JP2012140919A - Failure diagnosis device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure diagnosis device for an internal combustion engine adapted to enhance its failure diagnosis accuracy for each cylinder.SOLUTION: An ECU, upon calculating a work volume equivalent value Sneflt (#k) for each cylinder (step S1), compares it with a determination threshold th1 (step S3), and if it is determined to be less than the determination threshold th1 (YES in step S3), performs continuation time calculation processing after normal return (step S4) to calculate continuation time Txr (#k) after normal return. Then, the ECU, if the continuation time Txr (#k) after normal return is a predetermined value or more, performs summation of an abnormal continuation time counter ecrhidl (#k) (step 6), and if the abnormal continuation time counter ecrhidl (#k) is determined to be two seconds or more (YES in step S9), turns on an abnormal cylinder flag exdcyl (#k) (step S10).

Description

  The present invention relates to a failure diagnosis device for an internal combustion engine, and more particularly to a failure diagnosis device for an internal combustion engine that detects a failure of each cylinder.

  In a vehicle equipped with a diesel engine as an internal combustion engine, fuel injection control for each cylinder is generally executed. Here, there are individual differences in the injection characteristics of the fuel injection valve that injects fuel into each cylinder. Especially when the command value of the fuel injection amount is very small, such as during idle operation, the actual fuel injection amount between the cylinders Since the variation of the above becomes remarkable, the effect of performing the fuel injection control for each cylinder is reduced. Therefore, in order to suppress the variation in the actual injection amount between the cylinders based on the learning result by learning and detecting the fluctuation of the rotational speed caused by the variation in the fuel injection amount between the cylinders during the specific operation such as the idling operation. The injection amount correction is performed to correct the injection amount command value of the cylinder having the insufficient injection amount to the increase side.

  In such an internal combustion engine, a failure diagnosis device that determines whether or not a failure has occurred in a cylinder based on a torque difference between the cylinders and an injection amount correction is known (for example, see Patent Document 1). In the conventional internal combustion engine failure diagnosis apparatus described in Patent Document 1, when a torque difference between cylinders is calculated, an injection amount command value for each cylinder is corrected so as to eliminate the torque difference. When the torque difference between the cylinders is not resolved despite the large injection amount correction value, the cylinder is detected as abnormal.

  Further, the Ne signal pulse is taken as a rotation signal into a filter processing unit corresponding to a bandpass filter at a constant angular period, and an instantaneous torque equivalent value obtained by extracting only the rotational fluctuation component at each time point is calculated by the filter processing unit. By calculating the torque equivalent value into the integration processing unit and integrating the instantaneous torque equivalent value in the section for each combustion cycle of each cylinder, the work for each cylinder, which is the torque integrated value of each cylinder, is calculated for each cylinder. There is known one that determines whether or not a cylinder is abnormal depending on whether or not the work by cylinder is below a threshold (see, for example, Patent Document 2).

  The conventional failure diagnosis device for an internal combustion engine described in Patent Document 2 calculates the work amount of each cylinder using the instantaneous torque equivalent value detected from the Ne signal. If the amount of work is below a predetermined threshold value, it is determined that a failure has occurred in the cylinder. Further, the failure diagnosis device for an internal combustion engine determines the occurrence of a failure on the condition that learning of fuel injection characteristics for correcting variations in the fuel injection amount in each cylinder is executed. It was intended to reduce misdiagnosis of failure determination due to variation in quantity.

JP-A-2-277947 JP 2010-144533 A

  However, in the conventional failure diagnosis apparatuses described in Patent Document 1 and Patent Document 2 described above, when the fuel injection amount of a certain fuel injection valve is lower than the fuel injection amounts of other fuel injection valves. The correction value for the fuel injection amount is set so that the fuel injection amount for the cylinder increases. Therefore, a correction value is set so that the fuel injection amount is increased for the cylinder even when a temporary abnormality such as a clogging of the injection hole of the fuel injection valve or a valve opening is generated. Here, assuming that the cylinder returns to a normal state, the correction value during abnormality continues to be reflected in the correction value of the fuel injection amount by the smoothing process for a while, so that the correction value continues to increase. . Therefore, in the cylinder, the fuel is supplied in excess of the actually required fuel injection amount, and the work amount is increased. As a result, the work amount of the cylinders other than the cylinder is relatively decreased, and the failure diagnosis apparatus may erroneously determine that a failure has occurred in these cylinders. In particular, if the work amount of a cylinder that has returned from a failure increases, the work amount of the cylinder that reaches the combustion cycle next to that cylinder will decrease relative to the cylinder that has returned from the failure. There was a possibility of judging. Therefore, it has been necessary to improve the failure determination accuracy for each cylinder.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a failure diagnosis device for an internal combustion engine that can improve the failure determination accuracy for each cylinder.

