Abnormality diagnosing method for vehicle and abnormality diagnosing device for vehicle

Abstract

A vehicle has: an internal combustion engine (1); a throttle valve (6) disposed in an intake passage (3) and controlling the intake air amount; a second passage (33) connected to the intake passage (3) on the upstream side of the throttle valve (6) and capable of introducing fresh air into a crankcase (39); a third passage (34) connected to the intake passage (3) on the downstream side of the throttle valve (6) and capable of introducing blow-by gas into the intake passage (3); and a pressure sensor (53) capable of detecting an intake pressure in the intake passage (3) on the downstream side of the throttle valve (6). When the internal combustion engine (1) is motored while the degree of opening of the throttle valve (6) is reduced to a predetermined degree of opening, the presence or absence of an abnormality in the third passage (34) is diagnosed on the basis of the intake pressure detected by the pressure sensor (53) during the motoring.

Description

Vehicle abnormality diagnosis method and vehicle abnormality diagnosis device

[0001] The present invention relates to a vehicle abnormality diagnosis method and a vehicle abnormality diagnosis device.

[0002] For example, Patent Document 1 discloses an internal combustion engine equipped with a blow-by passage that connects a throttle downstream passage, which is the portion of the intake passage downstream of the throttle valve, to the crankcase, and a purge passage that connects a canister that adsorbs evaporated fuel from a fuel tank to the throttle downstream passage.

[0003] In Patent Document 1, when a deceleration fuel cut is performed to stop the fuel supply to the combustion chamber of the internal combustion engine as the vehicle decelerates, the purge valve is closed, and an abnormality diagnosis is performed to determine whether an abnormality has occurred in the blow-by passage based on the flow rate of blow-by gas that passes through the blow-by passage and is introduced into the throttle downstream passage when the purge valve is closed.

[0004] In Patent Document 1, the flow rate of blow-by gas introduced into the throttle downstream passage through the blow-by passage is estimated based on the flow rate of air passing through the throttle valve (throttle passing flow rate) detected by an air flow sensor and the pressure of intake air flowing through the throttle downstream passage (throttle downstream pressure) detected by an intake pressure sensor.

[0005] In Patent Document 1, the strength of the strong negative pressure formed in the throttle downstream passage during the deceleration fuel cut is affected by the vehicle operating conditions (e.g., vehicle speed, etc.) Therefore, when diagnosing the presence or absence of an abnormality in the blow-by passage using the pressure (negative pressure) in the throttle downstream passage, it is difficult to set a threshold value to be compared with the pressure (negative pressure) in the throttle downstream passage.

[0006] Therefore, in Patent Document 1, the flow rate of blow-by gas is used as a parameter for diagnosing abnormalities in the blow-by passage, and the detected value of the intake pressure sensor cannot be directly used as a parameter for diagnosing abnormalities.

[0007] That is, there is room for further improvement in diagnosing the presence or absence of an abnormality in the passage that introduces blow-by gas into the intake passage using parameters other than the flow rate of blow-by gas.

[0008] Japanese Patent Application Laid-Open No. 2022-167629

[0009] The present invention is a diagnostic method for a vehicle having an internal combustion engine, a first intake throttle valve disposed in the intake passage of the internal combustion engine and controlling the amount of intake air into the internal combustion engine, a fresh air introduction passage connected to the intake passage upstream of the first intake throttle valve and capable of introducing fresh air into the crankcase, a blow-by gas return passage connected to the intake passage downstream of the first intake throttle valve and capable of introducing blow-by gas into the intake passage, and a pressure sensor capable of detecting the intake pressure in the intake passage downstream of the first intake throttle valve, wherein when the internal combustion engine is motored with the first intake throttle valve reduced to a predetermined opening, the presence or absence of an abnormality in the blow-by gas return passage is diagnosed based on the intake pressure during motoring detected by the pressure sensor.

[0010] During motoring of the internal combustion engine, the pressure change caused by an abnormality in the blow-by gas recirculation passage is stable, so that an abnormality in the blow-by gas recirculation passage can be diagnosed based on the pressure in the intake passage.

[0011] 1 is a block diagram showing an example of a control flow when performing an abnormality diagnosis of a blow-by gas recirculation system;

[0012] An embodiment of the present invention will be described in detail below with reference to the drawings.

[0013] FIG. 1 is an explanatory diagram that schematically shows the system configuration of an internal combustion engine 1 according to a first embodiment of the present invention.

