JP2011226450A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of promptly supplying the amount of vaporized fuel necessary for ignition to the inside of a cylinder even at low-temperature start and of improving startability.SOLUTION: An ECU 60 determines whether or not a stop request to the engine is made (Step 106). When it is determined that the engine stop request is made, the ECU 60 determines whether or not remaining vaporized fuel amount Qg is Qgmin or less (Step 108). When the remaining vaporized fuel amount Qg is the start permission vaporized fuel amount Qgmin or less, the ECU 60 determines that gas fuel amount is run short of, and continues the operation of the engine until a vaporized fuel tank temperature Tgt gets to a generation permission temperature T1 or more (Step 110). Fuel of an injection amount equivalent to combination of the vaporized fuel tank temperature Tgt after elevation and alcohol concentration Cal is injected to the inside of a vaporized fuel tank 34 (Step 112).

Description

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

  Conventionally, for example, Patent Document 1 discloses a control device for an internal combustion engine using a fuel mainly composed of alcohol. Since alcohol is difficult to vaporize particularly at low temperatures, the internal combustion engine is provided with a vaporizing chamber for vaporizing fuel at the time of starting. 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.

  In the internal combustion engine, at the time of starting, 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 vaporizing chamber when an appropriate time has passed. 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 at a low temperature by receiving the heat of the heater in the decompressed vaporizing chamber, 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

  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. On the other hand, if an attempt is made to supply promptly, the amount required for ignition cannot be supplied. Therefore, in any case, there is a possibility that the startability is deteriorated in the conventional technique.

  The present invention has been made in order to solve the above-described problems. An internal combustion engine capable of quickly supplying an amount of vaporized fuel necessary for ignition into a cylinder even at a low temperature start and improving startability. An object of the present invention is to provide an engine control device.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
A fuel tank for storing fuel;
A 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;
Fuel property acquisition means for acquiring the property of the fuel stored in the fuel tank;
Vaporized fuel tank temperature acquisition means for acquiring the temperature in the vaporized fuel tank;
A residual vaporized fuel amount calculating means for calculating an amount of vaporized fuel stored in the vaporized fuel tank as a residual vaporized fuel amount using the property of the fuel and the temperature in the vaporized fuel tank;
Engine stop request determining means for determining the presence or absence of a stop request for the internal combustion engine;
A vaporized fuel amount comparison means for comparing a start-permitted vaporized fuel amount set in advance as a vaporized fuel amount necessary for starting the engine and the residual vaporized fuel amount when there is a stop request;
When the residual vaporized fuel amount is smaller than the start-permitted vaporized fuel amount, the temperature is higher than a preset production-permitted temperature as a temperature at which vaporized fuel of the start-permitted vaporized fuel amount can be generated in the fuel tank. Vaporized fuel tank temperature increasing means for increasing the temperature in the vaporized fuel tank;
In-tank fuel supply means for supplying the fuel in the fuel tank to the vaporized fuel tank when the temperature in the vaporized fuel tank becomes higher than the generation permission temperature;
It is characterized by providing.

The second invention is the first invention, wherein
The vaporized fuel tank temperature increasing means includes engine stop prohibiting means for prohibiting the stop of the internal combustion engine until the temperature in the vaporized fuel tank becomes higher than the generation permission temperature.

The third invention is the first or second invention, wherein
The fuel property acquisition means is a concentration sensor that detects an alcohol concentration in the fuel,
The vaporized fuel tank temperature raising means includes engine speed changing means for changing the speed of the internal combustion engine in accordance with the alcohol concentration.

  According to the first invention, the vaporized fuel is stored in the vaporized fuel tank before the engine is stopped, and is supplied to the combustion chamber when the engine is subsequently started. Therefore, the vaporized fuel can be supplied to the intake passage in a very short time compared to the case where the vaporized fuel is generated when the engine is started. In addition, according to the first invention, when there is an engine stop request, the residual vaporized fuel amount in the vaporized fuel tank is calculated, and when the residual vaporized fuel amount is smaller than the start permitted vaporized fuel amount, The temperature in the vaporized fuel tank can be raised to a temperature higher than the generation permission temperature, and the fuel in the fuel tank can be supplied to the vaporized fuel tank. Therefore, before the engine is stopped, the vaporized fuel that is less than the start-permitted vaporized fuel amount can be supplemented. For these reasons, the vaporized fuel in an amount necessary for ignition can be quickly supplied into the cylinder even at a low temperature start, and startability can be improved.

