JP6610080B2 - Evaporative fuel processing equipment - Google Patents

Description

  The present invention relates to a sealed tank type evaporated fuel processing apparatus.

  2. Description of the Related Art Conventionally, an evaporative fuel processing apparatus is known in which evaporative fuel generated in a fuel tank is adsorbed by a canister and the adsorbed fuel is purged to an intake system during operation of the engine. That is, the evaporated fuel is temporarily collected by the canister and sucked into the engine to prevent the evaporated fuel from being released into the atmosphere. In an engine equipped with such a fuel vapor processing apparatus, the fuel injection amount and the intake air amount are controlled in consideration of the amount of fuel vapor desorbed from the canister.

  On the other hand, in recent years, hybrid vehicles (PHEV, PHV) have been developed that travel mainly using a traveling motor and use an engine as an auxiliary. Such a hybrid vehicle has a shorter engine operation time than a vehicle using only the engine as a power source, and has less opportunity to purge the evaporated fuel adsorbed by the canister. In view of this, a technique has been proposed in which a sealing valve is provided on a passage connecting the fuel tank and the canister, and the fuel tank is kept sealed as long as possible to suppress fuel evaporation and adsorption to the canister (Patent Literature). 1 and 2).

Japanese Unexamined Patent Publication No. 2015-081528 JP 2014-092069 A

However, in the above-described closed tank system, the internal pressure of the fuel tank is likely to increase, and a long depressurization time before refueling may lead to user dissatisfaction. Moreover, since the average pressure of the fuel tank tends to be relatively high, there is room for improvement in terms of component protection.
One of the purposes of the present invention was created in view of the above-described problems, and provides an evaporative fuel processing apparatus that improves the component protection while reducing the pressure release time of the fuel tank. is there. It should be noted that the present invention is not limited to this purpose, and is an operational effect that is derived from each configuration shown in “Mode for Carrying Out the Invention” to be described later. Can be positioned as a purpose.

(1) The evaporative fuel processing device disclosed herein includes a canister that adsorbs evaporative fuel generated in a fuel tank and a passage connecting the fuel tank, and a sealing valve is interposed between the canister and the intake system of the engine. This is a sealed tank type evaporated fuel processing apparatus in which a bypass valve is provided on a passage connecting the two. The evaporative fuel processing apparatus includes a first control unit that opens the sealing valve according to a tank pressure of the fuel tank and performs a high-pressure purge for reducing the tank pressure. A second control unit configured to perform a canister purge for opening the bypass valve during operation of the engine and causing the intake system to suck the evaporated fuel adsorbed by the canister; Furthermore, after the end of the canister purge and before the engine is stopped, a third control unit is provided that performs a low pressure purge that opens the sealing valve regardless of the tank pressure and reduces the tank pressure.
Further, the third control unit determines whether or not the low-pressure purge is necessary according to the elapsed time since the latest refueling. In this case, it is preferable that the low pressure purge is performed when the elapsed time is less than a predetermined time, and the low pressure purge is not performed when the elapsed time is equal to or longer than the predetermined time.
Alternatively, the third control unit determines whether the low pressure purge is necessary according to the amount of fuel remaining in the fuel tank. In this case, it is preferable that the low pressure purge is performed if the fuel amount is equal to or greater than a predetermined amount, and the low pressure purge is not performed if the fuel amount is less than the predetermined amount.

  The third control unit preferably functions to maintain the operating state of the engine during the execution of the low pressure purge. For example, when the engine operating condition is not satisfied during the canister purge, the engine is not stopped immediately, but the third control unit maintains the engine operating state. It is preferred to perform a low pressure purge.

(2) It is preferable that the end condition of the low pressure purge is relaxed than the end condition of the high pressure purge. That is, it is preferable to give the low pressure purge a characteristic that it is easier to finish than the high pressure purge.
(3) When the tank pressure is equal to or higher than the first pressure, the first control unit preferably opens the sealing valve until the tank pressure becomes less than the second pressure. In this case, it is preferable that the third control unit opens the sealing valve until the tank pressure becomes lower than the third pressure higher than the second pressure. That is, the upper threshold (the third pressure) for closing the sealing valve by the low pressure purge is preferably higher than the upper threshold (the second pressure) for closing the sealing valve by the high pressure purge. .

  By performing the low pressure purge when the canister purge is completed, the fuel tank is depressurized regardless of the tank pressure, so the average pressure of the fuel tank can be reduced, and the pressure release time before fuel supply can be reduced. The component protection can be improved while shortening.

