Abstract:
A fuel hose should reduce noise during fuel injection into an engine, and should not interfere with other engine components. The fuel hose supplies fuel drawn up from a fuel tank to the fuel injection valves of the engine, and is formed from a resin material which is resistant to fuel. The fuel hose comprises a hose main body having a fuel passage, and an non-circular component formed as a result of at least part of the cross sectional shape of the hose main body being non-circular. The non-circular component has a plurality of ribs running in the axial direction along the hose main body, and absorbs pulsation by the varying of the cross sectional shape of the ribs in response to variations in the pressure on the fuel flowing through the fuel passage, thereby resisting alterations to the shape in the axial direction.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuel hose for supplying fuel drawn up from an automobile fuel tank to the fuel injection valves of the engine, and to a method for manufacturing this fuel hose. 
     2. Description of the Related Art 
     A fuel hose has conventionally been provided to the fuel supply system connecting an automobile fuel tank to the engine. FIG. 11 is a simplified structural diagram of a fuel supply system. In FIG. 11, an end of a metal fuel pipe  106  is connected to an automobile fuel tank  102  via a fuel pump  104 . Other end of the fuel pipe  106  is connected to and supported by a filter  110  fixed to a dash panel  108 . A fuel hose  112  is connected to the outlet of the filter  110 , and supplies fuel to the fuel injection valves  116  of the engine. The fuel hose  112  is usually formed from a rubber material, but there has been a changeover to resin materials in recent years in an effort to reduce weight and cost. 
     However, resinous fuel hoses have caused problems. When fuel is injected from the fuel injection valves  116 , there is a sudden drop in the fuel supply pressure within the fuel hose  112 . The sudden drop in fuel supply pressure becomes a pulse that propagates from the fuel hose  112  to the fuel pipe  106  and vibrates the dash panel  108  through the filter  110 . This causes noise. 
     At the least, the above-mentioned noise grates on the ear and is unpleasant to hear when operating an automobile. Accordingly, use of pulsation dampers has been required to reduce noise. Use of pulsation dampers, however, increases the number of parts, defeats the attempt to lower weight and adds to the cost of the system. 
     Another problem was that the fuel hose  112  was disposed in the cramped space of the engine compartment, with vibrations that occurred as the fuel supply pressure rose and fell interfered with other items in the engine compartment. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a fuel hose made of resin, which reduces noise during fuel injection into an engine and does not interfere with other engine components. 
     The first embodiment of the present invention, conceived in order to solve the above problems, is a fuel hose configured to supply fuel drawn up from a fuel tank to fuel injection valves of an engine. 
     The hose includes a main body with a fuel passage, in which the main body is made of. 
     The hose includes a non-circular component formed integrally with the hose main body, with the non-circular component having a plurality of ribs each extending in an axial direction along the hose main body. The ribs are constructed and arranged to vary the cross section of the non-circular component when a fuel pressure is applied to the fuel hose, thereby absorbing pulsating pressure occurring within the fuel hose. 
     The fuel hose pertaining to the first embodiment of the present invention supplies fuel drawn up from a fuel tank to the fuel injection valves of an engine. This fuel hose has a non-circular component with a plurality of ribs running in an axial direction along the hose main body. This non-circular component expands and contracts radially in response to pressure fluctuations that accompany fuel injection by the fuel injection valves. As a result, the non-circular component varies its volume capacity greatly during fuel injection in response to fluctuations in the fuel pressure inside the fuel hose, which attenuates the vibrations and suppresses the generation of noise. Thus, even if a resin material, that is lower in cost than rubber material, is used for the fuel hose, the effects of pulsation accompanying fuel injection can be reduced and noise suppressed to the same or greater extent than with a rubber hose. 
     Since a considerable pulse absorbing effect is thus provided by the non-circular component with this fuel hose, there is no need to use pulsation dampers as was described for the prior art, which affords a reduction in the number of parts. 
     Also, the changes in the shape of the non-circular component that accompany pressure fluctuations are primarily just in the radial direction, and there is no expansion and contraction in the axial direction, that is, along the axial direction of the fuel hose. Accordingly, expansion or contraction of the fuel hose causes no change in the path of the fuel hose, there is no interference with other nearby members, and there is no noise generated or any reduction in durability. 
     An example of a favorable shape for the non-circular component is for a plurality of ribs to be equidistantly disposed in ridges running in the axial direction of the fuel hose. 
