JPS6156406B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to swinging a rocker arm pivotally supported by a rocker shaft by a cam fixed to a single cam shaft disposed on a cylinder head. This invention relates to a valve operating mechanism for a single overhead camshaft type internal combustion engine that opens and closes valves arranged on both sides of a camshaft, and is particularly suitable for use in an internal combustion engine that has a third valve in addition to an intake valve and an exhaust valve. This invention relates to a valve train for a single overhead camshaft internal combustion engine, which allows the structure of the valve train to be simplified and has a large degree of freedom in designing the amount of valve lift.

2. Description of the Related Art One type of single overhead camshaft internal combustion engine is a so-called counterflow type internal combustion engine, which has a combustion chamber in which an intake port and an exhaust port are located on the same side of a cylinder head. It is usually used with a wedge-shaped or inclined bathtub-shaped combustion chamber and is characterized by strong compression turbulence, low octane requirements, and the possibility of high compression ratios. In this counterflow type internal combustion engine, the intake valve and exhaust valve are installed only on either the left or right side of the camshaft, so only one rocker shaft is required, and the valve mechanism is relatively simple. It has the characteristic of being.

In such a counterflow type internal combustion engine, for reasons such as exhaust gas countermeasures, in addition to the intake valve and exhaust valve, there is a sub-intake valve that supplies the air-fuel mixture to the sub-combustion chamber, or a sub-intake valve that supplies the air-fuel mixture in the combustion chamber. Some internal combustion engines are equipped with a third valve, such as a stirring valve, for supplying high-pressure air to create turbulence. An example of such an internal combustion engine with a sub-combustion chamber is shown in FIG. In the figure, 10 is the cylinder block of the engine, 11 is the cylinder head, 12 is the head cover, 13 is the piston, 14 is the main combustion chamber, 16 is the sub-combustion chamber, 18 is the spark plug, 20, 22
24 is an intake valve or an exhaust valve that opens and closes the intake passage 21 or the exhaust passage 23, respectively, which are arranged in a straight line on the right side of the camshaft; 26 is a camshaft that rotates in synchronization with engine rotation; 27 is a camshaft support; 28, 29,
30 is an intake valve cam, an exhaust valve cam, and an auxiliary intake valve cam fixed to the camshaft 26, respectively; 32 is an intake valve rocker arm 34 and an exhaust valve rocker arm 35 that open and close the intake valve 20 or the exhaust valve 22;
36 is the sub-intake valve 24.
40 is a valve spring of the intake valve 20 or exhaust valve 22; 41 is the same retainer; 42 is the same screw; 43 is the same nut; 44 is the auxiliary intake valve 24. 45 is a retainer, 46 is a screw, 47 is a nut, 48 is a rocker support that supports the rocker shafts 32 and 36, and 50 is a bolt that fixes the rocker support 48 to the cylinder head 11.

Problems to be Solved by the Invention In such a counterflow type internal combustion engine with an auxiliary combustion chamber, the intake valve 20 and the exhaust valve 22
Since the sub-intake valves 24 and 24 are installed separately on the left and right sides of the camshaft 26, two rocker shafts are also provided on the left and right sides accordingly. In this way, when there are three or more valves installed in the combustion chamber, it is most advantageous spatially to install the camshaft in the center and provide valves on the left and right sides of the camshaft. However, in that case, the camshaft is provided at the center, and the rocker ratio of the rocker arm of each valve is restricted by the size of the cylinder head, and has the disadvantage that it cannot be made very large.

Particularly, in an internal combustion engine in which a third valve such as a stirring valve or a piston valve is provided in the combustion chamber and the third valve is opened near the compression top dead center, the air-fuel mixture in the combustion chamber is disturbed. The amount of displacement of the stirring valve or piston valve must be quite large and the period of displacement must be short.

However, with the above structure, in order to increase the amount of displacement of the valve, it is necessary to increase the rocker ratio or increase the amount of lift of the cam, but in the latter case, the effect depends on the amount of lift. Since the angle also needs to be large and it becomes structurally difficult, it cannot be applied as is to internal combustion engines equipped with a third valve that requires a large displacement in a short period of time, such as an agitation valve or a piston valve. The problem was that I couldn't do it.

On the other hand, the single overhead camshaft type internal combustion engine includes a so-called cross-flow type internal combustion engine that has a combustion chamber in which an intake port and an exhaust port are installed on different sides of a cylinder head. This is different from the conventional example shown in FIG. 1 in that, as shown in FIG. 2, an intake valve 20, an intake passage 21, an exhaust valve 22, and an exhaust passage 23 are arranged on both sides of a camshaft 26, respectively. The other points are the same as those of the conventional example, so the explanation will be omitted. Also in this conventional example,
Since two rocker shafts were required, there was a problem in that the structure was complicated.

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a valve operating mechanism for a single overhead camshaft internal combustion engine that has a simple structure and has fewer restrictions on rocker ratio. .

Means for Solving the Problems In the present invention, a cam fixed to a single camshaft disposed on a cylinder head swings a rocker arm that is pivotally supported on a rocker shaft, and In a valve operating mechanism for a single overhead camshaft type internal combustion engine that opens and closes valves disposed in .

[Effect]

The arm of the rocker arm, that is, the valve operated by the rocker arm within the swing range of the rocker arm part from the center of the rocker shaft to the contact surface with the cam, is the rocker arm that narrows the cam shaft and operates the valve disposed on the other side. Since there is no rocker shaft, the swinging motion of the rocker arm of the valve on one side is not interfered with by the rocker shaft of the valve on the other side. Therefore, by changing the shape of the crankshaft of the rocker shaft, the rocker arm can easily create a rocker ratio optimal for various internal combustion engines.

