JP2010222978A - Control device for internal combustion engine - Google Patents

Abstract

In a control device for an internal combustion engine provided with an in-cylinder injection valve, a technique capable of suppressing an increase in the amount of PM generated when the engine is cold is provided.
When the EGR gas amount is increased while the port fuel injection ratio DIP is maintained at zero while the engine is cold, and the EGR gas amount Qegr reaches the EGR limit amount QLegr, the EGR gas amount Qegr is set. While maintaining the EGR limit amount QLegr, the port fuel injection ratio DIP is changed to a target injection ratio DIPt greater than zero. The target injection ratio DIPt is set higher as the difference between the EGR limit PM particle number NLpm and the target PM particle number increases.
[Selection] Figure 3

Description

  The present invention relates to a control device for an internal combustion engine.

  In an internal combustion engine equipped with an in-cylinder injection valve that directly injects fuel into a cylinder, vaporization of the fuel injected into the cylinder is difficult to be promoted when the engine is cold, and the injected fuel becomes the top surface of the engine piston (piston There is a tendency to adhere to a large amount on the top surface) and the inner circumferential surface (cylinder bore). This adhering fuel (hereinafter also referred to as “wet fuel”), particularly the adhering fuel on the top surface of the piston, is incompletely combusted and discharged from the cylinder during subsequent engine combustion. As a result, a large amount of black smoke and unburned components (collectively referred to as PM (Particulate Matter)) is generated, which causes deterioration of exhaust emissions.

JP 2006-258023 A JP 2003-227374 A JP-A-2005-207251

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for an internal combustion engine having an in-cylinder injection valve that directly injects fuel into a cylinder. It is to provide a technology capable of suppressing the increase.

  In order to solve the above-described problems, a control device for an internal combustion engine according to the present invention employs the following means.

  That is, an in-cylinder injection valve that directly injects fuel into the cylinder of the internal combustion engine, an intake valve injection valve that injects fuel into the intake passage of the internal combustion engine, and an exhaust gas discharged into the exhaust passage of the internal combustion engine And a total fuel injection amount that is the sum of the fuel injection amount by the cylinder injection valve and the fuel injection amount by the intake passage injection valve when the engine is cold The EGR gas amount is increased in a state where the injection ratio in the intake passage, which is the ratio of the fuel injection amount by the intake valve in the intake passage to zero, is maintained at zero, and the EGR limit amount is set to the upper limit EGR amount that maintains the engine combustion in a stable state When the gas amount has reached, the number of PM particles generated in the cylinder is changed by changing the injection ratio in the intake passage to a target injection ratio larger than zero while maintaining the EGR gas amount at the EGR limit amount. A cold PM reduction means for reducing to the target number of PM particles, and a PM particle number estimation means for estimating the PM particle number based on the EGR gas amount, wherein the cold PM reduction means has an EGR gas amount of The target injection ratio is set higher as the difference between the estimated value of the number of PM particles estimated when the EGR limit amount is reached and the target number of PM particles is larger.

  When the engine is cold, the temperature of the air-fuel mixture in the cylinder can be increased as the EGR gas amount is increased, so that an effect of improving the engine combustion state can be obtained. Therefore, the number of PM particles generated in the cylinder when the engine is cold correlates with the amount of EGR gas introduced into the engine by the EGR device. In the present invention, this correlation can be used to estimate the number of PM particles based on the amount of EGR gas when the engine is cold.

  Since EGR gas contains a large amount of inert components such as carbon dioxide, if a large amount of EGR gas is introduced too much, fluctuations in combustion may increase or misfire may occur. Therefore, in this configuration, the EGR gas amount is increased within a range where the EGR gas amount does not exceed the EGR limit amount. Thereby, the number of PM particles can be reduced while maintaining the engine combustion state in a stable state. Further, since the injection ratio in the intake passage at that time is maintained at zero, it is possible to reduce the generation amount of PM while improving the engine output and the traveling fuel consumption when the engine is cold.

