Centrifugal Pump
A centrifugal pump includes a housing and an impeller housed in the housing. The impeller has a main plate, a plurality of first blades, and a plurality of second blades. The first blades and the second blades extend radially along the main plate and have the same radial length. Each of the second blades has a low blade part and a high blade part extending radially from a radially outer end of the low blade part. When comparing the first blades and the second blades with each other at an equal distance from a rotational axis of the impeller, a height of the low blade part measured from the main plate is less than a height of each first blade measured from the main plate, and a height of the high blade part measured from the main plate is the same as that the height of each first blade.
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This application claims priority to Japanese patent application serial number 2019-048250, filed Mar. 15, 2019, which is hereby incorporated herein by reference in its entirety for all purposes.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable.
BACKGROUNDThis disclosure relates generally to centrifugal pumps.
One type of conventional centrifugal pump includes a housing defining a pump chamber therein and an impeller, which is housed in the pump chamber and has a plurality of blades. When the centrifugal pump is running, a fluid is suctioned into the pump chamber via an inlet port and supplied toward a central portion of the impeller. Most of the fluid flows from a space just above the central portion of the impeller into spaces between the blades through openings, each of which is defined by radially inner ends of circumferentially adjacent pairs of the blades. Then, the fluid is forced by the blades from the pump chamber to the outside via an outlet port.
BRIEF SUMMARYIn one aspect of this disclosure, a centrifugal pump includes a housing and an impeller configured to be rotated about a rotational axis in a rotational direction. The housing defines a discharge passage and a suction passage therein. The impeller is housed in the housing and is coaxially aligned with the suction passage. The impeller includes a main plate, a plurality of first blades extending across the main plate, and a plurality of second blades extending across the main plate. The main plate has a circular shape and a top surface facing the suction passage. The first blades extend radially along the top surface of the main plate. The second blades extend radially along the top surface of the main plate. The radial length of each first blade is equal to the radial length of each second blade. Each second blade has a low blade part and a high blade part extending radially outward from a radially outer end of the low blade part. The low blade part of each second blade has a height measured axially from the main plate that is less than a height of each first blade measured axially from the main plate when comparing the heights of the first blades and the heights of the low blade parts of the second blades at an equal radial distance from the rotational axis. The high blade part of each second blade has a height measured axially from the main plate that is the same as the height of each first blade when comparing the heights of the first blades and the heights of the high blade parts of the second blades at an equal radial distance from the rotational axis.
In accordance with this aspect, a difference between the amount of the fluid forced by each first blade and the amount of the fluid forced by each second blade can be reduced, while ensuring a relatively large area of each opening of the impeller. Accordingly, the pump efficiency of the centrifugal pump can be improved.
For a detailed description of the preferred embodiments of the present teaching, reference will now be made to the accompanying drawings.
In general, the shape of the blades of a centrifugal pump affects the pumping efficiency. Consequently, various types of blades have been provided for the purpose of improving the pump efficiencies of centrifugal pumps. For example, in Japanese Laid-Open Patent Publication No. H11-218097, an impeller includes a plurality of first blades and a plurality of second blades that are shorter than the first blades. The first blades extend radially from a central portion of the impeller to a radially outer periphery of the impeller. The second blades extend radially from a region spaced from the central portion of the impeller to a position proximal the radially outer periphery of the impeller. In such centrifugal pumps, the second blades do not extend to or proximal the central portion of the impeller. As a result, an opening is defined between the radially inner ends of each pair of circumferentially adjacent first blades. The area of each such opening can be increased to improve the pump efficiency. However, because the second blades are shorter than the first blades, the volume of a fluid forced by each second blade is generally less than the volume of the fluid forced by each first blade. Therefore, there has been a need for an improved centrifugal pump.
A centrifugal pump generally includes an impeller and a housing forming a pump chamber for housing the impeller therein. The impeller has a main plate with a substantially circular shape and a plurality of blades extending radially along a top surface of the main plate from proximal a center of the impeller to a radially outer periphery of the impeller. When the centrifugal pump is operated, the impeller is rotated about a rotational axis such in a rotational direction such that a fluid is forced forward by the blades of the impeller relative to the rotational direction in the pump chamber so as to flow radially outward. As a result, the centrifugal pump suctions the fluid into the pump chamber and discharges the fluid from the pump chamber.
