JPS63227911A - Single overhead camshaft type engine - Google Patents

Abstract

PURPOSE:To improve the cooling power of a spark plug and a cylinder head by forming a cooling air passage leading to the bottom of the spark plug placed around the center of a combustion chamber, on the wall between two indepen dent exhaust passages connected to two exhaust valves. CONSTITUTION:A cylinder head 32 is provided with two each intake and exhaust ports 46, 48 having respective openings to a combustion chamber, and each of the intake and exhaust ports 46, 48 is caused to open and close by intake/ exhaust valves being reciprocated, via respective rocker arms 104, 116, by the rotation of one overhead camshaft 36 crossing the neighborhood above the center of the combustion chamber. In this case, two independent exhaust pipes are connected to exhaust passages 22, 22 leading to respective exhaust ports 48, 48. Further, a spark plug 86 is provided between both exhaust passages 22, 22 in such a way that its ignition port is positioned in the neighborhood of the center of the combustion chamber. Also, a cooling air passage 82 leading to the spark plug 86 from the front part is allowed to form on a wall between both exhaust passages 22, 22.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a single overhead camshaft engine having one overhead camshaft that traverses near the upper center of the combustion chamber.

(Background of the Invention) Some engines of this type include two exhaust valves and a spark plug disposed between the two exhaust valves, but in this case, a problem arises in that the cooling performance of the spark plug deteriorates. In vehicles such as motorcycles that are equipped with this engine so that the exhaust valve is located in the running direction, it is considered that the exhaust valve is installed in the cylinder head above the cooling air passage so as to guide the running air near the ignition plug (for example, In other words, a cooling air passage from the front surface of the cylinder head to the base of the spark plug is formed above the exhaust passage communicating with both exhaust valves.

However, since the exhaust passage extends diagonally upward from the exhaust valve,
By forming the cooling passage above the exhaust passage in this way,
The opening position at the front of the cooling air passage is high and the area near the base of the ignition plug is low, resulting in a bent shape. Therefore, a problem arises in that the wind from the vehicle does not smoothly flow into the vicinity of the base of the ignition plug.

Further, in this case, it is difficult to form a large front opening of the cooling air passage, and it is also difficult to improve the cooling performance of the cylinder head.

(Object of the invention) The present invention is like this! This was done in consideration of the 19 circumstances, and it is possible to easily form a cooling air passage that smoothly guides the running air to the vicinity of the base of the ignition plug, and by making the opening large, it is possible to sufficiently improve the cooling performance of the cylinder head. 1. The purpose of the present invention is to provide an overhead camshaft engine.

(Structure of the Invention) According to the present invention, this object is to provide a one-head L camshaft that includes one overhead camshaft that crosses near the upper part of the center of the combustion chamber, and intake and exhaust valves that are opened and closed by this overhead camshaft. In a type engine, two exhaust valves, two exhaust passages that are connected to each exhaust valve and open forward independently of each other, and an ignition part are arranged between the two exhaust valves so that they are located near the center of the combustion chamber. This is achieved by a single overhead camshaft engine characterized by comprising an ignition plug, and a cooling air passage formed in the wall between the two exhaust passages and extending from the front to the base of the ignition plug.

If the cooling air passage is formed into a substantially vertically elongated shape that opens upward and forward, the area of the cooling air passage can be sufficiently expanded, and if the ignition plug is disposed within the cooling air passage, the cooling performance of the ignition plug will be further improved.

(Embodiment) Fig. 1 is a partially sectional side view of an embodiment of the present invention applied to a motorcycle, Fig. 2 is a central vertical sectional view showing the main parts of the engine, and Fig. 3 is the same as Fig. 2. FIG. 4 is a plan view showing the valve mechanism with the cylinder head cover removed, and FIG. 4 is a partially sectional plan view of the cylinder head cover to show how each rocker arm is attached.

In FIG. 1, reference numeral 10 indicates a main frame, 12 a front fork that supports a front wheel 14, and 16 a rear wheel.

Reference numeral 18 is a 4-valve, 1-overhead camshaft type, 1-cylinder engine, which is attached to the main frame 10 so that its intake passage 20 and exhaust passage 22 point toward the rear of the vehicle and the front of the vehicle, respectively. 24 is a carburetor that supplies air-fuel mixture to the intake passage 20; 26 is an exhaust pipe;
6 is bent so as to guide the exhaust gas discharged from the exhaust passage 22 from the front of the engine IO to the rear through the bottom of the engine IO.