     In a preferred embodiment of the first embodiment of the present invention, a bellows component is formed adjacent to the non-circular component in the axial direction of the hose. With this structure, if the fuel hose winds around a curved path, it can be easily bent in bellows area, and any movement of the non-circular component in the axial direction brought about by expansion and contraction can be restricted by the bellows component. Thus, the fuel hose can be easily routed through a cramped installation space in the engine compartment. 
     In another embodiment of the present invention, there are further provided a circular component that has a circular cross section that is connected to one end of the bellows component, and a tapered component that connects the circular component and the noncircular component whose cross sectional shape gradually varies from the cross sectional shape of the circular component to that of the non-circular component shape. 
     In addition to connecting to an ordinary pipe with a circular cross section, the non-circular component may be connected to a bellows component and/or an ordinary pipe. For example, a structure in which an ordinary pipe connects the non-circular component to the bellows component can be adopted by taking into account various parameters such as the pulse absorption action, mechanical strength, and routing of the hose. In this case, in order to facilitate routing, instead of employing a structure which bends at a bellows area, the fuel hose may be bent by pre-bending an ordinary pipe. 
     The material from which the fuel hose is formed can be a polyamide-, fluorine-, polyester-, polyketone-, or polysulfide-based resin, a thermoplastic elastomer, or an ethylene/vinyl alcohol copolymer. A plasticizer may also be added to the fuel hose to increase the flexibility of the fuel hose. 
     It is preferable for the fuel hose to be formed such that it will absorb pressure fluctuations of approximately 0.02 MPa on either side of a 0.3 MPa internal hose pressure of the liquid flowing through the fuel hose. 
     It is also preferable for the fuel hose to be formed such that the proportional volumetric change is at least 7 mm′/(MPa−mm). The term proportional volumetric change as used here refers to the amount of volumetric change when the pressure changes by 1 MPa per millimeter of fuel hose. 
     The present invention also includes a method for manufacturing a fuel hose. 
     The method includes a first step of forming a hose main body with a circular cross section by first extruding a resin material, and then in a second step forming a non-circular componentin the circular cross-sectional area. The non-circular section includes a plurality of ribs that extend in the axial direction along the hose main body. The cross sectional shape of the ribs can vary with the pressure on the fuel flowing through the fuel hose. 
     This manufacturing method allows non-circular components of different cross sectional shapes to be manufactured continuously and easily. 
     The second step preferably includes a step in which the non-circular component is formed with the ribs equidistantly disposed in ridges running in the axial direction along the fuel hose. 
     The second step may also include a step in which a bellows component is provided adjacent to the non-circular component in the axial direction. 
     In addition, the second step may also include a step of forming a circular component that has a circular cross section and is connected to one end of the bellows component, and a tapered component that inter-connects the circular component with the non-circular component, with cross sectional shape of the tapered component gradually varying from the cross sectional shape of the circular component to that of the non-circular component. 
     The second step may further include a step in which molds having molding surfaces for forming the circular component, the non-circular component, and the bellows component. Such molds may be disposed in a loop and move through a molding area. The circular component, the non-circular component, and the bellows component are formed in a desired sequence on the molding surfaces in the desired molds. The molding surfaces are connected to passages to which suction is applied by a suction pump so that the material will conform to the desired cross-sectional shape of the circular component, the non-circular component, and the bellows component. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified structural diagram of a fuel supply system in which the fuel hose pertaining to an embodiment of the present invention is used; 
     FIG. 2 is an external view of the fuel hose; 
     FIG. 3 is an oblique view of the fuel hose, enlarged to show the area around the bellows component and the non-circular component; 
     FIG. 4 is a cross section in the axial direction of the area around the bellows component; 
     FIG. 5 shows the shape of the bellows component in FIG. 4; 
     FIG. 6 is a cross section of the non-circular component; 
     FIG. 7 is a diagram illustrating how the non-circular component is radially distended; 
     FIG. 8 is a diagram illustrating the steps involved in manufacturing the fuel hose; 
     FIG. 9 is a cross section of the bellows mold in the axial direction; 
     FIG. 10 is a diagram illustrating the non-circular component mold; and 
     FIG. 11 is a simplified structural diagram of a fuel supply system. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a simplified structural diagram of a fuel supply system in which the fuel hose according to an embodiment of the present invention is used. In FIG. 1, a metal fuel pipe  13  is connected to an automobile fuel tank  11  via a fuel pump  12 . The fuel pipe  13  is connected to a filter  15  that is fixed to a dash panel  14  located at the rear of an engine compartment. A fuel hose  30  is connected to the outlet of the filter  15  via a quick connector  16 . The fuel hose  30  is routed through the engine compartment and is connected to the fuel injection valves  21  of the engine  20  by being connected to the fitting  19  of a delivery pipe  17 . 
