JP2009138569A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent fuel used for starting-up from being wastefully used while securing startability of an internal combustion engine. <P>SOLUTION: A fuel injection control device (electronic control device 1) is equipped with a fuel injection rate setting means which varies the fuel injection rate of a high volatile fuel FH having a high volatile stored in individual fuel tanks (first and second fuel tanks 41A, 41B) and a low volatile fuel FL having a lower volatile than the high volatile fuel FH, and a fuel injection control means for injecting the high volatile fuel FH and the low volatile fuel FL with the fuel injection rate. The fuel injection rate setting means is constituted so as to gradually decrease a fuel injection ratio of the high volatile fuel FH and gradually increases a fuel injection ratio of the low volatile fuel FL when the operation state of the internal combustion engine is in a quasi-stable operation state in cooling the engine. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection control device applied to an internal combustion engine that can be operated using a plurality of types of fuel having different fuel properties.

  In recent years, in the automobile industry, various efforts have been made to cope with changes in the environment surrounding automobiles. For example, in the field of internal combustion engines, efforts have been made for so-called multi-fuel internal combustion engines that can be operated even with fuels having different fuel properties. A vehicle equipped with this kind of multi-fuel internal combustion engine is generally called a flexible fuel vehicle (FFV). For example, any of gasoline fuel, alcohol fuel, or a mixed fuel thereof is used. However, it is known to improve the environmental performance such as the suppression of the consumption of fossil fuels such as gasoline fuel, which can be operated and the limits of reserves continue to be sought.

  Here, for example, the following Patent Document 1 discloses a multi-fuel internal combustion engine that operates by supplying gasoline fuel when alcohol fuel is the main fuel and the temperature of the internal combustion engine is equal to or lower than a predetermined value. Further, in Patent Document 2 below, an alcohol-mixed fuel (mixed fuel of alcohol fuel and gasoline fuel) is used as a main fuel, and if the alcohol concentration of the alcohol-mixed fuel is high and misfires at the time of starting the engine, auxiliary fuel is used. A multi-fuel internal combustion engine that operates by supplying gasoline fuel is disclosed. These multi-fuel internal combustion engines of Patent Documents 1 and 2 are intended to improve engine startability by supplying gasoline fuel having higher volatility than alcohol fuel or alcohol mixed fuel in each case.

  That is, an alcohol fuel that is a low-volatile fuel or an alcohol-mixed fuel with a high alcohol concentration has a higher latent heat of vaporization than a gasoline fuel that is a high-volatile fuel, and is difficult to evaporate. For this reason, when the engine temperature such as the in-cylinder temperature or the cooling water temperature of the internal combustion engine is low (especially during cold start), alcohol fuel or alcohol-mixed fuel with high alcohol concentration can evaporate in the combustion chamber. In addition, since an appropriate air-fuel mixture required for combustion is not formed, the alcohol fuel or the like cannot be ignited, or there is a high possibility of misfiring even if ignited. Therefore, in the multifuel internal combustion engines of these Patent Documents 1 and 2, the engine can be started by supplying gasoline fuel, which is a highly volatile fuel, in such a case.

Japanese Patent Publication No. 61-60258 JP-A-2-163451

  By the way, as the operation state of the internal combustion engine related to the engine start, the operation state at the start of the engine start operation (that is, the cranking operation) when the engine is cold (hereinafter referred to as “start-up operation state”), and the engine cold state. The transitional operation state (hereinafter referred to as “transient operation state”) in which the intake air amount greatly increases immediately after the start of the engine start-up operation, and the change in intake air amount that can be operated only with low-volatile fuel There is no operation state (hereinafter referred to as “stable operation state”), and a metastable operation state when the engine is cold from the transient operation state to the stable operation state. Here, the stable operation state refers to a state after complete explosion, for example. In addition, the metastable operation state refers to an operation state in which there is almost no change in the intake air amount, although it is not equivalent to a stable operation state in which operation with only a low-volatile fuel is possible. In other words, this metastable operation state can be operated even if the volatilization degree of the fuel is lower than that in the transient operation state, but the operation state becomes impossible if the volatilization degree is too low, such as only the low-volatile fuel. That is.

  Here, as in the multi-fuel internal combustion engines of Patent Documents 1 and 2 described above, there are internal combustion engines that use gasoline fuel when performing the engine start operation in order to enable engine start and prevent subsequent misfire. ing. In such an internal combustion engine, the capacity of the high-volatile fuel tank for gasoline fuel is often smaller than the low-volatile fuel tank for alcohol fuel or alcohol-mixed fuel as the main fuel. . For this reason, in such an internal combustion engine, it is preferable to suppress as much as possible the amount of gasoline fuel used that greatly affects the startability.

  However, the multi-fuel internal combustion engine disclosed in Patent Document 1 is operated using only gasoline fuel evenly, despite the transition from the transient operation state to the metastable operation state. In other words, this conventional multi-fuel internal combustion engine has a lower alcohol concentration than that of the low-volatile fuel, even though it cannot be operated with only the low-volatile fuel with a high alcohol concentration in the low-volatile fuel tank. Even if there is a possibility of driving with any other fuel, it operates with only gasoline fuel. For this reason, in this conventional multi-fuel internal combustion engine, there is a possibility that gasoline fuel (highly volatile fuel) with a small storage amount is wasted. When such gasoline fuel (highly volatile fuel) continues to be wasted, only gasoline fuel (highly volatile fuel) must be replenished frequently, which is inconvenient. There is a possibility that the engine cannot be started due to a shortage of volatile fuel.

  Further, the multi-fuel internal combustion engine of Patent Document 2 takes into account the economics of gasoline fuel, and in accordance with the alcohol concentration of the alcohol mixed fuel as the main fuel, the injector of the gasoline fuel as the auxiliary fuel with respect to the alcohol mixed fuel injector The drive rate is switched. Here, it is assumed that the switching is performed in a metastable operation state. In this case, after the switching, it is possible to operate with a fuel having a lower concentration than the alcohol concentration of the fuel in the combustion chamber at the time of the switching. That is, after the drive rate is switched, the consumption of gasoline fuel can be further reduced. However, since the multi-fuel internal combustion engine of Patent Document 2 operates with the set value (mixing ratio of main fuel and auxiliary fuel) at the time of switching after switching the driving rate, waste of gasoline fuel is not appropriately suppressed. . Therefore, this multi-fuel internal combustion engine also causes the same inconvenience as the multi-fuel internal combustion engine disclosed in Patent Document 1.

  Therefore, the present invention provides a fuel injection control device that can improve the disadvantages of the conventional example and prevent waste of fuel used for starting the internal combustion engine while ensuring startability of the internal combustion engine. Is the purpose.