It is a figure which shows the structure of the vehicle to which the evaporative fuel processing apparatus was applied. It is a flowchart which illustrates the control procedure during an engine stop. 3 is a flowchart illustrating a control procedure during engine operation.

  With reference to drawings, the evaporative fuel processing apparatus as embodiment is demonstrated. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment. Each configuration of the present embodiment can be implemented with various modifications without departing from the spirit thereof. Further, they can be selected as necessary, or can be appropriately combined.

[1. Device configuration]
FIG. 1 illustrates the configuration of a vehicle to which the evaporated fuel processing apparatus of this embodiment is applied. This vehicle is a hybrid vehicle having an EV (Electric Vehicle) mode that travels with the driving force of a traveling motor and a HEV (Hybrid Electric Vehicle) mode that travels using (or used in combination) the driving force of the engine 21. is there. When the engine 21 is operated, fuel is sucked up from the inside of the fuel tank 5 by a pump, and an amount of fuel corresponding to the traveling state of the vehicle is injected from the injector 22. The intake air amount is controlled by a throttle valve 25 interposed in the intake passage 23.

  The engine 21 is equipped with a purge passage 10 for collecting the evaporated fuel generated in the fuel tank 5 by the canister 6 and introducing it into the intake system. The purge passage 10 is provided with a tank passage 7 that connects the fuel tank 5 and the intake system of the engine 21, and a canister passage 8 that is branched from the tank passage 7 toward the canister 6. One end of the tank passage 7 is connected to, for example, the vicinity of the ceiling surface or the upper side of the fuel tank 5, and the other end is connected to the intake passage 23. The connection position of the tank passage 7 is set downstream of the throttle valve 25 (on the side closer to the cylinder of the engine 21). One end of the canister passage 8 is connected to the upper surface of the canister 6, and the other end is connected to the tank passage 7 so as to form a three-way.

The purge passage 10 is provided with a sealing valve 1, a bypass valve 2 and a purge valve 3 as valves for controlling the air flow in the passage.
The sealing valve 1 is an electromagnetic control valve for sealing the fuel tank 5, and is disposed at a position closer to the fuel tank 5 than a branch point between the tank passage 7 and the canister passage 8. The sealing valve 1 basically functions so as to always close the tank passage 7 and maintain the sealed state of the fuel tank 5. Further, when the internal pressure of the fuel tank 5 exceeds a predetermined value, the fuel tank 5 is opened. The sealing valve 1 of the present embodiment is a two-position switching valve that is turned on / off (opening or closing) according to the type and magnitude of the control signal.

  The bypass valve 2 is an electromagnetic control valve for opening or closing the canister passage 8 and is disposed at a branch point between the tank passage 7 and the canister passage 8. The bypass valve 2 is opened when the canister 6 is desired to adsorb the evaporated fuel or when the evaporated fuel adsorbed by the canister 6 is desired to be purged. The bypass valve 2 of the present embodiment is a two-position switching valve that is turned on and off according to the type and magnitude of the control signal, as with the sealing valve 1.

  The purge valve 3 is an electromagnetic control valve for opening or closing the tank passage 7 with respect to the intake passage 23, and is disposed at a position closer to the intake passage 23 than the branch point between the tank passage 7 and the canister passage 8. . The purge valve 3 is basically controlled so as to open the tank passage 7 with respect to the intake passage 23 during operation of the engine 21. Further, when the engine 21 is stopped, the tank passage 7 is controlled to be closed. The purge valve 3 of the present embodiment is a variable opening control valve that opens the tank passage 7 with an opening according to the magnitude of the control signal. The opening degree of the purge valve 3 can be set according to the operating state of the engine 21, the amount of evaporated fuel adsorbed by the canister 6, the amount of fuel remaining in the fuel tank 5, and the like.

  As shown in FIG. 1, an air release passage 9 that connects the canister 6 and the outside is attached to the upper surface of the canister 6. The air release passage 9 functions as a pressure release passage when the fuel vapor is adsorbed on the canister 6 and also functions as an outside air intake passage when the fuel vapor adsorbed on the canister 6 flows out to the intake passage 23. An air filter 20 is interposed in the atmosphere opening passage 9 where foreign substances in the outside air are removed.

