U.S. patent application number 11/836166 was filed with the patent office on 2008-05-15 for hermetic screw compressor.
Invention is credited to Eisuke Kato, Masayuki Urashin.
Application Number | 20080112832 11/836166 |
Document ID | / |
Family ID | 39369384 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080112832 |
Kind Code |
A1 |
Kato; Eisuke ; et
al. |
May 15, 2008 |
HERMETIC SCREW COMPRESSOR
Abstract
A hermetic screw compressor comprises a male rotor, a female
rotor engaging the male rotor, an electric motor connected to a low
pressure side shaft portion of the male rotor, a low pressure side
bearing for supporting the low pressure side shaft portion of each
of the rotors, a high pressure side bearing for supporting a high
pressure side shaft portion of each of the rotors, and a casing
containing the rotors, the electric motors and the bearings. A
contact type seal is arranged to seal a part of the low pressure
side shaft portion of the male rotor between the low pressure side
bearing and the electric motor, and a cover contains the seal and
is axially detachably attached to the casing so that the contact
type seal is attached to the casing through the cover.
Inventors: |
Kato; Eisuke; (Shizuoka,
JP) ; Urashin; Masayuki; (Shizuoka, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
39369384 |
Appl. No.: |
11/836166 |
Filed: |
August 9, 2007 |
Current U.S.
Class: |
418/201.1 |
Current CPC
Class: |
F04C 27/009 20130101;
F01C 21/02 20130101; F04C 18/16 20130101; F04C 23/008 20130101;
F04C 2240/605 20130101 |
Class at
Publication: |
418/201.1 |
International
Class: |
F04C 15/00 20060101
F04C015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2006 |
JP |
2006-304708 |
Claims
1. A hermetic screw compressor comprising, screw rotors each of
which includes a teeth portion, a low pressure side shaft portion
and a high pressure side shaft portion, an electric motor connected
to the low pressure side shaft portion of at least one of the screw
rotors, a low pressure side bearing for supporting the low pressure
side shaft portion, a high pressure side bearing for supporting the
high pressure side shaft portion, and a casing containing
hermetically the screw rotors, the electric motor, the low pressure
side bearing and the high pressure side bearing, wherein the
compressor further comprises a contact type seal arranged to seal a
part of the screw rotor between the electric motor and the low
pressure side bearing at the low pressure side shaft portion, and a
cover containing the contact type seal and detachably attached to
the casing.
2. The hermetic screw compressor according to claim 1, wherein the
screw rotor has a sleeve forming the part of the screw rotor with
which the contact type seal contacts, and a hardness of the sleeve
is higher than a hardness of the low pressure side shaft
portion.
3. The hermetic screw compressor according to claim 1, wherein the
screw rotors includes a pair of male and female rotors engaging
each other.
4. The hermetic screw compressor according to claim 1, wherein the
screw rotors includes a pair of screw rotor and gate roller
engaging each other.
5. A hermetic screw compressor comprising, a screw rotor including
a teeth portion of screw shape, and a rotor shaft monolithic with
the teeth portion, an electric motor connected to the rotor shaft
to be rotationally driven, a low pressure side bearing for
supporting an intake side of the rotor shaft, a high pressure side
bearing for supporting an exit side of the rotor shaft, and a
casing containing the screw rotor, the electric motor, the low
pressure side bearing and the high pressure side bearing, wherein
the compressor further comprises a contact type seal arranged to
seal the rotor shaft between the low pressure side bearing and the
electric motor, and a bearing holder for holding the low pressure
side bearing axially with respect to the casing, the bearing holder
containing the contact type seal so that the contact type seal is
attached to the casing through the bearing holder.
6. The hermetic screw compressor according to claim 5, wherein the
rotor shaft has a sleeve on which the contact type seal slides, and
a hardness of the sleeve is higher than a remainder part of the
rotor shaft.
7. A hermetic screw compressor comprising, a male rotor, a female
rotor engaging the male rotor, an electric motor connected to a low
pressure side shaft portion of the male rotor, a low pressure side
bearing for supporting the low pressure side shaft portion of each
of the rotors, a high pressure side bearing for supporting a high
pressure side shaft portion of each of the rotors, and a casing
containing the rotors, the electric motors and the bearings,
wherein the compressor further comprises a contact type seal
arranged to seal a part of the low pressure side shaft portion of
the male rotor between the low pressure side bearing and the
electric motor, and a cover containing the seal and axially
detachably attached to the casing so that the contact type seal is
attached to the casing through the cover, the low pressure side
shaft portion has a sleeve arranged to slide with respect to the
contact type seal, and a hardness of the sleeve is higher than a
hardness of a remainder part of the low pressure side shaft
portion.
