JPH07247872A - Compression ignition internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] By performing self-ignition combustion in the clevis region around the combustion chamber and starting the premixed fuel introduced into the center of the combustion chamber by the self-ignition combustion,
To obtain a highly efficient engine with little generation of HC and NOx. [Structure] Two intake valves 8a, 8b per cylinder and two intake ports 6a, 6b corresponding thereto, and intake air is concentrated in one of the intake ports 6a in a low speed and high load operation range to enter the cylinder. An SCV 21 that causes an intake swirl, a first fuel injection valve 11 that injects light oil into the intake stroke of the port 6a, and a second fuel injection that injects gasoline to the intake ports 6a and 6b outside the intake stroke. Valve 12 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compression ignition type internal combustion engine for supplying two kinds of fuels having different ignitability.

[0002]

2. Description of the Related Art A spark ignition type internal combustion engine ignites a premixed mixture of gasoline fuel with an ignition plug provided in a combustion chamber and mainly causes combustion by propagation of a turbulent flame. However, a drawback thereof is that at high load, knocking occurs due to self-ignition of fuel in the final combustion region far from the spark plug, and therefore it is difficult to increase the compression ratio for improving thermal efficiency.

Further, since the final combustion region is a low temperature portion such as the cylinder wall surface or the top land clevis region (groove-shaped region between the piston top land and the cylinder wall surface) at the time of partial load, a large amount of unburned HC is discharged. There is also a problem in terms of emission that a heat generation pattern becomes a high concentration of NOx.

On the other hand, in the compression ignition type internal combustion engine, fuel having a high self-igniting property such as light oil is injected and supplied to the combustion chamber whose temperature is high due to the high compression ratio and is burned mainly by diffusion combustion. Knocking does not occur at high load like ignition type, but the specific air output is low and the specific output is small, and when the load is low, a specific knocking sound is generated due to the combustion of premixed fuel formed by the initial injection fuel. There are drawbacks. Further, although emission of HC is very small in terms of emission, smoke and NOx are particularly problematic in a high load range. (Refer to "Automotive Technology Handbook", Vol. 1, page 28 et seq. Issued by Japan Society of Automotive Engineers, December 1, 1990.) The present invention provides a compression ignition type internal combustion engine which solves the problems of the conventional internal combustion engine. It is intended to be provided.

[0005]

According to the present invention, two intake valves per cylinder and two intake ports corresponding to the intake valves are provided.
A swirl generating means that concentrates intake air in one intake port to cause an intake swirl in a cylinder in a low-speed high-load operating region, a first fuel injection valve provided so as to face the port, and an intake port of each intake port. A fuel having a relatively high self-ignitability is supplied to the second fuel injection valve and the first fuel injection valve, which are provided upstream of the branch portion, and a fuel having a relatively high self-ignitability is supplied to the second fuel injection valve. Of a predetermined amount according to the operating state at that time by driving the first fuel injection valve inside the intake stroke and the second fuel injection valve outside the intake stroke. And control means for injecting fuel.

[0006]

When the intake valve is opened at low speed and high load, the intake flow is concentrated in one intake port through the swirl generating means, so that intake air is introduced into the cylinder substantially tangentially to the cylinder wall surface. This causes a swirl in the cylinder.

At this time, a highly self-igniting fuel is injected and supplied to the intake port via the first fuel injection valve,
This fuel is unevenly distributed near the cylinder wall surface due to the action of the swirl from the compression stroke to the combustion stroke.

This fuel self-ignites under high compression conditions at the end of the compression stroke and starts combustion near the cylinder wall surface.

On the other hand, the fuel injected and supplied outside the intake stroke through the second fuel injection valve is introduced into the cylinder through the intake ports upon entering the intake stroke, and is surrounded by the swirl and is generally in the combustion chamber. Will be urged to the central part of.

The air-fuel mixture formed by this fuel comes into contact with the above-mentioned self-ignited combustion gas to start combustion. The fuel from the second fuel injection valve is injected before the intake stroke is started and is sufficiently premixed with the air in the port, so that the fuel is efficiently burned under good air utilization. Further, since this combustion is performed near the center of the combustion chamber, knocking due to end gas formation near the cylinder wall surface due to flame propagation does not occur.

