JP2005105822A - Combustion state estimating device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimally control an internal combustion engine, by accurately determining a combustion state in a cylinder and properties of fuel. <P>SOLUTION: This combustion state estimating device has a means for acquiring a cylinder air quantity mc(k), a reference torque calculating means for calculating theoretical reference torque Tia(k) generated in the cylinder on the basis of the cylinder air quantity mc(k), a cylinder torque calculating means for calculating illustrated torque Ti(k) generated by actual combustion in the cylinder, and a determining means for determining the combustion state in the cylinder or the properties of the fuel on the basis of a result of comparing the reference torque Tia(k) with the illustrated torque Ti(k). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a combustion state estimation device for an internal combustion engine, and is particularly suitable for application to a device that estimates the combustion state in a cylinder and the properties of fuel supplied into the cylinder.

  2. Description of the Related Art Conventionally, a method is known in which an indicated mean effective pressure is obtained from a detection value of an in-cylinder pressure sensor mounted in a cylinder of an internal combustion engine, and a fuel property is determined based on the indicated mean effective pressure. For example, Japanese Patent Application Laid-Open No. 9-144591 describes a method for detecting the properties of fuel based on whether or not the calculated value of the indicated mean effective pressure is greater than or equal to a predetermined value.

JP-A-9-144591 JP-A-6-288289 Japanese Patent Application Laid-Open No. 7-29739

  However, for example, when the cranking time at the time of starting the engine or the engine speed is different, the in-cylinder air amount varies. When the in-cylinder air amount changes, the indicated mean effective pressure changes. In the method described in Japanese Patent Application Laid-Open No. 9-144591, the fluctuation of the indicated mean effective pressure due to the fluctuation of the in-cylinder air amount is not taken into consideration, so that the fuel property is accurately determined when the in-cylinder air quantity fluctuates. The problem of not being able to do arises.

  For example, when the in-cylinder air amount is small, the in-cylinder combustion is suppressed, so that the indicated mean effective pressure becomes small. If the fluctuation of the indicated mean effective pressure due to the in-cylinder air amount is not taken into account, even if the indicated mean effective pressure is reduced according to the in-cylinder air amount, the indicated mean effective pressure is caused by the properties of the fuel. It is assumed that it is erroneously determined that it has been lowered. Therefore, it is difficult to accurately determine the fuel properties by the method described in the above publication.

  The present invention has been made to solve the above-described problems, and it is an object of the present invention to accurately determine an in-cylinder combustion state and fuel properties and optimally control an internal combustion engine.

  In order to achieve the above object, the first invention provides means for obtaining a predetermined characteristic value that varies according to the in-cylinder air amount or the in-cylinder air amount, and the in-cylinder air amount or the predetermined characteristic value. Based on the reference torque calculating means for calculating the theoretical reference torque generated in the cylinder, the in-cylinder torque calculating means for calculating the in-cylinder torque generated by the actual combustion in the cylinder, the reference torque and the And determining means for determining the combustion state in the cylinder or the properties of the fuel based on the result of comparing the in-cylinder torque.

  According to a second aspect, in the first aspect, the predetermined characteristic value includes an intake pipe pressure or an engine speed.

  According to a third invention, in the first or second invention, the determination means determines a combustion state in the cylinder or a property of the fuel based on a degree of deviation between the reference torque and the cylinder torque. Features.

  According to a fourth invention, in the third invention, the determination means determines that the combustion state is deteriorated as the degree of deviation between the reference torque and the in-cylinder torque is larger.

  According to a fifth aspect, in the third aspect, the determination means determines that the property of the fuel is heavier as the degree of deviation between the reference torque and the in-cylinder torque is larger.

  According to a sixth aspect of the present invention, in the third to fifth aspects, the apparatus further comprises means for obtaining a relative ratio between the reference torque and the in-cylinder torque or a deviation between the reference torque and the in-cylinder torque. The means determines the degree of deviation between the reference torque and the in-cylinder torque based on the ratio or the deviation.

  In a sixth aspect based on the sixth aspect, the present invention further comprises an integrated value calculating means for calculating an integrated value of the ratio or the deviation, and the determining means is configured to determine the reference torque and the in-cylinder torque based on the integrated value. It is characterized by discriminating the degree of deviation.

  An eighth invention according to any one of the first to seventh inventions, further comprising crank angular acceleration calculating means for calculating a crank angular acceleration, wherein the in-cylinder torque calculating means is based on the crank angular acceleration. The torque is calculated.

  According to a ninth invention, in the eighth invention, there is provided storage means for storing a standard friction characteristic defining a relationship between a predetermined parameter and an engine friction torque, and the in-cylinder torque calculation means comprises the friction torque and the crank The in-cylinder torque is calculated based on the angular acceleration.

  In a tenth aspect based on the eighth or ninth aspect, the crank angular acceleration calculating means calculates the crank angular acceleration in a crank angle interval in which an average value of inertia torque due to reciprocating inertia mass is substantially zero. It is characterized by.

  According to an eleventh aspect of the present invention, in any one of the first to seventh aspects, an in-cylinder pressure detecting unit that detects an in-cylinder pressure is provided, and the in-cylinder torque calculating unit calculates the in-cylinder torque based on the in-cylinder pressure. It is characterized by doing.

  According to a twelfth aspect of the invention, in the eleventh aspect of the invention, the crank angular acceleration calculating means for calculating the crank angular acceleration and the in-cylinder pressure detecting means provided in (total number of cylinders −1) cylinders, The in-cylinder torque calculating means calculates the in-cylinder torque based on the crank angular acceleration and the in-cylinder pressure.

  According to the first invention, the reference torque is calculated from the in-cylinder air amount or the predetermined characteristic value that varies according to the in-cylinder air amount, and the combustion state or fuel is calculated based on the result of comparing the reference torque and the in-cylinder torque. Therefore, even if the in-cylinder air amount fluctuates due to factors such as variation, the in-cylinder combustion state or the fuel property can be accurately determined. Therefore, it becomes possible to optimally control the internal combustion engine based on the combustion state or the properties of the fuel.

  According to the second aspect of the present invention, the in-cylinder air amount fluctuates in accordance with the intake pipe pressure or the engine speed. Therefore, by acquiring the intake pipe pressure or the engine speed as a predetermined characteristic value, The reference torque can be calculated without calculating the internal air amount.

  According to the third invention, it is possible to determine the combustion state in the cylinder or the property of the fuel based on the degree of deviation between the reference torque and the in-cylinder torque.

  According to the fourth invention, when the in-cylinder combustion state deteriorates, the in-cylinder torque decreases, and the amount of air sent into the cylinder increases due to the decrease in engine speed, thereby increasing the reference torque. Accordingly, when the combustion state is deteriorated, the degree of deviation between the reference torque and the in-cylinder torque is increased, so that the combustion state can be determined based on the degree of deviation.

