JP2014109247A - Fuel supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress as much as possible the deterioration of a combustion state in a cylinder when (immediately after switching, particularly) switching from liquid fuel to gas fuel is performed, in a bi-fuel internal combustion engine.SOLUTION: A fuel control part (53) is arranged to control fuel injection operations in a liquid fuel injection valve (511) and a gas fuel injection valve (521), more in detail, to switch between fuel injection by the liquid fuel injection valve and fuel injection by the gas fuel injection valve. The injection control part comprises a fuel injection amount correcting part (534). The fuel injection correcting part corrects a decrease amount of an injection amount of the gas fuel in correction objective injection (fuel injection immediately after the switching from the liquid fuel to the gas fuel injection) more than normal injection (fuel injection after the correction objective injection).

Description

  The present invention relates to a fuel supply apparatus configured to be able to switch a fuel supplied into a cylinder of an internal combustion engine between a liquid fuel and a gaseous fuel.

  In recent years, gaseous fuel such as compressed natural gas (Compressed Natural Gas: hereinafter abbreviated as “CNG”) has attracted attention as a fuel for internal combustion engines from the viewpoint of reducing harmful components in exhaust gas. However, CNG has a lower energy density than liquid fuels such as gasoline and light oil. For this reason, the CNG internal combustion engine and a vehicle equipped with the same have a problem that the engine output becomes lower and the cruising distance becomes shorter than the liquid fuel internal combustion engine and the vehicle equipped with the same. At present, the number of locations where a general user of a vehicle can obtain gaseous fuel is small. For this reason, in a vehicle equipped with an internal combustion engine for gaseous fuel, there is a difficulty in moving over a long distance.

  Thus, a so-called bi-fuel internal combustion engine that can be used by switching between liquid fuel and gaseous fuel has been proposed (see, for example, Japanese Patent Laid-Open No. 7-34915). In such a bi-fuel internal combustion engine, the fuel supplied into the cylinder is appropriately switched between the liquid fuel and the gaseous fuel according to the operating state and the like. Thereby, the harmful components in the exhaust gas are reduced by using the gaseous fuel, and a high output and a sufficient cruising distance are ensured by using the liquid fuel.

JP 7-34915 A

  By the way, during the injection of the liquid fuel, the wall surface of the liquid fuel adheres to the intake passage (particularly in the cold state). For this reason, during the injection of liquid fuel (particularly when it is cold), an increase correction in consideration of wall surface adhesion may be performed on the fuel injection amount (see, for example, JP 2001-152924 A). ).

  In this regard, in the bi-fuel internal combustion engine, the liquid fuel adhered to the wall surface when the switching from the liquid fuel to the gaseous fuel is performed (particularly immediately after the switching) due to the influence of the wall surface adhesion and the increase correction as described above. When the gas is volatilized and sucked into the cylinder together with the gaseous fuel, there is a concern that the fuel mixture in the cylinder will be inadvertently rich and the combustion state will deteriorate. The present invention has been made to cope with such a problem.

  The fuel supply device which is the subject of the present invention is configured to be able to switch the fuel supplied into the cylinder of the internal combustion engine between liquid fuel and gaseous fuel. Here, the liquid fuel means a fuel in a liquid state at normal temperature and pressure (gasoline, light oil, dimethyl ether, alcohol, etc.). The gaseous fuel refers to a fuel in a gaseous state at normal temperature and pressure (CNG, liquefied natural gas, liquefied petroleum gas, hydrogen, etc.). The fuel supply device includes a liquid fuel injection valve, a gas fuel injection valve, and an injection control unit.

  The liquid fuel injection valve is provided so as to inject the liquid fuel in an intake port communicating with the cylinder. The gaseous fuel injection valve is provided so as to supply the gaseous fuel to the cylinder by injecting the gaseous fuel. More specifically, the injection control unit controls fuel injection operations in the liquid fuel injection valve and the gaseous fuel injection valve, and more specifically, fuel injection by the liquid fuel injection valve and fuel injection by the gaseous fuel injection valve. Is provided to switch between.

