JP2010090792A - Fuel alcohol concentration estimation device - Google Patents

Abstract

A fuel alcohol concentration estimation device capable of more accurately estimating an alcohol concentration is provided.
A fuel supply determining means determines the presence / absence of fuel refueling based on a detection result of a fuel storage amount detecting means, and a threshold setting means determines a first threshold value when a fuel refueling is performed. When the fuel refueling is not performed, a second threshold value larger than the first threshold value is set as the determination threshold value, and the feedback correction value based on the exhaust air / fuel ratio calculated by the correction value change degree calculation means is set. When the absolute value of the degree of change is larger than the determination threshold, the concentration estimated value update unit updates the estimated alcohol concentration of the fuel based on the degree of change of the feedback correction value.
[Selection] Figure 5

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 an 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 mixed fuel and to 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.

  Here, there is an engine in which a predetermined calculation cycle is set when it is detected that fueling has been performed, and fuel alcohol concentration estimation is executed within this calculation cycle (see, for example, Patent Document 1).

US Pat. No. 6,017,796

  However, if the fuel alcohol concentration estimation is executed only when it is detected that there has been refueling, for example, when the refueling amount is small and the fuel amount in the fuel tank is small, etc. Despite being done, if it is not refueled, it will be misdetected and there exists a possibility that estimation of alcohol concentration may not be performed. If estimation of the alcohol concentration of the fuel is not executed even though fuel is supplied in this manner, the alcohol concentration of the fuel cannot be accurately learned, and as a result, the air-fuel ratio may not be properly controlled.

  In order to solve such a problem, it is conceivable to periodically estimate the alcohol concentration of the fuel regardless of whether or not refueling has occurred. However, for example, when the engine is cold or during transient operation, the air-fuel ratio fluctuates greatly, and the correction value based on the exhaust air-fuel ratio may vary depending on factors other than changes in the alcohol concentration. Therefore, there is a possibility that the alcohol concentration of the fuel is erroneously learned only by performing the alcohol concentration estimation periodically.

  This invention is made | formed in view of such a situation, and it aims at providing the alcohol concentration estimation apparatus of the fuel which can learn alcohol concentration more correctly.

  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, and an exhaust air / fuel ratio detected by the exhaust air / fuel ratio detecting means. Correction value change degree calculating means for calculating the change degree of the feedback correction value based on the above, oil supply determining means for determining the presence or absence of refueling, and the degree of change in the feedback correction value according to the determination result of the oil supply determining means A threshold setting means for setting a determination threshold value for determining the degree of change, and when the degree of change in the feedback correction value is larger than the determination threshold, the alcohol concentration of the fuel based on the degree of change in the feedback correction value Concentration estimation value updating means for updating the estimated value, and the threshold value setting means has a first threshold value when the oil supply determination means determines that there is fueling. A fuel alcohol concentration estimation device that is set as the determination threshold value and sets a second threshold value that is larger than the first threshold value as the determination threshold value when the fuel supply determination unit determines that no fuel is supplied. It is in.

  In the first aspect, since the alcohol concentration estimation of the fuel is executed every time the engine is started regardless of whether or not fueling is performed, the alcohol concentration of the fuel is accurately learned even when the fueling is not detected. . Moreover, the mislearning of the alcohol concentration of fuel is effectively suppressed by appropriately changing the magnitude of the determination threshold depending on the presence or absence of fueling.

  Examples of the degree of change of the feedback correction value include a change rate (change rate) of the feedback correction value, but are not limited thereto, and may be, for example, a change amount of the feedback correction value.

  The second aspect of the present invention further includes estimated value update determining means for determining whether or not the alcohol concentration estimated value has been updated at least once, and the threshold value setting means is configured such that the oil supply determining means indicates that no oil is supplied. Determining and setting the second threshold value as the determination threshold value when the estimated value update determining unit determines that the alcohol concentration estimated value has not been updated by the concentration estimated value update unit; Determines that there is no refueling, and the estimated value update determining means determines a fourth threshold value that is smaller than the second threshold value when the estimated alcohol value estimated value is updated by the estimated concentration value update means. The fuel alcohol concentration estimating apparatus according to the first aspect is characterized by being set as follows.

  The third aspect of the present invention further includes estimated value update determining means for determining whether or not the alcohol concentration estimated value has been updated at least once, and the threshold value setting means includes that the oil supply determining means is refueled. Determining and setting the first threshold as the determination threshold when the estimated value update determining means determines that the estimated alcohol concentration value has not been updated by the estimated concentration value updating means; Is determined as having the third threshold value that is smaller than the first threshold value when the estimated value update determining unit determines that the estimated alcohol concentration value has been updated by the estimated concentration value updating unit. The fuel alcohol concentration estimation apparatus according to the first or second aspect is characterized by being set.

  In the second or third aspect, despite the fact that there is no substantial change in the alcohol concentration of the fuel, frequent estimation of the alcohol concentration of the fuel is suppressed, and the estimated alcohol concentration value is updated once. After this, the estimated alcohol concentration value can be updated without missing a slight concentration change.

  The fourth aspect of the present invention further includes consumption calculation means for calculating fuel consumption of the engine, wherein the threshold setting means has at least a fuel consumption calculated by the consumption calculation means within a predetermined range. In the fuel alcohol concentration estimation apparatus according to any one of the first to third aspects, the determination threshold value is set.

  In the fourth aspect, it is possible to suppress the useless update of the estimated alcohol concentration value during the period when the alcohol concentration of the fuel is not changed.

  According to a fifth aspect of the present invention, when the refueling determination means determines that refueling is present, the consumption calculation means calculates the fuel consumption after refueling, and the fuel consumption after refueling is the predetermined fuel consumption. When the threshold value setting means sets the determination threshold value when it is within a first predetermined range as a range, and the oil supply determination means determines that there is no fuel supply, the consumption calculation means after the engine is started And the threshold value setting means sets the determination threshold value when the fuel consumption amount after the start is within a second predetermined range as the predetermined range. In the apparatus for estimating the alcohol concentration of the fuel according to the embodiment.

