JP2007170203A - Combustion variation detection device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the presence or absence of combustion variation during the transient operation of an engine. <P>SOLUTION: An angular velocity sensor 33 is installed to detect the angular velocity of the crankshaft of the engine 1. An electronic control unit (ECU) 30 of the engine obtains the crank angle θmax at which the angular velocity of the crankshaft detected by the sensor 33 during the compression and combustion strokes of each cylinder is maximum, and compares it with the value of the θmax in the stroke cycles in the past for each cylinder. When the variation of the values of θmax this time exceeds a predetermined value, the ECU determines that the combustion variation of that cylinder occurs. By determining the combustion variation using the crank angle at which the angular velocity is maximum in place of the magnitude of the angular velocity itself, the ECU can accurately determine the presence or absence of the combustion variation without being affected by the acceleration and deceleration of the engine. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a combustion fluctuation detection apparatus for an internal combustion engine, and more particularly to a combustion fluctuation detection apparatus for an internal combustion engine that can accurately determine the presence or absence of engine misfire or combustion fluctuation even during transient operation of the engine.

As a combustion fluctuation detecting device for detecting misfire or combustion fluctuation of an internal combustion engine, for example, there is one described in Patent Document 1.
The apparatus of Patent Document 1 detects the time required for the crankshaft to rotate by a certain crank angle including the combustion stroke of each cylinder as the elapsed time T of the combustion stroke, and between the combustion stroke elapsed times T of adjacent cylinders. Deviation Δ between each deviation ΔT is further calculated from the deviation ΔT, and when the deviation Δ exceeds a predetermined value, incomplete combustion that causes misfire or reduced engine output occurs in any of the cylinders. It is determined.

  In the device of Patent Document 1, when the variation in the elapsed time of the combustion stroke of each cylinder (deviation of the elapsed time of the combustion stroke of the adjacent cylinder) becomes equal to or greater than a predetermined determination value, misfire or incomplete reduction in output is caused. It is determined that combustion has occurred.

  When incomplete combustion that causes misfire or reduced output occurs in any of the cylinders, the rotational speed of the crankshaft in the combustion stroke of that cylinder is lower than that of the other cylinders. For this reason, the elapsed time of the combustion stroke is longer in other cylinders than in other cylinders where misfire or incomplete combustion that reduces output occurs. For this reason, the deviation ΔT of T in the combustion stroke elapsed time between adjacent cylinders changes according to the presence or absence of misfire or incomplete combustion that reduces the output.

  Further, in the apparatus of Patent Document 1, the presence or absence of misfire or incomplete combustion that reduces the output is detected based on the magnitude of the deviation Δ between the deviations ΔT. The judgment of incomplete combustion that reduces misfire or output due to a change in grip on the road surface is not affected.

JP-A-6-10754 JP-A-9-280100 JP-A-5-149188

  The determination of the presence of engine misfire or incomplete combustion that reduces the output can be made based on the change in the rotation speed of the crankshaft as described above. In the case of detecting incomplete combustion that lowers the rotational speed of the crankshaft, as in the apparatus of Patent Document 1, the magnitude of the rotational speed and change amount of the crankshaft, or its differential value (angular acceleration), or these values Most of them judged the presence or absence of misfire or incomplete combustion that reduces output based on variations.

  However, if the presence or absence of misfire or incomplete combustion that reduces the output is determined based on the amount of change in the crankshaft rotation speed (angular velocity), the rate of change in angular acceleration, the amount of change itself, or its variation, Depending on the condition, it may be difficult to accurately determine whether there is misfire or incomplete combustion that reduces output.

  For example, during transient operation such as acceleration or deceleration of the engine, the crankshaft rotational speed increases or decreases even if misfire or incomplete combustion that reduces output does not occur. For this reason, if the presence or absence of misfiring or incomplete combustion that reduces the output is determined based on the amount of change in the crankshaft angular velocity or angular acceleration, an increase or variation in the amount of change in angular velocity or angular acceleration may occur during transient operation. When it becomes larger, it is impossible to determine whether the increase or variation in the amount of change is due to incomplete combustion that actually caused misfire or reduced output, or due to acceleration or deceleration of the engine, There are cases where it is impossible to accurately determine whether there is misfire or incomplete combustion that reduces output.