28 is a crankcase, 30 is a cylinder, 32 is a cylinder head, and 34 is a cylinder head cover (hereinafter referred to as head cover). A camshaft 36 is laterally supported between the joint surfaces of the cylinder head 32 and the head cover 34.
A sprocket 38 fixed to one end of the camshaft 36 is rotated at half the speed of the crankshaft 40 by a timing chain 42 that is rotated between the sprocket 38 and the crankshaft 40 . This camshaft 36 crosses near the upper part of the center of the combustion chamber 44. The cylinder head 32 has two intake ports 46, 46 (Figs. 2 and 3) that open into the combustion chamber 44, and two exhaust ports Mouth 48.
48 are formed and each intake [146.

46 communicates with the two intake passages 20.20, and each exhaust port 48.48 communicates with the two exhaust passages 22.22.
are communicating. In this embodiment, the exhaust pipe 26 (
1), and the exhaust air from each exhaust passage 22, 22 is separately discharged via these two exhaust pipes 26.

Reference numeral 50.50 denotes an intake valve, and as is clear from FIG. .46 is biased to close. In FIG. 3, reference numeral 58.58 indicates the axis of this intake valve 50.50, and as is clear from this figure, this axis 58.58 is perpendicular to the camshaft 36.

Reference numeral 60.60 denotes an exhaust valve, and as is clear from FIG. 48.48 is biased to close. In FIG. 3, 68°68 indicates the axis of the exhaust valves 60, 60, and as is clear from this figure, the exhaust valves 60, 6
0 are supported such that their upper parts gradually move away from each other.

The cylinder head 32 has each valve 50, 50, 60.

60 and each valve spring 54, 54, 64, 64 is fixed to the cylinder 30 (FIG. 1) by a four-piece bottle 70 shown in FIG.

As shown in FIG.
intake side cams 72. ．． 72 and two outer exhaust side cams 74 and 74 are formed, one cam 72 and two exhaust side cams 74 and 74 located on the outside.
and 74 are close to each other, while the inner cams 72 and 72 are spaced apart. Both ends and the center of the camshaft 36 are supported by three slide bearings 76, 78, and 80 formed between the joint surfaces of the cylinder rod 32 and the head cover 34. That is, the center bearing 8 located between the inner cams 72 and 72 is located near the upper part of the center of the combustion chamber 44.
0, it is pivoted. The bearing surface of this bearing 80 is
．． The diameter is smaller than the maximum diameter of cam 74, and in this embodiment, each cam 7
The diameter is even smaller than the minimum diameter part of 2.74.

The sprocket 38 is fixed to one end (upper side in FIG. 3) of the camshaft 36, and a gear mechanism (not shown) for detecting rotational speed is connected to the other end (lower side in FIG. 3).

tJS for the cylinder head 32 and head cover 34.
As shown in Figures 2 and 3, a cooling air passage 82 is formed. That is, between the exhaust valves 60 and 60, the engine 1
A vertically elongated gap opening forward and upward of 8 is formed,
In this embodiment, the gap further opens rearward from below the central bearing 80 through between the intake valves 50,50. The cooling air passage 82 has a substantially cylindrical space between the two exhaust valves 60 and 60 near the bearing 80, and this space serves as an ignition plug attachment/removal hole 84.

That is, the wall forming the attachment/detachment hole 84 is integrated with the bearing 80. In Figs. 2 and 3, 86 indicates this bearing 80.
The ignition plug 86 is arranged close to the ignition plug 86, and the ignition part of the ignition plug 86 is located near the center of the combustion chamber 44.

Since the bearing surface of the bearing 80 has a smaller diameter than the maximum diameter of the cam 72, 74, the spark plug 86 can be disposed closer to the camshaft 36. That is, the center of the camshaft 36, that is, the combustion chamber 4
If there is a cam near the upper part of the center of 4, a wall of the valve chamber that accommodates the valve mechanism (this wall also serves as the ignition plug attachment/removal hole 84) must be provided to avoid interference with the maximum diameter part of the cam. Not.

