JP5345466B2 - Evaporative fuel purge system - Google Patents

Description

  The present invention relates to an evaporative fuel purge system capable of suppressing the escape of evaporative fuel from a canister even when the engine is stopped for a long period of time.

  2. Description of the Related Art Conventionally, vehicles such as automobiles are provided with an evaporative fuel purge system in order to prevent fuel evaporative gas (evaporated fuel) generated in a fuel tank from being discharged into the atmosphere. This evaporative fuel purge system stores evaporative fuel in a canister, and purges and burns the intake system as a mixture of fresh air and evaporative fuel (evaporative gas) when a predetermined purge execution condition is satisfied.

  By the way, the concentration distribution of the evaporated fuel adsorbed by the adsorbent such as activated carbon provided in the canister tends to become lower toward the atmosphere opening passage, but the adsorbent is in one continuous space in the canister. In the case of being filled, a so-called migration phenomenon in which the evaporated fuel diffuses and moves toward the atmosphere opening passage having a low concentration as time elapses due to adsorption equilibrium.

  While the engine is running, the evaporated fuel adsorbed by the canister is purged by the intake system due to the negative pressure generated in the intake system, so that the evaporated fuel is not released from the air opening passage. .

  However, when the engine is stopped for a long time, the evaporated fuel is uniformly diffused in the canister due to the migration phenomenon. On the other hand, even if the engine is stopped, if the internal pressure of the fuel tank increases, the evaporated fuel generated in the fuel tank due to the differential pressure flows into the canister, so every time this new evaporated fuel flows into the canister The evaporated fuel adsorbed by the adsorbent on the atmosphere opening passage side is released to the atmosphere. Accordingly, the amount of evaporated fuel released from the atmospheric opening passage increases with time.

  As countermeasures, for example, in Patent Document 1 (Japanese Utility Model Publication No. 2546618) and Patent Document 2 (Japanese Patent Application Laid-Open No. 9-209849), a canister is provided with a main canister and a sub-canister, and both the canisters are connected through a diaphragm. By arranging them in series, when the engine is stopped, first, the evaporative fuel is uniformly filled into the main canister, and then the evaporative fuel overflowing from the main canister flows into the sub-canister side through the throttle.

  Therefore, when the engine is stopped, the evaporated fuel does not flow into the sub-canister until the main canister is uniformly diffused. Therefore, even if the engine is stopped for a long time, the release (blow-off) of the evaporated fuel to the atmosphere is suppressed. Can do.

  However, in the techniques disclosed in the above-mentioned documents, since it is necessary to configure one canister with a main canister and a sub-canister, the structure of the canister is complicated, and the volume of the entire canister is increased, and the product There is a problem that the cost becomes high.

  In view of the above circumstances, an object of the present invention is to provide an evaporative fuel purge system having a simple structure and capable of suppressing an increase in the volume of the entire canister and an increase in product cost.

In order to achieve the above object, according to the present invention, an evaporative gas chamber and an atmospheric chamber are formed in a canister main body containing an adsorbent for adsorbing evaporated fuel, with the adsorbent interposed therebetween. A tank is communicated and an intake system is communicated via a barge passage, a first atmosphere opening passage that is open to the atmosphere is communicated with the atmosphere chamber, and the first atmosphere opening passage is communicated with the first atmosphere opening passage. In the evaporative fuel purge system provided with the first valve body for opening and closing the opening passage, the side surface of the adsorbent on the atmosphere chamber side is opened to the atmosphere and has a passage resistance as compared with the first atmosphere opening passage. A large second atmospheric opening passage is communicated, and when the engine is stopped, the first valve body is closed and the first atmospheric opening passage is closed.

According to the present invention, the side surface of the adsorbent on the atmosphere chamber side is connected to the second atmosphere opening passage that is open to the atmosphere and has a passage resistance larger than that of the first atmosphere opening passage. Since the first atmospheric opening passage is closed by the valve body, the adsorbent is directly communicated with the atmosphere through the second atmospheric opening passage. Accordingly, it is difficult for the evaporated fuel to escape from the second atmospheric opening passage, and even if the engine is stopped for a long time, the blowout from the canister can be suppressed. In addition, since the adsorbent has a simple structure in which the second atmospheric opening passage is communicated with the adsorbent, it is possible to suppress an increase in the volume of the entire canister and an increase in product cost.

