JP2006336499A - Fuel supply device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel supply device for an internal combustion engine preventing deterioration of drivability by reducing torque shock at a time of change over of fuel. <P>SOLUTION: In this fuel injection device for the internal combustion engine, when a sub-ECU 26 receives injection condition signal of gasoline fuel to a first cylinder #1 from an ECU 23 and acquires valve open timing (excitation counter value) of a first injector 7 (S108: YES) after a fuel change over switch is turned on (S105:YES) and predetermined time elapses after an LPG fuel pump 35 starts operation (S107:YES), the sub-ECU 23 stops a gasoline fuel pump 10 and stops a first injector 7 (S109). At that time, the sub-ECU 26 turns LPGINJ flag on (S110) and drives a second injector 8 to supply and inject LPG fuel to each cylinder in an order of #1, #3, #4, #2 from the first cylinder #1 (S111). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel supply device that supplies a plurality of fuels to an internal combustion engine. More specifically, the present invention relates to a fuel supply device that selectively supplies gasoline and fuel other than gasoline to an internal combustion engine.

  Conventionally, an engine (so-called bi-fuel engine) that uses gasoline fuel and fuel other than gasoline (for example, LPG fuel) is known. In such an engine, the fuel to be used is appropriately switched according to the driving situation (Patent Document 1).

  In such a fuel supply system for a bi-fuel engine, generally, only gasoline fuel is supplied when the engine is started, and only fuel other than gasoline is supplied when the engine water temperature reaches a set temperature (steady operation state). It has become. As a result, the exhaust gas performance is improved during steady operation while ensuring the startability of the engine.

JP 2003-097326 A

  However, in the fuel supply system described above, there is a problem that an injection failure occurs when the fuel used is switched and the air-fuel ratio temporarily becomes lean. The reason why such an injection failure occurs is that cylinder discrimination is not performed when the supplied fuel is switched, and the fuel used is switched even during fuel injection.

  Further, when switching from gasoline fuel to fuel other than gasoline, there has been a problem that a delay in fuel supply occurs and the air-fuel ratio temporarily becomes lean. This fuel supply delay occurs because the fuel injection conditions (injector drive signal and valve opening time) are corrected to calculate the fuel injection conditions other than gasoline.

  In addition, there is a problem in that drivability deteriorates due to the occurrence of a relatively large torque shock if a fuel injection delay or fuel supply delay occurs during fuel switching and the air-fuel ratio temporarily becomes lean. .

  Accordingly, the present invention has been made to solve the above-described problems, and provides a fuel supply apparatus for an internal combustion engine that can reduce torque shock during fuel switching and prevent deterioration of drivability. This is the issue.

  The fuel supply device for an internal combustion engine according to the present invention, which has been made to solve the above problems, includes two fuel supply systems for supplying different fuels to the internal combustion engine, and the two fuel systems based on a fuel switching request. In a fuel supply device for an internal combustion engine that selectively switches the supply system and switches the fuel to be supplied to the internal combustion engine, each fuel supply system injects and supplies fuel to each cylinder of the internal combustion engine, and the fuel supply system before the switching is When the fuel switching request is generated in the middle of fuel injection to a certain cylinder, the fuel supply system before switching is switched from the predetermined cylinder that injects fuel after the cylinder that is injecting fuel to supply fuel by switching the fuel supply system. It is characterized by.

  In this fuel supply device for an internal combustion engine, when a fuel switching request is generated while fuel is being injected into a certain cylinder before switching, the fuel is supplied before switching after that cylinder. The fuel is supplied by switching from a predetermined cylinder to which fuel is injected and supplied by the system to a newly selected fuel supply system. Thereby, the fuel is always switched from the predetermined cylinder. That is, cylinder discrimination is performed when the fuel used is switched.

  For this reason, the fuel to be used is not switched while fuel is being injected and supplied to a cylinder having a fuel supply system before switching. Therefore, it is possible to prevent the occurrence of injection failure when the fuel used is switched. Therefore, since the air-fuel ratio does not temporarily become lean when the used fuel is switched, torque shock can be reduced, and drivability can be prevented from deteriorating.

  In the fuel supply device for an internal combustion engine of the present invention, the first fuel injection supply control means for calculating the fuel injection supply condition in one of the two systems based on the operating state of the internal combustion engine; It is desirable to have second fuel injection supply control means for calculating the fuel injection supply condition in the other fuel supply system of the system based on the calculation result of the first injection control means.

  Thereby, it is not necessary to calculate the fuel injection supply condition in the other fuel supply system of the two systems based on the operating state of the internal combustion engine, and the other of the two systems is calculated based on the calculation result of the first injection control means. A fuel supply device for a bi-fuel engine can be manufactured at low cost simply by adding a second fuel injection supply control means that only calculates the fuel injection supply condition in the fuel supply system. Then, by supplying gasoline fuel in one of the two systems, a conventional gasoline engine can be used as the first injection control means.

  Further, another embodiment of the fuel supply device for an internal combustion engine according to the present invention, which has been made to solve the above problems, includes two fuel supply systems for supplying different fuels to the internal combustion engine, and is based on permission to switch fuel. In the fuel supply apparatus for an internal combustion engine that selectively switches between the two fuel supply systems and switches the fuel to be supplied to the internal combustion engine, when the fuel supply system is switched based on the fuel switching permission, the fuel supply system after the switching Is characterized by supplying fuel to the internal combustion engine by performing asynchronous injection.

  In this internal combustion engine fuel supply device, when the fuel supply system is switched based on the fuel switching request, the fuel supply system after the switching performs asynchronous injection and supplies the fuel to the internal combustion engine. Absent. Therefore, when the fuel used is switched, the air-fuel ratio does not temporarily become lean due to a delay in fuel supply, and torque shock can be reduced, so that deterioration in drivability can be prevented.

In a fuel supply device for an internal combustion engine according to another aspect of the present invention, first fuel injection supply control means for calculating a fuel injection supply condition in one of the two systems based on an operating state of the internal combustion engine; The second fuel injection supply control means for calculating the fuel injection supply condition in the other fuel supply system of the two systems based on the calculation result of the first injection control means is desirable.

  Thereby, it is not necessary to calculate the fuel injection supply condition in the other fuel supply system of the two systems based on the operating state of the internal combustion engine, and in the other fuel supply system based on the calculation result of the first injection control means. A fuel supply device for a bi-fuel engine can be manufactured at low cost simply by adding a second fuel injection supply control unit that only calculates the fuel injection supply condition.

