JP4670888B2 - Device for acquiring value corresponding to alcohol concentration of fuel for internal combustion engine - Google Patents

Description

  The present invention relates to an alcohol concentration corresponding value acquisition device for an internal combustion engine fuel that acquires (estimates) a value corresponding to the concentration of alcohol contained in fuel supplied to a combustion chamber of the internal combustion engine.

  In recent years, a large amount of alcohol such as ethanol may be contained in gasoline supplied to an internal combustion engine as fuel. Such a mixed fuel of gasoline and alcohol (one kind of alcohol) is hereinafter referred to as “alcohol-containing fuel” or simply “fuel”. However, in this specification, “alcohol-containing fuel” and “fuel” include a case where alcohol is 0% and a case where alcohol is 100%. That is, both gasoline-only fuel and alcohol-only fuel are referred to as “alcohol-containing fuel” or “fuel”.

  The concentration of the alcohol contained in the fuel (the alcohol concentration of the fuel) changes each time fuel having an alcohol concentration different from the alcohol concentration of the fuel remaining in the fuel tank is supplied to the fuel tank. When the alcohol concentration of the fuel changes, the amount of fuel for making the air-fuel ratio of the mixed gas coincide with the stoichiometric air-fuel ratio, for example, changes. Furthermore, the torque generated by the engine changes as the alcohol concentration of the fuel changes. Therefore, it is effective to use the alcohol concentration of the fuel for the engine control represented by the control of the fuel supply amount. Therefore, it is desirable to accurately estimate the alcohol concentration of the fuel.

By the way, the lower heating value is the amount of heat that the fuel can generate per unit mass. For example, the lower heating value of gasoline is 40 (MJ / g), and the lower heating value of ethanol is 26 (MJ / g). Therefore, the lower heating value changes depending on the alcohol concentration of the fuel. Therefore, the conventional device burns fuel based on at least the pressure (in-cylinder pressure) P (θ) and the combustion chamber volume V (θ) in the combustion chamber at various crank angles θ from the start to the end of combustion of the mixed gas. The lower calorific value is estimated based on the calorific value, and the alcohol concentration of the fuel is estimated based on the estimated lower calorific value (see, for example, Patent Document 1). .
JP-A-1-88153

  However, it is not easy to accurately estimate the lower heating value based on the in-cylinder pressure P (θ) and the combustion chamber volume V (θ). This is because actual combustion varies depending on the state of mixing of fuel and air in the mixed gas used for combustion, the state of ignition energy caused by the secular change of the spark plug, and the like. Therefore, in order to accurately estimate the alcohol concentration using the lower calorific value, the lower calorific value is estimated for each cycle of many cycles, and the lower calorific value of each cycle is averaged over the many cycles. It is necessary to make it. Therefore, for example, the conventional apparatus cannot accurately determine the lower heating value until many cycles elapse after the engine is started, and cannot accurately estimate the alcohol concentration. As a result, until the alcohol concentration of the fuel is estimated after the engine is started, the “alcohol concentration of the fuel estimated accurately” cannot be reflected in the engine control (for example, control of the fuel injection amount). is there.

The present invention has been made to address the above problems. One of the objects of the present invention is a value (alcohol concentration) corresponding to the alcohol concentration based on the in-cylinder pressure at a predetermined timing after the start of the compression stroke for compressing the mixed gas and before the combustion of the mixed gas starts. By estimating (corresponding value , first alcohol concentration ), “a value corresponding to the concentration of alcohol actually contained in the fuel” can be obtained with high accuracy at an early stage and without being affected by fluctuations in the combustion state. The object is to provide an “alcohol concentration corresponding value acquisition device”. Furthermore, one of the objects of the present invention is to provide an apparatus that can determine whether or not the mixed gas supply means is abnormal by using the estimated first alcohol concentration. .

Specifically, the alcohol concentration corresponding value acquisition device according to the present invention is:
In-cylinder pressure acquisition means for acquiring an in-cylinder pressure that is a pressure in the combustion chamber of the internal combustion engine;
Mixed gas supply means for supplying a mixed gas containing fuel and air to the combustion chamber;
First acquisition means for acquiring a value corresponding to the concentration of alcohol contained in the fuel as an alcohol concentration corresponding value;
Is provided.

  Here, the “alcohol concentration corresponding value” may be a “value representing the alcohol concentration of the fuel itself” as will be described later, and “a value determined according to the alcohol concentration of the fuel (for example, correction of the fuel injection amount). Coefficient and ignition timing correction advance amount) ”or the like. In other words, the alcohol concentration corresponding value is a value that changes according to the alcohol concentration of the fuel, and may be a value that is uniquely determined if the alcohol concentration of the fuel is determined.

  By the way, alcohol is harder to evaporate than gasoline. Therefore, the lead vapor pressure (RVP) is greatly different between alcohol and gasoline. Reed vapor pressure refers to the vapor pressure when fuel at 0 to 1 ° C. is sealed in a sealed container, the container is warmed to 37.8 ° C. (100 F), and the vapor pressure reaches equilibrium. . Therefore, the reed vapor pressure of the fuel increases as the volatility of the fuel increases. In other words, the Reid vapor pressure decreases as the fuel alcohol concentration increases. Therefore, the inventor has obtained the knowledge that “if the fuel vapor pressure can be estimated, the alcohol concentration of the fuel can also be estimated”.

  On the other hand, when the intake valve is closed and the compression of the air-fuel mixture is started, the in-cylinder pressure gradually increases. The in-cylinder pressure P (θa) at this point (a predetermined timing after the start of the compression stroke and before the start of combustion and when the crank angle is the θa degree crank angle before the compression top dead center) is It can be considered proportional to the number of molecules that can behave as a gas in the combustion chamber. On the other hand, the reed vapor pressure of the fuel described above is proportional to the number of molecules that can behave as a gas. From the above, it is considered that the in-cylinder pressure P (θa) has a very strong correlation with the fuel reed vapor pressure. That is, the inventor obtained the knowledge that “the alcohol concentration corresponding value can be acquired based on the in-cylinder pressure P (θa)”. Hereinafter, the in-cylinder pressure P (θa) is also referred to as a pre-combustion in-cylinder pressure P (θa).

  FIGS. 1 and 2 show the in-cylinder pressure P (θ) at a crank angle θ and the measured in-cylinder pressure P (θ) for fuels having various ethanol concentrations (fuel consisting only of gasoline and ethanol). ) And a combustion chamber volume V (θ) at a crank angle θ, a value proportional to the product P (θ) · V (θ) is shown with respect to the crank angle θ. The product P (θ) · V (θ) is a value corresponding to the internal energy U of the gas in the combustion chamber, as will be described later. FIG. 2 is an enlarged view of a portion surrounded by the square Sq shown in FIG. Further, FIG. 3 is a graph in which “data when the crank angle θ is the 30-degree crank angle before compression top dead center (BTDC 30 deg.)” Of the data shown in FIGS. 1 and 2 is plotted. In this graph, the horizontal axis represents the ethanol concentration, and the vertical axis represents the internal energy U proportional to the product P (θ) · V (θ). The 30 degree crank angle before compression top dead center is a crank angle corresponding to the predetermined timing.

  The product P (θ) · V (θ) is a value obtained by multiplying the in-cylinder pressure P (θ) by the combustion chamber volume V (θ) at each crank angle θ, that is, a value obtained by multiplying the in-cylinder pressure P (θ) by a constant. Can be seen. Therefore, according to FIGS. 1 to 3 (particularly, FIG. 3), the above-mentioned knowledge that “the alcohol concentration corresponding value can be obtained based on the pre-combustion in-cylinder pressure P (θa)” is correct. It was confirmed.

  Therefore, the first acquisition unit of the alcohol concentration corresponding value acquisition device according to the present invention has a predetermined timing within the “period from the start of the compression stroke for compressing the mixed gas to before the start of the combustion of the mixed gas”. Based on the in-cylinder pressure and the in-cylinder pressure acquired by the in-cylinder pressure acquisition means, that is, the in-cylinder pressure P (θa) before combustion start, the alcohol contained in the fuel increases as the pre-combustion cylinder pressure P (θa) increases The value corresponding to the concentration of alcohol actually contained in the fuel is acquired as the alcohol concentration corresponding value in accordance with the relationship that the concentration of the fuel is small.

  At this time, the first acquisition means is likely to fluctuate depending on the combustion state “the in-cylinder pressure after the start of combustion of the mixed gas, and the in-cylinder pressure acquired by the in-cylinder pressure acquisition means (that is, the cylinder after the start of combustion). The alcohol concentration corresponding value can be obtained without using “internal pressure)”.

  Since the in-cylinder pressure P (θa) before starting combustion is the in-cylinder pressure before starting combustion, it is not affected by variations in the combustion state. Therefore, the alcohol concentration corresponding value obtained based on the pre-combustion in-cylinder pressure P (θa) is a highly accurate value without taking the average of the alcohol concentration corresponding values for many cycles. As a result, the alcohol concentration corresponding value acquisition device can acquire the alcohol concentration corresponding value immediately after the start of the engine starting operation or after a slight cycle has elapsed since the start, for example. It can be used to control the engine from an early point after the engine is started.

In this case, the first acquisition means is
An internal energy calculating means for calculating the internal energy of the gas in the combustion chamber at the predetermined timing based on the product of the cylinder internal pressure before the combustion start and the volume of the combustion chamber at the predetermined timing; It is preferable that the alcohol concentration corresponding value is acquired based on internal energy.

