U.S. patent application number 16/095112 was filed with the patent office on 2019-07-11 for turbo compressor and turbo refrigerator provided with same.
This patent application is currently assigned to MITSUBISHI HEAVY INDUSTRIES THERMAL SYSTEMS, LTD.. The applicant listed for this patent is MITSUBISHI HEAVY INDUSTRIES THERMAL SYSTEMS, LTD.. Invention is credited to Yasushi HASEGAWA, Shintaro OMURA.
Application Number | 20190211834 16/095112 |
Document ID | / |
Family ID | 60116801 |
Filed Date | 2019-07-11 |
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United States Patent
Application |
20190211834 |
Kind Code |
A1 |
HASEGAWA; Yasushi ; et
al. |
July 11, 2019 |
TURBO COMPRESSOR AND TURBO REFRIGERATOR PROVIDED WITH SAME
Abstract
To realize a reduction in cost and extension of the lifespan of
a auxiliary bearing which is disposed adjacent to a non-contact
bearing supporting a rotor shaft of a centrifugal compressor. A
centrifugal compressor (2) includes: a rotor shaft (15); an
electric motor (14) provided at an intermediate portion of the
rotor shaft (15) in a coaxial manner with the rotor shaft (15), the
electric motor (14) being configured to rotationally drive the
rotor shaft (15); an impeller (16) fixed to one end of the rotor
shaft (15) and forming a refrigerant compressing unit (7) which
compresses a refrigerant; main bearings (18a, 18b) formed of
non-contact bearings pivotally supporting the rotor shaft (15) at a
portion between the electric motor (14) and the impeller (16), and
at another end of the rotor shaft (15); auxiliary bearings (19a,
19b) disposed adjacent to the main bearings (18a, 18b), the
auxiliary bearings being configured to pivotally support the rotor
shaft (15) in place of the main bearings (18a, 18b) in a state
where functioning of the main bearings (18a, 18b) stops; and a
lubricating refrigerant supply unit (25) configured to supply the
refrigerant as a lubricant to an inside of the auxiliary bearings
(19a, 19b) in the state where the functioning of the main bearings
(18a, 18b) stops.
Inventors: |
HASEGAWA; Yasushi; (Tokyo,
JP) ; OMURA; Shintaro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI HEAVY INDUSTRIES THERMAL SYSTEMS, LTD. |
Tokyo |
|
JP |
|
|
Assignee: |
MITSUBISHI HEAVY INDUSTRIES THERMAL
SYSTEMS, LTD.
Tokyo
JP
|
Family ID: |
60116801 |
Appl. No.: |
16/095112 |
Filed: |
April 18, 2017 |
PCT Filed: |
April 18, 2017 |
PCT NO: |
PCT/JP2017/015636 |
371 Date: |
March 15, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/056 20130101;
F04D 29/058 20130101; F04D 29/58 20130101; F04D 29/063 20130101;
F25B 1/053 20130101; F25B 31/002 20130101; F04D 29/059 20130101;
F25B 1/10 20130101; F25B 2339/047 20130101; F04D 25/06 20130101;
F25B 31/008 20130101; F04D 17/10 20130101; F25B 25/005
20130101 |
International
Class: |
F04D 29/063 20060101
F04D029/063; F04D 17/10 20060101 F04D017/10; F04D 25/06 20060101
F04D025/06; F04D 29/059 20060101 F04D029/059; F25B 1/053 20060101
F25B001/053; F25B 31/00 20060101 F25B031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 22, 2016 |
JP |
2016-086202 |
Claims
1. A centrifugal compressor comprising: a rotor shaft; an electric
motor provided at an intermediate portion of the rotor shaft in a
coaxial manner with the rotor shaft, the electric motor being
configured to rotationally drive the rotor shaft; an impeller fixed
to one end of the rotor shaft and forming a refrigerant compressing
unit which compresses a refrigerant; a non-contact bearing
configured to pivotally support the rotor shaft at a portion
between the electric motor and the impeller, and a non-contact
bearing configured to pivotally support the rotor shaft at another
end of the rotor shaft; an auxiliary bearing disposed adjacent to
the non-contact bearing, the auxiliary bearing being configured to
pivotally support the rotor shaft in place of the non-contact
bearing in a state where functioning of the non-contact bearing
stops; and a lubricating refrigerant supply unit configured to
supply the liquid refrigerant as a lubricant to an inside of the
auxiliary bearing in the state where the functioning of the
non-contact bearing stops.
2. The centrifugal compressor according to claim 1, wherein the
lubricating refrigerant supply unit includes: a liquid refrigerant
storage unit in which the refrigerant in a liquid phase is stored;
a liquid refrigerant supply passage configured to connect the
auxiliary bearing and the liquid refrigerant storage unit with each
other; and a solenoid valve connected to the liquid refrigerant
supply passage, the solenoid valve being configured to close in an
energized state.
