Engine starting abnormality diagnostic device

Abstract

To provide an engine starting abnormality diagnosis device capable of easily narrowing down generation factors of long cranking abnormality at the time of staring an engine.SOLUTION: An engine starting abnormality diagnosis device discriminates the generation factors of long cranking abnormality in which engine starting is not completed even if a cranking period is a predetermined time or more at the time of starting an engine 1 with a plurality of cylinders. The engine starting abnormality diagnosis device is equipped with a rotation speed detecting portion 11 that detects the rotation speed of a crank shaft 10 when at least a part of the cylinders is in a compression stroke latter stage, and an abnormality diagnosing portion 100 that determines that the generation factors of the long cranking abnormality are electrical abnormality when the rotation speed detected by the rotation speed detecting portion is less than a predetermined threshold value, and determines that the generation factors of the long cranking abnormality are combustion abnormality when the rotation speed is more than the threshold value.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an engine start abnormality diagnosis device for determining the cause of long cranking abnormality at the start of an engine.

Background Art

[0002] For example, in Patent Document 1, in a diagnostic device for an internal combustion engine including a generator, a battery, and a starter, in order to diagnose the starting performance of the internal combustion engine at low cost and estimate the cause of deterioration of starting performance, sensor input means for processing the crank rotational speed and battery voltage, control means for controlling the starting state of the internal combustion engine, switch signal means for processing a key switch signal, performing an electrical system diagnosis based on the outputs of the sensor input means, the control means, and the switch signal means, and diagnosing the starting performance or starting property of the internal combustion engine based on the correlation between the output signal from the sensor input means and the output signal from the control means are described. In Patent Document 2, in order to enable appropriate countermeasures when rotational roughness abnormality occurs during the start of a diesel engine, an abnormal cause determination method having a determination step of determining whether the cause of the rotational roughness abnormality is combustion deterioration or an inappropriate combustion timing when the rotational roughness abnormality occurs is described. Specifically, based on the difference ΔNE2 between the current engine rotational speed NE n and the bottom value NE n ' immediately before combustion starts in the next combustion cylinder, discrimination between combustion deterioration such as misfire and combustion at an inappropriate combustion timing is described. In Patent Document 3, in a vehicle fault diagnosis control device having a function of outputting and storing different fault codes for each in-vehicle component in order to identify an engine installation or a poor engine start as a fault when a fault of a system or component cannot be specified, at the start, the starting rotational speed and the elapsed time after the starter is turned on are measured, the measured values are compared with preset values, and when the set conditions are satisfied, starting data is stored as a starting fault including an engine installation or a poor engine start.

Prior Art Documents

Patent Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2007-224832 [Patent Document 2] Japanese Patent Publication No. 2004-308586 [Patent Document 3] Japanese Patent Publication No. 2004-44407 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The causes of a long cranking anomaly, where the crankshaft is driven (cranked) by the starter motor for an abnormally long time compared to normal during engine startup, are numerous. When such a long cranking anomaly occurs, mechanics at service centers have to troubleshoot the problem by narrowing down the causes one by one, for example, by following a pre-prepared checklist, which can lead to a long time required to identify the cause and repair it. In view of the above-mentioned problems, the object of the present invention is to provide an engine starting abnormality diagnostic device that can easily narrow down the causes of long cranking abnormalities during engine starting. [Means for solving the problem]

