JPH06101482A - Direct cylinder injection type engine - Google Patents

Abstract

PURPOSE:To improve ignitability during stratified charge and to reduce an amount of discharged toxic component in exhaust gas by featuring arrangement of the fuel injection valve and the ignition plug of a direct fuel injection type engine. CONSTITUTION:Regarding the direction of a swirl flow, an injector A30, an injector B31, and an ignition plug 40 are arranged in a combustion chamber, in order, from the upper coarse. At the same time a radius extending from the central line of a cylinder is arranged short in order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct cylinder fuel injection engine, and more particularly to a stratified charge engine.

[0002]

2. Description of the Related Art Conventionally, there has been proposed a method of increasing a compression ratio to improve combustion efficiency in order to improve fuel efficiency and output of an engine. However, for example, in a gasoline engine, when the compression ratio becomes a high compression ratio of about 10, there is a problem that abnormal combustion called knocking occurs, resulting in output reduction, noise increase, piston melting loss, etc., and there is a limit to increasing the compression ratio. there were.

However, of the basic strokes of the engine, which are intake, compression, expansion, and exhaust, only the air is sucked in the intake stroke and the fuel is directly injected into the combustion chamber immediately before ignition by using the fuel injection valve. In the engine of the type, not only the knocking described above can be avoided, but also the stratified charge can be realized relatively easily by supplying the fuel spray injected from the fuel injection valve to the vicinity of the spark plug. The air-fuel ratio of the air-fuel mixture is greatly increased from the theoretical air-fuel ratio, for example, 14.7 for gasoline, so that a so-called lean mixture can be ignited and burned, and a lean burn generally called lean burn is relatively performed. It is easily feasible.

[0004]

However, in the above direct fuel injection type engine, the time required from the fuel injection from the fuel injection valve to the spark ignition from the spark plug is short, and the vaporization and atomization of the fuel until the spark ignition. Insufficient combustion occurs, resulting in increased emission of harmful exhaust gas such as unburned fuel and deterioration of ignition stability of air-fuel mixture.

In order to solve the above-mentioned problems, the actual construction of Sho 62-93
Japanese Patent No. 164 discloses a configuration in which a spark plug is arranged on the swirl downstream side of a fuel injection valve for ignition with respect to a swirl flow in a combustion chamber, and the fuel spray is directed to the spark plug to inject fuel spray in the vicinity of the spark plug. There is a thing which concentrates and improves ignition performance. By placing the fuel spray injected from the fuel injection valve installed in the combustion chamber on the swirl flow, the disturbance caused by the swirl flow is used to promote vaporization and atomization of the fuel spray while forming the fuel spray itself into a band shape. Therefore, diffusion of fuel spray can be prevented, and stratified charge can be realized relatively easily. However, the swirl flow is used to direct the fuel spray toward the spark plug, and since the swirl velocity flows along the cylinder wall surface, not only the fuel spray deviates in the cylinder radial direction, but also the fuel spray Some of them have a problem that they adhere to the inner wall of the cylinder and contribute to the increase of blow-by gas. That is, although the configuration disclosed in the above publication has the effect of improving ignitability,
As a compensation, there is a problem that the proportion of unburned fuel components in the exhaust gas increases.

The present invention has been made in view of the above circumstances, and it is possible to reduce unburned fuel components by forming stratified charge at an optimum position while improving vaporization and atomization of fuel. The purpose is to achieve both improvement of ignitability.

[0007]

[Means for Solving the Problems] Means for constructing the present invention in order to solve the above problems are as follows.

According to the first aspect of the present invention, a cylinder direct injection type in which a fuel injection valve for directly injecting fuel into the combustion chamber formed in the cylinder and an ignition plug for igniting the air-fuel mixture in the combustion chamber are provided. In the engine,

The fuel injection valve is provided at a position spaced a first predetermined distance in the radial direction with respect to the cylinder center line, and a spark plug is provided downstream with respect to the cylinder center line along the swirl flow in the combustion chamber. Spark plug provided at a position separated by a second predetermined distance longer than the first predetermined distance in the direction, and arranged downstream from the fuel injection valve arranged upstream of the swirl along the swirl flow formed in the combustion chamber. The fuel injection valve and the spark plug are arranged in the combustion chamber so that the second predetermined distance becomes longer as the distance in the swirl direction, which is the distance to the.

According to the second aspect of the present invention, each cylinder has two fuel injection valves and one spark plug, and is located upstream of the spark plug with respect to the swirl flow in the combustion chamber formed in the cylinder. The two fuel injection valves are arranged, and the first fuel injection valve on the side where the distance in the swirl direction is closer to the spark plug arranged in the combustion chamber and the upstream side in the swirl flow direction in the combustion chamber. And the second fuel injection valve whose distance in the swirl direction is farther from the spark plug is arranged in the order of increasing radius with respect to the cylinder center line.

