Patent Publication Number: US-6901912-B1

Title: Variable delivery fuel supply device

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a variable delivery fuel supply device which is used for an internal combustion engine for automobiles, in particular, for a cylinder injection type gasoline engine requiring highly pressurized fuel and which is capable of controlling an amount of fuel to be supplied to fuel injection valves. 
   2. Discussion of Background 
     FIG. 4  is a systematic diagram showing the construction of a conventional variable delivery fuel supply device, wherein reference numerals  1   a  through id designate fuel injection valves for injecting fuel into respective cylinders of an internal combustion engine, numeral  2  designates a delivery pipe for supplying fuel to the fuel injection valves  1   a - 1   d , numeral  3  a fuel pump for supplying pressurized fuel to the delivery pipe  2 , numeral  4  a low pressure fuel pump for supplying fuel from a fuel tank  5  to the fuel pump  3 , numeral  6  a check valve provided in a fuel passage  7 , numeral  8  a low pressure regulator for controlling pressure in the fuel passage  7 , numeral  9  a relief valve for relieving fuel from a fuel passage  10  through a fuel passage  11  to the fuel tank  5  when a fuel pressure in the delivery pipe  2  exceeds a predetermined value, and numeral  12  a return passage for returning fuel through the fuel pump  3  to the fuel tank  5 . 
   The fuel pump  3  comprises a cylinder, a plunger performing a reciprocating movement in the cylinder due to a driving action of a cam provided on a cam shaft of the internal combustion engine and a pressurizing chamber for sucking fuel during the reciprocating movement of the plunger to pressurize the fuel, although these structural components are not shown in the drawing. The fuel pump  3  is to receive fuel supplied from the fuel tank  5  through a fuel intake port  13 ; to feed the fuel into the pressurizing chamber via a fuel passage  14  and an intake valve  15  in a suction step; to supply forcibly the fuel pressurized in the pressurizing chamber to a discharge port  18  via a discharge valve  16  and a fuel pressure maintaining valve  17  in a discharge step; and to supply the fuel to the delivery pipe  2  through the fuel passage  10  whereby the fuel in the delivery pipe  2  is distributed to the respective fuel injection valves  1   a - 1   d.    
   Reference numeral  19  designates an electromagnetic valve disposed in the fuel pump  3 , which is to open and close a relief passage  20  for communicating the pressurizing chamber (not shown) in the fuel pump  3  with the fuel passage  14 . When control means (not shown) detect that a fuel pressure in the delivery pipe  2  reaches a predetermined value, the control means supply a valve-opening signal to the electromagnetic valve  19 . Then, the electromagnetic valve  19  is opened to communicate the pressurizing chamber, in which a highly pressurized fuel is stored, with the fuel passage  14  of low fuel pressure to thereby relieve the pressurized fuel. Thus, the fuel pressure in the delivery pipe  2  can be controlled by controlling an amount of fuel discharged from the fuel pump  3 . The fuel pressure of the delivery pipe  2  increases since fuel is supplied in a discharge step of the plunger of the fuel pump  3 . Accordingly, the valve-opening operation of the electromagnetic valve  19  is conducted in the discharge step. 
   In the conventional variable delivery fuel supply device having the above-mentioned structure, the discharge performance of the fuel pump  3  is so determined as to cover the fuel consumption rate of the internal combustion engine over the entire operational range. Accordingly, there is allowance in the discharge performance of the fuel pump in a normal state of operation, and the electromagnetic valve  19  is opened at every discharge step whereby the highly pressurized fuel flows in a pulse form in the fuel passage  14 . The pulsating flow of the pressurized fuel generates a pulse-like fuel pressure in the fuel passage  14  and the fuel passage  7  as supply passages for fuel of low pressure. The amplitude of a pressure pulsation will increase as a rotating speed of the internal combustion engine is increased, with the result that vibrations are generated in a fuel pipe such as the fuel passage  7  whereby noises are generated and damage is caused in the fuel pipe due to a mechanical stress by the vibrations. Further, the pressure pulsation creates a disturbance flow or cavitation in the passage for supplying fuel of low pressure, which may cause an unstable supply of fuel to the delivery pipe  2  and influences adversely the performance of the internal combustion engine. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a variable delivery fuel supply device capable of supplying stably fuel to an internal combustion engine without causing noises and a danger of the breaking of a fuel passage for feeding fuel of low pressure when an electromagnetic valve is operated to relieve a highly pressurized fuel. 
