JP5867372B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine. More specifically, the present invention relates to a control device for an internal combustion engine that can use a fuel in which a hydrocarbon-based fuel and alcohol are mixed.

  2. Description of the Related Art Conventionally, an internal combustion engine for an FFV (Flexible fuel Vehicle) that can use a fuel in which an alcohol such as ethanol and a hydrocarbon-based fuel such as gasoline are mixed is known as an internal combustion engine for an automobile. In addition, dual injection that includes a port injector that injects fuel into the intake port and an in-cylinder injector that directly injects fuel into the cylinder, and changes the injection ratio of the fuel that is injected between the two injectors according to the operating state of the internal combustion engine Types of internal combustion engines are also known. Moreover, as a dual injection type internal combustion engine for FFV having these characteristics, for example, Patent Document 1 includes a cylinder injector and a port injector, and a technology related to an internal combustion engine that injects fuel from these two types of injectors. Is disclosed.

JP 2006-214415 A

  By the way, there are a plurality of types of commercially available fuels having different alcohol concentrations. For this reason, in the case of a vehicle equipped with an FFV internal combustion engine, it is possible that a different type of fuel having a different alcohol concentration from that of the currently used fuel is supplied to the fuel tank. In that case, the alcohol concentration in the fuel in the fuel tank changes according to the amount of fuel supplied, but the alcohol concentration in the fuel sucked up from the fuel tank before refueling, that is, the fuel supply line connecting the fuel tank and the injector The alcohol concentration in the remaining fuel is the same as before refueling. As a result, fuel having the same alcohol concentration as that before refueling is injected from the injector for a while after refueling.

  In the conventional FFV internal combustion engine, the alcohol concentration in the fuel is learned from the correction amount of the air-fuel ratio feedback control, and the engine control is performed based on the learned alcohol concentration. Therefore, when the alcohol concentration in the fuel changes with refueling, the engine control is performed based on the unstable alcohol concentration until the alcohol concentration in the fuel injected from the injector converges to a certain value. . Therefore, in the conventional FFV internal combustion engine, the controllability of the air-fuel ratio feedback control is deteriorated during such a convergence period, which may lead to deterioration of emission and drivability.

  The above-mentioned problem becomes particularly remarkable in the dual injection internal combustion engine for FFV. In the dual-injection internal combustion engine, fuel is supplied to the two types of injectors via respective fuel supply lines. In addition, the fuel injection ratio that is injected between the two types of injectors is changed according to the operating state of the internal combustion engine. For this reason, the in-cylinder injector and the port injector may fall into a concentration transient state in which the alcohol concentration in the injected fuel is different. If the concentration transient state is prolonged, the convergence period described above is also affected, so that the controllability of the air-fuel ratio feedback control may be further deteriorated.

  The present invention has been made in view of the above problems. That is, an object of the present invention is to provide a control device for an internal combustion engine that can appropriately perform various controls such as air-fuel ratio feedback control even in a concentration transient state in a dual injection internal combustion engine for FFV.

In order to achieve the above object, the present invention provides a control device for an internal combustion engine,
A tank for storing fuel mixed with hydrocarbon fuel and alcohol;
An in-cylinder injector that directly injects fuel in the tank into a cylinder of an internal combustion engine;
A port injector for injecting fuel in the tank into an intake port of the internal combustion engine;
When the fuel injection ratio of the in-cylinder injector and the port injector is changed, there is no change in the alcohol concentration in the fuel injected from the in-cylinder injector and the port injector in two consecutive cycles. The assumption is made that the alcohol concentration in the fuel injected from the in-cylinder injector and the port injector, the alcohol concentration estimated from the exhaust air-fuel ratio corresponding to the combustion of the injected fuel, and the in-cylinder The relationship established between the fuel injection ratio of the fuel injected by the injector and the port injector, the alcohol concentration in the fuel respectively injected from the in-cylinder injector and the port injector in the cycle before the change, Injection in the cycle before and after the change Is an alcohol concentration estimated from exhaust air-fuel ratio corresponding to the combustion of fuel, the in-cylinder injector and the port injector in a cycle after the change by applying the injection ratio of the fuel in the cycle before and after the change Alcohol concentration estimating means for estimating the alcohol concentration in the fuel injected from each of the
It is characterized by providing.

The second invention is the first invention, wherein
When the injection ratio is changed after fuel is supplied to the tank, the alcohol concentration estimation means is configured to determine the fuel injected from each of the in-cylinder injector and the port injector in the cycle after the change based on the relationship. It is characterized by estimating the alcohol concentration in it.