[0005] To solve the above-mentioned problems, the engine starting abnormality diagnostic device of the present invention is an engine starting abnormality diagnostic device that determines the cause of a long cranking abnormality in which the engine does not start even if the cranking period is longer than a predetermined time when starting an engine having multiple cylinders, Crankshaft angle position A rotation speed detection unit that detects the rotation speed detection unit Based on the aforementioned angular position, the rotational speed of the crankshaft is calculated when at least some of the cylinders are in the later stages of the compression stroke. Abnormality Diagnosis Department and The abnormality diagnosis unit is equipped with,If the rotational speed is less than a predetermined threshold, it is determined that the cause of the long cranking abnormality is an electrical system abnormality, and if the rotational speed is greater than the threshold, it is determined that the cause of the long cranking abnormality is a combustion abnormality. thing, It is characterized by the following. If the long cranking abnormality is caused by a combustion abnormality, the starter motor will provide the crankshaft rotational speed necessary for normal starting, but the rotational speed will not increase normally from this point. On the other hand, if the long cranking abnormality is caused by an electrical system malfunction, such as a fault in the starter motor itself, the power supply unit that supplies power to the starter motor, or faulty wiring, the starter motor will not be able to obtain the crankshaft rotation speed necessary for normal starting. The difference in crankshaft rotation speed between combustion abnormalities and electrical system abnormalities becomes particularly noticeable in the later stages of the compression stroke in some cylinders, where the torque required for the starter motor to rotate the crankshaft is at its maximum. According to the present invention, by utilizing the above phenomenon and comparing the crankshaft rotational speed when at least some cylinders are in the later stages of the compression stroke with a threshold value, it becomes possible to easily and quickly narrow down whether the cause of the long cranking abnormality is a combustion abnormality or an electrical system abnormality. In this specification and in the claims, the late compression stroke refers to a range extracted from the range of angular positions (crank angles) of the crankshaft during the compression stroke, where the median of the extracted crank angles is later than 90 degrees before top dead center. Typically, the late compression stroke can be defined as the range from 90 degrees before top dead center to top dead center, but its start and end dates can be appropriately changed without departing from the above definition.

[0006] In the present invention, the engine can be configured as a 4-cylinder or 2-cylinder engine with equally spaced ignition. According to this method, it is easy to extract the crankshaft rotation speed in the region where the starter motor drive load during cranking becomes severe due to the action of the in-cylinder pressure of each cylinder and the valve spring reaction force of the valve train, and the effects described above can be appropriately obtained.

[0007] In the present invention, the threshold can be configured to be lower than the rotational speed of the crankshaft when at least some of the cylinders are in the later stages of the compression stroke during cranking when the starter motor is functioning normally. According to this, if the cranking by the starter motor is normal, the rotational speed of the crankshaft will exceed a threshold, allowing for accurate differentiation between electrical system abnormalities and combustion abnormalities. [Effects of the Invention]

[0008] As described above, the present invention provides an engine starting abnormality diagnostic device that can easily narrow down the causes of long cranking abnormalities during engine starting. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram schematically shows the configuration of an engine to which an embodiment of the engine starting abnormality diagnostic device to which the present invention is applied is provided. [Figure 2] This diagram shows the stroke progression of a four-stroke engine. [Figure 3] This diagram shows the state transitions during the compression stroke of a four-stroke engine. [Figure 4] This is a flowchart showing the operation of the engine starting abnormality diagnostic device of the embodiment during engine starting. [Figure 5] This figure shows an example of the engine speed change during a long cranking abnormality caused by a combustion abnormality. [Figure 6] This figure shows an example of the engine speed change during a long cranking abnormality caused by an electrical system malfunction.

Embodiment for Carrying Out the Invention

[0010] Hereinafter, an embodiment of an engine start abnormality diagnosis apparatus to which the present invention is applied will be described. The engine start abnormality diagnosis apparatus according to the embodiment is provided, for example, in a four-stroke internal combustion engine mounted as a driving power source in an automobile such as a passenger car. FIG. 1 is a diagram schematically showing the configuration of an engine in which the engine start abnormality diagnosis apparatus according to the embodiment is provided.

[0011] The engine 1 is, as an example, a horizontally opposed four-cylinder direct injection gasoline naturally aspirated engine. The engine 1 includes a crankshaft 10, a cylinder block 20 (20R, 20L), a cylinder head 30 (30R, 30L), an intake system 40, an exhaust system 50, an EGR device 60, an engine control unit (ECU) 100, and the like.

