JP2009257134A - Fuel supply system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To operate an internal combustion engine efficiently as far as possible, without depending on a mixing rate of two kinds of fuel for composing mixed fuel to be used. <P>SOLUTION: This fuel supply system has a detecting means 14 for generating output corresponding to respective including rates of the two kinds of fuel for composing the mixed fuel stored in a mixed fuel storage tank 2, a detecting means 15 for generating output corresponding to a residual quantity of respective kinds of fuels in a separated fuel storage tank 3 for storing the two kinds of fuels separated from the mixed fuel, and a fuel supply control means 21 for controlling respective supply quantities of the two kinds of fuels to the internal combustion engine so that respective supply rates of the two kinds of fuels to the internal combustion engine 4 are changed in response to the output of the detecting means 14 and 15. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel supply system for an internal combustion engine that uses two types of fuel having different octane numbers.

In recent years, for the purpose of environmental measures such as CO ₂ emission reduction, it is possible to operate using a mixed fuel made by mixing two types of fuels with different octane numbers, such as a mixed fuel made by adding ethanol to gasoline. Development of an internal combustion engine is underway.

  On the other hand, as a fuel supply system for an internal combustion engine that operates using two types of fuels having different octane numbers, for example, as seen in Patent Documents 1 and 2, suppression of the occurrence of knocking in the internal combustion engine, In order to reduce the exhaust performance and improve the exhaust performance, the supply ratio of the two types of fuel to the internal combustion engine (the ratio of the supply amount of each type of fuel to the total amount of fuel supplied in each combustion cycle of the internal combustion engine) A device that is changed according to an operating state such as a load is known.

  In the fuel supply system found in Patent Document 1, the mixed fuel stored in the main tank is separated into two types of fuel, a high-octane fuel and a low-octane fuel, and these two types of fuel are stored in separate sub-tanks. Then, each type of fuel is supplied from these sub tanks to the internal combustion engine. In this fuel supply system, basically, the fuel ignition system (self-ignition system and spark ignition system) is switched according to the load and rotation speed of the internal combustion engine, and the internal combustion engine using the self-ignition system During the operation, the supply ratio of each type of fuel is changed according to the load of the internal combustion engine.

  Further, in the fuel supply system found in Patent Document 2, each type of fuel is supplied to the internal combustion engine from a tank in which two types of fuel, a high-octane fuel and a low-octane fuel, are separately stored. In this fuel supply system, basically, the operation mode (stratified combustion mode and homogeneous combustion mode) of the internal combustion engine and the supply ratio of each type of fuel are changed according to the load and the rotational speed of the internal combustion engine. And make changes.

Furthermore, in the technologies found in these Patent Documents 1 and 2, in order to prevent the consumption of each of the two types of fuel stored in the different tanks from being biased to only one type of fuel, The remaining amount of each type of fuel in the tank is detected, and when the remaining amount of one type of fuel falls below a predetermined lower limit, the supply ratio of the one type of fuel to the internal combustion engine is reduced. (The supply ratio of the other type of fuel is increased).
JP 2001-5070 A JP 2003-201877 A

  By the way, the mixed fuel used in the internal combustion engine, such as the mixed fuel obtained by adding ethanol to gasoline, is not always uniformly determined for each of the two types of fuel composing the mixed fuel. A mixed fuel in which the content ratios of the two kinds of fuels are variously varied can be provided. For example, in the United States, a blended fuel in which ethanol is added to gasoline is provided with a 10% or 85% ethanol content, and further consideration is given to a blended fuel with a 20% ethanol content. Has been.

  And in the fuel supply system seen in the said patent documents 1 and 2, when the mixed fuel with which the content rate of each kind of fuel is not uniform as mentioned above is used, the following inconvenience will arise.

  That is, in the fuel supply system found in Patent Document 1, in the operation state of the internal combustion engine in the region where the fuel is ignited by the self-ignition method and the load of the internal combustion engine is relatively high, As long as the detected value of the remaining amount of high octane fuel is equal to or greater than a predetermined lower limit, the supply ratio of high octane fuel to the internal combustion engine is increased in order to prevent knocking. Further, in the operating state of the internal combustion engine in the region where the fuel is ignited by the self-ignition method and the load of the internal combustion engine is relatively low, the remaining amount detection value of the low octane fuel is a predetermined value. As long as it is equal to or higher than the lower limit of the value, the supply ratio of the low-octane fuel is increased in order to improve the ignitability of the fuel.

  Further, in the fuel supply system found in Patent Document 2, as long as the balance between the remaining detection values of the high octane fuel and the low octane fuel is balanced, the supply ratio of the low octane fuel is increased in the low load region of the internal combustion engine. However, in the high load region of the internal combustion engine, the supply ratio of high octane fuel is increased.

  On the other hand, in an internal combustion engine mounted as a driving force generation source in an automobile or the like, the internal combustion engine is frequently operated in a specific driving region depending on the driving characteristics of the driver, the main driving environment, and the like. There are many cases.

  In the fuel supply systems found in Patent Documents 1 and 2, for example, when the operation of the internal combustion engine in an operation region where it is preferable to increase the supply ratio of the high octane number fuel is frequently performed, If a mixed fuel having a relatively small content of octane fuel is used, the high octane fuel will be deficient at an early stage. Therefore, when it is not easy to obtain a mixed fuel with a relatively high content ratio of high octane fuel, and when there is a high frequency of using a mixed fuel with a relatively small content ratio of high octane fuel, the supply ratio of the high octane fuel is to be reduced. Even in the operating state of the internal combustion engine in a region where it is preferable to increase the number, in practice, the operating frequency is increased such that the supply ratio of the low octane fuel is increased.

  Further, in the fuel supply systems found in Patent Documents 1 and 2, contrary to the above, the operation of the internal combustion engine in the operation region where it is preferable to increase the supply ratio of the low octane number fuel is frequently performed. In addition, if a mixed fuel having a relatively low content of low-octane fuel is used, the low-octane fuel will be insufficient early. Therefore, when it is not easy to obtain a mixed fuel with a relatively large content ratio of low octane fuel, and when a mixed fuel with a relatively small content ratio of low octane fuel is used frequently, the supply ratio of the low octane fuel is reduced. Even in the operating state of the internal combustion engine in a region where it is preferable to increase the frequency, in practice, the frequency of operation that increases the supply ratio of the high-octane fuel must be increased.

  As described above, in the techniques shown in Patent Documents 1 and 2, the actual supply ratio of the two types of fuel to the internal combustion engine is preferably set depending on the mixing ratio of the two types of fuel composing the mixed fuel to be used. There is a case where the frequency of the supply ratio largely deviating from the supply ratio is increased. In such a case, the internal combustion engine cannot be operated efficiently, and the original power performance and exhaust performance (performance that can be realized when the remaining amount of two types of fuel is sufficient) or close to it. There is an inconvenience that there are many cases where the performance cannot be exhibited.

  The present invention has been made in view of such a background, and makes it possible to operate an internal combustion engine as efficiently as possible without depending on the mixing ratio of two types of fuel composing the mixed fuel to be used. An object is to provide a fuel supply system.

In order to achieve the above object, the fuel supply system of the present invention includes a mixed fuel storage tank that stores a mixed fuel obtained by mixing a first fuel and a second fuel, which are two types of fuels having different octane numbers, and the mixed fuel tank. A fuel supply system for supplying the two types of fuel to the internal combustion engine from the separated fuel storage tank, the fuel storage tank including the two types of fuel separated from the mixed fuel in the fuel storage tank;
A mixed fuel ratio detection means for generating an output corresponding to the content ratio of each of the two types of fuel in the mixed fuel in the mixed fuel storage tank;
A separated fuel remaining amount detecting means for generating an output corresponding to the remaining amount of each of the two types of fuel in the separated fuel storage tank;
The internal combustion engine so that the supply ratio of each of the two types of fuel to the whole fuel supplied to the internal combustion engine is changed according to the output of the mixed fuel ratio detection means and the output of the separated fuel remaining amount detection means. And a fuel supply control means for controlling the respective supply amounts of the two kinds of fuels (first invention).

  According to the first aspect of the invention, the fuel supply control means determines the supply ratio of each of the two types of fuel to the whole fuel supplied to the internal combustion engine, the output of the mixed fuel ratio detection means, and the separated fuel remaining amount. The supply amounts of the two types of fuel to the internal combustion engine are controlled so as to change in accordance with the output of the detection means. Therefore, the supply ratio of each type of fuel to the internal combustion engine is determined not only for the remaining amount of each of the two types of fuel in the separated fuel storage tank but also for the two types of fuel in the mixed fuel in the mixed fuel storage tank. It can adjust to the ratio suitable also for each content rate. For example, the mutual ratio of the supply ratios of the two types of fuel to the internal combustion engine may be the mutual ratio of the remaining amounts of the two types of fuel in the separated fuel storage tank or the mixing ratio in the mixed fuel storage tank. It is possible to minimize the frequency of fuel supply to the internal combustion engine that greatly deviates from the mutual ratio of the content ratios of the two types of fuel in the fuel. For this reason, according to the first aspect of the present invention, it is possible to prevent as much as possible the occurrence of unbalanced fuel consumption in which only one of the two types of fuel in the separated fuel storage tank is consumed at an early stage. Is possible. As a result, it is possible to prevent the occurrence of a situation in which the supply ratio of the two types of fuel to the internal combustion engine must be greatly deviated from the supply ratio at which the internal combustion engine can be operated efficiently and smoothly. Become.

