JP2011220235A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine which improves starting performance by quickly supplying vaporized fuel to a cylinder even upon cold start.SOLUTION: When a starting request of an engine 10 is generated, a vaporized fuel supply valve 42 and an atmosphere introduction valve 44 are always kept closed, and a throttle valve 18 is held in a fully closed position (step 202). Then, inner pressure Pt in a vaporized fuel tank 38 is detected and is compared with atmospheric pressure P0 (steps 204 to 206). As a result, when Pt>P0 is not established, in other words, there is negative pressure generated in the vaporized fuel tank 38, in a state where the atmospheric pressure valve 44 is always kept closed and the throttle valve 18 is held in the fully closed position, the vaporized fuel supply valve 42 is opened (step 208). Then, the atmosphere introduction valve 44 is opened with a predetermined time difference (step 210). Then, ignition start conditions are changed to start cranking (steps 212 to 214).

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 2007-332855 A JP 2001-241363 A JP 09-88740 A

  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 even when the fuel is difficult to vaporize at the time of cold start or the like, the vaporized fuel can be quickly supplied into the cylinder to improve the startability. An object of the present invention is to provide a control device for an internal combustion engine that can be made to operate.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A fuel tank for storing fuel;
A vaporized fuel tank that is connected to an intake passage of the internal combustion engine and stores 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;
A throttle valve for adjusting the amount of intake air on the upstream side of the connecting portion in 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, and generating vaporized fuel in the vaporized fuel tank;
A normally-closed air introduction valve that opens and closes a communication portion between the inside and the outside space of the vaporized fuel tank;
Determining means for determining whether or not an internal pressure of the vaporized fuel tank is smaller than an atmospheric pressure when a request for starting the internal combustion engine is generated;
When the determination means determines that the internal pressure of the vaporized fuel tank is smaller than the atmospheric pressure, the vaporized fuel supply valve is closed with the throttle valve and the air introduction valve closed before the cranking is performed. Valve control means for opening the valve and then opening the air introduction valve;
It is characterized by providing.

According to a second invention, in the first invention,
The valve control means includes
When the determination means determines that the internal pressure of the vaporized fuel tank is smaller than the atmospheric pressure, the vaporized fuel supply valve is closed with the throttle valve and the air introduction valve closed before the cranking is performed. Is opened, and the atmospheric introduction valve is opened after the internal pressure of the vaporized fuel tank and the internal pressure of the intake passage become equal.

According to a third invention, in the first or second invention,
The intake passage includes a surge tank provided on the downstream side of the throttle valve.

A fourth invention is any one of the first to third inventions,
The apparatus further comprises prohibiting means for prohibiting valve overlap between the intake valve and the exhaust valve when the internal combustion engine is stopped.

According to a fifth invention, in any one of the first to fourth inventions,
The fuel is a fuel containing alcohol.

  According to the present 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 pressure reduction 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.

  According to the first invention, when the inside of the vaporized fuel tank at the start is in a negative pressure environment, the vaporized fuel supply valve is closed with the throttle valve and the air introduction valve closed before the cranking is performed. The valve is opened. As a result, part of the residual air in the intake passage is sucked into the vaporized fuel tank, and the inside of the vaporized fuel tank and the intake passage are once brought to a negative pressure. For this reason, when the air introduction valve is subsequently opened, the vaporized fuel in the vaporized fuel tank is supplied into the intake passage together with the atmosphere. As a result, when cranking is performed, the vaporized fuel supplied into the intake passage can be quickly flowed into the cylinder, so that useless vaporized fuel that flows out to the exhaust system without being ignited can be reduced. . Therefore, the startability can be improved by effectively using the vaporized fuel, and the exhaust emission can be improved.

