JP2017002764A - Engine control device for mixed fuel of alcohol and gasoline - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an engine control device for mixed fuel of alcohol and gasoline of which high precise alcohol concentration can be estimated while its cost is low.SOLUTION: An absolute humidity of intake air is calculated under application of a relative humidity detected by an intake humidity sensor 3 and an air temperature detected by an air flow sensor 1, a volume of intake air is calculated in reference to the air temperature detected by the air flow sensor 1 and air mass, and oxygen mass in the intake air is calculated in reference to the calculated absolute humidity and volume of the intake air. A fuel volume is calculated in reference to a fuel injection pulse width and fuel mass is calculated in reference to the calculated fuel volume. A mole ratio of oxygen/fuel is calculated in reference to the calculated oxygen mass of intake air and fuel mass, alcohol concentration in the fuel is estimated in reference to a relation between the mole ratio of oxygen/fuel and an alcohol concentration in the fuel, and various engine control parameters are corrected in response to the estimated alcohol concentration.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an engine control apparatus that performs optimal engine control using estimation of alcohol concentration in fuel.

  In an in-cylinder injection gasoline engine for automobiles, the air-fuel ratio changes depending on the concentration of alcohol mixed in the fuel to be injected. Therefore, in order to control the engine with high efficiency and improve fuel efficiency, a mechanism for estimating the alcohol concentration in the fuel and controlling the engine according to the value is required.

  In the conventional Ramcon (air-fuel ratio feedback control using an air-fuel ratio (A / F) sensor), the alcohol concentration in the fuel is estimated and various engine control parameters are corrected according to the estimated value. Has been done.

  As a method for estimating the alcohol concentration in the fuel, there is a method of detecting the alcohol concentration of the fuel in the fuel tank using an alcohol concentration sensor, or the alcohol concentration in the fuel passing through the fuel intake pipe using the alcohol concentration sensor. A technique for detecting the concentration is known.

  By using these estimation methods, it is possible to estimate the alcohol concentration in the fuel and to correct various engine control parameters according to the value.

  However, the alcohol concentration sensor has low responsiveness and detection accuracy, is considered unsuitable for use for the purpose of controlling the engine with high efficiency and improving fuel consumption, and cannot be used.

  As a technique for such a problem, there is an alcohol concentration estimation method described in Patent Document 1. This technique utilizes the fact that the alcohol concentration in the fuel is determined in a one-to-one relationship with the humidity in the exhaust gas generated by supplying the fuel, and humidity sensors are used on each of the intake side and the exhaust side.

JP 62-189333 A

  The technique described in Patent Document 1 calculates the humidity in the exhaust gas generated by the fuel supply by subtracting the humidity in the intake air from the humidity in the exhaust gas, and the humidity in the exhaust gas and the alcohol volume ratio This is a technique for estimating the alcohol concentration in the fuel from the relationship graph.

  However, disposing a humidity sensor on each of the intake side and the exhaust side requires two humidity sensors, which increases the cost. Also, there should be a time difference between the intake air combusting with the fuel in the engine cylinder and being output as exhaust gas, and the exhaust generated by the fuel supply calculated based on the difference in humidity between the two. The humidity in the gas may not be exact.

  Therefore, a technique for improving the accuracy of the estimated alcohol concentration and more accurately correcting various control parameters using accurate humidity information measured by a single humidity sensor is required.

  An object of the present invention is to realize an engine control device for an alcohol / gasoline mixed fuel capable of estimating a high-precision alcohol concentration at a low cost.

  In order to achieve the above object, the present invention is configured as follows.

  In an alcohol / gasoline mixed fuel engine control apparatus, an intake humidity sensor for detecting the humidity of intake air sucked into a vehicle engine, and an airflow sensor for detecting the temperature and mass of the intake air sucked into the vehicle engine And an engine control unit for controlling the engine of the vehicle.

  The engine control unit calculates an oxygen mass of the intake air based on the humidity of the intake air detected by the intake humidity sensor and the temperature and mass of the intake air detected by the air flow sensor, and The mass of fuel supplied to the engine is calculated based on the width of the fuel injection pulse supplied to the fuel injection device, and the molar ratio of oxygen to fuel is calculated from the calculated mass of the fuel and the oxygen mass of the intake air. Is calculated, the alcohol concentration of the fuel is estimated from the calculated molar ratio, the engine control parameter is corrected according to the estimated alcohol concentration, and the engine of the vehicle is controlled.

