JP2011241807A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily supply evaporated fuel into a cylinder even at a low-temperature start for improving the starting performance in a control device of an internal combustion engine.SOLUTION: An engine 10 includes a normal fuel tank 32, an evaporated fuel tank 36, a tank ejection valve 38 and an evaporated fuel supply valve 40 or the like. At starting, an ECU 60 supplies, to a surge tank 20, the evaporated fuel stored in the evaporated fuel tank 36 during the operation of the engine. When the evaporated fuel runs short at the starting, fuel is ejected into the evaporated fuel tank 36 from the tank ejection valve 38 while the normal fuel ejection is prohibited, and the evaporated fuel supply valve 40 and an atmospheric air introduction valve 42 are opened simultaneously with the fuel ejection. Thereby, the evaporated fuel can be quickly supplied into the cylinder, not only when a sufficient amount of the evaporated fuel is stored at the starting but even when the evaporated fuel runs short.

Description

  The present invention relates to a control device for an internal combustion engine that uses a low volatility fuel such as alcohol fuel.

  As a conventional technique, for example, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-224878), a control device for an internal combustion engine using alcohol fuel is known. Since alcohol fuel is difficult to vaporize particularly at low temperatures, the internal combustion engine of the prior art is provided with a vaporization chamber for vaporizing the fuel at start-up. The vaporizing chamber has a sealed structure that is blocked from the outside, and is connected to the intake passage through a throttle passage. Further, the vaporizing chamber is provided with a starting fuel injection valve for injecting fuel therein and a heater for heating the injected fuel.

  When starting the internal combustion engine, first, the heater is operated when a start signal is output to the internal combustion engine, and then fuel is injected from the start fuel injection valve into the vaporization chamber when an appropriate time has elapsed. To do. When fuel is injected, the vaporization chamber is in a decompressed state due to the intake negative pressure due to cranking. As a result, the injected fuel is vaporized by receiving the heat of the heater in the vaporization chamber in the decompressed state, and is supplied to each cylinder through the intake passage. As described above, in the prior art, fuel is vaporized in the vaporizing chamber at the time of starting, thereby ensuring startability at the time of cold starting or the like.

JP 2007-224878 A JP 2001-107805 A JP-A-9-88740

  By the way, in the above-described prior art, after starting the heater at the start, fuel is injected into the vaporizing chamber to generate vaporized fuel. However, in this case, after the start signal is output to the internal combustion engine, the heater is heated, the injected fuel is heated, and the vaporization chamber is depressurized. As a result, vaporized fuel is generated. For this reason, in the prior art, there is a problem that it takes time to generate the vaporized fuel at the time of starting, and the vaporized fuel cannot be quickly supplied into the cylinder.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to quickly supply vaporized fuel into a cylinder even in a situation where the fuel is difficult to vaporize, such as at low temperature start. Another object of the present invention is to provide a control device for an internal combustion engine that can improve startability.

A first invention is a fuel tank for storing fuel;
An intake passage injection valve for injecting fuel in the fuel tank into the intake passage;
An in-cylinder injection valve that injects the fuel in the fuel tank into the cylinder;
A vaporized fuel tank connected to the intake passage and storing vaporized fuel vaporized by the fuel;
In-tank fuel supply means for supplying fuel in the fuel tank to the vaporized fuel tank;
A normally-closed vaporized fuel supply valve that opens and closes a connection between the vaporized fuel tank and the intake passage;
Vaporized fuel generating means for driving the fuel supply means in the tank with the vaporized fuel supply valve closed during operation of the internal combustion engine to generate vaporized fuel in the vaporized fuel tank;
When the amount of vaporized fuel held in the vaporized fuel tank when starting the internal combustion engine is equal to or greater than the required amount at startup, the vaporized fuel supply valve is opened, and the vaporized fuel tank is connected to the intake passage. Vaporized fuel supply means for supplying vaporized fuel;
When the amount of vaporized fuel held at the start of the internal combustion engine is smaller than the required amount at the start, the fuel supply means in the tank is driven in a state where the operation of the intake passage injection valve and the in-cylinder injection valve is prohibited. Vaporized fuel generation and supply means for opening the vaporized fuel supply valve;
It is characterized by providing.

  The second invention drives the intake passage injection valve when the amount of fuel adhering to the wall surface of the intake passage is larger than the reference amount after the vaporized fuel is supplied by the vaporized fuel generation and supply means. Auxiliary fuel injection means is provided.

  A third invention drives the in-cylinder injection valve when the amount of fuel adhering to the wall surface of the intake passage is equal to or less than a reference amount after the vaporized fuel is supplied by the vaporized fuel generation and supply means. In-cylinder injection means is provided.

4th invention is the normally closed valve provided in the position which can connect the inside of the said vaporization fuel tank, and external space, Comprising: The atmosphere introduction valve opened and closed with the said vaporization fuel supply valve,
A valve opening order switching means for switching the valve opening order of the respective valves based on the magnitude relationship between the pressure in the vaporized fuel tank and the atmospheric pressure when opening the vaporized fuel supply valve and the atmosphere introduction valve; ,
Is provided.

  In the fifth invention, alcohol fuel is used as the fuel.