  According to the second aspect of the present invention, the stop of the internal combustion engine can be prohibited until the temperature in the vaporized fuel tank becomes higher than the generation permission temperature. Therefore, it is possible to reliably replenish vaporized fuel that is less than the start-permitted vaporized fuel amount before stopping the engine.

  For example, as the alcohol concentration in the fuel is higher, energy is required to vaporize the fuel, so that the necessary production permission temperature is also higher. If the generation permission temperature increases, it takes time until the temperature in the vaporized fuel tank rises. According to the third invention, the engine speed can be made variable in accordance with the alcohol concentration. Therefore, control can be performed such that the higher the alcohol concentration, the higher the engine speed. Therefore, a series of controls performed after the engine stop request can be completed within a predetermined time.

1 is an overall configuration diagram for describing a system configuration of a first embodiment. 2 is a configuration diagram showing a control system of the system in Embodiment 1. FIG. It is a timing chart which shows the temperature in the vaporization fuel tank after the stop request | requirement, the fuel injection into a gas holding tank, and an engine state in the case of performing vaporization fuel supplement control. 3 is a flowchart illustrating control executed by an ECU in the first embodiment. The map data for speed change control for changing the engine speed NE during vaporized fuel replenishment control in accordance with the alcohol concentration in the fuel is shown. In Embodiment 2, it is a flowchart which shows the control performed by ECU.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
Hereinafter, Embodiment 1 of the present invention will be described 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 this embodiment includes an engine 10 as an internal combustion engine mounted on an FFV (Flexible Fuel Vehicle) that can use at least two types. It should be noted that the number of cylinders and the arrangement form of each cylinder in the present invention are not limited to those of the engine 10 of the present embodiment, and may be, for example, a 6-cylinder, 8-cylinder, or 12-cylinder engine. It may be a facing type or the like, and can take various forms. 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 intake port injection valve 26 and the in-cylinder injection valve 28 are configured to be supplied with alcohol mixed fuel stored in a liquid state in the fuel tank 32.

  Next, the fuel vaporization system mounted on the engine 10 will be described. In the present embodiment, it is assumed that vaporized fuel generated during operation of the engine is stored in a tank, and this vaporized fuel is used at the next start (details will be described later). Therefore, the fuel vaporization system includes a vaporized fuel tank 34, an in-tank injection valve 36, a vaporized fuel supply valve 38, an air introduction valve 40, a relief valve 42, and the like described below.

  The vaporized fuel tank 34 is formed as a pressure-resistant container (with a known volume) having a sealed structure, and is configured to store vaporized fuel obtained by vaporizing alcohol in the fuel tank 32. Further, the vaporized fuel tank 34 is installed at a position where heat is easily conducted from the engine 10, for example, in the engine room. The vaporized fuel tank 34 is provided with an in-tank injection valve 36. The in-tank injection valve 36 is configured to inject (supply) the fuel stored in the fuel tank 32 into the vaporized fuel tank 34. The in-tank injection valve 36 is constituted by, for example, a general fuel injection valve similar to the intake port injection valve 26 and the in-cylinder injection valve 28, and the fuel injection amount is controlled according to a control signal. The fuel injected from the in-tank injection valve 36 becomes vaporized fuel by being vaporized in the vaporized fuel tank 34.

  The vaporized fuel tank 34 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 38 constituted by a normally closed solenoid valve or the like. When the vaporized fuel supply valve 38 is closed, the vaporized fuel tank 34 and the surge tank 20 are disconnected, and vaporized fuel can be stored in the vaporized fuel tank 34. In addition, when the vaporized fuel supply valve 38 is opened, the surge tank 20 and the vaporized fuel tank 34 are communicated with each other, and the vaporized fuel stored in the vaporized fuel tank 34 is supplied to the surge tank 20.

  The vaporized fuel tank 34 is provided with an air introduction valve 40 at a position where the inside of the tank and the external space can communicate with each other. The atmosphere introduction valve 40 is constituted by a normally closed electromagnetic valve or the like, and the vaporized fuel tank 34 is released to the atmosphere when the valve is opened. When the vaporized fuel is supplied, the vaporized fuel supply valve 38 and the atmospheric introduction valve 40 are opened together with a slight time difference, and the atmospheric air is introduced into the vaporized fuel tank 34 from the atmospheric introduction valve 40 by the amount of vaporized fuel supplied. The Note that the vaporized fuel supply valve 38 and the air introduction valve 40 are kept closed except when vaporized fuel is supplied. The air introduction valve 40 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 40 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 34.

