JP7142554B2 - Evaporative fuel processing device - Google Patents

Description

The present disclosure relates to an evaporative fuel processing device that supplies evaporative fuel generated in a fuel tank to an internal combustion engine for processing.

The evaporated fuel processing device disclosed in Patent Document 1 extends the drive cycle and lowers the upper limit of the duty ratio in the duty control of the control valve while the canister is being purged into the internal combustion engine, and then reduces the purge concentration. have identified.

JP 2017-214836 A

When air-fuel ratio learning (learning to correct the amount of air-fuel ratio deviation), OBD control (air-fuel ratio sensor failure diagnosis control), or when a large amount of evaporated fuel is generated in the fuel tank, the purge concentration changes greatly. In such a case, it is necessary to detect the purge concentration in order to appropriately perform air-fuel ratio learning, OBD control, and air-fuel ratio control. In detecting the purge concentration in this manner, if the purge conditions are met, purge control is performed to ensure the purge flow rate and to perform accurate purge control in order to suppress the deterioration of the evaporative emissions due to the decrease in the purge flow rate. It is desired to detect concentration. Here, in Japanese Patent Laid-Open No. 2002-100001, in the evaporated fuel processing device, while the internal combustion engine is being purged from the canister, regardless of the magnitude of change in the purged concentration, the drive cycle is extended in the duty control of the control valve, and the duty cycle is increased. The purge concentration is specified after lowering the ratio upper limit.

Therefore, the present disclosure has been made to solve the above-described problems, and in a predetermined case where the change in the purge concentration can be large, the purge control is performed to ensure the purge flow rate and the accurate purge concentration is detected. It is an object of the present invention to provide an evaporative fuel processing device capable of

In one aspect of the present disclosure, which has been made to solve the above problems, a canister storing evaporated fuel, a purge passage for flowing purge gas containing the evaporated fuel from the canister to an internal combustion engine, and opening and closing the purge passage. In an evaporative fuel processing apparatus having a purge valve and a control section that performs purge control for supplying the purge gas from the canister to the internal combustion engine through the purge passage, the control section controls the purge valve by duty control. The purge control is performed while the purge control is performed, and in a predetermined case where the change in the purge concentration, which is the concentration of the evaporated fuel contained in the purge gas, may become large, the conditions for the duty control are detected, and the purge concentration is detected when the purge control is performed. Possible conditions are set , and the predetermined case is before the purge concentration is determined after the ignition switch of the vehicle in which the evaporated fuel processing device is installed is turned on, or before the concentration is determined, or When executing air-fuel ratio learning for correcting the amount of air-fuel ratio deviation, which is the amount of deviation between the detected value of the air-fuel ratio of the internal combustion engine and the target value, or executing self-diagnostic control of the air-fuel ratio detection unit that detects the air-fuel ratio. Characterized by being time .

According to this aspect, in a predetermined case where the change in the purge concentration can be large, the conditions for controlling the purge valve by the duty control are set to the conditions under which the purge concentration can be detected when the purge control is executed, so the purge control is performed. The purge concentration can be accurately detected while Therefore, in a predetermined case where the change in the purge concentration can be large, it is possible to detect the accurate purge concentration while ensuring the purge flow rate by performing the purge control.
In addition, before the concentration is determined, when air-fuel ratio learning is executed, or when self-diagnostic control of the air-fuel ratio detection unit is executed, purge control is performed to ensure the purge flow rate and accurate purge concentration can be detected.

Another aspect of the present disclosure, which has been made to solve the above problems, is to open and close a canister for storing fuel vapor, a purge passage for flowing purge gas containing the fuel vapor from the canister to an internal combustion engine, and the purge passage. and a control section that performs purge control for supplying the purge gas from the canister to the internal combustion engine through the purge passage, wherein the control section controls the purge valve through duty control. The purge control is performed while performing the purge control, and in a predetermined case where the change in the purge concentration, which is the concentration of the evaporated fuel contained in the purge gas, may become large, the condition of the duty control is set to the purge concentration when the purge control is executed. A detectable condition is set, and the predetermined case is a case in which an environment in which the change in the purge concentration is large is estimated from the information of the internal combustion engine or the fuel tank related to the change in the purge concentration. ,

According to this aspect, in a predetermined case where the change in the purge concentration can be large, the conditions for controlling the purge valve by the duty control are set to the conditions under which the purge concentration can be detected when the purge control is executed, so the purge control is performed. The purge concentration can be accurately detected while Therefore, in a predetermined case where the change in the purge concentration can be large, it is possible to detect the accurate purge concentration while ensuring the purge flow rate by performing the purge control.
In addition, when it is estimated that there is a large change in purge concentration from the information on the internal combustion engine or fuel tank related to changes in purge concentration, purge control is performed to ensure the purge flow rate and accurate purge concentration is detected. can.

In the above aspect, the information of the internal combustion engine related to the change in the purge concentration is information of an air-fuel ratio deviation amount, which is an amount of deviation between the detected value of the air-fuel ratio of the internal combustion engine and the target value. preferable.

