JP2003003897A - Self-ignition type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-ignition type engine capable of realizing a high temperature field required for activating a fuel with a minimum amount of air and reducing occurrence of fuel loss coming up with fuel activation. SOLUTION: A fuel-air mixture injection valve 8 for injecting the high temperature mixture obtained by mixing a high temperature air and a fuel directly into a combustion chamber 4 and a spark plug 9 disposed approaching the combustion chamber 4, are arranged adjacently to each other. During an intake stroke, the high temperature fuel-air mixture is injected by the injection valve 8, and during the injection period, a supplementary spark ignition is carried out by the spark plug 9, thus activating the fuel. At least one additional injection is performed during a compression stroke according to the load of the engine, and then a self-ignition is performed by the compression action of a piston 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-ignition type engine, for example, a 4-cycle direct injection spark ignition compression self-ignition type gasoline engine for automobiles, which does not lead to flame propagation due to compression self-ignition combustion. The present invention relates to a technique for improving the ignitability of a fuel and obtaining a desired combustion timing by activating (reforming) a part of the fuel by spark ignition.

[0002]

2. Description of the Related Art Combustion by compression self-ignition has an advantage that combustion can be performed at an air-fuel ratio on the lean side of the lean limit in normal spark ignition, since combustion is started at multiple points in a combustion chamber. However, since the progress of the pre-reaction of the fuel that determines the ignition timing is determined by the temperature / pressure change history during the compression stroke, there is a problem that the operating conditions for obtaining an appropriate ignition timing are limited.

For example, in the case of an engine which is set to self-ignite around the compression top dead center under operating conditions of relatively high load, when the load is low, self-ignition cannot be obtained by the compression top dead center. After the compression top dead center, the temperature and pressure in the combustion chamber drop, resulting in a loss of combustion opportunity and a misfire. As a method of avoiding such a misfire, the fuel supplied to the combustion chamber should be activated in advance to accelerate the progress of the pre-reaction during the compression stroke and shorten the time until preparation for self-ignition is completed. Can be considered.

For example, in Japanese Unexamined Patent Publication No. 2001-3771, the exhaust valve is closed early so that the burned gas of the previous cycle remains in the combustion chamber, and combustion is performed by the heat of this gas and auxiliary spark ignition. It is designed to generate radicals in the room.

[0005]

When reforming a fuel to generate active species such as aldehyde, it is effective to carry out spark ignition in an air-fuel mixture having a relatively high temperature. In the above-mentioned conventional technique, the burned gas in the previous cycle is used to obtain this high temperature, but in this case, there is a concern that fuel consumption may deteriorate due to an increase in cooling loss. That is, when the exhaust valve is closed early, compression work occurs while the piston moves up to the top dead center. This work is recovered as torque when the piston descends from top dead center, but it is not possible to recover the energy of heat that has been transferred from the hot burnt gas to the cooling water through the combustion chamber wall. .
If the amount of burnt gas remaining in the next cycle is increased in order to enhance the fuel reforming effect, the above cooling loss also increases.

The present invention has been made in view of the above problems, and a self-ignition engine capable of realizing a high temperature field necessary for fuel activation with as little air as possible and reducing loss due to fuel activation. The purpose is to provide.

[0007]

Therefore, according to the invention of claim 1, in the mixture injection valve for directly injecting the high temperature mixture obtained by mixing the high temperature air and the fuel into the combustion chamber, and the combustion chamber. And a spark ignition plug arranged facing the spark ignition plug, both of the injection of the high temperature mixture by the mixture injection valve and the spark ignition by the spark ignition plug are performed during an intake stroke.

According to a second aspect of the present invention, the mixture injection valve and the spark ignition plug are arranged adjacent to each other, and the spark produced by the spark ignition plug is provided during the injection period of the high temperature mixture produced by the mixture injection valve. It is characterized by performing ignition.
According to the invention of claim 3, in addition to the injection during the intake stroke by the mixture injection valve, at least one additional injection is performed during the compression stroke according to the engine load.

