Patent Publication Number: US-2020291956-A1

Title: Centrifugal Pump

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese patent application serial number 2019-044517, filed Mar. 12, 2019, which is hereby incorporated herein by reference in its entirety for all purposes. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND 
     This disclosure relates generally to centrifugal pumps. 
     One type of centrifugal pump includes an impeller rotated by a motor and a housing defining a pump chamber therein. The impeller is housed in the pump chamber and includes a main plate having a substantially circular shape and a plurality of blades on the main plate. The housing has an inlet port and an outlet port that each provide fluid communication between the inside and the outside of the pump chamber. The inlet port extends upward from the pump chamber and is coaxially aligned with the impeller. 
     Japanese Laid-Open Patent Publication No. 2015-190321 discloses another type of centrifugal pump in which the inlet port of the housing is bent in an L-shape. In particular, an inlet passage within the inlet port is divided into a connection passage part and a main passage part. The connection passage part extends upward from the pump chamber. The main passage part is connected to an upstream end of the connection passage part at a right angle. 
     BRIEF SUMMARY 
     In one aspect of this disclosure, a centrifugal pump includes an impeller configured to be rotated about an axis of rotation in a rotational direction and a housing defining a pump chamber that houses the impeller therein. The housing includes an inlet passage and an outlet passage, each of which provides fluid communication between the pump chamber and the outside of the housing. The pump chamber has an inflow part at an upstream end thereof. The inflow part has an inflow end at an upstream end thereof and may have a hollow tapered shape with a width that continuously decreasing toward the inflow end. The inlet passage includes a connection passage part that may have a cylindrical shape coupled to the inflow end of the inflow part and a main passage part that may have a cylindrical shape connected to the connection passage part, so as to form a bent shape. A central axis of the main passage part is oriented parallel to a reference plane that includes a central axis of the connection passage part. The main passage part is configured such that a flow direction of a fluid parallel to the central axis of the main passage part is the same as at least one part of the rotational direction of the impeller in a plan view along the axis of rotation of the impeller. 
     In accordance with this aspect, the main passage part is configured such that a flow direction of fluid along the central axis of the main passage part is same as the rotational direction of the impeller in at least one place. Thus, when fluid flowing linearly in the main passage part enters the connection passage part, the fluid rotates in a same direction as the rotational direction of the impeller while flowing through the connection passage part. Accordingly, the fluid can smoothly flow from the connection passage part into the inflow part of the pump chamber. Accordingly, non-uniform distribution of the fluid on the impeller can be reduced, thereby improving the performance of the centrifugal pump. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed description of the preferred embodiments of the present teaching, reference will now be made to the accompanying drawings. 
         FIG. 1  is a partial cross-sectional plan view of a first embodiment of a centrifugal pump. 
         FIG. 2  is a cross-sectional view of the centrifugal pump of  FIG. 1 , taken along section II-II of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the centrifugal pump of  FIG. 1 , taken along section III-III of  FIG. 1 . 
         FIG. 4  is a cross-sectional view of a second embodiment of a centrifugal pump. 
         FIG. 5  is a cross-sectional view of a third embodiment of a centrifugal pump. 
         FIG. 6  is a cross-sectional view of a fourth embodiment of a centrifugal pump. 
         FIG. 7  is a partial cross-sectional plan view of a fifth embodiment of a centrifugal pump. 
     
    
    
     DETAILED DESCRIPTION 
     The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment. 
     As previously described, Japanese Laid-Open Patent Publication No. 2015-190321 discloses a centrifugal pump in which the main passage part of the inlet is connected to the upstream end of the connection passage part of the inlet at a right angle. Consequently, a central axis of the main passage part is oriented perpendicular to a central axis of the connection passage part. Thus, fluid flowing through the main passage part tends to flow into the far side of the connection passage part. As a result, the volume of flow of the fluid proximal the far side of the connection passage part is typically greater than the volume of flow of the fluid proximal the near side of the connection passage part. This causes the fluid to enter the pump chamber in an imbalanced manner, such that the fluid is not dispersed uniformly over the impeller. Such lack of uniformity in the fluid distribution decreases the performance of the centrifugal pump. Therefore, there has been a need for an improved centrifugal pump. 
