JP5287103B2 - Method for predicting abnormal combustion of spark ignition engine, control device and control method for engine - Google Patents

Description

  The present invention relates to a technique for predicting and suppressing the occurrence of abnormal combustion of an engine such as pre-ignition.

  It has been conventionally known that when the compression ratio is increased, fuel efficiency is improved. However, when the compression ratio is increased, abnormal combustion such as knocking and pre-ignition is likely to occur.

  Here, the pre-ignition (hereinafter referred to as pre-ignition) is a normal combustion time point after the ignition of the air-fuel mixture in the cylinder due to a change in the operating environment of the engine (for example, MB10%, which is a crank angle at which the combustion mass ratio reaches 10%) It is a phenomenon of self-ignition before CA). Since the pre-ignition affects the reliability of the engine, conventionally, a technique for detecting and suppressing the occurrence of the pre-ignition with high accuracy has been proposed.

  For example, Patent Document 1 describes that whether or not post-pre-ignition, which is a precursor phenomenon of pre-ignition, is determined based on a combustion ion current, and retards the fuel injection increase amount or ignition timing.

  Patent Document 2 describes that a pre-ignition is detected or predicted, and the fuel injection timing is retarded when the pre-ignition occurs or is predicted.

Furthermore, Patent Document 3 describes that the intake valve closing timing is corrected to a timing at which the pre-ignition can be suppressed.
JP 2006-046140 A JP 2002-339780 A JP 2001-159348 A

  Performing the detection or prediction of the preig with high accuracy is a very important issue in order to suppress the occurrence of the preig and improve the reliability of the engine as in Patent Documents 2 and 3.

  Moreover, since patent document 1 detects the pre-ignition which actually generate | occur | produces, generation | occurrence | production of a pre-ignition cannot be estimated and suppressed beforehand.

  The present invention has been made in view of the above-described problems, and an object thereof is to realize a technique capable of improving the suppression effect by increasing the prediction accuracy of the preig so that the preig suppression control can be easily performed.

In order to solve the above-described problems and achieve the object, according to a first aspect of the present invention, there is provided a spark ignition type engine in which combustion control is preset for each engine load and speed in a low speed operation region. A step of determining a normal combustion time point at which a predetermined combustion mass ratio is reached in normal combustion after ignition by a parameter and storing the value; and a predetermined combustion mass ratio in abnormal combustion excluding the ignition timing from the combustion control parameter Determining the abnormal combustion time point at which the abnormal combustion time point is reached and storing the value, correcting the abnormal combustion time point according to a current external environmental factor, and the corrected abnormal combustion time point before the normal combustion time point. Yes Te, when the difference between the two time points is a predetermined value or more, the occurrence of the combustion control parameter abnormality to be corrected burning, and a step of predicting before combustion start, a That. As described above, the abnormal combustion is predicted based on the difference between the normal combustion time and the abnormal combustion time corrected by the external environmental factor, so that the prediction accuracy of the abnormal combustion is improved and the subsequent abnormal combustion suppression control is easily performed. .

In the second mode, the normal combustion time is set between the compression top dead center and the expansion stroke.
Thus, the torque drop by the pre-ignition suppression control can be suppressed by assuming that the combustion is normal until the time when the influence of abnormal combustion is small.

  In the third embodiment, each predetermined combustion mass ratio at the normal combustion time point and the abnormal combustion time point is stored as a map composed of data obtained by conducting an experiment in advance. Thus, by obtaining the normal combustion point and the abnormal combustion point in advance through experiments, it is possible to improve the prediction accuracy of abnormal combustion at the start point of combustion at which the predetermined combustion mass ratio is obtained.

Further, the fourth embodiment is a spark ignition engine control method in which ignition is obtained by combustion control parameters set in advance for each engine load and speed in a low speed operation region where the engine is at a predetermined speed or less. Abnormal combustion is obtained by calculating a difference between a normal combustion time point that reaches a predetermined combustion rate in the subsequent normal combustion and an abnormal combustion time point that reaches a predetermined combustion rate obtained by excluding the ignition timing from the combustion control parameters. the generation, and a step of predicting before the start of combustion, and a step of correcting the combustion control parameter in the direction of suppressing the abnormal combustion on the basis of the prediction result. Thus, since the pre-ignition is predicted based on the difference between the normal combustion time and the abnormal combustion time, the prediction accuracy of the pre-ignition is improved and the subsequent abnormal combustion suppression control is easily performed.

  In the fifth embodiment, the correction amount of the combustion control parameter is increased as the difference between the normal combustion time point and the abnormal combustion time point is larger. Thereby, abnormal combustion can be effectively suppressed according to the degree.

Further, according to a sixth aspect, in the spark ignition engine control device, when the engine is in a low speed operation region, a predetermined combustion mass is obtained in normal combustion after ignition by a combustion control parameter set in advance for each load and speed of the engine. A first computing means for obtaining a normal combustion time point that reaches the ratio, a first storage means for storing a parameter value at the normal combustion time obtained by the first computing means, and an ignition timing from the combustion control parameter. And a second computing means for obtaining an abnormal combustion time point at which a predetermined combustion mass ratio is reached in abnormal combustion, and a second parameter value for storing the parameter value at the abnormal combustion time obtained by the second computing means. Storage means; first correction means for correcting the abnormal combustion time point according to a current external environmental factor; and the corrected abnormal combustion time point is the normal combustion time. And before a the time point, when the difference between the two time points is a predetermined value or more, when the combustion control parameter abnormal combustion to be corrected is generated, a prediction means for predicting prior to the start combustion, the prediction result of the predicting means And a second correction means for correcting the combustion control parameter based on the second correction means. As described above, the abnormal combustion is predicted based on the difference between the normal combustion time and the abnormal combustion time corrected by the external environmental factor, so that the prediction accuracy of the abnormal combustion is improved and the subsequent abnormal combustion suppression control is easily performed. .