  When the EGR gas amount reaches the EGR limit amount, the intake passage injection ratio is changed from zero to a target injection ratio larger than that while the EGR gas amount is maintained at the EGR limit amount. Since the fuel injected from the intake valve injection valve is sufficiently mixed with the intake gas (fresh air + EGR gas) and then introduced into the cylinder, vaporization in the combustion chamber is easily promoted. Therefore, the fuel injected from the intake passage injection valve is less likely to adhere to the piston top surface and the cylinder bore than the fuel injected from the in-cylinder injection valve. Further, the fuel injection amount by the in-cylinder injection valve that easily adheres to the piston top surface or the like can be reduced by an amount corresponding to the fuel injection amount by the intake passage injection valve. Thereby, the amount of wet fuel can be reduced without further increasing the amount of EGR gas (while maintaining the amount within a range not exceeding the EGR limit amount). Therefore, the generation amount of PM can be reduced while suppressing deterioration of the engine combustion state.

  Here, the target number of PM particles means a target value of the number of PM particles when the engine is cold. For example, the number of PM particles generated in the cylinder when the engine load when the engine is cold is low can be adopted as the target number of PM particles.

  After the EGR gas amount reaches the EGR limit amount, the degree of reduction in wet fuel amount required to reduce the number of PM particles to the target PM particle number is the PM particle when the EGR gas amount reaches the EGR limit amount. The difference between the estimated value of the number and the target number of PM particles increases. Therefore, in the present invention, the target injection ratio is set higher as the difference between the estimated value of the number of PM particles and the target number of PM particles when the EGR gas amount reaches the EGR limit amount is larger. According to this, the number of PM particles can be reliably reduced to the target number of PM particles regardless of the size of the number of PM particles when the amount of EGR gas reaches the EGR limit amount.

  According to the present invention, in a control device for an internal combustion engine that includes an in-cylinder injection valve that directly injects fuel into a cylinder, an increase in the amount of PM generated when the engine is cold can be suppressed.

1 is a diagram illustrating a schematic configuration of an internal combustion engine and an intake / exhaust system thereof according to Embodiment 1. FIG. 5 is a PM particle number estimation map showing the relationship between the EGR gas amount Qegr at each engine load when the engine is cold and the number of PM particles Npm generated in the cylinder. It is the figure which showed notionally the content of cold PM reduction control in Example 1. FIG. 3 is a target injection ratio setting map showing a relationship between a PM particle number reduction request amount ΔNRpm and a target injection ratio DIPt in the combined injection / EGR quantitative processing of the first embodiment. FIG. 3 is a flowchart showing a cold PM reduction control routine executed when the engine is cold according to the first embodiment.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. It should be noted that the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are intended to limit the technical scope of the invention only to those unless otherwise specified. is not.

  [Embodiment 1] Embodiment 1 of an internal combustion engine control apparatus according to the present invention will be described. Here, the case where the present invention is applied to a gasoline engine for driving a vehicle will be described as an example. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment.

  The internal combustion engine 1 has a cylinder 2, and a piston 3 is slidably provided in the cylinder 2. An intake port 5 and an exhaust port 6 are opened in the combustion chamber 4 in the upper part of the cylinder 2. The intake port 5 is connected to the intake pipe 7, and the exhaust port 6 is connected to the exhaust pipe 8.

  The openings of the intake port 5 and the exhaust port 6 to the combustion chamber 4 are opened and closed by an intake valve 9 and an exhaust valve 10, respectively. The intake pipe 7 is provided with an in-port injection valve 12 that injects fuel into the intake port 5. An in-cylinder injection valve 13 that directly injects fuel into the cylinder is provided in the upper part of the cylinder 2. A spark plug 14 for igniting the air-fuel mixture protrudes from the combustion chamber 4. The cylinder 2 is provided with a water temperature sensor 15 that detects the cooling water temperature THw in the water jacket of the cylinder 2. The intake pipe 7 is provided with an air flow meter 11 for measuring the amount of air flowing through the intake pipe 7.

