JP2010144533A - Rough idle detecting device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rough idle detecting device of an internal combustion engine of high diagnostic accuracy, capable of precisely determining whether being a rough idle state of causing unpleasant vibration or not. <P>SOLUTION: This rough idle detecting device has a crank angle sensor 23 for detecting a crank rotating speed of an engine 1, a workload corresponding value calculating part 32 for extracting a variation component of the crank rotating speed by combustion in respective cylinders 2 based on rotating speed detecting information and calculating a workload corresponding value of integrating the extracted variation component, a torque corresponding valve calculating part 33 for calculating a torque corresponding value corresponding to generating torque in the respective cylinders 2 from a square difference in the crank rotating speed in a low speed rotation area of a relatively low speed in the expansion stroke starting timing of the respective cylinders 2 and a high speed rotation area where the crank rotating speed reaches a maximum speed area in its expansion stroke, and an abnormal cylinder detecting part 36 for determining that the combustion in the cylinders 2 less than a determining threshold value in these values, becomes a factor of the rough idle state by comparing the workload corresponding value and the torque corresponding value with a corresponding determining threshold value with respective cylinders 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rough idle detection device for an internal combustion engine, and more particularly, to an internal combustion engine that detects a rough idle state in which the engine speed during idle operation of the internal combustion engine fluctuates unstablely with respect to a target speed due to insufficient fuel injection amount or the like. The present invention relates to a rough idle detection device.

  In an internal combustion engine, for example, a vehicle engine, an engine speed during idle operation (hereinafter referred to as idle speed) is set to a target speed for idle speed control executed by an ECU (Electronic Control Unit). Although the fuel injection amount from the injector to the cylinder is controlled so that the actual fuel injection amount is insufficient or varied with respect to the command injection amount from the ECU to the injector, the engine speed becomes the target speed. On the other hand, it may fluctuate in an unstable manner and fall into a rough idle state that causes unpleasant vibration during idle operation (for example, during cold start). In view of this, there has been proposed a system that detects a rough idle state and can execute control for eliminating the rough idle state.

  As a conventional rough idle detection device for this type of internal combustion engine, it is determined whether or not the engine has been restarted at a high temperature based on the cooling water temperature during idling of the engine, and the actual injection amount becomes insufficient or fluctuates due to the generation of fuel vapor. At the time of high temperature restart that is easy to perform, there is a device that determines that a rough idle state has occurred when the count value of the misfire counter provided in the on-board diagnostic system of the engine exceeds a certain value. When it is determined that an idle state has occurred, the target rotational speed of the idle rotational speed control is set high to eliminate the rough idle state (see, for example, Patent Document 1).

Also, during idle speed control of a diesel engine, fuel injection is equally divided into a plurality of pilot injections to learn injection characteristics, while in an operating state where a certain injection amount is exceeded, engine rotation signal pulses are sent to each cylinder. Depending on the combustion cycle, it is taken into the filter processing unit corresponding to the bandpass filter, and the instantaneous torque equivalent value obtained by extracting only the rotational fluctuation component at each time point is calculated by the filter processing unit, and the instantaneous torque equivalent value is taken into the integration processing unit. There is one that learns the relative variation in the injection characteristics between the cylinders by calculating for each cylinder the amount of work for each cylinder, which is the torque integrated value of each cylinder, by integrating in the section for each combustion cycle of each cylinder ( For example, see Patent Document 2).
JP 2007-192081 A JP 2007-327341 A

  However, in the conventional rough idle detection device for an internal combustion engine, by using the count value of the misfire counter, rather than determining whether or not the engine is in the rough idle state only from the difference between the target rotational speed and the actual rotational speed. Although the diagnostic accuracy is high, the actual rotational fluctuation itself due to the combustion in each cylinder in the rough idle state accompanied by unpleasant vibration was not detected, so the diagnostic accuracy was not sufficient. Therefore, there is a possibility that an unnecessary increase in the fuel injection amount may be executed as rough idle elimination control even though the rough idle state with unpleasant vibration has not occurred. There was a problem.

  In addition, in the case where the instantaneous torque equivalent value is integrated over a certain interval for each combustion cycle of each cylinder, the variation in the injection characteristics among the cylinders can be grasped, but the same combustion is made to the integrated value for the cylinders whose expansion stroke is before and after. The actual rotation fluctuation due to combustion of each cylinder in the rough idle state with unpleasant vibrations may not be detected with high accuracy because the torque generated by the engine is likely to be affected. Improvements were needed to obtain diagnostic accuracy.

  Therefore, an object of the present invention is to provide a rough idle detection device for an internal combustion engine with high diagnostic accuracy that can accurately determine whether or not the engine is in a rough idle state.

  In order to achieve the above object, the rough idle detecting device for an internal combustion engine according to the present invention is: (1) the rotational speed of the crankshaft in an idle operation state in which the rotational speed of the crankshaft of the internal combustion engine is controlled to a target rotational speed; A rough idle detection device for an internal combustion engine that detects a rough idle state that fluctuates with respect to the target rotational speed, the rotational speed detection means for detecting the rotational speed of a crankshaft of the internal combustion engine, and the detection of the rotational speed detection means A work equivalent value calculating means for extracting a fluctuation component of the rotation speed of the crankshaft due to combustion in a cylinder of the internal combustion engine based on the information, and calculating a work equivalent value obtained by integrating the extracted fluctuation component; The rotation speed of the crankshaft reaches the maximum speed range in the relatively low-speed rotation region at the start of the expansion stroke of the cylinder and the expansion stroke of the cylinder. A torque equivalent value calculating means for calculating a torque equivalent value corresponding to the torque generated in the cylinder from a difference in square of the rotation speed of the crankshaft with respect to the high speed rotation region, and the work equivalent value and the torque equivalent value, respectively. In comparison with the determination threshold value corresponding to the abnormal cylinder, it is determined that combustion in the cylinder causes the rough idle state when the work equivalent value and the torque equivalent value are lower than the corresponding determination threshold values. And a determination unit.

