JPH0433383Y2 - - 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 valves for each cylinder.

<Prior art> As a conventional example of an intake system for this type of internal combustion engine,
There are the ones shown in Figures 5 to 7 (Japanese Patent Application Publication No.
(See Publication No. 55-51920).

That is, each cylinder of the engine has a first intake valve 1A,
Second intake valve 1B and first and second exhaust valves 2A, 2B
The intake port is divided into a first intake port 3A and a second intake port 3B, and the second intake port 3B is provided with an on-off valve 4. The opening/closing valve 4 is controlled to open and close by an actuator 7 operated by control negative pressure from a solenoid valve 6 driven by a control circuit 5 that detects engine operating conditions such as low speed or partial load region (hereinafter referred to as low speed region). .
In the low speed range, closing this on-off valve 4 provides the same effect as effectively closing the second intake valve 1B, introducing intake air from one side to form a swirl and preventing exhaust blowback. ing. During~
In high speed/high load ranges (hereinafter referred to as medium/high speed ranges), this on-off valve 4 is opened, and the first and second intake valves 1A,
Intake air is introduced from both sides of 1B to ensure intake air filling efficiency. Since the opening/closing valve 4 is infrequently opened in the normal operation range, the fuel injection valve 8 always performs combustion via the first intake valve 1A, as shown in FIG. 6, in order to obtain a stable air-fuel ratio and responsiveness. It is provided on the first intake port 3A side that introduces intake air into the chamber 9. 10 is a spark plug, 11 is an accumulator, 12 is a check valve, and 13 is a valve shaft. FIG. 7 shows the lift characteristics of the first and second intake valves 1A, 1B and the first and second exhaust valves 2A, 2B. First and second exhaust valves 2A, 2B
have the same lift characteristics, but compared to the lift characteristics of the second intake valve 1B, the lift characteristics of the first intake valve 1A are slower in opening timing, earlier in closing timing, and have a lower operating angle.
Both the maximum lift amounts are smaller, and if the first intake valve 1A is used for low speeds, the second intake valve 1B has lift characteristics for high speeds.

According to this configuration, in the low speed range, the on-off valve 4
is closed, and air is taken only from the first intake port 3A side, making use of the lift characteristics of the first intake valve 1A to improve fuel efficiency and stability by strengthening the swirl, as well as improving torque at low speeds. In this case, the on-off valve 4 is opened and air is taken in from the second intake port 3B side, and sufficient intake air filling efficiency is ensured by taking advantage of the lift characteristics of the second intake valve 1B, which is set to high-speed characteristics. I'm there.

<Problem to be solved by the invention> However, when the intake air flow rate increases to a certain extent in the medium speed range, the intake passage resistance increases with the opening and closing valve 4 closed, and the intake air flow rate introduced into the combustion chamber 9 becomes insufficient. Therefore, the opening and closing valve 4 is controlled at an intermediate opening to allow the intake air to be introduced into the combustion chamber 9 from the second intake port 3B as well.
For this reason, the on-off valve 4 is operated by a negative pressure actuator 7 as shown in FIG.
The valve opening was controlled to be gradually increased.

However, as described above, it is difficult to control the opening degree of the on-off valve 4 with high precision so as to gradually increase the opening degree.

The present invention was developed in view of the above-mentioned circumstances, and it ensures high swirl in low speed ranges such as idling, while reducing swirl in high speed ranges to achieve high intake air filling efficiency while maintaining the closed state of the on-off valve. An object of the present invention is to provide an intake system for an internal combustion engine that can widen the operating range in which a sufficient flow rate of intake air can be secured.

<Means for Solving the Problems> In order to solve the above problems, the present invention provides first and second intake ports opening into one combustion chamber, and connecting these first and second intake ports to the combustion chamber. A device comprising: first and second intake valves that open and close in front of each other; and an on-off valve that is disposed in the middle of the second intake port and opens and closes the second intake port depending on the engine operating state. In the valve state, the on-off valve includes a portion near the first intake port on the second intake port zenith side, and has an opening that opens at the top of the on-off valve or a side portion near the first intake port; The valve is characterized in that it can be opened and closed in two positions: open and closed.

