JPH0617712A - Evaporative fuel control device for engine - Google Patents

Abstract

PURPOSE:To eliminate possibility to release the inside pressure of a tank to the atmo sphere at the time of oiling, so as to prevent over filling by operating a second solenoid valve, and making such control as forcing the atmosphere to act on a pressure control valve. CONSTITUTION:An evaporation fuel control device is provided with a first passage 36 for communicating a fuel tank 16 with a canister 34, and a second passage 38 for communicating the canister 34 with an intake passage 10. A pressure control valve 42 is provided on the way of the first passage 36, a first solenoid valve 44 is provided on the way of the second passage 38, and a second solenoid valve 48 is provided on the way of a passage for communicating the intake passage 10 with the pressure control valve 42. Control is carried out in such a way as forcing an intake pipe negative pressure to act by means of the second solenoid valve 48 so as to open the pressure control valve 42 during operation of an engine 2. And also a control unit 52 is provided in order to carry out control in such a way that the second solenoid valve 48 is operated by the detected signal from a fuel level gage 50 when the amount of fuel in the fuel tank 16 attains a prescribed amount or more to force the atmosphere to act on the pressure control valve 42. It is thus possible to prevent over filling at the time of oiling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel control system for an engine, and more particularly to an evaporative fuel control system for an engine having a canister for adsorbing and retaining the evaporative fuel in a passage connecting an intake passage of the engine and a fuel tank. .

[0002]

2. Description of the Related Art Evaporative fuel that leaks into the atmosphere from a fuel tank, a float chamber of a vaporizer, etc., contains a large amount of hydrocarbons (HC) and is one of the causes of air pollution, and also causes fuel loss. Because of the connection, various techniques for preventing this are known. As a typical example, the evaporated fuel in the fuel tank is temporarily adsorbed and held in a canister containing an adsorbent such as activated carbon, and the evaporated fuel adsorbed and held in this canister is separated (purge) during engine operation.
There is an evaporative system that allows it to be supplied to the engine.

Further, as an engine fuel vapor control device, there is one disclosed in Japanese Patent Laid-Open No. 130254/1990. An evaporative gas treatment device for a fuel tank in an engine disclosed in this publication includes a communication passage that connects the fuel tank and a canister, and an on-off valve that opens and closes the communication passage.
The engine is stopped or the vehicle is stopped by the stop detection means for detecting the stop of the engine or the vehicle and the drive means for driving the opening / closing valve for a predetermined time after the stop of the engine or the stop of the vehicle is detected. After opening the open / close valve for a predetermined time, the evaporative gas in the fuel tank is introduced into the canister and collected, and even if the filler cap is opened during refueling, the evaporative gas released from the refueling port into the atmosphere. The amount is greatly suppressed.

[0004]

A conventional evaporated fuel control device for an engine will be described. In FIG. 9, 102 is an engine, 104 is an air cleaner, and 106.
Is a throttle valve, 108 is a surge tank, 110 is an intake passage, 112 is a combustion chamber, 114 is an exhaust passage, 116
Is a fuel tank. The engine 102 is provided with a fuel injection valve (not shown) in the intake passage 110 so as to be directed toward the combustion chamber 112. The fuel injection valve communicates with the fuel tank 116 via a fuel passage (not shown).

The fuel in the fuel tank 116 is fed by a fuel pump (not shown) to the fuel injection valve through the fuel passage, and is supplied to the combustion chamber 112 together with air for combustion. The exhaust gas generated by the combustion is exhausted through the exhaust passage 114.

An intake passage 110 of the engine 102, for example, a surge tank 10 downstream of the throttle valve 106.
8 is provided with a passage 132 connecting the fuel tank 116 and
A canister 134 for adsorbing and holding the evaporated fuel is provided in the middle of the passage 132.

The passage 132 is connected to the fuel tank 116.
Is formed by a first passage 136 that connects the canister 134 with the canister 134, and a second passage 138 that connects the canister 134 and the intake passage 110.

Further, the fuel tank 116 and the canister 13
A check valve 140 is provided in the first passage 136 between the four. The check valve 140 sets the pressure in the fuel tank 116 and the pressure in the canister 134 to a predetermined pressure and suppresses the amount of evaporated fuel (HC) generated in the fuel tank 116.

Further, a control unit (not shown) is provided, and the control unit includes a throttle sensor (not shown) for detecting the opening of the throttle valve 106 and the second passage 1.
The solenoid valves 144 provided in the middle of 38 are connected to each other.

A check valve 140 in the middle of the first passage 136 prevents overfilling during refueling.

