JP4876557B2 - Control device for spark ignition gasoline engine - Google Patents

Description

  The present invention relates to a control device for a spark ignition gasoline engine.

  In general, when performing premixed compression auto-ignition combustion (HCCI: Homogeneous-Charge Compression-Ignition Combustion, referred to as “compression self-ignition” in this specification), as shown in Patent Document 1, a pair of an exhaust stroke and an intake stroke overlap each other. The burned gas that has been lean-burned in the preceding cylinder in the exhaust stroke between the cylinders is introduced into the subsequent cylinder in the intake stroke as it is, or, as shown in Patent Document 2, the exhaust valve is closed in a predetermined operating range. A technique (so-called negative overlap) is known in which the burned gas remains in the combustion chamber by changing the timing and the opening timing of the intake valve. In particular, Patent Literature 1 discloses an ignition assist that executes spark ignition before compression top dead center at least on a predetermined low load side in order to promote compression self-ignition.

  Incidentally, as shown in Non-Patent Documents 1 and 2, compression self-ignition is a technique for intentionally generating a phenomenon called autoignition to reduce NOx and pumping loss. is there. As described in Non-Patent Document 1 or 2, this auto-ignition has a slow reaction, a multistage reaction, and a one-stage reaction in stages.

  The slow reaction occurs in a region of low pressure and low temperature (200 ° C. or lower), and does not occur in a normal engine. The multi-stage reaction is a “cold flame” that burns with a relatively slight temperature rise in a higher temperature range (a temperature range of about 300 ° C. to about 400 ° C.) than that in which a slow reaction occurs, and forms formaldehyde. It is a combustion reaction that occurs in a relatively short time and causes a “blue flame” that rapidly rises in temperature to generate CO and a “hot flame” that occurs after the blue flame and changes rapidly to a high temperature in stages. . The one-stage reaction is a phenomenon that occurs in a higher temperature region than the multistage reaction, and is a phenomenon that generates a hot flame immediately after ignition.

  FIG. 1 is a diagram showing the ignition limit of isooctane.

  With reference to FIG. 1, in the region indicated by LR (temperature region of about 300 ° C. to about 400 ° C.) in FIG. 1, a multistage reaction occurs and a cool flame is generated, whereby the air-fuel mixture is self-ignited. On the other hand, as shown by HR in FIG. 1, it is known that a one-step reaction occurs in other high temperature / high pressure regions.

  On the other hand, as described in Non-Patent Document 1 or 2, the time at which self-ignition occurs is calculated by the Arrhenius function (Arrhenius function),

(However, τ _D is the ignition delay, t is the elapsed time until the end-gas is compressed, and ti is the self-ignition time.)
The ignition delay τ _D in equation (1) is
τ _d = {A × exp (B / T)} / P ^C (2)
(However, A, B, and C are parameters that depend on the gas mixture, T is temperature, and P is pressure.)
Is a time function.
JP 2005-105974 A JP-A-10-266878 John B. Heywood, “Internal Combustion Engine Fundamentals” 464-P. 468 Published by Fujio Nagao, Third Lecture on “Internal Combustion Engine”, published by Yokendo Co., Ltd. 176-P. 180

  By the way, the inventors of the present invention have clarified that the above-described ignition assist is preferably performed at a timing for stimulating the thermal flame reaction in a relatively unstable operation state in which a multistage reaction occurs. I came.

On the other hand, as is clear from the equation (1), the self-ignition is a function depending on the ignition delay τ _D. As is apparent from the equation (2), this ignition delay τ _D depends on the temperature T and pressure P in the cylinder and changes every moment depending on the operating state. Therefore, the ignition assist must also be retarded according to changes in the temperature T and pressure P in the cylinder.

However, if ignition assist is executed at a fixed timing, misfire will occur if an ignition delay occurs due to a decrease in the outside air temperature or the like. As a result of this misfire, the in-cylinder temperature and the in-cylinder pressure of the cylinder are further rapidly reduced, and the ignition delay τ _D is also increased. If such a change in the ignition delay τ _D occurs in the multistage reaction region, spark ignition is executed at an earlier stage than the timing at which the hot flame reaction can be promoted, and misfire is repeated. On the other hand, when misfire is repeated, the uneven distribution of fuel in the combustion chamber becomes significant each time the misfire occurs. Thereafter, by further increasing the ignition delay τ _D , the ignition assist is executed at the timing of promoting the cold flame reaction, and it has been found that heavy knocking occurs due to the uneven distribution of fuel in the combustion chamber. It was. In particular, when the compression self-ignition is realized with a so-called negative overlap as in Patent Document 2, the in-cylinder air-fuel ratio becomes rich due to the negative overlap due to repeated misfires, so that knocking at the time of ignition becomes further remarkable. I understand that too.

  However, conventionally, since the ignition assist is executed exclusively based on the relationship between the load demand in the driving state and the engine speed, it has been impossible to control the timing of the appropriate ignition assist.

  The present invention has been made in view of the above problems, and performs ignition assist at an appropriate timing, avoids heavy knocking, and reliably realizes compression self-ignition operation even in an operation region in an unstable combustion state. It is an object of the present invention to provide a control device for a spark ignition gasoline engine that can be used.

In order to solve the above-described problems, the present invention is a control device for a spark ignition gasoline engine having a plurality of cylinders, and includes at least an engine based on operating state determining means for determining an operating state and determined operating state. and HCCI execution means for executing the compression-ignition operation at partial load operation region of an ignition assistance means for performing the ignition assistance in performing the compression-ignition operation at partial load operation region of at least the engine, the operating The state determination means has misfire detection means for detecting misfire, and when the misfire detection means does not detect misfire in the cylinder performing the compression self-ignition operation , the ignition assist means to cylinder while performing the spark ignition at a set reference assist timing in the latter half of the compression stroke before top dead center of the compression stroke, the cylinder If a misfire is detected, it compared the cylinder, as the control device for the spark-ignition gasoline engine, characterized in that at a timing retarded than the reference assist timing is to perform a spark ignition. In this aspect, when performing the compression self-ignition operation in the partial load operation region of the engine, the ignition assist means executes spark ignition at a predetermined reference assist timing, thereby promoting self-ignition and reliably performing compression self-ignition. It becomes possible to realize driving . On the other hand, if a misfire occurs in a cylinder that is performing compression self-ignition operation, the ignition timing is set in anticipation of in-cylinder temperature drop or pressure drop caused by misfire by retarding the spark ignition timing. Therefore, it is possible to prevent repeated misfires and heavy knocking induced thereby.

