JP6493503B1 - Engine evaporative fuel processing device - Google Patents

Abstract

An evaporative fuel processing apparatus for an engine capable of achieving both the suppression of evaporative fuel leakage into the atmosphere and the improvement of evaporative fuel concentration learning accuracy.
An injector 12, a canister 42, a purge pipe 43 for supplying purge fuel from the canister 42 to an intake passage 30, a purge valve 45 capable of opening and closing the purge pipe 43, a purge gas concentration is learned, and the purge valve 45 and the injector The PCM 100 controls the fuel injection amount of the injector 12 based on the purge gas concentration, and the PCM 100 prohibits learning of the purge gas concentration when the fuel injection amount after the reduction correction is smaller than the minimum injection amount Qinj_min. At the same time, when the prohibition of purge gas concentration learning continues for a predetermined period, the purge gas supplied to the intake passage 30 of the engine is reduced so that the fuel injection amount becomes larger than the minimum injection amount Qinj_min.
[Selection] FIG.

Description

  The present invention relates to an evaporated fuel processing apparatus for an engine, and more particularly to an evaporated fuel processing apparatus for an engine that learns the evaporated fuel concentration when supplying evaporated fuel via a purge valve and controls a purge valve and a fuel injection valve.

Conventionally, the evaporated fuel generated in the fuel tank is supplied into the cylinder through the intake passage and burned, thereby suppressing the release of the evaporated fuel into the atmosphere.
Further, since the evaporated fuel supplied into the cylinder affects the air-fuel ratio of the engine, the fuel concentration of the gas containing the evaporated fuel supplied into the cylinder, that is, the so-called purge gas concentration (hereinafter referred to as purge gas concentration) is learned. Controlling the injection amount of the fuel injection valve based on the purge gas concentration is also performed.

The control device for an internal combustion engine disclosed in Patent Document 1 is based on the engine stop time, the outside air temperature when the engine is stopped and the outside air temperature when the engine is started, the fuel temperature when the engine is stopped, and the fuel temperature when the engine is started. The amount of change in the purge gas concentration during the period is estimated, and the amount of change in the purge gas concentration during the engine stop period is used to correct the learned value of the purge gas concentration learned before the engine is stopped to set the highly accurate purge gas concentration. ing.
This prevents the exhaust emission and drivability from deteriorating due to the deviation of the learning value of the purge gas concentration during the engine stop period.

JP 2009-299627 A

In order to sufficiently suppress leakage of evaporated fuel to the atmosphere, it is necessary to maximize the amount of evaporated fuel supplied into the cylinder, in other words, to minimize the amount of fuel injected by the fuel injection valve.
On the other hand, because of the structure of the fuel injection valve, it is difficult to ensure the linearity characteristics between the injection pulse and the injection amount below a predetermined lower limit value, and there is a concern about engine torque fluctuation accompanying injection quantity fluctuation. The predetermined lower limit value of the fuel injection valve is greatly affected by aging degradation.
That is, when the fuel injection amount is smaller than the minimum injection amount that can ensure the linearity characteristic, there is a possibility that a deviation occurs between the target injection amount of the fuel injection valve and the fuel injection amount actually injected into the cylinder. It is not easy to grasp the exact amount of fuel supplied into the cylinder.

The control device for an internal combustion engine of Patent Document 1 improves the learning accuracy of the purge gas concentration at the time of starting the engine by correcting the learned value of the purge gas concentration learned before the engine is stopped.
However, in the technique of Patent Document 1, the purge flow rate is merely set based on the engine operating state, the learned value of the purge gas concentration, and the like, and in order to sufficiently suppress the leakage of evaporated fuel into the atmosphere, There is no mention of maximizing the amount of fuel vapor supplied to the plant.
Moreover, no consideration is given to the fact that the linearity characteristic between the injection pulse and the injection amount cannot be ensured below a predetermined lower limit value.
That is, in the technique of Patent Document 1, when the amount of evaporated fuel supplied into the cylinder is maximized, the linearity characteristic of the fuel injection valve cannot be ensured, so that the learning accuracy of the purge gas concentration may be lowered. It is necessary to improve.

  An object of the present invention is to provide an evaporative fuel processing device for an engine and the like capable of achieving both suppression of evaporative fuel leakage to the atmosphere and improvement of evaporative fuel concentration learning accuracy.

The fuel vapor processing apparatus for an engine according to claim 1 is a fuel injection valve for supplying fuel to the engine, a canister for adsorbing the fuel vapor evaporated in the fuel tank, and fuel vapor for the canister being supplied to the intake passage of the engine The engine is provided with a purge passage, a purge valve capable of opening and closing the purge passage, and a control means for learning the concentration of evaporated fuel when supplying evaporated fuel via the purge valve and controlling the purge valve and the fuel injection valve In the fuel processing apparatus, the control means reduces the fuel injection amount of the fuel injection valve based on the evaporated fuel concentration, and the fuel injection amount after the reduction correction is less than the minimum injection amount that ensures the linearity characteristic of the fuel injection valve. The evaporative fuel concentration learning is prohibited when it becomes less, and the evaporative fuel concentration learning prohibition continues for a predetermined period. Can, is characterized by weight loss of the supply amount of evaporative fuel supplied to the intake passage of the engine to the fuel injection amount is larger than the minimum injection amount.

In the fuel vapor processing apparatus for the engine, the control means reduces the fuel injection amount of the fuel injection valve based on the fuel vapor concentration. The fuel injection amount after the reduction correction secures the linearity characteristic of the fuel injection valve. Since the evaporative fuel concentration learning is prohibited when the amount is less than the amount, the inaccurate evaporative fuel concentration learning including the deviation component of the fuel injection valve is prohibited, thereby reducing the evaporative fuel concentration learning accuracy. Can be suppressed.
In addition, when the prohibition of the evaporative fuel concentration learning continues for a predetermined period, the control means reduces the supply amount of the evaporative fuel supplied to the intake passage of the engine so that the fuel injection amount becomes larger than the minimum injection amount. Therefore, the error in the evaporated fuel concentration learning value caused by the learning prohibition period can be eliminated at an early stage, and a large amount of fuel can be produced in a short time while suppressing fluctuations in the engine torque accompanying fluctuations in the fuel injection valve injection quantity. Evaporated fuel can be supplied to the engine.

