JP4207870B2 - Internal combustion engine control device and misfire determination method - Google Patents

Description

  The present invention relates to a control device and a misfire determination method for an internal combustion engine that generates power by burning a mixture of fuel and air in a cylinder.

  Conventionally, as an apparatus for detecting the combustion state of an internal combustion engine, a misfire determination index calculated based on the superimposed in-cylinder pressure signal is used by superimposing the in-cylinder pressure signal of each combustion chamber detected by the in-cylinder pressure detecting means. For example, a technique for determining a misfire state is known (for example, see Patent Document 1). In this way, if the in-cylinder pressure of each of the plurality of combustion chambers is superimposed, a remarkable change in the symmetry of the signal waveform around the top dead center will be recognized depending on the presence or absence of misfire. The misfire determination can be executed in the entire area.

JP-A-11-82150

  However, in the above-described conventional combustion state detection device for an internal combustion engine, basically, the misfire determination index is calculated by integrating the in-cylinder pressure detected by the in-cylinder pressure detecting means for each minute unit crank angle. For this reason, the calculation load in the conventional combustion state detection device is enormous, and it has not been easy in practice to apply the conventional device to, for example, a vehicle internal combustion engine.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a practical internal combustion engine controller and a misfire determination method that can accurately determine a misfire state in a cylinder with a low load.

  An internal combustion engine control apparatus according to the present invention includes an in-cylinder pressure detecting means for detecting in-cylinder pressure and an in-cylinder pressure detecting means in an internal combustion engine control apparatus for generating power by burning a mixture of fuel and air in a cylinder. Calculated by the control parameter calculating means for calculating a control parameter that is a product of the in-cylinder pressure detected by the value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined index; A difference calculating means for obtaining a difference between the plurality of control parameters, an integrating means for integrating the plurality of differences calculated by the difference calculating means, and a misfire state in the cylinder based on the integrated value calculated by the integrating means. And a misfire determination means capable of being determined.

  The control device for an internal combustion engine according to the present invention further includes an operation state determination unit that determines whether or not the internal combustion engine is in a predetermined operation state, and the misfire determination unit is configured to perform the predetermined operation of the internal combustion engine by the operation state determination unit. When it is determined that the vehicle is in the state, it is preferable to determine the misfire state in the cylinder based on the integrated value calculated by the integrating means.

A misfire determination method for an internal combustion engine according to the present invention is a misfire determination method for an internal combustion engine that generates power by burning a mixture of fuel and air in a cylinder.
(A) detecting in-cylinder pressure for at least three measurement points;
(B) For each measurement point, calculating a control parameter that is the product of the in-cylinder pressure detected in step (a) and the value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined index. When,
(C) obtaining a difference between the control parameters calculated in step (b);
(D) integrating a plurality of differences calculated in step (c);
(E) determining a misfire state in the cylinder based on the integrated value calculated in step (d).

  In this case, at least before step (e), the method further includes a step (f) of determining whether or not the internal combustion engine is in a predetermined operation state, and it is determined in step (f) that the internal combustion engine is in a predetermined operation state. In such a case, it is preferable to determine the misfire state in the cylinder based on the integrated value in step (e).

  According to the present invention, it is possible to realize a practical internal combustion engine control device and misfire determination method that can accurately determine the misfire state in a cylinder with a low load.

The inventors of the present invention have made extensive studies in order to enable highly accurate control of an internal combustion engine while reducing the calculation load. As a result, the inventors have focused on control parameters calculated based on the in-cylinder pressure detected by the in-cylinder pressure detecting means and the in-cylinder volume at the time of detecting the in-cylinder pressure. More specifically, the inventors set P (θ) as the in-cylinder pressure detected by the in-cylinder pressure detecting means when the crank angle is θ, and the in-cylinder volume when the crank angle is θ as V (Θ), where the specific heat ratio is κ, the in-cylinder pressure P (θ) and the value V ^κ (θ) obtained by raising the in-cylinder volume V (θ) to the specific heat ratio (predetermined index) κ The control parameter P (θ) · V ^κ (θ) obtained as a product (hereinafter referred to as “PV ^κ ” as appropriate) was focused on. The inventors of the present invention have a correlation between the change pattern of the heat generation amount Q in the cylinder of the internal combustion engine with respect to the crank angle and the change pattern of the control parameter PV ^κ with respect to the crank angle as shown in FIG. I found. In FIG. 1, −360 °, 0 °, and 360 ° correspond to the top dead center, and −180 ° and 180 ° correspond to the bottom dead center.