  ADVANTAGE OF THE INVENTION According to this invention, the engine control apparatus of the alcohol / gasoline mixed fuel which can estimate a highly accurate alcohol concentration can be implement | achieved at low cost.

It is a flowchart of the alcohol concentration estimation method in the fuel in Example 1 of this invention. 1 is a system diagram of an entire engine according to first to third embodiments of the present invention. It is a system block diagram which shows the structure of the control apparatus of the engine by Examples 1-3 of this invention. It is a graph which shows the relationship of the absolute humidity by the Examples 1-2 of this invention, relative humidity, and air temperature. It is a graph which shows the relationship between the molar ratio of oxygen / fuel by Example 1-3 of this invention, and the ethanol density | concentration in a fuel. It is a graph which shows the relationship between the molar ratio of oxygen / fuel by Example 1-3 of this invention, and the methanol density | concentration in a fuel. It is a relationship graph of the fuel-injection pulse width and fuel injection quantity by Examples 1-3 of this invention. It is a flowchart which uses the correction coefficient using the alcohol concentration estimated value by Examples 1-3 of this invention. It is a flowchart of the alcohol concentration estimation method in the fuel by Example 2 of this invention. It is a flowchart of the alcohol concentration estimation method in the fuel by Example 3 of this invention.

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

Example 1
In Embodiment 1 of the present invention, the humidity sensor is disposed only on the intake side, and the oxygen mass calculated from the humidity information and the fuel mass calculated from the fuel volume, which is known from the fuel injection pulse width, are used. Thus, the alcohol concentration in the fuel is estimated.

  The principle of Embodiment 1 of the present invention will be described.

  The chemical reaction formula when oxygen in the intake air and gasoline and ethanol in the fuel burn in the engine cylinder can be expressed as the following formula (1), where r is the ethanol content on a molar basis. .

xO ₂ + (1-r) * C _n H _m + (r) * C ₂ H ₅ OH → yH ₂ O + zCO ₂ (1)
In the above formula (1), x, y, z, n, and m are variables.

  When the oxygen, gasoline, and ethanol react without excess and deficiency and the chemical reaction formula (1) is established, the stoichiometry (theoretical air / fuel ratio) is detected by the air / fuel ratio (A / F) sensor 9 during complete combustion. ) Is detected.

  When stoichiometry is detected, the ideal air-fuel ratio depends on the composition of the fuel, that is, the ratio of gasoline to ethanol, and the ideal air-fuel ratio for gasoline only and ethanol is generally known as a known value. doing. Therefore, it is possible to calculate each ideal oxygen fuel ratio from these values, and when taking into consideration that the above chemical reaction equation (1) holds, the oxygen fuel ratio and the ethanol concentration in the fuel This relationship can be expressed as a linear graph in which the oxygen fuel ratio when the fuel contains only gasoline is the maximum value, and the oxygen fuel ratio when the fuel contains only ethanol is the minimum value.

  From this, if the respective masses can be calculated in order to obtain the molar ratio of oxygen to fuel, the ethanol concentration in the fuel can be estimated from the above-mentioned linear graph.

  The chemical reaction formula when oxygen in the intake air and gasoline and methanol in the fuel are burned in the engine cylinder is as follows: Can express.

xO ₂ + (1-t) * C _n H _m + (t) * CH ₃ OH → yH ₂ O + zCO ₂ (2)
Also in this case, the methanol concentration in the fuel can be estimated from a straight line graph based on the same concept as described above.

  First, a method for calculating the mass of oxygen will be described.

  An airflow sensor that measures the relative humidity [%] of the intake air, the intake air amount, and the intake temperature detected by the intake humidity sensor 3 in the stoichiometric state detected by the air-fuel ratio (A / F) sensor 9. The absolute humidity [g / l] of the intake air is calculated from the intake air temperature [K] detected by 1.

  On the other hand, in the stoichiometric state detected by the air-fuel ratio (A / F) sensor 9, the intake air temperature [K] detected by the air flow sensor 1 that measures the intake air amount and the intake air temperature, and the intake air The volume [l / s] of the intake air is calculated from the air mass [g / s] detected by the air flow sensor 1 that measures the amount and the intake air temperature.

  From the above-described absolute humidity [g / l] and volume [l / s] of the intake air, it is possible to determine the composition of the intake air, that is, the ratio of nitrogen, oxygen, and water. Mass [g / s] can be calculated.

