JP2010037968A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve low temperature startability in a cylinder injection type engine when alcohol fuel (100% alcohol or mixed fuel containing alcohol). <P>SOLUTION: When alcohol concentration of the fuel is not less than prescribed concentration and cooling water temperature is not higher than prescribed temperature, it is judged that injected fuel is not easily gasified, start target fuel pressure is set to an appropriate value according to alcohol concentration of fuel and cooling water temperature, and fuel injection of a fuel injection valve 21 is started after raising actual fuel pressure to pressure close to the start target fuel pressure by a high pressure pump 31 in start of the engine 11. Although high pressure fuel is directly injected into a cylinder by the fuel injection valve 21 after fuel injection start, time from fuel injection to start of combustion is shortened to start combustion and accelerate gasification of injected fuel before much injected fuel adheres on a cylinder inside wall surface, a piston and the like by executing compression stroke injection in which fuel is injected in compression stroke during engine start or a prescribed period after engine start. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine provided with a fuel injection valve for in-cylinder injection.

  In recent years, in response to social demands such as CO2 emission reduction and the use of alternative fuels for oil, internal combustion engines that can use gasoline, alcohol (ethanol, methanol, etc.), and alcohol-mixed fuels that are a mixture of gasoline and alcohol can be used as fuels. The demand for onboard vehicles is increasing. However, alcohol has a larger latent heat of vaporization than gasoline and is difficult to vaporize at low temperatures. Therefore, when alcohol fuel (100% alcohol or mixed fuel containing alcohol) is used, the low-temperature startability of the internal combustion engine deteriorates. There is a problem of doing.

  As a countermeasure against this, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-214415), a dual-injection type equipped with both a fuel injection valve for intake passage injection and a fuel injection valve for in-cylinder injection is used. In the internal combustion engine, when the alcohol concentration of the fuel is equal to or higher than a predetermined value and the temperature of the internal combustion engine (for example, cooling water temperature) is lower than the predetermined value, the fuel injection of the fuel injection valve for intake passage injection is stopped, and the in-cylinder injection In some cases, high-pressure fuel is directly injected into a cylinder with a fuel injection valve for atomizing the injected fuel to make it easier to vaporize.

  Further, as described in Patent Document 2 (Japanese Patent Laid-Open No. 4-214965), in an intake passage injection type internal combustion engine, the lower one of the temperature of the fuel and the temperature of the internal combustion engine is set to Compared with the startable determination temperature set based on the alcohol concentration, it is determined whether or not the start is possible, and if it is determined that the start is difficult, the injected fuel is easily heated and vaporized by the heater disposed in the intake passage There are also things to do.

In general, in-cylinder injection internal combustion engines supply high pressure fuel to a fuel injection valve by a high-pressure pump driven by a camshaft, so that the fuel pressure (fuel pressure) is suitable for starting when the internal combustion engine is started. It takes some time to rise to the area. Therefore, as described in Patent Document 3 (Japanese Patent Laid-Open No. 2003-328816), when the internal combustion engine is started, the fuel pressure is increased to a set fuel pressure suitable for starting by a high-pressure pump, and then fuel injection is started. There is one that performs boost start control.
JP 2006-214415 A JP-A-4-214965 JP 2003-328816 A

  In general, since the theoretical air-fuel ratio of alcohol is smaller than that of gasoline, it is necessary to increase the fuel injection amount when alcohol fuel is used. In the technique of Patent Document 1, when the alcohol concentration of the fuel is equal to or higher than a predetermined value and the temperature of the internal combustion engine is equal to or lower than the predetermined value, the fuel is directly injected into the cylinder by the fuel injection valve for in-cylinder injection. However, when alcohol fuel is used, it is necessary to increase the fuel injection amount, so if the time from when the fuel is injected until combustion is started is long, a lot of injected fuel is Combustion may start after adhering to a piston or the like. For this reason, wet fuel adhering to the cylinder inner wall surface, piston, etc. may increase, and low temperature startability may deteriorate, and the amount of wet fuel flowing down from the gap between the cylinder inner wall surface and the piston to the oil pan increases. Engine oil can be diluted with alcohol fuel and deteriorate.

