JPH0231546Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an internal combustion engine having two intake valves and one exhaust valve per combustion chamber. This invention relates to an intake two-valve internal combustion engine that forms a swirl in the air.

Generally, when an internal combustion engine is of a two-valve intake type, the total intake passage area becomes larger, which improves charging efficiency under high loads and enables high output to be obtained.However, on the other hand, in low load areas It becomes impossible to ensure an appropriate flow rate of the air-fuel mixture, and the miscibility of fuel and air deteriorates. For this purpose, intake 2
In valve type internal combustion engines, there is a need to improve combustion, especially in low load ranges.

On the other hand, in internal combustion engines, by forming a swirl in the air-fuel mixture in the combustion chamber, the mixture of fuel and air is improved, combustion efficiency is improved especially in the low load range, and idle stability is improved. It is known that as the fuel consumption increases, fuel consumption is reduced and the emission of unburned gas is further suppressed. Therefore, by making the internal combustion engine a two-valve intake type and by forming a swirl in the air-fuel mixture taken into the combustion chamber, it is possible to expect improved combustibility in the entire operating range.

Means for forming such a swirl include using a helical port in which a spiral portion is provided in the intake port upstream of the intake valve port, using a shroud valve in which a shroud is provided on the back surface of the valve body of the intake valve, or It is known to install the intake port eccentrically with respect to the combustion chamber.

By the way, with such a swirl forming means,
It is difficult to generate gas flow throughout the combustion chamber with one swirl. Further, when such a swirl forming means is provided, the inflow resistance of the air-fuel mixture inevitably increases and the filling efficiency decreases. Therefore, in the past, for example,
As seen in Publication No. 90441, Publication of Utility Model Application No. 53-87309, etc., the charging efficiency is improved by providing two intake valves per combustion chamber, and
Attempts have been made to generate gas flow over a wide range within the combustion chamber by forming intake flows in different directions in the air-fuel mixture drawn into the combustion chamber through each intake valve port.

However, with such a device, the swirl formed by one intake port is interfered with and weakened by the intake flow from the other intake port, so the swirl effect is not fully realized, especially at low loads. The problem is that it is not.

The present invention was developed in view of the above-mentioned problems, and is an internal combustion engine with a simple structure that further improves combustion efficiency, especially in the low load range, and ensures high charging efficiency. The main purpose is to obtain.

Another object of the present invention is that the flow of the air-fuel mixture drawn into the combustion chamber through the two intake valve ports is
The purpose is to prevent them from interfering with each other, thereby strengthening the swirl.

In order to achieve these objectives, this invention:
The combustion chamber has a roof shape, and two intake valve ports are arranged in parallel on one roof surface, and an exhaust valve port and an ignition source are arranged in parallel on the other roof surface, and this exhaust valve port is connected to the intake valve port. The ignition source is placed as close to the center of the combustion chamber as possible by arranging it so that it faces one side, and the intake port of the intake valve opening facing the exhaust valve opening is connected to the peripheral wall of the combustion chamber. A straight port is connected almost tangentially to the intake port, and the other intake port is a helical port. The straight port forms a large-diameter swirl along the circumferential wall surface of the cylinder bore, and the helical port forms a small-diameter swirl inside the large-diameter swirl in the same direction. That's what I do.

Furthermore, the opening timing of the intake valve of the helical port is set later than the opening timing of the intake valve of the straight port.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

1 and 2 show one cylinder of a multi-cylinder internal combustion engine according to an embodiment of the present invention. FIG. 1 is a view of the cylinder head viewed from below, and FIG. It is a longitudinal cross-sectional view of the main part. As is clear from these figures, a cylinder head 2 is assembled on the upper surface of the cylinder block 1. The cylinder block 1 is provided with a cylinder bore 1a, into which a piston 1b is slidably fitted. and,
A combustion chamber C is formed by the cylinder bore 1a, the cylinder head 2, and the top surface of the piston 1b.