In the above aspect, it is preferable that the fuel tank information related to the change in the purge concentration is information on the temperature of the fuel in the fuel tank.

In the above aspect, there is provided a purge pump that controls the flow rate of the purge gas flowing through the purge passage, and the control section sets the duty control condition to a condition that allows the purge concentration to be detected when the purge control is executed. Preferably, during setting, the rpm of the purge pump is controlled to a second predetermined rpm higher than the first predetermined rpm.

According to this aspect, since the pressure in the purge passage increases by increasing the pump rotation speed and increasing the purge flow rate, it becomes easier to detect the pressure in the purge passage. Therefore, a more accurate purge concentration can be detected.

In the above aspect, it is preferable that the upper limit value of the duty ratio in the duty control is set to a second upper limit value that is lower than the first upper limit value as a condition under which the purge concentration can be detected when the purge control is executed.

According to this aspect, the time for which the purge valve is closed can be lengthened. Therefore, the time during which the purge valve is closed is ensured, so that the purge concentration can be detected more reliably based on the measurement result of the pressure in the purge passage within the time during which the purge valve is closed. . Therefore, more accurate purge concentration can be detected.

In the above aspect, it is preferable that the drive period in the duty control is set to a second period longer than the first period as a condition for detecting the purge concentration during execution of the purge control.

According to this aspect, the time for which the purge valve is closed can be lengthened. Therefore, the time during which the purge valve is closed is ensured, so that the purge concentration can be detected more reliably based on the measurement result of the pressure in the purge passage within the time during which the purge valve is closed. . Therefore, more accurate purge concentration can be detected.

According to the evaporative fuel processing apparatus of the present disclosure, it is possible to accurately detect the purge concentration while ensuring the purge flow rate by performing the purge control in a predetermined case where the change in the purge concentration can be large.

1 is a schematic configuration diagram of an internal combustion engine system having an evaporated fuel processing device in first to third embodiments; FIG. It is a figure which shows the control flowchart which shows the control content performed by 1st Embodiment. It is a figure which shows an example of the control time chart which shows the content of control performed by 1st Embodiment. It is a figure which shows the control flowchart which shows the control content performed by 2nd Embodiment. It is a figure which shows an example of the control time chart which shows the content of control performed by 2nd Embodiment. It is a figure which shows the control flowchart which shows the control content performed by 3rd Embodiment. FIG. 4 is a diagram showing an example of a map that defines the relationship between atmospheric pressure and determination temperature; It is a figure which shows an example of the control time chart which shows the content of control performed by 3rd Embodiment.

Embodiments of the evaporated fuel processing device of the present disclosure will be described below.

[First Embodiment]
An evaporated fuel processing device 1 of the first embodiment will be described.

<Outline of internal combustion engine system>
First, before describing the fuel vapor processing device 1 of the present embodiment, an outline of an internal combustion engine system 10 having the fuel vapor processing device 1 will be described. The internal combustion engine system 10 is used in vehicles such as automobiles.

As shown in FIG. 1, in an internal combustion engine system 10, an intake passage 12 for supplying air (intake air) to the engine 11 (internal combustion engine) is connected. The intake passage 12 is provided with a throttle 13 (throttle valve) that opens and closes the intake passage 12 to control the amount of air flowing into the engine 11 (intake air amount). An air flow meter 14 and an air cleaner 15 for removing foreign matter from the air flowing into the intake passage 12 are provided upstream of the throttle 13 in the intake passage 12 (upstream in the flow direction of the intake air). As a result, in the intake passage 12 , air passes through the air cleaner 15 and is drawn toward the engine 11 .

An exhaust passage 16 through which exhaust gas discharged from the engine 11 flows is connected to the engine 11 . An air-fuel ratio sensor 17 (air-fuel ratio detector) for detecting the air-fuel ratio of the engine 11 , more specifically, the air-fuel ratio of the exhaust discharged from the engine 11 is provided in the exhaust passage 16 .

The internal combustion engine system 10 has an evaporated fuel processing device 1 . This vaporized fuel processing device 1 is a device for supplying purge gas containing vaporized fuel generated in a fuel tank 21 storing fuel to be supplied to the engine 11 to the engine 11 through an intake passage 12 for processing.

The internal combustion engine system 10 also has a control section 18 . The control unit 18 is part of an ECU (not shown) mounted on the vehicle. Note that the control unit 18 may be arranged separately from the ECU. The control unit 18 includes a CPU and memories such as ROM and RAM. The control unit 18 controls the internal combustion engine system 10 according to a program pre-stored in memory. The control unit 18 also acquires the detection results from the airflow meter 14, the air-fuel ratio sensor 17, and the first pressure sensor 29, the second pressure sensor 30, and the third pressure sensor 31, which will be described later. The control unit 18 is also a control unit of the evaporated fuel processing device 1 and controls the evaporated fuel processing device 1 .