  In order to achieve the above object, according to the first aspect of the present invention, fuel injection of a highly volatile high volatile fuel stored in an individual fuel tank and a low volatile fuel less volatile than the highly volatile fuel is provided. In a fuel injection control device comprising: a fuel injection ratio setting means for changing the ratio; and a fuel injection control means for injecting a high volatile fuel and a low volatile fuel at the fuel injection ratio. When the operation state of the internal combustion engine is in a metastable operation state when the engine is cold, the fuel injection ratio of the low volatile fuel is gradually increased while the fuel injection ratio of the high volatile fuel is gradually decreased. ing.

  Thus, the fuel injection control device according to the first aspect can suppress the waste of the highly volatile fuel without impairing the startability of the internal combustion engine.

  In order to achieve the above object, according to a second aspect of the present invention, in the fuel injection control apparatus according to the first aspect, the rate of decrease in the fuel injection ratio of the highly volatile fuel as the volatility of the low volatile fuel decreases. The fuel injection ratio setting means is configured so as to slow down.

  As a result, the fuel injection control device according to claim 2 slowly reduces the injection amount of the highly volatile fuel in a situation where the degree of volatilization of the low volatile fuel is low and the startability of the internal combustion engine is deteriorated. Therefore, it is possible to suppress a rapid increase in the volatilization degree of the fuel in the combustion chamber composed of the high volatile fuel and the low volatile fuel. Therefore, the fuel injection control device according to claim 2 does not impair the startability of the internal combustion engine.

  In order to achieve the above object, according to a third aspect of the present invention, in the fuel injection control apparatus according to the first or second aspect, the fuel injection ratio of highly volatile fuel decreases as the engine temperature of the internal combustion engine decreases. The fuel injection ratio setting means is configured to reduce the speed.

  As a result, the fuel injection control device according to the third aspect of the present invention can reduce the injection amount of the highly volatile fuel slowly in a situation where the engine temperature of the internal combustion engine is low and the startability is deteriorated. A rapid increase in the volatilization degree of the fuel in the combustion chamber composed of the volatile fuel and the low-volatile fuel can be suppressed. For this reason, the fuel injection control device according to claim 3 does not impair the startability of the internal combustion engine.

  In order to achieve the above object, according to a fourth aspect of the present invention, in the fuel injection control device according to the first, second, or third aspect, the amount of change in intake air within a predetermined time is a predetermined operating state determination value. If it is above, it is determined that the operating state of the internal combustion engine is in a transient operating state when the engine is cold, while it is determined that it is in a metastable operating state if the amount of change in intake air within a predetermined time is smaller than the operating state determination value. The fuel injection ratio setting means is configured such that the fuel injection ratio setting means is configured such that the lower the volatility of the low-volatile fuel is, the smaller the operation state determination value is.

  Thus, the fuel injection control device according to claim 4 determines that the low volatile fuel is in the transient operation state instead of the metastable operation state when the volatility degree of the low volatile fuel is low. It is possible to secure a sufficient amount of highly volatile fuel injection for stopping the reduction and realizing engine start. For this reason, the fuel injection control device according to claim 4 can suppress the adhesion of a part of the low-volatile fuel to the inner wall surface of the intake port, thereby preventing a reduction in output torque and misfire. .

  In order to achieve the above object, according to a fifth aspect of the present invention, in the fuel injection control device according to the first, second, third, or fourth aspect, the operating state determination value decreases as the engine temperature of the internal combustion engine decreases. Thus, the fuel injection ratio setting means is configured.

  As a result, the fuel injection control device according to claim 5 determines that the internal combustion engine is in the transient operation state instead of the metastable operation state when the engine temperature is low, and therefore reduces the injection amount of the highly volatile fuel. The injection amount of the highly volatile fuel sufficient for stopping the engine start can be ensured. For this reason, the fuel injection control device according to claim 5 can suppress the adhesion of a part of the low-volatile fuel to the inner wall surface of the intake port, thereby preventing a decrease in output torque and a misfire. .

  Here, as in the sixth aspect of the invention, the low-volatile fuel may be alcohol fuel or a fuel mainly composed of alcohol fuel, and the high-volatile fuel may be gasoline fuel.

  The fuel injection control device according to the present invention can prevent waste of highly volatile fuel used for starting the internal combustion engine while ensuring startability. Therefore, the fuel injection control device according to the first embodiment can reduce the number of times of supplying the highly volatile fuel while ensuring the startability of the internal combustion engine, that is, the number of frequent replenishment of the highly volatile fuel. User convenience can be improved. In addition, the fuel injection control device can avoid the situation where the engine cannot be started due to a shortage of highly volatile fuel.

  Embodiments of a fuel injection control device according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the embodiments.

  A fuel injection control device according to a first embodiment of the present invention will be described with reference to FIGS. In the following, the fuel injection control device will be described in detail while explaining an example of an internal combustion engine to be applied.

  The internal combustion engine exemplified here is a multi-fuel internal combustion engine mounted on a so-called flexible fuel vehicle that can be operated even with a fuel having different fuel properties, and has at least two types of volatility differences. The fuel is configured to be supplied individually. In this internal combustion engine, a low-volatile fuel having a low volatility is used as a main fuel, and a high-volatile fuel having a higher volatility than the low-volatile fuel is used as an auxiliary fuel. The auxiliary fuel (highly volatile fuel) is a fuel that is used in the aforementioned starting operation state, transient operation state, and metastable operation state. Here, an alcohol fuel or an alcohol mixed fuel such as ethanol, methanol, butanol or the like is illustrated as a low-volatile fuel having low volatility. Moreover, hydrocarbon fuels, such as gasoline fuel, are illustrated as a highly volatile fuel whose volatility is higher than that of the low volatile fuel. The alcohol mixed fuel is a fuel mainly composed of alcohol fuel, and is a mixed fuel of alcohol fuel and at least one kind of fuel having different fuel properties. The alcohol mixed fuel illustrated here is mixed with a hydrocarbon fuel (for example, gasoline fuel).

  The internal combustion engine is one in which various control operations such as combustion control are executed by an electronic control unit (ECU) 1 shown in FIG. In the first embodiment, it is assumed that a fuel injection control device is configured as one function of the electronic control device 1. The electronic control unit 1 includes a CPU (Central Processing Unit) (not shown), a ROM (Read Only Memory) that stores a predetermined control program and the like, and a RAM (Random Access) that temporarily stores the calculation result of the CPU. Memory) and a backup RAM for storing information prepared in advance.

  First, the configuration of the internal combustion engine exemplified here will be described with reference to FIG. Although only one cylinder is shown in FIG. 1, the present invention is not limited to this, and can be applied to a multi-cylinder multifuel internal combustion engine. In the present embodiment, description will be made assuming that a plurality of cylinders are provided.