  Further, the technique disclosed in Patent Document 2 has a drawback that it is not possible to meet the demand for cost reduction, which is an important technical problem in recent years, because it is necessary to provide a heater for heating the injected fuel.

  In the technique disclosed in Patent Document 3, in a cylinder injection internal combustion engine, when starting the internal combustion engine, the fuel pressure is increased to a set fuel pressure suitable for starting by a high-pressure pump and then fuel injection is started. However, the use of alcohol fuel is not assumed, and the fuel vaporization characteristics change depending on the alcohol concentration of the fuel and the temperature of the internal combustion engine, and the fuel pressure suitable for starting changes completely. Therefore, when applied to a system using alcohol fuel, the injected fuel cannot be sufficiently atomized, and the cold startability may deteriorate.

  The present invention has been made in consideration of these circumstances. Therefore, the object of the present invention is to improve the low-temperature startability when alcohol fuel is used while satisfying the demand for cost reduction. An object of the present invention is to provide an engine fuel injection control device.

  In order to achieve the above object, the invention according to claim 1 is directed to a fuel injection control device for an internal combustion engine having a fuel injection valve for in-cylinder injection, wherein the alcohol concentration of the fuel supplied to the fuel injection valve is determined as the alcohol concentration. It is detected or estimated by the judging means, and the temperature of the internal combustion engine or information related thereto (hereinafter referred to as “engine temperature etc.”) is detected or estimated by the engine temperature judging means, and the start injection control means The fuel injection end timing of the fuel injection valve is set to the compression stroke during the start of the internal combustion engine and / or for a predetermined period after the start when the alcohol concentration of the engine is equal to or higher than the predetermined value and the engine temperature is lower than the predetermined value. Is.

  In this configuration, the fuel injection valve for in-cylinder injection directly injects high-pressure fuel into the cylinder, so that the injected fuel can be atomized and easily vaporized. However, the alcohol concentration of the fuel exceeds a predetermined value. When the engine temperature or the like (for example, the cooling water temperature) is lower than a predetermined value, it is determined that the injected fuel is difficult to vaporize, and the fuel injection end timing is set to the compression stroke during a predetermined period during or after the internal combustion engine is started. Since the fuel can be injected mainly in the compression stroke, the time from the fuel injection to the start of combustion is shortened compared to the case where the fuel is injected in the intake stroke. Before the injected fuel adheres to the cylinder inner wall surface, the piston, or the like, combustion can be started to promote vaporization of the injected fuel. Thereby, even when alcohol fuel (100% alcohol or mixed fuel containing alcohol) is used, the wet fuel adhering to the inner wall surface of the cylinder, the piston, and the like can be reduced, and the low temperature startability can be improved. The amount of wet fuel flowing down from the gap between the cylinder inner wall surface and the piston to the oil pan can be reduced, and the dilution of engine oil can be reduced. In addition, since there is no need to provide a heater or the like for heating the injected fuel, it is possible to satisfy the demand for cost reduction, which is an important technical issue in recent years.

  In general, as the alcohol concentration of the fuel becomes higher, the fuel becomes harder to vaporize and as the temperature of the internal combustion engine becomes lower, the fuel becomes harder to vaporize. Therefore, as the alcohol concentration of the fuel becomes higher and / or the engine as in claim 2. The lower the temperature or the like, the closer the fuel injection end timing of the fuel injection valve is to the compression top dead center. In this way, the fuel injection timing is brought closer to the compression top dead center (that is, near the ignition timing) and the time from when the fuel is injected until the start of combustion is shortened so that the fuel is less likely to vaporize. It is possible to increase the wet fuel reduction effect.

  According to a third aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine which supplies a high pressure fuel to a fuel injection valve for in-cylinder injection with a high pressure pump. The temperature is detected or estimated by the concentration determining means, and the temperature of the internal combustion engine or information related thereto (hereinafter referred to as “engine temperature etc.”) is detected or estimated by the engine temperature determining means and supplied to the fuel injection valve. The fuel pressure (hereinafter referred to as “fuel pressure”) is detected by the fuel pressure detection means, the target fuel pressure at start is set by the start target fuel pressure setting means according to the alcohol concentration of the fuel and the engine temperature, etc. When starting, the fuel injection of the fuel injection valve may be prohibited by the injection prohibiting means until the difference between the starting target fuel pressure and the fuel pressure detected by the fuel pressure detecting means becomes a predetermined value or less.

