JP4986984B2 - Operation control method for internal combustion engine - Google Patents

Description

  The present invention relates to an operation control method for an internal combustion engine that operates using a mixed fuel of alcohol and gasoline.

  In recent years, for environmental measures, an internal combustion engine that can use a mixed fuel of alcohol such as ethanol and gasoline as a fuel has been used as a power source for automobiles and the like. As this type of mixed fuel, for example, E10 fuel in which ethanol is added to gasoline in a content ratio of 10% (volume%), E20 fuel in which ethanol is added to gasoline in a content ratio of 20% (volume%), ethanol There are provided a plurality of types of fuels having different alcohol concentrations in the fuel, such as E85 fuel added to gasoline at a content ratio of 85% (volume%).

  As a technique that can operate the internal combustion engine regardless of the alcohol concentration in the mixed fuel, for example, a technique found in Patent Document 1 has been proposed by the present applicant.

  In the technology found in Patent Document 1, water is added to a mixed fuel of alcohol and gasoline, and the resulting mixed liquid is mixed with a mixed liquid of alcohol and water (hereinafter sometimes referred to as an aqueous alcohol solution) and gasoline. To separate.

And in the technique seen in patent document 1, the separated alcohol aqueous solution and gasoline are supplied to an internal combustion engine, controlling the supply_amount | feed_rate separately, and this internal combustion engine is drive | operated. In this case, the internal combustion engine can be operated by the premixed compression ignition system and the spark ignition system, and these operation systems are switched according to the load of the internal combustion engine. In any of the operation methods, the supply amount of each of the aqueous alcohol solution and gasoline is set so that the octane number of the alcohol aqueous solution supplied to the internal combustion engine and the overall fuel of the gasoline becomes the octane number suitable for the intake temperature and load of the internal combustion engine. (And thus the mutual proportion of their supply) is controlled.
JP 2008-190478 A

  By the way, the gasoline in the above mixed fuel used in an internal combustion engine mounted on an automobile or the like is not necessarily the same property as ordinary regular gasoline, and for the reason of the manufacturing process, what is ordinary regular gasoline? There are many cases where the octane number is different. For example, the regular octane number of regular gasoline is about 90, whereas the octane number of gasoline in E10 fuel and the octane number of gasoline in E20 fuel are usually about 80 and about 70, respectively.

  Therefore, the octane number of gasoline in the mixed fuel differs depending on the type of the mixed fuel filled in the fuel tank for the internal combustion engine. In addition, if the type of fuel is different between the fuel mixture that is newly filled (replenished) in the fuel tank and the existing fuel mixture in the fuel tank, the octane number of the gasoline in the mixed fuel in which they are mixed is In other words, the octane number is intermediate between the octane number of gasoline in the newly filled mixed fuel and the gasoline octane number in the existing mixed fuel.

  In this way, the octane number of gasoline in the mixed fuel filled in the fuel tank as the fuel for the internal combustion engine is not constant and varies.

  However, the technique found in Patent Document 1 does not consider that the octane number of gasoline in the mixed fuel in the fuel tank varies as described above. For this reason, when the internal combustion engine is operated in a low load range where the required load is particularly low, there is a risk that misfire may occur if the operation is performed by the premixed compression ignition method effective for reducing NOx in the exhaust gas. . In order to prevent the occurrence of misfire, if the operating range (required load range of the internal combustion engine) in the premixed compression ignition system is narrowed, the premixed compression ignition system is used to reduce NOx in the exhaust. Even in a state where it is preferable to perform the operation at, there is an inconvenience that the operation by the spark ignition method is performed.

  The present invention has been made in view of such a background, and the range of the required load for operating the internal combustion engine by the compression ignition method is variable to a range suitable for the octane number of gasoline in the mixed fuel composed of alcohol and gasoline. It is an object of the present invention to provide an operation control method for an internal combustion engine that can perform the operation in the compression ignition method and the operation in the spark ignition method in a region suitable for each.

An operation control method for an internal combustion engine according to the present invention is an operation control method for an internal combustion engine that uses a mixed fuel of alcohol and gasoline as a fuel to achieve such an object. A separation step for separating, and an ignition method selection step for selecting one of a compression ignition method and a spark ignition method according to an operating state of the internal combustion engine including at least a required load of the internal combustion engine, The internal combustion engine is operated by the ignition method selected in the ignition method selection step while supplying the alcohol and gasoline separated in the separation step to the internal combustion engine at a supply ratio determined at least according to the operation state of the internal combustion engine. In the operation control method, the gasoline octane number estimation for estimating the octane number of the gasoline separated in the separation step is performed. Comprising the step, in response to the estimated octane number, the basic configuration to change the range of load demand on the engine for selecting a compression ignition system with the ignition system selection step.

According to this basic configuration , the required load of the internal combustion engine that selects the compression ignition method in the ignition method selection step according to the gasoline octane number estimated in the gasoline octane number estimation step (the gasoline octane number separated in the separation step) is determined. Change the range. For this reason, the range of the required load of the internal combustion engine that selects the compression ignition method in the ignition method selection step can be set to a range suitable for the octane number of gasoline in the mixed fuel. As a result, the operation by the compression ignition method and the operation by the spark ignition method can be performed in regions suitable for each.

In the basic configuration , the supply ratio of alcohol and gasoline to the internal combustion engine basically increases the supply ratio of gasoline to the total amount of fuel supplied to the internal combustion engine as the required load of the internal combustion engine is lower. Conversely, the higher the required load of the internal combustion engine, the higher the alcohol supply ratio relative to the total amount of fuel supplied to the internal combustion engine.

In the present invention, in the basic configuration, the compression ignition method is selected in the ignition method selection step so that the range of the required load for selecting the compression ignition method is expanded to the low load side as the estimated octane number is small. to change the range of load demand on the internal combustion engine (first invention).

That is, the smaller the octane number of gasoline separated from the mixed fuel, the higher the ignitability of the gasoline. Therefore, by relatively increasing the supply ratio of the gasoline to the internal combustion engine, the compression ignition method can be used with a low required load. Even if the internal combustion engine is operated, misfires can be prevented. Therefore, in the first aspect of the invention , the smaller the estimated octane number is, the wider the required load range for selecting the compression ignition method is on the low load side. Thereby, when the octane number of the gasoline separated from the mixed fuel is small, the operating range of the internal combustion engine that performs the operation in the compression ignition system can be expanded, and the effects such as NOx reduction in the exhaust gas of the internal combustion engine can be enhanced.

Further, in the present invention, in the basic configuration or the first invention, the supply ratio of the alcohol and gasoline supplies before SL internal combustion engine, the supply ratio of the alcohol to the total fuel supplied to the internal combustion engine, and the estimated the lower the octane number, such that higher Ru is determined in accordance with the octane number that the operating state and the estimation of the internal combustion engine (second invention).

  According to this, when the estimated octane number is relatively low, the supply ratio of alcohol to the whole fuel supplied to the internal combustion engine is increased. Therefore, particularly when the required load of the internal combustion engine is relatively high, The effect of preventing the occurrence of knocking can be enhanced. In contrast to the above, when the estimated octane number is relatively high, the alcohol supply ratio to the whole fuel supplied to the internal combustion engine is reduced, and particularly when the required load of the internal combustion engine is relatively low. In addition, the effect of preventing the occurrence of misfire can be enhanced.

Further, in the present invention, in the basic configuration, before Symbol separation step, the mixed fuel in the main fuel tank for storing the mixed fuel is supplied to the separation tank while mixing water into the blended fuel, the separation and gasoline a mixture of mixed fuel and water tanks, Ru preferably der be separated into an aqueous alcohol solution is a mixture of alcohol and water.

According to this , since the gasoline and the alcohol aqueous solution can be separated in the vertical direction by the specific gravity difference in the separation tank, the apparatus configuration for separating the mixed fuel can be simplified.

In the present invention, in the basic configuration, the separation step supplies the mixed fuel in the main fuel tank storing the mixed fuel to the separation tank while mixing the mixed fuel with water, and mixes the mixed fuel in the separation tank. In the step of separating the mixed liquid of fuel and water into gasoline and the aqueous alcohol solution that is a mixed liquid of alcohol and water, the gasoline separated from the mixed fuel as follows (gasoline in the separation tank) It is possible to estimate the octane number.

That is, when the mixed fuel is replenished to the main fuel tank, the remaining amount of the mixed fuel in the main fuel tank before the replenishment and the alcohol concentration of the mixed fuel, and the mixing of the main fuel tank after the replenishment A first step of measuring a remaining amount of fuel and an alcohol concentration of the mixed fuel, and a remaining amount of gasoline in the separation tank before the replenishment;
The main fuel tank was replenished from the measured value of the remaining fuel and alcohol concentration in the main fuel tank before replenishment and the measured remaining fuel and alcohol concentration in the main fuel tank after replenishment. A second step of estimating the alcohol concentration of the mixed fuel;
A third step of estimating an octane number of gasoline in the supplemented mixed fuel from an estimated value of alcohol concentration of the supplemented mixed fuel;
Before the replenishment, the gasoline octane number estimated last in the gasoline octane number estimation step, the estimated octane number of gasoline in the replenished mixed fuel, and the separation tank before replenishment A fourth step of setting a parameter that defines the relationship between the amount of gasoline used in the separation tank after the replenishment and the change in the octane number of gasoline in the separation tank from the measured value of the remaining amount of gasoline With
In the gasoline octane number estimating step, in the period immediately after replenishment of the mixed fuel to the main fuel tank, while measuring the amount of gasoline used in the separation tank from the end of the replenishment, Based on the parameters, the octane number of the gasoline separated in the separation step is estimated ( third invention). The third invention may be used in combination with the first invention or the second invention .

Here, when the mixed fuel is replenished to the main fuel tank, there is generally a correlation between the alcohol concentration of the replenished mixed fuel and the gasoline octane number of the mixed fuel. That is, for example, in E20 fuel, the octane number of gasoline in the fuel is about 70, and in E10 fuel, the octane number of gasoline in the fuel is about 80. Therefore, in the third invention , the alcohol concentration of the supplemented mixed fuel is estimated by the processes of the first to third steps, and the octane number of gasoline in the supplemented mixed fuel is calculated from the estimated value of the alcohol concentration. presume.

  On the other hand, the gasoline in the separation tank eventually becomes a main fuel tank as the gasoline remaining in the separation tank before replenishment of the mixed fuel to the main fuel tank is used by the operation of the internal combustion engine or the like. It will be replaced by the gasoline inside. Therefore, the octane number of gasoline in the separation tank changes from the octane number before replenishment to the octane number of gasoline in the mixed fuel after replenishment as the gasoline is used.

Therefore, in the third invention , the value of the octane number of gasoline in the separation tank last estimated in the gasoline octane number estimation step before the replenishment, the estimated value of the octane number of gasoline in the supplemented mixed fuel, A parameter defining the relationship between the measured value of the remaining amount of gasoline in the separation tank before refilling and the change in the amount of gasoline used in the separation tank after refilling and the change in octane number of gasoline in the separation tank Is set in advance.

  In the gasoline octane number estimation step, the measured value of the usage amount is measured while measuring the usage amount of gasoline in the separation tank from the end of the replenishment in a period immediately after the replenishment of the mixed fuel to the main fuel tank. And the parameter, the octane number of the gasoline separated in the separation step is estimated.

  As a result, the octane number of the gasoline separated in the separation step can be estimated in the period immediately after the replenishment of the mixed fuel to the main fuel tank.

Further, in the present invention, in the basic configuration, the first or second aspect, during operation of the internal combustion engine in front Symbol compression ignition mode, as follows, to estimate the octane number of gasoline separated from the mixed fuel Is also possible.

That is, during operation of the internal combustion engine in the compression ignition system, a fifth step of measuring the value of the combustion timing index parameter indicating the combustion timing of fuel in the internal combustion engine, and the combustion indicated by the measured value of the combustion timing index parameter A first operation amount for adjusting the supply ratio of alcohol and gasoline to the internal combustion engine is determined so that the timing coincides with the target combustion timing, and the supply ratio is adjusted according to the first operation amount. The gasoline octane number estimating step estimates the octane number of the gasoline separated in the separation step based on the first manipulated variable when the internal combustion engine is operated in the compression ignition system ( fourth invention). ).

