Patent Publication Number: US-6901913-B1

Title: Fuel pressure pulsation suppressing system

Description:
TECHNICAL FIELD 
   The invention relates to a fuel distribution system for a gasoline engine having a plurality of cylinders disposed in a straight, V-shape or horizontal opposed shape. In this type engine, such as V-6 or horizontal opposed six cylinders shape, to each three cylinders of right and left, one delivery pipe for distributing fuel is arranged, whereby on right and left sides of the engine a pair of delivery pipes are arranged. Further in detail, the invention relates to an improvement of a fuel distribution system for a gasoline engine having return-less type delivery pipes without a return circuit to a fuel tank from each delivery pipe. 
   BACKGROUND TECHNIQUE 
   Fuel delivery pipes are widely used in an electronic fuel injection system for a gasoline engine. There are two types; one is a return type having a return pipe in which fuel is delivered from a conduit having a fuel passage therein to fuel injectors via cylindrical sockets and then goes back to a fuel tank, and another is a non-return (return-less) type. Recently, for reducing vaporized gas caused by high temperature return fuel and for economical reasons, use of the non-return type is increasing and new problems are arising therefrom, those are, due to reflecting waves (shock waves) which are caused by reciprocal movements of valve operating spools for moving fuel injectors and due to fuel injection pressure pulsations, the fuel delivery pipes and their parts are vibrated thereby emitting uncomfortable noise. 
   Further, in those gasoline engines having a plurality of cylinders disposed in a V-shape or horizontal opposed shape and having a pair of right and left return-less type delivery pipes, injections are alternately done right and left, where at the moment of the valve opening or valve closing a kind of water hammer is produced. At a special engine rotation speed, a kind of standing wave is caused and a resonance is arised, pressure pulsations are increased, and further fuel injection instability and noise are increased. This phenomena are supposed to be a pulsation resonance in which a peculiar frequency of pressure pulsation wave becomes in coincident with a peculiar rotation speed of the engine, wherein the peculiar frequency are produced through overall overlapping process of the reflecting phenomena and passing phenomena caused in each boundary, such as a boundary between the delivery pipe and the fuel supply line. 
   In a so-called direct injection type engine in which fuel is directly injected into a combustion chamber, a high pressure supply pump is provided, and therefore a pulsation damper is provided so as to absorb the high pressure pulsations, whereby owing to its absorbing performance a resonance is not produced in general. However, in most cases having no pulsation damper, the resonance appears clearly, and the resonance point falls within the actual working rotation area of a gasoline engine. Accordingly, it is desired to eliminate the resonance. 
     FIG. 12  illustrates an ordinary automobile in which an automobile  11  (gasoline car) having an electronic fuel injection type V-shape engine  10  is provided with a supply line  13  from a fuel tank  12  to the engine  10 , and the line  13  is supported on a front panel or beneath a floor panel by a few or ten or so many clips  14 . Fuel supplied through the supply line  13  are transferred to the right and left connecting pipes  18 ,  19  by way of the branch connector  17 , and then to the pair of right and left delivery pipes  15 ,  16  each of which supplies fuel to one side three cylinders. The pair of right and left delivery pipes  15 ,  16  mounted on the engine supply fuel to injectors but are non-return (return-less) type having no return circuit to a fuel tank. 
   As shown, in such an internal combustion engine of a V-shape or horizontal opposed shape utilizing a pair of right and left return-less type delivery pipes, due to the differences of elasticity or sectional flow area between delivery pipes and supply pipes or connecting pipes, as mentioned above, at a special engine rotation speed, a kind of standing wave is caused and a resonance is arised, reflection and passing of pressure pulsations in a boundary are increased, and further fuel injection instability and noise are increased, whereby a problem that uncomfortable noise is transmitted to a driver is arised. 
   Japanese Patent unexamined publication Hei 11-6438 190261 entitled “Delivery pipe” suggests a method for eliminating an engine stop due to fuel pressure pulsations during idling rotation taking the fuel pressure pulsations and resonance rotation into account. 