Schematic configuration diagram of evaporative fuel purge system Cross-sectional view of the solenoid valve that opens and closes the canister and the atmosphere side passage of the canister when the engine is stopped Sectional view of the solenoid valve that opens and closes the canister and the atmosphere side passage of the canister during engine operation Cross section of the solenoid valve that opens and closes the canister and the atmosphere side passage of the canister during failure diagnosis Cross section of the solenoid valve that opens and closes the canister and the atmosphere side passage of the canister during refueling

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 in FIG. 1 denotes an intake system of the engine. The upstream of an intake manifold 1 a connected to an intake port of an engine (not shown) is gathered and communicated with the air chamber 2. An intake passage 3 communicates with the upstream side of the air chamber 2, a throttle valve 4 is interposed in the intake passage 3, and an air cleaner 5 is attached to the intake intake side of the intake passage 3.

  On the other hand, reference numeral 6 denotes a fuel tank. The upper side of the fuel tank 6 communicates with the upstream side of the evaporation passage 7 constituting the evaporation purge system, and the downstream side of the evaporation passage 7 communicates with the canister 8. Further, a two-way valve 9 is interposed in the evaporation passage 7. When the internal pressure of the fuel tank 6 rises, the 2-way valve 9 allows the evaporated fuel in the fuel tank 6 to escape to the canister 8 and suppresses the increase in the internal pressure of the fuel tank 6, while the internal pressure of the fuel tank 6 decreases. When this occurs, outside air is introduced into the fuel tank 6 to suppress a decrease in internal pressure of the fuel tank 6.

  As shown in FIGS. 2 to 5, the canister 8 contains an adsorbent 10 such as activated carbon, and an evaporation gas chamber 8 a is formed on one side of the adsorbent 10 and an air chamber 8 b is formed on the other side. Has been. Further, the downstream end of the evaporation passage 7 and the upstream end of the purge passage 11 are exposed to the evaporation gas chamber 8 a, and the downstream end of the purge passage 11 is communicated with the air chamber 2. Further, a purge control valve (PCV) 12 is interposed in the purge passage 11. In this embodiment, a duty solenoid valve that is fully closed at 0% and fully opened at 100% is employed as the PCV 12.

  In addition, one end of a separation atmosphere opening passage 13 serving as a first atmosphere opening passage communicating with the atmosphere communicates with the atmosphere chamber 8 b of the canister 8. On the other hand, one end of an adsorption atmosphere opening passage 14 as a second atmosphere opening passage is directly exposed to the side surface of the adsorbent 10 provided in the canister 8 on the atmosphere chamber 8 b side. Further, both the atmospheric opening passages 13 and 14 communicate with the multistage solenoid valve main body 15.

  As shown in FIGS. 2 to 5, the multistage solenoid valve main body 15 is formed with a first valve chamber 16 and a second valve chamber 17 on both sides, and a separation atmospheric opening is formed in the first valve chamber 16. The other end of the passage 13 is communicated, and the other end of the adsorption atmospheric opening passage 14 is communicated with the second valve chamber 17. Further, a T-shaped atmosphere release pipe 18 communicating with both valve chambers 16 and 17 is communicated with the multistage solenoid valve main body 15, and a merging portion 18a of the atmosphere release pipe 18 is opened to the atmosphere.

  The valve chambers 16 and 17 are respectively provided with first and second electromagnetic valves 16a and 17a as first and second valve bodies. The first electromagnetic valve 16a is normally closed and is opened by energizing the electromagnetic coil 16b. On the other hand, the second electromagnetic valve 17a is a normally open type and is closed by energizing the electromagnetic coil 17b.

  The separation atmosphere opening passage 13 communicated with the first valve chamber 16 is formed with a relatively large pipe diameter so that the atmosphere flows smoothly. On the other hand, the adsorption atmospheric opening passage 14 communicated with the second valve chamber 17 is formed with a relatively thin pipe diameter so as to increase the airflow resistance and function as a throttle.

  The electromagnetic valves 16a and 17a and the PCV 12 are controlled by a drive signal output from an electronic control unit (ECU) 21. The ECU 21 is composed of a known microcomputer or the like. On the input side, the ECU 21 has an ignition switch 22, a vehicle speed sensor 23 for detecting the vehicle speed, an engine speed sensor 24 for detecting the engine speed, and a fuel flap that is turned on when the fuel flap is opened. Sensors and switches for detecting parameters required for performing the evaporated fuel purge control, such as the switch 25, are connected.

  The ECU 21 controls the opening degree of the PCV 12 and the opening and closing of the electromagnetic valves 16 a and 17 a of the multistage electromagnetic valve main body 15 based on parameters output from sensors and switches. This evaporative fuel purge control is set in four modes: when the engine is stopped, when the engine is running, when a failure is diagnosed, and when refueling.

  Hereinafter, operations of the PCV 12 and the solenoid valves 16a and 17a in each mode will be described.

