JP2009191710A - Misfire detecting device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a misfire detecting device of an internal combustion engine capable of improving misfire determining accuracy particularly in a high rotational operation area, by reducing a difference from a desired value of a determining parameter for determining a misfire. <P>SOLUTION: The determining parameter MFJUD is calculated at each cylinder based on an engine speed parameter CRME and OMG for indicating an engine speed of an engine (S31). A correction quantity MFJOFFP is calculated by retrieving a correction quantity table preset according to an engine speed NE (S32). The correction quantity table is set according to a change in a pump loss in the engine caused by a change in the engine speed. A correction determining parameter MFJUDC is calculated by subtracting the correction quantity MFJOFFP from the determining parameter MFJUD (S33). When the correction determining parameter MFJUDC reaches a negative value, it is determined that the misfire is caused in a corresponding cylinder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a misfire detection device for an internal combustion engine, and more particularly to a device for determining the presence or absence of misfire based on a rotation speed parameter corresponding to the engine rotation speed.

  Patent Document 1 discloses a misfire detection apparatus that performs misfire determination based on a rotation speed parameter. In this device, the deviation between the reference rotational speed parameter detected when the piston of the cylinder to be determined is located near the top dead center and the rotational speed parameter detected every predetermined crank angle (6 degrees) is calculated. The integrated value calculated by integration is used as a determination parameter, and the presence or absence of misfire is determined from the comparison result between the determination parameter and the determination threshold.

  Patent Document 2 discloses an output fluctuation measuring method for an internal combustion engine. According to this method, the rotational speed change amount is used as a parameter representing the output fluctuation, and an accurate output fluctuation can be obtained regardless of the rotational speed by correcting the rotational speed change amount as the rotational speed increases.

JP 2007-198368 A Japanese Examined Patent Publication No. 4-61291

  In the apparatus disclosed in Patent Document 1, it is desirable that the value of the determination parameter during the fuel cut operation for cutting off the fuel supply to the engine is ideally “0”. However, since the value of the determination parameter deviates from “0” due to factors other than those described in Patent Document 1, it has been confirmed that there is a high possibility of erroneous determination particularly in the high-speed operation region of the engine. Yes.

  The technique disclosed in Patent Document 2 focuses on the fact that the relationship between the rotational speed change amount and the indicated mean effective pressure shows a substantially linear relationship, and the inclination of the straight line changes depending on the engine rotational speed. Therefore, even if the technique shown in Patent Document 2 is applied to the apparatus shown in Patent Document 1, it is difficult to solve the above problem.

  The present invention has been focused on the above-mentioned points, and improves the accuracy of misfire determination, particularly in the high-rotation operation region, by reducing the deviation of the determination parameter for determining misfire from the desired value. An object of the present invention is to provide a misfire detection apparatus for an internal combustion engine capable of

  In order to achieve the above object, the invention described in claim 1 is provided with a rotational speed parameter detecting means for detecting a rotational speed parameter (OMG) corresponding to the rotational speed of the internal combustion engine, and the detected rotational speed parameter (OMG) is included in the detected rotational speed parameter (OMG). In the misfire detection apparatus for an internal combustion engine that detects misfire of the engine based on the above, the rotational speed parameter detected when the piston of the cylinder to be misfired is in the vicinity of compression top dead center is set to a reference value (OMGR ((( k-1) NTDC)) as a reference value calculation means, and the reference value (OMGR ((k-1) NTDC)) and a rotational speed parameter (OMGR (i)) detected at each predetermined crank angle. Relative speed parameter calculation means for calculating a relative speed parameter (OMGREFMb) according to the deviation, and the relative speed parameter (OMGREFMb) is set to a crank angle 720 / N (N is the machine speed). The determination parameter calculation means for calculating the determination parameter (MFJUD) by integrating over the period of the number of cylinders), and correction according to the change in the pump loss of the engine accompanying the change in the rotational speed (NE) A correction unit that calculates an amount (MFJOFFP) and corrects the determination parameter (MFJUD) by the correction amount (MFJOFFP); and a determination unit that performs misfire determination based on the corrected determination parameter (MFJUDC). Features.

  According to a second aspect of the present invention, in the misfire detection device for an internal combustion engine according to the first aspect, the correction means includes a first component that increases linearly with respect to an increase in the rotational speed (NE), and the The correction amount (MFJOFFP) is calculated so as to change with a characteristic obtained by combining a second component that changes with the same characteristic as the change characteristic of the volume efficiency (ηv) of the engine with respect to an increase in the rotational speed (NE), and The determination parameter (MFJUD) is corrected by subtracting the correction amount (MFJOFFP) from the determination parameter (MFJUD).