In addition, an EGR (Exhaust Gas Recirculation) device 16 that recirculates (recirculates) part of the exhaust gas flowing through the exhaust pipe 8 to the intake pipe 7 as EGR gas is provided. The EGR device 16 includes an EGR pipe 17 that connects the exhaust pipe 8 and the downstream side of the air flow meter 11 in the intake pipe 7, and an EGR valve 18 that adjusts the EGR gas amount by changing the cross-sectional area of the EGR pipe 17. It is comprised.

  In this embodiment, the intake port 5 and the intake pipe 7 correspond to the intake passage in the present invention. Further, the exhaust port 6 and the exhaust pipe 8 correspond to the exhaust passage in the present invention. The in-port injection valve 12 corresponds to the intake passage injection valve in the present invention.

The internal combustion engine 1 configured as described above is provided with an ECU (Electronic Control Unit) 20 for controlling the internal combustion engine 1. The ECU 20 is connected to the internal combustion engine 1
This is a unit that controls the operating state of the internal combustion engine 1 in accordance with the operating conditions and the driver's request. Sensors such as an air flow meter 11, a water temperature sensor 15, a crank position sensor that detects the engine speed of the internal combustion engine 1, and an accelerator position sensor (both not shown) that detect the accelerator opening are connected to the ECU 20 via electric wiring. These output signals are input to the ECU 20. For example, the ECU 20 estimates the temperature in the cylinder 2 from the detection value of the water temperature sensor 15.

  The ECU 20 is electrically connected to an in-port injection valve 12, an in-cylinder injection valve 13, a spark plug 14, an EGR valve 18 and the like, and these devices are controlled by the ECU 20.

  For example, schematically, fuel injection from the in-cylinder injection valve 13 contributes to an increase in output performance of the internal combustion engine 1, and fuel injection from the in-port injection valve 12 contributes to uniformity of the air-fuel mixture. Therefore, the ECU 20 has a fuel injection amount from the in-port injection valve 12 (hereinafter referred to as “in-port fuel injection amount”) and a fuel injection amount from the in-cylinder injection valve 13 (hereinafter referred to as “in-cylinder fuel injection amount”). The ratio of the in-port injection amount to the total fuel injection amount that is the sum of the above (hereinafter referred to as “port fuel injection ratio DIP”) is appropriately controlled. This port fuel injection ratio DIP corresponds to the intake passage injection ratio in the present invention.

In addition, the ECU 20 is an EGR gas internal combustion engine 1 via the EGR pipe 17 of the EGR device 16.
(EGR gas amount) Qegr is controlled by adjusting the opening of the EGR valve 18 (hereinafter also referred to as “EGR opening”). Further, the ECU 20 can estimate and detect the current EGR gas amount Qegr based on the output signal of the air flow meter 11 and the control signal of the EGR opening degree.

  Next, control of the port fuel injection ratio DIP and the EGR gas amount Qegr when the engine is cold will be described. When the engine 1 is cold, such as when the internal combustion engine 1 is cold started, vaporization of the fuel injected from the in-cylinder injection valve 13 (hereinafter, this fuel is referred to as “in-cylinder injected fuel”) is not easily promoted. Therefore, it tends to adhere to the top surface of the piston 3 (hereinafter referred to as “piston top surface”) and the inner peripheral surface of the cylinder 2 (hereinafter referred to as “cylinder bore”). The adhered fuel (hereinafter referred to as “wet fuel”) is incompletely combusted and discharged from the cylinder during subsequent engine combustion. As a result, a large amount of PM (Particulate Matter) such as black smoke and unburned components is generated in the cylinder 2, which causes deterioration of exhaust characteristics.

  Therefore, in this embodiment, by adjusting the port fuel injection ratio DIP and the EGR gas amount Qegr when the engine is cold, the number of PM particles generated in the cylinder 2 is reduced below the target number of target PM particles. Control (hereinafter referred to as “cold PM reduction control”). This cold PM reduction control is executed by the ECU 20.