  In the fifth aspect, the period during which the alcohol concentration of the fuel is changing (the alcohol concentration estimable period) is more accurately determined, and the estimated value of the alcohol concentration of the fuel is updated at an appropriate timing.

  According to a sixth aspect of the present invention, when the fuel supply determining means determines that fuel supply is present, the threshold setting means has a fuel consumption amount after the fuel supply that exceeds the first predetermined range and the temperature of the engine. When the fuel supply determination means determines that there is no fuel supply when the fuel temperature is higher than a predetermined temperature, the fuel consumption after the start exceeds the second predetermined range and the engine temperature is higher than the predetermined temperature. Sometimes the fifth threshold value is further set as the determination threshold value, respectively, in the fuel alcohol concentration estimating apparatus according to the fifth aspect.

  In the sixth aspect, the estimated alcohol concentration value is updated again under a predetermined condition after the above-described alcohol concentration estimable period has elapsed. Thereby, even when the estimated value of the alcohol concentration is shifted, the estimated value of the alcohol concentration can be corrected to an accurate value.

  According to a seventh aspect of the present invention, in the sixth aspect, the fifth threshold set by the threshold setting means is set to the same value as the determination threshold set immediately before the fifth threshold. It is in the alcohol concentration estimation device for fuel.

  Also in the seventh aspect, after the elapse of the alcohol concentration estimation possible period, the alcohol concentration estimation value is updated again under a predetermined condition.

  According to an eighth aspect of the present invention, there is provided temperature correlation value detection means for detecting a temperature correlation value that correlates with the temperature of the engine, and the concentration estimated value update means is a fuel consumption amount calculated by the consumption amount calculation means. When the temperature correlation value detected by the temperature correlation value detecting means exceeds a predetermined value, the estimation of the alcohol concentration for updating the alcohol concentration estimation value is executed a predetermined number of times. The fuel alcohol concentration estimation apparatus according to any one of the fourth to seventh aspects is characterized.

  In the eighth aspect, when the temperature correlation value exceeds a predetermined value, that is, after it is determined that the engine has been sufficiently warmed up, the estimated fuel concentration is estimated a predetermined number of times. Even if there is a difference between the actual alcohol concentration and the actual alcohol concentration, the alcohol concentration can be re-estimated and corrected. Therefore, the air-fuel ratio can be controlled more appropriately.

  As described above, according to the present invention, the alcohol concentration of the fuel can be estimated more accurately. 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.

  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. A fuel level sensor 29 that detects the amount of fuel stored in the fuel tank 23 is provided in the fuel tank 23.

  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.

  For example, the air-fuel ratio of the engine 11 is appropriately controlled based on detection information from these various sensors. At this time, since the appropriate air-fuel ratio differs depending on the alcohol concentration of the fuel, it is necessary to accurately detect or estimate the alcohol concentration of the fuel in order to properly control the air-fuel ratio.

  In the fuel alcohol concentration estimation apparatus 10 of the present invention, as will be described in detail below, the alcohol concentration of the mixed fuel in the fuel tank 23 is appropriately estimated at a predetermined timing, so that the alcohol concentration of the fuel is determined whether or not fuel is supplied. So that it can be accurately grasped. Then, the air-fuel ratio in the combustion chamber 16 is favorably controlled by appropriately adjusting the fuel injection amount by the fuel injection valve 24 based on the estimated value.

  Next, the alcohol concentration estimation apparatus of the present embodiment will be described with reference to FIG.

  FIG. 2 is a functional block diagram showing an outline of a fuel alcohol concentration estimating apparatus according to the present invention. As shown in FIG. 2, the ECU 42 constituting the alcohol concentration estimation apparatus 10 includes a correction value change degree calculation unit 51, a fuel supply determination unit 52, a consumption calculation unit 53, an execution condition determination unit 54, and a threshold setting. A density estimation unit 50 including a means 55 and a density estimated value update means 56 is provided.

The correction value change degree calculation means 51 calculates the change degree of the feedback correction value based on the exhaust air / fuel ratio detected by the O ₂ sensor 41 which is the exhaust air / fuel ratio detection means. In the present embodiment, a feedback correction value change rate (hereinafter referred to as “correction value change rate”) ΔK is calculated as the feedback correction value change rate. Here, the feedback correction value is specifically for correcting the fuel injection amount injected from the fuel injection valve 24. However, the feedback correction value is not limited to this. For example, the feedback correction value is for correcting the intake air amount. May be. A method of calculating the correction value change rate ΔK will be described later.

  The fuel supply determination means 52 determines the presence or absence of fuel supply based on the detection result of the fuel level sensor 29 which is a fuel storage detection means. That is, the fuel supply determination unit 52 determines that “fuel supply is present” when the fuel level sensor 29 detects an increase in the fuel storage amount in the fuel tank 23, and the fuel level sensor 29 determines the fuel storage amount in the fuel tank 23. When the increase is not detected, it is determined that “no fuel supply”.

  The consumption calculation means 53 calculates the fuel consumption in the engine 11. That is, the consumption calculating means 53 calculates the amount of fuel consumed by the engine 11 after refueling (fuel consumption after refueling) when fuel refueling is performed, and when fuel refueling is not performed, The amount of fuel consumed after the engine 11 is started (fuel consumption after starting) is calculated. The method of calculating the fuel consumption amount by the consumption amount calculation means 53 is not particularly limited, but can be calculated based on the integrated value of the fuel injection amount by the fuel injection valve 24, for example.

  The execution condition determination unit 54 determines whether a condition (concentration estimation execution condition) for executing fuel alcohol concentration estimation is satisfied. Specifically, for example, the concentration estimation execution condition is established based on the fuel consumption (fuel consumption after refueling or fuel consumption after start-up), the cooling water temperature of the engine 11, the execution status of the purge process, and the like. It is determined whether or not.