  Even if the second fuel injection supply control means calculates the fuel injection supply condition in the other fuel supply system based on the calculation result of the first injection control means, as described above, the fuel supply system after switching is Since asynchronous injection is performed, there is no fuel supply delay when switching from one fuel supply system to the other fuel supply system. Note that there is no fuel supply delay when the other fuel supply system is switched to one fuel supply system. This is because the injection supply condition in one fuel supply system is calculated based on the operating state of the internal combustion engine.

  By performing asynchronous injection at the time of switching the fuel in this way, it is possible to prevent a fuel supply delay from occurring when switching from one fuel supply system to the other fuel supply system. However, when fuel is injected and supplied to a cylinder in one fuel supply system before switching, if the fuel switch request is switched to the other fuel supply system, an injection failure occurs.

  Therefore, in the fuel supply apparatus for an internal combustion engine according to another aspect of the present invention, each fuel supply system injects and supplies fuel to each cylinder of the internal combustion engine, and the fuel injection is performed in the middle of the cylinder having the one fuel supply system. When the fuel switching request is generated, it is desirable that the fuel supply is performed by switching from the predetermined cylinder in which the fuel is injected after the one of the fuel injection systems to the other fuel supply system.

  In this way, when a fuel switching request is generated while fuel is being injected into a cylinder with one fuel supply system before switching, the fuel supply system before switching after that cylinder By switching from the predetermined cylinder to which fuel is injected and supplied to the other fuel supply system after the switching, the fuel is always switched in the predetermined cylinder. That is, cylinder discrimination is performed when the fuel used is switched. Thereby, when fuel is injected and supplied to a cylinder with one fuel supply system, switching to the other fuel supply system is not performed. Therefore, it is possible to prevent the occurrence of injection failure when the fuel used is switched.

  In the internal combustion engine fuel supply apparatus according to another aspect of the present invention, the other fuel supply system performs asynchronous injection at a timing when the one fuel supply system starts fuel injection to the predetermined cylinder. Is desirable.

  By doing so, when switching from one fuel supply system to the other fuel supply system in a predetermined cylinder, it is possible to prevent injection omission and prevent fuel supply delay in the other fuel injection supply system. Therefore, since the air-fuel ratio does not temporarily become lean at the time of fuel switching, torque shock can be reduced, and deterioration of drivability can be prevented.

  Here, the other fuel supply system may perform asynchronous injection only on a predetermined cylinder, but it is more preferable to perform asynchronous injection on all cylinders. This is because when asynchronous injection is performed only for a predetermined cylinder, only the fuel supply delay in the predetermined cylinder is eliminated, but when asynchronous injection is performed for all cylinders, the fuel supply delay in all cylinders is eliminated. This is because the torque shock at the time of fuel switching can be further reduced.

  In the fuel supply device for an internal combustion engine according to another aspect of the present invention, the other fuel supply system may perform asynchronous injection to other than the predetermined cylinder at the same time as supplying fuel to the predetermined cylinder. It may be.

  By doing so, the fuel supply delay in the predetermined cylinder at the time of fuel switching is not eliminated, but the fuel supply delay in other than the predetermined cylinder can be eliminated. Even in this case, since the air-fuel ratio can be temporarily prevented from leaning at the time of fuel switching, torque shock can be reduced, and deterioration of drivability can be prevented.

  According to the fuel supply device for an internal combustion engine according to the present invention, as described above, it is possible to reduce the torque shock at the time of switching the fuel and prevent the drivability from deteriorating.

  BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a most preferred embodiment embodying a fuel supply device for an internal combustion engine of the present invention will be described in detail based on the drawings. In the present embodiment, the fuel supply device of the present invention is applied to an automobile engine system.

(First embodiment)
Therefore, the configuration of the engine system according to the first embodiment is shown in FIG. FIG. 1 is a diagram showing a schematic configuration of an engine system mounted on an automobile. In the engine system of FIG. 1, a multi-cylinder engine 1 is of a reciprocating type having a well-known structure. In this embodiment, the multi-cylinder engine 1 has four cylinders, a first cylinder # 1 to a fourth cylinder # 4. The engine 1 explodes and burns a combustible mixture of fuel and air sucked through the intake passage 2 in the combustion chambers of the cylinders # 1 to # 4, and discharges the exhausted gas through the exhaust passage 30. Thus, the piston is operated to rotate the crankshaft to obtain power.

  An air cleaner 3, an air flow meter 4, a throttle valve 5, and a chamber 6 are provided in the intake passage 2. Here, the throttle valve 5 is opened and closed in order to adjust the amount of air (intake amount) taken into the engine 1 through the intake passage 2. This valve 5 operates in conjunction with the operation of an accelerator pedal provided in the driver's seat. The chamber 6 is provided with an intake pressure sensor 27. The intake pressure sensor 27 detects the intake pressure in the intake passage 2 downstream from the throttle valve 5 and outputs an electric signal corresponding to the detected value.

  A first injector 7 and a second injector 8 are provided for each cylinder # 1 to # 4. The first injector 7 injects gasoline fuel into the intake ports of the cylinders # 1 to # 4. Gasoline fuel pumped from a gasoline fuel pump 10 provided in the gasoline fuel tank 9 is supplied to the first injector 7 through a gasoline fuel supply path 11. The gasoline fuel supplied in this manner is injected into the intake port when the first injector 7 is operated, forms a combustible mixture with air, and is taken into each cylinder # 1 to # 4. Excess fuel from the first injector 7 is returned into the gasoline fuel tank 9 through the return path 12.

  The second injector 8 injects LPG fuel into the intake ports of the cylinders # 1 to # 4. The LPG fuel pressurized by the LPG fuel pump 35 is supplied to the second injector 8 from the LPG fuel tank 13 that stores the LPG fuel through the LPG fuel supply system. The LPG fuel supplied in this way is injected into the intake port when the second injector 8 is operated, forms a combustible mixture with air, and is taken into the cylinders # 1 to # 4. Excess fuel from the second injector 8 is returned into the LPG fuel tank 13 through the return path 19 and the pressure regulator 20. The LPG fuel supply passage 14 is provided with a first shut-off valve 15 and a second shut-off valve 16, and a pressure sensor 17 that detects the pressure of the LPG fuel and a fuel temperature sensor 18 that detects the temperature of the LPG fuel. Is provided.