  In this configuration, when the internal combustion engine is started, the fuel injection can be started after the fuel pressure is raised to the target fuel pressure at the start by the high pressure pump. In this case, in the present invention, since the target fuel pressure at start-up can be set according to the alcohol concentration of the fuel, the engine temperature, etc., the vaporization characteristic of the fuel changes depending on the alcohol concentration of the fuel and the temperature of the internal combustion engine. Corresponding to the change of the appropriate fuel pressure, the target fuel pressure at start-up can be set to an appropriate fuel pressure. As a result, even when alcohol fuel is used, the injected fuel can be sufficiently atomized to promote vaporization, and the low-temperature startability can be improved.

  In this case, it is preferable that the target fuel pressure at start-up is increased as the alcohol concentration of the fuel increases and / or as the engine temperature or the like decreases. In this way, the target fuel pressure at the time of starting can be increased and the injected fuel can be further atomized as the fuel is harder to vaporize, and the vaporization promotion effect of the injected fuel can be enhanced.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the cylinder injection engine 11 which is a cylinder injection internal combustion engine, and a throttle valve whose opening is adjusted by a motor 14 on the downstream side of the air cleaner 13. 15 and a throttle opening sensor 16 for detecting the opening of the throttle valve 15 (throttle opening).

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake manifold 18 for introducing air into each cylinder of the engine 11 is provided in the surge tank 17. An intake air temperature sensor 19 that detects intake air temperature is provided upstream of the throttle valve 15, and an intake pipe pressure sensor 20 that detects intake pipe pressure is provided downstream of the throttle valve 15.

  A fuel injection valve 21 that directly injects fuel into the cylinder is attached to each cylinder of the engine 11. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each ignition plug 22. On the other hand, the exhaust pipe 23 of the engine 11 is provided with a catalyst 24 such as a three-way catalyst for purifying exhaust gas.

  Further, the cylinder block of the engine 11 has a coolant temperature sensor 25 (engine temperature determination means) that detects coolant temperature (engine temperature information), and a crank angle that outputs a pulse signal every time the crankshaft rotates a predetermined crank angle. A sensor 26 is attached, and a crank angle and an engine rotation speed are detected based on an output signal of the crank angle sensor 26. Further, the accelerator operation amount (depressed amount of the accelerator pedal) is detected by the accelerator sensor 27.

  The engine 11 can use any of gasoline, alcohol (ethanol, methanol, etc.), and alcohol mixed fuel obtained by mixing alcohol in gasoline as fuel, and any one of these gasoline, alcohol, alcohol mixed fuel can be refueled. The engine 11 is supplied. A low pressure pump 29 that pumps up the fuel is installed in the fuel tank 28 that stores the fuel. The low-pressure pump 29 is driven by an electric motor (not shown) that uses a battery (not shown) as a power source. The fuel discharged from the low pressure pump 29 is supplied to the high pressure pump 31 through the fuel pipe 30. The high pressure pump 31 is driven by the cam shaft of the engine 11. The fuel discharged from the high-pressure pump 31 is sent to the delivery pipe 32, and the high-pressure fuel is distributed from the delivery pipe 32 to the fuel injection valve 21 of each cylinder. The delivery pipe 32 is provided with a fuel pressure sensor 33 (fuel pressure detection means) that detects the fuel pressure (fuel pressure) in the delivery pipe 32.

  The delivery pipe 32 is provided with a relief valve 34, and a discharge port of the relief valve 34 is connected to the fuel tank 28 via a return pipe 35. The relief valve 34 is an electromagnetic drive type that can control the open / close state, and the fuel pressure in the delivery pipe 32 is held when the relief valve 34 is closed. When the relief valve 34 is opened, part of the fuel in the delivery pipe 32 is returned to the fuel tank 28 through the return pipe 35, and the fuel pressure in the delivery pipe 32 decreases.