One conventional method for improving the pump efficiency of a centrifugal pump is to increase the number of blades. However, when too many conventional blades are provided on the main plate of the impeller, a space near the central portion of the impeller is crowded with radially inner ends of the blades. Thus, an area of each opening, through which the fluid flows from a space just above the central portion of the impeller into spaces between the blades, is relatively small. In such state, the flow of fluid from the space just above the central portion of the impeller into the spaces between the blades is limited, so that the pump efficiency cannot be improved effectively. Each opening is defined by the radially inner ends of each pair of circumferentially adjacent blades and the top surface of the main plate near the center of the impeller. In this disclosure, the area of the opening may also be referred to as “opening area.”
To improve the pump efficiency of the centrifugal pump, embodiments described herein are directed to impellers having two kinds of blades for simultaneously increasing both the opening area and the number of the blades on the main plate. More specifically, as shown in
As described above, regarding the example of the impeller shown in
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.
A first embodiment will be described with reference to
As shown in
The shaft 20 has an upper end coaxially inserted into a central hole 142 of the impeller 140, such that the shaft 20 is configured to transmit torque, generated between the rotor 18 and the stator 22, to the impeller 140. The housing 16 includes a first housing part 24 and a second housing part 26. Each of the first housing part 24 and the second housing part 26 may be made from a resin material. The first housing part 24 and the second housing part 26 are coupled to each other to define a pump chamber 28. The impeller 140 is housed in the pump chamber 28, such that the impeller 140 can rotate in the pump chamber 28 without coming into contact with an inward facing surface of the housing 16. The first housing part 24 has a suction part 30 having a hollow cylindrical shape extending upward. The suction part 30 defines a suction passage 32 therein. The suction part 30 includes an inlet port 34 at an upstream end of the suction passage 32, i.e. at an opposite end to the pump chamber 28. The suction passage 32 provides fluid communication between the pump chamber 28 and the exterior of the centrifugal pump 10 via the inlet port 34. The first housing part 24 has a discharge part 36 extending in a tangential direction from an outer periphery of the impeller 140 (rightward in
The centrifugal pump 10 includes bearings 42, 44. Each of the bearings 42, 44 is composed of a ball bearing having both an outer ring and an inner ring, such that the outer ring is fixedly inserted into the second housing part 26 by press-fitting and that the inner ring is fixed on the shaft 20. Due to this configuration, the bearings 42, 44 support the shaft 20 while allowing the shaft 20 to rotate.
The second housing part 26 houses a control unit 46 at a lower end part thereof. The control unit 46 is coupled to a connector configured to be connected to an external power source, such as a battery mounted on the vehicle. The control unit 46 is configured to receive electric power from the external power source and to supply it to the stator 22.
Next, the impeller 140 will be described in detail. As shown in
The first blades 146 and the second blades 148 extend radially along the top surface of the impeller 140 on both the projection part 152 and the flat part 150. As shown in
As shown in
The second blades 148 have the same shape as each other, so that one of the second blades 148 will be described for convenience of explanation. As shown in
Next, an operation of the centrifugal pump 10 will be described with reference to
In accordance with the first embodiment, regarding the height from the main plate 144, the low blade part 156 of each second blade 148 is less than each first blade 146 when comparing the first blades 146 and the second blades 148 to each other at an equal distance from the rotational axis C. Thus, an opening area of each opening of the impeller 140 can be increased in comparison with a case where the height of each second blade 148 is the same as that of each first blade 146 over the entire radial length thereof. Further, in a space near the central portion of the impeller 140, most of the fluid flows radially outward due to inclination of the inclined surface 154, so that the amount of the fluid moved by the low blade part 156 of each second blade 148 is substantially the same as, and in particular, slightly less than the amount of the fluid moved by each first blade 146. Thus, the amount of the fluid forced by the second blades 148 can be increased, thereby decreasing a difference between the amount of the fluid forced by the first blades 146 and the amount of the fluid forced by the second blades 148. Such difference may cause pulsations in the fluid flow. Accordingly, the pump efficiency of the centrifugal pump 10 can be improved, while preventing the pulsations in the fluid flow.
The height of the low blade part 156 of each second blade 148 from the main plate 144 continuously increases moving radially outward from the radially inner end to the radially outer end thereof. Due to this configuration, the impeller 140 can be easily produced by using molds.
