JP2005180220A - Combustion temperature estimation method for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion temperature estimation method for an internal combustion engine, for accurately estimating a combustion temperature in a cylinder (combustion chamber) of the internal combustion engine, with simple structure. <P>SOLUTION: Upon each arrival of fuel injection start timing, a pre-combustion temperature of cylinder interior gas at the time of ignition (ignition-time compressed cylinder interior gas temperature Tpump) is estimated on the basis of the fact that the state of the cylinder interior gas changes adiabatically. The quantity of heat generated as a result of combustion of fuel is divided by the product of a post-combustion mole amount and constant-pressure specific heat of the cylinder interior gas, which can be obtained from the concentration proportions of gas components contained in intake gas, to thereby estimate a rise in temperature of the cylinder interior gas stemming from combustion (combustion ascribable temperature increase ΔTburn). Further, a rise in temperature of the cylinder interior gas stemming from an increase in combustion speed (combustion-speed ascribable temperature increase ΔTb_velo) is estimated on the basis of fuel injection pressure and an engine speed, which are factors affecting the combustion speed. Then, the highest combustion temperature Tflame is estimated by equation Tflame = Tpump + ΔTburn + ΔTb_velo. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a combustion temperature estimation method for estimating a combustion temperature in a cylinder (combustion chamber) of an internal combustion engine.

  The amount of emissions such as NOx discharged from an internal combustion engine such as a spark ignition type internal combustion engine or a diesel engine has a strong correlation with the combustion temperature (maximum combustion temperature, maximum flame temperature) in the cylinder. Therefore, it is effective to control the combustion temperature to a predetermined temperature in order to reduce the emission amount of NOx and the like. On the other hand, it is very difficult to actually measure the combustion temperature. Therefore, in order to control the combustion temperature to a predetermined temperature, it is necessary to accurately estimate the combustion temperature.

For this reason, the combustion chamber temperature state estimation device for an internal combustion engine described in Patent Document 1 below includes an exhaust temperature sensor that detects the temperature of exhaust gas discharged from the combustion chamber of the engine outside the combustion chamber. Based on the detected value outside the combustion chamber exhaust temperature, the temperature in the combustion chamber after the end of combustion having high correlation with the detected value (accordingly, the combustion temperature in the cylinder) is estimated.
JP 2002-54491 A

  In the above apparatus, it is assumed that there is a strong correlation between the exhaust temperature outside the combustion chamber and the combustion temperature when estimating the combustion temperature in the cylinder. However, in practice, there is not always a strong correlation between the two, and as a result, the combustion temperature may not be accurately estimated. Moreover, since the exhaust temperature sensor has an essential configuration, there are problems that the manufacturing cost increases and the configuration becomes complicated.

  The present invention has been made to cope with such a problem, and an object of the present invention is to estimate the combustion temperature of the internal combustion engine that can accurately estimate the combustion temperature in the cylinder (combustion chamber) of the internal combustion engine with a simple configuration. It is to provide a method.

  In the method for estimating the combustion temperature of an internal combustion engine according to the present invention, first, by using the fact that at least the in-cylinder gas existing in the cylinder is compressed in the cylinder, the ignition that is the in-cylinder gas temperature before combustion at the time of ignition. The gas temperature in the compression cylinder is estimated. Here, the ignition time is, for example, when the spark plug is ignited for a spark ignition type internal combustion engine, and for the diesel engine, the fuel injection timing (main injection is performed when main injection is performed after at least one pilot injection). This is the time when a predetermined ignition delay time has elapsed from the injection timing.

  The compression in-cylinder gas temperature at the time of ignition is, for example, based on the assumption that the state of the in-cylinder gas (ie, temperature and pressure) before combustion in the compression stroke (and the expansion stroke) changes adiabatically. It can be accurately and easily obtained based on a general expression representing the adiabatic change and the in-cylinder volume at the time of ignition.

  Further, in this estimation method, a combustion-induced temperature rise that is a temperature rise amount of the in-cylinder gas due to combustion based on at least a composition of the gas sucked into the cylinder and a calorific value due to combustion of the injected fuel The quantity is estimated. In general, the amount of temperature rise of in-cylinder gas due to combustion (and hence the amount of temperature rise due to combustion) is calculated based on the amount of heat generated by combustion of fuel, the specific heat (constant pressure specific heat) of cylinder gas involved in the combustion after combustion, and combustion It can be determined by dividing by the amount (in moles) of the in-cylinder gas involved in the subsequent combustion.

  Here, the constant-pressure specific heat and the number of moles of the in-cylinder gas involved in the combustion are the composition of the gas sucked into the cylinder (hereinafter also referred to as “intake”) (a plurality of components constituting the intake ( For example, it is a value that changes with the concentration ratio of oxygen and inert gas), for example, a value that increases with an increase in the concentration ratio of the inert gas in the intake air (details will be described later). Therefore, this combustion-induced temperature rise amount is the constant pressure specific heat and the number of moles of the in-cylinder gas involved in the combustion, which can be accurately obtained based on the composition of the intake air (for example, the concentration ratio of the inert gas in the intake air). In addition, it can be obtained with high accuracy based on the amount of heat generated by the combustion of fuel.

  Further, in this estimation method, the temperature increase amount due to the combustion speed, which is the temperature increase amount of the in-cylinder gas due to the increase in the combustion speed, is estimated based on a factor that affects the combustion speed in the cylinder. Generally, in a diesel engine, the ignition time is often later than the time corresponding to the compression top dead center (that is, the time corresponding to the expansion stroke). In the expansion stroke, the in-cylinder gas temperature decreases with time.

  Therefore, in this case, the maximum combustion temperature becomes higher as the time from the ignition time (that is, the combustion start time) until the in-cylinder gas temperature reaches the maximum combustion temperature is shorter. In other words, the higher the combustion speed in the cylinder after the start of combustion, the higher the (maximum) combustion temperature of the in-cylinder gas. The temperature rise amount of the in-cylinder gas is obtained as the combustion rate-induced temperature rise amount based on a factor that affects the in-cylinder combustion rate.

  Factors that affect the in-cylinder combustion speed include, for example, the fuel injection pressure, the rotational speed of the engine, the swirl ratio of gas sucked into the cylinder, and a supercharger disposed in the engine. The supercharging pressure by the same supercharger and the oxygen concentration in the gas sucked into the cylinder are mentioned.

  In this estimation method, a value obtained by adding the combustion-induced temperature increase amount and the combustion speed-induced temperature increase amount to the ignition compression cylinder gas temperature is estimated as the (maximum) combustion temperature in the cylinder. The maximum combustion temperature in the cylinder estimated in this way can be a value that accurately represents various actual phenomena as follows.

  That is, for example, if the ignition timing is delayed by delaying the fuel injection timing (in the expansion stroke), the estimated cylinder gas temperature during ignition decreases due to the increase in the cylinder volume during the ignition, and this As a result, the estimated maximum combustion temperature in the cylinder is lowered. This estimation result is in line with the actual phenomenon that the NOx generation amount decreases when the fuel injection timing is delayed.

Further, for example, when the concentration of the inert gas (for example, CO ₂ ) in the intake air is increased by increasing the EGR rate (the ratio of the EGR gas amount to the intake air amount), the in-cylinder gas involved in the combustion as described above. Since the constant pressure specific heat and the number of moles of both increase, the estimated increase in combustion-induced temperature decreases, and as a result, the estimated maximum combustion temperature in the cylinder decreases. This estimation result is in line with the actual phenomenon that the NOx generation amount decreases as the EGR rate increases.

  Further, for example, if the in-cylinder combustion speed is increased by increasing the fuel injection pressure and increasing the engine rotational speed, the estimated temperature increase due to the combustion speed increases. The maximum combustion temperature in the cylinder is increased. This estimation result is in line with the actual phenomenon that the amount of NOx generated increases as the fuel injection pressure increases and the engine speed increases. As described above, according to the combustion temperature estimation method according to the present invention, it is possible to accurately estimate the maximum combustion temperature in the cylinder so as to follow various actual phenomena with a simple configuration.

  In the combustion temperature estimation method according to the present invention, it is estimated based on the temperature of the gas sucked into the cylinder, the composition of the sucked gas, and the factors that increase the cylinder gas temperature before the combustion. It is preferable to estimate the compression-in-cylinder gas temperature during ignition based on the amount of increase in the compression-in-cylinder gas temperature during ignition. In this case, the factors for increasing the in-cylinder gas temperature before combustion are, for example, the amount of heat generated by the combustion of the fuel injected by the pilot before the fuel injection, and the glow plug. The amount of heat generated by the energization when the energization is performed.

  The gas temperature in the compression cylinder during ignition naturally varies depending on the intake air temperature. In addition, since the polytropic index to be used for in-cylinder gas that changes adiabatically changes depending on the composition of the intake air (and hence the composition of the in-cylinder gas), the above (based on a general formula representing the adiabatic change using the polytropic index) The gas temperature in the compression cylinder during ignition also varies depending on the composition of the intake air.

  Further, when the in-cylinder gas before combustion is given a heat quantity by energizing the glow plug or the like, the ignition-time compression in-cylinder gas temperature rises by an amount corresponding to the same heat quantity. The amount of increase in the temperature of the in-cylinder gas is obtained as the amount of increase in the temperature of the compression cylinder gas during ignition.

  From the above, the temperature of the gas (intake) sucked into the cylinder, the composition of the gas (intake) sucked in, and the amount of increase in the temperature of the compression cylinder gas at the time of ignition are as follows. It can be a value (parameter) that affects the gas temperature. Therefore, as described above, when estimating the compression-in-cylinder gas temperature during ignition, in addition to the in-cylinder gas being compressed in the cylinder, the above-mentioned three parameters are taken into consideration, so that the compression-in-cylinder gas temperature during ignition is calculated. Can be estimated with higher accuracy, and as a result, the (maximum) combustion temperature in the cylinder can also be estimated with higher accuracy.

