KR100196988B1 - Apparatus for processing vaporized fuel of an engine - Google Patents

Abstract

An object of the present invention is to provide a one-way valve in the passage for introducing the suction negative pressure to the exhaust shutoff valve so that the exhaust passage is not blocked even if the suction negative pressure decreases. To this end, the configuration of the present invention comprises a canister (3) for storing fuel evaporated in the fuel tank, an exhaust passage (4) for connecting the canister (3) and the intake pipe downstream of the intake throttling valve (6), An exhaust valve 5 for opening and closing the exhaust passage 4, a diaphragm actuator 8 for opening and closing the exhaust passage 4 in response to a negative pressure, and an atmospheric pressure in the negative pressure operating chamber of the diaphragm actuator 8. And a control means (11) for switching the suction negative pressure into the three-way valve (10) while simultaneously opening the exhaust valve (5) for switching the suction negative pressure and introducing the suction negative pressure into the three-way valve (10). In the evaporative fuel processing apparatus for an engine, a one-way valve (22) which is opened only when the pressure on the intake pipe side is lower than the three-way valve side is provided in the passage (21) for introducing the suction side pressure into the three-way valve (10). .

Description

Evaporative Fuel Treatment System of Engine

1 shows a system of an embodiment according to the invention.

2 is a cross-sectional view of a one-way valve of another embodiment.

3 shows a system of a conventional device.

* Explanation of symbols for main parts of the drawings

3: canister 4: discharge passage

5: discharge valve 6: intake throttling valve

7 intake pipe 8: diaphragm actuator

10 release valve 11 control unit

21: negative pressure introduction path 22: one-way valve

[Industrial use]

The present invention relates to an evaporative fuel treatment apparatus for an engine.

[Prior art]

An evaporative fuel treatment device is installed to prevent the evaporated fuel from being released into the atmosphere in the vehicle's fuel tank (see Japanese Patent Application Laid-Open No. 62-74161).

Referring to FIG. 3, the fuel evaporated in the fuel tank is introduced into the canister 3 through the passage 2 and adsorbed to the activated carbon 3a in the canister 3.

When the discharge valve 5 is opened by receiving a signal from a control unit (not shown), new air is introduced by the canister (by inlet pipe negative pressure, which is developed downstream of the throttle valve 6). 3) The evaporated fuel introduced into the air and separated from the activated carbon 3a by the fresh air is introduced into the intake pipe 7 together with the fresh air and combusted in the combustion chamber.

A normally closed diaphragm actuator 8 is provided in series with the discharge valve 5, which is driven by a purge cut valve 10. The discharge passage 4 is closed when atmospheric pressure is introduced into the actuator 8 in the off state of the discharge shutoff valve 10, but the operating pressure applied to the actuator 8 when the discharge shutoff valve 10 is turned on. This is switched from the atmospheric pressure to the suction negative pressure, thereby opening the discharge passage 4.

The function provided to the discharge shutoff valve 10 is mainly two types. The first is to completely block the discharge passage 4 outside the discharge conditions. For example, during idling, the air-fuel ratio is greatly changed even by the release of a small amount, thereby greatly affecting the stability of the engine. Although it depends also on specification, since the discharge valve 5 cannot prevent leakage in any structure, it is necessary to shut off the discharge passage 4 completely except discharge conditions.

The second function is a fail safe function. Since the discharge valve 5 opens due to a malfunction during idling and the engine rotation increases, when the engine speed reaches a predetermined value or more, the discharge shutoff valve 10 is turned off to block the discharge passage 4.

[Problem to Solve Invention]

However, although the discharge passage 4 is opened by introducing the suction negative pressure into the actuator 8 by turning on the discharge shutoff valve 10 in the discharge condition, when the throttle valve 6 is largely opened, the suction negative pressure decreases, The return spring of (8) cannot be resisted, and the discharge passage 4 is easily blocked. Emissions are generally carried out during feedback control of the air-fuel ratio in order to make the influence on the control fuel ratio as small as possible, and the air-fuel ratio is forced to the lean side when the emission gas is interrupted in the middle of the introduction of a high concentration of the emission gas. When the air-fuel ratio is largely changed and the air-fuel ratio is returned to the rich side, the air-fuel ratio feedback correction coefficient α is greatly changed, but the amount of CO and HC generation increases until the air-fuel ratio feedback correction coefficient α is settled.

The decrease in suction pressure occurs in many cases. For example, in an engine with a large displacement, the suction portion pressure decreases during acceleration at high elevations, whereas in an engine with a small displacement, the intake portion pressure drops during acceleration even if it is not high. In the same vehicle, when the heavy cargo is loaded, the amount of depressing of the accelerator pedal tends to be large and the suction pressure decreases.