[0014] The vehicle according to the present invention is, for example, a so-called series hybrid vehicle that does not use an internal combustion engine 1 as a power source. For example, when the remaining charge of an on-board battery (not shown) becomes low, the vehicle drives the internal combustion engine 1 to generate electricity with a generator (not shown) in order to charge the battery. The generator converts rotational energy generated in the internal combustion engine 1 into electrical energy, for example, to charge the battery. The generator also functions as an electric motor that drives the internal combustion engine 1, enabling motoring of the internal combustion engine 1. The generator may also function as a starter motor for the internal combustion engine 1. The electric power generated by the generator may be supplied directly to a drive motor that drives the drive wheels of the vehicle depending on the driving state, for example, rather than being used to charge the battery.

[0015] The internal combustion engine 1 is, for example, a multi-cylinder spark-ignition gasoline engine. Intake air is introduced into each cylinder of the internal combustion engine 1 via an intake manifold 2 that forms a part of an intake passage 3.

[0016] The intake passage 3 is provided with an air cleaner 4 that collects foreign matter in the intake air, an air flow meter 5 that detects the intake air volume, an electric throttle valve 6, an electric pressure control valve 7 located upstream of the throttle valve 6, and a pressure sensor 53.

[0017] The air flow meter 5 corresponds to an intake air amount detection sensor, and is disposed upstream of the pressure control valve 7. The air flow meter 5 has a built-in temperature sensor and is capable of detecting the intake air temperature.

[0018] The air cleaner 4 is disposed upstream of the air flow meter 5 .

[0019] The throttle valve 6 corresponds to the first intake throttle valve in the first embodiment and controls the amount of intake air into the internal combustion engine 1. The pressure control valve 7 corresponds to the second intake throttle valve in the first embodiment and controls the intake pressure upstream of a compressor 10, which will be described later. In other words, the pressure control valve 7 is capable of generating negative pressure upstream of the throttle valve 6.

[0020] The opening degrees of the throttle valve 6 and the pressure control valve 7 can be changed (controlled) by control signals from an engine control module (ECM) 8. A pressure sensor 53 is provided in the intake passage 3 downstream of the throttle valve 6 to detect the intake pressure in the intake passage.

[0021] The internal combustion engine 1 also has a turbocharger 9. The turbocharger 9 has a compressor 10 provided in the intake passage 3 and a turbine (not shown) provided in an exhaust passage (not shown). The compressor 10 and the turbine are arranged coaxially and rotate integrally. The compressor 10 is arranged upstream of the throttle valve 6 and downstream of the pressure control valve 7.

[0022] An intercooler 12 is provided in the intake passage 3 upstream of the throttle valve 6. The intercooler 12 is located downstream of the compressor 10 and is provided to cool the intake air compressed (pressurized) by the compressor 10 to improve charging efficiency.

[0023] An EGR passage (not shown) is connected downstream of the pressure control valve 7. One end of this EGR passage is connected to the exhaust passage, and the other end is connected to the intake passage 3 at a position downstream of the pressure control valve 7 and upstream of the compressor 10. The EGR passage enables exhaust gas recirculation (EGR), which recirculates part of the exhaust gas from the exhaust passage to the intake passage 3.

[0024] In FIG. 1, reference numeral 23 denotes an intake collector located downstream of the throttle valve 6.

[0025] A blow-by gas recirculation system 31 for treating blow-by gas, which introduces blow-by gas into the intake passage 3 and treats it, is connected to the intake passage 3. The blow-by gas recirculation system 31 is configured using a plurality of passages connected to a position downstream of the air flow meter 5 in the intake passage 3. Blow-by gas is combustion gas that has leaked from a combustion chamber 38 of the internal combustion engine 1 into a crankcase 39 of the internal combustion engine 1 through the gap between the cylinder and the piston.

[0026] The blow-by gas recirculation system 31 has a first passage 32 formed by a tubular first annular member, a second passage 33 formed by a tubular second annular member, a third passage 34 formed by a tubular third annular member, a check valve 35, and a PCV valve 37.

[0027] The first passage 32 connects (communicates) a position in the intake passage 3 between the throttle valve 6 and the pressure control valve 7 with the crankcase 39 of the internal combustion engine 1. One end of the first passage 32 is connected to a position in the intake passage 3 between the throttle valve 6 and the pressure control valve 7, and the other end is connected to the internal combustion engine 1 via a check valve 35. More specifically, one end of the first passage 32 is connected to a position in the intake passage 3 between the compressor 10 and the pressure control valve 7. The first passage 32 is capable of introducing blow-by gas in the crankcase 39 into the intake passage 3. More specifically, the first passage 32 can introduce blow-by gas into the intake passage 3 by reducing the opening of the pressure control valve 7 (closing the valve) and developing negative pressure downstream of the pressure control valve 7.

