JP2007309122A - Evaporated fuel treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaporated fuel treatment device applicable even to an idle stop vehicle, and capable of preventing the ratio from becoming the rich air-fuel ratio by evaporated fuel generated from a fuel tank. <P>SOLUTION: This evaporated fuel treatment device has a purge valve for opening and closing a pipe for communicating a canister for sucking the evaporated fuel generated in the fuel tank with an intake passage of an engine, and has an emission deterioration determining means (Step S37) for determining whether or not exhaust emission is deteriorated at that time, by reducing a corresponding quantity of an estimated fuel desporption quantity from fuel supplied to the engine, by estimating the fuel desorption quantity desorbing from the canister by using a canister mode, when controlling the purge valve for opening on the basis of the target purge ratio set so as not to deteriorate the exhaust emission, and a fuel excessive evaporation determining means (Step S38) for determining that an evaporated fuel quantity being generated in the fuel tank is excessive, when determining the deterioration in the exhaust emission by the emission deterioration determining means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for treating evaporated fuel generated from a fuel tank.

  Evaporated fuel is generated in the fuel tank. Therefore, a canister is provided between the fuel tank and the engine, and the evaporated fuel generated while the engine is stopped is adsorbed by the activated carbon of the canister. Then, when the engine is started, the fuel adsorbed by the activated carbon is desorbed using the suction negative pressure developed in the intake pipe downstream of the throttle valve, and the combustion process is performed (purge process).

  When the fuel desorbed from the canister is sucked into the engine, the air-fuel ratio becomes rich. Therefore, it is necessary to correct the fuel injection amount by a corresponding amount. Therefore, in Patent Document 1, a target purge rate (the ratio of the purge flow rate to the intake air flow rate) is set as high as possible without deteriorating engine combustion stability and exhaust emission during the purge process, and the target purge rate is realized. Thus, the purge valve is opened, and the amount of fuel desorbed from the canister (hereinafter referred to as “desorption amount”) is estimated using a canister model, and the fuel injection amount is corrected to decrease by the corresponding amount. By doing so, the purge process can be performed quickly.

  However, when the temperature is high as in summer, the rich air-fuel ratio may not be resolved even if the canister model is used to reduce the fuel injection amount as in Patent Document 1.

  That is, when the temperature is high, evaporated fuel is sequentially generated in the fuel tank. Therefore, when the purge valve is opened, not only the fuel adsorbed by the activated carbon but also evaporated fuel generated in the fuel tank is sucked into the engine. Therefore, since more fuel than the estimated amount based on the canister model is sucked into the engine, the method of Patent Document 1 in which only the amount of desorption from the canister is considered cannot solve the rich air-fuel ratio. Moreover, in a scene where the engine is started and the vehicle starts running, but is immediately trapped in a traffic jam, there is a risk of misfire due to the rich air-fuel ratio.

  Therefore, conventionally, when the outside air temperature is high and the evaporated fuel may become excessive, and the fuel injection amount is corrected based on the canister model and the rich air-fuel ratio still remains, the fuel is excessively evaporated. Judgment is made, and the opening degree of the purge valve is reduced to give priority to combustion stability over the purge process.

  However, such a determination needs to be performed in a state where the intake air amount is small and the operation state is stable.

  That is, the amount of evaporated fuel generated in the fuel tank is not affected by the amount of intake air, but the fuel injection amount increases according to the amount of intake air, so when the amount of intake air is large, the proportion of the fuel injection amount is small Therefore, it is regarded as an error range and the fuel over-evaporation state cannot be determined.

For this reason, conventionally, it is determined whether the fuel is in a fuel over-evaporation state during idle operation.
JP 2002-276479 A

  As described above, since the conventional method needs to be performed during idling to determine the fuel over-evaporation state, it cannot be applied to a so-called idle stop vehicle in which the engine is stopped when the vehicle is stopped.

  The present invention has been made paying attention to such conventional problems, and can determine the fuel over-evaporation state even during traveling, so that it can also be applied to an idle stop vehicle and a fuel tank. It is an object of the present invention to provide an evaporative fuel processing apparatus capable of preventing a rich air-fuel ratio from being generated by evaporative fuel generated from the fuel.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention opens and closes a canister (10) that adsorbs evaporated fuel generated in a fuel tank (20), and a pipe (22) that connects the canister (10) and an intake passage (31) of an engine (30). An evaporative fuel processing apparatus having a purge valve (14), and a target purge rate setting means (step S10) for setting a target purge rate so as not to deteriorate the exhaust emission, and opening the purge valve based on the target purge rate. A canister model (step S100) for estimating the amount of fuel desorbed from the canister when the valve is controlled, and a substantial amount of fuel desorbed estimated by the canister model for the fuel supplied to the engine The fuel injection amount adjusting means (100, 34) for correcting the amount of emissions and the emission for determining whether or not the exhaust emission has deteriorated Fuel over-evaporation determining means (step S37, S418) and when the deterioration of exhaust emission is determined by the emission deterioration determining means, it is determined that the amount of evaporated fuel generated in the fuel tank is excessive. S38, S47).

  According to the present invention, the target purge rate is set so as not to deteriorate the exhaust emission, and the amount of fuel desorbed from the canister is estimated by the canister model when the purge valve is controlled to open based on the target purge rate. The amount of evaporated fuel that is generated in the fuel tank when it is judged that exhaust emissions have deteriorated even though fuel is supplied to the engine by reducing the amount of fuel desorption estimated by the canister model. Is determined to be excessive, it is possible to accurately detect the excessive evaporation state of the fuel. Further, since the deterioration of exhaust emission is determined based on the fluctuation cycle of the air-fuel ratio feedback correction coefficient, it is possible to determine the fuel over-evaporation state even during traveling, and therefore it can be applied to an idle stop vehicle. .