While this wall is far from the center of the camshaft 36, according to the present application there is no cam at this position and there is a bearing 80, and the bearing surface has a smaller diameter than the maximum diameter of the cams 72, 74, so the wall of the valve train chamber can be brought closer to the center of the camshaft 36. Therefore, the ignition plug 86 can be disposed at an angle closest to vertical without greatly tilting the engine while keeping the overall height of the engine low, which is a preferable position for obtaining good combustion.

The cylinder head 32 and head cover 34 are provided with auxiliary ribs 88 and 90 on the cooling air flow side.

In particular, within the rib 88 of the cylinder head 32 is an oil passage 992 (
2), and this oil passage 92 supplies the lubricating oil after lubricating the exhaust valve 60 located below in FIG. 3 to the loading chamber of the valve spring 64 of the exhaust valve 60 located above in the same figure. The sprocket 38 is guided through the sprocket 38 into the housing chamber 94 (FIG. 3).

On the other hand, since the upper parts of both exhaust valves 60 and 60 are widened apart from each other, a large area can be secured on the inflow side of the cooling air passage 80 and the ignition plug attachment/detachment hole 84, and the cooling performance and attachment/detachment of the ignition plug 86 are improved. Improve further.

Note that the wall of the spark plug attachment/removal hole 84 formed in the cylinder head 32 and the head cover 34 functions as a kind of pillar, and the bearing 80 is formed integrally with this wall.
The rigidity of the cylinder head 32 and head cover 34 is also improved.

The head cover 34 is fixed to the cylinder head 32 by a large number of bolts 96-102, as shown in FIG. That is, the bearing 76.78 is the bolt 98.96.98.
At 98, the central bearing 80 is tightened with three bolts 100, and the outer periphery of the joint surface is tightened with a large number of bolts 102, respectively.

104.104 is an inner rocker arm that slides into sliding contact with the inner cam 72.72 from above and swings. The inner rocker arms 104, 104 are pivotally supported by a rocker arm shaft 106 inserted into the inner surface of the head cover 34 so as to be parallel to the cam shaft 36 (FIG. 4). One arm 108, 108 of this rocker arm 104, 104 slides into contact with the inner cam 72, 72 from above, and a local arm 110, 110 presses against the shaft end of each intake valve 50, 50. In FIG. 4, reference numeral 112 denotes a positioning bolt screwed into the head cover 34 from the inner surface so as to pass through the rocker arm shaft 106. That is, two of the numerous bolts 96 to 102 are attached to this rocker arm shaft 106.
A recess 114 is located at the position where the books 98, 100 (Fig. 4) interfere.
, 114 are formed, the recesses 114, 11
In order to fix the position of 4 and make it easier to insert the bolts 98 and roo when attaching the head cover 34 to the cylinder rad 32, the positioning pole 112 is required.

116.116 is an outer rocker arm that slides into contact with the outer cam 74.74 from above. These rocker arms 1
16, 116 are two rocker arm shafts 118 and 11 held in the head cover 34 so as to be parallel to the cam shaft.
It is pivoted on 8. This rocker arm 116, 116
One arm 120, 120 slides into contact with the outer cam 74, 74 from above, and the other arm 122, 122 presses the shaft end of each exhaust valve 60, 60. Note that 124° 124 is a positioning bolt passing through each rocker arm shaft 118, 118, and 126, 126 are four parts for avoiding interference with the bolt 100. Note that the cam shaft 36 is located at a position lower than each rocker arm shaft 106°118.

In this embodiment, the rocker arm 11 on the exhaust side is
6.116 is not only disposed outwardly with respect to the combustion chamber 44, but also the outer rocker arm 116°116 is arranged so that its arm 120°120 side is connected to the arms 122, 12 as shown in FIG.
Since it is formed to be wider than 2, the distance between the two rocker arm shafts 118 and 118 can be increased.
As a result, the ignition plug attachment/detachment hole 84 can be sufficiently enlarged. The point here is that the exhaust valves 60 and 60 are provided at an angle so that the distance between the upper parts thereof gradually increases as described above.
Of course, this contributes to the enlargement of the spark plug attachment/removal hole 84.

