JP2687074B2 - Evaporative fuel processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention connects a fuel tank and a canister via a charge passage provided with a two-way valve, and connects the canister and an engine intake passage via a purge passage. The present invention relates to an evaporative fuel processing apparatus in which a charge solenoid valve that opens and closes a bypass passage is provided in a bypass passage that bypasses a two-way valve.

[0002]

2. Description of the Related Art In such an evaporated fuel processing apparatus, the charge solenoid valve is closed and the bypass passage is closed when the engine is stopped, and the fuel tank and the canister communicate with each other via a two-way valve. Therefore, when the internal pressure of the fuel tank increases beyond a predetermined value due to the temperature rise, the two-way valve opens to supply the evaporated fuel to the canister, and at the same time, the internal pressure of the fuel tank is released to the atmosphere. Further, when the internal pressure of the fuel tank decreases below a predetermined value due to the temperature decrease, the two-way valve opens and the outside air is introduced into the fuel tank.

On the other hand, when the engine is in operation, the charge solenoid valve is opened to open the bypass passage, and the fuel tank and the canister communicate with each other without the two-way valve. In this state, the vaporized fuel charged in the canister is purged by the intake negative pressure generated in the intake passage of the engine, and the vaporized fuel sucked from the fuel tank is charged in the canister by the action of the negative intake pressure. .

However, if the atmospheric opening of the canister is blocked for some reason while the engine is operating and purging the evaporated fuel from the canister, the intake negative pressure directly acts on the fuel tank and the fuel tank is closed. There is an inconvenience of deformation. Therefore, when the intake negative pressure acting on the fuel tank during engine operation exceeds a predetermined value, the negative pressure control valve provided in the bypass passage is closed to prevent an excessive decrease in the internal pressure of the fuel tank. Have been proposed by the present applicant (Japanese Patent Application No. 3-55776).
No.).

[0005]

However, in the above-mentioned conventional device, since the negative pressure control valve operates regardless of the vapor concentration (purge concentration) passing through the purge passage downstream of the canister, the negative pressure control valve is adsorbed in the canister. Even when there is a large amount of evaporated fuel, that is, when the purge concentration is high, if the intake negative pressure is less than or equal to the predetermined value, the charge passage is opened and the canister continues to be charged, and eventually the evaporated fuel leaks from the canister. There is a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent excessive charging of a canister.

[0007]

In order to achieve the above object, the present invention connects a fuel tank and a canister via a charge passage having a two-way valve, and connects the canister and an intake passage of an engine. A purge concentration sensor for detecting a purge concentration of the purge passage in an evaporative fuel processing apparatus, which is connected through a purge passage and further includes a charge solenoid valve for opening and closing the bypass passage in a bypass passage bypassing the two-way valve. And a control means for closing the charge solenoid valve when the purge concentration detected by the purge concentration sensor exceeds a predetermined value.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention. FIG. 1 is an overall configuration diagram of an evaporated fuel processing apparatus, and FIG. 2 is a map showing a relationship between a measured purge flow rate and an actual purge flow rate. .

As shown in FIG. 1, the fuel pumped from the fuel tank T through the filter 1 and the fuel pump 2 is supplied to the fuel injection valve 4 of the engine E through the feed passage 3. The upper space of the fuel tank T and the downstream position of the throttle valve 6 provided in the intake passage 5 of the engine E are connected by a charge passage 7 and a purge passage 8, and a lower end is opened between the charge passage 7 and the purge passage 8. An open bottom type canister C is interposed.

The canister C stores activated carbon 11 as an adsorbent between the upper and lower filters 9 and 10. The charge passage 7 on the fuel tank T side opens inside the activated carbon 11 and the purge passage on the engine E side. 8 opens in the upper space of the upper filter 9, and the lower space of the lower filter 10 communicates with the atmosphere via the atmosphere opening passage 12.

A two-way valve 13 is provided in the charge passage 7 connecting the fuel tank T and the canister C. The two-way valve 13 opens when the internal pressure of the fuel tank T rises above a predetermined value above atmospheric pressure, and when the internal pressure of the fuel tank T drops below a predetermined value below the internal pressure of the canister C. And the fuel tank T and the canister C are communicated with each other. Note that the canister C side may have a negative pressure during purging, but in that case, the two-way valve 13 is kept closed.