Accordingly, an object of the present invention is to provide a one-way valve which is opened only when the pressure on the intake pipe side is lower than the discharge shutoff valve side in the passage for introducing the suction negative pressure to the discharge shutoff valve so that the discharge passage is not blocked even when the suction negative pressure decreases. will be.

[Means for solving the problem]

The present invention provides a canister for accumulating fuel evaporated in a fuel tank, a discharge passage connecting the canister and an intake pipe downstream of an intake throttling valve, a discharge valve for opening and closing the discharge passage, and a discharge passage corresponding to a negative pressure. A diaphragm actuator for opening the valve and closing the discharge passage in response to the atmospheric pressure, valve means for switching atmospheric pressure and suction negative pressure into the negative pressure operation chamber of the diaphragm actuator, and simultaneously opening the discharge valve under the discharge condition. An evaporative fuel processing apparatus for an engine having a control means for switching inlet pressure into a valve means, the method comprising: a one-way which is opened only when the pressure on the intake pipe side is lower than the valve means side in a passage for introducing the suction pressure on the valve means; The valve was installed.

[Action]

If the intake side pressure is switched by introducing the atmospheric pressure from the valve means, the intake throttle valve is not opened that much.When the intake side pressure is large, the intake pipe side pressure of the one-way valve is lower than the valve means side. The way valve opens.

When the throttling valve is opened in this state, the suction inlet pressure is close to atmospheric pressure, so the intake pipe side pressure of the one-way valve is higher than that of the valve means side, and the one-way valve is kept closed. That is, even if the throttle valve is moved to the open side, the passage pressure from the valve means side of the one-way valve to the negative pressure operating chamber of the diaphragm actuator does not decrease.

EXAMPLE

In FIG. 1, the fuel evaporated in the fuel tank is introduced into the canister 3 via the passage 2 and adsorbed to the activated carbon 3a in the canister 3. The canister 3 is connected to the intake pipe 7 downstream of the intake throttling valve 6 by a discharge passage 4, and a discharge valve 5 of normally closed driven by a stepping motor is installed in the discharge passage. do. The discharge valve may be linear solenoid type or duty controllable.

The opening and closing control of the discharge valve 5 is a control unit 11 composed of a computer. In the control unit 11 to which an operation condition signal from the air flow meter 12 or the O ₂ sensor 13 or the like is input, for example,

1 feedback control of air-fuel ratio

2 When it is satisfied that the intake air flow rate is equal to or greater than the predetermined value, it is determined that the discharge condition is performed, and the ON signal is output to the discharge valve 5.

When the discharge valve 5 is opened by receiving the ON signal, new air is introduced into the canister from the new air inlet path 3b installed at the lower part of the canister 3 by the suction negative pressure. The evaporated fuel separated from the activated carbon 3a by the fresh air is introduced into the intake pipe 7 together with the fresh air and combusted in the combustion chamber.

A normally closed diaphragm actuator 8 is installed in series with the discharge valve 5 and the actuator 8 is driven by a discharge shutoff valve 10.

The discharge shutoff valve 10 is a three-way solenoid valve as a valve means for switching between atmospheric pressure and suction inlet pressure. When the atmospheric pressure is introduced into the negative pressure operating chamber 8a of the actuator in the OFF state, the return spring 8b is provided. The diaphragm 8c is extruded below the drawing by the pressing force of the figure, and the discharge passage 4 is closed. However, when the discharge shutoff valve 10 is turned on, the suction negative pressure is introduced into the negative pressure operating chamber 8a. The diaphragm 8c is pulled upward in the drawing and the discharge passage 4 is opened against the return spring 8b.

Instead of the three-way solenoid valve, two solenoid valves are provided, and even when the two solenoid valves are alternately opened and closed, the atmosphere and the suction negative pressure can be switched.

The control unit 11 also controls the opening / closing of the discharge shutoff valve 10. An ON signal is outputted under the discharge condition, and an OFF signal is output from the control unit 11 under other conditions (including idling).

A one-way valve 22 in the form of an umbrella valve is provided in the passage (negative pressure introduction path) 21 for introducing the injection negative pressure into the discharge shutoff valve 10. In the one-way valve 22 that is opened and closed by the pressure difference before and after the passage, the umbrella valve 22c is released from the seat only when the pressure in the right chamber 22a in the figure is lower than the left chamber 22b. 21) is opened.

Now, the operation will be described.