  With this configuration, on the basis of the work equivalent value and the torque equivalent value, the actual rotation fluctuation due to the combustion of each cylinder in the rough idle state of the internal combustion engine is changed to the change in the work for every fixed period corresponding to the combustion period and each combustion of each cylinder. Therefore, it is possible to accurately grasp the change in the generated torque of the engine and accurately determine whether or not the engine is in the rough idle state and the cylinder that causes the rough idle detection apparatus. In addition, when the work equivalent value or the torque equivalent value is calculated for other control of the internal combustion engine, it is possible to detect the rough idle with high accuracy without increasing the calculation load.

  In the rough idle detection device for an internal combustion engine according to (1) above, (2) the work equivalent value calculation means includes a fluctuation component of the rotational speed of the crankshaft due to combustion in a plurality of cylinders of the internal combustion engine. Is extracted for each cylinder and integrated over a constant rotation interval for each combustion cycle of each cylinder, and the work equivalent value for each cylinder is calculated repeatedly for a preset number of repetitions, and the calculated value for the work equivalent value is averaged. The calculated equivalent work value is calculated, and the torque equivalent value calculation means calculates a relatively low speed rotation region at the start timing of the expansion stroke of each cylinder for each combustion cycle of each cylinder, A torque equivalent value corresponding to the torque generated in each cylinder is repeated by the number of repetitions from the difference in square of the rotation speed of the crankshaft in the high speed rotation area where the rotation speed of the crankshaft reaches the maximum speed area in the expansion stroke. To calculate returns, preferably calculates the torque equivalent value a calculated value of the torque equivalent value by averaging for respective cylinders.

  With this configuration, it is possible to more accurately grasp the actual rotational fluctuation in the idle state of the internal combustion engine based on the averaged work equivalent value and torque equivalent value, and whether or not the engine is in the rough idle state with high accuracy. It becomes a rough idle detection device with high diagnostic accuracy that can be determined. The averaging process here is, for example, a so-called annealing process that calculates an average value of the calculated value calculated this time and the calculated value obtained in the previous averaging process (hereinafter referred to as the previous value). Good.

  In the rough idle detection device for an internal combustion engine according to the above (1) and (2), (3) the abnormal cylinder determination means includes the averaged work equivalent value and the averaged torque equivalent. For cylinders whose values are lower than the corresponding determination threshold values, it is preferable to set an abnormality detection flag indicating that combustion in the cylinder causes the rough idle state.

  With this configuration, an abnormality detection flag is set for a cylinder that is likely to cause a rough idle state. By referring to this abnormality detection flag, the cause can be quickly grasped at the time of inspection for rough idle vibration. Serviceability is improved. The abnormality detection flag mentioned here is preferably stored as history information in a nonvolatile memory or a backup memory so that the flag setting state can be easily referred to as diagnostic information during maintenance at a dealer or the like. You may do it.

  In the rough idle detection device for an internal combustion engine according to the above (1) to (3), (4) a precondition set in advance as a condition for executing the rough idle state detection process of the internal combustion engine is satisfied. It is preferable that a precondition determination unit for determining whether or not the precondition is satisfied, and when the precondition is satisfied, the work equivalent value calculation unit and the abnormal cylinder determination unit execute the respective processes.

  With this configuration, since the detection process is executed only when the preconditions for executing the rough idle state detection process are satisfied, the computing resources responsible for the rough idle state detection process are required during normal operation. Can be allocated to other calculation processes, and the computational resources can be used effectively.

  In the rough idle detection device for an internal combustion engine described in (4) above, (5) the precondition is that an execution condition of a learning process for learning an injection characteristic of a fuel injection valve provided for each cylinder of the internal combustion engine. Satisfaction is satisfied, the accelerator opening is the minimum value, the vehicle speed of the vehicle powered by the internal combustion engine is zero, and the idling speed at the cold start of the internal combustion engine is when the warm-up is completed It is preferable that the conditions include that the idle-up control set to a higher rotational speed than the idle rotational speed is not executed.

  With this configuration, it is possible to accurately calculate the fluctuation of the idle rotation speed under a substantially constant condition in which the disturbance factor is suppressed.

  In the rough idle detection device for an internal combustion engine according to the above (5), (6) the precondition is that an auxiliary machine load of the internal combustion engine is not switched, and that the internal combustion engine mounted on the vehicle is installed in the internal combustion engine. It may include at least one of the conditions for the drive-coupled transmission to be in the neutral state.

  With this configuration, it is possible to accurately calculate fluctuations in the idle speed under substantially constant conditions in which disturbance factors are further suppressed.

  In the rough idle detection device for an internal combustion engine described in (4) above, (7) the internal combustion engine is a common-rail multi-cylinder diesel engine, and the precondition is executed by the fuel injection valve of the diesel engine. It is also preferable to include that the switching of the fuel injection conditions to be performed is prohibited.

  With this configuration, it is possible to accurately calculate the fluctuation of the idle speed under a certain condition in which the disturbance factor is more reliably suppressed.

  In the rough idle detection device for an internal combustion engine according to (7), (8) the work equivalent value calculation means and the torque equivalent value calculation means use the detection information of the rotation speed detection means as the detection information of the internal combustion engine. It is preferable to take in at a constant cycle corresponding to the number of cylinders and at different rotational phases.

  With this configuration, the work equivalent value and the torque equivalent value can be accurately calculated at the optimum timing for each calculation, and the concentration of the processing load of the calculation resources used in both calculation means can be avoided.

  In the rough idle detection device for an internal combustion engine according to the above (7) and (8), (9) the abnormal cylinder determination means compares the work equivalent value and the torque equivalent value with the corresponding determination threshold values. The first determination mode for determining whether or not the rough idle state, and comparing only one of the work equivalent value and the torque equivalent value with a corresponding determination threshold value, and It is preferable to be able to switch to the second determination mode for determining whether or not the engine is in the rough idle state.

  With this configuration, it becomes a device that can handle both the case where both the work equivalent value and the torque equivalent value are calculated, and the case where only one of the work equivalent value and the torque equivalent value is calculated. The present invention can be employed in a rough idle detection device for an internal combustion engine.

