U.S. patent application number 10/316418 was filed with the patent office on 2003-07-03 for shoe for swash plate type compressor and swash plate type compressor equipped with the shoe.
Invention is credited to Mera, Minoru, Murakami, Tomohiro, Ohkubo, Shino, Onoda, Akira, Sugioka, Takahiro, Sugiura, Manabu.
Application Number | 20030121412 10/316418 |
Document ID | / |
Family ID | 19186169 |
Filed Date | 2003-07-03 |
United States Patent
Application |
20030121412 |
Kind Code |
A1 |
Sugiura, Manabu ; et
al. |
July 3, 2003 |
Shoe for swash plate type compressor and swash plate type
compressor equipped with the shoe
Abstract
A shoe for a swash plate type compressor disposed between a
swash plate and a corresponding one of a plurality of pistons, the
shoe being characterized by comprising: a base body formed of an
aluminum alloy; and a metal plating film which covers at least a
portion of a surface of the base body.
Inventors: |
Sugiura, Manabu;
(Kariya-shi, JP) ; Sugioka, Takahiro; (Kariya-shi,
JP) ; Ohkubo, Shino; (Kariya-shi, JP) ; Onoda,
Akira; (Kariya-shi, JP) ; Murakami, Tomohiro;
(Kariya-shi, JP) ; Mera, Minoru; (Kariya-shi,
JP) |
Correspondence
Address: |
WOODCOCK WASHBURN LLP
ONE LIBERTY PLACE, 46TH FLOOR
1650 MARKET STREET
PHILADELPHIA
PA
19103
US
|
Family ID: |
19186169 |
Appl. No.: |
10/316418 |
Filed: |
December 11, 2002 |
Current U.S.
Class: |
92/70 |
Current CPC
Class: |
F05C 2201/0463 20130101;
F05C 2201/903 20130101; F05C 2201/0466 20130101; F05C 2253/12
20130101; F04B 27/0886 20130101 |
Class at
Publication: |
92/70 |
International
Class: |
F01B 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 12, 2001 |
JP |
2001-378450 |
Claims
What is claimed is:
1. A shoe for a swash plate type compressor disposed between a
swash plate and a corresponding one of a plurality of pistons, said
shoe comprising: a base body formed of an aluminum alloy; and a
metal plating film which covers at least a portion of a surface of
said base body.
2. A shoe according to claim 1, wherein said metal plating film
comprises an electroless plating film which contains at least one
of Ni and Co as a major constituent element.
3. A shoe according to claim 2, wherein said electroless plating
film comprises at least one electroless nickel plating film
selected from the group consisting of an Ni--P based film, an Ni--B
based film, an Ni--P--B based film, an Ni--P--W based film, an
Ni--B--W--based film, and an Ni--P--B--W based film.
4. A shoe according to claim 2, wherein said electroless plating
film comprises at least one electroless cobalt plating film
selected from the group consisting of a Co--P based film and a
Co--P--W based film.
5. A shoe according to claim 2, wherein said electroless plating
film comprises at least one electroless nickel-cobalt plating film
selected from the group consisting of an Ni--Co based film and an
Ni--Co--P based film.
6. A shoe according to claim 2, wherein said electroless plating
film contains polytetrafluoroethylene (PTFE).
7. A shoe according to claim 2, wherein said metal plating film
further comprises at least one covering film which is formed on a
surface of said electroless plating film and which contains at
least one of Sn, TiCN, TiN, CrN, and TiAlN.
8. A shoe according to claim 1, wherein said metal plating film
comprises an electroplating film which contains at least one of Ni,
Fe, Cr, and Co as a major constituent element.
9. A shoe according to claim 8, wherein said electroplating film
comprises at least one nickel electroplating film selected from the
group consisting of an Ni based film, an Ni--P based film, an Ni--W
based film, an Ni--Fe based film, an Ni--M0--W based film.
10. A shoe according to claim 8, wherein said electroplating film
comprises at least one ferrous electroplating film selected from
the group consisting of an Fe based film, an Fe--P based film, an
Fe--W based film, an Fe--C based film, and an Fe--N based film.
11. A shoe according to claim 8, wherein said electroplating film
comprises at least one chromium electroplating film selected from
the group consisting of a Cr based film and a Cr--Mo based
film.
12. A shoe according to claim 8, wherein said electroplating film
comprises at least one cobalt electroplating film selected from the
group consisting of a Co based film and a Co--W based film.
13. A shoe according to claim 1, wherein said metal plating film
contains at least one of SiC, Si.sub.3N.sub.4, Al.sub.2O.sub.3, and
CrC.
14. A shoe according to claim 1, wherein said metal plating film
has a hardness value of not smaller than Hv 300.
15. A shoe according to claim 1, wherein said metal plating film
covers at least a portion of said base body which, portion is held
in sliding contact with said swash plate.
16. A shoe according to claim 1, wherein said metal plating film
constitutes at least a part of an outer surface of said shoe.
17. A swash plate type compressor comprising: a swash plate; a
plurality of pistons; and a plurality of shoes as defined in claim
1, each of said plurality of shoes being disposed between said
swash plate and a corresponding one of said plurality of
pistons.
18. A swash plate type compressor according to claim 17, wherein
said swash plate is formed of a ferrous material.
19. A swash plate type compressor according to claim 17, wherein
said swash plate includes lubricating films formed on sliding
surfaces thereof which slide on said plurality of shoes.
20. A swash plate type compressor according to claim 17, further
comprising a displacement capacity changing mechanism for changing
a displacement capacity of said compressor by changing an
inclination angle of said swash plate.
Description
TITLE OF THE INVENTION
[0001] SHOE FOR SWASH PLATE TYPE COMPRESSOR AND SWASH PLATE TYPE
COMPRESSOR EQUIPPED WITH THE SHOE
[0002] This application is based on Japanese Patent Application No.
2001-378450 filed Dec. 12, 2001, the contents of which are
incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates in general to a shoe for a
swash plate type compressor, which shoe is disposed between a swash
plate and a piston of the swash plate type compressor. More
specifically, the present invention is concerned with such a shoe
formed of an aluminum alloy, and the swash plate type compressor
equipped with the shoe.
[0005] 2. Discussion of the Related Art
[0006] A swash plate type compressor is adapted to compress a gas
by converting a rotary movement of the swash plate into a
reciprocating movement of a plurality of pistons. Between the swash
plate which is rotated at a relatively high speed and each piston
which is reciprocated at a relatively high speed, a shoe as a
sliding member is disposed for permitting a smooth relative
movement therebetween. In the swash plate type compressor used in
an air conditioning system of an automotive vehicle, which
compressor is particularly required to have a reduced weight, it is
proposed to use an aluminum alloy for forming the shoe as one
component of the compressor.
[0007] The swash plate and the piston which slide on the shoe are
often formed of an aluminum alloy. In this case, the seizure is
likely to occur due to the sliding contact between the swash plate
and the shoe, and between the piston and the shoe, since the swash
plate, the piston, and the shoe are formed of similar materials
which contain the aluminum as a major component. Where the swash
plate or the piston is not formed of the aluminum alloy, e.g.,
where the swash plate is formed of a ferrous material, the seizure
will take place between the swash plate and the shoe since the shoe
slides on the swash plate under severe or heavy load conditions. In
addition, the shoe formed of the aluminum alloy tends to suffer
from damages such as scratches and dents on its surface due to
relatively low degrees of strength and hardness of the aluminum
alloy. The scratches formed on the surface of the shoe in turn give
damages the sliding surfaces of the swash plate and the piston on
which the shoe slides, resulting in deterioration of the sliding
characteristics of the compressor. Since the shoe slides under
heavy load conditions, the durability of the shoe is deteriorated
due to the low degrees of strength and hardness of the aluminum
alloy.
