JP2011220253A - Air-fuel ratio learning control device for bifuel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly learn an air-fuel ratio learning value for each of a gas fuel and a liquid fuel.SOLUTION: In a bifuel engine which is operated using a CNG (Compressed Natural Gas) and/or gasoline, an evaporated fuel treatment unit 35 purges vapors generated in a gasoline tank 13 in which gasoline is stored to an engine 1 to treat the vapors as necessary. When fuel used when the engine 1 is operated is switched between the CNG and the gasoline, an electronic control unit (ECU) 50 starts the learning of air-fuel ratio learning values (FGC, FGG) thereof after a lapse of a predetermined time. The ECU 50 prohibits the purge of the vapors by the evaporated fuel treatment unit 35 during the time from the start of the learning of the air-fuel ratio learning values (FGC, FGG) to the completion thereof.

Description

  The present invention relates to a bi-fuel engine that operates using at least one of gaseous fuel and liquid fuel, and more particularly to an air-fuel ratio learning control device for a bi-fuel engine that learns an air-fuel ratio learning value of the engine.

  2. Description of the Related Art Conventionally, a bi-fuel engine that operates using at least one of gaseous fuel such as compressed natural gas (CNG) and liquid fuel such as gasoline is known. An example of this type of technique is described in Patent Document 1 below. This prior art includes a vapor device (evaporated fuel processing device) that purges and processes evaporated fuel (vapor) generated in a fuel tank that stores gasoline, which is liquid fuel, into an intake passage of an engine. In this prior art, when the engine needs to be purged with vapor and the engine is operated with gaseous fuel, the engine is operated with liquid fuel by switching the gaseous fuel to liquid fuel. Therefore, the vapor is purged. As a result, the engine is prevented from deteriorating emission and knocking due to vapor purge.

  On the other hand, although it is not a bi-fuel engine, the following patent document 2 describes a technique related to an air-fuel ratio control device in an engine provided with an evaporated fuel supply means (evaporated fuel processing device). The air-fuel ratio control device uses an air-fuel ratio detecting means for detecting an air-fuel ratio, an air-fuel ratio adjusting means for adjusting the air-fuel ratio, a feedback correction amount calculating means for calculating an air-fuel ratio feedback correction amount, and a feedback correction amount. Learning correction amount calculating means for calculating the learning correction amount of the air-fuel ratio, air-fuel ratio control means for controlling the air-fuel ratio adjusting means based on the feedback correction amount and the learning correction amount, and the evaporated fuel in the fuel tank as the intake system Evaporative fuel supply means for purging the fuel. Then, when the evaporated fuel is purged into the intake system, and for a predetermined time after the purge is stopped, the learning correction amount is prohibited from being calculated, thereby preventing erroneous learning of the learning correction amount.

JP 2005-220802 A JP-A-3-222841 JP 2007-162632 A Japanese Patent Laid-Open No. 11-294212

  Incidentally, even in a bi-fuel engine as described in Patent Document 1, it is conceivable to employ an air-fuel ratio learning control apparatus as described in Patent Document 2. In this case, it is necessary to perform air-fuel ratio learning control for each of gas fuel and liquid fuel. However, there is a problem with the balance between the use switching of gas fuel and liquid fuel, vapor purge, and air-fuel ratio learning control. . That is, it becomes a problem at what timing the air-fuel ratio learning control should be executed for each of the gaseous fuel and the liquid fuel from the relationship with the vapor purge.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to suitably perform the balance between the use of gaseous fuel and liquid fuel, the purging of evaporated fuel, and the air-fuel ratio learning control, and the proper use of them. Thus, an object of the present invention is to provide an air-fuel ratio learning control device for a bi-fuel engine that can accurately learn an air-fuel ratio learning value for each of gas fuel and liquid fuel.

  In order to achieve the above object, the invention described in claim 1 is a bi-fuel engine that operates using at least one of gaseous fuel and liquid fuel, and includes a bi-fuel engine that includes a learning control means that learns an air-fuel ratio learning value. An air-fuel ratio learning control device for a fuel engine, wherein the bi-fuel engine includes evaporative fuel processing means for purging the bi-fuel engine and processing evaporative fuel generated in a fuel tank storing liquid fuel, and learning control The means is configured to start learning of the air-fuel ratio learning value when the fuel used during operation of the bi-fuel engine is switched between gaseous fuel and liquid fuel, and learning of the air-fuel ratio learning value is performed. It is intended that a prohibition unit for prohibiting the purge of the evaporated fuel by the evaporated fuel processing unit from the start to the completion is provided. That.

