JP2017067004A - Evaporation fuel treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaporation fuel treatment device capable of preventing the HAKA of an evaporation fuel without enlarging a canister, in processing lowering pressure in a fuel tank.SOLUTION: An evaporation fuel treatment device is equipped with a pressure sensor 27; an airtight valve 29 provided between a fuel tank 5 and a purge passage; a canister 7 which receives an evaporation fuel from the fuel tank 5, adsorbs the evaporation fuel, and is equipped with an atmosphere opening valve 25; a pressurizing pump 9; and a purge valve 11. When pressure detected by the pressure sensor 27 becomes a first predetermined value or more, the purge valve 11 and the atmosphere opening valve 25 are opened, and the pressurizing pump 9 is actuated to open the airtight valve 29. After the opening of the airtight valve 29, when the pressure detected by the pressure sensor 27 becomes a second predetermined value or below, the airtight valve 29 is closed, and the pressurizing pump 9 is stopped and the purge valve 11 is closed after the lapse of a predetermined time since the airtight valve 29 is closed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an evaporated fuel processing apparatus, and more particularly to an evaporated fuel processing apparatus applied to a closed tank system.

  2. Description of the Related Art Conventionally, there is known an evaporative fuel processing apparatus applied to a closed tank system including a canister for accumulating evaporative fuel generated when fuel is supplied to a fuel tank.

  In the closed tank system, a purge passage different from the fuel supply system to the engine is provided between the fuel tank and the engine intake pipe on the upstream side of the engine, and the evaporated fuel generated in the fuel tank at the time of fueling is temporarily Accumulate in the canister on the purge passage. Then, at a predetermined purge timing, a negative pressure is generated in the canister by operating a pump provided between the canister and the engine intake pipe on the purge passage, whereby the evaporation accumulated in the canister Fuel is supplied to the engine intake pipe. In the sealed tank system, the sealed valve provided between the fuel tank and the purge passage is closed so that the evaporated fuel in the fuel tank does not flow into the engine intake pipe except at the purge timing and at the time of fueling. As such an evaporative fuel processing apparatus, the one described in Patent Document 1 is known.

JP 2013-194602 A

  Generally, in a closed tank system, since the closed valve between the fuel tank and the purge passage is closed except during refueling, for example, the fuel is partially vaporized due to temperature rise in the fuel tank, and the fuel tank The internal pressure may increase. Therefore, in order to suppress an increase in the pressure in the fuel tank, it is necessary to reduce the pressure in the fuel tank at regular intervals.

  In order to reduce the pressure in the fuel tank, a negative pressure is generated in the purge passage using a pressurizing pump, and then the fuel is evaporated from the fuel tank through the purge passage. It is conceivable to supply the pipe.

  However, after the pressure of the fuel tank is reduced by the above-described method, the vaporized fuel remaining in the purge passage flows back into the canister simply by stopping the pressurizing pump and closing the sealing valve. There was a case. Thereby, a large amount of evaporated fuel may be adsorbed by the adsorbent in the canister such as activated carbon. When the evaporated fuel remaining in the purge passage is adsorbed by the canister, when the canister originally wants to adsorb the evaporated fuel, the canister's adsorbable capacity becomes insufficient, and the evaporated fuel breaks through the canister. There was a problem that. In order to solve this problem, it is necessary to increase the size of the canister and increase the capacity of adsorption.

  Therefore, the present invention has been made to solve the above-described problem, and in the process of reducing the pressure in the fuel tank, breakthrough of the evaporated fuel can be prevented without increasing the size of the canister. An object of the present invention is to provide a fuel vapor processing apparatus.

  In order to solve the above problems, the present invention provides a purge passage extending from a fuel tank toward an engine intake pipe, a tank internal pressure sensor for detecting a pressure in the fuel tank, and a gap between the fuel tank and the purge passage. A canister for receiving evaporative fuel from a fuel tank and adsorbing the evaporative fuel, the canister being provided on the purge passage on the downstream side of the seal valve, and having air in the canister A canister having an atmosphere release valve for introducing the pressure, a pressure pump connected to the downstream side of the canister on the purge passage, and a downstream side of the pressure pump on the purge passage. And a purge valve, wherein the pressure detected by the tank internal pressure sensor is a first predetermined value. When the upper limit is reached, the purge valve and the air release valve are opened, the pressure pump is operated, the seal valve is opened, and the valve is detected by the tank internal pressure sensor after the seal valve is opened. When the pressure becomes equal to or lower than a second predetermined value, the sealing valve is closed, and after the predetermined time has elapsed since the sealing valve was closed, the pressurizing pump is stopped and the purge valve is closed. .

