JP2010127160A - Alcohol concentration estimating device of fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alcohol concentration estimating device of fuel, restraining reduction in an estimating frequency of the alcohol concentration of the fuel. <P>SOLUTION: When a determining means determines that a transitional fuel correction quantity is larger than a second predetermined value being a value of a first predetermined value or less in the finishing timing of a period for performing purge processing, a purge means delays the finishing timing of the purge processing by a predetermined period from time when the transitional fuel correction quantity becomes the second predetermined value or less, and when a concentration estimation performing condition of including the fact of being a period of not performing the purge processing and the fact of being smaller in the transitional fuel correction quantity than the first predetermined value in a condition, is realized, a concentration estimating means updates an alcohol concentration estimating value by estimating the alcohol concentration of the fuel based on the exhaust air-fuel ratio detected by an exhaust air-fuel ratio detecting means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an alcohol concentration estimation apparatus that estimates an alcohol concentration of a fuel.

  In a vehicle engine such as an automobile, gasoline is generally used as a fuel. However, as is well known, there is an engine that can use a fuel mixed with alcohol. A vehicle equipped with an engine that can use a fuel in which alcohol is mixed in an arbitrary ratio (0% to 100%) is generally called FFV (Flexible Fuel Vehicle).

  In such an FFV engine, as in the gasoline engine, an oxygen sensor or LAFS (linear air-fuel ratio sensor) is provided to detect the exhaust air-fuel ratio from the oxygen concentration in the exhaust, and the exhaust air-fuel ratio becomes the target air-fuel ratio. Control is performed so that the fuel supply amount is feedback corrected so as to approach.

  At this time, in the FFV, it is necessary to appropriately control the fuel injection amount in consideration of the difference in characteristics of both fuels, such as the difference in the theoretical air-fuel ratio between gasoline and alcohol. That is, it is necessary to accurately grasp the alcohol concentration of the fuel and perform accurate fuel supply amount control according to the alcohol concentration. And in order to grasp | ascertain alcohol concentration correctly, it is necessary to learn alcohol concentration suitably according to the situation where alcohol concentration can change like the time of refueling.

Various methods have been proposed for detecting the alcohol concentration of the fuel. For example, the alcohol concentration is estimated based on an air-fuel ratio feedback correction value obtained from the exhaust air-fuel ratio. Then, when estimating the alcohol concentration of the fuel based on the feedback correction value as described above, it is determined whether or not the canister purge is performed, and the alcohol concentration estimation is performed in a state where the canister purge is not performed. (For example, refer to Patent Document 1).
JP 2004-251135 A

  As described above, the alcohol concentration estimation is executed and the alcohol concentration estimation value is updated in a state where the canister purge (purge process) is not performed, so that the alcohol concentration estimation accuracy can be improved. The air-fuel ratio fluctuates greatly during time and transient operation, and there is a factor that lowers the estimation accuracy of the alcohol concentration in addition to the purge process. However, other factors are not fully considered at present.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel alcohol concentration estimation apparatus capable of improving the estimation accuracy of the fuel alcohol concentration.

The present invention for solving the above-described problems is directed to an exhaust air / fuel ratio detecting means for detecting an exhaust air / fuel ratio of an engine capable of using a fuel mixed with alcohol, a canister for storing vaporized fuel, and a purge passage connecting the intake system of the engine. Purge means for performing a purge process for introducing the vaporized fuel into the intake system at a predetermined timing by opening and closing the engine, and a transient fuel correction amount for correcting excess or deficiency of the fuel amount in the cylinder of the engine due to transient operation Determining means for determining the degree of
Detected by the exhaust air-fuel ratio detection means when a concentration estimation execution condition is satisfied that includes at least the purge process not being executed and the transient fuel correction amount being smaller than a first predetermined value. An estimated concentration value updating means for updating the estimated alcohol concentration of the fuel based on the exhaust air-fuel ratio, wherein the purge means performs the transient by the determining means at the end time of the period when the purge process is not executed. When it is determined that the fuel correction amount has exceeded a second predetermined value equal to or less than the first predetermined value, the transient fuel correction amount is set to the second predetermined value as the end timing of the period during which the purge process is not performed. In the apparatus for estimating the alcohol concentration of fuel, the apparatus delays by a predetermined period from the time when the value becomes lower than the value.

