JP2012255423A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a discharge quantity of PM, in an internal combustion engine using a mixed fuel.SOLUTION: This control device (100) of the internal combustion engine controls the internal combustion engine (200) of using gas oil and alcohol as fuel respectively independently or by mixing. The control device of the internal combustion engine includes an alcohol concentration detecting means (420) for detecting the alcohol concentration in the fuel, an after-injection control means (440) for performing after-injection after main injection of the fuel, and an injection quantity adjusting means (430) for controlling the after-injection control means so as to reduce an injection quantity in the after-injection as the alcohol concentration in the fuel reduces.

Description

  The present invention relates to a technical field of a control device for an internal combustion engine that can use a mixed fuel obtained by mixing light oil and alcohol.

  This type of internal combustion engine is known to use a mixed fuel obtained by mixing a plurality of types of fuel (for example, a mixed fuel of light oil and alcohol). For example, the mixed fuel may be made variable by being mixed after being stored in different fuel tanks, for example. In this case, the mixing ratio of the mixed fuel is appropriately determined according to various conditions such as the operating state of the internal combustion engine. For example, Patent Document 1 proposes a technique for controlling the mixing ratio to be within a certain concentration range in order to prevent only one fuel from being excessively injected so as to deteriorate the exhaust gas properties. Patent Document 2 proposes a technique of performing injection mixed with alcohol when the main injection by light oil exceeds a predetermined time. Patent Document 3 proposes a technique of performing three-stage injection of light oil in the first stage, light oil + alcohol in the second stage, and only light oil in the third stage.

  On the other hand, in an internal combustion engine that uses light oil, a technique has been proposed in which a small amount of after-injection is performed after main injection, which is mainly intended to supply fuel. According to after-injection, PM (Particulate Matter: particulate matter) generated by main injection is recombusted to reduce the PM emission amount (see, for example, Patent Documents 4 and 5).

Japanese Patent Laid-Open No. 06-307307 JP 2003-161178 A JP 59-108844 A JP 2007-187149 A Japanese Patent Laid-Open No. 2003-278587

  While the above-described after injection can re-burn PM, the after injection itself also generates PM. For this reason, if injection is performed excessively in the after injection, there is a risk that PM is increased. Therefore, when performing after injection, it is preferable to control the injection amount so that the PM emission amount does not increase.

  Specifically, in the mixed fuel of light oil and alcohol, when the mixing ratio of alcohol decreases, the amount of PM generated by after-injection increases, and as a result, the amount of PM discharged increases. Therefore, when using a mixed fuel of light oil and alcohol, it is considered preferable to control after-injection according to the mixing ratio of alcohol.

  Here, Patent Documents 1 to 3 describe a mixed fuel of light oil and alcohol, but do not describe any after-injection. Further, Patent Documents 4 and 5 describe after-injection, but no consideration is given to the case where a mixed fuel of light oil and alcohol is used. Therefore, in these techniques, there is a technical problem that it is impossible to appropriately control the after-injection in the mixed fuel containing alcohol, and it is not possible to reliably reduce the PM emission amount.

  The present invention has been made in view of the above-described problems, and it is an object of the present invention to provide a control device for an internal combustion engine capable of reducing PM emission in an internal combustion engine using a mixed fuel containing alcohol. And

  In order to solve the above-described problems, an internal combustion engine control apparatus according to the present invention is a control apparatus for an internal combustion engine that uses light oil and alcohol alone or as a mixture, and detects alcohol concentration in the fuel. Detecting means, after-injection control means for performing after-injection after the main injection of the fuel, and the after-injection control means so that the lower the alcohol concentration in the fuel, the smaller the injection amount in the after-injection. Injection amount adjusting means for controlling.

  The internal combustion engine according to the present invention is, for example, an internal combustion engine mounted on a vehicle, and it is possible to use light oil and alcohol alone or in combination as fuel. That is, the internal combustion engine according to the present invention can be operated with a mixed fuel in which light oil and alcohol are mixed at various mixing ratios. The internal combustion engine takes out the force generated when the above-mentioned mixed fuel burns in the combustion chamber inside the cylinder as a driving force through an appropriate physical or mechanical transmission means such as a piston, a connecting rod and a crankshaft. Is configured to be possible.

