JP2013142305A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve air-fuel ratio controllability when starting, by simultaneously using intake passage injection by considering a characteristic of alcohol fuel, while securing startability by cylinder injection.SOLUTION: An ECU 50 injects fuel only from a cylinder injection valve 28 in at least a first cycle when starting an engine, and simultaneously uses fuel injection of an intake passage injection valve 26 on and after a second cycle. When an alcohol concentration in the fuel is a predetermined value or more, a portion of the fuel injected from the intake passage injection valve 26 in the second cycle, is injected from the intake passage injection valve 26 by moving up to the first cycle. Thus, even when the alcohol concentration in the fuel is high, a portion of an intake passage injection quantity of becoming excessive in the second cycle, is moved up to the first cycle, and this fuel can be burnt in the second cycle by a transport delay, and quantity of fuel to be burnt in the respective cycles can be properly controlled.

Description

  The present invention relates to a control device for an internal combustion engine that is mounted on a vehicle such as an FFV (Flexible-Fuel Vehicle) and uses alcohol fuel.

  As a conventional technique, for example, as disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-214415), it is applied to an internal combustion engine using alcohol fuel, and fuel is supplied from an intake passage injection valve to an intake passage (intake port). 2. Description of the Related Art There is known a control device for an internal combustion engine that executes intake passage injection for injection and in-cylinder injection for injecting fuel into a combustion chamber (in-cylinder) from an in-cylinder injection valve. In the prior art, in-cylinder injection is executed at the time of starting, and after starting, injection division control that selectively uses intake passage injection and in-cylinder injection is executed according to the operating state. According to the in-cylinder injection, the start can be performed earlier than the intake passage injection.

  On the other hand, as another conventional technique, Patent Document 2 (Japanese Patent Laid-Open No. 2009-191806) discloses an injection in consideration of a transport delay until the injected fuel reaches the cylinder in the intake passage injection. Control for increasing the amount of fuel (increase in transport delay) is disclosed. In this control, an increase value of the injected fuel is set according to the alcohol concentration in the fuel.

JP 2006-214415 A JP 2009-191806 A JP 2011-1848 A

  In the above-described prior art, when the alcohol concentration in the fuel is high at the time of engine start (starting), that is, when a large amount of fuel injection is required, the fuel may not be completely injected by in-cylinder injection alone. . In order to avoid this state, for example, in each cylinder, in-cylinder injection is executed in the first cycle after cylinder discrimination, and intake passage injection is used together in the second and subsequent cycles. However, at the time of start-up, since the water temperature is low and the alcohol fuel is difficult to vaporize, when the intake passage injection is performed, the transportation delay increase is executed according to the alcohol concentration in the fuel as described in Patent Document 2. There is a need to.

  Further, in the first intake passage injection in each cylinder, the amount of fuel that reaches the cylinder is reduced by the amount of fuel (port wet fuel) adhering to the wall surface of the intake port. It is also necessary to increase the amount only. Due to these factors, when the intake passage injection at the time of starting is performed in a state where the alcohol concentration in the fuel is high, the initial fuel injection amount increases, so that the required amount of fuel cannot be injected, There is a problem that the fuel injection amount varies greatly between the two, and the controllability of the air-fuel ratio deteriorates.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent fuel transportation delay and wall surface while ensuring startability by in-cylinder injection in an internal combustion engine using alcohol fuel. An object of the present invention is to provide a control device for an internal combustion engine that can improve air-fuel ratio controllability at the time of starting by appropriately using intake passage injection in consideration of the amount of adhesion.

The first invention is mounted on a plurality of cylinders of an internal combustion engine that uses gasoline and alcohol fuel, and an intake passage injection valve that injects fuel into the intake passage of each cylinder,
In-cylinder injection valves that are mounted on the cylinders and inject fuel into the cylinders;
Alcohol concentration acquisition means for acquiring the alcohol concentration in the fuel;
A first injection control means for injecting fuel from the in-cylinder injection valve in at least a first cycle when the engine is started;
A second injection control means for injecting fuel from both the intake passage injection valve and the in-cylinder injection valve after the second cycle at the time of engine start;
An early injection combined means for injecting a part of the fuel injected from the intake passage injection valve in the second cycle from the intake passage injection valve in the first cycle when the alcohol concentration in the fuel is a predetermined value or more;
It is characterized by providing.

