JP2019183809A - Control device of internal combustion engine - Google Patents

Abstract

To ensure good combustion when a jet flame becomes weak from a sub chamber.SOLUTION: A sub chamber (51) which has a first ignition plug (53) and a second ignition plug (54) are disposed on a top surface of a main combustion chamber (2). After the ignition action of the first ignition plug (53), the ignition action of the second ignition plug (54) is carried out. In this case, an ignition timing of the first ignition plug (53) and an ignition timing of a second ignition plug (54) are set to generate an initial flame of a mixture ignited by the second ignition plug (54) when turbulence occurs around the second ignition plug (54) by the jet flame ejected from the communication hole (52).SELECTED DRAWING: Figure 8

Description

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

  A sub chamber communicating with the main combustion chamber through a communication hole is formed on the top surface of the main combustion chamber, and a sub spark plug and a sub fuel injection valve are arranged in the sub chamber, and the main combustion chamber has a main chamber. An internal combustion engine in which a spark plug is disposed is known (see, for example, Patent Document 1). In this internal combustion engine, the air-fuel mixture in the main combustion chamber is first ignited by the main spark plug, and the air-fuel mixture in the sub-chamber is ignited by the sub-ignition plug when the pressure in the main combustion chamber rises slightly. When the air-fuel mixture in the auxiliary chamber is ignited, a jet flame is ejected from the communication hole of the auxiliary chamber into the main combustion chamber, and the air-fuel mixture in the main combustion chamber that has not yet been combusted is burned by the jet flame.

JP 2007-255370 A

  However, in this internal combustion engine, when the engine load is small and the ignition timing is retarded, such as during warm-up operation of the exhaust catalyst, idling operation, shift change, or deceleration operation, compression is performed. Since the temperature and pressure of the main combustion chamber at the end of the stroke are lowered, the flame of the air-fuel mixture in the main combustion chamber ignited by the main spark plug does not spread sufficiently in the main combustion chamber. Further, at this time, the jet flame ejected from the communication hole of the sub chamber into the main combustion chamber becomes weak, so that the air-fuel mixture in the main combustion chamber does not burn well, resulting in a misfire.

  In order to solve the above problem, according to the present invention, a sub chamber that communicates with the main combustion chamber through the communication hole and has the first spark plug is formed on the top surface of the main combustion chamber. In a control device for an internal combustion engine in which a jet flame is ejected from a communication hole when an air-fuel mixture in a sub chamber is burned by a spark plug, the main combustion chamber top surface of the jet flame side of the jet flame ejected from the communication hole is A second spark plug for igniting the air-fuel mixture in the combustion chamber is disposed, the second spark plug is ignited after the first spark plug is ignited, and around the second spark plug by a jet flame ejected from the communication hole Of the internal combustion engine in which the ignition timing of the first spark plug and the ignition timing of the second spark plug are set so that the initial flame of the air-fuel mixture ignited by the second spark plug is generated when the turbulence occurs. A control device is provided.

  If the second spark plug is arranged on the side of the jet region of the jet flame ejected from the communication hole, even if the jet flame weakens, turbulence occurs around the second spark plug due to the jet flame. At this time, since the initial flame of the air-fuel mixture ignited by the second spark plug is generated, the initial flame rapidly grows and propagates to the surroundings due to the generated disturbance. Thereby good combustion is obtained.

FIG. 1 is an overall view of an internal combustion engine. FIG. 2 is a view of the cylinder head as viewed from below. FIG. 3 is a side cross-sectional view of the internal combustion engine taken along the line AA of FIG. FIG. 4 is a view of a cylinder head according to another embodiment as viewed from below. 5A and 5B are an enlarged side sectional view around the sub chamber and a view taken along the BB section in FIG. 5A, respectively. FIG. 6 is a diagram showing a poor combustion region. FIG. 7 is a diagram showing a relationship between ignition in the sub chamber by the first spark plug and ignition in the main combustion chamber by the second spark plug. 8A, 8B, and 8C are diagrams illustrating the interval Int. 9A and 9B are diagrams showing the correction coefficient K1 and the correction coefficient K2, respectively. FIG. 10 is a diagram showing a map of the ignition timing ΘM of the second spark plug. FIG. 11 is a flowchart for performing the ignition control.

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

  On the other hand, the exhaust manifold 6 is connected to the inlet of the exhaust turbine 8 b of the exhaust turbocharger 8, and the outlet of the exhaust turbine 8 b 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 disposed in the EGR passage 15. Each 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 comprises a digital computer and is connected to each other by a bidirectional bus 21. 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 are connected. It comprises. 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. The Further, a crank angle sensor 32 that generates an output pulse every time the crankshaft rotates, for example, 30 ° is connected to the input port 25. 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 through corresponding drive circuits 28.