  A control device for an internal combustion engine according to the present invention is a control device that controls the above-described internal combustion engine. For example, one or a plurality of CPUs (Central Processing Units), MPUs (Micro Processing Units), various processors or various controllers, Alternatively, various processing units such as a single or a plurality of ECUs (Electronic Controlled Units), which may appropriately include various storage means such as ROM (Read Only Memory), RAM (Random Access Memory), buffer memory or flash memory, Various computer systems such as various controllers or microcomputer devices can be used.

  During operation of the control device for an internal combustion engine according to the present invention, the alcohol concentration in the fuel is detected by the alcohol concentration detection means. The alcohol concentration detection means includes, for example, an alcohol concentration sensor provided in a fuel tank in which the mixed fuel is stored. The alcohol concentration detection means may detect the alcohol concentration in the fuel as a specific numerical value, or only detect whether the alcohol concentration in the fuel is higher or lower than a preset reference value. It may be.

  Further, according to the control apparatus for an internal combustion engine according to the present invention, the after injection control means performs the after injection after the main fuel injection. Here, the “main injection” is an injection whose main purpose is the supply of fuel to the internal combustion engine. For example, it is applied to the load of the internal combustion engine (specifically, throttle opening, accelerator depression amount, etc.). The injection amount is determined accordingly. On the other hand, “after injection” is a relatively small amount of injection performed to re-combust PM generated by the main injection, and is performed after the main injection. By enabling after injection, it becomes possible to reduce the amount of PM emission.

  Here, in the present invention, in particular, the fuel injection amount in the above-described after injection is controlled by the injection amount adjusting means. Specifically, the injection amount adjusting means controls the after injection control means so that the lower the alcohol concentration in the fuel, the smaller the injection amount in the after injection. The injection amount adjusting means stores, for example, a plurality of control maps for determining the injection amount in after-injection for each alcohol concentration, and by switching the control map according to the detected alcohol concentration, injection corresponding to the alcohol concentration is performed. Determine the amount.

  Here, alcohol contains oxygen in the molecule and has a low cetane number compared to light oil, so it takes a long time to ignite, it has a low boiling point and fuel vaporization is fast, and it is sprayed due to low kinematic viscosity and low surface tension. Has the property of being atomized and easily vaporized. For this reason, when the mixing ratio of alcohol in the mixed fuel (in other words, alcohol concentration) increases, the amount of PM generated by after injection decreases. On the contrary, when the mixing ratio of alcohol in the mixed fuel occurs, the amount of PM generated by after injection increases.

  However, in the present invention, as described above, the amount of after-injection is reduced when the alcohol concentration is low. Therefore, it is possible to suppress an increase in the amount of PM generated due to a decrease in the alcohol concentration. That is, even if the characteristics of the fuel become easy to discharge PM, the increase in PM is offset by reducing the injection amount accordingly, and the PM discharge amount as a whole can be reduced or maintained.

  As described above, according to the control apparatus for an internal combustion engine according to the present invention, it is possible to reduce the PM emission amount in the internal combustion engine using the mixed fuel containing alcohol.

  In one aspect of the control apparatus for an internal combustion engine of the present invention, it is provided with fuel supply detection means for detecting fuel supply, and the alcohol concentration detection means detects the alcohol concentration in the fuel every time the fuel supply is detected. .

  According to this aspect, the fuel supply to the internal combustion engine is monitored by the fuel supply detection means. The fuel supply detection means includes, for example, a sensor that detects the amount of fuel stored in the fuel tank, and detects fuel supply when the amount of fuel stored increases.

  Particularly in this aspect, the alcohol detection means detects the alcohol concentration when the above-described oil supply detection means detects oil supply. That is, the alcohol detection means does not detect the alcohol concentration constantly or periodically, but detects the alcohol concentration when refueling is detected (more specifically, after refueling is finished).

