JPH0324836Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a technology for improving combustion during idling of an internal combustion engine.

<Prior Art> Conventional known technologies of this type include, for example, those shown in FIGS. 5 to 7.

To explain this, the opening timing of the low-speed intake valve 1 and high-speed intake valve 2 provided for each cylinder is changed, and the low-speed intake port 3 and high-speed intake port 4 that communicate with these intake valves 1 and 2 are changed. A high-speed intake port 4 is provided independently and is equipped with a high-speed intake valve 2 that has a large overlap with the exhaust valve 5.
An on-off valve 6 is provided in the engine, and the on-off valve 6 is closed in low speed ranges such as during idling to prevent exhaust gas from blowing back during the substantial valve overlap period, thereby improving combustion (Japanese Patent Publication No. 1973-
(See Publication No. 31724).

<Problems to be solved by the invention> However, with such a conventional method of blocking the intake port, it is difficult to reduce the volume of the high-speed intake port 4 downstream of the on-off valve 6 due to various restrictions. Therefore, it becomes about 15 to 20% of the cylinder volume. If the intake port volume in this part is large, the following problems will occur, especially during idling with a large intake negative pressure.

When the intake stroke ends and the high-speed intake valve 2 closes at the beginning of the compression stroke, the air-fuel mixture at the beginning of the compression stroke is trapped in the high-speed intake port 4, but the pressure of this air-fuel mixture is the same as when idling. It is in a state of negative pressure of about 400mmHg.

Therefore, when the high-speed intake valve 2 opens at the end of the exhaust stroke, the exhaust gas flows into the high-speed intake port 4 due to the pressure difference between the exhaust pressure and this negative pressure, and the inside of the intake port 4 reaches close to the exhaust pressure. The pressure rises and the exhaust gas (burnt gas), which occupies about half of the volume of the high-speed intake port 4, mixes with the air-fuel mixture in the combustion chamber 7 during the subsequent intake stroke, making it possible to sufficiently reduce the residual gas concentration. However, the effect of improving fuel efficiency is not as much as expected.

Therefore, as shown in FIGS. 8 and 9, fresh air close to atmospheric pressure is introduced into the high-speed intake port 4 on the downstream side of the on-off valve 6 through a fresh air introduction passage 9 with an orifice 8 interposed therein. After the high-speed intake valve 2 closes until it opens again, fresh air is sucked in by negative intake pressure, and the pressure difference between the high-speed intake valve 2 and the exhaust pressure is reduced. The applicant has proposed a method for significantly reducing the amount of burned gas mixed in the air-fuel mixture.

In both of these figures, the opening and closing valve 6 is controlled to open and close by a diaphragm actuator 10.

That is, when control pressure is supplied to the actuator 10, the output rod 11 expands, and the opening/closing valve 6 of each cylinder is opened from closed through the stroke of the link 12 and rod 13 connected thereto, and the rotation of the lever 14. Rotate it. The on-off valve 6 is biased in the valve closing direction by a spring 16 connected via a lever 15.

The supply of control pressure to the actuator 10 is interrupted by a solenoid valve 17, and the conditions for this interruption are determined by a pressure sensor 18 and a control unit 19 that detects engine operating conditions such as engine rotational speed. 2
0 is a limit switch that monitors the completion of actuation of the actuator 10.

A portion of the high-speed intake port 4 downstream of the on-off valve 6 communicates with an intake passage 22 upstream of the throttle valve 21 via a fresh air introduction passage 9, and the flow rate is regulated by an orifice 8. The pressure upstream of the throttle valve 21 is always close to atmospheric pressure, so under conditions of negative pressure in the high-speed intake port 4, fresh air upstream of the throttle valve 21 passes through the orifice 8 and flows to the high-speed downstream of the on-off valve 6. The air flows into the air intake port 4.

When fresh air is introduced in this manner, as shown by the solid line in FIG. 10, after the high-speed intake valve 2 closes, the pressure inside the high-speed intake port 4 downstream of the on-off valve 6 gradually approaches atmospheric pressure.

The orifice 8 controls the inflow amount of fresh air close to atmospheric pressure, and is used during the period of one crank rotation when the high-speed intake valve 2 is closed (during idling).
The size is set to be necessary and sufficient to bring the pressure inside the high-speed intake port 4 sufficiently close to atmospheric pressure in 0.1 seconds at 600 rpm (orifice 8 has a diameter of φ1).
~φ2 degree).

In this way, the exhaust gas filled in the combustion chamber 7 at a pressure close to atmospheric pressure (average value) at the end of the exhaust stroke when the high-speed intake valve 2 is opened is effectively suppressed from blowing back into the high-speed intake port 4. This makes it possible to significantly improve combustion performance.

For comparison, the case where fresh air is not introduced is shown by a broken line in FIG.