  The present invention is characterized in that the injection control unit includes a fuel injection amount correction unit. The fuel injection amount correction unit is provided to reduce and correct the fuel injection amount of the gaseous fuel in the correction target injection (injection of the gaseous fuel immediately after switching from the liquid fuel to the gaseous fuel). Specifically, for example, the fuel injection amount correction unit performs a decrease correction amount in the correction target injection according to an execution state of the increase correction during the injection of the liquid fuel by the liquid fuel injection valve in the cold state. May be configured to set.

  In the fuel supply apparatus of the present invention having such a configuration, the injection control unit supplies fuel to be supplied into the cylinder between the liquid fuel and the gaseous fuel according to an operating state of the internal combustion engine. To switch appropriately. Here, when the switching from the liquid fuel to the gaseous fuel is performed, the fuel injection amount correction unit sets the fuel injection amount of the gaseous fuel in the correction target injection at the normal time (in the same operation state). When the fuel injection is not the correction target injection), the amount of fuel is corrected to be reduced. Thereby, generation | occurrence | production of the deterioration of the combustion state (especially at the time of cold) by the fuel mixture in the said cylinder becoming rich carelessly can be suppressed favorably.

1 is a diagram showing a schematic configuration of an internal combustion engine to which an embodiment of the present invention is applied and its periphery. The time chart which shows the mode of the fuel injection performed with the fuel supply apparatus shown by FIG. The flowchart which shows the specific example of the fuel switching process performed by ECU shown by FIG. The flowchart which shows the specific example of the fuel-injection control performed by ECU shown by FIG. The flowchart which shows the specific example of the fuel-injection control performed by ECU shown by FIG. The figure which shows schematic structure of the modification of the fuel supply apparatus shown by FIG.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In addition, since a modification will prevent understanding of description of one consistent embodiment, if it is inserted during the description of the said embodiment, it is described collectively at the end.

<Apparatus Configuration of Embodiment>
Referring to FIG. 1, an internal combustion engine 10 to which the present embodiment is applied has a fuel supplied in a cylinder 11 provided therein between CNG as a gaseous fuel and gasoline as a liquid fuel. It is configured as a so-called bi-fuel engine that can be switched. Specifically, in the present embodiment, the internal combustion engine 10 has a plurality of (for example, four) cylinders 11 and generates the power for driving the drive wheels of the vehicle to rotate. It is mounted on. Hereinafter, first, the internal combustion engine 10 and the surrounding configuration will be described.

  A plurality of intake ports 12 and exhaust ports 13 are formed in the cylinder head of the internal combustion engine 10 so as to communicate with the cylinders 11. An intake port 12 and an exhaust port 13 are provided corresponding to each cylinder 11. The cylinder head in the internal combustion engine 10 is equipped with a plurality of intake valves 14 and an intake valve drive mechanism 15 for opening and closing these intake valves 14 at a predetermined timing. The intake valve 14 is provided to open and close the intake port 12 (switching between communication and non-communication between the cylinder 11 and the intake port 12). Similarly, the cylinder head in the internal combustion engine 10 is equipped with a plurality of exhaust valves 16 and an exhaust valve drive mechanism 17 for opening and closing these exhaust valves 16 at a predetermined timing. Further, a plurality of spark plugs 18 are attached to the cylinder head in the internal combustion engine 10. The spark plug 18 is provided corresponding to each cylinder 11, and generates a spark discharge for igniting the fuel mixture when a high voltage is applied at a predetermined timing via an ignition device including an ignition coil and the like. It occurs in the cylinder 11.

  Each cylinder 11 is connected to an intake passage 21 via an intake port 12. The intake passage 21 includes an intake pipe portion and an intake manifold branched from the intake pipe portion corresponding to each cylinder 11. A throttle valve 22 as a means for adjusting the intake air amount into the cylinder 11 is provided in the above-described intake pipe portion in the intake passage 21. The opening of the throttle valve 22 is adjusted by a throttle actuator 23 such as a DC motor.