A relief valve 4 is interposed on a bypass path formed so as to bypass the sealing valve 1 and connect the upstream side and the downstream side of the sealing valve 1. The relief valve 4 is a safety valve that defines an upper limit value P _MAX of the internal pressure of the fuel tank 5. When the pressure in the tank passage 7 on the fuel tank 5 side with respect to the sealing valve 1 is equal to or lower than a predetermined upper limit value _PMAX , the relief valve 4 is closed. On the other hand, when the pressure in the tank passage 7 on the fuel tank 5 side of the sealing valve 1 exceeds the upper limit value P _MAX , the relief valve 4 is opened and the fuel tank 5 is depressurized. This prevents the internal pressure of the fuel tank 5 from rising beyond the upper limit value _PMAX .

  The fuel tank 5 is provided with a fuel supply passage 19 for fuel supply, the tip of which is closed by a filler cap 17 and extends to the inside of the fuel lid 16. At the time of fuel supply, after the fuel lid 16 is opened by an occupant of the vehicle, the filler cap 17 is rotated and removed. The oil supply passage 19 is provided with a check valve 18 for preventing the backflow of fuel and the outflow of fuel vapor. The check valve 18 functions to allow inflow of fluid from the outside of the vehicle toward the fuel tank 5 and to prevent outflow of fluid in the reverse direction.

  The open / closed state (opening degree) of the sealing valve 1, the bypass valve 2, and the purge valve 3 is controlled by the control device 30 functioning as a computer. The control device 30 is an electronic device in which a processor such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit) and a ROM (Read Only Memory), a RAM (Random Access Memory), a nonvolatile memory, and the like are integrated. The processor here is, for example, a processing device (processor) including a control unit (control circuit), an arithmetic unit (arithmetic circuit), a cache memory (register), and the like. The ROM, RAM, and nonvolatile memory are memory devices that store programs and working data. The contents of the control executed by the control device 30 are recorded in the ROM, RAM, nonvolatile memory, and removable medium as firmware and application programs. When the program is executed, the contents of the program are expanded in the memory space in the RAM and executed by the processor.

An intake manifold pressure sensor 12, a tank pressure sensor 13, an engine speed sensor 14, and a lid opening sensor 15 are connected to the control device 30. The intake manifold pressure sensor 12 detects the internal pressure of the surge tank 24 provided downstream of the throttle valve 25 in the intake passage 23 as “intake manifold pressure P _IM (intake system pressure)”. Here, the pressure (magnitude of negative pressure) in the vicinity of the connection point between the intake passage 23 and the tank passage 7 is detected.

The tank pressure sensor 13 detects the internal pressure of the fuel tank 5 (gas portion pressure) as “tank pressure P”. The tank pressure sensor 13 is attached at a position above the fuel liquid level. The engine speed sensor 14 detects the rotational speed of the engine 21 (engine speed Ne). The lid opening sensor 15 is a proximity sensor that detects that the fuel lid 16 is opened. Information detected by these various sensors 12 to 15 is transmitted to the control device 30. The pressure detected by each of the intake manifold pressure sensor 12 and the tank pressure sensor 13 may be an absolute pressure or a gauge pressure based on the atmospheric pressure P _ATM .

[2. Control details]
The control device 30 according to the present embodiment performs five types of control including tank sealing control, pressure release control, canister purge control, high pressure purge control, and low pressure purge control. The tank sealing control and the pressure relief control are controls that can be performed while the engine 21 is not operating. In contrast, the remaining three types of control are performed when the engine 21 is in operation and the operating state of the engine 21 is relatively stable. In the present embodiment, either tank sealing control or pressure relief control is performed while the engine 21 is stopped, and basically, either canister purge control or high pressure purge control is performed while the engine 21 is operating. Shall be. Further, the low pressure purge control is performed in association with the canister purge control (that is, after the canister purge control is completed as necessary).

Here, the operating conditions of the engine 21 in this embodiment are illustrated below.
-During power generation using the driving force of the engine 21 (when the charge amount of the battery for travel is below a predetermined amount, when traveling on an uphill, during rapid acceleration, etc.)
・ When the engine is in an efficient driving state (during high speed driving, medium high speed, low load driving, etc.)
・ When you want to protect the drive system of the drive motor (when the temperature of the drive motor or inverter is outside the specified range, when using an air conditioner, etc.)
・ When you want to protect the drive system of the engine 21 (when the engine 21 has not been used for a long time)

  The engine 21 is controlled to be driven when any of the above operating conditions is satisfied, and to be stopped when the operating conditions are not satisfied. However, the operating state of the engine 21 is maintained only when the low pressure purge control is performed following the canister purge control. That is, the low pressure purge control functions to extend the operating conditions of the engine 21 and keep the engine 21 operating.

