JP2007198198A - Fuel control device for alcohol-mixed fuel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel control device for an alcohol-mixed fuel engine capable of accurately controlling a supply fuel quantity even if moisture is contained in alcohol-mixed fuel. <P>SOLUTION: In the fuel control device for the alcohol-mixed fuel engine provided with a fuel supply means 6 supplying alcohol-mixed fuel, an alcohol concentration detection means 30 detecting an alcohol concentration of the alcohol-mixed fuel, and a supply fuel quantity control means 20 controlling a supply fuel quantity to a predetermined target air fuel ratio according to an alcohol concentration, contained moisture concentration estimation means 20, 27 estimating a concentration of moisture contained in the alcohol-mixed fuel, and a correction means 20 correcting an alcohol concentration detection value by the alcohol concentration detection means according to the contained moisture concentration estimated by the contained moisture concentration estimation means are provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel control device for an engine, and more particularly to a fuel control device for an alcohol-mixed fuel engine mounted on a so-called flexible fuel vehicle using gasoline or an alcohol-mixed fuel obtained by mixing gasoline and alcohol.

  Alcohol fuel is considered promising as one of alternative fuels to petroleum fuel, and there is an example that is partially put into practical use as a so-called alcohol mixed fuel in which gasoline and alcohol are mixed. However, this alcohol-mixed fuel has different calorific value and vaporization characteristics compared to 100% gasoline fuel, and the characteristics also differ depending on the alcohol concentration indicating the mixing ratio to gasoline, so it is assumed that 100% gasoline fuel is used. If the alcohol-mixed fuel is used as it is in the engine, the control air-fuel ratio deviates from the stoichiometric air-fuel ratio, and the exhaust component changes or the drivability deteriorates.

  Therefore, for example, in Patent Document 1, in an air-fuel ratio control of an engine that uses an alcohol-containing fuel, an alcohol concentration detection sensor that detects an alcohol concentration based on a change in the dielectric constant of the fuel is used. It is disclosed to perform the control.

Japanese Patent Publication No. 6-29580

  By the way, in the alcohol concentration detection sensor that detects the alcohol concentration based on the change in the dielectric constant of the fuel, a high output value is generated when the dielectric constant of the fuel increases. It was found that the rate also showed different numbers. That is, as shown in FIG. 3, even if the alcohol concentration is the same, the output value of the alcohol concentration detection sensor increases as the moisture concentration contained in the fuel increases. In other words, the output value of the alcohol concentration detection sensor is the same. Even so, the true alcohol concentration varies with the moisture concentration.

  Therefore, even if the amount of fuel supplied is controlled based on the output value of the alcohol concentration detection sensor, there is no problem if the water concentration is 0%, but if the water concentration exceeds a predetermined value, the control becomes inaccurate and the emission is reduced. There was a problem of deteriorating the quality and reducing drivability.

  Therefore, an object of the present invention is to provide a fuel control device for an alcohol-mixed fuel engine that can accurately control the amount of fuel supplied even when the alcohol-mixed fuel contains moisture.

  A fuel control device for an alcohol-mixed fuel engine according to an embodiment of the present invention that achieves the above object includes a fuel supply unit that supplies an alcohol-mixed fuel, an alcohol concentration detection unit that detects an alcohol concentration of the alcohol-mixed fuel, and an alcohol concentration A fuel control device for an alcohol-mixed fuel engine comprising: a fuel-supply control unit that controls the amount of fuel supplied so as to achieve a predetermined target air-fuel ratio in accordance with the estimation of the concentration of water contained in the alcohol-mixed fuel And a correction means for correcting an alcohol concentration detection value obtained by the alcohol concentration detection means in accordance with the contained water concentration estimated by the contained water concentration estimation means.

  Here, the contained water concentration estimating means is based on an air-fuel ratio correction coefficient set based on a deviation between the predetermined target air-fuel ratio and a detected air-fuel ratio based on an output value of an air-fuel ratio detecting means provided in the exhaust system. The contained water concentration may be estimated in correspondence with the magnitude of the fuel injection characteristic learning value.

  According to the above aspect of the present invention, the alcohol concentration of the alcohol mixed fuel is detected by the alcohol concentration detecting means, and the amount of supplied fuel is controlled so as to be a predetermined target air-fuel ratio corresponding to the alcohol concentration. Then, the concentration of moisture contained in the alcohol-mixed fuel is estimated by the contained moisture concentration estimating means, and the alcohol concentration detection value by the alcohol concentration detecting means is corrected by the correcting means according to the estimated contained moisture concentration. The true alcohol concentration is required. As a result, the supplied fuel amount is accurately controlled by the supplied fuel amount control means so as to reach a predetermined target air-fuel ratio in accordance with the true alcohol concentration, so that deterioration of emission and drivability are suppressed.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic side view showing a system configuration according to an embodiment of a fuel control apparatus for an alcohol-mixed fuel engine, and FIG. 2 is a schematic plan view mainly showing a fuel system.