According to the present invention, when the injection ratio is changed, the above-described relation is that the alcohol concentration in the fuel respectively injected from the in-cylinder injector and the port injector in the cycle before the injection ratio change, and before and after the injection ratio change. Applying the alcohol concentration estimated from the exhaust air / fuel ratio corresponding to the combustion of the fuel injected in the cycle and the fuel injection ratio in the cycle before and after the change of the injection ratio, in the cylinder in the cycle after the injection ratio change Since the alcohol concentrations in the fuel injected from each of the injector and the port injector are estimated, these alcohol concentrations can be estimated even in a concentration transient state. That is, various controls such as air-fuel ratio feedback control can be appropriately performed even in a concentration transient state.

It is a figure which shows the system configuration | structure of embodiment. It is a timing chart for demonstrating each parameter in Formula (1) thru | or (6). It is the flowchart which showed the process of ECU30 in cycle j-1. It is the flowchart which showed the process of ECU30 in the cycle j. It is the flowchart which showed the process of ECU30 in cycle j + a-1. It is the flowchart which showed the process of ECU30 in cycle j + a.

[Description of Configuration of Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 6.
FIG. 1 is a diagram showing a system configuration of the present embodiment. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. The internal combustion engine 10 can use a fuel in which a hydrocarbon-based fuel (gasoline) and alcohol (ethanol) are mixed as a fuel, and has a cylinder injector DI and a port injector PFI for each cylinder. Is an institution. In FIG. 1, the internal combustion engine 10 is shown as an in-line four-cylinder type, but the number and arrangement of the cylinders are not limited to this.

  Further, the system of this embodiment includes a delivery pipe 12 for the in-cylinder injector DI and a delivery pipe 14 for the port injector PFI. The delivery pipes 12 and 14 are connected to a fuel pipe 16 common to them. The fuel pipe 16 is connected to a fuel tank 18 that stores fuel therein. The fuel in the fuel tank 18 is pumped to the fuel pipe 16 by a fuel pump (not shown), flows through the delivery pipes 12 and 14, and is injected from the in-cylinder injector DI and the port injector PFI. The fuel pipe 16 is provided with an alcohol concentration sensor 20 that detects the alcohol concentration. The fuel pipe 16 may be installed in the fuel tank 18.

  Further, the system of this embodiment includes an intake air flow rate detection sensor 22 and an air-fuel ratio sensor 24. The intake flow rate detection sensor 22 is a sensor that detects the flow rate of intake air flowing through the intake passage 26. The air-fuel ratio sensor 24 is a sensor that detects the oxygen concentration in the exhaust gas flowing through the exhaust passage 28.

  In addition, the system of the present embodiment includes an ECU (Electronic Control Unit) 30 as a control device. On the input side of the ECU 30, in addition to the alcohol concentration sensor 20, the intake flow rate detection sensor 22, and the air-fuel ratio sensor 24, various sensors necessary for controlling the internal combustion engine 10 (for example, a crank angle sensor for detecting the engine speed, a throttle valve) A throttle sensor or the like for detecting the degree of opening is electrically connected. On the other hand, various actuators such as a variable valve mechanism are electrically connected to the output side of the ECU 30 in addition to the in-cylinder injector DI and the port injector PFI and the fuel pump. The ECU 30 executes various programs related to the operation of the internal combustion engine 10 by executing predetermined programs based on input information from various sensors and operating various actuators.

[Features of this embodiment]
One of the controls of the internal combustion engine 10 performed by the ECU 30 is fuel injection control performed by operating the in-cylinder injector DI and the port injector PFI. One aspect of this fuel injection control is air-fuel ratio feedback control. In the air-fuel ratio feedback control, the fuel injection amount is controlled based on a signal from the air-fuel ratio sensor 24 in order to converge the air-fuel ratio of the air-fuel mixture in the combustion chamber to the target air-fuel ratio corresponding to the operating state of the internal combustion engine 10. The air-fuel ratio is adjusted.

  Another aspect of this fuel injection control is injection ratio control. The injection ratio control is to control the fuel injection ratio that is separately injected between the in-cylinder injector DI and the port injector PFI. In the injection ratio control, the injection ratio is changed according to the values of various physical quantities indicating the operation state of the internal combustion engine 10 such as the rotation speed, load, and cooling water temperature. The relationship between the various physical quantities and the injection ratio is defined in advance in the map, and the ECU 30 determines the injection ratio with reference to the map.

Incidentally, as a process different from the fuel injection control, the ECU 30 estimates the alcohol concentration in the fuel injected from the in-cylinder injector DI and the port injector PFI. Specifically, the ECU 30 calculates the alcohol concentration d _afs using the feedback correction amount calculated in the air-fuel ratio feedback control process, and stores it as a learning value. The stored learning value is used for various controls including the fuel injection control.

