U.S. patent application number 10/814712 was filed with the patent office on 2004-12-16 for refrigerant pump and cooling device employing same.
Invention is credited to Ashitani, Hiromasa, Ikeda, Akira, Nakano, Masao.
Application Number | 20040253127 10/814712 |
Document ID | / |
Family ID | 33508828 |
Filed Date | 2004-12-16 |
United States Patent
Application |
20040253127 |
Kind Code |
A1 |
Nakano, Masao ; et
al. |
December 16, 2004 |
Refrigerant pump and cooling device employing same
Abstract
A refrigerant pump employed in a semiconductor cooling device
includes a sealed casing, an electric motor having a stator
disposed outside the sealed casing and a rotor disposed within the
sealed casing, a pump mechanism juxtaposed with the electric motor,
and a drive shaft for transmitting a rotational force of the rotor
to the pump mechanism. The stator is positioned closer to the pump
mechanism than the rotor is.
Inventors: |
Nakano, Masao; (Koka-gun,
JP) ; Ikeda, Akira; (Kusatsu-shi, JP) ;
Ashitani, Hiromasa; (Otsu-shi, JP) |
Correspondence
Address: |
RATNERPRESTIA
P O BOX 980
VALLEY FORGE
PA
19482-0980
US
|
Family ID: |
33508828 |
Appl. No.: |
10/814712 |
Filed: |
March 31, 2004 |
Current U.S.
Class: |
417/423.7 ;
417/423.1 |
Current CPC
Class: |
F04B 17/03 20130101;
F04C 29/0085 20130101 |
Class at
Publication: |
417/423.7 ;
417/423.1 |
International
Class: |
F04B 049/00; F04B
017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2003 |
JP |
2003-164986 |
Claims
What is claimed is:
1. A refrigerant pump comprising: a sealed casing; an electric
motor having a stator disposed outside the sealed casing and a
rotor disposed within the sealed casing; a pump mechanism
juxtaposed with the electric motor; and a drive shaft for
transmitting a rotational force of the rotor to the pump mechanism,
wherein the stator is positioned closer to the pump mechanism than
the rotor is.
2. The refrigerant pump according to claim 1, wherein the drive
shaft has a large-diameter portion having first and second end
surfaces opposite to each other, the first end surface positioned
remote from the electric motor having a higher precision than the
second end surface.
3. The refrigerant pump according to claim 2, wherein a surface of
the drive shaft is carburized or nitrided.
4. A refrigerant pump comprising: a sealed casing; an electric
motor having a stator disposed outside the sealed casing and a
rotor disposed within the sealed casing; a pump mechanism
juxtaposed with the electric motor; a drive shaft for transmitting
a rotational force of the rotor to the pump mechanism; and a
bearing for rotatably supporting the drive shaft, wherein at least
one of the drive shaft ant the bearing has a carburized or nitrided
surface.
5. A refrigerant-circulating cooling device comprising a
refrigerant pump according to any one of claims 1 to 4, wherein the
refrigerant pump is free from oil.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a cooling device for
cooling, for example, a semiconductor element or elements or the
like, which generate a substantial quantity of heat, by utilization
of a change in phase between a liquid phase and a vapor phase of a
refrigerant. The present invention also relates to an oilfree
refrigerant pump employed in such a cooling device.
[0003] 2. Description of the Related Art
[0004] FIG. 1 depicts a conventional refrigerant pump as disclosed
in Japanese Laid-Open Patent Publication (examined) No. 7-47957.
The refrigerant pump shown therein includes a pump mechanism 31 and
an electric motor 32 for driving the pump mechanism 31. The
electric motor 32 includes a stator 33 and a rotor 34 rigidly
secured to a drive shat 35 that drives the pump mechanism 31. The
stator 33 is positioned in alignment with the rotor 34 in the axial
direction of the refrigerant pump.
[0005] In the above-described conventional refrigerant pump,
because the stator 33 is positioned in alignment with the rotor 34
in the axial direction of the refrigerant pump, which of opposite
surfaces of an eccentric portion of the drive shaft 35 receives a
thrust force is not determined and, hence, grinding or polishing of
both the opposite surfaces of the eccentric portion is required.