[0012] The crankshaft 10 is a rotating shaft that serves as the output shaft of the engine 1. A power transmission mechanism such as a transmission (not shown) is connected to one end of the crankshaft 10. The crankshaft 10 is formed with crank pins arranged eccentrically from the rotating shaft. A piston is connected to the crank pin via a connecting rod (not shown). At the end of the crankshaft 10, a crank angle sensor 11, which is a rotational speed detection unit for detecting the angular position of the crankshaft, is provided. The output of the crank angle sensor 11 is transmitted to the engine control unit 100. Based on the output of the crank angle sensor 11, the engine control unit 100 independently calculates the engine speed (crankshaft rotational speed) for each of a plurality of regions at the rotational angle position of the crankshaft 10.

[0013] The cylinder block 20 is configured as a two-part unit, consisting of a right cylinder block 20R and a left cylinder block 20L, so as to sandwich the crankshaft 10 from the left and right sides when it is mounted longitudinally on the vehicle body. A crankcase section is provided in the center of the cylinder block 20. The crankcase section is the space that houses the crankshaft 10. The crankcase is provided with a main bearing that rotatably supports the journal portion of the crankshaft 10. The right cylinder block 20R and the left cylinder block 20L, positioned on either side of the crankcase, each contain two cylinders (in the case of a four-cylinder engine) into which pistons are inserted and which reciprocate.

[0014] A knock sensor 21 is provided in the cylinder block 20. The knock sensor 21 has a piezoelectric element that generates an output voltage in response to vibrations of the cylinder block 20. The engine control unit 100 can detect the presence or absence of knocking based on the output waveform of the knock sensor 21, which is specific to when knocking occurs.

[0015] The cylinder heads 30 (right cylinder head 30R, left cylinder head 30L) are located at the ends (left and right ends) of the cylinder block 20 opposite to the crankshaft 10. The cylinder head 30 is composed of a combustion chamber 31, a spark plug 32, an intake port 33, an exhaust port 34, an intake valve 35, an exhaust valve 36, an intake camshaft 37, an exhaust camshaft 38, an injector 39, and the like. The combustion chamber 31 is formed by recessing the portion of the cylinder head 30 facing the piston crown surface, for example, in a pent-roof shape. The spark plug 32 generates a spark in response to an ignition signal from the engine control unit 100, igniting the fuel-air mixture. The spark plug 32 is located in the center of the combustion chamber 31.

[0016] The intake port 33 is a passage for introducing combustion air (fresh air) into the combustion chamber 31. The exhaust port 34 is a passage for discharging burnt gas (exhaust gas) from the combustion chamber 31. The intake valve 35 and exhaust valve 36 open and close the intake port 33 and exhaust port 34 at predetermined valve timings. For example, two intake valves 35 and two exhaust valves 36 are provided for each cylinder. The intake valve 35 and exhaust valve 36 are opened and closed by the intake camshaft 37 and exhaust camshaft 38, which rotate synchronously at half the rotational speed of the crankshaft 10. The intake camshaft 37 and exhaust camshaft 38 are equipped with a variable valve timing mechanism (not shown) on the cam sprocket portion that advances or retards the phase of each camshaft to change the opening and closing timing of each valve. The injector 39 injects fuel into the combustion chamber 31 to form a fuel-air mixture in response to an opening signal issued by the engine control unit 100. The injector 39 is configured such that the nozzle portion for injecting fuel is exposed into the cylinder from the area on the intake port 33 side of the inner surface of the combustion chamber 31.

[0017] The intake system 40 introduces air into the intake port 33. The intake system 40 is comprised of an intake duct 41, a chamber 42, an air cleaner 43, an airflow meter 44, a throttle valve 45, an intake manifold 46, an intake pressure sensor 47, and the like.

[0018] The intake duct 41 is a passage that introduces outside air and supplies it to the intake port 33. Chamber 42 is a space provided in communication with the vicinity of the inlet of the intake duct 41. The air cleaner 43 filters the air to remove dust and other particles. The air cleaner 43 is located downstream of the point in the intake duct 41 where it communicates with the chamber 42. The airflow meter 44 measures the airflow rate passing through the intake duct 41. The airflow meter 44 is located near the outlet of the air cleaner 43. The output of the airflow meter 44 is transmitted to the engine control unit 100.

