JP2020112075A - Vaporized fuel treatment device - Google Patents

Abstract

To improve vaporized fuel purge efficiency by effectively specifying a vapor concentration even during duty control while keeping a rate of cylinder distribution of vaporized fuel to an engine in an excellent state.SOLUTION: A vaporized fuel treatment device comprises: a purge passage 23 which guides vapor from a canister 21 to an intake passage 3; a purge pump 24 which pumps up the vapor from the canister 21 to the intake passage 3; a purge valve 25 which is brought under duty control so as to control a vapor flow rate of the purge passage 23; a pressure sensor 47 which specifies a vapor concentration etc.; and an electronic controller (ECU) 50 which controls the purge pump 24 in purging the vapor, and performs the duty control over the purge valve 25 based upon a target duty ratio and a target driving cycle. The ECU 50 when specifying the vapor concentration during the duty control execution calculates the target driving cycle based upon a requested duty ratio and a downtime, also calculates a maximum driving cycle corresponding to an engine speed, and sets the calculated target driving cycle to equal to or less than the calculated maximum driving cycle.SELECTED DRAWING: Figure 1

Description

The technique disclosed in this specification relates to an evaporated fuel processing apparatus that purges evaporated fuel generated in a fuel tank into an intake passage to process the evaporated fuel.

Conventionally, as this type of technology, for example, an "evaporated fuel processing device" described in Patent Document 1 below is known. This device is provided in a canister that collects evaporated fuel (vapor) generated in a fuel tank, a purge passage that guides the vapor collected in the canister to the intake passage of the engine, and a purge passage that is collected in the canister. A purge pump for pumping vapor to the intake passage, a control valve (purge valve) provided in the purge passage and configured to be openable and closable, and a communication state of the purge valve when purging vapor from the canister to the intake passage ( A control unit (ECU) configured to execute control (duty control) for repeatedly switching between the open state and the closed state (closed valve) at a predetermined duty ratio, and a means for specifying the purge concentration (vapor concentration). Prepare When the ECU is performing duty control of the purge valve to identify the vapor concentration, this device sets the purge valve closing time (pause time) in the duty control to a predetermined value or more to stabilize the vapor concentration. To get.

JP, 2017-214836, A

However, when the device described in Patent Document 1 is adopted in a multi-cylinder engine, the idle time of the purge valve in the duty control becomes long, so that the duty control cycle (drive cycle) also becomes long, and each engine The efficiency of evenly distributing the vapor to the cylinders may decrease. As a result, the output of the engine may be reduced and the exhaust air-fuel ratio may be roughened. The reason is that the pressure of the vapor between the canister and the intake passage periodically changes when the purge valve is opened and closed repeatedly when the purge valve is duty-controlled. This is because it is difficult to specify the vapor concentration when the vapor pressure changes periodically. Generally, in order to specify the vapor concentration, it is necessary to secure a sufficient down time of the purge valve in the duty control. However, if the drive cycle of the duty control is lengthened or the duty ratio of the purge control is set to an upper limit, the flow rate of the vapor to be purged may be reduced.

The disclosed technique has been made in view of the above circumstances, and an object thereof is to effectively specify the vapor concentration during duty control while maintaining a good cylinder distribution ratio of evaporated fuel to the engine. Accordingly, it is an object of the present invention to provide an evaporated fuel processing device capable of improving the purge efficiency of evaporated fuel.

In order to achieve the above object, the technique according to claim 1 is a canister for collecting evaporated fuel generated in a fuel tank, and an intake passage of an engine for purging evaporated fuel collected in the canister. To the intake passage, and a purge pump provided in the purge passage for pumping the evaporated fuel collected in the canister to the intake passage, and in the purge passage for adjusting the flow rate of the evaporated fuel in the purge passage. A purge valve opened and closed by duty control, an evaporated fuel concentration specifying means for specifying the concentration of the evaporated fuel to be purged, a purge pump is controlled and the purge pump is controlled when the evaporated fuel is purged from the canister to the intake passage. In an evaporative fuel processing apparatus including a control unit configured to perform duty control of a valve based on a predetermined target duty ratio and a predetermined target drive cycle, the control unit includes an evaporative fuel concentration specifying unit during execution of the duty control. When the concentration of evaporated fuel is specified by, the target drive cycle is calculated based on the predetermined required duty ratio and the pause time in the drive cycle, and the predetermined maximum drive cycle is calculated according to the engine speed. The purpose is to set the calculated target drive cycle to be equal to or less than the calculated maximum drive cycle.

