JP2011220114A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve stating performance by quickly supplying vaporized fuel to a cylinder even upon cold start.SOLUTION: An engine 10 includes a normal fuel tank 32, a vaporized fuel tank 38, an in-tank injection valve 40, and a vaporized fuel supply valve 42 and the like. An ECU 70 supplies vaporized fuel stored in the vaporized fuel tank 38 during engine running to a surge tank 20 upon start. In this case, the ECU 70 performs cranking in a closed state of a vaporized fuel supply valve 42 and a throttle valve 18, and discharges residual air of the surge tank 20 etc. by the cranking. When the discharging of the residual air is ended, supplying of vaporized fuel is started. Thus, flowing of the vaporized fuel together with the residual air to the cylinder is suppressed, and the vaporized fuel of a high concentration is quickly supplied into the cylinder immediately after the supplying start of the vaporized fuel.

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 Japanese Utility Model Publication No. 01-119874 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 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;
A vaporized fuel tank connected to the intake passage and storing vaporized fuel vaporized by the fuel;
In-tank fuel supply means for supplying fuel in the fuel tank to the vaporized fuel tank;
A normally-closed vaporized fuel supply valve that opens and closes a connection between the vaporized fuel tank and the intake passage;
A throttle valve for adjusting the amount of intake air upstream of the connecting 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 to generate vaporized fuel in the vaporized fuel tank;
A closed cranking means for performing cranking in a state in which the vaporized fuel supply valve and the throttle valve are closed at the time of starting the internal combustion engine;
Air discharge determination means for determining whether residual air existing in a space from the vaporized fuel supply valve to the combustion chamber in the intake passage is discharged by the operation of the valve closing cranking means;
Vaporized fuel supply means for opening the vaporized fuel supply valve and supplying vaporized fuel in the vaporized fuel tank to the intake passage when it is determined by the air discharge determination means that the residual air has been discharged;
It is characterized by providing.

  According to a second aspect of the invention, the air discharge determination means has a pressure determination value corresponding to a negative pressure state at the time when the residual air is discharged, and the intake passage is operated during the operation of the valve closing cranking means. When the internal pressure falls below the pressure determination value, it is determined that the residual air has been discharged.

  According to a third aspect of the present invention, the pressure determination value is variably set based on at least one parameter among the amount of vaporized fuel stored in the vaporized fuel tank, the amount of vaporized fuel required at start-up, and the battery voltage. Pressure judgment value variable means is provided.

4th invention is provided with the cranking frequency calculation means which calculates the cranking frequency required in order to exhaust the air which exists in the space from the vaporized fuel supply valve to the combustion chamber among the intake passages,
The air discharge determination means is configured to determine that the residual air has been discharged when the actual cranking count by the valve closing cranking means reaches the required cranking count.

According to a fifth aspect of the invention, the fuel injection valve is an in-cylinder injection valve, and an injected fuel boosting means for increasing the pressure of fuel supplied to the in-cylinder injection valve during cranking;
In-cylinder injection control means for driving the in-cylinder injection valve to inject fuel into the cylinder when supplying vaporized fuel by the vaporized fuel supply means.

  According to a sixth aspect of the present invention, even when it is determined that the residual air has been discharged by the air discharge determination unit, the supply of vaporized fuel is continued until the fuel pressure raised by the injected fuel boosting unit exceeds a predetermined fuel pressure determination value. Supply prohibition means for prohibiting

  The seventh invention includes fuel pressure judgment value varying means for variably setting the fuel pressure judgment value based on at least one parameter among the temperature of the internal combustion engine, the fuel property, and the fuel injection amount of the in-cylinder injection valve. .

  In an eighth aspect of the invention, an alcohol fuel is used as the fuel.

