Patent Publication Number: US-7722311-B2

Title: Pressure and current reducing impeller

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. patent application Ser. No. 11/330,271 filed on Jan. 11, 2006. The disclosure of the above application is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates to a secondary air fan used in a motor vehicle. 
   BACKGROUND OF THE INVENTION 
   When an engine goes through a cold start condition a secondary air flow fan can be used to inject air into the engine&#39;s exhaust system. The reason the air is injected into the exhaust system is so that oxygen is present in the exhaust system and causes excess hydrocarbons to be combusted. This also helps the catalytic converter to perform efficiently or achieve optimal temperature in a shorter amount of time. 
   An impeller fan can be used to create the air movement in the secondary air flow system. One phenomena that can occur with secondary air flow systems is what is referred to as “dead head” condition. A dead head condition is when the air flow or output channel from the impeller becomes blocked. In other words, due to impeller design the pump will reach dead head at relatively high pressures and prevent the downstream valve from closing. 
   Furthermore, as the pressure increases the electrical current drawn by the motor increases. This is an undesirable condition because it is a drag on the vehicle electrical system. Therefore, it is desirable to develop an impeller that would reduce the pressure at the dead head condition, and thus reduce the amount of current drawn by the impeller. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a pump having a housing with a torus and a stripper region that is a region between an inlet and outlet of the pump. The stripper region has a housing groove formed on the surface of the stripper region. The housing groove has a surface forming a length and width of the groove. The housing groove has at least one tapered depth section on said surface of said housing groove. The pump also has a cover connectable to the housing and cover. The cover extends over the housing groove formed on the surface of the stripper region. An impeller has a plurality of vanes that extend radially outward from an impeller frame, wherein the impeller is rotatably positioned between the housing and cover. The cover and the plurality of vanes are positioned in operable relation to said housing groove. 
   Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is a perspective view of the impeller fan; 
       FIG. 1   a  is a top plan view of a vane with Line A-A depicting the thickness of the vane; 
       FIG. 1   b  is a side plan view of a single vane with Line B-B depicting the height of the vane; 
       FIG. 2  is a cross-sectional view of the impeller fan; and, 
       FIG. 3  is a line graph showing the flow, back pressure, and current characteristics of the secondary air pump. 
       FIG. 4  is a perspective view of the impeller fan without a divider; 
       FIG. 5   a  is a sectional plan view of the pump housing having a housing groove with a tapered depth section formed thereon; 
       FIG. 5   b  is a sectional plan view of the pump cover having a cover groove with a tapered depth section formed thereon; 
       FIG. 6  is a partially broken away sectional view of the housing of  FIG. 5   a.    
       FIG. 7  is a sectional side view of the cover, housing and impeller assembly assembled; 
       FIG. 8  is a partially broken away perspective view of an alternate embodiment of the impeller fan. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
   Referring to  FIGS. 1 ,  1   a ,  1   b , and  2 , an impeller fan is generally shown at  10  and the impeller  10  has a casing  12 . The casing  12  has an inlet (not shown) and an outlet (not shown), in which the air flows in and out of the casing  12  respectfully. The center of the impeller  10  has an inner radial surface  14  that creates an axial bore where a shaft (not shown) can extend through the axial bore. The impeller fan  10  can then rotate. The impeller fan  10  has at least one radial support  16  that is spaced circumferentially around the inner radial surface  14 , and extends radially to an outer radial surface  18 . Therefore, the radial supports  16  connect the inner radial surface  14  with the outer radial surface  18 . 
   Vanes  32  are spaced circumferentially around the impeller frame  26 . The spacing of the vanes  32  around the outer radial surface  18  creates vane grooves  34  between each of the vanes  32 . The vanes  32  have a base  35  that is connected to an impeller frame  26 . The vanes  32  are angled at a point  40 , such that neither an outer angled surface  42  nor the base  35  extend directly radially from the impeller frame  26 . The vanes  32  have an inner angled surface  38  and the outer angled surface  42 , which meet at the point  40 , and the angle at which the vane  32  extends from the impeller frame  26  can be altered. Thus, the point  40  can be anywhere along the length of the vane  32 . 
   Furthermore, vanes  32  have a tapered thickness that is shown in  FIG. 1   a , which depicts a top view of a single vane  32  separated from the impeller  10 . The thickness of the vane is shown at Line A-A in  FIG. 1   a . Thus, the vane  32  has a thickness that is greater at point  40  than the thickness of the vane  32  at the base  35  and at a vane tip  33 . The thickness of the vane  32  can vary along its length or can be constant. 
     FIGS. 1   b  and  2  depict a side view of an individual vane shown in  FIGS. 1 and 1   a . The height of the vane  32  is shown along Line B-B in  FIG. 1   b . Between the base  35  and the point  40  of each vane  32  there is a pressure relief feature  37 . This pressure relief feature  37  is a curved recess of varying height in the vane  32  that will cause pressure relief as the vane moves within the casing  12 . In particular the pressure relief feature  37  will relieve pressure between the inlet and outlet of the pump which reduces pressure at a deadhead condition. The divider  36  can be located at any position along the height of the vane  32 . Additionally the divider  36  can extend radially anywhere from the base  35  to the tip  33  of the vane  32 . 
