JP2010084620A - Control method and control device for spark ignition engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method for a spark ignition engine achieving fail-safe of a preignition suppression control system. <P>SOLUTION: Failure of the preignition suppression control system is detected (S1101). When the failure is not detected, a step for normal time is performed (S1103) for controlling an engine by a first controlled variable for suppressing preignition. Meanwhile, when the failure is detected, steps for abnormal time are performed (S1104-S1108) for controlling the engine by a second controlled variable for suppressing the preignition. The second controlled variable is set to more strongly suppress the preignition in comparison with the first controlled variable. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control method and a control device for a spark ignition type engine, and more particularly to control for suppressing abnormal combustion in an engine such as a pre-ignition engine.

  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, pre-ignition (hereinafter referred to as pre-ignition) is a phenomenon in which the air-fuel mixture in the cylinder self-ignites before the normal combustion time after ignition (for example, MB 10% CA) due to a change in the operating environment of the engine. 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 Literature 1 describes that whether or not post-ignition, which is a pre-ignition phenomenon, is determined based on a combustion ion current, and that fuel injection increase or ignition timing is retarded at the time of occurrence.

  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 pre-ignition can be suppressed.

JP 2006-046140 A JP 2002-339780 A JP 2001-159348 A

  However, in the above-described conventional technology, no study has been made on the fail-safe design of the pre-ignition suppression control system. If such fail-safe design is not implemented, if the pre-ignition suppression control system fails for some reason, the pre-ignition suppression function does not work, causing abnormal noise due to frequent pre-ignition, engine output reduction, or engine damage. I could invite you.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a spark ignition engine control method and control device that realizes fail safe of a pre-ignition suppression control system.

  According to one aspect of the present invention, there is provided a vehicle engine control method including a pre-ignition suppression control system that predicts and suppresses pre-ignition in a spark ignition engine, and detects a failure of the pre-ignition suppression control system. A detection step, a normal time step of controlling the engine with a first control amount for suppressing pre-ignition when the failure is not detected in the detection step, and a case where the failure is detected in the detection step And an abnormal time step of controlling the engine with a second control amount for suppressing pre-ignition, wherein the second control amount is set so as to suppress pre-ignition more strongly than the first control amount. An engine control method is provided.

  According to this configuration, when a failure is detected, the first control amount at normal time is increased to the second control amount that suppresses pre-ignition more strongly, so that the pre-ignition suppression function works and is good. The state of the engine is secured.

  According to a preferred embodiment of the present invention, it is preferable that the second control amount is set so as to increase according to the number of devices in which the failure is detected in the detection step.

  According to this configuration, the control amount is increased according to the number of devices in which a failure is detected, so that pre-ignition can be effectively prevented.

  According to a preferred embodiment of the present invention, when the failure is detected in the detection step and the failure is a device that detects a parameter to be controlled in the pre-ignition suppression control, the abnormality is detected. In the time step, it is preferable to control the engine with a third control amount for suppressing pre-ignition more strongly than the second control amount.

  When a device that detects a parameter to be controlled in the pre-ignition suppression control fails, the pre-ignition suppression control becomes unstable. On the other hand, according to the above configuration, in such a case, the third control amount for more strongly suppressing the pre-ignition is forcibly used, so that the pre-ignition can be effectively suppressed.

  According to a preferred embodiment of the present invention, the first to third control amounts are preferably retards of the intake valve closing timing. As a result, the in-cylinder pressure is lowered and pre-ignition can be effectively suppressed.

  According to a preferred embodiment of the present invention, it is preferable that the third control amount is for making the intake valve closing timing the most retarded. As described above, when a device that detects a parameter to be controlled in the pre-ignition suppression control fails, the pre-ignition suppression control becomes unstable. In such a case, proper pre-ignition suppression control cannot be expected. On the other hand, according to the above configuration, the intake valve closing timing is set to the most retarded angle, so that the in-cylinder pressure can be greatly reduced and the pre-ignition can be reliably suppressed.

  According to another aspect of the present invention, there is provided a control device for a vehicle engine including a pre-ignition suppression control system that predicts and suppresses a pre-ignition in a spark ignition engine, and detects a failure of the pre-ignition suppression control system. Detecting means that detects when the failure is not detected by the detecting means, a normal-time control means that controls the engine with a first control amount for suppressing pre-ignition, and the detection means detects the failure. An abnormality control means for controlling the engine with a second control amount for suppressing pre-ignition when the second control amount suppresses the pre-ignition more strongly than the first control amount. An engine control device is provided, which is characterized in that it is set as follows.