  In order to achieve the above object, the failure diagnosis apparatus for an internal combustion engine according to the present invention provides (1) a rotation diagnosis of an output shaft of the internal combustion engine in the failure diagnosis apparatus for an internal combustion engine capable of independently controlling fuel injection amounts for a plurality of cylinders. A work amount calculating means for calculating a work amount in a combustion cycle of the plurality of cylinders based on a speed; and a time measuring means for measuring a duration in which the work amount calculated by the work amount calculating means is less than a determination threshold value; Failure determination means for determining that a cylinder whose duration time measured by the timing means is equal to or longer than a predetermined duration is abnormal, and the failure determination means indicates that any one of the cylinders has returned to normal from the abnormality. If it is determined, the time counting by the time measuring means is interrupted for a predetermined time.

  With this configuration, if any of the cylinders may return to normal from an abnormality and there is a possibility that the work amount in the cylinders other than the cylinder may vary, the failure determination based on the work amount is interrupted. Therefore, it is possible to prevent erroneous determination that an abnormality has occurred in these cylinders. Therefore, it is possible to accurately determine the abnormality of the cylinder.

  Further, in the failure diagnosis device for an internal combustion engine according to (1), (2) the failure determination means includes a duration time counted by the time measurement means on condition that the internal combustion engine is idling. Cylinders that are longer than a predetermined duration are determined to be abnormal.

  With this configuration, it is possible to accurately determine a cylinder abnormality that causes rough idle during idling of the internal combustion engine.

  In the internal combustion engine failure diagnosis apparatus according to (1) or (2), (3) an instantaneous maximum of the output shaft of the internal combustion engine in a combustion stroke of the plurality of cylinders during idle operation of the internal combustion engine. Each of the plurality of cylinders is calculated, and an injection amount correction means for setting a correction value of the fuel injection amount for the plurality of cylinders so that the instantaneous maximum rotation speeds of the plurality of cylinders are equal to each other. The predetermined time is set to a time longer than the time when the fluctuation of the correction value converges after the determined cylinder returns to normal.

  With this configuration, even when there is a high possibility that the amount of work fluctuates due to the normal return of the cylinder determined to be abnormal, the amount of work under such circumstances is not used for failure determination. Can be accurately determined.

  In the internal combustion engine failure diagnosis apparatus according to any one of (1) to (3), (4) when the failure determination means interrupts the time measurement by the time measurement means, the duration time counted by the time measurement means Is reset.

  With this configuration, even when there is a high possibility that the amount of work fluctuates due to the normal return of the cylinder determined to be abnormal, the amount of work under such circumstances is not used for failure determination. Can be accurately determined.

  Further, in the failure diagnosis device for an internal combustion engine according to (1) to (4) above, (5) if any of the plurality of cylinders is determined to be abnormal by the failure determination means, an abnormality is detected. It is characterized by comprising display means for displaying the occurrence of.

  With this configuration, it is possible to display that an abnormality has occurred in one of the cylinders, so that the driver can recognize the occurrence of an abnormality in the cylinder.

  ADVANTAGE OF THE INVENTION According to this invention, the failure diagnosis apparatus of the internal combustion engine which can raise the failure determination precision with respect to each cylinder can be provided.

1 is a schematic configuration diagram showing a fuel injection system including a failure diagnosis device for an internal combustion engine according to an embodiment of the present invention. It is a figure for demonstrating the work amount calculation process which concerns on embodiment of this invention. It is a figure for demonstrating the work amount equivalent value which concerns on embodiment of this invention. It is a figure for demonstrating the calculation process of the correction amount between cylinders concerning embodiment of this invention. It is a timing chart for explaining failure diagnosis control processing. It is a flowchart for demonstrating the failure diagnosis control process which concerns on embodiment of this invention. It is a flowchart for demonstrating the duration calculation process which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the configuration will be described.

  As shown in FIG. 1, the internal combustion engine failure diagnosis apparatus according to the present embodiment is equipped in a fuel injection system that injects fuel independently into each cylinder in a multi-cylinder internal combustion engine. In the present embodiment, a case will be described in which the engine 1 as an internal combustion engine is configured by a diesel engine having four cylinders, # 1 cylinder 2a, # 2 cylinder 2b, # 3 cylinder 2c, and # 4 cylinder 2d. . In the following description, when it is not necessary to distinguish between the cylinders, the cylinder 2 will be described. In FIG. 1, one of the four cylinders is shown as a cylinder 2.

  The fuel injection system includes a fuel tank 11 that stores fuel used in the engine 1, for example, light oil, a feed pump 12 that pumps up and discharges fuel in the fuel tank 11 by power transmitted from the engine 1, an engine 1 is configured as a pressurizing pump 15 that can pressurize the fuel discharged from the feed pump 12 by the power transmitted from 1 to a higher pressure, and a known variable throttle element that changes the opening degree according to a metering command signal input. A metering valve 13 interposed between the feed pump 12 and the pressurizing pump 15 to change the amount of fuel sucked into the pressurizing pump 15 in accordance with the input of the metering command signal, and the pressurizing pump 15 The common rail 17 capable of accumulating and storing the pressurized and discharged fuel at a high pressure, and four electric powers provided corresponding to the plurality of cylinders 2 of the engine 1. Includes a driven or a piezoelectric drive type injector 18, the.