SUMMARY OF THE INVENTION
[0008] It is therefore an object of the present invention to
provide a shoe formed of an aluminum alloy and having good sliding
characteristics, and a practically useful swash plate type
compressor equipped with the shoe. The objects may be achieved
according to any one of the following modes of the present
invention in the form of a shoe for a swash plate type compressor
and a swash plate type compressor equipped with the shoe. Each of
the following modes is numbered like the appended claims and
depends from the other mode or modes, where appropriate, to
indicate and clarify possible combinations of elements or technical
features of the present invention, for easier understanding of the
invention. It is to be understood that the present invention is not
limited to the technical features or any combinations thereof which
will be described for illustrative purpose only. It is to be
further understood that a plurality of elements or features
included in any one of the following modes of the invention are not
necessarily provided all together, and that the invention may be
embodied without some of the elements or features described with
respect to the same mode.
[0009] (1) A shoe for a swash plate type compressor disposed
between a swash plate and a corresponding one of a plurality of
pistons, the shoe comprising: a base body formed of an aluminum
alloy; and a metal plating film which covers at least a portion of
a surface of the base body.
[0010] The shoe for the swash plate type compressor according to
the present invention is characterized in that the metal plating
film is formed on the surface of its base body made of the aluminum
alloy. Owing to the metal plating film, the shoe exhibits good
sliding characteristics.
[0011] Various known metal plating films can be employed. Examples
of the metal plating film are described below. A preferable
composition and a preferable thickness of each metal plating film
will be described in the following DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENT. A method of forming the metal plating film,
i.e., a plating method, is not particularly limited. Namely, the
metal plating film may be formed under appropriate conditions
according to known methods as employed in the fields for plating
other articles while considering that the metal plating film is
formed on the surface of the shoe. The metal plating film formed on
the surface of the present shoe may be constituted by only one of
the plating films described below, or a plurality of those plating
films superposed on each other.
[0012] The aluminum alloy used for the base body of the shoe is not
particularly limited, but may be selected from among aluminum
alloys conventionally used for producing the shoe, and various
known aluminum alloys. For example, it is possible to use an Al--Si
alloy having a ratio of content of Al to Si which is nearly equal
to that at which an eutectic mixture is formed. The Al--Si alloy
is, for instance, A4032 according to the Japanese Industrial
Standard (JIS) H4100. The Al--Si alloy has a small coefficient of
thermal expansion and exhibits a good abrasion resistance, so that
the shoe formed of the Al--Si alloy exhibits good sliding
characteristics. It is also possible to use an Al--Cu--Mg alloy
such as A2017, A2024 according to the JIS H4100, which alloy has a
high degree of strength. The shoe formed of the Al--Cu--Mg alloy
exhibits high degrees of strength and durability.
[0013] (2) A shoe according to the above mode (1), wherein the
metal plating film comprises an electroless plating film which
contains at least one of Ni and Co as a major constituent
element.
[0014] The nickel-based or cobalt-based electroless plating permits
uniform formation of the metal plating film having a relatively
high degree of hardness, on the surface of the base body of the
shoe, for thereby improving the sliding characteristics of the
shoe.
[0015] (3) A shoe according to the above mode (2), wherein the
electroless plating film comprises at least one electroless nickel
plating film selected from the group consisting of an Ni--P based
film, an Ni--B based film, an Ni--P--B based film, an Ni--P--W
based film, an Ni--B--W--based film, and an Ni--P--B--W based
film.
[0016] The electroless nickel plating permits uniform formation of
the metal plating film on the surface of the base body of the shoe
as described above. In addition, the plating film formed by the
electroless nickel plating has a Vickers hardness value higher than
Hv 500, and exhibits high degrees of resistances to abrasion and
corrosion. Accordingly, the metal plating film formed by the
electroless nickel plating on the surface of the base body of the
shoe is effective to prevent the shoe from suffering from scratches
which cause deformation of the base body formed of the aluminum
alloy. Thus, the shoe according to the present mode exhibits
excellent sliding characteristics and durability when used for the
swash plate type compressor.
[0017] The advantages of the respective plating films described
above are as follows. The Ni--P based electroless nickel plating
film exhibits good adhesion with respect to the aluminum alloy of
the base body of the shoe, and a high degree of corrosion
resistance. Further, the Ni--P based film can be formed at a
relatively high rate and at a relatively low cost by using a
relatively inexpensive plating bath material. The Ni--B based
electroless nickel plating film and the Ni--P--B based electroless
nickel plating film have a high degree of hardness and exhibit good
resistances to abrasion and oxidation at a relatively high
temperature. In particular, the Ni--P--B based film has a hardness
value of not lower than Hv 650. The Ni--P--W based film, the
Ni--B--W--based film, and the Ni--P--B--W based film exhibit a
significantly high degree of abrasion resistance owing to tungsten
(W) included therein. Any suitable one of, or any suitable
combination of those plating films may be employed by taking into
account the advantages of the respective plating films.
[0018] The electroless nickel plating film may include two or more
of the above-described electroless nickel plating films having
respective different compositions and superposed on each other.
Where a plurality of plating films are described in the following
modes, only one of those plating films may be employed, or two or
more of those plating films which are superposed on each other may
be employed, for providing the meal plating film formed on the
surface of the base body of the shoe.
[0019] (4) A shoe according to the above modes (2) or (3), wherein
the electroless plating film comprises at least one electroless
cobalt plating film selected from the group consisting of a Co--P
based film and a Co--P--W based film.
[0020] The electroless cobalt plating film has excellent friction
characteristics. Where the base body of the shoe is covered with
the electroless cobalt plating film, the shoe exhibits good sliding
characteristics.
[0021] (5) A shoe according to any one of the above modes (2)-(4),
wherein the electroless plating film comprises at least one
electroless nickel-cobalt plating film selected from the group
consisting of an Ni--Co based film and an Ni--Co--P based film.
[0022] The electroless nickel-cobalt plating film has excellent
friction characteristics. Where the base body of the shoe is
covered with the electroless nickel-cobalt plating film, the shoe
exhibits good sliding characteristics.
[0023] (6) A shoe according to any one of the above modes (2)-(5),
wherein the electroless plating film contains
polytetrafluoroethylene (PTFE).
[0024] In the electroless plating film according to this mode, the
PTFE is deposited together with the matrix phase of the plating
film. Where the electroless plating film includes the PTFE therein,
the plating film exhibits good lubrication characteristics, for
thereby improving the sliding characteristics of the shoe.
[0025] (7) A shoe according to any one of the above modes (2)-(6),
wherein the metal plating film further comprises at least one
covering film which is formed on a surface of the electroless
plating film and which contains at least one of Sn, TiCN, TiN, CrN,
and TiAlN
[0026] The covering film which contains Sn exhibits excellent
sliding characteristics where the lubrication by the lubricant oil
is insufficient, since the Sn which is a soft metal has a function
similar to that of a solid lubricant. The covering film which
contains TiCN, TiN, CrN, or TiAlN has a high degree of hardness and
exhibits good abrasion resistance. Accordingly, the covering film
formed on the surface of the electroless plating film permits the
shoe to exhibit good sliding characteristics. The covering film
which contains Sn may be formed by electroplating or chemical
plating (e.g., autocatalytic deposition) while the covering film
which contains TiCN, TiN, CrN, or TiAlN may be formed by physical
vapor deposition (PVD), for instance.