  In recent years, lean burn engines that operate at an air-fuel ratio that is considerably leaner than the stoichiometric air-fuel ratio have been used to improve fuel consumption and reduce exhaust emissions. In general, a lean burn engine operates near the upper limit (lean limit) of the air-fuel ratio at which stable operation is possible, so combustion may easily deteriorate with slight changes in conditions.

  For this reason, in a lean burn engine, usually, the deterioration of combustion is detected at an early stage by constantly monitoring the presence or absence of misfire or incomplete combustion that lowers the output. The combustion stabilization control is performed so as to always maintain the combustion state of each cylinder in a favorable state.

  However, when the conventional combustion fluctuation detecting device based on the change amount of the crankshaft angular velocity or the like is used, as described above, in the case of transient operation (acceleration / deceleration operation), accurate misfire or incomplete combustion detection that reduces output is detected. In conventional lean burn engines, the lean air-fuel ratio operation is stopped during the transient operation and the theoretical air-fuel ratio operation is performed during the transient operation, or the incomplete combustion detection that causes misfire or lowers the output is performed during the transient operation. Therefore, lean burn operation with a fixed air-fuel ratio must be performed.

  However, if the stoichiometric air-fuel ratio operation is performed every time transient operation occurs, there is a problem that the fuel consumption of the engine deteriorates, and if the detection of misfire or incomplete combustion that reduces output is stopped during transient operation, There is a problem that the exhaust emission tends to deteriorate and the exhaust emission increases.

  An object of the present invention is to provide a highly reliable combustion fluctuation detection device for an internal combustion engine that can accurately detect the presence or absence of misfire or deterioration of combustion even during transient operation of the engine in view of the above-described problems of the prior art. .

  According to the first aspect of the present invention, the detection means for detecting a predetermined angular velocity parameter related to the crankshaft rotational angular velocity of the internal combustion engine, and the angular velocity parameter of each cylinder in a period from the latter half of the compression stroke to the end of the expansion stroke. Detects at least one of the crank angle at which the maximum value is obtained and the crank angle at which the minimum value is obtained, and determines the presence or absence of combustion deterioration in each cylinder based on a determination value calculated as a function of the detected crank angle An internal combustion engine combustion fluctuation detecting device.

  According to a second aspect of the present invention, there is provided the combustion fluctuation detecting device for an internal combustion engine according to the first aspect, wherein the angular velocity parameter is a crankshaft rotational angular velocity.

  According to a third aspect of the present invention, there is provided the combustion fluctuation detecting device for an internal combustion engine according to the first aspect, wherein the angular velocity parameter is a change rate of a crankshaft rotational angular velocity.

  According to a fourth aspect of the invention, there is provided the internal combustion engine combustion fluctuation detection device according to any one of the first to third aspects, wherein the determination value is a crank angle at which the angular velocity parameter takes a maximum value. Provided.

  According to a fifth aspect of the present invention, in the combustion fluctuation detecting device for an internal combustion engine according to any one of the first to third aspects, the determination value is a crank angle at which the angular velocity parameter takes a minimum value. Provided.

  According to a sixth aspect of the present invention, the determination value is an angular difference between a crank angle at which the angular velocity parameter takes a maximum value and a crank angle at which the angular value takes a minimum value. A combustion fluctuation detecting device for an internal combustion engine as described in 1) is provided.

  That is, in the combustion fluctuation detection device for an internal combustion engine according to claims 1 to 6, the point of determining whether misfire or deterioration of combustion is based on a parameter related to the angular velocity of crankshaft rotation is described in, for example, the above-mentioned Patent Document 1 or the like. This is the same as the conventional combustion fluctuation detection device described.

  However, while the conventional combustion fluctuation detection device determines the presence or absence of misfire or combustion deterioration based on the size, change amount, etc. of parameters related to angular velocity (for example, angular velocity, rate of change of angular velocity). Thus, in the combustion fluctuation detection device according to claims 1 to 6, the magnitude or change amount of the angular velocity parameter itself is not used, but misfire or combustion deterioration is caused by using the crank angle at which the angular velocity parameter value becomes a maximum value or a minimum value. This point is greatly different from the conventional apparatus of this type.

  In the apparatus according to the first to sixth aspects, for example, the crankshaft rotation angular velocity itself or the rate of change (angular acceleration) of the angular velocity is used as the angular velocity parameter.