  According to the present invention configured as above, when the pressure detected by the tank internal pressure sensor becomes equal to or higher than the first predetermined value, the purge valve and the atmosphere release valve are opened, and the pressure pump is operated. Can be made. Thereby, a negative pressure is generated on the downstream side of the pressurizing pump, and an airflow is generated from the air release valve through the canister to the pressurizing pump. Then, after the air flow is generated, the hermetic valve is opened to generate an air flow from the fuel tank to the pressure pump through the canister. The evaporated fuel in the fuel tank is sucked from the fuel tank and flows toward the canister. When the evaporated fuel enters the canister, the evaporated fuel flows from the canister toward the pressurization pump by the airflow flowing from the atmosphere release valve toward the pressurization pump. Thereby, the pressure in a fuel tank can be reduced. When the pressure in the fuel tank becomes equal to or lower than the second predetermined value, first, the sealed valve is closed to prevent new evaporated fuel from being released into the purge passage. Then, by keeping the purge valve open for a predetermined time and driving the pressurizing pump, the evaporated fuel remaining in the purge passage can flow toward the engine supply pipe. As a result, the remaining amount of the evaporated fuel in the purge passage can be significantly reduced, and the reverse flow toward the canister can be prevented.

  In the present invention, it is preferable that the second predetermined value is smaller than the first predetermined value.

  In the present invention, it is preferable that the pressurization pump is stopped by gradually decreasing the output of the pressurization pump.

  As described above, according to the present invention, when the pressure in the fuel tank is reduced, it is possible to prevent the evaporated fuel from breaking through without increasing the size of the canister.

It is a block diagram which shows the evaporative fuel processing apparatus by embodiment of this invention. It is a flowchart which shows operation | movement of the evaporative fuel processing apparatus by embodiment of this invention.

  Hereinafter, an evaporated fuel processing apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a fuel vapor processing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the evaporated fuel processing apparatus is configured to supply evaporated fuel generated in a fuel tank 5 to an engine intake pipe 3 connected to the engine 1. The evaporative fuel processing device includes a purge passage extending from the fuel tank 5 toward the engine intake pipe 3. On the purge passage, a canister 7, a pressurizing pump 9, and a purge valve 11 are provided from the upstream side. In this specification, “upstream side” and “downstream side” are defined based on the direction in which the evaporated fuel flows in the purge passage unless otherwise specified. The fuel tank 5 side in the purge passage extending from the fuel tank 5 as a starting point is referred to as “downstream side”, and the engine intake pipe 3 side in the purge passage terminating at the engine intake pipe 3 is referred to.

  The canister 7 is connected to the fuel tank 5 and adsorbs and accumulates the evaporated fuel flowing from the fuel tank 5. The canister 7 includes a first cylindrical container 7a and a second cylindrical body 7b that accommodate an adsorbent such as activated carbon, and is arranged at one end of the first cylindrical container 7a and the second cylindrical container 7b. The part is connected so that gas can go back and forth between the first cylindrical container 7a and the second cylindrical container 7b. The other end portion of the first cylindrical container 7a receives the evaporated fuel from the fuel tank 5, and allows the evaporated fuel accumulated in the canister 7 to flow toward the downstream side. The other end of the second cylindrical container 7 b is connected to a fresh air supply pipe 13 for supplying fresh air to the canister 7.

  Further, the side of the canister that is connected to the fresh air supply pipe 13 of the first cylindrical container 7a and the side that receives and discharges the evaporated fuel of the second cylindrical container 7b are not filled with the adsorbent. A space is formed. When the pressure in the fuel tank 5 is lowered as will be described later, the airflow flowing from the fuel tank 5 into the second cylindrical container 7b passes through the space where the adsorbent does not exist and passes through the purge passage. It flows toward the downstream side.