  According to the first invention, vaporized fuel can be generated during operation of the internal combustion engine, and the vaporized fuel can be stored in the vaporized fuel tank using natural decompression after the engine is stopped. Thereby, since it is not necessary to generate vaporized fuel at the time of starting, vaporized fuel can be rapidly supplied into the cylinder even at the time of low temperature starting. In addition, when vaporized fuel is supplied, cranking is performed with the vaporized fuel supply valve and the throttle valve closed by the closed cranking means, and residual air present in a part of the intake passage is discharged to the exhaust system. be able to. Thereby, at the time of starting, supply of vaporized fuel can be started in a negative pressure atmosphere in which residual air is exhausted by cranking, and it is possible to suppress vaporized fuel from flowing into the cylinder together with the residual air. it can. Further, by using this negative pressure atmosphere, the flow rate when the vaporized fuel flows out from the vaporized fuel tank can be increased, and the vaporized fuel can be supplied efficiently. Thereby, at the time of starting, high concentration vaporized fuel can be quickly flowed into the cylinder immediately after the start of supply of vaporized fuel, and useless vaporized fuel flowing out into the exhaust system without being ignited can be reduced. Therefore, it is possible to improve the startability by effectively using the vaporized fuel and to improve the exhaust emission.

  According to the second invention, the air discharge determination means can determine that the residual air has been discharged when the pressure in the intake passage falls below the pressure determination value during the operation of the valve closing cranking means. . Therefore, if the vaporized fuel supply means starts supplying vaporized fuel at the time of this determination, the vaporized fuel supply means can quickly supply vaporized fuel of high concentration into the cylinder.

  According to the third aspect of the invention, the pressure determination value varying means is configured to adjust the pressure based on at least one parameter among the amount of vaporized fuel stored in the vaporized fuel tank, the amount of vaporized fuel required at start-up, and the battery voltage. The judgment value can be set appropriately. Thereby, saving of vaporized fuel, preservation of battery performance, etc. can be performed according to the situation.

  According to the fourth aspect of the invention, the air discharge determination means can determine that the residual air has been discharged when the actual cranking count by the valve closing cranking means reaches the required cranking count. Therefore, if the vaporized fuel supply means starts supplying vaporized fuel at the time of this determination, the vaporized fuel supply means can quickly supply vaporized fuel of high concentration into the cylinder. Further, since the intake pressure sensor need not be used, the system configuration can be simplified.

  According to the fifth aspect of the present invention, the fuel pressure can be sufficiently increased using the cranking period by the valve closing cranking means before the in-cylinder injection is started. Then, by starting in-cylinder injection in this state, atomization of the injected fuel can be promoted. For this reason, at the time of start-up, the ignitability of the fuel can be enhanced while suppressing the consumption of the vaporized fuel by the synergistic effect of the atomized fuel and the vaporized fuel. Therefore, it is possible to reliably improve the startability when the remaining amount of vaporized fuel is small or at a very low temperature. Moreover, the fuel injection time can be shortened by sufficiently boosting the fuel. Thereby, since the setting range of the fuel injection timing is widened, it is possible to optimize the injection timing and effectively improve the exhaust emission and startability.

  According to the sixth aspect of the invention, the supply prohibiting means can prohibit the supply of vaporized fuel until the fuel pressure for in-cylinder injection exceeds a predetermined fuel pressure determination value. Thereby, supply of vaporized fuel and in-cylinder injection can be started at an appropriate timing when the in-cylinder injection pressure reaches the reference pressure.

  According to the seventh invention, the fuel pressure judgment value varying means appropriately sets the fuel pressure judgment value based on at least one parameter among the temperature of the internal combustion engine, the fuel property, and the fuel injection amount of the in-cylinder injection valve. be able to. Thereby, the minimum necessary injection pressure can be secured according to the situation without excessively increasing the in-cylinder injection pressure.

  According to the eighth 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. 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. 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 Embodiment 1 of this invention, it is a flowchart which shows the control performed by ECU. In Embodiment 1 of this invention, it is a flowchart which shows the control performed by ECU. In Embodiment 2 of this invention, it is a flowchart which shows the control performed by ECU. In Embodiment 3 of this invention, it is explanatory drawing which shows the state which uses together vaporized fuel and cylinder injection fuel at the time of starting. In Embodiment 3 of this invention, it is a flowchart which shows the control performed by ECU.

