft support structure for an internal combustion engine,
A cylinder head of an internal combustion engine;
A rocker arm incorporated in the cylinder head and supported at one end by a lash adjuster;
A camshaft comprising a cam that contacts the rocker arm;
A lower bearing that supports the camshaft from the cylinder head side;
A head cover that integrally includes an upper bearing that supports the camshaft from a side opposite to the lower bearing;
The head cover includes a viewing window that allows the rocker arm to be viewed in a state where the head cover is assembled on the cylinder head.

  According to the present invention, a sufficiently high rigidity can be imparted to the upper bearing by integrally providing the upper bearing with the head cover that seals the internal space of the internal combustion engine. Further, since the head cover is provided with a viewing window, the rocker arm can be seen through the head cover even when the head cover is placed on the cylinder head.

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 over all the 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.

  The intake cam included in the intake camshaft 26 regulates the position of the intake rocker arm 20 from above. Further, the exhaust cam provided in the exhaust cam shaft 28 regulates the position of the exhaust rocker arm 24 from above. As a result, the intake rocker arm 20 is sandwiched between the intake valve 16 and the lash adjuster 22 positioned below the intake rocker arm 20 and the intake cam positioned above the intake valve 16 and the lash adjuster 22. Similarly, the exhaust rocker arm 24 is sandwiched between the exhaust valve 18 and the exhaust side lash adjuster and the exhaust cam.

  When the intake cam 26 rotates under the above-described circumstances, a pressing force by the intake cam is periodically applied to the intake rocker arm 20. In accordance with the generation and disappearance of such a pressing force, the intake rocker arm 20 swings so that the intake valve 16 is opened and closed with the end portion supported by the lash adjuster 22 as the rotation center. As a result, the intake valve 16 opens and closes in synchronization with the rotation of the intake camshaft 26. By the same principle, the exhaust valve 18 opens and closes in synchronization with the rotation of the exhaust camshaft 28.

  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 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. The support structure of this embodiment has a part in the structure of the head cover 30. Hereinafter, the characteristic part will be described.

  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. More specifically, the intake visual window 44 and the exhaust visual window 46 are designed so that both of the following two conditions are satisfied.

First Condition The intake viewing window 44 is provided so that the intake rocker arm 20 (see FIG. 1) can be seen through the intake viewing window 44 in a state where the head cover 30 is assembled to the cylinder head 10. The exhaust viewing window 46 is provided so that the exhaust rocker arm 24 (see FIG. 1) can be seen through the exhaust viewing window 46 in a state where the head cover 30 is assembled to the cylinder head 10. The camshaft support structure of the present embodiment has the greatest feature in that the head cover 30 is configured to satisfy this condition.

  In particular, in the present embodiment, the intake viewing window 44 and the exhaust viewing window 46 are designed so that the intake rocker arm 20 and the exhaust rocker arm 24 can be viewed simultaneously from a single viewpoint. In other words, the intake visual window 44 and the exhaust visual window 46 are used when the operator faces the internal combustion engine from a specific direction (for example, from the intake side) in an assembly line or maintenance scene of the internal combustion engine. All the rocker arms 20 and 24 are provided so as to be visible without changing the standing position with respect to (without going around to the exhaust side).

Second Condition In addition, 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 significantly 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, in order to ensure the rigidity of the upper bearing 32, the portion (the most convex portion) is integrated with the head cover 30, that is, the adjacent upper bearing 32 is at least of the semicircular portion 36. It is desirable that the most convex portions are connected to each other.

  In other words, it is desirable that the intake visual window 44 and the exhaust visual window 46 do not intervene between the most convex portions of the semicircular portion 36 between the adjacent upper bearings 32. In the present embodiment, the intake visual window 44 and the exhaust visual window 46 are, more specifically, a region located immediately above the semicircular portion 36 so that the above requirement is satisfied, more specifically, a semicircle in FIG. The shape portion 36 is designed so as not to overlap with a region directly above the central portion (directly above the center of the camshafts 26 and 28).

(Oil shower structure)
With reference to FIG. 1 again, the structure above the head cover 30 will be described. As shown in FIG. 1, an intake oil shower 50 and an exhaust oil shower 52 are assembled to the head cover 30. In an internal combustion engine, it is necessary to inject oil into the intake cam and the exhaust cam in order to make the sliding with the intake rocker arm 20 smooth and the sliding with the exhaust rocker arm 24, respectively. is there.

  The intake oil shower 50 is a component for injecting oil into the intake cam via the intake visual window 44. The exhaust oil shower 52 is a component for injecting oil to the exhaust cam via the exhaust visual window 46. These are all fixed to an upper bearing 32 that supports the intake camshaft 26 and the exhaust camshaft 28.

