U.S. patent application number 09/908843 was filed with the patent office on 2002-03-07 for scroll compressor.
Invention is credited to Aoki, Masakazu, Kawabata, Natsuki, Machida, Shigeru, Shiinoki, Kazuaki, Yabe, Toshiaki.
Application Number | 20020028150 09/908843 |
Document ID | / |
Family ID | 26585944 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020028150 |
Kind Code |
A1 |
Kawabata, Natsuki ; et
al. |
March 7, 2002 |
Scroll compressor
Abstract
In a double toothed type scroll compressor, spiral wraps are
formed on both sides of an end plate of an orbiting scroll, and
wraps adapted to engage with the spiral wraps are formed on a
stationary scroll. A dust wrap is formed on a side diametrically
outside of the wrap of the stationary scroll. Grooves are formed on
ends of the respective wraps to receive therein seal members formed
of a high polymer material. Electric charge of static electricity
produced when the seal members slide on surfaces of the mating end
plate is made to flow from a bolt provided on an end of a
crankshaft to the stationary scroll through a brush, thereby
preventing accumulation of electric charge in a crankshaft.
Inventors: |
Kawabata, Natsuki; (Shimizu,
JP) ; Shiinoki, Kazuaki; (Shimizu, JP) ; Aoki,
Masakazu; (Shimizu, JP) ; Machida, Shigeru;
(Iwama, JP) ; Yabe, Toshiaki; (Shimizu,
JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
26585944 |
Appl. No.: |
09/908843 |
Filed: |
July 20, 2001 |
Current U.S.
Class: |
418/55.1 ;
418/55.2; 418/55.4 |
Current CPC
Class: |
F04C 29/0092 20130101;
F04C 29/04 20130101; F04C 18/0284 20130101; F04C 18/0223 20130101;
F04C 18/0253 20130101; F01C 21/08 20130101 |
Class at
Publication: |
418/55.1 ;
418/55.2; 418/55.4 |
International
Class: |
F04C 018/04; F01C
001/02; F01C 001/063; F04C 018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2001 |
JP |
2001-039345 |
Feb 18, 2000 |
JP |
2000-046713 |
Claims
What is claimed is:
1. A scroll compressor comprising: an orbiting scroll having a
spiral wrap; a stationary scroll having a spiral wrap adapted to
engage with the wrap of said orbiting scroll; a crankshaft for
driving said orbiting scroll; and a tip seal mounted on a tip end
of the wrap of at least one of said stationary scroll and said
orbiting scroll, and wherein at least one of said orbiting scroll
and said crankshaft is formed of an electrically conductive
material, and further comprising a conducting means for providing
electrical conduction of said orbiting scroll to said stationary
scroll in operation of said scroll compressor.
2. A scroll compressor comprising: an orbiting scroll having a
spiral wrap; a stationary scroll having a spiral wrap adapted to
engage with the wrap of said orbiting scroll; a crankshaft for
driving said orbiting scroll; and a tip seal mounted on a tip end
of the wrap of at least one of said stationary scroll and said
orbiting scroll, and wherein at least one of said orbiting scroll
and said crankshaft is subjected to insulator or nonconductor
coating surface treatment, and further comprising a conducting
means for providing electrical conduction of said orbiting scroll
to said stationary scroll in operation of said scroll
compressor.
3. The scroll compressor according to claim 1, wherein said
conducting means comprises a slip ring or a brush provided on an
end of said crankshaft to conduct static electricity accumulated in
said crankshaft to the outside of said crankshaft.
4. The scroll compressor according to claim 1, wherein said tip
seal is formed of an electrically conductive material, and a
surface of said orbiting scroll or said stationary scroll, with
which said tip seal contacts, is made electrically conductive.
5. The scroll compressor according to claim 1, wherein an annular
dust wrap is provided on a side diametrically outside of the wrap
of said stationary scroll, and a conductive dust seal is disposed
on a tip end of said dust wrap.
6. The scroll compressor according to claim 1, further comprising a
roll bearing for supporting said crankshaft, of which inner and
outer races are electrically connected to each other in
operation.
7. The scroll compressor according to claim 2, wherein said tip
seal is formed of an electrically conductive material, and that
surface of said orbiting scroll or stationary scroll, with which
said tip seal contacts, is electrically conductive.
8. The scroll compressor according to claim 2, further comprising
an annular dust wrap provided on a side diametrically outside of
the wrap of said stationary scroll, and an electrically conductive
dust seal arranged on a tip end of said dust wrap.
9. The scroll compressor according to claim 2, further comprising a
roll bearing for supporting said crankshaft, of which inner and
outer races are electrically connected to each other in
operation.
10. The scroll compressor according to claim 6, wherein said roll
bearing contains an electrically conductive grease.