8. The hermetic screw compressor according to claim 7, wherein the
low pressure side shaft portion and the high pressure side shaft
portion are monolithically included by each of the rotors, and the
low pressure side shaft portion of the male rotor is directly
connected to the electric motor to be rotationally driven.
9. The hermetic screw compressor according to claim 1, wherein the
contact type seal is an oil seal.
10. The hermetic screw compressor according to claim 1, wherein the
contact type seal is a mechanical seal.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a hermetic screw compressor
to be used in an air conditioner or refrigerator.
[0002] A hermetic screw compressor has a screw rotor, a
low-pressure side bearing for supporting the screw rotor, an
electric motor for driving the screw rotor and a casing containing
these elements. The electric motor may be arranged at either of
low-pressure side and high-pressure side, but in many cases, is
arranged at the low pressure side because the electric motor of
high temperature is cooled at the low pressure side by a
refrigerant gas of low-temperature and low pressure.
[0003] Further, a lubricating oil is generally supplied to a
bearing by a difference in pressure between the low pressure side
and the high-pressure side in the screw compressor. Since the oil
of high-temperature and high-pressure is supplied to the bearing
for supporting the screw rotor from an environment of the
discharged gas, the oil flowing to the electric motor at the
low-pressure side after lubricating the bearing of the low-pressure
side heats an electrically insulating member of the electric motor
to be deteriorated. Further, there is a problem of that the oil of
high-temperature flowing out therefrom is mixed the refrigerant gas
of low-temperature and low-pressure to be taken into tooth spaces
of the screw rotor so that the refrigerant gas of low-temperature
is heated by the oil to deteriorate a performance of the
compressor.
[0004] Therefore, JP-A-2-275086 (FIG. 5) discloses a non-contact
seal between the electric motor and the bearing of the low-pressure
side for preventing the oil from flowing from the bearing of the
low-pressure side to the low pressure side (the motor side).
BRIEF SUMMARY OF THE INVENTION
[0005] In JP-A-2-275086, a non-contact seal is used to obtain a
sealing utilizing a frictional resistance of viscous liquid and a
labyrinth effect, so its sealing performance is not sufficient for
preventing the oil from flowing out.
[0006] Further, it is difficult for a non-contact seal for
improving the oil sealing to be used, because it needs a
maintenance operation for an abrasion of the seal or a shaft
progressing in accordance with an increase of operating time period
of the compressor.
[0007] An object of the present invention is to provide a hermetic
screw compressor in which an oil of high temperature is prevented
from flowing from a bearing of low-pressure side to a low-pressure
side (motor side) and a maintenance is easy.
[0008] A first distinctive feature of the invention for achieving
the object is that in a hermetic screw compressor comprising screw
rotors each of which includes a teeth portion, a low pressure side
shaft portion and a high pressure side shaft portion, an electric
motor connected to the low pressure side shaft portion of at least
one of the screw rotors, a low pressure side bearing for supporting
the low pressure side shaft portion, a high pressure side bearing
for supporting the high pressure side shaft portion, and a casing
containing hermetically these elements, a contact type seal is
arranged to seal a part of the screw rotor between the electric
motor and the low pressure side bearing at the low pressure side
shaft portion, and a cover contains the contact type seal and is
detachably attached to the casing so that the contact type seal is
attached to the casing through the cover.
[0009] In this case, it is preferable that a sleeve forms the part
of the screw rotor with which the contact type seal contacts, and a
hardness of the sleeve is higher than a hardness of the low
pressure side shaft portion.
[0010] Incidentally, the screw rotors may include a pair of male
and female rotors engaging each other, or a pair of screw rotor and
gate roller engaging each other.
[0011] A second distinctive feature of the invention for achieving
the object is that in a hermetic screw compressor comprising a
screw rotor including a teeth portion of screw shape, and a rotor
shaft monolithic with the teeth portion, an electric motor
connected to the rotor shaft to be rotationally driven, a low
pressure side bearing for supporting an intake side of the rotor
shaft, a high pressure side bearing for supporting an exit side of
the rotor shaft, and a casing containing these elements, the
compressor further comprises a contact type seal arranged to seal
the rotor shaft between the low pressure side bearing and the
electric motor, and a bearing holder for holding the low pressure
side bearing axially with respect to the casing, and the bearing
holder contains the contact type seal so that the contact type seal
is attached to the casing through the bearing holder.
[0012] In this case, it is preferable that the rotor shaft has a
sleeve on which the contact type seal slides, and a hardness of the
sleeve is higher than a remainder part of the rotor shaft.
