JP2013113143A - Evaporated fuel treating device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaporated fuel treating device of an internal combustion engine which can suppress fluctuation in an air-fuel ratio without unnecessarily limiting a purge amount when purge is restarted, and can increase a purge execution frequency.SOLUTION: A purge control mechanism decreases an intake quantity of purge gas in accordance with an execution time of purge operation. and on condition that a stop time of purge operation does not reach a critical time, the purge control mechanism increases a set value of the intake quantity in the purge operation after a stop in accordance with the stop time (steps S25, S26). On condition that the stop time reaches the critical time, the purge control mechanism suppresses an increase in the set value of the intake quantity in the purge operation after the stop in accordance with the stop time (steps S28, S29). On condition that an air-fuel ratio is settled within a fixed range with respect to a reference value when the purge operation is restarted after the stop, the purge control mechanism enlarges a decrease degree of the intake quantity corresponding to the execution time of the purge operation than normal (steps S22, S23).

Description

  The present invention relates to an evaporated fuel processing apparatus for an internal combustion engine, and more particularly to an evaporated fuel processing apparatus for an internal combustion engine that is controlled so as to suppress fluctuations in an air-fuel ratio due to fuel purge.

  When highly volatile fuel is used in an internal combustion engine (hereinafter also referred to as an engine) for driving a vehicle, the evaporated fuel generated in the fuel tank or the like is adsorbed to a canister using activated carbon, and the canister is operated during engine operation. An evaporative fuel processing device that performs a purging operation for desorbing the fuel from the fuel and sucking it into the intake passage is provided. Further, in an internal combustion engine equipped with such an evaporative fuel processing device, an air-fuel ratio feedback control is performed in which the exhaust air-fuel ratio is monitored by an air-fuel ratio sensor and the air-fuel ratio follows the target air-fuel ratio based on the monitored air-fuel ratio. There are many. However, recent vehicles require idling stop (engine stop control during idling), fuel cut, etc., so-called eco-run control to improve fuel efficiency, so the purge operation stop period in the evaporative fuel processing device is required. The fuel vapor concentration tends to increase when the purge is resumed. Therefore, purge control is required to appropriately control the ratio of the purge flow rate to the intake air amount (hereinafter referred to as the purge rate) so that the air-fuel ratio does not fluctuate greatly when the purge is resumed.

  As a conventional evaporative fuel processing apparatus for an internal combustion engine that performs purge control, for example, when the fuel adsorption amount to the canister increases during the fuel purge stop period and the fuel concentration in the purge gas rises to a predetermined concentration, the purge is performed. There is known one that performs low duty control for reducing the purge rate at the time of restart (for example, see Patent Document 1).

  In addition, an integration counter is provided that performs an integration operation when a condition in which evaporative vapor is likely to occur in the fuel tank. If the condition in which fuel vapor is likely to occur is established during the fuel purge stop period, the integration counter is provided. On the other hand, during the fuel purge execution period, the integrated value of the integrated counter is counted down at a predetermined period, and as the integrated counter value increases, the fuel injection amount from the injector is decreased. What was made is known (for example, refer patent document 2).

  Further, the purged control valve calculates the purged fuel amount from the air-fuel ratio feedback correction coefficient during the predetermined period after the engine is started as a predetermined purge flow rate, and according to the fuel adsorption amount of the canister estimated based on this fuel amount. (For example, see Patent Document 3), when the idle stop time exceeds a predetermined time, the purge learning value is reset (for example, see Patent Document 4), or low duty ratio control. When the air-fuel ratio feedback amount is within a predetermined range at the time of returning from the above, there are known ones that return the reduced purge rate at a constant rate (see, for example, Patent Document 5).

JP-A-10-54308 JP 2005-248913 A JP 2010-024991 A JP 2006-002574 A JP 2007-192145 A

  However, in the conventional evaporative fuel processing apparatus for an internal combustion engine as described above, the idling stop time becomes long or the downhill road continues in a high temperature environment such as summer or at high altitudes, and thus fuel cut control continues for a long time. Then, since the purge stop time during which the adsorbed fuel cannot be removed from the canister continues, an appropriate purge amount (purge rate) may not be set when the purge is resumed. For this reason, since it is necessary to secure an appropriate purge rate, it may be necessary to temporarily limit idling stop, fuel cut, and the like.

  For example, in a conventional evaporative fuel processing apparatus provided with a counter that performs an accumulation operation during a purge stop period or a counter that performs an accumulation operation when a condition in which evaporative vapor is likely to occur in a fuel tank is satisfied, Environmental changes can be made to return the fuel vapor to liquid fuel. Therefore, if the purge control is executed based only on the accumulated time of the counter, the purge amount may be limited until it is not necessary to actually limit the purge amount, and the fuel consumption reduction effect by the eco-run control is impaired. It was.

  Even in other conventional evaporative fuel processing apparatuses, it is necessary to suppress the purge rate for a certain period from the time when the purge is resumed.

  In view of this, the present invention is capable of suppressing the fluctuation of the air-fuel ratio without unnecessarily limiting the purge amount when the purge is resumed even when the purge stop time becomes long, and sufficiently performing the fuel purge operation from the canister. It is an object of the present invention to provide an evaporative fuel processing device for an internal combustion engine that can be improved to a higher level and enables more fuel-efficient travel control.

  In order to solve the above problems, an evaporative fuel treatment apparatus for an internal combustion engine according to the present invention includes: (1) an adsorber that adsorbs evaporative fuel generated in a fuel supply mechanism of the internal combustion engine; and the adsorber that passes air through the adsorber. A purge mechanism for performing a purge operation for sucking the purge gas containing the fuel and air separated from the air into the intake pipe of the internal combustion engine, and controlling the intake amount of the purge gas into the intake pipe to control the air-fuel ratio of the internal combustion engine. And a purge control mechanism that suppresses fluctuations, wherein the purge control mechanism reduces the intake amount of the purge gas in accordance with the execution time of the purge operation, while The suction of the purge gas in the purge operation after the stop on condition that the stop time for stopping the purge operation does not reach a preset limit time The set value of the purge gas is increased according to the stop time, and on the condition that the stop time has reached the limit time, the set value of the intake amount of the purge gas in the purge operation after the stop is set to the stop time. In accordance with the execution time of the purge operation on the condition that the air-fuel ratio falls within a certain range with respect to a preset reference value when the purge operation is resumed after the stop. The degree of decrease in the set value of the inhalation amount is made larger than usual.

  With this configuration, the purge gas flow rate is controlled based on the stop time and execution time of the purge operation, but the air-fuel ratio of the internal combustion engine is within a certain error range with respect to the reference value when restarting after the purge operation is stopped. Then, the degree of decrease in the set value of the purge gas suction amount corresponding to the execution time of the purge operation is set to be larger than usual. Therefore, even if the purge stop time until the purge operation is restarted becomes longer, the purge operation is not limited unless the air-fuel ratio is actually increased by the purge gas at the time of restarting the purge operation. The air-fuel ratio fluctuation due to the purge operation can be suppressed without being limited to necessity, and the frequency of execution of the fuel purge operation from the canister can be sufficiently increased. As a result, an evaporative fuel processing apparatus for an internal combustion engine that enables travel control with lower fuel consumption becomes possible.