  In this aspect of the present invention, since the period during which the purge process is stopped (purge cut period) is ensured for a relatively long time, it is possible to suppress a decrease in the execution frequency of the alcohol concentration estimation for updating the alcohol concentration estimated value. Can do. Therefore, the estimation accuracy of the alcohol concentration of the fuel can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the execution frequency of fuel alcohol concentration estimation can be suppressed, and the estimation precision of fuel alcohol concentration can be improved. Therefore, the air-fuel ratio can be more appropriately controlled to effectively suppress the deterioration of exhaust gas performance, the deterioration of drivability, and the like.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the present invention will be described by exemplifying an engine system including an engine that can use a fuel in which alcohol is mixed and an engine control device that includes a fuel alcohol concentration estimation device.

  First, a schematic configuration of an engine system according to the present embodiment will be described with reference to FIG.

  The engine 11 shown in FIG. 1 is a so-called multi-point injection engine mounted on the FFV, and has a cylinder head 12 and a cylinder block 13. A piston 15 is accommodated in each cylinder 14 of the cylinder block 13 so as to be able to reciprocate. A combustion chamber 16 is formed by the piston 15, the cylinder 14, and the cylinder head 12. The piston 15 is connected to the crankshaft 18 via a connecting rod 17. The reciprocating motion of the piston 15 is transmitted to the crankshaft 18 via the connecting rod 17.

  An intake port 19 is formed in the cylinder head 12. An intake manifold 20 is connected to the intake port 19. The intake port 19 is provided with an intake valve 21, and the intake valve 21 communicates and blocks the combustion chamber 16 and the intake port 19. The intake manifold 20 is provided with a fuel injection valve 24 connected to a fuel tank 23 via a fuel pipe 22 so as to inject mixed fuel into the intake port 19.

  The fuel tank 23 is connected to a canister 25 for adsorbing the vaporized fuel in the fuel tank 23, and the canister 25 is connected to an intake pipe (intake passage) 27 constituting an intake system via a purge passage 26. . When a predetermined purge condition is established, the purge valve 28 provided in the purge passage 26 is opened, and the vaporized fuel adsorbed in the canister 25 is introduced from the purge passage 26 to the intake pipe (intake passage) 27. The This prevents the emission of transpiration fuel into the atmosphere. In the fuel tank 23, a fuel level sensor 29 is provided as a storage amount detection means for detecting the fuel storage amount in the fuel tank.

  An exhaust port 30 is further formed in the cylinder head 12. One end of an exhaust manifold 31 is connected to the exhaust port 30, and an exhaust pipe 32 is connected to the other end of the exhaust manifold 31. The exhaust port 30 is provided with an exhaust valve 33. Like the intake valve 21 in the intake port 19, the combustion chamber 16 and the exhaust port 30 are communicated and blocked by the exhaust valve 33.

  A spark plug 34 is attached to the cylinder head 12 for each cylinder. Each ignition plug 34 is connected to an ignition coil 35 that outputs a high voltage. A surge tank 36 is provided in the intake pipe 27 on the upstream side of the intake manifold 20. A throttle valve 37 that adjusts the intake air amount on the upstream side of the surge tank 36 and a throttle position sensor that detects the opening of the throttle valve 37 ( TPS) 38 is provided. Further, an air flow sensor 39 for measuring the intake air amount is interposed upstream of the throttle valve 37.

A three-way catalyst 40 that is an exhaust purification catalyst is interposed in the exhaust pipe 32 connected to the exhaust manifold 31. On the upstream side of the three-way catalyst 40, an O ₂ sensor 41 is provided as exhaust air / fuel ratio detection means for detecting the oxygen concentration in the exhaust gas before passing through the catalyst, that is, the exhaust air / fuel ratio.