   Although the previously mentioned pulsation damper is utilized in direct injection type engines and some ordinary fuel injection (multi point injection: MPI) type engines, it is not easy to adopt the damper due to space requirements and economical reasons. 
   Japanese Patent unexamined publication No. 2000-329031 entitled “Fuel delivery pipe” suggests to provide a flexible absorbing surface on an outside wall of the conduit of the delivery pipe so as to suppress pressure pulsations. 
   Japanese Patent unexamined publication Sho 60-240867 entitled “Fuel supply conduit for fuel injection device of an internal combustion engine” relates to an improvement of a fuel delivery pipe wherein at least one wall of the fuel supply conduit is comprised of an elastic member for damping the fuel pulsations. 
   Similarly, in Japanese Patent unexamined publication Hei 8-326622 entitled “Fuel pressure pulsation damping device” and Japanese Patent unexamined publication Hei 11-37380 entitled “Delivery pipe”, improvements of fuel delivery pipe so as to suppress the pulsation are described. 
   It is an object of the invention to provide a pressure pulsation suppressing system of a fuel piping which is arranged to an MPI type gasoline engine having a plurality of cylinders disposed in a straight, V-shape or horizontal opposed shape with one or a pair of right and left return-less type delivery pipes each having no return circuit to a fuel tank. 
   DISCLOSURE OF THE INVENTION 
   The invention provides, in the first embodiment, a pressure pulsation suppressing system of a fuel piping which is arranged to an MPI type gasoline engine having a plurality of cylinders disposed in a V-shape or horizontal opposed shape with a pair of right and left delivery pipes for distributing fuel to each cylinder, said right and left delivery pipes being connected by a connecting pipe, a fuel pump being accommodated within a fuel tank, said fuel pump and delivery pipe being connected by a supply pipe, and each delivery pipe being a return-less type having no return circuit to said fuel tank. 
   The invention is, in above system, characterized in that at least one section of a conduit (communication pipe) which constitutes said delivery pipe forms a flexible absorbing surface (face), and an orifice portion for damping pressure pulse wave caused by fuel injection is installed near a connection part between at least one delivery pipe and said supply pipe or said connecting pipe. 
   As a result of an adoption of said construction, pulsations are damped during the pressure pulsations pass through a narrow gap of the orifice thereby causing complex interference of reflecting waves, whereby generation of vibration is suppressed. If the orifice portion is arranged onto the absorbing surface, the pulsation suppressing effects are enhanced by accompanying with the vibration absorbing effects of the deflection of the absorbing surface. 
   The invention provides, in the second embodiment, a pressure pulsation suppressing system of a fuel piping which is arranged to an MPI type gasoline engine having a plurality of cylinders disposed in a straight shape with a delivery pipe for distributing fuel to each cylinder, a fuel pump being accommodated within a fuel tank, said fuel pump and delivery pipe being connected by a supply pipe, and each delivery pipe being a return-less type having no return circuit to said fuel tank. 
   This system is characterized in that at least one section of a conduit (communication pipe) which constitutes said delivery pipe forms a flexible absorbing surface (face), and an orifice portion for damping pressure pulse wave caused by fuel injection is installed near a connection part between said delivery pipe and said supply pipe. 
   Therefore, the invention can be applied to any of the types in which a plurality of cylinders are arranged in a straight, a V-shape or horizontal opposed shape. 
   Also in this system, if the orifice portion is arranged on the absorbing surface, the pulsation suppressing effects are enhanced by accompanying with the vibration absorbing effects of the deflection of the absorbing surface. 
   In this invention, the position and the number of the orifice are defined by experiments or analysis such that, especially while the engine is idling, the vibrations and pressure pulsations are minimized. Since the invention is directed to an insertion of an orifice into the passage of a fuel supply piping, it is applicable to existing automobiles. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing an overall pulsation suppressing system according to the first embodiment of the invention. 
