JP2012202241A - Method and device for diagnosis of failure in engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for diagnosis of failure in an engine, capable of reducing diagnostic manhours, and capable of achieving simplification of a constitution, by easily determining whether the occurrence of a misfire is caused by mechanical failure and in which cylinder the mechanical failure is caused.SOLUTION: The method and device 14 for diagnosis of failure in the engine 16 determine cylinders 22a-22d being a predetermined value or less in a variation value Δω as a compression pressure insufficient cylinder being insufficient in compression pressure, by detecting the variation value Δω of angular velocity of a crankshaft 24 corresponding to an explosion process with every cylinder 22 in a cranking rotation state, by generating the cranking rotation state for rotating the crankshaft 24, while stopping an explosion in the respective cylinders 22a-22d.

Description

  The present invention relates to an engine failure diagnosis method and a failure diagnosis device that specify a cylinder in which misfire has occurred and store a failure code indicating the cylinder.

  A technique for detecting the occurrence of misfire in each cylinder constituting an engine is known (Patent Document 1). In Patent Document 1, when the management ECU (117) determines that a misfire has occurred in the internal combustion engine (107), the management ECU controls the warning lamp (125) to light ([0027]).

  A technique for detecting an abnormality in the compression pressure of each cylinder is known (Patent Document 2). In Patent Document 2, cranking is performed to rotate the crankshaft (1a) while the fuel system and the ignition system are driven and stopped, and the engine is used by using the difference value of the instantaneous rotational speed between the set crank angles in the compression process of each cylinder. , And an abnormality in the compression pressure is detected based on the rotation fluctuation.

JP 2009-280082 A JP 2004-019465 A

  Although failure diagnosis and inspection / repair work are performed at a service base based on a warning such as lighting of a warning light in Patent Document 1, there are various causes of misfire, so it is a great effort to specify a repair point. Need.

  For example, as one of troubleshooting when a misfire occurs in a multi-cylinder engine, when an inspection item for confirming whether or not the compression pressure of the engine is normal is provided, the spark plug is removed and the spark plug is attached to the mounting hole. If a method of directly measuring the compression pressure of each cylinder by cranking rotation with a pressure gauge attached, or a method of checking all the valve clearances (intake valve and exhaust valve clearances) of each cylinder, this is used. Such mechanical inspection work requires a great deal of man-hours for disassembly and adjustment.

  The cause of misfire is roughly divided into electrical failure and mechanical failure. In particular, there is a problem that it takes time and effort because the mechanical failure requires disassembly and maintenance work.

  On the other hand, as described above, the abnormality detection of the compression pressure in Patent Document 2 uses the difference value of the instantaneous rotational speed between the set crank angles in the “compression process” in each cylinder. For this reason, it is necessary to newly provide a configuration (including software such as judgment logic) for detecting an abnormality in the compression pressure by detecting the difference value of the instantaneous rotational speed in the “compression process”. Complexity and high cost are inevitable.

  The present invention has been made in consideration of such problems, and the determination of misfire occurrence during operation of the engine is performed by detecting the fluctuation value of the angular velocity of the crankshaft corresponding to the explosion process during operation. By focusing on the fact that the misfire is determined and by partially utilizing the determination logic, whether or not the misfire is due to a mechanical failure and which cylinder has a mechanical failure It is an object of the present invention to provide an engine failure diagnosis method and a failure diagnosis device that can easily determine whether the engine is operating, reduce the number of diagnostic steps, and can simplify the configuration.

  According to the engine failure diagnosis method of the present invention, during operation of an engine having a plurality of cylinders, a variation value of the angular velocity of the crankshaft corresponding to the explosion process is detected for each cylinder, and a misfire occurrence cylinder in which misfire occurs. An engine failure diagnosis method that is monitored by a misfire monitoring section that determines a crankshaft rotation state in which a crankshaft is rotated while stopping an explosion in each cylinder. In this state, a variation value of the angular velocity of the crankshaft corresponding to the explosion process is detected for each cylinder, and a cylinder having the variation value equal to or less than a predetermined value is determined as a compression pressure deficient cylinder having insufficient compression pressure. And

  According to the present invention, in the cranking rotation state in which the crankshaft is rotated while stopping the explosion in each cylinder, the occurrence of the compression pressure abnormality in each cylinder is determined by detecting the fluctuation value of the angular speed of the crankshaft. Is possible. Therefore, it is possible to accurately determine whether or not there is a lack of compression pressure (mechanical failure), which is one of the causes of misfire occurrence, without disassembling the cylinders, and to improve engine failure diagnosis efficiency. it can.

  Further, in both the normal operation of the engine and the cranking rotation, the variation value of the angular velocity of the crankshaft corresponding to the explosion process is detected for each cylinder, and the cylinder with insufficient compression pressure is determined based on the variation value. For this reason, it becomes possible to use the logic for misfire determination which vehicle ECU has as logic for determination of a cylinder with insufficient compression pressure. Therefore, it is possible to simplify the configuration (including software such as determination logic) for determining a cylinder with insufficient compression pressure.

  Furthermore, it can be used not only for the case where a misfire-occurring cylinder occurs, but also for operation confirmation after engine assembly for inspection and maintenance.

  In the cranking rotation state, an individual average value that is an average value of fluctuation values of each cylinder is compared with an overall average value that is an average value of fluctuation values of all cylinders, and the individual average is compared with the overall average value. The cylinder having a small value may be determined to be the compression pressure deficient cylinder. Thereby, it is possible to determine a cylinder with insufficient compression pressure by a relative comparison between the cylinders. For this reason, even if a change in the voltage of the battery for the motor for driving the crankshaft, a change in the ambient temperature, or the like slightly affects the fluctuation value of the angular velocity of the crankshaft, it is less likely to be affected by the determination of the cylinder with insufficient compression pressure. be able to.

  The detection of the fluctuation value of the angular velocity of the crankshaft in the cranking rotation state may be started after a predetermined time has elapsed from the start of the motor that drives the crankshaft. As a result, it is possible to detect the fluctuation value in a state where the cranking rotation is stable, and therefore it is possible to accurately determine the cylinders with insufficient compression pressure.

  The voltage of the battery that drives the motor that drives the crankshaft may be monitored, and the determination of the cylinder with insufficient compression pressure may be stopped when the voltage of the battery drops below a predetermined voltage. Accordingly, it is possible to avoid erroneous determination of a cylinder with insufficient compression pressure by avoiding determination in a state where cranking rotation becomes unstable due to a decrease in battery voltage.

  When the temperature of the engine cooling water or the temperature of the engine oil is lower than a predetermined value, the determination of the cylinder with insufficient compression pressure may be stopped. For example, if a value that cannot be taken in a normal use environment is set as the predetermined value, it is possible to avoid erroneous determination of a cylinder with insufficient compression pressure by avoiding determination in a specific use environment. .