  In a preferred aspect, the HCCI execution means executes a reduced-cylinder operation in which only a specific cylinder performs a compression self-ignition operation in a predetermined low-load operation region in the partial load operation region, while in the partial load operation region. In the operating region on the high load side exceeding the predetermined low load, the number of operating cylinders is increased and the compression self-ignition operation is executed. When operating in the ignition operation, spark ignition is executed at a timing retarded from the reference assist timing. In this aspect, in the predetermined low load side operation region in the partial load operation region, the compression self-ignition operation is executed only in a specific cylinder, thereby improving fuel consumption and exhaust performance. Moreover, since this compression self-ignition operation is a reduced-cylinder operation in which only a specific cylinder is operated, the load per operating cylinder is amplified, so that even if the intake air temperature is relatively low, the cylinder The internal temperature rises quickly and combustion stability is improved. As a result, it is possible to realize compression self-ignition at a relatively low intake air temperature in the engine low-load operation region where compression self-ignition operation is most likely to be unstable, avoiding premature ignition by raising the intake air temperature. In addition, it becomes possible to maintain the improvement in fuel consumption in the low load operation region. On the other hand, when the operation state shifts to a high load side operation region that exceeds the predetermined low load in the partial load operation region, the operating rate is increased, so the cylinder that was operating during the reduced cylinder operation It is possible to prevent knocking at the same time, and when a cylinder that has been inactive during reduced-cylinder operation performs compression self-ignition operation, ignition assist is performed according to the in-cylinder temperature and in-cylinder pressure of the cylinder. Since the timing can be retarded, misfire can be reliably prevented even in a relatively unstable operating state when the operating rate of the cylinder is increased.

  In a preferred embodiment, the ignition assisting means promotes a cold flame reaction in the latter half of the compression stroke before the top dead center of the compression stroke as the reference assist timing in an operation region where a multistage reaction including a cold flame reaction occurs. The second spark ignition is executed to promote the thermal flame reaction after a predetermined time of the first spark ignition. Under the predetermined operating conditions, the second spark ignition is performed. According to the predetermined operating condition, retarding is performed with respect to the reference assist timing. In this aspect, ignition assistance corresponding to each of the cold flame reaction and the hot flame reaction can be executed in an unstable operation region where the multistage reaction occurs, and under the predetermined operating conditions, the ignition delay of the hot flame reaction is delayed. Since the ignition assist timing can be controlled in response to the above, reliable compression self-ignition can be realized.

As described above, according to the present invention, when a misfire occurs in a cylinder that is performing the compression self-ignition operation, it becomes possible to realize the ignition assist at a timing that takes into account the ignition delay. In the operating state determined only by the engine speed, misfires that could not be prevented sufficiently and heavy knocking due to repeated repetitions are reliably prevented to improve combustion stability, so that it is in an unstable combustion state Even in the operation region, there is a remarkable effect that the compression self-ignition operation can be surely realized.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 2 is a configuration diagram showing a schematic configuration of the control device 10 according to one embodiment of the present invention, and FIG. 3 is a schematic sectional view showing a structure of one cylinder of the four-cycle gasoline engine 20 according to FIG. .

  With reference to FIGS. 2 and 3, the illustrated control apparatus 10 includes a four-cycle gasoline engine 20 and a control unit 100 for controlling the engine 20.

  The engine 20 integrally includes a cylinder block 22 that rotatably supports the crankshaft 21 and a cylinder head 23 disposed on the upper portion of the cylinder block 22, and the cylinder block 22 and the cylinder head 23 include Four cylinders 24A to 24D arranged in the longitudinal direction of the crankshaft 21 are formed.

  Four pistons 26 connected to the crankshaft 21 via connecting rods 25 are fitted in the cylinders 24A to 24D. In the present embodiment, when the first cylinder 24A, the second cylinder 24B, the third cylinder 24C, and the fourth cylinder 24D are called from one end side in the cylinder row direction, the stroke in which the piston 26 moves up and down in each of the cylinders 24A to 24D. As shown in Table 1, the crank angle is 180 degrees each so that the combustion cycle of the cylinders 24A to 24D is in the order of the first cylinder 24A, the third cylinder 24C, the fourth cylinder 24D, and the second cylinder 24B. The phase difference is set.

  A combustion chamber 27 is formed in each of the cylinders 24A to 24D. At this time, in the present embodiment, between the two cylinders (first cylinder 24A and second cylinder 24B, third cylinder 24C and fourth cylinder 24D) in which the exhaust stroke and the intake stroke overlap, A piping structure is configured such that the burned gas is directly introduced from the cylinders 24A and 24D to the intake stroke side cylinders (referred to as subsequent cylinders in this embodiment) 24B and 24C. Has been. The geometric compression ratio of the preceding cylinders 24A and 24D is set in the range of 14 to 16, while the geometric compression ratio of the subsequent cylinders 24B and 24C is set between 11 and 12.

  FIG. 4 is a schematic plan view showing the cylinders 24A to 24D in an enlarged manner.

  With reference to FIGS. 3 and 4, a ceiling portion of the combustion chamber 27 is formed on the lower surface of the cylinder head 23 for each of the cylinders 24 </ b> A to 24 </ b> D, and the ceiling portion includes two portions extending from the central portion to the lower end of the cylinder head 23. It is a so-called pent roof type having an inclined surface.

  As described above, in configuring the piping structure that guides the burned gas from the preceding cylinders 24A, 24D to the succeeding cylinders 24B, 24C as they are, a pair of intake ports 28 are formed in the preceding cylinders 24A, 24D. In addition, a pair of intake ports 28a for introducing intake air from the intake system and intake ports 28b for introducing burned gas from the preceding cylinders 24A, 24D are formed in the subsequent cylinders 24B and 24C, respectively. . On the other hand, each of the preceding cylinders 24A and 24D is formed with an exhaust port 29a for discharging the burned gas to the exhaust system as it is and an exhaust port 29b for guiding the burned gas to the succeeding cylinders 24B and 24C. In addition, only one exhaust port 29 is formed in each of the subsequent cylinders 24B and 24C for discharging the burned gas to the exhaust system as it is. Further, the exhaust ports 29b of the preceding cylinders 24A and 24D are connected to the corresponding succeeding cylinders (in the example shown, the second cylinder 24B for the first cylinder 24A and the third cylinder for the fourth cylinder 24D by the inter-cylinder gas passage 54). 24C) and the intake port 28b.

  Furthermore, the intake ports 28, 28a, 28b and the exhaust ports 29, 29a, 29b are respectively provided with intake valves 30, 30a, 30b and exhaust valves 31, 31a, 31b. Each intake valve 30, 30 a, 30 b and each exhaust valve 31, 31 a, 31 b are driven to open and close at a predetermined timing by a known valve operating mechanism including camshafts 37, 38 and the like.

  A known tappet unit 36 is provided in each of the intake valves 30, 30a, 30b and the exhaust valves 31, 31a, 31b of the cylinders 24A to 24D. The tappet unit 36 is periodically driven by cams 37a and 38a of camshafts 37 and 38 of a valve mechanism provided in the cylinder head 23.