  According to the second invention, when the inside of the vaporized fuel tank at the time of starting is in a negative pressure environment, the vaporized fuel supply valve is closed with the throttle valve and the air introduction valve closed before the cranking is performed. After the valve is opened, the air introduction valve is opened after the internal pressure of the vaporized fuel tank and the internal pressure of the intake passage become equal. For this reason, according to the present invention, the air introduction valve is opened after the negative pressure in the intake passage is reliably reduced, so that the vaporized fuel in the vaporized fuel tank can be efficiently supplied into the intake passage.

  According to the third invention, the intake passage includes a surge tank. For this reason, according to the present invention, the vaporized fuel in the vaporized fuel tank can be efficiently supplied into the surge tank before starting to form an air-fuel mixture.

  According to the fourth invention, the overlap between the intake valve and the exhaust valve when the internal combustion engine is stopped is prohibited. Therefore, according to the present invention, when the vaporized fuel supply valve is opened and a part of the residual air in the intake passage is sucked into the vaporized fuel tank, the negative pressure is surely generated in the intake passage. be able to.

  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. It is explanatory drawing which shows the time change of the density | concentration of the vaporized fuel supplied in a cylinder in the comparative example which does not implement control by Embodiment 1 of this invention. It is a figure for demonstrating the valve control by Embodiment 1 of this invention. It is a figure for demonstrating the valve control by Embodiment 1 of this invention. It is a figure for demonstrating the valve control by Embodiment 1 of this invention. It is a figure for demonstrating the valve control by Embodiment 1 of this invention. In Embodiment 1 of this invention, it is explanatory drawing which shows the time change of the density | concentration of the vaporized fuel supplied in a cylinder. It is a flowchart which shows the routine performed in Embodiment 1 of this invention. It is a flowchart which shows the routine performed in Embodiment 1 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

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 present invention is not limited to a four-cylinder internal combustion engine. 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 constituted by an electronically controlled butterfly valve, and is opened and closed by an ECU 70 described later. The throttle valve 18 is opened and closed between a fully closed position and a fully opened position, and the amount of intake air flowing through the intake passage 12 is adjusted according to the opening. The surge tank 20 forms a space having a certain spread in the middle of the intake passage 12 and exhibits an attenuation effect of intake pulsation and the like. A downstream side of the surge tank 20 is connected to an intake port 24 of each cylinder via an intake manifold 22 including 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). These injection valves 26 and 28 are constituted by general electromagnetically driven fuel injection valves. Further, each cylinder includes an ignition plug 30 (see FIG. 2) for igniting the air-fuel mixture flowing into the cylinder, and an intake valve and an exhaust valve (not shown) for opening and closing the intake port 24 and the exhaust port, respectively. Is provided. Alcohol fuel stored in a liquefied state in the fuel tank 32 of the vehicle is supplied to the injection valves 26 and 28 described above.

  The engine 10 also includes a starter motor 36 that rotationally drives the crankshaft when starting. When the driver of the vehicle turns on the starter switch, an engine start request is generated to the ECU 70. Thereby, the ECU 70 executes an operation (cranking) for starting the starter motor 36 and rotating the crankshaft. Then, the cranking is stopped when the engine is started, that is, when the operation is shifted 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 38, an in-tank injection valve 40, a vaporized fuel supply valve 42, an air introduction valve 44, a relief valve 46, and the like described below.

  The vaporized fuel tank 38 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 38 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 40 injects (supplies) the fuel stored in the fuel tank 32 into the vaporized fuel tank 38, and constitutes the in-tank fuel supply means of the present embodiment. The in-tank injection valve 40 is configured by a general fuel injection valve similar to the injection valves 26 and 28, for example, and the fuel injection amount is controlled according to a control signal. The fuel injected from the in-tank injection valve 40 receives vaporized and vaporizes in the vaporized fuel tank 38 to become vaporized fuel.