  In the fuel vapor processing apparatus for an internal combustion engine of the present invention having the above-described configuration, (2) the purge control mechanism feedback controls the air-fuel ratio of the internal combustion engine so that the feedback value from the air-fuel ratio sensor matches the target value. The feedback value is acquired from the air-fuel ratio feedback control device, and the air-fuel ratio is within the fixed range with respect to the reference value on the condition that the magnitude of the feedback value is within a predetermined value corresponding to the fixed range. It is preferable to determine that it enters.

  In this way, when the purge is restarted, the change in the air-fuel ratio due to the restart of the purge can be accurately grasped from the change in the air-fuel ratio feedback value of the existing air-fuel ratio feedback control means, and the fluctuation of the air-fuel ratio is ensured while increasing the purge execution frequency. It becomes a low-cost evaporative fuel processing apparatus that can be suppressed. Moreover, it is no longer possible to give priority to a purge operation that is not necessary due to a misjudgment that the purge gas concentration is higher than the actual concentration, and the learning process for each operation region for air-fuel ratio feedback control at the time of purge resumption is delayed. This is also prevented.

  In the fuel vapor processing apparatus for an internal combustion engine according to the present invention, (3) the purge control mechanism includes a counting operation including an integration operation according to the stop time of the purge operation and a subtraction operation according to the execution time of the purge operation. The intake amount of the purge gas is controlled according to the stop time of the purge operation on the condition that the intake value of the purge gas is controlled based on the count value of While the purge suppression process is executed, the air-fuel ratio falls within the predetermined range with respect to the reference value when the purge suppression process is not executed and the purge operation is resumed after the stop. On the condition of the above, it is preferable to make the subtraction amount by the subtraction operation with respect to the count value larger than usual.

  In this case, whether or not purge suppression is necessary is determined only when necessary, and it is possible to suppress a wasteful transition from the normal purge state to the purge suppression state.

  In the case of having the configuration of (3) above, (4) the purge control mechanism is configured on the condition that the air-fuel ratio falls within the certain range with respect to the reference value when restarting the purge operation after the stop. It is preferable that the count value at the time of restart is reduced to a relatively small value to set a new count value, and the count operation is restarted using the new count value.

  In this way, when the purge suppression is substantially unnecessary, the count value can be decreased to ensure the frequency of execution of the purge operation.

  In the case of having the configuration of (4) above, (5) the purge control mechanism includes a counter that executes the counting process, and the air-fuel ratio is less than the reference value when the purge operation is restarted after the stop. More preferably, the count value of the counter is reset and the new count value is set on condition that the value falls within the certain range.

  In this case, the process is simple, and a sufficient purge execution frequency can be secured.

  In the case of having the configuration of (4) or (5), (6) the purge control mechanism is in a state where the air-fuel ratio is within the certain range with respect to the reference value when the purge operation is resumed after the stop. It is preferable to reduce the count value to a relatively small value on the condition that is continued for a preset waiting time.

  Thereby, the purge control can be performed without being affected by the fluctuation of the air-fuel ratio when the purge is resumed.

  In the fuel vapor processing apparatus for an internal combustion engine of the present invention, (7) the purge control mechanism is provided in the temperature of intake air or outside air of the internal combustion engine or the fuel supply mechanism when the purge operation is resumed after the stop. The ratio of the intake amount of the purge gas to the intake air amount of the internal combustion engine is variably controlled in accordance with the temperature of the fuel in the fuel tank, and the higher the intake air or outside air temperature or the fuel temperature It is preferable to limit the intake amount of the purge gas.

  With this configuration, when the intake air temperature, the outside air temperature, or the fuel temperature in the fuel tank is low, the flow rate of the purge gas that is not necessary is not limited. In this case, the purge control mechanism is configured such that the intake amount of the purge gas with respect to the intake air amount of the internal combustion engine according to the count value and the temperature of the intake air or outside air or the temperature of the fuel in the fuel tank. It is more preferable to variably control the ratio.

  According to the present invention, even if the purge stop time becomes longer, fluctuations in the air-fuel ratio can be suppressed without unnecessarily limiting the purge amount when restarting the purge. Therefore, the frequency of performing the fuel purge operation from the canister can be sufficiently increased. Therefore, it is possible to provide an evaporative fuel processing device for an internal combustion engine that enables travel control with lower fuel consumption.

1 is a schematic configuration diagram of an evaporated fuel processing apparatus for an internal combustion engine according to an embodiment of the present invention. FIG. 2A is a graph showing a change in the purge concentration learning value according to the purge time in the evaporated fuel processing apparatus for an internal combustion engine according to one embodiment of the present invention and the variation of the change due to the fuel temperature in the tank. The vertical axis represents the amount of change in the purge concentration learning value, and the horizontal axis represents the purge cut time. FIG. 2B is an explanatory diagram showing the difference in the degree of restriction of the purge resumption required purge amount according to the intake air temperature, where the vertical axis shows the intake air temperature and the horizontal axis shows the purge cut time. It is a flowchart which shows the general | schematic procedure of the purge rate control performed in the evaporated fuel processing apparatus of the internal combustion engine which concerns on one Embodiment of this invention. It is a flowchart which shows the general | schematic procedure of the purge rate restriction | limiting process performed in the evaporated fuel processing apparatus of the internal combustion engine which concerns on one Embodiment of this invention. FIG. 6 is a timing chart showing changes in control variables related to purge control when a vehicle is tested in a traveling pattern of an example in which traveling and stopping are repeated in a vehicle equipped with an evaporated fuel processing apparatus for an internal combustion engine according to an embodiment of the present invention. is there. It is a schematic block diagram of the evaporative fuel processing apparatus of the internal combustion engine which concerns on other embodiment of this invention. FIG. 7 is an explanatory diagram showing a difference in the degree of restriction of the purge resumption required purge amount according to the fuel temperature in the tank in the evaporated fuel processing apparatus for an internal combustion engine according to another embodiment of the present invention, where the vertical axis indicates the fuel temperature in the tank, and the horizontal The axis indicates the purge cut time.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(One embodiment)
1 to 5 show a schematic flow of a configuration and control of an evaporative fuel processing apparatus for an internal combustion engine according to an embodiment of the present invention. The present invention is an internal combustion engine using a volatile fuel and its control system. This is applied to a vehicle equipped with a fuel tank or the like.

  First, the configuration of the present embodiment will be described.

  As shown in FIG. 1, the vehicle 1 according to the present embodiment includes an engine 10 and a fuel tank 25 that stores fuel consumed by the engine 10, for example, gasoline, on the lower side of the vehicle body. Yes.

  The engine 10 is a spark ignition type multi-cylinder internal combustion engine, for example, a 4-cycle in-line 4-cylinder engine. The engine 10 has four cylinders 11c (only one is schematically shown in FIG. 1). Each cylinder 11c is formed with a combustion chamber 13 partitioned by a piston 12, and an intake valve. 16 and the exhaust valve 17 are provided so as to be opened and closed by a valve mechanism (not shown), and an ignition plug 18 is disposed so as to be exposed in the combustion chamber 13. The piston 12 in each cylinder 11c is connected to a corresponding crank-through portion of the crankshaft 15 via a connecting rod 14.

