U.S. patent application number 14/174609 was filed with the patent office on 2014-10-02 for refrigerant compressor.
This patent application is currently assigned to Hitachi, Ltd.. The applicant listed for this patent is Hitachi, Ltd.. Invention is credited to Masaki KOYAMA, Yuichi YANAGASE.
Application Number | 20140294643 14/174609 |
Document ID | / |
Family ID | 50028925 |
Filed Date | 2014-10-02 |
United States Patent
Application |
20140294643 |
Kind Code |
A1 |
KOYAMA; Masaki ; et
al. |
October 2, 2014 |
Refrigerant Compressor
Abstract
A refrigerant compressor includes a compressor mechanism part 2,
and a motor and a crank shaft 101 for driving the compressor
mechanism part, in a sealed case 100, and includes sliding bearings
103, 104, and 105 at least either in an engagement part between the
compressor mechanism part and the crank shaft or in a rotation
support part of the crank shaft. Further, an unleaded resin
impregnation material is used for at least one of the sliding
bearings, the crank shaft is made of a ferrous material, and a hard
carbon film including hydrogen is formed on a part of the crank
shaft sliding with the sliding bearing using the unleaded resin
impregnation material.
Inventors: |
KOYAMA; Masaki; (Tokyo,
JP) ; YANAGASE; Yuichi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi, Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Hitachi, Ltd.
Tokyo
JP
|
Family ID: |
50028925 |
Appl. No.: |
14/174609 |
Filed: |
February 6, 2014 |
Current U.S.
Class: |
418/55.5 |
Current CPC
Class: |
F04C 29/0057 20130101;
F04C 2230/91 20130101; F04C 2270/16 20130101; F16C 2360/42
20130101; F04B 39/0094 20130101; F04C 18/0215 20130101; F04C
29/0071 20130101; F04C 2240/54 20130101 |
Class at
Publication: |
418/55.5 |
International
Class: |
F04C 29/00 20060101
F04C029/00; F04C 18/02 20060101 F04C018/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2013 |
JP |
2013-071958 |
Claims
1. A refrigerant compressor comprising: a compressor mechanism
part, and a motor and a crank shaft for driving the compressor
mechanism part, in a sealed case, and a sliding bearing at least
either in an engagement part between the compressor mechanism part
and the crank shaft or in a rotation support part of the crank
shaft, wherein: an unleaded resin impregnation material is used for
at least one of the sliding bearings, the crank shaft is made of a
ferrous material, and a hard carbon film including hydrogen is
formed on a part of the crank shaft sliding with the sliding
bearing using the unleaded resin impregnation material.
2. The refrigerant compressor according to claim 1, wherein: the
hard carbon film is a diamond-like carbon film.
3. The refrigerant compressor according to claim 2, wherein:
hydrogen content of the diamond-like carbon film is 20 to 35 atom
%.
4. The refrigerant compressor according to claim 3, wherein: the
compressor mechanism part includes a orbiting scroll and a fixed
scroll, the crank shaft has a structure to include an eccentric
part at one end side, and to engage the eccentric part with an
orbiting scroll bearing provided in the orbiting scroll, a sliding
bearing using an unleaded resin impregnation material is used for
the orbiting scroll bearing, and a hard carbon film including
hydrogen is formed on the eccentric part of the crank shaft sliding
with the sliding bearing.
5. The refrigerant compressor according to claim 3, wherein: the
crank shaft has a structure to be supported by a main bearing
provided in a frame attached to the sealed case and a sub bearing
provided in a lower frame attached to the sealed case, a sliding
bearing using an unleaded resin impregnation material is used for
the sub bearing, and a hard carbon film including hydrogen is
formed on a sub shaft part of the crank shaft sliding with the
sliding bearing.
6. The refrigerant compressor according to claim 3, wherein: the
crank shaft has a structure to be supported by a main bearing
provided in a frame attached to the sealed case and a sub bearing
provided in a lower frame attached to the sealed case, a sliding
bearing using an unleaded resin impregnation material is used for
the main bearing, and a hard carbon film including hydrogen is
formed on a main shaft part of the crank shaft sliding with the
sliding bearing.