  First, in FIG. 1, an electronically controlled throttle valve (hereinafter referred to as an electric throttle valve) 4 is controlled by an intake passage 3 from an air cleaner 2 in a combustion chamber of each cylinder of an engine 1 mounted on a vehicle. In response, a predetermined amount of air is inhaled according to the operating state. An electromagnetic injector 6 is provided so as to directly inject the alcohol mixed fuel into the combustion chamber. The injector 6 is energized to the solenoid by an injection pulse signal output in an intake stroke or a compression stroke in synchronization with engine rotation from an electronic control unit (hereinafter referred to as ECU) 20 to be described later, and opens as described later. Further, an alcohol mixed fuel adjusted to a predetermined pressure is injected. The injected alcohol-mixed fuel diffuses into the combustion chamber in the case of intake stroke injection to form a homogeneous mixture, and in the case of compression stroke injection, the stratified mixture is concentrated around the spark plug 7. And is ignited by the spark plug 7 based on an ignition signal from the ECU 20, which will be described later, and combusts (homogeneous combustion or stratified combustion).

  Exhaust gas from the engine 1 is discharged from an exhaust passage 8, and an exhaust purification catalyst (for example, a three-way catalyst) 9 is interposed in the exhaust passage 8. A part of the exhaust gas is recirculated to the intake passage 3 downstream of the throttle valve 4 of the intake passage 3 by the EGR passage 11 through the electric control EGR valve 10.

  The fuel is sucked up from the fuel tank 12 by the low-pressure pump 13, pressurized to the target injection pressure by the high-pressure pump 15 connected via the low-pressure supply passage, and commonly connected to the injector 6. 16 is supplied. Reference numeral 17 denotes a return passage for returning excess fuel from the fuel delivery pipe 16 to the fuel tank 12.

  The ECU 20 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like, receives input signals from various sensors described later, performs arithmetic processing based on the signals, The operation of the electric throttle valve 4, the injector 6, the spark plug 7, the electric EGR valve 10, the low pressure pump 13 and the high pressure pump 15 is controlled.

  As the various sensors, a crank position sensor 21 for detecting the crankshaft rotation of the engine 1 is provided. When the number of cylinders is m, the crank position sensor 21 outputs a reference pulse signal at a predetermined crank angle position at every crank angle of 720 ° / m and outputs a unit pulse signal every 1 to 2 °. Therefore, the engine speed can be calculated from the period of the reference pulse signal. In addition, an intake air temperature sensor 23 that detects the intake air temperature in the air cleaner 2, an accelerator position sensor 24 that detects the amount of accelerator pedal depression (accelerator opening), and a throttle position sensor 25 that detects the opening of the electric throttle valve 4. A water temperature sensor 26 that detects the cooling water temperature of the engine 1, an air-fuel ratio sensor (linear air-fuel ratio sensor, oxygen sensor, etc.) 27 that outputs a signal corresponding to the exhaust air-fuel ratio or rich lean of the air-fuel mixture in the exhaust passage 8. The intake pipe pressure sensor 28 for detecting the pressure in the intake passage 3 downstream of the electric throttle valve 4, the fuel pressure sensor 29 for detecting the fuel pressure in the fuel delivery pipe 16, and the alcohol concentration of the alcohol-mixed fuel in the dielectric constant An alcohol concentration sensor 30 for detecting the change is provided.

  Next, an example of a true alcohol concentration calculation routine performed by the ECU 20 in the embodiment having the above system configuration will be described with reference to a flowchart shown in FIG.

  This calculation routine is executed every predetermined time (for example, 10 ms) after the engine is started. First, in step S410, the apparent alcohol concentration Alc 'of the alcohol mixed fuel fed into the fuel delivery pipe 16 is calculated based on the detection or measurement value from the alcohol concentration sensor 30. Then, in the next step S420, it is determined whether or not a fuel injection characteristic learning value (KG) calculated by a fuel injection characteristic learning value calculation routine, which will be described later, is greater than or equal to a predetermined value (= α).

  When the fuel injection characteristic learning value (KG) is smaller than the predetermined value in the determination in step S420, the alcohol concentration currently used for the control reflects the true alcohol concentration Alc, in other words, the apparent alcohol The routine is terminated assuming that the concentration Alc ′ is substantially equal to the true alcohol concentration Alc.

