JP6210238B2 - Evaporative fuel leak check system - Google Patents

Description

  The present invention relates to an evaporated fuel leak check system, and more particularly to an evaporated fuel leak check system in an evaporated fuel processing apparatus that supplies evaporated fuel to an engine intake pipe using a pressure pump.

  2. Description of the Related Art Conventionally, an evaporative fuel processing apparatus that includes a canister that contains an adsorbent such as activated carbon therein is known. The canister has a tank port connected to the fuel tank, a purge port connected to the intake system of the engine, and a drain port that releases the inside of the canister to the atmosphere. Then, the evaporated fuel generated by evaporating in the fuel tank flows into the canister from the tank port, and the flowing evaporated fuel is adsorbed by the adsorbent. The evaporated fuel adsorbed by the adsorbent is supplied to the engine intake system according to the engine operating state. That is, the canister and the engine intake pipe are connected by a purge pipe. The purge pipe is provided with a purge valve that is opened and closed according to the engine operating state. When the purge valve is opened, the purge pipe and the canister are opened. Communicating with the engine intake pipe. Since negative pressure is applied to the engine intake pipe in the operating state, negative pressure is applied to the purge pipe and the canister communicating with the engine intake pipe. As a result, outside air (air) is introduced into the canister from the drain port. Once introduced, an air flow is generated in the canister from the drain port to the purge port. The evaporated fuel is desorbed from the adsorbent by the air flow, and the desorbed evaporated fuel is supplied to the engine intake system via the purge pipe in a state of being mixed with air.

  In such an evaporative fuel processing apparatus, it is required that the ECU performs self-failure diagnosis and detects the presence or absence of the evaporative fuel leak in the purge passage at every predetermined drive timing. And as a leak check system of an evaporative fuel processing apparatus, there exists what was described in patent document 1. FIG.

JP 2007-198267 A

  The evaporative fuel processing apparatus described in Patent Document 1 includes an evaporative fuel supply pressurizing pump that generates a negative pressure for flowing evaporative fuel accumulated in a canister toward an engine intake pipe. When evaporative fuel is supplied to the engine intake pipe, the evaporative fuel supply pressure pump is operated to generate a negative pressure in the canister, and the evaporated fuel accumulated in the canister is supplied to the engine intake pipe. ing. When performing a leak check, the purge passage is hermetically closed, a negative pressure is generated in the purge passage by a leak check pressure pump, and the leak is detected by detecting this pressure. The presence or absence is detected.

  However, in Patent Document 1, in addition to an evaporative fuel supply pressurizing pump for generating a negative pressure in order to supply evaporative fuel to the engine intake pipe, a leak check addition that generates a negative pressure when performing a leak check is disclosed. Since a pressure pump is provided, it is not preferable in terms of cost increase and securing of a pump mounting location.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a leak check system that can appropriately perform a leak check without adding a leak check pressurizing pump.

In order to solve the above-described problems, the present invention provides an evaporated fuel supply pipe for supplying evaporated fuel in a fuel tank to a canister, and an accumulation for supplying evaporated fuel accumulated in the canister to an engine intake pipe. A fuel supply pipe, a fresh air supply pipe for supplying fresh air to the canister, a pressurization pump provided in the middle of the stored fuel supply pipe, and a downstream of the pressurization pump in the stored fuel supply pipe A purge pipe, and a bypass pipe branched from the fresh air supply pipe and connected to the upstream side of the pressurized pump of the accumulated fuel supply pipe without passing through the canister. , provided at the connection portion of the first valve comprising a three-way valve, the bypass pipe and the fresh air supply pipe provided at the connection between the storage fuel supply pipe and the bypass pipe between the canister and the pressure pump Includes a second valve comprising a three-way valve which, to close the purge valve, than the first valve with switching the first valve than the first valve storage fuel supply pipe connecting the downstream and the bypass pipe Shut off the connection between the stored fuel supply pipe on the upstream side and the pressurizing pump , and switch the second valve to connect the bypass pipe with the downstream side of the second valve of the fresh air supply pipe to operate the pressurizing pump. Thus, a negative pressure is generated in the bypass pipe, the canister, and the evaporated fuel supply pipe.

  According to the present invention configured as described above, the leak check is performed using the pressurizing pump that generates a negative pressure when the evaporated fuel is supplied to the engine intake pipe in both cases of operation and stop of the engine. It can be performed. As a result, it is not necessary to use a pressure pump for leak check, and the pressure pump used for supplying the evaporated fuel can be used as the pressure pump used for checking the leak.