As described above, the magnitudes of the angular velocity and the angular acceleration are greatly affected by the acceleration / deceleration operation of the engine.
However, according to the applicant's research, even in that case, the crank angle phase (crank angle) at which the angular velocity and angular acceleration take the maximum and minimum values in the stroke cycle of each cylinder only affects the combustion state of each cylinder. As a result, it has been found that the acceleration and deceleration of the engine is almost unaffected.

  Therefore, determination of misfire or deterioration of combustion is performed using the crank angle at which the angular velocity parameter is maximized or minimized as the determination value, or using the difference between the maximum crank angle and the minimum crank angle as the determination value. This makes it possible to accurately determine the combustion state that is not affected by the acceleration / deceleration of the engine.

  According to a seventh aspect of the present invention, the determination unit calculates the determination value for each stroke cycle of each cylinder, and the variation of the determination value for each cylinder in each stroke cycle is greater than or equal to a predetermined value. The combustion fluctuation detecting device for an internal combustion engine according to any one of claims 1 to 6, wherein it is determined that the combustion of the cylinder has deteriorated at the time of combustion.

  According to an eighth aspect of the present invention, the determination means calculates the determination value for each cylinder, and a variation of the determination value in one cylinder from an average value of the determination values in all cylinders is predetermined. The combustion fluctuation detection device for an internal combustion engine according to any one of claims 1 to 6, wherein it is determined that the combustion of the cylinder has deteriorated when the value exceeds the value.

  According to a ninth aspect of the present invention, the determination means calculates the determination value for each cylinder, and when the determination value for one cylinder is out of a predetermined range, combustion of that cylinder is not performed. The combustion fluctuation detection device for an internal combustion engine according to any one of claims 1 to 6, which is determined to be deteriorated.

  That is, in the seventh to ninth aspects of the invention, the cylinder that has misfired or deteriorated in combustion is determined based on the variation in the determination value calculated based on the crank angle.

  In this case, for example, this variation is obtained by determining the above-mentioned determination value for a plurality of stroke cycles for each cylinder, determining the average value of the determination values for each cylinder, and the determination value for that cylinder deviates from the average value by a predetermined value or more. In this case, it may be determined that misfire or deterioration of combustion has occurred in the cylinder, or an average of the determination values of all the cylinders is obtained, and the determination value of a certain cylinder is a predetermined value from the average value. When the above deviation occurs, it may be determined that misfire or deterioration of combustion has occurred in the cylinder.

  In addition, instead of comparing the average value of each cylinder or all the engine cylinders with the determination value, if the determination value itself of a certain cylinder is outside the predetermined range, misfire or deterioration of combustion occurs in that cylinder. It can also be determined. In this case, as a determination of whether or not the determination value is outside the predetermined range, whether or not the determination value is equal to or higher than a predetermined upper limit value or lower than a predetermined lower limit value, or a criterion determined according to operating conditions The determination may be made based on whether or not the ratio of the deviation between the value and the determination value to the reference value exceeds a predetermined value.

  As a result, it is possible to accurately determine the cylinder in which the deterioration of the combustion is caused during the transient operation, so that the above-described combustion stabilization control can be performed even during the transient operation in the lean burn engine. A lean air-fuel ratio operation can be performed.

  According to the invention described in each claim, since the deterioration of the combustion state of each cylinder can be accurately detected even during transient operation such as acceleration / deceleration of the engine, stable lean air-fuel ratio control is achieved even during transient operation. There is a common effect that can be performed.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an embodiment when the present invention is applied to an internal combustion engine for an automobile.

  In FIG. 1, reference numeral 1 denotes a vehicle internal combustion engine. In this embodiment, a four-cylinder lean burn engine that can be operated in a wide air-fuel ratio range including a lean air-fuel ratio is used as the engine 1.

1 is an electronic control unit (ECU) that controls the engine 1.
In the present embodiment, the ECU 30 is configured as a microcomputer having a known configuration including a ROM, a RAM, and a CPU, and controls the fuel injection and ignition timing of the engine 1, and in the present embodiment, a combustion fluctuation detection operation described later. I do.

In order to perform these controls, the ECU 30 receives a signal corresponding to the intake pressure of the engine 1 from an intake pressure sensor 35 provided in an intake manifold (not shown) of the engine 1 and an accelerator pedal (not shown) of the engine 1. 1) A signal corresponding to the accelerator pedal depression amount (accelerator opening) of the driver is input from the accelerator opening sensor 37 disposed in the vicinity, and also corresponds to the crank rotation speed (angular speed) of the engine 1. A signal is input from the crank angular velocity sensor 33.
Instead of the intake pressure sensor 35, an air amount sensor such as an air flow meter that can directly detect the engine intake air amount may be used.

