JP4572965B2 - Misfire detection device for internal combustion engine - Google Patents

Description

  The present invention relates to a misfire determination apparatus for an internal combustion engine. In particular, the present invention relates to a measure for improving the reliability of the determination operation in the misfire determination device that determines whether misfire has occurred based on the rotational fluctuation of the internal combustion engine.

  Conventionally, for example, when a phenomenon in which an air-fuel mixture is not ignited, for example, in a car internal combustion engine, a so-called “misfire” occurs, the unburned air-fuel mixture is discharged into the exhaust passage, which deteriorates exhaust emission and adversely affects the exhaust purification catalyst Is concerned.

  In view of this, attention has been paid to the fact that fluctuations in the engine rotational speed (hereinafter simply referred to as rotational fluctuations) increase when the misfire occurs, and a misfire determination apparatus that determines the occurrence of misfire based on this rotational fluctuation has been proposed. The basic principle of misfire determination in this type of device is as follows.

  First, when a misfire occurs in a certain cylinder, the engine speed in the expansion stroke of the cylinder (the stroke where the misfire has actually occurred and the explosion has not exploded) gradually decreases. As a result, the time required for the crankshaft to rotate at a constant crank angle during the expansion stroke of the cylinder in which this misfire has occurred is longer than that time during the expansion stroke of the other cylinders. Therefore, it is possible to determine whether or not misfire has occurred by measuring and comparing these times.

  Specifically, when a certain cylinder (for example, the third cylinder) is in the expansion stroke, the time required for the crankshaft to rotate at a constant crank angle during the expansion stroke, and a predetermined crank angle from the expansion stroke. Calculate the difference from the time required for the crankshaft to rotate at a certain crank angle during the expansion stroke of the cylinder (for example, the second cylinder) that had been in the expansion stroke before (eg, 360 ° before) (from the former time) Subtract the latter time). If the calculated value exceeds a predetermined threshold, it is determined that the rotational fluctuation of the internal combustion engine has increased, and it is determined that a misfire (misfire in the third cylinder) has occurred.

  In a vehicle for an OBD (On-Board Diagnostics System) compatible country, a misfire counter is provided in the control circuit, and the misfire counter is incremented every time a misfire occurrence is determined, and a predetermined number of engine revolutions (for example, 1000 revolutions) ) When the count value of the misfire counter per unit exceeds a predetermined value (for example, 30), the MIL (warning light) is turned on to prompt the driver to warn.

  Therefore, in a situation where the misfire is not accurately determined, for example, although the misfire has occurred, the misfire cannot be recognized, and the state in which the exhaust emission deteriorates continues. Further, it is erroneously determined that a misfire has occurred despite the fact that no misfire has occurred, and even if the actual number of misfires is smaller than the predetermined value, the MIL is lit up early. , The user feels uncomfortable.

  Therefore, in order to eliminate misjudgment of misfire, it is known that misfire has been determined when the temporal variation pattern of rotation fluctuation becomes a predetermined misfire pattern (for example, the following) (See Patent Document 1).

  What is disclosed in Patent Document 1 detects the time required for the crankshaft to rotate at a constant crank angle during the expansion stroke of each cylinder, and detects the time between cylinders in which the expansion stroke is performed at one interval ( In the case of a four-cylinder engine, the deviation of the above-mentioned time of cylinders in which the expansion stroke is performed at an angular interval of 360 ° is obtained, and this deviation exceeds the threshold, and the variation pattern of the deviation becomes a characteristic pattern when a misfire occurs. It is determined that a misfire has occurred. Specifically, the rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder exceeds a predetermined threshold, and the rotational fluctuation amount has reached the expansion stroke immediately before the expansion stroke of the misfire determination target cylinder. When the rotational fluctuation amount of the cylinder and the rotational fluctuation amount of the cylinder that has reached the expansion stroke immediately after the expansion stroke of the cylinder subject to misfire determination are particularly large, it is determined that misfire has occurred in this misfire determination target cylinder. Yes.

Further, in Patent Documents 2 to 4 below, in a vehicle having a torque converter with a lock-up clutch, threshold values for engine misfire determination are determined when the engine is in a lock-up state and when it is in a non-lock-up state. It is disclosed that it is different.
JP 2006-152971 A JP-A-4-171249 JP-A-10-331707 JP 2004-293350 A

  However, the inventor of the present invention has found that there is still a possibility that misjudgment of misfire occurs in the misfire judgment operation in each patent document as described above.

  Specifically, an automobile equipped with an automatic transmission (automatic transmission) as a transmission is provided with a lock-up clutch in the torque converter, and in the engaged state (lock-up state) of the lock-up clutch, the engine And the transmission are directly connected. In such a situation, when a misfire occurs and vibrations occur in the engine, the vibrations are transmitted to the transmission. When the vibration frequency matches the natural frequency of the transmission, the power train from the engine to the transmission The entire resonance phenomenon will occur. In a situation where such a resonance phenomenon occurs, the rotational fluctuation cannot be accurately recognized, and there is a possibility of misjudgment of misfire.

  An example of the occurrence situation of this misfire misjudgment will be described. The engine speed is measured by detecting the passage of the external teeth of the NE rotor integrally attached to the crankshaft by a crank angle sensor composed of an electromagnetic pickup. At this time, when the resonance phenomenon occurs, Resonance also occurs in the stay that supports the crank angle sensor, and the relative position between the crank angle sensor and the NE rotor fluctuates. For this reason, despite the fact that the rotational speed of the crankshaft fluctuates due to misfire, due to the resonance phenomenon, this rotational fluctuation cannot be accurately detected, and misfire occurs despite the occurrence of misfire. If not, it will be misjudged.

  In addition, in Patent Documents 2 to 4 described above, it is disclosed that the threshold value for misfire determination is different between when the lockup clutch is in the lockup state and when it is in the nonlockup state. No consideration is given to misjudgment of misfire caused by the resonance phenomenon of the entire power train, and only misfire judgment is performed based on whether or not the rotational fluctuation amount exceeds a predetermined threshold. Therefore, in these Patent Documents 2 to 4, there is still a possibility that misjudgment of misfire occurs.

  The present invention has been made in view of such points, and an object of the present invention is to provide a misfire determination apparatus that can avoid misjudgment of misfire caused by the resonance phenomenon.

-Principle of solving the problem-
The solution principle of the present invention taken to achieve the above object is to determine the presence or absence of misfire by recognizing the rotational fluctuation pattern of the internal combustion engine, and the lock-up clutch is used as the rotational fluctuation pattern for the determination. The misfire determination pattern is made different between when the lockup state is set and when the lockup state is not set. Furthermore, when the lockup clutch is in the lockup state, the misfire determination condition is relaxed so that it can be determined that the misfire has occurred even if the rotational fluctuation range is small compared to the case of the non-lockup state. Yes. This makes it possible to avoid misjudgment of misfire even in a situation where the resonance phenomenon occurs in the lock-up state.

-Solution-
Specifically, the present invention assumes a misfire determination device for an internal combustion engine causing loss fire determination of internal combustion engine coupled to the transmission via a fluid type power transmission device having a lockup clutch. For this misfire determination device, “the difference between the rotational speed of the cylinder currently in the expansion stroke and the rotational speed during the expansion stroke of the cylinder that had reached the expansion stroke two times before ignition at the ignition timing” is defined as the rotational fluctuation amount. When the rotational fluctuation amount exceeds a predetermined threshold, the cylinder that has reached the expansion stroke at that time is set as a misfire determination target cylinder in which misfire may occur. Then, in the non-lock-up state of the lock-up clutch, a misfire determination operation is performed depending on whether or not the rotation fluctuation pattern of the internal combustion engine is along the first rotation fluctuation pattern, and in the lock-up state of the lock-up clutch, There is provided a misfire determination means for performing a misfire determination operation depending on whether or not the rotation variation pattern of the internal combustion engine is along the second rotation variation pattern. The first rotational fluctuation pattern includes the amount of rotational fluctuation and the expansion stroke of the misfire determination target cylinder during the expansion stroke of the pre-ignition cylinder that has reached the expansion stroke immediately before the expansion stroke of the misfire determination target cylinder. The rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder is greater than a predetermined amount with respect to the rotational fluctuation amount during the expansion stroke of the post-ignition cylinder that has undergone an expansion stroke immediately thereafter, and the post-ignition cylinder The rotational fluctuation amount in the expansion stroke of the cylinder after two ignitions that has reached the expansion stroke immediately after the expansion stroke is substantially the same as the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder. Therefore, it is defined as a pattern in which positive and negative values are reversed. On the other hand, in the second rotational fluctuation pattern, the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder is larger than a predetermined amount with respect to the rotational fluctuation amount in the expansion stroke of the cylinder before one ignition, The difference between the rotational fluctuation amount in the expansion stroke of the cylinder after one ignition and the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder is equal to or less than a predetermined amount, and the expansion stroke of the cylinder after the two ignitions Is defined as a pattern in which the absolute value is substantially the same and the sign is opposite to the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder.
Further, as the second rotational fluctuation pattern, a difference between the rotational fluctuation amount during the expansion stroke of the cylinder before one ignition and the rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder is a predetermined amount or less. The rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder is greater than a predetermined amount with respect to the rotational fluctuation amount during the expansion stroke of the cylinder after the first ignition, and the expansion stroke of the cylinder after the second ignition. In some cases, the rotational fluctuation amount at the time is defined as a pattern in which the absolute value is substantially the same and the sign is opposite to the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder.