  Each cylinder 11 is connected to an exhaust passage 31 through an exhaust port 13. The exhaust passage 31 includes an exhaust pipe portion and an exhaust manifold branched from the exhaust pipe portion corresponding to each cylinder 11. The exhaust pipe section described above is provided with a catalyst 32 for purifying CO, HC, NOx and the like in the exhaust.

<< Configuration of fuel supply device >>
Next, the configuration of the fuel supply device 50 that supplies fuel to each cylinder 11 in the internal combustion engine 10 will be described. The fuel supply device 50 is configured to be able to switch the fuel supplied into the cylinder 11 between gasoline and CNG. Specifically, the fuel supply device 50 includes a gasoline supply unit 51, a CNG supply unit 52, and an injection control unit 53.

  The gasoline supply unit 51 includes a gasoline injection valve 511, a gasoline pipe 512, a gasoline tank 513, and a feed pump 514. A plurality of gasoline injection valves 511 are provided corresponding to each cylinder 11. The gasoline injection valve 511 as the “liquid fuel injection valve” of the present invention is mounted in the vicinity of the intake port 12 so as to inject gasoline supplied via the gasoline pipe 512 into the intake port 12. Each gasoline injection valve 511 is connected via a gasoline pipe 512 to a gasoline tank 513 in which gasoline is stored. A feed pump 514 for sending gasoline to the gasoline pipe 512 is provided in the gasoline tank 513.

  The CNG supply unit 52 includes a CNG injection valve 521, a gas pipe 522, a gas tank 523, a regulator 524, a first cutoff valve 525, and a second cutoff valve 526. A plurality of CNG injection valves 521 are provided corresponding to each cylinder 11. In the present embodiment, the CNG injection valve 521 as the “gaseous fuel injection valve” of the present invention injects CNG supplied through the gas pipe 522 into the intake port 12, thereby causing CNG into the cylinder 11. It is mounted in the vicinity of the intake port 12 so as to supply. Each CNG injection valve 521 is connected to a gas tank 523 via a gas pipe 522. The gas tank 523 is filled with CNG in a high pressure state (for example, 20 MPa).

  A regulator 524 is attached to the gas pipe 522. The regulator 524 is a so-called pressure reducing valve, and the pressure of the CNG supplied to the CNG injection valve 521 (injection side supply pressure) is reduced from a high pressure state in the gas tank 523 to a predetermined supply pressure. (For example, 0.4 MPa). A first shut-off valve 525 is attached to a connection portion between the gas tank 523 and the gas pipe 522. Similarly, a second shut-off valve 526 is attached to a connection portion between the regulator 524 and the gas pipe 522. The first shut-off valve 525 and the second shut-off valve 526 are normally closed electromagnetically driven valves that shut off the flow of the CNG fuel in the gas passage when not energized, while the CNG fuel in the gas passage when energized. It allows to flow.

  The injection control unit 53 selectively performs gasoline injection by the gasoline injection valve 511 and CNG injection by the CNG injection valve 521 (that is, only one of the injections for the same intake stroke in one cylinder 11 is performed). It is provided to control the fuel injection operation in the gasoline injection valve 511 and the CNG injection valve 521. Specifically, the injection control unit 53 includes an ECU 530 mainly composed of a microcomputer 531 including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The ECU 530 includes an interface and the like in addition to the microcomputer 531. The interface is a signal between the microcomputer 531 and various operation units (throttle actuator 23, gasoline injection valve 511, CNG injection valve 521, etc.) outside the ECU 530, sensors, switches, and the like described later. It is set up as an intermediary. The microcomputer 531 executes various control programs (control routines) stored in the ROM to calculate the fuel injection amount, the ignition timing, and the like based on inputs from various sensors described later, and the calculation results Based on this, a drive control signal for controlling the drive of the various operation units described above is output.

