JP2020084891A - Control device of internal combustion engine with auxiliary chamber - Google Patents

Abstract

To predict the occurrence of misfire.SOLUTION: On a top surface of a main combustion chamber (2), an auxiliary chamber (51) is formed, and a mixture in the main combustion chamber (2) is burned by jet flame blowing out from a communication hole (52) when mixture in the auxiliary chamber (51) is burned by an ignition plug (54). A sensor (55) is provided, which detects combustion timing in the auxiliary chamber (51). When the combustion timing in the auxiliary chamber (51) detected by the sensor (55) is delayed beyond the timing obtained in advance as timing of causing misfire, the occurrence of misfire is predicted.SELECTED DRAWING: Figure 11

Description

The present invention relates to a control device for an internal combustion engine with a sub chamber.

The main fuel gas is supplied into the main combustion chamber, and a sub-chamber is formed on the top surface of the main combustion chamber, the sub-chamber communicating with the main combustion chamber through a communication hole and having an ignition plug. An internal combustion engine with a sub-chamber is known in which the main fuel gas in the main combustion chamber is burned by a jet flame ejected from the communication hole when the sub-fuel gas supplied and burned by the spark plug is burned. There is (for example, refer to Patent Document 1). In this internal combustion engine with a sub-chamber, the peak value of the combustion pressure in the sub-chamber is detected, and the supply amount of the sub-fuel gas into the sub-chamber is controlled so that the peak value becomes the target value, whereby combustion in the sub-chamber is performed. I try to suppress the variation of.

JP, 2009-203952, A

By the way, in an internal combustion engine with a sub chamber in which the air-fuel mixture in the sub chamber is ignited by an ignition plug, the peak value of the combustion pressure in the sub chamber is delayed as the ignition timing is delayed. In this regard, as a result of repeated research, when the time when the peak value of the combustion pressure in the sub-chamber occurs is retarded beyond a certain time, even if the peak value of the combustion pressure in the sub-chamber is sufficiently high, It turned out that a misfire suddenly occurred. The reason for this is not clear, but it is probably because of the following reasons.

That is, the jet flame is ejected from the sub-chamber when the combustion pressure in the sub-chamber reaches the peak value and after a certain period of time elapses. Therefore, the combustion pressure in the sub-chamber reaches the peak value. If it is near the top dead center, the jet flame is ejected from the sub chamber when the piston is descending after the bottom dead center. However, when the piston descends, the temperature of the gas in the main combustion chamber rapidly decreases, so that the jet flame ejected from the sub chamber is cooled by the gas whose temperature has decreased in the surroundings. As a result, it is considered that the flame does not propagate to the surroundings in the main combustion chamber, which causes misfire. In this case, when the temperature in the main combustion chamber drops below a certain temperature, misfire is considered to occur, and therefore the timing at which the peak value of the combustion pressure in the sub chamber occurs is retarded beyond a certain time. Therefore, even if the peak value of the combustion pressure in the sub chamber is sufficiently high, it is considered that a misfire will occur suddenly.

Since misfire occurs even if the peak value of the combustion pressure in the sub chamber is sufficiently high as described above, even if the peak value of the combustion pressure in the sub chamber is detected as in the above-described known internal combustion engine with a sub chamber, The occurrence of misfire cannot be predicted. On the other hand, an operation control device that retards the ignition timing when a misfire is detected is also known, but in this case, a misfire occurs at least once, which is not preferable.
An object of the present invention is to provide a control device for an internal combustion engine with a sub-chamber that can accurately predict the occurrence of misfire.

According to the present invention, a sub chamber that communicates with the main combustion chamber through the communication hole is formed on the top surface of the main combustion chamber, and the spark plug is arranged in the sub chamber. In an internal combustion engine with a sub-chamber configured to burn the air-fuel mixture in the main combustion chamber by a jet flame ejected from the communication hole when the air-fuel mixture is burned, a sensor for detecting the combustion time in the sub-chamber is provided, Provided is a control device for an internal combustion engine with a secondary chamber, which predicts that a misfire will occur when the combustion timing in the secondary chamber detected by the sensor is retarded beyond a time required in advance to cause a misfire. ..

It is possible to accurately predict the occurrence of misfire.

