U.S. patent application number 16/311424 was filed with the patent office on 2019-10-31 for screw compressor.
The applicant listed for this patent is Hitachi Industrial Equipment Systems Co., Ltd.. Invention is credited to Toshikazu HARASHIMA, Hitoshi NISHIMURA, Kosuke SADAKATA, Masahiko TAKANO, Takeshi TSUCHIYA.
Application Number | 20190331115 16/311424 |
Document ID | / |
Family ID | 60901603 |
Filed Date | 2019-10-31 |
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United States Patent
Application |
20190331115 |
Kind Code |
A1 |
HARASHIMA; Toshikazu ; et
al. |
October 31, 2019 |
Screw Compressor
Abstract
A screw compressor that enhances performance of a compressor
main unit and a motor is provided. The screw compressor includes an
oil-injected compressor main unit that compresses air with
injecting oil in a compression chamber and an axial-gap motor that
drives the compressor main unit. A male rotor of the compressor
main unit has a suction-side shaft portion connected coaxially with
a rotor shaft of the motor. The screw compressor further includes a
suction-side bearing that rotatably supports the suction-side shaft
portion of the male rotor. The suction-side bearing restricts axial
movement of the suction-side shaft portion and bears a radial load
and axial loads in both directions.
Inventors: |
HARASHIMA; Toshikazu;
(Tokyo, JP) ; NISHIMURA; Hitoshi; (Tokyo, JP)
; TSUCHIYA; Takeshi; (Tokyo, JP) ; SADAKATA;
Kosuke; (Tokyo, JP) ; TAKANO; Masahiko;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi Industrial Equipment Systems Co., Ltd. |
Chiyoda ku Tokyo |
|
JP |
|
|
Family ID: |
60901603 |
Appl. No.: |
16/311424 |
Filed: |
July 4, 2016 |
PCT Filed: |
July 4, 2016 |
PCT NO: |
PCT/JP2016/069749 |
371 Date: |
December 19, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C 18/16 20130101;
F16C 2360/43 20130101; F04C 29/0085 20130101; H02K 1/2793 20130101;
H02K 2213/03 20130101; H02K 21/24 20130101; F01C 21/02 20130101;
H02K 2205/03 20130101; F04C 2240/50 20130101; F04C 23/02 20130101;
F04C 2240/809 20130101; F04C 29/026 20130101; H02K 5/1735 20130101;
F04C 2210/1005 20130101; F04C 2240/56 20130101; H02K 7/14 20130101;
F04C 2270/17 20130101 |
International
Class: |
F04C 29/02 20060101
F04C029/02; F04C 18/16 20060101 F04C018/16 |
Claims
1. A screw compressor including a liquid-injected compressor main
unit that includes a screw rotor and compresses gas with injecting
liquid in a compression chamber defined by a tooth groove of the
screw rotor and an axial-gap motor that drives the compressor main
unit, the screw rotor having a motor-side shaft portion connected
coaxially with a rotor shaft of the motor, the screw compressor
comprising: a bearing that rotatably supports the motor-side shaft
portion of the screw rotor, wherein the bearing restricts axial
movement of the motor-side shaft portion and bears a radial load
and axial loads in both directions.
2. The screw compressor according to claim 1, wherein the
compression chamber of the compressor main unit draws in gas via a
suction port on a side adjacent to the motor and discharges
compressed gas via a discharge port on a side opposite to the
motor, and the motor-side shaft portion is a suction-side shaft
portion.
3. The screw compressor according to claim 2, further comprising: a
gas-liquid separator, disposed on a discharge side of the
compressor main unit, for separating the liquid from the compressed
gas discharged from the compressor main unit.
4. The screw compressor according to claim 1, wherein the motor
includes a first rotor disposed on an output side of the rotor
shaft, a second rotor disposed on a non-output side of the rotor
shaft, and a stator disposed between the first rotor and the second
rotor, and a dimension of a gap between the first rotor and the
stator is greater than a dimension of a gap between the second
rotor and the stator at room temperature.