According to a third aspect of the present invention, the first fuel injection valve has a better atomization characteristic of fuel spray than the second fuel injection valve is used. The ones listed.

According to the structure of claim 4, the difference between the first predetermined distance and the second predetermined distance is reduced as the particle size of the fuel spray injected from the fuel injection valve becomes smaller. Characterized by having setting means for setting to,
The thing of Claim 2 thru | or 3.

[0013]

Some direct fuel injection engines use a swirl flow generated in the combustion chamber to disturb the fuel spray injected from the fuel injection valve in order to rapidly realize vaporization and atomization of the fuel. At this time, since the fuel spray moves along the swirl flow direction, it receives centrifugal force radially outward from the cylinder center line and moves toward the cylinder side surface,
The main flow part of the fuel spray deviates to the cylinder wall surface side from the spark plug and does not reach the spark plug, which lowers the ignitability, or a part of the fuel spray adheres to the cylinder wall surface and the amount of unburned fuel discharged It also has the problem of increasing.

The average particle diameter of the fuel spray injected from the fuel injection valve is substantially determined by the fuel injection pressure and the shape of the fuel injection valve injection port, especially the injection port diameter. That is, the fuel injection pressure and the shape of the injection port are both design items that are generally determined at the design stage, and are requirements that do not change during engine operation, so injection from the fuel injection valve is performed regardless of engine operating conditions. In order to reduce the average particle size of the fuel spray, it can be achieved by increasing the fuel injection pressure or by narrowing the injection port diameter. However, the former means for increasing the injection pressure is accompanied by an increase in the size of the fuel injection device. Therefore, in the latter means for reducing the diameter of the injection port, the fuel injection rate is reduced, and therefore the direct fuel injection type engine in which the fuel injection time is limited causes the injection amount to be limited.

Further, since the flow velocity of the swirl flow generated in the combustion chamber is low when the engine speed is low and is high when the engine speed is high, the swirl ratio, which is the ratio between the engine speed and the swirl flow velocity, changes too much. Without increasing the engine speed, the time from the fuel injection valve injecting fuel spray to the spark plug starting electrical discharge is shortened, and the engine speed is increased. During the period from the start of injection to the start of electric discharge at the spark plug, the fuel spray having a certain average particle size receives a centrifugal force from the swirl flow and moves toward the cylinder wall surface at an increased moving speed. That is, the moving distance that the fuel spray receives the centrifugal force from the swirl flow and moves toward the cylinder wall surface becomes substantially constant regardless of the engine speed. Therefore,

According to the first aspect of the invention, the fuel injection valve for injecting the fuel spray having a predetermined average particle size is provided at a position separated from the cylinder center line by a predetermined radius as a mounting position in the combustion chamber. By disposing the spark plug at a position offset from the predetermined radius to the cylinder wall surface side by the above moving distance with respect to the mounting position of the fuel injection valve, the mainstream portion of the fuel spray is surely brought into contact with the spark plug to improve ignitability. The problem of the unburned fuel adhering to the wall surface of the cylinder can be relatively easily alleviated by optimizing the arrangement of the fuel injection valve and the spark plug while securing the same.

According to the second aspect of the present invention, when the plurality of fuel injection valves are arranged on the upstream side of the spark plug in the swirl flow direction, the fuel spray injected from any of the fuel injection valves is surely provided in the vicinity of the spark plug. Fuel injection valves installed at positions far from the spark plug can be used for uniform air-fuel mixture by changing the swirl flow direction distances of multiple fuel injection valves. By using the injection valve for stratified charge, it has both fuel efficiency improvement and harmful component reduction in exhaust gas while ensuring combustion stability under any operating conditions from low load to high load.

According to the third aspect of the invention, the fuel injection valves having different atomization characteristics of the fuel spray are provided in the same cylinder, and the atomization characteristics are good for the fuel injection valve on the side closer to the spark plug with respect to the swirl flow direction distance. By using a fuel cell, it is possible to obtain the effect of improving fuel efficiency and reducing harmful components in exhaust gas by ensuring stratified charge while ensuring combustion stability even in an operating range where combustion stability is poor, such as during low load or idling. .

According to the fourth aspect of the present invention, the design means is provided by setting the setting means for reducing the difference between the first predetermined distance and the second predetermined distance according to the atomization characteristics of the fuel injection valve. At this time, it becomes easy to determine the arrangement of the spark plug and the fuel injection valve with respect to the combustion chamber, which leads to a reduction in design time.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic structure of a direct fuel injection type engine to which the present invention can be applied.

