JP2009150313A - Fuel property estimating device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately estimate a fuel property right after starting an internal combustion engine. <P>SOLUTION: A fuel property estimating device comprises a cylinder air amount calculating part 52 for calculating the amount of air in a cylinder, a reference torque calculating part 54 for calculating theoretical reference torque to be generated by the combustion of mixture having a theoretical air-fuel ratio in the cylinder, a torque fluctuation estimating part 58 for estimating a fluctuation of torque to be generated by combustion in the cylinder in accordance with the operated condition of the internal combustion engine and a prefixed reference fuel property, a cylinder torque estimating part 56 for estimating the size of torque in the cylinder generated by actual combustion in the cylinder, a cylinder torque calculating part 60 for calculating the probability distribution of the size of the torque corresponding to the fuel property in accordance with the reference torque and the fluctuation of torque to calculate probability corresponding to the size of the torque in the cylinder, and a fuel property estimating part 62 for estimating the fuel property in accordance with the probability corresponding to the size of the torque in the cylinder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel property estimation device for an internal combustion engine, and more particularly to a fuel property estimation device that estimates the property of fuel supplied into a cylinder of an internal combustion engine.

  Conventionally, a combustion state estimation device for estimating fuel properties has been known (Patent Document 1). This combustion state estimation device includes an in-cylinder air amount calculation device that calculates a reference torque corresponding to a change in the air amount from the first explosion at the time of starting the engine and generates an engine from an in-cylinder pressure sensor or a crank angular acceleration sensor. The actual torque (in-cylinder torque) to be estimated is estimated. The deviation of the in-cylinder torque from the reference torque is expressed as a deviation degree (for example, in-cylinder torque / reference torque). If the deviation is large according to the deviation degree, the fuel property is different from the fuel property given as a reference. Presumed to be on the heavy side.

In addition, with respect to the in-cylinder torque from the initial explosion to a predetermined number of cycles, the value of each cycle changes with some variation. This variation is essentially due to the engine generating torque with fluctuations. Therefore, in order to eliminate such variations due to the influence of torque fluctuations and extract changes due only to fuel properties, it is necessary to perform operations such as sampling a certain number of cycles and averaging them.
JP 2005-105822 A

  However, under strict exhaust regulations, it is required to grasp the fuel properties and optimize the lean limit of the injected fuel immediately after starting. However, in the estimation method based on multiple sampling as described above, starting There is a problem that the fuel properties cannot be estimated immediately after.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a fuel property estimation device for an internal combustion engine that can accurately estimate the fuel property immediately after starting the internal combustion engine.

  In order to achieve the above object, an internal combustion engine fuel property estimation apparatus according to the present invention includes an acquisition means for acquiring an in-cylinder air amount, an intake pipe pressure, or an engine speed, and the cylinder acquired by the acquisition means. A reference torque calculating means for calculating a theoretical reference torque generated by combustion of a mixture of stoichiometric air-fuel ratio in a cylinder based on the amount of internal air, the intake pipe pressure, or the engine speed; and the acquiring means Based on the in-cylinder air amount, the intake pipe pressure, or the operating conditions of the internal combustion engine including the engine speed and the predetermined fuel injection amount, and the predetermined reference fuel properties Estimated by the torque fluctuation estimating means for estimating the fluctuation of torque generated by combustion in the cylinder, the reference torque calculated by the reference torque calculating means, and the torque fluctuation estimating means. A probability distribution calculating means for calculating a probability distribution representing the magnitude of the torque to be generated based on the fluctuation of the torque, and an in-cylinder torque for calculating the magnitude of the in-cylinder torque generated by actual combustion in the cylinder. A fuel property estimating unit that estimates a fuel property based on the probability distribution calculated by the probability distribution calculating unit and the magnitude of the in-cylinder torque calculated by the in-cylinder torque calculating unit; , Including.

  According to the fuel property estimation device for an internal combustion engine according to the present invention, the acquisition unit acquires the in-cylinder air amount, the intake pipe pressure, or the engine speed. Based on the in-cylinder air amount, the intake pipe pressure, or the engine speed acquired by the acquiring means by the reference torque calculating means, the theoretical reference torque generated by the combustion of the air-fuel mixture of the theoretical air-fuel ratio in the cylinder is calculated. calculate.

  Then, the in-cylinder air amount, the intake pipe pressure, or the operating condition of the internal combustion engine including the engine speed and the predetermined fuel injection amount acquired by the acquiring unit by the torque fluctuation estimating unit, and a predetermined reference Based on the fuel properties, torque fluctuations generated by combustion in the cylinder are estimated. The probability distribution calculating means calculates a probability distribution representing the magnitude of the generated torque based on the reference torque calculated by the reference torque calculating means and the torque fluctuation estimated by the torque fluctuation estimating means. Further, the magnitude of the in-cylinder torque generated by the actual combustion in the cylinder is calculated by the in-cylinder torque calculating means.

  Here, the probability distribution representing the magnitude of the generated torque is a probability distribution representing the probability that the magnitude of torque is generated for each magnitude of torque.

  Then, the fuel property estimating means estimates the fuel property based on the probability distribution calculated by the probability distribution calculating means and the magnitude of the in-cylinder torque calculated by the in-cylinder torque calculating means.

  Thus, by estimating the fuel properties based on the probability distribution of the magnitude of the torque based on the variation of the torque according to the properties of the fuel and the magnitude of the in-cylinder torque generated by the actual combustion, the torque is estimated. Since the fuel properties can be estimated in consideration of variations due to the influence of fluctuations, the fuel properties can be accurately estimated immediately after startup.

  The fuel property estimation means according to the present invention can estimate the fuel property based on the probability with respect to the magnitude of the in-cylinder torque in the probability distribution. Accordingly, if the probability for the magnitude of the in-cylinder torque is low, it can be estimated that the fuel property is different from the reference fuel property.

  The fuel property estimation device for an internal combustion engine according to the present invention further includes update means for updating the reference fuel property to the fuel property estimated by the fuel property estimation means, and estimates by the torque fluctuation estimation means, probability distribution calculation The calculation by the means, the estimation by the fuel state estimation means, and the update by the update means can be repeated until the estimated change in the properties of the fuel converges within a predetermined range. This makes it possible to accurately estimate the properties of the fuel within a few cycles from the start.

  The fuel property estimation device for an internal combustion engine according to the present invention may further include a correction unit that corrects at least one of the fuel injection amount and the ignition timing based on the fuel property estimated by the fuel property estimation unit. As a result, the internal combustion engine can be operated at a fuel injection amount and ignition timing that match the estimated fuel properties.

