U.S. patent application number 10/373380 was filed with the patent office on 2003-09-04 for displacement type compressor and method of forming coating film.
Invention is credited to Endo, Yoshishige, Inaba, Koichi, Satoh, Eiichi, Sekiguchi, Koichi, Yamamoto, Akihiko, Yoshitomi, Yuji.
Application Number | 20030164352 10/373380 |
Document ID | / |
Family ID | 27806819 |
Filed Date | 2003-09-04 |
United States Patent
Application |
20030164352 |
Kind Code |
A1 |
Endo, Yoshishige ; et
al. |
September 4, 2003 |
Displacement type compressor and method of forming coating film
Abstract
A scroll type compressor comprises a stationary scroll and a
rotary scroll which is assembled with the stationary scroll so as
to define a closed space, the outer surface of the rotary scroll 22
is formed thereon with a tin compound film containing a tin
compound and having a thickness of 50 .mu.m. Such a coating film is
never peeled off from a member even after long time operation, and
is excellent in sealability and conformability, in the displacement
type compressor.
Inventors: |
Endo, Yoshishige;
(Tsuchiura-shi, JP) ; Satoh, Eiichi;
(Tsuchiura-shi, JP) ; Yamamoto, Akihiko;
(Ibaraki-ken, JP) ; Yoshitomi, Yuji; (Ibaraki-ken,
JP) ; Inaba, Koichi; (Tochigi-ken, JP) ;
Sekiguchi, Koichi; (Tochigi-ken, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-9889
US
|
Family ID: |
27806819 |
Appl. No.: |
10/373380 |
Filed: |
February 26, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10373380 |
Feb 26, 2003 |
|
|
|
09517048 |
Mar 2, 2000 |
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Current U.S.
Class: |
216/2 |
Current CPC
Class: |
F04C 18/0246 20130101;
C23C 22/60 20130101 |
Class at
Publication: |
216/2 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 1996 |
JP |
08-255569 |
Claims
What is claimed is:
1. A displacement type fluid compressor wherein a closed space
defined between a stator and a rotor is gradually decreased in
association with motion of the rotor so as to suck, compress and
discharge fluid, characterized in that at least one of surfaces of
parts where the stator and the rotor make contact with each other
is formed thereon with a tin compound coating film containing a tin
compound.
2. A displacement type fluid compressor as set forth in claim 1,
characterized in that the tin compound coating film has a thickness
of not less than 20 .mu.m.
3. A displacement type fluid compressor as set forth in claim 1,
characterized in that said tin compound is a compound of tin and
metal from which the stator or the rotor is formed.
4. A displacement type fluid compressor as set forth in claim 1,
characterized in that each of the outer surfaces of the stator and
the rotor is coated with the tin compound coating film.
5. A displacement type fluid compressor as set forth in claim 2,
characterized in that the tin compound is an iron group material
and a compound of tin.
6. A displacement type fluid compressor as set forth in any one of
claims 1 to 4, characterized in that the tin compound coating film
is formed in a mixed solution composed of stannate as a main
component.
7. A displacement type fluid compressor as set forth in claim 5,
characterized in that the stannate is potassium stannate.
8. An air-conditioning apparatus using the compressor as set forth
in any one of claims 1 to 7.
9. A method of forming a coating film containing a tin compound, on
at least one of a stator and a rotor of a displacement type
compressor in which a closed space defined between the stator and
the rotor is gradually decreased in association with motion of the
rotor so as to suck, compress and discharge fluid, characterized by
the steps of alkaline-degreasing an objective member, washing thus
alkaline-degreased objective member with pure water;
oxidation-etching the objective member washed with pure water,
dipping the objective member oxidation-etched in a mixed solution
containing stannate as a main component, so as to form a tin
compound coating film, washing the objective member formed with the
tin compound coating film with pure water, and drying and baking
the objective member washed with pure water.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a displacement type
compressor, and in particular to surface treatment preferable for
enhancing the efficiency of a scroll compressor used in an
air-conditioning unit, a refrigerator and an air compressor
unit.