The ECU (electronic control unit) 42 includes an input / output device, a storage device (memory such as ROM and RAM), a central processing unit (CPU), a timer counter, and the like. The ECU 42 performs comprehensive control of the engine 11. On the input side of the ECU 42, in addition to the throttle position sensor 38, airflow sensor 39, and O ₂ sensor 41 described above, a crank angle sensor 43 that detects the crank angle of the engine 11, and a water temperature sensor 44 that detects the coolant temperature of the engine 11. Etc. are connected, and detection information from these sensors is input.

  On the other hand, various output devices such as the fuel injection valve 24, the ignition coil 35, the throttle valve 37, and the purge valve 28 are connected to the output side of the ECU. These various output devices output parameter values such as fuel injection time, ignition timing, throttle opening, and valve opening / closing timing calculated by the ECU 42 from detection information from various sensors, and the combustion state in the combustion chamber 16 is output. Is controlled.

  In other words, the control device including the fuel alcohol concentration estimating apparatus 10 according to the present invention includes such various sensors and the ECU 42, and appropriately estimates the alcohol concentration of the fuel based on detection information from these various sensors. In both cases, the air-fuel ratio is appropriately controlled according to the estimated alcohol concentration of the fuel.

  Hereinafter, fuel alcohol concentration estimation control will be described.

  The ECU 42 includes a purge unit 51, a determination unit 52, and a concentration estimation unit 53 as the main components constituting the alcohol concentration estimation apparatus 10 according to the present embodiment.

  The purge means 51 controls the opening and closing of the purge valve 28 provided in the purge passage 26 and executes a purge process for introducing the vaporized fuel into the intake pipe 27 at a predetermined timing.

  The determination means 52 determines the degree of the transient fuel correction amount (transient fuel correction coefficient) for correcting the excess or deficiency of the fuel amount in the combustion chamber (in-cylinder) 16 of the engine 11 due to the transient operation. The transient fuel correction amount includes both a correction amount based on the wall surface adhesion amount of the intake system and a correction amount based on the wall surface adhesion amount of the combustion chamber (in-cylinder) 16 of the engine 11. Note that the wall surface adhesion amount of the intake system and the wall surface adhesion amount of the combustion chamber 16 are calculated by sequentially predicting the fuel amount adhering to the wall surface of the intake pipe and the evaporation amount of the adhering fuel.

The concentration estimation means 53 performs alcohol concentration estimation of the fuel based on the exhaust air / fuel ratio detected by the O ₂ sensor 41 that is the exhaust air / fuel ratio detection means when a predetermined concentration estimation condition is satisfied, thereby estimating the alcohol concentration. Update the value.

  Here, the concentration estimation condition includes at least that the purge process is not executed by the purge unit 51 and that the transient fuel correction amount is smaller than the first predetermined value. Normally, the purge process is performed at a predetermined interval by the purge unit 51. However, in the present invention, the purge unit 51 appropriately adjusts the period of the purge process based on the transient fuel correction amount.

  Specifically, when the purge means 51 has exceeded the second predetermined value, which is a value less than or equal to the first predetermined value, by the determination means 52 at the end time of the period when the purge process is not executed. If determined, the end time of the period in which the purge process is not executed is delayed by a predetermined period from the time when the transient fuel correction amount becomes equal to or less than the second predetermined value. As will be described in detail later, this can improve the frequency of execution of fuel alcohol concentration estimation.

  In the present embodiment, the purge unit 51 performs the purge process when the determination unit 52 determines that the transient fuel correction amount is greater than the second predetermined value at the end time of the period during which the purge process is being performed. Is ended by a predetermined period from the time when the transient fuel correction amount becomes equal to or less than the second predetermined value. Thereby, the estimation accuracy of the alcohol concentration of the fuel can be improved.

  Hereinafter, an example of alcohol concentration estimation control by the alcohol concentration estimation apparatus 10 will be described with reference to FIGS. 2 to 4 are flowcharts of alcohol concentration control. FIG. 5 is a timing chart for explaining the execution timing of the purge process.