  As described above, according to the fuel property estimation device for an internal combustion engine of the present invention, the probability distribution of the magnitude of the torque based on the variation of the torque according to the property of the fuel and the in-cylinder torque generated by the actual combustion. By estimating the fuel properties based on the size, it is possible to estimate the fuel properties in consideration of variations due to the effects of torque fluctuations, so the fuel properties can be accurately estimated immediately after starting. The effect of is obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a case where the properties of fuel supplied to a four-cylinder internal combustion engine are estimated will be described as an example.

  As shown in FIG. 1, an intake passage 12 and an exhaust passage 14 communicate with an internal combustion engine (engine) 10 of the fuel property estimation apparatus according to the present embodiment. The intake passage 12 includes an air filter 16 at an upstream end. The air filter 16 is assembled with an intake air temperature sensor 18 for detecting the intake air temperature THA (that is, the outside air temperature). An exhaust purification catalyst 32 is disposed in the exhaust passage 14.

  An air flow meter 20 is disposed downstream of the air filter 16. A throttle valve 22 is provided downstream of the air flow meter 20. A throttle sensor 24 that detects the throttle opening degree TA and an idle switch 26 that is turned on when the throttle valve 22 is fully closed are disposed in the vicinity of the throttle valve 22.

  A surge tank 28 is provided downstream of the throttle valve 22. In the vicinity of the surge tank 28, an intake pipe pressure sensor 29 for detecting the pressure in the intake passage 12 (intake pipe pressure) is provided. Further, a fuel injection valve 30 for injecting fuel into the intake port of the internal combustion engine 10 is disposed further downstream of the surge tank 28.

  Each cylinder of the internal combustion engine 10 includes a piston 34. A crankshaft 36 that is rotationally driven by the reciprocating motion is connected to the piston 34. The vehicle drive system and accessories (air conditioner compressor, alternator, torque converter, power steering pump, etc.) are driven by the rotational torque of the crankshaft 36. A crank angle sensor 38 for detecting the rotation angle of the crankshaft 36 is attached in the vicinity of the crankshaft 36. Further, a water temperature sensor 42 for detecting the cooling water temperature is attached to the cylinder block of the internal combustion engine 10. A predetermined cylinder among the four cylinders of the internal combustion engine 10 is provided with an in-cylinder pressure sensor 44 for detecting the in-cylinder pressure (in-cylinder pressure).

  The fuel property estimation apparatus of this embodiment includes an ECU (Electronic Control Unit) 40. The ECU 40 is connected to the various sensors described above, the fuel injection valve 30, and the like.

  In the fuel property estimation apparatus of the present embodiment configured as described above, the ECU 40 will be described with function blocks divided for each function realizing means determined based on hardware and software, as shown in FIG. Based on the intake pipe pressure detected by the intake pipe pressure sensor 29, an in-cylinder air amount calculation unit 52 that calculates the in-cylinder air amount that flows into the cylinder in each intake stroke, and the in-cylinder air amount and the assumed reference A reference torque calculation unit 54 that calculates a reference torque in each explosion stroke based on the fuel properties of the cylinder, and a cylinder generated by combustion each time an explosion stroke is performed based on the crank angular acceleration detected from the crank angle sensor 38. An in-cylinder torque estimation unit 56 that estimates the magnitude of the internal torque, a torque variation estimation unit 58 that estimates torque variation based on engine operating conditions, a reference torque and An in-cylinder torque probability calculation unit 60 that calculates a probability distribution of the magnitude of generated torque based on the torque fluctuation, and calculates a probability for the estimated magnitude of the in-cylinder torque in the probability distribution of the magnitude of torque; And a fuel property estimation unit 62 for estimating the property of the fuel based on the calculated probability for the in-cylinder torque.

  The ECU 40 also includes a fuel property storage unit 64 that stores the estimated fuel property, and a correction unit 66 that corrects each of the fuel injection amount and the ignition timing as the combustion control parameters based on the estimated fuel property. Is further provided.

  Here, as shown in FIG. 3, when the fuel is heavy, the reference torque after the start of the internal combustion engine 10 until the Nth explosion stroke is performed from the first explosion stroke (initial explosion). And in-cylinder torque change.

  In the intake stroke at the time of the first explosion, since a large amount of air is accumulated in the surge tank 28, a sufficient amount of air is sent into the cylinder. Accordingly, the in-cylinder air amount at the first explosion is large, and each of the reference torque and the in-cylinder torque has a relatively large value.

  Since the throttle valve 22 is normally closed when the engine is started, the air in the surge tank 28 decreases every time air is sent into the cylinder in the intake stroke after the first explosion. Therefore, after the first explosion, each time an intake stroke is performed, the amount of air sent into the cylinder decreases, and as shown in FIG. 3, each of the reference torque and the in-cylinder torque gradually decreases for each explosion stroke. I will do it.

  The reference torque is a theoretical torque generated when an air-fuel mixture of the fuel injected from the fuel injection valve 30 and the air flowing into the cylinder burns at the stoichiometric air-fuel ratio. Since the fuel injection amount at the start of the internal combustion engine is predetermined to a predetermined value, the reference torque changes according to the in-cylinder air amount, and the reference torque decreases as the in-cylinder air amount decreases.

  The in-cylinder torque is a value obtained by calculating the torque actually generated in the explosion stroke based on the crank angular acceleration. The torque actually generated in the explosion stroke decreases as the in-cylinder air amount decreases, but varies depending on the combustion state in the cylinder.

  Also, in the case of heavy fuel, as shown in FIG. 3 above, the fuel is difficult to evaporate and the air-fuel mixture is difficult to form, so the variation in in-cylinder torque after the initial explosion increases. On the other hand, in the case of light fuel, since the fuel injected from the fuel injection valve 30 is easily atomized, the in-cylinder combustion state is better than that of heavy fuel. Torque increases compared to heavy fuel. Further, in the case of light fuel, variation in in-cylinder torque after the first explosion is smaller than that of heavy fuel.

  As described above, the in-cylinder torque generally shows a downward-sloping trend, but the value of each cycle changes with some variation. This variation is essentially caused by the engine generating torque with fluctuations, and the variation depends on the fuel properties.

Since the in-cylinder air amount has a linear relationship with the intake pipe pressure (in-cylinder pressure), the in-cylinder air amount calculation unit 52 calculates the in-cylinder air amount mc (k) using the following equation (1). calculate.
mc (k) = A · pm (k) + B (1)

  However, pm (k) is the intake pipe pressure in the kth intake stroke from the first explosion, and is obtained from the detected value of the intake pipe pressure sensor 29 at the timing when the intake valve closes. A and B are fitness constants.

