JPH07127458A - Four-cycle engine - Google Patents

Abstract

PURPOSE:To prevent reduction of machinability to a value lower than those of five-valve and eight-valve and to improve performance higher than that of a four-valve engine. CONSTITUTION:Three each of intake ports 1 and exhaust ports 2 are provided and the intake ports and the exhaust ports are disposed on respective straight lines and in parallel to each other. Two ignition plugs 7 are arranged. Two ignition plugs 7 are arranged such that each ignition plug 7 is arranged in a space surrounded with four plugs in all consisting of two each of suction and exhaust plugs 5 and 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-stroke engine, and more particularly to the number and arrangement of intake / exhaust valves.

[0002]

2. Description of the Related Art A four-valve engine equipped with two intake and two exhaust valves can have a larger valve area than a two-valve engine.
It is superior to the 2-valve engine in terms of fuel efficiency. However, the performance of engine output, fuel consumption, etc.
It is determined by the size of the valve, the compression ratio, the combustion state, and the like, and these are in conflict with each other. That is, 4
For valve engines, the most appropriate values have been found for valve size, valve squeeze angle, piston stroke, and bore diameter, and even if these values are changed, the engine performance will not improve. Has reached. Therefore, in a 4-valve engine, it is difficult to expect performance improvement by devising the size of the valve in the future.

Then, an 8-valve or 5-valve engine appeared (for example, see Japanese Patent Laid-Open No. 61-185654). Examples of these are shown in FIGS. 3 and 4.

[0004]

However, the eight-valve engine has the intake and exhaust ports 1 and 2 as shown in FIG.
Too many numbers result in a non-circular cross section of the piston and cylinder bore 3. Therefore, the processing becomes difficult and the manufacturability is significantly reduced. Therefore, it is only used for very special engines.

On the other hand, a 5-valve engine is shown in FIG.
Although the cylinder bore 3 has a circular shape as shown in FIG. 3, the manufacturability is lower than that of the four valve because of the following reasons. That is, a 5-valve engine has three intake ports 1A,
Since 1B and 1A are not aligned in a straight line, FIG.
As described above, the intake valves 5A and 5B driven by the single cam shaft 4 have different sandwiching angles θa and θb from each other.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a four-stroke engine which is as manufacturable as a four-valve and has better performance than the four-valve.

[0007]

In order to achieve the above object, the present invention provides three intake valves and three exhaust valves, and the intake port opened and closed by the intake valve in plan view. The exhaust ports, which are arranged in a substantially straight line and which are opened and closed by the exhaust valve, are arranged in a straight line substantially parallel to the intake port in plan view, and are surrounded by the two intake ports and the exhaust port. Spark plugs are provided at two locations respectively.

According to the present invention, since the intake port and the exhaust port are arranged substantially in a straight line in plan view, the intake and exhaust valves have the same sandwich angle.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1 (a), in this four-cycle engine, the cylinder bore 3 has a circular cross section, and
It has three intake valves 5 and three exhaust valves 6. The three intake ports 1 opened and closed by the intake valves 5 are arranged in a straight line when viewed from above the axis Sc of the cylinder in FIG. 1B, that is, in the plan view of FIG. On the other hand, the three exhaust ports 2 opened and closed by the exhaust valve 6 are arranged in parallel with the intake port 1 and in a straight line in a plan view. The area of the intake port 1 is larger than the area of the exhaust port 2, and the intake port 1 is arranged closer to the center line Bc of the cylinder bore 3 than the exhaust port 2. Spark plugs 7 are arranged at locations surrounded by the two intake ports 5 and the two exhaust ports 6, respectively. In addition, the combustion chamber 8 of FIG.
Is, for example, a pent roof type.

Next, the performance of the 6-valve engine will be described in comparison with the conventional 4-valve engine. First, a comparison of output and fuel consumption will be described. 6
The intake and exhaust valves 5 and 6 of the valves are significantly smaller than the intake and exhaust valves 5 and 6 of the four valves of FIG. However, the six-valve intake / exhaust valves 5 and 6 shown in FIG.
Since it is smaller than the intake / exhaust valves 5 and 6 of the above four valves, it approaches the center Bc of the cylinder bore. Therefore,
The total sum of the diameters φ of the three valves of the six-valve intake / exhaust valves 5, 6 is slightly larger than that of the four valves. Therefore, since the circumferential lengths of the intake and exhaust valves 5, 6 become long, the intake and exhaust passage areas obtained by multiplying the circumferential lengths of the intake and exhaust valves 5, 6 by the stroke St of FIG. 1C, that is, the intake valve 5 or Since the area between the exhaust valve 6 and the valve seat 9 increases, the resistance to the flow of intake and exhaust, that is, the masking decreases.