  In the exhaust passage 30, an O 2 sensor 22 is provided on the upstream side of the three-way catalyst 31. The O2 sensor 22 detects the oxygen concentration Ox in the exhaust gas discharged from the engine 1 to the exhaust passage 30 and outputs an electrical signal corresponding to the detected value. The engine 1 is provided with a water temperature sensor 21. This water temperature sensor 21 detects the temperature (cooling water temperature) of the cooling water flowing inside the engine 1 and outputs an electrical signal corresponding to the detected value.

  A gasoline system selection switch 29 for supplying only gasoline fuel to the engine 1 is attached to the vehicle on which the engine system is mounted.

  Here, driving and stopping of the gasoline fuel pump 10 and opening / closing driving of the first injector 7 are controlled by an engine control computer (ECU) 23. A circuit from the fuel pump 10 and the first injector to the ECU 23 is connected to an LPG fuel control computer (sub ECU) 26 via relays 24 and 25. Thereby, when gasoline fuel is supplied by a signal from the ECU 23, the signal from the ECU 23 is cut by a command from the sub ECU 26, and the supply of the gasoline fuel is stopped.

  Further, the opening / closing operation of the second injector 8 and the opening / closing drive of the first cutoff valve 15 and the second cutoff valve 16 are controlled by an LPG fuel control computer (sub ECU) 26. Each signal from the pressure sensor 17 and the fuel temperature sensor 18 is input to the sub ECU 26.

  The ECU 23 is an ECU mounted on an original gasoline vehicle. In order to inject a gasoline injection amount that matches the engine operating conditions, the ECU 23 performs arithmetic processing based on each input signal and performs a gasoline injector ( A drive signal for the first injector 7 is output.

  The sub-ECU 26 receives the drive signal for the first injector 7 calculated by the ECU 23 and calculates the drive signal for the second injector 8 that matches the properties of the LPG fuel at that time. Specifically, based on the signals from the pressure sensor 17 and the fuel temperature sensor 18, correction is performed in consideration of the properties of the LPG fuel on the basis of the drive signal and valve opening time of the first injector 7. Calculate the drive signal. For this reason, driving signals A to D for gasoline injectors for four cylinders are input from the ECU 23 to the ECU 26.

  Next, the fuel supply operation in the engine system described above will be described with reference to FIG. FIG. 2 is a flowchart showing the details of fuel supply control in which cylinder discrimination is performed when fuel is switched (from gasoline fuel to LPG fuel), and fuel after switching is always injected and supplied from the first cylinder # 1.

  When the ignition switch is turned on when the engine is started (S101), the fuel pump 10 is driven to turn on the gasoline fuel supply system, and the shut-off valves 15 and 16 provided in the LPG fuel supply passage 14 are closed and the LPG fuel is turned on. The supply system is turned off (S102).

  When the engine is started (S103), the first injector 7 is driven, gasoline fuel is injected from the first injector 7, and supply of gasoline fuel is started. Since the LPG fuel supply path 14 is in a closed state, no LPG fuel is supplied to the engine 1. Therefore, the engine is started only with gasoline fuel.

  After the engine is started, the engine coolant temperature is detected by the water temperature sensor 21, and the sub ECU 26 determines whether or not the warm-up is completed based on the detection signal (S104). In the present embodiment, it is determined that the warming-up is completed when the coolant temperature is 80 ° C.

  When the warm-up is completed, it is determined by the sub ECU 26 whether or not the fuel switch is turned on (S105). The fuel changeover switch is used for determining whether gasoline fuel or LPG fuel is required based on the on / off state. In the present embodiment, when the ignition switch is turned on, the fuel changeover switch is always in an off state (requires supply of gasoline fuel), and is in an on state (requires supply of LPG fuel) after the warm-up is completed. Further, the fuel changeover switch is turned off when the gasoline system is selected by the gasoline system selection switch 29.

Here, in the prior art, when the fuel switch is turned on (that is, when a fuel switch request is generated), the fuel switch is switched to LPG fuel even during gasoline fuel injection. As a result, injection failure occurred at the time of fuel switching.
Therefore, in the present embodiment, as described below, the switching to the LPG fuel is always performed by the first cylinder # 1, so that no injection loss occurs when the fuel is switched.

  Specifically, when the fuel switch is turned on (S105: YES), the sub ECU 26 drives the LPG fuel pump 35 and opens the shutoff valves 15 and 16 of the LPG fuel supply path 14 (S106). . However, the second injector 8 is not driven. As a result, the LPG fuel is circulated in the LPG fuel supply system to prevent the LPG fuel from being vaporized in the vicinity of the second injector 8. When the fuel changeover switch is in the OFF state (S105: NO), gasoline fuel is supplied until the engine is stopped (S112).

  Then, after a predetermined time has elapsed since the LPG fuel pump 35 was driven (S107: YES), the sub ECU 26 sends an injection condition signal for gasoline fuel (drive signal for the first injector 7) from the ECU 23 to the first cylinder # 1. Wait for input (S108). The predetermined time is mapped and stored in the sub ECU 26 so as to change in relation to the LPG fuel.

  At this time, when the sub ECU 26 receives the gasoline fuel injection condition signal for the first cylinder # 1 from the ECU 23 and acquires the valve opening time (energization counter value) of the first injector 7 (S108: YES), the sub ECU 23 will The fuel pump 10 is stopped and the first injector 7 is stopped (S109). This turns off the gasoline fuel supply system. At this time, the injection execution flag of the first injector 7 is off, and gasoline fuel is not supplied to the first cylinder # 1.

  At this time, the sub ECU 26 turns on the LPGINJ flag (S110). When the LPGINJ flag is turned on, the second injector 8 is driven and LPG fuel is injected and supplied to each cylinder in order from the first cylinder # 1 (in the order of # 1, # 3, # 4, and # 2). (S111). Thereafter, LPG fuel is supplied until the engine is stopped (S112).

  As described above, since the switching from the gasoline fuel to the LPG fuel is always performed from the first cylinder # 1, the injection omission does not occur when the used fuel is switched. Therefore, since the air-fuel ratio does not temporarily become lean when the used fuel is switched, torque shock can be reduced, and deterioration of drivability can be prevented.