3. The centrifugal compressor according to claim 2, wherein the
liquid refrigerant storage unit is formed of a bottom portion of a
condenser where the refrigerant compressed by the refrigerant
compressing unit is to be condensed.
4. The centrifugal compressor according to claim 2, wherein the
liquid refrigerant storage unit is formed of a liquid refrigerant
jacket for cooling the electric motor, the liquid refrigerant
jacket being provided to a casing which houses the electric
motor.
5. The centrifugal compressor according to claim 2, wherein the
liquid refrigerant storage unit is formed of a pressure applying
container which stores the refrigerant in a liquid phase while
applying a pressure higher than an ambient pressure of the
auxiliary bearing.
6. The centrifugal compressor according to claim 1, wherein the
auxiliary bearing is formed of a rolling bearing, and a ceramic
material is adopted as a material for forming at least one of an
outer race, an inner race, and a rolling element of the auxiliary
bearing.
7. The centrifugal compressor according to claim 1, wherein the
auxiliary bearing is formed of a rolling bearing, and at least one
of an outer race, an inner race, and a rolling element of the
auxiliary bearing is coated with a material which allows formation
of a lubricating film with lubrication due to a low viscosity
fluid.
8. The centrifugal compressor according to claim 1, wherein the
auxiliary bearing is formed of a rolling bearing, and at least one
of an outer race, an inner race, and a rolling element of the
auxiliary bearing is coated with diamond-like carbon.
9. A centrifugal chiller comprising: the centrifugal compressor
described in claim 1; a condenser configured to condense the
refrigerant compressed by the centrifugal compressor; and an
evaporator configured to evaporate the refrigerant condensed.
Description
TECHNICAL FIELD
[0001] The present invention relates to a turbo compressor, and a
centrifugal chiller provided with the same.
BACKGROUND ART
[0002] As well known, a centrifugal chiller, such as one used as a
heat source for district heating and cooling, includes a
centrifugal turbine type centrifugal compressor which is driven by
an electric motor. As disclosed in Patent Literature 1, there is
known a centrifugal compressor where non-contact bearings, such as
magnetic bearings or gas bearings (air bearings), are used as
bearings for a rotor shaft so that the bearings have no rotational
resistance and, at the same time, no lubrication of the bearings is
required. The non-contact bearings support the rotor shaft in a
floating state with respect to the bearings. Accordingly,
rotational resistance of the bearings can be made extremely
small.
[0003] In this case, auxiliary bearings (touchdown bearings) are
provided, and the auxiliary bearings support the rotor shaft in
place of the non-contact bearings when power supply cuts off due to
power failure or the like so that the functioning of the
non-contact bearings stops. Rolling bearings are used for the
auxiliary bearings. A gap in a radial direction of the auxiliary
bearing is set smaller than that of the non-contact bearing.
Accordingly, when power supply cuts off, the rotor shaft is
supported (touched down) by the auxiliary bearings prior to
contacting with the non-contact bearings. Therefore, damage to the
non-contact bearings can be prevented.
CITATION LIST
Patent Literature
[0004] [PTL 1] Japanese Unexamined Patent Application, Publication
No. 2002-218708
SUMMARY OF INVENTION
Technical Problem
[0005] Rolling bearings are generally adopted for auxiliary
bearings. However, non-contact bearings require no lubrication or
no cooling so that a lubricant oil system is not provided.
Accordingly, the auxiliary bearings, formed of the rolling
bearings, are subject to perform grease lubrication or no
lubrication in many cases.
[0006] For this reason, there has been a problem that a lifespan of
the auxiliary bearing is short, or the number of touchdowns is
limited. For preventing such a problem, it is necessary to adopt
special steel as a material for forming the auxiliary bearings, or
to apply special surface treatment to an inner and outer races and
a rolling element, thus making a bearing system expensive.
[0007] The present invention has been made under such
circumstances, and it is an object of the present invention to
provide a centrifugal compressor which can realize a reduction in
cost and extension of the lifespan of a auxiliary bearing disposed
adjacent to a non-contact bearing supporting a rotor shaft, and to
provide a centrifugal chiller provided with the centrifugal
compressor.
Solution to Problem
[0008] To overcome the above-mentioned problem, the present
invention adopts the following means.
