WO2019017060A1

WO2019017060A1 - Control device for internal combustion engine

Info

Publication number: WO2019017060A1
Application number: PCT/JP2018/018956
Authority: WO
Inventors: 政弘山田; 沖　秀行; 一成小林; 聡文平星
Original assignee: 本田技研工業株式会社
Priority date: 2017-07-18
Filing date: 2018-05-16
Publication date: 2019-01-24
Also published as: BR112020001029A2; JP2020180550A

Abstract

Provided is a control device which is for an internal combustion engine that uses a fuel containing alcohol, and which is capable of ensuring a stable and good combustion state after the internal combustion engine is cold-started. The present invention is applied to an internal combustion engine 3 that uses a fuel containing alcohol and that directly injects the fuel into a cylinder 3a. A control device according to the present invention detects an engine water temperature TW as an engine temperature parameter indicating the temperature of the internal combustion engine 3, detects the ethanol concentration EC of the fuel, and detects an intake air amount GAIRCYL as a load of the internal combustion engine 3. Then, after a cold-start of the internal combustion engine 3, the control device selects, as a fuel injection mode, either intake process injection for injecting the fuel during an intake process or compression process injection for injecting the fuel during a compression process, on the basis of the detected engine water temperature TW, the detected ethanol concentration EC, and the detected intake air amount GAIRCYL, and executes the selected injection (step 9 in FIG. 2, FIG. 6, FIG. 12).

Description

Control device for internal combustion engine

The present invention relates to a control device for an internal combustion engine that injects fuel directly into a cylinder using a fuel containing alcohol, and more particularly to a control device that controls the injection timing of fuel in a low temperature state of the internal combustion engine.

Conventionally, as a control device for this type of internal combustion engine, for example, the one described in Patent Document 1 is known. In this control device, in order to improve the low-temperature startability of an internal combustion engine using an alcohol-containing fuel, fuel injection control is performed as follows during start-up and within a predetermined period until warm-up after start-up is completed. To be done.

First, the alcohol concentration of the fuel and the cooling water temperature are detected, and when the condition that the alcohol concentration is equal to or higher than the predetermined concentration and the cooling water temperature is equal to or lower than the predetermined temperature is satisfied, it is determined that And compression stroke injection that injects the fuel in the compression stroke while boosting the pressure of the fuel. On the other hand, when the above condition is not satisfied, that is, when the alcohol concentration is lower than the predetermined concentration and / or the cooling water temperature is higher than the predetermined temperature, it is determined that the injected fuel is in the easily vaporized state. Intake stroke injection is performed to inject the fuel in the intake stroke without boosting the fuel.

Unexamined-Japanese-Patent No. 2010-37968

As described above, in the conventional control device, the compression stroke injection is performed when the alcohol concentration is equal to or higher than the predetermined concentration and the cooling water temperature is equal to or lower than the predetermined temperature within a predetermined period until warm-up after startup is completed. Be done. However, as described later, depending on the load of the internal combustion engine, a better combustion state can be obtained by performing the intake stroke injection rather than the compression stroke injection even when the above conditions are satisfied after the low temperature start. confirmed. On the other hand, in the conventional control device, since the compression stroke injection is executed as long as the above-mentioned conditions regarding the alcohol concentration and the coolant temperature are satisfied, the good combustion state can not always be obtained, and the combustion fluctuation increases. There is a fear.

The present invention has been made to solve such a problem, and a control of an internal combustion engine capable of securing a stable and good combustion state after a low temperature start of the internal combustion engine using a fuel containing alcohol. It aims at providing an apparatus.

In order to achieve this object, the invention according to claim 1 is a control device of an internal combustion engine 3 which uses a fuel containing alcohol and injects the fuel directly into the cylinder 3a. Engine temperature parameter acquiring means (water temperature sensor 22) for acquiring an engine temperature parameter (engine water temperature TW) representing, alcohol concentration acquiring means (ethanol concentration sensor 24) for acquiring alcohol concentration (ethanol concentration EC) of fuel, and internal combustion engine Load acquiring means (air flow sensor 23) for acquiring the load (intake air amount GAIRCYL) of 3 and fuel according to the acquired engine temperature parameter, alcohol concentration and load of the internal combustion engine 3 after the low temperature start of the internal combustion engine 3; As the injection mode, intake stroke injection, which injects fuel in the intake stroke, and injection of fuel in the compression stroke That selects one of the compression stroke injection control means for executing (ECU 2, step 9 in FIG. 2, FIG. 6), characterized in that it comprises a, a.