RELATED ART
[0002] Conventionally, various surface treatment methods have been
proposed for a displacement type compressor in which a closed space
defined between a stator and a rotor is gradually decreased in
association with motion of the rotor so as to suck, compress and
discharge fluid, and in particular, for a scroll type compressor in
which a pair of scrolls (laps) angularly shifted from each other
and meshed with each other are subjected to circular motion,
relative to each other so as to move a closed space defined between
both laps toward the center part while the volume thereof is
compressed to discharge the compressed fluid from the center part.
The purpose of the surface treatment is to decrease leakage of
fluid to be compressed between the laps or between the laps and
associated planar plates (mirror plates), as far as possible, and
to make the slidability between the members making contact with
each other, satisfactory, thereby it is possible to prevent the
efficiency from being lowered due to frictional losses.
[0003] For example, Japanese Laid-Open Patent No. 55-81294
discloses a method for plating either one of scroll members with
copper or lead bronze. Further, Japanese Laid-Open Patent No.
58-57002 discloses a method as a method which satisfies both
wear-resistance and conformability between slidable parts, of
carrying out high-frequency quenching and manganese phosphate
coating treatment (leubrite treatment). Meanwhile, a method as a
method which prevents the laps of the scroll members and the mirror
plate from making direct contact with each other, comprising the
steps of forming grooves in the tip end parts of the laps along the
spiral thereof, and filling engineering plastic having satisfactory
slidability and wear-resistance in these grooves (tip seal process)
has been proposed. For example, Japanese Laid-Open 3-246389
discloses a method which can reduce gaps between the tip seals and
the grooves.
[0004] In such a case-that a slidable part of a scroll type
compressor is formed on its surface with a coating film such-as a
plating coating film, made of a material different from the
material of the member, the temperature and the pressure increase
during compression stroke, various conditions such that a
temperature difference and a pressure differential are caused
between the outer peripheral part and the center part, change, and
accordingly, repetitive stress is applied to the coating film which
therefore cracks in long time use so that the coating film peels
off. In the most worst case, fragments of the peeled-off coating
film would cause eccentric abrasion.
[0005] In such a case that the surface of the slidable part is
subjected to a phosphate manganese process, satisfactory
characteristics such as slidability and wear-resistance can be
obtained. However, the phosphate manganese coating film (leubrite
coating film) has a relatively high hardness and high surface
roughness. Accordingly, a relatively long time is required until
the slidable parts become conformable against each other during
assembly of the scroll type compressor, thereby the productivity
thereof has been inferior. For example, if a rotary scroll is
subjected to leubrite treatment so as to form a coating film having
a thickness of about 10 .mu.m, the time of longer than five hours
has been required until the performance of the compressor becomes
stable after the slidable parts are conformable therebetween.
Further, a self-glowing type coating film of this kind has a
limited thickness up to about 15 .mu.m at maximum.
[0006] As mentioned above, when the scroll type compressor is
operated, since a pressure differential and a temperature
difference are caused between the outer peripheral part or a gas
suction part and the center part or a gas discharge part, both
rotary scroll and stationary scroll would be deformed. This
deformation, in particular, the deformation of the rotary scroll in
the lap-heightwise direction, causes the gap between the rotary
scroll and the stationary scroll associated with the former to
increase, and as a result, leakage increases so that the efficiency
of the compressor is greatly lowered. In more detail, the
temperature and the pressure are both low at the outer peripheral
part, and both become higher and higher toward the center part.
Thus, large stress is exerted to the lap of the rotary scroll from
the center part to the outer peripheral part. Accordingly, it
deforms as if flower leafs are opened. Thus, the gap between the
tip end (lap) of the rotary scroll and the mirror surface for the
stationary scroll becomes wider toward the outer peripheral part
from the center part, and as a result, leakage increases so that
the efficiency of the compressor is lowered. The degree of this
deformation (heightwise deformation) which differs, depending upon
an operating condition of the compressor, becomes about 20 .mu.m at
maximum. Accordingly, since a conventional self-growing coating
film such as a leubrite coating film has a thickness up to about 15
.mu.m at maximum, the degree of this deformation cannot be absorbed
by the coating film.
