Title of Invention	"FUEL INJECTION CONTROL DEVICE FOR A MULTI-FUEL ENGINE"
Abstract	[Problem] To provide a fuel injection control device for a multi-fuel engine where a catalyzer does not become damaged even when there is a difference between an alcohol concentration learning value for a fuel and actual alcohol concentration. Resolving Means] At a fuel injection amount control unit 105, a reduction amount correction unit 105a reduces and corrects an amount of fuel injected by just a prescribed period when a learning value stored in a storage unit 103 is for a high concentration. A learning value reviewing unit 105b then reviews the learning value for E-concentration based on a value calculated by an 02 sensor 15 during reducing and correction of the amount of fuel injected. A switching determination unit 105c than determines whether or not the fuel injected has been switched over from fuel remaining within a fuel pipe 17 to fuel within the fuel tank. When the engine then starts and it is determined that the injected fuel has been switched over to the fuel within the fuel tank, when the learning value for the E-concentration is for a high-concentration and the engine load is in a high load state, the fuel injection amount control unit 105 refers to the fuel injection map according to the learning value and the obtained fuel injection quantity is reduced and corrected.

Title of Invention

"FUEL INJECTION CONTROL DEVICE FOR A MULTI-FUEL ENGINE"

Abstract

[Problem] To provide a fuel injection control device for a multi-fuel engine where a catalyzer does not become damaged even when there is a difference between an alcohol concentration learning value for a fuel and actual alcohol concentration. Resolving Means] At a fuel injection amount control unit 105, a reduction amount correction unit 105a reduces and corrects an amount of fuel injected by just a prescribed period when a learning value stored in a storage unit 103 is for a high concentration. A learning value reviewing unit 105b then reviews the learning value for E-concentration based on a value calculated by an 02 sensor 15 during reducing and correction of the amount of fuel injected. A switching determination unit 105c than determines whether or not the fuel injected has been switched over from fuel remaining within a fuel pipe 17 to fuel within the fuel tank. When the engine then starts and it is determined that the injected fuel has been switched over to the fuel within the fuel tank, when the learning value for the E-concentration is for a high-concentration and the engine load is in a high load state, the fuel injection amount control unit 105 refers to the fuel injection map according to the learning value and the obtained fuel injection quantity is reduced and corrected.

