JP2009138556A - Estimating device and estimating method of fuel concentration of flexible fuel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an estimating device and an estimating method of a fuel concentration of a flexible fuel engine capable of easily and accurately estimating the concentration of fuels even when an exclusive sensor capable of detecting the concentration of the fuels of composite fuel is not provided. <P>SOLUTION: An electronic control unit 15 of the flexible fuel engine 10 using the composite fuel of two kinds of fuels of alcohol and gasoline calculates the calorific value per unit mass of the burned composite fuel in combustion based on a combustion pressure detected by a cylinder pressure sensor 14, and estimates the alcohol concentration of the composite fuel in use based on the calculated calorific value. Therefore, the alcohol concentration of the composite fuel in use can be easily and accurately estimated without having the exclusive sensor capable of directly detecting the alcohol concentration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flexible fuel engine that uses a mixed fuel of two types of fuels having different calorific values per unit mass at the time of combustion, and estimates the concentration of each fuel contained in the mixed fuel in use. The present invention relates to a concentration estimation apparatus and estimation method.

  As is well known, in recent years, flexible fuel engines that can operate using a mixed fuel of alcohol and gasoline have attracted attention because of their low environmental impact. By the way, since the calorific value per unit mass differs between alcohol and gasoline, the fuel supply amount required to generate the same torque varies depending on the alcohol concentration of the mixed fuel. Incidentally, if the air-fuel ratio feedback is being executed, the fuel supply amount is adjusted so that the ratio of the amount of oxygen consumed by the combustion of the fuel to the amount of intake air is kept constant. The excess or deficiency of the fuel supply due to the difference will be corrected autonomously. However, the alcohol concentration of the mixed fuel must be understood in situations where the fuel supply amount is open controlled, such as when the engine is started, when the OT is increased to suppress excessive temperature rise of the catalyst, or when the WOT (Wide Open Throttle) is used. In this case, the fuel supply amount that is originally required cannot be obtained appropriately. In addition, problems such as deterioration of startability, inability to sufficiently suppress overheating of the catalyst, and inability to ensure sufficient WOT performance may occur.

Therefore, conventionally, in such a flexible fuel engine, as seen in Patent Documents 1 and 2, etc., a dedicated sensor for confirming the alcohol concentration of the mixed fuel is installed and the alcohol concentration detected by the sensor is adjusted. Thus, the fuel supply amount and the like are corrected. For example, Patent Document 2 is provided with a sensor for detecting the alcohol concentration of the mixed fuel from the difference in the refractive index of the light irradiated to the mixed fuel.
JP-A-5-099024 Japanese Patent Laid-Open No. 1-113558

  Thus, if the alcohol concentration of the mixed fuel in use is detected using a dedicated sensor, the fuel supply amount can be appropriately adjusted according to the alcohol concentration. However, for that purpose, it is necessary to additionally install a dedicated sensor for detecting the alcohol concentration, and an increase in the manufacturing cost is unavoidable.

Such a problem is common to flexible fuel engines using a mixed fuel of two kinds of fuels having different calorific values per unit mass at the time of combustion.
The present invention has been made in view of such a situation, and the problem to be solved is that the concentration of each fuel is determined even if a dedicated sensor capable of detecting the concentration of each fuel of the mixed fuel is not provided. An object of the present invention is to provide a fuel concentration estimation apparatus and estimation method for a flexible fuel engine that can be estimated easily and accurately.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
In order to solve the above-mentioned problem, the invention described in claim 1 includes a flexible fuel engine that uses a mixed fuel of two types of fuels having different calorific values per unit mass during combustion, and is included in the mixed fuel in use. A fuel concentration estimation device for a flexible fuel engine for estimating a concentration of each fuel, wherein the calorific value calculation means calculates a calorific value per unit mass at the time of combustion of the mixed fuel, and the respective calorific values based on the calorific value The gist of the invention is to provide a concentration estimation means for estimating the concentration of fuel.

  In a mixed fuel composed of two types of fuels having different calorific values per unit mass at the time of combustion, the calorific value per unit mass at the time of combustion naturally changes depending on the mixing ratio of each fuel. Therefore, the calorific value per unit mass of the burned mixed fuel can be obtained, and the concentration of each fuel can be estimated based on the calorific value. Therefore, according to the said structure, the density | concentration of each fuel of the mixed fuel in use can be estimated easily and exactly.