This internal combustion engine uses an alcohol-containing fuel and injects the fuel directly into the cylinder. Further, according to the control device of the internal combustion engine, an engine temperature parameter indicating the temperature of the internal combustion engine, the alcohol concentration of the fuel, and the load of the internal combustion engine are obtained. Then, after the low temperature start of the internal combustion engine, according to the acquired engine temperature parameter, alcohol concentration and load of the internal combustion engine, as the fuel injection mode, intake stroke injection that injects fuel in the intake stroke and fuel is injected in the compression stroke. One of the compression stroke injections to be selected is selected and executed.

As described above, after the low temperature start of the internal combustion engine, even if the temperature and the alcohol concentration of the internal combustion engine are the same condition, the injection mode in which the more stable combustion state can be obtained among the compression stroke injection and the intake stroke injection is It differs according to the load of the internal combustion engine. According to this configuration, the intake stroke injection or the compression stroke injection is selected according to the load of the internal combustion engine together with the engine temperature parameter and the alcohol concentration, so that a stable good combustion state is ensured after low temperature start of the internal combustion engine. be able to.

The invention according to claim 2 is the control apparatus for an internal combustion engine according to claim 1, wherein the control means is configured such that the temperature of the internal combustion engine represented by the engine temperature parameter is equal to or lower than a predetermined temperature TJUD and the alcohol concentration EC is a predetermined concentration If the load on the internal combustion engine is above a predetermined value (predetermined amount GAIRJUD) and the load on the internal combustion engine is less than a predetermined value, the intake stroke injection is performed (see FIG. Step 2 in FIG. 6, FIG. 6) is characterized.

Under the condition that the temperature of the internal combustion engine is lower than a predetermined temperature and the alcohol concentration is higher than a predetermined concentration (hereinafter referred to as "low temperature high concentration condition"), when obtaining a stable combustion state, the load of the internal combustion engine is relatively high. While compression stroke injection is suitable, it has been found that intake stroke injection is suitable when the load on the internal combustion engine is relatively low. The reason is estimated as follows.

That is, under low temperature and high concentration conditions, in addition to the high boiling point of the fuel due to the high alcohol concentration, the low temperature of the internal combustion engine makes it difficult for the fuel to vaporize. When the load of the internal combustion engine is high under such low temperature and high concentration conditions, the amount of fuel is large, and the degree to which the injected fuel becomes a liquid film on a piston in a low temperature state becomes high. Is further inhibited. If compression stroke injection is performed in such a situation, the fuel is injected at a higher temperature in the cylinder, and as a result, the formation of a liquid film of the fuel is suppressed and the vaporization of the fuel is promoted, resulting in a stable combustion state. Is estimated to be obtained. On the other hand, when the load of the internal combustion engine is low under high temperature and high concentration conditions, the amount of fuel is small, and the degree to which the injected fuel is converted to a liquid film is low. Is relatively small, and as a result, it is estimated that a stable combustion state can be obtained by the intake stroke injection.

The second aspect of the present invention is based on the above viewpoints, and performs compression stroke injection when the load of the internal combustion engine is equal to or higher than a predetermined value corresponding to a high load condition under low temperature and high concentration conditions. When it is less than the predetermined value, the intake stroke injection is performed, so that the compression stroke injection or the intake stroke injection can be appropriately selected according to the load of the internal combustion engine, and hence stable and good combustion state can be achieved after cold start of the internal combustion engine. It can be obtained surely.

The invention according to claim 3 is the control apparatus for an internal combustion engine according to claim 1 or 2, wherein the fuel injection amount GFUEL is increased when the fuel injection mode is switched from intake stroke injection to compression stroke injection. It is characterized by further comprising injection amount increasing / decreasing means (ECU 2, steps 33 to 35 in FIG. 13) for reducing the fuel injection amount GFUEL when the compression stroke injection is switched to the intake stroke injection.

When the fuel injection mode is switched, the fuel injection timing changes rapidly, so the degree of homogenization of the mixture of the injected fuel and air changes, and the combustion efficiency changes accordingly. For example, when the injection mode is switched to the compression stroke injection, the homogenization is insufficient because the generation time of the mixture is short, and local rich and the like in which the fuel is unevenly distributed in the cylinder tends to occur, and the combustion efficiency decreases. As a result, the air-fuel ratio becomes substantially lean, leading to a decrease in the output of the internal combustion engine. When the injection mode is switched to the intake stroke injection, the operation characteristic reverse to the above is obtained.

According to this configuration, the fuel injection amount is increased when the fuel injection mode is switched to the compression stroke injection, and the fuel injection amount is decreased when the fuel injection mode is switched to the intake stroke injection. It is possible to properly compensate for the fluctuation of the air-fuel ratio accompanying with the above and secure the required output of the internal combustion engine.