  An engine failure diagnosis apparatus according to the present invention detects a variation value of an angular velocity of a crankshaft corresponding to an explosion process for each cylinder during operation of an engine having a plurality of cylinders, and misfires are generated. An engine failure diagnosis apparatus that is monitored by a misfire monitoring unit that determines a crankshaft rotation state while stopping an explosion in each cylinder and generating a cranking rotation state. In this state, a fluctuation value of the angular velocity of the crankshaft corresponding to the explosion process is acquired for each cylinder, and a cylinder having the fluctuation value equal to or less than a predetermined value is determined as a compression pressure deficient cylinder having insufficient compression pressure. And

  According to the present invention, in the cranking rotation state in which the crankshaft is rotated while stopping the explosion in each cylinder, the occurrence of the compression pressure abnormality in each cylinder is determined by detecting the fluctuation value of the angular speed of the crankshaft. Is possible. Therefore, it is possible to accurately determine whether or not the compression pressure is insufficient (mechanical failure), which is one of the causes of misfire, without disassembling the cylinder. Therefore, it is possible to accurately determine whether or not there is a lack of compression pressure (mechanical failure), which is one of the causes of misfire occurrence, without disassembling the cylinders, and to improve engine failure diagnosis efficiency. it can.

  Further, in both the normal operation of the engine and the cranking rotation, the variation value of the angular velocity of the crankshaft corresponding to the explosion process is detected for each cylinder, and the cylinder with insufficient compression pressure is determined based on the variation value. For this reason, it becomes possible to use the logic for misfire determination which vehicle ECU has as logic for determination of a cylinder with insufficient compression pressure. Therefore, it is possible to simplify the configuration (including software such as determination logic) for determining a cylinder with insufficient compression pressure.

  Furthermore, it can be used not only for the case where a misfire-occurring cylinder occurs, but also for operation confirmation after engine assembly for inspection and maintenance.

1 is a block diagram showing a schematic configuration of an engine diagnosis system having an engine failure diagnosis apparatus (hereinafter also referred to as “diagnosis apparatus”) according to an embodiment of the present invention. It is a figure which shows the schematic structure inside the one cylinder. It is a figure which shows the external appearance of a crank angle sensor. It is a figure which shows an example of the output signal of a crank angle sensor. 7 is a flowchart for determining whether or not misfire has occurred in a cylinder during normal driving of the vehicle (during normal operation of the engine). An example of the relationship between the piston movement of each cylinder during normal operation of the engine and the magnitude of the load generated on the crankshaft due to the piston movement occurs when the cylinder is operating normally and when a misfire occurs It is a figure divided into time. It is a flowchart of determination of misfire generation by engine ECU. Relationship between crank angle and crank angular speed when each cylinder is operating normally and when misfiring has occurred in the first cylinder, and processes (intake process, compression process, explosion process and exhaust process) in each cylinder It is a figure which shows the example of. It is a figure which shows the relationship between the crank angle and angular velocity fluctuation | variation corresponding to the example of FIG. 8, and the explosion process of each cylinder. FIG. 5 is a flowchart for diagnosing whether or not a compression pressure failure has occurred in each cylinder when a warning of misfire has been issued by the engine ECU. It is a figure which shows an example of the change of an engine speed in case a tappet clearance is normal. An example of a change in engine speed when the deviation of the tappet clearance is large is shown. An example of a change in the engine speed NE when the compression pressure is not generated (the compression pressure is zero) is shown. An example of the relationship between the piston movement of each cylinder during cranking rotation and the magnitude of the load generated on the crankshaft due to the piston movement occurs when the cylinder is operating normally and when the compression pressure is insufficient. It is a figure divided and shown when. It is a 1st flowchart of determination of the compression pressure shortage by the said diagnostic apparatus. It is a 2nd flowchart of determination of lack of compression pressure by the diagnostic device. It is a figure which shows an example of the time chart at the time of performing the flowchart of FIG.15 and FIG.16. In the cranking rotation state, the crank angle and crank angular speed when each cylinder is operating normally and when the first cylinder is misfired, and the processes (intake process, compression process, explosion process and It is a figure which shows the example of a relationship with an exhaust process. It is a figure which shows the relationship between the crank angle and angular velocity fluctuation | variation corresponding to the example of FIG. 18, and the explosion process of each cylinder. When the first cylinder is abnormal and the second to fourth cylinders are normal, when the tappet clearance of the first cylinder is normal, when the deviation of the tappet clearance is small, the deviation of the tappet clearance is large. It is a figure which shows an example of the individual average value in each case and when the compression pressure is zero. It is a figure which shows the ratio of the individual average value with respect to the whole average value based on the individual average value of each cylinder of FIG. It is the figure which expanded and displayed a part of FIG. It is a figure which shows an example of the relationship between the angular velocity fluctuation | variation about each cylinder, an individual average value, the ratio of an individual average value and a whole average value, and the determination result of a diagnostic apparatus. An example of an index used when the diagnostic device determines that the cause of misfire in the misfire-occurring cylinder is a mechanical failure and displays the fact and subsequent inspection work and repair work on the display unit. FIG. A failure code stored in the engine ECU, a ratio calculated by the diagnostic device, a determination result of the diagnostic device, and a first example of a relationship between an inspection item and a confirmation part of the engine displayed by the diagnostic device based on the determination result are shown. FIG. The second example of the relationship between the failure code stored in the engine ECU, the ratio calculated by the diagnostic device, the determination result of the diagnostic device, and the inspection items and confirmation parts of the engine displayed by the diagnostic device based on the determination result is shown. FIG. The third example of the relationship between the failure code stored in the engine ECU, the ratio calculated by the diagnostic device, the determination result of the diagnostic device, and the inspection items and confirmation parts of the engine displayed by the diagnostic device based on the determination result is shown. FIG. 4 shows a fourth example of the relationship between a failure code stored in the engine ECU, a ratio calculated by the diagnostic device, a determination result of the diagnostic device, and an inspection item and a confirmation part of the engine displayed by the diagnostic device based on the determination result FIG. FIG. 10 shows a fifth example of a relationship between a failure code stored in the engine ECU, a ratio calculated by the diagnostic device, a determination result of the diagnostic device, and an inspection item and a confirmation part of the engine displayed by the diagnostic device based on the determination result FIG. FIG. 10 shows a sixth example of a relationship between a failure code stored in the engine ECU, a ratio calculated by the diagnostic device, a determination result of the diagnostic device, and an inspection item and a confirmation part of the engine displayed by the diagnostic device based on the determination result FIG.