  Further, the vaporized fuel tank 34 is provided with a normally closed relief valve 42 constituted by, for example, a check valve, a reed valve or the like. The relief valve 42 releases the pressure to the outside (for example, the intake passage 12) when the pressure in the vaporized fuel tank 34 exceeds a predetermined operating pressure. The operating pressure of the relief valve 42 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 34 is heated to a temperature around room temperature or slightly higher, and the saturated vapor pressure of the fuel becomes a pressure corresponding to this heating region. Thereby, the relief valve 42 is configured to release the air in the tank to the outside when the fuel injected into the vaporized fuel tank 34 is vaporized. The relief valve 42 also has a function as a safety valve that prevents the pressure in the tank from becoming excessive when the vaporized fuel tank 34 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 in the present embodiment. As shown in FIG. 2, the system of the present embodiment includes a sensor system including a plurality of sensors 44 to 54, and an ECU (Electronic Control Unit) 60 that controls the operating state of the engine 10.

  First, the sensor system will be described. The crank angle sensor 44 outputs a signal synchronized with the rotation of the crankshaft of the engine 10, and the ECU 60 detects the engine speed NE and the crank angle CA based on this output. be able to. The air flow sensor 46 detects the intake air amount, and the water temperature sensor 48 detects the temperature of the engine cooling water. The tank pressure sensor 50 detects the pressure in the vaporized fuel tank 34, and the tank temperature sensor 52 detects the temperature in the vaporized fuel tank 34 (hereinafter also referred to as “vaporized fuel tank temperature Tgt”). Furthermore, the fuel property sensor 54 detects the alcohol concentration (hereinafter, also referred to as “alcohol concentration Cal”) in the mixed fuel as the property of the fuel.

  In addition to the sensors 44 to 54 described above, 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 degree sensor for detecting the accelerator opening degree) is included, and these sensors are connected to the input side of the ECU 60. The present invention does not necessarily require the tank temperature sensor 52. For example, the tank temperature sensor 52 is not used, and the vaporization is performed based on the engine temperature, the operation history, the heat conduction characteristics to the vaporized fuel tank 34, and the like. The fuel tank temperature Tgt may be estimated.

  On the other hand, on the output side of the ECU 60, various types including the throttle valve 18, the intake port injection valve 26, the in-cylinder injection valve 28, the ignition plug 30, the in-tank injection valve 36, the vaporized fuel supply valve 38, the air introduction valve 40, and the like. Actuator is connected. The ECU 60 detects engine operation information using a sensor system, and performs operation control by driving each actuator based on the detection result. Specifically, the engine speed NE and the crank angle CA are detected based on the output of the crank angle sensor 44, and the intake air amount is detected by the air flow sensor 46. Further, while performing the normal fuel injection control described below, the ignition timing is determined based on the crank angle CA, and the spark plug 30 is driven.

  The normal fuel injection control is executed during the operation of the engine except when vaporized fuel supply control, which will be described later, is executed, and includes fuel injection control at start-up. In this fuel injection control, the fuel injection amount is calculated based on the intake air amount, the engine speed NE, the temperature of the engine coolant, and the like, and after determining the fuel injection timing based on the crank angle CA, the intake port injection valve 26 And the cylinder injection valve 28 is 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 60 executes vaporized fuel generation control and vaporized fuel supply control described below as control of the fuel vaporization system.

[Operation of Embodiment 1]
(Vaporized fuel generation control)
The vaporized fuel generation control is to vaporize fuel in the vaporized fuel tank 34 during operation of the engine 10 to generate vaporized fuel. More specifically, in the vaporized fuel generation control, fuel is injected from the in-tank injection valve 36 with the vaporized fuel supply valve 38 and the atmosphere introduction valve 40 closed. The injection amount Ql at this time is determined so that all of the injected fuel is vaporized based on the vaporized fuel tank temperature Tgt and the alcohol concentration Cal. Here, the relation of the fuel injection amount Ql to the combination of the vaporized fuel tank temperature Tgt and the alcohol concentration Cal is stored in advance in the ECU 60 as map data, for example. The injected fuel quickly evaporates and becomes vaporized fuel while expelling air in the tank from the relief valve 42. At this time, the relief valve 42 can prevent the vaporization of fuel from being suppressed by the air pressure in the tank, and can promote the generation of vaporized fuel. As a result, the vaporized fuel tank 34 is finally filled with vaporized fuel.