  The vaporized fuel tank 38 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 42 constituted by a normally closed (normally closed) electromagnetic valve or the like. When the vaporized fuel supply valve 42 is closed, the vaporized fuel tank 38 and the surge tank 20 are disconnected, and vaporized fuel can be stored in the vaporized fuel tank 38. Further, when the vaporized fuel supply valve 42 is opened, the tanks 20 and 38 are communicated with each other, and the vaporized fuel stored in the vaporized fuel tank 38 is supplied to the surge tank 20.

  The vaporized fuel tank 38 is provided with an air introduction valve 44 at a position where the inside of the tank can communicate with the external space. The air introduction valve 44 is constituted by a normally closed electromagnetic valve or the like, and when the valve is opened, the vaporized fuel tank 38 is released to the atmosphere. At the time of supplying the vaporized fuel, the vaporized fuel supply valve 42 and the atmosphere introduction valve 44 are opened together with a slight time difference, and the atmosphere is introduced from the atmosphere introduction valve 44 into the vaporized fuel tank 38 by the amount of vaporized fuel supplied. The These valves 42 and 44 are kept closed except when vaporized fuel is supplied. The air introduction valve 44 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 44 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 38.

  Further, the vaporized fuel tank 38 is provided with a normally closed relief valve 46 constituted by, for example, a check valve, a reed valve or the like. The relief valve 46 releases the pressure to the outside (for example, the intake passage 12) when the pressure in the vaporized fuel tank 38 exceeds a predetermined operating pressure. The operating pressure of the relief valve 46 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 38 is maintained at a temperature around room temperature or slightly higher, and the saturated vapor pressure of the fuel becomes a pressure corresponding to this temperature region. Accordingly, the relief valve 46 is configured to release the air in the tank to the outside when the fuel injected into the vaporized fuel tank 38 is vaporized. The relief valve 46 also has a function as a safety valve that prevents the pressure in the tank from becoming excessive when the vaporized fuel tank 38 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 the figure, the system according to the present embodiment includes a sensor system including a plurality of sensors described later, and an ECU (Electronic Control Unit) 70 that controls the operating state of the engine 10.

  First, the sensor system will be described. The crank angle sensor 48 outputs a signal synchronized with the rotation of the crankshaft of the engine 10, and the ECU 70 detects the engine speed and the crank angle based on this output. The air flow sensor 50 detects the intake air amount, and the water temperature sensor 52 detects the cooling water temperature of the engine. The tank pressure sensor 54 detects the pressure in the vaporized fuel tank 38, and the tank temperature sensor 56 detects the temperature in the vaporized fuel tank 38. The fuel property sensor 58 detects the alcohol concentration in the fuel as the property of the fuel.

  In addition to the above sensors, the sensor system includes various sensors (for example, an air-fuel ratio sensor that detects the exhaust air-fuel ratio, a throttle sensor that detects the opening degree of the throttle valve 18, an accelerator opening degree). And the like, and these sensors are connected to the input side of the ECU 70. The present invention does not necessarily require the tank temperature sensor 56. For example, the temperature in the tank may be estimated based on the engine temperature, the operation history, the heat conduction characteristics to the vaporized fuel tank 38, or the like. Good.

  On the other hand, on the output side of the ECU 70, various actuators including the throttle valve 18, the injection valves 26, 28, 40, the spark plug 30, the starter motor 36, the vaporized fuel supply valve 42, the air introduction valve 44, and the like are connected. . Then, the ECU 70 performs operation control by detecting engine operation information by a sensor system and 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 48, and the intake air amount is detected by the air flow sensor 50. 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 10 except when vaporized fuel supply control described later is executed, and includes fuel injection control at the time of starting. In this fuel injection control, the fuel injection amount is calculated based on the intake air amount, the engine speed, the temperature of the engine coolant, etc., and the fuel injection timing is determined based on the crank angle. Drive one or both. 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 70 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 38 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 40 with the vaporized fuel supply valve 42 and the air introduction valve 44 closed. At this time, the fuel injection amount is calculated so that all of the injected fuel is vaporized and the vapor pressure of the vaporized fuel becomes the saturated vapor pressure.