  According to the configuration of the above invention, when the fuel used during the operation of the bi-fuel engine is switched between the gaseous fuel and the liquid fuel, the learning control means starts learning the air-fuel ratio learning value. An air-fuel ratio learning value is learned for each of gas fuel and liquid fuel. In addition, since the prohibiting unit prohibits the evaporative fuel purging by the evaporative fuel processing unit from the start to the completion of the learning of the air-fuel ratio learning value, the evaporative fuel is purged during the learning of the air-fuel ratio learning value. The air-fuel ratio learning value is not erroneously learned by the evaporated fuel.

  In order to achieve the above object, according to a second aspect of the present invention, in the first aspect of the present invention, the learning control means is configured such that the fuel used during operation of the bi-fuel engine is a gas fuel and a liquid fuel. The purpose is to start learning of the air-fuel ratio learning value after a predetermined time has elapsed since switching.

  According to the configuration of the invention described above, in addition to the operation of the invention according to claim 1, the learning control means is configured to change the air-fuel ratio after a predetermined time has elapsed since the used fuel was switched between the gaseous fuel and the liquid fuel. Since learning of the learning value is started, it becomes possible to learn the air-fuel ratio learning value for the used fuel after the switching after the remaining amount of the used fuel before the switching disappears from the engine.

  In order to achieve the above object, according to a third aspect of the present invention, in the first or second aspect of the invention, the learning control means learns the air-fuel ratio learning value when the evaporated fuel purge is performed. The purpose is to stop.

  According to the configuration of the above invention, in addition to the operation of the invention according to claim 1 or 2, when the evaporated fuel purge is performed, the learning control means stops learning the air-fuel ratio learning value. The learning of the air-fuel ratio is not performed during the purge, and the air-fuel ratio learning value is not erroneously learned by the evaporated fuel.

  According to the first aspect of the present invention, the air-fuel ratio learning value can be accurately learned for each of the gaseous fuel and the liquid fuel.

  According to the second aspect of the present invention, the air-fuel ratio learning value can be learned more accurately by eliminating the influence of the used fuel before switching, in contrast to the effect of the first aspect of the invention.

  According to the invention described in claim 3, in addition to the effect of the invention described in claim 1 or 2, it is possible to eliminate the influence of the evaporated fuel to be purged and to learn the air-fuel ratio learning value more accurately.

1 is a schematic configuration diagram illustrating a bi-fuel engine system according to an embodiment. The flowchart which shows the content of fuel injection control in connection with the embodiment. The flowchart which shows the content of the air fuel ratio learning control for gasoline concerning the embodiment. The flowchart which shows the content of the air-fuel ratio learning control for CNG concerning the embodiment. The flowchart which shows the content of evaporative fuel process control concerning the embodiment.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment embodying an air-fuel ratio learning control apparatus for a bi-fuel engine according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a bi-fuel engine system including an air-fuel ratio learning control apparatus according to the present invention. The multi-cylinder engine 1 explodes and burns a combustible mixture of fuel and air supplied through an intake passage 2 in a combustion chamber 3 of each cylinder, and exhausts the exhaust gas after the combustion from the exhaust passage 4. . As a result, the engine 1 operates the piston 5 to rotate the crankshaft 6 to obtain power.

  An air cleaner 7 provided at the inlet of the intake passage 2 cleans the air sucked into the passage 2. The electronic throttle device 8 provided in the intake passage 2 operates to adjust the amount of air (intake amount) QA that flows through the passage 2 and is sucked into the combustion chamber 3 of each cylinder. The electronic throttle device 8 opens and closes a throttle valve 10 by an actuator 9. A throttle sensor 41 provided for the electronic slot device 8 detects the opening degree (throttle opening degree) TA of the throttle valve 10 and outputs an electric signal corresponding to the detected value. The intake pressure sensor 42 provided in the surge tank 2a of the intake passage 2 detects the intake pressure PM in the surge tank 2a and outputs an electric signal corresponding to the detected value.