  The feed pump 12 is constituted by a known low-pressure fuel pump such as a gear pump. The metering valve 13 is configured such that the fuel supply pressure from the feed pump 12 acts in the valve opening direction of the metering valve body, and is opened to the maximum opening when the internal coil is not energized. When the internal coil is energized, it is constituted by a variable throttle element that can reduce the opening according to a metering command signal input that is the energization amount.

  A relief valve (not shown) is provided between the feed pump 12 and the metering valve 13 so that excess fuel out of the fuel discharged from the feed pump 12 can be returned to the fuel tank 11 side.

  Although the detailed structure of the pressurizing pump 15 is not shown, a reciprocating plunger in the pump housing, a camshaft 15a as an input shaft for driving the plunger, and an eccentric cam on the inner end side of the camshaft 15a. It is constituted by a known pump having a cam ring rotatably mounted on a portion, and at least one additional unit that performs fuel suction, pressurization, and discharge operations by reciprocating movement of the plunger between the pump housing and the plunger. A pressure chamber is defined. The pressurizing pump 15 incorporates check valves on the suction port side and the discharge port side (not shown), and the backflow of fuel from the pressurization pump 15 to the feed pump 12 side is blocked by a check valve on the suction port side. At the same time, the reverse flow of fuel from the common rail 17 to the pressure pump 15 side is prevented by the check valve on the discharge side. The pressurizing pump 15 may be integrated with the feed pump 12 to constitute a fuel supply pump.

  The common rail 17 functions as pressure accumulating means for accumulating and storing the fuel pressurized and discharged by the pressure pump 15 at a high pressure without depending on the load and the engine speed, and supplying the fuel to each injector 18 at a stable pressure. It is supposed to be. The common rail 17 is provided with a relief valve (not shown) that limits the actual common rail pressure, which is the pressure of the fuel inside, to a preset upper limit value.

  The plurality of injectors 18 have an electromagnetic valve portion 18a wired to an EDU (Electronic Distribution Unit) 20 as these drive units, and a nozzle hole exposed in the combustion chamber 3 of each cylinder 2 at the tip, and high-pressure piping. And a fuel injection portion 18 b connected to the common rail 17 via 19. The fuel injection unit 18b is driven to open when energizing the electromagnetic valve unit 18a, and fuel is injected into the cylinder 2 from the injection hole.

  The EDU 20 is configured by a known unit that performs, for example, capacitive discharge type injection driving electronic power distribution to the electromagnetic valve portions 18a of the plurality of injectors 18. The EDU 20 is an electronic control unit that electronically controls the engine 1, that is, In accordance with an injection command signal from an ECU (Electronic Control Unit) 30, the plurality of injectors 18 are driven to open independently at the injection timing of the corresponding cylinder 2.

  The ECU 30 has a backup memory such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a non-volatile memory, although a specific hardware configuration is not shown. The ECU 30 further includes an input interface circuit including an A / D converter and the like, an output interface circuit including a driver and a relay switch, and another in-vehicle ECU such as a transmission ECU (hereinafter referred to as a T-ECU) that controls an automatic transmission. ) And a communication interface.

  The ECU 30 calculates the optimal injection timing and injection amount according to the rotation speed and load of the engine 1 and adjusts the opening of the metering valve 13 to change the fuel pressure in the common rail 17 to the operating state of the engine 1. The ROM stores a control program (hereinafter referred to as a fuel injection control program for the whole of these control programs) for following an appropriate target fuel pressure. The ECU 30 includes a first injection mode including at least one pilot injection and main injection prior to the main injection in the cylinder 2 at the injection timing at which the compression stroke is substantially completed among the plurality of cylinders 2 of the engine 1. An injection command signal is issued so that fuel is injected in any one of the second injection mode without pilot injection and only the main injection, and the third injection mode in which post injection is executed after the main injection. It is designed to generate.

  Further, the ECU 30 includes, for example, an accelerator opening sensor 21 for detecting an accelerator opening on a vehicle on which the engine 1 is mounted, a fuel pressure sensor 22 mounted on the common rail 17, and the rotational speed of the crankshaft 5 of the engine 1. A crank angle sensor 23 that detects the pulse using a magnetic gear type pulser 23b mounted on the camshaft 15a is connected. The ECU 30 takes in the detection signal Pc of the fuel pressure sensor 22 to detect the fuel pressure in the common rail 17, that is, the actual common rail pressure, and the operation state of the engine 1, for example, the accelerator opening sensor 21 and the crank angle sensor 23. The target common rail pressure is set according to the detection signal. The ECU 30 compares the target common rail pressure with the actual common rail pressure, and adjusts the opening of the metering valve 13 so that the actual common rail pressure in the common rail 17 matches the target common rail pressure.

  The ECU 30 further includes a sensor group such as a vehicle speed sensor 24 for detecting the vehicle speed and a water temperature sensor 25 for detecting the coolant temperature, a neutral switch 26 for turning on a neutral position indicator of a transmission (not shown), and a power source for the vehicle air conditioner. Switches such as an air conditioner switch 27 to be turned on are connected.