[2-1. Tank sealing control]
The tank sealing control is a control for preventing outflow of fuel vapor generated in the fuel tank 5 by closing the sealing valve 1 while the engine 21 is stopped. At this time, the purge valve 3 is also controlled to be closed. Thereby, the fuel tank 5 is double-blocked by the sealing valve 1 and the purge valve 3 with respect to the intake passage 23 of the engine 21. The open / close state of the bypass valve 2 is arbitrary, and in this embodiment, the open / close state is controlled to be an open state.

[2-2. Pressure release control]
In the pressure relief control, when the engine 21 is stopped, the fuel tank 5 is pressurized by opening the sealing valve 1 and the bypass valve 2 so that the internal pressure of the fuel tank 5 does not become excessively large compared to the atmospheric pressure P _ATM. This is the control to remove. The pressure relief control is performed immediately before refueling the fuel tank 5. At this time, the purge valve 3 is controlled to be closed. By opening the sealing valve 1 and the bypass valve 2, an air flow is generated from the fuel tank 5 to the outside through the atmosphere opening passage 9 of the canister 6. As a result, the tank pressure P of the fuel tank 5 decreases and the fuel vapor present in the fuel tank 5 and the purge passage 10 is recovered by the canister 6.

[2-3. Canister purge control]
The canister purge control is a control for purifying the canister 6 by opening the bypass valve 2 during operation of the engine 21 and sucking the fuel vapor adsorbed by the canister 6 into the intake passage 23. The canister purge control is performed when the engine 21 is in a stable operation and the pressure release control and the high pressure purge control are not performed. Further, when the operating condition of the engine 21 is not established, the canister purge control ends. Incidentally, even during the learning of fuel injection quantity and high load (when intake manifold pressure P _IM is not negative pressure), the canister purge control may be non-implementation.

  In the canister purge control, the purge valve 3 is controlled to be opened so that the fuel vapor is consumed by the engine 21. The opening degree of the purge valve 3 is adjusted according to the operating state of the engine 21. On the other hand, the sealing valve 1 is controlled to a closed state. That is, the canister 6 communicates with the intake passage 23 and the fuel tank 5 is shut off. Thereby, since the fuel vapor introduced from the purge passage 10 into the intake passage 23 is only the fuel vapor from the canister 6, the estimation accuracy of the fuel vapor amount is improved and the controllability of the engine 21 is improved.

[2-4. High pressure purge control]
In the high pressure purge control, the fuel tank 5 is purged (purified) by opening the sealing valve 1 according to the tank pressure P and sucking the fuel vapor in the fuel tank 5 into the intake passage 23 while the engine 21 is operating. Control). In this control, the purge valve 3 is controlled to be in an open state, and the bypass valve 2 is controlled to be in a closed state. That is, the fuel tank 5 communicates with the intake passage 23 and the canister 6 is shut off. Thereby, since the fuel vapor introduced from the purge passage 10 into the intake passage 23 is only the fuel vapor from the fuel tank 5, the estimation accuracy of the fuel vapor amount is improved and the controllability of the engine 21 is improved. .

The start condition and end condition of the high pressure purge control in this embodiment will be exemplified below.
= High pressure purge control start condition =
A. B. The engine 21 is operating and the operating state is stable. Tank pressure P is greater than or equal to first pressure P ₁ (where P ₁ <P _MAX )
= High pressure purge control end condition =
C. D. Engine 21 is stopped or operating condition is not stable. Tank pressure P is less than second pressure P ₂ (where P ₂ <P ₁ )
The high pressure purge control is started when both the conditions A and B are satisfied, and is ended when either of the conditions C and D is satisfied. Note that the condition A is satisfied when, for example, the coolant temperature of the engine 21 is equal to or higher than a predetermined value and the engine speed Ne is stable.

