JP4964183B2 - Fuel supply system for internal combustion engine - Google Patents

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. The 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, when the mixed fuel is separated into two types of fuel, each type of fuel cannot be generated separately. In an internal combustion engine mounted on a car or the like as a source for generating a propulsive force, the internal combustion engine is frequently operated in a specific operation region in accordance with the driving characteristics of the driver and the main driving environment. There are many cases. For this reason, in many cases, an operation in which the consumption of one of the two types of fuel separated from the mixed fuel is larger than the consumption of the other fuel is performed at a high frequency. In such a case, there is an imbalance between the remaining amounts of the two types of fuel separated from the mixed fuel, and only one of the fuels is insufficient early, or the remaining amount of the other fuel is separated due to the separation of the mixed fuel. Increases and the tank containing the other fuel becomes full.

  And in the technologies found in Patent Documents 1 and 2, when the remaining amount of one of the two types of fuel is insufficient, the supply ratio of the one fuel to the internal combustion engine is reduced and the other By increasing the fuel supply ratio, the balance of the remaining amount of each type of fuel is eliminated. Further, in the technique shown in Patent Document 2, when the remaining amount of one of the fuels becomes excessive, the supply ratio of the one fuel to the internal combustion engine is increased and the supply ratio of the other fuel is decreased. By doing so, the imbalance in the remaining amount of each type of fuel is resolved.

  However, in Patent Documents 1 and 2, since the unbalance in the remaining amount of each type of fuel is eliminated only by adjusting the supply ratio of each type of fuel to the internal combustion engine, the following inconveniences arise. there were. That is, in Patent Documents 1 and 2, for example, the operation of the internal combustion engine in the operation region where it is preferable to increase the supply ratio of the high octane number fuel is frequently performed, and the high octane number fuel is insufficient at an early stage. In some cases, a situation in which the supply ratio of low-octane fuel must be increased frequently occurs. Similarly, if the internal combustion engine is operated frequently in an operating region where it is preferable to increase the supply ratio of low-octane fuel, the supply ratio of high-octane fuel is low when low-octane fuel is insufficient early. There are frequent situations where it is necessary to increase the amount of

  Therefore, in Patent Documents 1 and 2, the frequency at which the internal combustion engine must be operated in a state where the supply ratio of each type of fuel is greatly deviated from the preferable supply ratio may increase. 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 is a ratio in which the supply ratio of two types of fuel obtained by separating from a mixed fuel to the internal combustion engine is greatly deviated from the supply ratio suitable for the operating state of the internal combustion engine. It is possible to prevent the occurrence of an imbalance between the remaining amounts of the two types of fuel obtained by separating from the mixed fuel, and to operate the internal combustion engine as efficiently as possible. An object of the present invention is to provide a fuel supply system that enables the above.

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;
To the internal combustion engine, 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 operating state of the internal combustion engine including at least the required load and the rotational speed of the internal combustion engine. Fuel supply control means for controlling the supply amount of each of the two types of fuel;
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;
When the remaining amount of one of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means is equal to or greater than a predetermined value, the one fuel is transferred to the separated fuel storage tank. And a fuel return means for returning to the mixed fuel storage tank .

According to this basic configuration, when the remaining amount of one of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means is greater than or equal to a predetermined value, that is, the separated fuel When the remaining amount of the one fuel in the storage tank is relatively large, the one fuel is returned from the separated fuel storage tank to the mixed fuel storage tank by the fuel return means.

  Here, the operating state of the internal combustion engine in which the supply ratio of the one fuel is relatively small and the supply ratio of the other fuel is relatively large (more specifically, one fuel with respect to the other fuel supply ratio) Operating ratio in which the ratio of the supply ratio of the fuel is larger than the ratio of the content ratio of one fuel to the content ratio of the other fuel in the mixed fuel). As the remaining amount increases, the remaining amount of the other fuel decreases. As a result, the one fuel becomes excessive with respect to the other fuel, and the one fuel may be insufficient.

However, according to the above basic configuration, when the one fuel exceeds a predetermined value, the one fuel is returned from the separated fuel storage tank to the mixed fuel storage tank, so that the one fuel in the separated fuel storage tank is In addition to being suppressed from increasing, at least in addition to the total supply amount of the two types of fuel supplied to the internal combustion engine, an extra amount corresponding to the return of the one fuel is separated from the mixed fuel in the mixed fuel storage tank. It is possible to replenish the separated fuel storage tank with the two types of fuel. That is, a part of the return of the one fuel can be replaced with the other fuel.