[0007] That is, even though the lap formed thereon with a coating
film having a certain thickness is assembled so that the coating
film surface thereof makes contact with a slidably mated part, and
the coating film is made into slidably contact with the slidably
mated part so as to be worn, for preventing the base metal of the
lap from making contact with the slidably mated part, when a force
deforming the lap in a direction in which the lap is pressed
against the slidably mated part in an operating condition is
produced, the base metal of the lap is inevitably made into contact
with the slidably mated part if the thickness of the coating film
is smaller than the degree of deformation of the lap. As a result,
the coating film at the tip end of the lap in the center part is
worn out completely, and accordingly, the base metal of the lap
slides on the mirror surface of the stationary scroll as the
slidably mated part. If the base metal is of iron group, that is,
it is a casting of, for example, FC250, the lap can hardly be worn.
Thus, unless this part is worn by operating the compressor for a
long time, the gap cannot become narrow, and accordingly, the
efficiency cannot be increased.
[0008] Meanwhile, a method in which a groove is formed in the tip
end part of the lap along the spiral, and engineering plastic which
is excellent in slidability and wear-resistance is filled in the
groove (tip seal method), can provide a stable slidability, but
spiralwise leakage (leaking through gaps between the rear surface
and side surface of the tip seal and the groove) is inevitably
caused. Thus, it is difficult to enhance the efficiency of the
compressor.
SUMMARY OF THE INVENTION
[0009] An object of the present invention is to provide a coating
film, in a displacement type compressor, which can be prevented
from being peeled off from a component even after long time
operation, and which is excellent in sealability and
conformability, thereby it is possible to actually provide a highly
efficient compressor.
[0010] The above-mentioned object can be fulfilled by a coating
film which is formed on either one or both of the surfaces of a
stator and a rotor where the stator and the rotor make contact with
each other, which contains a tin compound and which has a
predetermined thickness (which will be hereinbelow denoted as tin
compound coating film).
[0011] In order to form the tin compound film, a member to be
formed therewith is at first alkaline-degreased, and is then washed
with pure water. At this time, the alkali-degreasing solution is
preferably heated up to a temperature of, for example, about 50 to
80 deg. C. Then, the outer surface of the member is subjected to
oxidation-etching by using inorganic acid. As the inorganic acid,
any one of aqueous solutions of hydrochloric acid, sulfuric acid,
nitric acid or hydrofluoric acid or a mixed aqueous solution
thereof is used. At this time, this aqueous solution is preferably
be used at a room temperature, but may be heated up to a
temperature of about 50 deg. C. For example, in the case of using
nitric acid, an aqueous solution of 5 wt. % nitric acid is
preferably used. After etching, the member is washed with pure
water, and then an alkaline aqueous solution is prepared for pH
adjustment for the surface of the member. An aqueous solution in
which 0.5 to 1 wt. % of sodium hydroxide is dissolved, is
preferably used as the alkaline aqueous solution. After pH
adjustment, the member is again washed. Alternatively, after the
etching is carried out without carrying out the pH-regulation and
the washing after the pH adjustment, the member may be washed with
pure water, and then the next step may be directly taken.
[0012] Then, a coating film forming process is carried out with the
mixed aqueous solution containing stannate as a main component. In
addition to the stannate, a pH-regulator, a reaction accelerator, a
stabilizer and the like may preferably be added into the solution.
Potassium stannate, sodium hydroxide and sodium pyrophosphate or
sodium acetate are preferably used as the stannate, the
pH-regulator and the stabilizer, respectively. Further, sodium
hypophosphite or the like may be added in order to promote the
reducing reaction. At this time, the temperature of the solution is
set preferably to be in a range from 80 to 95 deg. C. Should the
temperature be lower than 80 deg. C., the reaction rate would be
insufficient so that a satisfactory stannate compound coating film
cannot be formed. Further, should it be higher than 95 deg. C., the
reaction within the mixed solution would be promoted before the
reaction with the member, thereby it is difficult to stably form
the compound with the member. Further, the time of formation of the
coating film can be arbitrarily set in accordance with a required
thickness thereof. After the processing, it is washed, and it is
preferably is dried and baked at a temperature, which is preferably
in a range from 150 to 200 deg. C.