  Further, in the combustion temperature estimation method according to the present invention, when the ignition time is before the time corresponding to the compression top dead center, the ignition time coincides with the time corresponding to the compression top dead center. It is assumed that the gas temperature in the compression cylinder during ignition is estimated.

  When the ignition time is before the time corresponding to the compression top dead center (that is, when the ignition time corresponds to the compression stroke), the cylinder after ignition (that is, during combustion or after combustion) It can be considered that the gas itself continues to be further compressed until the time corresponding to the compression top dead center, and as a result, the maximum combustion temperature in the cylinder also rises to the time corresponding to the compression top dead center. In other words, the maximum combustion temperature in the cylinder in this case matches the maximum combustion temperature when the ignition time coincides with the timing corresponding to the compression top dead center.

  Therefore, as described above, when the ignition time is before the time corresponding to the compression top dead center, it is assumed that the ignition time coincides with the time corresponding to the compression top dead center. By estimating the internal gas temperature, the maximum combustion temperature in the cylinder in the case where the ignition time is before the time corresponding to the compression top dead center can be estimated even more accurately.

  Hereinafter, an internal combustion engine (not shown) that implements a combustion temperature estimation method for an internal combustion engine according to an embodiment of the present invention and estimates the amount of NOx generated by combustion in a cylinder using the combustion temperature estimated by the method ( A control device of a diesel engine will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a whole system in which the control device for an internal combustion engine is applied to a four-cylinder internal combustion engine (diesel engine) 10. This system includes an engine main body 20 including a fuel supply system, an intake system 30 for introducing gas into a combustion chamber (in a cylinder) of each cylinder of the engine main body 20, and an exhaust system for discharging exhaust gas from the engine main body 20. 40, an EGR device 50 for performing exhaust gas recirculation, and an electric control device 60.

  A fuel injection valve (injection valve, injector) 21 is disposed above each cylinder of the engine body 20. Each fuel injection valve 21 is connected to a fuel injection pump 22 connected to a fuel tank (not shown) via a fuel pipe 23. In addition, a glow plug 24 is disposed above each cylinder so as to be adjacent to the fuel injection valve 21. Each glow plug 24 is electrically connected to the electric control device 60 and is energized by a signal from the electric control device 60 and generates heat only when the engine is in a predetermined operation state such as a warm-up operation state. A predetermined amount of heat is supplied to the in-cylinder gas existing in each cylinder.

  The fuel injection pump 22 is electrically connected to the electric control device 60, and the actual fuel is supplied by a drive signal from the electric control device 60 (command signal corresponding to (command) basic fuel injection pressure Pcrbase described later). The fuel is boosted so that the injection pressure (discharge pressure) becomes the command basic fuel injection pressure Pcrbase.

  Thereby, the fuel injection valve 21 is supplied with fuel whose pressure has been increased from the fuel injection pump 22 to the basic fuel injection pressure Pcrbase. The fuel injection valve 21 is electrically connected to the electric control device 60 and is driven by a drive signal from the electric control device 60 (a command signal corresponding to a (command) fuel injection amount (mass) qfin described later). The valve is opened for a predetermined time, whereby the fuel whose pressure has been increased to the commanded basic fuel injection pressure Pcrbase is directly injected into the combustion chamber of each cylinder by the commanded fuel injection amount qfin.

  The intake system 30 includes an intake manifold 31 connected to a combustion chamber of each cylinder of the engine body 20, an intake pipe 32 connected to an upstream side assembly of the intake manifold 31 and constituting an intake passage together with the intake manifold 31, an intake pipe A throttle valve 33 rotatably held in the throttle 32, a throttle valve actuator 33a for rotating the throttle valve 33 in response to a drive signal from the electric control device 60, and an intake pipe 32 upstream of the throttle valve 33. The mounted intercooler 34, the compressor 35a of the supercharger 35, and the air cleaner 36 disposed at the tip of the intake pipe 32 are included.

  The exhaust system 40 includes an exhaust manifold 41 connected to each cylinder of the engine body 20, an exhaust pipe 42 connected to a downstream gathering portion of the exhaust manifold 41, and a turbine of the supercharger 35 disposed in the exhaust pipe 42. And a diesel particulate filter (hereinafter referred to as “DPNR”) 43 interposed in the exhaust pipe 42. The exhaust manifold 41 and the exhaust pipe 42 constitute an exhaust passage.

  The DPNR 43 is a filter that includes a filter 43a formed of a porous material such as cordierite and collects particulates in exhaust gas that passes through the surface of the pores. DPNR43 includes alumina as a carrier, alkali metal such as potassium K, sodium Na, lithium Li, and cesium Cs, alkaline earth metal such as barium Ba and calcium Ca, and rare earth metal such as lanthanum La and yttrium Y. At least one selected from the above is supported together with platinum and functions as an NOx storage reduction catalyst that absorbs NOx and then releases and reduces the absorbed NOx.

  The EGR device 50 includes an exhaust recirculation pipe 51 that constitutes a passage for recirculating exhaust gas (EGR passage), an EGR control valve 52 interposed in the exhaust recirculation pipe 51, and an EGR cooler 53. The exhaust gas recirculation pipe 51 communicates the upstream exhaust passage (exhaust manifold 41) of the turbine 35b and the downstream intake passage (intake manifold 31) of the throttle valve 33. The EGR control valve 52 can change the amount of exhaust gas to be recirculated (exhaust gas recirculation amount, EGR gas flow rate) in response to a drive signal from the electric control device 60.

  The electrical control device 60 is connected to each other via a bus 61, a ROM 62 that stores programs executed by the CPU 61, tables (look-up tables, maps), constants, and the like, and the CPU 61 temporarily stores data as necessary. The microcomputer includes a RAM 63, a backup RAM 64 that stores data while the power is on, and holds the stored data while the power is shut off, an interface 65 including an AD converter, and the like.

  The interface 65 is an air flow rate (fresh air flow rate) measuring means, and is downstream of the hot-wire air flow meter 71 and the throttle valve 33 disposed in the intake pipe 32 and downstream of the portion to which the exhaust gas recirculation pipe 51 is connected. An intake air temperature sensor 72 provided in the intake passage, an intake pipe pressure sensor 73 disposed in the intake passage downstream of the throttle valve 33 and downstream of the portion to which the exhaust gas recirculation pipe 51 is connected, a crank position sensor 74, Connected to an accelerator opening sensor 75 and an intake oxygen concentration sensor 76 provided in an intake passage downstream of the throttle valve 33 and downstream of a portion to which the exhaust gas recirculation pipe 51 is connected. This signal is supplied to the CPU 61. The interface 65 is connected to the fuel injection valve 21, the fuel injection pump 22, the throttle valve actuator 33a, and the EGR control valve 52, and sends drive signals to these in accordance with instructions from the CPU 61. Yes.

  The hot-wire air flow meter 71 measures the mass flow rate (intake fresh air amount per unit time) of intake air (fresh air) passing through the intake passage, and indicates the same mass flow rate Ga (intake fresh air flow rate Ga). Is supposed to occur. The intake air temperature sensor 72 detects the intake air temperature and generates a signal representing the intake air temperature Tb. The intake pipe pressure sensor 73 detects the pressure of intake air (that is, intake pipe pressure) and generates a signal representing the intake pipe pressure Pb.

  The crank position sensor 74 detects the absolute crank angle of each cylinder and generates a signal that represents the crank angle CA and also represents the engine rotation speed NE that is the rotation speed of the engine 10. The accelerator opening sensor 75 detects an operation amount of the accelerator pedal AP and generates a signal representing the accelerator operation amount Accp. The intake oxygen concentration sensor 76 detects the oxygen concentration in the intake air (that is, the intake oxygen concentration) and generates a signal representing the intake oxygen concentration RO2_in.

(Outline of combustion temperature estimation method)
Next, an outline of the combustion temperature estimation method according to the embodiment of the present invention by the internal combustion engine control apparatus configured as described above (hereinafter also referred to as “the present apparatus”) will be described. FIG. 2 shows that gas (that is, intake air) is sucked into the cylinder of one cylinder of the engine 10 from the intake manifold 31, and the gas sucked into the cylinder (in-cylinder gas) is discharged to the exhaust manifold 41 after combustion. It is the figure which showed the mode that it was done typically.

  As shown in FIG. 2, fresh air sucked from the front end portion of the intake pipe 32 through the throttle valve 33 and intake air (and hence in-cylinder gas) from the exhaust recirculation pipe 51 through the EGR control valve 52. Inhaled EGR gas is included. The ratio of the EGR gas mass to the sum of the inhaled fresh air amount (fresh air mass) and the inhaled EGR gas amount (EGR gas mass) (that is, the EGR rate) depends on the electric control device 60 (CPU 61) according to the operating state. ) And the opening degree of the throttle valve 33 and the opening degree of the EGR control valve 52 which are appropriately controlled.

  Intake (that is, gas composed of fresh air and EGR gas) is sucked into the cylinder as the piston descends via the intake valve Vin opened in the intake stroke, and becomes in-cylinder gas. The in-cylinder gas is sealed in the cylinder by closing the intake valve Vin when the piston reaches bottom dead center (hereinafter referred to as “ATDC-180 °”). Compressed as the rise of. When the piston reaches the vicinity of the compression top dead center (hereinafter referred to as “ATDC 0 °”) (specifically, when the final fuel injection timing finjfin described later arrives), the apparatus The fuel is directly injected into the cylinder by opening the fuel injection valve 21 for a predetermined time corresponding to the injection amount qfin. As a result, the injected fuel mixes with the in-cylinder gas as time passes and diffuses in the cylinder as a mixture, and self-ignition occurs when a predetermined ignition delay time elapses. Burns due to

  In this embodiment, such combustion occurs only in a combustion region estimated as described later (hereinafter also referred to as “B region”, see FIG. 2), and excludes the B region in the combustion chamber. It is assumed that it does not occur in the non-combustion region (hereinafter also referred to as “A region”, see FIG. 2). The in-cylinder gas existing in the combustion chamber after combustion becomes exhaust gas and is discharged to the exhaust manifold 41 as the piston rises through the exhaust valve Vout that is open in the exhaust stroke. A part of the exhaust gas becomes EGR gas through the exhaust gas recirculation pipe 51 and is recirculated to the intake side, and the remaining exhaust gas is discharged to the outside through the exhaust pipe 42.