  In the microcomputer 531 in FIG. 1, functional blocks constructed on the microcomputer 531 by executing the above-described control program are shown. As shown in FIG. 1, in this embodiment, the microcomputer 531 includes a switching command output unit 532, a used fuel determination unit 533, a fuel injection amount correction unit 534, an injection timing setting unit 535, An injection signal output unit 536. Further, the fuel supply device 50 includes a throttle opening sensor 541, an intake pressure sensor 542, a crank position sensor 543, a cam position sensor 544, a cooling water temperature sensor 545, a first pressure sensor 546, and a second pressure sensor 547. And switches including a fuel selection switch 548 are provided.

  The switching command output unit 532 is provided so as to output a switching command signal based on the output signals from the sensors and switches described above. Here, the “switch command signal” is a signal for switching between gasoline injection by the gasoline injection valve 511 and CNG injection by the CNG injection valve 521. In other words, this switching command signal is output to switch the fuel supplied into the cylinder 11 (in this embodiment, there are two modes of switching from gasoline to CNG and switching from CNG to gasoline). Signal.

  The used fuel determination unit 533 switches between the gasoline injection command signal and the CNG injection command signal based on the output of the switching command signal from the switching command output unit 532, and the fuel injection amount correction unit 534, the injection timing setting unit 535, and It is provided to output toward the injection signal output unit 536. Here, the “gasoline injection command signal” is a signal output toward the injection signal output unit 536 or the like in order to inject gasoline with the gasoline injection valve 511. On the other hand, the “CNG injection command signal” is a signal output toward the injection signal output unit 536 or the like in order to inject CNG by the CNG injection valve 521. That is, the used fuel determination unit 533 selects (determines) the fuel to be supplied into the cylinder 11 between gasoline and CNG based on the output of the switching command signal from the switching command output unit 532. .

  The fuel injection amount correcting unit 534 includes an output signal (gasoline injection command signal or CNG injection command signal: the same applies hereinafter) from the fuel used determining unit 533 and output signals from sensors including the throttle opening sensor 541 and the like described above. Based on the above, a correction amount for a basic fuel injection amount in gasoline or CNG fuel injection (which is set according to an operating state by other means included in the ECU 530) is set (calculated) and output. It has become. In particular, in the present embodiment, the fuel injection amount correction unit 534 includes the CNG injection immediately after the output from the used fuel determination unit 533 is switched from the gasoline injection command signal to the CNG injection command signal (after switching to each cylinder 11). The reduction correction amount used for the correction target injection that is the first CNG injection) is set. This reduction correction amount is a correction for reducing the fuel injection amount in the above-described correction target injection in accordance with the gasoline injection situation (specifically, the state of gasoline adhering to the inner wall surface of the intake port 12) up to that point. Amount. Details of the setting of the reduction correction amount will be described later.

  The injection timing setting unit 535 sets the timing of fuel injection in the gasoline injection valve 511 and the CNG injection valve 521 based on the output signal from the used fuel determination unit 533 and the output signal from the sensors. Is provided.

  The injection signal output unit 536 sets the basic fuel injection amount, the correction amount set by the fuel injection amount correction unit 534, and the injection timing setting unit 535 when the gasoline injection command signal is received from the used fuel determination unit 533. A gasoline injection signal having a predetermined timing and a pulse width is output to the gasoline injection valve 511 based on the fuel injection timing. Similarly, the injection signal output unit 536 receives the basic fuel injection amount, the correction amount set by the fuel injection amount correction unit 534, and the injection timing setting unit when the CNG injection command signal is received from the used fuel determination unit 533. Based on the fuel injection timing set by 535, a CNG injection signal having a predetermined timing and a pulse width is output to the CNG injection valve 521.