The invention of claim 4 is characterized in that the ratio of the injection amount during the intake stroke to the total injection amount is made smaller as the engine load is larger. The invention of claim 5 is characterized in that the ratio of the injection amount during the intake stroke to the total injection amount is increased as the engine rotation speed is increased. The invention of claim 6 is characterized in that the timing of the spark ignition is retarded as the engine load increases.

According to a seventh aspect of the present invention, the spark ignition timing is advanced as the engine speed increases. The invention of claim 8 is characterized by comprising knocking detection means, and when the knocking detection means detects knocking, the ratio of the injection amount during the intake stroke is reduced.

According to a ninth aspect of the present invention, there is provided knocking detection means, and the spark ignition timing is retarded when the knocking detection means detects knocking. According to a tenth aspect of the present invention, the combustion stability detecting means is provided, and when the combustion stability detecting means detects combustion instability, the ratio of the injection amount during the intake stroke is increased.

According to an eleventh aspect of the present invention, there is provided combustion stability detecting means, and when the combustion stability detecting means detects combustion instability, the spark ignition timing is advanced.

[0013]

According to the first aspect of the present invention, during the intake stroke, the high temperature mixture obtained by mixing the high temperature air and the fuel is injected into the combustion chamber, and the high temperature mixture is supplemented to the high temperature mixture. It is possible to significantly improve the ignitability at the time of self-ignition combustion by the subsequent compression action of the piston by activating the fuel by igniting spark ignition and sufficiently diffusing the activated fuel in the cylinder. Since only the air necessary for forming the air-fuel mixture in the air injection valve needs to be heated to a high temperature, it is possible to obtain an effect that it is possible to reduce the loss caused by the fuel activation.

According to the second aspect of the present invention, the mixture injection valve and the spark ignition plug are arranged adjacent to each other, and the spark ignition is performed by the spark ignition plug during the injection period of the high temperature mixture by the mixture injection valve. As a result, good fuel reforming can be performed before the temperature of the high temperature mixture decreases. In other words, the temperature of the hot air-fuel mixture injected into the combustion chamber gradually decreases in the process of widely diffusing into the combustion chamber, so spark ignition for fuel reforming is performed simultaneously with injection of the hot air-fuel mixture. It is good to do it. Also, by generating active species early,
The active species can be diffused widely in the combustion chamber.

In the case of the air-fuel mixture injection valve, the vaporization of the fuel and the mixing with air are progressing inside the air-fuel mixture injection valve, so the injected air-fuel mixture is already a sufficiently homogeneous air-fuel mixture. Therefore, even if the injected mixture is directly ignited by spark ignition, the oxidation reaction of the fuel generated here is almost up to the partial oxidation reaction (reforming reaction). On the other hand, when the liquid fuel is injected into the high temperature combustion chamber, the fuel spray immediately after the injection has the fuel density and the fuel density is locally high (for example, fuel droplets In the surroundings, the oxidation reaction may not stop at the reforming reaction and may even reach complete oxidation (combustion).

According to the invention of claim 3, in addition to the injection during the intake stroke by the mixture injection valve, at least one additional injection is performed during the compression stroke according to the engine load,
The operating range of self-ignition combustion can be expanded to high loads. According to the invention of claim 4, by making the ratio of the injection amount during the intake stroke to the total injection amount smaller as the engine load is larger, the injection is performed during the intake stroke and the auxiliary ignition is performed when the engine is easily knocked at a high load. By doing so, the proportion of fuel to be activated can be reduced, self-ignition can be made relatively difficult to occur, and knocking can be avoided.

According to the fifth aspect of the present invention, the ratio of the injection amount during the intake stroke to the total injection amount is increased as the engine rotation speed increases, so that during high intake rotation during which high self-ignition is difficult to occur. By injecting and performing auxiliary ignition, the proportion of fuel to be activated is increased, self-ignition is facilitated, and stable self-ignition can be performed. According to the invention of claim 6, the spark ignition timing is retarded as the engine load is larger, and when the engine is easily knocked at a high load, the activation time of the fuel is shortened to reduce the proportion of the activated fuel. However, self-ignition is relatively unlikely to occur, and knocking can be avoided.

