JPH0415939Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an intake system for an internal combustion engine having two intake ports for each cylinder.

<Prior art> As a conventional intake device of this type, there is, for example, the one shown in FIG.
(see issue).

To explain the outline based on the figure, there are two intake ports 2A leading to the combustion chamber 1 for each cylinder of the internal combustion engine,
2B, and intake valves 3A and 3B for opening and closing these, and a throttle valve 4 for adjusting the intake air flow rate is provided in the middle of one intake port 2B. Then, when the throttle of the throttle valve 4 is increased, intake air flows into the combustion chamber 1 from the intake valve 3a mainly through the other intake port 2A. After this intake air flows into the combustion chamber 1, its inertia generates a swirl that rotates counterclockwise in the figure within the combustion chamber 1. On the other hand, when the opening amount of the throttle valve 4 is increased, intake air flows into the combustion chamber 1 from each intake valve 3A, 3B through the two intake ports 2A, 2B. At this time, the two intake air flows try to swirl in opposite directions and collide with each other in the combustion chamber 1, so that the occurrence of swirl is suppressed.

That is, by controlling the opening degree of the throttle valve 4, the swirl strength is controlled to match the engine operating condition.

<Problems to be solved by the invention> However, in such conventional intake systems, a throttle valve for adjusting the intake flow rate is provided for each cylinder, and these throttle valves are opened depending on the engine operating conditions. Since it is necessary to provide a control device and a drive device to control the temperature, the manufacturing cost is high, and the durability and
There were also problems with reliability.

In addition, there is an intake device that selectively opens and closes both intake ports at the branch point of the two intake ports (Japanese Unexamined Patent Publication No. 57
-88217) has also been proposed, but this also causes the same problem. In addition, in the valve opening overlap region of the intake valve and exhaust valve, that is, in a state where the piston is near top dead center and the exhaust stroke is about to end, while the intake stroke is about to start, the intake valve and exhaust valve open at the same time. The valve is open, but in such a case, intake gas in the intake port passes through the intake valve and exhaust valve and flows into the exhaust port, or conversely, exhaust gas in the exhaust port flows into the intake port. There is a problem with backflow gas that flows back into the port. Here, when two intake ports are provided, the opening of the port to the combustion chamber is closer to the exhaust port than in the case of one intake port, and as a result, the intake gas blows through to the exhaust port and the exhaust gas backflows to the intake port. As a result, flammability and exhaust emission performance tend to decrease.

The present invention was developed in view of the problems with the intake installation of conventional internal combustion engines, and it is designed to appropriately set the shape and arrangement of the two intake ports provided for each cylinder and the intake passage on the upstream side thereof. By doing so, it is possible to obtain the swirl strength according to the engine operating conditions without the need for a throttle valve, its drive device, and control device. By setting the
To provide an intake mounting for an internal combustion engine which can maintain good combustibility and exhaust emission performance by suppressing the blow-through of intake air to an exhaust port and the backflow of exhaust gas to an intake port.

<Means for solving the problem> For this reason, the present invention provides for each cylinder a high-swirl intake port that has a shape that has a high ability to generate swirl within the combustion chamber, and a shape that has a shape that has a low swirl generation function. The high swirl intake port is formed by extending in the axial direction of the intake passage upstream from the branch point with the low swirl intake port, and the passage wall near the branch point is The low swirl intake port is located in the tangential direction along the passage wall near the branch point of the intake passage on the upstream side of the branch point, or on the side away from the axis from the tangent line, and the low swirl intake port is located on the upstream side of the branch point. The intake passage is arranged so that its axial direction branches at a predetermined angle with respect to the intake passage, and furthermore, the passage cross-sectional area of the low-swirl type intake port is formed to be larger than the passage cross-sectional area of the high-swirl type intake port. , the distance between the opening of the low-swirl intake port in the combustion chamber and the opening of the exhaust port in the combustion chamber is set to be larger than the distance between the opening of the high-swirl intake port in the combustion chamber and the opening of the exhaust port. .

<Function> Since the intake flow rate is small in the low speed range of the engine, the pressure loss due to the intake flow in the high swirl intake port is small.

For this reason, the intake air is strongly influenced by inertia, and flows mainly through the high-swirl intake port, which has a smooth passage wall extending into the upstream intake passage, creating a strong swirl in the combustion chamber, causing fuel to flow into the intake passage. Mixability with air is improved, combustibility and exhaust characteristics are improved.

On the other hand, in the high-speed range of the engine, the intake flow rate is large, so the high-swirl intake port, which generates a stronger swirl, has greater intake flow resistance than the low-swirl intake port, resulting in increased pressure loss.