A charge solenoid valve 14 is provided in a bypass passage 7'that bypasses the two-way valve 13. Therefore, when the charge solenoid valve 14 is opened, the fuel tank T and the canister C communicate with each other via the bypass passage 7 ′ without the two-way valve 13.

In the purge passage 8 connecting the canister C and the intake passage 5 of the engine E, a purge solenoid valve 15 and a mass flow meter 16 such as a hot wire flow meter are provided. The mass flow meter 16 constitutes the purge concentration sensor of the present invention. When the purge solenoid valve 15 is opened, the canister C communicates with the intake passage 5, and when the purge solenoid valve 15 is closed, the communication between the canister C and the intake passage 5 is cut off.

The electronic control unit U consisting of a microcomputer includes a mass flow meter 16, an oxygen concentration sensor 17 for detecting the oxygen concentration O ₂ in the exhaust gas of the engine E, and a throttle for detecting the opening θ _TH of the throttle valve 6. An opening sensor 18, a water temperature sensor 19 for detecting a cooling water temperature Tw of the engine E, an engine speed sensor 20 for detecting a speed Ne of the engine E, and an ignition switch 21 are connected. The electronic control unit U arithmetically processes the signals from the respective sensors 16 to 20 and the ignition switch 21 in accordance with a program given in advance, performs feedback control or open loop control of the fuel injection time of the fuel injection valve 4, and also controls the canister. The charge solenoid valve 14 and the purge solenoid valve 15 associated with C are opened and closed.

Next, a method for detecting the vapor concentration β of the evaporated fuel in the purge passage 8, that is, the purge concentration will be described with reference to FIG.

The actual purge flow rate (actual evaporative mixture flow rate) Q1 flowing in the purge passage 8 is the vapor flow rate VQ due to the fuel vapor (vapor) adsorbed in the canister C coming from the fuel tank T and the canister C being released to the atmosphere. It is the total flow rate with the air flow rate Q2 of the air sucked from the port 12. The actual purge flow rate Q1 can be known from the engine speed Ne and the flow path resistance of the purge passage 8 and the canister C at that time, and is stored in the electronic control unit U in advance as a map. The actual purge flow rate Q1 is directly absorbed from the fuel tank T without being adsorbed by the canister C, and the purge passage 8
Although the vapor that passes through is also included, since it is a high-concentration fuel vapor, it will be included in the vapor flow rate VQ.

Next, the actual purge flow rate (actual evaporative mixture flow rate)
The relationship between Q1 (l / min) and the measured purge flow rate QH (l / min) detected by the mass flowmeter 16 will be described with reference to FIG. In FIG. 2, the horizontal axis represents the measured purge flow rate (quantity detected by the mass flow meter 16) QH, and the vertical axis represents the actual purge flow rate Q1.
Is shown. SA is a characteristic line of 0% vapor concentration, that is, Q1 / QH in pure air, and SB is a vapor concentration of 20%, S
C shows a characteristic curve of Q1 / QH at a vapor concentration of 50% and SD shows a vapor concentration of 100%, that is, an air concentration of 0%. When the vapor concentration is 0%, the measured purge flow rate QH displayed by the mass flow meter 16 becomes the actual purge flow rate Q1 as it is. For example, when QH = 35 (l / min), Q1 = 35
(L / min). At 100% vapor concentration,
The measured purge flow rate QH displayed by the mass flowmeter 16 does not indicate the actual purge flow rate Q1 as it is, and for example, QH = 35 (l /
min), Q1 = 8 (l / min). That is, as the vapor concentration β increases, the measured purge flow rate QH becomes larger than the actual purge flow rate Q1.

From the above, based on the measured purge flow rate QH displayed by the mass flow meter 16 and the actual purge flow rate (actual evaporative air-fuel mixture flow rate) Q1 obtained by map search from the engine speed Ne, the vapor concentration β from FIG. Is required.

Next, the operation of the embodiment of the present invention will be described.