The reference torque varies according to the in-cylinder air amount and can be expressed as a function of the in-cylinder torque. Since the in-cylinder air amount and the reference torque are in a linear relationship, the reference torque calculation unit 54 The reference torque T _ia (k) can be calculated based on the in-cylinder air amount mc (k) calculated by the above equation (1) using the following equation (2).
T _ia (k) = C · mc (k) + D (2)

However, C and D are predetermined constants representing the relationship between the reference torque T _ia (k) and the in-cylinder air amount mc (k). Note that C and D may be variables according to operating conditions and the like. As shown in the above equation (2), the reference torque T _ia (k) corresponds to the in-cylinder air amount mc (k) in the kth explosion stroke from the first explosion, that is, the kth explosion stroke from the first explosion. It can be calculated from the amount of in-cylinder air that flows into the cylinder during the intake stroke.

Thus, according to the above formulas (1) and (2), the reference torque T _ia (k) can be calculated based on the intake pipe pressure pm (k) detected from the intake pipe pressure sensor 29. . The relationship between the intake pipe pressure pm (k) and the in-cylinder air amount mc (k) is stored in a map, and the value of the in-cylinder air amount mc (k) corresponding to the intake pipe pressure pm (k) is stored. It may be obtained from a map.

  Further, since the reference torque is a function of the in-cylinder air amount, the reference torque may be obtained directly from a predetermined characteristic value that varies according to the in-cylinder air amount. For example, the in-cylinder air amount fluctuates according to the intake pipe pressure as described above, and also fluctuates according to the engine speed. Therefore, the relationship between the intake pipe pressure or the engine speed and the reference torque is acquired in advance. Alternatively, the reference torque may be obtained directly from the intake pipe pressure or the engine speed.

Cylinder torque estimator 56 calculates the estimated indicated torque T _i to be described below as cylinder torque generated by actual combustion. The estimated indicated torque _Ti is calculated using the following equation (3).

In the above equation (3), the estimated indicated torque _Ti is a torque generated in the crankshaft 36 by the combustion of the engine. Here, the right side of Equation (3) shows a torque consuming estimated indicated torque T _i.

On the right side of the above equation (3), J is the moment of inertia of the driven member driven by the combustion or the like of the mixture, d [omega / dt is the angular acceleration of the crankshaft 36, T _f is the friction torque of the drive unit, T _l is the running It shows the load torque that is sometimes received from the road surface. Here, J × (dω / dt) is a dynamic loss torque (= T _ac ) caused by the angular acceleration of the crankshaft 36. The friction torque _Tf is a torque due to mechanical friction of each fitting portion such as friction between the piston 34 and the inner wall of the cylinder, and includes torque due to mechanical friction of accessories. The load torque _Tl is a torque due to a disturbance such as a road surface condition during traveling. In the present embodiment, since the fuel property is estimated with the shift gear in the neutral state, T _l = 0 in the following description.

As shown in the above equation (3), the estimated indicated torque T _i is a dynamic loss torque T _ac (= J × (dω / dt)), friction torque T _f , and load torque T due to angular acceleration. _It is obtained as the sum of _l .

The estimated indicated torque _Ti is expressed using the following equation (4).

The right side of the above equation (4) shows a torque generated indicated torque T _i, T _gas is the torque due to cylinder gas pressure in the cylinder, T _inertia show no inertial torque due to reciprocating inertia mass such as a piston 34 Yes. Torque T _gas due to in-cylinder gas pressure is torque generated by combustion of the air-fuel mixture in the cylinder.

In addition, the torque T _gas due to the in-cylinder gas pressure from when the piston 34 of one of the four cylinders is at the top dead center (TDC) position to when it is at the bottom dead center (BDC) position. Increases rapidly and decreases. Here, the rapid increase in T _gas is due to the explosion of the air-fuel mixture in the combustion chamber in the explosion process. After the explosion, T _gas decreases and takes a negative value due to the influence of the cylinders in other compression strokes or exhaust strokes. Further, when the crank angle reaches BDC, the change in the volume of the cylinder becomes 0, whereby T _gas takes a value of 0.

The inertia torque T _inertia due to the reciprocating inertia mass is an inertia torque generated by the inertia mass of the reciprocating member such as the piston 34, irrespective of the torque T _gas due to the in-cylinder gas pressure. The reciprocating member repeats acceleration / deceleration, and T _inertia always occurs as long as the crankshaft 36 rotates, even if the angular velocity is constant.

When the crank angle when the piston 34 of one of the four cylinders is at the top dead center (TDC) position is 0 ° and the crank angle when the piston 34 is at the bottom dead center (BDC) position is 180 °, At the position where the crank angle is 0 °, the reciprocating member is stopped, and T _inertia = 0. When the crank angle advances from a position where the crank angle is 0 ° toward a position where the crank angle is 180 °, the reciprocating member starts to move from the stopped state. At this time, T _inertia increases in a negative direction due to _inertia of these members. When the crank angle reaches around 90 °, the reciprocating members are moving at a predetermined speed, so that the crankshaft 36 is rotated by the inertia of these members. Therefore, T _interia changes from a negative value to a positive value between TDC and BDC. Thereafter, when the crank angle reaches 180 °, the reciprocating member stops and T _inertia = 0.

However, paying attention to the section where the crank angle is 0 ° to 180 °, the average value of the inertia torque T _inertia due to the reciprocating inertia mass in this section is zero. This is because the member having the reciprocating inertia mass moves in the opposite direction at a crank angle of about 0 ° to 90 ° and a crank angle of about 90 ° to 180 °.

Therefore, if each torque of the above formulas (3) and (4) is calculated as an average value in a section from TDC to BDC, it can be calculated as an inertia torque T _inertia = 0 due to a reciprocating inertia mass. Thus, the inertia torque T _inertia caused by the reciprocating inertia mass can eliminate the influence on the indicated torque T _i, it is possible to accurately estimate the indicated torque T _i.

Further, when an average value of each torque in the interval from TDC to _BDC, the average value of _{T inertia} becomes zero, from equation (4), the torque due to the mean value and the in-cylinder gas pressure indicated torque _{T i} The average value of T _gas becomes equal.

Further, when the average value of the angular acceleration of the crankshaft 36 is obtained in the section from TDC to BDC, the average value of T _{inertia in} this section is 0, so the influence of the reciprocating inertia mass on the angular acceleration is eliminated. Angular acceleration can be obtained.

Then, to calculate the respective torque of the right-hand side of equation (3), a method of calculating the left side of the estimated indicated torque T _i. First, a method for calculating the dynamic loss torque _T ac attributed to angular acceleration (= J × (dω / dt )). In the present embodiment, a case where a crank angle signal is detected from the crank angle sensor 38 every 10 ° of rotation of the crankshaft 36 will be described as an example.

First, the fuel property estimation device according to the present embodiment calculates the dynamic loss torque _Tac caused by the angular acceleration as an average value in a section of a crank angle of 0 ° to 180 ° from the TDC position to the BDC position. . For this purpose, the apparatus of the present embodiment obtains angular velocities ω ₀ (k) and ω ₀ (k + 1) at two crank angle positions of TDC and BDC, respectively, and at the same time, the crankshaft 36 rotates from TDC to BDC. Δt (k) is obtained.