  FIG. 2 shows a bottom view of the top surface of the combustion chamber 2 shown in FIG. 1, and FIG. 3 shows a side sectional view of the engine body 1 taken along line AA 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. As shown in FIG. 3, the fuel injection valve 3 is disposed in the intake port 45. A variable valve timing device 48 for controlling the opening / closing valve timing of the pair of intake valves 44 is attached to the engine body 1 as shown in FIG. The variable valve timing device 48 is controlled based on the output signal of the electronic control unit 20, and the valve overlap amount between the intake valve 44 and the exhaust valve 46 is controlled by the variable valve timing device 48.

  On the other hand, referring to FIG. 2 and FIG. 3, a sub chamber casing 50 is attached to the central portion of the top surface of the main combustion chamber 2. FIG. 5A shows an enlarged side cross-sectional view of the sub chamber casing 50, and FIG. 5B shows a cross-sectional view taken along line BB of FIG. 5A. In the example shown in FIGS. 2, 3, 5 </ b> A, and 5 </ b> B, the sub chamber casing 50 has a thin hollow cylindrical shape with both ends closed, and is attached to the top surface of the main combustion chamber 2. . Further, the upper portion of the sub chamber casing 50 is located in the cylinder head 42, and only the lower portion of the sub chamber casing 50 is exposed in the main 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 periphery of the end of the sub chamber 51 on the main combustion chamber 2 side toward the periphery of the main combustion chamber 2. A plurality of communication holes 52 extending in the direction are formed.

  In this case, in the embodiment of the present invention, as shown in FIG. 5B, each communication hole 52 extends radially from the central axis of the sub chamber casing 50 at equal angular intervals with respect to the central axis of the sub chamber casing 50. In addition, as shown in FIG. 5A, each communication hole 52 extends slightly downward toward the periphery of the main combustion chamber 2. On the other hand, a first spark plug 53 for igniting the air-fuel mixture in the sub chamber 51 is disposed on the top surface of the sub chamber 51. The top surface of the main combustion chamber 2 is adjacent to the sub chamber casing 50. A second spark plug 54 for igniting the air-fuel mixture in the main combustion chamber 2 is arranged. The first spark plug 53 and the second spark plug 54 are connected to the output port 26 via the corresponding drive circuit 28.

  In the embodiment of the present invention, normally, the air-fuel mixture in the main combustion chamber 2 is combusted by the ignition action of one of the first spark plug 53 and the second spark plug 54. That is, when the intake valve 44 is opened, the fuel injected from the fuel injection valve 3 is supplied into the main combustion chamber 2 together with the intake air, whereby an air-fuel mixture is formed in the main combustion chamber 2. Next, when the compression stroke is started, the air-fuel mixture in the main combustion chamber 2 flows into the sub chamber 51 from the communication hole 52. Next, at the end of the compression stroke, when the air-fuel mixture in the main combustion chamber 2 is combusted by the first spark plug 53, an ignition action is performed by the first spark plug 53, whereby the air-fuel mixture in the sub chamber 51 is It is ignited. When the air-fuel mixture in the sub chamber 51 is ignited, as shown by F in FIGS. 2 and 3, a jet flame is ejected from each communication hole 52 into the main combustion chamber 2, and the jet flame F The air-fuel mixture in the main combustion chamber 2 is combusted.

  On the other hand, when the air-fuel mixture in the main combustion chamber 2 is combusted by the second spark plug 54, at the end of the compression stroke, the air-fuel mixture in the main combustion chamber 2 is ignited by the second spark plug 54, and the main combustion chamber The air-fuel mixture in 2 is combusted. In this case, the jet flame F is not ejected from the sub chamber 51. FIG. 4 shows a modification in which the positions of the sub chamber casing 50 and the second spark plug 54 are rotated by 90 ° around the cylinder axis with respect to the case shown in FIG. As can be seen from FIGS. 3 and 4, in any of the cases shown in FIGS. 3 and 4, the communication of the sub chamber 51 is performed so that the second spark plug 54 is positioned between a pair of adjacent jet flames F. The direction of the hole 52 is adjusted. That is, the direction of the communication hole 52 of the sub chamber 51 is adjusted so that the jet flame F does not directly collide with the second ignition plug 54 and the jet flame F flows through the side of the second ignition plug 54. In other words, the second spark plug 54 is disposed on the side of the jet region of the jet flame F jetted from the communication hole 52.

