Patent Publication Number: US-6336788-B1

Title: Regenerative type pumps

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to pumps, and more particularly, to regenerative type pumps, which are also known as Wesco pumps. 
     2. Description of the Related Art 
     An example of a regenerative type pump is disclosed in Japanese Laid-Open Patent Publication No. 3-18688 and has an impeller rotatably disposed within a pump casing. The pump casing has an inlet port and a discharge port, both of which are fixed in position on opposite sides of the impeller. A plurality of blade grooves are formed along the perimeter of the impeller. Fluid is drawn through the inlet port by the impeller and discharged through the discharge port along a travelling path of the impeller blade grooves. The upper portion of the pump casing has a groove beginning with a groove inlet portion and ending with the discharge port. A partition is formed between the groove inlet portion and the discharge port and the partition forms a terminal end of the fluid path within the pump casing. 
     In such a regenerative type pump, if some of the high-pressure fluid collides with the terminal end of the fuel path without being smoothly discharged through the discharge port, high frequency noise is generated. 
     In order to reduce such noise in the terminal end of the fluid path, Japanese Laid-Open Patent Publication No. 6-288381 discloses a regenerative type pump in which an opening end face of the discharge port that faces the impeller has an opening width that gradually decreases along the direction of rotation of the impeller. In this publication, the inventors allege that fluid will smoothly pass through the passage and gradually contact a wall surface that defines the opening end face having the gradually tapered opening. Therefore, the inventors stated that noises caused by such collisions are reduced. However, based upon experiments performed by the Applicant, even in this regenerative type pump, some of the high-pressure fluid still collides with the terminal end passage on the downstream side of the discharge port. Therefore, this known pump does not significantly reduce noise generated in the termination of the fluid passage. 
     SUMMARY OF THE INVENTION 
     It is, accordingly, an object of the present invention to teach improved regenerative type pumps. Preferably, such improved regenerative type pumps generate less noise than known pumps. 
     In one aspect of the present teachings, regenerative type pumps are constructed such that the fluid is smoothly discharged from the discharge port and the amount of high-pressure fluid that collides against the terminal end of the discharge port is minimized. 
     In another aspect of the present teachings, a groove of substantially constant width is circumferently formed within an inner pump cover on the side of the inner pump cover that faces the impeller. The groove begins with a groove inlet portion, ends with the discharge port and a partition is disposed between the groove inlet portion and the discharge port. 
     Preferably, the opening portion of the discharge port has a tapered portion and a damping portion. The tapered portion has an opening width that gradually decreases in the circumferential direction. The damping portion is contiguous with the tapered portion and has an opening width that is substantially constant in the circumferential direction. This design allows high-pressure fluid to be smoothly delivered to and discharged from the discharge port. Therefore, the amount of high-pressure fluid that collides with the terminal end of the discharge port is decreased and pump noise can be reduced. 
     A corner portion may exist between the wall surfaces of the tapered portion and the damping portion of the discharge port and a lower surface of the inner pump cover. In one embodiment, this corner portion is chamfered to permit fluid to smoothly flow from the tapered portion to the damping portion. As a result, the fluid flow rate is not abruptly decreased in the terminal end of the tapered portion and pump noise can be further reduced. 
     A front wall surface of the discharge port, which can be disposed forward in the direction of rotation of the impeller, preferably includes an oblique surface that forms an acute angle with the lower surface of the inner pump cover. Thus, the fluid can smoothly flow into the discharge port along the oblique surface, so that the pump efficiency can be enhanced. Further, the discharge port can be easily manufactured by injection molding, due to the oblique configuration of the front wall surface of the discharge port. 
     Further, a rear wall surface may be located in the discharge port and rearward in the direction of rotation of the impeller. This rear wall surface preferably includes an oblique surface that forms an acute angle with the lower surface of the inner pump cover. Thus, the fluid can smoothly flow into the discharge port, so that the pump efficiency can be enhanced. 
