JP6299801B2 - Engine control device - Google Patents

Description

  The present invention communicates fuel supply means for supplying fuel into a cylinder formed in an engine body, a canister for collecting evaporated fuel in a fuel tank, an intake passage connected to the engine body, the canister and the intake passage. Engine having a purge passage, a purge gas flow rate changing means for changing the flow rate of the purge gas passing through the purge passage, and an oxygen concentration detection means for detecting the oxygen concentration of the exhaust gas passing through the exhaust passage connected to the engine body The present invention relates to a control device.

  Conventionally, evaporative fuel generated in a fuel tank or the like is adsorbed by a canister and then introduced into an intake passage and burned in a cylinder. Further, in order to more appropriately control the amount of fuel supplied into the cylinder, the fuel concentration of the purge gas, which is a gas containing the evaporated fuel introduced into the intake passage, is estimated, and based on this, the injection amount of the injector is estimated It is also done to correct.

  For example, in Patent Document 1, an oxygen concentration sensor that detects the oxygen concentration of exhaust gas is provided in the exhaust passage, and an engine that performs feedback control of the injection amount of the injector so that the oxygen concentration of exhaust gas detected by this sensor becomes a target value In the system, it is disclosed to estimate the fuel concentration of the purge gas from the deviation between the feedback correction coefficient when the purge gas is not introduced into the intake passage and the feedback correction coefficient when the purge gas is introduced into the intake passage. Has been.

  According to the system of Patent Document 1, it is possible to estimate the fuel concentration of the purge gas relatively easily by using a feedback correction coefficient calculated for controlling the injection amount. That is, when the purge gas is introduced into the intake passage, the fuel content in the purge gas and the air-fuel ratio of the air-fuel mixture in the cylinder are reduced, and the exhaust oxygen concentration is reduced. Along with this, the feedback correction coefficient increases. Therefore, the fuel concentration of the purge gas can be estimated based on a deviation between the feedback correction coefficient when the purge gas is not introduced into the intake passage and the correction coefficient when the purge gas is introduced into the intake passage. .

Japanese Patent No. 3385919

  Here, if the fuel concentration of the purge gas is estimated as described above, even if the introduction amount of the purge gas into the intake passage suddenly decreases as the operating condition changes, the injection amount of the injector is increased by the decrease in the purge gas. By doing so, the amount of fuel supplied into the cylinder can be maintained at an appropriate amount.

  However, in the engine system in which the injection amount of the injector is feedback controlled based on the detection value of the oxygen concentration sensor provided in the exhaust passage as described above, the estimation of the purge gas fuel concentration is not completed. The following problems occur when sudden decrease occurs. That is, in the engine system, when the estimation of the fuel concentration of the purge gas is not completed, the injection amount of the injector is corrected only according to the amount of deviation from the target value of the detection value of the oxygen concentration sensor. Since the oxygen concentration sensor provided in the cylinder and the cylinder are separated from each other, there is a delay time from when the purge gas suddenly decreases until the oxygen concentration sensor detects a change in the air-fuel ratio of the air-fuel mixture in the cylinder. There is. Therefore, when the injection amount of the injector is simply feedback controlled based on the value detected by the oxygen concentration sensor, the injection amount of the injector is instantaneously increased in accordance with the increase of the air-fuel ratio in the cylinder accompanying the rapid decrease of the purge gas. The air-fuel ratio in the cylinder becomes larger than a desired value. Along with this, there arises a problem that acceleration performance and the like deteriorate.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an engine control apparatus that can more appropriately control the air-fuel ratio in a cylinder.

  In order to solve the above problems, a fuel supply means for supplying fuel into a cylinder formed in the engine body, a canister for recovering evaporated fuel in a fuel tank, an intake passage connected to the engine body, and the canister A purge passage communicating therewith, a purge gas flow rate changing means capable of changing a flow rate of the purge gas passing through the purge passage, and an exhaust oxygen concentration detecting means for detecting the oxygen concentration of the exhaust gas passing through the exhaust passage connected to the engine body. A purge gas concentration estimator for estimating the fuel concentration of purge gas flowing from the purge passage into the intake passage based on the oxygen concentration of the exhaust detected by the exhaust oxygen concentration detector; A fuel control unit that controls a fuel supply amount that is a fuel amount supplied into the cylinder by the fuel supply unit, and the fuel control unit includes: Based on the oxygen concentration of the exhaust detected by the oxygen concentration detecting means and the target value of the exhaust oxygen concentration, the fuel supply amount is feedback controlled so that these deviations approach zero, while the purge gas flow rate changing means If the purge gas concentration estimation unit has not yet completed the estimation of the fuel concentration of the purge gas when the purge gas flow rate is reduced below a preset reference flow rate by the control, the feedback control is performed on the fuel supply amount. It is characterized in that it is more than in the case of implementing (Claim 1).

  According to the present invention, since the fuel supply amount is feedback-controlled based on the oxygen concentration of the exhaust detected by the oxygen concentration detecting means, the oxygen concentration of the exhaust, and thus the air-fuel ratio in the cylinder, is controlled to an appropriate value. be able to. Moreover, when the purge gas flow rate is reduced before the estimation of the purge gas fuel concentration is completed, that is, the estimated amount of purge gas fuel concentration is used to estimate the increase in the air-fuel ratio in the cylinder. If this is not possible, the fuel supply amount is increased more than when normal feedback control is performed. Therefore, it is possible to suppress an excessive increase in the air-fuel ratio of the air-fuel mixture in the cylinder as the purge gas flow rate is reduced, and it is possible to appropriately control the air-fuel ratio of this air-fuel mixture.

  In the present invention, the purge gas concentration estimator increases the flow rate of the purge gas flowing into the intake passage by the purge gas flow rate changing means, and the oxygen concentration of the exhaust gas detected by the exhaust oxygen concentration detection means is the flow rate of the purge gas. The fuel concentration of the purge gas is estimated based on the amount that has changed with the increase, and the fuel control unit is configured to make the flow rate of the purge gas less than the reference flow rate during the estimation of the fuel concentration of the purge gas by the purge gas concentration estimation unit. When it is reduced, it is preferable to increase the fuel supply amount as compared with the case where the feedback control is performed.

  In this way, the fuel concentration of the purge gas can be estimated more accurately. On the other hand, in this estimation procedure, since it is necessary to see the change in oxygen concentration, it takes time to estimate. As a result, the operating conditions change during the estimation of the fuel concentration and before the estimation of the fuel concentration is completed, increasing the chance that the purge gas flow rate is reduced below the reference flow rate. It tends to be over the target value. On the other hand, in the present invention, the air-fuel ratio of the air-fuel mixture in the cylinder can be more appropriately controlled even when the flow rate of the purge gas is reduced. Can be estimated.

