JP2008101540A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine optimizing exhaust air-fuel ratio control by effectively utilizing blow-by and port injection during a valve overlap period in a control device for an internal combustion engine provided with a port injection valve and a cylinder injection valve. <P>SOLUTION: In this control device for the internal combustion engine, the internal combustion engine is provided with the port injection valve injecting fuel into an intake port and the cylinder injection valve injecting fuel into a combustion chamber, injecting fuel from the port injection valve and cylinder injection valve in accordance with operation conditions, and having the valve overlap period with both an intake valve and an exhaust valve opened, fuel is injected by at least the port injection valve during the valve overlap period within an engine operating region where intake pressure is higher than exhaust pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and in particular, includes a port injection valve that injects fuel into an intake port and a cylinder injection valve that injects fuel into a combustion chamber, and includes a port injection valve and a cylinder injection valve. The present invention relates to a control device for an internal combustion engine that injects fuel according to an operating state and has a valve overlap period in which both an intake valve and an exhaust valve are open.

  A port injection valve that injects fuel into the intake port and an in-cylinder injection valve that injects fuel into the combustion chamber. The fuel is injected from the port injection valve and the in-cylinder injection valve at an injection ratio determined according to the operating state. 2. Description of the Related Art An internal combustion engine that performs injection, that is, a double injection internal combustion engine is known.

  Further, it is widely known that a supercharger is applied to an internal combustion engine in order to improve the output of the internal combustion engine. In the double injection type internal combustion engine as well, a supercharger is intended to improve the output of the internal combustion engine. Development of a double-injection type internal combustion engine with a supercharger equipped with the

JP 2005-133632 A JP 2003-106145 A

  By the way, in a reciprocating internal combustion engine, a valve overlap, that is, a period in which both an intake valve and an exhaust valve are open may be provided from the viewpoint of improving volumetric efficiency and scavenging combustion gas efficiently. When such a valve overlap period is provided, due to the pressure difference between the intake pipe pressure and the exhaust pipe pressure, one of the air and fuel supplied from the intake port into the cylinder during the valve overlap period is provided. There is a case where a phenomenon (hereinafter referred to as “blow-through”) is caused in which the portion is discharged to the exhaust port as it is.

  In an internal combustion engine, a “blow-through” is generally produced during a valve overlap period in an engine operating region where the intake pressure is higher than the exhaust pressure.

  One problem with the double injection internal combustion engine is optimization of exhaust air / fuel ratio control in consideration of the above-mentioned “blow-through” from the viewpoint of air / fuel ratio control of the exhaust purification catalyst atmosphere.

  When an exhaust purification catalyst whose exhaust purification performance depends on the air-fuel ratio of the catalyst atmosphere is provided in the exhaust system of the internal combustion engine, in order to suppress the deterioration of exhaust emission, the exhaust gas flowing into the exhaust purification catalyst is suppressed. It is necessary to accurately control the air-fuel ratio and control the air-fuel ratio of the exhaust purification catalyst atmosphere to a desired air-fuel ratio. This also applies to the case where an exhaust purification catalyst whose exhaust purification performance depends on the air-fuel ratio of the catalyst atmosphere is disposed in the exhaust system in a double injection type internal combustion engine. It is conceivable that the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst varies with the variation of the “blow-through” state.

  For example, a three-way catalyst is known as an exhaust purification catalyst whose exhaust purification performance depends on the air-fuel ratio of the catalyst atmosphere. The three-way catalyst has a high purification rate near the stoichiometric air-fuel ratio, and when the three-way catalyst is disposed in the exhaust system, the air-fuel ratio of the three-way catalyst atmosphere is set to the stoichiometric air-fuel ratio in order to suppress the deterioration of exhaust emission. It is necessary to perform control to maintain. If there is air blow-off during the valve overlap period, the blow-through air flows into the three-way catalyst, and the air-fuel ratio of the three-way catalyst atmosphere is shifted to the lean air-fuel ratio side. Even in such a situation, in order to maintain the exhaust purification performance of the three-way catalyst, when performing control to maintain the air-fuel ratio of the three-way catalyst atmosphere at the stoichiometric air-fuel ratio by adjusting the air-fuel ratio of the air-fuel mixture in the combustion chamber In the combustion chamber, the air-fuel ratio of the three-way catalyst atmosphere is set to the stoichiometric air-fuel ratio by controlling the air-fuel ratio of the air-fuel mixture in the combustion chamber to a rich air-fuel ratio and setting the air-fuel ratio of the exhaust flowing into the three-way catalyst to a rich air-fuel ratio. Can be maintained. However, if the amount of air blown during the valve overlap period is excessively large, the air-fuel ratio of the three-way catalyst atmosphere is greatly shifted to the lean side, and in order to maintain the air-fuel ratio of the three-way catalyst atmosphere at the stoichiometric air-fuel ratio. Therefore, it is necessary to control the air-fuel ratio of the air-fuel mixture in the combustion chamber to an over-rich air-fuel ratio, which may lead to problems in internal combustion engine performance such as deterioration in fuel consumption and misfire. Therefore, in a double injection internal combustion engine having a valve overlap period, when an exhaust purification catalyst whose exhaust purification performance depends on the air / fuel ratio of the catalyst atmosphere is disposed in the exhaust system, the air / fuel ratio control of the exhaust purification catalyst atmosphere From this point of view, it is an issue to optimize the exhaust air / fuel ratio control in consideration of “blow-through”.