  According to a second aspect of the present invention, in the fuel concentration estimating apparatus for a flexible fuel engine according to the first aspect, the calorific value calculation means calculates a calorific value per unit mass at the time of combustion of the mixed fuel as a combustion pressure. The gist is to calculate from the detected value.

  From the combustion pressure at a certain point in time during combustion, the instantaneous calorific value at that point can be obtained. Therefore, as in the above configuration, the calorific value per unit mass at the time of combustion of the mixed fuel can be calculated from the detected value of the combustion pressure. In this case, since the fuel concentration can be estimated using an existing sensor for detecting the combustion pressure, a so-called in-cylinder pressure sensor, the estimation of the concentration of each fuel in the mixed fuel in use can It can be done without increasing it.

  According to a third aspect of the present invention, in the fuel concentration estimation apparatus of the flexible fuel engine according to the second aspect, the calorific value calculation means is a heat generation amount that is a heat generation amount per unit time due to combustion of the mixed fuel. And calculating the total amount of heat generated by combustion of the mixed fuel in one combustion cycle as a time integral value of the heat generation rate in one combustion cycle, and further calculating the total amount of heat generated The main point is to calculate the calorific value per unit mass at the time of combustion of the mixed fuel by dividing by the supply amount of the mixed fuel in the cycle.

More specifically, the estimation of the fuel concentration using the detected value of the combustion pressure by the calorific value calculation means of the estimation device according to claim 2 can be performed, for example, in the above-described manner.
According to a fourth aspect of the present invention, in the fuel concentration estimating apparatus of the flexible fuel engine according to the second aspect, the calorific value calculation means is a heat that is a heat generation amount per unit crank angle due to combustion of the mixed fuel. The generation rate is calculated from the detected value of the combustion pressure, and the total amount of heat generation due to combustion of the mixed fuel in one combustion cycle is obtained as the crank angle integral value of the heat generation rate in one combustion cycle, and further the heat generation amount The main point is to calculate the calorific value per unit mass at the time of combustion of the mixed fuel by dividing the total amount of fuel by the supply amount of the mixed fuel in the cycle.

More specifically, the estimation of the fuel concentration using the detected value of the combustion pressure by the calorific value calculation means of the estimation apparatus according to claim 2 can be performed in the above-described manner, for example.
According to a fifth aspect of the present invention, in the fuel concentration estimating apparatus for a flexible fuel engine according to any one of the first to fourth aspects, the concentration estimating means is calculated for each combustion cycle by the calorific value calculating means. The gist of the present invention is to obtain an average value of the prescribed number of combustion cycles for the calorific value per unit mass at the time of combustion of the mixed fuel, and to estimate the concentration of each fuel based on the average value.

  In the above configuration, the concentration of each fuel is estimated based on the average value in the multiple combustion cycles for the calorific value per unit mass at the time of combustion of the mixed fuel calculated for each combustion cycle. Will be able to do.

  The invention described in claim 6 is the apparatus for estimating the fuel concentration of a flexible fuel engine according to any one of claims 1 to 5, wherein the flexible fuel engine uses a mixed fuel of alcohol and gasoline. It is the gist of that.

Thus, the fuel concentration estimation apparatus according to claims 1 to 5 can be applied to a flexible fuel engine that uses a mixed fuel of alcohol and gasoline.
In order to solve the above-mentioned problem, the invention described in claim 7 includes a flexible fuel engine that uses a mixed fuel of two kinds of fuels having different calorific values per unit mass at the time of combustion, and is included in the mixed fuel in use. The gist of the method is to estimate the concentration of each fuel, which is to obtain a calorific value per unit mass during combustion of the mixed fuel and to estimate the concentration of each fuel based on the calorific value.

  In a mixed fuel composed of two types of fuels having different calorific values per unit mass at the time of combustion, the calorific value per unit mass at the time of combustion naturally changes depending on the mixing ratio of each fuel. Therefore, it is possible to obtain the calorific value per unit mass at the time of combustion of the mixed fuel and to estimate the concentration of each fuel based on the calorific value. Therefore, according to the estimation method, the concentration of each fuel in the mixed fuel in use can be estimated easily and accurately.