  Here, various signals at the time of fuel switching and the injection state for each cylinder will be described with reference to FIG. FIG. 3 is a timing chart showing various signals and injection states for each cylinder when the fuel switching control shown in FIG. 2 is performed.

  Prior to time t1, since the fuel changeover switch is in the off state, the LPG fuel pump / shut-off valve control signal is in the off state. On the other hand, the first injector control signal and the gasoline fuel pump control signal are on. For this reason, gasoline fuel is injected and supplied to each cylinder of the engine 1.

  At time t1, when the fuel changeover switch is turned on (S105: YES in FIG. 2), the LPG fuel pump / shutoff valve control signal is turned on. Thereby, the LPG fuel pump 35 is driven, and the shutoff valves 15 and 16 of the LPG fuel supply path 14 are opened (S106 in FIG. 2).

  In the prior art, when the fuel switch is turned on at time t1 (that is, when a fuel switching request is generated), the LPG is in spite of the gasoline fuel being injected into the first cylinder # 1. It will be switched to fuel. As a result, injection failure occurred at the time of fuel switching.

  However, in the present embodiment, at time t2, a predetermined time is reached after the LPG fuel pump 35 is driven (S107: YES in FIG. 2), and then at time t3, which is the injection end timing of the first cylinder # 1. When it reaches, the LPGING flag is turned on (S110 in FIG. 2), LPG fuel is injected and supplied to the first cylinder # 1, and the supplied fuel is switched to LPG fuel. Thereafter, LPG fuel is injected and supplied to each cylinder in the order of the third cylinder # 3, the fourth cylinder # 4, the second cylinder # 2, and the first cylinder # 1 again. As can be seen from FIG. 3, it is understood that switching from gasoline fuel to LPG fuel is performed in the first cylinder # 1, and no injection omission occurs at that time.

  In the above description, the case where the gasoline fuel is switched to the LPG fuel has been described, but the same control as described above is performed when the LPG fuel is switched to the gasoline fuel. Therefore, fuel supply control in the case of switching from LPG fuel to gasoline fuel will be described with reference to FIG. FIG. 4 is a flowchart showing details of fuel supply control in which cylinder discrimination is performed when fuel is switched (from LPG fuel to gasoline fuel), and fuel after switching is always injected and supplied from the first cylinder # 1.

  When the ignition switch is turned on when the engine is started (S121), the fuel pump 10 is driven to turn on the gasoline fuel supply system, and the shut-off valves 15 and 16 provided in the LPG fuel supply passage 14 are closed and the LPG fuel is turned on. The supply system is turned off (S122).

  When the engine is started (S123), the first injector 7 is driven, gasoline fuel is injected from the first injector 7, and supply of gasoline fuel is started. Since the LPG fuel supply path 14 is in a closed state, no LPG fuel is supplied to the engine 1. Therefore, the engine is started only with gasoline fuel.

  After the engine is started, the engine coolant temperature is detected by the water temperature sensor 21, and the sub ECU 26 determines whether or not the warm-up is completed based on the detection signal (S124). In the present embodiment, it is determined that the warming-up is completed when the coolant temperature is 80 ° C.

  When the warm-up is completed, the sub ECU 26 determines whether or not the fuel changeover switch is turned on (S125). When the fuel switch is turned on (S125: YES), the sub ECU 26 drives the LPG fuel pump 35 and opens the shutoff valves 15 and 16 of the LPG fuel supply path 14 (S126). However, the second injector 8 is not driven. As a result, the LPG fuel is circulated in the LPG fuel supply system to prevent the LPG fuel from being vaporized in the vicinity of the second injector 8. When the fuel switch is off (S125: NO), gasoline fuel is supplied until the engine is stopped (S136).

  Then, after a predetermined time has elapsed since the LPG fuel pump 35 was driven (S127: YES), the sub ECU 26 sends an injection condition signal (drive signal for the first injector 7) of gasoline fuel from the ECU 23 to the first cylinder # 1. Wait for input (S128). The predetermined time is mapped and stored in the sub ECU 26 so as to change in relation to the LPG fuel.

  At this time, when the sub ECU 26 receives an injection condition signal of gasoline fuel for the first cylinder # 1 from the ECU 23 and acquires the valve opening time (energization counter value) of the first injector 7 (S128: YES), the sub ECU 23 will The fuel pump 10 is stopped and the first injector 7 is stopped (S129). This turns off the gasoline fuel supply system. At this time, the injection execution flag of the first injector 7 is off, and gasoline fuel is not supplied to the first cylinder # 1.

  At this time, the sub ECU 26 turns on the LPGINJ flag (S130). When the LPGINJ flag is turned on, the second injector 8 is driven and LPG fuel is injected and supplied to each cylinder in order from the first cylinder # 1 (in the order of # 1, # 3, # 4, and # 2). (S131). Thereafter, LPG fuel is supplied until the engine is stopped (S136). Up to this point, the fuel supply control is the same as described above.

  Then, when the LPG fuel is supplied to the engine 1 and the LPG fuel is exhausted, etc., after the gasoline system is selected by the gasoline system selection switch 29 (S132: YES), the ECU 23 selects the first cylinder # 1. When the gasoline fuel injection condition signal is calculated (S133: YES), the gasoline fuel pump 10 is driven and the first injector 7 is driven (S134). Thereby, gasoline fuel is injected and supplied to each cylinder in order from the first cylinder # 1 (in the order of # 1, # 3, # 4, and # 2). Thereafter, gasoline fuel is supplied until the engine stops (S136).

  On the other hand, an injection condition signal for gasoline fuel for the first cylinder # 1 is input from the ECU 23 to the sub ECU 26. As a result, the sub ECU 26 stops the LPG fuel pump 35, closes the shutoff valves 15 and 16 of the LPG fuel supply path 14, and turns off the LPINJ flag (S135). As a result, the LPG fuel supply system is turned off and the LPG fuel is not supplied to the engine 1. Therefore, the fuel supplied to the engine 1 is switched from LPG fuel to gasoline fuel.

  As described above, even when the fuel supplied to the engine 1 is switched from the LPG fuel to the gasoline fuel, the switching is always performed from the first cylinder # 1, so that no injection omission occurs when the used fuel is switched. Therefore, since the air-fuel ratio does not temporarily become lean when the used fuel is switched, torque shock can be reduced, and deterioration of drivability can be prevented.

