JP2016108978A - Air-fuel ratio learning control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air-fuel ratio learning control device of an internal combustion engine capable of performing accurate learning control without the usage of a control valve.SOLUTION: An air-fuel ratio learning control device of an internal combustion engine (11) includes a fuel injection valve (22) for injecting fuel to an intake passage (18), a canister (24) communicated with the intake passage (18) so that evaporated gas is released to the intake passage (18), an oxygen sensor (31) for detecting concentration of remaining oxygen in exhaust gas circulating in an exhaust passage (19), and a control unit (25) for controlling an amount of fuel injected from the fuel injection valve (22) by performing learning control so that an air-fuel ratio based on a detection value from the oxygen sensor (31) approaches a target air-fuel ratio. The control unit (25) includes gas release amount calculating means for calculating an estimation value of a gas total release amount from the canister (24) in accordance with a state of the internal combustion engine (11).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an air-heat ratio learning control device for an internal combustion engine.

  Conventionally, the learning end condition is determined based on the deviation between the air-fuel ratio based on the detected value of the oxygen sensor and the target air-fuel ratio, and when the learning end condition is satisfied, the release of the evaporative gas (evaporated fuel) from the canister is permitted, and learning is performed. There is known an air-fuel ratio learning control device in which learning control is temporarily stopped when an end condition is not satisfied to allow evaporative gas to flow out (see, for example, Patent Document 1).

  However, the one disclosed in Patent Document 1 has a configuration including a control valve for controlling the flow of the evaporation gas from the canister to the intake passage. In such a configuration, not only the control valve is required. The structure for controlling the operation of the control valve is necessary, and the cost is increased. On the other hand, there is also a problem that it is desired to reduce the influence on the air-fuel ratio caused by the evaporation gas flowing into the intake passage.

  Therefore, in order to reduce the influence on the air-fuel ratio due to the inflow of the evaporative gas into the expiratory flow path with a simple configuration that avoids an increase in cost, while the evaporative gas in the expiratory passage from the canister is predicted to be released, It is known to apply a predetermined limit to the reduction in the fuel injection amount determined by the learning control (see, for example, Patent Document 2).

Japanese Patent No. 3,404,872 JP 2011-074848 A

  In the one disclosed in Patent Document 2, since the evaporative gas is normally discharged into the intake passage and burned during the warm-up operation, it is determined that the warm-up is finished when the engine coolant temperature reaches or exceeds a predetermined water temperature. Since it is determined that the release of the evaporative gas has been completed at a possible time, there is a disadvantage that the evaporative gas is originally not affected, and the restriction is imposed even when it is not necessary to restrict the learning control.

  The present invention has been made in view of this point, and an object of the present invention is to provide an air-fuel ratio learning control device for an internal combustion engine that can perform accurate learning control without using a control valve.

  An air-fuel ratio learning control device for an internal combustion engine according to the present invention includes a fuel injection valve that injects fuel into an intake passage, a canister that is provided so as to communicate with the intake passage so as to discharge an evaporation gas into the intake passage, An oxygen sensor for detecting the residual oxygen concentration of the exhaust gas flowing through the exhaust passage, and fuel injection from the fuel injection valve by performing learning control to bring the air heat ratio based on the detected value of the oxygen sensor closer to the target air heat ratio Control means for controlling the amount, wherein the control means comprises gas discharge amount calculation means for calculating a total gas discharge amount estimated value from the canister according to the state of the internal combustion engine.

  According to this configuration, it is possible to estimate the total amount of gas released from the canister according to the state of the internal combustion engine, and to estimate the presence or absence of the evaporative gas discharged from the canister to the intake passage. Since it is possible to estimate a situation that is not affected by evaporative gas, accurate learning control can be performed without using a control valve.

  In the air-fuel ratio learning control apparatus for an internal combustion engine according to the present invention, the gas emission amount calculating means is based on the instantaneous gas release map of the canister set in advance according to the engine speed and throttle opening of the internal combustion engine. It is preferable to calculate the estimated total gas release amount. In this case, it is possible to easily estimate the emission completion and remaining amount of the evaporation gas in the canister with the existing sensor configuration.