  According to the first invention, vaporized fuel can be generated during operation of the internal combustion engine, and the vaporized fuel can be stored in the vaporized fuel tank using natural decompression after the engine is stopped. Thereby, since it is not necessary to generate vaporized fuel at the time of starting, vaporized fuel can be rapidly supplied into the cylinder even at the time of low temperature starting. Also, when there is no vaporized fuel storage at start-up or when there is a shortage of vaporized fuel, vaporized fuel is efficiently generated in a state where normal fuel injection is prohibited by the vaporized fuel generation and supply means, and this is quickly generated in the cylinder. Can be supplied to. Therefore, startability can be improved.

  According to the second invention, after the vaporized fuel is supplied, if the amount of fuel adhering to the wall surface of the intake passage is larger than the reference amount of adhering fuel, the vaporized fuel generated on the wall surface of the intake passage is in the cylinder. Stable supply. In this case, the auxiliary fuel injection means can execute the intake passage injection as the auxiliary fuel injection, in which the injected fuel is easily vaporized even if it takes some time to supply the fuel into the cylinder. Thereby, the vaporized fuel generated on the wall surface of the intake passage and the injected fuel vaporized in the intake passage can be stably supplied into the cylinder. Therefore, it is possible to secure a sufficient amount of the fuel gas supplied into the cylinder and improve the startability.

  According to the third aspect, when the amount of fuel adhering to the wall surface of the intake passage is equal to or less than the reference amount, fuel injection into the cylinder can be executed by the in-cylinder injection means. Thereby, even when the vaporized fuel generated on the wall surface of the intake passage is small, an accurate amount of fuel can be immediately supplied into the cylinder by in-cylinder injection, and good combustibility can be ensured.

  According to the fourth aspect of the invention, the air introduction valve can cause air to flow into the tank as much as the vaporized fuel has flowed out of the vaporized fuel tank, whereby the vaporized fuel can be supplied smoothly. Further, the valve opening order switching means can open the air introduction valve after first opening the vaporized fuel supply valve when the pressure in the vaporized fuel tank is higher than the atmospheric pressure, for example. In other cases, the vaporization fuel supply valve can be opened after the air introduction valve is first opened. As a result, it is possible to prevent the vaporized fuel from flowing out into the atmosphere from the atmosphere introduction valve and the air on the intake passage side from flowing back into the vaporized fuel tank from the vaporized fuel supply valve.

  According to the fifth aspect of the present invention, even when alcohol fuel that is difficult to vaporize at low temperatures is used, vaporized fuel is stored in the vaporized fuel tank during operation of the internal combustion engine, and the vaporized fuel is supplied at the time of start-up. Can be improved.

It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a block diagram which shows the control system of the system in Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a flowchart which shows the control performed while driving | operation of an engine by ECU. In Embodiment 1 of this invention, it is a flowchart which shows the control performed at the time of engine starting by ECU. It is a flowchart which shows the vaporized fuel supply control in FIG.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an overall configuration diagram for explaining a system configuration according to the first embodiment of the present invention. The system of the present embodiment includes an engine 10 as an internal combustion engine mounted on an FFV (Flexible Fuel Vehicle). Although FIG. 1 illustrates a four-cylinder engine, the internal combustion engine of the present invention is not limited to four cylinders. The engine 10 includes an intake passage 12 that sucks intake air into a combustion chamber of each cylinder, and an exhaust passage 14 through which exhaust gas is discharged from the combustion chamber.

  An air cleaner 16, a throttle valve 18, and a surge tank 20 are provided in the intake passage 12 in order from the upstream side. The throttle valve 18 is configured by an electronically controlled butterfly valve, and adjusts the amount of intake air flowing through the intake passage 12 according to the opening degree. The surge tank 20 forms a space having a certain extent in the intake passage 12 in order to attenuate intake pulsation. The downstream side of the surge tank 20 is connected to the intake port 24 of each cylinder via an intake manifold 22 composed of a plurality of intake pipes. The surge tank 20, the intake manifold 22 and the intake port 24 constitute a part of the intake passage 12.

  Each cylinder of the engine 10 is provided with an intake port injection valve 26 that injects fuel into the intake port 24 and an in-cylinder injection valve 28 that directly injects fuel into the combustion chamber (inside the cylinder). The intake port injection valve 26 constitutes the intake passage injection valve of the present embodiment. Each cylinder is provided with an ignition plug 30 (see FIG. 2) for igniting the vaporized fuel, and an intake valve and an exhaust valve (not shown). Alcohol fuel stored in a liquefied state in the fuel tank 32 of the vehicle is supplied to the injection valves 26 and 28.

  The engine 10 also includes a starter motor 34 that rotationally drives the crankshaft at the start. When the driver of the vehicle turns on the starter switch, an engine start request is issued to the ECU 60 described later. Thereby, the ECU 60 executes the operation (cranking) for starting the starter motor 34 and rotating the crankshaft, and stops the cranking when the engine is started, that is, when it shifts to the independent operation.

  Next, the fuel vaporization system mounted on the engine 10 will be described. The present embodiment is characterized in that vaporized fuel generated during operation of the engine is stored in a tank, and this vaporized fuel is used at the next start. The fuel vaporization system includes a vaporized fuel tank 36, an in-tank injection valve 38, a vaporized fuel supply valve 40, an air introduction valve 42, a relief valve 44, and the like described below.