  In the above configuration, it is preferable that the purge gas concentration estimation unit stops the estimation of the fuel concentration of the purge gas when the flow rate of the purge gas decreases below the reference flow rate during the estimation of the fuel concentration of the purge gas. (Claim 3).

  In this way, it is possible to suppress an increase in the estimation error of the fuel concentration of the purge gas. That is, when the flow rate of the purge gas is reduced, the purge gas flow rate is not stable, so the correlation between the detection result of the oxygen concentration detection means and the fuel concentration of the purge gas is likely to be low, and this fuel concentration is likely to be erroneously estimated. Accordingly, if the estimation of the fuel concentration of the purge gas is stopped when the flow rate of the purge gas is reduced as in this configuration, this erroneous estimation can be suppressed.

  In the present invention, the fuel control unit sets a basic fuel supply amount based on the engine speed and the intake air amount, and detects the oxygen concentration of the exhaust detected by the oxygen concentration detecting means and the target of the exhaust oxygen concentration. A feedback correction amount is calculated such that a deviation from the value approaches zero, and the fuel supply amount is calculated by adding the feedback correction amount to the basic fuel supply amount, and the fuel of the purge gas by the purge gas concentration estimation unit is calculated. When the flow rate of the purge gas is reduced below the reference flow rate before the concentration estimation is completed, the feedback correction amount is preferably set to zero (claim 4).

  In this way, it is possible to more reliably suppress an excessive increase in the air-fuel ratio in the cylinder accompanying the reduction in the purge gas flow rate with a simple configuration.

  In the present invention, the fuel control unit stops the feedback control when the purge gas flow rate is reduced below the reference flow rate before the purge gas concentration estimation unit completes the estimation of the fuel concentration of the purge gas, and thereafter The feedback control is preferably restarted when a preset reference time has elapsed.

  In this way, it is possible to control the air-fuel ratio to a more appropriate value by increasing the feedback control execution opportunities while suppressing an excessive increase in the air-fuel ratio in the cylinder when the purge gas flow rate is reduced.

  Here, as an operation condition for reducing the flow rate of the purge gas to be less than the reference flow rate, a fuel learning unit that learns deviation amounts from a command value of the fuel amount supplied from the fuel supply means in a plurality of operation regions, respectively. In the engine provided, the engine main body is operated in an operation region where the learning by the fuel learning unit is not completed (Claim 6).

  Further, as an operating condition for reducing the flow rate of the purge gas below the reference flow rate, the engine body is operated in an operation region where the maximum flow rate of the purge gas that can flow into the intake passage is less than a preset purge permission flow rate. Time (claim 7).

  The present invention further includes a turbocharger including a compressor provided in the intake passage and a turbine provided in the exhaust passage, wherein the oxygen concentration detection means is downstream of the turbine in the exhaust passage. It is preferable to arrange on the side (claim 8).

  According to this configuration, in an engine that has a turbocharger and is configured to improve acceleration performance, as described above, it is possible to suppress an excessive increase in the air-fuel ratio in the cylinder as the purge gas flow rate decreases. Thus, since the deterioration of the acceleration performance due to the excessive increase in the air-fuel ratio can be suppressed, the acceleration performance can be improved more reliably.

  As described above, according to the engine control apparatus of the present invention, the air-fuel ratio in the cylinder can be more appropriately controlled.

It is a figure showing composition of an engine system concerning one embodiment of the present invention. It is the figure which showed the control block. It is the flowchart which showed the procedure of the basic control of the injection quantity. It is the flowchart which showed the estimation procedure of purge gas concentration. It is the flowchart which showed the control procedure of purge gas. It is the flowchart which showed the control procedure of the injection quantity at the time of purge cut. It is the figure which showed the time change of each parameter when the control which concerns on this embodiment is implemented. It is the figure which showed the time change of each parameter when the control which concerns on a comparative example is implemented.

(1) Overall Configuration of Engine FIG. 1 is a schematic configuration diagram of an engine system to which an engine control device according to an embodiment of the present invention is applied. The engine system of the present embodiment includes a four-stroke engine body 1, an intake passage 50 for introducing air (intake air) into the engine body 1, and an exhaust passage 60 for exhausting exhaust from the engine body 1 to the outside. And a purge system 20. The engine body 1 is, for example, a four-cylinder engine having four cylinders 2a arranged in a direction orthogonal to the paper surface of FIG.

  The engine system according to the present embodiment is a turbocharged engine having a turbocharger 59, a turbine 61 provided in the exhaust passage 60 and driven by exhaust, and a turbine 61 provided in the intake passage 50. And a compressor 52 that is driven to rotate and supercharges intake air.

  The engine body 1 includes a cylinder block 2 in which a cylinder 2a is formed, a cylinder head 3 provided on the upper surface of the cylinder block 2, and a piston 4 inserted into the cylinder 2a so as to be slidable back and forth. Yes. The piston 4 is connected to the crankshaft 15 via a connecting rod, and the crankshaft 15 rotates around the central axis according to the reciprocating motion of the piston 4. A combustion chamber 5 is formed above the piston 4.

  An injector (fuel supply means) 11 for injecting (supplying) fuel into the combustion chamber 5 is attached to the cylinder block 2.

  A spark plug 10 is attached to the cylinder head 3 for igniting an air-fuel mixture (fuel-air mixture) in the combustion chamber 5 by spark discharge. The cylinder head 3 has an intake port 6 for introducing air supplied from the intake passage 50 into the combustion chamber 5 of each cylinder 2a, an intake valve 8 for opening and closing the intake port 6, and combustion in each cylinder 2a. An exhaust port 7 for leading exhaust generated in the chamber 5 to the exhaust passage 60 and an exhaust valve 9 for opening and closing the exhaust port 7 are provided.

  The intake valve drive mechanism 18 that drives the intake valve 8 is provided with an intake opening / closing timing changing mechanism 18a that can change the opening / closing timing of the intake valve 8. In the present embodiment, the intake air amount that flows into the cylinder 2a can be changed by changing the opening / closing timing of the intake valve 8 by the intake air opening / closing timing changing mechanism 18a.

  In the intake passage 50, an air cleaner 51, a compressor 52, an intercooler 53, a throttle valve 54, and a surge tank 55 are provided in this order from the upstream side, and after being compressed by the compressor 52, the intercooler 53 is compressed in the combustion chamber 5. Chilled air is introduced. The throttle valve 54 is a valve that can open and close the intake passage 50, and the amount of intake air flowing through the intake passage 50 can be adjusted according to the opening of the throttle valve 54.