  Further, an alcohol concentration sensor 36 (alcohol concentration determination means) for detecting the alcohol concentration of the fuel is provided at an appropriate location in the fuel supply system from the fuel tank 28 to the fuel injection valve 21. In this embodiment, an alcohol concentration sensor 36 is provided in the fuel pipe 30 that connects the low pressure pump 29 and the high pressure pump 31. The alcohol concentration sensor 36 may be any type of alcohol concentration sensor. For example, a capacitance-type alcohol concentration sensor that detects the alcohol concentration by measuring the capacitance according to the dielectric constant of the fuel. Alternatively, an optical (transmission type) alcohol concentration sensor that measures the amount of light transmitted through the fuel (transmittance) to detect the alcohol concentration may be used.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 37. The ECU 37 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 21 can be changed according to the engine operating state. The ignition timing of the spark plug 22 is controlled.

Further, the ECU 37 performs a start injection control as follows by executing a start injection control routine of FIG. 2 described later.
When the alcohol concentration of the fuel is equal to or higher than the predetermined concentration and the coolant temperature (engine temperature information) is equal to or lower than the predetermined temperature, it is determined that the injected fuel is difficult to vaporize, and when the engine 11 is started, The fuel injection of the fuel injection valve 21 is prohibited until the difference from the actual fuel pressure (the fuel pressure detected by the fuel pressure sensor 33) becomes a predetermined value or less, and the fuel pressure is increased to the vicinity of the target fuel pressure at the start by the high-pressure pump 31. Start jetting. At that time, by setting the target fuel pressure at start-up according to the alcohol concentration of the fuel and the coolant temperature, the fuel vaporization characteristics change according to the alcohol concentration of the fuel and the engine temperature, so that the fuel pressure suitable for start-up changes Then, set the target fuel pressure at start to an appropriate value.

  After the fuel injection is started, the fuel injection valve 21 directly injects high-pressure fuel into the cylinder, whereby the injected fuel can be atomized and easily vaporized. However, the alcohol concentration of the fuel is higher than a predetermined concentration and is cooled. When the water temperature is equal to or lower than the predetermined temperature, it is determined that the injected fuel is difficult to vaporize, and during the predetermined period after the engine is started and after the engine is started, the compression stroke injection for injecting the fuel in the compression stroke is performed. Compared to the case where fuel is injected in the stroke, the time from when the fuel is injected until the start of combustion is shortened, and combustion is started before much injected fuel adheres to the cylinder inner wall surface, piston, etc. To accelerate the vaporization of the injected fuel.

The processing contents of the start injection control routine of FIG. 2 executed by the ECU 37 will be described below.
The start injection control routine shown in FIG. 2 is executed at a predetermined cycle while the ECU 37 is turned on, and serves as a start injection control means in the claims. When this routine is started, first, in step 101, the alcohol concentration of the fuel detected by the alcohol concentration sensor 36 is read, and the cooling water temperature detected by the cooling water temperature sensor 25 is read.

  Thereafter, the routine proceeds to step 102, where it is determined whether or not the injected fuel is in a region that is difficult to vaporize depending on whether or not the alcohol concentration of the fuel is equal to or higher than a predetermined concentration and the coolant temperature is equal to or lower than the predetermined temperature. The predetermined temperature for determining the cooling water temperature may be changed according to the alcohol concentration of the fuel.

  If it is determined in step 102 that the alcohol concentration of the fuel is equal to or higher than the predetermined concentration and the cooling water temperature is equal to or lower than the predetermined temperature (the injected fuel is a region that is difficult to vaporize), the process proceeds to step 103 and the compression stroke injection is performed. After the flag is turned on, the fuel injection timing corresponding to the alcohol concentration of the fuel and the coolant temperature is set with reference to the fuel injection timing setting map shown in FIG.

  Here, the map for setting the fuel injection timing in FIG. 3 shows that the region where the alcohol concentration of the fuel is equal to or higher than the predetermined concentration and the cooling water temperature is equal to or lower than the predetermined temperature (that is, the region where the injected fuel is hard to vaporize) is the alcohol concentration of the fuel. It is divided into two areas A and B according to the cooling water temperature.

  In region A (region where the alcohol concentration is very high), the amount of increase in the fuel injection amount increases and the injection time becomes longer, so that the fuel injection start timing becomes the intake stroke and the fuel injection end timing becomes the compression stroke. The fuel injection timing is set to the intake / compression stroke injection for injecting fuel from the intake stroke to the compression stroke.