When obtaining the angular velocity ω ₀ (k), for example, the time Δt ₀ (k), Δt ₁₀ (k) while the crank angle is rotated by 10 ° forward and backward from the TDC position is detected from the crank angle sensor 38. To do. Since the crankshaft 36 rotates 20 ° during the time Δt ₀ (k) + Δt ₁₀ (k), the angular velocity ω ₀ (k) [rad / s] is calculated by calculating the following equation (5). Can be calculated.
ω ₀ (k) = (20 / (Δt ₀ (k) + Δt ₁₀ (k))) × (π / 180) (5)

Similarly, when calculating the angular velocity ω ₀ (k + 1), the times Δt ₀ (k + 1) and Δt ₁₀ (k + 1) during which the crank angle is rotated 10 ° forward and backward from the BDC position are detected. Then, the angular velocity ω ₀ (k + 1) [rad / s] can be calculated by calculating the following equation (6).
ω ₀ (k + 1) = (20 / (Δt ₀ (k + 1) + Δt ₁₀ (k + 1))) × (π / 180)
... (6)
After obtaining the angular velocities ω ₀ (k), ω ₀ (k + 1), the following equation (7) is calculated, and the average value of the angular acceleration during the rotation of the crankshaft 36 from the TDC position to the BDC position is calculated. calculate.
Average value of angular acceleration = (ω ₀ (k + 1) −ω ₀ (k)) / Δt (k) (7)

Then, after obtaining the average value of the angular acceleration, the average value of the angular acceleration and the moment of inertia J are multiplied according to the right side of the above equation (3). Thereby, the average value of the dynamic loss torque T _ac (= J × (dω / dt)) while the crankshaft 36 rotates from TDC to BDC can be calculated. The inertia moment J of the drive unit is obtained in advance from the inertia mass of the drive component.

Next, a method for calculating the friction torque _Tf will be described. First, the average values of the friction torque T _f , the engine speed Ne, and the coolant temperature thw when the crankshaft 36 rotates 180 ° from TDC to BDC are used. In addition, the friction torque _Tf tends to increase as the engine speed Ne increases and also increase as the cooling water temperature thw decreases. The engine speed Ne and the coolant temperature thw as a variable parameter, to measure the friction torque T _f generated when rotating the crank shaft 36 from the TDC to the BDC, by calculating the average value, the friction torque T _f A map representing the relationship between the engine speed Ne of the internal combustion engine 10 and the coolant temperature thw is created in advance. Then, when estimating the fuel properties, the average value of the cooling water temperature and the average value of the engine speed in the section from TDC to BDC are applied to a map created in advance to obtain the average value of the friction torque _Tf . At this time, the coolant temperature is detected from the water temperature sensor 42, and the engine speed is detected from the crank angle sensor 38.

The behavior of the friction torque _Tf accompanying the variation of the crank angle is very complicated and has a large variation. However, since the behavior of the friction torque _Tf mainly depends on the speed of the piston 34, the average value of the friction torque _Tf for each section in which the average value of the inertia torque _Tinertia due to the reciprocating inertial mass is 0 is substantially constant. ing. Accordingly, by calculating the average value of the friction torque _Tf for each section (TDC → BDC) of the crank angle 0 ° to 180 ° where the average value of the inertia torque T _inertia due to the reciprocating inertia mass is 0, a complicated instantaneous behavior can be obtained. The indicated friction torque _Tf can be obtained with high accuracy. In addition, by setting the friction torque _Tf to an average value for each section, a map representing the relationship between the friction torque _Tf , the engine speed Ne of the internal combustion engine 10 and the coolant temperature thw can be accurately created. .

Further, as described above, the friction torque _Tf includes torque due to friction of auxiliary machinery. Here, the value of the torque due to the friction of the auxiliary machines varies depending on whether or not the auxiliary machines are operating. For example, the rotation of the engine is transmitted to a compressor of an air conditioner, which is one of the auxiliary machines, by a belt or the like, and torque due to friction is generated even when the air conditioner is not actually operating.

On the other hand, when the auxiliary machinery is operated, for example, when the air conditioner switch is turned on, the torque consumed by the compressor is larger than when the air conditioner is not operated. For this reason, the torque due to the friction of the auxiliary machinery increases, and the value of the friction torque _Tf also increases. Therefore, in order to accurately determine the friction torque _Tf , the operating state of the auxiliary machinery is detected, and when the auxiliary machinery is switched on, the friction torque T determined from the above map is used. It is desirable to correct the value of _f .

It is more preferable to correct the friction torque T _f in consideration of the difference between the temperature of the portion where the friction torque T _f is actually generated and the cooling water temperature at the time of extremely cold start. In this case, it is desirable to perform correction in consideration of the engine start time after the cold start, the in-cylinder inflow fuel amount and the like.

As described above, after finding the dynamic loss torque T _ac attributed to the angular acceleration and friction torque T _f, by adding the T _ac and T _f a (3) left side of the indicated torque T _i in equation calculate. The indicated torque T _i calculated here is calculated as an average value in a section of a crank angle from 0 ° to 180 ° from TDC to BDC. Therefore, since the average value of T _inert is 0 in this section, T _i = T _gas is obtained from the equation (4).

Based on the operating conditions of the internal combustion engine 10 configured from the engine speed, the in-cylinder air amount, the fuel injection amount, the ignition timing, the engine water temperature, and the valve timing, the torque fluctuation estimation unit 58 is expressed by the following equation (8). The torque fluctuation is obtained from the function shown.
Torque fluctuation = f (Ne, mc, A / F, SA, Tw, VT) (8)

  However, Ne is the engine speed, mc is the in-cylinder air amount, A / F is the air-fuel ratio, SA is the ignition timing, Tw is the engine water temperature, and VT is the valve timing. The air-fuel ratio A / F is obtained from the ratio between the in-cylinder air amount mc and the fuel injection amount. It should be noted that the relationship between the operating condition of the internal combustion engine and the torque fluctuation is obtained in advance through experiments or the like, and the function f of the above equation (8) is obtained based on the obtained relationship. Further, since the torque fluctuation also depends on the fuel properties, the function f in the above equation (8) is obtained according to each fuel property.

  In the torque fluctuation estimation unit 58, when it is assumed that the fuel property is the reference, the setting at the time of starting (SA, VT, fuel injection amount) and the observed value (Ne, mc, Tw,) when actually starting are Based on the above, the torque fluctuation is calculated according to the function f of the above equation (8) corresponding to the reference fuel property.