5. The screw compressor according to claim 1, wherein the motor
includes a rotor disposed on the rotor shaft, a first stator
disposed on an output side with respect to the rotor, and a second
stator disposed on a non-output side with respect to the rotor, and
a dimension of a gap between the rotor and the first stator is
smaller than a dimension of a gap between the rotor and the second
stator at room temperature.
6. The screw compressor according to claim 1, wherein the bearing
includes combined angular contact ball bearings for face to face
type or back to back type, and is held at a fixed position within a
casing.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to screw compressors
including liquid-injected compressor main units and axial-gap
motors that drive the compressor main units and, more particularly,
to a screw compressor in which a screw rotor of a compressor main
unit is coaxially connected with a rotary shaft of a motor.
BACKGROUND ART
[0002] Patent Document 1 discloses a screw compressor including a
liquid-injected compressor main unit and a radial-gap motor that
drives the compressor main unit. The following details the screw
compressor.
[0003] The radial-gap motor includes a rotor shaft, a rotor mounted
on the rotor shaft, and a stator spaced apart from the rotor in a
radial direction. The rotor shaft is rotated by magnetic action of
the stator and the rotor.
[0004] The compressor main unit includes a pair of intermeshing
male and female screw rotors. One of the screw rotors is coaxially
connected with the rotor shaft of the motor. Rotation of the rotor
shaft of the motor causes the one of the screw rotors to rotate,
which, in turn, rotates the other of the screw rotors in mesh with
the one of the screw rotors. As the pair of screw rotors rotates,
compression chambers defined by tooth grooves of the screw rotors
and an inner wall of a casing move in an axial direction. The
compression chamber draws in gas via a suction port (opening) on
one side in the axial direction and compresses the gas to thereby
discharge the compressed gas via a discharge port (opening) on the
other side in the axial direction.
[0005] The liquid-injected compressor main unit injects a liquid
into the compression chamber. The liquid injected in the
compression chamber seals gaps in the compression chamber
(specifically, a gap between the screw rotors and a gap between the
screw rotor and the casing) and cools the compressed gas.
[0006] The screw rotors each include a tooth portion having a
plurality of spiral teeth, a suction-side shaft portion (motor-side
shaft portion) connected with one side in the axial direction of
the tooth portion (suction side, or the motor side), and a
discharge-side shaft portion (opposite-side shaft portion)
connected with the other side in the axial direction of the tooth
portion (discharge side, or the side opposite to the motor). As
described previously, the suction-side shaft portion of one screw
rotor is connected coaxially with the rotor shaft of the motor.
[0007] The suction-side shaft portion of each screw rotor is
rotatably supported by a plurality of suction-side bearings. The
discharge-side shaft portion of each screw rotor is rotatably
supported by a plurality of discharge-side bearings. The
discharge-side bearings are a plurality of angular ball bearings
held at fixed positions inside the casing. The discharge-side
bearings restrict axial movement of the discharge-side shaft
portion of the screw rotor and bear a radial load and axial loads
in both directions (specifically, a forward direction extending
from the discharge side toward the suction side and a reverse
direction extending from the suction side toward the discharge
side). The suction-side bearings are a plurality of angular ball
bearings held axially movably in the casing. The suction-side
bearings permit axial movement of the suction-side shaft portion of
the screw rotor and support the radial load and the axial load in
the forward direction.
PRIOR ART DOCUMENT
Patent Document
[0008] Patent Document 1: JP-2004-150412-A (see FIGS. 1 to 3.)
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0009] For a reason of size reduction, for example, adoption of an
axial-gap motor in place of the radial-gap motor described above is
being studied. The axial-gap motor includes a rotor shaft, at least
one rotor mounted on the rotor shaft, and at least one stator
spaced apart from the rotor in the axial direction. The rotor shaft
is rotated by magnetic action of the stator and the rotor.
[0010] As in the configuration disclosed in Patent Document 1, the
suction-side shaft portion of one screw rotor may be connected
coaxially with the rotor shaft of the axial-gap motor.
Additionally, as in the configuration disclosed in Patent Document
1, the discharge-side bearings may restrict axial movement of the
discharge-side shaft portion (opposite-side shaft portion) of the
screw rotor and the suction-side bearings may permit axial movement
of the suction-side shaft portion (motor-side shaft portion) of the
screw rotor. The foregoing arrangements, however, pose the
following problem.