  The throttle opening sensor 541 is a sensor that generates an output corresponding to the opening (throttle opening) of the throttle valve 22 and is built in the throttle actuator 23. The intake pressure sensor 542 is a sensor that generates an output corresponding to the intake pipe pressure, and is attached to the intake pipe portion of the intake passage 21 on the downstream side of the throttle valve 22 in the intake flow direction. The crank position sensor 543 has a signal used for calculation (detection) of the engine rotational speed, specifically, a narrow pulse every time the crankshaft rotates 10 degrees and every time the crankshaft rotates 360 degrees. A signal having a wide pulse is output. The cam position sensor 544 generates a signal (G2 signal) having one pulse every time the intake camshaft included in the intake valve drive mechanism 15 rotates 90 degrees (that is, every time the crankshaft rotates 180 degrees). It is supposed to be. The coolant temperature sensor 545 is attached to the cylinder block so as to generate an output corresponding to the temperature of the coolant flowing through the cylinder block in the internal combustion engine 10.

  The first pressure sensor 546 is mounted in the vicinity of a connection portion between the regulator 524 and the gas pipe 522 (on the gas tank 523 side with respect to the regulator 524) so as to generate an output corresponding to the fuel pressure upstream of the regulator 524. The second pressure sensor 547 is mounted in the vicinity of the connection between the CNG injection valve 521 and the gas pipe 522 so as to generate an output corresponding to the fuel pressure downstream of the regulator 524 (that is, the above-described injection-side supply pressure). Yes. The fuel selection switch 548 is operated so that the driver of the vehicle equipped with the internal combustion engine 10 can select the fuel used for the operation of the internal combustion engine 10 (supply to the cylinder 11 and combustion in the cylinder 11). It can be operated by a person.

<Description of operation>
The operation (action / effect) according to the configuration of the present embodiment will be described below.

  The injection signal output unit 536 responds to the output signal from the fuel determination unit 533 (output signal for defining the fuel type to be injected this time: gasoline injection command signal or CNG injection command signal), the output signal, and the like. Based on the fuel injection timing set by the injection timing setting unit 535 and the correction amount appropriately set by the fuel injection amount correction unit 534 (including the normal air-fuel ratio feedback correction amount and the like), the gasoline injection valve 511 or An injection signal (the aforementioned gasoline injection signal or CNG injection signal) having a predetermined timing and a pulse width is output to the CNG injection valve 521. Thus, the gasoline injection valve 511 or the CNG injection valve 521 is driven based on the injection signal, and a desired fuel is injected at a desired amount and timing and supplied into the cylinder 11. Also in this embodiment, gasoline injection is performed at the time of start-up (particularly during cold start) as in a known device of this kind (Japanese Patent Laid-Open Nos. 11-324749 and 2003-206772). (See Japanese Laid-Open Patent Publication No. 2004-211161, etc.).

  When an event that causes a fuel switching request (for example, a change in operating state or an operation of the fuel selection switch 548 by the driver) occurs, the switching command output unit 532 appropriately outputs a switching command signal. That is, the switching command output unit 532 outputs a switching command signal based on the output signals from the sensors and the fuel selection switch 548. When the switching command signal is output from the switching command output unit 532, the fuel use determining unit 533 receives the switching command signal and, after a predetermined time elapses, the fuel injection amount correction unit 534, the injection timing setting unit 535, and the injection The output signal for the signal output unit 536 is switched between the gasoline injection command signal and the CNG injection command signal. By this switching, the gasoline injection by the gasoline injection valve 511 and the CNG injection by the CNG injection valve 521 are switched.

  Here, when the switching from gasoline to CNG is performed, there is a concern that the fuel mixture in the cylinder 11 will inadvertently become rich and the combustion state will deteriorate unless special fuel injection amount correction associated with such switching is performed. is there. Such enrichment occurs when volatilized gasoline is introduced into the cylinder 11 immediately after switching to CNG due to volatilization of adhering gasoline on the inner wall surface of the intake port 12 in addition to a predetermined amount of CNG. In particular, when cold, gasoline adheres to the inner wall surface of the intake port 12 significantly. Therefore, when switching to the CNG injection through the gasoline injection during the cold time (more specifically, during the cold start), the fear of the above-described combustion deterioration increases.