  Further, among these valves 30a-30b, 31a-31b, the exhaust valves 31a, 31b of the preceding cylinders 24A, 24D and the tappet units 36 of the intake valves 30a, 30b of the succeeding cylinders 24B, 24C are provided with the valves 30. A valve stop mechanism that switches between -30b and 31-31b between an operating state and a stopped state is provided. Since the structure of the valve stop mechanism itself is conventionally known as a so-called lost motion mechanism, detailed illustration thereof is omitted.

  FIG. 5 is a schematic plan view showing a circuit configuration for controlling the tappet unit 36 having a valve stop function.

  Referring to FIG. 5, the control unit 100 includes a control valve for the hydraulic oil circuit 110 that supplies hydraulic oil to the exhaust valves 31a of the preceding cylinders 24A and 24D and the tappet unit 36 of the intake valves 30a of the subsequent cylinders 24B and 24C. 111 is connected as an output element, and the control valve 113 of the hydraulic oil circuit 112 that supplies hydraulic oil to the exhaust valve 31b of the preceding cylinders 24A and 24D and the tappet unit 36 of the intake valve 30b of the subsequent cylinders 24B and 24C is output. Connected as an element. Each valve 30a, 30b, 31a, 31b is configured to be selectively opened and closed by the control unit 100. As a result, the control unit 100 can execute a plurality of operation modes such as compression self-ignition operation (reduced cylinder operation, all cylinder operation) and forced ignition operation of the engine 20.

  Next, referring to FIG. 3, a fuel injection valve 32 that receives a fuel injection pulse from the control unit 100 and injects fuel corresponding to the pulse width into the combustion chamber 27 is provided at the side of the combustion chamber 27. Is provided. The fuel injection valve 32 includes a needle valve and a solenoid (not shown). When a pulse signal is input from the control unit 100, the fuel injection valve 32 is driven for a time corresponding to the pulse width at the pulse input timing, and opens. An amount of fuel corresponding to the valve opening time is injected. The fuel injection valve 32 is supplied with fuel by a fuel pump (not shown) through a fuel supply passage and the like, and the fuel pressure is higher than the pressure in the combustion chamber 27 in the compression stroke. A supply system is configured.

  Referring to FIG. 4, each of the cylinders 24 </ b> A to 24 </ b> D is provided with three spark plugs 34 that are fixed to the cylinder head 23 and emit a spark in the combustion chamber 27. The spark plugs 34 are arranged along the cylinder diameter parallel to the ridge line portion of the piston 26, the center one is disposed on the cylinder bore center Z, and both sides are disposed on the side edge of the combustion chamber 27. Each ignition plug 34 is connected to an ignition circuit 35 capable of controlling the ignition timing by electronic control. By controlling the ignition circuit 35 by the control unit 100, the ignition plug 34 is selectively ignited. To be controlled.

  Next, referring to FIG. 2 and FIG. 3, a branch intake pipe 43 of the intake manifold 42 is connected to the intake ports 28, 28 a of the engine 20. The branch intake pipe 43 is provided for each of the cylinders 24 </ b> A to 24 </ b> D, and each of the branch intake pipes 43 is connected to the intake manifold 42 in a state where an intake passage having an equal length is formed. In the illustrated embodiment, the intake ports 28 and 28a of the cylinders 24A to 24D are arranged along the crankshaft direction, and the downstream end of the branch intake pipe 43 is the intake port of the cylinders 24A to 24D. It is formed in two forks corresponding to 28 and 28a. An open / close valve 44 is provided at the upstream side merge portion of the branch intake pipe 43. The on-off valve 44 is embodied by a three-way solenoid valve, and is configured such that the actuator 45 can individually open and close the aggregate portion of the branch intake pipe 43 by a desired amount.

  An intake passage 46 for introducing fresh air into the intake manifold 42 is connected to the upstream side of the intake manifold 42. A throttle valve 47 is provided in the intake passage 46.

  A branch exhaust pipe 51 is connected to the exhaust ports 29 and 29a. The downstream end of each branch exhaust pipe 51 is connected to the exhaust manifold 52. An exhaust passage 53 for discharging burned gas is connected to the exhaust manifold 52. A three-way catalyst 55 is provided in the exhaust passage 53 for exhaust purification. As is generally known, this three-way catalyst 55 has high purification performance for HC, CO, and NOx when the air-fuel ratio of the exhaust gas is in the vicinity of the stoichiometric air-fuel ratio (that is, the excess air ratio λ = 1). It is the catalyst shown.

  Next, an external EGR system 60 is provided between the intake manifold 42 and the exhaust manifold 52 to recirculate the exhausted burned gas to the intake manifold 42. The external EGR system 60 is connected to a recirculation passage 61 formed between the intake manifold 42 and the exhaust manifold 52, and includes an EGR cooler 62, an EGR valve 63, and an actuator 64 that drives the EGR valve 63. Valve system.

  FIG. 6 is a configuration diagram showing a configuration of an intake air heating system 70 as intake air heating means according to the embodiment of FIG.

  Referring to FIG. 6, a three-way solenoid valve 48 is provided in the intake passage 46 upstream of the throttle valve 47, and a heater 50 is provided in a bypass passage 49 connected to the three-way solenoid valve 48. ing. The three-way solenoid valve 48 is configured to be able to change the valve opening ratio under the control of the control unit 100, similarly to the on-off valve 44. Therefore, by switching the three-way solenoid valve 48, outside air can be introduced into the intake manifold 42 at a desired rate, or air heated by the heater 50 can be introduced into the intake manifold 42. .

  Further, a heating passage 71 is branchedly connected to the intake passage 46. In the middle of the heating passage 71, a cooling water heat exchanger 72 and an exhaust heat exchanger 73 are connected.

  The heating passage 71 is for returning the heat absorbed through the heat exchangers 72 and 73 to the intake side. On the downstream side of the heating passage 71, a branch pipe 71a branched for each of the cylinders 24A to 24D is provided, and each branch pipe 71a is connected to a port on the intake side of the corresponding on-off valve 44.

  The cooling water heat exchanger 72 is connected to the water cooling system 74 of the engine 20 to absorb the heat absorbed by the cooling water returning from the engine 20 to the radiator (not shown) into the intake air passing through the heating passage 71. Is.

  The exhaust heat exchanger 73 is connected to the exhaust passage 53 of the engine 20 to absorb the heat of burned gas into the intake air passing through the heating passage 71. The exhaust heat exchanger 73 is disposed on the downstream side of the cooling water heat exchanger 72 in the heating passage 71.

  In the present embodiment, the heater 50 and the heat exchangers 72 and 73 described above constitute a main part of the intake air heating system 70.