11. The scroll compressor according to claim 1, further comprising
a roll bearing for supporting said crankshaft, and wherein at least
one of inner and outer races, and rolling elements of said roll
bearing is formed of an electrical insulator.
12. The scroll compressor according to claim 1, further comprising
a roll bearing for supporting said crankshaft, and wherein at least
one of inner and outer races, and rolling elements of said roll
bearing is formed of a material, which forms a nonconductor
film.
13. The scroll compressor according to claim 12, wherein said
material forming a nonconductor film is a martensitic stainless
steel.
14. The scroll compressor according to claim 1, wherein said scroll
compressor is an oil-free compressor and wherein said orbiting
scroll has spiral wraps on both sides of an end plate, said
stationary scroll comprises a pair of stationary scroll members
each having a wrap adapted to engage with each of the wraps of said
orbiting scroll, and working chambers defined by the wraps of said
orbiting scroll and said stationary scroll are free of entry of an
oil such as lubricant or the like.
15. A scroll compressor comprising: an orbiting scroll having a
wrap; a stationary scroll having a wrap adapted to engage with the
wrap of said orbiting scroll; a crankshaft and an auxiliary
crankshaft disposed on a side diametrically outside of the wraps of
both said orbiting scroll and said stationary scroll and for
driving said orbiting scroll; a first pulley mounted on said
crankshaft and a second pulley mounted on said auxiliary
crankshaft; and a belt trained around outer peripheral sides of
said first and second pulleys; and wherein said belt are
electrically connected to said first and second pulleys.
16. A scroll compressor comprising: an orbiting scroll having a
wrap; a stationary scroll having a wrap adapted to engage with the
wrap of said orbiting scroll; a crankshaft and an auxiliary
crankshaft for driving said orbiting scroll and disposed on a side
diametrically outside of the wraps of both said orbiting scroll and
said stationary scroll; a first pulley mounted on said crankshaft
and a second pulley mounted on said auxiliary crankshaft; and a
belt trained around outer peripheral sides of said first and second
pulleys; and wherein electrical insulation is made between said
crankshaft and said first pulley and between said auxiliary
crankshaft and said second pulley.
17. An oil-free double toothed type scroll compressor comprising:
an orbiting scroll having spiral wraps on both sides of an end
plate; a pair of stationary scrolls having wraps adapted to engage
with the wraps of said orbiting scroll; a main crankshaft and an
auxiliary crankshaft for rotationally driving said orbiting scroll,
and disposed on a side diametrically outside of the wraps of both
said orbiting scroll and said stationary scrolls; a plurality of
roll bearings for supporting said main crankshaft and said
auxiliary crankshaft; first and second pulleys mounted on said main
crankshaft and auxiliary crankshaft, respectively; a resin belt
trained around said first and second pulleys; resin tip seals held
in grooves formed on tip ends of said orbiting scroll wraps and
said stationary scroll wraps; and static electricity discharging
means provided to discharge static electricity, which is produced
in said timing belt portion and said tip seal portions, from said
orbiting scroll to said stationary scrolls.
18. The scroll compressor according to claim 17, wherein said
static electricity discharge means is a slip ring provided on an
end of at least one of said main crankshaft and said auxiliary
crankshaft.
19. The scroll compressor according to claim 17, wherein said
static electricity discharge means comprises an electrically
conductive grease for preventing the accumulation of static
electricity in said roll bearings.
20. The scroll compressor according to claim 17, wherein said
bearings comprise grease-lubricated bearings, and wherein a base
oil of said grease is an ether-based synthetic oil and a thicker
therefor is a urea compound.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a scroll compressor having
spiral type scroll wraps, and more particularly, to a double
toothed type oil-free scroll compressor suitable for use in air
compressors.
[0002] Conventionally, scroll compressor have been used for
refrigeration and air conditioning, which comprise a stationary
scroll having a spiral wrap provided upright on an end plate and an
orbiting scroll having a wrap adapted to engage with the wrap of
the stationary scroll. In recent years, such scroll compressors
have also been used as an air compressor because of their
advantageous low noise.
[0003] Incidentally, convenience in use has increased a demand for
scroll compressors for air compression, which range from a low air
volume type for painting or the like to a high air volume type for
a factory air source or the like. In order to meet a demand for
high air volumes, a so-called double toothed type scroll compressor
having an orbiting scroll with wraps on both sides of an end plate
has gotten in the spotlight. An example of such double toothed type
scroll compressor is described in Japanese Patent Laid-Open Nos.
10-246189 and 10-252668.