     Additional objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a representative generative type pump; 
     FIG. 2 is a view of a first representative inner pump cover  9  as viewed from the side of the inner pump cover  9  that faces the impeller  16 ; 
     FIG. 3 is a view of the inner pump cover  9  from the opposite side of the side shown in FIG. 2; 
     FIG. 4 is a cross-sectional view of the inner pump cover  9 ; 
     FIG. 5 is an enlarged view of the discharge port  24  shown in FIG. 2; 
     FIG. 6 is an enlarged view of the opposite side of the discharge port that is shown in FIG. 3; 
     FIG. 7 is a cross-sectional view taken along line VII—VII shown in FIG. 5; 
     FIG. 8 is an enlarged view of FIG. 7; 
     FIG. 9 is a cross-sectional view taken along line IX—IX shown in FIG. 5; 
     FIG. 10 is a cross-sectional view taken along line X—X shown in FIG. 5; 
     FIG. 11 is a partial cross-sectional view of representative molding dies that can be utilized to mold inner pump cover  9 ; 
     FIG. 12 is a partial cross-sectional view of a second representative pump cover; 
     FIG. 13 is a cross-sectional view taken along line XIII—XIII shown in FIG. 12; 
     FIG. 14 is a graph showing the relationship between the shape of the inner pump cover discharge port and the noise generated by the pump; and 
     FIG. 15 is a graph showing the relationship between the chamfering angle of the inner pump cover discharge port and noise generated by the pump. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Regenerative type pumps generally include an impeller having a plurality of blade grooves formed along a perimeter of the impeller. The impeller is rotatably supported within a pump casing, which may comprise an outer pump cover having a fluid inlet port and an inner pump cover having a discharge port. Fluid can pass from the inlet port through the impeller and to the inner pump cover. The inner pump cover may include a fluid groove that circumferentially extends from a groove inlet portion to the discharge port and corresponds to the circular travelling path of the impeller blade grooves. A partition is typically formed between the groove inlet portion and the discharge port. 
     Preferably, an opening end face of the side of the discharge port that faces the impeller has a tapered portion and a damping portion. The tapered portion preferably has an opening width that gradually decreases in the circumferential direction. The damping portion is preferably contiguous with a downstream side of the tapered portion and has an opening width that is substantially constant in the circumferential direction. 
     A corner portion may exist between the wall surfaces defining the tapered portion and the damping portion of the discharge port and a lower surface of the inner pump cover. Preferably, this corner portion is chamfered. More preferably, the chamfering angle is between about 25° to 50°. 
     The discharge port may have a front wall surface located forward in the circumferential direction, which front wall surface may have an oblique surface that forms an acute angle with the lower surface of the inner pump cover. 
     The discharge port may have a rear wall surface that is located rearward in the direction of rotation of the impeller and includes an oblique surface that forms an acute angle with the lower surface of the inner pump cover. 
     Each of the additional features and method steps disclosed above and below may be utilized separately or in conjunction with other features and method steps to provide improved Regenerative type pumps and methods for designing and using such pumps. Representative examples of the present invention, which examples utilize many of these additional features and method steps in conjunction, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the following detail description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe some representative examples of the invention. 
     First Embodiment 
     FIG. 1 is a sectional view of a first representative embodiment, showing a fuel pump  1  for supplying fuel to a vehicle engine having a fluid inlet portion  3  and a motor receiving portion  2 . Preferably, a brush-type direct current motor is disposed within the motor receiving portion  2  and includes a magnet  5  coaxially disposed within a pump housing  4 . A rotor  6  is coaxially disposed within the magnet  5 . Bearing  10  rotatably supports a lower end portion  7   a  of a rotor shaft  7 , which is disposed within an inner pump cover  9 . The inner pump cover  9  is fixedly attached to the lower end of the pump housing  4 . An upper end portion  7   b  of the shaft  7  is rotatably supported by a bearing  13  disposed within a motor cover  12 . The motor cover  12  is fixedly attached to the upper end of the pump housing  4 . By supplying electric current to a rotor coil (not shown) via a terminal (not shown) provided on the motor cover  12 , the rotor  6  and thus the shaft  7  will rotate. Because motors that are capable of driving a fuel pump are well known in the art, further detailed description is not necessary. However, it should be noted that the motor is not limited to a brush-type direct current motor, but rather, various types of motors may be used with the present teachings. 
     The fluid inlet portion  3  preferably includes the inner pump cover  9 , an outer pump cover  15  and an impeller  16  disposed between the inner pump cover  9  and the outer pump cover  15 . The inner pump cover  9  and the outer pump cover  15  may be formed, for example, of die-cast aluminum. FIG. 2 shows an inner view of side of the inner pump cover  9  that go faces the impeller  16 . FIG. 3 is a view of the opposite side of the inner pump cover  9 . FIG. 4 is a cross-sectional view of the inner pump cover  9 . 
     The outer pump cover  15  may be secured, for example by caulking, to the lower end of the pump housing  4 . The outer pump cover  15  is thus fixed in position with respect to the inner pump cover  9 . A thrust bearing  18  is preferably fixed in the center of the outer pump cover  15  in order to receive the thrust load of the rotor shaft  7 . The inner pump cover  9  and the outer pump cover  15  form a pump casing  17 . As noted above, the impeller  16  is rotatably disposed within the pump casing  17 . 