[0011] The screw rotor expands by compression heat and the rotor
shaft of the motor expands by heat generated by the motor. The
restriction of the axial movement of the discharge-side shaft
portion of the screw rotor can considerably reduce changes in the
gap between a discharge-side end face of the tooth portion of the
screw rotor and a wall surface of the casing. Performance of the
compressor main unit can thereby be enhanced. Meanwhile, a gap
between the rotor and the stator of the motor is affected by not
only the thermal expansion of the rotor shaft of the motor, but
also the thermal expansion of the screw rotor, resulting in large
changes in the gap. Thus, performance of the motor is degraded.
[0012] The present invention has been accomplished in light of such
circumstances and one of the problems to be solved is to enhance
performance of the compressor main unit and the motor by reducing
changes in the gap between the discharge-side end face of the tooth
portion of the screw rotor and the wall surface of the casing and
in the gap between the rotor and the stator of the motor.
Means for Solving the Problem
[0013] To solve the foregoing problem, configurations defined in
the scope of the claims are applied. The present invention includes
a plurality of means for solving the problem. One exemplary aspect
of the present invention provides a screw compressor including a
liquid-injected compressor main unit that includes a screw rotor
and compresses gas with injecting liquid in a compression chamber
defined by a tooth groove of the screw rotor and an axial-gap motor
that drives the compressor main unit. The screw rotor has a
motor-side shaft portion connected coaxially with a rotor shaft of
the motor. The screw compressor includes a bearing that rotatably
supports the motor-side shaft portion of the screw rotor. In this
screw compressor, the bearing restricts axial movement of the
motor-side shaft portion and bears a radial load and axial loads in
both directions.
Effects of the Invention
[0014] The aspect of the present invention can reduce changes in a
gap between a discharge-side end face of a tooth portion of the
screw rotor and a wall surface of a casing and in a gap between the
rotor and the stator of the motor, to thereby enhance performance
of the compressor main unit and the motor.
[0015] Objects, configurations, and effects other than those
described above will become apparent from the following description
of embodiments.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a vertical cross-sectional view of a configuration
of a screw compressor according to a first embodiment of the
present invention, depicting a rated operation state of the
compressor.
[0017] FIG. 2 is a vertical cross-sectional view of a configuration
of the screw compressor according to the first embodiment of the
present invention, depicting a stationary state of the
compressor.
[0018] FIG. 3 is a vertical cross-sectional view of a configuration
of a screw compressor according to a first modification of the
present invention, depicting a stationary state of the
compressor.
[0019] FIG. 4 is a vertical cross-sectional view of a configuration
of a screw compressor according to a second modification of the
present invention, depicting a stationary state of the
compressor.
[0020] FIG. 5 is a vertical cross-sectional view of a configuration
of a screw compressor according to a second embodiment of the
present invention, depicting a rated operation state of the
compressor.
MODES FOR CARRYING OUT THE INVENTION
[0021] A first embodiment of the present invention will be
described with reference to FIGS. 1 and 2. FIGS. 1 and 2 are
vertical cross-sectional views of configurations of a screw
compressor according to the present embodiment. FIG. 1 depicts a
rated operation state (high temperature state) of the compressor.
FIG. 2 depicts a stationary state (room temperature state) of the
compressor.
[0022] The screw compressor of the present embodiment includes an
oil-injected compressor main unit 1 and a radial-gap motor 2, which
drives the compressor main unit 1. The compressor main unit 1 is
integrated with the motor 2. Specifically, the compressor main unit
1 and the motor 2 are disposed vertically such that screw rotors of
the compressor main unit 1 and a rotor shaft of the motor 2 to be
described later extend in the vertical direction. The motor 2 is
disposed on the upper side of the compressor main unit 1.
[0023] The motor 2 includes a rotor shaft (shaft) 3, a rotor 4A, a
rotor 4B, a stator 5, and a motor casing 6. The rotor 4A is mounted
on an output side (side adjacent to the compressor main unit 1) of
the rotor shaft 3. The rotor 4B is mounted on a non-output side
(side opposite to the compressor main unit 1) of the rotor shaft 3.