According to the configuration of the above technique, the control unit controls the purge pump when purging the evaporated fuel from the canister to the intake passage, and controls the purge valve based on a predetermined target duty ratio and a predetermined target drive cycle. To do. Here, the control means calculates the target drive cycle based on a predetermined required duty ratio and a predetermined rest time and determines the engine speed when the concentration of the evaporated fuel is specified during execution of the duty control. A predetermined maximum drive cycle corresponding to the calculated maximum drive cycle is set, and the calculated target drive cycle is set to be equal to or less than the calculated maximum drive cycle. Therefore, the target drive cycle is calculated according to the predetermined required duty ratio and the predetermined rest time, and the target drive cycle is set to be equal to or less than the maximum drive cycle according to the engine speed. In addition, the target drive cycle does not become longer than necessary.

In order to achieve the above object, the technique according to claim 2 is the technique according to claim 1, wherein the control means specifies the concentration of the evaporated fuel by the evaporated fuel concentration specifying means during execution of the duty control. The purpose is to calculate the target duty ratio based on the target drive cycle and the idle time that are set to the maximum drive cycle or less.

According to the configuration of the above technique, in addition to the operation of the technique according to claim 1, when the concentration of the evaporated fuel is specified during execution of the duty control, the target drive cycle set to the maximum drive cycle or less and the pause. Since the target duty ratio is calculated based on time, a suitable target duty ratio according to the set target drive cycle is used for duty control.

According to the technique of claim 1, while maintaining the cylinder distribution ratio of the evaporated fuel to the engine in a good state, the purge efficiency of the evaporated fuel can be improved by effectively specifying the concentration of the evaporated fuel during the duty control. Can be improved.

According to the technique described in claim 2, in addition to the effect of the technique described in claim 1, reduction of the flow rate of the vaporized fuel to be purged is ensured while securing a pause time necessary for specifying the concentration of the vaporized fuel. Can be suppressed, and good controllability of the air-fuel ratio of the engine can be achieved.

1 is a schematic diagram showing an engine system including an evaporated fuel processing device according to one embodiment. FIG. 9 is a flowchart showing the contents of calculation processing such as duty ratio according to the embodiment. 1 is a first map referred to in order to calculate a dwell time according to a sensor fuel pressure and a vapor concentration according to an embodiment. A 2nd map referred to in order to calculate the maximum drive cycle according to engine number concerning one embodiment. 9 is a time chart showing an example of behavior of (a) drive of a purge valve (opening and closing of a valve) and (b) detection value of a pressure sensor according to an embodiment. 9 is a flowchart showing the contents of purge control according to the embodiment. 9 is a time chart showing an example of behaviors of various parameters associated with calculation processing such as duty ratio and purge control according to the embodiment.

Hereinafter, an embodiment in which an evaporated fuel processing device is embodied will be described in detail with reference to the drawings.

[Outline of engine system]
FIG. 1 is a schematic diagram showing an engine system including an evaporated fuel processing device 30 mounted on a vehicle 60. The vehicle 60 can be assumed to be a normal gasoline engine vehicle or a hybrid vehicle. The engine 1 includes an intake passage 3 for sucking air or the like into the combustion chamber 2, and an exhaust passage 4 for discharging exhaust gas from the combustion chamber 2. The fuel stored in the fuel tank 5 is supplied to the combustion chamber 2. That is, the fuel in the fuel tank 5 is discharged into the fuel passage 7 by the fuel pump 6 built in the tank 5, and is pressure-fed to the injector 8 provided in the intake port of the engine 1. The pressure-fed fuel is injected from the injector 8 and is introduced into the combustion chamber 2 together with the air (intake air) flowing through the intake passage 3 to form a combustible air-fuel mixture for combustion. The engine 1 is provided with an ignition device 9 for igniting a combustible mixture.