Here, when the internal combustion engine is operated in the compression ignition system, the octane number of gasoline in the fuel supplied to the internal combustion engine is one factor that affects the actual combustion timing of the fuel in the internal combustion engine. Therefore, when the supply ratio is adjusted in accordance with the first operation amount by providing the fifth step and the sixth step, the first operation amount depends on the octane number of gasoline separated from the mixed fuel. Change. Therefore, in the fourth aspect of the invention , the octane number of the gasoline separated in the separation step is estimated based on the first manipulated variable. As a result, the octane number of gasoline separated from the mixed fuel can be estimated during operation of the internal combustion engine in the compression ignition combustion system.

In addition, you may use 3rd invention and 4th invention together. In this case, for example, immediately after replenishment of the mixed fuel to the main fuel tank (for example, when the amount of gasoline used in the separation tank is not more than a predetermined value), and the engine temperature of the internal combustion engine (for example, cooling water temperature) However, when the condition that the temperature is equal to or lower than the predetermined temperature is satisfied, the octane number of the gasoline separated from the mixed fuel (the gasoline in the separation tank) by the method of the third invention is estimated, and the compression when the above condition is not satisfied It is preferable to estimate the octane number of gasoline (gasoline in the separation tank) separated from the mixed fuel by the method of the fourth invention during operation in the ignition combustion system.

In the basic configuration, the first invention, or the second invention, it is also possible to estimate the octane number of gasoline separated from the mixed fuel as follows when the internal combustion engine is operated in the spark ignition system.

That is, when the internal combustion engine is operated by the spark ignition method, a seventh step of detecting whether or not knocking of the internal combustion engine has occurred, and the supply ratio of alcohol and gasoline to the internal combustion engine is prevented from occurring. The second operation amount is adjusted to be adjusted so that the value of the second operation amount is increased or decreased according to the detected presence or absence of the knocking, and the supply ratio is determined according to the second operation amount. The gasoline octane number estimating step estimates the octane number of the gasoline separated in the separation step based on the second manipulated variable when the internal combustion engine is operated by the spark ignition method ( first step) . 5 invention ).

Here, the octane number of gasoline supplied to the internal combustion engine is one factor affecting the presence or absence of occurrence of knocking in the internal combustion engine. Therefore, when the seventh step and the eighth step are provided and the supply ratio is adjusted according to the second operation amount, the second operation amount is the octane number of gasoline separated from the mixed fuel. Varies depending on Therefore, in the fifth aspect of the invention , the octane number of the gasoline separated in the separation step is estimated based on the second manipulated variable. As a result, the octane number of gasoline separated from the mixed fuel can be estimated during operation of the internal combustion engine in the spark ignition system.

In addition, you may use 5th invention , 3rd invention, or 4th invention together. In this case, when used in combination with the third invention , for example, immediately after replenishment of the mixed fuel to the main fuel tank (for example, when the total amount of gasoline and ethanol aqueous solution in the separation tank is less than a predetermined value), And when the condition that the engine temperature (for example, cooling water temperature) of the internal combustion engine is equal to or lower than a predetermined temperature is satisfied, the octane number of gasoline (gasoline in the separation tank) separated from the mixed fuel by the method of the third invention. It is preferable to estimate the octane number of gasoline (gasoline in the separation tank) separated from the mixed fuel by the method of the fifth invention at the time of operation in the spark ignition system when the above condition is not satisfied .
In the first invention, the second invention, the fourth invention, or the fifth invention, as in the third invention, in the separation step, the mixed fuel in the main fuel tank that stores the mixed fuel is It is preferable that the mixed fuel is mixed with water and supplied to the separation tank, and in the separation tank, the mixed liquid of the mixed fuel and water is separated into gasoline and an aqueous alcohol solution that is a mixed liquid of alcohol and water. (Sixth invention). Thereby, since gasoline and alcohol aqueous solution can be separated up and down by the difference in specific gravity in the separation tank, the configuration of the apparatus for separating the mixed fuel can be simplified.

  An embodiment of the present invention will be described with reference to FIGS. First, with reference to FIGS. 1-3, the structure of the operation control system of the internal combustion engine in this embodiment is demonstrated.

  Referring to FIG. 1, a fuel supply system 1 that supplies fuel to an internal combustion engine 5 in the present embodiment includes a main tank 2 that is a main fuel tank that contains a mixed fuel of alcohol and gasoline (sub-octane gasoline). A separation tank 3 that accommodates the alcohol and gasoline composing the mixed fuel in a state of being vertically separated, and a water tank 4 that stores water for separating the mixed fuel in the main tank 2 are provided. The alcohol is ethanol in this embodiment. In the following description, the mixed fuel stored in the main tank 2 is referred to as main fuel. The main fuel is, for example, E10 fuel, E20 fuel or the like.

  The internal combustion engine 5 operates in a premixed compression ignition system (hereinafter referred to as HCCI operation) referred to as an HCCI system (HCCI: Homogeneous Charge Compression Ignition) and in a spark ignition system referred to as an SI system (SI: Spark Ignition). It is an engine that can be operated (hereinafter referred to as SI operation). In the present embodiment, the internal combustion engine 5 is an engine having a plurality of cylinders (for example, four cylinders), and is mounted on the vehicle as a propulsive force generation source of the vehicle (not shown). Hereinafter, a schematic configuration of the internal combustion engine 5 (more specifically, a schematic configuration of the internal combustion engine 5 including an intake and exhaust system) will be described with reference to FIG. In FIG. 2, only a schematic configuration for one cylinder of the internal combustion engine 5 is representatively illustrated.

  Each cylinder 41 of the internal combustion engine 5 is formed in an engine base 42 composed of a cylinder block and a cylinder head. Each cylinder 41 accommodates a piston 43 that can reciprocate in the axial direction, and a space above the piston 43 (cylinder head side) is formed as a combustion chamber 44. Each piston 43 is connected to a crankshaft 46 that is an output shaft of the internal combustion engine 5 via a connecting rod 45, and the crankshaft 46 rotates as the piston 43 of each cylinder 41 reciprocates.

  The combustion chamber 44 of each cylinder 41 communicates with an intake manifold 49 through an intake port 48 opened and closed by an intake valve 47 and communicates with an exhaust manifold 52 through an exhaust port 51 opened and closed by an exhaust valve 50. is doing. The intake valve 47 and the exhaust valve 50 are driven to open and close via a valve drive mechanism (not shown) having a camshaft that interlocks with the rotation of the crankshaft 46. The intake valve 47 and the exhaust valve 50 may be electric valves.

  The intake manifold 49 corresponding to each cylinder 41 joins the common intake passage 53 for all the cylinders 41. The intake passage 53 is provided with an electric throttle valve 54. By controlling the opening degree of the throttle valve 54, the intake amount (air supply amount) of each cylinder 41 is operated. ing.

  The exhaust manifold 52 corresponding to each cylinder 41 merges into a common exhaust passage 55 for all the cylinders 41, and the exhaust gas generated in each cylinder 41 is a purification catalyst (not shown) provided in the exhaust passage 55. ) To be discharged through.

  The internal combustion engine 5 is provided with two fuel injection valves 6 and 7 for each cylinder 41. In the present embodiment, one of the fuel injection valves 6, 7, for example, the fuel injection valve 6 is a port injection type, and injects fuel toward the intake port 48 corresponding to each cylinder 41. The intake manifold 49 is mounted. The other fuel injection valve 7 is a direct injection type, and is mounted on the engine base 42 (cylinder head portion) so as to inject fuel directly into the combustion chamber 44 of each cylinder 41. .

  The fuel injection valves 6 and 7 can control the injection time and the valve opening timing by an ECU 30 to be described later. By the control, the fuel supply amount to each cylinder 41 (the supply amount per combustion cycle). ) And the fuel supply timing are controlled.

  In addition, one of these fuel injection valves 6 and 7, for example, the fuel injection valve 6 is an injection valve used to inject gasoline in the separated fuel supply mode, and the other fuel injection valve 7 This is an injection valve used for injecting ethanol in the separated fuel supply mode. Furthermore, one of the fuel injection valves 6, 7, for example, the fuel injection valve 6 is an injection valve used for injecting the main fuel in the main tank 2 in the non-separated fuel supply mode. Therefore, the fuel injection valve 6 is an injection valve shared by the separated fuel supply mode and the non-separated fuel supply mode. In this case, the fuel injection valve 7 is not used in the non-separated fuel supply mode.

  Note that both the fuel injection valves 6 and 7 may be of the port injection type. Further, instead of the fuel injection valve 6, the fuel injection valve 7 may be an injection valve that is shared between the separated fuel supply mode and the non-separated fuel supply mode.

  Further, the internal combustion engine 5 includes a spark plug 56 for each cylinder 41. The spark plug 56 is mounted on the engine base 42 (cylinder head portion) with its electrode facing the combustion chamber 44.

  In addition to the above-described configuration, the internal combustion engine 5 is provided with various sensors that detect the operating state of the internal combustion engine 5. For example, a crank angle sensor 57 that detects the rotation angle of the crankshaft 46, an intake pressure sensor 58 that detects the intake pressure (absolute pressure) of the internal combustion engine 5, and ions that flow when the air-fuel mixture burns in the combustion chamber 44 of each cylinder 41. Sensors such as an ion current sensor 59 for detecting current and an air-fuel ratio sensor 60 for detecting the air-fuel ratio of the air-fuel mixture burned in each cylinder 41 are provided, and the outputs of these sensors are input to the ECU 30 described later. ing.

  In this case, the crank angle sensor 57 is a sensor that outputs a pulse signal to the control device 2 every time the crankshaft 46 rotates by a predetermined angle. The output is used for grasping the crank angle, which is the rotation angle of the crankshaft 46, and the rotation speed of the crankshaft 46 as the time rate of change of the crank angle (that is, the rotational speed of the internal combustion engine 5). ) Is used to grasp.

  The intake pressure sensor 58 is attached to the intake passage 53 on the downstream side of the throttle valve 54 (in the vicinity of the junction of the intake manifold 49), and the pressure (absolute pressure) in the intake passage 53 at that location. Is detected as the intake pressure of the internal combustion engine 5.

  The air-fuel ratio sensor 60 is attached to the exhaust passage 55 in the vicinity of the collection location of the exhaust manifold 52 for each cylinder 41 of the internal combustion engine 5 and detects the air-fuel ratio represented by the oxygen concentration in the exhaust.

  The ion current sensor 59 includes a conductive probe 59a for passing the ion current and a signal generation unit 59b for converting the ion current flowing through the probe 59a into a voltage signal. In the present embodiment, the probe 59 is provided integrally with the spark plug 36 while being electrically insulated from the engine base 42.

  Although not shown, in addition to the sensors 57 to 60 described above, an engine temperature sensor for detecting the engine temperature (cooling water temperature) of the internal combustion engine 5, a hot water temperature sensor for detecting the temperature of the lubricating oil, and an intake air temperature are detected. An intake air temperature sensor that detects knocking of the internal combustion engine 5 (for example, a sensor that detects vibration of the engine base 42, in-cylinder pressure of each cylinder 41, combustion noise, etc.), and depression of an accelerator pedal of a vehicle in which the internal combustion engine 5 is mounted An accelerator sensor for detecting the amount is also provided, and the output of these sensors is also input to the ECU 30 described later.

  In the internal combustion engine 5 configured as described above, in the HCCI operation, at each required timing of each combustion cycle of each cylinder 41, one or both of the fuel injection valves 6 and 7 corresponding to the cylinder 41 are used. Fuel is supplied to the combustion chamber 44 of the cylinder 41. Then, an air-fuel mixture of the supplied fuel and air filled in the combustion chamber 44 in the intake stroke of the cylinder 41 is compressed in the compression stroke of the cylinder 44. As a result of the compression, the air-fuel mixture becomes hot and self-ignition combustion of the fuel is performed. In this HCCI operation, the air-fuel ratio of the air-fuel mixture in each cylinder 44 is an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio.

  In the SI operation, the air-fuel mixture in the combustion chamber 44 of each cylinder 41 is compressed in the compression stroke of the cylinder 41 as described above. Then, the fuel of the compressed air-fuel mixture is ignited and burned by an ignition spark emitted from the spark plug 56. In this SI operation, the air-fuel ratio of the air-fuel mixture in each cylinder 41 is an air-fuel ratio in the vicinity of the theoretical air-fuel ratio.