<Overview of Evaporative Fuel Processing Device>
Next, an overview of the evaporated fuel processing device 1 will be described.

As shown in FIG. 1, the evaporated fuel processing device 1 includes a canister 22, a purge passage 23, a purge pump 24, a purge valve 25, an atmosphere passage 26, a vapor passage 27, a filter 28, and a first pressure sensor. (P1) 29, a second pressure sensor (P2) 30, a third pressure sensor (P3) 31, and the like.

The canister 22 is connected to the fuel tank 21 via a vapor passage 27 and stores vaporized fuel flowing from the fuel tank 21 via the vapor passage 27 . Also, the canister 22 communicates with the purge passage 23 and the atmosphere passage 26 .

Purge passage 23 is connected to intake passage 12 and canister 22 . As a result, purge gas (gas containing evaporated fuel) flowing out of the canister 22 flows through the purge passage 23 and is supplied to the intake passage 12 .

The purge pump 24 is provided in the purge passage 23 and controls the flow rate of the purge gas flowing through the purge passage 23 . That is, the purge pump 24 sends the purge gas in the canister 22 to the purge passage 23 and supplies the purge gas sent to the purge passage 23 to the intake passage 12 .

The purge valve 25 is provided in the purge passage 23 at a position downstream of the purge pump 24 (downstream in the flow direction of the purge gas during execution of purge control), that is, at a position between the purge pump 24 and the intake passage 12 . there is The purge valve 25 opens and closes the purge passage 23 . When the purge valve 25 is closed (when the valve is closed), the purge gas in the purge passage 23 is stopped by the purge valve 25 and does not flow toward the intake passage 12 . On the other hand, when the purge valve 25 is open (when the valve is open), the purge gas flows into the intake passage 12 .

The atmosphere passage 26 has one end open to the atmosphere and the other end connected to the canister 22 to communicate the canister 22 to the atmosphere. Air taken in from the atmosphere flows through the air passage 26 through the filter 28 .

Vapor passage 27 is connected to fuel tank 21 and canister 22 . As a result, vaporized fuel in the fuel tank 21 flows into the canister 22 through the vapor passage 27 .

The first pressure sensor 29 detects pressure at a position downstream of the purge pump 24 in the purge passage 23 . The second pressure sensor 30 detects pressure at a position upstream of the purge pump 24 in the purge passage 23 . The third pressure sensor 31 detects the pressure difference between the pressure at a position upstream of the purge pump 24 in the purge passage 23 and the pressure at a position downstream of the purge pump 24 . Note that it is not necessary to provide all of the first pressure sensor 29, the second pressure sensor 30, and the third pressure sensor 31, and at least one of the first pressure sensor 29, the second pressure sensor 30, and the third pressure sensor 31 It is sufficient if one is provided.

In the evaporative fuel processing apparatus 1 having such a configuration, when the purge condition is established during operation of the engine 11, the control unit 18 controls the purge pump 24 and the purge valve 25, that is, drives the purge pump 24 while the purge valve is operated. 25 is opened to perform purge control. The purge control is control for supplying purge gas from the canister 22 to the engine 11 through the purge passage 23 and the intake passage 12 for processing. Further, when performing purge control, the control unit 18 controls the purge valve 25 by duty control.

While the purge control is being executed, the engine 11 is injected (supplied) with air sucked into the intake passage 12 and a fuel tank 21 via a fuel injection valve (fuel supply unit, not shown). Fuel and purge gas supplied by purge control are supplied. The control unit 18 adjusts the injection time of the fuel injection valve, the valve opening time of the purge valve 25, and the like, thereby adjusting the air-fuel ratio (A/F) of the engine 11 to an optimum air-fuel ratio (for example, the ideal air-fuel ratio). air-fuel ratio control is performed.

1, the purge passage 23 is connected to the intake passage 12 on the downstream side of the throttle 13, but if the supercharger 33 is provided on the upstream side of the throttle 13, supercharging A purge passage 32 may be provided upstream of the vessel 33 and connected to the intake passage 12 .

<Regarding detection control of purge concentration>
Next, the purge concentration detection control performed by the control unit 18 will be described. The "purge concentration" is the concentration of fuel vapor contained in the purge gas.

In the air-fuel ratio control, the controller 18 determines the amount of deviation between the air-fuel ratio detected by the air-fuel ratio sensor 17 (the detected value of the air-fuel ratio of the engine 11) and the target air-fuel ratio (the target value of the air-fuel ratio of the engine 11). A/F learning (A/F feedback learning, air-fuel ratio learning) is executed to correct the air-fuel ratio deviation amount. The control unit 18 also performs OBD control (failure diagnosis control (self-diagnosis control) of the air-fuel ratio sensor 17).