According to the seventh aspect of the present invention, the spark ignition timing is advanced as the engine rotational speed is higher, and the fuel activation time is lengthened to increase the activated fuel during high rotational speed at which self-ignition is difficult. The ratio can be increased to facilitate self-ignition, and stable self-ignition can be performed. Claim 8
According to the invention, when knocking is detected, the ratio of the injection amount during the intake stroke is reduced, whereby self-ignition becomes relatively difficult from the next cycle, and knocking can be avoided.

According to the ninth aspect of the present invention, when knocking is detected, the spark ignition timing is retarded, whereby self-ignition becomes relatively difficult from the next cycle, and knocking can be avoided. According to the tenth aspect of the present invention, when combustion instability is detected, by increasing the ratio of the injection amount during the intake stroke, self-ignition becomes easier from the next cycle, and combustion instability can be avoided.

According to the invention of claim 11, when the combustion instability is detected, the spark ignition timing is advanced,
From the next cycle, self-ignition becomes easier and combustion instability can be avoided.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a direct injection spark ignition compression self-ignition type gasoline engine showing an embodiment of the present invention. In the combustion chamber 4 defined by the cylinder 1, the cylinder head 2 and the piston 3, air under the control of a throttle valve (not shown) is supplied to the intake valve 7 through the intake manifold 5 and the intake port 6 forming the intake passage. Inhaled when opened.

A mixture injection valve 8 capable of directly injecting a high temperature mixture obtained by mixing high temperature air and fuel into the combustion chamber 4 is attached to the cylinder head 2 near the center thereof. At the same time, a spark ignition plug 9 facing the combustion chamber 4 is attached adjacent to the mixture injection valve 8. Here, to the mixture injection valve 8, an air pipe 12 for supplying high-temperature air obtained by electrically heating the air pressurized by the air pump 10 from the upstream side of the throttle valve in the intake passage by the heater 11 is supplied. In addition to being connected, a fuel pipe 14 for supplying fuel pressurized and guided by a fuel pump 13 from a fuel tank (not shown) is connected.

As shown in the schematic structural view of FIG. 2, the mixture injection valve 8 has a mixture injection valve body 8a to which the air pipe 12 is connected, and a fuel pipe 14 which is obliquely attached thereto. And a fuel injection valve 8b connected to the main body 8a. In addition to introducing high temperature air into the mixing chamber 8c of the main body 8a, fuel is injected from the fuel injection valve 8b to generate high temperature air and fuel in the mixing chamber 8c. Mix and vaporize the fuel at the same time. The high temperature mixture thus obtained is injected and supplied from the nozzle portion 8d into the combustion chamber.

Returning to FIG. 1, the exhaust gas after combustion is the exhaust valve 1
When the valve 5 is opened, the exhaust gas is discharged from the exhaust port 16 and the exhaust manifold 17 which form the exhaust passage. Further, an EGR passage 18 for returning a part of the exhaust gas from the exhaust manifold 17 to the intake manifold 5 is provided, and the EGR passage 18 has an EGR control valve 19 capable of adjusting an EGR amount (EGR rate).
Is installed.

An electronic control unit (engine control unit; hereinafter referred to as ECU) 20 for controlling the engine has a built-in microcomputer, in which a crank angle signal from a crank angle sensor 31 (the engine rotation speed N is thereby generated). Can be detected), accelerator opening sensor 32
An accelerator opening signal from the exhaust gas (from which the engine load T can be detected), an exhaust temperature signal from an exhaust temperature sensor 33,
A knocking detection signal or the like from the knocking sensor 34 is input.

Based on these input signals, the ECU 20 controls the mixture injection valve 8, the spark ignition plug 9, and the EGR control valve 19
Control the operation of. In particular, in this engine, the combustion control according to the operating condition is performed, so that the ECU 20 determines the combustion mode, which is the combustion mode, that is, the spark ignition combustion or the compression self-ignition combustion, according to the operating condition. Part 21
And a fuel injection amount control unit 22, a fuel injection timing control unit 23, an ignition timing control unit 24, for controlling the combustion temperature according to the determination result so as to optimize the combustion parameter in each combustion mode. The EGR rate controller 25 is provided. However, these are realized as a program of a microcomputer.