[0028] The check valve 35 has the function of allowing a flow from the crankcase 39 toward the intake passage 3 while prohibiting a flow from the intake passage 3 toward the crankcase 39 .

[0029] The second passage 33 connects (communicates) a position in the intake passage 3 between the pressure control valve 7 and the air flow meter 5 with the crankcase 39 of the internal combustion engine 1. One end of the second passage 33 is connected to a position in the intake passage 3 between the pressure control valve 7 and the air flow meter 5, and the other end is connected to the internal combustion engine 1. The second passage 33 constitutes a fresh air introduction passage, and is capable of introducing fresh air into the crankcase 39 of the internal combustion engine 1.

[0030] The third passage 34 connects (communicates) a position in the intake passage 3 downstream of the throttle valve 6 with a crankcase 39 of the internal combustion engine 1. One end of the third passage 34 is connected to a position in the intake passage 3 downstream of the throttle valve 6, and the other end is connected to the internal combustion engine 1 via a PCV valve 37. The third passage 34 corresponds to the blow-by gas recirculation passage in the first embodiment, and is capable of introducing blow-by gas in the crankcase 39 into the intake passage 3.

[0031] The PCV valve 37 corresponds to a blow-by gas control valve and controls the flow rate of gas in the third passage 34. The PCV valve 37 is, for example, a well-known differential pressure operated valve that is attached to the internal combustion engine 1 and operates to open when the pressure difference between the inlet pressure on the crankcase 39 side and the outlet pressure on the intake passage 3 side is large. More specifically, the PCV valve 37 prevents outside air from flowing back from the intake passage 3 into the crankcase 39 through the third passage 34, while discharging blow-by gas from the crankcase 39 to the intake passage 3 in accordance with the pressure difference. In other words, the internal combustion engine 1 can return blow-by gas to the intake passage 3 via the PCV valve 37 and the third passage 34 by utilizing the negative pressure downstream of the throttle valve 6.

[0032] The ECM 8 is a well-known digital computer equipped with a CPU, ROM, RAM, and an input / output interface. In addition to the detection signal from the air flow meter 5, the ECM 8 receives detection signals from various sensors, such as a crank angle sensor 51 that detects the crank angle of the crankshaft, an accelerator position sensor 52 that detects the amount of depression of the accelerator pedal, a pressure sensor 53 that detects the pressure in the intake manifold 2, an atmospheric pressure sensor 54 that detects the atmospheric pressure, a first position sensor 55 that detects the position of the throttle valve 6, and a second position sensor 56 that detects the position of the pressure control valve 7.

[0033] The crank angle sensor 51 is capable of detecting the engine speed of the internal combustion engine 1. The accelerator opening sensor 52 is capable of detecting the accelerator pedal change speed, which is the operation speed of the accelerator pedal.

[0034] Based on detection signals from various sensors, the ECM 8 controls the operation of the internal combustion engine 1. Specifically, when the remaining battery charge of the battery described above becomes low, the ECM 8 drives the internal combustion engine 1 to charge the battery.

[0035] Here, if there is an abnormality in the blow-by gas recirculation system 31, such as one end of the third tubular member that constitutes the third passage 34 falling off from the intake pipe that constitutes the intake passage 3, the other end of the third tubular member falling off from the PCV valve 37, a hole being formed in the third tubular member, or the PCV valve 37 falling off from the internal combustion engine 1, air will enter through the abnormal part.

[0036] Therefore, the ECM 8, which corresponds to a diagnostic unit, diagnoses the presence or absence of an abnormality in the blow-by gas recirculation system 31 as an abnormality diagnosis for the vehicle using the pressure in the intake passage 3. The abnormality diagnosis for the blow-by gas recirculation system 31 in the first embodiment is performed on an internal combustion engine 1 mounted on a vehicle for power generation, for example. The abnormality diagnosis for the blow-by gas recirculation system 31 is performed, for example, once during one trip of the vehicle. Here, one trip refers to, for example, the period from when the ignition switch of the vehicle is turned on to when the ignition switch is turned off.

[0037] When the internal combustion engine 1 is motored with the throttle valve 6 reduced to a predetermined opening (valve closed state), the ECM 8 diagnoses whether or not there is an abnormality in the blow-by gas recirculation system 31 based on the pressure detected by the pressure sensor 53. More specifically, the ECM 8 diagnoses that there is an abnormality in the third passage 34 of the blow-by gas recirculation system 31 when the difference (absolute value) between the pressure detected by the pressure sensor 53 while the internal combustion engine 1 is motoring and the pressure detected by the pressure sensor 53 while the internal combustion engine 1 is stopped is smaller than a predetermined differential pressure determination threshold.