  The alcohol concentration of the mixed fuel stored in the fuel tank varies when mixed fuel having different mixing ratios is supplied. In other words, it is considered that the alcohol concentration of the mixed fuel does not vary greatly unless refueling is performed. Therefore, if the alcohol concentration is detected when refueling is detected, the detection can be efficiently performed at a timing at which the alcohol concentration can change.

  The effect | action and other gain of this invention are clarified from the form for implementing invention demonstrated below.

It is a schematic diagram showing the whole composition of an engine system. It is a block diagram which shows the structure of ECU. It is a flowchart which shows the control processing of the after injection by the control apparatus of the internal combustion engine which concerns on embodiment. It is a graph which shows the correlation with alcohol concentration and an after injection amount.

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

  First, the configuration of the entire engine system according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram showing the overall configuration of the engine system. In FIG. 1, for convenience of explanation, among the elements constituting the engine system, only those closely related to the present embodiment are selectively illustrated, and the other elements are omitted as appropriate.

  In FIG. 1, the engine system according to this embodiment mainly includes an ECU 100, a compressor 110, a turbine 120, an engine 200, and a fuel tank 300.

  The ECU 100 is an example of the “control device for an internal combustion engine” of the present invention, and is an electronic control unit that includes, for example, a CPU, a ROM, a RAM, and the like and controls the entire operation of the engine system. The ECU 100 is configured to be able to execute various controls according to a control program stored in, for example, a ROM. A specific configuration of the ECU 100 will be described in detail later.

  The compressor 110 compresses the air that has flowed in and supplies the compressed air downstream. The turbine 120 rotates using exhaust gas supplied from the engine 200 via the exhaust pipe 215 as power. The turbine 110 is connected to the compressor 110 via a shaft, and is configured to be able to rotate integrally with each other. That is, the turbine 120 and the compressor 110 constitute a turbocharger.

  The engine 200 is a diesel engine that is a power source of a vehicle such as an automobile, and is an example of the “internal combustion engine” according to the present invention. The engine 200 is an in-line four-cylinder engine in which four cylinders 201 are arranged in series in a cylinder block.

  An air cleaner 101, an intake control valve 103, a compressor 110, an intercooler 113, and a throttle valve 208 are provided on the intake side (that is, the upstream side of the cylinder 201) in the engine 200.

  The air cleaner 101 purifies air sucked from the outside and supplies the air to the compressor 110 via the intake pipe 102. The amount of air supplied from the air cleaner is controlled by the intake control valve 103. The intercooler 113 provided downstream of the compressor 110 is configured to be able to cool the intake air and increase the supercharging efficiency of the air.

  A throttle valve 208 is installed downstream of the intercooler 113. The throttle valve 208 is configured such that its drive state is controlled by a throttle valve motor 209 electrically connected to the ECU 100. The throttle valve 208 basically controls the throttle valve motor 209 so as to obtain a throttle opening degree corresponding to the opening degree of an accelerator pedal (not shown). The driver's intention is controlled through the operation control of the throttle valve motor 209. It is also possible to adjust the throttle opening without interposing. That is, the throttle valve 208 is configured as a kind of electronically controlled throttle valve.

  The air-fuel mixture introduced into the cylinder 201 from the intake side is ignited by a compression ignition method, and an explosion process is performed in the cylinder 201. When the explosion process is performed, the burned air-fuel mixture (including a partially unburned air-fuel mixture) is discharged to an exhaust port (not shown) in the exhaust process following the explosion process. The exhaust discharged to the exhaust port is guided to the exhaust pipe 215.

  An EGR pipe 117, an HPLEGR control valve 118, a turbine 120, and an exhaust purification catalyst 122 are provided on the exhaust side of the engine 200 (that is, downstream from the cylinder 201).

  The EGR pipe 117 can recirculate the exhaust gas in the exhaust pipe 215 discharged from the engine 200 to the intake pipe 207 on the intake side of the engine 200. The EGR pipe 117 is provided with an EGR control valve 118 so that the amount of EGR gas can be adjusted. The EGR control valve 118 is an electromagnetic open / close valve that can take, for example, a fully open and fully closed binary open / close state, and is electrically connected to the ECU 100 so that the open / close state is controlled by the ECU 100. ing.