For this reason, the influence of the pressure loss on the intake air is greater than that of inertia, and the proportion of the intake air that is diverted to the low-swirl intake port increases. The intake flow generated by the low-swirl intake port has a low swirl ratio, so the pressure loss associated with the flow is small, and the charging efficiency is increased, and the swirl ratio required for good combustion increases as the rotation speed increases. decreases, so
Combustibility is also improved, resulting in higher output and fuel efficiency. Furthermore, by forming the passage cross-sectional area of the low-swirl type intake port to be larger than the passage cross-sectional area of the high-swirl type intake port, the intake air filling efficiency in the high speed range is increased and the output performance is increased as much as possible.

Furthermore, since the passage cross-sectional area of the high-swirl intake port on the side closer to the exhaust port is set smaller than the passage cross-sectional area of the other intake port, the intake blow-by gas and exhaust backflow gas flowing through the intake port are reduced. The low-swirl intake port, which has a passage cross-sectional area larger than the other intake port, is able to keep the flow rate low, and because it opens away from the exhaust port opening, it is less likely to cause blow-by or backflow, and the overall The flow rates of intake gas and exhaust backflow gas are reduced as much as possible.

<Example> Below, an example of the present invention will be described based on the drawings.

In FIG. 1 showing one embodiment, an internal combustion engine has a helical-shaped high-swirl intake port 12 that generates a relatively strong swirl in a combustion chamber 11 for each cylinder, that is, a swirl with a high swirl ratio;
The intake port 13 has a straight low swirl type intake port 13 that has a weak swirl generation function within the intake port.

Further, the high swirl type intake port 12 extends in the axial direction of the intake passage 14 upstream from the branch point with the low swirl type intake port 13, and the passage wall near the branch point is located near the branch point of the intake passage 14. It is formed so as to be continuous in the tangential direction along the passage wall.

On the other hand, the low swirl type intake port 13 is arranged so that its axial direction branches at a predetermined angle θ with respect to the axial direction of the intake passage 14.

The open ends of the high swirl type intake port 12 and the low swirl type intake port 13 are connected to the intake valves 15 and 1, respectively.
It is opened and closed by 6. 17 is an exhaust port, 18
is an exhaust valve. Then, the passage cross-sectional area of the low swirl type intake port 13 is set to the high speed type intake port 12.
In addition, the distance between the opening of the low swirl type intake port 13 in the combustion chamber 11 and the opening of the exhaust port 17 in the combustion chamber 11 is set to be larger than the 12 opening of the high swirl type intake port in the combustion chamber 11. The distance is set larger than the distance from the opening of the exhaust port 17.

Next, the effect will be explained.

The high-swirl intake port 12, which is helically curved, has a higher passage resistance than the straight, low-swirl intake port 13, but in the low speed range of the engine, the intake air flow is small, so the high swirl In the molded intake port 12 as well, the flow resistance of the intake air is small, and the pressure drop caused by the intake air flow is small. As described above, the high-swirl type intake port 12 extends from the intake passage 14 on the upstream side of the branch point, and the passage walls are connected smoothly on the same tangent line with the branch point in between. The intake air flows into the combustion chamber 11 from the high swirl intake port 12 through the intake valve 15 due to inertia.

Therefore, a strong swirl is generated within the combustion chamber 11, which promotes mixing of fuel and air, improving combustibility and improving output, fuel efficiency, and exhaust characteristics.

As the engine speed increases, the influence of the increased intake resistance of the high-swirl intake port 12 becomes stronger as the intake air flow rate increases, and the pressure drop increases, suppressing the intake flow.

That is, as the engine speed increases, the difference in pressure drop due to intake air flow between the high-swirl type intake port 12 with high passage resistance and the low-swirl type intake port 13 with low passage resistance increases, and the pressure drop increases due to the influence of inertia. In comparison, the influence of pressure drop becomes stronger, so the proportion of the flow diverted to the low swirl type intake port 13 increases, and in the high speed range above a certain level, the low swirl type intake port 1
More intake air flows through 3.

In this way, air is taken in even from the low-swirl intake port 13 with low passage resistance, and as a result, high filling efficiency can be ensured.

In addition, by forming the passage cross-sectional area of the low-swirl type intake port 13 to be larger than the passage cross-sectional area of the high-swirl type intake port 12, the intake air filling efficiency in the high speed range is further increased, and the output performance is increased as much as possible. .