Based on these specific matters, first, when the rotational fluctuation amount exceeds a predetermined threshold during driving of the internal combustion engine, it is determined that there is a possibility that misfire has occurred. When the lock-up clutch is in the non lock-up state, it performs the misfire determination operation depending on whether the rotation fluctuation pattern of the internal combustion engine is along the first rotational fluctuation patterns. That is, when the rotation fluctuation pattern of the internal combustion engine in the non-lock-up state is along the first rotation fluctuation pattern, it is determined that misfire has occurred. On the other hand, when the lock-up clutch is in the lockup state, it performs the misfire determination operation depending on whether the rotation fluctuation pattern of the internal combustion engine is along the second rotational fluctuation patterns. That is, when the rotational fluctuation pattern of the internal combustion engine in the lock-up state is along the second rotational fluctuation pattern, it is determined that misfire has occurred.

  And this 2nd rotation fluctuation pattern is prescribed | regulated as a thing with a small rotation fluctuation width compared with a 1st rotation fluctuation pattern. In other words, the pattern is such that the misfire determination condition is relaxed. For this reason, even when it is not determined that a misfire has occurred in the non-lock-up state of the lock-up clutch when a similar rotational fluctuation has occurred, a misfire has occurred in the lock-up state of the lock-up clutch. It will be determined. In other words, when the resonance between the internal combustion engine and the transmission occurs in the lockup state of the lockup clutch, misfire occurs because the rotational fluctuation is reduced by the influence of this resonance. However, according to this solution, the occurrence of misfire is detected by using a specific rotation fluctuation pattern (the second rotation fluctuation pattern). It becomes possible. In this way, it is accurately determined that misfire has occurred without being adversely affected by the resonance phenomenon, and the reliability of misfire determination can be improved.

  The following is mentioned as a configuration for defining a precondition for performing the misfire determination operation based on the second rotation variation pattern. In other words, when the lock-up clutch is in the lock-up state, the misfire determination is performed only when the gear position of the transmission is at a specific gear position where resonance between the internal combustion engine and the transmission may occur. The means is configured to perform a misfire determination operation based on the second rotation fluctuation pattern.

  The situation in which the resonance phenomenon between the internal combustion engine and the transmission occurs is limited. That is, this is a case where a misfire occurs when the transmission is at a specific gear position and at a specific internal combustion engine speed. For this reason, since the resonance phenomenon does not occur at any gear other than the specific gear, it is not necessary to perform the misfire determination operation based on the second rotation fluctuation pattern other than the specific gear. By not performing the misfire determination operation in such a situation, it is possible to minimize the execution timing of the misfire determination operation based on the second rotation variation pattern, and to avoid unnecessary misfire determination operation and lock It is possible to improve the reliability of misfire determination in the up state.

  One of the conditions for executing the misfire determination operation based on the second rotation fluctuation pattern is as follows. In other words, when the lockup clutch is in the lockup state, if it is determined that there is a possibility that misfire has occurred due to the rotational fluctuation amount of the internal combustion engine exceeding a predetermined threshold, the misfire has occurred. When the cylinder determined to have the possibility that the rotational fluctuation amount has exceeded a predetermined threshold even in the past combustion stroke, the misfire determination means is based on the second rotational fluctuation pattern for the cylinder. The misfire determination operation is performed.

  As described above, since the second rotation variation pattern loosens the misfire determination condition, there is a possibility that it may be erroneously determined that a misfire has occurred even though no misfire has occurred. . In view of this, in this solution, a cylinder that has been determined to have a possibility of misfire in the past is only used when it is determined that a misfire may have occurred again. On the other hand, a misfire determination operation for determining whether or not the rotation variation pattern is along the second rotation variation pattern is performed. Thereby, the misjudgment of the misfire can be prevented, and the reliability of the misfire judgment operation can be further improved.

  Specific examples of the misfire determination operation based on the second rotation fluctuation pattern include the following. When the lock-up clutch is in the lock-up state, if it is determined that there is a possibility that misfire has occurred due to the rotational fluctuation amount of the internal combustion engine exceeding a predetermined threshold, the expansion of the misfire determination target cylinder The amount of rotational fluctuation during the stroke, the amount of rotational fluctuation during the expansion stroke of the cylinder that had undergone the expansion stroke immediately before the expansion stroke of the cylinder subject to misfire determination, and the expansion stroke immediately after the expansion stroke of the cylinder subject to misfire determination The misfire determination operation is performed by comparing the change pattern of the rotational fluctuation amount during the expansion stroke of the cylinder and the second rotational fluctuation pattern.

  Thereby, the misfire determination operation based on the second rotation variation pattern can be specifically specified, and the practicality of the present invention can be enhanced.

  As described above, in the present invention, the rotation variation pattern of the internal combustion engine for determining the presence or absence of misfire is different depending on whether the lock-up clutch is in the lock-up state or the non-lock-up state. I am doing so. Furthermore, when the lockup clutch is in the lockup state, the misfire determination condition is relaxed so that it can be determined that the misfire has occurred even if the rotational fluctuation range is small compared to the case of the non-lockup state. Yes. Thereby, even in a situation where the resonance phenomenon between the internal combustion engine and the transmission occurs in the lockup state, erroneous determination of misfire can be avoided, and the reliability of misfire determination can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to an automobile four-cylinder gasoline engine will be described.

-Engine configuration description-
First, a schematic configuration of an engine (internal combustion engine) to which the misfire determination device according to the present embodiment is applied and its peripheral devices will be described with reference to FIG. As shown in FIG. 1, the engine 1 according to the present embodiment includes a cylinder block 1a having cylinder bores 2 for four cylinders (only one cylinder is shown in FIG. 1), and a cylinder head 1b. Each cylinder bore 2 is provided with a piston 3 provided so as to be movable up and down, and this piston 3 is connected to a crankshaft 10 which is an output shaft of the engine 1 via a connecting rod (connecting rod) 3a. In the cylinder bore 2, a combustion chamber 4 is defined by a space surrounded by the piston 3 and the cylinder head 1b.

  A spark plug 11 is attached to the cylinder head 1 b corresponding to each combustion chamber 4. The cylinder head 1b is provided with an intake port 5a and an exhaust port 6a communicating with each combustion chamber 4, and an intake passage 5 and an exhaust passage 6 are connected to the intake port 5a and the exhaust port 6a, respectively. . An intake valve 7 and an exhaust valve 8 are respectively provided at open ends of the intake port 5a and the exhaust port 6a that lead to the combustion chamber 4. The intake valve 7 and the exhaust valve 8 are opened and closed by an intake camshaft 31 and an exhaust camshaft 32 that are respectively rotated by the power of the crankshaft 10. The power of the crankshaft 10 is transmitted to the intake camshaft 31 and the exhaust camshaft 32 via a timing belt 35 and timing pulleys 33 and 34.

  In the vicinity of the intake port 5a, an injector (fuel injection valve) 9 is provided corresponding to each cylinder. Each injector 9 is supplied with fuel at a predetermined pressure via a fuel supply system (not shown).

  On the other hand, a surge tank 16 is provided in the intake passage 5, and a throttle valve 19 that is opened and closed according to the operation of an accelerator pedal 18 is provided on the upstream side of the surge tank 16. The amount of intake air introduced into the intake passage 5 is adjusted according to the opening of the throttle valve 19.

  When the operation of the engine 1 is started, the intake air is introduced into the intake passage 5 and fuel is injected from the injector 9, whereby the intake air and the fuel are mixed to become an air-fuel mixture. In the intake stroke of the engine 1, the intake port 5a is opened by the intake valve 7, whereby the air-fuel mixture is taken into the combustion chamber 4 through the intake port 5a. The air-fuel mixture taken into the combustion chamber 4 is compressed in the compression stroke, and then ignited by the spark plug 11. The air-fuel mixture explodes and burns, and a driving force is applied to the crankshaft 10 (expansion stroke). . The exhaust gas after combustion is discharged to the exhaust passage 6 (exhaust stroke) by opening the exhaust port 6a by the exhaust valve 8 and further purified through the catalyst 12, and then released to the outside. The spark plug 11 performs an ignition operation on the air-fuel mixture according to the application timing of the high voltage output from the igniter 13.

  The engine 1 is provided with various sensors as described below for detecting the operating state.

  A crank angle sensor 21 for detecting the rotation angle (crank angle CA) and the rotation speed (engine rotation speed NE) is disposed in the vicinity of the crankshaft 10. The crank angle sensor 21 outputs a pulse signal every predetermined crank angle (for example, 30 °). As an example of a crank angle detection method by the crank angle sensor 21, external teeth are formed at intervals of 30 ° on the outer peripheral surface of a rotor (NE rotor) (not shown) that is integrated with the crankshaft 10, and the external teeth The crank angle sensor 21 composed of an electromagnetic pickup is disposed so as to face. When the external teeth pass near the crank angle sensor 21 as the crankshaft 10 rotates, the crank angle sensor 21 generates an output pulse. In addition, as this rotor, the thing in which the external tooth formed in an outer peripheral surface was formed every 10 degrees may be applied. In this case, frequency division is performed in the engine control device (engine ECU) 40 to generate output pulses every 30 ° CA.