  In the air-fuel ratio learning control apparatus for an internal combustion engine according to the present invention, the control means calculates a feedback correction value so as to approach a target air-heat ratio based on a detection value of the oxygen sensor, and performs feedback control to perform feedback control. And an air-fuel ratio learning correction calculating means for calculating a difference between an average value of the feedback correction values and a median value thereof as an air-heat ratio learning correction value, and a final calculation for calculating a final injection time using the air-fuel ratio learning correction value. It is preferable that the air-fuel ratio learning correction value is calculated by the air-fuel ratio learning correction calculation unit when the estimated total gas release amount reaches a predetermined threshold value or more. In this case, for example, when the start of the learning correction value calculation is set to “after a predetermined time” by using the estimated total gas discharge amount for the determination of the gas discharge completion in the canister necessary for the start of the learning correction value calculation. Compared to, learning correction value calculation can be started at a more reasonable timing. This improves the immediacy and accuracy of learning, makes it possible to correct the fuel injection amount appropriately, and improves traveling performance.

  In the air-fuel ratio learning control apparatus for an internal combustion engine according to the present invention, it is preferable that the threshold value is set to be different for each arbitrary range of the throttle opening. In this case, the learning correction value calculation start condition varies depending on the throttle opening. Thus, for example, when the throttle is slightly opened, the evaporative gas is not easily released from the canister, but the threshold (Kn) is lowered and the learning control is not subject to unnecessary restrictions. That is, the learning correction value can be calculated in a relatively short time, and the immediacy and accuracy of learning are further improved.

  According to the air-fuel ratio learning control apparatus for an internal combustion engine of the present invention, accurate learning control can be performed without using a control valve, so that cost reduction and layout improvement can be achieved.

1 is a schematic diagram of an internal combustion engine according to an embodiment. It is a block diagram which shows the control unit which concerns on this Embodiment. It is a flowchart which shows operation | movement of the air-heat ratio learning control apparatus of the internal combustion engine which concerns on this Embodiment. It is a flowchart which shows the operation | movement of the learning permission determination in the air-heat ratio learning control apparatus of the internal combustion engine which concerns on this Embodiment. It is a flowchart which shows the evaporation flag process in the air-heat ratio learning control apparatus of the internal combustion engine which concerns on this Embodiment. It is explanatory drawing which shows the instantaneous purge flow rate map which concerns on this Embodiment. It is a flowchart which shows the evaporation flag determination in the air-heat ratio learning control apparatus of the internal combustion engine which concerns on this Embodiment. 6 is a timing chart showing an operation example of feedback correction and air-fuel ratio learning correction in the air-fuel ratio learning control apparatus for an internal combustion engine according to the present embodiment. It is a timing chart which shows the operation example of the evaporation flag process in the air-heat ratio learning control apparatus of the internal combustion engine which concerns on this Embodiment.

  Hereinafter, an air-fuel ratio learning control apparatus for an internal combustion engine according to the present embodiment will be described with reference to the accompanying drawings. The air-fuel ratio learning control apparatus for an internal combustion engine according to the present embodiment is not limited to the configuration shown below, and can be changed as appropriate. The air-fuel ratio learning control apparatus for an internal combustion engine may be applied to any vehicle, and can be applied to, for example, a motorcycle, a buggy type automatic three-wheeled vehicle, or an automatic four-wheeled vehicle.

  First, with reference to FIG.1 and FIG.2, schematic structure of the internal combustion engine which concerns on this Embodiment is demonstrated. FIG. 1 is a schematic diagram of an internal combustion engine according to the present embodiment. FIG. 2 is a block diagram showing a control unit according to the present embodiment.

  In FIG. 1, for example, an intake device 15 for supplying an air-fuel mixture to a combustion chamber 14 facing the top of a piston 13 slidably fitted to a cylinder bore 12 of a water-cooled internal combustion engine 11 mounted on a motorcycle. An exhaust device 16 for exhausting exhaust gas from the combustion chamber 14 is connected to the cylinder head 17 of the internal combustion engine 11. An intake passage 18 is formed in the intake device 15, and an exhaust passage 19 is formed in the exhaust device 16. A spark plug 20 is attached to the cylinder head 17 so that the tip of the cylinder head 17 faces the combustion chamber 14.