  Returning to FIG. 1, the main tank 2 is provided with a feed pump 8 that pressurizes the main fuel in the main tank 2 and supplies it to the separation tank 3. The feed pump 8 has an inlet port that opens into the main tank 2, and a discharge port that is connected to the separation tank 3 via a main fuel supply path 9. The feed pump 8 pressurizes the main fuel in the main tank 2 sucked from the suction port to a predetermined pressure, and the pressurized main fuel is supplied from the discharge port to the separation tank 3 through the main fuel supply path 9. I am trying to supply.

  The water tank 4 is provided with a feed pump 13 that pressurizes the water in the water tank 4 and supplies it to the separation tank 3. The feed pump 13 has a suction port opened into the water tank 4 and a discharge port connected to the separation tank 3 via a water supply path 14. The feed pump 13 pressurizes water sucked from the suction port to a pressure slightly higher than the pressure in the separation tank 3 (discharge pressure of the feed pump 7), and the pressurized water is supplied from the discharge port to the water. It is made to supply to the separation tank 3 through the supply path 14. In this case, the water supply path 14 is provided with a flow control valve 15, and the amount of water supplied to the separation tank 3 can be adjusted by controlling the opening degree of the flow control valve 15. ing.

  The separation tank 3 is a tank that contains gasoline in the upper part of the internal space and contains a mixed liquid of ethanol and water (hereinafter referred to as an ethanol aqueous solution) in the lower part.

  Here, in this embodiment, the main fuel supplied from the main tank 2 to the separation tank 3 and the water supplied from the water tank 4 are once stirred and mixed by a stirrer (not shown). It is like that. In this case, since ethanol in the mixed solution (mixed solution of ethanol, gasoline, and water) has higher hydrophilicity than gasoline, it is easily mixed with water. Moreover, the specific gravity of gasoline is smaller than the specific gravity of ethanol and water. For this reason, among the mixed liquids stirred in the separation tank 3, an ethanol aqueous solution that is a mixed liquid of ethanol and water and gasoline are naturally separated in the separation tank 3, and the internal space of the separation tank 3. Gasoline and ethanol aqueous solution will accumulate on the upper side and the lower side, respectively. In this case, the gasoline and the aqueous ethanol solution are accommodated in the separation tank 3 in a state where they are in contact with each other with the upper end surface of the aqueous ethanol solution as an interface. As a result, the gasoline and the ethanol aqueous solution are separated and accommodated in the separation tank 3, and the separation step in the present invention is realized. In this embodiment, the internal space of the separation tank 3 is always filled with the separated gasoline and ethanol aqueous solution, and these liquids are pressurized to a pressure approximately equal to the discharge pressure of the feed pump 8. It is kept in the state.

  Of the internal space of the separation tank 3 that separates and accommodates the gasoline and the aqueous ethanol solution in this way, the upper space where the gasoline accumulates is through the gasoline supply path 16 led out from the upper portion of the separation tank 3. The fuel injection valve 6 is connected. Thereby, the pressurized gasoline in the separation tank 3 is supplied to the fuel injection valve 6 via the gasoline supply path 16.

  In addition, a space on the lower side in which the aqueous ethanol solution is stored in the internal space of the separation tank 3 is connected to the fuel injection valve 7 via an ethanol supply path 17 led out from the lower portion of the separation tank 3. As a result, the pressurized aqueous ethanol solution in the separation tank 3 is supplied to the fuel injection valve 7 via the fifth fuel supply path 17.

  Further, of the internal space of the separation tank 3, the space on the upper side in which gasoline accumulates is connected to the main tank 2 via a gasoline return passage 18 led out from the upper portion of the separation tank 3 separately from the gasoline supply passage 16. It is connected. A flow rate control valve 19 is interposed in the gasoline return passage 18. In this case, by opening the flow control valve 19, the pressurized gasoline in the upper part of the internal space of the separation tank 3 can be returned to the main tank 2 through the gasoline return passage 18.

  The fuel supply system 1 in the present embodiment further includes a first ethanol concentration sensor 20 that generates an output corresponding to the content ratio (ethanol concentration) of ethanol in the main fuel in the main tank 2, and ethanol in the separation tank 3. A float sensor 21 that generates an output corresponding to the height of the interface between the aqueous solution and gasoline, and a second ethanol concentration that generates an output corresponding to the ethanol concentration in the aqueous ethanol solution supplied from the separation tank 3 to the fuel injection valve 7. A sensor 22, a main fuel remaining amount sensor 23 for detecting the remaining amount of main fuel in the main tank 2, and a control unit 30 for controlling the operation of the internal combustion engine 5 such as operation control of the fuel injection valves 6 and 7 , Referred to as ECU30).

  The first ethanol concentration sensor 20 is disposed in the main tank 2, and the second ethanol concentration sensor 22 is interposed in the middle of the fifth fuel supply path 17. These ethanol concentration sensors 20 and 22 are concentration sensors that react with ethanol.

  In the following description, in order to distinguish the ethanol concentrations detected by these ethanol concentration sensors 20 and 22, respectively, the ethanol concentration indicated by the output of the first ethanol concentration sensor 20 is the ethanol content ratio, and the output of the second ethanol concentration sensor 22 is The ethanol concentration shown may be called ethanol aqueous solution concentration.

  When the ethanol content in the main fuel in the main tank 2 is Et_r [%], the gasoline content (gasoline concentration) is 100−Et_r [%]. For this reason, if one of the ethanol content ratio and the gasoline content ratio in the main fuel in the main tank 2 is measured, the other is also indirectly measured. Therefore, instead of the first ethanol concentration sensor 20, a concentration sensor that can detect the gasoline concentration may be disposed in the main tank 2.

  The float sensor 21 is fitted into a guide rod 21a provided in the separation tank 3 so as to extend in the vertical direction, and is movable in the vertical direction along the guide rod 21a. The float sensor 21 has a specific gravity that is larger than the specific gravity of gasoline and smaller than the specific gravity of the aqueous ethanol solution. For this reason, the float sensor 21 floats at the position of the interface between the gasoline and the ethanol aqueous solution, and moves up and down as the interface moves up and down. The float sensor 21 generates an output corresponding to the relative position in the vertical direction with respect to the guide rod 21a. Therefore, the output of the float sensor 21 is an output corresponding to the height of the interface in the separation tank 3 (hereinafter referred to as interface height H_FL).

  Here, in this embodiment, since the internal space of the separation tank 3 is always filled with gasoline and an aqueous ethanol solution as described above, the remaining amount of gasoline in the separation tank 3 and the remaining amount of aqueous ethanol solution The sum is equal to the volume of the internal space of the separation tank 3 and takes a constant value. Further, the cross-sectional area (cross-sectional area viewed from above) of the separation tank 3 is substantially constant in the vertical direction. For this reason, the output of the float sensor 15 not only has a meaning as an output corresponding to the interface height H_FL in the separation tank 3 but also an output corresponding to the respective remaining amounts of gasoline and ethanol aqueous solution in the separation tank 3. As meaning.

  The ECU 23 is an electronic circuit unit including a CPU, a RAM, and a ROM (not shown). The output of each of the sensors 20 to 22 is input to the ECU 23 from various sensors such as the sensors 57 to 60 described above. Detection data relating to the operating state is input. The ECU 23 executes a predetermined control process related to the operation control of the internal combustion engine 5 based on these input data, map data stored in advance, and the like.

  In the present embodiment, as shown in FIG. 3, the ECU 30 has a gasoline octane number estimating means 30 a for estimating the octane number of gasoline in the main fuel, and an internal combustion engine 5 as the main functions realized by the control processing executed by the ECU 30. An operation mode determining means 30b for determining an operation mode and an operation control means 30c for controlling the operation of the internal combustion engine 5 through the fuel injection valves 6 and 7, the spark plug 56 and the throttle valve 54 are provided. In this case, the operation modes determined by the operation mode determination means 30b include an HCCI operation mode for performing the HCCI operation and an SI operation mode for performing the SI operation. The operation mode determination means 30b uses the gasoline octane number RON estimated by the gasoline octane number estimation means 30a (hereinafter referred to as gasoline octane number estimation value RON) as reference data for selectively determining these operation modes. .

  Further, the operation control means 30c is an internal combustion engine through the fuel injection valves 6 and 7, the spark plug 56 and the throttle valve 54 in a mode according to the operation mode determined by the operation mode determination means 30b and the change of the operation mode. 5 is controlled. In this control, the operation control means 30c uses the estimated octane value RON as reference data.

  Although not shown in FIG. 3, the ECU 30 controls the amount of water from the water tank 4 of the fuel supply system 1 to the separation tank 3 through the flow control valve 15 in addition to the above functional means. There is also a control means and a cathode return control means for controlling the return flow rate of gasoline from the separation tank 3 to the main tank 2 via the flow rate control valve 19. In this case, for example, the water amount control means controls the opening degree of the flow rate control valve 15 of the water supply path 14 so that the ethanol aqueous solution concentration indicated by the output of the second ethanol concentration sensor 22 is maintained at a constant value. Further, the gasoline return control means has a case where the interface height H_FL indicated by the output of the float sensor 21 is lower than a predetermined value and the ethanol aqueous solution in the separation tank 3 is short (the gasoline in the separation tank 3 is excessive). The flow control valve 19 of the gasoline return passage 18 is opened. As a result, a part of the gasoline in the separation tank 3 is returned to the main tank 2 via the gasoline return passage 18 and the remaining amounts of the gasoline and the aqueous ethanol solution in the separation tank 3 are prevented from becoming unbalanced. The

  Next, the control process of the ECU 30 will be described in more detail. First, with reference to FIGS. 4 to 13, processing related to the operation mode determination unit 30 b and the operation control unit 30 c will be described.

  The ECU 30 sequentially executes the processing of the flowchart shown in FIG. 4 at a predetermined arithmetic processing cycle during operation of the internal combustion engine 5. In the following, the ECU 30 first executes a process of determining the operation mode of the internal combustion engine 5 by the operation mode determination means 30b in S1.

  Specifically, this processing is executed as shown in the flowchart of FIG. That is, first, in S101, the operation mode determination unit 30b detects the rotational speed detection value Ne of the internal combustion engine 5 (hereinafter simply referred to as the rotational speed detection value Ne) and the net average effective pressure Pmi () of each cylinder 41 of the internal combustion engine 5. A so-called BMEP target value (hereinafter simply referred to as a target Pmi) and a current value of the gasoline octane number estimated value RON of the main fuel (a value in the current processing cycle) are acquired. Here, the rotation speed detection value Ne of the internal combustion engine 5 is a detection value recognized by the ECU 30 from the output of the crank angle sensor 57 as a temporal change rate of the crank angle indicated by the output of the crank angle sensor 57. The target Pmi is a target value determined by the ECU 30 in accordance with the detected value of the accelerator pedal depression amount of the vehicle on which the internal combustion engine 5 is mounted. In the present embodiment, this target Pmi has a meaning as an index representing the required load of the internal combustion engine 5. The gasoline octane number estimated value RON is an estimated value determined by an estimation process described later of the octane number estimating means 30a.

  As an index representing the required load of the internal combustion engine 5, the target torque of the internal combustion engine 5 (target value of output torque), the intake pressure, the intake air amount, and the like may be used instead of the target Pmi.

  Next, in S102, the operation mode determining means 30b determines the range of the net average effective pressure Pmi that defines the appropriate range of the required load of the internal combustion engine 5 that should perform the HCCI operation (hereinafter referred to as the Pmi appropriate range for HCCI operation). The upper limit value H_Lmt_Pmi and the lower limit value L_Lmt_Pmi are determined according to the current rotation speed detection value Ne and the gasoline octane number estimation value RON. In other words, the PMI appropriate range for HCCI operation is a region in which HCCI operation is more suitable than SI operation in order to reduce NOx in the exhaust of the internal combustion engine 5 and improve the thermal efficiency of the internal combustion engine 5. In addition, the HCCI operation can be suitably performed without causing misfire or knocking of the internal combustion engine 5.

  The processing of S102 will be described below with reference to FIGS. 6 (a), 6 (b) and FIG.