  An injector 21 (fuel injection valve) is attached to an intake port portion (not shown in detail) corresponding to each cylinder 11c of the engine 10, and each of the plurality of injectors 21 corresponding to the plurality of cylinders 11c is a delivery pipe 22. It is connected to the. The delivery pipe 22 is supplied with highly volatile fuel, for example gasoline, discharged from a fuel pump 23 in a fuel tank 25 mounted on the lower part on the rear side of the vehicle body via a pressure regulator 24. It has become. The fuel pump 23 and the pressure regulator 24 constitute a fuel supply mechanism together with the fuel tank 25.

  The intake pipe 26 of the engine 10 is provided with a surge tank 26a having a predetermined volume for suppressing intake pulsation and intake interference, and the intake air amount and intake air temperature are set in the vicinity of an air cleaner (not shown) on the upstream side. An air flow meter 27 and an intake air temperature sensor 28 to be detected, and a throttle valve 29 located between the air flow meter 27 and the surge tank 26a are mounted.

  Further, the exhaust pipe 31 of the engine 10 detects the exhaust air-fuel ratio in an exhaust purification catalyst device 32 made of a three-way catalyst and in the vicinity of the catalyst device 32, for example, in an exhaust passage upstream of the catalyst device 32. A limit current type A / F sensor 33 is attached. The A / F sensor 33 may be one that detects the exhaust air-fuel ratio downstream from the catalyst device 32, or may be an oxygen sensor that detects the exhaust oxygen concentration. Moreover, the structure which has both the A / F sensor 33 upstream from the catalyst apparatus 32 and the exhaust oxygen sensor downstream from the catalyst apparatus 32 may be sufficient.

  On the other hand, between the fuel tank 25 and the intake pipe 26 of the engine 10, for example, between the fuel tank 25 and the surge tank 26a, the evaporated fuel generated in the fuel tank 25 is discharged into the intake pipe 26 when the engine 10 is inhaled. An evaporative fuel processing device 40 (evaporated fuel processing means) that can be combusted is interposed.

  The evaporative fuel processing apparatus 40 includes a fuel tank 25, a canister 41 (adsorber), a fuel suction side pipe 42, a purge pipe 43, and an air introduction pipe 45, and a purge vacuum solenoid valve (hereinafter referred to as purge). And a purge control mechanism 47 having an ECU 50.

  The canister 41 incorporates an adsorbent (not shown) such as activated carbon, and is connected to the fuel tank 25 by a fuel intake side pipe 42 so as to adsorb evaporated fuel generated in the fuel tank 25. The purge pipe 43 is disposed between the canister 41 and the surge tank 26 a, and the purge VSV 44 is provided in the middle of the purge pipe 43. This purge VSV 44 is duty-controlled with the excitation current in the valve opening drive direction during operation of the engine 10, so that the purge VSV 44 is separated from the canister 41 by the intake negative pressure in the intake pipe 26 at a purge rate corresponding to the duty ratio PRG. The fuel can be sucked into the surge tank 26a as purge gas together with air. The air introduction pipe 45 is a pipe that can introduce the atmospheric pressure in the vicinity of the fuel tank 25 with the cap of the fuel tank 25 into the canister 41. The ECU 50 can control the purge rate by duty-controlling the purge VSV 44 based on various sensor information.

  Thus, the fuel vapor processing apparatus 40 is a fuel supply mechanism from the fuel tank 25 to the engine 10, particularly a canister 41 that adsorbs fuel vapor generated in the fuel tank 25, and the canister 41 is separated from the canister 41 through air. The purge mechanism 46 that performs a purge operation for sucking the purge gas containing fuel and air into the intake pipe 26 of the engine 10 and the intake amount of the purge gas into the intake pipe 26 are controlled to control the fluctuation of the air-fuel ratio in the engine 10. And a purge control mechanism 47 to suppress.

  The evaporative fuel processing device 40 allows the vaporized fuel vapor in the fuel tank 25 to be adsorbed to the canister 41 even when the engine 10 is stopped when the purge VSV 44 is closed. Can do. Further, the evaporated fuel processing device 40 opens the purge VSV 44 during the operation of the engine 10 in a state where the opening degree of the throttle valve 29 is smaller than a preset opening degree, and the engine is placed in the purge pipe 43. Thus, a purge operation can be performed in which the intake negative pressure of 10 is introduced and the fuel adsorbed in the canister 41 is released from the canister 41 and released into the intake air in the intake pipe 26.

  Although the detailed hardware configuration is not illustrated, the ECU 50 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a non-volatile backup memory, and an input / output interface circuit. A constant voltage power supply, a communication IC, and the like are included.

  An input interface circuit of the ECU 50 includes various sensors mounted on the engine 10, such as an air flow meter 27, an intake air temperature sensor 28, and an A / F sensor 33, as well as a crank position sensor 61, a throttle position sensor 62, a vehicle speed sensor. 63, a cam position sensor 64 and a water temperature sensor 65 are connected to each other. Then, sensor information from these sensor groups is taken into the ECU 50.

  The crank position sensor 61 detects the rotation angle Ne of the crankshaft 15, the throttle position sensor 62 detects the opening degree of the throttle valve 29, and the vehicle speed sensor 63 detects the vehicle speed of the vehicle 1. The cam position sensor 64 detects the rotation angle of a camshaft (not shown), and the water temperature sensor 65 detects the temperature thw of the cooling water in the water jacket 11 w of the engine 10.

  The output interface circuit of the ECU 50 includes an injector 21 corresponding to each cylinder 11, an igniter 66 (not shown) that drives the ignition plug 18 of each cylinder 11, a throttle motor 29 a that operates the opening of the throttle valve 29, and a purge A VSV 44 is connected to a relay switch circuit (not shown) that controls the supply of power to the fuel pump 23 and other actuators.

  The ECU 50 performs arithmetic processing based on sensor information fetched from the input interface circuit, set value information stored in advance in a ROM or backup memory (hereinafter referred to as ROM, etc.), map data, and the like, mainly in accordance with a control program stored in the ROM. And the control signal is output from the output interface circuit in accordance with the result, thereby controlling the engine 10 and the auxiliary machinery. Further, the ECU 50 can function as a purge concentration counter or a purge cut time integration counter, which will be described later, by its register function or the like.

  The ECU 50 determines the basic fuel injection time of the injector 21 corresponding to the fuel injection amount that becomes the target air-fuel ratio based on the intake air amount per rotation of the engine 10 obtained from the sensor information of the air flow meter 27 and the crank position sensor 61, for example. In order to execute the fuel injection from the injector 21 when a specific crank angle is reached with an appropriate fuel injection amount, a correction process based on each sensor signal is performed so that the optimal air-fuel ratio is obtained during this basic fuel injection time. In addition, a plurality of control values are calculated. Further, the ECU 50 calculates a plurality of control values for executing appropriate ignition timing, throttle opening control, and the like according to the operating state of the engine 10. Then, the injector 21 is driven from the output interface circuit of the ECU 50 to control the fuel injection signal for controlling the fuel injection amount in the engine 10 to the target injection amount and the ignition timing of the spark plug 18 via the igniter 66. An ignition timing control signal or a relay switching signal for turning on / off actuators such as the fuel pump 23 is output.