  The exhaust passage 60 is provided with a catalytic converter 63 containing a turbine 61 and a catalyst such as a three-way catalyst in order from the upstream side. The exhaust passage 60 is provided with a bypass passage 62a for bypassing the turbine 61, and a wastegate valve 62b for allowing the exhaust discharged from the engine body 1 to flow into the bypass passage 62a. ing.

  The cylinder block 2 is provided with an engine speed sensor SN1 for detecting the rotation angle of the crankshaft 15 and thus the engine speed.

  An air flow sensor SN <b> 2 for detecting the flow rate of the intake air flowing through the intake passage 50 is provided in a portion of the intake passage 50 between the air cleaner 51 and the compressor 52. A supercharging pressure sensor SN3 is provided between the throttle valve 54 and the intercooler 53 in the intake passage 50 to detect the supercharging pressure that is the pressure at this portion. The surge tank 55 is provided with an intake pressure sensor SN4 for detecting an intake pressure that is a pressure in the surge tank 55.

In the exhaust passage 60, a portion immediately upstream of the catalytic converter 63 and between the catalytic converter 63 and the turbine 61, an oxygen concentration of exhaust passing through this portion (hereinafter referred to as exhaust oxygen concentration). A linear O ₂ sensor SN5 (exhaust oxygen concentration detection means) is provided.

Thus, in the present embodiment, the turbine 61 is provided in the exhaust passage 60, and the linear O ₂ sensor SN 5 is provided further downstream of the turbine 61. Therefore, the separation distance between the cylinder 2a and the linear O ₂ sensor SN5 is particularly long.

(2) Purge System Next, the configuration of the purge system 20 will be described.

  The purge system 20 includes a canister 22, a purge passage 23 that communicates the canister 22 and the intake passage 50, and a purge valve (purge gas flow rate changing means) 24 that opens and closes the purge passage 23. In the present embodiment, the purge valve 24 is an electronically controlled valve.

  The canister 22 contains activated carbon that adsorbs fuel vapor in a detachable manner, and the canister 22 adsorbs and stores the evaporated fuel generated in the fuel tank 21. In addition to the purge passage 23, the canister 22 is connected with a fuel vapor pipe 22a into which fuel vapor in the fuel tank 21 flows, and an atmosphere open pipe 22b through which the canister 22 is opened to the atmosphere. Although not shown in the drawing, the air release pipe 22b is provided with an air filter for filtering the air flowing into the canister 22 and a valve for opening and closing the air release pipe 22b. The valve is opened when it is introduced, that is, when the evaporated fuel is purged.

  The purge passage 23 is branched into two on the downstream side of the purge valve 24, and the purge passage 23 is connected to two portions of the intake passage 50. That is, the purge passage 23 is connected to the canister 22 and provided with a common passage 23a provided with a purge valve 24, and a first branch passage 23c and a first branch passage 23b connecting the downstream end of the common passage 23a and the intake passage 50, respectively. And have.

  The downstream end of the first branch passage 23 c is connected to a portion of the intake passage 50 upstream of the compressor 52 via the ejector 25. The downstream end of the first branch passage 23 b is connected to the surge tank 55.

  The ejector 25 communicates a portion upstream of the compressor 52 and a portion downstream of the compressor 52 in the intake passage 50. In a state in which supercharging is performed by the turbocharger 59, the high-pressure intake air supercharged by the compressor 52 passes through the ejector 25 and flows from the downstream side of the compressor 52 to the upstream side of the compressor 52. Reflux to portion. The ejector 25 is provided with a sol (not shown) that increases the flow rate of the recirculated intake air, and the intake air passes through the ejector 25 at a high speed. Along with this, a negative pressure is generated in the ejector 25, whereby the purge gas in the first branch passage 23 c is sucked into the ejector 25 and flows into the upstream portion of the compressor 52 through this.

  Thus, when supercharging is performed by the turbocharger 59, the purge gas flows into the intake passage 50 through the first branch passage 23c.

  On the other hand, when the turbocharger 59 is not supercharged, the intake air does not recirculate through the ejector 25, so that the flow of the purge gas into the intake passage 50 through the first branch passage 23c stops. On the other hand, when the turbocharger 59 is not supercharged, the purge gas is provided at the downstream side of the throttle valve 54 to keep the pressure in the surge tank 55 low, and the purge gas is in the first branch. It flows into the intake passage 50 through the passage 23b. In addition, when supercharging is performed by the turbocharger 59, the pressure in the surge tank 55 becomes high. Therefore, in this case, the flow of purge gas into the intake passage 50 through the first branch passage 23b is stopped.

(3) Control System Next, the control system of the engine system will be described with reference to FIG. The engine system of the present embodiment is mounted on a vehicle such as an automobile and is controlled by an ECU (Engine Control Unit) 100 provided in the vehicle. As is well known, the ECU 100 is a microprocessor including a CPU, ROM, RAM, I / F, and the like.

Information from various sensors is input to the ECU 100. For example, ECU 100, the engine speed sensor SN1, air flow sensor SN2, boost pressure sensor SN3, an intake pressure sensor SN4, the linear _{O 2} sensor SN5 and are electrically connected, the input signal (engine rotation from the sensors Number, intake amount, boost pressure, intake pressure, exhaust oxygen concentration). Further, the vehicle is provided with an accelerator opening sensor SN6 for detecting the opening of an accelerator pedal (not shown) operated by the driver, and the detection result is also input to the ECU 100.

  The ECU 100 performs various calculations and the like based on input signals from the sensors (SN1 to SN6, etc.), and each part such as the spark plug 10, the injector 11, the intake opening / closing timing changing mechanism 18a, the throttle valve 54, the purge valve 24, and the like. To control.

  The ECU 100 functionally includes an initial injector learning unit (fuel learning unit) 101, an injection amount control unit (fuel control unit) 102, a purge flow rate estimation unit 103, and a purge concentration estimation unit (purge gas concentration estimation unit) 104. And have.

(I) Injector initial learning The injector initial learning unit 101 learns the amount of deviation from the command value of the amount of fuel injected from the injector 11 (fuel supply amount, hereinafter sometimes referred to as injection amount). That is, the injection amount of the injector 11 may deviate from the command value due to the individual difference or the like, and the injector initial learning unit 101 learns this deviation amount. Hereinafter, this deviation amount is referred to as an initial deviation amount, and this learning is referred to as initial learning.

The injector initial learning unit 101 detects the actual exhaust oxygen concentration (detected by the linear O ₂ sensor SN5) when various conditions such as the condition that the introduction of the purge gas into the intake passage 50 is stopped and the steady state are satisfied. Hereinafter, the initial deviation amount is learned based on the actual exhaust oxygen concentration).