Full Text	[Document] Specification [Title of the Invention] FUEL INJECTION CONTROL DEVICE FOR A MULTI-FUEL ENGINE [Technical Field] [0001] The present invention relates to a fuel injection control device for a multi-fuel engine, and particularly relates to a fuel injection control device for a multi-fuel engine for reducing the load on a catalyzer even when alcohol concentration of the fuel is made lower than the learning value. [Background Art] [0002] In recent years, alcohol fuels have shown promise as an alternative to fossil fuels from the point of view of environmental protection. FFV's (FFV: Flexible Fuel Vehicles) capable of travelling even on an alcohol fuel mixture that is a mixture of alcohol and gasoline, in addition to travelling on just gasoline, are being developed. In addition to the calorific value and the vaporization characteristics being different compared to fuel that is 100% gasoline, an alcohol/fuel mixture has different characteristics depending on the alcohol concentration indicating a mixing ratio with respect to gasoline. This means that when an alcohol fuel mixture is used in an engine for which the use of fuel that is 100% gasoline is assumed, a controlled fuel-air ratio departs from a theoretical fuel air ratio, so that an exhaust component increases or operability changes. Regarding this kind of technological problem, technology is disclosed in patent document 1 for obtaining the same equivalence ratio by correcting an amount of fuel injected to an engine according to an alcohol concentration of alcohol/fuel mixture. [0003] With an FFV, the concentration of oxygen within the exhaust gas while the vehicle is travelling is detected by an oxygen concentration sensor. Alcohol concentration within the fuel is then repeatedly learned based on the results of this detection and the amount of fuel injected is controlled based on the learning results. The learning results for the alcohol concentration are then repeatedly updated in memory. When a main switch is then turned off and then subsequently turned on again, learning results for the alcohol concentration for the previous time are read out from the memory. The amount of fuel injected can be controlled on the assumption that the fuel is of the alcohol concentration of the learned results. [Patent Document 1] Japanese Patent Publication Laid-open No. 2004-293491. DISCLOSURE OF INVENTION [Problems To Be Solved by the Invention] [0004] With the above conventional technology, when fuel of a different alcohol concentration is supplied after the main switch is turned off, the next time the engine is started the learning results for the alcohol concentration and the actual alcohol concentration will be different. [0005] The composition of ethanol contains oxygen atoms. The amount of oxygen per unit volume required for combustion can therefore be small compared to the combustion of gasoline. The amount of fuel injected is also increased as the alcohol concentration is increased in order to obtain the same equivalence ratio. When the actual alcohol concentration is lower than the alcohol concentration for the learned results, accidental firing occurs due to the air/fuel ratio being too rich and the load on the catalyzer therefore becomes substantial. [0006] In order to resolve the problems of the related art, it is therefore an object of the present invention to provide a fuel injection control device for a multi-fuel engine where a catalyzer is not damaged even if there is a difference between learning results for alcohol concentration relating to the fuel and actual alcohol concentration. [Means for resolving the problems] [0007] In order to achieve the above object, in the present invention, a fuel injection control device for a multi-fuel engine that controls an amount of fuel injected based on alcohol concentration of fuel is characterized by being provided with the following. [0008] (1) An oxygen concentration sensor that detects concentration of oxygen within an exhaust gas, an alcohol concentration learning unit that learns alcohol concentration of the injected fuel based on a value calculated by the oxygen concentration sensor, an alcohol concentration storage unit that stores learning values for the alcohol concentration, and a fuel injection amount control unit that controls an amount of fuel injected based on a learning value are provided. The fuel injection amount control unit comprises a reduction and correction unit that reduces and corrects the amount of fuel injected so as to be less than the injection amount corresponding to the read out learning value, and a reviewing unit that reviews the learning values based on values calculated by the oxygen concentration sensor during reduction and correction. The amount of fuel injected is reduced and corrected by just a prescribed period by the reduction and correction unit when the read out learning value is for a high concentration when the engine is starting, with the amount of fuel injected then being controlled thereafter based on the reviewed learning value. [0009] (2) A determining unit that determines whether or not the injected fuel has switched over from fuel remaining within a fuel pipe to fuel within a fuel tank is also provided. The fuel injection amount control unit reduces and corrects the amount of fuel injected by just a prescribed amount using the reduction and correction unit when the injected fuel switches over to the fuel within the fuel tank, with the amount of fuel injected being controlled thereafter based on the reviewed learning value. [0010] (3) The fuel injection amount control unit reduces and corrects the amount of fuel injected when the read out learning value is for a high concentration and the running state of the engine is in a high load region. [0011] (4) The reduction and correction of the amount of fuel injected can also be carried out in stages. [Effects of the Invention] [0012] According to the present invention, the following results are achieved. (1) When the engine starts up, when the learning value stored in relation to alcohol concentration of fuel is high, the amount of fuel injected is reduced and corrected until reviewing of this learning value is complete. This means that it is possible to prevent the air/fuel ratio from becoming over-rich even if actual alcohol concentration falls below the learning value in order to supply fuel of a low alcohol concentration during stopping. It is therefore possible to prevent a load on a catalyzer from becoming large. (2) It is also possible to reduce and correct the amount of fuel injected until reviewing of a learning value is complete not only when the engine is starting up, but also at the time of switching the injected fuel from fuel remaining within a fuel pipe to fuel within the fuel tank. It is therefore possible to prevent the learning value from being reviewed based on supplied fuel that remains in the fuel pipe. (3) The reduction and correction of the injected fuel is only carried out when the learning value is for a high concentration and the running state of the engine is for a high load region. It is therefore possible to prevent reduction and correction from being implemented under conditions where protection of the catalyzer is not necessary. (4) The reduction and correction of the injected fuel can also be carried out in stages. It is therefore possible to prevent the injected fuel from being excessively reduced and corrected. Best Mode for Carrying out the Invention [0013] The following is a detailed description with reference to the drawings of a preferred embodiment of the present invention. FIG. 1 is a diagram showing an overall configuration for an internal combustion engine and a fuel injection control system of an embodiment of the present invention. [0014] An intake pipe 2 and an exhaust pipe 7 are coupled to an engine 1. An air cleaner 3 is provided on the upstream side of the intake pipe 2. An amount of air taken into the engine 1 can be adjusted by a throttle valve 4 arranged within the intake pipe 2. An extent of opening of the throttle valve 4 can be detected by a throttle opening sensor (hereinafter denoted as a TH sensor) 11. [0015] An intake pipe absolute pressure sensor (expressed in the following as PBA sensor) 12 measures intake pipe absolute pressure PBA. An intake air temperature sensor (expressed as "TA sensor" in the following) 16 measures intake air temperature TA within the intake pipe 2. A water temperature sensor (hereinafter expressed as "TW sensor") 13 measures a circulating water temperature TW of the engine 1. A crank angle sensor (hereinafter, expressed as "CRK sensor") 14 measures a crank angle CRK that represents a crank position of the engine 1. [0016] A three-way catalytic converter 8 is provided on the downstream side of the exhaust pipe 7. An oxygen concentration sensor (hereinafter referred to as an 02 sensor) 15 for measuring oxygen concentration within the exhaust gas within the exhaust pipe 7 is provided between the engine 1 of the exhaust pipe 7 and the three-way catalytic converter 8. An Engine Control Unit (ECU) 10 executes various types of engine control including the control of fuel injection based on detection signals outputted by each of the sensors. An injector 5 opens a valve that opens in response to an injection control signal outputted by the ECU 10 and injects a fuel mixture of gasoline or gasoline and alcohol (in this embodiment, ethanol). [0017] FIG. 2 is a functional block view showing a configuration for main essential parts for the ECU 10. Numerals that are the same as previously are used to denote identical or similar portions. Aspects of the configuration that are not necessary for explaining the present invention are not included in the drawings. [0018] A fuel injection map is stored in a ROM 101 each fuel alcohol concentration (hereinafter referred to as E concentration). FIG. 3 is a view schematically representing storage contents of the ROM 101. In this embodiment, a Pb/Ne map, an Ne/TH map, and various correction coefficient tables and start control information are stored in a mutually correlated manner each fuel ethanol concentration (El, E2, E3, E4). [0019] As described previously, the composition of the ethanol contains oxygen atoms. This means that the amount of oxygen required per unit volume for combustion is small compared to when gasoline is combusted. The theoretical air/fuel ratio is therefore smaller when a fuel that is a mixture of ethanol and gasoline is used than the case when fuel of just gasoline is used. It is therefore necessary to set injection control information each mixture ratio for the ethanol and the gasoline in order for the engine 1 to run in an optimum state. [0020] On the other hand, when the ethanol is of a certain concentration, it is known from experimental results etc. that the same extent of control can be carried out as for when appropriate maps and tables for other concentrations are supplied as for with maps and tables for ensuring that the engine 1 runs in an optimum state even when another concentration is applied within a certain fixed range. [0021] In this embodiment, as shown in the example in FIG. 4, a range for ethanol concentration is set and four types El, E2, E3, E4 (where the alcohol concentration is E1 in advance as reference concentrations for ethanol within respective ranges. A Pb/Ne