When the discharge shutoff valve 10 is in the OFF state, the diaphragm because the negative pressure introduction path 9 and the passage 21 are blocked, and the negative pressure introduction path 9 is connected to the atmospheric introduction path l0b of the discharge shutoff valve. Atmosphere is introduced into the negative pressure operation chamber 8a of the actuator.

When the discharge shutoff valve 10 is turned on by the establishment of the discharge condition, the air inlet path 10b is blocked to connect the passage 9 and the negative pressure introduction path 21.

When the throttle valve 6 is not opened very much and the suction pressure is large, the one-way valve 22 is opened because the pressure of the right chamber 22a is lower than that of the left chamber 22b. This valve opening is continued until the pressure difference between the left and right chambers 22a and 22b becomes equal to or less than a predetermined value, and the passage from the left chamber 22b to the negative pressure operating chamber 8a is almost equal to the pressure of the right chamber 22a. (Ie, large suction pressure), the discharge passage 4 is opened.

When opening the throttle valve 6 from this state, since the suction inlet pressure is close to atmospheric pressure, the pressure in the right chamber 22a of the one-way valve is higher than the left chamber 22b, and the one-way valve 22 opens the passage 21. The passage pressure from the left side chamber 22b to the negative pressure operating chamber 8a is maintained at a state of suction negative pressure corresponding to the opening degree of the throttle valve immediately before the throttle valve 6 is moved to the open side. Therefore, when the throttling valve is opened, the passage pressure does not decrease from the left chamber 22b to the negative pressure operating chamber 8a correspondingly. Therefore, since the discharge passage 4 is not blocked even when the discharge valve is open, it does not cause an increase in CO and HC emissions due to the blocking of the discharge passage, and also does not significantly change the air-fuel ratio.

On the other hand, when the passage 9 and the negative pressure inlet passage 21 are blocked by the OFF shutoff valve 10 during idling and the passage 9 and the atmospheric inlet passage l0b are connected, the negative pressure of the passage 9 is reduced. It is released to the atmosphere and the discharge passage 4 is blocked. The one-way valve 22 does not affect the operation of the diaphragm actuator 8 when the discharge shutoff valve 10 is turned off.

2 shows a one-way valve 25 of another embodiment, in which the right passage 25a in the figure is connected to the intake pipe 7 side and the left passage 25b is located on the discharge shutoff valve 10 side. do. Also in this embodiment, the ball 25c is opened by moving to the right against the return spring 25d only when the pressure in the right passage 25a becomes lower than the pressure in the left passage 25b. In addition, although the two embodiments are mechanical one-way valves, it is also possible to shut off the negative pressure inlet passage 21 at the time of low load by using an electromagnetic valve. In this embodiment, the same effect as in Example 1 is generated.

[Effects of the Invention]

The present invention provides a canister for storing fuel evaporated in a fuel tank, a discharge passage connecting the canister and an intake pipe downstream of the intake throttling valve, a discharge valve opening and closing the discharge passage, and a discharge passage corresponding to a negative pressure. A diaphragm actuator for opening the valve and closing the discharge passage in response to the atmospheric pressure, valve means for switching the atmospheric pressure and the suction negative pressure into the negative pressure operating chamber of the diaphragm actuator, and opening the discharge valve under the discharge condition. An evaporative fuel processing apparatus for an engine provided with a control means for switching a negative pressure into a valve means, the one-way valve being opened only when the pressure on the intake pipe side is lower than the valve means side in a passage for introducing the suction negative pressure to the valve means. , The negative pressure operating chamber of the diaphragm actuator under high load at which the intake throttling valve is greatly opened. The discharge passage is not blocked by the introduction of the negative pressure decreases, it is possible to prevent an increase in CO, HC emissions thereby, nor does sikijido significantly changing the air-fuel ratio.

Claims (1)

A canister (3) for storing fuel evaporated in the fuel tank, a discharge passage (4) connecting the canister and an intake pipe (7) downstream of the intake throttling valve (6), and a discharge valve for opening and closing the discharge passage. (5) and a diaphragm actuator 8 for opening the discharge passage in correspondence with the negative pressure and closing the discharge passage in response to the atmospheric pressure, and switching the atmospheric pressure and the suction negative pressure into the negative pressure operation chamber of the diaphragm actuator. In the evaporative fuel processing apparatus of an engine having a valve means (10) and a control means (11) for opening and discharging the discharge valve under the discharge conditions and switching inlet pressure into the valve means. And a one-way valve (22) which opens only when the pressure on the intake pipe side is lower than the valve means side in the passage (21) for introducing the suction part pressure in the engine.