JPH11247721A - Discharge of evaporated fuel preventing device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the liberating of the evaporated fuel into the atmospheric air by keeping the negative pressure inside of a canister by a depressurizing means, so that the increase of the internal pressure of the canister when the quantity of the evaporated fuel is increased by the rise of the outside air temperature, can be absorbed by the negative pressure state during the stop of a vehicle. SOLUTION: When the purge is not executed to an intake pipe 12, a drain passage 44b communicated with the atmospheric air is closed, so that the internal pressure of a canister 44 is risen by the increase of the evaporation quantity of the fuel in accompany with the rise of the outside air temperature, and the evaporated fuel is finally flowed out to the atmospheric air through a relief valve 54 or the like during the stop of a vehicle. When an internal combustion engine 10 is stopped not during the oil feeding, a solenoid valve 48 is opened, and the solenoid valves 52, 50 are closed. Whereby the fuel tank 26 and the canister 44 are communicated, the negative pressure (intake negative pressure) in the fuel tank 26 before the stop of the engine is introduced into the canister 44, the increase of quantity of the evaporated fuel in a accompany with the rise of the outside air temperature is adsorbed by the negative pressure, and the liberating of the evaporated fuel to the atmospheric air can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing evaporative fuel emission from an internal combustion engine, and more particularly to a device for preventing evaporative fuel from being emitted when a vehicle stops.

[0002]

2. Description of the Related Art In a fuel tank mounted on a vehicle and connected to an internal combustion engine, when the vehicle is stopped after the engine temperature rises due to high load operation, or when the vehicle is exposed to a high external temperature while the vehicle is stopped, or for a long time, When the vehicle stops for a long time, fuel (gasoline) evaporates and is stored in the space above the liquid level. As a result, the internal pressure of the fuel tank increases, and when the filler cap of the fuel tank is opened at the time of refueling or the like, the evaporated fuel is released to the atmosphere.

In order to solve this problem, a canister is generally provided, and a fuel tank and an intake pipe are connected via a canister so that evaporated fuel generated during refueling or the like is adsorbed. Purging the intake pipe prevents the fuel vapor from being released to the atmosphere.

[0004]

However, when the purge to the intake pipe is not executed, the canister is closed because the drain passage communicating with the atmosphere is closed, and the canister is stopped. When the ambient temperature rises, the amount of fuel vapor increases, and when the internal pressure of the canister rises above atmospheric pressure, fuel permeation and leakage from the valve occur, and the fuel vapor diffuses to the atmosphere. There was a problem.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned inconvenience and to prevent evaporative fuel from escaping to the atmosphere even when the outside temperature rises while the vehicle is stopped. It is to provide an emission prevention device.

[0006]

According to one aspect of the present invention, a fuel tank connected to an internal combustion engine is directly connected to an intake pipe of the internal combustion engine.
And a second passage connecting the fuel tank and the intake pipe via a canister, a first valve for opening and closing the first passage, and the fuel passage in the second passage. A second valve provided between the tank and the canister to open and close a passage portion therebetween, and a third valve provided between the canister and the intake pipe in the second passage to open and close a passage portion therebetween. And a fourth valve for opening and closing the communication between the canister and the atmosphere, the engine operation detection detecting whether the internal combustion engine is operating or not. Means, when it is detected that the internal combustion engine is operating, open the first valve and close the second valve, and apply a negative pressure generated in the intake pipe to the fuel tank. To reduce the internal pressure of the fuel tank When it is detected that the fuel tank pressure reducing means and the internal combustion engine are not operating, the second valve is opened and the first, third, and fourth valves are closed. The valve is configured to include a canister pressure reducing means for introducing the reduced internal pressure of the fuel tank to the canister.

As a result, when the canister is stopped, the interior of the canister is maintained at a negative pressure, and even if the outside temperature rises and the amount of fuel vapor increases, the internal pressure of the canister increases, the increase is absorbed by the negative pressure. Therefore, the fuel vapor does not diffuse into the atmosphere.