map, an Ne/TH map, and various correction coefficient tables and start control information are then prepared in advance each respective reference concentration. [0022] There may be any number of reference concentrations providing there are three or more that may be appropriately allocated to any concentration from 0% to 100%. The respective maps and tables are set to have ranges where concentrations overlap as shown in FIG. 4. [0023] In this embodiment, sets of Pb/Ne maps, Ne/TH maps, various correction coefficient tables and start injection information prepared each ethanol reference concentration are denoted as "map sets", and there are also cases where map sets for each ethanol reference concentration are denoted as an El map set, an E2 map set, an E3 map set, and an E4 map set. [0024] Returning to FIG. 2, an alcohol concentration learning unit 102 learns the E-concentration of the injected fuel based on a measured value (voltage) V02 of the 02 sensor 15 representing the oxygen concentration within the exhaust pipe 7. The learning results are then repeatedly updated in a storage unit 103. An engine load detecting unit 104 detects current engine load based on the engine speed Ne and an extent of throttle opening TH. [0025] At a fuel injection control unit 105, the reduction amount correction unit 105a reduces and corrects the amount of fuel injected for just a prescribed period when a learning value stored in the storage unit 103 is a high concentration (E3 or E4 in this embodiment). A learning value revising unit 105b revises learning values for the E-concentration based on the measured values of the 02 sensor 15 during reduction and correction of the amount of fuel injected. A switching determination unit 105c determines whether or not the injected fuel has switched from the fuel remaining within a fuel pipe 17 to the fuel within the fuel tank. [0026] When the engine is started and it is determined by the switching determination unit 105c that the injected fuel is switched over to the fuel within the fuel tank, when the learning value for the E-concentration stored in the storage unit 103 is a high concentration and the engine load detected by the engine load detection unit 104 is a prescribed high load state, the fuel injection amount control unit 105 reduces and corrects an amount of injected fuel obtained by referring to a fuel injection map according to the learning value. The fuel injection amount control unit 105 then ends the reduction and correction when the learning value is reviewed by the learning value reviewing unit 105b during reducing and correcting of the injected fuel. [0027] A detailed description is now given of the operation of a first embodiment of the present invention while referring to a flowchart and a timing chart. FIG. 5 is a main flowchart showing a procedure for catalyzer (CAT) protection processing of a first embodiment of the present invention and mainly shows the operation of the ECU 10. FIG. 6 is a flowchart showing a procedure for "lean control" executed within the main flow. FIG. 8 and FIG. 10 are flowcharts showing procedures for "lean coefficient searching" and "MAP determination" executed within the respective "lean control". FIG. 11 is a flowchart showing a procedure for "E-determination point updating" executed within the "MAP determination". [0028] Here, first, the operation in the case where the engine is started in a state where the E-concentration within the fuel tank has fallen as far as the level E2 is described using a time series along the timing chart of FIG. 13 because gasoline is supplied during engine stopping regardless of whether the learning value for the E-concentration stored in the storage unit 103 (E-concentration learning value Eindex) is the level E4 of the highest concentration. [0029] In step S1 of the main flow (FIG. 5), an E-determination (alcohol concentration determination) point Pe representing the alcohol concentration determination history is referred to. The CAT protection processing of this embodiment is only executed at a time (first time) immediately after the engine starts, and a time (second time) where it is estimated that all of the fuel within the fuel pipes (i.e. fuel of an alcohol concentration prior to refueling) has been consumed and injection of fuel within the fuel tank has commenced. Here, Pe represents the number of times of execution of the CAT protection processing has been completed. If it is determined that Pe ≥2 in step S1, it is determined that the CAT protection processing has already been executed two times. Step S7 is then proceeded to, a lean (dilution) coefficient Kc1h is returned to an initial value of "1.0" (i.e. the fuel is not made lean) and the processing ends. [0030] On the other hand, an initial value for the E-determination point Pe is "0". It is therefore determined that Pe when the E-concentration learning value Eindex is a low concentration and the amount of fuel injected is relatively small. [0031] With regards to this, if the stored learning value Eindex is a high concentration such as level E4 or level E3 as in this embodiment, quantity reduction and correction is carried out by multiplying the fuel injection amount Tout with the lean coefficient Kc1h. As a result, step S3 where the air/fuel ratio is to be made lean is proceeded to. In step S3, the E-determination point Pe is referred to anew. If the E-determination point Pe is other than "1" (i.e. Pe = 0) , step S5 is proceeded to. If the E-determination point is "1", step S4 is proceeded to. Pe = 0 directly after the engine starts. Step S5 is then proceeded to, and first time "lean control" is executed. [0032] FIG. 6 is a flowchart showing a procedure for the "lean control". In step S21, it is determined whether or not a running state of the engine is in a high load region constituting a target of the CAT protection control based on the extent of opening of the throttle TH and the engine speed NE. In this embodiment, as shown in FIG. 7, if the extent of opening the throttle TH is greater than a prescribed reference extent of opening THref and the engine speed NE is greater than a prescribed reference speed NEref, the CAT protection control is determined to be a required high load region. Step S22 is then proceeded to. If the region is not a high load region, the processing ends. [0033] In step S22, a cooling water temperature TW is compared with a warm up determination threshold value TWref. If TW > TWref, it is determined that the warm up has ended and "searching for a lean coefficient" of step S26 is proceeded to. If TW ^ TWref, it is determined that this is prior to warm up. Step S23 is then proceeded to and a measurement value V02 of the 02 sensor 15 is compared with an active determination threshold value Vref1. If this is before the time T1 of FIG. 13, then V02 ≥ Vref1 and it is determined that the 02 sensor 15 is not-yef active and the processing therefore ends. With regards to this, if V02 is complete, step S24 is proceeded to and a 'lean coefficient search" is executed. [0034] In this embodiment, before warming up of the engine, the 02 sensor 15 becoming active is awaited in order to ensure drivability immediately after starting and a lean coefficient search (step S24) is executed. After warming up, the lean coefficient search (step S26) is executed from before the 02 sensor 15 becoming active. [0035] FIG. 8 is a flowchart showing a procedure for the "lean coefficient search". Here, an optimum lean coefficient Kclh is searched based on the cooling water temperature TW.[0036] In step S31, the cooling water temperature TW and a prescribed threshold value TWstep are compared in order to determine whether the injected fuel is made lean in stages (in this embodiment, two stages) or all in one go. If TW In step S33, a lean execution complete flag Fclh is referred to. Step S34 is then proceeded to because the flag Fclh is in the reset state (prior to making lean). In step S34, a prescribed count value is set to the first counter N1st that decides a period of implementation for the first stage of making fuel lean. In step S35, a first stage lean coefficient Kc1h1 ( corresponding to the current cooling water temperature TW is recorded at a time t2. In step S36, a lean execution complete flag Fc1h is set to "1". [0039] As a result, the lean coefficient Kc1h is multiplied with the fuel injection amount Tout calculated separately at the fuel injection amount control unit 105 by the reducing of correcting unit 106 so that amount of fuel injected is reduced. The air/fuel ratio therefore rises at the time t2 as shown in FIG. 13. As shown above, when retrieval of the lean coefficient search of step S24 (or step S26) is complete, step S25 of FIG. 6 is proceeded to and the MAP determination processing is implemented. [0040] FIG. 10 is a flowchart showing a procedure for the "MAP determination processing". The E-concentration learning value Eindex is then revised based on the output V02 OF THE 02 sensor 15. [0041] In step S50, a lean execution flag Fclh is referred to. In this case it is determined that Fc the1h = 1 (first stage) and step S51 is therefore proceeded to. In step S51, the first stage counter N1st is referred to and the main flow is immediately returned to until the first stage counter Nlst times out and the first stage of making lean is complete. [0042] Each of the processes described above are then repeated after this so that in the next "lean coefficient search process" (FIG. 8), in step S33, the lean execution flag Fc1h is determined to be "1" and step S37 is proceeded to. In step S37, the first stage counter N1st is referred to and step S38 is proceed to up until the counter Nlst times out. In step S38, as in step S35, the first stage lean coefficient Kc1h1 is retrieved from the first coefficient table correlated with the current E-concentration learning value Eindex taking the cooling water temperature TW as a parameter. In this embodiment, the lean coefficient Kclhl of the first coefficient table is fixed regardless of the cooling water temperature TW and the same value as for the previous time is therefore set. In step S39, as in step S36, the lean execution flag Fc1h1 is set to "1". The first stage current Nlst is then decremented in step S40. [0043] After this, at time t3 of FIG. 13, when the first stage counter Nlst times out and this is detected by step S51 of FIG. 10, step S52 is proceeded to. In step S52, the 02 sensor output V02 and the MAP switching threshold value Vref2 are compared in order to confirm the validity of the current E-concentration learning value Eindex. Here, it is determined that the sensor output V02 exceeds the MAP switching threshold value Vref 2 and the E-concentration learning value Eindex is not valid. A revision of the E-concentration learning value Eindex is then sent in advance to the second stage leaning. [0044] After this, when timing out of the first stage counter Nlst is also detected in step S37 of FIG. 8, the first stage of making leaner is complete, and step S41 is proceeded to in order to proceed to the second stage. In step S41, the lean execution flag Fc1h is referred to and step S42 is then proceeded to because that other than "2" is determined. In step S42, a prescribed count value is set to the second stage counter N2nd that decides the implementation period for the second stage of making lean. In step