[0038] The predetermined opening is a so-called closed state, which is about several degrees. Even when the throttle valve 6 of the internal combustion engine 1 is in the closed state, it does not actually completely block the inflow of intake air.

[0039] When a predetermined first condition is met, the ECM 8 detects the intake pressure during motoring using the pressure sensor 53. The first condition is a condition that permits measurement of the pressure in the intake manifold 2 while the internal combustion engine 1 is motoring in order to diagnose an abnormality in the blow-by gas recirculation system 31. The first condition may be, for example, that the internal combustion engine 1 is motoring, that fuel supply to the internal combustion engine 1 is stopped, that the engine speed of the internal combustion engine 1 is a predetermined first speed (e.g., approximately 1500 rpm), that the throttle valve 6 is reduced to a predetermined opening (e.g., a closed state with a valve opening of approximately several degrees), or that the intake air amount is equal to or less than a predetermined diagnostic air amount Q. Motoring may be performed, for example, in response to a request from an on-board diagnostic system (OBD) or may be performed to diagnose an abnormality in the blow-by gas recirculation system 31 after the internal combustion engine 1 has finished generating electricity.

[0040] When the internal combustion engine 1 is motoring, the fuel supply to the internal combustion engine 1 is stopped, the throttle valve 6 is closed, and the intake air amount detected by the air flow meter 5 falls below a predetermined amount, the ECM 8 determines that the first condition is met, and continuously measures the intake pressure in the intake manifold 2 (intake pressure during motoring) for a predetermined time (predetermined period), and records the average intake pressure during motoring, which is the average pressure over this predetermined time (predetermined period). The average intake pressure during motoring is the average value of the intake pressures during motoring measured while the first condition is met.

[0041] Furthermore, when the first condition is met, the ECM 8 measures the atmospheric pressure, intake temperature, and intake air volume, which are environmental conditions during motoring, in parallel (simultaneously) with measuring the intake pressure in the intake manifold 2. The ECM 8 then records the average atmospheric pressure during motoring, average intake temperature during motoring, and average intake air volume during motoring for a predetermined time (predetermined period) during which the intake pressure in the intake manifold 2 (intake pressure during motoring) is continuously measured. The average atmospheric pressure during motoring, average intake temperature during motoring, and average intake air volume during motoring are the average values ​​of the atmospheric pressure, intake temperature, and intake air volume, respectively, measured while the first condition is met.

[0042] When a predetermined second condition is met after recording the average motoring intake pressure, the ECM 8 detects the stop-time intake pressure with the pressure sensor 53. The second condition is a condition that permits measurement of the pressure in the intake manifold 2 when the internal combustion engine 1 is stopped in order to diagnose an abnormality in the blow-by gas recirculation system 31. The second condition is, for example, that a predetermined time has elapsed since the end of measurement of the motoring intake pressure, that fuel supply to the internal combustion engine 1 is stopped, that the engine speed of the internal combustion engine 1 is equal to or lower than a predetermined second speed (e.g., 100 rpm), that the vehicle speed is equal to or lower than a predetermined speed, etc.

[0043] If, within a predetermined time after the end of measurement of the intake pressure during motoring, fuel supply to the internal combustion engine 1 is stopped, the engine speed of the internal combustion engine 1 is equal to or lower than a second speed, and the vehicle speed is equal to or lower than a predetermined speed, the ECM 8 determines that the second condition is met, and continues to measure the intake pressure in the intake manifold 2 (intake pressure during stoppage) for a predetermined time (predetermined period), and records the average intake pressure during stoppage, which is the average pressure over this predetermined time (predetermined period).

[0044] Furthermore, when the second condition is met, the ECM 8 measures the atmospheric pressure, intake temperature, and intake air amount, which are environmental conditions when the internal combustion engine 1 is stopped, in parallel (simultaneously) with measuring the intake pressure in the intake manifold 2. Then, the ECM 8 records the average atmospheric pressure when the engine is stopped, the average intake temperature when the engine is stopped, and the average intake air amount when the engine is stopped for a predetermined time (predetermined period) during which the intake pressure in the intake manifold 2 (intake pressure when the engine is stopped) is continuously measured.

[0045] When a predetermined third condition is met with the average motoring intake pressure and the average stationary intake pressure continuously recorded, the ECM 8 diagnoses (determines) that there is an abnormality in the third passage 34 if a first pressure value, which is the absolute value of the pressure difference between a standard average motoring intake pressure (described later) and a standard average stationary intake pressure (described later), is smaller than a predetermined differential pressure determination threshold. The third condition is a condition permitting abnormality diagnosis (determination of abnormality) of the third passage 34, which is performed using the first pressure value and the differential pressure determination threshold, in order to diagnose an abnormality in the blow-by gas recirculation system 31. The third condition is, for example, that the difference between the motoring average atmospheric pressure and the stationary average atmospheric pressure is within a predetermined value, that the difference between the motoring average intake temperature and the stationary average intake temperature is within a predetermined value, that the sensors used for the abnormality diagnosis of the blow-by gas recirculation system 31 are not broken, etc.