The invention of claim 2 is characterized in that, in the invention of claim 1, the predetermined period is set by an elapsed time from the start of prohibition of the evaporative fuel concentration learning.
According to this configuration, the evaporative fuel concentration learning prohibition period can be set with a simple configuration.

According to a third aspect of the present invention, in the first aspect of the invention, the predetermined period is set by an integrated amount of evaporated fuel supplied to the intake passage of the engine from the start of prohibition of the evaporated fuel concentration learning. Yes.
According to this configuration, an error in the evaporated fuel concentration learning value caused by the learning prohibited period can be detected at an early stage, and the prohibited period of evaporated fuel concentration learning can be set with high accuracy.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the control means increases the fuel supply amount by a predetermined amount greater than the minimum injection amount. It is characterized by weight loss.
According to this configuration, the amount reduction correction for reducing the fuel injection amount of the fuel injection valve can be resumed from the time when the linearity characteristic of the fuel injection valve can be reliably ensured, and a large amount of evaporated fuel can be supplied to the engine at an early stage. Can do.

The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the control means sets a reference target fuel amount that is a target value of a total fuel amount to be supplied to the engine based on an operating state. When the purge valve is opened to supply the evaporated fuel to the intake passage and the evaporated fuel concentration is learned , the fuel injection amount is set to the minimum injection amount and the evaporated fuel is set to the reference target fuel amount. The fuel injection valve and the purge valve are controlled so as to obtain a maximum target evaporated fuel amount that is an amount obtained by subtracting the minimum injection amount from
According to this configuration, at the time of purge execution, the reference target fuel amount can be realized by the fuel supply by the fuel injection valve and the fuel supply by the purge, and the engine torque can be maintained at an appropriate value. Controllability of the quantity can be ensured.

  According to the evaporated fuel processing apparatus for an engine of the present invention, it is possible to achieve both the suppression of the leakage of evaporated fuel into the atmosphere and the improvement of the learning accuracy of the evaporated fuel concentration.

1 is a schematic view of an engine system to which an evaporated fuel processing apparatus for an engine according to an embodiment of the present invention is applied. It is the block diagram which showed the control system of the engine system. It is another figure which shows the relationship between the drive timing of a purge valve output part, and the opening / closing timing of a purge valve. It is the flowchart which showed the control procedure of the purge valve. It is the flowchart which showed the first half part of the calculation procedure of target purge mass flow rate. It is the flowchart which showed the second half part of the calculation procedure of target purge mass flow rate. It is the flowchart which showed the control procedure of the injector. It is the flowchart which showed the learning procedure of purge gas concentration. It is the flowchart which showed the control procedure of the throttle. It is the figure which showed the relationship between the injection pulse width and the injection quantity. It is the figure which showed the relationship between the injection quantity and dispersion | variation. 6 is a time chart showing the relationship among a command injection amount, a target purge mass flow rate, and a purge gas concentration learning value.

(1) Overall Configuration of Engine FIG. 1 is a diagram showing a configuration of an engine system to which an evaporated fuel processing apparatus for an engine according to an embodiment of the present invention is applied. The engine system of the present embodiment has a four-stroke engine 1, an intake passage 30 for introducing (intakes) combustion air into the combustion chamber 5 of each cylinder 2, and exhausting exhaust from the engine 1 to the outside. An exhaust passage 35, a fuel tank 41 for storing fuel, and a purge system 40 for supplying evaporated fuel generated in the fuel tank 41 to the engine 1. This engine system is provided in a vehicle, and the engine 1 is used as a drive source for the vehicle. The engine 1 is, for example, a four-cylinder engine having four cylinders 2 arranged in a direction orthogonal to the plane of FIG. 1, and is a gasoline engine mainly using gasoline as fuel.

The engine 1 has a cylinder block 3 in which a cylinder 2 is formed, a cylinder head 4 provided on the upper surface of the cylinder block 3, and a piston 11 that is inserted into the cylinder 2 so as to be slidable back and forth. . A combustion chamber 5 is formed above the piston 11.
The piston 11 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 11. The cylinder block 3 is provided with a rotational speed sensor SN1 that detects the rotational speed of the crankshaft 15 as the rotational speed of the engine.

The cylinder head 4 includes an injector 12 (fuel injection valve) and a spark plug 13 for igniting a mixture of fuel and air injected from the injector 12 by spark discharge, one for each cylinder 2. Is provided.
The injector 12 has a plurality of injection holes serving as fuel injection ports at the tip, and is provided so as to face the combustion chamber 5 of each cylinder 2 from the side on the intake side. A fuel rail 14 for storing fuel is connected to the injector 12 inside. The fuel rail 14 is connected to a fuel tank 41 via a pipe (not shown), and the fuel fed from the fuel tank 41 is stored in the fuel rail 14. The injector 12 receives the supply of fuel stored in the fuel rail 14 and injects the fuel into the cylinder 2.

The fuel rail 14 is provided with a fuel pressure sensor SN5 capable of detecting the fuel pressure stored in the fuel rail 14, that is, the fuel pressure injected by the injector 12.
The spark plug 13 has an electrode for discharging sparks at the tip, and is provided so as to face the combustion chamber 5 of each cylinder 2 from above.
The cylinder head 4 includes an intake port 6 for introducing air supplied from the intake passage 30 into the combustion chamber 5 of each cylinder 2, an intake valve 8 that opens and closes the intake port 6, and the combustion chamber 5 of each cylinder 2. Are provided with an exhaust port 7 for leading the exhaust gas generated in step 1 to the exhaust passage 35 and an exhaust valve 9 for opening and closing the exhaust port 7.

The intake passage 30 is composed of a single intake pipe 33 and a plurality of (four) independent intake passages 31 (in a direction orthogonal to the plane of FIG. 1) that individually connect the intake pipe 33 and the intake port 6 of each cylinder 2. Are lined up). A surge tank 32 having a predetermined volume is provided at the downstream end of the intake pipe 33, and an independent intake passage 31 extends from the surge tank 32 to each intake port 6.
A throttle valve 34 capable of opening and closing the passage of the intake pipe 33 is provided in a portion upstream of the surge tank 32 in the intake pipe 33.