  The invention according to claim 8 is the method for estimating the fuel concentration of the flexible fuel engine according to claim 7, wherein the calorific value per unit mass at the time of combustion of the mixed fuel is calculated from the detected value of the combustion pressure. Is the gist.

  From the combustion pressure at a certain point in time during combustion, the instantaneous calorific value at that point can be obtained. Therefore, as in the above estimation method, the calorific value per unit mass due to the combustion of the mixed fuel can be calculated from the detected value of the combustion pressure. In this case, the fuel concentration can be estimated using an existing sensor for detecting the combustion pressure, a so-called in-cylinder pressure sensor, and the estimation of the concentration of each fuel in the mixed fuel in use increases the manufacturing cost. Will be able to do without.

  According to a ninth aspect of the present invention, in the method for estimating the fuel concentration of the flexible fuel engine according to the eighth aspect, the heat generation rate, which is a heat generation amount per unit time due to combustion of the mixed fuel, is detected as the combustion pressure. And calculating a total amount of heat generated by combustion of the mixed fuel in one combustion cycle as a time integral value of the heat generation rate in one combustion cycle, and further calculating the total amount of generated heat of the mixed fuel in the cycle. The gist is to determine the calorific value per unit mass at the time of combustion of the mixed fuel by dividing by the supply amount.

More specifically, the estimation of the fuel concentration using the detected value of the combustion pressure by the estimation method according to claim 8 can be performed in the above-described manner, for example.
According to a tenth aspect of the present invention, in the method for estimating the fuel concentration of the flexible fuel engine according to the eighth aspect, a heat generation rate, which is a heat generation amount per unit crank angle due to combustion of the mixed fuel, is calculated as the combustion pressure. Calculated from the detected value, obtains the total amount of heat generated by combustion of the mixed fuel in one combustion cycle as the crank angle integral value of the heat release rate in one combustion cycle, and further calculates the total amount of heat generated in the mixing in the cycle The gist is to obtain the calorific value per unit mass at the time of combustion of the mixed fuel by dividing by the fuel supply amount.

More specifically, the estimation of the fuel concentration using the detected value of the combustion pressure by the estimation method according to claim 8 can be performed in the above-described manner, for example.
The invention according to claim 11 is the method for estimating the fuel concentration of the flexible fuel engine according to any one of claims 7 to 10, wherein the unit fuel mass per unit mass at the time of combustion of the mixed fuel calculated for each combustion cycle is used. The gist of the present invention is to obtain an average value in the prescribed number of combustion cycles and to estimate the concentration of each fuel based on the average value.

  In the above estimation method, the fuel concentration is estimated from the average value in a plurality of combustion cycles of the calorific value per unit mass at the time of combustion of the mixed fuel calculated for each combustion cycle. Therefore, according to the estimation method, the fuel concentration can be estimated more accurately.

  A twelfth aspect of the invention is the method for estimating the fuel concentration of a flexible fuel engine according to any one of the seventh to eleventh aspects, wherein the flexible fuel engine uses a mixed fuel of alcohol and gasoline. It is the gist of that.

  Thus, the fuel concentration estimating method according to claims 7 to 11 can be applied to a flexible fuel engine using a mixed fuel of alcohol and gasoline.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment in which a fuel concentration estimation device and estimation method for a flexible fuel engine according to the present invention is embodied will be described in detail with reference to FIGS.
FIG. 1 shows the overall configuration of a fuel concentration estimation apparatus for a flexible fuel engine according to this embodiment. The flexible fuel engine to which this embodiment is applied uses a mixed fuel of alcohol and gasoline. The flexible fuel engine 10 includes a fuel tank 11 that stores a mixed fuel of alcohol and gasoline, and an injector 12 that injects and supplies the mixed fuel stored in the fuel tank 11 to each cylinder. Yes. The combustion chamber 13 of each cylinder is provided with an in-cylinder pressure sensor 14 for detecting the internal pressure, that is, the combustion pressure.