[0008]

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

FIG. 1 is an overall view schematically showing a fuel vapor emission preventing device for an internal combustion engine according to the present application.

In the drawing, reference numeral 10 denotes an OHC in-line four-cylinder internal combustion engine, and the flow rate of intake air introduced from an air cleaner (not shown) disposed at the end of an intake pipe 12 is adjusted by a throttle valve 14. While being sent to the first to fourth cylinders (shown as "engine body 16" in the figure) via an intake manifold and an intake valve (both not shown).

An injector (fuel injection valve) 18 is provided near the upstream side of the intake valve of each cylinder to inject fuel. The air-fuel mixture injected and integrated with the intake air is ignited by a spark plug (not shown) and burns, and drives a piston (not shown).

The exhaust gas after combustion is sent to an exhaust pipe 22 via an exhaust valve and an exhaust manifold (both not shown), purified by a catalyst device (three-way catalyst) 24 and discharged outside the engine.

A fuel tank 26 is provided at an appropriate position of a vehicle (not shown) on which the internal combustion engine 10 is mounted, and is connected to the internal combustion engine 10. That is, the injector 18 is connected to the fuel tank 26 via the fuel supply pipe 28, and is supplied with the fuel (gasoline) stored in the fuel tank 26.
A fuel pump 30 is provided in the fuel supply pipe 28 to pump fuel.

The fuel tank 26 has an air-tight and liquid-tight structure, and the opening at the tip of the filler neck 26a is closed by a filler cap 26b. Space 2 above liquid level of fuel tank 26
6c is connected to the intake pipe 12 via a first passage 34 at a position downstream of the throttle valve 14. At an appropriate position in the first passage 34, an electromagnetic solenoid valve (first valve, hereinafter referred to as "NP
CS valve 36) is provided.

In the first passage 34, as described later, N
PCS valve 36 is opened and intake negative pressure is reduced to fuel tank 2
6 and is introduced into the space 26c above the liquid surface to be reduced in pressure. Therefore, when the filler cap 26a is opened at the time of refueling after stopping, the fuel vapor is prevented from being released to the atmosphere.

A cut-off valve 42 is provided near the connection between the fuel tank 26 and the first passage 34, and the first passage 34 is opened when the fuel tank 26 is inclined at a predetermined angle or more with respect to the vertical axis. To close.

Further, the internal combustion engine 10 has a canister 44 at an appropriate position, and the fuel tank 26 is connected to the intake pipe 12 and the downstream of the throttle valve 14 via the canister 44 by a second passage 46. That is, the space 26c above the liquid surface of the fuel tank 26 is connected to the canister 44 by the passage portion 46a, and the canister 44 is connected to the intake pipe 12 and downstream of the throttle valve 14 by the passage portion 46b.

A passage portion 46a connecting the fuel tank 26 and the canister 44 is provided with a second electromagnetic solenoid valve (a second valve, hereinafter referred to as a "VSV valve") 48 for opening and closing the passage portion 46a and for opening and closing the canister. A third electromagnetic solenoid valve (third valve; hereinafter, referred to as a "PCS valve") 50 is provided in a passage portion 46b connecting the intake pipe 12 to the passage portion 46b, and opens and closes the passage portion 46b.

The canister 44 contains therein an adsorbent 44a made of an activated carbon layer, and adsorbs fuel vapor,
Store. The canister 44 has a drain passage 44b communicating with the atmosphere, and a fourth electromagnetic solenoid valve (fourth valve; hereinafter, referred to as a “VSSV valve”) 52 provided therein.

The drain passage 44b has a bypass which bypasses the VSSV valve 52, and a pressure relief valve 54 is provided therein. The internal pressure of the canister 44,
When the pressure of the adsorbed fuel vapor rises and exceeds a predetermined pressure, the pressure relief valve 54 opens, and the fuel vapor diverges to the atmosphere.