Next, the combustion control in this embodiment will be described. Based on the above configuration, in the present embodiment, spark ignition combustion and compression self-ignition combustion can be switched according to the engine rotation speed and the operating conditions of the load, and as shown in FIG. Compressed self-ignition combustion is performed in a specific operating region (low and medium rotation / low and medium load region) by N and load T, and spark ignition combustion is performed in other operating regions.

FIG. 4 shows changes in injection timing and ignition timing, in-cylinder pressure and heat generation rate with respect to crank angle during compression self-ignition combustion. Further, FIG. 5 schematically shows the state of the engine at each timing in FIG. During the compression ignition combustion, in the intake stroke, specifically, the opening timing I of the intake valve 7
Between the VO and the intake bottom dead center BDC, the mixture injection valve 8
A high-temperature air-fuel mixture obtained by mixing high-temperature air and fuel is injected (intake stroke injection), and during this injection period, a relatively low ignition energy is applied to the injected high-temperature air-fuel mixture by the spark ignition plug 9. Auxiliary spark ignition (auxiliary ignition) is performed (Fig. 5
(See (A)).

Although a part of the fuel is activated (fuel reforming) by such auxiliary ignition, it does not lead to flame propagation. In the case of the mixture injection valve 8, vaporization of fuel and mixing with air are progressing inside the mixture injection valve 8, so that the injected mixture is already a sufficiently homogeneous mixture. Therefore, even if the injected mixture is directly ignited by spark ignition, the oxidation reaction of the fuel generated here is almost up to the partial oxidation reaction (reforming reaction).

The fuel thus activated diffuses into the cylinder as the intake stroke proceeds (see FIG. 5 (B)). In the compression stroke, the mixture injection valve 8 performs at least one additional injection (compression stroke injection) according to the engine load (see FIG. 5C). The fuel injected during the compression stroke mixes with the fuel that is injected and activated during the intake stroke and diffused in the cylinder, and the compression action of the piston 3 causes self-ignition in the vicinity of the compression top dead center TDC. , Start burning (see FIG. 5 (D)).

Since a large amount of fuel components that are easily self-ignited by activation of the fuel are included, the ignitability of the fuel is improved, and the operating range of self-ignition combustion can be expanded. Further, since only the air necessary for forming the air-fuel mixture in the air-fuel mixture injection valve 8 needs to be heated to a high temperature by using the heater 11 or the like, it is possible to reduce the loss caused by the fuel activation. Here, in the compression self-ignition combustion, the higher the engine speed and the smaller the load, the more difficult the self-ignition occurs. Therefore, as shown in FIG. 6, as the engine speed N is higher and the load T is smaller,
The ratio of the intake stroke injection amount (activated fuel) to the total injection amount is increased to facilitate self-ignition.

Further, when the auxiliary ignition timing IGT is ignited on the advance side, the time for fuel activation becomes longer and the self-ignition becomes easier. Therefore, as shown in FIG. 7, as the engine speed N is higher and the load T is smaller, the auxiliary ignition timing IGT is advanced to facilitate self-ignition. In this case, since it is desirable to perform spark ignition during the injection period of the high temperature mixture by the mixture injection valve 8, the auxiliary ignition timing IGT
It is desirable to change the intake stroke injection timing according to the change of.

The flow of combustion control in the present invention performed based on the above will be described with reference to the flowchart of FIG. S1
Then, the engine speed N and the load T are detected. In S2, the combustion mode is determined from the engine speed N and the load T based on the map of FIG. 3 whether it is in the spark ignition combustion operation region or the compression self-ignition combustion operation region. When it is determined that spark ignition combustion is to be performed, the routine proceeds to S3, where normal spark ignition combustion control is performed.