  FIG. 2 is a PM particle number estimation map showing the relationship between the EGR gas amount Qegr at each engine load when the engine is cold and the number of PM particles Npm generated in the cylinder 2. This figure shows the relationship between the EGR gas amount Qegr and the PM particle number Npm when the port fuel injection ratio DIP is zero. As shown in the figure, under the condition that the EGR gas amount Qegr is equal, the number of PM particles Npm corresponding to the engine load increases as the engine load increases. This is because the total fuel injection amount is higher at medium load (KLmid) than at low load (KLlo), and at higher load (KLhi) than at medium load (KLmid), and other conditions are equal. This is because the number of PM particles Npm increases as the amount of wet fuel increases.

  Further, under the condition where the engine loads are equal, the larger the EGR gas amount Qegr (for example, the greater the EGR opening degree), the larger the corresponding number of PM particles Npm. This is because EGR gas is already burned gas, and its temperature is relatively high. By introducing a large amount of high-temperature EGR gas into the internal combustion engine 1, the temperature of the air-fuel mixture increases, and the combustion state of the engine is improved. This is probably due to this.

  As described above, the number of PM particles Npm when the engine is cold is generally reduced as the EGR gas amount Qegr is increased, and the degree and degree of reduction in the number of PM particles Npm is smaller as the load is lower ( It will be gradual). When the load is low KLlo in this map, the relationship in which the number of PM particles Npm has a constant value is illustrated even when the EGR gas amount Qegr changes. The symbol Npmlo on the vertical axis represents the number of PM particles corresponding to a low load (KLlo). Incidentally, the number of PM particles Npmlo is the number of PM particles corresponding to the low load (KLlo), but when the engine load during the cold engine is a medium load or a high load, the cold PM reduction control is executed. It is adopted as the target number of PM particles. Hereinafter, the PM particle number Npmlo corresponding to the low load (KLlo) may be referred to as a target PM particle number Npmlo.

  As shown in the figure, when the port fuel injection ratio DIP is controlled to zero, in order to reduce the PM particle number Npm to the target PM particle number Npmlo when the engine is cold, the engine load is a medium load (KLmid). In this case, the EGR gas amount Qegr needs to be increased to Qegr1, and when the load is high (KLhi), it is necessary to increase it to Qegr2.

However, since EGR gas contains a lot of inert components such as carbon dioxide, a large amount of EG
If too much R gas is introduced, the fluctuation of combustion becomes large or misfire may be caused. Accordingly, the EGR gas amount Qegr has an upper limit value (hereinafter referred to as “EGR limit amount”) QLegr that can maintain engine combustion in a stable state. Therefore, in the cold PM reduction control in the present embodiment, the EGR gas amount Qegr is controlled within a range not exceeding the EGR limit amount QLegr.

  FIG. 3 is a diagram conceptually showing the contents of the cold PM reduction control in the present embodiment. The relationship among the engine load, the EGR gas amount Qegr, and the number of PM particles Npm shown in the figure is the same as that shown in FIG. 2, and the same reference numerals are synonymous.

  As described above, in order to reduce the PM particle number Npm to the target PM particle number Npmlo while maintaining the port fuel injection ratio DIP at zero, the EGR gas amount Qegr is set to Qegr2 (at high load (medium load)). It is necessary to increase to Qegr1). In this figure, the EGR limit amount QLegr is smaller (less) than Qegr1 and Qegr2. In addition, the range of QLegr to Qegr1 at the time of medium load and the range of QLegr to Qegr2 at the time of high load are represented by a chain line because the EGR gas amount Qegr is controlled within a range not exceeding the EGR limit amount QLegr. It is a representation. For convenience, in this figure, the EGR limit amount QLegr at the time of medium load (KLmid) and high load (KLhi) is shown as an equal value, but in reality, the EGR limit amount QLegr is an operating condition such as engine load. It can be changed according to.

