JPS5833376B2 - Intake system for supercharged engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an intake system for a supercharged engine.

Conventionally, it is well known that a turbocharger for intake supercharging is installed in the intake passage to improve intake air filling efficiency and increase output. Engines have a problem in that the pressure and temperature in the combustion chamber increase, which tends to cause knocking.

To deal with this knocking, methods have been proposed to lower the set level of boost pressure or install a cooler in the intake passage to lower the intake air temperature (for example, Japanese Utility Model Application No. 50-59405), but the former method In the latter case, a sufficient increase in output, which is the original purpose of a supercharger, could not be obtained, and in the latter case, there were drawbacks such as a complicated structure.

By the way, when we consider the intake air temperature, we find that this rise in intake air temperature is not only due to the adiabatic compression of the supercharger;
It has become clear that the dilution gas (residual exhaust gas) remaining in the combustion chamber has a considerable effect.

The present invention focuses on the fact that knocking is largely controlled by dilution gas remaining in the combustion chamber,
Under high load conditions, when the supercharger is essentially operating, the overlap between intake and exhaust air is used to scavenge the dilution gas in the combustion chamber using supercharging pressure, preventing a rise in intake air temperature.
The basic purpose is to prevent knocking without reducing output.

However, as mentioned above, if the overlap between intake and exhaust is increased to scavenge the dilution gas in the supercharging region, the pressure in the intake hoard is lower than the pressure in the exhaust port in the non-supercharging region. That is, during light load operation, there is a problem in that a large amount of dilution gas remains, resulting in extremely poor drivability.

The present invention has been made with attention to this point, and includes a primary intake port and a secondary intake port, and connects the primary intake port and the secondary intake port to a primary intake port having a primary throttle valve. and a secondary intake passage having a secondary throttle valve, and each intake passage is communicated with a turbocharger, and the opening timing of one of the intake ports is determined as the exhaust port closing timing. By setting the opening timing of the other intake port to be earlier than the opening timing of the one intake port mentioned above, and increasing the overlap between the exhaust port and one intake port, supercharging can be achieved. At the same time, by reducing the overlap of the other intake port, it simultaneously satisfies the low range of dilution gas brought in in the light load range. The present invention provides an intake system for a supercharged engine.

Embodiments of the invention will now be described in detail with reference to the accompanying drawings.

In the reciprocating engine shown in FIG.
A primary intake port 1 that is opened and closed by a primary intake valve 13 that is interlocked with a cam 12 for a combustion chamber 11 defined by;
2, which is opened and closed by a secondary intake valve 15 that is linked to a cam 14.
Next intake port 2 and exhaust valve 17 linked to cam 16
An exhaust port 18 that is opened and closed by the exhaust port 18 is provided.

The primary intake port 1 communicates with a primary intake passage 4 having a primary throttle valve 3, and the secondary intake port 2 communicates with a secondary intake passage 6 having a secondary throttle valve 5. It communicates with passage 19.

The primary intake passage 4 and the secondary intake passage 6 are connected to a turbo supercharger 7 that supercharges intake air by a blower 21 that is linked to a turbine 20 that is rotated by exhaust gas pressure in an exhaust passage 19 .

Fuel injection nozzles 8 and 9 are provided immediately downstream of each throttle valve 3 and 5 in the primary and secondary intake passages 4 and 6, respectively, and the output of the flow meter 22 is input to each fuel injection nozzle 8 and 9. The fuel injection amount is controlled by a controller 23.

Note that the passage diameter of the primary intake passage 4 is 2/3 that of the secondary intake passage.
It is set to a small diameter.

In the above configuration, as shown in FIG.
The secondary intake port 2 and the exhaust port 18 are set to overlap), and the opening timing of the primary intake port 1 by the primary intake valve 13 is set to be delayed from the opening timing of the secondary intake port 2 by the secondary intake valve 15. (so that the overlap is essentially zero).

In the supercharging region, that is, in the high-load operating region, the intake pressure is higher than the exhaust pressure, so the overlap between the secondary intake port 2 and the exhaust port 18 causes the residual exhaust gas, ie illusion gas, in the combustion chamber 11 to be transferred to the secondary intake. Air intake from port 2 will quickly scavenge air from exhaust port 18,
As a result, the dilution gas in the combustion chamber 11 is reduced 7, the temperature rise of the intake air due to the dilution gas is eliminated, and knocking is reduced.

In addition, in the light load operating range, the intake pressure becomes lower than the exhaust pressure (negative pressure), and the 2
Dilution gas flows into the secondary intake port 2, but since the primary intake port 1 does not overlap with the exhaust port 18, the dilution gas is not carried into the primary intake port 1, and the combustible gas is unnecessarily caused. will not be harmed.