  An air flow sensor SN <b> 2 for detecting the flow rate of air (intake air) taken into the engine 1 through this portion is provided on the upstream side of the throttle valve 34 in the intake pipe 33. In addition, the surge tank 32 is provided with an intake pressure sensor SN3 for detecting the pressure in the surge tank 32, that is, the pressure in the portion of the so-called intake pipe 33 downstream of the throttle valve 34.

  The exhaust passage 35 includes four independent exhaust passages 36 communicating with the exhaust ports 7 of the cylinders 2 and one exhaust pipe extending downstream from a portion where the downstream end portions of the independent exhaust passages 36 are gathered in one place. 38. In the present embodiment, the independent exhaust passages 36 of the two cylinders 2 whose exhaust order (the order in which the exhaust stroke is performed) are gathered in one passage, and the independent exhausts of the two cylinders 2 whose exhaust order is not continuous The passages 36 gather into one passage, and then these two passages are collected in the exhaust pipe 38. The exhaust pipe 38 is provided with a catalyst device 90 containing a catalyst such as a three-way catalyst.

Further, the exhaust passage 35 is provided with an A / F sensor SN4 for detecting the air-fuel ratio (ratio of air to fuel) of the exhaust gas, and thus the air-fuel mixture in the combustion chamber 5.
The purge system 40 includes a canister 42 that detachably adsorbs the evaporated fuel evaporated in the fuel tank 41, a purge air pipe 49 that introduces air into the canister 42, and a purge pipe 43 that connects the canister 42 and the intake pipe 33 ( Purge passage). The purge pipe 43 is connected to a portion of the intake pipe 33 between the throttle valve 34 and the surge tank 32.

The evaporated fuel adsorbed by the canister 42 is attached to and detached from the canister 42 by the air introduced from the purge air pipe 49. The evaporated fuel detached from the canister 42 is introduced into the intake pipe 23 through the purge pipe 43 together with air.
Hereinafter, a gas composed of evaporated fuel and air flowing through the purge pipe 43 is referred to as a purge gas.
The evaporated fuel contained in the purge gas is called purge fuel.

The purge pipe 43 is provided with a purge valve 45 that opens and closes the purge pipe 43. The purge valve 45 is a DUTY control valve, and is opened and closed by changing the DUTY ratio, which is the ratio of the valve opening period to the unit period that combines the valve opening period and the valve closing period. Has been changed.
The purge valve 45 is an electromagnetic valve, and the DUTY ratio is a ratio of the energization period to the unit period including one energization period and one non-energization period. The purge valve 45 is fully closed when the DUTY ratio is 0% and fully opened when 100%.
Hereinafter, opening the purge valve 45 and introducing purge gas into the intake pipe 33 (each cylinder 2) is referred to as performing purge.

(2) Control system The control system of an engine system is demonstrated using FIG. The engine system of this embodiment is controlled by a PCM (powertrain control module) 100 mounted on a vehicle. The PCM 100 is a microprocessor including a CPU, a ROM, a RAM, an I / F, and the like, and corresponds to a control unit according to the present invention.

Information from various sensors is input to the PCM 100. For example, the PCM 100 is electrically connected to the rotation speed sensor SN1, the airflow sensor SN2, the intake pressure sensor SN3, the A / F sensor SN4, and the fuel pressure sensor SN5, and receives input signals from these sensors.
The vehicle is also provided with an accelerator opening sensor SN6 for detecting the opening of an accelerator pedal (not shown) operated by a passenger, a vehicle speed sensor SN7 for detecting the vehicle speed, and the detection signals from these sensors are also sent to the PCM 100. Entered.
The PCM 100 executes various calculations based on input signals from the sensors (SN1 to SN7, etc.), and drives the injector 12, the purge valve 45 (actuator that drives the purge valve 45), and the throttle valve 34 (drives the throttle valve 34). Control signals by outputting command signals to the actuator).

The PCM 100 includes an injector control unit 102, a purge valve control unit 104, and a throttle valve control unit 106 as functional elements.
The injector control unit 102 performs a calculation related to the injector 12 and calculates a fuel injection amount that is a fuel amount injected from the injector 12 into the cylinder 2.
The purge valve control unit 104 performs a calculation related to the purge valve 45 and calculates a command value of the DUTY ratio of the purge valve 45 (hereinafter referred to as a purge valve command DUTY ratio as appropriate).
The throttle valve 34 performs calculations related to the throttle valve 34 and calculates a command value for the opening of the throttle valve 34.

  The PCM 100 also outputs an instruction signal corresponding to the fuel injection amount calculated by the injector control unit 102 to the injector 12, and an instruction signal corresponding to the purge valve command DUTY ratio calculated by the purge valve control unit 104. Is output to the purge valve 45, and the throttle valve output unit 116 is configured to output the throttle valve 34 command value calculated by the throttle valve control unit 106 to the throttle valve 34.

Each of the control units 102, 104, and 106 performs an operation at a predetermined frequency, and each of the output units 112, 114, and 116 inputs a command signal from each of the control units 102, 104, and 106 at a predetermined frequency. To output a signal.
In the present embodiment, the driving frequency of the purge valve output unit 114 (frequency for reading the purge valve command DUTY ratio to the purge valve control unit 104) and the opening / closing frequency of the purge valve 45 are set to the same frequency. Therefore, as shown in FIG. 3, the purge valve 45 is opened for an ON time which is a time obtained by multiplying the drive cycle T of the purge valve output unit 114 by the purge valve command DUTY ratio, and this ON time is determined from the drive cycle T of the purge valve output unit 114. Is closed for a period of time reduced, and the opening and closing of the purge valve output unit 114 is repeated every driving cycle T.

  Next, the calculation procedure of each control unit 102, 104, 106 will be described.

(Purge valve control procedure)
First, the control procedure of the purge valve 45 will be described with reference to FIGS.
Si (i = 1, 2,...) Indicates steps for each process.
As shown in the flowchart of FIG. 4, the PCM 100 first reads detection values of the sensors SN1 to SN7 and the like (S1).