  Here, in describing the specific contents of the cold PM reduction control, the case of high load (KLhi) will be described as an example. The ECU 20 increases the EGR gas amount Qegr while maintaining the fuel injection ratio DIP within a range in which the EGR gas amount Qegr does not exceed the EGR limit amount QLegr port when the engine is cold (hereinafter referred to as “cylinder”). Inner single injection / EGR increase processing). Here, the fact that the port fuel injection ratio DIP is maintained at zero means that fuel injection by only the in-cylinder injection valve 13 (hereinafter referred to as “in-cylinder single injection”) is performed. The in-cylinder injected fuel contributes to an increase in output performance of the internal combustion engine 1 as compared with the fuel injected from the in-port injection valve 12 (hereinafter referred to as “in-port injected fuel”). Therefore, until the EGR gas amount Qegr reaches the EGR limit amount QLegr, the output performance of the internal combustion engine 1 is improved by performing in-cylinder single injection. In addition, comparing the case of engine combustion with in-cylinder injected fuel and the case of engine combustion with in-port injected fuel, the former is superior in efficiency. Can be improved.

  The in-cylinder single injection / EGR increase processing is continued until the EGR gas amount Qegr reaches the EGR limit amount QLegr. When the EGR gas amount Qegr reaches the EGR limit amount QLegr, if the EGR gas amount Qegr is further increased, the combustion state is likely to be deteriorated. Therefore, the ECU 20 performs the process related to the cold PM reduction control. Switch from “in-cylinder single injection / EGR increase processing” to “composite injection / EGR quantitative processing”. More specifically, the “composite injection / EGR determination process” is to change the port fuel injection ratio DIP to a target injection ratio DIPt larger than zero while maintaining the EGR gas amount Qegr at the EGR limit amount QLegr. The setting of the target injection ratio DIPt will be described in detail later.

Here, when the port fuel injection ratio DIP is changed to a value larger than zero in the “composite injection / EGR determination process”, the fuel injection of the internal combustion engine 1 is changed from the in-cylinder single injection to the in-cylinder injection valve 13 and the in-port. The fuel injection is switched to the fuel injection combined with the injection valve 12 (hereinafter referred to as “composite injection”). Here, since the in-port injected fuel is sufficiently mixed with the intake gas (fresh air + EGR gas) and then introduced into the cylinder 2, vaporization is easily promoted in the combustion chamber. Therefore, there is an advantage that the in-port injected fuel is less likely to adhere to the piston top surface and the cylinder bore than the in-cylinder injected fuel. Further, by performing the above switching, the amount of in-cylinder injected fuel that easily adheres to the piston top surface or the like is reduced by the amount of in-port fuel injection that occupies the total fuel injection amount. Therefore, by switching the fuel injection to the internal combustion engine 1 from the single cylinder injection to the combined injection in this way, the EGR gas amount Qegr is not increased any more (that is, the EGR gas amount Qegr is maintained below the EGR limit amount QLegr). The amount of wet fuel can be reduced.

  Here, in the cold PM reduction control, this corresponds to when the EGR gas amount Qegr reaches the EGR limit amount QLegr (that is, when the in-cylinder single injection / EGR increase processing is switched to the combined injection / EGR quantitative processing). The number of PM particles is referred to as “EGR limit number of PM particles NLpm”. Here, when the EGR limit PM particle number NLpm corresponding to the engine load when the engine is cold is medium load (KLmid) and high load (KLhi) is plotted on the vertical axis of FIG. It is represented by NLpm2.

  Here, paying attention to the difference (NLpm−Npmlo) between the number of PM particles at the EGR limit NLpm and the target number of PM particles Npmlo, this value is the required amount of reduction in the number of PM particles required when performing the combined injection / EGR quantitative processing. (Hereinafter referred to as “PM particle number reduction requirement amount ΔNRpm”). As shown in the figure, the EGR limit PM particle number NLpm2 corresponding to the high load time (KLhi) is larger than the EGR limit PM particle number NLpm1 corresponding to the medium load time (KLmid) (NLpm2> NLpm1). For this reason, the PM particle number reduction request amount ΔNRpm is larger at the time of high load (KLhi) than at the time of medium load (KLmid) (ΔNRpm2> ΔNRpm1).