The main plate 144 includes the projection part 152 and the flat part 150 extending radially outward from the projection part 152. In a radially inner space positioned above the projection part 152, the fluid is not pressurized sufficiently by the first blades 146 and the second blades 148, and thus, the fluid flows along the inclined surface 154. In a radially outer space positioned above the flat part 150, the fluid is forced and sufficiently pressurized by the first blades 146 and the second blades 148 to be moved forward relative to the rotational direction R and radially outward. Accordingly, each second blade 148, having the low blade part 156 on the projection part 152 and the high blade part 158 extending over the entire radial length of the flat part 150, can sufficiently force the fluid to flow above the flat part 150.
The first blades 146 and the second blades 148 are alternately arranged at regular intervals in the circumferential direction of the impeller 140. Thus, the opening area of each opening of the impeller 140 can be held substantially constant in the circumferential direction of the impeller 140. Further, the difference between the amounts of the fluid forced by each of the first blades 146 and the second blades 148 can be decreased.
A second embodiment will be described with reference to
As shown in
As shown in
As shown in
The first blades 246 have the same shape as each other, so that one of the first blades 246 will be described in the interest of conciseness. The second blades 248 also have the same shape as each other, so that one of the second blades 248 will be described for convenience of explanation. As shown in
As shown in
In accordance with the second embodiment, the first blades 246 and the second blades 248 have the same radial length as each other. Each of the second blades 248 has the low blade part 256 and the high blade part 258. Each low blade part 256 is formed proximal the central portion of the impeller 240. The height of each low blade part 256 from the main plate 244 is less than that of each first blade 246 when comparing the first blades 246 and the second blades 248 to each other at an equal distance from the rotational axis C. Each high blade part 258 extends radially outward from the radially outer end of the corresponding low blade part 256. The height of each high blade part 258 from the main plate 244 is equal to that of each first blade 246 when comparing them to each other at an equal distance from the rotational axis C. Due to this configuration, the difference between the amount of the fluid forced by the first blades 246 and the amount of the fluid forced by the second blades 248 can be reduced, while increasing an opening area of each opening of the impeller 240. Accordingly, the pump efficiency of the centrifugal pump 10 can be improved.
The height of each second blade 248 from the main plate 244 increases at the boundary line B between the low blade part 256 and the high blade part 258 in the stepped manner. Thus, the height of each low blade part 256 can be sufficiently lowered over the whole radial length thereof.
Each second blade 248 includes the low blade part 256 formed on the projection part 252 only and the high blade part 258 extending radially over the whole radial length of the flat part 250. Thus, each second blade 248 has a sufficient height to pressurize and force the fluid to flow radially outward on the flat part 250.
Each first blade 246 has the thin blade part 260 and the thick blade part 262. The thin blade part 260 of each first blade 246 is thinner than each second blade 248 when comparing them to each other at an equal distance from the rotational axis C. The thickness of each thick blade part 262 is equal to that of each second blade 248 when comparing them to each other at an equal distance from the rotational axis C. Thus, the opening area of each opening of the impeller 240 can be increased in comparison with a case where each first blade 246 has the thickness same as the thick blade part 262 over the whole radial length thereof.
Each first blade 246 has the thin blade part 260 and the thick blade part 262, which extends radially outward from the radial outer end of the thin blade part 260 and is thicker than the thin blade part 260. Thus, the strength of each first blade 246 can be increased in comparison with a case where each first blade 246 has the thickness same as the thin blade part 260 over the whole radial length thereof.
The first blades 246 and the second blades 248 are alternately arranged in the circumferential direction of the impeller 240. Thus, the opening area of each opening of the impeller 240 can be held to be substantially constant in the circumferential direction of the impeller 240. Further, the difference between the amounts of the fluid forced by each of the first blades 246 and the second blades 248 can be decreased.
A third embodiment will be described with reference to
As shown in
Each of the first blades 346 and the second blades 348 extends radially from a radially inner periphery of the inclined surface 354 of the projection part 352 to a radially outer periphery of the flat part 350. As shown in
The first blades 346 have the same shape as each other, and the second blades 348 also have the same shape as each other. Thus, one of the first blades 346 and one of the second blades 348 will be described below in the interest of conciseness. Regarding each of the first blade 346 and the second blade 348, in the plan view along the rotational axis C, a radially inner end thereof is positioned, relative to the rotational direction R, in front of a virtual line extending radially from the rotational axis C to a radially outer end thereof. In the plan view, an upper edge of each of the first blades 346 and the second blades 348 is gently curved rearward relative to the rotational direction R moving radially outward.