     The impeller  16  is preferably molded from a resin and has a plurality of blade grooves  16   a  along the perimeter of the impeller  16 . The blade groove  16   a  may be of any form that will communicate fluid from the inlet port  22  in the outer pump cover  15  to the discharge port  24  in the inner pump cover  9 , such as the blade grooves  16   a  taught in WO 99/07990 and US patent application Ser. No. 09/269,739, which are hereby incorporated by reference. The impeller  16  may comprise a generally D-shaped engagement center hole  16   b  and the engagement stem portion  7   c  of the lower shaft portion  7   a  may have a corresponding D-shaped portion. By tightly fitting the engagement stem portion  7   c  within the engagement center hole  16   b , the impeller  16  is connected to the shaft  7 . As a result, the impeller  16  will together rotate with the shaft  7 . 
     As shown in FIGS. 1,  2  and  4 , a groove  21  is preferably formed in the circumferential direction of the inner pump cover  9 . Similarly, as shown in FIG. 1, a groove  20  also may be formed in the circumferential direction of the outer pump cover  15 . Both grooves  20  and  21  face the impeller  16  and are formed along the travelling path of the blade grooves  16   a  of the impeller  16 . 
     As shown in FIG. 1, an inlet port  22  is preferably formed in the outer pump cover  15  and a discharge port  24  is formed in the inner pump cover  9 . Fluid is communicated between the inlet port  22  and the discharge port  24  by means of the grooves  20  and  21  and the blade grooves  16   a  of the rotating impeller  16 . As shown in FIG. 2, a partition  25  is preferably formed between a groove inlet portion  23  and the discharge port  24  and serves to prevent back flow of fuel. A broken-line circle in FIG. 2 shows a preferred position of the inlet port  22  with respect to the groove inlet portion  23  and the discharge port  24 . That is, the inlet port  22  of the outer pump cover  15  is preferably disposed proximal to the groove inlet portion  23  of the inner pump cover  4 . 
     As shown in FIG. 1, the discharge port  24  extends through the inner pump cover  9  and communicates with an inner space  2   a  of the motor receiving portion  2 . 
     A preferred design for the discharge port  24  will now be explained with reference to FIGS. 5 to  10 . An opening end face of the side of the discharge port  24  that faces the impeller  16  preferably has a shape as shown in FIGS. 2 and 5. Specifically, the opening end face of the discharge port  24  that faces the impeller  16  has a tapered portion  24   a  and a damping portion  24   b . The tapered portion  24   a  is contiguous with the downstream end of the fluid groove  21  and has an opening width W that gradually decreases in the circumferential direction towards the discharge port  24 . The damping portion  24   b  is contiguous with the downstream side of the tapered portion  24   a  and has an opening width W that is substantially constant. 
     As shown in FIGS. 5,  9  and  10 , a corner portion  24   e  is formed at the intersection of wall surface  24   c  of the tapered portion  24   a , wall surface  24   d  of the damping portion  24   b  and a lower surface  9   a  of the inner pump cover  9 , which lower surface  9   a  faces the impeller  16 . In this representative embodiment, the corner portion  24   e  is chamfered at a chamfering angle θ1 with respect to the radial direction of the lower surface  9   a , as shown in FIG.  10 . 
     Further, as shown in FIG. 8, a front wall surface  24   f  of the discharge port  24  is located forward in the direction of rotation of the impeller  16 . Preferably, the front wall surface  24   f  forms an acute angle θ2 with the lower surface  9   a  of the inner pump cover  9 . The angle θ2 is the angle formed by the front wall surface  24   f  and the lower surface  9   a  with respect to the direction of rotation of the impeller  16 . An oblique surface  24   fa  is formed in the front end of the front wall surface  24   f  of the discharge port  24  and is preferably perpendicular to the lower surface  9   a . Thus, the front end of the front wall surface  24   f  does not have a pointed edge, which improves the durability of that portion of the inner pump cover  9 . 
     Further, as shown in FIG. 8, a rear wall surface  24   h  is located rearward of the discharge port  24  in the direction of rotation of the impeller  16 . Preferably, the rear wall surface also forms an acute angle θ3 with the lower surface  9   a . The angle θ3 is an angle of the lower surface  9   a  with respect to the direction of rotation of the impeller  16 . An oblique surface  24   ha  is formed in the rear end of the rear wall surface  24   h  and is preferably perpendicular to the lower surface  9   a . Thus, the rear end  24   ha  of the rear wall surface  24   h  also does not have a pointed edge, thereby improving the durability of that portion of the inner pump cover  9 . 