  FIG. 4 is a target injection ratio setting map showing the relationship between the PM particle number reduction request amount ΔNRpm and the target injection ratio DIPt in the combined injection / EGR quantitative processing of the present embodiment. The horizontal axis represents the PM particle number reduction request amount ΔNRpm, and the vertical axis represents the target injection ratio DIPt. The target injection ratio DIPt is set as a value larger than zero as described above. As the target injection ratio DIPt is set to a larger value, the reduction effect when reducing the amount of wet fuel adhering to the piston top surface or the cylinder bore surface can be enhanced.

  Therefore, in this target injection ratio setting map, the larger the PM particle number reduction request amount ΔNRpm, the larger the target injection ratio DIPt corresponding thereto. Thus, the ECU 20 controls the target injection ratio DIPt to be higher as the PM particle number reduction request amount ΔNRpm is larger. As a result, regardless of the engine load, the PM particle number Npm surely decreases from the EGR limit PM particle number NLpm to the target PM particle number Npmlo. Since the PM particle number reduction request amount ΔNRpm correlates with the engine load when the engine is cold, the target injection ratio DIPt can be set according to the engine load. In this case, for example, the engine load is adopted as a parameter on the horizontal axis of the map of FIG. 4, and the corresponding target injection ratio DIPt is set to a larger value as the engine load is higher. In this case, the ECU 20 controls the target injection ratio DIPt to be higher as the engine load at the time of cold PM reduction control is higher.

  FIG. 5 is a flowchart showing a cold PM reduction control routine executed when the engine is cold according to this embodiment. This routine is stored in advance in the ECU 20 and is repeated every predetermined time. In this embodiment, the ECU 20 that executes this routine corresponds to the cold PM reduction means and the PM particle number estimation means in the present invention. The initial values of the control signals to the EGR valve 18, the in-port injection valve 12, and the in-cylinder injection valve 13 when the ECU 20 executes this routine are “valve closed”, “OFF”, and “ON”, respectively. . That is, both the EGR opening degree Degr and the port fuel injection ratio DIP are controlled with 0 (zero) as an initial set value.

  In this routine, first, in S101, the ECU 20 determines whether or not in-cylinder single injection / EGR increase processing is currently being performed. If it is determined that the in-cylinder single injection / EGR increase process is not being performed, the process proceeds to step S102. If it is determined that the in-cylinder single injection / EGR increase process is being performed, the process proceeds to step S106.

  In step S102, it is determined whether the combined injection / EGR quantitative processing is currently being performed. If it is determined that the combined injection / EGR determination process is not in progress, the process proceeds to step S103. If it is determined that the combined injection / EGR determination process is in progress, the process proceeds to step S112.

  In step S103, the coolant temperature THw of the internal combustion engine 1 is detected based on the output signal of the coolant temperature sensor 15, and it is determined whether or not the coolant temperature THw is equal to or lower than the specified coolant temperature THwb. The specified water temperature THwb in the present embodiment is a water temperature that serves as a reference for determining whether or not the engine is cold. If the cooling water temperature THw is equal to or lower than this temperature, the ECU 20 determines that the engine water is cold. In this step, when it is determined that the cooling water temperature THw is equal to or lower than the specified water temperature THwb (THw ≦ THwb), the process proceeds to step S104.

  On the other hand, when it is determined that the cooling water temperature THw is higher than the specified water temperature THwb (THw> THwb), the ECU 20 determines that the engine is not cold, and then immediately exits this routine. In this case, the operation state in which in-cylinder single injection is performed continues without performing EGR by the EGR device 16. In this control routine, EGR is not performed during normal operation that is not when the engine is cold, because the number of PM particles generated in the cylinder 2 is small. However, what is EGR performed during normal operation? It is not disturbed.

  In step S104, the ECU 20 acquires the engine load factor KL based on the output signal of the accelerator position sensor, and determines whether the engine load factor KL is equal to or lower than the reference low load factor KLlo. The reference low load factor KLlo is the upper limit value of the engine load factor at which it is determined that the PM particle number Npm when the engine is cold will exceed the target PM particle number Npmlo when the cold PM reduction control is not executed. is there. The reference low load factor KLlo corresponds to the low load (KLlo) shown in FIGS.