A. Embodiment 1 FIG. Configuration (1) Overall Configuration FIG. 1 shows an engine diagnosis system 10 (hereinafter also referred to as “system 10”) having an engine failure diagnosis device 14 (hereinafter also referred to as “diagnosis device 14”) according to an embodiment of the present invention. It is a block diagram which shows schematic structure of these. The system 10 includes a vehicle 12 equipped with an engine 16 as a diagnosis target, and a diagnosis device 14 that diagnoses the engine 16.

(2) Vehicle 12
(A) Overall Configuration In addition to the engine 16, the vehicle 12 includes an engine electronic control device 18 (hereinafter referred to as “engine ECU 18” or “ECU 18”) that controls the operation of the engine 16, and an ignition switch 20 (hereinafter referred to as “IGSW 20”). .)

(B) Engine 16
As shown in FIG. 1, the engine 16 is a so-called in-line four-cylinder engine, and includes first to fourth cylinders 22 a to 22 d (hereinafter collectively referred to as “cylinder 22”), a crankshaft 24, and a crank angle sensor 26. A starter motor 28, a battery 30, a voltage sensor 32, and a temperature sensor 34.

  FIG. 2 shows a schematic configuration inside one cylinder 22. Each cylinder 22 has an intake valve 40, an exhaust valve 42, a fuel injection valve 44, a spark plug 46, and a piston 48. The intake valve 40, the exhaust valve 42, and the spark plug 46 are disposed facing the combustion chamber 50 of each cylinder 22.

  FIG. 3 shows the appearance of the crank angle sensor 26. FIG. 4 shows an example of the output signal Sa1 of the crank angle sensor 26. The crank angle sensor 26 detects the rotation angle (hereinafter referred to as “crank angle Ac”) [°] of the pulse rotor 52 provided on the crankshaft 24 and outputs it to the engine ECU 18. That is, as shown in FIG. 4, the output signal Sa1 of the crank angle sensor 26 outputs a pulse signal every time the pulse rotor 52 rotates by a predetermined angle (here, 6 °). The ECU 18 that has received the output signal Sa1 from the crank angle sensor 26 shapes the waveform of the output signal Sa1 into a signal Sa2. Then, the engine speed NE and the angular speed of the crankshaft 24 (hereinafter referred to as “crank angular speed ω” or “angular speed ω”) are detected by measuring the rising period P1 of the signal Sa2.

  The starter motor 28 drives the crankshaft 24 based on the electric power supplied from the battery 30. The voltage sensor 32 detects the output voltage Vb [V] of the battery 30 and outputs it to the ECU 18.

  The temperature sensor 34 detects the temperature Tw [° C.] of engine cooling water (not shown) and outputs it to the ECU 18. As will be described later, the temperature detected by the temperature sensor 34 may be an engine oil temperature To [° C.] (not shown).

(C) Engine ECU 18
The engine ECU 18 controls the operation of the engine 16 and includes an input / output unit 60, a calculation unit 62, and a storage unit 64 as shown in FIG.

(3) Diagnostic device 14
The diagnosis device 14 diagnoses a failure of the engine 16 and, as shown in FIG. 1, is connected to the engine ECU 18 via a data link connector 70 provided in the vehicle 12 for input / output of in-vehicle data. Cable 72, an input / output unit 74 to which the cable 72 is connected, an operation unit 76 such as a keyboard or a touchpad (not shown), a calculation unit 78 for controlling each unit and determining abnormality of each cylinder 22, and a calculation It has the memory | storage part 80 which memorize | stores various programs and data, such as a control program used in the part 78, and an abnormality diagnosis program, and the display part 82 which performs various displays.

  As a hardware configuration of the diagnostic device 14, for example, a commercially available notebook personal computer can be used.

  When an abnormality diagnosis of each cylinder 22 is performed using the diagnostic device 14, the cable 72 is connected to a data link connector 70 provided on an instrument panel (not shown) of the vehicle 12 with one end of the cable 72 connected to the input / output unit 74. The other end of 72 is connected. Thereafter, the diagnosis device 14 performs an abnormality diagnosis of each cylinder 22 in accordance with an operation from the operator (user) to the operation unit 76. At that time, the diagnostic device 14 operates the engine 16 via the engine ECU 18. Details of the abnormality diagnosis of each cylinder 22 performed by the diagnosis device 14 will be described later.

2. Abnormality diagnosis of cylinder 22 (1) Outline of abnormality diagnosis In this embodiment, when the vehicle 12 is running normally (during normal operation of the engine 16), the engine ECU 18 determines whether or not misfiring has occurred in the cylinders 22a to 22d. . Further, when the engine ECU 18 detects the occurrence of misfire, the cylinder 22a to 22d that has misfired is stored as a failure code and displayed on a warning light (not shown) on the instrument panel. When it is determined that misfire has occurred, the operator connects the diagnostic device 14 to the ECU 18 and performs a diagnostic operation, whereby the diagnostic device 14 determines whether there is a lack of compression pressure in the cylinders 22a to 22d. The worker performs the subsequent repair and inspection work based on the determination result by the diagnostic device 14.

(2) Misfire determination (a) Outline of misfire determination FIG. 5 is a flowchart in which the engine ECU 18 determines whether or not misfire has occurred in the cylinders 22a to 22d when the vehicle 12 is running normally (during normal operation of the engine 16). It is.

  In step S1, the ECU 18 determines whether or not misfire has occurred in each of the cylinders 22a to 22d. If no misfire has occurred in any of the cylinders 22a to 22d (S2: NO), the process returns to step S1. When a misfire has occurred in any of the cylinders 22a to 22d (S2: YES), in step S3, the ECU 18 stores a fact that a misfire has occurred and a failure code (DTC) indicating the cylinder 22a to 22d in which the misfire has occurred. Store in the unit 64. In step S4, the ECU 18 issues a warning such as turning on a warning lamp (not shown) to notify the user that an abnormality has occurred in the engine 16. The user who has received the warning brings the vehicle 12 to a repair shop or the like, for example.

(B) Principle of Misfire Determination FIG. 6 shows the relationship between the operation of the piston 48 of each cylinder 22a to 22d during normal operation of the engine 16 and the magnitude of the load L1 generated on the crankshaft 24 as the piston 48 operates. This example is shown in a model for the case of normal operation and the case of misfire. Here, the load L1 means a decrease in the engine speed NE [rpm], that is, a decrease in the angular velocity ω of the crankshaft 24.

  In the example of FIG. 6, in the intake process, the compression process, and the exhaust process, there is almost no difference in the load L1 between when the cylinder 22 is operating normally and when a misfire has occurred. On the other hand, in the explosion process, when the cylinder 22 is operating normally, the driving torque is generated by the explosion and the engine speed NE increases, so the load L1 is reduced.

  Therefore, it is possible to determine the occurrence of misfire based on the fact that the angular velocity ω in the explosion process is lower than that during normal operation (decrease in the fluctuation value).