  Incidentally, the ignition timing is usually retarded during warm-up operation, idling operation, shift change, and deceleration operation of the exhaust purification catalyst. That is, when the air-fuel mixture in the main combustion chamber 2 is burned by the first spark plug 53, the ignition timing of the first spark plug 53 is retarded, and the air-fuel mixture in the main combustion chamber 2 is retarded by the second spark plug 54. Is burned, the ignition timing by the second spark plug 54 is retarded. However, the temperature and pressure of the main combustion chamber 2 at the end of the compression stroke become low when the engine load is small, such as during warm-up operation, idling operation, shift change, or deceleration operation of the exhaust purification catalyst. Thus, when the temperature and pressure of the main combustion chamber 2 at the end of the compression stroke are thus lowered, it becomes difficult to favorably burn the air-fuel mixture in the main combustion chamber 2.

  That is, when the temperature and pressure of the main combustion chamber 2 at the end of the compression stroke are lowered, the temperature and pressure in the sub chamber 51 at the end of the compression stroke is also lowered. At this time, if the ignition timing of the first spark plug 53 is retarded, the temperature and pressure in the sub chamber 51 are low, so the combustion speed of the air-fuel mixture in the sub chamber 51 is slow, and the combustion in the sub chamber 51 The pressure does not increase. As a result, the jet flame F ejected from the communication hole 52 of the sub chamber 51 into the main combustion chamber 2 is weakened. When the jet flame F ejected into the main combustion chamber 2 is weakened, there is a risk that the air-fuel mixture in the main combustion chamber 2 is not burned well and misfires.

  On the other hand, when the ignition timing of the second spark plug 54 is retarded when the temperature and pressure of the main combustion chamber 2 at the end of the compression stroke are low in this way, the main spark chamber 54 ignites the main ignition chamber 54. Although the air-fuel mixture in the combustion chamber 2 is ignited to generate an initial flame, the generated initial flame is not sufficiently spread in the main combustion chamber 2. As a result, there is a risk that the air-fuel mixture in the main combustion chamber 2 is not burned well and misfires. In this way, a region that may be misfired when the air-fuel mixture is ignited by the first spark plug 53 or the second spark plug 54 is indicated by R in FIG. In the embodiment of the present invention, this region R is referred to as a poor combustion region. In FIG. 6, this poor combustion region R is shown as a region where the engine load is lower than a constant load and the ignition timing ΘA of the first spark plug 53 is retarded from the constant crank angle.

  However, when the engine load and the ignition timing ΘA of the first spark plug 53 are in the poor combustion region R, the second spark plug 54 is ignited after the first spark plug 53 is ignited, and the first ignition is performed. It has been found that if the interval Int between the ignition timing ΘA of the plug 53 and the ignition timing ΘM of the second ignition plug 54 is set appropriately, the air-fuel mixture in the main combustion chamber 2 can be burned well without causing misfire. is there. Next, this will be described with reference to FIGS.

  A solid line A in FIG. 7 indicates the fuel combustion ratio in the sub chamber 51 after ignition by the first spark plug 53, and a solid line M in FIG. 7 ignites by the second spark plug 54. The combustion ratio of the fuel in the main combustion chamber 2 after being broken is shown. Accordingly, the rising points of these solid lines A and M in FIG. 7 indicate the start of combustion. As shown in FIG. 7, combustion is started in the sub chamber 51 after a while after the ignition of the first spark plug 53, and in the main combustion chamber 2 after a while after the ignition of the second spark plug 54. Combustion starts. In this case, it can be seen from FIG. 7 that after the first ignition plug 53 is ignited, the time until the combustion is started in the sub chamber 51 is started in the main combustion chamber 2 after the second ignition plug 54 is ignited. It can be seen that it is considerably longer than the time required.

  On the other hand, when the combustion ratio of the fuel in the sub chamber 51 is close to 100%, the jet flame F is ejected from the communication hole 52, and the ejection timing of the jet flame F is indicated by ΘAX in FIG. In the main combustion chamber 2, combustion is started when the fuel combustion ratio in the main combustion chamber 2 starts to increase, and at this time, an initial flame of the air-fuel mixture ignited by the second spark plug 54 is generated. The The generation time of the initial flame of the air-fuel mixture is indicated by ΘMX in FIG. By the way, even in the poor combustion region R shown in FIG. 6, even when only the second spark plug 54 is ignited, the initial flame of the air-fuel mixture in the main combustion chamber 2 is generated. However, this initial flame disappears without sufficiently growing.

