JP2007278254A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine using hydrogen as fuel and surely improving startability without using a heater when starting up the internal combustion engine operable with alcohol or composite fuel of alcohol and gasoline. <P>SOLUTION: Hydrogen is produced from alcohol by a reformer 11 and the hydrogen is supplied to the engine along with alcohol in cold starting of the engine. At that time, the more intake-air temperature TA lowers, the more a start air-fuel ratio AFST is set to be on a lean side, and alcohol is supplied in a manner that an air-fuel ratio which is a ratio of air and alcohol reaches the start air-fuel ratio AFST. The hydrogen concentration is controlled so that the more the intake-air temperature TA lowers, the more the hydrogen concentration increases. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that can be operated with alcohol or a mixed fuel of alcohol and gasoline.

  An internal combustion engine that can be operated using alcohol as fuel instead of gasoline has a problem that startability is particularly poor because alcohol is less likely to vaporize than gasoline. In order to solve this problem, Patent Document 1 discloses that a part of alcohol is reformed into a gas fuel mainly composed of hydrogen and carbon monoxide, and the gas fuel obtained by the reforming is supplied at start-up. Thus, an alcohol fuel engine starter having improved startability is shown.

Japanese Patent Publication No.62-59215

  However, even if the gas fuel is used supplementarily, good startability may not be obtained depending on the engine temperature or the ambient temperature at the time of starting. The above-mentioned Patent Document 1 does not describe how much gas fuel is supplied, and the starter employs a method of ensuring a reliable startability by heating. This necessitates a heater for heating, resulting in a complicated structure and an increase in cost.

  The present invention has been made paying attention to this point, and when starting an internal combustion engine that can be operated by alcohol or a mixed fuel of alcohol and gasoline, hydrogen is used as a fuel and without using a heater. Another object of the present invention is to provide a control device for an internal combustion engine that can improve startability.

  In order to achieve the above object, an invention according to claim 1 is directed to a control device for an internal combustion engine (1) operable with alcohol or a mixed fuel of alcohol and gasoline. A hydrogen generation means (11) for generating hydrogen, a fuel supply means for supplying alcohol or the mixed fuel to the engine, and a hydrogen supply means for supplying hydrogen to the engine when the engine is started. The generation unit includes a concentration determination unit that determines a hydrogen concentration (H2ST) to be supplied to the engine in accordance with the temperature (TW) of the engine or the ambient temperature (TA) of the engine.

  According to a second aspect of the present invention, there is provided a control device for an internal combustion engine operable by alcohol, a hydrogen generation means for generating hydrogen from the alcohol, and a hydrogen supply means for supplying the hydrogen to the engine when the engine is started. And a starting air-fuel ratio determining means for determining a starting air-fuel ratio (AFST) at the time of starting the engine, and the engine so that the ratio of air and alcohol supplied to the engine becomes the starting air-fuel ratio (AFST). An alcohol supply means for supplying alcohol, wherein the hydrogen generation means determines a hydrogen concentration (H2ST) to be supplied to the engine according to a temperature (TW) of the engine or an atmospheric temperature (TA) of the engine. A density determining means is provided.

  According to the first aspect of the present invention, when the engine is started, hydrogen is supplied to the engine together with alcohol or alcohol-mixed fuel, and the concentration of hydrogen supplied to the engine is determined according to the temperature of the engine or the atmospheric temperature of the engine. Therefore, good startability can be obtained regardless of the temperature of the engine or the ambient temperature of the engine.

  According to the second aspect of the present invention, at the time of starting the engine, alcohol is supplied to the engine and hydrogen is supplied so that the ratio of air to alcohol becomes the determined starting air-fuel ratio. The hydrogen concentration supplied to the engine is determined according to the engine temperature or the engine ambient temperature. During cold starting when the engine temperature is low, alcohol is supplied so that the starting air-fuel ratio is leaner than the stoichiometric air-fuel ratio, thereby suppressing a decrease in the temperature in the combustion chamber due to latent heat of vaporization, and further adjusting the hydrogen concentration to the engine temperature or By setting according to the engine atmosphere temperature, the startability can be further improved.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. An internal combustion engine (hereinafter referred to as “engine”) 1 is a four-cylinder engine that can be operated using alcohol as a fuel. A throttle valve 3 is provided in the intake pipe 2 of the engine 1. A throttle valve opening sensor 22 for detecting the throttle valve opening TH is connected to the throttle valve 3, and a detection signal corresponding to the throttle valve opening TH is supplied to an electronic control unit (hereinafter referred to as “ECU”) 5. .