The direct fuel injection engine 1 of this embodiment includes an air supply passage 2, an air cleaner 3, an air flow sensor 4,
Intake air temperature sensor 5, throttle valve 6, surge tank 7, pressure sensor 8, throttle opening sensor 9
, Supercharger 10, bypass passage 11, bypass valve 12, bypass valve opening sensor 13, water temperature sensor 14, exhaust passage 20, catalyst 21, injector A30, injector B31, and fuel pressure control Valve 32,
The fuel pump 33, the fuel pressure sensor 34, the spark plug 40, the ignition coil 41, and the control unit 50.
It is composed of

2 and 3 show the arrangement of the injector A30, the injector B31, and the spark plug 40 with respect to the combustion chamber of the engine 1. The intake air taken into the combustion chamber of the engine 1 through the intake passage 2 arranged in the engine 1 is a flow that is pre-deflected with respect to the cylinder center line, so that the influence of the rising piston during the compression stroke is affected. Upon receipt, the intake air rotates at high speed around an axis that is near and parallel to the cylinder center line and forms a vortex called a swirl flow in the combustion chamber. The injector A3 is configured to inject the fuel spray in substantially the same direction as the swirl flow direction.
0 and injector B31 are provided. That is, the injectors and the spark plugs 40 are arranged in the vicinity of the streamline of the swirl main flow having the highest flow velocity of the swirl flow generated in the combustion chamber, and the swirl flow direction from the upstream side to the swirl flow direction, The injector A30, the injector B31, and the spark plug 40 are arranged in this order. The fuel pressurized by the fuel pump 33 is supplied to the injector A30 and the injector B31 through the fuel pressure control valve 32 so that the fuel is controlled to a predetermined fuel pressure.

The spark plug 40 is the control unit 5
A high voltage is induced in the ignition coil 41 by the ignition signal from 0, and spark discharge is started. Further, the timing when the spark plug 40 starts the spark discharge is arbitrarily changed according to the operating state of the engine. Since the air-fuel mixture cannot be ignited if there is no air-fuel mixture in the vicinity of the spark plug at the discharge timing of the spark plug 40, the fuel injection signal is transmitted from the control unit 50 to the injector A30 and the injector B31. B3
An ignition signal is transmitted from the control unit 50 to the ignition coil 41 after a lapse of a predetermined time until the fuel injected from No. 1 is supplied to the vicinity of the ignition plug by the swirl flow.

As shown in FIG. 3, an injector A30, an injector B31, and an ignition plug 40 are arranged in the combustion chamber of the engine 1, and the injector A30.
The distance in the swirl direction with respect to the swirl flow line between the engine and the spark plug 40 is l ₁ , the injector B31 and the spark plug 4
The distance in the swirl direction with respect to the swirl flow streamline with 0 is l
_2, the injector A30 and one of the cylinder center line to swirl the center line, the injector B31, defining a radius formed between each of the spark plugs 40 and _{D 1, D 2, D 3} . At this time, for the ratio h _{1 of} l ₁ and l ₂ , (D ₁
The ratio h ₂ between −D ₃ ) and (D ₂ −D ₃ ) has substantially the same numerical value, and the injector A 30 and the injector B 3 are set so that the absolute values of h ₁ and h ₂ are larger than 1.
1 and the spark plug 40 are arranged in the combustion chamber. The absolute value of h ₂ is mainly determined according to the swirl flow velocity v and the average particle diameter d of the fuel spray from the injector. The larger the value of v, or the larger the value of d. The absolute value of h ₂ is set to a large value according to.

In FIG. 3, the injector B31 is disposed between the two exhaust valves, and the heat received by the injector B31 and its fuel spray from the hot exhaust valve promotes the naturalization of the fuel spray and improves the ignitability. This leads to a reduction in unburned fuel emissions. Further, the fuel spray injected from the injector A30 also follows the streamline of the swirl flow before reaching the ignition plug 40, and therefore passes through the vicinity of the exhaust valve, which promotes the vaporization of the fuel spray. FIG. 4 is a control flowchart regarding control signals to the injector A30, the injector B31, and the spark plug 40.

