JP5925099B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that uses various fuels composed of gasoline and alcohol (ethanol).

  Recently, various types of internal combustion engines have been proposed which are intended to achieve low fuel consumption and high output by using various fuels of gasoline and alcohol and setting a relatively high compression ratio. In such an engine, if the alcohol concentration cannot be increased (the remaining amount of alcohol fuel that can be used is small), knocking may occur if left unattended.

  Therefore, if the alcohol concentration cannot be increased, for example, the ignition timing is retarded by the technique described in Patent Document 1, or the effective timing is reduced by correcting the intake valve closing timing by the technique described in Patent Document 2. It has been proposed to avoid it.

  Further, according to the technique described in Patent Document 3, a turbocharger is provided in an internal combustion engine using various fuels, and the knocking limit is set in combination with direct injection of alcohol fuel, compression ratio increase, boost, and / or engine downsizing. It has been proposed to improve fuel efficiency by reducing the fuel consumption.

Japanese Patent No. 4155175 JP 2008-106766 A JP 2009-144720 A

  In the technique described in Patent Document 1, stable operation can be continued without causing knocking even when the alcohol concentration cannot be increased by configuring as described above. However, MBT (Minimum Advance for Best Torque ) Cannot be ignited, so even if the same amount of fuel is supplied, the torque is reduced and the thermal efficiency and fuel consumption are reduced.

  Also in the technique described in Patent Document 2, lowering the effective compression ratio is not only reducing the amount of intake air, but also reducing the amount of fuel that can be input.

  The technique described in Patent Document 3 suggests that the knocking limit is reduced by a combination of alcohol fuel direct injection, compression ratio increase, boost, and / or engine downsizing, but the alcohol concentration increases. There was no specific suggestion about avoiding knocking when it was not possible (the remaining amount of usable alcohol fuel was low).

  Accordingly, an object of the present invention is to solve the above-described problems, to improve thermal efficiency and fuel consumption performance by using various fuels, and to avoid knocking while maintaining thermal efficiency and fuel consumption performance even when the alcohol concentration cannot be increased. Another object of the present invention is to provide a control device for an internal combustion engine.

In order to solve the above object, in the claim 1, timing can change the valve opening and closing the opening and closing timing of the intake valve provided with a variable mechanism and the ignition means and the turbocharger, which is injected from the injector gasoline In a control device for an internal combustion engine that produces an output by compressing a mixture produced by mixing various fuels consisting of alcohol and alcohol with intake air with a piston in a combustion chamber and igniting and burning by the ignition means, at least the engine speed and the engine It is determined whether or not the probability of occurrence of knocking is greater than or equal to a threshold value from the output torque, and when it is determined that the probability of occurrence of knocking is greater than or equal to the threshold value, the valve opening / closing timing variable mechanism is operated to with closing a control means for correcting the timing of said control means, when correcting the closing timing of the intake valve, the multi-fuel The alcohol concentration is determined whether it is possible to increase, when the alcohol concentration is determined to not increase, and constructed as to increase the intake pressure by operating the turbocharger.

In the control apparatus for an internal combustion engine according to claim 2, wherein the control means before with an alcohol concentration detection means for detecting the Kia alcohol concentration, the probability of occurrence of the knocking is determined to or higher than the threshold A target compression ratio is calculated based on the detected alcohol concentration, and the valve opening / closing timing variable mechanism is operated to correct the intake valve closing timing so as to achieve the calculated target compression ratio. did.

In the control apparatus for an internal combustion engine according to claim 3, the control means determines whether or not the intake air amount can reach a target value based on the calculated target compression ratio, and the intake air amount is determined to be the target value. While it is determined that the value cannot be reached, when the alcohol concentration is determined to be increaseable, the alcohol concentration is increased .

In the control apparatus for an internal combustion engine according to claim 4, the control means includes alcohol concentration detection means for detecting the alcohol concentration, and when it is determined that the probability of occurrence of knocking is equal to or greater than a threshold value, The turbocharger is operated based on the detected alcohol concentration to increase the intake pressure .

  In the control apparatus for an internal combustion engine according to claim 5, the injector is constituted by a first injector for injecting the various fuels and a second injector for injecting alcohol.

  In the control apparatus for an internal combustion engine according to claim 6, the first injector includes an injector that directly injects the various fuels into the combustion chamber, and the second injector is connected to the intake port in front of the combustion chamber. It comprised so that it might consist of the injector which injects alcohol.

