JP2011236814A - Device for control of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promptly supply vaporized fuel into a cylinder even at low temperature start, and to improve starting performance.SOLUTION: An engine 10 includes a vaporized fuel tank 36, an in-tank injection valve 38, a vaporized fuel supply valve 40 or the like. An air phase chamber 36B and a liquid phase chamber 36C are formed in the vaporized fuel tank 36. An ECU 70 supplies the vaporized fuel to a surge tank 20 at the start-up while accumulating the vaporized fuel generated during the drive of the engine in the air phase chamber 36B in advance. By this arrangement, the starting performance can be improved. Furthermore, the fuel is injected from the in-tank injection valve 38 on assumption that liquid phase fuel may remain in the liquid phase chamber 36C at the generation of the vaporized fuel, and the vaporized fuel can be generated even at cold staring. Furthermore, the vaporized fuel generated in the liquid phase chamber 36C during the drive is replenished to the air phase chamber 36B, and a large volume of the vaporized fuel can be accumulated in the air phase chamber 36B as much as possible.

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 2008-286101A JP 2003-239785 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 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;
A fuel injection valve for injecting fuel in the fuel tank into the intake passage and / or the combustion chamber;
Vaporization that has a vapor phase chamber connected to the intake passage and a liquid phase chamber connected to the vapor phase chamber, and stores vaporized fuel generated by vaporization of the fuel in the liquid phase chamber in the vapor phase chamber A fuel tank,
In-tank fuel supply means for supplying the fuel stored in the fuel tank to the liquid phase chamber of the vaporized fuel tank;
A normally-closed vaporized fuel supply valve which is provided at a connection portion between the vapor phase chamber of the vaporized fuel tank and the intake passage, and which opens and closes the connection portion;
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 gas phase chamber of the vaporized fuel tank;
Vaporized fuel supply means for opening the vaporized fuel supply valve at the start of the internal combustion engine and supplying vaporized fuel stored in the vapor phase chamber of the vaporized fuel tank to the intake passage during operation;
It is characterized by providing.

A second invention is a normally closed liquid phase fuel supply valve for connecting and blocking between the liquid phase chamber of the vaporized fuel tank and the intake passage,
When liquid phase fuel that has not been vaporized exists in the liquid phase chamber of the vaporized fuel tank, the liquid phase fuel supply valve is opened during operation of the internal combustion engine to supply the liquid phase fuel to the intake passage. Liquid phase fuel supply means.

A third invention comprises a fuel tank for storing fuel;
A fuel injection valve for injecting fuel in the fuel tank into the intake passage and / or the combustion chamber;
A vaporized fuel tank in which an upper side and a lower side are respectively connected to the intake passage and store vaporized fuel that is 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 which is provided at a connection portion between the upper side of the vaporized fuel tank and the intake passage, and which opens and closes the connection portion;
A normally closed liquid-phase fuel supply valve that is provided at a connection portion between the lower side of the vaporized fuel tank and the intake passage, and that opens and closes the connection portion;
Vaporized fuel generation means for driving the fuel supply means in the tank with the vaporized fuel supply valve and the liquid phase fuel supply valve closed during operation of the internal combustion engine to generate vaporized fuel in the vaporized fuel tank When,
Vaporized fuel supply that opens the vaporized fuel supply valve with the liquid phase fuel supply valve closed when the internal combustion engine is started, and supplies vaporized fuel stored in the vaporized fuel tank to the intake passage during operation Means,
When there is liquid phase fuel that is not vaporized in the vaporized fuel tank, the liquid phase fuel supply valve is opened with the vaporized fuel supply valve closed during operation of the internal combustion engine, and the liquid phase fuel is opened. Liquid phase fuel supply means for supplying fuel to the intake passage;
It is characterized by providing.

  According to a fourth aspect of the present invention, the liquid phase fuel supply means includes high load fuel supply means for opening the liquid phase fuel supply valve during high load operation of the internal combustion engine.

  According to a fifth aspect of the invention, the liquid phase fuel supply means opens the liquid phase fuel supply valve when the amount of the liquid phase fuel present in the vaporized fuel tank exceeds an upper limit determination value. Adjusting means is provided.

According to a sixth aspect of the invention, the vaporized fuel tank is provided with a normally closed air introduction valve that communicates and blocks the space in the tank with respect to the external space.
The liquid phase fuel supply means opens the air introduction valve after starting the supply of the liquid phase fuel when the pressure in the vaporized fuel tank is equal to or lower than the pressure in the intake passage. Tank pressure adjusting means for opening the liquid phase fuel supply valve is provided.

  According to the seventh invention, the vaporized fuel generating means is configured to generate the vaporized fuel at least before the warm-up of the internal combustion engine is completed.