  The pressure pump 9 has an inlet connected to the canister 7 and an outlet connected to the purge valve 11. The pressure pump 9 generates a negative pressure on the upstream side of the pressure pump 9 in the purge passage under the control of the ECU 15 during the purge to supply the evaporated fuel to the engine intake pipe 3. A positive pressure is generated downstream. Thereby, the evaporated fuel adsorbed in the canister 7 is sucked and can flow toward the downstream side of the canister 7.

  The purge valve 11 is provided immediately upstream of the engine intake pipe 3 and adjusts the supply amount of the evaporated fuel that has passed through the purge passage to the engine intake pipe 3. The opening and closing of the purge valve 11 is controlled by the ECU 15. When the purge valve 11 is open, the canister 7, the pressurizing pump 9, and the engine intake pipe 3 are connected, and when the purge valve 11 is closed, The connection between the canister 7 and the pressurizing pump 9 and the engine intake pipe 3 is cut off.

  Between the fuel tank 5 and the first cylindrical container 7a of the canister 7, there is provided an evaporated fuel supply pipe 17 for supplying the evaporated fuel generated in the fuel tank 5 into the first cylindrical container 7a. . The evaporated fuel supplied from the evaporated fuel supply pipe 17 to the first cylindrical container 7 a is adsorbed by the adsorbent in the canister 7 and accumulated in the canister 7. In addition, an accumulated fuel supply pipe 19 that supplies evaporated fuel accumulated in the canister 7 to the pressurizing pump 9 is provided between the canister 7 and the pressurizing pump 9. Further, the second cylindrical container 7 b is provided with a fresh air supply pipe 13 for supplying fresh air from the outside to the canister 7. An air release valve 25 that is controlled to be opened and closed by the ECU 15 is provided at the outside air inlet of the fresh air supply pipe 13.

  A pressure sensor 27 for measuring the pressure in the fuel tank 5 is provided in the fuel tank 5. The output of the pressure sensor 27 is supplied to the ECU 15, whereby the ECU 15 detects the pressure in the fuel tank 5.

  Further, a sealing valve 29 is provided between the fuel tank 5 and the evaporated fuel supply pipe 17. The sealed valve 29 is opened and closed under the control of the ECU 15. When the sealed valve 29 is open, the evaporated fuel in the fuel tank 5 flows into the canister 7 through the evaporated fuel supply pipe 17. On the other hand, when the sealing valve 29 is closed, the fuel tank 5 is sealed, and the evaporated fuel in the fuel tank 5 does not flow toward the downstream side but remains in the fuel tank 5.

  Next, the operation of the evaporated fuel processing apparatus will be described in detail.

  In the closed tank system, the evaporated fuel in the fuel tank 5 is supplied to the canister 7 only when refueling. During refueling, for example, when the refueling port is opened, the ECU 15 opens the sealing valve 29, thereby bringing the fuel tank 5 and the canister 7 into communication. At this time, the purge valve 11 is in a closed state, and the pressurizing pump 9 is stopped. When refueling is started, the evaporated fuel is supplied to the canister 7 through the sealing valve 29 and the evaporated fuel supply pipe 17 and accumulated. When refueling is completed and the refueling port is closed, the sealing valve 29 is closed and the fuel tank 5 is sealed.

  When the amount of evaporated fuel accumulated in the canister 7 becomes equal to or greater than a predetermined value, the evaporated fuel processing apparatus purges the evaporated fuel. For example, in a predetermined engine operating state, when the accumulated amount of evaporated fuel in the canister 7 exceeds a certain value, the ECU 15 opens the purge valve 11 and the air release valve 25 and operates the pressurizing pump 9. At this time, the sealing valve 29 is closed. As a result, a negative pressure is generated on the downstream side of the pressurizing pump 9, and the outside air flows into the fresh air introduction pipe 13 through the atmosphere release valve 25. And the outside air flows from the fresh air introduction pipe 13 into the first cylindrical container 7a of the canister, flows from one end of the first cylindrical container 7a to one end of the second cylindrical container 7b, and then The accumulated fuel supply pipe 19 flows. The evaporated fuel accumulated in the canister 7 is supplied to the downstream side along the flow of the outside air, and is supplied to the engine 1 through the engine supply pipe 3. As a result, the evaporated fuel accumulated in the canister 7 can flow along the arrow A and be supplied to the engine 1.

