JP2014132171A - Fuel supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome a problem of the occurrence of output reduction and the like due to the shortage of a fuel amount in cylinders when liquid fuel is switched to/from gas fuel (particularly right after switching) in a bi-fuel internal combustion engine.SOLUTION: An injection control unit (53) is provided so as to control fuel injection operations of a liquid fuel injection valve (511) and a gas fuel injection valve (521), more specifically, so as to switch the fuel injection by the liquid fuel injection valve to/from the fuel injection by the gas fuel injection valve. This injection control unit includes an injection-timing change portion (535). The injection-timing change portion is provided so that fuel injection timing of correction target injection (fuel injection right after the switching between the liquid fuel and the gas fuel) advances over that of normal injection (fuel injection after the corrected target 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

  In the bi-fuel internal combustion engine as described above, when switching between liquid fuel and gaseous fuel is performed (especially immediately after switching), there is a concern that the output of the fuel may be reduced due to a shortage of fuel in the cylinder. There is. The shortage of the fuel amount at the time of switching is caused by a delay in transportation of the fuel supply system, wall surface adhesion in the intake passage (which occurs in liquid fuel but not in gaseous fuel), and the like. 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 an injection timing changing unit. The injection timing changing unit sets the fuel injection timing in the correction target injection (fuel injection immediately after switching between the liquid fuel and the gaseous fuel) rather than the normal injection (fuel injection after the correction target injection). It is provided to advance.

  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. At this time, the injection timing changing unit advances the fuel injection timing in the correction target injection more than the normal injection. That is, the timing of fuel injection in the correction target injection immediately after switching between the liquid fuel and the gaseous fuel is made earlier than usual. As a result, when the fuel is switched (especially immediately after the switching), the shortage of the fuel amount in the cylinder is satisfactorily suppressed.

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 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-injection control performed by ECU 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). The fuel injection operation in the gasoline injection valve 511 and the CNG injection valve 521 is controlled (switching between fuel injection by the gasoline injection valve 511 and fuel injection by 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 stored in the ROM to calculate the fuel injection amount, ignition timing, and the like based on inputs from various sensors described later, and based on the calculation results, A drive control signal for controlling the drive of the various operation units 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 fuel determination unit 533, an injection timing setting unit 535, and an injection signal output unit 536. I have. 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. That is, this switching command signal is output to switch the fuel supplied into the cylinder 11 (in this embodiment, there are two switching modes, 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 on the basis of the output of the switching command signal from the switching command output unit 532, toward the injection timing setting unit 535 and the injection signal output unit 536. It is provided to output. Here, the “gasoline injection command signal” is a signal output toward the injection timing setting unit 535 and the injection signal output unit 536 in order to inject gasoline with the gasoline injection valve 511. On the other hand, the “CNG injection command signal” is a signal that is output toward the injection timing setting unit 535 and the injection signal output unit 536 in order to cause the CNG injection valve 521 to inject CNG. 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 injection timing setting unit 535 constituting the “injection timing changing unit” of the present invention includes an output signal (gasoline injection command signal or CNG injection command signal) from the used fuel determination unit 533, an output signal from the above-described sensors, The fuel injection timing in the gasoline injection valve 511 and the CNG injection valve 521 is set based on the above. In particular, in the present embodiment, the injection timing setting unit 535 performs the fuel injection immediately after the output from the used fuel determination unit 533 is switched between the gasoline injection command signal and the CNG injection command signal (switching for each cylinder 11). The correction amount at the time of switching is calculated to advance the fuel injection timing in the correction target injection that is the first injection of the subsequent fuel from the normal (that is, normal injection that is the fuel injection after the correction target injection). It is provided to do. Details of the calculation of the switching correction amount will be described later.

  When the injection signal output unit 536 receives a gasoline injection command signal from the used fuel determination unit 533, the fuel injection amount (this is set according to the operating state by other means included in the ECU 530: the same applies hereinafter). Based on the fuel injection timing set by the injection timing setting unit 535, a gasoline injection signal having a predetermined timing and a pulse width is output to the gasoline injection valve 511. Similarly, when the injection signal output unit 536 receives a CNG injection command signal from the used fuel determination unit 533, the injection signal output unit 536 performs CNG based on the fuel injection amount and the fuel injection timing set by the injection timing setting unit 535. A CNG injection signal having a predetermined timing and a pulse width is output to the 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 of the engine speed, specifically, a narrow pulse every time the crankshaft rotates 10 degrees and a wide pulse every time the crankshaft rotates 360 degrees. 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 uses the gasoline injection valve 511 or the CNG injection based on the output signal from the used fuel determination unit 533 and the fuel injection timing set by the injection timing setting unit 535 according to the output signal or the like. An injection signal (the above-described gasoline injection signal or CNG injection signal) is output to the valve 521. Thus, the gasoline injection valve 511 or the CNG injection valve 521 is driven based on the injection signal, and desired fuel is injected at a desired timing and supplied into the cylinder 11.