An eighth invention is a member that divides a space in the vaporized fuel tank into upper and lower portions, wherein the gas phase chamber is formed on the upper side of the tank and the liquid phase chamber is formed on the lower side. A separator;
A gas passage through which vaporized fuel generated in the liquid phase chamber flows into the gas phase chamber.

  In a ninth aspect, 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 vapor phase chamber of 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 quickly supplied into the cylinder even at the time of low temperature starting, and startability can be improved. Further, when the vaporized fuel is generated, the remaining liquid phase fuel without vaporization can be stored in the liquid phase chamber. That is, even when excess fuel is supplied by the tank fuel supply means, this fuel can be absorbed in the liquid phase chamber. Therefore, during operation of the internal combustion engine, vaporized fuel can be generated freely on the premise that liquid phase fuel may remain in a wide temperature range from cold to warm-up, and vaporized fuel can be generated. Can increase the timing. Further, in a state where liquid phase fuel is accumulated, vaporized fuel generated in the liquid phase chamber during operation of the internal combustion engine is always replenished to the gas phase chamber, and as much vaporized fuel as possible can be stored in the gas phase chamber. . Therefore, even when the short trip operation or the like is repeated, it is possible to avoid the shortage of vaporized fuel at the next start.

  According to the second invention, the liquid phase fuel supply means opens the liquid phase fuel supply valve during the operation of the internal combustion engine when the liquid phase fuel is present in the liquid phase chamber of the vaporized fuel tank. Fuel can be supplied to the intake passage. Thereby, the amount of the liquid phase fuel accumulated in the liquid phase chamber can be appropriately adjusted, and the liquid phase fuel can be effectively utilized.

  According to the third aspect, as in the case of the first aspect, it is not necessary to generate vaporized fuel at the time of start-up, so startability can be improved. Further, when the vaporized fuel is generated, the liquid phase fuel remaining without being vaporized can be stored in the lower side of the vaporized fuel tank, and the liquid phase fuel can be supplied from the liquid phase fuel supply valve to the intake passage. Therefore, during operation of the internal combustion engine, vaporized fuel can be freely generated on the premise that liquid phase fuel may remain in a wide temperature range from cold to warm-up. Further, in the state where the liquid phase fuel is accumulated, the liquid phase fuel is constantly vaporized during the operation of the internal combustion engine, so that as much vaporized fuel as possible can be stored in the vaporized fuel tank.

  According to the fourth aspect, when the vaporized fuel is generated, the light component of the fuel supplied into the vaporized fuel tank is vaporized relatively early. For this reason, heavy components having a relatively high octane number tend to remain in the liquid phase fuel. On the other hand, the high load fuel supply means can open the liquid phase fuel supply valve during high load operation. Therefore, during high load operation where knocking is likely to occur, liquid phase fuel having a relatively high octane number can be burned in the cylinder, and the occurrence of knocking can be suppressed using the liquid phase fuel.

  According to the fifth aspect, the liquid amount adjusting means can open the liquid phase fuel supply valve when the storage amount of the liquid phase fuel exceeds the upper limit determination value. Thereby, the storage amount of liquid phase fuel can be adjusted appropriately, and liquid phase fuel can be prevented from being excessively stored.

  According to the sixth aspect of the invention, the tank pressure adjusting means opens the air introduction valve when starting the supply of the liquid phase fuel in a state where the pressure in the vaporized fuel tank is equal to or lower than the pressure in the intake passage. The liquid phase fuel supply valve can be opened. Thereby, it is possible to prevent the air from flowing back into the vaporized fuel tank from the intake passage side.

  According to the seventh invention, the vaporized fuel generating means can generate the vaporized fuel even before the warm-up of the internal combustion engine is completed. As a result, it is possible to generate as much vaporized fuel as possible during operation, including during cold operation, and to avoid a situation in which vaporized fuel is not generated due to continuous cold operation.

  According to the eighth aspect of the invention, the upper vapor phase chamber and the lower liquid phase chamber can be formed in the vaporized fuel tank by the separator. The vaporized fuel generated in the liquid phase chamber can be caused to flow into the gas phase chamber by the gas passage.

  According to the ninth aspect of the invention, even when alcohol fuel that is difficult to vaporize at low temperatures is used, the 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. 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 vaporization fuel production | generation control performed by ECU. 4 is a flowchart showing vaporized fuel supply control executed by an ECU in the first embodiment of the present invention. In Embodiment 1 of this invention, it is a flowchart which shows the liquid phase fuel supply control performed by ECU. It is a whole block diagram for demonstrating the system configuration | structure of Embodiment 2 of this invention.

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.

  In the intake passage 12, an air cleaner 16, a throttle valve 18 and a surge tank 20 are provided in order from the upstream side. The throttle valve 18 is configured by an electronically controlled butterfly valve that is opened and closed between a fully closed position and a fully opened position, 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 middle of the intake passage 12 in order to exhibit an attenuation effect of intake pulsation and the like. 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). Further, 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). The injection valves 26 and 28 are configured to be supplied with alcohol fuel stored in a liquefied state in a fuel tank 32 of the vehicle.