  In the present embodiment, the number of revolutions of the internal combustion engine 5 and the upper limit value of the net average effective pressure Pmi at which HCCI operation should be performed, corresponding to each of a plurality of predetermined typical values of the octane number of gasoline, HCCI operation range setting data, which is data defining the relationship with the lower limit value, is stored and held in the ECU 30 in advance. Each HCCI operation range setting data uses the gasoline and ethanol aqueous solution in the separation tank 3 in a state where the gasoline in the separation tank 3 has an octane number corresponding to the HCCI operation range setting data. Thus, when the HCCI operation of the internal combustion engine 5 is performed, the range of the net average effective pressure Pmi that can suitably perform the HCCI operation without causing knocking or misfire is defined.

  More specifically, in the present embodiment, as shown in FIGS. 6A and 6B, two types of HCCI operation range setting data respectively corresponding to two types of gasoline octane numbers are, for example, a data table. It is prepared in the form of FIG. 6A corresponds to the case where the octane number of gasoline is “80”, for example, and the relationship between the rotational speed of the internal combustion engine 5 and the upper limit value of the PMI appropriate range for HCCI operation is represented by a curve a1. The relationship between the rotational speed and the lower limit value of the PMI appropriate range for HCCI operation is represented by a curve a2. Therefore, when the gasoline octane number estimated value RON is “80”, the range of Pmi between the curves a1 and a2 indicates the appropriate Pmi range for HCCI operation.

  FIG. 6B corresponds to the case where the octane number of gasoline is, for example, “70”, and the relationship between the rotational speed of the internal combustion engine 5 and the upper limit value of the PMI appropriate range for HCCI operation is represented by a curve b1. The relationship between the rotational speed and the lower limit value of the appropriate Pmi appropriate range for HCCI operation is represented by a curve b2. Therefore, when the gasoline octane number estimated value RON is “70”, the range of Pmi between the curves b1 and b2 indicates the appropriate Pmi range for HCCI operation.

  The octane number “80” is the standard octane number of gasoline in E10 fuel, and the octane number “70” is the standard octane number of gasoline in E20 fuel. In addition, curves a3 and b3 in FIGS. 6 (a) and 6 (b) represent the maximum net average effective pressure Pmi (Pmi corresponding to the maximum required load) possible in the SI operation, and are below the curves a3 and b3. The internal combustion engine 5 can be operated in the region on the side.

  In this case, as can be seen by comparing FIGS. 6 (a) and 6 (b), the Pmi appropriate range for HCCI operation is greater when the gasoline octane number is “80” than when it is “80”. , Pmi is expanded to the low area side (the low load area side). In other words, the lower limit value of the HCCI operation Pmi proper range when the gasoline octane number is “70” is lower than the lower limit value of the HCCI operation Pmi proper range when the gasoline octane number is “80”. It is low. This is because, in a situation where the required load of the internal combustion engine 5 is low (a situation where the target Pmi is low), it is possible to perform an appropriate HCCI operation while preventing misfire by using gasoline having a lower octane number. It is.

  Supplementally, in this embodiment, the amount of gasoline and ethanol aqueous solution supplied by the internal combustion engine 5 can be arbitrarily adjusted. Therefore, in a situation where the required load of the internal combustion engine 5 is relatively high (a situation where the target Pmi is relatively high), In order to properly perform HCCI operation without causing knocking of the engine 5, basically, the fuel in the separation tank 3 is supplied to the internal combustion engine 5 so that the supply amount of ethanol having an octane number higher than that of gasoline is sufficiently increased. (Gasoline and ethanol aqueous solution) will be supplied and HCCI operation will be performed. For this reason, the upper limit values of the PMI appropriate range for HCCI operation shown in FIGS. 6A and 6B are equal to each other without depending on the octane number of gasoline.

  In S102, the operation mode determination unit 30b uses the above-described two types of HCCI operation range setting data to set the upper limit of the HCCI operation Pmi appropriate range corresponding to the current rotational speed detection value Ne and the gasoline octane number estimation value RON. A value H_Lmt_Pmi and a lower limit L_Lmt_Pmi are determined. The determination process is executed as shown in the block diagram of FIG.

  That is, the operation mode determination unit 30b first executes the processing of the processing units S102a and S102b. In the processing unit S102a, based on the detected rotation speed value Ne of the internal combustion engine 5, based on the HCCI operating range setting data in FIG. 6A, the rotation speed detection when it is assumed that the octane number of gasoline is “80”. An upper limit value H_Lmt80 and a lower limit value L_Lmt80 of the PMI appropriate range for HCCI operation corresponding to the value Ne are obtained. Further, in the processing unit S102b, based on the rotation speed detection value Ne, based on the HCCI operation range setting data in FIG. 6B, the rotation speed detection value Ne when it is assumed that the octane number of gasoline is “70”. The upper limit value H_Lm70 and the lower limit value L_Lmt70 of the Pmi appropriate range for HCCI operation corresponding to the above are obtained.

  Next, the operation mode determination unit 30b executes the process of the processing unit S102c. In the processing unit S102c, from the upper limit value H_Lmt80 when the octane number is “80” and the upper limit value H_Lmt70 when the octane number is “70”, the PMI for HCCI operation corresponding to the estimated gasoline octane number RON is interpolated. The upper limit value H_Lmt_Pmi of the appropriate range is calculated. Similarly, from the lower limit L_Lmt80 when the octane number is “80” and the lower limit L_Lmt70 when the octane number is “70”, the PMI appropriate range for HCCI operation corresponding to the gasoline octane number estimated value RON by interpolation processing A lower limit value L_Lmt_Pmi is calculated.

  In the above interpolation process, the relationship between the octane number of gasoline and the upper limit value of the appropriate Pmi range for HCCI operation, and the relationship between the octane number of gasoline and the lower limit value of the Pmi appropriate range for HCCI operation are respectively linear functions ( The upper limit value H_Lmt_Pmi and the lower limit value L_Lmt_Pmi of the HCCI operating Pmi appropriate range corresponding to the gasoline octane number estimated value RON are calculated using the linear function.

  In this case, the Pmi appropriate range for HCCI operation is, as described above, the region where Pmi is lower (the region where the required load is lower) when the gasoline octane number is “70” than when it is “80”. Side). For this reason, as the gasoline octane number estimated value RON is lower by the processing of S102, the HCCI operation Pmi appropriate range is expanded to the low load side (Pmi is lower) so that the HCCI operation Pmi appropriate range is the gasoline octane number. It is set variably according to the estimated value RON.

  Returning to the description of FIG. 5, next, the operation mode determination unit 30 b executes the determination process of S <b> 103. In the determination process of S103, whether or not the target Pmi acquired in S101 exists between the upper limit value H_Lmt_Pmi and the lower limit value L_Lmt_Pmi of the PMI appropriate range for HCCI operation determined as described above (L_Lmt_Pmi ≦ target Pmi ≦ H_Lmt_PmiH Or not).

  When this determination result is negative, that is, when the target Pmi deviates from the HCCI operation Pmi appropriate range, the operation mode determination means 30b sets the SI operation mode as the operation mode of the internal combustion engine 5. Set (S104). When the determination result in S103 is affirmative and the target Pmi is within the PMI appropriate range for HCCI operation, the operation mode determination unit 30b sets the HCCI operation mode as the operation mode of the internal combustion engine 5 (S105). ).

  The above is the details of the processing of the operation mode determination means 30b in S1 of FIG.

  Supplementally, in the present embodiment, the ignition method selection step in the present invention is realized by the processing of S103 to S105.

  In the present embodiment, two types of HCCI operation range setting data are used, but more HCCI operation range setting data may be used.

  Next, the ECU 30 executes the processing of the operation control means 30c in S2 to S8 of FIG.

  That is, the operation control means 30c first determines in S2 whether or not the operation mode of the internal combustion engine 5 determined in S1 is the HCCI operation mode. If the determination result is affirmative, the operation control means 30c further determines in S3 whether or not the switching from the SI operation to the HCCI operation has been completed.

  Here, in the continuous SI operation and the continuous HCCI operation, the operation of the internal combustion engine 5 such as the supply ratio of gasoline and ethanol aqueous solution to be supplied from the separation tank 3 to each cylinder 41 of the internal combustion engine 5 is performed. Since the control mode is different, sudden switching between the SI operation and the HCCI operation may cause knocking or misfire of the internal combustion engine 5 or increase in NOx in the exhaust gas.

  For this reason, in this embodiment, the operation control means 30c is synchronized with the rotational speed of the internal combustion engine 5 for a temporary predetermined period when switching from SI operation to HCCI operation and when switching from HCCI operation to SI operation. In a predetermined period), operation control for switching them is performed.

  The determination process of S3 is a process of determining whether or not a predetermined period for performing operation control for switching from SI operation to HCCI operation has elapsed. If the determination result in S3 is affirmative, the operation control means 30c executes HCCI operation control processing (S5). If the determination result in S3 is negative, the operation control means 30c executes a control process for switching from the SI operation to the HCCI operation (S6).

  On the other hand, when the determination result of S2 is negative, that is, when the operation mode determined in S1 is the SI operation mode, the operation control means 30c, as in the determination process of S3, In S4, it is determined whether or not switching from HCCI operation to SI operation is completed (whether or not a predetermined period for performing operation control for switching from HCCI operation to SI operation has elapsed). If the determination result in S3 is affirmative, the operation control means 30c executes SI operation control processing (S7). If the determination result in S3 is negative, the operation control means 30c executes a control process for switching from the HCCI operation to the SI operation (S8).

  The control processes of S5 to S8 will be described more specifically below.

First, with reference to FIGS. 8-13, the process of the HCCI operation control in S5 and the process of the SI operation control in S7 will be described. In these processes, the operation control means 30c executes the process shown in the block diagram of FIG. 8 so that the amount of gasoline injected by the fuel injection valve 6 and the fuel injection quantity for each combustion cycle of each cylinder 41 of the internal combustion engine 5 are determined. The fuel injection time Ti_Ga for gasoline and the fuel injection time Ti_EW for ethanol are determined as operation amounts (control inputs) that respectively define the injection amount of the ethanol aqueous solution by the fuel injection valve 7, and the determined fuel injection times Ti_Ga and Ti_EW In response, the operation (opening time) of each of the fuel injection valves 6 and 7 is controlled. Specifically, the operation control means 30c first executes the processing of the ethanol basic supply ratio determination unit 301. In this process, the basic ratio of ethanol in the whole fuel supplied from the separation tank 3 to each cylinder 41 from the current rotational speed detection value Ne and target Pmi of the internal combustion engine 5 and the current gasoline octane number estimated value RON. The ethanol basic supply ratio Et_inj_rb, which is a value, is determined.

  Here, in this embodiment, in order to determine the ethanol basic supply ratio Et_inj_rb, for each operation mode of the HCCI operation mode and the SI operation mode, a plurality of typical values of the octane number of gasoline, for example, “80” And (70) as data defining the relationship between the rotation speed detection value Ne and the target Pmi and the ethanol basic supply ratio Et_inj_rb, corresponding to each of the two types of values “70” and “70”. The map data illustrated in b) and FIGS. 10A and 10B is stored and held in the ECU 30 in advance. FIG. 9A shows map data corresponding to a case where the operation mode is the HCCI operation mode and the octane number of the gasoline is “80”, for example. FIG. 9B shows that the operation mode is the HCCI operation mode. Further, map data corresponding to the case where the gasoline octane number is “70”, for example, FIG. 10A shows the case where the operation mode is the SI operation mode and the gasoline octane number is “80”, for example. Corresponding map data, FIG. 10B, is map data corresponding to the case where the operation mode is the SI operation mode and the octane number of the gasoline is, for example, “70”.

  These map data are based on the premise that the octane number of the actual gasoline in the separation tank 3 matches the octane number corresponding to each map data, and the operating state of the internal combustion engine 5 is the engine temperature (cooling water temperature), Assuming that the intake air temperature, the temperature of the lubricating oil, etc. (operating conditions other than the rotational speed of the internal combustion engine 5 and the required load) are within a certain standard range, knocking or misfire may occur. Therefore, the HCCI operation or SI operation of the internal combustion engine 5 is performed as efficiently as possible, and NOx and the like in the exhaust gas can be reduced as much as possible.

  In this case, in both the HCCI operation mode and the SI operation mode, the gasoline octane number is “80” in the region where the target Pmi is relatively high (the region where the required load is relatively high). However, the map data is set so that the ethanol basic supply ratio Et_inj_rb is larger when the octane number is “70”. In any of the operation modes of the HCCI operation mode and the SI operation mode, the map data is set so that the ethanol basic supply ratio Et_inj_rb increases as the target Pmi is higher (and the required load is higher).

