Abnormality detection device for internal combustion engine

Abstract

To provide an abnormality detection device for an internal combustion engine, which can accurately detect an abnormality in a PCV that returns blow-by gas to an intake side.SOLUTION: An abnormality detection device for an engine 1 sends blow-by gas from a storage part 22 to the intake side of a supercharger 9 via a return flow path 26, calculates a determination parameter based on the pressure in the storage part 22 in the state that an intake air volume is equal to or greater than a predetermined value, and determines an abnormality in the return flow path based on the determination parameter. The abnormality detection device has an intake air volume calculation part that calculates the intake air volume when calculating the determination parameter on the basis of an intake pipe pressure (27) of the engine, engine speed (31), and air-fuel ratio (29) in the exhaust gas generated by combustion in the engine.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a device for detecting an abnormality in an internal combustion engine equipped with a blow-by gas flow path that recirculates blow-by gas to an intake passage, and more particularly to a device for detecting an abnormality in a PCV (Positive Crankcase Ventilation) in an internal combustion engine equipped with a supercharger and configured to recirculate blow-by gas to the intake side of the supercharger. [Background technology]

[0002] Blow-by gas is fuel that has entered the crankcase or the like without being burned and vaporized, or fuel that has dissolved in oil and then vaporized, and it needs to be treated by being burned without being released into the atmosphere. PCV (Positive Crankcase Ventilation) is a treatment means for this purpose, and as described in Patent Document 1, for example, it connects the crankcase and the head cover, connects the head cover and the intake side of the turbocharger through a blow-by gas passage, and also provides a PCV valve between the head cover and the intake manifold that opens with intake negative pressure.

[0003] The blow-by gas passage is typically formed by a hose attached to the engine, and is exposed to the engine compartment. Therefore, the blow-by gas passage may deteriorate, develop a hole or crack, or become disconnected from the head cover or turbocharger, resulting in communication with the atmosphere. When such an abnormality occurs, even if the engine's intake pressure fluctuates, atmospheric air (outside air) flows into the blow-by gas passage and gas inside the passage flows out, so the internal pressure of the blow-by gas passage does not decrease significantly or fluctuate significantly. In other words, if an abnormality occurs in which outside air enters the blow-by gas passage due to a hole or crack, this will appear as an abnormality in the internal pressure of the blow-by gas passage. Therefore, the invention described in Patent Document 1 provides a sensor to detect the internal pressure of the blow-by gas passage and detects an abnormality in the blow-by gas passage based on the detected value of the sensor or fluctuations in the internal pressure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-186702 Summary of the Invention [Problem to be solved by the invention]

[0005] The device described in the aforementioned Patent Document 1 determines whether an abnormality exists based on the pressure or its fluctuation in the blow-by gas passage when the intake air volume is increased or decreased. The difference between the normal and abnormal pressure or its fluctuation becomes larger when the intake air volume is large. Therefore, the abnormality determination is performed when the intake air volume is relatively large. According to the description in Patent Document 1, the intake air volume is detected by an air flow meter. The air flow meter is usually built into the air filter or configured to detect the amount of air that has passed through the air filter. However, the point where the blow-by gas meets the intake air is usually downstream of the air filter (i.e., downstream of the air flow meter). Therefore, if suction is generated through the blow-by gas passage by, for example, supercharging, the amount of gas sucked through the blow-by gas passage does not appear in the value detected by the air flow meter. The device described in Patent Document 1 is configured to determine or detect an abnormality such as damage to the blow-by gas passage based on the air volume detected by the air flow meter, so even if the actual intake air volume is high due to such an abnormality, the detection value of the air flow meter is small, so the abnormality determination or detection is performed on the premise or condition that the intake air volume is low, which may result in an inaccurate abnormality determination or detection.In addition, an abnormality such as a hole in the blow-by gas passage may cause the intake air volume to be detected as lower than it actually is, which may reduce the opportunities to obtain parameters for abnormality determination, making it impossible to reliably detect an abnormality.

[0006] The present invention has been made against the background of the above circumstances, and aims to provide an abnormality detection device for an internal combustion engine that can accurately detect abnormalities in a PCV that returns blow-by gas to the intake side. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the present invention provides an engine abnormality detection device that sends blow-by gas from a storage section through a return passage to the intake side of a supercharger, calculates a judgment parameter based on the pressure in the storage section when the intake air amount is equal to or greater than a predetermined value, and judges an abnormality in the return passage based on the judgment parameter, and is characterized by having an intake air amount calculation section that calculates the intake air amount when calculating the judgment parameter based on the intake manifold pressure of the engine, the engine speed, and the air-fuel ratio in exhaust gas generated by combustion in the engine. [Effects of the Invention]