[0009] A centrifugal compressor according to a first aspect of the
present invention includes: a rotor shaft; an electric motor
provided at an intermediate portion of the rotor shaft in a coaxial
manner with the rotor shaft, the electric motor being configured to
rotationally drive the rotor shaft; an impeller fixed to one end of
the rotor shaft and forming a refrigerant compressing unit which
compresses a refrigerant; a non-contact bearing configured to
pivotally support the rotor shaft at a portion between the electric
motor and the impeller, and a non-contact bearing configured to
pivotally support the rotor shaft at another end of the rotor
shaft; an auxiliary bearing disposed adjacent to the non-contact
bearing, the auxiliary bearing being configured to pivotally
support the rotor shaft in place of the non-contact bearing in a
state where functioning of the non-contact bearing stops; and a
lubricating refrigerant supply unit configured to supply the
refrigerant as a lubricant to an inside of the auxiliary bearing in
the state where the functioning of the non-contact bearing
stops.
[0010] According to the centrifugal compressor having the
above-mentioned configuration, when power supply cuts off due to
power failure or the like so that the functioning of the
non-contact bearings stops, the auxiliary bearing supports the
rotor shaft in place of the non-contact bearing and, at the same
time, a refrigerant is supplied as a lubricant to the inside of the
auxiliary bearing by the lubricating refrigerant supply unit.
Accordingly, a lubrication state of the auxiliary bearing can be
improved, and a conventional bearing can be used without using a
special expensive bearing, thus realizing a reduction in cost and
extension of the lifespan of the auxiliary bearing.
[0011] In the above-mentioned configuration, the lubricating
refrigerant supply unit may include: a liquid refrigerant storage
unit in which the refrigerant in a liquid phase is stored; a liquid
refrigerant supply passage configured to connect the auxiliary
bearing and the liquid refrigerant storage unit with each other;
and a solenoid valve connected to the liquid refrigerant supply
passage, the solenoid valve being configured to close in an
energized state.
[0012] With the above-mentioned configuration, the solenoid valve,
which closes when in an energized state, opens when power supply
cuts off. Accordingly, the refrigerant in a liquid phase stored in
the liquid refrigerant storage unit is supplied to the auxiliary
bearing through the liquid refrigerant supply passage. According to
this configuration, without providing a control unit, a refrigerant
can be supplied to the auxiliary bearing by opening the solenoid
valve when power supply cuts off, thus realizing a reduction in
cost of the bearing system.
[0013] In the above-mentioned configuration, the liquid refrigerant
storage unit may be formed of a bottom portion of a condenser where
the refrigerant compressed by the refrigerant compressing unit is
to be condensed. A compressed and condensed refrigerant in a liquid
phase is stored in a bottom portion of the condenser, and the
pressure of this refrigerant in a liquid phase is higher than an
ambient pressure of the auxiliary bearings. Accordingly,
simultaneously with the opening of the solenoid valve, the
refrigerant is rapidly supplied to the auxiliary bearings due to a
pressure difference. Therefore, when power supply cuts off, a
refrigerant can be quickly supplied to the auxiliary bearings so as
to lubricate the auxiliary bearings, thus realizing extension of
the lifespan of the auxiliary bearings.
[0014] In the above-mentioned configuration, the liquid refrigerant
storage unit may be formed of a liquid refrigerant jacket for
cooling the electric motor, the liquid refrigerant jacket being
provided to a casing which houses the electric motor. The liquid
refrigerant jacket is positioned in the vicinity of the auxiliary
bearings, and a compressed and condensed refrigerant in a liquid
phase circulates through the liquid refrigerant jacket.
Accordingly, simultaneously with the opening of the solenoid valve
when power supply cuts off, the refrigerant in the liquid
refrigerant jacket can be easily supplied to the auxiliary bearings
due to a pressure difference or gravity. According to this
configuration, it is unnecessary to connect the centrifugal
compressor and peripheral equipment by the liquid refrigerant
supply passage and hence, the bearing system can be simplified.
[0015] In the above-mentioned configuration, the liquid refrigerant
storage unit may be formed of a pressure applying container which
stores the refrigerant in a liquid phase while applying a pressure
higher than an ambient pressure of the auxiliary bearing. With such
a configuration, simultaneously with the opening of the solenoid
valve when power supply cuts off, the refrigerant in the pressure
applying container is supplied to the auxiliary bearings due to a
pressure difference. According to this configuration, it is
unnecessary to provide a system which extracts a refrigerant
compressed by a centrifugal compressor and hence, the bearing
system can be simplified. Further, irrespective of the operation
state of the chiller, a lubricating refrigerant supply pressure can
be maintained at a value equal to or more than a required specified
value and hence, a lubricating refrigerant can be supplied with
certainty.
[0016] In the above-mentioned configuration, the auxiliary bearing
may be formed of a rolling bearing, and a ceramic material may be
adopted as a material for forming at least one of an outer race, an
inner race, and a rolling element of the auxiliary bearing. The
ceramic material has a small amount of thermal expansion so that an
amount of size variation of the bearing gap can be made small when
the temperature of the auxiliary bearing varies. Accordingly, a
fluid having low viscosity, such as a refrigerant, can favorably
lubricate the auxiliary bearings.