  Referring to FIG. 2, in order to detect the operating state of engine 20, air flow sensor SW <b> 1 is provided in intake passage 46, and intake air temperature sensor SW <b> 2 for predicting intake air temperature T downstream of on-off valve 44. (See FIG. 3). The cylinder block 22 is provided with a rotation speed sensor SW3 for detecting the rotation speed of the crankshaft 21 and an engine water temperature sensor SW4 for detecting the temperature of the cooling water (see FIG. 3). Further, the exhaust passage 53 is provided with an oxygen concentration sensor SW5 provided on the upstream side of the above-described three-way catalyst 55 for controlling the air-fuel ratio. Further, the heater 50 and the exhaust heat exchanger 73 are provided with temperature sensors SW7 and SW8, respectively, and the temperature of the intake air in the bypass passage 49 heated by the heater 50 and the temperature of the intake air in the heating passage 71 are measured. It can be detected. Further, the engine 20 is provided with a pressure sensor SW10 for detecting the in-cylinder pressure (see FIG. 3). In the present embodiment, misfire detection means for determining whether misfire has occurred from the crank angle CA and the in-cylinder pressure is embodied by the rotation speed sensor SW3 and the pressure sensor SW10.

  The engine 20 is provided with a control unit 100 as control means. The control unit 100 includes an air flow sensor SW1, an intake air temperature sensor SW2, an engine speed sensor SW3, an engine water temperature sensor SW4, an oxygen concentration sensor SW5, an accelerator opening sensor SW6 for detecting engine load, and temperature sensors SW7 and SW8. The pressure sensor SW10 is connected as an input element. Each of these sensors SW1 to SW10 is a specific example of the operating state detecting means in the present embodiment. On the other hand, an ignition circuit 35 of the ignition plug 34, an actuator 45 of the on-off valve 44, an actuator of the throttle valve 47, a three-way electromagnetic valve 48 of the intake passage 46, and a heater 50 are connected to the control unit 100 as control elements.

  Referring to FIG. 2, the control unit 100 includes a CPU 101, a memory 102, an interface 103, and a bus 104 that connects these units 101 to 103. The control unit 100 operates according to programs and data stored in the memory 102. The operation state determination means for determining is functionally configured.

  FIG. 7 is a characteristic diagram illustrating an example of operation region setting for performing control according to the operation state according to the embodiment of FIG. 2.

Referring to FIG. 7, in the illustrated embodiment, the compression self-ignition operation is executed in the partial load operation region D where the engine speed N is equal to or less than the predetermined engine speed N1, and the forced ignition operation by spark ignition is performed in the remaining region. Is set to run. Further, in the partial load operation region D in which the compression self-ignition operation is performed, in the predetermined low load side operation region D ₁ , while the reduced cylinder operation is performed, the high load side operation region D exceeding the predetermined low load is performed. _{In 2} , all-cylinder operation is executed.

  The control unit 100 is based on the control map shown in FIG. 7 stored in the memory 102, and the engine operating state (engine speed and engine load) checked by signals from the rotational speed sensor SW3 and the accelerator opening sensor SW6. ) Is in which operating region.

  When executing the compression self-ignition operation, the control unit 100 is in a two-cylinder connection state in which the burned gas of the preceding cylinders 24A and 24D is introduced into the succeeding cylinders 24B and 24C via the inter-cylinder gas passage 54.

  In this state, when executing the reduced cylinder operation, the control unit 100 closes the intake valve 30a of the succeeding cylinders 24B and 24C and shuts off the intake air to the succeeding cylinders 24B and 24C while operating the intake heating system 70, In addition, fuel supply and spark ignition are stopped and only the preceding cylinders 24A and 24D are operated. By executing this reduced-cylinder operation, the load per cylinder in operation can be relatively increased on the low load side where combustion stability is poor, such as during idle operation, until the intake air temperature T is increased. Therefore, it is possible to improve the combustion stability by the compression self-ignition operation.

  Further, when the control unit 100 executes the reduced cylinder operation of the preceding cylinders 24A and 24D in the partial load operation region D, the control unit 100 precedes the compression top dead center at least at a predetermined low load side in order to promote compression self-ignition. The ignition circuit 35 is driven so as to execute the ignition assist of the cylinders 24A and 24D.

On the other hand, in the operation region of the high load side than the predetermined load D _2, all-cylinder operation to all cylinders 24A~24D is running is executed. In this all-cylinder operation, the preceding cylinders 24A, 24D and the succeeding cylinders 24B, 24C are communicated. In the all-cylinder operation, the burnt gas in the preceding cylinders 24A and 24D is introduced into the succeeding cylinders 24B and 24C via the inter-cylinder gas passage 54, and the compression self-ignition operation is also performed in the succeeding cylinders 24B and 24C. It will be. In addition, even during the all-cylinder operation, the control unit 100 operates the intake air heating system 70 to adjust the intake air temperature according to the engine load.

  As a method for adjusting the intake air temperature, the target intake air temperature T and the intake air amount based on the engine operating state are previously stored in the memory 102 as a control map, and the air flow sensor SW1, the intake air temperature sensor SW2, the accelerator opening sensor SW6, the temperature The values are read from the control map so as to obtain the intake air temperature T and the target intake air amount from the detection values of the sensors SW7 and SW8, and the opening amounts of the throttle valve 47, the on-off valve 44, and the three-way solenoid valve 48 are adjusted. Is realized.

  On the other hand, when the forced ignition operation is executed, the control unit 100 controls the hydraulic oil circuits 110 and 112 to change the intake and exhaust flow state so that each cylinder 24A to 24D introduces fresh air to each cylinder independent state. The control valves 111 and 113 are driven to control the tappet unit 36.

  Further, the control unit 100 controls the injection amount and the injection timing from the fuel injection valve 32 according to the determined operating state.

  FIG. 8 is a graph showing the relationship between the fuel injection amount and the engine load for each of the cylinders 24A to 24D.

Referring to FIG. 8, a control map based on FIG. 8 is stored in memory 102 of control unit 100. In this control map, the operating region D ₁ of the low-load side of the reduced-cylinder operation is performed, the preceding cylinders 24A with an increase in the load is set so as to increase the fuel injection amount to 24D. On the other hand, in the operating region D ₂ of the high-load side, following cylinders 24B, the following cylinders 24B compressed at the beginning of self-ignition operation at 24C, supplies a predetermined amount of fuel to 24C, the preceding cylinders 24A, fuel to 24D The supply amount is set to be reduced by the predetermined amount.

  Further, after the subsequent cylinders 24B and 24C start operation, the fuel injection amount to the preceding cylinders 24A and 24D is maintained at a certain amount after the reduction, and only the fuel injection amount to the subsequent cylinders 24B and 24C is the engine load. It is set to increase with the increase.

  FIG. 9 is a graph showing the relationship between the indicated mean effective pressure (IMEP) and the indicated fuel consumption rate (ISFC) at 1500 rpm.