In FIG. 1, the solid line shows the in-cylinder pressure detected at predetermined minute crank angles in a predetermined model cylinder and the value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined specific heat ratio κ. This is a plot of the control parameter PV ^κ which is the product. In FIG. 1, the broken line is calculated and plotted with the heat generation amount Q in the model cylinder as Q =） dQ based on the following equation (1). In either case, for simplicity, κ = 1.32.

As can be seen from the results shown in FIG. 1, the change pattern of the heat generation amount Q with respect to the crank angle and the change pattern of the control parameter PV ^κ with respect to the crank angle are almost the same (similar), and in particular, Before and after the start of combustion of the air-fuel mixture (at the time of spark ignition for a gasoline engine and at the time of compression ignition for a diesel engine) (for example, in the range from about −180 ° to about 135 ° in FIG. 1) It can be seen that the change pattern of the control parameter PV ^κ agrees very well.

That is, the control parameter PV ^κ focused by the present inventors reflects the heat generation amount in the cylinder of the internal combustion engine as described above. Therefore, the amount of heat generated in a cylinder between two points ∫dQ (a value obtained by integrating dQ from θ _x to θ _y [however, θ _x <θ _y ], the same applies hereinafter) is controlled between the two points. Difference of parameter PV ^κ ΔPV ^κ = P (θ _y ) · V ^κ (θ _y ) −P (θ _x ) · V ^κ (θ _x )
Can be obtained as The difference ΔPV ^κ can be calculated with an extremely low load, and a calculation process with a large load such as an integration process for each minute unit crank angle is not required for the calculation.

On the other hand, when a misfire occurs in a certain cylinder, the amount of heat generation is smaller in that cylinder than in a cylinder where no misfire has occurred. Therefore, by utilizing the relationship between the heat generation amount in the cylinder and the misfire state, and the correlation between the heat generation amount in the cylinder and the control parameter PV ^κ found by the present inventors, The misfire state in the cylinder is determined at low load based on the difference ΔPV ^κ of the control parameter PV ^κ calculated based on the in-cylinder pressure detected by the internal pressure detecting means and the in-cylinder volume at the time of detection of the in-cylinder pressure. It becomes possible. However, the value of the control parameter PV ^κ also becomes small under an operating state where the in-cylinder pressure is relatively low, for example. In such a case, a significant difference in the difference ΔPV ^κ between the control parameters PV ^κ is not recognized between the normal state and the misfire state, and there is a possibility that the misfire state in the cylinder cannot be accurately determined. .

In view of such a point, in the present invention, the misfire state in the cylinder is determined based on an integrated value obtained by integrating a plurality of differences ΔPV ^κ indicating a heat generation amount between two certain points. That is, in the present invention, for example, in-cylinder pressure is detected for at least three measurement points between a certain timing before the start of combustion (spark ignition or compression ignition) and a certain timing after the start of combustion. A control parameter PV ^κ that is the product of the in-cylinder pressure and the value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined index is calculated. Furthermore, the difference ΔPV ^κ between the plurality of control parameters PV ^κ calculated in this way is obtained, and the obtained plurality of differences ΔPV ^κ are integrated. Then, if the integrated value of the obtained difference ΔPV ^κ is below a predetermined threshold, for example, it is determined that the cylinder is in a misfire state. Thus, according to the present invention, it is possible to accurately determine the misfire state in the cylinder while greatly reducing the calculation load.

