JP3031470B2 - 4 cycle engine - Google Patents

Description

The present invention relates to a five-valve four-stroke engine having, for example, three intake valves and two exhaust valves, and more particularly to flattening a ceiling wall of a combustion chamber. The present invention relates to an improvement in the shape of a combustion chamber and a valve arrangement structure capable of realizing a high output by smoothing intake and exhaust flows.

[Conventional technology]

In order to increase the output of a four-cycle engine, it is effective to flatten the ceiling wall of the combustion chamber and reduce the volume of the combustion chamber to increase the compression. In recent years, there has been a tendency to provide a plurality of intake valves and exhaust valves in order to improve intake and exhaust efficiency by increasing intake and exhaust port areas.
There is a valve engine.

As a structure around the combustion chamber in such an engine, there is a structure as shown in FIG. 6, for example. FIG.
Is a bottom view of the arrangement state of each valve as viewed from the inside of the combustion chamber, FIG. 4B is a sectional view taken along the line VI b-VI b of FIG.
FIG. 3 is a side view showing an arrangement state of each valve.

In the figure, 41 is a cylinder body having a bore 41a, 42 is a cylinder head having a combustion recessed chamber 42a, and the combustion recessed part 42a forms a ceiling wall of the combustion chamber A. 43a is a central intake valve, 43b and 43c are outer intake valves arranged on both outer sides in the cam axis direction of the central intake valve 43a, and 44a and 44b are exhaust valves.
Each is driven to open and close by an intake cam shaft and an exhaust cam shaft (not shown). In addition, 45 is a spark plug.

Here, when viewed from the side in the camshaft direction (see FIG. 6 (c)), each of the valves is arranged to be inclined outward, and when viewed from within the combustion chamber (see FIG. 6 (a)). , At right angles to the camshaft (parallel to each other). Further, as shown in FIG. 6 (c), the central intake valve 43a and the outer intake valves 43b, 43
3c is arranged so that its lower end surface is substantially the same. As a result, the combustion recess 42 constituting the ceiling wall of the combustion chamber A
In a, the inner surface is substantially flattened.

[Problems to be solved by the invention]

However, in the case of the above-mentioned conventional valve arrangement structure, since the outer intake valves 43b and 43c are arranged at the same height as the central intake valve 43a and in parallel in a plan view, the outer intake valves 43b and 43c are arranged on the outer peripheral side of the combustion chamber. There is a problem that the vertical wall 46 (hereinafter, referred to as masking 46) becomes high. When the masking 46 becomes high in this way, the intake flow or exhaust flow at the time of opening the valve is obstructed, so that the intake efficiency cannot be improved, or the reduction of the volume of the combustion chamber is limited, and eventually, the engine output cannot be increased. .

On the other hand, to reduce the masking 46, the outer intake valve
As shown by the two-dot chain line in FIGS. 6 (b) and (c), 43b and 43c may be located below the central intake valve 43a, whereby the masking 46 is reduced to 46 '. However, in this case, the central intake valve 43a and the outer intake valves 43b, 43
Since a large step is generated in the vicinity of the boundary portion 3c and the boundary portion 42b, the above-described flattening of the ceiling wall of the combustion chamber cannot be realized.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is possible to reduce the masking in the outer valve to make the flow of intake air and exhaust gas smooth and to make the ceiling wall surface of the combustion chamber flat. The aim is to provide a four-stroke engine that can achieve a high compression ratio and high output.

[Means for solving the problem]

According to the present invention, a combustion recess forming a ceiling wall of a combustion chamber is formed in a mating portion of a cylinder head, and three openings for an intake valve or an exhaust valve are formed in the combustion recess, and the three openings are provided. In a four-cycle engine in which an intake valve or an exhaust valve that opens and closes a valve opening is inclined outwardly so as to intersect a cylinder axis at a predetermined angle when viewed in the cam axis direction, the three valve openings provided above are provided. Of the valves that open and close, the outer valves arranged at one end and the other end in the cam axis direction are inclined to the one end and the other end so as to intersect the cylinder axis at a predetermined angle even when viewed in the direction perpendicular to the cam shaft. The height of each opening edge in the cylinder axis direction from the mating surface on a line connecting the center of the outer valve opening and the center of the inner valve opening located between the outer valve openings. It is characterized by being substantially the same.

