JPH05202812A - Evaporated fuel control device for engine - Google Patents

Abstract

PURPOSE:To provide an evaporated fuel control device for an engine, which enables a canister for absorbing fuel vapor evaporated from a fuel tank by incorporating an absorber in a container so as to sufficiently ensure the purge of the canister, and which may prevent the pressure of fuel vapor in the fuel tank from exceeding a predetermined value. CONSTITUTION:A valve 18 disposed in a passage 13 communicating a canister 10 to the upper space 12a of a fuel tank 12 may closes the passage 13, and a pressure sensor 17 detects the pressure of fuel vapor in the fuel tank 12. When the pressure sensor 17 detects the pressure of fuel vapor which is higher than a predetermined value, and when the purge of the canister is carried out, the valve 18 is operated by a control unit 22 so as to close he passage 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel control device for an engine, which prevents fuel vapor evaporated from a fuel tank of a vehicle from being diffused into the atmosphere.

[0002]

2. Description of the Related Art In a general gasoline engine vehicle, in order to prevent the fuel vapor evaporating from the fuel tank from being diffused into the atmosphere, as disclosed in, for example, Japanese Patent Laid-Open No. 60-8458, the above described The canister includes an adsorbent that adsorbs fuel vapor in a container. The fuel vapor adsorbed by the canister is sucked into the intake passage downstream of the throttle valve of the engine through a purge passage provided with a duty solenoid valve that opens the passage according to the operating state of the engine.

The canister container has a first passage for communicating the canister with the upper space of the fuel tank, a second passage for communicating the canister with the intake system (purge passage), and a second passage for communicating the canister with the atmosphere. Although the third passage is connected to the adsorbent, the first and second passages are connected to the same side with respect to the adsorbent. It is connected to the side opposite to the second passage side.

[0004]

By the way, in recent years, due to the revision of various laws and regulations for preventing air pollution, the maximum value of the internal pressure of the fuel tank has been regulated. Measures are taken to reduce the ventilation resistance of the first passage. Further, in order to increase the fuel vapor adsorption capacity of the canister, an increase in ventilation resistance of the canister cannot be avoided. Further, a drain cut solenoid valve and a filter are required to be installed in the third passage for communicating the canister with the atmosphere, and the ventilation resistance of the third passage is also increased. Therefore, the ventilation resistance of the canister is further increased. The result is similar to.

As described above, the ventilation resistance of the passage communicating between the fuel tank and the canister is lowered, and the ventilation resistance of the canister is increased. As a result, the tank internal pressure is originally equal to or slightly higher than the atmospheric pressure. When you open the duty solenoid valve in the passage and perform a purge,
The vaporized vapor in the fuel tank is directly drawn into the intake system, and the fuel vapor adsorbed in the canister is not purged,
As a result, the adsorption capacity of the canister is reduced.

Although the decrease in the adsorption capacity of the canister can be compensated by increasing the capacity of the canister, the increase in the capacity of the canister causes the size of the canister container to be increased, making it difficult to mount it on a vehicle.

In view of the above-mentioned problems, it is an object of the present invention to provide an evaporated fuel control device for an engine, which ensures that the fuel vapor adsorbed in the canister is purged to the intake rate when the purge is executed. To do.

[0008]

A fuel vapor control apparatus for an engine according to the present invention includes a passage closing means for closing a passage communicating between a fuel tank and a canister, and a pressure detecting means for detecting a fuel vapor pressure in the fuel tank. Means and a control means for actuating the passage blocking means in response to the detection that the fuel vapor pressure in the fuel tank is below a predetermined value by the detection means. To do.

The control means operates the passage blocking means only at the time of purging in which the fuel vapor adsorbed in the canister is sucked into the intake system.

[0010]

According to the present invention, the passage closing means is operated when the fuel vapor pressure in the fuel tank is equal to or lower than a predetermined value, whereby the evaporation adsorbed in the canister at the time of purging is performed. Since the fuel can be reliably purged, it is possible to prevent the adsorption capacity of the canister from decreasing without increasing the size of the canister.

Further, according to the present invention, when the fuel vapor pressure in the fuel tank exceeds a predetermined value, the passage blocking means is not operated, so that the fuel vapor in the fuel tank further rises. Can be prevented.

[0012]

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

FIG. 1 is a diagram showing a structure of an evaporated fuel control device according to the present invention, and an engine 1 in which only an intake system is shown.
In the intake passage 2, an air cleaner 3, an air flow meter 4 for detecting the intake air amount, a throttle valve 5, and a surge tank 6 are sequentially arranged from the upstream side to the downstream side.

Further, the intake passage 2 is provided with a bypass passage 7 for supplying air to the engine 1 by bypassing the throttle valve 5 during idling operation. In the middle of the bypass passage 7, the amount of air passing through the passage 7 is provided. A duty solenoid valve 8 for controlling the above is provided. The throttle valve 5 has a throttle opening sensor 9 provided with an idle switch for determining whether the throttle valve 5 is fully closed.
Is installed.