S43, a second stage lean coefficient clh2 is retrieved from the second coefficient table, an example of which is shown in FIG. 9, taking the cooling water temperature TW as a parameter. In step S44, a lean execution complete flag Fclh is set to "2". [0045] As a result, a second stage lean coefficient Kclh2 that is smaller than the first stage lean coefficient Kclhl is multiplied with the fuel injection amount Tout. The amount of fuel injected is therefore further reduced and the air/fuel ratio rises further upon the time t3 as shown in FIG, 13. As shown above, when the "lean coefficient searching" ends, FIG. 6 is again returned to and the "MAP determination processing" (FIG. 10) is again executed in step S25. [0046] In step S50 of FIG. 10, the lean execution flag Fclh is referred to and step S56 is proceeded to because a determination of Fclh = 2 is made here. In step S56, the 02 sensor output V02 and the MAP switching threshold value Vref2 are compared in order to confirm the validity of the current E-concentration learning value Einclex. Here, the sensor output V02 exceeds the MAP switching threshold value Vref2 and the current E-concentration learning value Eindex therefore cannot be determined to be valid. Step S57 is then proceeded to. In step S57, .the second stage counter N2nd is referred to, and the main flow (FIG. 5) is returned to immediately up until the counter N2nd times out. [0047] After this, the second counter N2nd times out at the time t4 of FIG. 13 and step S58 is proceeded to when this is detected in step S57 shown in FIG. 10. In step S58, the current E-concentration learning value Eindex is shifted by just the second stage to the low E side. Namely, if the current E-concentration. learning value Eindex is the level E4, the level E2 is switched over to. The "E-determination point updating processing" is then executed in step S59. [0048] FIG. 11 is a flowchart showing a procedure for E-determination point update processing. In step S71, the current E-determination point Pe is referred to and it is determined here that Pe FIG. 12 is a flowchart showing a procedure for a "fuel switching determination" executed separately in the background of the CAT protection processing. In step S11, an integral value STout for the fuel injection amount Tout for after starting the engine is compared with the fuel switching threshold value Tout_ref. The fuel switching reference value Tout_ref is set to a value capable of determining that all of the fuel remaining at the fuel pipe 17 has been injected. If ETout > Tout_ref, step S12 is proceeded to and it is taken that fuel switching is complete. On the other hand, if STout ≤ Tout_ref, step S13 is proceeded to and it is taken that fuel switching has not yet been achieved. [0050] Returning to FIG. 11, it has been determined that fuel switching has not yet been achieved immediately after starting of the engine. Step S74 is therefore proceeded to because it is determined that Pe = 0 and the current E-concentration learning value Eindex is determined. This is already E2 and as this is determined to be other than E3 and E4, step S76 is proceeded to. In step S7 6, the E-determination point Pe is updated by just "+2". [0051] If the E-determination point Pe is "2", in the main flow of FIG. 5, it is determined in S1 that Pe ≥ 2. The lean coefficient Kc1h is therefore returned to "1.0" in step S7 and the control ends. [0052] Next, the operation in the case where the E-concentration learning value Eindex stored in the storage unit 103 is a high concentration level E4 and remains the level EA even for the alcohol concentration within the fuel tank the next time that the engine starts is described using a time series with reference to the time chart of FIG. 14 and each of the flowcharts. If the stored E-concentration learning value Eindex is the high-concentration level E4, in step S35 for the lean coefficient search (FIG. 8), the first stage lean coefficient Kc1h1 is similarly recorded. As a result, the lean coefficient Kc1h is multiplied with the fuel injection amount Tout calculated separately by the fuel injection amount control unit 105 and the amount of fuel injected is therefore reduced. The air/fuel ratio therefore rises upon the timet2 in the example shown in FIG. 14. The first stage of making lean is then continued until the first stage counter N1st times out. [0053] After this, at a time t3, the first stage counter Nlst times out. Step S52 is then proceeded to when this is detected in step S51 of the MAP determination processing (FIG. 10). In step S52, the 02 sensor output V02 and the MAP switching threshold value Vref2 are compared in order to confirm the validity of the current E-concentration learning value Eindex. Here, the sensor output V02 is less than the MAP switching threshold value Vref2. It is therefore determined that the current E-concentration learning value Eindex is valid. Step S53 is then proceeded to and the current E-concentration learning value Eindex (E4) is maintained. The "E-determination point updating processing" is then executed in step S54. [0054] In the "E-determination point (Pe) updating processing of FIG. 11, in step S71, it is determined that the current E-determination point Pe is "0" and step S72 is proceeded to. In step S72, it is determined whether or not the fuel switching is complete. It is then determined that fuel switching over is not yet complete after starting of the engine. Step S73 is therefore proceeded to and the current E-determination point Pe is determined. Step S74 is therefore proceeded to because Pe = 0 and the current E-concentration learning value Eindex is determined. Step S75 is then proceeded to because E4 is determined here. The E-determination point Pe is then updated by " + 1" and Pe = 1. [0055] Returning to FIG. 10, in step S55, the lean coefficient Kc1h is returned to "1.0". Therefore, as shown in FIG. 14, the air/fuel ratio falls at the time t3. If the E-determination point Pe is updated, in the main flow of FIG. 5, step S4 is proceeded to from step S3. Switching over from the fuel within the fuel pipes to the fuel within the fuel tank is then awaited and lean control is then similarly executed a second time. [0056] In the above embodiments, a description is given where temperature of the engine is exemplified by water temperature but temperature of the engine can also be exemplified by oil temperature when an oil temperature sensor is provided. [0057] In this embodiment, in the first time lean control, if the results of the determination for the E-concentration learning value Eindex are still a high concentration level (E4, E3), lean control is implemented a second time. On the other hand, if the results of the determination for the E-concentration learning value Eindex have changed to a low concentration level (E2, El), the lean control is not implemented a second time. Further, in this embodiment, in the lean control the first and second times, lean control is only implemented a second time when the validity of the current E-concentration learning value Eindex cannot be confirmed when making lean the first time. If the validity of the E-concentration learning value Eindex can be confirmed when making lean the first time, making lean the second time can be omitted. Brief Description of the Drawings [0058] FIG. 1 is a diagram of an internal combustion engine and a fuel injection control system thereof of an embodiment of the present invention; FIG. 2 is a block diagram functionally expressing a configuration for an ECU; FIG. 3 is a view schematically expressing storage contents of a ROM; FIG. 4 is a view showing an example of a method for setting a range for ethanol concentration; FIG. 5 is a main flowchart of a catalyzer (CAT) protection process; FIG. 6 is a flowchart showing a procedure for "lean control"; FIG. 7 is a diagram showing conditions for determining that running conditions are in a high load region; FIG. 8 is a flowchart showing a procedure for "lean coefficient search processing"; FIG. 9 is a view showing an example of first and second coefficient tables (E4); FIG. 10 is a flowchart showing a procedure for "MAP determination processing"; FIG. 11 is a flowchart showing a procedure for "E-determination point update processing"; FIG. 12 is a flowchart showing a procedure for "fuel switching determination processing"; FIG. 13 is a timing chart showing lean control when alcohol concentration is changed from level E4 to level E2; and FIG. 14 is a timing chart showing lean control when the alcohol concentration is maintained at level E4. [Description of the Numerals] [0059] Engine 1, intake pipe 2, air cleaner 3, throttle valve 4, injector 5, exhaust pipe 7, three-way catalytic converter 8, engine control device 10, extent of throttle opening sensor 11, intake pipe absolute pressure sensor 12, water temperature sensor 13, crank angle sensor 14, 02 sensor 15, intake air temperature sensor 16 [Claim 1] A fuel injection ccnto.l device for a multi-fuel engine that controls an amount of fuel injected based on alcohol concentration of the fuel, said fuel injection control device comprising: an oxygen concentration sensor that detects concentration of oxygen within an exhaust gas; an alcohol concentration learning unit that learns alcohol concentration of the injected fuel based on a value calculated by the oxygen concentration sensor; an alcohol concentration storage unit that stores learning values for the alcohol concentration; and a fuel injection amount control unit that controls an amount of fuel injected based on a learning value, and the fuel injection amount control unit comprising: a reduction and correction unit that reduces and corrects the amount of fuel injected so as to be less than the injection amount corresponding to the read out learning value; and a reviewing unit that reviews the learning values based on values calculated by the oxygen concentration sensor during reduction and correction, wherein the amount of fuel injected is reduced and corrected by just a prescribed period by the reduction and correction unit when the read out learning value is for a high concentration when the engine is starting, with the amount of fuel injected then being controlled thereafter based on the reviewed learning value. [Claim 2] The fuel injection control device for a multi-fuel engine according to claim 1, further comprising a determining unit that determines whether or not the injected fuel has switched over from fuel remaining within a fuel pipe to fuel within a fuel tank, wherein the fuel injection amount control unit reduces and corrects the amount of fuel injected by just a prescribed amount using the reduction and correction unit when the injected fuel switches over to the fuel within the fuel tank, with the amount of fuel injected being controlled thereafter based on the reviewed learning value. [Claim 3] The fuel injection control device for a multi-fuel engine according to claim 1 or claim 2, wherein the fuel injection amount control unit reduces and corrects the amount of fuel injected when the read out learning value is for a high concentration and the running state of the engine is in a high load region. [Claim 4] The fuel injection control device for a multi-fuel engine according to any one of claims 1 to 3, wherein the reduction and correction of the amount of fuel injected is carried out in stages.