[0027] (8) A shoe according to any one of the above modes (1)-(7),
wherein the metal plating film comprises an electroplating film
which contains at least one of Ni, Fe, Cr, and Co as a major
constituent element.
[0028] The electroplating film containing at least one of Ni, Fe,
Cr, and Co as a major constituent element has a high degree of
hardness, so that such an electroplating film is suitably employed
as a covering film which covers the surface of the shoe formed of
the aluminum alloy. Further, the electroplating can be effected at
a lower cost than the above-described electroless plating, reducing
the cost of manufacture of the shoe.
[0029] (9) A shoe according to the above mode (8), wherein the
electroplating film comprises at least one nickel electroplating
film selected from the group consisting of an Ni based film, an
Ni--P based film, an Ni--W based film, an Ni--Fe based film, an
Ni--M0--W based film.
[0030] The nickel electroplating film is not likely to suffer from
defects such as pinholes and cracks, and exhibits a smoothing or
leveling effect for smoothing or leveling the surface of the base
body, in other words, improving the surface smoothness. Further,
the nickel electroplating film has a high degree of hardness. The
shoe whose surface is covered with the nickel electroplating film
exhibits good sliding characteristics owing to those
advantages.
[0031] (10) A shoe according to the above mode (8) or (9), wherein
the electroplating film comprises at least one ferrous
electroplating film selected from the group consisting of an Fe
based film, an Fe--P based film, an Fe--W based film, an Fe--C
based film, and an Fe--N based film.
[0032] The ferrous electroplating film can be formed at a
relatively low cost, for thereby reducing the cost of manufacture
of the shoe.
[0033] (11) A shoe according to any one of the above modes
(8)-(10), wherein the electroplating film comprises at least one
chromium electroplating film selected from the group consisting of
a Cr based film and a Cr--Mo based film.
[0034] The chromium electroplating film has a higher degree of
hardness and a lower coefficient of friction than the
above-described nickel electroplating film, for instance, so that
the shoe covered with the chromium electroplating film exhibits
good sliding characteristics.
[0035] (12) A shoe according to any one of the above modes
(8)-(11), wherein the electroplating film comprises at least one
cobalt electroplating film selected from the group consisting of a
Co based film and a Co--W based film
[0036] The cobalt electroplating film has good friction
characteristics, so that the shoe covered with the cobalt
electroplating film exhibits good sliding characteristics.
[0037] (13) A shoe according to any one of the above modes
(1)-(12), wherein the metal plating film contains at least one of
SiC, Si.sub.3N.sub.4, Al.sub.2O.sub.3, and CrC.
[0038] The above-described substances have high melting points and
high hardness values. Accordingly, the metal plating film
containing at least one of those substances exhibits excellent
abrasion resistance, so that the sliding characteristics of the
shoe formed of the aluminum alloy can be further improved. These
substances are contained in the metal plating film in the form of
fine particles, for instance. During formation of the metal plating
film, the fine particles of those substances are dispersed in the
plating bath, so that those substances are included in the formed
metal plating film.
[0039] (14) A shoe according to any one of the above modes
(1)-(13), wherein the metal plating film has a hardness value of
not smaller than Hv 300.
[0040] The shoe whose base body is formed of the aluminum alloy and
covered with the plating film having a Vickers hardness of not
lower than Hv 300 exhibits practically sufficient operating
performance. For increasing the abrasion resistance and effectively
preventing the shoe from being damaged, the metal plating film
preferably has the hardness of not lower than Hv 500, more
preferably not lower than Hv 600, still more preferably not lower
than Hv 700. For preventing excessive abrasion of the member on
which the shoe slides and protecting the member from being damaged
by fragments of the covering film which may peel off from the base
body, the metal plating film preferably has the hardness of not
higher than Hv 1500, more preferably not higher than Hv 1100.
[0041] (15) A shoe according to any one of the above modes
(1)-(14), wherein the metal plating film covers at least a portion
of the base body, which portion is held in sliding contact with the
swash plate.
[0042] In the swash plate type compressor, the shoe slides on the
swash plate and a corresponding one of the plurality of pistons.
Where the shoe is covered with the metal plating film at a portion
thereof which is held in sliding contact with the swash plate or
the piston, the shoe exhibits good sliding characteristics. In view
of the fact that the swash plate is rotated at a relatively high
speed, at least a portion of the base body of the shoe, which
portion is held in sliding contact with the swash plate, is
preferably covered with the metal plating film, as described in
this mode of the invention. For assuring high degrees of corrosion
resistance of the shoe and configurational stability of the shoe,
and easier plating operation, it is preferable to cover the entire
surface of the base body of the shoe with the plating film.
[0043] (16) A shoe according to any one of the above modes
(1)-(15), wherein the metal plating film constitutes at least a
part of an outer surface of the shoe.
[0044] The swash plate type compressor shoe according to the
present invention may include another covering film formed on the
surface of the metal plating film. For instance, a lubricating film
formed of a synthetic resin containing a solid lubricant may be
formed on the metal plating film. The lubricating film is effective
to improve the sliding characteristics of the shoe. The solid
lubricant may be selected from among molybdenum disulfide
(MoS.sub.2), boron nitride (BN), tungsten disulfide (WS.sub.2),
graphite, and polytetrafluoroethylene (PTFE), for instance, while
the synthetic resin may be selected from among polyamide imide,
epoxy resin, polyetherketone, and phenol resin, for instance. The
lubricating film may be formed such that the synthetic resin in
which the solid lubricant is dispersed is coated on the surface of
the metal plating film by spraying, for instance, and the resin is
hardened for providing the lubricating film. As described in this
mode, the metal covering film may not be covered with any other
covering film. The shoe without any additional covering film is
produced at a relatively low cost, and practically useful.
[0045] While there have been described various modes of the shoe
for the swash plate type compressor according to the present
invention, the shoe of the invention may have any one of the
technical features in the following modes relating to the swash
plate type compressor, depending upon the specific application of
the shoe.
[0046] (17) A swash plate type compressor comprising: a swash
plate; a plurality of pistons; and a plurality of shoes as defined
in any one of the above modes (1)-(16), each of the plurality of
shoes being disposed between the swash plate and a corresponding
one of the plurality of pistons.
[0047] The swash plate type compressor according to this mode of
the invention is equipped with the above-described shoe of the
present invention. Owing to the good sliding characteristics of the
shoe, the present swash plate type compressor exhibits excellent
durability while assuring a smooth operation thereof.
[0048] (18) A swash plate type compressor according to the above
mode (17), wherein the swash plate is formed of a ferrous
material.