  Further, the ECU 50 has an air-fuel ratio control program for executing known air-fuel ratio feedback control based on the detection information of the A / F sensor 33 so that the exhaust gas purification capability of the catalyst device 32 made of a three-way catalyst can be sufficiently extracted. ing. In this air-fuel ratio feedback control, a correction coefficient (hereinafter referred to as the air-fuel ratio) for correcting the fuel injection amount TAU of the injector 21 to increase or decrease so that the exhaust air-fuel ratio detected by the A / F sensor 33 becomes the target exhaust air-fuel ratio. The fuel ratio FB correction coefficient is calculated.

  Further, the ECU 50 establishes the air-fuel ratio FB execution condition that enables learning required for air-fuel ratio feedback control as the purge execution condition, and the water temperature condition suitable for purge execution (for example, 80 ° C. or more). Then, it is determined whether or not the condition that the integrated intake air amount condition is satisfied is satisfied. The purge operation is started on the basis that the purge execution condition is satisfied and learning of the air-fuel ratio FB correction coefficient described later is completed for a plurality of learning regions for each gas flow rate of the engine 10. Yes. For example, when the air-fuel ratio at a constant intake air amount falls within a predetermined value with respect to a reference value (for example, a value having an error of about 5 to 10% with respect to the theoretical air-fuel ratio) during vehicle travel, The learning is almost completed and the learning completion flag is set, and the purge operation is started after that stage. When the cooling water temperature thw is low as before the warm-up of the engine 10 is completed, the fuel increase other than the purge is performed by the water temperature correction, and the purge flow rate control is not executed.

  The learning of the air-fuel ratio FB correction coefficient for a plurality of learning regions for each gas flow rate is intended to suppress an air-fuel ratio shift due to deterioration of the sensors 27 and 28 of the intake system, the injector 21 and the like, and this learning is completed. Otherwise, it is difficult to accurately detect an air-fuel ratio shift caused by only the purge operation. Note that the learning process of the air-fuel ratio FB correction coefficient itself is the same as a known process and will not be described in detail here.

  The air-fuel ratio feedback conditions are, for example, that the engine 10 has been started, the fuel is not being cut, the detected water temperature thw of the water temperature sensor 65 is 70 ° C. or higher, and the fuel injection amount TAU is the minimum fuel injection amount of the injector 21. The above conditions are conditions such that the A / F sensor 33 is in an active state. If all of these conditions are satisfied, the feedback execution condition is satisfied, and if any one of the conditions is not satisfied, the condition is not satisfied.

  When the feedback execution condition is satisfied, the ECU 50 calculates the air-fuel ratio feedback value (correction amount) subjected to the smoothing process (averaging process) or the air-fuel ratio FB correction coefficient corresponding thereto.

  For example, in the case of the air-fuel ratio FB correction coefficient, the reference value is “1”. In this case, the output of the A / F sensor 33 is compared with a predetermined determination level, and the sensor output is inverted from rich to lean. When the sensor output is reversed, the air / fuel ratio flag is set to “0” (lean). When the sensor output is inverted from lean to rich, the air / fuel ratio flag set by the register function of the ECU 50 is set to “1” (rich). Based on the air-fuel ratio flag, the air-fuel ratio FB correction coefficient is manipulated in accordance with the output change of the A / F sensor 33. That is, when the air-fuel ratio flag changes from “0” to “1” or changes from “1” to “0”, the air-fuel ratio FB correction coefficient is increased or decreased in the direction of the change. Let the fixed amount skip. On the other hand, while the air-fuel ratio flag continues to be “1” or “0”, an integration process for gradually increasing or gradually decreasing the air-fuel ratio FB correction coefficient is executed. Further, the upper and lower limit guard processing is performed on the air-fuel ratio FB correction coefficient after such processing, and the air-fuel ratio FB correction coefficient that has been smoothed (averaged) every skip or every predetermined time is calculated. It is like that.

  Thus, the air-fuel ratio FB correction coefficient is calculated by performing the annealing process every predetermined time. In this case, the smoothed air-fuel ratio feedback value corresponds to a deviation from the reference value (= 1) of the smoothed air-fuel ratio FB correction coefficient, and the reference value of the air-fuel ratio feedback value is “0”. It becomes. Hereinafter, the smoothed air-fuel ratio FB correction coefficient or the air-fuel ratio feedback value is simply referred to as an air-fuel ratio feedback value.

  The ECU 50 is also equipped with a low fuel consumption travel control program. According to the low fuel consumption travel control program, the ECU 50 can execute so-called eco-run control for improving fuel efficiency by executing idling stop, fuel cut control when the accelerator is OFF, and the like. It can be done.

  In addition to the control function as described above, the ECU 50 performs a purge rate control that increases the amount of purge gas suction according to the purge operation stop time or decreases the purge operation execution time; When the purge operation is resumed after being stopped for a certain time or longer, the intake amount of the purge gas is decreased in accordance with the purge operation execution time on condition that the air-fuel ratio falls within a certain error range with respect to a preset reference value. The function to increase the degree than usual can be exhibited.

  Specifically, when the purge operation into the surge tank 26a is executed by the evaporated fuel processing device 40, the purge gas is sucked into the combustion chamber 13 from the intake air and the injector 21 together with the injected fuel. Therefore, the air-fuel ratio of the premixed gas sucked into the combustion chamber 13 varies not only with the intake air amount and the fuel injection amount from the injector 21 but also with the flow rate (air amount) of the purge gas and the concentration of fuel in the purge gas. Will do. Therefore, when the purge operation is executed, not only the intake air amount of the engine 10 but also the fuel injection amount injected from the injector 21 is corrected according to the flow rate of the purge gas and the fuel concentration in the purge gas.

  Therefore, the ECU 50 monitors the air-fuel ratio feedback value from the A / F sensor 33 (which may be the corresponding air-fuel ratio FB correction coefficient) every predetermined time, and the concentration of the evaporated fuel in the purge gas by the evaporated fuel processing device 40. Is learned as the purge concentration learning value. The purge concentration learning value here is a value corresponding to a correction coefficient for correcting the deviation of the air-fuel ratio due to the purge operation of the reference correction amount with a purge rate of 1%, for example, the fuel is not adsorbed to the canister 41, and the purge gas The purge concentration learning value is set to “0” when the concentration of the evaporated fuel therein becomes zero (when the air-fuel ratio feedback value becomes “0”).

  The purge concentration learning value is updated every time the air-fuel ratio feedback value is updated or whenever it changes by a predetermined value or more. In addition, when the air-fuel ratio feedback value is a positive value exceeding the reference value range (including a certain range substantially equal to the reference value “0”), the ECU 50 sets a predetermined value (for example, 0. 1%) is added to obtain the current purge concentration learning value. That is, when the air-fuel ratio feedback value becomes a positive value (lean side) value indicating that the air-fuel ratio feedback value is larger than the theoretical air-fuel ratio in order to correct the state of combustion at the actual air-fuel ratio leaner than the target air-fuel ratio, the purge concentration is set. The purge concentration learning value is updated by adding a predetermined value to increase it. On the contrary, when the air-fuel ratio feedback value is a negative value below the reference value range, that is, in order to correct the state of combustion at the actual air-fuel ratio richer than the target air-fuel ratio, the air-fuel ratio feedback value is the stoichiometric air-fuel ratio. When a negative value (rich side) indicating a smaller value is obtained, the ECU 50 subtracts a predetermined value (for example, 0.1%) from the previous purge concentration learning value so as to decrease the purge concentration, The purge concentration learning value is set.