  The vaporized fuel tank 36 is formed as a pressure-resistant container having a sealed structure, and is configured to store vaporized fuel obtained by vaporizing alcohol fuel in the fuel tank 32. The vaporized fuel tank 36 is installed at a position where heat is easily conducted from the engine 10 in, for example, the engine room. The in-tank injection valve 38 injects (supplies) the fuel stored in the fuel tank 32 into the vaporized fuel tank 36, and constitutes the in-tank fuel supply means of the present embodiment. The in-tank injection valve 38 is constituted by a general fuel injection valve similar to the injection valves 26 and 28, for example, and the fuel injection amount is controlled in accordance with a control signal. The fuel injected from the in-tank injection valve 38 is vaporized in the vaporized fuel tank 36 to become vaporized fuel.

  The vaporized fuel tank 36 is connected to the surge tank 20 on the downstream side of the throttle valve 18. The connecting portion is provided with a vaporized fuel supply valve 40 constituted by a normally closed solenoid valve or the like. When the vaporized fuel supply valve 40 is closed, the vaporized fuel tank 36 and the surge tank 20 are disconnected, and vaporized fuel can be stored in the vaporized fuel tank 36. Further, when the vaporized fuel supply valve 40 is opened, the tanks 20 and 36 are communicated with each other, and the vaporized fuel stored in the vaporized fuel tank 36 is supplied to the surge tank 20.

  The vaporized fuel tank 36 is provided with an air introduction valve 42 at a position where the inside of the tank can communicate with the external space. The air introduction valve 42 is constituted by a normally closed electromagnetic valve or the like, and releases the vaporized fuel tank 36 to the atmosphere when the valve is opened. At the time of supplying the vaporized fuel, the vaporized fuel supply valve 40 and the atmosphere introduction valve 42 are opened together with a slight time difference, and the atmosphere is introduced into the vaporized fuel tank 36 from the atmosphere introduction valve 42 by the amount of the vaporized fuel supplied. The These valves 40 and 42 are kept closed except when vaporized fuel is supplied. The air introduction valve 42 is connected to the intake passage 12 between the air cleaner 16 and the throttle valve 18. For this reason, when the air introduction valve 42 is opened, air that has been cleaned by the air cleaner 16 and is not affected by the negative intake pressure is introduced into the vaporized fuel tank 36.

  Further, the vaporized fuel tank 36 is provided with a normally closed relief valve 44 constituted by, for example, a check valve, a reed valve or the like. The relief valve 44 releases the pressure to the outside (for example, the intake passage 12) when the pressure in the vaporized fuel tank 36 exceeds a predetermined operating pressure. The operating pressure of the relief valve 44 is, for example, a large value. It is set to a pressure of about atmospheric pressure or a pressure about several tens of kPa higher than atmospheric pressure. This setting is based on the premise that, for example, the vaporized fuel tank 36 is maintained at a temperature of about room temperature or slightly higher than that, and the saturated vapor pressure of the fuel becomes a pressure corresponding to this temperature region. Accordingly, the relief valve 44 is configured to release the air in the tank to the outside when the fuel injected into the vaporized fuel tank 36 is vaporized. The relief valve 44 also has a function as a safety valve that prevents the pressure in the tank from becoming excessive when the vaporized fuel tank 36 is sealed.

  Next, the control system of the engine 10 will be described with reference to FIG. FIG. 2 is a configuration diagram showing a control system of the system according to the first embodiment of the present invention. As shown in this figure, the system of the present embodiment includes a sensor system including a plurality of sensors 46 to 56 and an ECU (Electronic Control Unit) 60 that controls the operating state of the engine 10.

  First, the sensor system will be described. The crank angle sensor 46 outputs a signal synchronized with the rotation of the crankshaft of the engine 10, and the ECU 60 can detect the engine speed and the crank angle based on this output. it can. The air flow sensor 48 detects the amount of intake air, and the water temperature sensor 50 detects the temperature of engine cooling water. The tank pressure sensor 52 detects the pressure in the vaporized fuel tank 36, and the tank temperature sensor 54 detects the temperature in the vaporized fuel tank 36. Further, the fuel property sensor 56 detects the alcohol concentration in the fuel as the property of the fuel.

  The sensor system includes various sensors (for example, an air-fuel ratio sensor for detecting the exhaust air-fuel ratio, a throttle sensor for detecting the opening degree of the throttle valve 18) other than the sensors 46 to 56, which are necessary for controlling the vehicle and the engine. An accelerator opening degree sensor for detecting the accelerator opening degree) is included, and these sensors are connected to the input side of the ECU 60. The present invention does not necessarily require the tank temperature sensor 54. For example, the tank temperature sensor 54 is not used, and the tank temperature is based on the engine temperature, operation history, heat conduction characteristics to the vaporized fuel tank 36, and the like. The internal temperature may be estimated.