  The ECU 30 generates, for example, a pulse signal from the crank angle sensor 23 based on detection information of the sensor group and set value information stored in advance in a backup memory of the switches, and the rotation speed signal and compression stroke of the engine 1. The cylinder transition signal from the engine to the combustion stroke is captured as a cylinder determination signal and the accelerator opening signal is captured to set the target rail pressure of the common rail 17 during operation of the engine 1 and according to the operation state of the engine 1 The injection timing and the fuel injection amount are calculated. The cylinder discrimination signal is, for example, a missing tooth signal corresponding to the missing tooth position of the pulsar 23b, a detection signal of a cylinder discrimination protrusion mounted on the crankshaft 5, or a detection indicating the rotation angle of the intake camshaft or exhaust camshaft. It may be a signal. Then, the ECU 30 outputs an opening adjustment signal Iv (see FIG. 1) to the metering valve 13 according to the calculated injection timing and fuel injection amount, or appropriately sends an injection command signal Iq to the electromagnetic valve portion 18a of the injector 18. To output.

  Further, the ECU 30 constituting the failure diagnosis apparatus cooperates with the crank angle sensor 23 as a rotation speed detection means for detecting the rotation speed of the crankshaft 5 of the engine 1 every preset detection unit angle, for example, every 10 degrees. In addition to exhibiting the functions, a program for exhibiting the functions of a condition determination unit 31, a work equivalent value calculation unit 32, a correction amount calculation unit 34, a rough idle determination unit 35, and an abnormal cylinder detection unit 36, which will be described later. And a map, set value information, and the like.

  Specifically, the condition determination unit 31 is a precondition determination unit that determines whether a precondition for rough idle abnormality detection processing that is set in advance when calculating the fuel injection amount for each cylinder 2 is satisfied. . The precondition of the rough idle abnormality detection processing here is an ignition stable state in which the engine 1 is in an idle stable state after a certain time has elapsed since the start of the engine 1, for example, the accelerator opening is 0 [%], and An air conditioner switch in which the neutral switch 26 indicating that the transmission is in the neutral state is ON and the coolant temperature level at which the injection amount learning processing can be performed has been reached and the so-called idle-up operation is not being performed and the auxiliary load is switched. 27 is not switched, the vehicle speed is 0 [km / h], and there is no abnormality in the sensor group related to detection of these conditions. As a precondition, further, switching of the number of pilot injections of the engine 1 (for example, switching to an arbitrary injection pattern among a plurality of injection patterns such as pilot injection twice, once, no pilot injection, and post injection), etc. It may be included that the engine is in a stable idle operation state in which processing for inducing combustion fluctuation is not performed.

  The work equivalent value calculation unit 32 has a built-in band filter corresponding to a rotation speed signal (hereinafter referred to as a rotation speed Ne) from the crank angle sensor 23 in accordance with the combustion cycle of each cylinder 2 in an operation state where the injection quantity is equal to or greater than a certain injection amount. The filter processing unit calculates an instantaneous torque equivalent value obtained by extracting only the rotational fluctuation component at each time point, and takes the instantaneous torque equivalent value into the integration processing unit for each combustion cycle of each cylinder 2. By integrating in this section, a work equivalent value that is a torque integrated value of each cylinder 2 is calculated for each cylinder 2. The integration section in the integration processing unit is set in a range of 180 ° CA from BTDC 90 ° to ATDC 90 °, for example, according to the combustion cycle of each cylinder 2. BTDC is before top dead center, ATDC is after top dead center, and CA is a crank rotation angle [degree]. Therefore, the work equivalent value calculation unit 32 constitutes a work calculation means.

  Specifically, as shown in FIG. 2, the work equivalent value calculation unit 32 samples the rotation speed Ne at every cycle of the output pulse of the crank angle sensor 23, for example, 10 ° CA, and a unit required for unit angle rotation. The 10 ° CA time that is the angle rotation time is calculated. Then, the work equivalent value calculation unit 32 corrects missing teeth for 10 ° CA time. The missing tooth correction is performed by, for example, comparing a waveform obtained from a value sampled in the vicinity of the missing tooth portion with a waveform obtained from a value sampled in the vicinity of 180 ° CA before the missing tooth portion. Is corrected every 360 ° CA so as to approach the waveform obtained from the value sampled in the vicinity of 180 ° CA before the missing tooth portion.

  The work equivalent value calculation unit 32 converts the corrected waveform into an instantaneous engine speed every 30 ° CA time. That is, the instantaneous Ne is calculated.

なお、（１）式中で、ζは、減衰係数、ωは、エンジン１の燃焼周波数に対応する応答周波数、ｓは、ラプラス演算子である。また、燃焼周波数は、４サイクルのエンジン１の燃焼周期（燃焼角度周期７２０°ＣＡ／気筒数ｎに対応する時間）の逆数から設定される。以下の説明では、燃焼角度周期が１８０°ＣＡであるものとして説明する。 Further, the work equivalent value calculation unit 32 executes filter processing in a built-in filter processing unit having a transfer function obtained by discretizing the following expression (1), and reduces the high-frequency component deviating from the rotation fluctuation frequency region of the crank rotation speed and the low-frequency component. An instantaneous torque equivalent value Neflt, which is a rotational fluctuation component at each time point from which the frequency component has been removed, is calculated.