Further, according to a seventh aspect of the present invention, there is provided a spark ignition type engine control apparatus, wherein a predetermined combustion mass is obtained in normal combustion after ignition by a combustion control parameter set in advance for each engine load and speed when the engine is in a low speed operation region. A first computing means for obtaining a normal combustion time point that reaches the ratio, a first storage means for storing a parameter value at the normal combustion time obtained by the first computing means, and an ignition timing from the combustion control parameter. And a second computing means for obtaining an abnormal combustion time point at which a predetermined combustion mass ratio is reached in abnormal combustion, and a second parameter value for storing the parameter value at the abnormal combustion time obtained by the second computing means. storage means, based on a difference between the normal combustion time and abnormal combustion time, the occurrence of abnormal combustion, a prediction means for predicting prior to start of combustion, the prediction means Based on the prediction result by, having a second correcting means for correcting the combustion control parameter in the direction of suppressing the abnormal combustion. Thus, abnormal combustion is predicted based on the difference between the normal combustion time point and the abnormal combustion time point, so that the prediction accuracy of the abnormal combustion is improved and the subsequent abnormal combustion suppression control is easily performed.

  In the eighth embodiment, each predetermined combustion mass ratio at the normal combustion time point and the abnormal combustion time point is stored as a map composed of data obtained by conducting an experiment in advance. Thus, by obtaining the normal combustion point and the abnormal combustion point in advance through experiments, it is possible to improve the prediction accuracy of abnormal combustion at the start point of combustion at which the predetermined combustion mass ratio is obtained.

  In the ninth embodiment, the correction amount by the first correction unit is increased as the intake air humidity is lower. Thus, the suppression effect can be enhanced in an environment where abnormal combustion is likely to occur, and the reliability of the engine can be improved.

  In the tenth mode, the correction amount by the first correction unit is increased as the intake air temperature is higher. Thus, the suppression effect can be enhanced in an environment where abnormal combustion is likely to occur, and the reliability of the engine can be improved.

  According to the present invention, the abnormal combustion is predicted based on the difference between the normal combustion time point and the abnormal combustion time point corrected by the external environmental factor, so that the prediction accuracy of the abnormal combustion is improved and the subsequent abnormal combustion suppression control is executed. It becomes easy to do.

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

  The embodiment described below is an example as means for realizing the present invention, and the present invention can be applied to a modified or modified embodiment described below without departing from the spirit of the present invention.

[Engine control unit]
FIG. 1 is a schematic configuration diagram showing an engine control system according to an embodiment of the present invention. FIG. 2 is a block diagram of an engine control system according to the embodiment of the present invention.

  As shown in FIG. 1, the engine 4 is a spark ignition direct injection engine, has four cylinders 11, and driving force is transmitted from the crankshaft 14 to the automatic transmission 5.

  The engine 4 includes a cylinder block 12 and a cylinder head 13 mounted thereon, and a cylinder 11 is formed inside the block 12. A crankshaft 14 is rotatably supported on the cylinder block 12, and the crankshaft 14 is connected to a piston 15 via a connecting rod 16.

  The piston 15 is slidably inserted into each cylinder 11, and defines a combustion chamber 17 together with the cylinder 11 and the cylinder head 13. Two intake ports 18 for each cylinder 11 are formed in the cylinder head 13 and communicate with the combustion chamber 17. Similarly, two exhaust ports 19 are formed in the cylinder head 13 for each cylinder 11, and each communicates with the combustion chamber 17.

  The intake valve 21 and the exhaust valve 22 are arranged so that the intake port 18 and the exhaust port 19 can be shut off (closed) from the combustion chamber 17, respectively. The intake valve 21 is driven by the intake valve drive mechanism 30 and the exhaust valve 22 is driven by the exhaust valve drive mechanism 40, thereby reciprocating at a predetermined timing to open and close the intake port 18 and the exhaust port 19.

  The intake valve drive mechanism 30 and the exhaust valve drive mechanism 40 have an intake camshaft 31 and an exhaust camshaft 41, respectively. The camshafts 31 and 41 are connected to the crankshaft 14 via a power transmission mechanism such as a chain or a sprocket.

  The intake valve drive mechanism 30 includes a variable valve timing (VVT) 32 that can continuously change the phase of the intake camshaft 31 within a predetermined angle range. The VVT 32 is provided between the power transmission mechanism and the intake camshaft 31. The VVT 32 is directly driven by the crankshaft 14 and is connected to a driven shaft (not shown) coaxially arranged with the intake camshaft 31 and the intake camshaft 31 with a control signal (valve phase) from the engine controller 100. Angle) It is configured to provide a phase difference according to VVTD. Thereby, adjustment of air quantity (effective compression ratio) is performed.

  The VVT 32 can be a phase variable mechanism such as a hydraulic type or an electromagnetic type. In the case of the hydraulic type, a plurality of liquid chambers arranged in the circumferential direction are provided between the driven shaft and the intake camshaft 31, and the above-described phase difference can be created by providing a pressure difference between these liquid chambers. In the case of the electromagnetic type, the electromagnet and the intake camshaft 31 are provided with a spring that generates an urging force that provides a phase difference in one direction between the driven shaft and the intake camshaft 31. A phase difference can be created.