7. The refrigerant compressor according to claim 4, wherein: the
crank shaft has a structure to be supported by a main bearing
provided to a frame attached to the sealed case and a sub bearing
provided in a lower frame attached to the sealed case, sliding
bearings using an unleaded resin impregnation material are used for
the main bearing and the sub bearing, and hard carbon films
including hydrogen are formed on a main shaft part and on a sub
shaft part of the crank shaft sliding with these sliding bearings.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese Patent
application serial no. 2013-071958, filed on Mar. 29, 2013, the
content of which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a refrigerant compressor
for refrigeration/air-conditioning, and especially relates to a
refrigerant compressor particularly suitable for a wide range drive
scroll compressor operated from a low speed to a high speed.
[0004] 2. Description of the Related Art
[0005] In a refrigerant compressor used for a refrigerating cycle
such as an air-conditioner and a refrigerator, to prevent burning
and abrasion in a high speed operation, a bearing material in which
a surface material is adjusted has been developed for a bearing
that supports a body of rotation of a motor and a compressor
mechanism part.
[0006] In addition, in recent years, with an increased interest in
reduction of energy consumption, efforts have been made to enhance
high efficiency and to realize downsizing of a compressor used in
the refrigerating cycle, especially in the air-conditioner.
[0007] The air-conditioner is often selected according to a maximum
air-conditioning load of a space (room) to be air conditioned. In
an actual operation, the air-conditioner is often operated in a low
load area because of an effect of high thermal insulation of the
building or heat generation from internal devices arranged in the
room to be air conditioned. Further, a cooling operation with low
ability is necessary at a low outdoor temperature.
[0008] Therefore, the compressor to be used for an air-conditioner
is frequently operated in a low speed rotation area, and efforts
have been made to develop a compressor capable of wide range drive
from a low speed to a ultra-high speed equivalent to the maximum
load of a conventional compressor by reducing a stroke volume, and
capable of being operated at high efficiency in an actual
operation.
[0009] Further, to enhance the efficiency in the low load area, an
ultra-low speed operation compared with the minimum rotation speed
(for example, 20 Hz) in a conventional compressor is realized, and
efforts have been made to reduce a friction loss of a sliding
portion such as a bearing in a low speed operation.
[0010] However, in the conventional compressor using a sliding
bearing, when being operated at a low speed, an effect of dynamic
pressure generation in a gap of the bearing becomes small and the
oil film thickness becomes small accordingly, and the compressor
can be easily transferred to a mixed lubrication area. Therefore,
there is a problem that the friction coefficient in the bearing
part is increased, and the friction loss cannot be decreased. In
addition, it is necessary to enhance burning resistance and
abrasion resistance in a bearing slide member.
[0011] Therefore, a compressor that realizes a low friction
coefficient and enhances the abrasion resistance in a slide member
inside the compressor has been proposed. For example, Japanese
Patent Application Laid-Open No. 2012-36878 discloses a refrigerant
compressor in which a rotation shaft rotatably supported by a
sliding bearing is made of a ferrous material, hard coating having
hardness of 1000 Hv or more is formed on a part sliding with a
bearing of a rotation shaft, and an unleaded resin impregnation
material is used for the sliding bearing.
SUMMARY OF THE INVENTION
[0012] The compressor disclosed in Japanese Patent Application
Laid-Open No. 2012-36878 has a configuration in which the rotation
shaft that constitutes a sliding portion with the sliding bearing
is made of a ferrous material, and the hard coating (thin film) is
formed on a sliding surface, the unleaded resin impregnation
material is used for the sliding bearing, and the hard coating has
the hardness of 1000 Hv or more (favorably, 1500 to 3000 Hv). In
addition, as the types of the hard coating, a chromium based film,
a titanium based film, a hard carbon based film, and a Si contained
hard carbon based film are disclosed.
[0013] However, it has been found out that, when the compressor is
intended to operate in an operation range of a ultra-low speed
where the rotation speed (operation frequency) is less than 20 Hz,
the oil film thickness of a bearing becomes thinner, and the
compressor is operated under the mixed lubrication condition where
contact between the shaft and the bearing (solid contact) is
started, and the friction coefficient is increased. Therefore, it
has turned out that there is a problem, even if the electric power
consumption is tried to be reduced by performing a ultra-low speed
operation at the time of a low load, the friction coefficient of
the bearing sliding portion is increased in the ultra-low speed
operation and the friction loss becomes large, and the electric
power consumption cannot be sufficiently decreased.
[0014] An object of the present invention is to reduce a friction
loss in a low speed operation where a compressor is operated under
a mixed lubrication condition, and especially, to obtain a highly
efficient refrigerant compressor in a low speed operation.