[0017] In the above-mentioned configuration, the auxiliary bearing
may be formed of a rolling bearing, and a material which allows
formation of a lubricating film with lubrication due to a low
viscosity fluid may be adopted as a material for forming at least
one of an outer race, an inner race, and a rolling element of the
auxiliary bearing. With such a configuration, a fluid having low
viscosity, such as a refrigerant, can favorably lubricate the
auxiliary bearings.
[0018] In the above-mentioned configuration, the auxiliary bearing
may be formed of a rolling bearing, and at least one of an outer
race, an inner race, and a rolling element of the auxiliary bearing
may be coated with diamond-like carbon. Diamond-like carbon allows
the formation of a lubricating film with lubrication due to a low
viscosity fluid and hence, a fluid having low viscosity, such as a
refrigerant, can favorably lubricate the auxiliary bearings.
[0019] A centrifugal chiller according to a second aspect of the
present invention includes: the centrifugal compressor described in
any one of the above-mentioned configurations; a condenser
configured to condense the refrigerant compressed by the
centrifugal compressor; and an evaporator configured to evaporate
the refrigerant condensed. With such a configuration, the
above-mentioned respective manner of operations and advantageous
effects can be acquired.
Advantageous Effects of Invention
[0020] As described above, according to the turbo compressor and
the centrifugal chiller provided with the same of the present
invention, it is possible to realize both of a reduction in cost
and extension of the lifespan of a auxiliary bearing disposed
adjacent to the non-contact bearing supporting the rotor shaft of
the centrifugal compressor.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is an overall view of a centrifugal chiller showing a
first embodiment of the present invention.
[0022] FIG. 2 is an enlarged longitudinal cross-sectional view of a
centrifugal compressor shown in FIG. 1.
[0023] FIG. 3 is an enlarged longitudinal cross-sectional view of a
centrifugal compressor showing a second embodiment of the present
invention.
[0024] FIG. 4 is an overall view of a centrifugal chiller showing a
third embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0025] Hereinafter, a plurality of embodiments of the present
invention are described with reference to drawings.
First Embodiment
[0026] FIG. 1 is an overall view of a centrifugal chiller showing a
first embodiment of the present invention. The centrifugal chiller
1 is configured to include: a centrifugal compressor 2 which
compresses a refrigerant; a condenser 3; an expansion valve 4; and
an evaporator 5. A refrigerant compressing unit 7 of the
centrifugal compressor 2 and the condenser 3 are connected with
each other by a discharge pipe 8. The condenser 3 and the
evaporator 5 are connected with each other by a refrigerant pipe 9.
The evaporator 5 and the centrifugal compressor 2 (refrigerant
compressing unit 7) are connected with each other by a suction pipe
10. The expansion valve 4 is connected to the refrigerant pipe
9.
[0027] In this centrifugal chiller 1, a refrigerant compressed by
the centrifugal compressor 2 (refrigerant compressing unit 7) is
fed to the condenser 3 through the discharge pipe 8, and is
subjected to heat exchange with cooling water in the condenser 3
and hence, heat of condensation is cooled so that the refrigerant
is condensed. The cooling water heated in the condenser 3 is
utilized for air heating conditioning or the like.
[0028] The refrigerant condensed in the condenser 3 passes through
the expansion valve 4 provided to the refrigerant pipe 9, thus
being adiabatically expanded, and fed to the evaporator 5. In the
inside of the evaporator 5, the refrigerant, which is adiabatically
expanded in the expansion valve 4 thus having a low temperature, is
subjected to heat exchange with water. Chilled water cooled in the
evaporator 5 is utilized for air cooling conditioning or as
industrial cooling water. The refrigerant which is vaporized due to
heat exchange with cooling water is sucked into the centrifugal
compressor 2 (refrigerant compressing unit 7) again through the
suction pipe 10, and is compressed. Hereinafter, this cycle is
repeated.
[0029] As also shown in FIG. 2, the centrifugal compressor 2 is
configured to include: a casing 13 forming an outer shell of the
centrifugal compressor 2; an electric motor 14; a rotor shaft 15;
impellers 16 forming the refrigerant compressing unit 7; a pair of
main bearings 18a, 18b; a pair of auxiliary bearings 19a, 19b
disposed adjacent to these main bearings 18a, 18b; and thrust
bearings 20a, 20b. The inside of the casing 13 is divided into an
electric motor chamber 13A and a compression chamber 13B by a
partition wall 13a. The electric motor 14 is housed in the electric
motor chamber 13A, and the refrigerant compressing unit 7
(impellers 16) is housed in the compression chamber 13B.