  The internal combustion engine includes a cylinder head 11, a cylinder block 12, and a piston 13 that form a combustion chamber CC. Here, the cylinder head 11 and the cylinder block 12 are fastened with bolts or the like via the head gasket 14 shown in FIG. 1, and the recess 11a on the lower surface of the cylinder head 11 and the cylinder bore 12a of the cylinder block 12 formed thereby. The piston 13 is disposed so as to be capable of reciprocating in the space. And the combustion chamber CC mentioned above is comprised by the space enclosed by the wall surface of the recessed part 11a of the cylinder head 11, the wall surface of the cylinder bore 12a, and the top surface 13a of the piston 13. FIG.

  This internal combustion engine sends air and fuel into the combustion chamber CC in accordance with operating conditions such as engine speed and engine load, and executes combustion control in accordance with the operating conditions. The air is sucked from the outside through the intake passage 21 and the intake port 11b of the cylinder head 11 shown in FIG. On the other hand, the fuel is supplied using the fuel supply device 50 shown in FIG.

  First, the air supply path will be described.

  On the intake passage 21 of the internal combustion engine, an air cleaner 22 for removing foreign matters such as dust contained in air introduced from the outside, and an intake air amount detection means 23 for detecting the amount of intake air from the outside are provided. ing. As the intake air amount detection means 23, an air amount detection sensor such as an air flow meter that directly detects the intake air amount, an intake pipe pressure sensor that detects the pressure in the intake passage 21 (ie, intake pressure), and the like are conceivable. When the latter intake pipe pressure sensor is used, the intake air amount is obtained indirectly from the intake pressure and the engine speed. In this internal combustion engine, the detection signal of the intake air amount detection means 23 is sent to the electronic control unit 1, and the electronic control unit 1 calculates the intake air amount, the engine load and the like based on the detection signal. The engine speed can be grasped from the detection signal of the crank angle sensor 16 that detects the rotation angle of the crankshaft 15.

  A throttle valve 24 capable of adjusting the flow rate of the air flowing into the combustion chamber CC and a throttle valve for opening and closing the throttle valve 24 are provided downstream of the intake air amount detecting means 23 on the intake passage 21. And an actuator 25. In the electronic control unit 1 of the first embodiment, the throttle valve actuator 25 is driven and controlled according to the operating conditions, and the throttle valve that adjusts the valve opening angle of the throttle valve 24 so that the valve opening degree according to the operating conditions is obtained. Control means are provided. Here, the throttle valve actuator 25 and the throttle valve control means constitute a throttle valve opening control means. Further, this internal combustion engine is provided with a throttle opening sensor 26 that detects the valve opening of the throttle valve 24 and transmits the detection signal to the electronic control unit 1.

  On the other hand, one end of the intake port 11b opens to the combustion chamber CC, and an intake valve 31 that opens and closes the opening is disposed in the opening portion. The number of openings may be one or more, and an intake valve 31 is provided for each opening. Therefore, in this internal combustion engine, air is sucked into the combustion chamber CC from the intake port 11b by opening the intake valve 31 and closed to the combustion chamber CC by closing the intake valve 31. Air inflow is blocked.

  Here, as the intake valve 31, for example, there is a valve that is driven to open and close in accordance with the rotation of an intake camshaft (not shown) and the elastic force of an elastic member (string spring). In this type of intake valve 31, by interposing a power transmission mechanism such as a chain or a sprocket between the intake side camshaft and the crankshaft 15, the intake side camshaft is interlocked with the rotation of the crankshaft 15, Open / close drive is performed at a preset opening / closing timing. In the internal combustion engine illustrated here, the intake valve 31 that is driven to open and close in synchronization with the rotation of the crankshaft 15 can be applied.

  However, the internal combustion engine may be provided with a variable valve mechanism such as a so-called variable valve timing and lift mechanism that can change the opening / closing timing and lift amount of the intake valve 31, and thereby the opening / closing timing of the intake valve 31. And the lift amount can be changed to a suitable one according to the operating conditions. Furthermore, in this internal combustion engine, a so-called electromagnetically driven valve that opens and closes the intake valve 31 using electromagnetic force may be used in order to obtain the same effect as the variable valve mechanism.

  Next, the fuel supply device 50 will be described.

  As the fuel supply device 50, fuels having different fuel properties stored in a plurality of fuel tanks are individually injected into the intake port 11b and / or the combustion chamber CC, or fuel stored in a plurality of fuel tanks It is conceivable that fuels having different properties are mixed at a desired fuel mixing ratio by a fuel mixing device or the like and injected into the intake port 11b and / or the combustion chamber CC. In the first embodiment, two types of fuel having different fuel properties (low volatile fuel FL stored in the first fuel tank 41A or high volatile fuel FH stored in the second fuel tank 41B) A representative example is a port injection type in which the injection ratio is varied and injected into each intake port 11b, and each fuel is introduced into the combustion chamber CC together with the intake air. Here, in the first embodiment, alcohol mixed fuel (mixed fuel of alcohol fuel and gasoline fuel) is stored in the first fuel tank 41A as the low volatile fuel FL, and the highly volatile fuel is stored in the second fuel tank 41B. It is assumed that gasoline fuel is stored as FH.

  Specifically, the fuel supply device 50 includes a fuel injection ratio setting means of the electronic control device 1 that sets a fuel injection ratio of the low volatile fuel FL and the high volatile fuel FH, and the low volatile fuel FL and the high volatile fuel. The target fuel injection amount setting means of the electronic control device 1 for setting the respective target fuel injection amounts of the fuel FH, and the electronic control device 1 for injecting the low volatile fuel FL and the high volatile fuel FH at the respective target fuel injection amounts. And the fuel injection control means.

  The fuel injection ratio setting means sets the fuel injection ratio between the low volatile fuel FL and the high volatile fuel FH between 0 to 10 and 10 to 0 in accordance with operating conditions such as engine speed and engine load. . Further, the target fuel injection amount setting means is configured to reduce the low volatile fuel FL and the high volatile fuel FH based on the fuel injection ratio, the target air-fuel ratio of the air-fuel mixture in the combustion chamber CC, and the intake air amount (engine load). Each target fuel injection amount is set. Note that the target air-fuel ratio of the air-fuel mixture in the combustion chamber CC is set according to the operating conditions.

  The fuel supply device 50 includes a first fuel supply unit that injects the low-volatile fuel FL into the intake port 11b, and a second fuel supply unit that injects the high-volatile fuel FH into the intake port 11b. Yes. Therefore, the fuel injection ratio setting means of the first embodiment sets the fuel injection ratio of the low volatile fuel FL injected to the first fuel supply means and the high volatile fuel FH injected to the second fuel supply means. It becomes.