[0049] The ferrous material is generally inexpensive, so that the
swash plate type compressor having the swash plate formed of the
ferrous material is relatively inexpensive. In the swash plate type
compressor of a variable capacity type, for instance, the
displacement capacity of the compressor is adjusted or changed by
changing an angle of the swash plate with respect to a plane
perpendicular to the rotation axis of the rotary drive shaft,
namely by changing an angle of inclination of the swash plate with
respect to the above-indicated plane. (The angle is hereinafter
referred to as an "inclination angle" of the swash plate.) While
the compressor is operated so as to maintain a predetermined
constant displacement capacity, the swash plate is desirably
rotated while being kept at a predetermined inclination angle. If
the swash plate has a relatively large mass, the inertial force
permits the swash plate to be rotated with high stability while
being kept at the predetermined inclination angle. Accordingly, the
swash plate type compressor equipped with the ferrous swash plate
exhibits a high degree of operating stability since the ferrous
swash plate having a relatively large mass can be rotated with high
stability. In the swash plate type compressor of variable capacity
type described above, if the ferrous swash plate is used in
combination with the shoe formed of a lightweight aluminum alloy,
the swash plate can be rotated with further higher stability. In
view of the fact that the configuration of the swash plate is
complicated, the ferrous swash plate is preferably formed by
casting. In view of this, the swash pate is desirably formed of
cast iron. Among various cast irons, it is preferable to use a
spheroidal graphite cast iron which exhibits high degrees of
strength and durability. In particular, the ductile cast iron FCD
700 according to the JIS G 5502 having a considerably high degree
of strength is preferably employed. The material used for the swash
plate is not particularly limited. For instance, the swash plate
may be formed of an aluminum alloy for reducing its weight.
[0050] If the ferrous swash plate is employed, the swash plate may
include, on the sliding surfaces thereof which slide on the shoes,
metal sprayed films formed of a material selected from the group
consisting of aluminum, copper, an aluminum alloy, and a copper
alloy, for improving the sliding characteristics. The swash plate
may be subjected to a quenching treatment on the sliding surfaces
thereof which slide on the shoes. Where the present shoe having the
metal covering film slides on the swash plate according to those
arrangements, the present shoe is not likely to suffer form seizure
and abrasion, for thereby effectively maintaining good sliding
characteristics. Accordingly, the shoe of the present invention is
suitably used in combination with the swash plate whose sliding
surfaces are covered with the metal sprayed films or subjected to
the quenching treatment.
[0051] (19) A swash plate type compressor according to the above
mode (17) or (18), wherein the swash plate includes lubricating
films formed on sliding surfaces thereof which slide on the
plurality of shoes.
[0052] The swash plate and the shoes slide on each other under
considerably heavy load conditions since the swash plate is rotated
at a relatively high speed. In the swash plate type compressor
having the swash plate whose sliding surfaces which slide on the
shoes are covered with the lubricating films, the friction between
the swash plate and the shoes is reduced, assuring a smooth
operation of the compressor.
[0053] The lubricating film formed on each sliding surface of the
swash plate may have a structure similar to that of the lubricating
film formed on the surface of the metal covering film of the shoe
described above. The lubricating film has a relatively low degree
of strength, and tends to peel off from the swash plate due to the
scratches formed on the shoe during the sliding contact with the
shoe. Where the shoe slides on the swash plate at its portion on
which the metal covering film is formed, the shoe is not likely to
suffer from any scratches at that portion owing to the metal
covering film, so that the lubricating film formed on each sliding
surface of the swash plate is prevented from being damaged by the
scratches of the shoe. Thus, the present swash plate type
compressor maintains good sliding characteristics for a long period
of service.
[0054] (20) A swash plate type compressor according to any one of
the above modes (17)-(19), further comprising a displacement
capacity changing mechanism for changing a displacement capacity of
the compressor by changing an inclination angle of the swash
plate.
[0055] In the swash plate type compressor of variable capacity
type, the displacement capacity of the compressor is generally
adjusted by changing the inclination angle of the swash plate with
respect to the plane perpendicular to the rotation axis of the
rotary drive shaft, for thereby changing the reciprocating stroke
of the pistons. In the thus arranged swash plate type compressor of
variable capacity type, when the swash plate is inclined with
respect to the above-indicated plane, the shoes have an elliptical
path on the swash plate. With an increase in the inclination angle
of the swash plate, the major axis of an ellipse of the path is
increased. Since the swash plate type compressor needs to be
compact, the size, i.e., the diameter of the swash plate, is made
small to such an extent that the swash plate does not interfere
with the pistons when the swash plate is not inclined. In other
words, the diameter of the swash plate is determined so as to
permit the shoes to engage the swash plate such that the end of the
shoe on the radially outer side of the swash plate is flush with
the outer circumferential surface of the swash plate, in other
words, to prevent the shoe from radially outwardly protruding from
the radially outer portion of the swash plate, when the swash plate
is not inclined. In the compressor having the thus designed swash
plate, when the swash plate is inclined at a relatively large
angle, the shoes engaging the pistons which are located near the
opposite ends of the major axis of the elliptical path of the
shoes, namely, the shoes engaging the pistons located near the
compression stroke end and the suction stroke end, respectively,
slide on the swash plate such that portions of the shoes radially
outwardly protrude from the radially outer portion of the swash
plate, depending upon the structure of the compressor. In this
case, the area of contact or engagement of the swash plate and the
shoes is undesirably reduced, so that a relatively large pressing
force of the shoes acts on the swash plate at its small surface
area contacting the shoes. The shoes may slide on the swash plate
while the shoes are inclined. In this case, the pressing force of
the shoes acts on portions of the swash plate in the vicinity of
its circumferential edges having an extremely small surface area.
Accordingly, the shoes used for the swash plate type compressor of
variable capacity type are operated under very severe or heavy load
conditions. Since the strength of the lubricating films formed on
the sliding surfaces of the swash plate is relatively small, the
lubricating films are likely to be worn when the shoes slide on a
small surface area of the swash plate as described above. Thus, in
the swash plate type compressor wherein the inclination angle of
the swash plate is changed, the shoes and the swash plate slide on
each other under very severe or heavy load conditions. The present
swash plate type compressor equipped with the shoes each having the
metal plating film formed on the surface thereof have good sliding
characteristics. In other words, the shoe of the present invention
is particularly advantageously applicable to the swash plate type
compressor of variable capacity type in which the inclination angle
of the swash plate is changed to change the displacement capacity
of the compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] The above and optional objects, features, advantages and
technical and industrial significance of the present invention will
be better understood and appreciated by reading the following
detailed description of a presently preferred embodiment of the
invention, when considered in connection with the accompanying
drawings, in which:
[0057] FIG. 1 is a front elevational view in cross section of a
swash plate type compressor equipped with shoes constructed
according to one embodiment of the present invention;
[0058] FIG. 2 is a front elevational view in cross section showing
the shoe and a portion of the swash plate which slides on the shoe;
and
[0059] FIG. 3 schematically shows a test device used for examining
the resistance of the shoe to seizure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0060] Referring to the accompanying drawings, there will be
described a presently preferred embodiment of this invention as
applied to a swash plate type compressor used for an air
conditioning system of an automotive vehicle, and a shoe installed
on the swash plate type compressor as one component of the
compressor.
[0061] Referring first to FIG. 1, there is shown a compressor of
swash plate type. In FIG. 1, reference numeral 10 denotes a
cylinder block having a plurality of cylinder bores 12 formed so as
to extend in its axial direction such that the cylinder bores 12
are arranged along a circle whose center lies on a centerline of
the. cylinder block 10. Single-headed pistons generally indicated
at 14 (hereinafter simply referred to as "piston 14") are
reciprocably received in the respective cylinder bores 12. To one
of the axially opposite end faces of the cylinder block 10, (the
left end face as seen in FIG. 1, which will be referred to as
"front end face"), there is attached a front housing 16. To the
other end face (the right end face as seen in FIG. 1, which will be
referred to as "rear end face"), there is attached a rear housing
18 through a valve plate 20. The front housing 16, rear housing 18
and cylinder block 10 cooperate to constitute a housing assembly of
the swash plate type compressor. The rear housing 18 and the valve
plate 20 cooperate to define a suction chamber 22 and a discharge
chamber 24, which are connected to a refrigerating circuit (not
shown) through an inlet 26 and an outlet 28, respectively. The
valve plate 20 has suction ports 32, suction valves 34, discharge
ports 36 and discharge valves 38.