[0030] The electric motor 14 is configured to include a stator 14a
and a rotor 14b. The stator 14a is fixed to the casing 13 side. The
rotor 14b is fixed to the rotor shaft 15, and rotates in the stator
14a. One end of the rotor shaft 15 penetrates the partition wall
13a and is inserted into the compression chamber 13B. The impellers
16 are provided to the inserted portion such that the impellers 16
rotate integrally with the rotor shaft 15, thus forming the
refrigerant compressing unit 7.
[0031] One main bearing (18a) out of the pair of main bearings 18a,
18b pivotally supports a portion of the rotor shaft 15 between the
electric motor 14 and the impeller 16, and the other main bearing
(18b) pivotally supports the other end (an end portion on the side
opposite to the impellers 16) of the rotor shaft 15. For these main
bearings 18a, 18b, known non-contact bearings, such as magnetic
bearings or gas bearings (air bearings) are used. With such a
configuration, rotational resistance can be reduced and no
lubrication is required.
[0032] The pair of auxiliary bearings 19a, 19b, which are disposed
adjacent to the main bearings 18a, 18b, are formed of rolling
bearings. The auxiliary bearings 19a, 19b pivotally support the
rotor shaft 15 in place of the main bearings 18a, 18b in a state
where the functioning of the main bearings 18a, 18b stops when
power supply cuts off, such as when power failure occurs. That is,
the auxiliary bearings 19a, 19b are so-called touchdown bearings.
The bearing gap of the auxiliary bearings 19a, 19b is designed to
be sufficiently smaller than the bearing gap of the main bearings
18a, 18b. For example, the bearing gap of the auxiliary bearings
19a, 19b is designed to be approximately half of the bearing gap of
the main bearings 18a, 18b. Accordingly, even in the case where the
functioning of the main bearings 18a, 18b stops so that the
auxiliary bearings 19a, 19b support the rotor shaft 15, the bearing
gaps of the main bearings 18a, 18b remain and hence, damage to the
main bearings 18a, 18b can be avoided.
[0033] The thrust bearings 20a, 20b are provided on opposite sides
of a disk-shaped thrust plate 15a, and the thrust plate 15a is
disposed at a distal end of the rotor shaft 15 on the other end
side. The thrust bearings 20a, 20b restricts the movement of the
rotor shaft 15 in the axial direction. In the same manner as the
main bearings 18a, 18b, the thrust bearings 20a, 20b are also
formed of non-contact bearings.
[0034] As shown in FIG. 1 and FIG. 2, the centrifugal compressor 2
is provided with a lubricating refrigerant supply unit 25. The
lubricating refrigerant supply unit 25 supplies a liquid
refrigerant as a lubricant to the inside of the auxiliary bearings
19a, 19b formed of rolling bearings which support the rotor shaft
15 in place of the main bearings 18a, 18b as described above when
power supply cuts off due to power failure or the like so that the
functioning of the main bearings 18a, 18b, formed of non-contact
bearings, stops. The lubricating refrigerant supply unit 25
includes: a liquid refrigerant storage unit 26 in which a
refrigerant R in a liquid phase is stored; a liquid refrigerant
supply passage 27 configured to connect the liquid refrigerant
storage unit 26 and the auxiliary bearings 19a, 19b with each
other; and a solenoid valve 28 connected to the liquid refrigerant
supply passage 27.
[0035] In this embodiment, a bottom portion of the condenser 3 is
utilized as the liquid refrigerant storage unit 26. A compressed
and condensed refrigerant R in a liquid phase is always stored in
the bottom portion of the condenser 3, and one end of the liquid
refrigerant supply passage 27 is connected to the bottom portion at
a position lower than the liquid surface of the refrigerant R in a
liquid phase. The other end of the liquid refrigerant supply
passage 27 is branched into two branch passages 27a, 27b. One
branch passage 27a is connected to one auxiliary bearing 19a, and
the other branch passage 27b is connected to the other auxiliary
bearing 19b. The solenoid valve 28 is connected to the liquid
refrigerant supply passage 27 at a section forward of where the
liquid refrigerant supply passage 27 is branched. The solenoid
valve 28 closes when in an energized state. That is, the solenoid
valve 28 is a normally-open solenoid valve.
[0036] With respect to the centrifugal chiller 1 and the
centrifugal compressor 2 having the above-mentioned configuration,
when power supply cuts off due to power failure or the like, the
functioning of the main bearings 18a, 18b, formed of non-contact
bearings, stops. Accordingly, the auxiliary bearings 19a, 19b
support the rotor shaft 15 in place of the main bearings 18a, 18b.