As shown in
As shown in
As shown in
The front surface 366F of the first outer blade part 366 extends from the top surface of the main plate 344 obliquely rearward relative to the rotational direction R of the impeller 340. The front surface 366F is contiguous with the front surface 364F of the first inner blade part 364. As shown in
In a cross-sectional view perpendicular to the longitudinal axis of the first outer blade part 366, an angle θ formed between the front surface 366F of the first outer blade part 366 and a first vertical reference line L, which extends parallel to the rotational axis C and passes through the upper end of the front surface 366F, is acute and continuously increases moving radially outward.
As shown in
As shown in
As shown in
In the plan view along the rotational axis of the impeller 340, the second inner blade part 368 is positioned, relative to the rotational direction R, in front of a radial reference line N2, which extends radially and passes through the rotational axis C and a connection part between the second inner blade part 368 and the second outer blade part 370. The connection part between the second inner blade part 368 and the second outer blade part 370 corresponds to a radially inner end of the second outer blade part 370. As shown in
As shown in
The front surface 370F of the second outer blade part 370 extends from the top surface of the main plate 344 obliquely rearward relative to the rotational direction R of the impeller 340. The front surface 370F is contiguous with the front surface 368F of the second inner blade part 368. The front surface 370F extends linearly between an upper end and a lower end thereof in a cross-sectional view perpendicular to a longitudinal axis of the second outer blade part 370. The front surface 370F may be gently curved in a concave or convex manner in some embodiments.
Although not illustrated, in a cross-sectional view perpendicular to the longitudinal axis of the second outer blade part 370, an angle formed between the front surface 370F of the second outer blade part 370 and a vertical reference line, which extends parallel to the rotational axis C and passes the upper end of the front surface 370F, is acute and continuously increases from the radially inside toward the radially outside.
As shown in
As shown in
As shown in
In accordance with the third embodiment, the first blades 346 and the second blades 348 have the same radial length as each other. Each second blade 348 has the low blade part 356 and the high blade part 358. Each low blade part 356 is formed near the central portion of the impeller 340. The height of each low blade part 356 from the main plate 344 is less than that of each first blade 346 when comparing them to each other at an equal distance from the rotational axis C. Each high blade part 358 extends radially outward from the radially outer end of the corresponding low blade part 356. The height of each high blade part 358 from the main plate 344 is equal to that of each first blade 346 when comparing them to each other at an equal distance from the rotational axis C. Due to this configuration, the difference between the amount of the fluid forced by the first blades 346 and the amount of the fluid forced by the second blades 348 can be reduced, while increasing the opening area of each opening of the impeller 340. Accordingly, the pump efficiency of the centrifugal pump 10 can be improved.
The height of the low blade part 356 of each second blade part 348 from the main plate 344 continuously increases moving radially outward. Thus, the impeller 340 can be easily produced by using molds.
The low blade part 356 of each second blade 348 is formed on the projection part 352 only, whereas the high blade part 356 of each second blade 348 extends radially over the whole radial length of the flat part 350. Thus, each second blade 348 has a sufficient height to pressurize and force the fluid to flow radially outward on the flat part 350.
The first blades 346 and the second blades 348 are alternately arranged in the circumferential direction of the impeller 340. Thus, the opening area of each opening of the impeller 340 can be held to be substantially constant in the circumferential direction of the impeller 340. Further, the difference between the amounts of the fluid forced by each of the first blades 346 and the second blades 348 can be decreased.
As mentioned above, the apparatuses and methods disclosed herein are not limited to the above-described embodiments. For example, the centrifugal pump may be used for pumping various fluids, such as air, water, or the like. The motor may be composed of a brushed motor. The main plate may have additional blades or grooves along a lower surface thereof. The projection part may be omitted, such that the main plate may have a flat top surface having a circular shape. The height of the low blade part may increase toward the radially inside.
The thickness of the thin blade part of each second blade may gradually increase toward the radial outside. Each second blade may have a thin blade part and a thick blade part instead of the first blades.
