JPH02238157A - Overhead camshaft internal combustion engine - Google Patents

Abstract

PURPOSE:To tighten fastener bolts without detaching bearing caps by setting the fastener bolts directly under bearing parts which support cam shafts, and forming insertion holes for a fastening tool, continuous with the bearing caps, the cam shafts and the bearing parts. CONSTITUTION:A crank case (a), a cylinder (b) and a cylinder head (c) are fastened with a plural number of fastener bolts 3, 3, respectively, In this case, a plural number of cam shafts 14, 14 which rotate intake and exhaust valves, respectively, are provided directly under the respective bolts 3, 3. Journal parts of cam shafts 14, 14 are supported between the bearing parts (c') of the cylinder head (c) and the bearing caps 16, 16. At respective positions with respect to the fastener bolts 3, 3 in the bearing parts (c'), the journal part and the bearing caps 16, 16, respective insertion holes 11, 17, 18 are formed, into which a mounting/removing tool for fastener bolts 3, 3 can be inserted, in a mutually continuous manner at specified rotation angle positions of the cam shafts 14, 14.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention is directed to tightening and fixing a cylinder head to a cylinder using a tightening bolt, and also attaching a camshaft to a bearing part on the cylinder head side and a bearing fixed to the cylinder head side. This relates to an overhead camshaft type internal combustion engine that is rotatably held between a cap and a camshaft that drives intake and exhaust valves to open and close.

BACKGROUND OF THE INVENTION In an internal combustion engine, a cylinder head is tightened to a cylinder by a tightening bolt. The tightening bolt is usually tightened with a tool from above, that is, from the cylinder head side, so especially in internal combustion engines with an overhead camshaft, the tool used to tighten the tightening bolt is attached to the camshaft or the bearing on the cylinder head side. It may interfere with the bearing cap that is being held, and it may not be possible to tighten it. 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 or its bearing cap. For this reason, there were problems in that the degree of freedom in arranging tightening bolts, camshafts, bearing caps, etc. was reduced, and the engine became larger.

In particular, in the case of an internal combustion engine that uses two overhead camshafts to drive the intake and exhaust valves to open and close, the camshafts must be placed outside of these tightening bolts so as not to interfere with them. There is also a problem in that the included angle of the valve becomes large and the degree of freedom in selecting the shape of the combustion chamber also decreases.

In addition, if the camshaft is a direct-acting type that directly opens and closes the intake/exhaust valve, or if the reaction force of the valve spring of the intake/exhaust valve is applied in the direction of pushing up the camshaft, the sliding surface on the bearing cap side It is desirable that measures be taken to prevent uneven wear from progressing excessively.

(Object of the invention) This invention was made in view of the above circumstances,
The cylinder head tightening bolts can be tightened efficiently without removing the bearing cap that holds the camshaft, increasing the degree of freedom in arranging the tightening bolts, camshafts, or bearing caps, and avoiding increasing the size of the engine. We also provide an overhead camshaft type internal combustion engine that can increase the degree of freedom in selecting the shape of the combustion chamber when using a double overhead camshaft type, and can also prevent uneven wear of the bearing cap that presses the camshaft from above. The purpose is to

(Structure of the Invention) According to the present invention, the object is to tighten and fix the cylinder head to the cylinder with a tightening bolt, and to provide a cam between the bearing portion on the cylinder head side and the bearing cap fixed opposite thereto. In an overhead camshaft internal combustion engine in which a shaft is rotatably held and the camshaft drives the intake and exhaust valves to open and close, the tightening bolt is disposed directly below the bearing portion, and a tightening tool for the tightening bolt is provided. An insertion hole for inserting a This is achieved by an overhead camshaft internal combustion engine characterized in that the bolt head or nut of the tightening bolt is accommodated in the insertion hole.

Here, the bolt head or nut may have a locking hole, such as a hexagonal hole, into which a tool inserted from the insertion hole is inserted, and in this case, a tool such as a hexagonal screwdriver is inserted through the insertion hole. This can then be tightened.

Further, a nut to be screwed into the tightening bolt is accommodated in the insertion hole on the bearing side, and a gap required for screwing the nut off is formed between the nut and the camshaft. can.

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

In these figures, (a) is the crankcase, (b)
is a cylinder, and (C) is a cylinder head, and these three are positioned via a positioning member (11. (2)) and are tightened and fixed via a plurality of tightening ports (3).

(4). (5) is a recess formed to face each mating surface of the crankcase (a) and cylinder (b); (6)
, (7) are recesses formed facing each mating surface of the cylinder (b) and cylinder head (C), and these recesses (4) . (5) (6) . Positioning members (1) and (2) are fitted into (7), respectively, to position the crankcase (a), cylinder (b), and cylinder head (C).