<Function> When the intake valve is initially opened, residual gas in the combustion chamber blows back toward the intake port, but this residual gas contains many components that become deposits such as carbon. Therefore, if this adheres to the area around the on-off valve, that is, on the seal between the on-off valve and the second intake port, problems such as sticking are likely to occur.

By the way, the residual gas has a higher temperature (usually 600°C or higher) than the fresh air being inhaled, and has a large density difference with the fresh air, so it flows toward the top of the first and second intake ports. tend to gather.

In other words, as in the present invention, the opening that is opened including the part near the first intake port on the top side of the second intake port is located at the upper part of the on-off valve in the closed state or the side part near the first intake port. If the valve is opened, the opening will be opened at a place where at least residual gas gathers in the closed state, so the second
The residual gas flowing along the zenith side of the intake port is
It is quickly introduced into the opening, reducing adhesion of carbon, etc. to other parts of the on-off valve.

On the other hand, carbon etc. adhere to the opening due to the residual gas being blown into the opening, but in the intake stroke after blowback, fresh air is introduced into the opening in the opposite direction to the blowback, so carbon etc. adhere to the opening. The carbon, etc. that have been removed are blown away toward the combustion chamber by fresh air. In other words, since the opening has a self-cleaning effect, it is possible to prevent the accumulation of carbon, etc., and to significantly prevent the opening/closing valve from becoming stuck.

At the same time, when the on-off valve is closed, the flow rate of intake air into the combustion chamber is much larger at the first intake port than at the second intake port, but the opening is on the side of the top of the second intake port. In other words, the opening is opened in a location that at least promotes swirl generation, and while a high swirl can be ensured in the combustion chamber, it is also possible to create a Expand the operating range where sufficient intake air can be secured.

<Example> Below, an example of the present invention will be described based on the drawings. In each embodiment, the same elements as in the conventional example are designated by the same reference numerals as in FIG. 5, and their explanation will be omitted.

1 and 2 show a first embodiment of the present invention.

In the figure, a butterfly-type on-off valve 21 is disposed in the middle of the second intake port 3B of each cylinder, and the on-off valve 21 is controlled to open and close in two positions: open and closed.

In each on-off valve 21, in the closed state, an opening 21A is formed by cutting out the zenith side (upper part in FIG. 1) of the second intake port 3B and communicating between the upstream and downstream sides of the on-off valve 21, i.e. , second intake port 3
The opening 21A, which is opened including the first intake port 3A on the B-zenith side, is opened above the on-off valve 21 in the closed state. Here, the opening area of the opening 21A is the second intake port 3.
It is set to approximately 1/5 of the flow path cross-sectional area of B.

The opening timing of the first intake valve (not shown) that opens and closes the first intake port 3A is determined by the opening timing of the first intake valve (not shown) that opens and closes the first intake port 3A.
The timing is set earlier than the opening timing of the second intake valve (not shown) which opens and closes the intake valve.

According to this configuration, in a low speed range such as idling operation in which the on-off valve 21 is closed, the on-off valve 21 is closed.
Since the opening area of the opening 21A that communicates between the upstream and downstream sides of the first intake port 3B is extremely smaller than the flow path cross-sectional area of the second intake port 3B, the flow from the first intake port 3A to the combustion chamber (Fig. (not shown) a large amount of intake air is introduced. Therefore, a high swirl can be formed in the low speed range.

Furthermore, since the first intake valve (not shown) disposed in the first intake port 3A is set to open earlier than the second intake valve disposed in the second intake valve port 3B, The proportion of intake air introduced from the first intake valve at the beginning of the intake stroke can be increased, that is, the intake air introduced from the first intake valve into the combustion chamber precedes the second intake valve, which helps strengthen the swirl. be done. Therefore, the cancellation of the swirl caused by the intake air introduced from the second intake valve through the opening 21A of the on-off valve can be suppressed to a small level.

On the other hand, in the medium speed range, the amount of intake air increases to some extent, but the flow path of the intake air introduced into the combustion chamber is opened and closed because the opening 21A is secured in addition to the main first intake port 3A. An increased intake air flow rate can be accommodated without opening the valve 21. Therefore, the required intake air flow rate can be ensured, for example, in a medium speed range, without having to control the opening/closing valve 21 with high precision at an intermediate opening degree. Specifically, the operating range in which the necessary intake air flow rate can be secured with the on-off valve 21 closed can be expanded from, for example, the conventional 3000 rpm to 3600 rpm. At this time, a swirl can be formed because the flow rate of intake air flowing in from the first intake port 3A is large.