  Hereinafter, the best mode for carrying out the present invention will be described in more detail with reference to the drawings. FIG. 1 is an overall configuration diagram of an engine including an evaporated fuel processing apparatus according to the present invention.

  A fuel injection valve 34 for each cylinder is provided in the intake passage 31 of the engine 30 downstream of the intake throttle valve 33. The exhaust passage 35 is provided with a three-way catalyst (not shown). The three-way catalyst exhibits maximum conversion efficiency when the air-fuel ratio in the exhaust gas is in a narrow range centered on the stoichiometric air-fuel ratio, reduces nitrogen oxide NOx in the exhaust gas, and produces hydrocarbon HC and monoxide. Carbon CO is oxidized.

  Therefore, the controller 100 inputs an intake air flow rate signal from the air flow meter 32, a signal from the crank angle sensor 37, an engine cooling water temperature signal from the water temperature sensor 38, etc., and the basic air-fuel ratio (theoretical) based on these signals. The basic injection pulse width Tp for obtaining an air / fuel mixture is calculated. The controller 100 calculates an air-fuel ratio feedback correction coefficient α based on the output signal of the oxygen sensor (O2 sensor) 36, and the basic injection pulse width Tp (engine) is calculated by the air-fuel ratio feedback correction coefficient α (air-fuel ratio feedback correction amount). The fuel injection pulse width Ti is obtained by correcting the basic amount of fuel supplied to the fuel, and the fuel injection valve 34 is controlled to open. By doing so, the air-fuel ratio in the exhaust gas matches the stoichiometric air-fuel ratio, and the three-way catalyst can exhibit the maximum conversion efficiency.

  The evaporative fuel processing apparatus 1 includes a canister 10, a bypass valve 11, a vacuum cut valve 12, a drain cut valve 13, and a purge valve 14, and these valves are controlled to be opened and closed by a controller 100, and a fuel tank of the engine 30. The evaporated fuel generated at 20 is processed.

  The canister 10 communicates with the fuel tank 20 via a pipe 21 and communicates with an intake passage 31 downstream of the throttle valve 33 of the engine 30 via a pipe 22. The canister 10 has a fuel adsorbent (activated carbon) 10a inside. The canister 10 includes an air release port 10b. The air release port 10 b is opened and closed by a drain cut valve 13.

  The bypass valve 11 and the vacuum cut valve 12 are provided in parallel with the pipe 21. The vacuum cut valve 12 opens when the internal pressure of the fuel tank 20 becomes lower than the atmospheric pressure.

  The purge valve 14 is provided in the pipe 22. The purge valve 14 is opened when the fuel adsorbed on the fuel adsorbent (activated carbon) 10a of the canister 10 is desorbed. The pipe 22 is provided with a pressure sensor 23 that measures the pressure in the pipe.

  The evaporated fuel generated in the fuel tank 20 is guided to the canister 10 through the pipe 21, only the fuel component is adsorbed by the activated carbon 10a of the canister 10, and the remaining air is released to the outside from the atmosphere opening 10b.

  When processing the fuel adsorbed on the activated carbon 10a, the purge valve 14 is opened, and fresh air is introduced into the canister 10 from the air release port 10b by the suction negative pressure developed downstream of the throttle valve 33. As a result, the fuel adsorbed on the activated carbon 10a is desorbed and sucked into the intake passage 31 of the engine 30 through the pipe 22 together with fresh air (hereinafter, this process is referred to as “purge process”).

  During the purge process, the controller 100 sets a target purge rate (a ratio of the purge flow rate to the intake air flow rate) as high as possible within a range not deteriorating engine combustion stability and exhaust emission, and realizes the target purge rate. The purge valve 14 is driven.

  Further, during the purge process, the fuel and air in the purge gas are supplied to the engine. Therefore, the fuel injection amount is corrected according to the purge rate and the purge concentration, and the air-fuel ratio fluctuation of the engine 30 is changed. Suppress.

  Therefore, the controller 100 estimates a desorbed fuel amount Dg from the canister 10 using a canister model described later, and calculates a purge correction coefficient FHOS based on the desorbed fuel amount Dg, the target purge rate, and the intake air mass. The basic injection pulse width Tp is corrected with the purge correction coefficient FHOS. By doing so, the effect of the purge on the exhaust air / fuel ratio is compensated by the purge correction coefficient FHOS, and the air / fuel ratio feedback correction coefficient α behaves in the same manner as when there is no purge. Therefore, the air-fuel ratio feedback correction coefficient α does not have to consider the influence on the disturbance due to the purge.

  Here, a method for setting the target purge rate will be described. FIG. 2 is a flowchart for explaining the contents of the target purge rate setting routine.

  In step S11, the controller 100 determines whether or not the current purge control is the first control. That is, the previous value of the target purge rate is required to set the target purge rate based on the adsorption state of the canister 10. However, since there is no previous value at the time of initial control, the target purge rate must be set without being based on the adsorption state of the canister 10 at that time. Therefore, it is determined whether or not the current control is the initial control. When it is the initial control, the process proceeds to step S12, and when it is not the initial control, the process proceeds to step S13.

  In step S <b> 12, the controller 100 sets a target purge rate that is not based on the adsorption state of the canister 10. A specific setting method will be described later.

  In step S <b> 13, the controller 100 sets a target purge rate based on the adsorption state of the canister 10. A specific setting method will be described later.

  FIG. 3 is a flowchart for explaining the contents of a target purge rate setting routine that is not based on the adsorption state of the canister.

  In step S121, the controller 100 calculates an integrated purge flow rate (total purge flow rate after starting the purge). The integrated purge flow rate is zero as an initial value at the start of the purge. After the purge starts, the purge flow rate is obtained from the previously calculated target purge rate and intake air flow rate, and the integrated purge flow rate is updated.

  In step S122, the controller 100 determines whether or not the integrated purge flow rate is larger than the purge pipe volume (the volume of the pipe from the canister 10 to the purge valve 14). If the integrated purge flow rate is larger than the purge pipe volume, the process proceeds to step S124; otherwise, the process proceeds to step S123.