: When the engine is stopped:
When the ignition switch 22 is turned off, the energization to the ECU 21 is stopped, and the ignition signal to the spark plug and the injection signal to the injector are shut off, so the engine stops. At the same time, energization of the drive signal from the ECU 21 to the PCV 12 and the solenoid valves 16a and 17a of the multistage solenoid valve body 15 is stopped. Then, the PCV 12 is fully closed, and as shown in FIG. 2, the first electromagnetic valve 16a is closed and the second electromagnetic valve 17a is opened.

  When the internal pressure of the fuel tank 6 increases while the engine is stopped, the evaporated fuel staying in the upper part of the fuel tank 6 passes through the evaporation passage 7 and is adsorbed by the adsorbent 10 of the canister 8 through the 2-way valve 9. Is done. At that time, the separation atmospheric opening passage 13 is closed by the first electromagnetic valve 16 a, while the second electromagnetic valve 17 a communicating with the adsorption atmospheric opening passage 14 is opened, so that the evaporated fuel is adsorbed by the adsorbent 10. The amount of air thus discharged is released to the atmosphere through the second valve chamber 17 and the atmosphere opening pipe 18 from the adsorption atmosphere opening passage 14 directly connected to the adsorbent 10.

  By the way, the concentration distribution of the evaporated fuel adsorbed by the adsorbent 10 becomes thinner as it moves from the evaporation gas chamber 8a toward the atmospheric chamber 8b. However, if the engine is stopped for a long time, the evaporated fuel adsorbed by the adsorbent 10 has a uniform concentration due to the progress of the migration phenomenon. Accordingly, when the first electromagnetic valve 16a communicating with the separation atmospheric opening passage 13 is opened when the engine is stopped, new evaporated fuel is introduced from the evaporation gas chamber 8b and the adsorbent 10 when the engine is stopped for a long time. Each time the fuel is adsorbed by the fuel, the evaporated fuel distributed in the adsorbent 10 on the atmosphere chamber 8b side is pushed out to the atmosphere chamber 8b and stays in the atmosphere chamber 8b, and is discharged to the atmosphere through the separation atmosphere opening passage 13. Will be.

  However, since the first electromagnetic valve 16a of the present embodiment is a normally closed type and the second electromagnetic valve 17a is a normally open type, when the engine is stopped, the first electromagnetic valve 16a is closed and the second electromagnetic valve 17a is open. The adsorption atmospheric opening passage 14 communicating with the second valve chamber 17 in which the second electromagnetic valve 17a is disposed has a narrow pipe diameter, and directly faces the side surface of the adsorbent 10 on the atmospheric chamber 8b side. Therefore, the evaporation gas adsorbed around the adsorbent 10 facing the adsorption atmospheric opening passage 14 is only released from the adsorption atmospheric opening passage 14. As described above, since the concentration distribution of the evaporated fuel adsorbed by the adsorbent 10 is the thinnest in the atmospheric chamber 8b, the concentration of the evaporated fuel in the portion where the adsorption atmospheric opening passage 14 is exposed is thin, Since the passage resistance is relatively larger than that of the separation atmospheric opening passage 13, the concentration of the evaporated fuel discharged through the adsorption atmospheric opening passage 14 can be further reduced. Therefore, the release (blow-off) of the evaporated fuel to the atmosphere can be greatly suppressed.

: When the engine is running:
When the ignition switch 22 is turned on, the ECU 21 energizes the electromagnetic coil 16b that drives the first electromagnetic valve 16a, and the first electromagnetic valve 16a is sucked and opened. Then, as shown in FIG. 3, the atmospheric opening passages 13 and 14 are communicated with the atmospheric opening pipe 18 through the valve chambers 16 and 17 to be in an open state. During engine operation, the ECU 21 controls the opening of the PCV 12 to a predetermined value according to the engine operating state.

  When the PCV 12 is opened, the negative pressure in the air chamber 2 is introduced into the canister 8 through the purge passage 11 and the evaporated fuel adsorbed by the adsorbent 10 is supplied to the intake system as an evaporation gas. At that time, since both the atmosphere opening passages 13 and 14 are opened to the atmosphere, the atmosphere is introduced into the canister 8 from both the atmosphere opening passages 13 and 14.

  In this embodiment, since the outside air is introduced into the canister 8 from the adsorption atmospheric opening passage 14 in addition to the separation atmospheric opening passage 13, the evaporated fuel adsorbed by the adsorbent 10 is efficiently purged to the intake system. Can be made.

: During failure diagnosis:
When the engine is operated, the ECU 21 determines failure diagnosis conditions. When the diagnosis conditions are satisfied, the ECU 21 closes the PCV 12 and energizes the electromagnetic coil 16b that operates the first electromagnetic valve 16a of the multistage electromagnetic valve body 15. And energizes the electromagnetic coil 17b that operates the second electromagnetic valve 17a. Then, since the first electromagnetic valve 16a is a normally closed type and the second electromagnetic valve 17a is a normally open type, both the electromagnetic valves 16a and 17a are closed.