(C) Details of Misfire Determination FIG. 7 is a flowchart of misfire occurrence determination by the ECU 18. In step S <b> 11, the ECU 18 acquires the crank angle Ac from the crank angle sensor 26. In step S12, the ECU 18 calculates the crank angular speed ω based on the acquired crank angle Ac.

  FIG. 8 shows the crank angle Ac and the crank angular speed ω when the cylinders 22a to 22d are operating normally and when the first cylinder 22a is misfiring, and the steps in the cylinders 22a to 22d ( An example of a relationship with an intake process, a compression process, an explosion process, and an exhaust process) is shown. In FIG. 8, a solid line 90 indicates the relationship between the crank angle Ac and the crank angular speed ω when each of the cylinders 22a to 22d is operating normally. A broken line 92 indicates the relationship between the crank angle Ac and the crank angular speed ω when misfire occurs in the first cylinder 22a.

  In the example of FIG. 8, the angular velocity ω rapidly decreases in the explosion process of the first cylinder 22a. For this reason, it can be determined that misfire has occurred in the first cylinder 22a.

  Returning to FIG. 7, in step S <b> 13, the ECU 18 removes a fluctuation component of the engine speed NE due to acceleration / deceleration of the vehicle 12 using a high-pass filter (not shown).

  In step S14, the ECU 18 performs a process of separating the process of each cylinder 22 (process separation process). Specifically, the crank angle Ac is divided according to the explosion process of each of the cylinders 22a to 22d. In this embodiment, since the engine 16 has four cylinders, a series of steps (intake → compression → explosion → exhaust) of each cylinder 22a to 22d corresponds to two rotations (720 °) of the crankshaft 24. Therefore, the explosion process of each of the cylinders 22a to 22d is made to correspond to each crank angle Ac of 180 ° (= 720 ° / 4).

  In step S15, the ECU 18 calculates the angular velocity fluctuation Δω in the explosion process of each cylinder 22. For example, the difference between the angular velocity ω at the start of the explosion process of each cylinder 22 and the angular velocity ω at the end can be set as the angular velocity fluctuation Δω. Alternatively, the difference between the maximum value and the minimum value of the angular velocity ω in the explosion process of each cylinder 22a to 22d may be used as the angular velocity fluctuation Δω.

  FIG. 9 shows the relationship between the crank angle Ac and the angular velocity fluctuation Δω corresponding to the example of FIG. 8 and the explosion process of each of the cylinders 22a to 22d. In FIG. 9, a solid line 100 indicates the relationship between the crank angle Ac and the angular velocity fluctuation Δω when each of the cylinders 22a to 22d is operating normally. A broken line 102 indicates the relationship between the crank angle Ac and the angular velocity fluctuation Δω when misfiring has occurred in the first cylinder 22a, and the angular velocity fluctuation Δω has a negative value at the cylinder position in the explosion stroke where the misfire has occurred. ing.

  Returning to FIG. 7, in step S <b> 16, the ECU 18 determines whether or not misfire has occurred in each of the cylinders 22 a to 22 d based on the angular velocity fluctuation Δω in the explosion process of each of the cylinders 22 a to 22 d. Specifically, as described above, when the angular velocity fluctuation Δω decreases and becomes a negative value, it is determined that misfire has occurred, and the cylinder in the explosion stroke corresponding to the position where the value becomes negative is determined as the misfire-occurring cylinder.

(D) Failure Code As described above, the failure code in this embodiment indicates that a misfire has occurred and the cylinders 22a to 22d in which the misfire has occurred. For example, when a misfire occurs in the first cylinder 22a, “P0301” is stored as the failure code. When a misfire occurs in the second cylinder 22b, “P0302” is stored as a failure code. When a misfire occurs in the third cylinder 22c, “P0303” is stored as a failure code. When a misfire occurs in the fourth cylinder 22d, “P0304” is stored as a failure code.

(3) Determination of insufficient compression pressure (a) Overview of determination of insufficient compression pressure FIG. 10 shows whether or not a defective compression pressure has occurred in the cylinders 22a to 22d when the engine ECU 18 warns of the occurrence of misfire. It is a flowchart which diagnoses.

  In step S <b> 21, the worker connects the diagnostic device 14 to the ECU 18 via the cable 72 and the data link connector 70. In step S <b> 22, the operator operates the operation unit 76 of the diagnostic device 14 and reads a failure code (DTC) from the ECU 18 to the diagnostic device 14.

  In step S23, the operator determines whether or not the read failure code indicates the occurrence of misfire. If the failure code does not indicate the occurrence of misfire (S23: NO), the worker executes a diagnosis work corresponding to the failure code in step S24.

  If the failure code indicates the occurrence of misfire (S23: YES), in step S25, the diagnostic device 14 determines whether or not the compression pressure is insufficient for the cylinder 22 (misfire occurrence cylinder) whose failure code indicates the occurrence of misfire. judge. In this determination, cranking rotation that rotates the crankshaft 24 while stopping the fuel supply and ignition in each of the cylinders 22a to 22d and preventing the explosion from occurring is used (details will be described later).

  If a shortage of compression pressure has occurred in the misfired cylinder (S26: YES), in step S27, the diagnostic device 14 determines that the cause of the misfire in the misfired cylinder is a mechanical failure. Then, a message to that effect and subsequent inspection work and repair work are displayed on the display unit 82. The worker performs inspection work and repair work according to the display.

  If there is no shortage of compression pressure in the misfired cylinder (S26: NO), in step S28, the diagnostic device 14 causes the misfire to occur in the misfired cylinder, not a mechanical failure. Then, it is determined that there is an electrical failure, and that fact and the subsequent inspection and repair work are displayed on the display unit 82. The worker performs inspection work and repair work according to the display.

(B) Determination Principle of Insufficient Compression Pressure As described above, in determining whether or not the compression pressure is insufficient in the present embodiment, cranking rotation that rotates the crankshaft 24 while stopping the explosion in each of the cylinders 22a to 22d is used. . As described above, when the crankshaft 24 is rotated while the explosion in each of the cylinders 22a to 22d is stopped, if a decrease in the compression pressure occurs in any of the cylinders 22a to 22d due to a deviation of the tappet clearance or the like, The engine speed NE or the crank angular speed ω varies greatly.

  FIG. 11 shows an example of a change in the engine speed NE when the tappet clearance TC is normal. FIG. 12 shows an example of a change in the engine speed NE when the deviation of the tappet clearance TC is large (for example, TC = 0.2 mm). FIG. 13 shows an example of a change in the engine speed NE when the compression pressure is not generated (the compression pressure is zero). In general, the tappet clearance refers to a gap between the intake valve or the shaft of the intake valve and the camshaft or the rocker arm. The tappet clearance affects the opening timing of the valve, which is the valve opening / closing point, and the operation timing of the valve.