  According to a third aspect of the present invention, in the misfire detection device for an internal combustion engine according to the first or second aspect, the correction means is a correction in which the correction amount (MFJOFFP) is set according to the rotational speed (NE). The correction amount table (MFJOFFP) is calculated using an amount table, and the correction amount table is set according to an average value (MFJFCAV) of the determination parameter obtained during a fuel cut operation for cutting off fuel supply to the engine. The correction amount (MFJOFFP) set in (1) is corrected.

  According to the first aspect of the present invention, the rotational speed parameter detected when the piston of the cylinder subject to misfire determination is near the compression top dead center is calculated as the reference value, and the reference value and the predetermined crank angle are calculated. A relative speed parameter is calculated according to the deviation from the rotational speed parameter detected every time. Then, the determination parameter is calculated by integrating the relative speed parameter over the period of the crank angle of 720 / N degrees, and the correction amount is calculated according to the change of the pump loss of the engine accompanying the change of the rotation speed, The determination parameter is corrected by the correction amount, and misfire determination is performed based on the corrected determination parameter. As a result of the examination, it has been found that the deviation of the determination parameter from the desired value is caused by a change in the pump loss of the engine. Therefore, by correcting the determination parameter in accordance with the change in the pump loss, the determination parameter The misalignment can be reduced, and the accuracy of misfire determination can be improved particularly in the high rotation region.

  According to the second aspect of the present invention, the first component that increases linearly with an increase in rotational speed and the second component that changes with characteristics similar to the characteristics of the change in volumetric efficiency of the engine with respect to an increase in rotational speed. The correction amount is calculated so as to change with the characteristics obtained by combining the two, and correction is performed by subtracting the correction amount from the determination parameter. By setting the correction amount in this way, the change in the rotational speed and the change in the volume efficiency of the engine accompanying the change are reflected in the correction amount, and the deviation of the determination parameter due to the pump loss can be corrected accurately. .

  According to the third aspect of the present invention, the correction amount is calculated using the correction amount table in which the correction amount is set according to the rotational speed, and is obtained during the fuel cut operation for cutting off the fuel supply to the engine. The correction amount set in the correction amount table is corrected according to the average value of the determination parameters. Therefore, even if the pump loss characteristic of the engine changes with time, the misfire determination accuracy can be maintained.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a control device thereof according to an embodiment of the present invention. An internal combustion engine (hereinafter simply referred to as “engine”) 1 has, for example, four cylinders and includes an intake pipe 2 and an exhaust pipe 5. A throttle valve 3 is provided in the intake pipe 2. The exhaust pipe 5 is provided with a catalytic converter 6 for purifying exhaust gas.

  The fuel injection valve 4 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). At the same time, it is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 20 and the opening time of the fuel injection valve 4 is controlled by a control signal from the ECU 20.

  An intake pressure sensor 11 for detecting the intake pressure PBA in the intake pipe 2 is provided immediately downstream of the throttle valve 3, and the detection signal is supplied to the ECU 20.

  A crank angle position sensor 12 that detects a rotation angle of a crankshaft (not shown) of the engine 1 is connected to the ECU 20, and a signal corresponding to the rotation angle of the crankshaft is supplied to the ECU 20. The crank angle position sensor 12 is a cylinder discrimination sensor that outputs a pulse (hereinafter referred to as “CYL pulse”) at a predetermined crank angle position of a specific cylinder of the engine 1, and relates to a top dead center (TDC) at the start of the intake stroke of each cylinder. A TDC sensor that outputs a TDC pulse at a crank angle position before a predetermined crank angle (every 180 degrees of crank angle in a four-cylinder engine) and one pulse (hereinafter referred to as “CRK”) with a constant crank angle cycle shorter than the TDC pulse (for example, a cycle of 6 °) The CYL pulse, the TDC pulse, and the CRK pulse are supplied to the ECU 20. These pulses are used for various timing controls such as fuel injection timing and ignition timing, and detection of engine speed (engine speed) NE. Further, the ECU 20 detects misfire in the engine 1 based on the CRK pulse generation time interval (hereinafter referred to as “time parameter”) CRME.