The second invention is a basic injection amount calculating means for calculating a basic injection amount to be injected from the intake passage injection valve;
A wall surface attached fuel amount means for calculating a wall surface attached fuel amount for compensating for fuel adhering to the wall surface of the intake passage,
In the second cycle, the second injection control means is configured to inject an amount of fuel obtained by adding the basic injection amount and the wall surface attached fuel amount from the intake passage injection valve.

  A third aspect of the invention relates to injection amount matching for increasing the fuel injection amount of the intake passage injection valve in the third cycle with respect to the cylinder in which the early injection combined means is not operated in the first cycle among the plurality of cylinders. Means.

  According to the first invention, even when the alcohol concentration in the fuel is high at the time of engine start and the fuel injection amount is large, a part of the intake passage injection amount that has become excessive in the second cycle is moved forward in the first cycle. Can do. Then, this advanced fuel can be burned in the second cycle due to transport delay, and the amount of fuel burned in each cycle can be controlled appropriately. Therefore, in an internal combustion engine using alcohol fuel, it is possible to appropriately use the intake passage injection in consideration of fuel transportation delay and wall adhesion while ensuring startability by in-cylinder injection. Controllability can be improved.

  According to the second invention, in the second cycle, the second injection control means can inject an amount of fuel obtained by adding the basic injection amount and the wall surface attached fuel amount from the intake passage injection valve. Thereby, even if a part of the injected fuel adheres to the wall surface of the intake passage, the amount of fuel flowing into the cylinder can be appropriately controlled.

  According to the third invention, the injection amount matching means can increase the fuel injection amount of the intake passage injection valve in the third cycle with respect to the cylinder in which the early injection combination means is not operated in the first cycle. . Thereby, the fuel injection amount of each cylinder can be matched (equalized) through the first to third cycles, and variation in the air-fuel ratio among the cylinders can be suppressed.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is explanatory drawing which shows the fuel-injection state of each cylinder about the case where the alcohol (gasoline) with zero alcohol concentration is used. It is explanatory drawing which shows the fuel-injection state of each cylinder at the time of engine starting. It is explanatory drawing which shows the fuel-injection state of each cylinder at the time of engine starting and after starting. In Embodiment 1 of this invention, it is a flowchart of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system of the present embodiment includes a multi-cylinder engine 10 as an internal combustion engine mounted on a vehicle such as an FFV. The engine 10 can use alcohol fuel and gasoline including, for example, methanol and ethanol. FIG. 1 exemplifies one cylinder among a plurality of cylinders mounted on the engine 10. Each cylinder of the engine 10 has a combustion chamber 14 formed by a piston 12, and the piston 12 is connected to a crankshaft 16. Further, the engine 10 includes an intake passage 18 that sucks intake air into each cylinder. The intake passage 18 is provided with an electronically controlled throttle valve 20 that adjusts the amount of intake air.

  On the other hand, the engine 10 includes an exhaust passage 22 that exhausts exhaust gas of each cylinder, and the exhaust passage 22 is provided with a catalyst 24 such as a three-way catalyst that purifies the exhaust gas. Each cylinder of the engine has an intake passage injection valve 26 for injecting fuel into the intake passage 18 (intake port), an in-cylinder injection valve 28 for injecting fuel into the combustion chamber 14 (in-cylinder), and an air-fuel mixture. An ignition plug 30 for igniting, an intake valve 32 for opening and closing the intake passage 18 with respect to the inside of the cylinder, and an exhaust valve 34 for opening and closing the exhaust passage 22 with respect to the inside of the cylinder are provided.