[0004] A scroll compressor, being one type of displacement type
compressors, must be formed with an enclosed space. In particular,
in the case of an oil-free compressor, any seal based on an oil
film is not provided, and so an elastic member called a tip seal is
disposed as a seal member between a tip end of a scroll wrap and an
end plate, which the scroll wrap faces. It is required that such
tip seal be excellent in sealing quality and low in friction.
Therefore, a high polymer material such as a fluorine contained
resin is often used for the tip seal.
[0005] It has proved from experimental studies conducted by the
inventors of the present application that the use of a resin
material for the tip seal may possibly cause the following
disadvantage. That is, scroll compressors, in particular, oil-free
scroll compressors for air compression, use grease-filled bearings
for supporting a crankshaft. In operation, oil films of the bearing
make electrical insulation between the crankshaft and a stationary
scroll and between the crankshaft and an orbiting scroll. Both
orbiting and stationary scroll members are formed by coating an
aluminum alloy stock with an alumite film, which is an insulator to
make electrical insulation between the orbiting scroll and the
stationary scroll.
[0006] In ordinary use, the compressor is used in a state in which
the stationary scroll is grounded. Meanwhile, the orbiting scroll
and the crankshaft are not grounded. When the compressor is started
in this state, static electricity is produced by sliding of the tip
seal on the end plate surface of the scroll member or by sliding of
a belt on pulleys, and has its electric charge accumulated in the
crankshaft and orbiting scroll. While an accumulating amount of
electric charge is not so much for a low capacity compressor, it
increases remarkably with an increase in compressor capacity. Such
electric charge generates an electric potential difference between
inner and outer races of a roll bearing, and thus hydrogen ions
induced accumulate in a location of high stresses within the
bearing. The accumulated hydrogen ions change the internal
structure of a bearing steel to create crack inside of the bearing
steel. In the worst case, the roll bearing may be damaged
electrically.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention has been devised to solve the
above-mentioned disadvantages involved in the prior art, and has
its object to operate a scroll compressor over a long term with
high reliability.
[0008] To attain the above object, a scroll compressor according to
the present invention comprises an orbiting scroll having a spiral
wrap; a stationary scroll having a spiral wrap adapted to engage
with the wrap of said orbiting scroll; a crankshaft for driving
said orbiting scroll; and a tip seal mounted on a tip end of the
wrap of at least one of said stationary scroll and said orbiting
scroll, and wherein at least one of said orbiting scroll and said
crankshaft is formed of an electrically conductive material, and
further comprises a conducting means for providing electrical
conduction of said orbiting scroll to said stationary scroll in
operation of said scroll compressor.
[0009] To attain the above object, another scroll compressor
according to the present invention comprises an orbiting scroll
having a spiral wrap; a stationary scroll having a spiral wrap
adapted to engage with the wrap of said orbiting scroll; a
crankshaft for driving said orbiting scroll; and a tip seal mounted
on a tip end of the wrap of at least one of said stationary scroll
and said orbiting scroll, and wherein at least one of said orbiting
scroll and said crankshaft is subjected to insulator or
nonconductor coating surface treatment, and further comprises a
conducting means for providing electrical conduction of said
orbiting scroll to said stationary scroll in operation of said
scroll compressor.
[0010] In any one of the above-described scroll compressors, a slip
ring or a brush may be provided on an end of said crankshaft to
conduct static electricity accumulated in said crankshaft to the
outside of said crankshaft; and said tip seal may be formed of an
electrically conductive material, and a surface of said orbiting
scroll or said stationary scroll, with which said tip seal
contacts, may be made electrically conductive. Further, it is
desired that an annular dust wrap is provided on a side
diametrically outside of the wrap of said stationary scroll, and a
conductive dust seal is disposed on a tip end of said dust
wrap.
[0011] Further, in any one of the above-described scroll
compressors, a roll bearing may be provided for supporting the
crankshaft, of which inner and outer races are electrically
connected to each other in operation; the roll bearing may contain
an electrically conductive grease; a roll bearing may be provided
for supporting the crankshaft, and wherein at least one of inner
and outer races, and rolling elements of the roll bearing may be
formed of an electrical insulator; and a roll bearing may be
provided for supporting the crankshaft, and at least one of inner
and outer races, and rolling elements of the roll bearing may be
formed of a material, which forms a nonconductor film. In addition,
the material forming a nonconductor film may be a martensitic
stainless steel.
[0012] To attain the above object, any one of the above-described
scroll compressors may be an oil-free compressor, the orbiting
scroll may have spiral wraps on both sides of an end plate, the
stationary scroll may comprise a pair of stationary scroll members
each having a wrap adapted to engage with each of the wraps of the
orbiting scroll, and working chambers defined by the wraps of the
orbiting scroll and the stationary scroll may be free of entry of
an oil such as lubricant or the like.