  As will be described in detail later, when P is the in-cylinder pressure, V is the volume of the combustion chamber, and κ is the specific heat ratio of the gas in the combustion chamber, the internal energy U is U = (1 / κ−1) · P · V It can obtain | require by the type | formula which becomes. Further, as described above, the pre-combustion in-cylinder pressure P (θa) at the predetermined timing after the start of the compression stroke and before the start of combustion is a value corresponding to the fuel reed vapor pressure. This is a value corresponding to the alcohol concentration of the fuel.

  Therefore, as in the above configuration, the in-cylinder pressure P (θa) before the start of combustion and the volume V (θa) of the combustion chamber when the in-cylinder pressure before the start of combustion is obtained (that is, at the predetermined timing). The “internal energy U (θa) of the gas in the combustion chamber at the predetermined timing” calculated based on the product of the above is also a value corresponding to the alcohol concentration of the fuel (see FIG. 3). Therefore, the alcohol concentration corresponding value can be obtained with high accuracy based on the calculated internal energy U (θa). Hereinafter, the internal energy U (θa) is also referred to as internal energy U (θa) before starting combustion.

Furthermore, such an alcohol concentration corresponding value acquisition device is:
Comprising a burned gas amount obtaining means for obtaining the amount of burned gas present in the combustion chamber at the start of the compression stroke;
The first acquisition means includes
Based on the acquired amount of burned gas, the alcohol concentration corresponding value according to the relationship that the concentration of alcohol contained in the fuel increases as the amount of burned gas increases even if the in-cylinder pressure before combustion starts is the same. It is suitable that it is comprised so that it may acquire.

  That is, the first acquisition means indicates that “the in-cylinder pressure P (θa) before the combustion start is a specific pressure (therefore, the magnitude of the internal energy U (θa) before the combustion calculated based on the specific pressure is specified). The alcohol concentration of the fuel when the amount of burned gas is the first burned gas amount "is" the in-cylinder pressure P (θa) before the start of combustion is the specified pressure (therefore, the specified A second burned gas amount whose burned gas amount is smaller than the first burned gas amount and the internal energy U (θa) before combustion calculated based on the pressure is the specific amount). The alcohol concentration corresponding value is calculated based on the acquired amount of burned gas so as to follow the relationship of “the alcohol concentration of the fuel in the case of

  The in-cylinder pressure P (θa) before starting combustion also depends on the amount of burned gas (internal EGR gas, residual gas) in the combustion chamber. In other words, the in-cylinder pressure P (θa) before the start of combustion can be considered to be the sum of the partial pressure P1 by the fuel molecules acting as a gas and the partial pressure P2 of the burned gas. Therefore, even if the in-cylinder pressure P (θa) before the start of combustion is the same, the partial pressure P2 of the burned gas increases as the amount of burned gas increases, so the partial pressure P1 due to the molecules of the fuel acting as gas is Small, and therefore the fuel reed vapor pressure is small.

  Similarly, the internal energy U (θa) before starting combustion also depends on the amount of burned gas in the combustion chamber. In other words, the internal energy U (θa) before the start of combustion can be considered to be the sum of the “internal energy U1 due to fuel molecules behaving as a gas” and the “internal energy U2 of burned gas”. Therefore, even if the internal energy U (θa) before the start of combustion is the same, the larger the amount of burned gas, the greater the burned gas internal energy U2, so the internal energy U1 due to the fuel molecules acting as gas is Small, and therefore the fuel reed vapor pressure is small.

  From the above, even if the in-cylinder internal pressure P (θa) before combustion start and the internal energy U (θa) before combustion start are the same, the larger the amount of burned gas, the smaller the lead vapor pressure of the fuel. It can be understood that the relationship “the concentration of alcohol to be produced is high” is established. Therefore, in an engine in which the amount of burned gas changes, the acquisition of the alcohol concentration corresponding value based on the pre-combustion cylinder pressure P (θa) or the pre-combustion internal energy U (θa) Thus, it is desirable to obtain the alcohol concentration corresponding value based on the amount of burned gas. Thereby, even if it is a case where the amount of burnt gas changes, the said alcohol concentration corresponding value can be acquired more accurately.

In the alcohol concentration corresponding value acquisition device of the present invention including these aspects ,
The first acquisition means includes
Wherein you get the same alcohol concentration as "concentration of alcohol contained in the fuel as the alcohol concentration correspondence value" becomes smaller as the combustion start before cylinder pressure P (.theta.a) is large. Alcohol concentration of fuel acquired by the first acquisition means this is referred to as a convenience, "first alcohol concentration".
Furthermore, in the alcohol concentration corresponding value acquisition device of the present invention,
The mixed gas supply means is configured to supply the fuel to the combustion chamber in response to an instruction signal (that is, an instruction fuel supply amount of fuel included in the instruction signal).
Furthermore, the alcohol concentration corresponding value acquisition device includes:
The command fuel supply amount is determined based on the operating state of the engine, and an instruction signal is sent to the mixed gas supply means so that fuel of the determined fuel supply amount is supplied from the mixed gas supply device to the combustion chamber. Fuel supply amount control means for delivering;
Heat generation amount estimation means for estimating an amount corresponding to a heat generation amount that is an amount of heat generated with combustion of the mixed gas at least during a period from the start of combustion of the mixed gas to the end of combustion;
An amount corresponding to the lower heat generation amount is calculated based on the estimated heat generation amount and the indicated fuel supply amount, and is included in the fuel based on the calculated lower heat generation amount. Second acquisition means for acquiring the concentration of alcohol as the second alcohol concentration;
An abnormality determination unit that determines that the mixed gas supply unit is abnormal when the magnitude of the difference between the acquired first alcohol concentration and the acquired second alcohol concentration is greater than a predetermined threshold;
It has.
This device calculates the amount corresponding to the lower heating value from the heat generation amount that is the amount of heat generated by the combustion of the mixed gas and the indicated fuel supply amount, and to the amount corresponding to the calculated lower heating value. Based on this, the concentration of alcohol contained in the fuel is acquired as the second alcohol concentration. In this case, the second alcohol concentration should be close to the first alcohol concentration if the indicated gas supply amount of fuel is supplied to the combustion chamber by correctly operating the mixed gas supply means. In other words, when the magnitude of the difference between the first alcohol concentration and the second alcohol concentration is greater than the predetermined threshold, the indicated fuel supply amount of fuel is not supplied to the combustion chamber, that is, the mixed gas supply means is abnormal. It can be determined that

  As described above, it is considered that the lead vapor pressure of the fuel increases as the in-cylinder pressure P (θa) before starting combustion (and hence the internal energy U (θa) before starting combustion) increases. Therefore, the apparatus having the above configuration determines the first alcohol concentration such that the first alcohol concentration decreases as the pre-combustion in-cylinder pressure P (θa) increases.

in this case,
The first acquisition means includes
Based on the product of the in-cylinder pressure P (θa) before combustion start and the volume V (θa) of the combustion chamber at the predetermined timing, the internal energy of the gas in the combustion chamber at the predetermined timing (internal energy before combustion start) U (θa)) may be included, and the first alcohol concentration may be acquired based on the calculated internal energy U (θa).

Furthermore, the alcohol concentration corresponding value acquisition device of the present invention for acquiring the first alcohol concentration is
Comprising a burned gas amount obtaining means for obtaining the amount of burned gas present in the combustion chamber at the start of the compression stroke;
The first acquisition means includes
It is preferable to acquire the first alcohol concentration such that the first alcohol concentration increases as the acquired amount of burned gas increases even if the in-cylinder pressure before the start of combustion is the same.

  As described above, when the pre-combustion in-cylinder pressure P (θa) is the same, the larger the amount of burned gas, the smaller the number of fuel molecules that behave as gas, so the fuel lead vapor pressure is smaller ( That is, it is considered that the alcohol concentration is high.

Embodiments of an alcohol concentration corresponding value acquisition device for internal combustion engine fuel according to the present invention will be described below with reference to the drawings. This alcohol concentration corresponding value acquisition device is also an engine control device (for example, a fuel injection amount control device, an ignition timing control device, etc.).
<First Embodiment>
(Constitution)
FIG. 4 shows an alcohol concentration corresponding value acquisition device (hereinafter also simply referred to as “first device”) according to an embodiment of the present invention, which is a piston reciprocating spark ignition type, multi-cylinder (4 cylinders), and 4 cycles. A schematic configuration of a system applied to the internal combustion engine 10 is shown. FIG. 4 shows only a cross section of a specific cylinder, but the other cylinders have the same configuration. The engine 10 can operate stably even if the fuel contains alcohol such as ethanol.

  The engine 10 includes a cylinder block portion 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head portion 30 fixed on the cylinder block portion 20, and “fuel and air are supplied to the cylinder block portion 20. An intake system 40 for supplying the “containing mixed gas” and an exhaust system 50 for releasing the exhaust gas discharged from the cylinder block unit 20 to the outside are included.

  The cylinder block unit 20 includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. The upper surfaces of the cylinder 21 and the piston 22 form a combustion chamber 25 together with the cylinder head portion 30.

  The cylinder head unit 30 includes an intake port 31 that communicates with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, an intake valve control device 33 that opens and closes the intake valve 32, an exhaust port 34 that communicates with the combustion chamber 25, an exhaust An exhaust valve 35 that opens and closes the port 34, an exhaust camshaft 36 that drives the exhaust valve 35, an ignition plug 37 provided in each cylinder, an igniter 38 that includes an ignition coil that generates a high voltage applied to each ignition plug 37, and each cylinder Is provided with an injector (fuel injection means, mixed gas supply means) 39 for injecting fuel of the indicated fuel supply amount included in the instruction signal.

  The intake valve control device 33 has a known configuration that adjusts and controls the relative rotation angle (phase angle) between an intake camshaft and an intake cam (not shown) by hydraulic pressure in response to an instruction signal. The valve opening timing (intake valve opening timing) can be changed.