  Such a flexible fuel engine 10 is controlled by an electronic control unit 15. The electronic control unit 15 includes a CPU that performs arithmetic processing related to various controls of the flexible fuel engine 10, a ROM that stores a control program and data, a RAM that temporarily stores arithmetic results of the CPU, and an external signal. The input / output port for input / output is provided. In addition to the detection signal of the in-cylinder pressure sensor 14, the electronic control unit 15 includes an NE sensor 16 for detecting the engine speed, an air flow meter 17 for detecting the intake air amount, and an accelerator operation amount. Detection signals of various sensors such as the accelerator sensor 18 are input. The electronic control unit 15 performs control of the flexible fuel engine 10 such as control of timing and amount of fuel injection by the injector 12 and control of ignition timing based on detection signals of these sensors.

  In this embodiment, the electronic control unit 15 estimates the alcohol concentration of the mixed fuel currently in use. Details of the alcohol concentration estimation by the electronic control unit 15 will be described below.

  In this embodiment, the total amount of heat generated by the combustion of the mixed fuel in one combustion cycle of each cylinder is obtained from the detected value of the combustion pressure by the in-cylinder pressure sensor 14. Then, the total amount of heat generated in one combustion cycle is divided by the amount (supply amount) of the mixed fuel injected and supplied from the injector 12 into the combustion cycle, so that the heat generated per unit mass when the mixed fuel is burned. Is calculated.

  At this time, the calculation of the total amount of heat generated by the combustion of the mixed fuel in one combustion cycle of each cylinder is performed in the following manner. The instantaneous calorific value at a certain point in the combustion cycle has a correlation with the combustion pressure at that point. That is, if the intensity of combustion increases and the instantaneous amount of heat generation increases, the combustion pressure increases accordingly. Therefore, from the combustion pressure at a certain point in the combustion cycle, the instantaneous calorific value at that point can be grasped. Incidentally, the relationship between the combustion pressure and the instantaneous calorific value can be obtained in advance through experiments or the like.

  In the present embodiment, the combustion pressure detected by the in-cylinder pressure sensor 14 is sampled for each predetermined crank angle, and each time, based on the sampled combustion pressure, the amount of heat generated per unit crank angle at that time, that is, The heat generation rate [MJ / ° CA] is calculated. FIG. 2 shows an example of the transition of the heat generation rate in one combustion cycle. In the figure, the area of the portion indicated by hatching is the total amount of heat generated in the combustion cycle. That is, if the integral value for the crank angle [° CA] is obtained for the heat generation rate [MJ / ° CA] in one combustion cycle, the total calorific value [MJ] of the combustion cycle can be obtained. Then, the total calorific value [MJ] of one combustion cycle obtained in this way is divided by the fuel supply amount [L] in that combustion cycle, so that the calorific value per unit mass at the time of combustion of the mixed fuel [MJ / L] Can be calculated.

  In the present embodiment, after starting the engine, the calorific value per unit mass at the time of combustion of the mixed fuel is calculated in a specified number of combustion cycles (for example, 200 times). The average value of the calorific value per unit mass at the time of combustion of the mixed fuel calculated in each of the prescribed number of combustion cycles is obtained.

  In this embodiment, the alcohol concentration of the mixed fuel currently in use is estimated from the average value of the calorific value per unit mass during combustion of the mixed fuel thus obtained. The estimation of the alcohol concentration here is performed in the following manner. That is, the calorific value per unit mass at the time of combustion differs between alcohol and gasoline. Specifically, the calorific value per unit mass of alcohol is about “20 MJ / L”, which is smaller than the calorific value “32 MJ / L” per unit mass of gasoline. Therefore, the calorific value per unit mass at the time of combustion of these mixed fuels changes in accordance with the mixing ratio of both fuels and consequently the alcohol concentration of the mixed fuel.

  FIG. 3 shows the relationship between the alcohol concentration [%] of such a mixed fuel and the calorific value [MJ / L] per unit mass. As shown in the figure, if the calorific value per unit mass at the time of combustion of the mixed fuel is known, the alcohol concentration can be uniquely determined.

  In the present embodiment, the relationship between the alcohol concentration of the mixed fuel and the calorific value per unit mass is stored in the ROM of the electronic control unit 15 in the form of a mathematical formula or a calculation map, and the above calculated unit mass is calculated. The alcohol concentration is estimated from the average value of the calorific value of the mixed fuel per hit. The relationship between the alcohol concentration of the mixed fuel and the calorific value per unit mass can be obtained in advance through experiments or the like.