In the present embodiment, a so-called linear rotation angle sensor using a Hall element is used as the angular velocity sensor 33, and a continuous signal corresponding to the crankshaft rotation angular velocity is output.
As the crank angular velocity sensor 33, for example, a cam shaft or a crank angle sensor that outputs a pulse signal at every predetermined rotation angle of the crank shaft or a cam angle sensor is used to measure the number of output pulses per unit time. Thus, a device that calculates the crank angular velocity can be used.

  The ECU 30 is connected to a fuel injection valve 11 that individually injects fuel into each cylinder of the engine 1 via a fuel injection circuit (not shown), and controls the fuel injection amount and fuel injection timing for each cylinder. An ignition timing circuit (not shown) is connected to the ignition plug 13 of each cylinder to control the ignition timing for each cylinder.

The ECU 30 calculates the engine intake air amount based on the crankshaft rotation speed (engine speed) detected by the angular velocity sensor 33 and the engine intake pressure detected by the intake pressure sensor 35 during the theoretical air-fuel ratio operation of the engine 1 ( Alternatively, using the engine intake air amount directly detected by the air amount sensor), the fuel injection amount for performing combustion at the stoichiometric air-fuel ratio in the engine 1 is calculated and injected from the fuel injection valve 11 into each cylinder.
Further, during the lean air-fuel ratio operation of the engine 1, the fuel injection amount to each cylinder is calculated based on the engine speed and the accelerator opening detected by the accelerator opening sensor 37, and the lean burn operation of the engine 1 is performed.

In lean burn operation, the engine is operated near the lean air-fuel ratio limit at which the engine can be operated, so that a slight change in the operating state may deteriorate the combustion state of the engine and cause incomplete combustion that reduces the engine output. .
Therefore, conventionally, at the time of lean burn operation, the deterioration of the combustion state of each cylinder is detected at an early stage, and when the deterioration occurs, the combustion state is increased by adjusting the fuel injection amount of the cylinder and adjusting the ignition timing. Control was taking place.

  However, as described above, most of the conventional combustion fluctuation detection devices judge the deterioration of the combustion state based on the crankshaft rotational speed and the magnitude and variation of the rate of change thereof. During operation, there was a problem that the deterioration of the combustion state could not be accurately determined.

  Therefore, during the conventional transient operation, the engine air-fuel ratio is controlled to the stoichiometric air-fuel ratio, or the fuel injection amount is fixed without performing the combustion state stabilization control (lean limit control) based on the presence or absence of the above-described combustion fluctuation. During driving, there were cases where fuel consumption increased and emissions deteriorated.

This problem will be described with reference to FIG.
FIG. 2 is a diagram showing changes in the crankshaft angular speed during engine operation, and FIG. 2A shows temporal changes in the crankshaft angular speed when the engine is in steady operation.

  As shown in FIG. 2, the crankshaft angular velocity increases and decreases with each stroke cycle of each cylinder (# 1 to 4 in FIG. 2), reaches a minimum (MIN) near the compression top dead center of each cylinder, and reaches a maximum during the explosion stroke ( MAX).

  As shown in FIG. 2A, when the engine is in steady operation and the engine speed is kept constant, the angular velocity of the crankshaft is repeatedly increased and decreased around a certain average value (AV). For example, if incomplete combustion that lowers the engine output occurs, the maximum value of the angular velocity of the cylinder becomes smaller than that of the other cylinders, so that the presence or absence of incomplete combustion can be easily determined.

  FIG. 2B is a view similar to FIG. 2A showing the crankshaft angular velocity during transient operation (acceleration) of the engine.

  For example, when the engine is accelerated, the average angular velocity of the crankshaft increases with time, and the in-cylinder pressure of each cylinder also increases. Therefore, as shown in FIG. 2B, the maximum value, minimum value, and amplitude of the angular velocity increase with time. Increase.

  For this reason, if the presence or absence of combustion fluctuation in each cylinder is determined by the maximum value or the minimum value of the angular velocity itself (or the difference between the maximum value and the minimum value, etc.), the crankshaft angular speed due to the acceleration / deceleration of the engine Therefore, it is impossible to clearly distinguish between the change in the engine speed and the change in the angular velocity due to the incomplete combustion that reduces the engine output, and it is impossible to accurately determine the presence or absence of the combustion fluctuation.