Similarly, the passage portion 46a is also connected to the VSV valve 4
8 is provided, and a second pressure relief valve 56 is provided therein. When the pressure in the passage portion 46a, that is, the pressure of the evaporated fuel flowing therethrough rises and exceeds a predetermined pressure, the second pressure relief valve 56 opens and the evaporated fuel flows bypassing the VSV valve 48. A similar cut valve 58 is provided near the connection between the fuel tank 26 and the second passage 46.

Returning to the description of FIG. 1, as shown, a camshaft (not shown) of the internal combustion engine 10 is provided with a crank angle sensor 60, and outputs a CYL signal for cylinder identification at a predetermined crank angle of a specific cylinder. Output and the TDC of each cylinder
A signal and a CRK signal for every 15 degrees of crank angle are output.

A throttle opening sensor 62 is connected to the throttle valve 14 to output a signal corresponding to the throttle opening θTH, and an absolute pressure sensor 64 is provided in the intake pipe 12 downstream of the throttle valve 14. A signal corresponding to the absolute pressure PBA in the pipe is output.

An intake air temperature sensor 66 is provided downstream of the throttle valve 14 to output a signal corresponding to the intake air temperature TA, and a water temperature sensor 68 is provided near the cylinder block of the engine body 16. And outputs a signal corresponding to the engine cooling water temperature TW.

Further, in the exhaust system, an air-fuel ratio sensor (O ₂ sensor) 70 is provided in the exhaust pipe 22 at a position downstream of the exhaust system collecting portion and upstream of the catalyst device 24, and the detection is performed in proportion to the oxygen concentration in the exhaust gas. Output a signal.

Further, the fuel tank 26 is provided with a fuel temperature sensor 72 for outputting a signal corresponding to the fuel (gasoline) temperature TGAS, and a pressure sensor 74 for providing a signal corresponding to the tank internal pressure PTANK (absolute pressure). At).

Further, as shown in FIG.
A switch 76 is provided near the filler cap 26b. The switch 76 is used for filling filler cap 2 when refueling.
When 6b is opened, an ON signal is output.

The outputs of the above-mentioned sensors are sent to an ECU (Electronic Control Unit) 80.

The ECU 80 includes a microcomputer, and includes a CPU, a ROM, a RAM, and the like.
NPCS as described below according to the instruction stored in M.
Duty control (duty ratio control in PWM; duty ratio 0 to 100%) of the valve 36 and the like is performed to adjust the opening degree and perform evaporative fuel emission prevention control.

The ECU 80 counts the CRK signal output from the crank angle sensor 60 to calculate the engine speed NE.

FIG. 3 is a flow chart for explaining the operation of the apparatus for preventing evaporative fuel emission of an internal combustion engine according to the present invention. Before describing the figure, the object of the present invention will be re-explained.

When the purging of the intake pipe 12 is not executed, the canister 44 is closed because the drain passage 44b communicating with the atmosphere is closed.
When the vehicle is stopped, the evaporation amount of the fuel vapor increases with an increase in the outside air temperature, and when the internal pressure of the canister 44 rises and exceeds the atmospheric pressure, the fuel vapor flows into the pressure relief valve 54 of the drain passage 44b or the VSSV valve. There is a problem that the gas leaks out of the air passage 48 or permeates through the second passage 46 and is emitted to the atmosphere.

To solve this problem, the relief pressure of the pressure relief valve 54 may be increased. However, since the pressure relief valve 54 also functions to prevent the fuel tank 26 from being damaged by an increase in the internal pressure, the pressure relief valve 54 functions as follows. If the relief pressure of the pressure relief valve 54 is increased, the fuel tank 2
6, it is necessary to increase the strength, so that the tank structure becomes complicated, the weight increases, and the cost increases.

Therefore, in order to solve the above-mentioned problem, the present invention opens the VSV valve 48 while the vehicle is stopped, connects the canister 44 to the fuel tank 26, and introduces the negative pressure in the fuel tank 26 to the canister 44. To prevent the release of fuel vapor.