  The threshold value setting unit 55 sets a determination threshold value for determining the magnitude of the change rate ΔK of the correction value according to the presence or absence of fuel supply when the concentration estimation execution condition is satisfied. For example, the threshold value setting means 55 sets the first threshold value as the determination threshold value when the fuel supply is performed, and the second threshold value that is larger than the first threshold value when the fuel supply is not performed. Is set as a determination threshold.

  Then, when the absolute value of the correction value change rate ΔK is larger than the determination threshold, the concentration estimated value update unit 56 updates the estimated alcohol concentration of the fuel based on the correction value change rate ΔK.

  Thus, in the alcohol concentration estimation apparatus 10 of the present invention, the absolute value of the change ratio ΔK, which is the magnitude of the change degree of the correction value calculated by the correction value change degree calculation means 51, regardless of the presence or absence of fuel supply, When the determination threshold value is larger than the determination threshold value set by the threshold value setting means 55, the estimated alcohol concentration value of the fuel is updated by the estimated concentration value update means 56.

  Thereby, the alcohol concentration of the fuel can be grasped more accurately. Therefore, the air-fuel ratio can be properly controlled. For example, when the amount of fuel supply is small and the amount of fuel in the fuel tank 23 is small, the fuel supply determination unit 52 may erroneously determine “no fuel supply”. In such a case, if the estimated alcohol concentration of the fuel is not updated, the air-fuel ratio cannot be properly controlled. However, according to the alcohol concentration estimation apparatus 10 of the present invention, the alcohol concentration estimated value is reliably updated even when the oil supply determination means 52 makes an erroneous determination. Therefore, the air-fuel ratio can be controlled more appropriately.

  Here, in the alcohol concentration estimation apparatus 10 of the present invention, the determination threshold value is not a constant value, and the threshold value setting unit 55 sets the value according to the determination result of the fuel supply determination unit 52. Thereby, the alcohol concentration of the fuel can be estimated more accurately.

  Specifically, when the refueling determination means 52 first determines that “refueling is present”, the probability that the actual refueling has been performed is extremely high. In such a case, the threshold value setting means 55 sets the determination threshold value to a relatively small value (first threshold value). As a result, the estimated alcohol concentration of the fuel is frequently updated.

  On the other hand, when the fuel supply determination means 52 determines that “no fuel supply”, the probability that the fuel supply has been performed is low, but the fuel supply may actually be performed as described above. In such a case, the threshold value setting means 55 sets the determination threshold value to a second threshold value that is larger than the first threshold value. That is, in actuality, fuel supply is performed, and the estimated alcohol concentration value of the fuel is updated when the change rate ΔK of the correction value changes relatively large. Thereby, erroneous estimation of the alcohol concentration of the fuel can be prevented, and the air-fuel ratio can be controlled more appropriately. In the present embodiment, the correction value change degree calculation means 51 calculates the correction value change ratio ΔK as the correction value change degree, and updates the estimated alcohol concentration value according to the magnitude of the correction ratio ΔK. However, for example, the estimated alcohol concentration value may be updated according to the amount of change in the correction value.

  Furthermore, in this embodiment, the concentration estimation unit 50 further includes an estimated value update determination unit 57 that determines whether or not the alcohol concentration estimated value has been updated at least once by the concentration estimated value update unit 56. The threshold setting unit 55 sets a determination threshold based on the determination result of the estimated value update determination unit 57 together with the determination result of the fuel supply determination unit 52.

  Specifically, the threshold setting unit 55 first determines that the fuel supply determination unit 52 determines that there is fuel supply, and the estimated value update determination unit 57 determines that the alcohol concentration estimated value has not been updated by the concentration estimated value update unit 56. The first threshold value is set as a determination threshold value, and the fuel supply determination unit 52 determines that there is fuel supply, and the estimated value update determination unit 57 determines that the alcohol concentration estimated value has been updated by the concentration estimated value update unit 56. A third threshold value smaller than the first threshold value is set as the determination threshold value.

  The threshold value setting means 55 determines the second threshold value when the refueling determination means 52 determines that there is no refueling and the estimated value update determination means 57 determines that the alcohol concentration estimated value has not been updated by the concentration estimated value update means 56. Is set as a determination threshold value, and when the oil supply determination unit 52 determines that no fuel supply is performed and the estimated value update determination unit 57 determines that the alcohol concentration estimated value is updated by the concentration estimated value update unit 56, the second threshold value is exceeded. A small fourth threshold is set as the determination threshold.

  That is, when the fuel supply determination unit 52 determines that there is fuel supply, the concentration estimated value update unit 56 updates the estimated alcohol concentration value of the first fuel when the absolute value of the change rate ΔK of the correction value exceeds the first threshold value. After the first alcohol concentration estimated value update is executed, the second and subsequent alcohol concentration estimated value updates are executed when a third threshold value smaller than the first threshold value is exceeded.

  If the refueling determination means 52 determines that there is no refueling, the concentration estimated value update means 56 estimates the alcohol concentration of the first fuel when the absolute value of the change rate ΔK of the correction value exceeds the second threshold value. After the value update is executed and the first alcohol concentration estimated value update is executed, the second and subsequent alcohol concentration estimated value updates are executed when a fourth threshold value smaller than the second threshold value is exceeded. It will be.

  As a result, in a situation where the alcohol concentration of the fuel is changing while suppressing the alcohol concentration estimated value from being frequently updated even though there is no substantial change in the alcohol concentration of the fuel, a slight concentration The alcohol concentration estimate can be updated without missing any changes.

  By the way, as described above, the threshold value setting means 55 sets a determination threshold value when the concentration estimation execution condition is satisfied. However, the execution condition determination means 54 determines the fuel consumption amount (fuel after fueling) calculated by the consumption amount calculation means 53. It is determined as one of the concentration estimation execution conditions that the consumption amount or the post-startup fuel consumption amount) is within a predetermined range. For example, as shown in the first row in FIG. 3, the fuel consumption (fuel consumption after refueling or fuel consumption after start-up) is in a range (first or second) between a first predetermined value A1 and a second predetermined value A2. 2, the execution condition determination unit 54 determines that one of the density estimation execution conditions is satisfied. Such a condition is determined for the following reason.