  On the other hand, on the output side of the ECU 60, various actuators including a throttle valve 18, injection valves 26, 28, and 38, a spark plug 30, a starter motor 34, a vaporized fuel supply valve 40, an air introduction valve 42, and the like are connected. . The ECU 60 detects the operation information of the engine by the sensor system, and controls the operation by driving each actuator based on the detection result. Specifically, the engine speed and the crank angle are detected based on the output of the crank angle sensor 46, and the intake air amount is detected by the air flow sensor 48. Further, while performing the normal fuel injection control described below, the ignition timing is determined based on the crank angle, and the spark plug 30 is driven.

  The normal fuel injection control is executed during the operation of the engine except when vaporized fuel supply control, which will be described later, is executed, and includes fuel injection control at start-up. In this fuel injection control, the fuel injection amount is calculated based on the intake air amount, the engine speed, the engine coolant temperature, etc., and the fuel injection timing is determined based on the crank angle, and then the injection valves 26 and 28 are driven. To do. In this case, the ratio of the injection amounts of the intake port injection valve 26 and the in-cylinder injection valve 28 is variably set according to the operating state of the engine and the properties of the fuel. Further, the ECU 60 executes vaporized fuel generation control and vaporized fuel supply control described below as control of the fuel vaporization system.

[Operation of Embodiment 1]
(Vaporized fuel generation control)
The vaporized fuel generation control is to vaporize the fuel in the vaporized fuel tank 36 during the operation of the engine 10 (preferably during the operation after the warm-up is completed) to generate vaporized fuel. More specifically, in the vaporized fuel generation control, fuel is injected from the in-tank injection valve 38 with the vaporized fuel supply valve 40 and the atmosphere introduction valve 42 closed. At this time, the fuel injection amount is determined so that all of the injected fuel is vaporized based on the temperature in the vaporized fuel tank 36, the alcohol concentration in the fuel, and the like. The injected fuel quickly evaporates and becomes vaporized fuel while expelling air in the tank from the relief valve 44. At this time, the relief valve 44 can prevent the vaporization of the fuel from being suppressed by the air pressure in the tank, and can promote the generation of the vaporized fuel. As a result, when the vaporization of the injected fuel is completed, the air in the tank is almost exhausted, and the vaporized fuel tank 36 is filled with the vaporized fuel at a pressure close to the saturated vapor pressure.

  By the vaporized fuel generation control described above, vaporized fuel can be stored in the vaporized fuel tank 36 during engine operation. And the vaporized fuel tank 36 can hold | maintain at least one part of vaporized fuel in a gaseous-phase state also at the time of the cold after an engine stop using the natural pressure reduction produced in a tank. The vaporized fuel generation control is preferably executed only when the temperature in the vaporized fuel tank 36 is equal to or higher than a predetermined determination temperature at which vaporized fuel can be generated.

(Vaporized fuel supply control)
In the vaporized fuel supply control, the vaporized fuel supply valve 40 and the air introduction valve 42 are opened when the engine is started, and the vaporized fuel stored in the vaporized fuel tank 36 is supplied to the surge tank 20. In the following description, first, control when a sufficient amount of vaporized fuel is stored in the vaporized fuel tank 36 when the engine is started will be described.

  The ECU 60 starts cranking when the starter switch is turned on. As a result, an intake negative pressure is generated in the surge tank 20 due to cranking. Therefore, the ECU 60 opens the vaporized fuel supply valve 40 and the atmospheric introduction valve 42 to take in the vaporized fuel in the vaporized fuel tank 36 as an intake negative. The surge tank 20 is supplied by pressure. At this time, since air flows into the vaporized fuel tank 36 from the atmosphere introduction valve 42 by the amount of vaporized fuel flowing out, the vaporized fuel can be supplied smoothly. Note that when supplying vaporized fuel, the intake port injection valve 26 and the in-cylinder injection valve 28 may be driven as necessary to use normal fuel injection together. Thereby, even if it is difficult to start with vaporized fuel alone, startability can be ensured by using normal fuel injection as an auxiliary.

  The vaporized fuel supplied from the vaporized fuel tank 36 to the surge tank 20 flows into the cylinder via the intake port 24, and is ignited and burned in the cylinder. As a result, when the combustion in each cylinder continues, the engine speed increases and the engine shifts to a self-sustained operation. The ECU 60 stops the cranking when confirming that the engine has started based on the engine speed or the like. Further, the vaporized fuel supply valve 40 and the air introduction valve 42 are closed, and the vaporized fuel supply control is ended. Then, normal fuel injection control for injecting fuel from the intake port injection valve 26 and the in-cylinder injection valve 28 is started.

  As described above, when the vaporized fuel stored during the operation of the engine is used, the vaporized fuel can be quickly supplied into the cylinder as compared with the case where the vaporized fuel is generated at the time of starting. Even at a low temperature start that is difficult to achieve, startability can be improved. Note that the vaporized fuel supply control is preferably executed only when the engine temperature at the time of starting (for example, the temperature of engine cooling water or the like) is equal to or lower than a predetermined determination temperature that requires vaporized fuel.