  In this way, the purge concentration learning value is updated so as to gradually change the detected air-fuel ratio in a direction approaching the theoretical air-fuel ratio depending on whether the detected air-fuel ratio is on the rich side or the lean side. This purge concentration learning value corresponds to the amount of fuel adsorbed in the canister 41, and is maintained in the RAM of the ECU 50 while being updated as described above.

  More specifically, the ECU 50 has a purge concentration learning value counter 51 that counts the purge concentration learning value within a range of a predetermined positive and negative count value. The purge concentration learning value counter 51 is a purge concentration learning value counter 51. When the value is updated, the value is counted up when the air-fuel ratio feedback value exceeds the reference value range, and when the purge concentration learning value is updated, the value is counted down when the air-fuel ratio feedback value falls below the reference value range. Based on the purge concentration learned value corresponding to the count value of the purge concentration learned value counter 51, the ECU 50 determines the purge flow rate for each purge operation (for example, the purge rate that is the ratio between the intake amount of purge gas and the intake air amount). ) And the fuel supply amount are calculated. That is, the ECU 50 executes a counting process including an integration operation corresponding to the purge operation stop time and a subtraction operation corresponding to the purge operation execution time, and controls the purge rate based on the count value obtained by the coefficient processing. The intake amount of the purge gas is controlled, and the fuel injection amount of the injector 21 is corrected to decrease by an amount corresponding to the supply amount of the purge gas to each cylinder 11 and the fuel concentration.

  Further, the ECU 50 calculates whether or not to calculate the intake pipe negative pressure (estimated value) at that time based on the throttle opening and the engine rotational speed Ne from the estimation map, and fully opens the purge VSV 44 with respect to the intake pipe negative pressure. Calculate a fully-open purge rate corresponding to the fully-open flow rate [L / min] in the state (opening degree (drive duty ratio) 100%) or a two-dimensional fully-open flow rate map (intake pipe negative pressure stored in advance in a ROM or the like) -Read from the fully open flow map. Further, in order to gradually increase the purge rate for each elapsed time immediately after the start of the purge from a small value, the target purge rate map stored in the ROM or the like is referred to, for example, during the initial concentration learning time immediately after the purge starts ( For example, for a period of about 1 minute, a minimum target purge rate epgrgtt (%) that is several percent or less is set, and the purge rate that gradually increases from the minimum purge rate to over 10% for the next gradual change period After that, the upper limit target purge rate is set. Further, the fuel in the purge gas cannot be accurately controlled like the fuel injection amount TAU from the injector 21, and when the purge rate of the purge gas becomes high, the air-fuel ratio is likely to be disturbed. In order to limit the purge rate so as not to reach the maximum correction amount TAUmin at, a tau correction limit purge rate epgrlm (%) calculated backward from the TAUmin is calculated. Then, based on these three purge rate limit values, the limit value at which the purge flow rate becomes the minimum is set as the final limit value, and the final final purge rate epgrmx is calculated by adding this final limit value limit (upper limit guard). Purge control is performed at the final final purge rate epgrmx.

  In addition, when the purge operation is stopped by idling stop, fuel cut control, or the like, the ECU 50 performs an integration operation that counts up every time when a preset count-up time is reached from the stop point, and from the stop point. Has a purge cut integrating counter 52 that measures the total stop time (hereinafter also referred to as purge cut time).

  Further, when the purge operation is resumed after the purge operation is stopped for a certain time or longer, the ECU 50 determines that the air-fuel ratio feedback value falls within a certain error range (for example, less than several percent) with respect to the reference value (= 0). With this condition, the function of increasing the degree of decrease in the purge gas intake amount according to the execution time of the purge operation, for example, the degree of countdown of the purge concentration learning value counter 51, can be exhibited.

  Specifically, the ECU 50 as the purge control mechanism 47 is operated by the function calculated as a control device that executes air-fuel ratio feedback control of the engine 10 when the purge operation is resumed after the purge operation is stopped for a predetermined time or longer. The fuel-air-fuel ratio is a value on the negative side of the stoichiometric air-fuel ratio and is relatively small (for example, if the fuel-air-fuel ratio feedback value is within a predetermined value) , -5% to 0%). When such a determination result is obtained, the count value of the purge cut integration counter 52 is reset to “0”. Note that the predetermined value here is set such that, for example, even if the purge operation is executed in the idle operation state, the air flow does not rise and the exhaust gas purification performance does not deteriorate.

  Furthermore, the ECU 50 performs the purge operation on the condition that the count value obtained by the counting process including the integration operation according to the stop time of the purge operation and the subtraction operation according to the execution time of the purge operation has reached a preset upper limit value. The low duty control is performed to suppress the increase in the intake amount of the purge gas according to the stop time. For example, when the count value (count value) of the purge cut integration counter 52 reaches a first count value corresponding to a long purge cut time, the low duty control referred to here is a required value of the purge gas suction amount thereafter. This is control (purge suppression control) that limits the drive duty of the purge VSV 44 by limiting an increase in the amount (hereinafter referred to as a required purge amount). Further, this low duty control is such that the count value of the purge cut integration counter 52 is longer than the first count value and is long enough to impair the proportional relationship between the purge cut time and the fuel concentration in the purge gas (for example, about 500 seconds). When the upper limit count value corresponding to the purge cut time (depending on the shape and size of the tank) is reached, for example, the count value of the purge concentration learning value counter 51 (purge concentration learning value) is set to zero adsorption amount of the canister 41 This is control for resetting to a corresponding count value (for example, “0”) or a preset lower limit value (minimum value of purge rate).

  The ECU 50 further determines that the purge suppression process has not been executed, and that the air-fuel ratio feedback value is within a certain range with respect to its reference value (= 0) when the purge operation is resumed after stopping for a certain period of time (for example, On the condition that it falls within the range of −5% to 0%), the subtraction amount by the subtraction operation at the time of the purge operation with respect to the count value of the purge cut integration counter 52 is made larger than usual.

  More specifically, the ECU 50 determines, for example, a purge cut integration counter at the time of restart, on condition that the air-fuel ratio feedback value falls within a certain range with respect to the reference value when restarting after stopping the purge operation for a predetermined time or longer. The count value of 52 is reduced to a relatively small value (for example, about a fraction), or a new count is set, or the count value of the purge cut integration counter 52 is reset to “0” and the new count is set. The purge cut time counting operation is restarted using the numerical value.

  Further, the ECU 50 sets the purge cut integration counter on condition that the state in which the air-fuel ratio feedback value is within a certain range with respect to the reference value continues for a preset waiting time when restarting after the purge operation is stopped. The count value of 52 is reduced to a relatively small value.