[Action]

According to the four-stroke engine according to the present invention, the height of each opening edge in the cylinder axial direction on the line connecting the center of the outer valve opening and the center of the inner valve opening is made substantially the same. In addition, the step generated at the boundary between the inner and outer valves can be reduced, and the ceiling wall surface of the combustion chamber can be entirely flattened. Further, in this case, since the outer valve is so-called radially arranged also inclined outward in the cam axis direction, the masking of the outer valve in the outer peripheral portion of the combustion chamber is reduced accordingly, and the flow of intake air or exhaust gas can be smoothed. As a result, high compression and high output of the engine can be achieved.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 5 are views for explaining a four-stroke engine according to one embodiment of the present invention. 1 (a) is a view of the ceiling wall portion of the combustion as viewed from the inside of the combustion chamber, and FIGS. 1 (b) and 1 (c) are cross-sectional views taken along line Ib-Ib of FIG. 1 (a). It is Ic-Ic line sectional drawing.

In the drawing, reference numeral 1 denotes a water-cooled type 4 employing the structure of the present embodiment.
This is a cycle single-cylinder 5-valve engine, in which a two-part cylinder head 3 composed of a lower head 5 and an upper head 6 is mounted on a cylinder body 2, and the upper surface of the upper head 6 is covered with a head cover 4. It has a structure.

On the mating surface 5a of the lower head 5 with the cylinder body 2, a combustion recess 7 constituting a combustion chamber A with a piston (not shown) inserted into a bore 2a of the cylinder body 2 is provided. The combustion recess 7 constitutes a ceiling wall of the combustion chamber A. An intake port 8 and an exhaust port 9 are formed in the lower head 5. The intake port 8 is branched into three passages, and the exhaust port 9 is branched into two passages, each of which is open to the combustion recess 7. Each exhaust valve opening 9a, 9b on the combustion chamber A side of the exhaust port 9 is
The central opening (inside opening) 8a for the intake valve of the intake port 8 is the central intake valve 11a, and the outer openings 8b and 8c for the intake valves on both outer sides are the outer intake valve 11b. , 11c
Each can be opened and closed.

Above each of the valves 11a to 11c, 10a and 10b, a two-part cotter 12 is provided.
a, a retainer 12b is mounted via the
b and the spring seat 12c of the lower head 5
d and 12e are interposed, whereby each valve is biased in the closing direction. Also, an inner pad is provided at the upper end of each of the above valves.
Exhaust lifters 13, 13 and intake lifters 14a to 14c are mounted via 12f, and each lifter is slidably supported by a guide hole 6a formed in the upper head 6.

An exhaust camshaft 15 and an intake camshaft 16 are arranged above the exhaust lifters 13, 13 and the exhaust lifters 14a to 14c, respectively. The exhaust cam shaft 15 includes a pair of exhaust cams 15a and 15b,
A journal 15c is formed between the two cams and substantially at the center, and the intake camshaft 16 has a central intake cam 16a, a pair of outer intake cams 16b and 16c formed outside thereof, , And a journal 16d formed substantially at the center. Each of the journals 15c, 16d is a bearing 6 of the upper head 6.
b and the bearing 17a of the cap 17 are pivotally supported. The cam surfaces of the exhaust cams 15a and 15b and the intake cams 16b and 16c have radially arranged exhaust valves 10a and 10b and intake valves 1 and 2, respectively.
The outside is formed in a high taper shape so as to be perpendicular to the axis of 1b, 11c.