  The ethanol basic supply ratio determining unit 301 uses these map data to determine the ethanol basic supply ratio Et_inj_rb corresponding to the current rotation speed detection value Ne and target Pmi of the internal combustion engine 5 and the gasoline octane number estimated value RON. .

  Specifically, the ethanol basic supply ratio determination unit 301 determines that the octane number of gasoline is “80” from the current rotational speed detection value Ne and the target Pmi of the internal combustion engine 5 in the HCCI operation control of S5. The ethanol basic supply ratio Et_inj_rb when assumed and the ethanol basic supply ratio Et_inj_rb when the gasoline octane number is assumed to be “70” are respectively shown in the map data of FIG. 9A and the map of FIG. 9B. Find based on data. And from these ethanol basic supply ratio Et_inj_rb, the ethanol basic supply ratio Et_inj_rb corresponding to the current gasoline octane number estimated value RON is calculated by the same interpolation process as the processing unit S102c of the operation mode determining means 30b.

  Further, in the SI operation control of S7, the ethanol basic supply ratio determination unit 301 assumes that the octane number of gasoline is “80” from the current rotational speed detection value Ne and the target Pmi of the internal combustion engine 5. The basic ethanol supply ratio Et_inj_rb and the basic ethanol supply ratio Et_inj_rb when the gasoline octane number is assumed to be “70” are based on the map data in FIG. 10A and the map data in FIG. Ask. And from these ethanol basic supply ratio Et_inj_rb, the ethanol basic supply ratio Et_inj_rb corresponding to the current gasoline octane number estimated value RON is calculated by the same interpolation process as the processing unit S102c of the operation mode determining means 30b.

  In this case, since the ethanol basic supply ratio Et_inj_rb is set as described above for the gasoline octane number “80” and “70”, both the HCCI operation mode and the SI operation mode are set. Even in the operation mode, in a region where the target Pmi is relatively high (region where the required load is relatively high), when the target Pmi and the rotation speed detection value Ne are constant, the lower the gasoline octane number estimated value RON is, the lower the value is. The ethanol basic supply ratio Et_inj_rb is increased, and the ethanol basic supply ratio Et_inj_rb is decreased as the gasoline octane number estimated value RON is higher.

  Next, the operation control means 30c is the actual ethanol supply ratio to each cylinder 41 of the internal combustion engine 5 by executing processing for correcting the ethanol basic supply ratio Et_inj_rb obtained as described above in the processing units 302 and 303. The actual ethanol supply ratio Et_inj_rat is determined.

  The correction process in the processing unit 302 prevents the actual combustion timing of the fuel in each cylinder 41 from deviating from the target combustion timing during the HCCI operation of the internal combustion engine 5 (during the HCCI operation control in S5). This is a process for correcting the ethanol basic supply ratio Et_inj_rb by multiplying the correction coefficient K_hcci for combustion timing adjustment determined as described later by the ethanol basic supply ratio Et_inj_rb.

  Further, the correction processing in the processing unit 303 is the knocking prevention determined as described later in order to prevent the occurrence of knocking of the internal combustion engine 5 during the SI operation of the internal combustion engine 5 (at the time of SI operation control in S7). This is a process of correcting the ethanol basic supply ratio Et_inj_rb by multiplying the correction coefficient K_si for use by the ethanol basic supply ratio Et_inj_rb.

  Note that, during the HCCI operation of the internal combustion engine 5 (during the HCCI operation control in S5), K_si = 1 is set, and the correction processing in the processing unit 303 is substantially omitted. Further, at the time of SI operation of the internal combustion engine 5 (at the time of SI operation control of S7), K_hcci = 1 is set, and the correction processing in the processing unit 302 is substantially omitted. Therefore, the actual ethanol supply rate Et_inj_rat is determined by Et_inj_rat = Et_inj_rb × K_hcci during HCCI operation, and the actual ethanol supply rate Et_inj_rat is determined by Et_inj_rat = Et_inj_rb × K_si during SI operation.

  The combustion timing adjustment correction coefficient K_hcci is determined by the operation control means 30c using the output of the ion current sensor 59 during the HCCI operation of the internal combustion engine 5 as described below.

  First, the relationship between the output of the ion current sensor 59 and the actual combustion timing of the fuel in each cylinder 41 of the internal combustion engine 5 will be described with reference to FIG. FIG. 11 illustrates the waveform of the detected value of the ion current of each cylinder 41 indicated by the output of the ion current sensor 50 (waveform with the horizontal axis as the crank angle). The waveform has a peak value (maximum value) when the crank angle is a certain value CA_ionmax in each combustion cycle. The crank angle CA_ionmax (hereinafter referred to as ion current peak crank angle CA_ionmax) at which the detected value of the ionic current becomes the maximum value has a strong correlation with the actual combustion timing of the fuel in each cylinder 41, and the combustion timing. It becomes an index value representing.

  Therefore, in this embodiment, the ionic current peak crank angle CA_ionmax in each cylinder 41 is used as a combustion timing index parameter that represents the actual combustion timing. Then, the operation control means 30c sequentially detects the value of the ion current peak crank angle CA_ionmax as the combustion timing index parameter based on the time series of the output of the ion current sensor 59. Thereby, the fifth step in the present invention is realized.

  Then, the operation control means 30c uses a feedback control law so that the detected value of the ion current peak crank angle CA_ionmax matches the target value CA_ionmax_obj of the ion current peak crank angle corresponding to the target combustion timing in each cylinder 41. The combustion timing adjustment correction coefficient K_hcci is sequentially determined. Specifically, the operation control unit 30c sequentially determines the combustion timing adjustment correction coefficient K_hcci by executing the processing shown in the block diagram of FIG. 12 in synchronization with the combustion cycle of each cylinder 41. That is, the operation control means 30c calculates the deviation ΔCA_ionmax (= CA_ionmax_obj−CA_ionmax) between the target value CA_ionmax_obj of the ionic current peak crank angle and the current detected value of the ionic current peak crank angle CA_ionmax by the calculation unit 302a. In this case, the target value CA_ionmax_obj is determined based on map data (not shown) from the current rotational speed detection value Ne of the internal combustion engine 5 and the target Pmi. Further, the operation control means 30c calculates a combustion timing adjustment correction coefficient K_hcci from the deviation ΔCA_ionmax by the F / B calculation unit 302b so that the deviation ΔCA_ionmax converges to “0”. In this case, for example, a proportional law is used as the feedback control law in the F / B calculation unit 302b. That is, the F / B calculation unit 302b calculates a combustion timing adjustment correction coefficient K_hcci by multiplying ΔCA_ionmax by a predetermined gain (proportional gain) and adding “1” thereto. The feedback control law is not limited to the proportional law, and other control law such as a PID law may be used.

  As described above, the combustion timing adjustment correction coefficient K_hcci is set so that the detected value of the ionic current peak crank angle CA_ionmax coincides with the target value CA_ionmax_obj during HCCI operation (HCC operation control in S5). The actual combustion timing in the cylinder 41 is determined by a feedback control law so as to coincide with the target combustion timing. In this case, when the actual combustion timing is retarded from the target combustion timing, the supply ratio of ethanol to the entire fuel supplied to each cylinder 41 is decreased to lower the octane number of the entire fuel. Therefore, the combustion timing adjustment correction coefficient K_hcci is determined to be smaller than “1”. Further, when the actual combustion timing is advanced from the target combustion timing, in order to increase the octane number of the entire fuel by increasing the supply ratio of ethanol to the entire fuel supplied to each cylinder 41 The combustion timing adjustment correction coefficient K_hcci is determined to be a value larger than “1”.

  In the present embodiment, the ionic current peak crank angle CA_ionmax is used as the combustion timing index parameter representing the actual combustion timing. For example, the in-cylinder pressure of each cylinder 41 is used as the combustion timing index parameter. It may be.

  Supplementally, the sixth step of the present invention is realized by the processing of the processing unit 302 of FIG. 8 and the processing shown in the block diagram of FIG.

  Further, the knocking prevention correction coefficient K_si is sequentially determined by the operation control means 30c by the process shown in the flowchart of FIG. 13 during the SI operation of the internal combustion engine 5.

  That is, the operation control means 30c determines in S331 whether or not the occurrence of knocking has been detected based on the output of a knocking detection sensor (not shown) during SI operation. The knocking detection sensor includes a sensor that detects vibration of the engine base 42, in-cylinder pressure of each cylinder 41, combustion noise, and the like. Further, the seventh step of the present invention is realized by the processing of S331.

  If the determination result in S331 is affirmative, the operation control means 30c increases the value of the knocking prevention correction coefficient K_si by a predetermined value (S332). The initial value of the knocking prevention correction coefficient K_is (the value at the start of the operation of the internal combustion engine 5 or at the start of the SI operation) is set to “1”.

  If the determination result in S331 is negative, the operation control unit 30c further determines in S333 that the knocking non-detection state (state in which the determination result in S331 is negative) has continued for a predetermined time or more. Judge whether or not. If the determination result is affirmative, that is, if the occurrence of knocking is not detected for a predetermined time or longer, the operation control means 30c sets the value of the knocking prevention correction coefficient K_si in S334. Decrease by a predetermined value. If the determination result in S333 is negative, the operation control unit 30c omits the process in S334 and maintains the value of the knocking prevention correction coefficient K_si as it is.

  As described above, the value of the knocking prevention correction coefficient K_si is determined so as to increase when the occurrence of knocking is detected. If the occurrence of knocking is not detected, the value of the knocking prevention correction coefficient K_si is decreased on condition that the state continues for a predetermined time or longer.

  As a result, when knocking occurs during SI operation of the internal combustion engine 5, the correction ratio coefficient for preventing knocking is increased so that the supply ratio of ethanol to the entire fuel supplied to each cylinder 41 is increased and, consequently, the octane number of the entire fuel is increased. The value of K_si is determined.

  Supplementally, the eighth step of the present invention is realized by the processing of the processing unit 303 of FIG. 8 and the processing of S332 and 334 of FIG.

  Returning to the description of FIG. 8, the operation control unit 30 c then executes the process of the ethanol required injection amount determination unit 304. The ethanol required injection amount determination unit 304 is configured to determine the amount of ethanol by the fuel injection valve 7 based on the current rotational speed detection value Ne and the target PMi of the internal combustion engine 5 and the actual ethanol supply rate Et_inj_rat determined as described above. The required injection amount Et_inj is determined. This process is executed as follows, for example.

  That is, the ethanol required injection amount determination unit 304 first determines the internal combustion engine 5 to realize the target Pmi from the current rotation speed detection value Ne and the target Pmi by using map data (not shown) stored and held in the ECU 30 in advance. The total calorific value of the entire fuel to be supplied to each of the cylinders 41 is obtained as the required total calorific value, and the amount of ethanol necessary to generate the required total calorific value is obtained as the ethanol required total amount Inj_all. The required ethanol total amount Inj_all is calculated by dividing the required total calorific value by the lower calorific value of ethanol.

  Then, the required ethanol injection amount determination unit 304 calculates the required ethanol injection amount Et_inj by multiplying the total required ethanol amount Inj_all obtained as described above by the actual ethanol supply ratio Et_inj_rat.

  Next, the operation control means 30c performs the process of the gasoline requirement injection amount determination part 305 and the process of the calculating part 306. In this case, the gasoline required injection amount determination unit 305 calculates the gasoline request injection amount Ga_inj from the ethanol request injection amount Et_inj and the ethanol request total amount Inj_all obtained as described above by the ethanol request injection amount determination unit 304 according to the following equation (1). Is calculated.

Ga_inj = ((Inj_all−Et_inj) × Lower heating value of ethanol) / Lower heating value of gasoline
...... (1)

The numerator of the equation (1) means a residual heat generation amount obtained by subtracting a heat generation amount corresponding to the ethanol required injection amount Et_inj from the required total heat generation amount corresponding to the ethanol required total amount Inj_all. Accordingly, the amount of gasoline required to generate the remaining heat generation amount is calculated as the gasoline required injection amount Ga_inj. The lower calorific value of gasoline in the formula (1) is the lower calorific value of gasoline having a standard octane number (for example, “80” or “70”).