  In Patent Document 1, an internal combustion engine having a port injection valve and an in-cylinder injection valve, and during the valve overlap period, fuel injection by the port injection valve (hereinafter referred to as port injection) is prohibited. A control device for an internal combustion engine that performs fuel injection by an internal injection valve (hereinafter referred to as in-cylinder injection) and performs in-cylinder injection after the exhaust valve is closed is disclosed. In addition, it is described that such a configuration reduces the fuel blow-through caused by the “blow-off” during the valve overlap period and suppresses the fuel consumption. However, Patent Document 1 does not disclose exhaust air / fuel ratio control means that considers “blow-through” for the purpose of air / fuel ratio control of the exhaust purification catalyst atmosphere of the internal combustion engine.

  Also in the double injection type internal combustion engine, there is a demand for further improvement in acceleration performance, as in a general internal combustion engine. In Patent Document 2, in an internal combustion engine with a supercharger having an in-cylinder injection valve, an air / fuel that is provided with an ignition auxiliary device in an exhaust system and can be combusted in the exhaust system by in-cylinder injection during a valve overlap period. Supercharging that increases the supercharging pressure and improves acceleration performance by forming a mixture, that is, by controlling the exhaust air / fuel ratio to a desired combustible air / fuel ratio by in-cylinder injection, and combusting the mixture by an ignition assist device An internal combustion engine with a machine is disclosed.

  However, the internal combustion engine with a supercharger disclosed in Patent Document 2 is an internal combustion engine that does not have a port injection valve, and an exhaust system in the internal combustion engine with a supercharger that has a port injection valve and an in-cylinder injection valve. No effective utilization means of port injection in forming a combustible air / fuel mixture at the same time, that is, in controlling the exhaust air / fuel ratio to a desired air / fuel ratio is not disclosed. Therefore, in a double injection type internal combustion engine having a valve overlap period, for example, when a system for improving the supercharging pressure by combusting fuel in an exhaust pipe is provided, the port is improved in terms of improving acceleration performance. One of the problems is to optimize the exhaust air-fuel ratio control that effectively uses the injection.

  In view of the above problems, the present invention includes a port injection valve that injects fuel into an intake port and an in-cylinder injection valve that injects fuel into a combustion chamber. An internal combustion engine that injects fuel and has a valve overlap period in which both an intake valve and an exhaust valve are open. From the viewpoint of improvement, an object of the present invention is to provide a control device for an internal combustion engine capable of optimizing exhaust air-fuel ratio control by effectively utilizing “blow-through” and port injection during a valve overlap period.

  According to the first aspect of the present invention, a port injection valve that injects fuel into the intake port and a cylinder injection valve that injects fuel into the combustion chamber, the port injection valve, the cylinder injection valve, An internal combustion engine that injects fuel in accordance with the operating state, and has a valve overlap period in which both the intake valve and the exhaust valve are open. A control device for an internal combustion engine is provided, wherein fuel is injected at least by the port injection valve during the valve overlap period in an operation region.

  In the internal combustion engine, there is a region where the intake pressure is higher than the exhaust pressure. During the valve overlap period in this region, a part of the fuel supplied from the intake port does not contribute to combustion, and “blow-through” is directly discharged to the exhaust system. When port injection is executed during a valve overlap period where there is such a “blow-through”, a portion of the port injected fuel is discharged into the exhaust system without contributing to combustion, resulting in deterioration of fuel consumption. . Therefore, in one embodiment of the prior art, control for prohibiting port injection is performed during a valve overlap period in which there is a blow-through from the viewpoint of preventing deterioration in fuel consumption.

  On the other hand, in the invention of claim 1, from the viewpoint of exhaust air / fuel ratio control, during the valve overlap period in the engine operation region where the intake pressure is higher than the exhaust pressure, that is, during the valve overlap period where there is a blow-through. , Dare to carry out port injection. This makes it possible to supply fuel that is part of the port-injected fuel and does not contribute to combustion to the exhaust system by utilizing the “blow-off” that occurs during the valve overlap period. Utilizing this makes it possible to control the exhaust air-fuel ratio to a predetermined air-fuel ratio.

  Here, the predetermined air-fuel ratio is appropriately set according to the operating state of the internal combustion engine and the control purpose. For example, when a three-way catalyst is provided as an exhaust purification catalyst in the exhaust system, a predetermined air-fuel ratio is set to an air-fuel ratio such that the air-fuel ratio of the three-way catalyst atmosphere is controlled to the stoichiometric air-fuel ratio. By controlling the air-fuel ratio of the original catalyst atmosphere to the stoichiometric air-fuel ratio, it becomes possible to suppress the deterioration of exhaust emission. In addition, when a system for improving the supercharging pressure by combusting fuel in the exhaust pipe is provided, the supercharging pressure can be reduced by setting the predetermined air-fuel ratio to an air-fuel ratio in which the fuel can be combusted in the exhaust pipe. Improvements can be made reliably.