[0013] To attain the above object, a still another scroll
compressor according to the present invention comprises an orbiting
scroll having a wrap; a stationary scroll having a wrap adapted to
engage with the wrap of the orbiting scroll; a crankshaft and an
auxiliary crankshaft disposed on a side diametrically outside of
the wraps of both the orbiting scroll and the stationary scroll and
for driving the orbiting scroll; a first pulley mounted on the
crankshaft and a second pulley mounted on the auxiliary crankshaft;
and a belt trained around outer peripheral sides of the first and
second pulleys; and the belt is electrically connected to the first
and second pulleys.
[0014] To attain the above object, a still further scroll
compressor according to the present invention comprises an orbiting
scroll having a wrap; a stationary scroll having a wrap adapted to
engage with the wrap of the orbiting scroll; a crankshaft and an
auxiliary crankshaft for driving the orbiting scroll and disposed
on a side diametrically outside of the wraps of both the orbiting
scroll and the stationary scroll; a first pulley mounted on the
crankshaft and a second pulley mounted on the auxiliary crankshaft;
and a belt trained around outer peripheral sides of the first and
second pulleys; and electrical insulation is made between the
crankshaft and the first pulley and between the auxiliary
crankshaft and the second pulley.
[0015] To attain the above object, a further scroll compressor
according to the present invention comprises an orbiting scroll
having spiral wraps on both sides of an end plate; a pair of
stationary scrolls having wraps adapted to engage with the wraps of
the orbiting scroll; a main crankshaft and an auxiliary crankshaft
for rotationally driving the orbiting scroll, and disposed on a
side diametrically outside of the wraps of both the orbiting scroll
and the stationary scrolls; a plurality of roll bearings for
supporting the main crankshaft and the auxiliary crankshaft; first
and second pulleys mounted on the main crankshaft and auxiliary
crankshaft, respectively; a resin belt trained around the first and
second pulleys; resin tip seals held in grooves formed on tip ends
of the orbiting scroll wraps and the stationary scroll wraps; and
static electricity discharging means provided to discharge static
electricity, which is produced in the timing belt portion and the
tip seal portions, from the orbiting scroll to the stationary
scrolls.
[0016] In the above-described scroll compressor, the static
electricity discharge means may be a slip ring provided on an end
of at least one of the main crankshaft and the auxiliary
crankshaft; and the static electricity discharge means may comprise
an electrically conductive grease for preventing the accumulation
of static electricity in the roll bearings. Also, it is desired
that the bearings comprise grease-lubricated bearings, and a base
oil of the grease is an ether-based synthetic oil and a thicker
therefor is a urea compound.
[0017] That is, in an oil-free scroll compressor, at least one of
the orbiting scroll and the crankshaft may be brought into contact
with the stationary scroll or other grounding members via an
electrically conductive member to maintain the orbiting scroll,
crankshaft, and the stationary scroll in the same electric
potential; or electrical damages on the bearings may be prevented
by arranging an insulator or the like even when electric potential
difference is present between the orbiting scroll, stationary
scroll, and the crankshaft.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0018] FIG. 1 is a longitudinal sectional view showing one
embodiment of a scroll compressor according to the present
invention;
[0019] FIG. 2 is a detailed sectional view of a tip seal portion
used for the scroll compressor shown in FIG. 1;
[0020] FIG. 3 is a detailed sectional view of a dust seal portion
used for the scroll compressor shown in FIG. 1;
[0021] FIG. 4 is a detailed sectional view of a crankshaft end
portion of the scroll compressor shown in FIG. 1;
[0022] FIG. 5 is a front view of a brush used in the embodiment
shown in FIG. 4;
[0023] FIG. 6 is a detailed sectional view of a modification of a
crankshaft end portion of the scroll compressor shown in FIG.
1;
[0024] FIG. 7 is a detailed sectional view of another modification
of a crankshaft end portion of the scroll compressor shown in FIG.
1;
[0025] FIG. 8 is a detailed sectional view of still another
modification of a crankshaft end portion of the scroll compressor
shown in FIG. 1;
[0026] FIG. 9 is a detailed sectional view of an end portion of the
scroll compressor shown in FIG. 1;
[0027] FIG. 10 is detailed sectional view of a modification of an
end portion of the scroll compressor shown in FIG. 1;
[0028] FIG. 11 is detailed sectional view of another modification
of an end portion of the scroll compressor shown in FIG. 1;
[0029] FIG. 12 is a sectional view of a bearing used in the scroll
compressor shown in FIG. 1; and
[0030] FIG. 13 is a partial sectional view of a compressor unit in
which a scroll compressor according to the present invention is
mounted.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Several embodiments of the present invention will now be
described with reference to the accompanying drawings.