  In this example, the valve opening period (the valve opening crank angle width) of the intake valve is constant. Therefore, when the intake valve opening timing is advanced or retarded by a predetermined angle, the intake valve closing timing is also advanced or retarded by the predetermined angle. Further, the opening timing and closing timing of the exhaust valve 35 are constant. Accordingly, the valve overlap period (period in which both the intake valve 32 and the exhaust valve 35 are open) changes as the intake valve opening timing is changed by the intake valve control device 33. Since the amount of burnt gas (combustion gas, internal EGR gas) discharged to the intake port 31 during the valve overlap period increases as the valve overlap period increases, the intake valve 32 moves after the valve overlap period. The amount of burned gas that flows into the combustion chamber 25 when the valve is opened also increases.

  The reference value 0 is used when the intake valve opening timing is set to the most retarded side by the intake valve control device 33, and the crank angle from the reference value to the intake valve opening timing that is actually controlled is set as the reference value. This is referred to as an intake valve advance angle VT. Therefore, the intake valve advance angle VT is a value corresponding to the valve overlap period. That is, the larger the intake valve advance angle VT, the longer the valve overlap period, and the greater the amount of burned gas contained in the combustion chamber 25 at the start of the compression stroke.

  The intake system 40 includes an intake manifold 41, an intake pipe (intake duct) 42, an air filter 43, a throttle valve 44, and a throttle valve actuator 44a.

  The intake manifold 41 is connected to the intake port 31 of each cylinder. More specifically, the intake manifold 41 includes a plurality of branch portions 41a connected to each intake port 31, and a surge tank portion 41b in which those branch portions are gathered. The intake pipe 42 is connected to the surge tank portion 41b. The intake manifold 41 and the intake pipe 42 constitute an intake passage. The air filter 43 is provided at the end of the intake pipe 42. The throttle valve 44 is rotatably provided in the intake pipe 42, and changes the opening cross-sectional area of the intake passage formed by the intake pipe 42 by rotating. The throttle valve actuator (throttle valve drive means) 44a is formed of a DC motor, and rotates the throttle valve 44 in response to an instruction signal.

  The exhaust system 50 includes an exhaust manifold 51 communicating with the exhaust port 34, an exhaust pipe (exhaust pipe) 52 connected to the exhaust manifold 51, an upstream three-way catalyst 53, and a downstream three-way catalyst 54. The upstream three-way catalyst 53 is disposed in the exhaust pipe 52. The downstream three-way catalyst 54 is disposed in the exhaust pipe 52 downstream of the upstream three-way catalyst 53. The exhaust port 34, the exhaust manifold 51, and the exhaust pipe 52 constitute an exhaust passage.

  On the other hand, this system includes a hot-wire air flow meter 61, a throttle position sensor 62, a cam position sensor 63, a crank position sensor 64, an in-cylinder pressure sensor 65 provided in each cylinder, a coolant temperature sensor 66, and an upstream of the first catalyst 53. An upstream air-fuel ratio sensor 67 disposed in the exhaust passage, a downstream air-fuel ratio sensor 68 disposed in the exhaust passage downstream of the first catalyst 53 and upstream of the second catalyst 54, an accelerator opening sensor 69, and An electric control device 70 is provided.

The hot-wire air flow meter 61 detects the mass flow rate per unit time of the intake air flowing through the intake pipe 42 and outputs a signal representing the mass flow rate Ga.
The throttle position sensor 62 detects the opening of the throttle valve 44 and outputs a signal representing the throttle valve opening TA.
The cam position sensor 63 outputs one pulse every time the intake camshaft rotates 90 degrees, 90 degrees, and 180 degrees from a predetermined angle.
The crank position sensor 64 outputs a pulse every time the crankshaft 24 rotates 10 degrees. The pulse output from the crank position sensor 64 is converted into a signal representing the engine rotational speed NE. Further, the crank angle θ of each cylinder is obtained based on signals from the cam position sensor 63 and the crank position sensor 64.

  The in-cylinder pressure sensor 65 detects the pressure in the corresponding combustion chamber 25 and outputs a signal representing the in-cylinder pressure P. The in-cylinder pressure P of each cylinder is acquired by the electric control device 70 every time the crank angle changes by a minute angle Δθ, and the in-cylinder pressure P (θ) is stored in a RAM 73 described later together with the crank angle θ of the cylinder from which the in-cylinder pressure P is acquired. Stored in the form of

The upstream air-fuel ratio sensor 67 and the downstream air-fuel ratio sensor 68 detect the upstream and downstream air-fuel ratios of the catalyst 53 and output signals representing the upstream and downstream air-fuel ratios, respectively.
The accelerator opening sensor 69 detects the operation amount of the accelerator pedal 81 operated by the driver, and outputs a signal representing the operation amount Accp of the accelerator pedal 81.

  The electrical control device 70 is connected to each other via a bus “CPU 71, a routine (program) executed by the CPU 71, a table (look-up table, map), a ROM 72 in which constants are stored in advance, and the CPU 71 temporarily stores data as necessary. A storage RAM 73, a backup RAM 74 capable of writing data when an ignition key switch (not shown) is in the ON position and holding the written data regardless of the position of the ignition key switch, and A microcomputer including an interface 75 including an AD converter. The interface 75 is connected to the sensors 61 to 69 and supplies signals from the sensors 61 to 69 to the CPU 71. The interface 75 sends a drive signal to the intake valve control device 33, the injector 39 of each cylinder and the throttle valve actuator 44a in accordance with an instruction from the CPU 71, and sends an ignition signal to the igniter 38 of each cylinder. .

(First estimation principle of alcohol concentration)
Next, the “first estimation principle of the alcohol concentration of fuel” adopted by the first device will be described. In the following, the alcohol concentration of fuel means the ratio of the volume of alcohol to the volume of fuel (alcohol-containing fuel) composed of gasoline and alcohol. However, the alcohol concentration of the fuel may be a ratio of the mass of the alcohol to the mass of the alcohol-containing fuel. Further, a description will be given below using ethanol (ethyl alcohol) as a representative example of alcohol. However, the alcohol concentration corresponding value acquisition apparatus according to the present invention can naturally be applied to the case of estimating the concentration of other alcohols such as methanol.

  Alcohol including ethanol is less likely to evaporate than gasoline. Accordingly, the lead vapor pressure (RVP), which is one index of fuel volatility, is greatly different between alcohol (for example, ethanol) and gasoline. Reed vapor pressure refers to the vapor pressure when fuel at 0 to 1 ° C. is sealed in a sealed container, the container is warmed to 37.8 ° C. (100 F), and the vapor pressure reaches equilibrium. . The higher the fuel volatility, the greater the reed vapor pressure.

  Therefore, the reed vapor pressure decreases as the fuel ethanol concentration increases. Therefore, if the fuel reed vapor pressure can be estimated, the fuel ethanol concentration can also be estimated.

By the way, it can be considered that the compression stroke after the intake valve 32 is closed and the gas in the combustion chamber 25 starts to be compressed is an adiabatic compression process. Further, it can be considered that the expansion stroke from when the fuel starts to burn after the compression stroke until the exhaust valve 35 opens is an adiabatic expansion process. Therefore, as is well known, the following equations (1) and (2) are derived from the first law of thermodynamics. In equations (1) and (2), Q is the amount of heat generated in the combustion chamber 25 (cumulative heating amount), and P is the pressure in the combustion chamber 25 (that is, the in-cylinder pressure, the pressure of the gas present in the combustion chamber 25). ), V is the volume of the combustion chamber 25, θ is the crank angle, W is the work performed by the gas in the combustion chamber 25 to the outside, and U is the internal energy of the gas in the combustion chamber 25. Further, κ is the specific heat ratio of the gas in the combustion chamber 25. More specifically, κ is the specific heat ratio of the gas existing in the combustion chamber 25 in the period from when it is sucked into the combustion chamber 25 until the substantial combustion starts, and after the substantial combustion starts, the combustion chamber This is the average specific heat ratio of the specific heat ratio of the gas existing in the combustion chamber 25 during the period from the discharge to 25. κ varies depending on the alcohol concentration of the fuel. However, the specific heat ratio of gasoline and the specific heat ratio of alcohol are sufficiently smaller than the specific heat ratio of, for example, monoatomic molecules or diatomic molecules. Therefore, it can be handled that the specific heat ratio of gasoline and the specific heat ratio of alcohol are substantially equal.

Since dW / dθ in the equation (2) is equal to P · dV / dθ, the equation (2) is rewritten as the following equation (3).

Accordingly, when dQ / dθ is eliminated from the above equations (1) and (3), the following equation (4) is obtained.

From this equation (4), equation (5) is obtained.

  From the equation (5), the internal energy U can be considered to be proportional to the gas pressure (in-cylinder pressure) P in the combustion chamber 25 (proportional to the product of the in-cylinder pressure P and the combustion chamber volume V). In other words, the internal energy U can be easily obtained by acquiring (measuring) the in-cylinder pressure P.

  On the other hand, the in-cylinder pressure P can be considered to be proportional to the number of molecules that can behave as gas in the combustion chamber 25. On the other hand, the reed vapor pressure of the fuel described above is proportional to the number of fuel molecules that can behave as a gas. Therefore, the fuel lead vapor pressure is determined as follows: “In a period from the start of the compression stroke for compressing the mixed gas to the start of combustion of the mixed gas (more preferably, before the ignition timing) during the compression stroke. (The predetermined timing of “)” has a strong correlation (proportional) with “the pressure and internal energy of the gas existing in the combustion chamber 25”.