[0062] A rotary drive shaft 50 is disposed in the cylinder block 10
and the front housing 16 such that the axis of rotation of the
drive shaft 50 is aligned with the centerline of the cylinder block
10. The drive shaft 50 is supported at its opposite end portions by
the front housing 16 and the cylinder block 10, respectively, via
respective bearings, such that the drive shaft 50 is rotatable
relative to the front housing 16 and the cylinder block 10. The
cylinder block 10 has a central bearing hole 56 formed in a central
portion thereof, and the bearing is disposed in this central
bearing hole 56, for supporting the drive shaft 50 at its rear end
portion. The front end portion of the drive shaft 50 is connected,
through a clutch mechanism such as an electromagnetic clutch, to an
external drive source (not shown) in the form of an engine of an
automotive vehicle. In operation of the compressor, the drive shaft
50 is connected through the clutch mechanism to the vehicle engine
in operation so that the drive shaft 50 is rotated about its
axis.
[0063] The rotary drive shaft 50 carries a swash plate 60 such that
the swash plate 60 is axially movable and tiltable relative to the
drive shaft 50. The swash plate 60 has a central hole 61 through
which the drive shaft 50 extends. The inner dimension of the
central hole 61 as measured in a vertical direction of FIG. 1
gradually increases in a direction from the axially intermediate
portion toward each of the axially opposite ends, and the
transverse cross sectional shape of the central hole 61 at each of
the axially opposite ends is elongated. To the drive shaft 50,
there is fixed a rotary member 62 as a torque transmitting member,
which is held in engagement with the front housing 16 through a
thrust bearing 64. The swash plate 60 is rotated with the drive
shaft 50 by a hinge mechanism 66 during rotation of the drive shaft
50. The hinge mechanism 66 guides the swash plate 60 for its axial
and tilting motions. The hinge mechanism 66 includes a pair of
support arms 67 fixed to the rotary member 62, guide pins 69 which
are formed on the swash. plate 60 and which slidably engage guide
holes 68 formed in the support arms 67, the central hole 61 of the
swash plate 60, and the outer circumferential surface of the drive
shaft 50.
[0064] The piston 14 indicated above includes an engaging portion
70 engaging the radially outer portion of the opposite surfaces of
the swash plate 60, and a head portion 72 formed integrally with
the engaging portion 70 and slidably fitted in the corresponding
cylinder bore 12. The head portion 72 of the piston 14 in the
present embodiment is made hollow, for thereby reducing the weight
of the piston 14. The head portion 72, cylinder bore 12, and valve
plate 20 cooperate with one another to define a pressurizing
chamber. The engaging portion 70 engages the radially outer portion
of the opposite surfaces of the swash plate 60 through a pair of
part-spherical-crown shoes 76. The shoes 76 will be described in
greater detail.
[0065] The rotary motion of the swash plate 60 is converted into a
reciprocating linear motion of the piston 14 through the shoes 76.
A refrigerant gas in the suction chamber 22 is sucked into the
pressurizing chamber of the cylinder bore 12 through the suction
port 32 and the suction valve 34, when the piston 14 is moved from
its upper dead point to its lower dead point, that is, when the
piston 14 is in the suction stroke. The refrigerant gas in the
pressurizing chamber of the cylinder bore 12 is pressurized by the
piston 14 when the piston 14 is moved from its lower dead point to
its upper dead point, that is, when the piston 14 is in the
compression stroke. The pressurized refrigerant gas in the
pressurizing chamber is discharged into the discharge chamber 24
through the discharge port 36 and the discharge valve 38. A
reaction force acts on the piston 14 in the axial direction as a
result of compression of the refrigerant gas in the pressurizing
chamber. This compression reaction force is received by the front
housing 16 through the piston 14, swash plate 60, rotary member 62
and thrust bearing 64.
[0066] The cylinder block 10 has an intake passage 80 formed
therethrough for communication between the discharge chamber 24 and
a crank chamber 86 which is defined between the front housing 16
and the cylinder block 10. The intake passage 80 is connected to a
solenoid-operated control valve 90 provided to control the pressure
in the crank chamber 86. The solenoid-operated control valve 90
includes a solenoid coil 92. The amount of electric current applied
to the solenoid coil 92 is controlled depending upon the air
conditioner load by a control device not shown constituted
principally by a computer.
[0067] The rotary drive shaft 50 has a bleeding passage 100 formed
therethrough. The bleeding passage 100 is open at one of its
opposite ends to the central bearing hole 56, and is open at the
other end to the crank chamber 86. The central bearing hole 56
communicates at its bottom with the suction chamber 22 through a
communication port 104.
[0068] The present swash plate type compressor is of variable
capacity type. By controlling the pressure in the crank chamber 86
by utilizing a difference between the pressure in the discharge
chamber 24 as a high-pressure source and the pressure in the
suction chamber 22 as a low pressure source, a difference between
the pressure in the pressurizing chamber of the cylinder bore 12
and the pressure in the crank chamber 86 is regulated to change the
angle of inclination of the swash plate 60 with respect to a plane
perpendicular to the axis of rotation of the drive shaft 50, for
thereby changing the reciprocating stroke (suction and compression
strokes) of the piston 14, whereby the displacement capacity of the
compressor can be adjusted. Described in detail, by energization
and de-energization of the solenoid coil 92 of the
solenoid-operated control valve 90, the crank chamber 86 is
selectively connected to and disconnected from the discharge
chamber 24, so that the pressure in the crank chamber 86 is
controlled. The displacement capacity changing mechanism in the
swash plate type compressor of the present embodiment for changing
the displacement capacity of the compressor is constituted by the
hinge mechanism 66, cylinder bores 12, pistons 14, suction chamber
22, discharge chamber 24, central bearing hole 56, crank chamber
86, bleeding passage 100, communication port 104, control device
not shown, etc.
[0069] The cylinder block 10 and each piston 14 are formed of an
aluminum alloy. The piston 14 is coated at its outer
circumferential surface with a fluoro resin film which prevents a
direct contact of the aluminum alloy of the piston 14 with the
aluminum alloy of the cylinder block 10 so as to prevent seizure
therebetween, and makes it possible to minimize the amount of
clearance between the piston 14 and the cylinder bore 12. Other
materials may be used for the cylinder block 10, the piston 14, and
the coating film.
[0070] The end portion of the engaging portion 70 of the piston 14,
which is remote from the head portion 72, has a U-shape in cross
section. Described in detail, the engaging portion 70 has a base
section 124 which defines the bottom of the U-shape, and a pair of
substantially parallel arm sections 120, 122 which extend from the
base section 124 in a direction perpendicular to the axis of the
piston 14. The two opposed lateral walls of the U-shape of the
engaging portion 70 have respective recesses 128 which are opposed
to each other. Each of these recesses 128 is defined by a
part-spherical inner surface of the lateral wall. The
part-spherical inner surfaces of the recesses 128 are located on
the same spherical surface.