   The pressure relief feature  37  in the height of the vanes  32  changes the flow characteristics of impeller fan  10 , so that a dead head pressure is reduced when compared to the dead head pressure created by a standard impeller fan. The vanes  32  in combination with the pressure relief feature  37  all contribute to pressure relief provided by the impeller fan  10 . If the divider  36  is used, it will create an upper flow area  48  and a lower flow area  50 . The impeller fan  10  having vanes  32  in conjunction with the divider  36  increases the flow, whereas an impeller fan that has no divider  36  decreases the flow. 
   The pressure relief feature  37  of the vanes  32  and the divider  36  create a flow rate in the upper flow area  48  and a flow rate in the lower flow area  50 . Both the upper flow area  48  and the lower flow area  50  have a pressure leakage between the inlet and outlet along the sealing area via the pressure relief feature  37 . The leakage reduces the pressure in the upper flow area  48  and the lower flow area  50 , which in turn reduces the dead head pressure. Thus, the reduction of the dead head pressure also reduces the amount of current drawn by the impeller fan  10 . 
     FIG. 4  depicts an embodiment where the impeller  10  has no divider extending between the vanes  32 . However, the vanes  32  still have the pressure relief feature  37 . 
   Referring to  FIG. 3 , the flow, backpressure, and current characteristics are compared between a secondary air system using the impeller fan  10  and a standard impeller fan (one that does not have a vane design as the present invention). A line  52  depicts the flow and back pressure characteristics of the standard impeller fan. Line  56  shows that as the back pressure increases in the standard impeller fan the current continues to increase. Thus, the standard impeller fan causes the back pressure to increase to a final value that is to great for the secondary air system, and the back pressure is greater than 22 kPa when the flow is at 0.0 L/min. However, when the impeller fan  10  is used in the secondary air system the back pressure does not reach a maximum back pressure that is as high as that of a standard impeller fan, as shown by line  54 . Therefore, when the flow is at 0.0 L/min the back pressure is approximately 22 kPa, which is lower than the standard dead head condition. Thus, the dead head pressure of the impeller fan  10  is approximately 20% less than a standard impeller. Likewise, the current draw of the impeller fan  10  is approximately 25% lower at the dead head condition, than a standard impeller fan at a dead head condition. Moreover, line  56  shows the amount of electrical current drawn by the standard impeller fan from the vehicle electrical system (not shown) as the back pressure increases. If a dead head condition is desired in the secondary air system, the system may not function properly if the back pressure is over 25 kPa. These high back pressures result in high current drain in excess of 60 A. However, impeller fan  10  not only results in max back pressure less than 25 kpa but also does not draw as much current as the standard fan. Thus, the impeller fan  10  puts less strain on the vehicle electrical system. 
   Referring to  FIGS. 5-7  an alternate embodiment of a pump  100  is depicted. The pump  100  has a housing  102  and a cover  104  is connectable to the housing  102  when the pump  100  is assembled. 
   The cover  104  has an inlet  106  and outlet  108 . The cover has a torus  110  that defines the path of air flow between the inlet  106  and the outlet  108 . A stripper region  112  of the cover  104  separates the inlet  106  and outlet  108 . The stripper region  112  forms a sealing surface for sealing off flow between the inlet  106  from the outlet  108 . Although this particular embodiment of the invention shows the inlet  106  and outlet  108  located on the cover  104 , it is within the scope of this invention for the inlet  106  and outlet  108  to be located in the housing  102 . The stripper region  112  has a cover groove  114  that provides pressure relief between the inlet  106  and outlet  108 . The cover groove  114  has a surface forming a length, width and depth. The cover groove  114  can be continuous across the stripper region  112  or it can be a plurality of interrupted grooves. The length, width and depth of the cover groove can also vary. 
   The housing  102  has a torus  116  that aligns with the torus  110  of the cover  104  when the pump  100  is assembled. The presence of a torus on both cover  104  and housing  102  is not required by the present invention. The torus  116  on the housing  102  defines a path of air flow between the inlet  106  and outlet  108 . The housing  102  also has a stripper region  118  that aligns with the stripper region  112  of the cover  104 . The stripper region  118  can also form a sealing surface for sealing off flow between the inlet  106  and outlet  108 . The housing groove  120  has a surface forming a length, width and depth. The housing groove  120  can be continuous across the stripper region  118  or can be a plurality of interrupted grooves. The length, width and depth of housing groove  120  can also vary. The housing groove  120  has at least one tapered depth section on said surface of said housing groove  120 . 
   The housing groove  120  also assists in the pressure relief feature of the pump  100 . However, it is not necessary that both the housing  102  and cover  104  each have grooves in order for the advantages of the present invention to be realized. It is within the scope of this invention for only one groove to be used. 
   Referring to  FIG. 8 , another embodiment of the invention having a modified impeller fan  200  is shown. The impeller fan  200  has vanes  202  having a pressure relief feature  37  and vanes  204  having no pressure relief feature and alternating with the vanes  202 . While this particular embodiment of the invention depicts the vanes  202  alternating from the vanes  204  it is within the scope of this invention for the vanes to be arranged in virtually any order. For example it is possible to have two or more vanes with pressure relief features or to have two or more vanes without pressure relief features. The arrangement of the vanes will depend on the particular need of a given application. 
   The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.