  Here, various signals at the time of the fuel switching and the injection state for each cylinder will be described with reference to FIG. FIG. 5 is a timing chart showing various signals and injection states for each cylinder when the fuel switching control shown in FIG. 4 is performed.

  Prior to time t1 until the gasoline system is selected by the gasoline system selection switch 29, the fuel changeover switch is in the on state. The LPGINJ flag is also in the on state, and the LPG fuel pump / shutoff valve control signal is in the on state. On the other hand, the first injector control signal and the gasoline fuel pump control signal are off. For this reason, LPG fuel is injected and supplied to each cylinder of the engine 1.

  At time t1, when a gasoline system is selected by the gasoline system selection switch 29 (S132: YES in FIG. 4), the fuel changeover switch is turned off, but the LPG fuel pump / shutoff valve control signal and the LPGINJ flag are Since the engine 1 is kept on, LPG fuel continues to be supplied to the engine 1.

  The supply of the LPG fuel is performed until time t2, which is the injection timing of the gasoline fuel for the next cylinder # 1. At time t2, the first injector control signal and the gasoline fuel pump control signal are turned on, and gasoline fuel is injected and supplied to the first cylinder # 1 (S134 in FIG. 4). At this time, the LPGING flag is turned off, and the LPG fuel pump / shutoff valve control signal is also turned off. As a result, the LPG fuel pump 35 is stopped and the shutoff valves 15 and 16 of the LPG fuel supply path 14 are closed (S135 in FIG. 4). This completes the switching from LPG fuel to gasoline fuel.

  Thereafter, after time t2, gasoline fuel is injected and supplied to each cylinder in the order of the first cylinder # 1, the third cylinder # 3, the fourth cylinder # 4, and the second cylinder # 2. As can be seen from FIG. 5, since the switching from the LPG fuel to the gasoline fuel is also performed in the first cylinder # 1, it is understood that no injection failure occurs.

  As described above in detail, in the engine system according to the first embodiment, since the fuel is always switched in the first cylinder # 1, the fuel is injected and supplied to a certain cylinder. Even when a fuel switching request is occasionally generated, the fuel is not switched during the injection supply. Accordingly, no injection omission occurs when the fuel is switched, so that the air-fuel ratio does not temporarily become lean. As a result, torque shock is reduced, so that deterioration in drivability is prevented.

(Second Embodiment)
In the second embodiment, the configuration of the engine system is the same as that of the first embodiment, but the fuel supply operation to the engine is different. Specifically, the point of performing asynchronous injection when switching the fuel supplied to the engine is different from the first embodiment. For this reason, below, it demonstrates focusing on a different point from 1st Embodiment.

  The fuel supply control according to the second embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing the content of fuel supply control for performing asynchronous injection when the fuel is switched (from gasoline fuel to LPG fuel).

  In the second embodiment, when the ignition switch is turned on when the engine is started (S201), the fuel pump 10 is driven to turn on the gasoline fuel supply system, and the shutoff valve 15 provided in the LPG fuel supply path 14; 16 is closed and the LPG fuel supply system is turned off (S202).

  When the engine is started (S203), the first injector 7 is driven, gasoline fuel is injected from the first injector 7, and supply of gasoline fuel is started. Since the LPG fuel supply path 14 is in a closed state, no LPG fuel is supplied to the engine 1. Therefore, the engine is started only with gasoline fuel.

After the engine is started, the engine coolant temperature is detected by the water temperature sensor 21, and the sub ECU 26 determines whether or not the warm-up is completed based on the detection signal (S204). In the present embodiment, it is determined that the warming-up is completed when the coolant temperature is 80 ° C.
When the warm-up is completed, the sub ECU 26 determines whether or not the fuel switch is turned on (S205).

Here, in the prior art, when the fuel switch is turned on (that is, when a fuel switch request is generated), the fuel switch is switched to LPG fuel even during gasoline fuel injection. As a result, injection failure occurred at the time of fuel switching.
Therefore, in the present embodiment, as in the first embodiment, switching to the LPG fuel is always performed in the first cylinder # 1, so that no injection loss occurs at the time of fuel switching.

  That is, when the fuel switch is turned on (S205: YES), the sub ECU 26 drives the LPG fuel pump 35 and opens the shutoff valves 15 and 16 of the LPG fuel supply path 14 (S206). However, the second injector 8 is not driven. As a result, the LPG fuel is circulated in the LPG fuel supply system to prevent the LPG fuel from being vaporized in the vicinity of the second injector 8. When the fuel changeover switch is off (S205: NO), gasoline fuel is supplied until the engine is stopped (S213).

  Then, after a predetermined time has elapsed after the LPG fuel pump 35 is driven (S207: YES), the sub ECU 26 sends an injection condition signal for gasoline fuel (drive signal for the first injector 7) from the ECU 23 to the first cylinder # 1. Wait for input (S208).

  At this time, when the sub ECU 26 receives an injection condition signal of gasoline fuel for the first cylinder # 1 from the ECU 23 (S208: YES), the LPGINJ flag is turned on (S209). Then, the second injector 8 is driven to perform asynchronous injection of LPG fuel into the first cylinder # 1 (S210). That is, LPG fuel is injected and supplied at the start timing of gasoline fuel injection to the first cylinder # 1. Thereby, it is possible to prevent a fuel supply delay that occurs when the gasoline fuel is switched to the LPG fuel. The injection time for asynchronous injection is set to an optimum time by experiment or the like.

  Thereafter, when the sub ECU 26 acquires the valve opening time (energization counter value) of the first injector 7, the sub ECU 26 stops the gasoline fuel pump 10 and stops the first injector 7 (S211). This turns off the gasoline fuel supply system. At this time, the injection execution flag of the first injector 7 is off, and gasoline fuel is not supplied to the first cylinder # 1.

  At this time, the LPG fuel is supplied from the second injector 8 to the first cylinder # 1, and thereafter the LPG fuel is supplied to each cylinder in order (in the order of # 1, # 3, # 4, and # 2). Is supplied by injection (S212). Then, LPG fuel is supplied until the engine stops (S213). As described above, since the switching from the gasoline fuel to the LPG fuel is always performed from the first cylinder # 1, no injection omission occurs when the used fuel is switched.