   In accordance with the present invention, there is provided a variable delivery fuel supply device which comprises fuel injection valves for injecting fuel to respective cylinders of an internal combustion engine, a fuel pump which sucks fuel from a fuel intake port through an intake valve into a pressurizing chamber by a reciprocating movement of a plunger in a cylinder to pressurize the fuel and supplies the pressurized fuel into the fuel injection valves through a discharge valve, a damper chamber having a pressure damper, which is communicated with a fuel passage at a position between the fuel intake port and the intake valve in the fuel pump, a relief passage for communicating the pressurizing chamber of the fuel pump with the fuel passage, and an electromagnetic valve for opening and closing the relief passage, which is adapted to control an amount of pressurized fuel to be supplied to the fuel injection valves by relieving pressurized fuel in the pressurizing chamber to the fuel passage at the time of opening the valve. 
   In the above-mentioned invention, the damper chamber having a pressure damper may be formed integrally with the fuel pump. 
   Further, the relief passage may be communicated with the fuel passage at a position between the damper chamber including a pressure damper and the intake valve. 
   Further, an orifice may be formed in the relief passage. 
   Further, the pressure damper may be formed of a metallic bellows or a metallic diaphragm. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is a systematic diagram showing the construction of the variable delivery fuel supply device according to a first embodiment of the present invention; 
       FIG. 2  is a cross-sectional view of a fuel pump used for the variable delivery fuel supply device of the first embodiment of the present invention; 
       FIG. 3  is a cross-sectional view of a fuel pump used for the variable delivery fuel supply device according to a second embodiment of the present invention; and 
       FIG. 4  is a systematic diagram showing the construction of a conventional variable delivery fuel supply device. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
   The variable delivery fuel supply device according to a first embodiment of the present invention will be described with reference to  FIGS. 1 and 2  wherein the same reference numerals designate the same or corresponding parts. 
   Embodiment 1 
   In  FIG. 1 , reference numerals  1   a  through  1   d  designate fuel injection valves for injecting fuel to the respective cylinders in an internal combustion engine, numeral  2  designates a delivery pipe which supplies fuel to the fuel injection valves  1   a - 1   d , numeral  3  a fuel pump for supplying pressurized fuel to the delivery pipe  2 , numeral  4  a low pressure fuel pump for supplying fuel from a fuel tank  5  to the fuel pump  3 , numeral  6  a check valve provided in a fuel passage  7 , numeral  8  a low pressure regulator for controlling a pressure in the fuel passage  7 , numeral  9  a relief valve to relieve fuel to the fuel tank  5  via a fuel passage  10  and a fuel passage  11  when a fuel pressure in the delivery pipe  2  exceeds a predetermined value and numeral  12  a return passage to return fuel from the fuel pump  3  to the fuel tank  5 . 
   In the fuel pump  3  shown in  FIG. 2 , reference numeral  21  designates a cylinder, numeral  22  a plunger which performs a reciprocating movement in the cylinder  21  to suck fuel into a pressurizing chamber  24  in which the sucked fuel is pressurized, wherein the plunger is driven by a driving cam of the internal combustion engine (although they are not shown in  FIG. 2 ) by means of a roller  23 , numeral  25  a spring for urging always the plunger  22  in a direction of expanding the pressurizing chamber  24 , numeral  26  a spring for urging the roller  23  toward a side of the cam shaft (not shown), and numeral  27  a bellows made of metal which is for sealing fuel possibly leaking from a gap between the cylinder  21  and the plunger  22 . Numeral  14  designates a fuel passage communicated with a fuel intake port  13  (as shown in FIG.  1 ). The fuel passage  14  is also communicated with the pressurizing chamber  24  through an intake valve  15 . Numeral  18  designates a fuel discharge port connected to the delivery pipe  2  by means of the fuel passage  10 . The fuel discharge port  18  is communicated with the pressurizing chamber  24  through a high-pressure fuel passage  28  and a discharge valve  16 . 
   For the driving cam (not shown), a multi-ridge type driving cam having, for instance,  4  ridges,  5  ridges or  6  ridges is used in order to reduce the occurrence of pressure pulsation of fuel in the delivery pipe  2 . Accordingly, reed valves having high response characteristics are used for the intake valve  15  and the discharge valve  16 . 
   Numeral  29  designates a damper chamber having a pressure damper  30  formed of a metallic bellows, which maintains a predetermined air pressure. The fuel passage  14  communicated with the fuel intake port  13  is connected to the intake valve  15  and further, the pressurizing chamber  24  via the damper chamber  29 . An electromagnetic valve  19  is provided with a valve unit comprising a valve  31  and a valve seat  32 , which is adapted to open and close a relief passage  20  communicated with the pressurizing chamber  24  and the fuel passage  14 . When the electromagnetic valve  19  is opened, fuel pressurized in the pressurizing chamber  24  flows through the relief passage  20  to the fuel passage  14 . 
   An orifice  33  is formed in the relief passage  20  at a position between the damper chamber  29  communicated with the fuel passage  14  and the intake valve  15 , namely, it is opened at a side of a downstream of the fuel passage  14  with respect to the pressure damper  30 . With such measures, a possible increase of the amplitude of pressure pulsation caused by the relieving of the pressurized fuel from the electromagnetic valve  19  can be reduced. 
