JP5327084B2 - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, suppressing difference in engine torque caused by a difference in the concentration of alcohol while reducing voltage required for an ignition plug when the concentration of alcohol in fuel is high. <P>SOLUTION: In this device, increase correction control for increasingly correcting the amount of fuel injected and ignition timing control are performed as operation control over the internal combustion engine 10. Both ignition timing and the increase correction amount in the increase correction control are engine controlled variables changing the voltage required for the ignition plug 16 and the engine controlled variables with the engine torque changing directions when the required voltage is changed so as to be changed in the same direction being mutually different. A control mode for the ignition timing and a control mode for the increase correction amount are changed according to the concentration of alcohol so that the required voltage when the concentration of alcohol is high is lowered in comparison with the voltage required for the ignition plug 16 when the concentration of alcohol in the fuel is low. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a control device for an internal combustion engine that can use alcohol and gasoline as fuel.

  In recent years, an internal combustion engine that can use alcohol and gasoline as fuel has been put into practical use. This internal combustion engine can be operated using only alcohol or only gasoline as fuel, and can also be operated using a mixed fuel in which alcohol and gasoline are mixed at an arbitrary ratio.

  Since alcohol (for example, ethanol) used as a fuel for an internal combustion engine has a larger latent heat of vaporization than gasoline, the temperature of the combustion chamber of the internal combustion engine increases as the alcohol concentration of the fuel supplied during the operation of the internal combustion engine increases. Lower. As the temperature in the combustion chamber becomes low in this way, it becomes difficult to generate sparks by the spark plug, so the minimum required spark plug (specifically, between the electrodes) to generate the spark properly. The applied voltage, so-called required voltage, becomes high. If this required voltage exceeds the upper limit of the voltage that can be applied to the spark plug, an appropriate spark may not be generated in the combustion chamber and the fuel may not burn properly.

  Therefore, conventionally, Patent Document 1 describes an execution mode of operation control of the internal combustion engine so as to lower the required voltage when the alcohol concentration of the fuel is high so that the required voltage of the spark plug does not exceed the upper limit of the applied voltage. A device to change has been proposed. Specifically, in this device, the ignition timing of the internal combustion engine is changed according to the alcohol concentration of the fuel. This makes it possible to apply a voltage to the spark plug when the alcohol concentration of the fuel is high in a state where the pressure in the combustion chamber is low, that is, in a state where sparks are easily generated by the spark plug. Becomes lower. In this way, in the above apparatus, the required voltage of the spark plug is prevented from exceeding the upper limit of the applied voltage.

JP 2008-115804 A

  By the way, when the ignition timing is changed during operation of the internal combustion engine, the output torque (engine torque) of the internal combustion engine changes. Therefore, if the ignition timing is simply changed according to the alcohol concentration of the fuel, the engine torque does not become constant, but varies depending on the alcohol concentration of the fuel. Such a difference in engine torque is not preferable because it becomes a factor that hinders the precise operation of the internal combustion engine.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress a difference in engine torque caused by a difference in alcohol concentration while suppressing a required voltage of a spark plug when the alcohol concentration of fuel is high. An object of the present invention is to provide a control device for an internal combustion engine that can perform the above-described operation.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
The invention described in claim 1 is an internal combustion engine that can use gasoline and alcohol as fuel, and performs control of operation of the internal combustion engine in which fuel is ignited through spark discharge by a spark plug. The engine control amount is an engine control amount that changes the required voltage of the spark plug, and the change direction of the engine torque when the required voltage is changed so as to change in the same direction. The engine control amount is set, and the operation control includes the ignition timing control for controlling the ignition timing of the internal combustion engine and the fuel injection amount of the internal combustion engine so that the air-fuel ratio becomes a richer ratio than the stoichiometric air-fuel ratio. and a boost correction control for increasing correction, the two engine control amount is an increase correction amount of the ignition timing and the increase correction control, the fuel Alcohol concentration is compared to the voltage required at low so that the required voltage when the concentration is high is low, control of the increase correction amount of the ignition timing and the increase correction control in accordance with the alcohol concentration of the fuel The gist is to change the mode.

According to the above configuration, when the alcohol concentration of the fuel supplied to the internal combustion engine is high, that is, in the same control mode as when the alcohol concentration is low, the operation control of the internal combustion engine (ignition timing control for controlling the ignition timing of the internal combustion engine and When the increase voltage correction control for increasing the fuel injection amount of the internal combustion engine so that the air-fuel ratio becomes a richer ratio than the stoichiometric air-fuel ratio is executed, the required voltage of the spark plug may be unnecessarily high. The required voltage can be kept low by changing the control mode of the two engine control amounts (ignition timing and increase correction amount of the increase correction control) . In addition, when changing the control mode of the engine control amount, at least a part of the change of the engine torque due to the change of the control mode of one engine control amount and the change of the engine torque due to the change of the control mode of the other engine control amount. Since at least a part of the engine control amount can be offset, it is possible to suppress a change in the engine torque accompanying a change in the control mode of the engine control amount. Therefore, it is possible to suppress the difference in engine torque caused by the difference in alcohol concentration while suppressing the required voltage of the spark plug when the alcohol concentration of fuel is high.

In particular, in the above configuration, the ignition timing control execution mode is changed so that the ignition timing of the internal combustion engine becomes an advanced timing when the alcohol concentration of the fuel is high, so that ignition is performed in a state where the pressure in the combustion chamber is low. Since the voltage is applied to the plug, the required voltage of the spark plug can be kept low.