  According to this configuration, when a failure is detected, the first control amount at normal time is increased to the second control amount that suppresses pre-ignition more strongly, so that the pre-ignition suppression function works and is good. The state of the engine is secured.

  ADVANTAGE OF THE INVENTION According to this invention, the control method and control apparatus of a spark ignition engine which implement | achieve the fail safe of a pre-ignition suppression control system are provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, It shows only the specific example advantageous for implementation of this invention. In addition, not all combinations of features described in the following embodiments are indispensable as means for solving the problems 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. The engine control system includes a pre-ignition suppression control system that performs pre-ignition suppression control.

  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, an oxygen concentration O ₂ of the exhaust gas from the oxygen concentration sensor 74, etc. 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-ignition 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 = MB 10% 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 Liven Good-Wu integral formula as will be described later. .

  MB10% CA is defined by the following equation.

For example, the pre-ig intensity under the condition of 1000 rpm / ce 0.9 in FIG. 7A is X ₁₀ (normal combustion map) −X ₁₀ (pre-ig map) = 15−25 = −10 in the initial condition before correction. Since the generation timing comes after the 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, effective 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, X ₁₀ (preig map) = + 4. Therefore, as shown in FIG. 8B, X ₁₀ (normal combustion map) −X ₁₀ (pre-ig map) = 15−4 = + 11, and the occurrence of pre-ig 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, X ₁₀ (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). Since the self-ignition becomes harder as the ratio becomes lower), the correction amount is decreased. As the fuel injection timing is retarded (retarded) as shown in FIG. 10 (c), it becomes easier to ignite near normal combustion MB10% CA. The correction amount is increased, and as the split injection ratio increases (as the late injection amount increases) as shown in FIG. 10D, ignition becomes easier near normal combustion MB10% CA, so the correction amount is decreased. Further, as shown in FIG. 10E, the self-ignition becomes difficult as the air-fuel ratio becomes smaller (rich side) or the air-fuel ratio becomes larger (lean side) at the stoichiometric air-fuel ratio 14.7 that is most easily ignited. 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, when the preig map is corrected so that the fuel injection timing in FIG. 10C is changed from 280 ° CA (X ₁₀ = 0) to 20 ° CA (X ₁₀ = −15). , X ₁₀ (normal combustion MB ₁₀ % CA) −X ₁₀ (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.

  The preig suppression control in the present embodiment is substantially as described above. However, the present invention is not limited to a specific pre-ignition suppression control algorithm, and can be appropriately applied to various pre-ignition suppression control algorithms.

  Further, instead of the above-described preig prediction process, for example, a process of detecting a preig actually generated using a knocking detection signal NK from the knock sensor 80 or a conventional combustion ion current can be used.

[Fail safe control]
Hereinafter, a fail-safe embodiment related to the pre-ignition suppression control system as described above will be described.

  Hereinafter, sensor devices that are fed back to the VVT 32 and detect parameters to be controlled in the pre-ignition suppression control are referred to as “suppression systems”. This suppression system includes, for example, a cam angle sensor 35 as a VVT angle sensor that detects intake valve closing timing (hereinafter referred to as “IVC”), an oxygen concentration sensor 74 that detects an oxygen concentration that defines an air-fuel ratio, and knocking. A knock sensor 80 for detection is included.

  On the other hand, sensor devices that detect correction parameters used in the above-described pre-ignition suppression control are referred to as “detection systems”. This detection system includes, for example, an intake air temperature sensor 77 and an intake air humidity sensor 78. It will be readily appreciated by those skilled in the art that an outside air temperature sensor, a surge tank temperature sensor, an intake port temperature sensor, or the like can be used instead of the intake air temperature sensor 77. Further, when an octane number detection estimation unit and an EGR rate detection estimation unit are provided, these units can also be included in the detection system.

  FIG. 11 is a flowchart showing the fail-safe control process of the pre-ignition suppression control system in the present embodiment. This fail safe control process is repeatedly executed by the engine controller 100 at a predetermined cycle.

  First, in step S1101, a failure of each device in the pre-ignition control system is detected. Here, for example, a failure table describing the failure status of each device is configured in the memory 102, and when a failure of a certain device is detected, the failure flag of that device in the failure table is set (0 → 1). )

  Next, in step S1102, the presence / absence of a failure is determined. If there is no failure, the normal process is executed. That is, the process proceeds to step S1103, and the pre-ig prediction / suppression control as described above is executed as the IVC normal control. Here, the retard angle of IVC controlled in the above-described pre-ig prediction / suppression control is the first control amount for suppressing the pre-ig.