[2-5. Low pressure purge control]
The low pressure purge control purges the fuel tank 5 by opening the sealing valve 1 and sucking the fuel vapor in the fuel tank 5 into the intake passage 23 regardless of the tank pressure P during the operation of the engine 21. (Purification) control. In this control, the purge valve 3 is controlled to be in an open state, and the bypass valve 2 is controlled to be in a closed state. The low pressure purge control is performed after the canister purge control is finished and before the engine 21 is stopped. Further, unlike the high pressure purge control, in the low pressure purge control, the operating state of the engine 21 is positively controlled so that the engine 21 does not stop at least until the control is completed. Therefore, when the canister purge control is finished, even if the operating condition of the engine 21 is not satisfied, the operating state of the engine 21 is maintained and the low pressure purge control is started.

The start condition and end condition of the low-pressure purge control are exemplified below. The low pressure purge control is started when both the conditions E and F are satisfied, and is ended when the condition G is satisfied. The upper limit threshold P ₃ (third pressure P ₃ ) for closing the sealing valve 1 by low pressure purge control is higher than the upper threshold P ₂ (second pressure P ₂ ) for closing the sealing valve 1 by high pressure purge control. It is set high. That is, the end condition for the low pressure purge control is more relaxed than the end condition for the high pressure purge control.
= Low pressure purge control start condition =
E. F. Immediately after canister purge control is performed. The elapsed time from the most recent refueling time is less than a predetermined time = the end condition of the low pressure purge control =
G. Tank pressure P is less than third pressure P ₃ (however, P ₂ <P ₃ <P ₁ )

The relationship between the name of the control and the open / close state of the sealing valve 1, the bypass valve 2 and the purge valve 3 in the present embodiment is summarized as follows.

[3. Control configuration]
As a control configuration for carrying out the various controls described above, the control device 30 is provided with a high pressure purge control unit 31, a canister purge control unit 32, and a low pressure purge control unit 33. These indicate some functions of a program executed by the control device 30 and are realized by software. However, some or all of the functions may be realized by hardware (electronic control circuit), or may be realized by using software and hardware together.

The high pressure purge control unit 31 (first control unit) controls high pressure purge control, and the start condition and end condition of the high pressure purge control are determined here. The high pressure purge control unit 31 has a function of reducing the tank pressure P by opening the sealing valve 1 when the tank pressure P is equal to or higher than the first pressure P ₁ . Further, the high pressure purge control unit 31 has a function of opening the sealing valve 1 until the tank pressure P becomes less than the second pressure P ₂ when the tank pressure P is equal to or higher than the first pressure P ₁ . The opening degree of the purge valve 3 can be set according to the operating state of the engine 21 and the amount of fuel remaining in the fuel tank 5.

  The canister purge control unit 32 (second control unit) controls the canister purge control, and the start condition and end condition of the canister purge control are determined here. The canister purge control unit 32 has a function of sucking the evaporated fuel adsorbed by the canister 6 into the intake passage 23 by opening the bypass valve 2 while the engine 21 is operating. The opening degree of the purge valve 3 can be set according to the operating state of the engine 21 and the amount of evaporated fuel adsorbed by the canister 6.

The low-pressure purge control unit 33 (third control unit) controls low-pressure purge control, and the start condition and end condition of the low-pressure purge control are determined here. The low-pressure purge control unit 33 has a function of reducing the tank pressure P by opening the sealing valve 1 regardless of the magnitude of the tank pressure P after the end of the canister purge control and during operation of the engine 21. In the low pressure purge control, even if the tank pressure P does not exceed the first pressure P ₁ , the fuel tank 5 is depressurized. Therefore, the average pressure of the fuel tank 5 tends to decrease, and the pressure release time before fuel supply is reduced. It is shortened and component protection is improved.

  Further, the low pressure purge control unit 33 has a function of maintaining the operating state of the engine 21 during execution of the low pressure purge control. For example, when the operating condition of the engine 21 is not satisfied during the canister purge control, the engine 21 is not stopped immediately, but the operating state of the engine 21 is maintained and the low pressure purge control is performed. . Thereby, the tank pressure P can be reduced using the opportunity that the engine 21 is operating. Such a control configuration is suitable for a hybrid vehicle that can travel without operating the engine 21 for a long time.

Further, the low pressure purge control unit 33 has a function of opening the sealing valve 1 until the tank pressure P becomes lower than the third pressure P ₃ higher than the second pressure P ₂ . In the low-pressure purge control, the end condition is relaxed compared to the high-pressure purge control, and the low-pressure purge control ends at a slightly higher pressure than when the high-pressure purge control ends. As a result, the execution time of the low pressure purge control is shorter than that of the high pressure purge control. The opening degree of the purge valve 3 can be set according to the operating state of the engine 21 and the amount of fuel remaining in the fuel tank 5.