The exhaust purification catalyst 122 is provided on the exhaust pipe 121 and purifies HC (hydrocarbon), CO ₂ (carbon dioxide) and NOx (nitrogen oxide) contained in the exhaust gas that has passed through the turbine 120.

  The fuel tank 300 stores a mixed fuel of light oil and alcohol serving as fuel for the engine 200. The fuel stored in the fuel tank 300 is supplied via a fuel supply pipe 310 to an injector 210 that injects fuel into the cylinder 201. Note that the fuel injection pressure in the injector 210 is variable and is controlled in the ECU 100.

  The amount of fuel stored in the fuel tank 300 is detected by the fuel sensor 320 and can be transmitted to the ECU 100. In addition, the alcohol concentration of the fuel is detected by the alcohol concentration sensor 330 and can be transmitted to the ECU 100. It should be noted that the alcohol concentration of the fuel may be detectable not in the fuel tank 300 but in the fuel supply pipe 310 or the like.

  Next, a specific configuration of the ECU 100 that is the control device for the internal combustion engine according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing the configuration of the ECU.

  In FIG. 2, ECU 100 includes an oil supply detection unit 410, an alcohol concentration detection unit 420, an after injection amount determination unit 430, and an after injection control unit 440.

  The fuel supply detection unit 410 is an example of the “fuel supply detection unit” of the present invention, and detects fuel supply to the fuel tank 300. Specifically, the fuel supply detection unit 410 detects the remaining amount of fuel in the fuel tank 300 by the fuel sensor 320, and detects that fuel supply has been performed when the remaining amount of fuel has increased. The detection of refueling by the refueling detection unit 410 can be transmitted to the alcohol concentration detection unit 420.

  The alcohol concentration detector 420 is an example of the “alcohol concentration detector” of the present invention, and detects the alcohol concentration of the fuel stored in the fuel tank 300. The alcohol concentration detection unit 420 detects the alcohol concentration of the fuel using the alcohol concentration sensor 330 provided in the fuel tank 300. The alcohol concentration is not directly detected, but may be a value (that is, an estimated value) calculated indirectly. The detected alcohol concentration can be transmitted to the after injection amount determining unit 430.

  The after injection amount determining unit 430 is an example of the “injection amount adjusting means” of the present invention, and determines the amount of fuel injected from the injector 210 in the after injection (hereinafter referred to as “after injection amount” as appropriate). Specifically, the after injection amount determination unit 430 determines the after injection amount according to the alcohol concentration of the fuel detected by the alcohol concentration detection unit 420. However, the after injection amount determining unit 430 may determine the after injection amount using other parameters in addition to the alcohol concentration. The after-injection amount determining unit 430 stores a plurality of after-injection amount control maps for each alcohol concentration of fuel, for example, and determines the after-injection amount by switching the control map according to the alcohol concentration.

  The after-injection control unit 450 is an example of the “after-injection control unit” of the present invention, and is used for re-combusting PM generated by the main injection after the main injection mainly for supplying fuel to the engine 200. Each part of the engine 200 is controlled to perform after injection. By enabling after injection, it becomes possible to reduce the amount of PM emission.

  The ECU 100 configured to include each part described above is an electronic control unit configured integrally, and all the operations related to each part are configured to be executed by the ECU 100. However, the physical, mechanical, and electrical configurations of the above-described parts according to the present invention are not limited thereto. For example, each of these parts includes various ECUs, various processing units, various controllers, microcomputer devices, and the like. It may be configured as a computer system or the like.

  Next, processing performed by the ECU 100 that is the control device for the internal combustion engine according to the present embodiment and effects thereof will be described with reference to FIGS. FIG. 3 is a flowchart showing after-injection control processing by the control apparatus for an internal combustion engine according to this embodiment. FIG. 4 is a graph showing the correlation between the alcohol concentration and the after injection amount.

  In FIG. 3, when the control device for the internal combustion engine according to the present embodiment is operating, first, it is detected by the fuel supply detection unit 410 whether or not fuel has been supplied (step S101). If refueling is not detected (step S101: NO), the following processes of steps S102 and S103 are omitted.