  Specifically, in the present embodiment, the injector initial learning unit 101 estimates the amount of fuel actually injected from the injector 11 based on the actual exhaust oxygen concentration, and sets the amount of deviation between the estimated value and the command value as an initial value. Learning as the amount of deviation. That is, the actual exhaust oxygen concentration is obtained by subtracting the amount of oxygen used to burn the fuel for the amount of injection from the amount of oxygen contained in the amount of intake, and the amount of exhaust (the total amount of intake and injection) The actual injection amount is calculated from the above relationship using the intake air amount detected by the air flow sensor SN2 and the actual exhaust oxygen concentration.

Here, as described above, the amount of intake air detected by the airflow sensor SN2 is used to calculate the initial deviation amount. Since the linear O ₂ sensor SN5 outputs a value that reflects the difference in intake air amount, the initial deviation amount learning by the injector initial learning unit 101 also corrects the difference in intake air amount. . On the other hand, the amount of deviation of the intake air amount varies depending on the amount of intake air, such as increasing when the intake air amount is large. Therefore, in the present embodiment, the initial learning of the injector 11 is performed for each of a plurality of operation regions set according to the intake air amount, and the initial deviation amount of the injector 11 is calculated for each operation region. As will be described later, the injection amount of the injector 11 is corrected by the learning value of the initial deviation amount calculated in the operation region corresponding to the current intake air amount.

(Ii) Basic control of injection amount The injection amount control unit 102 is a part that controls the injection amount of the injector 11. Here, the basic control of the injection amount will be described with reference to the flowchart of FIG.

First, in step S1, the injection amount control unit 102 calculates the engine speed detected by the engine speed sensor SN1, the intake air amount detected by the air flow sensor SN2, and the actual exhaust oxygen concentration detected by the linear O ₂ sensor SN5. Read.

  After step S1, the process proceeds to step S2. In step S2, a basic injection amount and a target exhaust oxygen concentration are set. These are preset according to operating conditions. For example, the ECU 100 stores the basic injection amount and the target exhaust oxygen concentration for the engine speed and the intake air amount in a map, and the injection amount control unit 102 determines the current engine speed and the intake air amount from each map. Each value corresponding to the quantity is extracted. The target exhaust oxygen concentration is a value corresponding to the basic injection amount, and is set to the exhaust oxygen concentration when the fuel for the basic injection amount is supplied into the cylinder 2a.

  After step S2, the process proceeds to step S3. In step S3, the basic injection amount set in step S2 is corrected with the initial deviation amount. Specifically, the operation region corresponding to the current intake air amount is selected from the plurality of operation regions set for the intake air amount as described above, and the learning value of the initial deviation amount calculated in this operation region is extracted. Then, the initial deviation amount is added to the basic injection amount to obtain the basic injection amount.

  After step S3, the process proceeds to step S4. In step S4, it is determined whether or not the estimation of the purge gas concentration that is the fuel concentration of the purge gas has been completed.

  If the determination in step S4 is yes and the estimation of the purge gas concentration is complete, the process proceeds to step S5. In step S5, the amount of fuel (hereinafter sometimes referred to as purge fuel) contained in the purge gas introduced into the cylinder 2a, that is, the amount of fuel derived from the purge gas among the fuel in the cylinder 2a is estimated. Specifically, the injection amount control unit 102 estimates the amount of purge fuel based on the purge gas concentration estimated by the purge concentration estimation unit 104 and the purge flow rate estimated by the purge flow rate estimation unit 103. The estimation procedure by these estimation units 103 and 104 will be described later.

  After step S5, the process proceeds to step S6. In step S6, the basic injection amount set in step S3 is corrected with the purge fuel amount. Specifically, the purge fuel amount is subtracted from the basic injection amount.

After step S6, the process proceeds to step S7. In step S7, an exhaust O ₂ feedback correction amount (feedback correction amount, exhaust O ₂ _F / B amount) is calculated based on the actual exhaust oxygen concentration and the target exhaust oxygen concentration.

Specifically, the injection amount control unit 102 calculates the deviation between the actual exhaust oxygen concentration and the target exhaust oxygen concentration, and calculates the exhaust O ₂ feedback correction amount based on this deviation so that the deviation becomes zero. To do. For example, a value obtained by performing PI control and adding a value obtained by multiplying a deviation of the exhaust oxygen concentration by a preset proportional gain and a value obtained by integrating a value obtained by multiplying the deviation by a preset integral gain. Is calculated as the exhaust gas O ₂ feedback correction amount.

After step S7, the process proceeds to step S8. In step S8, the basic injection amount (if the determination in step S4 is YES, the basic injection amount corrected in step S6 is used) is corrected by the exhaust O ₂ feedback correction amount calculated in step S7, and finally. Use a proper injection amount. Specifically, the final injection amount is obtained by adding the exhaust O ₂ feedback correction amount to the basic injection amount.

On the other hand, if the determination in step S4 is no, the process proceeds to step S7. Then, as described above, the exhaust O ₂ feedback correction amount is calculated, and the process proceeds to step S9, where the basic injection amount is corrected with the exhaust O ₂ feedback correction amount. However, in this case, the basic injection amount is the basic injection amount after being corrected in step S3, and an amount obtained by correcting the basic injection amount set in step S2 with the initial deviation amount is used.

(Iii) Purge flow rate estimation The purge flow rate estimation unit 103 is a part that estimates a purge flow rate that is a flow rate of purge gas flowing through the purge passage 23. The purge flow rate estimating unit 103 purges the purge gas flowing through the first branch passage 23c based on the pressure downstream of the compressor 52 detected by the supercharging pressure sensor SN3, the pressure of the canister 22, and the opening of the purge valve 24. The flow rate is calculated. The purge flow rate estimation unit 103 also purges the purge gas flowing through the first branch passage 23b based on the pressure in the surge tank 55 detected by the intake pressure sensor SN4, the pressure of the canister 22, and the opening of the purge valve 24. The flow rate is calculated. Here, the canister 22 is open to the atmosphere, and the pressure of the canister 22 is atmospheric pressure.

(Iv) Purge Gas Concentration Estimation The purge concentration estimation unit 104 is a part that estimates the purge gas concentration. This estimation procedure will be described with reference to FIG.

  First, in step S10, the purge concentration estimation unit 104 determines whether or not a purge concentration estimation condition that is a condition for determining whether or not to perform purge gas concentration estimation is satisfied.

  In this embodiment, it is determined that the purge concentration estimation condition is satisfied when the purge is started (including when the purge is once stopped and then restarted), and the purge gas concentration is estimated.

  That is, when the determination in step S10 is YES, the process proceeds to step S11 and the subsequent estimation process is performed. On the other hand, if the determination in step S10 is NO, the process ends without estimating the purge gas concentration.