  Here, 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 a switching command signal is output from the switching command output unit 532, the fuel use determination unit 533 outputs output signals to the injection timing setting unit 535 and the injection signal output unit 536 after a predetermined time has elapsed after receiving the switching command signal. And switching 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.

  In this way, when the gasoline injection by the gasoline injection valve 511 and the CNG injection by the CNG injection valve 521 are switched, the injection timing setting unit 535 sets the fuel injection timing in the correction target injection described above from the normal injection. Also advance. That is, the timing of fuel injection in the correction target injection, which is fuel injection immediately after switching between gasoline injection and CNG injection (fuel injection corresponding to the first intake stroke in each cylinder 11 after switching), Be faster than usual. Thereby, the occurrence of a shortage of the fuel amount in the cylinder 11 when the fuel is switched (particularly immediately after the switching) is satisfactorily suppressed.

  Specifically, in the present embodiment, the injection timing setting unit 535 determines the basic injection timing based on the current used fuel (determined by a signal received from the used fuel determining unit 533) and the operating state. (Fuel injection timing assuming normal injection) is calculated. Further, the injection timing setting unit 535 is configured to switch the fuel (that is, triggered by the output of the switching command signal from the switching command output unit 532) based on the operating state parameter such as the engine speed and the fuel injection amount. The above-mentioned switching correction amount is calculated. Then, when the current fuel injection is the correction target injection, the injection timing setting unit 535 corrects the fuel injection timing of the correction target injection by correcting the basic injection timing by the correction amount at the time of switching.

  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, and in the “fuel injection timing”, the upper side indicates the advance side (the lower side indicates the retard side).

  When the fuel selection switch 548 is operated from the gaseous fuel (CNG) side to the liquid fuel (gasoline) side at the time t1, the switching is possible (for example, the remaining amount of gasoline in the gasoline tank 513 is sufficient). In some cases, a switching command signal is output. Then, the fuel is actually switched from CNG to gasoline at time t2 after a predetermined time has elapsed from time t1. Similarly, when the fuel selection switch 548 is operated from the liquid fuel (gasoline) side to the gaseous fuel (CNG) side at time t3, a switching command signal is output when switching is possible. Then, at time t4 after a predetermined time has elapsed from time t3, the fuel is actually switched from gasoline to CNG.

  In this embodiment, as shown in FIG. 2, the fuel injection timing is advanced by the correction target injection immediately after time t2 (that is, the fuel supply timing to each cylinder 11 is adjusted). Will be faster than usual). Thereby, the occurrence of a shortage of fuel in the cylinder 11 immediately after switching is suppressed as much as possible. In particular, in the present embodiment, the fuel injection correction for suppressing the shortage of the fuel amount in the cylinder 11 immediately after switching performs the fuel injection in the gasoline injection valve 511 and the fuel injection in the CNG injection valve 521 at the same time. Done without. Therefore, it is possible to perform good injection control while suppressing an increase in control load and adaptation man-hours as much as possible.

  Similarly, also in the correction target injection immediately after time t4, the advance correction of the fuel injection timing is executed. In addition, when the injection timing correction is not performed, the cause of the shortage of the fuel amount in the cylinder 11 that occurs when the switching between the liquid fuel and the gaseous fuel is performed is the switching of the gaseous fuel to the liquid fuel. The case differs from the case of switching from liquid fuel to gaseous fuel. For this reason, the injection timing advance amount at the time of switching from the gas fuel to the liquid fuel and the injection timing advance amount at the time of the switching from the liquid fuel to the gas fuel are the above-mentioned even under the condition where the operation state is constant. Different due to the difference.

  A specific example of the operation procedure will be described with reference to the flowcharts of FIGS. Each routine shown in this flowchart is executed by the microcomputer 531 provided in the ECU 530 at every predetermined timing (for example, every 4 msec or every predetermined crank angle). 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. When the current fuel switching is from liquid fuel to gaseous fuel (step 330 = YES), the process proceeds to step 340, and a switching correction flag (liquid to gas switching) is set. On the other hand, if the current fuel switching is from gas fuel to liquid fuel (step 330 = NO), the process proceeds to step 345, and a switching correction flag (at the time of gas-to-liquid switching) is set.

  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.

  In the fuel injection control routine shown in FIG. 4, first, at step 410, the fuel used in the current fuel injection (whether it is gasoline or CNG) is based on the output from the used fuel determining unit 533. Is obtained. Next, in step 420, an operation state parameter (engine speed, etc.), which is a control parameter representing the current operation state, is acquired based on outputs from the above-described sensors and switches. Subsequently, in step 430, the above-described fuel injection amount and basic injection timing are calculated based on the operation state parameter acquired in step 420. Thereafter, the process proceeds to step 440.

  In step 440, whether or not the current fuel injection is a correction target injection is determined based on the setting state of each flag described above. When the current fuel injection is the correction target injection (step 440 = YES), the process proceeds to steps 450 to 470 and the correction process at the time of switching is executed, whereas the current fuel injection is not the correction target injection. In (Step 440 = NO), the process proceeds to Step 480, and a predetermined correction process during normal injection is performed as necessary.