In Equation (1), ζ is a damping coefficient, ω is a response frequency corresponding to the combustion frequency of the engine 1, and s is a Laplace operator. The combustion frequency is set from the reciprocal of the combustion cycle (combustion angle cycle 720 ° CA / time corresponding to the number of cylinders n) of the engine 1 of four cycles. In the following description, it is assumed that the combustion angle cycle is 180 ° CA.

  As shown in FIG. 3, in the integration processing unit of the work equivalent value calculation unit 32, when the instantaneous torque value Neflt (broken line 52) is calculated from the rotational speed Ne (solid line 51) as described above, the cycle for every 30 ° CA is calculated. The instantaneous torque value Neflt is taken in and integrated in a 180 ° CA interval for each fixed period corresponding to the combustion period of each cylinder 2, so that the work amount W ( # 1) to W (# 4) are calculated. Note that # 1 to # 4 are cylinder numbers, and the combustion of the engine 1 is repeated in the order of # 1, # 3, # 4, and # 2. Also, in the case where the cylinders are not distinguished, explanation will be made as #k.

  Further, the work amount equivalent value calculation unit 32 sets a reference work amount average Wnominal based on the calculated work amounts W (# 1) to W (# 4), and the work amount W (# 1) for each cylinder. ) To W (# 4) and a work average value Wnominal are calculated as work equivalent values Sneflt (# 1) to Sneflt (# 4) in each cylinder 2. Here, the work amounts W (# 1) to W (# 4) calculated by the work amount equivalent value calculation unit 32 are caused by torsional vibration or the like even when there is no variation in the actual fuel injection amount of each cylinder 2. The value changes. Therefore, the work equivalent value calculation unit 32 may correct the work average value Wnominal for each cylinder 2 based on the rotational speed Ne and the fuel injection amount Q. In this case, the correspondence between the rotational speed Ne and the fuel injection amount Q and the correction value is obtained in advance by experimental measurement and stored in the ROM.

  The abnormal cylinder detection unit 36 compares the work equivalent values Sneflt (# 1) to Sneflt (# 4) for each cylinder 2 calculated by the work equivalent value calculation unit 32 with the determination threshold th1 and corresponds to the work amount. When the value is below the determination threshold th1, it is determined that a failure has occurred in the cylinder 2, and the abnormal cylinder flag exdcyl (#k) is turned on. As will be described later, under a specific condition, the work equivalent value Sneflt may fall below the determination threshold th1 even though no failure has occurred in the cylinder 2. Therefore, in the present embodiment, the abnormal cylinder detection unit 36 is prevented from erroneously determining that a failure has occurred in the cylinder 2 even under such conditions.

  The correction amount calculation unit 34 corrects the fuel injection amount Q for each cylinder 2 so that the difference in instantaneous maximum rotation speed in the combustion stroke of each cylinder 2 is reduced in order to suppress vibration when the engine 1 is idle. ing. The correction amount calculation unit 34 samples the rotational speed Ne at every cycle of the output pulse of the crank angle sensor 23, that is, every 10 ° CA, and is corrected by the missing tooth correction, similarly to the above-described work amount equivalent value calculation unit 32. The 10 ° CA time is calculated. Further, the correction amount calculation unit 34 converts the instantaneous value Ne into every 10 ° CA, or twice or three times the cycle, based on the calculated 10 ° CA time.

  Then, as shown in FIG. 4, the correction amount calculation unit 34 calculates the instantaneous maximum rotational speed Nemax (# 1) to Nemax (# 4) in each cylinder 2 from the waveform of the instantaneous Ne, and the cylinder in which the combustion stroke moves back and forth. The difference between the two instantaneous maximum rotational speeds, that is, the rotational deviation is calculated. The correction amount calculation unit 34 performs the current combustion if the instantaneous maximum rotational speed Nemax (# k + 1) of the cylinder that has reached the current combustion stroke is greater than the instantaneous maximum rotational speed Nemax (#k) of the cylinder that has just reached the combustion stroke. The inter-cylinder correction amount QCY for the cylinder that has reached the stroke is made negative, and the instantaneous maximum rotation speed Nemax (# of the cylinder that has reached the current combustion stroke is compared to the instantaneous maximum rotation speed Nemax (#k) of the cylinder that has just reached the combustion stroke. If k + 1) is small, the inter-cylinder correction amount QCY with respect to the fuel injection amount Q is made positive.

  At this time, the correction amount calculation unit 34 adjusts the average value of the inter-cylinder correction amounts QCY for all the cylinders 2 to be close to zero.

  Further, the correction amount calculation unit 34 calculates an average value of the injection amount correction value before the current fuel injection and the injection amount correction value calculated this time in order to prevent the value of each fuel injection from fluctuating rapidly. Thus, a so-called annealing process is performed in which the average value is used as the inter-cylinder correction amount QCY for the next fuel injection amount.