  According to the present invention, the actual rotational fluctuation in the rough idling state of the internal combustion engine is determined based on both the work equivalent value and the torque equivalent value. It is possible to provide a rough idle detection device for an internal combustion engine with high diagnostic accuracy that can be accurately grasped as a change in torque and can accurately determine whether or not the engine is in a rough idle state.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a fuel injection system including a rough idle detection device for an internal combustion engine according to an embodiment of the present invention, and FIG. 2 is executed by the rough idle detection device for an internal combustion engine according to an embodiment. It is explanatory drawing of two types of rotation speed detection periods.

  First, the configuration will be described.

  As shown in FIG. 1, the rough idle detection device for an internal combustion engine according to the present embodiment includes a plurality of cylinders 2 (only one in FIG. 1) of a multi-cylinder internal combustion engine, for example, a four-cylinder diesel engine. It is equipped with a fuel injection system for injecting fuel (shown).

  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 using power from the engine 1, and This is configured as a pressurizing pump 15 that can pressurize the fuel discharged from the feed pump 12 to a higher pressure by the power of the motor, and a known variable throttle element that changes the opening according to the metering command signal input. A metering valve 13 is interposed between the pump 12 and the pressurizing pump 15 and changes the amount of fuel sucked into the pressurizing pump 15 in accordance with the input of the metering command signal. A common rail 17 capable of accumulating and storing discharged fuel at a high pressure, and a plurality of, for example, four electromagnetic drives provided corresponding to the plurality of cylinders 2 of the engine 1. It includes an injector 18 of formula or a piezoelectric-driven, the.

  The feed pump 12 is a known low-pressure fuel pump constituted by, for example, a gear pump.

  The metering valve 13 is configured such that, for example, 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. On the other hand, when the internal coil is energized, it is a variable aperture element that can reduce the opening according to the metering command signal input that is the energization amount.

  A relief valve (not shown) that can return surplus discharged fuel from the feed pump 12 to the fuel tank 11 side is provided between the feed pump 12 and the metering valve 13.

  Although the detailed structure of the pressurizing pump 15 is not shown, a plunger that can reciprocate in the pump housing, a camshaft 15a as an input shaft that drives the plunger, and an eccentricity on the inner end side of the camshaft 15a. A known cam ring having a cam ring rotatably mounted on a cam portion, and at least one pressurizing operation for sucking, pressurizing and discharging fuel between the pump housing and the plunger by reciprocating movement of the plunger The room 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 accumulates and stores the fuel pressurized and discharged by the pressure pump 15 at a high pressure without depending on the load and the engine speed, and can supply the fuel to each injector 18 at a stable pressure. The common rail 17 is provided with a relief valve (not shown) for limiting the actual common rail pressure, which is the pressure of the fuel inside the common rail 17, to a preset upper limit value, for example.

  The plurality of injectors 18 have an electromagnetic valve portion 18a wired to an EDU (Electronic Distribution Unit) 20 serving as a drive unit, and a nozzle hole (not indicated) exposed in the combustion chamber 3 in each cylinder 2. And a fuel injection portion 18b that is connected to the common rail 17 by a high-pressure pipe 19 and is driven to open the fuel from the nozzle hole into the cylinder 2 when the solenoid valve portion 18a is energized.

  The EDU 20 is 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, an ECU ( In accordance with the injection command signal from the electronic control unit 30, the plurality of injectors 18 are driven to open independently at the injection timing of the corresponding cylinder 2.

  ECU 30 includes 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 illustrated. An input interface circuit including a converter, an output interface circuit including a driver and a relay switch, and a communication interface with another in-vehicle ECU such as a transmission control ECU (hereinafter referred to as a T-ECU) for controlling an automatic transmission; It is comprised including.

  The ECU 30 calculates the optimal injection timing and injection amount according to the rotational 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. A control program for following the target fuel pressure suitable for the engine (hereinafter referred to as a fuel injection control program, which refers to the whole of these control programs) is stored in the ROM, and is built into the plurality of cylinders 2 of the engine 1. Of the first injection mode including at least one pilot injection and the main injection prior to the main injection, and the second injection without the pilot injection and only the main injection. Injection so that fuel is injected in any one injection mode among the mode and the third injection mode in which post injection is executed after main injection It is adapted to generate a decree signal.

  The ECU 30 includes an accelerator opening sensor 21 that detects an accelerator opening degree on a vehicle (not shown) on which the engine 1 is mounted, a fuel pressure sensor 22 that is mounted on the common rail 17, and a crankshaft of the engine 1. 5 is connected to a crank angle sensor 23 (rotational speed detecting means) that detects a rotational speed of 5 using, for example, a magnetic gear type pulser 23b mounted on the camshaft 15a. The ECU 30 receives the detection signal Pc from the fuel pressure sensor 22 to detect the fuel pressure in the common rail 17, that is, the actual common rail pressure, and the operating state of the engine 1, for example, the accelerator opening sensor 21 and the crank angle sensor. The target common rail pressure set according to the detection signal 23 is compared with the actual common rail pressure, and the opening of the metering valve 13 is adjusted so that the actual common rail pressure in the common rail 17 matches the target common rail pressure. It has become.

  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 follows, for example, a pulse from the crank angle sensor 23 based on detection information of the sensor group and setting value information stored in advance in a backup memory of the switches in accordance with a control program stored in advance in the ROM. Cylinder discrimination signal (for example, a missing tooth signal corresponding to the missing tooth position of the pulsar 23b or a cylinder mounted on the crankshaft 5) that can discriminate a cylinder that makes a transition from the rotation speed signal of the engine 1 and the compression stroke to the expansion stroke. And the accelerator opening signal, and the target rail pressure of the common rail 17 during operation of the engine 1 is set, and the injection timing and fuel injection amount corresponding to the operating state of the engine 1 are set. Further, an opening adjustment signal Iv (see FIG. 1) to the metering valve 13 and an injector And it outputs the timely injection command signal Iq of 8 to the solenoid valve portion 18a.