  From the above, the inventor stated that “a specific timing after the start of the compression stroke in which the mixed gas is compressed in the combustion chamber 25 and before the start of the combustion of the mixed gas (θa degree crank angle before compression top dead center = By obtaining the in-cylinder pressure (in-cylinder pressure before combustion start) P (θa) at BTDCθadeg) and applying the in-cylinder pressure P (θa) to the above equation (5), the internal energy U (θa) at the same specific timing is obtained. From the estimated internal energy U (θa), it was found that the “value corresponding to the ethanol concentration of the fuel” can be estimated.

  Further, since the value (1 / κ−1) · V in the above equation (5) can be regarded as a constant when focusing on the specific timing during the compression stroke, the equation (5) expresses “the in-cylinder pressure P (θa) as a constant. The internal energy U (θa) can be obtained by doubling. " Therefore, the inventor obtained knowledge that the “value corresponding to the ethanol concentration of the fuel” can be estimated based on the pre-combustion cylinder pressure P (θa) at a specific timing (BTDCθadeg) during the compression stroke. It was. The above is the first estimation principle of the alcohol concentration of the fuel.

  The “value corresponding to the ethanol concentration (alcohol concentration) of the fuel” is uniquely determined if the value that changes according to the ethanol concentration (alcohol concentration) of the fuel, that is, the ethanol concentration (alcohol concentration) of the fuel is determined. Value. This “value corresponding to the ethanol concentration (alcohol concentration) of the fuel” is also referred to as “ethanol concentration corresponding value (alcohol concentration corresponding value)” for convenience. The ethanol concentration corresponding value (alcohol concentration corresponding value) may be the ethanol concentration (alcohol concentration) itself.

  The above-mentioned “specific timing during the compression stroke (BTDCθadeg)” is preferably a crank angle of 60 degrees to 20 degrees before compression top dead center and immediately before the ignition timing, for example, a crank angle of 30 degrees before compression top dead center. It is preferable. As the specific timing is retarded (that is, closer to the compression top dead center), the in-cylinder pressure increases, so noise can be reduced (S / N can be improved) and the fuel state approaches a pressure equilibrium state. (Ie, approaching the pressure equilibrium where the lead vapor pressure is measured).

  1 and 2 show the crank angle of the internal energy U calculated by applying the actually measured in-cylinder pressure to the above equation (5) for fuels having various ethanol concentrations (fuel consisting only of gasoline and ethanol). 6 is a graph showing a change with respect to θ. FIG. 2 is an enlarged view of a portion surrounded by the square Sq shown in FIG. The data shown in these figures shows that the intake valve 32 is closed at a predetermined timing of 120 degrees before compression top dead center to 150 degrees before compression top dead center, and the intake valve advance angle VT is constant. It is obtained when the value is maintained.

  In these graphs, the crank angle 0 indicates “compression top dead center”, the region where the crank angle θ is a negative value indicates the region before compression top dead center (BTDC), and the crank angle θ is a positive value. Indicates after compression top dead center (ATDC). For example, “−30” indicates that the crank angle θ is 30 degrees before compression top dead center, and “30” indicates that the crank angle θ is 30 degrees after compression top dead center. Further, in these graphs, E0 (solid line), E20 (dashed line), E50 (one-dot chain line), and E100 (two-dot chain line) are fuel ethanol concentrations of 0, 20, 50, and 100 (volume%), respectively. The internal energy U for the fuel is shown.

  When combustion starts, heat is generated with a chemical reaction between the fuel and oxygen. The heat is used for work W performed by the gas in the combustion chamber 25 to the outside and for increasing the internal energy U of the gas in the combustion chamber 25. In other words, a sudden increase in the internal energy U means that combustion has substantially started. Therefore, as is apparent from FIG. 1, the combustion starts near the top dead center. Therefore, the gas in the combustion chamber 25 is compressed at a specific timing (for example, 30 ° crank angle before compression top dead center) during the compression stroke, but combustion is not started. As is apparent from FIG. 2, it is understood that the internal energy decreases as the alcohol concentration increases at a specific timing during the compression stroke (see arrow A in FIG. 2).

  FIG. 3 is a graph showing the relationship between the internal energy U and the ethanol concentration EtOH of the fuel at the 30 ° crank angle before compression top dead center in the data shown in FIG. FIG. 3 also shows that the ethanol concentration EtOH can be estimated from the internal energy U (θa) by estimating the internal energy U (θa) at a specific timing (BTDCθadeg) during the compression stroke.

  Further, FIG. 5 is a graph showing the result of measuring the change of the internal energy U with respect to the crank angle θ a plurality of times for a fuel having a constant ethanol concentration. According to FIG. 5, it can be understood that, for example, the internal energy U with respect to the crank angle θ varies after the time point when combustion substantially starts (around 15 degrees before compression top dead center). This is considered to be due to the fact that the state of combustion fluctuates from one combustion to another under the influence of variations in the fuel mixture state, burned gas amount variation, ignition state variation, and the like.

  On the other hand, it can be understood from FIG. 5 that, for example, the internal energy U at a timing further before the crank angle 20 degrees before compression top dead center hardly varies between different cycles. Therefore, based on the internal energy U (θa) at a specific timing during the compression stroke, the ethanol concentration can be accurately estimated without calculating the average of the internal energy U (θa) of a plurality of cycles.

(Actual operation)
Next, the actual operation of the first device will be described with reference to a flowchart. The CPU 71 performs the ethanol concentration acquisition (estimation) routine shown in FIG. 6 at a predetermined minute after the start of the engine start operation (when an unillustrated ignition key switch is changed from the OFF position to the start position). It is executed repeatedly every time. Accordingly, when the predetermined timing is reached, the CPU 71 starts the process from step 600 and proceeds to step 610, where the current time is “the crank angle of any cylinder after starting the start operation of the engine 10 is the crank angle θa degrees before the compression top dead center. It is determined whether or not it is immediately after “at the first arrival at the corner (BTDCθadeg)”.

  At this time, if the current time is not immediately after “the time when the crank angle of any cylinder has reached the θa degree crank angle before the compression top dead center after the start operation of the engine 10 is started”, the CPU 71 determines “ No "is determined, the process proceeds directly to step 695, and this routine is temporarily terminated.

  On the other hand, when the current time is immediately after “the time when the crank angle of any cylinder reaches the crank angle of θa degrees before compression top dead center after the start operation of the engine 10 is started”, the CPU 71 determines in step 610. It determines with "Yes", the process of step 620 thru | or step 640 described below is performed in order, it progresses to step 695, and this routine is once complete | finished. In the following, the cylinder whose crank angle has reached the crank angle for the first time before the compression top dead center is called “crank angle reaching cylinder” for convenience.

Step 620: The CPU 71 acquires a pre-combustion in-cylinder pressure P (θa) based on the output of the in-cylinder pressure sensor 65 provided in the cylinder that has reached the crank angle.
Step 630: The CPU 71 applies the in-cylinder pressure P (θa) acquired in step 620 and the volume V (θa) of the combustion chamber 25 at the specific crank angle θa (BTDCθadeg) of the compression stroke to the above equation (5). By doing this, the internal energy U (θa) before starting combustion is calculated (acquired). Note that the volume V (θa) of the combustion chamber 25 is stored in the ROM 72 in advance.

  Step 640: The CPU 71 calculates the relationship between the internal energy U (θa) before starting combustion and the ethanol concentration EtOH (volume%) in a predetermined table MapEtOH (U), and calculates the internal energy U (before starting combustion) calculated in step 630 above. By applying θa), the actual ethanol concentration EtOH is calculated (estimated). The table MapEtOH (U) is created on the basis of “data obtained in advance by experiment” representing the relationship between the internal energy U (θa) before combustion start and the ethanol concentration EtOH, and is stored in the ROM 72. As described above, the ethanol concentration EtOH of the fuel is estimated immediately after starting. The ethanol concentration EtOH calculated in step 640 is stored in the backup RAM 74. According to the table MapEtOH (U), the ethanol concentration EtOH decreases as the internal energy U (θa) before the start of combustion increases.

  Further, the CPU performs the fuel injection routine shown in the flowchart of FIG. 7 every time the crank angle of an arbitrary cylinder coincides with a predetermined crank angle before intake top dead center (for example, 90 degrees crank angle before intake top dead center) θf. It is supposed to be executed repeatedly. The cylinder whose crank angle coincides with the predetermined crank angle θf before the intake top dead center and reaches the intake stroke is hereinafter also referred to as “fuel injection cylinder”. Therefore, when the crank angle of an arbitrary cylinder reaches the predetermined crank angle θf, the CPU 71 starts processing from step 700 in FIG. 7, sequentially performs the processing from step 710 to step 770 described below, and proceeds to step 795. The routine is temporarily terminated.

Step 710: The CPU 71 applies the current engine rotational speed NE and the current intake air amount Ga to a table MapMc that predetermines the relationship between the engine rotational speed NE and the intake air amount Ga and the in-cylinder intake air amount Mc. Then, the current in-cylinder intake air amount Mc taken into the fuel injection cylinder is estimated and determined. The in-cylinder intake air amount Mc may be obtained by a known air model.
Step 720: The CPU 71 sets the stoichiometric air-fuel ratio stoich to the target air-fuel ratio abyfr . This stoichiometric air-fuel ratio stoich is a value (for example, 14.5) when the ethanol concentration of the fuel is 0% by volume (that is, when the fuel is made only of gasoline).
Step 730: The CPU 71 calculates the basic fuel injection amount Fbase by dividing the in-cylinder intake air amount Mc by the target air-fuel ratio abyfr (that is, the stoichiometric air-fuel ratio stoich).