  Hereinafter, a specific combustion temperature estimation method implemented by the present apparatus will be described. In this combustion temperature estimation method, every time the final fuel injection timing finjfin arrives for a cylinder to which fuel is to be injected (hereinafter referred to as “fuel injection cylinder”) (the predetermined ignition delay). After the elapse of time), the maximum combustion temperature Tflame of the in-cylinder gas due to the combustion generated in the region B is estimated. This device calculates the maximum combustion temperature Tflame according to the following equation (1).

Tflame = Tpump + ΔTburn + ΔTb_velo (1)

  In the above equation (1), Tpump is the in-cylinder gas temperature during compression, which is the in-cylinder gas temperature before combustion during ignition. ΔTburn is a combustion-induced temperature rise amount that is a temperature rise amount of the in-cylinder gas due to combustion. ΔTb_velo is the amount of temperature increase of the in-cylinder gas due to the increase in combustion speed. Hereinafter, the acquisition method of these values is demonstrated separately.

<Acquisition of gas temperature Tpump in compression cylinder during ignition>
In order to obtain the ignition compression cylinder gas temperature Tpump, first, it is assumed that there is no heat exchange between the cylinder gas and the outside in the compression stroke and the expansion stroke. Then, the in-cylinder gas state changes adiabatically, so that the in-cylinder gas temperature Ta changes according to the crank angle CA (ATDC) as shown by the solid line in FIG. (In other words, the ignition-in-compression cylinder gas temperature Tpump) can be obtained according to the following equation (2), which is a general equation representing an adiabatic change.

Tpump ＝ Ta0 ・ (Va0 / Vig) ^κ-1 ... (2)

  In the above equation (2), Ta0 is the in-cylinder gas temperature at the bottom dead center at ATDC-180 °. Since the in-cylinder gas temperature is considered to be substantially equal to the intake air temperature Tb at ATDC-180 °, the in-cylinder gas temperature Ta0 at the bottom dead center is acquired as the intake air temperature Tb detected by the intake air temperature sensor 72 at ATDC-180 °. can do. Va0 is the cylinder volume at the bottom dead center at ATDC-180 °. Since the in-cylinder volume Va can be expressed as a function Va (CA) of the crank angle CA based on the design specifications of the engine 10, the in-cylinder volume Va0 at the bottom dead center can also be obtained based on this function.

  In the above equation (2), Vig is the in-cylinder volume at the time of ignition. Here, since ignition is the time when a predetermined ignition delay time has elapsed from the fuel injection timing, as shown in FIG. 3, the crank angle CAig at the time of ignition is the fuel injection corresponding to the final fuel injection timing finjfin. It can be obtained as a value delayed from the current crank angle CAinj by the crank angle ΔCAdelay corresponding to the ignition delay time. Therefore, the cylinder volume Vig at the time of ignition can be obtained as Va (CAig).

  In the above equation (2), κ is a polytropic index. Here, the polytropic index κ to be used for the in-cylinder gas that changes adiabatically varies depending on the composition of the intake air (and hence the composition of the in-cylinder gas). Therefore, in this example, the intake oxygen concentration RO2_in detected by the intake oxygen concentration sensor 76 (specifically, the intake gas at the bottom dead center that is the intake oxygen concentration RO2_in detected at the bottom dead center (ATDC-180 °)). Based on the oxygen concentration RO2c) and the function g for obtaining the polytropic index from the intake oxygen concentration, the polytropic index κ can be obtained as g (RO2c).

  As described above, in principle, the present apparatus obtains the compression-in-cylinder in-cylinder gas temperature Tpump according to the above equation (2). As a result, as shown by the solid line in FIG. 3, the compression-in-cylinder gas temperature Tpump is before the timing when ignition (ignition crank angle CAig) corresponds to compression top dead center (ATDC 0 °). In some cases (i.e., when the ignition time corresponds to the compression stroke), the ignition time rises later, while when the ignition time is later than the time corresponding to the compression top dead center (i.e. When the ignition time corresponds to the expansion stroke), the ignition time decreases as the ignition time is delayed.

  By the way, when the ignition time is before the time corresponding to the compression top dead center, the in-cylinder gas itself after ignition (that is, during or after combustion) is further compressed until the time corresponding to the compression top dead center. As a result, it is considered that as a result, the maximum combustion temperature Tflame according to the above equation (1), which is the final calculation target, also increases until the time corresponding to the compression top dead center. That is, in this case, the maximum combustion temperature Tflame is preferably matched with the maximum combustion temperature when the ignition time coincides with the timing corresponding to the compression top dead center.

  Therefore, when the ignition time (that is, the ignition crank angle CAig) is before the time corresponding to the compression top dead center, it is assumed that the ignition time coincides with the time corresponding to the compression top dead center. Replaces the value of the in-cylinder volume Vig with Va (CAig) and determines the in-cylinder gas temperature Tpump at the time of ignition according to the above equation (2) as the in-cylinder volume Vtop (constant value) at ATDC 0 °. As a result, as shown by the broken line in FIG. 3, the ignition-time compressed cylinder gas temperature Tpump in this case is estimated as the cylinder gas temperature Ta1 (constant value) at the compression top dead center.

  The case where it is assumed that there is no heat exchange between the in-cylinder gas and the outside in the compression stroke and the expansion stroke has been described above. However, actually, when the glow plug 24 is energized, the in-cylinder gas in the compression stroke and the expansion stroke receives a predetermined amount of heat from the glow plug 24, and as a result, the in-cylinder gas at the time of ignition. The temperature (therefore, the in-cylinder in-cylinder gas temperature Tpump) rises by an amount corresponding to this amount of heat.

  Therefore, when the glow plug 24 is energized, the present apparatus adds the in-cylinder gas temperature increase ΔTpump (= Tglow (this example) corresponding to the heat amount to the compression-in-cylinder gas temperature Tpump during ignition determined as described above. Then, a value obtained by adding a constant value)) is estimated as a final ignition compression cylinder gas temperature. As described above, the in-cylinder gas temperature Tpump at the time of ignition includes at least the above equation (2) related to adiabatic compression, the intake temperature Tb at the bottom dead center (ATDC-180 °), and the composition of the intake air (the above lower This is estimated every time the final fuel injection timing finjfin arrives, based on the dead-center intake oxygen concentration RO2c) and the in-cylinder gas temperature rise amount ΔTpump.

<Acquisition of combustion-induced temperature rise ΔTburn>
In order to obtain the combustion-induced temperature increase ΔTburn, which is the temperature increase of the in-cylinder gas due to combustion, the combustion per mol of injected fuel is considered. Then, the combustion-induced temperature increase amount ΔTburn can be expressed by the following equation (3).

ΔTburn ＝ Qfuel / (Cp ・ ngas) (3)

In the above equation (3), Qfuel is a calorific value due to combustion per mol of injected fuel, and is a known value (constant) that is uniquely determined by the composition of the fuel. Cp is the constant pressure specific heat of the in-cylinder gas after combustion involved in the combustion of 1 mol of fuel. ngas is the number of moles of in-cylinder gas after combustion involved in the combustion of 1 mol of fuel. Therefore, in order to obtain the combustion-induced temperature increase ΔTburn according to the above equation (3), it is necessary to obtain the constant pressure specific heat Cp and the number of moles ngas. Here, the chemical reaction formula for the combustion per 1 mol of fuel (C _m H _n ) containing typical gas components in the intake air is expressed by the following formula (4).

In the above equation (4), the values m and n are uniquely determined by the composition of the injected fuel. For example, in the case of a standard fuel used in a diesel engine, m = 15.75 , N = 30.55. α, β, and γ are the number of moles of CO ₂ , H ₂ O, and N ₂ that are inert gases involved in the combustion of 1 mol of fuel. That is, here, attention is paid to four components of O ₂ and inert gases CO ₂ , H ₂ O, and N ₂ as gas components in the intake air. As can be easily understood from the right side of the above equation (4), the number of moles ngas of the cylinder gas after combustion involved in the combustion of 1 mol of fuel and the constant pressure specific heat Cp (equivalent constant pressure specific heat) are as follows: It can be expressed by the formula (5) and the following formula (6). In the following formula (6), Cp_CO ₂ , Cp_H ₂ O, and Cp_N ₂ are constant-pressure specific heats of CO ₂ , H ₂ O, and N ₂ , respectively.

  Therefore, as can be understood from the above equations (5) and (6), in order to obtain the number of moles ngas and the constant pressure specific heat Cp, it is necessary to obtain the number of moles α, β, and γ. On the other hand, these values change according to the composition of the intake air (specifically, the concentration (ratio) of the above four components constituting the intake air). It is necessary to determine the concentration (ratio) of the component in the intake air. Therefore, hereinafter, a method of acquiring the respective concentrations of the four components in the intake air will be described.

In the following, [X] in, [X] egr, and [X] air (X: O ₂ , CO ₂ , H ₂ O, N ₂ ) are the mass concentration of the component X in the intake air and the EGR of the component X The mass concentration in the gas and the mass concentration in the fresh air of the component X are respectively expressed. [X] air is a known value (eg, [CO ₂ ] air = [H ₂ O] air = 0, [O ₂ ] air = 0.233, [N ₂ ] air = 0.767).