The stator 5 is disposed between the rotors 4A and 4B so as to be
spaced axially apart from the rotors 4A and 4B. The motor casing 6
houses thereinside the rotors 4A and 4B and the stator 5 and
supports the stator 5.
[0024] As depicted in the figure, the motor casing 6 includes a
motor main casing and an end cover removably mounted in an upper
end opening of the motor main casing. The rotors 4A and 4B are each
a permanent magnet type rotor, for example. The stator 5 is a
winding type stator, for example. The rotor shaft 3 is rotated by
magnetic action of the rotors 4A and 4B and the stator 5.
[0025] The compressor main unit 1 includes a pair of intermeshing
male and female screw rotors (specifically, a male rotor 7 and a
female rotor not depicted) and a compressor main unit casing 8,
which houses thereinside the screw rotors. Tooth grooves in the
screw rotors and an inner wall of the compressor main unit casing 8
define compression chambers 9. The compressor main unit casing 8
includes a main casing 10 and a suction-side casing 11, which is
coupled with an upper side (suction side) of the main casing 10.
The suction-side casing 11 is coupled with the motor main
casing.
[0026] The male rotor 7 is coaxially connected with the rotor shaft
3 of the motor 2. Rotation of the rotor shaft 3 of the motor 2
causes the male rotor 7 to rotate and the female rotor in mesh with
the male rotor 7 to rotate. The rotation of the male rotor 7 and
the female rotor causes the compression chamber 9 to move in the
axial direction. The compression chamber 9 draws in air (gas) from
a suction flow path 13 via a suction port 12 (opening) on one side
in the axial direction (the side adjacent to the motor) and
compresses the air to thereby discharge the compressed air
(compressed gas) to a discharge flow path 15 via a discharge port
14 (opening) on the other side in the axial direction (the side
opposite to the motor).
[0027] The oil-injected (liquid-injected) compressor main unit 1 is
configured to inject oil (liquid) into the compression chamber 9 on
a suction stroke. The oil injected in the compression chamber 9
seals gaps in the compression chamber 9 (specifically, a gap
between the male rotor 7 and the female rotor and a gap between the
male rotor 7 or the female rotor and the casing 8) and cools the
compressed air.
[0028] The male rotor 7 includes a tooth portion 16 having a
plurality of spiral teeth, a suction-side shaft portion (motor-side
shaft portion) 17 connected with one side in the axial direction of
the tooth portion 16, and a discharge-side shaft portion
(opposite-side shaft portion) 18 connected with the other side in
the axial direction of the tooth portion 16. Similarly, the female
rotor includes a tooth portion, a suction-side shaft portion, and a
discharge-side shaft portion. The suction-side shaft portion 17 of
the male rotor 7 is coaxially connected with the rotor shaft 3 of
the motor 2 as described previously by being integrally molded with
the rotor shaft 3 of the motor 2.
[0029] The tooth portion 16 of the male rotor 7 and the tooth
portion of the female rotor are housed in a tooth portion housing
chamber 19 of the main casing 10. The discharge-side shaft portion
18 of the male rotor 7 and the discharge-side shaft portion of the
female rotor are housed in the main casing 10. The suction-side
shaft portion 17 of the male rotor 7 and the suction-side shaft
portion of the female rotor are housed in the suction-side casing
11.
[0030] The suction-side shaft portion 17 of the male rotor 7 is
rotatably supported by a plurality of suction-side bearings 20. The
discharge-side shaft portion 18 of the male rotor 7 is rotatably
supported by a single discharge-side bearing 21. The suction-side
bearings 20 are a plurality of angular ball bearings (specifically,
combined angular contact ball bearings for face to face type or
back to back type) and outer rings thereof are held at fixed
positions in the suction-side casing 11 and inner rings thereof are
fixed at fixed positions of the suction-side shaft portion 17 of
the male rotor 7. The suction-side bearings 20 restrict axial
movement of the suction-side shaft portion 17 of the male rotor 7
and bear a radial load and axial loads in both directions
(specifically, a forward direction extending from the discharge
side toward the suction side and a reverse direction extending from
the suction side toward the discharge side).