  A throttle valve 21 for controlling the amount of air flowing through the intake passage 18 is disposed in the intake device 15 so as to be openable and closable. A fuel injection valve 22 for injecting fuel into the intake passage 18 downstream of the throttle valve 21 is additionally provided. Further, between the intake passage 18 downstream of the throttle valve 21 and the fuel tank 23, a canister 24 that always communicates with the intake passage 18 is provided so as to discharge the evaporated gas to the intake passage 18.

  The operation of the ignition timing by the spark plug 20 and the fuel injection amount from the fuel injection valve 22 is controlled by the control unit 25. A detection value of a throttle position sensor 26 provided coaxially with the throttle valve 21, a detection value of an intake pressure sensor 27 that measures the pressure of the intake passage 18, and a coaxial shaft 28 connected to the piston 13. The detected value of the crank angle sensor 29, the detected value of the water temperature sensor 30 for detecting the coolant temperature of the engine cooling water, and the oxygen sensor attached to the exhaust device 16 so as to detect the residual oxygen concentration in the exhaust gas flowing through the exhaust passage 19. 31 detection values are input to the control unit 25.

  As shown in FIG. 2, in the control unit 25, the basic injection time calculating means 41 includes an engine speed detected by the crank angle sensor 29 and a throttle opening or intake pressure sensor detected by the throttle position sensor 26. The basic fuel injection time is calculated from the intake air amount of the internal combustion engine 11 estimated based on the intake pressure detected by the engine 27.

  The feedback correction calculation means 42 performs feedback control by calculating a feedback correction value so as to approach the target air-fuel ratio based on the oxygen concentration obtained by the oxygen sensor 31. That is, the degree of exhaust rich or lean is determined based on the oxygen sensor 31, and the feedback correction value is calculated based on the determination result.

  Further, the air-fuel ratio learning correction calculating unit 43 calculates the difference between the average value of the current feedback correction values obtained by the feedback correction calculating unit 42 and the median value (1.00) of the correction values as the air-fuel ratio learning correction value. To do. That is, correction is performed so that the current feedback correction value approaches the median value.

  The final injection time calculation means 44 is obtained by the basic injection time obtained by the basic injection time calculation means 41, the feedback correction value obtained by the feedback correction calculation means 42, and the air-fuel ratio learning correction calculation means 43. An operation is performed based on the air-fuel ratio learning correction value, a final injection time is calculated, and the fuel injection valve 22 is driven at the calculated final injection time.

  Further, in the control unit 25, the learning permission determination means 45 determines whether or not to allow the air-fuel ratio learning correction calculation means 43 to perform learning control.

  Further, in the control unit 25, the gas emission amount calculating means 46 calculates an estimated value of the total amount of evaporated evaporative gas from the canister 24 (hereinafter referred to as a total gas emission amount estimated value) according to the state of the internal combustion engine 11. The gas discharge amount calculation means 46 is preset according to the engine speed (NE) of the internal combustion engine 11 and the throttle opening (VT) or intake pressure (PM) for estimating the load state of the internal combustion engine 11. Based on the instantaneous gas release map of the canister 24, an estimated total gas release amount is calculated.

  Hereinafter, the air-heat ratio learning control will be described in detail with reference to FIGS. FIG. 3 is a flowchart showing the operation of the air-heat ratio learning control apparatus for the internal combustion engine according to the present embodiment. As shown in FIG. 3, first, the outputs of the various sensors 26, 27, 29, and 31 are read (S11). That is, the engine speed (NE) from the crank angle sensor 29, the throttle opening (VT) from the throttle position sensor 26, the intake pressure (PM) from the intake pressure sensor 27, and the coolant temperature from the water temperature sensor 30 (Temperature). ) Is input to the control unit 25.

  Next, it is determined whether or not the internal combustion engine 11 is in operation based on whether or not the engine speed (NE) is equal to or greater than a predetermined value (S12). If the internal combustion engine 11 is in operation, a learning permission determination is performed (S13). The learning permission determination is to determine whether or not the learning control (S15 described later) by the air-fuel ratio learning correction calculating unit 43 can be performed. The learning permission determination will be described in detail later. On the other hand, if the internal combustion engine 11 is not operating, the process is terminated.