An air cleaner 10, a throttle device 11, and a surge tank 12 are provided in the intake passage 3 from its inlet side to the engine 1. The throttle device 11 includes a throttle valve 11 a and is opened/closed to adjust the flow rate of intake air flowing through the intake passage 3. The opening/closing of the throttle valve 11a is interlocked with the operation of the accelerator pedal (not shown) by the driver. The surge tank 12 smoothes the intake pulsation in the intake passage 3.

[Configuration of Evaporative Fuel Processing Device]
In FIG. 1, the evaporated fuel processing device 30 of this embodiment is configured to process the evaporated fuel (vapor) generated in the fuel tank 5 without releasing it into the atmosphere. This device has a canister 21 for collecting vapor generated in the fuel tank 5, an evaporated fuel passage (vapor passage) 22 for guiding vapor from the fuel tank 5 to the canister 21, and a canister 21. A purge passage 23 for guiding the vapor to the intake passage 3, a purge pump 24 provided in the purge passage 23 for pumping the vapor collected in the canister 21 to the intake passage 3, and a downstream of the purge pump 24. A purge valve 25 provided in the purge passage 23 and opened/closed by duty control for adjusting the flow rate of vapor in the purge passage 23, and an atmosphere passage 26 for introducing the atmosphere into the canister 21. In addition, the evaporated fuel processing device 30 further includes a pressure sensor 47 and an electronic control unit (ECU) 50 described later.

The canister 21 contains an adsorbent such as activated carbon. The canister 21 includes an air inlet 21a for introducing the atmosphere, an inlet 21b for introducing the vapor, and an outlet 21c for leading out the vapor. The inside of the canister 21 communicates with the atmosphere via the atmosphere passage 26. That is, the tip of the atmosphere passage 26 extending from the atmosphere port 21 a communicates with the inlet of the fuel filler cylinder 5 a of the fuel tank 5. An air filter 27 for collecting dust and the like in the air is provided in the atmosphere passage 26. Further, the tip of the vapor passage 22 extending from the inlet 21 b of the canister 21 communicates with the inside of the fuel tank 5. The tip of the purge passage 23 extending from the outlet 21c of the canister 21 communicates with the intake passage 3 between the throttle device 11 and the surge tank 12.

In this embodiment, the purge valve 25 is configured by a motor-operated valve so that the opening degree is variable, and is duty-controlled so as to adjust the opening degree as described later. Generally, the duty control of the purge valve 25 is control in which the valve opening and the valve closing are switched by a predetermined duty ratio and a predetermined drive cycle. In this duty control, when the purge valve 25 is opened, the canister 21 and the intake passage 3 communicate with each other via the purge passage 23, and when the purge valve 25 is closed, the canister 21 and the intake passage 3 are closed. The purge passage 23 between and is blocked. When the purge valve 25 is duty-controlled, the above communication and interruption are periodically repeated. The cycle (time) required to open and close the valve is called a "driving cycle", and the ratio of the valve opening time (pulse time) to the driving cycle is called a "duty ratio". On the other hand, the purge pump 24 has a variable discharge amount in order to pump the vapor from the canister 21 to the purge passage 23. As the purge pump 24, for example, a turbine type pump can be adopted.

In the evaporated fuel processing apparatus 30 configured as described above, the vapor generated in the fuel tank 5 is introduced into the canister 21 via the vapor passage 22 and is temporarily collected by the canister 21. When the engine 1 is operating, the throttle device 11 (throttle valve 11a) is opened, the purge pump 24 is operated, and the purge valve 25 is duty-controlled. As a result, the vapor collected in the canister 21 is guided from the canister 21 to the intake passage 3 via the purge passage 23 and purged. In the state where the purge is performed in this manner, the canister 21 and the intake passage 3 are not continuously communicated with each other, but the purge valve 25 is intermittently opened and closed when the purge valve 25 is repeatedly opened and closed. Communication is interrupted intermittently when the valve is closed intermittently.