At the same time, the timing for opening the primary intake port 1 by the primary intake valve 13 precedes the timing for closing the exhaust port 18 by the exhaust valve 17 (primary intake port 1 and exhaust port 18
The opening timing of the secondary intake port 2 by the secondary intake valve 15 is set to be later than the opening timing of the primary intake port 1 by the primary intake valve 13 (so that the overlap is substantially This section explains the effect when the value is set to zero).

In the supercharging region, that is, in the high-load operation region, due to the overlap between the primary intake port 1 and the exhaust port 18, the dilution gas in the combustion chamber 11 is quickly scavenged from the exhaust port 18 with the intake air from the primary intake port 2. As a result, the dilution gas in the combustion chamber 11 decreases,
As in the case above, knocking is reduced.

In addition, in the light load operating range, dilution gas is brought into only the primary intake port 1, contrary to the case where the secondary intake port 2 is overlapped and the primary intake port 1 is not overlapped. Since the fuel is not brought into the secondary intake boat 2, the combustibility is not unnecessarily impaired as in the case described above.

As shown in FIG. Dilution in the supercharging range can be achieved without unnecessarily impairing drivability at light loads by setting a large setting or by providing an overlap on one intake port and making the overlap on the other intake port virtually zero. This is intended to improve gas scavenging and reduce the occurrence of knocking due to a rise in temperature of intake air, but the intake port providing the overlap may be on the primary side or the secondary side. However, it may be selected appropriately depending on the characteristics of the engine.

In other words, if the secondary intake port is provided with an overlap, and the overlap of the primary intake port is set to be smaller than that of the secondary side, or if the overlap is set to be smaller than that of the secondary side, the primary intake port will be provided with an overlap during light load operation. Compared to , during the overlap period, the wall flow of fuel flowing on the wall of the intake passage is 1
Since it is not disturbed by the inflow of dilution gas into the secondary intake port, it has the advantage of stably supplying fuel for each cycle. However, if the primary intake port is provided with an overlap and the secondary intake port overlap is set to be smaller than the primary side or to zero, the above-mentioned On the contrary, although the total amount of dilution gas decreases, there is a drawback that the wall flow of fuel flowing through the primary intake passage becomes unstable.

(In this case, if the injection nozzle 8 on the primary intake passage side is provided near the intake port as shown by the phantom line, the wall flow will not become unstable.

) Therefore, for engines that are susceptible to the effects of illusion gas at light loads, it is better to set the overlap of the intake ports to the primary intake port; For engines that are susceptible to damage, it is better to provide overlap at the secondary intake ports.In short, the overlap setting for each intake port depends on various factors such as the air-fuel ratio, fuel supply position, and intake passage area ratio. Appropriate depending on engine specifications.

Just choose.

In addition, in the above embodiment, the closing timing of the primary intake port and the secondary intake port is set to approximately the same time after the bottom dead center (B, D, C), so the opening time of both intake ports is maximized. Therefore, the intake amount of the air-fuel mixture can be secured without unnecessarily increasing the diameter of the primary intake port, and low-speed stability can be further improved.

In addition, in the above embodiment, a fuel injection device is used, but a carburetor may also be used.

As is clear from the above description, the present invention allows one of the primary and secondary intake ports to overlap the exhaust port, and opens the other intake port later than the opening timing of the other intake port. Because it is set as follows, without compromising combustion stability in light load range,
Knocking in the supercharging region can be reduced as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a side view of the system of an intake system for a supercharged engine according to the present invention, and FIG. 2 is a graph showing the opening/closing timing of intake and exhaust valves. 1...Primary intake port, 2...Secondary intake port, 3
...Primary throttle valve, 4...Primary intake passage, 5...2
Secondary throttle valve, 6... Secondary intake passage, 7... Supercharger, 1
8...Exhaust port.

Claims (1)

[Claims] The primary intake port and the secondary intake port are provided with an 11th intake port and a secondary intake port, and the primary intake port and the secondary intake port are connected to a primary intake passage having a primary throttle valve and a secondary intake passage having a secondary throttle valve. An engine equipped with a supercharger, which communicates with an intake passage, connects the primary intake passage and the secondary intake passage to a supercharger, and further supplies fuel from at least the primary intake passage. , The opening timing of one of the primary intake port and the secondary intake port is set to precede the closing timing of the exhaust boat, and the opening timing of the other intake port is set to precede the opening timing of the one intake port. An intake system for an engine with a supercharger, characterized in that the intake system is set to be delayed in time. 2. The intake system for a supercharged engine according to claim 1, wherein the one intake port is a primary intake port, and the other intake port is a secondary intake port. 3. The intake system for a supercharged engine according to claim 1, wherein the one intake port is a secondary intake port, and the other intake port is a primary intake port.