  FIG. 4 shows a flowchart of an “alcohol concentration estimation routine” employed in this embodiment. The processing of this routine is executed by the electronic control unit 15 immediately after the start of the engine start.

  When this routine is started in response to the engine start, first, in step S10, the electronic control unit 15 obtains the supply amount of the mixed fuel per one combustion cycle of the cylinder to be combusted from the RAM. Subsequently, in step S20, the electronic control unit 15 calculates the calorific value per unit mass of the mixed fuel in the combustion cycle in the above manner from the detection value of the in-cylinder pressure sensor 14 during combustion of the cylinder. In step S30, the electronic control unit 15 stores the calculation result in its own RAM.

  Thereafter, the electronic control unit 15 repeatedly executes the processes of the above steps S10 to S30 for the combustion cycle of the specified number of times (for example, 200 times). When the calculated number of calorific values reaches the specified number of times (S40: YES), the electronic control unit 15 calculates an average value of the calorific value per unit mass for the calculated specified number of combustion cycles in step S50. . Further, in the subsequent step S60, the electronic control unit 15 is currently used based on the average value of the calorific value per unit mass from the relationship between the alcohol concentration of the mixed fuel stored in the ROM and the calorific value per unit mass. The estimated value of the alcohol concentration of the mixed fuel is calculated, and the processing of this routine in the current trip is terminated.

  After that, the electronic control unit 15 performs the open control of the fuel supply amount in a situation where the air-fuel ratio feedback control is not performed, such as when the engine is started, when the OT is increased to suppress overheating of the catalyst, or when the WOT is performed. Under such circumstances, the fuel supply amount is appropriately corrected based on the alcohol concentration thus estimated.

  In this embodiment, the processing of the electronic control unit 15 in step S20 of the alcohol concentration estimation routine corresponds to the processing performed by the calorific value calculation means. Further, the processing of the electronic control unit 15 in step S60 of the alcohol concentration estimation routine corresponds to the processing performed by the concentration estimation means.

According to the fuel concentration estimating apparatus for a flexible fuel engine of the present embodiment described above, the following effects can be obtained.
(1) In this embodiment, the electronic control unit 15 calculates the calorific value per unit mass of the burned mixed fuel, and estimates the alcohol concentration of the mixed fuel based on the calorific value. More specifically, the alcohol concentration is estimated through the following procedures a) to d). That is, a) a heat generation rate that is a heat generation amount per unit crank angle due to combustion of the mixed fuel is calculated from a detected value of the combustion pressure. b) The total amount of heat generated by combustion of the mixed fuel in one combustion cycle is obtained as the crank angle integral value in one combustion cycle of the calculated heat generation rate. c) Calculate the calorific value per unit mass at the time of combustion of the mixed fuel by dividing the total amount of calorific value obtained by the supply amount of the mixed fuel in the cycle. d) An estimated value of the alcohol concentration of the mixed fuel is calculated based on the calorific value. Therefore, the alcohol concentration of the mixed fuel in use can be estimated easily and accurately.

  (2) The gist of the present embodiment is to calculate the calorific value per unit mass at the time of combustion of the mixed fuel from the detected value of the combustion pressure. From the combustion pressure at a certain point in time during combustion, the instantaneous calorific value at that point can be obtained. Therefore, the calorific value per unit mass at the time of combustion of the mixed fuel can be calculated from the detected value of the combustion pressure. In this case, since the fuel concentration can be estimated using an existing sensor for detecting the combustion pressure, so-called in-cylinder pressure sensor 14, the estimation of the alcohol concentration of the mixed fuel in use increases the manufacturing cost. Will be able to do without.