[0013] A third distinctive feature of the invention for achieving
the object is that in a hermetic screw compressor comprising a male
rotor, a female rotor engaging the male rotor, an electric motor
connected to a low pressure side shaft portion of the male rotor, a
low pressure side bearing for supporting the low pressure side
shaft portion of each of the rotors, a high pressure side bearing
for supporting a high pressure side shaft portion of each of the
rotors, and a casing containing these elements, a contact type seal
is arranged to seal a part of the low pressure side shaft portion
of the male rotor between the low pressure side bearing and the
electric motor, a cover contains the seal and axially detachably
attached to the casing so that the contact type seal is attached to
the casing through the cover, the low pressure side shaft portion
has a sleeve arranged to slide with respect to the contact type
seal, and a hardness of the sleeve is higher than a hardness of a
remainder part of the low pressure side shaft portion.
[0014] In this case, the low pressure side shaft portion and the
high pressure side shaft portion may be monolithically included by
each of the rotors, while the low pressure side shaft portion of
the male rotor may be directly connected to the electric motor to
be rotationally driven.
[0015] The contact type seal may be an oil seal or a mechanical
seal.
[0016] According to the invention, since a contact type seal is
arranged to seal a part of the screw rotor between the electric
motor and the low pressure side bearing at the low pressure side
shaft portion, and a cover contains the contact type seal and is
detachably attached to the casing so that the contact type seal is
attached to the casing through the cover, a hermetic screw
compressor of high performance and high reliability in which an oil
of high temperature and high pressure is prevented from flowing to
the low pressure side, and an ease of maintenance is improved, is
obtainable.
[0017] When a contact type seal is arranged between the electric
motor and the low pressure side bearing to prevent the oil from
flowing from the low pressure side bearing to the low pressure side
(motor side), the sealing performance is significantly improved,
but a maintenance is necessary, because the seal or the shaft to be
seal is worn away in accordance with an increase of compressor
operating time period. According to the invention, the contact type
seal is arranged in the screw compressor while the contact type
seal is detachably attached, so that the hermetic screw compressor
of high performance and high reliability with improved ease of
maintenance is obtainable.
[0018] Hereafter, embodiments of the invention will be described
with making reference to the drawings.
[0019] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0020] FIG. 1 is a longitudinally cross sectional view showing an
embodiment of the invention.
[0021] FIG. 2 is an enlarged partially cross sectional view showing
a low-pressure side in the vicinity of a bearing.
[0022] FIG. 3 is an enlarged partially cross sectional view showing
a low-pressure side in the vicinity of a bearing in a second
embodiment of the invention.
[0023] FIG. 4 is an enlarged partially cross sectional view showing
a low-pressure side in the vicinity of a bearing in a third
embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] FIG. 1 is a cross sectional view showing a hermetic screw
compressor as an embodiment of the invention. Although a hermetic
twin-screw compressor of the invention will be described below, the
invention is not applicable only to the twin-screw type, but also
to a single-screw type including a screw rotor and a gate rotor
engaging each other.
[0025] A hermetic screw compressor has a motor casing 1, a main
casing 2 and an discharge casing 3 hermetically connected to each
other. The motor casing 1 contains a driving motor 4 for driving a
compressing mechanism. The main casing 4 has cylindrical bores 5
and 6, and intake ports 7 and 8 for introducing a refrigerant gas
into the cylindrical bores 5 and 6. The cylindrical bores 5 and 6
contains male and female rotors 16 and 17 engaging each other and
supported by roller bearings 9, 10, 11, 12 and 13 and ball bearings
14 and 15, and the male rotor 16 is directly connected to the
driving motor 4 at a low-pressure side. The main casing 2 has an
oil separator 18 and an oil tank integrally formed with each
other.
[0026] The discharge casing 3 containing the roller bearings 11 and
13 and the ball bearings 14 and 15 includes a discharge path (not
shown) for the refrigerant gas communicating with the oil separator
18 of the main casing 2, and the discharge casing 3 is fixed to the
main casing 2 by bolts or the like. Further, a shield plate 22 is
attached to an end of the discharge casing 3 to cover bearing
chambers 20 and 21 containing the roller bearings 11 and 13 and the
ball bearings 14 and 15.
[0027] The main casing 2 and the discharge casing 3 include
lubricating passages for making communications between the oil tank
19 of the main casing and the bearings.
[0028] Next, a flow of each of the refrigerant gas and the oil is
described.