  In step S123, the controller 100 sets the initial purge rate (a small value of 1% or less) as the target purge rate. This small value is set for the following reason. That is, if the purge is started when the integrated purge flow rate has not reached the purge pipe volume, the low concentration purge gas present in the purge pipe is supplied to the engine. Even in such a case, if the target purge rate is set as shown in and after step S124, the air-fuel ratio fluctuation due to the low-concentration purge gas is small, so it is determined that a large amount of purge is possible and a large purge rate is set. There is a risk. However, when a large purge rate is set in this way, a large amount of desorbed fuel is suddenly supplied, so that the combustion stability of the engine 10 is deteriorated. Therefore, when the integrated purge flow rate does not reach the purge pipe volume, the target purge rate is set and the initial purge rate (a small value of 1% or less) is set.

  In step S124, the controller 100 calculates a difference between the target air-fuel ratio feedback deviation and the actual air-fuel ratio feedback deviation (hereinafter referred to as “air-fuel ratio feedback deviation difference”). The target air-fuel ratio feedback deviation is a deviation (= | tα-100 |%) of the target value tα of the air-fuel ratio feedback correction coefficient with respect to the reference value (100%) of the air-fuel ratio feedback correction coefficient. The actual air-fuel ratio feedback deviation is a deviation (= | α-100 |%) of the actual air-fuel ratio feedback correction coefficient α with respect to the reference value (100%) of the air-fuel ratio feedback correction coefficient. For example, when the target value tα of the air-fuel ratio feedback correction coefficient is set to 80% for the purpose of ensuring a large purge flow rate within a range in which air-fuel ratio fluctuation due to purge can be sufficiently absorbed by the air-fuel ratio feedback control, The air-fuel ratio feedback deviation is set to 20%.

  In step S125, the controller 100 searches the characteristic table shown in FIG. 4 stored in advance in the ROM to obtain the purge rate change amount according to the difference in the air-fuel ratio feedback deviation. The absolute value of the purge rate change amount increases as the absolute value of the difference in the air-fuel ratio feedback deviation increases, thereby improving the convergence to the target value. However, even if the absolute value of the difference in the air-fuel ratio feedback deviation is the same, the absolute value of the purge rate change amount differs depending on whether it is positive or negative. As for the absolute value of the purge rate change amount, the negative value is larger than the positive value. This characteristic is obtained when the difference in air-fuel ratio feedback deviation is shifted to the negative side, the air-fuel ratio feedback correction coefficient α is smaller than the target 80%, and on the opposite positive side. This is because the engine stability and emission are likely to be deteriorated by disturbances other than purge, as compared with the case of deviation, which is disadvantageous. In other words, changing the characteristics of the purge change amount according to the sign of the difference in the air-fuel ratio feedback deviation is to quickly return the control point to the safe side in order to improve engine combustion stability and prevent emissions from deteriorating. Because.

  In step S126, the controller 100 calculates the current value of the target purge rate by adding the purge rate change calculated in step S125 to the previous value of the target purge rate.

  According to this process, an optimum purge rate can be set regardless of the adsorption state of the canister 10, and even when a purge with a concentration higher than expected is supplied, the target is received in response to fluctuations in the air / fuel ratio. The purge rate is changed as appropriate, and an optimal purge rate can always be set.

  FIG. 5 is a flowchart for explaining the contents of a target purge rate setting routine based on the adsorption state of the canister.

  In step S131, the controller 100 sets a purge change amount limit value. A specific setting method will be described later.

  In step S132, the controller 100 sets a maximum purge rate. A specific setting method will be described later.

  In step S133, the controller 100 determines whether or not the previous value of the target purge rate matches the maximum purge rate. If they match, the process proceeds to step S134; otherwise, the process proceeds to step S135.

  In step S134, the controller 100 sets the previous value of the target purge rate as the target purge rate as it is.

  In step S135, the controller 100 determines whether or not the previous value of the target purge rate is below the maximum purge rate. If it is lower, the process proceeds to step S136, and if not, the process proceeds to step S137.

  In step S136, the controller 100 sets the target purge rate by adding the purge rate change limit value to the previous value of the target purge rate.

  In step S137, the controller 100 sets the target purge rate by subtracting the purge rate change limit value from the previous value of the target purge rate.

  FIG. 6 is a flowchart for explaining the contents of the purge change amount limit value setting routine.

  In step S1311, the controller 100 calculates the purge gas air-fuel ratio (purge air-fuel ratio) based on the desorption amount and the purge flow rate calculated by the canister model. The purge air-fuel ratio may be detected using an HC sensor, but can be obtained inexpensively and accurately if calculated by calculation.

  In step S1312, the controller 100 estimates the purge air-fuel ratio error based on operating conditions, for example, parameters such as engine speed, engine load, and intake air flow rate. Specifically, for example, it is obtained with reference to a characteristic table shown in FIG. According to FIG. 7A, the purge air-fuel ratio error increases as the intake air flow rate decreases and the purge rate decreases. Alternatively, it may be obtained with reference to a characteristic table shown in FIG. According to FIG. 7B, the purge air-fuel ratio error increases as the purge air-fuel ratio decreases.

  In step S1313, the controller 100 corrects the purge air-fuel ratio obtained in step S1311 based on the purge air-fuel ratio error.

  In step S1314, the controller 100 calculates a purge rate change amount limit value based on the corrected purge air-fuel ratio. The purge rate change limit value is a limit value for keeping the air-fuel ratio change of the engine 10 that occurs when the purge rate is changed within an air-fuel ratio fluctuation range that can be absorbed by air-fuel ratio feedback control without deteriorating emissions. It is.

  FIG. 8 is a flowchart for explaining the contents of the maximum purge rate setting routine.