  When the estimated fuel alcohol concentration value is updated after fuel refueling, if the fuel consumption after refueling or the fuel consumption after starting is less than the first predetermined value A1, the fuel tank 23 and the fuel injection valve 24 are used. There is a possibility that the fuel remaining in the fuel pipe 22 that connects the two (that is, the fuel before refueling) affects the estimation of the alcohol concentration. On the other hand, when the fuel consumption amount exceeds the second predetermined value A2, the fuel before refueling is almost replaced with the fuel after refueling, and the alcohol concentration of the fuel does not substantially change.

  For this reason, in the present embodiment, the threshold value setting means 55 sets the determination threshold value when the fuel consumption amount is within the predetermined range as described above. That is, the estimated alcohol concentration value is updated by the estimated concentration value updating means 56 when the fuel consumption is within a predetermined range.

  Further, in the present embodiment, the estimated alcohol concentration of the fuel is updated again even after the engine 11 is sufficiently warmed up. That is, when the post-startup fuel consumption calculated by the consumption calculation means 53 exceeds the second predetermined value A2 and the temperature of the cooling water of the engine 11 is higher than the predetermined temperature, the threshold setting means 55 sets the fifth threshold value. Is set as the determination threshold. In the present embodiment, the threshold setting unit 55 sets a fifth threshold, which is the same value as the determination threshold set immediately before, as the determination threshold. Then, when the absolute value of the change rate ΔK of the correction value exceeds the determination threshold, the estimated alcohol concentration of the fuel is updated again. As a result, the air-fuel ratio can be controlled more appropriately.

  Hereinafter, an example of alcohol concentration estimation control by the alcohol concentration estimation apparatus 10 will be described with reference to the flowcharts of FIGS. 4 to 6.

  As shown in FIG. 4, it is first determined in step S1 whether the engine stall mode or the start mode is established. That is, it is determined whether the ignition is on but the engine 11 is not started. If the above mode is established (step S1: Yes), the post-startup fuel consumption is reset (ΣFLS (k) = 0) in step S2. The post-startup fuel consumption is the amount of fuel consumed after the engine 11 is started, and is calculated by the consumption calculation means 53 as described above.

  Next, in step S3, it is determined whether or not the fuel supply flag is off. The fuel supply flag is a flag that is set to ON when the fuel supply determination unit 52 determines that there is fuel based on the detection result of the fuel level sensor 29 in the fuel tank 23 in a step that will be described later. The case where the fuel supply flag is set to OFF will be described later. The fuel supply flag is set to OFF in the initial setting.

  Here, when the fuel refueling flag is set to OFF (step S3: Yes), the start-up estimation flag is set to ON in step S4, and when the fuel refueling flag is set to ON (step S3: Yes) Step S3: No), the start-up estimation flag is set to OFF in step S5. As described above, since the refueling flag is set to OFF in the initial setting, when the ignition is turned ON in the initial setting state, the start estimation flag is set to ON in step S4, and then the process proceeds to step S7. .

  Here, the start-by-start estimation flag is a flag that is set to ON when the fuel supply flag is set to OFF in step S4. Then, the threshold value setting means 55 sets the determination threshold value to a predetermined value, as will be described later, depending on whether or not the start-up estimation flag and the fuel supply flag are set to ON. The case where the start-up estimation flag is set to off will be described later. The start-up estimation flag is set to off by default.

  In step S7, it is determined whether or not the fuel supply flag is set to ON. For example, since the fuel supply flag is set to OFF in the initial setting (step S7: No), the process proceeds to step S8, and the fuel consumption after refueling is reset (ΣFL (k) = 0). The fuel consumption after refueling ΣFL (k) is the amount of fuel consumed after refueling, and is calculated by the consumption calculation means 53 as described above.

  Next, in step S9, the fuel supply determination means 52 determines whether or not the fuel level (fuel storage amount) in the fuel tank 23 has increased based on the presence or absence of fuel supply, that is, the detection result of the fuel level sensor 29. If the fuel level has changed (increased), that is, if the refueling determination means 52 determines that “refueling is present” (step S9: No), the fuel refueling flag is set to ON in step S10 and step is performed. In S11, the start-by-start estimation flag is set to OFF, and then the process proceeds to Step S21 described later.

  On the other hand, when the fuel level in the fuel tank 23 has not increased, that is, when the fuel supply determination means 52 determines “no fuel supply” (step S9: Yes), the fuel supply flag is kept off. Then, in step S12, it is determined whether or not the start-by-start estimation flag is set to ON. If the start-by-start estimation flag is set to ON (step S12: Yes), the process proceeds to step S41. If the start-by-start estimation flag is set to OFF (step S12: No), It progresses to step S61 mentioned later.

  If the fuel refueling flag is set to ON in step S7 (step S7: Yes), the fuel consumption amount ΣFL (k) after refueling is calculated by the consumption calculating means 53 in step S13, and then the process proceeds to step S21. .

  When the processing of step S1 to step S13 is completed, if the fuel supply flag is set to on, the process proceeds to step S21, where the fuel supply flag is set to off and the start-up estimation flag is turned on. If set, the process proceeds to step S41. Further, when both the fuel supply flag and the start-up estimation flag are both set to OFF, the process proceeds to step S61.

  First, the processing when the fueling flag is set to ON, that is, when the fueling determination means 52 determines “with fueling” (at the time of fueling) will be described. When the process proceeds from step S11 or step S13 to step S21, as shown in FIG. 5, first, the execution condition determination means 54 is a period in which the alcohol concentration of fuel can be estimated (hereinafter referred to as “concentration estimable period”). It is determined whether or not there is a period in which the alcohol concentration of the fuel injected from the fuel injection valve 24 is changing. Specifically, whether or not the fuel consumption after refueling ΣFL (k) calculated by the consumption calculation means 53 is within the first predetermined range, that is, the first predetermined value A1 to the second predetermined value A2. It is determined whether or not it is within a range (see the first stage in FIG. 3).