The head cover 34 has a rocker arm 104°104.1
16, 116, rocker arm shaft 106, 118, 118
are assembled in advance, and the positioning bolts 112, 124 are
, 124, each recess 114, 126, 126 is
After positioning the cylinder in the position shown in the figure, the cylinder is fitted onto the rod 32, and each bolt 96 to 102 is tightened.

During operation of this engine 18, the camshaft 26 rotates, and the cams 72, 72, 74, 74 move to the rocker arms '104, 10.
4, 116, and 116 to open and close the intake valves 50, 50 and exhaust valves 60, 60 according to predetermined intake and exhaust timings. While the vehicle is running, running air flows into the cooling air passage 82 formed between the exhaust valves 60 and 60, particularly sufficiently cooling the area around the threaded portion of the ignition plug 86. A portion of the cooling air passes between the intake valves 50 and 50 to the rear of the engine 18, and the other portion flows out from the spark plug attachment/removal hole 84 to the upper side of the engine 18.

(Effects of the Invention) As described above, the first aspect of the present invention is that the two exhaust passages are made independent, and the cooling air passage that guides the cooling air to the ignition plug is formed on the wall between the two exhaust passages. Because of this, the front opening of the cooling air passage can be lowered to a height near the base of the ignition plug, and the running air is smoothly guided to the vicinity of the base of the ignition plug. Therefore, the cooling performance of the spark plug is improved. Furthermore, the walls of the exhaust passage are also cooled at the same time, improving the cooling performance of the cylinder head.

By widening the gap between the two exhaust passages, the cooling air passage can secure a sufficiently large opening area and can guide sufficient cooling air.

In particular, if this cooling air passage is made into a nearly vertical shape that opens upward and forward, and the ignition plug is placed within it, the opening area will be sufficiently increased, and the cooling air will be able to be applied to the entire ignition plug, further improving the cooling performance. Improve.

If the two intake passages are made independent and a gap is formed in the wall between the two intake passages that communicates with the cooling air passage, the heat dissipation area of the combustion chamber, that is, the heat transfer area to the air, will increase, and the cylinder head This has the effect of further improving cooling performance.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a motorcycle to which an embodiment of the present invention is applied, FIG. 2 is a central vertical sectional side view of the main parts thereof, and FIG. 3 is a plan view showing the state in which the head cover is removed in FIG. 2. FIG. 4 is a partially sectional plan view of the head cover. 18... Engine, 36... Camshaft, 50... Intake valve, 60... Exhaust valve, 72.74... Cam, 76.78... Bearing, 80... Center bearing , 82...Cooling air passage, 84...Ignition plug attachment/removal hole, 86...Ignition plug, 104...Inner rocker arm, 116...Outer rocker arm. Patent applicant Yamaha Motor Co., Ltd. Agent Patent attorney Yama 1) Fumio (and 1 other person)

Claims (3)

[Claims] (1) In a single overhead camshaft engine equipped with one overhead camshaft that crosses near the upper part of the center of the combustion chamber, and intake and exhaust valves that are opened and closed by this overhead camshaft, two exhaust valves and one two exhaust passages that are connected to the exhaust valve and open forward independently of each other; an ignition plug disposed between the two exhaust valves so that the ignition part is located near the center of the combustion chamber; and a wall between the two exhaust passages. A single overhead camshaft engine characterized by having a cooling air passage formed in the front and extending from the front to the base of the ignition plug. (2) The single overhead camshaft according to claim 1, wherein the cooling air passage is formed in a substantially vertically elongated shape that opens upward and forward, and the ignition plug is located within this cooling air passage. formula engine. (3) In a single overhead camshaft engine that is equipped with one overhead camshaft that crosses the vicinity above the center of the combustion chamber, and intake and exhaust valves that are opened and closed by this overhead camshaft, two exhaust valves and one two exhaust passages that are connected to the exhaust valve and open forward independently of each other; an ignition plug disposed between the two exhaust valves so that the ignition part is located near the center of the combustion chamber; and a wall between the two exhaust passages. A cooling air passage is formed and extends from the front to the base of the ignition plug, a plurality of intake valves, and two intake passages that are connected to the intake valves and open rearward independently of each other. A single overhead camshaft type engine characterized by communication from the bottom of the camshaft to a gap provided in the wall between both intake passages.