Patent Publication Number: US-7217085-B2

Title: Fuel pump of low fuel intake resistance

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application is based on and claims priority from Japanese Patent Application 2004-374068, filed Dec. 24, 2004, the contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a fuel pump that has a pump housing and an inlet port at a side of the pump housing. 
   2. Description of the Related Art 
   A fuel pump that has a pump housing, a pump passage having an inlet port, a motor and an impeller housed in the pump housing is well-known for pressurizing fuel in the pump passage, as disclosed in U.S. Pat. No. 6,942,447 B2 or JP-A-2004-100675 that is a counter part of the U.S. patent. 
   In the above fuel pump, the inlet port is opened at a circumferential side of the pump housing or the impeller to take fuel into the pump passage formed along the periphery of the impeller. Therefore, the fuel intake resistance of this type is smaller than another type of fuel pump that has an inlet port opened in the direction perpendicular to the rotation direction of the impeller. That is, the pump efficiency of the former fuel pump is higher than the latter fuel pump. 
   Incidentally, the pump efficiency P eff  is expressed as follows: 
   P eff =(P×Q)/(T×N), wherein: T is a torque of the motor; N is a rotation speed of the motor; P is a pressure of fuel; and Q is a quantity of fuel discharged from the pump. 
   If the fuel intake resistance is reduced, the quantity of fuel to be discharged by the pump increases, and the pump efficiency increases. 
     FIG. 5  shows a fuel pump in which an inlet port  212  of a pump passage  210  is formed on a side of a pump housing  200 . In the fuel pump, an intake resistance is generated when fuel is taken from portions around the inlet port  212  into the pump passage  210 . In particular, the streamlines of the fuel flow peel off when the direction of the fuel flow sharply changes at an edge  214  of the inlet port  212 . Accordingly, the effective sectional area of the fuel passage for taking fuel into the pump passage  210  reduces, resulting in that the fuel intake resistance increases to thereby reduce the pump efficiency. 
   SUMMARY OF THE INVENTION 
   Therefore, an object of the invention is to provide an improved fuel pump that has a high pump efficiency. 
   According to a feature of the invention, a fuel pump includes a motor section, a pump section, a feed passage member having a feed passage and a suction filter. The pump section includes an impeller and a pump housing having a pump passage extending along the outer periphery of the impeller so that the impeller can pressurize fuel that is fed from the suction filter through the feed passage. In the pump section, the pump passage has an inlet port opening at a side of the pump housing, and the feed passage smoothly extends toward the inlet port to be connected thereto at one end thereof. 
   With the above construction, fuel flows from the suction filter to the pump passage without peeling off. Therefore, the intake resistance of the fuel becomes lower. As a result, the pump efficiency is improved. 
   Preferably, the feed passage extends in line with the upstream portion of the pump passage. Further, one end of the feed passage connected to the pump passage has approximately the same cross-sectional area as the inlet port of the pump passage. Furthermore, the feed passage may have a shape tapering off toward the inlet port. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings: 
       FIG. 1  illustrates a longitudinal cross-section of a fuel pump according to the first embodiment of the invention; 
       FIG. 2  is a cross-sectional plan view of the fuel pump shown in  FIG. 1  cut along line II-II; 
       FIG. 3  is an enlarged view of a portion around an inlet port of a pump passage of the fuel pump according to the first embodiment; 
       FIG. 4  is a cross-sectional plan view of the fuel pump according to the second embodiment of the invention; and 
       FIG. 5  is a cross-sectional plan view of a prior art fuel pump. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   A fuel pump  10  according to the first embodiment will be described with reference to  FIGS. 1–3 . 
   The fuel pump  10  is an in-tank type fuel pump that is to be disposed in a fuel tank to pressurize fuel taken therein from the fuel tank via a suction filter  70 . The fuel discharged from the fuel pump  10  is supplied to an internal combustion engine. The fuel pump  10  includes a motor section  12 , a pump section  13  that is driven by the motor section  12 , an end support cover  14 , metal housing  16 , a filter cover  60 , etc. 
   The motor section  12  is a brushless motor that is constituted of a stator core  20 , coils  22  and a rotor  30 . The stator core  20  is constituted of axially laminated thin magnetic steel plates. The stator core  20  has six teeth that are disposed at equal intervals in the circumferential direction thereof to project toward the center of the motor section  12 . Each coil  22  is wound around one of the teeth. The stator  20  and the coils  22  are molded in the end support cover  14 . The metal housing  16  is also insert-molded in the end support cover  14  to support a pump cover  40 . The metal housing  16  has a plurality of through holes  16   a  in which a portion of resinous material of the end support cover  14  is filled. 