   In the operation of the variable delivery fuel supply device according to the first embodiment of the present invention, when the low pressure pump  4  is actuated as soon as the internal combustion engine is operated, fuel is supplied from the fuel tank  5  to the fuel pump  3 . When the fuel pump  3  is driven by the internal combustion engine, the discharge valve  16  is closed and the intake valve  15  is opened at a suction step of the plunger  22  whereby fuel is sucked into the pressurizing chamber  24  through the fuel intake port  13  and the fuel passage  14 , and at a discharge step of the plunger  22 , the intake valve  15  is closed and the discharge valve  16  is opened whereby pressurized fuel is supplied forcibly to the delivery pipe  2  via the high pressure fuel passage  28 , the fuel discharge port  18  and the fuel passage  10 . When the engine is stopped, the fuel pressure in the fuel pump  3  will decrease. However, a fuel pressure maintaining valve  17  is provided in the fuel passage  10  in this embodiment, and therefore, the fuel pressure in the delivery pipe  2  can be maintained for a predetermined time by closing the fuel pressure maintaining valve  17 . 
   When a fuel pressure in the delivery pipe  2  exceeds a predetermined value, the control means detects the fact and supplies a valve-opening signal to the electromagnetic valve  19 . Then, the electromagnetic valve  19  is opened to communicate the pressurizing chamber  24 , in which a discharge step is conducted, with the fuel passage  14  through the relief passage  20  so that the pressurized fuel in the pressurizing chamber  24  is relieved to the fuel passage  14 , and on the other hand, it stops the fuel to discharge to the delivery pipe  2  whereby a fuel pressure in the delivery pipe  2  is maintained to a predetermined value. 
   In the variable delivery fuel supply device according to the first embodiment of the present invention, since the damper chamber  29  having the pressure damper  30  is communicated with the fuel passage  14 , and pressurized fuel is relieved to the fuel passage  14  at the point between the damper chamber  29  and the intake valve  15 , a pulsation of the pressurized fuel relieved to the fuel supply passage can be absorbed and relaxed by the pressure damper  30  and a reduced pulsation is applied to the fuel pipe such as the fuel passage  7 . Accordingly, the occurrence of noises and a mechanical stress as seen in the conventional device can be minimized. Further, the reduced pressure pulsation suppresses the occurrence of a disturbance of flow or cavitation in a low pressure fuel supply pipe such as the fuel passage  14 . Further, the supply of fuel from the fuel pump to the delivery pipe  2  can stably be conducted and an adverse effect to the performance of the internal combustion engine is avoidable. 
   Further, since the orifice  33  is formed in the relief passage  20 , the pressurized fuel in the pressurizing chamber  24  is discharged to the fuel passage  14  through the orifice  33  to reduce the pressure pulsation in the fuel passage  14 , whereby the occurrence of noises or a mechanical stress can further be reduced. The connecting point of the relief passage  20  to the fuel passage  14  to discharge the pressurized fuel should be close to the pressure damper  30  since it is effective to suppress a pressure pulsation. Further, the connecting point should be at a side of the intake valve  15  with respect to the pressure damper  30  since the pressure pulsation applied to the fuel pipe such as the fuel passage  7  can be reduced and it is easy to form the damper chamber  29  integrally with the fuel pump  3 . 
   Embodiment 2 
   The variable delivery fuel supply device according to a second embodiment of the present invention will be described with reference to FIG.  3 . The construction of the second embodiment is substantially the same as that of the first embodiment except that a pressure damper  34  is formed of a diaphragm. In this case too, the same effect is obtainable. In the second embodiment, the size of the damper chamber  29  can be reduced and the integrally formed fuel pump  3  can be small in size. Further, it is preferable to use a metallic diaphragm since a relatively high pressure is frequently applied to the diaphragm of the pressure damper  34 . 
   As described above, according to the variable delivery fuel supply device of the present invention, the damper chamber is formed so as to be connected to the fuel passage at a position between the fuel intake port and the intake valve in the fuel pump; the pressure damper formed of a metallic bellows or a metallic diaphragm is disposed in the damper chamber, and pressurized fuel in the pressurizing chamber is relieved to the fuel passage between the damper chamber and the intake valve. Accordingly, it is possible to suppress a pressure pulsation of the pressurized fuel due to the relieving and to eliminate the occurrence of noises and a damage of the fuel pipe. Thus, the variable delivery fuel supply device of highly reliable and capable of conducting a stable fuel supply is obtainable. 
   Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. 
   The entire disclosure of Japanese Patent Application JP2000-55337 filed on Mar. 1, 2000 including specification, claims, drawings and summary are incorporated herein by reference in its entirety.