Further, the low-pressure purge control unit 33 has a function of determining whether or not the low-pressure purge control is necessary according to the elapsed time from the latest refueling or according to the amount of fuel remaining in the fuel tank 5.
For example, the low pressure purge control is performed when the elapsed time from the most recent refueling is less than a predetermined time, and the low pressure purge control is not performed when the elapsed time is equal to or longer than the predetermined time. That is, when a predetermined time or more has passed since the most recent refueling, the fuel is in a so-called “dead” state (a state in which the ratio of the volatile components to the whole decreases and the fuel becomes difficult to evaporate). The low pressure purge control is stopped even immediately after the canister purge control is performed.

  When the open / close state of the sealing valve 1 is controlled according to the amount of fuel in the fuel tank 5, the low pressure purge control unit 33 performs low pressure purge control if the amount of fuel remaining in the fuel tank 5 is equal to or greater than a predetermined amount. On the other hand, if the fuel amount is less than the predetermined amount, it is determined that the tank pressure P is unlikely to increase even if the fuel evaporates in the fuel tank 5, and the low-pressure purge control is not performed. As a result, the remaining fuel is prevented from further evaporating due to the reduced pressure in the fuel tank 5.

[4. flowchart]
2 and 3 are flowcharts illustrating control procedures for performing the various controls described above. 2 mainly corresponds to the control contents while the engine 21 is stopped, and FIG. 3 mainly corresponds to the control contents during the stable operation of the engine 21. The control flag F in these flows indicates the execution status of the high pressure purge control or the low pressure purge control, and is set to F = 1 during the execution of either control. The control flag G indicates the implementation status of the canister purge control, and is set to G = 1 during and immediately after the implementation of the canister purge control. Further, the control flag H indicates the implementation status of only the low pressure purge control, and is set to H = 1 during the implementation of the low pressure purge control.

As shown in FIG. 2, first, information detected by the various sensors 12 to 15 is input to the control device 30 (step A1), and it is determined whether or not the operating condition of the engine 21 is satisfied (step A2). Here, if the operating condition of the engine 21 is satisfied, the engine 21 is driven, or if the engine 21 is operating, the operating state is maintained (step A3). Further, in the subsequent step A4, it is determined whether or not the operating state of the engine 21 is stable. If the engine 21 is stable, the process proceeds to step A14 in FIG. On the other hand, when the operating state of the engine 21 is not stable, the process proceeds to step A10, the control flag F is set to F = 0, and the control in this calculation cycle ends. The operating state of the engine 21 is determined using a known method based on the engine speed Ne, the intake manifold pressure P _IM , the coolant temperature, the vehicle speed, the required torque, the fuel injection amount, the intake air amount, and the like.

On the other hand, if the operating condition of the engine 21 is not satisfied in step A2, the engine 21 is stopped on condition that the control flag G is G = 0, or the stopped state is maintained if the engine 21 is stopped. (Steps A5 and A6). When the control flag G is G = 1, the canister purge control is performed at least immediately before, so the process proceeds to step A20 in FIG.
In step A7 performed while the engine 21 is stopped, it is determined whether or not the fuel lid 16 is opened. If the fuel lid 16 is opened, pressure release control is performed (step A8). In the pressure relief control, the sealing valve 1 and the bypass valve 2 are opened, and the fuel tank 5 is decompressed. On the other hand, if the fuel lid 16 is not opened, tank sealing control is performed (step A9). In the tank sealing control, the sealing valve 1 and the purge valve 3 are closed, and the outflow of fuel vapor generated in the fuel tank 5 is prevented. In step A10 following steps A8 and A9, the control flag F is set to F = 0, and the control in this calculation cycle ends.

  In step A14 of FIG. 3, it is determined whether or not the control flag F is F = 0. If this condition is satisfied, the process proceeds to step A15. If not, the process proceeds to step A23. In steps A15 to A22, conditions for starting high pressure purge control, canister purge control, and low pressure purge control are determined. In steps A23 to A31, conditions for ending high pressure purge control and low pressure purge control are determined.

In step A15, the high pressure purge control start condition B is determined. Here, the conditions for starting the high-pressure purge control if P <P ₁ not satisfied, the canister purge control is started (step A16). At this time, the sealing valve 1 is controlled to the closed state, and the bypass valve 2 and the purge valve 3 are controlled to the open state. In addition, the control flag G is set to G = 1 (step A18) on condition that the elapsed time from the most recent refueling time is less than the predetermined time (step A17). If the elapsed time since the most recent refueling is a predetermined time or more, the control flag G remains G = 0 even if the canister purge control is performed, so the low pressure purge control is not performed. .