  First, it is determined whether or not it is a concentration estimation period as one of the concentration estimation conditions. That is, it is determined whether or not the alcohol concentration of the fuel injected from the fuel injection valve 24 is changing. Specifically, as shown in FIG. 2, first, in step S1, it is determined whether or not the fuel supply flag is set to ON. The fuel supply flag is a flag that is set to ON when fuel supply is executed, specifically, when an increase in fuel is detected by the fuel level sensor 29 in the fuel tank 23 in a later-described step. .

  If the fuel supply flag is set to OFF in step S1 (step S1: No), it is determined that it is not the concentration estimation period, and the process proceeds to step S2. When the process proceeds to step S2, the concentration estimation condition is not satisfied, and the alcohol concentration of the fuel is not estimated in the subsequent steps. In step S2, it is determined whether or not there is an increase in the fuel level (fuel storage amount) in the fuel tank 23 detected by the fuel level sensor 29. If the fuel level is increasing (step S2: Yes), it is determined that fuel refueling has been executed, and the fuel refueling flag is set to ON in step S3. Further, after the refueling fuel consumption ΣFL (k) is reset in step S4, the process proceeds to step S8 described later. If the fuel level has not increased (step S2: No), the fuel refueling flag is kept off and the process proceeds to step S4.

  On the other hand, if the fuel supply flag is set to ON in step S1 (step S1: Yes), a post-fuel supply fuel consumption amount ΣFL (k), which is the amount of fuel consumed after fuel supply in step S5, is calculated. Then, in step S6, it is determined whether or not the fuel consumption after refueling ΣFL (k) is equal to or less than a predetermined amount. When the fuel consumption after refueling ΣFL (k) is equal to or less than the predetermined amount (step S6: Yes), it is determined that the concentration estimation period is in progress, and the process proceeds to step S17 described later.

  If the fuel consumption after refueling ΣFL (k) is larger than the predetermined amount in step S6 (step S6: No), it is determined that it is not the concentration estimation period (the concentration estimation period has ended), and in step S7. After the fuel supply flag is set to OFF, the process proceeds to step S4.

  When it is determined that it is not the concentration estimation period and the process proceeds from step S4 to step S8, the purge means 51 is set to a predetermined timing based on the purge timer time (purge introduction timer time Tin (k) and purge cut timer time Tct (k)). Execute purge processing at That is, the purge means 51 controls the opening / closing state of the purge valve 28, thereby controlling the start timing and end timing of the purge process.

  Specifically, in step S8, it is determined whether or not the purge introduction mode is set (period in which the purge process is being executed). If it is determined that the purge introduction mode is set (step S8: Yes), in step S9. The purge introduction timer time Tin (k) is calculated by subtracting one calculation cycle time from the previous purge introduction timer time Tin (k-1). Next, it is determined whether or not the purge introduction timer time Tin (k) is 0 (step S10). That is, it is determined whether the period of the purge introduction mode has exceeded a predetermined time. If Tin (k)> 0 (step S10: No), it is determined that the period of the purge introduction mode does not exceed the predetermined time, and the purge introduction mode is continued.

  If Tin (k) = 0 (step S10: Yes), it is determined that the period of the purge introduction mode has exceeded a predetermined time, and the purge cut timer time Tct (k) is set to the first cut by the purge means 51. The timer time Cth1 is set (step 11), and the purge valve 28 is closed and switched to the purge cut mode (step S12).

  If it is determined in step S8 that the mode is not the purge introduction mode (the purge cut mode) (step S8: No), one calculation cycle time is subtracted from the previous purge cut timer time Tct (k-1) in step S13. Thus, the purge cut timer time Tct (k) is calculated. Next, in step S14, it is determined whether or not the purge cut timer time Tct (k) is zero. That is, it is determined whether or not the period during which the purge process is not performed exceeds a predetermined time. If Tct (k)> 0 (step S14: No), it is determined that the period during which the purge process is not performed does not exceed the predetermined time, and the purge cut mode is continued. When Tct (k) = 0 (step S14: Yes), it is determined that the period during which the purge process is not performed exceeds a predetermined time, and the purge introduction timer time Tin (k) is set to the first time by the purge unit 51. The introduction timer time Inh1 is set (step S15). Further, the purge valve 28 is opened and switched to the purge introduction mode (step S16).