  In region B (region in which the alcohol concentration is lower than region A), the fuel injection timing is set so that both the fuel injection start timing and the fuel injection end timing are in the compression stroke, and the fuel is injected in the compression stroke. Set to inject. In this case, the fuel injection end timing is set closer to the compression top dead center as the alcohol concentration of the fuel increases, and the fuel injection end timing is set closer to the compression top dead center as the coolant temperature decreases.

  Thereafter, the routine proceeds to step 104, the boost start control flag is set to ON, and the target fuel pressure at start is set according to the alcohol concentration of the fuel and the cooling water temperature with reference to the map of the target fuel pressure at start in FIG. To do.

  Here, the map of the target fuel pressure at start-up in FIG. 4 shows that the region where the alcohol concentration of the fuel is equal to or higher than the predetermined concentration and the cooling water temperature is equal to or lower than the predetermined temperature (that is, the region where the injected fuel is difficult to vaporize) According to the water temperature, it is divided into a plurality of regions C to E, and the target fuel pressure at start is set for each of the regions C to E, so that the target fuel pressure at start is increased as the alcohol concentration of the fuel increases, and the cooling water temperature The lower the is, the higher the target fuel pressure at start is set. For example, in region E in FIG. 4, the target fuel pressure at start is set to 8 MPa, in region D the target fuel pressure at start is set to 12 MPa, and in region C, the target fuel pressure at start is set to 16 MPa. The process in step 104 serves as a starting target fuel pressure setting means in the claims.

  On the other hand, if it is determined in step 102 that the alcohol concentration of the fuel is lower than the predetermined concentration or the cooling water temperature is higher than the predetermined temperature, it is determined that the injected fuel is easily vaporized, and the process proceeds to step 105. After the compression stroke injection flag is reset to OFF, the fuel injection timing is set so that both the fuel injection start timing and the fuel injection end timing are the intake stroke, and the intake stroke injection for injecting fuel in the intake stroke is performed. Set as follows. In a region where the fuel injection amount is large, the fuel may be set to be injected in the compression stroke after being injected in the intake stroke. Thereafter, the process proceeds to step 106, and the boost start control flag is reset to OFF.

  Thereafter, the routine proceeds to step 107, where it is determined whether or not the engine is being started (cranking) or within a predetermined time after the engine is started (the elapsed time from completion of the engine start is within a predetermined time). Here, the predetermined time is set to a time shorter than the time required to complete the warm-up of the engine 11.

  If it is determined in step 107 that the engine is being started or within a predetermined time after the engine is started, the routine proceeds to step 108, where it is determined whether or not the boost start control flag is on. If it is determined in step 108 that the boost start control flag is ON, the process proceeds to step 109, the actual fuel pressure detected by the fuel pressure sensor 33 is read, and then the process proceeds to step 110, where the target fuel pressure at start and the actual fuel pressure are detected. It is determined whether or not the difference from the fuel pressure is smaller than the predetermined value. If it is determined that the difference between the target fuel pressure at start and the actual fuel pressure is greater than or equal to the predetermined value, the actual fuel pressure increases to near the target fuel pressure at start. If not, the process proceeds to step 111, and fuel injection is prohibited. The processing in step 111 serves as an injection prohibiting means in the claims.

  Thereafter, when it is determined in step 110 that the difference between the target fuel pressure at start and the actual fuel pressure is smaller than a predetermined value, it is determined that the actual fuel pressure has increased to near the target fuel pressure at start. Then, it is determined whether or not the compression stroke injection flag is ON. If it is determined that the compression stroke injection flag is ON, the process proceeds to step 113, and the compression stroke injection for injecting fuel in the compression stroke is executed (or Intake / compression stroke injection is performed in which fuel is injected from the intake stroke to the compression stroke). If it is determined in step 112 that the compression stroke injection flag is off, the routine proceeds to step 114 where the intake stroke injection is executed.

  On the other hand, if it is determined in step 108 that the boost start control flag is off, the routine proceeds to step 115, where it is determined whether or not the compression stroke injection flag is on, and the compression stroke injection flag is off. If it is determined that there is, the routine proceeds to step 116 where the intake stroke injection for injecting fuel in the intake stroke is executed. If it is determined in step 115 that the compression stroke injection flag is on, the process proceeds to step 117, and the compression stroke injection is executed.