  Step 740: The CPU 71 reads from the backup RAM 74 the alcohol concentration EtOH calculated by the routine shown in FIG. Therefore, if the alcohol concentration EtOH has not been updated from the start of the current engine start operation to the present time, “the alcohol concentration EtOH at the end of the previous engine operation” is used as the alcohol concentration EtOH in step 740.

  Step 750: The CPU 71 sets the correction coefficient k (which is an alcohol concentration correction coefficient and also the “alcohol concentration corresponding value”) to a table Mapk in which the relationship between the ethanol concentration EtOH and the correction coefficient k is determined in advance in step 740. By applying the ethanol concentration EtOH read in this way, the correction coefficient k at the present time is determined. According to this Mapk, the correction coefficient k is 1.0 when the ethanol concentration EtOH is 0% by volume, and is determined so as to increase as the ethanol concentration EtOH increases.

Step 760: The CPU 71 obtains the final fuel injection amount Fi by multiplying the basic fuel injection amount Fbase by the correction coefficient k obtained in step 750 (by correcting the basic fuel injection amount Fbase with the correction coefficient k). .
Step 770: The CPU 71 issues an injection instruction to the injector 39 so that the final fuel injection amount Fi (indicated fuel supply amount) is injected from the injector 39 for the fuel injection cylinder.

  As described above, the basic fuel injection amount Fbase necessary for obtaining the theoretical air-fuel ratio (target air-fuel ratio abyfr) is supplied by the correction coefficient k when fuel containing no ethanol is supplied. That is, the final fuel injection amount Fi increases as the ethanol concentration EtOH increases.

As described above, the first device is
In-cylinder pressure acquisition means (in-cylinder pressure sensor 65) for acquiring an in-cylinder pressure P that is a pressure in the combustion chamber 25 of the internal combustion engine 10,
Mixed gas supply means for supplying a mixed gas containing fuel and air to the combustion chamber (see the injector 39 and step 770 in FIG. 7);
The in-cylinder pressure is acquired at a predetermined timing (θa degree crank angle before compression top dead center) within a period from the start of the compression stroke for compressing the mixed gas to before the combustion of the mixed gas starts. The in-cylinder pressure obtained by the in-cylinder pressure obtaining unit based on the in-cylinder pressure P (θa) before starting combustion, which is obtained by the means, and after the combustion of the mixed gas is started. The relationship that the concentration of alcohol contained in the fuel is smaller as the in-cylinder pressure P (θa) before the start of combustion is larger without referring to the in-cylinder pressure after the start (see the table MapEtOH (U) in step 640 of FIG. 6) According to the first acquisition method, the “value corresponding to the concentration of alcohol actually contained in the fuel (for example, ethanol concentration EtOH, correction coefficient k, etc.)” is acquired as the alcohol concentration corresponding value. Stages (see step 630, step 640 in FIG. 6, step 740 and step 750 in FIG. 7);
Is provided.

  Since the in-cylinder pressure P (θa) before starting combustion is the pressure of the gas in the combustion chamber 25 before starting combustion, it is not affected by variations in the combustion state. Therefore, the alcohol concentration corresponding value obtained based on the in-cylinder pressure P (θa) before starting combustion is a highly accurate value without taking an average for a plurality of cycles. As a result, the first device can acquire the alcohol concentration corresponding value immediately after the start of the engine starting operation, for example, and can use the alcohol concentration corresponding value for engine control immediately after the engine starts.

  Further, the first acquisition means of the first device is a product of the in-cylinder pressure P (θa) before combustion start and the volume V (θa) of the combustion chamber 25 at the predetermined timing (crank angle θa before compression top dead center). Based on (P (θa) · V (θa)) “includes internal energy calculation means for calculating the internal energy U (θa) of the gas in the combustion chamber (see step 630 in FIG. 6). 1 acquisition means is configured to acquire alcohol concentration corresponding values (ethanol concentration EtOH, correction coefficient k, etc.) based on the calculated internal energy U (θa) (step 640 in FIG. 6, FIG. 7). (See steps 740 and 750).

In addition, the 1st apparatus calculated | required internal energy U ((theta) a), calculated | required ethanol concentration EtOH from the internal energy U ((theta) a), and also calculated | required the correction coefficient k from the ethanol concentration EtOH. On the other hand, the first device is configured to obtain the internal energy U (θa) and directly obtain the correction coefficient k (the alcohol concentration corresponding value) without obtaining the ethanol concentration EtOH from the internal energy U (θa). Also good.

<Second Embodiment>
Next, an alcohol concentration corresponding value acquisition device (hereinafter also referred to as “second device”) according to a second embodiment of the present invention will be described. As described in the description of the above formula (5), the ethanol concentration EtOH can be estimated based on the in-cylinder pressure P (θa) before starting combustion, which is the in-cylinder pressure at a specific timing (BTDCθadeg) during the compression stroke. Therefore, the second device is configured to directly obtain the ethanol concentration from the pre-combustion in-cylinder pressure P (θa) without calculating the internal energy U (θa).

  More specifically, the CPU 71 of the second apparatus executes the fuel injection routine shown in FIG. 7 and the ethanol concentration acquisition routine shown in FIG. 8 instead of FIG. The routine shown in FIG. 7 has already been described. Therefore, the routine shown in FIG. 8 will be described below. In FIG. 8, steps for performing the same processing as the steps shown in FIG. 6 are denoted by the same reference numerals as those given for such steps in FIG. 6. Detailed description of these steps will be omitted as appropriate.

  The routine shown in FIG. 8 is a routine in which step 630 and step 640 of the routine shown in FIG. Therefore, the CPU 71 determines that the execution time of step 610 is immediately after “the time when the crank angle of any cylinder has reached the θa degree crank angle before the compression top dead center after the start operation of the engine 10 is started”. Steps 620 and 810 described below are sequentially performed, and the process proceeds to Step 895 to end the present routine tentatively.

Step 620: The CPU 71 acquires the in-cylinder pressure P (θa) before starting combustion based on the output of the in-cylinder pressure sensor 65 provided in the cylinder whose crank angle has reached the crank angle before the compression top dead center θa degree.
Step 810: The CPU 71 obtains the relationship between the pre-combustion in-cylinder pressure P (θa) and the ethanol concentration EtOH (volume%) in a predetermined table MapEtOH (P) in the above-described step 620 in-cylinder pre-combustion pressure P ( By applying θa), the actual ethanol concentration EtOH is calculated (estimated). The table MapEtOH (P) is created on the basis of “data obtained in advance by experiment” representing the relationship between the in-cylinder pressure P (θa) before starting combustion and the ethanol concentration EtOH, and is stored in the ROM 72. According to the table MapEtOH (P), the ethanol concentration EtOH decreases as the pre-combustion in-cylinder pressure P (θa) increases. As described above, the ethanol concentration EtOH of the fuel is estimated immediately after starting. The ethanol concentration EtOH calculated in step 810 is stored in the backup RAM 74.

  The ethanol concentration EtOH estimated in this way is read out by the process of step 740 in FIG. 7 and used when the correction coefficient k is determined by the process of step 750. Accordingly, the fuel injection amount Fi increases as the ethanol concentration EtOH of the fuel increases.

  As described above, the second device is included in the fuel based on the in-cylinder pressure P (θa) before starting combustion and the in-cylinder pressure P (θa) before starting firing, without obtaining the internal energy U (θa). Provided with a first acquisition means for calculating an alcohol concentration corresponding value (ethanol concentration EtOH, correction coefficient k, etc.) in accordance with the relationship that the concentration of the alcohol is low (see table MapEtOH (P) in step 810 of FIG. 8). (See step 810 in FIG. 8).

  The second device acquires the in-cylinder pressure P (θa) before starting combustion, determines the ethanol concentration EtOH from the in-cylinder pressure P (θa) before starting combustion, and further calculates the correction coefficient k from the ethanol concentration EtOH. It was. On the other hand, the second device acquires the in-cylinder pressure P (θa) before starting combustion, and acquires the in-cylinder pressure P before starting combustion without obtaining the ethanol concentration EtOH from the acquired in-cylinder pressure P (θa) before starting combustion. The correction coefficient k (value corresponding to the alcohol concentration) may be directly obtained from (θa).

<Third Embodiment>
Next, an alcohol concentration corresponding value acquisition device (hereinafter also referred to as “third device”) according to a third embodiment of the present invention will be described. When the third device obtains the alcohol concentration corresponding value based on the internal energy U (θa) before the start of combustion, the first device is only in consideration of the amount of burnt gas remaining in the combustion chamber 25 at the start of the compression stroke. It is different from the device.

  As understood from the above equation (5), the internal energy U is also proportional to the temperature T of the gas in the combustion chamber 25. From this, it is considered that the internal energy U also depends on the amount of burned gas in the combustion chamber 25. In other words, the internal energy U (θa) before the start of combustion can be considered as the sum of “energy U1 due to fuel molecules acting as gas” and “energy U2 due to burned gas molecules”. Therefore, even if the internal energy U (θa) before the start of combustion is the same, the larger the amount of burned gas, the greater the energy U2 due to the burnt gas molecules, so the energy U1 due to the fuel molecules acting as gas is Get smaller. Therefore, when the alcohol concentration is estimated based on the internal energy U (θa) before the start of combustion, the alcohol concentration can be estimated with higher accuracy when the burned gas amount is taken into consideration. The third device is based on such knowledge.