[0008] According to the present invention, the amount of air taken into the cylinder is calculated based on the intake manifold pressure, engine speed, and air-fuel ratio in the exhaust gas, so the intake air amount can be accurately calculated when determining the judgment parameter. That is, in a configuration in which gas reaching the turbocharger through the recirculation passage does not pass through an air flow meter, if outside air is taken in due to an abnormality such as a hole in the recirculation passage, the intake air amount will be greater than the amount obtained by the air flow meter. However, in the present invention, the actual intake air amount is calculated without using such an air flow meter, so the intake air amount can be accurately determined when determining the judgment parameter. In other words, it is possible to avoid or suppress an intake air amount being calculated that is lower than it actually is, and the resulting reduction in opportunities to determine the judgment parameter (i.e., opportunities to determine an abnormality). [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic diagram illustrating an embodiment of the present invention excluding a controller. [Figure 2] FIG. 2 is a block diagram showing the functional configuration of a controller. [Figure 3] 10 is a time chart showing an example of changes in vehicle speed, intake air amount, number of calculations, PCV pressure, and determination (detection) parameters when PCV abnormality is detected. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0011] The engine in an embodiment of the present invention is a heat engine that outputs mechanical power by explosively burning a mixture of fuel and air, and a gasoline engine is one example. Figure 1 mainly shows a schematic view of the intake system of engine 1, with pistons 3 housed in each of a plurality of cylinders 2 so that they reciprocate while maintaining an airtight state, and the pistons 3 are connected to a crankshaft 5 housed in a crankcase 4. Combustion chambers 6 defined inside the cylinders 2 by the pistons 3 are provided with intake ports 7 and exhaust ports 8, and the intake port 7 is connected to a compressor 10 in a turbocharger (supercharger) 9, and the exhaust port 8 is connected to a turbine 11 in the turbocharger 9.

[0012] More specifically, an air filter 14 having an air flow meter 13 is connected to an intake port 12 of the compressor 10. A throttle valve 17 is connected to a discharge port 15 of the compressor 10 via an air cooler 16. An intake manifold 18 is provided in communication with each intake port 7, and the throttle valve 17 is in communication with the intake manifold 18.

[0013] A head cover 20 is provided above a cylinder block 19 in which the cylinders 2 are formed. Blow-by gas is temporarily stored inside this head cover 20, and therefore a communication section 21 is provided to guide the blow-by gas inside the crankcase 4 into the head cover 20. This head cover 20 corresponds to the storage section in this embodiment of the present invention.

[0014] The head cover 20 is configured to return blow-by gas inside the head cover 20 to the intake side of the engine 1. First, the head cover 20 is provided with a first separator 22 that is connected to the interior of the head cover 20 and the communication part 21. This separator 22 is connected to the intake manifold 18 by a pipe 23. A PCV valve 24 is provided at the connection part of the pipe 23 to the separator 22. The PCV valve 24 is a well-known valve that opens due to the negative pressure of the intake manifold 18 and allows blow-by gas to flow into the intake manifold 18. The head cover 20, the pipe 23, and the PCV valve 24 can be integrally formed with the head cover or the cylinder block 19 (not shown), or can be configured to be integrally fastened by bolts or the like.

[0015] In the example shown in FIG. 1 , a second separator 25 is provided in the head cover 20. The second separator 25 may be formed integrally with the first separator 22. The second separator 25 is connected to the interior of the head cover 20 and is also connected to the compressor 10 via a hose 26. The connection point is between the air filter 14 and the compressor 10, downstream of the air flow meter 13. Therefore, when the turbocharger 9 (compressor 10) is rotating and drawing in air (when supercharging is being performed), blow-by gas inside the head cover 20 is drawn in and sent to the intake manifold 18 together with the air, and when supercharging is not actually being performed, air that has passed through the air filter 14 may be led into the interior of the head cover 20 via the hose 26. As described above, the hose 26 is intended to connect the head cover 20 and the turbocharger 9, and therefore is necessarily configured to be exposed to the outside of the engine 1, and this hose 26 corresponds to the return path in this embodiment of the present invention.

[0016] A pressure sensor 27 is connected to the intake manifold 18, detecting the pressure (kPa: intake pipe pressure) therein and outputting a signal. In addition, a PCV pressure sensor 28 is provided on the second separator 25, detecting the pressure (kPa) in a hose 26 that sends blow-by gas to the intake side of the turbocharger 9. The PCV pressure sensor 28 is located upstream (on the head cover 20 side) of an abnormality such as a hole that may occur in the hose 26. In addition, an air-fuel ratio sensor 29 is provided, detecting the air-fuel ratio (A / F) of exhaust gas flowing from the exhaust port 8 to the turbocharger 9 (turbine 11) and outputting a signal. The air-fuel ratio sensor 29 can also be configured to detect the air-fuel ratio of exhaust gas flowing out from the turbine 11.

