US20080112824A1

US20080112824A1 - Pump

Info

Publication number: US20080112824A1
Application number: US11/558,438
Authority: US
Inventors: Motoi Sawasaki; Takenori Kawashima; Masashi Nishimura
Original assignee: Nidec Shibaura Corp
Current assignee: Nidec Shibaura Corp
Priority date: 2006-11-09
Filing date: 2006-11-09
Publication date: 2008-05-15

Abstract

In a pump having a rotor inside a pump chamber which is formed inside a case which is formed of a resin material, and a resin mold compound in which an armature is molded with resin, a metallic cover is provided on a portion of an outer surface of the case inside the pump, wherein the portion has inferior durability compared with the rest of the outer surface.

Description

BACKGROUND OF THE INVENTION

1. Technical Field
The present invention relates to pumps, and more particularly to a pump having improved hydraulic pressure resistance by increasing the durability of the exterior and interior of the pump, having therein a case formed of a resin material.
2. Description of the Related Art
There is a growing demand for a device such as a water heater to become smaller in dimensions, lighter in weight and energy efficient. Such demand is also expected of a pump installed in the aforementioned device or the like.
A pump in general comprises a DC brushless motor having a rotor which is sealed inside a case, a stator affixed outside the case for driving the rotor, and an impeller which is connected to the rotor and is located in a pump chamber therein.
FIG. 8 is a diagram showing a schematic cross sectional view in an axial direction of an example of a conventional pump. As shown in FIG. 8, a pump 100 has arranged therein a rotor 121 in an interspace between an upper case 111 and a lower case 112 which are formed of a resin material. The pump 100 also includes an annular shaped stator 122 along an outer circumferential surface of the rotor 121. A pump having such configuration is commonly referred to as a canned type pump.
The upper case 111 and the lower case 112 sandwich an O-shaped ring (hereinafter, referred to as an O-ring) 115, and seal an inner portion of the pump 100. Also, a pump chamber 116 is provided at an upper portion of the interspace. An intake portion 113 and a discharge portion 117, which are connected to each other in the pump chamber for, respectively, intaking and discharging fluid, protrude outwardly from the upper case 111. The aforementioned configuration is to be formed integrally.
The rotor 121 is supported and allowed to freely rotate in a radial direction by a cylinder shaped sleeve 125 located surrounding a fixed shaft 123 which is affixed at a center of the pump 100 inside the lower case 112. Also, a thrust washer 124 is provided at top and bottom portions of the sleeve 125 so as to support in the axial direction and allow the rotor to freely rotate.
The rotor 121 comprises an impeller base portion 126 which is connected to the sleeve 125, an impeller 127 which is affixed above the impeller base portion 126, and a rotor magnet 128 which is surroundingly affixed to the rotor 121. The rotor magnet 128 is provided within a cup shaped portion 112 a in the lower case 112.
The stator 122 comprises an annular shaped resin mold compound 133 including therein a molded resin 132 in which a printed circuit board 131 and an armature 134 which includes therein an annular shaped laminated core 129 and a coil 130 are provided.
The resin mold compound 133 is located on an outer circumferential surface of the rotor magnet 128 of the rotor 121 and is affixed to the lower case 112. The resin mold compound 133 and the rotor 121 configure the DC brushless motor. When an electric current is applied to the stator 122 via the printed circuit board 131 from an external power supply (not shown in the figures), the impeller 127 rotates along with the rotor 121. Due to the rotation of the impeller 127, fluid is taken in through the intake portion 113 to the pump chamber 116. Then, the fluid pressured by the impeller 127 will be discharged from the discharge portion 117.
For the aforementioned pump 100, metallic cases having a superior durability than the resin based upper case 111 and the lower case 112 are used so as to sustain expansion, which is caused by the hydraulic pressure, of the resin based upper case 111 and the lower case 112, and to improve hydraulic pressure resistance of the pump 100.
However, forming a metal plate into a three-dimensional case by methods such as pressing and welding will be a difficult task. Further, the pressing process is a costly process. Furthermore, such pump requires countermeasures against increased weight thereof and corrosion.
Also, according to the pump 100 as shown in FIG. 8, at a contact portion 136 where the lower case 112 and the annular shaped resin mold compound 133 make contact with each other, the resin mold compound 133 will be affected, via the lower case 112, by the pressure which is generated within the pump. When the pressure within the pump is increased, due to thin resin layers at the contact portion 136, the resin mold compound 133 may be damaged (e.g., occurrences of crack). Ultimately, if the pressure continues, the resin mold compound 133 may be detached from the lower case 112.
Also, in the pump 100, a gap S may be generated between an inner circumferential surface of the resin mold compound 133 affixed to the lower case 112 and an outer circumferential surface of the lower case 112. Each time the case 112 is affected by the pressure from the pump, the gap S may be repeatedly widened. Then, a weld line having a weak connection is likely to be cracked and, thus, water leakage of the pump 100 may occur.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to a pump having a structure in which a metallic cover is attached to a case, which is formed of a resin material, so as to increase the durability of the pump having therein the case. Also, the present invention relates to the pump having a structure in which a reinforcement board is provided to the case so as to increase the durability of the case inside the pump. The present invention improves, without any significant increase in weight and a production cost thereof, hydraulic pressure resistance of the pump thereby increasing the durability of the pump.
Further, since the metallic cover is attached to a resin mold compound having molded therein an armature, the durability of the resin mold compound will be increased.
Furthermore, the metallic cover can be embedded in either the case or the resin mold compound.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram showing a schematic cross sectional view, in an axial direction, of a pump according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a plan view of the pump shown in FIG. 1 as seen from a side of a fluid intake portion.