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 a spark plug 30 (see FIG. 2) that ignites the air-fuel mixture flowing into the cylinder, and an intake valve and an exhaust valve (not shown) that open and close 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 fuel tank 32 is provided with a fuel pump (not shown) for sending fuel stored in the fuel tank 32 toward the injection valves 26 and 28. The in-cylinder injection fuel system is provided with a booster pump 34 that further increases the pressure of the fuel delivered by the fuel pump to a reference pressure for in-cylinder injection (for example, about 10 to 20 MPa). . The booster pump 34 is constituted by, for example, a mechanical pump connected to the camshaft of the engine, and operates when the camshaft rotates.

  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 is vaporized 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 this figure, the system of the present embodiment includes a sensor system including a plurality of sensors 48 to 64 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 intake pressure sensor 54 detects the pressure of intake air at the position of the surge tank 20, for example, and the ECU 70 detects the pressure Ps in the surge tank 20 based on the output of the intake pressure sensor 54. The intake air temperature sensor 56 detects the temperature of intake air. On the other hand, the tank pressure sensor 58 detects the pressure in the vaporized fuel tank 38, and the tank temperature sensor 60 detects the temperature in the vaporized fuel tank 38. The fuel property sensor 62 detects the alcohol concentration in the fuel as the property of the fuel. Further, the fuel pressure sensor 64 detects the pressure of fuel boosted by the booster pump 34, that is, the injection pressure of fuel injected from the in-cylinder injection valve 28.

  In addition to the sensors 48 to 64, 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 of the throttle valve 18, and the like). An accelerator opening sensor for detecting the accelerator opening, etc.) are included, and these sensors are connected to the input side of the ECU 70. The present invention does not necessarily require the intake pressure sensor 54 or the tank temperature sensor 60. As an example, the intake air pressure may be estimated based on the intake air amount, the rotational speed, etc. of the engine without using the intake pressure sensor 54. In addition, the tank temperature sensor 60 may not be used, and the tank internal temperature may be estimated based on the engine temperature, operation history, heat conduction characteristics to the vaporized fuel tank 38, and the like.

  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 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 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 together with the vaporized fuel, and causes the concentration of the vaporized fuel to decrease 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 the time t1 at which the vaporized fuel starts to flow into the cylinder, and is necessary for combustion at the first ignition (first cycle) at the time t2. Reach concentration. At this time t2, ignition in the first cycle is performed. During the period from time t1 to 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.

  For this reason, in this embodiment, before starting the supply of vaporized fuel, first, the vaporized fuel supply valve 42 is closed and the cranking is executed in a state where the throttle valve 18 is held at the fully closed position. Thereby, the residual air in the surge tank 20 and the like is discharged to the exhaust system by cranking. At this time, by fully closing the throttle valve 18, the fresh air can be prevented from flowing into the surge tank 20 and the residual air can be discharged efficiently. In the present embodiment, it is determined whether residual air has been exhausted by cranking, and supply of vaporized fuel is started when this determination is satisfied.

  More specifically, the pressure in the surge tank 20 decreases as the residual air is discharged, and becomes a predetermined negative pressure state when the discharge is sufficiently completed. The ECU 70 stores a pressure determination value Pc corresponding to the predetermined negative pressure state in advance. Then, when the pressure Ps in the surge tank 20 falls below the pressure judgment value Pc corresponding to the predetermined negative pressure state, the ECU 70 regards that residual air is discharged by cranking, and supplies vaporized fuel. Is configured to start.