  Normally, when the fuel injection amount of the internal combustion engine is increased and corrected so that the air-fuel ratio becomes a richer ratio than the stoichiometric air-fuel ratio, in a region where the increase correction amount is small, the combustion chamber increases as the amount of fuel burned increases. Since the temperature of the spark plug increases, the required voltage of the spark plug decreases. On the other hand, when the increase correction amount increases, the influence of the latent heat of vaporization of the fuel increases, so the temperature in the combustion chamber decreases and the required voltage of the spark plug increases. Therefore, in the above configuration, in the above-described device in which the increase correction amount of the increase correction control is set in the region where the increase correction amount is large, the increase correction control is performed so that the increase correction amount decreases when the alcohol concentration of the fuel is high. By changing the execution mode, the influence of the latent heat of vaporization is reduced and the temperature in the combustion chamber is increased, so that the required voltage of the spark plug can be kept low.

  According to the above configuration, the required voltage of the spark plug when the alcohol concentration of the fuel is high is obtained by changing the execution mode of the ignition timing control and the execution mode of the increase correction control in accordance with the alcohol concentration of the fuel. Can be kept low.

  Moreover, when the execution mode of the ignition timing control is changed so that the ignition timing becomes the advance timing, the change acts to increase the engine torque, whereas the increase correction amount of the increase correction control. When the execution mode of the control is changed so as to reduce the engine torque, the change acts to reduce the engine torque.

  Therefore, according to the above configuration, at least a part of the increase in the engine torque due to the change in the execution mode of the ignition timing control and the at least a part of the decrease in the engine torque due to the change in the execution mode of the increase correction control can be offset. It is possible to suppress changes in the engine torque due to changes in the execution mode of these controls.

According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect , the internal combustion engine has a variable valve mechanism for changing a valve opening characteristic of the engine valve, and the control device includes: The variable operation according to the alcohol concentration of the fuel so that the intake air amount of the internal combustion engine when the concentration is high is smaller than the intake air amount of the internal combustion engine when the alcohol concentration of the fuel is low. The gist is to change the control mode of the valve mechanism.

  In the above configuration, when the alcohol concentration of the fuel is high, the control mode of the variable valve mechanism is changed so that the amount of intake air is reduced. Therefore, the pressure in the combustion chamber is lowered and the required voltage of the spark plug is lowered. Become. Moreover, when the control mode of the variable valve mechanism is changed in this way, the change acts to reduce the engine torque.

  Therefore, according to the above configuration, the alcohol concentration of the fuel can be increased with a high degree of freedom by changing the control mode of the variable valve mechanism in addition to changing the execution mode of the ignition timing control and the increase correction control as described above. The difference in engine torque due to the difference in alcohol concentration can be suppressed while the required voltage of the spark plug at a high time is kept low.

According to a third aspect of the present invention, there is provided a control device for performing operation control of an internal combustion engine that can use gasoline and alcohol as fuel and in which the fuel is ignited through spark discharge by a spark plug. The engine control amount is an engine control amount that changes the required voltage of the spark plug, and the change direction of the engine torque when the required voltage is changed so as to change in the same direction. An engine control amount is set, the internal combustion engine has a variable valve mechanism that changes a valve opening characteristic of the engine valve, and the operation control includes an ignition timing control that controls an ignition timing of the internal combustion engine; and a hydraulic control of the variable valve mechanism, the two engine control amount, Ri operation amount der ignition timing and the variable valve mechanism of the internal combustion engine, wherein The ignition timing of the internal combustion engine and the variable valve mechanism according to the alcohol concentration of the fuel so that the required voltage when the concentration is high is lower than the required voltage when the alcohol concentration of the fuel is low The gist is to change the control mode of the operation amount .

According to the above configuration, when the alcohol concentration of the fuel supplied to the internal combustion engine is high, that is, in the same control mode as when the alcohol concentration is low, the operation control of the internal combustion engine (ignition timing control for controlling the ignition timing of the internal combustion engine and When there is a possibility that the required voltage of the spark plug may become unnecessarily high when the variable valve mechanism operation control is executed, the two engine control amounts (ignition timing of the internal combustion engine and variable valve mechanism operation amount) The required voltage can be kept low by changing the control mode. In addition, when changing the control mode of the engine control amount, at least a part of the change of the engine torque due to the change of the control mode of one engine control amount and the change of the engine torque due to the change of the control mode of the other engine control amount. Since at least a part of the engine control amount can be offset, it is possible to suppress a change in the engine torque accompanying a change in the control mode of the engine control amount. Therefore, it is possible to suppress the difference in engine torque caused by the difference in alcohol concentration while suppressing the required voltage of the spark plug when the alcohol concentration of fuel is high.
In particular, in the above configuration, the ignition timing control execution mode is changed so that the ignition timing of the internal combustion engine becomes an advanced timing when the alcohol concentration of the fuel is high, so that ignition is performed in a state where the pressure in the combustion chamber is low. Since the voltage is applied to the plug, the required voltage of the spark plug can be kept low. Further, if the execution mode of the operation control of the variable valve mechanism is changed so that the amount of intake air is reduced when the alcohol concentration of the fuel is high, the pressure in the ignition plug is reduced because the pressure in the combustion chamber is reduced. It becomes like this. According to the above configuration, by changing the execution mode of the ignition timing control and the execution mode of the operation control of the variable valve mechanism in accordance with the alcohol concentration of the fuel in this way, ignition when the alcohol concentration of the fuel is high The required voltage of the plug can be kept low.

  Moreover, when the execution mode of the ignition timing control is changed so that the ignition timing becomes the advance side, the change acts to increase the engine torque, whereas the intake air amount is reduced. When the control mode of the variable valve mechanism is changed, the change acts to reduce the engine torque. Therefore, according to the above configuration, at least a part of the increase in the engine torque due to the change in the execution mode of the ignition timing control and the at least a part of the decrease in the engine torque due to the change in the control mode of the variable valve mechanism are offset. Therefore, it is possible to suppress the engine torque from changing due to the change in the execution mode of these controls.