Full Text

[Document] Specification
[Title of the Invention]
FUEL INJECTION CONTROL DEVICE FOR A MULTI-FUEL ENGINE
[Technical Field]
[0001]
The present invention relates to a fuel injection control device for a multi-fuel engine, and particularly relates to a fuel injection control device for a multi-fuel engine for reducing the load on a catalyzer even when alcohol concentration of the fuel is made lower than the learning value.
[Background Art]
[0002] In recent years, alcohol fuels have shown promise as an alternative to fossil fuels from the point of view of environmental protection. FFV's (FFV: Flexible Fuel Vehicles) capable of travelling even on an alcohol fuel mixture that is a mixture of alcohol and gasoline, in addition to travelling on just gasoline, are being developed. In addition to the calorific value and the vaporization characteristics being different compared to fuel that is 100% gasoline, an alcohol/fuel mixture has different characteristics depending on the alcohol concentration indicating a mixing ratio with respect to gasoline. This means that when an alcohol fuel mixture is used in an engine for which the use of fuel that is 100% gasoline is assumed, a controlled fuel-air ratio departs from a theoretical fuel air ratio, so that an exhaust component increases or operability changes. Regarding this kind of technological problem, technology is disclosed in

patent document 1 for obtaining the same equivalence ratio by correcting an amount of fuel injected to an engine according to an alcohol concentration of alcohol/fuel mixture. [0003]
With an FFV, the concentration of oxygen within the exhaust gas while the vehicle is travelling is detected by an oxygen concentration sensor. Alcohol concentration within the fuel is then repeatedly learned based on the results of this detection and the amount of fuel injected is controlled based on the learning results. The learning results for the alcohol concentration are then repeatedly updated in memory. When a main switch is then turned off and then subsequently turned on again, learning results for the alcohol concentration for the previous time are read out from the memory. The amount of fuel injected can be controlled on the assumption that the fuel is of the alcohol concentration of the learned results. [Patent Document 1]
Japanese Patent Publication Laid-open No. 2004-293491. DISCLOSURE OF INVENTION
[Problems To Be Solved by the Invention] [0004]
With the above conventional technology, when fuel of a different alcohol concentration is supplied after the main switch is turned off, the next time the engine is started the learning results for the alcohol concentration and the actual alcohol concentration will be different. [0005]

The composition of ethanol contains oxygen atoms. The amount
of oxygen per unit volume required for combustion can therefore
be small compared to the combustion of gasoline. The amount
of fuel injected is also increased as the alcohol concentration
is increased in order to obtain the same equivalence ratio.
When the actual alcohol concentration is lower than the alcohol
concentration for the learned results, accidental firing
occurs due to the air/fuel ratio being too rich and the load
on the catalyzer therefore becomes substantial.
[0006]
In order to resolve the problems of the related art, it is
therefore an object of the present invention to provide a fuel
injection control device for a multi-fuel engine where a
catalyzer is not damaged even if there is a difference between
learning results for alcohol concentration relating to the
fuel and actual alcohol concentration.
[Means for resolving the problems]
[0007]
In order to achieve the above object, in the present invention,
a fuel injection control device for a multi-fuel engine that
controls an amount of fuel injected based on alcohol
concentration of fuel is characterized by being provided with
the following.
[0008]
(1) An oxygen concentration sensor that detects concentration
of oxygen within an exhaust gas, an alcohol concentration
learning unit that learns alcohol concentration of the

injected fuel based on a value calculated by the oxygen concentration sensor, an alcohol concentration storage unit that stores learning values for the alcohol concentration, and a fuel injection amount control unit that controls an amount of fuel injected based on a learning value are provided. The fuel injection amount control unit comprises a reduction and correction unit that reduces and corrects the amount of fuel injected so as to be less than the injection amount corresponding to the read out learning value, and a reviewing unit that reviews the learning values based on values calculated by the oxygen concentration sensor during reduction and correction. The amount of fuel injected is reduced and corrected by just a prescribed period by the reduction and correction unit when the read out learning value is for a high concentration when the engine is starting, with the amount of fuel injected then being controlled thereafter based on the reviewed learning value. [0009]
(2) A determining unit that determines whether or not the injected fuel has switched over from fuel remaining within a fuel pipe to fuel within a fuel tank is also provided. The fuel injection amount control unit reduces and corrects the amount of fuel injected by just a prescribed amount using the reduction and correction unit when the injected fuel switches over to the fuel within the fuel tank, with the amount of fuel injected being controlled thereafter based on the reviewed learning value.

[0010]
(3) The fuel injection amount control unit reduces and
corrects the amount of fuel injected when the read out learning
value is for a high concentration and the running state of the
engine is in a high load region.
[0011]
(4) The reduction and correction of the amount of fuel
injected can also be carried out in stages.
[Effects of the Invention] [0012]
According to the present invention, the following results are achieved.
(1) When the engine starts up, when the learning value stored
in relation to alcohol concentration of fuel is high, the amount
of fuel injected is reduced and corrected until reviewing of
this learning value is complete. This means that it is
possible to prevent the air/fuel ratio from becoming over-rich
even if actual alcohol concentration falls below the learning
value in order to supply fuel of a low alcohol concentration
during stopping. It is therefore possible to prevent a load
on a catalyzer from becoming large.
(2) It is also possible to reduce and correct the amount of
fuel injected until reviewing of a learning value is complete
not only when the engine is starting up, but also at the time
of switching the injected fuel from fuel remaining within a
fuel pipe to fuel within the fuel tank. It is therefore
possible to prevent the learning value from being reviewed

based on supplied fuel that remains in the fuel pipe.
(3) The reduction and correction of the injected fuel is only carried out when the learning value is for a high concentration and the running state of the engine is for a high load region. It is therefore possible to prevent reduction and correction from being implemented under conditions where protection of the catalyzer is not necessary.
(4) The reduction and correction of the injected fuel can also be carried out in stages. It is therefore possible to prevent the injected fuel from being excessively reduced and corrected.
Best Mode for Carrying out the Invention [0013]
The following is a detailed description with reference to the drawings of a preferred embodiment of the present invention. FIG. 1 is a diagram showing an overall configuration for an internal combustion engine and a fuel injection control system of an embodiment of the present invention. [0014]
An intake pipe 2 and an exhaust pipe 7 are coupled to an engine 1. An air cleaner 3 is provided on the upstream side of the intake pipe 2. An amount of air taken into the engine 1 can be adjusted by a throttle valve 4 arranged within the intake pipe 2. An extent of opening of the throttle valve 4 can be detected by a throttle opening sensor (hereinafter denoted as a TH sensor) 11. [0015]