[0013] Since this stannate compound coating film is formed not by
coating the member with a material different from that of the
member as a plated coating film, but by forming a compound with the
member, it is possible to prevent peel-off of the coating film from
the member or the like. In this arrangement, although sufficient
sealability and conformability can be obtained only by coating
either one of the stator and the rotor with the stannate coating
film, but the similar characteristic can be obtained by coating
both of them. This stannate compound coating film is particularly
preferable for the member made of a material selected from an iron
group including cast iron and carbon steel. In this case, the
compound is Fe--Sn compound which exhibits excellent
conformability.
[0014] The thus formed stannate compound coating film has a surface
roughness on a relatively soft surface made of the Fe--Sn compound
and is porous, and accordingly, no cracks caused by stress occur in
the coating film, different from a plated coating film, and as
well, the conformability can be obtained in a relatively short time
(excessive thickness may be decreased by abrasion), that is, the
frictional coefficient thereof is low so that the friction loss is
also low. Further, since it is porous, it is effectively retentive
of oil in such a case that the stannate compound coating film
slides, making contact with the associated member under the present
of oil.
[0015] It is noted that sodium stannate, in addition to potassium
stannate, can exhibit a similar result when it is used as the
stannate.
[0016] Explanation will be hereinbelow made of preferred
embodiments of the present invention with reference to the drawings
in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a view for explaining a procedure in an embodiment
of the present invention;
[0018] FIG. 2 is a longitudinal sectional view illustrating a
scroll type compressor in an embodiment of the present
invention;
[0019] FIG. 3 is an enlarged sectional view illustrating a part of
FIG. 3;
[0020] FIG. 4 is a sectional photograph illustrating the structure
of a tin compound coating film according to the present
invention;
[0021] FIG. 5 is a graph for explaining the characteristic of a
scroll type compressor incorporating the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] Explanation will be made of embodiments of the present
invention with reference to FIGS. 1 to 4.
[0023] FIG. 1 shows a coating process according to the present
invention. An FC250 member to be formed with a tin compound coating
film is at first washed through alkaline-degreasing (using
degreasing liquid FC315 made of Nihon Parkerizing Co., for 5
minutes at a temperature of 65 deg. C.), and thereafter, it is
washed with pure water. Then, the outer surface of the member is
dipped in an aqueous solution containing 5 wt. % of nitric acid for
5 minutes after it is heated up to 30 deg. C., and after
oxidation-etching, it is washed with a stream of ion-exchange
water.
[0024] Thereafter, a stannate mixed solution composed of the
following components, and the above-mentioned FC250 member to be
processed is dipped in the mixed solution under such a condition
such as a temperature of 85 deg. C. for 20 minutes, in order to
form a stannate compound coating film.
1 Stannate Mixed Solution K.sub.2SnO.sub.3 .multidot. 3H.sub.2O:
4.5 wt. % NaOH: 1.0 wt. % CH.sub.3COONa .multidot. 3H.sub.2O: 1.0
wt. % Na.sub.4P.sub.2O.sub.7: 0.5 wt. % H.sub.2O: the balance
[0025] Thereafter, washing with pure water is carried out, and then
drying and baking are made in a furnace at a temperature of 150
deg. C. for 30 minutes.
[0026] The result of analysis for the surface of the tin compound
coating film formed under the above-mentioned condition showed that
the thickness of the coating film is about 50 .mu.m, and the thin
film X-ray diffraction analysis gave the results listed in Table
1.