Note the increase correction control, such as by claim 4, including a control for increasing correction of the fuel injection amount to suppress the temperature rise of the exhaust gas purifying catalyst in an apparatus in which the exhaust purification catalyst provided in an exhaust passage of the internal combustion engine.

In addition to the mechanism for changing the valve opening period of the engine valve (the period from the valve opening timing to the valve closing timing [so-called valve operating angle]), the variable valve mechanism is an engine valve according to claim 5. Includes a valve timing changing mechanism for changing the opening / closing timing (so-called valve timing).

1 is a schematic diagram illustrating a schematic configuration of a control device for an internal combustion engine according to an embodiment of the present invention. The graph which shows an example of the relationship between ignition timing, the required voltage of a spark plug, and engine torque. The graph which shows an example of the relationship between the valve timing of an intake valve, the required voltage of a spark plug, and engine torque. The graph which shows an example of the correction coefficient of increase correction | amendment control, the required voltage of a spark plug, and an engine torque. The graph which shows an example of the relationship between the alcohol concentration of a fuel, the required voltage of a spark plug, and an engine torque.

Hereinafter, an embodiment of a control device for an internal combustion engine according to the present invention will be described.
FIG. 1 shows a schematic configuration of an internal combustion engine to which the control device according to the present embodiment is applied and its peripheral devices.

  As shown in FIG. 1, air is sucked into the combustion chamber 11 of the internal combustion engine 10 through the intake passage 12 and fuel injected from the fuel injection valve 13 is supplied. The fuel stored in the fuel tank 14 is pumped to the fuel injection valve 13 by a fuel pump 15. When ignition is performed through spark discharge by the spark plug 16 with respect to the air-fuel mixture composed of the intake air and the injected fuel in the combustion chamber 11, the air-fuel mixture burns and the piston 17 reciprocates, whereby the internal combustion engine. Ten crankshafts 18 rotate. The air-fuel mixture after combustion is sent as exhaust gas from the combustion chamber 11 of the internal combustion engine 10 to the exhaust passage 19. An exhaust gas purification catalyst 20 for purifying exhaust gas is provided in the exhaust passage 19 of the internal combustion engine 10.

  The internal combustion engine 10 can be operated using only alcohol (specifically, ethanol) or only gasoline as fuel, and in addition, a mixed fuel in which alcohol and gasoline are mixed at an arbitrary ratio. The thing which can be operated using is adopted. Further, the internal combustion engine 10 is provided with a valve timing changing mechanism 22 for changing the opening / closing timing (so-called valve timing) of the intake valve 21.

  As peripheral devices of the internal combustion engine 10, various sensors for detecting the operating state are provided. As such a sensor, for example, a throttle sensor for detecting the opening degree of the throttle valve 23 (throttle opening degree TA) provided in the intake passage 12 or for detecting the rotational speed of the crankshaft 18 (engine rotational speed NE). And an air flow meter for detecting the amount of air sucked into the combustion chamber 11 (intake air amount GA). Further, a position sensor for detecting the valve timing VT of the intake valve 21, a water temperature sensor for detecting the temperature of the cooling water (cooling water temperature THW) of the internal combustion engine 10, and the air-fuel ratio of the air-fuel mixture through the oxygen concentration of the exhaust gas. An air-fuel ratio sensor for detection and a knock sensor for detecting whether knocking has occurred are provided. In addition, an accelerator sensor for detecting the operation amount of the accelerator pedal 24 (accelerator operation amount ACC), a remaining amount sensor for detecting the amount of fuel stored in the fuel tank 14 (remaining fuel amount), and the like Is provided.

  An electronic control unit 30 is provided as a peripheral device of the internal combustion engine 10. The electronic control unit 30 temporarily stores a CPU that performs arithmetic processing for various controls related to the operation of the internal combustion engine 10, a non-volatile memory (ROM) in which a control program and data are stored, a CPU calculation result, and the like. A volatile memory (RAM), a nonvolatile memory (EEPROM), and an input / output port for inputting / outputting signals to / from the outside. Output signals from the various sensors described above are input to the electronic control unit 30. The electronic control unit 30 performs various calculations based on the output signals of these sensors, and executes various engine controls related to the operation of the internal combustion engine 10 based on the calculation results.

  Specifically, the engine control includes operation control of the fuel injection valve 13 (fuel injection control), operation control of the ignition plug 16 (ignition timing control), and operation control of the valve timing changing mechanism 22 (valve timing control). Then, operation control (throttle control) of the throttle valve 23 is executed. Hereinafter, these engine controls will be described separately.

First, throttle control will be described.
In the throttle control, a control target value (target throttle opening Tta) for the throttle opening TA is calculated based on the accelerator operation amount ACC and the engine speed NE. The operation of the throttle valve 23 (specifically, the throttle motor 25 connected to the throttle valve 23) is controlled so that the target throttle opening degree Tta and the actual throttle opening degree TA coincide with each other. By adjusting the passage cross-sectional area of the intake passage 12 through such throttle control, the intake air amount is adjusted in accordance with the operating state of the internal combustion engine 10.

Next, valve timing control will be described.
In the valve timing control, a control target value (target valve timing Tvt) for the valve timing VT is calculated based on the engine load KL and the engine speed NE. Then, the operation of the valve timing changing mechanism 22 (specifically, the actuator 26 connected to the mechanism 22) is controlled so that the target valve timing Tvt matches the actual valve timing VT. The engine load KL is calculated based on the intake air amount GA and the engine rotational speed NE. Through such valve timing control, the valve timing VT is adjusted so that air is efficiently sucked into the combustion chamber 11 in accordance with the operating state of the internal combustion engine 10.