  According to the fifth aspect, in the case of heavy fuel, the in-cylinder torque decreases, and the amount of air sent into the cylinder increases due to the decrease in the engine speed, thereby increasing the reference torque. Therefore, in the case of heavy fuel, the degree of deviation between the reference torque and the in-cylinder torque becomes large, so that it is possible to determine the properties of the fuel based on the degree of deviation.

  According to the sixth aspect, the degree of deviation between the reference torque and the in-cylinder torque can be determined from the relative ratio between the reference torque and the in-cylinder torque or the deviation between the reference torque and the in-cylinder torque. Accordingly, it is possible to determine the combustion state in the cylinder or the properties of the fuel based on this ratio or deviation.

  According to the seventh invention, by calculating the relative ratio of the reference torque and the in-cylinder torque or the integrated value of the deviation between the reference torque and the in-cylinder torque, the torque calculation value is obtained due to accidental deterioration of combustion or the like. Even when variations occur, it is possible to accurately determine the combustion state in the cylinder or the properties of the fuel.

  According to the eighth aspect, since the in-cylinder torque can be calculated based on the crank angular acceleration, it is possible to determine the in-cylinder combustion state or the fuel property with a simple configuration.

  According to the ninth aspect, since the in-cylinder torque can be accurately obtained in consideration of the friction torque, the combustion state in the cylinder or the property of the fuel can be determined with high accuracy.

  According to the tenth invention, by calculating the crank angular acceleration in a crank angle section in which the average value of the inertia torque due to the reciprocating inertia mass is substantially zero, The influence on the calculated value of torque can be eliminated. Accordingly, the in-cylinder torque can be accurately calculated, and the combustion state in the cylinder or the properties of the fuel can be determined with high accuracy.

  According to the eleventh aspect, the in-cylinder torque can be accurately calculated based on the detected in-cylinder pressure, and the combustion state in the cylinder or the properties of the fuel can be determined with high accuracy.

  According to the eleventh aspect, since the in-cylinder torque is calculated based on the crank angular acceleration and the detected in-cylinder pressure, it is not necessary to provide in-cylinder pressure detecting means for all the cylinders. Therefore, the manufacturing cost of the combustion state estimation device can be reduced.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a combustion state estimating device for an internal combustion engine and its surrounding structure according to each embodiment of the present invention. In the following embodiments, a four-cylinder internal combustion engine is illustrated. As shown in FIG. 1, an intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. 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).

  As shown in FIG. 1, the combustion state estimation device 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 combustion state estimation device of the present embodiment configured as described above, the ECU 40 calculates the in-cylinder torque due to combustion every time an explosion stroke is performed based on the crank angular acceleration detected from the crank angle sensor 38. Further, the ECU 40 obtains the in-cylinder air amount that flows into the cylinder in each intake stroke based on the detection value of the intake pressure sensor 29, and obtains the reference torque in each explosion stroke from the in-cylinder air amount. The fuel property is determined based on the degree of deviation between the in-cylinder torque and the reference torque.

  FIG. 2 is a characteristic diagram showing how the reference torque and the in-cylinder torque fluctuate from the initial explosion stroke (initial explosion) to the Nth explosion stroke after the internal combustion engine 10 is started. Here, FIG. 2A shows the case where the fuel property is light, and FIG. 2B shows the case where the fuel property is heavy.

  The reference torque is a theoretical torque when the 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 time of starting the engine is set to a predetermined value in advance, the reference torque varies according to the in-cylinder air amount, and 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 varies in accordance with the in-cylinder combustion state. The smaller the in-cylinder air amount, the worse the combustion state. Therefore, the in-cylinder torque decreases as the in-cylinder air amount decreases.

  As shown in FIG. 2 (A) and FIG. 2 (B), in the intake stroke at the time of the first explosion, a large amount of air is accumulated in the surge tank 28, so that a sufficient amount of air is sent into the cylinder. It is done. Accordingly, the in-cylinder air amount at the first explosion is large, and the reference torque and the in-cylinder torque are relatively large values.

  Since the throttle valve 22 is normally closed at the time of start-up, 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, every time an intake stroke is performed, the amount of air sent into the cylinder decreases, and as shown in FIGS. 2 (A) and 2 (B), the reference torque and cylinder for each explosion stroke are reduced. The internal torque gradually decreases.

  As shown in FIGS. 2 (A) and 2 (B), in the case of light fuel, the fuel injected from the fuel injection valve 30 is easily atomized, so the in-cylinder combustion state is better than that of heavy fuel. Thus, the in-cylinder torque at the first explosion and each subsequent cycle becomes larger than that of heavy fuel. In addition, in the case of heavy fuel, the fuel is difficult to atomize and an air-fuel mixture is difficult to be formed. Therefore, variation in in-cylinder torque after the first explosion is larger than that of light fuel.

  On the other hand, with respect to the reference torque, the reference torque in each cycle after the first explosion is smaller for light fuel. This is because when the fuel is light, the in-cylinder combustion state is good, and the rate of increase in engine speed is greater than that of heavy fuel. That is, in the case of light fuel, the engine speed greatly increases after the first explosion, and the pressure in the surge tank 28 becomes more negative than in the case of heavy fuel. Therefore, in the case of light fuel, the in-cylinder air amount after the first explosion is smaller than that of heavy fuel, and the fuel injection amount is the same for both light fuel and heavy fuel. And as shown to FIG. 2 (B), the reference torque of the light fuel after the first explosion becomes small compared with a heavy fuel.

  Thus, in the case of heavy fuel that has a large amount of fuel adhering to the wall surface of the intake passage 12 (intake port) and is difficult to atomize, the amount of fuel in the cylinder that contributes to combustion immediately after the first explosion is reduced from the fuel injection valve 30. Since it decreases with respect to the injection amount, the in-cylinder torque is lower than that of light fuel. On the other hand, in the case of heavy fuel, since the engine speed immediately after the first explosion is relatively small, more air is sent from the surge tank 28 into the cylinder, and the reference torque is larger than that of light fuel. Therefore, the degree of deviation between the reference torque immediately after the first explosion and the in-cylinder torque is greater for heavy fuel than for light fuel.

  From this point of view, the combustion state estimation device according to the present embodiment determines the property of the fuel based on the degree of deviation between the reference torque and the in-cylinder torque. When it is attempted to determine the fuel properties only with the in-cylinder torque, the in-cylinder torque may not include an error in the determination of the fuel properties because the torque variation factor due to the in-cylinder air amount is not taken into consideration. However, according to the present embodiment, the variation in the in-cylinder air amount is reflected in the reference torque obtained in synchronization with the in-cylinder torque, so that the fuel can be accurately calculated in consideration of the factor of torque fluctuation due to the in-cylinder air amount. Can be determined. Further, as described above, since the reference torque and the in-cylinder torque fluctuate in opposite directions in accordance with the properties of the fuel, the determination of the fuel properties from the degree of divergence between the reference torque and the in-cylinder torque makes the determination S The / N ratio can be increased, and the properties of the fuel can be determined with higher accuracy.