  (3) In this embodiment, the calorific value per unit mass at the time of combustion of the mixed fuel calculated for each combustion cycle is determined in the prescribed number of combustion cycles, and the alcohol concentration is determined based on the average value. I try to estimate. Therefore, more accurate estimation can be performed.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the average value in the 200 combustion cycles is obtained for the calorific value per unit mass at the time of combustion of the mixed fuel calculated for each combustion cycle, and the mixed fuel currently in use is calculated based on the average value. The alcohol concentration was estimated. The number of combustion cycles for obtaining the average of the calorific values can be changed as appropriate. For example, when a higher alcohol concentration estimation accuracy is required, the number of combustion cycles may be increased, and when an earlier concentration estimation is required, the number of combustion cycles may be decreased. Further, when the accuracy of concentration estimation is not particularly required, it is possible to estimate the alcohol concentration based only on the calorific value per unit mass at the time of combustion of one combustion cycle mixed fuel.

  In the above embodiment, the heat generation rate [MJ / ° CA], which is the amount of heat generated per unit crank angle due to the combustion of the air-fuel mixture, is calculated from the detected value of the combustion pressure, and the crank for one combustion cycle of such heat generation rate is calculated. The total amount [MJ] of the calorific value due to the combustion of the mixed fuel in one combustion cycle is obtained as the angular integral value. Instead, the heat generation rate [MJ / sec, etc.], which is the amount of heat generated per unit time by the combustion of the air-fuel mixture, is calculated from the detected value of the combustion pressure, and the time integral value for one combustion cycle of such heat generation rate is calculated. It is also possible to obtain the total amount of heat generated [MJ] due to the combustion of the mixed fuel in one combustion cycle. For example, when sampling of combustion pressure is performed at predetermined time intervals, the time integral value is used as described above, so that the calculation of the total calorific value in one combustion cycle is required because the time crank angle conversion is unnecessary. The amount can be reduced.

  In the above embodiment, the total amount of heat generated by the combustion of the mixed fuel in one combustion cycle is obtained, and further, the total amount of heat generated is divided by the supply amount of the mixed fuel in that cycle, so that The calorific value per unit mass of was calculated. The calorific value calculation logic is not limited to this and can be changed as appropriate. For example, the above calorific value can be estimated more simply by using the maximum value of the combustion pressure in one combustion cycle as an index value of the total calorific value due to the combustion of the mixed fuel in one combustion cycle. It is also possible to calculate the calorific value per unit mass.

  In the above embodiment, the calorific value per unit mass at the time of combustion of the mixed fuel is obtained from the combustion pressure detected by the in-cylinder pressure sensor 14, but, similarly to the combustion pressure, the unit mass at the time of combustion of the mixed fuel If there is a sensor value that correlates with the amount of heat generated per hit, it is possible to calculate the amount of heat generated using the sensor value.

  In the above embodiment, the case where the present invention is applied to a flexible fuel engine that uses a mixed fuel of alcohol and gasoline has been described, but the present invention is also applied to a flexible fuel engine that uses a mixed fuel composed of other fuel combinations. The invention is equally applicable. In short, if it is a flexible fuel engine that uses a mixed fuel of two types of fuels with different calorific values per unit mass during combustion, the estimation device and estimation method of the present invention can be applied to the currently used mixed fuel. The concentration of each fuel contained can be estimated.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic which shows typically the whole structure about one Embodiment of the estimation apparatus of the fuel concentration of the flexible fuel engine of this invention. The graph which shows transition of the heat release rate in 1 combustion cycle. The graph which shows the relationship between the calorific value of the mixed fuel per unit mass, and the alcohol concentration of the mixed fuel. The flowchart which shows the process sequence of the alcohol concentration estimation routine applied to the estimation apparatus and estimation method of the fuel concentration of the flexible fuel engine of the said embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Flexible fuel engine, 11 ... Fuel tank, 12 ... Injector, 13 ... Combustion chamber, 14 ... In-cylinder pressure sensor, 15 ... Electronic control unit (heat generation amount calculation means, concentration estimation means), 16 ... NE sensor, 17 ... Air flow Meter, 18 ... accelerator sensor.