  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 70 described later. As a result, the ECU 70 performs an 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, a liquid phase fuel supply valve 46, and the like described below.

  The vaporized fuel tank 36 stores vaporized fuel obtained by vaporizing alcohol fuel in the fuel tank 32, and is formed as a gas-liquid separation type pressure-resistant container. As a specific configuration example, the vaporized fuel tank 36 includes a separator 36A that divides the space in the tank up and down, a gas phase chamber 36B formed on the upper side in the tank by the separator 36A, and a separator 36A. The liquid phase chamber 36C formed on the lower side in the tank and the gas passage 36D connecting the gas phase chamber 36B and the liquid phase chamber 36C. 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. For this reason, the vaporized fuel tank 36 is maintained at a high temperature during the operation of the engine, and the fuel in the tank is easily vaporized.

  The in-tank injection valve 38 injects (supplies) the fuel stored in the fuel tank 32 into the liquid phase chamber 36C of 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 becomes vaporized fuel by being vaporized in the liquid phase chamber 36C. The vaporized fuel flows into the gas phase chamber 36B via the gas passage 36D and is stored in the gas phase chamber 36B.

  The gas phase chamber 36 </ b> B located on the upper side in the vaporized fuel tank 36 is connected to the surge tank 20. 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 vapor phase chamber 36B of the vaporized fuel tank 36 is disconnected from the surge tank 20, and vaporized fuel can be stored in the vapor phase chamber 36B. When the vaporized fuel supply valve 40 is opened, the gas phase chamber 36B and the surge tank 20 are communicated with each other, and the vaporized fuel stored in the gas phase chamber 36B is supplied to the surge tank 20.

  Further, the vaporized fuel tank 36 is provided with a normally closed air introduction valve 42 for communicating and blocking the gas phase chamber 36B with respect to the external space. The atmosphere introduction valve 42 is constituted by a normally closed electromagnetic valve or the like, and the vaporized fuel tank 36 is released to the atmosphere when the valve is opened. At the time of supplying 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 gas phase chamber 36B from the atmosphere introduction valve 42 by the amount of supply of vaporized fuel. The 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 gas phase chamber 36B.

  Further, a normally closed relief valve 44 configured by, for example, a check valve, a reed valve, or the like is provided in the vapor phase chamber 36B of the vaporized fuel tank 36. The relief valve 44 releases the pressure to the outside (for example, the intake passage 12) when the pressure in the gas phase chamber 36B 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. Thereby, the relief valve 44 is configured to release the air in the gas phase chamber 36B to the outside when the fuel injected into the liquid phase chamber 36C of 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.

  On the other hand, the bottom surface portion of the liquid phase chamber 36C located on the lower side in the vaporized fuel tank 36 is connected to the surge tank 20 through a different path from the gas phase chamber 36B. The connection portion is provided with a liquid phase fuel supply valve 46 constituted by a normally closed electromagnetic valve or the like. The liquid phase fuel supply valve 46 is controlled by an ECU 70 described later, and connects and disconnects the liquid phase chamber 36 </ b> C and the surge tank 20. Thereby, the liquid phase fuel supply valve 46 is the fuel in the liquid phase remaining without being vaporized from the fuel injected from the in-tank injection valve 38 into the liquid phase chamber 36C (hereinafter referred to as liquid phase fuel). Is supplied to the surge tank 20 as it is. The liquid phase fuel supply valve 46 is held in a closed state except when a liquid phase fuel supply control described later is executed.

  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 48 to 60 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 can detect the engine speed and the crank angle based on this output. it can. The air flow sensor 50 detects the intake air amount, and the water temperature sensor 52 detects the temperature of the engine coolant as the engine temperature of the engine 10. The intake pressure sensor 54 detects the pressure Pmv in the surge tank 20, the tank pressure sensor 56 detects the pressure in the vaporized fuel tank 36, and the tank temperature sensor 58 detects the temperature in the vaporized fuel tank 36. Furthermore, the fuel property sensor 60 detects the alcohol concentration in the fuel as the property of the fuel.