  A cam angle sensor 22 is disposed in the vicinity of the intake camshaft 31. The cam angle sensor 22 is normally used as a cylinder discrimination sensor, and outputs a pulse signal corresponding to, for example, the compression top dead center (TDC) of the first cylinder # 1. That is, the cam angle sensor 22 outputs a pulse signal for each rotation of the intake camshaft 31. As an example of a cam angle detection method by the cam angle sensor 22, external teeth are formed at one place on the outer peripheral surface of the rotor integrally formed with the intake camshaft 31, and the external teeth are faced with an electromagnetic pickup. The cam angle sensor 22 is arranged, and when the external teeth pass in the vicinity of the cam angle sensor 22 as the intake cam shaft 31 rotates, the cam angle sensor 22 generates an output pulse. . Since this rotor rotates at half the rotational speed of the crankshaft 10, an output pulse is generated every time the crankshaft 10 rotates 720 °. In other words, an output pulse is generated each time a specific cylinder reaches the same stroke (for example, when the first cylinder # 1 reaches top dead center).

  The surge tank 16 is provided with a pressure sensor 23 for detecting the pressure in the intake passage 5 (intake pipe pressure PM). The pressure sensor 23 outputs a signal corresponding to the pressure in the surge tank 16.

  The above is the schematic configuration of the engine 1 according to the present embodiment.

-Automatic transmission-
Next, an automatic transmission that transmits the rotational power from the engine 1 and performs a shift operation will be described. FIG. 2 is a schematic configuration diagram showing a connection state between the engine 1 and the automatic transmission 50. FIG. 3 is a diagram showing a schematic configuration of a torque converter (fluid power transmission device) 53.

  As shown in these drawings, the automatic transmission 50 changes the rotational power input from the engine 1 to the input shaft 51 and outputs it to the drive wheels via the output shaft 52. A transmission mechanism 54, a hydraulic control device 55, and the like are included.

  The torque converter 53 is rotationally connected to the engine 1 and includes a pump impeller 53a, a turbine runner 53b, a stator 53c, a one-way clutch 53d, a stator shaft 53e, and a lockup clutch 53f.

  The lock-up clutch 53f allows the pump impeller 53a (input side) and the turbine runner 53b (output side) of the torque converter 53 to be directly connected, and the pump impeller 53a and the turbine runner 53b are connected as necessary. The state is switched between a directly engaged state, a released state in which the pump impeller 53a and the turbine runner 53b are disconnected, and a half-engaged state (slip state) intermediate between these engaged state and released state. The conditions for this switching will be described later.

  The engagement force control of the lockup clutch 53f is performed by controlling the hydraulic pressure with respect to the pump impeller 53a (input side) and the turbine runner 53b (output side) by the lockup control valve 56.

  The speed change mechanism unit 54 includes, for example, a plurality of planetary gears, clutches, brakes, one-way clutches, and the like. For example, the speed change mechanism 54 is capable of shifting 6 forward speeds and 1 reverse speed. The hydraulic control device 55 is configured to establish appropriate gears (forward 1st to 6th gears, reverse gear) by individually engaging and releasing the clutches and brakes of the transmission mechanism 54. . Since the structure of the speed change mechanism 54 and the control operation by the hydraulic control device 55 are known, detailed illustration and explanation are omitted here.

-Engine control device 40, transmission control device 45-
The hydraulic control device 55 is controlled by a transmission control device 45. That is, an appropriate shift stage, that is, a power transmission path in the speed change mechanism portion 54 is established by the control of the hydraulic control device 55 by the transmission control device 45.

  As shown in FIG. 4, the engine control device 40 and the transmission control device 45 are connected so as to be able to send and receive information necessary for engine control and transmission control.

  Although not shown, the engine control device 40 and the transmission control device 45 are both generally known ECUs (Electronic Control Units), and are respectively a CPU (Central Processing Unit), a ROM (Read Only Memory), A RAM (Random Access Memory) and a backup RAM are provided.

  The ROM stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU executes arithmetic processing based on various control programs and maps stored in the ROM. The RAM is a memory for temporarily storing calculation results in the CPU, data input from each sensor, and the like. The backup RAM is a non-volatile memory for storing data to be saved when the engine 1 is stopped. is there.

  As shown in FIG. 4, the engine control device 40 is connected to various sensors for detecting the operating state of the engine 1, such as the crank angle sensor 21, the cam angle sensor 22, and the pressure sensor 23. Each sensor signal is input. The engine control device 40 controls each part of the engine 1 such as the actuator 19a of the throttle valve 19 and the injector 9. Further, the engine control device 40 is provided with a misfire counter 41. The misfire counter 41 is incremented every time it is recognized that a misfire has occurred in the engine 1 by a misfire determination operation described later. It has become.

  The transmission control device 45 includes an input shaft rotational speed sensor 61 that detects the rotational speed of the input shaft 51, an output shaft rotational speed sensor 62 that detects the rotational speed of the output shaft 52, and an accelerator pedal 18 that is operated by a driver. An accelerator opening sensor 63 for detecting the degree, a shift position sensor 64 for detecting the shift lever position of the automatic transmission 50, a wheel speed sensor 65 for detecting the speed of the driving wheel (wheel speed), and the like are connected.

  The transmission control device 45 outputs a lockup clutch control signal to the lockup control valve 56. Based on the lock-up clutch control signal, the lock-up control valve 56 controls the engagement pressure of the lock-up clutch 53f, and the above-mentioned lock-up clutch 53f is engaged (torque state), released (complete slip state), The semi-engaged state (slip state: also called flex lockup state) is switched.

  Further, the transmission control device 45 outputs a solenoid control signal (hydraulic command signal) to the hydraulic control device 55 of the automatic transmission 50. Based on this solenoid control signal, a linear solenoid valve, an on-off solenoid valve, and the like provided in the hydraulic control circuit of the hydraulic control device 55 are controlled, and predetermined gears (first to sixth gears, reverse gear) Etc.), each clutch, each brake, etc. of the automatic transmission 50 is engaged or released to a predetermined state.

-Lock-up clutch operation map-
The above-described switching operation between the engaged state, the released state, and the half-engaged state of the lockup clutch 53f is performed according to a lockup clutch operation map as shown in FIG. 5, for example. This lockup clutch operation map uses the vehicle speed V and the accelerator opening θTH as parameters, and according to the vehicle speed V and the accelerator opening θTH, the lockup clutch 53f is engaged (locked up), released (torque converter). State) and a semi-engaged state (flex lock-up state: slip state), and is stored in the ROM of the transmission control device 45.

  That is, based on the vehicle speed V and the accelerator opening θTH, it is determined whether the vehicle belongs to the engagement region (lock-up operation region), the release region (torque converter operation region), or the slip region (flex lock-up operation region). Then, the lock-up control valve 56 is controlled so that the determined region is operated, and the lock-up clutch 53f is controlled to be engaged, released, or half-engaged. It should be noted that the state of the lock-up clutch 53f is determined by a lock-up clutch operation map (a map for controlling the lock-up clutch 53f according to the vehicle speed and the throttle opening) instead of the accelerator opening θTH. You may make it switch.

  In the flex lockup operation region, the power transmission loss of the torque converter 53 is suppressed as much as possible while absorbing the rotational fluctuation of the engine 1 for the purpose of improving the fuel consumption as much as possible without impairing drivability. In addition, slip control of the lock-up clutch 53f is executed. Regarding the slip control of the lockup clutch 53f, the rotational speed difference (slip amount) NSLP (= NE−NT) between the turbine rotational speed NT and the engine rotational speed NE is controlled to the target rotational speed difference (target slip amount: for example, 50 rpm). Therefore, a drive signal is output to the solenoid valve that controls the lockup clutch 53f. Of the slip control, slip control during deceleration traveling is, for example, a shift that transmits to the engine 1 the reverse input from the drive wheel side that occurs during forward traveling when the accelerator opening θTH is substantially zero and coasting (decelerated traveling). The speed of the engine, that is, the speed at which the engine braking action is obtained, is performed, and the turbine rotational speed NT and the engine rotational speed NE are gradually decreased as the vehicle decelerates. When the lock-up clutch 53f is slip-engaged in this way, the engine rotational speed NE is raised to near the turbine rotational speed NT, so that the control state (fuel cut state) for suppressing the fuel supply amount to the engine 1 is longer. It is maintained and fuel economy improves.

-Configuration and operation for misfire determination-
Next, a configuration for engine misfire determination (configuration of misfire determination apparatus) and its operation, which are characteristic parts of the present embodiment, will be described.