As a result, according to the basic configuration, when the remaining amount of the one fuel exceeds the predetermined value, the one fuel becomes excessive with respect to the other fuel, or the other fuel becomes insufficient. It is possible to prevent the remaining amount of the two types of fuel in the separated fuel storage tank from becoming unbalanced as much as possible. As a result, in order to prevent the imbalance, the frequency of occurrence of a situation in which the supply ratio of the two types of fuel supplied to the internal combustion engine needs to be greatly deviated from the supply ratio suitable for the operating state of the internal combustion engine is minimized. can do.

Therefore, according to the above basic configuration , the supply ratio of the two types of fuel obtained by separating from the mixed fuel to the internal combustion engine is adjusted to a ratio greatly deviating from the supply ratio suitable for the operating state of the internal combustion engine. While suppressing the occurrence of an imbalance between the remaining amounts of the two types of fuel obtained by separating from the mixed fuel, the internal combustion engine can be operated as efficiently as possible.

In the present invention, on the premise of the above basic configuration , the fuel return means has the separated fuel storage tank when the remaining amount of the one fuel indicated by the output of the separated fuel remaining amount detecting means is a predetermined value or more. The return flow rate, which is the flow rate of the one fuel to be returned to the mixed fuel storage tank, is increased as the remaining amount of the one fuel increases, and the return flow rate is set to the output of the separated fuel remaining amount detection means. A return flow means for controlling in response is provided (first invention) .

According to the first aspect of the invention , when returning the one fuel to the mixed fuel storage tank, the return flow rate increases as the remaining amount of the one fuel in the separated fuel storage tank increases. It is possible to quickly reduce the remaining amount of the one of the fuels, and to quickly reduce the imbalance between the two types of remaining fuel in the separation storage tank.

Further, in the present invention, on the premise of the above basic configuration, there is provided a mixed fuel ratio detecting means for generating an output corresponding to each content ratio of the two types of fuel in the mixed fuel in the mixed fuel storage tank, and the fuel The return means is configured to return the one fuel to be returned from the separated fuel storage tank to the mixed fuel storage tank when the remaining amount of the one fuel indicated by the output of the separated fuel remaining amount detection means is a predetermined value or more. The return flow rate, which is a flow rate, is controlled in accordance with the output of the mixed fuel ratio detection unit so that the return flow rate increases as the content ratio of the one fuel indicated by the output of the mixed fuel ratio detection unit increases. Return flow rate control means (second invention) .

That is, as the content ratio of the one fuel increases, the amount of the one fuel that can be separated / generated from the unit amount of the mixed fuel increases. Therefore, the two types of fuel newly separated from the mixed fuel are When supplied and stored in the separated fuel storage tank, the remaining amount of the one fuel in the separated fuel storage tank is likely to increase as compared with the remaining amount of the other fuel. Therefore, in the second aspect of the invention , the return flow rate is controlled according to the output of the mixed fuel ratio detection means as described above. Thereby, it is possible to appropriately suppress an increase in the one fuel in the separated fuel storage tank and to prevent the remaining amounts of the two types of fuel in the separated fuel storage tank from becoming unbalanced.

The first invention and the second invention are more preferably combined. That is, on the premise of the basic configuration , it comprises 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, the fuel return means, A return that is the flow rate of the one fuel to be returned from the separated fuel storage tank to the mixed fuel storage tank when the remaining amount of the one fuel indicated by the output of the separated fuel remaining amount detection means is a predetermined value or more. The flow rate increases as the remaining amount of the one fuel increases, and the return flow rate increases as the content rate of the one fuel indicated by the output of the mixed fuel ratio detection means increases. It is more preferable to provide a return flow rate control means for controlling the return flow rate according to the outputs of the separated fuel remaining amount detection means and the mixed fuel ratio detection means ( third invention ).

According to the third aspect of the invention , the effects of both the first and second aspects of the invention can be achieved.

In addition, in the first aspect of the invention, when the mixed fuel ratio detecting 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 is provided, the fuel return And means for mixing the predetermined value so that the predetermined value related to the remaining amount of the one fuel increases as the content ratio of the one fuel indicated by the output of the mixed fuel ratio detecting means increases. You may make it change according to the output of a fuel ratio detection means ( 4th invention ).

In the second or third aspect of the invention having the mixed fuel ratio detecting means, as in the fourth aspect of the invention , the fuel return means is configured such that the predetermined value related to the remaining amount of the one fuel is equal to the mixing ratio. the greater the content of one of the fuel indicated by the fuel ratio detecting means, so that large, the predetermined value may be changed according to the output of the mixed fuel ratio detecting means (fifth aspect) .

According to the fourth and fifth aspects of the present invention , the operation of returning the one fuel from the separated fuel storage tank to the mixed fuel storage tank by the fuel return means includes the content ratio of the two types of fuel in the mixed fuel. As a result, it is possible to start at a timing suitable for the amount of two types of fuel that can be generated from the unit amount of the mixed fuel.