  In addition to the sensors 48 to 60, the sensor system includes various sensors necessary for vehicle and engine control (for example, an air-fuel ratio sensor that detects an exhaust air-fuel ratio, a throttle sensor that detects the opening of the throttle valve 18, An accelerator opening sensor that detects the accelerator opening, an intake air temperature sensor that detects the intake air temperature, and the like. These sensors are connected to the input side of the ECU 70. The present invention does not necessarily require the tank temperature sensor 58. For example, the tank temperature sensor 58 is not used, and the tank temperature sensor 58 is used 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 70, there are various types including the throttle valve 18, the injection valves 26, 28, 38, the spark plug 30, the starter motor 34, the vaporized fuel supply valve 40, the air introduction valve 42, the liquid phase fuel supply valve 46 and the like. Actuator is connected. Then, the ECU 70 performs operation control by detecting engine operation information using 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 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 engine load (load factor) is calculated based on the intake air amount and the engine speed, and the fuel injection amount is calculated based on the intake air amount, load, engine coolant temperature, and the like. Then, the fuel injection timing is determined based on the crank angle, and the injection valves 26 and 28 are driven. 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, vaporized fuel supply control, and liquid phase 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 fuel in the vaporized fuel tank 36 during operation of the engine 10 to generate vaporized fuel. More specifically, in the vaporized fuel generation control, the vapor phase fuel supply valve 40, the air introduction valve 42, and the liquid phase fuel supply valve 46 are closed, and the liquid phase chamber of the vaporized fuel tank 36 is supplied from the in-tank injection valve 38. Fuel is injected into 36C. At this time, the fuel injection amount is determined based on the temperature in the vaporized fuel tank 36, the alcohol concentration in the fuel, and the like so that vaporized fuel at least equal to or greater than the startup required amount Fgas is generated. The details of the startup required amount Fgas will be described later.

  The injected fuel is vaporized in the liquid phase chamber 36C and becomes vaporized fuel. The vaporized fuel flows into the gas phase chamber 36B through the gas passage 36D by its own vapor pressure, and expels air in the gas phase chamber 36B from the relief valve 44. Therefore, the relief valve 44 can avoid the suppression of fuel vaporization by the air pressure in the tank, and promote the generation of 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.

  As described above, the vaporized fuel generation control vaporizes alcohol fuel that is difficult to vaporize at low temperatures. Therefore, the vaporized fuel generation control is basically executed after the warm-up is completed, that is, in a state where the vaporized fuel tank 36 is warmed up by the heat of the engine. Is preferred. However, in the present embodiment, a liquid phase chamber 36 </ b> C is provided in the vaporized fuel tank 36. For this reason, for example, when the vaporized fuel generation control is executed during the cold operation, the remaining injected fuel (liquid phase fuel) without being vaporized is stored in the liquid phase chamber 36C. Accordingly, the vaporized fuel generation control is performed when, for example, the amount of vaporized fuel held in the vaporized fuel tank 36 is less than the required fuel amount Fgas at the start even during cold operation (before completion of warm-up). Executed.

  The startup required amount Fgas is the amount of vaporized fuel required when starting the engine, and is variably set based on, for example, the outside air temperature or engine temperature (engine cooling water temperature, etc.) at the time of startup. The ECU 70 stores map data for calculating the starting required amount Fgas based on the outside air temperature and the engine temperature in advance. 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.

  According to the vaporized fuel generation control described above, vaporized fuel can be stored in the vapor phase chamber 36B of the vaporized fuel tank 36 during engine operation. The vaporized fuel tank 36 can hold at least a part of the vaporized fuel in a gas phase state even when the engine is cold after the engine is stopped by using natural pressure reduction generated in the tank.

  In the present embodiment, since the vapor-liquid separation type vaporized fuel tank 36 is provided, the vaporized fuel is generated in the gas phase chamber 36B, and the remaining liquid phase fuel is stored in the liquid phase chamber 36C. Can do. That is, even when excessive fuel is injected by the in-tank injection valve 38, this fuel can be absorbed by the liquid phase chamber 36C. For this reason, in the present embodiment, the vaporized fuel is generated before the warm-up of the engine is completed. Therefore, during operation of the engine, vaporized fuel can be generated freely on the premise that liquid phase fuel may remain in a wide temperature range from cold to warm-up, and vaporized fuel can be generated. The timing can be increased. As a result, it is possible to generate as much vaporized fuel as possible during operation, including during cold operation, and to avoid a situation in which vaporized fuel is not generated due to continuous cold operation.

  Further, in the present embodiment, it is possible to intentionally store the liquid phase fuel in the liquid phase chamber 36C by intentionally injecting excess fuel when the vaporized fuel is generated. Including this case, in a state where the liquid phase fuel is accumulated in the liquid phase chamber 36C, vaporized fuel generated in the liquid phase chamber 36C during the operation of the engine is always replenished to the gas phase chamber 36B, and the gas phase chamber 36B is filled. As much vaporized fuel as possible can be stored. Therefore, even when an operation in which the engine is stopped in a short time after the start (so-called short trip operation) is repeated, it is possible to avoid a shortage of vaporized fuel at the next start.