  In the control apparatus for an internal combustion engine according to claim 1, when it is determined that at least the probability of occurrence of knocking is equal to or greater than a threshold value from the engine speed and the engine output torque, the valve opening / closing timing variable mechanism is operated to perform intake air. When correcting the valve closing timing and correcting the intake valve closing timing, it is determined whether or not the alcohol concentration can be increased, and when it is determined that the alcohol concentration cannot be increased, the turbocharger is operated to operate the intake pressure. Therefore, when it is determined that the probability of occurrence of knocking is greater than or equal to the threshold value, knocking can be avoided even when the alcohol concentration cannot be increased by correcting the closing timing of the intake valve.

  That is, in an Otto cycle where the volume ratio (compression ratio) for compressing intake air is equal to the expansion ratio, the thermal efficiency increases as the compression ratio is increased. However, in a normal gasoline engine, if the compression ratio is increased too much, knocking occurs. While increasing the mechanical compression ratio, the intake valve closing angle is corrected to reduce the intake amount, and the effective compression ratio is suppressed similarly to the Otto cycle, so that the expansion ratio (mechanical compression ratio) that substantially controls the thermal efficiency is increased. By using the Atkinson cycle (also called “mirror cycle”), knocking can be avoided even when the alcohol concentration cannot be increased. In addition, since the ignition timing is not retarded, thermal efficiency and fuel consumption are not reduced.

  On the other hand, when the intake valve closing timing is corrected, the intake air amount is reduced, but when it is determined that the alcohol concentration cannot be increased, that is, the remaining amount of usable alcohol fuel is small, in other words, the intake valve When it is determined that the closing time of the engine must be corrected, the turbocharger is operated to increase the intake pressure, so that a decrease in the intake air amount can be avoided as a result, and therefore Even when the alcohol concentration cannot be increased, it is possible to prevent the output and torque from decreasing and improve the thermal efficiency and fuel efficiency.

  In the control apparatus for an internal combustion engine according to claim 2, when it is determined that the probability of knocking is equal to or greater than a threshold value, a target compression ratio is calculated based on the detected alcohol concentration, and the calculated target is calculated. Since the valve opening / closing timing variable mechanism is operated so as to achieve a compression ratio and the intake valve closing timing is corrected, in addition to the above effects, knocking is performed while maintaining thermal efficiency and fuel efficiency even when the alcohol concentration cannot be increased. Can be avoided more reliably.

In the control device for an internal combustion engine according to claim 3, it is determined whether or not the intake air amount can reach the target value based on the calculated target compression ratio, and it is determined that the target value cannot be reached. When it is determined that the alcohol concentration can be increased, the alcohol concentration is increased. In addition to the above-described effects, by increasing the alcohol concentration and operating the internal combustion engine at a desired compression ratio, the original thermal efficiency and fuel consumption can be increased. can it to maintain the performance.

In the control device for an internal combustion engine according to claim 4, when it is determined that the probability of occurrence of knocking is equal to or greater than a threshold value, the supercharger is operated based on the detected alcohol concentration to reduce the intake pressure. since it is configured as increase, in addition to the effects mentioned above, and to reliably prevent a reduction in output torque even when the alcohol concentration can not be increased to improve the thermal efficiency and fuel efficiency can Rukoto.

  In the control apparatus for an internal combustion engine according to claim 5, since the injector is constituted by the first injector for injecting various fuels and the second injector for injecting alcohol, in addition to the above effects, gasoline and alcohol Compared to the case where the multi-fuel consisting of is injected from a single injector, a desired amount of alcohol can be reliably supplied to the internal combustion engine.

  In the control apparatus for an internal combustion engine according to claim 6, the first injector is composed of an injector that directly injects various fuels into the combustion chamber, and the second injector is composed of an injector that injects alcohol into the intake port in front of the combustion chamber. In addition to the effects described above, the first injector is made of an injector that directly injects various fuels into the combustion chamber, so that abnormal combustion can be avoided by the latent heat of the injected various fuels, and the second By configuring the injector to be an injector that injects alcohol into the intake port, the accuracy and cost of components such as a pressure pump can be reduced, and the configuration can be simplified.

