JP2009133245A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of controlling slippage of an air-fuel ratio due to fuel adhering on an intake port. <P>SOLUTION: The control device (electronic control device 1) for the internal combustion engine provided with a fuel port injection means (fuel injection valve 54 or the like) injecting fuel F to the intake port 11b and a throttle valve actuator 25 adjusting flow rate of intake air by controlling valve opening a throttle valve 24 is provided with a throttle valve control means issuing an instruction to a throttle valve actuator 25 to set valve close speed of the throttle valve 24 lower when the alcohol concentration of fuel F is low and/or the temperature of the internal combustion engine is high as the alcohol concentration of the fuel F is high and/or the temperature of the internal combustion engine is low. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that can be operated using a plurality of types of fuel having different fuel properties.

  In recent years, in the automobile industry, various efforts have been made to cope with changes in the environment surrounding automobiles. For example, in the field of internal combustion engines, efforts have been made for so-called multi-fuel internal combustion engines that can be operated even with fuels having different fuel properties. A vehicle equipped with this kind of multi-fuel internal combustion engine is generally called a flexible fuel vehicle (FFV). For example, any of gasoline fuel, alcohol fuel, or a mixed fuel thereof is used. However, it is known to improve the environmental performance such as the suppression of the consumption of fossil fuels such as gasoline fuel, which can be operated and the limits of reserves continue to be sought. For example, Patent Document 1 below discloses a multi-fuel internal combustion engine that operates by supplying gasoline fuel when alcohol fuel is the main fuel and the temperature of the internal combustion engine is equal to or lower than a predetermined value.

  Here, in Patent Document 2 below, the opening speed of the throttle valve when operating with alcohol fuel in order to eliminate the difference in the generation state of the output of alcohol fuel and gasoline fuel when the same accelerator opening is set. A throttle valve control method that is slower than when operating with fuel is disclosed.

Japanese Patent Publication No. 61-60258 Japanese Patent Laid-Open No. 3-57831

  Incidentally, low-volatile fuels such as alcohol fuels and alcohol-mixed fuels having a high alcohol concentration have a higher latent heat of vaporization than high-volatile fuels such as gasoline fuels, and are difficult to evaporate. For example, ethanol has a boiling point as high as 78.5 ° C. and is difficult to evaporate at lower temperatures. Therefore, when the engine temperature of the internal combustion engine is low, such as during cold start, when low-volatile fuel is injected into the intake port, a part of it adheres to the inner wall surface of the intake port without evaporating. May not be atomized. Further, the amount of attachment of the intake port to the inner wall surface increases as the degree of volatilization of the low-volatile fuel decreases (that is, as the alcohol concentration increases).

  Here, the operating state of the internal combustion engine has a small change in intake air amount (for example, a small amount of change in accelerator opening) and a large change in intake air amount (for example, the amount of change in accelerator opening). It can be broadly divided into transient operation states. In the state where the intake air amount is increased even in the transient operation state, the amount of fuel supplied into the combustion chamber increases accordingly, so the intake port of the low-volatile fuel injected into the intake port The amount of adhesion to the inner wall surface will increase.

  In the situation where low volatile fuel is attached to the inner wall surface of the intake port, when the throttle valve is closed by returning the accelerator pedal or the like, the attached fuel enters the combustion chamber and becomes empty. The fuel ratio will be disturbed. Specifically, when the throttle valve closes under such circumstances, the negative pressure in the combustion chamber increases and the intake air flow velocity increases, so that the low pressure adhering to the inner wall surface of the intake port Volatile fuel rides on the flow of intake air and is guided into the combustion chamber. At that time, the control device for the internal combustion engine sets the fuel injection amount so as to become the target air-fuel ratio in accordance with the intake air amount that has decreased with the closing operation of the throttle valve, and executes the fuel injection control.

  However, in the combustion chamber at that time, the actual air-fuel ratio shifts to the rich side from the target air-fuel ratio by the amount of fuel adhering to the inner wall surface of the intake port that has been sucked. Therefore, in this case, for example, although the driver expects the vehicle to decelerate by returning the accelerator pedal, the output torque increases as the air-fuel ratio shifts to the rich side. You may not be able to get a feeling of slowdown. In other words, in this case, drivability may be deteriorated. Further, when the actual air-fuel ratio becomes a rich air-fuel ratio due to the deviation, the generation amount of harmful substances typified by hydrocarbon (HC) may increase and the emission performance may be deteriorated.

  Therefore, an object of the present invention is to provide a control device for an internal combustion engine that can improve the disadvantages of the conventional example and can suppress the deviation of the air-fuel ratio due to the fuel adhering to the intake port.