  Therefore, according to the first invention, it is possible to operate the internal combustion engine as efficiently as possible without depending on the mixing ratio of the two types of fuel composing the mixed fuel to be used.

  The separated fuel storage tank may be a tank that individually stores each of the two types of fuels (separate tanks for each fuel). It may be a tank in which the fuel is accommodated while being in contact with the top and bottom.

In the first invention, more specifically, the fuel supply control means is responsive to an operating state of the internal combustion engine including at least a required load and a rotational speed of the internal combustion engine and an output of the mixed fuel ratio detection means. A basic supply ratio setting means for setting a basic supply ratio defining parameter for specifying the basic supply ratio of each of the two types of fuel supplied to the internal combustion engine; and a basic supply ratio specification set by at least the basic supply ratio setting means An actual supply ratio determining means for determining a supply ratio of the two kinds of fuels actually supplied to the internal combustion engine based on a parameter and an output of the separated fuel remaining amount detecting means;
The basic fuel supply ratio setting means increases the ratio of the first fuel content ratio to the second fuel content ratio in the mixed fuel in the main tank indicated by the output of the mixed fuel ratio detection means. The basic supply ratio defining parameter is set so that the basic supply ratio of the second fuel is increased and the basic supply ratio of the second fuel is decreased.
The actual supply ratio determining means is defined by the basic supply ratio defining parameter in a state where at least the remaining amounts of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means are within a predetermined range. Preferably, the basic supply ratio of each of the two types of fuel is determined as the supply ratio of the two types of fuel that is actually supplied to the internal combustion engine (second invention).

  According to the second aspect of the present invention, at least in the state where the respective remaining amounts of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means are within a predetermined range, the basic supply ratio defining parameter is used. The basic supply ratio of each of the two types of fuel is determined as the supply ratio of the two types of fuel that is actually supplied to the internal combustion engine. The basic supply ratio defining parameter is set as described above. Therefore, in the above state, as in the second invention, the larger the ratio of the first fuel content ratio to the second fuel content ratio in the mixed fuel in the main tank, the larger the first fuel to the internal combustion engine. The supply ratios of the two types of fuel that are actually supplied to the internal combustion engine are determined so as to increase the supply ratio of the second fuel and decrease the supply ratio of the second fuel. Therefore, in the above state, the ratio of the actual supply ratio of the first fuel to the internal combustion engine and the supply ratio of the second fuel is determined so that the amount of the first fuel that can be generated separately from the mixed fuel and the second fuel Large deviation from the ratio with the amount of fuel can be suppressed as much as possible. Therefore, the remaining amount of each of the two types of fuel in the separated fuel tank is easily maintained within the predetermined range as an appropriate range, and a situation occurs that deviates from the predetermined range at an early stage. Can be prevented.

  In the second aspect of the invention, the actual supply ratio determining means further includes a lower limit value of the predetermined range in which the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means corresponds to the first fuel. And the remaining amount of the second fuel is larger than the upper limit value of the predetermined range corresponding to the second fuel, the supply ratio of the first fuel actually supplied to the internal combustion engine is Preferably, the supply ratio is determined to be smaller than the basic supply ratio corresponding to one fuel and the supply ratio of the second fuel is determined to be larger than the basic supply ratio corresponding to the second fuel (first 3 invention).

  In the third aspect of the invention, the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means is smaller than the lower limit value of the predetermined range corresponding to the first fuel, and the remaining amount of the second fuel. When the amount is larger than the upper limit value of the predetermined range corresponding to the second fuel, the remaining amount of the first fuel in the separated fuel storage tank is short and the remaining amount of the second fuel is the first. This corresponds to a state in which the remaining amount of fuel is excessive. In this state, since the actual supply ratio of each of the two types of fuel to the internal combustion engine is determined as described above, consumption of the first fuel in the separated fuel storage tank accompanying the operation of the internal combustion engine is suppressed. , Promoting the consumption of the second fuel, preventing the remaining amount of the first fuel in the separated fuel storage tank from further decreasing, and the remaining amount of the second fuel relative to the remaining amount of the first fuel It is possible to prevent further increase. As a result, the remaining amount of each type of fuel in the separation storage tank can be returned to an appropriate predetermined range.

  In the second or third aspect of the invention, the actual supply ratio determining means is a predetermined amount in which at least the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means is not less than the upper limit value of the predetermined range. In the state where the remaining amount of the second fuel is smaller than the lower limit value of the predetermined range, the supply ratio of the first fuel actually supplied to the internal combustion engine is determined as the mixed fuel ratio detection means. And determining the larger one of the content ratio of the first fuel in the mixed fuel in the main tank indicated by the output and the basic supply ratio corresponding to the first fuel, and the internal combustion engine It is preferable to determine the supply ratio of the remaining fuel obtained by subtracting the first fuel from the entire fuel to be supplied as the supply ratio of the second fuel (fourth invention).

  In the fourth aspect of the invention, the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means is larger than a predetermined value equal to or higher than the upper limit value of the predetermined range, and the remaining amount of the second fuel is In a state smaller than the lower limit of the predetermined range, the remaining amount of the first fuel in the separated fuel storage tank is excessive compared to the remaining amount of the second fuel, and the remaining amount of the second fuel is insufficient. Corresponds to a state of slightness. In this state, since the actual supply ratios of the two types of fuel to the internal combustion engine are determined as described above, the consumption of the first fuel in the separated fuel storage tank accompanying the operation of the internal combustion engine is promoted. , Suppressing consumption of the second fuel, preventing the remaining amount of the first fuel in the separated fuel storage tank from further increasing relative to the remaining amount of the second fuel, and remaining amount of the second fuel Can be further prevented from decreasing. As a result, the remaining amount of each type of fuel in the separation storage tank can be returned to an appropriate predetermined range.

  In the second aspect of the invention, at least in the state where the remaining amounts of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means are within the predetermined range, the output of the mixed fuel ratio detecting means is used. When the content ratio of the high octane fuel having a higher octane number is less than or equal to a predetermined value among the content ratio of the first fuel and the content ratio of the second fuel shown, the operating state of the internal combustion engine is predetermined The ignition timing of the fuel supplied to the internal combustion engine is set to a retarded ignition timing than when the high octane number side fuel content is equal to or lower than a predetermined value when the engine is operating in a high load region. It is preferable to provide an ignition timing control means for controlling (the fifth invention).

  That is, in the second aspect of the invention, the lower the content ratio of the high-octane fuel with a higher octane number, the lower the content ratio of the first fuel and the second fuel content indicated by the output of the mixed fuel ratio detection means. As the content ratio of the low-octane fuel having a lower octane number is higher, the supply ratio of the high-octane fuel to the internal combustion engine is reduced and the supply ratio of the low-octane fuel is increased. For this reason, when the content ratio of the high octane fuel in the mixed fuel is relatively small, knocking of the internal combustion engine is likely to occur particularly in an operation state where the required load of the internal combustion engine is relatively high. Therefore, in the second invention, the ignition timing control means is provided. Thereby, the occurrence of knocking of the internal combustion engine can be prevented.

  In the third aspect of the invention, when the first fuel is a high-octane fuel having a higher octane number than that of the second fuel, at least the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means. In a state where the amount is smaller than the lower limit value of the predetermined range corresponding to the first fuel and the remaining amount of the second fuel is larger than the upper limit value of the predetermined range corresponding to the second fuel, the internal combustion engine Ignition timing control means for controlling the ignition timing of the fuel to be supplied to an ignition timing that is retarded from the ignition timing in a state where the respective remaining amounts of the two types of fuel are within the predetermined range. Preferred (sixth invention).

  That is, in the third aspect of the invention, at least the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means is smaller than the lower limit value of the predetermined range corresponding to the first fuel, and the second In a state where the remaining amount of fuel is larger than the upper limit value of the predetermined range corresponding to the second fuel, the supply ratio of the first fuel is a state in which the remaining amounts of the two types of fuel are within the predetermined range. It becomes smaller than the supply ratio of the first fuel at. For this reason, when the first fuel is a high-octane fuel, knocking of the internal combustion engine is likely to occur. Therefore, in the sixth invention, the ignition timing control means is provided. Thereby, the occurrence of knocking of the internal combustion engine can be prevented.

  The fifth invention may be combined with the third invention or the fourth invention. The sixth invention may be combined with the fourth invention or the fifth invention.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a diagram schematically showing an overall configuration of a fuel supply system for an internal combustion engine according to the present embodiment. Referring to the figure, a fuel supply system 1 of the present embodiment includes a main tank 2 that contains a mixed fuel obtained by mixing a first fuel and a second fuel, which are two types of fuels having different octane numbers, and a mixture thereof. A separation tank 3 that contains the first fuel and the second fuel constituting the fuel in a vertically separated state, and supplies two types of fuel to the internal combustion engine 4 separately from the separation tank 3. The main tank 2 and the separation tank 3 correspond to the mixed fuel storage tank and the separation fuel storage tank in the present invention, respectively.