  The engine 1 of this embodiment is a bi-fuel engine that operates using at least one of compressed natural gas (CNG) as a gaseous fuel and gasoline as a liquid fuel, and a gasoline supply device 11 that supplies gasoline, And a CNG supply device 21 for supplying CNG. The gasoline supply device 11 includes a plurality of gasoline injectors 12 provided corresponding to the respective cylinders, and a gasoline tank 13 and a gasoline line 14 that supply gasoline to the injectors 12. The gasoline tank 13 is provided with a gasoline pump 15 that pumps gasoline. The gasoline pressure-fed from the gasoline tank 13 to the gasoline line 14 to each gasoline injector 12 is injected and supplied to the intake port of each cylinder by controlling the injectors 12.

  The CNG supply device 21 includes a plurality of CNG injectors 22 provided corresponding to each cylinder, and a CNG cylinder 23 and a CNG line 24 that supply CNG to the injectors 22. The CNG line 24 is provided with a CNG cutoff valve and a regulator (both not shown). The CNG supplied from the CNG cylinder 23 to each CNG injector 22 through the CNG line 24 is injected and supplied to the intake port of each cylinder by controlling the injector 22.

  A plurality of spark plugs 31 provided in the engine 1 corresponding to each cylinder perform an ignition operation in response to a high voltage output from the igniter 32. The ignition timing of each spark plug 31 is determined by the high voltage output timing from the igniter 32.

  The catalytic converter 33 provided in the exhaust passage 4 incorporates a three-way catalyst 34 for purifying the exhaust discharged from the engine 1 to the exhaust passage 4. The oxygen sensor 43 provided in the exhaust passage 4 detects the oxygen concentration Ox in the exhaust discharged from the engine 1 to the exhaust passage 4 and outputs an electric signal corresponding to the detected value.

  The rotational speed sensor 44 provided in the engine 1 detects the rotational speed of the crankshaft 6, that is, the engine rotational speed NE, and outputs an electrical signal corresponding to the detected value. A water temperature sensor 45 provided in the engine 1 detects the temperature (cooling water temperature) THW of the cooling water flowing inside the engine 1 and outputs an electrical signal corresponding to the detected value.

  The engine 1 of this embodiment includes an evaporated fuel processing device 35 as an evaporated fuel processing means. This device 35 collects and processes the evaporated fuel (vapor) generated in the gasoline tank 13 without releasing it into the atmosphere. This apparatus includes a canister 37 that temporarily collects vapor generated in the gasoline tank 13 through a vapor line 36. The canister 37 contains an adsorbent (not shown) that adsorbs vapor. A purge line 38 extending from the canister 37 is connected to the intake passage 2 downstream from the electronic throttle device 8. During operation of the engine 1, intake negative pressure generated in the intake passage 2 acts on the canister 37 through the purge line 38, so that vapor (fuel component) collected in the canister 37 is purged into the intake passage 2 through the purge line 38. Is done. The purged vapor is taken into the combustion chamber 3 of the engine 1 for combustion and processed. A purge control valve 39 provided in the purge line 38 is controlled to adjust the vapor purge flow rate in the purge line 38.

  In this embodiment, the electronic control unit (ECU) 50 inputs various signals output from the throttle sensor 41, the intake pressure sensor 42, the oxygen sensor 43, the rotation speed sensor 44, and the water temperature sensor 45. Based on these input signals, the ECU 50 controls the injectors 12, 22, the igniter 32, the purge control valve 39, and the like in order to execute fuel injection control including air-fuel ratio control, vapor purge control, ignition timing control, and the like. To do.

  Here, the fuel injection control is to control the fuel injection amount and the fuel injection timing by controlling the injectors 12 and 22 in accordance with the operating state of the engine 1. The air-fuel ratio control is feedback control of the air-fuel ratio of the engine 1 to a predetermined target air-fuel ratio such as the theoretical air-fuel ratio by controlling the injectors 12 and 22 based on the detection signal of the oxygen sensor 43. The ignition timing control is to control the ignition timing by each spark plug 31 by controlling the igniter 32 according to the operating state of the engine 1.