  In order to achieve the above object, according to the first aspect of the present invention, a fuel port injection means for injecting fuel into the intake port, a throttle valve actuator for adjusting the flow rate of the intake air by controlling the valve opening of the throttle valve, In the control apparatus for an internal combustion engine, the higher the alcohol concentration of the fuel or / and the lower the engine temperature of the internal combustion engine, the lower the closing speed of the throttle valve. Throttle valve control means is provided for instructing the throttle valve actuator to be slower than when the temperature is high.

  Thus, the control apparatus for an internal combustion engine according to claim 1 can suppress an increase in the negative pressure in the combustion chamber when the throttle valve is closed, and can also suppress the intake air flow velocity at that time. For this reason, this control device can reduce the intake amount of the fuel adhering to the intake port at that time into the combustion chamber, and therefore, the deviation of the air-fuel ratio of the air-fuel mixture generated at that time from the target air-fuel ratio. Can be suppressed.

  According to a second aspect of the present invention, in the control apparatus for an internal combustion engine according to the first aspect, the air-fuel mixture in the combustion chamber is ignited when the throttle valve closing speed control by the throttle valve control means is executed. Ignition control means for retarding the ignition timing of the ignition means is provided.

  When the throttle valve closing speed is slowed down, the intake air amount increases, and the fuel injection amount increases accordingly, so that the output torque may increase. The control apparatus for an internal combustion engine according to claim 2 can suppress the increase in the output torque by performing the retard control of the ignition timing at that time.

  The control apparatus for an internal combustion engine according to the present invention reduces the inflow amount of the adhering fuel into the combustion chamber by slowing the closing speed of the throttle valve when the fuel is adhering to the intake port. The deviation of the air-fuel ratio is suppressed. Therefore, this control device can suppress an increase in output torque and a deterioration in emission performance that are not intended by the driver due to the deviation.

  Embodiments of an internal combustion engine control apparatus according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

  An embodiment of a control device for an internal combustion engine according to the present invention will be described with reference to FIGS. In the following, the control device will be described in detail while explaining an example of an internal combustion engine to be applied.

  The internal combustion engine exemplified here is a so-called flexible fuel vehicle that can be operated even by using fuels having different fuel properties such as gasoline fuel, alcohol fuel (ethanol, methanol, butanol, etc.) or a mixed fuel thereof. 1 is a multi-fuel internal combustion engine, in which various control operations such as combustion control are executed by an electronic control unit (ECU) 1 shown in FIG. In other words, in this embodiment, it is assumed that the control device for the internal combustion engine is configured by various control functions of the electronic control device 1. The electronic control unit 1 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores a predetermined control program and the like, and a RAM (Random Access) that temporarily stores the calculation result of the CPU. Memory) and a backup RAM for storing information prepared in advance.

  First, the configuration of the internal combustion engine exemplified here will be described with reference to FIG. Although only one cylinder is shown in FIG. 1, the present invention is not limited to this, and can be applied to a multi-cylinder multifuel internal combustion engine. In the present embodiment, description will be made assuming that a plurality of cylinders are provided.

  The internal combustion engine includes a cylinder head 11, a cylinder block 12, and a piston 13 that form a combustion chamber CC. Here, the cylinder head 11 and the cylinder block 12 are fastened with bolts or the like via the head gasket 14 shown in FIG. 1, and the recess 11a on the lower surface of the cylinder head 11 and the cylinder bore 12a of the cylinder block 12 formed thereby. The piston 13 is disposed so as to be capable of reciprocating in the space. And the combustion chamber CC mentioned above is comprised by the space enclosed by the wall surface of the recessed part 11a of the cylinder head 11, the wall surface of the cylinder bore 12a, and the top surface 13a of the piston 13. FIG.

  This internal combustion engine sends air and fuel into the combustion chamber CC in accordance with operating conditions such as engine speed and engine load, and executes combustion control in accordance with the operating conditions. The air is sucked from the outside through the intake passage 21 and the intake port 11b of the cylinder head 11 shown in FIG. On the other hand, the fuel is supplied using the fuel supply device 50 shown in FIG.

  First, the air supply path will be described.