In this case, when the high-speed intake valve 2 is closed, gas does not enter or exit the high-speed intake port 4, so the pressure inside the high-speed intake port 4 downstream of the on-off valve 6 remains until the high-speed intake valve 2 opens next time. is maintained at a constant negative pressure of about half the atmospheric pressure.

Therefore, when the high-speed intake valve 2 starts to open, the exhaust gas filling the combustion chamber 7 rapidly flows into the high-speed intake port 4 due to a large pressure difference, and the high-speed intake port 4 downstream of the on-off valve 6 is Approximately half of the volume of the exhaust gas remains at near atmospheric pressure, expands at once during the subsequent intake stroke, and mixes into the combustion chamber 7, so even if the on-off valve 6 is provided, a considerable amount of residual gas still exists. Therefore, no significant improvement in combustion can be expected.

By the way, in this case, when the on-off valve 6 is closed in a low speed range other than idling, the differential pressure across the on-off valve 6 decreases compared to when idling, and the fresh air introduction time decreases due to the increase in rotational speed. , there is a certain amount of exhaust blowback, and this is actively used to eliminate so-called internal combustion caused by residual gas.
It is also possible to perform EGR to reduce NOx.

However, if exhaust gas blows back with the on-off valve 6 closed, the exhaust will come into contact with the on-off valve 6, and carbon and tar in the exhaust will adhere to the outer circumference of the on-off valve 6 and the support shaft 23. This may cause malfunction of the on-off valve 6 or poor sealing performance.

The purpose of this invention is to prevent the exhaust gas blown back into the high-speed intake port from coming into contact with the on-off valve when the on-off valve is closed, thereby solving problems such as malfunction and poor sealing of the on-off valve. shall be.

<Means for Solving the Problems> For this reason, the present invention includes a low-speed intake port and a high-speed intake port for each cylinder, and the high-speed intake port is closed in a low-speed region and opened in a high-speed region. In an intake system for an internal combustion engine equipped with an on-off valve, a fresh air introduction passage that introduces fresh air close to atmospheric pressure is provided downstream of the on-off valve of the high-speed intake port of each cylinder, and a fresh air outlet of the fresh air introduction passage is provided. is arranged near the on-off valve and parallel to the passage cross section of the high-speed intake port, or toward the upstream side of the high-speed intake port.

<Operation> With the configuration of the present invention, even if combustion exhaust flows into the high-speed intake port during the overlap period between the intake valve and exhaust valve installed in the high-speed intake port, the new exhaust gas is introduced from upstream of the throttle valve. An air curtain is formed near the downstream side of the on-off valve, and this air curtain prevents the surface of the on-off valve from being directly exposed to exhaust gas, thereby preventing malfunction and poor sealing of the on-off valve. be able to.

<Example> The example shown in FIGS. 1 to 4 will be described below. The same elements as the conventional example and the prior application example (including those not shown in the embodiment drawings) are shown in FIGS.
The explanation will be given using the same reference numerals as in FIG. 9.

FIG. 1 shows a first embodiment, in which the throttle valve 2
The fresh air outlet 41a of the fresh air introduction passage 41, which connects the upstream intake passage 22 and the downstream part of the on-off valve 6 of the high-speed intake port 4, is located near the downstream side of the on-off valve 6, and The air intake port 4 is oriented in the tangential direction of the inner wall and is slightly inclined toward the upstream side.

Further, an orifice 43 is interposed inside the housing 42 in which the on-off valve 6 is housed inside the fresh air outlet 41a.

In this way, the fresh air introduced from the fresh air outlet 41a of the fresh air introduction passage 41 swirls along the circumferential direction of the high-speed intake port 4 and the on-off valve 6, and the surface of the on-off valve 6 Since the air is blown out toward and along the surface, an air curtain covering the entire downstream side of the on-off valve 6 is formed.

Therefore, even if combustion exhaust flows into the high-speed intake port 4 during the overlap period between the high-speed intake valve 2 and the exhaust valve 5 on the high-speed intake port 4 side in the low-speed region where the on-off valve 6 closes, the on-off valve 6 closes. The air curtain formed near the downstream side of the on-off valve 6 can effectively prevent the surface of the on-off valve 6 from being directly exposed to the exhaust gas, and prevent malfunction of the on-off valve 6 due to adhesion and accumulation of carbon and tar in the exhaust gas. Therefore, it is possible to effectively prevent problems such as problems and poor sealing performance.

In the second embodiment shown in FIG. 2, the fresh air outlet ports 51a and 51b of the fresh air introduction passage 51 are formed by branching into a V-shape inside the housing 52, and an orifice 53 is interposed on the upstream side of the branching point. equipped.

Each fresh air outlet 5 branched into these two directions
1a and 51b are provided so that their opening directions are oriented in the tangential direction of the inner wall of the high-speed intake port 4, and are inclined toward the upstream side.