  FIG. 9 shows the change of the internal energy U with respect to the crank angle θ when the fuel having the same ethanol concentration is used and the intake valve advance angle VT is set to various values (that is, the burnt gas amount is changed). It is the graph which showed a mode. In this graph, the crank angle 0 indicates “compression top dead center”, and the crank angle −30 indicates a 30-degree crank angle before compression top dead center. VT0 (broken line), VT20 (solid line), and VT40 (one-dot chain line) indicate internal energy when the intake valve advance angle VT is a 0 degree crank angle, a 20 degree crank angle, and a 40 degree crank angle, respectively. Therefore, VT40 indicates “internal energy U when the amount of burned gas (residual gas concentration) is maximum due to the most advanced intake valve opening timing”, and VT0 indicates “the latest intake valve opening timing is the latest. The internal energy U ”when the burned gas amount (residual gas concentration) is the minimum is shown.

  FIG. 10 plots data when the crank angle is 30 ° crank angle before compression top dead center (BTDCθadeg) from the data consisting of the internal energy U (θ) and the intake valve advance angle VT shown in FIG. It is a graph. The horizontal axis of this graph is the intake valve advance angle VT (the valve overlap amount, that is, the burned gas amount), and the vertical axis is the internal energy U (θa) before the start of combustion.

  9 and 10, even if the fuel has the same ethanol concentration, the amount of burnt gas at the start of the compression stroke increases as the intake valve advance angle VT increases and the valve overlap amount increases. It was confirmed that the internal energy U (θa) before the start of combustion increases as the value increases. Therefore, as shown in FIG. 11, the ethanol concentration EtOH decreases as the internal energy U (θa) before combustion starts increases, and as the intake valve advance angle VT becomes a value on the advance side (that is, valve overlap). The larger the amount and the larger the amount of burned gas at the start of the compression stroke), the larger. The third device estimates the ethanol concentration EtOH of the fuel using the relationship shown in FIG.

  Next, the operation of the third device will be described. The CPU 71 of the third device executes the fuel injection routine shown in FIG. 7 and the ethanol concentration acquisition routine shown in FIG. 12 instead of FIG. The routine shown in FIG. 7 has already been described. Therefore, the routine shown in FIG. 12 will be described below. In FIG. 12, steps for performing the same processing as the steps shown in FIG. 6 are denoted by the same reference numerals as those given for such steps in FIG. 6. Detailed description of these steps will be omitted as appropriate.

The routine shown in FIG. 12 is a routine in which step 640 of the routine shown in FIG. 6 is replaced with step 1210 and step 1220. Therefore, the CPU 71 executes step 610 immediately after “the time when the crank angle of any cylinder that has finished combustion after the start of the starting operation of the engine 10 first reaches the crank angle θa degrees before compression top dead center”. If there is, the routine proceeds to step 620, where the in-cylinder pressure P (θa) before starting combustion is obtained based on the output of the in-cylinder pressure sensor 65 provided in the cylinder whose crank angle reaches the crank angle before the compression top dead center for the first time. To do. Next, the CPU 71 proceeds to step 630 and calculates (acquires) the internal energy U (θa) before starting combustion using the above equation (5). Thereafter, the CPU 71 sequentially performs the processing of step 1210 and step 1220 described below, proceeds to step 1295, and once ends this routine.

  Step 1210: The CPU 71 acquires the current intake valve advance angle VT. As described above, the valve overlap amount increases as the intake valve advance angle VT advances (increases), and therefore the amount of burned gas existing in the combustion chamber 25 at the start of the compression stroke increases. In other words, the processing of this step 1210 achieves the function of the burned gas amount obtaining means for obtaining the amount of burned gas existing in the combustion chamber 25 at the start of the compression stroke.

  Note that the CPU 71 executes an intake valve advance angle control routine (not shown) to predetermine the relationship between the throttle valve opening TA (or load factor KL) and the engine rotational speed NE, and the intake valve advance angle VT. The current intake valve advance angle VT is determined by applying the current throttle valve opening degree TA and the current engine speed NE to the intake valve advance angle table MapVT. Further, in the intake valve advance angle control routine, the CPU 71 sends a drive signal to the intake valve control device 33 so that the actual intake valve advance angle coincides with the determined intake valve advance angle VT.

  Step 1220: The CPU 71 calculates the relationship between the internal energy U (θa) and the intake valve advance angle VT and the ethanol concentration EtOH (volume%) in a predetermined table MapEtOH (U, VT) in the above step 630. The actual ethanol concentration EtOH is calculated (estimated) by applying the internal energy U (θa) and the current intake valve advance angle VT acquired in step 1210.

  This table MapEtOH (U, VT) is created based on “data obtained in advance by experiment” representing the relationship between the internal energy U (θa), the intake valve advance angle VT, and the ethanol concentration EtOH, and is stored in the ROM 72. Has been. According to this table MapEtOH (U, VT), the ethanol concentration EtOH is determined so as to decrease as the internal energy U (θa) increases. Furthermore, according to the table MapEtOH (U, VT), the more the intake valve advance angle VT becomes a value on the advance side (that is, the greater the valve overlap amount, the greater the amount of burned gas at the start of the compression stroke). Since the internal energy due to the fuel molecules acting as a gas is small, the ethanol concentration EtOH is required to be large.

  As described above, the ethanol concentration EtOH of the fuel is estimated immediately after starting. In addition, the ethanol concentration EtOH calculated in step 1220 is stored in the backup ram 74. The ethanol concentration EtOH estimated in this way is read out by the process of step 740 in FIG. 7 and used when the correction coefficient k is determined by the process of step 750. Accordingly, the fuel injection amount Fi increases as the ethanol concentration EtOH of the fuel increases.

  As described above, the third device includes the in-cylinder pressure acquisition unit, the mixed gas supply unit, and the first acquisition unit, like the first and second devices. Furthermore, the third device includes burned gas amount acquisition means (see step 1210 in FIG. 12) for acquiring (estimating) the amount of burned gas present in the combustion chamber 25 at the start of the compression stroke. . In addition, the first acquisition means of the third device has the same in-cylinder pressure P (θa) before combustion start (accordingly, internal energy U (θa) before combustion start) based on the acquired amount of burned gas. In addition, according to the relationship that the concentration of alcohol contained in the fuel increases as the amount of burned gas obtained increases (see the graph in FIG. 11 and the table MapEtOH (U, VT) in step 1220 in FIG. 12). Concentration corresponding values (ethanol concentration EtOH, correction coefficient k, etc.) are configured to be acquired. Therefore, even when the burnt gas amount fluctuates, the alcohol concentration correspondence value can be acquired with higher accuracy.

  The third device estimated the ethanol concentration EtOH of the fuel by using the table MapEtOH (U, VT) in step 1220 of FIG. On the other hand, the third device can also be configured to obtain the ethanol concentration EtOH of the fuel by calculation.

More specifically, as shown in FIG. 11, the ethanol concentration EtOH of the fuel is substantially proportional to the internal energy U (θa) before starting combustion. Therefore, if the correction amount by the burned gas is set as C, the ethanol concentration EtOH of the fuel can be obtained based on the following equation (6). In equation (6), ku is an adapted proportionality constant.

Further, the ethanol concentration EtOH is substantially proportional to the intake valve advance angle VT. Therefore, as shown in FIG. 13 and the following equation (7), the correction C by the burned gas can be obtained by calculation. Therefore, the third device can obtain the ethanol concentration EtOH by calculation based on the equations (6) and (7).

  In addition, the third device estimates the ethanol concentration EtOH from the internal energy U (θa) before the start of combustion and the intake valve advance angle VT. In contrast, the third device acquires the in-cylinder pressure P (θa) and the intake valve advance angle VT before starting combustion, and obtains the ethanol concentration EtOH from the in-cylinder pressure P (θa) and the intake valve advance angle VT before starting combustion. May be.

  Further, the third device corrects the correction coefficient k (the alcohol concentration corresponding value) without estimating the ethanol concentration EtOH from either the internal energy U (θa) or the in-cylinder pressure P (θa) and the intake valve advance angle VT. May be directly determined.

<Fourth embodiment>
Next, an alcohol concentration corresponding value acquisition apparatus (hereinafter also referred to as “fourth apparatus”) according to a fourth embodiment of the present invention will be described. As with the first to third devices, the fourth device is “internal energy U (θa) before combustion start or in-cylinder pressure P (θa) before combustion start” at “specific crank angle θa (BTDCθadeg) during the compression stroke”. Is used to calculate the alcohol concentration (ethanol concentration). Hereinafter, the alcohol concentration obtained based on “internal energy U (θa) before combustion start or in-cylinder pressure P (θa) before combustion start” in this way is referred to as “first alcohol concentration” for convenience.

  Further, the fourth device employs the second estimation principle of alcohol concentration described below. According to the second estimation principle, the alcohol concentration is acquired based on the “lower heating value (amount corresponding to the lower heating value)”. The alcohol concentration acquired based on the lower heating value (the amount corresponding to the lower heating value) is referred to as “second alcohol concentration” for convenience. Then, the fourth device determines whether the difference between the first alcohol concentration and the second alcohol concentration is greater than a predetermined threshold, and determines the difference between the first alcohol concentration and the second alcohol concentration. Is greater than a predetermined threshold value, it includes an abnormality determination unit that determines that the “mixed gas supply unit that supplies the mixed gas containing fuel to the engine 10”, which includes the injector 39 or the like, is abnormal.

(Second estimation principle of alcohol concentration)
Here, the second estimation principle of the alcohol concentration will be described. The lower heating value is the amount of heat that the fuel can generate per unit mass. For example, the lower heating value of gasoline is 40 (MJ / g), and the lower heating value of ethanol is 26 (MJ / g). Therefore, the lower heating value changes depending on the alcohol concentration of the fuel. Therefore, the fourth device obtains a value corresponding to the lower heating value (a lower heating value equivalent value that is a value representing the lower heating value) as follows, and determines the alcohol concentration based on the lower heating value equivalent value. Obtain (estimate).