On the other hand, the tightening bolt (3) has threaded portions (3b) and (3C) formed at both ends with a shaft portion (3a) in the middle,
The lower threaded part (3b) is screwed into the screw hole (8) formed in the crankcase (a), and the shaft part (3a) is inserted into the cylinder (b) and the cylinder head (C). Hole (9). (It is loosely inserted into 101 with a gap.

(11) is the insertion hole (10) of the shilling head (C)
It is a first insertion hole that is connected to the upper end and has a larger diameter than that, and the upper end is the cylinder head (c) described later.
It opens in the bearing part (C') on the upper surface.

The upper threaded portion (3c) of the tightening bolt (3) faces the insertion hole (11).

(12) is a tightening bolt (
3) is a nut screwed onto the threaded portion (3C), and its lower end engages with the bottom of the insertion hole (11) via the washer (13). This nut (12) has a screw hole (12a) in the lower half that screws into the threaded part (3C) of the tightening bolt (3).
) is formed, and a locking hole (12b) is formed in the upper half. The locking hole (12b) has a hexagonal cross section, and a tool such as a hexagonal wrench can be locked in the locking hole (12b) to tighten or loosen the nut (12). By tightening the nut (12) in this way, the cylinder head (C) and the cylinder (b) are tightened.
) and the crankcase (a) are tightened and fixed via tightening bolts (3). Note that above this nut (121), as is clear from FIG.
) is provided with a gap required for unscrewing it from the threaded portion (3C) of the tightening bolt (3).

Meanwhile, two camshafts (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 attached to the tightening bolt (3) so that its axis coincides with the axis of the tightening bolt (3).
The bearing part (C') formed in the cylinder head (cl) and the bearing cap { 16}.Here, the bearing part (C') formed in the cylinder head (C) has the first insertion hole (11
) is open, the journal portion (14') of the camshaft (14) faces the tightening bolt (3) housed therein at the portion facing the insertion hole (11).

(17) is the journal portion (14) of the camshaft (14).
) is a second insertion hole provided at a position corresponding to the tightening bolt (3), and penetrates in the radial direction of the camshaft (14) to insert the tightening port at a predetermined rotational position of the camshaft (14). (
3) and the axis lines are aligned.

(18) is a third insertion hole provided in the bearing cap (l6) so as to communicate with the second insertion hole (17),
Its axis coincides with the axis of the tightening bolt (3), and an opening is formed on the upper surface of the bearing cap (16), and its opening end is the plug member (l).
9) is liquid-tightly closed. As a result, the first, second, and third insertion holes (11), (17), and (18) are inserted into the cam shaft (
At the predetermined rotation angle position of 14), the tightening bolt (3) is continuously inserted so that the tool for attaching and detaching it can be inserted therein.

(20) is a cover that covers the cap (.16) and the camshaft (14). This cover (20) has bolts (2
l) is fixed to the bearing cap (16), its peripheral edge abuts the upper surface of the cylinder head (c), and its inner surface presses the plug member (19) from above. In the figure (1
4'') is a large diameter part formed in the middle part of the camshaft (14) and connected to the journal part (14'l), and the side surface of the part is in contact with the wall surface of the bearing cap (16), and the camshaft (14) It is designed to receive the thrust load acting on it.

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).
Plug member (19) that fits into the third insertion hole (l8) of
). Then, rotate the camshaft (14) to
The insertion hole (17) is aligned so as to be continuous with the insertion hole (18) and the first insertion hole (11). That is, the insertion holes (11), (17), and (18) are positioned on the same axis as the tightening bolt (3), which can be operated by directly rotating the camshaft (14) or using the crankshaft. This is done by indirectly rotating the camshaft (14) via a shaft (not shown).

In this embodiment, a means for directly rotating the camshaft (l4) is provided. In other words, the camshaft (14) has
A locking portion (14a) having a hexagonal cross section allows a tool to be locked to the portion exposed by removing the cover (20).
) is provided. The insertion hole (17) is aligned by rotating the camshaft (l4) using the locking part (14al), but in the embodiment, the two camshafts (14) are linked with each other by a timing chain. and rotated,
All of those insertion holes (17) are tightened at the same time (3
) to make the work easier.

With the second insertion hole (17) aligned in this way, the third insertion hole (18) and the second insertion hole (17) are aligned.
), the cylinder head (c) is further tightened by inserting a tightening tool into the first insertion hole (11), engaging the tool with the nut (12), and tightening it.