In S1, the control unit 50 detects the engine speed, the throttle opening, the intake air amount, and the crank angle in order to determine the operating state of the engine. In S2, the basic fuel injection amount required according to the operating state of the engine is determined from the above detection result. In S3, the load of the engine is detected from the above detection result, and in S4, it is determined whether or not the load is equal to or more than a predetermined load. When the engine has a high load, S5 and S6
Then, the fuel injection amount of each of the injectors A30 to B31 is determined based on the basic fuel injection amount determined in S2. That is, when the engine is operating under a high load, the air-fuel mixture in the combustion chamber needs to be more uniformly supplied than the stratified supply, and as a result, the fuel of the injector A30 having a long swirl direction distance to the spark plug 40 as shown in FIG. The injection amount is larger than that of the injector B31. Here, in FIG. 5, the ratio of the injection amount QA of the injector A30 or the injection amount QB of the injector B31 to the total injection amount Q of the injector A30 and the injector B31 is plotted on the vertical axis, and the engine load is plotted on the horizontal axis. It is the diagram which showed the relationship. Also,
When it is determined in S4 that the engine is under a predetermined load, the engine misfire determination is performed in S9 after determining the fuel injection amount of each of the injectors A30 to B31 in S7 and S8 as in S5 and S6 above. , S10, when it is determined that the engine has misfired, the injector B31 obtained in S8 is determined.
The fuel injection amount is increased in step S11. That is, particularly during light load operation, the basic fuel injection amount is small, and the air-fuel ratio of the air-fuel mixture in the vicinity of the spark plug 40 becomes leaner than the stoichiometric air-fuel ratio, so that misfire easily occurs. When the engine misfires, the injector B having a short swirl distance to the spark plug 40 is judged.
The fuel injection rate of 31 is increased.

By delaying the injection start timing of the injector B31 even during the expansion stroke of the engine, so-called post-combustion combustion is promoted, and HC, CO, etc. in the exhaust gas,
It is also possible to reduce harmful components such as Nox.

[0028]

According to the invention of the present application, by arranging the fuel injection valve and the spark plug of a direct injection type engine, the ignitability at the time of stratified charge and the reduction of the emission of harmful components in the exhaust gas are reduced. It is compatible.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a direct fuel injection engine to which the present application can be applied.

FIG. 2 is a schematic front view of a combustion chamber of a direct fuel injection engine.

FIG. 3 is a schematic plan view of a combustion chamber of a direct fuel injection engine.

FIG. 4 is a flowchart regarding control of a fuel injection valve.

FIG. 5 is a graph showing a relationship between a fuel injection ratio of injector A and injector B and an engine load.

[Explanation of symbols]

Engine ... 1, Air supply passage ... 2, Air cleaner ... 3, Air flow sensor ... 4, Intake air temperature sensor ... 5, Throttle valve ... 6, Surge tank ... 7, Pressure sensor ... 8, Throttle opening sensor ... 9, Supercharger … 10, bypass passage… 1
1, bypass valve ... 12, bypass valve opening sensor ... 13, water temperature sensor ... 14, exhaust passage ... 20, catalyst ... 2
1, injector A ... 30, injector B ... 31, fuel pressure control valve ... 32, fuel pump ... 33, fuel pressure sensor ...
34, spark plug ... 40, ignition coil ... 41, control unit ... 50

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Sakurai 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Motor Corporation

Claims (4)

[Claims] 1. A direct injection engine in a cylinder, comprising: a fuel injection valve for directly injecting fuel into a combustion chamber formed in a cylinder; and a spark plug for igniting an air-fuel mixture in the combustion chamber. Is provided at a position spaced apart from the cylinder centerline by a first predetermined distance in the radial direction, and a spark plug is provided downstream in the radial direction with respect to the cylinder centerline along the swirl flow in the combustion chamber. A swirl direction, which is a distance from a fuel injection valve disposed upstream of the swirl along with a swirl flow formed in the combustion chamber to a spark plug disposed downstream of the fuel injection valve, which is disposed at a longer second predetermined distance. An in-cylinder direct injection engine characterized in that a fuel injection valve and an ignition plug into the combustion chamber are arranged such that the second predetermined distance becomes longer as the distance becomes longer. 2. A cylinder having two fuel injection valves and one spark plug, wherein the two fuel injection valves are provided upstream of the spark plug with respect to a swirl flow in a combustion chamber formed in the cylinder. And a first fuel injection valve on the side where the swirl distance is closer to the spark plug with respect to the upstream side in the swirl flow direction in the combustion chamber, and the spark plug is disposed in the combustion chamber. The structure of a direct injection engine for a cylinder according to claim 1, wherein the second fuel injection valve on the side farther from the plug is arranged at a position where the radius with respect to the cylinder center line becomes longer in order. 3. The in-cylinder direct injection type according to claim 2, wherein the first fuel injection valve has a better atomization characteristic of fuel spray than the second fuel injection valve. engine. 4. A setting means is provided for setting such that the difference between the first predetermined distance and the second predetermined distance is reduced as the particle size of the fuel spray injected from the fuel injection valve becomes smaller. The in-cylinder direct injection engine according to claim 2 or 3, characterized in that.