[0071] As shown in FIG. 2, each of the pair of shoes 76 has a
substantially part-spherical crown shape, and includes a generally
convex part-spherical surface 132 and a generally flat surface 138.
Strictly speaking, the flat surface 138 is a slightly convex curved
surface (e.g., a convex part-spherical surface having a
considerably large radius of curvature), and includes a tapered
portion formed at a radially outer portion thereof. The
part-spherical surface 132 has a cylindrical portion formed
adjacent to the flat surface 138. The boundary between the convex
curved surface and the tapered portion, the boundary between the
tapered portion and the cylindrical portion, and the boundary
between the cylindrical portion and the part-spherical convex
surface, are rounded so as to have respective different small radii
of curvature. The pair of shoes 76 slidably engage the
part-spherical inner surfaces of the recesses 128 of the piston 14
at their part-spherical surfaces 132 and slidably engage the
radially outer portion of the opposite surfaces of the swash plate
60, i.e., the sliding surfaces 140, 142 of the swash plate 60, at
their flat surfaces 138. In other words, each shoe 76 slides on the
swash plate at its flat surface 138 and slides on the piston 14 at
its part-spherical surface 132. The pair of shoes 76 are designed
such that their convex part-spherical surfaces 132 are located on
the same spherical surface. In other words, each shoe 76 has a
part-spherical crown shape whose size is smaller than a hemi-sphere
by an amount corresponding to a half of the thickness of the swash
plate 60.
[0072] The shoe 76 includes a base body 146 and a metal plating
film 148 which covers the surface of the base body 146, more
specifically, the entire surface of the base body 146. In FIG. 2,
the thickness of the metal plating film 148 is exaggerated for
easier understanding.
[0073] The base body 146 is formed of an Al--Si alloy, i.e., A 4032
according to the JIS H 4100, which contains aluminum as a major
component, and silicon. Various kinds of aluminum alloy can be used
as the material for the base body 146 of the present shoe 76. The
shoe may be produced according to the following method, for
instance. Initially, there is prepared a bar-shaped member having a
predetermined diameter. The bar-shaped member is prepared by
extruding a billet which is formed of an aluminum alloy having a
predetermined composition and which is obtained by casting. The
bar-shaped member is cut into a plurality of pieces each having a
predetermined length, by a shearing device or a sawing machine.
Each cut piece is subjected to cold forging by using a press
including a suitable die assembly, so that the cut piece is formed
into a roughly-shaped precursor shoe. The method of producing the
present shoe is not limited to cold forging, but may be selected
from among known methods such as hot forging, casting, punching by
a press, machining, etc., and any suitable combination thereof.
Thereafter, the roughly-shaped precursor shoe may be subjected to a
suitable heat treatment. In general, a so-called T6 treatment
(according to the JIS H 0001) is conducted, wherein the
roughly-shaped precursor shoe is subjected to an artificial age
hardening treatment after it has been subjected to a solution heat
treatment. The shoe which has been subjected to the T6 treatment
exhibits significantly high degrees of strength and hardness. The
T6 treatment may be replaced with other heat treatment such as a T7
treatment (according to JIS H 0001), wherein the roughly-shaped
precursor shoe which has been subjected to the solution heat
treatment is subjected to an over-aging treatment which is
conducted beyond conditions of the artificial age hardening
treatment at which the maximum strength is obtained. After the heat
treatment, a grinding operation is effected on the roughly-shaped
precursor shoe, so that the roughly-shaped precursor shoe is formed
into a predetermined shape corresponding to that of the base body
of the shoe. Since the base body 146 of each shoe is formed of the
aluminum alloy, the swash plate type compressor equipped with the
shoes has a reduced weight.
[0074] The metal plating film 148 formed on the surface of the shoe
76 may be selected from among those described in the SUMMARY OF THE
INVENTION. The advantages of the respective plating films are
described above. The method of forming each of the plating films
may be suitably selected from among any known method. Where the
metal plating film 148 of the shoe 76 is constituted by a single
film selected from among those plating films, the composition and
thickness of each plating film is determined as described below.
The following TABLE 1 indicates respective compositions of various
electroless plating films while TABLE 2 indicates respective
compositions of various electroplating films. The thickness of each
of the electroless plating films and electroplating films is as
follows. Namely, the lower limit of the film thickness is 10 .mu.m,
for assuring a substantial effect of the plating film, more
preferably 20 .mu.m for assuring a higher effect. The upper limit
of the film thickness is preferably 150 .mu.m, more preferably 100
.mu.m, for preventing adverse influences due to an excessively
large thickness value, and for reducing the cost of manufacture. In
the following TABLE 1 and TABLE 2, "LOWER LIMIT 1" indicates a
preferable lower limit value indicative of the amount of each
element included in each plating film for assuring a substantial
effect by addition of that element, or by formation of the plating
film, while "LOWER LIMIT 2" indicates a more preferable lower limit
value indicative of the amount of each element included in each
plating film for assuring a higher effect. "UPPER LIMIT 2"
indicates a preferable upper limit value indicative of the amount
of each element included in each plating film for preventing
adverse influences by addition of that element, or due to an
excessively large thickness value of the film, or for reducing the
cost of manufacture, while "UPPER LIMIT 1" indicates a more
preferable upper limit value indicative of the amount of each
element. In the following TABLE 1 and TABLE 2, the element whose
amount is indicated by a symbol "-" means a major component of the
plating film, and constitutes a substantial part of the balance. In
TABLE 1 and TABLE 2, the amount of each element is represented by %
by weight per 100% by weight of the plating film.