  As a result, the space from the fuel tank 6 to the PCV 12 becomes a closed space, and the internal pressure of the closed space rises with the elapse of time due to the evaporated fuel generated from the fuel tank 6. After a predetermined time, whether there is a leak in the closed space between the fuel tank 6 and the PCV 12 based on the tank internal pressure detected by an internal pressure sensor (not shown) that detects the pressure in the upper space of the fuel tank 6. Find out.

: When refueling:
When refueling, the ignition switch 22 is turned off and a fuel flap (not shown) is opened. When the fuel flap is opened, the fuel flap switch 25 is turned ON. The fuel flap switch 25 is a relay switch. When the fuel flap switch 25 is turned on, power is supplied to the ECU 21 and the ECU 21 is activated. And from this ECU21, it supplies with electricity to the electromagnetic coil 16b which operates the 1st solenoid valve 16a of the multistage solenoid valve main body 15, and opens this 1st solenoid valve 16a.

  Then, as shown in FIG. 5, the atmospheric opening passages 13, 14 are communicated with the atmospheric release pipe 18 via the valve chambers 16, 17 to be in an open state. The PCV 12 is kept closed.

  When fuel is supplied to the fuel tank 6, the evaporated fuel staying in the upper space is adsorbed to the canister 8 via the evaporation passage 7 as the oil level in the fuel tank 6 rises. In addition, by opening the solenoid valve 16a, the ventilation resistance of the canister 8 is lowered, and smooth oil supply performance can be ensured.

At that time, the evaporative gas of the adsorbent 10 is released to the atmosphere through both the atmospheric opening passages 13 and 14, but generally, when refueling, the vehicle is self-propelled to the refueling stand, so the engine was stopped. In the state, the concentration of the evaporated fuel on the side of the atmospheric chamber 8b of the adsorbent 10 is low, and therefore there is almost no blow-through of the evaporated fuel from the atmospheric opening passages 13 and 14 to the atmosphere.

  Thus, in this embodiment, when the ignition switch 22 is turned off to stop the engine, the first electromagnetic valve 16a is closed and the second electromagnetic valve 17a is opened. Only the adsorbing atmospheric opening passage 14 with a narrow pipe diameter facing the air is communicated with the atmosphere. Therefore, even if the state where the engine is stopped for a long time is continued, the blow-through of the evaporated fuel diffused in the adsorbent 10 due to the migration phenomenon can be suppressed. Furthermore, since the adsorbent 10 has a simple structure in which the adsorbing air opening passage 14 is communicated with the adsorbent 10, it is possible to suppress an increase in the volume of the entire canister 8 and an increase in product cost.

  The present invention is not limited to the above-described embodiment. For example, the adsorption atmospheric opening passage 14 is provided with a restriction such as an orifice in the inside thereof without reducing the pipe diameter so as to increase the passage resistance. Also good.

1 ... Intake system,
3 ... Intake passage,
6 ... Fuel tank,
7 ... Evapo passage,
8 ... canister,
8a ... Evapogas chamber,
8b ... Atmospheric chamber,
10 ... Adsorbent,
11 ... purge passage,
12 ... Purge control valve,
13 ... Atmospheric opening passage for separation,
14 ... Atmospheric opening passage for adsorption,
15 ... Multistage solenoid valve body,
16 ... 1st valve chamber,
16a, 17a ... solenoid valves,
16b, 17b ... electromagnetic coils,
17 ... Second valve chamber,
18 ... Open-air pipe,
18a ... Junction,
22 ... Ignition switch,
23 ... Vehicle speed sensor,
24. Engine speed sensor,
25 ... Fuel flap switch

Noto 2546618 gazette JP 9-209849 A

Claims (2)

An evaporative gas chamber and an atmospheric chamber are formed in a canister main body containing an adsorbent for adsorbing evaporated fuel, with the adsorbent interposed therebetween, and a fuel tank is connected to the evaporative gas chamber via an evaporative passage and a barge passage is provided. And a first valve body that opens and closes the first atmosphere opening passage to the first atmosphere opening passage. In the provided fuel vapor purge system,
The side surface of the adsorbent on the atmosphere chamber side is opened to the atmosphere and communicated with a second atmosphere opening passage having a larger passage resistance than the first atmosphere opening passage,
An evaporative fuel purge system, wherein the first valve body is closed and the first atmospheric opening passage is closed when the engine is stopped. A second valve body is provided in the second atmospheric opening passage, and both the first valve body and the second valve body are closed during failure diagnosis of the evaporated fuel purge system. The evaporated fuel purge system according to claim 1 .

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