  The system of the present embodiment includes a sensor system including various sensors necessary for engine control, and an ECU (Engine Control Unit) 50 that controls the operating state of the engine. First, the sensor system will be described. The crank angle sensor 40 outputs a signal synchronized with the rotation of the crankshaft 16, and the air flow sensor 42 detects the intake air amount of the engine. The water temperature sensor 44 detects the temperature of the engine cooling water (engine water temperature) as an example of the engine temperature, and the intake air temperature sensor 46 detects the temperature of the intake air (outside air temperature). The alcohol concentration sensor 48 detects the alcohol concentration in the fuel, and constitutes the alcohol concentration acquisition means of the present embodiment. Various other sensors are included in the sensor system, and these sensors are connected to the input side of the ECU 50. In addition, an actuator such as a throttle valve 20, fuel injection valves 26 and 28, and a spark plug 30 is connected to the output side of the ECU 50.

  Then, the ECU 50 drives each actuator based on engine operation information detected by the sensor system, and performs operation control. Specifically, based on the output of the crank angle sensor 40, cylinder discrimination for discriminating the stroke of each cylinder (the position of the piston 12) is executed, and the engine speed (engine speed) and the crank angle are detected. To do. Note that cylinder discrimination is performed only at the start. The ECU 50 detects the intake air amount by the air flow sensor 42, calculates the load factor (engine load) based on the engine speed and the intake air amount, and also calculates the intake air amount, the load factor, the engine water temperature, The fuel injection amount is calculated based on parameters such as the alcohol concentration of the engine and the acceleration / deceleration state of the engine.

  Then, the injection timing of the injection valves 26 and 28 is determined based on the crank angle, and fuel is injected from the injection valves 26 and 28 when the injection timing arrives. At this time, the ECU 50 selects one of fuel injection by the intake passage injection valve 26 (intake passage injection) and fuel injection by the in-cylinder injection valve 28 (in-cylinder injection) according to the operating state, temperature state, and the like of the engine. Or do both. Alternatively, after calculating the total fuel injection amount, which is the sum of the intake passage injection amount and the in-cylinder injection, based on the parameters, while performing both injections, the intake passage injection amount and the cylinder are determined according to the operating state of the engine. The ratio of the internal injection amount (fuel injection ratio) is changed. The ECU 50 determines the ignition timing according to the operating state of the engine and drives the spark plug 30 when the ignition timing has arrived. Thus, the air-fuel mixture is combusted in each cylinder and the engine is operated.

[Features of Embodiment 1]
Alcohol fuel is basically low in volatility and tends to increase the amount of fuel injection, and this tendency is particularly noticeable at start-up. For this reason, at the time of start-up, there is a demand for improving the combustibility by directly injecting alcohol fuel into the cylinder. However, when the alcohol concentration in the fuel is high, the fuel may not be completely injected only by in-cylinder injection. For example, in each cylinder, in-cylinder injection is executed in the first cycle after cylinder discrimination. It is preferable to use intake passage injection together after the cycle. However, in the intake passage injection, the time until the fuel injected into the intake passage arrives in the cylinder (transport delay) and the fuel injected by the first intake passage injection adheres to the wall surface of the intake passage. It is necessary to consider the amount that does not contribute to combustion (wall-attached fuel). Therefore, in the present embodiment, the following control is executed in consideration of the transport delay of the injected fuel and the amount of wall surface adhesion.

  First, FIG. 2 is an explanatory diagram showing the fuel injection state of each cylinder when a fuel (gasoline) having a zero alcohol concentration is used. In FIG. 2, a 6-cylinder engine is taken as an example, and numbers (# 1 to # 6) are assigned to the respective cylinders in the order in which fuel injection is performed. Moreover, the calculation time of each parameter mentioned in the following description is only an example in the present embodiment, and does not limit the present invention. At the time of fuel injection, first, a total fuel injection amount (target value) is calculated by a known method based on parameters such as the intake air amount, engine load, engine water temperature, and alcohol concentration in the fuel. Then, the ECU 50 executes the following control in the first cycle, the second cycle, the third cycle and thereafter after the engine is started.