[0046] By setting the third condition, the ECM 8 does not perform diagnosis when there is a large change between the environmental conditions when the intake pressure is measured during motoring and the environmental conditions when the intake pressure is measured during a stop.

[0047] When the third condition is met, the ECM 8 corrects the recorded average motoring intake pressure and average stationary intake pressure to values ​​for predetermined standard environmental conditions. That is, when the third condition is met, the ECM 8 corrects (converts) the average motoring intake pressure to a standard average motoring intake pressure, which is a value for standard environmental conditions, and corrects (converts) the average stationary intake pressure to a standard average stationary intake pressure, which is a value for standard environmental conditions. The standard environmental conditions are, for example, standard atmospheric pressure (1 atm) and standard intake temperature (e.g., 25°C).

[0048] The ECM 8 then calculates the differential pressure determination threshold using the average motoring intake air amount. Figure 2 is an explanatory diagram that schematically shows the correlation between the differential pressure determination threshold, the first pressure value, and the intake air amount detected by the air flow meter 5. The abnormality diagnosis of the blow-by gas recirculation system 31 is performed in a failure diagnosis implementation region where the intake air amount is equal to or less than the diagnostic air amount Q based on the first condition.

[0049] In the blow-by gas recirculation system 31, if there is no abnormality in the third passage 34, the first pressure value, which is the pressure difference within the intake manifold 2 between motoring and stopped, becomes large, and if there is an abnormality in the third passage 34, the first pressure value, which is the pressure difference within the intake manifold 2 between motoring and stopped, becomes small.

[0050] A characteristic line C1 shown by a solid line in Fig. 2 indicates the first pressure value when there is no abnormality in the third passage 34. A characteristic line C2 shown by a thin dashed line in Fig. 2 indicates the first pressure value when there is an abnormality in the third passage 34. A characteristic line C3 shown by a thick dashed line in Fig. 2 indicates the differential pressure determination threshold value.

[0051] The differential pressure determination threshold is set to a value between the characteristic line C1 and the characteristic line C2, taking into consideration various variations. That is, the differential pressure determination threshold is set to a value greater than the possible value of the first pressure value when an abnormality exists in the third passage 34, taking into consideration various variations. The differential pressure determination threshold is set to a smaller value as the intake air amount increases (is larger).

[0052] Furthermore, since the first pressure value decreases as the altitude increases, if the differential pressure determination threshold is set to decrease as the altitude increases, it is possible to perform abnormality diagnosis of the blow-by gas recirculation system 31 regardless of the altitude. In other words, the differential pressure determination threshold and the first pressure value may be corrected according to the altitude, for example, the differential pressure determination threshold may be corrected to decrease as the altitude increases, or the first pressure value may be corrected to increase as the altitude increases.

[0053] Product variations in the pressure sensor 53 are cancelled out by using the pressure difference (difference) between the intake pressure during motoring and the intake pressure when the internal combustion engine 1 is stopped.

[0054] If the first pressure value is equal to or greater than the calculated differential pressure determination threshold, the ECM 8 determines that there is no abnormality in the third passage 34 and that there is no abnormality in the blow-by gas recirculation system 31. On the other hand, if the first pressure value is less than the calculated differential pressure determination threshold, the ECM 8 determines that there is some abnormality in the third passage 34 and that there is an abnormality in the blow-by gas recirculation system 31.

[0055] If the ECM 8 determines that there is an abnormality in the blow-by gas recirculation system 31 for two consecutive trips, it notifies the driver by turning on a warning light or the like.

[0056] The abnormality diagnosis of the blow-by gas recirculation system 31 of the first embodiment described above is performed while the internal combustion engine 1 is motoring, so the pressure change (relative to the pressure change under normal conditions) caused by an abnormality in the third passage 34 is stable, and therefore an abnormality in the third passage 34 (blow-by gas recirculation passage) can be diagnosed based on the pressure in the intake passage 3.

[0057] Unlike the inside of the crankcase 39, the intake passage 3 is a closed space that is directly affected by pumping when the internal combustion engine 1 pumps for diagnostic purposes, so even in an abnormal state (when there is a leak or a hole), a relatively large negative pressure develops and it is difficult for a difference to be noticed between this and the negative pressure under normal conditions.