  Therefore, in the present embodiment, the fuel injection amount correction unit 534 is the correction target described above, which is CNG injection immediately after switching from gasoline to CNG (CNG injection corresponding to the intake stroke in the first cylinder 11 after switching). The CNG injection amount in the injection is corrected to be smaller than that in the normal state (when the CNG injection is not the correction target injection in the same operation state). Thereby, it is possible to satisfactorily suppress the occurrence of deterioration of the combustion state (particularly during cold, more specifically during cold start) due to the fuel mixture in the cylinder 11 being inadvertently rich.

  That is, in the present embodiment, the fuel injection amount correction unit 534, when the output from the used fuel determination unit 533 is switched from the gasoline injection command signal to the CNG injection command signal, The amount of reduction correction according to the gasoline adhering state on the inner wall surface of the intake port 12 is set. Specifically, the fuel injection amount correction unit 534 performs a decrease correction amount in accordance with an execution state of increase correction during gasoline injection by the gasoline injection valve 511 during cold weather (more specifically, an integrated value of the increase correction). Set. Then, the fuel injection amount correction unit 534 uses the set reduction correction amount to set the normal injection amount in the correction target injection (when it is assumed that the CNG injection is not the correction target injection in the same operation state). The injection amount is corrected.

  The state of fuel injection at the time of switching will be described in more detail using the time chart of FIG. For ease of explanation, FIG. 2 shows an example of fuel switching by operating the fuel selection switch 548. In the figure, the horizontal axis indicates the passage of time.

  When the fuel selection switch 548 is operated from the liquid fuel (gasoline) side to the gaseous fuel (CNG) side at time t1, the switching is possible (for example, the remaining amount of CNG in the gas tank 523 is sufficient). In the case), a switching command signal is output. Then, the fuel is actually switched from gasoline to CNG at time t2 after a predetermined time has elapsed from time t1.

  Here, in the present embodiment, as shown in FIG. 2, the fuel injection amount is corrected to decrease in the correction target injection that is the CNG injection immediately after time t2. Thereby, as described above, the occurrence of the deterioration of the combustion state in the cylinder 11 immediately after switching from gasoline to CNG is suppressed as much as possible.

  A specific example of the operation procedure will be described with reference to the flowcharts of FIGS. Each routine shown in these flowcharts is executed at predetermined timings (for example, every 4 msec or every predetermined crank angle) by the microcomputer 531 provided in the ECU 530. In the figure, “S” indicates “step”.

  In the fuel switching routine shown in FIG. 3, first, at step 310, it is determined whether or not a fuel switching request has been made by the switching command output unit 532 (at this stage, the switching command signal has not been output yet). Absent). This fuel switching request is generated based on output signals from the sensors and the fuel selection switch 548 described above. When the fuel switching request has not occurred (step 310 = NO), the processing after step 320 is skipped, and this routine ends.

  If a fuel switching request has occurred (step 310 = YES), the process proceeds to step 320. In step 320, it is determined whether or not fuel switching is permitted. That is, for example, even if there is a fuel switching request, switching should not be performed when the remaining amount of fuel to be switched is small or when the fuel supply system to be switched is abnormal. Therefore, when the fuel switching is not permitted (step 320 = NO), the processing after step 330 is skipped, and this routine ends.

  When switching of fuel is permitted (step 320 = YES), a switching command signal is output from the switching command output unit 532, and the process proceeds to step 330 and subsequent steps. In step 330, it is determined whether or not the current fuel switching is from liquid fuel to gaseous fuel. If the current fuel switching is from liquid fuel to gaseous fuel (step 330 = YES), the process proceeds to step 340, and the switching correction flag is set. On the other hand, when the current fuel switching is from gas fuel to liquid fuel (step 330 = NO), the process of step 340 is skipped.

  In this way, after the flag processing according to the determination result in step 330 (that is, the fuel switching mode) is performed, the processing proceeds to step 350 where the fuel switching (the output from the used fuel determining unit 533) (Switching between the gasoline injection command signal and the CNG injection command signal) is executed, and this routine ends.