  In FIG. 14, an example of the relationship between the operation of the piston 48 of each cylinder 22a to 22d during cranking rotation and the magnitude of the load L1 generated in the crankshaft 24 in accordance with the operation of the piston 48 operates normally. The model is shown separately when the compression pressure is insufficient and when the compression pressure is insufficient. The load L1 here indicates a decrease in the engine speed NE [rpm], that is, a decrease in the crank angular speed ω. Further, since the explosion in each of the cylinders 22a to 22d is stopped during the cranking rotation, the explosion process in FIG. 14 is not actually accompanied by an explosion. In other words, it should be noted that the explosion process here refers to a process of making the range of the crank angle Ac equal to the explosion process during normal operation.

  In the example of FIG. 14, the case where the operation is normal and the case where the compression abnormality occurs are compared, and the difference in the load L1 is compared with the intake process, the explosion process, and the exhaust process. The compression process is particularly large. This is because the compression load becomes small when gas leakage occurs in any part of the cylinder 22.

  In the engine 16 composed of a plurality of cylinders 22a to 22d, the angular speed fluctuation Δω is set to have regularity by shifting the phase of the process of each cylinder 22a to 22d. In normal operation, a stable cranking rotation is obtained. However, when a compression abnormality occurs in any of the cylinders 22a to 22d, the compression load is not applied as described above, and the angular velocity fluctuation Δω is disturbed.

  In the present invention, focusing on this point, the difference in load L1 in the compression process is not directly used, but the angular velocity fluctuation Δω in the explosion process is used as in the case of misfire determination (FIG. 9 and the like). In the cranking rotation including the cylinders 22a to 22d in which the compression pressure is insufficient, the crank angular speed ω increases in the compression process of the cylinder in which the compression pressure is insufficient, but the reaction causes the angular speed ω to increase in the next process (explosion process). This is based on the fact that the decrease occurs. Accordingly, it is possible to determine whether or not the compression pressure is insufficient based on a decrease (variation) in the angular velocity ω in the explosion process. Therefore, it is possible to use the logic for misfire determination as the logic for determination of a cylinder with insufficient compression pressure.

(C) Details of determination of insufficient compression pressure FIG. 15 is a first flowchart of determination of insufficient compression pressure by the diagnostic device 14, and FIG. 16 is a second flowchart of determination of insufficient compression pressure by the diagnostic device 14. FIG. 17 is an example of a time chart when the flowcharts of FIGS. 15 and 16 are executed.

  In FIG.15 S31, the diagnostic apparatus 14 displays the request | requirement of warm-up operation on the display part 82. FIG. The worker who sees the request turns on the IGSW 20 and starts the warm-up operation (time t1). The warm-up operation here refers to, for example, increasing the engine speed NE to a predetermined value for warm-up (for example, 3000 rpm).

  In step S32, the diagnostic device 14 determines whether or not the warm-up has been completed. Specifically, the diagnostic device 14 acquires the temperature Tw from the temperature sensor 34 via the ECU 18, and determines whether or not the temperature Tw is equal to or higher than a threshold value THw indicating the end of the warm-up operation. If the warm-up has not ended (S32: NO), step S32 is repeated.

  When the warm-up is finished (S32: YES), in step S33, the diagnostic device 14 displays a request for the end of the warm-up operation on the display unit 82. The request includes a request to turn on the IGSW 20 again after the IGSW 20 is turned off. The worker who sees the request turns off the IGSW 20 (time t2), and turns on the IGSW 20 again (time t3) to start measurement.

  When the IGSW 20 is turned on again (S34: YES), in step S35, the diagnostic device 14 acquires the voltage Vb of the battery 30 from the voltage sensor 32 via the ECU 18, and the voltage Vb is a threshold (battery voltage) related to the voltage Vb. It is determined whether or not the threshold value TH_Vb) is exceeded. The battery voltage threshold value TH_Vb is a threshold value for determining whether or not the cranking rotation by the starter motor 28 becomes unstable.

  If the voltage Vb is less than the battery voltage threshold TH_Vb (S35: NO), the determination of insufficient compression pressure is terminated at this point. When the voltage Vb is equal to or higher than the battery voltage threshold TH_Vb (S35: YES), in step S36 of FIG. 16, the diagnostic device 14 requests the ECU 18 for the angular velocity variation Δω in the explosion process for each of the cylinders 22a to 22d (time point). t4). The request includes prohibiting explosion in each of the cylinders 22a to 22d (stopping the fuel supply and keeping the ignition signal OFF).

  In step S37, the diagnostic device 14 requests a failure code from the ECU 18 (time t5). Upon receiving the request, the ECU 18 transmits a failure code to the diagnostic device 14. The diagnostic device 14 uses the received fault code in subsequent processing.

  In step S38, the diagnostic device 14 displays on the display unit 82 that the operator is requested to perform a cranking operation. The worker who sees the request performs a cranking operation by rotating a starter motor (not shown) (time t6).

  In step S39, the diagnosis device 14 determines whether or not the engine speed NE (cranking speed) acquired through the ECU 18 is equal to or greater than a threshold value TH_NE. The threshold value TH_NE is a threshold value for determining whether or not the engine speed NE can stably determine whether the compression pressure is insufficient, and is, for example, 50 rpm. If the engine speed NE is not equal to or higher than the threshold value TH_NE (S39: NO), step S39 is repeated. Although not shown, cranking is performed when the predetermined time (for example, 30 seconds) does not exceed the threshold value TH_NE. Cancel the request and exit the diagnosis. If the engine speed NE is equal to or greater than the threshold value TH_NE (S39: YES), in step S40, the diagnosis device 14 determines whether a predetermined time (for example, 1 second) has elapsed since the engine speed NE is equal to or greater than the threshold value TH_NE. Determine whether or not. If the predetermined time has not elapsed (S40: NO), the process returns to step S39.

  When the predetermined time has elapsed (S40: YES), in step S41, the diagnostic device 14 acquires the angular velocity fluctuation Δω from the ECU 18 (time points t7 to t8). That is, the ECU 18 detects the angular velocity variation Δω by the same processing as steps S11 to S15 in FIG. When the detection and transmission of the angular velocity fluctuation Δω by the ECU 18 is finished, the operator finishes the cranking according to the display on the display unit 82 of the diagnostic device 14 (finished after the end of the detection of the angular velocity fluctuation Δω by the ECU 18). You may).

  FIG. 18 shows the crank angle Ac and the crank angular speed ω when each cylinder 22a to 22d is operating normally and when the first cylinder 22 is misfiring in the cranking rotation state, and each cylinder 22a. An example of the relationship with the processes (intake process, compression process, explosion process, and exhaust process) in ˜22d is shown as a model. In FIG. 18, a solid line 110 indicates the relationship between the crank angle Ac and the crank angular speed ω when each of the cylinders 22a to 22d is operating normally. A broken line 112 shows the relationship between the crank angle Ac and the crank angular velocity ω when misfire occurs in the first cylinder 22a.