  According to the above configuration, at the time of starting, supply of vaporized fuel can be started in a negative pressure atmosphere in which residual air from the surge tank 20 and the like is discharged by cranking. For this reason, it can suppress that vaporized fuel flows in in a cylinder with residual air. Further, the large intake negative pressure in the surge tank 20 is used to increase the flow velocity (flow rate) when the vaporized fuel flows out of the vaporized fuel tank 38, so that the vaporized fuel can be supplied efficiently. Thereby, at the time of start-up, the high concentration vaporized fuel can be quickly flowed into the cylinder immediately after the vaporized fuel supply starts.

  FIG. 4 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 t1 at which vaporized fuel starts to flow into the cylinder to the time 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 exhaust emission at the start can be improved.

  In addition, the pressure determination value Pc described above may be set as a constant, but at least one of the amount of vaporized fuel stored in the vaporized fuel tank 38, the amount of vaporized fuel required at the time of starting, and the battery voltage. It is good also as a structure set variably based on a parameter. More specifically, for example, when the vaporized fuel in the vaporized fuel tank 38 is small, it is necessary to start efficiently with a small amount of vaporized fuel. In this case, it is preferable to supply vaporized fuel after further increasing the negative pressure in the surge tank 20. For this reason, in the present embodiment, the pressure determination value Pc is set lower as the amount of vaporized fuel stored in the vaporized fuel tank 38 is smaller. The amount of vaporized fuel stored in the tank is, for example, the temperature and pressure in the tank when fuel is injected into the vaporized fuel tank 38 in vaporized fuel production control, and the temperature in the tank after natural decompression. It can be calculated based on

  Further, the amount of vaporized fuel required at the time of start-up decreases as the outside air temperature or the engine temperature of the engine increases. When the required amount of vaporized fuel is small, the supply operation can be performed smoothly without putting the surge tank 20 in an extremely negative pressure state. For this reason, in the present embodiment, the pressure determination value Pc is set higher as the amount of vaporized fuel required at the time of start-up is smaller (or the outside air temperature or the engine temperature is higher). Note that the amount of vaporized fuel required at the time of starting can be calculated based on the outside air temperature or the engine temperature by acquiring data beforehand through experiments or the like.

  Further, the decompression of the surge tank 20 is realized by cranking. However, when the battery voltage is low, it is preferable to shorten the cranking time to preserve the battery performance. For this reason, in the present embodiment, the pressure determination value Pc is set higher as the battery voltage is lower. These settings are realized, for example, by creating map data in which the relationship between each parameter and the pressure determination value Pc is converted into data, and storing the map data in the ECU 70 in advance. According to the above configuration, the pressure determination value Pc can be appropriately set based on each parameter, and the pressure in the surge tank 20 can be maintained in the minimum negative pressure state without wastefully reducing the pressure. it can.

[Specific Processing for Realizing Embodiment 1]
Next, specific processing for realizing the above-described control will be described with reference to FIGS. 5 and 6. First, FIG. 5 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. 5 is repeatedly executed during engine operation.

  In the routine shown in FIG. 5, first, the temperature T in the vaporized fuel tank 38 is detected by the tank temperature sensor 60 (step 100), and it is determined whether or not this tank temperature T is higher than the determination temperature T1 (step 100). 102). Here, the determination temperature T1 is set corresponding to the lower limit value of the temperature at which vaporized fuel can be generated, and is a determination temperature for permitting fuel injection in the tank. When the determination in step 102 is satisfied, since the temperature of the fuel is easily vaporized, the amount of fuel injected into the vaporized fuel tank 38 is calculated, and the vaporized fuel supply valve 42 and the air introduction valve 44 are closed. The inner injection valve 40 is driven (step 104). Thereby, vaporized fuel is stored in the vaporized fuel tank 38.

  Next, FIG. 6 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 while the engine is operating. In the routine shown in FIG. 6, first, it is determined whether or not the ignition switch (IGSW) is turned on (step 200). When this determination is established, the vaporized fuel supply valve 42 and the air introduction valve 44 are closed, and the throttle valve 18 is held at the fully closed position (step 202). Further, the pressure determination value Pc is calculated based on the various parameters described above (step 204). Then, the starter motor 36 is activated to start cranking (step 206). Thereby, the pressure in the surge tank 20 decreases as the discharge of residual air proceeds.