In addition, in the high speed range, as shown in Fig. 2, each on-off valve 21 is fully opened, so intake air is introduced into the combustion chamber from the first and second intake ports 3A and 3B as in the conventional example, weakening the swirl. while ensuring high filling efficiency. On the other hand, the intake air introduced into the combustion chamber is first introduced from the first intake port 3A,
Subsequently, since the air is introduced from the second intake port 3B, it is possible to obtain strong turbulence within the combustion chamber, resulting in good mixing of air and fuel, and improvement in air-fuel mixture formation.

Furthermore, since the opening 21A is formed, the air-fuel mixture flows through the opening 21A, preventing it from staying upstream of the on-off valve 21, and preventing the mixture from becoming concentrated when the on-off valve 21 is opened. can.

In addition, at the initial stage of opening of the first and second intake valves, residual gas in the combustion chamber flows into the first and second intake ports 3.
The residual gas blows back toward the A and 3B sides, but this blowback of residual gas is noticeable in the low speed range when the on-off valve 21 is closed or during idling when the suction negative pressure is large.

This residual gas contains many components that become deposits such as carbon, so this remains around the on-off valve 21, that is, on the seal between the on-off valve 21 and the second intake port 3B. If it gets stuck, it can easily cause problems such as sticking.

By the way, the residual gas has a higher temperature (usually 600°C or higher) than the fresh air that is inhaled, and the difference in density between the residual gas and the fresh air is large. Flow tends to gather on the sides.

In other words, as in this embodiment, when the opening 21A that communicates the upstream and downstream of the on-off valve 21 is opened on the top side of the second intake port 3B where a large amount of residual gas gathers, the on-off valve 21 is in the closed state. The residual gas flowing along the zenith side of the second intake port 3B is
Opening 21 quickly forms a smooth flow path.
A, and the adhesion of carbon and the like to other parts of the on-off valve 21 is reduced.

On the other hand, carbon etc. adhere to the opening 21A due to the residual gas being blown, but after blowing back, during the suction stroke, the opening 21A
Since fresh air is introduced from upstream in the opposite direction to the blowback, carbon and the like adhering to the opening 21A are blown away toward the combustion chamber by the fresh air.

In other words, since the opening 21A has a self-cleaning effect, it is possible to prevent the accumulation of carbon, etc.
This makes it possible to significantly prevent A's stagnation.

At the same time, the flow rate of intake air into the combustion chamber when the on-off valve 21 is closed is the same as that at the second intake port 3B.
However, since the opening 21A is opened including the area near the first intake port 3A on the zenith side of the second intake port 3B, that is, at least The opening 21A is opened at a location that promotes swirl generation, and a high swirl can be ensured within the combustion chamber.

If the opening 21A is opened by cutting out only the side far from the first intake port 3A, the intake air introduced into the combustion chamber from this opening 21A is as follows.
Since the swirl is introduced in a direction that cancels the rotational direction of the swirl generated in the combustion chamber, the object of the present invention cannot be achieved.

By the way, in a device that mainly injects and supplies fuel from the first intake port, when the on-off valve 21 is opened without forming the opening 21A, the air-fuel mixture introduced into the combustion chamber from the first intake port is transferred to the second intake port. However, when the on-off valve 21 is closed, most of the intake air is introduced into the combustion chamber along with the fuel through the first intake port. Therefore, the mixture formation can be improved. Therefore, in this embodiment, the operating range in which the on-off valve 21 is closed can be expanded, and the air-fuel mixture formation can be improved.

It is also conceivable to increase the flow path area of the first intake port 3A while decreasing the flow path area of the second intake port 3B, and to control the opening and closing of the on-off valve 21 without providing the opening 21A. In some cases, the intake air filling efficiency in the medium speed range can be improved, but the swirl becomes larger than before in the high speed range.

3 and 4 show other embodiments of the invention.