  Then, the fuel injected from the in-tank injection valve 40 is quickly vaporized and becomes vaporized fuel while expelling the air in the tank from the relief valve 46. At this time, the relief valve 46 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 fuel is completed, the air in the tank is almost exhausted, and the vaporized fuel tank 38 is filled with the vaporized fuel in a pressure state close to the saturated vapor pressure.

  By the vaporized fuel generation control described above, vaporized fuel can be stored in the vaporized fuel tank 38 during engine operation. And the vaporized fuel tank 38 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 38 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 42 and the air introduction valve 44 are opened when the engine is started, and the vaporized fuel stored in the vaporized fuel tank 38 is supplied to the surge tank 20. Specifically, first, the ECU 70 detects that a start request has occurred when the starter switch is turned on. Then, with the vaporized fuel supply valve 42 and the air introduction valve 44 closed and the throttle valve 18 held in the fully closed position, the starter motor 36 is energized to start cranking. As a result, intake negative pressure is generated in the surge tank 20 by cranking.

  Then, the ECU 70 opens the vaporized fuel supply valve 42 and the air introduction valve 44 when the intake negative pressure in the surge tank 20 has sufficiently increased. Thereby, the vaporized fuel in the vaporized fuel tank 38 is supplied into the surge tank 20 by the intake negative pressure. At this time, since the air flows into the vaporized fuel tank 38 from the atmosphere introduction valve 44 by the amount of vaporized fuel flowing out, the vaporized fuel is supplied smoothly. When the vaporized fuel supply valve 42 and the air introduction valve 44 are opened, if the pressure in the vaporized fuel tank 38 is equal to or higher than atmospheric pressure, the vaporized fuel supply valve 42 is opened first. On the other hand, if the pressure in the vaporized fuel tank 38 is lower than the atmospheric pressure, the air introduction valve 44 is opened first. Thereby, it is possible to prevent the vaporized fuel in the tank from flowing out into the atmosphere and the air from flowing back into the vaporized fuel tank 38 from the surge tank 20.

  The vaporized fuel supplied from the vaporized fuel tank 38 to the surge tank 20 flows into the cylinder via the intake port 24, and is ignited and burned in the cylinder. Then, the ECU 70 stops the cranking when the start is confirmed by an increase in the engine speed or the like. Further, the vaporized fuel supply valve 42 and the air introduction valve 44 are closed, and the vaporized fuel supply control is terminated. Then, normal fuel injection control is started, and fuel is injected from the intake port injection valve 26 and the in-cylinder injection valve 28. Note that switching from vaporized fuel to normal fuel injection is not necessarily performed after engine start has been confirmed. For example, the normal fuel injection may be switched when a necessary amount of vaporized fuel is supplied at the time of starting. Further, vaporized fuel may be supplied to each cylinder only at the time of combustion in the first cycle, and normal fuel injection control may be executed at the time of combustion after the second cycle.

  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.

  By the way, when the above-described supply of vaporized fuel is started, air (residual air) exists in the space from the vaporized fuel supply valve 42 to the combustion chamber in the intake passage 12. When the supply of the vaporized fuel is started, the residual air is sucked into the cylinder before the vaporized fuel, and causes a decrease in the concentration of the vaporized fuel immediately after the supply is started. To be precise, the space is a space formed inside the surge tank 20, the intake manifold 22, and the intake port 24. The space in the surge tank 20 occupies most of the space. For this reason, in the following description, the residual air in the space is referred to as residual air in the surge tank 20 or the like.