  The liquid fuel injection control routine shown in FIG. 4 is started at every predetermined timing described above when the fuel used in the current fuel injection is liquid fuel (gasoline). In this routine, first, in step 410, an operation state parameter (engine speed, etc.), which is a control parameter representing the current operation state, is acquired based on the outputs from the above-described sensors and switches. Next, in step 420, the basic fuel injection amount and the basic injection timing (set by the injection timing setting unit 535; the same applies hereinafter) are set based on the operating state parameter acquired in step 420. The Thereafter, the process proceeds to step 430.

  In step 430, it is determined based on the operation state parameter acquired in step 420 whether or not the current operation state is cold. Specifically, in step 430, the microcomputer 531 determines whether or not the coolant temperature acquired (detected) based on the output of the coolant temperature sensor 545 is equal to or lower than a predetermined threshold temperature. If the current operating state is cold (step 430 = YES), the process proceeds to steps 440-460. On the other hand, if the current operating state is not cold (step 430 = NO), the process proceeds to step 480.

  In step 440, based on the operation state parameter acquired in step 420 and a map (look-up table) stored in advance in the ROM of the microcomputer 531, the cold increase correction amount (the intake air during the cold state). A gasoline injection increase correction amount in consideration of gasoline adhesion to the inner wall surface of the port 12 is set. Such cold increase correction is already well known at the time of filing of the present application as described above, and therefore, detailed description thereof is omitted. Next, in step 450, integration of the cold increase correction amount is performed. That is, the cold increase correction amount set this time is added to the integrated value up to the previous execution time of this routine. In step 460, the above-described basic fuel injection amount is corrected using the currently set cold increase correction amount (note that the normal air-fuel ratio feedback correction value is also used in this step as necessary. It is reflected together.) On the other hand, in step 480, the basic fuel injection amount is corrected using a normal air-fuel ratio feedback correction value.

  In this manner, after the correction for the basic fuel injection amount is appropriately performed, the process proceeds to step 490. In step 490, the gasoline injection valve 511 controls the driving of the gasoline injection valve 511 based on the fuel injection amount acquired through the correction process in step 460 or 480, so that a desired amount of gasoline is injected. Thereafter, this routine ends.

  The gaseous fuel injection control routine shown in FIG. 5 is started at every predetermined timing described above when the fuel used in the current fuel injection is gaseous fuel (CNG). In this routine, first, in step 510, an operation state parameter (engine speed, etc.), which is a control parameter representing the current operation state, is acquired based on the outputs from the above-described sensors and switches. Next, in step 520, the basic fuel injection amount and the basic injection timing are set based on the operation state parameter acquired in step 520. Thereafter, the process proceeds to step 530.

  In step 530, it is determined based on the setting state of the correction flag at the time of switching whether or not the current gaseous fuel injection is the above-described correction target injection. When the switching correction flag is set (step 530 = YES), the process proceeds to steps 540 to 560 (570). On the other hand, when the switching correction flag is reset (step 530 = NO), the process proceeds to step 580.

  In step 540, a reduction correction amount for the CNG injection amount is set according to the state of adhesion of gasoline on the inner wall surface of the intake port 12. Specifically, in step 540, the microcomputer 531 corrects the decrease based on the integrated value of the cold increase correction amount described above and a map (lookup table) stored in advance in the ROM of the microcomputer 531. Set the amount. Next, in step 550, the above-described basic fuel injection amount is corrected using the above-described reduction correction amount (note that the normal air-fuel ratio feedback correction value is also reflected in this step as necessary. ) That is, in step 550, the injection amount correction using the above-described reduction correction amount is further performed on the normal injection amount (the basic fuel injection amount or the fuel injection amount corrected by the normal air-fuel ratio feedback correction value). .

  In the following step 560, it is determined whether or not the correction target injection is completed. Here, in the present embodiment, the correction target injection is performed once in each cylinder 11. For this reason, when the correction target injection is executed once for each cylinder 11 (step 560 = YES), the process proceeds to step 570, and the switching correction flag is reset. At this time, the integrated value of the above-mentioned cold increase correction amount is also reset. On the other hand, when the correction target injection has not been executed once in each cylinder 11 (step 560 = NO), the process of step 570 is skipped.