  Here, for example, in the # 1 cylinder 2a, it is assumed that a failure such as clogging of the injection hole of the fuel injection section 18b or valve opening has occurred, and the actual fuel injection amount has temporarily decreased. In this case, when the abnormal cylinder detection unit 36 determines that the work equivalent value Sneflt (# 1) is less than the determination threshold th1 and an abnormal duration counter ecrhidl (# 1) described later is equal to or greater than a predetermined value, the abnormal cylinder flag Set exdcyl (# 1) to ON. On the other hand, since the instantaneous maximum rotational speed Nemax (# 1) decreases due to a decrease in the actual fuel injection amount, the rotational deviation of the # 1 cylinder 2a is a negative value with respect to the # 2 cylinder 2b that immediately reaches the combustion stroke. It becomes. Therefore, the correction amount calculation unit 34 increases the inter-cylinder correction amount QCY (# 1) with respect to the fuel injection amount Q (# 1).

  At the same time, since the rotational deviation of the # 3 cylinder 2c that reaches the combustion stroke next to the # 1 cylinder 2a becomes a positive value with respect to the # 1 cylinder 2a, the correction amount calculation unit 34 corrects the inter-cylinder correction for the # 3 cylinder 2c. The quantity QCY (# 3) is set to a negative value.

  Thereafter, it is assumed that the nozzle hole clogging and the valve opening trap in the # 1 cylinder 2a are resolved and the normal state is restored. At this time, the abnormal cylinder detection unit 36 switches the abnormal cylinder flag exdcyl (# 1) from ON to OFF, but the inter-cylinder correction amount QCY (# 1) is increased for a while due to the effect of the annealing process. Therefore, the # 1 cylinder 2a injects the fuel excessively, the work amount W (# 1) increases, and the work average value Wnominal also increases accordingly. On the other hand, since the inter-cylinder correction amount QCY (# 3) remains negative for a while due to the effect of the annealing process, the work amount W (# 3) is lower than the work amount average value Wnominal, and the work amount The work equivalent value Sneflt (# 3) represented by the difference between W (# 3) and the work average value Wnominal is smaller than the determination threshold th1.

  For this reason, in the conventional failure diagnosis apparatus, although the # 3 cylinder 2c is normal, the work equivalent value Sneflt (# 3) is smaller than the determination threshold th1, and therefore the # 3 cylinder 2c fails. Was supposed to be falsely detected.

  FIG. 5 is a diagram for explaining the cause of such erroneous detection, and it is assumed that the nozzle hole clogging occurs in the # 1 cylinder 2a at time T1. In this case, the work equivalent value Sneflt (# 1) decreases to a negative value, and the inter-cylinder correction amount QCY (# 1) becomes a positive value in order to increase the instantaneous maximum rotational speed Nemax (# 1). . In FIG. 5, since the nozzle hole is clogged, the work equivalent value Sneflt (# 1) is a negative value regardless of the increase in the inter-cylinder correction amount QCY (# 1).

  Then, at the time T2 when the abnormal duration counter ecrhidl (# 1) is equal to or greater than a predetermined value, the abnormal cylinder flag exdcyl (# 1) is turned ON, and the fact that the # 1 cylinder 1a is abnormal is recorded in the OBD.

  Thereafter, it is assumed that the injection hole clogging that has occurred in the # 1 cylinder 2a is eliminated at time T3. At this time, since the inter-cylinder correction amount QCY (# 1) continues to take a positive value by the annealing process, the work amount equivalent value Sneflt (# 1) is also a positive value.

  On the other hand, the inter-cylinder correction amount QCY (# 3) has a negative value so that the rotational deviation between the # 1 cylinder 2a and the # 3 cylinder 2c becomes small in T1 to T2 where the nozzle hole clogging occurs in the # 1 cylinder 2a. taking it. Therefore, even after the injection hole clogging that has occurred in the # 1 cylinder 2a is eliminated at time T3, it continues to take a negative value for a while. Therefore, the work amount W (# 3) in the # 3 cylinder 2c is smaller than the work amount average value Wnominal, and the work amount equivalent value Sneflt (# 3) is a negative value. For this reason, in the conventional failure diagnosis apparatus, at time T4, the abnormal continuation time counter ecrhidl (# 3) becomes equal to or larger than a predetermined value, and the abnormal cylinder flag exdcyl (# 1) is set even though the # 3 cylinder 2c is not broken. Was turned on.

  On the other hand, in the present embodiment, the abnormal cylinder detection unit detects that the abnormal cylinder flag exdcyl (# 1) for the # 1 cylinder 2a has changed from ON to OFF after the normal return to each cylinder 2. The continuation time Txr (#k) is accumulated, and when the continuation time Txr (#k) after this normal recovery becomes equal to or greater than a predetermined value, the accumulation of the abnormal continuation time counter ecrhidl (#k) is executed. Yes. This predetermined value is determined after the value of the inter-cylinder correction amount QCY for the cylinders other than the cylinder 2 converges after the recovery of one of the cylinders 2 from the failure, so that the work equivalent value Sneflt (#k) also converges. It is set as a time longer than the required time. In the present embodiment, this predetermined value is set to 3 seconds and corresponds to the time from T3 to T5 in FIG. Here, convergence means that the value of the inter-cylinder correction amount QCY coincides with the value of the inter-cylinder correction amount QCY that was originally set when no failure occurred in any of the cylinders 2 or erroneous detection. It means that it has approached a value that cannot be generated.