  Next, a method for calculating the mass [g / s] of the fuel will be described.

The fuel volume [mm ³ ] can be calculated from the fuel injection pulse width that controls the fuel injection amount.

  On the other hand, the mass [g / s] of the fuel can be calculated by multiplying the specific gravity of the fuel, which is a known value.

  From the oxygen mass [g / s] of the intake air calculated above and the mass [g / s] of the fuel, it is possible to calculate the amounts of oxygen and fuel (mol), respectively. The molar ratio of the fuel can be obtained, and the ethanol concentration or the methanol concentration in the fuel can be estimated from the linear graph.

  The first embodiment of the present invention based on the above principle will be described below.

  FIG. 1 is a flowchart of an alcohol concentration estimation method according to Embodiment 1 of the present invention, FIG. 2 is a system diagram of the entire engine according to Embodiment 1 of the present invention, and FIG. 3 is a control of the engine according to Embodiment 1 of the present invention. It is a system block diagram which shows the structure of an apparatus.

  First, with reference to FIG. 2 and FIG. 3, an overall engine system and an engine control apparatus according to Embodiment 1 of the present invention will be described.

In FIG. 2, an engine 100 is an automobile gasoline engine that performs spark ignition combustion. The engine 100 includes an air flow sensor 1 that measures intake air mass and intake air temperature, an electronic control throttle 2 that adjusts intake pipe pressure, an intake humidity sensor 3 that detects intake humidity, and an intake air O ₂ that detects the amount of oxygen. A sensor 4 and an intake pressure sensor 7 for detecting atmospheric pressure are provided at appropriate positions in the intake pipe.

  Here, the intake humidity sensor 3 is a sensor capable of detecting relative humidity and absolute humidity. The engine 100 is also provided with a fuel injection device (injector) 13 for injecting fuel into the cylinder 14 of each cylinder, and an ignition plug 16 for supplying ignition energy.

  The cylinder head is provided with a variable valve 5 that adjusts gas flowing into or out of the cylinder. By adjusting the variable valve 5, the intake air amount of all cylinders is adjusted. Although not shown, a high-pressure fuel pump for supplying high-pressure fuel to the fuel injection device 13 is connected to the fuel injection device 13 by a fuel pipe, and in the fuel pipe, a fuel injection pressure is measured. A fuel pressure sensor is provided.

  Furthermore, a three-way catalyst 10 that purifies the exhaust and an air-fuel ratio detector, an air-fuel ratio (A / F) sensor 9 that detects the air-fuel ratio of the exhaust on the upstream side of the three-way catalyst 10 is exhausted. Each tube 15 is disposed at an appropriate position.

  Signals obtained from the airflow sensor 1, the intake humidity sensor 3, the intake O2 sensor 4, the intake pressure sensor 7, the fuel level sensor 8, the air-fuel ratio (A / F) sensor 9, and the battery voltage sensor 17 are transmitted to an engine control unit (ECU ) 20. A signal supplied from the accelerator opening sensor 12 is sent to the ECU 20. The accelerator opening sensor 12 detects the depression amount of the accelerator pedal, that is, the accelerator opening. The ECU 20 calculates the required torque based on the output signal of the accelerator opening sensor 12. That is, the accelerator opening sensor 12 is used as a required torque detection sensor that detects a required torque for the engine. Moreover, ECU20 calculates the rotational speed of an engine based on the output signal of a crank angle sensor.

  The ECU 20 optimally calculates main operating amounts of the engine such as the air flow rate, the fuel injection amount, the ignition timing, and the fuel pressure based on the operating state of the engine obtained from the outputs of the various sensors.

  The fuel injection amount calculated by the ECU 20 is converted into a valve opening pulse signal and sent to the injector 13. Further, an ignition signal is sent to the spark plug 16 so that ignition is performed at the ignition timing calculated by the ECU 20. The throttle opening calculated by the ECU 20 is sent to the electronic control throttle 2 as a throttle drive signal.

  Fuel is injected into the air that flows into the cylinder 14 from the intake pipe through the intake valve to form an air-fuel mixture. The air-fuel mixture explodes due to a spark generated from the spark plug 16 at a predetermined ignition timing, and the piston is pushed down by the combustion pressure to become the driving force of the engine. Further, the exhaust gas after the explosion is sent to the three-way catalyst 10 through the exhaust pipe 15, and the exhaust components are purified in the three-way catalyst 10 and discharged to the outside.