       FIG. 2  is an outline sectional view showing an absorbing surface installed on the conduit. 
       FIG. 3  is a perspective view showing an overall pulsation suppressing system according to another example. 
       FIG. 4  is a vertical sectional view showing the connecting construction between the orifice and the conduit. 
       FIG. 5  is a vertical sectional view showing the connecting construction between the orifice and the conduit. 
       FIG. 6  is a graph showing pressure variations by changing the sectional area of the orifice. 
       FIG. 7  is a vertical sectional view showing an example of providing an orifice near connecting portion between the conduit and a flexible tube. 
       FIG. 8  is a perspective view showing an overall pulsation suppressing system according to the second embodiment of the invention. 
       FIG. 9  is an outline sectional view showing a preferable example of the orifice portion. 
       FIG. 10  is an outline sectional view showing a modified example of the orifice portion. 
       FIG. 11  is an outline sectional view showing a modified example of the orifice portion. 
       FIG. 12  is a perspective view showing a fuel piping system of an automobile. 
   

   BEST MODE FOR UTILIZING THE INVENTION 
   Other features and advantages of the invention will become apparent from the following descriptions referring to the embodiments of the attached drawings. 
     FIG. 1  shows an overall pressure pulsation suppressing system  20  for a fuel piping system according to the first embodiment of the invention, and  FIG. 2  shows a construction of an absorbing surface. The engine shown in  FIG. 1  is an MPI type gasoline engine having six cylinders disposed in a V-shape or horizontal opposed shape with a pair of right and left delivery pipes  15 ,  16  for distributing fuel to each cylinder, and the right and left delivery pipes are connected by connecting pipes  18 ,  19 . In the fuel tank  12 , as widely known, a fuel pump  8  and a pressure regulator  9  are accommodated, and the fuel pump and delivery pipe are connected by a supply pipe  13 . Each of the delivery pipes  15 ,  16  is a return-less type having no return circuit to the fuel tank  12 . 
   Fuel is supplied from the introducing pipe  21  which constitutes a part of the supply line  13  and then transferred to the right and left connecting pipes  18 ,  19  by way of the branch connector  17 , and then introduced into the right and left conduits  1 ,  2  which extend along the longitudinal direction. From the sockets  3  which are provided with the right and left conduits  1 ,  2 , fuel is supplied toward fuel injectors (not shown) along the direction of the arrow. 
   In addition, it is possible to connect each rear end of the conduits  1 ,  2  by a connecting pipe  22  thereby forming a loop shape of the delivery pipe. Since the right and left injectors works alternately, the connecting pipe  22  gives no influence upon the fuel injection. Connecting lines and pipes are made by plastic or metallic materials. 
   Based upon the charasteristics of the invention, as shown in  FIG. 2 , a part of the box-shape section of the conduits  1 ,  2  which constitutes the delivery pipes  15 ,  16  is formed into a flexible absorbing surface which can absorb vibration. In  FIG. 2A , the upper surface  5  opposing to the socket  3  which is connected to a fuel injector is made by a thin plate thereby providing the absorbing surface. In  FIG. 2B , the side surface  6  is made by a thin plate thereby providing the absorbing surface. 
   In  FIG. 1 , near the connections between the connecting pipes  18 ,  19  located at the fuel inlet sides of the corresponding delivery pipes  15 ,  16  and the pipes  15 ,  16 , orifice portions  26 ,  27  for damping pressure pulse wave caused by fuel injection are provided. The constructions of the orifice portions  26 ,  27  are described below. 
     FIG. 3  shows an overall pressure pulsation suppressing system  30  for fuel piping system according to another embodiment of the invention. The engine shown in  FIG. 3  is an MPI type gasoline engine having six cylinders disposed in a V-shape or horizontal opposed shape with a pair of right and left delivery pipes  31 ,  32  for distributing fuel to each cylinder, and the right and left delivery pipes are connected by connecting pipes  34 . Each of the delivery pipes  31 ,  32  is a return-less type having no return circuit to the fuel tank. 