  In the next processing, the pressure Ps in the surge tank 20 detected by the intake pressure sensor 54 is read (step 208), and it is determined whether or not the pressure Ps has decreased below the pressure determination value Pc (step 210). If the determination in step 210 is not satisfied, the remaining air has not been sufficiently discharged, so the processing in steps 206 to 210 is repeated until the determination is satisfied, and the cranking is continued.

  On the other hand, if the determination in step 210 is satisfied, the remaining air has been sufficiently discharged, so the initial ignition cylinder that is initially ignited at the start is determined based on the result of the cylinder determination process or the like (step 212). . Then, in accordance with the intake stroke of the first ignition cylinder, the vaporized fuel supply valve 42 and the air introduction valve 44 are opened, and the supply of vaporized fuel is started (step 214). Subsequently, ignition is sequentially started from the first ignition cylinder (step 216). Next, for example, when an amount of vaporized fuel necessary for starting is supplied, the vaporized fuel supply valve 42 and the air introduction valve 44 are closed, and the supply of vaporized fuel is stopped (step 218). Then, normal fuel injection control (startup injection control) is started, and fuel is injected from the intake port injection valve 26 and the in-cylinder injection valve 28 (step 220).

  In the first embodiment, steps 100 to 104 shown in FIG. 5 show a specific example of the vaporized fuel generating means in claim 1. Further, steps 202 and 206 shown in FIG. 6 are specific examples of the valve closing cranking means in claim 1, step 210 is a specific example of the air discharge determination means in claims 1 and 2, and step 214 is the vaporization in claim 1. Specific examples of the fuel supply means are shown. Step 204 shows a specific example of the pressure determination value varying means in claim 3.

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 as in the first embodiment (FIGS. 1, 2, and 5), it is determined whether residual air has been discharged based on the number of crankings. It is characterized by having a configuration for judging. 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]
Residual air in the surge tank 20 or the like is discharged to the exhaust system by the total cylinder volume of the engine (= 1 cylinder volume × the number of cylinders) every time the number of crankings increases by one. Here, it is assumed that the number of times of cranking is counted once every time the crankshaft rotates by one combustion cycle (720 ° CA). Therefore, the number of times of cranking required until the residual air is exhausted is obtained by dividing the air amount Vs of residual air existing in the surge tank 20 or the like (hereinafter referred to as surge tank air amount Vs) by the total cylinder volume. Can be obtained.

  Based on this principle, the present embodiment calculates the number of crankings necessary to discharge residual air, and supplies vaporized fuel when the actual number of crankings reaches the required number of crankings. Is configured to start. According to this configuration, the supply of vaporized fuel can be started when the residual air is exhausted without using the intake pressure sensor 54. Therefore, according to the present embodiment, it is possible to obtain substantially the same operational effects as those of the first embodiment, and it is possible to simplify the system configuration and promote cost reduction.

[Specific Processing for Realizing Embodiment 2]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 7 is a flowchart showing the control executed by the ECU in the second embodiment of the present invention. The routine shown in this figure is executed repeatedly during operation of the engine, instead of FIG. 6 of the first embodiment.

  In the routine shown in FIG. 7, first, in steps 300 and 302, the same processing as in steps 200 and 202 shown in FIG. 6 is performed. Next, the air amount Vs in the surge tank is calculated based on the known volume and atmospheric pressure of the surge tank 20 and the intake air temperature detected by the intake air temperature sensor 56 (step 304). Based on the surge tank air amount Vs and the total cylinder volume, the number of times of cranking Nc required to discharge the residual air is calculated (step 306). In the next process, based on the result of the cylinder discrimination process or the like, the initial ignition cylinder to be ignited first is determined when the required number of crankings have been completed (step 308). If the timing at which the vaporized fuel actually flows into the cylinder is delayed due to an intake air delay or the like, the initial ignition may be delayed by that amount.