Here, when A/F learning and OBD control are executed, if the purge concentration changes significantly while purge control is being executed, there is a possibility of erroneous learning in A/F learning and the possibility of proper OBD control. Because of this possibility, it is common practice to turn off the purge control. However, if the purge control is stopped, the purge flow rate (the flow rate of the purge gas that is supplied to the engine 11 and processed) will decrease, and there is a risk that evaporative emissions will deteriorate (the amount of evaporated fuel discharged into the atmosphere will increase). be.

Therefore, in the present embodiment, the control unit 18 executes purge control if the purge condition is satisfied even during execution of A/F learning or OBD control. Then, when executing such purge control, the control unit 18 detects an accurate purge concentration, and based on this detection result, suppresses erroneous learning of A/F learning and appropriately performs OBD control. to control. Accordingly, the control unit 18 appropriately performs A/F learning and OBD control while suppressing deterioration of evaporative emissions due to a decrease in the purge flow rate.

Further, in the present embodiment, the control unit 18 similarly controls the control unit 18 after the ignition switch of the vehicle in which the evaporated fuel processing device 1 is mounted is turned on and before the concentration is determined (before the purge concentration is first determined). In addition, control is performed to detect an accurate purge concentration when executing purge control.

(Description of flow chart)
Specifically, the control unit 18 performs control based on the control flowchart shown in FIG. 2 as the purge concentration detection control.

As shown in FIG. 2, the control unit 18 operates during execution of purge control (during purge control) (step S1: YES), before concentration determination, or during execution of A/F learning (A/F learning or when a certain condition is met (step S2: YES) when OBD control is being executed (OBD control is being executed), processing for enabling detection of an accurate purge concentration even when purge control is being executed. I do.

Here, the purge concentration is obtained by measuring the pressure (closing pressure) in the purge passage 23 with pressure sensors (the first pressure sensor 29, the second pressure sensor 30, and the third pressure sensor 31), and based on this measurement result. detected.

Therefore, when the purge control is stopped, the purge valve 25 is kept closed, so that the control unit 18 can easily detect the purge concentration based on the pressure measurement result in the purge passage 23 by the pressure sensor. can do.

However, in this embodiment, the purge valve 25 is controlled by duty control when the purge control is executed. Therefore, when the purge control is executed, the control unit 18 causes the pressure sensor to detect the pressure in the purge passage 23 only when the purge valve 25 is closed at a predetermined duty ratio (ratio of the valve opening time in one cycle). The purge concentration can be detected based on the pressure measurement results. Then, when the purge control is executed, if the purge valve 25 is closed for a short time, it is difficult to detect an accurate purge concentration. In particular, in the duty control of the purge valve 25, if the duty ratio is high and the drive period (the period during which the purge valve 25 is opened and closed once) is short, it becomes even more difficult to detect the purge concentration accurately.

Therefore, as a process for enabling accurate detection of the purge concentration even when purge control is executed, first, the control unit 18 sets the pump rotation speed (the rotation speed of the purge pump 24) to a second predetermined rotation speed ( For example, 40,000 rpm) (step S3). That is, the control unit 18 sets the pump rotation speed from a first predetermined rotation speed (for example, 30,000 rpm) to a second predetermined rotation speed higher than the first predetermined rotation speed. Here, the first predetermined number of revolutions is the normal number of revolutions during execution of the purge control.

Next, the control unit 18 changes the upper limit value of the duty ratio (upper limit duty of PCV) in the duty control of the purge valve 25 from the first upper limit value (for example, 100%) to a second upper limit value lower than the first upper limit value. (eg, 40%) (step S4). Here, the first upper limit value is the upper limit value of the normal duty ratio when purge control is executed.

Further, in step S4, the control unit 18 changes the drive cycle in the duty control of the purge valve 25 from the first cycle (eg, 100 ms) to a second cycle (eg, 150 ms) longer than the first cycle (step S4). S4). Here, the first cycle is a normal drive cycle during execution of purge control.

In this manner, as a process for enabling accurate detection of the purge concentration even when the purge control is executed, the control unit 18 sets the duty control condition of the purge valve 25 to the purge concentration when the purge control is executed. Set to detectable conditions. Specifically, the controller 18 sets the upper limit value of the duty ratio in the duty control of the purge valve 25 to a value lower than a first upper limit value (for example, 100%) as a condition under which the purge concentration can be detected during execution of the purge control. 2 Set the upper limit (eg, 40%). In addition, the control unit 18 sets the drive cycle in the duty control of the purge valve 25 to a second cycle (eg, 150 ms) longer than the first cycle (eg, 100 ms) as a condition for detecting the purge concentration during execution of the purge control. do.

Further, while the control unit 18 sets the conditions for the duty control of the purge valve 25 to the conditions under which the purge concentration can be detected when the purge control is executed, the control unit 18 sets the pump rotation speed to the first predetermined rotation speed (for example, 30,000 rpm) is controlled to a second predetermined rotation speed (eg, 40,000 rpm) to increase the purge flow rate.