FIG. 3 is a diagram showing a plan view, as seen from a side of, a pump according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a schematic cross sectional view, in the axial direction, of a pump according to a third embodiment of the present invention.

FIG. 5 is an enlarged view of a portion A shown in FIG. 4.

FIG. 6 is a diagram showing a schematic cross sectional view, in the axial direction, of a pump according to a fourth embodiment of the present invention.

FIG. 7 is an enlarged view of a portion B shown in FIG. 6.

FIG. 8 a diagram showing a schematic cross sectional view, in the axial direction, of an embodiment of a conventional pump.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of a pump according to the present invention will be described with reference to FIGS.

First Embodiment

FIG. 1 is a diagram showing a schematic cross sectional view in an axial direction of a pump 10 according to a first embodiment of the present invention. FIG. 2 is a plan view of FIG. 1. As shown in FIG. 1, the pump 10 comprises: an upper case 11 and a lower case 12, which are formed of a resin material; a rotor 21 which rotates around a predetermined central axis J1, and which is located in a space generated between the upper case 11 and the lower case 12 which are joined together; and a ring shaped stator 22 which is located along an outer circumference of the rotor 21 and outside of the lower case 12. The pump 10 is commonly referred to as a canned type pump wherein the lower case 12 is provided between the rotor 21 and the stator 22. Note that, in the description of the preferred embodiments of the present invention herein, words such as upper, lower, left, right, upward, downward, top, and bottom for describing positional relationships between respective members and directions merely indicate positional relationships and directions in the drawings. Such words do not indicate positional relationships and directions of the members mounted in an actual device.
The upper case 11 and the lower case 12 sandwich an O-ring 15, and seal an inner portion of the pump 10. At an upper portion of an interspace portion generated by the upper case 11 and the lower case 12, a pump chamber 16 is provided. An intake portion 13 and a discharge portion 17 which are connected to each other in the pump chamber 16 protrude outwardly from the upper case 11. The aforementioned configuration is to be formed integrally.
The rotor 21, sharing the same axis as the central axis J1, is supported and allowed to freely rotate, via a sleeve 25 and a thrust washer 24 located at both top and bottom of the sleeve 25, by a stator shaft 23 fixed between the upper and lower cases 11 and 12.
The rotor 21 comprises: an impeller ba1se portion 26 which is connected to the sleeve 25 formed of the resin material (e.g., polyphenylene sulfide) having a tribological property; an impeller 27 which is connected to a top portion of the impeller base portion 26; and a rotor magnet 28 which is located surrounding the sleeve 25. The rotor magnet 28 is located inside a cup shaped area provided in a center portion of the lower case 12.
The stator 22 comprises: an armature 30 including therein an annular shaped laminated core 29 and a coil 29 a; and a printed circuit board 31. The printed circuit board 31 and the armature 30 are molded in a molded resin 32 configuring an annular shaped resin mold compound 33.
The resin mold compound 33 is located on an outer surface of the lower case 12 which is located along an outer circumferential surface of the rotor magnet 28 in the rotor 21. The resin mold compound 33 is affixed to, so as to cover, an outer circumferential surface and a portion of a bottom of the cup shaped lower case 12. Further, the resin mold compound 33 extends radially outwardly from the cup shaped lower case 12 is affixed to, so as to cover, an outer surface forming the pump chamber 16. Since the outer surface of the lower case 12 and the resin mold compound 33 make contact with each other as described above, the resin mold compound 33 is able to sustain expansion of the lower case 12 even if the pressure within the lower case 12 is increased.