Referring to FIG. 9, when the operation is performed by operating all the cylinders 24 </ b> A to 24 </ b> D without any external EGR in the low load side operation region D ₁ , the illustrated fuel consumption rate becomes close to 200. In contrast, in the operating region D _1, if you perform a reduced-cylinder operation, the increase in the load per cylinder, the illustrated fuel consumption rate, is significantly reduced.

According to the above configuration, when the operating state is determined to be operating region D ₁ of the low-load side, the control unit 100 closes the intake valve 30a according to the following cylinders 24B, 24C, preceding cylinders 24A, 24D Only operate and perform fuel injection. As a result, the compression self-ignition operation is executed in the preceding cylinders 24A and 24D, and the burned gas is introduced into the succeeding cylinders 24B and 24C. At this time, the fuel injection amount to the preceding cylinders 24A and 24D is increased as the engine load increases. Further, during this reduced-cylinder operation, ignition is performed to assist ignition in the preceding cylinders 24A and 24D at least on the low load side. Thereby, the compression self-ignition operation in the preceding cylinders 24A and 24D is reliably executed, and the combustion stability is improved.

Then, the engine load is increased, when the operating state is determined to be operating region D ₂ of the high-load side, the control unit 100 performs the fuel injection to all the cylinders 24A to 24D, by operating all the cylinders Execute compression self-ignition operation. At this time, the fuel injection amount to the preceding cylinders 24A and 24D is decreased, and the fuel injection amount to the subsequent cylinders 24B and 24C is set to the amount of decrease in the preceding cylinders 24A and 24D, and the operation is started. At the same time, after the subsequent cylinders 24B and 24C start operation, the fuel injection amount to the preceding cylinders 24A and 24D is maintained at a constant amount, and only the fuel injection amount to the subsequent cylinders 24B and 24C increases the engine load. The amount is increased along with.

  Next, details of the ignition assist control in the present embodiment will be described.

  FIG. 10 is a graph showing the relationship between misfire and knocking performed by the present inventor. More specifically, the engine rotation speed N = 1500 rpm, so-called negative overlap is performed, and four types of ignition assist timing are shown. The result of having tested timing TS1-TS4 is shown. As conditions for negative overlap, the exhaust valve is closed early (EX closed = 90 ° CA before top dead center), and the intake valve is opened slowly (IN open = 80 ° CA after top dead center). In FIG. 10, the horizontal axis represents the number of cycles of the same cylinder, and the vertical axis represents the maximum pressure (MPa).

  Conventionally, the ignition assist has been fixed at the timing of TS3. In this case, once a misfire occurred, it was confirmed that heavy knocking occurred after repeating a few misfires. Even in the case of TS2 and TS4, heavy knocking occurs after misfires are repeated several times.

  On the other hand, when the ignition timing is retarded so as to be close to the compression top dead center as in TS1, after the misfire has occurred, spontaneous combustion occurs appropriately, and then combustion that does not cause knocking although it is somewhat unstable. It was found that characteristics were obtained.

  Although the detailed reason for these phenomena has not been clearly grasped yet, the inventor presumes that the reason is as follows.

  FIG. 11 is a graph showing a multistage reaction, where (A) shows the case of a multistage reaction region and (B) shows the case of a single stage reaction region.

Referring to FIG. 11A, the ignition delay τ _D until the thermal flame reaction HTR occurs when the multistage reaction occurs is the physical ignition delay τ _ph (no reaction such as fuel atomization, heating, evaporation). Time period)
τ _D = τ _ph + τ _d1 + τ _d2 (3)
Since each ignition delay τ _ph , τ _d1 , τ _d2 is calculated by the equation (2) described in the problem column, all depend on the in-cylinder pressure and the in-cylinder temperature.

By the way, the cause of misfire is that the in-cylinder temperature and the in-cylinder pressure are lowered. For example, even when the cylinder that has been stopped during the reduced cylinder operation as described above is operated or is in operation This phenomenon is likely to occur when suddenly cold air is inhaled. For this reason, since it is considered that the in-cylinder temperature is lowered at the time when misfire occurs, the value of the ignition delay τ _D is larger from the equation (2). As a result, it is considered that the timing suitable for activating the hot flame reaction HTR shown in FIG. 11 (A) is retarded to the compression top dead center, and misfires are repeated.

By repeating this misfire, the in-cylinder temperature and the in-cylinder pressure further decrease, and the air-fuel ratio in the cylinder becomes rich due to the negative overlap. In addition, the uneven distribution of fuel proceeds due to a decrease in the in-cylinder temperature. In this state, if the ignition delay τ _{D is} further increased, the spark ignition timing set for stimulating the hot flame reaction coincides with the timing for stimulating the cold flame reaction. Is considered to cause heavy knocking.

  From the above consideration, in the present embodiment, when a misfire occurs in the HCCI operation region, a control program for avoiding repeated misfires and quickly returning to stable combustion operation is installed in the control unit 100. (See FIGS. 12 to 14).

  Next, the ignition assist timing when no misfire has occurred will be considered.

In the multistage reaction region, a cold flame reaction LTR with a blue flame occurs after a predetermined time (ignition delay τ _d1 ) has elapsed since the start of the oxidation reaction. In general, since the cold flame reaction and the blue flame reaction are usually difficult to distinguish, in the example shown in the drawing, both are used as the cold flame reaction LTR. In the period during which the cold flame reaction LTR occurs (ignition delay τ _d2 ), 5% to 10% of the chemical energy is liberated, but a large amount of formaldehyde is generated as a combustion product, which is further added as an intermediate product. It will play a major role in chain-branching reactions. The branched chain reaction of formaldehyde is explosive and causes a so-called chain-branching explosion to produce a blue flame. At this point (the boundary between the region where the cold flame reaction LTR occurs and the region where the hot flame reaction HTR occurs), all of the original hydrocarbons are oxidized to CO by the blue flame. When the blue flame is generated, if the temperature is sufficiently high and the concentration of the active center is sufficiently high, a hot flame HTR is generated, and the oxidation reaction of hydrocarbon shifts to the final stage. Therefore, in the present embodiment, in order to effectively promote such a multistage reaction, the first spark ignition F1 that promotes the cold flame reaction LTR is executed in the latter half of the compression stroke before the top dead center of the compression stroke, It is set to execute the second spark ignition F2 that promotes the thermal flame reaction HTR after a predetermined time of the first spark ignition F1.

  The ignition timing CA1 of the first spark ignition F1 is preferably 20 to 15 msec before compression top dead center as the so-called “reference assist timing”. Further, as the ignition timing CA2 of the second spark ignition F2, a range from 7 msec to 5 msec before the compression top dead center is preferable as a so-called “reference assist timing”. This has been found as a suitable range for the inventors of the present invention as a result of diligent research to reduce the fluctuation rate of the indicated mean effective pressure (referred to herein as “COV (Coefficient Of Variability)”).