  Thereby, the failure diagnosis apparatus according to the present embodiment causes the abnormal duration counter eccrhidl (#k) for the cylinder that reaches the combustion stroke next to the cylinder due to the return of the cylinder in which the failure has occurred. Therefore, the erroneous detection of the failure of the cylinder 2 is prevented from occurring.

  Further, the abnormal cylinder detection unit 36 integrates the abnormal duration counter ecrhidl (#k) when the duration Txr (#k) after normal recovery becomes 3 seconds or more, and the present invention is thus incorporated in the present invention. Such time counting means is configured. Then, the abnormal cylinder detection unit 36 turns on the abnormal cylinder flag exdcyl (#k) when the abnormal duration counter ecrhidl (#k) is equal to or greater than a predetermined value. A failure determination unit is configured.

  In addition, when the abnormal cylinder flag exdcyl (#k) is turned on, the rough idle determination unit 35 determines that an abnormality that causes rough idle has occurred in the cylinder 2, and turns on the rough idle abnormality detection flag. To do. And the rough idle determination part 35 displays the signal showing abnormality of rough idle by OBD. The rough idle determination unit 35 may display a signal representing the abnormality of the rough idle on an offboard failure diagnosis tool.

  Next, failure diagnosis control processing according to the present embodiment will be described with reference to FIGS.

  Note that the following processing is executed at predetermined time intervals by the CPU constituting the ECU 30 and realizes a program that can be processed by the CPU.

  As shown in FIG. 6, first, the ECU 30 calculates the work equivalent values Sneflt (# 1) to Sneflt (# 4) for each cylinder 2 based on the rotational speed signal input from the crank angle sensor 23 by the method described above. Calculate (step S1).

  Next, the ECU 30 determines whether or not a precondition for performing the rough idle abnormality detection process is satisfied (step S2). As described above, as described above, the ignition is turned on, the engine is started, the neutral switch is turned on, the accelerator opening is fully closed, the vehicle speed is 0, the electric load is not changed, and the shift position is not changed. There are conditions.

  If it is determined that the precondition is satisfied (YES in step S2), the ECU 30 proceeds to step S3. On the other hand, when it is determined that the precondition is not satisfied (NO in step S2), the process proceeds to step S7.

  Next, the ECU 30 compares the work equivalent value Sneflt (#k) for each cylinder 2 calculated in step S1 with the determination threshold th1 (step S3), and the work equivalent value Sneflt (in any cylinder 2). If it is determined that #k) is less than the determination threshold value h1 (YES in step S3), the process proceeds to step S4. On the other hand, when it is determined that the work equivalent value Sneflt (#k) for all the cylinders 2 is equal to or greater than the determination threshold th1 (NO in step S3), the process proceeds to step S7.

  Next, the ECU 30 executes a duration calculation process after normal return (step S4), and the time that has elapsed since the cylinder 2 that was determined to be abnormal in the process before this time returns to normal, that is, normal recovery. The subsequent duration Txr (k) is calculated.

  As shown in FIG. 7, the ECU 30 first determines for each cylinder 2 whether or not the abnormal cylinder flag exdcyl (#k) has changed from ON to OFF in the continuation time calculation processing after normal return (step). S21). If the ECU 30 determines that any of the abnormal cylinder flags exdcyl (#k) has changed from ON to OFF (YES in step S21), the ECU 30 proceeds to step S22 and sets the abnormal cylinder flag exdcyl (#k). For the corresponding cylinder 2, the duration Txr (#k) after normal return is cleared.

  On the other hand, if the ECU 30 determines that the abnormal cylinder flag exdcyl (#k) has not changed from ON to OFF, that is, the normal return state continues (NO in step S21), the ECU 30 proceeds to step S23. Transition is made and the continuation time Txr (#k) after normal recovery is integrated.

  Returning to FIG. 6, the ECU 30 determines whether or not the duration Txr (#k) after normal return is equal to or greater than a predetermined value (step S5). In the present embodiment, the ECU 30 determines whether or not the duration Txr (# k−1) after normal return has become 3 seconds or more.

  If ECU 30 determines that continuation time Txr (# k-1) after normal return has reached 3 seconds or more (YES in step S5), ECU 30 accumulates abnormal continuation time counter ecrhidl (#k) (step S6). The process proceeds to S9.

  On the other hand, if ECU 30 determines that duration Txr (# k-1) after normal return is less than 3 seconds (NO in step S5), the process proceeds to step S7 and clears abnormal duration counter ecrhidl (#k). To do. Then, the rough idle abnormality detection flag is turned off (step S8).

  When the process proceeds to step S9, the ECU 30 determines whether or not the abnormal duration counter ecrhidl (#k) is equal to or greater than a predetermined value. In the present embodiment, the ECU 30 is configured to determine whether or not the abnormal duration counter ecrhidl (#k) has reached 2 seconds or more.