   Fuel is supplied from the introducing pipe  33  which constitutes a part of the supply line  13  to the left conduit  1 , and then the fuel leaving the conduit  1  is transferred to the right conduit  2  by way of the connecting pipe  34 . From the sockets  3  which are attached to the right and left conduits  1 ,  2 , fuel is supplied toward fuel injectors (not shown) along the direction of the arrow. 
   Based upon the charasteristics of the invention, similarly as shown in  FIG. 2 , a part of the box-shape section of the conduits  1 ,  2  which constitutes the delivery pipes  31 ,  32  is formed into a flexible absorbing surface which can absorb vibration. 
   In addition, near the connection between the delivery pipe  31  and the supply pipe  13  and near the connection between the delivery pipe  32  and the connecting pipe  34 , orifice portions  36 ,  37  for damping pressure pulse wave caused by fuel injection are provided. The constructions of the orifice portions  36 ,  37  are described below. 
     FIGS. 4A ,  4 B show the outlines of the connecting construction between the orifice and the conduit.  FIG. 4A  shows a detail of the orifice portion  26  in  FIG. 1 , wherein the inside of the tubular portion is separated by an orifice plate  40 . At the center of the orifice plate  40 , a small orifice or aperture  40   a  is drilled. The inside diameter of the aperture  40   a  can be optimized by an experiment. 
     FIG. 4B  shows a detail of the orifice portion  36  in  FIG. 3 , wherein the inside of the tubular portion is separated by an orifice plate  40 . At the center of the orifice plate  40 , a small aperture  40   a  is drilled. The inside diameter of the aperture  40   a  can be optimized by an experiment. In this example, one wall of the conduits  1  which constitutes the delivery pipes  31  is formed into a flexible absorbing surface  5 . Since the orifice portion  36  is connected to the absorbing surface  5 , vibration suppressing effects are enhanced. 
     FIG. 5  shows an embodiment for making an experiment of best size of the orifice diameter, wherein an orifice portion  26  is pressed into the front end of the connecting pipe  18 , the front end  26   b  of the orifice portion  26  is fixed into an opening la which is drilled onto the conduit  1 , whereby fuel passes through the orifice aperture  26   a  into the conduit  1 . At the side of the conduit  1 , similarly as shown in  FIG. 2 , a flexible absorbing surface is formed. 
   The outside diameter of the connecting pipe  18  is 8 mm, the wall thickness is 0.7 mm, the inside diameter is 6.6 mm, the sectional flow area Ac is about 34.2 square mm. The orifice aperture  26   a  is a circle having an inside diameter 3 mm, and its sectional flow area Ao is 7.1 square mm. The sectional flow area ratio Ao:Ac is about 0.2:1. 
     FIG. 6  shows a result of experiment in which pressure variations are tested by changing the inside diameter Ao of the orifice. The horizontal axis shows a rate of Ao/Ac, and the vertical axis shows width of variations of peak pressure under special rotation speed of the engine as the pressure kPa. In this example, when the resonance occurs, the rotation speed was 1500 rpm. As shown in this graph, as the orifice diameter is minimized and the sectional area rate becomes below 1 which corresponds to non-orifice condition, pulsation is damped. Near the point of the rate 0.25, effects appear, and when the rate becomes below 0.2, the effects become great. Accordingly, if the peculiar value of the pressure pulsation wave exists in this piping system, it becomes possible to lower the resonance level below the current level. As a result, quantity of fuel injection does not give bad influence upon the rotation performance of the engine. The standing flow at the point of the connecting pipe gives influence upon the quantity of fuel injection, and if the pressure loss at the orifice becomes great, the standing flow is decreased. However, as far as the minimum flow size of the orifice is kept more than a predetermined value, the standing flow is not badly influenced and also quantity of fuel injection is not badly influenced. Further, it has been confirmed that the ratio of air and fuel is not badly influenced. 