  In the example of FIG. 18, the rotation in the explosion stroke after the compression process of the first cylinder 22a is disturbed, and the angular velocity ω is rapidly reduced.

  FIG. 19 shows the relationship between the crank angle Ac and the angular velocity fluctuation Δω corresponding to the example of FIG. 18 and the explosion process of each cylinder 22. In FIG. 19, a solid line 120 indicates the relationship between the crank angle Ac and the angular velocity fluctuation Δω when each cylinder 22 is operating normally. A broken line 122 indicates the relationship between the crank angle Ac and the angular velocity fluctuation Δω when misfire occurs in the first cylinder 22. In the example of FIG. 18, in order to easily understand the state where the compression pressure failure has occurred, a case where compression loss (a state where the compression pressure is zero) occurs in the compression process of the first cylinder 22a is shown. In the example of FIG. 19, the angular velocity fluctuation Δω decreases in the explosion process of the first cylinder 22a. This is because the compression load is not applied in the compression process of the first cylinder 22a, and the angular speed fluctuation Δω increases correspondingly, and the reaction causes the angular speed fluctuation Δω to decrease in the explosion process of the first cylinder 22a. In this way, it is possible to determine that a shortage of compression pressure has occurred in the first cylinder 22a by comparing each explosion process.

  Returning to FIG. 16, in step S42, the diagnostic device 14 calculates the individual average value AVEr, the overall average value AVEt, and the ratio R1 based on the acquired angular velocity fluctuation Δω (time points t8 to t9). The individual average value AVEr is an average value of the angular velocity fluctuation Δω in the explosion process for each cylinder 22. The overall average value AVEt is an average value of the individual average values AVEr of all the cylinders 22. The ratio R1 is individual average value AVEr / overall average value AVEt.

  In step S43, the diagnostic device 14 determines the presence or absence of a mechanical failure for each cylinder 22 based on the failure code DTC acquired in step S37 and the ratio R1 calculated in step S42, and displays the determination result on the display unit 82. (Time t10 to t11).

  That is, the diagnosis device 14 determines whether or not there is a shortage of compression pressure in the misfire-occurring cylinder based on the ratio R1 for each cylinder 22a to 22d. Specifically, when the ratio R1 is lower than a threshold value (compression pressure deficiency determination threshold value TH2) for determining whether or not there is a compression pressure deficiency, the ECU 18 determines that a compression pressure deficiency has occurred in the misfire occurrence cylinder. To do. In the present embodiment, the threshold value TH2 is 100%.

  In FIG. 20, when the first cylinder 22a among the cylinders 22a to 22d is abnormal and the second to fourth cylinders 22b to 22d are normal, the tappet clearance TC of the first cylinder 22a is normal (for example, , TC = 0.23 mm), when the deviation of the tappet clearance TC is small (for example, TC = 0.13 mm), when the deviation of the tappet clearance TC is large (for example, TC = 0.05 mm), and compression An example of the individual average value AVEr in each case where the pressure is zero is shown.

  That is, the solid line 130 indicates the individual average value AVEr when the tappet clearance TC is normal (for example, TC = 0.23 mm). A broken line 132 indicates the individual average value AVEr when the deviation of the tappet clearance TC is small (for example, TC = 0.13 mm). An alternate long and short dash line 134 indicates the individual average value AVEr when the deviation of the tappet clearance TC is large (for example, TC = 0.05 mm). A two-dot chain line 136 indicates the individual average value AVEr when the compression pressure is zero.

  FIG. 21 is a diagram showing a ratio R1 (= AVEr / AVEt) of the individual average value AVEr to the overall average value AVEt based on the individual average value AVEr of each cylinder 22a to 22d in FIG. FIG. 22 is an enlarged view of a part of FIG. The solid line 140 in FIGS. 21 and 22 corresponds to the first cylinder 22a, the broken line 142 corresponds to the second cylinder 22b, the alternate long and short dash line 144 corresponds to the third cylinder 22c, and the alternate long and two short dashes line 146 to the fourth cylinder 22d. Correspond.

  FIG. 23 is a diagram illustrating an example of the relationship among the angular velocity fluctuation Δω, the individual average value AVEr, the ratio R1 (= AVEr / AVEt), and the determination result of the diagnostic device 14 for each cylinder 22. In the example of FIG. 23, the individual average value AVEr of the first cylinder 22a is 44.4 [rad / s], the individual average value AVEr of the second cylinder 22b is 54.0, and the individual average of the third cylinder 22c. The value AVEr is 53.9, and the individual average value AVEr of the fourth cylinder 22d is 55.8. Therefore, the overall average value AVEt is 52.03 [rad / s].

  The ratio R1 of the first cylinder 22a is 85% (= 44.4 / 52.03), the ratio R1 of the second cylinder 22b is 104% (= 54.0 / 52.03), and the third The ratio R1 of the cylinder 22c is 104% (= 53.9 / 52.03), and the ratio R1 of the fourth cylinder 22d is 107% (= 55.8 / 52.03).

  Accordingly, it is the first cylinder 22a that has the ratio R1 lower than the threshold value TH2 (100% in the present embodiment), and the first cylinder 22a is determined to be a cylinder with insufficient compression pressure. Here, if the failure code stored in the ECU 18 indicates the occurrence of misfire in the first cylinder 22a, the first cylinder 22a is determined to be “impossible” requiring a mechanical failure check. On the other hand, since the ratio R1 of the second to fourth cylinders 22b to 22d is not less than the threshold value TH2, it is determined that the mechanical failure check is not necessary regardless of the content of the failure code.

(D) Determination result of the diagnostic device 14 FIG. 24 shows that the diagnostic device 14 determines that the cause of the misfire in the misfire-occurring cylinder is a mechanical failure, to that effect, and the subsequent inspection and repair work. Is shown on the display unit 82, and is displayed in three stages at the above-described ratio R1. That is, “small deviation of tappet clearance”, “large deviation of tappet clearance”, and “compression failure”. The “compression failure” mentioned here includes scratches in the cylinders 22a to 22d, defective piston rings (not shown), and the like.

  When the ratio R1 is slightly smaller than 100%, the diagnostic device 14 displays the inspection work and the repair work when the deviation of the tappet clearance TC is small on the display unit 82. When the ratio R1 is considerably smaller than 100%, the diagnosis device 14 displays the inspection work and the repair work when the deviation of the tappet clearance TC is large on the display unit 82. When the ratio R1 is extremely smaller than 100%, the diagnostic device 14 displays the inspection work and the repair work when the compression failure occurs on the display unit 82.

