Fuel supply apparatus and control method for internal combustion engine

A canister, a cut valve which closes a fresh air intake of the canister, and a pressure sensor which detects a pressure in a fuel vapor path shut off by closing a purge control valve and the cut valve are disposed at the inside of a fuel tank, and a fuel supply control unit which controls the cut valve and the purge control valve, and which carries out a leak diagnosis on the basis of a detected result of the pressure sensor is disposed at the inside of the fuel tank.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fuel supply apparatus supplying fuel to an internal combustion engine and a method for controlling the fuel supply apparatus.

2. Description of the Related Art

Japanese Unexamined Patent Publication No.07-091330 discloses a fuel vapor purge system which traps fuel vapor generated inside a fuel tank in a canister, and which purges the fuel vapor trapped in the canister, into an intake passage via a purge passage at which a purge control valve is provided.

Further, the above Publication discloses a method for diagnosing whether there is any leak at the above-described fuel vapor purge system.

In the leak diagnosis, a drain cut valve is provided at a fresh air intake of the canister, and a discharge opening of an air pump is connected along the purge passage at the downstream of the purge control valve.

Here, due to air being supplied to the purge passage by the air pump in a state in which the drain cut valve and the purge control valve are closed, a diagnostic zone including the purge passage, the canister, and the fuel tank is pressurized.

Then, it is diagnosed whether there is any leak on the basis of a change of pressure in the diagnostic zone accompanying the pressurization.

By the way, in addition to providing the fuel vapor purge system, when a drain cut valve, an air pump, a pressure sensor, or the like which are for a leak diagnosis are provided thereat, there has been the problem that a large number of controlled system parts and sensors in the fuel supply apparatus are used, and the wirings with a control unit are made longer and complicated.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to configure wirings between a control unit and controlled system parts/sensors so as to be short and simple in a fuel supply apparatus.

In order to achieve the above described object, in the present invention, devices and a control unit are disposed in a fuel tank, and the devices in the fuel tank are controlled by the control unit disposed in the fuel tank.

PREFERRED EMBODIMENT

FIG. 1shows a fuel supply apparatus having a fuel vapor purge system for an internal combustion engine on a vehicle.

A fuel pump31is installed in a fuel tank1.

Fuel discharged from the fuel pump31is supplied to a fuel injection valve3via a fuel piping32.

A fuel pressure sensor33detecting a fuel pressure in the fuel piping32is provided at a portion, which is positioned in the fuel tank1, of the fuel piping32.

A fuel supply control unit21installed inside the fuel tank1controls to drive the fuel pump31in accordance with a fuel pressure detected at the fuel pressure sensor33.

Further, detection signals of a fuel level sensor34and a fuel temperature sensor35are inputted to the fuel supply control unit21.

The fuel injection valve3is provided at an intake port4of each cylinder of an internal combustion engine2, and is driven to open by an injection pulse signal outputted from an engine control unit22.

Note that the fuel supply control unit21and the engine control unit22are configured so as to be capable of intercommunication via a communication line.

Purge air including fuel vapor which has been purged from a canister6is supplied to an intake air collector5at the upstream side of the fuel injection valve3via a purge passage7.

A throttle valve8is installed at the upstream side of the intake air collector5.

An intake air flow of the internal combustion engine2is adjusted in accordance with an opening of the throttle valve8.

A purge control valve9is installed along the way of the purge passage7.

A purge air amount supplied to the internal combustion engine2via the purge passage7is controlled in accordance with an opening of the purge control valve9.

The canister6is one in which adsorbent such as activated charcoal or the like is filled in a container, and is installed at the upper portion in the fuel tank1.

A fresh air intake pipe11is connected to a fresh air intake6aprovided at the canister6.

The fresh air intake pipe11is installed so as to pass through the wall of the fuel tank1and to be extended up to the exterior of the fuel tank1, and is released in the atmosphere outside of the fuel tank1.

Further, a fuel vapor inlet6breleased in the fuel tank1via a cut valve12is provided at the canister6.

The cut valve12is a mechanical valve which usually opens and closes at the time of being sunk in liquid.

Fuel vapor generated inside the fuel tank1is absorbed into the adsorbent in the canister6via the fuel vapor inlet6bwhen the cut valve12is opened.

On the other hand, the purge passage7is connected to a fuel vapor outlet6cof the canister6.

Here, the purge control valve9is controlled by the fuel supply control unit21.

The fuel supply control unit21controls to open the purge control valve9when a purge permission condition is established during an operation of the internal combustion engine2.

When the purge control valve9opens, an intake negative pressure of the internal combustion engine2acts on the canister6, and as a result, the fuel vapor which has been absorbed in the canister6is detached by the fresh air, which is introduced through the fresh air intake6a.

Then, the purge gas including the detached fuel vapor is sucked in the intake air collector5through the purge passage7.

Further, in the present embodiment, a function of diagnosing whether there is any leak in the fuel vapor path from the fuel tank1up to the purge control valve9is provided.

For the leak diagnosis, a drain cut valve13is provided at a portion, which is positioned in the fuel tank1, of the fresh air intake pipe11, and an air pump14supplying air into the purge passage7is installed in the fuel tank1.

The air pump14is disposed in the vicinity of the canister6in the fuel tank1,.

A discharge opening14aof the air pump14and the purge passage7in the fuel tank1are connected through an air supply pipe15.

Note that it can be configured such that air is supplied into the fuel tank1by the air pump14due to the discharge opening14a of the air pump14being released inside the fuel tank1.