The motor according to the present invention is a component of the brushless DC motor such that when the stator 22 is supplied with an electric current from the printed circuit board 31, a rotating magnetic field will be generated in the stator 22, thereby rotating the rotor 21. When the rotor 21 rotates, the impeller 27 connected to the rotor 21 rotates. Then the fluid will be sucked in to the inner portion of the pump chamber 16 through the intake portion 13, directed by the impeller 27 to flow in a predetermined direction, and discharged through the discharge portion 17.
In the pump 10 according to the present embodiment, an annular shaped metallic cover 1 is provided covering over an outer surface of the upper case 11. The metallic cover 11 is secured by a screw 2 at four points to the upper case 11. Here, the screws 2 each are to be used at points avoiding the pump chamber 16 so as to avoid exposing the screws 2 to the inner portion of the pump chamber 16. If the screws 2 are exposed to the inner portion of the pump chamber 16, the fluid inside the inner portion may leak outside thereof. Also, if screws 2 not long enough to penetrate the metallic cover 1 are used, the metallic cover 1 will not be secured to the upper case 11. Also, providing a layer having an increased thickness for the upper case 11 so that long screws 2 can be used, the dimensions of the pump 10 will be large. In order to solve the aforementioned problems, the screws 2 are provided ideally at points avoiding the pump chamber 16.
In general, in a pump, which has a case formed of a resin material, whose rated total head is approximately 13 m or smaller, and whose rated flow is approximately 30 L/min or smaller, a maximum internal pressure of fluid a pump chamber can withstand is between, approximately, 200 KPa to 250 KPa. When the internal pressure is to be greater than 250 KPa, a metallic case will be necessary in order to sustain the expansion. However, when the upper case 11, which is formed of the resin material, has applied thereon the metallic cover 1 in the pump 10 according to the present embodiment, an internal pressure up to approximately 1000 KPa can be withstood. Therefore, the pump 10 can be used for a pump in which the internal pressure of the fluid in a pump chamber exceeds approximately 250 KPa.
The metallic cover 1 provides an opening 3 for insertion of the intake portion 13 which protrudes from the upper case 11. Also, the metallic cover 1 can be easily manufactured by pressing a stainless steel plate or an aluminum base plate. Also, the metallic cover 1 can be attached to the pump 10 easily. Also, the metallic cover 1 is attached, to the upper case 11, stretching over a weld line (not shown in the figures) which is generated when the upper case 11 is formed by a die. Since the upper case 11 is most vulnerable at the weld line, when the metallic cover 1 is affixed covering over the weld line on the upper case 11, damages (e.g., occurrence of crack or expansion) can be prevented.
The metallic cover 1 is to be secured by the screw 2 at, at least, one point on both sides of the weld line. By this, the metallic cover 1 will be able to prevent damages from being done to the weld line even when the internal pressure within the pump chamber 16 increases.
The metallic cover 1 increases the durability of the pump 10 having therein the upper case 11 and the lower case 12, which are formed of the resin material, to an extent of the durability of a pump having therein a metallic case. Further, the metallic cover 1 can easily be manufactured and attached to the cases while keeping a weight increase of the pump 10 to a minimum. Further, the metallic cover 1 can increase the durability of upper case 11 which is repeatedly pressured by the internal pressure of the fluid inside the pump chamber 16. As a result, a pump having the metallic cover 1 will last long and have an increased durability.
Further, a metallic cover different from the metallic cover 1 can be provided on a surface, of the lower case 12, making contact with the armature 30 in the axial direction. Note that the non-metallic-cover-1-metallic-cover provides an opening for insertion of the cup shaped lower case 12. By this, the lower case 12 can be sandwiched from both sides thereof in the axial direction, thereby constrictedly securing the pump chamber 16. By this, the durability of the pump 10 against the internal pressure of the fluid within the pump chamber 16 will be increased.

