JPH0367008A - Valve device of four-cycle engine - Google Patents

Abstract

PURPOSE:To produce a small and light engine with a high combustion efficiency, in which knocking due to self-igniting is prevented, by installing an electrode of igni tion plug in the center of the top of a combustion chamber, and arranging the ignition plug on the exhaust valve side inclined approx. symmetrically to the central suction valve. CONSTITUTION:Engine concerned is equipped with five valves altogether in the cylinder head part 2, wherein three suction valves 13 are installed on one side of periphery surrounding the center of a combustion chamber 12 while two exhaust valves 14 are installed on the other side. These valves 13, 14 are arranged so that the extension lines of their axes intersect at the common intersection point O on the axis of the bore 3a of cylinder part 3 and pass within the opening 5 of a crank case 4. Even with multi-valve type engine the wall surface of the combustion chamber 12 can be formed in a smooth concave spherical surface with the point O as the radius center of the curvature by eliminating steps between the valve seat faces 15, and increase in the output is attained due to enhancement of the combusting characteristics. An ignition electrode 17b is located in the center of the combustion chamber to ensure that transfer of the flame is made uniformly in the chamber, and also generation of knockings is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a valve device for a four-stroke engine for driving a vehicle or for general use.

(Conventional technology) One cylinder has two intake valves and two exhaust valves.
In engines with more than one valve, a so-called DOHC type is known in which the intake and exhaust valves are driven by separate camshafts (for example, Japanese Patent Laid-Open No. 57-17631
1).

In this type of engine, a relatively open space is left above the combustion chamber, so the spark plug can be placed in the center of the space, and by arranging it this way, the spread of the flame surface from ignition is evened out. As a result, combustion takes place in a short time, and an improvement in combustion efficiency can be expected. In addition, if flame propagation is uneven, pressure differences will occur locally within the combustion chamber, resulting in self-ignition due to a sudden pressure increase in the unburned area, and knocking due to this. Such inconvenience can also be prevented by arranging it.

(Problems to be Solved by the Invention) Although the DOHC type engine has the above-mentioned advantages, since it uses two camshafts, the cylinder head is relatively large and heavy, and it is difficult to achieve a smaller and lighter cylinder head. When used in required motorcycle engines, further weight reduction is desired. Therefore, using one camshaft5
Although it is possible to reduce weight by using the OIIC type, it is difficult to install the spark plug in the center of the combustion chamber because it is obstructed by the camshaft, and if it is placed off center, the combustion effect will decrease and knocking will occur. In order to avoid this, if the spark plug is placed in the center and the camshaft is offset from the center, the lengths of the rocker arms on both sides will be extremely different, which may cause design problems such as setting the fulcrum. with difficulties.

(Means for Solving the Problems) The present invention aims to solve the above-mentioned problems, and the means for achieving the object is to provide a plurality of intake valves and exhaust valves in one cylinder. In a valve device for a four-cycle engine, in which valves are arranged and the valves are driven to open and close by a single camshaft via a rocker arm, the camshaft is arranged to cross approximately above the center of the combustion chamber, and the camshaft is Three intake valves are arranged on one side of the shaft, and two exhaust valves are arranged on the other side, and the ignition electrode is placed on the exhaust valve side across the camshaft, approximately symmetrical to the central intake valve, and the ignition electrode is placed in the combustion chamber. It is characterized by a slanted arrangement of the spark plug, which faces approximately the center of the top.

(Function) The ignition plug is placed on the exhaust valve side symmetrically with the central intake valve, so the ignition plug can be installed and removed without being obstructed by the camshaft, and the ignition electrode is located in the center of the combustion chamber, which improves combustion. is done uniformly.

(Example) Next, an example of the present invention will be described with reference to the drawings. In addition to the arrangement of the intake valve, exhaust valve, and spark plug described above, this embodiment has a structure that allows easy machining of the bore of each valve.

In the drawing, (1) shows the engine body of a four-stroke monoblock engine mounted on the two-wheeled vehicle body A, and the main body (1)
) is composed of a cast product of, for example, a magnesium alloy, which is integrally molded from the cylinder head part (2> to the cylinder part (3) and the crankcase part (4), and the lower surface of the crankcase part (4) An opening (5) consisting of a cast hole facing the bore (3a) of the cylinder part (3) is formed in the cylinder part (3), and the cylinder head (3b) is screwed into the bore (3a). Attach the oil pan (6) to the
When disassembling and reassembling the engine, the oil pan (6) is removed and the piston (8) is assembled to the crankshaft (7) to insert the assembly into the engine body (1) through the opening (5).
It can be inserted and removed freely.

Furthermore, in the illustrated example, the transmission case part (9) extending rearward from the crankcase part (4) is also connected to the engine body (
1), and is installed in the mission case part (9) with the - side surface open and assembled to the mission mechanism (1 (mission holder C11 with 11 covered on the open surface)). I tried to force it.