  The first fuel supply means sucks the low-volatile fuel FL from the first fuel tank 41A and sends it to the first fuel passage 51A, and the low-volatile fuel FL in the first fuel passage 51A. A first fuel delivery pipe 53A distributed to each cylinder, and a fuel injection valve (fuel injection means) for each cylinder that injects the low-volatile fuel FL supplied from the first fuel delivery pipe 53A into each intake port 11b. 54A. The first fuel supply means injects the low volatile fuel FL in accordance with the fuel injection conditions such as the fuel injection timing according to the target fuel injection amount set by the target fuel injection amount setting means and the operating conditions. The fuel injection control means is configured to drive and control the first feed pump 52A and the fuel injection valve 54A based on the injection conditions. Therefore, in the first fuel supply means, the low volatile fuel FL is sucked up from the first fuel tank 41A by the first feed pump 52A, and the low volatile fuel FL is injected from the fuel injection valve 54A under the fuel injection condition. The

  The second fuel supply means includes a second feed pump 52B that sucks up the highly volatile fuel FH from the second fuel tank 41B and sends it to the second fuel passage 51B, and the highly volatile fuel in the second fuel passage 51B. A second fuel delivery pipe 53B that distributes FH to each cylinder, and a fuel injection valve (fuel injection) for each cylinder that injects highly volatile fuel FH supplied from the second fuel delivery pipe 53B to each intake port 11b. Means) 54B. The second fuel supply means injects the highly volatile fuel FH in accordance with the fuel injection conditions such as the fuel injection timing according to the target fuel injection amount set by the target fuel injection amount setting means and the operating conditions. The fuel injection control means is configured to drive and control the second feed pump 52B and the fuel injection valve 54B based on the injection conditions. Therefore, in the second fuel supply means, the highly volatile fuel FH is sucked up from the second fuel tank 41B by the second feed pump 52B, and the highly volatile fuel FH is injected from the fuel injection valve 54B under the fuel injection conditions. The

  The low volatile fuel FL and the high volatile fuel FH supplied to the intake port 11b in this way are mixed with the air described above in the intake port 11b, and into the combustion chamber CC together with the opening of the intake valve 31. Supplied with. Then, the air-fuel mixture in the combustion chamber CC is burned by the ignition operation of the spark plug 61 when the ignition timing according to the operating conditions is reached. The in-cylinder gas (combustion gas) after the combustion is discharged from the combustion chamber CC to the exhaust port 11 c shown in FIG. 1 and released to the atmosphere through the exhaust passage 81.

  An exhaust valve 71 that opens and closes an opening between the exhaust port 11c and the combustion chamber CC is disposed. The number of openings may be one or more, and the exhaust valve 71 described above is provided for each opening. Accordingly, in this internal combustion engine, combustion gas is discharged from the combustion chamber CC to the exhaust port 11c by opening the exhaust valve 71, and closing the exhaust valve 71 to the combustion gas exhaust port 11c. Is blocked.

  Here, as the exhaust valve 71, as in the intake valve 31 described above, a valve with a power transmission mechanism, a valve with a variable valve mechanism such as a so-called variable valve timing & lift mechanism, or a so-called electromagnetically driven valve is used. Can be applied.

  Further, an exhaust gas purification device 82 is disposed on the exhaust passage 81, and the exhaust gas purification device 82 purifies harmful substances in the exhaust gas.

  By the way, the internal combustion engine of the first embodiment uses the low volatile fuel FL mainly as the main fuel in the stable operation state, and uses the high volatile fuel FH in the starting operation state, the transient operation state, and the metastable operation state. Used as fuel. Here, for example, when the idling state continues for a long time, or when the engine stop state of the internal combustion engine continues in a so-called hybrid vehicle using the internal combustion engine and the electric motor as drive sources, the stable operation state is once entered. Even after becoming stable, the stable operation state may return to the metastable operation state. For this reason, the highly volatile fuel FH is used not only in the start-up operation state, transient operation state and metastable operation state related to engine start, but also when returning from the stable operation state to the metastable operation state or in an internal combustion engine in a hybrid vehicle. Also used when restarting. That is, the highly volatile fuel FH is injected when the operation is impossible only with the low volatile fuel FL.

  For this reason, the high-volatile fuel FH is less frequently used than the low-volatile fuel FL. For this reason, the capacity of the second fuel tank 41B that stores the highly volatile fuel FH is smaller than that of the first fuel tank 41A that stores the low volatile fuel FL. Therefore, waste of the highly volatile fuel FH is not preferable. In the first embodiment, the fuel injection control device (electronic control device 1) is configured so as to prevent the waste of the highly volatile fuel FH.

  Here, in the start-up operation state and the transient operation state described above, an increase in the engine temperature is observed but the temperature is still low, so the degree of volatilization mainly composed of the highly volatile fuel (gasoline fuel) FH or the highly volatile fuel FH. The fuel is operated with a high fuel (that is, an alcohol mixed fuel having a low alcohol concentration). The alcohol mixed fuel having a low alcohol concentration is realized in the combustion chamber CC by setting the fuel injection ratio of the low volatile fuel FL and the high volatile fuel FH to an appropriate value. It is of alcohol concentration that enables operation in the transition period. As shown in FIG. 2, the internal combustion engine of the first embodiment is exemplified as using an alcohol mixed fuel having a low alcohol concentration in the starting operation state and the transient operation state.

  On the other hand, in the metastable operation state, the change in the intake air amount has almost disappeared, so that the internal combustion engine can be operated even if the volatilization degree of the fuel in the combustion chamber CC is reduced. More specifically, the internal combustion engine can be operated even if the alcohol concentration of the alcohol mixed fuel generated in the combustion chamber CC is higher than that of the low alcohol concentration alcohol mixed fuel. That is, in the metastable operation state, as shown in FIG. 2, the fuel injection ratio of the low volatile fuel FL is increased while the fuel injection ratio of the high volatile fuel FH is decreased as the change in the intake air amount decreases. By doing so, the internal combustion engine can be operated while suppressing the consumption of the highly volatile fuel FH. Therefore, the fuel injection ratio setting means of the fuel injection control apparatus (electronic control apparatus 1) of the first embodiment uses the fuel injection ratio in the metastable operation state to suppress the consumption of the highly volatile fuel FH and the internal combustion engine. It is set to an appropriate value that can achieve both driving operations.