  In addition, the ECU 50 as the purge control mechanism, when restarting after the purge operation is stopped, according to the temperature of the intake air or the outside air of the engine 10, the ratio of the intake amount of the purge gas to the intake air amount of the engine 10, that is, the purge rate As the temperature of the intake air or outside air of the engine 10 is higher, the purge amount, that is, the intake amount of the purge gas can be limited.

  Specifically, as shown in FIG. 2A, the purge concentration learning value has a tendency to increase toward the minus side as the purge cut time Tpc, which is the stop time of the purge operation, becomes longer. The degree of the change greatly differs depending on the tank internal combustion temperature which is influenced by the outside air temperature and the like. Therefore, as shown in FIG. 2 (b), for example, when the purge operation is resumed in a state where the intake air temperature (which may be the outside air temperature or the fuel temperature in the tank) is high, the immediately preceding purge cut time is relatively short. If there is a purge control that requires a moderate degree of restriction of the purge operation, and the purge purge time that is required is large if the previous purge cut time is relatively long, the intake air temperature is low. When the previous purge cut is restarted, if the previous purge cut time is relatively short, the degree of restriction of the purge operation that is required is small, and if the previous purge cut time is relatively long, the restriction of the purge operation that is required The degree of restriction of the required purge amount is changed according to the air temperature so that the degree becomes medium.

  The outside air temperature in the vicinity of the fuel tank 25 is determined by conducting a preliminary experiment on the relationship between the intake air temperature detected by the intake air temperature sensor 28, the intake air temperature in various driving conditions and vehicle driving conditions, and the outside air temperature in the vicinity of the fuel tank 25. It is possible to estimate by grasping and making it possible to calculate by a map or a calculation formula. Alternatively, the intake air temperature in the intake pipe 26 may be detected at a portion where the temperature is high in the engine room or the portion where heat is likely to be transmitted to the fuel tank 25 side.

  Next, the operation will be described.

  In the present embodiment configured as described above, the purge rate as shown in FIG. 3 is shown in a state where a key switch (ignition switch) (not shown) of the vehicle 1 is turned on by the ECU 50 constituting the purge control mechanism 47. Control and update processing such as purge concentration as shown in FIG. 4 are executed.

  First, the purge rate control shown in FIG. 3 is executed by interruption processing at predetermined time intervals when the key switch is turned on. Here, the purge rate is a ratio of the flow rate (air amount) of the purge gas supplied from the evaporated fuel processing device 40 to the intake air amount of the engine 10.

  In this purge rate control, first, in step S11, it is determined whether or not a water temperature condition (cooling water temperature thw ≧ 80 ° C. or more) and an air-fuel ratio feedback condition are satisfied (step S11). At this time, if both the water temperature condition and the air-fuel ratio feedback condition are satisfied (Yes in step S11), it is next determined whether or not the air-fuel ratio feedback control is being performed (step S12).

  When either of the conditions is not satisfied in the first step S11 (No in Step S11), or when the air-fuel ratio feedback control is not being performed in the next Step S12 (No in Step S12), the purge execution flag is used. Is reset and the purge rate is set to zero (steps S18 and S19), and the current process is terminated.

  When the air-fuel ratio feedback control is being performed in step S12 (in the case of Yes in step S12), after setting the purge execution flag (step S13), the fully opened purge rate epgr100 (%), the target purge rate epgrgt (%) and The tau correction limit purge rate epgrlm (%) is sequentially calculated (steps S14 to S16).

  Then, based on these three purge rate limit values, the final purge rate epgrmx is calculated with the limit value at which the purge flow rate is minimized as the final limit value (step S17).

  The update processing of the purge concentration and the like in FIG. 4 is repeatedly executed under the key switch on state.

  First, it is determined whether or not the purge operation is to be resumed after stopping for a certain period of time (step S21). The first determination step S21 is repeated at a constant cycle until the determination result is Yes.

  When the purge operation is to be resumed after stopping for a certain period of time and the determination result of the first determination step S21 is Yes, then the air-fuel ratio feedback value (annealing value) is within a predetermined value with respect to the reference value For example, it is determined whether or not the error of the detected air-fuel ratio with respect to the stoichiometric air-fuel ratio is within a range of -5% to 0% (step S22).

  At this time, if the air-fuel ratio feedback value is within a predetermined value with respect to the reference value, the count value of the purge cut integration counter 52 is reset to “0” (step S23). This is because even after the purge cut time has been long enough to determine that the purge concentration is indeterminate, it can be detected from the air-fuel ratio feedback value that the fuel concentration in the purge gas is not high. The purge concentration learning value corresponding to the fuel adsorption amount of the canister 41 is returned to “0”, and the count value of the purge cut integration counter 52 is separated from the upper limit count value that is a condition for shifting to the low duty control. This is a process for ensuring sufficient.

  On the other hand, if the air-fuel ratio feedback value is out of the predetermined value with respect to the reference value at this time, it is next determined whether or not the purge operation is being performed (step S24). If the purge operation is being performed (Yes in step S24), the count value of the purge cut integration counter 52 is subtracted according to the purge operation execution time (step S25), and if the purge operation is not being performed (step S25). In the case of No in step S24), the count value of the purge cut integration counter 52 is added according to the purge operation stop time (step S26).

  Next, an upper / lower limit guard process is performed on the count value of the purge cut integration counter 52 with “0” as a lower limit and the above-described upper limit count value as an upper limit value (step S27).

  Next, it is checked whether or not the count value of the purge cut integration counter 52 is equal to the upper limit value (step S28). If the count value of the purge cut integration counter 52 has reached the upper limit value (Yes in step S28). ), The process shifts to the low duty control of the purge VSV 44 (step S29). If the count value of the purge cut integration counter 52 has not reached the upper limit, the count value of the purge cut integration counter 52, the intake air temperature, etc. Accordingly, the purge rate is limited (step S30).

  In the present embodiment in which the processing as described above is executed, the engine 10 is stopped for a relatively long time while the vehicle 1 is stopped or while the vehicle 1 is traveling due to idling stop control or fuel cut control while the vehicle 1 is traveling. If the accelerator off state continues, the fuel cut state may continue for a relatively long time.

  In such a case, the execution time of the purge operation cannot be sufficiently ensured by merely estimating the concentration of the evaporated fuel gas from the integrated value of the purge cut time. If the air-fuel ratio of the internal combustion engine is within a certain error range with respect to the reference value when the purge operation is resumed after the purge operation is stopped for a relatively long time, the purge gas is not only controlled based on the flow rate of the purge gas. The degree of decrease in the flow rate of the purge gas corresponding to the operation execution time becomes larger than usual.

  Therefore, even if the stop time until the purge operation is restarted becomes long, the purge operation is not limited unless the air-fuel ratio is actually increased by the purge gas at the time of restarting the purge operation, and the purge amount is unnecessary. Without being limited to the above, fluctuations in the air-fuel ratio due to the purge operation can be suppressed, and the execution frequency of the fuel purge operation from the canister can be sufficiently increased. As a result, the evaporative fuel processing device 40 enables the fuel 1 to travel with lower fuel consumption.