In addition, in the cylinder head part (2), as shown in Figure T55, there is an intake valve a surrounding the center of the combustion chamber ab and surrounding it.
3 and two exhaust valves 04 on the other side to form a 5-valve engine as a whole. The extension line of the axis line is the cylinder part (
3) so as to intersect at a common intersection O on the axis of the bore (3a) and the above-mentioned opening (5) in the crankcase part <4>.
It was assumed that it would be placed so that it would pass through the inside.

According to this, as shown in FIG. 6, the conventional seat rivet tool (
'IG, insert it through the opening (5) and process each valve seat surface (I9), that is, the extension line of each valve axis passes through the opening (5). , the tool ('IO) can be attached to any valve seat surface ('1
5) can be inserted into the engine body (1) from the opening (5) along the valve axis without causing any interference with the valve seat surface (I9), and Since the extension lines of each valve axis intersect at a common intersection O on the bore axis, the tool (IO is moved downward relative to the cylinder head part <2> with the intersection O as the center, and its axis are aligned with the valve axis line of each valve seat surface (15) in order, and all valve seat surfaces (+51
can also be processed with high precision.

In addition, when doing this, even in a multi-valve engine, the height difference between each valve seat surface (19) is eliminated and the combustion chamber ('1
It becomes possible to form the two wall surfaces into smooth concave spherical surfaces with the center of curvature at the intersection O, and output can be increased by improving combustibility. A plug hole 17a is provided at a position facing the center one of the three intake valves 13, into which the ignition plug 17 is screwed, and the ignition electrode 17b is located at the center of the combustion chamber. With this configuration, flame propagation is performed uniformly within the combustion chamber, and occurrence of knocking is prevented.

In the drawing (IO is the camshaft, (one is the rocker arm,
■ is the water pump, 0 is the oil pump, ■ is the engine body (
1) indicates a side cover removably attached to the side surface, and ■ indicates a head cover detachably attached to the cylinder head portion (2).

In this way, if the intake valve and exhaust valve are arranged so that the extension lines of their respective axes intersect at a common intersection on the bore axis of the cylinder section and pass through the opening on the bottom surface of the crankcase section, a monoblock engine can be created. Even if the cylinder head is formed separately, all the valve seat surfaces can be machined with high accuracy by using a counter-cutting tool similar to that used for processing the valve seat surfaces of conventional engines and inserting it through the opening. In addition, pressure leakage from the valve seat surface is prevented, and the wall surface of the combustion chamber can be formed into a smooth concave spherical surface with the center of curvature at the intersection, thereby increasing the output of the engine.

(Effects of the Invention) As described above, in the present invention, the ignition electrode of the spark plug is located at the center of the top of the combustion chamber, so the flame propagation is uniform and the combustion efficiency is good. Since no pressure increase occurs, there is no knocking caused by self-ignition, and the spark plug is placed approximately symmetrically with the intake valve in the center and placed on the exhaust valve side, so it is placed approximately in the center above the cylinder. Since the spark plug can be attached and removed without being obstructed by the camshaft, it can be applied to engines that use a single camshaft despite the large number of valves, and is effective in reducing the size and weight of the engine.

[Brief explanation of drawings]

1 and 2 are side views of one side and the other side of the engine equipped with the device of the present invention, respectively, and FIG. 3 is a sectional view taken along the line ■-■ in FIG. 1. FIG. 4 is a side view of the engine shown in FIG. 5 is a plan view of the cylinder head, and FIG. 6 is a sectional view of the main parts for explaining the machining of the valve seat surface. <1)...Engine body (2)...Cylinder head section (3)...Cylinder section (3a)...
Bore (4)...Crankcase part (5)...Opening ('13...Intake valve O@...Exhaust valve ('171...3 people outside the spark plug Fig. 5)

Claims (1)

[Claims] 1. In a valve device for a four-stroke engine in which a plurality of intake valves and exhaust valves are arranged in one cylinder, and these are driven to open and close by a single camshaft via a rocker arm. , the camshaft is arranged so as to cross substantially above the center of the combustion chamber, three intake valves are arranged on one side of the camshaft, two exhaust valves are arranged on the other side, and the camshaft is sandwiched between the two. A valve device for a four-cycle engine, characterized in that an ignition plug is arranged at an angle on the exhaust valve side, the spark plug being approximately symmetrical to the central intake valve and having an ignition electrode facing approximately the center of the top of the combustion chamber. 2. 4 as set forth in claim 1, characterized in that the camshaft is biased toward the intake valve side from the center of the combustion chamber.
Cycle engine valve equipment. 3. The valve device for a four-cycle engine according to claim 1 or 2, wherein the intake valve and the exhaust valve are arranged at positions approximately equidistant from the center of the combustion chamber.