JPH0146689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine in which a cam bearing pedestal for supporting a camshaft of a valve train is removably bonded to a cylinder head.

In such an internal combustion engine, before the cam bearing pedestal is attached to the cylinder head, the camshaft, rocker shaft, rocker arm, etc. can be assembled to the cam bearing pedestal to form a valve train assembly. Although this has the advantage of being easy to disassemble and maintain, it has the disadvantage of increasing the weight of the engine due to the cam bearing stand. Therefore, it is desirable for the cam bearing stand to be as light as possible while maintaining sufficient hand-holding rigidity for the valve train.

On the other hand, in recent years, due to the trend toward higher engine output, the development of four-valve engines, in which each cylinder has one pair of intake and exhaust valves, has progressed. Since the electrode of the spark plug needs to face the center of the combustion chamber of the cylinder, the spark plug is arranged approximately on the axis of the cylinder. By the way, when the cam bearing pedestal is adopted in such an engine, a removable hole for the ignition plug must be drilled in the cam bearing pedestal, which causes the problem of reducing the rigidity of the cam bearing pedestal. .

The present invention has been made in view of the above technical background, and an object of the present invention is to provide an internal combustion engine having a cam bearing stand that has sufficient rigidity and is lightweight, although it has a hole for attaching and detaching a spark plug. The purpose is to
The features include a frame portion that frames the outer periphery of the cam bearing pedestal, and a plurality of first partition wall portions that extend in a direction perpendicular to the axis of the camshaft and are integrally connected to the frame portion. and a second partition wall intersecting with the first partition wall parts and also integrally connected to the frame part, a bearing hole into which the camshaft fits is formed in the first partition wall part, A cylindrical wall portion defining an attachment/detachment hole for an ignition plug screwed onto the cylinder head is integrally connected to the first and second partition walls.

Hereinafter, one embodiment of the present invention will be explained with reference to the drawings.The internal combustion engine shown in FIG. 1 is a V-type multi-cylinder engine, so two
It has two cylinder rows C ₁ and C ₂ . Both cylinder rows
Since the structures of C ₁ and C ₂ are symmetrical, only the left cylinder row C ₁ will be described below.

A cylinder head 3 is superimposed and bonded to the upper surface of a cylinder block 2 having a cylinder 1 via a gasket 4. A piston 5 is slidably fitted into the cylinder 1, and a combustion chamber 6 is recessed in the bottom surface of the cylinder head 3 facing the piston 5.

The ceiling surface 7 of the combustion chamber 6 is aligned with the axis Ac of the cylinder 1.
It is made up of two ceiling slopes 7a, 7b descending on both sides from a ridge line L passing near the ridge line L, and one ceiling slope 7a has a pair of intake ports 8, 8.
However, on the other ceiling slope 7b, a pair of exhaust ports 9, 9 are opened in parallel along the ridge line L, respectively. Each pair of intake valves 1 is configured to open and close the intake ports 8, 8 and the exhaust ports 9, 9.
0,10 and exhaust valves 11,11 are provided in the cylinder head 3. Valve guides 12,12 and 13,1
3, each of which is slidably supported. At that time, with a plane P that includes the cylinder axis Ac and is parallel to the ridge line L as a boundary, the intake valves 10, 10 are located on the valley V side between both cylinder rows C ₁ , C ₂ , and the exhaust valves 11, 11 are located on the opposite side. and both valves 10, 11 are tilted in opposite directions relative to said plane P.

As shown in FIGS. 2 and 4, the cylinder head 3 includes a spark plug 14 with an electrode facing the combustion chamber 6.
is screwed onto the spark plug 14, and the intake valve 10,
10; Cylinder axis surrounded by 11, 11
It is located approximately along Ac.

A cam bearing stand 15 is mounted on the top surface of the cylinder head 3.
and head cover 16 are sequentially bonded together to form a valve chamber 17, and the intake valve 10,
10 and the exhaust valves 11, 11 are provided with a valve operating device 18, which has the following configuration.

The intake valves 10, 10 and the exhaust valves 11, 11 include
Valve springs 19, 19 and 20, 20 are respectively attached to bias these toward the closing side.

Almost directly above the intake valves 10, 10, and therefore closer to the valley V side than the cylinder axis Ac, there is a crankshaft (both not shown) via a timing transmission.
A single cam shaft 21 is disposed parallel to the plane P, and the shaft 21 is interlocked with the journal 21j.
is rotatably held between the cam bearing stand 15 and a bearing cap 24 connected with bolts 22 and 23. Disposing the camshaft 21 so as to be shifted toward the valley V side in this manner is effective in reducing the maximum outer dimensions of both cylinder rows C ₁ and C ₂ as much as possible, thereby reducing the size of the V-type engine.