  FIG. 3 is an explanatory diagram showing temporal changes in the concentration of vaporized fuel supplied into the cylinder in a comparative example in which the control according to Embodiment 1 of the present invention is not performed. As shown in this figure, the vaporized fuel concentration in the cylinder gradually increases from time t1 at which vaporized fuel begins to flow into the cylinder, and is necessary for combustion at the first ignition (first cycle) at time t2. Reach concentration. At this time t2, ignition in the first cycle is performed. During the period from time t1 to time t2, residual air in the surge tank 20 and the like flows into the cylinder together with the vaporized fuel, so that the vaporized fuel concentration in the cylinder does not reach the level required for ignition and ignition is performed. I can't do it. Therefore, the vaporized fuel flowing into the cylinder during this period (the outflow fuel indicated by the hatched portion in FIG. 3) flows out into the exhaust passage 14 as unburned fuel. As a result, the comparative example has a problem that vaporized fuel is wasted at the time of start-up, and not only the startability is deteriorated but also exhaust emission is deteriorated.

  Therefore, in the system according to the present embodiment, when a request for starting the engine 10 is generated, vaporized fuel is mixed in the surge tank 20 prior to the start of cranking. Hereinafter, a detailed description will be given with reference to FIGS. When a request for starting the engine 10 is generated, the pressure in the vaporized fuel tank 38 is first detected by the tank pressure sensor 54 prior to the start of cranking. When the pressure is lower than the atmospheric pressure, that is, when the vaporized fuel tank 38 is in a negative pressure environment, the atmospheric introduction valve 44 is normally closed and the throttle valve 18 is held in the fully closed position. Then, the vaporized fuel supply valve 42 is opened. FIG. 4 is a diagram for explaining the gas flow when the vaporized fuel supply valve 42 is opened in the system according to the first embodiment of the present invention. As shown in this figure, when the vaporized fuel supply valve 42 is opened, a part of residual air such as the surge tank 20 moves into the vaporized fuel tank 38 due to the negative pressure A in the vaporized fuel tank 38. FIG. 5 is a diagram for explaining a state after the gas flow shown in FIG. 4 is generated. As described above, since the throttle valve 18 is held in the fully closed position, fresh air is prevented from flowing into the surge tank 20. For this reason, as shown in FIG. 5, the pressures of the vaporized fuel tank 38 and the surge tank 20 are balanced at the negative pressure B, and the gas flow is temporarily stopped.

  Next, the air introduction valve 44 is opened while the vaporized fuel supply valve 42 is held at the open position. FIG. 6 is a diagram for explaining a gas flow when the air introduction valve 44 is opened in the system according to the first embodiment of the present invention. As shown in this figure, when the air introduction valve 44 is opened, the air upstream of the throttle valve 18 moves into the vaporized fuel tank 38 due to the negative pressure B in the vaporized fuel tank 38. Along with this, a part of the vaporized fuel in the vaporized fuel tank 38 moves into the surge tank 20. FIG. 7 is a diagram for explaining a state after the gas flow shown in FIG. 6 occurs. As shown in this figure, when a part of the vaporized fuel in the vaporized fuel tank 38 flows into the surge tank 20, a mixture of the vaporized fuel is formed in the surge tank 20. When the vaporized fuel supply control described above is executed thereafter, the mixture (vaporized fuel) in the surge tank 20 quickly flows into the cylinder via the intake port 24 due to the cranking negative pressure, It is ignited and burns.

  Thus, according to the system of the first embodiment described above, the air-fuel mixture can be generated in the surge tank 20 before the start of cranking. As a result, when the engine 10 is started, the high concentration vaporized fuel can be promptly flowed into the cylinder immediately after the vaporized fuel supply starts.

  FIG. 8 is an explanatory diagram showing temporal changes in the concentration of vaporized fuel supplied into the cylinder in the first embodiment of the present invention. As shown in this figure, according to the present embodiment, the period from the time point t1 at which vaporized fuel starts to flow into the cylinder to the time point t2 at which ignition of the first cycle is performed is shorter than that in the comparative example shown in FIG. can do. Thereby, useless vaporized fuel (outflow fuel) flowing out to the exhaust system without being ignited can be reduced, and the vaporized fuel can be effectively utilized. Therefore, startability can be improved and emission characteristics at the time of start can be improved.