Claims (12)

Fuel concentration estimation device for a flexible fuel engine that estimates the concentration of each fuel contained in the mixed fuel in use for a flexible fuel engine that uses a mixed fuel of two types of fuels that differ in calorific value per unit mass during combustion Because
A calorific value calculating means for calculating a calorific value per unit mass at the time of combustion of the mixed fuel;
Concentration estimating means for estimating the concentration of each fuel based on the calorific value;
An apparatus for estimating fuel concentration of a flexible fuel engine, comprising: The apparatus for estimating fuel concentration of a flexible fuel engine according to claim 1, wherein the calorific value calculation means calculates a calorific value per unit mass at the time of combustion of the mixed fuel from a detected value of combustion pressure. . The calorific value calculation means calculates a heat generation rate, which is a heat generation amount per unit time due to combustion of the mixed fuel, from a detected value of the combustion pressure, and as a time integral value of the heat generation rate in one combustion cycle. By calculating the total amount of heat generated by combustion of the mixed fuel in one combustion cycle, and further dividing the total amount of heat generated by the supply amount of the mixed fuel in that cycle, The apparatus for estimating the fuel concentration of the flexible fuel engine according to claim 2, wherein the calorific value of the fuel is calculated. The calorific value calculation means calculates a heat generation rate, which is a heat generation amount per unit crank angle due to combustion of the mixed fuel, from a detected value of the combustion pressure, and a crank angle integral of the heat generation rate in one combustion cycle. As a value, a total amount of the calorific value due to the combustion of the mixed fuel in one combustion cycle is obtained, and further, the total amount of the calorific value is divided by the supply amount of the mixed fuel in the cycle, so that The apparatus for estimating the fuel concentration of a flexible fuel engine according to claim 2, wherein the calorific value per unit mass is calculated. The concentration estimating means obtains an average value in a prescribed number of combustion cycles for the calorific value per unit mass at the time of combustion of the mixed fuel calculated for each combustion cycle by the calorific value calculating means, and sets the average value to the average value. The fuel concentration estimation device for a flexible fuel engine according to any one of claims 1 to 4, wherein the concentration of each fuel is estimated based on the fuel concentration. The said flexible fuel engine uses the mixed fuel of alcohol and gasoline, The fuel concentration estimation apparatus of the flexible fuel engine of any one of Claims 1-5. A method for estimating the concentration of each fuel contained in a mixed fuel in use for a flexible fuel engine using a mixed fuel of two kinds of fuels having different calorific values per unit mass at the time of combustion,
A method for estimating the fuel concentration of a flexible fuel engine, wherein the calorific value per unit mass at the time of combustion of the mixed fuel is obtained, and the concentration of each fuel is estimated based on the calorific value. The method for estimating the fuel concentration of a flexible fuel engine according to claim 7,
A method for estimating a fuel concentration of a flexible fuel engine, wherein a calorific value per unit mass at the time of combustion of the mixed fuel is calculated from a detected value of combustion pressure. The method for estimating the fuel concentration of a flexible fuel engine according to claim 8,
A heat generation rate, which is a heat generation amount per unit time due to combustion of the mixed fuel, is calculated from the detected value of the combustion pressure, and the mixed fuel in one combustion cycle is obtained as a time integral value of the heat generation rate in one combustion cycle. To calculate the calorific value per unit mass at the time of combustion of the mixed fuel by dividing the total calorific value by the supply amount of the mixed fuel in the cycle. A method for estimating the fuel concentration of a flexible fuel engine. The method for estimating the fuel concentration of a flexible fuel engine according to claim 8,
A heat generation rate that is a heat generation amount per unit crank angle due to combustion of the mixed fuel is calculated from a detected value of the combustion pressure, and the crank angle integral value of the heat generation rate in one combustion cycle is calculated as the crank angle integral value in one combustion cycle. The total amount of heat generated by the combustion of the mixed fuel is calculated, and the total amount of generated heat is divided by the supply amount of the mixed fuel in the cycle to determine the amount of heat generated per unit mass when the mixed fuel is burned. A method for estimating the fuel concentration of a flexible fuel engine. In the fuel concentration estimation method of the flexible fuel engine according to any one of claims 7 to 10,
Obtaining an average value of the prescribed number of combustion cycles for the calorific value per unit mass at the time of combustion of the mixed fuel calculated for each combustion cycle, and estimating the concentration of each fuel based on the average value A method for estimating the fuel concentration of a flexible fuel engine. In the fuel concentration estimation method of the flexible fuel engine according to any one of claims 7 to 11,
The said flexible fuel engine uses the mixed fuel of alcohol and gasoline, The estimation method of the fuel concentration of the flexible fuel engine characterized by the above-mentioned.

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