FIG. 1 is an overall view of an internal combustion engine with a sub chamber. FIG. 2 is a view of the cylinder head when viewed from below. FIG. 3 is a side sectional view of the internal combustion engine with a sub chamber, taken along the section AA of FIG. 2. FIG. 4 is an enlarged side sectional view around the sub chamber. FIG. 5 is a cross-sectional view of the sub chamber casing taken along the line BB of FIG. FIG. 6 is a diagram showing jet flames ejected from the sub chamber. FIG. 7 is a diagram showing the sub injection amount and the main injection amount. FIG. 8 is a diagram showing a pressure change in the sub chamber. FIG. 9 is a diagram showing the indicated mean effective pressure. 10A and 10B are diagrams showing the retard limit crank angle. FIG. 11 is a flow chart for performing ignition timing retard control. FIG. 12 is a flow chart for performing ignition timing retard control.

FIG. 1 shows an overall view of an internal combustion engine with a sub chamber that uses gasoline as a fuel. Referring to FIG. 1, 1 is an engine body, 2 is a main combustion chamber of each cylinder, 3 is a main fuel injection valve provided for each cylinder, 4 is a surge tank, 5 is an intake branch pipe, and 6 is exhaust. Show manifolds respectively. The surge tank 4 is connected to the outlet of the compressor 8a of the exhaust turbocharger 8 via the intake duct 7, and the inlet of the compressor 8a is connected to the air cleaner 10 via the intake air amount detector 9. A throttle valve 11 driven by an actuator is arranged in the intake duct 7, and an intercooler 12 for cooling intake air flowing in the intake duct 7 is arranged around the intake duct 7.

On the other hand, the exhaust manifold 6 is connected to the inlet of the exhaust turbine 8b of the exhaust turbocharger 8, and the outlet of the exhaust turbine 8b is connected to the exhaust purification catalytic converter 14 via the exhaust pipe 13. The exhaust manifold 5 and the surge tank 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 15, and an EGR control valve 16 is arranged in the EGR passage 15. Each main fuel injection valve 3 is connected to a fuel distribution pipe 17, and this fuel distribution pipe 17 is connected to a fuel tank 19 via a fuel pump 18.

The electronic control unit 20 is composed of a digital computer, and a ROM (read only memory) 22, a RAM (random access memory) 23, a CPU (microprocessor) 24, an input port 25 and an output port 26 which are connected to each other by a bidirectional bus 21. It is equipped with. The output signal of the intake air amount detector 9 is input to the input port 25 via the corresponding AD converter 27. A load sensor 31 that generates an output voltage proportional to the amount of depression of the accelerator pedal 30 is connected to the accelerator pedal 30, and the output voltage of the load sensor 31 is input to the input port 25 via the corresponding AD converter 27. It Further, the input port 25 is connected to a crank angle sensor 32 that generates an output pulse each time the crankshaft rotates, for example, 30°. The CPU 24 calculates the engine speed from the output pulse of the crank angle sensor 32. On the other hand, the output port 26 is connected to the main fuel injection valve 3, the actuator for driving the throttle valve 11, the EGR control valve 16, and the fuel pump 18 via the corresponding drive circuit 28.

3 shows a sectional view of the engine body 1 shown in FIG. 1, and FIG. 2 shows a bottom view of the top surface of the combustion chamber 2 shown in FIG. 2 and 3, 41 is a cylinder block, 42 is a cylinder head mounted on the cylinder block 41, 43 is a piston reciprocating in the cylinder block 41, 44 is a pair of intake valves, and 45 is an intake port. , 46 are a pair of exhaust valves, and 47 is an exhaust port. On the other hand, referring to FIGS. 2 to 5, a sub-chamber casing 50 is attached to the central portion of the top surface of the main combustion chamber 2. In the examples shown in FIGS. 2 to 5, the sub-chamber casing 50 has a thin hollow cylindrical shape with both ends closed, and the main axis of the sub-chamber casing 50 extends in the direction of the center axis of the cylinder. It is attached to the top surface of the combustion chamber 2. A sub-chamber 51 is formed in the sub-chamber casing 50, and the sub-chamber casing 50 has a radial shape from the peripheral portion of the end portion of the sub-chamber 51 on the main combustion chamber 2 side toward the peripheral portion of the main combustion chamber 2. A plurality of communication holes 52 extending in the vertical direction are formed.