  In the present embodiment, the first fuel and the second fuel constituting the mixed fuel are, for example, ethanol and gasoline, respectively. Therefore, the first fuel is a high octane fuel and the second fuel is a low octane fuel. Further, in the present embodiment, the internal combustion engine 4 is a spark ignition type internal combustion engine having a plurality of cylinders (not shown) (for example, four cylinders), and each cylinder is used for the first fuel (for gasoline). A fuel injection valve 5 and a fuel injection valve 6 for second fuel (for ethanol) are provided. FIG. 1 representatively shows fuel injection valves 5 and 6 for one cylinder. In the present embodiment, these fuel injection valves 5 and 6 are fuel injection valves that perform fuel injection by a port injection method.

  The internal combustion engine 4 may be a compression ignition type (self-ignition type) internal combustion engine. The internal combustion engine 4 may be a single cylinder internal combustion engine. Further, the fuel injection method of the two types of fuel for each cylinder of the internal combustion engine 4 is not limited to the port injection method, and the fuel injection method of any one type of fuel may be the in-cylinder injection method.

  The main tank 2 is provided with a feed pump 7 for stirring and pressurizing a mixed liquid obtained by mixing water with the mixed fuel in the main tank 2 and supplying the mixed liquid to the separation tank 3. In this case, the suction port of the feed pump 7 is communicated with the mixed fuel liquid in the main tank 2 and a water tank 8 provided separately from the main tank 2 and the separation tank 3 as a tank for storing water. It is connected via a water supply path 9. Further, the discharge port of the feed pump 7 is connected to the lower part of the separation tank 3 via the mixed fuel supply path 10. The feed pump 7 sucks and mixes the mixed fuel in the main tank 2 and the water in the water tank 8 through the suction port, and also mixes the mixture (mixed fuel and water). The mixture is agitated and pressurized to a predetermined pressure, and the agitated and pressurized mixed liquid is supplied to the separation tank 3 from the discharge port via the mixed fuel supply path 10.

  In addition, a flow control valve 11 is interposed in the water supply path 10, and the amount of water mixed with the mixed fuel can be adjusted by controlling the opening degree of the flow control valve 11. .

  The separation tank 3 is a tank that contains gasoline in the upper side of the internal space and a mixed liquid of ethanol and water (ethanol aqueous solution) in the lower side.

  Here, in this embodiment, the liquid mixture supplied to the separation tank 3 by the feed pump 7 is a mixture of gasoline and ethanol mixed with water. And ethanol of this liquid mixture is more hydrophilic than gasoline. Moreover, the specific gravity of gasoline is smaller than the specific gravity of ethanol and water. For this reason, among the liquid mixture supplied to the separation tank 3, the ethanol aqueous solution composed of ethanol and water mixed in the supply process and gasoline are naturally separated in the separation tank 3, and the separation tank 3 Gasoline and ethanol aqueous solution will accumulate on the upper side and the lower side of the internal space, respectively. In this case, the gasoline and the aqueous ethanol solution are accommodated in the separation tank 4 in a state where they are in contact with each other with the upper end surface of the aqueous ethanol solution as an interface. Thereby, the gasoline and the ethanol aqueous solution are separated and stored in the separation tank 3. In the present embodiment, the internal space of the separation tank 3 is always filled with the separated gasoline and ethanol aqueous solution, and the mixed fuel and water are mixed so that these liquids are pressurized to a predetermined pressure. Is supplied to the separation tank 3 by the feed pump 7.

  Of the internal space of the separation tank 3 that separates and accommodates the gasoline and the aqueous ethanol solution in this way, the space on the upper side in which the gasoline is accumulated passes through the gasoline supply path 12 led out from the upper portion of the separation tank 3. The fuel injection valve 5 is connected. As a result, the pressurized gasoline in the separation tank 3 is supplied to the fuel injection valve 5 through the gasoline supply path 12. Then, by opening the fuel injection valve 5, pressurized gasoline is injected from the fuel injection valve 5 and supplied to the cylinders of the internal combustion engine 4.

  In addition, the space on the lower side where the aqueous ethanol solution is stored in the internal space of the separation tank 3 is connected to the fuel injection valve 6 for ethanol via an ethanol supply path 13 led out from the lower portion of the separation tank 3. Yes. As a result, the pressurized aqueous ethanol solution in the separation tank 3 is supplied to the fuel injection valve 6 via the ethanol supply path 13. Then, by opening the fuel injection valve 6, a pressurized ethanol aqueous solution is injected from the fuel injection valve 6 and supplied to the cylinder of the internal combustion engine 4.

  The fuel supply system 1 of the present embodiment has the above-described configuration, a ratio sensor 14 that generates an output corresponding to the content ratio of gasoline and ethanol in the mixed fuel in the main tank 2, and ethanol in the separation tank 3. A float sensor 15 for generating an output corresponding to the height of the interface between the aqueous solution and gasoline, an ethanol concentration sensor 16 for detecting the ethanol concentration in the aqueous ethanol solution supplied to the fuel injection valve 6 for ethanol, and the fuel injection A control unit 17 (hereinafter referred to as ECU 17) that controls the operation of the valves 5 and 6 and the ignition device (not shown) of the internal combustion engine 4 is provided. The ratio sensor 14 corresponds to the mixed fuel ratio detection means in the present invention, and the float sensor 15 corresponds to the separated fuel remaining amount detection means in the present invention.

  The ratio sensor 14 is disposed in the main tank 2, and is constituted by, for example, a concentration sensor that detects the content ratio (concentration) of ethanol in the mixed fuel in the main tank 2. In this case, when the ethanol content in the mixed fuel indicated by the output of the ratio sensor 8 is Et_r [%], the gasoline content is 100−Et_r [%]. Accordingly, the ratio sensor 8 generates an output corresponding to the content ratios of ethanol and gasoline in the mixed fuel in the main tank 2. Hereinafter, the ethanol content ratio Et_r [%] in the mixed fuel indicated by the output of the ratio sensor 8 is referred to as a mixed fuel ethanol ratio Et_r, and the gasoline content ratio is referred to as a mixed fuel gasoline ratio Ga_r (= 100−Et_r [%]). Further, a set of the mixed fuel ethanol content ratio Et_r and the mixed fuel gasoline content ratio Ga_r may be collectively referred to as a mixed fuel mixing ratio.

  In addition, the ratio sensor 8 may be configured by a concentration sensor that detects the content ratio (concentration) of gasoline in the mixed fuel.

  The float sensor 15 is fitted to a guide rod 18 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 18. The float sensor 15 has a specific gravity greater than the specific gravity of gasoline and smaller than the specific gravity of the aqueous ethanol solution. For this reason, the float sensor 15 floats at the position of the interface between gasoline and an aqueous ethanol solution, and moves up and down as the interface moves up and down. The float sensor 15 generates an output corresponding to the relative position in the vertical direction with respect to the guide rod 18. Therefore, the output of the float sensor 15 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 is not only 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. In the present embodiment, the remaining amount of gasoline + the remaining amount of ethanol aqueous solution = the volume of the internal space of the separation tank 3 (constant). The higher the interface height H_FL, the lower the remaining amount of gasoline, and at the same time, The remaining amount (and hence the remaining amount of ethanol) increases.

  In this embodiment, the ethanol concentration sensor 16 is attached to the ethanol supply path 16 and generates an output corresponding to the concentration of ethanol in the aqueous ethanol solution flowing through the ethanol supply path 16. Hereinafter, the ethanol concentration indicated by the output of the ethanol concentration sensor 16 is referred to as an ethanol aqueous solution concentration EW_r. The ethanol concentration sensor 16 may be arranged at the lower part in the separation tank 3.

  The ECU 17 is an electronic circuit unit including a CPU, a RAM, and a ROM (not shown). The outputs of the sensors 14 to 16 are input to the ECU 17 and an operation state such as the rotational speed of the internal combustion engine 4 from various sensors (not shown). Detection data indicating is input. The ECU 17 executes predetermined control processing based on these input data, map data stored and held in advance, and the like, and fuel injection valves 5 and 6 for each cylinder of the internal combustion engine 4 (not shown). Controls the operation of the ignition device.

  FIG. 2 is a block diagram showing more specific control processing functions of the ECU 17. As shown in FIG. 2, the ECU 17 includes a fuel injection control unit 21 and an ignition timing control unit 22 as its main functional means.

  The fuel injection control unit 21 is an operation amount (control) that defines an injection amount of gasoline by the fuel injection valve 5 and an injection amount of ethanol aqueous solution by the fuel injection valve 6 for each combustion cycle of each cylinder of the internal combustion engine 4. The fuel injection time Ti_Ga for gasoline and the fuel injection time Ti_Et for ethanol as inputs are determined, and the operations of the fuel injection valves 5 and 6 are controlled according to the determined fuel injection times Ti_Ga and Ti_Et, respectively. The fuel injection control unit 21 corresponds to fuel supply control means in the present invention.

  Further, the ignition timing control unit 22 determines an ignition timing IG in each cylinder of the internal combustion engine 4 for each combustion cycle of each cylinder of the internal combustion engine 4 and controls an ignition device (not shown) according to the determined ignition timing IG. To do. The ignition timing control unit 22 corresponds to the ignition timing control means in the present invention.

  In addition, although illustration is abbreviate | omitted, ECU17 also has a control part which controls the flow control valve 11 of the said water supply path 9. As shown in FIG. In the present embodiment, the controller controls the flow rate according to the output of the ethanol concentration sensor 16 or the output of the ratio sensor 14 so that the ethanol concentration of the ethanol aqueous solution in the separation tank 3 is maintained at a constant concentration. The opening degree of the control valve 11 is controlled.