(Basic structure of the visual window cover)
As shown in FIG. 1, an intake visual window cover 54 and an exhaust visual window cover 56 are assembled on the head cover 30. Both the intake visual window cover 54 and the exhaust visual window cover 56 are made of magnesium.

  The intake visual window cover 54 is a member for covering the intake visual window 44, and is assembled to the head cover 30 so that the intake oil shower 50 is accommodated therein. On the other hand, the exhaust viewing window cover 56 is a member for covering the exhaust viewing window 46, and the exhaust oil shower 52 is assembled to the head cover 30 so as to be contained therein.

(Oil filler)
An oil filler 58 is provided in the exhaust viewing window cover 56. The oil filler 58 is a supply hole for supplying oil to the internal combustion engine. The structure and shape of the oil filler 58 are designed according to the type of the internal combustion engine, the type of vehicle on which the internal combustion engine is mounted, and the like so that smooth oil supply is possible with the internal combustion engine mounted on the vehicle. Has been.

  When an internal combustion engine is used in the market, the lid of the oil filler 58 may be forgotten to be closed after the oil is supplied. The exhaust viewing window cover 56 is provided with an oil scattering prevention structure (not shown) for minimizing the amount of oil splashed to the outside from the oil filler 58 when the internal combustion engine is operated under such circumstances. It has been. The structure for effectively preventing the scattering of oil is inevitably different depending on the type of the internal combustion engine and the mounting posture of the internal combustion engine on the vehicle. For this reason, the oil splash prevention structure is also designed in accordance with the type of the internal combustion engine, the vehicle type on which the internal combustion engine is mounted, and the like, similar to the oil filler 58.

(PCV room)
In an internal combustion engine, blow-by gas may flow out of the cylinder into the cylinder head 10. Further, oil used for lubricating each part circulates inside the cylinder head 10. For this reason, in order to ventilate the blow-by gas, it is necessary to provide a separation chamber (hereinafter referred to as “PCV room”) for separating the blow-by gas and the oil at any location.

  According to a general configuration, the PCV room is formed by raising a part of the head cover. On the other hand, in the present embodiment, the inside of the intake visual window cover 54 (the concave portion of the intake visual window cover 54 in FIG. 1) and the inside of the exhaust visual window cover 56 (the recess of the exhaust visual window cover 56 in FIG. 1). Part) is used as a PCV room.

  FIG. 3 is a cross-sectional view obtained by cutting the intake visual window cover 54 along the longitudinal direction. As shown in FIG. 3, a gas-liquid separation chamber 60 in which blow-by gas mixed with oil flows is provided inside the intake visual window cover 54. An oil dropping plate 62 is incorporated below the gas-liquid separation chamber 60. Further, a gas inflow region 64 that is not covered by the oil dropping plate 62 is formed at one end (the left end in FIG. 3) of the intake visual window cover 54. Further, a gas outlet hole 66 is provided at the other end (right end in FIG. 3) of the intake visual window cover 54.

  FIG. 4 is a perspective view of the oil dripping plate 62. As shown in FIG. 4, the oil dropping plate 62 is provided with a large number of oil dropping holes 68. The oil dripping plate 62 has a plurality of obstacle walls 70. The oil dripping hole 68 is also provided in the obstacle wall 70.

  According to the configuration shown in FIG. 3, the blow-by gas containing oil mainly flows into the intake visual hole cover 54 from the gas inflow region 64. The gas that has flowed in flows into the gas-liquid separation chamber 60 from the gas inflow region 64 and proceeds in the gas-liquid separation chamber 60 toward the gas outlet hole 66 while being blocked by the obstacle wall 70.

  In the process in which the blow-by gas travels through the gas-liquid separation chamber 60, the oil in the gas is captured by the wall surface of the intake visual window cover 54 and the oil dropping plate 62. The oil thus captured drops from the oil dropping hole 68 and returns to the cylinder head 10 through the intake visual observation window 44 again. Then, only the blow-by gas after the oil is separated is led out from the gas lead-out hole 66 for ventilation.

  The inside of the exhaust visual window cover 56 is also configured in the same manner as the intake visual window cover 54. For this reason, according to the camshaft support structure of the present embodiment, the inside of the intake visual window cover 54 and the inside of the exhaust visual window cover 56 are effectively used as a PCV room to efficiently ventilate blow-by gas. It can be carried out.

[Assembly process and main effects of Embodiment 1]
FIG. 5 is an exploded perspective view for explaining the assembly process of the camshaft support structure of the present embodiment. When assembling the support structure of this embodiment, first, the intake valve 16, the exhaust valve 18, the lash adjuster 22, and the like are assembled to the cylinder head 10. Next, as shown in FIG. 5, the intake rocker arm 20 and the exhaust rocker arm 24 are placed thereon.