The invention according to claim 4 is the control apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the control means executes compression stroke injection at the time of low temperature start of the internal combustion engine 3 and has a high alcohol concentration. It is characterized in that the fuel injection timing is set to be more retarded (step 4 in FIG. 2, FIGS. 3 to 5).

According to this configuration, at the time of low temperature start of the internal combustion engine, the compression stroke injection is performed, and the fuel injection timing is set more retarded as the alcohol concentration becomes higher. Thus, the higher the alcohol concentration, that is, the lower the degree of vaporization of the fuel, the more fuel vaporization is promoted by injecting the fuel in a state where the in-cylinder temperature is higher. A stable combustion state can be secured, and low temperature startability can be improved.

It is a figure showing an internal combustion engine and its control device to which the present invention is applied. It is a flow chart which shows control processing of fuel injection time. It is a starting time map for calculating the injection end time at the time of starting. FIG. 4 is a diagram of the start-up map of FIG. 3; It is a figure which shows the relationship between the ethanol concentration in the low temperature conditions of the starting time map of FIG. 3, and the injection end time. It is a warming up operation map for calculating the injection end time at the time of warming up operation. It is a figure which shows the relationship of the injection timing and the torque of an internal combustion engine in low-temperature heavy load conditions. It is a figure which shows the relationship between ethanol concentration, a combustion fluctuation rate, etc. when the intake stroke injection is performed in low temperature and high load conditions. It is a figure similar to FIG. 8 when compression-stroke injection is performed in low temperature and high load conditions. FIG. 10 is a view similar to FIG. 8 and FIG. 9 when an intake stroke injection and a compression stroke injection are used selectively with a threshold value under the low temperature and high load condition. It is a map at the time of normal operation for calculating the injection end time at the time of normal operation. It is a timing chart which shows the operation example obtained by control processing of FIG. It is a flowchart which shows the correction | amendment process of the fuel injection quantity accompanying switching of the injection mode. 14 is a timing chart showing an example of calculation of a fuel correction amount by the correction processing of FIG. 13;

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an internal combustion engine (hereinafter referred to as "engine") 3 to which the present invention is applied and its control device. The engine 3 is mounted on a vehicle (not shown), and can use a mixture of ethanol and gasoline as a fuel containing alcohol.

The engine 3 is, for example, a four-cylinder engine having four cylinders 3a (only one shown). A combustion chamber 3d is formed between a piston 3b and a cylinder head 3c of each cylinder 3a, and a fuel injection valve 4 and an ignition plug 5 are provided in the cylinder head 3c for each cylinder 3a. The fuel is directly injected from the fuel injection valve 4 into the combustion chamber 3d. Further, the fuel injection valve 4 and the ignition plug 5 are electrically connected to the ECU (electronic control unit) 2, and the injection amount and injection timing of the fuel from the fuel injection valve 4 and the ignition timing of the ignition plug 5 It is controlled by the control signal from.

A throttle valve 7 is provided in the intake passage 6. The throttle valve 7 has a butterfly valve element 7a and a TH actuator 7b for driving the valve element 7a. The TH actuator 7b is driven by a control signal from the ECU 2, whereby the opening degree of the valve body 7a is controlled, and the amount of air sucked into the cylinder 3a is controlled.

The engine 3 is provided with various sensors 21 to 24 shown below, and their detection signals are inputted to the ECU 2.

The crank angle sensor 21 outputs a CRK signal as a pulse signal and a TDC signal as the crankshaft 3 e of the engine 3 rotates. The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 calculates the number of revolutions NE of the engine 3 (hereinafter referred to as "the number of engine revolutions") based on the CRK signal. The TDC signal is a signal representing that the piston 3b is in the vicinity of TDC (intake air TDC) at the start of the intake stroke in any of the cylinders 3a, and when the engine 3 has four cylinders, it outputs power at every crank angle 180 °. Be done.

The water temperature sensor 22 detects an engine water temperature TW, which is the temperature of cooling water circulating in the cylinder block of the engine 3. Further, the air flow sensor 23 detects the amount of air GAIR flowing through the intake passage 6. The ECU 2 calculates an intake air amount GAIRCYL which is an air amount sucked into each cylinder 3a based on the detection signal.

The ethanol concentration sensor 24 is provided in the middle of a fuel passage (not shown) connected to the fuel injection valve 4 and the fuel tank, and detects the ethanol concentration EC of the fuel. Note that, for convenience of explanation, a fuel having an ethanol concentration EC of ○% is appropriately described as "E 燃料 fuel".

The ECU 2 is constituted by a microcomputer including a CPU, a RAM, a ROM, an E2PROM, an I / O interface (all not shown) and the like, and based on the detection signals of the various sensors 21 to 24 described above, Various engine control processes are executed according to the stored control program. In the present embodiment, the ECU 2 corresponds to the control means and the injection amount increasing and decreasing means.