  The phase angle of intake camshaft 31 is detected by cam angle sensor 35, and its output signal VVTA is input to engine controller 100.

  The spark plug 51 is attached to the cylinder head 13. The ignition mechanism 52 receives a control signal (ignition timing) SA from the engine controller 100 and energizes the ignition plug 51 so that a spark is generated at a desired ignition timing. As a result, the ignition timing is adjusted.

  The fuel injection valve 53 is attached to one side (intake side in the figure) of the cylinder head 13 with a known structure. The tip of the fuel injection valve 53 faces the combustion chamber 17 so as to be positioned below the two intake ports 18 in the vertical direction and in the middle of the two intake ports 18 in the horizontal direction.

  The fuel supply mechanism 54 includes a high-pressure pump (not shown) that boosts and supplies fuel to the fuel injection valve 53, piping and hoses that supply fuel from the fuel tank to the high-pressure pump, and the fuel injection valve 53. And an electric circuit to be driven. This electric circuit receives a control pulse signal (fuel injection amount FP and injection timing FT) from the engine controller 100 to actuate a solenoid of the fuel injection valve 53, and a predetermined amount of fuel is injected into the combustion chamber 17 at a predetermined injection timing. Inject into.

  The intake port 18 communicates with the surge tank 55 a through an intake passage 55 b in the intake manifold 55. An intake air flow from an air cleaner (not shown) passes through the throttle body 56 and is supplied to the surge tank 55a. A throttle valve 57 is disposed on the throttle body 56. The throttle valve 57 throttles the intake air flow toward the surge tank 55a and adjusts the flow rate thereof. The throttle actuator 58 receives the control signal (throttle opening) TVO from the engine controller 100 and adjusts the opening of the throttle valve 57. Thereby, the amount of air (intake pipe pressure) is adjusted.

  The exhaust port 19 communicates with a passage in the exhaust pipe via an exhaust passage in the exhaust manifold 60. An exhaust gas purification system having one or more catalytic converters 61 is arranged in the exhaust passage downstream of the inside of the exhaust manifold 60.

  Further, in order to circulate a part of the exhaust gas to the intake system (hereinafter referred to as EGR), the intake manifold 55 (downstream of the throttle valve 57) and the exhaust manifold 60 are connected by an EGR pipe 62. Since the pressure on the exhaust side is higher than that on the intake side, a part of the exhaust gas flows into the intake manifold 55 (EGR gas), and is mixed with fresh air drawn from the intake manifold 55 into the combustion chamber 17. . An EGR valve 63 is disposed in the EGR pipe 62, and the flow rate of EGR gas is adjusted by the valve 63. The EGR valve / actuator 64 receives the control signal EGR from the engine controller 100 and adjusts the opening degree of the EGR valve 63.

  As shown also in FIG. 2, the engine controller 100 is a controller based on a well-known microcomputer, and executes a program storing engine control procedures to be described later as the pre-ignition prediction unit 101a and the pre-ignition suppression unit 101b. A central processing unit (CPU) 101, a memory 102 configured by, for example, a RAM or a ROM and storing data such as an engine control program and a combustion control parameter table 102a, and an input / output (I / O) for inputting / outputting electric signals ) Bus 103.

  The engine controller 100 includes an accelerator opening signal α from an accelerator opening sensor 75 that detects the amount of depression of an accelerator pedal, a vehicle speed signal VSP from a vehicle speed sensor 76 that detects the rotational speed of the output shaft of the automatic transmission 5, Intake air temperature TA from intake air temperature sensor 77, intake air humidity TM from intake air humidity sensor 78, cooling water temperature TE from engine water temperature sensor 79, knocking detection signal NK from knock sensor 80, fuel pressure P from fuel pressure sensor 81, Various inputs such as an intake air flow rate AF from the air flow sensor 71, an intake manifold pressure MAP from the intake pressure sensor 72, a crank angle pulse signal CA from the crank angle sensor 73, and an oxygen concentration O2 of the exhaust gas from the oxygen concentration sensor 74 are received. receive. The engine controller 100 calculates the engine speed ne based on the crank angle pulse signal CA.

  Further, the engine controller 100 controls the engine 4 control parameters such as a predetermined throttle opening TVO, a fuel injection amount FP and an injection timing FT, an ignition timing SA, a valve phase angle VVTD, and the like based on the various inputs described above. And outputs these signals to the throttle actuator 58, the fuel supply mechanism 54, the ignition mechanism 52, the VVT 32, and the like.

  The engine controller 100 also outputs a power generation control signal Ge to the alternator 82, a shift control signal AT to the transmission mechanism 6 of the automatic transmission 5, and a lockup control signal L / U to the lockup mechanism 7.

[Preig prediction / suppression method]
FIG. 4 is a diagram for explaining the pre-ignition predicted according to the present embodiment.

  As shown in FIG. 4A, in the present embodiment, it occurs before CA (Crank Angle) reaching MB (Mass Burn: combustion mass ratio) 10% in normal combustion after ignition (ignition). The initial pre-ignition to be performed and the runaway pre-ignition that occurs before ignition can be predicted. In the following, a method for predicting the initial pre-ig will be mainly described.

  Further, as shown in FIG. 4B, the initial pre-ignition is performed when the engine is operated at a low speed (about 750 to 2000 rpm) when starting at traction, when starting on a slope, when overshifting, or the like. Occurs at high load when the load increases rapidly. This is thought to be due to the fact that when a high load is applied under a high compression ratio, the air-fuel ratio is brought to a richer side than the stoichiometric air-fuel ratio, resulting in an environment in which self-ignition tends to occur.