[0058] On the other hand, if an attempt is made to maintain a constant engine speed through combustion self-rotation in order to develop negative pressure for diagnostic purposes, the engine speed may become unstable in the event of an abnormality, such as a loss of the PCV valve 37 or the third tubular member, due to an increase in the intake air volume, which may prevent the expected development of negative pressure in the event of an abnormality. Furthermore, if an attempt is made to maintain a constant engine speed by transmitting wheel rotation to the engine, for example, in the case of a stepped automatic transmission, the engine speed may not remain constant when the vehicle speed changes. In the case of a continuously variable transmission, attempting to maintain a constant engine speed by transmitting wheel rotation to the engine requires changing the gear ratio, which affects drivability and complicates control, making it difficult to maintain a constant engine speed as desired, resulting in unstable pressure under normal conditions. In such cases, measures such as increasing the margin of the differential pressure determination threshold described above are required to prevent misdiagnosis, which may make diagnosis more difficult or reduce diagnostic accuracy.

[0059] In contrast, motoring is not affected by changes in intake air volume or vehicle speed, and does not affect drivability, so the engine speed can be kept stable and constant. Even if there is the above-mentioned circumstance where a relatively large negative pressure develops within the intake passage 3 and it is difficult for a difference to occur between this and the negative pressure under normal conditions, if pumping of the internal combustion engine 1 is performed by motoring, the pressure in the intake passage 3 expected under both abnormal and normal conditions can be stably obtained, making it possible to perform highly accurate diagnosis using the output of the pressure sensor 53, which is a general-purpose intake pressure sensor.

[0060] Therefore, the pressure sensor 53 is not provided for diagnosing abnormalities in the third passage 34 (blow-by gas recirculation passage), and an existing sensor that detects the intake pressure in the intake manifold 2 can be used.

[0061] When diagnosing abnormalities in the blow-by gas recirculation system 31, if the pressure in the intake passage 3 is used as a diagnostic parameter when diagnosing abnormalities in the third passage 34, the pressure sensor 53, which is a general-purpose intake pressure sensor, can be used, and no additional sensor is required.

[0062] Furthermore, the ease of stabilizing the engine speed at a constant value means that negative pressure in the intake passage 3 can be sufficiently developed during normal operation (when there is no abnormality in the third passage 34) without closing the second passage 33, which provides the option of not providing a diagnostic on-off valve in the second passage 33 that is closed when diagnosing whether or not there is an abnormality in the third passage 34. In other words, by diagnosing an abnormality in the third passage 34 based on the pressure in the intake passage 3 during motoring, the ECM 8 can diagnose an abnormality in the blow-by gas recirculation system 31 even if a diagnostic on-off valve that is closed when diagnosing whether or not there is an abnormality in the third passage 34 is not provided in the second passage 33.

[0063] FIG. 3 is a flowchart showing an example of a control flow when diagnosing an abnormality in the blow-by gas recirculation system 31.

[0064] In step S1, it is determined whether or not an abnormality diagnosis has been performed on the blow-by gas recirculation system 31 during the current trip. If it is determined in step S1 that an abnormality diagnosis has been performed on the blow-by gas recirculation system 31 during the current trip, the current routine is terminated. If it is determined in step S1 that an abnormality diagnosis has not been performed on the blow-by gas recirculation system 31 during the current trip, the routine proceeds to step S2.

[0065] In step S2, it is determined whether various motoring parameters, such as the intake pressure during motoring and the environmental conditions during motoring (atmospheric pressure, etc.), measured when the first condition is met during the current trip have been recorded. If the various measured values ​​measured when the first condition is met in step S2 have not been recorded, the process proceeds to step S3. If the various measured values ​​measured when the first condition is met in step S2 have been recorded, the process proceeds to step S6.

[0066] In step S3, it is determined whether the first condition is met. If it is determined in step S3 that the first condition is met, the process proceeds to step S4. If it is determined in step S3 that the first condition is not met, the current routine is terminated.

[0067] In step S4, the intake pressure during motoring is recorded.

[0068] In step S5, the environmental conditions during motoring, such as atmospheric pressure, intake air temperature, and intake air volume, are recorded.

[0069] In step S6, it is determined whether the second condition is met. If it is determined in step S6 that the second condition is met, the process proceeds to step S7. If it is determined in step S6 that the second condition is not met, the current routine is terminated.

[0070] In step S7, the intake pressure at the time of stopping is recorded.

[0071] In step S8, the environmental conditions when the internal combustion engine 1 is stopped are recorded. The environmental conditions when the internal combustion engine 1 is stopped include the atmospheric pressure, the intake air temperature, and the intake air amount.