  The in-cylinder torque probability calculation unit 60 is based on the reference torque calculated by the reference torque calculation unit 54 and the torque fluctuation estimated by the torque fluctuation estimation unit 58. A probability distribution of torque magnitude according to the properties is calculated. The in-cylinder torque probability calculation unit 60 calculates a probability for the magnitude of the in-cylinder torque based on the magnitude of the in-cylinder torque estimated by the in-cylinder torque estimation unit 56 and the probability distribution of the magnitude of the torque. To do.

  Here, the principle of the present embodiment will be described. In an internal combustion engine, it is possible to estimate the torque generated by the engine from operating conditions (in-cylinder air amount, engine speed, throttle opening, fuel injection amount, ignition timing, water temperature, etc.). However, even if the driving conditions are constant, torque fluctuations always occur, so the torque value estimated at that time is a value with a certain probability (usually, the estimated torque value is expressed as variation). Is within the width to be).

  Further, since the magnitude of the torque varies depending on the fuel properties (light and heavy), it is possible to estimate the fuel properties by examining the deviation from the reference torque estimated from the operating conditions. However, since the reference torque is a value with stochastic fluctuation, the estimated value of the fuel property is also a correct estimated value within a certain probability range. On the other hand, torque fluctuations vary depending on the operating conditions and fuel properties of the internal combustion engine. Therefore, by calculating the relationship between the operating conditions and fuel properties and torque fluctuations in advance through experiments, etc., and formulating or mapping them, The probability for the magnitude of torque to be generated is determined according to the fuel properties. Then, a change in the fuel property is stochastically calculated from the determined probability of torque.

  By performing the probabilistic estimation based on the torque fluctuation as described above in each cycle at the time of starting, it is possible to accurately estimate the fuel property within several cycles.

  Therefore, in the fuel property estimation device according to the present embodiment, the fuel property estimation unit 62 estimates the fuel property based on the probability with respect to the magnitude of the in-cylinder torque calculated by the in-cylinder torque probability calculation unit 60. For example, as shown in FIG. 4, first, the probability with respect to the magnitude of the in-cylinder torque (see observed value 1 in FIG. 4) in the torque magnitude probability distribution according to the currently assumed reference fuel property A. P1 is calculated, and then a probability distribution with respect to the magnitude of the torque corresponding to the fuel property B (heavy fuel or light fuel property) that gives the same probability P1 to the magnitude of the in-cylinder torque (true) The fuel property is within the width X in FIG. 4). Then, corresponding to the observed value 2 of the magnitude of in-cylinder torque obtained in the next cycle, the torque corresponding to the probability P2A obtained from the probability distribution of the magnitude of torque corresponding to the fuel property A and the fuel property B Probability P2B obtained from the probability distribution of the magnitude of each is calculated, and if P2A> P1, the fuel property A is used as the next reference fuel property as it is. On the other hand, if P2B> P1, the next reference fuel property is updated to fuel property B. Then, the above processing is repeated (in FIG. 4, the fuel property C giving the probability P2B is obtained next, and the processing similar to the above is performed for the fuel properties B and C using the observed values 2 and 3). In this way, the above process is repeated, the reference fuel property is constantly updated in the direction in which the probability increases, and the updated reference fuel property is set as the estimated value of the fuel property to be the next reference fuel property.

  Note that when the probability of the in-cylinder torque obtained from the probability distribution of the magnitude of torque according to the reference fuel property is small, that is, the estimated in-cylinder torque is the upper and lower limits of the torque fluctuation range (torque fluctuations). If it is expressed by standard deviation σ and exceeds the upper and lower limits based on conditions defined by 2σ etc., it is possible to immediately determine that the deviation between the in-cylinder torque and the reference torque is due to fuel properties. Considering the deviation as a difference in fuel properties, the fuel property of the next reference is updated to a fuel property that gives a probability distribution of torque with the maximum probability for the observed value.

  The correction unit 66 corrects each of the fuel injection amount and the ignition timing as the combustion control parameter based on the updated reference fuel property. For example, as shown in FIG. 5, in the setting at the first explosion, the engine speed when determining the setting value of the next cycle without the in-cylinder torque reaching the reference torque is the ideal value. If the fuel property is lower (see FIG. 5A) and the fuel property is estimated to be heavier, the fuel injection amount is corrected to be larger than ideal or to suppress the retard of the ignition timing (FIG. 5). 5 (B), (C), the magnitude of the engine speed corresponds to the magnitude of the torque).

  In addition, the engine speed of the third cycle becomes excessive from the ideal by setting the second cycle (see FIG. 5A), and the fuel property is lighter if the fuel property is excessively estimated on the heavy side. Is estimated, the fuel injection amount and the ignition timing are corrected in directions opposite to those estimated when the fuel property is heavy (see FIGS. 5B and 5C). . By repeating these several cycles, the fuel injection amount and the ignition timing are corrected so as to reach the ideal value.

  In the fuel property estimation apparatus configured as described above, when the driver turns on an ignition switch (not shown), the ECU 40 executes a fuel property estimation processing routine shown in FIG.

  First, in step 100, a predetermined initial value (for example, a value representing a standard fuel property) is set as a reference fuel property stored in the fuel property storage unit 64. In step 102, a fuel injection amount is set. As the ignition timing SA and the valve timing VT, the set values at the start are set.

  In step 104, it is determined whether the engine has been started, that is, whether the engine speed has reached a predetermined value or more, and the process waits in step 104 until the engine is started. If it is determined that the engine has been started, the routine proceeds to step 105.

In step 105, based on the crank angular speed obtained from the crank angle of the crank angle sensor 38, the estimated indicated torque T _i (k) as the in-cylinder torque is estimated according to the above equation (3). In step 105, as will be described below, an average value of angular acceleration in the section of the crank angle 0 ° to 180 ° in the explosion stroke of the current number k of cycles is obtained, and the estimated indicated torque T _i (k) is calculated. .

First, parameters necessary for torque calculation are acquired. Specifically, parameters such as engine speed (Ne (k)), cooling water temperature (thw (k)), angular velocity (ω ₀ (k), ω ₀ (k + 1)), time (Δt (k)), etc. To get. Then, the friction torque T _f (k) is calculated. As described above, the friction torque T _f (k) is a function of the engine speed (Ne (k)) and the cooling water temperature (thw (k)), and the average value in the section from TDC to BDC from the map described above. Ask.

Further, when the switches of the auxiliary machinery are turned on (ON), the obtained friction torque T _f (k) is corrected. Specifically, the correction is performed by a method such as multiplying T _f (k) by a predetermined correction coefficient or adding a predetermined correction value to T _f (k).

Next, a dynamic loss torque T _ac (k) resulting from the angular acceleration is calculated. Here, T _ac (k) = J × ((ω ₀ (k + 1) −ω ₀ (k)) / Δt (k)) is calculated, and the average of the dynamic loss torque in the section from TDC to BDC A value T _ac (k) is calculated.