On the other hand, referring to FIG. 11B, when the operation region is a one-step reaction region, a hot flame reaction occurs promptly after a predetermined ignition delay τ _d elapses, and the cold flame no longer exists. In such a case, if the ignition assist as shown in FIG. 11 (A) is executed a plurality of times, the combustion characteristics are worsened, and there is a concern that the fuel consumption and the exhaust performance will deteriorate. Therefore, in the present embodiment, the normal ignition assist F indicated by the broken line in FIG. 11B is executed on the low load side, and the second load is indicated on the high load side as indicated by the solid line in FIG. Only spark ignition F2 is executed as backup ignition. Furthermore, in this embodiment, when this backup operation region is on the high load side, as shown in the figure, the ignition timing CA2 of the second spark ignition F2 is near the compression top dead center (including after the compression top dead center). It is set. As a result, the hot flame reaction HTR is promoted, the heat generation rate is increased after the compression top dead center, the rapid combustion is realized, and the improvement of fuel consumption can be promoted.

  The control unit 100 is based on the control map corresponding to FIG. 7 stored in the memory 102, and the engine operating state (engine speed and engine speed) investigated by signals from the rotational speed sensor SW3 and the accelerator position sensor SW6. It is determined which operating region the engine load) is in. Then, based on the control maps corresponding to FIGS. 11 (A) and 11 (B), in the ignition assist operation region, at the timing shown in FIG. 11 (A), and in the backup ignition operation region, at the timing shown in FIG. 11 (B). Each is configured to drive the ignition circuit 35.

  On the other hand, when the forced ignition operation is executed, the control unit 100 controls each of the hydraulic oil circuits described above to change the intake / exhaust flow state so that each cylinder 24A to 24D introduces fresh air to each cylinder independent state. The tappet unit 36 is controlled by driving the control valve.

  Further, the control unit 100 controls the injection amount and the injection timing from the fuel injection valve 32 according to the determined operating state.

  12 to 14 are flowcharts of the control program according to the present embodiment.

  First, referring to FIG. 12, the control unit 100 determines the operating state based on the signal from each input element described above, and determines whether or not the current operating state is the HCCI operating region D (step). S100). If it is not in the HCCI operation region D, the intake / exhaust flow state is changed so that each cylinder 24A to 24D introduces fresh air to each cylinder independent state and is switched to the normal forced ignition operation mode (step S101). Thereafter, the process proceeds to step S100.

  On the other hand, if it is determined in step S100 that it is in the HCCI operation region D, the preceding cylinders 24A, 24D and the succeeding cylinders 24B, 24C are communicated to shift to the HCCI operation mode (step S102). Based on the above-described operating conditions, the reduced cylinder operation is executed on the low load side, and the all cylinder operation is executed on the high load side.

  Next, the control unit 100 determines whether misfire has occurred in the cylinders 24A to 24D that are operating after the compression top dead center has elapsed, based on the detection values of the rotation speed sensor SW3 and the pressure sensor SW10 (step S103). If a misfire has occurred, it is assumed that a so-called “predetermined operating condition” has been established, and the flow from step S104 is executed. In the present embodiment, when the transition from the reduced cylinder operation to the all cylinder operation is performed and the subsequent cylinders 24B and 24C that have been inactive during the reduced cylinder operation are operated, Trying to do.

  If the misfire detection is YES in step S103, that is, if it is determined that the “predetermined operating condition” is satisfied, first, whether or not the HCCI operation can be executed in the cylinder, whether the operating state is Determination is made (step S104). With this determination, the control unit 100 performs verification of the operation state.

If it is determined in step S105 that the HCCI operation cannot be performed, the control unit 100 immediately switches the operation mode to the SI operation. On the other hand, when it is determined that the HCCI operation is possible, it is further determined whether or not the operation region is a multistage reaction region (step S106). As described with reference to FIGS. 11A and 11B, if the operation region is a multistage reaction region, in order to effectively promote the multistage reaction, the latter half of the compression stroke before the top dead center of the compression stroke. The first spark ignition F1 for promoting the cold flame reaction LTR is executed, and the second spark ignition F2 for promoting the hot flame reaction HTR is executed after a predetermined time after the first spark ignition F1. Yes. Therefore, when misfire occurs during operation in the multistage reaction region, first, τ _d1 and τ _d2 are calculated (step S107), and a control map for determining a delay time and an ignition assist timing determined in advance through experiments or the like. The timing of the second spark ignition F2 is read from M11, the retard amount is set (step S108), and the first and second spark ignitions F1 and F2 are executed based on the set timing (step S109). ).

  FIGS. 15A and 15B are timing charts showing the timing of ignition assist when misfiring occurs. FIG. 15A shows the control in the multi-stage reaction region, and FIG. 15B shows the control in the single-step reaction region.

Referring to FIG. 15A, when the multistage reaction occurs, in the present embodiment, the first spark ignition F1 is the second spark ignition at an ignition timing of 20 msec to 15 msec before compression top dead center. F2 is executed at an ignition timing of 7 msec to 5 msec before compression top dead center. Here, if misfire occurs, the second spark ignition F2 is retarded according to the ignition delay τ _D by the above-described flow, so that repeated misfire is prevented as much as possible. It is possible. Further, by determining the retard amount according to the ignition delay τ _D , it becomes possible to stimulate the thermal flame reaction at a suitable timing substantially according to the in-cylinder temperature and the in-cylinder pressure. Misfires can be reliably prevented.

Returning to FIG. 12, when the operation region is the one-step reaction region in step S106, as shown in FIG. 15B, the normal ignition assist F is executed on the low load side. When a misfire occurs in such an operating region, first, τ _d is calculated (step S110), and the spark ignition F is determined from the control map M12 that determines the delay time and ignition assist timing determined in advance through experiments or the like. The timing is read, a retard amount is set (step S111), and spark ignition F is executed based on the set timing (step S112).

Referring to FIG. 15B, spark ignition F is executed in the low load side operation region where the one-stage reaction occurs. Here, if misfire occurs, the spark ignition F is set according to the ignition delay τ _d by the above-described flow, so that it is possible to prevent repeated misfire as much as possible as shown in the figure. It has become. Also, by determining the set amount according to the ignition delay τ _d , it becomes possible to stimulate the thermal flame reaction at a suitable timing substantially according to the in-cylinder temperature and the in-cylinder pressure. Misfires can be reliably prevented.

  After step S109 or step S112, the control unit 100 returns to step S103 again to prevent repeated misfires.

  Next, referring to FIG. 13, if no misfire has occurred in step S103, the control unit 100 estimates the in-cylinder pressure of the succeeding cylinders 24B and 24C, and detects the in-cylinder temperature, thereby operating. It is determined whether or not the state is a multistage reaction region (step S121). If it is determined by this determination that the operating state is the multistage reaction region, the control unit 100 calculates the current engine speed N and torque τ (step S122), and calculates the calculated engine speed N. And the torque τ are stored in the memory 102 as the target engine speed Nt and the target torque τt, respectively (step S123).