[0032] FIG. 1 is a longitudinal sectional view showing a body block
of a so-called double toothed type scroll compressor, in which
wraps are formed on both sides of an end plate of an orbiting
scroll. The compressor of this type is mainly used for air
compression as schematically shown in FIG. 13. In FIG. 13, with a
compressor unit 50, a motor 60 is installed on a base provided at a
bottom of a housing 51. Driving force of the motor 60 is
transmitted to a scroll compressor 68 by a belt 64 trained around a
pulley mounted on a rotating shaft of the motor 60. The scroll
compressor 68 has its leg portions supported on a compressor
support member 62 provided in the housing 51. A fan 56 for cooling
the motor 60, the scroll compressor 68, and a compressed air having
been compressed by the scroll compressor is mounted on an end of
the rotating shaft of the motor 60 opposite to a side where the
pulley is installed. When the motor 60 is rotated, an air
surrounding the compressor unit 50 is caused to flow through an
intake port formed in the housing 51 in a direction indicated by
arrow 66 to be introduced to a suction side of the fan 56, thus
cooling a heat exchanger 54 disposed in a duct 52 formed on a
discharge side of the fan 56.
[0033] In FIG. 1, a double toothed type scroll compressor 100
comprises an orbiting scroll 1 having spiral scroll wraps 31 and 32
formed on both surfaces of an end plate 30, a stationary scroll 2
(left-hand side in FIG. 1) and a stationary scroll 3 (right-hand
side in FIG. 1) having spiral scroll wraps 41, 42 formed on end
plates 44, 45 and adapted to engage with the wraps 32, 32 of the
orbiting scroll 1 to define a compression chamber, a main
crankshaft 4 for driving the orbiting scroll 1, an auxiliary
crankshaft 5 rotated in synchronization with the main crankshaft 4,
a timing belt 6 for making the auxiliary crankshaft 5 and the main
crankshaft 4 in synchronism with each other, a timing pulley 7
around which the timing belt 6 is trained, and a V pulley 8 for use
in transmitting the power of a motor (not shown), which drives the
main crankshaft 4, to the main crankshaft 4. A discharge port 9 is
formed substantially centrally of the stationary scroll 3 to allow
discharge of the compressed air therethrough.
[0034] The double toothed type scroll compressor constructed as
described above operates in the following manner. Power generated
by the motor is transmitted to the V pulley 8 through a V belt.
Thereby, the main crankshaft 4 is rotated, and the power is
transmitted to the auxiliary crankshaft 5 through the timing belt 6
and the timing pulley 7 for synchronization to rotate the auxiliary
crankshaft 5 in synchronism with the main crankshaft 4. When both
the crankshafts 4 and 5 are rotated synchronously, the orbiting
scroll 1 moves eccentrically relative to both the stationary
scrolls 2 and 3 without rotation on its axis. A fluid is sucked
through a suction port (not shown) to be compressed as the orbiting
motion of the orbiting scroll 1 proceeds, and is then discharged
through the discharge port 9. In addition, in order to prevent dust
from entering into the compression chamber, ring-shaped dust wraps
10A and 10B are formed on outer-diameter sides of both the wraps 41
and 42 of the stationary scroll 1.
[0035] FIG. 2 shows a detailed cross section of the stationary
scroll wrap. The stationary scroll on the left-hand side in FIG. 1
is taken as an example. A groove 43 is formed at a tip end of the
wrap 41 of the stationary scroll 2 to extend in a spiral direction,
and a tip seal 11 is loosely fitted in the groove 43. The tip seal
11 serves to prevent the compressed gas in the compression chamber
from leaking in the spiral direction of the wrap 41 and in a radial
direction (from a central portion to an outer peripheral side) of
the orbiting scroll 1. The tip seal 11 is disposed at a wrap tip
end of at least one of the orbiting scroll 1 and the stationary
scrolls 2, 3. In operation, the tip seal slides on the end plate
surface of a scroll member opposite to that scroll member, on which
the tip seal is disposed.
[0036] FIG. 3 shows a detailed cross section of the dust wrap 10B
formed on the stationary scroll 2 on the left-hand side in FIG. 1.
The dust wrap 10B is formed on an outer periphery side of the wrap
41 of the stationary scroll 2. A groove 46 is circumferentially
formed on an end of the dust wrap 10B opposite to the end plate 44
surface. A dust seal 12 is housed in the groove 46 in a manner to
be pushed up by a backup tube 13. When the orbiting scroll 1 is
assembled to the stationary scroll 2, elasticity of the backup tube
13 and the dust seal 12 brings the dust seal 12 into close contact
with the end plate 30 surface of the orbiting scroll 1 to prevent
dust from entering into the compression chamber.