[0031] The discharge-side bearing 21 is a cylindrical roller
bearing (specifically, cylindrical roller bearing in which an outer
ring or an inner ring has no flanges and the outer ring and the
inner ring are axially movable relative to each other) and the
outer ring thereof is held at a fixed position in the main casing
10 and the inner ring thereof is fixed at a fixed position of the
discharge-side shaft portion 18 of the male rotor 7. The
discharge-side bearing 21 bears a radial load, while permitting
axial movement of the discharge-side shaft portion 18 as a result
of thermal expansion of the male rotor 7.
[0032] Similarly, the suction-side shaft portion of the female
rotor is rotatably supported by suction-side bearings 20. The
discharge-side shaft portion of the female rotor is rotatably
supported by discharge-side bearing 21.
[0033] Effects of the present embodiment will be described
below.
[0034] In the present embodiment, the suction-side bearings 20
restrict axial movement of the suction-side shaft portion
(motor-side shaft portion) of the male rotor 7 and the
discharge-side bearing 21 permits axial movement of the
discharge-side shaft portion 18 (opposite-side shaft portion) of
the male rotor 7. Thus, a gap between a discharge-side end face of
the tooth portion 16 of the male rotor 7 and a wall surface of the
casing 8 is affected by the thermal expansion of the male rotor 7,
but not by the thermal expansion of the rotor shaft 3 of the motor
2. Changes can thus be reduced in the gap between the
discharge-side end face of the tooth portion 16 of the male rotor 7
and the wall surface of the casing 8. Similarly, changes can also
be reduced in a gap between a discharge-side end face of the tooth
portion of the female rotor and a wall surface of the casing 8.
Thus, dimensions of the gaps described previously can be reduced to
prevent leakage of compressed air and performance of the compressor
main unit 1 can be enhanced.
[0035] A gap between the rotor 4A and the stator 5 and a gap
between the rotor 4B and the stator 5 are affected by the thermal
expansion of the rotor shaft 3 of the motor 2, but not the thermal
expansion of the male rotor 7. Thus, changes can be reduced in the
gap between the rotor 4A and the stator 5 and the gap between the
rotor 4B and the stator 5. Thus, motor efficiency can be enhanced
by setting dimensions of the foregoing gaps to optimum values and
performance of the motor 2 can be improved.
[0036] Consider a case, as a comparative example, in which axial
movement of the discharge-side shaft portion of the male rotor or
the discharge-side shaft portion of the female rotor is restricted
by a plurality of angular ball bearings and axial movement of the
suction-side shaft portion of the male rotor or the suction-side
shaft portion of the female rotor is restricted by a single
cylindrical roller bearing. As compared with such a comparative
example, the present embodiment can have the discharge-side shaft
portion 18 of the male rotor 7 and the discharge-side shaft portion
of the female rotor shorter in length. Thus, the compressor main
unit 1 can be reduced in size. Or, because a degree of freedom in
design of the discharge flow path 15 is increased, performance of
the compressor main unit 1 can be enhanced.
[0037] Dimensions of the gaps in the present embodiment will be
described below.
[0038] A dimension D of the gap between the discharge-side end face
of the tooth portion 16 of the male rotor 7 and the wall surface of
the casing 8 under a rated operation state (at high temperature) of
the compressor is given by expression (1) given below, where Do
denotes a dimension of the gap between the discharge-side end face
of the tooth portion 16 of the male rotor 7 and the wall surface of
the casing 8 under a stationary state (at room temperature) of the
compressor (Do>D). Where, .DELTA.Ls denotes an amount of thermal
expansion of the tooth portion 16 and .DELTA.Lb denotes an amount
of thermal expansion of the tooth portion housing chamber 19
(.DELTA.Ls>.DELTA.Lb).
D=Do-(.DELTA.Ls-.DELTA.Lb) (1)
[0039] Because D>0, the dimension Do of the gap between the
discharge-side end face of the tooth portion 16 of the male rotor 7
and the wall surface of the casing 8 under the stationary state (at
room temperature) of the compressor is given by expression (2)
given below.