  By the vaporized fuel generation control described above, vaporized fuel can be stored in the vaporized fuel tank 34 while the engine is operating. And the vaporized fuel tank 34 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 executed only in the warm state, that is, only when the temperature in the vaporized fuel tank 34 is equal to or higher than a predetermined temperature at which vaporized fuel can be generated (hereinafter also referred to as “generation permission temperature T1”). It is preferable. The generation permission temperature T1 is a temperature that changes according to the alcohol concentration Cal. The relationship of the generation permission temperature T1 with respect to the alcohol concentration Cal is stored in advance in the ECU 60 as map data, for example.

(Vaporized fuel supply control)
In the vaporized fuel supply control, the vaporized fuel supply valve 38 and the atmosphere introduction valve 40 are opened when the engine is started, and the vaporized fuel stored in the vaporized fuel tank 34 is supplied to the surge tank 20. More specifically, first, the ECU 60 detects that a start request has occurred when the starter switch is turned on, and starts cranking. As a result, an intake negative pressure is generated in the surge tank 20 due to cranking. Therefore, the ECU 60 opens the vaporized fuel supply valve 38 and the air introduction valve 40 to take the vaporized fuel in the vaporized fuel tank 34 into the intake negative. The surge tank 20 is supplied by pressure.

  At this time, since the air flows into the vaporized fuel tank 34 from the atmosphere introduction valve 40 by the amount of vaporized fuel flowing out, the vaporized fuel can be supplied smoothly. When opening the atmosphere introduction valve 40, if the pressure in the vaporized fuel tank 34 is equal to or higher than atmospheric pressure, the vapor introduction fuel supply valve 38 is first opened and then the atmosphere introduction valve 40 is opened. . On the other hand, when the pressure in the tank is lower than the atmospheric pressure, the air introduction valve 40 is first opened and then the vaporized fuel supply valve 38 is opened. Thereby, it is possible to prevent the vaporized fuel in the tank from flowing out into the atmosphere and the air from flowing back from the surge tank 20 into the vaporized fuel tank 34.

  The vaporized fuel supplied from the vaporized fuel tank 34 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 NE increases and the engine shifts to a self-sustained operation. The ECU 60 stops the cranking when confirming that the self-sustained operation is started by increasing the engine speed NE. Further, the vaporized fuel supply valve 38 and the air introduction valve 40 are closed, and the vaporized fuel supply control is terminated. 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. It should be noted 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 temperature that requires vaporized fuel.

  The above-described vaporized fuel supply control can exert an effect by storing a sufficient amount of vaporized fuel during operation of the engine. However, for example, when an operation that is stopped in a short time after the engine is started (so-called short trip operation) is repeated, the amount of vaporized fuel stored in the vaporized fuel tank 34 tends to be insufficient. When the engine is cold started in this state, the amount of vaporized fuel necessary for starting is not supplied to the intake system, which causes a problem that startability is deteriorated. In particular, in an in-cylinder direct injection engine, the interval period from fuel injection to ignition is short. For this reason, there is a possibility that the startability is remarkably lowered without supplying a sufficient amount of vaporized fuel to the intake system.

  Therefore, in the present embodiment, when the engine is requested to stop, the amount of vaporized fuel remaining in the vaporized fuel tank 34 (hereinafter also referred to as “residual vaporized fuel amount Qg”) is calculated. When the residual vaporized fuel amount Qg is smaller than a predetermined gaseous fuel amount (hereinafter also referred to as “start-permitted vaporized fuel amount Qgmin”) required for starting the engine, fuel injection control for replenishing the shortage The engine stop is delayed until (vaporized fuel replenishment control) is executed, where the start-permitted vaporized fuel amount Qgmin is a value that varies depending on the alcohol concentration Cal.The relationship between the start-permitted vaporized fuel amount Qgmin and the alcohol concentration Cal is For example, it is stored in advance in the ECU 60 as map data.