  In this embodiment, the presence / absence of combustion fluctuation is determined based on the crankshaft angular velocity as in the prior art, but instead of using the maximum or minimum value itself, such as the crankshaft angular velocity and its rate of change, the crankshaft The point which judges the presence or absence of combustion fluctuation | variation based on the crank angle from which angular velocity and its change rate take the maximum value or the minimum value differs greatly from the conventional one.

  FIG. 3 is a diagram illustrating changes in crankshaft angular velocity and in-cylinder pressure from a compression stroke to an expansion stroke of a certain cylinder. In FIG. 3, a curve S shows a case where the combustion state is deteriorated (when the generated torque is small), and a curve L shows a case where the combustion state is good (when the generated torque is large).

  As shown in FIG. 3, when the curve S and the curve L are compared, the crank angle at which the angular velocity becomes minimum moves to the retard side when the combustion deteriorates (FIG. 3, Smin and Lmin), and the crank at which the angular velocity becomes maximum. If the combustion worsens, the angle moves to the advance side (Smax and Lmax).

  Further, as a result of applicants' research, it has been found that the crank angle at which the angular velocity is minimized and the crank angle at which the angular velocity is maximized do not vary greatly depending on the engine speed or acceleration / deceleration.

  In this way, the crank angle at which the angular speed is minimized is retarded as the in-cylinder pressure becomes maximum and the engine speed is hardly influenced by the angular speed as shown in the in-cylinder pressure curve of FIG. This is considered to be because the crank angle at which is minimized is substantially corresponding to the crank angle at which the in-cylinder pressure is maximized.

  In addition, the crank angle at which the angular velocity is maximized affects the magnitude of work to be externalized. Therefore, the larger the work (generated torque), that is, the better the combustion, the more the angular velocity is compared to the worse combustion state. The maximum crank angle is considered to move to the retard side.

  As described above, when the crankshaft angular velocity is used as the angular velocity parameter, the crank angle at which the angular velocity is maximized (hereinafter referred to as “θmax”) and the crank angle at which the angular velocity is minimized (hereinafter referred to as “θmin”) are respectively combusted. It can be used as a determination value for determining the state.

  Further, the difference Δθ = θmax−θmin between the above θmax and θmin becomes a value corresponding to the combustion period and takes a small value when the combustion deteriorates (see FIG. 3). It can be used as a judgment value.

For example, when the above judgment value is continuously calculated for a certain cylinder and this judgment value falls within a certain variation range, it is considered that the combustion state is stable, but the variation in this judgment value is large. If it is large, it can be determined that the combustion state is not stable and the combustion is deteriorated.
Also, instead of continuously calculating the above-mentioned determination value for a certain cylinder, the above-mentioned determination value is calculated for all the cylinders of the engine. It is also possible to judge that it is getting worse.

  In the above description, the determination value is calculated using the crank angular velocity as the angular velocity parameter. However, not only the angular velocity but also the change rate of the angular velocity (angular acceleration) is used as the angular velocity parameter. It has been found that the maximum crank angle dθmax and the minimum crank angle dθmin, or the difference between them, Δdθ = dθmax−dθmin, can be used as the determination value in the same manner as described above.

  In this way, by detecting the presence or absence of combustion fluctuation using the judgment value calculated based on the crank angle at which the angular velocity parameter takes the maximum value or the minimum value, the engine speed changes as in engine transient operation, etc. In this case, the combustion fluctuation can be accurately determined.

  In this embodiment, by detecting the combustion fluctuation based on the determination value calculated using any one of the angular velocity parameters, the presence or absence of the combustion fluctuation of the engine is accurately detected without being affected by the transient operation of the engine. Therefore, it is possible to control fuel injection and ignition timing so as to obtain stable combustion even during transient operation.

Hereinafter, the combustion fluctuation detection operation of the present embodiment will be specifically described with reference to FIG.
FIG. 4 is a flowchart for explaining the combustion fluctuation detection operation of the present embodiment when the angular velocity is used as the angular velocity parameter and the crank angle θmax at which the angular velocity has a maximum value is used as the determination value.

  In the operation of FIG. 4, θmax is obtained for each cylinder, and the deviation σ of the current θmax value from the average value AVG of θmax for the past several stroke cycles of the cylinder is not less than a predetermined value (variation is not less than a predetermined value). In this case, it is determined that the combustion state has deteriorated in this cylinder.