  The above-described vaporized fuel supply control can exert an effect by storing a sufficient amount of vaporized fuel during operation of the engine. However, for example, when an operation that is stopped in a short time after the engine is started (so-called short trip operation) is repeated, the amount of vaporized fuel stored in the vaporized fuel tank 36 tends to be insufficient. If a cold start or the like is performed in this state, a sufficient amount of vaporized fuel is not supplied to the intake system, and the startability is reduced. For this reason, in the present embodiment, first, the amount of vaporized fuel held in the vaporized fuel tank 36 at the start of the engine (the amount held at startup) is estimated. Then, the amount of vaporized fuel required at startup (startup required amount) Fgas is calculated, and when the start-time possessed amount is equal to or greater than the startup required amount Fgas, the above-described normal vaporized fuel supply control is executed. On the other hand, when the starting amount is less than the starting request amount Fgas, vaporized fuel generation and supply control is executed. Hereinafter, these processes will be described.

(Process for estimating the amount held at start-up)
During the operation of the engine, the vaporized fuel generation control described above is executed, so that the vaporized fuel tank 36 is filled with vaporized fuel at a pressure close to the saturated vapor pressure. In this state, when the engine is stopped, natural decompression occurs in the tank, so that most of the vaporized fuel remains as a gas. At this time, the amount of vaporized fuel held in the tank depends on the temperature in the tank when vaporized fuel generation control is executed (when fuel is injected by the tank injection valve 38) and in the tank after natural pressure reduction (when starting) Varies with temperature. The ECU 60 stores in advance map data in which the relationship between the tank temperature at the above two points in time and the remaining amount of vaporized fuel is converted into data. For this reason, the ECU 60 can calculate the amount of vaporized fuel held based on the tank temperatures at the two points in time detected by the tank temperature sensor 54 and the known tank capacity.

  Further, when vaporized fuel is consumed without being generated due to a short trip operation or the like, a consumption amount of vaporized fuel may be calculated, and a correction may be performed to subtract the consumption amount from the possessed amount. Specifically, first, the ECU 60 supplies the vaporized fuel tank 36 detected by the pressure in the surge tank 20 detected by an intake pressure sensor (not shown) or the like and the tank pressure sensor 52 when supplying vaporized fuel. The pressure difference ΔP with the internal pressure is calculated. Next, the supply amount of vaporized fuel per unit time is calculated based on the flow path area (stored in advance) when the vaporized fuel supply valve 40 is opened and the calculated value of the differential pressure ΔP. Then, while calculating the supply amount per unit time at a constant sampling cycle, the calculated value is integrated during the supply of the vaporized fuel, thereby calculating the integrated supply amount (consumption amount) of the vaporized fuel. The vaporized fuel consumption calculated in this way is stored in a nonvolatile memory or the like mounted on the ECU 60, and is used as a parameter for correcting the vaporized fuel holding amount at the next start. By the above processing, when the engine is started, the amount of vaporized fuel held at that time can be estimated.

(Calculation process of required amount at start-up)
In this calculation process, the amount of vaporized fuel required when the engine is started is calculated as the required amount Fgas at the time of start. The startup required amount Fgas is a determination value that is compared with the amount of vaporized fuel held as described above. The startup required amount Fgas is variably set based on, for example, the outside air temperature or engine temperature (engine cooling water temperature or the like) at startup. The ECU 60 stores in advance map data for calculating the starting required amount Fgas based on the outside air temperature and the engine temperature. At start-up, the lower the outside air temperature and the engine temperature, the more vaporized fuel is required. For this reason, the map data is set so that the startup required amount Fgas increases as the intake air temperature is lower and the coolant temperature is lower.

  Accordingly, the ECU 60 can calculate an appropriate startup required amount Fgas corresponding to the temperature environment based on the outputs of the water temperature sensor 50 and the intake air temperature sensor. Further, the startup required amount Fgas is also affected by the concentration of vaporized fuel supplied at startup. On the other hand, in the present embodiment, as described above, the vaporized fuel is stored in the vaporized fuel tank 36 in a prescribed state close to the saturated vapor pressure, and the startup required amount Fgas is the vaporized fuel in this state. It is set on the assumption that is supplied.

(Vaporized fuel generation and supply control)
When the vaporized fuel does not exist in the vaporized fuel tank 36 at the time of starting the engine, or when the amount of vaporized fuel held is smaller than the required fuel amount Fgas at the start, vaporized fuel generation and supply control is executed. In this control, after realizing a state in which the fuel is easily vaporized at the start, vaporized fuel is generated and immediately supplied into the cylinder. In vaporized fuel generation and supply control, first, fuel injection, which may be used in combination with normal vaporized fuel supply control, is prohibited. That is, the operation of the intake port injection valve 26 and the in-cylinder injection valve 28 is prohibited. Then, fuel is injected from the in-tank injection valve 38, and the vaporized fuel supply valve 40 and the air introduction valve 42 are opened together with (almost simultaneously with) the fuel injection. The relationship between the operation timing of the in-tank injection valve 38 and the operation timing of the vaporized fuel supply valve 40 (and the air introduction valve 42) does not necessarily have to be the same. May be. That is, in the vaporized fuel generation and supply control, the valves 40 and 42 may be opened when the in-tank injection valve 38 is driven with the operation of the intake port injection valve 26 and the in-cylinder injection valve 28 prohibited. It is.