(Vaporized fuel supply control)
In the vaporized fuel supply control, when the engine is started, the vaporized fuel supply valve 40 and the air introduction valve 42 are opened, and the vaporized fuel stored in the vapor phase chamber 36B of the vaporized fuel tank 36 is supplied to the surge tank 20. It is. More specifically, first, when cranking is started by turning on the starter switch, intake negative pressure is generated in the surge tank 20 due to cranking. At this time, the ECU 70 opens the vaporized fuel supply valve 40 and the air introduction valve 42, and supplies the vaporized fuel in the gas phase chamber 36B to the surge tank 20 by intake negative pressure. The liquid phase fuel supply valve 46 is kept closed.

  As a result, when vaporized fuel in the gas phase chamber 36B flows out to the surge tank 20, the air flows into the gas phase chamber 36B from the atmosphere introduction valve 42 accordingly, so that the vaporized fuel can be supplied smoothly. When opening the atmosphere introduction valve 42, if the pressure in the vaporized fuel tank 36 is equal to or higher than the atmospheric pressure, the vaporization fuel supply valve 40 is first opened and then the atmosphere introduction valve 42 is opened. . On the other hand, when the pressure in the tank is lower than the atmospheric pressure, the air introduction valve 42 is first opened and then the vaporized fuel supply valve 40 is opened. This prevents vaporized fuel in the gas phase chamber 36B from flowing out from the atmosphere introduction valve 42 into the atmosphere, and prevents air in the surge tank 20 from flowing back from the vaporized fuel supply valve 40 into the gas phase chamber 36B. Can do.

  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 70 stops the cranking when confirming that the self-sustaining operation is started by increasing the engine speed. 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. The vaporized fuel supply control is preferably executed only when the engine temperature at the start is equal to or lower than a predetermined determination temperature that requires vaporized fuel.

(Liquid phase fuel supply control)
In the liquid phase fuel supply control, when the liquid phase fuel is present in the liquid phase chamber 36C of the vaporized fuel tank 36, the liquid phase fuel supply valve 46 is opened during the operation of the engine, and the liquid phase fuel in the liquid phase chamber 36C. Phase fuel is supplied to the surge tank 20. At this time, the vaporized fuel supply valve 40 is held in a closed state, and the air introduction valve 42 is opened as necessary as described later. The liquid phase fuel supplied to the surge tank 20 is vaporized in the middle of the intake passage by the heat transmitted from the engine and flows into the cylinder as vaporized fuel. For this reason, it is preferable to execute the liquid phase fuel supply control after the warm-up operation is completed. According to the above control, the amount of the liquid phase fuel accumulated in the liquid phase chamber 36C can be appropriately adjusted while constantly replenishing the vaporized fuel using the liquid phase fuel, and the liquid phase fuel can be effectively used. Can be used.

  In the liquid phase fuel supply control, the liquid phase fuel supply valve 46 is intermittently opened and closed in accordance with the properties of the fuel, the temperature environment, etc., and the valve opening time and valve opening timing are appropriately controlled. Thereby, the supply amount and supply timing of the liquid phase fuel are appropriately controlled so that, for example, all the liquid phase fuel is vaporized and then flows into the cylinder. Further, during the operation of the engine, normal fuel injection control by the injection valves 26 and 28 is executed. When the liquid phase fuel supply control is executed, the injection valves 26 and 28 are controlled according to the supply amount of the liquid phase fuel. The fuel injection amount is reduced. Thereby, the fuel gas supplied in a cylinder can be hold | maintained in moderate density | concentration.

  On the other hand, when the vaporized fuel is generated, light components of the fuel injected into the vaporized fuel tank 36 are vaporized relatively early. For this reason, heavy components having a relatively high octane number tend to remain in the liquid phase fuel. Therefore, in the present embodiment, the liquid phase fuel supply valve 46 is opened during high load operation, and liquid phase fuel supply control is executed. As a result, during high-load operation where knocking is likely to occur, liquid phase fuel having a relatively high octane number can be burned in the cylinder, and the occurrence of knocking can be suppressed using the liquid phase fuel.

  Even when the high load operation is not performed, when a large amount of liquid phase fuel is accumulated in the vaporized fuel tank 36, liquid phase fuel supply control is executed. Specifically, the storage amount of the liquid phase fuel accumulated in the liquid phase chamber 36C is calculated, and when the storage amount exceeds the upper limit determination value Flimit, the liquid phase fuel supply valve 46 is opened. The upper limit determination value Flimit is set corresponding to the volume of the liquid phase chamber 36C or the upper limit of the liquid level allowed in the tank. Thereby, the storage amount of liquid phase fuel can be adjusted appropriately, and it can prevent that liquid phase fuel overflows from liquid phase chamber 36C.

[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 vaporized fuel generation control executed by the ECU 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 alcohol concentration in the fuel is detected based on the output of the fuel property sensor 60 (step 100). Further, the temperature and pressure in the vaporized fuel tank 36 are detected based on the outputs of the tank pressure sensor 56 and the tank temperature sensor 58 (step 102). In addition to these detection processes, engine coolant temperature, intake air temperature detection, and the like are also executed. In the next process, an appropriate fuel injection amount is calculated based on, for example, the alcohol concentration in the fuel, the temperature and volume in the vaporized fuel tank 36, and the in-tank injection valve 38 is set so that this fuel injection amount is realized. Drive (step 104).