Next, a method for calculating the in-cylinder torque and the reference torque will be described. In this embodiment, to calculate the estimated indicated torque T _i to be described below as a cylinder torque. First, a description will be given of equations used for calculating the estimated indicated torque T _i. In the present embodiment, the combustion state is estimated using the following equations (1) and (2).

In the expressions (1) and (2), the indicated torque T _i (estimated indicated torque T _i ) is a torque generated in the crankshaft 36 by the combustion of the engine. Here, (2) the right side shows the torque generated indicated torque T _i, shows a torque consuming (1) is on the right side indicated torque T _i.

(1) On the right side of the formula, 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 time of running The load torque received from the road surface is shown. 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 this embodiment, in order to estimate the combustion state with the shift gear in the neutral state, T _l = 0 in the following description.

Further, in (2) of the right _{side, T gas} is the torque due to cylinder gas pressure in the cylinder (in-cylinder _{torque), T inertia} represents the inertial torque due to reciprocating inertia mass such as a piston 34. Torque T _gas due to in-cylinder gas pressure is torque generated by combustion of the air-fuel mixture in the cylinder. In order to accurately estimate the combustion state, it is necessary to obtain the torque T _gas by the cylinder gas pressure.

As shown in the equation (1), the indicated torque T _i can be obtained as the sum of dynamic loss torque J × (dω / dt) due to angular acceleration, friction torque T _f , and load torque T _l. it can. However, as shown in the equation (2), the indicated torque T _i and the torque T _gas due to the in-cylinder gas pressure do not coincide with each other, so that the combustion state cannot be accurately estimated from the indicated torque T _i .

FIG. 3 is a characteristic diagram showing the relationship between each torque and crank angle in equation (2). In FIG. 2, the vertical axis of the torque magnitude, the horizontal axis represents the crank angle, the one-dot chain line indicated torque T _i in FIG. 3, the solid line a torque T _gas by the in-cylinder gas pressure, the broken lines Indicates the inertia torque T _inertia due to the reciprocating inertia mass. Here, FIG. 3 shows the characteristics in the case of four cylinders. TDC and BDC in FIG. 3 are the top dead center (TDC) or the bottom dead center of the piston 34 of one of the four cylinders. The crank angle (0 °, 180 °) in the (BDC) position is shown. When the internal combustion engine 10 has four cylinders, each time the crankshaft 36 rotates 180 °, an explosion (expansion) stroke is performed for each cylinder, and the torque characteristics from TDC to BDC in FIG. 3 are repeated for each explosion. appear.

As shown by the solid line in FIG. 3, the torque T _gas due to the in-cylinder gas pressure rapidly increases and decreases between TDC and BDC. 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. When the crank angle reaches BDC, the change in the volume of the cylinder becomes zero, whereby T _gas takes a value of zero.

On the other hand, 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 crank rotates, even if the angular velocity is constant. As shown by the broken line in FIG. 3, the member that reciprocates is stopped at the position where the crank angle is TDC, and T _inertia = 0. When the crank angle advances from TDC toward BDC, 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. After that, when the crank angle reaches BDC, the reciprocating member stops and T _inertia = 0.

As shown in the equation (2), the indicated torque T _i is the sum of the torque T _gas caused by the in-cylinder gas pressure and the inertia torque T _inertia caused by the reciprocating inertia mass. For this reason, as shown by the one-dot chain line in FIG. 3, between TDC and BDC, the indicated torque T _i increases due to an increase in T _gas due to the explosion of the air-fuel mixture, and once decreases, then increases again due to T _inertia . It shows the complicated behavior.

However, paying attention to a section with a crank angle of 180 ° from TDC to BDC, 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, when the torques in the equations (1) and (2) are calculated as average values from TDC to BDC, the inertia torque T _inertia due to the reciprocating inertia mass can be calculated as zero. As a result, it is possible to eliminate the influence of the inertia torque T _inertia due to the reciprocating inertia mass on the indicated torque T _i, and it is possible to accurately estimate the indicated torque T _i . Therefore, it is possible to easily estimate an accurate combustion state based on the indicated torque T _i.

When the average value of each torque in the interval from TDC to _{BDC, T} the average value of _inertia becomes zero, from equation (2), the torque T by the average value and the in-cylinder gas pressure indicated torque _{T i} The average value of _gas becomes equal. Therefore, it is possible to estimate accurately the combustion state based on the indicated torque T _i.

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. Therefore, it is possible to calculate the angular acceleration caused only by the combustion state, and it is possible to accurately estimate the combustion state based on the angular acceleration.

Then, (1) to calculate the respective torque of the right side of the equation, a method for obtaining the left-hand side indicated torque T _i. First, a method of calculating dynamic loss torque T _ac = J × (dω / dt) resulting from angular acceleration will be described. FIG. 4 is a schematic diagram showing a method for obtaining the angular acceleration of the crankshaft 36. As shown in FIG. 4, in this embodiment, a crank angle signal is detected from the crank angle sensor 38 every 10 ° of rotation of the crankshaft 36.

The combustion state estimation apparatus according to the present embodiment calculates the dynamic loss torque _Tac caused by the angular acceleration as an average value in a section with a crank angle of 180 ° from TDC to BDC. 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, as shown in FIG. 4, the time Δt ₀ (k) and Δt ₁₀ (k) during which the crank angle is rotated 10 ° forward and backward from the TDC position are calculated. It is detected from the crank angle sensor 38. Since the crankshaft 36 rotates 20 ° during the time Δt ₀ (k) + Δt ₁₀ (k), ω ₀ (k) = (20 / (Δt ₀ (k) + Δt ₁₀ (k))) By calculating x (π / 180), ω ₀ (k) [rad / s] can be calculated. Similarly, when calculating ω ₀ (k + 1), the times Δt ₀ (k + 1) and Δt ₁₀ (k + 1) during which the crank angle rotates by 10 ° forward and backward from the BDC position are detected. _{Then, ω 0 (k + 1)} = (20 / (Δt 0 (k + 1) + Δt 10 (k + 1))) × (π / 180) ω by computing ₀ (k + 1) can be calculated [rad / s].

After obtaining the angular velocities ω ₀ (k), ω ₀ (k + 1), (ω ₀ (k + 1) −ω ₀ (k)) / Δt (k) is calculated, and the crankshaft 36 rotates from TDC to BDC. The average value of the angular acceleration is calculated.

  After the average value of angular acceleration is obtained, the average value of angular acceleration and the moment of inertia J are multiplied according to the right side of equation (1). As a result, an average value of dynamic loss torque 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.