Next, ignition timing control will be described.
In the ignition timing control, a control basic value (base ignition timing Abse) for the ignition timing is calculated based on the engine load KL and the engine speed NE, and a knock correction amount Kn is calculated according to the occurrence of knocking. . Then, the control target value (required ignition timing Acal) of the ignition timing is calculated by reflecting the knock correction amount Kn in the base ignition timing Abse. The operation of the spark plug 16 is controlled so that the air-fuel mixture is ignited at the required ignition timing Acal. Through such ignition timing control, the ignition timing is adjusted in accordance with the operating state of the internal combustion engine 10 so that a large engine torque can be obtained while appropriately suppressing the occurrence of knocking.

Next, fuel injection control will be described.
In the fuel injection control, first, the basic fuel injection amount QBASE is calculated based on the engine load KL and the engine speed NE. As the basic fuel injection amount QBASE, a fuel injection amount capable of setting the air-fuel ratio of the air-fuel mixture to a desired ratio (for example, the theoretical air-fuel ratio) in the operating state determined by the engine load KL and the engine speed NE is calculated. .

  Thereafter, the air-fuel ratio feedback correction coefficient FAF is calculated based on the difference between the actual air-fuel ratio detected by the air-fuel ratio sensor and the target air-fuel ratio, provided that the execution condition of the air-fuel ratio feedback control is satisfied. The Specifically, when the actual air-fuel ratio is a richer ratio than the target air-fuel ratio, a predetermined amount is subtracted from the air-fuel ratio feedback correction coefficient FAF, and when the actual air-fuel ratio is a lean ratio, the air-fuel ratio feedback correction coefficient A predetermined amount is added to the FAF. In addition, when the actual air-fuel ratio is switched from the rich ratio to the lean ratio from the target air-fuel ratio, or when the lean ratio is switched to the rich ratio, the air-fuel ratio feedback correction coefficient FAF is stepped. Increase / decrease (skip).

  Further, learning of the air-fuel ratio learning value KG and the alcohol concentration learning value KGal is executed based on the air-fuel ratio feedback correction coefficient FAF on condition that the execution condition of the learning process is satisfied. As the air-fuel ratio learning value KG and the alcohol concentration learning value KGal, there are values that can compensate for the steady deviation between the air-fuel ratio feedback correction coefficient FAF and its basic value (= “1.0”). To be learned. In particular, as the alcohol concentration learning value KGal, a value that can compensate for the difference between the actual alcohol concentration of the fuel and the reference concentration in the deviation amount is learned.

  In this learning process, the update of the air-fuel ratio learning value KG calculates the average value FAFAVE of the air-fuel ratio feedback correction coefficient FAF in the most recent preset predetermined period and subtracts “1.0” from the average value FAFAVE. The value is added to the air-fuel ratio learning value KG.

  Here, when the alcohol concentration of the fuel supplied to the internal combustion engine 10 changes, the oxygen concentration of the exhaust gas changes accordingly. In the present embodiment, since air-fuel ratio feedback control is executed, if the alcohol concentration of the fuel in the fuel tank 14 changes due to fuel replenishment, the air-fuel ratio feedback correction coefficient FAF accompanies the change in the oxygen concentration of the exhaust due to this change. Will change. In view of this point, in the learning process, the alcohol concentration learning value KGal is also updated in the same manner as the air-fuel ratio learning value KG.

  However, the process of learning the alcohol concentration learning value KGal is performed by executing the process of learning the air-fuel ratio learning value KG over a predetermined period thereafter, on condition that it is determined that the fuel supply into the fuel tank 14 has been performed. It is executed after prohibition. By learning the alcohol concentration learning value KGal in this way, when the fuel tank 14 is refueled, the subsequent change in the air-fuel ratio feedback correction coefficient FAF is accompanied by the change in the alcohol concentration of the fuel. As a result, the alcohol concentration learning value KGal is updated in accordance with the change in the air-fuel ratio feedback correction coefficient FAF. It should be noted that the fuel supply to the fuel tank 14 can be determined based on the detection of an increase in the remaining amount of fuel by the remaining amount sensor.

  Incidentally, when the execution condition of the air-fuel ratio feedback control is not established, “1.0” is set as the air-fuel ratio feedback correction coefficient FAF. That is, in this case, the air-fuel ratio feedback control is not executed. Further, when the execution condition of the learning process is not established, the learning process is not executed.

  In this way, after the air-fuel ratio feedback correction coefficient FAF is set and the learning process is appropriately executed, the air-fuel ratio learning value KG and the alcohol concentration learning value KGal are read. The air-fuel ratio learning value KG and the alcohol concentration learning value KGal are added to the air-fuel ratio feedback correction coefficient FAF, and a value obtained by multiplying the added value by the basic fuel injection amount QBASE is calculated as the final fuel injection amount QFIN. Is done.

  In the fuel injection control, the fuel injection time TAU, that is, the valve opening time of the fuel injection valve 13 is calculated based on the final fuel injection amount QFIN, and the fuel injection valve 13 is driven to open based on the fuel injection time TAU. The Thus, an amount of fuel corresponding to the final fuel injection amount QFIN is injected from the fuel injection valve 13 and supplied to the combustion chamber 11 of the internal combustion engine 10. As described above, in the fuel injection control, control (so-called air-fuel ratio control) is performed for adjusting the fuel injection amount so that the actual air-fuel ratio of the air-fuel mixture becomes the target air-fuel ratio.