  FIG. 3 is a flowchart showing a pre-ig prediction / suppression procedure executed by the engine controller of the present embodiment.

  In FIG. 3, first, the pre-ignition prediction unit 101a of the engine controller 100 executes a pre-ignition prediction routine, which will be described in detail later (S1). As a result, if it is determined that the occurrence of the pre-ignition is predicted (YES in S2), the pre-ignition suppression unit 101b executes a pre-ignition suppression routine described in detail later (S3). Thereafter, the engine controller 100 executes engine control based on the engine control program stored in the memory 102 and the preset combustion control parameter table 102a (S4).

  If it is determined that the occurrence of the pre-ignition is not predicted (NO in S2), the engine controller 100 does not execute the pre-ignition suppression routine, and stores the engine control program and the combustion control parameter table 102a stored in the memory 102. Based on this, engine control is executed (S4).

  Here, the pre-ignition prediction routine in S1 of FIG. 3 will be described in detail.

  In FIG. 3, the pre-ignition prediction unit 101a includes a combustion control parameter table (air / fuel ratio (A / F), intake valve closing timing (VVTD)) set in advance for each engine load (ce: intake charge amount) and rotation speed ne. Referring to a table including fuel injection timing (FT), ignition timing (SA), EGR rate, etc .: see FIG. 7), first, a time point at which normal combustion MB10% CA after ignition is reached is obtained by calculation or experiment. The data is stored as a normal combustion map (S11, FIG. 7 (a)).

  Next, the pre-ignition prediction unit 101a excludes the ignition timing SA from the combustion control parameter table 102a, obtains a time point at which the pre-ig MB 10% CA is reached by calculation or experiment, and stores the data as a pre-ig map (S12, FIG. 7). (B)).

  Next, the pre-ig prediction unit 101a corrects the pre-ig map according to external environmental factors such as the current engine operating state (S13).

  Here, as shown in FIGS. 6A to 6D, correction is made according to the intake air temperature, intake air humidity, octane number, and effective compression ratio that affect the combustion state as the external environmental factors. For example, as shown in FIG. 6 (a), the higher the intake air temperature, the easier the self-ignition, the higher the correction amount, and the correction amount is expanded. The correction amount increases as the intake air temperature increases at 25 ° C and the engine speed increases. On the contrary, as the intake air temperature is lower than 25 ° C. and the engine speed is lower, the inclination of decrease in the correction amount becomes smaller. Further, as shown in FIG. 6B, the higher the intake humidity (absolute humidity), the more difficult the self-ignition, so the correction amount is decreased. The higher the engine speed, the greater the inclination of the decrease in the correction amount. Further, as shown in FIG. 6C, the higher the octane number, the more difficult the self-ignition, and thus the correction amount is decreased. The octane number can be determined from, for example, the retard amount of the ignition timing. Further, as shown in FIG. 6D, the higher the actual compression ratio due to production variation and carbon adhesion, the easier the self-ignition, and thus the correction amount is increased. The actual compression ratio can be determined by detecting the intake valve closing timing and the in-cylinder pressure with a sensor or the like.

  Then, the pre-IG prediction unit 101a corrects the combustion control parameter table when the corrected pre-IG MB 10% CA is in front of the normal combustion MB 10% CA and the difference between the two timings is a predetermined value or more. It is predicted that a power pre-ignition will occur (S2). Here, the predetermined value is, for example, 5 ° CA / 750 rpm, and the range of normal combustion MB 10% CA includes the case where the ignition timing is retarded to the expansion stroke. In this way, it is possible to suppress a decrease in torque due to the pre-ignition suppression control by regarding the combustion as normal combustion until the time when the influence of the pre-ig is small.

  7 to 9 show specific examples of the pre-ig prediction procedure of FIG.

  Here, as shown in FIG. 5, as the pre-ignition characteristic, the heat generation amount due to combustion increases and the pre-ig strength increases as it is in front of the normal combustion MB 10% CA. This pre-ignition intensity represents an index indicating how long the pre-ignition occurs with respect to normal combustion MB 10% CA, and is defined by the following equation.

Pre-ignition intensity = MB10% CA normal combustion map-MB 10% CA pre-ignition map In addition, in this embodiment, the occurrence of pre-ignition is predicted by obtaining the self-ignition time t1 after ignition using the following Livengood-Wu integral formula as will be described later. .

MB10% CA is defined by the following equation.

For example, the preig intensity under the condition of 1000 rpm / ce0.9 in FIG. 7A is X10 (normal combustion map) −X10 (preig map) = 15−25 = −10 in the initial condition before correction, and the preig occurrence timing Since it is after normal combustion MB10% CA, it can be predicted that pre-ignition will not occur.

  On the other hand, when the engine operating state changes (intake air temperature TA is 25 ° C. → 70 ° C., octane number RON is 96 → 91 RON, actual compression ratio ε is 14 → 15), first, as shown in FIG. Further, when the preig intensity is calculated using the above-mentioned Livengood-Wu integral formula, X10 (preigmap) = + 4. Therefore, as shown in FIG. 8B, X10 (normal combustion map) −X10 (preig map) = 15−4 = + 11, and the occurrence of preig is predicted.

  On the other hand, as shown in FIGS. 9A to 9C, there is a method of calculating the pre-ignition intensity using each correction parameter. In this case, X10 (preig map) = + 25 (preig map initial condition) −6.0 (intake air temperature correction amount) −7.5 (octane number correction amount) −7.5 (compression ratio ε correction amount) = + 4. Thus, the pre-ig intensity can also be calculated by adding the respective correction amounts.