  If the current gaseous fuel injection is not the correction target injection described above (step 530 = NO), in step 580, normal fuel injection correction (normal air-fuel ratio feedback correction) is performed.

  In this manner, after the correction for the basic fuel injection amount is appropriately performed, the process proceeds to step 590. In step 590, the drive of the CNG injection valve 521 is controlled based on the fuel injection amount acquired through the correction processing in step 550 or 580, so that a desired amount of CNG is injected by the CNG injection valve 521. Thereafter, this routine ends.

<Modification>
Hereinafter, some typical modifications will be exemplified. In the following description of the modified examples, the same reference numerals as those in the above embodiment can be used for portions having the same configurations and functions as those described in the above embodiment. And about description of this part, the description in the above-mentioned embodiment shall be used suitably in the range which is not technically consistent. Needless to say, the modifications are not limited to those listed below. In addition, a part of the above-described embodiment and all or a part of the plurality of modified examples can be combined appropriately as long as they are technically consistent.

  The present invention is not limited to the specific apparatus configuration described above. That is, for example, as shown in FIG. 6, the CNG injection valve 521 may be mounted on the internal combustion engine 10 so as to inject gaseous fuel directly into the cylinder 11. Further, the number of cylinders 11 and the number of CNG injection valves 521 are not particularly limited.

  The present invention is not limited to the specific processing mode described above. That is, for example, the switching command signal may be an instruction (command) or a flag setting. The calculation of the correction amount may be acquisition using a map (lookup table), or may be calculation by a predetermined calculation formula (calculation program). Further, the map storage location may be other than ROM (for example, backup RAM). The “backup RAM” is a non-volatile memory that stores data and the like so as to be rewritable during power supply and retains the data and the like even when power supply is stopped, such as a flash ROM, an EEPROM (registered trademark), or the like. Corresponds to this.

  The correction target injection is the first injection of the fuel after switching to each cylinder 11 (the intake stroke in each cylinder 11 after the output from the fuel determining unit 533 is switched from the gasoline injection command signal to the CNG injection command signal). The fuel injection is not limited to the above. That is, for example, the correction target injection may be performed until the intake stroke in each cylinder 11 arrives several times after the output from the used fuel determination unit 533 is switched from the gasoline injection command signal to the CNG injection command signal. .

  When setting (calculating) the reduction correction amount, a well-known fuel adhesion model (Japanese Patent Laid-Open No. 7-139393) is used in place of the integrated value of the increase correction amount during cold (particularly during cold start) as described above. (See Japanese Laid-Open Patent Publication No. 11-223145, Japanese Unexamined Patent Application Publication No. 2003-97304, etc.).

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder, 12 ... Intake port, 50 ... Fuel supply device, 53 ... Injection control part, 511 ... Gasoline injection valve, 521 ... CNG injection valve, 534 ... Fuel injection amount correction | amendment part.

Claims (2)

A fuel supply device (50) configured to be able to switch a fuel supplied into a cylinder (11) of an internal combustion engine (10) between a liquid fuel and a gaseous fuel,
A liquid fuel injection valve (511) provided to inject the liquid fuel in an intake port (12) communicating with the cylinder;
A gaseous fuel injection valve (521) provided to inject the gaseous fuel to supply the gaseous fuel to the cylinder;
An injection control unit (53) for controlling a fuel injection operation in the liquid fuel injection valve and the gaseous fuel injection valve so as to switch between fuel injection by the liquid fuel injection valve and fuel injection by the gaseous fuel injection valve;
With
The injection control unit
A fuel injection amount correction unit (534) is provided so as to correct the fuel injection amount of the gaseous fuel in a correction target injection that is a fuel injection immediately after switching from the liquid fuel to the gaseous fuel. A fuel supply device characterized by that. The fuel supply device according to claim 1,
The fuel injection amount correction unit sets a decrease correction amount in the correction target injection according to an execution state of the increase correction during the injection of the liquid fuel by the liquid fuel injection valve in the cold state. A fuel supply device.

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