  Next, it is determined whether or not a learning flag (learn_flag) indicating the final output of the learning permission determination is “1” (S14). If the learning flag is “1”, learning control in this cycle is permitted, learning control is performed (S15), the air heat ratio learning correction value is reflected in the final injection time, and the fuel injection valve 22 is controlled. (S16). On the other hand, if the learning flag is not “1”, the learning control in the current cycle is not permitted, and the process returns to S11.

Details of the learning permission determination will be described with reference to FIG. FIG. 4 is a flowchart showing the learning permission determination operation in the air-heat ratio learning control apparatus for the internal combustion engine according to the present embodiment. As shown in FIG. 4, at least one flag process (S21) is performed according to various operating states such as the engine speed (NE) and the throttle opening (VT). Examples of the learning control determination flag output by this flag processing include, but are not limited to, the following.
-Engine speed-throttle opening flag (NE-VT_flag)
・ Water temperature flag (Temperature_flag)
・ Δ throttle opening flag (ΔVT_flag)
-Evapo flag (evapo_flag)

  The state of the learning control determination flag output in S21 is determined (S22). If all the flag values are “1”, the learning flag (learn_flag) is set to “1” (S23), If the value of any one flag is not “1”, the value of the learning flag is set to “0” (S24).

  With reference to FIG. 5, the evaporative flag process among the at least one flag process shown in S21 of FIG. 4 will be described in detail. FIG. 5 is a flowchart showing an evaporation flag process in the air-heat ratio learning control apparatus for the internal combustion engine according to the present embodiment. The evaporation flag process refers to determining whether or not to set the evaporation flag under different conditions depending on the throttle opening (VT) value. As shown in FIG. 5, first, the engine speed (NE) and the throttle opening (VT) are read (S31).

  The gas discharge amount calculation means 46 stores in advance an instantaneous purge flow rate map searched from the engine speed and throttle opening, and uses the current engine speed (NE) and throttle opening (VT) read in S31. The current instantaneous purge flow rate (flow_I (NE, VT)) is searched (S32). FIG. 6 is an explanatory diagram showing an instantaneous purge flow rate map according to the present embodiment. As shown in FIG. 6, the instantaneous purge flow rate map is a secondary array with the engine speed (NE) on the x-axis, the throttle opening (VT) on the y-axis, and the instantaneous purge flow (flow_I) on the z-axis. .

  Next, the gas discharge amount calculation means 46 adds the current instantaneous purge flow rate (flow_I) to the previous total purge flow rate (flow_T) to calculate the total purge flow rate (flow_T) up to this time (S33). That is, the instantaneous purge flow rate (flow_I (NE, VT)) retrieved at predetermined intervals from the time of engine start is integrated to obtain the total purge flow rate (flow_T) from the time of engine start, that is, the estimated total gas discharge amount. calculate.

  Next, the process branches to three or more processes depending on the current throttle opening (VT). That is, for example, if VT <A (S34), the evaporation flag determination (1) is performed (S35). If A ≦ VT <B (S36), the evaporation flag determination (2) is performed (S37). If B ≦ VT, an evaporation flag determination (3) is performed (S38).

  The evaporation flag determinations (1) to (3) will be described. FIG. 7 is a flowchart showing evaporation flag determination in the air-heat ratio learning control apparatus for the internal combustion engine according to the present embodiment. The evaporation flag determination refers to determining whether or not to set an evaporation flag based on the total purge flow rate (flow_T). As shown in FIG. 7, it is determined whether or not the total purge flow rate (flow_T) up to this time is equal to or greater than a threshold Kn (n is an integer of 1 or more) (S41). The threshold (Kn) is different for each arbitrary range of the throttle opening (VT). Evaporation flag determination (1), that is, when VT <A, threshold value K1 is set. Evaporation flag determination (2), that is, when A ≦ VT <B, threshold value K2 is set, and evaporation flag determination (3), that is, B ≦ VT. In this case, the threshold value K3 is used as the threshold value. Here, the relationship between the threshold values K1 to K3 is K1 <K2 <K3. That is, the smaller the throttle opening (VT), the smaller the threshold is set, and the larger the throttle opening (VT), the larger the threshold is set.