[0072] In step S9, it is determined whether the third condition is met. If it is determined in step S9 that the third condition is met, the process proceeds to step S10. If it is determined in step S9 that the third condition is not met, the process proceeds to step S12.

[0073] In step S10, the intake pressure during motoring and the intake pressure during stop are corrected to values ​​for standard environmental conditions. That is, in step S10, various parameters such as the intake pressure during motoring and the intake pressure during stop are corrected to values ​​conforming to the standard environmental conditions.

[0074] In step S11, the presence or absence of an abnormality in the blow-by gas recirculation system 31 is determined using various parameters corrected to values ​​conforming to standard environmental conditions.

[0075] In step S12, various parameters such as the intake pressure during motoring, the intake pressure during stopping, and various environmental conditions that were recorded when the first and second conditions were met during the current trip are cleared.

[0076] Another embodiment of the present invention will now be described, in which the same components as those in the first embodiment described above are designated by the same reference numerals and redundant description will be omitted.

[0077] FIG. 4 is an explanatory diagram showing a schematic outline of the system configuration of an internal combustion engine 1 according to a second embodiment of the present invention.

[0078] The system configuration of the internal combustion engine 1 in the second embodiment is substantially the same as that in the first embodiment, except that the third passage 34 in the first embodiment is omitted.

[0079] In the second embodiment, the pressure control valve 7 corresponds to the first intake throttle valve, and the first passage 32 corresponds to the blow-by gas recirculation passage. A pressure sensor 53 is provided in the intake passage 3 downstream of the pressure control valve 7 to detect the intake pressure in the intake passage.

[0080] In the second embodiment, the ECM 8, which corresponds to the diagnosing unit, diagnoses whether or not there is an abnormality in the blow-by gas recirculation system 31 based on the pressure detected by the pressure sensor 53 when the internal combustion engine 1 is motored with the throttle valve 6 fully open and the pressure control valve 7 reduced to a predetermined opening (valve closed state). In the second embodiment, the ECM 8 diagnoses that there is an abnormality in the first passage 32 of the blow-by gas recirculation system 31 when the difference (absolute value) between the pressure detected by the pressure sensor 53 while the internal combustion engine 1 is motoring and the pressure detected by the pressure sensor 53 while the internal combustion engine 1 is stopped is smaller than a predetermined differential pressure judgment threshold.

[0081] In the second embodiment, abnormality diagnosis of the blow-by gas recirculation system 31 is performed based on the pressure in the intake passage 3, since the pressure change (relative to the pressure change under normal conditions) caused by an abnormality in the first passage 32 is stable while the internal combustion engine 1 is motoring.

[0082] The pressure sensor 53 is not provided for diagnosing abnormalities in the first passage 32 (blow-by gas recirculation passage), and an existing sensor for detecting the intake pressure in the intake manifold 2 can be used.

[0083] When diagnosing abnormalities in the blow-by gas recirculation system 31, if the pressure in the intake passage 3 is used as a diagnostic parameter when diagnosing abnormalities in the first passage 32, the pressure sensor 53, which is a general-purpose intake pressure sensor, can be used, and no additional sensor is required.

[0084] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0085] For example, in the first and second embodiments described above, the check valve 35 in the first passage 32 may be omitted.

[0086] For example, when diagnosing an abnormality in the blow-by gas recirculation system 31, the diagnosis may be performed without converting (correcting) the average motoring intake pressure and the average stationary intake pressure to values ​​under standard environmental conditions.

[0087] For example, the abnormality diagnosis of the blow-by gas recirculation system 31 in each of the above-described embodiments can be applied to vehicles other than series hybrid vehicles as long as motoring of the internal combustion engine 1 is possible.

[0088] For example, in the abnormality diagnosis of the blow-by gas recirculation system 31 in the first embodiment described above, it is also possible to determine that there is an abnormality in the third passage 34 of the blow-by gas recirculation system 31 when the motoring intake pressure or the average motoring intake pressure is higher than a predetermined pressure determination threshold. For example, if the third passage 34 of the blow-by gas recirculation system 31 becomes detached, air will flow in from the downstream side of the throttle valve 6 even when the throttle valve 6 is closed. This causes the degree of negative pressure development in the intake manifold 2 to be weak even during motoring, and the pressure will not drop completely. Therefore, the ECM 8 may determine that there is an abnormality in the third passage 34 of the blow-by gas recirculation system 31 when the motoring intake pressure or the average motoring intake pressure is higher than a predetermined pressure determination threshold. The pressure determination threshold is set, for example, taking into account various variations, so as to be higher than the possible value of the motoring intake pressure or the average motoring intake pressure when there is an abnormality in the third passage 34. In this case, the pressure determination threshold may be corrected to be smaller as the altitude increases, or the motoring intake pressure or average motoring intake pressure may be corrected to be larger as the altitude increases.