     A representative method for operating the fluid pump shown in FIGS. 1-10 will now be explained. When the rotor  6  rotates, the impeller  16  that is connected to the shaft  7  of the rotor  6  rotates in the direction shown by arrow R in FIGS. 2 and 7. Thus, the blade grooves  16   a  formed in the impeller  16  also rotate. Fluid, e.g. fuel from a fuel tank, is drawn into the inlet port  22  by the rotating impeller blades  16   a , is discharged through the discharge port  24 , passes through the inner space  2   a  of the motor receiving portion  2  and is exhausted at high pressure from the delivery port  28  formed in the motor cover  12 . The fluid may be fuel that is supplied to a fuel injector (not shown). 
     In this embodiment, the opening end face of the discharge port  24  on the side of the inner pump cover  9  that faces the impeller  16  has the tapered portion  24   a  and the damping portion  24   b . The tapered portion  24   a  is contiguous with the fluid groove  21  and has an opening width W that gradually decreases along the direction of rotation of the impeller  16 . The damping portion  24   b  is contiguous with the tapered portion  24   a  and has an opening width W that is substantially constant along the direction of rotation of the impeller  16 . Accordingly, most of the pressurized fuel that has been delivered to the discharge port  24  smoothly flows through the tapered portion and the damping portion of the opening end face of the discharge port  24  and is discharged from the discharge port  24  to the inner space  2   a  of the motor receiving portion  2 . Therefore, the amount of high-pressure fluid that collides with a terminal end passage on the downstream side of the discharge port  24  is decreased, thereby reducing pump noise. 
     Further, the chamfered corner portion  24   e  permits fuel to smoothly flow from the tapered portion  24   a  to the damping portion  24   b  of the opening end face of the discharge port  24 . Thus, pump noise can be further reduced. 
     In addition, the front wall surface  24   f  of the discharge port  24  can be formed at an acute angle with respect to the lower surface  9   a  of the inner pump cover  9  to permit the fuel to smoothly flow into the discharge port  24 . Thus, pump efficiency can be enhanced. 
     Finally, the discharge port  24  can be easily manufactured by injection molding the obliquely formed front wall surface  24   f  of the discharge port  24 . FIG. 11 is a partial cross-sectional view of representative molding dies for molding the inner pump cover  9  by using, for example, an upper die  30  and a lower die  32 . Because the front wall surface  24   f  of the discharge port  24  includes an oblique surface, the upper die  30  and the lower die  32  can be readily removed after forming the inner pump cover  9 . 
     Second Embodiment 
     A second representative embodiment will now be explained with reference to FIGS. 12 and 13, which is a modification of the first representative embodiment. Thus, only the modified portions of the first representative embodiment will be discussed in detail and components that are identical to or equivalent to components in the first embodiment will be identified by the same numerals as in the first embodiment. 
     In the second representative embodiment, a corner portion  24   g  is defined by wall surface  24   c  of the tapered portion  24   a , wall surface  24   d  of the damping portion  24   b  of the discharge port  24  and the lower surface  9   a  of the inner  10  pump cover  9 . In this embodiment the corner portion  24   g  is not chamfered. While the chamfered surface  24   e  (see FIGS. 5,  8  and  9 ) of the first representative embodiment is not provided, pump noise can still be reduced over known pumps. 
     EXPERIMENTAL RESULTS 
     Noise (dB) generated by operating the two fuel pumps of the first and second representative embodiment was measured and compared to noise generated by operating the known fuel pump described in Japanese Laid-Open Patent Publication No. 6-288381. FIG. 14 shows the measurement results, wherein Pa represents the noise level of the known fuel pump, Pb represents the noise level of the fuel pump of the second representative embodiment and Pc represents noise level of the fuel pump of the first representative embodiment. The ordinate represents the noise level in decibels (dB). The chamfered surface  24   e  of the fuel pump of the first embodiment was formed with a chamfering angle θ1 of 35°. As shown from FIG. 14, the fuel pump of the second representative embodiment was noticeably quieter than the known fuel pump and the fuel pump of the first embodiment was even quieter. 
     Further, the relationship between the chamfering angle θ1 of the chamfered surface  24   e  of the inner pump cover  9  and pump operating noise (dB) was measured for four fuel pump constructed with chamfered surfaces  24   e  according to the first representative embodiment. FIG. 15 shows the measurement results, in which the abscissa represents the chamfering angle θ1 and the ordinate represents the noise level (dB). As shown in FIG. 15, improved noise reduction can be obtained when the chamfering angle θ1 is between about 25° to 50°. 
     The present invention is not limited to the constructions that have been described as the representative embodiments, but rather, may be added to, changed, replaced with alternatives or otherwise modified without departing from the spirit and scope of the invention. For example, the application of the pump of the present invention is not limited to supply of vehicle fuel, but it may be used to supply a variety of fluids, such as water.