In this way, the combustion is started by the fuel mixture having a high cetane number concentrated near the wall surface of the cylinder by the swirl, and the premixture by the fuel having low self-ignitability introduced in the center of the cylinder is burned. As a result, HC from the cylinder wall or clevis area during low load operation
Emissions and knocking in the high load operation range are suppressed, and air utilization is improved to improve smoke and fuel efficiency.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1 or 2, 1 is a cylinder,
2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is an exhaust port, 6a and 6b are intake ports, 7 is an exhaust valve, 8
Reference numerals a and 8b are intake valves, and 9 is an intake manifold.

As shown in FIG. 2, the intake manifold 9 is branched from the middle to form two intake ports 6a for each cylinder.
Connect to 6b. The first intake port 6a is located at the bottom of the first intake port 6a so that the first intake port 6a is oriented near the umbrella portion of the intake valve 8a.
Electromagnetic fuel injection valve 11 is provided, and the intake manifold 9 upstream of the electromagnetic fuel injection valve 11 has intake ports 6a, 6
The second electromagnetic fuel injection valve 12 is provided so as to be located on the upstream side of the branch portion of b.

A fuel having a high cetane number with a high self-ignitability, such as light oil, is supplied from the fuel tank 14 to the first fuel injection valve 11 via the first fuel supply means 13.
Further, the second fuel supply means 1 is provided in the second fuel injection valve 12.
Fuel having a lower self-ignitability than that of the fuel, for example, gasoline is supplied from the fuel tank 16 through 5.

Although not shown, each fuel supply means 13 and 15 is provided with a pump for pumping fuel, a regulator for adjusting the discharge pressure of the pump to a constant value, a return passage for returning excess fuel to the tank side, and the like. Each fuel injection valve 11,1
2 is designed to inject and supply a quantity of fuel proportional to the valve opening time while supplying a constant pressure fuel.

Reference numeral 17 is a control means composed of a microcomputer or the like for driving the fuel injection valves 11 and 12 to open and close. The load sensor 19 and the engine speed sensor 20 output a load signal corresponding to the opening of the throttle valve 18. Fuel injection by determining the injection supply amount (pulse width of the drive signal corresponding to the valve opening time of the injection valve) of each of the above fuels based on the output from Valve 11,
Control twelve.

The timing for injecting and supplying the fuel is set during the intake stroke in which the intake valves 6a and 6b of the first fuel injection valve 11 open, and during the other period of the second fuel injection valve 12. ing.

On the other hand, a swirl control valve (S) as a swirl generating means is provided in the middle of the intake manifold 9 so as to be located upstream of the second fuel injection valve 12.
CV) 21 is interposed.

The SCV 21 is supported by a horizontal valve shaft 22 so that it can be opened and closed. As shown in FIG. 2, in the valve closed state, the notch 23 formed on the side of the first intake port 6a. 2 to increase the intake flow velocity and concentrate the high-speed intake flow on the side of the first intake port 6a, whereby the intake air is introduced tangentially to the cylindrical surface of the cylinder 1 in the counterclockwise direction in FIG. Causes swirl in the cylinder.

The SCV 21 is opened / closed by the control means 17 via an actuator (not shown) based on the signals from the sensors 19 and 20, and is closed in a low speed and high load operating state, and in other operating ranges. Control to fully open.

An appropriate compression ratio differs depending on the scale and use of the engine, but in the case of a small automobile engine, for example, it is set to be equal to or slightly lower than that of a general diesel engine, for example, about 18 to 20.

Next, the operation will be described.

At low speed and high load, when the intake valves 8a, 8b are opened, the speeded-up intake flow is concentrated to the first intake port 6a via the SCV 21, and a substantially horizontal swirl is generated in the cylinder 1. .

At this time, the light oil injected and supplied to the intake port 6a via the first fuel injection valve 11 is unevenly distributed near the cylinder wall surface together with the swirl up to the compression top dead center.

Since light oil has a high cetane number and high self-ignitability, it easily self-ignites under high compression conditions at the end of the compression stroke,
Combustion starts near the cylinder wall.

On the other hand, the gasoline fuel injected and supplied outside the intake stroke through the second fuel injection valve 12 is introduced into the cylinder 1 through the intake ports 6a and 6b when entering the intake stroke, and is almost in the combustion chamber. Combustion is started by contacting the above-mentioned combustion gas due to self-ignition at the central part of.