  If the ECU 30 determines that the abnormal continuation time counter ecrhidl (#k) has reached 2 seconds or more (YES in step S9), the ECU 30 turns on the abnormal cylinder flag exdcyl (#k) (step S10). Then, the rough idle abnormality detection flag is turned ON (step S12), and the process proceeds to step S13.

  On the other hand, when the ECU 30 determines that the abnormal continuation time counter ecrhidl (#k) has not reached 2 seconds (NO in step S9), the ECU 30 proceeds to step S11 and turns off the abnormal cylinder flag exdcyl (#k). (Step S11) and the rough idle abnormality detection flag is turned off (step S8).

  When the process proceeds to step S13, the ECU 30 determines whether or not the rough idle abnormality detection flag is ON (step S13). If it is determined that the rough idle abnormality detection flag is ON (YES in step S13), the ECU 30 proceeds to step S14 and notifies the rough idle abnormality.

  On the other hand, when it is determined that the rough idle abnormality detection flag is OFF (NO in step S13), the ECU 30 proceeds to step S15 and notifies the rough idle normality.

  As described above, the failure diagnosis apparatus for an internal combustion engine according to the embodiment of the present invention is equivalent to the work amount in the cylinders 2 other than the cylinder 2 due to any one of the cylinders 2 returning to normal from the abnormality. When there is a possibility that the value Sneflt (#k) may fluctuate, the failure determination based on the work equivalent value Sneflt (#k) is interrupted, so that it is erroneously determined that an abnormality has occurred in these cylinders 2. Can be prevented. Therefore, the abnormality of the cylinder 2 can be accurately determined.

  Further, since the cylinder 2 whose abnormal duration counter ecrhidl (#k) is equal to or longer than the predetermined duration is determined to be abnormal on the condition that the engine 1 is idling, the cause of rough idling during the idling operation of the engine 1 is determined. Therefore, it is possible to accurately determine the abnormality of the cylinder 2 that becomes.

  Further, since it is possible to display that an abnormality has occurred in any of the cylinders 2, the driver can be made aware of the occurrence of an abnormality in the cylinder 2.

  In addition, in the above description, the case where the engine 1 was comprised with the diesel engine of 4 cylinders was demonstrated. However, the engine 1 may have a plurality of cylinders other than the four cylinders, and may be constituted by a gasoline engine as long as fuel can be injected independently into each cylinder.

  As described above, the failure diagnosis device for an internal combustion engine according to the present invention has an effect of improving the failure determination accuracy for each cylinder, and is a failure diagnosis device for an internal combustion engine that detects a failure of each cylinder. Useful.

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder 3 Combustion chamber 4 Transmission mechanism 5 Crankshaft 18 Injector 18a Solenoid valve part 18b Fuel injection part 19 High pressure piping 20 EDU
21 Accelerator opening sensor 22 Fuel pressure sensor 23 Crank angle sensor 23b Pulsar 24 Vehicle speed sensor 30 ECU
31 Condition Determination Unit 32 Work Equivalent Value Calculation Unit 34 Correction Amount Calculation Unit 35 Rough Idle Determination Unit 36 Abnormal Cylinder Detection Unit

Claims (5)

In the internal combustion engine failure diagnosis apparatus capable of independently controlling the fuel injection amounts for a plurality of cylinders,
A work amount calculating means for calculating a work amount in a combustion cycle of the plurality of cylinders based on a rotation speed of an output shaft of the internal combustion engine;
A time measuring means for measuring a duration time during which the work amount calculated by the work amount calculating means is less than a determination threshold;
Failure determination means for determining that a cylinder whose duration measured by the timing means is equal to or longer than a predetermined duration is abnormal,
The failure diagnosis device for an internal combustion engine, wherein when the failure determination means determines that any of the cylinders has returned to normal from an abnormality, the time measurement by the time measurement means is interrupted for a predetermined time.   2. The failure determining means determines that a cylinder whose duration time measured by the timing means is equal to or longer than a predetermined duration is abnormal on the condition that the internal combustion engine is idling. An internal combustion engine failure diagnosis apparatus according to claim 1. During the idling operation of the internal combustion engine, the instantaneous maximum rotational speeds of the output shafts of the internal combustion engine in the combustion strokes of the plurality of cylinders are respectively calculated, and the plurality of cylinders are configured so that the instantaneous maximum rotational speeds are equal to each other. An injection amount correction means for setting a correction value of the fuel injection amount for the cylinder;
The said failure determination means sets the time longer than the time when the fluctuation | variation of the said correction value converges after the cylinder determined to be abnormal resets normally as the said predetermined time, The Claim 1 or Claim 2 characterized by the above-mentioned. The internal combustion engine failure diagnosis apparatus according to claim.   The said failure determination means resets the continuation time measured by the said time measuring means, when interrupting the time measuring by the said time measuring means, The claim of any one of Claim 1 thru | or 3 characterized by the above-mentioned. Diagnostic apparatus for internal combustion engine.   5. The display device according to claim 1, further comprising a display unit configured to display an occurrence of an abnormality when any one of the plurality of cylinders is determined to be abnormal by the failure determination unit. The failure diagnosis device for an internal combustion engine according to claim 1.

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