Preignition determination device for internal combustion engine

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 pre-ignition determining device for an internal combustion engine. [Background technology]

[0002] For example, in the internal combustion engine described in Patent Document 1, the occurrence of pre-ignition 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] JP 2013-160200 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in an internal combustion engine that uses hydrogen as fuel, there are cases where the vibration generated when pre-ignition occurs is small, which makes it difficult to determine the occurrence of pre-ignition based on the peak value of the output value of the vibration sensor. [Means for solving the problem]

[0005] A pre-ignition determination device for an internal combustion engine that solves the above problem is a device that determines the occurrence of pre-ignition based on the output value of a vibration sensor provided in an internal combustion engine that uses hydrogen as fuel. This pre-ignition determination device executes an integration process that calculates an integrated value of the output value within a predetermined period prior to the ignition timing of the mixture, and a determination process that determines the occurrence of pre-ignition based on the integrated value. Effect of the Invention

[0006] This pre-ignition determination device for an internal combustion engine can appropriately determine the occurrence of pre-ignition even when pre-ignition occurs with little vibration. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine according to one embodiment. [Diagram 2] FIG. 2 is a diagram showing a configuration of a signal processing circuit. [Diagram 3] FIG. 3 is a flowchart showing a procedure of the process executed by the control device. [Figure 4] FIG. 4 is a flowchart showing a procedure of a process executed by the control device in the modified example of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, one embodiment of a pre-ignition determining device for an internal combustion engine will be described with reference to FIGS. <Configuration of an internal combustion engine> 1, a cylinder 4 is provided in a cylinder block 2 of an internal combustion engine 1. A piston 5 is provided in the cylinder 4, and the piston 5 is connected to a crankshaft 7 via a connecting rod 6.

[0009] A cylinder head 3 is attached to the top of the cylinder block 2. A combustion chamber 8 is formed in each cylinder 4 between the top surface of the piston 5 and the cylinder head 3. In addition, the cylinder head 3 is provided with an in-cylinder injection valve 35 that directly injects hydrogen gas, which is the fuel for the internal combustion engine 1, into the cylinder, and an ignition plug 11 that sparks and ignites the air-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 a part of an intake passage through which intake air flows. The intake port 9 is connected to an intake passage 20 provided 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 an exhaust passage 30. <About the control device> The control device 100 includes a CPU 110, a memory 120 in which control programs and data are stored, and a signal processing circuit 200. The CPU 110 executes the programs stored in the memory 120 to perform various engine controls and the like.

[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 amount GA, and a water temperature sensor 45 that detects the coolant temperature TW, which is the temperature of the coolant for 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 vibration of the cylinder 4, an accelerator sensor 49 that detects an accelerator operation amount ACCP, which is the amount of operation of the accelerator pedal, and the like.

[0013] The control device 100 calculates the engine speed NE based on the output signal Scr of the crank angle sensor 41. The control device 100 also calculates an engine load factor KL based on the engine speed NE and the intake air amount GA. The engine load factor KL represents the ratio of the current cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 1 is steadily operated with the throttle valve 14 fully open at the current engine speed NE. The cylinder inflow air amount 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 control of the opening of the throttle valve 14, control of the injection of fuel injected from the in-cylinder injection valve 35, and control of ignition of the spark plug 11. The control device 100 also functions as a pre-ignition determination device that determines the occurrence of pre-ignition.

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

[0016] Here, hydrogen has a wider range of flammable concentrations than gasoline and can ignite even when the air-fuel ratio of the mixture is lean, so pre-ignition can occur even immediately after fuel is injected. Depending on the position of the heat source that caused the pre-ignition, that is, the ignition starting point of the pre-ignition, the vibrations that occur in the cylinder may be less than those of pre-ignition that occurs in an internal combustion engine that uses gasoline as fuel. Therefore, in this embodiment, it is possible to appropriately determine the occurrence of such pre-ignition with less 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 integrator 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, and generates a filtered signal KNF by filtering the output signal KN within the detection period GP.

[0018] The detection period GP is a predetermined period before the ignition timing of the air-fuel mixture and is expressed in crank angles. More specifically, it is a period that is less susceptible to the influence of combustion in the cylinder that burned before the cylinder that is the subject of the current judgment, and includes a period near the time when the in-cylinder pressure is maximum when pre-ignition occurs. For example, the detection period GP can be set to a period from the start of fuel injection performed during the compression stroke to the compression top dead center. In addition, the filter frequency set when performing the filter process is preset to an appropriate value to remove vibrations when the intake valve 12 and exhaust valve 13 are seated, vibrations generated when the in-cylinder injection valve 35 is driven, ignition noise of the ignition plug 11, and the like.

[0019] The full-wave rectifier circuit 220 generates an absolute value signal KNA by converting the filtered signal KNF into an absolute value. That is, the full-wave rectifier circuit 220 inverts the sign of the filtered signal KNF that is negative among the filtered signals KNF to convert it into a positive value.

[0020] The integrating circuit 230 calculates an integrated value KNS by integrating the absolute value signal KNA generated by the full-wave rectifying circuit 220. That is, the integrating circuit 230 calculates an integrated value KNS which is a value obtained by integrating the absolute value of the filtered 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 Fig. 3 is realized by the CPU 110 executing a program stored in the memory 120. The process shown in Fig. 3 is executed every time the integrated value KNS is calculated. Note that, hereinafter, the step number of each process is represented by a number preceded by "S".