However, by using the check valve 140, the internal pressure of the tank is set to a pressure somewhat higher than the atmospheric pressure, and the internal pressure of the tank is constantly maintained at a constant level (accumulation).

As a result, when refueling at a refueling place such as a gas station, the cap portion 1 of the fuel tank 116 is
When 16A is opened, the internal pressure of the tank is released to the atmosphere, and the evaporated fuel (HC) in the fuel tank is released, which is a cause of air pollution.

According to the evaporative regulation which is planned to be adopted from the US 95MY (model year), the tank internal pressure during engine operation is at a predetermined level, for example, 10 inches mm.
It is regulated below Ag, and development of an engine fuel vapor control device that can cope with this evaporative regulation is earnestly desired.

[0014]

Therefore, in order to eliminate the above-mentioned inconvenience, the present invention has a vaporized fuel for an engine having a canister for adsorbing and holding the vaporized fuel in a passage connecting an intake passage of the engine and a fuel tank. In the control device, the passage is formed by a first passage that connects the fuel tank and the canister and a second passage that connects the canister and the intake passage, and a pressure control valve is provided in the middle of the first passage. The first solenoid valve is installed in the middle of the two passages,
A communication passage for connecting the intake passage and the pressure control valve is provided, a second solenoid valve is provided in the middle of the communication passage, a fuel level gauge for detecting the amount of fuel is provided in the fuel tank, and a fuel level gauge for detecting the amount of fuel is provided during operation of the engine. The two solenoid valves are used to control the intake pipe negative pressure to open the pressure control valve, and when the fuel in the fuel tank exceeds a predetermined amount, the second solenoid valve is activated by the detection signal from the fuel level gauge. It is characterized in that a control unit is provided which operates and controls the pressure control valve so as to act the atmosphere.

[0015]

With the invention as described above, during operation of the engine, the intake pipe negative pressure is applied to the pressure control valve by the second solenoid valve, and the pressure control valve is controlled to open so that the tank internal pressure is approximately atmospheric pressure. When the pressure in the fuel tank becomes equal to or more than a predetermined amount, the second solenoid valve is operated by the detection signal from the fuel level gauge, and the pressure control valve is controlled to act on the atmosphere, The connection between the fuel tank and the canister is cut off to prevent overfilling during refueling.

[0016]

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

1 to 4 show a first embodiment of the present invention. 1, 2 is an engine, 4 is an air cleaner, 6 is a throttle valve, 8 is a surge tank, 1
Reference numeral 0 is an intake passage, 12 is a combustion chamber, 14 is an exhaust passage, and 16 is a fuel tank. The engine 2 is provided with a fuel injection valve 18 in the intake passage 10 in the direction of the combustion chamber 12. The fuel injection valve 18 is communicated with the fuel tank 16 via a fuel passage 20.

The fuel passage 20 includes a fuel supply passage 22 for supplying fuel from the fuel tank 16 to the fuel injection valve 18.
A fuel return passage 24 for returning a predetermined amount of fuel or more into the fuel tank 16, and a filter 2 provided in the middle of the fuel supply passage 22.
6 is provided, and a return volume 28 is provided in the fuel return passage 24.

The fuel in the fuel tank 16 is the fuel pump 30.
Is sent to the fuel injection valve 18 via the fuel supply passage 22, and is supplied to the combustion chamber 12 together with air for combustion. The exhaust gas generated by the combustion is exhausted through the exhaust passage 14.

An intake passage 10 of the engine 2, for example, a passage 32 for connecting the surge tank 8 and the fuel tank 16 on the downstream side of the throttle valve 6 is provided, and a canister 34 for adsorbing and holding evaporated fuel is provided in the passage 32.

The passage 32 is formed by a first passage 36 that connects the fuel tank 16 and the canister 34, and a second passage 38 that connects the canister 34 and the intake passage 10.

A check valve 40 is provided in the middle of the first passage 36, and the check valve 40 sets the pressure in the fuel tank 16 and the pressure in the canister 22 to predetermined pressures so that the fuel vapor in the fuel tank 16 is evaporated. (H
The amount of C) is suppressed.

A pressure control valve 42 is provided in the middle of the first passage 36, and a first solenoid valve 4 is provided in the middle of the second passage 38.
4 is provided, and a communication passage 46 that connects the intake passage 10 and the pressure control valve 42 is provided.
A second solenoid valve 48 is provided on the way, and a fuel level gauge 50 for detecting the amount of fuel is provided in the fuel tank 16.

When the engine 2 is in operation, the second solenoid valve 48 exerts a negative pressure on the intake pipe to control the pressure control valve 42 to open and to control the fuel tank 1.
When the amount of fuel in 6 exceeds a predetermined amount, the detection signal from the fuel level gauge 50 causes the second solenoid valve 4
The control unit 52 is provided to control the pressure control valve 42 so that the pressure control valve 42 is operated by the atmosphere.