Gasoline from the second fuel injection valve 12 is injected before the intake stroke is started and the fuel is injected into the ports 6a, 6a.
Since it is sufficiently premixed with the air in b, it burns efficiently with good air utilization.

In this way, combustion is started by the light oil having a high self-ignitability which is unevenly distributed near the wall surface of the cylinder 1 by the swirl, and the premixed fuel with gasoline having a low self-ignitability introduced into the center of the cylinder by this combustion Combustion is started.

Gasoline burns in a premixed state in a state of being sufficiently mixed with air, and unlike the conventional combustion by flame propagation toward the periphery of the combustion chamber, it is caused by light oil in the vicinity of the center of the combustion chamber. Combustion is started by coming into contact with the compression ignition combustion part, so that knocking due to spontaneous ignition of the end gas does not occur and combustion is excellent.

Further, unburned HC near the cylinder wall surface or in the topland clevis region generated by the low temperature quench layer burns together with the combustion of light oil in the peripheral portion of the combustion chamber 4 due to the swirl, and the peripheral portion of the combustion chamber 4 has a volume. Is small, the initial combustion ratio is small, and therefore, a heat generation pattern with less NOx generation is obtained.

On the other hand, since the ignition combustion is started by the self-ignition of light oil, it is necessary to burn the air-fuel mixture having the same lean air-fuel ratio (excess air ratio) as the conventional diesel engine by diffusion combustion even in the partial load operation range. In addition, since it is not necessary to restrict the intake air, it is possible to greatly improve the thermal efficiency.

Further, by closing the SCV 21 even in the partial load operation range, the mixing action of the swirl promotes the mixing of the fuel and air to obtain a better combustion property, so that the generation of smoke can be suppressed. it can. In addition, since the main fuel (gasoline) can be supplied to the combustion chamber in a premixed state, smoke is not generated even in a high load operation range, and air is used well, so fuel consumption and output are also improved.

The swirl generating means is not limited to the SCV 21 described above, but may be a valve operating mechanism in which one intake valve 8a is opened earlier than the other intake valve 8b. It may be.

[0035]

As described above, according to the present invention, the fuel having a low self-ignitability introduced into the central portion of the cylinder is started by the fuel mixture having a high cetane number concentrated near the wall surface of the cylinder by the swirl. As a result, the premixture is burned, which suppresses HC emissions from the cylinder wall or clevis area during low load operation and knocking in high load operation area, and improves smoke utilization by improving air utilization. It is possible to improve fuel efficiency and specific output while reducing fuel consumption.

Further, the present invention does not require an ignition system such as a spark ignition type engine, and can reduce the precious metal carrying rate when a catalyst is used in the exhaust system due to a small amount of HC and NOx. There is also an advantage that it can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

FIG. 2 is a plan sectional view of an intake port portion of the embodiment.

[Explanation of symbols]

 1 cylinder 2 piston 3 cylinder head 4 combustion chamber 5 exhaust port 6a first intake port 6b second intake port 7 exhaust valve 8a first intake valve 8b second intake valve 9 intake manifold 11 first fuel injection valve 12 2nd fuel injection valve 13 1st fuel supply means 15 2nd fuel supply means 17 Control means 18 Throttle valve 19 Load sensor 20 Rotation speed sensor 21 Swirl control valve (SCV) 23 Notch

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location F02D 41/34 F 9247-3G C 9247-3G 41/40 A 9247-3G F02M 37/00 341 E 61/14 310 Z

Claims (1)

[Claims] 1. An intake swirl is generated in a cylinder by concentrating intake air into two intake valves per cylinder and two intake ports corresponding thereto and one intake port in a low speed and high load operation range. Swirl generating means, a first fuel injection valve provided so as to face the port, a second fuel injection valve provided at an upstream side of a branch portion of each intake port, and a first fuel The fuel supply means for supplying fuel having a relatively high self-ignitability to the injection valve and the fuel having a relatively low self-ignitability to the second fuel injection valve, and the first fuel injection valve in the intake stroke A compression ignition internal combustion engine, comprising: a control unit that drives each of the second fuel injection valves outside the stroke to inject a predetermined amount of fuel according to the operating state at that time.