An execution example of the start injection control of the present embodiment described above will be described with reference to the time charts of FIGS.
As shown in FIG. 5, when the alcohol concentration of the fuel is lower than the predetermined concentration, it is determined that the injected fuel is easily vaporized even when the cooling water temperature is lower than the predetermined temperature, and cranking of the engine 11 is started. Later, at the time t1 before the actual fuel pressure rises to the target fuel pressure during engine operation (for example, when the cylinder discrimination is completed), the fuel injection is permitted and the intake stroke injection is executed.

  On the other hand, as shown in FIG. 6, when the alcohol concentration of the fuel is equal to or higher than the predetermined concentration, it is determined that the injected fuel is difficult to vaporize at the time of low temperature start where the cooling water temperature is equal to or lower than the predetermined temperature. Later, fuel injection is prohibited until the difference between the target fuel pressure at start and the actual fuel pressure becomes a predetermined value or less. After that, at the time t2 when it is determined that the difference between the target fuel pressure at start and the actual fuel pressure is smaller than the predetermined value, it is determined that the actual fuel pressure has increased to near the target fuel pressure at start, and fuel injection is permitted and compression is performed. Perform stroke injection.

  At this time, in this embodiment, since the target fuel pressure at start-up is set according to the alcohol concentration of the fuel and the coolant temperature (engine temperature information), the fuel vaporization characteristics change depending on the alcohol concentration of the fuel and the engine temperature. Accordingly, the target fuel pressure at the start can be set to an appropriate value in response to the change in the fuel pressure suitable for the start. Thereby, even when alcohol fuel (alcohol or alcohol mixed fuel) is used, the injected fuel can be sufficiently atomized to promote vaporization, and the low-temperature startability can be improved.

  Furthermore, in this example, the higher the alcohol concentration of the fuel, the higher the target fuel pressure at start-up, and the lower the coolant temperature, the higher the target fuel pressure at start-up. The target fuel pressure at start-up can be increased, and the injected fuel can be further atomized, and the vaporization promotion effect of the injected fuel can be enhanced.

  Further, in this embodiment, when the alcohol concentration of the fuel is equal to or higher than the predetermined concentration and the cooling water temperature is equal to or lower than the predetermined temperature, it is determined that the injected fuel is difficult to vaporize, and a predetermined time elapses during and after the engine start. Since the compression stroke injection is performed until the fuel is injected, the time until the combustion is started after the fuel is injected is shortened compared to the intake stroke injection, so that much injected fuel is injected into the cylinder inner wall surface, the piston, etc. Before adhering to the fuel, combustion can be started to promote vaporization of the injected fuel. As a result, even when alcohol fuel is used, the wet fuel adhering to the cylinder inner wall surface and the piston can be reduced, the low temperature startability can be improved, and the wet fuel can be removed between the cylinder inner wall surface and the piston. The amount of oil flowing down from the oil pan to the oil pan can be reduced, and the dilution of the engine oil can be reduced. In addition, since there is no need to provide a heater or the like for heating the injected fuel, it is possible to satisfy the demand for cost reduction, which is an important technical issue in recent years.

  Further, in this embodiment, the fuel injection end timing is brought closer to the compression top dead center as the alcohol concentration of the fuel becomes higher, and the fuel injection end timing is brought closer to the compression top dead center as the cooling water temperature becomes lower. The more difficult it is to vaporize, the closer the fuel injection timing is to the compression top dead center (that is, near the ignition timing), and the time from fuel injection until combustion starts can be shortened. The reduction effect can be enhanced.

  In the above embodiment, when the alcohol concentration of the fuel is equal to or higher than the predetermined concentration and the cooling water temperature is equal to or lower than the predetermined temperature, a predetermined period during the engine start and after the engine start (a period until a predetermined time elapses after the engine start is completed). ), The compression stroke injection may be performed only during engine startup, or the compression stroke injection may be performed only during a predetermined period after engine startup.

  In the above embodiment, the target fuel pressure at start-up is increased as the alcohol concentration of the fuel increases, and the target fuel pressure at start-up is increased as the coolant temperature decreases. However, the alcohol concentration of the fuel increases or the coolant temperature increases. The target fuel pressure at start-up may be increased as the value decreases.