In addition, in the first aspect of the invention, when the mixed fuel ratio detecting 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 is provided, the fuel return means, if the content of the one fuel indicated by the output of the mixed fuel ratio detecting means is below a predetermined value, to return to the mixed fuel containing tank one fuel said from said separating fuel storage tank It is preferably prohibited ( sixth invention ).

In the second to fifth inventions provided with the mixed fuel ratio detecting means, as in the sixth invention , the fuel return means contains the one fuel indicated by the output of the mixed fuel ratio detecting means. When the ratio is equal to or greater than a predetermined value, it is preferable to prohibit the return of the one fuel from the separated fuel storage tank to the mixed fuel storage tank ( seventh invention ).

That is, when the one fuel is returned from the separated fuel storage tank to the mixed fuel storage tank, the content ratio of the one fuel in the mixed fuel in the mixed fuel storage tank increases and the content ratio of the other fuel decreases. It will be. When the content ratio of the other fuel with respect to the content ratio of the one fuel in the mixed fuel becomes minute, the separated fuel storage tank may be supplemented with two types of fuel separated from the mixed fuel. It becomes difficult to reduce the remaining amount of one fuel in the tank relative to the remaining amount of the other fuel. Therefore, in the sixth and seventh inventions , when the content ratio of the one fuel indicated by the output of the mixed fuel ratio detecting means is not less than a predetermined value, in other words, one of the mixed fuels in the mixed fuel storage tank. When the content ratio of the other fuel with respect to the fuel content ratio becomes small, it is prohibited to return the one fuel from the separated fuel storage tank to the mixed fuel storage tank. Thereby, it can suppress that a fuel return means operate | moves wastefully, and can reduce energy consumption.

In addition, in the first aspect of the invention, when the mixed fuel ratio detecting 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 is provided, the fuel supply The control means is configured to control each of the two types of fuel with respect to the whole fuel supplied to the internal combustion engine according to the operating state of the internal combustion engine, the output of the separated fuel remaining amount detection means, and the output of the mixed fuel ratio detection means. It is preferable to control the supply amounts of the two kinds of fuel to the internal combustion engine so as to change the supply ratio ( eighth invention ).

In the second to seventh aspects of the invention having the mixed fuel ratio detection means, as in the eighth aspect of the invention , the fuel supply control means includes the operating state of the internal combustion engine and the output of the separated fuel remaining amount detection means. Each of the two types of fuel to the internal combustion engine so as to change the supply ratio of each of the two types of fuel to the whole fuel supplied to the internal combustion engine according to the output of the mixed fuel ratio detection means It is preferable to control the supply amount ( the ninth invention ).

According to these eighth or ninth inventions , not only the operating state of the internal combustion engine but also the remaining amount of each type of fuel in the separated fuel storage tank and the content ratio of each type of fuel in the mixed fuel. The supply ratio of two types of fuel supplied to the engine can be adjusted. For this reason, even if it is difficult to eliminate the imbalance between the remaining amounts of the two types of fuel in the separated fuel storage tank only by returning the one fuel to the mixed fuel storage tank, the imbalance Can be eliminated.

In the first to ninth aspects of the invention , the separated fuel storage tank may be a tank for storing each of the two types of fuels (a separate tank for each fuel). The two types of fuel composing the fuel include a high-octane fuel having hydrophilicity (for example, ethanol), a low-octane fuel having a lower octane number than the high-octane fuel and a specific gravity smaller than that of the high-octane fuel and water ( For example, the separated fuel storage tank is preferably configured as follows. That is, the separated fuel storage tank comprises a high-octane fuel solution and a low-octane fuel obtained by mixing the high-octane fuel and water, and a lower portion and an upper portion of the internal space of the separated fuel storage tank depending on their specific gravity. And a tank containing the high-octane fuel aqueous solution and the low-octane fuel so that the internal space is filled with the high-octane fuel aqueous solution and the low-octane fuel. ( 10th invention ).

In the tenth aspect of the invention provided with such a separated fuel storage tank, a mixed liquid obtained by adding water to the mixed fuel in the mixed fuel storage tank and mixing it is supplied to the separated fuel storage tank, thereby providing a high octane fuel aqueous solution. And low-octane fuel will be separated and contained. In this case, the sum of the remaining amounts of the two types of fuel (high octane number aqueous fuel solution and low octane number fuel) in the separated fuel storage tank is kept constant, and when the remaining amount of one fuel increases, the remaining amount of the other fuel remains. The amount will decrease. The total amount of the high-octane fuel aqueous solution and the low-octane fuel flowing out from the separated fuel storage tank to the internal combustion engine or the mixed fuel storage tank is replenished with the mixed fuel in the mixed fuel storage tank and the water mixed therewith. It becomes.