  Below, the detail of the control processing of the said fuel-injection control part 21 and the ignition timing control part 22 is demonstrated.

  In this embodiment, the fuel injection control unit 21 is a normal candidate value for a required value (hereinafter referred to as an ethanol supply ratio) of the ethanol supply ratio with respect to the entire fuel supplied to each cylinder of the internal combustion engine 4 for each combustion cycle. A first supply ratio determination unit 23 and a second supply ratio determination unit 24 for determining a first ethanol supply ratio Et_inj_r1 and a second ethanol supply ratio Et_inj_r2 which are auxiliary candidate values, respectively, and the first ethanol supply The selection unit 25 that selects one of the ratio Et_inj_r1 and the second ethanol supply ratio Et_inj_r2 as the actual ethanol supply ratio Et_inj_r that is the actual ethanol supply ratio to the internal combustion engine 4, and the fuel according to the actual ethanol supply ratio Et_inj_r An ethanol required injection amount determining unit 26 that determines a required injection amount Et_inj of ethanol by the injection valve 6 is provided. Further, the fuel injection control unit 21 calculates the gasoline required injection amount Ga_inj for determining the gasoline required injection amount Ga_inj by the fuel injection valve 5, and the calculation for converting the ethanol required injection amount Et_inj to the ethanol aqueous solution required injection amount EW_inj. Unit 28, and flow rate / time conversion units 29 and 30 for converting the gasoline required injection amount Ga_inj and the ethanol aqueous solution required injection amount EW_inj into the gasoline fuel injection time Ti_Ga and the ethanol fuel injection time Ti_Et, respectively.

  Then, the fuel injection control unit 21 first executes the processes of the first supply rate determination unit 23 and the second supply rate determination unit 24.

  In this case, the first supply ratio determination unit 23 is an ethanol that is a basic value of the first ethanol supply ratio Et_inj_r1 according to the operating state of the internal combustion engine 4 and the mixing ratio of the mixed fuel in the main tank 2. The basic supply ratio Et_inj_rb is determined, and the ethanol basic supply ratio Et_inj_rb is corrected according to the interface height H_FL in the separation tank 3 to determine the first ethanol supply supply ratio Et_inj_r1. Since the fuel supplied to the internal combustion engine 4 is two types of fuel, ethanol and gasoline, the ethanol supply ratio and gasoline supply ratio to the entire fuel supplied to each cylinder of the internal combustion engine 4 for each combustion cycle are as follows. If any one of the supply ratios is X [%], the other supply ratio is 100-X [%] (the other supply ratio is uniquely determined from one supply ratio). For this reason, if the ethanol basic supply ratio Et_inj_rb is determined, the basic value of the gasoline supply ratio (hereinafter referred to as the gasoline basic supply ratio Ga_inj_rb) will be defined as a result. In the present embodiment, the ethanol basic supply rate Et_inj_rb corresponds to the basic supply rate defining parameter in the present invention.

  In order to perform the process of determining the first ethanol supply ratio Et_inj_r1 as described above, the first supply ratio determination unit 23 uses the rotational speed NE (internal combustion engine 4) as an index indicating the operating state of the internal combustion engine 4. The detected value of the rotational speed of the output shaft of the engine 4 and the target IMEP that is the target value of the indicated mean effective pressure (IMEP) of each cylinder of the internal combustion engine 4 are input, and as the output of the ratio sensor 14 The detected value of the mixed fuel ethanol ratio Et_r and the detected value of the interface height H_FL as the output of the float sensor 15 are input. The target IMEP has a meaning as an index representing the required load of the internal combustion engine 4. The target IMEP is set according to, for example, the accelerator operation amount (depression amount) or the vehicle speed of a vehicle equipped with the internal combustion engine 4 as a propulsive force generation source.

  Then, the first supply ratio determination unit 23 determines the ethanol basic supply ratio Et_inj_rb, the ethanol basic supply ratio determination unit 23a, and the k_R1 determination that determines the first correction coefficient k_R1 for correcting the ethanol basic supply ratio Et_inj_rb. Unit 23b, and a correction calculation unit 23c that corrects the ethanol basic supply ratio Et_inj_rb with the first correction coefficient k_R1. The ethanol basic supply ratio determining unit 23a corresponds to the basic supply ratio setting means in the present invention.

  In this case, the detected value of the rotational speed NE of the internal combustion engine 1 and the target IMEP are input to the ethanol basic supply ratio determination unit 23a, and the mixed fuel ethanol ratio Et_r (detected value) indicated by the output of the ratio sensor 14 Is entered. Then, the ethanol basic supply ratio determination unit 23a determines the ethanol basic supply ratio from the values of these input items based on a predetermined map (NE, target IMEP, and map that defines the relationship between Et_r and Et_inj_rb). Determine Et_inj_rb. 3A, 3B, and 3C are graphs illustrating the maps.

  In the present embodiment, the mixed fuel ethanol ratio Et_r is classified into three types of “small”, “medium”, and “large”, and the number of rotations for each mixed fuel ethanol ratio Et_r of each type of size. A map that defines the relationship between NE, target IMEP, and ethanol basic supply ratio Et_inj_rb is prepared. In this case, Et_r [%] is Et_r <Et_r (1) with respect to the first predetermined value Et_r (1) and the second predetermined value Et_r (2) (Et_r (2)> Et_r (1)) determined in advance. If Et_r is “small”, Et_r (1) ≦ Et_r ≦ Et_r (2), Et_r is “medium”, and Et_r> Et_r (2) Is “Large”.

  The maps illustrated in FIGS. 3A, 3 </ b> B, and 3 </ b> C are maps corresponding to the cases where the mixed fuel ethanol ratio Et_r is “small”, “medium”, and “large”, respectively. In each map, basically, the NE and the target IMEP are set such that the ethanol basic supply ratio Et_inj_rb increases as the rotational speed NE of the internal combustion engine 1 decreases or as the target IMEP increases (the required load increases). And Et_inj_rb are set.

  In the map of FIG. 3B corresponding to the case where the mixed fuel ethanol ratio Et_r is “medium”, even if the ignition timing is set to a so-called MBT (MBT: Minimum Advance for Best Torque), the internal combustion engine 4 The relationship between NE and target IMEP and Et_inj_rb is set so that the occurrence of knocking can be suitably suppressed.

  In the map of FIG. 3A corresponding to the case where the mixed fuel ethanol ratio Et_r is “small”, when the NE and the target IMEP are constant, the mixed fuel ethanol ratio Et_r is “medium”. On the other hand, the ethanol basic supply ratio Et_inj_rb is reduced (the gasoline basic supply ratio Ga_inj_rb is increased), so that the consumption of ethanol accompanying the operation of the internal combustion engine 4 is suppressed and the consumption of gasoline is promoted. The relationship between the NE, the target IMEP, and Et_inj_rb is set. Further, in the map of FIG. 3C corresponding to the case where the mixed fuel ethanol ratio Et_r is “large”, when the NE and the target IMEP are constant, the mixed fuel ethanol ratio Et_r is “medium”. In contrast, the ethanol basic supply ratio Et_inj_rb is increased (the gasoline basic supply ratio Ga_inj_rb is decreased), the consumption of ethanol accompanying the operation of the internal combustion engine 4 is promoted, and the consumption of gasoline is suppressed. The relationship between NE and target IMEP and Et_inj_rb is set.

  Therefore, when the NE and the target IMEP are kept constant, the larger the mixed fuel ethanol ratio Et_r (the smaller the mixed fuel gasoline ratio Ga_r), in other words, the mixed fuel ethanol content ratio relative to the mixed fuel gasoline content ratio Ga_r. As the ratio (Et_r / Ga_r) increases, the ethanol basic supply ratio Et_inj_rb is determined such that the ethanol basic supply ratio Et_inj_rb increases and the gasoline basic supply ratio decreases.

  In the present embodiment, the ethanol basic supply ratio Et_inj_rb is changed in three stages with respect to the mixed fuel ethanol ratio Et_r, but it may be changed continuously. In that case, for example, the size of the mixed fuel ethanol ratio Et_r is classified in finer increments, and a map as shown in FIG. 3 is prepared for each value of Et_r, and the rotational speed NE is set. The ethanol basic supply ratio Et_inj_rb may be determined from the detected value, the target IMEP, and the mixed fuel ethanol ratio Et_r by the map and the interpolation calculation.

  Further, instead of the ethanol basic supply ratio Et_in_rb, the gasoline basic supply ratio Ga_inj_rb may be determined as the basic supply ratio defining parameter.

  In addition, among the input items to the ethanol basic supply ratio determining unit 23a, the mixed fuel gasoline ratio Ga_r (= 100−Et_r [%]) is used instead of the mixed fuel ethanol ratio Et_r, or the ratio thereof is changed. A value (Ga_r / Et_r or Et_r / Ga_r) may be used.

  Of the input items to the ethanol basic supply ratio determination unit 23a, the items related to the operating state of the internal combustion engine 4 are used as an index representing the required load of the internal combustion engine 4 instead of the target IMEP. (Required value of output torque), detected value of intake pipe internal pressure, and detected value of intake flow rate may be used. Furthermore, in addition to the index indicating the required load and the rotational speed NE, the engine temperature (cooling water temperature) of the internal combustion engine 4 may be added to the input item as an index indicating the operating state of the internal combustion engine 4.