At the same time, the solenoid valve 28, which closes when in an
energized state, opens due to cutoff of power supply.
[0037] A refrigerant R in a liquid phase is stored in the liquid
refrigerant storage unit 26, which is disposed at the bottom
portion of the condenser 3, and the pressure of the refrigerant R
is higher than the ambient pressure of the auxiliary bearings 19a,
19b (an inner pressure of the casing 13). Accordingly,
simultaneously with the opening of the solenoid valve 28, the
refrigerant R is supplied to the auxiliary bearings 19a, 19b
through the liquid refrigerant supply passage 27 (branch passages
27a, 27b) due to a pressure difference. Therefore, the refrigerant
R in a liquid phase is supplied as a lubricant to the inside of the
auxiliary bearings 19a, 19b so that the auxiliary bearings 19a, 19b
are lubricated and cooled.
[0038] As described above, the centrifugal compressor 2 includes
the lubricating refrigerant supply unit 25 which supplies a
refrigerant R in a liquid phase as a lubricant to the inside of the
auxiliary bearings 19a, 19b, which support the rotor shaft 15 in
place of the main bearings 18a, 18b formed of non-contact bearings,
in a state where the functioning of the main bearings 18a, 18b
stops. Accordingly, a lubrication state of the auxiliary bearings
19a, 19b when power supply cuts off can be improved, and
conventional bearings can be used without using special expensive
bearings. Therefore, it is possible to realize both of a reduction
in cost and extension of the lifespan of the auxiliary bearings
19a, 19b.
[0039] For the solenoid valve 28 which opens the liquid refrigerant
supply passage 27 when power supply cuts off, a normally-open
solenoid valve which closes when in an energized state is adopted.
Accordingly, without providing a dedicated control unit, a
refrigerant R can be supplied to the auxiliary bearings 19a, 19b by
opening the solenoid valve 28 when power supply cuts off.
Therefore, it is possible to realize a reduction in cost of a
bearing system.
[0040] The liquid refrigerant storage unit 26 is a supply source of
a refrigerant R in a liquid phase to be supplied as a lubricant to
the inside of the auxiliary bearings 19a, 19b, and the liquid
refrigerant storage unit 26 is formed of the bottom portion of the
condenser 3. A compressed and condensed refrigerant R in a liquid
phase is stored in the bottom portion of the condenser 3, and the
pressure of the refrigerant R in a liquid phase is higher than the
ambient pressure of the auxiliary bearings 19a, 19b. Accordingly,
simultaneously with the opening of the solenoid valve 28, the
refrigerant R is rapidly supplied to the auxiliary bearings 19a,
19b due to a pressure difference. Therefore, when power supply cuts
off, the refrigerant R can be quickly supplied to the auxiliary
bearings 19a, 19b so as to lubricate the auxiliary bearings 19a,
19b, thus realizing extension of the lifespan of the auxiliary
bearings 19a, 19b.
[0041] A ceramic material may be adopted as a material for forming
at least one of an outer race, an inner race, and a rolling element
of the auxiliary bearings 19a, 19b, formed of rolling bearings. The
ceramic material has a small amount of thermal expansion so that an
amount of size variation of the bearing gap can be made small when
the temperature of the auxiliary bearings 19a, 19b varies.
Accordingly, a fluid having low viscosity, such as the refrigerant
R in a liquid phase, can favorably lubricate the auxiliary bearings
19a, 19b.
[0042] Further, as a material for forming at least one of the outer
race, the inner race, and the rolling element of the auxiliary
bearings 19a, 19b, a material which easily allows the formation of
a lubricating film with lubrication due to a low viscosity fluid
may be adopted. Alternatively, the outer race, the inner race, or
the rolling element may be coated with a material, such as
diamond-like carbon. With such a configuration, a fluid having low
viscosity, such as the refrigerant R in a liquid phase, can
favorably lubricate the auxiliary bearings 19a, 19b.
Second Embodiment
[0043] FIG. 3 is an enlarged longitudinal cross-sectional view of a
centrifugal compressor 2A showing a second embodiment of the
present invention. The centrifugal compressor 2A differs from the
centrifugal compressor 2 of the first embodiment with respect to a
point that a liquid refrigerant jacket 31, which extends along the
circumferential direction, is formed at an intermediate portion in
the axial direction of a casing 13 for the centrifugal compressor
2A. The liquid refrigerant jacket 31 is originally configured to
cool an electric motor 14 (stator 14a), and a refrigerant R in a
liquid phase which is compressed and condensed thus being cooled
and having a low temperature circulates through the liquid
refrigerant jacket 31. Other configurations are similar to
corresponding configurations of the centrifugal compressor 2 of the
first embodiment and hence, corresponding components are given the
same characters, and repeated description is omitted.