[0019] The throttle valve 45 is a butterfly valve that controls the output of engine 1 by adjusting the airflow rate. The throttle valve 45 is located near the connection point between the intake duct 41 and the intake manifold 46. The throttle valve 45 is driven to open and close by an electric throttle actuator (not shown) according to a target throttle opening set by the engine control unit 100 in accordance with the driver's requested torque, etc. Furthermore, the throttle valve 45 is equipped with a throttle sensor that detects its opening degree, and its output is transmitted to the engine control unit 100. The intake manifold 46 is a branch pipe that distributes air to the intake port 33 of each cylinder. The intake manifold 46 is located downstream of the throttle valve 45. The intake pressure sensor 47 detects the air pressure (intake pressure) inside the intake manifold 46. The output of the intake pressure sensor 47 is transmitted to the engine control unit 100.

[0020] The exhaust system 50 discharges the exhaust gas emitted from the exhaust port 34 to the outside. The exhaust system 50 is comprised of an exhaust manifold 51, an exhaust pipe 52, a front catalytic converter 53, a rear catalytic converter 54, a silencer 55, an air-fuel ratio sensor 56, a rear O2 sensor 57, and the like.

[0021] The exhaust manifold 51 is a manifold that collects the exhaust gases coming out of the exhaust ports 34 of each cylinder. The exhaust pipe 52 is a conduit that discharges exhaust gas from the exhaust manifold 51 to the outside. The front catalytic converter 53 and rear catalytic converter 54 are located in the middle section of the exhaust pipe 52, and are used to filter HC and NO from the exhaust gas. X It is equipped with a three-way catalyst for purifying CO, etc. The front catalytic converter 53 is located adjacent to the outlet of the exhaust manifold 51, and the rear catalytic converter 54 is located on the outlet side of the front catalytic converter. The Silencer 55 reduces the acoustic energy of exhaust gases. The silencer 55 is located near the outlet of the exhaust pipe 52.

[0022] The air-fuel ratio sensor 56 is located between the outlet of the exhaust manifold 51 and the inlet of the front catalytic converter 53. The rear O2 sensor 57 is located between the outlet of the front catalytic converter 53 and the inlet of the rear catalytic converter 54. The air-fuel ratio sensor 56 and the rear O2 sensor 57 both detect the amount of oxygen in the exhaust gas by generating an output voltage corresponding to the oxygen concentration in the exhaust gas. The air-fuel ratio sensor 56 is a linear output sensor that can detect oxygen concentration over a wider range of air-fuel ratios compared to the rear O2 sensor 57. The outputs of both the air-fuel ratio sensor 56 and the rear O2 sensor 57 are transmitted to the engine control unit 100.

[0023] The EGR device 60 extracts a portion of the exhaust gas from the exhaust manifold 51 as EGR gas and introduces it into the intake manifold 46 to perform exhaust gas recirculation (EGR). The EGR device 60 includes an EGR flow path 61, an EGR cooler 62, an EGR valve 63, and the like.

[0024] The EGR passage 61 is a pipeline that introduces exhaust gas (EGR gas) from the exhaust manifold 51 to the intake manifold 46. The EGR cooler 62 cools the EGR gas flowing through the EGR passage 61 by heat exchange with the coolant of the engine 1. The EGR cooler 62 is located in the middle of the EGR flow path 61. The EGR valve 63 is a metering valve that adjusts the flow rate of EGR gas passing through the EGR passage 61. The EGR valve 63 is located downstream of the EGR cooler 62 in the EGR flow path 61. The EGR valve 63 has a valve body that is driven to open and close by an electric actuator such as a solenoid, and its opening degree is controlled by the engine control unit 100 using an opening degree map set based on a predetermined target EGR rate (EGR gas flow rate / intake air flow rate).