  On the intake passage 21 of the internal combustion engine, an air cleaner 22 for removing foreign matters such as dust contained in air introduced from the outside, and an intake air amount detection means 23 for detecting the amount of intake air from the outside are provided. ing. As the intake air amount detection means 23, an air amount detection sensor such as an air flow meter that directly detects the intake air amount, an intake pipe pressure sensor that detects the pressure in the intake passage 21 (ie, intake pressure), and the like are conceivable. When the latter intake pipe pressure sensor is used, the intake air amount is obtained indirectly from the intake pressure and the engine speed. In this internal combustion engine, the detection signal of the intake air amount detection means 23 is sent to the electronic control unit 1, and the electronic control unit 1 calculates the intake air amount, the engine load and the like based on the detection signal. The engine speed can be grasped from the detection signal of the crank angle sensor 16 that detects the rotation angle of the crankshaft 15.

  Further, on the intake passage 21 downstream of the intake air amount detecting means 23, a throttle valve 24 capable of adjusting the flow rate of intake air flowing into the combustion chamber CC, and a throttle for driving the throttle valve 24 to open and close. And a valve actuator 25. In the electronic control device 1 of this embodiment, the throttle valve actuator 25 is driven and controlled in accordance with the operating conditions, and the throttle valve control for adjusting the valve opening angle of the throttle valve 24 so that the valve opening degree according to the operating conditions is obtained. Means are provided. Here, the throttle valve actuator 25 and the throttle valve control means constitute a throttle valve opening control means. Further, this internal combustion engine is provided with a throttle opening sensor 26 that detects the valve opening of the throttle valve 24 and transmits the detection signal to the electronic control unit 1.

  On the other hand, one end of the intake port 11b opens to the combustion chamber CC, and an intake valve 31 that opens and closes the opening is disposed in the opening portion. The number of openings may be one or more, and an intake valve 31 is provided for each opening. Therefore, in this internal combustion engine, air is sucked into the combustion chamber CC from the intake port 11b by opening the intake valve 31 and closed to the combustion chamber CC by closing the intake valve 31. Air inflow is blocked.

  Here, as the intake valve 31, for example, there is a valve that is driven to open and close in accordance with the rotation of an intake camshaft (not shown) and the elastic force of an elastic member (string spring). In this type of intake valve 31, by interposing a power transmission mechanism such as a chain or a sprocket between the intake side camshaft and the crankshaft 15, the intake side camshaft is interlocked with the rotation of the crankshaft 15, Open / close drive is performed at a preset opening / closing timing. In the internal combustion engine illustrated here, the intake valve 31 that is driven to open and close in synchronization with the rotation of the crankshaft 15 can be applied.

  However, the internal combustion engine may be provided with a variable valve mechanism such as a so-called variable valve timing and lift mechanism that can change the opening / closing timing and lift amount of the intake valve 31, and thereby the opening / closing timing of the intake valve 31. And the lift amount can be changed to a suitable one according to the operating conditions. Furthermore, in this internal combustion engine, a so-called electromagnetically driven valve that opens and closes the intake valve 31 using electromagnetic force may be used in order to obtain the same effect as the variable valve mechanism.

  Next, the fuel supply device 50 will be described.

  This fuel supply device 50 injects fuel in one fuel tank into the intake port 11b, injects fuel in one fuel tank into the intake port 11b and the combustion chamber CC, and into a plurality of fuel tanks The stored fuel having different fuel properties is mixed by a fuel mixing device or the like and injected into the intake port 11b, the mixed fuel is injected into the intake port 11b and the combustion chamber CC, and the fuel in one fuel tank is injected. It is possible to inject fuel into the combustion chamber CC while injecting fuel into the intake port 11b and different fuel properties in the other fuel tank. In this embodiment, a port injection type in which the fuel F stored in one fuel tank 41 is injected into the intake port 11b and led to the combustion chamber CC together with the intake air is shown as a representative example.

  Specifically, the fuel supply device 50 distributes the fuel F in the fuel passage 51 to each cylinder, and a feed pump 52 as a fuel pump that sucks the fuel F from the fuel tank 41 and sends it to the fuel passage 51. A fuel delivery pipe 53 and a fuel injection valve (fuel injection means) 54 for each cylinder that injects fuel F supplied from the fuel delivery pipe 53 into each intake port 11b.

  The fuel supply device 50 controls the feed pump 52 and the fuel injection valve 54 to be controlled by the fuel injection control means of the electronic control unit 1 according to the operating conditions, whereby the target fuel injection amount and the fuel corresponding to the operating conditions are controlled. The fuel F is configured to be injected under fuel injection conditions such as the injection timing and the fuel injection period. For example, the fuel injection control means causes the fuel F to be sucked up from the fuel tank 41 by the feed pump 52 and causes the fuel injection valve 54 to perform injection under the fuel injection conditions corresponding to the operating conditions.