  Further, the ECU 30 functions in cooperation with the crank angle sensor 23 as a rotational speed detecting means for detecting the rotational speed of the crankshaft 5 of the engine 1 at a preset detection unit angle, for example, every 10 degrees. In addition, in order to exhibit the functions of a condition determination unit 31, a work equivalent value calculation unit 32, a torque equivalent value calculation unit 33, an average value calculation unit 34, a precondition establishment time counter 35, and an abnormal cylinder detection unit 36, which will be described later. Program, 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 for the rough idle abnormality detection processing here is an idle stable state in which a fixed time has elapsed from the start of the engine 1, for example, an automatic transmission located at the rear stage of the engine 1 with an accelerator opening of 0 [%]. Switching of the air conditioner switch 27, which is the switching of the auxiliary machine load, not the so-called idle-up operation, when the neutral switch 26 indicating the neutral state is ON and the coolant temperature level at which the injection amount learning process can be performed has been reached. No, the vehicle speed is 0 [km / h], and there is no abnormality in the sensor group related to detection of these conditions. In the present embodiment, 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 two pilot injections, once, no pilot injection, and post injection), etc. This is a condition that the engine is in a stable idle operation state in which a process for inducing a combustion fluctuation is not performed.

  For example, as described in Patent Document 2 described above, the work equivalent value calculation unit 32 uses a rotation speed signal (hereinafter referred to as a rotation speed Ne) from the crank angle sensor 23 in each cylinder in an operation state where the injection amount is equal to or greater than a certain injection amount. Incorporating the instantaneous torque equivalent value into the built-in filter processing unit corresponding to the bandpass filter according to the combustion cycle of 2 and calculating the instantaneous torque equivalent value by extracting only the rotational fluctuation component at each time point in the filter processing unit It is a work equivalent value calculating means for calculating for each cylinder 2 a work equivalent value that is a torque integrated value of each cylinder by taking in the processing section and integrating in a section for each combustion cycle of each cylinder. The integral interval in the section is set in the 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].

  Specifically, in the work equivalent value calculation unit 32, the rotation speed Ne is sampled every period of the output pulse of the crank angle sensor 23, for example, every 10 ° CA, and the transfer function obtained by discretizing the following equation (2). In the built-in filter processing unit having the above, by performing the filter processing represented by the following equation (1), the high-frequency component and the low-frequency component deviating from the rotational fluctuation frequency region of the crank rotational speed are removed, and the rotational fluctuation component at each time point is removed. The instantaneous torque equivalent value Neflt can be calculated.

  In the equation (1), Ne (i) is the current sampling value of the rotation speed Ne, Ne (i-2) is the sampling value of the rotation speed Ne two times before, and Neflt (i− 1) is the previous calculated value of the instantaneous torque equivalent value Neflt, Neflt (i-2) is the calculated value of the instantaneous torque equivalent value Neflt, and these values are a part of the work equivalent value calculation unit 32. It is stored in a specific work memory area in the RAM of the ECU 30. k1 to k4 are constants, and are stored in the ROM or nonvolatile memory of the ECU 30. In Equation (2), ζ is a damping coefficient, ω is a response frequency corresponding to the combustion frequency of the engine 1, s is a Laplace operator, and constants k1 to k4 in Equation (1) are ω. = Set to a fixed value based on the combustion frequency. 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 engine 1 has four cylinders and the combustion angle cycle is 180 ° CA.

  In the integration processing unit of the work equivalent value calculation unit 32, the instantaneous torque value Neflt is taken every 10 ° CA or twice or three times as long as it, and a 180 ° CA interval for every constant cycle corresponding to the combustion cycle of each cylinder 2 Is integrated to calculate a work amount equivalent value Sneflt # 1 to Sneflt # 4 for each cylinder, which is an integrated value of instantaneous torque values for each cylinder 2. 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.

  The torque equivalent value calculation unit 33, when the precondition for the rough idle abnormality detection process is satisfied, the low speed rotation angle region Ra of the crankshaft 5 when the compression stroke is almost completed in each cylinder 2 and the start time of the expansion stroke is reached. A torque equivalent value corresponding to the generated torque in each cylinder 2 is calculated from the difference between the squares of the rotational speeds of the crankshaft 5 and the high speed rotation region Rb of the crankshaft 5 in the expansion (explosion) stroke of each cylinder 2. Torque equivalent value calculation means.

  The low-speed rotation angle region Ra here corresponds to a rotation angle region in which the rotation speed of the crankshaft 5 reaches the minimum speed range due to the compression operation of the air in the cylinder 2 under the idle operation state where the precondition is satisfied. An angle region that is a multiple of the detection unit angle, which is a detection unit of 5 rotations, for example, a rotation angle region of 60 degrees from BTDC 20 ° to ATDC 40 ° as shown in FIGS. 2 (a) and 2 (b). Has been. The high-speed rotation angle region Rb corresponds to a rotation angle region in which the rotation speed of the crankshaft 5 reaches the maximum speed region in the expansion stroke of each cylinder 2, and a plurality of detection unit angles that are detection units of rotation of the crankshaft 5. A double angle region, for example, a rotation angle region of 60 degrees from ATDC 50 ° to ATDC 110 ° is set. Since the engine is in the idle stable state, the average value of the engine rotation speed Ne [rpm] is, for example, about 600 [rpm].

More specifically, the torque equivalent value calculated by the torque equivalent value calculation unit 33 is a relatively long rotation required for the crankshaft 5 to pass through the low-speed rotation angle region Ra at the expansion stroke start timing of each cylinder 2. The crank rotational speed Nea [rpm] on the low speed side obtained from the time Δta [μsec] by the following equation (3) and the relative required for the crankshaft 5 to pass through the high speed rotational angle region Rb in the expansion stroke of each cylinder 2. The difference between the squares of both rotational speeds Nea and Neb (Nea ² −Neb ² ) is obtained based on the high-speed crank rotational speed Neb [rpm] obtained by the following equation (4) from the short rotational time Δtb. The obtained value ΔNe ² = Nea ² −Neb ² .

That is, when the rotational inertia moment of the motion system of the engine 1 is I, the kinetic energy (1/2) I (2πNea) in the low speed rotation angle region Ra is generated by the torque generated by the combustion in the cylinder 2 in the expansion (explosion) stroke. ) kinetic energy from the ² in the high-speed rotation angle region Rb (1/2) when I ^(2πNeb) kinetic energy of the engine 1 to ² is increased, the generated torque at the cylinder 2, generally (1/2) I (2 [pi ) ² (Nea ² -Neb ² ), which is proportional to (Nea ² -Neb ² ), so that the generated torque can be grasped from this ΔNe ² . Here, 2πNea and 2πNeb are angular velocities [rad / sec], respectively.