  FIG. 5 shows a state in which the camshafts 26 and 28 are placed on the rocker arms 20 and 24 for convenience. The rocker arms 20 and 24 are not dropped from the intake and exhaust valves 16 and 18 and the lash adjuster 22 when the camshafts 26 and 28 are fixed at appropriate positions as shown in FIG. However, until the camshafts 26 and 28 are properly assembled, they are simply placed on the intake / exhaust valves 16 and 18 and the lash adjuster 22 and can be dropped from above.

  In assembling the support structure of this embodiment, the camshafts 26 and 28 are held between the upper bearing 32 and the lower bearing 34 of the head cover 30 before being placed on the rocker arms 20 and 24. That is, the camshafts 26 and 28 are first placed on a predetermined number of lower bearings 34 arranged appropriately. The head cover 30 is covered from above, and the head cover 30 and the lower bearing 34 are fastened. Alternatively, first, the camshafts 26 and 28 are appropriately placed on the inverted head cover 30. Next, the lower bearing 34 is fixed to the head cover 30 so that the camshafts 26 and 28 are appropriately held.

  In the assembly process of the present embodiment, the head cover 30 is then placed over the cylinder head 10 so that the camshafts 26 and 28 are placed on all the rocker arms 20 and 24 in an appropriate positional relationship. It is done. At this time, since the rocker arms 20 and 24 are in a state where they can be dropped off, the operation of covering the head cover 30 on the cylinder head 10 needs to be performed sufficiently carefully.

  In the present embodiment, the head cover 30 includes the intake viewing window 44 and the exhaust viewing window 46 as described above. For this reason, in the process of assembling the head cover 30, the operator can proceed with the work while viewing the rocker arms 20 and 24 through the viewing windows 44 and 46. Further, the operator easily confirms whether or not all the rocker arms 20 and 24 are in an appropriate state through the viewing windows 44 and 46 after the operation of placing the head cover 30 is completed. be able to.

  In particular, in this embodiment, the intake viewing window 44 and the exhaust viewing window 46 are configured so that the intake rocker arm 20 and the exhaust rocker arm 24 can be simultaneously viewed from a single viewpoint. For this reason, in the assembling process of the head cover 30, a single operator can easily perform the assembling work while visually checking the rocker arms 20 and 24 and the confirmation work after the assembling.

  For the above reasons, according to the support structure of the present embodiment, it is possible to reliably prevent the rocker arms 20 and 24 from falling off during the assembly process while using a configuration in which the upper bearing 32 is integrated with the head cover 30. For this reason, according to the support structure of the present embodiment, excellent productivity can be realized while using the head cover 30 integrally including the upper bearing 32.

  Oil showers 50 and 52 are assembled to the head cover 52. Next, the viewing window covers 54 and 56 are fixed to the head cover 30 so that the oil showers 50 and 52 are accommodated therein. These operations may be performed either before or after the head cover 30 is attached to the cylinder head 10.

  When the above steps are completed, the spark plug unit 72 is assembled from the top of the head cover 30 for each cylinder. A chain case 74 is attached to the side surfaces of the cylinder head 10 and the head cover 30.

[Other effects]
According to the camshaft support structure of the present embodiment, the rocker arms 20 and 24 can be easily visually recognized simply by removing the viewing window covers 54 and 58 even after the internal combustion engine is assembled. Visual observation of the rocker arms 20 and 24 may be required during maintenance and inspection of the internal combustion engine even after the vehicle is shipped. According to the structure of this embodiment, such a request can be easily met. For this reason, according to the camshaft support structure of the present embodiment, good workability can be realized with respect to maintenance and inspection of the internal combustion engine.

  Further, according to the camshaft support structure of the present embodiment, as described above, the upper bearings 32 are connected at least at the most convex portions of the semicircular portion. For this reason, according to the structure of the present embodiment, the intake air viewing window 44 and the exhaust air viewing window 46 are provided in the head cover 30, and the material of the head cover 30 is magnesium that is less rigid than aluminum or cast iron. The upper bearing 32 can be provided with sufficient rigidity.

  In the camshaft support structure of the present embodiment, the head cover 30, the lower bearing 34, and the viewing window covers 54 and 56 are made of magnesium. When these members are made into magnesium, they are significantly lighter than when they are made of aluminum or cast iron. For this reason, according to the camshaft support structure of the present embodiment, it is possible to achieve a significant weight reduction and a low center of gravity of the internal combustion engine.

  Further, according to the camshaft support structure of the present embodiment, the oil showers 50 and 52 are directly fixed to the upper bearing 32. According to such a configuration, the distance between the oil showers 50 and 52 and the intake cam or the exhaust cam can be sufficiently shortened. In this case, the positional relationship between the two is determined only by the accuracy of the upper bearing 32. For this reason, according to this structure, the oil injection accuracy by the oil showers 50 and 52 can be increased.