     A first embodiment will be described with reference to  FIGS. 1 to 3 . The first embodiment of a centrifugal pump  10  is a purge pump mounted on a vehicle, such as an automobile. The purge pump is configured to compensate for a shortage of purge gas flowing from a canister to an air intake passage of an internal combustion engine. In each drawing, directions of the centrifugal pump  10  are illustrated for convenience of explanation, however, these directions do not limit a mounting direction of the centrifugal pump  10  on the vehicle. 
     As shown in  FIG. 2 , the centrifugal pump  10  includes a housing  11  having a substantially hollow cylindrical shape. The housing  11  may be made from a resin material, a metal material, or other suitable material. The centrifugal pump  10  also includes a pump section  12  at an upper portion of the housing  11  and a motor section  14  positioned below the pump section  12 . The motor section  14  has a brushless motor and includes a rotational shaft  15  extending in the vertical direction. The motor section  14  may also be referred to herein as “motor.” 
     The housing  11  defines a pump chamber  17  in an upper portion thereof. The pump chamber  17  has a hollow short cylindrical shape and is coaxially aligned with the rotational shaft  15  of the motor section  14 . The housing  11  is divided into an upper housing member  11   a  and a lower housing member  11   b  coupled to the upper housing member  11   a . The pump chamber  17  is defined by the upper housing member  11   a  and the lower housing member  11   b . The rotational shaft  15  of the motor section  14  penetrates the lower housing member  11   b  so as to protrude into the pump chamber  17 . 
     The pump chamber  17  has an inflow part  18  positioned at a center of an upper portion of the pump chamber  17  and a volute part  19  disposed at an outer circumferential part of the pump chamber  17 . The inflow part  18  has an inflow end  18   a  at an upper end thereof, such that fluid flows into the inflow part  18  via the inflow end  18   a . The inflow part  18  has a tapered shape with a width that gradually decreases in cross-sectional area moving toward the inflow end  18   a , i.e. toward the upstream side. 
     The upper housing member  11   a  includes an inlet port  22  at an upper portion thereof. The inlet port  22  is a tubular defining an inlet passage  23  therein, such that the pump chamber  17  is in fluid communication with the outside of the housing  11  via the inlet passage  23 . Details of the inlet passage  23  will be described hereinbelow. 
     As shown in  FIG. 1 , the housing  11  includes an outlet port  27  having a hollow cylindrical shape extending leftward from a front portion of the housing  11 . In a plan view of the centrifugal pump  10 , the outlet port  27  extends tangentially from an outer circumference of the housing  11 , i.e. leftward. The outlet port  27  defines an outlet passage  28  therein, such that the volute part  19  of the pump chamber  17  is in a fluid communication with the outside of the housing  11  via the outlet passage  28 . 
     As shown in  FIG. 2 , an impeller  30  is rotatably housed in the pump chamber  17 . The impeller  30  includes a main plate  32  and a plurality of blades  34  extending from the main plate  32 . The main plate  32  has a substantially circular plate shape in a plan view. In addition, the main plate  32  has a convex part  32   a  having a truncated conical shape at a central portion of an upper surface thereof. The convex part  32   a  is coaxially positioned along the main plate  32 . The convex part  32   a  has a shaft hole  33  at a central portion thereof. Shaft hole  33  is coaxially aligned with main plate  32  and rotational shaft  15 . The blades  34  protrude upward from the upper surface of the main plate  32  and extend in a substantially radial direction along the upper surface of the main plate  32 . Each of the blades  34  has an elongated rectangular shape extending in the radial direction of the impeller  30 . A radially inner end of each blade  34  is positioned in a lower portion of the inflow part  18  of the pump chamber  17 . The impeller  30  may be made from a resin material, metal material, or other suitable material. 
     The rotational shaft  15  of the motor section  14  is inserted into the shaft hole  33  of the impeller  30  and fixably secured thereto. Thus, when the motor section  14  is running, the impeller  30  rotates with the rotational shaft  15 . As shown in  FIG. 1 , in the plan view of the centrifugal pump  10 , the impeller  30  rotates about its central axis in a rotational direction R in a clockwise direction. 
     When the motor section  14  is driven using electricity supplied from an external power source, the impeller  30  is rotated together with the rotational shaft  15 , so that fluid, i.e. purge gas in this embodiment, is suctioned into the pump chamber  17  via the inlet passage  23 . The purge gas is pressurized and then discharged into the outflow passage  28  via rotation of the impeller  30 . The purge gas may be pumped by the centrifugal pump  10  in this manner. 