[0017] The abnormality detection device in the embodiment of the present invention is a device that can accurately detect the intake air amount (g / sec) even when the detection value of the air flow meter 13 fluctuates depending on the presence or absence of an abnormality in the intake system of blow-by gas via the hose 26, and is also configured to detect an abnormality in the intake system of blow-by gas via the hose 26, and is equipped with a controller 30 that performs this detection. The controller 30 is an electronic control device that is mainly a computer made up of an arithmetic element (CPU), memory elements (RAM, ROM), various interfaces, etc., and is configured to perform calculations according to a predetermined program using input data and pre-stored data, and to output the results of the calculations as signals for control.

[0018] 2 is a block diagram illustrating the functional configuration of controller 30. First, examples of input data include the pressure inside intake manifold 18 detected by pressure sensor 27, the pressure in hose 26 (return passage) detected by PCV pressure sensor 28, the air-fuel ratio of exhaust gas detected by air-fuel ratio sensor 29, and engine speed (rpm) detected by engine speed sensor 31. Further, examples of pre-stored data include a threshold value for determining whether the intake air amount has exceeded a prerequisite amount for determining an abnormality such as a hole in hose 26 (a so-called PCV abnormality), a threshold value for determining whether the time or number of times the intake air amount has increased has reached the number of times to start determination, and a threshold value for determining whether the normality or abnormality is determined based on a determination parameter.

[0019] The controller 30 includes an intake air amount calculation unit 30A that calculates the amount of air taken into the engine 1 using the pressure inside the intake manifold 18 detected by the pressure sensor 27, the engine speed detected by the engine speed sensor 31, and the air-fuel ratio of the exhaust gas detected by the air-fuel ratio sensor 29. The intake air amount calculation unit 30A calculates the intake air amount by, for example, estimating the air flow rate based on the engine speed, calculating the intake air amount based on the estimated value and the pressure, and then correcting the calculated value by the air-fuel ratio to determine the final intake air amount. The controller 30 also includes an intake air amount determination unit 30B that determines whether the intake air amount thus determined has increased to a level at which a PCV abnormality determination is performed. Because a certain amount of intake air amount is required to determine a PCV abnormality, the controller 30 is configured to determine whether the intake air amount is equal to or greater than a predetermined threshold value as a prerequisite for the determination. In other words, the intake air amount for determining a PCV abnormality is determined based on the pressure in the intake manifold 18, the engine speed, and the air-fuel ratio.

[0020] The controller 30 is provided with a determination parameter calculation unit 30C that calculates a determination parameter based on fluctuations in the PCV pressure detected by the PCV pressure sensor 28 when the intake air amount exceeds a predetermined threshold and increases. The determination parameter can be an appropriate parameter based on fluctuations in the PCV pressure, such as the time period during which the PCV pressure fluctuates or the number of times the PCV pressure fluctuates. For example, the parameter can be the cumulative integral value of the amount of fluctuation in the PCV pressure when fluctuations in the PCV pressure continue for a predetermined period of time when the intake air amount exceeds a predetermined threshold and increases.

[0021] The controller 30 is provided with a determination unit 30D that determines whether the system is normal or abnormal based on the determination parameter thus obtained. If the hose 26 is closed to the outside (atmosphere) because no abnormality such as a hole has occurred, fluctuations in the intake air volume directly affect the PCV pressure, and the determination parameter based on fluctuations in the PCV pressure gradually increases. In contrast, if the hose 26 has an abnormality such as a hole and is connected to the outside air, outside air flows in and out of the hose 26, and fluctuations in the PCV pressure relative to fluctuations in the intake air volume become slower or smaller. Therefore, the determination parameter is less likely to increase and remains at a small value. The determination unit 30D determines whether the system is normal or abnormal by comparing the determination parameter thus changing with, for example, a predetermined threshold value. The determination result thus obtained is output as a signal for, for example, on-board diagnostics (OBD).

[0022] An example of the PCV abnormality detection control by the controller 30 will be described with reference to the time chart shown in Fig. 3. In this example, a vehicle equipped with the engine 1 described above starts moving from a stopped state, and an upshift occurs as the vehicle speed increases, or the accelerator pedal is temporarily released, causing the engine speed to temporarily decrease as it increases, and then the vehicle speed and engine speed increase again.

[0023] Such changes in vehicle speed are shown in Figure 3(a), and when the accelerator pedal (not shown) is depressed at time t1, the amount of intake air into engine 1 gradually increases, as shown in Figure 3(b), and the output torque of engine 1 increases accordingly, causing the vehicle to start moving and the vehicle speed to gradually increase. Furthermore, the intake air amount increases due to the increased throttle opening, and the PCV pressure also decreases accordingly. If there is no PCV abnormality, such as a hole in hose 26, i.e., if the PCV is in a normal state, the PCV pressure will decrease significantly in response to the increase in the amount of intake air, as shown by line A in Figure 3(d).