  When it is determined that the engine load factor KL is equal to or lower than the reference low load factor KLlo (KL ≦ KLlo), the PM emission amount can be maintained sufficiently low without performing the cold PM reduction control. It is determined that it is possible to exit this routine. On the other hand, when it is determined that the engine load factor KL is higher than the reference low load factor KLlo (KL> KLlo), it is determined that the exhaust emission is deteriorated unless the cold PM reduction control is executed, and the process proceeds to step S105. . The engine load factor KL at this time corresponds to the medium load (KLmid) and the high load (KLhi) in FIGS.

  In step S105, the ECU 20 opens the EGR valve 18. Specifically, the EGR valve 18 is opened by changing the control command value of the EGR opening degree Degr from zero to Degr (i) larger than zero, and the EGR gas is supplied to the internal combustion engine 1 via the EGR pipe 17. To introduce. As described above, since the initial setting value of the port fuel injection ratio DIP is 0 (zero), the in-cylinder single injection / EGR increase processing is started by performing the processing in this step. Then, once the processing of this step is completed, this routine is temporarily exited.

Next, the process of step S106 that proceeds after it is determined in step S101 of this routine that the in-cylinder single injection / EGR increase process is being performed will be described. In step S106, the ECU 20 determines whether or not the current EGR gas amount Qegr has reached the EGR limit amount QLegr. The current EGR gas amount Qegr can be obtained based on the output signal of the air flow meter 11 and the control command value Degr (i) of the EGR opening degree Degr. Further, the EGR limit amount QLegr can be set in advance for each operating state of the internal combustion engine 1 based on empirical rules such as experiments. Alternatively, it may be determined whether or not the EGR gas amount Qegr has reached the EGR limit amount QLegr based on a parameter that can determine whether the combustion state of the internal combustion engine 1 is good or bad. For example, an air-fuel ratio sensor (not shown) that outputs an electrical signal corresponding to the air-fuel ratio of the exhaust is installed in the exhaust pipe 8, and the amount of EGR gas when the fluctuation amount of the output signal of this sensor exceeds a specified value. It can also be determined that Qegr has exceeded the EGR limit amount QLegr.

  In this routine, if it is determined that the EGR gas amount Qegr has reached the EGR limit amount QLegr (Qegr ≧ QLegr), the process proceeds to step S107, and if not (Qegr <QLegr), the process proceeds to step S108. First, the process of step S108 will be described. In this step, the control command value for the EGR opening degree Degr is changed from Degr (i) to Degr (i + α) on the opening side by a predetermined opening degree. That is, processing for increasing the EGR opening degree Degr by a predetermined opening degree from the current opening degree is performed. When the processing of this step is completed, this routine is temporarily exited. That is, in this case, the in-cylinder single injection / EGR increase processing is continued.

  In step S107, the ECU 20 assigns the current EGR gas amount Qegr (that is, coincides with the EGR limit amount QLegr) and the engine load factor KL to the PM particle number estimation map shown in FIG. Estimate NLpm. In the subsequent step S109, the PM particle number reduction required amount ΔNRpm is calculated by subtracting the target PM particle number Npmlo from the EGR limit-time PM particle number NLpm estimated in step S107 (ΔNRpm = NLpm−Npmlo).

  In subsequent step S110, the ECU 20 calculates the target injection ratio DIPt by substituting the PM particle number reduction request amount ΔNRpm calculated in step S109 into the target injection ratio setting map shown in FIG. In the subsequent step S111, the ECU 20 changes the port fuel injection ratio DIP from zero to the target injection ratio DIPt obtained in step S110. By performing the process of this step, the combined injection / EGR quantitative process is started. Then, once the processing of this step is completed, this routine is temporarily exited.

  Next, the process of step S112 that proceeds when it is determined in step S102 of this routine that the combined injection / EGR determination process is being performed will be described. In step S112, the ECU 20 determines whether or not an end condition for the combined injection / EGR determination process is satisfied. Specifically, when the cooling water temperature THw is higher than the specified water temperature THwb or the engine load factor KL is equal to or lower than the reference low load factor KLlo, the termination condition of the process is established. If it is determined in this routine that the combined injection / EGR quantitative process termination condition is satisfied, the process proceeds to step S113. On the other hand, if this is not the case, this routine is temporarily exited. In this case, the combined injection / EGR quantitative process is continued.