Further, in the embodiment of the present invention, the sub fuel injection valve 53 is arranged in the central portion of the top surface of the sub chamber 51, and the spark plug 54 is arranged in the peripheral portion of the top surface of the sub chamber 51. Further, a sensor 55 for detecting the combustion timing in the sub chamber 51 is arranged near the top surface of the sub chamber 51. In this embodiment, the sensor 55 for detecting the combustion timing in the sub chamber 51 is a pressure sensor for detecting the combustion pressure in the sub chamber 51. As shown in FIG. 1, the sub fuel injection valve 53 of each cylinder is connected to a fuel distribution pipe 56, and this fuel distribution pipe 56 is connected to the fuel tank 19 via a fuel pump 57. The output signal of the sensor 55 is input to the input port 25 via the corresponding AD converter 27, and the auxiliary fuel injection valve 53 and the spark plug 54 of each cylinder are output via the corresponding drive circuit 28 to the output port 26. Connected to.

In the internal combustion engine with the auxiliary chamber shown in FIGS. 1 to 5, when the intake valve 44 is opened, the fuel injected from the main fuel injection valve 3 is supplied into the main combustion chamber 2 together with the intake air, whereby the main combustion is performed. A mixture is formed in the chamber 2. Next, when the compression stroke is started, a part of the air-fuel mixture in the main combustion chamber 2 uniformly flows into the sub chamber 51 from all the communication holes 52. Next, in the latter half of the compression stroke, as shown by F in FIG. 4, the fuel is injected from the auxiliary fuel injection valve 53 into the auxiliary chamber 51. Next, at the end of the compression stroke, the ignition plug 54 ignites and the mixture in the sub chamber 51 is burned. When the air-fuel mixture in the sub chamber 51 is burned, as shown in FIG. 6, jet flame J is ejected from each communication hole 52, and the air-fuel mixture in the main combustion chamber 2 is burned by these jet flames J. Be punished.

FIG. 7 shows the relationship between the required injection amount Qt and the main injection amount Qm from the main fuel injection valve 3 and the sub injection amount Qa from the sub fuel injection valve 53. The required injection amount Qt, the main injection amount Qm, and the sub injection amount Qa have a relationship of the required injection amount Qt=main injection amount Qm+sub injection amount Qa. In the embodiment of the present invention, as can be seen from FIG. 7, the ratio (Qa/Qm) of the sub injection amount Qa from the sub fuel injection valve 53 to the main injection amount Qm from the main fuel injection valve 3 is normally the required injection. It is constant regardless of the quantity Qt. In the example shown in FIG. 7, the sub injection amount Qa is set to about 5% of the required injection amount Qt regardless of the required injection amount Qt.

As described above, when the timing at which the peak value Pmax of the combustion pressure in the sub chamber 51 is generated is retarded beyond a certain time, the peak value Pmax of the combustion pressure in the sub chamber 51 is sufficiently high. However, it is known that a misfire suddenly occurs. This will be described with reference to FIGS. 8 and 9. Referring to FIG. 8, the vertical axis of FIG. 8 shows the pressure P in the sub chamber 51, and the horizontal axis of FIG. 8 shows the crank angle after compression top dead center (ATDC).

Further, in FIG. 8, the solid line shows the change of the pressure P in the sub chamber 51 when the misfire does not occur, and the broken line shows the change of the pressure P in the sub chamber 51 when the misfire occurs. There is. As shown in FIG. 8, the peak value Pmax of the pressure P in the sub-chamber 51 becomes high when combustion is performed in the sub-chamber 51 regardless of whether or not the misfire occurs. Therefore, it is not possible to judge from the magnitude of the peak value Pmax of the pressure P in the sub chamber 51 whether or not a misfire has occurred.

On the other hand, the crank angle when the pressure P in the sub chamber 51 reaches the peak value Pmax is referred to as the pressure peak crank angle Pmax CA, and the horizontal axis of FIG. 9 is represented by after compression top dead center (ATDC). The pressure peak crank angle Pmax CA is shown, and the vertical axis of FIG. 9 shows the indicated mean effective pressure (IMPE) of the engine. Note that each point in FIG. 9 shows an experimental value representing the relationship between the pressure peak crank angle Pmax CA and the indicated mean effective pressure (IMPE). As shown in FIG. 9, when the pressure peak crank angle Pmax CA is retarded beyond a certain crank angle CX, that is, the pressure peak crank angle Pmax CA is retarded with respect to a certain crank angle CX. Then, the indicated mean effective pressure (IMPE) suddenly becomes zero, that is, misfire occurs.