  In step S1321, the controller 100 sets the purge rate upper limit PVMX based on the size of the purge valve 14. This purge rate upper limit PVMX is the purge rate when the purge valve 14 is at the maximum opening. If a target purge rate larger than the purge rate when the purge valve 14 is at the maximum opening is set, the purge rate cannot be matched with the target purge rate. For this reason, the calculation error of FHOS becomes large, the air-fuel ratio fluctuation becomes large, and emission deterioration occurs. The larger the purge valve size, the larger the purge gas flow rate. Therefore, the purge rate upper limit PVMX is set larger as the purge valve size is larger.

  In step S1322, the controller 100 determines the purge rate upper limit value based on the performance of the fuel injection valve 15 based on the relationship between the minimum fuel injection pulse width determined according to the performance of the fuel injection valve 15, the previous value of the target purge rate, and the purge correction coefficient. Set TIMNMX. When the purge rate increases, the amount of fuel supplied to the engine 10 by the purge increases, so it is necessary to reduce the fuel injection amount of the fuel injection valve 15 by the increase amount, but the injection accuracy of the fuel injection valve 15 is ensured. Requires a certain amount of fuel injection. Therefore, in order to ensure the injection accuracy of the fuel injection valve 15, an upper limit value TIMNMX is set for the purge rate.

  In step S1323, the controller 100 assumes all the operation regions that can be assumed from the current operation region, predicts the minimum purge rate in the operation region, and determines the purge rate upper limit from the minimum purge rate and the purge rate change limit value. Set the value PRMNMX. For example, when acceleration is performed with the accelerator fully open, the target purge rate is set to a very small value, but if the target purge rate is set to a large value immediately before the accelerator is fully opened, the amount of change in the purge rate is The purge rate cannot be made to follow the target purge rate because it is limited to the change amount limit value or less. Since this follow-up delay causes an increase in emissions, the purge rate upper limit value PRMNMX is set based on the minimum purge rate that can be assumed so as not to cause such follow-up delay.

  In step S1324, the controller 100 monitors the air-fuel ratio feedback correction coefficient α, and if it is equal to or less than a predetermined value, sets the largest value among the purge rates at which the air-fuel ratio feedback correction coefficient α is equal to or greater than the predetermined value as the purge rate upper limit value ALPMX. To do. The upper limit value ALPMX is provided so that the air-fuel ratio feedback correction coefficient α is controlled to be within 100 ± 25% in the air-fuel ratio feedback control, but the air-fuel ratio feedback correction coefficient α is set to the limit value (for example, 80 %) In the case of being controlled in the vicinity, if a large amount of purging is performed, disturbances other than purging will occur and it will easily be out of the control range.

  In step S1325, the controller 100 selects the smallest value from the four upper limit values PVMX, TIMNMX, PRMNMX, and ALPMX, and sets that value as the maximum purge rate.

  In the target purge rate setting routine (S13) based on the adsorption state of the canister 10, the target purge rate is set so as to reach the maximum purge rate within the range of the purge rate change amount limit value, so that exhaust emission is not deteriorated. The best purge rate can be set when performing a large amount of purge. In addition to the upper limits PVMX, TIMNMX, and ALPMX that are determined by physical limits and the current operating range, the upper limit is determined so that even if the operating range changes, the maximum purge rate in that range can be shifted without delay. Since the maximum purge rate is set in consideration of the value PRMNMX, it is possible to set the best purge rate that enables a large-scale purge that does not deteriorate the exhaust emission even if the operating condition changes.

  Next, a method for estimating the desorbed fuel amount Dg based on the canister model will be described with reference to FIG.

  In step S101, the controller 100 calculates the current value Y of the amount of fuel adsorbed by the canister 10 according to the following equation (1).

  In step S102, the controller 100 calculates the activated carbon temperature T by the following equation (2).

  This activated carbon temperature calculation formula is composed of past temperature (right side first term), temperature drop due to desorption (right side second term), and temperature rise due to heat transfer (right side third term). The activated carbon temperature T is calculated in this way because the desorption index n (T) in the following equation (3) is affected by the activated carbon temperature T, and in particular, when the desorption amount is large, the decrease in the activated carbon temperature T. This is because the influence of this on the fuel desorption characteristics in the canister 10 cannot be ignored.

  In step S103, the controller 100 calculates the desorption amount Dgk at the reference purge flow rate by the following equation (3).

  This equation (3) applies the idea of adsorption / desorption phenomenon (Freundlich's equation) to the desorption phenomenon of the canister 10, and thereby expresses the fuel desorption characteristics from the canister 10 almost accurately. can do. The Freundlich equation is described in “Theory on the Surface II” (Maruzen, Tsukada), p.25-p.27, p.108-p115.

  In step S104, the controller 100 calculates the desorption amount by the following equation (4).

  The desorption amount calculation formula (4) corresponding to the purge flow rate calculates the desorption amount Dg by linear approximation since the purge flow rate and the desorption amount are substantially proportional. In this case, the amount of desorption at the reference flow rate is obtained from equation (3), and the amount of desorption is calculated by multiplying this by the purge flow rate in equation (4), but equations (3), (4) May be combined into one expression.

  Therefore, the canister model is composed of the above formulas (1) to (4), and this canister model is shown in FIG. 10 as a control block diagram. The canister model includes an adsorption amount calculation unit B101, an activated carbon temperature calculation unit B102, a reference desorption amount calculation unit B103, and a flow rate equivalent desorption amount calculation unit B104, and each part corresponds to the equations (1) to (4), respectively. .

  By the way, conventionally, when the outside air temperature is high and the evaporated fuel may become excessive, and the fuel injection amount is reduced based on the canister model and the rich air-fuel ratio still remains, the fuel over-evaporation state is Judgment is made, and the opening degree of the purge valve is reduced to give priority to combustion stability over the purge process. However, such a determination must be performed in a state where the intake air amount is small and the driving state is stable, and it must be performed during the idling operation, and thus cannot be applied to a so-called idle stop vehicle.