Further, in the four-valve engine of FIG. 2, since the valves 5 and 6 themselves are large, the space S on the cylinder wall 3a side of the intake valve 5 is small. Therefore, the intake air M (or exhaust air) of FIG. 2C collides with the cylinder wall 3a, and the flow thereof is likely to be disturbed. On the other hand, in the 6-valve engine of FIG. 1A, since the valves 5 and 6 themselves are small, the space S on the cylinder wall 3a side of the intake valve 5 becomes large. Therefore, as shown in FIG. 1C, since the intake air M is smoothly guided into the cylinder 10 by the cylinder wall 3a, the flow of the intake air M (or the exhaust gas) becomes smooth, and the masking becomes small.

Since the valve diameter of the 6-valve is small, the area of the portion (shaded portion) S1 where the intake / exhaust valves 5, 6 of FIG. 1A are close to the bore 3 is the shaded portion of the 4-valve of FIG. Since it is smaller than S2, the masking also becomes small.

The six-valve intake / exhaust valves 5 and 6 are
Since it is smaller than the four-valve intake / exhaust valves 5 and 6 of FIG. 2B, the height H of the combustion chamber 8 above the piston (not shown) becomes low as shown in FIG. 1B. Therefore, since the combustion chamber 8 becomes small, a large compression ratio can be obtained even if the intake / exhaust valves 5, 6 are made as large as possible.

Further, as shown in FIG. 1 (a), since the spark plug 7 is arranged in all of the spaces surrounded by the four valves 5 and 6, the propagation distance of the flame is shortened. The bore diameter can be increased to reduce the piston stroke. Therefore, the larger intake / exhaust valve 5,
6 can be adopted.

Further, since the two spark plugs 7, 7 are provided, the torque curve of the engine output can be smoothed by making the ignition timings of the two spark plugs 7, 7 different from each other. Therefore, the waste of work is reduced, and the fuel efficiency is also improved.

As described above, in this 6-valve engine, the masking becomes smaller and the compression ratio increases,
Further, since the torque curve can be smoothed as needed, the output of the engine and the fuel consumption are improved as compared with the 4-valve type.

Next, the idling state and the engine speed limit will be compared. As described above, in the 6-valve of FIG. 1A, the masking becomes small, so that the negative pressure of the intake air becomes large even if the opening timing of the intake valve 5 is narrowed. Therefore, the idling state is stable.

Further, the diameters of the intake and exhaust valves 5 and 6 of the six valves are about (2/3) times as large as that of the four valves of FIG. Therefore, the area of a single valve is about (4
/ 9) times and the total area of the intake valve 5 of 4 valves is 2
-If A, the total area of the three intake valves 5 of 6 valves is 3 x (4/9) -A = (4/3) -A. Therefore, since the total area of the valves is small, The total weight is also reduced. Therefore, the intake and exhaust valves 5 and 6 of FIG.
Since the total load of the valve spring (not shown) that restores is also small, the torque fluctuation of the valve train is small, and the rotation fluctuation during idling is also small.
The idling condition is stable. Also, the mechanical loss and the mechanical sound are reduced.

Further, as described above, since the intake / exhaust valves 5, 6 are lighter in the 6-valve, the inertial force when the valves reciprocate becomes smaller. Therefore, the limit of the rotational speed due to the valve train is significantly improved. If the rotational speed limit is determined by the piston / crank system instead of the valve system, as described above, the combustion propagation distance becomes shorter and the compression ratio becomes larger. The stroke can be reduced to raise the limit of the number of rotations.

Next, a comparison with the conventional 5 valves will be described. As shown in FIG. 1 (a), this 6-valve engine has three intake ports 1 (and exhaust ports 2)
Since they are arranged in a straight line, even if the sandwiching angle θ of each intake valve 5 in FIG. 1B is set to the same value, one intake cam shaft and one exhaust cam shaft (not shown) The intake and exhaust valves 5 and 6 can be operated. Therefore, unlike the five-valve engine of FIG. 4B, it is not necessary to use two types of sandwiching angles θa and θb of the intake valves 5A and 5B, which facilitates processing and improves manufacturability.