Next, in S2, the PCM 100 calculates a throttle limit flow rate.
The throttle limit flow rate is a throttle passage air flow rate which is a mass flow rate of air passing through the throttle valve 34 when the throttle valve 34 is at the minimum opening. The minimum opening is the smallest opening among the openings at which the throttle valve 34 can properly change the throttle passing air flow rate by changing the opening. That is, the flow rate of air passing through the throttle can be basically changed by changing the opening of the throttle valve 34. However, when the opening of the throttle valve 34 is set to a very small opening near the fully closed position, the throttle valve Even if the opening degree change of 34 is performed, the throttle passage air flow rate becomes less than a predetermined value close to 0 and hardly changes, and the minimum opening degree is an opening degree at which the throttle passage air flow rate becomes a predetermined value or less. The throttle minimum opening is set in advance, and is set to 0.5% of the fully opened opening, for example. Further, the throttle limit flow rate is set in advance by experiments or the like. For example, the PCM 100 stores a table of engine speed and throttle limit flow rate, and extracts a value corresponding to the current engine speed from this table.

Next, in S3, the PCM 100 calculates a target intake air amount. The target intake air amount is a mass flow rate of air to be supplied to the engine 1 (specifically, to be supplied to each cylinder 2).
The PCM 100 calculates a required torque that is a torque required for the engine 1 based on the accelerator opening, the vehicle speed, and the like, and calculates and calculates the charging efficiency of the cylinder 2 necessary to realize the required torque. A target intake air amount is calculated based on the charging efficiency and the engine speed.

Next, in S4, the PCM 100 calculates a cylinder required fuel amount Qcyl (reference target fuel amount) based on the operating state of the engine body. The cylinder required fuel amount Qcyl is the total amount of fuel to be supplied to the engine 1 (specifically, to be supplied to each cylinder 2).
The PCM 100 calculates the required cylinder fuel amount Qcyl based on the charging efficiency calculated as described above, the engine speed, and the like.

Next, in S5, the PCM 100 determines whether or not a purge execution condition that is an operation condition for executing the purge is satisfied. For example, when the fuel is cut, it is determined that the purge execution condition is not satisfied.
If the determination in S5 is NO and the purge execution condition is not satisfied, the PCM 100 proceeds to S6 to stop the purge, and is the target value of the volume flow rate of the purge gas introduced into the engine 1 (each cylinder 2). The target purge volume flow rate is set to 0, and the process proceeds to S14.
On the other hand, if the determination in S5 is YES and the purge execution condition is satisfied, the PCM 100 proceeds to S7.

In S7, the PCM 100 sets a minimum injection amount Qinj_min. The minimum injection amount Qinj_min is a minimum value of the injection amount of the injector 12 that ensures the linearity characteristic of the injector 12. Specifically, under a condition where the fuel pressure is constant, the injection amount of the injector 12 basically increases or decreases in proportion to the command value.
However, as shown in FIG. 10 in which the horizontal axis is the injection period corresponding to the injection pulse width, that is, the injection amount command value, and the vertical axis is the actual injection amount, the injection amount and the injection are in the region A1 where the injection amount is less than the predetermined amount. The injection amount is proportional to the injection pulse width only in the region A2 where the injection amount is not less than the predetermined amount, and the minimum injection amount Qinj_min corresponding to the injection pulse width τmin is not proportional to the pulse width. It is quantitative.

Here, the minimum injection amount Qinj_min varies depending on the fuel pressure.
Therefore, in S7, the minimum injection amount Qinj_min is set based on the fuel pressure.
In the present embodiment, the PCM 100 stores a relationship between the fuel pressure previously obtained through experiments or the like and the minimum injection amount Qinj_min in a table, and the PCM 100 uses the table to determine a value corresponding to the current fuel pressure from the minimum injection amount. Extracted as Qinj_min.

In S8, it is determined whether or not the flag F is 1.
If the flag F is 1 as a result of the determination in S8, since learning of the fuel concentration of the purge gas (hereinafter referred to as purge gas concentration) is being executed, the process proceeds to S9.
If the flag F is not 1 as a result of the determination in S8, since the purge gas concentration learning is not executed, the process proceeds to S10. Note that 1 is assigned to the flag F while the purge gas concentration learning is being executed, and 0 is assigned to the flag F while the purge gas concentration learning is stopped.

Next, in S9, a target maximum purge fuel amount Qcharge_max is calculated.
This target maximum purge fuel amount Qcharge_max is the maximum value of the evaporated fuel amount that can be supplied to the engine 1 (each cylinder 2) in a state where the linearity characteristics of the injector 12 are ensured and the output torque of the engine 1 is set to the required torque. It is calculated by subtracting the minimum injection amount Qinj_min from the cylinder required fuel amount Qcyl.

Next, in S10, it is determined whether or not a predetermined time has elapsed since the purge gas concentration learning was prohibited.
As a result of the determination in S10, when a predetermined time has elapsed since the purge gas concentration learning was prohibited, the process proceeds to S11, and when the predetermined time has not elapsed since the purge gas concentration learning was prohibited, the process proceeds to S12. In this embodiment, the learning prohibition period is counted by a predetermined timer mechanism (not shown) from the time when the purge gas concentration learning is prohibited, and compared with a predetermined time set in advance as a determination threshold.

In S11, the target maximum purge fuel amount Qcharge_max is gradually decreased, and the process proceeds to S12.
Specifically, a value obtained by subtracting the reference decrease amount β from the target maximum purge fuel amount Qcharge_max held last time is corrected as a target maximum purge fuel amount Qcharge_max.
The reference decrease amount β is stored in advance by experiments or experience values.
In S12, the current target maximum purge fuel amount Qcharge_max is held.
Thus, during the purge gas concentration learning prohibition period, the target maximum purge fuel amount Qcharge_max calculated in S9 is held, and after the end of the purge gas concentration learning prohibition period, the target maximum corrected by the reference decrease amount β is decreased. The purged fuel amount Qcharge_max is held.