Each on-off valve 22 disposed in the middle of the second intake port 3B of each cylinder has a valve on the first intake port 3A side.
Opening 22A that communicates upstream and downstream of the on-off valve 22
In other words, the opening 22A that is opened including the first intake port 3A side on the zenith side of the second intake port 3B is the side side of the opening/closing valve 22 near the first intake port 3A in the closed state. It is established in the department. And, similarly to the first embodiment,
The opening timing of the first intake valve is set earlier than that of the second intake valve.

According to this configuration, in addition to the same effects as in the embodiment described above, there are the following effects. That is, since the opening 22A is formed on the side closer to the first intake port 3A, the opening 22A when the on-off valve 22 is fully closed.
Since the intake air flowing through the opening flows toward the center of the combustion chamber and flows into the combustion chamber, the cancellation of swirl caused by this can be reduced compared to the embodiment described above. Can be suppressed.

In addition, the residual gas blown back from the combustion chamber is
Although it is mainly blown back along the zenith side of the second intake port 3B, when the on-off valve 22 is closed,
Since the opening 22A is opened at least in a place where the blown back combustion gas collects, the residual gas is
The opening 22 is quickly formed while forming a smooth flow path.
A, and the frequency of adhesion of carbon and the like to other parts of the on-off valve 22 is reduced.

In addition, during the suction stroke after the blowback, fresh air is introduced into the opening 22A in the opposite direction to the blowback. In other words, the opening 22A has a self-cleaning effect, which significantly affects the stay of the on-off valve 22. It can be prevented.

At the same time, the flow rate of intake air into the combustion chamber when the on-off valve 22 is closed is the same as that at the second intake port 3B.
However, since the opening 22A is arranged on the side near the first intake port 3A, the opening is placed in a place that promotes swirl generation. Since 22A is opened, a high swirl can be ensured in the combustion chamber.

In each of the above embodiments, since openings are provided in the on-off valves, the main purpose of closing the on-off valves 21 and 22 is to form a swirl, and the effect of preventing intake air from blowing back is weakened. The closing timings of the second intake valve and the second intake valve may be set to be substantially the same.

Furthermore, if the first intake valve (not shown) installed in the first intake port 3A is set to open earlier than the second intake valve installed in the second intake port 3B, it is possible to The ratio of intake air flow rate introduced into the combustion chamber from the first intake valve can be increased,
As a result, the swirl is strengthened and the openings 21A, 2
The reduction in swirl caused by providing 2A can be compensated for.

<Effects of the invention> As explained above, according to the invention, even if the residual gas in the combustion chamber containing a large amount of deposit-forming components such as carbon is blown back toward the intake port side when the on-off valve is closed, It is possible to prevent the accumulation of carbon, etc. on the on-off valve, and it is possible to significantly prevent the on-off valve from becoming stuck.

In addition, the opening that communicates upstream and downstream of the on-off valve is
Since it is installed in a place that at least encourages swirl generation, it is possible to ensure a high swirl in the combustion chamber when the on-off valve is closed, that is, it is possible to ensure the swirl formation effect in the operating region where the on-off valve is in the closed state. Therefore, the operating range in which a sufficient amount of intake air can be secured when the on-off valve is closed can be expanded.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of the main parts showing one embodiment of the present invention, Fig. 2 is a diagram for explaining the same operation as above, and Fig. 3 is a diagram of the main parts showing another embodiment of the invention. ,
Fig. 4 is a diagram for explaining the action of the above, Fig. 5 is a plan view showing a conventional example of an intake system for an internal combustion engine, Fig. 6 is an enlarged view of the same, and Fig. 7 is a lift characteristic diagram of the same. be. 3A...First intake port, 3B...Second intake port, 21, 22...Opening/closing valve, 21A, 22A...
…Aperture.

Claims (1)

[Scope of utility model registration request] first and second intake ports that open into one combustion chamber; first and second intake valves that open and close these first and second intake ports facing the combustion chamber;
In an intake system for an internal combustion engine, the intake system includes an on-off valve that is disposed in the middle of an intake port and opens and closes the second intake port according to engine operating conditions, wherein the on-off valve in the closed state is located at the top of the second intake port. The on-off valve has an opening that opens at the top of the on-off valve or on the side near the first intake port, and the on-off valve is opened and closed in two positions: open and closed. An intake system for an internal combustion engine, characterized by: