JP2569076B2 - Ignition timing control device for supercharged engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ignition timing control device for a supercharged engine for effectively scavenging residual exhaust gas in a combustion chamber of an engine and improving combustibility. It is about.

(Prior Art) In an engine equipped with a supercharger, in order to prevent the temperature of the combustion chamber from rising due to the exhaust gas remaining in the combustion chamber and to prevent knocking, the residual exhaust gas in the combustion chamber is Conventionally, scavenging is performed using a supercharging pressure.

For example, Japanese Unexamined Patent Publication No. 61-185628 discloses that, during driving of a supercharger, a period from the start of opening of an intake valve to the end of closing of an exhaust valve (so-called overlap period) is defined as an operating state of an engine. The engine with a supercharger is shown in which the exhaust gas is pushed out of the combustion chamber by using the pressure of the supercharger and the exhaust gas is scavenged to improve the combustibility.

The relationship between the intake and exhaust pressures and the load in such a supercharged engine is generally shown in the graph of FIG. In the figure, the intake pressure is indicated by a solid line 41,
The exhaust pressure is indicated by broken lines 42, respectively.

As shown in this figure, in the low engine load range,
The intake pressure is lower than the atmospheric pressure, and knocking is unlikely to occur. In addition, in the high load region of the engine, the intake pressure (supercharging pressure) exceeds the exhaust pressure, and scavenging of the combustion chamber can be performed using the supercharging pressure as described above. Also, the occurrence of knocking is prevented.

However, in the middle load region where the load is slightly lower than the point P shown in the figure, that is, the point where the supercharging pressure and the exhaust pressure match, a state in which the knocking occurs where the intake pressure exceeds the atmospheric pressure is relatively likely to occur. In addition, since the exhaust pressure is higher than the intake pressure, the effect of preventing knocking as described above is hardly obtained. That is, in the conventional turbocharged engine as described above, knocking is likely to occur in a medium load region where the intake pressure is lower than the exhaust pressure, even if knocking is prevented in a high load region where the intake pressure exceeds the exhaust pressure. There were drawbacks.

(Object of the Invention) In view of the above circumstances, the present invention provides an ignition timing control device for a supercharged engine that can prevent knocking even in a medium load region where the supercharging pressure is lower than the exhaust pressure. With the goal.

(Structure of the Invention) The present invention relates to an engine with a supercharger provided with a supercharger and configured to scavenge exhaust gas in a combustion chamber with supercharged air when an opening period of an intake port and an exhaust port overlap each other. Control means is provided for controlling the ignition timing of the engine such that the ignition timing in the medium load region in which the atmospheric pressure exceeds the supercharging pressure is later than the ignition timing in the high load region in which the supercharging pressure exceeds the exhaust pressure. .

With this configuration, the ignition timing in the medium load region where the exhaust pressure exceeds the supercharging pressure is delayed from the ignition timing in the high load region, so that the scavenging effect of the supercharging pressure is obtained in this medium load region. If not, knocking is prevented.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a view schematically showing a supercharged engine 1 provided with the device of the present invention, and FIG. 2 is a plan view thereof. As shown in the figure, the combustion chamber 2 of the engine 1 includes:
A spark plug 3 is provided and a first intake port 4
a, a second intake port 4b, and an exhaust port 5 are provided. The first intake port 4a
A second intake passage 7 independent of the first intake passage 6 is connected to the intake port 4b, and an exhaust passage 8 is connected to the exhaust port 5 respectively. A fuel injection valve 9 is provided in the first intake passage 6, and an opening / closing control valve 10 is provided in the second intake passage 7.

The first intake port 4a, the second intake port 4b, and the exhaust port 5 are a first intake valve 11, a second intake valve 12,
In this embodiment, the opening period of the first intake port 4a and the opening period of the exhaust port 5 do not overlap, and the second intake port
The opening / closing timing of each port is set so that the open period of 4b and the open period of the exhaust port 5 overlap for a predetermined period.

The first intake passage 6 and the second intake passage 7 join the intake passage 14 on the upstream side of the fuel injection valve 9 and the opening / closing control valve 10, and a throttle valve 15 is provided in the intake passage 14. An air cleaner 16 and an air flow meter 17 are provided on the upstream side.

A mechanical supercharger 18 is provided in the intake passage 14 downstream of the throttle valve 15.
A bypass passage 19 that bypasses 18 is provided, and a control valve 20 that opens and closes the bypass passage 19 is provided in the bypass passage 19.

Further, the engine 1 has a control unit (control means) 21. This control unit 21
Has an air amount detection signal from the air flow meter 17,
An engine speed detection signal from a crank angle sensor (not shown), an intake pressure detection signal from a pressure sensor (not shown), and the like are input. The control unit 21 Outputs a drive signal to the opening / closing control valve driving means 22 to control the opening / closing of the opening / closing control valve 10, and outputs a control signal to the spark plug 3 to control the ignition timing.

Regarding the opening and closing of the on-off control valve 10, the on-off control valve 10 is closed in the low-load low-rotation region of the engine so that supercharging from the second intake port 4b is not performed, and the on-off control valve 10 is opened in other regions The supercharged air is sent into the combustion chamber.

The ignition timing of the ignition plug 3 is set as shown in FIG. As shown in the figure, in the region from low load to medium load (in FIG. 4, the region where the exhaust pressure exceeds the intake pressure almost up to the point P), the ignition timing increases as the load increases. The ignition timing is set so as to delay the load. Conversely, in the region from the medium load to the full load (in FIG. 4, in the region after the point P, the intake pressure exceeds the exhaust pressure), the load is large. The ignition timing is set so that the ignition timing is advanced as the time becomes.

That is, in the engine 1, the ignition timing in the medium load region where the exhaust pressure exceeds the intake pressure (supercharging pressure) is delayed from the ignition timing in the high load region where the intake pressure (supercharging pressure) exceeds the exhaust pressure, The ignition timing is set so that the retard angle of the ignition timing becomes maximum in this medium load region.

In the engine 1 having such a configuration, in the low-load low-speed operation region, the on-off control valve 10 is closed,
Intake is performed only at the first intake port 4a, which has almost no overlap with the exhaust port 5 during the open period. On the other hand, since the intake pressure and the exhaust pressure are in a low state below the atmospheric pressure as shown in FIG. 4, knocking hardly occurs in this low load region.

Further, in a high load region close to the full load state, the opening / closing control valve 10 is opened, so that the intake is also performed by the second intake port 4b having an overlap with the exhaust port 5 with respect to the open period. Moreover, the supercharging pressure at this time is
Since the exhaust pressure exceeds the exhaust pressure as shown in FIG. 4, when the opening period of the second intake port 4b and the exhaust port 5 overlaps, the residual gas in the combustion chamber 2 is reduced by the effect of the supercharging pressure. It is pushed out and scavenging in the combustion chamber 2 is performed. Therefore, the occurrence of knocking is prevented by such a scavenging effect.

On the other hand, in the medium load region where the exhaust pressure is higher than the supercharging pressure, the above scavenging effect is not sufficiently obtained,
In addition, although the intake and exhaust pressures are relatively high, the third
As shown in the figure, since the ignition timing in the middle load region is set later than the ignition timing in the high load region, knocking is prevented by such a retard of the ignition timing.

As described above, in this device, in the middle load region where the exhaust pressure exceeds the supercharging pressure, the ignition timing in that region is
Since the ignition timing is set further than the ignition timing in the high load region, knocking can be prevented even if the scavenging effect by the supercharging pressure is not sufficiently obtained. In addition, since such a medium load region is not particularly frequently used, even if the ignition timing is delayed as described above, the combustion efficiency of the engine is hardly affected.

Conversely, in a high load region where a sufficient scavenging effect can be obtained, knocking is prevented without unnecessarily delaying the ignition timing.

(Effects of the Invention) As described above, the present invention relates to an engine with a supercharger in which exhaust gas in a combustion chamber is scavenged by supercharged air when an opening period of an intake port and an exhaust port overlap each other. However, since the ignition timing in the medium load region exceeding the supercharging pressure is delayed from the ignition timing in the high load region where the supercharging pressure exceeds the exhaust pressure, a sufficient scavenging effect by the supercharging pressure can be obtained. There is an effect that knocking can be prevented even in a medium load region where no knocking occurs.

[Brief description of the drawings]

FIG. 1 is a structural view of an engine according to an embodiment of the present invention,
FIG. 2 is a plan view of the engine, FIG. 3 is a graph showing the relationship between load and ignition timing in the engine, and FIG. 4 is a graph showing the relationship between load and intake and exhaust pressure in a general turbocharged engine. It is. 1 ... engine, 2 ... combustion chamber, 3 ... spark plug, 4a
... First intake port, 4b Second intake port, 5 Exhaust port, 21 Control unit (control means).

Claims (1)

(57) [Claims] A supercharged engine provided with a supercharger, wherein the supercharging air scavenges exhaust gas in a combustion chamber when an intake port and an exhaust port are open during an overlap period. Supercharging characterized by comprising control means for controlling the ignition timing of the engine such that the ignition timing in the medium load region exceeding the atmospheric pressure is later than the ignition timing in the high load region in which the supercharging pressure exceeds the exhaust pressure. Timing control device for engine with engine.