Specifically, in the first embodiment, the fuel injection ratio of the high volatile fuel FH is decreased and the fuel injection ratio of the low volatile fuel FL is increased at a predetermined reduction rate dQ _FH / dt or an increase rate dQ _FL / dt. I do. For the reduction rate dQ _FH / dt and the increase rate dQ _FL / dt, those set in advance based on experiments and simulations conducted from the viewpoint of suppressing consumption of the highly volatile fuel FH and realizing the operation of the internal combustion engine are used. . Here, the decrease rate dQ _FH / dt and the increase rate dQ _FL / dt are fixed values. In the illustration of FIG. 2, since almost no change appears in the intake air amount KL in the metastable operation state, the decrease rate dQ _FH / dt and the increase rate dQ _FL / dt are set to the same value, for example.

  Hereinafter, the calculation processing operation of the fuel injection control device (electronic control device 1) of the first embodiment will be described based on the flowchart of FIG.

  First, the fuel injection ratio setting means of the electronic control unit 1 determines whether or not a request for injection of the highly volatile fuel FH (hereinafter referred to as “highly volatile fuel injection request”) is made (step). ST5). This determination is made, for example, by the fuel injection control means of the electronic control unit 1 whether an instruction to inject the highly volatile fuel FH to the second feed pump 52B of the second fuel supply means and the fuel injection valve 54B is made. It may be done depending on whether or not.

  When it is determined in step ST5 that the highly volatile fuel injection request has not been made, the fuel injection ratio setting means once ends this calculation processing operation.

  On the other hand, when it is determined that a highly volatile fuel injection request has been made, the fuel injection ratio setting means calculates an intake air change amount ΔKLt within the operation state determination time t1 (step ST10), and this intake air It is determined whether or not the change amount ΔKLt is smaller than the operating state determination value α (step ST15).

  The determination in step ST15 is for determining whether the current operation state is a transient operation state or a metastable operation state. In other words, since it is possible to determine the transient operation state or the metastable operation state by observing the change in the intake air amount KL within the predetermined time (the operation state determination time t1), the transient operation is performed when the intake air change amount ΔKLt is large. When the intake air change amount ΔKLt is small, it is determined that the state is a metastable operation state. For this reason, the operating state determination value α may be set in advance through experiments and simulations for the intake air change amount ΔKL on the transient operating state side corresponding to the boundary between the transient operating state and the metastable operating state.

  When it is determined in step ST15 that the intake air change amount ΔKLt is greater than or equal to the operation state determination value α, the fuel injection ratio setting unit determines that the current operation state is a transient operation state, and performs this calculation processing operation. Finish once.

  If it is determined in step ST15 that the intake air change amount ΔKLt is smaller than the operation state determination value α, the fuel injection ratio setting means determines that the current operation state is a metastable operation state. Then, the current intake air amount KL (= KL1) obtained by the intake air amount detection means 23 is read (step ST20).

The fuel injection ratio setting means reduces the fuel injection rate of the high volatile fuel FH at the predetermined reduction rate dQ _FH / dt described above and reduces the low volatile fuel FL at the predetermined increase rate dQ _FL / dt described above. The fuel injection ratio is increased by increasing the fuel injection ratio (step ST25).

Here, the fuel injection ratio setting means passes the set value of the fuel injection ratio to the target fuel injection amount setting means of the electronic control unit 1, and the target fuel injection of the low-volatile fuel FL is supplied to the target fuel injection amount setting means. The target fuel injection amount of the amount and the highly volatile fuel FH is set. Then, the fuel injection control means that receives the set value of each target fuel injection amount from the target fuel injection amount setting means controls the first fuel supply means and the second fuel supply means, and each of the target fuel injection quantity is set. A low volatile fuel FL and a high volatile fuel FH are injected in an amount. Thus, the high volatility fuel FH, the fuel injection amount of the high-volatility fuels FH which was reduced by the weight loss rate dQ FH _{/ dt} (hereinafter referred to as "high volatility fuel injection amount".) Is injected at Q _FH On the other hand, the low-volatile fuel FL is the fuel injection amount of the low-volatile fuel FL increased at the predetermined increase rate dQ _FL / dt (hereinafter referred to as “low-volatile fuel injection amount”) Q _FL . Be injected.

Subsequently, the fuel injection ratio setting means reads the high volatility fuel injection amount Q _FH weight loss and low volatility fuel injection amount Q of intake air amount at the time of performing the increase of the _FL KL (= KL2) (step ST30) .

  The fuel injection ratio setting means is configured to decrease the high volatile fuel FH and increase the low volatile fuel FL based on the intake air amount KL2 at the time of step ST30 and the intake air amount KL1 at the time of step ST20. Is obtained (step ST35), and it is determined whether or not the intake air change amount ΔKL is smaller than the operating state determination value β (step ST35). Step ST40).

  The determination in step ST40 is whether the operation state when the decrease in the high volatile fuel FH and the increase in the low volatile fuel FL is maintained in the metastable operation state, or the same as in the transient operation state or This is for determining whether or not the intake air amount KL has changed so much that it corresponds to the transient operation state. Therefore, the driving state determination value β may be the driving state determination value α in step ST15, or may be set to a value smaller than the driving state determination value α.

  If it is determined in step ST40 that the intake air change amount ΔKL is greater than or equal to the operation state determination value β, the fuel injection ratio setting means determines that the current operation state is a transient operation state or is equivalent to the intake air amount KL. This calculation processing operation is temporarily terminated.

If it is determined in step ST40 that the intake air change amount ΔKL is smaller than the operation state determination value β, the fuel injection ratio setting means indicates that the current operation state remains in the metastable operation state. It is determined whether or not the injection of the high volatile fuel FH is completed by the reduction control of the high volatile fuel FH in the above-described step ST5, that is, whether or not the high volatile fuel injection amount Q _FH has become zero (step S5). ST45).

Here, when the injection of the highly volatile fuel FH continues, the fuel injection ratio setting means returns to step ST4, reads the current intake air amount KL (= KL1), proceeds to step ST20, and first The reduced and increased high volatile fuel FH and low volatile fuel FL are decreased and increased again at the predetermined reduction rate dQ _FH / dt and the predetermined increase rate dQ _FL / dt, respectively. Thereafter, the fuel injection ratio setting means repeats the arithmetic processing from step ST20 to step ST45 until an affirmative determination (determination of the end of injection of the highly volatile fuel FH) is made in step ST45. Thereby, as shown in FIG. 2, the high volatile fuel FH and the low volatile fuel FL are respectively set to a predetermined reduction rate dQ _FH / dt and a predetermined increase rate in the metastable operation state after the operation state determination time t1 has elapsed. The amount is gradually decreased and increased at dQ _FL / dt.