  In this embodiment, the ECU 50 corresponds to a learning control unit and a prohibiting unit of the present invention. The ECU 50 has a known configuration including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM, and the like. The ROM stores in advance predetermined control programs related to the various controls described above. The ECU (CPU) 50 executes the various controls described above in accordance with these control programs.

  Next, processing contents of fuel injection control including air-fuel ratio control among various controls executed by the ECU 50 will be described with reference to FIGS. FIG. 2 is a flowchart showing the contents of the fuel injection control. FIG. 3 is a flowchart showing the contents of the air-fuel ratio learning control for gasoline. FIG. 4 is a flowchart showing the contents of air-fuel ratio learning control for CNG.

  When the processing shifts to the routine of FIG. 2, in step 100, the ECU 50 outputs various signals relating to the throttle opening degree TA, the intake pressure PM, the engine speed NE, the coolant temperature THW, and the oxygen concentration Ox from the various sensors 41-45. Read.

  Thereafter, in step 110, the ECU 50 determines whether or not the current operation condition is a gasoline operation using gasoline based on the read various signals TA, PM, NE, THW, and Ox. If the determination result is affirmative, the ECU 50 proceeds to step 120 in order to execute gasoline injection control.

  In step 120, the ECU 50 calculates a gasoline basic injection amount TAUGB. The ECU 50 calculates the basic gasoline injection amount TAUGB by referring to predetermined function data (map) based on the read intake pressure PM and engine rotational speed NE.

  Thereafter, in step 130, the ECU 50 calculates various correction values KC such as high temperature correction. The ECU 50 calculates various correction values KC based on the read intake pressure PM, cooling water temperature THW, and the like.

  Thereafter, in step 140, the ECU 50 reads the gasoline feedback correction value FAFG. The ECU 50 makes this correction value FAFG known by a separate calculation routine so that the actual air-fuel ratio A / F obtained from the oxygen concentration Ox detected by the oxygen sensor 43 becomes the predetermined target air-fuel ratio (theoretical air-fuel ratio). And is stored in the RAM.

  Thereafter, in step 150, the ECU 50 reads the gasoline air-fuel ratio learning value FGG. The ECU 50 calculates the air-fuel ratio learning value FGG by a separate air-fuel ratio learning control routine based on the oxygen concentration Ox detected by the oxygen sensor 43 and stores it in the backup RAM. Here, the gasoline air-fuel ratio learning value FGG corresponds to a deviation between the actual air-fuel ratio A / F obtained from the oxygen concentration Ox and a predetermined target air-fuel ratio (theoretical air-fuel ratio). This air-fuel ratio learning value FGG reflects the injection state of gasoline from the gasoline injector 12, and further, mechanical individual differences and changes over time of the gasoline injector 12 and the gasoline pump 15 constituting the gasoline supply device 11.

  Here, the air-fuel ratio learning control for gasoline will be described. FIG. 3 shows a gasoline air-fuel ratio learning control routine. When the process proceeds to this routine, in step 300, the ECU 50 determines whether or not a predetermined time has elapsed after the fuel switching. Here, for example, “10 seconds” can be applied as the “predetermined time”. This waiting time of “predetermined time” corresponds to a time from when the fuel to be used is switched to when the fuel before switching remaining in the intake passage 2 and the combustion chamber 3 disappears or longer.

  If the determination result in step 300 is negative, the ECU 50 sets a purge prohibition flag Fpc to “1” in step 350 in order to prohibit vapor purge. That is, in this embodiment, when the predetermined time has not elapsed after the fuel switching, the ECU 50 prohibits the purge of the vapor on the assumption that the learning of the gasoline air-fuel ratio learning value FGG is incomplete.

  On the other hand, if the determination result in step 300 is affirmative, the ECU 50 proceeds to step 310 and determines whether there is an air-fuel ratio learning completion history related to gasoline. If the determination result is affirmative, the ECU 50 proceeds to step 340 and resets the purge prohibition flag Fpc to “0” in order to allow vapor purge. On the other hand, when this determination result is negative, the ECU 50 proceeds to step 320.