A torque equivalent value ΔNe ² equivalent to the generated torque in each cylinder 2 calculated by the torque equivalent value calculation unit 33, and a work equivalent value Sneflt for every fixed period equivalent to the combustion cycle calculated by the work equivalent value calculation unit 32. # 1 to Sneflt # 4 are taken into the average value calculation unit 34, respectively. In the following description, an arbitrary cylinder number is assumed to be #k.

  Each time the average value calculation unit 34 takes in the work equivalent values Sneflt # 1 to Sneflt # 4 calculated this time by the work equivalent value calculation unit 32, the work equivalent value efic_efficout [#k (i )] In the corresponding work memory area, and the value einstab_eficoutav [#k (i-1)] stored in the memory as the calculated value after the previous averaging process and the current work-equivalent value for each cylinder An average value with efic_eficout [#k (i)] is calculated, and the calculation result is used as a work amount equivalent average value einstab_eficoutav [#k (i)] that is a work amount equivalent value after the current averaging process. They are stored in the memory area. Here, the variable i corresponds to the number of condition establishment determinations in the condition determination unit 31 and corresponds to the counter value of the precondition establishment time counter 35.

Further, every time the average value calculation unit 34 takes in the torque equivalent values ΔNe ² [# 1] to ΔNe ² [# 4] for each cylinder 2 calculated by the torque equivalent value calculation unit 33, the current torque equivalent value. edom2_edom2 [#k (i)] is held in the corresponding working memory area, and the value einstab_edom2av [#k (i-1)] stored in the memory as the calculated value after the previous averaging process An average value with the torque equivalent value edom2_edom2 [#k (i)] is calculated, and the calculation result is set as a torque equivalent average value einstab_edom2av [#k (i)] that is a torque equivalent value after the current averaging process. It is stored in the working memory area.

  In other words, the average value calculation unit 34 is equivalent to the work amount equivalent value einstab_efficatav [#k (i)] and the torque equivalent average corresponding to the values calculated this time by the work equivalent value calculation unit 32 and the torque equivalent value calculation unit 33, respectively. The value einstab_edom2av [#k (i)] is changed from the previous value obtained by the previous averaging process to the work amount equivalent average value einstab_eficoutav [#k (i-1)] and the torque equivalent average value einstab_edom2av [#k ( The so-called annealing process is executed by calculating an average value of i-1)].

  The precondition completion time counter 35 is sequentially incremented (+1) until the set value is 200, for example, and the condition determination number in the condition determination unit 31 is 200, and when the set value is reached, the final value is reached. Are output to the abnormal cylinder detection unit 36 as detection information, the work equivalent average value einstab_eficoutav [#k (i)] and the torque equivalent average value einstab_edom2av [#k (i)] stored in the average value calculation unit 34. The abnormal cylinder detection unit 36 requests an abnormal cylinder detection process. The count-up state of the precondition satisfaction time counter 35 is cleared in response to a clear request signal from the abnormal cylinder detection unit 36, for example.

  That is, the work equivalent value calculation unit 32 and the average value calculation unit 34 together constitute the work equivalent value calculation means referred to in the present invention, and the rotation of the crankshaft 5 due to combustion in the plurality of cylinders 2 of the engine 1. While extracting the fluctuation component of the speed Ne for each cylinder 2, integration is performed in a constant rotation interval (180 ° CA) for each combustion cycle of each cylinder 2, and the work equivalent value efic_efficout [#k (i)] for each cylinder 2 is obtained. A work-equivalent average obtained by repeatedly calculating a preset number of repetitions, for example, 200 times, and averaging the calculated values efic_eficout [#k (1)] to efic_eficout [#k (200)] The value einstab_eficoutav [#k (i)] is calculated.

Further, the torque equivalent value calculating unit 33 and the average value calculating unit 34 constitute torque equivalent value calculating means according to the present invention, and are different from the work equivalent value calculating means for each combustion cycle of each cylinder 2. The rotation speed Ne corresponding to the crank rotation signal from the crank angle sensor 23 is taken in with the crank rotation phase, and the relatively low-speed rotation region Ra at the start time of the expansion stroke of each cylinder 2 and the expansion stroke of each cylinder 2 A torque equivalent value corresponding to the torque generated in each cylinder 2 from the square difference (Nea ² −Neb ² ) of the rotational speed Ne of the crankshaft 5 with respect to the high speed rotational range Rb where the rotational speed of the crankshaft 5 reaches the maximum speed range. edom2_edom2 [#k (i)] is repeatedly calculated for the number of repetitions, for example, 200 times, and the calculated value edom2_ A torque equivalent average value einstab_edom2av [#k (i)] obtained by averaging edom2 [#k (1)] to edom2_edom2 [#k (200)] is calculated.

  The abnormal cylinder detection unit 36 averages the work equivalent value and the torque equivalent value, that is, the work equivalent average value einstab_eficoutav [#k (i)] and torque output from the average value calculation unit 34 for each cylinder 2. When the equivalent average value einstab_edom2av [#k (i)] is compared with the corresponding determination threshold values h1 and h2, the cylinder 2 when the work equivalent value and the torque equivalent value are lower than the corresponding determination threshold values. An abnormal cylinder determination process is performed to determine that combustion in the engine causes a rough idle state.

  Further, the abnormal cylinder detection unit 36 has the work equivalent average value einstab_eficoutav [#k (i)] and the torque equivalent average value einstab_edom2av [#k (i)] for each cylinder 2 output from the average value calculation unit 34, respectively. For the cylinder 2 that falls below both the determination threshold values h1 and h2, corresponding to the rough idle state detection flag einstab_exrough indicating that the combustion in the cylinder 2 causes the rough idle state, and the rough idle indicating the cylinder number of the cylinder 2 The cylinder flag einstab_excyl is set and stored in the diagnostic information storage area in the RAM of the ECU 30 and / or in the backup memory. The diagnostic information storage area in the memory can be read by the external diagnostic device 100 when the external diagnostic device 100 is connected to a known inspection communication port of the ECU 30, and can be inspected or maintained by a dealer or the like. Sometimes it is referred to.