  The fuel injection valve 6 is provided for each cylinder in the middle of the intake pipe 2 and slightly upstream of an intake valve (not shown) between the engine 1 and the throttle valve 3. Further, a hydrogen injection valve 7 that injects hydrogen when the engine 1 is started is provided in the vicinity of the fuel injection valve 6. The fuel injection valve 6 is connected to a fuel tank 9 via a fuel supply pipe 8, and the hydrogen injection valve 7 is connected to a reformer 11 via a hydrogen supply pipe 12. Fuel, that is, alcohol (for example, ethanol) is supplied to the reformer 11 through the fuel passage 10. The reformer 11 reacts water and oxygen in the air with alcohol to generate hydrogen.

  The fuel injection valve 6 and the hydrogen injection valve 7 are electrically connected to the ECU 5, and the valve opening time is controlled by a signal from the ECU 5. An intake pipe absolute pressure sensor 23 that detects the intake pipe absolute pressure PBA and an intake air temperature sensor 24 that detects the intake air temperature TA are mounted on the downstream side of the throttle valve 3 of the intake pipe 2. Detection signals from these sensors are supplied to the ECU 5.

  An engine speed sensor 25 for detecting the engine speed (engine speed) is attached around the camshaft or crankshaft (not shown) of the engine 1. The engine speed sensor 25 outputs a pulse (TDC pulse) at a predetermined crank angle position every 180 degrees rotation of the crankshaft of the engine 1. An engine cooling water temperature sensor 26 for detecting the engine cooling water temperature TW is attached to the main body of the engine 1, and the detection signal is supplied to the ECU 5.

FIG. 2 is a block diagram showing a configuration of the reformer 11. The reformer 11 includes a low temperature plasma reactor 33 and a gas recovery unit 34.
The low temperature plasma reactor 33 promotes the chemical reaction represented by the following formulas (1) to (3) by the low temperature plasma, and generates a mixed gas of hydrogen, carbon dioxide, water, and carbon monoxide. Formulas (1) to (3) show a partial oxidation reaction, a complete oxidation reaction, and a gas shift reaction. Any conventionally known apparatus that generates low-temperature plasma can be used, such as a pulse corona type, a silent discharge type, and a packed bed type.

C ₂ H ₅ OH + 1 / 2O ₂ → 2CO + 3H ₂ (1)
C ₂ H ₅ OH + 3O ₂ → 2CO ₂ + 3H ₂ O (2)
CO + H ₂ O → CO ₂ + H ₂ (3)
The gas recovery unit 34 recovers and outputs hydrogen from the mixed gas.

FIG. 3 is a flowchart of a process for performing alcohol supply control when the engine is cold-started. This process is executed by the CPU of the ECU 5 in synchronization with the TDC pulse.
In step S11, the AFST table shown in FIG. 5A is retrieved according to the intake air temperature TA, and the starting air-fuel ratio AFST is calculated. The AFST table is set so that the starting air-fuel ratio AFST increases (leanes) as the intake air temperature TA decreases. In FIG. 5A, intake air temperatures TA1, TA2, and TA3 are, for example, −25 ° C., 10 ° C., and 25 ° C., and air-fuel ratios AF1, AF2, and AF3 are, for example, 20, 10, and 9 (alcohol fuel). Is equivalent to the theoretical air-fuel ratio).

In step S12, the valve opening time TAL of the fuel injection valve 6 is calculated according to the starting air-fuel ratio AFST and the engine speed NE. That is, the valve opening time TAL is determined according to the engine speed NE so that the mass ratio (air-fuel ratio) of alcohol and air in the air-fuel mixture supplied to the engine 1 becomes the starting air-fuel ratio AFST.
In step S13, drive control of the fuel injection valve 6 is performed according to the calculated valve opening time TAL.

FIG. 4 is a flowchart of a process for performing hydrogen supply control at the time of cold start of the engine. This process is also executed by the CPU of the ECU 5 in synchronization with the generation of the TDC pulse.
In step S21, the H2ST table shown in FIG. 5B is retrieved according to the intake air temperature TA, and the starting hydrogen concentration H2ST is calculated. The H2ST table is set so that the starting hydrogen concentration H2ST increases as the intake air temperature TA decreases. In FIG. 5B, the intake air temperatures TA1, TA2, and TA3 are the same as those in FIG. 5A, and the hydrogen concentrations H2N1 and H2N2 are, for example, 8% and 2% (volume concentration). When the intake air temperature TA is equal to or higher than the temperature TA3, the engine can be started without supplying hydrogen, so the starting hydrogen concentration H2ST is set to “0”.