  In step S113, the ECU 20 closes the EGR valve 18 by changing the control command value of the EGR opening degree Degr to zero. Thereby, the recirculation of the EGR gas by the EGR device 16 is stopped. In this step, the ECU 20 returns the set value of the port fuel injection ratio DIP to 0 (zero). Thereby, the fuel injection control to the internal combustion engine 1 is switched from the combined injection to the in-cylinder single injection. As described above, when the combined injection / EGR quantitative process is terminated by the process of this step, the present routine is temporarily exited.

In this control routine, after a negative determination is made in step S106, the current EGR gas amount Qegr and the engine load factor KL are substituted into the PM particle number estimation map shown in FIG. 2 before performing the process of step S108. The corresponding current PM particle number Npm may be estimated. Then, the magnitude relationship between the estimated value of the PM particle number Npm and the target PM particle number Npmlo is compared, and the process proceeds to step S108 only when the estimated value of the PM particle number Npm is larger than the target PM particle number Npmlo. If the estimated value of the current PM particle number Npm is equal to or less than the target PM particle number Npmlo, there is no need to increase the EGR gas amount Qegr any more. In that case, it is preferable to maintain this control state until the cooling water temperature THw becomes higher than the specified water temperature THwb and the warm-up of the internal combustion engine 1 is completed.

  As described above, according to the cold PM reduction control in the present embodiment, the “in-cylinder single injection / EGR increase processing” is performed until the EGR gas amount Qegr reaches the EGR limit amount QLegr. It is possible to reduce the number of PM particles Npm while improving output and driving fuel consumption. Then, after the EGR gas amount Qegr reaches the EGR limit amount QLegr, the “combined injection / EGR quantitative processing” is performed, so that the combustion state of the internal combustion engine 1 is maintained in a stable state and the number of PM particles Npm is set to the target PM. The number of particles can be reduced to Npmlo or less. As a result, a large amount of PM is suppressed from being discharged when the engine is cold. Therefore, in the control device for the internal combustion engine 1 to which the cold PM reduction control according to this embodiment is applied, it is possible to reliably suppress the deterioration of the exhaust emission when the engine is cold.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Piston 4 ... Combustion chamber 5 ... Intake port 6 ... Exhaust port 7 ... Intake pipe 8 ... Exhaust pipe 12 ... port Inner injection valve 13 .. In-cylinder injection valve 14 .. Spark plug 16 .. EGR device 17 .. EGR pipe 18 .. EGR valve 20 .. ECU

Claims (1)

An in-cylinder injection valve that directly injects fuel into the cylinder of the internal combustion engine;
An intake valve injection valve for injecting fuel into the intake passage of the internal combustion engine;
An EGR device for introducing a part of the exhaust gas discharged into the exhaust passage of the internal combustion engine into the engine as EGR gas;
The ratio of the fuel injection amount by the intake passage injection valve to the total fuel injection amount which is the sum of the fuel injection amount by the in-cylinder injection valve and the fuel injection amount by the intake passage injection valve when the engine is cold When the EGR gas amount is increased while the injection ratio in the intake passage is maintained at zero, and the EGR gas amount reaches the upper limit EGR amount at which engine combustion is maintained in a stable state, the EGR gas amount is set to the EGR gas amount. A cold PM reduction means for reducing the number of PM particles generated in the cylinder to the target PM particle number by changing the injection ratio in the intake passage to a target injection ratio larger than zero while maintaining the limit amount;
PM particle number estimation means for estimating the number of PM particles based on the amount of EGR gas;
With
The cold PM reduction means sets the target injection ratio as the difference between the estimated value of the number of PM particles estimated when the EGR gas amount reaches the EGR limit amount and the target PM particle number is larger. A control apparatus for an internal combustion engine, characterized by being set high.

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