  In step 320, the ECU 50 executes an air-fuel ratio learning process for gasoline. That is, the ECU 50 calculates the gasoline air-fuel ratio learning value FGG by a known method. The calculated gasoline air-fuel ratio learned value FGG is stored as a learned value in the backup RAM of the ECU 50 corresponding to the values of various parameters relating to the operating state of the engine 1.

  That is, in this embodiment, the ECU 50 starts learning the gasoline air-fuel ratio learning value FGG after waiting for a predetermined time when the fuel used during operation of the engine 1 is switched from CNG to gasoline. is there.

  Thereafter, in step 330, the ECU 50 determines whether or not air-fuel ratio learning relating to gasoline has been completed. That is, the ECU 50 determines whether or not the calculation of the gasoline air-fuel ratio learning value FGG is completed based on the air-fuel ratio feedback state. When this determination result is negative, the ECU 50 executes the process of step 350 as described above. On the other hand, if the determination result is affirmative, the ECU 50 resets the purge prohibition flag Fpc to “0” in order to allow vapor purge in step 340.

Returning to the description of the flowchart of FIG. 2, in step 160, the ECU 50 calculates the final gasoline injection amount TAUG based on the following calculated formula (1) based on the various parameters calculated above.
TAUG ← TAUGB * KC * FAFG * FGG (1)

  In step 170, the ECU 50 executes gasoline injection control by controlling each gasoline injector 12 based on the calculated gasoline injection amount TAUG.

  On the other hand, if the determination result of step 110 in FIG. 2 is negative, the ECU 50 proceeds to step 180 in order to execute CNG injection control.

  In step 180, the ECU 50 calculates a CNG basic injection amount TAUCB. The ECU 50 calculates the CNG basic injection amount TAUCB by referring to predetermined function data (map) based on the read intake pressure PM and engine rotational speed NE.

  Thereafter, in step 190, the ECU 50 calculates various correction values KC such as high temperature correction. The ECU 50 calculates various correction values KC based on the read intake pressure PM, cooling water temperature THW, and the like.

  Thereafter, in step 200, the ECU 50 reads the CNG feedback correction value FAFC. The ECU 50 makes the correction value FAFC known by a separate calculation routine so that the actual air-fuel ratio A / F obtained from the oxygen concentration Ox detected by the oxygen sensor 43 becomes the predetermined target air-fuel ratio (theoretical air-fuel ratio). And is stored in the RAM.

  Thereafter, in step 210, the ECU 50 reads the CNG air-fuel ratio learning value FGC. The ECU 50 calculates the air-fuel ratio learning value FGC by a separate air-fuel ratio learning control routine based on the oxygen concentration Ox detected by the oxygen sensor 43 and stores it in the backup RAM. Here, the CNG air-fuel ratio learning value FGC corresponds to a deviation between the actual air-fuel ratio A / F obtained from the oxygen concentration Ox and a predetermined target air-fuel ratio (theoretical air-fuel ratio). This air-fuel ratio learning value FGC reflects the state of CNG injection from the CNG injector 22, and further, the mechanical individual difference of the CNG injector 22 constituting the CNG supply device 21, changes with time, and the like.

  Here, the air-fuel ratio learning control related to CNG will be described. FIG. 4 shows a CNG air-fuel ratio learning control routine. When the process proceeds to this routine, in step 400, the ECU 50 determines whether or not a predetermined time has elapsed after the fuel switching. This “predetermined time” is the same as in the case of the air-fuel ratio learning control for gasoline.

  If the determination result in step 400 is negative, the ECU 50 sets a purge prohibition flag Fpc to “1” in step 450 to prohibit vapor purge. That is, in this embodiment, when the predetermined time has not elapsed after the fuel switching, the ECU 50 prohibits the purge of vapor because the learning of the CNG air-fuel ratio learning value FGC is incomplete.

  On the other hand, if the determination result in step 400 is affirmative, the ECU 50 proceeds to step 410 and determines whether or not there is an air-fuel ratio learning completion history regarding CNG. If the determination result is affirmative, the ECU 50 proceeds to step 440 and resets the purge prohibition flag Fpc to “0” in order to allow vapor purge. On the other hand, when this determination result is negative, the ECU 50 proceeds to step 420.