1TABLE 1 <Electroless plating film> LOWER LOWER UPPER UPPER
PLATING FILMS ELEMENTS LIMIT 1 LIMIT 2 LIMIT 1 LIMIT 2 Ni--P based
film Ni -- -- -- -- P .ltoreq.0.05 .ltoreq.0.5 .gtoreq.10
.gtoreq.15 Ni--B based film Ni -- -- -- -- B .ltoreq.0.05
.ltoreq.0.1 .gtoreq.5 .gtoreq.10 Ni--P--B based film Ni -- -- -- --
P .ltoreq.0.05 .ltoreq.0.5 .gtoreq.10 .gtoreq.15 B .ltoreq.0.01
.ltoreq.0.05 .gtoreq.0.2 .gtoreq.2 Ni--P--W based film Ni -- -- --
-- P .ltoreq.0.05 .ltoreq.0.5 .gtoreq.10 .gtoreq.15 W .ltoreq.0.05
.ltoreq.1 .gtoreq.35 .gtoreq.40 Ni--B--W based film Ni -- -- -- --
B .ltoreq.0.01 .ltoreq.0.05 .gtoreq.2 .gtoreq.5 W .ltoreq.0.05
.ltoreq.3 .gtoreq.35 .gtoreq.40 Ni--P--B--W based film Ni -- -- --
-- P .ltoreq.0.05 .ltoreq.0.5 .gtoreq.10 .gtoreq.15 B .ltoreq.0.01
.ltoreq.0.01 .gtoreq.0.2 .gtoreq.2 W .ltoreq.0.01 .ltoreq.0.01
.gtoreq.0.5 .gtoreq.1 Co--P based film Co -- -- -- -- P
.ltoreq.0.05 .ltoreq.0.5 .gtoreq.10 .gtoreq.15 Co--P--W based film
Co -- -- -- -- P .ltoreq.0.05 .ltoreq.0.5 .gtoreq.10 .gtoreq.15 W
.ltoreq.0.05 .ltoreq.1 .gtoreq.35 .gtoreq.40 Ni--Co based film Ni
-- -- -- -- Co <0 .ltoreq.10 .gtoreq.90 >100 Ni--Co--P based
film Ni -- -- -- -- Co .ltoreq.2 .ltoreq.10 .gtoreq.90 .gtoreq.98 P
.ltoreq.0.05 .ltoreq.0.5 .gtoreq.10 .gtoreq.15 (unit: % by
weight)
[0075]
2TABLE 2 <Electroplating film> LOWER LOWER UPPER UPPER
PLATING FILM ELEMENT LIMIT 1 LIMIT 2 LIMIT 1 LIMIT 2 Ni based film
Ni -- -- -- -- N--P based film Ni -- -- -- -- P .ltoreq.0.1
.ltoreq.0.2 .gtoreq.10 .gtoreq.15 Ni--W based film Ni -- -- -- -- W
.ltoreq.0.05 .ltoreq.1 .gtoreq.40 .gtoreq.50 Ni--Fe based film Ni
-- -- -- -- Fe .ltoreq.1 .ltoreq.2 .gtoreq.30 .gtoreq.40 Ni--Mo--W
based film Ni -- -- -- -- Mo .ltoreq.0.05 .ltoreq.1 .gtoreq.40
.gtoreq.50 W .ltoreq.0.05 .ltoreq.1 .gtoreq.40 .gtoreq.50 Fe based
film Fe -- -- -- -- Fe--P based film Fe -- -- -- -- P .ltoreq.0.05
.ltoreq.0.1 .gtoreq.5 .gtoreq.10 Fe--W based film Fe -- -- -- -- W
.ltoreq.0.05 .ltoreq.1 .gtoreq.60 .gtoreq.70 Fe--C based film Fe --
-- -- -- C .ltoreq.0.05 .ltoreq.0.1 .gtoreq.5 .gtoreq.7 Fe--N based
film Fe -- -- -- -- N .ltoreq.0.05 .ltoreq.0.1 .gtoreq.5 .gtoreq.7
Cr based film Cr -- -- -- -- Cr--Mo based film Cr -- -- -- -- Mo
.ltoreq.0.05 .ltoreq.1 .gtoreq.40 .gtoreq.50 Co based film Co -- --
-- -- Co--W based film Co -- -- -- -- W .ltoreq.0.05 .ltoreq.1
.gtoreq.40 .gtoreq.50 (unit: % by weight)
[0076] As described above, the electroless plating film may contain
the PTFE therein. In other words, the PTFE may be deposited
together with the matrix phase of the plating film. For obtaining a
substantial effect by addition of the PTFE, the PTFE is preferably
included in the electroless plating film in an amount of not
smaller than 0.5% by weight, more preferably not smaller than 0.7%
by weight, per 100% by weight of the electroless plating film, for
obtaining a higher effect. The strength of the plating film is
undesirably lowered by addition of an excessively large amount of
the PTFE. In view of this, it is practically preferable that the
PTFE is included in the plating film in an amount of not greater
than 12% by weight, more preferably not greater than 10% by
weight.
[0077] As described above, the electroless plating film may be
covered with at least one covering film which contains at least one
of Sn, TiCN, TiN, CrN, and TiAlN, so that the electroless plating
film and the at least one covering film formed thereon cooperate to
constitute the metal plating film 148. In this case, the lower
limit value of the thickness of each of the at least one covering
film is preferably 0.1 .mu.m for obtaining a substantial effect by
provision of the covering film, more preferably 0.5 .mu.m for
obtaining a higher effect. The upper limit value of the thickness
of each of the at least one covering film is preferably 5 .mu.m,
more preferably 4 .mu.m, for preventing adverse influences due to
an excessively large thickness value and for reducing the cost of
manufacture.
[0078] The metal plating film may include at least one of SiC,
Si.sub.3N.sub.4, Al.sub.2O.sub.3, and CrC. The lower limit value of
the amount of each of those substances included in the metal
plating film is preferably 0.5% by weight for obtaining a
substantial effect by addition of the substance, more preferably 1%
by weight for a higher effect, per 100% by weight of the metal
plating film. The upper limit value of the amount of each substance
included in the metal plating film is preferably 20% by weight,
more preferably 15% by weight, per 100% by weight of the metal
plating film, for preventing adverse influences due to addition of
an excessively large amount of the substance and for reducing the
cost of manufacture.
[0079] There will be next described a structure of the swash plate
60. The swash plate 60 which engages the shoes 76 includes a base
body 160 formed of spheroidal graphite cast iron, generally called
as ductile cast iron such as FCD 700 according to the JIS G 5502.
The swash plate 60 includes sliding surfaces 140, 142 which are to
be held in sliding contact with the shoes 76. (In FIG. 2, only one
sliding surface 140 is shown.) At each portion of the base body 160
of the swash plate 60 providing each of the sliding surfaces 140,
142, a metal sprayed film in the form of an aluminum sprayed film
162 and a lubricating film 164 are formed in this order. In FIG. 2,
the thickness of each of the aluminum sprayed film 162 and the
lubricating film 164 is exaggerated for easier understanding. The
lubricating film 164 is formed of a synthetic resin in the form of
polyamideimide in which MoS.sub.2 and graphite are dispersed. The
lubricating film 164 has a thickness of 60 .mu.m, and is effective
to reduce the friction between the sliding surfaces of the swash
plate 60 and the shoe 76. The aluminum sprayed film 162 has a
thickness of 60 .mu.m, and is effective to maintain good sliding
characteristics of the shoe 76 while preventing a direct contact of
the base body 160 of the swash plate 60 with the shoe 76 even when
the lubricating film 164 is removed or separated due to abrasion,
for instance.
[0080] The swash plate type compressor according to the present
embodiment exhibits good sliding characteristics and assures smooth
operation thereof owing to the advantages provided by the shoe 76
and the swash plate 60 described above. Accordingly, the present
swash plate type compressor exhibits excellent durability while
maintaining good sliding characteristics for a long period of
service. The metal plating film 148 formed on the surface of the
shoe 76 is particularly effective to improve the sliding
characteristics of the compressor.
[0081] While the presently preferred embodiment of this invention
has been described above, for illustrative purpose only, it is to
be understood that the present invention is not limited to the
details of the illustrated embodiment. For example, the principle
of the invention is applicable to a swash plate type compressor
equipped with double-headed pistons each having head portions on
the opposite sides of the engaging portion which engages the swash
plate, or a swash plate type compressor of fixed capacity type. It
is to be understood that the present invention may be embodied with
various changes and improvements such as those described in the
SUMMARY OF THE INVENTION, which may occur to those skilled in the
art.
[0082] <Experiments for confirming the properties of the shoe
for the swash plate type compressor>
[0083] There were produced, according to the illustrated
embodiment, various swash plate type compressor shoes having
respective different metal plating films. The following experiments
were conducted on those shoes, for examining the resistance of the
shoes to seizure by using a test device, and the sliding
characteristics of some of the shoes by effecting a so-called
"dry-locking" test (which will be described in greater detail)
while the shoes are installed on the swash plate type
compressor.