As described above, in the fuel injection control device of the first embodiment, in the metastable operation state in which the intake air amount KL hardly changes, the highly volatile fuel injection amount Q _FH is reduced to the predetermined reduction rate dQ _FH / dt. The low volatile fuel injection amount Q _FL is gradually increased at a predetermined increase rate dQ _FL / dt. For this reason, this fuel injection control device can suppress the waste of highly volatile fuel (gasoline fuel) FH that can be stored only in a small amount without impairing the startability of the internal combustion engine. Therefore, the fuel injection control device according to the first embodiment reduces the number of times the highly volatile fuel (gasoline fuel) FH is supplied while ensuring the startability of the internal combustion engine, that is, the frequent use of the highly volatile fuel (gasoline fuel) FH. Since the frequency | count of replenishment can be reduced, a user's convenience can be improved. In addition, the fuel injection control device can avoid the situation where the engine cannot be started due to a shortage of highly volatile fuel (gasoline fuel) FH.

Here, in the above-described example, the decrease in the high volatile fuel FH and the increase in the low volatile fuel FL are made using the decrease rate dQ _FH / dt and the increase rate dQ _FL / dt set in advance as fixed values. It is carried out.

  Strictly speaking, however, the degree of volatilization (alcohol concentration) of the fuel in the combustion chamber CC generated by the high volatile fuel FH and the low volatile fuel FL is the same as that of the high volatile fuel FH and the low volatile fuel FL. Not only the fuel injection ratio but also the volatility (alcohol concentration) of the low-volatile fuel FL as the main fuel changes. That is, the degree of volatilization of the fuel in the combustion chamber CC becomes lower as the degree of volatilization of the low-volatile fuel FL is lower even at the same fuel injection ratio. In other words, the alcohol concentration of the alcohol mixed fuel in the combustion chamber CC becomes higher as the low-volatile fuel FL has a higher alcohol concentration even at the same fuel injection ratio. Therefore, when the volatilization degree of the low-volatile fuel FL is low (the alcohol concentration is high), the startability when the engine is cold is inferior than when the volatilization degree is high (the alcohol concentration is low). Also, the startability when the engine is cold becomes worse as the engine temperature is lower.

Accordingly, for the decrease rate dQ _FH / dt and the increase rate dQ _FL / dt, the degree of volatilization (alcohol concentration) of the low-volatile fuel FL in the first fuel tank 41A and the engine temperature (for example, the water temperature sensor 17 shown in FIG. 1). It is preferable to change the temperature according to the cooling water temperature detected by (1). Specifically, as shown in FIG. 4, as the volatilization degree of the low-volatile fuel FL is lower (the alcohol concentration is higher), the decrease rate dQ _FH / dt and the increase rate dQ _FL / dt are made slower. That is, as the volatilization degree of the low-volatile fuel FL becomes lower (the alcohol concentration becomes higher), the high-volatile fuel injection amount _QFH is slowly decreased and the low-volatile fuel injection amount _QFL is slowly increased. Like that. Similarly, as shown in FIG. 4, the decrease rate dQ _FH / dt and the increase rate dQ _FL / dt are made slower as the engine temperature is lower. That is, as the engine temperature decreases, the high volatile fuel injection amount Q _FH is slowly decreased and the low volatile fuel injection amount Q _FL is increased slowly.

Here, FIG. 4 shows a decrease rate dQ _FH / dt and an increase rate dQ _FL / dt depending only on the volatilization degree of the low-volatile fuel FL, or a decrease rate dQ _FH / dt and an increase rate only according to the engine temperature. dQ _FL / dt. Therefore, the decrease rate dQ _FH / dt and the increase rate dQ _FL / dt may be obtained from map data using either the degree of volatilization of the low-volatile fuel FL or the engine temperature as a parameter. Further, the reduction rate dQ _FH / dt and the increase rate dQ _FL / dt may be obtained from map data using both the volatilization degree of the low-volatile fuel FL and the engine temperature as parameters. The map data is set in advance based on the results of experiments or simulations in which low-volatile fuel FL having a different volatility is injected or the engine temperature is changed.

  The fuel injection ratio setting means in this case performs substantially the same arithmetic processing operation as the above-described example of FIG. 3 as shown in the flowchart of FIG. For this reason, the difference will be described below.

  When it is determined in step ST5 that a highly volatile fuel injection request has been made, the fuel injection ratio setting means acquires information on the degree of volatilization (alcohol concentration) of the low volatile fuel FL in the first fuel tank 41A. At the same time (step ST6), the engine temperature is detected (step ST7).

  In step ST6, for example, the alcohol concentration of the low-volatile fuel FL is read from a storage means such as a RAM. The alcohol concentration is estimated based on, for example, the detection value of the exhaust sensor 83 on the exhaust passage 81 (the oxygen concentration in the exhaust gas by the O2 sensor or the air-fuel ratio of the exhaust gas by the A / F sensor). This is an estimated value when only the first fuel supply means is driven during the engine operation (that is, only the low-volatile fuel FL is injected). Further, the alcohol concentration may be detected by an alcohol concentration sensor 55A disposed in the first fuel tank 41A, the first fuel passage 51A, etc. constituting the first fuel supply means, or may be acquired from fuel supply information or the like. Good.

Then, the fuel injection ratio setting means obtains and sets the reduction rate dQ _FH / dt and the increase rate dQ _FL / dt according to the degree of volatilization (alcohol concentration) of the low-volatile fuel FL and the engine temperature from the map data described above. (Step ST8). The decrease rate dQ _FH / dt and the increase rate dQ _FL / dt become slower as the volatilization degree of the low-volatile fuel FL is lower (the alcohol concentration is higher) and as the engine temperature is lower.

The fuel injection ratio setting means in this case sets the reduction rate dQ _FH / dt and the increase rate dQ _FL / dt in this way, and then proceeds to step ST10 described above to perform the same arithmetic processing as illustrated in FIG. I do.

As a result, when the volatility of the low-volatile fuel FL is low (the alcohol concentration is high) or the engine temperature is low, the high-volatile fuel injection amount Q _FH is slowly reduced while the low-volatile fuel injection amount Q _FL. Is slowly increased. Therefore, at that time, the rapid increase in the volatilization degree of the fuel (the alcohol concentration of the alcohol mixed fuel) in the combustion chamber CC composed of the high volatile fuel FH and the low volatile fuel FL can be suppressed. Can be started, and misfire after starting can be prevented, so that the startability of the internal combustion engine is not impaired.

On the other hand, when the alcohol concentration of the low volatile fuel FL is low or the engine temperature is high, the low volatile fuel injection amount _QFL is quickly increased while the high volatile fuel injection amount _QFH is rapidly decreased. Therefore, at that time, it is possible to more appropriately reduce the consumption of the highly volatile fuel (gasoline fuel) FH while ensuring the startability of the internal combustion engine.