Second Embodiment

Next, a pump according to a second embodiment of the present invention will be described with reference to FIG. 3. FIG. 3 is a diagram showing a plan view, as seen from a side of, a pump according to a second embodiment of the present invention. In FIG. 3, elements similar to those illustrated in FIG. 1 are denoted by similar reference numerals, and description thereof is omitted.
In the first embodiment, the metallic cover 1 covers over only the top surface in the axial direction of the upper case 11. In the second embodiment, however, a metallic cover is provided on both top and bottom surfaces of a pump 70 so as to sandwich, and to provide additional durability, to the pump 70. That is, according to FIG. 3, a metallic cover 71 which covers over a top surface of the upper case 11 and a resin mold compound side metallic cover 72 which covers over a bottom surface of the resin mold compound 33 are provided on the upper case 11. The metallic cover 71 and the resin mold compound side metallic cover 72 each are secured to the upper case 11 at four points by a screw 73. A cylinder shaped collar 78 is provided between the resin mold compound side metallic cover 72 and the resin mold compound 33. The resin mold compound side metallic cover 72 and the resin mold compound 33 each have predetermined points (not shown in the figures) for the screw 73. Also, the upper case 11 and the metallic cover 71 each have predetermined points (not shown in the figures) for the screw 73. Since the metallic cover 71 and the resin mold compound side metallic cover 72 are provided, the durability of the upper case 11 and the resin mold compound 33 will be increased. In particular, the resin mold compound side metallic cover 72 affixed to the resin mold compound 33 increases the durability of the resin mold compound 33 so as for the resin mold compound 33 to withstand greater internal pressure of fluid within the pump chamber 16 than the resin mold compound 33 without the resin mold compound side metallic cover 72.
Note that, a planar shape of the metallic cover 71 and that of the resin mold compound side metallic cover 72 may be adjusted (e.g., round shape, substantially rectangle, or square) in accordance with a configuration of the pump.
Also, the metallic cover 71 and the resin mold compound side metallic cover 72 are affixed to a pump base 80 by a plurality of screws 82. The pump base 80 is used to mount the pump 70 onto an apparatus. The pump base 80 has an extension portion 81, which extends toward the metallic cover 71 and toward the resin mold compound side metallic cover 72. A portion of the extension portion 81 overlaps with a portion of the metallic cover 72 and with a portion of the resin mold compound side metallic cover 72. At the portions where the extension portion 81 and metallic cover 72 overlap one another, and where the extension portion 81 and the resin mold compound side metallic cover 72 overlap one another, openings 83 for insertion of the screws 82 are provided. The pump base 80 is formed by pressing a metal plate. That is, the pump base 80 can be manufactured inexpensively.
Since a primary object of the pump base 80 is to facilitate the connection between the pump 70 and the apparatus (not shown in the figures) onto which the pump 70 is to be mounted, the metallic cover 71 and the resin mold compound side metallic cover 72 are not designed to withstand a great amount of pressure. However, the metallic cover 71 and the resin mold compound side metallic cover 72 need to sustain expansion which may occur to the upper case 11 and the resin mold compound 33, and therefore durability thereof against the pressure need to be increased. Thus, the metallic cover 71 and the resin mold compound side metallic cover 72 are designed to be thicker than a thickness of the plate forming the pump base 80. The thickness of the metallic cover 71 and that of the resin mold compound side metallic cover 72 each are, preferably, greater than, approximately, 2 mm. When the thickness of the metallic cover 71 and that of the resin mold compound side metallic cover 72 each are greater than approximately 2 mm, the metallic cover 71 and the resin mold compound side metallic cover 72 can sustain an expansion, of the uppercase 11 and the resin mold compound 33, caused by the internal pressure within the pump chamber 16. When the metallic cover 71 and the resin mold compound side metallic cover 72 each having a thickness smaller than, approximately, 2 mm are used, it is preferable that a rib is provided to the metallic cover 71 and the resin mold compound side metallic cover 72 in order to increase the durability of the metallic cover 71 and the resin mold compound side metallic cover 72. When such rib is provided to the metallic cover 71 and the resin mold compound side metallic cover 72 each having the thickness smaller than approximately 2 mm, the metallic cover 71 and the resin mold compound side metallic cover 72 will have the durability equivalent to that of the metallic cover 71 and the resin mold compound side metallic cover 72 having the thickness of, or greater than, approximately 2 mm.
Also, the metallic cover 71 and the resin mold compound side metallic cover 72 have preferably a same shape with one another. When the metallic cover 71 and the resin mold compound side metallic cover 72 have the same shape, they can be manufactured by using the same die, thereby reducing the production cost thereof. That is, pumps according to the present embodiment can be provided at low cost. When the metallic cover 71 and the resin mold compound side metallic cover 72 are manufactured by using the same die, the resin mold compound side metallic cover 72 will have an opening for the intake portion and an opening for a drainage plug in a same manner as the metallic cover 71. In order to prevent the resin mold compound 33 from being exposed externally through the openings and to increase the durability of the resin mold compound 33, a rib will be provided to the openings.