1 is a schematic diagram showing an overall control apparatus for an internal combustion engine according to an embodiment of the present invention. It is a block diagram which shows the operation | movement of ECU shown in FIG. 1 functionally. Fig. 3 is a flowchart showing more specifically the operation of the ECU shown in Fig. 2. 3 is an explanatory diagram showing calculation of the occurrence probability of knocking referred to in the processing of the flow chart of FIG. 3 is an explanatory diagram showing the characteristics of the effective compression ratio with respect to the alcohol concentration mentioned in the processing of the flow chart. FIG. 4 is an explanatory diagram showing characteristics of the effective compression ratio with respect to the intake valve closing timing, which is referred to in the processing of the flow chart of FIG. 3. FIG. 4 is an explanatory diagram showing intake valve closing timing referred to in the processing of the flow chart of FIG. 3.

  The best mode for carrying out the control apparatus for an internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing an overall control apparatus for an internal combustion engine according to an embodiment of the present invention.

  In FIG. 1, reference numeral 10 denotes a four-cylinder (cylinder) four-cycle internal combustion engine (only one cylinder is shown; hereinafter referred to as “engine”) mounted on a vehicle (not shown). In the engine 10, a compressor 14 a of the turbocharger 14 is disposed in the intake pipe 12.

  The intake air is forcibly compressed and sucked from an air cleaner (not shown) by the compressor 14a and flows through the intake pipe 12, is cooled by the intercooler 14b and reaches the throttle valve 16, where the flow rate is adjusted and the intake manifold 18 flows. When two intake valves (only one is shown) 20 are opened (opened), they flow into the combustion chamber 22.

  The throttle valve 16 is mechanically disconnected from the accelerator pedal 24 disposed on the vehicle driver's seat floor, and the opening and closing of the throttle valve 16 is controlled by a DBW (Drive By Wire) mechanism 26. That is, the throttle valve 16 is connected to an actuator (electric motor) 26a of the DBW mechanism 26, and is opened and closed by being driven by the actuator 26a.

  A first injector (fuel injection valve) 30 is disposed at a position facing the combustion chamber 22, and a second injector (fuel injection valve) 32 is disposed in the intake port 18 a in front of the intake valve 20.

  Various fuels stored in the main fuel tank 34 are pumped to the first injector 30 by a main fuel pump 34 a disposed inside the tank, and are pumped through the fuel supply pipe 36. The first injector 30 directly injects the various fuels fed under pressure into the combustion chamber 22. Hereinafter, the first injector 30 is also referred to as a “direct injection injector”.

  As the multi-fuel, it is planned to use a fuel having a relatively low alcohol concentration, such as a mixed fuel of gasoline and ethanol (ethyl alcohol), specifically, a mixed fuel (E10) of 90% gasoline and 10% ethanol.

  On the other hand, the various fuels stored in the main fuel tank 34 are pumped up by the sub fuel pump 34b and sent to the separation device 42 via the conduit 40, where they are separated and extracted into alcohol components and other components.

  The separated alcohol component is stored in the sub fuel tank 44 as alcohol fuel having a certain range of alcohol concentration, and the other components are returned to the main fuel tank 34 via the pipe 46. The alcohol fuel stored in the sub fuel tank 44 is pumped up by a fuel pump 44 a disposed inside the tank, and is pumped to the second injector 32 through the fuel supply pipe 50.

  The second injector 32 injects the pumped alcohol fuel into the intake port 18a. Hereinafter, the second injector 32 is also referred to as a “port injector”. The injected alcohol fuel flows into the combustion chamber 22 when the intake valve 20 is opened.

  The direct injection injector 30 or the port injector 32 is electrically connected to an ECU (Electronic Control Unit) 54 through a driver (drive circuit; shown in FIG. 2) 52 and indicates a valve opening (opening) time from the ECU 54. When the drive signal is supplied through the driver 52, the valve is opened, and fuel corresponding to the valve opening time is injected into the combustion chamber 22 or the intake port 18a. The injected fuel is mixed with the inflowing air to generate an air-fuel mixture.

  A spark plug 56 is disposed in the combustion chamber 22. The spark plug 56 is connected to an ignition device 60 such as an igniter. When an ignition signal is supplied from the ECU 54 via the driver 52, the ignition device 60 generates a spark discharge between the electrodes of the spark plug 56. The air-fuel mixture is ignited and combusted thereby, and drives the piston 62 slidably accommodated in the combustion chamber 22 downward.

  Inside the cylinder block 64 in which the combustion chamber 22 is formed, a crankshaft (not shown) that is connected to the piston 62 and converts the vertical motion of the piston 62 into rotational motion is accommodated.