  However, when a turbulence occurs around the second spark plug 54 when the initial flame is generated, the initial flame grows rapidly and the flame propagates throughout the main combustion chamber 2. . As a result, the air-fuel mixture in the main combustion chamber 2 burns well without causing misfire. Therefore, in order to burn the air-fuel mixture in the main combustion chamber 2 satisfactorily, it is necessary to generate turbulence around the second spark plug 54 when the initial flame is generated. In this case, when the jet flame F is ejected from the communication hole 52 of the sub chamber 51, turbulence occurs around the jet flame F. Therefore, when the jet flame F is ejected, a disturbance occurs around the second spark plug 54 disposed on the side of the jet flame F ejection region, and an initial flame generated around the second spark plug 54 is generated. Can grow rapidly.

  That is, as shown in FIG. 7, when the initial flame generation timing ΘMX is matched with the jet flame F ejection timing ΘAX, the initial flame can be rapidly grown, and the air-fuel mixture in the main combustion chamber 2 is It becomes possible to burn well without causing misfire. Therefore, in the embodiment of the present invention, the ignition timing ΘA of the first spark plug 53 and the ignition timing ΘM of the second spark plug 54 are set so that the jet timing ΘAX of the jet flame F and the generation timing ΘMX of the initial flame overlap. The interval Int is set. That is, the first flame of the air-fuel mixture ignited by the second spark plug 54 is generated when the surroundings of the second spark plug 54 are disturbed by the jet flame F ejected from the communication hole 52. The ignition timing ΘA of the ignition plug 53 and the ignition timing ΘM of the second ignition plug 54 are set.

  Next, an optimal interval Int between the ignition timing ΘA of the first spark plug 53 and the ignition timing ΘM of the second spark plug 54 will be described with reference to FIGS. 8A to 8C. A solid line td in FIG. 8A represents an elapsed period (ΘA to ΘAX) from when the first spark plug 53 is ignited to when jet flame F is ejected at a certain engine load, that is, jet flame ejection delay time ( ΘA to ΘAX) and the ignition timing ΘA of the first spark plug 53 are shown, and a solid line td in FIG. 8B indicates a jet flame ejection delay time td () at an ignition timing ΘA of a certain first spark plug 53. (ΘA to ΘAX) and the engine load are shown.

  That is, as the ignition timing ΘA of the first spark plug 53 is retarded, the temperature and pressure in the sub chamber 51 at the time of ignition of the first spark plug 53 become lower, and the combustion time of the air-fuel mixture in the sub chamber 51 is reduced. become longer. Therefore, as shown by the solid line in FIG. 8A, the jet flame ejection delay time td becomes longer as the ignition timing ΘA of the first spark plug 53 is retarded. On the other hand, when the engine load becomes low, the temperature and pressure in the sub chamber 51 at the time of ignition of the first spark plug 53 become low, and the combustion time of the air-fuel mixture in the sub chamber 51 becomes long. Therefore, as shown by the solid line in FIG. 8B, the jet flame ejection delay time td becomes longer as the engine load becomes lower.

On the other hand, as can be seen from FIG. 7, when the ignition action of the second spark plug 54 is performed before the jet flame F ejection timing ΘAX, Δt time, the jet flame F ejection timing ΘAX and the generation of the initial flame Time ΘMX overlaps. Accordingly, the optimum elapsed time until the ignition action of the second spark plug 54 is performed is earlier by Δt time than the jet flame ejection delay time td as shown by a chain line tf in FIGS. 8A and 8B. It's time. Note that in FIG. 8A, .theta.a _O and .theta.M _O shows an example of optimum combination of ignition timing of the ignition timing and the second ignition plug 54 of the first spark plug 53. On the other hand, in FIGS. 8A and 8B, the optimum elapsed time tf until the ignition action of the second spark plug 54 is performed represents the optimum interval Int. Therefore, it can be seen from FIGS. 8A and 8B that the optimum interval Int can be obtained based on the ignition timing ΘM of the second spark plug 54 and the engine load.

  FIG. 8C is a diagram showing the optimum interval Int shown in FIGS. 8A and 8B as a function of the ignition timing ΘM of the second spark plug 54 and the engine load. In FIG. 8C, each solid line indicates an equiinterval line. It can be seen from FIG. 8C that the optimum interval Int becomes longer as the engine load becomes lower and becomes longer as the ignition timing ΘM of the second spark plug 54 is retarded. The relationship between the optimum interval Int shown in FIG. 8C and the engine load and the ignition timing ΘM of the second spark plug 54 is stored in the ROM 23 in advance.