  As described above, in this embodiment, when switching from gasoline fuel to LPG fuel, asynchronous injection is performed during a period in which supply delay occurs in LPG fuel supply to the regular first cylinder. Thereby, the supply delay of the LPG fuel to the first cylinder # 1 does not occur when switching from gasoline fuel to LPG fuel. Therefore, since the air-fuel ratio does not temporarily become lean when the used fuel is switched, torque shock can be reduced, and deterioration of drivability can be prevented.

  Here, various signals at the time of fuel switching and the injection state for each cylinder will be described with reference to FIG. FIG. 7 is a timing chart showing various signals and injection states for each cylinder when the fuel switching control shown in FIG. 6 is performed.

  Prior to time t1, since the fuel changeover switch is in the off state, the LPG fuel pump / shut-off valve control signal is in the off state. On the other hand, the first injector control signal and the gasoline fuel pump control signal are on. For this reason, gasoline fuel is injected and supplied to each cylinder of the engine 1.

  At time t1, when the fuel switch is turned on (S205 in FIG. 6: YES), the LPG fuel pump / shut-off valve control signal is turned on. As a result, the LPG fuel pump 35 is driven and the shutoff valves 15 and 16 of the LPG fuel supply path 14 are opened (S206 in FIG. 6).

  Thereafter, at time t2, a predetermined time is reached after the LPG fuel pump 35 is driven (S207 in FIG. 6: YES). Then, when the time t3 is reached, which is the gasoline fuel injection start timing for the first cylinder # 1, the LPGINJ flag is turned on (S209 in FIG. 6), and the LPG fuel is supplied to the first cylinder # 1. Asynchronous injection is performed (shaded area in FIG. 7). Thus, the supplied fuel is switched to the LPG fuel.

  When the time t4 is reached, which is the timing at which gasoline fuel is injected into the first cylinder # 1, the first injector control signal and the gasoline fuel pump control signal are turned off (S211 in FIG. 6). Further, LPG fuel is injected and supplied to the first cylinder # 1, and thereafter, the third cylinder # 3, the fourth cylinder # 4, the second cylinder # 2, and again the first cylinder # 1 in order of the first cylinder # 1. Then, LPG fuel is injected and supplied (S212 in FIG. 6). From FIG. 7, when switching from gasoline fuel to LPG fuel is performed in the first cylinder # 1, asynchronous injection of LPG fuel is performed at the injection start timing of gasoline fuel, causing a delay in supply of LPG fuel. I understand that there is no.

  Subsequently, a modification of the second embodiment will be described. In the first modified example, asynchronous injection is performed not only for the first cylinder # 1 but also for all cylinders at the time of fuel switching. This first modification will be described with reference to FIG. FIG. 8 is a flowchart showing the contents of fuel supply control for performing asynchronous injection to all cylinders when the fuel is switched (from gasoline fuel to LPG fuel).

  In the first modification, when the ignition switch is turned on when the engine is started (S221), the fuel pump 10 is driven to turn on the gasoline fuel supply system, and the shutoff valves 15 and 16 provided in the LPG fuel supply passage 14 are turned on. Is closed and the LPG fuel supply system is turned off (S222).

  When the engine is started (S223), the first injector 7 is driven, gasoline fuel is injected from the first injector 7, and supply of gasoline fuel is started. Since the LPG fuel supply path 14 is in a closed state, no LPG fuel is supplied to the engine 1. Therefore, the engine is started only with gasoline fuel.

  After the engine is started, the engine coolant temperature is detected by the water temperature sensor 21, and the sub ECU 26 determines whether or not the warm-up is completed based on the detection signal (S224). When the warm-up is completed, the sub ECU 26 determines whether or not the fuel changeover switch is turned on (S225).

  When the fuel selector switch is turned on (S225: YES), the sub ECU 26 drives the LPG fuel pump 35 and opens the shutoff valves 15 and 16 of the LPG fuel supply path 14 (S226). However, the second injector 8 is not driven. When the fuel changeover switch is off (S225: NO), gasoline fuel is supplied until the engine is stopped (S233).

  Then, after a predetermined time has elapsed since the LPG fuel pump 35 was driven (S227: YES), the sub ECU 26 sends an injection condition signal for gasoline fuel to the first cylinder # 1 from the ECU 23 (drive signal for the first injector 7). Wait for input (S228).

  At this time, when the sub ECU 26 receives an injection condition signal of gasoline fuel for the first cylinder # 1 from the ECU 23 (S228: YES), the LPGINJ flag is turned on (S229). Then, the second injector 8 is driven to perform asynchronous injection of LPG fuel into all the cylinders # 1 to # 4 (S230). That is, LPG fuel is injected and supplied to all cylinders at the start timing of gasoline fuel injection to the first cylinder # 1. Thereby, it is possible to prevent the fuel supply delay that occurs when the gasoline fuel is switched to the LPG fuel in all the cylinders.

  Thereafter, when the sub ECU 26 obtains the valve opening time (energization counter value) of the first injector 7, the sub ECU 26 stops the gasoline fuel pump 10 and stops the first injector 7 (S231). This turns off the gasoline fuel supply system. At this time, the injection execution flag of the first injector 7 is off, and gasoline fuel is not supplied to the first cylinder # 1.

  At this time, the LPG fuel is supplied from the second injector 8 to the first cylinder # 1, and thereafter the LPG fuel is supplied to each cylinder in order (in the order of # 1, # 3, # 4, and # 2). Is supplied by injection (S232). Then, LPG fuel is supplied until the engine is stopped (S233). As described above, since the switching from the gasoline fuel to the LPG fuel is always performed from the first cylinder # 1, no injection omission occurs when the fuel is switched.

  As described above, in the first modified example, when the gasoline fuel is switched to the LPG fuel, the asynchronous injection is performed on all the cylinders. Thereby, when switching from gasoline fuel to LPG fuel, supply delay of LPG fuel does not occur in all cylinders. Therefore, since the air-fuel ratio does not temporarily become lean when the fuel used is switched, torque shock can be further reduced, and deterioration of drivability can be effectively prevented.

  Here, various signals at the time of the fuel switching and the injection state for each cylinder will be described with reference to FIG. FIG. 9 is a timing chart showing various signals and injection states for each cylinder when the fuel switching control shown in FIG. 8 is performed.