The combustion chamber C has a roof shape, and therefore, the cylinder head 2 is formed with a pair of roof surfaces 2a and 2b that are inclined on both sides, respectively. As shown in FIG. 1, a first intake valve port 3 and a second intake valve port 4 are arranged in parallel on one roof surface 2a. These intake valve ports 3 and 4 are opened and closed by intake valves (not shown), respectively.

The first intake valve port 3 is connected to a straight port-shaped first intake port 5 that extends substantially tangentially to the peripheral wall surface of the combustion chamber C, that is, the peripheral wall surface of the cylinder bore 1a. This intake port 5 is
Since the roof surface 2a through which the intake valve port 3 opens is inclined, it forms a large angle with respect to the axis of the cylinder bore 1a, that is, it is nearly horizontal when viewed in FIG. Therefore, the intake air taken in through the intake port 5 is distributed within the combustion chamber C along the peripheral wall surface of the cylinder bore 1a. Further, a second intake port 6 having a helical port shape is connected to the second intake valve port 4 . The second intake port 6 has a portion adjacent to the upstream side of the intake valve port 4 in the form of a screw with a small diameter and a small pitch, and as shown in FIG. 2, that portion is directed downward. There is. The direction of the threading is the same as the direction in which intake air is drawn into the combustion chamber C through the first intake port 5. First and second intake ports 5, 6
are adapted to be connected to a common carburetor through an opening 7 provided on one side of the cylinder head 2.

On the other roof surface 2b of the cylinder head 2,
An exhaust valve port 8 is located at a position opposite to the first intake valve port 3,
Further, an ignition source 9 is provided at a position facing the second intake valve port 4.
are arranged side by side. This arrangement of the three valve ports 3, 4, and 8 allows the ignition source 9 to be located close to the center of the combustion chamber C. The exhaust valve port 8 is an exhaust valve (not shown)
The exhaust board 10 connected thereto is connected to the exhaust manifold through an opening 11 provided on the other side of the cylinder head 2.

In this embodiment, the ignition source 9 is a torch ignition device with an auxiliary chamber, and the rich mixture supplied into the auxiliary combustion chamber 12 is ignited and combusted by the ignition plug 13. The resulting flame jet is ejected from torch nozzles 14 and 15 to combust the lean air-fuel mixture within the combustion chamber C. The flame jet ejected from this one torch nozzle 14 is made to reach the vicinity of the first intake valve port 3,
The flame jet ejected from the other torch nozzle 15 is configured to reach the vicinity of the second intake valve port 4 . In addition, for such a torch igniter with a subchamber, the lower surface S of the ignition source 9 is connected to the roof surface 2.
The piston 1 has a flat surface that protrudes downward from the cylinder head 2 and substantially coincides with the lower surface of the cylinder head 2.
A tight area is formed between the top surface of b and the top surface of b.

The intake valve that opens and closes the first intake valve port 3 and the second intake valve port 4, and the exhaust valve that opens and closes the exhaust valve port 8, are operated by a commonly used single overhead cam mechanism with a simple structure. It is becoming more and more common. The intake valve opening timing of the second intake valve port 4 is made later than the intake valve opening timing of the first intake valve port 3.

In the internal combustion engine configured in this way, during operation, an air-fuel mixture is taken into the combustion chamber C through the first intake port 5 and the second intake port 6.
At this time, as described above, the flow of intake air taken in through the first intake port 5 becomes a large swirl along the peripheral wall surface of the cylinder bore 1a, as shown by arrow A in FIGS. 1 and 2. On the other hand, since the second intake port 6 is a helical port with a small diameter and small pitch, the flow of intake air taken in through it is directed to the second intake valve port 4 as shown by arrow B in FIGS.
It becomes a small pitch swirl that goes downwards. Therefore, a large-diameter swirl A and a small-diameter swirl B inside the large-diameter swirl A are formed in the combustion chamber C, and gas flow occurs throughout the combustion chamber C. Moreover, these swirl A,
Since the winding directions B are in the same direction, they will not interfere with each other and be weakened, and even if they merge, the effect will be small.

