JP2010065558A - Combustion stabilizing device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve combustion stability in HCCI combustion regardless of an octane value of high octane value fuel. <P>SOLUTION: This invention is provided with: a first fuel supply means for supplying the high octane value fuel to a combustion chamber of an internal combustion engine; a second fuel supply means for directly injecting and supplying low octane value fuel into the combustion chamber when the internal combustion engine exists in a predetermined premixed compression ignition combustion area; an estimated octane value calculating means S42 for calculating an estimated octane value of the high octane value fuel; and injection quantity control means S44 and S45 for controlling an injection quantity of the low octane value fuel so as to stabilize premixed compression ignition combustion in response to the estimated octane value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a combustion stabilization device for an internal combustion engine.

A conventional internal combustion engine includes a first fuel injection valve that injects gasoline, which is a high octane fuel, into an intake port, and a second fuel injection valve, which directly injects light oil, which is a low octane fuel, into a combustion chamber. A high temperature atmosphere with high octane fuel is formed in the room, and sprays of low octane fuel are scattered in the atmosphere to promote spontaneous ignition. Homogeneous Charge Compression Ignition (hereinafter referred to as “HCCI combustion”) (Refer to Patent Document 1, for example). Thereby, in the explosion stroke, the flame spreads from a plurality of locations in the combustion chamber, so that the substantial combustion speed is increased and combustion can be completed before knocking occurs.
JP 2004-197660 A

  However, the internal combustion engine may be supplied with high octane number fuels having different octane numbers (ignitability) (for example, high-octane gasoline and regular gasoline). Therefore, in the above-described conventional internal combustion engine, if the injection amount of the low octane fuel is set on the assumption that the regular gasoline is supplied as the high octane fuel, the self-ignitability deteriorates when the high octane fuel is supplied. The combustion becomes unstable. Further, if the injection amount of low-octane fuel is set on the assumption that high-octane fuel is supplied as high-octane fuel, knocking is likely to occur when regular gasoline is supplied, and combustion becomes unstable.

  The present invention has been made paying attention to such a conventional problem, and an object thereof is to improve the combustion stability during HCCI combustion.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention provides a first fuel supply means (35) for supplying high-octane fuel to the combustion chamber (23) of the internal combustion engine (1) and the internal combustion engine (1) in a predetermined premixed compression ignition combustion region. A second fuel supply means (36) for directly injecting and supplying a low octane fuel to the combustion chamber (23), an estimated octane number calculating means (S42) for calculating an estimated octane number of the high octane fuel, and the estimation Injection quantity control means (S44, S45) for controlling the injection quantity of the low-octane fuel so that the premixed compression ignition combustion is stabilized in accordance with the octane number.

  According to the present invention, since the injection amount of the low octane fuel is controlled so as to stabilize the HCCI combustion according to the octane number of the high octane fuel, the combustion stability during the HCCI combustion is improved regardless of the octane number of the high octane fuel. be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic view of an engine 1 according to a first embodiment of the present invention.

  The engine 1 includes a cylinder block 2 and a cylinder head 3 that covers the top of the cylinder block 2.

  A cylinder 21 is formed in the cylinder block 2. A piston 22 is slidably provided on the cylinder 21. The cylinder block 2, the cylinder head 3, and the piston 22 form a pent roof type combustion chamber 23.

  The cylinder head 3 includes an intake port 31, an exhaust port 32, an intake valve 33, an exhaust valve 34, a first fuel injection valve 35, a second fuel injection valve 36, and an ignition plug 37.

  The intake port 31 is a flow path for introducing air into the combustion chamber 23, and one end opens on one inclined surface of the combustion chamber 23.

  The exhaust port 32 is a flow path for discharging exhaust gas generated in the combustion chamber 23, and opens to the other inclined surface of the combustion chamber 23.

  The intake valve 33 opens and closes the opening of the intake port 31 according to the vertical movement of the piston 22.