(Vaporized fuel replenishment control)
The vaporized fuel supplement control will be described with reference to FIG. FIG. 3 is a timing chart showing the vaporized fuel tank temperature Tgt, the fuel injection into the vaporized fuel tank 34, and the engine state after the stop request when the vaporized fuel supplement control is executed. As shown in FIG. 3, when the stop request is generated (time t1) and the amount of vaporized fuel is small, the operation of the engine 10 is continued and the vaporized fuel tank temperature Tgt is raised. Then, when the vaporized fuel tank temperature Tgt becomes higher than the generation permission temperature T1 (time t2), fuel is injected from the in-tank injection valve 36. Thereby, the fuel of the start permission vaporization fuel amount can be reliably ensured in the vaporization fuel tank 34. Therefore, the engine 10 can be smoothly started without causing a shortage of vaporized fuel at the next start after the engine stops.

[Specific Processing for Realizing Embodiment 1]
Next, a specific process for realizing the above-described control will be described with reference to FIG. First, FIG. 4 is a flowchart showing vaporized fuel replenishment control executed by the ECU 60 in the first embodiment of the present invention.

  In the routine shown in FIG. 4, the ECU 60 first detects the alcohol concentration Cal by the fuel property sensor 54 (step 100), detects the vaporized fuel tank temperature Tgt by the tank temperature sensor 52 (step 102), and vaporizes with the alcohol concentration Cal. From the fuel tank temperature Tgt, the residual vaporized fuel amount Qg in the vaporized fuel tank 34 is calculated (step 104). As described above, the relationship of the fuel injection amount Ql to the combination of the vaporized fuel tank temperature Tgt and the alcohol concentration Cal is stored in the ECU 60 in advance. Therefore, the injection amount Ql can be obtained by detecting the vaporized fuel tank temperature Tgt and the alcohol concentration Cal. Further, as described above, the injection amount Ql is determined so that all of the injection amount is vaporized. Therefore, the residual vaporized fuel amount Qg can be obtained as a correlation value of the injection amount Ql.

  Subsequently, the ECU 60 determines whether or not there is a stop request for the engine (step 106). Whether there is an engine stop request can be determined by whether the ignition switch is ON or OFF. That is, in another routine, the state of the ignition switch is acquired, and it is determined whether it is ON or OFF. When the ignition switch is ON, the ECU 60 determines that there is no engine stop request. When the ignition switch is OFF, the ECU 60 determines that there is an engine stop request.

  If it is determined that there is no engine stop request, the ECU 60 determines that the engine is operating and ends this routine. On the other hand, if it is determined that there is an engine stop request, the ECU 60 determines whether or not the residual vaporized fuel amount Qg is equal to or less than Qgmin (step 108). As described above, the relationship between the start permission vaporized fuel amount Qgmin and the alcohol concentration Cal is stored in the ECU 60 in advance. Therefore, the residual vaporized fuel amount Qg and the start-permitted vaporized fuel amount Qgmin obtained from the alcohol concentration Cal detected in step 100 are compared to determine whether the residual vaporized fuel amount Qg is equal to or less than Qgmin.

  If the residual vaporized fuel amount Qg ≦ start-permitted vaporized fuel amount Qgmin, the ECU 60 determines that the gaseous fuel amount is insufficient, and operates the engine until the vaporized fuel tank temperature Tgt becomes equal to or higher than the production permitted temperature T1. (Step 110). Thereby, the engine warm-up operation is continued, and the vaporized fuel tank temperature Tgt is raised to the generation permission temperature T1 or higher. Then, an injection amount of fuel for the combination of the increased vaporized fuel tank temperature Tgt and the alcohol concentration Cal is injected into the vaporized fuel tank 34 (step 112). On the other hand, when the residual vaporized fuel amount Qg> the start-permitted vaporized fuel amount Qgmin, the ECU 60 determines that the gaseous fuel amount is sufficient and supplies fuel from the intake port injection valve 26 and / or the in-cylinder injection valve 28. In addition, the ignition by the spark plug 30 is also stopped (step 114).

  As described above in detail, according to the routine shown in FIG. 4, when the residual vaporized fuel amount Qg is equal to or less than the start permitted vaporized fuel amount Qgmin when the engine stop is requested, the vaporized fuel tank temperature Tgt is equal to or higher than the generation permitted temperature T1. The fuel can be injected into the vaporized fuel tank 34. Thereby, the fuel of the start permission vaporization fuel amount can be reliably ensured in the vaporization fuel tank 34. Therefore, the engine 10 can be started smoothly without causing a shortage of vaporized fuel at the next start after the engine stops.