  According to the second aspect of the present invention, the estimated blow-through amount that is the amount of fuel that blows through the exhaust system without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period is calculated. When the estimated blow-through amount calculated by the estimated blow-through amount calculation means is less than a predetermined value, it is prohibited to inject fuel by the port injection valve during the valve overlap period. A control device for an internal combustion engine according to claim 1 is provided.

  As described above, for example, when a three-way catalyst is disposed in the exhaust system, the three-way catalyst can be maintained by adjusting the air-fuel ratio of the air-fuel mixture in the combustion chamber in order to maintain the exhaust purification performance of the three-way catalyst. When performing control to maintain the air-fuel ratio of the original catalyst atmosphere at the stoichiometric air-fuel ratio, if there is air blow-off during the valve overlap period, the air-fuel ratio of the air-fuel mixture in the combustion chamber is controlled to be rich air-fuel ratio. It is possible to maintain the air-fuel ratio of the three-way catalyst atmosphere at the stoichiometric air-fuel ratio, but if the air blow-off amount during the valve overlap period is excessively large, the air-fuel ratio of the three-way catalyst atmosphere is reduced to the stoichiometric air-fuel ratio. In order to maintain the fuel ratio, it is necessary to control the air-fuel ratio of the air-fuel mixture in the combustion chamber to an over-rich air-fuel ratio, which leads to problems in internal combustion engine performance such as deterioration in fuel consumption and further misfire. there is a possibility.

  According to the first aspect of the present invention, the port injection is performed during the valve overlap period in the engine operation region in which the intake pressure is higher than the exhaust pressure, and fuel is supplied to the exhaust system by using “blow-through”. The exhaust air-fuel ratio can be controlled to a predetermined air-fuel ratio, and the air-fuel mixture in the combustion chamber can be controlled to an over-rich air-fuel ratio state even when the amount of air blown during the valve overlap period is excessively large Instead, the air-fuel ratio of the catalyst atmosphere can be controlled to a predetermined air-fuel ratio.

  By the way, when the amount of fuel blown during the valve overlap period is small, that is, when the amount of air blown during the valve overlap period is small, the air-fuel ratio of the catalyst atmosphere is reduced to the lean air-fuel ratio due to the air blow-through. There is no significant shift to the side. Therefore, in order to maintain the exhaust purification performance of the three-way catalyst, even if the air-fuel ratio of the three-way catalyst atmosphere is controlled to be maintained at the stoichiometric air-fuel ratio only by adjusting the air-fuel ratio of the air-fuel mixture in the combustion chamber, It is possible to maintain the air-fuel ratio of the three-way catalyst atmosphere at the stoichiometric air-fuel ratio by adjusting the air-fuel ratio of the air-fuel mixture in the combustion chamber to an appropriate rich air-fuel ratio that does not cause the air-fuel ratio. That is, when the blow-through amount is small, even if the air-fuel ratio of the three-way catalyst atmosphere is controlled to be maintained at the stoichiometric air-fuel ratio only by adjusting the air-fuel ratio of the air-fuel mixture in the combustion chamber, It is possible to maintain the air-fuel ratio of the three-way catalyst atmosphere at the stoichiometric air-fuel ratio without controlling the air-fuel ratio of the air-fuel ratio to the rich air-fuel ratio.

  Accordingly, in the invention of claim 2, when the estimated blow-through amount, which is the amount of fuel blown into the exhaust system without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period, is less than a predetermined value, The fuel injection by the port injection valve during the valve overlap period is prohibited, and the fuel supply to the exhaust system by the port injection during the valve overlap period is prohibited. As a result, excessive fuel supply to the exhaust system due to port injection during the valve overlap period can be reduced, and fuel consumption can be improved.

  According to the third aspect of the present invention, the estimated blow-through amount that is the amount of fuel that blows into the exhaust system without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period is calculated. A blow-through amount calculating means; and an actual blow-through amount calculating means for calculating an actual blow-through amount that is the amount of fuel actually blown out without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period; A cylinder that injects fuel by the in-cylinder injection valve based on a difference between the estimated blow-through amount calculated by the estimated blow-through amount calculation means and the actual blow-through amount calculated by the actual blow-through amount calculation means 3. The control apparatus for an internal combustion engine according to claim 1, wherein the corrected fuel injection by the injection is executed.

  In general, the amount of fuel injected by port injection is calculated and set before the timing of actual fuel injection.

  For this reason, the operation state when the injected fuel amount is calculated may differ from the operation state when the fuel is actually injected, and the estimated blow-through used when calculating the fuel amount injected by the port injection. There may be a difference between the amount and the actual actual blow-through amount.