     As shown in  FIG. 2 , the inlet passage  23  is divided into a main passage part  24  and a connection passage part  25 , each of which has a cylindrical cross-sectional shape. The connection passage part  25  extends upward from the inflow end  18   a  of the inflow part  18 . The main passage part  24  is connected to the connection passage part  25 , so as to extend radially outward from the connection passage part  25  and form a bent shape therewith. More specifically, in this embodiment, the main passage part  24  is connected to the connection passage part  25  to form substantially a right angle along one plane, for instance a plane including the left-right and front-rear directions with the main passage part  24  extending rightward. The connection passage part  25  has the same inner diameter as the inflow end  18   a . The inner diameter of the main passage part  24  is equal to or greater than the inner diameter of the connection passage part  25 . For example, the inner diameter of the main passage part  24  may be about one and a half times greater than the inner diameter of the connection passage part  25 . 
       FIG. 1  illustrates a reference plane  25   s  containing a central axis  25   c  of the connection passage part  25  and extending radially in the right-left direction, and oriented parallel to a central axis  24   c  of the main passage part  24 . In the plan view of the centrifugal pump  10  of  FIG. 1 , the central axis  24   c  of the main passage part  24  is positioned in front of (and oriented parallel to) the reference plane  25   s . That is, the central axis  24   c  of the main passage part  24  deviates forward from the reference plane  25   s  by an offset distance L such that a flow direction F parallel to the central axis  24   c  is substantially the same as the rotational direction R of the impeller  30  in at least one place in the plan view of the centrifugal pump  10 . The central axis  25   c  of the connection passage part  25  is coaxially aligned with the rotational axis of the impeller  30 . 
     In the plane view of the centrifugal pump  10 , the main passage part  24  is directly connected to the connection passage part  25 , on one side of the connection part closer to the reference plane  25   s  (the rear side in  FIG. 1 ), such that an inner surface  24   a  of the main passage part  24  and an inner surface  25   a  of the connection passage part  25  form a sharp corner  26  having a convex shape. The inlet port  22  includes an inclined surface  29 , connecting the main passage part  24  to the connection passage part  25 , on the other side farther from the reference plane  25   s  (the front side in  FIG. 1 ), such that the inner surface  24   a  is gently continued to the inner surface  25   a  via the inclined surface  29 . 
     As shown in  FIG. 2 , the inflow end  18   a  of the pump chamber  17  is positioned proximal the midpoint between the central axis  24   c  and a bottom surface  24   b  of the main passage part  24  in the vertical direction. Due to this arrangement, a part of the main passage part  24  is in direct fluid communication with the inflow part  18 . More specifically, a lower end part of the main passage part  24  is in direct fluid communication with the upper end of the inflow part  18 . 
     As shown in  FIG. 1 , the outlet port  27  has a hollow cylindrical cross-sectional shape defining the outlet passage  28  therein. The outlet passage  28  extends in a tangential direction from the pump chamber  17 , such that a flow direction in the outlet passage  28  is substantially the same as the rotational direction R at a connection portion between the outlet passage  28  and the pump chamber  17 . The inlet port  22  extends rightward, and the outlet port  27  extends leftward. So, the central axis  24   c  of the main passage part  24  is oriented parallel to a central axis  28   c  of the outlet passage  28 . In this embodiment, the plan view of the centrifugal pump  10  corresponds to a view along an axial direction of the pump chamber  17 . The term “parallel” may include “substantially parallel.” 
     In accordance with the first embodiment, the central axis  24   c  of the main passage part  24  is not included in the reference plane  25   s , the plane which includes the central axis  25   c  of the connection passage part  25 , such that the flow direction F along the central axis  24   c  is substantially the same as the rotational direction R of the impeller  30  in at least one place, in the plan view of the centrifugal pump  10 . Thus, when the fluid flowing in the main passage part  24  enters the connection passage part  25 , the fluid rotates in a same direction S as the rotational direction R of the impeller  30  while flowing through the connection passage part  25 . That is, while the fluid flows through the connection part  25 , it has a rotational flow component. As a result, flow of the fluid can smoothly transition from the connection passage part  25  into the inflow part  18  of the pump chamber  17 . Accordingly, non-uniform distribution of the fluid on the impeller  30  can be reduced, thereby improving the performance of the centrifugal pump  10 . 