  In step 420, the ECU 50 executes an air-fuel ratio learning process for CNG. That is, the ECU 50 calculates the CNG air-fuel ratio learning value FGC by a known method. The calculated CNG air-fuel ratio learned value FGC is stored as a learned value in the backup RAM of the ECU 50 corresponding to the values of various parameters related to the operating state of the engine 1.

  That is, in this embodiment, the ECU 50 starts learning the CNG air-fuel ratio learning value FGC after waiting for a predetermined time when the fuel used when the engine 1 is operated is switched from gasoline to CNG. is there.

  Thereafter, in step 430, the ECU 50 determines whether or not air-fuel ratio learning regarding CNG is completed. That is, the ECU 50 determines whether or not the calculation of the CNG air-fuel ratio learning value FGC is completed based on the air-fuel ratio feedback state. When this determination result is negative, the ECU 50 executes the process of step 450 as described above. On the other hand, if the determination result is affirmative, the ECU 50 resets the purge prohibition flag Fpc to “0” in step 440 to allow vapor purge.

Returning to the description of the flowchart of FIG. 2, in step 220, the ECU 50 calculates the final CNG injection amount TAUC based on the following calculated formula (2) based on the various parameters calculated above.
TAUC ← TAUCB * KC * FAFC * FGC (2)

  In step 230, the ECU 50 executes CNG injection control by controlling each CNG injector 22 based on the calculated CNG injection amount TAUC.

  Next, evaporative fuel processing control executed in response to the above fuel injection control will be described. FIG. 5 is a flowchart showing the contents of the evaporated fuel processing control.

  When the process proceeds to this routine, in step 500, the ECU 50 outputs various signals relating to the throttle opening TA, the intake pressure PM, the engine speed NE, the coolant temperature THW, the oxygen concentration Ox, etc. from the various sensors 41-45. Read.

  Thereafter, in step 510, the ECU 50 determines whether or not a predetermined purge condition is satisfied. That is, the ECU 50 determines whether or not a condition for purging vapor from the canister 37 to the intake passage 2 is satisfied based on the read intake pressure PM, engine speed NE, cooling water temperature THW, and the like. If this determination result is negative, the ECU 50 proceeds to step 550 and closes the purge control valve 39 in order to stop the purge.

  On the other hand, if the determination result in step 510 is affirmative, the ECU 50 determines in step 520 whether vapor purge should be prohibited from the relationship with the air-fuel ratio learning control. The ECU 50 makes this determination based on the value of the purge prohibition flag Fpc set in correspondence with the air-fuel ratio learning control as described above. If the determination result is affirmative, the ECU 50 proceeds to step 550 and closes the purge control valve 39 in order to prohibit vapor purge.

  That is, in this embodiment, the ECU 50 sets the purge prohibition flag Fpc to “1” from the start to the completion of learning of the air-fuel ratio learning values FGG and FGC, thereby evaporating fuel processing apparatus. Vapor purging by 35 is prohibited.

  On the other hand, when the determination result in step 520 is negative, in step 530, the ECU 50 calculates the purge duty value PDY. The ECU 50 refers to this purge duty value by referring to predetermined function data (map) based on the intake pressure PM, the engine rotational speed NE, etc., in order to adjust the vapor purge flow rate in accordance with the operating state of the engine 1. PDY is calculated.

  Thereafter, in step 540, the ECU 50 opens the purge control valve 39 based on the calculated purge duty value PDY. That is, the opening degree of the purge control valve 39 is controlled. Thus, the vapor purge flow rate from the canister 37 to the intake passage 2 is adjusted according to the operating state of the engine 1.

  According to the air-fuel ratio learning control apparatus for a bi-fuel engine of this embodiment described above, when the fuel to be used is switched from CNG to gasoline during operation of the engine 1, the ECU 50 performs the gasoline air-fuel ratio learning value FGG. ECU 50 starts learning the CNG air-fuel ratio learning value FGC when the fuel to be used is switched from gasoline to CNG. Therefore, the gasoline air-fuel ratio learning value FGG and the CNG air-fuel ratio learning value FGC Each is learned individually. In addition, the ECU 50 prohibits vapor purge by the evaporated fuel processing device 35 from the start to the completion of learning of the air-fuel ratio learning values FGG, FGC, so that the air-fuel ratio learning values FGG, FGC During learning, the vapor is not purged into the intake passage 2, and the air-fuel ratio learning values FGG and FGC are not erroneously learned by the vapor. Therefore, each of the CNG air / fuel ratio learning value FGC and the gasoline air / fuel ratio learning value FGG can be accurately learned.