Do>.DELTA.Ls-.DELTA.Lb (2)
[0040] A dimension Ma of the gap between the rotor 4A and the
stator 5 under the rated operation state (at high temperature) of
the compressor is given by expression (3) given below. Where, Mao
denotes a dimension of the gap between the rotor 4A and the stator
5 under the stationary state (at room temperature) of the
compressor and .DELTA.Ma denotes an amount of change in the
dimension of the gap between the rotor 4A and the stator 5
(.DELTA.Ma>0).
Ma=Mao-.DELTA.Ma (3)
[0041] A dimension Mb of the gap between the rotor 4B and the
stator 5 under the rated operation state (at high temperature) of
the compressor is given by expression (4) given below. Where, Mbo
denotes a dimension of the gap between the rotor 4B and the stator
5 under the stationary state (at room temperature) of the
compressor and .DELTA.Mb denotes an amount of change in the
dimension of the gap between the rotor 4B and the stator 5
(.DELTA.Mb>0, .DELTA.Mb.apprxeq..DELTA.Ma).
Mb=Mbo+.DELTA.Mb (4)
[0042] Because preferably Ma.apprxeq.Mb holds, preferably the
relation of expression (5) given below holds.
Mao>Mbo (5)
[0043] The first embodiment has been described for an exemplary
configuration in which the axial-gap motor 2 includes the two
rotors 4A and 4B and the one stator 5 disposed between the rotors
4A and 4B. This configuration is, however, illustrative only and
not limiting and various changes may be made therein without
departing from the spirit and scope of the invention. Specifically,
the axial-gap motor is only required to include at least one rotor
and at least one stator disposed to be spaced apart from the rotor
in the axial direction.
[0044] Specifically, as in a first modification depicted in FIG. 3,
for example, an axial-gap motor 2A may include a rotor 4 mounted on
a rotor shaft, a stator 5A disposed on an output side (side
adjacent to a compressor main unit 1) with respect to the rotor 4,
and a stator 5B disposed on a non-output side (side opposite to the
compressor main unit 1) with respect to the rotor 4. Effects
identical to the effects achieved by the first embodiment can be
achieved even in the modification.
[0045] Dimensions of gaps in the present modification will be
described. A dimension Mc of a gap between the rotor 4 and the
stator 5A under the rated operation state (at high temperature) of
the compressor is given by expression (6) given below. Where, Mco
denotes a dimension of the gap between the rotor 4 and the stator
5A under the stationary state (at room temperature) of the
compressor and .DELTA.Mc denotes an amount of change in the
dimension of the gap between the rotor 4 and the stator 5A
(.DELTA.Mc>0).
Mc=Mco+.DELTA.Mc (6)
[0046] A dimension Md of a gap between the rotor 4 and the stator
5B under the rated operation state (at high temperature) of the
compressor is given by expression (7) given below. Where, Mdo
denotes a dimension of the gap between the rotor 4 and the stator
5B under the stationary state (at room temperature) of the
compressor and .DELTA.Md denotes an amount of change in the
dimension of the gap between the rotor 4 and the stator 5B
(.DELTA.Md>0, .DELTA.Mc.apprxeq..DELTA.Md).
Md=Mdo-.DELTA.Md (7)
[0047] Because preferably Mc.apprxeq.Md holds, preferably the
relation of expression (8) given below holds.
Mco<Mdo (8)
[0048] The first embodiment has been described for an exemplary
configuration in which the compressor main unit casing 8 includes
the main casing 10 and the suction-side casing 11, which is coupled
with the upper side (suction side) of the main casing 10. This
configuration is, however, illustrative only and not limiting and
various changes may be made therein without departing from the
spirit and scope of the invention.
[0049] Specifically, as in a second modification depicted in FIG.