As described above, the fuel injection control device in this case is capable of reducing the high volatile fuel injection amount Q _FH and reducing the low volatile fuel injection amount at an appropriate speed according to the alcohol concentration of the low volatile fuel FL and the engine temperature. Q _FL can be increased. For this reason, the fuel injection control device in this case can appropriately suppress the waste of the highly volatile fuel (gasoline fuel) FH that can be stored only in a small amount. Therefore, the fuel injection control device in this case can further improve the convenience of the user accompanying the decrease in the number of times of supplying the highly volatile fuel (gasoline fuel) FH while ensuring the startability of the internal combustion engine. It is also possible to appropriately avoid the situation where the engine cannot be started due to a shortage of highly volatile fuel (gasoline fuel) FH.

  Next, a second embodiment of the fuel injection control device according to the present invention will be described with reference to FIGS. The fuel injection control device of the second embodiment is prepared as a function of the electronic control device 1 as in the first embodiment. The same internal combustion engine as that to which the fuel injection control device is applied is exemplified as in the first embodiment.

Here, in the fuel injection control device of the first embodiment described above, the comparison determination of the intake air change amount ΔKLt and the operation state determination value α within the operation state determination time t1, the reduction of the highly volatile fuel FH, and the low volatile fuel A comparison determination is made between the intake air change amount ΔKL and the operating state determination value β while the FL increase is being executed, and if the intake air change amount ΔKLt is smaller than the operating state determination value α, the intake air When the change amount ΔKL is smaller than the operating state determination value β, it is determined that the operating state of the internal combustion engine is a metastable operating state. In this case, when the high-volatile fuel FH is being injected, the low-volatile fuel injection amount _QFL is increased while the high-volatile fuel injection amount QFH of the high-volatile fuel _FH is decreased. Is going. That is, when the injection of the highly volatile fuel FH is being executed, the highly volatile fuel injection amount Q _FH of the highly volatile fuel FH is decreased after the change in the intake air amount KL becomes smaller.

However, when the volatilization degree of the low-volatile fuel FL in the first fuel tank 41A is low (the alcohol concentration is high) or the engine temperature is low, a part of the intake port is injected by the injection of the low-volatile fuel FL. Since it adheres to the inner wall surface of 11b without evaporating, the total fuel injection amount of the high volatile fuel FH and the low volatile fuel FL is less than the target value and the output torque is reduced (in other words, the engine rotation Instability such as sluggish rise in number) and misfire. Therefore, such a case, even if the change in increase and decrease of the intake air amount KL was smaller, without executing the control according to the increase of the weight loss and low volatility fuel injection amount Q _FL highly volatile fuel injection amount Q _FH In addition, it is preferable to operate only with the highly volatile fuel FH.

  Therefore, the fuel injection control device of the second embodiment changes the operation state determination values α and β according to the volatilization degree (alcohol concentration) of the low-volatile fuel FL in the first fuel tank 41A and the engine temperature, The startability of the internal combustion engine is not impaired while suppressing waste of volatile fuel (gasoline fuel) FH.

  Specifically, the operating state determination values α and β are decreased as the volatilization degree of the low-volatile fuel FL decreases (the alcohol concentration increases) and as the engine temperature decreases. Thereby, in step ST15 and step ST40 of Example 1, the operation state of the internal combustion engine becomes more quasi as the volatilization degree of the low-volatile fuel FL becomes lower (the alcohol concentration becomes higher) and the engine temperature becomes lower. It is difficult to determine that the vehicle is in a stable operation state. That is, in the second embodiment, as the volatilization degree of the low-volatile fuel FL becomes lower (the alcohol concentration becomes higher) and the engine temperature becomes lower, the increase / decrease change in the intake air amount KL becomes smaller. Otherwise, it is not determined that the operating state of the internal combustion engine is a metastable operating state.

  The operating state determination values α and β may be obtained from map data using either the degree of volatilization of the low-volatile fuel FL or the engine temperature as a parameter. Alternatively, the operating state determination values α and β may be obtained from map data using both the volatilization degree of the low-volatile fuel FL and the engine temperature as parameters. The map data is set in advance based on the results of experiments or simulations in which low-volatile fuel FL having a different volatility is injected or the engine temperature is changed.

  Hereinafter, the calculation processing operation of the fuel injection control device (electronic control device 1) of the second embodiment will be described based on the flowchart of FIG.

  The fuel injection control device of the second embodiment may be based on the flowchart of FIG. 3 of the first embodiment described above, or may be based on the flowchart of FIG. 5 of the first embodiment. Here, an example based on FIG. 5 will be described. Therefore, the fuel injection ratio setting means of the electronic control unit 1 of the second embodiment performs substantially the same arithmetic processing operation as illustrated in FIG. For this reason, the difference will be mainly described below.

The fuel injection ratio setting means includes information on the degree of volatilization (alcohol concentration) of the low-volatile fuel FL in the first fuel tank 41A acquired in step ST6 when the high-volatile fuel injection request is made, and step The operating state determination values α and β corresponding to the engine temperature detected in ST7 are obtained from the map data described above and set (step ST9). The operating state determination values α and β become smaller as the degree of volatilization of the low-volatile fuel FL is lower (the alcohol concentration is higher) and as the engine temperature is lower. For example, as shown in FIG. 7, if the operation state determination value α _{al / th} is set when the volatility of the low-volatile fuel FL is high (the alcohol concentration is low) or the engine temperature is high, the low volatility When the volatilization degree of the fuel FL is low (the alcohol concentration is high) or the engine temperature is low, an operating state determination value α _{ah / tl} smaller than the operating state determination value α _{al / th} is set.

  The fuel injection ratio setting means in this case sets the operating state determination values α and β in this way, and then proceeds to step ST10 to perform the same arithmetic processing as illustrated in FIG. 5 (FIG. 3).

For example, it is assumed that the operation state determination value α _{al / th} when the degree of volatilization of the low-volatile fuel FL shown in the lower part of FIG. 7 is high (alcohol concentration is low) or when the engine temperature is high is a fixed value without change To do. In FIG. 7, it is assumed that the intake air change amount ΔKLt within the operation state determination time t1 is as shown in the lower diagram, that is, the intake air amount KL is increased during the operation state determination time t1. In the case of FIG. 7, since “ΔKLt <α _{al / th} ”, the operation state of the internal combustion engine is determined to be a metastable operation state in step ST15, and the high volatile fuel injection amount Q _FH is reduced. And the control which concerns on the increase in the low volatile fuel injection amount _QFL is performed. However, when the low-volatile fuel FL at that time has a low volatility (high alcohol concentration) or the engine temperature is low, the high-volatile fuel injection amount Q _FH is reduced as described above. And the increase in the low-volatile fuel injection amount _QFL deteriorates the startability of the internal combustion engine.