Then, the estimated indicated torque T _i (k) is calculated. Here, T _i (k) = T _ac (k) + T _f (k) is calculated to calculate T _i (k). When T _f (k) is corrected, the calculation is performed using T _f (k) after correction. The estimated indicated torque T _i (k) obtained here is the average value of the section from TDC to BDC.

  In step 106, the engine speed Ne is detected from the output value of the crank angle sensor 38, and in step 108, based on the intake pipe pressure pm (k) at the cycle number k from the first explosion obtained from the intake pipe pressure sensor 29. Then, in-cylinder air amount mc (k) is calculated according to the above equation (1).

In step 110, based on the in-cylinder air amount mc (k) calculated in step 108, the reference torque T _ia (k) is calculated according to the above equation (2). In the next step 112, the air-fuel ratio A obtained from the engine speed Ne obtained in step 106, the in-cylinder air amount mc (k) calculated in step 108, and the fuel injection amount set in step 102. / F, ignition timing SA set in step 102, engine water temperature Tw actually observed at the start, valve timing VT set in step 102, and reference fuel property set in step 100 Thus, torque fluctuation is calculated according to the above equation (8).

  In the next step 113, a probability distribution of the magnitude of torque corresponding to the reference fuel property is calculated based on the reference torque calculated in step 110 and the torque fluctuation calculated in step 112.

  In step 116, the probability with respect to the estimated indicated torque magnitude estimated in step 105 is calculated from the torque magnitude probability distribution corresponding to the reference fuel property calculated in step 113 or step 118 described later. calculate.

  In step 118, a probability distribution of the magnitude of torque corresponding to the fuel property giving the same probability as the probability for the estimated indicated torque calculated in step 105 is calculated. When the probability distribution of torque magnitude is calculated in step 118, the same probability as the probability distribution of torque magnitude corresponding to the reference fuel property is obtained with respect to the estimated estimated torque magnitude. Depending on the fuel properties to be given, the engine speed Ne obtained in step 106, the in-cylinder air amount mc (k) calculated in step 108 and the above step 102 or the steps described later, as in step 112 above. The air-fuel ratio A / F obtained from the fuel injection amount set at 126, the ignition timing SA set at step 102 or step 126 described later, the engine water temperature Tw actually observed at the start, and the step 102 Based on the set valve timing VT, torque fluctuation is calculated according to the function of the above equation (8). Then, a probability distribution of torque magnitude is calculated based on the reference torque in step 110 and the calculated torque fluctuation.

  In the next step 120, based on the crank angular velocity obtained from the crank angle of the crank angle sensor 38, the magnitude of the estimated indicated torque is estimated according to the above equation (3).

  In step 122, the probability of the estimated indicated torque estimated in step 120 obtained from the probability distribution of the torque magnitude according to the reference fuel property and the torque calculated in step 118 are calculated. The probability with respect to the magnitude of the estimated indicated torque estimated in step 120, obtained from the magnitude probability distribution, is calculated.

  In step 124, the fuel property that gives a higher probability than the probability calculated in step 116 is stored and updated in the fuel property storage unit 64 as the next reference fuel property. In the next step 126, each of the fuel injection amount and the ignition timing as the combustion control parameter is corrected based on the fuel property updated in step 124.

  In step 128, it is determined whether or not the change in the fuel property due to the update in step 124 has converged within a predetermined range. If the change in the fuel property due to the update is larger than the predetermined range, it is determined that the fuel has not converged, the process returns to step 106, and steps 106 to 126 are repeated for the next cycle. On the other hand, if the change in the fuel property due to the update is within the predetermined range in step 128, it is determined that the fuel property has converged, and the fuel property estimation processing routine is terminated.

  As described above, when the fuel property estimation processing routine is executed, the fuel property is accurately estimated in several cycles after the engine is started. Also, while estimating the fuel properties, the fuel injection amount and the ignition timing are corrected according to the estimated fuel properties, and when the repeatedly estimated fuel properties converge, the ideal fuel injection amount and the ignition timing are And ideal engine speed is realized.

  As described above, according to the fuel property estimation device according to the first embodiment, the cylinder generated by the actual combustion from the probability distribution of the magnitude of the torque based on the fluctuation of the torque according to the reference fuel property. By obtaining the probability for the magnitude of the internal torque and estimating the fuel properties based on this probability, it is possible to estimate the fuel properties in consideration of variations due to the effects of torque fluctuations. From this, it is possible to accurately estimate the fuel properties.

  Further, it is possible to start the engine by probabilistically estimating the fuel property repeatedly using the probability distribution of the magnitude of the torque based on the fluctuation of the torque according to the estimated fuel property until the estimated fuel property converges. Fuel properties are accurately estimated within a few cycles after the first explosion.

  Further, based on the estimated fuel property, the subsequent fuel injection amount and ignition timing can be corrected, and optimization can be performed so as to achieve both improvement of drivability and reduction of emissions.

  In the above embodiment, the case where the function for calculating the torque fluctuation is obtained for each fuel property has been described as an example, but the operation condition of the internal combustion engine and the relationship between the fuel property and the torque fluctuation are obtained, Based on the obtained relationship, a function for calculating torque fluctuation may be obtained. In this case, torque fluctuations corresponding to the reference fuel properties may be calculated according to the function obtained based on the operating conditions of the internal combustion engine and the reference fuel properties.

  In addition, the operation condition of the internal combustion engine used for obtaining the torque fluctuation has been described as an example where the engine speed, the in-cylinder air amount, the fuel injection amount, the ignition timing, the engine water temperature, and the valve timing are configured. However, the present invention is not limited to this, and it is only necessary that the operating conditions of the internal combustion engine include the in-cylinder air amount, the intake pipe pressure, or the engine speed and the fuel injection amount.

  In addition, the case where the fuel injection amount and the ignition timing are corrected based on the updated reference fuel property every time the reference fuel property is updated has been described as an example, but after the repeatedly estimated fuel property has converged The fuel injection amount and ignition timing may be corrected based on the last updated reference fuel property.

  Next, a fuel property estimation apparatus according to the second embodiment will be described. In addition, since the structure of the fuel property estimation apparatus which concerns on 2nd Embodiment is the same as that of 1st Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.

  In the second embodiment, in order to improve the convergence of the update of the fuel property, the same probability as the probability distribution of the magnitude of the torque according to the reference fuel property with respect to the estimated magnitude of the in-cylinder torque. Is different from the first embodiment in that an intermediate fuel property between the fuel property giving the fuel pressure and the reference fuel property is updated as the next reference fuel property.