  On the other hand, if it is determined in step S420 that the fuel injection characteristic learning value (KG) is equal to or greater than a predetermined value, it is determined that the true alcohol concentration Alc has not been detected as a result of water being mixed in the alcohol-mixed fuel. Then, the water concentration Water (%) in the alcohol-mixed fuel is estimated from the fuel injection characteristic learning value (KG). The relationship between the fuel injection characteristic learning value (KG) and the water concentration Water (%) in the alcohol-mixed fuel is as shown in the graph of FIG. 5, and the water concentration increases as the fuel injection characteristic learning value (KG) increases. There is a proportional relationship in which Water (%) also increases. Based on this relationship, the value of the water concentration Water (%) corresponding to the fuel injection characteristic learning value (KG) is obtained in advance through experiments or the like and stored in the map.

  When the water concentration Water (%) is estimated in step S430, the process proceeds to step S440, where the apparent alcohol concentration Alc ′ calculated in step S410 and the water concentration Water (%) obtained in step S430 above are obtained. Based on this, the true alcohol concentration Alc is calculated, and this routine ends. More specifically, the alcohol concentration sensor 30 detects the alcohol concentration of the alcohol-mixed fuel based on the change in the dielectric constant, but the output value of the alcohol concentration detection sensor 30 is the same as shown in FIG. However, since the true alcohol concentration Alc changes corresponding to the water concentration Water (%), the apparent alcohol based on the alcohol concentration detection value by the alcohol concentration sensor 30 according to the estimated water concentration Water (%). The concentration Alc ′ is corrected, and the true alcohol concentration Alc is obtained.

  More specifically, referring to FIG. 3, when the output value of the alcohol concentration detection sensor 30 is D, the true alcohol concentration in the case of the water concentration Water (= 0%) is Alc0, and the water concentration Water ( = 5%), the true alcohol concentration is Alc5, and the true alcohol concentration in the case of the water concentration Water (= 10%) is Alc10. The relationship between the true alcohol concentration Alc, the apparent alcohol concentration Alc ', and the water concentration Water (%) is also obtained in advance through experiments or the like and stored in the map.

  Here, the outline of the air-fuel ratio feedback and learning control routine used for calculating the fuel injection characteristic learning value (KG) described above will be described.

  First, the fuel injection amount TAU injected and supplied from the injector 6 to the engine 1 is the engine speed calculated based on the pulse signal from the crank position sensor 21 in order to obtain a predetermined target air-fuel ratio (for example, the theoretical air-fuel ratio). With respect to the basic injection amount TAUBSE based on the intake pipe pressure PM detected by the NE and the intake pipe pressure sensor 28, a correction coefficient (for example, an intake coefficient) corresponding to detection signals detected and inputted to various sensors according to the state of the engine 1 is used. The air temperature correction coefficient THA, the water temperature correction coefficient TWA, the alcohol concentration correction coefficient ALC, etc.), the air / fuel ratio feedback correction coefficient FAF, and the air / fuel ratio learning value KG are multiplied, for example, by the following equation.

TAU = TAUBSE × (THA × TWA × ALC...) × FAF × (1 + KG)
Here, the intake air temperature correction coefficient THA is a correction coefficient in accordance with the intake air temperature detected by the intake air temperature sensor 23. When the intake air temperature is low, the air density increases, so the air temperature increases. The water temperature correction coefficient TWA increases. Is a correction coefficient corresponding to the cooling water temperature detected by the above, and is set to be larger than 1 so as to increase the amount when the cooling water temperature is low. The alcohol concentration correction coefficient ALC is a correction coefficient corresponding to the alcohol concentration detected by the alcohol concentration sensor 30, and is set to increase when the alcohol concentration is high. The air-fuel ratio feedback correction coefficient FAF is determined based on the output of the air-fuel ratio sensor 27 to determine whether the air-fuel ratio is rich or lean. If the air-fuel ratio is rich, the air-fuel ratio feedback correction coefficient FAF is decreased by a predetermined integral with respect to the previous value so as to decrease. On the contrary, when the air-fuel ratio is lean, it is set to increase by a predetermined integral with respect to the previous value so as to increase. Further, at the time of rich / lean reversal, the air-fuel ratio feedback correction coefficient FAF is set so as to be increased or decreased by a predetermined proportion with respect to the previous value.

  The learning control routine used to calculate the fuel injection characteristic learning value (KG) is executed as shown in the flowchart of FIG. 6, for example. In this learning control routine, first, in step S610, it is determined whether air-fuel ratio feedback control is being performed. Specifically, for example, it is determined by whether or not the air-fuel ratio sensor 27 has been warmed up, or whether or not it is within a predetermined operating range, and this routine is terminated when the air-fuel ratio feedback control is not being performed. (At this time, the air-fuel ratio feedback correction coefficient FAF is held at the previous value), and the process proceeds to step S620 and subsequent steps only when it is established.