When the ignition switch 21 is off,
That is, while the engine E is stopped, the charge solenoid valve 14 and the purge solenoid valve 15 are both kept closed. In this state, when the temperature of the fuel tank T rises and the internal pressure of the fuel tank T rises due to the evaporation of the fuel, the two-way valve 13 opens and the fuel vapor flows into the canister C through the charge passage 7 there. It is prevented from being adsorbed by the activated carbon 11 and leaking to the outside. At the same time, the internal pressure of the fuel tank T is released to the outside from the atmosphere opening passage 12 of the canister C, and the internal pressure of the fuel tank T is prevented from rising excessively.
Further, when the internal pressure of the fuel tank T decreases due to the temperature decrease while the engine E is stopped, it is possible to prevent the internal pressure of the fuel tank T from excessively decreasing due to the introduction of outside air into the fuel tank T through the route opposite to the above. To be done.

From the time when the ignition switch 21 is turned on to start the engine E until the operating condition becomes stable,
That is, the fuel injection amount of the fuel injection valve 4 is opened by the electronic control unit U until the oxygen concentration sensor 17 is activated, the cooling water temperature rises, and the engine speed becomes equal to or higher than a predetermined value until the idling state is released. Loop controlled. In this open loop control state, the purged fuel from the canister C becomes a disturbance factor that changes the air-fuel ratio, so the adsorbed fuel is not purged in the canister C, and the charge solenoid valve 14 is stopped as when the engine E is stopped.
The purge solenoid valve 15 is kept closed.

When a predetermined time elapses after the engine E is started and the operating condition becomes stable, the fuel injection amount of the fuel injection valve 4 is switched from the open loop control to the feedback control. This feedback control is performed by the oxygen concentration sensor 17
Is carried out by feeding back the oxygen concentration output from the fuel injection system and multiplying the basic injection time by the feedback correction coefficient to determine the fuel injection time.

In the feedback control region, both the charge solenoid valve 14 provided in the charge passage 7 and the purge solenoid valve 15 provided in the purge passage 8 are opened, and the fuel tank T and the canister C are connected via the two-way valve 13. However, the canister C communicates with the intake passage 5 of the engine E.
In this state, the air introduced from the atmosphere release passage 12 of the canister C due to the negative pressure generated in the intake passage 5 is sucked through the purge solenoid valve 15 of the purge passage 8 and adsorbed on the activated carbon 11 of the canister C. The adsorbed fuel is purged and supplied to the intake passage 5. At the same time, the negative pressure in the intake passage 5 acts on the fuel tank T via the opened charge solenoid valve 14, so that the evaporated fuel in the fuel tank T passes through the opened charge solenoid valve 14 to pass through the canister. Supplied to C.

Now, while the engine E is operating, the canister C is
When the purge is being performed, the vapor concentration β (purge concentration) in the purge passage 8 is monitored by the mass flow meter 16 as described above. When the purge concentration exceeds a preset reference value for some reason, that is, when the adsorbed fuel amount in the canister C excessively increases, the charge solenoid valve 14 is controlled to be closed by the electronic control unit U. The charge to the canister C is suppressed. This prevents the evaporated fuel from being excessively charged in the canister C and leaking to the outside from the atmosphere opening passage 12.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various design changes can be made.

[0027]

As described above, according to the present invention, when the purge concentration detected by the purge concentration sensor exceeds a predetermined value, the control means closes the charge solenoid valve, so that the canister is not overcharged. It is possible to prevent the fuel from leaking from the canister.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an evaporated fuel processing device.

FIG. 2 is a map showing the relationship between the measured purge flow rate and the actual purge flow rate.

[Explanation of symbols]

 5 intake passage 7 charge passage 7'bypass passage 8 purge passage 13 two-way valve 14 charge solenoid valve 16 mass flow meter (purge concentration sensor) C canister E engine T fuel tank U electronic control unit (control means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Japanese Patent Laid-Open No. 4-262047 (JP, A) Actual flat 4-17156 (JP, U) Actual flat 4-105954 (JP, U)

Claims (1)

(57) [Claims] 1. A fuel tank (T) and a canister (C) are connected via a charge passage (7) provided with a two-way valve (13), and an intake passage for a canister (C) and an engine (E). A charge solenoid valve (14), which is connected to (5) via a purge passage (8), and which opens and closes the bypass passage (7 ') in a bypass passage (7') bypassing the two-way valve (13). In the evaporative fuel processing apparatus, the purge concentration sensor (16) for detecting the purge concentration in the purge passage (8) and the purge concentration detected by the purge concentration sensor (16) when the purge concentration exceeds a predetermined value. An evaporated fuel processing device, comprising: a control unit (U) for closing the charge solenoid valve (14).