  In step S21, the fuel consumption after refueling ΣFL (k) is less than the second predetermined value A2 (step S21: Yes), and the fuel consumption after refueling ΣFL (k) is greater than or equal to the first predetermined value A1. If this is the case (step S22: Yes), it is determined that it is a concentration estimable period. On the other hand, when the fuel consumption after refueling ΣFL (k) is greater than or equal to the second predetermined value A2 (step S21: No), or when the fuel consumption after refueling ΣFL (k) is less than the first predetermined value A1 (Step S22: No), it is determined that it is not the concentration estimation possible period.

  If it is determined that the concentration can be estimated, then in step S23, air-fuel ratio (A / F) learning by feedback control is prohibited, and the purge cycle is switched to a special setting.

  During the concentration estimation possible period, it is considered that the alcohol concentration of the fuel injected from the fuel injection valve 24 changes with fuel refueling as described above. Therefore, if A / F learning is performed by feedback control, the air-fuel ratio There is a risk of mis-learning. For this reason, A / F learning is prohibited when the concentration estimation is possible.

  In addition, if purging is performed when the fuel alcohol concentration is estimated in the steps described later, the exhaust air-fuel ratio may change accordingly, and the alcohol concentration may be erroneously learned. For this reason, as shown in FIG. 3, for example, the concentration estimated value update unit 56 can be executed at a timing (for example, time T1, T2, T3) of a period during which purging is prohibited (purge cycle: OFF). preferable. When the purge cycle is a normal setting, the period during which the purge is performed is relatively long. For this reason, when it is determined that the concentration estimable period is reached, the purge cycle is set as a special setting to shorten the purge cut cycle so that the alcohol concentration can be estimated frequently.

  Next, in step S24, the execution condition determination means 54 determines whether or not other alcohol concentration estimation execution conditions are satisfied, for example, whether or not conditions such as purge execution status and cooling water temperature are satisfied. judge.

If the execution condition determination unit 54 determines that these alcohol concentration estimation execution conditions are satisfied (step S24: Yes), then the correction value change degree calculation unit 51 is detected by the O ₂ sensor 41. Based on the exhaust air-fuel ratio, a change rate ΔK of a correction value (A / F correction value) when feedback control of the air-fuel ratio is calculated (step S28).

  In this embodiment, before the change rate ΔK of the A / F correction value is calculated, it is determined in step S25 whether or not the fuel consumption after refueling ΣFL (k) is equal to or greater than the second predetermined value A2. Is done. If the fuel consumption after refueling ΣFL (k) is equal to or greater than the second predetermined value A2 (step S25: Yes), the concentration estimation execution condition flag is set to ON in step S26, and the fuel consumption after refueling ΣFL ( If k) is less than the second predetermined value A2 (step S25: No), the concentration estimation execution condition flag is set to OFF in step S27. The necessity of these processes will be described later.

  Specifically, the correction value change degree calculation means 51 calculates the change rate ΔK of the A / F correction value by the following procedures (I) to (IV) (step S28).

(I) An average value KI_AVE of A / F correction values is calculated.
(II) The A / F correction value KPRST is calculated by the following formula (1).
KPRST = {KI_AVE + (KLRN-1)} × KALCH (1)

  Note that “KLRN” is an A / F learning correction value stored as a fixed value when A / F learning is prohibited, “KALCH” is an alcohol concentration correction value, and is “1” by default. It is imitated.

(III) The A / F correction reference value KBASE is calculated by the following equation (2).
KBASE = {1+ (KLRN-1)} × KALCH (2)
(IV) The change ratio ΔK of the A / F correction value is calculated by the following formula (3).
ΔK = (KPRST−KBASE) / KBASE (3)

  After the change rate ΔK of the A / F correction value is calculated in this way, in step S29, the estimated value update determination unit 57 determines whether or not the alcohol concentration estimated value by the concentration estimated value update unit 56 has been updated at least once. Determine. Specifically, the estimated value update determination means 57 determines whether or not the density change flag is set to OFF. The concentration change flag is a flag that is set to ON when the estimated alcohol concentration value is updated.

  Next, the threshold value setting means 55 sets a determination threshold value for the correction value change rate ΔK. As described above, the process proceeds to step S21 when the refueling determination unit 52 determines that “refueling is present”. For this reason, when the concentration change flag is set to OFF in step S29, that is, when it is determined that the alcohol concentration estimated value has not been updated (step S29: Yes), the threshold setting means 55 is set in step S30. The first threshold Th1 is set as the determination threshold. On the other hand, when the concentration change flag is set to ON, that is, when it is determined that the estimated alcohol concentration value has been updated at least once (step S29: No), the threshold setting means 55 in step S31 A third threshold value Th3 that is smaller than the threshold value of 1 is set as the determination threshold value.

  In step S32, whether or not the absolute value (| ΔK |) of the change rate of the correction value is larger than the determination threshold (first threshold Th1 or third threshold Th3) set by the threshold setting unit 55. Determined. If | ΔK |> “determination threshold” (step S32: Yes), the alcohol concentration correction value KALCH is updated after the concentration change flag is set to ON in step S33 (step S34).

  Thereafter, the concentration estimated value update unit 56 refers to, for example, a map showing the relationship between the alcohol concentration of the fuel and the alcohol concentration correction value, and estimates the alcohol concentration of the fuel based on the alcohol concentration correction value updated in step S34. The value is updated (step S35), and the process returns.