  In the next processing, it is determined whether or not the actual cranking count N has reached the required cranking count Nc while performing cranking (steps 310 and 312). When this determination is established, it is determined that the residual air has been discharged, and the supply of vaporized fuel is started (step 314). Subsequently, as in the first embodiment, ignition is sequentially started from the initial ignition cylinder, and when the required amount of vaporized fuel is supplied, the supply is stopped and the routine proceeds to normal start-up injection control (step 316, step 316). 318, 320). On the other hand, if the determination in step 312 is not satisfied, it is determined that the remaining air has not been exhausted. Therefore, the processing in steps 310 to 312 is repeated until the determination is satisfied, and the cranking is continued.

  In the second embodiment, steps 302 and 310 shown in FIG. 7 show a specific example of the valve closing cranking means in claim 1. Further, step 312 shows a specific example of the air discharge determination means in claims 1 and 4, and step 314 shows a specific example of the vaporized fuel supply means in claim 1, respectively.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIGS. Although the present embodiment employs almost the same configuration and control (FIGS. 1, 2, and 5) as in the first embodiment, the supply of vaporized fuel and the fuel injection into the cylinder are used in combination. It is characterized by having a configuration. 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 3]
At the time of starting, for example, when the remaining amount of vaporized fuel is small or the temperature environment is extremely low, it may be difficult to start with vaporized fuel alone. In such a case, in the present embodiment, as shown in FIG. 8, not only the vaporized fuel is supplied at the start, but also the fuel injection into the cylinder is used together. FIG. 8 is an explanatory diagram showing a state in which vaporized fuel and in-cylinder injected fuel are used together at the time of start in Embodiment 3 of the present invention.

  Here, since high injection pressure is required for fuel injection in the cylinder, the fuel pressure is maintained at the reference pressure for in-cylinder injection in the fuel system that supplies fuel to the in-cylinder injection valve 28. For this purpose, a booster pump 34 is provided (see FIG. 1). However, since the booster pump 34 is a mechanical pump driven by the camshaft of the engine, a certain amount of time is required between the start of cranking and the pressure at the end of the fuel system reaching the reference pressure. Time is needed. In contrast, in the present embodiment, as in the first embodiment, the cranking is continued until the residual air is exhausted. For this reason, the pressure of the fuel system can be stably increased to the reference pressure using the cranking period.

  Specifically, in the present embodiment, first, the fuel injection pressure for in-cylinder injection is increased by the boost pump 34 during the cranking period, and this fuel injection pressure is in-cylinder injection pressure Pinj by the fuel pressure sensor 64. Detect as. Even if it is determined that the residual air has been discharged, the supply of vaporized fuel is prohibited until the in-cylinder injection pressure Pinj exceeds a predetermined fuel pressure determination value Prc. Here, the predetermined fuel pressure determination value Prc is set corresponding to the above-described reference pressure for in-cylinder injection. When the in-cylinder injection pressure Pinj exceeds the fuel pressure determination value Prc, supply of vaporized fuel is started and fuel injection from the in-cylinder injection valve 28 is started.

  According to the above configuration, the fuel injection pressure can be sufficiently increased during the cranking period, and then fuel injection can be started from the in-cylinder injection valve 28, and atomization of the injected fuel can be promoted. . And the ignitability of fuel can be improved, suppressing the consumption of vaporized fuel by the synergistic effect of the atomized fuel and vaporized fuel. Therefore, it is possible to reliably improve the startability when the remaining amount of vaporized fuel is small or at a very low temperature. Moreover, in the present embodiment, the fuel injection time can be shortened by sufficiently increasing the in-cylinder injection pressure. Thereby, since the setting range of the fuel injection timing is widened, it is possible to optimize the injection timing and effectively improve the exhaust emission and startability.