Next, in S13, a target purge mass flow rate is calculated based on the target maximum purge fuel amount Qcharge_max.
5 and 6 are flowcharts showing the calculation procedure of the target purge mass flow rate in S13.

  As shown in FIG. 5, the PCM 100 first calculates the target maximum intake manifold equivalent ratio based on the target maximum purge fuel amount Qcharge_max and the like (S21). The intake manifold equivalent ratio is the equivalent ratio of gas in the intake pipe 33 (specifically, the equivalent ratio of the gas in the intake pipe 33 immediately before being introduced into the cylinder 2), and the target maximum intake manifold equivalent ratio is the target maximum This is the intake manifold equivalent ratio that is estimated to be realized when the evaporated fuel corresponding to the purge fuel amount Qcharge_max is introduced into the intake pipe 33.

  Specifically, the PCM 100 calculates the mass flow rate of the purge gas necessary for introducing the purge fuel corresponding to the target maximum purge fuel amount Qcharge_max into the intake pipe 33 from the target maximum purge fuel amount Qcharge_max and the purge gas concentration. The target maximum intake manifold equivalent ratio is calculated from the gas amount obtained by combining the mass flow rate of the purge gas and the mass flow rate of the air detected by the air flow sensor SN2 (hereinafter referred to as the fresh air amount) and the target maximum purge fuel amount Qcharge_max. The procedure for calculating the purge gas concentration will be described later.

  In this embodiment, the intake manifold equivalent ratio is configured to increase toward the target maximum intake manifold equivalent ratio. In S22 to S24, the temporary target intake manifold equivalent ratio (the target value of the intake manifold equivalent ratio at each time) ( i) is gradually increased toward the target maximum intake manifold equivalent ratio.

  Specifically, in S22, the temporary target intake manifold equivalent ratio (i) is calculated by adding the reference increase amount to the temporary target intake manifold equivalent ratio (i-1) that is the previously calculated temporary target intake manifold equivalent ratio. To do. The initial value of the provisional target intake manifold equivalent ratio is 0, and the reference increase amount is a preset value. In the present embodiment, the temporary target intake manifold equivalent ratio is initialized (returned to 0) when the vehicle is stopped, and the purge is stopped along with the fuel cut or the like while the vehicle is running. Even if it is done.

  Next, in S23, it is determined whether or not the provisional target intake manifold equivalent ratio (i) is greater than or equal to the target maximum intake manifold equivalent ratio. If this determination is YES, the provisional target intake manifold equivalent ratio (i) is set to the target maximum intake manifold equivalent ratio in S24, and the process proceeds to S25. On the other hand, if the determination in S23 is NO, the process proceeds to S25.

  Here, the purge valve 45 is controlled so that the provisional target intake manifold equivalent ratio (i) is realized. Therefore, basically, the intake manifold equivalent ratio becomes the provisional target intake manifold equivalent ratio (i). For example, sufficient purge fuel is introduced into the intake pipe 33 because the actual value of the purge gas concentration is lower than the estimated value. If this is not possible, the provisional target intake manifold equivalent ratio (i) greatly deviates from the current intake manifold equivalent ratio (estimated value), and the temporary target intake manifold equivalent ratio (i) becomes excessive. Therefore, in the present embodiment, when the deviation amount is large, the provisional target intake manifold equivalent ratio (i) is corrected so as to approach the actual intake manifold equivalent ratio.

  Specifically, in S25, it is determined whether or not the difference between the provisional target intake manifold equivalent ratio (i) and the current intake manifold equivalent ratio is less than a preset reference deviation amount. Note that the current intake manifold equivalent ratio is separately estimated based on the detection value of the A / F sensor, the intake air amount, the intake pressure, and the like.

If the determination in S25 is NO and the difference between the temporary target intake manifold equivalent ratio (i) and the current intake manifold equivalent ratio is large, the process proceeds to S26, and the temporary target intake manifold equivalent ratio (i) is corrected. Specifically, the provisional target intake manifold equivalent ratio (i) is corrected so as to approach the current intake manifold equivalent ratio. Thereafter, the process proceeds to S27.
On the other hand, if the determination in S25 is YES and the difference between the provisional target intake manifold equivalent ratio (i) and the current intake manifold equivalent ratio is small, the process proceeds to S27.

  In S27, a temporary target purge mass flow rate is calculated based on the calculated temporary target intake manifold equivalent ratio (i). The provisional target purge mass flow rate is the mass flow rate of purge gas necessary to realize the provisional target intake manifold equivalent ratio (i), and is calculated based on the provisional target intake manifold equivalent ratio (i), the fresh air amount, and the purge gas concentration. The

Next, in S28, the temporary target purge mass flow rate calculated in S27 is temporarily advanced and corrected to determine the target value of the purge gas mass flow rate in the vicinity of the purge valve 45.
That is, the provisional target intake manifold equivalent ratio (i) is a target value of the equivalent ratio of the gas in the intake pipe 33 immediately before being introduced into the cylinder 2, and before the purge gas reaches the cylinder 2 from the vicinity of the purge valve 45. There is a delay. Therefore, in the present embodiment, this delay is treated as a primary delay, the temporary target purge mass flow rate calculated based on the temporary target intake manifold equivalent ratio (i) is corrected to the primary advance, and the purge mass to be realized in the vicinity of the purge valve 45 A provisional target purge mass flow rate, which is a flow rate target value, is calculated.

In S29 shown in FIG. 6, the throttle limit flow rate calculated in S2 is subtracted from the target intake air amount calculated in S3, and the subtracted value is set as the upper limit purge amount.
Next, in S30, it is determined whether or not the provisional target purge mass flow rate calculated in S28 is equal to or less than the upper limit purge amount.

If the determination in S30 is NO and the provisional target purge mass flow rate is larger than the upper limit purge amount, the process proceeds to S31, and the target purge mass flow rate is set to the upper limit purge amount.
On the other hand, if the determination in S30 is YES, the process proceeds to S32, and the target purge mass flow rate is set to the provisional target purge mass flow rate set in S28.
In this way, in the present embodiment, the target purge mass flow rate is set within a range that does not exceed the upper limit purge amount, that is, the amount obtained by subtracting the throttle limit flow rate from the target intake air amount. The target purge mass flow rate is set so that the amount of evaporated fuel introduced into the inside gradually increases toward the target maximum purge fuel amount Qcharge_max.