  The exhaust valve 34 opens and closes the opening of the exhaust port 32 according to the vertical movement of the piston 22.

  The first fuel injection valve 35 injects high-octane fuel for generating output toward the opening of the intake port 31. In this embodiment, gasoline is used as the high octane fuel.

  The second fuel injection valve 36 directly injects low-octane fuel for promoting ignition into the combustion chamber 23. In this embodiment, light oil is used as the low-octane fuel.

  The spark plug 37 is provided at the center of the top wall of the combustion chamber 23 and ignites a mixture of high-octane fuel injected from the first fuel injection valve 35 and intake air.

  The controller 4 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 4 receives signals from various sensors such as a knock sensor 41 that detects knocking.

  The controller 4 refers to a combustion form switching map stored in advance, and switches the combustion form to HCCI combustion or spark ignition combustion (hereinafter referred to as “SI combustion”) according to the operating state of the engine 1.

  FIG. 2 is a combustion mode switching map.

  As shown in FIG. 2, the controller 4 uses the high-octane fuel injected from the first fuel injection valve 35 without using the spark plug 37 in the predetermined HCCI combustion region of low rotation and low load, HCCI combustion is performed to compress and ignite a premixed mixture of low-octane fuel injected from the fuel injection valve 36 and air. On the other hand, in the other SI region, using the spark plug 37, SI combustion is performed to sparkly ignite the premixed gas of the high-octane fuel injected from the first fuel injection valve 35 and air.

  FIG. 3 is a flowchart for explaining the combustion stabilization control executed by the controller 4. The controller 4 executes this routine at a predetermined calculation cycle (for example, 10 ms) while the engine 1 is operating.

  In step S1, the controller 4 determines whether or not the operating state of the engine 1 is within the HCCI combustion region. If the operating state of the engine 1 is not within the HCCI combustion region, the controller 4 proceeds to step S2, and if within the HCCI combustion region, the controller 4 proceeds to step S3.

  In step S2, the controller 4 sets the HCCI combustion permission flag to 0. The HCCI combustion permission flag is a flag that is set to 1 when the operating state of the engine 1 is in the HCCI combustion region.

  In step S3, the controller 4 executes SI combustion processing. Since the SI combustion process is not the main part of the present invention, the description thereof is omitted.

  In step S4, the controller 4 executes an HCCI combustion process. Specific contents will be described later with reference to FIG.

  FIG. 4 is a flowchart for explaining the HCCI combustion process.

  In step S41, the controller 4 determines whether or not the HCCI combustion permission flag is set to 1. If the HCCI combustion permission flag is set to 1, the controller 4 proceeds to step S44, and if the HCCI combustion permission flag is set to 0, the controller 4 proceeds to step S42.

  In step S42, the controller 4 executes an octane number estimation process for the high octane number fuel. Specific contents will be described later with reference to FIG.

  In step S43, the controller 4 sets the HCCI combustion permission flag to 1.

  In step S44, the controller 4 determines the basic value of the injection amount of the high octane fuel injected from the first fuel injection valve 35 and the second fuel injection valve when the octane number of the high octane fuel is assumed to be 95 (first reference octane number). A basic value of the injection amount of the low octane fuel injected from 36 is calculated according to the engine operating state. In addition, all the numerical values of the octane number described in this specification are numerical values of the research octane number (RON; Research Octane Number). Assuming that the octane number of high-octane gasoline is approximately 100 and the octane number of regular gasoline is approximately 90, the first reference octane number is an intermediate value.

  In step S45, the controller 4 corrects the injection amount of the high octane fuel injected from the first fuel injector 35 and the second fuel injector 36 in accordance with the estimated octane number of the high octane fuel estimated in step S32. The correction value of the injection amount of the low octane fuel to be calculated is calculated. Details of the correction value calculation method will be described later with reference to FIGS. 7 and 8.

  In step S <b> 46, the controller 4 injects the injection amount obtained by correcting the basic value with the correction value from the first fuel injection valve 35 and the second fuel injection valve 36.