The purge passage 23 is provided with a passage 29 that connects the suction side and the discharge side of the purge pump 24. That is, the suction side and the discharge side of the purge pump 24 are connected via the passage 29. A pressure difference (differential pressure) between the suction side pressure and the discharge side pressure of the purge pump 24 acts on the passage 29.

[About electrical configuration of engine system]
In this embodiment, various sensors 41 to 47 are provided to detect the operating state of the engine 1. The air flow meter 41 provided near the air cleaner 10 detects the amount of air taken into the intake passage 3 as the intake air amount Ga, and outputs an electric signal according to the detected value. The throttle sensor 42 provided in the throttle device 11 detects the opening of the throttle valve 11a as the throttle opening TA and outputs an electric signal according to the detected value. The intake pressure sensor 43 provided in the surge tank 12 detects the pressure in the surge tank 12 as the intake pressure PM, and outputs an electric signal according to the detected value. The water temperature sensor 44 provided in the engine 1 detects the temperature of the cooling water flowing inside the engine 1 as the cooling water temperature THW, and outputs an electric signal according to the detected value. A rotation speed sensor 45 provided in the engine 1 detects a rotation angular velocity of a crankshaft (not shown) of the engine 1 as an engine rotation speed NE, and outputs an electric signal according to the detected value. An air-fuel ratio sensor (A/F sensor) 46 provided in the exhaust passage 4 detects the hydrocarbon concentration HC in the exhaust and outputs an electric signal according to the detected value. A pressure sensor 47 provided in the passage 29 detects a pressure difference acting on the passage 29 and outputs an electric signal according to the detected value.

In this embodiment, an electronic control unit (ECU) 50 that manages various controls inputs various signals output from various sensors 41 to 47. The ECU 50 controls the injector 8, the ignition device 9, the purge valve 25, and the purge pump 24 based on these input signals to execute fuel injection control, ignition timing control, duty ratio calculation processing, and purge control. ing.

Here, the fuel injection control is to control the fuel injection amount and the fuel injection timing by controlling the injector 8 according to the operating state of the engine 1. The ignition timing control is to control the ignition timing of the combustible mixture by controlling the ignition device 9 according to the operating state of the engine 1. The duty ratio calculation processing is to calculate the target duty ratio FPD and the target drive cycle TPF used to control the duty of the purge valve 25 according to the operating state of the engine 1. The purge control is to control the flow rate of vapor purged from the canister 21 to the intake passage 3 by controlling the purge valve 25 and the purge pump 24 according to the operating state of the engine 1.

The pressure sensor 47 described above is provided to identify the concentration of the vapor flowing through the purge passage 23 (vapor concentration Cv). The pressure sensor 47 is configured to detect a pressure difference. The ECU 50 is adapted to identify the vapor concentration Cv by a known method (calculation by Bernoulli's equation) based on this pressure difference. In this embodiment, as an example, the pressure sensor 47 and the ECU 50 configure the evaporated fuel concentration specifying means in the disclosed technique.

In this embodiment, the ECU 50 controls the purge pump 24 when purging vapor from the canister 21 to the intake passage 3, and also causes the purge valve 25 to perform a duty cycle based on a predetermined target duty ratio FPD and a predetermined target drive cycle TPF. Is configured to control. The ECU 50 corresponds to an example of control means in the disclosed technique. The ECU 50 has a known configuration including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM and the like. The ROM stores in advance a predetermined control program relating to the various controls described above. The ECU (CPU) 50 is adapted to execute the various controls described above according to these control programs.

In this embodiment, well-known contents are adopted for the fuel injection control and the ignition timing control, and the duty ratio calculation processing and the purge control will be described in detail below.

[About duty ratio calculation processing]
First, the duty ratio calculation processing will be described. FIG. 2 is a flowchart showing the processing contents. The ECU 50 periodically executes this routine every predetermined time.