4, for example, a compressor main unit casing 8 may include a main
casing 10A, a suction-side casing 11, which is coupled with an
upper side (suction side) of the main casing 10A, and a
discharge-side casing 22, which is coupled with a lower side
(discharge side) of the main casing 10A. Then, the main casing 10A
may house the tooth portions of the screw rotors and the
discharge-side casing 22 may house the discharge-side shaft
portions of the screw rotors and the discharge-side bearings. In
such a modification, machining accuracy of the discharge flow path
15 can be enhanced compared with the first embodiment.
[0050] Additionally, in the first embodiment, the compressor main
unit 1 has been described as an oil-injected type to compress air
with injecting oil in the compression chamber 9. This configuration
is, however, illustrative only and not limiting and various changes
may be made therein without departing from the spirit and scope of
the invention. Specifically, the compressor main unit may, for
example, be a water-injected type (liquid-injected type) to
compress air (gas) with injecting water (liquid) in the compression
chamber 9. The same effects as those described above can be
achieved in this case, too.
[0051] In the first embodiment, the screw compressor has been
described for an exemplary configuration in which the screw rotors
of the compressor main unit 1 and the rotor shaft 3 of the motor 2
extend in the vertical direction. This configuration is, however,
illustrative only and not limiting and various changes may be made
therein without departing from the spirit and scope of the
invention. Specifically, the screw compressor may be configured
such that the screw rotors of the compressor main unit and the
rotor shaft of the motor extend in the horizontal direction. The
same effects as those described above can be achieved in this case,
too.
[0052] A second embodiment of the present invention will be
described below with reference to FIG. 5. FIG. 5 is a vertical
cross-sectional view of a configuration of a screw compressor
according to the present embodiment of the present invention,
depicting the rated operation state (high temperature state) of the
compressor. In the present embodiment, like or corresponding parts
are identified by the same reference numerals as those used in the
first embodiment and descriptions for those parts will be omitted
as appropriate.
[0053] The screw compressor in the present embodiment includes an
oil-injected compressor main unit 1, an axial-gap motor 2 which
drives the compressor main unit 1, and an oil separator 23
(gas-liquid separator) which separates oil (liquid) from compressed
air (compressed gas) discharged from the compressor main unit 1.
The compressor main unit 1, the motor 2, and the oil separator 23
are integrated with each other. Specifically, the compressor main
unit 1 and the motor 2 are disposed vertically such that screw
rotors of the compressor main unit 1 and a rotor shaft 3 of the
motor 2 extend in the vertical direction. The motor 2 is disposed
on an upper side (suction side) of the compressor main unit 1 and
the oil separator 23 is disposed on a lower side (discharge side)
of the compressor main unit 1.
[0054] The oil separator 23 includes an inner tube 24 and an outer
tube casing 26. The inner tube 24 is disposed on a lower side of
the compressor main unit 1. The outer tube casing 26 is integrally
molded with a compressor main unit casing 8 and forms a swirl flow
path 25 between a lower portion of the compressor main unit 1 and
the inner tube 24. The swirl flow path 25 is connected with a
discharge flow path 15 of the compressor main unit 1.
[0055] Compressed air discharged from the compressor main unit 1 is
given a swirl in the swirl flow path 25 (see the arrow in FIG. 5),
so that oil contained in the compressed air is centrifugally
separated. The separated oil falls along the outer tube casing 26
and is collected in an oil storage portion 27 formed on a lower
side of the outer tube casing 26. The oil collected in the oil
storage portion 27 is supplied to a compression chamber 9 on a
suction stroke by way of a flow path not depicted. Meanwhile, the
compressed air from which the oil has been separated flows into an
inside of the inner tube 24 and flows out through a flow path not
depicted.
[0056] As in the first embodiment, in the present embodiment, too,
suction-side bearings 20 restrict axial movement of the
suction-side shaft portion (motor-side shaft portion) of the screw
rotor and a discharge-side bearing 21 permits axial movement of the
discharge-side shaft portion (opposite-side shaft portion) of the
screw rotor. Thus, changes are reduced in the gap between the
discharge-side end face of the tooth portion of the screw rotor and
the wall surface of the casing and in the gap between the rotor and
the stator of the motor, so that performances of the compressor
main unit 1 and of the motor 2 can be improved.