  Prior to time t1, since the fuel changeover switch is in the off state, the LPG fuel pump / shut-off valve control signal is in the off state. On the other hand, the first injector control signal and the gasoline fuel pump control signal are on. For this reason, gasoline fuel is injected and supplied to each cylinder of the engine 1.

  At time t1, when the fuel changeover switch is turned on (S225 in FIG. 8: YES), the LPG fuel pump / shutoff valve control signal is turned on. As a result, the LPG fuel pump 35 is driven and the shutoff valves 15 and 16 of the LPG fuel supply path 14 are opened (S226 in FIG. 8).

  Thereafter, at time t2, a predetermined time is reached after the LPG fuel pump 35 is driven (S227 in FIG. 8: YES). Then, when the time t3 is reached, which is the gasoline fuel injection start timing for the first cylinder # 1, the LPGINJ flag is turned on (S229 in FIG. 8), and the LPG for all the cylinders # 1 to # 4 is turned on. Asynchronous fuel injection is performed (shaded area in FIG. 9). Thus, the supplied fuel is switched to the LPG fuel.

  When the time t4 is reached, which is the timing for ending the injection of gasoline fuel for the first cylinder # 1, the first injector control signal and the gasoline fuel pump control signal are turned off (S231 in FIG. 8). Further, LPG fuel is injected and supplied to the first cylinder # 1, and thereafter, the third cylinder # 3, the fourth cylinder # 4, the second cylinder # 2, and again the first cylinder # 1 in order of the first cylinder # 1. The LPG fuel is injected and supplied (S232 in FIG. 8). From FIG. 9, when switching from gasoline fuel to LPG fuel is performed in the first cylinder # 1, asynchronous injection of LPG fuel is performed on all cylinders # 1 to # 4 at the start timing of gasoline fuel injection. It can be seen that there is no supply delay of the LPG fuel.

  Next, a second modification will be described. In the second modification, asynchronous injection is performed at the injection start timing of LPG fuel. This second modification will be described with reference to FIG. FIG. 10 is a flowchart showing the content of fuel supply control in which asynchronous injection is performed at the injection start timing of LPG fuel when the fuel is switched (from gasoline fuel to LPG fuel).

  In the second modification, when the ignition switch is turned on when the engine is started (S241), the fuel pump 10 is driven to turn on the gasoline fuel supply system, and the shutoff valves 15 and 16 provided in the LPG fuel supply passage 14 are turned on. Is closed and the LPG fuel supply system is turned off (S242).

  When the engine is started (S243), the first injector 7 is driven, gasoline fuel is injected from the first injector 7, and supply of gasoline fuel is started. Since the LPG fuel supply path 14 is in a closed state, no LPG fuel is supplied to the engine 1. Therefore, the engine is started only with gasoline fuel.

  After the engine is started, the engine cooling water temperature is detected by the water temperature sensor 21, and the sub ECU 26 determines whether or not the warming-up is completed based on the detection signal (S244). When the warm-up is completed, it is determined by the sub ECU 26 whether or not the fuel switch is turned on (S245).

  When the fuel switch is turned on (S245: YES), the sub ECU 26 drives the LPG fuel pump 35 and opens the shutoff valves 15 and 16 of the LPG fuel supply path 14 (S246). However, the second injector 8 is not driven. When the fuel changeover switch is off (S245: NO), gasoline fuel is supplied until the engine is stopped (S253).

  Then, after a predetermined time has elapsed since the LPG fuel pump 35 was driven (S247: YES), the sub-ECU 26 generates a gasoline fuel injection condition signal (drive signal for the first injector 7) from the ECU 23 to the first cylinder # 1. Waiting for input (S248).

  At this time, when the sub ECU 26 receives the injection condition signal of the gasoline fuel for the first cylinder # 1 from the ECU 23 and acquires the valve opening time (energization counter value) of the first injector 7 (S248: YES), the LPGINJ flag is turned on. In addition, the gasoline fuel pump 10 is stopped and the first injector 7 is stopped (S250). This turns off the gasoline fuel supply system. At this time, the injection execution flag of the first injector 7 is off, and gasoline fuel is not supplied to the first cylinder # 1.

  When the LPGINJ flag is turned on, LPG fuel is supplied from the second injector 8 to the first cylinder # 1, and LPG fuel is supplied to # 2, # 3, and # 4 other than the first cylinder. Asynchronous injection is performed. That is, the LPG fuel is injected and supplied by asynchronous injection to the cylinders other than the first cylinder at the injection start timing of the LPG fuel to the first cylinder # 1. As a result, when the gasoline fuel is switched to the LPG fuel, it is possible to prevent a delay in the fuel supply except for the first cylinder.

  Thereafter, LPG fuel is injected and supplied to each cylinder in order (in the order of # 3, # 4, # 2, and # 1) (S252). Then, LPG fuel is supplied until the engine is stopped (S253). Since the switching from the gasoline fuel to the LPG fuel is always performed from the first cylinder # 1, no injection omission occurs when the used fuel is switched.

  As described above, in the second modified example, when the gasoline fuel is switched to the LPG fuel, the asynchronous injection is performed to the cylinders other than the first cylinder at the timing when the LPG fuel is injected to the first cylinder # 1. Is done. Thereby, when switching from gasoline fuel to LPG fuel, a delay in the supply of LPG fuel does not occur except in the first cylinder. Therefore, since the air-fuel ratio does not temporarily become lean when the used fuel is switched, torque shock can be reduced, and deterioration of drivability can be prevented.

  Here, various signals at the time of fuel switching and the injection state for each cylinder will be described with reference to FIG. FIG. 11 is a timing chart showing various signals and injection states for each cylinder when the fuel switching control shown in FIG. 10 is performed.

  Prior to time t1, since the fuel changeover switch is in the off state, the LPG fuel pump / shut-off valve control signal is in the off state. On the other hand, the first injector control signal and the gasoline fuel pump control signal are on. For this reason, gasoline fuel is injected and supplied to each cylinder of the engine 1.

  At time t1, when the fuel switch is turned on (S245 in FIG. 10: YES), the LPG fuel pump / shut-off valve control signal is turned on. As a result, the LPG fuel pump 35 is driven and the shutoff valves 15 and 16 of the LPG fuel supply path 14 are opened (S246 in FIG. 10).