[0025] The engine control unit (ECU) 100 comprehensively controls the engine 1 and its auxiliary equipment. The engine control unit 100 is configured to include information processing means such as a CPU, storage means such as RAM and ROM, an input / output interface, and a bus connecting these. Furthermore, the engine control unit 100 is equipped with an accelerator pedal sensor (not shown) that detects the amount of accelerator pedal depression by the driver (not shown). The engine control unit 100 has a function to set the driver-requested torque based on the output of the accelerator pedal sensor, etc. The engine control unit 100 controls the throttle valve opening, boost pressure, fuel injection amount, fuel injection timing, ignition timing, valve timing, etc., so that the torque actually generated by the engine 1 approaches the set driver-requested torque.

[0026] Furthermore, the engine control unit 100 controls the starting of the engine 1 by switching the starter motor 120 on and off via the starter relay 110. The starter motor 120 is an electric motor that rotates the crankshaft 10 when starting the engine 1. The starter relay 110 is a relay that switches the power supply state from a power source such as a battery (not shown) to the starter motor 120. The starter relay 110 switches the power supply to the starter motor on and off in response to a command from the engine control unit 100. When the engine 1 is requested to be started, the engine control unit 100 rotates the crankshaft 10 using the starter motor 120 and also initiates ignition and fuel injection. Subsequently, if the rotational speed of the crankshaft 10 detected by the crank angle sensor 11 exceeds a predetermined starting completion determination value (completion determination value), the engine 1 is considered to have started and the starter motor is stopped.

[0027] Furthermore, the engine control unit 100 also functions as an abnormality diagnosis unit that determines whether the cause of a long cranking abnormality, in which the engine 1 fails to start despite the starter motor 120 being driven for a predetermined time or longer, is a combustion abnormality or an electrical system abnormality. An electrical system malfunction is a condition in which the starter motor 120 cannot generate the torque necessary for starting. A combustion abnormality means that while cranking by the starter motor 120 is normal, the combustion condition necessary for starting, which increases engine speed through combustion, cannot be maintained. The following explains in detail.

[0028] In this embodiment, the engine 1 has first to fourth cylinders arranged from the front end side of the crankshaft 10, and performs equally spaced ignition (equally spaced combustion) at 180-degree intervals of crank angle (CA) in the order of first cylinder - third cylinder - second cylinder - fourth cylinder. Figure 2 shows the progression of strokes in a four-stroke engine. In Figure 2, the left side shows the transition from the top dead center at the end of the exhaust stroke (exhaust top dead center) through the intake stroke and compression stroke to the top dead center at the end of the compression stroke (compression top dead center). The right side also shows the progression from top dead center of compression through the combustion stroke and exhaust stroke to top dead center of exhaust.

[0029] In the engine 1 of this embodiment, since ignition is performed at equal intervals of 180 degrees of crank angle, the intake stroke, compression stroke, combustion stroke, and exhaust stroke are performed simultaneously in each cylinder. For example, the compression stroke of the first cylinder occurs simultaneously with the exhaust stroke of the second cylinder, the intake stroke of the third cylinder, and the combustion stroke of the fourth cylinder. In this case, focusing on any single cylinder, during the intake stroke, the intake negative pressure increases in accordance with the rotation of the crankshaft 10, and the torque required for cranking tends to increase. During the compression stroke, as the compression reaction force inside the cylinder increases, the torque required for cranking tends to increase in proportion to the rotation of the crankshaft 10.

[0030] Furthermore, during the combustion stroke shown in the right-hand diagram of Figure 2 (note that in reality, this is before engine start-up and combustion is likely not taking place), the torque required for cranking tends to decrease due to the decrease in compression pressure. During the exhaust stroke, the exhaust pressure increases as the gases inside the cylinder are expelled, which tends to increase the torque required for cranking.