  The CRK sensor includes a pulse wheel that is fixed to the crankshaft and has teeth formed at regular angular intervals on the outer periphery, and a pickup coil that is disposed to face the pulse wheel. An AC signal is generated in the pickup coil by the rotation of the pulse wheel, and the AC signal is converted into a CRK pulse and output.

  The ECU 20 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, a central processing unit (hereinafter referred to as “CPU”). A storage circuit for storing various calculation programs executed by the CPU and calculation results, an output circuit for supplying a control signal to the fuel injection valve 4 and the like. The CPU of the ECU 20 performs misfire detection described below.

  The misfire determination method in the present embodiment is basically the same as that described in Patent Document 1 described above, and the present embodiment uses a determination parameter MFJUD for performing misfire determination as a pump for the engine 1. The correction is made according to the change characteristic of the loss.

  FIG. 2 is a diagram for explaining a problem in the misfire detection device disclosed in Patent Document 1. FIG. 2A shows a determination parameter MFJUD obtained when a fuel cut operation is performed (NE = 6800 rpm). Show. In principle, the determination parameter MFJUD of all the cylinders should be “0”, but is shifted in the positive direction (torque generation direction) as a whole (deviation DMFJ is generated).

  In order to investigate this cause, the in-cylinder pressure (combustion chamber pressure) of each cylinder of the engine 1 during the fuel cut operation is detected, and this is caused by the torque change characteristic calculated from the detected in-cylinder pressure and the theoretically determined inertial force. By comparing the torque change characteristics, it was confirmed that the deviation DMFJ occurred due to the pump loss of the engine. FIG. 2B is a diagram showing the relationship between the intake pressure PBA and the determination parameter MFJUD when the fuel cut operation is performed. The solid line L1 indicates the characteristics obtained by the experiment, and the broken line L2 is detected. The characteristic calculated based on the cylinder pressure waveform is shown. It can be confirmed that the two are almost the same.

  FIG. 2C shows characteristics at the time of normal combustion and occurrence of misfire, and a solid line L3 corresponds to the time of normal combustion and a broken line L4 corresponds to the time of occurrence of misfire. As is clear from this figure, when the intake pressure PBA is low (during low-load operation where the intake air flow rate is low), the determination parameter value at the time of misfire is close to “0”, and erroneous determination is likely to occur. I can confirm. 2B and FIG. 2C, the scale of the vertical axis is different, and the actual determination parameter value of the solid line L1 shown in FIG. 2B is the solid line shown in FIG. 2C. Less than L3.

  Since the pump loss increases as the intake air flow rate increases, the pump loss increases as the intake pressure PBA increases, and basically increases as the engine speed NE increases. However, the volumetric efficiency ηv of the engine changes as the engine speed NE changes, and the pump loss is affected by the change characteristic of the volumetric efficiency ηv. Therefore, the actual correction amount table (MFJOFFP table shown in FIG. 5A) does not have a characteristic that the correction amount MFJOFFP increases monotonously with an increase in the engine speed NE.

  In the present embodiment, a correction parameter table (MFJOFFP table shown in FIG. 5A) for calculating a correction value MFJOFFP by measuring the determination parameter value obtained during the fuel cut operation while changing the engine speed NE is stored in advance. The determination parameter MFJUD is corrected by a correction amount MFJOFFP that is created and calculated using this correction amount table. The correction amount MFJOFFP set based on the determination parameter value obtained during the fuel cut operation is smaller than the appropriate value during the high load operation where the intake pressure PBA is high. However, as shown in FIG. 2 (c), the higher the intake pressure PBA, the larger the difference between the determination parameter value at normal time and the determination parameter value at the time of misfire occurrence. Is hard to get up. Therefore, the determination accuracy can be improved by the correction using the correction amount MFJOFFP.

  FIG. 3 is a flowchart of a process for performing misfire determination based on the time parameter CRME detected by the CRK sensor. This process is executed in synchronization with the TDC pulse by the CPU of the ECU 20. Note that the time parameter CRME (i), which is the generation time interval of the CRK pulse generated every crank angle of 6 degrees, is data for the crank angle of 720 degrees (i = 0 to ND-1, the number of data ND is 120). It is stored in a buffer memory in the storage circuit. Further, if the cylinder identification number in the ignition order is k (= 1 to 4) and the number of data in one TDC period is NTDC (NTDC = 30 in the present embodiment), the parameter i is set by one execution of this process. (K-1) An operation from NTDC to (kNTDC-1) is performed. For example, when the current process performs an operation corresponding to the first cylinder (k = 1), the parameter i takes a value from 0 to (NTDC-1), and the current process is the third cylinder (k = When the calculation corresponding to 3) is performed, the parameter i takes a value from 2NTDC to (3NTDC-1).