  The misfire determination device according to the present embodiment includes the engine control device 40. The engine control device 40 receives the output signals of the sensors 21 to 24, respectively. Based on these signals, the engine control device 40 calculates the crank angle CA, the engine speed NE, the current operating cylinder (for example, the cylinder that is currently in the expansion stroke), the intake pipe pressure PM, and the like. Based on the calculation results, a misfire determination operation described later is executed.

  Next, the misfire determination operation of the misfire determination device will be described. This misfire determination device uses T1 as the time required to rotate 0 ° to 30 ° CA from the 360 ° crank angle (CA) to the retard side with reference to the compression top dead center of each cylinder. The time required for 90 ° to 120 ° CA rotation is calculated as T2. Each of the times T1 and T2 is a time required for 30 ° CA corresponding to an angle estimated for the time required for the crankshaft 10 to rotate 30 ° CA for each ignition to be maximized and an angle estimated to be minimized. It is.

  In addition, when the piston 3 of the cylinder for which the above-described times T1 and T2 are to be calculated rotates from 0 ° to 30 ° CA toward the retarded side after 360 ° CA from the position where the top dead center is reached. The time required is calculated as T3, and the time required for 90 ° to 120 ° CA rotation to the retard side is calculated as T4. These times T3 and T4 are also the required time of 30 ° CA corresponding to the angle estimated for the time required for the crankshaft 10 to rotate 30 ° CA at each ignition and the angle estimated to be the minimum. It is.

Then, based on these times T1, T2, T3, T4, the rotational fluctuation amount ΔNE0 is expressed by the following equation: ΔNE0 = (T4-T3) − (T2-T1) (1)
Calculate from

  As a result, the rotational fluctuation amount reflecting the difference with respect to the rotational speed of the cylinder that has reached the expansion stroke on the 360 ° advance side (cylinder whose ignition timing is 2 before ignition) in the rotational speed of the cylinder currently in the expansion stroke is obtained. be able to.

  If misfire occurs in any of the cylinders and the engine rotation speed decreases, the elapsed time required for the crankshaft 10 to rotate at a constant crank angle becomes longer. That is, the value of (T4-T3) in the above equation (1) is larger than the value of (T2-T1). Therefore, an elapsed time required for the crankshaft 10 to rotate at a constant crank angle during the expansion stroke of each cylinder is detected, and the length of this elapsed time is applied to the above equation (1) to calculate the calculated rotational fluctuation amount ΔNE0. Based on this, it is recognized whether or not there is a possibility of misfire, and this is used for a misfire determination issuing operation to be described later.

  Further, the misfire determination apparatus uses ΔNE0 as the calculation amount at the present time (starting determination of whether or not misfire has occurred), and the calculation amount before the ignition (ignition timing) with respect to the rotational fluctuation amount calculated by the above equation (1). Is the change amount of rotation obtained during the expansion stroke of the cylinder before one ignition) is ΔNE1, the calculation amount before ignition is ΔNE2, the calculation amount before ignition is ΔNE3, and the misfire is calculated based on the change pattern of these rotation variations. The presence or absence of occurrence is determined. Specific determination operation will be described later.

  In the present embodiment, as described above, since the deviation (rotational fluctuation amount) ΔNE0 of the elapsed time in the cylinder whose crank angle phase is 360 ° apart is obtained, even if there is a manufacturing error in the NE rotor. The above calculation is executed based on the recognition of the same external teeth, and the rotational fluctuation amount ΔNE0 is not affected by the manufacturing error of the NE rotor, and the rotational fluctuation amount ΔNE0 can be accurately calculated.

  The feature of the present embodiment is that the fluctuation in rotation for misfire determination occurs when the lock-up clutch 53f is in a lock-up state (including the flex lock-up state) and in a non-lock-up state (release state). The pattern (misfire determination pattern) is different from each other. That is, in the engagement region (lock-up operation region) or slip region (flex lock-up operation region) set based on the vehicle speed V and the accelerator opening θTH, and in the release region (torque converter operation region) Thus, the rotational fluctuation patterns for misfire determination are made different from each other.

  More specifically, when the lock-up clutch 53f is in the non-lock-up state, whether or not the rotation fluctuation pattern of the engine 1 is in line with the first rotation fluctuation pattern peculiar to the occurrence of misfire in the non-lock-up state. While the misfire determination operation is performed, whether the rotation variation pattern of the engine 1 is in accordance with the second rotation variation pattern peculiar to the occurrence of misfire in the lockup state when the lockup clutch 53f is in the lockup state A misfire determination operation is performed depending on whether or not (misfire determination operation by a misfire determination means). The second rotational fluctuation pattern is set to have a smaller rotational fluctuation width than the first rotational fluctuation pattern. That is, when the lock-up clutch 53f is in the lock-up state, the misfire determination condition is relaxed so that it can be determined that a misfire has occurred even if the rotation fluctuation range is small compared to the case of the non-lock-up state. ing.

−Rotational fluctuation pattern when misfire occurs−
In the discrimination operation, among the rotation fluctuation amounts ΔNE0 to ΔNE3 (one cycle of the temporal change pattern in the discrimination operation), the expansion stroke is particularly started before the second ignition (when the rotation fluctuation amount ΔNE0 which is the determination operation start timing is calculated). When the calculated amount ΔNE2 when the cylinder before two ignitions has reached the expansion stroke at the ignition timing with respect to the cylinder being turned on becomes equal to or greater than a predetermined value (threshold value) N1 (the rotational fluctuation amount of the engine 1 is a predetermined threshold value) When the misfire determination is performed with the cylinder that has reached the expansion stroke when exceeding the misfire determination target cylinder), whether or not misfire has occurred is determined based on the relationship between the rotational fluctuation amounts ΔNE0 to ΔNE3.

  The predetermined value N1 is, for example, map-calculated as a smaller value as the engine speed NE is higher. This is due to the following reason. Usually, when the engine speed NE increases, the required times T1 to T4 are calculated as short times. For this reason, the rotational fluctuation amount ΔNE calculated based on the equation (1) is also calculated as a small value. Therefore, the predetermined value N1 is calculated as a smaller value as the engine rotational speed NE becomes faster, so that the determination can be made while eliminating the influence of the change in the engine rotational speed NE as much as possible.

  Further, the predetermined value N1 is set to a larger value as the intake pipe pressure PM is higher, and similarly, for example, a map calculation is performed. This is due to the following reason. In the control of the engine 1, more fuel is usually injected from the injector 9 as the intake pipe pressure increases. For this reason, the higher the intake pipe pressure PM, the higher the combustion pressure of the air-fuel mixture in the combustion chamber 4, and a greater driving force is applied to the crankshaft 10 of the engine 1. As a result, when the intake pipe pressure PM is high, the minimum times T2 and T4 on the minimum side are calculated as shorter times than when the pressure PM is low. The rotational fluctuation amount ΔNE calculated based on the value is calculated as a large value. Therefore, by calculating the predetermined value N1 as a larger value as the intake pipe pressure PM becomes higher, it is possible to make a determination after eliminating the influence of the change in the intake pipe pressure PM as much as possible.

  Hereinafter, a specific rotation fluctuation pattern for misfire determination will be described.

  FIG. 6 shows an example of a rotational fluctuation pattern that is a relationship between the rotational fluctuation amounts ΔNE0 to ΔNE3 when a misfire occurs when the lockup clutch 53f is in the non-lockup state (first rotational fluctuation pattern). ). That is, when the lock-up clutch 53f is in the non-lock-up state, the presence or absence of misfire (in this case, the third cylinder # 3) depends on whether or not the rotation fluctuation pattern is along the rotation fluctuation pattern shown in FIG. The presence or absence of misfire in the country).

  In addition, the solid line in FIG. 7 shows an example of a rotation variation pattern that is a relationship between the rotation variation amounts ΔNE0 to ΔNE3 when a misfire occurs when the lockup clutch 53f is in the lockup state (second variation). Rotation fluctuation pattern). That is, when the lock-up clutch 53f is in the lock-up state, the presence or absence of misfire depends on whether or not the rotation fluctuation pattern is along the rotation fluctuation pattern shown in FIG. 7 (also in this case, the third cylinder # 3 The presence or absence of misfire in the country).

  As shown in FIGS. 6 and 7, in the present embodiment, if the first cylinder is # 1, and similarly, the second to fourth cylinders are # 2 to # 4, respectively, # 1 → # 3 The ignition of the air-fuel mixture in each cylinder is executed in the order of # 4 → # 2.

  When the misfire occurs when the lock-up clutch 53f is in the non-lock-up state, the change patterns (time-dependent change patterns) of the rotational fluctuation amounts ΔNE0 to ΔNE3 show the following tendencies.

  That is, as shown in FIG. 6, for example, when misfire occurs in the third cylinder # 3 (cylinder for misfire determination) before the second ignition, the rotation calculated during the expansion stroke of the third cylinder # 3. The fluctuation amount ΔNE2 is calculated based on the rotational fluctuation amount ΔNE3 calculated during the expansion stroke of the first cylinder # 1 (the cylinder before 1 ignition in the present invention) immediately before and the fourth cylinder # 4 (1 in the present invention) immediately after that. This is particularly larger than the rotational fluctuation amount ΔNE1 calculated during the expansion stroke of the post-ignition cylinder). In addition to this, the rotational fluctuation amount ΔNE0 calculated during the expansion stroke of the second cylinder # 2 (the cylinder after two ignitions in the present invention) this time is substantially equal to the rotational fluctuation amount ΔNE2 and the absolute value thereof. It is the same, and the positive and negative values take opposite values.