     FIGS. 7A ,  7 B,  7 C show examples in which the connecting pipes are made by resin materials such as a nylon tube or a rubber hose. In  FIG. 7A , into the end plate  1   b  of the conduit  1 , a connector  75  is inserted, and an orifice portion  77  is inserted within a parallel portion of a resin tube  76  which is overlapped onto the connector  75 . In  FIG. 7B , into the central hole  75   a  of the connector  75 , an orifice portion  77  is inserted. In  FIG. 7C , the central hole  78  of the connector  75  is formed into a slender orifice. In each example, near the connecting portion between the delivery pipe and the connecting pipe, an orifice for damping pressure pulsation wave caused by fuel injection is provided. 
     FIG. 8  shows a fuel pressure pulsation suppressing system  90  according to the second embodiment of the invention. In this system  90 , the gasoline engine has a plurality of cylinders disposed in a straight shape with a delivery pipe  15 , a fuel pump  8  is accommodated within a fuel tank  12 , and the fuel pump and the delivery pipe are connected by a supply pipe  13 . The delivery pipe  15  is a return-less type having no return circuit to the fuel tank. 
   Based upon the charasteristics of the invention, a flexible absorbing surface is provided with the conduit  1 , similarly as shown in FIG.  2 . In addition, near the connecting portion between the delivery pipe  15  and the supply pipe  13 , an orifice portion  26  for damping pressure pulsation wave caused by fuel injection is provided. 
     FIGS. 9 ,  10 ,  11  show examples in which the absorbing surfaces composed of the wall of the delivery pipe are provided with orifice portions. In  FIG. 9 , to the absorbing surface  5  of the delivery pipe  1 , an orifice portion  44  is connected by welding or brazing, and an orifice plate  50  is arranged within the pipe and pressed therein by an adaptor socket  43 . Within the adaptor socket  43 , an O-ring  46  is inserted for sealing, and to the upper end of the socket, a connecting pipe  42  is connected by press fit, brazing or similar settling means. The inside diameter of the orifice aperture  50   a , which is centrally drilled in the orifice plate  50 , can be optimized by an experiment. 
     FIGS. 10A ,  10 B,  10 C,  10 D show modified examples of the example of FIG.  9 .  FIG. 10E  shows an example wherein the front end of the connecting pipe  58 , which is connected to the side of the conduit  1 , is swaged or shrinked and formed into an orifice aperture  58   a .  FIG. 10F  shows an example wherein the front end of the connecting pipe  59 , which is connected to the end of the conduit  1 , is swaged or shrinked and formed into an orifice aperture  59   a . The inside diameter of the small apertures  58   a ,  59   a  can be optimized by an experiment. 
     FIGS. 11A ,  11 B show examples in which a plurality of orifice plates are provided. In  FIG. 11A , in addition to the orifice portion  64  similar to that of  FIG. 9 , an adaptor socket  63 , a connecting pipe  62 , and an O-ring  66 , three orifice plates  70  and two adaptor rings  67  are inserted. 
   In  FIG. 11B , four orifice plates  80 ,  81 ,  82 ,  83  are inserted into the orifice portion  84 , and the orifice apertures located on each orifice plate are arranged alternately so as to change the phase. Due to the difference of the phase, energy absorption and vibration suppressing effects are enhanced. 
   As described above in detail, according to the invention, pulsations are damped during the pressure pulsations pass through a narrow gap of the orifice thereby causing complex interference of reflecting waves, whereby generation of vibration is suppressed. Since at least one wall is formed into an absorbing surface composed of a thin plate, if the orifice portion is arranged on the absorbing surface, the pulsation suppressing effects are enhanced by accompanying with the vibration absorbing effects of the deflection of the absorbing surface. The technical effects of the invention are great. 
   Possibility of Industrial Utilization 
   The invention can be applied to a fuel distribution system of a gasoline engine having a plurality of cylinders disposed in a straight, v-shape or horizontal opposed shape, especially of return-less type without a return circuit to a fuel tank.