In the tenth invention , it is preferable that the one fuel returned from the separated fuel storage tank to the mixed fuel storage tank is a low-octane fuel.

  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 two types of fuel composing the mixed fuel include, for example, ethanol as a high octane fuel and gasoline as 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.

  Further, of the internal space of the separation tank 3, the space on the upper side where gasoline accumulates is connected to the main tank 2 via a gasoline return passage 18 led out from the upper portion of the separation tank 3 separately from the gasoline supply passage 12. It is connected. A flow rate control valve 19 is interposed in the gasoline return passage 18. In this case, by opening the flow rate control valve 19, the pressurized gasoline in the upper part of the internal space of the separation tank 3 returns to the main tank 2 via the gasoline return passage 18.

  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.

  Further, the ECU 17 includes a gasoline return control unit 41. The gasoline return control unit 41 controls the operation of the flow rate control valve 19 in the gasoline return passage 18 and thus controls the flow rate of gasoline returned from the separation tank 3 to the main tank 2 (hereinafter referred to as gasoline return flow rate). It is. In the present embodiment, the gasoline return control unit 41, the gasoline return passage 18 and the flow rate control valve 19 implement the fuel return 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, the ignition timing control part 22, and the gasoline return control part 41 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 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 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.

  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 maps of FIGS. 3A, 3B, and 3C basically show the operating state in the low load region where the target IMEP of the internal combustion engine 4 is relatively low. Except for the main operating states of the internal combustion engine 1, the ethanol basic supply ratio Et_inj_rb is set to be larger than the mixed fuel ethanol ratio Ga_r. For this reason, the ratio of the remaining amount of ethanol to the remaining amount of gasoline in the separation tank 3 tends to decrease.

  Supplementally, in this 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 rate Et_in_rb, the gasoline basic supply rate Ga_inj_rb may be determined.

  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 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.

  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. Then, the flow rate / time conversion unit 30 calculates the ethanol fuel injection time Ti_Et from the input ethanol required injection amount Et_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 is MBT for any combination of 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 in 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 becomes maximum when it is assumed that 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. 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.

  Next, the gasoline return control unit 41 will be described. Referring to FIG. 2, the gasoline return control unit 41 corrects a basic operation amount du0 that is predetermined as an operation amount (control input) of the flow control valve 19 that defines the basic value of the gasoline return amount. The k_R3 determining unit 41a that determines the correction coefficient k_R3, and the value of the return permission flag Fret that indicates whether or not to allow the return of gasoline from the separation tank 3 to the main tank 2 are indicated by “1” and “0”, respectively. A return enable / disable determining unit 41b that performs the correction operation unit that determines the operation amount Ret_duty for actual control of the flow control valve 19 by correcting the basic operation amount du0 according to the third correction coefficient k_R3 and the return enable / disable flag Fret. 41c. In the present embodiment, the control of the gasoline return flow rate by the operation of the flow rate control valve 19 is performed by so-called duty control in which a pulse signal is input to the drive circuit unit of the flow rate control valve 19. For this reason, the operation amount of the flow control valve 19 is a duty ratio. Hereinafter, the basic operation amount du0 and the operation amount Ret_duty are referred to as a basic operation duty du0 and an actual operation duty Ret_duty, respectively.

  And the gasoline return control part 41 performs the process of the k_R3 determination part 41a and the return permission determination part 41b first. In this case, the k_R3 determining unit 41a determines the third correction coefficient k_R3 according to the mixing ratio of the mixed fuel in the main tank 2 and the remaining amount of the ethanol aqueous solution and gasoline in the separation tank 3. In order to execute this process, the k_R3 determining unit 41a includes the mixed fuel ethanol ratio Et_r (detected value) indicated by the output of the ratio sensor 14 and the interface height H_FL (detected value) indicated by the output of the float sensor 15. Are entered. Then, the k_R3 determining unit 41a determines the third correction coefficient k_R3 from the values of these input items based on a predetermined map (a map that defines the relationship between Et_r and H_FL and k_R3). The third correction coefficient k_R3 is a correction coefficient by which the basic operation amount du0 is multiplied, and 0 ≦ k_R3 ≦ 1.