     In the fuel supply system, fuel is drawn up from the fuel tank  11  by the fuel pump  12  and pumped through the fuel pipe  13  and the filter  15  to the fuel hose  30 . Fuel is then injected into the engine  20  as the fuel injection valves  21  are opened and closed. The fuel supply pressure fluctuates as the fuel is injected. More specifically, the pressure fluctuates by about 0.02 MPa on either side of a 0.3 MPa pressure at the outlet of the fuel hose  30  where it is connected to the fuel injection valves  21 . 
     FIG. 2 is an external view of the fuel hose  30 . The fuel hose  30  is made from one or more layers of resin material and includes cylindrical circular components  31 , non-circular components  34 , and bellows components  33  that are connected to and integrally molded with the circular components  31 , and non-circular components  34 . Fuel hose  30  also has connector terminals  32   a  and  32   b  at each end, respectively. The material from which the fuel hose  30  is formed can be a polyamide-, fluorine-, polyester-, polyketone-, or polysulfide-based resin, a thermoplastic elastomer, or an ethylene/vinyl alcohol copolymer. A plasticizer can also be added in order to increase the flexibility of the fuel hose itself. When the material of the fuel hose  30  is a polyamide resin, N-nbutylsulfonamide is added in an amount of 2 to 20 wt %, and when it is a thermoplastic elastomer, a paraffin- or naphthene-based oil is added in an amount of 1 to 30 wt %. 
     FIG. 3 is an oblique view of the fuel hose  30 , enlarged to show the area around the bellows component  33  and the non-circular component  34 . FIG. 4 is a cross sectional view in the axial direction of the bellows component  33 . In FIGS. 3 and 4, the bellows component  33  is formed as a series of peaks  33   a  and valleys  33   b,  and is flexible in the axial direction. The flexibility of the fuel hose  30  is based on the number of bellows components  33 , the type and hardness of the resin material, and other such parameters. The fuel hose  30  is formed so as to satisfy requirements such as pressure resistance and flow quantity, and so that the proportional volumetric change will be at least 7 mm 3 /(MPa·mm). The proportional volumetric change refers to the amount of volumetric change when the pressure changes by 1 MPa per millimeter of fuel hose. 
     As an example of the shape of the bellows components  33  for satisfying the requirement for proportional volumetric change in the fuel hose  30 , if the outside diameter D 1  of the fuel hose  30  is 6 to 17 mm, then as shown in the detail cross section of FIG. 5, the height h of the peaks of the bellows component  33  is 1 to 7 mm, the thickness t 1  of each peak is greater than 0.3 mm and less than 1.7 mm, the thickness t 2  of each valley is greater than 0.3 mm and less than 1.7 mm, with the above-mentioned thicknesses t 1  and t 2  each preferably being 0.5 to 1.0 mm, in which case the pitch length P can be 2 to 8 mm. 
     FIG. 6 is a cross section of the non-circular component  34 . In FIGS. 2,  3  and  6 , the non-circular component  34  is formed between two bellows components  33  and is integral therewith. The non-circular component  34  includes a plurality of ribs  34   a  equidistantly disposed around the axial direction of the fuel hose  30 . Specifically, the ribs  34   a  protrude in ridges running in the axial direction, making the outer shape of the fuel hose  30  non-circular. The ribs  34   a  are distended by the pressure of the fuel flowing through the passage inside the fuel hose  30 . As shown in FIG. 7, this non-circular component  34  is deformed by the fuel flowing through the fuel passage so that the cross sectional shape of the above-mentioned ribs  34   a  becomes closer to circular. 
     As shown in FIG. 3, the bellows component  33  and the non-circular component  34  are inter-connected by the circular component  31 , with the portion between the non-circular component  34  and the circular component  31  comprising a tapered component  35 . This tapered component  35  is structured such that the non-circular component  34  gradually takes on a circular cross section until it connects with the circular component  31 . The tapered component  35  reduces the stress applied to the end of the non-circular component  34 . 
     With the above-mentioned fuel hose  30 , the bellows component  33  and the noncircular component  34  undergo a considerable change in their volume according to fluctuations in the pressure of the fuel flowing through the fuel hose  30 . These changes absorb the vibrational energy that accompanies the pressure fluctuations, which allows the pulsation accompanying fuel injection to be attenuated and any associated noise suppressed. 