  In step S11, the purge gas concentration is reset. That is, even if the purge gas concentration is estimated in the past, the purge gas concentration is reset to 0 when the determination in step S10 is YES.

  After step S11, the process proceeds to step S12. In step S12, the purge valve 24 is opened to start purging. After step S12, the process proceeds to step S13.

In step S13, it is determined whether or not the integrated value of the purge flow rate after the start of the purge in step S12 is greater than or equal to a preset estimated allowable flow rate. This estimated permitted flow rate is a value corresponding to the amount of purge gas that has flowed into the intake passage 50 until the purge gas that has started to flow from the purge passage 23 into the intake passage 50 reaches the portion where the linear O ₂ sensor SN5 is disposed. Therefore, it is set in advance by experiments or the like. That is, in step S13, it is determined whether or not the exhaust gas detected by the linear O ₂ sensor SN5 includes exhaust gas related to the purge gas (exhaust gas generated by combustion of the fuel included in the purge gas) after the purge is started. doing.

  If the determination in step S13 is NO and the integrated value of the purge flow rate is less than the estimated allowable flow rate, the process proceeds to step S14. In step S14, the opening degree of the purge valve 24 is increased. That is, in this embodiment, the opening degree of the purge valve 24 is gradually increased until the determination in step S13 becomes YES.

When the determination in step S13 is YES and the integrated value of the purge flow rate is equal to or higher than the estimated allowable flow rate, it is estimated that the exhaust gas related to the purge gas is included in the exhaust gas detected by the linear O ₂ sensor SN5. Proceed to step S15.

In step S15, the exhaust O ₂ feedback correction amount at the current time (when the determination in step S13 is YES) is stored as a first estimation feedback amount (first estimation O ₂ F / B amount). Further, the current purge flow rate estimated by the purge flow rate estimation unit 103 is stored as the first estimation purge flow rate. After step S15, the process proceeds to step S16.

  In step S16, the opening degree of the purge valve 24 is further increased. After step S16, the process proceeds to step S17.

  In step S17, it is determined whether or not a predetermined time set in advance has elapsed after the execution of step S15.

  If the determination in step S17 is NO and the predetermined time has not yet elapsed since step S15 was performed, the process returns to step S16, and the opening degree of the purge valve 24 is further increased.

  On the other hand, if the determination in step S17 is YES and a predetermined time has elapsed after the execution of step S15, the process proceeds to step S18. That is, the opening degree of the purge valve 24 is gradually increased after the execution of step S15 until a predetermined time elapses.

In step S18, the exhaust O ₂ feedback correction amount at the current time (when the determination in step S17 is YES) is stored as a second estimation feedback amount (second estimation O ₂ F / B amount), and the current The purge flow rate is stored as the second estimation purge flow rate. After step S18, the process proceeds to step S19.

  In step S19, the purge gas concentration is calculated based on the first estimation feedback amount, the second estimation feedback amount, the first estimation purge flow rate, and the second estimation purge flow rate.

  Specifically, a value obtained by dividing a value obtained by subtracting the first estimation feedback amount from the second estimation feedback amount by a value obtained by subtracting the first estimation purge flow rate from the second estimation purge flow rate is used as the purge gas concentration. calculate.

  That is, in the present embodiment, as the purge flow rate increases from the first estimation purge flow rate to the second estimation purge flow rate, the amount of fuel supplied into the cylinder 2a increases from the second estimation feedback amount. The purge gas concentration is calculated by dividing the difference in the feedback amount by the difference in the purge flow rate.

As described above, in this embodiment, when the purge is started and restarted, the purge gas concentration is estimated. Then, the purge flow concentration is gradually increased, and the purge gas concentration is estimated based on the change in the exhaust O ₂ feedback correction amount associated therewith.

(Iv) Control of Purge Valve The control of the purge valve 24 performed by the ECU 100 in normal times (except during the estimation of the purge gas concentration) will be described with reference to the flowchart of FIG.

  First, in step S21, the ECU 100 determines whether or not the current operation region is a region where initial learning of the injector 11 is not completed. Specifically, it is determined whether or not the current intake air amount is a value included in a region where initial learning has not yet been performed.

  If the determination in step S21 is YES and the operation is performed in an area where the initial learning has not been completed yet, the process proceeds to step S29, and purge cut (stoppage of the purge gas into the intake passage 50) is performed. That is, in step S29, assuming that the purge cut condition is satisfied, the purge valve 24 is fully closed to stop the flow of purge gas into the intake passage 50.

  On the other hand, if the determination in step S21 is no, the process proceeds to step S22.

  In step S22, it is determined whether or not it is an acceleration after the fuel cut, that is, whether or not it is an acceleration after the injection from the injector 11 is stopped. If the determination in step S22 is yes, the process proceeds to step S29. Then, as described above, the purge valve 24 is fully closed to perform purge cut.

  On the other hand, if the determination in step S22 is no, the process proceeds to step S23. In step S23, it is determined whether or not the intake air amount is in a low flow rate region below a predetermined value set in advance. If the determination in step S23 is yes, the process proceeds to step S29. Then, the purge valve 24 is fully closed to perform purge cutting.

  On the other hand, if the determination in step S23 is no, the process proceeds to step S24. In step S24, a target purge flow rate that is a target of the purge flow rate is set based on the intake air amount. Specifically, a predetermined ratio of the intake air amount is set as a target value for the purge flow rate.

  After step S24, the process proceeds to step S25. In step S25, the opening degree of the purge valve 24 corresponding to the purge flow target value set in step S24 is determined. Then, a command is issued to the purge valve 24 (an actuator (not shown) for driving the purge valve 24) so that the opening degree is realized.

  As described above, in the present embodiment, the operation in the operation region where the initial learning of the injector 11 is not yet performed, the acceleration after the fuel cut, or the operation in the operation region where the intake amount is less than the predetermined value is performed. Sometimes, purge purge conditions are satisfied, purge purge is performed, otherwise the purge flow rate is adjusted according to the intake air amount.

  Specifically, when the initial learning of the injector 11 has not been performed yet, it is preferable to first perform the initial learning so that the injection amount is appropriately controlled. As described above, this initial deviation amount is calculated on the assumption that the deviation amount between the actual exhaust oxygen concentration and the exhaust oxygen concentration is based on the deviation amount from the command value of the injection amount of the injector 11. Accordingly, when the injector 11 is operating in a region where the initial learning has not yet been performed, the initial learning is first performed, and at this time, the purge is performed so that the fuel component contained in the purge gas is not included in the actual exhaust oxygen concentration. Make a cut.

  In addition, since the flow rate of the purge gas may not be stable immediately after the fuel cut, in this embodiment, the purge cut is also performed during acceleration after the fuel cut.