  In the fuel injection control of the present embodiment, in addition to executing such air-fuel ratio control, the air-fuel ratio of the air-fuel mixture becomes a richer ratio than the stoichiometric air-fuel ratio in order to suppress the temperature rise of the exhaust purification catalyst 20. Increase correction control for increasing the fuel injection amount is executed.

  In this increase correction control, first, a correction coefficient Kot is calculated based on the engine load KL, the engine speed NE, and the coolant temperature THW. The correction coefficient Kot is multiplied by the air-fuel ratio feedback correction coefficient FAF when calculating the final fuel injection amount QFIN. That is, a value that satisfies the relational expression (QFIN = QBSE × [FAF × Kot + KG + KGal]) based on the basic fuel injection amount QBASE, the air-fuel ratio learning value KG, the alcohol concentration learning value KGal, and the correction coefficient Kot is the final fuel injection amount QFIN. Calculated. As the correction coefficient Kot, a value capable of accurately avoiding an excessive increase in the temperature of the exhaust purification catalyst 20 is calculated. Further, the increase correction of the fuel injection amount by the increase correction control is almost always executed on condition that the execution condition is satisfied, except when the temperature of the internal combustion engine 10 is low.

  Here, as described above, the spark plug 16 increases as the alcohol concentration of the fuel (specifically, fuel stored in the fuel tank 14) supplied to the internal combustion engine 10 during operation of the internal combustion engine 10 increases. The required voltage becomes high. For this reason, in the present embodiment, even when the alcohol concentration of the fuel is high, the same alcohol is used so that the required voltage of the spark plug 16 does not exceed the upper limit of the voltage range that can be applied to the spark plug 16. Various engine control execution modes are changed according to the concentration.

  By the way, although the required voltage of the spark plug 16 is lowered, simply changing the engine control execution mode changes the output torque (engine torque) of the internal combustion engine 10. That is, the engine torque is not constant and varies depending on the alcohol concentration of the fuel. Such a difference in engine torque is not preferable because it becomes a factor that hinders the precise operation of the internal combustion engine 10.

  In view of this point, in the present embodiment, execution of ignition timing control is performed so as to suppress a difference in engine torque caused by a difference in alcohol concentration while suppressing a required voltage of the spark plug 16 when the alcohol concentration of fuel is high. The mode, the execution mode of the increase correction control, and the mode of execution of the valve timing control are each changed according to the alcohol concentration.

  Specifically, the alcohol concentration of the fuel (specifically, the alcohol concentration learning value KGal) is added to the calculation parameters used to calculate the base ignition timing Abse, the correction coefficient Kot, and the target valve timing Tvt. In the ignition timing control, the base ignition timing Abse is calculated from the ignition timing calculation map based on the engine load KL, the engine speed NE, and the alcohol concentration learning value KGal. In the increase correction control, the correction coefficient Kot is calculated from the correction coefficient calculation map based on the engine load KL, the engine speed NE, the coolant temperature THW, and the alcohol concentration learning value KGal. Further, in the valve timing control, the target valve timing Tvt is calculated from the valve timing calculation map based on the engine load KL, the engine speed NE, and the alcohol concentration learning value KGal. Each calculation map (ignition timing calculation map, correction coefficient calculation map, valve timing calculation map) is stored in the electronic control unit 30 and is referred to when calculating each control value.

  Each calculation map includes an engine operation state determined by each calculation parameter based on the results of experiments and simulations and control values (base ignition timing Abse, correction coefficient Kot, target valve timing Tvt) suitable for the same operation state. Relationships are obtained in advance and stored. In addition, as each calculation map, a relationship that matches when the alcohol concentration of the fuel is low (for example, 0% concentration) is stored with the high concentration map that stores the relationship that matches when the alcohol concentration of the fuel is high (for example, 100% concentration). Two types of maps, the low-concentration map that has been set, are set. Then, by interpolating the map for high concentration and the map for low concentration with the alcohol concentration learning value KGal (for example, linear interpolation), a value corresponding to the alcohol concentration of the fuel is calculated as each control value. In addition, each calculation map keeps the required voltage of the spark plug 16 low when the relationship among the control values (base ignition timing Abse, correction coefficient Kot, and target valve timing Tvt) is appropriate, that is, when the alcohol concentration of the fuel is high. On the other hand, it is set separately so as to be able to suppress a difference in engine torque caused by a difference in alcohol concentration.

Hereinafter, execution modes of the ignition timing control, the increase correction control, and the valve timing control according to the alcohol concentration of the fuel will be described separately.
First, the execution mode of ignition timing control will be described.

FIG. 2 shows an example of the relationship between the ignition timing, the required voltage of the spark plug 16, and the engine torque under the condition that the fuel injection amount and the intake air amount are constant.
Normally, in the operation control of the internal combustion engine 10, the ignition timing is set to a timing that is ahead of the compression top dead center. Therefore, as the ignition timing is set to the advance timing, the voltage is applied to the ignition plug 16 in a state where the pressure in the combustion chamber 11 is low, that is, in a state in which sparks are easily generated by the ignition plug 16. become. Therefore, as indicated by the line L1 in FIG. 2, the required voltage of the spark plug 16 decreases as the ignition timing becomes the advance timing.

  Based on this point, in the ignition timing control according to the present embodiment, the higher the alcohol concentration of the fuel is, the higher the ignition timing (specifically, the base ignition timing Abse) becomes in accordance with the alcohol concentration. The ignition timing is changed in a form. Specifically, the relationship in which the most advanced timing (timing Ahi in the example shown in FIG. 2) in the set range (region A in the example shown in FIG. 2) is calculated as the base ignition timing Abse is the ignition timing calculation map. The relationship for calculating the most retarded timing (timing Alow in the example shown in FIG. 2) is set in the low concentration map of the ignition timing calculation map. Thereby, when the alcohol concentration of the fuel is high, that is, when the operation control of the internal combustion engine is executed in the same control manner as when the alcohol concentration is low, the required voltage of the spark plug 16 may become unnecessarily high. The required voltage of the spark plug 16 is kept low by changing the ignition timing to the advance timing.