   The rotor  30 , which includes a shaft  32 , a rotary core  34  and a cylindrical permanent magnet  36 , is disposed inside the stator core  20 . The permanent magnet  36  is disposed to surround the rotary core  34 . The permanent magnet  36  has eight magnetic poles  37  formed in the rotating direction. The eight magnetic poles  37  are alternately polarized into N or S on the outer periphery thereof opposite the stator core  20 . 
   The pump section  13  includes the pump cover  40 , a pump casing  42 , an impeller  50 , etc. The pump cover  40  and the pump casing  42  form a cylindrical pump housing that supports and houses the impeller  50  so as to freely rotate therein. The pump casing  42  is sandwiched between the end support cover  14  and the pump cover  40  by means of the metal housing  16 . The pump cover  40  and the pump casing  42 , as a pump housing, provide two pump passages  110 ,  114  extending in a C-shape along the outer periphery of the impeller  50  on the opposite sides thereof. 
   The pump passage  110  has an inlet port  111  on the side of the pump cover  40 , an intake passage  112  at the upstream portion thereof adjacent to the inlet port  11  and a main passage  113  at the middle thereof. The pump passage  114  has an inlet port  115  at the upstream end thereof on the side of the pump casing  42 , an intake passage  116  at the upstream portion thereof adjacent to the inlet port  115  and a main passage  117  at the middle thereof. The fuel taken into the respective main passages  113 ,  117  is pressurized and discharged from respective discharge ports (not shown) of the pump casing  42  into fuel passage  120  between the stator core  20  and the rotor  30  and discharged from discharge port  122  of the fuel pump  10 . 
   The filter cover  60  is a resinous member force-fitted to the outer periphery of the pump section  13 . The filter cover  60  has a fuel inlet  62  at a side thereof and a fuel passage  100 . The suction filter  70  is force-fitted to the filter cover  60  to remove foreign particles contained in fuel. As shown in  FIG. 3 , the fuel from which foreign particles are removed by the suction filter  70  is taken into the fuel passage  100  of the filter cover  60  and divided into two feed passages  102 ,  104 , whose downstream ends are, respectively, smoothly connected to the intake passage  112 ,  116  of the pump passages  110 ,  114  at the inlet ports  111 ,  115 . The metal housing  16  has apertures  16   b  that respectively connect the feed passages  102 ,  104  and the inlet ports  111 ,  115 . Each of the feed passages  102 ,  104  is surrounded by a tapering wall that gradually narrows toward the inlet port  111  or  115 . Accordingly, no edge is formed at the inlet ports  111 ,  115 , so that the intake resistance of the feed passages  102 ,  104  can be kept to be low. 
   As shown in  FIG. 3 , the feed passages  102 ,  104  extend toward the inlet ports  111 ,  115  on the same plane as the pump passages  110 ,  114 , so that the direction in which the feed passages  102 ,  104  extend toward the inlet ports  111 ,  115  is almost the same as the direction in which intake passages  112 ,  116  extending between the inlet ports  111 ,  115  and the main passages  113 ,  117 . The feed passages  102 ,  104  are respectively connected to the inlet ports  111 ,  115  in the same shape and cross section thereof without a step or the like. Therefore, the fuel that is filtered by the suction filter  70  flows straight from the feed passages  102 ,  104  through the inlet ports  111 ,  115  into the pump passages  110 ,  114 . Therefore, the streamlines of the fuel flow are prevented from peeling off, so that the increase in the intake resistance can be prevented. 
   Second Embodiment 
   A fuel pump according to the second embodiment of the invention will be described with reference to  FIG. 4 . The same reference numeral hereafter indicates the same or substantially the same part, portion or component as the first embodiment. 
   A pump passage  130  formed in a pump casing  80  of the fuel pump according to the second embodiment has a fuel inlet port  131  whose cross-sectional area is formed to be larger than the cross-sectional area of the end of the feed passage  104  connected to the inlet port  131 . The feed passage  104  extends toward the inlet port  131  on the same plane as the pump passage  130 . The feed passages  104  is surrounded by the tapering wall  105  that gradually narrows toward the inlet port  115  in the same manner as the first embodiment. Although there is a small step between the feed passage  104  and the inlet port  131 , peeling-off of the stream lines is not so significant as that of the prior art discussed with reference to  FIG. 5 . 
   Variations 
   The tapering wall  105  may be replaced by a straight wall as far as the cross-sectional area of the end of the feed passage  104  connected to the inlet port  131  is approximately the same as the cross-sectional area of the inlet port  131 . 
   The motor section may be replaced by a permanent magnet type motor or other common DC motor. 
   In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments of the present invention without departing from the scope of the invention as set forth in the appended claims. Accordingly, the description of the present invention is to be regarded in an illustrative, rather than a restrictive, sense.