Here, in the second embodiment, when the degree of volatilization of the low-volatile fuel FL is low (the alcohol concentration is high) or when the engine temperature is low, the lower diagram of FIG. 7 shows the degree of volatility and the engine temperature. The operating state determination value α _{ah / tl} (<α _{al / th} ) is set in step ST9. Accordingly, in the second embodiment, since “ΔKLt> α _{ah / tl} ” as shown in the lower diagram of FIG. 7, the operating state of the internal combustion engine is determined to be a transient operating state in step ST15 and is highly volatile. control according to the increase of the weight loss and low volatility fuel injection amount Q _FL sexual fuel injection amount Q _FH is not executed.

Here, since the intake air amount KL is increased as described above, for example, the high volatile fuel injection amount Q _FH and the low volatile fuel injection amount Q _FL are set at the previous increase rate according to the increase amount. Increase the amount. For this reason, the high volatile fuel injection amount Q _FH is reduced when judged by the wrong value of the operating state judgment value α _{al / th} , but in the second embodiment, it is increased conversely. . Further, the low volatile fuel injection amount Q _FL gradually increases as compared with the case where it is determined based on the incorrect operation state determination value α _{al / th} . In other words, the fuel injection control device of the second embodiment reduces the high volatile fuel injection amount Q _FH when the volatility of the low volatile fuel FL is low (alcohol concentration is high) or when the engine temperature is low. When the startability of the internal combustion engine may deteriorate due to the above, it is determined that the engine is in a transient operation state instead of a metastable operation state, so the reduction in the highly volatile fuel injection amount Q _FH is stopped, A sufficient amount of the highly volatile fuel injection amount Q _FH can be ensured for realizing the engine start. Further, at that time, the increasing rate dQ _FL / dt of the low volatile fuel injection amount Q _FL can be kept low. Therefore, at that time, it is possible to suppress the adhesion of a part of the low volatile fuel FL to the inner wall surface of the intake port 11b, and it is possible to prevent a decrease in output torque and a misfire due to this.

As described above, the fuel injection control device according to the second embodiment changes the operating state determination values α and β to appropriate values according to the volatilization degree (alcohol concentration) of the low-volatile fuel FL and the engine temperature. In addition to the effect of the fuel injection control device of the first embodiment, it is possible to avoid the deterioration of the startability of the internal combustion engine due to the decrease in the highly volatile fuel injection amount _QFH . That is, the fuel injection control apparatus of the second embodiment ensures the convenience of the user accompanying the decrease in the number of refueling times of the highly volatile fuel (gasoline fuel) FH as in the first embodiment, and the low volatile fuel FL. The startability of the internal combustion engine according to the volatilization degree (alcohol concentration) and the engine temperature can be ensured more accurately.

  As described above, the fuel injection control device according to the present invention is useful for a technique for preventing waste of fuel (highly volatile fuel) used for starting an internal combustion engine while ensuring startability of the internal combustion engine.

It is a figure shown about an example of the internal combustion engine used as the application object of the fuel-injection control apparatus which concerns on this invention. It is a time chart which shows an example of the control of Example 1 which concerns on the reduction | decrease of the high volatile fuel injection amount, and the increase of the low volatile fuel injection amount. 3 is a flowchart for explaining an arithmetic processing operation of the fuel injection control apparatus according to the first embodiment. It is a time chart which shows an example of other controls of Example 1 concerning reduction of the high volatile fuel injection amount, and increase of the low volatile fuel injection amount. It is a flowchart explaining the other arithmetic processing operation of the fuel-injection control apparatus of Example 1. FIG. It is a flowchart explaining the arithmetic processing operation | movement of the fuel-injection control apparatus of Example 2. FIG. It is a time chart which shows a state when the operating state determination value is changed to an appropriate value according to the volatilization degree of low-volatile fuel and the engine temperature, and when the operating state determination value is set to an incorrect value.

Explanation of symbols

1 Electronic control device (fuel injection control device)
17 Water temperature sensor 41A First fuel tank 41B Second fuel tank 50 Fuel supply device 51A First fuel passage 51B Second fuel passage 54A, 54B Fuel injection valve 55A Alcohol concentration detection sensor 83 Exhaust sensor CC Combustion chamber dQ _FH / dt Decrease rate dQ _FL / dt Increase rate FH High volatile fuel FL Low volatile fuel Q _FH High volatile fuel injection amount Q _FL Low volatile fuel injection amount α, α _{ah / tl} , α _{al / th} , β Operating state judgment value ΔKL , ΔKLt Change in intake air

Claims (6)

A fuel injection ratio setting means for varying a fuel injection ratio between a highly volatile high volatile fuel stored in an individual fuel tank and a low volatile fuel less volatile than the high volatile fuel; and the fuel injection ratio In a fuel injection control device comprising: a fuel injection control means for injecting the high volatile fuel and the low volatile fuel;
The fuel injection ratio setting means is configured to reduce the fuel injection ratio of the low volatile fuel while gradually decreasing the fuel injection ratio of the high volatile fuel when the operation state of the internal combustion engine is in a metastable operation state when the engine is cold. A fuel injection control device configured to gradually increase an injection ratio.   2. The fuel injection according to claim 1, wherein the fuel injection ratio setting means is configured to slow down the rate of decrease in the fuel injection ratio of the high-volatile fuel as the volatility of the low-volatile fuel is lower. Control device.   3. The fuel according to claim 1, wherein the fuel injection ratio setting means is configured to slow down a decrease rate of the fuel injection ratio of the highly volatile fuel as the engine temperature of the internal combustion engine is lower. Injection control device.   The fuel injection ratio setting means determines that the operation state of the internal combustion engine is in a transient operation state when the engine is cold if the amount of change in intake air within a predetermined time is equal to or greater than a predetermined operation state determination value, If the amount of change in the intake air within a predetermined time is smaller than the operating state determination value, it is determined to be in the metastable operating state, and further, the lower the degree of volatilization of the low-volatile fuel, the lower the operating state determination value. The fuel injection control device according to claim 1, wherein the fuel injection control device is configured so as to reduce the fuel consumption.   5. The fuel injection control device according to claim 1, wherein the fuel injection ratio setting means is configured to decrease the operating state determination value as the engine temperature of the internal combustion engine decreases. .   The fuel according to any one of claims 1 to 5, wherein the low-volatile fuel is alcohol fuel or fuel mainly composed of alcohol fuel, and the high-volatile fuel is gasoline fuel. Injection control device.

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