  In the following, Gcyl is the total gas mass of the intake air that has been sucked into the cylinder in one intake stroke (hereinafter referred to as “total in-cylinder gas amount Gcyl”), and Gegr is one of the intake air in one intake stroke. Is the mass of EGR gas sucked into the cylinder from the EGR device 50 (hereinafter referred to as “EGR gas amount”), and Gm is a part of the intake air from the tip of the intake pipe 32 in one intake stroke. The mass of fresh air sucked into the cylinder (hereinafter referred to as “intake fresh air amount”).

  Here, the in-cylinder total gas amount Gcyl can be obtained according to the following equation (7) based on the gas state equation at ATDC-180 °.

Gcyl = (Pa0 ・ Va0) / (R ・ Ta0) (7)

  In the above equation (7), Pa0 is the in-cylinder gas pressure at the bottom dead center at ATDC-180 °. Since the cylinder gas pressure is considered to be substantially equal to the intake pipe pressure Pb at ATDC-180 °, the cylinder gas pressure Pa0 at the bottom dead center is the intake pipe pressure detected by the intake pipe pressure sensor 73 at ATDC-180 °. It can be acquired as Pb. R is the gas constant of the in-cylinder gas. Ta0 and Va0 are the bottom dead center in-cylinder gas temperature and the bottom dead center in-cylinder volume, respectively, as in equation (2) above.

  Further, the intake fresh air amount Gm includes the intake fresh air amount per unit time (intake fresh air flow rate Ga) measured by the air flow meter 71, the engine speed NE based on the output of the crank position sensor 74, and the intake fresh air. This can be obtained based on a function f (Ga, NE) for obtaining the intake fresh air amount per intake stroke using the flow rate Ga and the engine rotational speed NE as arguments. As the intake fresh air flow rate Ga and the engine rotational speed NE, the bottom fresh center intake fresh air flow rate Ga0 and the bottom dead center engine rotational speed NE0 acquired by each sensor at ATDC-180 ° are used, respectively.

  Further, since the in-cylinder total gas amount Gcyl is the sum of the EGR gas amount Gegr and the intake fresh air amount Gm, the EGR gas amount Gegr can be obtained as described above, and the in-cylinder total gas amount Gcyl and the intake gas It can be obtained based on the fresh air amount Gm and the following equation (8).

Gegr ＝ Gcyl-Gm (8)

Hereinafter, first, a method for obtaining the concentration of CO _{2 in} the intake air (hereinafter referred to as “intake CO ₂ concentration”) [CO ₂ ] in will be described. Since the intake CO ₂ concentration is equal to the CO ₂ concentration in the in-cylinder gas sucked into the cylinder before combustion, “the mass of CO _{2 in} fresh air sucked into the cylinder relative to the total gas amount Gcyl in the cylinder”
[CO ₂ ] air · Gm and CO ₂ mass in EGR gas sucked into the cylinder [CO ₂ ] egr · Gegr
Can be determined according to the following equation (9).

Here, the CO ₂ concentration [CO _2] egr of the EGR gas (passing through the exhaust valve Vout) is considered equal to the CO ₂ concentration in the exhaust gas, the CO ₂ concentration of the same in the exhaust gas cylinder gas after combustion The concentration of CO _{2 in the} medium. The CO ₂ concentration in the in-cylinder gas after combustion is “the value obtained by adding the current command fuel injection amount (mass) qfinc (= qfin) to the in-cylinder total gas amount Gcyl”. CO ₂ mass in the air
[CO ₂ ] air · Gm and CO ₂ mass in EGR gas sucked into the cylinder [CO ₂ ] egr · Gegr
And “the sum of the masses of CO ₂ generated by combustion”.

The mass of CO ₂ generated by combustion can be expressed as KCO ₂ · qfinc, where the mass of CO ₂ generated by combustion of fuel per unit mass is KCO ₂ . In addition, as can be understood from the above equation (4), the combustion of 1 mol of fuel (C _m H _n ) m
Since mol of CO ₂ is generated, if the molecular weight of the fuel (C _m H _n ) is Mfuel, and the molecular weight of CO ₂ is MCO ₂ (= 44), the mass (m · MCO ₂ ) CO ₂ will be generated. Therefore, KCO ₂ is
m · (MCO ₂ / Mfuel). From the above, the CO ₂ concentration [CO ₂ ] egr in the EGR gas can be obtained according to the following formula (10), and the following formula (11) is obtained by arranging the following formula (10).

Then, by substituting the above equation (11) into the above equation (9), the following equation (12) is obtained, and the intake CO ₂ concentration [CO ₂ ] in can be obtained according to the following equation (12). In the following formula (12), R is an EGR rate, and R = Gegr / Gcyl.

Next, a method for obtaining the concentration of H ₂ O in the intake air (hereinafter referred to as “intake H ₂ O concentration”) [H ₂ O] in will be described. Intake H _{2 O} concentration [H _{2 O]} in is in the same manner as method of acquiring the intake CO ₂ concentration [CO _2] in the above, the [CO _2] in the above (9) to (12) [H ₂ O] and KCO ₂ can be rewritten to KH ₂ O. That is, the intake H ₂ O concentration [H ₂ O] in can be obtained according to the following equation (13).

In the above equation (13), KH ₂ O is the mass of H ₂ O generated by the combustion of fuel per unit mass. As can be understood from the above equation (4), combustion of 1 mol of fuel (C _m H _n ) (n / 2)
Since mol of H ₂ O is generated, _{assuming that} the molecular weight of the fuel (C _m H _n ) is Mfuel and the molecular weight of H ₂ O is MH ₂ O (= 18), the mass {(n / 2) H ₂ O of MH ₂ O} is generated. Therefore, KH ₂ O is
It can be calculated as (n / 2) · (MH ₂ O / Mfuel).

Next, the concentration of N ₂ in the air intake (hereinafter referred to as "intake N ₂ concentration".) [N _2] obtaining method in described. N ₂ is not generated in the cylinder by the combustion of the fuel (C _m H _n ), and is not consumed in the cylinder. Therefore, the intake N ₂ concentration [N _2] in rewrites the a (9) ~ (12) [ CO 2] in formula [N _2], and can be obtained by deleting the term of KCO ₂ . That is, the intake N ₂ concentration [N ₂ ] in can be obtained according to the following equation (14).

Next, the concentration of O ₂ in air (hereinafter, referred to as "the intake O ₂ concentration".) [O _2] obtaining method in described. O ₂ in the in-cylinder gas is consumed in the cylinder by combustion of fuel (C _m H _n ). O ₂ mass consumed by combustion is KO ₂ · qfinc, where O ₂ mass consumed by combustion of fuel per unit mass is KO ₂
It can be expressed as. Therefore, the intake _{O 2} concentration _{[O 2]} in rewrites the a (9) ~ (12) [ CO 2] in formula _{[O 2],} and is obtained by rewriting the KCO ₂ to "-KO _2" be able to. That is, the intake O ₂ concentration [O ₂ ] in can be expressed according to the following equation (15).

Here, because the combustion of fuel (C _m H _n) 1 mol is (m + n / 4) O 2 in mol is consumed as can be understood from the above equation (4), Mfuel the molecular weight of the fuel (C _{m H n)} When the molecular weight of O ₂ is MO ₂ (= 32), the mass {(m + n / 4) · MO ₂ } of O ₂ is consumed by the combustion of the fuel of mass Mfuel. Therefore, KO ₂ in the above equation (15) is (m + n / 4) · (MO ₂ / Mfuel)
Can be obtained as

It should be noted that KO ₂ and Gm can be calculated from the above equation (15) using the theoretical air-fuel ratio stoich = KO ₂ / [O ₂ ] air and the excess air ratio λ = Gm / (stoich · qfinc). When deleted, the following equation (16) is obtained. Further, in consideration of the relationship of “(1 / stoich) ≈0” in the following equation (16), the intake O ₂ concentration [O ₂ ] in is expressed by the following (17 ) Can be obtained according to the equation.

As described above, the mass concentration [X] in (X: O ₂ , CO ₂ , H ₂ O, N ₂ ) in the intake air of the above four components can be obtained. Next, a method for obtaining the number of moles α, β, γ using this result will be described. When the mass concentration in the intake of the above four components is obtained, the ratio of the mass concentration in the intake of the four components
[O ₂ ] in: [CO ₂ ] in: [H ₂ O] in: [N ₂ ] in can be obtained. The ratio of the mass concentration of the four components in the intake air is the same as the four components in the cylinder gas sucked into the cylinder (more specifically, the gas present in the fuel region (B region)). Is assumed to be maintained as a mass concentration ratio.

On the other hand, the ratio of the mass concentration of the four components in the cylinder gas is equal to the ratio of the mass of the four components in the cylinder gas. As can be understood from the above equation (4), the ratio of the number of moles of the four components in the cylinder gas is (m + n / 4): α: β: γ. The mass ratio of the four components is
It can be expressed as (m + n / 4) MO ₂ : αMCO ₂ : βMH ₂ O: γMN ₂ . From the above, the following equation (18) is established.

  If the above equation (18) is used, the number of moles α, β, γ can be determined according to the following equations (19) to (21).

  Thus, when the number of moles α, β, γ is obtained, the number of moles ngas and the constant pressure specific heat Cp can be obtained according to the above formula (5) and the above formula (6). The combustion-induced temperature rise amount ΔTburn can be obtained according to the above equation (3).

  As described above, this apparatus uses the above equations (3) to (21) to calculate at least the composition of the intake air (concentration ratio of gas components in the intake air) and the calorific value (Qfuel) due to combustion of the injected fuel. Based on this, every time the final fuel injection timing finjfin arrives, the combustion-induced temperature rise amount ΔTburn is obtained.