  As a result, fuel is injected from the in-tank injection valve 38 into the liquid phase chamber 36C and vaporized fuel is generated, so the amount of vaporized fuel generated is calculated (step 106). In this calculation process, the amount of vaporized fuel is calculated based on, for example, the pressure in the tank changed after fuel injection, the temperature in the tank, the temperature characteristic of the saturated vapor pressure of alcohol, and the like. Note that the temperature characteristic data of the saturated vapor pressure is stored in the ECU 70 in advance. In the next processing, as described above, the starting required amount Fgas is calculated based on the engine water temperature, the intake air temperature, etc., and it is determined whether the amount of vaporized fuel at that time is larger than the starting required amount Fgas. (Step 108).

  When the determination in step 108 is satisfied, since a sufficient amount of vaporized fuel is generated in the in-tank injection valve 38, the control is terminated as it is. If the determination in step 108 is not established, the processes in steps 102 to 108 are repeated until a larger amount of vaporized fuel than the starting required amount Fgas is generated. Thus, for example, during a cold operation, when a sufficient amount of vaporized fuel is generated in the tank, the liquid phase fuel is stored in the liquid phase chamber 36C. This liquid phase fuel is used by the control shown in FIG.

  Next, FIG. 4 is a flowchart showing vaporized fuel supply control executed by the ECU 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, first, it is determined whether or not the ignition switch (IGSW) is turned on (step 200). When this determination is established, the alcohol concentration in the fuel is detected (step 202). Further, the engine water temperature at the start is detected based on the output of the water temperature sensor 52 (step 204).

  Next, it is determined whether or not the starter switch is turned on (step 206). When this determination is established, the starter motor 34 is activated to perform cranking (step 208). Then, a cylinder discrimination process is executed during cranking to determine whether the cylinder discrimination process has been completed (step 210). Subsequently, after the cylinder discrimination is completed, a vaporized fuel supply determination temperature ethw1 is calculated, and it is determined whether or not the engine water temperature at the start is lower than the vaporized fuel supply determination temperature ethw1 (step 212). 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 60 as the alcohol concentration in the fuel is higher (that is, as the fuel volatility is lower).

  If the determination in step 212 is established, it is difficult to start unless vaporized fuel is used. Therefore, the processes in steps 214 to 226 are executed to supply vaporized fuel. As described above, this process is performed while switching the opening order of the vaporized fuel supply valve 40 and the atmospheric introduction valve 42 based on the magnitude relationship between the pressure (pressure in the tank) P of the vaporized fuel tank 36 and the atmospheric pressure P0. The vaporized fuel is supplied to the surge tank 20. More specifically, first, it is determined whether or not the tank internal pressure P is greater than the atmospheric pressure P0 (step 214). When this determination is satisfied, the vaporized fuel supply valve 40 is opened and then the atmospheric introduction valve 42 is opened. Is opened, and the two valves 40 and 42 are closed when a sufficient amount of vaporized fuel for starting is supplied (steps 216 to 220). If the determination in step 214 is not satisfied, the vapor introduction fuel supply valve 40 is opened after the atmosphere introduction valve 42 is opened, and then the valves 40 and 42 are closed (steps 222 to 226). . On the other hand, if the determination in step 212 is not satisfied, normal start-up injection control is executed, and fuel is injected from the intake port injection valve 26 and the in-cylinder injection valve 28 (step 228).

  Next, FIG. 5 is a flowchart showing liquid phase fuel supply control executed by the ECU 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. 5, first, the alcohol concentration in the fuel, the temperature in the vaporized fuel tank 36, and the pressure P are detected (steps 300 and 302). Then, the amounts of vaporized fuel and liquid phase fuel present in the vaporized fuel tank 36 are calculated (step 304). Here, the amount of vaporized fuel is calculated by the same process as step 106 in FIG. Further, the amount of liquid phase fuel is calculated by subtracting the amount of vaporized fuel from the fuel injection amount calculated in step 104 in FIG.

  Next, it is determined whether or not the amount of liquid phase fuel is larger than a predetermined liquid phase fuel use determination value Fliq (step 306). Here, the liquid-phase fuel use determination value Fliq is a determination value for determining whether or not the liquid-phase fuel accumulated in the liquid-phase chamber 36C is an amount that needs to be used. Therefore, if the determination in step 306 is not established, the control is terminated as it is. On the other hand, when the determination in step 306 is established, it is determined whether or not a high-load operation is being performed (step 308). More specifically, in step 308, it is determined whether or not the engine load calculated by the ECU 70 is equal to or greater than a predetermined load determination value corresponding to a high load.