In step S11, the time parameter CRME (i) is converted into the rotational speed OMG (i) [rad / s] by the following equation (1).
OMG (i) = Dθ / CRME (i) (1)
Here, Dθ is an angular interval of 4π / ND for measuring the time parameter CRME, and is π / 30 [rad] in the present embodiment.

In step S12, 720 degree filter processing is executed by the following equation (2), and the post-filter processing rotation speed OMGR (i) is calculated. The 720 degree filter process is a process for canceling a linear change in a cycle period and extracting a relatively short cycle fluctuation. The 720 degree filter processing is caused by torque applied to the engine 1 from the load side of the engine 1 (torque applied from a tire or an accessory of a vehicle driven by the engine 1 or torque due to friction of sliding parts of the engine 1). This is to remove the rotational fluctuation component.
OMGR (i) = OMG (i) − (OMG (ND) −OMG (0)) × Dθ × i / 4π
(2)

In step S13, the relative rotational speed OMGREF is calculated by the following equation (3).
OMGREF (i) = OMGR (i) -OMGR ((k-1) NTDC) (3)
Here, OMGR ((k-1) NTDC) is the reference rotational speed, and the post-filter processing rotational speed when the piston of the cylinder to be determined is at the compression top dead center (the top dead center at which the combustion stroke starts). It corresponds to.

In step S14, inertial force rotation speed OMGI (k) is calculated by the following equation (4). The inertial force rotational speed OMGI is the mass of the reciprocating parts (piston and connecting rod) of the engine 1, the length of the connecting rod, the crank radius, and the rotating parts on the load side of the engine 1, such as a crank pulley, torque converter, and lock-up clutch. It is calculated according to the moment of inertia I. In Equation (4), K is a constant set to a predetermined value, and the moment of inertia I is calculated in advance according to the engine specifications.
OMGI (k) = K.OMG ((k-1) NTDC) / 2I (4)

In step S15, the inertial force rotation speed OMGI (k) calculated by the equation (4) is applied to the following equation (5) to calculate the inertial force rotation speed OMGIa (i) at each sample timing. The reason why the inertial force rotational speed OMGI (k−2) before the 2TDC period is applied in the equation (5) is that the calculation accuracy is higher when the center value in the above-described 720 degree filter processing is used. Since the parameter k is a cylinder identification number, k = 0 and −1 correspond to k = N (= 4) and N−1 (= 3), respectively.
OMGIa (i) = OMGI (k−2) × {cos (N · Dθ · i / 2) −1}
(5)

In step S16, the inertia force rotational speed OMGIa (i) calculated in step S15 is applied to the following equation (6) to calculate the first corrected relative rotational speed OMGREFMa (i).
OMGREFMa (i) = OMGREF (i) -OMGIa (i) (6)

In step S17, the first correction relative rotational speed OMGREFMa (i) calculated in step S16 and the combustion correlation function FCR (i) calculated by the following equation (7) are applied to the following equation (8) to obtain the second correction. The relative rotational speed OMGREFMb (i) is calculated. The combustion correlation function FCR (i) is a function that approximates a change in rotational speed when normal combustion is performed in the engine and there is no disturbance affecting the detection value of the crank angle position sensor. By multiplying by the combustion correlation function FCR (i), it is possible to eliminate the influence of disturbance due to the crankshaft torsion or the detection error of the time parameter CRME by the crank angle position sensor.
FCR (i) = {1-2 cos (N · Dθ · i / 2)} / 2 (7)
OMGREFMb (i) = OMGREFMa (i) × FCR (i) (8)

  In step S18, the MFJUDC (k) calculation process of FIG. 4 is executed to calculate the correction determination parameter MFJUDC (k).

  In step S19, it is determined whether or not the correction determination parameter MFJUDC (k) is a negative value. If the answer is negative (NO), it is determined that normal combustion has been performed, and the misfire flag FMF (k ) Is set to “0” (step S20). On the other hand, when MFJUDC (k) <0, the cylinder corresponding to the cylinder identification number k (in this embodiment, k = 1, 2, 3, and 4 are the # 1, # 3, and # 4 cylinders, respectively. It is determined that misfire has occurred in the cylinder and cylinder # 2), and a misfire flag FMF (k) is set to “1” (step S21).