[0024] Such increases in intake air volume and decreases in PCV pressure are calculated as the number of calculations. An example is shown in Figure 3(c), where an increase in intake air volume and a decrease in PCV pressure that continues for a predetermined period of time is counted as "1 occurrence," and an integrated value is calculated. This integration is also performed when the intake air volume is increasing beyond a predetermined threshold. The PCV pressure is integrated for each count while the intake air volume is increasing beyond the predetermined threshold, and this integrated value is used as the determination parameter (detection parameter).

[0025] In the example shown in Figure 3, the accumulation of the judgment parameter begins at time t2 when the intake air volume exceeds a predetermined threshold (shown by the dashed line in Figure 3(b)), and continues until time t3 when the increase in intake air volume stops. Similarly, if the intake air volume starts to increase again, accumulation of the judgment parameter begins again at time t4 when the intake air volume exceeds the predetermined threshold and continues until time t5 when the increase in intake air volume stops. During this process, when the count value shown in Figure 3(c) (count value of the increase in intake air volume) reaches the predetermined threshold shown by the dashed line in Figure 3(c), a normal / abnormal judgment is made using the judgment parameter as the result of the accumulation.

[0026] When the hose 26 and other components are normal and the PCV pressure changes as shown by line A in (d) of Figure 3, the fluctuation in the PCV pressure is large, so the determination parameter reaches a large value early, as shown by line G in (e) of Figure 3. Therefore, at time t5, the determination parameter exceeds the determination threshold. Therefore, in this case, a "normal" determination is made.

[0027] On the other hand, if the hose 26 is disconnected or has a hole or other abnormality, the negative intake pressure of the engine 1 will draw outside air into the hose 26, reducing the fluctuation (decrease) in the PCV pressure as shown by line B in FIG. 3(d). As a result, the integrated value during the period in which the intake air amount exceeds a predetermined threshold and increases, i.e., the period in which the determination parameter is integrated, will remain small as shown by line F in FIG. 3(e), and the value of the determination parameter will be below the determination threshold even at time t5 when the normal / abnormal determination is made. Therefore, in this case, an "abnormal" determination will be made.

[0028] In conclusion, in this embodiment of the present invention, because an abnormality in the blow-by gas recirculation system does not particularly affect the intake air volume, an abnormality (PCV abnormality) such as a hole or disconnection in the hose 26 (the blow-by gas recirculation path) can be accurately detected. In particular, because the intake air volume is calculated based on the pressure inside the intake manifold 18, the engine speed, and the air-fuel ratio of the exhaust gas, there is no significant difference in the calculated (detected) intake air volume between when the PCV is normal and when the PCV is abnormal. In other words, compared to determining the intake air volume using an air flow meter installed on the air filter side, the intake air volume is not detected as being lower than the actual amount. As a result, a state in which the intake air volume exceeds a predetermined threshold and fluctuates can be reliably detected to determine the determination parameter. Therefore, a PCV abnormality can be accurately and quickly determined without missing an opportunity to determine the PCV abnormality.

[0029] The present invention can be implemented by making appropriate modifications other than the above-described embodiment. For example, the return path may be configured by a metal pipe instead of a hose. Furthermore, the above-described separators 22, 25 may be part of the storage section, and may be configured to separate part of the interior of the head cover, rather than being configured to be attached to the outside of the head cover. In short, the present invention is not limited to the above-described embodiment, and can be implemented by making appropriate modifications within the scope of the purpose or gist of the present invention. [Explanation of symbols]

[0030] 1 engine 2 cylinders 3 pistons 4 crankcase 5 crankshaft 6 Combustion chamber 7 Intake port 8 exhaust port 9. Turbocharger 10 Compressor 11 Turbine 12 Intake port 13 Air flow meter 14 Air filter 15 Outlet 16 Air Cooler 17 Throttle valve 18 Intake manifold 19 Cylinder block 20 Headcover 21 Communication section 22 Separator 23 Conduit 24 PCV valve 25 Separator 26 Hose 27 Pressure Sensor 28 PCV pressure sensor 29 Air-fuel ratio sensor 30 Controllers 30A Intake air volume calculation section 30B Intake air volume determination unit 30C Judgment parameter calculation unit 30D Judgment section 31 Engine RPM Sensor

Claims

[Claim 1] An abnormality detection device for an engine, which sends blow-by gas from a storage section to an intake side of a turbocharger through a return passage, calculates a judgment parameter based on a pressure in the storage section in a state in which an intake air amount is equal to or greater than a predetermined value, and judges an abnormality in the return passage based on the judgment parameter, an intake air amount calculation unit that calculates the intake air amount when determining the judgment parameter based on the intake pipe pressure of the engine, the engine rotation speed, and the air-fuel ratio in exhaust gas generated by combustion in the engine; An engine abnormality detection device characterized by:

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