Magnet pump with rear thrust bearing member

A rear thrust bearing member is disposed to be in frictional contact with an axial end face of a spindle supported in a cantilever fashion in the neighborhood of and on the rear side of an impeller. Frictional heat that is generated in this part is satisfactorily diffused with a cooling effect provided by the rotation of the impeller in the pump casing and a heat diffusion effect provided by the circulating effect. Thus, a temperature rise of the frictional portions is suppressed, and adverse effects of heat on the surrounding member are prevented.

BACKGROUND OF THE INVENTION 
This invention relates to a magnet pump, in which a magnet coupling between 
a drive and a driven magnet facing each other rotationally drives an 
impeller in a pump chamber for a pumping operation and, more particularly, 
to improvements in a front and a rear side thrust bearing, particularly 
the rear thrust bearing member for supporting the thrust acting on a 
driven rotor portion including an impeller. 
A prior art magnetic pump of this type has a structure as shown, for 
instance, in FIG. 3. The well-known magnet pump 1 as shown in FIG. 3 
comprises a front casing having a suction port 3 extending in the axial 
direction as shown by axis line X--X and a discharge port 4 extending 
circumferentially, an impeller 6 rotationally disposed in the pump chamber 
2 and having a front side portion (i.e., right side in the Figure) facing 
the suction port 3, a cylindrical rear casing with a bottom cooperating 
with a front casing 5 to enclose the pump chamber 2 liquid tight, a driven 
rotor 10 disposed outside a rear casing 7, having a ring-like drive magnet 
8 and receiving a rotational drive torque from a drive motor (not shown) 
disposed in a pump body 9, a driven rotor 12 disposed in the rear casing 
7, having a ring-like driven magnet 11 facing and forming a magnet 
coupling with the drive magnet 8 via the rear casing and rotatable in 
unison with the impeller, and a spindle 14 secured at the distal end 
thereof to the bottom 7a of the rear casing 7 via an integral boss 13 
projecting from the bottom 7a and having an extended end portion 
projecting axially for rotatably supporting the driven rotor 12 on the 
extended end portion via a sleeve-like bearing 15. 
In the above well-known magnet pump 1, the rotation of the drive rotor 10 
causes rotational driving of the driven rotor 12 to cause rotation of the 
impeller 6, thus causing fluid to be pumped to flow into the pump chamber 
2 through the suction port 3 as shown by the arrow and be sent out through 
the discharge port 4 as shown by the arrow. In this pumping operation, the 
fluid in the pump chamber 2 partly flows as a circulating flow into the 
depth of the rear casing 7. In the circulating flow, the fluid flows into 
the frictional contact portions 15a defined between the sleeve-like 
bearing 15 integral with the driven rotor 12 and the spindle 14 from the 
rear end side of the bearing 15 as shown by dashed line arrows to come out 
to the front end side and pass through a central communication hole 16 
provided in the impeller 6, thereby providing a cooling effect to suppress 
increased heat generation by the friction of the frictional contact 
portions 15a and also providing a lubricating action. In the frictional 
contact portions 15a, a fluid passage groove is formed, which is a helical 
groove or like a spline. 
During the pumping operation, a negative pressure prevails on the front 
side of the impeller 6 that faces the suction port 3, while the driven 
rotor section including the driven rotor 12 and the impeller 6 normally 
receives a thrust in the direction toward the suction port 3, i.e., in the 
direction toward the front. Thus, ring-like front thrust bearing 17 is 
provided in the front casing 5 for supporting the thrust, and a mouth ring 
18 provided on the side of the impeller 6 is in frictional contact with 
the front thrust bearing 17. 
Further, a thrust may act on the driven rotor section in the direction 
opposite to the direction toward the suction port 3, i.e., in the rearward 
direction. This results from vibration of the driven rotor section in the 
thrust direction while the driven rotor portion remains rotating, which is 
caused when the pump is operated idly or abnormally due to trapping of 
air, or a like cause. Thus, a rear thrust bearing member 19 for supporting 
the rearward thrust acting on the driven rotor section is provided on a 
boss 13 around the spindle 14, so that the rear end of the sleeve-like 
bearing 15 is in frictional contact with the rear thrust bearing member 18 
in the event of the generation of a rearward thrust. 