As shown in FIG. 3, the camshaft 21 is connected to the intake valve 1.
0, 10 and exhaust valves 11, 11, each pair of intake cams 21i, 21i and exhaust cams 21e,
21e, the intake cams 21i, 21i are arranged adjacent to and on both sides of the journal 21j, and the exhaust cams 21e, 21e are further arranged on both sides thereof. Intake cams 21i, 21i and intake valves 10, 10
a pair of first cam followers 25, 2 between the head of the
5 is interposed. This first cam follower 25, 2
5 is equipped with an adjusting bolt 26 at each base end, and a spherical end 26a at the tip of the adjusting bolt 26 is rotatably engaged with a spherical recess 27a of a support bolt 27 screwed onto the cylinder head 3. .

The first and second support shafts 28, 29 are attached to the cam bearing stand 15.
are fixed by bolts 22 and 30, respectively, and at that time, both support shafts 28 and 29 are connected to the intake and exhaust valves 10 and 1.
0: Axis line Ap of the spark plug 14 between 11 and 11
The camshafts 21 and 21 are arranged parallel to the camshaft 21 so as to be sufficiently separated from each other. The first support shaft 28 near the intake valves 10, 10 has a pair of second cam followers 31, 3 that engage with the intake cams 21i, 21i, respectively.
The second support shaft 29, which swingably supports the exhaust valves 11 and 11, has a pair of bell crank type rocker arms 33, which engage the heads of the exhaust valves 11 and 11 via adjustment bolts 32, respectively. 33 is swingably supported. A pair of push rods 34, 34 are interposed between the opposing surfaces of the second cam followers 31, 31 and the rocker arms 33, 33, respectively.

In addition to the aforementioned bolts 22 and 30, a dedicated bolt 37 is also used to connect the cam bearing stand 15 to the cylinder head 3.

A series of attachment/detachment holes 38 into which a tool for attaching/detaching the spark plug 14 is inserted are provided in the cylinder head 3 and the cam bearing stand 15 in an area surrounded by the support shafts 28, 29 and the push rods 34, 34. This attachment/detachment hole 38 is opened to the outer surface of the head cover 16 via a partition tube 36 interposed between the cam bearing stand 15 and the head cover 16.

In this case, both support shafts 28 and 29 are spaced sufficiently apart from each other, and both push rods 34 and 34 are
is engaged with the exhaust cams 21e, 21e at both outer positions, and a wide gap is secured therebetween, so the attachment/detachment hole 38 is formed to be large enough to allow the spark plug 14 to be easily attached/detached. be able to.

Now, the structure of the cam bearing stand 15 will be explained with reference to FIGS. 4 to 9. The basic shape of the cam bearing stand 15 is a rectangle that is long in the axial direction of the camshaft 21, and a frame frames the four sides of the outer periphery of the cam bearing stand 15. Part 15a and
A plurality of first partition walls 15b, 15b... that integrally connect the opposite long sides of the frame 15a, and a plurality of first partition walls 15b, 15b... that are perpendicular to the opposite long sides of the frame 15a. It is composed of a second partition wall portion 15c that connects the short sides. Each first partition wall portion 15b
has a semicircular bearing hole 39 into which the camshaft 21 fits.
and bearing bosses 40 and 41 into which the support shafts 28 and 29 fit, respectively, are formed, and the first partition part 15
A plurality of cylindrical wall portions 15d, 15d, . . ., defining the attachment/detachment holes 38, 38, are formed at each intersection of the second partition wall portion 15c, 15b, .b, 15b, . Thus, the cylindrical wall portion 15d is integrally connected to both the partition walls 15b and 15c.

Next, the operation of this embodiment will be described. For assembly, first, the camshaft 21, support shafts 28, 29, etc. are attached to the cam bearing stand 15 to form an assembly of the valve train 18. Next, the cam bearing stand 15, which is the base of this assembly, is superimposed on the upper surface of the cylinder head 3 and fastened with bolts 22, 30, and 37. The rest of the assembly is carried out in the conventional manner.