  In the present embodiment, the map for determining the third correction coefficient k_R3 is set as shown in the graph illustrated in FIG. 7A, for example. In the map illustrated in the graph of FIG. 7A, the third correction coefficient k_R3 is set as follows with respect to the interface height H_FL when the mixed fuel ethanol ratio Et_r is constant. That is, when the detected value of the interface height H_FL is equal to or less than the predetermined value H_FL (min), k_R3 is set to “1”. When the detection value of the interface height H_FL is larger than H_FL (min), k_R3 is set to a value smaller than “1”. In this case, as the detected value of H_FL approaches the predetermined target value H_FL (3) (as the remaining amount of ethanol in the separation tank 3 increases and the remaining amount of gasoline decreases), k_R3 becomes “ K_R3 is set so as to approach 0 ". Further, when the detected value of H_FL becomes equal to or greater than the target value H_FL (3), k_R3 is set to “0”. Further, when the detected value of the interface height H_FL is a value between H_FL (min) and H_FL (3), the third correction coefficient k_R3 is such that k_R3 decreases as the mixed fuel ethanol ratio Et_r increases. Set to Therefore, when the detected value of the interface height H_FL is a value between H_FL (min) and H_FL (3), the third correction coefficient k_R3 increases as the detected value of the interface height H_FL increases (separation tank 3). As the remaining amount of the ethanol aqueous solution increases and the remaining amount of gasoline decreases, or as the mixed fuel ethanol ratio Et_r increases (the mixed fuel gasoline ratio Ga_r decreases), it decreases (to “0”). Set to approach).

  The target value H_FL (3) in the map of FIG. 7A means the target value of the interface height H_FL to be reached by returning the gasoline from the separation tank 3 to the main tank 2. It is set to a value smaller than the predetermined value H_FL (max) (for example, a value within the preferred range [H_FL (1), H_FL (2)]). In the map of FIG. 7A, the target value H_FL (3) is a constant value regardless of the mixed fuel ethanol ratio Et_r (regardless of the mixed ratio of the mixed fuel in the main tank 2). ing. However, the target value H_FL (3) may be changed according to the mixing ratio of the mixed fuel in the main tank 2. An example of the map in that case is the graph illustrated in FIG. In the map illustrated in the graph of FIG. 7B, the target value H_FL (3) is smaller as the mixed fuel ethanol ratio Et_r is larger (as the mixed fuel gasoline ratio Ga_r is smaller). Other than this, the form of change in the value of the third correction coefficient k_R3 with respect to the interface height H_FL and the mixed fuel ethanol ratio Et_r is the same as in the case of the map of FIG.

  Supplementally, if the remaining amount of the ethanol aqueous solution and the remaining amount of gasoline in the separation tank 3 when the interface height H_FL is the target value H_FL (3) are Q_Et (3) and Q_Ga (3), Q_Et ( 3) and Q_Ga (3) have meanings as the target value for the remaining amount of ethanol in the separation tank 3 and the target value for the remaining amount of gasoline when the gasoline is returned from the separation tank 3 to the main tank 2, respectively. . The third correction coefficient k_R3 determined according to the map of FIG. 7 (a) or FIG. 7 (b) is used when the remaining amount of gasoline in the separation tank 3 is equal to or greater than the target value Q_Ga (3) (ethanol aqueous solution). Is set to a value larger than “0” in the case where the remaining amount is Q_Et (3) or less). In this case, the remaining amount of gasoline in the separation tank 3 is not less than the target value Q_Ga (3) and not more than the value corresponding to H_FL (min) (the remaining amount of the ethanol aqueous solution is not more than Q_Et (3)). In a state where the value is equal to or higher than the value corresponding to H_FL (min)), the third correction coefficient k_R3 is larger as the remaining amount of gasoline in the separation tank 3 is larger (the remaining amount of aqueous ethanol solution is smaller) or mixed. The smaller the fuel ethanol ratio Et_r (the larger the mixed fuel gasoline ratio Ga_r), the larger the fuel ethanol ratio Et_r (the closer to “1”).

  Supplementally, in the present invention, the remaining amount of the one fuel being equal to or greater than a predetermined value corresponds to the remaining amount of gasoline being equal to or greater than the target value Q_Ga (3) in the present embodiment.

  Further, the mixed fuel ethanol ratio Et_r (detected value) indicated by the output of the ratio sensor 14 is input to the return possibility determination unit 41b. Then, the return possibility determination unit 41b compares the detected value of the mixed fuel ethanol ratio Et_r with a predetermined minute predetermined value Et_r (x) (for example, 3 [%]), and the detected value of Et_r ≦ Et_r (x ), In order to prohibit the return of gasoline from the separation tank 3 to the main tank 2 (in order to prevent Et_r from becoming smaller), the value of the return permission flag Fret is set to “0”. To do. Further, when the detected value of Et_r> Et_r (x), the return enable / disable determining unit 41b sets the value of the return enable / disable flag Fret to permit the return of gasoline from the separation tank 3 to the main tank 2. Set to “1”. When the detected value of the mixed fuel ethanol ratio Et_r ≦ Et_r (x), setting the value of Fret to “0” means that the detected value of the mixed fuel gasoline ratio Ga_r ≧ 100−Et_r (x) [ %], It is equivalent to setting the value of Fret to “0” (prohibiting the return of gasoline).