  On the other hand, when misfire occurs when the lock-up clutch 53f is in the lock-up state, the change pattern (time-dependent change pattern) of the rotational fluctuation amounts ΔNE0 to ΔNE3 shows the following tendency.

  That is, as shown by a solid line in FIG. 7, for example, when misfire occurs in the third cylinder # 3 (cylinder for misfire determination) before the second ignition, it is calculated during the expansion stroke of the third cylinder # 3. The rotational fluctuation amount ΔNE2 is particularly larger than the rotational fluctuation amount ΔNE3 calculated during the expansion stroke of the first cylinder # 1 (the cylinder before one ignition in the present invention) immediately before that. Further, the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3 and the rotational fluctuation amount calculated during the expansion stroke of the fourth cylinder # 4 (the post-ignition cylinder in the present invention) immediately after that are calculated. There is no significant difference from ΔNE1. In addition to this, the rotational fluctuation amount ΔNE0 calculated during the expansion stroke of the second cylinder # 2 (the cylinder after two ignitions in the present invention) this time is substantially equal to the rotational fluctuation amount ΔNE2 and the absolute value thereof. It is the same, and the positive and negative values take opposite values.

  That is, conventionally, there is a large difference between the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3 and the rotational fluctuation amount ΔNE1 calculated during the expansion stroke of the fourth cylinder # 4 immediately thereafter. In the present embodiment, it has been determined that no misfire has occurred, but in the present embodiment, such a rotation variation pattern is used only when the lockup clutch 53f is in the lockup state or the flex lockup state. Even so, it is determined that misfire has occurred. That is, in the second rotation fluctuation pattern, the change between the rotation fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3 and the rotation fluctuation amount ΔNE1 calculated during the expansion stroke of the fourth cylinder # 4 is changed. In the first rotational fluctuation pattern (the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3 in the first rotational fluctuation pattern and the rotation calculated during the expansion stroke of the fourth cylinder # 4) The change is defined as smaller than the change amount ΔNE1.

  In the misfire determination device of the present embodiment, attention is paid to the fact that the change pattern of the rotational fluctuation amounts ΔNE0 to ΔNE3 is different between the occurrence of misfire in the lock-up state and the occurrence of misfire in the non-lock-up state. Accordingly, the following conditions are stored in advance in the ROM in the engine control device 40.

(A) ΔNE2 × A <| ΔNE0 |, and (b) ΔNE2 × B ≧ ΔNE3, and (c) ΔNE2 × C ≧ ΔNE1.
On the condition that the logical product of (a) to (c) is satisfied, it is determined that a misfire has occurred in the cylinder (third cylinder # 3) having the rotational fluctuation amount ΔNE2.

  Here, each of the above values A, B, and C is set as a positive constant less than “1”, and these values are for the case where the lockup clutch 53f is in the lockup state or the flex lockup state. And a value that is different from a value that is targeted for a case in the non-lock-up state. For example, each of the values A, B, and C indicates that the lock-up clutch 53f is in the lock-up state or the flex lock-up state more than the value (the value in the first rotation variation pattern) that is targeted for the non-lock-up state A value for a certain case (a value in the second rotation variation pattern) is set smaller.

  In this way, the values A, B, and C are made different depending on whether the lock-up clutch 53f is in the lock-up state or the flex-lock-up state and the non-lock-up state. Creating a pattern and a second rotational variation pattern, along the first rotational variation pattern when in a non-lock-up state, or along the second rotational variation pattern when in a lock-up state Whether or not a misfire has occurred is determined.

  Further, these constants A to C are calculated based on the engine speed NE. Specifically, each of the predetermined values A to C is calculated as a smaller value as the engine speed NE increases. This is due to the following reason.

  As described above, when the engine rotational speed NE increases, the rotational fluctuation amounts ΔNE0 to ΔNE3 are calculated as small values accordingly. Therefore, by calculating the predetermined values A to C as smaller values as the engine speed NE is higher, the change patterns of the rotational fluctuation amounts ΔNE0 to ΔNE3 and the misfire patterns can be obtained from the engine rotational speed NE. It is possible to compare after eliminating the influence of change as much as possible.

  When the logical product conditions (a) to (c) are satisfied, the change pattern of the rotation fluctuation amounts ΔNE0 to ΔNE3 is a misfire pattern, and the cause of the increase in the rotation fluctuation amount ΔNE2 is the occurrence of misfire. It is determined that there is a possibility of misfire.

  Furthermore, in the misfire determination apparatus according to the present embodiment, it is determined whether or not misfire has occurred at a frequency that causes deterioration of exhaust emission or deterioration of the catalyst 12 based on the detection frequency of misfire occurrence. Specifically, when the misfire occurrence detection frequency is high, it is determined that the misfire is abnormal, assuming that misfire has occurred at a frequency that may cause deterioration of exhaust emission, deterioration of the catalyst 12, or the like.

  Hereinafter, the procedure of misfire determination processing in the present embodiment will be described with reference to the flowcharts of FIGS. 8 and 9. The control routine shown in FIGS. 8 and 9 is repeatedly executed in the engine control device 40, for example, every 180 ° CA rotation of the crankshaft 10 (in the case of four cylinders).

  As shown in FIGS. 8 and 9, in this process, first, it is determined whether or not a precondition for determining misfire (misfire detection) is satisfied (step ST1). In this determination, through the determination based on the above preconditions, there is no possibility that the engine speed NE will fluctuate greatly due to factors other than the occurrence of misfire, and the condition that the fluctuation of the engine speed NE accompanying the occurrence of misfire can be accurately detected It is determined whether it is below. Note that the preconditions include, for example, that a predetermined time has elapsed since the air conditioner was switched on / off, and that a predetermined time has elapsed since the shift lever was operated. .

  If it is determined that the above precondition is not satisfied (NO determination in step ST1), the engine 1 cannot currently accurately determine the fluctuation of the engine speed NE due to the occurrence of misfire. This processing is once terminated.

  On the other hand, if it is determined that the precondition is satisfied (YES determination in step ST1), the count value of the detection counter (1000 rev counter) is incremented (step ST2). This count value is used as the total number of determinations that serves as a calculation reference for the detection frequency of misfire occurrence when determining the misfire abnormality described later.

  Thereafter, the threshold value N1 is map-calculated based on the engine speed NE and the intake pipe internal pressure PM, and it is determined whether or not the rotational fluctuation amount ΔNE calculated in the above-described manner is larger than the threshold value N1 (step ST3). ). The map used for the map calculation is a map for calculating the predetermined value N1 from the engine rotational speed NE and the intake pipe internal pressure PM, and the relationship between the engine rotational speed NE, the intake pipe internal pressure PM, and the predetermined value N1 is as follows. It is set after being obtained by experiments. This map is also stored in advance in an appropriate memory in the engine control device 40.

  If it is determined that the rotational fluctuation amount ΔNE is greater than the predetermined value N1 (YES in step ST3), the process proceeds to step ST4, where it is determined that the rotational fluctuation amount ΔNE is greater than the predetermined value N1. It is determined whether or not there is a history of misfire in the cylinder for which it is determined that there is a possibility that misfire has occurred. That is, it is determined whether or not there is a history that the rotational fluctuation amount ΔNE exceeds the predetermined value N1 in the past combustion stroke for the cylinder. If there is no history of misfiring and NO is determined in step ST4, the process proceeds to step ST10. On the other hand, there is a history of misfiring, and YES is determined in step ST4. If so, the process proceeds to step ST5.

  In step ST5, it is determined whether or not the current shift (shift stage) of the automatic transmission 50 is a specific preset shift stage. The specific shift speed is a shift speed at which the resonance phenomenon between the engine 1 and the automatic transmission 50 may occur when the lockup clutch 53f is in the lockup state. In other words, it is determined whether or not the vehicle is currently traveling at a gear position where the resonance phenomenon may occur. The resonance phenomenon between the engine 1 and the automatic transmission 50 occurs when the automatic transmission 50 is at a specific gear position and at a specific engine speed (for example, the engine speed is at the second gear speed). Occurs when the engine speed is 4000 rpm or when the gear position is the third speed and the engine speed is 3500 rpm). The gear speed at which this resonance phenomenon occurs varies depending on the natural frequency of the engine 1 and the automatic transmission 50 and the like. That is, the gear stage in which the resonance phenomenon occurs differs depending on the vehicle type. For this reason, the specific shift speed set here is obtained in advance by experiments or the like and stored in the ROM.

  If the current gear position of the automatic transmission 50 is not the above-mentioned specific gear position and NO is determined in step ST5, the process proceeds to step ST10, while the current gear position of the automatic transmission 50 is the above-mentioned specific gear position. If there is, the process moves to step ST6.