Further, one end of a suction pipe17which is installed so as to pass through the wall of the fuel tank1and to be extended up to the exterior is connected to the suction port of the air pump14, and the other end of the suction pipe17is released into the atmosphere via an air cleaner18.

Moreover, a pressure sensor16detecting an internal pressure of the purge passage7is provided in the fuel tank1.

The drain cut valve13and the air pump14are controlled by the fuel supply control unit21, and a detection signal of the pressure sensor16is inputted to the fuel supply control unit21.

The fuel supply control unit21shuts the purge control valve9and the drain cut valve13after stopping the internal combustion engine2, and closes the fuel vapor path from the fuel tank1up to the purge control valve9, and next, supplies air to the closed fuel vapor path due to the air pump14being started.

Here, in a case in which there is no leak in the closed fuel vapor path, a pressure detected at the pressure sensor16rises up to a predetermined pressure.

Accordingly, in a case in which a pressure detected at the pressure sensor16does not reach the predetermined pressure, generation of leak is estimated.

After the closed fuel vapor path is pressurized up to the predetermined pressure, the air pump14is stopped, and leak can be diagnosed on the basis of a pressure drop level and a pressure drop rate thereafter. Further, decompression is carried out due to air in the closed fuel vapor path being sucked by the air pump14, and the pressure is reduced, and leak can be diagnosed on the basis of a change of pressure at the time of the decompression, or a pressure rise level and a pressure rise rate after stopping the decompression.

Here, the control function of the fuel supply control unit21will be described in accordance with the functional block diagram inFIG. 2.

The fuel supply control unit21and the engine control unit22are configured so as to be capable of intercommunication via a network101.

The engine control unit22transmits information on an engine rotational speed Ne, an atmospheric pressure, a basic fuel injection quantity Tp, a fuel injection quantity Ti by a fuel injection valve, a number of injection cylinders, or the like with respect to the fuel supply control unit21.

On the other hand, the fuel supply control unit21transmits information on a pressure in the fuel tank, a result of malfunction detection for a pump current, a fuel level, or the like with respect to the engine control unit22.

At a fuel pressure control indicated value operation part102of the fuel supply control unit21, a target fuel pressure and a fuel consumption are calculated on the basis of the information on an engine rotational speed Ne, an atmospheric pressure, a basic fuel injection quantity Tp, a fuel injection quantity Ti, a number of injection cylinders, or the like.

At a fuel pump control unit (FPCM)103, a feedback duty is calculated on the basis of a deviation between a fuel pressure detected at the fuel pressure sensor33and the target fuel pressure, and a basic duty is calculated on the basis of the fuel consumption.

Then, due to the sum of the feedback duty and the basic duty being outputted to a motor driving circuit104, the fuel pump31is driven.

Further, a function of detecting malfunction in electric current in the fuel pump31is provided at the motor driving circuit104, and when malfunction is detected, a signal denoting that the electric current in the fuel pump31is abnormal is transmitted to the engine control unit22.

Further, when an operating instruction for a leak diagnosis is outputted from the engine control unit22to the fuel supply control unit21, a purge control unit105of the fuel supply control unit21controls the air pump14, the purge control valve9, and the cut valve13, and carries out a leak diagnosis on the basis of detection signals of the pressure sensor16and the fuel temperature sensor35. Then, the result of the leak diagnosis is outputted to the engine control unit22.

Moreover, the fuel supply control unit21calculates a fuel level (residual quantity) on the basis of a detection signal of the fuel level sensor34, and outputs the signal of the fuel level to the engine control unit22.

In accordance with the above-described embodiment, the canister6configuring the fuel vapor purge system, and the drain cut valve13, the air pump14, and the pressure sensor16which are for a leak diagnosis are disposed in the fuel tank1, and the air pump14is disposed in the vicinity of the canister6.

Therefore, the overall length of the piping configuring the fuel vapor purge system can be shortened.

Further, because the coupling portions between the canister6and respective pipings and the coupling portions between the air supply path and the fuel vapor path through the air pump14are disposed in the space in the fuel tank1, even in a case in which a leak is brought about at the coupling portion, fuel vapor leaks in the fuel tank1, and leaking of fuel vapor into the atmosphere can be avoided.

Moreover, because the drain cut valve13, the air pump14and the pressure sensor16, and the fuel supply control unit21are arranged in the vicinity, handling of a harness is simplified.

Further, provided that it is configured such that the both control units21and22have information in common by communication between the fuel supply control unit21and the engine control unit22, the signal lines between the both control units21and22can be simplified.

Moreover, the fuel supply control unit21, the air pump14, and the canister6disposed in the fuel tank1can be integrated, and in accordance therewith, the spatial efficiency can be improved.

The fuel supply control unit21is configured as shown inFIG. 3, which can prevent fuel from permeating the inside of the control unit21.

In the fuel supply control unit21shown inFIG. 3, a circuit substrate21a and a connector21bare connected with a bonding wire21c, and the circuit substrate21a, the bonding wire21c, and the connector21bare sealed in a resin mold21d.

Grooves21ewhich function as stoppers for preventing the connector being slipped off, and which are for preventing fuel from permeating are formed at the basic terminal side of the connector21b.

In the above-described embodiment, it is configured such that a leak diagnosis is carried out on the basis of a detected result at the pressure sensor16. However, the pressure sensor16is omitted, and a leak diagnosis may be carried out on the basis of a load on the air pump14.

The entire contents of Japanese Patent Application NO. 2003-432995, filed Dec. 26, 2003 are incorporated herein by reference.

While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to these skilled in the art from this various change and modification can be made herein without departing from the scope of the invention as defined in the appended claims.

Furthermore, the foregoing description of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.