Further, in the case of 5 valves, the intake valves 5A, 5
Since the sandwiching angles θa and θb of B are different from each other, the shape of the upper portion of the combustion chamber 8 is not smooth, which reduces the propagation speed of the flame and causes a reduction in output. On the other hand, in the 6-valve shown in FIG. 1, the three intake valves 5 have the same sandwiching angle θ (FIG. 1B), so that the shape of the upper portion of the combustion chamber 8 becomes smooth. Therefore, the flame propagation speed becomes faster than 5 valves.

Further, regarding masking of intake air, 4
As described in the comparison with the valve, since the intake valve 5 in FIG. 1A is separated from the bore 3, it is improved as compared with the case of 5 valves.

By the way, in the five valve shown in FIG. 4A, two spark plugs cannot be provided because of the arrangement of the five intake and exhaust valves 5 and 6. On the other hand, in the 6-valve of FIG. 1A, since the intake valve 5 and the exhaust valve 6 are arranged in parallel with each other, the spark plugs 7 are provided in the spaces surrounded by the four valves 5 and 6, respectively. Can be provided.
Therefore, the flame propagation distance is shorter than 5 valves.

Moreover, the torque curve of the engine output can be made smooth by slightly differentiating the ignition timings of the two spark plugs.

Thus, this 6-valve engine
Compared to a 5-valve engine with the same bore stroke ratio,
Since the flame propagation speed is increased, masking is improved, and the torque curve of the engine can be smoothed, even if the area of the intake valve 5 is smaller than that of the five valves, it is equivalent to that of the five valves. You can expect engine output.

Further, in the five-valve engine of FIG. 4, since the number of exhaust valves 6 is two, the area of the exhaust valves 6, that is, the weight of one exhaust valve 6 is lighter than that of the four valves. Absent. Therefore, the limit of the number of revolutions determined by the inertial force of the reciprocating valve does not rise to the same extent. On the other hand, in the 6-valve shown in FIG. 1, as described in comparison with the 4-valve, the limit of the rotational speed is greatly improved.

Of course, in the 6-valve engine, since the bore 3 is circular, unlike the 8-valve, machining of the piston and the bore 3 does not become extremely difficult.

In the present invention, the three intake ports 1 and the exhaust ports 2 may be arranged substantially in a straight line, and may be arranged substantially parallel to each other.

[0029]

As described above, according to the present invention, not only three intake / exhaust valves are provided, but three intake ports and exhaust ports are arranged substantially in a straight line and in parallel with each other. Since two spark plugs are provided, the productivity such as 5 valves and 8 valves does not decrease, and performance such as engine output and fuel consumption is improved over 4 valves, and a good idling state is obtained. Furthermore, the limit of the number of rotations can be improved.

In particular, this 6-valve engine has a higher flame propagation speed, improved masking, and a smoother torque curve than the 5-valve engine with the same bore stroke ratio. Therefore, even if the area of the intake valve is smaller than that of the five valves, the engine output equivalent to that of the five valves can be expected. Further, if the bore stroke ratio is changed to make the bore diameter larger and the piston stroke smaller than that of the 5-valve engine, the area of the intake valve, the compression ratio and the flame propagation speed equivalent to those of the 5-valve can be obtained. The masking and rotation limits are improved, and the exhaust valve can be made larger. As a result, a high-performance engine with a larger output than that of a 5-valve engine can be obtained.

[Brief description of drawings]

FIG. 1 is a plan conceptual diagram and a longitudinal sectional conceptual diagram showing an embodiment of a four-stroke engine of the present invention.

FIG. 2 is a conceptual diagram of a conventional 4-valve 4-cycle engine.

FIG. 3 is a schematic plan view of an 8-valve 4-cycle engine.

FIG. 4 is a conceptual diagram of a 5-valve 4-cycle engine.

[Explanation of symbols]

1 ... Intake port, 2 ... Exhaust port, 3 ... Bore, 5 ... Intake valve, 6 ... Exhaust valve, 7 ... Spark plug.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area F02F 1/42 K 8109-3G F02P 15/08 302 A

Claims (1)

[Claims] 1. A four-cycle engine having a plurality of intake valves and exhaust valves, and a cylinder having a circular bore, wherein three intake valves and three exhaust valves are provided, and the intake valves open and close. Intake port,
The exhaust ports, which are arranged in a substantially straight line in a plan view and which are opened and closed by the exhaust valve, are arranged in a straight line in a substantially parallel manner with the intake port in a plan view, and are arranged in the two intake ports and the exhaust port. A four-cycle engine characterized in that spark plugs are provided at two enclosed locations.