The possible reasons for such a sudden misfire are as described above. Thus, if the pressure peak crank angle Pmax CA is retarded beyond a certain crank angle CX, misfire occurs. Therefore, this crank angle CX should retard the pressure peak crank angle Pmax CA without causing misfire. It shows the possible retard angle limit. Therefore, this crank angle CX is hereinafter referred to as a retard limit crank angle. The retard limit crank angle CX has been previously obtained by an experiment as a timing for causing a misfire. By the way, when the engine load increases, the sub-injection amount Qa increases, so that the jet flame J becomes stronger. Therefore, even if the pressure peak crank angle Pmax CA moves to the retard side, misfire hardly occurs. Therefore, as the engine load increases, the retard limit crank angle CX becomes closer to the retard side.

On the other hand, when the pressure peak crank angle Pmax CA is the same, the jet flame J becomes weaker because the crank angle at which the jet flame J is jetted becomes slower as the engine speed increases, so that the pressure peak crank angle Pmax becomes larger. If CA is not moved to the advance side, misfire will occur. Therefore, as the engine speed becomes higher, the retard limit crank angle CX becomes more advanced. Therefore, the retard limit crank angle CX has a value as shown in FIG. 10A. The solid line in FIG. 10A represents the equal delay angle limit crank angle CX. The retard limit crank angle CX with respect to the engine load and the engine speed is previously obtained by an experiment, and the retard limit crank angle CX obtained by the experiment as a function of the engine speed and the engine load is shown in FIG. 10B. It is previously stored in the ROM 23 in the form of a map as shown.

In the embodiment according to the present invention, for example, the ignition timing retard control is performed when knocking occurs, and the ignition timing is retarded in order to warm up the exhaust purification catalyst in the converter 14 at the engine cold start. Angle control is performed. When such ignition timing retard control is performed, in the embodiment of the present invention, the ignition timing retard operation is performed within a range in which the pressure peak crank angle Pmax CA does not exceed the retard limit crank angle CX.

As described above, in the embodiment according to the present invention, the occurrence of misfire is predicted using the pressure peak crank angle Pmax CA of the pressure P in the sub chamber 51. In this case, it is considered that the occurrence of misfire can be predicted even by using the pressure peak crank angle of the pressure in the main combustion chamber 2. However, the pressure peak crank angle of the pressure in the main combustion chamber 2 is significantly different from the pressure peak crank angle Pmax CA of the pressure P in the sub chamber 51 due to manufacturing variations and operating conditions. Even using the pressure peak crank angle of the pressure P in the combustion chamber 2, it is difficult to predict the occurrence of misfire. Therefore, in the embodiment according to the present invention, the occurrence of misfire is predicted using the pressure peak crank angle Pmax CA of the pressure P in the sub chamber 51, which is relatively unaffected by manufacturing variations and operating conditions.

That is, in the embodiment according to the present invention, the sub chamber 51 communicating with the main combustion chamber 2 through the communication hole 52 is formed on the top surface of the main combustion chamber 2, and the spark plug 54 is provided in the sub chamber 51. An internal combustion engine with a sub-chamber, which is arranged so as to burn the air-fuel mixture in the main combustion chamber 2 by a jet flame ejected from the communication hole 52 when the air-fuel mixture in the sub-chamber 51 is burned by the spark plug 54. In the sub chamber 51, a sensor 55 for detecting the combustion timing in the sub chamber 51 is provided, and the combustion timing in the sub chamber 51 detected by the sensor 55 exceeds the time required in advance to cause misfire. When retarded, misfire is predicted to occur.

By the way, in the embodiment according to the present invention, the retard flag is set when it is requested to perform the retard control of the ignition timing. Next, with reference to FIG. 11, an example of ignition timing retard control performed using the retard flag will be described. FIG. 11 shows a routine for executing this ignition timing retard control, and this routine is executed by interruption at regular time intervals.

Referring to FIG. 11, first, at step 100, it is judged if the retard flag is set or not. When the retard flag is not set, the processing cycle is completed. On the other hand, when the retard flag is set, the routine proceeds to step 101, where the pressure peak crank angle Pmax CA obtained based on the detection value of the pressure sensor 55 is read. Next, at step 102, it is determined whether or not the pressure peak crank angle Pmax CA is smaller than the retard limit crank angle CX, that is, whether the pressure peak crank angle Pmax CA is on the advance side of the retard limit crank angle CX. To be determined. When the pressure peak crank angle Pmax CA is smaller than the retard limit crank angle CX, that is, when the pressure peak crank angle Pmax CA is on the advance side of the retard limit crank angle CX, the routine proceeds to step 103.