  According to the invention of claim 3, the corrected fuel injection control by the in-cylinder injection is executed based on the difference between the estimated blow-through amount used when calculating the fuel amount injected by the port injection and the actual actual blow-through amount. Is done. As a result, there is a difference between the estimated blow-through amount used when calculating the amount of fuel injected by port injection and the actual actual blow-through amount, and the exhaust to the exhaust system by port injection using the blow-through during the valve overlap period. Even if the fuel supply amount is less than the desired amount required to bring the exhaust air / fuel ratio to the predetermined air / fuel ratio, the shortage can be compensated for by corrected fuel injection by the in-cylinder injection valve, and the exhaust air / fuel ratio can be reduced. It becomes possible to control to a predetermined air-fuel ratio with high accuracy.

  According to the description of each claim, a port injection valve that injects fuel into the intake port and an in-cylinder injection valve that injects fuel into the combustion chamber, the port injection valve and the in-cylinder injection valve are brought into an operating state. In accordance with an internal combustion engine that injects fuel in response and has a valve overlap period in which both an intake valve and an exhaust valve are open, air-fuel ratio control and acceleration performance of the exhaust purification catalyst atmosphere of the internal combustion engine From the viewpoint of improving the air-fuel ratio, there is a common effect that the exhaust air-fuel ratio control can be optimized by effectively utilizing the “blow-through” and the port injection during the valve overlap period.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing a hardware configuration common to the embodiments of the present invention.
In FIG. 1, reference numeral 1 denotes a spark ignition type internal combustion engine, and the internal combustion engine 1 includes a cylinder head 1a and a cylinder block 1b. The cylinder head 1 a includes an intake port 5, an exhaust port 6, an intake valve 7, an exhaust valve 8, and an ignition plug 40, and a high voltage current is supplied to the ignition plug 40 from an ignition coil 41.

  The piston 2 connected to the crankshaft 3 reciprocates in the cylinder block 1b, and a combustion chamber 1c is formed between the piston 2 and the cylinder head 1a. A crank angle sensor 52 is attached to the cylinder block 1b, and the engine speed is calculated based on a signal from the crank angle sensor 52. A water temperature sensor 53 for detecting the cooling water temperature is attached to the cylinder block 1b.

  An intake valve timing adjustment device 70 that adjusts the phase of the valve opening period of the intake valve 7 in accordance with operating conditions is attached to the intake cam 7c. Similarly, an exhaust valve timing adjusting device 80 that adjusts the phase of the valve opening period of the exhaust valve 8 in accordance with operating conditions is attached to the exhaust cam 8c.

  In FIG. 1, a port injection valve 31 for injecting fuel into the intake port 5 and an in-cylinder injection valve 32 for injecting fuel into the combustion chamber 1c are attached to the cylinder head 1a. The port injection valve 31 and the in-cylinder injection valve 32 are supplied with fuel from a fuel tank (not shown) by a fuel pump (not shown) via a fuel pipe (not shown).

  An intake pipe 10 is connected to the intake port 5, and an air cleaner 11 is attached to the upstream end of the intake pipe 10. An air flow meter 51 for detecting the intake air amount is disposed immediately downstream of the air cleaner 11. A throttle valve 12 is disposed downstream of the air flow meter 51. The throttle valve 12 is driven by a throttle motor 13. On the other hand, an accelerator pedal sensor 50 for detecting the depression amount of the accelerator pedal 14 is attached to the accelerator pedal 14, and the throttle valve 12 is operated by the throttle motor 13 in accordance with the depression amount of the accelerator pedal 14 detected by the accelerator pedal sensor 50. The degree of opening is changed.

  An exhaust pipe 20 is connected to the exhaust port 6, and a three-way catalyst 21 is disposed in the exhaust pipe 20. A first air-fuel ratio sensor 22 is disposed near the upstream side of the three-way catalyst 21, and a second air-fuel ratio sensor 23 is disposed near the downstream side of the three-way catalyst 21. The exhaust gas generated in the combustion chamber 1c is led to the exhaust pipe 20 through the exhaust port 6 whose flow path is opened and closed by the exhaust valve 8, is purified by the three-way catalyst 21, and is discharged. Based on the outputs of the first air-fuel ratio sensor 22 and the second air-fuel ratio sensor 23, the fuel injection amount injected from the port injection valve 31 and the in-cylinder injection valve 32 is feedback-controlled so that a predetermined air-fuel ratio is obtained.

  An intake pressure sensor 54 for measuring the intake pressure is attached to the intake passage, and an exhaust pressure sensor 55 for measuring the exhaust pressure is attached to the exhaust passage.

  The intake pipe 10 is provided with a compressor 90B of the supercharger 90. Further, the exhaust pipe 20 is provided with an exhaust turbine 90A of the supercharger 90, and exhaust gas generated by combustion in the combustion chamber 1c of each cylinder passes through the exhaust manifold to the exhaust turbine 90A of the supercharger 90. be introduced. When the exhaust turbine 90A is operated by the flow of the introduced exhaust, the compressor 90B on the intake pipe side operates in conjunction with the gas, and gas compression is performed on the intake pipe side. The pressure of the intake pipe 10 is increased by the compression of the gas, and the gas is efficiently filled into the combustion chamber by the pressure.