  Exhaust gas (exhaust gas) generated by the combustion flows from the exhaust manifold 74 to the exhaust pipe 76 through the exhaust port 72 when two exhaust valves (only one is shown) 70 are opened. A turbine 14c of the turbocharger 14 is disposed in the exhaust pipe 76, and is rotated (driven) by exhaust gas. The turbine 14c is mechanically connected to the compressor 14a, and the compressor 14a is rotated (driven) accordingly to forcibly suck and suck the intake air.

  The exhaust pipe 76 is provided with a bypass passage 76a that bypasses the turbine 14c. A waste gate valve 14d is disposed in the bypass passage 76a. An actuator 14d1 composed of an electromagnetic solenoid valve is attached to the wastegate valve 14d.

  When the actuator 14d1 is energized, it drives the wastegate valve 14d to the open position and opens the bypass passage 76a. The rotational speed of the turbine 14c is controlled by adjusting the opening degree of the waste gate valve 14d via the actuator 14d1, and thus the supercharging pressure of the turbocharger 14 is controlled.

  A catalyst device (not shown) is disposed in the exhaust pipe 76 downstream of the bypass passage 76a. Exhaust gas is discharged to the atmosphere outside the engine after removing harmful components such as HC, CO, NOx by the catalyst device.

  The cylinder head 64 a is provided with a valve opening / closing timing variable mechanism (hereinafter referred to as “VTC”) 80. The VTC 80 is a hydraulic motor that can change the timing for opening and closing the combustion chamber of the intake valve, which is defined as a phase angle (VTC angle) of the camshaft with respect to the crankshaft by driving the camshaft via hydraulic pressure. In addition to the VTC 80, a mechanism capable of changing the opening / closing phase angle and the lift amount of the intake cam 80b according to a plurality of cams may be provided.

  A crank angle sensor 82 is disposed in the vicinity of the crankshaft of the engine 10. The crank angle sensor 82 includes a magnetic pickup that outputs a signal corresponding to the rotation of the pulsar 82a fixed to the crankshaft. The crank angle sensor 82 is a cylinder discrimination signal and TDC (top dead center) of each cylinder or a TDC indicating a crank angle in the vicinity thereof. A CRK signal obtained by subdividing the signal and the TDC signal is output.

  An air flow meter 84 having a temperature detecting element is disposed in the intake pipe 12 and outputs a signal corresponding to an intake (air) amount Q taken from the air cleaner and an intake air temperature TA.

  In the intake pipe 12, a throttle pre-pressure sensor 85 is disposed upstream of the throttle valve 16, outputs a signal indicating the intake pipe pressure PBA upstream of the throttle valve 16 in absolute pressure, and a MAP sensor 86 is disposed downstream. Then, a signal indicating the intake pipe pressure PBA at the downstream position of the throttle valve 16 in absolute pressure is output.

  A cam sensor 88 is disposed on the camshaft to output a signal indicating the phase angle of the camshaft with respect to the crankshaft, and a throttle opening sensor 90 is disposed on the DBW mechanism 26 to position the throttle valve 16 (throttle opening). A signal corresponding to the degree TH) is output.

  A water temperature sensor 92 is disposed in a cooling water passage (not shown) formed in the cylinder block 64 of the engine 10 and outputs a signal corresponding to the engine cooling water temperature (engine temperature) TW. 94 is arranged to output a signal corresponding to vibration generated in the engine 10 due to knocking.

  In the exhaust system, an A / F sensor (wide area air-fuel ratio sensor) 96 is arranged upstream of the catalyst device, and in a wide range from the stoichiometric air-fuel ratio to rich or lean, in other words, the actual air concentration. A signal indicating the fuel ratio KACT is output.

  The pipe 40 connecting the main fuel tank 34 and the separation device 42 is provided with the alcohol sensor 100 and the alcohol concentration of the various fuels flowing through the pipe 40, more specifically the various fuels stored in the main fuel tank 34, is determined. A level sensor 102 is disposed in the sub fuel tank 44, and a signal indicating the level (liquid level height) of alcohol fuel stored in the sub fuel tank 44, in other words, a signal indicating the remaining amount of alcohol fuel. Is output.

  An accelerator opening sensor 104 is provided in the vicinity of the accelerator pedal 24, and outputs a signal corresponding to the accelerator opening AP indicating the amount by which the driver depresses the accelerator pedal. A vehicle speed sensor 106 is provided in the vicinity of a drive shaft (not shown), and outputs a pulse signal per predetermined angular rotation of the drive shaft.