[0084] <Shoes used in the Experiments>
[0085] Initially, there were prepared base bodies of the shoe by
first forging, in a cold state, an Al--Si alloy corresponding to
the above-described A 4032, then conducting a grinding operation
after the T6 treatment. On the surfaces of the thus prepared base
bodies, there were formed respective different metal plating films,
which were surface-treated by buffing, so that fifteen shoes (#1
through #15) were produced. The shoes #1-#8 include respective
different electroless plating films while the shoes #9-#15 include
respective different electroplating films. The following Table 3
shows the composition, the thickness, and the hardness of each of
the metal plating films formed on the respective shoes. The amount
of each element included in each metal plating film is represented
by % by weight. The shoe #1 includes an Ni--P based electroless
nickel plating film which contains the PTFE. The shoes #3-#7
include an Ni--P--B--W based electroless nickel plating film, and
respective different covering films formed of Sn, TiCN, TiN, CrN,
and TiAlN, respectively. In each of the shoes #3-#7, the
Ni--P--B--W based electroless nickel plating film and the covering
film cooperate to provide the metal plating film. Accordingly, the
thickness value of the plating film in each of the shoes #3-#7
indicated in TABLE 3 corresponds to a sum of the thickness of the
Ni--P--B--W based electroless nickel plating film and the thickness
of the covering film, while the hardness value of the plating film
in each of the shoes #3-#7 indicated in TABLE 3 shows the hardness
of the Ni--P--B--W based electroless nickel plating film. In
"REMARKS" in TABLE 3, there are indicated the amount of PTFE
included in the plating film of the shoe #1, and the thickness of
each of the covering films respectively formed of Sn, TiCN, TiN,
CrN, and TiAlN, which covering films are provided on the respective
Ni--P--B--W based electroless nickel plating films in the shoes
#3-#7.
3TABLE 3 Thickness Hardness of the of the Composition film film No.
of metal plating film (.mu.m) (Hv) REMARKS Electroless plating #1
Ni-8%P/PTFE 25 350 the amount of PTFE: 8% (23 vol %) #2 Ni-0.3%B 25
750 #3 Ni-2%P-0.03%B-0.1%W/Sn 26 700 the thickeness of Sn: 1 .mu.m
#4 Ni-2%P-0.03%B-0.1%W/TiCN 27 700 the thickeness of TiCN: 2 .mu.m
#5 Ni-2%P-0.03%B-0.1%W/TiN 27 700 the thickeness of TiN: 2 .mu.m #6
Ni-2%P-0.03%B-0.1%W/CrN 27 700 the thickeness of CrN: 2 .mu.m #7
Ni-2%P-0.03%B-0.1%W/TiAlN 27 700 the thickeness of TiAlN: 2 .mu.m
#8 Co-5%P 25 550 Electroplating #9 Ni-5%P 25 600 #10 Ni-5%P 25 700
#11 Ni-30%W 25 600 #12 Ni-20%Fe 25 600 #13 Fe-1%P 25 550 #14 Cr 25
800 #15 Co-17%W 25 350
[0086] <Experiment for examining the seizure resistance of the
shoes>
[0087] The following test was conducted on each of the shoes #1-#15
produced as described above, for examining its resistance to
seizure. In the test, each shoe 76 was pressed against the sliding
surface of a suitable swash plate 60 by a pressing jig 190 under a
suitable load, as shown in FIG. 3. In this state, the swash plate
60 was rotated. For each shoe 76, there was measured a time from a
moment of starting of the sliding contact between the swash plate
and the shoe and to a moment at which the seizure took place was
measured. (The time is hereinafter referred to as "seizure time").
The swash plate 60 used in the test is similar to that described in
the DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT. Namely, the
swash plate 60 is formed of the above-described FCD 700, and
includes the aluminum sprayed film and the lubricating film formed
in this order on each sliding surface thereof. In the test, each
shoe was subjected to the load applied by the pressing jig 190 such
that the pressing force applied to the shoe from the swash plate
was 8.5 N/mm.sup.2 which corresponds to a quotient obtained by
dividing the pressing load applied to the shoe from the pressing
jig, by the area of the flat surface of the shoe. Further, the
peripheral speed of the swash plate 60 on sliding surface which
slides on the shoe was 10.5 m/s. The test was conducted in the
absence of the lubricating oil between the swash plate and each
shoe, i.e., in a non-lubricating state. The results of the test are
indicated in the following TABLE 4 in which the above-indicated
seizure time measured for each shoe is shown. As is apparent from
the results in TABLE 4, the shoes #1-#15 showed relatively long
seizure times in the non-lubricating state. Accordingly, it is
confirmed that all of the shoes #1-#15 exhibit excellent seizure
resistance. Thus, the shoes #1-#15 are capable of exhibiting
excellent sliding characteristics.
4TABLE 4 <Results of the test for examining the seizure
resistance of the shoes> No. Seizure time (seconds) #1 30 #2 60
#3 30 #4 24 #5 24 #6 24 #7 24 #8 30 #9 30 #10 30 #11 60 #12 30 #13
60 #14 36 #15 30
[0088] <Experiment for examining the sliding characteristics of
the shoes according to dry-locking test>
[0089] On the shoes #1, #2, #8, #11, #13, and #15 as representative
examples, a dry-locking test was conducted in the following manner,
by installing each shoe on the swash plate type compressor. The
swash plate type compressor used in the test is similar to that
described in the DESCRIPTION OF PREFERRED EMBODIMENT, and a
detailed explanation of which is dispensed with. With each shoe
being installed on the compressor, the compressor was operated in
the absence of the refrigerant, in other words, in the
non-lubricating state (i.e., in a dry state), such that the
rotating speed of the swash plate was 1000 rpm. In this state,
there was measured, for each shoe, a time from a moment of starting
of the compressor to a moment at which the compressor was subjected
to a so-called "dry-locking" phenomenon. The dry-locking phenomenon
means that the compressor suffers form seizure between the swash
plate and the shoe while the swash plate and the shoe slide on each
other in the non-lubricating state, so that the swash plate and the
shoe are prevented from sliding on each other due to the seizure.
In the shoe which received the largest pressing force from the
swash plate, this pressing force was about 6.8N/mm.sup.2 which
corresponds to a quotient obtained by dividing the load applied to
the shoe from the swash plate, by the area of the flat surface of
the shoe. The results of the test are shown in the following TABLE
5 in which the above-indicated time for each shoe is shown.
5TABLE 5 <Results of the dry-locking test> Time from a moment
of starting of compressor to a moment at which compressor was
subjected to No. dry-locking (seconds) #1 42 #2 50 #8 50 #11 39 #13
35 #15 32
[0090] As is apparent from the results indicated in the above TABLE
5, the above-indicated time was more than 20 seconds in all cases
when the compressor was equipped with the selected shoes, i.e., #1,
#2, #8, #11, #13, and #15. In the swash plate type compressor, the
shoes are lubricated by the lubricating oil which is mixed or
contained in the refrigerant. While the compressor is not operated,
the refrigerant is liquefied, and stored in the compressor. In this
case, the shoes are placed in the substantially non-lubricating
state. Since it takes about 20 seconds for the refrigerant to
circulate in the compressor after the starting of the operation of
the compressor, the shoes are kept in the non-lubricating state
during the time period of about 20 seconds. As is apparent from the
results indicated in TABLE 5, the compressor did not suffer from
the dry-locking phenomenon during the time period (i.e., during the
non-lubricating state) in all cases when the compressor was
equipped with the above-indicated selected shoes. Accordingly, each
of the shoes exhibits excellent sliding characteristics without
suffering any trouble during its practical use.
* * * * *