Third Embodiment

FIG. 4 is a diagram showing a schematic cross sectional view in the axial direction of a pump 50 according to a third embodiment of the present invention. FIG. 5 is an enlarged view of a portion A shown in FIG. 4. As shown in FIG. 4, the pump 50 is a canned type pump, wherein the pump 50 has a common structure as the pump 10 according to the first embodiment. In FIG. 4, elements similar to those illustrated in FIG. 1 are denoted by similar reference numerals, and the description of the structure of the pump 50 is omitted.
The pump 50 according to the third embodiment comprises a stator 22 including an annular shaped resin mold compound 34 having therein the molded resin 32 in which the armature 30 and the printed circuit board 31 are provided. In the armature 30, the ring shaped laminated core 29 and the coil 29 a are provided.
The resin mold compound 34 includes therein an annular shaped reinforcement board 5 which is formed of a metal plate. The reinforcement board 5 is located at a molded resin portion 32 a, in the resin mold compound 34, between a cup shaped bottom portion 35 and the lower case 12. The contact between the resin mold compound 34 and the lower case 12 is similar to the contact between the resin mold compound 33 and the lower case 12 according to the first embodiment.
The reinforcement board 5 which is formed of a non-magnetic material (e.g., stainless steel or aluminum alloy). The reinforcement board 5 is formed by embedding (e.g., insert molding) in the molded resin 32 when the resin mold compound 34 is formed by molding the stator 22 and the printed circuit board 31. The reinforcement board 5 is located near or attached to an electronic component which is mounted on the printed circuit board 31 and emits heat so as for the electronic component to alleviate the heat.
The reinforcement board 5 can: increase the durability of the molded resin portion 32 a having an inferior durability compared with the rest of the molded resin 32; and alleviate the pressure conducted to the resin mold compound 34 from the bottom portion 35. That is, the reinforcement board 5 prevents damages (e.g., occurrence of crack) from being done to the resin mold compound 34, thereby preventing the stator 22 from being damaged, and prevents the resin mold compound 34 from being detached from the lower case 12.
Also, in order to increase the durability of the pump 50, an annular shaped reinforcement board 18 is provided by an insertion molding so as to surround a protruding portion of the intake portion 13.