  In FIG. 2, reference numeral 6 is an intake manifold, 8 is a fuel level sensor, and 17 is a battery voltage sensor. The fuel level sensor 8 detects the level of fuel in a fuel tank that stores engine fuel.

  Next, in FIG. 3, an airflow sensor 1, an intake humidity sensor 3, an intake O2 sensor 4, an intake pressure sensor 7, a fuel level sensor 8, an air-fuel ratio (A / F) sensor 9, an accelerator opening sensor 12, a battery voltage sensor. The output signal 17 is input to the input circuit 20 a of the ECU 20. However, the input signal is not limited to these. The input signal of each input sensor is sent to the input port in the input / output port 20b. The value sent to the input port 20b is stored in the RAM 20c and processed by the CPU 20e. A control program describing the contents of the arithmetic processing is written in advance in the ROM 20d. The ROM 20d also has a relationship between absolute humidity, relative humidity, and air temperature (FIG. 4), a relationship between oxygen / fuel molar ratio and ethanol concentration in fuel (FIG. 5), an oxygen / fuel molar ratio and fuel. The relationship between the methanol concentration in the fuel (FIG. 6) and the relationship between the fuel injection amount and the fuel injection pulse width (FIG. 7) are stored.

  A value indicating the operation amount of each actuator calculated according to the control program is stored in the RAM 20c, then sent to the output port in the input / output port 20b, and sent to each actuator via each drive circuit. In the case of Embodiment 1 of the present invention, there are an electronic control throttle drive circuit 20f, an injector drive circuit 20g, and an ignition device drive circuit 20h as drive circuits. Each circuit controls an electronic control throttle 2, a fuel injection device (injector) 13, and a spark plug 16, respectively. In the first embodiment of the present invention, the ECU 20 is provided with the drive circuit. However, the present invention is not limited to this, and any of the drive circuits may be provided in the ECU 20.

  Next, a method for estimating the alcohol concentration in fuel according to the first embodiment of the present invention will be described. The method for estimating the alcohol concentration in the fuel is that the CPU 20e in the ECU 20 inputs the input to the input circuit 20a, the processing program stored in the ROM 20d, the relationship between the ethanol concentration in the fuel and the oxygen / fuel molar ratio, the fuel This is performed based on the relationship between the methanol concentration in the fuel and the molar ratio of oxygen / fuel and the relationship between the fuel injection pulse width and the fuel injection amount.

In step S101 of FIG. 1, after the stoichiometry is detected by the air-fuel ratio (A / F) sensor 9, a relationship graph (FIG. 7) between a fuel injection pulse width and a fuel injection amount, which will be described later, is used in step S102. Then, the fuel volume [mm ³ ] is calculated from the fuel injection pulse width commanded to the fuel injection device 13 and is multiplied by the specific gravity of the fuel in step S103, thereby obtaining the mass [g / s] of the fuel. Is calculated.

  At the same time, the relative humidity “%” detected by the intake humidity sensor 3 in step S104 and the air temperature [K] detected by the airflow sensor 1 that measures the intake air amount and the intake temperature in step S105. ] And the oxygen mass [g / s] in the intake air in step S109 using the air mass [g / s] detected by the air flow sensor 1 that measures the intake air amount and the intake air temperature in step S106. calculate.

  Next, the flow until the oxygen mass [g / s] in the intake air in step S109 is calculated will be described.

  In step S107, in order to calculate the absolute humidity [g / l] of the intake air, the relative humidity “%” detected by the intake humidity sensor 3 in step S104, the intake air amount and the intake temperature in step S105. The air temperature [K] detected by the air flow sensor 1 that measures the above is used. For the calculation, a relational graph of absolute humidity, relative humidity, and air temperature, which will be described later, FIG. 4 (wet air diagram) is used. In FIG. 4, the atmospheric pressure is 101.325 kPa (seawater level), but in order to calculate a more accurate value, it is necessary to take into account the value of the atmospheric pressure detected by the intake pressure sensor 7.

  The relative humidity “%” is an index indicating the ratio of the maximum amount of water that the air can contain, but in order to estimate the composition of the intake air in step S109, a specific numerical value of the amount of water is necessary. Therefore, this step of calculating the absolute humidity [g / l] of the intake air is necessary.