Returning to FIG. 4, after the target purge mass flow rate is set, the process proceeds to S14.
In S14, the target purge volume flow rate is calculated by converting the target purge mass flow rate into the volume flow rate based on the temperature and pressure of the purge gas.
In the present embodiment, the temperature and pressure of the purge gas are atmospheric temperature and pressure.

After execution of S14, a purge valve command DUTY ratio is calculated based on the target purge volume flow rate (S15).
In this embodiment, the differential pressure across the purge valve 45 is calculated, and the purge valve command DUTY ratio is determined based on this differential pressure and the target purge volume flow rate.

Specifically, the pressure loss of the purge pipe 43 is calculated, and the value obtained by subtracting this pressure loss from the atmospheric pressure is set as the pressure upstream of the purge valve 45 of the purge pipe 43, and the intake pressure detected by the intake pressure sensor SN3. Is the pressure downstream of the purge valve 45, and the differential pressure across the purge valve 45 is calculated. Further, the relationship between the differential pressure, the purge volume flow rate, and the DUTY ratio of the purge valve is set in advance by a map by experiment or the like and stored in the PCM 100. The PCM 100 calculates the differential pressure before and after the purge valve 45 from this map. Then, the DUTY ratio corresponding to the target purge volume flow rate is extracted and determined as the purge valve command DUTY ratio.
When the process proceeds to S6 and the target purge volume flow rate is set to 0, the purge valve command DUTY ratio becomes 0%.

In S16, it is determined whether or not the purge valve command DUTY ratio is 0% or less.
As a result of the determination in S16, when the purge valve command DUTY ratio is greater than 0%, that is, when the purge valve 45 is opened (including when the valve opening is continued), the process proceeds to S17.
In S17, the drive frequency of the purge valve output unit 114 and the opening / closing frequency of the purge valve 45 are set based on the engine speed and the like. In the present embodiment, the higher the engine speed, the higher the driving frequency of the purge valve output unit 114 is set, and the higher the purge gas concentration, the higher the driving frequency of the purge valve output unit 114. Set.

  Specifically, in the present embodiment, when the engine speed is equal to or lower than a preset first speed, the drive frequency of the purge valve output unit 114 is set to the first frequency, and the engine speed is greater than the first speed and When the rotation speed is lower than the second rotation speed (> first rotation speed), the drive frequency is set to a second frequency higher than the first frequency. When the engine rotation speed is higher than the second rotation speed, the drive frequency is set to be higher than the second frequency. Is set to a high third frequency. The first frequency, the second frequency, and the third frequency are set to 5 Hz, 10 Hz, and 15 Hz, respectively, for example.

On the other hand, S1 6 result of the determination in the case purge valve command DUTY ratio is less than 0%, if the purge valve 45 is closed (even if the closing is continued), the process proceeds to S18.
In S18, the drive frequency of the purge valve output unit 114 is set to the maximum frequency regardless of the engine speed. This maximum frequency is a frequency set in S13, that is, a frequency higher than the drive frequency of the purge valve output unit 114 set when the purge valve 45 is open, and is set in advance.

The maximum frequency is set to the drive frequency (calculation frequency) of the purge valve control unit 104. That is, the drive frequency of the purge valve control unit 104 is set to be higher than the drive frequency of the purge valve output unit 114 when the purge valve 45 is open, and when the purge valve 45 is closed, The drive frequency of the purge valve output 114 is set to the drive frequency of the purge valve control unit 104. The drive frequency of the purge valve control unit 104 is, for example, 100 Hz.
Thus, in this embodiment, when the purge valve 45 is closed, the drive frequency of the purge valve output unit 114 is set to the maximum frequency, and the purge valve output unit 114 reads the signal to the purge valve control unit 104 in the shortest cycle. A signal is output to the purge valve 45 at the shortest cycle.

  After S17 or S18, the process proceeds to S19. In S19, the purge valve command DUTY ratio signal set in S11 is output to the purge valve 45 at the drive frequency set in S17 or S18.

(Injector control procedure)
Next, the calculation procedure of the injection amount of the injector 12 (command injection amount which is a command value of the injection amount of the injector 12) will be described using FIG.
The injector control process is repeatedly executed at a predetermined cycle, and is executed in parallel with the purge valve control process shown in FIGS.

  First, in S41, the PCM 100 reads the cylinder required fuel amount Qcyl calculated in S4, the purge valve command DUTY ratio set in S15, and the like.

Next, in S42, the actual purge volume flow rate that is the current purge volume flow rate and the volume flow rate of the purge gas introduced into the engine 1 is estimated.
Specifically, after calculating the basic volumetric flow rate of the purge gas based on the current DUTY ratio of the purge valve 45 and the differential pressure across the purge valve 45 calculated in the calculation process of S11, The flow rate of the purge gas is estimated by correcting with the voltage supplied to the purge valve 45, the drive frequency of the purge valve 45 (drive frequency of the purge valve output unit 114), and the temperature around the purge valve 45.

Next, in S43, the actual purge volume flow rate calculated in S42 is converted into a mass flow rate to calculate the actual purge mass flow rate, and the actual purge fuel amount Qpurge_r that is the amount of evaporated fuel currently introduced into the engine 1 is estimated. (S44). Specifically, the actual purge fuel amount Qcharge_r is calculated based on the actual purge mass flow rate and the purge gas concentration calculated in S43.
Next, in S45, a value obtained by subtracting the actual purge fuel amount Qpurge_r from the cylinder required fuel amount Qcyl is calculated as a basic injection amount, and this basic injection amount is A / F_feedback corrected to calculate a command injection amount (S46). ).
In the present embodiment, the injection amount of the injector 12 is corrected so that the actual air-fuel ratio of the gas in the exhaust passage 35 detected by the A / F sensor SN4 becomes a preset target value. The basic injection amount is corrected with this correction amount.