The impeller may include a plurality of third blades each having a low blade part and a high blade part. In such case, the height of the low blade part of each third blade from the main plate is lower or higher than that of each second blade when comparing them to each other at an equal distance from the rotational axis of the impeller.
The numbers of the first blades, the second blades, and the third blades may be different from each other. However, the first blades, the second blades, and the third blades are preferably arranged on the main plate in the circumferential direction on the basis of a repetitive order pattern.
The blades may not be arranged at regular intervals in the circumferential direction. However, the blades are preferably positioned on the main plate on the basis of a predetermined regularity. For example, in a case where the impeller includes first blades, second blades, and third blades repeatedly, a first predetermined circumferential distance between the first blade and the second blade may be greater than a second predetermined circumferential distance between the second blade and the third blade in each repeating unit.
Claims
1. A centrifugal pump, comprising:
- a housing defining a discharge passage and a suction passage therein; and
- an impeller configured to rotate about a rotational axis in a rotational direction, wherein the impeller is disposed in the housing and is coaxially aligned with the suction passage, wherein:
- the impeller comprises: a main plate having a circular shape and a top surface facing the suction passage; a plurality of first blades extending radially along the top surface of the main plate, and a plurality of second blades extending radially along the top surface of the main plate,
- a radial length of each of the first blades is equal to a radial length of each of the second blades,
- each of the second blades has a low blade part and a high blade part extending radially outward from a radially outer end of the low blade part,
- a height of the low blade part measured from the main plate is less than a height of each of the first blades measured from the main plate when comparing the first blades and the second blades with each other at an equal distance from the rotational axis, and
- a height of the high blade part measured from the main plate is the same as the height of each of the first blades measured from the main plate when comparing the first blades and the second blades with each other at an equal distance from the rotational axis.
2. The centrifugal pump of claim 1, wherein the height of the low blade part measured from the main plate continuously increases moving radially outward along the low blade part.
3. The centrifugal pump of claim 1, wherein the height of each second blade measured from the main plate increases at a boundary between the low blade part and the high blade part thereof in a stepped manner.
4. The centrifugal pump of claim 1, wherein:
- the main plate has a projection part protruding in an axial direction along the rotational axis and a flat part extending radially outward from a radially outer periphery of the projection part,
- the flat part is oriented perpendicular to the rotational axis,
- an axial length of the projection part increases moving radially inward along the projection part, and
- the low blade part is formed on the projection part and does not extend along the flat part.
5. The centrifugal pump of claim 4, wherein:
- each of the first blades includes a thin blade part and a thick blade part,
- the thick blade part extends radially outward from a radially outer end of the thin blade part,
- a thickness of the thin blade part relative to the rotational direction is less than a thickness of each of the second blades relative to the rotational direction when comparing the first blades and the second blades with each other at an equal distance from the rotational axis, and
- a thickness of the thick blade part relative to the rotational direction is the same as of the thickness of each of the second blades when comparing the first blades and the second blades with each other at an equal distance from the rotational axis.
6. The centrifugal pump of claim 5, wherein the thin blade part is formed on the projection part and does not extend along the flat part.
7. The centrifugal pump of claim 4, wherein:
- each of the second blades includes a thin blade part and a thick blade part,
- the thick blade part extends radially outward from a radially outer end of the thin blade part,
- a thickness of the thin blade part relative to the rotational direction is less than a thickness of each of the first blades relative to the rotational direction when comparing the first blades and the second blades with each other at an equal distance from the rotational axis, and
- a thickness of the thick blade part relative to the rotational direction is the same as the thickness of each of the first blades when comparing the first blades and the second blades with each other at an equal distance from the rotational axis.
8. The centrifugal pump of claim 7, wherein the thin blade part is formed on the projection part and does not extend along the flat part.
9. The centrifugal pump of claim 1, wherein the plurality of first blades and the plurality of second blades are arranged in a regular manner relative to the rotational direction.
10. The centrifugal pump of claim 9, wherein the plurality of first blades and the plurality of second blades are alternately arranged in the rotational direction.
Type: Application
Filed: Mar 13, 2020
Publication Date: Sep 17, 2020
Applicant: AISAN KOGYO KABUSHIKI KAISHA (Obu-shi)
Inventors: Hironori SUZUKI (Obu-shi), Yoshihiko HONDA (Obu-shi)
Application Number: 16/818,218