  In step S108, in order to calculate the volume [l / s] of the intake air, in step S105, the air temperature [K] detected by the air flow sensor 1 that measures the intake air amount and the intake air temperature; In step S106, the air mass [g / s] detected by the air flow sensor 1 that measures the intake air amount and the intake air temperature is used. The following gas equation of state (3) is used for the calculation. Here, as the pressure P, the value of the atmospheric pressure detected by the intake pressure sensor 7 is used.

PV = nRT = (w / M) RT → V = ((w / M) RT) / P (3)
In the above formula (3), P is pressure, V is volume, R is gas constant, T is temperature, w is gas mass, M is gas molar mass (molecular weight), and n is gas substance mass (mol). Number).

  In step S109, in order to estimate the composition in the intake air and calculate the oxygen mass [g / s], the absolute humidity [g / l] of the intake air calculated in step S107 is calculated in step S108. In addition, the volume of intake air [l / s] is used. With this information, it is possible to calculate the amount of moisture in the air, and since the ratio of nitrogen and oxygen in the air is generally known, the composition of the intake air, that is, nitrogen, oxygen, water The ratio can be determined and therefore the oxygen mass [g / s] of the intake air can be calculated.

  In step S110, in order to calculate the molar ratio of oxygen / fuel, the fuel mass [g / s] calculated in step S103 and the oxygen mass [g / s] calculated in step S109 are used. From the respective masses calculated above, it is possible to calculate the substance amount (number of moles) of oxygen and fuel, and hence the oxygen / fuel molar ratio can be determined.

  In step S111, the oxygen / fuel molar ratio calculated in step S110 is used to estimate the alcohol concentration in the fuel. For the estimation, a graph showing the relationship between the molar ratio of oxygen / fuel and the ethanol concentration in the fuel shown in FIG. 5 described later, or the molar ratio of oxygen / fuel and the methanol in fuel shown in FIG. 6 described later. Use the graph of concentration relationship.

  In step S112, in order to perform more accurate correction of various control parameters, the alcohol concentration in the fuel estimated in step S111 is used.

  FIG. 4 is a relationship graph (humid air diagram) of absolute humidity, relative humidity, and air temperature. In step S107 of FIG. 1, the relative humidity “%” detected by the intake humidity sensor 3 in step S104, and It is used to calculate the absolute humidity [g / l] of the intake air using the air temperature [K] detected by the air flow sensor 1 that measures the intake air amount and the intake air temperature in step S105. .

  FIG. 5 is a graph showing the relationship between the oxygen / fuel molar ratio and the ethanol concentration in the fuel. In step S111 of FIG. 1, the fuel is calculated using the oxygen / fuel molar ratio calculated in step S110. Used to estimate the alcohol concentration in the medium.

  The ideal air-fuel ratio at the time of detecting stoichiometry depends on the composition in the fuel, that is, the ratio of gasoline to ethanol, and the ideal air-fuel ratio of gasoline only and ethanol only is generally known as a known value. Existing.

  Therefore, it is possible to calculate the ideal oxygen fuel ratio from these values. The relationship between the oxygen fuel ratio and the ethanol concentration in the fuel is that the gasoline-only oxygen fuel ratio is the maximum value and the ethanol-only oxygen fuel ratio is the minimum value. And can be expressed as a straight line graph.

  FIG. 6 is a graph showing the relationship between the molar ratio of oxygen / fuel and the concentration of methanol in the fuel. In step S111 of FIG. 1, the fuel ratio is calculated using the molar ratio of oxygen / fuel calculated in step S110. Used to estimate the alcohol concentration in the medium.

  The ideal air-fuel ratio at the time of detecting stoichiometry depends on the composition of the fuel, that is, the ratio of gasoline to methanol, and the ideal air-fuel ratio for gasoline only and methanol is generally known as a known value. doing.

  Therefore, it is possible to calculate each ideal oxygen fuel ratio from these values, and the relationship between the oxygen fuel ratio and the methanol concentration in the fuel is such that the oxygen fuel ratio of gasoline alone is the maximum value, and the oxygen fuel ratio of methanol alone is calculated. It can be expressed as a straight line graph with the minimum value.