  As described above, the start time and end time of the purge process are normally controlled based on the purge timer time (the purge introduction timer time Tin (k) and the purge cut timer time Tct (k)). For example, as shown in the first stage of FIG. 5A, when the purge introduction timer time Tin (k) is set to the first introduction timer time Inh1 at time T0, the second stage of FIG. 5A. As shown, it is switched to the purge introduction mode. Thereafter, Tin (k) is successively subtracted, and when Tin (k) = 0 at time T1, the purge cut timer time Tct (k) is set to the first cut timer time Cth1, and the purge introduction mode is switched to the purge cut mode. It is done. When Tct (k) = 0 at time T2, Tin (k) is again set to the first introduction timer time Inh1, and the purge introduction mode is switched to the purge introduction mode.

  In this embodiment, the purge process start time and end time are controlled by subtracting the purge cut timer time and the purge introduction timer time. Of course, the purge process is controlled by adding the purge timer time. Also good.

  On the other hand, if it is determined that the concentration estimation period is reached and the process proceeds from step S6 to step S17, the delay timer time Td (k) is set together with the purge timer time (purge introduction timer time Tin (k) and purge cut timer time Tct (k)). ), The purge introduction mode and the purge cut mode are switched at a predetermined timing. Then, when the concentration estimation condition including the purge cut mode and the transient fuel correction amount being smaller than the first predetermined value K1 is satisfied, the alcohol concentration of the fuel is estimated.

  Here, the delay timer is a timer for controlling the timing for switching between the purge introduction mode and the purge cut mode based on the wall surface adhering fuel amount, that is, for delaying the end timing or the start timing of the purge process. In the present invention, the delay time of the purge process is delayed by this delay timer, thereby ensuring the frequency of execution of fuel alcohol concentration estimation and improving the accuracy of estimation of fuel alcohol concentration.

  Specifically, first, in step S17, the determination means 52 sets the second predetermined value K2 (see FIG. 5) in which the transient fuel correction amount (transient fuel correction coefficient) based on the wall surface attached fuel amount is equal to or less than the first predetermined value K1. It is determined whether it has been exceeded. When the transient fuel correction amount is larger than the second predetermined value K2 (step S17: Yes), the purge timer 51 then sets the delay timer time Td (k) to the predetermined time H1 (step S18), and step S19. Proceed to On the other hand, if the transient fuel correction amount is equal to or smaller than the second predetermined value K2 in step S17 (step S17: No), then in step S20, the delay timer time Td (k) is calculated, and the process proceeds to step S19.

  Note that the second predetermined value K2 may be a value equal to or less than the first predetermined value K1, but is set to a value approximately equal to the first predetermined value K1, for example. Further, the first predetermined value K1 and the second predetermined value K2 may be the same value. In this case, “the transient fuel correction amount has fallen below the second predetermined value K2” is the concentration estimation condition. Will be included.

  In step S19, it is determined whether or not the purge introduction mode is set. If it is determined that the purge introduction mode is set (step S19: Yes), the purge introduction timer time Tin (k) is calculated in step S21. Next, in step S22, it is determined whether or not the purge introduction timer time Tin (k) is zero. That is, it is determined whether or not the period during which the purge process is performed exceeds a predetermined time. If Tin (k)> 0 (step S22: No), the period during which the purge process is being performed does not exceed the predetermined time, and thus the process returns with the purge introduction mode continued.

  If Tin (k) = 0 (step S22: Yes), it is further determined whether or not the delay timer time Td (k) = 0 (step S23). Here, when Td (k) = 0 is not satisfied (step S23: No), the end time of the purge process is delayed and the process returns while the purge introduction mode is continued.

  On the other hand, when Td (k) = 0 (step S23: Yes), the purge means 51 sets the purge cut timer time Tct (k) to the second cut timer time Cth2 shorter than the first cut timer time. While being set (step S24), the purge valve 28 is closed and switched to the purge cut mode (step S25). As a result, one of the concentration estimation conditions “purge cut in progress” is established. In addition, since the transition fuel correction amount is sufficiently reduced by delaying the end timing of the period during which the purge process is being performed, it is one of the concentration estimation conditions when “purge cut in progress” is satisfied. The “transient fuel correction amount is smaller than the first predetermined value K1” is also established.