  Further, when the execution mode of the ignition timing control is changed in accordance with the alcohol concentration of the fuel as described above, as shown by a line L2 in FIG. 2, the ignition timing is a timing on the advance side due to the high alcohol concentration. When the change is made, the change acts to increase the engine torque.

Next, the execution aspect of valve timing control is demonstrated.
FIG. 3 shows an example of the relationship between the valve timing VT of the intake valve 21, the required voltage of the spark plug 16, and the engine torque under the conditions where the fuel injection amount and the ignition timing are constant.

  Normally, in the operation control of the internal combustion engine, the valve timing of the intake valve is set so that the intake efficiency of the internal combustion engine is as high as possible. Therefore, if the valve timing VT (for example, timing Blow in FIG. 3) set in the operation control of the internal combustion engine 10 is changed, the intake efficiency of the internal combustion engine 10 is lowered accordingly, and the intake air amount is reduced. Then, as shown by a line L3 in FIG. 3, when the amount of intake air decreases in this way, voltage application to the spark plug 16 is performed in a state where the pressure in the combustion chamber 11 is low. The required voltage of the spark plug 16 is lowered.

  In view of this point, in the valve timing control according to the present embodiment, the higher the alcohol concentration of the fuel, the smaller the intake air amount (specifically, the target valve timing Tvt becomes the retarded timing). Thus, the execution mode of the valve timing control is changed according to the alcohol concentration. Specifically, the relationship in which the most retarded timing (timing Bhi in the example shown in FIG. 3) in the set range (region B in the example shown in FIG. 3) is calculated as the target valve timing Tvt is the valve timing calculation map. Is set to a high density map. In addition, the relationship for calculating the most advanced timing (timing Blow in the example shown in FIG. 3) in the set range is set in the low concentration map of the valve timing calculation map. Thus, when the fuel alcohol concentration is high and the required voltage of the spark plug 16 may become unnecessarily high, the amount of intake air is reduced, so that the required voltage of the spark plug 16 can be kept low.

  Further, if the execution mode of the valve timing control is changed in accordance with the alcohol concentration of the fuel in this way, the valve timing VT is reduced due to the high alcohol concentration as shown by the line L4 in FIG. When the timing is changed to the retarded timing, the change acts to reduce the engine torque.

Next, an execution mode of the increase correction control will be described.
FIG. 4 shows an example of the relationship between the correction coefficient Kot of the increase correction control, the required voltage of the spark plug 16, and the engine torque under the condition that the intake air amount and the ignition timing are constant.

  Normally, when the fuel injection amount of the internal combustion engine is increased and corrected so that the air-fuel ratio of the air-fuel mixture becomes a richer ratio than the stoichiometric air-fuel ratio, the increase correction amount is small as shown by an example of a line L5 in FIG. In the small increase region (region C in the example shown in FIG. 4), the temperature in the combustion chamber increases as the amount of fuel to be burned increases, so the required voltage of the spark plug decreases. On the other hand, when the increase correction amount increases, the influence of the latent heat of vaporization of the fuel increases as the fuel injection amount increases, so that the temperature in the combustion chamber decreases and the required voltage of the spark plug increases. Therefore, in the large increase region where the increase correction amount is large (in the example shown in FIG. 4, the region on the richer side than region C), the required voltage of the spark plug increases as the increase correction amount increases, unlike the small increase region.

  In view of this point, in the increase correction control according to the present embodiment, the correction coefficient Kot and the engine operation are set so that the correction coefficient Kot is set in the above-described multiple increase region (specifically, region D in the example shown in FIG. 4). A relationship with the state is defined. Then, the execution mode of the increase correction control is changed according to the alcohol concentration so that the value at which the increase correction amount decreases as the alcohol concentration of the fuel increases is calculated as the correction coefficient Kot. Specifically, the lean side value (value Dhi in the example shown in FIG. 4) with the smallest increase correction amount in the set range (area D in the example shown in FIG. 4) is calculated as the correction coefficient Kot. Is set in the high density map of the correction coefficient calculation map. In addition, the relation that the rich side value (the value Dlow in the example shown in FIG. 4) with the largest increase correction amount in the set range is calculated is set in the low density map of the correction coefficient calculation map. As a result, the higher the alcohol concentration of the fuel, the smaller the influence of the latent heat of vaporization of the fuel and the higher the temperature in the combustion chamber 11. Therefore, even if the alcohol concentration increases, the spark plug 16 The required voltage can be kept low.

  In addition, when the fuel injection amount of the internal combustion engine is increased and corrected so that the air-fuel ratio of the air-fuel mixture becomes a richer ratio than the stoichiometric air-fuel ratio, basically, as the increase correction amount increases, the amount of fuel that burns increases. The engine torque increases as the quantity increases. Therefore, as shown by the line L6 in FIG. 4, when the correction coefficient Kot is changed so that the higher the alcohol concentration of the fuel, the leaner the value, the correction coefficient Kot increases due to the higher alcohol concentration of the fuel. When the value is changed to a lean value where the correction amount decreases, the change acts to reduce the engine torque.