2TABLE 1 Crystal Phase FeSnO(OH).sub.5 .alpha.-Fe FeC C(Graphite)
Processed Film ++++ +++ + ++++ ++++: Very Large Quantity, +++:
Large Quantity, +: Small Quantity
[0027] FeSnO(OH).sub.5 detected therein is FeO(OH).Sn(OH)4. From
Table 4, it is understood that a sufficient quantity of Fe--Sn
compound was created. It is noted that Carbon or C detected similar
to the Fe--Sn compound is contained in the member made of cast iron
(by 3 to 4 wt. %). Since carbon exists by a large quantity at the
surface as mentioned above, a satisfactory result is brought about
for the slidability.
[0028] Next, explanation will be made of an example in which the
tin compound coating film is applied for a scroll type compressor.
Referring to FIG. 2 which shows the structure of the scroll type
compressor, a stationary scroll 21 as a stator is composed of a
mirror plate 21a and a spiral scroll lap 21b, the scroll lap 21b
being formed in its outer peripheral part with a suction port 23
for gas, and in its center part with a discharge port 24. The
stationary scroll 21 is coupled to a casing 25 through the
intermediary of an annular seal member 214 so that the scroll lap
21b is directed toward the casing 25. Meanwhile a rotary scroll 22
as a rotor is composed of a mirror plate 22a having a bearing 28 at
its enter thereof, and a spiral scroll lap 22b standing upright to
the mirror plate 22a. The rotary scroll 22 is located with respect
to the stationary scroll 21 so that the scroll lap 21b is meshed
with the scroll lap 22b, and the peripheral edge part of the mirror
plate 22a is slidably clamped between the stationary scroll 21 and
the casing 25 in a sandwich-like configuration. The rotary scroll
25 is meshed with the stationary scroll 21 so that the angle
between a line connecting between the center of the rotary scroll
22 and the outer peripheral side terminal end of the lap and a line
connecting between the center of the stationary scroll 21 and the
outer peripheral side terminal end of the lap is held to be
constant, and accordingly, the rotary scroll 25 is inhibited from
revolving at the outer peripheral part of the mirror plate 22a by
means of a plurality of pin ranks 26 which are fixed at their one
end to the casing 25 through the intermediary of bearings 27.
[0029] Further, a drive shaft 210 is provided for turning the
rotary scroll 22, relative to the stationary scroll, without
allowing the same revolving, the drive shaft 210 being supported by
an upper bearing 212a and a lower bearing 212b which are secured to
the casing 25. The drive shaft 210 has at its tip end a crank shaft
29 which is coupled to the rotary scroll 22 through the bearing 28.
Further, the drive shaft 210 is fitted thereon with a bearing seal
member 213 between the upper bearing 212a and the lower bearing
member 212b so as to block fluid flowing along the drive shaft. The
crank shaft 29 of the drive shaft 210 is provided thereto with a
balance weight 211 for balancing a centrifugal force induced in
association with the turning motion of the rotary scroll 22.
Further, the outer peripheral part of the mirror plate 22a is
slidably held between the stationary scroll 21 and the casing 25 in
order to ensure stable motion for the rotary scroll 22. Grease of a
perfluoropolyether group is used as a lubricant in the bearings 27,
28, 212a. Further, a seal member 216 for preventing the grease from
leaking is provided at the lower end position of the bearing 29 for
the crankshaft 29.
[0030] The scroll type compressor having the above-mentioned
configuration is operated as follows, a closed space defined
between the stationary scroll lap 21b and the rotary scroll lap 22b
is shifted from the outer peripheral side to the center side of the
laps through the turning of the rotary scroll 22 so that its volume
is decreased, and accordingly, gas compressed in this closed space
is fed to the outside through the discharge port 24 formed in the
stationary scroll 21 around the center of the latter.
[0031] Next, explanation will be made of the main part according to
the present invention. FIG. 3 which shows a part of FIG. 2 by an
enlarged scale. In this example shown, the rotary scroll 22 is
formed thereon with a tin compound coating film 1. In this
embodiment, the surface of a rotary scroll which makes contact with
a flow passage into which gas flows from the suction part 23 and
from which gas flows out through the discharge port 24 is coated
with the tin compound coating film in its entirety, and
accordingly, no gas leaks from the flow passage in the member,
intermediary thereof. In this arrangement, when the rotary scroll
and the stationary scroll are regularly combined, a conforming
margin of about 10 .mu.m is ensured each of contact parts. In other
words, the dimensions of contact parts are set so that rotary
scroll and the stationary scroll overlap with each other by about
10 .mu.m. Although the tin compound coating film basically reacts
with Fe in the member, it does not self-grow dimensionally, and
therefore, the above-mentioned setting can be made in a relatively
simple manner.