  Next, the preig suppression procedure in S3 of FIG. 3 will be described.

  FIGS. 10A to 10E illustrate the correction parameters used for the preig suppression control.

  Here, as shown in FIGS. 10A to 10E, correction parameters such as EGR rate, intake valve closing timing, fuel injection timing, split injection ratio (late injection amount / total injection amount × 100), air-fuel ratio, and the like. Is preset. For example, as the EGR rate becomes higher as shown in FIG. 10 (a), the air-fuel ratio becomes higher and the self-ignition becomes difficult. Therefore, the correction amount is decreased, and as the intake valve closing timing becomes later as shown in FIG. 10 (b) (effective compression). The lower the ratio), the more difficult it is to self-ignite, so the correction amount is reduced, and as the fuel injection timing is retarded as shown in FIG. 10 (c), it becomes easier to ignite near normal combustion MB10% CA, so the correction amount is increased. As shown in FIG. 10D, the greater the split injection ratio (the greater the late injection amount), the easier it is to ignite near normal combustion MB10% CA, so the correction amount is reduced. Further, as shown in FIG. 10E, the self-ignition becomes harder as the air-fuel ratio becomes smaller (rich side) or the air-fuel ratio becomes larger (lean side) at the stoichiometric air-fuel ratio of 14.7 which is the easiest to ignite. Reduce the amount.

  As a priority order for correction, it is preferable to execute the pre-ignition suppression control in the order of the fuel injection timing, the split injection ratio, the intake valve closing timing, the air-fuel ratio, and the EGR rate in consideration of control responsiveness.

  Specifically, as the preig suppression control, for example, if the preig map is corrected so that the fuel injection timing in FIG. 10C is changed from 280 ° CA (X10 = 0) to 20 ° CA (X10 = −15), X10 (Normal combustion MB 10% CA) −X10 (pre-IG MB 10% CA) = 15−15 = ± 0.

  As described above, in S4 of FIG. 3, the combustion control parameter is corrected so as to increase the correction amount as the pre-ignition intensity increases, and the engine is controlled while suppressing the occurrence of the pre-ignition based on the corrected combustion control parameter. .

  As described above, according to the present embodiment, the preig prediction accuracy is improved by obtaining the preig intensity, and the subsequent preig suppression control is easily performed. Further, by preliminarily obtaining the time points at which normal combustion MB10% CA and pre-IG MB 10% CA after ignition are reached by experiments, it is possible to improve the prediction accuracy of the pre-ignition at the time when combustion starts to be MB 10% CA.

<1. Preig suppression control by air-fuel ratio according to preig intensity>
Next, the preig suppression control by the air-fuel ratio will be described.

  The following embodiment is not limited to the above-described method of predicting the pre-ignition, and may be configured to detect the pre-ignition actually generated using, for example, a knock detection signal NK from the knock sensor 80 or a conventional combustion ion current. .

  FIG. 11A is a diagram showing the pre-ignition limit for each engine speed and fuel injection timing in relation to the air-fuel ratio and the effective compression ratio.

  From FIG. 11A, in the low-speed and high-load operation region (in other words, in a state where the air-fuel ratio in which pre-ignition is likely to occur is homogeneous), the pre-ig can be suppressed by changing the air-fuel ratio to the rich side with the theoretical air-fuel ratio as a boundary. I understand. For example, taking 750 rpm / injection timing 280 ° as an example, if the air-fuel ratio is 13 / effective compression ratio 9.5 at time A and exceeds the pre-ignition limit, the air-fuel ratio is changed to the rich side as at time B. Thus, since the pre-ignition limit is not exceeded, the pre-ignition can be suppressed.

  This is because, in particular, a direct injection engine injects fuel directly into the cylinder. Therefore, if the air-fuel ratio is made rich, the amount of injected fuel increases and the temperature in the cylinder decreases, making it difficult for the fuel to burn. Because.

  Further, as shown in FIG. 11B, when the engine is operated in a low speed region, the amount of change to the rich side is increased as the air-fuel ratio before the change is closer to the theoretical air-fuel ratio. It can be seen that the pre-ignition suppressing effect can be enhanced.

  Further, as shown in FIG. 11C, in the case of 750 rpm / injection timing 20 °, the pre-ignition limit becomes higher than 750 rpm / injection timing 280 °. Thereby, it turns out that it becomes difficult to generate a pre-ignition by retarding the fuel injection timing.

  Therefore, in the present embodiment, when pre-ignition is predicted or detected in the low-speed operation region of the engine, the air-fuel ratio is changed to the rich side, and the air-fuel ratio change width becomes closer to the stoichiometric air-fuel ratio as the air-fuel ratio before the change is closer. To prevent pre-ig. Thereby, it is possible to suppress the pre-ignition without reducing the torque in the low speed and high load operation region where the torque is required. That is, even if the air-fuel ratio is changed to the lean side from FIGS. 11 (a) and 11 (b), the pre-ig suppression effect can be obtained, but with this, the fuel is reduced and the torque is reduced.

  On the other hand, a restriction value (air-fuel ratio = 10 at which soot may be generated) is provided for the amount of change in the air-fuel ratio to the rich side, and if the change amount of the air-fuel ratio exceeds the restriction value, fuel injection is performed. I try to retard the time. Here, while retarding the fuel injection timing and performing split injection with compression stroke injection, it is possible to suppress pre-ignition while suppressing an increase in smoke associated with further enrichment. In the case of a direct injection engine, the same effect can be obtained by increasing the fuel injection pressure. Here, the fuel injection pressure is detected by the fuel pressure sensor 81.