<Acquisition of combustion rate-induced temperature rise ΔTb_velo>
The in-cylinder gas temperature Ta rises from the temperature at the time of ignition (ie, the compressed in-cylinder gas temperature Tpump at the time of ignition) by the combustion-induced temperature increase ΔTburn to the temperature (Tpump + ΔTburn) (ie, from the time of ignition to the in-cylinder) A predetermined time (hereinafter referred to as “maximum temperature arrival time”) is required until the gas temperature Ta reaches the maximum combustion temperature Tflame. On the other hand, when the ignition time is later than the time corresponding to the compression top dead center (that is, the time corresponding to the expansion stroke), the cylinder volume Va increases as time elapses. The gas temperature Ta decreases (the increase in the in-cylinder gas temperature Ta due to combustion is suppressed).

  Therefore, the shorter the maximum temperature reaching time, the higher the maximum combustion temperature Tflame of the in-cylinder gas. In other words, the maximum combustion temperature Tflame increases as the in-cylinder combustion speed after the start of combustion increases. The temperature rise amount of the in-cylinder gas corresponds to the combustion rate-induced temperature rise amount ΔTb_velo. Hereinafter, a method of obtaining the combustion rate-induced temperature increase ΔTb_velo will be described with reference to FIG.

  There are various factors that can affect the in-cylinder combustion speed. In this example, the fuel injection pressure Pcrc (= the commanded basic fuel injection pressure Pcrbase) and the engine speed NE (specifically) Specifically, select the engine speed NE0 at bottom dead center. If the current fuel injection pressure Pcrc or the bottom dead center engine speed NE0 increases, the combustion speed also increases.

  Here, the combustion speed when the current fuel injection pressure Pcrc and the bottom dead center engine speed NE0 are the reference fuel injection pressure Pcrref and the reference engine speed NEref, respectively, is defined as the normal combustion speed. When the in-cylinder combustion speed becomes the normal combustion speed, the maximum combustion temperature Tflame of the in-cylinder gas is equal to the temperature (Tpump + ΔTburn) (hereinafter referred to as “maximum combustion temperature at normal combustion speed Tig”). (Accordingly, the combustion rate-induced temperature increase ΔTb_velo = 0).

  Then, the maximum temperature arrival time reduction amount Δtadv from the maximum temperature arrival time corresponding to the normal combustion speed is expressed by the following equation (22) as a function of the current fuel injection pressure Pcrc and the bottom dead center engine speed NE0. be able to.

Δtadv = t0 + Ka · Pcrc + Kb · NE0 (22)

  In the above equation (22), t0 is a negative constant, and Ka and Kb are positive constants. t0, Ka, Kb are set so that Δtadv = 0 when the current fuel injection pressure Pcrc and the bottom dead center engine speed NE0 are the reference fuel injection pressure Pcrref and the reference engine speed NEref, respectively. Is the value to be The Δtadv equivalent advance amount ΔCAadv, which is the advance amount of the crank angle CA corresponding to the maximum temperature arrival time reduction amount Δtadv obtained by the above equation (22), is equal to the maximum temperature arrival time reduction amount Δtadv and the bottom dead center. It can be obtained as h (tadv, NE0) based on the hour engine rotation speed NE0 and the function h having Δtadv and NE0 as arguments.

  Then, as shown in FIG. 4, the in-cylinder gas having the maximum combustion temperature Tig at the normal combustion speed at the ignition crank angle CAig (accordingly, the ignition in-cylinder volume Vig) changes adiabatically, Due to adiabatic change from the crank angle CAig during ignition to the corrected ignition crank angle CAadv (according to the above-mentioned Δtadv equivalent advance angle amount ΔCAadv) (accordingly, the corrected in-cylinder volume Vadv (= Va (CAadv))) It is assumed that the temperature is compressed to Tadv.

  Then, the value obtained by subtracting the maximum combustion temperature Tig at the normal combustion speed from the temperature Tadv indicates that the time when the in-cylinder gas temperature reaches the maximum combustion temperature Tflame as compared with the case where the combustion speed becomes the normal combustion speed. It can be considered that this corresponds to the amount of increase in the in-cylinder gas temperature that is caused by the amount corresponding to the maximum temperature arrival time reduction amount Δtadv (accordingly, the combustion velocity-induced temperature increase ΔTb_velo). Therefore, the combustion rate-induced temperature rise amount ΔTb_velo is obtained according to the following equation (23).

ΔTb_velo ＝ Tig ・ (Vig / Vadv) ^κ-1 −Tig (23)

  As described above, this apparatus uses the above formulas (22), (23), etc., and this time the fuel injection pressure Pcrc, which is a factor affecting the in-cylinder combustion speed, and the engine speed at bottom dead center Based on NE0, every time the final fuel injection timing finjfin arrives, a combustion-induced temperature rise amount ΔTb_velo is obtained.

  Then, every time the final fuel injection timing finjfin arrives, the present apparatus increases the combustion-induced temperature increase ΔTburn and the combustion speed-induced temperature increase to the compression cylinder gas temperature Tpump at the time of ignition according to the above equation (1). A value obtained by adding the amount ΔTb_velo is estimated as the maximum combustion temperature Tflame of the in-cylinder gas. The above is the outline of the combustion temperature estimation method according to the present invention.

(Outline of NOx generation amount estimation method)
Next, an outline of the NOx generation amount estimation method using the estimated maximum combustion temperature Tflame performed by the present apparatus will be described. In this NOx generation amount estimation method, every time the final fuel injection timing finjfin arrives for the fuel injection cylinder, the actual NOx generation amount NOxact generated by combustion in the region B is estimated in the immediately following explosion (expansion) stroke. Go.

  The actual NOx amount generated NOxact is a value obtained by multiplying the amount of combustion generated NOx per unit fuel amount (hereinafter referred to as “combustion generated NOx rate RNOx_burn”) by the current command fuel injection amount qfinc (24 ) Can be obtained according to the equation.

NOxact ＝ RNOx_burn ・ qfinc (24)

  Here, the combustion-generated NOx rate RNOx_burn in the above equation (24) is estimated by the following equation (25). In the following equation (25), e is the base of the natural logarithm. As described above, RO2c is the intake oxygen concentration at bottom dead center, qfinc is the current command fuel injection amount, Pcrc is the current command fuel injection pressure (= Pcrbase), and Tflame is the above equation (1) It is the maximum combustion temperature in the explosion process this time is required. K0 to K4 are fitness constants determined as will be described later based on typical known multiple regression analysis.

RNOx_burn ＝ e ^K0・ (RO2c) ^K1・ (qfinc) ^K2・ (Pcrc) ^K3・ e ^{(K4 / Tflame)}・ ・ ・ (25)

  That is, the above equation (25) is an empirical equation for obtaining the combustion generation NOx rate RNOx_burn. The combustion generation NOx rate RNOx_burn estimated by the above equation (25) is the bottom dead center intake oxygen concentration RO2c, the current command fuel injection amount qfinc, the current command fuel injection pressure Pcrc, and the maximum combustion temperature. More specifically, it is a function of Tflame, and more specifically, the power of the bottom dead center intake oxygen concentration RO2c, the power of the current command fuel injection amount qfinc, the power of the current command fuel injection pressure Pcrc, and the maximum combustion temperature Tflame Is calculated on the basis of the product of an exponential function with the value determined according to the exponent.

  The adaptation constants K0 to K4 can be determined by conducting the following experiment, for example. That is, first, by operating the engine 10 with the EGR control valve 52 closed, all the exhaust gas discharged from the exhaust valve Vout (and hence NOx in the exhaust gas) is discharged from the exhaust passage to the outside. To be done. As a result, the NOx amount in the exhaust gas discharged to the outside from the exhaust passage becomes equal to the actual NOx generation amount NOxact. Therefore, the actual NOx generation amount is measured by measuring the NOx emission amount based on the output of a predetermined NOx concentration sensor. NOxact (thus, combustion NOx rate RNOx_burn (= NOxact / qfinc)) can be measured.

  Next, in this state, the bottom dead center intake oxygen concentration RO2c, the current commanded fuel injection amount qfinc, the current commanded fuel injection pressure Pcrc, and the maximum combustion temperature Tflame determined by the above equation (1) The combinations of these values are sequentially changed to form various predetermined patterns, and the combustion-generated NOx rate RNOx_burn is sequentially measured for each pattern.

  And based on many data regarding the relationship between the combination of each said value obtained as a result of such an operation | work (experiment), and the value of the measured combustion generation NOx rate RNOx_burn, the said well-known predetermined multiple regression analysis Can be used to find the adaptation constants K0 to K4. Here, at least the adaptation constants K1 to K3 are determined to be positive values, and the adaptation constant K4 is determined to be a negative value.

  Accordingly, as can be understood from the above equation (25), the combustion generation NOx rate RNOx_burn (accordingly, the actual NOx generation amount NOxact) estimated and calculated according to the equation (25) is the bottom dead center intake oxygen concentration RO2c, this time Any value among the command fuel injection amount qfinc, the current command fuel injection pressure Pcrc, and the maximum flame temperature Tflame increases. This is in line with the following actual phenomenon.

  That is, first, when the intake oxygen concentration RO2_in increases, the actual NOx generation amount NOxact increases. This is a phenomenon based on the fact that oxygen is a material that generates NOx, and naturally, when the amount of oxygen in the combustion chamber increases, NOx is easily generated.

  Further, when the fuel injection amount qfin increases, the actual NOx generation amount NOxact increases. This is because the load applied to the engine 10 increases as the fuel injection amount qfin increases, so that the fuel injection amount qfin increases as the temperature of the inner wall surface of the combustion chamber increases (i.e., This phenomenon is based on the fact that NOx is more likely to be generated as the load applied to the engine increases.