When the engine is operated, the camshaft 21 is rotationally driven by the crankshaft via a timing transmission (not shown). When the intake stroke of the piston 5 is started, the peaks of the intake cams 21i, 21i swing the first cam followers 25, 25 toward the intake valves 10, 10, respectively.
The valves 0 and 10 open against the elastic force of the valve springs 19 and 19, and at the end of the intake stroke, the intake cams 21i and 2
1i passes through the first cam follower 25, 25, the intake valves 10, 10 are connected to the valve springs 19, 1
The valve closes with an elastic force of 9. During this time, an air-fuel mixture is drawn into the combustion chamber 6 from an air-fuel mixture generating device such as a carburetor (not shown) through the intake ports 8, 8.

When the piston 5 approaches the end of its compression stroke, the compressed gas in the combustion chamber 6 is ignited by a spark discharge from the spark plug 14, and the piston 5 moves to an expansion stroke. At this time, since the spark plug 14 is located at or near the cylinder axis Ac, the combustion chamber 6
The flame propagation distance to each peripheral edge is approximately equal, so the combustion time is shortened to the minimum and high output is achieved.

When the exhaust stroke of the piston 5 is started, the peaks of the exhaust cams 21e and 21e are aligned with the second cam follower 3.
1 and 31 are swung toward the push rods 34 and 34, the push rods 34 and 34 are displaced and the rocker arms 33 and 33 are swung toward the exhaust valves 11 and 11, whereby the exhaust valves 11 and 11 are The valves open against the elastic force of the valve springs 20, 20, and at the end of the exhaust stroke, the peaks of the exhaust cams 21e, 21e pass the second cam followers 31, 31, so the exhaust valves 11, 11 are opened by the valve springs 20. , 20, the valve closes. During this time, exhaust gas is discharged from the combustion chamber 6 to the exhaust ports 9, 9.

During such operation of the engine, the cam bearing pedestal 15 always receives a large load from the valve train 18, but the cam bearing pedestal 15
b, 15c, and both partition walls 15
b, 15c are reinforced by the cylindrical wall portion 15d and have sufficient rigidity, so that they can withstand the above load and continue to firmly support the valve train 18.

The ignition plug 14 is attached and detached by inserting a special tool into the partition tube 36 and the attachment/detachment hole 38, fitting it onto the head of the ignition plug 14, and rotating the tool.

As described above, according to the present invention, the cam bearing stand is
A frame portion that frames the outer periphery of the cam bearing stand; a plurality of first partition wall portions that extend in a direction perpendicular to the axis of the camshaft and are integrally connected to the frame portion; A second partition wall integrally connected to the frame part, a bearing hole into which the camshaft fits is formed in the first partition part, and an attachment/detachment hole for the ignition plug screwed to the cylinder head is defined. The first and second cylindrical wall parts
Since it is integrally connected to the partition wall, the cylindrical wall portion defining the mounting/detaching hole for the ignition plug can be effectively used to reinforce the first and second partition wall parts, even though the ignition plug has a mounting/detaching hole. It is possible to obtain a cam bearing stand with high rigidity, and since there is no waste material, it is lightweight. Therefore, it is possible to firmly support the valve train and contribute to reducing the weight of the engine.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional front view of the main parts of an internal combustion engine according to an embodiment of the present invention, Fig. 2 is a bottom view of the cylinder head in Fig. 1, and Fig. 3 is a cylinder head shown with the head cover removed. 4 is a sectional view taken along the line - 3 in FIG. 3, FIG. 5 is a plan view of the cam bearing stand shown in FIG. 1, and FIGS. 6, 7, 8, and 9. are the - line, - line, in Figure 5.
- line and - line sectional views. 14... Spark plug, 15... Cam bearing stand, 15a
...Frame part, 15b...First partition part, 15c...Second partition part, 15d...Cylindrical wall part, 18...Valve train, 21...Camshaft, 25...First cam follower, 28, 29...First and second support shafts, 31...Second cam follower, 33...Rocker arm, 34...
...Push rod, 36...Partition tube, 38...Attachment/detaching hole, 39...Bearing hole, 40, 41...Bearing boss.

Claims (1)

[Claims] 1. In an internal combustion engine in which a cam bearing pedestal supporting a camshaft of a valve train is removably superimposed on a cylinder head, the cam bearing pedestal is connected to a frame portion that frames the outer periphery of the cam bearing pedestal, and a frame portion that frames the outer periphery of the cam bearing pedestal, and the cam a plurality of first partitions extending in a direction perpendicular to the axis of the shaft and integrally connected to the frame; and a second partition intersecting the first partitions and also integrally connected to the frame. A bearing hole into which the camshaft fits is formed in the first partition wall part, and a cylindrical wall part defining an attachment/detachment hole for an ignition plug screwed to the cylinder head is formed in the first partition wall part. and an internal combustion engine, characterized in that the engine is integrally connected to the second partition wall.