  In step S22, it is determined whether the cylinder identification number k is equal to the number N of cylinders. If the answer is negative (NO), the cylinder identification number k is incremented by "1" (step S24). If k = N, the cylinder identification number k is returned to “1” (step S23).

  The misfire determination is performed for each cylinder by the processing of FIG.

FIG. 4 is a flowchart of the MFJUDC (k) calculation process executed in step S18 of FIG.
In step S31, a determination parameter MFJUD (k) is calculated as an integrated value of 1TDC period of the second corrected relative rotational speed OMGREFMb (i) by the following equation (9).

  In step S32, the MFJOFFP table shown in FIG. 5A is searched according to the engine speed NE, and the correction amount MFJOFFP is calculated. The MFJOFFP table has a first component that linearly increases with an increase in the engine speed NE, and a first characteristic that changes with a characteristic similar to the change characteristic of the volumetric efficiency ηv with respect to the engine speed NE shown in FIG. The characteristic is set to be a combination of two components. In FIG. 5, the predetermined rotational speeds NE0, NE1, and NE2 are, for example, 2000 rpm, 3000 rpm, and 6000 rpm, respectively.

In step S33, the determination parameter MFJUD calculated in step S31 and the correction amount MFJOFFP calculated in step S32 are applied to the following equation (10) to calculate the correction determination parameter MFJUDC.
MFJUDC (k) = MFJUD (k) −MFJOFFP (10)

  FIG. 6 is a diagram showing a comparison between the determination parameter MFJUD calculated for each cylinder and the correction determination parameter MFJUDC. FIG. 6A corresponds to the state where the fuel cut operation is performed, and FIG. 6B corresponds to the state where misfire occurs in the # 2 cylinder and the # 3 cylinder during the normal operation.

  As is clear from FIG. 6A, all the correction determination parameters MFJUDC during the fuel cut operation are “0”, and it can be confirmed that the deviation DMFJ in the determination parameter MFJUD before correction is eliminated.

In addition, in the determination parameter MFJUD before correction shown in FIG. 6B, the determination parameter values of the # 2 cylinder and the # 3 cylinder are close to “0” which is the determination threshold value, and erroneous determination is likely to occur. On the other hand, in the correction determination parameter MFJUDC, it can be confirmed that the correction determination parameter values of the # 2 cylinder and the # 3 cylinder are away from “0” and the margin increases. Here, when the margin SN is defined by the following equation (11), the determination parameter before correction is 4.24 for the # 2 cylinder and 4.38 for the # 3 cylinder. On the other hand, the correction determination parameters are improved to 7.85 and 8.03, respectively.
SN = | MFJUDAVE | / σ (11)
Here, MFJUUDAVE is an average value of a large number of determination parameter values calculated for one cylinder, and σ is a standard deviation of the large number of determination parameter values.

  As described above, in the present embodiment, the correction amount MFJOFFP is calculated using the MFJOFFP table set according to the change characteristic of the pump loss, the correction parameter MFJUDP is corrected by the correction amount MFJOFFP, and the correction determination parameter MFJUDC is calculated. Since the misfire determination is performed using the correction determination parameter MFJUDC, the deviation of the determination parameter from the ideal value can be reduced, and the accuracy of the misfire determination can be improved particularly in the high rotation region.

  Further, the correction amount MFJOFFP changes with a characteristic obtained by synthesizing a component that linearly increases with an increase in the rotational speed and a component that changes with a characteristic similar to the change characteristic of the volumetric efficiency ηv of the engine with respect to the increase in the rotational speed. Since the MFJOFFP table is set, the change in the engine speed NE and the change in the volumetric efficiency ηv accompanying the change in the engine speed NE are reflected in the correction amount MFJOFFP, and the deviation of the determination parameter MFJUD due to the pump loss is reduced. It can be corrected accurately.

  In the present embodiment, the crank angle position sensor 12 and the ECU 20 constitute a rotation speed parameter detection means, and the ECU 20 constitutes a reference value calculation means, a relative speed parameter calculation means, a determination parameter calculation means, a correction means, and a determination means. . Specifically, step S11 in FIG. 3 corresponds to a part of the rotation speed parameter detection means, steps S13 to S17 correspond to the reference value calculation means and relative speed parameter calculation means, and step S18 corresponds to the determination parameter calculation means and Steps S19 to S21 correspond to a determination unit. Step S31 in FIG. 4 corresponds to a determination parameter calculation unit, and steps S32 and S33 correspond to a correction unit.