  The interface height H_FL (detection value) indicated by the output of the float sensor 15 is input to the k_R1 determination unit 23b. Then, the k_R1 determination unit 23b determines the first correction coefficient k_R1 from the interface height H_FL based on a predetermined data table (a data table indicating the relationship between H_FL and k_R1). The first correction coefficient k_R1 is a correction coefficient to be multiplied by the ethanol basic supply ratio Et_inj_rb, and 0 ≦ k_R1 ≦ 1. FIG. 4 is a graph illustrating a data table for determining the first correction coefficient k_R1. This data table represents a membership function that associates the degree of the remaining amount of the aqueous ethanol solution in the separation tank 3 corresponding to the interface height H_FL with the value of the first correction coefficient k_R1 (0 ≦ k_R1 ≦ 1). .

  Here, in the present embodiment, a suitable predetermined range [H_FL (1), H_FL (2)] of the interface height H_FL in the separation tank 3, that is, the predetermined values H_FL (1) and H_FL (2) (> H_FL (1)) is defined in advance as a lower limit value and an upper limit value, respectively. This range is a range in which neither the remaining amount of the ethanol aqueous solution nor the remaining amount of gasoline in the separation tank 3 causes excess or deficiency, for example, near the center in the vertical direction of the internal space of the separation tank 3. Set to range. In the data table of FIG. 4, k_R1 is set to “1” when the detected value of the interface height H_FL is equal to or greater than the lower limit value H_FL (1). When the detected value of the interface height H_FL is smaller than the lower limit value H_FL (1) (when the remaining amount of the ethanol aqueous solution in the separation tank 3 is insufficient), k_R2 is a value smaller than “1”. Set to In this case, k_R1 is set such that k_R1 approaches “0” as the detected value of H_FL approaches a predetermined value H_FL (min) that is smaller than the lower limit value H_FL (1). Further, when the detected value of H_FL becomes equal to or smaller than a predetermined value H_FL (min), k_R1 is set to “0”.

  Thereafter, when the interface height H_FL is the above lower limit value H_FL (1), the remaining amount of ethanol aqueous solution and the remaining amount of gasoline in the separation tank 3 are set as Q_Et (1) and Q_Ga (1), respectively. When H_FL is the above upper limit value H_FL (2), the remaining amount of the ethanol aqueous solution and the remaining gasoline amount in the separation tank 3 are Q_Et (2) (> Q_Et (1)), Q_Ga (2) (<Q_Ga (1 ))far. In this case, the range [Q_Et (1), Q_Et (2)] where Q_Et (1) and Q_Et (2) are the lower limit value and the upper limit value, respectively, is a suitable range for the remaining amount of ethanol aqueous solution in the separation tank 3 means. Similarly, the ranges [Q_Ga (2), Q_Ga (1)] where Q_Ga (2) and Q_Ga (1) are the lower limit and upper limit respectively mean a suitable range of the remaining amount of gasoline in the separation tank 3 To do. Then, the first correction coefficient k_R1 set by the data table of FIG. 4 indicates that the remaining amount of the ethanol aqueous solution is not less than the lower limit value Q_Et (1) in terms of the correspondence between the remaining amount of the ethanol aqueous solution and the remaining amount of gasoline. And when the remaining amount of gasoline is less than or equal to the upper limit value Q_Ga (1) (including the case where the remaining amount of ethanol aqueous solution and the remaining amount of gasoline are in the above preferred ranges), set so that k_R1 = 1 Will be. The first correction coefficient k_R1 is set so that k_R1 <1 when the remaining amount of the ethanol aqueous solution is smaller than the lower limit value Q_Et (1) and the remaining amount of gasoline is larger than the upper limit value Q_Ga (1). Will be. The ranges [Q_Et (1), Q_Et (2)], [Q_Ga (2), Q_Ga (1)] correspond to the predetermined ranges in the second to ninth inventions, respectively.

  The ethanol basic supply ratio Et_inj_rb and the first correction coefficient k_R1 determined as described above are input to the correction calculation unit 23c. Then, the correction calculation unit 23c determines the first ethanol supply rate Et_inj_r1 by multiplying the ethanol basic supply rate Et_inj_rb by the first correction coefficient k_R1. In this case, since 0 ≦ k_R1 ≦ 1, the first ethanol supply rate Et_inj_r1 is determined to be equal to or smaller than the ethanol basic supply rate Et_inj_rb.

  When the interface height H_FL in the separation tank 3 is equal to or higher than the lower limit value H_FL (1) by the processing of the first supply ratio determination unit 23 described above (the remaining amount of ethanol aqueous solution in the separation tank 3 and gasoline) In this case, the remaining amount of each is in the preferable range [Q_Et (1), Q_Et (2)], [Q_Ga (2), Q_Ga (1)]), and k_R1 = 1, so the ethanol basic supply ratio Et_inj_rb Is determined as the first ethanol supply ratio Et_inj_r1 as it is. In this case, the first ethanol supply ratio Et_inj_r1 depends on the operating state of the internal combustion engine 4 (NE and target IMEP) and the mixed fuel ethanol ratio Et_R (mixed fuel mixture ratio in the main tank 2). Will be determined. When the interface height H_FL in the separation tank 3 is smaller than the lower limit value H_FL (1), in other words, the remaining amount of the ethanol aqueous solution in the separation tank 3 is smaller than the lower limit value Q_Et (1) and gasoline. When the remaining amount of the fuel is larger than the upper limit value Q_Ga (1), k_R1 <1, so the first ethanol supply ratio Et_inj_r1 suppresses the consumption of ethanol in the separation tank 3 accompanying the operation of the internal combustion engine 4. On the other hand, the ratio is determined to be smaller than the basic ethanol supply ratio Et_inj_rb so as to promote consumption of gasoline.

  The second supply ratio determination unit 24 sets the mixed fuel ethanol ratio Et_r (detected value) indicated by the output of the ratio sensor 14 as a basic value of the second ethanol supply ratio Et_inj_r2, and uses this basic value Et_r in the separation tank 3. The second ethanol supply ratio Et_inj_r2 is determined by correcting according to the interface height H_FL.

  In order to perform this process, the mixed fuel ethanol ratio Et_r (detected value) and the detected value of the interface height H_FL are input to the second supply ratio determining unit 24.

  The second supply ratio determining unit 24 includes a k_R2 determining unit 24a that determines a second correction coefficient k_R2 for correcting the mixed fuel ethanol ratio Et_r as a basic value of the second ethanol supply ratio Et_inj_r2. A correction calculation unit 24b that corrects the mixed fuel ethanol ratio Et_r (detection value) with the correction coefficient k_R2.

  In this case, the interface height H_FL (detection value) is input to the k_R2 determination unit 24a. Then, the k_R2 determination unit 24a determines the second correction coefficient k_R2 based on a predetermined data table (a data table indicating the relationship between H_FL and k_R2) from the detected value of the interface height H_FL. The second correction coefficient k_R2 is a correction coefficient by which the mixed fuel ethanol ratio Et_r is multiplied, and 0 ≦ k_R2 ≦ 1. FIG. 5 is a graph illustrating a data table for determining the second correction coefficient k_R2. Similar to the data table of FIG. 4, this data table sets the degree of the remaining amount of the ethanol aqueous solution in the separation tank 3 indicated by the detected value of the interface height H_FL to the value of the second correction coefficient k_R2. Represents an associated membership function.

  In the data table of FIG. 5, when the detected value of the interface height H_FL is equal to or less than the upper limit value H_FL (2), k_R2 is set to “0”. When the detected value of the interface height H_FL is larger than the upper limit value H_FL (2) (when the remaining amount of the ethanol aqueous solution in the separation tank 3 is excessive compared to the remaining amount of gasoline), k_R2 Is set to a value larger than “0”. In this case, k_R2 is set such that k_R2 approaches “1” as the detected value of H_FL approaches a predetermined value H_FL (max) that is greater than the upper limit value H_FL (2). Further, when the detected value of H_FL becomes equal to or greater than a predetermined value H_FL (max), k_R2 is set to “1”.

  The second correction coefficient k_R2 determined as described above and the mixed fuel ethanol ratio Et_r (detected value) are input to the correction calculation unit 24b. Then, the correction calculation unit 24b determines the second ethanol supply ratio Et_inj_r2 by multiplying the detected value of the mixed fuel ethanol ratio Et_r by the second correction coefficient k_R2. In this case, since 0 ≦ k_R2 ≦ 1, the second ethanol supply ratio Et_inj_r2 is determined with the detected value of the mixed fuel ethanol ratio Et_r as the upper limit value.

  When the interface height H_FL in the separation tank 3 is equal to or less than the upper limit value H_FL (2) by the processing of the second supply ratio determination unit 24 described above (the remaining amount of ethanol aqueous solution in the separation tank 3 and gasoline) The remaining correction amount is in a suitable range [Q_Et (1), Q_Et (2)], [Q_Ga (2), Q_Ga (1)]), and the second correction coefficient k_R2 = 0. The 2-ethanol supply ratio Et_inj_r2 is set to “0”. When the interface height H_FL in the separation tank 3 is larger than the upper limit value H_FL (2), in other words, the remaining amount of the ethanol aqueous solution in the separation tank 3 is larger than the upper limit value Q_Et (2). When the remaining amount of gasoline is smaller than the lower limit value Q_Ga (2), k_R2> 0, so the second ethanol supply ratio Et_inj_r2 is the consumption of ethanol in the separation tank 3 accompanying the operation of the internal combustion engine 4 In order to suppress the consumption of gasoline while promoting, it is brought close to the same ratio as the detected value of the mixed fuel ethanol ratio Et_r. In this case, the remaining amount of the aqueous ethanol solution in the separation tank 3 becomes equal to or larger than the remaining amount corresponding to the predetermined value H_FL (max) of the interface height H_FL, and the remaining amount of gasoline becomes the predetermined value H_FL. When the remaining amount is equal to or less than the remaining amount corresponding to (max), the second ethanol supply ratio Et_inj_r2 is determined to be the same ratio as the detected value of the mixed fuel ethanol ratio Et_r.