  In S41, if the evaporation flag determination is YES, the evaporation flag is set to “1” (S42), and if the evaporation flag determination is NO, the evaporation flag is set to “0” (S43).

  Here, the throttle position sensor 26 is used as a sensor for estimating the load state of the internal combustion engine 11 and the y-axis of the instantaneous purge flow rate map is the throttle opening (VT). And the y-axis may be the intake pressure (PM).

  By the above-described evaporation flag process, the total purge flow rate (flow_T) (instantaneous value) corresponding to the estimated total gas discharge amount from the canister 24 according to the state of the internal combustion engine 11 (engine speed (NE) and throttle opening (VT)). When the purge flow rate (flow_I) is equal to or greater than the threshold Kn, the evaporation flag is set to “1”. In S22 shown in FIG. 4, if the other learning determination flag is “1”, the learning flag is set to “1”. As a result, since the learning flag is “1” in S14 shown in FIG. 3, learning control (S15) is performed.

FIG. 8 is a timing chart showing an operation example of feedback correction and air-fuel ratio learning correction in the internal combustion engine air-heat ratio learning control apparatus according to the present embodiment. Note that the numerical values shown in FIG. 8 and thereafter are provisional numerical values used for explaining the concept of the present invention and can be changed as appropriate. In FIG. 8, the line (1) indicates the O ₂ feedback correction median (1.00), the line (2) indicates the O ₂ feedback correction average value, and the line (3) indicates the O ₂ feedback correction value. Line (4) indicates the air-fuel ratio learning correction value. As shown in FIG. 8, in step S1-1, the control unit 25 monitors the correction value for O ₂ feedback correction and calculates an average value. Here, the average value (0.95) of O ₂ feedback correction and the median value (1.00) are different by 0.05.

In the S1-2 stage, learning control is performed at the timing of T11. The difference between the average value and the median value of the O ₂ feedback correction at the S1-1 stage was 0.05, but the air-fuel ratio learning correction value at this stage was subtracted by 0.01 to reach 0.99. Since the injection time was corrected by the air-fuel ratio learning correction value, the average value of O ₂ feedback correction was offset by 0.01, and the difference from the median value (1.00) was 0.04.

In step S1-3, the air-fuel ratio learning value is updated again (0.01 subtraction) at the timing of T12, the air-fuel ratio learning correction value becomes 0.98, and the deviation amount of the average value of O ₂ feedback correction is 0. .03. Thereafter, the same processing is repeated until the deviation amount becomes 0.00.

  FIG. 9 is a timing chart showing an operation example of the evaporation flag process in the air-heat ratio learning control apparatus for the internal combustion engine according to the present embodiment. In FIG. 9, the line (a) indicates the evaporation flag, the line (b) indicates the threshold value (kn), the line (c) indicates the total purge flow rate (flow_T), and the line (d) indicates the instantaneous purge flow rate (flow_I). ), And the line (e) indicates the throttle opening (VT). As shown in FIG. 9, in step S2-1, the internal combustion engine 11 is in operation, and the instantaneous purge flow rate (flow_I) is retrieved from the current throttle opening (VT) and engine speed (NE). Further, the instantaneous purge flow rate (flow_I) is integrated every certain period, and the total purge flow rate (flow_T) is calculated. The threshold value (kn) is searched for each throttle opening (VT). In this S2-1 stage, the total purge flow rate (flow_T) is smaller than the threshold value (kn), so the evaporation flag was “0”.

  In the S2-2 stage, the total purge flow rate (flow_T) becomes larger than the threshold value (kn) at the timing of T21, so the evaporation flag becomes “1”.

  In step S2-3, the value of the threshold (kn) is changed by the throttle opening (VT) at the timing of T22. Here, since the total purge flow rate (flow_T) again became smaller than the threshold value (kn), the evaporation flag became “0”. Thereafter, during the operation of the internal combustion engine 11 (S2-4 stage, S2-5 stage and thereafter), the evaporation flag determination based on the comparison between the total purge flow rate (flow_T) and the threshold value (kn) is performed at timings T23, T24. Repeat with.

