Patent Publication Number: US-2005129527-A1

Title: Jet pump device

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
      The present invention relates to a jet pump device disposed inside a fuel tank of an automobile and the like for sucking fuel inside the fuel tank into a chamber of a fuel pump module, or sucking air into the fuel tank via a ventilation channel connected to a canister.  
      A fuel pump supplies fuel from a fuel tank to an internal combustion engine. The fuel pump sucks fuel, and a pressure regulator controls a pressure of fuel. A part of fuel is relieved as surplus fuel, and returned to the fuel tank. Japanese Patent Publication (Kokai) No. 11-50925 has disclosed a suction pump for sucking fuel in a sub-tank into a main-tank using surplus fuel.  
      Such a suction pump spouts surplus fuel from a nozzle portion to generate jet-pump effect, so that fuel in a sub-tank is sucked and sent to a main-tank with surplus fuel. In such a suction pump, a negative pressure is generated on a supply side of surplus fuel, i.e., a side of a pressure regulator. A relief valve is provided for relieving the negative pressure. When a pressure inside a flow path for supplying surplus fuel to the nozzle portion exceeds a certain level, the relief valve opens to discharge a part of surplus fuel just before the nozzle portion. Consequently, in the conventional pump, it is difficult to efficiently utilize surplus fuel for sucking fuel.  
      In view of the problem described above, an object of the present invention is to provide a jet pump device for sucking fuel using surplus fuel relieved by a pressure regulator, in which it is possible to efficiently utilize a flow pressure of surplus fuel to suck fuel.  
      Further objects and advantages of the invention will be apparent from the following description of the invention.  
     SUMMARY OF THE INVENTION  
      In order to achieve the objects described above, according to the present invention, a jet pump device includes jet-pump portions formed of discharge nozzles for discharging surplus fuel relieved by a pressure regulator and outlets formed in front of the discharge nozzles. The jet-pump portions are arranged at more than two places such that the discharge nozzles are situated inside a chamber and the outlets communicate with the chamber. The chamber is provided with a suction path for sucking fuel or air.  
      The pressure regulator is provided inside a fuel line between a fuel pump and an internal combustion engine for relieving surplus fuel to regulate a pressure. The jet pump device of the invention has more than two jet-pump portions. Accordingly, it is possible to reduce an increase in a negative pressure on a side of the pressure regulator associated with generation of jet-pump effect, while the jet pump device efficiently utilizes a flow pressure of surplus fuel.  
      According to the present invention, a distribution device may be provided for selectively supplying surplus fuel to at least one of the discharge nozzles of the jet-pump portions arranged at more than two places according to a pressure of surplus fuel.  
      With this structure, when the pressure of surplus fuel is high, it is possible to supply surplus fuel to all or more than two of the discharge nozzles. When the pressure of surplus fuel is low, it is possible to supply surplus fuel to one or more than two of the discharge nozzles. That is, regardless of a change in the pressure of surplus fuel, it is possible to maintain the jet-pump effect of the jet pump device, i.e., a suction mount of fuel or air.  
      According to the jet pump device of the present invention, it is possible to efficiently utilize the flow pressure of surplus fuel relieved by the pressure regulator, thereby smoothly sucking fuel or air. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a sectional view of a jet pump device; and  
       FIG. 2  is a view showing the jet pump device provided with a distribution device. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      Hereunder, preferred embodiments of the present invention will be explained with reference to  FIGS. 1 and 2 .  FIG. 1  is a cross sectional view showing a structure of a jet pump device JP according to an embodiment.  FIG. 2  is a view showing the jet pump device JP provided with a distribution device  5  for selectively supplying surplus fuel to at least one of jet-pump portions E of the jet pump device JP.  
      In the embodiment, the jet pump device JP is provided inside a fuel tank of an automobile and the like for sucking fuel inside the fuel tank into a chamber of a fuel pump module, or sucking air into the fuel tank via a ventilation channel connecting the fuel tank to a canister.  
      The jet pump device JP sucks fuel into the chamber. Accordingly, even when fuel in the fuel tank becomes low, a fuel pump disposed inside the chamber of the fuel pump module can continuously supply fuel to an internal combustion engine. The jet pump device JP also sucks air into the fuel tank to increase an inner pressure of the fuel tank. Accordingly, a pressure sensor can detect a change in the inner pressure of the fuel tank td detect unexpected leakage of fuel evaporation emission from the fuel tank.  
      The jet pump device JP includes more than two jet-pump portions E having discharge nozzles  1  for discharging surplus fuel relieved by the pressure regulator and outlets  2  formed in front of the discharge nozzles  1 . It is arranged such that the discharge nozzles  1  are positioned inside a chamber  3 , and the outlets  2  communicate with the chamber  3 . A suction path  4  is connected to the chamber  3  for sucking fuel or air.  