  When gasoline is used, first, only in-cylinder injection is executed in the first cycle when the engine is started, and in-cylinder injection and intake passage injection are used in combination in the second cycle. In this case, the first cycle aims to improve the startability by injecting the fuel directly into the cylinder. In addition, the intake passage injection is used together in the second cycle, for example, avoiding the shortage of the fuel injection amount in the second cycle due to the decrease in the fuel pressure of the system caused by the in-cylinder injection in the first cycle, and the intake passage The purpose is to attach fuel to the wall of the (intake port). In the first intake passage injection, a relatively large amount of fuel tends to adhere to the wall surface of the intake passage and does not contribute to the formation of the air-fuel mixture. Therefore, in the first intake passage injection executed in the second cycle, the intake passage injection amount is calculated by adding the basic injection amount and the wall surface attached fuel amount.

  Here, the basic injection amount is set based on the above-described total fuel injection amount and fuel injection ratio, and serves as a base for the intake passage injection amount. The amount of fuel attached to the wall surface corresponds to the amount of fuel attached to the wall surface of the fuel injected into the intake passage, and is calculated by a known method based on the intake passage injection amount, engine water temperature, alcohol concentration, and the like. In the present invention, when the alcohol concentration in the fuel is lower than a predetermined concentration reference value, only in-cylinder injection may be executed in the second cycle. That is, when the alcohol concentration is lower than the concentration reference value and the in-cylinder injection amount in the first cycle is so small that it does not cause a decrease in the fuel pressure of the system, the intake passage injection is not executed in the second cycle, A required amount of fuel is injected only by internal injection.

  Next, fuel injection control when alcohol fuel is used will be described with reference to FIG. FIG. 3 is an explanatory view showing the fuel injection state of each cylinder at the time of engine start. As shown in this figure, in the present embodiment, different fuel injection controls are executed for the first cycle, the second cycle, and the third and subsequent cycles when the engine is started.

(First cycle)
In at least the first one cycle at the time of engine start (after cylinder discrimination), in the same manner as in the case of gasoline, only in-cylinder injection is executed to start fuel injection to improve startability. At this time, since the intake passage injection is not executed, the target in-cylinder injection amount becomes a value corresponding to the aforementioned total fuel injection amount. In the first cycle of fuel injection, since it is not necessary to consider the decrease in fuel pressure due to the previous fuel injection, in-cylinder injection is executed regardless of the alcohol concentration. Thereby, at the time of start-up, the alcohol fuel which is hard to vaporize can be directly injected into the cylinder to improve the combustibility.

(2nd cycle)
In the second and subsequent cycles when the engine is started, fuel injection is performed using both intake passage injection and in-cylinder injection. In particular, when alcohol fuel is used, the fuel injection amount tends to increase as compared to gasoline. Therefore, the fuel pressure in the system may drop due to the in-cylinder injection in the first cycle, and the fuel injection amount in the second cycle may be insufficient. There is. For this reason, after the second cycle, the fuel injection amount is ensured by using the intake passage injection and the in-cylinder injection together. Thereby, even when the alcohol concentration in the fuel is high, the fuel injection control can be stably executed. As described in the case of gasoline, when the alcohol concentration in the fuel is lower than the concentration reference value, it is determined that only the in-cylinder injection can be handled, and the intake passage injection is executed even in the second cycle. Alternatively, only the in-cylinder injection may be performed.

(Early injection control)
As described above, the intake passage injection is used together in the second and subsequent cycles. However, if the alcohol concentration in the fuel becomes higher than a certain level, the fuel corresponding to the total fuel injection amount is obtained even if the intake passage injection and the in-cylinder injection are used together. May not be able to be sprayed. Therefore, in the present embodiment, the alcohol concentration at which the amount of fuel injected from the two injection valves 26 and 28 is a practical maximum value is set as a predetermined value, and the alcohol concentration in the fuel is higher than the predetermined value. In this case, the early injection combined control is executed in which a part of the fuel to be injected in the second cycle is injected in the first cycle. In the early injection combined control, as shown in FIG. 3, a part of the intake passage injection amount injected in the second cycle (hereinafter referred to as a transport delay injection amount) is advanced (early) in the first cycle. The intake passage is injected. The transport delay injection amount is set to increase as the alcohol concentration in the fuel increases. Further, the early injection combined control may be executed for all the cylinders, but as illustrated in FIG. 3, it may be configured to be executed only for some of the cylinders as necessary.

