JPH02238156A - Overhead camshaft internal combustion engine - Google Patents

Abstract

PURPOSE:To tighten fastener bolts without detaching cam shafts by setting a plural number of the fastener bolts along the cam shafts below the cam shafts, and forming escape parts which prevents the occurrence of interference with a bolt fastening tool, at the cam shafts. CONSTITUTION:A crank case (a), a cylinder (b) and a cylinder head (c) are positioned through a plural number of positioning members 1, 2, respectively, and are fastened and fixed through a plural number of fastener bolts 3, 3. In this case, a plural number of cam shafts 14,14 which rotate intake and exhaust valves, respectively, are provided above the cylinder head (c), and the cam shafts 14, 14 are, respectively, set coaxially with the bolts 3, 3 above them. At journal parts of the cam shafts 14, 14 insertion holes 17, 17 which serve as escape parts to penetrate to the radial direction is formed. Into the insertion holes 17, 17, a tool to fasten nuts 12 of the fastener bolts 3, 3 are inserted. Consequently, the fastener bolts 3,3 are tightened without detaching the cam shafts 14, 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an overhead camshaft type internal combustion engine in which a cylinder head is tightened and fixed to a cylinder by a plurality of tightening bolts located below a camshaft.

BACKGROUND OF THE INVENTION In internal combustion engines, a cylinder head is typically tightened 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 tighten the bolt efficiently. There may be things you can't do. Generally, in internal combustion engines, it is desirable to be able to retighten the cylinder head without disassembling the camshaft or valve mechanism. ,
These cylinder head tightening bolts must be placed so that the tightening tool does not interfere with the camshaft or the like. 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, there is a problem in that the angle between the intake and exhaust valves becomes large, and the degree of freedom in selecting the shape of the combustion chamber is also reduced.

(Object of the invention) This invention was made in view of the above circumstances,
The tightening bolts on the cylinder head can be tightened efficiently without removing the camshaft, increasing the degree of freedom in arranging the tightening bolts and camshaft, and avoiding increasing the size of the engine. It is an object of the present invention to provide an overhead camshaft internal combustion engine that can increase the degree of freedom in selecting the shape of the combustion chamber when the combustion chamber shape is selected.

(Structure of the Invention) According to the present invention, the object is to provide an overhead camshaft type internal combustion engine in which a cylinder head is tightened and fixed to a cylinder by a plurality of tightening bolts, and in which the tightening bolts are arranged below the camshaft in the longitudinal direction. The camshaft is arranged along the camshaft, and a relief part is formed on the camshaft to avoid interference with a tool that simultaneously tightens the respective tightening bolts corresponding to the respective tightening bolts at a predetermined rotational amount of the camshaft. This is achieved by an overhead camshaft internal combustion engine.

(Embodiment) FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view taken along line 11-II.

In these figures, (a) is the crankcase, (b)
is a cylinder, (C) is a cylinder head, and these three are positioning members (1). (2), and is tightened and fixed via a plurality of tightening bolts (3).

+4). ! 5) is a recess formed to face each mating surface of the crankcase (a) and cylinder fb); and (6). +7) are recesses formed facing each mating surface of the cylinder (b) and the cylinder head (c), and these recesses (4) +5) . +61.
(7) and the positioning member (1) respectively. (2) are fitted together to position the crankcase (a), cylinder (b) and cylinder head (c).

On the other hand, the tightening port (3) has a shaft (3a) in the middle and threaded parts (3b) and (3c) formed at both ends, and the lower threaded part (3b) It is screwed into a screw hole (8) formed in the crankcase (a), and the shaft part (3
A) is inserted through the insertion holes (9) and (10) formed in the cylinder (b) and the cylinder head (C) with a gap therebetween.

(1l) is the cylinder head (Cl insertion hole (10
) is a housing hole formed in a larger diameter than the upper end of the housing hole (11), the upper end of which opens into a bearing part (C') on the upper surface of the cylinder head (C), which will be described later. The upper threaded portion (3c) of the tightening bolt (3) is facing.

(12) is a tightening bolt (3) facing into the accommodation hole (11).
), and its lower end engages with the bottom of the accommodation hole (11) via a washer (13).

This nut (12) has a screw hole (12al) formed in its lower half to be screwed into the threaded portion (3c) of the tightening bolt (3), and a locking hole (12bl) formed in its upper half. The locking hole (12b) has a hexagonal cross section, and allows a tool such as a hex wrench to be fitted and locked to tighten or loosen the nut (12).In this way, the nut (12) can be tightened or loosened. (12), the cylinder head (C), cylinder (bl) and crankcase (a) are tightened.
) are tightened and fixed together by the tightening port (3).