  Incidentally, FIG. 5 shows a purge execution flag, a count value of the purge cut integration counter 52, a low duty flag, and a purge concentration learning value when a running test in which the vehicle 1 is repeatedly run and stopped (including an idling stop state) is performed. The change in the drive duty ratio [%] of the purge VSV 44 is shown. Although the detected air-fuel ratio and the air-fuel ratio feedback value of the A / F sensor 33 are not shown in the figure, the air-fuel ratio feedback value here is exclusively used when the purge operation is performed during the operation of the engine 10. The value is on the minus side (rich side) with respect to the fuel ratio, and the purge concentration learning value is similarly on the minus side.

  However, in the conventional purge control indicated by the two-dot chain line in the figure, the count value of the purge cut integration counter increases as time passes, and the count of the purge cut integration counter is counted when a certain amount of time has passed. The value reaches the upper limit value, and the low duty execution flag for requesting the shift to the low duty control is set.

  On the other hand, in this embodiment, if the air-fuel ratio feedback value is within a predetermined value with respect to the reference value when the purge is resumed, the count value of the purge cut integration counter 52 is reset to “0”. Unless the air-fuel ratio is actually increased by the purge gas, the purge operation is not limited. Therefore, there is no need to unnecessarily limit the drive duty ratio (purge rate) as in the conventional VSV drive duty indicated by the two-dot chain line in the figure, and it is sufficient as in the VSV drive duty indicated by the solid line in the figure. In addition, the purge rate can be increased to suppress fluctuations in the air-fuel ratio due to the purge operation. Therefore, the execution frequency of the fuel purge operation from the canister 41 can be sufficiently increased. Moreover, if the air-fuel ratio feedback value is within a predetermined value with respect to the reference value, for example, even if the purge operation is executed in an idle state, it is possible to reliably suppress the blow-up and the deterioration of the exhaust gas purification performance.

  In the present embodiment, the ECU 50 that constitutes the purge control mechanism 47 acquires the air-fuel ratio feedback value from its specific function unit as a control device that executes the air-fuel ratio feedback control of the engine 10, and the air-fuel ratio feedback value. Is within the predetermined value, it is determined that the detected air-fuel ratio falls within a certain error range with respect to the theoretical air-fuel ratio that is the reference value. Therefore, when the purge operation is restarted, the change in the air-fuel ratio due to the restart of the purge can be accurately grasped from the change in the air-fuel ratio feedback value of the existing air-fuel ratio feedback control means, and the estimation of the air-fuel ratio based on the purge concentration learning value is transient. Even under such a condition that the estimated value becomes inaccurate, a low-cost device that can reliably suppress fluctuations in the air-fuel ratio while increasing the frequency of purge execution. In addition, since it is not erroneously determined that the purge gas concentration is higher than the actual concentration and priority is not given to the unnecessary purge operation, the learning process for each operation region for air-fuel ratio feedback control at the time of restarting the purge is delayed. Is also prevented.

  Furthermore, in the present embodiment, the low duty control (purge suppression process) is executed on the condition that the count value of the purge cut integration counter 52 has reached the upper limit value, while the low duty control is not executed, On the condition that the air-fuel ratio falls within a certain range with respect to the reference value when the purge operation is resumed, the subtraction amount by the subtraction operation for the count value of the purge cut integration counter 52 is made larger than usual. Therefore, it is determined whether or not purge suppression is necessary, and it is possible to effectively suppress unnecessary transition from the normal purge state to the purge suppression state.

  In addition, the ECU 50 sets the count value of the purge cut integration counter 52 at the restart to a relatively small value on condition that the air-fuel ratio feedback value falls within a certain range with respect to the reference value when the purge operation is restarted. By subtracting, for example, a new count value can be set as a reset, and the counting operation can be resumed using the new count value. Therefore, when there is substantially no need for purge suppression, the count value can be made sufficiently small to ensure a sufficient purge execution frequency.

  In addition, the ECU 50 counts the count value of the purge cut integration counter 52 on condition that the state in which the air-fuel ratio feedback value is within a certain range with respect to the reference value continues for a preset waiting time when the purge operation is resumed. Is reduced to a relatively small value, so that it is possible to perform purge control that is not easily affected by fluctuations in the air-fuel ratio when restarting the purge operation.

  Further, in the present embodiment, in addition to the above control using the count value of the purge cut integration counter 52, the purge rate is variably controlled according to the temperature of the intake air or the outside air of the engine 10 when the purge operation is resumed. Since the purge amount can be limited as the temperature of the intake air or the outside air is higher, an unnecessary purge gas flow rate is not limited when the temperature of the intake air or the outside air is low.

  As described above, according to the present embodiment, even when the purge stop time becomes long, the air-fuel ratio fluctuation can be suppressed without unnecessarily limiting the purge amount when the purge is resumed, so that the fuel purge operation from the canister 41 is executed. The frequency can be increased sufficiently. As a result, it is possible to provide the evaporative fuel processing device 40 for an internal combustion engine that enables travel control with lower fuel consumption.

  In each of the above-described embodiments, the ECU 50 constituting the purge control mechanism 47 responds to the count values of the purge concentration learning value counter 51 and the purge cut integration counter 52 and the intake air temperature or the outside air temperature of the engine 10. Although the variable control of the purge rate is executed, the fuel temperature in the fuel tank 25 may be used instead of the outside air temperature around the engine 10. Next, an embodiment in such a case will be described.

(Other embodiments)
6 and 7 show an evaporated fuel processing apparatus for an internal combustion engine according to another embodiment of the present invention.

  As shown in FIG. 6, the present embodiment is provided with an in-tank fuel temperature sensor 71 for detecting the temperature of the fuel in the fuel tank 25 in addition to the configuration of the evaporated fuel processing apparatus of the above-described embodiment. is there. Therefore, here, the same configuration as that of the evaporated fuel processing apparatus of the above-described embodiment is indicated by the same reference numeral in FIG. 6, and differences from the evaporated fuel processing apparatus of the above-described embodiment will be described.

  In the present embodiment, the ECU 50 as the purge control mechanism, in addition to the purge rate control according to the count value of the purge cut integration counter 52 and the air-fuel ratio feedback value as described above, at the time of restart after the purge operation is stopped, According to the fuel temperature thf in the fuel tank 25 obtained from the fuel temperature sensor 71 in the tank (or according to the fuel temperature thf obtained from the fuel temperature sensor 71 in the tank and the temperature of intake air or outside air of the engine 10). ), The purge rate is variably controlled. The purge amount, that is, the purge gas intake amount can be limited as the fuel temperature thf obtained from the in-tank fuel temperature sensor 71 (or the temperature of the intake air or the outside air of the engine 10) increases.

  More specifically, based on the relationship between the purge concentration learning value and the tank internal combustion temperature as shown in FIG. 2A, as shown in FIG. If the immediately preceding purge cut time is relatively short when the purge operation is resumed with the fuel temperature thf being high, the required purge operation is limited to a medium degree and the immediately preceding purge cut time is relatively long. In the case of purge control in which the degree of restriction of the required purge operation becomes large if necessary, when the purge is resumed when the fuel temperature in the tank thf is low, the purge required if the previous purge cut time is relatively short If the degree of restriction of the operation is small and the previous purge cut time is relatively long, the degree of restriction of the required purge amount is set so that the required degree of restriction of the purge operation becomes medium. Depending on the f and is adapted to change.