An intake pipe absolute pressure sensor (expressed in the following as PBA sensor) 12 measures intake pipe absolute pressure PBA. An intake air temperature sensor (expressed as "TA sensor" in the following) 16 measures intake air temperature TA within the intake pipe 2. A water temperature sensor (hereinafter expressed as "TW sensor") 13 measures a circulating water temperature TW of the engine 1. A crank angle sensor (hereinafter, expressed as "CRK sensor") 14 measures a crank angle CRK that represents a crank position of the engine 1. [0016]
A three-way catalytic converter 8 is provided on the downstream side of the exhaust pipe 7. An oxygen concentration sensor (hereinafter referred to as an 02 sensor) 15 for measuring oxygen concentration within the exhaust gas within the exhaust pipe 7 is provided between the engine 1 of the exhaust pipe 7 and the three-way catalytic converter 8. An Engine Control Unit (ECU) 10 executes various types of engine control including the control of fuel injection based on detection signals outputted by each of the sensors. An injector 5 opens a valve that opens in response to an injection control signal outputted by the ECU 10 and injects a fuel mixture of gasoline or gasoline and alcohol (in this embodiment, ethanol). [0017]
FIG. 2 is a functional block view showing a configuration for main essential parts for the ECU 10. Numerals that are the same as previously are used to denote identical or similar

portions. Aspects of the configuration that are not necessary for explaining the present invention are not included in the drawings. [0018]
A fuel injection map is stored in a ROM 101 each fuel alcohol concentration (hereinafter referred to as E concentration). FIG. 3 is a view schematically representing storage contents of the ROM 101. In this embodiment, a Pb/Ne map, an Ne/TH map, and various correction coefficient tables and start control information are stored in a mutually correlated manner each fuel ethanol concentration (El, E2, E3, E4). [0019]
As described previously, the composition of the ethanol contains oxygen atoms. This means that the amount of oxygen required per unit volume for combustion is small compared to when gasoline is combusted. The theoretical air/fuel ratio is therefore smaller when a fuel that is a mixture of ethanol and gasoline is used than the case when fuel of just gasoline is used. It is therefore necessary to set injection control information each mixture ratio for the ethanol and the gasoline in order for the engine 1 to run in an optimum state. [0020]
On the other hand, when the ethanol is of a certain concentration, it is known from experimental results etc. that the same extent of control can be carried out as for when appropriate maps and tables for other concentrations are supplied as for with maps and tables for ensuring that the

engine 1 runs in an optimum state even when another
concentration is applied within a certain fixed range.
[0021]
In this embodiment, as shown in the example in FIG. 4, a range
for ethanol concentration is set and four types El, E2, E3,
E4 (where the alcohol concentration is E1 in advance as reference concentrations for ethanol within
respective ranges. A Pb/Ne map, an Ne/TH map, and various
correction coefficient tables and start control information
are then prepared in advance each respective reference
concentration.
[0022]
There may be any number of reference concentrations providing
there are three or more that may be appropriately allocated
to any concentration from 0% to 100%. The respective maps and
tables are set to have ranges where concentrations overlap as
shown in FIG. 4.
[0023]
In this embodiment, sets of Pb/Ne maps, Ne/TH maps, various
correction coefficient tables and start injection information
prepared each ethanol reference concentration are denoted as
"map sets", and there are also cases where map sets for each
ethanol reference concentration are denoted as an El map set,
an E2 map set, an E3 map set, and an E4 map set.
[0024]
Returning to FIG. 2, an alcohol concentration learning unit
102 learns the E-concentration of the injected fuel based on

a measured value (voltage) V02 of the 02 sensor 15 representing the oxygen concentration within the exhaust pipe 7. The learning results are then repeatedly updated in a storage unit 103. An engine load detecting unit 104 detects current engine load based on the engine speed Ne and an extent of throttle opening TH. [0025]
At a fuel injection control unit 105, the reduction amount correction unit 105a reduces and corrects the amount of fuel injected for just a prescribed period when a learning value stored in the storage unit 103 is a high concentration (E3 or E4 in this embodiment). A learning value revising unit 105b revises learning values for the E-concentration based on the measured values of the 02 sensor 15 during reduction and correction of the amount of fuel injected. A switching determination unit 105c determines whether or not the injected fuel has switched from the fuel remaining within a fuel pipe 17 to the fuel within the fuel tank. [0026]
When the engine is started and it is determined by the switching determination unit 105c that the injected fuel is switched over to the fuel within the fuel tank, when the learning value for the E-concentration stored in the storage unit 103 is a high concentration and the engine load detected by the engine load detection unit 104 is a prescribed high load state, the fuel injection amount control unit 105 reduces and corrects an amount of injected fuel obtained by referring to a fuel

injection map according to the learning value. The fuel injection amount control unit 105 then ends the reduction and correction when the learning value is reviewed by the learning value reviewing unit 105b during reducing and correcting of the injected fuel. [0027]
A detailed description is now given of the operation of a first embodiment of the present invention while referring to a flowchart and a timing chart. FIG. 5 is a main flowchart showing a procedure for catalyzer (CAT) protection processing of a first embodiment of the present invention and mainly shows the operation of the ECU 10. FIG. 6 is a flowchart showing a procedure for "lean control" executed within the main flow. FIG. 8 and FIG. 10 are flowcharts showing procedures for "lean coefficient searching" and "MAP determination" executed within the respective "lean control". FIG. 11 is a flowchart showing a procedure for "E-determination point updating" executed within the "MAP determination". [0028]
Here, first, the operation in the case where the engine is started in a state where the E-concentration within the fuel tank has fallen as far as the level E2 is described using a time series along the timing chart of FIG. 13 because gasoline is supplied during engine stopping regardless of whether the learning value for the E-concentration stored in the storage unit 103 (E-concentration learning value Eindex) is the level E4 of the highest concentration.

[0029]
In step S1 of the main flow (FIG. 5), an E-determination (alcohol concentration determination) point Pe representing the alcohol concentration determination history is referred to. The CAT protection processing of this embodiment is only executed at a time (first time) immediately after the engine starts, and a time (second time) where it is estimated that all of the fuel within the fuel pipes (i.e. fuel of an alcohol concentration prior to refueling) has been consumed and injection of fuel within the fuel tank has commenced. Here, Pe represents the number of times of execution of the CAT protection processing has been completed. If it is determined that Pe ≥2 in step S1, it is determined that the CAT protection processing has already been executed two times. Step S7 is then proceeded to, a lean (dilution) coefficient Kc1h is returned to an initial value of "1.0" (i.e. the fuel is not made lean) and the processing ends. [0030]
On the other hand, an initial value for the E-determination point Pe is "0". It is therefore determined that Pe
when the E-concentration learning value Eindex is a low concentration and the amount of fuel injected is relatively small. [0031]
With regards to this, if the stored learning value Eindex is a high concentration such as level E4 or level E3 as in this embodiment, quantity reduction and correction is carried out by multiplying the fuel injection amount Tout with the lean coefficient Kc1h. As a result, step S3 where the air/fuel ratio is to be made lean is proceeded to. In step S3, the E-determination point Pe is referred to anew. If the E-determination point Pe is other than "1" (i.e. Pe = 0) , step S5 is proceeded to. If the E-determination point is "1", step S4 is proceeded to. Pe = 0 directly after the engine starts. Step S5 is then proceeded to, and first time "lean control" is executed. [0032]
FIG. 6 is a flowchart showing a procedure for the "lean control". In step S21, it is determined whether or not a running state of the engine is in a high load region constituting a target of the CAT protection control based on the extent of opening of the throttle TH and the engine speed NE. In this embodiment, as shown in FIG. 7, if the extent of opening the throttle TH is greater than a prescribed reference extent of opening THref and the engine speed NE is greater than a prescribed reference speed NEref, the CAT protection control is determined to be a required high load region. Step S22 is then proceeded to.