Furthermore, because the drive shaft 35 is not pushed in only one
direction, it sometimes oscillates, giving rise to noises.
[0006] FIG. 2 depicts another conventional refrigerant pump as
disclosed in Japanese Laid-Open Patent Publication (unexamined) No.
3-233188. The refrigerant pump shown therein includes a pump
mechanism 41 and an electric motor 42 for driving the pump
mechanism 41, wherein a stator 43 is positioned in alignment with a
rotor 44 in the axial direction of the refrigerant pump, as in the
refrigerant pump of FIG. 1.
[0007] The refrigerant pump of FIG. 2 also includes a relatively
expensive bushing 45 disposed inside a bearing 46 for rotatably
supporting a drive shaft 47.
[0008] In the refrigerant pump of FIG. 2, the use of the relatively
expensive bushing 45 inside the bearing 46 results in an increase
in cost. In the case where a lubricating oil is used to lubricate
the bearing 46, there is a good chance that the lubricating oil
enters a cooling system employing a cold plate, and adhesion of the
lubricating oil to the cold plate lowers the heat transfer
performance.
SUMMARY OF THE INVENTION
[0009] The present invention has been developed to overcome the
above-described disadvantages.
[0010] It is accordingly an objective of the present invention to
provide a reliable refrigerant pump that is low in noise level and
can be manufactured at a low cost.
[0011] Another objective of the present invention is to provide a
high-performance cooling device employing the refrigerant pump
referred to above.
[0012] In accomplishing the above and other objectives, the
refrigerant pump according to the present invention includes a
sealed casing, an electric motor having a stator disposed outside
the sealed casing and a rotor disposed within the sealed casing, a
pump mechanism juxtaposed with the electric motor, and a drive
shaft for transmitting a rotational force of the rotor to the pump
mechanism, wherein the stator is positioned closer to the pump
mechanism than the rotor is.
[0013] This construction generates, during operation of the
refrigerant pump, a thrust force that acts to push the drive shaft
towards the pump mechanism so that the drive shaft may be stably
held in contact at a surface thereof with a component part opposed
thereto, making it possible to provide a quiet and reliable
refrigerant pump. Furthermore, it is sufficient if grinding or
polishing is carried out with respect to only the contact surface
of the drive shaft with the component part opposed thereto,
resulting in a relatively inexpensive refrigerant pump.
[0014] Advantageously, the surface of the drive shaft is carburized
or nitrided, making it possible to provide an oilfree refrigerant
pump. A bearing for rotatably supporting the drive shaft may have a
carburized or nitrided surface. In the case where the refrigerant
pump is free from oil, a reduction in heat transfer performance
that has been hitherto caused by oil entering a refrigerating cycle
can be avoided, making it possible to provide a high-performance
cooling device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above and other objectives and features of the present
invention will become more apparent from the following description
of a preferred embodiment thereof with reference to the
accompanying drawings, throughout which like parts are designated
by like reference numerals, and wherein:
[0016] FIG. 1 is a sectional view of a conventional refrigerant
pump;
[0017] FIG. 2 is a sectional view of another conventional
refrigerant pump;
[0018] FIG. 3 is a sectional view of a refrigerant pump according
to the present invention; and
[0019] FIG. 4 is a refrigerating cycle of a semiconductor cooling
device in which the refrigerant pump of FIG. 3 is employed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0020] This application is based on an application No. 2003-164986
filed Jun. 10, 2003 in Japan, the content of which is herein
expressly incorporated by reference in its entirety.
[0021] Referring now to the drawings, there is shown in FIG. 3 a
refrigerant pump embodying the present invention, which includes a
sealed casing 1, an electric motor having a stator 2 and a rotor 4,
and a pump mechanism 5 juxtaposed with the electric motor and
disposed within and fixed to the sealed casing 2. The stator 2 is
disposed outside the sealed casing 1, while the rotor 4 is rigidly
secured to a drive shaft 3 disposed within the sealed casing 1. The
drive shaft 3 has a large-diameter portion having opposite end
surfaces 3a, 3b.