[0031] Furthermore, the state transitions during the compression process will be explained in more detail. Figure 3 shows the state transitions during the compression stroke of a four-stroke engine. The compression stroke is the period from 180 degrees CA before top dead center to top dead center. In the first half of the compression stroke (for example, from 180 degrees CA before top dead center to 90 degrees CA before top dead center), the compression reaction force is relatively low, and the reaction forces of the valve springs of the other cylinders act in a direction that gives rotational driving force to the crankshaft 10.

[0032] In contrast, during the latter half of the compression stroke (for example, from 90 degrees CA before top dead center to top dead center), the compression reaction force becomes relatively higher than in the first half, and the reaction forces of the valve springs of the other cylinders act in a direction that resists the rotation of the crankshaft 10. As a result, the torque required by the starter motor 120 to crank the crankshaft 10 is maximized when any one cylinder is in the latter half of the compression stroke. Therefore, if there is a problem with the starter motor 120 itself, the wiring including the starter relay 110, or the power supply such as the battery (an electrical system malfunction), the torque of the starter motor 120 will decrease, causing a particularly significant decrease in the rotational speed of the crankshaft 10 compared to normal conditions, especially in the latter half of the compression stroke.

[0033] Next, the operation of the engine starting abnormality diagnostic device of this embodiment will be described. Figure 4 is a flowchart showing the operation of the engine starting abnormality diagnostic device of the embodiment during engine starting. The following explains each step in order.

[0034] <Step S01: Determine whether or not an engine start request is made> The engine control unit 100 determines, when the engine 1 is stopped, whether there is an engine start request, such as an engine start operation by the driver using an ignition switch (not shown), or an engine restart request in idle stop control. If there is an engine start request, proceed to step S02; otherwise, terminate the series of processes.

[0035] <Step S02: Engine start-up> The engine control unit 100 starts supplying power to the starter motor 120 using the starter relay 110, thereby starting the starter motor 120. This initiates cranking, in which the crankshaft 10 is rotated by the starter motor 120. Furthermore, the engine control unit 100 opens the throttle valve 45 to a predetermined starting open position, and initiates ignition by the spark plug 32 and fuel injection by the injector 39. Then, proceed to step S03.

[0036] <Step S03: Start of cranking time measurement> In step S02, the engine control unit 100 starts measuring (counting up the timer value) the elapsed time since the starter motor 120 began to drive (hereinafter referred to as cranking time). Then proceed to step S04.

[0037] <Step S04: Start monitoring rotational speed in the latter half of compression> The engine control unit 100 calculates the average rotational speed of the crankshaft 10 (hereinafter referred to as the second-half compression rotational speed) when any one cylinder (for example, the first cylinder) is in the second half of the compression stroke (from 90 degrees CA before top dead center to top dead center) based on the output of the crank angle sensor 11, and starts monitoring it. Then, proceed to step S05.

[0038] <Step S05: Compare engine speed with the complete combustion detection value> The engine control unit 100 compares the rotational speed of the crankshaft 10 (hereinafter referred to as engine speed), which is calculated based on the output of the crank angle sensor 11, with a preset complete combustion determination value. The complete combustion detection value is a threshold value set considering the engine speed reached when engine 1 starts up successfully. If the engine speed exceeds the threshold for complete combustion, proceed to step S06; otherwise, proceed to step S07.

[0039] <Step S06: Complete explosion determined> The engine control unit 100 determines that the engine 1 has started up successfully and thus establishes a complete combustion condition. The starter motor 120 is stopped when a complete combustion is determined. After that, the series of processes will be terminated.

[0040] <Step S07: Compare cranking time with abnormality detection value> The engine control unit 100 compares the cranking time, which was measured in step S03, with a preset abnormality judgment value. The abnormality detection value is set to be longer than a predetermined value than the cranking time required for normal engine starting, for example, it can be set to 3 seconds or more. If the cranking time exceeds the abnormality threshold, a long cranking abnormality has occurred, where engine 1 does not start normally despite prolonged cranking, and the process proceeds to step S08. Otherwise, the process returns to step S05 and repeats.