  For example, referring to the example at the time of refueling shown in FIG. 3, first, in the determination at time T1, as shown in the fourth stage (F / B correction value) in the figure, the change rate ΔK (ΔK1) of the correction value at time T1. Is larger than the determination threshold (first threshold Th1), the alcohol concentration is updated as indicated by the solid line in the fifth row (alcohol concentration) in the figure. Since the alcohol concentration is updated once at time T1, in the determination of time T2, it is determined whether or not the change rate ΔK (ΔK2) of the correction value at time T2 is larger than the determination threshold (third threshold Th3). In the example, since ΔK2> Th3, the alcohol concentration is updated. In the subsequent determination (for example, determination at time T3), if the change rate ΔK of the correction value is larger than the determination threshold (third threshold Th3), the alcohol concentration is updated as illustrated.

  Returning to FIG. 5, when | ΔK | ≦ “determination threshold” in step S 32, that is, when the change rate ΔK of the correction value is relatively small (No in step S 32), the concentration estimated value update unit 56 determines that the fuel Returned without updating the alcohol concentration estimate.

  If the engine 11 is started in step S1, that is, if the engine stall mode or the start mode is not established (step S1: No), the consumption calculation means 53 in step S6 causes the post-start fuel consumption ΣFLS ( k) is calculated. Further, since the fuel supply flag is set to ON (step S7: Yes), after the consumption calculating means 53 calculates the fuel consumption after fueling ΣFL (k) in step S13, the above-described processing is repeated.

  Thus, while repeating the series of processes described above, the fuel consumption after refueling ΣFL (k) gradually increases (step S8). When the fuel consumption after refueling ΣFL (k) becomes equal to or greater than the second predetermined value A2 in step S21, it is then determined in step S36 whether or not the concentration estimation execution condition flag is set to ON. This concentration estimation execution condition flag is a flag that is set to ON when the fuel consumption after refueling ΣFL (k) is equal to or greater than the second predetermined value A2 in steps S25 to S27 described above. Then it is off.

  Therefore, when the determination in step S36 is performed for the first time, the concentration estimation execution condition flag is set to OFF (step S36: No), and the process proceeds to step S22. When the determination in step S36 is made, the fuel consumption after refueling ΣFL (k) is always greater than or equal to the first predetermined value A1 (step S22: Yes), and thereafter, the processing in steps S23 to S35 is performed.

  That is, in the present embodiment, when the fuel consumption after refueling ΣFL (k) is in the range (first predetermined range) between the first predetermined value A1 and the second predetermined value A2, the concentration estimated value update unit 56 The fuel alcohol concentration estimation is repeatedly executed, and after the fuel consumption after refueling ΣFL (k) exceeds the second predetermined value A2, another one is performed at a predetermined timing (for example, time T3 in FIG. 3). I try to run it once.

  Further, when the fuel consumption after refueling ΣFL (k) exceeds the second predetermined value A2 (step S25: Yes), and then the alcohol concentration estimation is performed, the concentration estimation execution condition flag is turned on in step S26. Is set. Therefore, when it is determined in step S36 whether or not the concentration estimation execution condition flag is on, the concentration estimation execution condition flag is set to on (step S36: Yes), and then fuel refueling in step S37. The flag is set off. In step S38, A / F learning is permitted and the purge cycle is switched to the normal setting. Further, the density change flag is set to OFF, the density estimation execution condition flag is set to OFF, and then the process returns.

  If the fuel supply flag is set to OFF in step S37 as described above and the process returns to step S1, the process proceeds to step S61 without proceeding to step S21. That is, by providing the above-described steps S25 to S27, after the fuel consumption after refueling ΣFL (k) exceeds the second predetermined value A2, the alcohol concentration of the fuel is estimated once more. ing.

  Next, a process when the refueling flag is off and the start-up estimation flag is on, that is, when the refueling determination means 52 determines “no refueling” (when not refueling) will be described. The processing at the time of non-fueling is basically the same as the processing at the time of fueling described above, but the threshold setting means 55 sets the determination threshold to a value different from that at the time of fueling. Further, it is determined based on the post-startup fuel consumption ΣFLS (n) whether or not the alcohol concentration estimation period is possible.

  As shown in FIG. 6, the process proceeds from step S12 to step S41, and it is determined whether or not the post-startup fuel consumption ΣFLS (k) is within a second predetermined range. Then, when the post-startup fuel consumption amount ΣFLS (k) is within the second predetermined range, that is, the post-startup fuel consumption amount ΣFLS (k) is less than the second predetermined value A2 (step S41: Yes), and When it is equal to or greater than the first predetermined value A1 (step S42: Yes), it is determined that it is the concentration estimable period. On the other hand, when the fuel consumption after starting ΣFLS (k) is greater than or equal to the second predetermined value A2 (step S41: No), and when the fuel consumption after starting ΣFLS (k) is less than the first predetermined value A1 (Step S42: No), it is determined that it is not the concentration estimation possible period.

  Note that each of the first predetermined range and the second predetermined range described above is described as a range of the first predetermined value A1 to the second predetermined value A2 for the sake of convenience. The predetermined range of 2 is actually a different numerical range.

  If it is determined that the concentration can be estimated, the air-fuel ratio (A / F) learning by the feedback control is prohibited in step S43 and the purge cycle is switched to the special setting in the same manner as the processing at the time of refueling. Further, in step S44, it is determined whether or not an alcohol concentration estimation execution condition is satisfied. If the alcohol concentration estimation execution condition is satisfied (step S44: Yes), it is determined in step S45 whether or not the post-startup fuel consumption ΣFLS (k) is equal to or greater than a second predetermined value A2. If it is equal to or greater than the predetermined value A2 (step S45: Yes), the concentration estimation execution condition flag is set to ON (step S46). If it is less than the second predetermined value A2 (step S45: No), the concentration estimation execution condition is set. The flag is set to off (step S47). Next, a change rate ΔK of a correction value (A / F correction value) for feedback control of the air-fuel ratio is calculated (step S48).