  In the processing of the calculation unit 306, the ethanol required injection amount Et_inj calculated by the ethanol required injection amount determination unit 304 is divided by the detected value of the ethanol aqueous solution concentration EW_r indicated by the output of the second ethanol concentration sensor 22. The required aqueous ethanol solution injection amount EW_inj is obtained.

  The gasoline required injection amount Ga_inj may be determined as follows. That is, a gasoline demand total amount as the amount of gasoline necessary to generate the demand total heat generation amount is obtained (the demand total heat generation amount is divided by the lower heat generation amount of gasoline), and the actual ethanol supply is supplied to the gasoline demand total amount. The gasoline demand injection amount Ga_inj is determined by multiplying the gasoline supply ratio (= 100−Et_inj_rat [%]) corresponding to the ratio Et_inj_rat. In this case, the gasoline required injection amount Ga_inj may be determined before the ethanol required injection amount Et_inj.

  Next, the operation control means 30c executes the processing of the flow rate / time conversion units 307 and 308.

  In this case, the flow rate / time conversion unit 307 uses the gasoline required injection amount Ga_inj determined by the gasoline required injection amount determination unit 305 based on the table data stored in advance in the ECU 30 or a predetermined arithmetic expression. The fuel injection time Ti_Ga is obtained. In addition, the flow rate / time conversion unit 308 calculates the ethanol fuel injection time Ti_EW based on the table data stored in advance in the ECU 30 or a predetermined calculation formula from the ethanol aqueous solution required injection amount EW_inj obtained by the calculation unit 306. Ask for.

  The operation control means 30c performs fuel injection according to the gasoline fuel injection time Ti_Ga and ethanol fuel injection time Ti_EW determined as described above during the HCCI operation control in S5 and the SI operation control in S7. The valve opening time of the valves 6 and 7 is controlled. In this case, the operation control means 30c determines the valve opening start timing (injection timing) of each of the fuel injection valves 5 and 6 based on map data (not shown) from the rotation speed detection value Ne of the internal combustion engine 5 and the target Pmi. Control to timing. The map data is prepared separately for HCCI operation and SI operation.

  Further, during SI operation (SI operation control in S7), the operation control means 30c determines the discharge timing of the spark plug 30, that is, the fuel ignition timing, the detected rotational speed value Ne of the internal combustion engine 5 and the target. Control is performed at a timing determined based on map data (not shown) from Pmi.

  In addition, during the HCCI operation and the SI operation, the operation control means 30c controls the throttle valve 54 as follows. That is, the target intake pressure of the internal combustion engine 5 appropriate for realizing the target Pmi is determined from the current rotational speed detection value NE of the internal combustion engine 5 and the target Pmi based on map data (not shown). The map data is prepared separately for HCCI operation and SI operation. Then, the operation control means 30c controls the opening degree of the throttle valve 54 by feedback control so that the detected value of the intake pressure indicated by the output of the intake pressure sensor 58 matches the target intake pressure.

  The above is the details of the HCCI operation control in S5 and the SI operation control in S7.

  In both the HCCI operation control and the SI operation control, when determining the actual ethanol supply ratio Et_inj_rat, in addition to the correction process using the combustion timing adjustment correction coefficient K_hcci or the knocking prevention correction coefficient K_si, the internal combustion engine 5 may be applied to the ethanol basic supply ratio Et_inj_rb for the purpose of optimizing the combustion state in the transition period in which the operation state 5 changes relatively rapidly. In the SI operation control, a correction process for making the air-fuel ratio detected by the air-fuel ratio sensor 60 coincide with the target air-fuel ratio may be performed on the ethanol basic supply ratio Et_inj_rb. Further, in both the HCCI operation control and the SI operation control, the actual ethanol supply ratio Et_inj_rat is appropriately adjusted in accordance with the interface height H_FL and the ethanol content ratio Et_r in the main tank 2, so that the inside of the separation tank 3. The remaining amount of gasoline and the remaining amount of ethanol aqueous solution may be prevented from becoming excessively unbalanced.

  Next, the switching control process in S6 and S7 will be described. In addition, these processes combine the additional process with the process similar to the control process at the time of HCCI operation, or the control process at the time of SI operation.

  In the process of S6, that is, the process of control for switching from SI operation to HCCI operation, the operation control means 30c calculates the fuel injection time Ti_Ga for gasoline and the fuel injection time Ti_EW for ethanol by the same process as during HCCI operation. To do. However, since Ti_Ga and Ti_EW calculated here are not the injection times actually used for operation control of the internal combustion engine 5, in the following description, for convenience, the fuel injection reference values for gasoline Ti_Ga, ethanol are used respectively. This is referred to as a fuel injection reference value Ti_EW.

  The operation control means 30c then sets the gasoline fuel injection time Ti_Ga and the ethanol fuel injection time Ti_EW at the end of the SI operation (timing immediately before the operation mode is switched from the SI operation mode to the HCCI operation mode). The calculated values are gradually changed in a predetermined change pattern, and finally determined so as to converge to the gasoline fuel injection reference value Ti_Ga and the ethanol fuel injection reference value Ti_EW.

  The operation control means 30c controls the valve opening times of the fuel injection valves 6 and 7, respectively, according to the gasoline fuel injection time Ti_Ga and the ethanol fuel injection time Ti_EW determined as described above. In this case, the operation control means 30c determines the opening timing (injection timing) of each of the fuel injection valves 5, 6 from map data (for HCCI operation) (not shown) from the detected rotation speed Ne of the internal combustion engine 5 and the target Pmi. The timing is determined based on the map data. Furthermore, the operation control means 30c has a predetermined change pattern at the basic timing determined based on the same map data as that during SI operation, based on the ignition timing of the ignition plug 30 from the detected rotation speed value Ne of the internal combustion engine 5 and the target Pmi. Are sequentially controlled at the timing when the correction amount is added, and finally the discharge operation of the spark plug 30 is stopped. The control of the throttle valve 54 is the same as during HCCI operation.

  The above is the process of the control for switching from SI operation to HCCI operation in S6.

  In the process of S7, that is, the process of control for switching from the HCCI operation to the SI operation, the operation control means 30c performs the same fuel injection time Ti_Ga and ethanol fuel injection time Ti_EW as in the SI operation. Is calculated. However, since Ti_Ga and Ti_EW calculated here are not the injection time itself actually used for operation control of the internal combustion engine 5 as in the case of the process of S7, in the following explanation, each of them is gasoline. The fuel injection reference value Ti_Ga for ethanol and the fuel injection reference value Ti_EW for ethanol are called.

  The operation control means 30c then sets the gasoline fuel injection time Ti_Ga and the ethanol fuel injection time Ti_EW at the end of the HCCI operation (timing immediately before the operation mode is switched from the HCCI operation mode to the SI operation mode). The calculated values are gradually changed in a predetermined change pattern, and finally determined so as to converge to the gasoline fuel injection reference value Ti_Ga and the ethanol fuel injection reference value Ti_EW.

  The operation control means 30c controls the valve opening times of the fuel injection valves 6 and 7, respectively, according to the gasoline fuel injection time Ti_Ga and the ethanol fuel injection time Ti_EW determined as described above. In this case, the operation control means 30c determines the opening timing (injection timing) of each of the fuel injection valves 5, 6 from map data (for HCCI operation) (not shown) from the detected rotation speed Ne of the internal combustion engine 5 and the target Pmi. The timing is determined based on the map data. Furthermore, the operation control means 30c has a predetermined change pattern at the basic timing determined based on the same map data as that during SI operation, based on the ignition timing of the ignition plug 30 from the detected rotation speed value Ne of the internal combustion engine 5 and the target Pmi. Are sequentially controlled at the timing to which the correction amount is added, and finally the ignition timing is converged to the basic timing. The control of the throttle valve 54 is the same as during SI operation.

  The above is the control processing for switching from SI operation to HCCI operation in S7.

  Next, processing of the gasoline octane number estimating means 30a will be described. This process realizes the gasoline octane number estimation step in the present invention.

  The ECU 30 causes the gasoline octane number estimating means 30a to execute the processing shown in the flowchart of FIG. 14 at a predetermined calculation processing cycle. This process is performed at a lower speed than the processes of the operation mode determination unit 30b and the operation control unit 30c.

  The gasoline octane number estimating means 30a first detects the operating state of the internal combustion engine 5 from the output of the sensor in S11. Specifically, the gasoline octane number estimation means 30a acquires the detected rotation speed Ne and the target Pmi of the internal combustion engine 5 in the same manner as in S101 (see FIG. 5), and further cools the internal combustion engine 5 by a sensor (not shown). The detection value of the water temperature, the detection value of the intake air temperature, the detection value of the temperature of the lubricating oil, and the like are acquired.

  Next, in S12, the gasoline octane number estimating means 30a determines whether or not the fuel outflow integrated amount of the separation tank 3 is smaller than a predetermined value. Here, the accumulated fuel outflow amount is the total accumulated amount of fuel (gasoline and ethanol aqueous solution) flowing out from the separation tank 3 after the main fuel is replenished to the main tank 2 (hereinafter referred to as refueling). Means the total amount of fuel used in the separation tank 3. In the present embodiment, this accumulated fuel spill amount is the accumulated amount of fuel supplied from the separation tank 3 to the internal combustion engine 5 and the accumulated amount of gasoline returned from the separation tank 3 to the main tank 2 via the gasoline return passage 18. Is the sum of The gasoline octane number estimating means 30a resets the fuel outflow integrated amount to “0” every time the main tank 2 is refueled, and calculates the fuel outflow integrated amount from each refueling to the next refueling. Like to do. In this case, the gasoline supply amount and the ethanol aqueous solution supply amount respectively defined by the gasoline fuel injection time Ti_Ga and the ethanol fuel injection time Ti_EW are cumulatively added to the internal combustion engine 5 from the separation tank 3. An integrated amount of fuel is calculated. Further, the cumulative amount of gasoline returned from the separation tank 3 to the main tank 2 is calculated by cumulatively adding the flow rate in the gasoline return passage 18 defined by the control command for the flow rate control valve 19. Then, by calculating the sum of these integrated amounts, the integrated fuel outflow amount of the separation tank 3 is calculated.

  Note that the calculated value of the accumulated fuel outflow amount until the next refueling is stored and held in a nonvolatile memory (not shown) such as an EEPROM while the internal combustion engine 5 is stopped.

  If the determination result in S12 is affirmative, it means that the total amount of fuel flowing out from the separation tank 3 after refueling the main tank 2 is small, and that the state is immediately after refueling. In this case, the gasoline octane number estimating means 30a next determines whether or not the current cooling water temperature of the internal combustion engine 5 (detected value acquired in S11) is lower than a predetermined temperature in S13, that is, the internal combustion engine 5 It is determined whether or not it is cold.

  Here, in the present embodiment, during operation of the internal combustion engine 5, basically, the octane number of gasoline in the separation tank 3 is determined by the HCCI operation octane number estimation process or the SI operation octane number estimation process described later. Estimate (determine gasoline octane number estimate RON). However, in the cold state of the internal combustion engine 5 where the combustion of fuel in each cylinder 41 is likely to be unstable, the accuracy of estimating the octane number of gasoline that is moderate to the octane number estimation process for HCCI operation or the octane number estimation process for SI operation Is prone to decline.

  Therefore, if the determination result in S13 is affirmative, the gasoline octane number estimating means 30a executes an octane number estimation process for refueling immediately after S14.

  If the determination result of S12 or the determination result of S13 is negative, the gasoline octane number estimation means 30a determines that the previous operation mode (operation mode in the previous calculation processing cycle) is the HCCI operation mode in S15. Determine whether or not. Then, the gasoline octane number estimating means 30a executes the HCCI operation octane number estimation process when the determination result of S15 is affirmative (S16), and if negative, the gasoline octane number estimation unit for SI operation is estimated. The process is executed (S17).

  Hereinafter, the octane number estimation process immediately after refueling, the HCCI operation octane number estimation process, and the SI operation octane number estimation process will be specifically described.

  The octane number estimation process immediately after refueling is executed as follows. The gasoline octane number estimating means 30a executes pre-preparation processing for the octane number estimation processing for immediately after refueling when the main tank 2 is refueled. This pre-preparation process is executed every time the main tank 2 is refueled, and is a process for calculating a rate of change dRon / dQg described later.