  In the vaporized fuel generation and supply control, normal fuel injection is prohibited by ensuring space and time for vaporizing the fuel injected into the vaporized fuel tank 36 (hereinafter referred to as in-tank injected fuel). It is aimed. That is, when the vaporized fuel supply valve 40 is opened, at least a part of the fuel injected into the tank evaporates in the middle of the vaporized fuel while flowing through the flow path from the surge tank 20 to the cylinder through the intake port 24. It becomes. At this time, if normal fuel injection is performed in the above-described distribution path, the injected fuel is vaporized, whereby the intake port 24 and the wall surface in the cylinder are cooled, and the atmospheric temperature of the distribution path is lowered, and the tank The vaporization of the internal injection fuel will be hindered. Therefore, in the present embodiment, by prohibiting normal fuel injection, it is possible to prevent the ambient temperature of the circulation path from being lowered, and to ensure a sufficient space and time suitable for fuel vaporization in the circulation path. be able to.

  For this reason, even when vaporized fuel is inevitably generated at the time of starting, vaporization of fuel injected into the tank is promoted by using a wide space from the surge tank 20 to the inside of the cylinder and a time when the fuel passes through the space. The vaporized fuel can be generated quickly and efficiently. Further, by performing the fuel injection by the in-tank injection valve 38 and the opening of the valves 40 and 42 together, it is possible to cause the injected fuel to flow into the surge tank 20 in the shortest time and to start vaporization in a wide space. The generation of vaporized fuel can be further promoted.

  Further, in the vaporized fuel generation and supply control, the vaporized fuel supply valve 40 and the air introduction valve 42 are closed when an amount of vaporized fuel corresponding to the startup required amount Fgas is supplied. Then, auxiliary fuel injection is executed by one of the injection valves 26 and 28 based on the amount of fuel adhering to the wall surface of the flow path (hereinafter referred to as intake passage fuel adhering amount). Specifically, the ECU 60 first calculates the intake passage fuel adhesion amount based on parameters such as the injection amount of the fuel injected into the tank, the elapsed time from the start of injection, the engine temperature, and the wall surface area of the flow path. The relationship between these parameters and the intake passage fuel adhesion amount can be obtained by experiments or the like, and is stored in advance in the ECU 60 as map data.

  When the intake passage fuel adhesion amount is larger than the reference adhesion amount Fwet, the intake port injection valve 26 performs fuel intake port injection. When the intake passage fuel adhesion amount is equal to or less than the reference adhesion amount Fwet, in-cylinder injection of fuel is executed by the in-cylinder injection valve 28. As described above, the reason why the intake port injection and the in-cylinder injection are properly used as the auxiliary fuel injection is as follows. First, considering the ease of vaporization of the injected fuel, it is preferable that the fuel injection is basically performed at a position as far as possible from the inside of the cylinder, that is, by intake port injection. However, in the intake port injection, compared with the in-cylinder injection, the time until the injected fuel reaches the cylinder becomes longer and the injected fuel adheres to the wall surface of the intake port so that the fuel that reaches the cylinder There is a characteristic that the amount is likely to fluctuate.

  On the other hand, when the amount of fuel adhering to the intake passage is large, the fuel adhering to the wall surface of the intake passage is vaporized so that the vaporized fuel is stably supplied into the cylinder. Does not matter so much. Therefore, when the intake passage fuel adhesion amount is larger than the reference adhesion amount Fwet, the intake port injection is performed in which the injected fuel is easily vaporized even if it takes some time to supply the fuel into the cylinder. Here, the reference adhesion amount Fwet is set corresponding to the lower limit value of the intake passage fuel adhesion amount so that the characteristics of the intake port injection do not become a problem.

  Therefore, when the intake port injection is executed, the vaporized fuel generated from the wall surface of the intake passage and the injected fuel vaporized in the intake port can be stably supplied into the cylinder. As a result, a sufficient amount of the fuel gas supplied into the cylinder can be ensured and the startability can be improved. On the other hand, when the intake passage fuel adhesion amount is equal to or less than the reference adhesion amount Fwet, the vaporized fuel generated on the wall surface of the intake passage is small. Therefore, in this case, an accurate amount of fuel is immediately supplied into the cylinder by in-cylinder injection. Thereby, even when the intake passage fuel adhesion amount is small, good combustibility can be ensured.

  Therefore, according to the vaporized fuel generation and supply control, even when the vaporized fuel does not exist at the start or when the vaporized fuel is insufficient, the vaporized fuel is efficiently generated in a state where normal fuel injection is prohibited, and this is generated in the cylinder. Can be supplied promptly. An auxiliary fuel that supplements the fuel supply into the cylinder can be injected by the intake port injection or the in-cylinder injection. At the time of this fuel injection, the intake port injection and the fuel are injected according to the vaporization state of the fuel injected into the tank. In-cylinder injection can be used properly. Thereby, an auxiliary fuel injection can be used effectively and an engine can be started smoothly.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIGS. 3 to 5. First, FIG. 3 is a flowchart showing the control executed by the ECU during the operation of the engine in the first embodiment of the present invention. The routine shown in FIG. 3 is repeatedly executed during operation of the engine.