  Furthermore, the abnormal cylinder detection unit 36 averages the work equivalent value and the torque equivalent value, that is, the work equivalent average value einstab_efficatav [#k (i)] and the torque equivalent average value einstab_edom2av [#k (i). ] To the determination threshold values h1 and h2 corresponding to each of them to determine whether or not the engine is in the rough idling state, the work equivalent average value einstab_efficoutav [#k (i)] and the torque equivalent average It is possible to switch to the second determination mode in which only one of the values einstab_edom2av [#k (i)] is compared with the corresponding determination threshold value h1 or h2 to determine whether or not it is in the rough idle state. Setting value information that sets which judgment mode is used is an example. If it stored in the ECU30 in ROM or in the memory for backup.

  Next, the operation will be described.

  FIG. 3 is a flowchart of the detection process executed in the rough idle detection device for the internal combustion engine of the present embodiment. During operation of the engine 1, the ECU 30 performs the process shown in FIG. 3 at a preset calculation cycle. Repeatedly executed.

  First, the condition determining unit 31 determines whether or not the above-described precondition for the rough idle abnormality detection process is satisfied (step S11).

  At this time, if it is determined that the precondition for the rough idle abnormality detection process is satisfied, the engine 1 is operated in a stable state with no load fluctuation.

  When the precondition for the rough idle abnormality detection process is satisfied (in the case of YES at step S11), after the precondition completion time counter 35 is incremented (step S12), the work equivalent value calculation unit 32 performs a plurality of engine 1 The fluctuation component of the rotational speed Ne of the crankshaft 5 due to combustion in the cylinder 2 is extracted for each cylinder 2 and integrated in a constant rotation section (180 ° CA) for each combustion cycle of each cylinder 2 to correspond to the work amount. The values Sneflt # 1 to Sneflt # 4 are calculated, and these calculated values are taken into the average value calculation unit 34 as the work equivalent value efic_efficout [#k (i)], and are calculated as the calculated values after the previous averaging process. An average value with the value einstab_eficoutav [#k (i−1)] stored in the average value calculation unit 34 is calculated, and the calculation result It is stored as the workload corresponding average value einstab_eficoutav after this averaging process [#k (i)] (step S13).

At the same time, the torque equivalent value calculation unit 33 takes in the rotational speed Ne at a different crank rotation phase than the work amount equivalent value calculation unit 32 for each combustion cycle of each cylinder 2. The difference between the squares of the rotational speed Ne between the relatively low-speed rotation region Ra at the start of the expansion stroke and the high-speed rotation region Rb where the rotation speed of the crankshaft 5 reaches the maximum speed region in the expansion stroke of each cylinder 2. Torque equivalent values ΔNe ² [# 1] to ΔNe ² [# 4] corresponding to the generated torque of each cylinder 2 are calculated from (Nea ² −Neb ² ), and these calculated values are stored in the average value calculation unit 34 at this time. The value einstab_edom2av [#k (i−1)] that is taken in as the torque equivalent value edom2_edom2 [#k (i)] and stored in the memory as the calculated value after the previous averaging process Result of calculating the average value is stored in memory as a torque equivalent average einstab_edom2av after this averaging process [#k (i)] (step S13).

  Next, it is determined whether or not the count value of the precondition satisfaction time counter 35 has reached 200 times (step S14). If it has not reached (NO in step S14), the current process ends.

  In this case, when the precondition for the rough idle abnormality detection process is satisfied next, the above-described series of calculation and averaging processes are repeated again.

  That is, until the count value of the precondition satisfaction time counter 35 reaches 200 times, the work equivalent value calculation unit 32 repeatedly calculates the work equivalent value efic_efficout [#k (i)] and corresponds to the work equivalent. A work-equivalent average value einstab_eficoutav [#k (i)] that has been smoothed by sequential average value calculation from the calculated value efic_eficout [#k (1)] to efic_eficout [#k (200)] is calculated, On the other hand, the torque equivalent value calculation unit 33 repeatedly calculates the torque equivalent value edom2_edom2 [#k (i)] for each cylinder 2, and calculates the torque equivalent value edom2_edom2 [#k (1) for each cylinder 2. )] To edom2_edom2 [#k (200)] So that the torque-equivalent average value einstab_edom2av that the smoothing process by the value calculated [#k (i)] is calculated.

  On the other hand, when the count value of the precondition satisfaction time counter 35 reaches 200 times (in the case of YES at step S14), the abnormal cylinder detection unit 36 performs the work amount for each cylinder 2 based on the output from the average value calculation unit 34. The equivalent average value einstab_eficoutav [#k (i)] and the torque equivalent average value einstab_edom2av [#k (i)] are compared with the corresponding determination threshold values h1 and h2 (step S15).

  At this time, if the work-equivalent average value einstab_eficoutav [#k (i)] and the torque-equivalent average value einstab_edom2av [#k (i)] are equal to or higher than the corresponding determination threshold values h1, h2 (NO in step S15). In this case, the idle normal flag einstab_exprough indicating that the idle operation state is normal is set (step S16).

  On the contrary, if the work equivalent average value einstab_eficoutav [#k (i)] and the torque equivalent average value einstab_edom2av [#k (i)] are values corresponding to the respective determination threshold values h1 and h2 (YES in step S15) ), A rough idle abnormality detection flag einstab_exdrow indicating that a rough idle abnormal cylinder has been detected, and a rough idle abnormal cylinder flag einstab_exdcl indicating the cylinder number of the rough idle abnormal cylinder are set (step S17).

  Next, the count value of the precondition fulfillment time counter 35 is cleared (step S18), and the current process ends.

  In the next detection process, if the condition determination unit 31 determines that the precondition for the rough idle abnormality detection process is satisfied (YES in step S11), the above-described series of processes (steps S12 to S18) is performed again. If it is determined that the precondition for the rough idle abnormality detection process is not satisfied by the condition determination unit 31 (NO in step S11), the count value of the precondition satisfaction time counter 35 is cleared as it is (step S18). Next processing is completed.