Furthermore, since the passage cross-sectional area of the high-swirl type intake port 12 on the side closer to the exhaust port 17 is set smaller than the passage cross-sectional area of the other low-swirl type intake port 13, The flow rate of the flowing intake blow-through gas and exhaust backflow gas can be suppressed to a low level. On the other hand, the low-swirl type intake port 13 whose passage cross-sectional area is set larger than that of the high-swirl type intake port 12 is located away from the exhaust port 17 opening. Since it is open, blow-through and backflow are less likely to occur, and overall the flow rates of intake blow-through gas and exhaust backflow gas are reduced as much as possible. As a result, good combustibility and exhaust emission performance can be maintained.

Furthermore, the swirl generated in the combustion chamber 11 by the high swirl type intake port 12 is weakened by the intake air flow flowing into the combustion chamber 11 from the low swirl type intake port 13 (the swirl ratio is decreased). in general,
As the engine speed increases, the swirl ratio required for good combustion decreases (particularly noticeable in direct injection diesel engines), so the proportion of intake air flow from the low swirl type intake port 13 is increased to reduce the swirl ratio. By reducing this, it is possible to obtain a swirl ratio that matches the engine speed, thereby improving combustibility.

Therefore, in conjunction with the above-mentioned improvement in charging efficiency, output, fuel consumption, and exhaust characteristics in medium and high speed ranges can also be improved.

In addition, compared to conventional systems that include a throttle valve and its drive and control device, the swirl ratio is automatically adjusted depending on the engine operating conditions using only the intake port shape, so it can be implemented at extremely low cost. , and has excellent reliability.

FIG. 2 shows a second embodiment, in which the wall portion corresponding to the branching point between the intake passage 21 and the low-swirl intake port 22 is directed toward the high-swirl intake port 12 in the same configuration as the first embodiment. A protruding portion 23 is formed. Other configurations are the first
This embodiment is the same as that of the embodiment, and is given the same reference numeral.

That is, with respect to the tangent along the passage wall of the intake passage 21 forming the protrusion 23, the passage wall near the branch point of the high swirl type intake port 12 is located on the side away from the axis.

This device has the same basic function as the first embodiment, but the intake air guided along the protrusion 23 further enhances the function of deflecting the air to the high-swirl intake port 12 in the low speed range, and the swirl The generation function will be enhanced. In other words, the speed range in which the flow is biased toward the high-swirl intake port 12 and the swirl is strengthened is made larger than that in the first embodiment.

In the embodiment shown above, the low-swirl type intake port is straight, so there is almost no swirl generation function in the entire operating range. By oriented in the opposite direction to the port, a wider swirl ratio control range can be obtained, or control can be performed with improved matching between each rotational speed range and the swirl ratio.

<Effects of the invention> As explained above, according to the invention, by devising the shape of the high-swirl intake port and the low-swirl intake port and the arrangement relationship with the upstream intake passage, the entire operating range of the engine can be achieved. The swirl ratio can be automatically controlled to match the operating conditions, and since a throttle valve and its drive/control circuit are not required, it can be implemented at low cost and has excellent reliability. In addition, by appropriately setting the passage cross-sectional area of each intake port and the positional relationship with the exhaust port, we can improve output performance in the high-speed range while reducing the flow rate of intake blow-through gas and exhaust backflow gas as much as possible. It is also possible to maintain good performance and exhaust emission performance.

[Brief explanation of drawings]

FIG. 1 is a plan view showing one embodiment of the present invention, FIG. 2 is a plan view showing a second embodiment of the present invention, and FIG.
The figure is a plan view showing a conventional example. 11... Combustion chamber, 12... High swirl type intake port, 13, 22... Low swirl type intake port,
14, 21... Intake passage on the upstream side of the branch point.

Claims (1)

[Scope of utility model registration request] Each cylinder has a high-swirl intake port with a shape that has a high ability to generate swirl within the combustion chamber,
The high swirl intake port is formed by extending in the axial direction of the intake passage upstream from the branching point with the low swirl intake port, and ,
The passage wall near the branch point is located in the tangential direction along the passage wall near the branch point of the intake passage upstream of the branch point, or on the side away from the axis from the tangent line, and low swirl type intake air is provided. The ports are arranged so that the axial direction thereof branches at a predetermined angle with respect to the intake passage upstream of the branch point, and further, the passage cross-sectional area of the low-swirl type intake port is set to the passage cross-sectional area of the high-swirl type intake port. The area is larger than the area, and the distance between the opening of the low-swirl intake port in the combustion chamber and the opening of the exhaust port in the combustion chamber is smaller than the distance between the opening of the high-swirl intake port in the combustion chamber and the opening of the exhaust port. An intake system for an internal combustion engine, characterized in that the air intake system is set large.