  Thus, in the control device according to the present embodiment, the ignition timing control is performed so that the required voltage when the alcohol concentration is high is lower than the required voltage of the spark plug 16 when the alcohol concentration of the fuel is low. The execution mode, the increase correction control execution mode, and the valve timing control execution mode are respectively changed. Specifically, as the alcohol concentration of the fuel is higher, the execution mode of the ignition timing control is changed so that the ignition timing becomes the advanced timing, and the increase correction is performed so that the increase correction amount of the fuel injection amount is reduced. The execution mode of the control is changed, and further, the execution mode of the valve timing control is changed so that the valve timing VT of the intake valve 21 becomes the timing on the retard side. Therefore, even when the alcohol concentration of the fuel becomes high, the required voltage of the spark plug 16 can be kept low.

  Further, in the ignition timing control of the present embodiment, the ignition timing is changed so as to become the advance timing as the alcohol concentration is higher, so that the change acts to increase the engine torque. Become. On the contrary, in the valve timing control, the valve timing VT is changed so that the intake air amount becomes smaller as the alcohol concentration is higher, so that the change acts to reduce the engine torque. Similarly, in the increase correction control, the correction coefficient Kot is changed so that the increase correction amount of the fuel injection amount becomes smaller as the alcohol concentration of the fuel becomes higher, so that the change acts to decrease the engine torque. To do.

  Therefore, in the control device according to the present embodiment, the ignition timing and the increase correction amount (specifically, the correction coefficient Kot) are both engine control amounts that change the required voltage of the spark plug 16, and the required voltage is in the same direction. When the engine torque is changed so as to change to two, the engine torque changes in two different engine control amounts. Similarly, both the ignition timing and the valve timing VT are engine control amounts that change the required voltage of the spark plug 16, and changes in the engine torque when the required voltage is changed to change in the same direction. There are two engine control amounts with different directions.

  Therefore, when the alcohol concentration of the fuel is high, a part of the increase in the engine torque due to the change to the advance timing side of the ignition timing and the engine torque due to the change in the correction coefficient Kot to a value at which the increase correction amount decreases. At least a part of the decrease is offset. Further, when the alcohol concentration of the fuel is high, a part of the increase in the engine torque due to the change of the ignition timing to the advance side and the decrease of the engine torque due to the change of the valve timing VT to the retard side. At least a part of it is offset.

  FIG. 5 shows an example of the relationship between the alcohol concentration of the fuel, the required voltage of the spark plug 16, and the engine torque. In FIG. 5, the solid line indicates the above relationship with respect to the apparatus of the present embodiment, and the two-dot chain line indicates the above relationship with respect to the comparative example apparatus in which only the execution mode of the ignition timing control is changed according to the alcohol concentration of the fuel. Indicates.

  As shown in FIG. 5, in the present embodiment (solid line), ignition timing control, increase correction control, and valve according to the alcohol concentration of the fuel in order to keep the required voltage of the spark plug 16 low when the alcohol concentration is high. Although the execution mode of the timing control is changed, the change in the engine torque accompanying the change is suppressed to be smaller than that of the device of the comparative example (two-point difference line). Therefore, according to the control device of the present embodiment, it is possible to suppress the difference in engine torque caused by the difference in alcohol concentration while suppressing the required voltage of the spark plug 16 when the alcohol concentration of fuel is high.

  In the present embodiment, the control modes of the three engine control amounts such as the ignition timing, the correction coefficient Kot, and the valve timing VT are changed according to the alcohol concentration. Therefore, the control mode of each engine control amount is set with a high degree of freedom compared with a device that changes only the control mode of two engine control amounts such as the ignition timing and the correction coefficient Kot or the ignition timing and the valve timing VT. Accordingly, it is possible to accurately reduce both the required voltage of the spark plug 16 and the suppression of the difference in engine torque.

  Incidentally, in the device of the above comparative example, if the ignition timing is simply changed to the advance timing in order to keep the required voltage of the spark plug 16 low, the engine torque becomes unnecessarily large. For this reason, the strength of the internal combustion engine and its peripheral devices must be set in accordance with the engine torque, and there is a risk that the strength becomes unnecessarily high. In this regard, according to the present embodiment, since the engine torque is prevented from becoming unnecessarily large when the alcohol concentration of the fuel is high, the occurrence of the inconvenience can be suppressed.

As described above, according to the present embodiment, the effects described below can be obtained.
(1) The ignition timing, the correction coefficient Kot, and the valve timing VT are set so that the required voltage when the alcohol concentration is high is lower than the required voltage of the spark plug 16 when the alcohol concentration of the fuel is low. The control mode of one engine control amount was changed according to the alcohol concentration. Therefore, the difference in engine torque due to the difference in alcohol concentration can be suppressed while suppressing the required voltage of the spark plug 16 when the alcohol concentration of fuel is high.

  (2) The control modes of the three engine control amounts such as the ignition timing, the correction coefficient Kot, and the valve timing VT are changed according to the alcohol concentration. Therefore, the control mode of each engine control amount is set with a high degree of freedom compared with a device that changes only the control mode of two engine control amounts such as the ignition timing and the correction coefficient Kot or the ignition timing and the valve timing VT. Accordingly, it is possible to accurately reduce both the required voltage of the spark plug 16 and the suppression of the difference in engine torque.

The embodiment described above may be modified as follows.
・ Increase correction control to increase the fuel injection amount so that the air-fuel ratio of the mixture becomes richer than the stoichiometric air-fuel ratio. An increase correction control other than the increase correction control for suppressing the temperature increase of the exhaust purification catalyst 20, such as control, may be executed.

  Only the two engine control amounts of the ignition timing and the correction coefficient Kot or only the control mode of the two engine control amounts of the ignition timing and the valve timing VT may be changed according to the alcohol concentration. In this case, the two engine control amounts are in an appropriate relationship, that is, a relationship in which a difference in engine torque caused by a difference in alcohol concentration can be suppressed while suppressing a required voltage of the spark plug 16 when the alcohol concentration of fuel is high. Therefore, the control modes of the two engine control amounts may be set separately.