As noted above, the sleeve-like bearing is brought to a state with its rear 
end in frictional contact with the rear thrust bearing member in the event 
of the idling operation of the pump or an abnormal operation thereof, such 
as air trapping. At this time, frictional heat is generated in the 
frictional contact portions, and this poses a problem. More specifically, 
the rear thrust bearing member, unlike the front thrust bearing member, is 
provided in the depth of the rear casing therefore, diffusion of the 
frictional heat is inferior, and when the temperature is increased, the 
bearing parts are seized. Particularly, where the rear casing or like 
enclosure member is a synthetic resin molding, the heat has an adverse 
effect of causing damage to these parts due to fusing. Further, when the 
rear end of the sleeve-like bearing is brought into frictional contact 
with the rear thrust bearing member, the circulating flow entering the 
frictional contact portions defined around the spindle generates heat and 
generate circulation failure, thus making the problem more significant. 
To solve the problem, it has been proposed to provide a heat isolation 
structure adopting a heat insulating material such as to surround the 
frictional contact portions of the rear thrust bearing or the like. In 
this case, a cost increase due to the provision of the heat insulation 
structure is inevitable. In addition, since the heat insulation material 
prevents diffusion of heat, the frictional contact portions are quickly 
elevated in temperature even by a short period of idling, and what is 
commonly called heat shock is liable to be generated by priming fluid 
supplied into the pump chamber immediately afterwards. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a magnet pump, which can 
greatly suppress frictional heat generation in the frictional contact 
portions in the event of generation of idling or like abnormal operation 
of the pump, has no need of providing any heat insulation structure around 
the frictional contact portions, permits use of a resin molding for the 
rear casing or like surrounding member, and permits durability improvement 
and cost reduction of the entire pump. 
To attain the above object of the present invention, according to the 
present invention there is provided a magnet pump including a front casing 
defining an inner pump chamber and having an axially extending suction 
port and a circumferentially extending discharge port, an impeller 
rotatably disposed in the pump chamber, the impeller having a front side 
portion facing the suction port and a rear side portion opposite to the 
front side portion, a cylindrical rear casing with a bottom, cooperating 
with the front casing to enclose the pump chamber fluid tight, a drive 
rotor disposed outside the rear casing and having a drive magnet, a driven 
rotor having a driven magnet facing and forming a magnet coupling with the 
drive magnet and rotatable in unison with the impeller which is mounted on 
a front side portion of the driven rotor, a spindle secured to the rear 
casing, the spindle having an extended end portion axially projecting 
toward the suction port and rotatably supporting the driven rotor and the 
impeller thereon, and a rear thrust bearing member for supporting a 
rearward thrust acting on the driven rotor and the impeller in the 
direction opposite to the direction toward the suction port, in that the 
spindle has an axial end face at the extended end portion, and the rear 
thrust bearing member is disposed to be in frictional contact with the 
axial end face of the spindle. 
Further, according to the present invention there is provided a magnet pump 
in which support means for supporting the rear thrust bearing member is 
provided on the rear side portion of the impeller or on the front side 
portion of the driven rotor. 
Further, according to the present invention there is provided a magnet pump 
in which either one of the rear thrust bearing member and the axial end 
face of the spindle has a spherically shaped contact portion, and in which 
the spindle is fixed at the distal end thereof and projects in a 
cantilever fashion. 
With the magnet pump with the rear thrust bearing member according to the 
present invention, the rear thrust bearing member is disposed such that it 
is capable of frictional contact with the axial end face of the spindle, 
and the support portion for supporting the rear thrust bearing member is 
provided on the rear side of the impeller, or on the front side of the 
driven rotor. Thus, when the driven rotor and the impeller are vibrated in 
the thrust direction while being moved in the rearward direction, the rear 
thrust bearing member is brought into contact with the axial end face of 
the spindle in the stationary state. The rear thrust bearing member, 
unlike the depth of the rear casing, is disposed on the back rear side in 
the neighborhood of the impeller. Thus, ready heat diffusion is 
obtainable. In addition, a cooling effect with stirring of the impeller in 
the pump casing is obtainable. Thus, the heat generated by the friction 
between the rear thrust bearing member and the axial end face of the 
spindle can be diffused satisfactorily, and the temperature rise of the 
frictionally movable part including the thrust bearing member can be 
suppressed. Further, since the flow path of the circulating flow passing 
between the spindle and the sleeve-like bearing is not blocked. Thus, a 
satisfactory cooling action around and lubricating action of the spindle 
can be maintained. Further, the circulating flow is provided to the rear 
thrust bearing member as well, and thus further satisfactory heat 
diffusion is obtainable. 