      In the embodiment, the jet-pump portions E are disposed at three places. Each of the jet-pump portions E is composed of the discharge nozzle  1  formed at an end of a relief line (flow path)  6  for surplus fuel and the outlet  2  positioned in front of the discharge nozzle  1 . The discharge nozzle  1  protrudes downwardly from an inner wall  30   a  of an upper structural member  30  of the chamber  3 , and is integrated with the upper structural member  30 .  
      The discharge nozzle  1  has a size decreasing toward an end thereof. An external surface of the discharge nozzle  1  is a taper face  10  along an imaginary external surface of a cone, and an inside diameter of the discharge nozzle  1  decreases toward the end thereof. The outlet  2  is formed in an inner wall  31   a  of a lower structural member  31  of the chamber  3 . In the embodiment, an upper-tube end  21  of an outlet tube  20  is integrated with the lower structural member  31  of the chamber  3 , so that the outlet  2  is formed by the upper-tube end  21  of the outlet tube  20 . The outlets  2  are formed in bottom portions of conical depressions  23  with a diameter gradually decreasing toward rims  22  of the outlets  2 . The discharge nozzles  1  have ends situated in the depressions  23  to form a space between external surfaces of the discharge nozzles  1  and wall faces of the depressions  23 .  
      When surplus fuel is discharged from the discharge nozzles  1 , a negative pressure is effectively generated between the depressions  23  and the discharge nozzles  1 . Accordingly, fuel or air is sucked into the chamber  3  through the suction path  4  due to the negative pressure, and sent to an outside of the chamber  3  with surplus fuel via the outlets  2 . When fuel inside the fuel tank at an outside of a chamber of a fuel pump module is sucked through the suction path  4 , and the outlets  2  are connected to the chamber of the fuel pump module, the jet pump device JP supplies fuel inside the fuel tank into the chamber of the fuel pump module with surplus fuel. When air is sucked through the suction path  4 , and the outlets  2  are connected to the fuel tank, the jet pump device JP supplies air into the fuel tank with surplus fuel.  
      In the embodiment, the lower structural member  31  of the chamber  3  has an open top face  31   b  and the outlets  2  at a bottom thereof. The upper structural member  30  of the chamber  3  includes the discharge nozzles  1  and is connected to a suction tube  40  of the suction path  4 . The upper structural member  30  is tightly fitted into the open top face  31   b , so that the upper structural member  30  and the lower structural member  31  are combined to form the jet pump device JP.  
      A pressure regulator is provided inside a fuel line between the fuel pump and the internal combustion engine for reliving surplus fuel to regulate a pressure. In the embodiment, the jet pump device JP has more than two jet-pump portions E. Accordingly, it is possible to minimize an increase in the negative pressure on a side of the pressure regulator associated with generation of jet-pump effect, while a flow pressure of surplus fuel is efficiently utilized on a side of the jet pump device JP.  
      As shown in  FIG. 2 , a distribution device  5  may be provided for selectively supplying surplus fuel to at least one of the discharge nozzles  1  of the jet-pump portions E arranged at more than two places according to a pressure of surplus fuel. More specifically, the jet pump device JP may be provided with the distribution device  5  in the middle of the relief line  6  for surplus fuel.  
      When the internal combustion engine consumes a large amount of fuel, i.e., an automobile is moving, only a small amount of surplus fuel is relieved. Accordingly, a pressure of surplus fuel supplied to the discharge nozzles  1 , i.e., a pressure in the relief line  6  between the discharge nozzles  1  and the pressure regulator, decreases. To the contrary, when an automobile is idling, a large amount of surplus fuel is relieved, and the pressure of surplus fuel supplied to the discharge nozzles  1 , i.e., the pressure in the relief line  6  between the discharge nozzles  1  and the pressure regulator, increases. If surplus fuel is constantly and equally supplied to the discharge nozzles  1  of the jet-pump portions E regardless of the pressure change, the jet-pump effect of the jet pump device JP declines.  
      With the structure of the invention, when the pressure of surplus fuel is high, surplus fuel can be supplied to all or more than two of the discharge nozzles  1 . When the pressure of surplus fuel is low, surplus fuel can be supplied one or more than two of the discharge nozzles  1 . Accordingly, regardless of a change in the pressure of surplus fuel, it is possible to maintain the jet-pump effect of the jet pump device, i.e., a suction mount of fuel or air.  
      The distribution device  5  may be formed of an adjusting valve provided in the relief line  6 . According to the pressure of surplus fuel flowing through the relief line  6 , the adjusting valve selectively produces an usual condition wherein surplus fuel is sent to all of more than two of the discharge nozzles  1 ; a partly-closed condition wherein surplus fuel is sent to only a part of the discharge nozzles  1 ; and a closed condition wherein surplus fuel is sent to only one of the discharge nozzles  1 .  
      The disclosure of Japanese Patent Application No. 2003-412920, filed on Dec. 11, 2003, is incorporated in the application.  
      While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.