  25 to 30, the failure code stored in the ECU 18, the rate R <b> 1 calculated by the diagnostic device 14, the determination result of the diagnostic device 14, and the inspection of the engine 16 displayed by the diagnostic device 14 based on the determination result are shown. First to sixth examples of relationships between items and confirmation sites are shown.

  In FIG. 25, the failure code indicates that the first cylinder 22a is a misfire-occurring cylinder, and the first cylinder 22a has a compression pressure deficient cylinder because the ratio R1 is below the threshold value TH2 (= 100%). It is determined that Since the first cylinder 22a is a misfire-occurring cylinder and a compression pressure deficient cylinder, the diagnosis result by the diagnosis device 14 becomes “impossible” that requires a mechanical failure check. Then, the diagnosis device 14 displays “tappet clearance failure” and “compression failure” as inspection items or confirmation parts for the first cylinder 22a according to the ratio R1 of the first cylinder 22a. On the other hand, since the second to fourth cylinders 22b to 22d are neither misfire-occurring cylinders nor compression pressure-deficient cylinders, it is determined as “OK” that does not require a mechanical failure check.

  In FIG. 26, the failure code indicates that the first cylinder 22a and the third cylinder 22c are misfiring cylinders, and the ratio R1 of the first cylinder 22a is below the threshold value TH2 (= 100%). From this, it is determined that the cylinder is under compression pressure. Since the first cylinder 22a is a misfire-occurring cylinder and a cylinder with insufficient compression pressure, the diagnosis result by the diagnosis device 14 is “impossible”. Then, the diagnosis device 14 displays “tappet clearance failure” and “compression failure” as inspection items or confirmation parts for the first cylinder 22a according to the ratio R1 of the first cylinder 22a. On the other hand, the second cylinder 22b and the fourth cylinder 22d are neither misfire-occurring cylinders nor compression pressure-deficient cylinders, and the third cylinder 22c is a misfire-occurring cylinder but not a compression pressure-deficient cylinder. The cylinders 22b to 22d are determined as “possible”.

  In FIG. 27, although the ratio R1 of the first cylinder 22a is lower than the threshold value TH2 (= 100%), the failure code does not indicate the misfire occurrence cylinder for any of the cylinders 22a to 22d. For this reason, the diagnostic device 14 determines “OK” for any of the cylinders 22a to 22d.

  In FIG. 28, the failure code indicates that the first to third cylinders 22a to 22c are misfiring cylinders, and the ratio R1 of the first to third cylinders 22a to 22c has a threshold value TH2 (= 100%). Therefore, the cylinder is determined to be a cylinder with insufficient compression pressure. Since the first to third cylinders 22a to 22c are misfire-occurring cylinders and insufficient compression pressure cylinders, the diagnosis result by the diagnosis device 14 is “impossible”. Then, the diagnosis device 14 sets “incompressible compression” as an inspection item or confirmation part for the first cylinder 22a and “large tappet clearance deviation” as an inspection item or confirmation part for the second cylinder 22b according to the ratio R1. In addition, “small tappet clearance deviation” is displayed as an inspection item or a confirmation part for the third cylinder 22c. On the other hand, the fourth cylinder 22d is determined as “possible” because it is neither a misfired cylinder nor a cylinder with insufficient compression pressure.

  In FIG. 29, the failure code indicates that the first cylinder 22a and the third cylinder 22c are misfiring cylinders, and the ratio R1 of the first cylinder 22a and the third cylinder 22c is the threshold value TH2 (= 100%). Therefore, the cylinder is determined to be a cylinder with insufficient compression pressure. Since the first cylinder 22a and the third cylinder 22c are misfiring cylinders and cylinders with insufficient compression pressure, the diagnosis result by the diagnosis device 14 is “impossible”. Then, in accordance with the ratio R1, the diagnostic device 14 displays “defective compression” as an inspection item or confirmation part for the first cylinder 22a and “bad tappet clearance” as an inspection item or confirmation part for the third cylinder 22c. To do. On the other hand, since the second cylinder 22b and the fourth cylinder 22d are neither misfiring cylinders nor cylinders with insufficient compression pressure, they are determined to be “permitted”.

  In FIG. 30, the failure code indicates that the fourth cylinder 22d is a misfire-occurring cylinder, and the ratio R1 of the first to third cylinders 22a to 22c is below the threshold value TH2 (= 100%). From this, it is determined that the cylinder is under compression pressure. The first to third cylinders 22a to 22c are cylinders that are undercompressed pressure but are not misfired cylinders, and the fourth cylinder 22d is a cylinder that is misfired but is not undercompressed pressure. For this reason, the diagnostic device 14 determines that all of the first to fourth cylinders 22a to 22d are “possible”.

  As can be seen from the examples of FIGS. 25 to 30 as described above, in this embodiment, the misfire occurrence cylinder indicated by the failure code matches the cylinder with insufficient compression pressure whose ratio R1 is lower than the threshold value TH2 (= 100%). Only when this is done, it is determined that a mechanical failure has occurred, and an inspection item or confirmation site corresponding to the ratio R1 is indicated.

3. As described above, according to the present embodiment, by detecting the angular velocity fluctuation Δω in the cranking rotation state in which the crankshaft 24 is rotated while stopping the explosion in each of the cylinders 22a to 22d, It is possible to determine the occurrence of a compression pressure abnormality in the cylinders 22a to 22d. Accordingly, it is possible to accurately determine whether or not the compression pressure is insufficient (mechanical failure), which is one of the causes of misfire, without disassembling the cylinders 22a to 22d. Can be improved.

  In both the normal operation of the engine 16 and the cranking rotation, the angular velocity fluctuation Δω corresponding to the explosion process is detected for each of the cylinders 22a to 22d, and the cylinder with insufficient compression pressure is determined based on the angular velocity fluctuation Δω. For this reason, it is possible to use the logic for determining the misfire that the ECU 18 has as the logic for determining the cylinders with insufficient compression pressure. Therefore, it is possible to simplify the configuration (including software such as determination logic) for determining a cylinder with insufficient compression pressure.

  Furthermore, it can be used not only for the case where a misfire-occurring cylinder occurs but also for checking the operation after the assembly of the engine 16 during inspection and maintenance.

  In the cranking rotation state, the individual average value AVEr and the overall average value AVEt are compared, and it is determined that the cylinders 22a to 22d having the individual average value AVEr smaller than the overall average value AVEt are cylinders with insufficient compression pressure.

  Thereby, a compression pressure deficient cylinder can be determined by relative comparison of each cylinder 22a-22d. For this reason, even if a change in the voltage Vb of the battery 30 for the starter motor 28 for driving the crankshaft 24, a change in the ambient temperature, or the like has some influence on the angular velocity fluctuation Δω, it is hardly affected by the determination of the cylinder with insufficient compression pressure. can do.