Incidentally, the control parameter PV ^kappa for the difference Pv ^kappa between there is a risk that a significant difference is not observed, cylinder pressure, such as the occurrence of fouling of the idle time and the ignition plug is if relatively low. When the in-cylinder pressure is high to some extent, in general, there is a significant difference in the difference ΔPV ^κ of the control parameter PV ^κ between two certain points between normal combustion and misfire. In such a case, the misfire state in the cylinder can be determined based on the difference ΔPV ^κ . Therefore, it is determined whether or not the internal combustion engine is in a predetermined operating state, and when it is determined that the internal combustion engine is in a predetermined operating state where the in-cylinder pressure is low (only), based on the integrated value of the difference ΔPV ^κ. A determination of a misfire condition may be performed. As a result, only when the internal combustion engine is in a predetermined operating state, the integration process of the difference ΔPV ^κ needs to be executed. Therefore, it is possible to further reduce the calculation load required for the misfire determination of the internal combustion engine. .

  Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram showing an internal combustion engine according to the present invention. The internal combustion engine 1 shown in FIG. 1 generates power by burning a fuel / air mixture in a combustion chamber 3 formed in a cylinder block 2 and reciprocating a piston 4 in the combustion chamber 3. Is. The internal combustion engine 1 is preferably configured as a multi-cylinder engine, and the internal combustion engine 1 of the present embodiment is configured as a four-cylinder engine, for example.

  The intake port of each combustion chamber 3 is connected to an intake pipe (intake manifold) 5, and the exhaust port of each combustion chamber 3 is connected to an exhaust pipe 6 (exhaust manifold). In addition, an intake valve Vi and an exhaust valve Ve are provided for each combustion chamber 3 in the cylinder head of the internal combustion engine 1. Each intake valve Vi opens and closes a corresponding intake port, and each exhaust valve Ve opens and closes a corresponding exhaust port. Each intake valve Vi and each exhaust valve Ve are operated by, for example, a valve operating mechanism (not shown) having a variable valve timing function. Further, the internal combustion engine 1 has a number of spark plugs 7 corresponding to the number of cylinders, and the spark plugs 7 are disposed in the cylinder heads so as to face the corresponding combustion chambers 3.

  The intake pipe 5 is connected to a surge tank 8 as shown in FIG. An air supply line L1 is connected to the surge tank 8, and the air supply line L1 is connected to an air intake port (not shown) via an air cleaner 9. A throttle valve (in this embodiment, an electronically controlled throttle valve) 10 is incorporated in the middle of the air supply line L1 (between the surge tank 8 and the air cleaner 9). On the other hand, as shown in FIG. 2, for example, a front-stage catalyst device 11 a including a three-way catalyst and a rear-stage catalyst device 11 b including a NOx storage reduction catalyst are connected to the exhaust pipe 6.

  Furthermore, the internal combustion engine 1 has a plurality of injectors 12, and each injector 12 is disposed on the cylinder head so as to face the corresponding combustion chamber 3 as shown in FIG. 2. Each piston 4 of the internal combustion engine 1 is configured as a so-called deep dish top surface type, and has a concave portion 4a on its upper surface. In the internal combustion engine 1, fuel such as gasoline is directly injected from each injector 12 toward the recess 4 a of the piston 4 in each combustion chamber 3 in a state where air is sucked into each combustion chamber 3. As a result, in the internal combustion engine 1, the fuel / air mixture layer is formed (stratified) in the vicinity of the spark plug 7 so as to be separated from the surrounding air layer. And stable stratified combustion can be performed. The internal combustion engine 1 of the present embodiment is described as a so-called direct injection engine, but is not limited to this, and the present invention can be applied to an intake pipe (intake port) injection type internal combustion engine. Not too long.

  Each of the spark plugs 7, the throttle valve 10, the injectors 12, the valve operating mechanism and the like described above are electrically connected to an ECU 20 that functions as a control device for the internal combustion engine 1. The ECU 20 includes a CPU, a ROM, a RAM, an input / output port, a storage device, and the like, all not shown. As shown in FIG. 2, various sensors including the crank angle sensor 14 of the internal combustion engine 1 are electrically connected to the ECU 20. The ECU 20 uses the various maps stored in the storage device and the spark plug 7, the throttle valve 10, the injector 12, the valve operating mechanism, etc. so as to obtain a desired output based on the detection values of various sensors. To control.

