JP2013119827A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To early start the jetting of fuel by changing the jetting form according to the condition while securing the jetting quantity of the fuel in the start using alcohol fuel.SOLUTION: An ECU 50 basically executes both of intake path jetting and cylinder jetting to secure the fuel jetting quantity when the concentration of alcohol in the fuel is equal to or below the concentration determining value (γ) in the start. Where, when the delay period (empit-edit) which is the difference between an intake path initial jetting timing (empit) and the cylinder initial jetting timing (edit) is larger than the delay determining value α, the intake path jetting is prohibited and only the cylinder jetting is executed at least in the initial one cycle after the cylinder discrimination. As a result, in a case where the start of the engine is delayed when the intake path initial jetting timing (empit) arrives and the fuel jetting is started, the initial fuel jetting (cylinder jetting) in the cylinder jetting timing (edit) is capable of being rapidly started.

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 Laid-Open No. 2006-214415), intake passage injection in which fuel is injected from an intake passage injection valve into an intake passage (intake port) using alcohol fuel. There is known a control device for an internal combustion engine capable of executing in-cylinder injection for injecting fuel from a in-cylinder injection valve into a combustion chamber (in-cylinder). In the prior art, only in-cylinder injection is executed at the time of starting. According to this configuration, the fuel adhering to the wall surface of the intake passage is vaporized with a delay by performing the intake passage injection, so that excessive fluctuation (roughness) of the air-fuel ratio can be suppressed.

JP 2006-214415 A JP 2009-167838 A

  In the prior art described above, when the alcohol concentration in the fuel is high, the fuel injection amount (fuel injection period) increases, the fuel pressure decreases, and the combustibility may deteriorate. In response to this, as disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2009-167838), it is conceivable to perform both intake passage injection and in-cylinder injection at the time of starting. However, in the in-cylinder injection, if the crank angle is determined at the start and the cylinder discrimination is completed, fuel injection can be sequentially started from that point to the cylinder immediately before the intake top dead center (TDC). In the intake passage injection, the injection may not be started immediately like the in-cylinder injection.

  More specifically, for example, when the alcohol concentration in the fuel is high at the time of start-up, the fuel injection amount greatly increases. Therefore, the injection timing of the intake passage injection is extremely early compared to the in-cylinder injection (an example is given). And about BTDC 500 ° CA). In this case, even when the cylinder discrimination is completed at the time of starting, there is a case where the injection timing of the intake passage injection does not arrive for a long period of about 500 ° CA (a period in which the crankshaft makes about one and a half revolutions). For this reason, in the prior art, if the intake passage injection is used at the time of starting, there is a risk that the period from the start of cranking to the intake passage injection is limited (rate-limiting condition) and the engine start is delayed. There is a problem that startability is reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is an internal combustion engine using an alcohol fuel, and an injection mode according to the situation while ensuring a fuel injection amount at the time of starting. It is an object of the present invention to provide a control device for an internal combustion engine capable of improving the startability by switching fuel injection at an early stage.

A first invention is provided in a plurality of cylinders of an internal combustion engine using alcohol fuel, and an intake passage injection valve for injecting fuel into an intake passage;
An in-cylinder injection valve that is provided in the plurality of cylinders and injects fuel into the cylinder;
Alcohol concentration acquisition means for acquiring the alcohol concentration in the fuel;
When the alcohol concentration in the fuel is equal to or higher than a predetermined concentration determination value at the time of starting the internal combustion engine, both intake passage injection for injecting fuel from the intake passage injection valve and in-cylinder injection for injecting fuel from the in-cylinder injection valve A double-valve drive control means for executing
A delay period calculating means for calculating a delay period corresponding to a time from the start of cranking to the first intake passage injection timing, targeting a cylinder of which the intake passage injection timing first arrives at start-up among the plurality of cylinders; ,
In the state where the both valve drive control means is operated, when the delay period is larger than a predetermined delay judgment value, the intake passage injection is prohibited at least in the first cycle at the start and only the in-cylinder injection is performed. One-valve drive control means to be executed;
It is characterized by providing.

A second timing calculating means for calculating the first intake passage injection timing;
A second timing calculating means for calculating the first in-cylinder injection timing for the cylinder in which the in-cylinder injection timing first arrives at the start of the plurality of cylinders;
The delay period calculating means calculates a difference between the first intake passage injection timing and the first in-cylinder injection timing as the delay period.