  In this embodiment, the ECU 50 starts learning the air-fuel ratio learning values FGG and FGC after a predetermined time has elapsed since the fuel used was switched between CNG and gasoline. For this reason, it becomes possible to learn the air-fuel ratio learning values FGG and FGC for the used fuel after switching after the remaining amount of used fuel before switching disappears from the intake passage 2 and the combustion chamber 3. As a result, it is possible to more accurately learn each of the CNG air-fuel ratio learned value FGC and the gasoline air-fuel ratio learned value FGG by eliminating the influence of the fuel used before switching.

  Further, in this embodiment, when the vapor purge is performed, the ECU 50 stops learning the air-fuel ratio learning values FGG, FGC. Therefore, learning of the air-fuel ratio learning values FGG and FGC is not performed during the purge of vapor, and the air-fuel ratio learning values FGG and FGC are not erroneously learned by the vapor. As a result, it is possible to more accurately learn the CNG air-fuel ratio learning value FGC and the gasoline air-fuel ratio learning value FGG without the influence of the purged vapor.

  In this embodiment, since the air-fuel ratio learning values FGG and FGC can be accurately learned as described above in the bi-fuel engine that operates using at least one of CNG and gasoline, the air-fuel ratio learning values FGC, FGG can be suitably reflected in the calculation of the CNG injection amount TAUC and the gasoline injection amount TAUG. For this reason, each of the fuel injection control of CNG and the fuel injection control of gasoline can be suitably performed according to the operating state of the engine 1, and the deterioration of the emission of the engine 1 and the occurrence of knocking can be suppressed.

  In addition, this invention is not limited to the said embodiment, In the range which does not deviate from the meaning of invention, a part of structure can be changed suitably and it can implement as follows.

  (1) In the above embodiment, CNG is used as the gaseous fuel and gasoline is used as the liquid fuel. However, the types of the gaseous fuel and the liquid fuel are not limited to CNG and gasoline, and can be changed as appropriate. .

  (2) In the bi-fuel engine of the above embodiment, the fuel injection control of CNG that is a gaseous fuel and the fuel injection control of gasoline that is a liquid fuel are selectively switched and executed. Accordingly, the CNG fuel injection control and the gasoline fuel injection control may be executed simultaneously.

  The present invention can be used for a fuel injection control device of a bi-fuel engine and an automobile equipped with them.

1 Engine 2 Air intake passage 11 Gasoline supply device 12 Gasoline injector 13 Gasoline tank (fuel tank)
14 Gasoline line 15 Gasoline pump 21 CNG supply device 22 CNG injector 23 CNG cylinder 24 CNG line 35 Evaporated fuel processing device (evaporated fuel processing means)
36 Vapor line 37 Canister 38 Purge line 39 Purge control valve 50 ECU (learning control means, prohibition means)

Claims (3)

A bi-fuel engine air-fuel ratio learning control device comprising learning control means for learning an air-fuel ratio learning value in a bi-fuel engine operated using at least one of gas fuel and liquid fuel,
The bi-fuel engine comprises evaporative fuel processing means for purging the bi-fuel engine to process evaporative fuel generated in a fuel tank storing the liquid fuel,
The learning control means is configured to start learning of the air-fuel ratio learning value when fuel used during operation of the bi-fuel engine is switched between the gaseous fuel and the liquid fuel,
The bi-fuel engine is provided with prohibiting means for prohibiting purging of the evaporated fuel by the evaporated fuel processing means from the start to completion of learning of the air-fuel ratio learning value. Fuel ratio learning control device.   The learning control means starts learning the air-fuel ratio learning value after a predetermined time has elapsed since the fuel used during operation of the bi-fuel engine is switched between the gaseous fuel and the liquid fuel. The air-fuel ratio learning control apparatus for a bi-fuel engine according to claim 1.   3. The air-fuel ratio learning control device for a bi-fuel engine according to claim 1, wherein the learning control unit stops learning of the air-fuel ratio learning value when the purge of the evaporated fuel is performed.

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