Fourth Embodiment

FIG. 6 is a diagram showing a schematic cross sectional view in the axial direction of a pump 60 according to a fourth embodiment of the present invention. FIG. 7 is a diagram showing an enlarged portion B shown in FIG. 6. The pump 60 as shown in FIG. 6 is a canned type pump having a common structure as the pumps 10 and 50, respectively, according to the first and the third embodiments. In FIG. 6, elements similar to those illustrated in FIG. 4 are denoted by similar reference numerals, and the description of the structure of the pump 60 is omitted.
The pump 60 according to the fourth embodiment comprises, similarly as the pump 10 described above, the stator 22 and the printed circuit board 31 which are molded in the molded resin 32 forming the annular shaped resin mold compound 33, wherein the stator 22 includes the ring shaped laminated core 29 and the coil.
The resin mold compound 33 is affixed along the outer circumferential surface of the rotor magnet 28 of the rotor 21, and along the outer circumferential surface of the lower case 12. There is a minute gap S between the inner circumferential surface of the resin mold compound 33 and the outer circumferential surface of the lower case 12.
A filler 6 is provided in the gap S between the resin mold compound 33 and the lower case 12 of the pump 60 according to the present embodiment of the invention. The filler 6 is provided by applying it on the internal circumferential surface of the resin mold compound 33 and/or the outer circumferential surface of the lower case 12 before the resin mold compound 33 is attached to the lower case 12.
The filler 6 may be an oil, a rubber or a resin substance. A silicon (e.g., rubber or resin) filler is beneficial in that, when applied on the lower case 12, the expansion of the lower case 12 can be sustained. Also, the silicon case 12 can be easily applied and is inexpensive.
By this, the expansion of the lower case 12 due to the internal pressure of the fluid within the pump chamber 16 can be sustained, thereby preventing the occurrence of a crack at the weld line of the lower case 12.
As described above, the pump according to the present invention provides: (1) the metallic cover 1 on the surface of the upper case formed of the resin material; (2) the metallic cover 1 on the surface of the upper case 11 and on the surface of the resin mold compound 33; (3) the reinforcement board 5 in the resin mold compound 33 at the portion thereof where the resin mold compound 33 and the lower case 12 make contact with each other; and (4) the filler 6 in the gap S between resin mold compound 33 and the lower case 12. Note, however, that aforementioned 4 elements each can be applied separately or simultaneously.
While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention. Further, the present invention can be applied to an automatic feed water pump, an axial pump, or to a pump commonly referred to as a reversible pump, having therein a plurality of discharge portions, in which fluid inside the pump is directed to a predetermined discharge portion by an impeller provided therein.
Further, the stator 22 according to the present invention is not necessarily limited to as described above. The stator 22 can be formed by, after attaching the armature 30 to the lower case 12, filling a space, which is generated by an exterior wall integrally formed with the lower case 12, with a potting material. The space generated by the exterior wall can be provided separately from the lower case 12 or can be attached to the uppercase 11.
Although the forgoing description assumes that a metallic plate (e.g., metallic cover and reinforcement board) is, in order to reinforce the durability of the pump, provided to the upper case the lower case and the resin mold compound, this is not limited thereto. Since an object of the invention is to provide an element to the upper case, the lower case and the resin mold compound so as to increase the durability of the upper case, the lower case and the resin mold compound, the element can be formed of a resin material having a high degree of hardness or a carbon fiber. For example, a reinforcement element for covering over the upper case, the lower case and the resin mold compound can be in any shape if the element is able to cover over the lower case and the resin mold compound.
The pump according to the present invention can be used for a water heater which is used for a heating system, a bath room and a kitchen.