  The output of the sensor group described above is input to the ECU 54. The ECU 54 includes a microcomputer and includes a CPU, a ROM, a RAM, an I / F, and the like. The ECU 54 measures (detects) the engine speed NE and the vehicle speed V by measuring the time interval between the output of the crank angle sensor 82 (CRK signal) and the output of the vehicle speed sensor 106 among the input signals.

  FIG. 2 is a block diagram functionally showing the operation of the ECU 54. The ECU 54 executes the illustrated process based on the input sensor output.

  As will be described below, the ECU 54 includes a fuel injection / ignition control unit 54a, in which the engine speed detected by the crank angle sensor 82 and the intake air flow detected by the air flow meter 84 (or the intake pipe detected by the MAP sensor 86). The basic value of the fuel injection amount is calculated according to appropriate characteristics from basic parameters such as pressure (intake pressure) and intake air temperature.

  The calculated basic value is an air-fuel ratio feedback correction coefficient calculated based on A / F (air-fuel ratio) detected from the A / F sensor 96, or a correction coefficient calculated according to knocking detected from the knocking sensor 94. Are added (or multiplied) and corrected based on the other parameters shown in the figure to calculate the fuel injection amount.

  Further, the injection ratio and the injection amount of the various fuels injected from the direct injector 30 and the alcohol fuel injected from the port injector 32 are calculated by the injection time, and the number of injections and the injection timing are calculated.

  The injection ratio is determined according to the load state of the engine 10, and for example, all of the fuel injection amount is injected from the direct injection injector 30 as various fuels at low load, and part of the fuel injection amount is direct injection injector at medium and high loads. It is determined that various fuels from 30 and a part are injected from the port injector 32 as alcohol fuel. The injection ratio of alcohol fuel from the port injector 32 is set so as to increase as the load increases.

  Further, the ignition timing is calculated according to appropriate characteristics, and is corrected by a correction coefficient calculated according to knocking detected from the knocking sensor 94. A control value is calculated based on the calculated fuel injection amount and ignition timing, and is supplied to the direct injection injector 30, the port injector 32, and the spark plug 56 via the driver 52.

  Further, in the intake air amount control unit 54b, a required output required by the driver is calculated by searching for appropriate characteristics from the accelerator opening AP, the vehicle speed, and the engine speed, and the calculated required output is satisfied. Thus, the target intake air amount is calculated according to the fuel injection amount calculated by the fuel injection / ignition control unit 54a.

  Next, a target throttle (TH) opening, a target boost pressure, and a target VTC angle are calculated based on the calculated target intake air amount, and the calculated value, actual opening, actual boost pressure, A feedback correction coefficient is added (or multiplied) so that the deviation from the actual angle decreases, and a control value is calculated and supplied to the DBW mechanism 26, the wastegate valve actuator 14d1 and the VTC 80 via the driver 52.

  FIG. 3 is a flowchart showing the operation of the ECU 54 more specifically. The illustrated program is executed at predetermined time intervals.

  In the following description, the target intake air amount and the fuel injection amount calculated in S10 are read, and the process proceeds to S12 to detect the alcohol concentration of the currently used fuel. That is, the alcohol concentration of various fuels stored in the main fuel tank 34 is detected from the output of the alcohol sensor 100.

  Next, in S14, it is determined whether or not the knocking occurrence probability (probability of knocking) is equal to or higher than a threshold value. The knocking occurrence probability means a value (for example, point a) obtained by searching the characteristic (map) shown in FIG. 4 with the engine speed NE and the engine torque.

  Therefore, the determination in S14 is made by comparing the value obtained by the search (for example, point a) with the threshold value b and determining whether or not the value is higher.

  Returning to the explanation of the flow chart of FIG. 3, when the result in S14 is negative and it is determined that the knocking occurrence probability is not equal to or higher than the threshold value, the process proceeds to S16, and the target phase angle of the intake cam 80b of the VTC 80 is changed to the normal phase angle. (In other words, the engine 10 is set to a phase angle corresponding to the valve opening / closing timing at which the engine 10 is operated at the compression ratio of the ordinary Otto cycle (the compression ratio and the expansion ratio are equal)), and the VTC 80 is operated so as to be the phase angle. Let

  On the other hand, when the result in S14 is affirmative and it is determined that the knocking occurrence probability is equal to or higher than the threshold value, the process proceeds to S18, and a compression ratio at which knocking does not occur is selected. That is, the characteristic (map) shown in FIG. 5 is searched based on the alcohol concentration detected in S12, and the effective compression ratio is selected (in other words, calculated as the target compression ratio).