In the above-described example, the dynamic loss torque _Tac due to the angular acceleration is obtained from the angular velocities at the TDC and the BDC. However, the section from the TDC to the BDC is further divided into a plurality of sections. Dynamic loss torque due to acceleration may be obtained, and these loss torques may be averaged to obtain loss torque _Tac every 180 °. For example, the crank angle from TDC to BDC is divided into 6 equal parts every 30 °, and the dynamic loss torque T _ac between TDC and BDC is obtained by calculating and averaging the dynamic loss torque every 30 °. You may obtain | require the average value of. As a result, the number of crank angular velocity detection points can be increased, and the crank angle detection error can be minimized.

Next, a method for calculating the friction torque _Tf will be described. FIG. 5 is a map showing the relationship between the friction torque _Tf , the engine speed (Ne) of the internal combustion engine 10 and the coolant temperature (thw). In FIG. 5, the friction torque T _f , the engine speed (Ne), and the cooling water temperature (thw) are average values when the crankshaft 36 is rotated 180 ° from TDC to BDC. Further, the cooling water temperature becomes higher in the order of thw1 → thw2 → thw3. As shown in FIG. 5, the friction torque _Tf tends to increase as the engine speed (Ne) increases and increase as the cooling water temperature (thw) decreases. The map of FIG. 5 measures the friction torque _Tf generated when the crankshaft 36 is rotated from TDC to BDC by varying the engine speed (Ne) and the coolant temperature (thw) as parameters, and the average value thereof. It is created in advance by calculating. Then, when estimating the combustion state, the average value of the coolant temperature and the average value of the engine speed in the section from TDC to BDC are applied to the map of FIG. 5 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. Therefore, by _obtaining the average value of the friction torque ^Tf for each section (TDC → BDC) with a crank angle of 180 ° where the average value of the inertia torque T _inertia due to the reciprocating inertia mass is zero, the friction torque showing a complex instantaneous behavior is obtained. _Tf can be obtained with high accuracy. Moreover, the map shown in FIG. 5 can be accurately created by setting the friction torque ^Tf to an average value for each section.

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 obtained from the map of FIG. It is desirable to correct the value of _Tf .

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.

After obtaining the dynamic loss torque T _ac and the friction torque T _f due to angular acceleration, by adding the T _ac and T _f (1) to calculate the left-hand side indicated torque T _i in equation. The indicated torque T _i calculated here is calculated as an average value of a section having a crank angle of 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 (2).

FIG. 6 is a schematic diagram showing the relationship between the indicated torque T _i (k) (= T _gas (k)) calculated from the equation (1) and each stroke of each cylinder. Here, k is a cycle counter, and T _i (k) is the indicated torque in the kth explosion stroke from the first explosion. As shown in FIG. 6, when the internal combustion engine 10 is composed of four cylinders # 1 to # 4, the explosion stroke is performed in the order of # 1, # 3, # 4, and # 2 every 180 ° rotation of the crankshaft 36. Is done. When the indicated torque T _i is sequentially calculated for each explosion stroke, that is, every crank angle of 180 °, the indicated torque T _i (k) corresponds to the explosion of the cylinder # 1, as shown in FIG. Similarly, the indicated torque T _i (k−2) is the explosion of cylinder # 4, the indicated torque T _i (k−1) is the explosion of cylinder # 2, and the indicated torque T _i (k + 1) is # 3. The indicated torque T _i (k + 2) corresponds to the explosion of the cylinder # 4.

Here, focusing on the stroke in which the indicated torque T _i (k) is generated, # 1 is the explosion stroke, # 3 is the compression stroke, # 4 is the intake stroke, and # 2 is the exhaust stroke. Here, compression, intake, the torque of the exhaust stroke, since it is very small compared to the torque due to cylinder gas pressure generated by the explosion stroke, the indicated torque T _i torque by the in-cylinder gas pressure generated by explosion # 1 It can be regarded as T _gas . Accordingly, by calculating the indicated torque in the order of T _i (k−2), T _i (k−1), T _i (k), T _i (k + 1), and T _i (k + 2), # 4, # 2 , # 1, # 3, # 4, the torque T _gas by the cylinder gas pressure due to the explosion of each cylinder can be calculated.

Next, a method for calculating the reference torque will be described. As described above, 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 T _ia (k) can be calculated from the following equation (3).

T _ia (k) = A · mc (k) + B (3)

In the formula (3), mc (k) is the in-cylinder air amount in the kth explosion stroke from the first explosion. A and B are predetermined constants representing the relationship between the reference torque T _ia (k) and the in-cylinder air amount mc (k), but may be variables according to operating conditions and the like. As shown in the equation (3), the reference torque T _ia (k) is the in-cylinder air amount mc (k) in the kth explosion stroke from the first explosion, that is, the intake air corresponding to the kth explosion stroke from the first explosion. It can be calculated from the amount of air flowing into the cylinder during the stroke.

  Since the in-cylinder air amount mc (k) in the equation (3) is linearly related to the intake pipe pressure (in-cylinder pressure), it can be calculated from the following equation (4).

mc (k) = C · pm (k) + D (4)

  In equation (4), 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. In the equation (4), C and D are conformity constants.

Thus, according to the equations (3) and (4), 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 as a map, and the value of the in-cylinder air amount mc (k) corresponding to the intake pipe pressure pm (k) is mapped. You may get from.

  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 varies according to the intake pipe pressure as described above, and also varies according to the engine speed, so that 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.

After calculating the estimated indicated torque _T i (k) and the reference torque _T ia (k), obtaining the degree of deviation of both torque by comparing the estimated indicated torque _T i (k) and the reference torque _T ia (k). The degree of deviation is determined from, for example, the ratio r (k) of the estimated indicated torque T _i (k) to the reference torque T _ia (k). The ratio r (k) is calculated from the following equation (5).

r (k) = T _i (k) / T _ia (k) (5)

In the equation (5), T _i (k) is the estimated indicated torque calculated in the kth explosion stroke from the first explosion as described above. On the other hand, the reference torque T _ia (k) is obtained from the in-cylinder air amount mc (k) that flows into the cylinder during the intake stroke (k-th intake stroke from the first explosion) in the same cycle as the k-th explosion stroke from the first explosion. This is the calculated torque. Therefore, when calculating r (k), the cylinder air amount mc (k) is first obtained in the intake stroke of the same cycle as the kth explosion stroke from the first explosion, and is based on the cylinder air amount mc (k). After calculating the reference torque T _ia (k), the value is held. Then, when the explosion stroke is performed in the cycle, the estimated indicated torque T _i (k) is calculated, and using T _i (k) and the retained T _ia (k), the equation (5) By calculating, r (k) is calculated.