  In the fuel property estimation device according to the second embodiment, the fuel property estimation unit 62 estimates the fuel property based on the probability with respect to the magnitude of the in-cylinder torque calculated by the in-cylinder torque probability calculation unit 60. For example, as shown in FIG. 7, first, the probability with respect to the magnitude of in-cylinder torque (see observed value 1 in FIG. 7) in the probability distribution of torque magnitude according to the currently assumed reference fuel property A. P1 is calculated, and then a probability distribution of the magnitude of torque according to the fuel property B (heavy fuel or light fuel property) that gives the same probability P1 to the magnitude of in-cylinder torque is obtained. Then, the next reference fuel property is updated to the fuel property B ′ (fuel property corresponding to the center of the width X) that is intermediate between the reference fuel property A and the fuel property B. Then, the above processing is repeated (in FIG. 7, for the next observed value 2, a fuel property C giving the same probability P2 as the fuel property B ′ is obtained next, and is intermediate between the fuel property B ′ and the fuel property C. Update the fuel properties to the fuel properties of the next standard). Thus, the above process is repeated, and the update of the fuel property is converged at high speed (as shown in FIG. 7, the probability P2 of the next observation value 2 with respect to the reference B ′ is almost the maximum value of the probability distribution. Converges fast).

  Next, a fuel property estimation processing routine according to the second embodiment will be described with reference to FIG. In addition, about the process similar to 1st Embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  First, in step 100, a predetermined initial value is set as a reference fuel property stored in the fuel property storage unit 64. In step 102, the fuel injection amount, the ignition timing SA, and the valve timing VT are set. Set the starting value.

  In step 104, it is determined whether the engine has been started. If it is determined that the engine has been started, the process proceeds to step 105, where the estimated indicated torque as in-cylinder torque is estimated.

  In step 106, the engine speed Ne is detected from the output value of the crank angle sensor 38. In the next step 108, the in-cylinder air amount mc (k) is calculated.

In step 110, a reference torque T _ia (k) is calculated based on the in-cylinder air amount mc (k) calculated in step 108. In the next step 112, the engine speed Ne obtained in step 106, the in-cylinder air amount mc (k) calculated in step 108, and the fuel injection amount set in step 102 or step 126 described later are used. Obtained air-fuel ratio A / F, ignition timing SA set in step 102 or step 120 described later, engine water temperature Tw actually observed at the start, valve timing VT set in step 102, and step 100 Alternatively, the torque fluctuation is calculated according to the above equation (8) based on the reference fuel property set in step 124 described later.

  In the next step 113, a probability distribution of torque magnitude according to the reference fuel property is calculated. In step 116, from the torque probability distribution according to the reference fuel property calculated in step 113, the above step is calculated. The probability with respect to the magnitude of the estimated indicated torque estimated at 105 is calculated. Then, in step 118, a probability distribution of torque magnitude corresponding to the fuel property giving the same probability as the probability for the estimated indicated torque magnitude calculated in step 116 is calculated.

  In the next step 250, the fuel property storage unit uses the intermediate fuel property between the reference fuel property stored in the fuel property storage unit 64 and the fuel property obtained in step 118 as the next reference fuel property. 64 to store and update.

  In the next step 126, each of the fuel injection amount and the ignition timing as the combustion control parameter is corrected based on the fuel property updated in step 250.

  In step 128, it is determined whether or not the fuel property update in step 124 has converged. If the fuel property after the update has changed, it is determined that the fuel property has not converged, the process returns to step 105, and steps 105 to 118, 250, and 126 are repeatedly executed for the next cycle. On the other hand, if the updated fuel properties are the same for the predetermined number of times in step 128, it is determined that the fuel properties have converged, and the fuel property estimation processing routine is terminated.

  As described above, in the update of the reference fuel property, the fuel property that gives the same probability as the probability distribution of the magnitude of the torque according to the reference fuel property to the estimated magnitude of the in-cylinder torque, By updating the fuel property in the middle of the fuel property as the next reference fuel property, the update of the fuel property can be converged at high speed.

  In the above embodiment, when the reference fuel property is updated, an intermediate fuel property that gives the same probability to the estimated magnitude of the in-cylinder torque is changed to the following reference property. However, the present invention is not limited to this, and the fuel property between two fuel properties that give the same probability to the magnitude of the in-cylinder torque is expressed as follows. The fuel property may be used. In this case, as shown in FIG. 9, first, the magnitude of the in-cylinder torque (see the observed value 1 in FIG. 9) in the probability distribution of the magnitude of torque according to the currently assumed reference fuel property A. Next, a probability distribution of torque magnitude according to fuel property B (heavy fuel property or light fuel property) that gives the same probability P1 to the magnitude of in-cylinder torque is calculated. Ask. Then, the next reference fuel property is updated to a fuel property B ″ that divides the width X between the reference fuel property A and the fuel property B into 1−α: α (1 ≧ α ≧ 0). Then, the above processing is repeated (in FIG. 9, the fuel property C ″ that gives the same probability P2 as the fuel property B ″ is obtained for the next observed value 2, and the fuel property B ″ and the fuel property C ′ are obtained. The fuel property that divides the width X between ′ and 1−α: α is updated so as to be the next reference fuel property).

  Next, a fuel property estimation apparatus according to the third embodiment will be described. Since the configuration of the fuel property estimation device according to the third embodiment is the same as that of the first embodiment, the same reference numerals are given and description thereof is omitted.

  The third embodiment is different from the first embodiment in that the in-cylinder torque is estimated from the in-cylinder pressure.

In the fuel property estimation apparatus according to the third embodiment, in-cylinder torque estimation unit 56 estimates in-cylinder torque due to combustion each time an explosion stroke is performed based on the in-cylinder pressure detected from in-cylinder pressure sensor 44. To do. The in-cylinder torque estimation unit 56 calculates actually measured _indicated torque T _{i_cps} described below as in-cylinder torque. For example, when the # 1 cylinder includes the in-cylinder pressure sensor 44, the actually measured torque T _{i_cps} is calculated using the following equation (9).

In the above equation (9), _{Ti_cps} is a _{value obtained by converting} an actually measured indicated torque (actually _{indicated average} indicated torque) averaged over one cycle (crank angle 720 °) in a section of 720 ° CA / number of cylinders. N is the number of cylinders, and P _{# 1} (θ) is the in-cylinder pressure of the # 1 cylinder calculated for each crank angle θ, and is obtained from the detection value of the in-cylinder pressure sensor 44. V _{# 1} (θ) is the in-cylinder volume of the # 1 cylinder calculated for each crank angle θ, and the crankshaft detected from the specifications (bore × stroke, combustion chamber volume, etc.) of the internal combustion engine and the crank angle sensor 38. It is calculated from the corner.