  According to the present embodiment, the pre-ignition is suppressed in the engine where the effective compression ratio in the low speed and high load operation region is set higher than the effective compression ratio in the low speed and low load operation region. By setting the air / fuel ratio to be able to be performed, the pre-ignition can be effectively suppressed. Here, the effective compression ratio is changed by changing the intake valve closing timing.

  Further, it is possible to increase the homogeneity of the air-fuel mixture in the low-speed and high-load operation region to secure the torque while reducing the generation of smoke, and to effectively suppress the pre-ignition in this region.

<2. Preig suppression control by fuel injection timing according to preig intensity>
Next, the pre-ignition suppression control based on the fuel injection timing will be described.

  The following embodiment is not limited to the above-described method of predicting the pre-ignition, and may be configured to detect the pre-ignition actually generated using, for example, a knock detection signal NK from the knock sensor 80 or a conventional combustion ion current. .

  From FIG. 11 (a), it can be seen that comparing the 750 rpm / injection timing 20 ° (retard side) with the 750 rpm / injection timing 280 ° increases the pre-ignition limit when the injection timing is retarded. From FIG. 12, the pre-ignition limit is higher as the fuel injection timing before retarding the fuel injection timing is later (closer to the compression top dead center).

  Therefore, in the present embodiment, in the low-speed and high-load operation region of the engine, fuel injection (batch injection or split injection) is executed within the period from the intake stroke to the first half of the compression stroke where the air-fuel ratio is in a homogeneous state and smoke is suppressed. If the pre-ignition is predicted or detected, the fuel injection timing is retarded and the retard amount of the fuel injection timing is increased as the fuel injection timing before the retard control is earlier.

  Note that, as shown in FIG. 13, the retard limit of the batch injection timing is 160 ° CA before the compression top dead center at the injection end timing, and the retard beyond this causes the combustion stability to deteriorate significantly. That is, when retarding the injection end timing of batch injection, a timing (160 ° CA before compression top dead center) at which the combustion fluctuation rate suddenly increases (combustion stability deteriorates) appears, and retarded from this timing. Is impossible from the combustion side. For this reason, it is preferable to set the retard allowable time in the case of batch injection in the first half of the compression stroke. In addition, when retarding from 160 ° CA before compression top dead center, combustibility deteriorates, and naturally, pre-ignition hardly occurs.

  Further, as described above, the injection timing is retarded and the air-fuel ratio is changed to the rich side below the stoichiometric air-fuel ratio, so that the pre-ignition can be suppressed with good responsiveness while suppressing the decrease in the effective compression ratio.

  According to the present embodiment, the pre-ignition is suppressed in the engine where the effective compression ratio in the low speed and high load operation region is set higher than the effective compression ratio in the low speed and low load operation region. By setting the air / fuel ratio to be able to be performed, the pre-ignition can be effectively suppressed. Here, the effective compression ratio is changed by changing the intake valve closing timing.

<3. Preig suppression control by engine speed according to preig intensity>
Next, the preig suppression control based on the engine speed will be described.

  The following embodiment is not limited to the above-described method of predicting the pre-ignition, and may be configured to detect the pre-ignition actually generated using, for example, a knock detection signal NK from the knock sensor 80 or a conventional combustion ion current. .

  FIG. 14 is a diagram illustrating the pre-ignition limit for each engine having a different effective compression ratio in relation to the engine speed and the effective compression ratio.

  From FIG. 14, in the low-speed and high-load operation region (in other words, the air-fuel ratio in which pre-ignition is likely to occur is uniform), the pre-ignition limit increases when the engine speed is increased regardless of the engine's inherent effective compression ratio. I understand that. In addition, the pre-ignition limit can be increased by increasing the amount of increase in the rotational speed as the engine rotational speed is higher.

  Therefore, in the present embodiment, when the pre-ignition is predicted or detected in the low-speed and high-load operation region of the engine, the engine speed is increased, and the engine speed before the engine speed control associated with the pre-ignition prediction or detection is increased. The higher the value, the larger the increase in the rotational speed.

  Specifically, the engine speed is released when the lockup mechanism 7 of the automatic transmission 5 described with reference to FIG. 2 is locked up in the pre-ig prediction region shown in FIG. The lockup control signal L / U is raised so as to release half (half clutch state)). FIG. 16 is a diagram showing a change in the engine speed when the lockup is released from the lockup. As shown in I to III of FIG. 16, it can be seen that the engine speed increases instantaneously when the lock-up is released.

  Further, the engine speed can be instantaneously reduced by reducing the resistance of an auxiliary machine such as an alternator driven by the engine, that is, by outputting the power generation control signal Ge to the alternator 82 described in FIG. Can be raised.

  Further, as described above, by increasing the engine speed and changing the air-fuel ratio to the rich side below the stoichiometric air-fuel ratio, it is possible to suppress priming with good responsiveness while suppressing a decrease in the effective compression ratio. .

    According to the present embodiment, the pre-ignition is suppressed in the engine where the effective compression ratio in the low speed and high load operation region is set higher than the effective compression ratio in the low speed and low load operation region. By setting the air / fuel ratio to be able to be performed, the pre-ignition can be effectively suppressed. Here, the effective compression ratio is changed by changing the intake valve closing timing.

<Preig suppression control that combines fuel injection, engine speed, and effective compression ratio>
Next, the pre-ignition suppression control that combines the fuel injection, the engine speed, and the effective compression ratio will be described.