  The third correction coefficient k_R3 determined as described above and the return enable / disable flag Fret are input to the correction calculation unit 41c. Then, the correction calculation unit 41c determines the actual operation duty Ret_duty by multiplying the basic operation duty du0 by the third correction coefficient k_R3 and the return enable / disable flag Fret. In this case, the actual operation duty Ret_duty is determined to be the same value or smaller than the basic operation duty du0. Accordingly, the basic operation duty du0 is an operation amount that defines the maximum amount of gasoline flow. The gasoline return flow rate corresponding to the basic operation duty du0 is a predetermined flow rate so that the pressure in the separation tank 3 does not drop below a predetermined value.

  And the gasoline return control part 41 carries out duty control of the said flow control valve 19 according to the actual operation duty Ret_duty determined by the correction | amendment calculating part 41c as mentioned above. At this time, the gasoline in the separation tank 3 is returned to the main tank 2 via the gasoline return passage 18 at a gasoline return flow rate defined by the actual operation duty Ret_duty.

  When the detected value of the interface height H_FL of the separation tank 3 is equal to or less than the predetermined target value H_FL (3) by the processing of the gasoline return control unit 41 described above, that is, the remaining amount of gasoline in the separation tank 3 is When the target value Q_Ga (3) or higher corresponding to H_FL (3) or higher and the remaining amount of the ethanol aqueous solution is equal to or lower than the target value Q_Et (3) corresponding to H_FL (3), gasoline in the separation tank 3 Is the gasoline return flow rate according to the remaining amount of gasoline in the separation tank 3 and the remaining amount of ethanol aqueous solution and the mixing ratio of gasoline and ethanol in the mixed fuel (however, the flow rate below the predetermined flow rate corresponding to the basic operation duty du0) ) Is returned to the main tank 2. When the detected value of the mixed fuel ethanol ratio Et_r is equal to or smaller than the predetermined value Et_r (x) (the mixed fuel gasoline ratio Ga_r is equal to or larger than the predetermined value (100−Et_r [%]), Regardless of the remaining amount of gasoline and ethanol aqueous solution, the return of the gasoline in the separation tank 3 to the main tank 2 is prohibited (the gasoline return flow rate is maintained at “0”).

  The above is the details of the control processing of the fuel injection control unit 21, the ignition timing control unit 22, and the gasoline return control unit 41 in the present embodiment.

  In this embodiment, as described above, the ethanol basic supply ratio Et_inj_rb is mixed in the main operating state of the internal combustion engine 1 except for the operating state in the low load region where the target IMEP of the internal combustion engine 4 is relatively low. Since the ratio is set to be larger than the fuel ethanol ratio Ga_r, the ratio of the remaining amount of ethanol to the remaining amount of gasoline in the separation tank 3 tends to decrease. However, when the remaining amount of gasoline in the separation tank 3 becomes equal to or greater than the target value Q_Ga (3), the gasoline in the separation tank 3 is returned to the main tank 2. Then, the gasoline return is replenished by the mixed fuel / water mixture supplied from the feed pump 7 to the separation tank 3, so that a part of the gasoline return is replaced by the ethanol aqueous solution. The Rukoto.

  For this reason, the ethanol and gasoline supply ratios to the internal combustion engine 4 are determined by the actual ethanol supply ratio Et_injr determined by the fuel injection control unit 21 and the corresponding gasoline supply ratio (100−Et_injr [%]). In this way, it is possible to suppress the remaining amount of gasoline in the separation tank 3 from becoming excessive (the remaining amount of the aqueous ethanol solution is insufficient). Therefore, the remaining amount of gasoline and ethanol in the separation tank 3 are suppressed while suppressing the occurrence of a situation in which the supply ratio of ethanol and gasoline to the internal combustion engine 4 deviates from the ratio suitable for the operating state of the internal combustion engine 4 as much as possible. It is possible to suppress an imbalance between the remaining amount of the aqueous solution.

  When the gasoline is returned from the separation tank 3 to the main tank 2, the operation amount of the flow rate control valve 19 (actual operation duty Ret_duty), and hence the gasoline return flow rate, is the remaining amount of gasoline and ethanol aqueous solution in the separation tank 3. And the mixing ratio of the mixed fuel in the main tank 3, the gasoline in the separation tank 3 can be returned to the main tank 2 at a gasoline return flow rate suitable for the remaining amount and the mixing ratio. .

  When the gasoline content in the separation tank 3 is returned to the main tank 2 and the ethanol content ratio (mixed fuel ethanol ratio Et_r) of the mixed fuel in the main tank 2 becomes minute, the gasoline in the separation tank 3 is main. Since the return operation of the tank is prohibited (the gasoline return flow rate is maintained at “0”), it is possible to prevent the flow control valve 19 from operating wastefully and to reduce energy consumption.