In particular, as mentioned above, the intake valve opening timing of the first intake valve port 3 is set to be earlier than the intake valve opening timing of the second intake valve port 4, so that the form of swirl A can be further accelerated. . Therefore, interference between swirls A and B can be further suppressed.

In this way, a swirl is formed throughout the combustion chamber C and is maintained, improving the mixing properties of the air-fuel mixture within the combustion chamber C, and the ignition source 9 is activated at the end of the compression stroke. When the flame is ignited, the flame propagates rapidly and the ignition source 9 is set as a torch igniter so that combustion within the combustion chamber C is carried out in a short time. Immediately after ignition, the fuel is applied to the high-temperature exhaust valve side, which further accelerates the start of combustion. Due to the arrangement of the three valve ports as described above, if the ignition source 9 is located near the center of the combustion chamber C, the distance that the flame jet reaches from the torch nozzles 14 and 15 will be shortened, so that the entire load range Rapid combustion takes place and knocking is also suppressed. However, it is not always necessary to use a torch ignition device as the ignition source 9, and even when a spark plug is attached, a sufficient improvement in combustion efficiency can be achieved.

As is clear from the above explanation, according to the present invention, two intake valve ports are provided on one roof surface of a roof-shaped combustion chamber, and an exhaust valve port is provided on the other roof surface, thereby creating a cross-flow type combustion chamber. This combustion chamber increases intake and exhaust efficiency, and in particular, one of the intake ports connected to the intake valve port is a straight port with less resistance to the inflow of the air-fuel mixture, ensuring high charging efficiency. can do.

Since the straight port is installed so as to be substantially tangential to the peripheral wall surface of the combustion chamber, a large swirl can be formed along the peripheral wall surface of the cylinder bore. Moreover, the exhaust valve port is located at a position opposite to the intake valve port of the straight port, and the ignition source is located at a position opposite to the other intake valve port, so the ignition source becomes a hindrance to the formation of swirl. Therefore, it is also possible to provide a squeeze area on the lower surface of the ignition source as in the above embodiment.

In addition, since the other intake port is a helical port, a small-diameter swirl is formed in the same direction as the swirl formed by the straight port, so a swirl is formed throughout the combustion chamber. As a result,
Combustion efficiency can be particularly improved in a low load range. Moreover, by setting a time difference between the opening timings of the two intake valves, the timing of the generation of the two swirls is shifted, so these swirls do not interfere with each other and become weaker, and a strong swirl can be generated. It can last until the time of combustion. Therefore, the mixture with the residual gas in the combustion chamber is improved, and the emission of harmful gases can also be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a bottom view of a cylinder head showing an embodiment of an intake two-valve internal combustion engine according to the present invention;
The figure is a longitudinal sectional view of the internal combustion engine. 1... Cylinder block, 1a... Cylinder bore, 2... Cylinder head, 2a, 2b... Roof surface, 3... First intake valve port, 4... Second intake valve port, 5... First intake port , 6... Second intake port, 8... Exhaust valve port, 9... Ignition source, A... Swirl, B... Swirl, C... Combustion chamber.

Claims (1)

[Claims for Utility Model Registration] The combustion chamber C has a roof shape, and a first intake valve port 3 and a second intake valve port 4 are arranged side by side on one roof surface 2a, and on the other roof surface 2b, An exhaust valve port 8 facing the first intake valve port 3 and an ignition source 9 facing the second intake valve port 4 are arranged in parallel, and a first intake port 5 is connected to the first intake valve port 3.
is a straight port arranged substantially tangentially to the peripheral wall surface of the combustion chamber C, and a second intake port 6 connected to the second intake valve port 4;
is a helical port that forms a swirl B that is in the same direction as the swirl A formed by the first intake port 5 and has a smaller diameter than the swirl A, and the opening timing of the intake valve that opens and closes the first intake valve port 3 is A two-valve intake internal combustion engine characterized in that the opening timing of the intake valve that opens and closes the second intake valve port 4 is delayed.