In-cylinder pressure estimation device for internal combustion engine

Abstract

The present application provides an in-cylinder pressure estimation device of an internal combustion engine. The present application aims to improve the estimation accuracy of the maximum in-cylinder pressure. A control device functioning as an in-cylinder pressure estimation device of an engine performs an early combustion determination process that determines whether early combustion has occurred in a cylinder. The control device performs an in-cylinder pressure estimation process that estimates the maximum in-cylinder pressure in the case where early combustion is determined to have occurred in the cylinder in the early combustion determination process. The control device estimates the maximum in-cylinder pressure in the in-cylinder pressure estimation process based on the engine speed, the engine load factor, and an angular velocity variation ratio. The angular velocity variation ratio is a quotient obtained by dividing the reduction amount of the crank angle speed in a second interval that is a portion of a first interval that is an interval spanning a compression stroke and a combustion stroke after the compression stroke by the reduction amount of the crank angle speed in the first interval.

Description

Technical Field

[0001] This invention relates to a cylinder pressure estimation device for an internal combustion engine. Background Technology

[0002] Patent Document 1 discloses an abnormal combustion detection device for an internal combustion engine, which determines whether knocking or pre-ignition has occurred based on the output of a vibration sensor that detects vibrations in the cylinder block. This abnormal combustion detection device determines the type of abnormal combustion based on the peak value of the amplitude of the abnormal combustion signal output from the vibration sensor and the crankshaft angle (CA) at which the peak value is generated, i.e., the peak angle.

[0003] The aforementioned abnormal combustion detection device determines that pre-ignition has occurred rather than detonation when the peak value exceeds the pre-ignition determination threshold. In the overlapping interval between the detonation detection interval and the pre-ignition detection interval, the pre-ignition determination threshold is set to a value greater than the maximum peak value expected when detonation occurs.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2013-160200 Summary of the Invention

[0005] The higher the engine speed, the higher the maximum in-cylinder pressure at which pre-ignition occurs. The higher the engine load, the higher the maximum in-cylinder pressure at which pre-ignition occurs. Therefore, the maximum in-cylinder pressure at which pre-ignition occurs can be estimated based on engine speed and engine load. However, there is still room for improvement in estimating the maximum in-cylinder pressure at which pre-ignition occurs.

[0006] According to one aspect of the present invention, an in-cylinder pressure estimation device for an internal combustion engine is provided, the internal combustion engine having a cylinder, wherein the in-cylinder pressure estimation device for the internal combustion engine includes a processing circuit configured to perform: a pre-ignition determination process to determine whether pre-ignition has occurred in the cylinder; and an in-cylinder pressure estimation process, wherein if the pre-ignition determination process determines that pre-ignition has occurred in the cylinder, the maximum in-cylinder pressure in the cylinder is estimated, wherein the processing circuit is configured to estimate the maximum in-cylinder pressure based on engine speed, engine load rate, and a quotient obtained by dividing the decrease in crankshaft angular velocity of a second interval (a portion of a first interval spanning the compression stroke and the combustion stroke following the compression stroke) by the decrease in crankshaft angular velocity of the first interval, i.e., an angular velocity variation ratio.

[0007] Invention Effects

[0008] Based on the above structure, the processing circuit estimates the maximum cylinder pressure according to engine speed, engine load rate, and angular velocity variation ratio. Therefore, compared with a structure that estimates the maximum cylinder pressure based solely on engine speed and engine load rate, the estimation accuracy of the maximum cylinder pressure can be improved. Attached Figure Description

[0009] Figure 1 This diagram illustrates the control device that functions as the cylinder pressure estimation device of the internal combustion engine according to the first embodiment.

[0010] Figure 2 It means Figure 1 The flowchart shows the process performed by the control device.

[0011] Figure 3 (a) is a graph showing the change in crankshaft angular velocity when the crankshaft angle is B110 and pre-ignition occurs. Figure 3 (b) is a graph showing the change in crankshaft angular velocity when the crankshaft angle is B70 and pre-ignition occurs.

[0012] Figure 4 This is a graph illustrating an example of the relationship between the angular velocity variation ratio and the maximum cylinder pressure.