Further, with the structure in which either one of the frictional contact 
portions of the axial end face of the spindle and the rear thrust bearing 
member is spherical in shape, the area of the frictional contact is 
reduced, and the heat generation can be reduced extremely. It is thus 
possible to permit a synthetic resin molding to be used as the rear casing 
or like surrounding member without the need of adopting a heat insulation 
structure or a like special measure. A magnet pump which is very durable 
and readily permits cost reduction, thus can be provided. 
The above features and advantages of the present invention will be more 
fully understood from the detailed description of the preferred 
embodiments when the same is read with reference to the accompanying 
drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment of the magnet pump will be described with reference to FIGS. 
1 and 2. FIG. 1 shows a magnet pump 20, having a pump body 21 
accommodating an internal drive motor (not shown). A front casing 22, 
which is mounted on the pump body, defines an inner pump chamber 23 and a 
suction port 24 extending in an axial direction along axis X--X, and a 
circumferentially extending discharge port 25. An impeller 26 is rotatably 
disposed in the pump chamber 23 and has a front side (right side in the 
Figure) facing the suction port 24. A ring-like front thrust bearing 
member 27 is provided in the front casing 22 which is in frictional 
contact with a mouth ring 28 provided on the impeller 26. A cylindrical 
rear casing 29 with a bottom, is assembled in the pump body 21 and 
cooperates with the front casing 22 to enclose the pump chamber 23 fluid 
tight. A drive motor 30 is disposed outside the rear casing 29, and has a 
ring-like drive magnet 31 which receives rotational drive torque from the 
drive motor in the pump body 21. A driven rotor 32 is disposed in the rear 
casing 29, having a ring-like driven magnet 33 facing and forming a 
magnetic coupling with the drive magnet 31 via the rear casing 29 and 
rotatable in unison with the impeller 26. A spindle 34 is fixed to the 
bottom 29a of the rear casing 29 at the distal end thereof by a boss 35 
integral with and projecting from the bottom 29a and has an extended end 
portion 34a extending axially in a cantilever fashion. 
The driven rotor 32 is rotatably supported on the extended end portion 34a 
of the spindle 34 via a sleeve-like bearing 36. The bearing 36 is secured 
to the driven rotor 32 and has its frictional portion with respect to the 
spindle 34 formed with a flow groove or in the form of splines. During 
pumping fluid in the chamber 23 partly flows as a circulating flow into 
the depth of the rear casing 29, and as shown by the dashed line arrows it 
enters between the frictional contact portions 36a from the rear end of 
the bearing 36 to provide a cooling effect and lubricating effect. 
At the start of the pumping operation, the drive rotor 30 is rotated with 
energization of the drive motor, thus causing rotation of the driven rotor 
32 on the spindle 34 in unison with the impeller 26. As a result, fluid to 
be pumped flows through the suction port 24 into the pump chamber 23 as 
shown by the arrow to be fed out through the discharge port 25 to a 
destination portion (not shown). 
The structure part of the magnet pump described above is the same as the 
prior art structure described earlier with reference to FIG. 3. As for the 
materials of the various parts, the impeller 26, the rear casing 29 and 
the driven rotor 32 are fabricated from a synthetic resin as synthetic 
resin moldings. The sleeve-like bearing 36, the front thrust bearing 
member 27, the mouth ring 28 and the spindle 35 are desirably manufactured 
by using ceramic materials excellent in corrosion resistance, hardness, 
etc. 
In the embodiment of the magnet pump shown in FIG. 1, a structural part 
relating to the rear thrust bearing member as a feature of the present 
invention will now be described. On the back side or rear side of the 
impeller 26 opposite the front side facing the suction port 24, the back 
center of the impeller 26 has an integral boss-like support 40, which 
supports a rear thrust bearing member 41 projecting along the axis line 
X--X. The rear thrust bearing member 41 extending from the support 40 has 
a spherically shaped frictional contact portion 41a as shown, which faces 
a flat axial end face 42 of the spindle 34. The impeller 26 has 
communication holes 43 for circulating the fluid to be pumped. Each 
communication hole 43 is formed from each side of a central portion of the 
impeller 26 since the rear thrust bearing member 41 is disposed on the 
central portion. 
