JPH0377377B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to an overhead camshaft internal combustion engine in which the cylinder head is tightened and fixed to the cylinder by a plurality of tightening bolts located below the camshaft. .

BACKGROUND OF THE INVENTION In internal combustion engines, a cylinder head is typically secured to a cylinder by a plurality of tightening bolts. Since the tightening bolt is usually tightened with a tool from above, that is, from the cylinder head side, especially in internal combustion engines with an overhead camshaft, the tool used to tighten the tightening bolt may interfere with the camshaft, making it difficult to efficiently tighten the bolt. It may be impossible to tighten. Generally, in internal combustion engines, it is desirable to be able to retighten the cylinder head without disassembling the camshaft or valve mechanism. The cylinder head tightening bolt must be positioned so that the tightening tool does not interfere with the camshaft, etc. As a result, there were problems in that the degree of freedom in arranging tightening bolts and camshafts was reduced and the engine became larger.

Particularly in the case of an internal combustion engine in which intake and exhaust valves are directly driven to open and close by two overhead camshafts, the camshafts must be placed outside of these bolts so as not to interfere with them. For this reason, the suction
There was also the problem that the narrowing angle of the exhaust valve became large, reducing the degree of freedom in selecting the shape of the combustion chamber.

(Objective of the Invention) The present invention was made in view of the above circumstances, and it is possible to efficiently tighten the tightening bolt of the cylinder head without removing the camshaft, and the flexibility in arrangement of the tightening bolt and the camshaft is increased. An object of the present invention is to provide an overhead camshaft type internal combustion engine that can avoid increasing the size of the engine by increasing the engine size, and can increase the degree of freedom in selecting the shape of the combustion chamber when using a dual overhead camshaft type. It is.

(Structure of the Invention) According to the present invention, the object is to provide an overhead camshaft internal combustion engine in which a cylinder head is tightened and fixed to the cylinder by a plurality of tightening bolts, and in which the tightening bolts are positioned below the camshaft for the length thereof. The camshaft is arranged along the direction, and the camshaft is provided with relief portions corresponding to the respective tightening bolts simultaneously at predetermined rotational positions of the camshaft to avoid interference with tools for tightening the respective tightening bolts. This is achieved by a distinctive overhead camshaft internal combustion engine.

(Example) Fig. 1 is a sectional view showing one embodiment of the present invention, and Fig. 2 is a sectional view showing an embodiment of the present invention.
The figure is a sectional view taken along the - line.

In these figures, a is the crankcase, b
1 is a cylinder, and c is a cylinder head. These three members are positioned via positioning members 1 and 2, and are fastened and fixed via a plurality of tightening bolts 3.

4 and 5 are recesses formed to correspond to the mating surfaces of the crankcase a and cylinder b, and 6 and 7 are recesses formed to face the mating surfaces of the cylinder b and cylinder head c. Recesses 4, 5,
Positioning members 1 and 2 are fitted to 6 and 7, respectively, to position the crankcase a, cylinder b, and cylinder head c.

On the other hand, the tightening bolt 3 has a shaft part 3a in the middle and threaded parts 3b and 3c formed at both ends, and the lower threaded part 3b is inserted into a threaded hole 8 formed in the crankcase a. The shaft portion 3a is inserted into the insertion holes 9, 10 formed in the cylinder b and the cylinder head c with a gap.

Reference numeral 11 denotes a housing hole connected to the upper end of the insertion hole 10 of the cylinder head c and formed with a larger diameter than that, and the upper end thereof is connected to the upper end of the insertion hole 10 of the cylinder head c, which will be described later.
The upper threaded portion 3c of the tightening bolt 3 faces into this accommodation hole 11 which opens into the bearing portion c' on the upper surface.

A nut 12 is screwed onto the threaded portion 3c of the tightening bolt 3 facing into the housing hole 11, and its lower end engages with the bottom of the housing hole 11 via a washer 13.

This nut 12 has a screw hole 12a formed in its lower half to be screwed into the threaded portion 3c of the tightening bolt 3, and a locking hole 12b formed in its upper half. The locking hole 12b has a hexagonal cross section, and allows a tool such as a hexagonal wrench to be fitted and locked to tighten or loosen the nut 12. In this manner, by tightening the nut 12, the cylinder head c, cylinder b, and crankcase a are tightened and fixed to each other by the tightening bolt 3.

On the other hand, two camshafts 14, 14 are provided at the upper part of the cylinder head c to open and close an intake valve and an exhaust valve (both not shown), respectively.

This camshaft 14 is arranged above the bolt 3 so that its axis substantially coincides with the axis of the tightening bolt 3, and has multiple shear portions 1 in the longitudinal direction.
4' is pivotally supported. That is, the camshaft 14 is rotatably held in a bearing formed by a bearing part c' formed in the cylinder head c and a bearing cap 16 fixed to the upper surface thereof with a bolt 15.

Here is the bearing part formed in the cylinder head c.
Since the housing hole 11 is open at c', the journal portion 14' of the camshaft 14 has a tightening bolt 3 housed therein at the portion facing the housing hole 11.
to face.

Reference numeral 17 denotes an insertion hole as a relief part formed in the journal part 14' of the camshaft 14 so as to pass through it in the radial direction of the camshaft 14, and the insertion hole 17 corresponds to the tightening bolt 3 to allow the camshaft 14 to rotate in a predetermined manner. It communicates with the housing hole 11 on the cylinder head c side at the position, and its axis coincides with the tightening bolt 3. The insertion hole 17 as a relief part is for inserting a tool for tightening the nut 12 of the tightening bolt 3, as will be described later. It is not limited to this, but it may be provided at a location other than that.