  According to the first invention, in the state where the alcohol concentration in the fuel is equal to or higher than the predetermined concentration determination value, when the start of the internal combustion engine is delayed when the fuel injection is started after the intake passage initial injection timing comes, the cylinder is In at least the first cycle after the determination, the first fuel injection (in-cylinder injection) can be started at the in-cylinder initial injection timing. Accordingly, fuel injection can be started early without waiting for the intake passage initial injection timing, and the start timing of the internal combustion engine can be advanced. Then, at an appropriate timing after the second cycle, the combined use of the intake passage injection and the in-cylinder injection can be started to ensure the fuel injection amount. On the other hand, if waiting until the intake passage initial injection timing does not become the rate-limiting condition for starting, the intake passage injection and the in-cylinder injection are used together from the first cycle after cylinder discrimination, and it is sufficient from the initial stage of cranking. A large amount of fuel can be injected. Therefore, the injection mode can be switched appropriately according to the situation at the time of start, and startability can be improved.

  According to the second invention, the delay period corresponding to the time from the start of cranking to the arrival of the intake passage initial injection timing can be calculated based on the in-cylinder initial injection timing. As a result, in the first cycle after cylinder discrimination, it is possible to accurately determine which one of the both-valve drive control means and the one-valve drive control means is operated to start the fuel injection most quickly.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a flowchart of the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. 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 engine cooling water (engine water temperature) as an example of the engine temperature. The alcohol concentration sensor 46 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, and the alcohol concentration in the fuel. The fuel injection amount is calculated based on the above. 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. Further, the ignition timing is determined according to the operating state of the engine, and the spark plug 30 is driven 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]
In general, in an engine using an alcohol fuel, the fuel injection amount (fuel injection period) tends to increase as the alcohol concentration in the fuel increases. In particular, when the alcohol concentration is high at the start (during cold start), the increase in the fuel injection amount becomes significant. If fuel injection at the time of start-up is executed in such a state, the fuel supply pressure (fuel pressure) to the injection valves 26 and 28 may decrease, and the combustibility may deteriorate. On the other hand, if both the intake passage injection and the in-cylinder injection are executed at the time of starting to secure the fuel injection amount, the startability is deteriorated due to the delay of the start of the intake passage injection. That is, when the fuel injection amount is large, the injection timing of the intake passage injection is set to an extremely early timing as compared with the in-cylinder injection. As a result, depending on the initial position of the crankshaft 16 at the start of cranking, even if the cylinder discrimination is completed, the injection timing of the intake passage injection does not arrive over a long period of, for example, several hundreds of degrees CA. The engine starts slowly. For this reason, in the present embodiment, when the alcohol concentration in the fuel is high at the start, the following control is executed in accordance with the delay of the intake passage injection.

(Double valve drive control)
The double-valve drive control performs both intake passage injection and in-cylinder injection when the alcohol concentration in the fuel is equal to or higher than a predetermined concentration determination value γ at the start of the engine. Here, the concentration determination value γ is set, for example, as a lower limit value of the alcohol concentration such that the fuel pressure decreases (the fuel injection amount is insufficient) unless the intake passage injection is used in addition to the in-cylinder injection. Therefore, when the alcohol concentration in the fuel is high and there is a concern about a decrease in fuel pressure, the fuel is injected from the two injection valves 26 and 28 to ensure a desired fuel injection amount, and the combustibility at the start is improved. It can be stabilized. On the other hand, at the time of start-up, there is a demand to improve the combustibility by injecting a large amount of alcohol fuel, which is basically low in volatility, directly into the cylinder. For this reason, when the alcohol concentration in the fuel is less than the concentration determination value γ, the intake passage injection is not executed, but only the in-cylinder injection is executed.

(Delay calculation control)
In the above-described double-valve drive control, when cranking is started at the time of starting, the timing at which intake passage injection should be started (intake passage injection timing) sequentially arrives for each cylinder. The intake passage injection timing is set so that a required amount of fuel injection is completed, for example, in the vicinity of the intake top dead center or in the first half of the intake stroke, and the time required for the injected fuel to reach the cylinder is also set. Set in consideration. For this reason, the intake passage injection timing is set earlier with respect to the intake top dead center as the fuel injection amount (fuel injection period) increases. Further, the intake passage injection timing that arrives first at the start of all the cylinders (hereinafter referred to as the intake passage initial injection timing “empit”) varies depending on the initial position of the crankshaft 16.

  On the other hand, at the time of starting, the timing (in-cylinder injection timing) at which in-cylinder injection should be started for each cylinder also sequentially arrives. In-cylinder injection timing (hereinafter referred to as in-cylinder initial injection timing edit) that first arrives at start-up among all the cylinders changes in accordance with the initial position of the crankshaft 16 like the intake passage initial injection timing empit. . However, since the in-cylinder injection basically needs to be started immediately before the intake top dead center of each cylinder, the value of the in-cylinder initial injection timing edit is a relatively small value corresponding to the phase difference between the cylinders. The range of change is also limited. Therefore, at the time of starting, in most cases, the in-cylinder initial injection timing edit arrives earlier than the intake passage initial injection timing empit. That is, the intake passage initial injection timing empit is delayed from the in-cylinder initial injection timing edit (a retarded crank angle). Therefore, when the double valve drive control is executed, the intake passage initial injection timing empit The larger the is, the slower the engine start.

