JP5093510B2 - Fuel alcohol concentration estimation device - Google Patents

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.

According to a first aspect of the present invention for solving the above problems, an exhaust air / fuel ratio detecting means for detecting an exhaust air / fuel ratio of an engine capable of using fuel mixed with alcohol, a canister for storing a vaporized fuel, an intake system of the engine, And a purge means for performing a purge process for introducing the vaporized fuel into the intake system at a predetermined timing by opening and closing a purge passage connecting the engine, and correcting an excess or deficiency of the fuel amount in the cylinder of the engine due to a transient operation Determining means for determining the degree of the transient fuel correction amount to be performed, and at least a concentration estimation period in which the alcohol concentration of the fuel injected from the fuel injection valve changes with fuel refueling and the purge process When the concentration estimation condition including that it is not executed is satisfied, the fuel altitude is determined based on the exhaust air / fuel ratio detected by the exhaust air / fuel ratio detecting means. Comprising a concentration estimated value updating means for updating Lumpur density estimates, wherein the purge means, depending on the degree of the transient fuel compensation amount to be determined by the determination unit, and change the predetermined timing, The end time of the period during which the purge process is executed when the determination means determines that the transient fuel correction amount is greater than the first predetermined value at the end time of the period during which the purge process is being executed. Is delayed by a predetermined period from the time when the transient fuel correction amount becomes equal to or less than the first predetermined value, and the concentration estimation condition is that the transient fuel correction amount is a second predetermined value greater than or equal to the first predetermined value. The purge means includes a condition that the transition fuel correction amount is greater than the first predetermined value by the determination means at the end time of the period in which the purge process is not executed. If it is constant, an alcohol fuel, characterized in that to delayed a predetermined period end timing from the time when the transient fuel compensation amount is equal to or less than the first predetermined value of period in which the purge process is not executed It is in the concentration estimation device.

In the first aspect, since the estimation of the alcohol concentration of the fuel is performed in a state where the purge process is stopped and the transient fuel correction amount is small, the estimation accuracy of the alcohol concentration is improved. Further, even when the concentration estimation condition includes that “the transient fuel correction amount has fallen below the second predetermined value”, the period during which the purge process is not performed is extended, so that the alcohol concentration of the fuel is increased. A decrease in the estimation execution frequency can be suppressed.

  As described above, according to the present invention, the estimation accuracy of the alcohol concentration of fuel can be improved. In addition, it is possible to suppress a decrease in the frequency of execution of fuel alcohol concentration estimation. 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, the airflow sensor 39, and the 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 means 51, a determination means 52, and a concentration estimation means 53 as the main components constituting the fuel alcohol concentration estimation apparatus 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. 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 unit 51 determines that the transient fuel correction amount is larger than the first predetermined value by the determination unit 52 at the end time of the period during which the purge process is being performed, the purge process is performed. The end time of the period being executed is delayed by a predetermined period from the time when the transient fuel correction amount becomes equal to or less than the first predetermined value. Further, in the present embodiment, when the purge unit 51 determines that the transient fuel correction amount is larger than the first predetermined value by the determination unit 52 at the end time of the period when the purge process is not executed, the purge process is performed. The end timing of the period in which 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 first predetermined value. As will be described in detail later, this improves the estimation accuracy of the alcohol concentration of the fuel.

  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 S11), 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, when 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 ), The purge introduction mode and the purge cut mode are switched at a predetermined timing. When the concentration estimation condition including the purge cut mode is satisfied, the alcohol concentration of the fuel is estimated.

  Here, the delay timer is a timer for controlling the timing of switching between the purge introduction mode and the purge cut mode based on the amount of fuel attached to the wall surface, that is, for delaying the end timing or start timing of the purge process. And in this invention, the estimation precision of the alcohol concentration of a fuel is improved by delaying the completion | finish time or start time of purge processing by this delay timer. More specifically, even in the purge cut mode, when the amount of fuel attached to the wall surface is large, there is a possibility that the alcohol concentration is erroneously estimated even if the alcohol concentration estimation of the fuel is executed. For this reason, in the present invention, by delaying the end timing or the start timing of the purge process by the delay timer, the alcohol concentration estimation of the fuel is executed when the purge cut mode is reached and the amount of fuel attached to the wall surface is small. I try to do it.

  Specifically, in step S17, the determination unit 52 determines whether or not the transient fuel correction amount (transient fuel correction coefficient) based on the wall surface attached fuel amount is larger than the first predetermined value K1. When the transient fuel correction amount is larger than the first predetermined value K1 (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 first predetermined value K1 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.

  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, if Td (k) = 0 is not satisfied (step S23: No), the end timing of the purge process is delayed, and the process is returned 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 satisfied, and “a state where the transient fuel correction amount is small” is realized.

  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 S62, it is determined whether the air-fuel ratio control is in feedback control or not. In step S63, it is determined whether or not the coolant temperature of the engine 11 is higher than a predetermined temperature.