     As the fuel hose  30  absorbs such pressure fluctuations, the bellows components  33  are moved by the force in the axial direction by the volumetric changes, while the non-circular components  34  are distended primarily in the radial direction and do not expand or contract in an axial direction. In other words, the non-circular components  34  act to restrict movement of the bellows components  33  in an axial direction. Therefore, as pressure fluctuations occur, the fuel hose  30  does not move as indicated by the broken line in FIG. 1, and does not interfere with other parts or make noise. 
     Also, because a non-circular component  34  is disposed between the bellows components  33 , the fuel hose  30  can be bent at the bellows components  33  to route it through a curved path, and the non-circular component  34  will interfere with this routing, so installation is simple even in a cramped engine compartment. 
     Furthermore, although the fuel hose  30  is made of a resin, because a considerable pulse absorbing effect that is equal to or better than that of a rubber hose is provided by the non-circular component  34 , there is no need to use pulsation dampers as is described as prior art, which affords a reduction in the number of parts. 
     Also, because the fuel hose  30  is formed from a resin, the cost is lower than when rubber is used. 
     The same or better effect as with a rubber hose can be obtained as long as the proportional volumetric change of the fuel hose  30  is at least 7 mm 3 /(MPa−mm), but 15 mm 3 /(MPa−mm) or higher is preferable because there will be virtually no perceptible noise. FIG. 8 is a diagram illustrating the steps involved in manufacturing the fuel hose  30 . The fuel hose  30  is manufactured by using extrusion or a mold to form the external shape of the hose. In FIG. 8, a hose manufacturing apparatus  50  comprises an extruder  51  for extruding a resin tube  30 A, a mold unit  52  for forming the external shape of the resin tube  30 A extruded from the extruder  51 , and a conveyor (not shown) for conveying the mold unit  52  in a loop. 
     The mold unit  52  comprises a circular component mold  53 , a bellows mold  54 , and an non-circular component mold  55 , with these disposed in a loop on both sides of the route over which the rubber tube is conveyed. The circular component mold  53  has a cylindrical cavity for forming a circular cross sectional shape. FIG. 9 is a cross section of the bellows mold  54  in the axial direction. As shown in FIG. 9, the bellows mold  54  has a molding surface  54   a  with an undulating cross sectional shape. for forming the bellows components  33 . Suction passages  54   b  that connect to a suction pump (not shown) are included in this molding surface  54   a.  FIG. 10 is an oblique view of the non-circular component mold  55 . The non-circular component mold  55  has a molding surface  55   a  with an undulating cross sectional shape in the direction perpendicular to the axial direction for forming the non-circular component  34 . Suction passages  55   b,  that are connected to the suction pump, are also provided in the molding surface  55   a.    
     The steps for manufacturing the fuel hose  30  with the above-mentioned hose manufacturing apparatus  50  will now be described. As shown in FIG. 8, the resin tube  30 A is extruded from the extruder  51 , and once this resin tube  30 A reaches a forming area FA, either the circular component mold  53 , the bellows mold  54 , or the non-circular component mold  55  of the mold unit  52 , which are conveyed one after the other, in a selected sequence, in a loop by the conveyor, will enclose or surround the outer periphery of the resin tube  30 A, and the mold will be tightened from both sides. Suction is then applied by the suction apparatus through the suction passages  54   b  or  55   b  which pulls the resin tube  30 A tightly against the molding surfaces  54   a  or  55   a.  Specifically, the resin tube  30 A assumes the circular form of the component  31  with a circular cross section when molded by the circular component mold  53 , or it assumes the shape of the bellows component  33  when molded by the bellows mold  54 , or assumes the shape of the noncircular component  34  when molded by the non-circular component mold  55 . Thus, the fuel hose  30  can be continuously formed with different cross sectional shapes depending on which mold component is used by the hose manufacturing apparatus  50 . 
     Since the fuel hose  30  can thus be continuously manufactured by a molding step that follows an extrusion step, there is no increase in cost. 
     The fuel hose  30  can be manufactured by any ordinary method that allows the molding of the bellows components  33  and the non-circular components  34 , and a variety of methods can be employed, examples of which include injection molding, continuous extrusion blow molding, and single part blow molding. 
     The present invention is not limited to the above examples, and can be worked in a variety of embodiments within the scope of the essence thereof. 
     The non-circular components  34  are formed as a star shape by the ribs  34   a,  but there are no particular restrictions as long as the shape is one that allows for easy radial distention from a non-circular shape. A polyhedral shape, for example, may be used. 
     The present invention is not restricted to the above embodiments, but there may be many other modifications, changes, and alterations without departing from the scope or spirit of the main characteristics of the present invention.