  Further, when the fuel injection pressure Pcr increases, the actual NOx generation amount NOxact increases. This is because the degree of atomization of the fuel increases due to an increase in the fuel injection speed in accordance with the increase in the fuel injection pressure Pcr. This is a phenomenon based on the fact that NOx is more likely to be generated as the fuel consumption increases (that is, the degree of atomization of the injected fuel increases).

  Further, when the maximum combustion temperature Tflame increases, the actual NOx generation amount NOxact increases. This is a phenomenon based on the fact that the chemical reaction in which NOx is generated from nitrogen is promoted as the gas temperature increases. From the above, if the combustion-generated NOx rate RNOx_burn is calculated according to the above equation (25), the combustion-generated NOx rate RNOx_burn (accordingly, the actual NOx generation according to the above equation (24) is performed so as to follow at least the four actual phenomena. The amount NOxact) can be estimated with high accuracy. The above is the outline of the NOx generation amount estimation method.

(Overview of fuel injection control)
The present apparatus that implements the NOx generation amount estimation method sequentially calculates the target NOx generation amount NOxt per operation cycle based on the fuel injection amount qfin and the engine rotational speed NE. Then, the present apparatus feedback-controls the final fuel injection start timing finjfin and the opening degree of the EGR control valve 52 so that the previously estimated actual NOx generation amount NOxact matches the target NOx generation amount NOxt.

  Specifically, when the value of the actual NOx generation amount NOxact estimated last time is larger than the target NOx generation amount NOxt, the final fuel injection start timing finjfin for the current fuel injection cylinder is set to be greater than the basic fuel injection timing finjbase. The opening of the EGR control valve 52 is delayed by a predetermined amount, and is increased by a predetermined opening from the current value. As a result, the maximum combustion temperature Tflame for the current fuel injection cylinder is controlled to be low, and as a result, the actual NOx generation amount NOxact generated in the current fuel injection cylinder matches the target NOx generation amount NOxt. .

  On the other hand, when the value of the actual NOx generation amount NOxact estimated last time is smaller than the target NOx generation amount NOxt, the final fuel injection start timing finjfin for the current fuel injection cylinder is set by a predetermined amount from the basic fuel injection timing finjbase. The opening degree of the EGR control valve 52 is reduced from the current value by a predetermined opening degree earlier. As a result, the maximum combustion temperature Tflame for the current fuel injection cylinder is controlled to be higher, and as a result, the actual NOx generation amount NOxact generated in the current fuel injection cylinder is made to coincide with the target NOx generation amount NOxt. . The above is the outline of the fuel injection control.

(Actual calculation method of combustion-generated NOx rate RNOx_burn)
In order to calculate the combustion-generated NOx rate RNOx_burn according to the above equation (25), calculation of “power” and calculation of “multiplication” are required. However, generally, when a “power” operation is performed using a microcomputer, the calculation load increases, and when a “multiplication” operation is performed using the microcomputer, the calculation accuracy tends to decrease. Therefore, in order to avoid the operation of “power” and the operation of “multiplication”, this apparatus (CPU 61) actually obtains the natural logarithm of both sides in the above equation (25), and the following equation (26) Is used to calculate the combustion-generated NOx rate RNOx_burn only by the table search and the “addition” operation.

log (RNOx_burn) = K0 + K1 · log (RO2c) + K2 · log (qfinc) + K3 · log (Pcrc) + K4 / Tflame (26)

  That is, the present apparatus obtains the tables Maplog1 (RO2c), Maplog2 (qfinc), Maplog3 () stored in advance in the ROM 62 in order to obtain the terms from the second term to the fifth term on the right side of the equation (26). Pcrc), and Mapinvpro (Tflame), table search values dataMap1 (= K1 · log (RO2c)), dataMap2 (= K2 · log (qfinc)), dataMap3 (= K3 · log (Pcrc)), and dataMap4 (= K4 / Tflame) is determined, and “log (RNOx_burn)” is obtained according to the following equation (27) accompanied by “addition”.

log (RNOx_burn) = K0 + dataMap1 + dataMap2 + dataMap3 + dataMap4 (27)

  Then, this apparatus is based on the table Mapinvlog (log (RNOx_burn)) stored in advance in the ROM 62 in order to obtain the combustion generation NOx rate RNOx_burn from “log (RNOx_burn)” obtained according to the above equation (27). The fuel generation NOx rate RNOx_burn is obtained. As a result, the calculation load on the CPU 61 can be reduced and a decrease in calculation accuracy can be prevented.

(Actual operation)
Next, actual operation of the control apparatus for an internal combustion engine configured as described above will be described.
<Control of fuel injection amount, etc.>
The CPU 61 is configured to repeatedly execute a routine for controlling the fuel injection amount and the like shown by the flowchart in FIG. 5 every elapse of a predetermined time. Therefore, when the predetermined timing is reached, the CPU 61 starts the process from step 500, proceeds to step 505 and proceeds to step 505 from the accelerator opening Accp, the engine speed NE, and the (command) fuel injection from the table (map) Mapqfin shown in FIG. Find the quantity qfin. The table Mapqfin is a table that defines the relationship between the accelerator opening degree Accp, the engine rotational speed NE, and the fuel injection amount qfin, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 510 and determines the basic fuel injection timing finjbase from the fuel injection amount qfin, the engine speed NE, and the table Mapfinjbase shown in FIG. The table Mapfinjbase is a table that defines the relationship between the fuel injection amount qfin and the engine rotational speed NE and the basic fuel injection timing finjbase, and is stored in the ROM 62.

  Thereafter, the CPU 61 proceeds to step 515 to determine the basic fuel injection pressure Pcrbase from the fuel injection amount qfin, the engine speed NE, and the table MapPcrbase shown in FIG. The table MapPcrbase is a table that defines the relationship between the fuel injection amount qfin, the engine rotational speed NE, and the basic fuel injection pressure Pcrbase, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 520, and determines the target NOx generation amount NOxt from the fuel injection amount qfin, the engine rotation speed NE, and the table MapNOxt shown in FIG. The table MapNOxt is a table that defines the relationship between the fuel injection amount qfin, the engine rotational speed NE, and the target NOx emission amount NOxt, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 525 to determine the latest actual NOx generation amount NOxact (specifically, calculated at the previous fuel injection timing) obtained from the determined target NOx generation amount NOxt by a routine described later. Is stored as the NOx generation amount deviation ΔNOx.

  Subsequently, the CPU 61 proceeds to step 530 to determine the injection timing correction value Δθ from the NOx generation amount deviation ΔNOx and the table MapΔθ shown in FIG. The table MapΔθ is a table that defines the relationship between the NOx generation amount deviation ΔNOx and the injection timing correction value Δθ, and is stored in the ROM 62.

  Next, the CPU 61 proceeds to step 535 and corrects the basic injection timing finjbase with the injection timing correction value Δθ to determine the final fuel injection timing finjfin. Thus, the injection timing is corrected according to the NOx generation amount deviation ΔNOx. In this case, as is apparent from FIG. 10, as the NOx generation amount deviation ΔNOx becomes a positive value, the injection timing correction value Δθ becomes a positive value and the final fuel injection timing finjfin becomes the advance side, and the NOx generation occurs. The injection timing correction value Δθ becomes a large negative value as the quantity deviation ΔNOx becomes a large negative value (the absolute value is large), and the final fuel injection timing finjfin is shifted to the retard side.

  Subsequently, the CPU 61 proceeds to step 540 to determine whether or not the injection start timing for the fuel injection cylinder (that is, the determined final fuel injection timing finjfin) has arrived. Immediately proceed to 595 to end the present routine tentatively.

  On the other hand, if “Yes” is determined in the determination of step 540, the CPU 61 proceeds to step 545 and determines the fuel of the determined (command) fuel injection amount qfin from the fuel injection valve 21 for the fuel injection cylinder. In addition to injecting at the basic fuel injection pressure Pcrbase, it is determined in the subsequent step 550 whether or not the NOx generation amount deviation ΔNOx is a positive value, and if “Yes” is determined, the process proceeds to step 555 and the EGR control valve After the opening degree of 52 is reduced by a predetermined opening degree from the current value, the process proceeds to step 570.

  If the determination in step 550 is “No”, the CPU 61 proceeds to step 560 and determines whether or not the NOx generation amount deviation ΔNOx is a negative value. In the determination of step 560, when the CPU 61 determines “Yes”, the CPU 61 proceeds to step 570 after increasing the opening of the EGR control valve 52 by a predetermined opening from the current value, and determines “No”. In other words, when the value of the NOx generation amount deviation ΔNOx is “0”, the routine proceeds to step 570 without changing the opening degree of the EGR control valve 52.

  In this way, the opening degree of the EGR control valve 52 is changed according to the NOx generation amount deviation ΔNOx. In step 570, the CPU 61 stores the value of the actually injected fuel injection amount qfin as the current fuel injection amount qfinc. In the subsequent step 575, the CPU 61 stores the basic fuel injection pressure Pcrbase, which is the actual injection pressure. After the value is stored as the current fuel injection pressure Pcrc, the routine proceeds to step 595 and this routine is temporarily terminated. As described above, control of the fuel injection amount, the fuel injection timing, the fuel injection pressure, and the opening degree of the EGR control valve 52 is achieved.

<Calculation of maximum combustion temperature>
Further, the CPU 61 repeatedly executes a routine for calculating the maximum combustion temperature Tflame shown in the flowchart of FIG. 11 every elapse of a predetermined time. Accordingly, when the predetermined timing is reached, the CPU 61 starts processing from step 1100, proceeds to step 1105, and determines whether or not the current time coincides with ATDC-180 °.

  Now, assuming that the current time is before ATDC-180 °, the CPU 61 makes a “No” determination at step 1105 to immediately proceed to step 1145, where the fuel injection start timing for the fuel injection cylinder (ie, It is determined whether or not the final fuel injection timing (finjfin) has arrived. Since the current time is before ATDC-180 °, the CPU 61 makes a “No” determination at step 1145 to immediately proceed to step 1195 to end the present routine tentatively.