  Furthermore, 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 in the range between the lower limit value H_FL (1) and the upper limit value H_FL (2). The state, that is, the state in which the remaining amount of the ethanol aqueous solution and the remaining amount of gasoline in the separation tank 3 are in suitable ranges [Q_Et (1), Q_Et (2)], [Q_Ga (2), Q_Ga (1)], respectively. Then, the ethanol basic supply ratio Et_inj_rb determined as described above according to the operating state of the internal combustion engine 4 and the mixture ratio of the mixed fuel in the main tank 2 is determined as the actual ethanol supply ratio 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, FIGS. 8A, 8 </ b> B, and 8 </ b> C 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 the case where the control for returning the gasoline in the separation tank 3 to the main tank 2 is omitted in this embodiment (this is when the return permission flag Fret is forcibly maintained at “0”). In the comparative example of FIG. 2), the change over time of the ethanol injection amount and the remaining amount of ethanol in the separation tank 3 are shown by a solid line and a broken line graph, respectively. In FIG. 8A, an example of the change over time in the ignition timing in the comparative example is shown with a two-dot chain line.

  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 will decrease. When the remaining amount of ethanol in the separation tank 3 decreases to some extent, the ethanol injection amount is reduced even if the target IMEP is constant (even if the operating state of the internal combustion engine 1 is constant). On the other hand, in the present embodiment, when the remaining amount of ethanol in the separation tank 3 decreases to some extent, the gasoline in the separation tank 3 is returned to the main tank 2, thereby increasing the gasoline in the separation tank 3 and ethanol. Reduction of the aqueous solution is effectively suppressed. As a result, the ethanol injection amount can be maintained at an amount suitable for the operation state such as the target IMEP of the internal combustion engine 4. Further, as shown in FIG. 8A, the ignition timing in the comparative example is controlled to the retarded ignition timing when the ethanol injection amount is reduced to some extent even if the target IMEP is constant. On the other hand, in the present embodiment, the ignition timing is maintained at the ignition timing (MBT) at which the operation of the internal combustion engine 1 can be performed efficiently while the target IMEP is constant.

  In the above embodiment, the gasoline and the ethanol aqueous solution are accommodated in the single separation tank 3. However, these 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. Then, for example, when two types of fuel are separated from the mixed fuel without using water and are stored in their separate fuel storage tanks, either one or both of the two types of fuels are used. May be returned to the mixed fuel storage tank according to the remaining amount of each type of fuel in the separated fuel storage tank. For example, when gasoline and ethanol separated from the mixed fuel are stored in separate fuel storage tanks, when the remaining amount of gasoline exceeds a predetermined value, the gasoline is stored in the fuel mixture storage tank. You may make it perform any one or both of returning and returning this ethanol to a mixed fuel storage tank, when the residual amount of ethanol becomes more than predetermined value.

  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. FIGS. 7A and 7B are graphs illustrating a map used in the process of the k_R3 determining unit 41a illustrated in FIG. 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) 15) Float sensor (separated fuel remaining amount detecting means), 17 ... Control device, 21 ... Fuel injection control unit (fuel supply control means), 18 ... Gasoline return passage (fuel return means), 19 ... Flow control valve (Fuel return means), 41... Gasoline return control section (fuel return means).

Claims (10)