  Thus, in this embodiment, the work equivalent average value einstab_eficoutav [#k (i)] and the torque equivalent average value einstab_edom2av [] obtained by measuring the actual rotational speed of the crankshaft 5 of the engine 1 and using different calculation methods. #K (i)] is used to detect a change in work for each constant angular period (180 ° CA) corresponding to the combustion period of each cylinder 2 and a change in generated torque for each combustion of each cylinder 2. Therefore, whether or not the actual fuel injection amount from the injector 18 is insufficient or fluctuates, the actual rotation speed fluctuates with respect to the target rotation speed set by the ECU 30, and whether or not a rough idle state with unpleasant vibrations is properly determined. It becomes a rough idle detection device with high diagnostic accuracy that can be determined easily. Moreover, when the work equivalent value or the torque equivalent value is calculated for other control of the engine 1, highly accurate rough idle detection can be performed without increasing the calculation load in the ECU 30.

  In the present embodiment, when the rough idle detection condition is satisfied for a certain time (for example, the time when the precondition satisfying time counter value reaches 200 times) or more, the work equivalent average value einstab_eficoutav [# k (i)] and the torque equivalent average value einstab_edom2av [#k (i)], the rough idle detection is performed, so that the actual rotation fluctuation and the rough idle vibration for each combustion of each cylinder 2 in the rough idle state of the engine 1 are detected. It is possible to accurately detect the cylinder 2 that is a factor that occurs.

  Further, in addition to the setting of the rough idle abnormality detection flag einstab_exrough indicating that the rough idle abnormal cylinder has been detected, the work equivalent average value einstab_eficoutav [#k (i)] and the torque equivalent average value einstab_edom2av [#k (i) ] Is set to a rough idle abnormal cylinder flag einstab_excl as a cylinder that is highly likely to cause a rough idle state for cylinders 2 that are lower than the corresponding determination threshold values h1 and h2, and can be read at the time of diagnosis by the external diagnostic apparatus 100 Therefore, the rough idling abnormality detection flag einstab_exrough and the rough idling abnormal cylinder flag ei at the time of inspection or maintenance at the dealer or the like for rough idling vibration. By referring to Stab_exdcl, the occurrence and the cause of rough idle can be grasped quickly and reliably, thereby improving serviceability.

  In addition, in the present embodiment, since the detection process described above is executed only when the precondition for executing the rough idle abnormality detection process is satisfied, the CPU in the ECU 30 responsible for the detection process of the rough idle state is executed. Processing capacity can be assigned to other calculation processes required during normal operation, and computational resources can be used effectively.

  Further, the precondition for detecting rough idle abnormality is a learning process for learning the injection characteristics of the injectors 18 provided for each cylinder 2 of the engine 1 (for example, the fuel injection amount of each injector 18 under idle speed control). The execution condition of the variation learning process) is satisfied, the accelerator opening is the minimum value (0%), and the vehicle speed of the vehicle powered by the engine 1 is zero [km / h]. Including the condition that the idling-up control in which the idling speed at the cold start of the engine 1 is set higher than the idling speed at the completion of warm-up is not executed, the disturbance factor is almost suppressed. Under certain conditions, it is possible to accurately detect fluctuations in idle speed.

  In addition, the precondition includes at least one of the conditions that the auxiliary load (such as an air conditioner) of the engine 1 is not switched and the transmission is in the neutral state, and is a common rail type multi-cylinder diesel engine. Since it is further included in the precondition that switching of the fuel injection condition (combustion mode) executed by the injector 18 of an engine 1 is prohibited, the fluctuation of the idling speed is changed under a substantially constant condition in which the disturbance factor is further suppressed. Can be calculated with high accuracy.

  In addition, the actual rotation number of the crankshaft 5 is measured with a constant cycle corresponding to the number of cylinders of the engine 1 and with mutually different rotation phases, and the average value corresponding to the work amount is accurately calculated at the optimal timing for each calculation. Since rough idle detection and rough idle abnormal cylinder detection are performed based on einstab_eficoutav [#k (i)] and torque equivalent average value einstab_edom2av [#k (i)], the processing load of the CPU (calculation resource) of the ECU 30 is increased. Concentration can be avoided.

  Further, since the abnormal cylinder detection unit 36 can be switched between the first determination mode and the second determination mode, the ECU 30 of the engine 1 is a control specification for calculating both the work equivalent value and the torque equivalent value. In addition, even if the control specifications calculate only one of the work equivalent value and the torque equivalent value, each can be supported, and the rough idle detection device can be applied to engines of various specifications.

  In the above-described embodiment, the determination threshold value h1 corresponding to both the work equivalent average value einstab_eficoutav [#k (i)] and the torque equivalent average value einstab_edom2av [#k (i)] for each cylinder 2; An abnormality detection flag indicating that combustion in the cylinder 2 causes a rough idle state is set for the cylinders 2 both lower than h2, but the work equivalent average value einstab_eficoutav [#k] for each cylinder 2 is set. (I)] and the torque equivalent average value einstab_edom2av [#k (i)], in which at least one of the cylinders 2 is below the corresponding determination threshold value h1 or h2, combustion in the cylinder 2 causes the rough idle state. You can set a flag to indicate that Plural types of rough idle abnormalities having different diagnosis levels depending on whether only one of the predetermined threshold values h1 and h2 is lower than the determination threshold values h1 and h2 or not is an abnormal cylinder candidate A detection flag can also be set.

  In the above-described embodiment, the rotation measurement period for calculating the work equivalent value and the torque equivalent value is set to a period having a different phase for each combustion cycle. By setting the low-speed rotation angle region Ra and the high-speed rotation region Rb within the measurement period, the rotation measurement period for calculating the torque equivalent value is set to the same phase as the rotation measurement period for calculating the work equivalent value. You can also

  As described above, the rough idle detecting device for an internal combustion engine according to the present invention can accurately grasp the actual rotational fluctuation in the rough idle state based on both the work equivalent value and the torque equivalent value. It is possible to provide a rough idle detection device for an internal combustion engine with high diagnostic accuracy that can accurately determine whether or not the engine is in a state. This is useful for general rough idle detection devices for internal combustion engines that detect a rough idle state in which the engine rotational speed of the engine fluctuates in an unstable manner with respect to the target rotational speed.