  In step ST6, it is determined whether or not the lockup clutch 53f is in the flex lockup state. Specifically, it is determined whether or not the flex lockup flag is “1”. If NO is determined in step ST6 instead of the flex lockup state, the process proceeds to step ST7. On the other hand, if the flex lockup state is determined YES in step ST6, the process proceeds to step ST8.

  In step ST7, it is determined whether or not the lockup clutch 53f is in a lockup state. Specifically, it is determined whether or not the lockup flag is “1”. If NO is determined in step ST7 instead of the lock-up state, the process proceeds to step ST10, whereas if YES is determined in step ST7 in the lock-up state, the process proceeds to step ST8.

  In step ST8, it is determined whether or not the difference between the turbine speed of the automatic transmission 50 and the engine speed is equal to or less than a predetermined determination value. That is, it is confirmed that the flex lockup state or the lockup state is established based on each rotation speed. If YES is determined in step ST8, the process proceeds to step ST9. If NO is determined, the process proceeds to step ST10.

  In step ST9, misfire determination is performed based on the second rotation variation pattern used when the lockup clutch 53f is in the flex lockup state or the lockup state. Specifically, it is determined whether or not the rotation variation pattern conforms to the second rotation variation pattern shown in FIG. 7, and the rotation variation pattern of the engine 1 is along the second rotation variation pattern. In that case, Yes is determined in step ST9 and the process proceeds to step ST11.

  On the other hand, if NO is determined in any of steps ST4, ST5, ST7, ST8, the lockup clutch 53f is not in the lockup state and is not in the flex lockup state, and the process proceeds to step ST10.

  In step ST10, misfire determination is performed based on the first rotation fluctuation pattern used when the lockup clutch 53f is in a non-lockup state that is neither in the flex lockup state nor in the lockup state. Specifically, it is determined whether or not the rotation variation pattern conforms to the first rotation variation pattern shown in FIG. 6, and the rotation variation pattern of the engine 1 is along the first rotation variation pattern. In that case, Yes is determined in step ST10 and the process proceeds to step ST11.

  As described above, when it is determined in step ST9 or step ST10 that a misfire has occurred, the count value of the misfire counter is incremented in step ST11, and then the process proceeds to step ST12. Further, when it is determined that the rotational fluctuation amount ΔNE is equal to or less than the threshold value N1 (NO determination in step ST3), or even if the rotational fluctuation amount ΔNE exceeds the threshold value N1, any of the above patterns (first rotational fluctuation pattern) If it is determined that it does not belong to the second rotation fluctuation pattern (NO in step ST9 or step ST10), the process jumps to the processing after step ST12 without performing the counting operation of the misfire counter.

  In the processing after step ST12, it is first determined whether or not the count value of the detection counter (1000 rev counter) is equal to or greater than a predetermined condition satisfaction count value (for example, 1000) (step ST12). In this determination, it is determined whether or not the total number of detections has reached a reference number (for example, equivalent to 1000 rotations of the crankshaft 10) for determining the detection frequency of misfire occurrence.

  If it is determined that the total number of detections has reached the reference number (YES in step ST12), it is next determined whether or not the count value of the misfire counter is equal to or greater than a predetermined number of abnormal times (for example, 30). (Step ST13). That is, in this determination, it is determined whether or not the occurrence of misfire has been detected at a frequency of a predetermined number or more during the total number of detections.

  When it is determined that the count value of the misfire counter is greater than or equal to a predetermined value (abnormal number value) (YES determination in step ST13), the exhaust emission may deteriorate or the catalyst 12 may deteriorate. As misfire has occurred, it is determined that misfire is abnormal (step ST14). In this case, for example, this abnormality determination is stored as an abnormality history, or an abnormal lamp (MIL) is turned on. Then, after resetting the count value of each counter to “0” (step ST15), the process returns.

  On the other hand, when it is determined that the count value of the detection counter is less than the predetermined value (NO determination in step ST12), the total number of detections is not reached the reference number, and the process returns.

  If it is determined that the count value of the misfire counter when the count value of the detection counter (1000 rev counter) reaches a predetermined value is less than the predetermined value (abnormal number value) (NO determination in step ST13), Assuming that the misfire occurrence detection frequency is not so high, each count value is reset to “0” in this case as well (step ST15), and the process returns.

  As described above, according to the present embodiment, the effects described below can be obtained.

  As a change pattern of the rotation fluctuation amounts ΔNE0 to ΔNE3, a first rotation fluctuation pattern as a misfire determination pattern when the lock-up clutch 53f is in the non-lock-up state (a rotation fluctuation pattern peculiar when misfire occurs in the non-lock-up state) ) And a second rotation fluctuation pattern (rotational fluctuation pattern peculiar when misfire occurs in the lock-up state) as the misfire determination pattern when the lock-up clutch 53f is in the lock-up state. I am doing so. And this 2nd rotation fluctuation pattern is set as a thing with a small rotation fluctuation range compared with a 1st rotation fluctuation pattern, and is a pattern which loosens misfire determination conditions. For this reason, when resonance between the engine 1 and the automatic transmission 50 occurs in the lock-up state of the lock-up clutch 53f, conventionally, the rotational fluctuation is reduced by the influence of this resonance. Although there was a high possibility that even if a misfire occurred, it could not be detected. However, according to the misfire determination operation of this embodiment, a specific rotation variation pattern (the second rotation variation pattern) is used. This makes it possible to detect the occurrence of misfire. Thus, it is accurately determined that misfire has occurred without being adversely affected by the resonance phenomenon, and the reliability of misfire determination can be improved.

(Modification of second rotation variation pattern)
In the above-described embodiment, the second rotation variation pattern is defined as follows. That is, the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3, which is the misfire determination target cylinder, is compared with the rotational fluctuation amount ΔNE3 calculated during the expansion stroke of the first cylinder # 1 immediately before it. Particularly, there is a large difference between the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3 and the rotational fluctuation amount ΔNE1 calculated during the expansion stroke of the fourth cylinder # 4 immediately thereafter. It was defined as not occurring. Not limited to this, it may be defined as follows.

  That is, as indicated by the one-dot chain line in FIG. 7, when misfire occurs in the third cylinder # 3 (cylinder for misfire determination), the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3. Is particularly larger than the rotational fluctuation amount ΔNE1 calculated during the expansion stroke of the fourth cylinder # 4 (the cylinder after one ignition in the present invention) immediately after that, and during the expansion stroke of the third cylinder # 3. There is no significant difference between the calculated rotational fluctuation amount ΔNE2 and the rotational fluctuation amount ΔNE3 calculated during the expansion stroke of the first cylinder # 1 immediately before that (the cylinder before one ignition in the present invention). The rotational fluctuation amount ΔNE0 calculated during the expansion stroke of the second cylinder # 2 (the post-ignition cylinder in the present invention) is substantially the same as the rotational fluctuation amount ΔNE2 and has a positive / negative sign. As a pattern that takes the opposite value, the second rotation fluctuation pattern It is intended to define the emissions.

  In addition, you may make it prescribe | regulate both the 2nd rotation fluctuation pattern in the said embodiment and the 2nd rotation fluctuation pattern in this modification as a rotation fluctuation pattern in which misfire has generate | occur | produced in the lockup state. . In this case, in the above conditional expressions (a) to (c), values (values in the second rotation variation pattern) A and B when the lock-up clutch 53f is in the lock-up state or the flex lock-up state , C are provided with two types, a value corresponding to the second rotation fluctuation pattern indicated by a solid line in FIG. 7 and a value corresponding to the second rotation fluctuation pattern indicated by a one-dot chain line in FIG.

  Further, the second rotation variation pattern may be defined as a pattern described below.

  In other words, as indicated by a two-dot chain line in FIG. 7, when misfire occurs in the third cylinder # 3 (cylinder for misfire determination), the rotational fluctuation amount calculated during the expansion stroke of the third cylinder # 3. ΔNE2 is particularly larger than the rotational fluctuation amount ΔNE1 calculated during the expansion stroke of the fourth cylinder # 4 (the cylinder after one ignition in the present invention) immediately after that, and immediately before the third cylinder # 3. The rotational fluctuation amount ΔNE3 calculated during the expansion stroke of the first cylinder # 1 (the cylinder before one ignition in the present invention) is particularly larger than the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3. In addition, the rotational fluctuation amount ΔNE0 calculated during the expansion stroke of the second cylinder # 2 (the cylinder after the two ignitions in the present invention) is almost the same as the rotational fluctuation amount ΔNE2. And the second rotation as a pattern in which positive and negative values take opposite values It prescribes the dynamic pattern. That is, the following conditional expression is satisfied.

(G) ΔNE3> ΔNE2 and (h) ΔNE1 <ΔNE2 and (i) | ΔNE0 | ≈ΔNE2
Furthermore, the second rotation variation pattern may be defined as a pattern described below.