  Supplementally, in the present embodiment, the detection value of the interface height H_FL is used to determine the first correction coefficient k_R1 and the second correction coefficient k_R2, but instead of this, the ethanol aqueous solution in the separation tank 3 is used. The detection value of the remaining amount or the detection value of the remaining amount of gasoline may be used, or the ratio of these remaining amounts may be used.

  In the present embodiment, when the detected value of the interface height H_FL is a value between the upper limit value H_FL (2) and a predetermined value H_FL (max) larger than this, the second correction coefficient k_R2 is set to “0”. However, when the detected value of H_FL is equal to or higher than the upper limit value H_FL (2), k_R2 may be set to “1”.

  The fuel injection control unit 21 executes the processes of the first supply ratio determination unit 24 and the second supply ratio determination unit 25 described above, and then performs the process of the selection unit 25 and the process of the ethanol required injection amount determination unit 26. Are executed sequentially.

  The selection unit 25 receives the first ethanol supply rate Et_inj_r1 and the second ethanol supply rate Et_inj_r2 determined by the processes of the first supply rate determination unit 24 and the second supply rate determination unit 25, respectively. The selection unit 25 selects the larger one of the first ethanol supply rate Et_inj_r1 and the second ethanol supply rate Et_inj_r2 as the actual ethanol supply rate Et_inj_r. That is, Et_inj_r = max (Et_inj_r1, Et_inj_r2).

  In this case, as long as the interface height H_FL is equal to or less than the upper limit value H_FL (2), the second ethanol supply rate Et_inj_r2 is always 0, so the first ethanol supply rate Et_inj_r1 is determined as the actual ethanol supply rate Et_inj_r. .

  When the interface height H_FL is larger than the upper limit value H_FL (2), that is, when the gasoline in the separation tank 3 is insufficient, the remaining amount of the ethanol aqueous solution is excessive as compared with the remaining amount of gasoline. Furthermore, in order to suppress the consumption of gasoline while promoting the consumption of ethanol, the larger one of the first ethanol supply ratio Et_inj_r1 (= ethanol basic supply ratio Et_inj_rb) and the second ethanol supply ratio Et_inj_r2 is The ethanol supply ratio Et_inj_r is determined. Therefore, the actual ethanol supply ratio Et_inj_r is determined to be a ratio equal to or higher than the ethanol basic supply ratio Et_inj_rb. In particular, the remaining amount of the aqueous ethanol solution in the separation tank 3 becomes equal to or greater than the remaining amount corresponding to the predetermined value H_FL (max) of the interface height H_FL, and the remaining amount of gasoline is equal to the predetermined value H_FL ( When the remaining amount is equal to or less than the remaining amount corresponding to (max), the actual ethanol supply ratio Et_inj_r is determined to be the larger ratio of the detected value of the mixed fuel ethanol ratio Et_r and the ethanol basic supply ratio Et_inj_rb Will be. That is, the actual ethanol supply ratio Et_inj_r is determined to be equal to or greater than Et_r and equal to or greater than Et_inj_rb. In this case, as a result, the actual gasoline supply ratio (= 100−Et_inj_r [%]) as the gasoline supply ratio actually supplied to the internal combustion engine 4 corresponding to the actual ethanol supply ratio Et_inj_r The fuel gasoline ratio Ga_r or less is determined. Therefore, when the interface height H_FL is equal to or greater than the predetermined value H_FL (max), the actual ethanol supply ratio Et_inj_r and the corresponding actual gasoline supply ratio are the ratio of the actual ethanol supply ratio to the actual gasoline supply ratio. Is determined to be greater than or equal to the ratio of the mixed fuel ethanol ratio to the mixed fuel gasoline ratio.

  Supplementally, in the present embodiment, the k_R1 determination unit 23b, the correction calculation unit 23c, the second supply ratio determination unit 24, and the selection unit 25 implement an actual supply ratio determination unit in the present invention.

  Next, the detected value of the rotational speed NE of the internal combustion engine 4 and the target IMEP are input to the ethanol required injection amount determination unit 26 as indices representing the operating state of the internal combustion engine 4 and are determined by the selection unit 25 as described above. The actual ethanol supply ratio Et_inj_r is input. Then, the ethanol required injection amount determination unit 26 determines the ethanol required injection amount Et_inj from these input values. This process is executed as follows, for example.

  That is, the ethanol required injection amount determination unit 26 first determines the fuel to be supplied to the internal combustion engine 4 in order to realize the target IMEP from the detected value of the rotational speed NE and the target IMEP using a predetermined map (not shown). The total total calorific value is obtained as the required total calorific value, and the amount of ethanol required 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 26 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_r.

  Next, the fuel injection control unit 21 executes the processing of the gasoline required injection amount determination unit 27 and the processing of the calculation unit 28. In this case, the ethanol required injection amount Et_inj and the ethanol required total amount Inj_all calculated by the ethanol required injection amount determining unit 26 are input to the gasoline required injection amount determining unit 27.

  Then, the gasoline required injection amount determination unit 27 calculates the gasoline required injection amount Ga_inj from the input ethanol required injection amount Et_inj and the ethanol required total amount Inj_all according to the following equation (1).

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.

  Further, the ethanol required injection amount Et_inj calculated by the ethanol required injection amount determination unit 26 and the detected value of the ethanol aqueous solution concentration EW_r by the ethanol concentration sensor 16 are input to the calculation unit 28. Then, the calculation unit 28 obtains the ethanol aqueous solution required injection amount EW_inj by dividing the ethanol required injection amount Et_inj by the ethanol aqueous solution concentration EW_r.

  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 required gasoline injection amount Ga_inj is determined by multiplying the ratio Et_inj_r by the gasoline supply ratio (= 100−Et_inj_r [%]). In this case, the gasoline required injection amount Ga_inj may be determined before the ethanol required injection amount Et_inj.

  After calculating the gasoline required injection amount Ga_inj and the ethanol aqueous solution required injection amount EW_inj as described above, the fuel injection control unit 21 executes the processes of the flow rate / time conversion units 29 and 30.

  In this case, the gasoline required injection amount Ga_inj is input to the flow rate / time conversion unit 29. Then, the flow rate / time conversion unit 29 obtains the gasoline fuel injection time Ti_Ga from the input gasoline demand injection amount Ga_inj based on a predetermined data table or a predetermined arithmetic expression. Further, the ethanol aqueous solution required injection amount EW_inj is input to the flow rate / time conversion unit 30. The flow rate / time conversion unit 30 obtains the ethanol fuel injection time Ti_Et from the input ethanol aqueous solution required injection amount EW_inj based on a predetermined data table or a predetermined arithmetic expression.

  The fuel injection control unit 21 controls the operation of the fuel injection valves 5 and 6 in accordance with the gasoline fuel injection time Ti_Ga and the ethanol fuel injection time Ti_Et determined as described above. That is, the valve opening time of the fuel injection valve 5 is controlled to the gasoline fuel injection time Ti_Ga, and the valve opening time of the fuel injection valve 6 is controlled to the ethanol fuel injection time Ti_Et. In this case, the valve opening start timing of each of the fuel injection valves 5 and 6 is determined according to the operating state such as the rotational speed NE of the internal combustion engine 4 and the target IMEP.

  According to the control process of the fuel injection control unit 21, fuel injection of ethanol and gasoline is performed from the fuel injection valves 5 and 6 at a supply ratio defined by the actual ethanol supply ratio Et_inj_r.

  Next, the ignition timing control unit 22 will be described. Referring to FIG. 2, the ignition timing control unit 22 determines a basic ignition timing IG_b, which is a basic value of the ignition timing, and a basic ignition timing IG_b for correcting the basic ignition timing IG_b in the retarding direction. A retard correction amount determination unit 32 that determines the retard correction amount ΔIG, and a correction calculation unit 33 that corrects the basic ignition timing IG_b using the retard correction amount ΔIG are provided.

  The ignition timing control unit 22 first executes processing of the basic ignition timing determination unit 31 and processing of the retard correction amount determination unit 32. In this case, the basic ignition timing determination unit 31 is input with the detected value of the rotational speed NE of the internal combustion engine 4 and the target IMEP as an index representing the operating state of the internal combustion engine 4, and the ratio sensor 14 Is detected value of the mixed fuel ethanol ratio Et_r. Then, the basic ignition timing determination unit 31 determines the basic ignition timing IG_b from the values of these input items based on a predetermined map (NE, target IMEP, map that defines the relationship between Et_r and IG_b). To do. FIGS. 6A and 6B are graphs illustrating the maps.