     As previously described, the main passage part  24  and the connection passage part  25  intersect at the sharp corner  26  on the one side closer to the reference plane  25   s . The sharp corner  26  facilitates generation of the rotational flow in the connection passage part  25 , thereby improving the performance of the centrifugal pump  10 , in comparison with a case where the main passage part  24  gently transitions to the connection passage part  25 , without the sharp corner  26 . 
     A part of the main passage part  24  is in direct fluid communication with the inflow part  18 . Thus, a part of the fluid flowing through the main passage part  24  can flow directly into the inflow part  18  of the pump chamber  17 , without passing through the connection passage part  25 . This reduces the moving distance of a portion of the fluid flow. Accordingly, in comparison with a case where the whole of the main passage part  24  is indirectly connected to the inflow part  18  via the connection passage part  25 , the performance of the centrifugal pump  10  can be increased. 
     In the plan view of the centrifugal pump  10 , the central axis  24   c  of the main passage part  24  is oriented parallel to the central axis  28   c  of the outlet passage  28 . Thus, in comparison with a case where the central axes  24   c ,  28   c  are not oriented parallel with each other in the plan view of the centrifugal pump  10 , a pipe can be easily connected to each of the main passage part  24  and the outlet passage  28 , thereby improving the mountability of the centrifugal pump  10  on a vehicle, etc. In the plan view of the centrifugal pump  10 , the inlet passage  23  may be oriented in the same direction as the outlet passage  28 , e.g. leftward in  FIG. 1 . 
     A second embodiment will be described with reference to  FIG. 4 . The second embodiment is substantially the same as the first embodiment described above, with some differences regarding the inlet passage  23 . Thus, while the differences will be described, similar configurations will not be described in the interest of conciseness. As shown in  FIG. 4 , the bottom surface  24   b  of the main passage part  24  is even with the inflow end  18   a  of the pump chamber  17 , in the vertical direction. Due to this configuration, the main passage part  24  is indirectly connected, via the connection passage part  25 , to the inflow part  18 . Thus, the axial length of the connection passage part  25  is longer than that of the first embodiment. 
     A third embodiment will be described with reference to  FIG. 5 . The third embodiment is substantially the same as the first embodiment described above, with some differences regarding the inlet passage  23 . Thus, while the differences will be described, similar configurations will not be described in the interest of conciseness. As shown in  FIG. 5 , the bottom surface  24   b  of the main passage part  24  is positioned above the inflow end  18   a  of the pump chamber  17  in the vertical direction. Accordingly, the main passage part  24  is indirectly connected, via the connection passage part  25 , to the inflow part  18  such that the axial length of the connection passage part  25  is longer than those of both the first embodiment and the second embodiment. 
     A fourth embodiment will be described with reference to  FIG. 6 . The fourth embodiment is substantially the same as the first embodiment described above, with some differences regarding the inlet passage  23 . Thus, while the differences will be described, similar configurations will not be described in the interest of conciseness. As shown in  FIG. 6 , the main passage part  24  extends obliquely upward, such that an angle formed by the central axis  24   c  of the main passage part  24  and the central axis  25   c  of the connection passage part  25  is about 110 degree. The degree of inclination can be set freely based on various requirements, such as a mounting space. 
     A fifth embodiment will be described with reference to  FIG. 7 . The fifth embodiment is substantially the same as the first embodiment described above, with some differences regarding the outlet passage  28 . Thus, while the differences will be described, similar configurations will not be described in the interest of conciseness. As shown in  FIG. 7 , the main passage part  24  extends in the right-left direction, and the outlet passage  28  extends in the front-rear direction, such that the central axis  24   c  of the main passage part  24  is oriented perpendicular to the central axis  28   c  of the outlet passage  28  in the plan view of the centrifugal pump  10 . The outlet passage  28  may be oriented such that the central axis  28   c  crosses the central axis  24   c  at any angle. The term “perpendicular” includes “substantially perpendicular” in this disclosure. 
     As stated above, the technique disclosed in this application is not limited to the above-described embodiments. For example, the centrifugal pump  10  may be used for pumping various fluids, such as air, other than the above described purge gas. The brushless motor of the motor section  14  may be replaced with a brushed motor. The centrifugal pump  10  may be composed of the pump section  12  only, such that the rotational shaft  15  is rotated by a driving source that is provided outside the centrifugal pump  10 . The impeller  30  may be made from a metal or other material.