  The fuel F supplied to the intake port 11b in this way is supplied into the combustion chamber CC together with the opening of the intake valve 31, while being mixed with the air described above in the intake port 11b. Here, the target fuel injection amount of the fuel F fed into the combustion chamber CC and the intake air amount of the air are determined by the air-fuel ratio control means of the electronic control unit 1 according to the target air-fuel ratio corresponding to the operating conditions. The air-fuel ratio-controlled air-fuel mixture in the combustion chamber CC is combusted by an ignition operation of an ignition plug (ignition means) 61 when the ignition timing according to the operating conditions is reached. The ignition timing of the ignition plug 61 is controlled by the ignition control means of the electronic control unit 1. The in-cylinder gas (combustion gas) after being burned is discharged from the combustion chamber CC to the exhaust port 11c shown in FIG. 1 and discharged to the atmosphere through the exhaust passage 81.

  An exhaust valve 71 that opens and closes an opening between the exhaust port 11c and the combustion chamber CC is disposed. The number of openings may be one or more, and the exhaust valve 71 described above is provided for each opening. Accordingly, in this internal combustion engine, combustion gas is discharged from the combustion chamber CC to the exhaust port 11c by opening the exhaust valve 71, and closing the exhaust valve 71 to the combustion gas exhaust port 11c. Is blocked.

  Here, as the exhaust valve 71, as in the intake valve 31 described above, a valve with a power transmission mechanism, a valve with a variable valve mechanism such as a so-called variable valve timing & lift mechanism, or a so-called electromagnetically driven valve is used. Can be applied.

  Further, an exhaust gas purification device 82 is disposed on the exhaust passage 81, and the exhaust gas purification device 82 purifies harmful substances in the exhaust gas.

  By the way, the internal combustion engine of the present embodiment enables operation with various fuels F having different fuel properties as described above. For this reason, the driver does not always supply the alcohol-mixed fuel having the same fuel mixture ratio as that of the current situation because the alcohol-mixed fuel is stored in the fuel tank 41 at the present time. There is also the possibility of refueling alcohol fuel or gasoline fuel. In the first place, alcohol blended fuel provided at a fueling facility is not always available with the same fuel blend ratio. Furthermore, although the main component of gasoline fuel provided at a fueling facility is gasoline fuel depending on the country or region, it may be provided as alcohol mixed fuel in which alcohol fuel is mixed with the gasoline fuel.

  In other words, the fuel F having the same alcohol concentration is not always stored in the actual fuel tank 41, particularly after refueling. Accordingly, the fuel F may be a highly volatile high volatile fuel mainly composed of gasoline fuel, or may be a low volatile low volatile fuel composed mainly of alcohol fuel. Sometimes it is.

  Here, assuming that the fuel F becomes a low-volatile fuel, as described above, the fuel F injected into the intake port 11b when the internal combustion engine is in a transient operation state (intake of the intake air amount) is As the volatilization level decreases (that is, the alcohol concentration increases) and the engine temperature decreases, a part of the volatilization easily adheres to the inner wall surface of the intake port 11b. Similarly, when the throttle valve 24 is closed by returning the accelerator pedal (not shown) under the condition that the fuel (low volatile fuel) F is adhered to the inner wall surface of the intake port 11b. The internal combustion engine is in a transient operation state while the intake air amount is decreasing, and as described above, the fuel (hereinafter also referred to as “port-attached fuel”) F adhering to the inner wall surface of the intake port 11b is the combustion chamber CC. The actual air-fuel ratio shifts to the rich side with respect to the target air-fuel ratio by the amount of the fuel adhering to the port adhering to the port F. Therefore, in this case, the drivability may deteriorate and the emission performance may deteriorate.

  Therefore, the control device for the internal combustion engine of the present embodiment reduces the intake amount of the port-attached fuel F into the combustion chamber CC in the transient operation state (while the intake air amount is decreasing) in which the accelerator pedal is returned by the driver. Configure accordingly.

  The intake of the fuel adhering to the port F is an event that occurs due to the closing operation of the throttle valve 24 when the driver returns the accelerator pedal. Specifically, the intake of the fuel F in the combustion chamber CC accompanying the closing operation is performed. It is generated by increasing negative pressure and speeding up the intake flow velocity. Here, the intake amount of the port-attached fuel F increases as the negative pressure in the combustion chamber CC increases and as the intake flow velocity increases. The negative pressure in the combustion chamber CC increases as the throttle valve closing speed of the throttle valve 24 (hereinafter referred to as “throttle valve closing speed”) increases, and the throttle valve closing speed also increases as the intake air flow rate. It gets faster. That is, it is considered that the intake amount of the fuel adhering to the port F increases as the throttle valve closing speed increases.