Reference numeral 10 designates an adsorbent (activated carbon) 11 in a container 10a.
In the canister provided inside, a passage 13 for communicating the canister 10 with the upper space 12a of the fuel tank 12 and a purge passage 14 for communicating the canister 10 with the surge tank 6 of the intake passage 2 are provided with an adsorbent material in the canister container 10a. Passages 15 connected to each other on the same side with respect to 11, that is, on the upper side in FIG. 1, and for communicating the canister 10 with the atmosphere.
However, with respect to the adsorbent 11, the side opposite to the passages 13 and 14 side,
That is, it is connected to the lower side of FIG. Fuel tank 12
A negative pressure valve cap 12b is attached to the.

The end of the passage 13 for communicating the canister 10 with the upper space 12a of the fuel tank 12 on the fuel tank 12 side is provided with two branch passages 13a via a separator 16.
A pressure sensor 17 for detecting the fuel vapor pressure in the upper space of the fuel tank 12 is attached to one branch passage 13a. A normally open solenoid valve 18 that can close the passage 13 is disposed in the middle of the passage 13. The valve 18 is not limited to a solenoid valve and may be a valve of another type. A duty solenoid valve 19 for controlling the flow rate of the fuel vapor drawn into the intake passage 2 through the purge passage 14 is provided in the middle of the purge passage 14. Further, a drain cut solenoid valve 20 and a filter 21 are arranged in the passage 15 communicating with the atmosphere.

A control unit 22 controls the fuel injection amount from a fuel injection valve (not shown) on the basis of the outputs of the air flow meter 4, the throttle opening sensor 9 and other various sensors (not shown). At the same time, during idle operation, the amount of air passing through the bypass passage 7 is adjusted, and the duty solenoid valve 8 is duty-controlled so that the idle speed approaches the set value. Further, the control unit 22 duty-controls the duty solenoid valve 19 in the purge passage 14 in accordance with the operating state of the engine 1 to purge the fuel vapor adsorbed in the canister 10 and suck it into the intake passage 2.

Further, if the fuel vapor pressure in the fuel tank 12 detected by the pressure sensor 17 is equal to or lower than a predetermined value at the time of performing the purge, the control unit 22 operates the solenoid valve 18 to close the passage 13 and close the fuel. While the tank 12 and the canister 10 are shut off to ensure that the canister 10 is purged, when the fuel vapor pressure in the fuel tank 12 exceeds a predetermined value and when the purge is not executed even when the fuel vapor pressure is below the predetermined value. , The solenoid valve 18 is deactivated, the passage 13 is opened, the fuel vapor in the fuel tank 12 is adsorbed to the canister 10,
It prevents the fuel vapor pressure in the fuel tank 12 from rising.

FIG. 2 is a flow chart showing a control routine of the solenoid valve 18 executed by the control unit 22.

First, in step S1, the pressure sensor 1
7 output is read, and in the next step S2, the fuel tank 1
Check whether the fuel vapor pressure in 2 has exceeded a predetermined value.
When the determination in step S2 is "YES", the process proceeds to step S3, the solenoid valve 18 is not operated, and the passage 13 is left open to prevent the pressure in the fuel tank 12 from rising and The evaporated fuel in 12 is adsorbed to the canister 10.

On the other hand, when the determination in step S2 is "NO", that is, when the fuel vapor pressure in the fuel tank 12 is equal to or lower than the predetermined value, the process proceeds to step S4, and it is checked whether or not the purge is being executed. If so, the solenoid valve 18 is actuated in step S5 to close the passage 13 and ensure the purge. If the purge is not executed, the process proceeds to step S3, the passage 13 is opened, and the fuel vapor in the fuel tank 12 is removed from the canister 1.
Adsorb to 0.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an evaporated fuel control device according to the present invention.

FIG. 2 is a flowchart showing a control routine for a passage blocking valve.

[Explanation of symbols]

 1 Engine 2 Intake Passage 10 Canister 11 Adsorbent 12 Fuel Tank 13 First Passage 14 Second Passage (Purge Passage) 15 Third Passage 17 Pressure Sensor 18 Solenoid Valve 19 Duty Solenoid Valve 20 Drain Cut Solenoid Valve 21 Filter 22 control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Yamada 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (2)

[Claims] 1. A first passage that has an adsorbent in a container for adsorbing fuel vapor evaporated from a fuel tank, the first passage communicating the canister with the upper space of the fuel tank, and the canister. A second passage communicating with the system is connected to the adsorbent in the canister container on the same side as each other, and a third passage communicating the canister with the atmosphere is provided in the canister container with respect to the adsorbent. An evaporative fuel control system for an engine, comprising: a valve connected to the side opposite to the second passage side, the second passage being provided with a valve for controlling a purge amount of fuel vapor passing through the second passage. The passage closing means for closing the first passage, the pressure detecting means for detecting the fuel vapor pressure in the fuel tank, and the fuel vapor pressure in the fuel tank are equal to or more than a predetermined value. If it is detected by said detecting means is, the fuel vapor control system for an engine characterized by comprising a control means for actuating the passage blocking means in response thereto. 2. The control means closes the first passage by operating the passage closing means only when performing a purge for sucking the fuel vapor adsorbed in the canister into the intake system. The evaporated fuel control device for an engine according to claim 1.