  Further, an additional ignition auxiliary device 43 is disposed in front of the exhaust turbine 90A of the supercharger 90 in the exhaust system. The additional ignition auxiliary device 43 plays the role of increasing the supercharging pressure and improving the acceleration performance by burning the fuel in the exhaust pipe.

  An electronic control unit (hereinafter referred to as ECU) 100 is formed by connecting an input port 101, an output port 102, a CPU 103, a ROM 104, a RAM 105, and the like with a common bus. A signal detected by each sensor is input to the ECU 100, and a control signal for performing control related to the present invention is sent to each actuator.

  Hereinafter, fuel injection control for controlling the exhaust air-fuel ratio to a predetermined air-fuel ratio, which is executed in each embodiment of the present invention having the basic hardware configuration as described above, will be described.

  First, the first embodiment will be described. In the first embodiment, the estimated blow-through amount during the valve overlap period is calculated, and it is determined whether or not to perform port injection by the port injection valve 31 based on the calculated estimated blow-through amount. Exhaust air / fuel ratio control by port injection during the valve overlap period is executed when the estimated blow-through amount is a predetermined value or more. In the first embodiment, the air-fuel ratio of the exhaust flowing into the exhaust purification catalyst is controlled to a predetermined air-fuel ratio. However, the present invention is not limited to this. For example, fuel is burned in the exhaust pipe. The exhaust air / fuel ratio may be controlled to a predetermined air / fuel ratio that can be controlled.

FIG. 2 is a flowchart of fuel injection control according to the first embodiment for controlling the exhaust air-fuel ratio to a predetermined air-fuel ratio.
First, in step 201, out of the amount of fuel supplied to the combustion chamber during the valve overlap period, which is used when calculating the amount of fuel injected by port injection, the exhaust system is not contributed to combustion. An estimated blow-through amount that is the amount of fuel blown through is calculated.

  In the first embodiment, the estimated blow-through amount is a map for calculating the blow-through amount based on the intake pressure, exhaust pressure, engine speed, intake air amount, valve overlap period, etc. It is calculated by the ECU 100 using a blow-through amount map created based on such data. The map is used by being stored in the memory of the ECU 100 or the like.

  The intake pressure is detected from the intake pressure sensor 54, the exhaust pressure is detected from the exhaust pressure sensor 55, and the intake air amount is detected from the air flow meter 51. Further, the valve overlap period is calculated by the ECU 100 based on the intake / exhaust valve opening / closing control timings of the intake valve timing adjusting device 70 and the exhaust valve timing adjusting device 80. Further, the engine speed is calculated based on a signal from the crank angle sensor 52.

  As described above, in the first embodiment, it contributes to combustion among the fuel supplied to the combustion chamber during the blow-through amount, that is, the valve overlap period, used when calculating the amount of fuel injected by port injection. The estimated blow-through amount calculation means for calculating the estimated blow-through amount that is the amount of fuel that blows through the exhaust system without performing the operation is an air flow meter 51, a crank angle sensor 52, an intake pressure sensor 54, an exhaust pressure sensor 55, an intake valve timing adjustment device 70, The exhaust valve timing adjustment device 80, the blow-through amount calculation map, and the ECU 100 are included.

  When the estimated blow-through amount is calculated in step 201, the process proceeds to the subsequent step 202, and ECU 100 determines whether or not the calculated estimated blow-through amount is equal to or greater than a predetermined value. Here, the predetermined value is appropriately determined depending on the operating state and design specifications. If it is determined that the calculated estimated blow-by amount is equal to or greater than a predetermined value, the process proceeds to step 203.

  The three-way catalyst 21 has a high purification rate in the vicinity of the stoichiometric air-fuel ratio, and it is necessary to control the air-fuel ratio of the three-way catalyst atmosphere to the stoichiometric air-fuel ratio in order to suppress the deterioration of exhaust emission. As described above, the air-fuel ratio in the combustion chamber is adjusted in order to maintain the exhaust purification performance of the three-way catalyst 21 when the amount of air blown during the valve overlap period is excessively large. In the case where the air-fuel ratio of the three-way catalyst atmosphere is controlled to be maintained at the stoichiometric air-fuel ratio only by this, the air-fuel ratio in the combustion chamber is controlled to an over-rich air-fuel ratio. Furthermore, there is a possibility of causing an internal combustion engine performance problem such as misfire.