  Therefore, in the control apparatus for the internal combustion engine of the present embodiment, when the fuel F is a low-volatile fuel and the accelerator pedal is returned, the throttle valve closing speed is higher than when the fuel F is a high-volatile fuel. The throttle valve control means of the electronic control device 1 is configured so as to slow down.

  Here, the amount of fuel adhered to the port F increases as the degree of volatilization of the fuel F decreases (the alcohol concentration increases) and as the engine temperature decreases. Therefore, when the fuel F is a low-volatile fuel and the accelerator pedal is returned, the throttle valve control means has a higher volatility (alcohol) as the fuel F has a lower volatility (higher alcohol concentration). The throttle valve closing speed is made slower than that of the fuel F having a low concentration. Further, in this throttle valve control means, when the fuel F is a low-volatile fuel and the accelerator pedal is returned, the lower the engine temperature, the slower the throttle valve closing speed than when the engine temperature is high. Further, the amount of fuel F adhering to the inner wall surface of the intake port 11b increases as the degree of volatilization of the fuel F is lower (the alcohol concentration is higher) and the engine temperature is lower. When the fuel is a volatile fuel and the accelerator pedal is returned, the degree of volatilization of the fuel F is lower (the alcohol concentration is higher) and the lower the engine temperature is, the higher the degree of volatilization of the fuel F is (the alcohol concentration is higher). (Lower) and slower than when the engine temperature is low.

  On the other hand, as described above, when the fuel F is a low-volatile fuel and the internal combustion engine is in a transient operation state in which the intake air amount is increasing (in other words, when the accelerator pedal is depressed), the fuel F Is attached to the inner wall surface of the intake port 11b. In the combustion chamber CC, the amount of fuel supplied to the combustion chamber CC is reduced relative to the target value by the amount of the fuel adhering to the port F, and the output torque is reduced when the air-fuel ratio becomes leaner than the target air-fuel ratio. Will be reduced. That is, the internal combustion engine in this case cannot generate a target output, and the responsiveness may be deteriorated.

  Further, as described above, when a deviation occurs in the air-fuel ratio, the fuel injection amount is set to the target air-fuel ratio by, for example, feedback control. For example, when the air-fuel ratio is on the lean side with respect to the target air-fuel ratio, control is performed to increase the fuel injection amount to the target air-fuel ratio. However, when the engine temperature is low, the engine temperature rises every time combustion is performed in the combustion chamber CC, so that the amount of fuel adhering to the port F decreases and further adhered by the previous fuel injection. There is a possibility that the port-attached fuel F evaporates and is sent to the combustion chamber CC together with the fuel F injected this time. For this reason, in that case, there is a possibility that the air-fuel ratio which has been on the lean side exceeds the target air-fuel ratio and shifts to the rich side. Therefore, under the situation where the air-fuel ratio shifts due to the fuel adhering to the port F, if the lean air-fuel ratio is caused by the shift, the amount of harmful substances represented by nitrogen oxide (NOx) increases, and the shift If the air-fuel ratio becomes rich due to the above, the production amount of harmful substances represented by hydrocarbons (HC) will increase. That is, under such circumstances, there is a possibility that the emission performance is deteriorated.

  For this reason, the throttle valve control means of the present embodiment has a throttle valve 24 that is more volatile when the fuel F is a low volatile fuel and the accelerator pedal is depressed than when the fuel F is a high volatile fuel. The valve opening speed (hereinafter referred to as “throttle valve opening speed”) is reduced.

  Here, as described above, the attached amount of the port-attached fuel F increases as the degree of volatilization of the fuel F decreases (the alcohol concentration increases) and as the engine temperature decreases. Further, the adhesion amount increases as the degree of volatilization of the fuel F is lower (the alcohol concentration is higher) and the engine temperature is lower. Therefore, when the fuel F is a low-volatile fuel and the accelerator pedal is depressed, the lower the degree of volatilization of the fuel F (the higher the alcohol concentration), the higher the degree of volatilization (alcohol). The throttle valve opening speed is made slower than in the case of the fuel F having a low concentration. Further, in this throttle valve control means, when the fuel F is a low-volatile fuel and the accelerator pedal is depressed, the throttle valve opening speed is made slower as the engine temperature is lower than when the engine temperature is higher. In addition, when the fuel F is a low-volatile fuel and the accelerator pedal is depressed, the throttle valve control means includes a throttle valve that has a lower volatility of the fuel F (higher alcohol concentration) and lower engine temperature. The valve opening speed is made slower than when the volatilization degree of the fuel F is high (the alcohol concentration is low) and the engine temperature is low.