In S47, the command injection amount calculated in S46 is injected into the injector 12.
Thus, in the present embodiment, the injection amount of the injector 12 is basically set to an amount obtained by subtracting the actual purge fuel amount Qpurge_r, that is, the amount of purge fuel introduced into the engine 1, from the cylinder required fuel amount Qcyl. .

(Purge concentration estimation procedure)
Next, the learning procedure of the purge gas concentration used in S44 will be described.
As shown in the flowchart of FIG. 8, first, the PCM 100 determines whether or not a purge execution condition, which is an operation condition for executing the purge, is satisfied (S51).
If the purge execution condition is satisfied as a result of the determination in S51, the process proceeds to S52, and if the purge execution condition is not satisfied, the process proceeds to S60.

Next, in S52, it is determined whether or not the command injection amount calculated in S46 is larger than a value obtained by adding the determination threshold value α to the minimum injection amount Qinj_min.
As shown in FIG. 11 in which the horizontal axis indicates the injection amount of the injector 12 and the vertical axis indicates variations between the target injection amount and the actual injection amount, the variation in the vicinity of the minimum injection amount Qinj_min increases due to the structure of the injector 12. Therefore, the purge gas concentration cannot be learned with a correct value. Therefore, in the present embodiment, the purge gas concentration learning is performed in a region where the command injection amount is larger than the value obtained by adding the determination threshold value α to the minimum injection amount Qinj_min having a small variation.
The determination threshold value α is obtained in advance by experiments or experience values.

If the command injection amount is larger than the value obtained by adding the determination threshold value α to the minimum injection amount Qinj_min as a result of the determination in S52, the actual air-fuel ratio is detected by the A / F sensor SN4 (S53), and the process proceeds to S54.
In S54, a deviation (deviation) between a preset target value of the air-fuel ratio of the exhaust passage 35 and the actual air-fuel ratio is detected, and the process proceeds to S55.
In S55, the purge gas concentration is estimated by learning.
Specifically, assuming that the deviation detected in S54 is caused by supplying evaporated fuel to the engine 1, the purge gas concentration is estimated and calculated based on this deviation amount and the flow rate of the purge gas.
In S56, 1 is substituted into the flag F, the set purge gas concentration is held (S57), and the process returns.

As a result of the determination in S52, when the command injection amount is equal to or smaller than the value obtained by adding the determination threshold value α to the minimum injection amount Qinj_min, the process proceeds to S58.
In S58, it is determined whether or not the command injection amount is larger than the minimum injection amount Qinj_min.
As a result of the determination in S58, when the command injection amount is larger than the minimum injection amount Qinj_min, the accuracy differs depending on whether or not the learning prohibition period is reached until the previous processing, and therefore the process proceeds to S59.
If the command injection amount is equal to or smaller than the minimum injection amount Qinj_min as a result of the determination in S58, the linearity characteristic of the injector 12 cannot be secured, and the process proceeds to S60.

In S59, it is determined whether or not the flag F is 1.
As a result of the determination in S59, when the flag F is 1, even if the command injection amount is equal to or less than the value obtained by adding the determination threshold value α to the minimum injection amount Qinj_min, the previous process ensures the accuracy by executing the purge gas concentration learning. Therefore, the process proceeds to S53 to learn the purge gas concentration.
If the flag F is not 1 as a result of the determination in S59, since the previous process is within the learning prohibition period and accuracy cannot be ensured, the region from the minimum injection amount Qinj_min to the minimum injection amount Qinj_min + α is regarded as a dead zone region. Then, the process proceeds to S60.
In S60, the purge gas concentration learned value estimated in the previous process is set to the current purge gas concentration learned value, and the process proceeds to S61.
In S61, 0 is substituted for the flag F, and the process proceeds to S57.

(Throttle valve control procedure)
Next, a procedure for calculating the throttle target opening, which is the target value of the opening of the throttle valve 34, will be described based on the flowchart of FIG.
The throttle valve control process is repeatedly executed at a predetermined cycle, and is executed in parallel with the purge valve control process shown in FIGS. 4 to 6 and the injector control process shown in FIGS.

First, in S71, the PCM 100 reads the target intake air amount calculated in S2 and the target purge mass flow rate set in S31 or S32.
Next, in S72, the target purge mass flow rate is subtracted from the target intake air amount to calculate a throttle target intake air amount that is a target value of air passing through the throttle valve 34.

  Next, in S73, the throttle target opening is calculated based on the throttle target intake air amount. In the present embodiment, the relationship between the engine speed, the opening of the throttle valve 34, and the amount of air passing through the throttle valve 34 is obtained in advance by experiments or the like and stored in the PCM 100 as a map. Then, an opening corresponding to the current engine speed and the throttle target intake air amount calculated in S52 is extracted and set as the throttle target opening.

  In S74, the opening of the throttle valve 34 is changed to the throttle target opening, and the process returns. Here, the target purge mass flow rate and thus the amount of purge gas introduced into the intake pipe 32 is controlled so as not to exceed the upper limit purge amount, that is, the amount obtained by subtracting the throttle limit flow rate from the target intake amount. Therefore, the throttle passing air flow rate is controlled to be equal to or higher than the throttle limit flow rate, and the opening degree of the throttle valve 34 is controlled to be equal to or higher than the minimum opening degree.

Next, the operation and effect of the evaporated fuel processing apparatus for the engine will be described based on the time chart of FIG.
As shown in FIG. 12, from time t0, the command injection amount of the injector 12 after the reduction correction, which is reduced based on the purge gas concentration, gradually decreases toward the minimum injection amount Qinj_min, and the target purge mass flow rate gradually increases. The purge gas concentration learning value gradually increases as the target purge mass flow rate increases.
As a result of the gradual decrease of the command injection amount from the injector 12, at the time t1 when the command injection amount of the injector 12 reaches the minimum injection amount Qinj_min, the decrease of the command injection amount is prohibited and the learning of the purge gas concentration is prohibited.