  Next, the control unit 100 calculates the indicated mean effective pressure, and monitors the change to calculate the COV (step S124), and determines whether or not it is equal to or less than the reference value (5% in the present embodiment). Determination is made (step S125). Here, if the calculated COV exceeds 5%, the ignition timings of the first spark ignition F1 and the second spark ignition F2 are set from the control map M1 based on the timing chart of FIG. Then, spark ignitions F1 and F2 are executed at the set ignition timing (step S127).

  Thus, the first spark ignition F1 is executed to promote the cold flame reaction LTR shown in FIG. 11A, and further, the second spark ignition F2 is executed to cause the hot flame reaction HTR. Is promoted, and compression self-ignition can be reliably realized. In this compression self-ignition, COV is greatly reduced, and compression self-ignition operation with high combustion stability can be realized.

  The control unit 100 calculates the COV again after each spark ignition F1, F2, and determines whether the COV has been reduced to 5% or less (step S128). If the COV is not stable, that is, if it exceeds 5%, the process returns to step S100 to determine the operation state, and in some cases, the operation is switched to the SI operation. As another embodiment, when it is determined in step 110 that the COV exceeds 5%, the process returns to step S126, and the ignition assistance by the first and second spark ignitions F1 and F2 is performed again. May be executed.

  If it is determined in step S128 that the COV has been reduced to 5% or less, the engine speed N and the torque τ are calculated again (step S129). This calculation is a step for verifying whether or not the engine speed N and the torque τ have changed with respect to the target engine speed Nt and the target torque τt set in step S105 by the ignition assist. . When the calculation in step S129 ends, the control unit 100 compares the values N and τ with the target engine speed Nt and the target torque τt set in step S105, respectively (steps S130 and S131), and any one of the calculated values N If τ varies, the fuel injection amount is set based on the predetermined control map M2 (step S132), and the fuel injection amount is changed based on the set fuel injection amount (step S133). Thereafter, control returns to step S100.

  Next, the flow in the case where it is the HCCI operation region D but not the multistage reaction region in step S123 will be described.

  Since a one-step reaction occurs mainly on the high load side or the warm side of the HCCI operation region D, it is determined in this region whether or not the operation state requires backup ignition (step S141). If it is determined that the backup ignition is unnecessary, the process returns to step S100 in FIG. On the other hand, when it is determined that the backup ignition is necessary, the backup ignition timing is set based on the control map M3 based on the timing chart of FIG. 11B (step S142), and the backup is performed at the set timing. Ignition is executed (step S143). As shown in FIG. 11B, this backup ignition is realized by executing the second spark ignition F2 in the vicinity of the compression top dead center. This backup ignition ensures compensation in the case of poor ignition.

As described above, in the present embodiment, when the compression self-ignition operation is performed in the partial load operation region D of the engine 20, the control unit 100 performs spark ignition at a predetermined reference assist timing, so that self-ignition is performed. It is possible to promote and reliably realize the compression self-ignition operation, and at least the predetermined operation condition determined by the in-cylinder temperature and the in-cylinder pressure (when there is a misfire or the reduced cylinder operation is stopped) For example, when the cylinder is operated, it is possible to realize the ignition assist at a timing that takes into account the ignition delays τ _D and τ _d .

In the present embodiment, in the predetermined low load side operation region D ₁ in the partial load operation region D, only the preceding cylinders 24A and 24D perform the reduced cylinder operation in which the compression self-ignition operation is performed, while the partial load operation region in operating region D ₂ of the high-load side exceeding a predetermined low load out and D, following cylinders 24B, 24C is also running, is intended to perform compression self-ignition operation in all the cylinders 24A to 24D, the control unit 100 When the succeeding cylinders 24B and 24C that have been stopped during the reduced-cylinder operation are operated in the compression self-ignition operation, in step S103, spark ignition is executed at a timing retarded from the reference assist timing (FIG. 15). (See (A)). Therefore, in this embodiment, among the partial load operation region D, the operating region D ₁ of the predetermined low-load side, the preceding cylinders 24A, by compression-ignition operation is executed in 24D only, fuel consumption and exhaust performance Improvements can be made. In addition, since this compression self-ignition operation is a reduced cylinder operation in which only the preceding cylinders 24A and 24D operate, the load per operating cylinder is amplified, so even if the intake air temperature is relatively low The in-cylinder temperature is quickly increased, and the combustion stability is improved. As a result, it is possible to achieve compression self-ignition at a relatively low intake air temperature in a low-load operation region where compression self-ignition operation is most likely to be unstable, avoiding premature ignition by raising the intake air temperature. It becomes possible to maintain the improvement in fuel consumption in the low load operation region.

On the other hand, when the operation state shifts to the high load side operation region D ₂ exceeding the predetermined low load in the partial load operation region D, the operation rate is increased, so that the operation state is reduced. It is possible to prevent knocking in the preceding cylinders 24A and 24D, and when the succeeding cylinders 24B and 24C that have been stopped during the reduced cylinder operation perform the compression self-ignition operation, the succeeding cylinders 24B and 24C Because the timing of ignition assist can be retarded according to the in-cylinder temperature and the in-cylinder pressure of the cylinder, misfires can be reliably ensured even in relatively unstable operating conditions when the operating rates of the cylinders 24A to 24D are increased. It becomes possible to prevent.

  In the present embodiment, the control unit 100 has a function as misfire detection means for detecting misfire, and when the control unit 100 detects misfire, the misfired cylinder is assumed to be under a predetermined operating condition. The spark ignition is retarded. For this reason, in the present embodiment, the timing of ignition assist can be retarded in anticipation of in-cylinder temperature drop and pressure drop caused by misfire, so it is possible to prevent repeated misfires and heavy knocking induced thereby. Become.

In the present embodiment, in the operation region where the multistage reaction occurs, the first spark ignition F1 that promotes the cold flame reaction LTR is performed as the reference assist timing in the second half of the compression stroke before the top dead center of the compression stroke, The second spark ignition F2 for promoting the thermal flame reaction HTR is executed after a predetermined time after the first spark ignition F1, and the second spark ignition F2 is applied to the predetermined operation under predetermined operating conditions. Depending on the conditions, the retard is performed more than the reference assist timing. For this reason, in the present embodiment, in the unstable operation region where the multistage reaction occurs, it is possible to execute the ignition assist corresponding to each of the cold flame reaction LTR and the hot flame reaction HTR. Since the ignition assist timing can be controlled in accordance with the ignition delays τ _D and τ _d of the flame reaction HTR, it is possible to realize reliable compression self-ignition.

  The above-described embodiments are merely preferred specific examples of the present invention, and the present invention is not limited to the above-described embodiments.

  For example, when a misfire occurs in an operation region where a one-step reaction occurs, control as shown in FIG. 16 may be adopted instead of the control from step S110 to step S112 in FIG.