When the processing shifts to this routine, in step 100, the ECU 50 takes in the vapor concentration Cv, the intake air amount Ga, the engine speed NE, the sensor fuel pressure Pfs, and the required duty ratio DPD during execution of the purge control. Here, the ECU 50 takes in the intake air amount Ga based on the detected value of the air flow meter 41, and takes in the engine rotational speed NE based on the detected value of the rotational speed sensor 45. The ECU 50 also takes in the vapor concentration Cv, the sensor fuel pressure Pfs, and the required duty ratio DPD. The ECU 50 separately calculates the vapor concentration Cv based on the detection value of the pressure sensor 47. The ECU 50 separately calculates the sensor fuel pressure Pfs based on the detection value of the pressure sensor 47 when the purge valve 25 is closed. Further, the ECU 50 separately calculates the required duty ratio DPD based on the injector ratio (the ratio of the fuel injected from the injector 8).

Next, in step 110, the ECU 50 determines whether or not there is a vapor concentration detection request (concentration detection request) during execution of the purge control. Here, the concentration detection request is mainly issued when the periodic valve closing time (pause time) in the duty control of the purge valve 25 becomes sufficient. If the determination result is affirmative, the ECU 50 shifts the processing to step 120, and if the determination result is negative, the ECU 50 shifts the processing to step 190.

When there is a concentration detection request, in step 120, the ECU 50 calculates the required downtime TPP based on the sensor fuel pressure Pfs and the vapor concentration Cv. In this embodiment, as an example, the ECU 50 calculates the pause time TPP (unit is “ms”) according to the sensor fuel pressure Pfs and the vapor concentration Cv by referring to the first map shown in FIG.

Next, in step 130, the ECU 50 calculates the maximum drive cycle TMPF in duty control based on the engine speed NE. In this embodiment, for example, the ECU 50 calculates the maximum drive cycle TMPF according to the engine speed NE by referring to the second map shown in FIG. The maximum drive cycle TMPF defines the upper limit value of the target drive cycle in duty control, and the unit is "ms". In order to distribute the purged vapor concentration Cv to the cylinders of the engine 1 as evenly as possible, it is necessary to set the target drive cycle TPF for duty control to be equal to or less than the maximum drive cycle TMPF.

FIG. 5 is a time chart showing an example of the behavior of (a) driving of the purge valve 25 (opening and closing of the valve) and (b) detection value of the pressure sensor 47. The maximum drive cycle TMPF means the time required for one cycle of opening and closing of the purge valve 25, like the target drive cycle TPF and the required drive cycle TDPF described later. Further, the rest time TPP means the closing time of the purge valve 25. Here, in order to accurately specify the vapor concentration Cv, it is necessary to detect a stable pressure difference by the pressure sensor 47, and for that purpose, it is necessary to secure the pause time TPP to some extent.

Next, in step 140, the ECU 50 calculates the target drive cycle TPF for duty control based on the required duty ratio DPD and the pause time TPP, for example, by the following first calculation formula (F1).
TPF ← TPP*100/(100-DPD) (F1)

Next, in step 150, the ECU 50 determines whether the target drive cycle TPF is larger than the maximum drive cycle TMPF. If the determination result is affirmative, the ECU 50 shifts the processing to step 160, and if the determination result is negative, the ECU 50 shifts the processing to step 180.

In step 160, the ECU 50 sets the target drive cycle TPF to the maximum drive cycle TMPF that is the upper limit value. That is, the target drive cycle TPF is set to the maximum drive cycle TMPF or less.

Next, in step 170, the ECU 50 calculates the target duty ratio FPD for duty control based on the target drive cycle TPF and the pause time TPP, for example, by the following second calculation formula (F2), and the subsequent processing. Ends once.
FPD ← (TPF-TPP)*100/TPF ... (F2)

Further, in step 180, the ECU 50 sets the target duty ratio FPD for duty control to the required duty ratio DPD, and thereafter ends the processing once.