  That is, as indicated by the broken line in FIG. 7, when misfire occurs in the third cylinder # 3 (cylinder for misfire determination), the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3 is In particular, it is larger than the rotational fluctuation amount ΔNE3 calculated during the expansion stroke of the first cylinder # 1 (the cylinder before one ignition in the present invention) immediately before, and the fourth cylinder immediately after the third cylinder # 3. The rotational fluctuation amount ΔNE1 calculated during the expansion stroke of No. cylinder # 4 (the cylinder after one ignition in the present invention) is particularly larger than the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3. Further, the rotational fluctuation amount ΔNE0 calculated during the expansion stroke of the second cylinder # 2 (the cylinder after the two ignitions in the present invention) this time is substantially the same as the rotational fluctuation amount ΔNE2 and has the same absolute value. Second rotation fluctuation as a pattern in which positive and negative values take opposite values It is intended to define the turn. That is, the following conditional expression is satisfied.

(J) ΔNE3 <ΔNE2 and (k) ΔNE1> ΔNE2 and (l) | ΔNE0 | ≈ΔNE2
(Modified example to determine bad road running)
In the above-described embodiment, the misfire determination when the lock-up clutch 53f is in the non-lock-up state and the misfire determination when the lock-up clutch 53f is in the lock-up state are performed. In addition, in this modification, when the lock-up clutch 53f is in the lock-up state, it is possible to distinguish between a situation where a misfire has occurred and a situation where the vehicle is traveling on a rough road. This will be specifically described below.

  When the lock-up clutch 53f is in the lock-up state, if the vehicle travels on a rough road, the engine rotational speed fluctuates abruptly due to the influence of road surface unevenness, etc., and the rotational fluctuation does not occur. May increase and exceed the threshold value N1, and misjudgment of misfire may be made. For this reason, it is necessary to identify whether the cause of the rotation fluctuation exceeding the threshold value N1 is due to misfire or due to bad road running, and it is necessary to increment the misfire counter only when it is due to misfire.

  In this modification, when the rotational fluctuation amount of the engine 1 becomes large when the lock-up clutch 53f is in the lock-up state, whether the cause is a misfire or a rough road traveling. I try to distinguish. By this determination, the misfire counter increment due to misfire misjudgment can be avoided.

  In this determination operation, among the above-described rotation variation amounts ΔNE0 to ΔNE3 (one cycle of the time-dependent change pattern in the determination operation), especially before the second ignition (when the rotation variation amount ΔNE0 which is the determination operation start timing is calculated, an expansion stroke is reached. Based on the relationship between the rotational fluctuation amounts ΔNE0 to ΔNE3 when the calculated amount ΔNE2 of when the cylinder before two ignitions has reached the expansion stroke at the ignition timing with respect to the cylinder in question is greater than or equal to a predetermined value (threshold value) N1. Then, it is determined whether there is a possibility that this is due to a misfire abnormality or a bad road traveling.

  Also in the present embodiment, the predetermined value N1 is, for example, map-calculated as a smaller value as the engine speed NE is higher. The reason is the same as in the above embodiment. The predetermined value N1 is calculated, for example, as a larger value as the intake pipe pressure PM is higher. The reason is the same as that in the above embodiment.

  As described above, when a misfire occurs when the lockup clutch 53f is in the lockup state, as shown in FIG. 7, for example, the misfire occurs in the third cylinder # 3 (the misfire determination target cylinder) before the second ignition. Is generated during the expansion stroke of the first cylinder # 1 (the cylinder before ignition in the present invention) immediately before it. This is particularly larger than the calculated rotation fluctuation amount ΔNE3. Further, the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3 and the rotational fluctuation amount calculated during the expansion stroke of the fourth cylinder # 4 (the post-ignition cylinder in the present invention) immediately after that are calculated. There is no significant difference from ΔNE1. In addition to this, the rotational fluctuation amount ΔNE0 calculated during the expansion stroke of the second cylinder # 2 (the cylinder after two ignitions in the present invention) this time is substantially equal to the rotational fluctuation amount ΔNE2 and the absolute value thereof. It is the same, and the positive and negative values take opposite values.

  On the other hand, when traveling on rough roads, a state in which the amount of rotational fluctuation is large continues for a relatively long time. That is, as shown in FIG. 10 as an example of the relationship between the rotational fluctuation amounts ΔNE0 to ΔNE3 during the rough road traveling, the rotational fluctuation calculated during the expansion stroke of the third cylinder # 3 before the second ignition during the rough road traveling. The amount ΔNE2 is larger in value than the ΔNE3 calculated during the expansion stroke of the first cylinder # 1 immediately before and the rotational fluctuation amount ΔNE1 calculated during the expansion stroke of the fourth cylinder # 4 immediately after that. It doesn't take a prominent value. Further, the rotational fluctuation amount ΔNE0 calculated during the expansion stroke of the second cylinder # 2 this time has a high correlation with the rotational fluctuation amount ΔNE2 as in the case of misfire (the absolute value is substantially the same and the value is opposite in sign) There is no relationship).

  Further, the rough road pattern is not limited to that shown in FIG. 10, and when the rotational fluctuation amount ΔNE2 calculated during the expansion stroke of the third cylinder # 3 exceeds the threshold N1, the fourth cylinder immediately after that When it is detected that the rotational fluctuation amount ΔNE1 calculated during the # 4 expansion stroke exceeds the rotational fluctuation amount ΔNE2, it may be determined that the vehicle is traveling on a rough road.

  In the misfire determination device of this example, paying attention to the fact that the change pattern of the rotational fluctuation amounts ΔNE0 to ΔNE3 is different between when the misfire occurs in the lockup state and when traveling on a rough road, Each condition is stored in advance in a ROM in the engine control device 40.

That is, as a condition (misfire pattern) for determining that the change pattern of the rotational fluctuation amounts ΔNE0 to ΔNE3 is a change pattern when there is a possibility of misfire, the following condition (a) ΔNE2 × A < | ΔNE0 |, and (b) ΔNE2 × B ≧ ΔNE3, and (c) ΔNE2 × C ≧ ΔNE1.
Is predetermined. On the condition that the logical product of (a) to (c) is satisfied, it is possible to determine that the rotation fluctuation amount ΔNE2 is particularly large.

In addition, as a condition (bad road pattern) for determining that the change pattern of the rotational fluctuation amounts ΔNE0 to ΔNE3 is a change pattern when traveling on a rough road, the following condition (d) − (ΔNE2 × D)> ΔNE0, or (e) ΔNE2 × E ≦ ΔNE3, or (f) ΔNE2 × F ≦ ΔNE1
Is also predetermined. On the condition that the logical sum of these (d) to (f) is satisfied, it is possible to determine that a state in which the rotational fluctuation amount is large continues for a relatively long time.

  Here, each of the above values A, B, C, D, E, and F is set as a positive constant less than “1”, and their relations are A> D, B <E, and C <F, respectively. It is determined to be. The values A, B, and C in the conditions (a) to (c) for determining misfire in the lockup state are the same as those corresponding to the second rotation variation pattern in the above-described embodiment.

  Further, these constants A to F are calculated based on the engine speed NE. Specifically, each of the predetermined values A to F is calculated as a smaller value as the engine speed NE increases. This is due to the following reason.

  As described above, when the engine rotational speed NE increases, the rotational fluctuation amounts ΔNE0 to ΔNE3 are calculated as small values accordingly. Therefore, by calculating each of the predetermined values A to F as a smaller value as the engine rotational speed NE is higher, the change pattern of these rotational fluctuation amounts ΔNE0 to ΔNE3, the misfire pattern, and the bad road pattern are determined as the engine rotation speed. The comparison is made after eliminating the influence of the change in the speed NE as much as possible.

  When the logical product conditions (a) to (c) are satisfied, the change pattern of the rotational fluctuation amounts ΔNE0 to ΔNE3 is a misfire pattern (a pattern in which misfire occurs in the lockup state). The cause of the increase in the rotational fluctuation amount ΔNE2 is determined as “possibility of misfiring” because there is a possibility of misfiring.

  On the other hand, when the logical sum conditions (d) to (f) are satisfied, the change pattern of the rotational fluctuation amounts ΔNE0 to ΔNE3 is a bad road pattern, and it is bad that the rotational fluctuation amount ΔNE2 is large. “Bad road driving” is determined to be caused by road driving.

  Thus, according to the misfire determination process according to the present example, the rotational fluctuation of the engine 1 is large through the pattern determination based on the prestored misfire occurrence pattern (misfire occurrence pattern in the lockup state) and the rough road running pattern. It becomes possible to accurately determine whether the cause of the failure is due to misfire or traveling on a rough road. Only when it is determined that the reason why the rotational fluctuation amount ΔNE exceeds the predetermined value N1 is due to misfire of the engine 1, a misfire counter described later is incremented. Accordingly, it is possible to accurately identify the detection of misfire occurrence in the non-lock-up state, the detection of misfire occurrence in the lock-up state, and the increase in the amount of rotational fluctuation caused by traveling on a rough road.