[0013] Figure 5 This is a diagram used to illustrate the cylinder pressure estimation device for the internal combustion engine according to the second embodiment. Figure 5 (a) is a graph showing the change in crankshaft angular velocity when the crankshaft angle is B110 and pre-ignition occurs. Figure 5 (b) is a graph showing the change in crankshaft angular velocity when the crankshaft angle is B70 and pre-ignition occurs.

[0014] Figure 6 This is a graph illustrating an example of the relationship between the angular velocity variation ratio and the maximum cylinder pressure involved in the second embodiment. Detailed Implementation

[0015] (First Embodiment)

[0016] Hereinafter, the cylinder pressure estimation device of the internal combustion engine according to the first embodiment will be described with reference to the accompanying drawings.

[0017] <Structure of Engine 10>

[0018] First, refer to Figure 1 The structure of engine 10 will be described. In this embodiment, engine 10 is an internal combustion engine that uses hydrogen as fuel. Engine 10 may also be an internal combustion engine that uses gasoline as fuel. Engine 10 has a plurality of cylinders 11. None of the plurality of cylinders 11 has a cylinder pressure sensor. Figure 1Only one of the multiple cylinders 11 is shown in the diagram. Combustion of the air-fuel mixture occurs in each of the multiple cylinders 11. The engine 10 includes an intake passage 12 that serves as an intake path for introducing intake air into the cylinders 11 and an exhaust passage 13 that serves as an exhaust path for discharging exhaust gas from the cylinders 11. Furthermore, the engine 10 includes a cylinder injector 14 that injects fuel into the cylinders 11 to form an air-fuel mixture. The cylinder injector 14 is configured to open the fuel passage by rising inward through a valve body. That is, the cylinder injector 14 is an inward-opening valve type injector. The engine 10 also includes an ignition device 15 that ignites the air-fuel mixture in the cylinders 11 by spark discharge. A throttle valve 16 is provided in the portion of the intake passage 12 downstream of the compressor impeller 21. By changing the opening degree of the throttle valve 16, the amount of intake air introduced into the cylinders 11 can be adjusted. The engine 10 generates driving force for the vehicle by rotating the crankshaft 17 through combustion of the air-fuel mixture in the cylinders 11.

[0019] Engine 10 includes a turbocharger 20. The turbocharger 20 has a compressor impeller 21 located in the intake passage 12 and a turbine impeller 22 located in the exhaust passage 13. The compressor impeller 21 and the turbine impeller 22 are connected via a turbine shaft 23. A bypass passage 24 is provided in the exhaust passage 13 to allow exhaust gas to flow downstream, bypassing the turbine impeller 22. A catalyst device 39, containing a catalyst carrier 19 carrying an exhaust gas purification catalyst, is provided downstream of the confluence of the bypass passage 24 and the exhaust passage 13. An exhaust gas valve 25 is provided in the exhaust passage 13 to open and close the outlet of the bypass passage 24. An exhaust gas temperature sensor 18 for detecting exhaust gas temperature is provided in the exhaust passage 13.

[0020] <Structure of Control Device 30>

[0021] Engine 10 is controlled by control unit 30. Control unit 30 also functions as a cylinder pressure estimation device. Control unit 30 includes a control unit 31 and a read-only memory (ROM) 32. Control unit 31 includes a central processing unit (CPU) and random access memory (RAM). The ROM 32 stores programs and data for controlling engine 10. Control unit 31 controls engine 10 by reading and executing programs from ROM 32.

[0022] The control device 30 receives the detection results from various sensors used to detect the operating status of the engine 10. These sensors include an air flow meter 33, a vehicle speed sensor 34, a throttle position sensor 35, a crankshaft angle sensor 36, a boost pressure sensor 37, a vibration sensor 38, and an exhaust temperature sensor 18.

[0023] Air flow meter 33 is a sensor that detects the intake air volume as the flow rate of intake air flowing through intake passage 12. In this embodiment, air flow meter 33 is located upstream of compressor impeller 21 in intake passage 12. Vehicle speed sensor 34 is a sensor that detects the speed of the vehicle. Control device 30 can calculate engine load rate based on the detection value from air flow meter 33. Engine load rate represents the ratio of the current cylinder air inflow at the current engine speed to the cylinder air inflow when the engine 10 is running stably with throttle valve 16 fully open. In addition, cylinder air inflow is the amount of air that flows into each of the plurality of cylinders 11 during the intake stroke.