[0032] It is noted that the compressor having newly assembled is
operated preferably at a low speed so as to conform slide parts
with each other upon starting of operation thereof. Further, with
the use of a device which is exclusively used for running-in, and
which can change the eccentricity of the rotary scroll with respect
to the stationary scroll, the rotary scroll is assembled with the
stationary scroll with zero eccentricity therebetween, and then,
the eccentricity is gradually changed up to a regular value while
the rotary scroll is rotated at a low speed so that they may both
conform with each other.
[0033] An Fe--Sn compound coating film (tin compound coating film)
is relatively soft and is excellent slidability, different from a
conventional leubrite coating film, and accordingly, the
above-mentioned overlap part can be polished in a relatively short
time by the surface of the stationary scroll so as to conform with
the latter. In such a manner, a gap at the tip end of the lap upon
deformation of the lap can be decreased so as to allow leakage of
gas to be substantially zero. Thus, the efficiency of the
compressor can be remarkably enhanced, and as well, the time
required for conforming operation for the slide parts during
assembly can be shortened, thereby it is possible to enhance the
manufacturing efficiency. The thickness of the tin compound coating
film 1 which is formed by dipping the rotary scroll 22 or the
stationary scroll 21 in the stannate mixed solution, should be set
in consideration with the degree of deformation of the scroll lap.
However, it is desirable in view of a room for the conforming
margin to set the thickness thereof to about 20 .mu.m.
[0034] FIG. 4 is a sectional photograph of the scroll formed with
the tin compound coating film having a thickness of about 60 .mu.m.
Thus, according to the present invention, the thickness of the
coating film can be increased, and accordingly, even though the
degree of deformation of the tip end of the lap is about 20 .mu.m
in the operating condition, the coating film can have a thickness
which can afford to sufficiently absorb such a deformation.
[0035] Further, FIG. 5 shows the characteristic of the scroll type
compressor manufactured as mentioned above. In this figure, the
time elapsing from a start of operation of the compressor is taken
on the abscissa, and the frictional coefficient as the index
indicating the degree of conformability is taken on the ordinate.
The characteristic of a conventional leubrite coating film is also
shown in this figure for the purpose of comparison. It is clear
from this figure that the compressor incorporating the tin compound
coating film according to the present invention can stabilize its
frictional coefficient by about two hours, and further, the
frictional coefficient thereof is low in comparison with that
incorporating the leubrite coating film. As to the performance of
this compressor, the overall adiabatic efficiency is
.eta.ad=88%.
[0036] The above-mentioned embodiment shows an example in which the
slide surface of the scroll type compressor is formed thereon with
a coating film containing a tin compound. However, even though
slide parts of a screw compressor, a rotary compressor, a
reciprocating compressor or the like is formed thereon with a
coating film containing a tin compound, the similar effects can be
obtained.
[0037] Further, when such an enhanced performance compressor is
used in an air-conditioner, the air-condition can have an excellent
performance.
[0038] As mentioned above, according to the present invention, the
coating film containing a tin compound can be formed on a component
surface where the stator and the rotor make contact with each
other, in a relatively simple manner, and further, the coating film
is never peeled off even after long time operation, that is, the
coating film which is excellent in sealability and conformability,
thereby it is possible to actually provide a compressor with a high
degree of accuracy. Further, since the members are dimensionally
overlapped with each other, and since they are slid with each other
so as to be conformed with each other by polishing, it is possible
to eliminate the necessity of severe dimensional accuracy during
fabrication of the members, as has been required conventionally.
Further, no unevenness occurs in performance in
mass-production.
* * * * *