[0022] When the series of processes shown in FIG. 3 is started, the control device 100 acquires the calculated integrated value KNS (S100). Next, the control device 100 acquires a threshold value KNSref (S110). In the process of S110, the control device 100 acquires the 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 speed NE and the engine load factor KL. The engine speed NE and the engine load factor KL referred to at this time are, for example, the instantaneous value of the engine speed NE at a predetermined timing in the detection period GP and the instantaneous value of the engine load factor KL at a predetermined timing in the detection period GP. In addition, the engine speed NE and the engine load factor KL referred to at this time may be, for example, the average value of the engine speed NE in the detection period GP and the average value of the engine load factor KL in the detection period GP.

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

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

[0025] Then, when the process of S130 has been executed, or when a negative determination is made in the process of S120, the control device 100 ends this process. <Actions and Effects of the Present Embodiment> (1) An integration process is executed to calculate an integrated value KNS of the output signal KN of the knocking sensor 48 in the detection period GP before the ignition timing of the air-fuel mixture, and a determination process is executed 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 the threshold value KNSref. In this manner, 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 the abnormal combustion in which pre-ignition occurs and the normal combustion in which pre-ignition does not occur becomes clear. Therefore, even when pre-ignition occurs with little vibration, such as in an internal combustion engine 1 using hydrogen as fuel, the occurrence of pre-ignition can be appropriately determined.

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

[0027] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0028] The determination process in the above embodiment is a process for determining the occurrence of pre-ignition by comparing the integrated value KNS with the threshold value KNSref. Alternatively, the integrated value KNS calculated when pre-ignition is not occurring may be set as a normal value. Then, as the determination process, a process for determining the occurrence of pre-ignition may be executed by comparing the ratio of the calculated integrated value KNS to the normal value with a predetermined threshold value KNRref.

[0029] The procedure of the determination process in this modified example is shown in Fig. 4. When the series of processes shown in Fig. 4 is started, the control device 100 acquires the calculated integrated 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 the 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 speed NE and the engine load factor KL. The engine speed NE and the engine load factor KL referred to at this time are, for example, the instantaneous value of the engine speed NE at a predetermined timing in the detection period GP and the instantaneous value of the engine load factor KL at a predetermined timing in the detection period GP. In addition, the engine speed NE and the engine load factor KL referred to at this time may be, for example, the average value of the engine speed NE in the detection period GP and the average value of the engine load factor KL in the detection period GP.

[0030] Next, the control device 100 judges whether or not the ratio between the integrated value KNS and the reference value KNSb is equal to or greater than a threshold value KNRref (S220). The ratio between the integrated value KNS and the reference value KNSb is a value obtained by dividing the integrated value KNS by the reference value KNSb. The magnitude of the threshold value KNRref is preset so that it can be accurately determined that pre-ignition has occurred based on the ratio between the integrated value KNS and the reference value KNSb being equal to or greater than the threshold value KNRref.

[0031] Then, when it is determined that the ratio between the integrated value KNS and the reference value KNSb is equal to or greater than the threshold value 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 has occurred within the detection period GP.

[0032] Then, when the process of S230 has been executed, or when a negative determination is made in the process of S220, the control device 100 ends this process. In this modified example, unlike the above embodiment in which the integrated value KNS is directly compared with the threshold value KNSref, the threshold value KNRref can be set to a constant fixed value. Also, the integrated value KNS calculated during normal combustion when pre-ignition is not occurring varies depending on the engine operating state. In this regard, according to this modified example, the reference value KNSb is set based on the engine operating state, so the reference value KNSb can be set appropriately.

[0033] The integrated value KNS may be calculated by the CPU 110 through calculation processing. 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., ASIC, etc.) that processes at least a part of the software processing executed in the above embodiment. That is, the control device 100 may have any of the following configurations (a) to (c). (a) A processing device 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 device and a program storage device that execute a part 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, the software circuit including the processing device and the program storage device, and the dedicated hardware circuit may be multiple. 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., the computer-readable medium, includes any available medium 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 an output value of a vibration sensor provided in an internal combustion engine that uses hydrogen as fuel, an integration process for calculating an integrated value of the output value within a predetermined period of time prior to the ignition timing of the air-fuel mixture; A determination process for determining the occurrence of pre-ignition based on the integrated value is executed. A pre-ignition detection device for an internal combustion engine.

2. The determination process is a process for determining the occurrence of pre-ignition by comparing the integrated value with a predetermined threshold value.

2. The pre-ignition determining device for an internal combustion engine according to claim 1.

3. The threshold value is a value that is set based on the engine operating state. The pre-ignition determining device for an internal combustion engine according to claim 2.

4. When the integrated value calculated when pre-ignition does not occur is set as a normal value, The determination process is a process for determining the occurrence of pre-ignition by comparing a ratio between the integrated value calculated in the integration process and the normal value with a predetermined threshold value.

2. The pre-ignition determining device for an internal combustion engine according to claim 1.

5. The normal value is a value that is set based on the engine operating condition.

5. The pre-ignition determining device for an internal combustion engine according to claim 4.

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