  In the first embodiment described above, 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 34 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. . This modification can be similarly applied to Embodiment 2 described later.

  In the first embodiment described above, the engine 10 provided with 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 either the intake port injection valve 26 or the in-cylinder injection valve 28 but includes only the other. This modification can be similarly applied to Embodiment 2 described later.

  In the first embodiment described above, the relief valve 42 is used to release the air in the vaporized fuel tank 34 to the outside. However, the relief valve 42 may be omitted and the air introduction valve 40 may be controlled by the ECU 60. That is, the ECU 60 opens the air introduction valve 40 when supplying the vaporized fuel in the vaporized fuel tank 34 to the surge tank 20 and when the pressure in the vaporized fuel tank 34 exceeds a predetermined operating pressure. Also good.

  Moreover, in Embodiment 1 mentioned above, the engine 10 which uses alcohol mixed fuel was mentioned as an example, and was demonstrated. However, the present invention is not limited to this, and can also be applied to a gasoline alternative fuel having the same evaporation characteristics as alcohol (for example, low volatility with a single component and high vaporization latent heat). This modification can be similarly applied to Embodiment 2 described later.

  In Embodiment 1 described above, the vaporized fuel tank temperature Tgt is increased by continuing the operation of the engine 10 during the vaporized fuel replenishment control. However, the method of increasing the vaporized fuel tank temperature Tgt is not limited to this method, and other methods such as providing a heat source such as an electric heater outside the vaporized fuel tank 34 and energizing the heater are used. Thus, the vaporized fuel tank temperature Tgt may be increased. Further, the vaporized fuel tank temperature Tgt may be increased by a combination of energizing the heater while continuing the warm-up operation of the engine 10. This modification can be similarly applied to Embodiment 2 described later.

  In the first embodiment described above, the vaporized fuel supply valve 38 is the “in-tank fuel supply means” in the first invention, and the tank temperature sensor 52 is the “vaporized fuel tank temperature acquisition means” in the first invention. The fuel property sensor 54 corresponds to the “fuel property acquisition means” in the first invention. Further, by executing the processing of step 104 in FIG. 4, the “remaining vaporized fuel amount calculating means” in the first aspect of the invention executes the processing of step 106, thereby determining “engine stop request determination in the first aspect of the invention. The means "executes the process of step 108, and the" vaporized fuel amount comparing means "in the first invention executes the process of step 110, whereby the" vaporized fuel tank temperature increasing means "in the first invention is executed. ”, The“ in-tank fuel supply means ”in the first aspect of the present invention is realized by executing the processing of step 112.

  In the first embodiment described above, the “engine stop prohibiting means” in the second aspect of the present invention is realized by executing the processing of step 110.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. This embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 6 described later in the configuration shown in FIGS. 1 and 2.

[Features of Embodiment 2]
As described above, according to the vaporized fuel replenishment control of the first embodiment, it is possible to reliably ensure the fuel of the start permission vaporized fuel amount in the vaporized fuel tank 34. However, since the start permission vaporized fuel amount Qgmin is a value that varies depending on the alcohol concentration Cal, the start permission vaporized fuel amount Qgmin may be a large value depending on the alcohol concentration Cal. Further, as described above, since the generation permission temperature T1 is determined based on the vaporized fuel tank temperature Tgt and the alcohol concentration Cal, the generation permission temperature T1 may be increased depending on the alcohol concentration Cal. From these facts, depending on the alcohol concentration Cal, it may take time to raise the vaporized fuel tank temperature Tgt to the generation permission temperature T1 or higher.

  Therefore, in the present embodiment, the engine speed change control for changing the engine speed NE during the vaporized fuel replenishment control is executed according to the alcohol concentration Cal. FIG. 5 shows map data for rotational speed change control stored in advance in the ECU 60. As shown in FIG. 5, as the alcohol mixing ratio (%) in the fuel increases, the fuel evaporation characteristic decreases. Therefore, control for increasing the engine speed NE is performed so as to compensate for this. On the contrary, if the alcohol mixing ratio (%) is small, the fuel evaporation characteristic does not deteriorate so much, and the engine speed NE is suppressed. Thereby, the engine operation period after the engine stop request can be set to a predetermined time or less.