  The fuel pressure determination value Prc described above may be set as a constant, but is variably set based on at least one parameter among the temperature of the engine 10, the properties of the fuel, and the fuel injection amount of the in-cylinder injection valve 28. It is good also as composition to do. Specifically, for example, when the engine temperature (for example, engine coolant water temperature) is low or the alcohol concentration in the fuel is high, the fuel injection amount tends to increase. It is preferable to increase the pressure to shorten the injection time. Therefore, in the present embodiment, the fuel pressure determination value Prc is set higher as the engine temperature is lower and the alcohol concentration in the fuel is higher. Similarly, the fuel pressure determination value Prc is set higher as the fuel injection amount is larger. These settings are realized, for example, by creating map data in which the relationship between each parameter and the fuel pressure determination value Prc is converted into data and storing the map data in the ECU 70 in advance.

  According to the above configuration, the fuel pressure determination value Prc can be appropriately set based on each parameter. That is, the minimum necessary injection pressure can be ensured according to the situation without excessively increasing the in-cylinder injection pressure. Thereby, the injection time of fuel can be shortened and the setting range of injection timing can be expanded. The fuel injection amount of the in-cylinder injection valve 28 at the time of starting is, for example, the difference between the remaining amount of vaporized fuel (the maximum supply amount of vaporized fuel) in the vaporized fuel tank 38 and the required fuel at the time of startup, or the cryogenic start. It is determined based on the difference between the required fuel at the time and the maximum supply amount of vaporized fuel, etc., and can be obtained by experiments or the like. Further, as the engine temperature, for example, lubricating oil or the temperature of the engine body may be used.

[Specific Processing for Realizing Embodiment 3]
Next, specific processing for realizing the above-described control will be described with reference to FIG. FIG. 9 is a flowchart showing the control executed by the ECU in the third embodiment of the present invention. The routine shown in this figure is executed repeatedly during operation of the engine, instead of FIG. 6 of the first embodiment.

  In the routine shown in FIG. 9, first, in steps 400 to 410, processing substantially similar to that in steps 200 to 210 shown in FIG. 6 is performed. However, in step 404, processing for calculating the fuel pressure determination value Prc based on the various parameters described above is also executed. If it is determined in step 410 that the pressure Ps in the surge tank 20 has decreased below the pressure determination value Pc, the in-cylinder injection pressure Pinj detected by the fuel pressure sensor 64 is read (step 412).

  Next, it is determined whether or not the in-cylinder injection pressure Pinj is higher than the fuel pressure determination value Prc. When this determination is satisfied, the in-cylinder injection pressure has sufficiently increased during cranking. Therefore, in steps 416 to 426, Processing substantially similar to steps 212 to 220 shown in FIG. 6 is executed. However, in step 420, in-cylinder injection control for injecting fuel from the in-cylinder injection valve 28 is executed. On the other hand, if the determination in step 414 is not satisfied, the in-cylinder injection pressure has not yet sufficiently increased. Therefore, the supply of vaporized fuel and the in-cylinder injection are prohibited until this determination is satisfied, and steps 406 to 414 are performed. Repeat the process. Thereby, supply of vaporized fuel and in-cylinder injection can be started at an appropriate timing when the in-cylinder injection pressure reaches the reference pressure.

  In the third embodiment, the booster pump 34 constitutes an injected fuel booster that increases the pressure of the fuel supplied to the in-cylinder injection valve 28 during cranking. Steps 402 and 406 shown in FIG. 9 show a specific example of the valve closing cranking means in claim 1, and step 410 shows a specific example of the air discharge determination means in claims 1 and 2. Further, step 414 is a specific example of the supply prohibition means in claim 6, step 418 is a specific example of the vaporized fuel supply means in claim 1, and step 420 is a specific example of the in-cylinder injection control means in claim 5. Each is shown. Further, step 404 shows a specific example of the pressure judgment value varying means in claim 3 and a specific example of the fuel pressure judgment value varying means in claim 7.