  Next, in S20, the target phase angle of the intake cam 80b of the VTC 80 is set so that the effective compression ratio (target compression ratio) selected in S18 is reached (decreased). That is, the valve closing timing of the intake valve 20 is corrected by operating the VTC 80, more specifically, the valve timing is advanced and changed to the valve closing timing of the early closing Atkinson.

  More specifically, the characteristic (map) shown in FIG. 6 is searched based on the effective compression ratio selected in S18, and the closing timing of the intake valve 20 is set to an arbitrary value between ABDC-80 degrees and ABDC-20 degrees. Set to the value of.

  FIG. 7 shows the opening / closing timing of the intake valve 20 (and the exhaust valve 70). In the process of S20, the closing timing of the intake valve 20 is set to an arbitrary value between ABDC-80 degrees (ATDC 100 degrees) and ABCD-20 degrees (ATDC 160 degrees), in other words, the bottom dead center BDC of the intake stroke. Set to corner.

  In addition to the early closing Atkinson in the Atkinson cycle, there is a late closing Atkinson that reduces the intake amount by delaying the closing angle of the intake valve and discharging the once sucked air, both of which can obtain the same effect Therefore, in the process of S20, the VTC 80 may be operated to delay the valve closing timing of the intake valve 20 so that the delayed closing Atkinson is performed.

  Returning to the description of the flowchart of FIG. 3, the process then proceeds to S22, in which it is determined whether or not the target intake air amount (read in S10) can be reached by the effective compression ratio (target compression ratio) selected in S18. In other words, since it may happen that the target intake air amount is not reached by lowering the effective compression ratio, the determination is made here as a precaution.

  When the result in S22 is affirmative, the subsequent processing is skipped. On the other hand, when the result in S22 is negative and it is determined that the target intake air amount cannot be reached, the process proceeds to S24, and the remaining amount of alcohol is detected. That is, the remaining amount of alcohol fuel stored in the sub fuel tank 44 is detected from the output of the level sensor 102.

  Next, the process proceeds to S26, whether the detected remaining amount of alcohol fuel is not less than a predetermined value that is set as appropriate, in other words, whether the alcohol concentration can be increased (whether the alcohol fuel supplied to the engine 10 can be increased). to decide.

  When the result in S26 is affirmative, the program proceeds to S28, in which the alcohol fuel stored in the sub fuel tank 44 is injected from the port injector 32 into the intake port 18a (the alcohol concentration of the fuel supplied to the engine 10 is increased).

  Next, in S30, the effective compression ratio is returned to the original value because alcohol is injected. That is, the target phase angle of the intake cam 80b of the VTC 80 is set to a phase angle corresponding to the valve opening / closing timing operated at the compression ratio of the normal Otto cycle, and the VTC 80 is operated so as to be the phase angle. Next, the process proceeds to S12 and the above processing is repeated.

  On the other hand, when the result in S26 is negative and it is determined that the alcohol concentration cannot be increased (the alcohol fuel supplied to the engine 10 cannot be increased), the process proceeds to S32, where the turbocharger is controlled by controlling the opening degree of the wastegate valve 14d. 14 boost pressure is increased and intake pressure is increased.

  This will be described with reference to FIG. 5 again. FIG. 5 is an explanatory diagram showing the relationship between the effective compression ratio and the intake pressure at the same torque in addition to the characteristics of the effective compression ratio with respect to the alcohol concentration.

  In the case where the effective compression ratio is represented by the characteristic 1 in FIG. 5, the effective compression ratio needs to be reduced according to the characteristic 2 or 3 because the knocking occurrence region (shown by hatching) is entered in all the detected alcohol concentrations. However, at this time, there is a case where the intake air pressure decreases according to the decrease in the effective compression ratio and the target intake air amount cannot be reached.

  Therefore, in this embodiment, the supercharging pressure of the turbocharger 14 is increased, and thus the intake pressure is increased. For example, if the detected alcohol concentration is Da and the intake pressure P1 at the time of characteristic 1 is 0 kPa, the intake pressure P2 at the time of characteristic 2 is increased to 40 kPa, for example, by increasing the boost pressure. In this case, the intake pressure P3 can be increased to 80 kPa, for example.