If the region is not a high load region, the processing ends.
[0033]
In step S22, a cooling water temperature TW is compared with
a warm up determination threshold value TWref. If TW > TWref,
it is determined that the warm up has ended and "searching for
a lean coefficient" of step S26 is proceeded to. If TW ^ TWref,
it is determined that this is prior to warm up. Step S23 is
then proceeded to and a measurement value V02 of the 02 sensor
15 is compared with an active determination threshold value
Vref1. If this is before the time T1 of FIG. 13, then V02 ≥
Vref1 and it is determined that the 02 sensor 15 is not-yef
active and the processing therefore ends. With regards to this,
if V02 is complete, step S24 is proceeded to and a 'lean coefficient
search" is executed.
[0034]
In this embodiment, before warming up of the engine, the 02
sensor 15 becoming active is awaited in order to ensure
drivability immediately after starting and a lean coefficient
search (step S24) is executed. After warming up, the lean
coefficient search (step S26) is executed from before the 02
sensor 15 becoming active.
[0035]
FIG. 8 is a flowchart showing a procedure for the "lean
coefficient search". Here, an optimum lean coefficient Kclh
is searched based on the cooling water temperature TW.[0036]
In step S31, the cooling water temperature TW and a prescribed

threshold value TWstep are compared in order to determine whether the injected fuel is made lean in stages (in this embodiment, two stages) or all in one go. If TW In step S33, a lean execution complete flag Fclh is referred to. Step S34 is then proceeded to because the flag Fclh is in the reset state (prior to making lean). In step S34, a prescribed count value is set to the first counter N1st that decides a period of implementation for the first stage of making fuel lean. In step S35, a first stage lean coefficient Kc1h1 (
corresponding to the current cooling water temperature TW is recorded at a time t2. In step S36, a lean execution complete flag Fc1h is set to "1". [0039]
As a result, the lean coefficient Kc1h is multiplied with the fuel injection amount Tout calculated separately at the fuel injection amount control unit 105 by the reducing of correcting unit 106 so that amount of fuel injected is reduced. The air/fuel ratio therefore rises at the time t2 as shown in FIG. 13. As shown above, when retrieval of the lean coefficient search of step S24 (or step S26) is complete, step S25 of FIG. 6 is proceeded to and the MAP determination processing is implemented. [0040]
FIG. 10 is a flowchart showing a procedure for the "MAP determination processing". The E-concentration learning value Eindex is then revised based on the output V02 OF THE 02 sensor 15. [0041]
In step S50, a lean execution flag Fclh is referred to. In this case it is determined that Fc the1h = 1 (first stage) and step S51 is therefore proceeded to. In step S51, the first stage counter N1st is referred to and the main flow is immediately returned to until the first stage counter Nlst times out and the first stage of making lean is complete. [0042] Each of the processes described above are then repeated after

this so that in the next "lean coefficient search process" (FIG. 8), in step S33, the lean execution flag Fc1h is determined to be "1" and step S37 is proceeded to. In step S37, the first stage counter N1st is referred to and step S38 is proceed to up until the counter Nlst times out. In step S38, as in step S35, the first stage lean coefficient Kc1h1 is retrieved from the first coefficient table correlated with the current E-concentration learning value Eindex taking the cooling water temperature TW as a parameter. In this embodiment, the lean coefficient Kclhl of the first coefficient table is fixed regardless of the cooling water temperature TW and the same value as for the previous time is therefore set. In step S39, as in step S36, the lean execution flag Fc1h1 is set to "1". The first stage current Nlst is then decremented in step S40. [0043]
After this, at time t3 of FIG. 13, when the first stage counter Nlst times out and this is detected by step S51 of FIG. 10, step S52 is proceeded to. In step S52, the 02 sensor output V02 and the MAP switching threshold value Vref2 are compared in order to confirm the validity of the current E-concentration learning value Eindex. Here, it is determined that the sensor output V02 exceeds the MAP switching threshold value Vref 2 and the E-concentration learning value Eindex is not valid. A revision of the E-concentration learning value Eindex is then sent in advance to the second stage leaning. [0044] After this, when timing out of the first stage counter Nlst

is also detected in step S37 of FIG. 8, the first stage of making leaner is complete, and step S41 is proceeded to in order to proceed to the second stage. In step S41, the lean execution flag Fc1h is referred to and step S42 is then proceeded to because that other than "2" is determined. In step S42, a prescribed count value is set to the second stage counter N2nd that decides the implementation period for the second stage of making lean. In step S43, a second stage lean coefficient clh2 is retrieved from the second coefficient table, an example of which is shown in FIG. 9, taking the cooling water temperature TW as a parameter. In step S44, a lean execution complete flag Fclh is set to "2". [0045]
As a result, a second stage lean coefficient Kclh2 that is smaller than the first stage lean coefficient Kclhl is multiplied with the fuel injection amount Tout. The amount of fuel injected is therefore further reduced and the air/fuel ratio rises further upon the time t3 as shown in FIG, 13. As shown above, when the "lean coefficient searching" ends, FIG. 6 is again returned to and the "MAP determination processing" (FIG. 10) is again executed in step S25. [0046]
In step S50 of FIG. 10, the lean execution flag Fclh is referred to and step S56 is proceeded to because a determination of Fclh = 2 is made here. In step S56, the 02 sensor output V02 and the MAP switching threshold value Vref2 are compared in order to confirm the validity of the current E-concentration

learning value Einclex. Here, the sensor output V02 exceeds the MAP switching threshold value Vref2 and the current E-concentration learning value Eindex therefore cannot be determined to be valid. Step S57 is then proceeded to. In step S57, .the second stage counter N2nd is referred to, and the main flow (FIG. 5) is returned to immediately up until the counter N2nd times out. [0047]
After this, the second counter N2nd times out at the time t4 of FIG. 13 and step S58 is proceeded to when this is detected in step S57 shown in FIG. 10. In step S58, the current E-concentration learning value Eindex is shifted by just the second stage to the low E side. Namely, if the current E-concentration. learning value Eindex is the level E4, the level E2 is switched over to. The "E-determination point updating processing" is then executed in step S59. [0048]
FIG. 11 is a flowchart showing a procedure for E-determination point update processing. In step S71, the current E-determination point Pe is referred to and it is determined here that Pe FIG. 12 is a flowchart showing a procedure for a "fuel switching determination" executed separately in the background of the

CAT protection processing. In step S11, an integral value
STout for the fuel injection amount Tout for after starting
the engine is compared with the fuel switching threshold value
Tout_ref. The fuel switching reference value Tout_ref is set
to a value capable of determining that all of the fuel remaining
at the fuel pipe 17 has been injected. If ETout > Tout_ref,
step S12 is proceeded to and it is taken that fuel switching
is complete. On the other hand, if STout ≤ Tout_ref, step
S13 is proceeded to and it is taken that fuel switching has
not yet been achieved.
[0050]
Returning to FIG. 11, it has been determined that fuel switching
has not yet been achieved immediately after starting of the
engine. Step S74 is therefore proceeded to because it is
determined that Pe = 0 and the current E-concentration learning
value Eindex is determined. This is already E2 and as this
is determined to be other than E3 and E4, step S76 is proceeded
to. In step S7 6, the E-determination point Pe is updated by
just "+2".
[0051]
If the E-determination point Pe is "2", in the main flow of
FIG. 5, it is determined in S1 that Pe ≥ 2. The lean
coefficient Kc1h is therefore returned to "1.0" in step S7 and
the control ends.
[0052]
Next, the operation in the case where the E-concentration
learning value Eindex stored in the storage unit 103 is a high