From time t2 when the prohibition of purge gas concentration learning continues for a predetermined period, the target purge mass flow rate is gradually decreased by the reference decrease amount β, and accordingly, the command injection amount of the injector 12 is gradually increased.
It should be noted that, for a while after time t2, since there is a variation between the basic injection amount that is the target injection amount of the injector 12 and the actual injection amount, the prohibition of purge gas concentration learning is continued. At time t3 when the command injection amount of the injector 12 reaches the minimum injection amount Qinj_min + α, execution of purge gas concentration learning is permitted.
Then, from time t4 when the deviation of the purge gas concentration learning value converges within a predetermined value, the command injection amount (basic injection amount) is gradually decreased and the target purge mass flow rate is gradually increased.

  According to the fuel vapor processing apparatus according to the first embodiment, the PCM 100 secures the linearity characteristic of the injector 12 with the fuel injection amount after the reduction correction for reducing the basic injection amount (command injection amount) of the injector 12 based on the purge gas concentration. Since learning of the purge gas concentration is prohibited when it becomes smaller than the minimum injection amount Qinj_min, the learning of the evaporative fuel concentration including the deviation component of the injector 12 is prohibited, thereby suppressing the decrease in the learning accuracy of the purge gas concentration. can do. The PCM 100 reduces the purge gas supplied to the intake passage 30 of the engine so that the fuel injection amount becomes larger than the minimum injection amount Qinj_min when the prohibition of purge gas concentration learning continues for a predetermined period. The error in the learned purge gas concentration can be eliminated at an early stage, and a large amount of purge gas can be supplied to the engine 1 in a short time while suppressing fluctuations in the engine torque associated with fluctuations in the injection amount of the injector 12. it can.

  The predetermined period (time t1 to time t2) during which purge gas concentration learning is prohibited is set according to the elapsed time from the start of prohibiting purge gas concentration learning. Therefore, the purge gas concentration learning prohibition period can be set with a simple configuration.

  The PCM 100 reduces the fuel injection amount until the fuel injection amount becomes an injection amount that is larger than the minimum injection amount Qinj_min by the determination threshold value α, and therefore, the basic injection amount (command) The reduction correction for reducing the injection amount) can be restarted, and a large amount of purge fuel can be supplied to the engine 1 at an early stage.

  When the PCM 100 sets the cylinder required fuel amount Qcyl, which is a target value of the total fuel amount to be supplied to the engine 1 based on the operating state, and opens the purge valve 45 to supply the evaporated fuel to the intake passage 30, The injector 12 and the purge valve 45 are controlled so that the injection amount is set to the minimum injection amount Qinj_min and the target maximum purge fuel amount Qpurge_max is obtained by subtracting the minimum injection amount Qinj_min from the cylinder required fuel amount Qcyl. Thereby, at the time of purge execution, the cylinder required fuel amount Qcyl can be realized by the fuel supply by the injector 12 and the fuel supply by the purge, and the engine torque can be maintained at an appropriate value, and the controllability of the injection amount of the injector 12 can be maintained. Can be secured.

Next, a modified example in which the embodiment is partially changed will be described.
1] In the above embodiment, the example in which the predetermined period (time t1 to time t2) for prohibiting purge gas concentration learning is set according to the elapsed time from the start of prohibiting purge gas concentration learning has been described. It may be set by the integrated amount of purge fuel supplied to the engine intake passage. Thereby, the error of the purge gas concentration learning value caused by the learning prohibition period can be detected at an early stage, and the purge gas concentration learning prohibition period can be set with high accuracy.

2] In the above embodiment, during the purge, the amount of evaporated fuel introduced into the engine is gradually increased toward the target maximum purge fuel amount, and the injection amount of the injector is gradually decreased toward the minimum injection amount. As described above, as the purge execution condition is satisfied, these amounts may be changed to the target maximum purge fuel amount and the minimum injection amount at once.

3) In addition, those skilled in the art can implement the present invention in a form in which various modifications are added to the above-described embodiment or a combination of the above-described embodiments without departing from the spirit of the present invention. Various modifications are also included.

1 Engine 12 Injector 30 Intake passage 41 Fuel tank 42 Canister 43 Purge pipe 45 Purge valve 100 PCM

Claims (5)

A fuel injection valve that supplies fuel to the engine, a canister that adsorbs evaporated fuel evaporated in a fuel tank, a purge passage that supplies evaporated fuel from the canister to the intake passage of the engine, and the purge passage can be opened and closed In an evaporated fuel processing apparatus for an engine, comprising: a purge valve; and a control means for learning the evaporated fuel concentration when supplying evaporated fuel through the purge valve and controlling the purge valve and the fuel injection valve.
When the fuel injection amount after the reduction correction for reducing the fuel injection amount of the fuel injection valve based on the evaporated fuel concentration is smaller than the minimum injection amount that ensures the linearity characteristic of the fuel injection valve, while prohibiting the learning of the vaporized fuel concentration, when said prohibiting the fuel vapor concentration learning continues for a predetermined time period, the fuel injection amount of the supply amount of evaporative fuel supplied to the intake passage of the engine than the minimum injection amount An evaporative fuel processing device for an engine, characterized in that the amount is reduced so as to increase.   2. The evaporated fuel processing apparatus for an engine according to claim 1, wherein the predetermined period is set based on an elapsed time from the start of prohibition of the evaporated fuel concentration learning.   2. The evaporated fuel processing apparatus for an engine according to claim 1, wherein the predetermined period is set by an integrated amount of evaporated fuel supplied to an intake passage of the engine from the start of prohibition of the evaporated fuel concentration learning. 4. The control unit according to claim 1, wherein the control unit reduces the supply amount of the evaporated fuel until the fuel injection amount becomes an injection amount that is a predetermined amount larger than the minimum injection amount. 5. Engine evaporative fuel processing device. The control means sets a reference target fuel amount that is a target value of the total fuel amount to be supplied to the engine based on an operating state, opens the purge valve to supply the evaporated fuel to the intake passage, and When learning the evaporated fuel concentration, the fuel injection amount is set to the minimum injection amount, and the evaporated fuel is set to a maximum target evaporated fuel amount that is an amount obtained by subtracting the minimum injection amount from the reference target fuel amount. The fuel vapor processing apparatus for an engine according to any one of claims 1 to 4, wherein the fuel injection valve and the purge valve are controlled.