On the other hand, when it is determined that the compression self-ignition combustion is to be performed, the compression self-ignition combustion control is performed in S4 to S14. The control of the compression self-ignition combustion will be described below. In S4, the EGR rate for appropriately increasing the in-cylinder temperature by the EGR gas is calculated from the engine rotation speed N and the load T based on a map (not shown).

At S5, based on a map (not shown),
The EGR control valve opening is calculated and controlled from the EGR rate and the actually detected exhaust temperature. Here, the target EG
It is natural that the opening degree of the EGR control valve is increased as the R rate is increased. Correct the opening to the larger side. However, EG
If the combustion timing control based on the R rate is not performed, these S4,
S5 is omitted.

At S6, the intake stroke injection quantity q1 and the compression stroke injection quantity q2 are calculated. Specifically, first, based on the map of FIG. 6, the ratio M of the intake stroke injection amount to the total injection amount q is calculated from the engine rotation speed N and the load T. Here, the ratio M of the intake stroke injection amount is set to be larger as the rotation speed becomes higher and the load becomes lower. Then, the intake stroke injection amount q1 = total injection amount q × M, and the compression stroke injection amount q2 = total injection amount q × (1-M) are calculated. The total injection amount q is calculated by a known method from the intake air amount, the engine rotation speed, the target air-fuel ratio and the like.

However, in the routine of the previous cycle, if there is a command to reduce or increase the ratio of the intake stroke injection amount in S12 or S14 described later, the ratio M is used after correcting the map value. In S7, the auxiliary ignition timing IGT is calculated from the engine speed N and the load T based on the map of FIG. Here, the auxiliary ignition timing IGT
Is set to the advanced side as the rotation speed becomes high and the load becomes low.

However, in the routine of the previous cycle, when there is a command to retard or advance the auxiliary ignition timing in S12 or S14 described later, the auxiliary ignition timing IGT is corrected. In S8, intake stroke injection is executed. That is, a predetermined injection timing or auxiliary ignition timing I during the intake stroke
At the injection timing set according to GT, the mixture injection valve 8 performs fuel injection (mixture mixture injection) for the intake stroke injection amount q1 set in S6.

At S9, auxiliary ignition during the intake stroke is executed. That is, during the intake stroke, especially during the intake stroke injection by the mixture injection valve 8, the auxiliary ignition timing IG set in S7 is set.
At T, spark ignition is performed by the spark ignition plug 9. S
At 10, the compression stroke injection is executed. That is, at a predetermined injection timing during the compression stroke, the mixture injection valve 8 performs fuel injection (mixture injection) for the compression stroke injection amount q2 set in S6.

In S11, the presence or absence of knocking is determined based on the signal from the knocking sensor (this portion corresponds to knocking detecting means). If knocking is detected, the routine proceeds to S12, where the ratio M of the intake stroke injection amount in the next cycle is decreased, or the auxiliary ignition timing I in the next cycle is set.
Retard GT or at least do one
Avoids knocking by making self-ignition relatively difficult to occur.

If there is no knocking, the process proceeds to S13.
In S13, the rotation fluctuation is detected from the signal of the crank angle sensor, and the combustion stability is determined based on the fluctuation (this portion corresponds to the combustion stability detecting means). When combustion instability is detected, the process proceeds to S14, at least one of increasing the ratio M of the intake stroke injection amount in the next cycle, advancing the auxiliary ignition timing IGT in the next cycle, It facilitates self-ignition and avoids combustion instability.

By controlling in this way, stable self-ignition combustion can be realized while preventing knocking and deterioration of combustion stability. In the present embodiment, the high temperature air is obtained by mounting the electric heater on the air pipe 12 to the mixture injection valve 8. However, the method for obtaining the high temperature air is not limited to this, and the electric heater is not limited to this. Other heating means other than the above may be used, and the heating position may be brought closer to the mixture injection valve 8.

[Brief description of drawings]

FIG. 1 is a system diagram of an engine showing an embodiment of the present invention.

FIG. 2 is a schematic structural diagram of a mixture injection valve.

FIG. 3 is a diagram showing an operating region in which compression self-ignition combustion is performed.

FIG. 4 is an explanatory diagram of control of compression self-ignition combustion.