  In the present embodiment, the relationship between the rotational speed NE, the target IMEP, and the basic ignition timing IG_b for each of the case where the mixed fuel ethanol ratio Et_r is the “small” and the case that the “medium” or “large”. A map that prescribes The map illustrated in FIG. 6A corresponds to the case where the mixed fuel ethanol ratio Et_r is “small”, and the map illustrated in FIG. 6B illustrates that the mixed fuel ethanol ratio Et_r is “medium” or This map corresponds to the case of “large”.

  In this case, the map of FIG. 6B is set so that the basic ignition timing IG_b becomes MBT for a set of arbitrary NE and target IMEP. This is because when the mixed fuel ethanol ratio Et_r is “medium” or “large”, the map shown in FIG. 3B or FIG. 3C is used in the control process of the fuel injection control unit 21. As long as the remaining amount of ethanol in the separation tank 3 is equal to or greater than the lower limit value Q_Et (1), the actual ethanol supply ratio Et_inj_r is a supply that can suppress the occurrence of knocking of the internal combustion engine 1 even when the ignition timing is set to MBT This is because the ratio is determined to be a ratio (≧ first ethanol supply ratio Et_inj_r1).

  The map in FIG. 6A shows a high load region where the target IMEP is a predetermined value or more (a high load region where the required load of the internal combustion engine 4 is a predetermined value or more), and the basic ignition timing IG_b is later than the MBT. The ignition timing is set to be on the corner side. That is, when the mixed fuel ethanol ratio Et_r is “small”, the map shown in FIG. 3A is used in the control process of the fuel injection control unit 21, so the ethanol ( Even if the remaining amount of high octane fuel is sufficiently high, the actual ethanol supply ratio Et_inj_r is set to a smaller supply ratio than when the mixed fuel ethanol ratio Et_r is “medium” or “large”. For this reason, if the ignition timing is set to MBT, knocking of the internal combustion engine 1 may occur when the operation state of the internal combustion engine 4 is the operation state in the high load region. For this purpose, the map of FIG. 6A is set as described above.

  On the other hand, the retardation correction amount determining unit 32 receives the first correction coefficient k_R1 determined by the k_R1 determining unit 23b. Then, the retardation correction amount determination unit 32 calculates a retardation correction amount ΔIG from the first correction coefficient k_R1 by the following equation (2).

ΔIG = Δb × (1-k_R1) (2)

Here, Δb on the right side of the equation (2) is an ignition timing at which the efficiency of the internal combustion engine 1 is maximized when it is assumed that the actual ethanol supply ratio Et_inj_r is determined to be equal to or greater than the ethanol basic supply ratio Et_inj_rb. When it is assumed that the basic ignition timing IG_b and the actual ethanol supply ratio Et_inj_r are determined to be “0” (assuming that ethanol is not supplied to the internal combustion engine 4 and only gasoline is supplied), It is set as a difference from the ignition timing (ignition timing retarded from IG_b) that can be avoided. Note that the latter ignition timing is obtained based on a map or the like from the detected value of the rotational speed NE and the target IMEP.

  Accordingly, the retardation correction amount ΔIG calculated by the equation (2) is set to “0” when the first correction coefficient k_R1 is “1”, and is retarded when k_R1 <1. Set to the amount of direction correction.

  The basic ignition timing IG_b determined as described above and the retardation correction amount ΔIG are input to the correction calculation unit 33. Then, the correction calculation unit 33 determines the ignition timing IG by subtracting the retardation correction amount ΔIG from the basic ignition timing IG_b.

  The ignition timing control unit 22 controls the discharge timing of an ignition device (not shown) for each cylinder of the internal combustion engine 4 according to the ignition timing IG thus determined.

  The above is the details of the control processing of the fuel injection control unit 21 and the ignition timing control unit 22 in the present embodiment.

  In this embodiment, since the control process of the fuel injection control unit 21 is executed as described above, the interface height H_FL in the separation tank 3 is between the lower limit value H_FL (1) and the upper limit value H_FL (2). In other words, the remaining amount of the aqueous ethanol solution and the remaining amount of gasoline in the separation tank 3 are suitable ranges [Q_Et (1), Q_Et (2)], [Q_Ga (2), Q_Ga (1), respectively. ], The basic ethanol supply rate Et_inj_rb determined as described above in accordance with the operating state of the internal combustion engine 4 and the mixing ratio of the mixed fuel in the main tank 2 is determined as the actual ethanol supply rate Et_inj_r. . Therefore, the frequency at which the internal combustion engine 4 is operated in a state where the ratio of the actual ethanol supply ratio Et_inj_r and the actual gasoline supply ratio Ga_inj_rb is greatly deviated from the ratio of the mixed fuel ethanol content ratio Et_r and the mixed fuel gasoline ratio Ga_r. Less. Therefore, the remaining amount of each of the aqueous ethanol solution and gasoline in the separation tank 3 is easily maintained in a suitable range, and it is possible to prevent the excess or deficiency of either one of the fuels as much as possible.

  Further, in this way, the remaining amount of the ethanol aqueous solution and the remaining amount of gasoline in the separation tank 3 are within the preferable ranges [Q_Et (1), Q_Et (2)], [Q_Ga (2), Q_Ga (1)], respectively. In the existing state, the actual ethanol supply ratio Et_inj_r (= Et_inj_rb) when the mixed fuel ethanol content ratio Et_r is “small” is the actual ethanol supply ratio Et_inj_r (where Et_r is “medium” or “large”). = Et_inj_rb), the supply ratio is smaller than that, which may cause knocking of the internal combustion engine 4. However, in this situation, the actual ignition timing IG is determined to be the basic ignition timing IG_b determined according to the map shown in FIG. 6 (a) or (b) by the control process of the ignition timing control unit 22. Is done. For this reason, when the operating state (the rotational speed NE and the target IMEP) of the internal combustion engine 4 is kept constant, the ignition timing IG determined when the mixed fuel ethanol content ratio Et_r is “small” The ignition timing is retarded from the ignition timing IG determined when the engine is “medium” or “large”. This prevents knocking of the internal combustion engine 4 when the mixed fuel ethanol content ratio Et_r is “small”.

  In addition, the interface height H_FL in the separation tank 3 becomes smaller than the lower limit value H_FL (1), the remaining amount of ethanol in the separation tank 3 becomes insufficient, and the remaining amount of gasoline becomes the remaining amount of ethanol. In contrast, the actual ethanol supply ratio Et_inj_r is determined to be smaller than the ethanol basic supply ratio Et_inj_rb (Et_inj_r × k_R1), and the actual gasoline supply ratio Et_inj_r is determined as the gasoline basic supply ratio Ga_int_rb (= 100− Et_inj_r [%]). For this reason, while suppressing the consumption of the ethanol aqueous solution in the separation tank 3 accompanying the operation of the internal combustion engine 4, the consumption of gasoline is promoted, and consequently the remaining amount of ethanol in the separation tank 3 is further reduced, or It is prevented that the remaining amount of gasoline further increases. As a result, in a situation where it is preferable to supply ethanol to the internal combustion engine 4 in order to prevent the occurrence of knocking of the internal combustion engine 4, it is possible to prevent a situation where the ethanol cannot be supplied as much as possible. Can be prevented.

  Further, in this state where the remaining amount of ethanol in the separation tank 3 becomes insufficient and the remaining amount of gasoline becomes excessive relative to the remaining amount of ethanol, the actual ethanol supply ratio Et_inj_r Since the ratio is determined to be smaller than the supply ratio Et_inj_rb, the internal combustion engine 4 may be knocked regardless of whether the mixed fuel ethanol content ratio Et_r is “small”, “medium”, or “large”. However, in this situation, since the first correction coefficient k_R1 is set to a value smaller than “1”, the actual ignition timing IG is retarded from the basic ignition timing IG_b by the equation (2). The ignition timing is determined. Thereby, occurrence of knocking of the internal combustion engine 4 can be prevented.

  In addition, the interface height H_FL in the separation tank 3 becomes larger than the upper limit value H_FL (2), the gasoline in the separation tank 3 becomes scarce, and the remaining amount of the ethanol aqueous solution is smaller than the remaining amount of gasoline. When it becomes excessive, the actual ethanol supply ratio Et_inj_r is determined to be a ratio equal to or higher than the ethanol basic supply ratio Et_inj_rb. In particular, the remaining amount of the aqueous ethanol solution in the separation tank 3 becomes equal to or greater than the remaining amount corresponding to the predetermined value H_FL (max) of the interface height H_FL, and the remaining amount of gasoline is equal to the predetermined value H_FL ( When the remaining amount is equal to or less than the remaining amount corresponding to (max), the actual ethanol supply ratio Et_inj_r is determined to be the larger ratio of the detected value of the mixed fuel ethanol ratio Et_r and the ethanol basic supply ratio Et_inj_rb Is done. For this reason, the remaining amount of gasoline can be increased while the remaining amount of the aqueous ethanol solution in the separation tank 3 is rapidly reduced by the mixed solution of ethanol, water, and gasoline supplied from the feed pump 7. As a result, in a situation where it is preferable to supply gasoline to the internal combustion engine 4 such as when the internal combustion engine 4 is operated at a low load, it is possible to prevent the occurrence of a situation where the gasoline cannot be supplied as much as possible. .

  As described above, according to the present embodiment, knocking of the internal combustion engine 4 is prevented while preventing the remaining amount of the aqueous ethanol solution in the separation tank 3 and the remaining amount of gasoline from becoming unbalanced. It is possible to drive efficiently in the obtained driving state.