  Next, the threshold value setting means 55 sets a determination threshold value for the correction value change rate ΔK. As described above, the process proceeds to step S41 when the fuel supply determination unit 52 determines that “no fuel supply”. Therefore, when the concentration change flag is set to OFF in step S49, that is, the alcohol concentration estimated value is not yet determined. When it is determined to be updated (step S49: Yes), in step S50, the threshold setting unit 55 sets the second threshold Th2 that is larger than the first threshold Th1 as the determination threshold. On the other hand, when the concentration change flag is set to ON, that is, when it is determined that the estimated alcohol concentration value has been updated at least once (step S49: No), the threshold setting means 55 is changed to step S51. A fourth threshold value Th4 that is smaller than the threshold value 2 is set as the determination threshold value. Note that the fourth threshold Th4 is approximately the same value as the above-described third threshold Th3.

  In step S52, it is determined whether or not the absolute value (| ΔK |) of the change rate of the correction value is larger than the set determination threshold (second threshold Th2 or fourth threshold Th4). If |> “determination threshold” (step S52: Yes), the alcohol concentration correction value KALCH is updated after the concentration change flag is set to ON in step S53 (step S54). Thereafter, the concentration estimated value updating means 56 updates the fuel alcohol concentration estimated value (step S55), and the process returns.

  For example, in the case of non-fuel supply shown in FIG. 3, first, in the determination at time T1, as shown in the sixth stage (F / B correction value) in the figure, the change rate ΔK (ΔK3 of the correction value at time T1 is shown. ) Is smaller than the determination threshold (second threshold Th2), the alcohol concentration is not updated as shown in the seventh row (alcohol concentration) in the figure. After that, since the change rate ΔK (ΔK4) of the correction value is larger than the determination threshold (second threshold Th2) at the time of determination at time T2, the alcohol concentration is updated for the first time at time T2. In the subsequent determination (for example, determination at time T3), if the change rate ΔK of the correction value is larger than the determination threshold (fourth threshold Th4), the alcohol concentration is updated as illustrated.

  Returning to FIG. 6, if | ΔK | ≦ “determination threshold” in step S 52, that is, if the correction value change rate ΔK is relatively small (No in step S 52), the concentration estimated value update unit 56 determines that the fuel Returned without updating the alcohol concentration estimate.

  The fuel consumption after starting ΣFLS (k) gradually increases while repeating a series of processes at the time of non-fuel supply (step S6). When the post-startup fuel consumption ΣFLS (k) becomes equal to or greater than the second predetermined value A2 in step S41, it is then determined in step S56 whether or not the concentration estimation execution condition flag is set to ON. When the determination in step S56 is performed for the first time, the concentration estimation execution flag is set to OFF (step S56: No), and the process proceeds to step S42. When the determination in step S56 is made, the fuel consumption after refueling ΣFL (k) is always greater than or equal to the first predetermined value (step S42: Yes), and thereafter, the processing in steps S43 to S55 is performed.

  Further, if the post-startup fuel consumption ΣFLS (k) exceeds the second predetermined value A2 (step S45: Yes) and then the alcohol concentration estimation is performed, the concentration estimation execution condition flag is turned on in step S46. Is set. Therefore, when proceeding to step S56 thereafter, the concentration estimation execution condition flag is set to ON (step S56: Yes), and then in step S57, the start-up estimation flag is set to OFF. In step S58, A / F learning is permitted and the purge cycle is switched to the normal setting. Further, the density change flag is set to OFF, the density estimation execution condition flag is set to OFF, and then the process returns.

  Thus, after returning to step S1 after the start-by-start estimation flag is set off in step S57, the process proceeds to step S61 without proceeding to step S41. That is, by providing the above-described steps S45 to S47, after the post-startup fuel consumption ΣFLS (k) exceeds the second predetermined value A2, the predetermined timing (for example, time T3 in FIG. 3) is performed only once. Thus, the alcohol concentration estimation of the fuel is executed.

  Next, processing when both the fueling flag and the start-up estimation flag are both off, that is, the process proceeds to step S61 as described above will be described.

  As shown in FIG. 7, first, in step S61, the execution condition determination unit 54 determines whether or not the coolant temperature exceeds a predetermined temperature Te1 based on the detection result of the water temperature sensor 44 as a temperature correlation value detection unit. Judgment is made (see FIG. 3). In step S61, based on the temperature correlation value correlated with the temperature of the engine 11 detected by the temperature correlation detecting means, it is determined whether or not the engine 11 is sufficiently warmed up and in a stable state. In the present embodiment, the coolant temperature is detected by the water temperature sensor 44 as the temperature correlation value, but the temperature correlation value is not limited to this. For example, the oil temperature of the engine 11 or the warm temperature of the engine 11 is not limited. It may be a travel distance or an elapsed time correlated with the machine state.

  If the temperature of the cooling water is higher than the predetermined temperature Te1 (step S61: Yes), it is then determined in step S62 whether the post-warming concentration estimation execution count N is less than the predetermined count. The post-warm concentration estimation execution count N is the number of times the fuel alcohol concentration estimation is executed after the engine 11 is sufficiently warmed up, and is zero in the initial setting.

  When the post-warm-up concentration estimation execution count N is smaller than the predetermined count (step S62: Yes), A / F learning by feedback control is prohibited and the purge cycle is switched to a special setting in step S63. Further, in step S64, it is determined whether or not the alcohol concentration estimation execution condition is satisfied. If the alcohol concentration estimation execution condition is satisfied (step S64: Yes), the post-warmup concentration estimation execution count N is added once (step S65).

  Thereafter, in step S66, the correction value change degree calculation means 51 calculates a correction value change rate ΔK when the air-fuel ratio is feedback controlled at a predetermined timing (for example, time T4 shown in FIG. 3). Next, the threshold value setting means 55 sets the same value as the determination threshold value set immediately before it, for example, the fifth threshold value Th5 that is the same value as the third threshold value Th3 or the fourth threshold value Th4 as the determination threshold value ( Step S67). In step S67, the threshold setting unit 55 may set, for example, the second threshold Th2 or the first threshold Th1 as the determination threshold.