  The following embodiment is not limited to the above-described method of predicting the pre-ignition, and may be configured to detect the pre-ignition actually generated using, for example, a knock detection signal NK from the knock sensor 80 or a conventional combustion ion current. .

  FIG. 17 is a diagram schematically illustrating the pre-ignition suppression control according to the present embodiment.

  In this embodiment, when the pre-ignition is predicted or detected in the low-speed operation region of the engine, first, as the first pre-ignition suppression control (FIG. 17A), the engine speed is increased, and then the pre-ignition is continued. When predicted or detected, as the second pre-ignition suppression control (FIG. 17 (c)), a control for forcibly reducing the effective compression ratio by the intake valve closing timing is executed.

  Here, until the engine speed reaches the pre-ignition suppression speed, as the third pre-ignition suppression control (FIG. 17B), the above-described fuel injection (air-fuel ratio or injection timing) is controlled in the pre-ignition suppression direction. When the pre-ignition is predicted or detected even after the engine speed is increased, as the second pre-ig suppression control (FIG. 17C), the effective compression ratio is forcibly decreased by the intake valve closing timing. Execute.

  The third pre-ignition suppression control (FIG. 17B) is executed before the engine speed is increased after the pre-ignition is predicted or detected, and even after the engine speed reaches the pre-ig suppression speed. Until it is suppressed (FIG. 17D).

  Here, the engine speed is increased by controlling the automatic transmission and the auxiliary machine as described above.

  In the third suppression control, the pre-ignition is performed while retarding the effective compression ratio by retarding the fuel injection timing (collective or divided injection) or changing the air-fuel ratio to the rich side below the stoichiometric air-fuel ratio. Can be suppressed.

  According to this embodiment, the pre-ignition can be suppressed while setting the effective compression ratio in the low speed and high load operation region to be higher than the effective compression ratio in the low speed and low load operation region. Here, the effective compression ratio is changed by changing the intake valve closing timing.

  FIG. 18 is a flowchart showing the pre-ignition suppression control executed by the engine controller of the present embodiment.

  In FIG. 18, first, in S21, the above-described pre-ig prediction procedure is executed to determine whether or not the occurrence of the pre-ig is predicted. When the occurrence of the pre-ignition is predicted in S21, the process proceeds to S22.

  In S22, the above-described 1. And 2. Pre-ignition suppression control is executed by fuel injection (air-fuel ratio (FIG. 10 (e)), injection timing (FIG. 10 (c)), and divided injection ratio (FIG. 10 (d))) according to the pre-ig intensity.

  In S23, it is determined whether or not the occurrence of the pre-ig has been suppressed by the pre-ig suppression control in S22. If the occurrence of the pre-ignition cannot be suppressed in S23, the process proceeds to S24. If the occurrence of the pre-ignition can be suppressed, S24 is skipped and the process proceeds to S25.

  In S24, the above-mentioned 3. Pre-ignition suppression control based on the engine speed corresponding to the pre-ig intensity is executed.

  In S25, it is determined whether or not the engine speed has reached a speed for suppressing pre-ignition in S24. If the pre-ignition suppression rotational speed is reached in S25, the process proceeds to S26. If the pre-ignition suppression rotational speed has not been reached, the process returns to S22 to continue the pre-ignition suppression control by fuel injection.

  In S26, it is determined whether or not the occurrence of the pre-ignition can be suppressed by the pre-ignition suppression control in S24. If the occurrence of the pre-ignition cannot be suppressed in S26, the process proceeds to S27. If the occurrence of the pre-ignition can be suppressed, the process returns to S21 and the pre-ignition prediction procedure is executed.

  In S27, the pre-ignition suppression control based on the effective compression ratio (the intake valve closing timing (FIG. 10B)) corresponding to the pre-ig intensity described above is executed.

  In S28, it is determined whether or not the occurrence of the pre-ignition can be suppressed by the pre-ignition suppression control in S27. If the generation of the pre-ignition cannot be suppressed in S28, the process returns to S22 and the pre-ignition suppression control by the fuel injection is continued. If the occurrence of pre-ignition can be suppressed, the process proceeds to S29.

  In S29, since the pre-ignition can be suppressed, the routine proceeds to normal engine control according to the combustion control map during normal combustion.

  As described above, according to the present embodiment, pre-ignition occurs in an engine in which the effective compression ratio in the low-speed and high-load operation region where pre-ignition is likely to occur is set higher than the effective compression ratio in the low-speed and low-load operation region. Is predicted, first, the pre-ignition suppression control based on the fuel injection and the engine speed is executed to improve the control responsiveness without reducing the engine torque.

It is a schematic structure figure showing an engine control system of an embodiment concerning the present invention. It is a block diagram of the engine control system of the embodiment according to the present invention. It is a flowchart which shows the pre-ig prediction / suppression procedure which the engine controller of this embodiment performs. It is a figure (a) explaining the pre-ignition estimated by this embodiment, and a figure (b) showing the driving state where pre-ignition is easy to occur. It is a figure which shows the relationship between MB10% CA, the amount of heat generation, and pre-ig intensity. It is a figure which illustrates each correction parameter for correcting an MB10% CA preig map. A specific example of the pre-ig prediction procedure of FIG. 3 is shown. A specific example of the pre-ig prediction procedure of FIG. 3 is shown. A specific example of the pre-ig prediction procedure of FIG. 3 is shown. It is a figure which illustrates the correction parameter used for preig suppression control. The figure which shows a pre-ignition limit by the relationship between an air fuel ratio and an effective compression ratio (a), the figure (b) which shows the variation | change_quantity of an air fuel ratio in (a), and the figure (c) which shows the injection timing retard amount in (a). is there. It is a figure which shows a pre-ignition limit by the relationship between a fuel-injection timing and an effective compression ratio. It is a figure which shows a pre-ignition limit by the relationship between fuel-injection timing and a combustion fluctuation rate. It is a figure which shows the pre-ignition limit for every engine from which an effective compression ratio differs with the relationship between an engine speed and an effective compression ratio. It is a figure which shows the on / off map of the lockup in a pre-IG prediction area | region by the relationship between an engine speed and an engine load. It is a figure which shows the change of an engine speed when lockup is cancelled | released. It is a figure which shows typically the preig suppression control of this embodiment. It is a flowchart which shows the pre-ignition suppression control which the engine controller of this embodiment performs.