If P ≧ P ₁ in step A15, high-pressure purge control is performed (step A19), the sealing valve 1 and the purge valve 3 are controlled to be opened, and the bypass valve 2 is controlled to be closed. Thereafter, the control flag F is set to F = 1 (step A22). Thus, in the operation cycle of the next time, as long as the operating conditions of the engine 21 is satisfied, the flow advances from step A14 to step A23, the high-pressure purge control is continued until the tank pressure P becomes the second pressure P less than ₂ (Steps A24 to A27).

  On the other hand, if the operating condition of the engine 21 is not satisfied during the canister purge control, the process proceeds from step A2 to step A5. At this time, since the control flag G is G = 1, the process proceeds to step A20 and low pressure purge control is performed. That is, when the canister purge control has been performed immediately before, the low pressure purge control having a relatively short execution time is selected instead of the high pressure purge control. Thereafter, the control flag H is set to H = 1, and the control flag F is set to F = 1 (steps A21 and A22).

In the next calculation cycle, as long as the operating conditions of the engine 21 is satisfied, the flow advances to step A28 via step A23 from step A14, low-pressure purge control until the tank pressure P is less than the third pressure P ₃ Continue (steps A28 to A31). Further, during the execution of the low pressure purge control, since the control does not proceed from step A5 to step A6, the operating state of the engine 21 is maintained. When the end condition of the low pressure purge control is satisfied, the values of all control flags F, G, H are reset to zero (step A31), and the process can proceed from step A5 to step A6. Therefore, if the operating condition of the engine 21 is not satisfied, the process proceeds from step A2 to steps A5 and A6, and the engine 21 is stopped.

[5. Action, effect]
(1) In the above evaporative fuel processing apparatus, the low pressure purge control is prepared separately from the high pressure purge control, and the low pressure purge control is performed when the canister purge control is finished. The low pressure purge control, unlike the high-pressure purge control, the tank pressure P may be carried out even in the less than a pressure P _1. Therefore, compared with the case where the low pressure purge control is not performed, the average pressure of the fuel tank 5 can be reduced, and the component protection can be improved. In addition, since the average pressure in the fuel tank 5 decreases, the pressure release time before fueling can be shortened. Furthermore, since the time for performing the pressure relief control is shortened, the closed state of the sealing valve 1 when the engine 21 is stopped can be maintained for a longer time, and the evaporation of fuel in the fuel tank 5 is suppressed. be able to.

(2) In the low pressure purge control, the end condition (condition for closing the sealing valve 1) is relaxed compared to the high pressure purge control. As a result, the time during which the low pressure purge control is performed can be shortened while the tank pressure P is lowered, and the operating time of the engine 21 can be shortened to suppress the deterioration of fuel consumption.
(3) In the low pressure purge control, the pressure as the threshold value at which the sealing valve 1 is closed is set higher than in the high pressure purge control (that is, the second pressure P ₂ <the third pressure P ₃ ). . Such a condition setting contributes to stopping the depressurization of the fuel tank 5 in a higher pressure state, and can shorten the control execution time. Therefore, the operating time of the engine 21 can be shortened and deterioration of fuel consumption can be suppressed.

  The high-pressure purge control can be said to be a control method for managing the tank pressure P with a relatively large amplitude and as few times as possible. On the other hand, the low pressure purge control is a control method for managing the tank pressure P by increasing the number of executions with a relatively small amplitude. In any of the methods, an equivalent average pressure can be realized by adjusting the amplitude of the tank pressure P and the frequency of execution. However, in a hybrid vehicle that can travel without operating the engine 21 for a long time, there are few opportunities for the evaporated fuel to be consumed by the engine 21, and therefore the low-pressure purge control that is frequently performed is more advantageous in terms of control. .