Embodiments of the present invention will be described in detail below with reference to the drawings. A first embodiment of the present invention is an application of the present invention to a valve operating mechanism of a single overhead camshaft type internal combustion engine in which a third valve, a stirring valve, is provided in addition to an intake valve and an exhaust valve. , as shown in FIGS. 3 and 4, a stirring valve 72 is provided in place of the sub-intake valve in the conventional example shown in FIG. It has a structure in which it is supported by a rocker arm that is pivotally supported by a rocker arm 70. The rocker shaft 70 has a substantially crank shape, and the rocker arms 34 and 35 for opening and closing the intake and exhaust valves 20 and 22, respectively, are supported by the intake and exhaust valve side shaft portion 70A of the rocker shaft 70, and open and close the stirring valve 72. The rocker arm 74 for this purpose differs from the conventional example in that it is pivotally supported by the stirring valve side shaft portion 70B of the rocker shaft 70. 66 is each Rotsuka arm 3
This is a shim to separate 4, 35, and 74.
The other points are the same as those of the conventional example, so the explanation will be omitted.

The rocker shaft 70 is installed so that its center of symmetry is directly above the camshaft 26, but this installation position may be offset to the right or left, and the combination of valves may be It's okay to get used to it.

Reference numerals 28, 29, and 76 are cams for driving the rocker arms 34, 35, and 74, respectively, and are fixed to the camshaft 26 so as to rotate together with the camshaft 26. Also code 78
is a bolt for fixing the rocker shaft 70 to the rocker support 48 so that it does not rotate.

In this embodiment, when the camshaft 26 rotates, the cams 28, 29 fixed to the camshaft 26,
Due to the convex portion 76, the rocker arms 34, 35, 7
4 are each pressed at a predetermined timing to operate the valve. Locker arm 74 of stirring valve 72
The arm length l from the center of the rocker shaft to the stirring valve 72
It is desirable that the ratio (locker ratio) l _V /l _C of the rocker arm 74, which is the same as _V , to the arm length l _C from the center of the rocker axis to the contact surface with the cam (rocker ratio) is 1 to 4. Although not shown, the rocker arms 34 and 35 may be supported by the stirring valve side shaft portion 70B, and the rocker arm 74 may be supported by the intake/exhaust valve side shaft portion 70A. In this way, the rocker arms 34 and 35 may be supported by the shaft portion _70A on the intake and exhaust valve side. Since _C can be made long, the displacement amount of the stirring valve 72 can be increased without increasing the lift amount of the cam 76 too much. Therefore, the burden on the cam to increase the amount of displacement of the valve can be reduced.

For example, as shown in FIG.
4 is assembled, and the rocker shafts are connected to each other by a dowel pin 82 to form a crank shape. In this case, the rocker arm can be assembled relatively easily. Alternatively, the rocker shaft 70 may have a single crank structure as shown in FIG. 6, and the bearing portion of the rocker arm 74 may be
It is also possible to have a structure that can be divided as shown in FIG. 7 and fixed with bolts 84.

In this embodiment as well, compared to the case where two rocker shafts are provided, the valve operated by the rocker arm is located within the swing range of the arm of the rocker arm, and the valve is located on the other side of the cam shaft. Since there is no rocker shaft of the rocker arm that operates the rocker arm, there is no interference of the rocker shaft with the rocking motion of each rocker arm. Therefore, the rocker ratio can be increased by changing the shape of the crank of the rocker shaft. or,
It is possible to use a single rocker shaft without much modification to the conventional rocker arm and camshaft, and it is relatively inexpensive.

In the embodiment described above, the present invention was applied to a valve mechanism of an internal combustion engine having a third valve, but the scope of application of the present invention is not limited to this. It is clear that the present invention can be similarly applied to an internal combustion engine having a cross-flow type combustion chamber disposed in a 3D combustion chamber, and further to an internal combustion engine in which a third valve is added to the cross-flow type combustion chamber.

As is clear from the above description, the present invention has the excellent effect of simplifying the valve operating mechanism and increasing the degree of freedom in designing the valve lift amount without increasing the size of the valve operating mechanism.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the valve mechanism of a single overhead camshaft internal combustion engine with a conventional sub-combustion chamber, and Figure 2 is a cross-sectional view of the valve mechanism of an internal combustion engine with a conventional cross-flow combustion chamber. FIG. 3 is a plan view showing a valve mechanism of a single overhead camshaft internal combustion engine having a stirring valve according to a first embodiment of the present invention; FIG.
The figure is a sectional view thereof, FIG. 5 is a sectional view showing the rocker shaft structure in the first embodiment, and FIG. 6 is a plan view showing another structure of the rocker shaft in the first embodiment.
FIG. 7 is a front view showing the rocker arm structure in the first embodiment as well. 11... Cylinder head, 20... Intake valve, 2
2... Exhaust valve, 26... Camshaft, 28, 29, 7
6...Cam, 34, 35, 74...Rocker arm, 72...Third valve, 70...Crank-shaped rocker shaft, 70A...Intake/exhaust valve side shaft portion, 70B...
Stirring valve side shaft.

Claims (1)

[Claims] 1 A single cam fixed to a single camshaft disposed on the cylinder head swings a rocker arm pivotally supported by the rocker shaft to open and close valves disposed on both sides of the camshaft. 1. A valve operating mechanism for a single overhead camshaft internal combustion engine, wherein the rocker arm is pivotally supported by a single cran-shaped rocker shaft.