It is a schematic block diagram of the fuel-injection system provided with the rough idle detection apparatus of the internal combustion engine which concerns on one Embodiment of this invention. It is explanatory drawing of two types of rotation speed detection periods performed with the rough idle detection apparatus of the internal combustion engine which concerns on one Embodiment of this invention. It is a flowchart of the detection process performed in the rough idle detection apparatus of the internal combustion engine which concerns on one Embodiment of this invention.

Explanation of symbols

1 engine (internal combustion engine)
2 cylinder 3 combustion chamber 5 crankshaft 11 fuel tank 12 feed pump 13 metering valve 15 pressurizing pump 15a camshaft 17 common rail 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 (rotation speed detecting means)
24 Vehicle speed sensor 25 Water temperature sensor 26 Neutral switch 27 Air conditioner switch 30 ECU (electronic control unit, rotation speed detection means)
31 Condition determining unit (precondition determining means)
32 Work equivalent value calculation unit (work equivalent value calculation means)
33 Torque equivalent value calculation unit (torque equivalent value calculation means)
34 Average value calculation unit (work equivalent value calculation means, torque equivalent value calculation means)
35 Precondition fulfillment time counter 36 Abnormal cylinder detector (abnormal cylinder determination means)
100 diagnostic device h1, h2 judgment threshold

Claims (9)

A rough idle detection device for an internal combustion engine for detecting a rough idle state in which the rotational speed of the crankshaft fluctuates with respect to the target rotational speed under an idle operation state in which the rotational speed of the crankshaft of the internal combustion engine is controlled to a target rotational speed. There,
Rotational speed detection means for detecting the rotational speed of the crankshaft of the internal combustion engine;
Based on the detection information of the rotation speed detection means, a fluctuation component of the rotation speed of the crankshaft due to combustion in the cylinder of the internal combustion engine is extracted, and a work equivalent value obtained by integrating the extracted fluctuation component is calculated. A work equivalent value calculating means;
2 of the rotational speed of the crankshaft in the relatively slow low speed rotation region at the start timing of the expansion stroke of the cylinder and the high speed rotation region in which the rotational speed of the crankshaft reaches the maximum speed region in the expansion stroke of the cylinder. Torque equivalent value calculating means for calculating a torque equivalent value corresponding to the torque generated in the cylinder from the difference in power;
Comparing the work equivalent value and the torque equivalent value with the corresponding determination threshold values, and when the work equivalent value and the torque equivalent value are lower than the corresponding determination threshold values, combustion in the cylinder is performed. A rough idle detecting device for an internal combustion engine, comprising: an abnormal cylinder determining unit that determines that the rough idle state is caused. The work equivalent value calculating means extracts a fluctuation component of the rotation speed of the crankshaft due to combustion in a plurality of cylinders of the internal combustion engine for each cylinder, and integrates it in a constant rotation interval for each combustion cycle of each cylinder. A work equivalent value for each cylinder is repeatedly calculated for a preset number of repetitions, and a work equivalent value obtained by averaging the calculated values of the work equivalent values is calculated.
The torque equivalent value calculating means has a relatively slow low-speed rotation region at the start of the expansion stroke of each cylinder and a maximum rotation speed of the crankshaft in the expansion stroke of each cylinder for each combustion cycle of each cylinder. A torque equivalent value corresponding to the torque generated in each cylinder is repeatedly calculated by the number of repetitions from the difference between the squares of the rotation speed of the crankshaft in the high-speed rotation region reaching the speed range, and the torque equivalent value for each cylinder 2. The rough idle detection device for an internal combustion engine according to claim 1, wherein a torque equivalent value obtained by averaging the calculated values is calculated.   The abnormal cylinder determining means is configured to perform combustion in the rough idle for the cylinder in which the averaged work equivalent value and the averaged torque equivalent value are lower than the corresponding determination threshold values. 3. The rough idle detection device for an internal combustion engine according to claim 1, wherein an abnormality detection flag indicating that the state is a factor is set. Precondition determining means for determining whether or not a precondition set in advance as a condition for executing the processing for detecting the rough idle state of the internal combustion engine is satisfied;
The claim according to any one of claims 1 to 3, wherein when the precondition is satisfied, the work equivalent value calculation means and the abnormal cylinder determination means execute respective processes. A rough idle detection device for an internal combustion engine as described.   The precondition is that an execution condition of a learning process for learning an injection characteristic of a fuel injection valve provided for each cylinder of the internal combustion engine is satisfied, an accelerator opening is a minimum value, and the internal combustion engine is The vehicle speed of the vehicle as the power source is zero, and the idling-up control is not executed in which the idling speed at the cold start of the internal combustion engine is set higher than the idling speed at the completion of warm-up. The rough idle detection device for an internal combustion engine according to claim 4, wherein each of the conditions is included.   The precondition is that each of at least one of the conditions that an auxiliary load of the internal combustion engine is not switched and a transmission mounted on the vehicle and connected to the internal combustion engine is in a neutral state. The rough idle detection device for an internal combustion engine according to claim 5, comprising: The internal combustion engine is a common rail multi-cylinder diesel engine;
5. The rough idle detection device for an internal combustion engine according to claim 4, wherein the precondition includes prohibition of switching of a fuel injection condition executed by the fuel injection valve of the diesel engine.   The work equivalent value calculating means and the torque equivalent value calculating means fetch the detection information of the rotational speed detecting means at a constant cycle corresponding to the number of cylinders of the internal combustion engine and at mutually different rotational phases. The rough idle detection device for an internal combustion engine according to claim 7.   A first determination mode in which the abnormal cylinder determination means compares the work-equivalent value and the torque-equivalent value with a corresponding determination threshold value to determine whether or not the rough idle state is set; and the work amount It is possible to switch to the second determination mode in which only one of the equivalent value and the torque equivalent value is compared with the corresponding determination threshold value to determine whether or not the rough idle state is set. The rough idle detection device for an internal combustion engine according to claim 7 or 8, characterized in that the internal combustion engine is a rough idle detection device.

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