  When the condition that the air-fuel ratio control is being feedback controlled (step S62: Yes) and the water temperature is higher than the predetermined temperature is satisfied (step S63: Yes), the time during which these conditions are further satisfied (Condition establishment time) Tst (k) is calculated (step S64), and 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 air-fuel ratio control is not under feedback control (step S62: No), or even when the air-fuel ratio control is under feedback control (step S62: Yes), when the water temperature is equal to or lower than the predetermined temperature (step S62). S63: No), it is determined that the concentration estimation condition is not satisfied (not satisfied), the condition satisfaction time Tst (k) is reset in step S67, and the condition satisfaction flag is set to OFF in step S68.

  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 first predetermined value K1 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 first predetermined value K1.

  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 first predetermined value K1, 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 transient fuel correction amount becomes equal to or smaller than the first predetermined value K1 after the time T5 (step S17: No), the delay timer time Td (k) is sequentially subtracted for each 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 satisfied, and “a state where the transient fuel correction amount is small” is realized. 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.

  As described above, in this embodiment, during the purge process (purge introduction mode), the purge process end time is delayed based on the magnitude of the transient fuel correction amount, the purge cut is being performed, and the transient fuel correction amount is compared. The estimated alcohol concentration of fuel is updated in a small state. Thereby, the estimation accuracy of the alcohol concentration of the fuel can be improved. Therefore, the air-fuel ratio can be always properly controlled to effectively suppress the deterioration of exhaust gas performance and the deterioration of drivability.

  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 first predetermined value K1 (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 at the time T8, the transient fuel correction amount is still larger than the first predetermined value K1. 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 transient fuel correction amount becomes equal to or less than the first predetermined value K1 after the time T9 (step S17: No), the delay timer time Td (k) is sequentially subtracted every calculation cycle (step S20). At this time, since the purge cut mode is continued until the transient fuel correction amount becomes sufficiently small, the estimated alcohol concentration of the fuel is updated with the transient fuel correction amount being relatively small. Accuracy can be improved. 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.

  In this way, when the purge process is not executed (purge cut mode), the purge cut end timing (purge process start timing) is delayed based on the magnitude of the transient fuel correction amount. The estimated value of the alcohol concentration of the fuel is updated while the purge is being cut and the transient fuel correction amount is relatively small.

  The delay timer time Td (k) is set to such a value that the purge cut end timing is delayed until the transient fuel correction amount becomes sufficiently small so that the alcohol concentration is accurately estimated. For this reason, by delaying the purge cut end timing, the estimated alcohol concentration of the fuel is updated in a state where the transient fuel correction amount is relatively small. Thereby, the estimation precision of alcohol concentration can be improved.

  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.

  In the present embodiment, as the condition satisfaction determination process in step S26, whether or not the condition that the air-fuel ratio control is feedback control and the coolant temperature is higher than a predetermined temperature is satisfied, and these conditions are satisfied. In the above example, it is determined whether or not the time (condition establishment time) continues longer than the predetermined time. However, the conditions determined in the condition establishment determination process are not limited to these. Absent. For example, as shown in FIG. 7, first, at step S61, whether or not the transient fuel correction amount has fallen below a second predetermined value K2 (see FIG. 5B) that is equal to or greater than the first predetermined value K1 described above. After that, step S62 to step S65 described above may be performed. That is, the condition (concentration estimation condition) for executing the alcohol concentration estimation may include that “the transient fuel correction amount has fallen below the second predetermined value K2”.

  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. The second predetermined value K2 may be a value equal to or greater than the first predetermined value K1, but is set to a value approximately equal to the first predetermined value K1, for example. That is, “the transient fuel correction amount is below the first predetermined value K1” may be included in the concentration estimation condition.

  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 first predetermined value K1 which is smaller than the second predetermined value K2 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.

  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 purge processing. 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 the other 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 the degree of the transient fuel correction amount for correcting the excess or deficiency of the fuel amount in the cylinder of the engine due to the transient operation;
Concentration estimation conditions are satisfied, including at least a concentration estimation period in which the alcohol concentration of the fuel injected from the fuel injection valve changes with fuel refueling and that the purge process is not executed A concentration estimated value updating means for updating the estimated alcohol concentration of the fuel based on the exhaust air / fuel ratio detected by the exhaust air / fuel ratio detecting means,
Comprising
The purge means changes the predetermined timing according to the degree of the transient fuel correction amount determined by the determination means, and the transition means performs the transient by the determination means at the end time of the period during which the purge process is executed. When it is determined that the fuel correction amount is larger than the first predetermined value, the end timing of the period during which the purge process is performed is determined from the time when the transient fuel correction amount becomes equal to or less than the first predetermined value. Delayed for a certain period,
The concentration estimation condition includes a condition that the transient fuel correction amount is below a second predetermined value that is equal to or greater than the first predetermined value, and the purge means is in a period during which the purge process is not executed. When the determination unit determines that the transient fuel correction amount is larger than the first predetermined value at the end time, the transient fuel correction amount is set to the end time of the period when the purge process is not performed. An apparatus for estimating the alcohol concentration of a fuel, wherein the apparatus is delayed by a predetermined period from a time when the value becomes equal to or less than a predetermined value of 1 .

Images