  Hereinafter, the calculation processing operation of the fuel injection control device (electronic control device 1) of the present embodiment will be described based on the flowchart of FIG.

  First, the alcohol concentration determination means of the electronic control unit 1 determines the alcohol concentration of the fuel F (step ST5). The alcohol concentration may be estimated based on, for example, a detection value of the exhaust sensor 83 on the exhaust passage 81 (oxygen concentration in exhaust gas by the O 2 sensor or air-fuel ratio of exhaust gas by the A / F sensor). You may detect with the alcohol concentration sensor 42 arrange | positioned in any component (here fuel tank 41) of the tank 41 or the fuel supply apparatus 50. FIG. Moreover, you may acquire the alcohol concentration of the fuel F from fuel supply information etc.

  Further, the electronic control unit 1 detects the engine temperature by the engine information detecting means (step ST10). For example, here, the temperature of the cooling water of the internal combustion engine is detected based on the detection value of the water temperature sensor 17 shown in FIG.

  Further, the engine information detection means obtains the accelerator opening change amount based on the detected value of the accelerator opening sensor 91 shown in FIG. 1 which detects the driver's accelerator pedal operation (accelerator opening) (step ST15).

  Then, the throttle valve control means of the electronic control unit 1 determines the accelerator pedal operation mode by the driver based on the accelerator opening change amount (step ST20). The determination of the accelerator pedal operation mode is to determine whether the driver has performed an accelerator pedal return operation or an accelerator pedal depression operation.

  When it is determined in step ST20 that the accelerator pedal is returned, the throttle valve control means obtains the target throttle valve closing speed (step ST25), and calculates the target throttle opening based on the target throttle valve closing speed. (Step ST30).

  Here, FIG. 3 shows an example of the calculation result of the target throttle valve closing speed and the target throttle opening according to the engine temperature, and FIG. 4 shows the fuel F volatilization degree (alcohol concentration) according to the level. An example of calculation results of the target throttle valve closing speed and the target throttle opening is shown.

  As shown in FIG. 3, in step ST25, the lower the engine temperature, the slower the target throttle valve closing speed is set. Therefore, in step ST30, the target throttle opening is set so that the throttle valve 24 is gradually closed as the engine temperature decreases. The relationship between the engine temperature and the target throttle valve closing speed should be prepared as map data that can be controlled in advance by conducting experiments and simulations to suppress the deterioration in drivability and emission performance associated with the accelerator pedal return operation described above. .

  As shown in FIG. 4, in step ST25, the lower the degree of volatilization of the fuel F, the lower the target throttle valve closing speed is set as the alcohol F is lower (the alcohol concentration is higher). Accordingly, in step ST30, the target throttle opening is set so that the throttle valve 24 is closed slowly as the degree of volatilization of the fuel F decreases (the alcohol concentration increases). The relationship between the degree of volatilization of the fuel F (alcohol concentration) and the target throttle valve closing speed is map data that can be used in experiments and simulations in advance to suppress deterioration in drivability and emission performance associated with the accelerator pedal return operation described above. You should prepare as. Further, when considering the engine temperature in FIG. 4, the target throttle valve closing speed is set so that the throttle valve 24 is more slowly closed as the engine temperature is lower.

  After obtaining the target throttle valve closing speed and the target throttle opening in this manner, the electronic control unit 1 causes the throttle valve control means, the fuel injection control means, the ignition control means, etc. Combustion control in the operating state is executed (step ST35).

  As a result, the throttle valve 24 operates toward the valve closing side more slowly than the throttle valve closing speed associated with the accelerator pedal return operation during normal times (when the current throttle valve closing speed control is not performed). For this reason, in this case, the increase in the negative pressure in the combustion chamber CC can be suppressed and the intake air flow rate can be reduced compared with the normal time, so the intake amount of the port-attached fuel F into the combustion chamber CC is reduced. Thus, the difference between the actual air-fuel ratio and the target air-fuel ratio can be kept small. Therefore, in this case, since the increase in output torque accompanying the shift to the rich side of the air-fuel ratio is suppressed, the driver can feel the desired vehicle deceleration feeling accompanying the accelerator pedal return operation, You don't feel uncomfortable. Further, in this case, since the generation amount of harmful substances such as hydrocarbons accompanying the shift of the air-fuel ratio to the rich side can be suppressed, it is possible to suppress the deterioration of the emission performance.

  Next, when it is determined in step ST20 that the accelerator pedal is depressed, the throttle valve control means obtains a target throttle valve opening speed (step ST40), proceeds to step ST30, and this target throttle valve opening speed. Based on the above, the target throttle opening is calculated.