  Further, when it is determined that the combustion fluctuation has occurred in this operation, an operation for adjusting the fuel injection amount and the ignition timing to stabilize the combustion is performed.

  That is, in the operation of FIG. 4, the crankshaft rotational angular velocity of the engine 1 is obtained based on the output of the angular velocity sensor 33 in step 401. The angular velocity is detected every predetermined rotation angle of the crankshaft (for example, every 1 to 10 degrees).

  In step 403, the detected angular velocity is filtered. In the present embodiment, in order to accurately obtain the angular velocity of the crankshaft rotation, a filtering process is performed to remove an angular velocity fluctuation component having a relatively high frequency caused by the torsional vibration of the crankshaft from the angular velocity signal by a low-pass filter.

  In step 405, cylinder discrimination is performed as to which cylinder's angular velocity detection section the current crankshaft rotation phase is in. Of the stroke cycle of the cylinder, the stroke to detect the crank angle at which the angular velocity is maximized or minimized is from the compression stroke to the explosion stroke section. In step 405, it is determined which cylinder is currently performing the combustion fluctuation determination by determining which cylinder is currently in this section.

  After the cylinder is determined in step 405, it is determined in step 407 whether or not the angular velocity detection section (that is, the compression / explosion stroke) of this cylinder has ended. If the detection section has not yet ended, the process returns to step 401 to return to the angular velocity. Continue detection of.

  If the detection section is completed in step 407, the process proceeds to step 409, where the crank rotation angle θmax when the detected angular velocity is maximum is obtained.

  In step 411, the average value AVGi of θmax for the past several stroke cycles of this cylinder is read from a predetermined storage location, and in step 413, the deviation σ (σ = | θmax−AVGi) from the average value AVGi of θmax detected this time is read. Is calculated.

  In step 415, the average value AVGi is updated using the current value of θmax and stored in a predetermined storage location to prepare for the next execution of this operation.

  Next, at step 417, based on the deviation σ calculated at step 415, it is determined whether or not this cylinder is currently deteriorating in combustion.

  The determination in step 417 is made based on whether or not the deviation σ is greater than or equal to a predetermined value α, that is, whether or not θmax detected this time varies greatly from the value of θmax for the past several cycles.

  Instead of determining the variation based on the magnitude of the deviation σ itself, the variation may be determined to be large when the ratio (σ / AVGi) of the deviation σ to the average value AVGi is greater than a predetermined value. Good.

  If the variation of θmax is not large in step 117 (ie, σ <α), the combustion has not deteriorated in this cylinder, so the process returns to step 401 again to start the angular velocity detection, and the next ignition It is determined whether or not there is a deterioration in combustion in the cylinders in the order.

  If it is determined in step 417 that combustion has deteriorated (that is, if σ ≧ α), the routine proceeds to step 419, where combustion stabilization control is performed.

  In the control of step 419, combustion is stabilized by increasing the fuel injection amount by a predetermined amount and retarding the ignition timing by a predetermined amount. That is, as long as it is determined in step 417 that the combustion has deteriorated, the fuel injection amount and the ignition timing are adjusted by a predetermined amount, and finally stable combustion can be obtained in this cylinder.

  When step 419 ends, step 401 is executed again, and the combustion fluctuation determination operation is performed for the next cylinder.

  In the example of FIG. 4, the crank angle θmax at which the angular velocity is maximized is described as the determination value. However, the crank angle θmin at which the angular velocity is minimized, or the crank angle dθmax at which the angular acceleration is maximized or Even when the crank angle dθmin that is minimized is used, the operation situation is the same as that in FIG.

  In the example of FIG. 4, the presence or absence of combustion deterioration is determined based on whether or not the deviation σ between the determination value θmax and the average value AVGi of θmax of the cylinder is equal to or greater than a predetermined value α. Is within a predetermined range (between the upper limit value and the lower limit value), or the value of θmax is a deviation σ = | θmax from a reference value β determined in advance for each operating state (engine speed and intake air amount) It may be determined that combustion deterioration has occurred when the ratio of −β | and β is greater than a predetermined value.

FIG. 5 shows a modification of FIG. 4 when Δθ = θmax−θmin is used as the determination value.
In the operation of FIG. 5, the operations in steps 501 to 507 are the same as the steps 401 to 407 in the operation of FIG.