  In the routine shown in FIG. 3, first, the temperature T in the vaporized fuel tank 36 is detected by the tank temperature sensor 54 (step 100), and it is determined whether or not the tank temperature T is higher than the determination temperature T1 (step 100). 102). Here, the determination temperature T1 is set corresponding to the lower limit value of the temperature at which vaporized fuel can be generated, and is a determination temperature for permitting fuel injection in the tank. When the determination in step 102 is satisfied, since the temperature of the fuel is easily vaporized, the amount of fuel injected into the vaporized fuel tank 36 is calculated, and the vaporized fuel supply valve 40 and the air introduction valve 42 are closed. The inner injection valve 38 is driven (step 104). Thereby, vaporized fuel can be stored in the vaporized fuel tank 36 during operation of the engine.

  Next, FIG. 4 is a flowchart showing the control executed by the ECU when starting the engine in the first embodiment of the present invention. The routine shown in this figure is repeatedly executed during operation of the engine. In the routine shown in FIG. 4, it is first determined whether or not the ignition switch (IGSW) is turned on (step 200). When this determination is established, the alcohol concentration in the fuel, the engine water temperature (cooling water temperature), the temperature and pressure in the vaporized fuel tank 36 are detected based on the outputs of the sensors 50 to 56 (step 202). Then, the amount of vaporized fuel at start-up is estimated by the above-described estimation process (step 204).

  In the next process, it is determined whether or not the starter switch is turned on (step 206). When this determination is satisfied, cranking is executed (step 208). Then, it is determined whether or not the engine water temperature is lower than the vaporized fuel supply determination temperature ethw1 (step 210). Here, the vaporized fuel supply determination temperature ethw1 is a determination temperature for permitting the supply of vaporized fuel, and is set corresponding to the upper limit value of the engine temperature that requires vaporized fuel. The vaporized fuel supply determination temperature ethw1 is set to a higher temperature based on the output of the fuel property sensor 56 as the alcohol concentration in the fuel is higher (that is, the lower the fuel volatility is). If the determination in step 210 is not satisfied, the engine temperature is not so low as to require vaporized fuel, so that normal startup injection control is executed without using vaporized fuel (step 212).

  On the other hand, when the determination in step 210 is satisfied, it is difficult to start unless vaporized fuel is used. Therefore, the startup required amount Fgas is calculated by the calculation process described above. Then, it is determined whether or not the starting amount held in step 204 is less than the starting required amount Fgas (step 214). When this determination is established, the amount of vaporized fuel is insufficient, so the vaporized fuel generation and supply control described above is executed in steps 216 to 224.

  More specifically, in step 216, a fuel injection amount capable of generating an amount of vaporized fuel corresponding to the startup required amount Fgas is calculated, and in-tank injection valve 38 in a state where normal fuel injection is prohibited. Drive. In step 218, vaporized fuel supply control described in FIG. 5 to be described later is executed to supply vaporized fuel from the vaporized fuel tank 36 to the surge tank 20. Next, in step 220, after the supply of vaporized fuel is completed, the intake passage fuel adhesion amount is calculated as described above, and it is determined whether or not this calculated value is larger than the reference adhesion amount Fwet.

  When the determination in step 220 is satisfied, the intake port injection valve 26 is driven in step 222 to inject fuel into the intake port 24. If the determination in step 220 is not established, the cylinder injection valve 28 is driven in step 224 to inject fuel into the cylinder. Note that in steps 222 and 224, the fuel injection amount is calculated such that the startability can be ensured by supplementing the supply amount of the vaporized fuel. On the other hand, if the determination in step 214 is not established, a sufficient amount of vaporized fuel is held in the vaporized fuel tank 36, so that vaporized fuel is not generated at the start, and normal vaporized fuel supply control is executed. (Step 226).

  Next, FIG. 5 is a flowchart showing the vaporized fuel supply control executed in steps 218 and 226 in FIG. In the routine shown in FIG. 5, it is first determined whether or not the pressure in the vaporized fuel tank 36 detected by the tank pressure sensor 52 is higher than the atmospheric pressure P0 (step 300). When this determination is established, the vaporized fuel supply valve 40 is first opened to reduce the pressure in the vaporized fuel tank 36, and then the atmospheric introduction valve 42 is opened to supply vaporized fuel (step) 302, 304). If the determination in step 300 is not established, the air introduction valve 42 is first opened to increase the pressure in the vaporized fuel tank 36 to atmospheric pressure, and then the vaporized fuel supply valve 40 is opened. Thus, vaporized fuel is supplied (steps 308 and 310). In any case, the vaporized fuel supply valve 40 and the air introduction valve 42 are closed when the vaporized fuel has been supplied (steps 306 and 312). Thereby, vaporized fuel can be prevented from flowing out into the atmosphere from the atmosphere introduction valve 42, and air in the surge tank 20 can be prevented from flowing back into the vaporized fuel tank 36 from the vaporized fuel supply valve 40.

  In the first embodiment, steps 100 to 104 shown in FIG. 3 show a specific example of the vaporized fuel generating means in claim 1. Steps 214 and 226 shown in FIG. 4 show a specific example of the vaporized fuel supply means in claim 1, and steps 214 to 218 show a specific example of the vaporized fuel generation and supply means. Further, steps 220 and 222 show a specific example of the auxiliary fuel injection means in claim 1, and steps 220 and 224 show a specific example of the in-cylinder injection means in claim 2, respectively. On the other hand, steps 300 to 312 shown in FIG. 5 show a specific example of the valve opening order switching means in claim 3.