  Next, an operation for reducing the pressure in the fuel tank 5 will be described. As described above, since the sealing valve 29 is closed except during refueling, the inside of the fuel tank 5 is sealed except during refueling. Therefore, when the fuel in the fuel tank 5 is vaporized, the pressure in the fuel tank 5 increases. Therefore, it is necessary to reduce the pressure in the fuel tank 5 at a predetermined timing, for example, before refueling, so that evaporated fuel is not released from the refueling port when the refueling port is opened. Moreover, it is preferable not to perform the operation | movement which reduces the pressure in the fuel tank 5 during the purge process mentioned above.

  FIG. 2 is a flowchart showing an operation when the pressure in the fuel tank is reduced. As shown in FIG. 2, when the pressure in the fuel tank 5 is reduced, the ECU 15 determines whether the pressure in the fuel tank 5 detected by the pressure sensor 27 in step S1 is equal to or higher than a first predetermined value. to decide. With this process, it can be determined whether the pressure in the fuel tank 5 needs to be reduced.

  Next, the ECU 15 determines whether or not a purge process is being executed in step S2. If the purge process is not being executed, the ECU 15 drives the pressure pump 9 in step S3. Thereafter, in step S4, the ECU 15 performs valve control, and opens the purge valve 11 and the atmosphere release valve 25 while maintaining the closed valve 29 in the closed state. As a result, an air flow from the atmosphere release valve 25 toward the engine intake pipe 3 is generated. In addition, you may perform the process of step S3 and the process of step S4, changing order.

  Next, the ECU 15 opens the sealing valve 29 in step S5. When the sealing valve 29 is opened, the evaporated fuel in the fuel tank 5 is supplied with evaporated fuel by the negative pressure generated by the pressurizing pump 9 and the negative pressure generated by the air flow from the atmosphere release valve 25 to the engine supply pipe 3. It flows toward the second cylindrical container 7b of the canister 7 through the pipe 17. Since the air flow from the first cylindrical container 7a toward the accumulated fuel supply pipe 19 is generated in the second cylindrical container 7b, when the evaporated fuel enters the second cylindrical container 7b, the evaporated fuel is As shown by the arrow B in FIG. 1, it does not flow to the atmosphere release valve 25 side from the inlet from the evaporated fuel supply pipe 17 to the second cylindrical container 7b, and passes only through the space where no adsorbent exists, and immediately It is discharged from the second cylindrical container 7 b toward the accumulated fuel supply pipe 19. The evaporated fuel is supplied to the engine intake pipe 3 through the purge valve 11.

  Next, in step S6, the ECU 15 determines whether or not the pressure in the fuel tank 15 has become equal to or lower than a second predetermined value based on the detection result of the pressure sensor 27. The second predetermined value is a value smaller than the first predetermined value that serves as a threshold when the pressure in the fuel tank 15 is reduced. And the start of the process which reduces the next pressure can be delayed by making 2nd predetermined value smaller than 1st predetermined value.

  If it is determined in step S6 that the pressure in the fuel tank 5 has become the second predetermined value or less, the ECU 15 closes the sealing valve 29 in step S7. As a result, no new evaporated fuel is supplied from the fuel tank 5 to the purge passage. Next, in step S8, the ECU 15 waits for a predetermined time after the sealing valve 29 is closed. If the predetermined time has elapsed, the ECU 15 closes the purge valve 11 in step S9. The evaporative fuel remaining in the purge passage can be supplied to the engine intake pipe 3 by continuing to drive the pressurizing pump 9 with the purge valve 11 open until a predetermined time elapses in step S8.

  Then, the ECU 15 stops the pressurizing pump 9 in step S10 and ends the series of processes. When stopping the pressurizing pump 9, it is preferable to gradually reduce the output of the pressurizing pump 9 in consideration of the burden on the pressurizing pump 9.