  Therefore, in the delay calculation control, when the crank angle is determined at the start and the cylinder discrimination is completed, the intake passage initial injection timing “empit” and the in-cylinder initial injection timing “edit” are determined based on the current crank angle and the result of cylinder discrimination. Are calculated, and a delay period (empit-edit) which is a difference between the two is calculated. Here, the delay time (empit-edit) corresponds to the time (delay time) from the start of cranking to the intake passage initial injection timing empit, and this delay time is calculated based on the in-cylinder initial injection timing edit. It is a thing. The intake passage initial injection timing “empit”, the in-cylinder initial injection timing “edit”, and the delay time (empit−edit) are respectively calculated as crank angles.

(Single valve drive control)
When the delay period (empit-edit) is larger than the predetermined delay determination value α, the engine start delay (from cranking) is started when the intake passage injection is started after waiting until the intake passage initial injection timing empit arrives. It is determined that the delay of the transition to the independent operation) exceeds the allowable limit, and the single valve drive control is executed. The delay determination value α is set in advance corresponding to the allowable limit of the start delay. In the one-valve drive control, the intake passage injection is prohibited and only the in-cylinder injection is executed in at least the first one cycle after cylinder discrimination. In the second and subsequent cycles, it may be determined that the intake passage injection can be executed when the intake passage injection timing has arrived in each cylinder, and the control may shift to the both-valve drive control.

  On the other hand, in the state where the execution condition for the double valve drive control is satisfied (the alcohol concentration in the fuel is equal to or higher than the concentration determination value γ), if the delay period (empit-edit) is less than or equal to the delay determination value α, the intake passage It is determined that waiting until the arrival of the initial injection timing “empit” does not become the rate-limiting condition for starting (that is, it is not necessary to limit only to in-cylinder injection by the one-valve drive control), and both valves from the first cycle after cylinder discrimination Execute drive control.

  According to the above control, when the engine start is delayed when the fuel injection is started after the intake passage initial injection timing empit arrives, at least in the first cycle after cylinder discrimination, the first in-cylinder initial injection timing edit Fuel injection (in-cylinder injection) can be started. That is, even without waiting until the intake passage initial injection timing “empit”, fuel injection can be started at an early stage, and the start timing of the engine (time when the autonomous operation is started) can be advanced. Then, at an appropriate timing after the second cycle, it is possible to shift to the both-valve drive control and secure the fuel injection amount.

  On the other hand, if waiting for the intake passage initial injection timing empit is not the rate-limiting condition for starting, the two-valve drive control is executed from the first cycle after cylinder discrimination, and a sufficient amount from the initial stage of cranking is executed. Fuel can be injected. Therefore, the injection mode can be switched appropriately according to the situation at the time of start (the initial position of the crankshaft 16), and the startability can be improved. In the present embodiment, a delay period (empit-edit) corresponding to the time from the start of cranking to the arrival of the intake passage initial injection timing “empit” is calculated based on the in-cylinder initial injection timing “edit”. be able to. As a result, in the first cycle after cylinder discrimination, it is possible to accurately determine which one of the double-valve drive control and the single-valve drive control is executed to start the fuel injection most quickly.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 2 is a flowchart of 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 46.

  Next, in step 108, it is determined whether or not the starter switch is ON. If it is ON, in step 110, the engine water temperature ethw is a predetermined temperature range suitable for starting by in-cylinder injection (α1 < It is determined whether or not it is within ethw <α2), and if this determination is satisfied, in step 112, the outside air temperature etha is a predetermined temperature range suitable for starting by in-cylinder injection (β1 <etha <β2) It is determined whether or not it is within the range. Here, α1 and β1 correspond to the lower limit values of the respective temperature ranges, and α2 and β2 correspond to the lower limit values of the respective temperature ranges, and these values are set in advance by experiments or the like.

  If both the determinations in steps 110 and 112 are established, at least the in-cylinder injection is performed, so in step 114, it is determined whether or not the alcohol concentration ealch in the fuel is higher than the determination value γ. If this determination is established, in step 116, the starter motor is driven to execute (start) cranking. Subsequently, in step 118, crank angle detection and cylinder discrimination are executed based on the output of the crank angle sensor 40, and it is determined whether or not these processes are completed. If the determination in step 118 is satisfied, the process proceeds to step 120. If the determination is not satisfied, the process in step 116 is continued until the cylinder determination is completed.