  Here, there is a transport delay before the fuel injected into the intake passage reaches the cylinder. For this reason, when the fuel injection period of the second cycle becomes too long (the fuel cannot be completely injected), at least part of the fuel does not contribute to the combustion of the second cycle due to transport delay. For this reason, in the early injection combined control, fuel that is not in time for the combustion in the second cycle is injected in the first cycle in advance to compensate for the fuel transportation delay. The transport delay injection amount that is brought forward in the first cycle is set so that the total amount of fuel that merges with the injected fuel and flows into the cylinder in the second cycle becomes an appropriate amount. Further, the transport delay injection amount does not necessarily need to coincide with the amount by which the intake passage injection amount in the second cycle is decreased, and a larger amount of fuel may be injected as the transport delay injection amount.

  The transport delay injection amount is, for example, by using a known calculation model that models the behavior of the injected fuel, so that the engine speed, load factor, intake passage injection amount, in-cylinder injection amount, alcohol concentration in the fuel, It is calculated based on parameters such as transport delay from the intake passage injection valve 26 to the cylinder. Further, in the early injection combined control, the injection amount and the number of injections of the intake passage injection may be variably set according to the transport delay injection amount, and the total amount of the injected fuel may be controlled to coincide with the transport delay injection amount. According to the early injection combined control, even if the alcohol concentration in the fuel is high at the time of engine start and the fuel injection amount is large, a part of the intake passage injection amount that has become excessive in the second cycle is moved forward in the first cycle. Can do. Then, this advanced fuel can be burned in the second cycle due to transport delay, and the amount of fuel burned in each cycle can be controlled appropriately.

(3rd cycle and after)
In the first cycle, the intake passage injection amount is increased by the transportation delay injection amount and the wall surface attached fuel amount in the first and second cycles. For this reason, after the third cycle, the intake passage injection amount (or its fuel increase coefficient, etc.) is reduced according to the fuel that has been increased so far, and the fuel injection amount that is temporarily excessive is compensated (absorbed). To do. The intake passage injection amount is set so as to increase as the fuel increase coefficient increases. Further, when the intake passage injection amount is decreased, the number of injections may be increased as shown in FIG.

  FIG. 4 is an explanatory view showing the fuel injection state of each cylinder at the time of starting the engine and after starting. This figure shows an example of specific control. As shown in FIG. 3, after the third cycle, the fuel increase coefficient of intake passage injection is gradually decreased. At this time, the decreasing rate of the fuel increase coefficient is set to be larger as the alcohol concentration in the fuel is higher. That is, when the fuel having a high alcohol concentration is used, the intake passage injection amount in the first and second cycles is greatly increased. Therefore, the intake passage injection amount is rapidly reduced in the third and subsequent cycles. Further, when the alcohol concentration is low, an increase in the intake passage injection amount in the first and second cycles is relatively suppressed, and therefore, the intake passage injection amount is gradually decreased in the third and subsequent cycles.

  Further, in the cylinder in which the early injection combined control is not executed in the first cycle (for example, the cylinders # 1, # 2, and # 3 in FIG. 3), the intake passage injection amount is set to the transport delay injection in the third cycle. Increase by the amount. That is, at the start of the third cycle, some cylinders (# 4, # 5, # 6 cylinders) that have performed early injection combined control and other cylinders (# 1, # 2) that have not performed the control. , # 3 cylinder), the fuel injection amount varies. Therefore, in the third cycle, the intake passage injection amount of the cylinder for which the early injection combined control has not been executed is increased by the amount of the transport delay injection amount. Thereby, the fuel injection amount of each cylinder can be matched (equalized) through the first to third cycles, and variation in the air-fuel ratio among the cylinders can be suppressed.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 5 is a flowchart of the control executed by the ECU in the first embodiment of the present invention. In the routine shown in this figure, first, at step 100, it is determined whether or not the ignition switch (IG) is ON. If it is ON, the routine proceeds to step 102. In steps 102, 104, and 106, the engine water temperature ethw, the outside air (environment) temperature etha, and the alcohol concentration ealch in the fuel are calculated based on the output of the sensor system. The alcohol concentration ealch may be estimated based on the exhaust air / fuel ratio without using the alcohol concentration sensor 48.