As described above, the reference torque T _ia (k) is a theoretical torque when the air-fuel mixture in the cylinder burns at the stoichiometric air-fuel ratio, and the ignition timing is calculated as MBT (Minimum Spark Advance for Best Torque). doing. Therefore, the reference torque T _ia (k) is usually calculated as a value larger than the in-cylinder torque T _i (k), and the value of r (k) is smaller than 1.

Since the calculated value of r (k) may include an error due to combustion variations, the accuracy of determination is determined when the fuel property is determined based on r (k) calculated only in one cycle after the first explosion. May deteriorate. Therefore, after the first explosion, the value of r (k) calculated in several cycles is integrated to obtain an integrated value Sr (k), and the combustion state and the properties of the fuel are determined based on Sr (k). desirable. As a result, even if there is a variation in the estimated indicated torque T _i (k) due to the variation in combustion, it is possible to determine the combustion state and the properties of the fuel with high accuracy.

FIG. 7 is a schematic diagram showing the relationship between the properties and combustion state of the fuel and the value of Sr (k). As the value of r (k) is larger, the values of T _ia (k) and T _i (k) are approximated, and the degree of divergence between T _ia (k) and T _i (k) is smaller. Therefore, as shown in FIG. 7, the larger the value of Sr (k), the better the combustion state, and it can be determined that the property of the fuel is light. On the other hand, the value of Sr as (k) is small _T ia (k) and _T i (k) are _different, the degree of deviation _T ia (k) and _T i (k) is increased. Therefore, as shown in FIG. 7, the smaller the value of Sr (k), the more the combustion state deteriorates, and it can be determined that the fuel property is heavy.

  In the case of heavy fuel, the fuel is likely to adhere to the intake port, and immediately after the first explosion, the intake passage 12 is not sufficiently warmed, so that the fuel attached to the wall surface of the intake port is difficult to atomize. Therefore, by performing the determination immediately after the first explosion, the combustion state in the cylinder and the properties of the fuel are accurately reflected in the calculated value of the in-cylinder torque (estimated indicated torque), and the combustion state and the properties of the fuel are high. It is possible to determine with accuracy. This makes it possible to determine the combustion state and the properties of the fuel early after the first explosion. In addition, air-fuel ratio feedback control is performed after a predetermined period from the first explosion, and the air-fuel ratio is controlled according to the combustion state and fuel properties, and the combustion state and fuel properties are reflected in the calculated value of the in-cylinder torque. May not be. Therefore, from this point of view, it is preferable to perform the determination immediately after the first explosion.

  Next, a processing procedure in the combustion state estimation device of the present embodiment will be described based on the flowchart of FIG. First, in step S1, it is determined whether a determination condition for determining the combustion state is satisfied. Here, it is determined whether or not the current cycle number k has reached a predetermined cycle number N, that is, whether or not k = N. If k ≠ N, since the current cycle number has not reached N, it is determined that the number of times of calculation of r (k) for determining the combustion state and fuel properties is insufficient, and the process proceeds to step S2. . Then, further r (k) is calculated after step S2. On the other hand, if k = N, the process proceeds to step S7. In step S1, the total amount of fuel injected from the fuel injection valve 30 between the initial explosion and the current cycle is compared with a predetermined threshold value, and the total fuel injection amount is determined to be a predetermined threshold value. It is good also as progressing to step S7 when exceeding.

In step S2, the intake pipe pressure pm (k) in the intake stroke of the current cycle k is detected from the intake pipe pressure sensor 29. At this time, the intake pipe pressure pm (k) corresponding to the in-cylinder air amount can be calculated by detecting the intake pipe pressure pm (k) at the timing when the intake valve closes as described above. In the next step S3, the in-cylinder air amount mc (k) is calculated from the above-described equation (4) using the intake pipe pressure pm (k). In the next step S4, the reference torque T _ia (k) is calculated from (3) described above using the in-cylinder air amount mc (k).

In the next step S5, the estimated indicated torque T _i (k) is calculated. Here, the average value of the angular acceleration is obtained in the section of the crank angle of 180 ° in the explosion stroke of the current number of cycles k, and the estimated indicated torque T _i (k) is calculated.

In the next step S6, the ratio r (k) of the estimated indicated torque T _i (k) to the reference torque T _ia (k) is calculated. Then, r (k) is added to the accumulated value Sr (k−1) of r (k) up to the previous cycle k−1 to obtain the accumulated value Sr (k) up to the current cycle k. Then, the value of the cycle counter is updated to k + 1, and the process ends (END).

If k = N in step S1, the process for determining the combustion state and the fuel properties is performed in step S7. Here, for example, the magnitude relationship between the integrated value Sr (k) of r (k) up to the current cycle and a predetermined threshold value T is compared, and the integrated value Sr (k) is determined to be the predetermined threshold value T. Is exceeded, it is determined that the degree of deviation between the reference torque T _ia (k) and the estimated indicated torque T _i (k) is small, and it is determined that the fuel property is light (combustion state good). On the other hand, when the integrated value Sr (k) is less than or equal to the predetermined threshold value T, it is determined that the degree of deviation between the reference torque T _ia (k) and the estimated indicated torque T _i (k) is large, and the fuel properties are heavy. It is determined that the quality (combustion state deterioration).

  In step S7, without comparing the integrated value Sr (k) with the threshold value T, the combustion state and the properties of the fuel are continuously determined based on the magnitude of the integrated value Sr. Good.

9, the estimated indicated torque T _i in step S5 in FIG. 8 a flowchart illustrating a method of calculating the _(k), for each power stroke of each cylinder, that is, estimated indicated torque T _i for each crank angle 180 ° _(k) The process which calculates is shown. Hereinafter, a process of calculating the estimated indicated torque T _i (k) will be described based on the flowchart of FIG. First, in step S11, it is determined whether or not an operating condition for calculating the estimated indicated torque T _i (k) is satisfied. Here, it is determined whether or not the operating condition is a steady state and a no-load state. If the operating condition is satisfied, the process proceeds to step S12, and if not satisfied, the process ends (END).

  In the next step S12, it is determined whether or not the crank angle position is the torque calculation timing. If it is time to calculate the torque, the process proceeds to step S13. If it is not time to calculate the torque, the process ends (END).

In step S13, 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.

In the next step S14, 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 coolant temperature (thw (k)), and is an average value in the section from TDC to BDC from the map of FIG. Ask for.

In the next step S15, it is determined whether or not the auxiliary equipment is switched on. When the switch is on (ON), the process proceeds to step S16, and the friction torque T _f (k) obtained in step S14 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). If the switch is off in step S15, the process proceeds to step S17.

In step S17, a dynamic loss torque T _ac (k) due to 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.

In the next step S18, 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). If T _f (k) is corrected in step S16, the calculation is performed using the corrected T _f (k). The estimated indicated torque T _i (k) obtained here is the average value of the section from TDC to BDC.