Explanation of symbols

4 Engine 5 Automatic transmission 6 Transmission mechanism 7 Lock-up mechanism 11 Cylinder 32 VVT
51 Spark Plug 52 Ignition Mechanism 53 Fuel Injection Valve 54 Fuel Supply Mechanism 71 Air Flow Sensor 72 Intake Pressure Sensor 73 Crank Angle Sensor 74 Oxygen Concentration Sensor 75 Accelerator Opening Sensor 76 Vehicle Speed Sensor 77 Intake Temperature Sensor 78 Intake Humidity Sensor 79 Water Temperature Sensor 80 Knock Sensor 81 Fuel pressure sensor 82 Alternator 100 Engine controller

Claims (10)

In a spark ignition engine,
Obtaining a normal combustion time point at which a predetermined combustion mass ratio is reached in normal combustion after ignition, and storing the value in accordance with combustion control parameters set in advance for each engine load and speed in a low-speed operation region; ,
Determining the abnormal combustion time point at which the predetermined combustion mass ratio is reached in the abnormal combustion by excluding the ignition timing from the combustion control parameter, and storing the value;
Correcting the abnormal combustion time point according to a current external environmental factor;
When the corrected abnormal combustion time point is before the normal combustion time point and the difference between the two time points is greater than or equal to a predetermined value , occurrence of abnormal combustion for which the combustion control parameter should be corrected is predicted before the start of combustion. And an abnormal combustion prediction method comprising the steps of:   The abnormal combustion prediction method according to claim 1, wherein the normal combustion time point is set before an expansion stroke after compression top dead center.   2. The abnormal combustion according to claim 1, wherein each predetermined combustion mass ratio at the time of normal combustion and the time of abnormal combustion is stored as a map composed of data obtained by conducting an experiment in advance. Prediction method. A control method for a spark ignition engine,
A normal combustion point in time when the engine reaches a predetermined combustion rate in normal combustion after ignition determined by a combustion control parameter set in advance for each load and speed of the engine in a low speed operation region where the engine speed is equal to or less than a predetermined number of revolutions; Obtaining a difference from the abnormal combustion time point that reaches a predetermined combustion rate obtained by excluding the ignition timing from the control parameters, and predicting the occurrence of abnormal combustion before the start of combustion ;
And a step of correcting the combustion control parameter in a direction to suppress abnormal combustion based on the prediction result.   The engine control method according to claim 4, wherein the correction amount of the combustion control parameter is increased as the difference between the normal combustion time point and the abnormal combustion time point is larger. In the control device of the spark ignition engine,
First calculation means for obtaining a normal combustion time point at which a predetermined combustion mass ratio is reached in normal combustion after ignition according to a combustion control parameter set in advance for each load and speed of the engine in a low speed operation region;
First storage means for storing a parameter value at the time of normal combustion determined by the first calculation means;
Second computing means for obtaining an abnormal combustion time point at which a predetermined combustion mass ratio is reached in the abnormal combustion by excluding the ignition timing from the combustion control parameter;
Second storage means for storing a parameter value at the time of abnormal combustion determined by the second calculation means;
First correcting means for correcting the abnormal combustion time point according to a current external environmental factor;
When the abnormal combustion time point after the correction is before the normal combustion time point and the difference between the two time points is equal to or greater than a predetermined value, an abnormal combustion that should correct the combustion control parameter occurs is predicted before the start of combustion. Prediction means to
An engine control device comprising: a second correction unit that corrects the combustion control parameter based on a prediction result by the prediction unit. In the control device of the spark ignition engine,
First calculation means for obtaining a normal combustion time point at which a predetermined combustion mass ratio is reached in normal combustion after ignition according to a combustion control parameter set in advance for each load and speed of the engine in a low speed operation region;
First storage means for storing a parameter value at the time of normal combustion determined by the first calculation means;
Second computing means for obtaining an abnormal combustion time point at which a predetermined combustion mass ratio is reached in the abnormal combustion by excluding the ignition timing from the combustion control parameter;
Second storage means for storing a parameter value at the time of abnormal combustion determined by the second calculation means;
Predicting means for predicting the occurrence of abnormal combustion before the start of combustion based on the difference between the normal combustion time and the abnormal combustion time;
An engine control apparatus comprising: a second correction unit that corrects the combustion control parameter in a direction to suppress the abnormal combustion based on a prediction result by the prediction unit.   The predetermined combustion mass ratio at the time of normal combustion and the time of abnormal combustion is stored as a map composed of data obtained by performing an experiment in advance. Engine control device.   The engine control apparatus according to claim 6, wherein the correction amount by the first correction unit is increased as the intake air humidity is lower.   The engine control apparatus according to claim 6, wherein the correction amount by the first correction unit is increased as the intake air temperature is higher.

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