Claims

1. A pump, comprising:

a pump chamber formed, for forming therein a pathway for fluid, inside a case formed of a resin material;

at least one intake portion connected to the pump chamber for intaking therein the fluid;

at least one discharge portion connected to the pump chamber for discharging therefrom the fluid;

a rotor located inside the pump chamber and having therein a rotor magnet, wherein the rotor rotates along a predetermined rotary shaft;

an impeller rotating along with the rotor so as to direct the fluid to a predetermined direction;

a stator located opposing to the rotor magnet while having a gap therebetween and located outside of the pump chamber, wherein the stator includes therein an armature which is a generator of a magnetic field; and

a metallic cover affixed, for increasing durability of the case, to a portion of the case to which an internal pressure generated by the fluid inside the pump chamber is applied.

2. The pump according to claim 1, wherein the metallic cover covers over a weld line generated on a surface of the case, and is affixed to the case on one side and the other side of the weld line.

3. The pump according to claim 1, wherein the internal pressure of the fluid inside the pump chamber is greater than approximately 250 KPa.

4. The pump according to claim 1, wherein the metallic cover is affixed to the case by a screw at a portion of the case radially outside of the pump chamber.

5. The pump according to claim 1, wherein:

the case includes an upper case and a lower case in an axial direction; the lower case is cup shaped for containing therein the rotor; and

the metallic cover is affixed to a top surface in an axial direction of the upper case.

6. The pump according to claim 1, wherein:

the metallic cover is located on top side and bottom side in an axial direction of the case; and

the case is, due to the metallic cover provided thereto, constrictedly secured in the axial direction.

7. The pump according to claim 1, wherein:

the stator includes therein a resin mold compound having formed therein an armature molded with the resin material; and

the resin mold compound is located for making contact with an outer surface of the case.

8. The pump according to claim 5, wherein:

the resin mold compound is located for making contact with at least an outer circumferential surface of the cup shape of the lower case.

9. The pump according to claim 7, wherein a resin-mold-compound-side metallic cover is affixed to an outer surface of the resin mold compound so as to cover over the outer surface of the resin mold compound.

10. The pump according to claim 9, wherein the case and the resin mold compound are, due to the metallic cover and the resin mold compound side cover respectively provided thereto, constrictedly secured in the axial direction.

11. The pump according to claim 8, wherein a resin-mold-compound-side metallic cover is affixed to the outer surface of the resin mold compound so as to cover over the outer surface of the resin mold compound.

12. The pump according to claim 11, wherein the case and the resin mold compound are, due to the metallic cover and the resin mold compound side cover respectively provided thereto, constrictedly secured in the axial direction.

13. The pump according to claim 10, wherein the metallic cover and the resin mold compound side metallic cover each are affixed to a pump base to which a corresponding pump is attached.

14. The pump according to claim 9, wherein a shape of the metallic cover and that of the resin mold compound side metallic cover are substantially identical.

15. The pump according to claim 14, wherein:

the metallic cover has formed thereon an opening at an area thereof corresponding to the intake portion; and

provided is a rib for preventing an exposure, to an outside of the pump, of the resin mold compound at an area of the opening, and for increasing durability of the resin mold compound.