concentration level E4 and remains the level EA even for the alcohol concentration within the fuel tank the next time that the engine starts is described using a time series with reference to the time chart of FIG. 14 and each of the flowcharts. If the stored E-concentration learning value Eindex is the high-concentration level E4, in step S35 for the lean coefficient search (FIG. 8), the first stage lean coefficient Kc1h1 is similarly recorded. As a result, the lean coefficient Kc1h is multiplied with the fuel injection amount Tout calculated separately by the fuel injection amount control unit 105 and the amount of fuel injected is therefore reduced. The air/fuel ratio therefore rises upon the timet2 in the example shown in FIG. 14. The first stage of making lean is then continued until the first stage counter N1st times out. [0053]
After this, at a time t3, the first stage counter Nlst times out. Step S52 is then proceeded to when this is detected in step S51 of the MAP determination processing (FIG. 10). In step S52, the 02 sensor output V02 and the MAP switching threshold value Vref2 are compared in order to confirm the validity of the current E-concentration learning value Eindex. Here, the sensor output V02 is less than the MAP switching threshold value Vref2. It is therefore determined that the current E-concentration learning value Eindex is valid. Step S53 is then proceeded to and the current E-concentration learning value Eindex (E4) is maintained. The "E-determination point updating processing" is then executed

in step S54.
[0054]
In the "E-determination point (Pe) updating processing of FIG.
11, in step S71, it is determined that the current
E-determination point Pe is "0" and step S72 is proceeded to.
In step S72, it is determined whether or not the fuel switching
is complete. It is then determined that fuel switching over
is not yet complete after starting of the engine. Step S73
is therefore proceeded to and the current E-determination
point Pe is determined. Step S74 is therefore proceeded to
because Pe = 0 and the current E-concentration learning value
Eindex is determined. Step S75 is then proceeded to because
E4 is determined here. The E-determination point Pe is then
updated by " + 1" and Pe = 1.
[0055]
Returning to FIG. 10, in step S55, the lean coefficient Kc1h
is returned to "1.0". Therefore, as shown in FIG. 14, the
air/fuel ratio falls at the time t3. If the E-determination
point Pe is updated, in the main flow of FIG. 5, step S4 is
proceeded to from step S3. Switching over from the fuel within
the fuel pipes to the fuel within the fuel tank is then awaited
and lean control is then similarly executed a second time.
[0056]
In the above embodiments, a description is given where
temperature of the engine is exemplified by water temperature
but temperature of the engine can also be exemplified by oil
temperature when an oil temperature sensor is provided.

[0057]
In this embodiment, in the first time lean control, if the results of the determination for the E-concentration learning value Eindex are still a high concentration level (E4, E3), lean control is implemented a second time. On the other hand, if the results of the determination for the E-concentration learning value Eindex have changed to a low concentration level
(E2, El), the lean control is not implemented a second time. Further, in this embodiment, in the lean control the first and second times, lean control is only implemented a second time when the validity of the current E-concentration learning value Eindex cannot be confirmed when making lean the first time. If the validity of the E-concentration learning value Eindex can be confirmed when making lean the first time, making lean the second time can be omitted. Brief Description of the Drawings
[0058]
FIG. 1 is a diagram of an internal combustion engine and a fuel
injection control system thereof of an embodiment of the
present invention;
FIG. 2 is a block diagram functionally expressing a
configuration for an ECU;
FIG. 3 is a view schematically expressing storage contents of
a ROM;
FIG. 4 is a view showing an example of a method for setting
a range for ethanol concentration;
FIG. 5 is a main flowchart of a catalyzer (CAT) protection

process;
FIG. 6 is a flowchart showing a procedure for "lean control";
FIG. 7 is a diagram showing conditions for determining that
running conditions are in a high load region;
FIG. 8 is a flowchart showing a procedure for "lean coefficient
search processing";
FIG. 9 is a view showing an example of first and second
coefficient tables (E4);
FIG. 10 is a flowchart showing a procedure for "MAP
determination processing";
FIG. 11 is a flowchart showing a procedure for "E-determination
point update processing";
FIG. 12 is a flowchart showing a procedure for "fuel switching
determination processing";
FIG. 13 is a timing chart showing lean control when alcohol
concentration is changed from level E4 to level E2; and
FIG. 14 is a timing chart showing lean control when the alcohol
concentration is maintained at level E4.
[Description of the Numerals]
[0059]
Engine 1, intake pipe 2, air cleaner 3, throttle valve 4,
injector 5, exhaust pipe 7, three-way catalytic converter 8,
engine control device 10, extent of throttle opening sensor
11, intake pipe absolute pressure sensor 12, water temperature
sensor 13, crank angle sensor 14, 02 sensor 15, intake air
temperature sensor 16

[Claim 1] A fuel injection ccnto.l device for a multi-fuel engine that controls an amount of fuel injected based on alcohol concentration of the fuel, said fuel injection control device comprising:
an oxygen concentration sensor that detects concentration of oxygen within an exhaust gas;
an alcohol concentration learning unit that learns alcohol concentration of the injected fuel based on a value calculated by the oxygen concentration sensor; an alcohol concentration storage unit that stores learning values for the alcohol concentration; and
a fuel injection amount control unit that controls an amount of fuel injected based on a learning value,
and the fuel injection amount control unit
comprising:
a reduction and correction unit that reduces and
corrects the amount of fuel injected so as to be less
than the injection amount corresponding to the read out
learning value; and
a reviewing unit that reviews the learning values
based on values calculated by the oxygen concentration
sensor during reduction and correction,
wherein the amount of fuel injected is reduced and corrected by just a prescribed period by the reduction and correction unit when the read out learning value is for a high concentration when the engine is starting, with the amount of

fuel injected then being controlled thereafter based on the reviewed learning value.
[Claim 2] The fuel injection control device for a multi-fuel engine according to claim 1, further comprising a determining unit that determines whether or not the injected fuel has switched over from fuel remaining within a fuel pipe to fuel within a fuel tank, wherein the fuel injection amount control unit reduces and corrects the amount of fuel injected by just a prescribed amount using the reduction and correction unit when the injected fuel switches over to the fuel within the fuel tank, with the amount of fuel injected being controlled thereafter based on the reviewed learning value.
[Claim 3]
The fuel injection control device for a multi-fuel engine according to claim 1 or claim 2, wherein the fuel injection amount control unit reduces and corrects the amount of fuel injected when the read out learning value is for a high concentration and the running state of the engine is in a high load region.
[Claim 4] The fuel injection control device for a multi-fuel engine according to any one of claims 1 to 3, wherein the reduction and correction of the amount of fuel injected is carried out in stages.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=ZCvISh5xcHIgVxiovO+1FA==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

279938

Indian Patent Application Number

2587/CHE/2009

PG Journal Number

06/2017

Publication Date

10-Feb-2017

Grant Date

03-Feb-2017

Date of Filing

26-Oct-2009

Name of Patentee

HONDA MOTOR CO., LTD.

Applicant Address

1-1, MINAMI-AOYAMA 2-CHOME, MINATO-KU, TOKYO 107-8556

Inventors:

#	Inventor's Name	Inventor's Address
1	ITO, ATSUSHI	C/O HONDA R&D CO.,LTD., 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA 351-0193
2	TAKAHASHI, YOICHI	C/O HONDA R&D CO.,LTD., 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA 351-0193
3	HORIE, HIDEYA	C/O HONDA R&D CO.,LTD., 4-1, CHUO 1-CHOME, WAKO-SHI, SAITAMA 351-0193

PCT International Classification Number

F02D 41/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2008-278518	2008-10-29	Japan