Also, if the nut (l2) is loosened, there is a gap above this nut (l2) necessary for unscrewing this nut (12), so the cylinder head (Cl) can be brought into close contact with the cylinder (bl). The retaining nut (12) can be unscrewed and the cylinder head can be removed without disassembling the camshaft or valve mechanism.

On the other hand, a bearing cap (I) bearing the camshaft (14)
6) and the bearings of the cylinder head (C) need to be lubricated, but this lubrication is performed by lubricating oil that is pumped from inside the crankcase (ai). The lubricating oil is sent into the positioning member (1) between the crankcase (a) and the sill ring (bl), and from there the tightening bolt (3)
It passes between the shaft portion (3a) and the insertion holes (9), (10) and is sent to the passageway (22) communicating with the insertion hole (10) on the cylinder head (C) side. The lubricating oil is supplied from the passageway (22) to a first tube located at the end of each camshaft (14).
Two passages (23), (2) communicating with the insertion hole (11) of
4), and these passages (23) and (24)
into each insertion hole (11).

The lubricating oil that has flowed into the insertion hole (11) is jetted upward from the gap between the insertion hole (11) and the nut (12) to lubricate the journal portion (14') of the camshaft (C).

This lubricating oil also enters the insertion hole (17) of the camshaft (l4) and from there into the passageway (25) extending perpendicularly to this insertion hole (l7) in the axial direction of the camshaft (14). Inflow. The lubricating oil is then sent to the other insertion hole (11) through the passage (25) and lubricates the bearing portion around the hole (11). Here, since the spring force of the intake/exhaust valve acts on the camshaft (14) from below upward, the bearing cap (14)
6) A large amount of pressure is always applied to the sliding surface. But the third
Since the insertion hole (l8) has a smaller diameter than the first insertion hole (11), the area of the sliding surface on the bearing cap (16) side becomes larger, causing excessive wear on the sliding surface and uneven wear. There is no need to worry about it occurring.

(Effects of the Invention) As described above, in this invention, a tightening bolt for fixing the cylinder head to the cylinder is arranged directly under the bearing part on the cylinder head side that supports the camshaft from below, and a tightening tool for the tightening bolt is inserted. Since the insertion hole is continuously formed in the bearing camber, camshaft, and bearing part, the tightening bolt can be tightened without removing the bearing cap. Also, since interference between the tool and the camshaft and bearing cap can be avoided, the degree of freedom in arranging the tightening bolt, camshaft and bearing cap increases, making it possible to downsize the engine. In particular, when there are two overhead camshafts, it is possible to bring both camshafts closer together to reduce the angle between the intake and exhaust valves and obtain a desirable combustion chamber shape. In addition, since the first insertion hole on the cylinder head side has a larger diameter than the third insertion hole on the bearing cap side, the area of the sliding surface on the bearing cap side becomes larger, so the reaction force of the intake and exhaust valves Even if a large amount of friction is applied to the bearing cap side, the wear can be suppressed and uneven wear of the bearing can be prevented.

Note that if the first insertion hole accommodates a nut that is screwed into the tightening bolt, and this nut has a locking hole on its top surface into which the tip of a tool fits, a tool such as a hexagonal bar screwdriver cannot be used. , compared to using a box wrench etc.
The insertion hole can be made small in diameter.

Further, if a space necessary for screwing and unscrewing the nut is provided above the nut, the sill head can be easily attached and detached.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and the figure is a cross-sectional view taken along the line II--II in FIG. a)...Crankcase, b)...Cylinder, C)...Cylinder head, 3)...Tightening bolt, 11)...First insertion hole, 14)...Camshaft , 17)...second insertion hole,

Claims (3)

[Claims] (1) The cylinder head is tightened and fixed to the cylinder with a tightening bolt, and the camshaft is rotatably held between the bearing part on the cylinder head side and the bearing cap fixed opposite thereto, and the camshaft is In an overhead camshaft internal combustion engine in which the intake and exhaust valves are driven to open and close, the tightening bolt is disposed directly below the bearing portion, and an insertion hole for inserting a tightening tool for the tightening bolt is provided in the bearing cap. is formed continuously on the camshaft and the bearing part, the insertion hole on the bearing part side has a larger diameter than the insertion hole on the bearing cap side, and the bolt head of the tightening bolt is inserted into the insertion hole on the bearing part side. or an overhead camshaft internal combustion engine characterized by housing a nut. (2) The overhead camshaft internal combustion engine according to claim 1, wherein the bolt head or nut has a locking hole into which a tool inserted through the insertion hole engages. (3) A nut to be screwed into the tightening bolt is housed in the insertion hole on the bearing side, and a gap required for screwing the nut off is formed between the nut and the camshaft. An overhead camshaft internal combustion engine according to claim (1).