In the present invention, preferably, when the engine is operated, the purge valve is closed and the first valve is switched to connect the upstream side and the downstream side of the first valve of the accumulated fuel supply pipe and to connect the bypass pipe and the pressurizing pump. blocked, and then the second valve is fully closed, by operating the pressure pump, accumulation fuel supply pipe, negative pressure is generated in the canister and fuel vapor supply pipe performs leak check of the fuel vapor, When the engine is stopped, the purge valve is closed, the first valve is switched to connect the downstream side of the accumulated fuel supply pipe to the bypass pipe and the bypass pipe, and the accumulated fuel supply pipe and the pressure pump upstream of the first valve are connected. blocks the connection between, and switches the second valve than the second valve of the fresh air supply pipe connected to the downstream side and the bypass pipe by operating the pressure pump, Bypass tube, the canister, and negative pressure is generated in the fuel vapor supply pipe performs leak check of the fuel vapor.

  According to the present invention having such a configuration, when performing a leak check when the engine is stopped, the inside of the canister and the accumulated fuel supply pipe can be connected via the bypass pipe. In general, when the evaporated fuel accumulated in the canister is supplied to the engine intake pipe, the fresh air is introduced into the canister from the fresh air supply pipe by the negative pressure generated by operating the pressurizing pump. An air flow is generated toward the accumulated fuel supply pipe. In this case, among the evaporated fuel accumulated in the canister, the evaporated fuel on the upstream side of the flow of fresh air is mixed with fresh air and supplied to the engine intake pipe. Therefore, normally, the amount of accumulated evaporated fuel in the vicinity of the fresh air supply pipe is small compared to other parts. Then, as in the present invention, when performing a leak check when the engine is stopped, air with a small amount of evaporated fuel in the vicinity of the fresh air supply pipe in the canister first flows in the direction of the engine intake pipe. This makes it difficult for air with a large amount of evaporated fuel to reach the vicinity of the engine intake pipe. Therefore, when the engine is restarted, it is possible to prevent the evaporated fuel from being supplied to the engine intake pipe and exhausted from the engine in an incombustible state.

  As described above, according to the present invention, it is possible to appropriately perform a leak check without adding a leak check pressurizing pump.

1 is a schematic diagram of a leak check system according to an embodiment of the present invention. It is the schematic of the leak check system by embodiment of this invention, and is a figure for demonstrating the flow of the evaporated fuel during purge. It is the schematic of the leak check system by embodiment of this invention, and is a figure for demonstrating the flow of the air in the leak check in driving | running | working. It is a flowchart which shows operation | movement of the leak check system by embodiment of this invention. It is the schematic of the leak check system by embodiment of this invention, and is a figure for demonstrating the flow of the air in the leak check in a stop. It is a flowchart which shows operation | movement of the leak check system by embodiment of this invention.

  Hereinafter, a leak check system according to an embodiment of the present invention will be described with reference to the drawings.

  First, with reference to FIG. 1, the structure of the evaporative fuel processing apparatus in which the leak check system is mounted and the leak check system will be described. 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 accumulates evaporated fuel flowing from the fuel tank 5. Canister 7 is a first cylindrical container 7a and the second cylindrical body 7b to accommodate the adsorbent such as activated carbon which arranged in parallel, one of the first cylindrical container 7a and the second cylindrical container 7b The ends are connected so that gas can flow between the first cylindrical container 7a and the second cylindrical container 7b. The other end portion of the second cylindrical container 7b 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 first cylindrical container 7 a is connected to a fresh air supply pipe 13 for supplying fresh air to the canister 7.

  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 second cylindrical container 7b of the canister 7, there is provided an evaporated fuel supply pipe 17 for supplying the evaporated fuel generated in the fuel tank into the second cylindrical container 7b . The evaporated fuel supplied from the evaporated fuel supply pipe 17 to the second cylindrical container 7 b 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. The first cylindrical container 7 a is provided with a fresh air supply pipe 13 for supplying fresh air from the outside to the canister 7. Then, the fresh air supply pipe 13, between the storage fuel supply pipe 19, without passing through the housing 7, and a bypass pipe 21 for connecting the fresh air supply pipe 13 and the accumulated fuel supply pipe 19 is provided Yes.

Further, a bypass valve 23 constituted by a three-way valve is provided at a connection portion between the accumulated fuel supply pipe 19 and the bypass pipe 21, and a connection portion between the fresh air supply pipe 13 and the bypass pipe 21 is provided. Is provided with a fresh air valve 25 constituted by a three-way valve.

Under the control of the ECU 15, the bypass valve 23 (1) cuts off the connection between the bypass pipe 21 and the accumulated fuel supply pipe 19 and connects the canister 7 and the pressurizing pump 9, or (2) the bypass pipe 21. The storage fuel supply pipe 19 is connected to the downstream side of the bypass valve 23, and the connection between the storage fuel supply pipe 19 upstream of the bypass valve 23 and the pressurizing pump 9 is cut off. .