FIG. 2 shows the control processing of the fuel injection timing executed by the ECU 2. In this process, the operating state including the time of starting the engine 3 is determined, and the injection end timing EOI is set as the fuel injection timing according to the determined operating state. This process is repeatedly performed in synchronization with the generation of the TDC signal.

In this process, first, in step 1 (shown as “S1”; the same applies to the following), it is determined whether the engine 3 is starting. In this case, "under starting" refers to a period from the start of cranking to the time when the engine speed NE completely rises above the predetermined idle speed. As a result of this determination, when the engine 3 is starting, the in-cylinder temperature counter value CT described later is incremented (step 2), and the predetermined engine speed NE is lower than the idle speed. It is determined whether or not it is smaller (step 3). If the answer is YES, the process proceeds to step 4 to execute start control and end the present process.

In this startup control, the injection end timing EOI is calculated by searching the startup map shown in FIG. 3 according to the detected engine coolant temperature TW and ethanol concentration EC. The start-up map is obtained by setting the injection end timing EOI with respect to the engine coolant temperature TW and the ethanol concentration EC so as to obtain good startability (for example, the shortest start-up time).

As shown in FIG. 4, in this start-up map, the injection end timing EOI is set within the compression stroke regardless of the engine coolant temperature TW and the ethanol concentration EC. That is, at the time of start, compression stroke injection for injecting fuel in the compression stroke is performed. It has been confirmed that, at the time of start-up, regardless of the engine coolant temperature TW and the ethanol concentration EC, a better startability can be obtained in the compression stroke injection than in the intake stroke injection in which the fuel is injected in the intake stroke. It is for.

Further, the injection end timing EOI is set to be more retarded as the engine coolant temperature TW is lower. This is because as the engine coolant temperature TW is lower, the fuel is less likely to be vaporized and the combustion state is likely to be deteriorated. Therefore, the fuel is injected with the in-cylinder temperature higher by delaying the injection end timing EOI. This is to promote the vaporization of the fuel.

Further, FIG. 5 shows the relationship between the ethanol concentration EC and the injection end timing EOI when the engine coolant temperature TW is at a constant low temperature condition (for example, 0 ° C.) from the start-up map. As also shown in FIG. 5, the injection end timing EOI is set more retarded so as to approach the compression TDC as the ethanol concentration EC is higher. This is because the higher the ethanol concentration EC, the higher the boiling point of the fuel, the less the fuel is vaporized and the combustion state is apt to deteriorate, so the injection end timing EOI is later than in the case of the engine water temperature TW described above. By doing this, the fuel is injected in a state where the in-cylinder temperature is higher to promote the vaporization of the fuel.

Referring back to FIG. 2, when the answer to step 3 is NO, and the engine rotational speed NE ≧ the predetermined rotational speed NREF holds, the engine rotational speed NE is considered to have risen to some extent, and the process proceeds to step 5 until the start is completed. Transition control is executed, and this processing ends.

In this transition control, the injection end timing EOI, which has been set within the compression stroke at the time of start-up, is advanced toward the target value within the intake stroke after the start is completed. More specifically, for example, as shown in FIG. 12, in the case of fuel E0 to E64 having a low ethanol concentration EC, since the low temperature startability is high, the injection end timing EOI corresponds to the intake stroke at the start of transition control. It will be instantly changed to the target value within. On the other hand, in the case of E85 fuel or E100 fuel having a high ethanol concentration, since the low temperature startability is low, the injection end timing EOI is gradually changed toward the target value in the intake stroke. Thus, it is possible to smoothly shift the injection end timing EOI to the target value after the start is completed while securing a stable low temperature startability.

Returning to FIG. 2, when the answer to step 1 is NO and the start of the engine 3 is completed, it is determined whether the engine water temperature TW is lower than a predetermined temperature TJUD (for example, 0 ° C.) (step 6) . If the answer is YES, it is determined that the engine 3 has been cold started, and then the in-cylinder temperature counter value CT is incremented (step 7) as in the case of step 2 and the in-cylinder temperature counter value CT is predetermined. It is determined whether the threshold value CJUD or more (step 8).

The in-cylinder temperature counter value CT is reset to 0 by an unshown process when the ignition switch is turned on, and is incremented in steps 2 and 7. Therefore, the in-cylinder temperature counter value CT generally indicates the number of combustions of the engine 3 from the start start time, and when the engine 3 is started at low temperature, the increase amount of the in-cylinder temperature by the combustion from the start start time Represent. Therefore, when the answer to step 8 is NO, and the in-cylinder temperature counter value CT has not reached the threshold value CJUD, the in-cylinder temperature does not rise to the temperature corresponding to the completion of the warm-up. If it is determined that the warm-up operation is being performed, the process proceeds to step 9, the warm-up operation control is executed, and the present process is ended. The warm-up operation includes a low-load warm-up idle operation following a low-temperature start and a high-load warm-up drive operation when the vehicle travels.