[Specific Processing in First Embodiment]
Next, specific processing for realizing the above-described control will be described with reference to FIGS. 9 and 10. First, FIG. 9 is a flowchart showing vaporized fuel generation control executed by the ECU 70 in the first embodiment of the present invention. The routine shown in FIG. 9 is repeatedly executed during engine operation.

  In the routine shown in FIG. 9, first, the temperature T in the vaporized fuel tank 38 is detected by the tank temperature sensor 56 (step 100). Next, it is determined whether or not the tank internal temperature T is higher than the determination temperature T1 (step 102). Here, the determination temperature T1 is set in correspondence with 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. As a result, when it is recognized that T> T1 is established, it is determined that the fuel is in a temperature state at which vaporization is likely to occur, the amount of fuel injected into the vaporized fuel tank 38 is calculated, and vaporized fuel supply is performed. The in-tank injection valve 40 is driven with the valve 42 and the air introduction valve 44 closed (step 104). Thereby, vaporized fuel is stored in the vaporized fuel tank 38.

  Next, FIG. 10 is a flowchart showing vaporized fuel supply control executed by the ECU 70 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. 10, first, it is determined whether or not the ignition switch (IGSW) is turned on (step 200). As a result, when the determination is not accepted, this routine is immediately terminated.

  On the other hand, if the determination in step 200 is confirmed, it is determined that a request for starting the engine 10 has been generated, the process proceeds to the next step, and the vaporized fuel supply valve 42 and the air introduction valve 44 are normally set. A process of maintaining the throttle valve 18 in the fully closed position is performed (step 202). Next, the internal pressure Pt of the vaporized fuel tank 38 is detected using the tank pressure sensor 54 (step 204).

  In the routine shown in FIG. 10, it is next determined whether or not the internal pressure Pt of the vaporized fuel tank 38 detected in step 204 is higher than the atmospheric pressure P0 (step 206). As a result, if the establishment of Pt> P0 is recognized, the process proceeds to step 214 described later. On the other hand, if the establishment of Pt> P0 is not recognized in step 206, it is determined that a negative pressure is generated in the vaporized fuel tank 38, the process proceeds to the next step, and the atmosphere introduction valve 44 is turned on. The vaporized fuel supply valve 42 is opened with the normally closed state and the throttle valve 18 held in the fully closed position (step 208). As a result, a part of the residual air such as the surge tank 20 flows into the vaporized fuel tank 38.

  Next, the atmospheric introduction valve 44 is opened with the vaporized fuel supply valve 42 opened and the throttle valve 18 held in the fully closed position (step 210). Thereby, the vaporized fuel in the vaporized fuel tank 38 flows into the surge tank 20 and is mixed.

  Next, the ignition start condition is changed (step 212). Specifically, the crank angle period from the start of cranking to the ignition of the first cycle is set earlier than the normal time. Next, the starter motor 36 is activated to start cranking (step 214). Thereby, the vaporized fuel in the surge tank 20 is supplied into the cylinder and ignited, whereby the engine 10 is started.

  As described above, according to the system of the present embodiment, when a request for starting the engine 10 is generated, a mixture of vaporized fuel is formed in the surge tank 20 prior to the start of cranking. As a result, since the required amount of vaporized fuel can be supplied to the engine 10 as soon as cranking is started, an early start request during cold weather can be satisfied. In addition, since the outflow fuel that flows out to the exhaust system without being ignited can be reduced, it is possible to improve the emission characteristics at the start.

  By the way, in the system of Embodiment 1 mentioned above, the surge tank 20 was mentioned as an example as a supply part of the vaporization fuel with respect to the intake passage 12, and was demonstrated. However, the present invention is not limited to this, and the vaporized fuel tank 38 may be connected to an arbitrary portion of the intake passage 12 and the vaporized fuel may be supplied to this portion as long as it is downstream of the throttle valve 18.