[0037] In addition, in terms of sliding property, heat resistance
and elasticity, a high polymer material containing a
tetrafluoroethylene resin is used to form the dust seal and the tip
seal. The dust seal and the tip seal generate heat due to their
sliding motions. Therefore, when heat resistance is further
desired, a heat resistant resin such as polyimide resins may be
used.
[0038] Since the tip seal and the dust seal are formed mainly of a
high polymer material as described above, static electricity is
produced when they slide on the end plate surface of the mating
scroll member. In the case where no lubricant is introduced into
the compression chamber especially as in the case of air
compressors, or in the case where nonconductor coating treatment is
applied, such static electricity is liable to accumulate in the
member, in which it is produced.
[0039] Also, the pulleys mounted on the crankshaft and the
auxiliary crankshaft and the timing belt trained around the pulleys
transmit power while slipping slightly in ordinary operation. A
material composed mainly of a resin material is used as a material
for the belt to ensure flexibility. As a result, static electricity
will be produced in the pulley portions.
[0040] Incidentally, with the scroll compressor according to the
present invention, the orbiting scroll housed in a cover
constituted by the stationary scroll is rotationally driven by the
crankshaft and the auxiliary crankshaft, so that static electricity
will accumulate unless a conduction path is secured between the
crankshaft or the auxiliary crankshaft and the orbiting scroll or
the stationary scroll. Thereupon, the inventors have pushed forward
experimental studies on influences of static electricity on the
scroll compressor.
[0041] The studies have revealed that whether a difference in
electric potential is great or small, static electricity has less
influence on equipments provided that a discharge path is secured.
If an insulating portion is present in the discharge path, however,
the insulating portion is charged with electricity. If the
insulating portion is disposed on a roll bearing, both inner and
outer races of the roll bearing, respectively, are charged with
electricity when the scroll compressor is operated. As a result,
there has been obtained a knowledge that an electric potential
difference is produced between the inner and outer races.
[0042] Furthermore, when an electric potential difference was
produced between the inner and outer races of the roll bearing, a
bearing damage pattern that has not been reported before was
obtained. Even if static electricity was produced, such a damage
pattern was not obtained merely by slippage of a belt, for example,
in the case of a motor.
[0043] Fatigue failure caused by a cyclic stress is most common as
a damage pattern of a roll bearing, and the nominal service life of
the bearing is determined based on such fatigue failure. When a
roll bearing is damaged due to rolling fatigue, various structural
changes generate in the bearing. A typical damage is one caused
near a location where a maximum shearing stress acts, such as
stripes generated in a specific direction and crack developing from
impurities present near a location where the maximum shearing
stress acts. In addition to such damage caused by fatigue failure,
there is the possibility of electrolytic corrosion if an electric
potential difference is produced between inner and outer races of
the bearing. Usually, if an electric potential difference caused
electrolytic corrosion on the roll bearing, a pattern resembling a
washboard would be developed on the rolling surface.
[0044] However, the damage pattern, in the present invention,
caused by an electric potential difference of static electricity
was a pattern different from any of the above-described patterns.
Depending on experimental conditions, a service life in some cases
decreased to about one tenth of the nominal service life (also
referred to as L10 life) of a bearing based on rolling fatigue.
[0045] It has been inferred as a result of experiments as pushed
forward that the following mechanism is responsible for such a
damage pattern that has not been conventionally reported. An
orbiting scroll, crankshaft, and an auxiliary crankshaft are
charged with static electricity, which is produced when tip seals
and dust seals mounted on wrap ends of the orbiting scroll and the
stationary scroll slide on an end plate of a mating scroll or when
a belt trained around pulleys mounted on the crankshaft and the
auxiliary crankshaft makes slippage. Thus, electric potential
differences generate between the orbiting scroll, crankshaft,
auxiliary crankshaft, and the stationary scroll.
[0046] Grease being a lubricant for the roll bearings for bearing
the crankshaft and the auxiliary crankshaft is decomposed into
water by electric potential differences thus produced. As
decomposition of the grease proceeds, hydrogen is generated from
the grease. When the crankshaft and the auxiliary crankshaft are
rotated, vibrations or the like produce incomplete portions in an
oil film formed by the oil content in the grease, and hydrogen
generated from such incomplete portions enters into the bearing
steel. Such hydrogen accumulates near a location where a maximum
shearing stress is caused in the rolling elements, inner and outer
races of the bearing. The inventors of the present application have
experimentally confirmed the above-described fact that hydrogen
enters into the bearing steel.
[0047] In addition, the scroll compressor according to the present
invention employs the timing belt and the belt for transmission of
driving force of the motor, and so is liable to cause a so-called
local contact phenomenon that load on bearings supporting the
crankshaft and the auxiliary crankshaft is offset toward one side
in a circumferential direction. As a result, excessive shearing
forces are produced on the rolling elements of the roll bearing to
make the oil film break with ease.