  The detection of the angular velocity fluctuation Δω in the cranking rotation state is started after a predetermined time has elapsed from the start of the starter motor 28 that drives the crankshaft 24 (after a predetermined time has elapsed since the engine speed NE exceeded the threshold value TH_NE). As a result, it is possible to detect the fluctuation value in a state where the cranking rotation is stable, and therefore it is possible to accurately determine the cylinders with insufficient compression pressure.

  The voltage Vb of the battery 30 that drives the starter motor 28 that drives the crankshaft 24 is monitored, and when the voltage Vb falls below the threshold value TH_Vb, the determination of a cylinder with insufficient compression pressure is stopped. Accordingly, it is possible to avoid erroneous determination of a cylinder with insufficient compression pressure by avoiding determination in a state where cranking rotation becomes unstable due to a decrease in the voltage Vb of the battery 30.

  When the engine coolant temperature Tw is lower than the threshold value THw, the determination of the cylinder with insufficient compression pressure is stopped. As a result, if the threshold THw is set to a value that cannot be taken in a normal operating environment, for example, it is possible to avoid erroneous determination of a cylinder with insufficient compression pressure by avoiding determination in a specific operating environment. It becomes.

B. Modifications It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification. For example, the following configuration can be adopted.

  In the above embodiment, the diagnosis device 14 is used for diagnosis of the engine 16 of the vehicle 12, but is not limited thereto, and can be used for other devices having an engine (for example, a moving body such as a ship). In the above embodiment, the diagnostic device 14 communicates with the engine ECU 18 from the outside of the vehicle 12, but may be mounted inside the vehicle 12. In other words, the engine ECU 18 can have the function of the diagnostic device 14.

  In the above embodiment, the engine 16 is an in-line four-cylinder engine, but the arrangement and number of the cylinders 22a to 22d are not limited to this. For example, the engine 16 may be a V type 6 cylinder engine. In this case, a series of steps of 6 cylinders (intake → compression → explosion → exhaust) corresponds to two rotations (720 °) of the crankshaft 24. Therefore, the explosion process of each cylinder is made to correspond to every crank angle Ac of 120 ° (= 720 ° / 6).

  In the above embodiment, the misfire determination and the determination of insufficient compression pressure are used in combination. However, the present invention is not limited to this, and only the determination of misfire or determination of insufficient compression pressure may be used.

  In the above-described embodiment, both the fuel supply system (fuel injection valve 44 and the like) and the ignition system (ignition plug 46 and the like) are stopped during the cranking operation, but it is sufficient that no explosion occurs in the cylinders 22a to 22d. For example, only the fuel supply system may be stopped.

  In the above-described embodiment, it is determined whether or not the determination of the cylinder with insufficient compression pressure is stopped using the engine cooling water temperature Tw. However, the present invention is not limited to this. For example, an engine oil temperature To (not shown) may be used instead or in addition to the temperature Tw.

DESCRIPTION OF SYMBOLS 12 ... Vehicle 14 ... Engine failure diagnostic apparatus 16 ... Engine 18 ... Engine ECU (misfire monitoring part)
22, 22a to 22d ... cylinder 24 ... crankshaft 28 ... starter motor 30 ... battery

Claims (10)

While operating an engine having a plurality of cylinders, misfire monitoring is performed to detect the variation value of the angular velocity of the crankshaft corresponding to the explosion process for each cylinder and to determine the misfire occurrence cylinder in which misfire has occurred based on the variation value. An engine failure diagnosis method monitored by a part,
A cranking rotation state in which the crankshaft is rotated while stopping the explosion in each cylinder is generated, and in the cranking rotation state, a variation value of the angular velocity of the crankshaft corresponding to the explosion process is detected for each cylinder, and the variation A method for diagnosing an engine failure, characterized in that a cylinder having a value equal to or less than a predetermined value is determined to be a compression pressure deficient cylinder having insufficient compression pressure. The engine failure diagnosis method according to claim 1,
In the cranking rotation state, an individual average value that is an average value of fluctuation values of each cylinder is compared with an overall average value that is an average value of fluctuation values of all cylinders.
A method for diagnosing an engine failure, wherein a cylinder having the individual average value smaller than the overall average value is determined to be the compression pressure deficient cylinder. The engine failure diagnosis method according to claim 1 or 2,
The engine failure diagnosis method, wherein the detection of the fluctuation value of the angular velocity of the crankshaft in the cranking rotation state is started after a predetermined time has elapsed from the start of the motor that drives the crankshaft. The engine failure diagnosis method according to claim 1 or 2,
Monitoring the voltage of the battery that drives the motor that drives the crankshaft;
An engine failure diagnosis method, wherein when the voltage of the battery drops below a predetermined voltage, the determination of the cylinder with insufficient compression pressure is stopped. The engine failure diagnosis method according to any one of claims 1 to 4,
A method for diagnosing an engine failure, characterized in that when the temperature of engine cooling water or the temperature of engine oil is lower than a predetermined value, the determination of the cylinder with insufficient compression pressure is stopped. While operating an engine having a plurality of cylinders, misfire monitoring is performed to detect the variation value of the angular velocity of the crankshaft corresponding to the explosion process for each cylinder and to determine the misfire occurrence cylinder in which misfire has occurred based on the variation value. An engine failure diagnosis device monitored by a part,
A cranking rotation state in which the crankshaft is rotated while stopping the explosion in each cylinder is generated, and in the cranking rotation state, a variation value of the angular velocity of the crankshaft corresponding to the explosion process is acquired for each cylinder, and the variation A failure diagnosis device for an engine, wherein a cylinder having a value equal to or less than a predetermined value is determined as a compression pressure deficient cylinder having insufficient compression pressure. The engine failure diagnosis device according to claim 6,
In the cranking rotation state, an individual average value that is an average value of fluctuation values of each cylinder is compared with an overall average value that is an average value of fluctuation values of all cylinders.
An engine failure diagnosis apparatus characterized in that a cylinder having the individual average value smaller than the overall average value is determined to be the compression pressure deficient cylinder. The engine failure diagnosis device according to claim 6 or 7,
Acquisition of the fluctuation value of the angular speed of the crankshaft in the cranking rotation state is started after a predetermined time has elapsed from the start of the motor that drives the crankshaft. The engine failure diagnosis device according to claim 6 or 7,
Monitoring the voltage of the battery that drives the motor that drives the crankshaft;
The engine failure diagnosis device, wherein when the voltage of the battery drops below a predetermined voltage, the determination of the cylinder with insufficient compression pressure is stopped. In the engine failure diagnosis device according to any one of claims 6 to 8,
An engine failure diagnosis device, wherein when the temperature of engine coolant or the temperature of engine oil is lower than a predetermined value, the determination of the cylinder with insufficient compression pressure is stopped.

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