  Here, FIG. 5 shows an example of the calculation result of the target throttle valve opening speed and the target throttle opening according to the engine temperature, and FIG. 6 shows the fuel F volatilization degree (alcohol concentration) according to the level. An example of calculation results of the target throttle valve opening speed and the target throttle opening is shown.

  As shown in FIG. 5, in step ST40, the lower the engine temperature, the slower the target throttle valve opening speed is set. Accordingly, in step ST30, the target throttle opening is set so that the throttle valve 24 is slowly opened as the engine temperature decreases. The relationship between the engine temperature and the target throttle valve opening speed is prepared as map data that can be tested and simulated in advance, and that can suppress the deterioration of the responsiveness of the internal combustion engine and the deterioration of the emission performance caused by the depression operation of the accelerator pedal described above. Just keep it.

  Further, as shown in FIG. 6, in step ST40, the lower the degree of volatilization of the fuel F, the lower the target throttle valve opening speed is set as the alcohol F is lower (the alcohol concentration is higher). Accordingly, in step ST30, the target throttle opening is set so that the throttle valve 24 is slowly opened as the degree of volatilization of the fuel F decreases (the alcohol concentration increases). The relationship between the degree of volatilization (alcohol concentration) of the fuel F and the target throttle valve opening speed is determined by conducting experiments and simulations in advance to suppress the deterioration of the response of the internal combustion engine and the deterioration of the emission performance caused by the depression of the accelerator pedal. What is necessary is just to prepare as map data to obtain. Further, when considering the engine temperature in FIG. 6, the target throttle valve opening speed is set so that the throttle valve 24 is opened more slowly as the engine temperature is lower.

  After obtaining the target throttle valve opening speed and the target throttle opening in this manner, the electronic control unit 1 proceeds to the above step ST35, and the accelerator valve is provided to the throttle valve control means, fuel injection control means, ignition control means, etc. The combustion control in the transient operation state accompanying the pedal depression operation is executed.

  As a result, the throttle valve 24 operates toward the valve opening side more slowly than the throttle valve opening speed associated with the depression operation of the accelerator pedal at the normal time (when the current throttle valve opening speed control is not performed). Therefore, in this case, since the intake air amount is smaller than that in the normal time, the fuel injection amount is also reduced accordingly, and the amount of fuel F adhering to the inner wall surface of the intake port 11b can be reduced. At this time, in the combustion chamber CC, the difference between the actual air-fuel ratio and the target air-fuel ratio is suppressed to be small, and the air-fuel ratio remains the target air-fuel ratio even if the accelerator pedal is depressed when the fuel F is a low-volatile fuel. However, it does not shift greatly to the lean side. Therefore, in this case, since the decrease in the output torque accompanying the shift of the air-fuel ratio to the lean side can be suppressed, it is possible to avoid the deterioration of the responsiveness of the internal combustion engine. Further, in this case, since the amount of the fuel adhering to the port F is reduced, it is possible to suppress the shift of the air-fuel ratio to the lean side with respect to the target air-fuel ratio when the accelerator pedal is depressed, Then, the amount of the port-attached fuel F evaporated as the engine temperature rises into the combustion chamber CC is small, and the shift of the air-fuel ratio to the rich side with respect to the target air-fuel ratio can be suppressed. In other words, in this case, since the amount of the fuel adhering to the port F is reduced, the amount of harmful substances generated due to the deviation of the air-fuel ratio can be suppressed, so that deterioration of the emission performance can be suppressed. .

  By the way, as described above, when the accelerator pedal returning operation is performed, the throttle valve 24 is slowly closed, so that the intake air amount becomes larger than that during the normal accelerator pedal returning operation. Therefore, in this case, a larger fuel injection amount than the normal time is set in accordance with the intake air amount, so even if the deviation of the air-fuel ratio can be avoided, the driver does not intend to perform the operation by returning the accelerator pedal. There is a risk that the internal combustion engine will generate a larger output torque than is done. In other words, in the above-described example, the throttle valve 24 is gently closed to reduce the intake amount of the port-attached fuel F into the combustion chamber CC and increase the output torque accompanying the shift of the air-fuel ratio to the rich side. On the other hand, there is a possibility that the output torque increases due to an increase in the intake air amount and the fuel injection amount.

  Therefore, here, a control apparatus for an internal combustion engine configured to avoid such a situation will be described. Specifically, the control device (electronic control device 1) of the internal combustion engine is configured to suppress an increase in output torque by performing retard control of the ignition timing of the spark plug 61. That is, when the throttle valve control means executes the throttle valve closing speed control described above, the ignition control means of the electronic control device 1 is configured so as to also execute the retard timing control of the ignition timing.