  Hereinafter, the case where the current fuel injection is the correction target injection (step 440 = YES) will be described in detail. First, in step 450, the switching correction amount is calculated, and the basic injection timing is calculated based on the switching correction amount. Is corrected. In the present embodiment, the switching correction amount is calculated (determined) based on a map (look-up table) using the engine speed and the fuel injection amount as parameters. Next, in step 460, it is determined whether or not the switching correction 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 in each cylinder 11 (step 460 = YES), the process proceeds to step 470, and the switching correction flag is reset. On the other hand, when the correction target injection has not been executed once in each cylinder 11 (step 460 = NO), the process of step 470 is skipped.

  As described above, after an appropriate process is performed according to whether or not the current fuel injection is a correction target injection, the process proceeds to step 490. In step 490, fuel injection is executed at an appropriate amount and timing by driving the gasoline injection valve 511 or the CNG injection valve 521 based on the injection signal appropriately set by each process prior to step 490. 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, 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).

  The correction target injection is the first injection of the fuel after switching to each cylinder 11 (the first cylinder 11 after the output from the fuel determining unit 533 is switched between the gasoline injection command signal and the CNG injection command signal). The fuel injection is not limited to the intake stroke at (1). That is, for example, the correction target injection is performed until the intake stroke in each cylinder 11 arrives several times after the output from the used fuel determination unit 533 is switched between the gasoline injection command signal and the CNG injection command signal. May be.

  The regulator 524 may be a so-called “variable pressure regulator” in which the injection side supply pressure (the pressure of CNG supplied to the CNG injection valve 521) is variably configured. In such a configuration, the injection side supply pressure, that is, the fuel pressure, may be corrected to the rising side in the correction target injection at the time of switching from the liquid fuel to the gaseous fuel. Specifically, in this case, the fuel pressure in the correction target injection is set to be higher than the fuel pressure in normal injection after the correction target injection.

  That is, as shown in FIG. 5, when the fuel selection switch 548 is operated from the liquid fuel (gasoline) side to the gaseous fuel (CNG) side at time t5, switching is possible. A switching command signal is output. Then, at time t6 after a predetermined time has elapsed from time t5, the fuel is actually switched from gasoline to CNG.

  In this case, first, the injection side supply pressure is set to a relatively high pressure for correction target injection (step 610). The setting (correction) of the injection side supply pressure is started at time t5. Next, the injection pulse width for the correction target injection is set (step 620). Here, it is assumed that the flowchart of FIG. 6 is described as a subroutine executed in the process of step 450 in the flowchart of FIG. In this specific example, the injection pulse width for the correction target injection is set so that the normal injection and the fuel injection amount (injection mass) after the correction target injection are substantially the same.

  As described above, in the correction target injection, the injection-side supply pressure is higher than the subsequent normal injection. For this reason, the injection pulse width for correction target injection becomes shorter than the subsequent injection pulse width for normal injection. Thereafter, until the time t7 when the correction at the time of switching (correction target injection) ends, gaseous fuel is injected with a relatively high fuel pressure for the correction target injection and a relatively short injection pulse width for the correction target injection. Done. As shown in FIG. 5, when the time t7 when the correction at the time of switching (correction target injection) ends, the injection-side supply pressure is set to the pressure for normal injection, and the injection pulse is also used for normal injection. Set to something.

  Thus, in this modification, the fuel pulse at the time of the correction target injection is increased and corrected, so that the injection pulse at the time of the correction target injection can be set short. Shortening the injection pulse is effective as a countermeasure for delaying fuel transportation because the end point of injection in one fuel injection is thereby advanced. Furthermore, since the injection pulse is shortened, the degree of freedom in correcting the injection timing is also increased. Therefore, according to the present modification, the fuel injection correction can be performed even better when the fuel is switched (particularly immediately after the switching).

  Note that the number of injection pulses between times t6 and t7 in FIG. 5 can be appropriately set according to the configuration of the internal combustion engine 10, the operating state parameters, and the like. In addition, when there are a plurality of injection pulses between the times t6 and t7, the fuel pressure increase correction is performed only on a part of them (for example, the first half between the times t6 and t7, or the one immediately after the time t6). May be.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder, 12 ... Intake port, 50 ... Fuel supply apparatus, 53 ... Injection control part, 511 ... Gasoline injection valve, 521 ... CNG injection valve, 535 ... Injection timing setting 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
The fuel injection timing in the correction target injection, which is fuel injection immediately after switching between the liquid fuel and the gaseous fuel, is provided so as to advance with respect to the normal injection, which is the fuel injection after the correction target injection. A fuel supply apparatus comprising an injection timing changing section (535).   Fuel pressure correction provided to set the supply pressure of the gaseous fuel to the gaseous fuel injection valve higher than the normal injection in the correction target injection immediately after switching from the liquid fuel to the gaseous fuel The fuel supply device according to claim 1, further comprising a section (536).

Images