  As the EGR rate increases, the combustion speed in the sub chamber 51 decreases, and as a result, the jet flame ejection delay time Id becomes longer. As the jet flame ejection delay time Id becomes longer, the optimum interval Int becomes longer. Therefore, in the embodiment of the present invention, the interval Int is increased as the EGR rate increases by multiplying the interval Int by the correction coefficient K1 shown in FIG. 9A. Further, when the valve overlap amount between the intake valve 44 and the exhaust valve 46 increases, the residual gas amount in the main combustion chamber 2 increases, and when the residual gas amount increases, the combustion speed in the sub chamber 51 decreases, The jet flame ejection delay time Id becomes longer. As the jet flame ejection delay time Id becomes longer, the optimum interval Int becomes longer. Therefore, in the embodiment of the present invention, the interval Int is increased as the valve overlap amount is increased by multiplying the interval Int by the correction coefficient K2 shown in FIG. 9B.

  On the other hand, in the poor combustion region R shown in FIG. 6, the ignition timing ΘM of the second spark plug 54 is controlled so that the combustion in the main combustion chamber 2 is performed at the optimum timing. As shown in FIG. 10, the optimum ignition timing ΘM of the second spark plug 54 in the poor combustion region R is stored in advance in the ROM 23 as a function of the engine load and the engine speed. The ignition timing ΘA of the first spark plug 53 is obtained from the optimal ignition timing ΘM of the second spark plug 54 and the optimal interval Int.

  FIG. 11 shows an ignition control routine. This routine is executed by interruption every predetermined time. Referring to FIG. 11, first, at step 100, it is judged if the current engine load and the ignition timing ΘA of the first spark plug 53 are within the poor combustion region R shown in FIG. When the current engine load and the ignition timing ΘA of the first spark plug 53 are within the poor combustion region R, the routine proceeds to step 101, where the optimal ignition timing ΘM of the second spark plug 54 is determined from the map shown in FIG. Is read. Next, at step 102, the optimum interval Int is read from the relationship shown in FIG. 8C.

  Next, at step 103, a correction coefficient K1 is calculated from the relationship shown in FIG. 9A. Next, at step 104, the correction coefficient K2 is calculated from the relationship shown in FIG. 9B. Next, at step 105, the final interval Into is calculated by multiplying the interval Int by the correction coefficient K1 and the correction coefficient K2. Next, at step 106, a crank angle CInto corresponding to the interval Into is calculated by multiplying the final interval Into (sec) by a conversion factor ((engine speed N / 60) · 360). Next, at step 107, the ignition timing ΘA of the first spark plug 53 is calculated by subtracting the crank angle CInto from the ignition timing ΘM of the second spark plug 54. Next, the routine proceeds to step 108 where ignition processing is performed.

  On the other hand, if it is determined in step 100 that the current engine load and the ignition timing ΘA of the first spark plug 53 are not within the poor combustion region R shown in FIG. In step 109, when the air-fuel mixture in the main combustion chamber 2 is burned by the first spark plug 53, the previously stored ignition timing ΘA of the first spark plug 53 is acquired, and the second spark plug 54 When the air-fuel mixture in the combustion chamber 2 is burned, the previously stored ignition timing ΘM of the second spark plug 54 is acquired. Next, the routine proceeds to step 108 where ignition processing is performed.

2 Main Combustion Chamber 3 Fuel Injection Valve 44 Intake Valve 46 Exhaust Valve 50 Subchamber Casing 51 Subchamber 52 Communication Hole 53 First Spark Plug 54 Second Spark Plug

Claims (1)

  A sub chamber that communicates with the main combustion chamber through the communication hole and has the first spark plug is formed on the top surface of the main combustion chamber, and communicates when the air-fuel mixture in the sub chamber is burned by the first spark plug. In a control apparatus for an internal combustion engine in which a jet flame is ejected from a hole, a second spark plug for igniting an air-fuel mixture in the main combustion chamber is formed on the top surface of the main combustion chamber on the side of the jet flame ejected from the communication hole. The second spark plug is ignited after the first spark plug is ignited, and ignited by the second spark plug when turbulence occurs around the second spark plug due to the jet flame ejected from the communication hole. A control device for an internal combustion engine, wherein the ignition timing of the first spark plug and the ignition timing of the second spark plug are set so that an initial flame of the mixed gas mixture is generated.

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