  When the fuel supply detection unit 410 detects fuel supply (step S101: YES), the alcohol concentration detection unit 420 detects the fuel alcohol concentration (step S102). The alcohol concentration of the mixed fuel stored in the fuel tank 300 varies when mixed fuel having different mixing ratios is supplied. In other words, it is considered that the alcohol concentration of the mixed fuel does not vary greatly unless refueling is performed. Therefore, if the alcohol concentration is detected when refueling is detected, the detection can be efficiently performed at a timing at which the alcohol concentration can change.

  When the alcohol concentration is detected, the after injection amount determining unit 430 changes the control map for determining the after injection amount based on the detected alcohol concentration (step S103). Specifically, the after injection amount determination unit 430 stores a plurality of control maps for determining the after injection amount for each alcohol concentration. Then, the after injection amount determination unit 430 selects a control map corresponding to the alcohol concentration detected from the plurality of control maps.

  When the control map is changed, in the subsequent after injection control, the injection amount determining unit 430 determines the after injection amount using the changed control map. Then, the after-injection control unit 440 controls the injector 210 so that the determined after-injection amount is realized. Thus, in the control apparatus for an internal combustion engine according to the present embodiment, after-injection control according to the alcohol concentration is performed.

  The control maps for determining the after injection amount described above are set so that the after injection becomes smaller as the alcohol concentration becomes lower. Therefore, the alcohol concentration and the after injection amount have a relationship as shown in FIG. 4, for example.

  Here, alcohol contains oxygen in the molecule and has a low cetane number compared to light oil, so it takes a long time to ignite, it has a low boiling point and fuel vaporization is fast, and it is sprayed due to low kinematic viscosity and low surface tension. Has the property of being atomized and easily vaporized. For this reason, when the mixing ratio of alcohol in the mixed fuel (in other words, alcohol concentration) increases, the amount of PM generated by after injection decreases. On the contrary, when the mixing ratio of alcohol in the mixed fuel occurs, the amount of PM generated by after injection increases.

  On the other hand, in the present embodiment, as described above, the amount of after-injection is reduced when the alcohol concentration is low. Therefore, it is possible to suppress an increase in the amount of PM generated due to a decrease in the alcohol concentration. That is, even if the characteristics of the fuel become easy to discharge PM, the increase in PM is offset by reducing the injection amount accordingly, and the PM discharge amount as a whole can be reduced or maintained.

  As described above, according to the control apparatus for an internal combustion engine according to the present embodiment, it is possible to reduce the PM emission amount in the internal combustion engine using the mixed fuel containing alcohol.

  In the above-described embodiment, the method of selecting the after injection amount control map in accordance with the alcohol concentration has been described. However, the lower the alcohol concentration, the smaller the after injection amount is determined. For example, other methods may be used. That is, the specific method for determining the after injection amount is not particularly limited.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. The control device is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 100 ... ECU, 101 ... Air cleaner, 110 ... Compressor, 113 ... Intercooler, 117 ... EGR pipe, 118 ... EGR control valve, 120 ... Turbine, 122 ... Exhaust gas purification catalyst, 200 ... Engine, 201 ... Cylinder, 207 ... Intake pipe , 208 ... Throttle valve, 210 ... Injector, 300 ... Fuel tank, 310 ... Fuel supply pipe, 320 ... Fuel sensor, 330 ... Alcohol concentration sensor, 410 ... Refueling detector, 420 ... Alcohol concentration detector, 430 ... After injection amount Determining unit, 440 ... after injection control unit.

Claims (2)

A control device for an internal combustion engine that uses light oil and alcohol alone or in combination as fuel,
Alcohol concentration detection means for detecting the alcohol concentration in the fuel;
After-injection control means for performing after-injection after the main injection of the fuel;
An internal combustion engine control device comprising: an injection amount adjusting unit that controls the after injection control unit so that an injection amount in the after injection decreases as the alcohol concentration in the fuel decreases. Refueling detection means for detecting refueling of the fuel,
2. The control apparatus for an internal combustion engine according to claim 1, wherein the alcohol concentration detection unit detects an alcohol concentration in the fuel every time the fuel supply is detected.

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