  The control device according to the present embodiment also changes the configuration of the control device according to the present embodiment to an internal combustion engine equipped with a variable valve mechanism for changing the valve opening characteristics of the engine valve other than the valve timing changing mechanism 22. Can be applied. As such a variable valve mechanism, a mechanism for changing the valve opening period of the intake valve 21 (a period from the valve opening timing to the valve closing timing [so-called valve operating angle]), or a valve timing of the exhaust valve is changed. And a mechanism for changing the valve operating angle of the exhaust valve. According to such a configuration, by changing the control mode of the valve opening characteristic (valve timing or valve operating angle) of the engine valve in accordance with the alcohol concentration of the fuel, the demand of the spark plug 16 is changed according to the change in the intake air amount accompanying this. Both voltage and engine torque can be changed. Therefore, the opening characteristic of such an engine valve is used as an engine control amount for suppressing a difference in engine torque caused by a difference in alcohol concentration while suppressing a required voltage of the spark plug 16 when the alcohol concentration of fuel is high. Can do.

  A throttle opening TA is added as one of the engine control amounts used to suppress the difference in engine torque caused by the difference in alcohol concentration while suppressing the required voltage of the spark plug 16 when the alcohol concentration of fuel is high. You may do it. According to such a configuration, by changing the control mode of the throttle opening degree TA according to the alcohol concentration of the fuel, both the required voltage of the spark plug 16 and the engine torque are changed by the change of the intake air amount accompanying this. Can do.

  Applied to an internal combustion engine having an EGR passage communicating with the intake passage and the exhaust passage and an EGR valve provided in the EGR passage, and through the operation control of the EGR valve based on the operating state of the internal combustion engine, the intake passage from the exhaust passage In the control device for adjusting the amount of exhaust gas recirculated, the opening degree of the EGR valve may be added as one of the engine control amounts. According to such a configuration, by changing the control mode of the opening degree of the EGR valve according to the alcohol concentration, the required voltage of the spark plug 16 can be changed by the accompanying temperature change in the combustion chamber, and the intake air The engine torque can be changed by changing the amount.

  A concentration sensor for detecting the alcohol concentration of the fuel may be provided, and the alcohol concentration detected by the concentration sensor may be used for calculating the engine control amount.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Combustion chamber, 12 ... Intake passage, 13 ... Fuel injection valve, 14 ... Fuel tank, 15 ... Fuel pump, 16 ... Spark plug, 17 ... Piston, 18 ... Crankshaft, 19 ... Exhaust passage, DESCRIPTION OF SYMBOLS 20 ... Exhaust gas purification catalyst, 21 ... Intake valve, 22 ... Valve timing change mechanism, 23 ... Throttle valve, 24 ... Accelerator pedal, 25 ... Throttle motor, 26 ... Actuator, 30 ... Electronic control unit

Claims (5)

In a control device for performing operation control of an internal combustion engine that can use gasoline and alcohol as fuel and in which the fuel is ignited through spark discharge by a spark plug,
The engine control amount controlled in the operation control is an engine control amount that changes the required voltage of the spark plug, and the change direction of the engine torque when the required voltage is changed in the same direction. Two different engine control amounts are set,
The operation control includes ignition timing control for controlling the ignition timing of the internal combustion engine and increase correction control for increasing and correcting the fuel injection amount of the internal combustion engine so that the air-fuel ratio becomes a richer ratio than the stoichiometric air-fuel ratio. ,
The two engine control amounts are an increase correction amount of the ignition timing and the increase correction control,
The ignition timing and the increase correction of the increase correction control according to the alcohol concentration of the fuel so that the required voltage when the concentration is high is lower than the required voltage when the alcohol concentration of the fuel is low. A control device for an internal combustion engine, characterized in that the control mode of the quantity is changed. The control apparatus for an internal combustion engine according to claim 1 ,
The internal combustion engine has a variable valve mechanism that changes a valve opening characteristic of the engine valve,
The control device adjusts the alcohol concentration of the fuel so that the intake air amount of the internal combustion engine when the concentration is high is smaller than the intake air amount of the internal combustion engine when the alcohol concentration of the fuel is low. A control device for an internal combustion engine, wherein the control mode of the variable valve mechanism is changed accordingly. In a control device for performing operation control of an internal combustion engine that can use gasoline and alcohol as fuel and in which the fuel is ignited through spark discharge by a spark plug,
The engine control amount controlled in the operation control is an engine control amount that changes the required voltage of the spark plug, and the change direction of the engine torque when the required voltage is changed in the same direction. Two different engine control amounts are set,
The internal combustion engine has a variable valve mechanism that changes a valve opening characteristic of the engine valve,
The operation control includes ignition timing control for controlling the ignition timing of the internal combustion engine and operation control for the variable valve mechanism.
The two engine control amount, Ri operation amount der ignition timing and the variable valve mechanism of the internal combustion engine,
The ignition timing of the internal combustion engine and the variable valve are set according to the alcohol concentration of the fuel so that the required voltage when the concentration is high is lower than the required voltage when the alcohol concentration of the fuel is low. A control apparatus for an internal combustion engine, characterized by changing a control mode of an operation amount of a mechanism . The control apparatus for an internal combustion engine according to claim 1 or 2 ,
The internal combustion engine is provided with an exhaust purification catalyst in its exhaust passage,
The control device for an internal combustion engine, wherein the increase correction control is control for increasing the fuel injection amount so as to suppress a temperature rise of the exhaust purification catalyst. The control device for an internal combustion engine according to claim 2 or 3 ,
The control apparatus for an internal combustion engine, wherein the variable valve mechanism is a valve timing changing mechanism for changing an opening / closing timing of an engine valve.

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