[0029] The refrigerant gas of low-temperature and low-pressure
flowing from an inlet port 29 of the motor casing 1 passes a
strainer 30 for collecting contaminant, and subsequently passes a
gas passage between the driving motor 4 and the motor casing 1 and
an air-gap between a stator 4a and a motor rotor 4b to cool the
driving motor 4. The refrigerant gas is taken from the inlet port 7
and 8 of the main casing 2 into a compression chamber formed by the
main casing 2 and teeth surfaces of the male and female screw
rotors engaging each other after cooling the motor. Subsequently,
the refrigerant gas is hermetically contained by the compressing
chamber formed by the main casing 2 and teeth surfaces of the male
and female screw rotors engaging each other in accordance with a
rotation of the male rotor 16 connected to the driving motor 4 so
that the refrigerant gas compressed by decrease in volume of the
compressing chamber becomes of high-temperature and high-pressure
to be discharged through a discharge passage (not shown) in the
discharge casing into the oil separator 18 formed monolithically
with the main casing 2. During the compression, a radial part of a
compression reaction force applied to the male and female rotors is
borne by the roller bearings 9, 10, 11, 12 and 13, and a thrust
part thereof is borne by the ball bearings 14 and 15. The oil for
lubricating and cooling these bearings flows from the oil tank 19
at the high-pressure area of the main casing 2 through the
lubricating passages for these bearings with the differential
pressure to be discharged with the refrigerant gas into the oil
separator 18. The oil is separated from the compressed refrigerant
gas in the oil separator 18 to be stored in the oil tank 19
monolithically formed with the main casing 2. The compressed
refrigerant gas separated from the oil is discharged from the
discharge port of the main casing 2.
[0030] FIG. 2 is an enlarged partial view showing the vicinity of
the bearings 9, 10 and 12 at the low-pressure side as shown in FIG.
1. The oil supplied from the oil tank 19 at the high-pressure side
passes through the lubricating passage 23a the roller bearings 11
and 13 and the ball bearings 14 and 15 at the high-pressure side to
be lubricated. On the other hand, a part of the oil passing the
lubricating passage 23b is supplied to the roller bearing 12
arranged at the low-pressure side to support the female rotor 17,
and the remainder part thereof passing the lubricating passages 23c
and 23d is supplied to the roller bearings 9 and 10 arranged at the
low-pressure side to support the male rotor 16.
[0031] In the embodiment, a contact type seal 24 is arranged
between the roller bearings 9 and 10 and the driving motor 4. In
this case, the contact type seal 24 is an oil-seal. Further, the
contact type seal 24 is contained by a bearing cover 25 mounted on
the main casing 2. Therefore, the oil of high-temperature and high
pressure is prevented from flowing to the low-pressure side so that
the electrically insulating member of the driving motor 4 and the
refrigerant gas of low-pressure and low-temperature are prevented
from being heated excessively by the oil to obtain high performance
and reliability. Further, since the contact type seal 24 is
contained by the bearing cover 24 to be detachably mounted, the
maintenance of the contact type seal 24 is easily done by detaching
the bearing cover 25 when the abrasion of sealing region of the
contact type seal 24 progresses in accordance with an increase of
operating time period of the compressor.
Embodiment 2
[0032] FIG. 3 shows a second embodiment and corresponds to FIG.
2.
[0033] In this embodiment, a sleeve 26 is fitted on a shaft portion
27 at the low-pressure side of the male rotor 16. When the contact
type seal 24 is the oil seal whose material is rubber or plastic, a
material of the shaft for the seal is steel or casting iron so that
the seal is worn away in accordance with the increase of the
compressor operating time period. On the contrary, when a
contaminant such as iron powder or the like exists on the sealing
area, the shaft is worn away so that the male rotor 16 should be
exchanged for the maintenance to increase the cost therefore. In
this embodiment, the sleeve 26 is fitted on the shaft portion 27 of
the low-pressure side and a hardness of the sleeve 26 is higher
than that of the shaft portion 27 to restrain the abrasion of the
sleeve 26 so that it is difficult for the sleeve 26 to be worn away
and the sleeve 26 is exchangeable to improve an ease of maintenance
and to decrease the cost of maintenance when the sleeve is worn
away.
Embodiment 3
[0034] FIG. 4 shows a third embodiment and corresponds to FIG.
2.
[0035] In this embodiment, the contact type seal is a mechanical
seal 28. The mechanical seal 28 has a complex structure in
comparison with the oil seal, but brings about an improved sealing
performance so that a provability of that the oil of high pressure
and high temperature flows to the low pressure side is decreased
significantly to obtain the hermetic screw compressor of improved
performance and reliability.
[0036] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
* * * * *