  As described above, according to the fuel vapor supply apparatus according to the embodiment of the present invention, when the pressure detected by the pressure sensor 27 exceeds a predetermined value, the purge valve 11 and the atmosphere release valve 25 are opened. And the pressurizing pump 9 can be operated. Thereby, a negative pressure is generated on the downstream side of the pressurizing pump 9, and an airflow is generated from the atmosphere release valve 25 through the canister 7 toward the pressurizing pump. Then, after the air flow is generated, the hermetic valve 29 is opened to generate an air flow from the fuel tank 5 to the pressurizing pump 9 through the canister 7. The evaporated fuel in the fuel tank 5 is sucked from the fuel tank 5 and flows toward the canister 7. When the evaporated fuel enters the canister 7, the evaporated fuel flows from the canister 7 toward the pressurizing pump 9 by the airflow flowing from the atmosphere release valve 25 toward the pressurizing pump 9. Thereby, the pressure in the fuel tank 5 can be reduced. When the pressure in the fuel tank 5 becomes equal to or lower than the second predetermined value, first, the sealed valve 29 is closed to prevent new evaporated fuel from being discharged into the purge passage. The vaporized fuel remaining in the purge passage can be made to flow toward the engine supply pipe 3 by keeping the purge valve 11 open for a predetermined time and driving the pressure pump 9. As a result, the remaining amount of the evaporated fuel in the purge passage can be greatly reduced, and the reverse flow toward the canister 7 can be prevented.

  In the above-described embodiment, in the operation of lowering the pressure in the fuel tank 5, after the air flow from the atmosphere release valve 25 toward the engine intake pipe 3 is generated, the ECU 15 opens the sealing valve 29. It was. However, as a timing for opening the sealing valve 29, for example, a flow rate sensor is provided in the accumulated fuel supply pipe 19 on the upstream side of the pressurizing pump 9, and a sufficient flow velocity is obtained in the accumulated fuel supply pipe 19 by the flow rate sensor. After detecting this, the sealing valve 29 may be opened. Thereby, it is possible to prevent the evaporated fuel from contacting the adsorbent of the canister 7 more reliably.

5 Fuel tank 7 Canister 9 Pressure pump 11 Purge valve 15 ECU
25 Air release valve 27 Pressure sensor 29 Sealed valve

Claims (4)

A purge passage extending from the fuel tank toward the engine intake pipe;
A tank internal pressure sensor for detecting the pressure in the fuel tank;
A sealing valve provided between the fuel tank and the purge passage;
A canister for receiving evaporated fuel from a fuel tank and adsorbing evaporated fuel, provided on the downstream side of the sealed valve on the purge passage, and an atmospheric release valve for introducing air into the canister A canister comprising:
A pressurizing pump connected to the downstream side of the canister on the purge passage;
An evaporative fuel processing apparatus comprising: a purge valve provided on a downstream side of the pressurizing pump on the purge passage;
When the pressure detected by the tank internal pressure sensor is equal to or higher than a first predetermined value, the purge valve and the atmosphere release valve are opened, the pressure pump is operated, and the sealing valve is opened.
After the opening of the sealing valve, when the pressure detected by the tank internal pressure sensor becomes equal to or lower than a second predetermined value, the sealing valve is closed and the pressurization is performed after a predetermined time has elapsed since the sealing valve was closed. An evaporative fuel processing apparatus characterized by stopping the pump and closing the purge valve.   The evaporated fuel processing apparatus according to claim 1, wherein the second predetermined value is smaller than the first predetermined value.   The evaporative fuel processing apparatus according to claim 1, wherein the pressurization pump is stopped by gradually decreasing an output of the pressurization pump. An evaporative fuel supply unit that connects the canister and the fuel tank on the purge passage;
An accumulated fuel supply unit that connects the canister and the purge valve on the purge passage;
A fresh air supply unit that connects the canister and the atmosphere release valve;
The canister is filled with an adsorbent that adsorbs evaporated fuel at one end to which the fresh air supply unit is connected, and at the other end to which the evaporated fuel supply unit and the stored fuel supply unit are connected. A space where the adsorbent is not present is formed,
The evaporated fuel received from the fuel tank flows through the space where the adsorbent is not present to the accumulated fuel supply unit.
The evaporative fuel processing apparatus of any one of Claims 1 thru | or 3.

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