On the other hand, when there is no concentration detection request, the routine proceeds from step 110 to step 190, where the ECU 50 sets the target duty ratio FPD to the required duty ratio DPD.

Next, in step 200, the ECU 50 sets the target drive cycle TPF for duty control to a predetermined required drive cycle TDPF, and then ends the subsequent processing.

Here, the target duty ratio FPD and the target drive cycle TPF calculated as described above are used for the duty control of the purge valve 25 in the purge control described later.

[Purge control]
Next, the purge control will be described. FIG. 6 shows the contents by a flowchart. The ECU 50 periodically executes this routine every predetermined time.

When the process shifts to this routine, in step 300, the ECU 50 waits until the purge control execution condition is satisfied and shifts the process to step 310. The ECU 50 determines that the purge control execution condition is satisfied when, for example, the detected cooling water temperature THW is equal to or higher than a predetermined value and the predetermined air-fuel ratio is obtained based on the detected hydrocarbon concentration HC. You can judge.

In step 310, the ECU 50 operates the purge pump 24. The ECU 50 controls the rotation speed of the purge pump 24 to a predetermined value (for example, 1000 rpm).

Next, in step 320, the ECU 50 determines whether or not the change (concentration change) in the vapor concentration Cv is small. If the determination result is affirmative, the ECU 50 shifts the processing to step 330, and if the determination result is negative, the ECU 50 shifts the processing to step 380.

In step 330, the ECU 50 waits until the counter value NC counted by the counter reaches the first predetermined number of times C1 and shifts the processing to step 340. Here, the counter value NC means the number of cycles of the opening and closing of the purge valve 25 in the duty control. The ECU 50 determines whether it is time to specify the vapor concentration Cv based on the determination in step 330. Then, when the counter value NC reaches the first predetermined number of times C1, the ECU 50 determines that it is the timing to specify the vapor concentration Cv and shifts the processing to step 340.

In step 340, the ECU 50 takes in the target duty ratio FPD and the target drive cycle TPF for duty control, which are obtained by the above-described arithmetic processing.

Next, at step 350, the ECU 50 duty-controls the purge valve 25 based on the target duty ratio FPD and the target drive cycle TPF.

Next, in step 360, the ECU 50 specifies the vapor concentration Cv. The ECU 50 calculates and specifies the vapor concentration Cv based on the pressure difference detected by the pressure sensor 47 by a known method (calculation by Bernoulli's equation).

Then, in step 370, the ECU 50 resets the counter value NC and returns the process to step 300.

On the other hand, in step 380 after shifting from step 320, the ECU 50 shifts the processing to step 390 after waiting for the counter value NC to reach the second predetermined number C2 (C2<C1). The ECU 50 determines whether or not it is time to specify the vapor concentration Cv based on the determination in step 380. Then, when the counter value NC reaches the second predetermined number of times C2, the ECU 50 determines that it is time to specify the vapor concentration Cv, and shifts the processing to step 390.

Here, the second predetermined number of times C2 is smaller than the first predetermined number of times C1 used in step 330. That is, the frequency of specifying the vapor concentration Cv increases. As a result, if the change in the vapor concentration Cv is large, the frequency with which the vapor concentration Cv is specified is increased. As a result, it is possible to appropriately specify the vapor concentration Cv that greatly changes, and it is possible to prevent the air-fuel ratio of the engine 1 from largely deviating due to the change of the vapor concentration Cv.

In step 390, the ECU 50 increases the rotation speed of the purge pump 24 to a predetermined value.

Next, in step 400, the ECU 50 takes in the target duty ratio FPD and the target drive cycle TPF for the duty control, which are obtained by the above-described arithmetic processing.

Next, in step 410, the ECU 50 duty-controls the purge valve 25 based on the target duty ratio FPD and the target drive cycle TPF, then shifts the processing to step 360, and executes the processing of steps 360 and 370.