  The internal combustion engine 1 has in-cylinder pressure sensors (in-cylinder pressure detecting means) 15 including semiconductor elements, piezoelectric elements, magnetostrictive elements, optical fiber detecting elements, and the like corresponding to the number of cylinders. Each in-cylinder pressure sensor 15 is disposed on the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 3, and is electrically connected to the ECU 20 via an A / D converter (not shown). Each in-cylinder pressure sensor 15 provides the ECU 20 with a voltage signal (a signal indicating a detected value) corresponding to the pressure (in-cylinder pressure) applied to the pressure receiving surface in the combustion chamber 3. The detected values of the crank angle sensor 14 and each in-cylinder pressure sensor 15 are sequentially given to the ECU 20 every minute time, and stored in a predetermined storage area (buffer) of the ECU 20 by a predetermined amount.

  Next, the procedure of misfire determination processing in the internal combustion engine 1 will be described with reference to FIG.

When the internal combustion engine 1 is started, the ECU 20 repeatedly executes the misfire determination routine shown in FIG. 3 every minute time. In this case, the ECU 20 first acquires the rotational speed of the internal combustion engine 1 based on the signal from the crank angle sensor 14 and determines whether or not the idle operation of the internal combustion engine 1 is being executed based on the acquired rotational speed. (S10). When the ECU 20 determines that the idle operation is being executed in S10, the ECU 20 sets a predetermined flag to “0” (S12), and before each combustion chamber 3 starts combustion (spark ignition or compression ignition). In-cylinder pressures P (θ ₁ ), P (θ ₂ ) at a plurality of measurement points (crank angles = θ ₁ , θ ₂ , θ ₃ , θ ₄ ) determined between the timing and a certain timing after the start of combustion , P (θ ₃ ) and P (θ ₄ ) are read from a predetermined storage area (S14). In the present embodiment, the plurality of measurement points are, for example, θ ₁ = −60 ° (60 ° before top dead center), θ ₂ = 60 ° (60 ° after top dead center), θ ₃ = 90 ° (top dead center). 90 ° after the point) and θ ₄ = 120 ° (120 ° after the top dead center).

When the ECU ₂₀ acquires the in-cylinder pressures P (θ ₁ ), P (θ ₂ ), P (θ ₃ ), and P (θ ₄ ) for each combustion chamber 3, the in-cylinder pressure P (θ _i ) is obtained in S 16. And the in-cylinder pressure P (θ _i ), that is, the in-cylinder volume V (θ _i ) when the crank angle becomes θ _i , the specific heat ratio κ (in this embodiment, κ = 1.32). The control parameter PV ^κ _i which is the product of the value raised to the power of is calculated for each combustion chamber 3 for each measurement point (where i = 1, 2, 3, 4). That is, for each combustion chamber 3, the ECU 20 controls the control parameter PV ^κ ₁ , which is the product of the in-cylinder pressure P (θ ₁ ) and the in-cylinder volume V (θ ₁ ) to the power of the specific heat ratio κ, and the cylinder A control parameter PV ^κ ₂ that is the product of the internal pressure P (θ ₂ ) and the cylinder volume V (θ ₂ ) raised to the specific heat ratio κ, the cylinder pressure P (θ ₃ ), and the cylinder volume The control parameter PV ^κ ₃ , which is the product of V (θ ₃ ) raised to the specific heat ratio κ, the in-cylinder pressure P (θ ₄ ), and the in-cylinder volume V (θ ₄ ) raised to the specific heat ratio κ A control parameter PV ^κ ₄ which is a product of the values is calculated. The values of V ^κ (θ ₁ = −60 °), V ^κ (θ ₂ = 60 °), V ^κ (θ ₃ = 90 °) and V ^κ (θ ₄ = 120 °) used here are calculated in advance. And stored in the storage device.

When the control parameters PV ^κ ₁ , PV ^κ ₂ , PV ^κ _3, and PV ^κ ₄ are obtained as described above, the ECU 20 determines the difference ΔPV ^κ ₂₋ between the plurality of control parameters PV ^κ for each combustion chamber 3. ₁ , ΔPV ^κ _3-2 and ΔPV ^κ _4-3 are calculated (S18). That is, the ECU 20 determines the differences ΔPV ^κ _2-1 , ΔPV ^κ _3-2 and ΔPV ^κ _4-3 in S16.
ΔPV ^κ _2-1 = ΔPV ^κ ₂ -ΔPV ^κ ₁
ΔPV ^κ _3-2 = ΔPV ^κ ₃ −ΔPV ^κ ₂
ΔPV ^κ ₄₋₃ = ΔPV ^κ ₄ −ΔPV ^κ ₃
Calculate as