  In the present invention, in the case of a rich air-fuel ratio, attention is paid to the fact that the fluctuation amplitude of the air-fuel ratio feedback correction coefficient α is increased and the fluctuation period is shortened in order to correct the rich air-fuel ratio. The over-evaporation state is determined.

  Below, the concrete control logic of the controller 100 is demonstrated along a flowchart.

  FIG. 11 is a main flowchart for explaining the operation of the fuel vapor processing apparatus according to the present invention.

  In step S1, the controller 100 determines whether purge is being executed. If purging is being performed, the process proceeds to step S2, and if not, the process is temporarily exited.

  In step S2, the controller 100 determines whether or not the purge concentration has been estimated. If completed, the process proceeds to step S4, and if not, the process proceeds to step S3.

  In step S3, the controller 100 performs a fuel over-evaporation state determination before the concentration estimation is completed. Details will be described later.

  In step S4, the controller 100 performs fuel over-evaporation state determination after completion of concentration estimation. Details will be described later.

  FIG. 12 is a flowchart for explaining the contents of a fuel over-evaporation state determination routine before completion of concentration estimation.

  In step S31, the controller 100 increments the α variation timer.

  In step S32, the controller 100 determines whether or not the α variation timer has exceeded a specified time. Until it exceeds, the process proceeds to step S33, and when it exceeds, the process proceeds to step S39.

  In step S33, the controller 100 determines whether or not the previous value αz of the air-fuel ratio feedback correction coefficient α is equal to or larger than the fluctuation range lower limit value MIN and the current air-fuel ratio feedback correction coefficient α is smaller than the fluctuation range lower limit value MIN. To do. That is, it is determined whether or not the air-fuel ratio feedback correction coefficient α is smaller than the fluctuation range lower limit value MIN for the first time this time. Until this condition is satisfied, the process is temporarily exited. When the condition is satisfied, the process proceeds to step S34.

  In step S34, the controller 100 determines whether or not the α fluctuation counter is zero. If zero, the process proceeds to step S35, and if not, the process proceeds to step S36.

  In step S35, the controller 100 resets the α variation timer.

  In step S36, the controller 100 increments the α fluctuation counter.

  In step S37, the controller 100 determines whether or not the α fluctuation counter has exceeded a specified value. If so, the process proceeds to step S38, and if not, the process is temporarily exited.

  In step S38, the controller 100 determines that the fuel is in an over-evaporated state, and adjusts the opening of the purge valve to be reduced. In addition, the α variation timer is reset and the α variation counter is reset after one job.

  In step S39, the controller 100 resets the α fluctuation counter.

  FIG. 13 is a flowchart for explaining the contents of a fuel over-evaporation state determination routine after completion of concentration estimation.

  In step S41, the controller 100 determines whether or not the air-fuel ratio feedback correction coefficient α is hunting. Details will be described later.

  In step S42, the controller 100 determines whether or not hunting is being performed. Until the hunting, the process is temporarily exited. When the hunting is started, the process proceeds to step S43.

  In step S43, the controller 100 determines whether or not the current state is passive calibration. Passive calibration will be described later.

  In step S44, the controller 100 determines base deviation. Details will be described later.

  In step S45, the controller 100 determines whether or not the base is shifted. If there is a base deviation, the process proceeds to step S47, and if not, the process proceeds to step S46.

  In step S46, the controller 100 performs active calibration. The active calibration will be described later.

  In step S47, the controller 100 determines that the fuel is in an over-evaporated state, and adjusts the opening of the purge valve to be reduced.

  FIG. 14 is a flowchart for explaining the contents of a routine for determining whether or not the air-fuel ratio feedback correction coefficient α is hunting.

  In step S411, the controller 100 increments the α fluctuation timer.

  In step S412, the controller 100 determines whether or not the α variation timer has exceeded a specified time. Until it exceeds, the process proceeds to step S413, and when it exceeds, the process proceeds to step S420.

  In step S413, the controller 100 determines whether or not the previous value αz of the air-fuel ratio feedback correction coefficient α is equal to or less than the fluctuation range upper limit value MAX and the current air-fuel ratio feedback correction coefficient α is greater than the fluctuation range upper limit value MAX. To do. That is, it is determined whether or not the air-fuel ratio feedback correction coefficient α has become larger than the fluctuation range upper limit value MAX for the first time this time. Until this condition is satisfied, the process proceeds to step S414, and when satisfied, the process proceeds to step S415.

  In step S414, the controller 100 determines whether or not the previous value αz of the air-fuel ratio feedback correction coefficient α is greater than or equal to the fluctuation range lower limit value MIN and the current air-fuel ratio feedback correction coefficient α is smaller than the fluctuation range lower limit value MIN. To do. That is, it is determined whether or not the air-fuel ratio feedback correction coefficient α is smaller than the fluctuation range lower limit value MIN for the first time this time. Until this condition is satisfied, the process is temporarily exited. When the condition is satisfied, the process proceeds to step S415.

  In step S415, the controller 100 determines whether or not the α fluctuation counter is zero. If zero, the process proceeds to step S416; otherwise, the process proceeds to step S417.

  In step S416, the controller 100 resets the α variation timer.

  In step S417, the controller 100 increments the α fluctuation counter.

  In step S418, the controller 100 determines whether or not the α fluctuation counter exceeds a specified value. If so, the process proceeds to step S419, and if not, the process is temporarily exited.

  In step S419, the controller 100 determines hunting. In addition, the α variation timer is reset and the α variation counter is reset after one job.

  In step S420, the controller 100 resets the α fluctuation counter.

  FIG. 15 is a flowchart for explaining the contents of the base deviation routine.

  In step S441, the controller 100 increments the base check timer.

  In step S442, the controller 100 determines whether or not the base check timer has exceeded a specified time. The process proceeds to step S443 until it exceeds, and if it exceeds, the process proceeds to step S448.