FIG. 7 is a graph showing the relationship between the fuel injection pulse width and the fuel injection amount, and is used when calculating the fuel volume [mm ³ ] from the fuel injection pulse width in step S102 of FIG. is there. The flow rate is determined by the valve opening pulse width of the fuel injection device (injector) 13, and FIG. 7 shows the linearity of the fuel injection pulse width and the fuel injection amount. In the region where the pulse width is small, the valve (needle) of the injector 13 cannot be fully opened, so that the injection amount is not stable and the linearity is also greatly deviated.

  The flow rate characteristics are stable when the fuel injection pulse width is from 1.5 msec to 9.0 msec. When the fuel injection pulse width is 9.0 msec or more, the valve of the injector 13 is not completely closed, and the fuel injection amount increases. Usually, a region where the linearity of a small injection region having a pulse width of 1.5 msec or less and a large injection region having a pulse width of 9.5 msec or more cannot be secured is not used.

  FIG. 8 is a flowchart using the correction coefficient using the estimated alcohol concentration value according to the first embodiment of the present invention, and shows the conditions for using the correction coefficient using the estimated alcohol concentration value. The operation shown in FIG. 8 is executed by the CPU 20e of the ECU 20.

  After detecting the ignition ON in step S801 in FIG. 8, it is determined in step S802 whether fuel has been supplied during the ignition OFF period. Immediately before the previous ignition OFF, the fuel level detected by the fuel level sensor 8 is held (stored) in a ROM (memory) 20d in the ECU 20, and this and the fuel detected when the ignition is turned ON this time. When the levels are compared and the value is increased, it can be determined that fuel supply has been performed. Further, when the previous fuel level is not maintained, for example, even when this time is the first ignition ON for the vehicle, it is determined that the fuel has been supplied regardless of the comparison result of the fuel level.

  If it is determined in step S802 that fuel supply has been performed, the correction coefficient using the estimated alcohol concentration is updated in step S803, and if it is not determined that fuel supply has been performed, step S803 is performed. In S804, the learning control correction coefficient is updated. Thereafter, using one of the selected correction coefficients, in step S805, the fuel injection amount is adjusted, the ignition timing is adjusted, and the intake air amount is adjusted. As a result, it is possible to avoid interference between two irrelevant correction coefficients and perform more accurate adjustment.

  As described above, in the first embodiment of the present invention, the absolute humidity of the intake air is calculated using the relative humidity detected by the intake humidity sensor 3 and the air temperature detected by the airflow sensor 1, and the airflow sensor 1 detects the absolute humidity. The volume of intake air is calculated from the calculated air temperature and air mass, and the oxygen mass in the intake air is calculated from the absolute humidity and volume of the calculated intake air. On the other hand, the fuel volume is calculated from the fuel injection pulse width, and the fuel mass is calculated from the calculated fuel volume.

  Then, the molar ratio of oxygen / fuel is calculated from the calculated oxygen mass in the intake air and the mass of fuel, and the alcohol concentration in the fuel is estimated from the relationship between the molar ratio of oxygen / fuel and the alcohol concentration in the fuel. The engine control parameters are corrected according to the estimated alcohol concentration.

  Therefore, according to the first embodiment of the present invention, the accuracy of the estimated alcohol concentration is improved by using accurate humidity information measured by a single humidity sensor, and more accurate correction of various control parameters can be performed. Therefore, it is possible to realize an engine control apparatus for alcohol / gasoline mixed fuel that can be performed at low cost and can estimate alcohol concentration with high accuracy.

(Example 2)
Next, a second embodiment of the present invention will be described. Note that the overall engine system, the configuration of the engine control device, the relationship between the oxygen / fuel molar ratio and the ethanol concentration in the fuel, the relationship between the oxygen / fuel molar ratio and the methanol concentration in the fuel, the fuel injection pulse width and the fuel Since the flow of the correction coefficient using the relationship between the injection amount and the estimated alcohol concentration value is the same as that in the first embodiment, illustration and detailed description thereof are omitted.

  FIG. 9 is a flowchart of a method for estimating the alcohol concentration in fuel according to the second embodiment of the present invention.

  The difference between the first embodiment and the second embodiment of the present invention is that the intake air shown in step S913 of FIG. 9 is used instead of using the relative humidity [%] detected by the intake humidity sensor 3 shown in step S104 of FIG. The absolute humidity [g / l] detected by the humidity sensor 3 is used.

  In general, there are humidity sensors that can detect only relative humidity and those that can detect relative humidity and absolute humidity. This determines which type of humidity sensor to use depending on the application. For example, when fuel injection is used to control the amount of inflow air, a humidity sensor capable of detecting relative humidity and absolute humidity is used.