The base circle D1 of the outer intake cams 16b and 16c has a larger diameter than the base circle D2 of the central intake cam 16a. Here, the base circle of each of the cams having a tapered shape is
It means the base circle at the point where the axis E of the intake and exhaust valves intersects the intake and exhaust cam surfaces. By setting the diameter of the base circle in this way, the lower end surface of each valve forms a substantially same plane while the central intake valve 11a and the outer intake valves 11b and 11c have the same length.

One end of each of the exhaust camshaft 15 and the intake camshaft 16 is supported by a ball bearing 18. This is the above exhaust cam
This is to bear a thrust load generated due to the tapered shape of the outer intake cams 15a, 15b or the outer intake cams 16b, 16c. A transmission gear 19 meshing with each other is mounted on the other end of the exhaust cam shaft 15 and the intake cam shaft 16, and each gear 19 is connected to a connecting flange 19a formed at one end thereof.
And a connecting plate 20 connected to the camshafts 15 and 16 by a key 21 and further fastened and fixed by a lock nut 22.
The camshafts 15 and 16 are connected by inserting 20a. The exhaust cams 15a and 15b are connected to the exhaust lifter 13.
In addition, the intake cams 16a to 16c are in contact with the intake lifters 14a to 14c, respectively, and the exhaust valves 10a and 10b and the intake valves 11a to 11c are rotated by rotating the exhaust cam shaft 15 and the intake cam shaft 16.
It is configured to open and close c.

As shown in FIG. 1, the intake and exhaust valves are arranged radially about a center of the combustion recess 7, that is, a spark plug 12 inserted into the center of the bore 2a. That is, the exhaust valves 10a and 10b are inclined so that the axis E intersects the cylinder axis G at an angle θ2 and intersects the axis F of the exhaust camshaft 15 when viewed from the side in the camshaft direction ( (See Fig. 2).
It is inclined to the right outside. When viewed from the side in the camshaft direction, the intake valves 11a to 11c are inclined such that the axis E intersects the cylinder axis G at an angle θ1 and intersects the axis F of the intake camshaft 16 (see FIG. 2), the central intake valve 11a is orthogonal to the intake camshaft 16 when viewed from a plane, and the outer intake valve 11a
Like the exhaust valve, b and 11c are inclined to the left and right outside in the cam axis direction. When this is viewed in the direction perpendicular to the camshaft as shown in FIG. 5, the axis E of the outer intake valves 11b and 11c intersects the cylinder axis G at an angle θ1 ′.

Here, the surface shape of the combustion recess 7 will be described in detail.
Line B connecting the centers C1 of the openings 8a and 8b of the intake port 8
1, and the height of the opening edges 7a, 7b from the mating surface 5a on the line B1 connecting the centers C1 of the openings 8a, 8c is the same.
The height of the opening edge from the mating surface is the same for the opening edges 7c and 7d on the line B2 connecting the centers C2 of the openings 9a and 9b of the exhaust port 9, and the center C1 The same applies to the opening edges 7e and 7f on the line B3 connecting C2.

Reference numeral 23 denotes a combustion injection device, which connects an intake pipe 23b provided with a slide type throttle valve 23a to an intake side opening 8d of the intake port 8, attaches a fuel injection valve 23c to the intake pipe 23b. Is directed to the downstream side of the throttle valve 23a.

 Next, the operation and effect of this embodiment will be described.

According to the engine of the present embodiment, the central opening of the intake port 8
8a and the opening edges 7a and 7b on the line B1 connecting the centers of the outer openings 8b and 8c are substantially the same in the cylinder axial direction, and further, the opening on the line B2 connecting the exhaust openings. The heights of the edges 7e, 7f on the line B3 connecting the edges 7c, 7d, the outer opening and the exhaust opening are also substantially the same. Therefore, a step formed between the valves on the inner surface of the combustion recessed portion 7, that is, the ceiling wall of the combustion chamber is made small, and the ceiling wall surface of the combustion chamber can be entirely flattened.