  Thereafter, the CPU 61 repeatedly executes the processing of steps 1100, 1105, 1145, and 1195 until the arrival of ATDC-180 °. When ATDC-180 ° is reached, the CPU 61 determines “Yes” when it proceeds to step 1105, and proceeds to step 1110. In step 1110, the intake air temperature sensor 72, the intake pipe pressure sensor 73, and the air flow are determined. The intake air temperature Tb, the intake pipe pressure Pb, the intake fresh air flow rate Ga, and the engine rotational speed NE at the present time (that is, ATDC-180 °) detected by the meter 71 and the crank position sensor 74 are respectively dead. Stored as the in-cylinder gas temperature Ta0, the in-cylinder gas pressure Pa0 at the bottom dead center, the intake fresh air flow rate Ga0 at the bottom dead center, and the engine rotational speed NE0 at the bottom dead center.

  Next, the CPU 61 proceeds to step 1115 to store the inspiratory oxygen concentration RO2_in at the present time (that is, ATDC-180 °) detected by the inspiratory oxygen concentration sensor 76 as the bottom dead center inspiratory oxygen concentration RO2c, and then to step 1120 Then, in-cylinder total gas amount Gcyl is obtained according to the above equation (7). Here, the values stored in step 1110 are used as the bottom dead center in-cylinder gas pressure Pa0 and the bottom dead center in-cylinder gas temperature Ta0.

  Subsequently, the CPU 61 proceeds to Step 1125 to obtain the intake fresh air amount Gm based on the bottom dead center intake fresh air flow rate Ga0, the bottom dead center engine rotation speed NE0, and the function f. In step 1130, the EGR gas amount Gegr is obtained based on the in-cylinder total gas amount Gcyl obtained in step 1120, the intake fresh air amount Gm, and the above equation (8). Next, the CPU 61 proceeds to step 1135, obtains the EGR rate R based on the intake fresh air amount Gm, the EGR gas amount Gegr, and the formula described in step 1135, and in the subsequent step 1140, The excess air ratio λ is obtained based on the intake fresh air amount Gm, the current fuel injection amount qfinc stored in the previous step 570, and the formula described in step 1140. Then, the CPU 61 proceeds to step 1145 to determine “No”, immediately proceeds to step 1195, and once ends this routine.

  Thereafter, the CPU 61 repeatedly executes the processing of steps 1100, 1105, 1145, and 1195 again until the fuel injection timing (that is, the final fuel injection timing finjfin) comes. When the final fuel injection timing finjfin arrives, the CPU 61 makes a “Yes” determination at step 1145 to proceed to step 1150. At step 1150, the final fuel injection timing finjfin and the predetermined ignition delay time. From the above, obtain the crank angle CAig during ignition.

  Next, the CPU 61 executes a routine for calculating the ignition compression in-cylinder gas temperature Tpump shown in the flowchart of FIG. That is, the CPU 61 starts processing from step 1200, proceeds to step 1205, and obtains the polytropic index κ based on the latest bottom dead center inspiratory oxygen concentration RO2c obtained in step 1115 and the function g. .

  Next, the CPU 61 proceeds to step 1210 to determine whether or not the latest ignition crank angle CAig obtained in the previous step 1150 is an angle delayed from ATDC 0 ° and determine “Yes”. Then, the process proceeds to step 1215, and the cylinder volume corresponding to the same ignition crank angle CAig is stored as it is as the ignition cylinder volume Vig. On the other hand, if “No” is determined in step 1210, the CPU 61 proceeds to step 1220 to store the in-cylinder volume Vtop corresponding to the top dead center (ATDC 0 °) as the ignition in-cylinder volume Vig.

  Subsequently, the CPU 61 proceeds to step 1225 to determine whether or not the glow plug 24 is energized. When determining “Yes”, the CPU 61 proceeds to step 1230 and sets the predetermined value Tglow to the in-cylinder gas temperature increase amount. If it is stored as ΔTpump and it is determined as “No”, the value of the in-cylinder gas temperature increase ΔTpump is set to “0” in step 1235.

  Then, the CPU 61 proceeds to step 1240, and the latest bottom dead center in-cylinder gas temperature Ta0 obtained in the previous step 1110, the ignition in-cylinder volume Vig, the in-cylinder gas temperature increase amount ΔTpump, Based on the equation described in step 1240, the compression-in-cylinder in-cylinder gas temperature Tpump is obtained, and the process proceeds to step 1160 in FIG.

When the CPU 61 proceeds to step 1160, the CPU 61 executes a routine for calculating the combustion-induced temperature increase ΔTburn shown in the flowchart of FIG. That is, the CPU 61 starts the process from step 1300 and proceeds to step 1305, where the latest ERG rate R obtained in the previous step 1135, the latest air excess rate λ obtained in the step 1140, and the above (17 ) The intake air O ₂ concentration [O ₂ ] in is obtained based on the formula described in step 1305 corresponding to the formula.

Next, the CPU 61 proceeds to step 1310, in which the EGR rate R, the current fuel injection amount qfinc, the latest intake fresh air amount Gm obtained in the previous step 1125, and the step corresponding to the above equation (12). The intake CO ₂ concentration [CO ₂ ] in is obtained based on the formula described in 1310. Similarly, the CPU 61 proceeds to step 1315 to obtain the intake H ₂ O concentration [H ₂ O] in according to the above equation (13), and then at step 1320, according to the above equation (14), the intake N ₂ concentration [N _2]. ] Ask for.

Subsequently, the CPU 61 proceeds to step 1325 to obtain the mole number α based on the intake CO ₂ concentration [CO ₂ ] in, the intake O ₂ concentration [O ₂ ] in, and the equation (19). Similarly, in step 1330, the number of moles β is determined according to the above equation (20), and in step 1335, the number of moles γ is determined according to the above equation (21).

  Next, the CPU 61 proceeds to step 1340 to obtain the post-combustion cylinder gas mole number ngas based on the obtained mole numbers α, β, γ and the above equation (5), and in step 1345, the same mole number. The post-combustion in-cylinder gas constant pressure specific heat Cp is obtained based on α, β, γ and the above equation (6). Then, the CPU 61 proceeds to step 1350, obtains the combustion-induced temperature increase ΔTburn based on the post-combustion cylinder gas mole number ngas, the post-combustion cylinder gas constant pressure specific heat Cp, and the above equation (3). The process proceeds to step 1165 in FIG.

  When the CPU 61 proceeds to step 1165, the CPU 61 executes a routine for calculating the combustion rate-induced temperature increase ΔTb_velo shown by the flowchart in FIG. That is, the CPU 61 starts the process from step 1400, proceeds to step 1405, and adds the latest combustion in-cylinder gas temperature Tpump at the time of ignition calculated at the previous step 1240 to the latest combustion cause determined at the previous step 1350. The value obtained by adding the temperature rise ΔTburn is stored as the maximum combustion temperature Tig at the normal combustion speed.

  Next, the CPU 61 proceeds to step 1410, the current fuel injection pressure Pcrc stored in the previous step 575, the latest bottom dead center engine speed NE0 stored in the previous step 1110, and the above (22) The maximum temperature arrival time reduction amount Δtadv is obtained based on the equation, and in step 1415, Δtadv is calculated based on the maximum temperature arrival time reduction amount Δtadv, the bottom dead center engine speed NE0, and the function h. The equivalent advance amount ΔCAadv is obtained.

  Subsequently, the CPU 61 proceeds to step 1420 to set an angle obtained by advancing by the Δtadv equivalent advance amount ΔCAadv from the latest ignition crank angle CAig obtained in the previous step 1150 as a corrected ignition crank angle CAadv, and then continues. In step 1425, it is determined whether or not the corrected ignition crank angle CAadv is an angle delayed from ATDC 0 °.

  If the determination in step 1425 is “Yes”, the CPU 61 proceeds to step 1430 and stores the in-cylinder volume corresponding to the same corrected ignition crank angle CAadv as the corrected ignition in-cylinder volume Vadv. On the other hand, if “No” is determined in step 1425, the CPU 61 proceeds to step 1435 and stores the in-cylinder volume Vtop corresponding to the top dead center (ATDC 0 °) as the corrected ignition in-cylinder volume Vadv.

  Next, the CPU 61 proceeds to step 1440, where the ignition-time in-cylinder volume Vig obtained in the previous step 1215 or step 1220, the corrected ignition-time in-cylinder volume Vadv, and the normal combustion speed-time maximum combustion temperature Tig. Based on the above equation (23), the combustion rate-induced temperature increase ΔTb_velo is obtained, and the process proceeds to step 1170 in FIG. Then, when the CPU 61 proceeds to step 1170, the latest ignition compression cylinder gas temperature Tpump obtained in the previous step 1240, the latest combustion-induced temperature increase ΔTburn obtained in the previous step 1350, and the previous After obtaining the latest combustion rate-induced temperature rise amount ΔTb_velo obtained in step 1440 and the maximum combustion temperature Tflame of the in-cylinder gas based on the above equation (1), the routine proceeds to step 1195 to end the present routine tentatively. .

  Thereafter, the CPU 61 repeatedly executes the processing of steps 1100, 1105, 1145, and 1195 until ATDC-180 ° for the next fuel injection cylinder comes. As described above, the new maximum in-cylinder gas maximum combustion temperature Tflame is obtained each time the fuel injection start timing comes.

<Calculation of NOx generation amount>
Further, the CPU 61 repeatedly executes a routine for calculating the actual NOx generation amount NOxact shown in the flowchart of FIG. 15 every elapse of a predetermined time. Accordingly, when the predetermined timing is reached, the CPU 61 starts processing from step 1500 and proceeds to step 1505 to determine whether or not the fuel injection start timing (that is, the final fuel injection timing finjfin) has arrived. If YES in step 1595, the flow immediately proceeds to step 1595 to end the present routine tentatively.