[0041] <Step S08: Compare the rotational speed in the latter half of the compression period with the factor determination threshold> The engine control unit 100 compares the half-compression rotational speed, which was started to be monitored in step S04, with a preset factor determination threshold. The cause determination threshold is a threshold used to distinguish between combustion abnormalities and electrical system abnormalities as the causes of long cranking abnormalities. The cause determination threshold is set to be, for example, a predetermined amount lower than the half-compression rotational speed of the crankshaft 10 before starting when the starter motor 120 is operating normally. If the rotational speed in the latter half of compression is less than the threshold for determining the cause, the process proceeds to step S10. If the rotational speed in the latter half of compression is equal to or greater than the threshold for determining the cause, the process proceeds to step S09.

[0042] <Step S09: Combustion abnormality detected> The engine control unit 100 determines that the cause of the long cranking abnormality is a combustion abnormality, such as poor mixture formation, ignition failure, or misfire, and establishes a combustion abnormality determination. After that, the series of processes will be terminated.

[0043] <Step S10: Electrical system abnormality detected> The engine control unit 100 determines that the cause of the long cranking abnormality is an electrical system abnormality, such as a failure of the starter motor 120 itself, or the power supply or circuit that supplies power to the starter motor 120, and establishes an electrical system abnormality determination. After that, the series of processes will be terminated.

[0044] Figure 5 shows an example of the change in engine speed during a long cranking abnormality caused by a combustion abnormality. The horizontal axis represents time, and the vertical axis represents engine speed. (The same applies to Figure 6.) In the example shown in Figure 5, the starter motor 120 operates, stabilizing the engine speed at approximately 300 rpm. However, the combustion conditions are not sufficient to increase the engine speed to the level required for starting, resulting in a long cranking abnormality.

[0045] Figure 6 shows an example of the change in engine speed during a long cranking abnormality caused by an electrical system malfunction. In the example shown in Figure 6, the insufficient torque of the starter motor 120 results in intermittent engine rotational behavior in which the engine speed increases and stalls repeatedly. Furthermore, the engine speed during such long cranking abnormalities is lower than in cases of combustion abnormalities (for example, below 150 rpm). When there is an electrical system malfunction, the engine rotation behavior becomes intermittent, making it difficult to distinguish between combustion abnormalities and electrical system abnormalities by comparing the so-called typical engine speed (instantaneous value) with a predetermined threshold. Furthermore, even if the average engine speed is calculated and compared to a threshold, it is not possible to distinguish between a state where the engine is rotating steadily, such as during a combustion abnormality, and a state where it is rotating intermittently due to an electrical system malfunction.

[0046] In contrast, in this embodiment, the rotational speed of the crankshaft 10 during the latter half of the compression stroke, which is an engine rotation state suitable for narrowing down the cause, can be extracted and compared with a threshold value. This allows for the appropriate determination of the cause of the long cranking abnormality into combustion abnormality and electrical system abnormality.

[0047] According to the embodiments described above, the following effects can be obtained. (1) By comparing the rotational speed of the crankshaft 10 when at least some cylinders are in the later stages of the compression stroke with a cause determination threshold, it becomes possible to easily and quickly narrow down whether the cause of the long cranking abnormality is a combustion abnormality or an electrical system abnormality. (2) Since engine 1 is a horizontally opposed 4-cylinder engine with equally spaced ignition, it is easy to extract the crankshaft rotation speed (second half of compression rotation speed) in the region where the starter motor drive load during cranking becomes severe due to the action of the in-cylinder pressure of each cylinder and the valve spring reaction force of the valve train, and the above-mentioned effects can be appropriately obtained. (3) The cause determination threshold is set lower than the rotational speed in the latter half of the compression stroke during cranking when the starter motor 120 is functioning normally. Therefore, when cranking by the starter motor 120 is functioning normally, the rotational speed in the latter half of the compression stroke will exceed the cause determination threshold, making it possible to accurately distinguish between electrical system abnormalities and combustion abnormalities.