More specifically, the pressure control valve 42 has a first
It is provided between the canister 34 and the check valve 40 on the way of the passage 36.

The communication passage 46 is the second passage 38.
Of the pressure chamber 54 of the pressure control valve 42.
Have been contacted.

The pressure control valve 42 includes a diaphragm 56.
Is pressed by the urging force of the spring 58 and the pressure control valve 4
Arrange 2 to close. Then, the urging force of the spring 58 is adjusted so as to perform the opening operation when the tank internal pressure becomes equal to or higher than a preset set value, and the pressure control valve 42 is provided with a check valve function.

When the engine 2 is in operation, the control unit 52 opens the pressure control valve 42 against the biasing force of the spring 58 by applying a negative pressure to the intake pipe by the second solenoid valve 48 as shown in FIG. Control accordingly.

Further, the control unit 52 controls the fuel level gauge when the fuel in the fuel tank 16 becomes a predetermined amount or more by refueling, that is, in a so-called full state in which the internal capacity of the fuel tank 16 is sufficiently filled. The second solenoid valve 48 is operated by the detection signal from the pressure control valve 4
It is controlled so that the atmosphere is made to act on 2.

Further, the control unit 52 includes a fuel injection valve 1
8, fuel pump 30, first solenoid valve 44
, Second solenoid valve 48, fuel level gauge 5
0, an intake air temperature sensor 60 provided in the air cleaner 4, and an exhaust sensor 62 provided in the exhaust passage 14 for detecting the oxygen concentration are connected to each other.

Reference numeral 64 is a fuel hose through which the fuel passes when the fuel is supplied to the fuel tank 16, and 66 is a breather hose of the fuel tank 16.

Next, the operation will be described.

When the engine 2 is stopped and the fuel tank 1
When the amount of fuel in 6 is not full, the fuel level gauge 50 does not turn on as shown in FIG. 3 and acts on the pressure chamber 54 of the pressure control valve 42 via the second solenoid valve 48. Negative pressure is not generated,
The fuel tank 16 and the canister 34 are shut off from each other.

When the tank internal pressure exceeds a preset value when the engine 2 is stopped, the pressure control valve 42 is opened against the biasing force of the spring 58, and the pressure control valve 42 is opened. Check valve function reduces the tank internal pressure below the set value.

During operation of the engine 2 during idling, the negative pressure of the intake pipe acts on the pressure chamber 54 of the pressure control valve 42 via the second solenoid valve 48, as shown in FIG. The pressure control valve 42 is opened against the urging force of the fuel tank 16 to establish communication between the fuel tank 16 and the canister 34.

Further, when the engine 2 is in operation and refueling, the intake pipe negative pressure acts on the pressure chamber 54 of the pressure control valve 42 via the second solenoid valve 48. When the so-called full state in which the internal capacity of the fuel tank 16 is sufficiently filled, a detection signal from the fuel level gauge 50 is input to the control unit 52, as shown in FIG. The second solenoid valve 4 according to the control signal from
8 is operated to open to the atmosphere, the atmosphere is made to act on the pressure chamber 54 of the pressure control valve 42, and the space between the fuel tank 16 and the canister 34 is shut off.

At this time, when the second solenoid valve 48 is returned to connect the pressure chamber 54 of the pressure control valve 42 to the intake passage 10 side, a decrease in the fuel amount is detected by the fuel level gauge 50 and detected. The signal is input to the control unit 52, and the control signal is output from the control unit 52 to the second solenoid valve 48.

With this, the fuel tank 16 and the canister 34 can be shut off when the engine 2 is stopped, and when the tank internal pressure becomes equal to or higher than a preset value when the engine 2 is stopped. , Spring 5
It is possible to open the pressure control valve 42 against the urging force of No. 8 and the check valve function of the pressure control valve 42 can reduce the tank internal pressure to less than the set value, and refuel at a refueling place such as a gas station. Fuel tank 1
Even if the cap portion 16A of 6 is opened, there is no fear that the tank internal pressure will be released to the atmosphere, and the evaporated fuel (HC) in the fuel tank 16 will not be released to the atmosphere, and the cause of air pollution can be eliminated. , Practically advantageous.

Further, since the fuel tank 16 and the canister 34 can be in communication with each other when the engine 2 is operating, the tank internal pressure can be made substantially equal to the atmospheric pressure. Therefore, even if the engine is stopped and fueling is performed after moving the vehicle to a fueling location such as a gas station, there is no fear that the tank internal pressure will be released to the atmosphere.