  As a result, when the effective compression ratio is set to a value that does not cause knocking, even if it is determined that the target intake air amount cannot be reached, the boost pressure is increased to increase the intake pressure. The target intake air amount can be reached. In other words, by adjusting the decrease in the effective compression ratio and the increase in the supercharging pressure as appropriate, even when the alcohol concentration cannot be increased (the remaining amount of usable alcohol fuel is small), the output / torque is prevented from decreasing and the thermal efficiency is increased. Fuel efficiency can be improved.

As described above, in this embodiment, the timing can change the valve opening and closing the opening and closing timing varying mechanism (VTC) 80 of the intake valve 20 ignition means (spark plug 56, ignition system 60) and the turbocharger 14 And a mixture produced by mixing various fuels made of gasoline and alcohol injected from the injector (first injector 30) with the intake air is compressed by the piston 62 in the combustion chamber 22, and is ignited and burned by the ignition means. In the control device for the internal combustion engine (engine) 10 that generates an output, whether or not the probability of occurrence of knocking is at least a threshold value is determined from at least the engine speed (engine speed) NE and the engine output torque (engine torque). When the probability of occurrence of knocking is determined to be greater than or equal to a threshold value, the valve opening / closing timing variable mechanism is operated. Provided with a control means for correcting (ECU 54, S10 from S20) the closing timing of the intake valve Te, wherein, when correcting the closing timing of the intake valve, whether can increase the alcohol concentration of the multi-fuel or determined (S24, S26), when the alcohol concentration is determined to not increase, the turbocharger is operated to increase the intake pressure (S32) Owing to this configuration, the probability of occurrence of knocking When it is determined that the threshold value is exceeded, the closing timing of the intake valve 20 is corrected, so that knocking can be avoided even when the alcohol concentration cannot be increased.

  That is, in an Otto cycle where the volume ratio (compression ratio) for compressing intake air is equal to the expansion ratio, the thermal efficiency increases as the compression ratio is increased. However, in a normal gasoline engine, if the compression ratio is increased too much, knocking occurs. While increasing the mechanical compression ratio, the intake valve closing angle is corrected to reduce the intake amount, and the effective compression ratio is suppressed similarly to the Otto cycle, so that the expansion ratio (mechanical compression ratio) that substantially controls the thermal efficiency is increased. By using the Atkinson cycle, knocking can be avoided even when the alcohol concentration cannot be increased. In addition, since the ignition timing is not retarded, thermal efficiency and fuel consumption are not reduced.

  On the other hand, correcting the closing timing of the intake valve 20 causes a reduction in the intake air amount (target intake air amount), but it is determined that the alcohol concentration cannot be increased, that is, the remaining amount of usable alcohol fuel is small. In other words, when it is determined that the closing timing of the intake valve must be corrected, the turbocharger 14 is operated to increase the boost pressure so that the intake pressure is increased. As a result, it is possible to avoid a decrease in the intake air amount, and therefore, even when the alcohol concentration cannot be increased, a decrease in output / torque can be prevented to improve thermal efficiency and fuel efficiency.

Also, the control unit, before Kia alcohol alcohol concentration detecting means for detecting the concentration (alcohol sensor 100, ECU 54, S12) comprises a, when the probability of occurrence of the knocking is determined to or above the threshold, the detection Based on the alcohol concentration thus calculated, a target compression ratio is calculated, and the valve opening / closing timing variable mechanism is operated so as to achieve the calculated target compression ratio to correct the closing timing of the intake valve (S18, S20). Since it comprised, in addition to an above-described effect, even when alcohol concentration cannot be increased, knocking can be avoided more reliably while maintaining thermal efficiency and fuel efficiency.

Further, the control unit may pre comprises an alcohol concentration detection means for detecting the Kia alcohol concentration (alcohol sensor 100, ECU 54, S12), when the probability of occurrence of the knocking is determined to or higher than the threshold (S14) the since the detected based on the alcohol concentration by operating the turbocharger to increase the intake pressure (S32) as configured, in addition to the effects mentioned above, the output torque even when the alcohol concentration can not be increased It is possible to improve the thermal efficiency and fuel efficiency by reliably preventing the decrease.