On the other hand, if the answer to step 8 is YES and the in-cylinder temperature counter value CT has reached the threshold value CJUD, it is determined that the warm-up operation has ended, and the process proceeds to step 10 to execute normal operation control. This process ends. Also, when the answer to step 6 is NO and the engine 3 is not cold started, the process proceeds to step 10 to execute normal operation control.

In the warm-up operation control of the step 9, the injection end timing EOI is retrieved by searching the warm-up operation map shown in FIG. 6 according to the engine water temperature TW, the ethanol concentration EC, the engine speed NE and the intake air amount GAIRCYL. Calculate This warm-up operation map secures combustion stability during warm-up operation (cold condition) of the engine 3 and suppresses the amount of oil dilution (the amount of ethanol mixed in the engine oil) and the amount of soot generation The injection end timing EOI is set for the above four input parameters from the viewpoint of

In this warm-up operation time map, the engine water temperature TW is lower than a predetermined temperature TJUD (for example, 0 ° C.) corresponding to a low temperature state (low temperature condition), and the predetermined concentration EJUD (for example 75%) corresponding to a high concentration state of ethanol The injection end timing EOI is set within the compression stroke when the above (high concentration condition) and the intake air amount GAIRCYL is equal to or higher than the predetermined amount GAIRJUD corresponding to the high load condition (high load condition). Thus, the compression stroke injection is performed. On the other hand, in the warm-up operation map, when at least one of the low temperature condition, the high concentration condition and the high load condition is not satisfied, the injection end timing EOI is set within the intake stroke. Is executed.

As described above, during the warm-up operation, the compression stroke injection or the intake stroke injection is selectively performed in accordance with the above-described conditions. The reason will be described below. FIG. 7 is obtained when the fuel injection timing is changed from the intake stroke to the compression stroke under the low temperature, high concentration, high load conditions where the engine water temperature TW, the ethanol concentration EC, and the intake air amount GAIRCYL satisfy the above conditions, respectively. The torque (engine torque) TRQ of the engine 3 is illustrated. As shown in the figure, when the intake stroke injection is performed, it can be seen that the engine torque TRQ is 0, the engine 3 is misfired, and a combustion failure occurs. This is because fuel having a high ethanol concentration EC is inherently difficult to vaporize, and when intake stroke injection is performed under low temperature and high load conditions, the fuel becomes a liquid film on piston 3 b in a low temperature state, etc. It is presumed that the fuel is less likely to be vaporized.

On the other hand, when compression stroke injection is performed, a large engine torque TRQ is generated, and it can be seen that good combustibility is obtained. This is because the in-cylinder temperature is higher in the compression stroke than in the intake stroke, and therefore, when the compression stroke injection is performed under the low temperature and high load condition, the film formation of fuel on the piston 3b occurs as in the intake stroke injection. It is presumed that the combustion state is improved by promoting the vaporization of the fuel.

Also, FIGS. 8 and 9 show (a) the combustion fluctuation rate RCC, (b) the amount of generation with respect to the ethanol concentration EC, obtained when the intake stroke injection and the compression stroke injection are respectively performed under the low temperature and high load conditions. The relationship between QS, (c) oil dilution amount (hereinafter referred to as "OD amount") QOD, and (d) injection end timing EOI is shown.

As shown in FIG. 8, in the case of intake stroke injection, the combustion fluctuation rate RCC is sufficiently smaller than the judgment value RCCJ in the region where the ethanol concentration EC is less than about 85%, while the ethanol concentration EC is In a region larger than about 85%, it rapidly increases and exceeds the judgment value RCCJ. The soot generation amount QS is sufficiently smaller than the judgment value QSJ in the entire region of the ethanol concentration EC. Also, the OD amount QOD may exceed the determination value QODJ in a region where the ethanol concentration EC is larger than about 85%.

On the other hand, as shown in FIG. 9, in the case of compression stroke injection, the combustion fluctuation rate RCC tends to increase slightly in the region where the ethanol concentration EC is larger than about 60%, but the total ethanol concentration EC It is very small in the region and sufficiently below the judgment value RCCJ. The soot generation amount QS is very large in the region where the ethanol concentration EC is smaller than about 60%, and exceeds the judgment value QSJ, whereas it is almost zero in the region larger than about 60%. Further, the OD amount QOD is sufficiently smaller than the judgment value QODJ in the entire region of the ethanol concentration EC.