[Specific Processing for Realizing Embodiment 2]
Next, specific processing for realizing the above-described rotation speed change control will be described with reference to FIG. FIG. 6 is a flowchart showing the control executed by the ECU 60 in the second embodiment of the present invention. The routine shown in FIG. 6 is repeatedly executed during the operation of the engine instead of the routine shown in FIG. 4 of the first embodiment.

  In the routine shown in FIG. 6, first, the ECU 60 executes the same processing as steps 100 to 108 in FIG. 4 in steps 200 to 208. If the remaining vaporized fuel amount Qg ≦ start permission vaporized fuel amount Qgmin in step 208, the engine speed NE when the engine operation is continued is calculated using the map data shown in FIG. 5 (step 210). Then, the warm-up operation is continued at the calculated engine speed NE, and the vaporized fuel tank temperature Tgt is raised to the generation permission temperature T1 or higher (step 212). Then, an injection amount of fuel corresponding to the combination of the increased vaporized fuel tank temperature Tgt and the alcohol concentration Cal is injected into the vaporized fuel tank 34 (step 214). On the other hand, if the residual vaporized fuel amount Qg> the start-permitted vaporized fuel amount Qgmin in step 208, the fuel supply from the intake port injection valve 26 and / or the in-cylinder injection valve 28 is stopped, and in addition, by the spark plug 30 Ignition is also stopped (step 216).

  As described above in detail, according to the routine shown in FIG. 6, the engine speed NE can be changed according to the alcohol concentration Cal during the vaporized fuel replenishment control. Therefore, it is possible to reliably secure the fuel of the start permission vaporized fuel amount in the vaporized fuel tank 34, and at the same time, the engine operation period after the engine stop request can be made to be a predetermined time or less.

  In the second embodiment, the “engine speed varying means” according to the third aspect of the present invention is implemented when the ECU 60 executes the process of step 210 of FIG. 6 using the map data shown in FIG. .

DESCRIPTION OF SYMBOLS 10 Engine 12 Intake passage 14 Exhaust passage 16 Air cleaner 18 Throttle valve 20 Surge tank 22 Intake manifold 24 Intake port 26 Intake port injection valve 28 In-cylinder injection valve 30 Spark plug 32 Fuel tank 34 Vaporized fuel tank 36 In-tank injection valve 38 Vaporized fuel Supply valve 40 Air introduction valve 42 Relief valve 44 Crank angle sensor 46 Air flow sensor 48 Water temperature sensor 50 Tank pressure sensor 52 Tank temperature sensor 54 Fuel property sensor 60 ECU

Claims (3)

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;
Fuel property acquisition means for acquiring the property of the fuel stored in the fuel tank;
Vaporized fuel tank temperature acquisition means for acquiring the temperature in the vaporized fuel tank;
A residual vaporized fuel amount calculating means for calculating an amount of vaporized fuel stored in the vaporized fuel tank as a residual vaporized fuel amount using the property of the fuel and the temperature in the vaporized fuel tank;
Engine stop request determining means for determining the presence or absence of a stop request for the internal combustion engine;
A vaporized fuel amount comparison means for comparing a start-permitted vaporized fuel amount set in advance as a vaporized fuel amount necessary for starting the engine and the residual vaporized fuel amount when there is a stop request;
When the residual vaporized fuel amount is smaller than the start-permitted vaporized fuel amount, the temperature is higher than a preset production-permitted temperature as a temperature at which vaporized fuel of the start-permitted vaporized fuel amount can be generated in the fuel tank. Vaporized fuel tank temperature increasing means for increasing the temperature in the vaporized fuel tank;
In-tank fuel supply means for supplying the fuel in the fuel tank to the vaporized fuel tank when the temperature in the vaporized fuel tank becomes higher than the generation permission temperature;
A control device for an internal combustion engine, comprising:   2. The internal combustion engine according to claim 1, wherein the vaporized fuel tank temperature increasing unit includes an engine stop prohibiting unit that prohibits the internal combustion engine from being stopped until a temperature in the vaporized fuel tank becomes higher than a generation permission temperature. Engine control device. The fuel property acquisition means is a concentration sensor that detects an alcohol concentration in the fuel,
3. The control device for an internal combustion engine according to claim 1, wherein the vaporized fuel tank temperature increasing means includes engine speed changing means for changing the speed of the internal combustion engine in accordance with the alcohol concentration.

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