[0015] In order to achieve the above object, the present invention
provides a refrigerant compressor including: a compressor mechanism
part, and a motor and a crank shaft for driving the compressor
mechanism part, in a sealed case, and a sliding bearing at least
either in an engagement part between the compressor mechanism part
and the crank shaft or in a rotation support part of the crank
shaft, wherein: an unleaded resin impregnation material is used for
at least one of the sliding bearings, the crank shaft is made of a
ferrous material, and a hard carbon film including hydrogen is
formed on a part of the crank shaft sliding with the sliding
bearing using the unleaded resin impregnation material.
[0016] According to a refrigerant compressor of the present
invention, a friction loss in a low speed operation where the
compressor enters a mixed lubrication area can be reduced.
Therefore, there is an effect of obtaining a highly efficient
refrigerant compressor especially in a low speed operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a vertical cross sectional view illustrating an
embodiment 1 of a refrigerant compressor of the present
invention;
[0018] FIG. 2 is an enlarged cross sectional view illustrating an
enlarged II portion of FIG. 1;
[0019] FIG. 3 is a diagram illustrating comparison of frictional
properties of bearing sliding portions; and
[0020] FIG. 4 is a diagram describing a relationship between
hydrogen content and a friction coefficient of a DLC film.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Hereinafter, a specific embodiment of a refrigerant
compressor of the present invention will be described with
reference to the drawings. Note that portions denoted with the same
reference sign represent the same portion in FIGS. 1 and 2.
Embodiment 1
[0022] An embodiment 1 of a refrigerant compressor of the present
invention will be described with reference to FIGS. 1 to 4. FIG. 1
is a vertical cross sectional view illustrating an embodiment 1 of
a refrigerant compressor of the present invention, FIG. 2 is an
enlarged cross sectional view illustrating an enlarged II portion
of FIG. 1, FIG. 3 is a diagram illustrating comparison of
frictional properties of bearing sliding portions, and FIG. 4 is a
diagram describing a relationship between hydrogen content and a
friction coefficient of a DLC film.
[0023] In the present embodiment, an example of a case where a
present invention is applied to a scroll compressor as the
refrigerant compressor will be described. First, a basic
configuration of the scroll compressor will be described with
reference to FIG. 1.
[0024] A scroll compressor 1 includes a compressor mechanism part 2
including a fixed scroll 110, a orbiting scroll 120, and the like,
a driving part 3 for driving the compressor mechanism part 2, and
the like, and these devices are provided inside a sealed case
(chamber) 100. The driving part 3 includes a motor made of a rotor
107 and a stator 108, a crank shaft 101 integrally rotating with
the rotor 107 of the motor, and the like.
[0025] Further, a frame 160 provided with a main bearing 104 that
supports the compressor mechanism part 2 and rotatably supports a
main shaft part 101b of the crank shaft 101 is fixed in the sealed
case 100 by means of welding and the like. Further, a lower frame
170 is also attached to a lower part in the sealed case 100 by
means of welding and the like, and a sub bearing housing 171
provided with a sub bearing 105 for rotatably supporting a sub
shaft part 101c at a lower part of the crank shaft 101 is attached
to the lower frame 170.
[0026] The fixed scroll 110 includes a mirror plate 110b, a swirl
body (scroll lap) 110a provided in the mirror plate 110b in a
standing manner, a discharge port 110e provided approximately in
the center of the mirror plate 110b, and the like. In addition, the
orbiting scroll 120 includes an end plate (mirror plate) 120b, a
swirl body (scroll lap) 120a provided in the end plate 120b in a
standing manner, a bearing boss part 120e provided in the center of
a back surface side of the end plate 120b, and the like. The swirl
body 110a of the fixed scroll 110 and the swirl body 120a of the
orbiting scroll 120 are engaged, so that a compression chamber 130
is formed.
[0027] A orbiting scroll bearing 103 is fixedly provided in the
bearing boss part 120e of the orbiting scroll 120, and an eccentric
part 101a of the crank shaft 101 is inserted to the orbiting scroll
bearing 103. In addition, the reference sign 134 represents an
Oldham-coupling ring, and a key of the Oldham-coupling ring 134 is
engaged with a key groove formed in a back surface of the end plate
120b of the orbiting scroll and with a key groove formed in the
frame 160. With such a structure, when the crank shaft 101 rotates
and the eccentric part 101a is subjected to an eccentric motion,
the orbiting scroll 120 revolves without rotating.