In FIG. 10, based on the results of FIG. 8 and FIG. 9 described above, intake stroke injection is performed on the lower concentration side than the predetermined concentration EJUD (for example, 75%) as a threshold, and compression stroke injection is performed on the high concentration side. Shows the results obtained when the From FIG. 10, by switching between the intake stroke injection and the compression stroke injection, the combustion fluctuation rate RCC is sufficiently lower than the determination value RCCJ in the entire range of the ethanol concentration EC, and a good combustion state is secured. It is understood that the soot generation amount QS and the OD amount QOD are sufficiently lower than the respective determination values QSJ and QODJ, and are suppressed.

Returning to FIG. 2, in the normal operation control of step 10, the injection end timing EOI is obtained by searching the normal operation map shown in FIG. 11 according to the engine water temperature TW, the engine speed NE and the intake air amount GAIRCYL. calculate. During normal operation, since the engine 3 is in a high temperature state, it is possible to secure combustion stability by intake stroke injection. Therefore, in the normal operation time map, the injection end timing EOI is set within the intake stroke regardless of the intake air amount GAIRCYL or the like, whereby the intake stroke injection is always performed during the normal operation.

FIG. 12 shows an operation example when the engine 3 is started at a low temperature, which is obtained by the control processing of the fuel injection timing of FIG. 2 described above. First, assuming that cranking for starting the engine 3 is started at time t1, the start control (step 4) is executed until the engine speed NE reaches the predetermined speed NJUD (t1 to t2). Be done. In this start-up control, the injection end timing EOI is set within the compression stroke according to the start-up map of FIG. 3 and compression stroke injection is executed, and the injection end timing EOI is slower as the ethanol concentration EC is higher. It is set on the corner side. Further, the in-cylinder temperature counter value CT is incremented from the start of the start.

Thereafter, transition control (step 5) is executed until the start of the engine 3 is completed (t2 to t3). As described above, in this transition control, the injection end timing EOI set within the compression stroke in the start control is immediately for E0 to E64 fuel, and gradually for E85 fuel and E100 fuel. Is changed to the target value in the intake stroke after completion of the start.

When starting of the engine 3 is completed, warm-up control (step 9) is executed, and the injection end timing EOI is set according to the warm-up operation map of FIG. In this example, since the low load warm-up idle operation is performed following the completion of the start (t3 to t4), the injection end timing EOI is set within the intake stroke during this period, and the intake stroke injection is executed. .

Thereafter, when transitioning from warm-up idle operation to high-load warm-up operation (t4), in the case of fuel E0 to E64, the above-described high concentration condition does not hold, so the injection end timing EOI is within the intake stroke. The intake stroke injection is continuously performed with values set according to the engine speed NE, the intake air amount GAIRCYL, and the like. On the other hand, in the case of E85 fuel and E100 fuel, the low temperature condition, the high concentration condition and the high load condition are all satisfied, so the injection end timing EOI depends on the engine speed NE in the compression stroke and the intake air amount GAIRCYL, etc. The compression stroke injection is performed.

Thereafter, when the in-cylinder temperature counter value CT reaches the threshold value CJUD (t5), it is determined that the warm-up operation is finished, and the normal operation control (step 10) is executed. In the normal operation control, the injection end timing EOI is set within the intake stroke according to the normal operation map of FIG. 11, and the intake stroke injection is performed. In this example, for the E85 fuel and the E100 fuel, the injection end timing EOI is held at the value at the end of the warm-up operation control from time t5 to t6, and thereafter, within the intake stroke according to the normal operation map Is changed to the value of (solid line). Alternatively, it is also possible to gradually change the injection end timing EOI in this case as shown by the broken line.

As described above, according to the present embodiment, in the warm-up operation after the low temperature start of the engine 3, the intake air corresponding to the load of the engine 3 in addition to the engine water temperature TW and the ethanol concentration EC representing the temperature of the engine 3 Since the intake stroke injection or the compression stroke injection is selected and executed according to the amount GAIRCYL, it is possible to ensure a stable good combustion state after the low temperature start of the engine 3.

More specifically, low temperature conditions in which the engine water temperature TW is equal to or lower than a predetermined temperature TJUD corresponding to a low temperature state, high concentration conditions in which the ethanol concentration EC is equal to or higher than a predetermined concentration EJUD corresponding to a high concentration state, and the intake air amount GAIRCYL When all the high load conditions equal to or higher than the predetermined amount GAIRJUD corresponding to the high load condition are satisfied, compression stroke injection is performed, while at least one of the low temperature condition, the high concentration condition and the high load condition is satisfied. When not, perform the intake stroke injection. As a result, the compression stroke injection or the suction stroke injection can be appropriately selected according to the load of the engine 3, and therefore, a stable, good combustion state can be reliably obtained after the engine 3 has been cold started. Further, as shown in FIG. 10, it is possible to sufficiently suppress the soot generation amount QS and the OD amount QOD particularly under the low temperature and high load condition.