  When the determination in step 308 is established, the processing of steps 312 to 320 described later is executed, and the liquid phase fuel in the vaporized fuel tank 36 is supplied to the surge tank 20. On the other hand, if the determination in step 308 is not established, it is determined whether or not the amount of liquid phase fuel is larger than the above-described upper limit determination value Flimit (step 310). When this determination is established, the storage amount of the liquid phase fuel is close to the upper limit, so the routine proceeds to step 312. If the determination in step 310 is not established, the amount of liquid phase fuel stored is within an allowable range, and no high load operation is performed. Therefore, until the determination is established in either step 308 or 310 This determination process is repeated.

  Next, in the processing of steps 312 to 320, the liquid phase in the liquid phase chamber 36C is taken into consideration while considering the magnitude relationship between the tank internal pressure P of the vaporized fuel tank 36 and the pressure (intake pressure) Pmv in the surge tank 20. Fuel is supplied to the surge tank 20. More specifically, first, in step 312, it is determined whether or not the tank internal pressure P is higher than the intake pressure Pmv. When this determination is made, there is no possibility of air flowing back from the surge tank 20 into the vaporized fuel tank 36. Therefore, as described above, the liquid phase fuel supply valve 46 is opened and closed at an appropriate timing, and the liquid phase chamber 36C is opened. The liquid phase fuel inside is supplied to the surge tank 20 (step 314).

  On the other hand, if the determination in step 312 is not satisfied, the atmosphere introduction valve 42 is first opened, and the atmosphere is introduced into the vaporized fuel tank 36 that is in a negative pressure state equal to or lower than the intake pressure (step 316). As a result, the pressure in the vaporized fuel tank 36 rises to near atmospheric pressure. Next, the liquid phase fuel supply valve 46 is opened (step 318). Then, these valves 42 and 46 are closed at an appropriate timing (step 320). According to the valve control described above, air can be prevented from flowing back into the vaporized fuel tank 36 from the surge tank 20 side when supplying the liquid phase fuel.

  In the first embodiment, steps 100 to 108 shown in FIG. 3 show a specific example of the vaporized fuel generating means in claim 1, and steps 200 to 226 shown in FIG. A specific example of the means is shown. Further, steps 300 to 320 shown in FIG. 5 show a specific example of the liquid phase fuel supply means in claim 2. Further, steps 308, 314, 318 are specific examples of the high load fuel supply means in claim 3, and steps 310, 314, 318 are specific examples of the liquid amount adjusting means in claim 4, steps 312, 316, 318. These respectively show specific examples of the tank pressure adjusting means in claim 5.

  In the first embodiment, the gas-liquid separation type vaporized fuel tank 36 and the liquid-phase fuel supply valve 46 are provided. However, the present invention is not limited to this, and the liquid-phase fuel supply valve 46 is omitted. It is good. Also in this case, since the liquid phase fuel is stored in the vaporized fuel tank 36 and the function of replenishing the vaporized fuel with the liquid phase fuel is provided, it is possible to obtain the effects according to these functions. .

  In the first embodiment, the vapor phase chamber 36B and the liquid phase chamber 36C are formed in one vaporized fuel tank 36. However, the present invention is not limited to this, and for example, a gas phase chamber and a liquid phase chamber may be formed by separate tanks, and a gas passage through which vaporized fuel flows may be provided between these two tanks.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. Although the present embodiment employs substantially the same configuration and control (FIGS. 2 to 5) as the first embodiment, a vaporized fuel tank 80 that is not a gas-liquid separation type is used. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[Features of Embodiment 2]
FIG. 6 is an overall configuration diagram for explaining a system configuration according to the second embodiment of the present invention. As shown in this figure, in the present embodiment, a vaporized fuel tank 80 having no separator or the like is provided. The vaporized fuel supply valve 40 is connected to the upper side of the vaporized fuel tank 80, and the liquid phase fuel supply valve 46 is connected to the lower side (bottom surface) of the vaporized fuel tank 80. In the present embodiment configured as described above, it is possible to obtain substantially the same operational effects as in the first embodiment.

  In the embodiment, the storage amount of the liquid phase fuel stored in the vaporized fuel tanks 36 and 80 is obtained by calculation processing. However, the present invention is not limited to this. For example, the storage amount of the liquid phase fuel may be detected using a sensor or the like that detects the amount of liquid in the tank or the liquid level.

  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 tanks 36 and 80 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. It is.

  In the embodiment, the vaporized fuel tanks 36 and 80 are 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 tanks 36 and 80 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 tanks 36 and 80, and the vaporized fuel tanks 36 and 80 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 tanks 36 and 80, and the vaporized fuel tanks 36 and 80 may be heated by the exhaust heat. With these configurations, the saturated vapor pressure of the fuel in the vaporized fuel tanks 36 and 80 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.