[0044] Also in the centrifugal compressor 2A, when power supply
cuts off due to power failure or the like so that the functioning
of main bearings 18a, 18b, formed of non-contact bearings, stops,
auxiliary bearings 19a, 19b support a rotor shaft 15 in place of
the main bearings 18a, 18b. Further, the centrifugal compressor 2A
is provided with a lubricating refrigerant supply unit 32 which
supplies a refrigerant as a lubricant to the inside of the
auxiliary bearings 19a, 19b. In this lubricating refrigerant supply
unit 32, the liquid refrigerant jacket 31 is utilized as a liquid
refrigerant storage unit 33 in which a refrigerant R in a liquid
phase is stored.
[0045] Further, the lubricating refrigerant supply unit 32
includes: a pair of liquid refrigerant supply passages 34a, 34b,
which connect the liquid refrigerant jacket 31 and the auxiliary
bearings 19a, 19b with each other; and solenoid valves 35a, 35b
which are respectively connected to the liquid refrigerant supply
passages 34a, 34b. Each of the solenoid valves 35a, 35b is a
normally-open solenoid valve which closes when in an energized
state in the same manner as the solenoid valve 28 in the first
embodiment.
[0046] In the centrifugal compressor 2A having the above-mentioned
configuration, when power supply cuts off due to power failure or
the like, the functioning of the main bearings 18a, 18b, formed of
non-contact bearings, stops so that the auxiliary bearings 19a, 19b
support the rotor shaft 15 in place of the main bearings 18a, 18b.
At the same time, the solenoid valves 35a, 35b, which close in an
energized state, open due to cutoff of power supply. Accordingly, a
refrigerant R in a liquid phase stored in the liquid refrigerant
jacket 31 is supplied to the auxiliary bearings 19a, 19b through
the liquid refrigerant supply passages 34a, 34b due to a pressure
difference or gravity. Therefore, the refrigerant R in a liquid
phase is supplied as a lubricant to the inside of the auxiliary
bearings 19a, 19b so that the auxiliary bearings 19a, 19b are
lubricated and cooled.
[0047] In this centrifugal compressor 2A, the liquid refrigerant
jacket 31 is utilized as the liquid refrigerant storage unit 33 of
the lubricating refrigerant supply unit 32. The liquid refrigerant
jacket 31 is positioned in the vicinity of the auxiliary bearings
19a, 19b, and a compressed and condensed refrigerant R in a liquid
phase circulates through the liquid refrigerant jacket 31.
Accordingly, simultaneously with the opening of the solenoid valves
35a, 35b when power supply cuts off, the refrigerant R in the
liquid refrigerant jacket 31 can be easily supplied to the
auxiliary bearings 19a, 19b. According to this configuration, it is
unnecessary to connect the centrifugal compressor 2A and peripheral
equipment by a refrigerant supply passage and hence, a bearing
system can be simplified.
Third Embodiment
[0048] FIG. 4 is an overall view of a centrifugal chiller showing a
third embodiment of the present invention. In this centrifugal
chiller 1A, the configuration of the centrifugal compressor 2 per
se is similar to the configuration of the centrifugal compressor in
the first embodiment (see FIG. 1, FIG. 2) and hence, corresponding
components are given the same characters, and repeated description
is omitted.
[0049] The centrifugal chiller 1A is also provided with a
lubricating refrigerant supply unit 40 which supplies a refrigerant
R as a lubricant to the inside of auxiliary bearings 19a, 19b which
support a rotor shaft 15 in place of main bearings 18a, 18b when
power supply cuts off. The lubricating refrigerant supply unit 40
includes: a liquid refrigerant storage unit 41 in which a
refrigerant R in a liquid phase is stored; a liquid refrigerant
supply passage 27 which connects the liquid refrigerant storage
unit 41 and the auxiliary bearings 19a, 19b with each other; and a
solenoid valve 28 connected to the liquid refrigerant supply
passage 27. In the same manner as the liquid refrigerant supply
passage 27 in the first embodiment, the liquid refrigerant supply
passage 27 in this embodiment is branched into branch passages 27a,
27b, and connected to the auxiliary bearings 19a, 19b. However, the
liquid refrigerant supply passage 27 in this embodiment differs
from the first embodiment with respect to a point that an end
portion of the liquid refrigerant supply passage 27 on the upstream
side is connected not to a condenser 3 but to the liquid
refrigerant storage unit 41. In the same manner as the first
embodiment, the solenoid valve 28 is a normally-open solenoid valve
which closes when in an energized state.
[0050] For the liquid refrigerant storage unit 41, a pressure
applying container 43 is used which stores a refrigerant R in a
liquid phase while applying a pressure higher than an ambient
pressure of the auxiliary bearings 19a, 19b to the refrigerant R.
