Pre-ignition detection device for internal combustion engines

Abstract

To appropriately determine occurrence of preignition even when vibration caused by the preignition is small.SOLUTION: A control device 100 determines occurrence of preignition on the basis of an output value obtained by a knocking sensor 48 provided in an internal combustion engine 1 that uses hydrogen as fuel. The control device 100 executes integration processing for calculating an integrated value of the output value obtained by the knocking sensor 48 in a specified period before ignition timing of an air-fuel mixture and determination processing for determining occurrence of preignition on the basis of the integrated value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a preignition determination device for an internal combustion engine.

Background Art

[0002] For example, in the internal combustion engine described in Patent Document 1, the occurrence of preignition is determined by comparing the peak value of the output value of a vibration sensor provided in the internal combustion engine with a predetermined threshold value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an internal combustion engine using hydrogen as fuel, there are cases where the vibration generated when preignition occurs is small. Therefore, it may be difficult to determine the occurrence of preignition based on the peak value of the output value of the vibration sensor.

Means for Solving the Problems

[0005] The preignition determination device for an internal combustion engine that solves the above problems is a device that determines the occurrence of preignition based on the output value of a vibration sensor provided in an internal combustion engine using hydrogen as fuel. This preignition determination device executes an integration process for calculating an integrated value of the output value within a predetermined period before the ignition timing of the air-fuel mixture, and a determination process for determining the occurrence of preignition based on the integrated value.

Effects of the Invention

[0006] This internal combustion engine pre-ignition detection device can appropriately detect the occurrence of pre-ignition even when it is a low-vibration pre-ignition. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic diagram of an internal combustion engine in one embodiment. [Figure 2] Figure 2 shows the configuration of the signal processing circuit. [Figure 3] Figure 3 is a flowchart showing the steps of the process performed by the control device. [Figure 4] Figure 4 is a flowchart showing the procedure of processing performed by the control device in a modified example of the same embodiment. [Modes for carrying out the invention]

[0008] An embodiment of a pre-ignition determination device for an internal combustion engine will be described below with reference to Figures 1 to 3. <Configuration of an internal combustion engine> As shown in Figure 1, the cylinder block 2 of the internal combustion engine 1 is provided with a cylinder 4. A piston 5 is provided inside the cylinder 4, and the piston 5 is connected to the crankshaft 7 via a connecting rod 6.

[0009] A cylinder head 3 is assembled to the top of the cylinder block 2. In the cylinder 4, a combustion chamber 8 is formed between the top surface of the piston 5 and the cylinder head 3. The cylinder head 3 is also equipped with an in-cylinder injection valve 35 for directly injecting hydrogen gas, which is the fuel for the internal combustion engine 1, into the cylinder, and a spark plug 11 for igniting the fuel mixture in the combustion chamber 8, for each cylinder of the internal combustion engine 1.

[0010] Furthermore, the cylinder head 3 is provided with an intake port 9 and an exhaust port 10 connected to the combustion chamber 8. The intake port 9 constitutes part of the intake passage through which intake air flows. The intake port 9 is connected to an intake passage 20, which is equipped with a throttle valve 14 for adjusting the amount of intake air. The intake port 9 is also provided with an intake valve 12 for opening and closing the intake port 9.

[0011] The exhaust port 10 is provided with an exhaust valve 13 that opens and closes the exhaust port 10. The exhaust port 10 is connected to the exhaust passage 30. <About the control device> The control device 100 includes a CPU 110, a memory 120 that stores control programs and data, a signal processing circuit 200, and the like. The CPU 110 executes the programs stored in the memory 120 to perform various engine control functions.

[0012] Various sensors are connected to the control device 100. For example, the control device 100 is connected to a crank angle sensor 41 that detects the rotation angle of the crankshaft 7, an air flow meter 44 that detects the intake air volume GA, and a water temperature sensor 45 that detects the coolant temperature TW of the internal combustion engine 1. The control device 100 is also connected to a knocking sensor 48, which is a vibration sensor that outputs an output signal KN according to the magnitude of the vibration of the cylinder 4, and an accelerator sensor 49 that detects the accelerator pedal operation amount ACCP.

[0013] The control device 100 calculates the engine rotational speed NE based on the output signal Scr from the crank angle sensor 41. The control device 100 also calculates the engine load ratio KL based on the engine rotational speed NE and the intake air volume GA. The engine load ratio KL represents the ratio of the current cylinder inflow air volume to the cylinder inflow air volume when the internal combustion engine 1 is operated steadily with the throttle valve 14 fully open at the current engine rotational speed NE. The cylinder inflow air volume is the amount of air that flows into each cylinder during the intake stroke.

[0014] The control device 100 performs various engine controls, such as controlling the opening degree of the throttle valve 14, controlling the injection of fuel injected from the in-cylinder injection valve 35, and controlling the ignition of the ignition plug 11. Further, the control device 100 also functions as a pre-ignition determination device that determines the occurrence of pre-ignition.

[0015] <Regarding the determination of pre-ignition> The control device 100 functions as a pre-ignition determination device that determines the occurrence of pre-ignition.