  In step S443, the controller 100 determines whether or not the air-fuel ratio feedback correction coefficient α is in the base deviation-free region. If it is in the region without base deviation, the process proceeds to step S444; otherwise, the process proceeds to step S445.

  In step S444, the controller 100 resets the base deviation timer.

  In step S445, the controller 100 increments the base deviation timer.

  In step S446, the controller 100 determines whether or not the base deviation timer has exceeded a specified time. The process is temporarily exited until it exceeds, and when it exceeds, the process proceeds to step S447.

  In step S447, the controller 100 determines base deviation. Also resets the base check timer and base deviation timer.

  In step S448, the controller 100 determines that there is no base deviation and resets the base check timer.

  FIG. 16 is an explanatory diagram of passive calibration and active calibration.

  As shown in FIG. 16A-1, the passive calibration detects the value of the air-fuel ratio feedback correction coefficient α when the purge rate is increased by 10%, for example. If there is no base deviation and the base is 100%, the detection value is 90%, for example, as shown by the solid line in FIG. However, if there is a base shift and the base is 90%, for example, the detection value is 80% as shown by the broken line in FIG. In this way, the presence or absence of base deviation can be determined from the detected value. Moreover, since it can be determined by the detected value of the air-fuel ratio feedback correction coefficient α, it can be detected quickly. However, when there is a base shift, the variation of the air-fuel ratio feedback correction coefficient α is not accurate. Therefore, there is a possibility that hunting cannot be accurately determined in step S41.

  On the other hand, as shown in FIG. 16 (b-1), the active calibration detects the amount of change in the air-fuel ratio feedback correction coefficient α when the purge rate is increased by, for example, 10% and then returned to 0%. In this case, the variation of the air-fuel ratio feedback correction coefficient α is the same regardless of the presence or absence of base deviation (that is, ΔA = ΔB in FIG. 16B-2), and hunting can be accurately determined.

  Next, the operation of the fuel vapor processing apparatus according to the present invention will be described with reference to the time chart shown in FIG. FIG. 17 is a time chart showing the operation of the fuel vapor processing apparatus before the concentration estimation is completed. In addition, step numbers are written together with S to make it easy to understand the correspondence with the flowchart.

  While purging is in progress (FIG. 17B; Yes in step S1) and the purge concentration estimation is not completed (No in step S2), the fuel over-evaporation state determination before completion of concentration estimation is performed ( Step S3). From time t10 to time t11 in FIG. 17, the α fluctuation timer is incremented (FIG. 17D; step S31).

  At time t11, the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit value MIN (FIG. 17A; Yes in step S33), and the α fluctuation counter is 0 (FIG. 17C); in step S34. Yes), the α variation timer is reset (FIG. 17D; step S35), and the α variation counter is incremented to 1 (FIG. 17C; step S36).

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit MIN at time t12 (FIG. 17A; Yes in step S33), the α fluctuation counter is incremented to 2 (FIG. 17C); step S36 ).

  When the α variation timer exceeds the specified time at time t13 (FIG. 17D; Yes in step S32), the α variation counter and the α variation timer are reset (FIGS. 17C and 17D; step S36).

  At time t14, the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit value MIN (FIG. 17A; Yes at step S33), and the α fluctuation counter is 0 (FIG. 17C); at step S34. Yes), the α variation timer is reset (FIG. 17D; step S35), and the α variation counter is incremented to 1 (FIG. 17C; step S36).

  When the purge is stopped at time t15 (FIG. 17B; No at step S1), until the purge is started at time t17 (FIG. 17B; Yes at step S1), the air-fuel ratio feedback correction coefficient α is obtained at time t16. Even if becomes smaller than the fluctuation range lower limit value MIN (FIG. 17A), the α fluctuation counter and the α fluctuation timer hold the current values (FIGS. 17C and 17D).

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit MIN at time t18 (FIG. 17A; Yes in step S33), the α fluctuation counter is incremented to 2 (FIG. 17C); step S36 ).

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit MIN at time t19 (FIG. 17A; Yes in step S33), the α fluctuation counter is incremented to 3 (FIG. 17C); step S36 ), Because the α fluctuation counter exceeds the specified value (FIG. 17C; Yes in step S37), it is determined that the fuel is in a fuel over-evaporation state, and the flag is set (FIG. 17E; step S38).

  FIG. 18 is a time chart showing the operation of the fuel vapor processing apparatus after the concentration estimation is completed and in active calibration.

  After purging is being executed (FIG. 18B; Yes in step S1) and the purge concentration estimation is completed (Yes in step S2), the fuel over-evaporation state determination after completion of concentration estimation is performed (step S4). ). From time t200 to t201 in FIG. 18, the α variation timer is incremented (FIG. 18D; step S411).

  At time t201, the air-fuel ratio feedback correction coefficient α becomes larger than the fluctuation range upper limit MAX (FIG. 18A; Yes in step S413), and the α fluctuation counter is 0 (FIG. 18C); in step S415. (Yes), the α fluctuation timer is reset (FIG. 18D; step S416), and the α fluctuation counter is incremented to 1 (FIG. 18C; step S417).

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit MIN at time t202 (FIG. 18A; Yes in step S414), the α fluctuation counter is incremented to 2 (FIG. 18C); step S417. ).

  When the air-fuel ratio feedback correction coefficient α becomes larger than the fluctuation range upper limit MAX at time t203 (FIG. 18A; Yes in step S413), the α fluctuation counter is incremented to 3 (FIG. 18C); step S417. ).

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit MIN at time t204 (FIG. 18A; Yes in step S414), the α fluctuation counter is incremented to 4 (FIG. 18C); step S417. ).

  When the α variation timer exceeds the specified time at time t205 (FIG. 18D; Yes in step S412), the α variation counter and the α variation timer are reset (FIGS. 18C and 18D; step S420).