  Thereafter, at time t2, after reaching a predetermined time after the LPG fuel pump 35 is driven (S247 in FIG. 10: YES), when reaching time t3, which is the injection end timing of the next cylinder # 1, The LPGINJ flag is turned on (249 in FIG. 10), LPG fuel is injected and supplied to the first cylinder # 1, and LPG is supplied to the cylinders # 2, # 3, and # 4 other than the first cylinder. Asynchronous fuel injection is performed (shaded area in FIG. 11). Thus, the supplied fuel is switched to the LPG fuel. Thereafter, LPG fuel is injected and supplied to each cylinder in the order of the third cylinder # 3, the fourth cylinder # 4, the second cylinder # 2, and the first cylinder # 1 again (S252 in FIG. 10). From FIG. 11, when switching from gasoline fuel to LPG fuel is performed in the first cylinder # 1, the LPG for the cylinders # 2, # 3 and # 4 other than the first cylinder at the start timing of LPG fuel injection. It can be seen that the asynchronous injection of fuel is performed and no delay in the supply of LPG fuel occurs in cylinders # 2, # 3, and # 4 other than the first cylinder.

  As described above, in the engine system according to the second embodiment as described in detail, when switching from gasoline fuel to LPG fuel, asynchronous injection of LPG fuel is performed. Will not occur. Thereby, since the air-fuel ratio does not temporarily become lean when the fuel is switched, torque shock is reduced, so that deterioration in drivability is prevented.

  It should be noted that the above-described embodiment is merely an example and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, gasoline fuel and LPG fuel are illustrated as different fuels, but CNG fuel can be used instead of LPG fuel.

  In the above-described embodiment, the fuel switching is performed in the first cylinder # 1, but the fuel switching is performed in the cylinders (# 2, # 3, # 4) other than the first cylinder # 1. It can also be.

It is a figure showing a schematic structure of an engine system concerning an embodiment. It is a flowchart which shows the content of the fuel supply control which performs cylinder discrimination | determination when fuel is switched (from gasoline fuel to LPG fuel) and always injects and supplies the fuel after switching from the first cylinder # 1. FIG. 3 is a timing chart showing various signals and injection states for each cylinder when the fuel switching control shown in FIG. 2 is performed. FIG. 7 is a flowchart showing the contents of fuel supply control in which cylinder discrimination is performed when fuel is switched (from LPG fuel to gasoline fuel) and fuel after switching is always injected and supplied from the first cylinder # 1. 5 is a timing chart showing various signals and injection states for each cylinder when the fuel switching control shown in FIG. 4 is performed. It is a flowchart which shows the content of the fuel supply control which performs asynchronous injection when switching a fuel (from gasoline fuel to LPG fuel). It is a timing chart which shows the injection state with respect to each signal and each cylinder at the time of performing fuel switching control shown in FIG. FIG. 8 is a flowchart showing the contents of fuel supply control for performing asynchronous injection to all cylinders when the fuel is switched (from gasoline fuel to LPG fuel). It is a timing chart which shows the injection state with respect to each signal and each cylinder at the time of performing fuel switching control shown in FIG. It is a flowchart which shows the content of the fuel supply control which performs asynchronous injection at the injection start timing of LPG fuel when fuel is switched (from gasoline fuel to LPG fuel). It is a timing chart which shows the injection state with respect to each signal and each cylinder at the time of performing fuel switching control shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Intake passage 7 1st injector 8 2nd injector 9 Gasoline fuel tank 10 Gasoline fuel pump 13 LPG fuel tank 15 Shut-off valve 16 Shut-off valve 21 Water temperature sensor 23 ECU
26 Sub ECU
29 Gasoline system selection switch 35 LPG fuel pump

Claims (7)

A fuel supply device for an internal combustion engine that includes two fuel supply systems that supply different fuels to the internal combustion engine, and that selectively switches between the two fuel supply systems based on a fuel switching request and switches fuel supplied to the internal combustion engine In
Each fuel supply system injects and supplies fuel to each cylinder of the internal combustion engine,
When the fuel switching request is generated in the middle of fuel injection to a cylinder with a fuel supply system before switching, the fuel supply system is changed from a predetermined cylinder in which the fuel supply system before switching injects fuel after the cylinder during fuel injection. A fuel supply apparatus for an internal combustion engine, wherein the fuel supply is performed by switching. The fuel supply apparatus for an internal combustion engine according to claim 1,
First fuel injection supply control means for calculating the fuel injection supply condition in one of the two systems based on the operating state of the internal combustion engine;
Fuel for an internal combustion engine, comprising: second fuel injection supply control means for calculating a fuel injection supply condition in the other fuel supply system of the two systems based on a calculation result of the first injection control means Feeding device. A fuel supply device for an internal combustion engine that includes two fuel supply systems that supply different fuels to the internal combustion engine, and that selectively switches between the two fuel supply systems based on a fuel switching request and switches fuel supplied to the internal combustion engine In
The fuel supply device for an internal combustion engine, wherein when the fuel supply system is switched based on the fuel switching request, the fuel supply system after the switching performs asynchronous injection. The fuel supply device for an internal combustion engine according to claim 3,
First fuel injection supply control means for calculating the fuel injection supply condition in one of the two systems based on the operating state of the internal combustion engine;
Fuel for an internal combustion engine, comprising: second fuel injection supply control means for calculating a fuel injection supply condition in the other fuel supply system of the two systems based on a calculation result of the first injection control means Feeding device. The fuel supply apparatus for an internal combustion engine according to claim 4,
Each fuel supply system injects and supplies fuel to each cylinder of the internal combustion engine,
When the fuel switching request is generated in the middle of fuel injection to a cylinder with one fuel supply system, the other fuel supply from a predetermined cylinder in which the one fuel supply system injects fuel after the cylinder in which fuel is being injected A fuel supply apparatus for an internal combustion engine, wherein the fuel supply is performed by switching to a system. The fuel supply apparatus for an internal combustion engine according to claim 5,
The fuel supply system for an internal combustion engine, wherein the other fuel supply system performs asynchronous injection at a timing when the one fuel supply system starts fuel injection to the predetermined cylinder. The fuel supply apparatus for an internal combustion engine according to claim 5,
The fuel supply system for an internal combustion engine, wherein the other fuel supply system performs the fuel injection supply to the predetermined cylinder and at the same time performs the asynchronous injection to other than the predetermined cylinder.

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