[0016] Here, compared with gasoline, hydrogen has a wider range of flammable concentrations, can be ignited even when the air-fuel ratio of the air-fuel mixture is lean, and pre-ignition may occur immediately after fuel injection. And depending on the position of the heat source where pre-ignition occurs, that is, the ignition origin of pre-ignition, the vibration generated in the cylinder may be less than the vibration of pre-ignition generated in an internal combustion engine using gasoline as fuel. Therefore, in the present embodiment, it is possible to appropriately determine the occurrence of pre-ignition with less such vibration.

[0017] As shown in FIG. 2, the signal processing circuit 200 includes a filter circuit 210, a full-wave rectifier circuit 220, and an integration circuit 230. The filter circuit 210 acquires the output signal KN of the knocking sensor 48 and the output signal Scr of the crank angle sensor 41 at a predetermined sampling period. Then, by performing filter processing on the output signal KN within the detection period GP, a filtered signal KNF is generated.

[0018] The detection period GP is a predetermined period before the ignition timing of the air-fuel mixture and is a period represented by the crank angle. More specifically, it is a period that is less affected by the combustion in the cylinder that burned one cylinder before the cylinder to be determined this time, and includes the period near the time when the in-cylinder pressure becomes maximum at the time of pre-ignition. For example, the detection period GP can be set to a period from the start timing of fuel injection executed during the compression stroke to top dead center of compression. Further, the filter frequency set when performing the filter process is set in advance to an appropriate value in order to exclude vibrations at the time of seating of the intake valve 12 and the exhaust valve 13, vibrations generated when driving the in-cylinder injection valve 35, ignition noise of the ignition plug 11, and the like.

[0019] The full-wave rectifier circuit 220 generates an absolute value signal KNA obtained by absolute value conversion of the post-filter signal KNF. That is, the full-wave rectifier circuit 220 reverses the sign of the post-filter signal KNF that is a negative value among the post-filter signals KNF and converts it into a positive value.

[0020] The integration circuit 230 calculates an integrated value KNS obtained by integrating the absolute value signal KNA generated by the full-wave rectifier circuit 220. That is, the integration circuit 230 calculates an integrated value KNS that is a value obtained by integrating the absolute value of the post-filter signal KNF generated from the output signal KN within the detection period GP. The control device 100 executes a determination process for determining the occurrence of pre-ignition by comparing the integrated value KNS with a threshold value KNSref.

[0021] FIG. 3 shows the procedure of the pre-ignition determination process executed by the control device 100. The process shown in this FIG. 3 is realized by the CPU 110 executing a program stored in the memory 120. Further, the process shown in FIG. 3 is executed every time the integrated value KNS is calculated. Hereinafter, the step numbers of each process are represented by numbers with "S" added at the beginning.

[0022] When starting the series of processes shown in FIG. 3, the control device 100 acquires the calculated integrated value KNS (S100). Next, the control device 100 obtains a threshold value KNSref (S110). In the process of S110, the control device 100 obtains a threshold value KNSref set based on the engine operating state. That is, the control device 100 sets the threshold value KNSref based on the engine rotational speed NE and the engine load ratio KL. The engine rotational speed NE and engine load ratio KL referenced at this time are, for example, the instantaneous value of the engine rotational speed NE at a predetermined timing in the detection period GP and the instantaneous value of the engine load ratio KL at a predetermined timing in the detection period GP. Alternatively, the engine rotational speed NE and engine load ratio KL referenced at this time may be, for example, the average value of the engine rotational speed NE and the average value of the engine load ratio KL in the detection period GP.

[0023] The threshold KNSref is a value equivalent to the cumulative KNS value calculated during normal combustion when pre-ignition is not occurring. The magnitude of this threshold KNSref is set so that it is possible to accurately determine whether pre-ignition is occurring based on whether the cumulative KNS value is equal to or greater than the threshold KNSref.

[0024] Next, the control device 100 determines whether the accumulated value KNS is greater than or equal to the threshold KNSref (S120). If it is determined that the accumulated value KNS is greater than or equal to the threshold KNSref (S120: YES), the control device 100 determines that pre-ignition has occurred (S130). In other words, the control device 100 determines that pre-ignition occurred within the above detection period GP.

[0025] Then, if the process in S130 is executed, or if a negative determination is made in the process in S120, the control device 100 terminates this process. <Operation and Effects of This Embodiment> (1) An integration process is performed to calculate the integrated value KNS of the output signal KN of the knocking sensor 48 within the detection period GP prior to the ignition timing of the air-fuel mixture, and a determination process is performed to determine the occurrence of pre-ignition based on the integrated value KNS. In this determination process, the occurrence of pre-ignition is determined by comparing the integrated value KNS with a threshold value KNSref. In this way, the occurrence of pre-ignition is determined based on the integrated value KNS of the output signal KN of the knocking sensor 48. Therefore, compared to the case where the occurrence of pre-ignition is determined based on the peak value of the output signal KN of the knocking sensor 48, the difference between abnormal combustion in which pre-ignition occurs and normal combustion in which pre-ignition does not occur becomes clear. Accordingly, even in cases where pre-ignition with little vibration occurs, such as in the internal combustion engine 1 using hydrogen as fuel, the occurrence of pre-ignition can be appropriately determined.