FIG. 14 shows changes in “(A) in-cylinder pressure P, (B) P (θ) · V (θ) ^κ, and (C) internal energy U calculated by the above equation (5)” with respect to the crank angle θ. Is shown. Also in FIG. 14, the crank angle 0 indicates “compression top dead center”, the region where the crank angle θ is a negative value indicates the region before compression top dead center (BTDC), and the crank angle θ is a positive value. Indicates after compression top dead center (ATDC).

In FIG. 14B, P (θ) · V (θ) ^κ is indicated by a solid line, and the amount of heat generated in the combustion chamber 25 (integrated amount of generated heat, cumulative heating amount) Q is indicated by a broken line. ing. From the comparison between the two, it can be understood that the change pattern of the heat generation amount Q substantially coincides with the change pattern of P (θ) · V (θ) ^κ . That is, the heat generation amount Q can be acquired based on P (θ) · V (θ) ^κ .

By the way, the lower heating value is the amount of heat that the fuel can generate per unit mass. Therefore, the fourth apparatus, as shown in FIG. 15, to calculate the amount [Delta] P · V ^kappa corresponding to the heat generation amount Q of fuel by one combustion. This amount ΔP · ^Vκ is referred to as a “heat generation equivalent amount” for convenience.

More specifically, the fourth device calculates P (θs) · V (θs) ^κ when the crank angle θ is θs degrees before compression top dead center (for example, θs = 60 degrees crank angle). get. Further, the fourth device acquires P (θe) · V (θe) ^κ when the crank angle θ is the θe degree crank angle after compression top dead center (for example, θe = 60 degree crank angle). Thereafter, the fourth device obtains a difference between them, that is, a value obtained by subtracting P (θs) · V (θs) ^κ from P (θe) · V (θe) ^κ as a heat generation equivalent amount ΔP · V ^κ .

  When the crank angle θ is the θs degree crank angle before the compression top dead center, both the intake valve 32 and the exhaust valve 35 are closed in the compression stroke toward the target combustion stroke (expansion stroke) and the ignition timing is reached. It is a time when it has advanced sufficiently. That is, it is a time when the mixed gas does not generate any heat. The time point when the crank angle θ is the θe degree crank angle after compression top dead center is a predetermined time later than the latest time when combustion of the mixed gas in the target combustion stroke is substantially finished, and the exhaust valve is opened. It is a time advanced from the time.

In the fourth device, “P (θ) · V (θ) ^κ ” when the crank angle θ is between the θs degree crank angle before compression top dead center and the θe degree crank angle after compression top dead center. The maximum value MAX and the minimum value MIN may be acquired, and the difference (MAX−MIN) may be acquired as the heat generation equivalent amount ΔP · ^Vκ .

That is, the fourth device at least from the start of combustion of the mixed gas (for example, the ignition timing or the point at which P · V ^κ starts abrupt increase) to the end of combustion (for example, P · V ^κ after the ignition timing). Heat generation to estimate (acquire) an amount (equivalent heat generation) ΔP · V ^κ corresponding to the heat generation amount that is the amount of heat generated with the combustion of the mixed gas during the period until the start of decrease) A quantity estimation means is provided.

Further, the fourth device divides the “heat generation equivalent amount ΔP · V ^κ ” by the fuel injection amount τ (= the value obtained by converting the fuel injection amount Fi into mass) proportional to the mass of the fuel subjected to the combustion. Thus, a value corresponding to the lower heating value (lower heating value equivalent value) LHV is estimated. Although the fuel injection amount τ varies depending on the alcohol concentration, it is close to the extent that no problem arises even if the gasoline concentration and the alcohol concentration are substantially equal to each other.

  Then, the fourth device sets “estimated lower heating value equivalent value LHV” in the table MapEtOH (LHV) shown in FIG. 16 which defines the relationship between the lower heating value equivalent value LHV and the alcohol concentration (ethanol concentration EtOH). By applying, the second alcohol concentration EtOH2 is estimated. According to this table MapEtOH (LHV), the larger the estimated lower heating value equivalent value LHV, the smaller the second alcohol concentration EtOH2 is obtained. The above is the second estimation principle of the alcohol concentration.

(Actual operation)
Next, the actual operation of the fourth device will be described. The CPU 71 of the fourth device executes the routines shown in FIGS. 6 and 7 and the abnormality determination routine shown in FIG. The routines shown in FIGS. 6 and 7 have already been described. Therefore, the routine shown in FIG. 17 will be described below.

  The CPU 71 executes the routine shown in the flowchart of FIG. 17 when the crank angle of each cylinder reaches the crank angle of 60 degrees after the compression top dead center (when the expansion stroke is substantially finished). . Therefore, when the crank angle of an arbitrary cylinder reaches 60 ° crank angle after compression top dead center, the CPU 71 starts processing from step 1700, sequentially performs the processing of steps 1710 to 1740 described below, and proceeds to step 1750. .

  Step 1710: The CPU 71 reads the ethanol concentration EtOH acquired in step 640 of FIG. 6 as the first ethanol concentration EtOH1. That is, the first ethanol concentration EtOH1 is the ethanol concentration EtOH acquired based on the internal energy U (θa) before starting combustion. The CPU 71 may execute the routine shown in FIG. 8 instead of FIG. 6 and may read the ethanol concentration EtOH acquired in step 810 of FIG. 8 as the first ethanol concentration EtOH1 in step 1710.

Step 1720: The CPU 71 calculates the “heat generation equivalent amount ΔP · V ^κ ” for the combustion immediately before the cylinder whose crank angle has reached 60 ° crank angle after compression top dead center (hereinafter referred to as “combustion end cylinder”). calculate. That is, the CPU 71 acquires P (−60) · V (−60) ^κ = P (BTDC60deg) · V (BTDC60deg) ^κ when BTDC is 60 deg, and P (60) · V (60 when ATDC is 60 deg. ) ^Κ = P (ATDC60deg) · V (ATDC60deg) is obtained, and the difference (= P (60) · V (60) ^κ− P (−60) · V (−60) ^κ )) is obtained as a heat generation equivalent amount ΔP • Obtain as V ^κ . The CPU 71 acquires the in-cylinder pressure P every time a predetermined minute crank angle elapses, and associates the crank angle θ at the time when the in-cylinder pressure P is acquired with the acquired in-cylinder pressure P. The cylinder pressure P is stored in the RAM 73 as the cylinder pressure P (θ). Further, a table MapV (θ) in which the relationship between the combustion chamber volume V and the crank angle θ is predetermined is stored in the ROM 72. The CPU 71 acquires the combustion chamber volume V (θ) based on the table MapV (θ) and the crank angle θ.

Step 1730: CPU 71 obtains the lower heating value equivalent value LHV by the heat generation amount corresponding [Delta] P · V ^kappa acquired in step 1720 is divided by the fuel supply amount (supply fuel mass) tau. The fuel supply amount (supply fuel mass) τ is the mass of the fuel that should have been used for the immediately preceding combustion of the combustion end cylinder (the final value based on the injection instruction given to the injector 39 in step 770 in FIG. 7). The value obtained by converting the fuel injection amount Fi into mass).

  Step 1740: The CPU 71 applies the lower calorific value equivalent value LHV calculated in step 1730 to the table MapEtOH2 that predetermines the relationship between the lower calorific value equivalent value LHV and the alcohol concentration EtOH2, thereby determining the current alcohol concentration. The second alcohol concentration is determined as EtOH2. According to the table MapEtOH2, the alcohol concentration EtOH2 decreases as the lower heating value equivalent value LHV increases.

  Next, the CPU 71 proceeds to step 1750, where the magnitude of the difference (absolute value of the difference) between the first ethanol concentration EtOH1 read in step 1710 and the second ethanol concentration EtOH2 determined in step 1740 is determined to be abnormal. It is determined whether or not the threshold (predetermined threshold) IJOth is greater.

  By the way, if the mixed gas supply means including the injector 39 is operating normally, that is, the final fuel based on the injection instruction issued from the injector 39 to the injector 39 of the cylinder whose combustion has ended in step 770 of FIG. If the fuel of the injection amount (indicated fuel supply amount) Fi ”is supplied to the combustion chamber 25, the second alcohol concentration EtOH2 should be close to the first alcohol concentration EtOH1. In other words, if the magnitude of the difference between the second alcohol concentration EtOH2 and the first alcohol concentration EtOH1 is larger than the predetermined threshold value IJOth, it can be considered that the mixed gas supply means is abnormal.

  Therefore, if “the difference between the second alcohol concentration EtOH2 and the first alcohol concentration EtOH1” is larger than the predetermined threshold value IJOth, the CPU 71 determines “Yes” in step 1750 and proceeds to step 1760 to mix. The value of the gas supply means abnormality flag XIJO is set to “1”. The value of the mixed gas supply means abnormality flag XIJO is stored in the backup RAM 74. Next, the CPU 71 proceeds to step 1770 to turn on a warning lamp (not shown). Thereafter, the CPU 71 proceeds to step 1795 to end the present routine tentatively.

  On the other hand, if “the magnitude of the difference between the second alcohol concentration EtOH2 and the first alcohol concentration EtOH1” is equal to or smaller than the predetermined threshold value IJOth, the CPU 71 determines “No” in step 1750 and proceeds to step 1780. Then, the value of the mixed gas supply means abnormality flag XIJO is set to “0”. Thereafter, the CPU 71 proceeds to step 1795 to end the present routine tentatively.

  As described above, the fourth device includes the mixed gas supply means (injector 39) that supplies fuel to the combustion chamber 25 in accordance with the instruction signal.