  Based on this, in step 203, when it is determined that the calculated estimated blow-through amount is equal to or greater than a predetermined value, that is, among the fuel supplied to the combustion chamber during the valve overlap period, it contributes to combustion. If it is determined that the amount of fuel blown through the exhaust system is large, the exhaust air-fuel ratio is set to a predetermined air-fuel ratio that can control the air-fuel ratio of the three-way catalyst atmosphere to the stoichiometric air-fuel ratio based on the calculated estimated blow-through amount. Port injection fuel amount by port injection during valve overlap period required to control the engine is calculated, and port injection during valve overlap period is executed to control the air-fuel ratio of the three-way catalyst atmosphere to the theoretical air-fuel ratio Is done. As a result, the fuel injected from the port injection valve can be supplied to the exhaust system using “blow-off” during the valve overlap period, and the amount of air blow-off during the valve overlap period is excessively large. Even in such a case, the air-fuel ratio of the three-way catalyst atmosphere can be controlled to the stoichiometric air-fuel ratio without controlling the air-fuel mixture in the combustion chamber to the over-rich air-fuel ratio state.

  Preferably, the air-fuel ratio of the air-fuel mixture in the combustion chamber is controlled to the most fuel-efficient air-fuel ratio by in-cylinder injection by the in-cylinder injection valve 32.

  In step 202, when it is determined that the calculated estimated blow-through amount is less than the predetermined value and not more than the predetermined value, that is, among the fuel supplied to the combustion chamber during the valve overlap period, it contributes to combustion. When it is determined that the amount of fuel blown through the exhaust system is small, the air blow-off amount during the valve overlap period is small, and the air-fuel mixture in the combustion chamber is emptied to maintain the exhaust purification performance of the three-way catalyst. Even if the air-fuel ratio of the three-way catalyst atmosphere is maintained at the stoichiometric air-fuel ratio only by adjusting the fuel ratio, the air-fuel ratio of the air-fuel mixture in the combustion chamber is set to an appropriate rich air-fuel ratio that does not cause misfire. By adjusting the air-fuel ratio, it is possible to maintain the air-fuel ratio of the three-way catalyst atmosphere at the stoichiometric air-fuel ratio. That is, when the blow-through amount is small, even if the air-fuel ratio of the three-way catalyst atmosphere is controlled to be maintained at the stoichiometric air-fuel ratio only by adjusting the air-fuel ratio of the air-fuel mixture in the combustion chamber, It is possible to control the air-fuel ratio of the three-way catalyst atmosphere to the stoichiometric air-fuel ratio without controlling the air-fuel ratio to an over-rich air-fuel ratio.

  Therefore, if it is determined in step 202 that the calculated estimated blow-through amount is not greater than or equal to the predetermined value, that is, if it is determined that the calculated estimated blow-through amount is less than the predetermined value, step 204 Then, port injection for fuel supply to the exhaust system using the blow-through during the valve overlap period is prohibited. As a result, excessive fuel supply to the exhaust system due to port injection during the overlap period can be reduced, and fuel consumption can be improved.

  Next, a second embodiment of the fuel injection control for controlling the exhaust air-fuel ratio to a predetermined air-fuel ratio in the embodiment of the present invention having the basic hardware configuration shown in FIG. 1 will be described. In the second embodiment, the exhaust air-fuel ratio is controlled to a predetermined air-fuel ratio that allows the fuel to be burned in the exhaust pipe by the additional ignition auxiliary device 43 in order to increase the boost pressure and improve the acceleration performance. However, the present invention is not limited to this. For example, the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst may be controlled to a predetermined air-fuel ratio.

  In general, the amount of fuel injected by port injection is calculated before the timing of actual fuel injection. For this reason, the operating state when the amount of fuel injected by port injection is calculated may differ from the operating state when the fuel is actually injected, and is used when calculating the amount of fuel injected by port injection. There may be a difference between the estimated blow-through amount that is the blow-through amount and the actual blow-through amount that is the actual blow-through amount when the port injection is actually executed.

  Based on this, the second embodiment contributes to combustion among the fuel supplied to the combustion chamber during the valve overlap period used when calculating the amount of fuel injected by port injection. The difference between the estimated blow-through amount, which is the amount of fuel blown into the exhaust system without any difference, and the actual blow-through amount, which is the amount of fuel actually blown out without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period Based on the above, corrected fuel injection by in-cylinder injection is executed.

  As a result, there is a difference between the estimated blow-through amount used when calculating the amount of fuel injected by port injection and the actual actual blow-through amount, and the exhaust to the exhaust system by port injection using the blow-through during the valve overlap period. Desired necessary for controlling the exhaust air / fuel ratio to a predetermined air / fuel ratio at which the fuel can be burned in the exhaust pipe by the additional ignition auxiliary device 43 in order to increase the boost pressure and improve the acceleration performance. Even when the amount is insufficient, the shortage can be compensated by correction fuel injection by in-cylinder injection, and the exhaust air-fuel ratio can be accurately controlled to a predetermined air-fuel ratio.