  At time t206, the air-fuel ratio feedback correction coefficient α becomes larger than the fluctuation range upper limit value MAX (FIG. 18A; Yes in step S413), and the α fluctuation counter is 0 (FIG. 18C); in step S415. (Yes), the α fluctuation timer is reset (FIG. 18D; step S416), and the α fluctuation counter is incremented to 1 (FIG. 18C; step S417).

  When the purge is stopped at time t209 (FIG. 18B; No in step S1), until the purge is started at time t212 (FIG. 18B; Yes in step S1), the air-fuel ratio feedback correction coefficient α varies. Even if the value becomes smaller than the lower limit value MIN (time t210) or the air-fuel ratio feedback correction coefficient α becomes larger than the fluctuation range upper limit value MAX (time t211; FIG. 18A), the α fluctuation counter and the α fluctuation timer The current value is held (FIGS. 18C and 18D).

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit value MIN at time t213 (FIG. 18A; Yes in step S414), the α fluctuation counter is incremented to 4 (FIG. 18C); step S417. ).

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit MIN at time t215 (FIG. 18A; Yes in step S414), the α fluctuation counter is incremented to 6 (FIG. 18C); step S417. ), Since the α fluctuation counter exceeds the specified value (FIG. 18C; Yes in step S418), the hunting of the air-fuel ratio feedback coefficient α is determined and the flag is set (FIG. 17F; step S419).

  In FIG. 18, active calibration is being performed (FIG. 18E). Thereafter, it is determined that the fuel is in a fuel over-evaporation state, and a flag is set (FIG. 18F; step S47).

  FIG. 19 is a time chart showing the operation of the fuel vapor processing apparatus after the completion of concentration estimation and when there is no base deviation in passive calibration.

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit MIN at time t314 (FIG. 19A; Yes in step S414), the α fluctuation counter is incremented to 5 (FIG. 19C); step S417. ).

  When the air-fuel ratio feedback correction coefficient α becomes larger than the fluctuation range upper limit MAX at time t315 (FIG. 19A; Yes in step S413), the α fluctuation counter is incremented to 6 (FIG. 19C); step S417. ), Because the α fluctuation counter exceeds the specified value (FIG. 19C; Yes in step S418), hunting of the air-fuel ratio feedback coefficient α is determined and a flag is set (FIG. 19G; step S419).

  At time t316, the base check timer starts to be incremented (FIG. 19 (H); step S441), and the air-fuel ratio feedback correction coefficient α remains within the base deviation-free region (Yes at step S443), and at the specified time at time t317. Is passed (FIG. 19 (H); Yes in step S442), it is determined that there is no base deviation (step S448). The flag is set (FIG. 19F; step S47).

  FIG. 20 is a time chart showing the operation of the evaporated fuel processing apparatus after the completion of concentration estimation and when there is a base deviation in passive calibration.

  When the air-fuel ratio feedback correction coefficient α becomes smaller than the fluctuation range lower limit MIN at time t414 (FIG. 20 (A); Yes in step S414), the α fluctuation counter is incremented to 5 (FIG. 20 (C); step S417). ).

  When the air-fuel ratio feedback correction coefficient α becomes larger than the fluctuation range upper limit MAX at time t415 (FIG. 20A; Yes in step S413), the α fluctuation counter is incremented to 6 (FIG. 20C); step S417. ), Since the α fluctuation counter has exceeded the specified value (FIG. 20C; Yes in step S418), the hunting of the air-fuel ratio feedback coefficient α is determined and the flag is set (FIG. 20G; step S419).

  At time t416, the base check timer starts to be incremented (FIG. 20 (H); step S441). When the air-fuel ratio feedback correction coefficient α deviates from the base deviation-free region at time t417 (FIG. 20 (A); No at step S443). ), The base deviation timer is incremented (FIG. 20I; Step S445).

  When the air-fuel ratio feedback correction coefficient α returns to the region without base deviation at time t418 (FIG. 20A; Yes at step S443), the base deviation timer is reset (FIG. 20I; step S444), and at time t419. When the air-fuel ratio feedback correction coefficient α is out of the base deviation-free region (FIG. 20A; No in step S443), the base deviation timer is incremented (FIG. 20I; step S445).

  When the air-fuel ratio feedback correction coefficient α exceeds the specified time while leaving the base deviation-free region at time t420 (FIG. 20A; Yes in step S446), it is determined that there is a base deviation (step S447). If the base deviation is determined, active calibration is performed (step S46). If hunting is still determined (Yes in step S42), it is determined that the fuel is excessively evaporated and a flag is set (step S47).

  According to this embodiment, the target purge rate is set so as not to deteriorate the exhaust emission, and the amount of fuel desorbed from the canister is estimated by the canister model when the purge valve is controlled to open based on the target purge rate. However, when it is judged that exhaust emissions have deteriorated even though fuel is supplied to the engine by reducing the substantial amount of fuel desorption estimated by the canister model, the evaporated fuel generated in the fuel tank Since it is determined that the amount is excessive, it is possible to accurately detect the excessive evaporation state of the fuel. Further, the deterioration of exhaust emission is determined based on the fluctuation cycle of the air-fuel ratio feedback correction coefficient. Also, while purge control is stopped, the fluctuation count of the air-fuel ratio feedback correction coefficient before the purge control is stopped and the elapsed time from the start of the count are held. When the purge control is restarted, the count is restarted from the held count and the elapsed time. Thus, the fuel over-evaporation state can be determined even during traveling, and the present invention can be applied to an idle stop vehicle.

  The fluctuation period of the air-fuel ratio feedback correction coefficient is detected quickly by the passive calibration method. Further, when the passive calibration method cannot be detected well, a base deviation check is performed, and if there is a base deviation, the active calibration method is changed, so accurate detection is possible in any case.

  When it is determined that the amount of evaporated fuel generated in the fuel tank is excessive, the opening of the purge valve is reduced, so that a rich air-fuel ratio in the cylinder can be prevented.