  Further, according to the camshaft support structure described above, the maintenance and inspection of the oil showers 50 and 52 can be easily performed only by removing the viewing window covers 54 and 56. For this reason, the camshaft support structure of the present embodiment can achieve good workability with respect to maintenance and inspection of the oil showers 50 and 52.

  In the camshaft support structure of the present embodiment, as described above, the oil filler 58 and the oil scattering prevention structure are provided not on the head cover 30 but on the exhaust viewing window cover 56. As described above, the oil filler 58 and the oil scattering prevention structure may be required to have different designs depending on the type of the internal combustion engine, the type of vehicle on which the internal combustion engine is mounted, and the like. According to the structure of the present embodiment, it is possible to meet the demand without making any changes to the cylinder head 30 or the like by recreating only the exhaust viewing window 56. For this reason, according to the camshaft support structure of this embodiment, the versatility of components, such as the cylinder head 30, can be improved.

  Further, in the camshaft support structure of the present embodiment, the PCV room is provided in the viewing window covers 54 and 56 as described above. For this reason, according to this structure, the structure of the head cover 30 can be simplified and the productivity of the internal combustion engine can be enhanced as a whole. Furthermore, according to this structure, the specification of the PCV room can be changed only by changing the viewing window covers 54 and 56. The specifications of the PCV room may vary from vehicle model to vehicle model due to space constraints in the engine room. According to the structure of the present embodiment, such a request can be appropriately met by simply changing the viewing window covers 54 and 56. Thus, the camshaft support structure of the present embodiment can improve the versatility of components such as the head cover 30 also in this respect.

[Modifications of Embodiment 1]
By the way, in the first embodiment described above, all the upper bearings 32 are connected to the adjacent upper bearings at least at the most convex part of the semicircular part, but the present invention is limited to this. It is not a thing. That is, the upper bearing 32 may include a semicircular portion that is not connected to the adjacent upper bearing at the most convex portion.

  In the first embodiment described above, the oil dripping plate 62 is arranged in the viewing window covers 54 and 56 to configure the PCV room, but the method for configuring the PCV room is the same. It is not limited. For example, the PCV room may be configured by simply attaching the visual window covers 54 and 56 to the head cover 30 without using the oil dripping plate 62.

  In the first embodiment described above, the head cover 30, the lower bearing 34, and the viewing window covers 54 and 56 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 rocker arms 20 and 24 can be removed from the intake and exhaust valves 16 and 18 and the lash adjuster 22 until the camshafts 26 and 28 are assembled. However, the present invention is not necessarily based on such a configuration. That is, the rocker arm may be held by a rocker shaft or the like and may not fall off. Even in such a case, according to the support structure having the viewing windows 44 and 46 in the head cover 30, it is possible to obtain at least an effect that the workability of maintenance / inspection after the vehicle is shipped can be improved.

  In the first embodiment described above, the lower bearing 34 divided into a plurality of members is used, but the present invention is not limited to this. That is, in the present invention, a ladder frame type lower bearing in which a plurality of lower bearings 34 are connected in a ladder shape may be used.

  In the first embodiment described above, the observation windows 44 and 46 are provided so that the adjacent upper bearings 32 are connected to each other at least at the most convex portions of the semicircular portion 36. This condition (the second condition described above) can be rephrased as follows. That is, in the first embodiment, the most convex part of the semicircular part 36 is the part where the reaction force accompanying the opening of the intake valve 16 and the exhaust valve 18 acts most strongly. Therefore, this condition can be said in other words that the viewing windows 44 and 46 are provided so that the adjacent upper bearings 32 are connected to each other at the portions where the reaction force that is the strongest when the valve element is opened. .

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 sectional drawing obtained by cut | disconnecting the intake visual observation window cover shown in FIG. 1 along a longitudinal direction. FIG. 4 is a perspective view of the oil dropping plate shown in FIG. 3. It is a disassembled perspective view for demonstrating the assembly | attachment process of the camshaft support structure of Embodiment 1 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 Head cover 32 Upper bearing 34 Lower bearings 36 and 38 Semicircular part 44 Intake viewing window 46 Exhaust viewing window 50 Intake Oil shower 52 Exhaust oil shower 54 Intake visual window cover 56 Exhaust visual window cover 58 Oil filler 60 Gas-liquid separation chamber 62 Oil drip plate

Claims (1)

A cylinder head of an internal combustion engine;
A rocker arm incorporated in the cylinder head and supported at one end by a lash adjuster;
A camshaft comprising a cam that contacts the rocker arm;
A lower bearing that supports the camshaft from the cylinder head side;
A head cover that integrally includes an upper bearing that supports the camshaft from a side opposite to the lower bearing;
The camshaft support structure for an internal combustion engine, wherein the head cover is provided with a viewing window that allows the rocker arm to be viewed when assembled on the cylinder head.

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