  The estimated blow-through amount may be set so as to be calculated so that the exhaust air-fuel ratio is controlled to be leaner than the predetermined air-fuel ratio. In corrected fuel injection by in-cylinder injection, the exhaust air / fuel ratio that is leaner than the predetermined air / fuel ratio can be controlled to a predetermined air / fuel ratio by supplying fuel into the exhaust gas. The exhaust air-fuel ratio that is richer than the fuel ratio cannot be controlled to a predetermined air-fuel ratio. When the estimated blow-through amount is set to be calculated so that the exhaust air-fuel ratio is controlled to be leaner than the predetermined air-fuel ratio, the exhaust air-fuel ratio is controlled to be richer than the predetermined air-fuel ratio. Therefore, the corrected fuel injection by the in-cylinder injection can always be effectively used, and the exhaust air / fuel ratio can be more reliably set to the predetermined air / fuel ratio. Control to maintain the air-fuel ratio becomes possible.

  FIG. 3 is a flowchart of the fuel injection control according to the second embodiment for controlling the exhaust air-fuel ratio to a predetermined air-fuel ratio.

  First, in step 301, the amount of fuel to be injected by port injection, which is used when calculating the amount of fuel blown through, that is, the fuel supplied to the combustion chamber during the valve overlap period, is made into the exhaust system without contributing to combustion. An estimated blow-through amount that is the amount of fuel blown through is calculated. The estimated blow-through amount is calculated by an estimated blow-through amount calculation unit similar to that described in the description of step 201 in the flowchart of the first embodiment shown in FIG. Therefore, the description about the calculation method of the estimated blow-through amount here is abbreviate | omitted.

  When the estimated blow-through amount is calculated in step 301, the process proceeds to subsequent step 302. In step 302, based on the calculated estimated blow-through amount, the additional ignition auxiliary device 43 exhausts the fuel to a predetermined air-fuel ratio that can be burned in the exhaust pipe in order to increase the boost pressure and improve the acceleration performance. A port injection fuel amount by port injection during the valve overlap period necessary for controlling the air-fuel ratio is calculated, and exhaust air-fuel ratio control by port injection during the valve overlap period is executed. When port injection is executed at step 302, the routine proceeds to the subsequent step 303.

  In step 303, an actual blow-through amount that is the amount of fuel actually blown out without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period is calculated. The actual blow-through amount is a map for calculating the blow-through amount based on the intake pressure, the exhaust pressure, the engine speed, the intake air amount, the valve overlap period, and the like, similarly to the estimated blow-through amount calculating means for calculating the estimated blow-through amount. Thus, the ECU 100 uses the blow-through amount map created in advance based on data such as experiments and analysis evaluations.

  Therefore, the actual blow-through amount calculating means for calculating the actual blow-through amount that is the amount of fuel actually blown out without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period is the estimated blow-through amount calculation means. It will be almost the same. That is, the actual blow-through amount calculation means includes the air flow meter 51, the crank angle sensor 52, the intake pressure sensor 54, the exhaust pressure sensor 55, the intake valve timing adjustment device 70, the exhaust valve timing adjustment device 80, the blow-through amount calculation map, and the ECU 100. Configured.

  However, the estimated blow-through amount is calculated based on the intake pressure or exhaust pressure when calculating the amount of fuel injected by port injection, whereas the actual blow-through amount is the intake pressure when actually performing port injection. It is different in that it is calculated based on the exhaust pressure or the like.

  When the actual blow-through amount is calculated in step 303, the process proceeds to subsequent step 304. In step 304, correction fuel injection by in-cylinder injection is executed based on the difference between the estimated blow-through amount and the actual blow-through amount.

  FIG. 4 is a time chart showing one embodiment of corrected fuel injection by in-cylinder injection. In the embodiment shown in FIG. 4, the case where the control device of the present invention is applied to a four-cylinder internal combustion engine will be described for convenience. However, the present invention can also be applied to a multi-cylinder internal combustion engine such as a six-cylinder or an eight-cylinder. . In the embodiment shown in FIG. 4, an embodiment in which the intake stroke is performed in the order of the # 1, # 3, # 4, and # 2 cylinders is shown, but the embodiment is limited to this. There is nothing.

  In the embodiment shown in FIG. 4, first, at a predetermined point in the exhaust stroke before the valve overlap period of the first cylinder, the estimated blow-through amount during the valve overlap period is calculated, and the estimated blow-through amount is calculated. Based on this, the amount of port injection fuel injected during the valve overlap period is calculated. Next, when the first cylinder enters the valve overlap period, fuel of the calculated port injection fuel amount is injected by port injection. Next, the actual blow-through amount is calculated based on the intake pressure, the exhaust pressure, etc. when the port injection is actually performed. Based on the difference between the estimated blow-through amount and the actual blow-through amount, the corrected fuel injection is performed by in-cylinder injection in the third cylinder in the exhaust stroke.

  The third cylinder is in the exhaust stroke when the first cylinder is in the intake stroke, and by performing in-cylinder injection in the exhaust stroke, fuel can be supplied to the exhaust system, and the estimated blow-through amount and the actual blow-through amount Even if there is a difference, the exhaust air-fuel ratio can be controlled to a predetermined air-fuel ratio.