[0024] Throttle position sensor 35 is a sensor that detects the amount of accelerator pedal depressed. Crank angle sensor 36 is a sensor that detects the crankshaft angle, which is the rotation angle of crankshaft 17. Boost pressure sensor 37 is a sensor that detects the boost pressure, which is the intake air pressure, in the portion of the intake passage 12 that is downstream of compressor impeller 21 and upstream of throttle valve 16. Vibration sensor 38 is used to detect vibration of engine 10. The control unit 31 of control device 30 can determine whether pre-ignition has occurred based on the vibration detected by vibration sensor 38. The control unit 31 controls the fuel injection quantity and timing of cylinder injector 14, the ignition timing of ignition device 15, throttle opening, etc., based on the detection results of these sensors.

[0025] <Processing performed by control device 30>

[0026] refer to Figures 2-4 The processing performed by the control device 30 will be explained. The control device 30 begins upon the start of the engine 10. Figure 2 The control device 30 repeatedly executes the processing during the operation of the engine 10. Figure 2 The processing.

[0027] In step S200, control device 30 determines whether the crankshaft angle of each of the plurality of cylinders 11 falls within the pre-ignition detection range. For one cylinder 11, the pre-ignition detection range is, for example, the range from 150° before top dead center (BTDC) to top dead center (TDC). Here, top dead center refers to the crankshaft angle at the boundary between the compression stroke and the combustion stroke when the piston reaches its highest position in cylinder 11. If control device 30 makes a negative determination in step S200 (S200: NO), the process ends. Figure 2 The process is as follows. If the control device 30 makes a positive determination in step S200 (S200: YES), it proceeds to step S202.

[0028] In step S202, the control device 30 performs a pre-ignition determination process to determine whether pre-ignition has occurred in the cylinder 11. As described above, the control device 30 can determine whether pre-ignition has occurred based on vibration detected by the vibration sensor 38. For example, the control device 30 can determine whether pre-ignition has occurred based on the amplitude of the vibration detected by the vibration sensor 38 being greater than a threshold. Alternatively, the control device 30 can determine whether pre-ignition has occurred based on changes in the crankshaft angular velocity.

[0029] After step S202, the control device 30 proceeds to step S204. In step S204, the control device 30 performs cylinder pressure estimation processing to estimate the maximum cylinder pressure in cylinder 11. Based on steps S202 and S204, the control device 30 determines in the pre-ignition determination process that pre-ignition has occurred in cylinder 11 and performs cylinder pressure estimation processing.

[0030] In the cylinder pressure estimation process, the control device 30 estimates the maximum cylinder pressure based on engine speed, engine load rate, and angular velocity variation ratio. In this embodiment, the control device 30 uses a three-dimensional graph that establishes a corresponding relationship between the combination of engine speed, engine load rate, and angular velocity variation ratio and the maximum cylinder pressure to estimate the maximum cylinder pressure. The estimated maximum cylinder pressure tends to be higher the higher the engine speed, higher the engine load rate, and higher the angular velocity variation ratio.

[0031] Engine load rate represents the ratio of the current cylinder airflow at the current engine speed to the cylinder airflow when the engine 10 is running stably with the throttle valve 16 fully open. The angular velocity variation ratio is the quotient obtained by dividing the decrease in crankshaft angular velocity in the second interval (a portion of the first interval spanning the compression stroke and the subsequent combustion stroke) by the decrease in crankshaft angular velocity in the first interval. In the first embodiment, the second interval is the interval included in the compression stroke.

[0032] like Figure 3 As shown, the first interval is from B60 to A30. The first interval spans the compression stroke (180°BTDC~TDC) and the subsequent combustion stroke (TDC~180°ATDC). The second interval is from B60 to B30. Figure 3 In this context, X°BTDC (0 < X ​​< 720) is recorded as BX. Furthermore, in... Figure 3In this code, X°ATDC (0 < X ​​< 720) is denoted as AX. ATDC is an abbreviation for after top dead center. The crankshaft angular velocity at an angle of X° is denoted as ω(X). The ratio of angular velocity variation is {ω(B60) - ω(B30)} ÷ {ω(B60) - ω(A30)}.