  Next, in step 120, a target value of the intake passage injection amount is calculated by a known method based on parameters such as the intake air amount, the engine load, the engine water temperature, and the alcohol concentration in the fuel. Specifically, first, a total fuel injection amount that is the sum of the intake passage injection amount and the in-cylinder injection amount is calculated based on the above parameters. Then, a ratio (injection ratio) between the intake passage injection amount and the in-cylinder injection amount is calculated based on the operation region obtained based on the above parameters, and the intake passage injection amount is calculated based on the injection ratio and the total fuel injection amount. The target value of is calculated. Furthermore, the intake passage injection timing of each cylinder is calculated based on the target value of the intake passage injection amount, and the first arrival among the intake passage injection timings of all cylinders based on these calculated values and the current crank angle. The intake passage initial injection timing empit is calculated.

  Next, in step 122, the target value of the in-cylinder injection amount is calculated based on the difference between the total fuel injection amount and the intake passage injection amount, and the in-cylinder injection timing of each cylinder is calculated. Then, based on these calculated values and the current crank angle, the first in-cylinder injection timing “edit” that comes first among the in-cylinder injection timings for all the cylinders is calculated.

  Next, in step 124, a delay period (empit-edit) is calculated, and it is determined whether or not the calculated value is larger than the delay determination value α, that is, whether or not “empit> edit + α” is satisfied. If this determination is satisfied, in step 126, in-cylinder injection is executed only for the first cycle (initial injection) after cylinder discrimination, and in-cylinder injection and intake passage injection are performed in the second and subsequent cycles. Combined. On the other hand, if the determination in step 124 is not satisfied, in step 128, in-cylinder injection and intake passage injection are used together from the first cycle after cylinder determination.

  If the determination in step 114 is not established, it is determined that the alcohol concentration in the fuel is relatively low. In this case, cranking is started in step 130, and crank angle detection and cylinder discrimination are executed. Subsequently, in step 132, in-cylinder injection is executed for all cylinders from the first cycle after cylinder discrimination. Further, if the determination is not established in any of steps 110 and 112, it is determined that the temperature environment is not suitable for in-cylinder injection. In this case, cranking is started in step 134, and crank angle detection and cylinder discrimination are executed. Subsequently, in step 136, intake passage injection is executed for all cylinders from the first cycle after cylinder discrimination.

  It should be noted that at the start by the above routine, whether in-cylinder injection is performed, in which intake passage injection is performed, or in which both are used together, after cranking is completed and the operation is shifted to independent operation, Depending on the operating state, either one of the intake passage injection and the in-cylinder injection is executed, or both are used together to execute injection division control in which the injection ratio is variably set.

  In the first embodiment, step 128 and the double valve drive control in FIG. 2 show a specific example of the double valve drive control means in claim 1, and the step 126 and the single valve drive control show a specific example of the single valve drive control means. Is shown. Further, step 120 shows a specific example of the first timing calculation means in claim 2, step 122 shows a specific example of the second timing calculation means, and step 124 calculates the delay period in claims 1 and 2. A specific example of the means is shown.

DESCRIPTION OF SYMBOLS 10 Engine 12 Piston 14 Combustion chamber 16 Crankshaft 18 Intake passage 20 Throttle valve 22 Exhaust passage 24 Catalyst 26, 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 Alcohol concentration sensor (Alcohol concentration acquisition means)
50 ECU

Claims (2)

An intake passage injection valve that is provided in a plurality of cylinders of an internal combustion engine that uses alcohol fuel and injects fuel into the intake passage;
An in-cylinder injection valve that is provided in the plurality of cylinders and injects fuel into the cylinder;
Alcohol concentration acquisition means for acquiring the alcohol concentration in the fuel;
When the alcohol concentration in the fuel is equal to or higher than a predetermined concentration determination value at the time of starting the internal combustion engine, both intake passage injection for injecting fuel from the intake passage injection valve and in-cylinder injection for injecting fuel from the in-cylinder injection valve A double-valve drive control means for executing
A delay period calculating means for calculating a delay period corresponding to a time from the start of cranking to the first intake passage injection timing, targeting a cylinder of which the intake passage injection timing first arrives at start-up among the plurality of cylinders; ,
In the state where the both valve drive control means is operated, when the delay period is larger than a predetermined delay determination value, the intake passage injection is prohibited at least in the first cycle after cylinder determination, and only the in-cylinder injection is performed. One-valve drive control means for executing
A control device for an internal combustion engine, comprising: First timing calculating means for calculating the first intake passage injection timing;
A second timing calculating means for calculating the first in-cylinder injection timing for the cylinder in which the in-cylinder injection timing first arrives at the start of the plurality of cylinders;
2. The control device for an internal combustion engine according to claim 1, wherein the delay period calculation unit calculates a difference between the first intake passage injection timing and the first in-cylinder injection timing as the delay period.

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