  As described above, according to the air-fuel ratio learning control device for an internal combustion engine according to the present embodiment, the gas discharge amount calculation means 46 in the control unit 25 has the gas from the canister 24 according to the state of the internal combustion engine 11. Since the estimated total discharge amount is calculated, it is possible to estimate whether or not the evaporative gas is discharged into the intake passage 18. At this time, a control valve (purge solenoid valve) is provided, and a situation that is not affected by the evaporative gas can be estimated even if the evaporative gas is not shut off. Therefore, accurate learning control can be performed without using the control valve.

  Further, since it is not necessary to provide a control valve, costs can be reduced and layout can be improved.

  Further, since the gas discharge amount calculating means 46 calculates the amount of evaporation of the evaporation gas from the canister 24 based on the instantaneous purge flow rate map set in advance from the engine speed (NE) and the throttle opening (VT). With the existing sensor configuration, it is possible to easily estimate the gas discharge completion and the remaining gas amount in the canister 24.

  In addition, the learning permission determination unit 45 uses the estimated total gas discharge amount (total purge flow rate flow_T) to determine the completion of gas discharge in the canister 24 necessary for starting the learning correction value calculation, for example, learning correction. The learning correction value calculation can be started at a more rational timing than when the value calculation start is “after a predetermined time”. This improves the immediacy and accuracy of learning, makes it possible to correct the fuel injection amount appropriately, and improves traveling performance.

  Further, the throttle opening (VT) condition is divided into a plurality of ranges, and the threshold value (Kn) is changed for each range. Therefore, the learning correction value calculation start condition varies depending on the throttle opening (VT). Thus, for example, when the throttle is slightly opened, the evaporative gas is not easily released from the canister 24, but the threshold (Kn) is lowered and the learning control is not subjected to unnecessary restriction. That is, the learning correction value can be calculated in a relatively short time, and the immediacy and accuracy of learning are further improved.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  In the above embodiment, the throttle opening (VT) is used as the parameter of the instantaneous purge flow map, but intake pressure (PM) may be used instead. Also, other parameters such as intake air temperature and engine coolant temperature may be added as appropriate.

  As described above, the present invention provides an air-fuel ratio learning control apparatus for an internal combustion engine, and is useful for engines such as motorcycles and automobiles.

DESCRIPTION OF SYMBOLS 11 Internal combustion engine 15 Intake device 16 Exhaust device 18 Intake passage 19 Exhaust passage 22 Fuel injection valve 24 Canister 25 Control unit 26 Throttle position sensor 29 Crank angle sensor 31 Oxygen sensor 41 Basic injection time calculation means 42 Feedback correction calculation means 43 Air heat ratio Learning correction means 44 Final injection time calculation means 45 Learning permission determination means 46 Gas emission amount calculation means

Claims (4)

A fuel injection valve that injects fuel into the intake passage, a canister that is connected to the intake passage so as to release the evaporation gas to the intake passage, and a residual oxygen concentration in the exhaust gas that flows through the exhaust passage is detected. An oxygen sensor, and a control means for controlling a fuel injection amount from the fuel injection valve by performing learning control for bringing an air heat ratio based on a detection value of the oxygen sensor close to a target air heat ratio,
An air-heat ratio learning control apparatus for an internal combustion engine, characterized in that the control means comprises a gas emission amount calculation means for calculating an estimated value of total gas emission from the canister according to the state of the internal combustion engine.   The gas discharge amount calculating means calculates the estimated total gas discharge amount based on a gas instantaneous discharge map of the canister set in advance according to an engine speed and a throttle opening of the internal combustion engine. The air-heat ratio learning control apparatus for an internal combustion engine according to claim 1. The control means includes feedback correction calculation means for performing feedback control by calculating a feedback correction value so as to approach a target air-heat ratio based on a detection value of the oxygen sensor, an average value of the feedback correction value, and a median value thereof An air-fuel ratio learning correction calculating means for calculating the difference between the air-fuel ratio learning correction value and a final injection time calculating means for calculating a final injection time using the air-fuel ratio learning correction value,
The air-fuel ratio learning correction value is calculated by the air-fuel ratio learning correction calculating means when the estimated total gas release amount reaches a predetermined threshold value or more. An air-heat ratio learning control device for an internal combustion engine.   4. The air-heat ratio learning control device for an internal combustion engine according to claim 3, wherein the threshold value is set to be different for each arbitrary range of the throttle opening.

Images