  Further, when the intake air amount is less than a predetermined value, the purge flow rate needs to be lowered accordingly. However, if the purge flow rate is low, the flow rate is not stable, and the air-fuel ratio of the air-fuel mixture in the cylinder 2a is unstable. become. In particular, when the purge valve 24 is a valve that is DUTY controlled, the flow rate is difficult to stabilize if the purge flow rate is low. Therefore, in the present embodiment, purge cut is performed in an area where the intake air amount is less than a predetermined value.

(V) Fuel Control at Purge Cut Next, the injection amount control procedure performed by the injection amount control unit 102 when purge cut is performed will be described with reference to the flowchart of FIG.

  First, in step S31, the injection amount control unit 102 determines whether the purge cut condition is satisfied. In the present embodiment, as described above, the purge cut condition is satisfied during operation in the operation region where the initial deviation amount of the injector 11 has not yet been learned, during acceleration after fuel cut, and during operation in the low flow region. It is determined that

  If the determination in step S31 is no, the process proceeds to step S39. In step S39, the basic control described in (ii) is performed. That is, the basic injection amount set based on the engine speed and the intake air amount is corrected by the initial deviation amount and the purge fuel amount (when the estimation of the purge gas concentration is completed), and this is feedback-corrected by the exhaust oxygen concentration To do.

  On the other hand, if the determination in step S31 is no, the process proceeds to step S32. In step S32, it is determined whether or not the estimation of the purge gas concentration is incomplete.

  Here, in this embodiment, as described above, when the purge is started and restarted, the purge gas concentration is estimated accordingly. That is, the purge gas concentration is estimated not only when the purge is started for the first time after the engine is started, but also when the purge is temporarily stopped during the running or the like and then the purge is resumed. Accordingly, until the first estimation of the purge gas concentration after the engine is started, the purge is resumed as described above in addition to the period from the start of the estimation of the purge gas concentration to the end of the estimation. Accordingly, the period from the start of the estimation of the purge gas concentration to the end of the estimation is also a period in which the estimation of the purge gas concentration is not completed.

  If the determination in step S32 is NO and the estimation of the purge gas concentration has been completed, that is, if the initial purge gas concentration after engine startup has been completed, or if the purge gas concentration is not being estimated, step S39 Proceed to to implement basic control.

  On the other hand, if the determination in step S32 is YES and the purge gas concentration is not yet estimated, that is, if the initial purge gas concentration after starting the engine is not completed or the purge gas concentration is being estimated. The process proceeds to step S33.

In step S33, the exhaust O ₂ feedback correction amount (O ₂ _F / B) is set to 0, and the exhaust oxygen concentration feedback control is stopped. That is, in step S33, steps S7 and S8 are omitted in the flowchart of FIG. Here, when the estimation of the purge gas concentration is not completed as described above, steps S5 and S6 are also omitted in the flowchart of FIG. Therefore, in step S33, the injection amount is set to the basic injection amount calculated in step S3 in the flowchart of FIG. After step S33, the process proceeds to step S34.

  In step S34, the estimation of the purge gas concentration is stopped. After step S34, the process proceeds to step S35.

  In step S35, it is determined whether or not a preset reference time has elapsed after the determination in step S31 is YES, that is, purge purge is started.

The reference time is a time until the combustion gas generated in the cylinder 2a immediately before the purge cut is performed passes through a portion where the linear O ₂ sensor SN5 is disposed, and is set in advance by an experiment or the like. Yes. That is, in step S35, the exhaust gas related to the purge gas generated in the cylinder 2a immediately before the purge cut (exhaust gas generated by combustion of the fuel contained in the purge gas) finishes passing through the linear O ₂ sensor SN5 and becomes the purge gas. It is determined whether or not the exhaust gas that does not include such exhaust gas has reached the linear O ₂ sensor SN5.

When determination of step S35 is NO, it returns to step S33 and implements step S34 and S35. That is, until the reference time elapses after the purge cut is started, the exhaust O ₂ feedback correction amount is maintained at 0, and feedback control of the exhaust oxygen concentration of the injection amount is continuously stopped. Then, the injection amount of the injector 11 is controlled to the basic injection amount (the basic injection amount calculated in step S3 in the flowchart of FIG. 3). In addition, the estimation of the purge gas concentration continues to be stopped.

  On the other hand, if the determination in step S35 is YES and the reference time has elapsed since the purge cut was started, the process proceeds to step S36.

  In step S36, the feedback control based on the exhaust oxygen concentration of the injection amount of the injector 11 is resumed.

As described above, in the present embodiment, when the purge cut is performed and the estimation of the purge gas concentration is incomplete (including the case where the purge gas concentration is being estimated), the estimation of the purge gas concentration is stopped and the exhaust gas is exhausted. The O ₂ feedback correction amount is set to 0, and the feedback control based on the exhaust oxygen concentration of the injection amount of the injector 11 is stopped. Then, the injection amount of the injector 11 is set to a basic injection amount that does not include the exhaust O ₂ feedback correction amount. On the other hand, when the reference time elapses after the purge cut is started, the feedback control based on the exhaust oxygen concentration of the injection amount of the injector 11 is resumed.

(4) Operation and the like As described above, in the engine system according to the present embodiment, the injection amount is feedback-controlled based on the actual exhaust oxygen concentration and the target exhaust oxygen concentration detected by the linear O ₂ sensor SN5. . For this reason, the injection amount supplied to the cylinder 2a and thus the air-fuel ratio of the air-fuel mixture in the cylinder 2a can be more reliably set to an appropriate value.

On the other hand, when the purge cut is performed before the estimation of the purge gas concentration is completed, the exhaust O ₂ feedback correction amount is set to 0, the injection amount is set as the basic injection amount, and the injection amount feedback based on the exhaust oxygen concentration is fed back. Control is stopped. Therefore, by performing this feedback control, it is possible to suppress the amount of fuel supplied into the cylinder 2a from being reduced and the air-fuel ratio of the air-fuel mixture in the cylinder 2a from becoming excessive.

This will be specifically described with reference to FIGS. FIG. 7 shows that when the control according to the present embodiment is performed and the purge cut is performed before the estimation of the purge gas concentration is completed, the exhaust O ₂ feedback correction amount is set to 0 and the injection based on the exhaust oxygen concentration is performed. The total fuel amount (the amount of fuel injected from the injector 11 and the amount of fuel contained in the purge gas) that is the total amount of fuel supplied to the cylinder 2a when the accelerator feedback control is stopped And the time variation of the air-fuel ratio of the air-fuel mixture in the cylinder 2a, the exhaust oxygen concentration, and the exhaust O ₂ feedback correction amount (exhaust O ₂ F / B amount). On the other hand, FIG. 8 is a comparative example, and shows a time change of each parameter when the feedback control is continued when the purge cut is performed before the estimation of the purge gas concentration is completed. In FIGS. 7 and 8, the time change when the purge cut is performed due to the acceleration being performed at time t <b> 1 and the operation region shifting to the region where the initial learning of the injector 11 has not been completed. Is shown. 7 and 8 show changes when purge cut is performed during the purge gas concentration estimation during the start (resumption) of the purge, and the period up to time t1, It is for this estimation that the purge flow rate is gradually increased.