  Further, in the system of the first embodiment described above, the vaporized fuel tank 38 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 38 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 38, and the vaporized fuel tank 38 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 38 to heat the vaporized fuel tank 38 with exhaust heat. With these configurations, the saturated vapor pressure of the fuel in the vaporized fuel tank 38 can be increased, and the amount of vaporized fuel that can be stored can be increased.

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

  Further, the system of the first embodiment described above is based on an engine in which the valve overlap between the intake valve and the exhaust valve is not provided when the engine is stopped before starting. For this reason, when using an engine with a valve overlap, control may be performed so as to prohibit a state with a valve overlap when the start control is executed. As a result, air can be prevented from flowing from the exhaust system into the surge tank 20 where the negative pressure is generated, so that the vaporized fuel in the vaporized fuel tank 38 can be efficiently mixed into the surge tank 20. it can.

  In the system of the first embodiment described above, the air introduction valve 44 is opened in step 210 while the throttle valve 18 is held at the fully closed position. It is not limited to the position. That is, the opening of the throttle valve may be adjusted so that the air-fuel ratio of the air-fuel mixture formed in the surge tank 20 becomes the target air-fuel ratio.

  In the first embodiment described above, the ECU 70 executes the process of step 104, so that the “vaporized fuel generating means” in the first invention executes the process of step 206. The “valve control means” according to the first aspect of the present invention is realized by the “determination means” according to the first aspect of the invention executing the processes of steps 208 to 210 described above.

10 Engine (Internal combustion engine)
12 Intake passage 14 Exhaust passage 16 Air cleaner 18 Throttle valve 20 Surge tank 22 Intake manifold 24 Intake port 26 Intake port injection valve 28 In-cylinder injection valve 32 Fuel tank 36 Starter motor 38 Vaporized fuel tank 40 In-tank injection valve 42 Vaporized fuel supply valve 44 Air introduction valve 46 Relief valve 48 Crank angle sensor 50 Air flow sensor 52 Water temperature sensor 54 Tank pressure sensor 56 Tank temperature sensor 58 Fuel property sensor 70 ECU

Claims (5)

A fuel tank for storing fuel;
A vaporized fuel tank that is connected to an intake passage of the internal combustion engine and stores 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;
A throttle valve for adjusting the amount of intake air on the upstream side of the connecting portion in 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, and generating vaporized fuel in the vaporized fuel tank;
A normally-closed air introduction valve that opens and closes a communication portion between the inside and the outside space of the vaporized fuel tank;
Determining means for determining whether or not an internal pressure of the vaporized fuel tank is smaller than an atmospheric pressure when a request for starting the internal combustion engine is generated;
When the determination means determines that the internal pressure of the vaporized fuel tank is smaller than the atmospheric pressure, the vaporized fuel supply valve is closed with the throttle valve and the air introduction valve closed before the cranking is performed. Valve control means for opening the valve and then opening the air introduction valve;
A control device for an internal combustion engine, comprising: The valve control means includes
When the determination means determines that the internal pressure of the vaporized fuel tank is smaller than the atmospheric pressure, the vaporized fuel supply valve is closed with the throttle valve and the air introduction valve closed before the cranking is performed. 2. The control device for an internal combustion engine according to claim 1, wherein the air introduction valve is opened after the internal pressure of the vaporized fuel tank and the internal pressure of the intake passage become equal to each other.   3. The control apparatus for an internal combustion engine according to claim 1, wherein the intake passage includes a surge tank provided on the downstream side of the throttle valve.   4. The control apparatus for an internal combustion engine according to claim 1, further comprising prohibiting means for prohibiting valve overlap between the intake valve and the exhaust valve when the internal combustion engine is stopped.   5. The control device for an internal combustion engine according to claim 1, wherein the fuel is a fuel containing alcohol.

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