  Before the purge concentration estimation is completed, the number of times that the air-fuel ratio feedback correction coefficient falls below the allowable fluctuation range is counted, and it is determined whether or not the specified count is reached within a predetermined time. The number of times the fuel ratio feedback correction coefficient exceeds and falls below the allowable fluctuation range is counted, and the determination is made based on whether or not the specified count number has been reached within a predetermined time. If the specified count is not reached within a predetermined time, the determination is performed again, so that erroneous determination can be prevented.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

It is a whole block diagram of an engine provided with the evaporative fuel processing apparatus by this invention. It is a flowchart explaining the content of the target purge rate setting routine. It is a flowchart explaining the content of the target purge rate setting routine which is not based on the adsorption state of a canister. It is a figure which shows the characteristic table for calculating | requiring the purge rate change amount according to the difference of an air fuel ratio feedback deviation. It is a flowchart explaining the content of the target purge rate setting routine based on the adsorption state of a canister. It is a flowchart explaining the content of the purge change amount limit value setting routine. It is a figure which shows the characteristic table for estimating the error of a purge air fuel ratio. It is a flowchart explaining the content of the maximum purge rate setting routine. It is a flowchart explaining the content of the desorption amount calculation routine by a canister model. It is a control block diagram which shows a canister model. It is a main flowchart explaining operation | movement of the evaporative fuel processing apparatus by this invention. It is a flowchart explaining the content of the fuel over-evaporation state determination routine before completion of concentration estimation. It is a flowchart explaining the content of the fuel over-evaporation state determination routine after completion of concentration estimation. It is a flowchart explaining the contents of a routine for determining whether or not the air-fuel ratio feedback correction coefficient α is hunting. It is a flowchart explaining the content of a base deviation routine. It is explanatory drawing about a passive calibration and an active calibration. It is a time chart which shows operation | movement of the evaporative fuel processing apparatus before completion of density | concentration estimation. It is a time chart which shows operation | movement of the evaporative fuel processing apparatus in active calibration after completion of density | concentration estimation. It is a time chart which shows operation | movement of the evaporative fuel processing apparatus after the completion of density | concentration estimation, and when there is no base deviation of passive calibration. It is a time chart which shows operation | movement of the evaporative fuel processing apparatus when there exists a base shift | offset | difference of passive calibration after completion | finish of density | concentration estimation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Evaporative fuel processing apparatus 10 Canister 14 Purge valve 20 Fuel tank 22 Piping 30 Engine 31 Intake passage 34 Fuel injection valve (fuel injection amount adjustment means)
100 controller step S10 target purge rate setting means step S100 canister model steps S37, S418 emission deterioration judging means steps S38, S47 fuel over-evaporation judging means

Claims (9)

A canister that adsorbs the evaporated fuel generated in the fuel tank;
A purge valve that opens and closes a pipe that communicates the canister and the intake passage of the engine;
An evaporative fuel processing apparatus comprising:
Target purge rate setting means for setting the target purge rate so as not to deteriorate the exhaust emission,
A canister model for estimating a fuel desorption amount desorbed from the canister when the purge valve is controlled to open based on the target purge rate;
A fuel injection amount adjusting means for reducing and correcting a substantial amount of the fuel desorption amount estimated by the canister model with respect to the fuel supplied to the engine;
An emission deterioration determining means for determining whether or not the exhaust emission has deteriorated;
A fuel over-evaporation determining unit that determines that the amount of evaporated fuel generated in the fuel tank is excessive when the emission deterioration determining unit determines that the exhaust emission deteriorates;
The evaporative fuel processing apparatus characterized by having. The emission deterioration determining means determines whether or not the exhaust emission has deteriorated based on the fluctuation period of the air-fuel ratio feedback correction coefficient.
The evaporative fuel processing apparatus according to claim 1. The emission deterioration determining means counts the number of times the air-fuel ratio feedback correction coefficient falls below the allowable fluctuation range before the purge concentration estimation is completed, and determines exhaust gas deterioration when the specified count number is reached within a predetermined time. ,
The evaporative fuel processing apparatus of Claim 1 or Claim 2 characterized by the above-mentioned. After the purge concentration estimation is completed, the emission deterioration determining means counts the number of times that the air-fuel ratio feedback correction coefficient exceeds and falls below the allowable fluctuation range, and when the specified number of counts is reached within a predetermined time, the exhaust emission deterioration Determine
The evaporative fuel processing apparatus of Claim 1 or Claim 2 characterized by the above-mentioned. While the purge control is stopped, the emission deterioration determining means holds the fluctuation count of the air-fuel ratio feedback correction coefficient before the purge control is stopped and the elapsed time from the start of the count. Resume from counting and elapsed time,
The evaporative fuel processing apparatus of Claim 3 or Claim 4 characterized by the above-mentioned. The emission deterioration judging means detects the fluctuation of the air-fuel ratio feedback correction coefficient by a passive calibration method, and when the specified count number is reached within a predetermined time, there is no base deviation in the fluctuation of the air-fuel ratio feedback correction coefficient. Whether or not
The evaporative fuel processing apparatus according to claim 3, wherein the evaporative fuel processing apparatus is configured as described above. The emission deterioration determining means determines the deterioration of exhaust emission when determining that there is no base deviation.
The evaporative fuel processing apparatus according to claim 6. When it is determined that there is a base deviation, the emission deterioration determining means detects a change in the air-fuel ratio feedback correction coefficient by an active calibration method, and when the specified count number is reached within a predetermined time, the exhaust emission is determined. To judge the deterioration of
The evaporative fuel processing apparatus according to claim 6. When the fuel over-evaporation determining means determines that the amount of evaporated fuel being generated in the fuel tank is excessive, the opening of the purge valve is reduced,
The evaporative fuel processing apparatus according to any one of claims 1 to 8, wherein the evaporative fuel processing apparatus is characterized in that:

Images