  In step S68, it is determined whether or not the absolute value (| ΔK |) of the change rate of the correction value is greater than a set determination threshold (fifth threshold Th5). If | ΔK |> “determination threshold” (step S68: Yes), the alcohol concentration correction value KALCH is updated in step S69, and the estimated alcohol concentration of fuel is updated in step S70 (see FIG. 3). ), Then returned.

  If the cooling water temperature is equal to or lower than the predetermined temperature Te1 in step S61 (step S61: No), the post-warming concentration estimation execution count N is reset (N = 0) in step S71, and the alcohol concentration of the fuel is estimated. Is not executed, A / F learning is permitted in step S72, the purge cycle is switched to the normal setting, and then the process returns.

  Thus, even after the engine 11 is sufficiently warmed up, the estimation of the alcohol concentration of the fuel is completed by executing and estimating the alcohol concentration of the fuel a predetermined number of times (for example, about 2 or 3 times). Even if there is a deviation from the actual alcohol concentration, the alcohol concentration can be re-estimated and corrected. Therefore, the air-fuel ratio can be controlled more appropriately.

  As mentioned above, although 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, of course, the present invention can be applied to other types of engines such as an in-cylinder injection type. it can.

It is a schematic structure figure of an engine system concerning one embodiment. It is a functional block diagram which shows the outline of the alcohol concentration estimation apparatus of the fuel which concerns on one Embodiment. It is a timing chart explaining the alcohol concentration estimation method of the fuel concerning the present invention. It is a flowchart which shows the alcohol concentration estimation method of the fuel which concerns on one Embodiment. It is a flowchart which shows the alcohol concentration estimation method of the fuel which concerns on one Embodiment. It is a flowchart which shows the alcohol concentration estimation method of the fuel which concerns on one Embodiment. It is a flowchart which shows the alcohol concentration estimation method of the fuel which concerns on one Embodiment.

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 (8)

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
A correction value change degree calculating means for calculating a change degree of the feedback correction value based on the exhaust air / fuel ratio detected by the exhaust air / fuel ratio detecting means;
Refueling determination means for determining the presence or absence of refueling;
Threshold setting means for setting a determination threshold for determining the magnitude of the degree of change of the feedback correction value according to the determination result of the oil supply determination means;
A concentration estimated value updating means for updating the estimated alcohol concentration of the fuel based on the degree of change of the feedback correction value when the magnitude of the degree of change of the feedback correction value is larger than the determination threshold;
The threshold value setting means sets a first threshold value as the determination threshold value when the oil supply determination means determines that there is oil supply, and more than the first threshold value when the oil supply determination means determines that there is no oil supply. A fuel alcohol concentration estimation apparatus characterized in that a large second threshold is set as the determination threshold. Further comprising estimated value update determining means for determining whether or not the alcohol concentration estimated value has been updated at least once;
The threshold setting means includes
The second threshold value is set as the determination threshold value when the fuel supply determination unit determines that no fuel supply is performed and the estimated value update determination unit determines that the alcohol concentration estimated value has not been updated by the concentration estimated value update unit. Is set, and when the oil supply determination means determines that there is no fuel supply and the estimated value update determination means determines that the alcohol concentration estimated value has been updated by the concentration estimated value update means, it is smaller than the second threshold value. 4. The fuel alcohol concentration estimating apparatus according to claim 1, wherein a fourth threshold value is set as the determination threshold value. Further comprising estimated value update determining means for determining whether or not the alcohol concentration estimated value has been updated at least once;
The threshold setting means includes
The first threshold value is used as the determination threshold value when the oil supply determination unit determines that there is refueling and the estimated value update determination unit determines that the alcohol concentration estimated value is not updated by the concentration estimated value update unit. A first value that is smaller than the first threshold value when the fuel supply determination means determines that there is fuel supply and the estimated value update determination means determines that the estimated alcohol concentration value has been updated by the concentration estimated value update means. 3. The fuel alcohol concentration estimation apparatus according to claim 1, wherein a threshold value of 3 is set as the determination threshold value. A consumption calculating means for calculating the fuel consumption of the engine;
The threshold value setting unit sets the determination threshold value when at least the fuel consumption amount calculated by the consumption amount calculation unit is within a predetermined range. The alcohol concentration estimation apparatus of fuel as described. When the refueling determination means determines that refueling is present, the consumption calculation means calculates the fuel consumption after refueling, and the fuel consumption after refueling is within a first predetermined range as the predetermined range. When the threshold value setting means, the threshold value setting means sets the determination threshold value,
When the fuel supply determining means determines that no fuel is supplied, the consumption amount calculating means calculates the fuel consumption amount after the engine is started, and the fuel consumption amount after the start is a second range as the predetermined range. 5. The fuel alcohol concentration estimation apparatus according to claim 4, wherein the threshold value setting means sets the determination threshold value when it is within a predetermined range. The threshold setting means includes
When the fuel supply determination unit determines that fuel supply is present, the fuel supply determination unit supplies the fuel when the fuel consumption after the fuel supply exceeds the first predetermined range and the temperature of the engine is higher than a predetermined temperature. If it is determined that there is no fuel consumption after the start exceeds the second predetermined range and the engine temperature is higher than a predetermined temperature,
6. The fuel alcohol concentration estimation apparatus according to claim 5, wherein a fifth threshold value is further set as the determination threshold value.   7. The fuel alcohol concentration estimation apparatus according to claim 6, wherein the fifth threshold value set by the threshold value setting means is set to the same value as the determination threshold value set immediately before the fifth threshold value. A temperature correlation value detecting means for detecting a temperature correlation value correlated with the temperature of the engine;
The concentration estimated value update means includes
To update the estimated alcohol concentration value when the fuel consumption calculated by the consumption calculation means exceeds a predetermined range and the temperature correlation value detected by the temperature correlation value detection means exceeds a predetermined value. The alcohol concentration estimation apparatus for fuel according to any one of claims 4 to 7, wherein the estimation of the alcohol concentration is performed a predetermined number of times.

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