[0022] As shown in FIG. 3, the stator 2 is positioned closer to the
pump mechanism than the rotor 4 is. More specifically, a central
plane 2a of the stator 2 in the axial direction thereof is
positioned offset from a central plane 4a of the rotor 4 in the
axial direction thereof such that the former is positioned closer
to the pump mechanism 5 than the latter by a distance L.
[0023] A rotational force of the rotor 4 is transmitted to the pump
mechanism 5 via the drive shaft 3. The pump mechanism 5 includes a
cylinder bearing 7, a plurality of pump components 8, and a suction
plate 6. The cylinder bearing 7 serves both as a bearing for
rotatably supporting the drive shaft 3 and a cylinder defining a
pump chamber. The surface of the drive shaft 3 is carburized or
nitrided, while the inside of the refrigerant pump is free from
oil. The surface of the cylinder bearing 7 may be carburized or
nitrided in place of the drive shaft 3, or both of them may be
carburized or nitrided.
[0024] FIG. 4 depicts a refrigerating cycle of a semiconductor
cooling device in which an oilfree refrigerant pump referred to
above is employed. The semiconductor cooling device shown in FIG. 4
includes a cold plate 21 for cooling a highly exothermic
semiconductor element or elements that tend to emit a substantial
amount of heat when in operation, a condenser 22, and an oilfree
refrigerant pump 23, all connected in series with each other to
define a refrigerating cycle. An outlet of the condenser 22 and an
inlet of the cold plate 21 are connected with each other with the
refrigerant pump 23 interposed therebetween, while an outlet of the
cold plate 21 and an inlet of the condenser 22 are connected with
each other.
[0025] A refrigerant is filled in this refrigerating cycle. The
condenser 22 is adapted to be cooled by a fan 24.
[0026] The cooling device is so designed that a liquid refrigerant
emerging first from the condenser 22 is supplied towards the cold
plate 21 by the oilfree refrigerant pump 23. The cold plate 21 so
supplied with the liquid refrigerant absorbs heat generated by the
highly exothermic semiconductor element and, in the course of
absorption of the heat, a change in phase from the liquid
refrigerant to a vapor refrigerant takes place within the cold
plate 21. The vapor refrigerant is then supplied to the condenser
22 that is then cooled by the fan 24 so that the vapor refrigerant
within the condenser 22 undergoes a phase change to a liquid
refrigerant.
[0027] According to the above-described construction, because the
axial central plane 2a of the stator 2 is positioned closer to the
pump mechanism 5 than the axial central plane 4a of the rotor 4,
when the electric motor is energized, a thrust force as indicated
by an arrow A that acts to push the rotor 4 towards the pump
mechanism 5 is created, as show in FIG. 3. This thrust force also
acts to push towards the suction plate 6 the drive shaft 3 to which
the rotor 4 is rigidly secured so that the end surface 3a of the
large-diameter portion of the drive shaft 3 may be stably held in
contact with the suction plate 6. On the other hand, the end
surface 3b of the large-diameter portion of the drive shaft 3
remote from the suction plate 6 is brought into contact with the
cylinder bearing 7 under a considerably small pressure or is not
brought into contact therewith.
[0028] Accordingly, grinding or polishing is required with respect
to only the end surface 3a of the large-diameter portion of the
drive shaft 3. That is, the end surface 3a remote from the electric
motor has a higher precision than the end surface 3b, resulting in
an inexpensive drive shaft. Furthermore, noises that have been
hitherto caused by oscillation of the drive shaft 3 are
reduced.
[0029] In addition, because the surface of the drive shaft 3 is
carburized or nitrided, and the inside of the refrigerant pump is
free from oil, a reduction in the heat transfer coefficient between
the refrigerant and an object to be cooled (the cold plate in this
case) that has been hitherto caused by oil contamination of the
refrigerating cycle can be reduced, making it possible to prevent
the cooling power from reducing.
[0030] Although the present invention has been fully described by
way of examples with reference to the accompanying drawings, it is
to be noted here that various changes and modifications will be
apparent to those skilled in the art. Therefore, unless such
changes and modifications otherwise depart from the spirit and
scope of the present invention, they should be construed as being
included therein.
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