  Under the control of the ECU 15, the fresh air valve 25 (1) disconnects the connection between the fresh air supply pipe 13 and the bypass pipe 21 and connects the inlet of the fresh air supply pipe 13 and the canister 7 ( 2) The bypass pipe 21 is connected to the downstream side of the fresh air valve 25 in the fresh air introduction pipe 13, and the connection between the inlet side of the fresh air introduction pipe and the canister 7 is cut off from the fresh air valve 25. It is configured.

  A pressure sensor 27 for measuring the pressure in the purge passage is further provided on the purge passage. The output of the pressure sensor 27 is supplied to the ECU 15, whereby the ECU 15 detects a change in pressure in the purge passage. In the present embodiment, the pressure sensor 27 is provided in the middle of the evaporated fuel supply pipe 17, but the position of the pressure sensor 27 may be any position as long as it is on the purge passage.

Next, control when supplying evaporated fuel to the engine intake pipe 3 will be described in detail with reference to FIG. When evaporative fuel is supplied to the engine intake pipe 3, the ECU 15 opens the purge valve 11, controls the fresh air valve 25 so that fresh air flows from the fresh air supply pipe 13 to the canister 7, and further bypass valve 23 Is connected to connect the canister 7 and the pressurizing pump 9. Further, the ECU 15 operates the pressurizing pump 9. In such a state, the evaporated fuel in the fuel tank 5 is accumulated in the canister 7 through the evaporated fuel supply pipe 17. Then, fresh air is sucked from the inlet of the fresh air introduction pipe 13 by the suction force of the pressurizing pump 9 and supplied to the canister 7. The fresh air flowing into the canister 7 flows toward the downstream side by the suction force of the pressurizing pump 9. The evaporated fuel accumulated in the canister 7 rides on the flow of fresh air, flows downstream through the accumulated fuel supply pipe 19, passes through the purge valve 11, and flows into the engine intake pipe 3. Thereby, the evaporated fuel accumulated in the canister 7 is supplied to the engine intake pipe 3.

Next, with reference to FIG. 3 and FIG. 4, the operation when performing a leak check when the engine is driven will be described in detail. When performing a leak check when the engine is driven, when a series of processes starts, the ECU 15 closes the purge valve 11 and fully closes the fresh air valve 25 in step S1. Thereby, all the connections between the inlet of the fresh air introduction pipe 13, the bypass pipe 21 and the canister 7 are cut off, and further, the bypass valve 23 is controlled so that the canister 7 and the pressurizing pump 9 are connected via the accumulated fuel supply pipe 19. Thus, an airtight path is formed between the fuel tank 5 and the pressurizing pump 9 on the purge passage. Then, the leak check system detects whether or not there is a leak in the purge passage by determining whether or not a constant negative pressure can be maintained in the airtight path. When performing a leak check, the ECU 15 operates the pressurizing pump 9 in step S <b> 2 to apply a negative pressure upstream of the pressurizing pump 9. Then, the ECU 15 monitors the output of the pressure sensor 27. In step S3, for example, if the output of the pressure sensor 27 is constant for a few seconds after stabilization, the purge passage is kept airtight and there is a leak. It is determined that the process is not to be performed, and the series of processing ends. On the other hand, if the output of the pressure sensor 27 is not stable even after a predetermined time has elapsed since the pressurization pump 9 is operated, and if it is not kept constant for several seconds, there is a leak in the purge passage. Judgment is made, and a series of processing ends.

Next, with reference to FIG. 5 and FIG. 6, the operation when performing a leak check when the engine is stopped will be described in detail. When performing a leak check when the engine is stopped, in step S11, the ECU 15 closes the purge valve 11 and opens the fresh air valve 25 so that the canister 7 and the pressure pump 9 are connected through the bypass pipe 21. Further, the bypass valve 23 is controlled so that the canister 7 and the pressurizing pump 9 are not connected via the accumulated fuel supply pipe 19. As a result, an airtight path extending from the fuel tank 5 through the first cylindrical container 7a and the second cylindrical body 7b of the canister 7 to the pressurizing pump 9 is formed on the purge passage. When performing a leak check, the ECU 15 activates the pressure pump 9 in step S <b> 12 to apply a negative pressure upstream of the pressure pump 9. Then, the ECU 15 monitors the output of the pressure sensor 27. If the output of the pressure sensor 27 is constant for several seconds after the output of the pressure sensor 27 is stabilized in step S3, for example, the purge passage is kept airtight and there is no leak. Is determined, and the series of processing ends. On the other hand, if the output of the pressure sensor 27 is not stable even after a predetermined time has elapsed since the pressurization pump 9 is operated, and if it is not kept constant for several seconds, there is a leak in the purge passage. Judgment is made, and a series of processing ends. When the engine is stopped, the first cylindrical container 7a and the second cylindrical body 7b of the canister 7 are included in the leak check passage, so that the evaporated fuel remaining in the purge passage is downstream of the purge passage. It can be prevented from flowing to the side. That is, at the time of purging described with reference to FIG. 2, fresh air first flows into the canister from the first cylindrical container 7a, and the evaporated fuel accumulated in the first cylindrical container 7a is separated from the adsorbent to downstream. Transport to. Therefore, normally, the remaining amount of the evaporated fuel in the first cylindrical container 7a is extremely smaller than the remaining amount of the evaporated fuel in the second cylindrical container 7b. Therefore, when the engine is stopped, first, the air in the first cylindrical container 7 a is sucked by the pressurizing pump 9, whereby the fuel vapor can be prevented from flowing downstream from the pressurizing pump 9. Then, by restarting the engine with almost no evaporated fuel between the pressurizing pump 9 and the purge valve 11, the evaporated fuel is brought into the engine 1 whose temperature has not risen sufficiently immediately after the restart. Can be prevented from being supplied. Thereby, it is possible to suppress the evaporated fuel from passing through the engine 1 without being burned and being exhausted.