  FIG. 16 is a flowchart according to another embodiment of the present invention. In FIG. 16, steps S100 to S105 in FIG. 12 are the same and are omitted. FIG. 17 is a timing chart showing the timing of ignition assist when a misfire occurs based on the flow of FIG. 16, wherein (A) shows the control in the multi-stage reaction region, and (B) shows the control in the single-step reaction region. Each is shown.

Referring to FIG. 16, when a misfire occurs in the operation region where the one-step reaction occurs (NO in step S106), in the embodiment shown in FIG. 16, the ignition delay τ _d is calculated (step S210), and thereafter Based on the calculated ignition delay τ _d , in addition to the spark ignition F executed at the reference assist timing, a preliminary spark ignition Fa ignited at a timing advanced from the spark ignition F is set (step S211). As shown in FIG. 17B, after the preliminary spark ignition Fa is executed, the spark ignition F executed at the reference assist timing is executed (step S212).

  The preliminary spark ignition Fa is for stimulating the cold flame reaction. When the preliminary spark ignition Fa is set in step S211, the spark ignition F is determined from the control map M22 that determines the delay time and the ignition assist timing determined in advance through experiments or the like. The advance amount is set by reading the timing.

  Also in this aspect, under the predetermined operating condition, the preliminary spark ignition Fa advanced by a predetermined amount from the reference assist timing is executed before the spark ignition F executed at the reference assist timing, so that misfiring or the like occurs. The cold flame reaction LTR by the preliminary spark ignition is promoted even in an unstable operation region that is easily unstable, and it is possible to realize reliable compression self-ignition.

  The present invention can be similarly applied to a type that realizes compression self-ignition with a negative overlap as disclosed in Patent Document 2. Further, in the type that realizes compression self-ignition with negative overlap, the present invention is similarly applied even when the reduced cylinder operation is performed in the case of a multi-cylinder engine and the operation rate is changed. It is possible to apply.

  It goes without saying that various modifications can be made within the scope of the claims of the present invention.

It is a diagram which shows the ignition limit of isooctane. It is a block diagram which shows schematic structure of the control apparatus which concerns on one Embodiment of this invention. FIG. 3 is a schematic cross-sectional view showing a structure of one cylinder of the four-cycle gasoline engine according to FIG. 2. It is a plane schematic diagram expanding and showing a cylinder. It is a schematic plan view showing a circuit configuration for controlling a tappet unit having a valve stop function. It is a block diagram which shows the structure of the intake-air heating system as an intake-air heating means which concerns on embodiment of FIG. It is a characteristic view which shows an example of the driving | operation area | region setting for performing control according to the driving | running state which concerns on embodiment of FIG. It is a graph which shows the relationship between the illustration mean effective pressure (IMEP) at the time of 1500 rpm, and the illustration fuel consumption rate (ISFC). It is a graph which shows the relationship between the illustration mean effective pressure (IMEP) at the time of 1500 rpm, and the illustration fuel consumption rate (ISFC). It is a graph which shows the relationship between misfire and knocking which this inventor implemented. It is a graph which shows a multistage reaction, (A) is the case of a multistage reaction area | region, (B) is the case of a single stage reaction area | region. It is a flowchart of the control program which concerns on this embodiment. It is a flowchart of the control program which concerns on this embodiment. It is a flowchart of the control program which concerns on this embodiment. It is a timing chart which shows the timing of ignition assistance in case of misfire, (A) has shown the control in a multistage reaction area, (B) has each shown the control in a one-stage reaction area. It is a flowchart which concerns on another embodiment of this invention. It is a timing chart which shows the timing of the ignition assistance when misfire occurs based on the flow of FIG. 16, (A) shows the control in a multistage reaction area | region, (B) has shown the control in a one-stage reaction area | region, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Control apparatus 20 4 cycle gasoline engine 24A, 24B Leading cylinder 24C, 24D Successive cylinder 27 Combustion chamber 32 Fuel injection valve 34 Spark plug (an example of one element of ignition assistance means)
35 Ignition circuit (one element example of ignition assist means)
100 control unit (an example of operation state determination means, HCCI execution means, ignition assist means, misfire detection means)
CA1 ignition timing CA2 ignition timing D HCCI operation region (partial load operation region)
D ₁ Partial load operation area (reduction cylinder operation area)
D ₂ Partial load operation area (all cylinder operation area)
F ignition assist F1 first spark ignition F2 second spark ignition N engine speed Nt target engine speed SW1 air flow sensor (one example of operating state determination means)
SW2 intake air temperature sensor (one element example of operating state determination means)
SW3 Rotational speed sensor (Example of one element of the driving state determination means)
SW4 engine water temperature sensor (one element example of operation state determination means)
SW5 oxygen concentration sensor (an example of one element of the operation state determination means)
SW6 Accelerator opening sensor (one element example of driving state determination means)
SW10 pressure sensor (one element example of operating state determination means)

Claims (3)

A spark ignition gasoline engine control apparatus having a plurality of cylinders,
Driving state determination means for determining the driving state;
HCCI execution means for executing compression self-ignition operation at least in the partial load operation region of the engine based on the determined operating state;
Ignition assist means for performing ignition assist when performing compression self-ignition operation at least in the partial load operation region of the engine,
The operating state determination means includes misfire detection means for detecting misfire,
Said ignition assisting means, by the misfire detecting means, when a misfire in the cylinder running compression-ignition operation is not detected, to the cylinder, in the latter half of the compression stroke before top dead center of the compression stroke Spark ignition is executed at a set reference assist timing, and when a misfire is detected in the cylinder , spark ignition is executed for the cylinder at a timing retarded from the reference assist timing. A spark ignition gasoline engine control device. In the control device of the spark ignition type gasoline engine according to claim 1,
The HCCI execution means executes a reduced-cylinder operation in which only a specific cylinder performs a compression self-ignition operation in a predetermined low-load operation region in the partial load operation region, while the predetermined low-load operation region in the partial load operation region. In the operating region on the high load side that exceeds the load, the number of operating cylinders is increased and the compression self-ignition operation is executed.
The ignition assist means is configured to execute spark ignition at a timing retarded from the reference assist timing when a cylinder that has been stopped during the reduced-cylinder operation is operated in a compression self-ignition operation. Control device for spark ignition gasoline engine. In the control device of the spark ignition type gasoline engine according to claim 1 or 2 ,
In the operation region where a multistage reaction including a cool flame reaction occurs, the ignition assist means performs a first spark ignition that promotes the cool flame reaction in the latter half of the compression stroke before the top dead center of the compression stroke as the reference assist timing. And performing a second spark ignition that promotes a thermal flame reaction after a predetermined time of the first spark ignition, and under the predetermined operating condition, the second spark ignition is performed in the predetermined operation. A control device for a spark ignition type gasoline engine, wherein the retarder is retarded from the reference assist timing according to conditions.

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