  The above-described alcohol concentration estimation process is performed on the assumption that the alcohol concentration in the fuel in the fuel tank 18 is constant. However, when different types of fuel having different alcohol concentrations are supplied to the fuel tank 18, the alcohol concentration in the fuel changes, so that the alcohol concentration in the fuel in the delivery pipes 12, 14 and the fuel pipe 16 is not maintained for a while. It becomes stable. This is because the fuel before refueling remains in the delivery pipes 12 and 14 and the fuel pipe 16 as described above. The change in the injection ratio is intended to maximize the engine performance, and is performed regardless of the above-described refueling of different fuels. Therefore, when different types of fuel are supplied, there is a possibility that the in-cylinder injector and the port injector will be in a concentration transition state in which the alcohol concentration in the injected fuel is different.

As a countermeasure against such a concentration transition, for example, when the refueling of a different type of fuel is detected, for example, control for forcibly changing the injection ratio can be temporarily performed. If the injection ratio is forcibly changed, the concentration transient factor based on the difference in the path length of the delivery pipes 12 and 14 and the difference in the injection pressure can be alleviated, so that the concentration transient state can be eliminated early. However, the cancellation of the concentration transient state and the change in the injection ratio are in a trade-off relationship. For example, leading to deterioration of the startability and emission if higher than necessary injection ratio k _DI of in-cylinder injector DI at startup. Furthermore, thus the fuel consumption is deteriorated when higher than necessary injection ratio k _PFI of said port injector PFI in the operation mode area you want to prioritize fuel economy.

Therefore, in the present embodiment, the alcohol concentration is estimated by a process different from the normal time when the concentration is transient. Specifically, the ECU 30 performs the processing using the following equations (1) and (2), and in the cycle j after changing the injection ratio, the alcohol concentration d _DI (j) in the fuel injected from the in-cylinder injector and The alcohol concentration d _PFI (j) in the fuel injected from the port injector is estimated.
d _DI (j) = {− d _afs (j + a) × k _PFI (j−1) + d _afs (j + a−1) × k _PFI (j)} / {k _PFI (j) −k _PFI (j−1) } ... (1)
d _PFI (j) = [d _afs (j + a) × {1-k _PFI (j−1)} − d _afs (j + a−1) × (1-k _PFI (j)) / {k _PFI (j) − k _PFI (j-1)} (2)
(However, in the above formulas (1) and (2), k _PFI (j−1) and k _PFI (j) are the share ratios of the port injectors in the cycle before and after the change, and d _afs (j + a−1), d _afs (j + a) is an alcohol concentration estimated from the air-fuel ratio feedback correction amount corresponding to the combustion of the injected fuel in the cycle before and after the change, and a is a variable corresponding to a transport delay from the fuel injection to the air-fuel ratio sensor 24. is there.)

The ECU 30 is assumed to store the above formulas (1) and (2) therein. The above formulas (1) and (2) are expressed by the following formulas (3) and (4) that are established for the alcohol concentration in the fuel injected from each injector before and after the change of the injection ratio, and before and after the change of the injection ratio. The following equations (5) and (6) are obtained based on the assumption that there is no change in the alcohol concentration in the fuel injected from each injector.
d _DI (j) × {1−k _PFI (j)} + d _PFI (j) × k _PFI (j) = d _afs (j + a) (3)
d _DI (j−1) × {1−k _PFI (j−1)} + d _PFI (j−1) × k _PFI (j−1) = d _afs (j + a−1) (4)
d _DI (j) = d _DI (j−1) (5)
d _PFI (j) = d _PFI (j−1) (6)

FIG. 2 is a timing chart for explaining each parameter in the above formulas (1) to (6). The ECU 30 refers to the parameters in the cycles j−1, j, j + a−1, j + a shown in FIG. 2 and applies them to the above formulas (1) and (2) to determine the alcohol concentration d _DI (j), d _PFI. (J) is estimated. The estimated alcohol concentrations d _DI and d _PFI are stored as learning values. The transport delay a is separately calculated based on the signal from the intake flow rate detection sensor 22.

As described above, according to the present embodiment, the alcohol concentrations d _DI (j) and d _PFI (j) can be estimated without forcibly changing the injection ratio during a concentration transition. In other words, the alcohol concentration d _DI (j), d _PFI (j) can be estimated while performing the injection ratio control similar to that in the normal state even during the concentration transition. Therefore, it is possible to appropriately execute various controls based on the stored learned value while maintaining the engine performance at a high level.