  Next, a condition establishment determination process is executed to determine whether other concentration estimation conditions are established (step S26). Here, as the condition establishment determination process after the purge introduction mode is switched to the purge cut mode, for example, as shown in FIG. 6, first, in step S61, the transient fuel correction amount is the first predetermined value described above. It is determined whether or not the value is smaller than the value K1 (see FIG. 5B). The method for estimating (calculating) the transient fuel correction amount is not particularly limited. For example, a known method described in Japanese Patent No. 3552255, Japanese Patent No. 4129628, or the like may be used.

  Next, in step S62, it is determined whether the air-fuel ratio control is in feedback control, and in step S63, it is determined whether the coolant temperature of the engine 11 is higher than a predetermined temperature. The condition that the transient fuel correction amount is smaller than the first predetermined value K1 (step S61: Yes), the air-fuel ratio control is being feedback controlled (step S62: Yes), and the water temperature is higher than the predetermined temperature is satisfied. If it is present (step S63: Yes), the time during which these conditions are satisfied (condition establishment time) Tst (k) is calculated (step S64). Next, it is determined whether or not the condition establishment time Tst (k) continues longer than a predetermined time (step S65). If the condition establishment time Tst (k) continues longer than the predetermined time (step S65: Yes), it is determined that the concentration estimation condition is established, and the condition establishment flag is set to ON (step S66). .

  On the other hand, when the transient fuel correction amount is greater than or equal to the first predetermined value K1 (step S61: No), when the air-fuel ratio control is not under feedback control (step S62: No), or when the water temperature is lower than the predetermined temperature (Step S63: No), it is determined that the concentration estimation condition is not satisfied (not satisfied), the condition satisfaction time is reset (Tst (k) = 0) in step S67, and the condition is satisfied in step S68. The flag is set off.

  When such a condition determination process is completed and other concentration estimation conditions are satisfied, that is, when the condition satisfaction flag is set to ON (step S27: Yes), the alcohol concentration is estimated by the concentration estimation means 53. Estimation is executed and the alcohol concentration estimated value is updated (step S28). On the other hand, when the other concentration estimation conditions are not satisfied, that is, when the condition satisfaction flag is set to OFF (step S27: No), the alcohol concentration estimated value is returned without being updated.

  The processing here will be described with reference to FIG. When the transient fuel correction amount shown in the third row in the figure exceeds the second predetermined value K2 at time T3 (step S17: Yes), the delay timer time Td (k) shown in the fourth row in the figure is the predetermined time H1. (Step S18). Therefore, the delay timer time Td (k) is maintained at the predetermined time H1 until the time T5 when the transient fuel correction amount exceeds the second predetermined value K2.

  For example, at time T3, the purge introduction mode is set (step S19: Yes), and the purge introduction timer time Tin (k) is not 0 (step S22: No). Return to S1. Thereafter, Tin (k) = 0 at time T4 (step S22: Yes), but at time T4, the transient fuel correction amount is larger than the second predetermined value K2, and the delay timer time Td (k) is predetermined. The time H1 remains unchanged (step S23: No). In this case, the purge introduction timer time Tin (k) and the purge cut timer time Tct (k) are both maintained at 0, and the purge introduction mode is continued. That is, the purge introduction mode is continued after the end time of the purge process is delayed.

  Thereafter, when the time T5 is passed and the transient fuel correction amount becomes equal to or smaller than the second predetermined value K2 (step S17: No), the delay timer time Td (k) is sequentially subtracted every calculation cycle (step S20). When the delay timer time Td (k) = 0 is reached at time T6 (step S23: Yes), the purge cut timer time Tct (k) is set to the second cut timer time Cth2 (step S24), and the purge is performed. The mode is switched to the cut mode (step S25). As a result, one of the concentration estimation conditions “purge cut is in progress” is established. Further, when the “purge cut” condition is satisfied, the transient fuel correction amount is sufficiently reduced, and therefore the condition “the transient fuel correction amount is smaller than the first predetermined value K1” is also satisfied. Yes.