  On the other hand, if there is a failure, the process after step S1104 is performed as an abnormal process. In step S1104, it is determined whether or not the detected failure is a suppression system failure. If it is not a failure in the suppression system, it is determined in step S1105 whether there is a failure in the detection system. If NO in step S1105, that is, if the detected failure is neither a failure in the suppression system nor a failure in the detection system, the process proceeds to step S1103 as in the case of no failure, and the above-described IVC normal control is performed. Such pre-ignition prediction / suppression control is executed. On the other hand, when the detected failure is a detection system failure, the IVC normal control cannot be performed properly. Specifically, at least the pre-ig map correction as described above cannot be properly performed. In this case, the process proceeds to step S1106.

  In step S1106, the number of failure points in the detection system is counted. In step S1107, the IVC is controlled to be retarded according to the number of failure points in the detection system. For example, if the total number of devices used in the detection system is β and the angle obtained by equally dividing from no delay to the most retarded angle is β, and the number of failure points in the detection system counted in step S1106 is N, in step S1107 , Retard IVC by N · β. However, instead of dividing the total number of devices used in the detection system from no delay to the most retarded angle, the devices used in the detection system are divided unevenly according to the degree of influence on the pre-ig intensity, etc. May be. Here, the retard angle of IVC controlled in step S1107 is the second control amount for suppressing the pre-ignition. In step S1107, the second control amount is set so as to suppress the pre-ignition more strongly than the first control amount controlled in the IVC normal control in step S1103.

  By retarding the IVC in this way, the in-cylinder pressure is lowered and the pre-ig can be effectively suppressed.

  If it is determined in step S1104 that the detected failure is a suppression system failure, the process proceeds to step S1108. In this case, it can be said that this is a serious failure of the pre-ignition suppression control system, and proper pre-ignition prediction / suppression control can no longer be expected. Therefore, in step S1108, IVC is forcibly controlled to the most retarded angle as the third control amount. Thus, by setting IVC to the most retarded angle, the in-cylinder pressure is greatly reduced, and the pre-ignition can be reliably suppressed.

  Note that, regardless of whether the detected failure is a suppression system or a detection system, a fail-safe in which IVC is set to the most retarded angle in step S1108 is also conceivable. However, in that case, a decrease in engine output torque is inevitable. In contrast, in the above-described embodiment, in the case of a detection system failure, the IVC is not set to the most retarded angle, but is controlled to an intermediate delay angle according to the number of failure of the detection system. There is an advantage that torque reduction can be prevented as much as possible.

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. It is a figure which shows the specific example of the pre-ig prediction procedure of FIG. It is a figure which shows the specific example of the pre-ig prediction procedure of FIG. It is a figure which shows the specific example of the pre-ig prediction procedure of FIG. It is a figure which illustrates the correction parameter used for preig suppression control. It is a flowchart which shows the fail safe control process of the pre-ignition suppression control system in an embodiment.

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 (6)

A control method for an engine of a vehicle including a pre-ignition suppression control system for predicting and suppressing pre-ignition in a spark ignition engine,
A detection step of detecting a failure of the pre-ignition suppression control system;
A normal time step of controlling the engine with a first control amount for suppressing pre-ignition when the failure is not detected in the detection step;
An abnormal time step of controlling the engine with a second control amount for suppressing pre-ignition when the failure is detected in the detection step;
Have
The engine control method, wherein the second control amount is set so as to suppress pre-ignition more strongly than the first control amount.   2. The engine control method according to claim 1, wherein the second control amount is set to increase according to the number of devices in which the failure is detected in the detection step.   When the failure is detected in the detection step, and the failure is a device that detects a parameter to be controlled in the pre-ignition suppression control, in the abnormal time step, the second control amount The engine control method according to claim 1 or 2, wherein the engine is controlled with a third control amount for suppressing pre-ignition more strongly.   The engine control method according to claim 3, wherein the first to third control amounts are retards of intake valve closing timing.   5. The engine control method according to claim 4, wherein the third control amount makes the intake valve closing timing the most retarded. A control device for a vehicle engine including a pre-ignition suppression control system that performs prediction and suppression of pre-ignition in a spark ignition engine,
Detecting means for detecting a failure in the pre-ignition suppression control system;
Normal time control means for controlling the engine with a first control amount for suppressing pre-ignition when the failure is not detected by the detection means;
An abnormality control means for controlling the engine with a second control amount for suppressing pre-ignition when the failure is detected by the detection means;
Have
2. The engine control apparatus according to claim 1, wherein the second control amount is set to suppress pre-ignition more strongly than the first control amount.

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