  In the embodiment shown in FIG. 4, it is shown that the corrected fuel injection is executed in the exhaust stroke of the third cylinder, but the corrected fuel injection may be executed in the expansion stroke. Further, in the intake stroke of the first cylinder after the valve overlap period, the air-fuel ratio of the air-fuel mixture in the combustion chamber is controlled to the air-fuel ratio with the best combustion efficiency by in-cylinder injection.

  Next, a third embodiment of the fuel injection control for controlling the exhaust air-fuel ratio to a predetermined air-fuel ratio in the embodiment of the present invention having the basic hardware configuration shown in FIG. 1 will be described.

  FIG. 5 is a flowchart of fuel injection control of the third embodiment for controlling the exhaust air-fuel ratio to a predetermined air-fuel ratio. Each of step 401 to step 404 in the flowchart shown in FIG. 5 corresponds to step 201 to step 204 shown in FIG. Step 405 and step 406 respectively correspond to step 303 and step 304 shown in the flowchart shown in FIG.

In the fuel injection control of the third embodiment for controlling the exhaust air-fuel ratio shown in FIG. 5 to a predetermined air-fuel ratio, in order to control the exhaust air-fuel ratio to a predetermined air-fuel ratio, during the valve overlap period Whether or not to perform port injection is determined based on the estimated blow-through amount, and corrected fuel injection by in-cylinder injection is performed based on the difference between the estimated blow-through amount and the actual blow-through amount.
As a result, the fuel injected from the port injection valve can be supplied to the exhaust system using “blow-off” during the valve overlap period, and the amount of air blow-off during the valve overlap period is excessively large. Even in such a case, it is possible to control the air-fuel ratio of the three-way catalyst atmosphere to the stoichiometric air-fuel ratio without controlling the air-fuel mixture in the combustion chamber to the over-rich air-fuel ratio state. Further, it is possible to reduce the fuel supply to the exhaust system due to the port injection during the overlap period, and to improve the fuel consumption. Further, even when there is a difference between the blow-through amount used when calculating the fuel amount to be injected by the port injection and the actual blow-through amount, the corrected fuel injection by the in-cylinder injection is executed, so that a predetermined air-fuel ratio is obtained. In addition, the exhaust air / fuel ratio can be accurately controlled.

  As described above, in the control apparatus for an internal combustion engine according to the present invention, fuel is injected from the port injection valve during the valve overlap period in the engine operation region where the intake pressure is higher than the exhaust pressure, and is brought about during the valve overlap period. The main feature is that the injected fuel is supplied to the exhaust system using the “blow-through”, and the exhaust air-fuel ratio is controlled to a predetermined air-fuel ratio.

It is a figure which shows the hardware constitutions common to each embodiment of this invention. 3 is a flowchart of fuel injection control according to the first embodiment for controlling the exhaust air-fuel ratio to a predetermined air-fuel ratio. 6 is a flowchart of fuel injection control according to a second embodiment for controlling an exhaust air-fuel ratio to a predetermined air-fuel ratio. It is a time chart figure showing one embodiment of correction fuel injection by in-cylinder injection. It is a flowchart of fuel injection control of 3rd embodiment for controlling an exhaust air fuel ratio to a predetermined air fuel ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Intake port 6 Exhaust port 7 Intake valve 8 Exhaust valve 10 Intake pipe 20 Exhaust pipe 21 Three way catalyst 31 Port injection valve 32 In-cylinder injection valve 40 Spark plug 51 Air flow meter 52 Crank angle sensor 54 Intake pressure sensor 55 Exhaust pressure sensor 70 Intake valve timing adjustment device 80 Exhaust valve timing adjustment device 90 Supercharger 100 ECU

Claims (3)

An internal combustion engine that includes a port injection valve that injects fuel into an intake port and an in-cylinder injection valve that injects fuel into a combustion chamber, and injects fuel from the port injection valve and the in-cylinder injection valve in accordance with an operating state. In a control device for an internal combustion engine having a valve overlap period in which an intake valve and an exhaust valve are both open,
Fuel is injected by at least the port injection valve during the valve overlap period in the engine operation region where the intake pressure is higher than the exhaust pressure.
A control device for an internal combustion engine. An estimated blow-through amount calculating means for calculating an estimated blow-through amount that is the amount of fuel blown into the exhaust system without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period;
When the estimated blow-through amount calculated by the estimated blow-through amount calculating means is less than a predetermined value, it is prohibited to inject fuel by the port injection valve during the valve overlap period.
The control apparatus for an internal combustion engine according to claim 1. Estimated blow-through amount calculating means for calculating an estimated blow-through amount that becomes the amount of fuel blown into the exhaust system without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period;
An actual blow-through amount calculating means for calculating an actual blow-through amount that is the amount of fuel actually blown out without contributing to combustion among the fuel supplied to the combustion chamber during the valve overlap period;
Corrected fuel by in-cylinder injection in which fuel is injected by the in-cylinder injection valve based on the difference between the estimated blow-through amount calculated by the estimated blow-through amount calculation means and the actual blow-through amount calculated by the actual blow-through amount calculation means The control apparatus for an internal combustion engine according to claim 1 or 2, wherein injection is performed.

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