Then, after performing the processing of steps S3 and S4, the control unit 18 measures the pressure in the purge passage 23 when the purge valve 25 is closed (the pressure when the PCV is closed) using a pressure sensor, Based on this measurement result, the purge concentration is detected (step S5).

If the condition of step S2 is not satisfied (step S2: NO), the control unit 18 sets the pump rotation speed to the first predetermined rotation speed (for example, 30,000 rpm) (step S6), and the air-fuel ratio The purge concentration is detected from the deviation amount (A/F F/B deviation) (step S7). Thereby, purge control can be performed stably.

Further, when the purge control is stopped (step S1: NO), the control unit 18 sets the pump rotation speed to a first predetermined rotation speed (eg, 30,000 rpm) (step S8). Next, the control unit 18 measures the pressure in the purge passage 23 when the purge valve 25 is closed (the pressure when the PCV is closed) using a pressure sensor, and determines the purge concentration based on the measurement result. It is determined whether the detection is completed (step S9). Then, when the detection of the purge concentration is completed (step S9: YES), the control unit 18 stops the purge pump 24 (sets the pump rotation speed to 0 rpm), or sets the pump rotation speed higher than the first predetermined rotation speed. A low low rotation speed (a third predetermined rotation speed, for example, 10,000 rpm) is set (step S10).

(Description of time chart)
By performing control based on the control chart shown in FIG. 2, an example of the control time chart shown in FIG. 3 is implemented.

As shown in FIG. 3, first, assume that the ignition switch (ignition SW) is turned on (ON) at time T1. After that, it is assumed that the purge control is executed from time T2 to time T3 before the concentration is determined. It is also assumed that purge control is executed during the execution of A/F learning from time T4 to time T5. It is also assumed that the purge control is executed during the execution of the OBD control from time T8 to time T9.

Therefore, from the time T2 to the time T3, from the time T4 to the time T5, and from the time T8 to the time T9, processing is performed to enable accurate detection of the purge concentration even when the purge control is executed. Specifically, the pump rotation speed is set to 40,000 rpm (second predetermined rotation speed), the upper limit of the duty ratio (PCVDuty) in the duty control of the purge valve 25 is set to 40% (second upper limit), and the duty ratio of the purge valve 25 is set to 40% (second upper limit). The control drive cycle (PCV drive cycle) is set to 150 ms (second cycle). In this manner, the purge flow rate is increased, and in the duty control of the purge valve 25, the duty ratio is lowered and the drive period is lengthened. Then, the purge concentration (purge A/F) is detected based on the pressure measurement results of the pressure sensors (concentration sensor, first pressure sensor 29, second pressure sensor 30, and third pressure sensor 31).

<About the effect of this embodiment>
As described above, in the evaporative fuel processing apparatus 1 of the present embodiment, the control unit 18 sets the duty of the purge valve 25 before the concentration is determined, when A/F learning is executed, or when the OBD control is executed. A control condition is set to a condition that allows the purge concentration to be detected when the purge control is executed.

In this way, the control unit 18 controls the purge valve 25 in a predetermined case where the change in purge concentration can be large, such as before concentration determination, when A/F learning is executed, or when OBD control is executed. is set to a condition that allows the purge concentration to be detected when the purge control is executed. Therefore, it is possible to accurately detect the purge concentration while performing purge control. Therefore, before the concentration is determined, when A/F learning is executed, or when OBD control is executed, the purge control is performed to ensure the purge flow rate and the accurate purge concentration can be detected. Therefore, it is possible to appropriately perform concentration determination, A/F learning, or OBD control based on the detected purge concentration while suppressing deterioration of evaporative emissions due to a decrease in purge flow rate.

On the other hand, the control unit 18 controls the purge valve 25 by duty control before concentration determination, when A/F learning is executed, or when OBD control is not executed (when the change in purge concentration is small). Set the condition to be a normal condition. That is, the control unit 18 sets the pump rotation speed to a first predetermined rotation speed (for example, 30,000 rpm), the upper limit value of the duty ratio in the duty control of the purge valve 25 to a first upper limit value (for example, 100%), and the purge valve 25 duty control is controlled to the first period (for example, 100 ms). Thereby, purge control can be performed stably.

Further, while the control unit 18 sets the duty control condition of the purge valve 25 to a condition that allows the purge concentration to be detected when the purge control is executed, the control unit 18 sets the pump rotation speed to a first predetermined rotation speed (for example, 30,000 rpm). is controlled to a second predetermined rotation speed (for example, 40,000 rpm).

Since the pressure in the purge passage 23 increases by increasing the purge flow rate by increasing the pump rotation speed in this manner, the pressure in the purge passage 23 can be easily detected by the pressure sensor. Therefore, a more accurate purge concentration can be detected.

Further, as a condition for detecting the purge concentration during execution of the purge control, the upper limit of the duty ratio in the duty control of the purge valve 25 is set to a second upper limit (for example, 40%) lower than the first upper limit (for example, 100%). %).