[0057] Additionally, the discharge-side shaft portion of the screw
rotor can be made shorter in length as in the first embodiment.
This feature increases the degree of freedom in design of the
discharge flow path 15 and the swirl flow path 25, so that
performance of the compressor main unit 1 and performance of the
oil separator 23 can be improved.
[0058] It is noted that, in the second embodiment, the screw
compressor has been described as having a configuration including
the oil-injected compressor main unit 1, which compresses air with
injecting oil in the compression chamber 9, and the oil separator
23, which separates oil from the compressed air discharged from the
compressor main unit 1. This configuration is, however,
illustrative only and not limiting and various changes may be made
therein without departing from the spirit and scope of the
invention. Specifically, the screw compressor may include, for
example, a compressor main unit that is a water-injected type
(liquid-injected type) and a water separator (gas-liquid
separator). The compressor main unit compresses air (gas) with
injecting water (liquid) in the compression chamber 9. The water
separator separates water from the compressed air (compressed gas)
discharged from the compressor main unit. The same effects as those
described above can be achieved in this case, too.
[0059] Additionally, the first and second embodiments have been
described for a configuration in which a plurality of angular ball
bearings (specifically, combined angular contact ball bearings for
face to face type or back to back type) are employed as the
suction-side bearings 20, which rotatably support the suction-side
shaft portion of each screw rotor. This configuration is, however,
illustrative only and not limiting and various changes may be made
therein without departing from the spirit and scope of the
invention. Specifically, any other type of rolling bearing may be
employed when the suction-side bearings 20 restrict axial movement
of the suction-side shaft portion of the screw rotor and support
the radial load and the axial loads in both directions.
[0060] Specifically, as one suction-side bearing that rotatably
supports the suction-side shaft portion of each screw rotor, a
double-row angular ball bearing for face to face type or back to
back type or a deep-groove ball bearing may be employed. Or, as a
plurality of suction-side bearings that rotatably support the
suction-side shaft portion of each screw rotor, a plurality of
tapered roller bearings (specifically, combined tapered roller
bearings for face to face type or back to back type) may be
employed. Alternatively, as one suction-side bearing that rotatably
supports the suction-side shaft portion of each screw rotor, a
double-row tapered roller bearing for face to face type or back to
back type may be employed.
[0061] Additionally, the first and second embodiments have been
described for a configuration in which a cylindrical roller bearing
is employed as a single discharge-side bearing that rotatably
supports the discharge-side shaft portion of each screw rotor. This
configuration is, however, illustrative only and not limiting and
various changes may be made therein without departing from the
spirit and scope of the invention. Specifically, any other type of
rolling bearing may be employed when the discharge-side bearing
permits axial movement of the discharge-side shaft portion of the
screw rotor. Specifically, the rolling bearing may be held in the
casing movably in the axial direction.
[0062] Additionally, the first and second embodiments have been
described for an exemplary configuration in which the rotor shaft 3
of the motor 2 is integrally molded with the suction-side shaft
portion 17 of the male rotor 7 to thereby be coaxially connected
therewith. This configuration is, however, illustrative only and
not limiting and various changes may be made therein without
departing from the spirit and scope of the invention. Specifically,
the rotor shaft 3 of the motor 2 may be coaxially connected with
the suction-side shaft portion 17 of the male rotor 7 through a
coupling. Alternatively, the rotor shaft 3 of the motor 2 may be
coaxially connected with the suction-side shaft portion of the
female rotor. In either case, the same effects as those described
above can be achieved.
REFERENCE SIGNS LIST
[0063] 1 Compressor main unit
[0064] 2, 2A Motor
[0065] 3 Rotor shaft
[0066] 4, 4A, 4B Rotor
[0067] 5, 5A, 5B Stator
[0068] 7 Male rotor (Screw rotor)
[0069] 8 Compressor main unit casing
[0070] 9 Compression chamber
[0071] 11 Suction-side casing
[0072] 12 Suction port
[0073] 14 Discharge port
[0074] 17 Suction-side shaft portion (Motor-side shaft portion)
[0075] 20 Suction-side bearing
[0076] 23 Oil separator (Gas-liquid separator)
* * * * *