(4) By controlling the open / closed state of the sealing valve 1 according to the elapsed time since the most recent refueling, the condition of fuel depletion (ease of fuel evaporation) and the depressurization frequency of the fuel tank 5 are made to correspond to each other. The pressure reduction can be started under the situation where the tank pressure P is expected to increase. On the other hand, under conditions where it is difficult for the tank pressure P to increase (for example, a situation where several months have passed since the previous refueling), the fuel pressure in the fuel tank 5 is further evaporated by not performing pressure reduction. Can be suppressed.
(5) The same applies when the open / close state of the sealing valve 1 is controlled in accordance with the amount of fuel in the fuel tank 5, and the amount of fuel remaining in the fuel tank 5 is associated with the frequency of decompression of the fuel tank 5. be able to.

[6. Modified example]
In the above-described embodiment, the sealing valve 1 and the bypass valve 2 are two-position switching valves, and the purge valve 3 is a variable opening control valve. However, the types of these valves can be arbitrarily changed, The same applies to the setting of the opening. For example, by setting the respective opening according to the operating state of the engine 21, the amount of evaporated fuel adsorbed by the canister 6, the amount of fuel remaining in the fuel tank 5, etc. 21) can be accurately adjusted.

  In the above-described embodiment, any one of the tank sealing control and the pressure relief control is performed while the engine 21 is stopped, and any of the canister purge control, the high pressure purge control, and the low pressure purge control is performed while the engine 21 is operating. Although what was implemented was illustrated, the specific combination of control (correspondence relationship of the operating state of the engine 21 and the control content) is not limited to this. For example, tank sealing control and pressure release control while the engine 21 is stopped may be omitted, and pressure release control may be performed not only when the engine 21 is stopped but also during stable operation. By adopting a control configuration in which low-pressure purge control is performed at least after the canister purge control is finished and before the engine is stopped, the same operations and effects as those in the above-described embodiment can be achieved.

DESCRIPTION OF SYMBOLS 1 Sealing valve 2 Bypass valve 3 Purge valve 4 Relief valve 5 Fuel tank 6 Canister 7 Tank passage 8 Canister passage 9 Atmospheric release passage 10 Purge passage 30 Controller 31 High pressure purge control section (first control section)
32 Canister purge control unit (second control unit)
33 Low pressure purge controller (third controller)
P Tank pressure

Claims (5)

A sealing valve is interposed on a passage connecting the canister for adsorbing evaporated fuel generated in the fuel tank and the fuel tank, and a bypass valve is interposed on a passage connecting the canister and the intake system of the engine. In a closed tank type evaporative fuel treatment device,
A first control unit that opens the sealing valve according to a tank pressure of the fuel tank and performs a high-pressure purge to reduce the tank pressure;
A second control unit that opens a bypass valve during operation of the engine and performs a canister purge for sucking the evaporated fuel adsorbed by the canister into the intake system;
A third controller that performs low-pressure purge to open the sealing valve regardless of the magnitude of the tank pressure and to reduce the tank pressure after the canister purge is finished and before the engine is stopped ,
The evaporative fuel processing apparatus, wherein the third control unit determines whether or not the low-pressure purge is necessary in accordance with an elapsed time since the latest refueling . A sealing valve is interposed on a passage connecting the canister for adsorbing evaporated fuel generated in the fuel tank and the fuel tank, and a bypass valve is interposed on a passage connecting the canister and the intake system of the engine. In a closed tank type evaporative fuel treatment device,
A first control unit that opens the sealing valve according to a tank pressure of the fuel tank and performs a high-pressure purge to reduce the tank pressure;
A second control unit that opens a bypass valve during operation of the engine and performs a canister purge for sucking the evaporated fuel adsorbed by the canister into the intake system;
A third controller that performs low-pressure purge to open the sealing valve regardless of the magnitude of the tank pressure and to reduce the tank pressure after the canister purge is finished and before the engine is stopped ,
The evaporative fuel processing apparatus, wherein the third control unit determines whether or not the low-pressure purge is necessary according to the amount of fuel remaining in the fuel tank . End condition of the low pressure purge, characterized in that it is more relaxed than the termination condition of the high-pressure purging, the evaporative fuel processing apparatus according to claim 1 or 2 wherein. The first control unit, when the tank pressure is equal to or higher than the first pressure, opens the sealing valve until the tank pressure becomes less than the second pressure,
The said 3rd control part opens the said sealing valve until the said tank pressure becomes less than the 3rd pressure higher than the said 2nd pressure , The any one of Claims 1-3 characterized by the above-mentioned. Evaporative fuel processing device. 5. The evaporated fuel processing according to claim 2 , wherein the third control unit determines whether or not the low-pressure purge is necessary in accordance with an elapsed time since the latest refueling. apparatus.

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