  As described above, according to the leak check system according to the present embodiment, the pressurizing pump that generates a negative pressure when supplying the evaporated fuel to the engine intake pipe 3 in both cases of operation and stop of the engine. 9 can be used to perform a leak check. As a result, it is not necessary to use a separate pressure pump for leak check, and the pressure pump 9 used at the time of supplying evaporated fuel can also serve as the pressure pump used at the time of leak check.

  Furthermore, according to the leak check system according to the present embodiment, when the leak check is performed when the engine is stopped, the inside of the canister 7 and the accumulated fuel supply pipe 19 can be connected via the bypass pipe 21. Then, when performing a leak check when the engine is stopped, the air with a small content of the evaporated fuel in the vicinity of the fresh air supply pipe 13 in the canister 7 is first caused to flow in the direction of the engine intake pipe 3. It becomes difficult for air with a large content of evaporated fuel to reach the vicinity of the engine intake pipe 3. Therefore, when the engine is restarted, it is possible to prevent the evaporated fuel from being supplied to the engine intake pipe 3 and exhausted from the engine 1 in an incombustible state.

3 Engine intake pipe 5 Fuel tank 7 Canister 9 Pressure pump 11 Purge valve 13 Fresh air supply pipe 17 Evaporated fuel supply pipe 19 Accumulated fuel supply pipe 21 Bypass pipe 23 Bypass valve 25 Fresh air valve 27 Pressure sensor

Claims (2)

An evaporative fuel supply pipe for supplying evaporative fuel in the fuel tank to the canister;
An accumulated fuel supply pipe for supplying evaporated fuel accumulated in the canister to an engine intake pipe;
A fresh air supply pipe for supplying fresh air to the canister;
A pressurizing pump provided in the middle of the accumulated fuel supply pipe;
A purge valve provided downstream of the pressurizing pump in the accumulated fuel supply pipe;
A leak check system for an evaporative fuel processing apparatus comprising:
A bypass pipe branched from the fresh air supply pipe and connected to the upstream side of the pressurized pump of the stored fuel supply pipe without passing through the canister;
A first valve comprising a three-way valve provided at a connection portion between the accumulated fuel supply pipe and the bypass pipe between the canister and the pressurizing pump;
A second valve composed of a three-way valve provided at a connection portion between the bypass pipe and the fresh air supply pipe;
The purge valve is closed, the first valve is switched to connect the downstream side of the stored fuel supply pipe with respect to the first valve and the bypass pipe, and the upstream side of the stored valve with respect to the first valve. By disconnecting the connection with the pressurizing pump and switching the second valve to connect the bypass pipe with the downstream side of the second valve of the fresh air supply pipe and operating the pressurizing pump. A leak check system comprising: generating a negative pressure in the bypass pipe, in the canister, and in the evaporated fuel supply pipe. When the engine is operated, the purge valve is closed, the first valve is switched to connect the upstream side and the downstream side of the first valve of the stored fuel supply pipe, and the connection between the bypass pipe and the pressurizing pump is cut off . and by the second valve it is fully closed, by operating the pressure pump, the storage fuel supply pipe, perform leak check of the evaporative fuel negative pressure is generated in the canister and the fuel vapor supply pipe ,
When the engine is stopped, the purge valve is closed and the first valve is switched to connect the downstream side of the stored fuel supply pipe with respect to the first valve and the bypass pipe, and the stored fuel on the upstream side of the first valve. wherein the supply pipe and disconnects the pressurizing pump, and connecting the bypass pipe downstream of the second valve by switching the second valve the fresh air supply pipe, said pressure pump 2. The leak check system according to claim 1, wherein by operating, a leak pressure of the evaporated fuel is checked by generating a negative pressure in the bypass pipe, the canister, and the evaporated fuel supply pipe.

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