In the section from TDC to BDC, since the average value of inertia torque T _inertia due to reciprocating inertia mass = 0, the estimated indicated torque T _i (k) obtained from equation (2) is the torque due to in-cylinder gas pressure. T _gas (k).

As described above, according to the first embodiment, combustion is performed in consideration of fluctuations in the in-cylinder air amount using the reference torque T _ia (k) and the in-cylinder torque (estimated indicated torque T _i (k)). It becomes possible to determine the state and the properties of the fuel. As a result, even when the in-cylinder air amount fluctuates due to the cranking time at the start, the engine speed, etc., the combustion state can be estimated with high accuracy. Further, since the reference torque T _ia (k) and the in-cylinder torque (estimated indicated torque T _i (k)) vary in opposite directions depending on the properties of the fuel, the fuel is determined based on the degree of deviation between the reference torque and the in-cylinder torque. By determining the properties of the fuel, the S / N ratio of the determination can be increased, and the properties of the fuel can be determined with higher accuracy.

Further, according to the combustion state estimation device of the present embodiment, since the average value of the angular acceleration of the crankshaft 36 is calculated in a section where the average value of the inertia torque T _inertia due to the reciprocating inertia mass is 0, T _internal is calculated as follows. The influence on the angular acceleration can be eliminated, and the angular acceleration and the dynamic loss torque T _ac due to the angular acceleration can be obtained only from the information corresponding to the combustion state. Further, since the average value of the friction torque is obtained in the section where the average value of the inertia torque T _inertia due to the reciprocating inertia mass is 0, the friction torque T _f is accurately obtained without being affected by the instantaneous friction behavior. be able to. Therefore, it is possible to determine the absolute value of the estimated indicated torque T _i that corresponds to the combustion state at high accuracy, it becomes possible to accurately estimate the combustion state based on the estimated indicated torque T _i.

In the example described above, the section where the average value of inertia torque T _inertia due to reciprocating inertia mass is 0 is set to 180 °, but the section where the average value of T _inertia is 0 may be set wider. In the case of a four-cylinder internal combustion engine, since the minimum unit of the section where the average value of inertia torque T _inertia due to reciprocating inertia mass is 0 is 180 °, the interval where the average value of T _inert is 0 at an integral multiple of 180 ° Can be set. For example, when the frequency of estimating the estimated indicated torque T _i may be low, such as when torque control is performed using the estimated torque, a wider angle range such as 360 ° or 720 ° may be set. .

In the above-described example, the present invention is applied to a four-cylinder internal combustion engine, but even in an internal combustion engine other than the four-cylinder engine, by _obtaining a section where the average value of torque T _inertia due to reciprocating inertia mass is zero, The combustion state can be estimated as in the case of four cylinders. FIG. 10 is a diagram showing torque characteristics in an internal combustion engine other than the four-cylinder engine, and is a characteristic diagram showing the relationship between each torque and crank angle in equation (2), as in FIG. Here, FIG. 10A shows the case of a single cylinder, and FIG. 10B shows the case of 6 cylinders.

As shown in FIG. 10A, in the case of a single cylinder, one explosion stroke is performed every crank angle of 720 °, and the torque T _gas due to the in-cylinder gas pressure repeatedly increases and decreases with each explosion. . Then, the average value of the torque _{T inertia} caused by the reciprocating inertia mass in the interval of the crank angle 360 ° to 540 ° (dotted line) is zero. Therefore, the combustion state can be accurately estimated by obtaining the angular acceleration and the estimated indicated torque for each section.

The same applies to the case of the six cylinders shown in FIG. In the case of six cylinders, six explosion strokes are performed at every crank angle of 720 °, so that the torque T _gas due to the in-cylinder gas pressure repeatedly increases and decreases every 120 ° of the crank angle. And the average value of the inertia torque _Tinertia by a reciprocating inertia mass becomes 0 in the area of a crank angle 0 degree-120 degrees. Therefore, by obtaining the angular acceleration and estimated indicated torque for each crank angle of 120 °, the influence of the reciprocating inertial mass can be eliminated, and the combustion state can be accurately estimated. Since the crank rotation angle of one cycle is 720 °, particularly in the case of a multi-cylinder internal combustion engine, the angle range obtained by calculating (720 ° / number of cylinders) is the range where the average value of T _inert is 0. The minimum unit can be used.

In the above-described example, the average values of the crank angular acceleration, the loss torque, and the friction torque are calculated in a section where the average value of the inertia torque T _inertia due to the reciprocating inertia mass is 0. However, information other than the average value, for example, torque May be calculated in this interval. Since the influence of _Tinteria is excluded in this section, it is possible to accurately estimate the combustion state using other parameters such as an integrated value.

In the above-described example, the combustion state is estimated with the load torque T _l = 0. However, the load torque T _l is obtained based on information such as an inclination sensor and is used for estimating the indicated torque T _i , so that the vehicle travels. in the entire operating range it is possible to obtain the indicated torque T _i in. This makes it possible to reliably estimate the combustion state even when, for example, cold hesitation due to load changes occurs during cold start.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. In the second embodiment, the actually measured indicated torque T _{i_cps} is calculated from the detection value of the in-cylinder pressure sensor 44, and the properties of the fuel are determined using the actually measured _indicated torque T _{i_cps} and the reference torque T _ia .

As shown in FIG. 1, when the internal combustion engine 10 includes the in-cylinder pressure sensor 44, the actually measured indicated torque T _{i_cps} can be calculated from the detection value of the in-cylinder pressure sensor 44. For example, when the # 1 cylinder includes the in-cylinder pressure sensor 44, the actually measured _indicated torque T _{i_cps} can be calculated from the following equation (6).

In the equation (6), _{Ti_cps} is a value obtained by converting measured actual indicated torque (actual average indicated torque) averaged in one cycle (crank angle 720 °) in a section of 720 ° CA / number of cylinders. 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 the in-cylinder gas in one cycle (converted in a section of 720 ° CA / cylinder number), and, as shown in the equation (6), P for each crank angle θ. _It is obtained by calculating the product of _{# 1} (θ) and dV _{# 1} (θ) / dθ, calculating the average value (Average) in the section of one cycle, and multiplying by the number N of cylinders.

FIG. 11 is a schematic diagram showing the relationship between the calculated estimated indicated torque T _i (k) (= T _gas (k)) and the actually measured _indicated torque T _{i — cps} (k) and each stroke of each cylinder. As in FIG. 6, when the internal combustion engine 10 is composed of four cylinders # 1 to # 4, the explosion stroke is performed in the order of # 1, # 3, # 4, and # 2 every 180 ° rotation of the crankshaft 36. The estimated indicated torque T _i can be sequentially calculated from the equation (1) every explosion stroke, that is, every crank angle of 180 °.