In the above construction, during the steady-state operation of the pump, 
the driven rotor 32 together with the impeller 26 receives a thrust 
directed in the direction toward the front of the pump, thus, it is 
rotated in a state that the mouth ring 28 is brought into frictional 
contact with the front thrust bearing member 27. During this time, the 
rear thrust bearing member 41 is out of contact with the axial end face 42 
of the spindle. However, when the driven rotor part is caused to undergo 
vibrations in the axial direction and receives a rearward thrust due to 
such cause as idling of the pump or trapping of air, the frictional 
contact portion 41a of the rear thrust bearing member 41 is brought into 
contact with the axial end face 42 of the extended end portion 34a of the 
spindle 34, thus receiving a rearward thrust. As the driven rotor part 
continues to rotate in this contact state, frictional heat is generated in 
the frictional contact portions 41a. However, the place where the 
generation of the frictional heat is located is not in the depth of the 
rear casing 29 as in the prior art structure, but is found in the 
neighborhood of and right after the rear side of the impeller 26. Thus, 
the cooling effect due to rotation of the impeller 26 in the front casing 
22 can be readily received. It is thus possible to obtain satisfactory 
heat diffusion of the frictional heat and suppression of the temperature 
rise around the frictional portions. 
Further, with the frictional contact portion 41a of the rear thrust bearing 
member 41 made to be spherical in shape, the area of frictional contact 
with the axial end face of the spindle is reduced, and thus it is possible 
to further suppress heat generation in that locality. 
Further, unlike the prior art structure, no rear thrust bearing member is 
provided between the rear end of the sleeve-like bearing 36 and the boss 
35, and a gap is maintained therebetween at all times even with the rear 
thrust bearing member 41 in contact with the axial end face of the spindle 
34. Thus, as shown by the dashed line arrows, the fluid that reaches the 
depth of the rear casing 29 flows as a circulating flow between the 
frictional portions 36a from the rear end of the bearing 36, comes out 
from the front end and passes through the communication holes 43 formed in 
the impeller 26. Thus, the cooling action and lubricating action between 
the sleeve-like bearing 36 and spindle 34 is satisfactory at all times, 
thus precluding the possibility of seizure or damage to these parts. 
Further, since the circulating flow is provided around the rear thrust 
bearing member 41, heat diffusion is further promoted. 
FIG. 2 shows a modification structure of the rear thrust bearing member 
shown in the embodiment of FIG. 1. In FIG. 2, parts like those in FIG. 1 
are designated by like reference numerals. In this modified structure, a 
support portion for supporting the rear thrust bearing member 41 is 
provided, in lieu of providing it on the impeller 26, on an intermediate 
member 44 forming the front side. The intermediate member 44 constitutes a 
part of the driven rotor 32. Specifically, the intermediate member 44 is 
cylindrical and has a front portion 44a, and it is secured to the outer 
periphery part of the sleeve-like bearing 36, with its front portion 44a 
located between the axial end face 42 of the spindle 35 and the rear side 
of the impeller 26. The bottom 44a serves as the support portion, to which 
the rear thrust bearing member 41 is secured. 
In the above modified structure, the frictional contact portion 41a of the 
rear thrust bearing member 41 has a flat surface shape, whereas the axial 
end face 42 is provided with a frictional contact portion 42a having a 
spherical shape. With the provision of the spherical frictional,contact 
portion on one of the mutually frictional contact portions, the above 
effect is obtainable. However, with the frictional contact portions both 
having flat surfaces, an effect which is not obtainable in the prior art 
is obtainable. Thus, the structure, in which the frictional portions are 
spherical in shape, is not limitative. 
The bottom 44a of the intermediate member 44 has a communication hole 45, 
which is communicated with a communication hole 43 and which is formed in 
the central portion of the impeller 26. The circulating flow which gets 
out of the frictional parts 36a of the sleeve-like bearing 36 is 
circulated as shown by the dashed line, whereby the frictional heat 
generated in the rear thrust bearing member 41 is more satisfactorily 
diffused. 
While the embodiment of the present invention and the modified structure 
thereof have been described in the foregoing, they are by no means 
limitative of the present invention.