  FIG. 5 is a flowchart for explaining the octane number estimation process of the high octane number fuel.

  In step S421, the controller 4 sets the ignition timing to the base ignition timing for high-octane gasoline (about octane number 100 (second reference octane number)), performs SI combustion, and detects the knock intensity.

  In step S422, the controller 4 refers to the table of FIG. 6 and estimates the octane number of the high octane fuel according to the knock intensity.

  FIG. 6 is a table for estimating the octane number of the high octane fuel from the knock intensity. This table is obtained in advance by experiments or the like and stored in the controller 4.

  As shown in FIG. 6, the controller 4 estimates that the octane number of the high octane fuel is smaller as the knock strength is larger. This is because it can be judged that the higher the knock strength, the better the ignitability of the high octane fuel.

  FIG. 7 is a table for calculating the injection amount correction value of the high-octane fuel from the octane number of the high-octane fuel. This table is obtained in advance by experiments or the like and stored in the controller 4.

  As shown in FIG. 7, when the octane number is 95, the injection amount correction value for the high octane number fuel is set to zero. As the octane number becomes larger than 95, the injection amount of the high octane fuel decreases with respect to the basic value. As the octane number becomes smaller than 95, the injection amount of the high octane fuel increases with respect to the basic value.

  FIG. 8 is a table for calculating the injection amount correction value of the low octane fuel from the octane number of the high octane fuel. This table is obtained in advance by experiments or the like and stored in the controller 4.

  As shown in FIG. 8, when the octane number is 95, the injection amount correction value for the low octane number fuel is set to zero. As the octane number becomes larger than 95, the injection amount of the low octane number fuel increases with respect to the basic value, and as the octane number becomes smaller than 95, the injection amount of the low octane number fuel decreases with respect to the basic value.

  As shown in FIGS. 7 and 8, when the octane number of the high-octane fuel is greater than 95 and the ignitability of the premixed gas becomes relatively poor, the injection amount of the low-octane fuel is reduced by reducing the injection amount of the high-octane fuel. By increasing the HCCI combustion can be stabilized. On the other hand, when the octane number of the high-octane fuel is smaller than 95 and the ignitability of the premixed gas is relatively good, by increasing the injection amount of the high-octane fuel and decreasing the injection amount of the low-octane fuel, Can be avoided.

  According to the present embodiment described above, the octane number of the high octane number fuel is estimated, and the injection amounts of the high octane number fuel and the low octane number fuel are corrected according to the estimated octane number. Thus, conventionally, HCCI combustion can be performed even in an operation region where combustion becomes unstable depending on the octane number of the high-octane fuel or an operation region where knocking occurs. That is, the operating range in which HCCI combustion can be performed can be expanded.

  In HCCI combustion, the premixed gas is self-ignited using the in-cylinder pressure of the engine 1, and therefore combustion is started at a plurality of locations as compared with SI combustion in which combustion is started from one point. Therefore, it is not necessary to propagate combustion, and combustion at a lean air-fuel ratio becomes possible, improving fuel efficiency. Therefore, fuel consumption can be improved by expanding the operating range in which HCCI combustion can be performed.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. This embodiment determines whether the high-octane fuel is high-octane gasoline or regular gasoline, and calculates a correction value for the injection amount of the high-octane fuel and a correction value for the injection amount of the low-octane fuel based on the determination result. This is different from the first embodiment. Hereinafter, the difference will be mainly described. In the embodiment described below, the same reference numerals are used for portions that perform the same functions as those of the first embodiment described above, and redundant descriptions are omitted as appropriate.

  FIG. 9 is a table for determining whether the high-octane fuel is high-octane gasoline or regular gasoline from the knock intensity.

  As shown in FIG. 9, the controller 4 determines that the high-octane fuel is regular gasoline if the knock intensity is greater than a predetermined knock intensity. On the other hand, if the knock strength is smaller than the predetermined knock strength, it is determined that the high-octane fuel is high-octane gasoline.