  For example, in this case, as shown in the flowchart of FIG. 7, the ignition control means determines the ignition timing retard amount (hereinafter referred to as “ignition retard amount”) when it is determined in step ST20 that the accelerator pedal is returned. Set (step ST27). The illustration in FIG. 7 is the same as the above-described illustration in FIG. 2 except for the steps described here. For this reason, only the differences will be described here.

  Here, as shown in FIG. 8, the ignition timing is set to the retard side as the target throttle valve closing speed is slower. Accordingly, here, the ignition retard amount is set after the calculation of the target throttle valve closing speed in step ST25. For example, the relationship between the target throttle valve closing speed and the ignition delay amount can be prepared as map data that can suppress the increase in output torque due to an increase in the intake air amount and the fuel injection amount through experiments and simulations in advance. That's fine.

  Thereby, in step ST35, the retard control of the ignition timing according to the target throttle valve closing speed is performed, and the transient operation state combustion control is executed. For this reason, in the internal combustion engine at that time, the throttle valve closing speed is slowed down, so that the intake air amount and the fuel injection amount increase to increase the output torque. It will be reduced by control. That is, in the internal combustion engine at that time, the increased output torque is offset by retarding the ignition timing. Therefore, the control device for the internal combustion engine in this case can make the driver feel the deceleration feeling of the desired vehicle accompanying his own accelerator pedal return operation, and is more comfortable. .

  The slower the target throttle valve closing speed is, the slower the ignition timing is set. In other words, the lower the degree of volatilization of the fuel F (the higher the alcohol concentration), the lower the engine temperature. This is equivalent to setting the ignition timing to the retard side. Therefore, with respect to the ignition control means, when the throttle valve closing speed control is executed by the throttle valve control means, the ignition timing is retarded as the degree of volatilization of the fuel F is lower (the alcohol concentration is higher) and the engine temperature is lower. You may comprise so that it may set to the side. For this reason, the ignition retard amount in step ST27 in this case is set in step ST5 after the accelerator pedal returning operation is determined and before the transient operation state combustion control in step ST35 is executed. What is necessary is just to perform according to the engine temperature of step ST10.

  As described above, the control apparatus for an internal combustion engine according to the present invention is useful for a technique for suppressing the deviation of the air-fuel ratio caused by the fuel adhering to the intake port.

It is a figure shown about an example of the internal combustion engine used as the application object of the control apparatus of the internal combustion engine which concerns on this invention. It is a flowchart explaining an example of the arithmetic processing operation | movement in the control apparatus of the internal combustion engine which concerns on this invention. It is an example of the time chart of the target throttle opening according to the accelerator opening and engine temperature at the time of an accelerator pedal return operation. It is an example of the time chart of the target throttle opening according to the accelerator opening and alcohol concentration at the time of accelerator pedal return operation. It is an example of the time chart of the target throttle opening according to the accelerator opening and engine temperature at the time of accelerator pedal depression operation. It is an example of the time chart of the target throttle opening according to the accelerator opening and alcohol concentration at the time of accelerator pedal depression operation. It is a flowchart explaining the other example of the arithmetic processing operation | movement in the control apparatus of the internal combustion engine which concerns on this invention. It is an example of a time chart of an accelerator opening, a target throttle opening, and an ignition timing at the time of an accelerator pedal returning operation.

Explanation of symbols

1 Electronic control device (fuel injection control device)
11b Intake port 17 Water temperature sensor 24 Throttle valve 25 Throttle valve actuator 26 Throttle opening sensor 41 Fuel tank 42 Alcohol concentration sensor 50 Fuel supply device 61 Spark plug 54 Fuel injection valve 83 Exhaust sensor 91 Accelerator opening sensor CC Combustion chamber F Fuel

Claims (2)

In a control device for an internal combustion engine, comprising: a fuel port injection unit that injects fuel into an intake port; and a throttle valve actuator that controls a valve opening of a throttle valve to adjust a flow rate of intake air.
The higher the alcohol concentration of the fuel or / and the lower the engine temperature of the internal combustion engine, the slower the closing speed of the throttle valve than when the alcohol concentration of the fuel is low or / and the engine temperature of the internal combustion engine is high. A control apparatus for an internal combustion engine, characterized by further comprising throttle valve control means for giving an instruction to the throttle valve actuator.   Ignition control means is provided for retarding the ignition timing of the ignition means for igniting the air-fuel mixture in the combustion chamber when the throttle valve closing speed control by the throttle valve control means is executed. The control device for an internal combustion engine according to claim 1.

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