[0048] (modified version) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, all of which fall within the technical scope of the present invention. (1) The configuration of the engine starting abnormality diagnostic device and the engine is not limited to the configuration of the embodiment described above and can be changed as appropriate. The specific configurations of each element constituting these can be modified as appropriate. For example, in the embodiment, a configuration may be adopted in which a function realized by a common unit is divided into multiple units. Furthermore, the configuration and arrangement of sensors are not particularly limited. (2) In the embodiment, the engine was, for example, a horizontally opposed 4-cylinder direct-injection gasoline engine with equally spaced ignition, but the fuel injection method and the presence or absence of a supercharger are not particularly limited and can be changed as appropriate. Furthermore, the present invention is not limited to gasoline engines, but can also be applied to other engines with different combustion cycles, such as Otto cycle engines, Atkinson cycle engines, and diesel cycle engines that use fuels other than gasoline. (3) The cylinder layout and number of cylinders in the embodiment are examples only and can be changed as appropriate. In particular, for multi-cylinder engines that fire at equal intervals every 180 degrees or 360 degrees of crank angle (typically, horizontally opposed 4-cylinder engines, as well as inline 4-cylinder, inline 2-cylinder, and horizontally opposed 2-cylinder engines), the same effects as those of the embodiment can be obtained. (4) In this embodiment, the late-stage of the compression stroke is defined as, for example, the rotational speed of the crankshaft 10 from 90 degrees CA before top dead center to top dead center. Alternatively, the late-stage of the compression stroke may be defined as a range in which a portion of the range of angular positions (crank angles) of the crankshaft during the compression stroke is extracted, such that the median value of the extracted crank angles is later than 90 degrees before top dead center. [Explanation of symbols]

[0049] 1 Engine 10 Crankshaft 11 Crank angle sensor 20 Cylinder Block 20R Right cylinder block 20L Left cylinder block 21 Knock Sensor 30 Cylinder head 30R Right cylinder head 30L Left cylinder head 31 Combustion chamber 32 Spark plugs 33 Intake ports 34 Exhaust port 35 Intake valve 36 Exhaust valve 37 Intake camshaft 38 Exhaust camshaft 39 Injector 40 Intake system 41 Intake duct 42 Chamber 43 Air cleaner 44 Airflow meter 45 Throttle valve 46 Intake manifold 47 Intake pressure sensor 50 Exhaust System 51 Exhaust Manifold 52 Exhaust pipe 53 Front catalytic converter 54 Rear catalytic converter 55 Silencer 56 Air-fuel ratio sensor 57 Rear O2 sensor 60 EGR device 61 EGR channel 62 EGR cooler 63 EGR valve 100 Engine Control Unit (ECU) 110 Starter relay 120 Starter motor

Claims

1. An engine starting abnormality diagnostic device for determining the cause of a long cranking abnormality in which the engine does not start even if the cranking period is longer than a predetermined time when starting an engine having multiple cylinders, A rotational speed detection unit that detects the angular position of the crankshaft, An abnormality diagnosis unit calculates the crankshaft rotation speed when at least some cylinders are in the later stages of the compression stroke, based on the angular position detected by the rotation speed detection unit. Equipped with, The abnormality diagnosis unit determines that the cause of the long cranking abnormality is an electrical system abnormality when the rotational speed is less than a predetermined threshold, and determines that the cause of the long cranking abnormality is a combustion abnormality when the rotational speed is greater than the threshold. An engine starting abnormality diagnostic device characterized by the following.

2. The engine is a four-cylinder or two-cylinder engine with evenly spaced ignition. The engine starting abnormality diagnostic device according to claim 1, characterized by the following:

3. The threshold is set lower than the crankshaft rotational speed when at least some cylinders are in the later stages of the compression stroke during cranking when the starter motor is functioning normally. An engine starting abnormality diagnostic device according to claim 1 or claim 2, characterized by the above.

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