  When the other concentration estimation conditions are satisfied (step S27: Yes), as shown in FIG. 4, the alcohol concentration estimation based on the exhaust air / fuel ratio is executed in step S28, and the alcohol concentration estimated value is updated.

  Thus, the concentration that the transient fuel correction amount is smaller than the first predetermined value K1 by delaying the purge cut end timing by a predetermined period from the time when the transient fuel correction amount becomes equal to or less than the second predetermined value K2. The estimation condition is satisfied, and the estimated alcohol concentration of the fuel is updated. That is, in this embodiment, during the purge process (purge introduction mode), the purge process end timing is delayed based on the magnitude of the transient fuel correction amount, the purge is being cut, and the transient fuel correction amount is relatively small. In the state, the estimated alcohol concentration of the fuel was updated. Thereby, the estimation accuracy of the alcohol concentration of the fuel can be improved. Therefore, the air-fuel ratio can be appropriately controlled to effectively suppress the deterioration of exhaust gas performance, the deterioration of drivability, and the like.

  On the other hand, if the purge introduction mode is not set in step S19, that is, if the purge cut mode is set (step S19: No), the purge cut timer time Tct (k) is calculated in step S29, and then the purge cut timer is set in step S30. It is determined whether or not the time Tct (k) is zero. That is, it is determined whether or not the period during which the purge process is not performed exceeds a predetermined time.

  If Tct (k) = 0 (step S30: Yes), it is further determined whether or not the delay timer time Td (k) = 0 (step S31). If Td (k) = 0 (step S31: Yes), the purge introduction timer time Tin (k) is shorter than the first introduction timer time by the purge means 51. The second introduction timer time Inh2 (Step S32). Then, the purge valve 28 is opened and switched to the purge introduction mode (step S33), and then the process returns.

  If Tct (k)> 0 (step S30: No), the purge cut mode is continued. Further, when Tct (k) = 0 (step S30: Yes) and Td (k)> 0 (step S31: No), the end timing of the period during which the purge process is not executed is delayed. Thus, the purge cut mode is continued.

  As described above, when the purge cut mode is continued, the process proceeds to step S26, where the above-described condition satisfaction determination process is executed, and when the concentration estimation condition is satisfied (step S27: Yes), the alcohol concentration estimated value is updated. (Step S28).

  The processing here will be described with reference to FIG. For example, at time T7, the purge cut mode is set (step S19: No), and the purge cut timer time Tct (k) is not 0 but is in the purge cut period (step S29: No). Further, since the transient fuel correction amount is larger than the second predetermined value K2 (step S17: Yes), the delay timer time Td (k) is set to the predetermined time H1 (step S18).

  Thereafter, Tct (k) = 0 at time T8 (step S29: Yes), but the transient fuel correction amount is still larger than the second predetermined value K2 at time T8. Therefore, the delay timer time Td (k) remains the predetermined time H1 (step S30: No). In this case, both the purge cut timer time and the purge introduction timer time are maintained at 0, and the purge cut mode is continued. That is, the purge cut start time is delayed and the purge cut mode is continued.

  Thereafter, when the time T9 is passed and the transient fuel correction amount becomes equal to or less than the second predetermined value K2 (step S17: No), the delay timer time Td (k) is sequentially subtracted every calculation cycle (step S20). At this time, since the concentration estimation condition that the transient fuel correction amount is smaller than the first predetermined value K1 is also satisfied, the estimated alcohol concentration value of the fuel is updated. In addition, since the purge cut end time is delayed in this manner, the period during which the concentration estimation condition is satisfied continues for a relatively long time. When the delay timer time Td (k) = 0 at time T10 (step S31: Yes), the purge introduction timer time Tin (k) is set to the second introduction timer time Inh2 at step S32, and step S33. After switching to purge introduction mode, return.