  Example 1 mentioned above is a more suitable example when the humidity sensor which detects only relative humidity is used.

  On the other hand, Example 2 is an example in the case of using a humidity sensor capable of detecting absolute humidity.

  Therefore, in the second embodiment, the air flow sensor 1 that measures the relative humidity “%” detected by the intake humidity sensor 3 in step S104 and the intake air amount and the intake temperature in step S105 in step S107 of FIG. The calculation step for calculating the absolute humidity [g / l] based on the air temperature [K] detected by the above is omitted.

  In the second embodiment of the present invention, the correction coefficient using the estimated alcohol concentration value can be calculated with a smaller number of steps and good response.

  Steps S101 to S103, S105, S106, and S108 to S112 shown in FIG. 1 have the same contents as Steps S901 to S903, S905, S906, and S908 to S912 shown in FIG. 9, and Steps S104 and S107 in FIG. Instead, step S913 of detecting the absolute humidity by the intake humidity sensor 3 is shown in FIG.

  In the second embodiment of the present invention, as in the first embodiment, in step S909 in FIG. 9, the composition in the intake air is estimated, and the oxygen mass [g / s] is calculated in step S913. The absolute humidity [g / l] of the intake air and the volume [l / s] of the intake air calculated in step S908 are used. With this information, it is possible to calculate the amount of moisture in the air, and since the ratio of nitrogen and oxygen in the air is generally known, the composition of the intake air, that is, nitrogen, oxygen, water The ratio can be determined and therefore the oxygen mass [g / s] of the intake air can be calculated.

  Thereafter, in step S911, the oxygen / fuel molar ratio calculated in step S910 is used to estimate the alcohol concentration in the fuel. For the estimation, a graph showing the relationship between the oxygen / fuel molar ratio and the ethanol concentration in the fuel shown in FIG. 5, or the relationship between the oxygen / fuel molar ratio and the methanol concentration in the fuel shown in FIG. A graph showing is used.

  Also in the second embodiment of the present invention, the same effect as in the first embodiment can be obtained, and the correction coefficient using the estimated alcohol concentration value can be calculated with a smaller number of steps and good responsiveness.

(Example 3)
Next, Embodiment 3 of the present invention will be described. Note that the overall engine system, the configuration of the engine control device, the relationship between the oxygen / fuel molar ratio and the ethanol concentration in the fuel, the relationship between the oxygen / fuel molar ratio and the methanol concentration in the fuel, the fuel injection pulse width and the fuel Since the flow of the correction coefficient using the relationship between the injection amount and the estimated alcohol concentration value is the same as that in the first embodiment, illustration and detailed description thereof are omitted.

  FIG. 10 is a flowchart of the method for estimating the alcohol concentration in fuel according to the third embodiment of the present invention.

The difference between the first embodiment and the third embodiment of the present invention is that the intake air O shown in step S1014 of FIG. 10 is used instead of using the relative humidity [%] detected by the intake humidity sensor 3 shown in step S104 of FIG. _The oxygen mass [g / s] calculated by the _two sensors 4 is used. When the highly accurate intake O ₂ sensor 4 is used for engine control, the oxygen mass can be calculated by the intake O ₂ sensor 4.

By calculating the oxygen mass with the intake O ₂ sensor 4, steps S 104, S 105, S 106, S 107, S 108, and S 109 in FIG. 1 are omitted, and the responsiveness is reduced with a smaller number of steps. Then, it becomes possible to calculate a correction coefficient using the estimated alcohol concentration value.

Step S101~S103 shown in FIG. 1, S110 to S112, the step S1001~S1003 shown in FIG. 10, a similar content as S1010～S1012, instead of step S104~S109 of FIG. 1, the intake _{O 2} sensor Step S1014 for calculating the oxygen mass according to 4 is shown in FIG.

  In the third embodiment of the present invention, as in the first embodiment of the present invention, the oxygen / fuel mole ratio calculated in step S1010 is used to estimate the alcohol concentration in the fuel in step S1011 of FIG. Use the ratio. For the estimation, a graph showing the relationship between the oxygen / fuel molar ratio and the ethanol concentration in the fuel shown in FIG. 5, or the relationship between the oxygen / fuel molar ratio and the methanol concentration in the fuel shown in FIG. Use a graph that shows.