  Moreover, although each structure was illustrated individually in Embodiment 2, 3, this invention is not restricted to this, You may implement | achieve the structure which combined Embodiment 2,3.

  In the embodiment, the surge tank 20 has been described as an example of the supply portion of the vaporized fuel to the intake passage 12. However, the present invention is not limited to this, and the vaporized fuel tank 38 may be connected to any part of the intake passage 12 and the vaporized fuel may be supplied to this part as long as it is downstream of the throttle valve 18. .

  In the embodiment, the vaporized fuel tank 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.

  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 Booster pump (Injected fuel booster)
36 Starter motor 38 Vaporized fuel tank 40 In-tank injection valve (in-tank fuel supply means)
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 Intake pressure sensor 56 Intake temperature sensor 58 Tank pressure sensor 60 Tank temperature sensor 62 Fuel property sensor 64 Fuel pressure sensor 70 ECU

Claims (8)

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 connected to the intake passage and storing vaporized fuel vaporized by the fuel;
In-tank fuel supply means for supplying fuel in the fuel tank to the vaporized fuel tank;
A normally-closed vaporized fuel supply valve that opens and closes a connection between the vaporized fuel tank and the intake passage;
A throttle valve for adjusting the amount of intake air upstream of the connecting 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 to generate vaporized fuel in the vaporized fuel tank;
A closed cranking means for performing cranking in a state in which the vaporized fuel supply valve and the throttle valve are closed at the time of starting the internal combustion engine;
Air discharge determination means for determining whether residual air existing in a space from the vaporized fuel supply valve to the combustion chamber in the intake passage is discharged by the operation of the valve closing cranking means;
Vaporized fuel supply means for opening the vaporized fuel supply valve and supplying vaporized fuel in the vaporized fuel tank to the intake passage when it is determined by the air discharge determination means that the residual air has been discharged;
A control device for an internal combustion engine, comprising:   The air discharge determination means has a pressure determination value corresponding to a negative pressure state at the time when the residual air is discharged, and the pressure in the intake passage is determined as the pressure determination during operation of the valve closing cranking means. The control device for an internal combustion engine according to claim 1, wherein when the value falls below a value, it is determined that the residual air has been discharged.   Pressure determination value variable means for variably setting the pressure determination value based on at least one parameter among the amount of vaporized fuel stored in the vaporized fuel tank, the amount of vaporized fuel required at start-up, and the battery voltage The control device for an internal combustion engine according to claim 2 provided. Cranking number calculating means for calculating the number of cranking times required to discharge air existing in the space from the vaporized fuel supply valve to the combustion chamber in the intake passage;
2. The internal combustion engine according to claim 1, wherein the air discharge determination unit determines that the residual air has been discharged when an actual number of crankings by the valve-closing cranking unit reaches the required number of crankings. Engine control device. The fuel injection valve is an in-cylinder injection valve, and an injected fuel boosting means for increasing the pressure of fuel supplied to the in-cylinder injection valve during cranking;
In-cylinder injection control means for driving the in-cylinder injection valve to inject fuel into the cylinder when supplying vaporized fuel by the vaporized fuel supply means;
The control apparatus for an internal combustion engine according to any one of claims 1 to 4, further comprising:   Supply prohibiting means for prohibiting the supply of vaporized fuel until the pressure of the fuel raised by the injected fuel boosting means exceeds a predetermined fuel pressure determination value even if it is determined that the residual air is discharged by the air discharge determining means The control apparatus for an internal combustion engine according to claim 5, comprising:   7. A fuel pressure judgment value varying means for variably setting the fuel pressure judgment value based on at least one of a temperature of an internal combustion engine, a fuel property, and a fuel injection amount of the in-cylinder injection valve. The internal combustion engine control device described.   The control device for an internal combustion engine according to any one of claims 1 to 7, wherein alcohol fuel is used as the fuel.

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