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. . In FIG. 11, the stroke in which the estimated indicated torque T _i (k) is calculated is shown as a region A surrounded by a broken line, and the stroke in which the actually measured indicated torque T _{i_cps} (k) is calculated is shown as a region B # 1 surrounded by a one-dot chain line. ing. During steady operation, the torque generated in the intake stroke in the region A and the torque generated in the intake stroke in the region B # 1 can be regarded as substantially the same. Similarly, the torque generated in the compression and exhaust strokes in the region A and the torque generated in the compression and exhaust strokes in the region B # 1 can be regarded as substantially the same. Further, the explosion stroke in the area A and the explosion stroke in the area B # 1 are common. 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 with 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 . In addition, the measured _indicated torque T _{i_cps} (k + 2) is _calculated from the four strokes of intake, compression, explosion and exhaust of the # 4 cylinder in the k + 2 cycle, and from the four strokes of intake, compression, explosion and exhaust of the # 2 cylinder in the k + 3 cycle. The actually measured _indicated torque T _{i — cps} (k + 3) can be calculated. In FIG. 11, a region B # 3 and a region B # 4 in which the strokes where the actually measured _indicated torque T _{i_cps} (k + 1), the actually measured _indicated torque T _{i_cps} (k + 2), and the actually measured _indicated torque T _{i_cps} (k + 3) are calculated are surrounded by a one-dot chain line. And region B # 2. Thus, by providing the cylinder pressure sensors 44 in all the cylinders, the actually measured _indicated torques T _{i_cps} (k) to T _{i_cps} (k + 3) corresponding to the estimated indicated torques T _i (k) to T _i (k + 3). Can be sequentially calculated.

After calculating the actual indicated torque _{T I_cps} determines the properties of the combustion state and the fuel using measured indicated torque _{T I_cps} and the reference torque _{T ia.} In steady operation immediately after starting, the estimated indicated torques T _i (k) to T _i (k + 3)... And the measured _indicated torques T _{i_cps} (k) to T _{i_cps} (k + 3). _Therefore , it is possible to determine the combustion state and the properties of the fuel using the actually measured _indicated torque T _{i_cps} instead of the estimated _indicated torque T _{i in} the first embodiment.

Next, a method of reducing the number of cylinders provided with the in-cylinder pressure sensor 44 by using the estimated _indicated torque T _i (k) and the actually measured _indicated torque T _{i_cps} (k) will be described. FIG. 12 is a schematic diagram showing the relationship between the estimated indicated torque T _i (k) (= T _gas (k)) and the actually measured _indicated torque T _{i — cps} and each stroke of each cylinder, as in FIG. 11. Here, FIG. 12 shows a case where the in-cylinder pressure sensor 44 is provided in three cylinders # 1, # 3, and # 4.

In FIG. 11 described above, the actually measured _indicated torque T _{i_cps} is obtained for each section of the crank angle of 720 ° (one cycle), but in FIG. 12, the cylinders of # 1, # 3, and # 4 are provided for each crank angle of 180 °. Actual measured _indicated torques _{Ti_cps # 1} , _{Ti_cps # 3} , _{Ti_cps # 4} are calculated. The actually measured _indicated torque _{Ti_cps for} each crank angle of 180 ° can be calculated by setting the torque calculation section of equation (6) to the crank angle of 180 °. For example, the actually measured _indicated torque T _{i_cps # 1} (k) in the section of the crank angle 180 ° corresponding to the explosion stroke of the # 1 cylinder in the k-th cycle is P for each crank angle θ as shown in the following equation (7). It is obtained by calculating a product of _{# 1} (θ) and dV _{# 1} (θ) / dθ and calculating an average value (Average) in a section of a crank angle of 180 ° (180 ° CA).

Similarly, for the # 3 and # 4 cylinders provided with the in-cylinder pressure sensor 44, the following expressions (8) and (9) are calculated in the same crank angle 180 ° section as the explosion stroke of the # 1 cylinder in the k-th cycle. , The measured _indicated torque T _{i_cps # 3} (k) in the compression stroke of the # 3 cylinder and the measured _indicated torque T _{i_cps # 4} (k) in the intake stroke of the # 4 cylinder can be calculated, respectively.

On the other hand, the estimated indicated torque T _i (k) calculated based on the detected value of the crank angle sensor 38 is a torque generated in each stroke of the region A surrounded by a broken line in FIG. Measured _indicated torque T _{i_cps # 1} (k) in the explosion stroke, measured _indicated torque T _{i_cps # 3} (k) in the compression stroke of the # 3 cylinder, measured _indicated torque T _{i_cps # 4} (k) in the intake stroke of the # 4 cylinder, This corresponds to the total torque of the measured _indicated torque T _{i_cps # 2} (k) in the exhaust stroke of the # 2 cylinder. Therefore, from the estimated indicated torque _T i (k), the measured indicated torque _{T i_cps # 1 (k),} T i_cps # 3 (k), by subtracting the sum of the _{T i_cps #} 4 (k), the cylinder pressure sensor 44 It is possible to calculate the torque (T _{i # 2} (k)) corresponding to the actually measured _indicated torque T _{i_cps # 2} (k) of the # 2 cylinder not provided with.

In a similar _{manner, T i_cps # 1 (k +} 1), T i_cps # 3 (k + 1), T i_cps # 4 (k + 1), and _T i (k + 1) from the not provided with the cylinder pressure sensor 44 # 2 cylinder of the actual measurement shown Torque (T _{i # 2} (k + 1)) corresponding to torque T _{i_cps # 2} (k + 1) can be calculated, and T _{i # 2} (k + 2), T _{i # 2} (k + 3). It is possible to calculate.

When obtaining the indicated mean effective pressure, the indicated mean effective pressure is the work for one cycle of one cylinder, so the indicated mean effective pressure P _{i # 2} (i) of the # 2 cylinder is 1 cycle (crank angle 720 °). ) T _{i # 2} (k), T _{i # 2} (k + 1), T _{i # 2} (k + 2), T _{i # 2} (k + 3) calculated in the section of ). That is, the indicated mean effective pressure P _{i # 2} (i) can be calculated from the following equation (10).

  Therefore, the illustrated mean effective pressure (IMEP) can be calculated without providing the in-cylinder pressure sensor 44 for one of the four cylinders, and the same information extraction as when the in-cylinder pressure sensor 44 is installed in all cylinders is possible. It becomes. Therefore, the manufacturing cost of the combustion state estimation device can be reduced. Similarly, for N-cylinder engines other than the four cylinders, it is possible to calculate the torque of all the cylinders and the indicated mean effective pressure by providing in-cylinder pressure sensors 44 for N-1 cylinders.

In this case, the calculation section of the actually measured _indicated torque _{Ti_cps} is not limited to the crank angle of 180 °. For example, as in the case of FIG. 11, the measured _indicated torques _{Ti_cps # 1} , _{Ti_cps # 3} , _{Ti_cps # 4} of the cylinders _{# 1} , _{# 3} , and _{# 4} are calculated in the section of the crank angle 720 ° (1 cycle). , by subtracting the sum of the measured indicated torque _{T i_cps # 1, T i_cps #} 3, T i_cps # 4 from the estimated indicated torque _{T i} calculated in interval of the crank angle 720 °, # 2 cylinder in the interval of the crank angle 720 ° The torque corresponding to the actually measured _indicated torque _{Ti_cps # 2} may be calculated. At this time, the estimated indicated torque T _i is calculated using the angular velocities detected at both ends of the section of the crank angle of 720 °.

When the crank angle is detected, the edge position of the rotor provided on the crankshaft 36 is detected by the crank angle sensor 38. Since the crankshaft 36 rotates twice in the section of the crank angle 720 °, the crank angle 720 ° The angular velocities detected at both ends of this section are detected at the same portion of the rotor provided on the crankshaft 36. Therefore, even if the manufacturing error in the edge of the rotor has occurred, that the error due to manufacturing error without would be included in the torque calculation value, for calculating an estimated indicated torque T _i with high precision it can. Similarly, by the crank angle (n is a natural number) n rotation to calculate the estimated indicated torque T _i in the interval to, even if the manufacturing error in the edge of the rotor occurs, accurately estimated indicated torque T _i Can be calculated.

As described above, according to the second embodiment, the measured state torque T _{i_cps} is used instead of the estimated indicated torque T _i (k), so that the combustion state and the fuel property are determined as in the first embodiment. It becomes possible to do. Further, by using a combination of the measured indicated torque T _{I_cps} the estimated indicated torque T _i, it is possible to determine the nature of the combustion state and the fuel without providing a cylinder pressure sensor 44 in all cylinders. Therefore, the manufacturing cost of the combustion state estimation device can be reduced.

It is a schematic diagram for demonstrating the combustion state estimation apparatus of the internal combustion engine concerning Embodiment 1, 2 of this invention, and its surrounding structure. It is a characteristic view which shows a mode that a reference | standard torque and in-cylinder torque are fluctuate | varied. It is a characteristic view showing the relationship between the indicated torque, the torque due to in-cylinder gas pressure, the inertia torque due to reciprocating inertia mass, and the crank angle. It is a schematic diagram which shows the method of calculating | requiring the angular acceleration of a crankshaft. It is a schematic diagram which shows the map showing the relationship between friction torque, engine speed, and cooling water temperature. It is a schematic diagram which shows the relationship between the estimated indicated torque and each stroke of each cylinder. It is a schematic diagram which shows the relationship between the property and combustion state of a fuel, and ratio r (k) of reference torque T _ia (k) with respect to estimated indicated torque T _i (k). 3 is a flowchart showing a processing procedure of the combustion state estimation apparatus according to the first embodiment. It is a flowchart which shows the procedure of the process which calculates presumed illustration torque. It is a characteristic view which shows the torque characteristic in the case of a single cylinder and 6 cylinders. It is a schematic diagram which shows the relationship between the estimated indicated torque and the actually measured indicated torque, and each stroke of each cylinder. FIG. 5 is a schematic diagram showing the relationship between estimated indicated torque, actually measured indicated torque, and each stroke of each cylinder when an in-cylinder pressure sensor is provided in three of the four cylinders.

Explanation of symbols

29 Intake pipe pressure sensor 38 Crank angle sensor 40 ECU
44 In-cylinder pressure sensor

Claims (12)

Means for obtaining an in-cylinder air amount or a predetermined characteristic value that varies according to the in-cylinder air amount;
A reference torque calculating means for calculating a theoretical reference torque generated in the cylinder based on the in-cylinder air amount or the predetermined characteristic value;
In-cylinder torque calculating means for calculating in-cylinder torque generated by actual combustion in the cylinder;
Based on the result of comparing the reference torque and the in-cylinder torque, determination means for determining the combustion state in the cylinder or the property of the fuel;
A combustion state estimation device for an internal combustion engine, comprising:   The combustion state estimating device for an internal combustion engine according to claim 1, wherein the predetermined characteristic value includes an intake pipe pressure or an engine speed.   The combustion state of the internal combustion engine according to claim 1 or 2, wherein the determination means determines a combustion state in the cylinder or a property of the fuel based on a degree of deviation between the reference torque and the in-cylinder torque. Estimating device.   4. The combustion state estimating device for an internal combustion engine according to claim 3, wherein the determination unit determines that the combustion state is deteriorated as the degree of deviation between the reference torque and the in-cylinder torque is larger.   4. The combustion state estimating apparatus for an internal combustion engine according to claim 3, wherein the determining means determines that the property of the fuel is heavier as the degree of deviation between the reference torque and the in-cylinder torque is larger. Means for obtaining a relative ratio between the reference torque and the in-cylinder torque or a deviation between the reference torque and the in-cylinder torque;
The combustion state of the internal combustion engine according to any one of claims 3 to 5, wherein the determination unit determines a degree of deviation between the reference torque and the in-cylinder torque based on the ratio or the deviation. Estimating device. An integrated value calculating means for calculating an integrated value of the ratio or the deviation;
The combustion state estimation device for an internal combustion engine according to claim 6, wherein the determination means determines a degree of deviation between the reference torque and the in-cylinder torque based on the integrated value. Crank angular acceleration calculating means for calculating crank angular acceleration is provided,
The combustion state estimating device for an internal combustion engine according to any one of claims 1 to 7, wherein the in-cylinder torque calculating means calculates the in-cylinder torque based on the crank angular acceleration. A storage means for storing a standard friction characteristic that defines a relationship between the predetermined parameter and the engine friction torque;
9. The combustion state estimating apparatus for an internal combustion engine according to claim 8, wherein the in-cylinder torque calculating means calculates the in-cylinder torque based on the friction torque and the crank angular acceleration.   10. The combustion of the internal combustion engine according to claim 8, wherein the crank angular acceleration calculating unit calculates the crank angular acceleration in a crank angle section in which an average value of inertia torque due to reciprocating inertial mass is substantially zero. State estimation device. In-cylinder pressure detecting means for detecting the in-cylinder pressure,
The combustion state estimating device for an internal combustion engine according to any one of claims 1 to 7, wherein the in-cylinder torque calculating means calculates the in-cylinder torque based on the in-cylinder pressure. Crank angular acceleration calculating means for calculating crank angular acceleration;
The in-cylinder pressure detecting means provided in (total number of cylinders -1) cylinders,
12. The combustion state estimating device for an internal combustion engine according to claim 11, wherein the in-cylinder torque calculating means calculates the in-cylinder torque based on the crank angular acceleration and the in-cylinder pressure.

Images