  Also in this embodiment, not only the flow rate of the purge gas is controlled based on the stop time and execution time of the purge operation, but also the air-fuel ratio of the engine 10 is used as a reference when the purge operation is resumed after the purge operation is stopped for a relatively long time. If the value falls within a certain error range, the degree of decrease in the purge gas flow rate corresponding to the execution time of the purge operation becomes larger than usual.

  Therefore, even if the stop time until the purge operation is restarted becomes long, the purge operation is not limited unless the air-fuel ratio is actually increased by the purge gas at the time of restarting the purge operation. ) Can be suppressed without unnecessarily limiting, and the frequency of execution of the purge operation of the fuel from the canister 41 can be sufficiently increased.

  In addition, in the present embodiment, even when the fuel temperature in the fuel tank 25 is low, there is no need to limit the flow rate of the purge gas that is not necessary. Therefore, also in the present embodiment, it is possible to provide the evaporative fuel processing device 40 that makes it possible to control the vehicle 1 with lower fuel consumption.

  In each of the above-described embodiments, gasoline is used as the volatile fuel, but other fuels such as a fuel having a high alcohol mixing ratio may be used.

  Further, when the purge operation is resumed, the increase in the subtraction amount due to the subtraction operation of the purge cut integration counter 52 when the air-fuel ratio feedback value is within a predetermined value with respect to the reference value can be made the largest subtraction amount by the counter reset. However, the present invention is not limited to this, and may be changed to another lower limit or a minimum count value.

  Further, the time td (see FIG. 5) required for grasping the air-fuel ratio feedback value at the time when the purge operation is resumed is not particularly mentioned, but the time when the air-fuel ratio changes transiently immediately after the purge is resumed (for example, 1 to 2 seconds).

  As described above, the present invention can suppress fluctuations in the air-fuel ratio without unnecessarily limiting the purge amount when restarting the purge even if the purge stop time becomes long. Therefore, the frequency of the purge operation of the fuel from the canister can be reduced. It is possible to provide an evaporative fuel processing apparatus for an internal combustion engine that can be sufficiently enhanced and that enables a fuel-efficient travel control. Such an evaporative fuel processing apparatus for an internal combustion engine is useful for all evaporative fuel processing apparatuses for an internal combustion engine that are controlled so as to suppress fluctuations in the air-fuel ratio due to fuel purge.

1 vehicle 10 engine (internal combustion engine)
11w Water jacket 13 Combustion chamber 15 Crankshaft 21 Injector (fuel injection valve)
23 Fuel pump (fuel supply mechanism)
24 Pressure regulator (fuel supply mechanism)
25 Fuel tank (fuel supply mechanism)
26 Intake pipe 26a Surge tank 27 Air flow meter (Intake system sensor)
28 Intake air temperature sensor (intake system sensor)
29 Throttle valve 31 Exhaust pipe 32 Catalytic device 33 A / F sensor (air-fuel ratio sensor)
40 Evaporative fuel processing equipment 41 Canister (adsorber)
42 Fuel Intake Side Pipe 43 Purge Pipe 44 Purge VSV (Purge Required Vacuum Solenoid Valve, Purge Control Valve)
46 Purge mechanism 47 Purge control mechanism 50 ECU
51 Purge concentration learning value counter 52 Purge cut integration counter 61 Crank position sensor 62 Throttle position sensor 63 Vehicle speed sensor 64 Cam position sensor 65 Water temperature sensor 66 Igniter

Claims (7)

An adsorber that adsorbs the evaporated fuel generated in the fuel supply mechanism of the internal combustion engine, and a purge operation that sucks the fuel released from the adsorber through the adsorber and the purge gas containing the air into the intake pipe of the internal combustion engine An evaporative fuel processing apparatus for an internal combustion engine, comprising: a purge mechanism that executes the control, and a purge control mechanism that controls an amount of the purge gas sucked into the intake pipe to suppress fluctuations in the air-fuel ratio in the internal combustion engine. ,
The purge control mechanism reduces the suction amount of the purge gas in accordance with the execution time of the purge operation, while the stop time for stopping the purge operation does not reach a preset limit time. In the purge operation after the stop, the set value of the intake amount of the purge gas in the purge operation after the stop is increased according to the stop time, and the stop time has reached the limit time. An increase in the set amount of the purge gas in accordance with the stop time is suppressed, and the air-fuel ratio falls within a predetermined range with respect to a preset reference value when the purge operation is resumed after the stop. On the condition described above, an evaporative fuel processing apparatus for an internal combustion engine, wherein the degree of decrease in the set value of the intake amount according to the execution time of the purge operation is made larger than usual.   The purge control mechanism acquires the feedback value from an air-fuel ratio feedback control device that feedback-controls the air-fuel ratio of the internal combustion engine so that the feedback value from the air-fuel ratio sensor matches a target value, and the magnitude of the feedback value 2. The evaporation of the internal combustion engine according to claim 1, wherein the air-fuel ratio is determined to fall within the predetermined range with respect to the reference value on the condition that is within a predetermined value corresponding to the predetermined range. Fuel processor.   The purge control mechanism controls the suction amount of the purge gas based on a count value obtained by a counting process including an integration operation according to the stop time of the purge operation and a subtraction operation according to the execution time of the purge operation, On the condition that the count value has reached a preset upper limit value, the purge suppression process is executed to suppress the increase in the intake amount of the purge gas in accordance with the stop time of the purge operation, while the purge suppression process is executed. On the condition that the air-fuel ratio falls within the predetermined range with respect to the reference value when the purge operation is resumed after the stop, and the subtraction amount by the subtraction operation with respect to the count value The evaporative fuel processing device for an internal combustion engine according to claim 1 or 2, wherein the evaporative fuel processing device is larger than usual.   The purge control mechanism sets the count value at the time of restart to a relatively small value on condition that the air-fuel ratio falls within the predetermined range with respect to the reference value when the purge operation is restarted after the stop. 4. The evaporated fuel processing apparatus for an internal combustion engine according to claim 3, wherein a new count value is subtracted and a new count value is set, and the counting operation is restarted using the new count value.   The purge control mechanism includes a counter that executes the counting process, and the counting is performed on the condition that the air-fuel ratio falls within the predetermined range with respect to the reference value when the purge operation is resumed after the stop. The evaporated fuel processing apparatus for an internal combustion engine according to claim 4, wherein the count value of the counter is reset and the new count value is set.   The purge control mechanism is configured on the condition that, when the purge operation is resumed after the stop, the state in which the air-fuel ratio is within the certain range with respect to the reference value continues for a preset waiting time. 6. The evaporated fuel processing apparatus for an internal combustion engine according to claim 4, wherein the numerical value is reduced to a relatively small value.   The purge control mechanism is configured to change the internal combustion engine according to a temperature of intake air or outside air of the internal combustion engine or a temperature of fuel in a fuel tank provided in the fuel supply mechanism when restarting the purge operation after the stop. 2. The ratio of the intake amount of the purge gas to the intake air amount is variably controlled, and the intake amount of the purge gas is limited as the temperature of the intake air or outside air or the temperature of the fuel increases. The evaporated fuel processing device for an internal combustion engine according to any one of claims 6 to 6.

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