  Therefore, when the air-fuel ratio feedback control is being performed, the routine proceeds to step S620, where it is determined whether or not the air-fuel ratio feedback correction coefficient FAF is 1. If the air-fuel ratio feedback correction coefficient FAF is 1, the routine is terminated assuming that the fuel injection amount is appropriately controlled. If not, the process proceeds to step S630.

  In step S630, it is determined whether or not the air-fuel ratio feedback correction coefficient FAF is smaller than 1. If the determination is affirmative (YES), the process proceeds to step S640. If the determination is negative (NO), the process proceeds to step S660. In these steps S640 and S660, it is determined whether or not the state in which the air-fuel ratio feedback correction coefficient FAF is smaller than 1 and larger than 1 has occurred successively a predetermined number of times. In other words, it is determined whether or not the rich state and the lean state are continuously continued for a predetermined number of learning times (for example, 30 times) satisfying the learning condition. Note that the fact that the rich state or the lean state continues for a predetermined number of times means that the supplied alcohol-mixed fuel and / or the injector 6 have unique characteristics. In step S640 and step S660, respectively, when the learning condition is satisfied (YES), the process proceeds to step S650 and step S670, respectively, and the fuel injection characteristic learning value (KG) is updated.

  The fuel injection characteristic learning value (KG) updated in step S650 due to the continuation of the rich state is obtained by subtracting a predetermined value from the learning value before the update, and a new fuel injection characteristic learning value (in which the learning result is reflected) KG), and the fuel injection characteristic learning value (KG) updated in step S670 by continuing the lean state is a new fuel injection in which a predetermined value is added to the learning value before the update and the learning result is reflected. The characteristic learning value (KG) is used. In step S640 and step S660, when the predetermined number of times is not exceeded, that is, when the determination is negative (NO), this routine is terminated because the learning accuracy is not sufficient, and the update of the learning value is prohibited.

  In the present embodiment, as described above, when the apparent alcohol concentration Alc ′ based on the alcohol concentration detection value by the alcohol concentration sensor 30 is corrected and the true alcohol concentration Alc is obtained, the true alcohol concentration Alc is obtained. Using the corresponding alcohol concentration correction coefficient ALC, the above-described fuel injection amount TAU is obtained, and the engine 1 is operated. Thus, the fuel injection amount is accurately controlled so as to achieve a predetermined target air-fuel ratio in accordance with the true alcohol concentration Alc, so that deterioration of emissions and drivability are suppressed.

  In the above description, the case of the alcohol mixed fuel in which alcohol is mixed with gasoline has been described. However, it goes without saying that the present invention is also applicable to the case where only alcohol is used as the fuel. From this point of view, in the present specification, the alcohol mixed fuel is used to include the case where the alcohol is 100%.

1 is a schematic side view showing a system configuration according to an embodiment of a fuel control device for an alcohol-mixed fuel engine according to the present invention. Similarly, it is a schematic plan view mainly showing a fuel system. It is a graph which shows the influence of moisture concentration in the relationship between alcohol concentration and a dielectric constant. It is a flowchart which shows an example of the true alcohol concentration calculation control routine in one Embodiment of this invention. It is a graph which shows the relationship between a learning value and moisture concentration. It is a flowchart which shows an example of the air fuel ratio feedback used for calculating the fuel injection characteristic learning value in one Embodiment of this invention, and a learning control routine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 4 Electric throttle valve 6 Injector 7 Spark plug 10 Electric EGR valve 20 Electronic control unit 21 Crank position sensor 27 Air-fuel ratio sensor 28 Intake pipe pressure sensor 30 Alcohol concentration sensor

Claims (2)

Fuel supply means for supplying alcohol mixed fuel, alcohol concentration detection means for detecting the alcohol concentration of the alcohol mixed fuel, and supply fuel amount control for controlling the amount of supplied fuel so as to reach a predetermined target air-fuel ratio according to the alcohol concentration A fuel control device for an alcohol-mixed fuel engine comprising:
Containing moisture concentration estimating means for estimating the concentration of moisture contained in the alcohol mixed fuel;
Correction means for correcting the alcohol concentration detection value by the alcohol concentration detection means according to the contained water concentration estimated by the contained water concentration estimation means;
A fuel control device for an alcohol-mixed fuel engine. The moisture content estimation means includes a fuel injection characteristic based on an air-fuel ratio correction coefficient set based on a deviation between the predetermined target air-fuel ratio and a detected air-fuel ratio based on an output value of an air-fuel ratio detection means provided in an exhaust system. 2. The fuel control apparatus for an alcohol-mixed fuel engine according to claim 1, wherein the moisture content concentration is estimated in correspondence with the magnitude of the learning value.

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