18 is a communication hole provided in the bearing cap 16 so as to communicate with the insertion hole 17, and its axis coincides with the axis of the tightening bolt 3 so that the bearing cap 1
6 is opened at the upper surface thereof, and the open end thereof is liquid-tightly closed by a plug member 19. 20 is a cover that covers the outer periphery of the cap 16 and the camshaft 14, and the bolt 2
1 to the bearing cap 16. The inner surface of the cover 20 presses the plug member 19 from above, and the lower end of its periphery is in liquid-tight contact with the upper surface of the cylinder head c.

Note that 14'' in the figure is a large diameter portion formed in the middle of the camshaft 14 and connected to the journal portion 14', and the side surface of the large diameter portion abuts against the wall surface of the bearing cap 16 to reduce the thrust load acting on the camshaft 14. It is becoming more and more popular.

In an internal combustion engine configured as described above, if you want to tighten the cylinder head c after assembly, first remove the cover 20 and remove the plug member 1 that fits into the communication hole 18 of the bearing cap 16.
Remove 9. The communication hole 18 and the accommodation hole 1
The position of the insertion hole 17 is adjusted by rotating the camshaft 14 to a position where the camshaft 14 communicates with the insertion hole 17 through the insertion hole 17. In this state, the insertion hole 17 is located on the extension of the axis of the tightening bolt 3. This rotational operation of the camshaft 14 is performed by directly rotating the camshaft 14 or by indirectly rotating the camshaft 14 via a crankshaft (not shown).

In this embodiment, means for directly rotating the camshaft 14 is provided. That is, camshaft 1
4 is provided with a locking portion 14a having a hexagonal cross-section and capable of locking a tool in a portion exposed when the cover 20 is removed. Therefore, the insertion hole 17 is aligned by locking a tool in the locking portion 14a and rotating the camshaft 14. In this embodiment, the two camshafts 14 are rotated in conjunction with each other, and their respective insertion holes 17 are all simultaneously aligned with the axis of the tightening bolt 3, which improves work efficiency. good. Particularly when sequentially tightening the tightening bolts 3 at diagonal positions, the work can be carried out efficiently and easily without rotating the camshaft 14.

In this way, the camshaft 14 is rotated to a predetermined rotational angle position and the insertion hole 17 is aligned, and then the accommodation hole 11 is inserted through the communication hole 18 and the insertion hole 17.
The cylinder head c is further tightened by inserting a tightening tool into the nut 12, engaging the tool with the nut 12, and tightening it.

On the other hand, the bearing cap 16 that pivotally supports the camshaft 14 and the bearing portion of the cylinder head c need to be lubricated. The lubrication is performed by lubricating oil pumped from inside the crankcase a. That is, the lubricating oil sent out from inside the crankcase a is sent into the positioning member 1 between the crankcase a and the cylinder b, and from there passes between the shaft portion 3a of the tightening bolt 3 and the insertion holes 9 and 10. Then, it is sent to a passage 22 communicating with the insertion hole 10 on the side of the cylinder head c. Then, this lubricating oil is distributed from the passage 22 to two passages 23 and 24 that connect the end of each camshaft 14 to the corresponding accommodation hole 11, and is distributed through these passages 23 and 24 to each accommodation hole 11. sent inward.

The lubricating oil that has flowed into the housing hole 11 is ejected upward from between the inner wall of the housing hole 11 and the nut 12, and is caused to leak between the bearing of the journal portion 14' of the camshaft 14, that is, the bearing portion c and the bearing cap 16. Lubricate sliding surfaces. Further, this lubricating oil enters the insertion hole 17 of the camshaft 14, and from there flows into a passage 25 that extends in the axial direction of the camshaft 14, perpendicular to the insertion hole 17. Then, the lubricating oil is sent through the passage 25 to another accommodation hole 11 connected to another bearing,
The bearing portion around this accommodation hole 11 is lubricated.

(Effects of the Invention) As described above, in this invention, a plurality of tightening bolts are arranged below the camshaft along the camshaft, and a relief part is formed on the camshaft to avoid interference with a tool for tightening the bolts. This allows the tightening bolt to be tightened without removing the camshaft. In particular, the relief parts are formed at almost the same rotational position of the camshaft, so once the camshaft is set in a position where it will not interfere with the tool, all the tightening bolts can be tightened without interfering with the camshaft. The work can be done efficiently if the tightening bolts are tightened evenly in order. Also, since interference between the tool and the camshaft is avoided, the degree of freedom in arranging the tightening bolts and camshaft increases, making it possible to downsize the engine. Particularly in the case of a direct-acting type engine having two overhead camshafts, it is possible to bring both camshafts close together to reduce the angle between the intake and exhaust valves, thereby obtaining a desired combustion chamber shape.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a sectional view taken along the - line. a...Crankcase, b...Cylinder, c...
...Cylinder head, 3...Tightening bolt, 14...
Camshaft, 17...insertion hole as a relief part.

Claims (1)

[Scope of Claims] 1. In an overhead camshaft internal combustion engine in which a cylinder head is tightened and fixed to the cylinder by a plurality of tightening bolts, the tightening bolts are arranged below the camshaft along its length, and , an overhead camshaft internal combustion system, characterized in that the camshaft is formed with relief portions simultaneously corresponding to the respective tightening bolts at predetermined rotational positions of the camshaft to avoid interference with a tool for tightening the tightening bolts; institution.