  Next, in step 108, it is determined whether or not the starter switch is ON. If it is ON, the process proceeds to step 110. In step 110, crank angle detection and cylinder discrimination are executed based on the output of the crank angle sensor 40 while driving (starting) cranking by driving the starter motor. Next, in step 112, as shown in FIG. 3 described above, the fuel injection mode is determined in consideration of the transport delay corresponding to the alcohol concentration in the fuel. That is, the in-cylinder injection amount and the intake passage injection amount are calculated for each cycle according to the alcohol concentration, and the number of intake passage injections (the number of cylinders) and the transport delay amount are calculated. In step 114, the number of intake passage injection increases and the injection amount are calculated in consideration of the transport delay according to the alcohol concentration in the fuel.

  Next, at step 116, as shown in FIG. 4 described above, a fuel injection increase coefficient corresponding to the number of intake passage injections is calculated. In step 118, in-cylinder injection and intake passage injection are executed based on the calculation results of the respective steps. After the engine shifts to the self-sustained operation by the above routine, either the intake passage injection or the in-cylinder injection is executed or the injection ratio is set to be variable by using both in accordance with the operating state of the engine. Blowing control is executed.

  As described above in detail, according to the present embodiment, in an engine using alcohol fuel, intake passage injection is appropriately performed in consideration of fuel transportation delay and wall adhesion while ensuring startability by in-cylinder injection. The air-fuel ratio controllability at the time of starting can be improved.

  In the first embodiment, the in-cylinder injection in the first cycle shown in FIG. 3 shows a specific example of the first injection control means in claim 1, and the intake passage injection and the in-cylinder injection in the second and subsequent cycles. Shows a specific example of the second injection control means. Further, the intake manifold injection in the first cycle shows a specific example of the early injection combined means. The basic injection amount and the wall surface adhering fuel amount in the second cycle are specific examples of the basic injection amount calculating means and the wall surface adhering fuel amount means in claim 2, respectively. In addition, in the third cycle, the control for increasing the intake passage injection amount of the cylinder for which the early injection combined control has not been executed by the amount of the transport delay injection amount is a specific example of the injection amount matching means in claim 3. .

10 Engine 12 Piston 14 Combustion chamber 16 Crankshaft 18 Intake passage 20 Throttle valve 22 Exhaust passage 24 Catalysts 26 and 28 Fuel injection valve 30 Spark plug 32 Intake valve 34 Exhaust valve 40 Crank angle sensor 42 Air flow sensor 44 Water temperature sensor 46 Intake temperature sensor 48 Alcohol concentration sensor (Alcohol concentration acquisition means)
50 ECU

Claims (3)

An intake passage injection valve mounted on a plurality of cylinders of an internal combustion engine that uses gasoline and alcohol fuel, and injects fuel into the intake passage of each cylinder;
In-cylinder injection valves that are mounted on the cylinders and inject fuel into the cylinders;
Alcohol concentration acquisition means for acquiring the alcohol concentration in the fuel;
A first injection control means for injecting fuel from the in-cylinder injection valve in at least a first cycle when the engine is started;
A second injection control means for injecting fuel from both the intake passage injection valve and the in-cylinder injection valve after the second cycle at the time of engine start;
An early injection combined means for injecting a part of the fuel injected from the intake passage injection valve in the second cycle from the intake passage injection valve in the first cycle when the alcohol concentration in the fuel is a predetermined value or more;
A control device for an internal combustion engine, comprising: Basic injection amount calculating means for calculating a basic injection amount to be injected from the intake passage injection valve;
A wall surface attached fuel amount means for calculating a wall surface attached fuel amount for compensating for fuel adhering to the wall surface of the intake passage,
The said 2nd injection control means becomes a structure which inject | pours the fuel of the quantity which added the said basic injection amount and the said wall surface attached fuel amount from the said intake passage injection valve in the said 2nd cycle. Control device for internal combustion engine.   An injection amount matching means for increasing the fuel injection amount of the intake passage injection valve in the third cycle for the cylinder in which the early injection combined means is not operated in the first cycle among the plurality of cylinders. Item 3. The control device for an internal combustion engine according to Item 1 or 2.

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