-Other embodiments-
The above embodiment may be modified as follows.
In the above embodiment and the modification, the case where the present invention is applied to a four-cylinder gasoline engine for automobiles has been described, but the present invention is not limited to this and can be applied to various engines.
In the above embodiment and the modification, the predetermined value N1 is calculated based on the engine speed NE and the intake pipe pressure PM, but is not limited thereto. For example, the predetermined value N1 may be calculated based on one of the engine speed NE and the intake pipe pressure PM, or may be calculated based on another parameter. In the system for detecting the intake air amount instead of the intake pipe pressure PM, the intake air amount may of course be substituted. On the other hand, the predetermined value N1 may be set as a constant value. In short, the predetermined value N1 may be calculated or set as long as the change in the rotational fluctuation amount ΔNE accompanying the occurrence of misfire can be suitably monitored.
In the embodiment and the modified example, the constants A to F are calculated based on the engine rotational speed NE. However, the present invention is not limited to this. For example, the constants A to F are calculated based on the intake pipe pressure PM and the intake air amount. Or may be calculated based on other parameters. Further, each of the constants A to F may be set as a constant value. In short, the constants A to F may be calculated or set as long as the misfire pattern and the rough road pattern can be set as suitable patterns.
In the above embodiment, the detection frequency of misfire occurrence is obtained by counting the total number of detections by the detection counter (1000 rev counter) and the number of times of misfire occurrence detection by the misfire counter. Is also optional.
In the above embodiment, the rotation fluctuation amount is calculated from the above equation (1), but the present invention is not limited to this. In short, the calculation mode of the rotation fluctuation amount may be appropriately changed as long as the fluctuation of the engine rotation speed due to the occurrence of misfire can be grasped.
In the above embodiment, the deviation ΔNE of the elapsed time in the cylinder whose crank angle phase is 360 ° apart is obtained, but the cylinders to be compared for obtaining this deviation ΔNE are not limited to this. Further, the rotation angle of the crankshaft 10 for obtaining the elapsed times T1 to T4 used for the calculation of the deviation ΔNE is not limited to 30 °, and any angle can be set.

It is a figure which shows schematic structure of the engine and its peripheral device to which the misfire determination apparatus which concerns on embodiment is applied. 1 is a schematic configuration diagram illustrating a power train of a vehicle according to an embodiment. 1 is a schematic configuration diagram of an automatic transmission schematically showing a schematic configuration of a torque converter. FIG. It is a schematic block diagram which shows the control block containing an engine control apparatus and a transmission control apparatus. It is a figure which shows the lockup clutch action | operation map used for control of a lockup clutch. It is a figure which shows an example of the 1st rotation fluctuation pattern used in a non-lock-up state. It is a figure which shows an example of the 2nd rotation fluctuation pattern used in a lockup state and a flex lockup state. It is a flowchart figure which shows a part of procedure of misfire determination processing operation | movement. It is a flowchart figure which shows the other part of the procedure of misfire determination processing operation | movement. It is a figure which shows an example of the change pattern of the rotation fluctuation amount at the time of rough road driving | running | working.

Explanation of symbols

1 engine (internal combustion engine)
50 Automatic transmission 53 Torque converter (fluid power transmission device)
53f Lock-up clutch 54 Transmission mechanism portion N1 Threshold value # 1 First cylinder (cylinder before one ignition)
# 2 2nd cylinder (2 cylinders after ignition)
# 3 Third cylinder (cylinder for misfire determination)
# 4 4th cylinder (cylinder after 1 ignition)

Claims (5)

In misfire identification device for an internal combustion engine causing loss fire determination of internal combustion engine coupled to the transmission via a fluid type power transmission device having a lockup clutch,
“The difference in the rotational speed of the cylinder currently in the expansion stroke with respect to the rotational speed in the expansion stroke of the cylinder that had reached the expansion stroke before the second ignition at the ignition timing” is the rotational fluctuation amount,
When the rotational fluctuation amount exceeds a predetermined threshold, the cylinder that has reached the expansion stroke at that time is set as a misfire determination target cylinder that may cause misfire,
In the non-lock-up state of the lock-up clutch, a misfire determination operation is performed depending on whether or not the rotation fluctuation pattern of the internal combustion engine is in line with the first rotation fluctuation pattern, and in the lock-up state of the lock-up clutch, the internal combustion engine Comprises a misfire determination means for performing a misfire determination operation depending on whether or not the rotation variation pattern of the second rotation variation pattern is along the second rotation variation pattern,
The first rotational fluctuation pattern is obtained immediately after the rotational fluctuation amount and the expansion stroke of the misfire determination target cylinder during the expansion stroke of the cylinder before one ignition that has reached the expansion stroke immediately before the expansion stroke of the misfire determination target cylinder. The rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder is greater than a predetermined amount with respect to the rotational fluctuation amount during the expansion stroke of the cylinder after one ignition that has reached the expansion stroke, and the expansion of the cylinder after the one ignition is performed. The rotational fluctuation amount in the expansion stroke of the post-ignition cylinder that has reached the expansion stroke immediately after the stroke is substantially the same as the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder. While it is defined as a pattern in which positive and negative values are reversed,
In the second rotational fluctuation pattern, the rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder is greater than a predetermined amount relative to the rotational fluctuation amount during the expansion stroke of the cylinder before one ignition, and the one ignition The difference between the rotational fluctuation amount in the expansion stroke of the rear cylinder and the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder is equal to or less than a predetermined amount, and the above-described difference in the expansion stroke of the post-ignition cylinder. The internal combustion engine characterized in that the rotational fluctuation amount is defined as a pattern in which the absolute value is substantially the same and the sign is opposite to the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder. Misfire detection device. In a misfire determination device for an internal combustion engine that performs a misfire determination of an internal combustion engine connected to a transmission via a fluid power transmission device having a lock-up clutch,
“The difference in the rotational speed of the cylinder currently in the expansion stroke with respect to the rotational speed in the expansion stroke of the cylinder that had reached the expansion stroke before the second ignition at the ignition timing” is the rotational fluctuation amount,
When the rotational fluctuation amount exceeds a predetermined threshold, the cylinder that has reached the expansion stroke at that time is set as a misfire determination target cylinder that may cause misfire,
In the non-lock-up state of the lock-up clutch, a misfire determination operation is performed depending on whether or not the rotation fluctuation pattern of the internal combustion engine is in line with the first rotation fluctuation pattern, and in the lock-up state of the lock-up clutch, the internal combustion engine Comprises a misfire determination means for performing a misfire determination operation depending on whether or not the rotation variation pattern of the second is along the second rotation variation pattern,
The first rotation fluctuation pattern is obtained immediately after the rotation fluctuation amount and the expansion stroke of the misfire determination target cylinder during the expansion stroke of the cylinder before one ignition that has reached the expansion stroke immediately before the expansion stroke of the misfire determination target cylinder. The rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder is greater than a predetermined amount with respect to the rotational fluctuation amount during the expansion stroke of the cylinder after one ignition that has reached the expansion stroke, and the expansion of the cylinder after the one ignition is performed. The rotational fluctuation amount in the expansion stroke of the post-ignition cylinder that has reached the expansion stroke immediately after the stroke is substantially the same as the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder. While it is defined as a pattern in which positive and negative values are reversed,
In the second rotational fluctuation pattern, a difference between the rotational fluctuation amount during the expansion stroke of the cylinder before one ignition and the rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder is equal to or less than a predetermined amount, The rotational fluctuation amount during the expansion stroke of the misfire determination target cylinder is greater than a predetermined amount with respect to the rotational fluctuation amount during the expansion stroke of the cylinder after the first ignition, and the above-described operation during the expansion stroke of the cylinder after the second ignition. The internal combustion engine characterized in that the rotational fluctuation amount is defined as a pattern in which the absolute value is substantially the same and the sign is opposite to the rotational fluctuation amount in the expansion stroke of the misfire determination target cylinder. Misfire detection device. In the internal combustion engine misfire determination apparatus according to claim 1 or 2,
The misfire determination means is provided only when the shift stage of the transmission is in a specific shift stage where resonance between the internal combustion engine and the transmission may occur when the lock-up clutch is in the lock-up state. A misfire determination device for an internal combustion engine configured to perform a misfire determination operation based on the second rotation fluctuation pattern. In the misfire determination device for an internal combustion engine according to claim 1, 2, or 3,
The misfire determination means, when it is determined that there is a possibility that misfire has occurred because the rotational fluctuation amount of the internal combustion engine exceeds a predetermined threshold when the lockup clutch is in the lockup state. When a cylinder determined to have a possibility of misfire has a rotational fluctuation amount exceeding a predetermined threshold even in the past combustion stroke, the misfire based on the second rotational fluctuation pattern for this cylinder A misfire determination device for an internal combustion engine configured to perform a determination operation. In the misfire determination device for an internal combustion engine according to any one of claims 1 to 4,
The misfire determination means, when it is determined that there is a possibility that misfire has occurred because the rotational fluctuation amount of the internal combustion engine exceeds a predetermined threshold when the lockup clutch is in the lockup state. The amount of rotational fluctuation during the expansion stroke of the cylinder subject to misfire determination, the amount of rotational fluctuation during the expansion stroke of the cylinder that had reached the expansion stroke immediately before the expansion stroke of the cylinder subject to misfire determination, and the expansion stroke of the cylinder subject to misfire determination A misfire determination operation is performed by comparing a change pattern of the rotational fluctuation amount during the expansion stroke of the cylinder that has just reached the expansion stroke with the second rotational fluctuation pattern. A misfire determination device for an internal combustion engine.

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