In step 103, a constant value ΔIG, for example, 0.5 degrees, is added to the ignition timing IG, that is, the ignition timing IG is retarded by the constant value ΔIG. Next, at step 104, it is judged if the ignition timing IG is smaller than the target ignition timing B, for example, ATDC 3 degrees, that is, if the ignition timing IG is on the advance side of the target ignition timing B. To be done. When the ignition timing IG is on the advance side of the target ignition timing B, the processing cycle is completed. On the other hand, when the ignition timing IG reaches the target ignition timing B, the routine proceeds to step 105, where the retard flag is reset.

On the other hand, when it is determined in step 102 that the pressure peak crank angle Pmax CA is not smaller than the retard limit crank angle CX, that is, the pressure peak crank angle Pmax CA is advanced from the retard limit crank angle CX. If it is determined that there is not, the process proceeds to step 106. At this time, there is a high possibility that a misfire will occur, and therefore, a warning lamp that indicates an abnormality is turned on.

On the other hand, an ion generation detection sensor can be used as the sensor 55 for detecting the combustion timing in the sub chamber 51. In this ion generation detection sensor, when a combustion flame arrives between a pair of probes arranged in the sub chamber 51, an ion current flows between the probes, and the combustion in the sub chamber 51 occurs due to the generation of this ion current. Can be detected. FIG. 12 shows a routine for executing ignition timing retard control using the ion generation detection sensor 55, and this routine is also executed by interruption at regular time intervals. The contents of steps other than steps 201 and 202 in the routine shown in FIG. 12 are the same as the contents of corresponding steps other than steps 101 and 102 in the routine shown in FIG.

Referring to FIG. 12, first, at step 200, it is judged if the retard flag is set or not. When the retard flag is not set, the processing cycle is completed. On the other hand, when the retard flag is set, the routine proceeds to step 201, where the pressure peak crank angle Pmax CA obtained based on the detection value of the ion generation detection sensor 55 is read. Next, at step 202, it is determined whether or not the pressure peak crank angle Pmax CA is smaller than the retard limit crank angle CX, that is, whether the pressure peak crank angle Pmax CA is on the advance side of the retard limit crank angle CX. To be determined. When the pressure peak crank angle Pmax CA is smaller than the retard limit crank angle CX, that is, when the pressure peak crank angle Pmax CA is on the advance side of the retard limit crank angle CX, the routine proceeds to step 203.

In step 203, a constant value ΔIG, for example, 0.5 degrees, is added to the ignition timing IG, that is, the ignition timing IG is retarded by the constant value ΔIG. Next, at step 204, it is judged if the ignition timing IG is smaller than the target ignition timing B, for example, ATDC 3 degrees, that is, if the ignition timing IG is on the advance side of the target ignition timing B. To be done. When the ignition timing IG is on the advance side of the target ignition timing B, the processing cycle is completed. On the other hand, when the ignition timing IG reaches the target ignition timing B, the routine proceeds to step 205, where the retard flag is reset.

On the other hand, when it is determined in step 202 that the pressure peak crank angle Pmax CA is not smaller than the retard limit crank angle CX, that is, the pressure peak crank angle Pmax CA is advanced from the retard limit crank angle CX. If it is determined that there is not, the routine proceeds to step 206. At this time, there is a high possibility that a misfire will occur, and therefore, a warning lamp that indicates an abnormality is turned on.

2 Main combustion chamber 3 Main fuel injection valve 44 Intake valve 46 Exhaust valve 51 Sub-chamber 52 Communication hole 53 Sub-fuel injection valve 54 Spark plug 55 Sensor

Claims (1)

A sub chamber that communicates with the main combustion chamber through a communication hole is formed on the top surface of the main combustion chamber, and a spark plug is arranged in the sub chamber.The spark plug burns the air-fuel mixture in the sub chamber. In a control device for an internal combustion engine with a sub chamber, which is configured to burn the air-fuel mixture in the main combustion chamber by a jet flame sometimes ejected from the communication hole, a sensor for detecting the combustion timing in the sub chamber is provided. A control device for an internal combustion engine with a sub-chamber, which predicts that a misfire will occur when the detected combustion timing in the sub-chamber is retarded beyond a time required in advance to cause a misfire.

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