The pressure applying container 43 includes: a container body 44
having a cylindrical shape, for example; a piston 45 which is
provided in the container body 44 in a slidable manner in the axial
direction; and a spring 46 which biases the piston 45 to an end
surface (an end surface on the lower side in this embodiment) of
the container body 44 to which the liquid refrigerant supply
passage 27 is connected. The refrigerant R in a liquid phase stored
in the pressure applying container 43 (container body 44) is
pressed by the spring 46 by way of the piston 45 so that a pressure
higher than an ambient pressure of the auxiliary bearings 19a, 19b
(an inner pressure of the casing 13) is applied to the refrigerant
R.
[0051] In the centrifugal chiller 1A and the centrifugal compressor
2 having the above-mentioned configuration, when power supply cuts
off due to power failure or the like, the functioning of the main
bearings 18a, 18b, formed of non-contact bearings, stops so that
the auxiliary bearings 19a, 19b support the rotor shaft 15 in place
of the main bearings 18a, 18b. At the same time, the solenoid valve
28, which closes when in an energized state, opens due to cutoff of
power supply.
[0052] The refrigerant R in a liquid phase is stored in the
pressure applying container 43 forming the liquid refrigerant
storage unit 41, and a pressure higher than the ambient pressure of
the auxiliary bearings 19a, 19b is applied to the refrigerant R by
a biasing force of the spring 46. Accordingly, the refrigerant R is
supplied to the auxiliary bearings 19a, 19b through the liquid
refrigerant supply passage 27 (branch passages 27a, 27b) due to a
pressure difference simultaneously with the opening of the solenoid
valve 28. Therefore, the refrigerant R in a liquid phase is
supplied as a lubricant to the inside of the auxiliary bearings
19a, 19b so that the auxiliary bearings 19a, 19b are lubricated and
cooled.
[0053] According to this configuration, it is unnecessary to
provide a system which extracts a refrigerant compressed by the
centrifugal compressor 2 and hence, a bearing system can be
simplified. Further, irrespective of the operation state of the
centrifugal chiller 1A, a liquid lubricating refrigerant supply
pressure can be maintained at a value equal to or more than a
required specified value and hence, a liquid lubricating
refrigerant can be supplied with certainty. The structure of the
pressure applying container 43 is not always limited to the
above-mentioned configuration. For example, the weight of a weight
may be applied to the piston 45 instead of the biasing force of the
spring 46. Alternatively, the structure may be changed to a
so-called accumulator structure where the inside of the pressure
applying container 43 is divided into two parts in the axial
direction by a rubber film, a nitrogen gas or the like is sealed in
one chamber closed, and a refrigerant R is stored in the other
chamber to which the refrigerant supply passage 27 is
connected.
[0054] As has been described above, according to the centrifugal
compressors 2, 2A and the centrifugal chillers 1, 1A provided with
the centrifugal compressors 2, 2A of the above-mentioned each
embodiment, when the functioning of the main bearings 18a, 18b,
formed of non-contact bearings supporting the rotor shaft 15 of the
centrifugal compressors 2, 2A, stops, a liquid refrigerant can be
supplied as a lubricant to the auxiliary bearings 19a, 19b, which
are disposed adjacent to the main bearings 18a, 18b. Accordingly,
it is possible to realize a reduction in cost and extension of the
lifespan of the auxiliary bearings 19a, 19b.
[0055] The present invention is not limited to the configurations
of the above-mentioned respective embodiments, and changes and
modifications may be suitably made. Embodiments obtained by making
such changes or modifications also fall within the scope of the
present invention. For example, the overall configuration or
application of the centrifugal chillers 1, 1A and the configuration
or the like of the centrifugal compressors 2, 2A described in the
above-mentioned embodiment merely form one example, and
modifications can be applied to the respective components.
REFERENCE SIGNS LIST
[0056] 1, 1A centrifugal chiller [0057] 2, 2A centrifugal
compressor [0058] 3 condenser [0059] 5 evaporator [0060] 7
refrigerant compressing unit [0061] 13 casing [0062] 14 electric
motor [0063] 15 rotor shaft [0064] 16 impeller [0065] 18a, 18b main
bearing (non-contact bearing) [0066] 19a, 19b auxiliary bearing
[0067] 25, 32, 40 lubricating refrigerant supply unit [0068] 26,
33, 41 liquid refrigerant storage unit [0069] 27, 34a, 34b liquid
refrigerant supply passage [0070] 28, 35a, 35b solenoid valve
[0071] 31 liquid refrigerant jacket [0072] 43 pressure applying
container [0073] R refrigerant
* * * * *