  Also in the third embodiment of the present invention, the same effect as in the first embodiment can be obtained, and the correction coefficient using the estimated alcohol concentration value can be calculated with a smaller number of steps and good responsiveness.

  In addition, this invention is not limited to above-described Examples 1-3, Various modifications are included. For example, the above-described first to third embodiments are described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

  Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment.

  Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit.

  Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor.

1 ... intake air amount and the air flow sensor for measuring the intake air temperature, 2 ... electronic control throttle, 3 ... intake humidity sensor, 4 ... intake _{O 2} sensor, 5 ... variable valve, 6 - ..Intake manifold, 7 ... Intake pressure sensor, 8 ... Fuel level sensor, 9 ... Air-fuel ratio (A / F) sensor, 10 ... Three-way catalyst, 12 ... Accelerator opening sensor , 13 ... Fuel injection device (injector), 14 ... Cylinder, 15 ... Exhaust pipe, 16 ... Spark plug, 17 ... Battery voltage sensor, 20 ... ECU, 20a ... Input circuit, 20b ... input / output port, 20c ... RAM, 20d ... ROM, 20e ... CPU, 20f ... electronically controlled throttle drive circuit, 20g ... injector drive circuit, 20h ...・ Ignition device drive times Road, 100 ... engine

Claims (5)

An intake humidity sensor for detecting the humidity of the intake air taken into the engine of the vehicle;
An air flow sensor for detecting the temperature and mass of the intake air sucked into the engine of the vehicle;
The oxygen mass of the intake air is calculated based on the humidity of the intake air detected by the intake humidity sensor and the temperature and mass of the intake air detected by the air flow sensor and supplied to the fuel injection device of the engine of the vehicle The mass of fuel supplied to the engine is calculated based on the width of the injected fuel pulse, and the molar ratio of oxygen to fuel is calculated from the calculated mass of the fuel and the oxygen mass of the intake air. An alcohol / gasoline mixture comprising: an engine control unit that estimates an alcohol concentration of the fuel from the molar ratio, corrects a control parameter of the engine according to the estimated alcohol concentration, and controls the engine of the vehicle. Fuel engine control device. In the engine control device of the alcohol / gasoline mixed fuel according to claim 1,
An air-fuel ratio sensor for detecting an air-fuel ratio of the exhaust gas of the engine, wherein the intake humidity sensor is a relative humidity sensor or an absolute humidity sensor, and the engine control unit detects the stoichiometry when the air-fuel ratio sensor detects a stoichiometry In which the oxygen mass of the intake air is calculated based on the humidity of the intake air detected by the intake humidity sensor and the temperature and mass of the intake air detected by the air flow sensor. Fuel engine control device. The engine control device for alcohol / gasoline mixed fuel according to claim 2,
The engine control unit performs adjustment of the fuel injection amount of the fuel injection device, adjustment of the ignition timing of the engine, and adjustment of the intake air amount to the engine according to the estimated alcohol concentration in the fuel. Characteristic engine control device for alcohol / gasoline mixed fuel. The engine control device for alcohol / gasoline mixed fuel according to claim 3,
A fuel level sensor that detects a fuel level in a fuel tank that stores the fuel of the engine; a memory that stores a correction coefficient for correcting the control parameter of the engine and a learning control correction coefficient; and the engine control unit includes: When it is determined that the fuel has been supplied to the fuel tank according to the fuel level detected by the fuel level sensor, the correction coefficient stored in the memory is updated, and the fuel is supplied to the fuel tank. An engine control apparatus for alcohol / gasoline mixed fuel, wherein the learning control correction coefficient is updated if it is determined that the learning control correction coefficient has not been determined. An O ₂ sensor for detecting an oxygen mass of intake air taken into a vehicle engine;
An air-fuel ratio sensor for detecting the air-fuel ratio of the engine exhaust;
When the air-fuel ratio sensor detects stoichiometry, the mass of fuel supplied to the engine is calculated based on the width of the fuel injection pulse supplied to the fuel injection device of the engine of the vehicle, and the calculated The molar ratio of oxygen to fuel is calculated from the mass of fuel and the oxygen mass detected by the O ₂ sensor, the alcohol concentration of the fuel is estimated from the calculated molar ratio, and the engine control is performed according to the estimated alcohol concentration. And an engine control unit for correcting the parameters and controlling the engine of the vehicle.

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