Further, since the outer intake valves 11b, 11c and the exhaust valves 10a, 10c are also inclined outwardly in the cam axis direction and are arranged in a so-called radial manner, the masking 7g in the outer peripheral portions of the combustion chambers of the outer intake valves 11b, 11c is accordingly increased. Masking of exhaust valves 10a, 10b 7
f becomes small, whereby the flow of intake air or exhaust gas can be smoothed. Further, by reducing the masking and flattening the ceiling wall, the volume of the combustion chamber can be reduced, and as a result, high compression and high output of the engine can be achieved.

In this embodiment, the intake cam 16 for the outer intake valves 11b and 11c is used.
Since the base circle D1 of b, 16c is larger in diameter than the base circle D2 of the central intake valve 16a, the lower end surfaces of the intake valves 11a to 11c are made substantially flush as described above, and the ceiling wall of the combustion chamber is entirely formed. The central intake valve 11a and the outer intake valves 11b and 11c can be made to have the same size while being flattened, so that only one type of intake valve can be used.

In the above embodiment, five intake valves and two exhaust valves are used.
Although the valve engine has been described, the present invention is applicable not only to the case of three intake valves but also to the case of having two outer valves and one inner valve as in the case of three exhaust valves. Also applicable to

〔The invention's effect〕

As described above, according to the four-stroke engine of the present invention, the outer valve is radially arranged, and the height of the opening edge on the line connecting the outer valve opening and the inner valve opening from the mating surface is substantially the same. As a result, the ceiling wall surface of the combustion chamber can be entirely flattened and the masking can be reduced, and as a result, there is an effect that the output of the engine can be increased.

[Brief description of the drawings]

1 to 5 are views for explaining a four-stroke engine according to an embodiment of the present invention. FIG. 1 (a) is a bottom view of a valve arrangement state viewed from the inside of a combustion chamber, and FIG. (B) and FIG. 1 (c) are cross-sectional views taken along line Ib-Ib and Ic-Ic of FIG. 1 (a), respectively, and FIG. 1 (d) is a side view showing a valve arrangement state. , FIG. 2 and FIG. 3 are sectional side views,
FIG. 4 is a plan view with the head cover removed, FIG. 5 is a side view of the intake camshaft portion, FIG. 6 is a diagram showing a conventional example, and FIG. 6 (a) is a combustion chamber in a valve arrangement state. FIG. 6 (b) is a sectional view taken along the line VIb-VIb of FIG. 6 (a), and FIG. 6 (c) is a side view showing the valve arrangement state. In the figure, 1 is an engine, 3 is a cylinder head, 5a is a mating surface, 7 is a combustion recess, 7a and 7b are opening edges, 8, 9 are intake ports and exhaust ports, and 8a is a central opening (port for a non-tilt valve). 8b, 8c are outside openings (opening of tilt valve port), 11a
Is an inner intake valve (non-tilt valve), 11b and 11c are outer intake valves (tilt valves), 15 and 16 are exhaust and intake camshafts, A is a combustion chamber, C1 is a center, and B1 is a line connecting centers. is there.

Claims (1)

(57) [Claims] 1. A combustion recess forming a ceiling wall of a combustion chamber is formed in a mating portion of a cylinder head, and three intake valve openings or three exhaust valve openings are formed in the combustion recess. In a four-stroke engine in which an intake valve or an exhaust valve that opens and closes a valve opening is inclined outwardly so as to intersect a cylinder axis at a predetermined angle when viewed in the cam axis direction, the three valve openings provided above are provided. Of the valves that open and close, the outer valves disposed at one end and the other end in the cam shaft direction are further disposed at the one end and the other end so as to intersect the cylinder axis at a predetermined angle even when viewed in the direction perpendicular to the cam shaft. The height of each opening edge in the cylinder axis direction from the mating surface on a line connecting the center of the outer valve opening and the center of the inner valve opening located between the outer valve openings. 4 cycles characterized by substantially the same Engine.