16. A pump, comprising:

a pump chamber formed inside a case, formed of a resin material, for forming a pathway for fluid;

a rotor located inside the pump chamber and having therein a rotor magnet, the rotor rotating along a predetermined rotary shaft;

an impeller rotating along with the rotor so as to direct the fluid to a predetermined direction; and

a stator located opposing to the rotor magnet, while having a gap therebetween, outside of the pump chamber, wherein the stator includes therein an armature which is a generator of a magnetic field, wherein:

the stator includes therein a resin mold compound having formed therein an armature molded with the resin material;

the resin mold compound and the case make contact with each other and are affixed to each other; and

a metallic cover, for increasing durability of the resin mold compound, is affixed to a portion of the resin mold compound.

17. A pump, comprising:

a stator located opposing to the rotor magnet, while having a gap therebetween, outside of the pump chamber;

the stator including therein a resin mold compound molding therein an armature which is a generator of a magnetic field;

the resin mold compound located such that a portion thereof makes contact with an outer surface of the case; and

a reinforcement board embedded in the portion of the resin mold compound making contact with the case.

18. The pump according to claim 14, wherein:

the case includes an upper case and a lower case in an axial direction;

the lower case is cup shaped for containing therein the rotor;

the resin mold compound is provided so as to cover over at least a portion of a circumferential surface and a portion of a bottom surface of the cup shaped lower case; and

a reinforcement board is embedded at a bottom portion of the cup shaped lower case opposing the rotor magnet.

19. The pump according to claim 18, wherein:

the resin mold compound has embedded therein a control circuit board below the stator;

the control circuit board has a surface facing the bottom portion of the cup shaped lower case in the axial direction; and

the reinforcement board is embedded between the bottom portion and the control circuit board in the axial direction.

20. The pump according to claim 17, wherein the reinforcement board is formed of a material selected from the group consisting of stainless steel and aluminum alloy.

21. The pump according to claim 17, wherein:

a case side reinforcement board is embedded for increasing durability of the case against an internal pressure of the fluid inside the pump chamber; and

the case side reinforcement board is provided at an area surrounding the intake portion of the case.

22. A pump, comprising:

a stator located opposing to the rotor magnet, while having a gap therebetween, outside of the pump chamber, wherein the stator includes therein an armature which is a generator of a magnetic field;

a metallic cover affixed, for increasing durability of the case, to a portion of the case to which an internal pressure generated by the fluid inside the pump chamber is applied; and

a case side reinforcement board being embedded for increasing durability of the case against an internal pressure of the fluid inside the pump chamber, wherein the case side reinforcement board is provided at an area surrounding the intake portion of the case.

23. The pump according to claim 22, wherein:

24. A pump, comprising:

a filler provided in a space between the resin mold compound and the outer surface of the case.

25. The pump 25 according to claim 24, wherein:

the case includes an upper case and a lower case in an axial direction;

the lower case is cup shaped for containing the rotor via a gap surrounding a circumferential surface and a bottom surface of the rotor magnet in the rotor;

a filler is provided at a portion of a space between an outer circumferential surface and a bottom surface of the cup shaped lower case, and an inner circumferential surface of the resin mold compound.

26. The pump according to claim 24, wherein the filler is provided covering over a weld line generated on the case and on the resin mold compound.

27. The pump according to claim 24, wherein the filler is silicon based.

28. The pump according to claim 1, wherein the metallic cover is thicker than, approximately, 2 mm.

29. The pump according to claim 1, wherein:

the metallic cover is thinner than, approximately, 2 mm; and

the metallic cover has provided thereon a rib so as to increase durability of the metallic cover.

30. A pump, comprising:

a stator located opposing to the rotor magnet, while having a gap therebetween, outside of the pump chamber, wherein the stator includes therein an armature which is a generator of a magnetic field; and

a reinforcement element affixed, for increasing durability of the case, to a portion of the case to which an internal pressure generated by the fluid inside the pump chamber is applied.

31. The pump according to claim 30, wherein:

32. The pump according to claim 1, wherein the pump is used for a water heater used for a heating system operable to simultaneously distribute hot water to a plurality of outlets.