The measured average _indicated torque T _{i — cps} is obtained as the work of cylinder gas in one cycle (converted in a section of 720 ° CA / number of cylinders), and as shown in the above equation (9), for each crank angle θ. The product of P _{# 1} (θ) and dV _{# 1} (θ) / dθ is obtained, the average value (Average) is calculated in one cycle interval, and the number N of cylinders is multiplied. In the following, the internal combustion engine 10 is composed of four cylinders # 1 to # 4, and the explosion stroke is performed in the order of # 1, # 3, # 4, and # 2 for every 180 ° rotation of the crankshaft 36. Will be described as an example.

When the in-cylinder pressure sensor 44 is attached to the # 1 cylinder, the actually measured _indicated torque T _{i — cps} (k) is obtained from the four strokes (1 cycle) of intake, compression, explosion, and exhaust of the # 1 cylinder at the kth cycle from the first explosion. Desired.

During steady operation, the torque generated in the intake stroke for which the estimated indicated torque T _i (k) is calculated in the first embodiment, and the torque generated in the stroke for which the actually measured _indicated torque T _{i_cps} (k) is calculated, Can be regarded as substantially identical. Further, as described above, the actually measured _indicated torque T _{i_cps} (k) is calculated as an average value in the section of one cycle, so that the torque of the explosion stroke having the largest torque is averaged in the section of one cycle.

Therefore, by multiplying the number of cylinders N (the number of times the explosion stroke is performed in one cycle of # 1 cylinder), the measured torque T _{i_cps} (k) corresponding to the torque generated in the explosion stroke of the # 1 cylinder in the kth cycle. ) Can be calculated. When the operating state is a steady state, the estimated indicated torque T _i (k) and the actually measured _indicated torque T _{i_cps} (k) are substantially equal to each other.

Similarly, by providing in-cylinder pressure sensors 44 to the # 2 to # 4 cylinders, the actually measured _indicated torques T _{i_cps} (k + 1) to T _{i_cps} (k + 3) can be calculated. That is, the actually measured _indicated torque T _{i_cps} (k + 1) can be calculated from the four strokes of intake, compression, explosion, and exhaust of the # 3 cylinder in the (k + 1) th _cycle . Also, the measured _indicated torque T _{i — cps} (k + 2) is obtained from the four strokes of intake, compression, explosion, and exhaust of the # 4 cylinder in the k + 2 cycle, and 4 of intake, compression, explosion, and exhaust of the # 2 cylinder in the k + 3 cycle. The measured _indicated torque T _{i — cps} (k + 3) can be calculated from the stroke. Thus, by providing the in-cylinder pressure sensors 44 in all the cylinders, the measured indicated torque T corresponding to the estimated indicated torques T _i (k) to T _i (k + 3)... Explained in the first embodiment. _{i_cps} (k) to T _{i_cps} (k + 3)... can be sequentially calculated.

After calculating the actual indicated torque _{T I_cps} determines the properties of the fuel using measured indicated torque _{T I_cps} and the reference torque _{T ia} as cylinder torque. In steady operation immediately after start-up, the estimated indicated torques T _i (k) to T _i (k + 3)... Described in the first embodiment and the actually measured _indicated torques T _{i_cps} (k) to T _{i_cps} (k + 3) are described. because ... is substantially equal respectively, using measured indicated torque T _{I_cps} instead of the estimated indicated torque T _i in the first embodiment, it is possible to determine the property of the fuel.

  In addition, since it is the same as that of 1st Embodiment about the structure and process of the fuel property estimation apparatus other than the above, those description is abbreviate | omitted.

It is sectional drawing which shows the structure of the fuel property estimation apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of ECU of the fuel property estimation apparatus which concerns on the 1st Embodiment of this invention. It is a graph which shows the fluctuation | variation of a reference | standard torque and an in-cylinder torque after the start of an internal combustion engine until it performs N explosion strokes from the first explosion stroke. It is a figure for demonstrating the method to update the following reference | standard fuel property in the fuel property estimation apparatus which concerns on the 1st Embodiment of this invention. (A) Graph showing actual and ideal movements of engine speed, (B) Graph showing actual and ideal movements of ignition timing, and (C) Actual movement of fuel injection amount. And a graph showing ideal movement. It is a flowchart which shows the content of the fuel property estimation process routine in ECU of the fuel property estimation apparatus which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the method to update the following reference | standard fuel property in the fuel property estimation apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the content of the fuel property estimation process routine in ECU of the fuel property estimation apparatus which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the other method of updating the fuel characteristic of the following reference | standard.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 26 Combustion chamber 29 Intake pipe pressure sensor 38 Crank angle sensor 44 In-cylinder pressure sensor 52 In-cylinder air amount calculation part 54 Reference torque calculation part 56 In-cylinder torque estimation part 58 Torque fluctuation estimation part 60 In-cylinder torque probability calculation part 62 Fuel property estimation unit 64 Fuel property storage unit 66 Correction unit

Claims (4)

An acquisition means for acquiring an in-cylinder air amount, an intake pipe pressure, or an engine speed;
Based on the in-cylinder air amount acquired by the acquisition means, the intake pipe pressure, or the engine speed, a theoretical reference torque generated by combustion of a stoichiometric air-fuel mixture in the cylinder is calculated. A reference torque calculating means;
The in-cylinder air amount acquired by the acquiring means, the intake pipe pressure, or the operating condition of the internal combustion engine including the engine speed and a predetermined fuel injection amount, and a predetermined reference fuel property Torque fluctuation estimating means for estimating the fluctuation of torque generated by combustion in the cylinder based on
A probability distribution calculating means for calculating a probability distribution representing the magnitude of torque to be generated based on the reference torque calculated by the reference torque calculating means and the fluctuation of the torque estimated by the torque fluctuation estimating means;
In-cylinder torque calculating means for calculating the magnitude of the in-cylinder torque generated by actual combustion in the cylinder;
Fuel property estimation means for estimating fuel properties based on the probability distribution calculated by the probability distribution calculation means and the magnitude of the in-cylinder torque calculated by the in-cylinder torque calculation means;
A fuel property estimation device for an internal combustion engine, including:   The fuel property estimation device for an internal combustion engine according to claim 1, wherein the fuel property estimation means estimates the property of the fuel based on a probability with respect to the magnitude of the in-cylinder torque in the probability distribution. Update means for updating the reference fuel property to the fuel property estimated by the fuel property estimation means;
The estimation by the torque fluctuation estimation unit, the calculation by the probability distribution calculation unit, the estimation by the fuel state estimation unit, and the update by the update unit are continued until the estimated change in the property of the fuel converges within a predetermined range. 3. The fuel property estimation device for an internal combustion engine according to claim 1, wherein the fuel property estimation device is repeated.   4. The internal combustion engine according to claim 1, further comprising a correcting unit that corrects at least one of a fuel injection amount and an ignition timing based on a fuel property estimated by the fuel property estimating unit. 5. Fuel property estimation device.

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