  Further, in the above embodiment, the fuel injection end timing is brought closer to the compression top dead center as the alcohol concentration of the fuel becomes higher, and the fuel injection end timing is brought closer to the compression top dead center as the cooling water temperature becomes lower. The higher the alcohol concentration or the lower the coolant temperature, the closer the fuel injection end time is to the compression top dead center.

  In the above embodiment, the coolant temperature detected by the coolant temperature sensor 25 is used as the engine temperature information. However, the oil temperature, the intake air temperature, etc. may be used instead of the coolant temperature. Alternatively, the engine temperature may be estimated based on one or more of the cooling water temperature, the oil temperature, the intake air temperature, and the like.

  In the above-described embodiment, the alcohol concentration sensor 36 detects the alcohol concentration of the fuel. However, in the case of a system that does not include the alcohol concentration sensor 36, for example, an air-fuel ratio feedback correction amount, an air-fuel ratio shift The alcohol concentration of the fuel may be estimated based on at least one of the amount, the combustion stability (engine rotation fluctuation), the engine torque, the fuel pressure increase rate at the time of high temperature start, and the like.

  In addition, the present invention is not limited to the in-cylinder injection engine as shown in FIG. 1, and is a dual-injection engine having both a fuel injection valve for intake port injection and a fuel injection valve for in-cylinder injection. Can also be applied.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a flowchart explaining the flow of a process of a starting injection control routine. It is a figure which shows notionally an example of the map for fuel injection timing setting. It is a figure which shows notionally an example of the map of the target fuel pressure at the time of starting. It is a time chart explaining the example of execution of starting injection control when the alcohol concentration of fuel is low. It is a time chart explaining the example of execution of starting injection control when the alcohol concentration of fuel is high.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 15 ... Throttle valve, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 25 ... Cooling water temperature sensor (engine temperature determination means), 28 ... Fuel tank , 29 ... low pressure pump, 31 ... high pressure pump, 33 ... fuel pressure sensor (fuel pressure detection means), 36 ... alcohol concentration sensor (alcohol concentration determination means), 37 ... ECU (starting injection control means, starting target fuel pressure setting means, injection) Prohibited means)

Claims (4)

In a fuel injection control device for an internal combustion engine provided with a fuel injection valve for in-cylinder injection,
Alcohol concentration determination means for detecting or estimating the alcohol concentration of fuel supplied to the fuel injection valve;
Engine temperature determination means for detecting or estimating the temperature of the internal combustion engine or information related thereto (hereinafter referred to as “engine temperature etc.”);
When the alcohol concentration of the fuel is equal to or higher than a predetermined value and the engine temperature is equal to or lower than a predetermined value, the fuel injection end timing of the fuel injection valve is set to the compression stroke during the start of the internal combustion engine and / or a predetermined period after the start A fuel injection control device for an internal combustion engine.   2. The fuel injection end timing of the fuel injection valve approaches the compression top dead center as the alcohol concentration of the fuel increases and / or as the engine temperature decreases. A fuel injection control device for an internal combustion engine as described. In a fuel injection control device for an internal combustion engine that supplies high pressure fuel to a fuel injection valve for in-cylinder injection with a high-pressure pump,
Alcohol concentration determination means for detecting or estimating the alcohol concentration of fuel supplied to the fuel injection valve;
Engine temperature determination means for detecting or estimating the temperature of the internal combustion engine or information related thereto (hereinafter referred to as “engine temperature etc.”);
Fuel pressure detecting means for detecting the pressure of fuel supplied to the fuel injection valve (hereinafter referred to as “fuel pressure”);
A starting target fuel pressure setting means for setting a starting target fuel pressure according to the alcohol concentration of the fuel and the engine temperature;
Injection prohibiting means for prohibiting fuel injection of the fuel injection valve until a difference between the starting target fuel pressure and the fuel pressure detected by the fuel pressure detecting means when the internal combustion engine is started becomes a predetermined value or less. A fuel injection control device for an internal combustion engine.   The fuel for an internal combustion engine according to claim 3, wherein the starting target fuel pressure setting means increases the starting target fuel pressure as the alcohol concentration of the fuel increases and / or as the engine temperature or the like decreases. Injection control device.

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