Furthermore, the fourth device is
The commanded fuel supply amount Fi is determined based on the operating state of the engine (see Steps 710 to 760 in FIG. 7), and the fuel of the determined commanded fuel supply amount Fi is the mixed gas supply means (injector 39, etc.). ) Includes a fuel supply amount control means (see step 770 in FIG. 7) for sending an instruction signal to the mixed gas supply means.

In addition, the fourth device
An amount corresponding to a heat generation amount (a heat generation equivalent amount ΔP · V ^κ ) that is an amount of heat generated with combustion of the mixed gas is estimated at least during a period from the start of combustion of the mixed gas to the end of combustion. Heat generation amount estimation means (see step 1730 in FIG. 17);
An amount corresponding to the lower heating value (low heating value equivalent value LHV) is calculated based on the heating value corresponding to the estimated heat generation amount ΔP · V ^κ and the indicated fuel supply amount Fi. The second acquisition means (step 1720 in FIG. 17) acquires the concentration of alcohol contained in the fuel as the second alcohol concentration EtOH2 based on the amount corresponding to the calculated lower heating value (lower heating value equivalent value LHV). Through step 1740).
“The magnitude of the difference between the acquired first alcohol concentration EtOH1 (see step 640 in FIG. 6 and step 1710 in FIG. 17) and the acquired second alcohol concentration EtOH2” is determined from the predetermined threshold IJOth. An abnormality determination means (see Step 1750 to Step 1780 in FIG. 17) for determining that the mixed gas supply means is abnormal when
It has.

  Therefore, the fourth device can determine whether or not the mixed gas supply means is abnormal by using the first alcohol concentration and the second alcohol concentration.

  As described above, the alcohol concentration corresponding value acquisition device according to each embodiment of the present invention can detect the value corresponding to the concentration of alcohol actually contained in the fuel at an early stage and without being affected by the fluctuation of the combustion state. (Alcohol concentration correspondence value) "can be obtained with high accuracy. Furthermore, it can be said that these devices are provided with engine control amount correction means for correcting the control amount (fuel injection amount or the like) of the engine 10 by “the alcohol concentration corresponding value or the first alcohol concentration”. Therefore, these devices can control the engine 10 according to the alcohol concentration immediately after the engine 10 is started.

  The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention. For example, the ignition timing may be corrected based on the alcohol concentration (first alcohol concentration EtOH1) obtained by using the pre-combustion in-cylinder pressure P (θa) in each embodiment. In this case, it is desirable to advance the ignition timing as the alcohol concentration (first alcohol concentration EtOH1) is higher. That is, the ignition timing advance angle correction amount that increases as the first ethanol concentration EtOH1 increases is obtained, and the basic ignition that is adapted to a fuel whose first ethanol concentration EtOH1 is 0% by volume (that is, a fuel consisting only of gasoline). The timing may be advanced by the ignition timing advance correction amount.

  Further, the fourth device acquires the second ethanol concentration EtOH2 for a plurality of combustions, and uses the obtained average value of the plurality of second ethanol concentrations EtOH2 in step 1750 of FIG. The second ethanol concentration EtOH2 may be adopted. Further, the first to fourth devices may calculate the first alcohol concentration (first ethanol concentration) a plurality of times, and adopt the average value as the final first alcohol concentration.

It is the graph which showed the internal energy of the gas in a combustion chamber with respect to a crank angle about the fuel which has various ethanol concentrations. It is the graph which expanded the square frame shown in FIG. Of the data shown in FIGS. 1 and 2, “data when the crank angle is 30 degrees before compression top dead center” is shown in a graph in which the horizontal axis is ethanol concentration and the vertical axis is internal energy. It is a figure. It is the schematic of the internal combustion engine to which the alcohol concentration corresponding | compatible value acquisition apparatus (1st apparatus) of the fuel for internal combustion engines which concerns on 1st Embodiment of this invention is applied. It is a graph showing the result of having measured the internal energy with respect to a crank angle several times about the fuel of fixed ethanol concentration. It is the flowchart which showed the routine which CPU of 1st apparatus performs. It is the flowchart which showed the routine which CPU of 1st apparatus performs. It is the flowchart which showed the routine which CPU of the alcohol concentration corresponding | compatible value acquisition apparatus (2nd apparatus) which concerns on 2nd Embodiment of this invention performs. It is the graph which showed the mode of the change with respect to the crank angle of internal energy at the time of using the fuel with the same ethanol concentration and setting the intake valve advance angle to various values. Of the data consisting of the internal energy and the intake valve advance angle shown in FIG. 9, the data when the crank angle is 30 degrees before the compression top dead center, the horizontal axis is the intake valve advance angle, It is the figure shown in the graph whose is internal energy. It is the graph which showed the relationship between ethanol concentration, internal energy before a combustion start, and an intake valve advance angle. It is the flowchart which showed the routine which CPU of the alcohol concentration corresponding | compatible value acquisition apparatus (3rd apparatus) which concerns on 3rd Embodiment of this invention performs. It is the graph which showed "the correction | amendment part of alcohol concentration by burnt gas" used when the 3rd apparatus calculates | requires alcohol concentration by calculation. It is the figure which showed the mode of the change of "(A) cylinder pressure, (B) P * V ( ^kappa ), and (C) internal energy" with respect to a crank angle. It is the figure which showed the mode of the heat_generation | fever equivalent amount with respect to a crank angle (a quantity equivalent to heat generation amount). It is the graph (table) which showed the relationship between low calorific value equivalent value LHV and alcohol concentration (ethanol concentration). It is the flowchart which showed the routine which CPU of the alcohol concentration corresponding | compatible value acquisition apparatus (4th apparatus) which concerns on 4th Embodiment of this invention performs.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Cylinder block part, 21 ... Cylinder, 22 ... Piston, 25 ... Combustion chamber, 30 ... Cylinder head part, 31 ... Intake port, 32 ... Intake valve, 33 ... Intake valve control apparatus, 34 ... Exhaust Port, 35 ... Exhaust valve, 37 ... Spark plug, 38 ... Igniter, 39 ... Injector, 40 ... Intake system, 41 ... Intake manifold, 42 ... Intake pipe, 44 ... Throttle valve, 44a ... Throttle valve actuator, 50 ... Exhaust system 51 ... Exhaust manifold, 52 ... Exhaust pipe, 53 ... Three-way catalyst, 54 ... Three-way catalyst, 61 ... Hot-wire air flow meter, 62 ... Throttle position sensor, 63 ... Cam position sensor, 64 ... Crank position sensor, 65 ... In-cylinder pressure sensor 66 ... cooling water temperature sensor 69 ... accelerator opening sensor 70 ... electric control unit, 71 ... CPU, 74 ... backup RAM.

Claims (3)

In-cylinder pressure acquisition means for acquiring an in-cylinder pressure that is a pressure in the combustion chamber of the internal combustion engine;
Mixed gas supply means for supplying a mixed gas containing fuel and air to the combustion chamber;
Combustion start that is in-cylinder pressure at a predetermined timing within a period from the start of the compression stroke for compressing the mixed gas to before the start of combustion of the mixed gas, which is the in-cylinder pressure acquired by the in-cylinder pressure acquisition means The in-cylinder pressure before the start of combustion is based on the in-cylinder pressure after starting combustion based on the in-cylinder pressure after the start of combustion, which is the in-cylinder pressure after the start of combustion of the mixed gas. First acquisition means for acquiring, as an alcohol concentration corresponding value, a value corresponding to the concentration of alcohol actually contained in the fuel according to the relationship that the concentration of alcohol contained in the fuel is smaller as the
Equipped with a,
The first acquisition means includes
Acquire the alcohol concentration corresponding value of the fuel for the internal combustion engine that acquires the same alcohol concentration as the first alcohol concentration so that the concentration of the alcohol contained in the fuel as the alcohol concentration corresponding value decreases as the pre-combustion cylinder pressure increases. A device ,
The mixed gas supply means is configured to supply the fuel to the combustion chamber in response to an instruction signal,
Furthermore, the alcohol concentration corresponding value acquisition device includes:
The command fuel supply amount is determined based on the operating state of the engine, and an instruction signal is sent to the mixed gas supply means so that fuel of the determined fuel supply amount is supplied from the mixed gas supply device to the combustion chamber. Fuel supply amount control means for delivering;
Heat generation amount estimation means for estimating an amount corresponding to a heat generation amount that is an amount of heat generated with combustion of the mixed gas at least during a period from the start of combustion of the mixed gas to the end of combustion;
An amount corresponding to the lower heat generation amount is calculated based on the estimated heat generation amount and the indicated fuel supply amount, and is included in the fuel based on the calculated lower heat generation amount. Second acquisition means for acquiring the concentration of alcohol as the second alcohol concentration;
An abnormality determination unit that determines that the mixed gas supply unit is abnormal when the magnitude of the difference between the acquired first alcohol concentration and the acquired second alcohol concentration is greater than a predetermined threshold;
A device for acquiring a value corresponding to alcohol concentration.   In the alcohol concentration corresponding value acquisition device according to claim 1,
  The first acquisition means includes
  An internal energy calculating means for calculating the internal energy of the gas in the combustion chamber at the predetermined timing based on the product of the cylinder internal pressure before the combustion start and the volume of the combustion chamber at the predetermined timing; An alcohol concentration corresponding value acquisition device configured to acquire the first alcohol concentration based on internal energy.   The alcohol concentration corresponding value acquisition device according to claim 1 or 2,
  Comprising a burned gas amount obtaining means for obtaining the amount of burned gas present in the combustion chamber at the start of the compression stroke;
  The first acquisition means includes
  An alcohol concentration corresponding value acquisition device that acquires the first alcohol concentration so that the first alcohol concentration increases as the acquired amount of burned gas increases even if the in-cylinder pressure before the start of combustion is the same.

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