The present invention is not limited to the embodiment described above, and various modifications can be made. For example, the determination parameter MFJUD is calculated even during the fuel cut operation, the average value MFJFCAV of the determination parameter MFJUD value during the fuel cut operation is calculated, and the MFJOFFP table according to the average value NEAV of the engine speed NE during that period The set value MFJOFFP (NE) may be corrected by the following equation (11). CL in Expression (11) is an annealing coefficient set to about 0.02, for example, and MFJOFFP (NE) on the right side is a table setting value before correction.
MFJOFFP (NE) = CL × MFJFCAV
(1-CL) x MFJOFFP (NE) (11)
Thus, by correcting the MFJOFFP table setting value, it is possible to maintain the accuracy of misfire determination even when the pump loss characteristic changes with time.

  In the above-described embodiment, the misfire determination is performed by converting the time parameter CRME to the rotational speed OMG. However, as shown in Patent Document 1, the misfire determination is performed using the time parameter CRME itself as the rotational speed parameter. You may do it.

  The MFJOFFP table may calculate the correction amount MFJOFFP according to the detected engine speed NE and the intake pressure PBA instead of the MFJOFFP map according to the engine speed NE and the intake pressure PBA. The MFJOFFP map is set so that the correction amount MFJOFFP increases as the intake pressure PBA increases, and the correction amount MFJOFFP changes with respect to the engine speed NE as in the MFJOFFP table shown in FIG.

  In the above-described embodiment, an example in which the present invention is applied to a four-cylinder engine is shown, but the present invention can be applied regardless of the number of cylinders. The present invention can also be applied to misfire determination of a gasoline engine or a diesel engine that directly injects fuel into a combustion chamber. Furthermore, the present invention can be applied to misfire determination of a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

It is a figure which shows the structure of the internal combustion engine and its control apparatus concerning one Embodiment of this invention. It is a figure for demonstrating the problem in the conventional method. It is a flowchart of the process which performs misfire determination. It is a flowchart of the process which calculates the correction | amendment determination parameter (MFJUDC) performed by the process of FIG. It is a figure which shows the table referred by the process of FIG. It is a figure for demonstrating the effect of correction | amendment of a determination parameter.

Explanation of symbols

1 Internal combustion engine 12 Crank angle position sensor (rotational speed parameter detection means)
20 Electronic control unit (rotation speed parameter detection means, reference value calculation means, relative speed parameter calculation means, determination parameter calculation means, correction means, determination means)

Claims (3)

In a misfire detection device for an internal combustion engine, comprising a rotation speed parameter detection means for detecting a rotation speed parameter according to the rotation speed of the internal combustion engine, and detecting misfire of the engine based on the detected rotation speed parameter.
A reference value calculation means for calculating, as a reference value, the rotational speed parameter detected when the piston of the cylinder subject to misfire determination is near the compression top dead center;
A relative speed parameter calculating means for calculating a relative speed parameter in accordance with a deviation between the reference value and a rotational speed parameter detected for each predetermined crank angle;
Determination parameter calculation means for calculating a determination parameter by integrating the relative speed parameter over a period of a crank angle of 720 / N (N is the number of cylinders of the engine);
Correction means for calculating a correction amount according to a change in pump loss of the engine accompanying a change in the rotational speed, and correcting the determination parameter by the correction amount;
A misfire detection apparatus for an internal combustion engine, comprising: a determination unit that performs misfire determination based on a corrected determination parameter.   The correction means combines a first component that increases linearly with an increase in the rotational speed and a second component that changes with a characteristic similar to the change characteristic of the volumetric efficiency of the engine with respect to the increase in the rotational speed. 2. The misfire detection apparatus for an internal combustion engine according to claim 1, wherein the correction amount is calculated so as to change according to the characteristic, and the determination parameter is corrected by subtracting the correction amount from the determination parameter. .   The correction means calculates the correction amount using a correction amount table in which the correction amount is set in accordance with the rotational speed, and is obtained during a fuel cut operation for cutting off fuel supply to the engine. The misfire detection device for an internal combustion engine according to claim 1 or 2, wherein the correction amount set in the correction amount table is corrected according to an average value of the determination parameter.

Images