[0033] Figure 4 This is a graph illustrating the relationship between the ratio of angular velocity variation and maximum cylinder pressure when engine speed and engine load rate are set constant. For example... Figure 4 As shown, the higher the angular velocity variation ratio, the higher the estimated maximum cylinder pressure.

[0034] After step S204, control device 30 proceeds to step S206. In step S206, control device 30 performs damage estimation processing. This damage estimation processing is based on the maximum in-cylinder pressure estimated in step S204. Damage estimation processing, for example, is a process of estimating the magnitude of damage caused by combustion gases flowing into the in-cylinder injector 14. For example, in the damage estimation processing, if the estimated maximum in-cylinder pressure is greater than a threshold, control device 30 performs fuel cut-off. Instead, the higher the estimated maximum in-cylinder pressure, the more the control device 30 can reduce the amount of fuel injected into cylinder 11. After ending step S206, control device 30 terminates... Figure 2 The process.

[0035] <Function of the first implementation method>

[0036] Figure 3 (a) is a graph showing the change in crankshaft angular velocity when the crankshaft angle is B110 and pre-ignition occurs. Figure 3 (b) is a graph showing the change in crankshaft angular velocity when the crankshaft angle is B70 and pre-ignition occurs. Engine speed and engine load are constant for all of these conditions. The earlier the pre-ignition occurs, the more likely a decrease in crankshaft angular velocity will occur in the early stages.

[0037] As mentioned above, the angular velocity variation ratio is the quotient obtained by dividing the decrease in crankshaft angular velocity in the second interval by the decrease in crankshaft angular velocity in the first interval. Specifically, the angular velocity variation ratio is {ω(B60) - ω(B30)} ÷ {ω(B60) - ω(A30)}.

[0038] exist Figure 3 In the example shown, the angular velocity variation ratio when pre-ignition occurs at B110 is higher than that when pre-ignition occurs at B70. Figure 4 As shown, the higher the angular velocity variation ratio, the higher the estimated maximum cylinder pressure. Therefore, regarding Figure 3(a) The estimated maximum in-cylinder pressure is higher than that for Figure 3 (b) Estimated maximum cylinder pressure.

[0039] <Effects of the first implementation method>

[0040] (1-1) The control device 30, which functions as an in-cylinder pressure estimation device for the engine 10 having cylinder 11, performs a pre-ignition determination process (S202) to determine whether pre-ignition has occurred in cylinder 11. If the control device 30 determines in the pre-ignition determination process that pre-ignition has occurred in cylinder 11, it performs an in-cylinder pressure estimation process (S204) to estimate the maximum in-cylinder pressure in cylinder 11. In the in-cylinder pressure estimation process, the control device 30 estimates the maximum in-cylinder pressure based on engine speed, engine load rate, and angular velocity variation ratio. The angular velocity variation ratio is the quotient obtained by dividing the decrease in crankshaft angular velocity in the second interval (a portion of the first interval spanning the compression stroke and the combustion stroke following the compression stroke) by the decrease in crankshaft angular velocity in the first interval.

[0041] There is a tendency for the maximum cylinder pressure to be higher the earlier pre-ignition occurs. The reason for this tendency will now be explained. As pre-ignition occurs earlier, the combustion period before the original ignition timing becomes longer. This is because more energy is generated by combustion caused by pre-ignition, thus increasing the maximum cylinder pressure. Therefore, there is a tendency for the maximum cylinder pressure to be higher the earlier pre-ignition occurs.

[0042] There is a tendency for the crankshaft angular velocity to decrease earlier in the first interval as pre-ignition occurs. The angular velocity variation ratio is correlated with the timing of the crankshaft angular velocity decrease in the first interval. Therefore, the maximum in-cylinder pressure is correlated with the angular velocity variation ratio.

[0043] Based on the above structure, the control device 30 estimates the maximum cylinder pressure based on engine speed, engine load rate, and angular velocity variation ratio. Therefore, compared with a structure that estimates the maximum cylinder pressure based solely on engine speed and engine load rate, the estimation accuracy of the maximum cylinder pressure can be improved.

[0044] (1-2) The second interval is the interval included in the compression stroke. The higher the angular velocity variation ratio, the higher the estimated maximum in-cylinder pressure. There is a tendency for pre-ignition to occur earlier, and for the crankshaft angular velocity to decrease earlier due to pre-ignition. The earlier the crankshaft angular velocity decreases, the higher the angular velocity variation ratio is when the second interval is the interval included in the compression stroke.

[0045] Therefore, the higher the angular velocity variation ratio, the higher the maximum cylinder pressure. Based on the above structure, this tendency can be reflected in the estimation of the maximum cylinder pressure. (1-3) The control device 30 is configured to estimate the maximum cylinder pressure using a three-dimensional graph that establishes a corresponding relationship between the combination of engine speed, engine load rate, and angular velocity variation ratio and the maximum cylinder pressure.

[0046] Compared to the structure that estimates the maximum cylinder pressure by correcting the temporary maximum cylinder pressure calculated based on engine speed and engine load rate according to the angular velocity variation ratio, the process of estimating the maximum cylinder pressure is simpler.

[0047] (1-4) In the first embodiment, the angular velocity variation ratio is {ω(B60) - ω(B30)} ÷ {ω(B60) - ω(A30)}. This means that, compared to the second embodiment described later, where the angular velocity variation ratio is {ω(TDC) - ω(A30)} ÷ {ω(B60) - ω(A30)}, it is easier to capture pre-ignition occurring earlier. Therefore, in the first embodiment, the estimation accuracy of the maximum in-cylinder pressure related to pre-ignition occurring earlier is high.

[0048] (Second Implementation)

[0049] In particular, refer to Figure 5 and Figure 6 The cylinder pressure estimation device for an internal combustion engine according to the second embodiment will be described below. Hereinafter, descriptions of structures common to both the second and first embodiments will be omitted. In the first embodiment, the second interval is the interval included in the compression stroke; in contrast, in the second embodiment, the second interval is the interval included in the combustion stroke. Consequently, in the first embodiment, the higher the angular velocity variation ratio, the higher the estimated maximum cylinder pressure; in contrast, in the second embodiment, the lower the angular velocity variation ratio, the higher the estimated maximum cylinder pressure.

[0050] like Figure 5 As shown, the first interval is from B60 to A30. The second interval is from TDC to A30. As mentioned above, the angular velocity variation ratio is the quotient obtained by dividing the decrease in crankshaft angular velocity in the second interval by the decrease in crankshaft angular velocity in the first interval. Specifically, the angular velocity variation ratio is {ω(TDC) - ω(A30)} ÷ {ω(B60) - ω(A30)}.

[0051] like Figure 6 As shown, the lower the angular velocity variation ratio, the higher the estimated maximum cylinder pressure.

[0052] <Function of the second implementation method>

[0053] Figure 5(a) is a graph showing the change in crankshaft angular velocity when the crankshaft angle is B110 and pre-ignition occurs. Figure 5 (b) is a graph showing the change in crankshaft angular velocity when the crankshaft angle is B70 and pre-ignition occurs. Engine speed and engine load are constant for all of these conditions. The earlier the pre-ignition occurs, the more likely a decrease in crankshaft angular velocity will occur in the early stages.

[0054] As mentioned above, the angular velocity variation ratio is the quotient obtained by dividing the decrease in crankshaft angular velocity in the second interval by the decrease in crankshaft angular velocity in the first interval. Specifically, the angular velocity variation ratio is {ω(TDC) - ω(A30)} ÷ {ω(B60) - ω(A30)}.

[0055] exist Figure 5 In the example shown, the angular velocity change ratio when pre-ignition occurs at B110 is lower than that when pre-ignition occurs at B70. Figure 6 As shown, the lower the angular velocity variation ratio, the higher the estimated maximum cylinder pressure. Therefore, regarding Figure 5 (a) The estimated maximum in-cylinder pressure is higher than that for Figure 5 (b) Estimated maximum cylinder pressure.

[0056] <Effects of the second implementation method>

[0057] (2-1) The second interval is the interval included in the combustion stroke. The lower the angular velocity variation ratio, the higher the estimated maximum cylinder pressure.

[0058] There is a tendency that the earlier pre-ignition occurs, the earlier the crankshaft angular velocity decreases due to pre-ignition. The earlier the crankshaft angular velocity decreases, the lower the angular velocity variation ratio is when the second interval is included in the combustion stroke.

[0059] Therefore, the lower the angular velocity variation ratio, the higher the maximum cylinder pressure. Based on the above structure, this tendency can be reflected in the estimation of the maximum cylinder pressure.

[0060] (2-2) In the second embodiment, the angular velocity variation ratio is {ω(TDC) - ω(A30)} ÷ {ω(B60) - ω(A30)}. This means that, compared to the first embodiment where the angular velocity variation ratio is {ω(B60) - ω(B30)} ÷ {ω(B60) - ω(A30)}, it is easier to capture pre-ignition that occurs later. Therefore, in the second embodiment, the estimation accuracy of the maximum in-cylinder pressure related to pre-ignition that occurs later is high.

[0061] (Example of amendment)

[0062] The following elements are included as factors that allow for modifications to the first and second embodiments described above. The following modification examples can be implemented in combination without technical inconsistencies.

[0063] • Regarding the first and second embodiments described above, steps S200 and / or S206 can be omitted.

[0064] Regarding the first and second embodiments described above, the specific ranges of the first and second intervals can be appropriately changed.

[0065] In the first and second embodiments described above, the control device 30 estimates the maximum cylinder pressure using a three-dimensional graph that establishes a corresponding relationship between the combination of engine speed, engine load rate, and angular velocity variation ratio and the maximum cylinder pressure. However, this is merely an example. For instance, the control device 30 may estimate the maximum cylinder pressure by correcting the temporary maximum cylinder pressure calculated based on the engine speed and engine load rate according to the angular velocity variation ratio.

[0066] In the first and second embodiments described above, the control device 30 performs software processing. However, this is merely an example. For instance, the control device 30 may include dedicated hardware circuitry for processing at least a portion of the software processing performed in the above embodiments. The dedicated hardware circuitry may be, for example, an Application Specific Integrated Circuit (ASIC). That is, the control device 30 may have any of the following structures: (a) The control device 30 includes a processing device that executes all processing according to a program and a program storage device such as a ROM that stores the program. That is, the control device 30 includes a software execution device. (b) The control device 30 includes a processing device that executes a portion of the processing according to a program and a program storage device. Furthermore, the control device 30 includes dedicated hardware circuitry for executing the remaining processing. (c) The control device 30 includes dedicated hardware circuitry for executing all processing. Here, there may be multiple software execution devices and / or dedicated hardware circuitry. That is, the above processing can be executed by a processing circuitry that includes at least one of a software execution device and dedicated hardware circuitry. There may be multiple software execution devices and dedicated hardware circuitry included in the processing circuitry. Program storage devices, also known as computer-readable media, include storage devices of any available medium that can be accessed by a general-purpose or special-purpose computer.

[0067] Symbol Explanation

[0068] 10- Engine (internal combustion engine), 11- Cylinder, 30- Control device (cylinder pressure estimation device).

Claims

1. A cylinder pressure estimation device for an internal combustion engine, the internal combustion engine having cylinders, characterized in that, It includes a processing circuit, which is configured to execute: Pre-ignition detection processing determines whether pre-ignition has occurred in the cylinder; and The cylinder pressure estimation process estimates the maximum cylinder pressure when pre-ignition is determined to have occurred in the cylinder during the pre-ignition detection process. The processing circuit is configured to estimate the maximum cylinder pressure in the cylinder pressure estimation process based on the engine speed, engine load rate, and the angular velocity variation ratio, which is the quotient obtained by dividing the decrease in crankshaft angular velocity of the second interval (a portion of the first interval spanning the compression stroke and the combustion stroke following the compression stroke) by the decrease in crankshaft angular velocity of the first interval.

2. The cylinder pressure estimation device for an internal combustion engine according to claim 1, characterized in that, The second interval is the interval included in the compression stroke, and the higher the angular velocity variation ratio, the higher the estimated maximum cylinder pressure.

3. The cylinder pressure estimation device for an internal combustion engine according to claim 1, characterized in that, The second interval is the interval included in the combustion stroke, and the lower the angular velocity variation ratio, the higher the estimated maximum in-cylinder pressure.

4. The cylinder pressure estimation device for an internal combustion engine according to any one of claims 1 to 3, characterized in that, The processing circuit is configured to estimate the maximum cylinder pressure using a three-dimensional graph that establishes a corresponding relationship between the combination of the engine speed, the engine load rate, and the angular velocity variation ratio and the maximum cylinder pressure.

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