[0028] A suction pipe 140 that sucks a refrigerant gas and a
discharge pipe 150 that discharges a compressed refrigerant gas are
attached to the sealed case 100. When the orbiting scroll 120 is
revolved by the driving part 3, the refrigerant gas is sucked
through the suction pipe 140, passes through a suction part formed
at an outer periphery side of the fixed scroll 110, is taken in to
the compression chamber 130 and is compressed, and is then
discharged from the discharge port 110e to the discharge chamber
136 at an upper part of the sealed case 100. The refrigerant gas
discharged to the discharge chamber 136 passes through a groove
(not illustrated) in the shaft direction formed in an outer
peripheries of the fixed scroll 110 and the frame 160, flows in a
lower space of the frame 160, and is discharged from the discharge
pipe 150.
[0029] An oil reservoir 131 is formed in a bottom part of the
sealed case 100, and the oil stored here passes through an oil
supply passage 102 formed inside the crank shaft 101, by an oil
supply pump 106 provided at a lower end part of the crank shaft
101, and is supplied to the orbiting scroll bearing 103, the main
bearing 104, and the sub bearing 105. The oil that has lubricated
the sub bearing 105 is directly returned to the oil reservoir 131,
and the oil that has lubricated the main bearing 104 passes through
an oil pipe 185 and is returned to the oil reservoir 131. After the
oil supplied to a space of the bearing boss part at an upper end
part of the eccentric part 101a lubricates the orbiting bearing
103, most of the oil passes through the oil pipe 185 and is
returned to the oil reservoir 131. A part of the oil passes through
an oil supply groove 120f, and flows into a back pressure chamber
180 formed at a back surface of the end plate of the orbiting
scroll 120. The back pressure chamber 180 is formed of the fixed
scroll 110, the orbiting scroll 120, and the frame 160.
[0030] The oil supply groove 120f is formed in a lower surface of
the bearing boss part 120e in a radial direction as illustrated in
FIG. 2. A circumferential groove 161 is formed in a part of the
frame 160 facing the lower surface of the bearing boss part 120e so
that a large amount of oil does not flow from the oil supply groove
120f to the back pressure chamber 180, and a seal ring 162 is
mounted to the circumferential groove 161. Accordingly, a space at
a discharge pressure at an inner periphery side of the seal ring
162 and a space (back pressure chamber) at an outer periphery side
of the seal ring 162 are sealed, and the oil in the space at the
inner periphery side of the seal ring 162 flows into the back
pressure chamber 180 side only through the narrow oil supply groove
120f.
[0031] The oil supplied to the back pressure chamber 180 lubricates
a sliding portion of the Oldham-coupling ring 134, and the like, is
then supplied to the compression chamber 130 through a back
pressure valve passage (not illustrated) provided with a back
pressure control valve, and the like, lubricates sliding portions
of the swirl bodies 110a and 120a, and the like, and is discharged
to the discharge chamber 136 together with a compressed refrigerant
gas. Then, the oil flows into a lower space of the frame 160, is
separated from the refrigerant gas, and is returned into the oil
reservoir 131.
[0032] The pressure of the back pressure chamber 180 is controlled
to an intermediate pressure between a suction pressure and a
discharge pressure by the back pressure control valve (differential
pressure control mechanism) (not illustrated). In addition, since
the oil at a discharge pressure is supplied to the space within the
bearing boss part 120e (bearing boss part space), the space is at
the discharge pressure. By the pressure of the bearing boss part
space at the discharge pressure and the pressure of the back
pressure chamber 180 controlled to the intermediate pressure, the
end plate 120b of the orbiting scroll 120 is pressed to the fixed
scroll 110 in close contact.
[0033] Note that the reference sign 204 represents a thrust bearing
provided in a part of the frame 160 facing a flange part 101d
provided in the crank shaft 101.
[0034] A compression operation of the scroll compressor structured
as described above will be described. When the rotor 107 and the
crank shaft 101 are rotated by driving the motor, the orbiting
scroll 120 starts to be revolved associated with the rotation. With
this revolving, the refrigerant gas sucked through the suction pipe
140 is taken in to the compression chamber 130 formed of the swirl
body 120a of the orbiting scroll 120 and the swirl body 110a of the
fixed scroll 110 being meshed with each other, and the volume is
decreased as the compression chamber 130 moves in the center
direction, so that the compression operation is performed. The
refrigerant gas compressed to a high pressure is discharged from
the discharge port 110e of the fixed scroll 110 to the sealed case
100, and is finally discharged outside through the discharge pipe
150.