[0026] (2) The threshold KNSref is a value set based on the engine operating state. The cumulative value KNS calculated during normal combustion when pre-ignition does not occur changes depending on the engine operating state. In this respect, according to this embodiment, since the threshold KNSref is set based on the engine operating state, the threshold KNSref can be set appropriately.

[0027] <Example of changes> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0028] The determination process in the above embodiment was a process that determined the occurrence of preignition by comparing the accumulated value KNS with the threshold KNSref. Alternatively, the accumulated value KNS calculated when preignition does not occur may be considered as the normal value. Then, as a determination process, a process may be executed that determines the occurrence of preignition by comparing the ratio of the calculated accumulated value KNS to the normal value with a predetermined threshold KNRref.

[0029] Figure 4 shows the processing steps for the determination process in this example of modification. When the series of processes shown in Figure 4 is started, the control device 100 acquires the calculated cumulative value KNS (S200). Next, the control device 100 acquires a reference value KNSb (S210). The reference value KNSb is the normal value described above. In the process of S210, the control device 100 acquires a reference value KNSb set based on the engine operating state. That is, the control device 100 sets the reference value KNSb based on the engine rotation speed NE and the engine load ratio KL. The engine rotation speed NE and engine load ratio KL referenced at this time are, for example, the instantaneous value of the engine rotation speed NE at a predetermined timing in the detection period GP and the instantaneous value of the engine load ratio KL at a predetermined timing in the detection period GP. Alternatively, the engine rotation speed NE and engine load ratio KL referenced at this time may also be, for example, the average value of the engine rotation speed NE and the average value of the engine load ratio KL in the detection period GP.

[0030] Next, the control device 100 determines whether the ratio of the integrated value KNS to the reference value KNSb is greater than or equal to the threshold KNRref (S220). The ratio of the integrated value KNS to the reference value KNSb is the value obtained by dividing the integrated value KNS by the reference value KNSb. The magnitude of the threshold KNRref is predetermined so that it can accurately determine whether a pre-ignition has occurred based on whether the ratio of the integrated value KNS to the reference value KNSb is greater than or equal to the threshold KNRref.

[0031] Then, if the ratio of the cumulative value KNS to the reference value KNSb is determined to be greater than or equal to the threshold KNRref (S220: YES), the control device 100 determines that pre-ignition has occurred (S230). In other words, the control device 100 determines that pre-ignition occurred within the above detection period GP.

[0032] Then, if the process in S230 is executed, or if a negative determination is made in the process in S220, the control device 100 terminates this process. In this modified example, unlike the above embodiment in which the cumulative value KNS and the threshold KNSref are directly compared, the threshold KNSref can be set to a constant fixed value. Furthermore, the cumulative value KNS calculated during normal combustion when pre-ignition does not occur changes depending on the engine operating state. In this respect, according to this modified example, the above reference value KNSb is set based on the engine operating state, so the reference value KNSb can be set appropriately.

[0033] The cumulative value KNS may be calculated using the arithmetic processing of CPU 110. The control device 100 includes a CPU 110 and a memory 120, and executes software processing. However, this is merely an example. The control device 100 may include, for example, a dedicated hardware circuit (e.g., an ASIC) that processes at least a portion of the software processing performed in the above embodiment. That is, the control device 100 may have any of the following configurations (a) to (c): (a) A processing unit that executes all of the above processing according to a program, and a program storage device such as a memory that stores the program. (b) A processing unit and a program storage device that execute a portion of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software circuits with processing units and program storage devices, and multiple dedicated hardware circuits. That is, the above processing may be executed by a processing circuit that includes at least one of one or more software circuits and one or more dedicated hardware circuits. The program storage device, i.e., computer-readable media, includes any available media that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0034] 1…Internal combustion engine 2…Cylinder block 3…Cylinder head 4…Cylinder 5... Piston 6…Connecting rod 7... Crankshaft 8… Combustion chamber 9…Intake port 10... Exhaust port 12…Intake valve 13… Exhaust valve 14…Throttle valve 20…Intake passage 30... Exhaust passage 35…In-cylinder injection valve 41... Crank angle sensor 44... Air flow meter 45...Water temperature sensor 48... Knocking sensor 49... Accelerator sensor 100...Control device

Claims

1. A device for determining the occurrence of pre-ignition based on the output value of a vibration sensor installed in an internal combustion engine that uses hydrogen as fuel, An integration process that calculates the cumulative value of the output values ​​within a predetermined period prior to the ignition timing of the air-fuel mixture, A determination process is performed to determine the occurrence of a pre-ignition based on the cumulative value, When the cumulative value calculated when no preignition occurs is considered the normal value, the determination process is a process that determines the occurrence of preignition by comparing the ratio of the cumulative value calculated in the accumulation process to the normal value with a predetermined threshold. A device for determining the pre-ignition state of an internal combustion engine.

2. The aforementioned normal value is set based on the engine operating conditions. A pre-ignition determination device for an internal combustion engine according to claim 1.

Images