Hereinafter, this will be described with reference to the flowchart of FIG.

The program shown in the figure is executed for 80 ms after the ignition switch is turned on in the ECU 80.
ec, and the processing is continued at the same time via the backup power supply for a predetermined time after the ignition switch is turned off and the vehicle is stopped.

First, in S10, it is determined whether or not the internal combustion engine 10 is operating, more specifically, whether or not the engine speed NE is equal to or higher than the cranking speed to generate an intake negative pressure. When it is determined that the fuel is being supplied, the process proceeds to S12 to determine whether or not the fuel is being supplied.

This determination is made by looking at the output of the switch 76. However, since the engine is operating, the result is normally denied, and the routine proceeds to S14, where it is determined whether or not the canister purge condition is satisfied. The canister purge condition is satisfied in a predetermined operation state.

When the result in S14 is affirmative, the program proceeds to S16, in which the VSV valve 48 is closed, and the VSSV valve 52 and the PCS valve 50 are opened.

The opening control of the PCS valve 50 is performed in accordance with predetermined canister purge control characteristics. Also,
Since the vaporized fuel to be purged is a disturbance to the air-fuel ratio control, the amount of vaporized fuel to be purged is estimated in a fuel injection amount calculation routine (not shown), and the fuel injection amount is calculated so as to subtract the amount. Since the canister purge control itself has no direct relation to the gist of the present invention,
Description is omitted.

On the other hand, if the result in S14 is NO, S
Proceeding to 18, the VSV valve 48, the VSSV valve 52,
And all the PCS valves 50 are closed.

Subsequently, the program proceeds to S20, in which it is determined whether or not the fuel tank negative pressure condition is satisfied. The fuel tank negative pressure condition is also satisfied in the predetermined operating state, and when the result in S20 is affirmative, the routine proceeds to S22, where the fuel tank negative pressure control is executed,
The NPCS valve 36 is opened and the VSV valve 48 is opened.
Is closed. When the result in S20 is NO, the program proceeds to S24, in which the NPCS valve 36 and the VSV valve 48 are closed.

The NPCS valve opening control is also performed according to predetermined characteristics so that the fuel tank negative pressure becomes a target value.
The details do not directly relate to the gist of the present invention, so that the description will be omitted.

If the answer in S12 is affirmative in a special situation, such as when the driver himself refuels, the process proceeds to S26.
The VSV valve 48 and the VSSV valve 52 are opened, and the PCS valve 50 is closed. This is because the evaporated fuel generated during the refueling operation is sent to the canister 44 to be adsorbed.

On the other hand, if the result in S10 is negative, the program proceeds to S28, in which it is determined whether or not refueling is in progress. If the result is affirmative, the program proceeds to S30, and the VSV valve 48 and V
The SSV valve 52 is opened and the PCS valve 50 is opened.
Is closed.

On the other hand, when the result in S28 is NO, the program proceeds to S32, where the VSV valve 48 is opened, and the VSSV valve 52 and the PCS valve 50 are closed. That is, when the vehicle is stopped but not refueling, the VSV valve 48 is opened, and the VSSV valve 52 and the PCS valve 50 are closed.

Thus, the fuel tank 26 and the canister 44 are connected via the passage portion 46a, and the negative pressure in the fuel tank 26 is introduced into the canister 44. As a result, the interior of the canister 44 is in a negative pressure state, and when the vehicle is stopped, the outside air temperature increases and the amount of fuel vapor increases, so that even if the internal pressure of the canister increases, the increase is negative pressure. Absorbed. Therefore, the fuel vapor does not escape to the atmosphere.