  Further, the control means determines whether or not the intake air amount can reach the target value based on the calculated target compression ratio, and determines that the intake air amount cannot reach the target value (S22). When it is determined that the alcohol concentration can be increased (S26), the alcohol concentration is increased (S28). Therefore, the alcohol concentration is increased and the engine is operated at a desired compression ratio. Thermal efficiency and fuel efficiency can be maintained.

  Further, since the injector is constituted by the first injector 30 for injecting the various fuels and the second injector 32 for injecting the alcohols, in addition to the effects described above, the multiple fuels made of gasoline and alcohol are used as a single injector. As compared with the case of injecting from the engine, a desired amount of alcohol can be reliably supplied to the internal combustion engine.

  The first injector 30 is an injector that directly injects the various fuels into the combustion chamber 22, and the second injector 32 is an injector that injects the alcohol into the intake port 18a in front of the combustion chamber. In addition to the above-described effects, the first injector 30 is made of an injector that directly injects the various fuels into the combustion chamber 22, so that abnormal combustion can be avoided due to the latent heat of the injected various fuels. When the two injectors 32 are made of injectors that inject alcohol into the intake port 18a, the accuracy and cost of components such as a pressure pump can be reduced, and the configuration can be simplified.

  In the above description, the main fuel tank 34 stores various fuels including alcohol fuel, and the sub fuel tank 44 stores alcohol fuel. However, the main fuel tank 34 stores gasoline fuel and the sub fuel tank 44 stores alcohol fuel. You may do it.

  DESCRIPTION OF SYMBOLS 10 Internal combustion engine (engine), 14 Turbocharger, 14a Compressor, 14c Turbine, 14d Wastegate valve, 14d1 Wastegate valve actuator, 16 Throttle valve, 18 Intake manifold, 18a Intake port, 20 Intake valve, 22 Combustion chamber , 26 DBW mechanism, 30 first (direct injection) injector, 32 second (port) injector, 34 main fuel tank, 42 separator, 44 sub fuel tank, 54 ECU (electronic control unit), 56 spark plug (ignition means) ), 60 ignition device (ignition means), 80 VTC (variable valve opening timing mechanism), 82 crank angle sensor, 84 air flow meter, 86 MAP sensor, 90 throttle opening sensor, 96 A / F sensor, 100 alcohol sensor, 02 level sensor, 104 an accelerator opening sensor

Claims (6)

Closing timing able to change a valve opening and closing timing of the intake valve provided with a variable mechanism and the ignition means and the turbocharger, the air-fuel mixture generated by a multi-fuel consisting of petrol and alcohol, which is injected from the injector is mixed with intake In a control device for an internal combustion engine that generates an output by being compressed by a piston in a combustion chamber and ignited and burned by the ignition means, whether or not the probability of occurrence of knocking is at least a threshold value from the engine speed and the engine output torque Determining, when it is determined that the probability of occurrence of knocking is greater than or equal to a threshold value, the control means for operating the valve opening and closing timing variable mechanism to correct the closing timing of the intake valve, the control means, wherein when correcting the closing timing of the intake valve, it is determined whether or not the alcohol concentration of the various fuel can increase the Al When Lumpur concentration is determined to be not increased, the control apparatus for an internal combustion engine, characterized in that to increase the intake pressure by operating the turbocharger. Said control means before with an alcohol concentration detection means for detecting the Kia alcohol concentration, when the probability of occurrence of the knocking is determined to or above the threshold, the target compression ratio based on the detected alcohol concentration was 2. The control apparatus for an internal combustion engine according to claim 1, wherein the valve opening / closing timing variable mechanism is operated to correct the closing timing of the intake valve so as to achieve the calculated target compression ratio.   The control means determines whether or not the intake air amount can reach a target value based on the calculated target compression ratio, and determines that the intake air amount cannot reach the target value, while the alcohol concentration increases. 3. The control apparatus for an internal combustion engine according to claim 2, wherein when it is determined that the alcohol concentration is possible, the alcohol concentration is increased.   The control means includes alcohol concentration detection means for detecting the alcohol concentration, and when the probability of occurrence of knocking is determined to be equal to or higher than a threshold, the turbocharger is controlled based on the detected alcohol concentration. The control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the intake pressure is increased by operating.   5. The control device for an internal combustion engine according to claim 1, wherein the injector includes a first injector that injects the various fuels and a second injector that injects alcohol. 6.   6. The first injector includes an injector that directly injects the various fuels into the combustion chamber, and the second injector includes an injector that injects the alcohol into an intake port in front of the combustion chamber. The internal combustion engine control device described.