Also, as a condition for detecting the purge concentration during purge control, the drive period in the duty control of the purge valve 25 is set to a second period (eg, 150 ms) longer than the first period (eg, 100 ms).

As a result, the period during which the purge valve 25 is closed can be lengthened. Therefore, the time during which the purge valve 25 is closed is ensured, so that the purge concentration can be determined more reliably based on the pressure sensor in the purge passage 23 within the time during which the purge valve 25 is closed. can be detected. Therefore, more accurate purge concentration can be detected.

[Second embodiment]
Next, the second embodiment will be described. Components that are the same as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

<Regarding detection control of purge concentration>
In the present embodiment, the purge concentration detection control performed by the control unit 18 will be described.

When a large amount of evaporative fuel is generated in the fuel tank 21, the purge concentration may change greatly. It is possible to reduce the However, if the purge flow rate is reduced, there is a risk that evaporative emissions will deteriorate.

Therefore, in the present embodiment, even when a large amount of vaporized fuel is generated in the fuel tank 21, the control unit 18 intentionally reduces the purge flow rate if the purge condition is satisfied. Purge control is executed without Then, the control unit 18 detects an accurate purge concentration when executing such purge control, and based on the detection result, performs control so as to suppress the influence on the air-fuel ratio control. As a result, even when a large amount of evaporated fuel is generated in the fuel tank 21, the control unit 18 can appropriately control the air-fuel ratio by suppressing deterioration of evaporative emissions due to a decrease in the purge flow rate. can be controlled.

(Description of flow chart)
Specifically, the control unit 18 performs control based on the control flowchart shown in FIG. 4 as the purge concentration detection control.

As shown in FIG. 4, when the purge control is executed (during purge control) (step S11: YES), the control unit 18 sets the air-fuel ratio deviation amount (A/F F/B deviation) to a predetermined value (for example, , −15%) or less (step S12: YES), a process is performed to enable accurate detection of the purge concentration even when the purge control is executed. Here, when a large amount of evaporated fuel is generated in the fuel tank 21, the amount of air-fuel ratio deviation becomes equal to or less than a predetermined value, and the amount of deviation of the air-fuel ratio toward the rich side increases. Therefore, in this way, in the present embodiment, the control unit 18 sets the amount of air-fuel ratio deviation to be equal to or less than the predetermined value, and the amount of deviation of the air-fuel ratio to the rich side increases. When fuel vapor is expected to occur, processing is performed to enable detection of an accurate purge concentration even when purge control is being executed.

Therefore, first, the control unit 18 clears (sets to "0") the purge-on integrated time (integrated time during which purge control is executed) or the purge-on integrated flow rate (integrated amount of purge flow rate due to execution of purge control) ( step S13). Next, if the purge-on integrated time or the purge-on integrated flow rate after the process of step S13 is less than a predetermined value (for example, 10 sec, 20 L) (step S14: YES), the control unit 18 controls the first embodiment (FIG. 2), the purge concentration is detected after performing the process (steps S15, S16) for enabling accurate detection of the purge concentration even when the purge control is executed. (Step S17).

In this way, when the control unit 18 is estimated to be in an environment with a large change in the purge concentration from the air-fuel ratio deviation amount, which is the information of the engine 11 related to the change in the purge concentration, the fuel tank 21 It is expected that a large amount of evaporated fuel is generated. When it is expected that a large amount of vaporized fuel is generated in the fuel tank 21, the controller 18 sets the duty control condition of the purge valve 25 so that the purge concentration can be detected when the purge control is executed. Set the conditions and detect the correct purge concentration while performing purge control.

(Description of time chart)
By performing control based on the control chart shown in FIG. 4, an example of the control time chart shown in FIG. 5 is implemented.

As shown in FIG. 5, at time T12, when the purge control was executed, the air-fuel ratio deviation (A/F F/B deviation) became -15% or less, so the integrated purge-on time and purge-on integrated flow rate set to "0". Thereafter, the purge control is executed from time T11 to time T12, the purge-on integrated time is less than 10 sec, and the purge-on integrated flow rate is less than 20L. Therefore, when the pump rotation speed is set to 40,000 rpm (second predetermined rotation speed), the upper limit of the duty ratio (PCDuty) in the duty control of the purge valve 25 is set to 40% (second upper limit), and the purge valve 25 is driven in the duty control, A cycle (PCV drive cycle) is set to 150 ms (second cycle). In this manner, the purge flow rate is increased, and in the duty control of the purge valve 25, the duty ratio is lowered and the drive period is lengthened. Then, the purge concentration (purge A/F) is detected based on the pressure measurement results of the pressure sensors (concentration sensor, first pressure sensor 29, second pressure sensor 30, and third pressure sensor 31).

Also, between the time T13 and the time T14, the air-fuel ratio deviation (A/F F/B deviation) became -15% or less, but the purge control is stopped. After that, purge control is executed from time T14 to time T15. At this time, the purge-on integrated time is less than 10 sec, and the purge-on integrated flow rate is less than 2.0L. Therefore, during the period from time T14 to time T15, similarly to the period from time T12 to time T13, the pump rotation speed, the duty ratio in the duty control of the purge valve 25, and the drive cycle are set, and the purge concentration is detected. be done.