Further, at the time of low temperature start of the engine 3, the compression stroke injection is performed, and the injection end timing EOI is set to be more retarded as the ethanol concentration EC is higher. As a result, fuel vaporization is promoted by injecting fuel in a state where the temperature in the cylinder is higher as the degree of vaporization of fuel is lower, so that a stable combustion state according to ethanol concentration EC can be secured. The cold startability can be improved.

Next, the fuel injection amount correction process will be described with reference to FIGS. 13 and 14. The present process is for compensating for the fluctuation of the air-fuel ratio accompanying the switching between the compression stroke injection and the intake stroke injection, and is repeatedly executed by the ECU 2 in synchronization with the generation of the TDC signal.

In this process, first, at step 21, it is judged if the compression stroke injection flag F_FCMP is equal to the previous value F_FCMPZ. The compression stroke injection flag F_FCMP is set to "1" when compression stroke injection is being performed, and is set to "0" when intake stroke injection is being performed, by a process not shown.

If the answer to this step 21 is NO, that is, if the current processing cycle corresponds immediately after the injection mode has switched from one of compression stroke injection and intake stroke injection to the other, correction of the fuel injection amount is to be performed. The fuel amount correction flag F_FCHG is set to "1" (step 22), and a counter value i representing the number of corrections is set to 1 (step 23). Next, the fuel correction amount CGF is set to a predetermined initial value CGINI (step 24), and the process proceeds to step 33 described later.

If the answer to step 21 is YES and it is not immediately after the switching of the injection mode, it is determined whether the fuel amount correction flag F_FCHG is "1" (step 25). If the answer is YES and the fuel injection amount is already being corrected, the counter value i is incremented (step 26), and it is determined whether the counter value i is less than or equal to a predetermined value NHLD (for example 2) 27). If the answer is YES, the fuel correction amount CGF is held at the previous value CGF (= initial value CGINI) (step 28), and the process proceeds to step 33.

If the answer to step 27 is NO, and the counter value i exceeds the predetermined value NHLD, a value obtained by subtracting the predetermined decrease amount ΔGF from the previous fuel correction amount CGF is set as the current fuel correction amount CGF (step 29). Next, it is determined whether the fuel correction amount CGF is larger than 0 (step 30). If the answer is YES, the process proceeds to step 33 as it is.

On the other hand, when the answer to step 30 is NO, and the fuel correction amount CGF becomes 0 or less, the fuel correction amount CGF is set to 0 (step 31), and the fuel injection amount correction is ended. The amount correction flag F_FCHG is set to "0" (step 32), and the process proceeds to step 33. In addition, after the step 32 is performed, the answer to the step 25 is NO, and in this case, the process proceeds to the step 33.

As a result of calculation as described above, the fuel correction amount CGF is set to a large initial value CGINI at the time of switching of the injection mode as shown in FIG. 14 and during the subsequent (NHLD-1) combustion cycles, After being held at the initial value CGINI, it decreases by a predetermined amount of reduction ΔGF every combustion cycle and converges to the value 0.

Referring back to FIG. 13, in step 33 following the

steps

24, 28, 30 or 32, it is determined whether the compression stroke injection flag F_FCMP is "1". If this answer is YES and the switching of the injection mode this time is the switching from the intake stroke injection to the compression stroke injection, the fuel correction amount CGF calculated as described above is used to calculate the fuel injection amount GFUEL by the following equation (1 ) (Step 34), and the present process ends.
GFUEL = GBS · KGF + CGF (1)

Here, GBS is a basic value of the fuel injection amount calculated according to the intake air amount GAIRCYL and the engine rotational speed NE, KGF is an air-fuel ratio correction coefficient for achieving the target air-fuel ratio, engine water temperature TW and It is a total correction coefficient obtained by mutually multiplying various correction coefficients according to the operating state of the engine 3 including the intake temperature and the like.

According to this equation (1), the fuel injection amount GFUEL is increased by the amount of the fuel correction amount CGF when switching to the compression stroke injection, so the air-fuel ratio fluctuation to the lean side accompanying this switching is appropriately compensated. And the required engine power can be secured.

On the other hand, if the answer to step 33 is NO, and the current injection mode switching is switching from compression stroke injection to intake stroke injection, the fuel correction amount CGF is used, and the fuel injection amount GFUEL is expressed by the following equation (2) The calculation is performed (step 35), and the process ends.
GFUEL = GBS · KGF-CGF ... (2)
According to this equation (2), the fuel injection amount GFUEL is decreased by the amount of the fuel correction amount CGF when switching to the intake stroke injection, so that the fluctuation of the air-fuel ratio to the rich side accompanying this switching is appropriately compensated. And the required engine power can be secured.