According to the duty ratio calculation processing and the purge control, the ECU 50 determines the predetermined required duty ratio DPD when the vapor concentration Cv is specified by the pressure sensor 47 and the ECU 50 during the duty control (purge control). The target drive cycle TPF is calculated based on the pause time TPP in the drive cycle, the predetermined maximum drive cycle TMPF is calculated according to the engine speed NE, and the calculated target drive cycle TPF is calculated. It is designed to be set below TMPF. When the vapor concentration Cv is similarly specified during execution of the duty control (purge control), the ECU 50 also sets the target duty ratio FPD based on the target drive cycle TPF and the pause time TPP set to the maximum drive cycle TMPF or less. Is calculated. Then, when purging vapor from the canister 21 into the intake passage 3 (during purge control), the ECU 50 controls the purge pump 24 and sets the purge valve 25 to a predetermined target duty ratio FPD and a predetermined target drive cycle TPF. The duty control is performed based on.

Here, FIG. 7 is a time chart showing an example of the behavior of various parameters associated with the above-described duty ratio calculation processing and purge control. 7, (a) shows the engine speed NE, (b) shows the purge control, (c) shows the concentration detection request, (d) shows the required duty ratio DPD and the target duty ratio FPD, and (e) shows The target drive cycle TPF and the maximum drive cycle TMPF are shown, and (f) shows the drive of the purge valve 25, respectively.

In FIG. 7, at time t1, when the engine speed NE of (a) exceeds a certain value, the purge control of (b) is turned on (executed), and the required duty ratio DPD and the target duty ratio FPD of (d). Starts to increase from "0", and the purge valve 25 of (f) starts to drive. At this time, the target drive cycle TPF and the maximum drive cycle TMPF are set to predetermined reference values.

After that, when the concentration detection request of (c) is turned on at time t2, the target drive cycle TPF and the maximum drive cycle TMPF of (e) increase, respectively. As a result, as shown in (f), the purge valve 25 Drive changes. That is, the drive cycle and duty ratio for opening and closing the purge valve 25 change.

Here, since the target drive cycle TPF of (e) is smaller than the maximum drive cycle TMPF between time t2 and time t3, the target duty ratio FPD of (d) becomes the same as the required duty ratio DPD, and the target The duty ratio FPD and the target drive cycle TPF are used for duty control of the purge valve 25.

After that, when the engine speed NE of (a) falls below a certain value at time t3, the maximum drive cycle TMPF of (e) becomes smaller than the target drive cycle TPF. After that, from time t3 to time t4, (e) when the target drive cycle TPF becomes larger than the maximum drive cycle TMPF, the target drive cycle TPF is set to the maximum drive cycle TMPF, and the target duty ratio FPD of (d) is set. The target duty ratio FPD becomes smaller than the required duty ratio DPD, and the target duty ratio FPD and the target drive cycle TPF are used for duty control of the purge valve 25.

After that, at time t4, when the density detection request of (c) disappears (OFF), the target drive cycle TPF and the maximum drive cycle TMPF of (e) return to predetermined reference values, and as a result, the required duty of (d) The ratio DPD and the target duty ratio FPD are the same.

Then, at time t5, when the purge control of (b) is turned off (not executed), the required duty ratio DPD and the target duty ratio FPD of (d) are both “0”, and the purge valve 25 of (f) is closed. It stops in the valve state.

[Operation and Effect of Evaporative Fuel Treatment Device]
According to the fuel vapor processing apparatus 30 in this embodiment described above, the ECU 50 controls the purge pump 24 and purges the purge valve 25 at a predetermined target duty ratio when purging vapor from the canister 21 to the intake passage 3. Duty control is performed based on the FPD and a predetermined target drive cycle TPF. Here, when the vapor concentration Cv is specified during execution of the duty control, the ECU 50 calculates the target drive cycle TPF based on the predetermined required duty ratio DPD and the predetermined rest time TPP, and also the engine speed NE. A predetermined maximum drive cycle TMPF according to the above is calculated, and the calculated target drive cycle TPF is set to be equal to or less than the calculated maximum drive cycle TMPF. Therefore, the target drive cycle TPF is calculated according to the predetermined required duty ratio DPD and the predetermined pause time TPP, and the target drive cycle TPF is set to the maximum drive cycle TMPF or less according to the engine speed NE. The target drive cycle TPF does not become longer than necessary after securing the predetermined pause time TPP. Therefore, it is possible to improve the vapor purging efficiency by effectively specifying the vapor concentration Cv even during the duty control while maintaining the vapor cylinder distribution ratio to the engine 1 in a good state.