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,
To the internal combustion engine, 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 operating state of the internal combustion engine including at least the required load and the rotational speed of the internal combustion engine. Fuel supply control means for controlling the supply amount of each of the two types of fuel;
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;
When the remaining amount of one of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means is equal to or greater than a predetermined value, the one fuel is transferred to the separated fuel storage tank. and a fuel return means returning said mixed fuel storage tank from
The fuel returning means returns the one fuel to the mixed fuel containing tank from the separated fuel containing tank when the remaining amount of the one fuel indicated by the output of the separated fuel remaining quantity detecting means is a predetermined value or more. Provided is a return flow rate control means for controlling the return flow rate according to the output of the separated fuel remaining amount detection means so that the return flow rate, which is the flow rate of the fuel, increases as the remaining amount of the one fuel increases. A fuel supply system characterized by. 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,
To the internal combustion engine, 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 operating state of the internal combustion engine including at least the required load and the rotational speed of the internal combustion engine. Fuel supply control means for controlling the supply amount of each of the two types of fuel;
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;
When the remaining amount of one of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means is equal to or greater than a predetermined value, the one fuel is transferred to the separated fuel storage tank. It means fuel return back to the mixed fuel storage tank from
A mixed fuel ratio detecting 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,
The fuel returning means returns the one fuel to the mixed fuel containing tank from the separated fuel containing tank when the remaining amount of the one fuel indicated by the output of the separated fuel remaining quantity detecting means is a predetermined value or more. The return flow rate corresponding to the output of the mixed fuel ratio detection unit is increased so that the return flow rate, which is the flow rate of fuel, increases as the content ratio of the one fuel indicated by the output of the mixed fuel ratio detection unit increases. And a return flow rate control means for controlling the fuel supply system. 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,
To the internal combustion engine, 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 operating state of the internal combustion engine including at least the required load and the rotational speed of the internal combustion engine. Fuel supply control means for controlling the supply amount of each of the two types of fuel;
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;
When the remaining amount of one of the two types of fuel indicated by the output of the separated fuel remaining amount detecting means is equal to or greater than a predetermined value, the one fuel is transferred to the separated fuel storage tank. It means fuel return back to the mixed fuel storage tank from
A mixed fuel ratio detecting 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,
The fuel returning means returns the one fuel to the mixed fuel containing tank from the separated fuel containing tank when the remaining amount of the one fuel indicated by the output of the separated fuel remaining quantity detecting means is a predetermined value or more. The return flow rate, which is the flow rate of fuel, increases as the remaining amount of the one fuel increases, and the return flow rate increases as the content rate of the one fuel indicated by the output of the mixed fuel ratio detection means increases. A fuel supply system comprising return flow rate control means for controlling the return flow rate according to the outputs of the separated fuel remaining amount detection means and the mixed fuel ratio detection means so as to increase . 2. The fuel supply system according to claim 1 , further comprising: a mixed fuel ratio detection unit that generates an output corresponding to a content ratio of each of the two types of fuel in the mixed fuel in the mixed fuel storage tank, wherein the fuel return unit includes The predetermined value related to the remaining amount of the one fuel is set so that the predetermined value becomes larger as the content ratio of the one fuel indicated by the output of the mixed fuel ratio detecting means increases. A fuel supply system, wherein the fuel supply system is changed according to the output of the detection means. 4. The fuel supply system according to claim 2, wherein the predetermined value related to the remaining amount of the one fuel has a large content ratio of the one fuel indicated by the mixed fuel ratio detecting means. The fuel supply system is characterized in that the predetermined value is changed according to the output of the mixed fuel ratio detecting means so as to increase. 2. The fuel supply system according to claim 1 , further comprising: a mixed fuel ratio detection unit that generates an output corresponding to a content ratio of each of the two types of fuel in the mixed fuel in the mixed fuel storage tank, wherein the fuel return unit includes When the content ratio of the one fuel indicated by the output of the mixed fuel ratio detection means is equal to or less than a predetermined value, it is prohibited to return the one fuel from the separated fuel storage tank to the mixed fuel storage tank. A fuel supply system characterized by that. The fuel supply system according to any one of claims 2 to 5 , wherein the fuel return means is configured such that the content ratio of the one fuel indicated by the output of the mixed fuel ratio detection means is equal to or less than a predetermined value. The fuel supply system forbids the return of the one fuel from the separated fuel storage tank to the mixed fuel storage tank. 2. The fuel supply system according to claim 1 , further comprising: a mixed fuel ratio detection unit that generates an output corresponding to a content ratio of each of the two types of fuel in the mixed fuel in the mixed fuel storage tank. Is the supply ratio of each of the two types of fuel to the whole fuel supplied to the internal combustion engine according to the operating state of the internal combustion engine, the output of the separated fuel remaining amount detection means, and the output of the mixed fuel ratio detection means A fuel supply system for controlling the supply amounts of the two types of fuel to the internal combustion engine so as to change the engine. The fuel supply system according to any one of claims 2 to 7 , wherein the fuel supply control means includes an operating state of the internal combustion engine, an output of the separated fuel remaining amount detecting means, and an output of the mixed fuel ratio detecting means. And controlling the respective supply amounts of the two types of fuel to the internal combustion engine so as to change the respective supply ratios of the two types of fuel to the whole fuel supplied to the internal combustion engine. Fuel supply system. The fuel system according to any one of claims 1 to 9 , wherein the two types of fuel constituting the mixed fuel are a high-octane fuel having hydrophilicity, a lower octane number than the high-octane fuel, and The high-octane fuel and the low-octane fuel having a specific gravity smaller than that of water, and the separated fuel storage tank comprises a high-octane fuel solution and a low-octane fuel obtained by mixing the high-octane fuel and water. The separated fuel storage tank is separated into a lower portion and an upper portion of the internal space of the separated fuel storage tank and stored in contact with each other at the interface, and the internal space is filled with the high octane fuel aqueous solution and the low octane fuel. A fuel supply system characterized by being a tank that accommodates the high octane fuel aqueous solution and the low octane fuel