  In this pre-preparation process, the remaining amount of the mixed fuel in the main tank 2 and the entanol content ratio in the mixed fuel at the start and end of refueling of the main tank 2 are the main fuel remaining amount sensor 23. And detected through the first ethanol concentration sensor 20. Further, the remaining amount VolG of gasoline in the separation tank 3 at the start of refueling is measured from the output of the float sensor 21 (detected value of the interface height H_FL). Thereby, the first step in the present invention is realized.

  Then, the gasoline octane number estimating means 30a newly replenishes the main tank 2 using the detected value by the main fuel remaining amount sensor 23 before and after refueling the main tank 2 and the detected value by the first ethanol concentration sensor 20. The ethanol content ratio Et_rB of the main fuel (hereinafter referred to as supplementary fuel) is estimated. Specifically, the gasoline octane number estimating means 30a is configured to detect the main fuel remaining amount (volume) VolA in the main tank 2 detected via the main fuel remaining amount sensor 23 at the start of refueling of the main tank 2, and the refueling end. The remaining amount (volume) VolC of the main fuel in the main tank 2 detected by the main fuel remaining amount sensor 23, the ethanol content ratio Et_rA of the main fuel detected by the first ethanol concentration sensor 20 at the start of refueling, and the end of refueling From time to time, the ethanol content ratio Et_rB in the supplementary fuel is estimated from the ethanol content ratio Et_rC of the main fuel detected by the first ethanol concentration sensor 20. Thereby, the second step according to the present invention is realized.

Et_rB = (Et_rC × VolC−Et_rA × VolA) / VolB (2)
However, VolB = VolC−VolA

The numerator on the right side of the formula (2) is the difference between the volume of ethanol in the main fuel after refueling (= Et_rC × VolC) and the volume of ethanol in the main fuel before refueling (= Et_rA × VolA), that is, It represents the volume of ethanol in the supplementary fuel. Further, the denominator of the formula (2) represents the volume of the supplementary fuel.

  Next, the gasoline octane number estimating means 30a estimates a rough octane number RonB of gasoline of the supplementary fuel from the ethanol content ratio Et_rB of the supplementary fuel estimated as described above.

  Here, in the present embodiment, standard octane values of a plurality of types of typical main fuel gasoline that can be replenished to the main tank 2, such as E10 fuel and E20 fuel, are stored in advance in the ECU 30 as a database. . The standard octane value is, for example, “80” for E10 fuel and “70” for E20 fuel. Then, the gasoline octane number estimating means 30a identifies the main fuel type corresponding to the estimated value by referring to the data bale from the estimated value of the ethanol content ratio Et_rB of the supplementary fuel, and the main type of the identified type The standard octane number value of the fuel is determined as a rough estimate of the octane number RonB of the supplementary fuel gasoline. Thereby, the 3rd step in the present invention is realized.

  Next, the gasoline octane number estimating means 30a calculates the gasoline octane number RonB of the supplementary fuel estimated as described above, the gasoline octane number RonA of the main fuel before refueling, and the main fuel before and after refueling used in the calculation of the equation (2). From the detected values of the remaining amounts VolA and VolC and the volume of supplementary fuel VolB (= VolC−VolA), the octane number RonC of the main fuel gasoline in the main tank 2 after refueling is estimated by the following equation (3).

RonC = (RonA x VolA + RonB x VolB) / VolC (3)

That is, the octane number RonC of the main fuel gasoline in the main tank 2 after refueling is estimated by obtaining a weighted average of RonA and RonB using VolA / VolC and VolB / VolC as weighting factors. In this case, the gasoline octane number RonA of the main fuel before refueling is the gasoline octane number which is the octane number of gasoline in the separation tank 3 estimated by the gasoline octane number estimation means 30a during operation of the internal combustion engine 5 before refueling. The latest value of the estimated value RON is used.

  Here, the gasoline in the separation tank 3 is not the main fuel gasoline itself in the main tank 2 immediately after refueling, but by operating the internal combustion engine 5 (consuming the gasoline in the separation tank 3), The main fuel in the main tank 2 is replaced with gasoline.

  In this case, as shown in the graph of FIG. 15, the octane number of gasoline in the separation tank 3 is approximately linear from the initial value (= RonA) before the main tank 2 is refueled. It can be considered that the main fuel in the main tank 2 changes toward the octane number RonC of gasoline. In the graph of FIG. 15, RonA> RonC is exemplified. Further, the accumulated gasoline spillage on the horizontal axis in FIG. 15 means the accumulated amount of gasoline spilled from the separation tank 3 after refueling.

  Therefore, in the present embodiment, the gasoline octane number estimating means 30a calculates the estimated value of the octane number RonC of the gasoline as the main fuel after refueling calculated by the equation (3) and the estimated value of the gasoline octane number RON of the separation tank 3 before refueling. From the latest value (= RonA) and the remaining amount of gasoline VolG in the separation tank 3 measured from the output of the float sensor 21 at the start of refueling (detected value of the interface height H_FL), Calculate the change rate dRon / dQg of gasoline in the separation tank 3 relative to the total gasoline spillage in the separation tank 3 (that is, the slope of the graph in FIG. 5), and store this value until the next refueling. Keep it. Thereby, the advance preparation process is completed.

dRon / dQg = (RonC−RonA) / VolG (4)

Supplementally, in the present embodiment, the fourth step in the present invention is realized by the process of estimating the octane number RonC by the above formula (3) and the process of calculating the change rate dRon / dQg by the formula (4). The In this case, the rate of change dRon / dQg is a parameter that defines the relationship between the amount of gasoline used (outflow) in the separation tank 3 after refueling and the change in the octane number of gasoline in the separation tank 3. have.

  The gasoline octane number estimation means 30a obtains the estimated gasoline octane number value RON of the separation tank 3 using the change rate dRon / dQg determined in the preliminary preparation process as described above in the octane number estimation process immediately after refueling.

  Specifically, the gasoline octane number estimating means 30a measures the accumulated gasoline spillage amount, which is the accumulated amount of gasoline spilled from the separation tank 3 after refueling, in the same manner as the accumulated fuel spill amount. In this case, the cumulative amount of gasoline supplied from the separation tank 3 to the internal combustion engine 5 is calculated by cumulatively adding the gasoline supply amount defined by the gasoline fuel injection time Ti_Ga. Further, the cumulative amount of gasoline returned from the separation tank 3 to the main tank 2 is calculated by cumulatively adding the flow rate in the gasoline return passage 18 defined by the control command for the flow rate control valve 19. Then, by calculating the sum of these integrated amounts, the integrated gasoline outflow amount of the separation tank 3 is calculated. Alternatively, a value (cumulative amount of the ethanol aqueous solution supplied from the separation tank 3 to the internal combustion engine 5) obtained by cumulatively adding the supply amount of the ethanol aqueous solution defined by the fuel injection time Ti_EW for ethanol from the fuel outflow integrated amount is obtained. By subtracting, the gasoline outflow integrated amount may be calculated.

  Then, the gasoline octane number estimating means 30a calculates the following from the gasoline spill accumulated amount obtained as described above, the latest value (= RonA) of the gasoline octane number estimated value RON of the separation tank 3 before refueling, and the rate of change dRon / dQg. A new gasoline octane number estimated value RON is obtained from equation (5).

RON = RonA + (dRon / dQg) x gasoline spill cumulative amount ... (5)

The above is the details of the octane number estimation process immediately after refueling. As can be seen from the flowchart of FIG. 14, the octane number estimation process immediately after refueling is an estimation process that is executed only immediately after refueling and when the internal combustion engine 5 is in the cold state.

  Next, the octane number estimation process during HCCI operation will be described. In this estimation process, the combustion timing adjustment correction coefficient K_hcci for correcting the ethanol basic supply ratio Et_inj_rb during HCCI operation is used to obtain the gasoline octane number estimated value RON.

  Here, the map data used to determine the ethanol basic supply ratio Et_inj_rb (the map data in FIGS. 9A and 9B and FIGS. 10A and 10B) is the separation tank as described above. 3 is based on the assumption that the octane number of the actual gasoline in 3 matches the octane number corresponding to each map data, and the operating state (engine temperature (cooling water temperature), intake air temperature, lubricating oil temperature, etc.) of the internal combustion engine 5 ( Knocking or misfiring occurs on the assumption that the internal combustion engine 5 is in a steady operating state (hereinafter referred to as a reference operating state) in which the rotational speed and operating conditions other than the required load are within a predetermined standard range. Therefore, it is possible to perform the HCCI operation or SI operation of the internal combustion engine 5 with as high efficiency as possible, and to realize the combustion of fuel so that NOx in the exhaust gas can be reduced as much as possible. Is set to

  Therefore, if the actual octane number of gasoline in the separation tank 3 (hereinafter simply referred to as the actual gasoline octane number) is different from the estimated gasoline octane number RON used to determine the ethanol basic supply ratio Et_inj_rb, the actual fuel This causes the combustion timing to deviate from the target combustion timing, and the combustion timing adjustment correction coefficient K_hcci deviates from “1”. Accordingly, in the reference operation state in the HCCI operation mode, an error in the estimated gasoline octane number RON with respect to the actual gasoline octane number becomes a factor affecting the combustion timing adjustment correction coefficient K_hcci, and the value of the combustion timing adjustment correction coefficient K_hcci Is an index value representing the degree of error of the gasoline octane number estimated value RON.

  Therefore, in the present embodiment, in the HCCI operation octane number estimation process, the gasoline octane number estimation means 30a executes the process shown in the block diagram of FIG. 16 when the operation state of the internal combustion engine 5 is the reference operation state. Thus, the gasoline octane number estimated value RON of the separation tank 3 is obtained.

  Specifically, the gasoline octane number estimating means 30a obtains a deviation (= 1−K_hcci) between “1” and the combustion timing adjustment correction coefficient K_hcci by the calculation unit S116a. Then, the gasoline octane number estimating means 30a obtains a correction amount (operation amount) of the gasoline octane number estimated value RON by the F / B calculation unit 116b so that the deviation is converged to “0”. In this case, a feedback control law such as a proportional law is used in the calculation of the F / B calculation unit 116b.

  Next, the gasoline octane number estimating means 30a sets the correction amount obtained by the F / B calculating section 116b to the previous value of the gasoline octane number estimated value RON (the value obtained by the gasoline octane number estimating means 30a in the previous processing) by the calculating section 116c. By adding, a new gasoline octane number estimated value RON is calculated.

  As described above, in the HCCI operation octane number estimation process, the gasoline octane number estimated value RON is sequentially updated by feedback control so that the combustion timing adjustment correction coefficient K_hcci converges to “1”. As a result, when the operating state of the internal combustion engine 5 such as the engine temperature and the intake air temperature (the operating state other than the rotational speed and the target Pmi) becomes the reference operating state, the actual combustion of fuel in each cylinder 41 of the internal combustion engine 5 The gasoline octane number estimated value RON is obtained so that the timing can coincide with the target combustion timing.

  The above is the details of the HCCI operation octane number estimation process. In the present embodiment, the gasoline octane number estimated value RON is updated when the operation state of the internal combustion engine 5 is the reference operation state. However, the engine temperature, the intake air temperature, and the like of the internal combustion engine 5 are changed from the reference operation state. In the case of deviating, the gasoline octane number estimated value RON may be obtained by adding correction according to the engine temperature or intake air temperature.

  Next, SI operation octane number estimation processing will be described. In this estimation process, the knocking prevention correction coefficient K_si for correcting the ethanol basic supply ratio Et_inj_rb during SI operation is used to obtain the gasoline octane number estimated value RON.

  When the operating state other than the rotational speed and the required load of the internal combustion engine 5 is the reference operating state, the combination of the rotational speed and the required load of the internal combustion engine 5 that causes slight knocking is approximately in the separation tank 3. It is thought to depend on the octane number of gasoline.

  Therefore, in the present embodiment, when it is assumed that the operation state such as the engine temperature and the intake air temperature of the internal combustion engine 5 is the reference operation state, the rotational speed and target of the internal combustion engine 5 that may cause slight knocking. A range of Pmi (hereinafter referred to as knocking occurrence range) is set in advance and stored in the ECU 30. The gasoline octane number estimating means 30a detects the rotational speed of the internal combustion engine 5 when the internal combustion engine 5 is operating in the SI operation mode when the internal combustion engine 5 is in the reference operation state such as the engine temperature or the intake air temperature. When the value Ne and the target Pmi are in the knocking occurrence range, the process shown in the block diagram of FIG. 17 is performed to obtain the estimated gasoline octane number RON of the separation tank 3.