  Here, FIG. 7 is a graph illustrating the relationship between the load (IMEP) and the efficiency of the internal combustion engine 4 of the present embodiment by a solid line. The broken line graph in the figure illustrates a comparative example in the case where only fuel is supplied to the internal combustion engine 4. As shown in the figure, according to the present embodiment, since ethanol is appropriately supplied to the internal combustion engine 4, knocking of the internal combustion engine 4 is prevented in the operating state of the internal combustion engine 4 in the middle load and high load regions. While preventing appropriately, the efficiency of this internal combustion engine 4 can be improved rather than the case where only gasoline is used (comparative example).

  FIGS. 8A, 8B, and 8C are graphs for explaining an example of the effect of the present embodiment. FIG. 8A shows an example of the change over time of the target IMEP (required load) and ignition timing of the internal combustion engine 4 in the present embodiment, respectively, with a solid line and a broken line graph. FIG. 8B is a graph with solid lines and broken lines, respectively, showing examples of changes over time in the ethanol injection amount of the internal combustion engine 4 (the ethanol required injection amount Et_inj) and the remaining amount of ethanol in the separation tank 3 in the present embodiment. Show. Further, FIG. 8C shows a case where the control of the supply ratio of ethanol and gasoline according to the interface height H_FL in the separation tank 3 is omitted in this embodiment (this is the first correction coefficient k_R1, (Corresponding to the case where the second correction coefficient k_R2 is forcibly maintained at “1” and “0”, respectively), an example of the change over time of the ethanol injection amount and the remaining amount of ethanol in the separation tank 3, respectively, This is shown by a broken line graph.

  When the target IMEP of the internal combustion engine 4 is changed as shown by the solid line graph in FIG. 8A, in the comparative example, the ethanol in the separation tank 3 is shown as shown by the broken line graph in FIG. The remaining amount of the battery drops to “0”. Thereafter, the ethanol injection amount becomes “0”, and ethanol cannot be supplied to the internal combustion engine 4. On the other hand, in this embodiment, when the remaining amount of ethanol in the separation tank 3 is reduced to some extent, the ethanol injection amount is reduced, and the remaining amount of ethanol is prevented from being reduced to “0”. . Further, in this embodiment, when the ethanol injection amount is reduced in this way, as shown in FIG. 8A, the ignition timing is controlled to the retard side even if the target IMEP is constant. The occurrence of knocking of the engine 4 is prevented.

  In the embodiment described above, the first fuel is ethanol and the second fuel is gasoline. However, the first fuel may be gasoline and the second fuel may be ethanol.

  In the embodiment, the gasoline and the ethanol aqueous solution are accommodated in the single separation tank 3. However, the gasoline and the ethanol aqueous solution may be accommodated in separate tanks after the separation. . In that case, instead of the float sensor 15, a sensor for separately detecting the remaining amount of gasoline and the remaining amount of ethanol may be provided. Further, the separation of the two types of fuel from the mixed fuel may be performed by a method other than the method shown in the present embodiment.

  Further, the two types of fuel composing the mixed fuel are not limited to the combination of ethanol and gasoline. For example, naphtha, kerosene, or a mixed fuel containing light oil may be used instead of gasoline. Moreover, you may use the mixed fuel containing alcohol, such as methanol, instead of ethanol.

1 is a diagram schematically showing an overall configuration of a fuel supply system according to an embodiment of the present invention. The block diagram which shows the control processing function of the control unit (ECU) with which the fuel supply system of FIG. 1 was equipped. FIGS. 3A, 3 </ b> B, and 3 </ b> C are graphs illustrating a map used in the process of the ethanol basic supply ratio determination unit 23 a illustrated in FIG. 2. The graph which illustrates the data table used by the process of the k_R1 determination part 23b shown in FIG. The graph which illustrates the data table used by the process of the k_R2 determination part 24a shown in FIG. 6A and 6B are graphs illustrating a map used in the processing of the basic ignition timing determination unit 31 shown in FIG. The graph for demonstrating the effect of embodiment. 8A, 8B, and 8C are graphs for explaining the effects of the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel supply system, 2 ... Main tank (mixed fuel storage tank), 3 ... Separation tank (separate fuel storage tank), 4 ... Internal combustion engine, 5, 6 ... Fuel injection valve, 14 ... Ratio sensor (mixed fuel ratio detection) Means), 15 ... float sensor (separated fuel remaining amount detecting means), 17 ... control device, 21 ... fuel injection control section (fuel supply control means), 22 ... ignition timing control section (ignition timing control means), 23a ... ethanol Basic supply ratio determination unit (basic supply ratio setting means), 23b... K_R1 determination section (actual supply ratio determination means), 23c... Correction calculation section (actual supply ratio determination means), 24. Ratio determining means), 25... Selection unit (actual supply ratio determining means).

Claims (6)

A mixed fuel storage tank that stores a mixed fuel obtained by mixing a first fuel and a second fuel, which are two types of fuels having different octane numbers, and the two types of fuel separated from the mixed fuel in the mixed fuel storage tank A fuel supply system for supplying the two types of fuel to the internal combustion engine from the separated fuel storage tank,
A mixed fuel ratio detection means for generating an output corresponding to the content ratio of each of the two types of fuel in the mixed fuel in the mixed fuel storage tank;
A separated fuel remaining amount detecting means for generating an output corresponding to the remaining amount of each of the two types of fuel in the separated fuel storage tank;
The internal combustion engine so that the supply ratio of each of the two types of fuel to the whole fuel supplied to the internal combustion engine is changed according to the output of the mixed fuel ratio detection means and the output of the separated fuel remaining amount detection means. A fuel supply system comprising fuel supply control means for controlling the respective supply amounts of the two types of fuels. 2. The fuel supply system according to claim 1, wherein the fuel supply control means is responsive to an operating state of the internal combustion engine including at least a required load and a rotational speed of the internal combustion engine and an output of the mixed fuel ratio detection means. A basic supply ratio setting means for setting a basic supply ratio specifying parameter for specifying the basic supply ratio of each of the two types of fuel supplied to the engine, and at least a basic supply ratio specifying parameter set by the basic supply ratio setting means; An actual supply ratio determining means for determining a supply ratio of the two kinds of fuels actually supplied to the internal combustion engine based on the output of the separated fuel remaining amount detecting means;
The basic fuel supply ratio setting means increases the ratio of the first fuel content ratio to the second fuel content ratio in the mixed fuel in the main tank indicated by the output of the mixed fuel ratio detection means. The basic supply ratio defining parameter is set so that the basic supply ratio of the second fuel is increased and the basic supply ratio of the second fuel is decreased.
The actual supply ratio determining means is defined by the basic supply ratio defining parameter in a state where at least the remaining amounts of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means are within a predetermined range. A fuel supply system, wherein basic supply ratios of the two kinds of fuels are determined as supply ratios of the two kinds of fuels that are actually supplied to the internal combustion engine.   3. The fuel supply system according to claim 2, wherein the actual supply ratio determining means is configured so that at least the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means is within the predetermined range corresponding to the first fuel. In a state where the remaining amount of the second fuel is smaller than the lower limit value and larger than the upper limit value of the predetermined range corresponding to the second fuel, the supply ratio of the first fuel actually supplied to the internal combustion engine is The supply ratio is determined to be smaller than the basic supply ratio corresponding to the first fuel, and the supply ratio of the second fuel is determined to be higher than the basic supply ratio corresponding to the second fuel. And fuel supply system.   4. The fuel supply system according to claim 2, wherein the actual supply ratio determining means is a predetermined amount in which at least the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means is not less than an upper limit value of the predetermined range. In the state where the remaining amount of the second fuel is smaller than the lower limit value of the predetermined range, the supply ratio of the first fuel actually supplied to the internal combustion engine is determined as the mixed fuel ratio detection means. And determining the larger one of the content ratio of the first fuel in the mixed fuel in the main tank indicated by the output and the basic supply ratio corresponding to the first fuel, and the internal combustion engine A fuel supply system, wherein the supply ratio of the remaining fuel obtained by subtracting the first fuel from the entire fuel to be supplied is determined as the supply ratio of the second fuel.   3. The fuel supply system according to claim 2, wherein at least a remaining amount of each of the two types of fuel indicated by an output of the separated fuel remaining amount detecting means is within the predetermined range. Of the content ratio of the first fuel and the content ratio of the second fuel indicated by the output, when the content ratio of the high octane fuel having a higher octane number is equal to or less than a predetermined value, the operating state of the internal combustion engine is The ignition timing of the fuel to be supplied to the internal combustion engine when the operating state is in a predetermined high load region is set so that the ignition timing of the retarded side is higher than that in the case where the fuel content ratio on the high octane number side is equal to or lower than the predetermined value A fuel supply system comprising ignition timing control means for controlling the timing.   4. The fuel supply system according to claim 3, wherein the first fuel is a high-octane fuel having an octane number higher than that of the second fuel, and at least the remaining amount of the first fuel indicated by the output of the separated fuel remaining amount detecting means. Is smaller than the lower limit value of the predetermined range corresponding to the first fuel and the remaining amount of the second fuel is larger than the upper limit value of the predetermined range corresponding to the second fuel. Ignition timing control means for controlling the ignition timing of the fuel to be supplied to an ignition timing that is retarded from the ignition timing in a state where the respective remaining amounts of the two types of fuel are within the predetermined range. And fuel supply system.