  FIG. 10 is a table for calculating the injection amount correction value of the high octane fuel based on the determination result of whether the high octane fuel is high-octane gasoline or regular gasoline.

  As shown in FIG. 10, if the high-octane fuel is high-octane gasoline, the controller 4 decreases the injection amount of the high-octane fuel by a fixed amount from the basic value. On the other hand, if the high-octane fuel is regular gasoline, the injection amount of the high-octane fuel is increased by a certain amount from the basic value.

  FIG. 11 is a table for calculating an injection amount correction value for low-octane fuel based on the determination result of whether the high-octane fuel is high-octane gasoline or regular gasoline.

  As shown in FIG. 11, if the high-octane fuel is high-octane gasoline, the controller 4 increases the injection amount of the low-octane fuel by a certain amount from the basic value. On the other hand, if the high-octane fuel is regular gasoline, the injection amount of the low-octane fuel is reduced from the basic value by a certain amount.

  According to the present embodiment described above, unlike the first embodiment, it is possible to easily determine whether the gasoline is a high-octane gasoline or a regular gasoline without having to continuously estimate the octane number of the high-octane fuel. Similar effects can be obtained.

  Note that the present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

It is a schematic diagram of an engine. It is a combustion mode switching map. It is a flowchart explaining combustion stabilization control. It is a flowchart explaining an HCCI combustion process. It is a flowchart explaining the octane number estimation process of a high octane number fuel. It is a table which estimates the octane number of a high octane fuel from knock intensity. It is a table which calculates the injection amount correction value of the high octane fuel according to the first embodiment. It is a table which calculates the injection amount correction value of the low octane number fuel by 1st Embodiment. It is a table which judges whether high octane fuel is high-octane gasoline or regular gasoline from knock intensity. It is a table which calculates the injection amount correction value of the high octane fuel according to the second embodiment. It is a table which calculates the injection amount correction value of the low octane number fuel by 2nd Embodiment.

Explanation of symbols

1 engine (internal combustion engine)
23 Combustion chamber 35 First fuel injection valve (first fuel supply means)
36 Second fuel injection valve (second fuel supply means)
37 Spark plugs (spark ignition means)
S42 Designated octane number calculation means S44 Injection amount control means, basic injection amount calculation means S45 Injection amount control means, basic injection amount correction means

Claims (5)

First fuel supply means for supplying high octane fuel to the combustion chamber of the internal combustion engine;
Second fuel supply means for directly injecting and supplying low-octane fuel to the combustion chamber when the internal combustion engine is in a predetermined premixed compression ignition combustion region;
An estimated octane number calculating means for calculating an estimated octane number of the high octane fuel;
An injection amount control means for controlling the injection amount of the low octane fuel so that the premixed compression ignition combustion is stabilized according to the estimated octane number;
A combustion stabilization device for an internal combustion engine, comprising: The injection amount control means includes
Basic injection amount calculating means for calculating a basic injection amount of the low octane fuel when the octane number of the high octane fuel is a predetermined first reference octane number;
When the estimated octane number is larger than the first reference octane number, the basic injection amount of the low octane number fuel is increased, and when the estimated octane number is smaller than the first reference octane number, the basic injection amount of the low octane number fuel is decreased. Injection amount correction means;
The combustion stabilization device for an internal combustion engine according to claim 1, comprising: The combustion stabilization apparatus for an internal combustion engine according to claim 2, wherein the first reference octane number is an intermediate value between the octane number of high-octane gasoline and the octane number of regular gasoline. Comprising spark ignition means for igniting the fuel supplied to the combustion chamber by sparks;
The estimated octane number calculating means estimates the high octane fuel based on the knock intensity when the high octane fuel is ignited at the ignition timing when the octane number of the high octane fuel is a predetermined second reference octane number. The combustion stabilization apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein an octane number is calculated. The combustion stabilization apparatus for an internal combustion engine according to claim 4, wherein the second reference octane number is an octane number of high-octane gasoline.

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