  As shown in FIG. 8, purging is performed during the period up to time t1, and a predetermined amount of purge gas is introduced into the cylinder 2a. When feedback control is performed in this state, the injection amount of the injector 11 becomes smaller than the basic injection amount indicated by the broken line by the fuel amount of the purge gas. In other words, in addition to the fuel injected from the injector 11, fuel contained in the purge gas is also supplied into the cylinder 2a. Therefore, assuming that the injection amount of the injector 11 is the basic injection amount, the fuel in the cylinder 2a becomes excessive and the exhaust oxygen concentration becomes smaller than the target exhaust oxygen concentration. Therefore, feedback control based on the exhaust oxygen concentration is performed, and the exhaust O2 feedback correction amount is set to a value smaller than 0 so that the exhaust oxygen concentration becomes the target exhaust oxygen concentration, and the injection amount of the injector 11 is smaller than the basic injection amount. Value. At this time, since the estimation of the purge gas concentration is not completed as described above, the basic injection amount is the basic injection amount calculated in step S3 of FIG.

  In this state, when the acceleration is accelerated at time t1 and the purge cut is performed, the basic injection amount increases with the acceleration. However, in the example shown in FIG. 8, the feedback control is continued even after time t1. Therefore, as shown in FIG. 8, the total fuel amount becomes insufficient from time t1 to time t2, and the air-fuel ratio of the air-fuel mixture in the cylinder 2a increases.

That is, the linear O ₂ sensor SN5 is disposed at a position separated from the cylinder 2a. Therefore, when purge cut is performed at time t1 and the introduction of fuel related to the purge gas into the cylinder 2a is stopped, the air-fuel ratio of the air-fuel mixture in the cylinder 2a increases accordingly, but in the linear O ₂ sensor SN5, The change can be detected only at time t2. Therefore, even after time t1, the exhaust O ₂ feedback correction amount is the same value as that when the purge gas is introduced, which is the value immediately before time t1. Therefore, immediately after time t1, despite the purge cut being performed, the same exhaust O ₂ feedback correction amount as when purge gas is introduced is subtracted from the basic injection amount, and the total fuel amount is insufficient. As a result, the air-fuel ratio of the air-fuel mixture in the cylinder 2a increases. As a result, the feeling of acceleration deteriorates.

After time t2, the change in the air-fuel ratio of the air-fuel mixture in the cylinder 2a due to the purge cut is detected by the linear O ₂ sensor SN5. Accordingly, the exhaust O ₂ feedback correction amount increases accordingly. The total fuel amount is increased. Accordingly, the air-fuel ratio in the cylinder 2a approaches the target value.

On the other hand, as shown in FIG. 7, in this embodiment, when purge cut is performed at time t1, the exhaust O ₂ feedback correction amount is set to 0, and the feedback control is stopped. Accordingly, the total fuel amount is made the basic injection amount, and the total fuel amount is made larger than that of the comparative example of FIG. Therefore, it is possible to suppress an excessive increase in the air-fuel ratio in the cylinder 2a immediately after time t1, and the air-fuel ratio can be controlled appropriately. And thereby, acceleration performance can be improved.

  Here, when the feedback control is stopped, the exhaust oxygen concentration and the air-fuel ratio in the cylinder 2a do not completely follow the target values. However, as described above, the basic injection amount corresponds to the target exhaust oxygen concentration. Since this is a set value, the amount of deviation from these target values can be kept small.

  In this embodiment, the feedback control is resumed at the time when the reference time Lt has elapsed since the purge cut was made at time t1. Therefore, after time t3, the exhaust oxygen concentration and the air-fuel ratio in the cylinder 2a follow the target values.

  As described above, according to the present embodiment, the injection amount supplied to the cylinder 2a and thus the air-fuel ratio of the air-fuel mixture in the cylinder 2a can be more reliably set to an appropriate value.

  In the present embodiment, the purge flow rate is estimated, and the concentration of the fuel that is the purge gas concentration and contained in the purge gas is estimated. When this estimation is completed, the purge gas is included in the purge gas from these estimated values. The fuel amount is estimated and the injection amount is corrected accordingly. Therefore, the amount of fuel supplied to the cylinder 2a and the air-fuel ratio can be more reliably set to appropriate values.

  In this embodiment, the purge flow rate is gradually increased, and the purge gas concentration is estimated based on the change in the exhaust oxygen concentration at this time. That is, only the increase in the fuel amount corresponding to the increase in the purge flow rate is extracted, and the purge gas concentration is estimated based on this. Therefore, the purge gas concentration can be estimated more accurately. On the other hand, in this estimation procedure, since it is necessary to look at the change in the exhaust oxygen concentration, it takes a long time to estimate. Therefore, a purge cut may occur during the estimation of the purge gas concentration, and the air-fuel ratio of the cylinder 2a is excessively increased accordingly. There is a risk of becoming. In contrast, in the present embodiment, as described above, the air-fuel ratio can be appropriately controlled even when a purge cut occurs before the estimation of the purge gas concentration is completed. Therefore, the estimation accuracy of the purge gas concentration can be increased while appropriately controlling the air-fuel ratio.

  In the present embodiment, when the purge cut is performed, the estimation of the purge gas concentration is stopped. Therefore, although the purge gas is not introduced, the purge gas concentration is estimated based on the exhaust oxygen concentration or the like, and it is possible to suppress an increase in estimation error accompanying this.

(5) Modified Example In the above embodiment, when the purge cut occurs before the estimation of the purge gas concentration is completed, the injection amount is set to a value larger than that during feedback control by setting the exhaust O ₂ feedback correction amount to 0. However, the injection amount may be increased by a procedure other than setting the exhaust O ₂ feedback correction amount to zero. For example, the basic injection amount may be corrected with a correction amount that is smaller than the exhaust O ₂ feedback correction amount calculated during feedback control.

  Further, feedback control may be continued when a purge cut occurs before the estimation of the purge gas concentration is completed. However, if the feedback control is stopped until the reference time elapses as described above, the air-fuel ratio in the cylinder 2a can be more reliably set to an appropriate value.