  As described above, when the transient fuel correction amount is included in the concentration estimation condition, the period during which the concentration estimation condition is satisfied becomes longer by delaying the purge cut end timing. The decrease in frequency is suppressed. In addition, the transient fuel correction amount is relatively small during the purge cut. In particular, the transient fuel correction amount becomes smaller by delaying the purge cut end timing with reference to the second predetermined value K2 that is smaller than the first predetermined value K1, which is the determination criterion of the concentration estimation condition. . That is, it is possible to simultaneously realize the concentration estimation conditions “purge cut is in progress” and “transient fuel correction amount is small”.

  Therefore, it is possible to improve the estimation accuracy of the alcohol concentration of the fuel while suppressing a decrease in the execution frequency of the alcohol concentration estimation, and to more appropriately control the air-fuel ratio according to the alcohol concentration of the fuel.

  In the present embodiment, as described above, the second introduction timer time Inh2 and the cut timer time Cth2 in the concentration estimation period are the same as the first introduction timer time Inh1 and the first cut timer time Cth1 that are not in the concentration estimation period. On the other hand, a small value (short time) is set. Further, the ratio of the second cut timer time Cth2 to the second introduction timer time Inh2 is set to be relatively larger than the ratio of the first cut timer time Cth1 to the first introduction timer time Inh1. ing. Thereby, the execution frequency of alcohol concentration estimation can be secured in the concentration estimation period, and the release of the vaporized fuel into the atmosphere can be prevented by increasing the purge introduction time during normal times other than the concentration estimation period.

  As mentioned above, although one Embodiment of this invention was described, of course, this invention is not limited to this Embodiment. For example, in the above-described embodiment, the present invention has been described by exemplifying an intake pipe injection type engine. However, the present invention can be applied to various engines such as a direct injection type engine and a diesel engine.

It is a schematic structure figure of an engine system concerning one embodiment. It is a flowchart which shows an example of the alcohol concentration estimation process of the fuel which concerns on this invention. It is a flowchart which shows an example of the alcohol concentration estimation process of the fuel which concerns on this invention. It is a flowchart which shows an example of the alcohol concentration estimation process of the fuel which concerns on this invention. It is a timing chart for demonstrating the execution timing of a purge process. It is a flowchart which shows an example of the alcohol concentration estimation process of the fuel which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Alcohol concentration estimation apparatus 11 Engine 12 Cylinder head 13 Cylinder block 14 Cylinder 15 Piston 16 Combustion chamber 17 Connecting rod 18 Crankshaft 19 Intake port 20 Intake manifold 21 Intake valve 22 Fuel pipe 23 Fuel tank 24 Fuel injection valve 25 Canister 26 Purge passage 27 Intake pipe 28 Purge valve 29 Fuel level sensor 30 Exhaust port 31 Exhaust manifold 32 Exhaust pipe 33 Exhaust valve 34 Spark plug 35 Ignition coil 36 Surge tank 37 Throttle valve 38 Throttle position sensor 39 Air flow sensor 40 Three-way catalyst 41 O ₂ sensor 42 ECU
43 Crank angle sensor 44 Water temperature sensor

Claims (1)

An exhaust air / fuel ratio detecting means for detecting an exhaust air / fuel ratio of an engine capable of using fuel mixed with alcohol; and
Purge means for performing a purge process for opening and closing a purge passage connecting a canister for storing the vaporized fuel and an intake system of the engine to introduce the vaporized fuel into the intake system at a predetermined timing;
Determination means for determining a degree of a transient fuel correction amount for correcting an excess or deficiency of the fuel amount in the cylinder of the engine due to the transient operation;
Detected by the exhaust air-fuel ratio detection means when a concentration estimation execution condition is satisfied that includes at least the purge process not being executed and the transient fuel correction amount being smaller than a first predetermined value. Concentration estimated value updating means for updating the alcohol concentration estimated value of the fuel based on the exhaust air-fuel ratio;
Comprising
The purge means, when it is determined by the determination means that the transient fuel correction amount has exceeded a second predetermined value equal to or less than the first predetermined value at the end time of the period when the purge process is not executed. An apparatus for estimating the alcohol concentration of a fuel, wherein an end time of a period in which the purge process is not performed is delayed by a predetermined period from a point in time when the transient fuel correction amount becomes equal to or less than the second predetermined value.

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