  However, in the operation of FIG. 5, only θmax was obtained in step 409 in the operation of FIG. 4, whereas in step 509-1, in addition to θmax, the crank angle θmin at which the angular velocity takes a minimum value is obtained. -2 in which the determination value Δθ is obtained as Δθ = | θmax−θmin |, and in steps 511 to 515, the average value AVGθi of Δθ for the past several stroke cycles of this cylinder is used. It is different.

  In the operation of FIG. 5, the same effect can be obtained by performing the same operation using the crank angles dθmax and dθmin at which the angular acceleration is maximized and minimized instead of the crank angles θmax and θmin at which the angular velocity is maximized and minimized. Can be obtained.

4 and 5, the average value of θmax or Δθ is used as an average value of the past several stroke cycles of the corresponding cylinder to determine the magnitude of variation such as θmax this time. (Steps 411 to 417 in FIG. 4 and Steps 511 to 517 in FIG. 5).
However, instead of using the average value for each cylinder, θmax and the like of all the cylinders are obtained for one cycle or a plurality of cycles of the engine, and the average values of θmax, Δθ and the like for all the cylinders are obtained, and FIG. You may make it use for the dispersion | variation determination of 5.

  As described above, in this embodiment, the presence or absence of combustion deterioration is determined using the crank angle at which the angular velocity parameter is maximized or minimized, not based on the magnitude of the angular velocity parameter related to the crankshaft angular velocity. Thus, it is possible to accurately determine the presence or absence of combustion deterioration even during transient operation such as acceleration / deceleration.

It is a figure explaining schematic structure of an embodiment at the time of applying the present invention to an internal-combustion engine for vehicles. It is a figure explaining the problem in the conventional combustion fluctuation determination method. It is a figure explaining the combustion fluctuation detection principle outline in this invention. It is a flowchart explaining one Embodiment of combustion fluctuation | variation detection operation of this invention. It is a flowchart explaining one Embodiment of combustion fluctuation | variation detection operation of this invention.

Explanation of symbols

1 Engine Body 11 Fuel Injection Valve 30 Electronic Control Unit (ECU)
33 Angular velocity sensor

Claims (9)

Detecting means for detecting a predetermined angular velocity parameter related to the crankshaft rotational angular velocity of the internal combustion engine;
For each cylinder of the engine, at least one of a crank angle at which the angular velocity parameter takes a maximum value and a crank angle at which the angular velocity parameter takes a minimum value is detected in a period from the start of the compression stroke to the end of the expansion stroke, and as a function of the detected crank angle Determining means for determining the presence or absence of combustion deterioration in each cylinder based on the calculated determination value;
An internal combustion engine combustion fluctuation detection device comprising:   The combustion fluctuation detection device for an internal combustion engine according to claim 1, wherein the angular velocity parameter is a crankshaft rotation angular velocity.   The combustion fluctuation detection device for an internal combustion engine according to claim 1, wherein the angular velocity parameter is a change rate of a crankshaft rotation angular velocity.   4. The combustion fluctuation detection device for an internal combustion engine according to claim 1, wherein the determination value is a crank angle at which the angular velocity parameter takes a maximum value. 5.   The combustion fluctuation detection device for an internal combustion engine according to any one of claims 1 to 3, wherein the determination value is a crank angle at which the angular velocity parameter takes a minimum value.   The combustion fluctuation detection device for an internal combustion engine according to any one of claims 1 to 3, wherein the determination value is an angle difference between a crank angle at which the angular velocity parameter takes a maximum value and a crank angle at which the angular speed parameter takes a minimum value.   The determination means calculates the determination value for each stroke cycle of each cylinder, and when the variation of the determination value for each cylinder in each stroke cycle exceeds a predetermined value, the combustion of the cylinder deteriorates The combustion fluctuation detection device for an internal combustion engine according to any one of claims 1 to 6, wherein   The determination means calculates the determination value for each cylinder, and when a variation of the determination value in one cylinder from an average value of the determination values of all the cylinders exceeds a predetermined value, the determination value of the cylinder The combustion fluctuation detection device for an internal combustion engine according to any one of claims 1 to 6, wherein it is determined that the combustion has deteriorated.   The determination unit calculates the determination value for each cylinder, and determines that the combustion of the cylinder has deteriorated when the determination value in one cylinder is out of a predetermined range. The combustion fluctuation detection device for an internal combustion engine according to any one of the above.

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