[0048] That is, the bearing is damaged under the influence of
hydrogen generated from the water content contained in grease, such
hydrogen entering into bearing parts such as the rolling elements,
inner and outer races, and the like of the bearing to change the
structure of a portion or portions, into which hydrogen enters. As
a result, crack generates in the bearing parts, and exhibits itself
as damages of the bearing when it reaches a surface or surfaces of
the bearing parts. This phenomenon is quite different from the
conventional phenomenon of electrolytic corrosion, and does take
place before three factors of grease, a bearing load (including
fluctuating loads) above some level, and electric potential
difference of static electricity are all present.
[0049] Thereupon, the present invention provides static electricity
removing means or electrical discharge means in order to prevent a
bearing from being damaged by static electricity that may possibly
be produced in a scroll compressor. Concrete examples therefor are
shown in FIG. 4 and the following figures. FIG. 4 is a partial
detailed sectional view of a crankshaft. In an embodiment shown in
FIG. 4, the crankshaft 4 is grounded to the stationary scroll 3. A
round head bolt 14 is mounted to a shaft end of the crankshaft 4. A
brush 15, details of which are shown in FIG. 5, is mounted on an
outer surface side of the stationary scroll 3 to be capable of
coming in contact with a head 14A of the bolt 14 provided on the
end of the crankshaft 4.
[0050] When the crankshaft 4 is rotated, electric charge of static
electricity produced on the tip seals and the dust seals flows to
the crankshaft 4. The electric charge then flows from the end of
the crankshaft 4 to the bolt 14, and then to the stationary scroll
3 via the bolt head 14A and the brush 15. Thereby, it is possible
to prevent accumulation of electric charge on the crankshaft 4.
Preferably, the head 14A of the bolt 14 is of spherical shape so as
to decrease the abrasion speed of the brush. For the simplicity of
constitution, the bolt 14 may be omitted and the brush 15 may be
brought into direct contact with the crankshaft 4. In this case as
well, a spherical-shaped end of the shaft can reduce the contact
resistance between the brush and the shaft end. While the brush is
provided on the stationary scroll side in this embodiment, it may
be provided on the crankshaft side.
[0051] The brush 15 is composed of a brush portion 15A and a plate
portion 15B. The brush portion 15A is formed of a conductor such as
metal, carbon, and electrically conductive resins. The brush
portion 15A is desirably high in abrasion resistance because it
slides on the bolt head 14A or the crankshaft end. An electric
conductor of good elasticity such as phosphor bronze and stainless
steel is used to form the plate portion 15B. Elasticity of the
plate portion 15B makes it possible to push the brush portion 15A
surely against the bolt head 14A or the crankshaft end. When
electricity is removed with the use of the brush in this manner,
the inner and outer races of the roll bearing are made identical to
each other in electric potential, which can suppress decomposition
of water content in the grease with an electric potential
difference as energy.
[0052] Several modifications of the above-described embodiment, in
which a brush is disposed on an end of a crankshaft and electric
charge is allowed to flow to the stationary scroll via the brush,
are shown in FIG. 6 and the following figures. An attachment 16
adapted to contact with a brush 15 is mounted on an end of the
crankshaft 4. Meanwhile the stationary scroll 3 mounts thereon the
brush 15 by way of an adapter 17. Contact of the brush 15 and the
attachment 16 with each other can attain the same function and
effect as those of the embodiment shown in FIG. 4.
[0053] With an arrangement shown in FIG. 7, a brush 18 is mounted
on the stationary scroll 3 to be brought into contact with a bolt
25 mounted on an end of the crankshaft 4 or the crankshaft 4 itself
or via a ball 26, thus permitting discharge of electric charge
flowing to the crankshaft 4. In this modification, the brush 18 is
composed of a hollow bolt 18A mounted on the stationary scroll 3, a
brush portion 18C held in the bolt 18A, and a spring 18B held also
in the hollow bolt. The brush portion 18C is subjected to a biasing
force by the spring 18B. This modification has an advantage that a
suitable biasing force is always applied to the brush portion by
the spring.
[0054] While in any one of the above-described modifications a
brush is used to allow electric charge to flow from an end of the
crankshaft to the stationary scroll, FIG. 8 shows an example of the
use of a slip ring in place of the brush. FIG. 8 is a detailed
cross sectional view of an end of the crankshaft. A slip ring 20 is
mounted on the crankshaft 4, and is connected to the stationary
scroll 3 with a conducting wire 21. In this case as well, the same
effect as those of the above-described embodiment and modifications
can be obtained.
[0055] FIGS. 9 to 11 inclusive show examples, in which the orbiting
scroll 1 and the stationary scroll 2 are grounded to discharge
static electricity produced by the tip seals and the dust seals.