Further, when the engine 2 is in operation and refueling, first the pressure control valve 42 is opened and the fuel tank 16 is opened.
When the so-called full state in which the internal capacity of the fuel cell is sufficiently filled, the second solenoid valve 48 should be opened to the atmosphere by the control signal from the control unit 52 that inputs the detection signal from the fuel level gauge 50. By being able to operate, the atmosphere acts on the pressure chamber 54 of the pressure control valve 42 when the tank is full, and the gap between the fuel tank 16 and the canister 34 is shut off to prevent overfilling during refueling. be able to.

FIGS. 5 to 8 show a second embodiment of the present invention, and the portions having the same functions as those of the first embodiment described above will be designated by the same reference numerals.

The feature of this second embodiment is that the fuel tank 1 is replaced with the fuel level gauge of the first embodiment.
6 is that a pressure sensor 70 for detecting the tank internal pressure is provided.

That is, the intake passage 1 of the engine 2
0, for example, the surge tank 8 downstream of the throttle valve 6
A passage 32 that connects the fuel tank 16 to the fuel tank 16 is provided, and a canister 34 that adsorbs and holds the evaporated fuel is provided in the passage 32.

The passage 32 is formed by a first passage 36 that connects the fuel tank 16 and the canister 34, and a second passage 38 that connects the canister 34 and the intake passage 10.

Further, a check valve 40 is provided in the middle of the first passage 36, and the pressure inside the fuel tank 16 and the pressure inside the canister 22 are set to predetermined pressures by the check valve 40. (H
The amount of C) is suppressed.

Further, the fuel tank 16 of the first passage 36
The pressure sensor 70 is connected between the check valve 40 and the check valve 40 via a pressure passage 72.

A pressure control valve 42 is provided in the middle of the first passage 36, and a first solenoid valve 4 is provided in the middle of the second passage 38.
4 is provided, and a communication passage 46 that connects the intake passage 10 and the pressure control valve 42 is provided.
A second solenoid valve 48 is provided on the way.

When the engine 2 is in operation, the second solenoid valve 48 exerts a negative pressure on the intake pipe to control the pressure control valve 42 to open and to control the fuel tank 1
A control unit 52 is provided which controls the second solenoid valve 48 to operate the pressure control valve 42 to act on the atmosphere by the detection signal from the pressure sensor 70 when the tank internal pressure in 6 exceeds a predetermined value. .

The control unit 52 includes a fuel injection valve 18 and
Fuel pump 30, first solenoid valve 44, second
A solenoid valve 48, an intake air temperature sensor 60 arranged in the air cleaner 4, an exhaust gas sensor 62 arranged in the exhaust passage 14 for detecting oxygen concentration, and a pressure sensor 70 are connected to each other.

Thus, as shown in FIG. 7, the fuel tank 16 and the canister 34 can be shut off when the engine 2 is stopped, and the tank internal pressure is set to a preset value when the engine 2 is stopped. In the above case, the pressure control valve 42 can be opened against the urging force of the spring 58, and the check valve function of the pressure control valve 42 can be used to open the tank as in the first embodiment. There is no fear that the internal pressure of the tank will be released to the atmosphere even if the cap portion 16A of the fuel tank 16 is opened when the internal pressure can be reduced to less than the set value and the fuel is refueled at a refueling place such as a gas station. The evaporated fuel (HC) in the fuel tank 16 is not released to the atmosphere and the cause of air pollution can be eliminated, which is practically advantageous.

Further, as shown in FIG. 6, when the engine 2 is in operation, the fuel tank 16 and the canister 34 can be in communication with each other, so that the tank internal pressure can be reduced as in the first embodiment. The pressure may be approximately equal to the atmospheric pressure. Therefore, even if the engine is stopped and fueling is performed after moving the vehicle to a fueling location such as a gas station, there is no fear that the tank internal pressure will be released to the atmosphere.

Further, as shown in FIG. 8, when the engine 2 is in operation and fuel is being supplied, the pressure control valve 42 is first opened so that the fuel tank 16 is fully filled with the so-called full tank state. The second solenoid valve is controlled by the control signal from the control unit 52 which inputs the detection signal from the pressure sensor 70 when the tank internal pressure sharply increases due to the increase in the fuel supply amount and the tank internal pressure exceeds a predetermined value. By allowing 48 to be opened to the atmosphere, the atmosphere acts on the pressure chamber 54 of the pressure control valve 42 when the tank internal pressure exceeds a predetermined value, and the fuel tank 16 and the canister 34 are shut off from each other. Therefore, it is possible to prevent overfilling during refueling.