  Assuming that the fuel injection start time has arrived, the CPU 61 proceeds to step 1510, where the table is based on the latest bottom dead center intake oxygen concentration RO2c obtained in the previous step 1115 and the table Maplog1. The search value dataMap1 (= K1 · log (RO2c)) is obtained.

  Similarly, the CPU 61 proceeds to step 1515 to obtain the table search value dataMap2 (= K2 · log (qfinc)) based on the current fuel injection amount qfinc stored in the previous step 570 and the table Maplog2. In step 1520, the table search value dataMap3 (= K3 · log (Pcrc)) is obtained based on the current fuel injection pressure Pcrc stored in the previous step 575 and the table Maplog3. The table search value dataMap4 (= K4 / Tflame) is obtained based on the latest maximum combustion temperature Tflame obtained in the previous step 1170 and the table Mapinvpro.

  Next, the CPU 61 proceeds to step 1530 to obtain “log (RNOx_burn)” according to the above equation (27), and in subsequent step 1535, based on the log (RNOx_burn) and the table Mapinvlog, the combustion generation NOx rate RNOx_burn is calculated. Ask. Then, the CPU 61 proceeds to step 1540 to calculate the actual fuel injection amount qfinc, the combustion generation NOx rate RNOx_burn, and the actual NOx generation amount NOxact according to the above equation (24), and then proceeds to step 1595 to execute this routine. Is temporarily terminated. Thereafter, the CPU 61 repeatedly executes the processing of steps 1500, 1505 and 1595 until the fuel injection start timing for the next fuel injection cylinder comes.

  As described above, a new actual NOx generation amount NOxact is obtained every time the fuel injection start time comes. The new actual NOx generation amount NOxact is used in step 525 of FIG. 5 as described above. As a result, the final fuel injection start timing finjfin for the next fuel injection cylinder and the opening of the EGR control valve 52 are opened. The feedback control is performed based on the new actual NOx generation amount NOxact.

  As described above, according to the combustion temperature estimation method for an internal combustion engine according to the embodiment of the present invention, the fact that the state of the in-cylinder gas adiabatically changes every time the fuel injection start timing arrives is used in principle. Then, estimate the in-cylinder gas temperature before combustion at ignition (compression cylinder gas temperature Tpump at ignition), and calculate the calorific value Qfuel from the combustion of the fuel from the composition of the gas in the intake air (concentration ratio of gas components) The amount of in-cylinder gas temperature rise due to combustion (combustion-induced temperature rise ΔTburn) is estimated by dividing the product by the product of the number of moles of in-cylinder gas after combustion involved in combustion, ngas, and constant-pressure specific heat Cp. Based on the fuel injection pressure Pcrc and the engine rotational speed NE0, which are factors affecting the combustion speed, the temperature rise amount of the in-cylinder gas due to the increase in the combustion speed (combustion speed-induced temperature rise amount ΔTb_velo) is estimated. Then, a value obtained by adding the combustion-induced temperature increase ΔTburn and the combustion speed-induced temperature increase ΔTb_velo to the compression-in-cylinder gas temperature Tpump during ignition is estimated as the maximum combustion temperature Tflame in the cylinder. Therefore, as described above, the maximum combustion temperature Tflame of the in-cylinder gas can be estimated with high accuracy so as to follow various actual phenomena with a simple configuration.

  The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, in the above embodiment, the fuel injection pressure and the engine speed are adopted as factors that affect the in-cylinder combustion speed. However, the swirl ratio of the gas sucked into the cylinder, the excess by the supercharger At least one of the supply pressure and the oxygen concentration in the gas sucked into the cylinder may be adopted as a factor that affects the combustion speed in the cylinder.

  In the above embodiment, the amount of heat generated by energizing the glow lamp is employed as a factor for generating the amount of increase in the compression cylinder gas temperature during ignition (cylinder gas temperature increase ΔTpump). The amount of heat generated by combustion of fuel injected by pilot injection when pilot injection is performed prior to time finjfin (main injection) may be employed as the same factor. In this case, the amount of heat generated by the combustion of the fuel injected by the pilot injection based on the injection amount of the fuel by the pilot injection and the timing of the pilot injection (the time interval (interval) between the main injection timing and the pilot injection timing), etc. It is preferable that the temperature rise amount of the in-cylinder gas is calculated.

1 is a schematic configuration diagram of an entire system in which a control device for an internal combustion engine that implements a fuel temperature estimation method for an internal combustion engine according to an embodiment of the present invention is applied to a four-cylinder internal combustion engine (diesel engine). It is the figure which showed typically a mode that gas was suck | inhaled from the intake manifold in the cylinder (in-cylinder) of a certain cylinder, and the in-cylinder gas suck | inhaled in the cylinder was discharged | emitted to an exhaust manifold. It is the graph which showed the relationship between the crank angle and cylinder gas temperature in case cylinder gas carries out adiabatic change in a compression stroke and an expansion stroke. It is a figure for demonstrating that the maximum combustion temperature of cylinder interior gas rises by the increase in a combustion speed. 2 is a flowchart showing a routine for controlling a fuel injection amount and the like executed by a CPU shown in FIG. 6 is a table for determining a fuel injection amount to be referred to when the CPU shown in FIG. 1 executes the routine shown in FIG. 6 is a table for determining a basic fuel injection timing to be referred to when the CPU shown in FIG. 1 executes the routine shown in FIG. 6 is a table for determining a basic fuel injection pressure to be referred to when the CPU shown in FIG. 1 executes the routine shown in FIG. 6 is a table for determining a target NOx generation amount to be referred to when the CPU shown in FIG. 1 executes the routine shown in FIG. 6 is a table for determining an injection timing correction value to be referred to when the CPU shown in FIG. 1 executes the routine shown in FIG. FIG. 2 is a flowchart showing a routine for executing calculation of a combustion temperature executed by a CPU shown in FIG. 1. FIG. 3 is a flowchart showing a routine for executing calculation of an ignition compression in-cylinder gas temperature executed by a CPU shown in FIG. 1. FIG. 3 is a flowchart showing a routine for performing calculation of a combustion-induced temperature increase amount executed by a CPU shown in FIG. 1. FIG. FIG. 2 is a flowchart showing a routine for executing calculation of a combustion rate-induced temperature increase executed by a CPU shown in FIG. 1. FIG. FIG. 3 is a flowchart showing a routine for performing calculation of a NOx generation amount (actual NOx generation amount) executed by a CPU shown in FIG. 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... Fuel injection valve, 22 ... Pump for fuel injection, 24 ... Glow plug, 31 ... Intake manifold, 32 ... Intake pipe, 41 ... Exhaust manifold, 42 ... Exhaust pipe, 50 ... EGR device, 52 ... EGR control valve, 60 ... Electric control device 61 ... CPU 71 ... Air flow meter 72 ... Intake air temperature sensor 73 ... Intake pipe pressure sensor 74 ... Crank position sensor 76 ... Intake oxygen concentration sensor

Claims (5)

A method for estimating a combustion temperature of an internal combustion engine for estimating a combustion temperature in a cylinder of the internal combustion engine,
Using the fact that at least the in-cylinder gas existing in the cylinder is compressed in the cylinder, an in-cylinder gas temperature during ignition that is an in-cylinder gas temperature before combustion at the time of ignition is estimated,
Based on at least the composition of the gas sucked into the cylinder and the amount of heat generated by the combustion of the injected fuel, an amount of temperature increase due to combustion, which is the amount of temperature increase of the cylinder gas due to combustion, is estimated,
Based on a factor that affects the in-cylinder combustion speed, the temperature increase amount due to the combustion speed that is the temperature increase amount of the in-cylinder gas due to the increase in the combustion speed is estimated,
A combustion temperature estimation method for an internal combustion engine, wherein a value obtained by adding the combustion-induced temperature rise amount and the combustion speed-induced temperature rise amount to the compression-in-cylinder gas temperature during ignition is estimated as a combustion temperature in the cylinder. The combustion temperature estimation method for an internal combustion engine according to claim 1,
Increase amount of the compression cylinder gas temperature at the time of ignition estimated based on the temperature of the gas sucked into the cylinder, the composition of the gas sucked, and the factors that increase the cylinder gas temperature before the combustion When,
A method for estimating a combustion temperature of an internal combustion engine that estimates a gas temperature in a compression cylinder during ignition based on the above. The method for estimating a combustion temperature of an internal combustion engine according to claim 2,
As a factor for raising the in-cylinder gas temperature before the combustion, when the pilot injection is performed prior to the fuel injection, the amount of heat generated by the combustion of the fuel injected by the pilot and the energization to the glow plug are performed. At least one of the heat generated by the same energization in the case,
A method for estimating the combustion temperature of an internal combustion engine that estimates the amount of increase in the temperature of the compression cylinder gas during ignition based on the above. In the internal combustion engine combustion temperature estimation method according to any one of claims 1 to 3,
When the ignition time is earlier than the time corresponding to the compression top dead center, it is assumed that the ignition time coincides with the time corresponding to the compression top dead center. A method for estimating a combustion temperature of an internal combustion engine to be estimated. In the combustion temperature estimation method of the internal combustion engine according to any one of claims 1 to 4,
The fuel injection pressure, the rotational speed of the engine, the swirl ratio of the gas sucked into the cylinder, and the supercharger are provided in the engine as factors that affect the combustion speed in the cylinder. At least one of the supercharging pressure by the same supercharger and the oxygen concentration in the gas sucked into the cylinder,
A combustion temperature estimation method for an internal combustion engine that estimates the amount of increase in temperature due to combustion speed based on

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