<About the effect of this embodiment>
As described above, in the evaporative fuel processing device 1 of the present embodiment, the control unit 18, based on information on the amount of air-fuel ratio deviation (A/F F/B deviation) (information on the engine 11 related to changes in purge concentration), Predict whether the environment is such that the change in purge concentration is large. As a result, when the environment is estimated to have a large change in the purge concentration, the control unit 18 sets the duty control condition of the purge valve 25 to a condition that allows the purge concentration to be detected when the purge control is executed. .

In this way, when it is estimated from the information on the amount of air-fuel ratio deviation (A/F F/B deviation) that the environment is one in which there is a large change in the purge concentration, the conditions for controlling the purge valve 25 by duty control are determined by the purge control. Since the purge concentration is set to a detectable condition during the execution of , the purge concentration can be accurately detected while performing purge control. Therefore, when a large amount of vaporized fuel is generated in the fuel tank 21 and it is estimated that the purge concentration is greatly changed, the purge control is performed to ensure the purge flow rate and the accurate purge concentration can be detected. Therefore, even if a large amount of evaporated fuel is generated in the fuel tank 21, the air-fuel ratio can be adjusted appropriately based on the detected purge concentration while suppressing the deterioration of the evaporative emission due to the decrease in the purge flow rate. can be controlled.

In addition, by estimating whether or not the environment has a large change in the purge concentration before purging using the information of the engine 11 related to the change in the purge concentration, the conditions for the duty control of the purge valve 25 can be set in advance to execute the purge control. Sometimes the purge concentration can be set to detectable conditions. Therefore, even if past purge concentration data is not stored in the controller 18, the timing of sending the purge gas is advanced based on the accurate purge concentration.

[Third embodiment]
Next, the third embodiment will be described. Components that are the same as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

<Regarding detection control of purge concentration>
In the present embodiment, the purge concentration detection control performed by the control unit 18 will be described.

(Description of flow chart)
Specifically, the control unit 18 performs control based on the control flowchart shown in FIG. 6 as purge concentration detection control.

As shown in FIG. 6, when the purge control is being executed (during purge control) (step S31: YES), the control unit 18 determines that a large amount of evaporated fuel (vapor) is being generated in the fuel tank 21. If it is expected (step S32: YES), purge control is performed as in the first embodiment (steps 3, S4, and S5 in FIG. 2) and the second embodiment (steps S15, S16, and S17 in FIG. 4). After performing processing (steps S33 and S34) to enable detection of an accurate purge concentration even during execution of , the purge concentration is detected (step S35).

Here, in step S32, if the tank fuel temperature (the temperature of the fuel in the fuel tank 21) is equal to or higher than the judgment temperature (hiss (error): -2°C), the control unit 18 of evaporated fuel is expected to occur. Alternatively, if the purge concentration (purge A/F) is a predetermined value (for example, 1.0 (hiss (error): +0.2)) or less in step S32, the control unit 18 causes the fuel tank 21 to of evaporated fuel is expected to occur. Note that the determination temperature (predetermined determination temperature) is calculated from the atmospheric pressure based on a map that defines the relationship between the atmospheric pressure and the determination temperature as shown in FIG.

In this way, the control unit 18 estimates that the environment is such that the change in the purge concentration is large from the tank fuel temperature and the purge concentration (purge A/F), which are the information of the fuel tank 21 related to the change in the purge concentration. In this case, it is assumed that a large amount of evaporated fuel is generated in the fuel tank 21 . When it is expected that a large amount of vaporized fuel is generated in the fuel tank 21, the controller 18 sets the duty control condition of the purge valve 25 so that the purge concentration can be detected when the purge control is executed. Set the conditions and detect the correct purge concentration while performing purge control.

(Description of time chart)
By performing control based on the control chart shown in FIG. 6, an example of the control time chart shown in FIG. 8 is implemented.

As shown in FIG. 8, at time T24, when the purge control was executed, the tank fuel temperature became 40° C. or higher and the purge A/F became 1.0 or lower. Therefore, when the pump rotation speed is set to 40,000 rpm (second predetermined rotation speed), the upper limit of the duty ratio (PCDuty) in the duty control of the purge valve 25 is set to 40% (second upper limit), and the purge valve 25 is driven in the duty control, A cycle (PCV drive cycle) is set to 150 ms (second cycle). In this manner, the purge flow rate is increased, and in the duty control of the purge valve 25, the duty ratio is lowered and the drive period is lengthened. Then, the purge concentration (purge A/F) is detected based on the pressure measurement results of the pressure sensors (concentration sensor, first pressure sensor 29, second pressure sensor 30, and third pressure sensor 31).