In this way, fresh air is introduced in opposite directions along the circumferential direction from two places, and the part where the flow velocity is high increases, so the effect of the fresh air as an air curtain is increased, and the pollutants in the exhaust are reduced. The effect of preventing adhesion and deposition is increased.

In the third embodiment shown in FIG. 3, a fresh air outlet of a fresh air introduction passage 62 is formed by cutting out downstream parts of the on-off valve 6 on both sides of the on-off valve 6 on both sides of the support shaft 61 of the on-off valve 6. 62a, 62b are formed, and branch passages 62c, 62d are connected to the housing 6, and these fresh air outlets 62a, 62b communicate with each other when the on-off valve 6 is closed.
3, and an orifice 64 is interposed in the fresh air introduction passage 62 on the upstream side of the branch passage 62d.

In this way, the housing 63 of the support shaft 61
Since fresh air is blown out from the vicinity of both ends that are freely slidably supported on the inner wall, the effect of preventing contaminants from adhering to the exhaust gas from accumulating on these parts is particularly great, and the smooth rotation of the support shaft 61 can be maintained well. is large.

In this case, the fresh air outlets 62a, 62b
are sufficiently close to the on-off valve 6, so the opening direction may be parallel to the on-off valve 6.

A fourth embodiment is shown in FIG. 4, in which fresh air outlets 71a and 71b of a fresh air introduction passage 71 are formed to branch into two directions inside a housing 72.
It is provided in a direction perpendicular to the support shaft 23 of the on-off valve 6 and inclined toward the upstream direction of the high-speed intake port 4 when the on-off valve 6 is closed.

An orifice 73 is installed upstream from the branch point of the fresh air blow-off ports 71a and 71b.

By the way, if pollutants in the exhaust gas adhere and accumulate on both ends 6a and 6b of the opening/closing valve 6 in the direction perpendicular to the support shaft 23, the sticking force due to the viscosity of the deposits will increase the rotational resistance when the valve is opened, resulting in a large start. moment is required.

Therefore, as in this embodiment, fresh air is blown out from a direction perpendicular to the support shaft 23 of the on-off valve 6 to prevent the contaminants from adhering and accumulating on both ends 6a and 6b. 6 is suppressed, and the actuator 10 for operating the on-off valve 6 is suppressed.
The driving force can also be reduced.

<Effects of the invention> As explained above, according to the invention, a fresh air introduction passage for introducing fresh air close to atmospheric pressure is provided downstream of the on-off valve of the high-speed intake port of each cylinder, and the fresh air introduction passage is By arranging the fresh air outlet near the on-off valve and parallel to the passage cross section of the high-speed intake port, or toward the upstream side of the high-speed intake port, the overlap between the high-speed intake valve and the exhaust valve is avoided. Even if combustion exhaust flows into the high-speed intake port during this period, the fresh air introduced from upstream of the throttle valve will form an air curtain in the vicinity of the downstream side of the on-off valve in the high-speed intake port, causing the surface of the on-off valve to This eliminates the risk of direct exposure to exhaust gas, prevents contaminants such as carbon and tar in the exhaust from accumulating near the on-off valve, and maintains good operability and sealing performance of the on-off valve over a long period of time. This effect can be obtained.

[Brief explanation of drawings]

FIG. 1A is a plan sectional view of a main part showing a first embodiment of the present invention, FIG. FIG. 2B is a cross-sectional view of the main part of FIG. Figure, Figure 4A
is a plan sectional view of a main part showing a fourth embodiment of the present invention,
FIG. 4B is a cross-sectional view taken from FIG.
Fig. 6 is a graph showing the lift characteristics of the intake and exhaust valves of the above engine, Fig. 7 is a longitudinal sectional view of the main parts of the above device, and Fig. 8 is an overall outline of the intake system for an internal combustion engine proposed by the applicant. FIG. 9A is a side view of the mounting part of the on-off valve used in the above device, FIG. 9B is a plan view of the same, and FIG. 10 is a time chart showing the characteristics of each part of the same device. . 1...Intake valve for low speed, 2...Intake valve for high speed, 3
...Intake port for low speed, 4...Intake port for high speed, 6...Opening/closing valve, 41, 51, 62, 71...
Fresh air introduction passage, 41a, 51a, 51b, 62
a, 62b, 71a, 71b... Fresh air outlet.

Claims (1)

[Scope of utility model registration request] In an intake system for an internal combustion engine, each cylinder is provided with a low-speed intake port and a high-speed intake port, and the high-speed intake port is provided with an on-off valve that closes in a low-speed region and opens in a high-speed region. A fresh air introduction passage that introduces fresh air close to atmospheric pressure is provided downstream of the on-off valve of the high-speed intake port, and the fresh air outlet of the fresh air introduction passage is located near the on-off valve and has a cross section of the passage of the high-speed intake port. An intake device for an internal combustion engine, characterized in that it is arranged parallel to or toward the upstream side of a high-speed intake port.