  Furthermore, 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 (fuel injection valve)
28 In-cylinder injection valve (fuel injection valve)
32 Fuel tank 34 Starter motor 36, 80 Vaporized fuel tank 36A Separator 36B Gas phase chamber 36C Liquid phase chamber 36D Gas passage 38 In-tank injection valve (in-tank fuel supply means)
40 Vaporized fuel supply valve 42 Air introduction valve 44 Relief valve 46 Liquid phase fuel supply valve 54 Intake pressure sensor 56 Tank pressure sensor 58 Tank temperature sensor 60 Fuel property sensor 70 ECU

Claims (9)

A fuel tank for storing fuel;
A fuel injection valve for injecting fuel in the fuel tank into the intake passage and / or the combustion chamber;
Vaporization that has a vapor phase chamber connected to the intake passage and a liquid phase chamber connected to the vapor phase chamber, and stores vaporized fuel generated by vaporization of the fuel in the liquid phase chamber in the vapor phase chamber A fuel tank,
In-tank fuel supply means for supplying the fuel stored in the fuel tank to the liquid phase chamber of the vaporized fuel tank;
A normally-closed vaporized fuel supply valve which is provided at a connection portion between the vapor phase chamber of the vaporized fuel tank and the intake passage, and which opens and closes the connection portion;
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 gas phase chamber of the vaporized fuel tank;
Vaporized fuel supply means for opening the vaporized fuel supply valve at the start of the internal combustion engine and supplying vaporized fuel stored in the vapor phase chamber of the vaporized fuel tank to the intake passage during operation;
A control device for an internal combustion engine, comprising: A normally closed liquid-phase fuel supply valve for connecting and blocking between the liquid-phase chamber of the vaporized fuel tank and the intake passage;
When liquid phase fuel that has not been vaporized exists in the liquid phase chamber of the vaporized fuel tank, the liquid phase fuel supply valve is opened during operation of the internal combustion engine to supply the liquid phase fuel to the intake passage. Liquid phase fuel supply means;
The control device for an internal combustion engine according to claim 1, comprising: A fuel tank for storing fuel;
A fuel injection valve for injecting fuel in the fuel tank into the intake passage and / or the combustion chamber;
A vaporized fuel tank in which an upper side and a lower side are respectively connected to the intake passage and store vaporized fuel that is 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 which is provided at a connection portion between the upper side of the vaporized fuel tank and the intake passage, and which opens and closes the connection portion;
A normally closed liquid-phase fuel supply valve that is provided at a connection portion between the lower side of the vaporized fuel tank and the intake passage, and that opens and closes the connection portion;
Vaporized fuel generation means for driving the fuel supply means in the tank with the vaporized fuel supply valve and the liquid phase fuel supply valve closed during operation of the internal combustion engine to generate vaporized fuel in the vaporized fuel tank When,
Vaporized fuel supply that opens the vaporized fuel supply valve with the liquid phase fuel supply valve closed when the internal combustion engine is started, and supplies vaporized fuel stored in the vaporized fuel tank to the intake passage during operation Means,
When there is liquid phase fuel that is not vaporized in the vaporized fuel tank, the liquid phase fuel supply valve is opened with the vaporized fuel supply valve closed during operation of the internal combustion engine, and the liquid phase fuel is opened. Liquid phase fuel supply means for supplying fuel to the intake passage;
A control device for an internal combustion engine, comprising:   The control device for an internal combustion engine according to claim 2 or 3, wherein the liquid phase fuel supply means includes high load fuel supply means for opening the liquid phase fuel supply valve during high load operation of the internal combustion engine.   The liquid phase fuel supply means includes a liquid amount adjusting means for opening the liquid phase fuel supply valve when the amount of the liquid phase fuel existing in the vaporized fuel tank exceeds an upper limit determination value. Item 5. The control device for an internal combustion engine according to any one of Items 2 to 4. The vaporized fuel tank is provided with a normally closed air introduction valve that communicates and blocks the space in the tank with respect to the external space,
The liquid phase fuel supply means opens the air introduction valve after starting the supply of the liquid phase fuel when the pressure in the vaporized fuel tank is equal to or lower than the pressure in the intake passage. The control apparatus for an internal combustion engine according to any one of claims 2 to 5, further comprising tank pressure adjusting means for opening the liquid phase fuel supply valve.   The control apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the vaporized fuel generation means is configured to generate the vaporized fuel at least before the warm-up of the internal combustion engine is completed. A member that divides the space in the vaporized fuel tank into upper and lower portions, the separator that forms the gas phase chamber on the upper side in the tank and the liquid phase chamber on the lower side;
A gas passage for allowing the vaporized fuel generated in the liquid phase chamber to flow into the gas phase chamber;
The control device for an internal combustion engine according to claim 1, comprising:   The control device for an internal combustion engine according to any one of claims 1 to 8, wherein alcohol fuel is used as the fuel.

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