[Specific processing in this embodiment]
Next, the estimation process described above will be specifically described with reference to FIGS. 3 to 6 exemplify processes in a specific cycle, these processes are assumed to be repeated every cycle of the internal combustion engine 10.

FIG. 3 is a flowchart showing the processing of the ECU 30 in cycle j-1. As shown in FIG. 3, the ECU 30 calculates and stores the port injector share ratio k _PFI (j−1) (S100).

FIG. 4 is a flowchart showing processing of the ECU 30 in cycle j. As shown in FIG. 4, the ECU 30 first calculates and stores a port injector share ratio k _PFI (j) (S200). Subsequently, the ECU 30 determines whether or not the injection ratio has been changed (S210). Specifically, the ECU 30 compares the stored sharing ratio k _PFI (j−1) with the sharing ratio k _PFI (j). If both are different, it can be determined that the injection ratio has been changed, so the ECU 30 detects the intake flow rate (S220). On the other hand, if the two are equal, it can be determined that the injection ratio has not been changed, so the ECU 30 ends the current process. Subsequent to S220, the ECU 30 calculates a transport delay a (S230). The ECU 30 stores in advance a map that defines the relationship between the intake air flow rate and the transport delay a, applies the intake air flow rate detected in S220 to this map, calculates the transport delay a, and waits until cycle j + a-1. .

FIG. 5 is a flowchart showing the processing of the ECU 30 in cycle j + a-1. As shown in FIG. 5, the ECU 30 detects and stores the alcohol concentration d _afs (j + a−1) from the air-fuel ratio feedback correction amount (S300).

FIG. 6 is a flowchart showing the processing of the ECU 30 in cycle j + a. As shown in FIG. 6, the ECU 30 first detects and stores the alcohol concentration d _afs (j + a) from the air-fuel ratio feedback correction amount (S400). Subsequently, the ECU 30 calculates alcohol concentrations d _PFI (j) and d _DI (j) (S410, S420). Specifically, ECU 30 may, S100 distribution ratio _k PFI stored at (j-1) of FIG. 3, distribution ratio _k PFI stored in S200 in FIG. 4 (j), the alcohol concentration is stored in S300 in FIG. 5 _{d afs} The alcohol concentrations d _afs (j + a) stored in (j + a−1) and S400 are applied to the above formulas (1) and (2), respectively, to calculate the alcohol concentrations d _PFI (j) and d _DI (j). ,Remember.

As described above, according to the processing shown in FIGS. 3 to 6, when the injection ratio is changed from cycle j-1 to cycle j, the alcohol concentrations d _DI (j) and d _PFI (j) are changed in cycle j + a. Can be calculated and stored. Therefore, various controls such as the fuel injection control can be appropriately executed based on the stored learned value.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12, 14 Delivery pipe 16 Fuel pipe 18 Fuel tank 20 Alcohol concentration sensor 22 Intake flow rate detection sensor 24 Air-fuel ratio sensor 26 Intake passage 28 Exhaust passage 30 ECU

Claims (2)

A tank for storing fuel mixed with hydrocarbon fuel and alcohol;
An in-cylinder injector that directly injects fuel in the tank into a cylinder of an internal combustion engine;
A port injector for injecting fuel in the tank into an intake port of the internal combustion engine;
When the fuel injection ratio of the in-cylinder injector and the port injector is changed, there is no change in the alcohol concentration in the fuel injected from the in-cylinder injector and the port injector in two consecutive cycles. The assumption is made that the alcohol concentration in the fuel injected from the in-cylinder injector and the port injector, the alcohol concentration estimated from the exhaust air-fuel ratio corresponding to the combustion of the injected fuel, and the in-cylinder The relationship established between the fuel injection ratio of the fuel injected by the injector and the port injector, the alcohol concentration in the fuel respectively injected from the in-cylinder injector and the port injector in the cycle before the change, Injection in the cycle before and after the change Is an alcohol concentration estimated from exhaust air-fuel ratio corresponding to the combustion of fuel, the in-cylinder injector and the port injector in a cycle after the change by applying the injection ratio of the fuel in the cycle before and after the change Alcohol concentration estimating means for estimating the alcohol concentration in the fuel injected from each of the
A control device for an internal combustion engine, comprising:   When the injection ratio is changed after fuel is supplied to the tank, the alcohol concentration estimation means is configured to determine the fuel injected from each of the in-cylinder injector and the port injector in the cycle after the change based on the relationship. The control apparatus for an internal combustion engine according to claim 1, wherein the alcohol concentration in the engine is estimated.

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