  Specifically, the gasoline octane number estimating means 30a obtains the deviation (= 1−K_si) between “1” and the knocking prevention correction coefficient K_si by the calculation unit S117a. Then, the gasoline octane number estimating means 30a obtains a correction amount (operation amount) of the gasoline octane number estimated value RON by the F / B calculation unit 117b so that the deviation is converged to “0”. In this case, a feedback control law such as a proportional law is used in the calculation of the F / B calculation unit 117b.

  Next, the gasoline octane number estimating means 30a uses the correction amount obtained by the F / B calculating section 117b as the previous value of the gasoline octane number estimated value RON (the value obtained by the gasoline octane number estimating means 30a in the previous processing) by the calculating section 117c. By adding, a new gasoline octane number estimated value RON is calculated.

  As described above, in the octane number estimation process during SI operation, the gasoline octane number estimated value RON is sequentially updated by feedback control so that the knocking prevention correction coefficient K_si converges to “1”. As a result, when the operating state other than the rotational speed of the internal combustion engine 5 and the target Pmi is the reference operating state, and the rotational speed detection value Ne and the target Pmi are within the knocking occurrence range, the gasoline octane number estimated value RON is obtained. Will be.

  The above is the details of the octane number estimation process during SI operation. In the present embodiment, the gasoline octane number estimated value RON is updated when the operating state other than the rotational speed of the internal combustion engine 5 and the target Pmi (required load) is the reference operating state. When the engine temperature, the intake air temperature, or the like deviates from the reference operation state, the gasoline octane number estimated value RON may be obtained by adding a correction according to the engine temperature or the intake air temperature.

  According to the present embodiment described above, the octane number of gasoline in the separation tank 3 is estimated, and the PMI appropriate range for HCCI operation for performing HCCI operation is variable according to the estimated value (gasoline octane number estimated value RON). Is set automatically. For this reason, the Pmi appropriate range for HCCI operation suitable for the octane number of gasoline in the separation tank 3 can be set. In particular, when the gasoline octane number estimated value RON is low, the PMI proper range for HCCI operation can be expanded to the side where the net average effective pressure Pmi is low (the side where the required load is low), so NOx etc. in the exhaust of the internal combustion engine 5 can be reduced. The operating range of the internal combustion engine 5 that can be reduced can be expanded.

  Further, an ethanol basic supply ratio Et_inj_rb, which is a basic value of the ratio of ethanol in the whole fuel supplied from the separation tank 3 to each cylinder 41 of the internal combustion engine 5, is variably determined according to the gasoline octane number estimated value RON. . For this reason, the supply ratio of gasoline and ethanol supplied from the separation tank 3 to each cylinder 41 of the internal combustion engine 5 can be set to a supply ratio suitable for the octane number of gasoline in the separation tank 3.

  In the embodiment described above, the case where the alcohol in the main fuel is ethanol has been described as an example, but the alcohol may be, for example, methanol.

The figure which shows schematic structure of the fuel supply system in the operation control system of the internal combustion engine in one Embodiment of this invention. The figure which shows schematic structure of the principal part structure of the internal combustion engine in embodiment. The block diagram which shows the main functions of the control unit (ECU) shown in FIG. The flowchart which shows the process regarding the operation mode determination means and the operation control means of the control unit (ECU) shown in FIG. The flowchart which shows the process of S1 of FIG. 6A and 6B are diagrams showing two types of HCCI operation range setting data used in the process of S102 of FIG. The block diagram which shows the process of S102 of FIG. The block diagram which shows the process of the operation control means performed by S5 and S7 of FIG. 9A and 9B are diagrams showing map data used in the ethanol basic supply ratio determination unit shown in FIG. 10A and 10B are diagrams showing map data used in the ethanol basic supply ratio determination unit shown in FIG. The graph which shows the output characteristic of the ion current sensor with which the internal combustion engine of embodiment was equipped. The block diagram which shows the process which determines the correction coefficient K_hcci for combustion timing adjustment shown in FIG. 9 is a flowchart showing processing for determining a knocking prevention correction coefficient K_si shown in FIG. The flowchart which shows the process of the gasoline octane number estimation means of the control unit (ECU) shown in FIG. The graph for demonstrating the process of S14 of FIG. The block diagram which shows the process of S16 of FIG. The block diagram which shows the process of S17 of FIG.

Explanation of symbols

  2 ... main tank (main fuel tank), 3 ... separation tank, 5 ... internal combustion engine, 30a ... gasoline octane number estimation means, 30b ... operation mode determination means.

Claims (6)

An operation control method for an internal combustion engine using a mixed fuel of alcohol and gasoline as a fuel, the separation step for separating alcohol and gasoline from the mixed fuel, and the operation of the internal combustion engine including at least a required load of the internal combustion engine An ignition method selection step for selecting either the compression ignition method or the spark ignition method according to the state, and the alcohol and gasoline separated in the separation step according to at least the operating state of the internal combustion engine In the operation control method for causing the internal combustion engine to operate with the ignition method selected in the ignition method selection step while supplying the internal combustion engine with the determined supply ratio,
A gasoline octane number estimating step for estimating the octane number of the gasoline separated in the separation step, and the smaller the estimated octane number , the larger the required load range for selecting the compression ignition method to the low load side. An operation control method for an internal combustion engine, wherein a range of a required load of the internal combustion engine for selecting a compression ignition system in the ignition system selection step is changed according to the estimated octane number . An operation control method for an internal combustion engine using a mixed fuel of alcohol and gasoline as a fuel, the separation step for separating alcohol and gasoline from the mixed fuel, and the operation of the internal combustion engine including at least a required load of the internal combustion engine An ignition method selection step for selecting either the compression ignition method or the spark ignition method according to the state, and the alcohol and gasoline separated in the separation step according to at least the operating state of the internal combustion engine In the operation control method for causing the internal combustion engine to operate with the ignition method selected in the ignition method selection step while supplying the internal combustion engine with the determined supply ratio,
A gasoline octane number estimation step for estimating the octane number of the gasoline separated in the separation step, and the range of the required load of the internal combustion engine for selecting the compression ignition method in the ignition method selection step is changed according to the estimated octane number ;
The supply ratio of alcohol to gasoline supplied to the internal combustion engine is such that the supply ratio of alcohol to the whole fuel supplied to the internal combustion engine is higher as the estimated octane number is lower. An operation control method for an internal combustion engine, which is determined according to the estimated octane number . An operation control method for an internal combustion engine using a mixed fuel of alcohol and gasoline as a fuel, the separation step for separating alcohol and gasoline from the mixed fuel, and the operation of the internal combustion engine including at least a required load of the internal combustion engine An ignition method selection step for selecting either the compression ignition method or the spark ignition method according to the state, and the alcohol and gasoline separated in the separation step according to at least the operating state of the internal combustion engine In the operation control method for causing the internal combustion engine to operate with the ignition method selected in the ignition method selection step while supplying the internal combustion engine with the determined supply ratio ,
In the separation step, the mixed fuel in the main fuel tank that stores the mixed fuel is supplied to the separation tank while mixing water with the mixed fuel, and the mixed liquid of the mixed fuel and water is supplied to the gasoline in the separation tank. And an alcohol aqueous solution that is a mixture of alcohol and water,
A gasoline octane number estimating step for estimating the octane number of the gasoline separated in the separation step ;
When the mixed fuel is replenished to the main fuel tank, the remaining amount of the mixed fuel in the main fuel tank and the alcohol concentration of the mixed fuel before the replenishment, and the mixed fuel of the main fuel tank after the replenishment A first step of measuring a remaining amount and an alcohol concentration of the mixed fuel, and a remaining amount of gasoline in the separation tank before the replenishment;
The main fuel tank was replenished from the measured value of the remaining fuel and alcohol concentration in the main fuel tank before replenishment and the measured remaining fuel and alcohol concentration in the main fuel tank after replenishment. A second step of estimating the alcohol concentration of the mixed fuel;
A third step of estimating an octane number of gasoline in the supplemented mixed fuel from an estimated value of alcohol concentration of the supplemented mixed fuel;
Before the replenishment, the gasoline octane number estimated last in the gasoline octane number estimation step, the estimated octane number of gasoline in the replenished mixed fuel, and the separation tank before replenishment A fourth step of setting a parameter that defines the relationship between the amount of gasoline used in the separation tank after the replenishment and the change in the octane number of gasoline in the separation tank from the measured value of the remaining amount of gasoline With
According to the octane number estimated in the gasoline octane number estimation step, the range of the required load of the internal combustion engine for selecting the compression ignition method in the ignition method selection step is changed,
In the gasoline octane number estimating step, in the period immediately after replenishment of the mixed fuel to the main fuel tank, while measuring the amount of gasoline used in the separation tank from the end of the replenishment, An operation control method for an internal combustion engine of the internal combustion engine , wherein the octane number of the gasoline separated in the separation step is estimated based on a parameter . An operation control method for an internal combustion engine using a mixed fuel of alcohol and gasoline as a fuel, the separation step for separating alcohol and gasoline from the mixed fuel, and the operation of the internal combustion engine including at least a required load of the internal combustion engine An ignition method selection step for selecting either the compression ignition method or the spark ignition method according to the state, and the alcohol and gasoline separated in the separation step according to at least the operating state of the internal combustion engine In the operation control method for causing the internal combustion engine to operate with the ignition method selected in the ignition method selection step while supplying the internal combustion engine with the determined supply ratio,
A gasoline octane number estimating step for estimating the octane number of the gasoline separated in the separation step ;
A fifth step of measuring a value of a combustion timing index parameter representing an actual combustion timing of fuel in the internal combustion engine during operation of the internal combustion engine in the compression ignition method;
A first operation amount for adjusting the supply ratio of alcohol and gasoline to the internal combustion engine is determined so that the combustion timing indicated by the measured value of the combustion timing index parameter coincides with the target combustion timing, and the first operation amount is determined. And a sixth step of adjusting the supply ratio according to the operation amount,
According to the octane number estimated in the gasoline octane number estimation step, the range of the required load of the internal combustion engine for selecting the compression ignition method in the ignition method selection step is changed,
The gasoline octane number estimation step estimates the octane number of the gasoline separated in the separation step based on the first manipulated variable when the internal combustion engine is operated in the compression ignition system. . An operation control method for an internal combustion engine using a mixed fuel of alcohol and gasoline as a fuel, the separation step for separating alcohol and gasoline from the mixed fuel, and the operation of the internal combustion engine including at least a required load of the internal combustion engine An ignition method selection step for selecting either the compression ignition method or the spark ignition method according to the state, and the alcohol and gasoline separated in the separation step according to at least the operating state of the internal combustion engine In the operation control method for causing the internal combustion engine to operate with the ignition method selected in the ignition method selection step while supplying the internal combustion engine with the determined supply ratio,
A gasoline octane number estimating step for estimating the octane number of the gasoline separated in the separation step ;
A seventh step of detecting whether or not knocking of the internal combustion engine occurs during operation of the internal combustion engine in the spark ignition method;
The second manipulated variable for adjusting the supply ratio of alcohol and gasoline to the internal combustion engine so as to prevent the occurrence of knocking is determined based on the detected presence or absence of the occurrence of knocking. And an eighth step of determining to increase or decrease and adjusting the supply ratio according to the second operation amount,
According to the octane number estimated in the gasoline octane number estimation step, the range of the required load of the internal combustion engine for selecting the compression ignition method in the ignition method selection step is changed,
The gasoline octane number estimating step estimates the octane number of the gasoline separated in the separation step based on the second manipulated variable during operation of the internal combustion engine in the spark ignition method. . The operation control method for an internal combustion engine according to any one of claims 1, 2, 4, and 5 ,
In the separation step, the mixed fuel in the main fuel tank that stores the mixed fuel is supplied to the separation tank while mixing water with the mixed fuel, and the mixed liquid of the mixed fuel and water is supplied to the gasoline in the separation tank. And an alcohol aqueous solution, which is a mixed liquid of alcohol and water, and an operation control method for an internal combustion engine.