In step S22, the valve opening time TH2 of the hydrogen injector 7 is calculated according to the starting hydrogen concentration H2ST and the engine speed NE. That is, the valve opening time TH2 is determined according to the engine speed NE so that the hydrogen concentration H2N in the air-fuel mixture supplied to the engine 1 becomes the starting hydrogen concentration H2ST.
In step S23, drive control of the hydrogen injector 7 is performed according to the calculated valve opening time TH2.

  According to the processing shown in FIGS. 3 and 4, alcohol is supplied so that the ratio of air to alcohol (air-fuel ratio) AF becomes the determined starting air-fuel ratio AFST, and when the intake air temperature TA is low (TA <TA3), hydrogen is supplied. Then, as the intake air temperature TA becomes lower, the starting air-fuel ratio AFST is set to the lean side, and the starting hydrogen concentration H2ST is set to be higher. Thereby, at the time of cold start with a low engine temperature, the engine startability can be further improved by supplying hydrogen while suppressing a decrease in the temperature in the combustion chamber due to the latent heat of vaporization of alcohol.

  In the present embodiment, the reformer 11 corresponds to hydrogen generation means, the fuel injection valve 6, the fuel supply pipe 8, and the ECU 5 constitute fuel supply means, and the hydrogen injection valve 7, the hydrogen supply pipe 12, and the ECU 5 A hydrogen supply unit is configured, and the ECU 5 configures a concentration determination unit and a starting air-fuel ratio determination unit. Specifically, the process of FIG. 3 corresponds to a part of the fuel supply means and the starting air-fuel ratio determining means, and the process of FIG. 4 corresponds to a part of the hydrogen supply means and the concentration determination means.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the start air-fuel ratio AFST and the start hydrogen concentration H2ST are determined according to the intake air temperature TA as the ambient temperature of the engine 1 using the table shown in FIG. The starting air-fuel ratio AFST and the starting hydrogen concentration H2ST may be determined according to the indicated engine coolant temperature TW. As the table used in this case, a table in which the horizontal axis in FIG. 5 is changed to the engine cooling water temperature TW can be used almost as it is.

  In the above-described embodiment, the engine start control using 100% alcohol fuel is shown. However, the same control can be performed for an engine using a mixed fuel of alcohol and gasoline. However, the stoichiometric air-fuel ratio of the mixed fuel is intermediate between the stoichiometric air-fuel ratio (14.7) of gasoline and the stoichiometric air-fuel ratio (9) of alcohol, and changes depending on the mixing ratio RMIX of both fuels. Is corrected according to the mixture ratio RMIX, and the starting air-fuel ratio AFST is determined using the corrected table.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a block diagram which shows the structure of the reformer shown in FIG. It is a flowchart of the process which performs fuel supply control at the time of engine starting. It is a flowchart of the process which performs hydrogen supply control at the time of engine starting. It is a figure which shows the table referred by the process of FIG. 3 or FIG.

Explanation of symbols

1 Internal combustion engine 5 Electronic control unit (fuel supply means, hydrogen supply means, concentration determination means, starting air-fuel ratio determination means 6 Fuel injection valve (fuel supply means)
7 Hydrogen injection valve (hydrogen supply means)
8 Fuel supply pipe (fuel supply means)
9 Fuel tank 10 Fuel passage 11 Reformer (hydrogen generating means)
12 Hydrogen supply pipe (hydrogen supply means)
24 Intake air temperature sensor 26 Engine coolant temperature sensor

Claims (2)

In a control device for an internal combustion engine operable with alcohol or a mixed fuel of alcohol and gasoline,
Hydrogen generating means for generating hydrogen from the alcohol or a mixed fuel of alcohol and gasoline;
Fuel supply means for supplying alcohol or the mixed fuel to the engine;
A hydrogen supply means for supplying the hydrogen to the engine when starting the engine;
The control device for an internal combustion engine, wherein the hydrogen generation means includes a concentration determination means for determining a hydrogen concentration supplied to the engine in accordance with a temperature of the engine or an atmospheric temperature of the engine. In a control device for an internal combustion engine operable by alcohol,
Hydrogen generating means for generating hydrogen from the alcohol;
Hydrogen supply means for supplying the hydrogen to the engine when the engine is started;
A starting air-fuel ratio determining means for determining a starting air-fuel ratio when starting the engine;
Alcohol supply means for supplying the alcohol to the engine so that a ratio of air and alcohol supplied to the engine becomes the starting air-fuel ratio;
The control device for an internal combustion engine, wherein the hydrogen generation means includes a concentration determination means for determining a hydrogen concentration supplied to the engine in accordance with a temperature of the engine or an atmospheric temperature of the engine.

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