On the other hand, two camshafts (14), (14) are provided at the top 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 tightening bolt (3) so that its axis substantially coincides with the axis of the tightening bolt (3), and the camshaft (14) is supported by a plurality of shear portions (14') in its longitudinal direction. has been done. That is, the bearing part (C') formed in the cylinder head (C) and the bolt (l5) on the upper surface of the bearing part (C').
The camshaft (14) is rotatably held in a bearing formed by a bearing cap (16) fixed to the camshaft (14).

Here, the bearing part (C') formed in the cylinder head (C)
) has the accommodation hole (1l) open, so the journal portion (14') of the camshaft (14) is inserted into the accommodation hole (1l).
In the part facing l), the tightening bolt (
3) Facing.

(l7) is the journal portion (14) of the camshaft (14).
'1 is an insertion hole as a relief part formed to penetrate in the radial direction of the camshaft (14), and the tightening bolt (3)
Correspondingly, at a predetermined rotational position of the camshaft (14), it passes through the accommodation hole (11) on the cylinder head (c) side, and its axis coincides with the tightening port (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 the journal portion (14') of the camshaft (14), but may be provided at a position other than there.

(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).
) The opening is opened on the upper surface, and the opening end is liquid-tightly closed with a plug member (19). (20) is a cover that covers the outer periphery of the cap (16) and the camshaft (14);
1) is fixed 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).

In addition, (14'') in the figure is a large diameter part formed in the middle part of the camshaft (14) and connected to the journal part (14'l). It is adapted to receive a thrust load acting on the shaft (14).

In an internal combustion engine configured in this way, if you want to tighten the cylinder head (C) after assembly, first remove the cover (20) and remove the bearing cap (20).
Remove the plug member (19) that fits into the communication hole (18) of 16). The camshaft (1) is located at a position where the communication hole (18) and the accommodation hole (11) communicate with each other via the insertion hole (17).
4) to align the position of the insertion hole (17). In this state, the insertion hole (17) is inserted into the tightening bolt (
3) will be located on the axis line extension.

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, the camshaft (14) has a locking portion (14a) with a hexagonal cross section that can be locked with a tool on the portion exposed when the cover (20) is removed.
) is provided. Therefore, by locking a tool in this locking portion (14a) and rotating the camshaft (14), the insertion hole (17) is aligned. In this embodiment, the two camshafts (14) are rotated in conjunction with each other, so that their respective insertion holes (17) are simultaneously aligned with the axis of the tightening bolt (3). Workability is good because there are In particular, 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 (1l) is inserted through the communication hole (l8) and the insertion hole (17). )
The cylinder head (c) is further tightened by inserting a tightening tool into the nut 2), engaging the tool with the nut 2), and tightening it.

On the other hand, a bearing cap (1) that supports the camshaft (14)
It is necessary to lubricate the bearings of the cylinder head (c) and the cylinder head (c), but this lubrication is performed by lubricating oil that is pumped from inside the crankcase (c). 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 the lubricating oil is sent to the tightening bolt (3).
The shaft portion (3a) and the insertion hole (9). (10) and is sent to a passageway (22) communicating with the insertion hole (10) on the cylinder head (c) side. Then, this lubricating oil flows through two passages (23), (2
4), and these passages (23) and (24)
and into each accommodation hole (11).

The lubricating oil that has flowed into the accommodation hole (11) is squirted upward from between the inner wall of the accommodation hole (1l) and the nut (l2), and is then sprayed upward from the space between the inner wall of the accommodation hole (1l) and the nut (l2), and is then released into the bearing of the journal portion (14') of the camshaft (l4). In other words, it lubricates the sliding surfaces between the bearing (Cl) and the bearing cap (16).This lubricating oil also lubricates the sliding surfaces of the bearing (Cl) and the bearing cap (16).
) into the insertion hole (17) and from there into this insertion hole (1
7) into a passageway (25) extending in the axial direction of the camshaft (14). Then, the lubricating oil is sent to another housing hole (1l) connected to another bearing through the passage (25), and lubricates the bearing portion around this housing hole (11).

(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 you to tighten the tightening bolt 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. Especially in the case of a direct drive type with two overhead camshafts,
By bringing both camshafts closer together, it is possible to reduce the angle between the intake and exhaust valves and obtain a desirable combustion chamber shape.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention, and FIG. 2 is a sectional view taken along II-II MA thereof. a)...Crankcase, b)...Cylinder, C)...Cylinder head, 3)...Tightening bolt, 14)...Camshaft, 17)...Insertion as a relief part Hole. Patent applicant Yamaha Motor Co., Ltd.

Claims (1)

[Scope of Claims] 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 the cam An overhead camshaft type internal combustion engine, characterized in that the shaft 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 that tightens the tightening bolts.