5 is a schematic diagram showing the state of the engine at each timing in FIG.

FIG. 6 is a characteristic diagram of the ratio of the intake stroke injection amount to the rotation speed and the load.

FIG. 7 is a characteristic diagram of auxiliary ignition timing with respect to rotation speed and load.

FIG. 8: Combustion control flowchart

[Explanation of symbols]

4 Combustion chamber 7 intake valve 8 Mixture injection valve 8a Mixture injection valve body 8b fuel injection valve 8c mixing chamber 8d nozzle part 9 Spark spark plug 10 Air pump 11 heater 12 Air piping 13 Fuel pump 14 Fuel piping 20 ECU

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/38 F02D 41/38 D 45/00 362 45/00 362J 368 368A F02M 45/02 F02M 45/02 53/00 53/00 J 61/14 310 61/14 310S 67/02 67/02 69/04 69/04 G F02P 5/15 F02P 5/15 D 5/152 C 5/153 (72) Inventor Komatsu Hiroyuki 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Akihiro Iiyama 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Nissan Motor Co., Ltd. F-term (reference) 3G022 CA09 DA01 DA02 EA02 EA07 FA06 GA01 GA05 GA08 GA10 3G023 AA00 AA02 AB06 AC01 AD03 AF01 AG01 AG03 AG05 3G066 AA02 AA07 AB02 AD12 BA01 BA14 BA21 BA22 CC46 CC63 CD22 CD25 CD26 DA01 DA04 DA09 DB09 DB13 DC00 DC01 DC04 DC05 DC09 DC13 3G084 AA01 BA13 BA15 BA17 BA20 CA09 DA00 DA02 DA11 EB08 EB11 FA10 FA25 FA27 FA34 FA37 FA38 3G301 HA01 HA02 HA04 HA16 JA02 JA04 JA22 KA06 KA08 KA09 KA23 KA24 KA25 LA00 LA01 NE01 NC11 MA11 NE11 NC01 MA12 MA11 NE11 NC02 MA11 MA01 MA12 MA01 NA01 NE11 PD15A PD15Z PE01Z PE03Z PE09A PF03Z

Claims (11)

[Claims] 1. A mixture injection valve for directly injecting a high-temperature mixture obtained by mixing high-temperature air and fuel into a combustion chamber, and a spark ignition plug arranged facing the combustion chamber, A self-ignition engine, wherein both injection of a high temperature mixture by the mixture injection valve and spark ignition by the spark ignition plug are executed during an intake stroke. 2. The mixture injection valve and the spark ignition plug are arranged adjacent to each other, and spark ignition by the spark ignition plug is executed during injection of a high temperature mixture by the mixture injection valve. The self-ignition type engine according to claim 1. 3. In addition to the injection during the intake stroke by the mixture injection valve, at least one additional injection is performed during the compression stroke according to the engine load. The self-igniting engine described. 4. A self-ignition engine according to claim 3, wherein the ratio of the injection amount during the intake stroke to the total injection amount is made smaller as the engine load is larger. 5. The self-ignition engine according to claim 3, wherein the ratio of the injection amount during the intake stroke to the total injection amount is increased as the engine speed increases. 6. The self-ignition engine according to any one of claims 1 to 5, wherein the spark ignition timing is retarded as the engine load increases. 7. The self-ignition engine according to claim 1, wherein the spark ignition timing advances as the engine speed increases. 8. A knocking detection means is provided, and when the knocking detection means detects knocking, the ratio of the injection amount during the intake stroke is reduced. The self-igniting engine described in 1. 9. A knocking detection means is provided, and when the knocking detection means detects knocking, the spark ignition timing is retarded. The self-igniting engine described. 10. The method according to claim 3, further comprising combustion stability detecting means, wherein when the combustion stability detecting means detects combustion instability, the ratio of the injection amount during the intake stroke is increased. The self-igniting engine according to claim 5. 11. The method according to claim 1, further comprising combustion stability detecting means, wherein the spark ignition timing is advanced when the combustion stability detecting means detects combustion instability. The self-ignition engine according to any one of 1.