  In the embodiment, the intake port injection is executed when the intake passage fuel adhesion amount is larger than the reference adhesion amount Fwet, and the in-cylinder injection is executed otherwise. However, according to the present invention, it is only necessary to execute the intake port injection when the intake passage fuel adhesion amount is larger than the reference adhesion amount Fwet, and it is not always necessary to perform in-cylinder injection. In the embodiment, the intake port injection valve 26 is exemplified as the intake passage injection valve. However, in the present invention, the intake port injection valve 24 may be injected into an appropriate portion of the intake passage 12 by the intake passage injection valve. There is no need to inject fuel.

  In the embodiment, the surge tank 20 has been described as an example of the supply portion of the vaporized fuel to the intake passage 12. However, the present invention is not limited to this, and the vaporized fuel tank 36 may be connected to any part of the intake passage 12 and the vaporized fuel may be supplied to this part as long as it is downstream of the throttle valve 18. .

  In the embodiment, the vaporized fuel tank 36 is arranged in a place where heat from the engine 10 is easily transmitted. However, the present invention is not limited to this, and the vaporized fuel tank 36 may be positively heated by the heat generated by the engine 10. For example, a cooling water pipe may be provided between the engine 10 and the vaporized fuel tank 36, and the vaporized fuel tank 36 may be heated by the engine cooling water. Further, a heat conducting member such as a heat pipe may be provided between the exhaust passage 14 and the vaporized fuel tank 36, and the vaporized fuel tank 36 may be heated by the exhaust heat. With these configurations, the saturated vapor pressure of the fuel in the vaporized fuel tank 36 can be increased, and the amount of vaporized fuel that can be stored can be increased.

  Further, in the embodiment, the engine 10 including both the intake port injection valve 26 and the in-cylinder injection valve 28 has been described as an example. However, the present invention is not limited to this, and the present invention may be applied to an internal combustion engine that does not include any one of the injection valves 26 and 28 but includes only the other.

  In the embodiment, the engine 10 using alcohol fuel has been described as an example. However, the present invention is not limited to this, and can be applied to normal gasoline and various fuels obtained by adding components other than alcohol to gasoline.

10 Engine (Internal combustion engine)
12 Intake passage 14 Exhaust passage 16 Air cleaner 18 Throttle valve 20 Surge tank (intake passage)
22 Intake manifold (intake passage)
24 Intake port (intake passage)
26 Intake port injection valve (intake passage injection valve)
28 In-cylinder injection valve 32 Fuel tank 34 Starter motor 36 Vaporized fuel tank 38 In-tank injection valve (in-tank fuel supply means)
40 Vaporized fuel supply valve 42 Air introduction valve 44 Relief valve 52 Tank pressure sensor 54 Tank temperature sensor 56 Fuel property sensor 60 ECU

Claims (5)

A fuel tank for storing fuel;
An intake passage injection valve for injecting fuel in the fuel tank into the intake passage;
An in-cylinder injection valve that injects the fuel in the fuel tank into the cylinder;
A vaporized fuel tank connected to the intake passage and storing vaporized fuel vaporized by the fuel;
In-tank fuel supply means for supplying fuel in the fuel tank to the vaporized fuel tank;
A normally-closed vaporized fuel supply valve that opens and closes a connection between the vaporized fuel tank and the intake passage;
Vaporized fuel generating means for driving the fuel supply means in the tank with the vaporized fuel supply valve closed during operation of the internal combustion engine to generate vaporized fuel in the vaporized fuel tank;
When the amount of vaporized fuel held in the vaporized fuel tank when starting the internal combustion engine is equal to or greater than the required amount at startup, the vaporized fuel supply valve is opened, and the vaporized fuel tank is connected to the intake passage. Vaporized fuel supply means for supplying vaporized fuel;
When the amount of vaporized fuel held at the start of the internal combustion engine is smaller than the required amount at the start, the fuel supply means in the tank is driven in a state where the operation of the intake passage injection valve and the in-cylinder injection valve is prohibited. Vaporized fuel generation and supply means for opening the vaporized fuel supply valve;
A control device for an internal combustion engine, comprising:   Auxiliary fuel injection means for driving the intake passage injection valve is provided when the amount of fuel adhering to the wall surface of the intake passage after the supply of vaporized fuel by the vaporized fuel generation and supply means is larger than the reference amount of attachment. The control apparatus for an internal combustion engine according to claim 1.   In-cylinder injection means for driving the in-cylinder injection valve when the amount of fuel adhering to the wall surface of the intake passage is equal to or less than a reference adhesion amount after the vaporized fuel is supplied by the vaporized fuel generation and supply means. The control apparatus for an internal combustion engine according to claim 1 or 2. A normally closed valve provided at a position where the inside of the vaporized fuel tank and the external space can communicate with each other, and an atmospheric introduction valve that opens and closes together with the vaporized fuel supply valve;
A valve opening order switching means for switching the valve opening order of the respective valves based on the magnitude relationship between the pressure in the vaporized fuel tank and the atmospheric pressure when opening the vaporized fuel supply valve and the atmosphere introduction valve; ,
The control apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising:   The control apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein alcohol fuel is used as the fuel.

Images