The present invention is not limited to the first and second embodiments described above, and various application modifications are possible.

For example, in the first and second embodiments of the present invention, the fuel level gauge and the pressure sensor are used to detect the full state of the fuel tank, but the full state of the fuel tank can be detected. It is sufficient to use a sensor for detecting the fuel weight or other sensors.

[0055]

As described in detail above, according to the present invention, a passage is formed by the first passage connecting the fuel tank of the engine and the canister, and the second passage connecting the canister and the intake passage. A pressure control valve is provided in the middle of one passage, a first solenoid valve is provided in the middle of the second passage, a communication passage that connects the intake passage and the pressure control valve is provided, and a second solenoid valve is provided in the middle of the communication passage. A fuel level gauge is installed in the tank to detect the amount of fuel,
During operation of the engine, the second solenoid valve exerts a negative pressure on the intake pipe to control the pressure control valve to open, and when the amount of fuel in the fuel tank exceeds a predetermined amount, a detection signal from the fuel level gauge is used. Since the control unit for controlling the second solenoid valve to operate the pressure control valve to act on the atmosphere is provided, it is possible to establish communication between the fuel tank and the canister when the engine is operating, and the tank internal pressure is substantially equal to the atmospheric pressure. Even if the pressures are the same, there is no fear that the tank internal pressure will be released to the atmosphere during refueling.
Further, when the engine is operating and refueling, first the pressure control valve is opened, and when the internal capacity of the fuel tank is sufficiently filled and exceeds a predetermined amount, a control unit for inputting a detection signal from the fuel level gauge. Since the second solenoid valve can be operated to open to the atmosphere by the control signal from, the atmosphere acts on the pressure control valve, the fuel tank and the canister are shut off, and overfilling at the time of refueling can be prevented. Further, if a check valve function is added to the pressure control valve, the fuel tank and the canister can be shut off when the engine is stopped, and the tank internal pressure becomes equal to or higher than a preset value when the engine is stopped. In this case, the check valve function can be used to open the pressure control valve.This check valve function can lower the tank internal pressure to below the set value and open the fuel tank cap when refueling. However, there is no fear that the tank internal pressure is released to the atmosphere, the evaporated fuel (HC) in the fuel tank is not released to the atmosphere, and the cause of air pollution can be eliminated, which is practically advantageous.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an evaporated fuel control device for an engine showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram of an evaporated fuel control device during engine operation.

FIG. 3 is a schematic diagram of an evaporated fuel control device when the engine is stopped.

FIG. 4 is a schematic diagram of an evaporated fuel control device during engine operation and during refueling.

FIG. 5 is a configuration diagram of an evaporated fuel control device for an engine showing a second embodiment of the present invention.

FIG. 6 is a schematic diagram of an evaporated fuel control device during engine operation.

FIG. 7 is a schematic diagram of an evaporated fuel control device when the engine is stopped.

FIG. 8 is a schematic diagram of an evaporated fuel control device during engine operation and during refueling.

FIG. 9 is a schematic configuration diagram of an evaporated fuel control device for an engine showing a conventional technique of the present invention.

[Explanation of symbols]

 2 engine 4 air cleaner 6 throttle valve 8 surge tank 10 intake passage 14 exhaust passage 16 fuel tank 18 fuel injection valve 20 fuel passage 22 fuel supply passage 24 fuel return passage 30 fuel pump 32 passage 34 canister 36 first passage 38 second passage 42 Pressure control valve 44 First solenoid valve 46 Communication passage 48 Second solenoid valve 50 Fuel level gauge 52 Control section 54 Pressure chamber 56 Diaphragm 58 Spring 60 Intake temperature sensor 62 Exhaust sensor

Claims (1)

[Claims] 1. An evaporative fuel control apparatus for an engine, comprising: a canister for adsorbing and holding evaporated fuel in a passage connecting an intake passage of an engine and a fuel tank; and a first passage and a canister for connecting the fuel tank and the canister. And a second passage that connects the intake passage to the intake passage, the passage is formed, and a pressure control valve is provided in the middle of the first passage.
A fuel level for detecting the amount of fuel in the fuel tank is provided by providing a first solenoid valve in the middle of the passage, a communication passage connecting the intake passage and the pressure control valve, and a second solenoid valve in the middle of the communication passage. A gauge is provided to control the intake pipe negative pressure by the second solenoid valve to open the pressure control valve during operation of the engine, and a fuel level gauge when the fuel in the fuel tank exceeds a predetermined amount. An evaporative fuel control device for an engine, comprising: a control unit that operates a second solenoid valve in response to a detection signal from the control unit to control the pressure control valve to act on the atmosphere.