Further, according to the configuration of this embodiment, when the vapor concentration Cv is specified during execution of the duty control, the target duty ratio is set based on the target drive cycle TPF and the pause time TPP set to the maximum drive cycle TMPF or less. Since the FPD is calculated, a suitable target duty ratio FPD according to the set target drive cycle TPF is used for duty control. Therefore, it is possible to prevent the flow rate of the purged vapor from decreasing. For this reason, it is possible to suppress the decrease in the flow rate of the vapor to be purged while securing the pause time TPP necessary for specifying the vapor concentration Cv, and achieve good controllability of the air-fuel ratio of the engine 1. it can.

The disclosed technique is not limited to the above-described embodiment, and a part of the configuration may be appropriately modified and implemented without departing from the gist of the disclosed technique.

(1) In the above-described embodiment, in the engine system without the supercharger, the purge passage 23 is connected to the intake passage 3 downstream of the throttle valve 11a to purge the vapor. On the other hand, in the engine system including the supercharger, the purge passage can be connected to the intake passage upstream of the throttle valve and downstream of the air flow meter to purge the vapor.

(2) In the above embodiment, the evaporative fuel concentration specifying means is configured by the ECU 50 and the pressure sensor 47 that measures the pressure difference between the suction side and the discharge side of the purge pump 24, but only the pressure on the discharge side of the purge pump is detected. The fuel vapor concentration specifying means may be configured by the pressure sensor and the ECU.

(3) In the above-described embodiment, the pressure sensor 47 and the ECU 50 constitute the evaporated fuel concentration specifying means, but the concentration sensor that directly detects the concentration of the evaporated fuel may also constitute the evaporated fuel concentration specifying means.

The disclosed technology can be applied to a gasoline engine system, a diesel engine system, and an engine system of a hybrid vehicle.

1 engine 3 intake passage 5 fuel tank 21 canister 23 purge passage 24 purge pump 25 purge valve 30 evaporated fuel processing device 47 pressure sensor (evaporated fuel concentration specifying means)
50 ECU (control means, fuel vapor concentration specifying means)
NE engine speed Cv vapor concentration DPD required duty ratio TPP rest time TPF target drive cycle TMPF maximum drive cycle FPD target duty ratio

Claims (2)

A canister for collecting the evaporated fuel generated in the fuel tank,
A purge passage leading to an intake passage of the engine for purging the vaporized fuel collected in the canister,
A purge pump provided in the purge passage for pressure-feeding the vaporized fuel collected in the canister to the intake passage,
A purge valve provided in the purge passage and opened and closed by duty control to adjust the flow rate of the evaporated fuel in the purge passage;
Evaporative fuel concentration specifying means for specifying the concentration of the evaporated fuel to be purged,
When purging the evaporated fuel from the canister to the intake passage, the purge pump is controlled, and the purge valve is duty-controlled based on a predetermined target duty ratio and a predetermined target drive cycle. In the evaporated fuel processing device including
The control means, when the concentration of the evaporated fuel is specified by the evaporated fuel concentration specifying means during execution of the duty control, based on a predetermined required duty ratio and a predetermined pause time in a drive cycle, Evaporation characterized by calculating a target drive cycle, calculating a predetermined maximum drive cycle according to the engine speed, and setting the calculated target drive cycle to be equal to or less than the calculated maximum drive cycle. Fuel processor. The evaporated fuel processing device according to claim 1,
The control means, based on the target drive cycle and the pause time set to be equal to or less than the maximum drive cycle when the concentration of the evaporated fuel is specified by the evaporated fuel concentration specifying means during execution of the duty control. The evaporated fuel processing apparatus is characterized in that the target duty ratio is calculated.

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