FIGS. 9 to 11 inclusive are partial, longitudinal cross sectional
views showing a scroll compressor and an outer peripheral side
portion of a wrap. In FIG. 9, a brush 18 mounted on the stationary
scroll 2 is caused to slide on the surface of the end plate 30 of
the orbiting scroll 1. Also, in FIG. 10, an electrically conductive
plate 19 is mounted on the orbiting scroll 1 to permit the brush 18
to slide thereon. This modification has an advantage that mounting
and dismounting of the brush are facilitated.
[0056] In FIG. 11, the same brush 15 as one shown in FIG. 5 is
mounted on the stationary scroll 2 to slide on a surface of the end
plate 30 of the orbiting scroll 1. In this modification as well,
the same effect as those of the above-described embodiment and
modification can be obtained. In addition, it goes without saying
that the brush 15 may be mounted on the orbiting scroll 1 to slide
on the surface of the end plate of the stationary scroll 2.
[0057] Incidentally, it has proved that static electricity
generates at the tip seals and the dust seals, and so the tip seals
11 and the dust seals 12 are made to be formed of an electrically
conductive material, and, a mating member, e.g. the stationary
scroll is also formed of an electrically conductive material.
Furthermore, in the case where surface treatment applied on the
stationary scroll comprises an electrically conductive film,
electric charge will not accumulate on the orbiting scroll 1, thus
enabling avoiding any inconvenience caused by static
electricity.
[0058] Also, electric charge of static electricity produced on the
seal portions flows to the bearings disposed near the crankshaft.
Therefore, a shield plate 25 of the roll bearing, shown in FIG. 12,
for supporting the crankshaft is formed of an electrically
conductive material to bring both of an inner race 22 and an outer
race 23 into contact therewith. Thereby, at least one of the
crankshaft 4 and the orbiting scroll 1 can be grounded. In
addition, in FIG. 12, the roll bearing holds a grease 26 between
the inner and outer races 22 and 23 and balls 24. When the grease
26 is made electrically conductive, at least one of the crankshaft
4 and the orbiting scroll 1 can also be grounded. Furthermore, when
a base oil of the grease 26 is ether oil and the thickener thereof
is urea, the oil film in operation becomes thicker to provide for
the same effect as that of an insulating film such as oxide film,
described later.
[0059] At least any one of the inner race 22, the outer race 23 and
the balls 24 of the roll bearing for rotationally supporting the
crankshaft is coated with an insulating film such as oxide film.
Alternatively, these members are formed of a ceramic material or a
stainless steel material coated with a nonconductive film. The
reason for this is that even when static electricity is produced,
the oxide film or the stainless steel material can restrain entry
of hydrogen into the bearing steel and thus a change in the
structure of the bearing steel.
[0060] Moreover, in the case where a driving surface of at least
one of the V belt 64 for driving the V pulley 8, shown in FIG. 13,
and the timing belt 6 is made electrically conductive, it is
possible to suppress generation of electric charge. The V pulley is
made an insulator to prevent electric charge produced by slippage
between the belt and pulleys from flowing to the crankshaft side.
Thereby, the bearing can be prevented from being damaged.
[0061] Possible causes for inconveniences in the bearings of the
scroll compressor according to the present invention reside in
existence of static electricity, hydrogen generated from
decomposition of a water content contained in a grease, and
possible breakage of a grease oil film, as described above.
Therefore, most simply, generation of inconveniences on the
bearings can be prevented by reducing an amount of the water
content. This can be coped with by limiting the water content in
the grease to 0.2% or less. Also, when a substance having high
oxidation stability and thermal stability is chosen as a base oil
of the grease and a substance having high heat resistance,
waterproofness, and shear stability is chosen as a thickener of the
grease, breakage of a grease oil film can be prevented to prolong
the service life of the bearings. In this connection, it is desired
that the base oil be an ester-based synthetic oil and the thickener
be a urea compound.
[0062] While in any one of the above-described embodiments and
modifications, static electricity collected in the orbiting scroll,
crankshaft, and the auxiliary crankshaft is discharged or
communicated to the stationary scroll, the same effect can also be
obtained by discharging or communicating such static electricity to
the compressor support member, on which the scroll compressor is
mounted. Further, while an explanation has been given by way of a
double toothed type scroll compressor, the present invention is not
limited to such double toothed type scroll compressor but is
applicable to all types of scroll compressors, in which static
electricity presumably generates.
[0063] As described above, according to the present invention,
static electricity produced by sliding of members, such as the seal
members, the belt and the like, containing a resin material can be
prevented from flowing to the bearing portions to damage the
bearings, so that the scroll compressor can be operated over a long
term with high reliability.
* * * * *