As described above, this embodiment employs the internal combustion engine 1
And a second passage connecting the fuel tank 26 and the intake pipe 12 via a canister 44 directly connecting the fuel tank 26 and the intake pipe 12 of the internal combustion engine. 46, a first valve (NPCS valve 36) for opening and closing the first passage 34,
A passage portion 46 provided between the fuel tank 26 and the canister 44 in the second passage 46
and a third valve (PCS) provided between the canister 44 and the intake pipe 12 in the second passage 46 to open and close a passage portion 46b therebetween. Valve 50) and the canister 4
4th opening and closing the communication (drain passage 44b) between the fourth and the atmosphere
And an engine operation detecting means (ECU 80, ECU 80) for detecting whether or not the internal combustion engine is operating.
When the crank angle sensor 60, S10) detects that the internal combustion engine is operating, it opens the first valve (NPCS valve 36) and closes the second valve (VSV valve 48). A fuel tank pressure reducing means (ECU 80, S20, S2) for reducing the internal pressure of the fuel tank by introducing a negative pressure generated in the intake pipe into the fuel tank;
2) and when it is detected that the internal combustion engine is not operating, the second valve is opened, and the first, third, and fourth valves are closed, Therefore, the canister is provided with a canister pressure reducing means (ECU80, S32) for introducing the reduced internal pressure of the fuel tank to the canister.

In the above-described embodiment, the ECU 80 is operated even after the vehicle is stopped. However, an electric circuit is provided, and the output of the switch 76 is input. May be opened. Since the VSV valve 48 is always opened even when the vehicle is stopped, the fuel vapor generated during refueling work can be sent to the canister 44 without operating the ECU 80 even after the vehicle is stopped.

In the above-described embodiment, an electromagnetic solenoid valve that can be duty-driven is used for the above-mentioned sui NPCS valve 36 and the like, but an electromagnetic solenoid valve having a linear opening characteristic may be used.

[0051]

According to the first aspect of the present invention, when the canister is stopped, the interior of the canister is maintained at a negative pressure, and the internal pressure of the canister increases even if the outside air temperature rises and the amount of evaporated fuel increases. Since the increased amount is absorbed by the negative pressure, the evaporated fuel does not diffuse into the atmosphere.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the overall configuration of an apparatus for preventing fuel vapor emission from an internal combustion engine according to the present invention.

FIG. 2 is an explanatory diagram showing a switch for judging refueling provided in a fuel tank in the apparatus of FIG. 1;

FIG. 3 is a flowchart showing the operation of the apparatus in FIG. 1;

[Explanation of symbols]

Reference Signs List 10 internal combustion engine 12 intake pipe 26 fuel tank 34 first passage 36 electromagnetic solenoid valve (first valve; NPCS valve) 44 canister 46 second passage 48 second electromagnetic solenoid valve (second valve VS
V valve) 50 Third electromagnetic solenoid valve (third valve, PC
S valve 52 52 fourth electromagnetic solenoid valve (fourth valve; VS
SV valve) 60 Crank angle sensor (engine operating state detecting means) 76 Switch 80 ECU (Electronic control unit)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02M 37/00 301 B60K 15/02 L

Claims (1)

[Claims] 1. A first passage that directly connects a fuel tank connected to an internal combustion engine and an intake pipe of the internal combustion engine, and a second passage that connects the fuel tank and the intake pipe via a canister. A first valve that opens and closes the first passage, and a second valve that is provided between the fuel tank and the canister in the second passage and opens and closes a passage portion therebetween. A third valve provided between the canister and the intake pipe in the second passage to open and close a passage portion therebetween, and a fourth valve to open and close communication between the canister and the atmosphere. An apparatus for preventing evaporative fuel release in an internal combustion engine, comprising: a. Engine operation detecting means for detecting whether the internal combustion engine is operating, b. When it is detected that the internal combustion engine is operating, while opening the first valve, closing the second valve,
Fuel tank pressure reducing means for introducing a negative pressure generated in the intake pipe into the fuel tank to reduce the internal pressure of the fuel tank; and c. When it is detected that the internal combustion engine is not operating,
Canister pressure reducing means for opening the second valve, closing the first valve, the third valve, and the fourth valve, thereby introducing the reduced internal pressure of the fuel tank to the canister. A fuel vapor emission preventing device for an internal combustion engine, comprising: