Patent Publication Number: US-7213584-B2

Title: Fuel supply apparatus and control method for internal combustion engine

Description:
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. 
   The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings. 

   
     BRIEF EXPLANATION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a fuel supply apparatus in an embodiment; 
       FIG. 2  is a functional block diagram of a fuel supply control unit in the embodiment; and 
       FIG. 3  is a sectional view of the fuel supply control unit in the embodiment. 
   

   PREFERRED EMBODIMENT 
     FIG. 1  shows a fuel supply apparatus having a fuel vapor purge system for an internal combustion engine on a vehicle. 
   A fuel pump  31  is installed in a fuel tank  1 . 
   Fuel discharged from the fuel pump  31  is supplied to a fuel injection valve  3  via a fuel piping  32 . 
   A fuel pressure sensor  33  detecting a fuel pressure in the fuel piping  32  is provided at a portion, which is positioned in the fuel tank  1 , of the fuel piping  32 . 
   A fuel supply control unit  21  installed inside the fuel tank  1  controls to drive the fuel pump  31  in accordance with a fuel pressure detected at the fuel pressure sensor  33 . 
   Further, detection signals of a fuel level sensor  34  and a fuel temperature sensor  35  are inputted to the fuel supply control unit  21 . 
   The fuel injection valve  3  is provided at an intake port  4  of each cylinder of an internal combustion engine  2 , and is driven to open by an injection pulse signal outputted from an engine control unit  22 . 
   Note that the fuel supply control unit  21  and the engine control unit  22  are configured so as to be capable of intercommunication via a communication line. 
   Purge air including fuel vapor which has been purged from a canister  6  is supplied to an intake air collector  5  at the upstream side of the fuel injection valve  3  via a purge passage  7 . 
   A throttle valve  8  is installed at the upstream side of the intake air collector  5 . 
   An intake air flow of the internal combustion engine  2  is adjusted in accordance with an opening of the throttle valve  8 . 
   A purge control valve  9  is installed along the way of the purge passage  7 . 
   A purge air amount supplied to the internal combustion engine  2  via the purge passage  7  is controlled in accordance with an opening of the purge control valve  9 . 
   The canister  6  is 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 tank  1 . 
   A fresh air intake pipe  11  is connected to a fresh air intake  6   a  provided at the canister  6 . 
   The fresh air intake pipe  11  is installed so as to pass through the wall of the fuel tank  1  and to be extended up to the exterior of the fuel tank  1 , and is released in the atmosphere outside of the fuel tank  1 . 
   Further, a fuel vapor inlet  6   b  released in the fuel tank  1  via a cut valve  12  is provided at the canister  6 . 
   The cut valve  12  is a mechanical valve which usually opens and closes at the time of being sunk in liquid. 
   Fuel vapor generated inside the fuel tank  1  is absorbed into the adsorbent in the canister  6  via the fuel vapor inlet  6   b  when the cut valve  12  is opened. 
   On the other hand, the purge passage  7  is connected to a fuel vapor outlet  6   c  of the canister  6 . 
   Here, the purge control valve  9  is controlled by the fuel supply control unit  21 . 
   The fuel supply control unit  21  controls to open the purge control valve  9  when a purge permission condition is established during an operation of the internal combustion engine  2 . 
   When the purge control valve  9  opens, an intake negative pressure of the internal combustion engine  2  acts on the canister  6 , and as a result, the fuel vapor which has been absorbed in the canister  6  is detached by the fresh air, which is introduced through the fresh air intake  6   a.    
   Then, the purge gas including the detached fuel vapor is sucked in the intake air collector  5  through the purge passage  7 . 
   Further, in the present embodiment, a function of diagnosing whether there is any leak in the fuel vapor path from the fuel tank  1  up to the purge control valve  9  is provided. 
   For the leak diagnosis, a drain cut valve  13  is provided at a portion, which is positioned in the fuel tank  1 , of the fresh air intake pipe  11 , and an air pump  14  supplying air into the purge passage  7  is installed in the fuel tank  1 . 
   The air pump  14  is disposed in the vicinity of the canister  6  in the fuel tank  1 ,. 
   A discharge opening  14   a  of the air pump  14  and the purge passage  7  in the fuel tank  1  are connected through an air supply pipe  15 . 
   Note that it can be configured such that air is supplied into the fuel tank  1  by the air pump  14  due to the discharge opening  1   4 a of the air pump  14  being released inside the fuel tank  1 . 
   Further, one end of a suction pipe  17  which is installed so as to pass through the wall of the fuel tank  1  and to be extended up to the exterior is connected to the suction port of the air pump  14 , and the other end of the suction pipe  17  is released into the atmosphere via an air cleaner  18 . 
   Moreover, a pressure sensor  16  detecting an internal pressure of the purge passage  7  is provided in the fuel tank  1 . 
   The drain cut valve  13  and the air pump  14  are controlled by the fuel supply control unit  21 , and a detection signal of the pressure sensor  16  is inputted to the fuel supply control unit  21 . 
   The fuel supply control unit  21  shuts the purge control valve  9  and the drain cut valve  13  after stopping the internal combustion engine  2 , and closes the fuel vapor path from the fuel tank  1  up to the purge control valve  9 , and next, supplies air to the closed fuel vapor path due to the air pump  14  being started. 
   Here, in a case in which there is no leak in the closed fuel vapor path, a pressure detected at the pressure sensor  16  rises up to a predetermined pressure. 
   Accordingly, in a case in which a pressure detected at the pressure sensor  16  does 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 pump  14  is 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 pump  14 , 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 unit  21  will be described in accordance with the functional block diagram in  FIG. 2 . 
   The fuel supply control unit  21  and the engine control unit  22  are configured so as to be capable of intercommunication via a network  101 . 
   The engine control unit  22  transmits 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 unit  21 . 
   On the other hand, the fuel supply control unit  21  transmits 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 unit  22 . 
   At a fuel pressure control indicated value operation part  102  of the fuel supply control unit  21 , 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 sensor  33  and 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 circuit  104 , the fuel pump  31  is driven. 
   Further, a function of detecting malfunction in electric current in the fuel pump  31  is provided at the motor driving circuit  104 , and when malfunction is detected, a signal denoting that the electric current in the fuel pump  31  is abnormal is transmitted to the engine control unit  22 . 
   Further, when an operating instruction for a leak diagnosis is outputted from the engine control unit  22  to the fuel supply control unit  21 , a purge control unit  105  of the fuel supply control unit  21  controls the air pump  14 , the purge control valve  9 , and the cut valve  13 , and carries out a leak diagnosis on the basis of detection signals of the pressure sensor  16  and the fuel temperature sensor  35 . Then, the result of the leak diagnosis is outputted to the engine control unit  22 . 
   Moreover, the fuel supply control unit  21  calculates a fuel level (residual quantity) on the basis of a detection signal of the fuel level sensor  34 , and outputs the signal of the fuel level to the engine control unit  22 . 
   In accordance with the above-described embodiment, the canister  6  configuring the fuel vapor purge system, and the drain cut valve  13 , the air pump  14 , and the pressure sensor  16  which are for a leak diagnosis are disposed in the fuel tank  1 , and the air pump  14  is disposed in the vicinity of the canister  6 . 
   Therefore, the overall length of the piping configuring the fuel vapor purge system can be shortened. 
   Further, because the coupling portions between the canister  6  and respective pipings and the coupling portions between the air supply path and the fuel vapor path through the air pump  14  are disposed in the space in the fuel tank  1 , even in a case in which a leak is brought about at the coupling portion, fuel vapor leaks in the fuel tank  1 , and leaking of fuel vapor into the atmosphere can be avoided. 
   Moreover, because the drain cut valve  13 , the air pump  14  and the pressure sensor  16 , and the fuel supply control unit  21  are arranged in the vicinity, handling of a harness is simplified. 
   Further, provided that it is configured such that the both control units  21  and  22  have information in common by communication between the fuel supply control unit  21  and the engine control unit  22 , the signal lines between the both control units  21  and  22  can be simplified. 
   Moreover, the fuel supply control unit  21 , the air pump  14 , and the canister  6  disposed in the fuel tank  1  can be integrated, and in accordance therewith, the spatial efficiency can be improved. 
   The fuel supply control unit  21  is configured as shown in  FIG. 3 , which can prevent fuel from permeating the inside of the control unit  21 . 
   In the fuel supply control unit  21  shown in  FIG. 3 , a circuit substrate  21  a and a connector  21   b  are connected with a bonding wire  21   c , and the circuit substrate  21   a , the bonding wire  21   c , and the connector  21   b  are sealed in a resin mold  21   d.    
   Grooves  21   e  which 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 connector  21   b.    
   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 sensor  16 . However, the pressure sensor  16  is omitted, and a leak diagnosis may be carried out on the basis of a load on the air pump  14 . 
   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.