The difference ΔPV ^κ _2-1 indicates the amount of heat generated in each combustion chamber 3 between the timing when the crank angle θ = θ ₁ and the timing when θ = θ _2, and the difference ΔPV ^κ _3-2 is The amount of heat generated in each combustion chamber 3 between the timing when the crank angle θ = θ ₂ and the timing when θ = θ ₃ is shown, and the difference ΔPV ^κ _4-3 becomes the crank angle θ = θ _3. timing indicates the amount of heat generated in the respective combustion chambers 3 between the timing at which the θ = θ _4. As described above, by the processes from S 12 to S 16, the difference ΔPV ^κ of the control parameter PV ^κ that favorably reflects the heat generation amount between the plurality of measurement points is easily and quickly calculated for each combustion chamber 3. As a result, the calculation load on the ECU 20 can be greatly reduced as compared with the case where the in-cylinder pressure is integrated for each minute unit crank angle to determine the misfire state in each combustion chamber 3.

Here, the difference ΔPV ^κ indicating the amount of heat generated in any one of the combustion chambers 3 between two points varies depending on the degree of misfire in the combustion chamber 3. In such a state, the difference ΔPV ^κ is smaller than a predetermined threshold value. Further, when the combustion chamber 3 is in a complete misfire state, the difference ΔPV ^κ is further smaller (theoretically zero or less) than the threshold value. Therefore, by utilizing such a relationship between the difference ΔPV ^κ and the misfire state, the misfire state in the cylinder can be determined with a low load based on the difference ΔPV ^κ of the control parameter PV ^κ .

However, under-cylinder pressure is relatively low operating conditions such as during idling, from becoming the control parameter PV value of ^kappa is small, between the normal combustion and misfire, the control parameter PV ^kappa There is a possibility that a significant difference is not recognized in the difference ΔPV ^κ between the two, and the misfire state in the cylinder cannot be accurately determined. That is, according to the experiments by the present inventors, under an operation state in which the in-cylinder pressure is relatively low, such as during idling, between two certain points acquired during a misfire (including a semi-misfire state). the distribution of the difference Pv ^kappa, and the distribution of the differential Pv ^kappa between the two points to be acquired at the time of combustion, as shown in FIG. 4, it was found that there is a risk of overlap.

On the other hand, even in an operating state where the in-cylinder pressure is relatively low, such as during idling, if a plurality of differences ΔPV ^κ calculated within a predetermined range are added up, a misfire (semi-misfire state) As shown in FIG. 5, the integrated value of the difference ΔPV ^κ acquired at the time of combustion and the integrated value acquired at the time of combustion are distributed in a clearly separated form. In view of such points, in the internal combustion engine 1 of the present embodiment, when the differences ΔPV ^κ _2-1 , ΔPV ^κ _3-2, and ΔPV ^κ _4-3 are obtained in S18, these are determined for each combustion chamber 3. The differences ΔPV ^κ _2-1 , ΔPV ^κ _3-2 and ΔPV ^κ _4-3 are integrated, and the obtained integrated value S is stored in a predetermined storage area of the RAM (S20). In the internal combustion engine 1, the misfire state in the cylinder is determined based on the integrated value S obtained by integrating a plurality of these differences ΔPV ^κ .

When the integrated value S of the difference ΔPV ^κ is obtained in S20, the ECU 20 determines for each combustion chamber 3 whether or not the integrated value S is lower than a predetermined first threshold value α (S22). When the ECU 20 determines in S22 that the integrated value S of the differences ΔPV ^κ for all the combustion chambers 3 is not less than the first threshold value α, it is considered that no misfire has occurred in any of the combustion chambers 3. , The process returns to S10 and the series of subsequent processing is repeated.

If it is determined in S22 that the accumulated value S of the difference ΔPV ^κ is lower than the first threshold value α for at least one of the combustion chambers 3, the ECU 20 causes the inside of the combustion chamber 3 to be in a semi-misfire state. A counter (not shown) corresponding to the combustion chamber is incremented by 1 (S24). Further, the ECU 20 determines whether or not the count value of the counter is below a predetermined threshold value (S26). If the ECU 20 determines in S26 that the count value of the counter is below the threshold value, the ECU 20 uses the predetermined map or the like to open the throttle valve 10, the fuel injection amount from the injector 12, the intake valve Vi, and / or Or, in the case of an internal combustion engine equipped with an exhaust gas recirculation system, at least one of the exhaust gas recirculation rates is corrected according to the integrated value S of the difference ΔPV ^κ obtained in S20, for example. (S28).

That is, in the internal combustion engine 1, if the integrated value S of the difference ΔPV ^κ of the control parameter PV ^κ is less than the first threshold value α, but the frequency of the integrated value S is less than the first threshold value α, the combustion chamber 3 Misfires occurring in are considered temporary. In such a case, the throttle opening, the fuel injection amount, the valve opening / closing timing, and the like are corrected as appropriate (S28), whereby the subsequent misfire in the combustion chamber 3 is suppressed.

Further, when the ECU 20 determines in S26 that the count value of the counter is equal to or greater than the threshold value, that is, when it is determined that the number of misfire occurrences in the combustion chamber 3 is equal to or greater than the threshold value, the ECU 20 resets the counter. (S30). Further, the ECU 20 determines whether or not the flag is “0” (S32). When the ECU 20 determines that the flag is “0”, the integrated value S of the difference ΔPV ^κ determined in S20 is the second threshold value. It is determined whether it is below β (where β <α) (S34). When it is determined in S34 that the integrated value S of the difference ΔPV ^κ is lower than the second threshold value β, the ECU 20 causes the combustion chamber 3 to be completely misfired due to a problem with the spark plug 7, for example. A predetermined warning is displayed (S36).

When it is determined in S34 that the integrated value S of the difference ΔPV ^κ is not less than the second threshold value β, the ECU 20 uses the predetermined map or the like to open the throttle valve 10 and the fuel from the injector 12. For example, in an internal combustion engine equipped with an exhaust gas recirculation system, at least one of the injection amount, the intake valve Vi and / or the exhaust valve Ve, and at least one of the exhaust gas recirculation rates, the difference ΔPV obtained in S20, for example. Correction is performed according to the integrated value S of ^κ (S28). That is, in the internal combustion engine 1, even if the number of misfire occurrences in a certain combustion chamber 3 exceeds the above threshold, if the integrated value S of the difference ΔPV ^κ is not less than the second threshold β, the throttle The opening degree, the fuel injection amount, the valve opening / closing timing, and the like are appropriately corrected (S28), thereby suppressing the subsequent misfire in the combustion chamber 3. After the process of S28 or S36, the ECU 20 returns to S10 and repeats a series of subsequent processes.

Thus, in the internal combustion engine 1, when the in-cylinder pressure is relatively low, such as during idling, the in-cylinder pressure P (θ) detected by the in-cylinder pressure sensor 15 and the in-cylinder pressure P (θ). The misfire state in the combustion chamber 3 based on the integrated value S obtained by integrating a plurality of differences ΔPV ^κ of the control parameter PV ^κ , which is the product of the in-cylinder volume V (θ) and the value raised to the power of the predetermined index κ. Is accurately determined at low load. In the internal combustion engine 1, when it is determined that the combustion chamber 3 is in a misfire state (semi-misfire state), the throttle opening, the fuel injection amount, the valve opening / closing timing, the exhaust gas recirculation rate, etc. At least one of the above is corrected. Thereby, according to the internal combustion engine 1, it becomes possible to always obtain a desired output while maintaining a good rotation speed.

On the other hand, if it is determined in S10 that the idling operation of the internal combustion engine 1 is not being executed, the ECU 20 sets the flag to “1” (S38), and the crank angle is set to θ _a for each combustion chamber 3. The in-cylinder pressures P (θ _a ) and P (θ _b ) at the first timing and the second timing at which the crank angle becomes θ _b are read from a predetermined storage area (S40).

Here, the first timing is set after each intake valve Vi is opened and before ignition by each spark plug 7, and when combustion is started in each combustion chamber 3 (at the time of ignition) It is preferable that the timing is set sufficiently before. In the present embodiment, the first timing is, for example, the timing at which the crank angle indicated by the signal from the crank angle sensor 14 becomes −60 ° (θ _a = −60 °, that is, 60 ° before the top dead center). Has been. Also, the second timing is set after ignition by each spark plug 7 and before each exhaust valve Ve is opened, and when the combustion of the air-fuel mixture in the combustion chamber 3 is almost completed. preferable. In the present embodiment, the second timing is, for example, a timing at which the crank angle indicated by the signal from the crank angle sensor 14 becomes 90 ° (θ _b = 90 °, that is, 90 ° after the top dead center). Yes.

When the ECU 20 acquires the in-cylinder pressures P (θ _a ) and P (θ _b ) for each combustion chamber 3, the specific pressure is obtained from the in-cylinder pressure P (θ _a ) and the in-cylinder volume V (θ _a ) in S 42. Control that is the product of the control parameter PV ^κ _a , which is the product of the value raised to the ratio κ, the in-cylinder pressure P (θ _b ), and the value of the in-cylinder volume V (θ _b ) raised to the power of the specific heat ratio κ The parameter PV ^κ _b is calculated. The values of V ^κ (θ _a = −60 °) and V ^κ (θ _b = 90 °) used here are calculated in advance and stored in the storage device. When the control parameters PV ^κ _a and PV ^κ _b are obtained as described above, the ECU 20 calculates the difference between the control parameters PV ^κ between the first and second timings for each combustion chamber 3.
^{_{ΔPV κ b-a = PV κ}} b -PV κ a
And is stored in a predetermined storage area of the RAM (S44).

This difference ΔPV ^κ _b−a is the amount of heat generated in each combustion chamber 3 between the first timing and the second timing (between two predetermined points), that is, from the first timing to the second timing. The amount of heat generated in the combustion chamber 3 during this period is shown. As described above, the difference ΔPV ^κ _b−a of the control parameter PV ^κ well reflecting the heat generation amount between the first timing and the second timing is simplified for each combustion chamber 3 by the processing from S40 to S44. And it is calculated promptly. Thereby, compared with the case where the in-cylinder pressure is integrated for each minute unit crank angle and the misfire state in each combustion chamber 3 is determined, the calculation load in the ECU 20 can be greatly reduced.

Here, the control parameter PV ^kappa each other for the difference Pv ^kappa there is a risk that a significant difference is not observed in the in-cylinder pressure of the idle time and the like are cases relatively low. When the in-cylinder pressure is high to some extent, in general, there is a significant difference in the difference ΔPV ^κ of the control parameter PV ^κ between two certain points between normal combustion and misfire. In such a case, the misfire state in the cylinder can be determined based on the difference ΔPV ^κ _b−a . For this reason, if ECU20 calculates | requires difference (DELTA) PV ( ^kappa) _b-a in S44, it will be determined for every combustion chamber 3 whether difference (DELTA) PV ( ^kappa) _b-a is less than the predetermined threshold value (gamma) (S46). . As a result, when the internal combustion engine 1 is in an operating state other than idling, the calculation process of the difference ΔPV ^κ is omitted, so that the calculation load required for the misfire determination of the internal combustion engine 1 can be further reduced.

If it is determined in S46 that the difference ΔPV ^κ _{b−a of} all the combustion chambers 3 is not less than the threshold value γ, the ECU 20 regards that no misfire has occurred in any of the combustion chambers 3 and returns to S10. Repeat the series of processing thereafter. Further, when it is determined in S46 that the difference ΔPV ^κ _b−a is lower than the threshold value γ for at least one of the combustion chambers 3, the processes after S24 described above are executed. Here, if it is determined in S10 that the idling operation of the internal combustion engine 1 is not being executed, the flag is set to “1” in S38, so a negative determination is made in S32. In this case, the ECU 20 determines whether or not the difference ΔPV ^κ _b−a obtained in S44 is below _a predetermined threshold value ε (where ε <γ) (S48).

If it is determined in S48 that the difference ΔPV ^κ _b−a is less than the threshold value ε, the ECU 20 considers that the interior of the combustion chamber 3 is in a complete misfire state due to, for example, a problem with the spark plug 7 or the like. A predetermined warning is displayed (S36). If it is determined in S34 that the difference ΔPV ^κ _b−a is not less than the threshold value ε, the ECU 20 uses a predetermined map or the like to open the throttle valve 10, the fuel injection amount from the injector 12, The difference ΔPV ^κ _b−a obtained in S20 is the opening / closing timing of the intake valve Vi and / or the exhaust valve Ve, and further, in an internal combustion engine equipped with an exhaust gas recirculation system, at least one of the exhaust gas recirculation rates is obtained in S20. The correction is made according to (S28).

In the present embodiment, the misfire determination is performed based on the integrated value S of the difference ΔPV ^κ of the control parameter PV ^κ only when the idling operation of the internal combustion engine 1 is being performed. However, the present invention is not limited to this. Absent. That is, the misfire determination using the integrated value S may be performed when it is determined that the in-cylinder pressure is relatively decreased in the internal combustion engine 1. As an operation state in which the in-cylinder pressure is relatively lowered, for example, a case where the spark plug 7 is twisted can be cited. In order to perform misfire determination using the integrated value S when the spark plug 7 is burned, for example, after a negative determination is made in S10 of FIG. 3, the spark plug 7 is beaten by a predetermined method. It is preferable that the process after S12 is executed when an affirmative determination is made.

  Moreover, although the above-mentioned internal combustion engine 1 was demonstrated as what is a gasoline engine, it is not restricted to this, and it cannot be overemphasized that this invention can be applied to a diesel engine. In particular, the present invention is effective when applied to rich misfire determination when performing rich operation in a diesel engine and misfire determination when performing so-called lean limit operation in various internal combustion engines.

It is a graph which shows the correlation between control parameter PV ( ^kappa) used in this invention, and the amount of heat generation in a combustion chamber. 1 is a schematic configuration diagram showing an internal combustion engine according to the present invention. 3 is a flowchart for explaining misfire determination processing in the internal combustion engine of FIG. 2. It is a frequency distribution diagram of the difference Pv ^kappa control parameter PV ^kappa between certain two points. FIG. 5 is a frequency distribution diagram of integrated values obtained by integrating differences ΔPV ^κ between a plurality of control parameters PV ^κ obtained within a predetermined range.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Combustion chamber 4 Piston 7 Spark plug 10 Throttle valve 12 Injector 14 Crank angle sensor 15 In-cylinder pressure sensor Ve Exhaust valve Vi Intake valve

Claims (4)

In a control device for an internal combustion engine that generates power by burning a mixture of fuel and air in a cylinder,
In-cylinder pressure detecting means for detecting in-cylinder pressure;
Control parameter calculating means for calculating a control parameter that is a product of the in-cylinder pressure detected by the in-cylinder pressure detecting means and a value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined index;
Difference calculating means for obtaining a difference between a plurality of control parameters calculated by the control parameter calculating means;
Integrating means for integrating the plurality of differences calculated by the difference calculating means;
A control apparatus for an internal combustion engine, comprising: misfire determination means capable of determining a misfire state in the cylinder based on the integrated value calculated by the integration means.   When the internal combustion engine is further determined to be in a predetermined operation state, further comprising an operation state determination unit, wherein the misfire determination unit is determined by the operation state determination unit that the internal combustion engine is in a predetermined operation state 2. The control apparatus for an internal combustion engine according to claim 1, wherein a misfire state in the cylinder is determined based on an integrated value calculated by the integrating means. In a misfire determination method for an internal combustion engine that generates power by burning a mixture of fuel and air in a cylinder,
(A) detecting in-cylinder pressure for at least three measurement points;
(B) For each measurement point, a control parameter that is the product of the in-cylinder pressure detected in step (a) and the value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined index is calculated. Steps,
(C) obtaining a difference between the control parameters calculated in step (b);
(D) integrating the plurality of differences calculated in step (c);
And (e) determining a misfire state in the cylinder based on the integrated value calculated in step (d).   At least before step (e), (f) further comprises a step of determining whether or not the internal combustion engine is in a predetermined operating state, and it is determined in step (f) that the internal combustion engine is in a predetermined operating state. 2. The misfire determination method for an internal combustion engine according to claim 1, wherein in step (e), a misfire state in the cylinder is determined based on the integrated value.

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