[0089] The above-described embodiments relate to a vehicle diagnostic method and a vehicle diagnostic device.

Claims

1. A diagnostic method for a vehicle having an internal combustion engine, a first intake throttle valve arranged in the intake passage of the internal combustion engine and controlling the amount of intake air into the internal combustion engine, a fresh air introduction passage connected to the intake passage upstream of the first intake throttle valve and capable of introducing fresh air into the crankcase, a blow-by gas return passage connected to the intake passage downstream of the first intake throttle valve and capable of introducing blow-by gas into the intake passage, and a pressure sensor capable of detecting the intake pressure in the intake passage downstream of the first intake throttle valve, the method comprising: when the internal combustion engine is motored with the first intake throttle valve reduced to a predetermined opening, diagnosing whether or not there is an abnormality in the blow-by gas return passage based on the intake pressure during motoring detected by the pressure sensor.

2. The vehicle abnormality diagnosis method according to claim 1, wherein the fresh air intake passage does not have a control valve capable of adjusting the flow of fresh air in the passage.

3. A vehicle abnormality diagnosis method as described in claim 2, in which a first pressure value, which is the pressure difference between the intake pressure at the time of stopping detected by the pressure sensor when the internal combustion engine is stopped and the intake pressure at the time of motoring, is smaller than a predetermined differential pressure judgment threshold, and a diagnosis is made that there is an abnormality in the blow-by gas return passage.

4. A vehicle abnormality diagnosis method as described in claim 3, wherein the differential pressure judgment threshold is corrected to be smaller when the altitude is high than when the altitude is low, or the first pressure value is corrected to be larger when the altitude is high than when the altitude is low, and the presence or absence of an abnormality in the blow-by gas recirculation passage is diagnosed.

5. A vehicle abnormality diagnosis method according to claim 2, wherein if the intake pressure during motoring is greater than a predetermined pressure determination threshold, it is diagnosed that there is an abnormality in the blow-by gas recirculation passage.

6. A vehicle abnormality diagnosis method as described in claim 5, in which the presence or absence of an abnormality in the blow-by gas recirculation passage is diagnosed by correcting the pressure judgment threshold to be smaller when the altitude is high than when the altitude is low, or by correcting the intake pressure during motoring to be larger when the altitude is high than when the altitude is low.

7. A method for diagnosing abnormalities in a vehicle as described in claim 1, comprising: a throttle valve arranged in the intake passage; a second intake throttle valve located upstream of the throttle valve; a first passage capable of introducing fresh air into the crankcase from the upstream side of the second intake throttle valve; a second passage located between the throttle valve and the second intake throttle valve and capable of introducing blow-by gas into the intake passage; a third passage located downstream of the second intake throttle valve and capable of introducing blow-by gas into the intake passage; and a blow-by gas control valve for controlling the flow of blow-by gas in the third passage, wherein the first intake throttle valve is the throttle valve and the blow-by gas return passage is the third passage.

8. A method for diagnosing abnormalities in a vehicle as described in claim 1, comprising: a throttle valve disposed in the intake passage; the fresh air introduction passage being capable of introducing fresh air into the crankcase from the upstream side of the throttle valve; the blow-by gas return passage being capable of introducing blow-by gas into the intake passage at a position downstream of the throttle valve; and the first intake throttle valve being the throttle valve.

9. A method for diagnosing abnormalities in a vehicle as described in claim 1, comprising: a throttle valve disposed in the intake passage; and a pressure control valve located upstream of the throttle valve; the fresh air introduction passage is capable of introducing fresh air into the crankcase from the upstream side of the pressure control valve; the blow-by gas recirculation passage is capable of introducing blow-by gas into the intake passage at a position between the throttle valve and the pressure control valve; and the first intake throttle valve is the pressure control valve.

10. An abnormality diagnosis device for a vehicle comprising: an internal combustion engine; a first intake throttle valve disposed in an intake passage of the internal combustion engine and controlling the amount of intake air into the internal combustion engine; a fresh air introduction passage connected to the intake passage upstream of the first intake throttle valve and capable of introducing fresh air into a crankcase; a blow-by gas return passage connected to the intake passage downstream of the first intake throttle valve and capable of introducing blow-by gas into the intake passage; a pressure sensor capable of detecting the intake pressure in the intake passage downstream of the first intake throttle valve; and a diagnosis unit that diagnoses the presence or absence of an abnormality in the blow-by gas return passage based on the intake pressure during motoring detected by the pressure sensor when the internal combustion engine is motored with the first intake throttle valve reduced to a predetermined opening.

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