<About the effect of this embodiment>
As described above, in the evaporated fuel processing device 1 of the present embodiment, the control unit 18 estimates from the tank fuel temperature whether or not the environment is such that the change in the purge concentration is large. As a result, when the environment is estimated to have a large change in the purge concentration, the control unit 18 sets the duty control condition of the purge valve 25 to a condition that allows the purge concentration to be detected when the purge control is executed. .

In this way, when the tank fuel temperature (information of the fuel tank 21 related to the change in purge concentration) indicates that the environment has a large change in the purge concentration, the condition for controlling the purge valve 25 by duty control is set to Since the purge concentration is set to a detectable condition while the control is being executed, the purge concentration can be accurately detected while performing the purge control. Therefore, when a large amount of vaporized fuel is generated in the fuel tank 21 and it is estimated that the purge concentration is greatly changed, the purge control is performed to ensure the purge flow rate and the accurate purge concentration can be detected. Therefore, even if a large amount of evaporated fuel is generated in the fuel tank 21, the air-fuel ratio can be adjusted appropriately based on the detected purge concentration while suppressing the deterioration of the evaporative emission due to the decrease in the purge flow rate. can be controlled.

It should be noted that the above-described embodiment is merely an example and does not limit the present disclosure in any way, and of course various improvements and modifications are possible without departing from the gist of the present disclosure.

1 Evaporated fuel processing device 10 Internal combustion engine system 11 Engine 12 Intake passage 17 Air-fuel ratio sensor 18 Control unit 21 Fuel tank 22 Canister 23 Purge passage 24 Purge pump 25 Purge valve 29 First pressure sensor (P1)
30 second pressure sensor (P2)
31 third pressure sensor (P3)

Claims (7)

a canister storing evaporated fuel;
a purge passage for flowing purge gas containing the evaporated fuel from the canister to the internal combustion engine;
a purge valve that opens and closes the purge passage;
a control unit that performs purge control for supplying the purge gas from the canister to the internal combustion engine through the purge passage;
In an evaporative fuel processing device having
The control unit
performing the purge control while controlling the purge valve by duty control;
setting the duty control condition to a condition in which the purge concentration can be detected when the purge control is executed in a predetermined case where a change in the purge concentration, which is the concentration of the evaporated fuel contained in the purge gas, can be large ;
The predetermined case is
Before determining the concentration after the ignition switch of the vehicle in which the fuel vapor processing device is installed is turned on and before the purge concentration is determined;
Alternatively, during execution of air-fuel ratio learning for correcting the amount of air-fuel ratio deviation, which is the amount of deviation between the detected value of the air-fuel ratio of the internal combustion engine and the target value,
Alternatively, when executing self-diagnostic control of an air-fuel ratio detection unit that detects the air-fuel ratio,
An evaporative fuel processing device characterized by: a canister storing evaporated fuel;
a purge passage for flowing purge gas containing the evaporated fuel from the canister to the internal combustion engine;
a purge valve that opens and closes the purge passage;
a control unit that performs purge control for supplying the purge gas from the canister to the internal combustion engine through the purge passage;
In an evaporative fuel processing device having
The control unit
performing the purge control while controlling the purge valve by duty control;
setting the duty control condition to a condition in which the purge concentration can be detected when the purge control is executed in a predetermined case where a change in the purge concentration, which is the concentration of the evaporated fuel contained in the purge gas, can be large;
The predetermined case is
a case where it is estimated that the environment is one in which the change in the purge concentration is large, based on the information on the internal combustion engine or the fuel tank related to the change in the purge concentration;
An evaporative fuel processing device characterized by: In the evaporative fuel processing device of claim 2 ,
The information of the internal combustion engine related to the change in the purge concentration is information of an air-fuel ratio deviation amount, which is an amount of deviation between a detected value and a target value of the air-fuel ratio of the internal combustion engine;
An evaporative fuel processing device characterized by: In the evaporative fuel processing device of claim 2 ,
The information of the fuel tank related to the change in the purge concentration is information of the temperature of the fuel in the fuel tank;
An evaporative fuel processing device characterized by: In the evaporated fuel processing device according to any one of claims 1 to 4 ,
a purge pump for controlling the flow rate of the purge gas flowing through the purge passage;
The controller controls the rotation speed of the purge pump to a second predetermined rotation speed higher than a first predetermined rotation speed while the duty control condition is set to a condition that allows the purge concentration to be detected when the purge control is executed. to control the number of revolutions,
An evaporative fuel processing device characterized by: In the evaporated fuel processing device according to any one of claims 1 to 5 ,
setting the upper limit value of the duty ratio in the duty control to a second upper limit value that is lower than the first upper limit value as a condition under which the purge concentration can be detected when the purge control is executed;
An evaporative fuel processing device characterized by: In the evaporated fuel processing device according to any one of claims 1 to 6 ,
setting the drive cycle in the duty control to a second cycle longer than the first cycle as a condition for detecting the purge concentration during execution of the purge control;
An evaporative fuel processing device characterized by:

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