In the above embodiment, the exhaust O ₂ feedback correction amount is set to 0 when the purge cut is performed before the purge gas concentration is estimated and the purge valve 24 is fully closed and the purge flow rate becomes zero. As described above, this control may be performed when the flow rate of the purge gas is less than the reference flow rate set to a value greater than 0.

  Further, in this way, when the flow rate of the purge gas is less than the reference flow rate set to a value larger than 0, the estimation of the purge gas concentration may be stopped. That is, when the flow rate of the purge gas is low, the purge gas flow rate is not stable. Therefore, the correlation between the detection result of the oxygen concentration detection means and the purge gas concentration tends to be low, and this purge gas concentration is likely to be erroneously estimated. Therefore, if the estimation of the purge gas concentration is stopped when the purge gas flow rate falls below the reference flow rate as described above, this erroneous estimation can be suppressed.

  Moreover, the operation conditions for performing purge cut are not limited to the above. In particular, the control for stopping the purge cut at the time of acceleration after the fuel cut is omitted, and the purge gas may be introduced also at the time of the acceleration after the fuel cut. On the other hand, as described above, when the operation of the engine body is started in the operation region where the initial learning of the injector 11 is not completed, it is preferable to perform the purge cut in the low flow rate region where the intake air amount is low.

Moreover, although the said embodiment demonstrated the case where an engine system had a turbocharger, the turbocharger 59 may be abbreviate | omitted. However, if the control according to this embodiment is applied to an engine that has a turbocharger and is configured to improve acceleration performance, as described above, the air-fuel ratio in the cylinder becomes excessive as the purge gas flow rate decreases. Therefore, it is possible to suppress the deterioration of the acceleration performance due to the excessive increase in the air-fuel ratio, so that the acceleration performance can be improved more reliably. When the turbocharger 59 is provided, as described above, the distance between the cylinder 2a and the linear O ₂ sensor SN5 becomes longer, and the air-fuel ratio change of the air-fuel mixture in the cylinder 2a is linear O _2. Since the time until detection by the sensor SN5 becomes longer, the influence of feedback control of the injection amount with the exhaust oxygen concentration when the purge flow rate is reduced while the estimation of the purge gas concentration is incomplete is increased. Therefore, it is more effective if the control according to the present embodiment is applied to the engine system provided with the turbocharger 59.

  In the above-described embodiment, the purge gas concentration estimation condition is assumed to be satisfied when the purge is started (including when the purge is once stopped and then restarted). When purging is continuously performed, the purge gas concentration may be periodically estimated.

1 Engine body 11 Injector (fuel supply means)
22 Canister 23 Purge passage 24 Purge valve 50 Intake passage 101 Injector initial learning section (fuel learning section)
102 Injection amount control unit (fuel control unit)
104 Purge concentration estimation unit (purge gas concentration estimation unit)
SN5 linear O ₂ sensor (exhaust oxygen concentration detection means)

Claims (8)

A fuel supply means for supplying fuel into a cylinder formed in the engine body, a canister for recovering evaporated fuel in the fuel tank, an intake passage connected to the engine body, a purge passage communicating the canister, and the purge A control apparatus for an engine comprising purge gas flow rate changing means capable of changing a flow rate of purge gas passing through a passage and exhaust oxygen concentration detecting means for detecting an oxygen concentration of exhaust gas passing through an exhaust passage connected to an engine body. And
A purge gas concentration estimator for estimating the fuel concentration of the purge gas flowing from the purge passage into the intake passage based on the oxygen concentration of the exhaust detected by the exhaust oxygen concentration detector;
A fuel control unit that controls a fuel supply amount that is the amount of fuel supplied to the cylinder by the fuel supply means;
The fuel control unit includes:
Based on the oxygen concentration of the exhaust detected by the oxygen concentration detecting means and the target value of the exhaust oxygen concentration, the fuel supply amount is feedback controlled so that these deviations approach zero,
When the purge gas flow rate changing means has reduced the purge gas flow rate to less than a preset reference flow rate and the purge gas concentration estimation unit has not yet completed the estimation of the purge gas fuel concentration, the fuel supply amount The control device for the engine is characterized in that the number is increased as compared with the case where the feedback control is performed. The engine control device according to claim 1,
The purge gas concentration estimation unit increases the flow rate of the purge gas flowing into the intake passage by the purge gas flow rate changing unit, and the oxygen concentration of the exhaust gas detected by the exhaust oxygen concentration detection unit increases with the increase of the purge gas flow rate. Estimating the fuel concentration of the purge gas based on the amount changed,
When the purge gas flow rate is reduced to less than the reference flow rate during estimation of the fuel concentration of the purge gas by the purge gas concentration estimation unit, the fuel control unit determines the fuel supply amount from the case where the feedback control is performed. An engine control device characterized in that it also increases. The engine control device according to claim 2,
The purge gas concentration estimator stops the estimation of the fuel concentration of the purge gas when the flow rate of the purge gas decreases below the reference flow rate during estimation of the fuel concentration of the purge gas. . The engine control device according to any one of claims 1 to 3,
The fuel control unit includes:
The basic fuel supply amount is set based on the engine speed and the intake air amount, and feedback correction is performed so that the deviation between the exhaust oxygen concentration detected by the oxygen concentration detecting means and the target value of the exhaust oxygen concentration approaches zero. Calculating the fuel supply amount by adding the feedback correction amount to the basic fuel supply amount,
The engine control device is characterized in that the feedback correction amount is set to zero when the purge gas flow rate is reduced below the reference flow rate before the purge gas concentration estimation unit completes the estimation of the fuel concentration of the purge gas. . An engine control apparatus according to any one of claims 1 to 4,
The fuel control unit stops the feedback control when the purge gas flow rate is reduced below the reference flow rate before the purge gas concentration estimation unit completes the estimation of the fuel concentration of the purge gas. An engine control device that resumes the feedback control when time elapses. An engine control apparatus according to any one of claims 1 to 5,
A fuel learning unit that learns a deviation amount from a command value of the fuel amount supplied from the fuel supply means in each of a plurality of operation regions;
The engine control apparatus according to claim 1, wherein the purge gas flow rate changing means is controlled so that the flow rate of the purge gas is less than the reference flow rate in an operation region where the learning by the fuel learning unit is not completed. The engine control device according to any one of claims 1 to 6,
The engine control apparatus according to claim 1, wherein the purge gas flow rate changing means is controlled so that the flow rate of the purge gas is less than the reference flow rate when the intake air amount introduced into the engine body is less than a predetermined value. The engine control device according to any one of claims 1 to 7,
The engine control device further comprising a turbocharger including a compressor provided in the intake passage and a turbine provided in the exhaust passage.

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