In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, in order to calculate the injection end timing EOI during warm-up operation, one warm-up operation map (FIG. 6) common to warm-up idle operation and warm-up drive operation is used. A map for driving may be created, and the corresponding map may be used according to the determined driving state. Further, in the embodiment, although the injection end timing EOI is calculated as the fuel injection timing, the present invention is not limited to this, and for example, the injection start timing may be calculated.

Further, in the correction process of the fuel injection amount in FIG. 13, the fuel correction amount CGF is calculated, and the fuel injection amount GFUEL is increased or decreased by adding or subtracting the product of the basic value GBS and the total correction coefficient KGF. Not limited to. For example, the fuel injection amount GFUEL is mapped to include the increase / decrease amount corresponding to the fuel correction amount CGF, and the fuel injection amount GFUEL is read directly from the map according to the TDC number from switching of the injection mode and the switching direction. You may do so. Further, the method of calculating the fuel correction amount CGF shown in the embodiment is merely an example, and the configuration of the details can be changed.

In the embodiment, the engine water temperature TW is used as the engine temperature parameter representing the temperature of the internal combustion engine, but instead, another appropriate parameter, for example, the intake temperature or oil temperature of the engine 3 is used It is also good. Furthermore, in the embodiment, the completion determination of the warm-up operation is performed based on the in-cylinder temperature counter value CT, but instead, it may be performed based on an engine temperature parameter such as the above engine water temperature TW. .

Similarly, in the embodiment, the intake air amount GAIRCYL is used as a parameter corresponding to the load of the engine 3, but instead, other appropriate parameters such as a fuel injection amount, a required torque, and an accelerator opening of the vehicle may be used. The degree or the like may be used. In the embodiment, the ethanol concentration EC is detected using the ethanol concentration sensor 24, but the operating parameter of the engine 3 having a high correlation with the ethanol concentration EC, for example, the feedback correction amount of the air fuel ratio or the detected air fuel ratio You may acquire by estimation from the magnitude | size of deviation of, etc.

Furthermore, in the embodiment, although a mixed fuel of ethanol and gasoline is used as the alcohol-containing fuel, it is needless to say that a mixed fuel of methanol and gasoline may be used. In addition, it is possible to change suitably the configuration of the details within the scope of the present invention.

2 ECU (control means, injection amount increase / decrease means)
3 Engine (internal combustion engine)
3a cylinder 10 fuel injection valve 22 water temperature sensor (means for acquiring engine temperature parameter)
23 Air flow sensor (load acquisition means)
24 Ethanol concentration sensor (alcohol concentration acquisition means)
TW engine water temperature (engine temperature parameter)
EC ethanol concentration (alcohol concentration)
GAIRCYL Intake air amount (load of internal combustion engine)
EOI injection end timing (fuel injection timing)
TJUD predetermined temperature EJUD predetermined concentration GAIRJUD predetermined amount (predetermined value)
GFUEL Fuel injection amount CGF Fuel correction amount

Claims

A control device for an internal combustion engine that uses a fuel containing alcohol and injects the fuel directly into a cylinder,
Engine temperature parameter acquisition means for acquiring an engine temperature parameter representing the temperature of the internal combustion engine;
Alcohol concentration acquisition means for acquiring the alcohol concentration of the fuel;
Load acquiring means for acquiring the load of the internal combustion engine;
After the low temperature start of the internal combustion engine, according to the acquired engine temperature parameter, alcohol concentration, and load of the internal combustion engine, as a fuel injection mode, intake stroke injection that injects fuel in the intake stroke and fuel is injected in the compression stroke Control means for selecting and executing one of the compression stroke injections
A control device for an internal combustion engine, comprising:
The control means performs the compression when the load of the internal combustion engine is equal to or higher than a predetermined value when the temperature of the internal combustion engine represented by the engine temperature parameter is lower than a predetermined temperature and the alcohol concentration is higher than a predetermined concentration. The control system for an internal combustion engine according to claim 1, wherein stroke injection is performed and the intake stroke injection is performed when a load of the internal combustion engine is less than the predetermined value.
When the fuel injection mode is switched from the intake stroke injection to the compression stroke injection, the fuel injection amount is increased, and when the compression stroke injection is switched from the intake stroke injection, the fuel injection amount is decreased The control device of an internal combustion engine according to claim 1 or 2, further comprising:
The control means executes the compression stroke injection at the time of low temperature start of the internal combustion engine, and sets the fuel injection timing to be more retarded as the alcohol concentration is higher. A control device for an internal combustion engine according to any one of 3 to 3.