[0035] The oil that has lubricated the orbiting scroll bearing 103,
the main bearing 104, and the like is supplied to the back pressure
chamber 180 through the oil supply groove 120f formed in an end
surface of the bearing boss part 120e. The refrigerant gas is
included in the oil, and when the oil flows into the back pressure
chamber 180 at a lower pressure than the discharge pressure, the
gas included in the oil expands and increases the pressure in the
back pressure chamber 180. However, the pressure of the back
pressure chamber 180 is controlled by the back pressure control
valve (differential pressure control mechanism) to maintain a
constant pressure difference with respect to the suction pressure.
This pressure is an intermediate pressure between the suction
pressure and the discharge pressure, and can press the orbiting
scroll 120 into the fixed scroll 110 with appropriate pressing
force.
[0036] Next, load application and a contact state in a bearing in
the scroll compressor will be described. When the crank shaft 101
rotates, centrifugal force of the orbiting scroll 120 and gas
compression force acting on the orbiting scroll 120 act on the
crank shaft 101 through the orbiting bearing 103. Therefore, in the
crank shaft 101, a load acts on the eccentric part 101a positioned
at an end part in a direction perpendicular to the shaft direction.
Since such a load acting on the eccentric part 101a, the crank
shaft 101 goes into so-called a cantilever state. Since the crank
shaft 101 in the cantilever state is supported by the main bearing
104 and the sub bearing 105, the crank shaft 101 is elastically
deformed in the direction perpendicular to the shaft direction, and
causes deflection.
[0037] Due to the deflection, the crank shaft 101 causes slight
inclination in each of the orbiting scroll bearing 103, the main
bearing 104, and the sub bearing 105, and so-called partial contact
in which the shaft obliquely comes in contact with the bearing is
more likely to occur. Especially, since it is structured such that
the main bearing 104 and the sub bearing 105 positioned at both
sides of the motor take care of the crank shaft 101, the
inclination and partial contact are more likely to occur in the
eccentric part 101a and the main shaft part 101b.
[0038] Therefore, in the scroll compressor of the present
embodiment, the unleaded resin impregnation material having a soft
surface and capable of elastic deformation against the partial
contact of the shaft is used for the orbiting scroll bearing 103
and the main bearing 104. Accordingly, the solid contact of the
shaft and the bearing can be avoided and an oil film can be formed.
The unleaded resin impregnation material uses, for example, PTFE
(polytetrafluoroethylene) as the resin material, and is impregnated
on a porous bronze-based alloy. As the resin material, other than
the above, POM (polyacetal), PBT (polybutylene terephthalate), PPS
(polyphenylene sulfide), PEEK (polyetheretherketone), and the like
can also be used.
[0039] Further, in the present embodiment, a hard DLC (diamond-like
carbon) film described below is used for the shaft side facing the
bearing using the unleaded resin impregnation material. To avoid
the partial contact of the shaft and to prevent an increase in
friction loss due to the contact in the bearing, combination of the
shaft and the bearing becomes important.
[0040] Further, assembling errors of the scroll compressor are
easily accumulated in the sub bearing 105. Therefore, a rolling
bearing is frequently used to allow the assembling errors to some
extent. However, the rolling bearing is expensive, and thus, when
an inexpensive sliding bearing is used, an increase in friction
loss due to the contact in the bearing can be suppressed by
decreasing the assembling errors as much as possible, and
preventing the partial contact in the bearing by avoiding
inclination arrangement of the crank shaft 101. However, to improve
the assembly accuracy, large-scale work associated with large-scale
change of manufacturing processes is required.
[0041] Therefore, by having the combination of the shaft and the
bearing that can allow some assembling errors, suppress an increase
in friction loss even if the partial contact is caused, and assure
reliability, a highly efficient, reliable, inexpensive compressor
can be realized. Therefore, in the present embodiment, the PTFE
based unleaded resin impregnation material is also used for the sub
bearing 105, similarly to the turning bearing 103 and the main
bearing 104, and the inclination of the shaft within the sliding
bearing can be allowed.
[0042] Typically, a tin-copper-antimony (Sn--Cu--Sb) based alloy,
called white metal, is often used for the sliding bearing material
of industrial machinery. Alternatively, copper (Cu) based or
aluminum (Al) based soft metal may be used. The soft metal material
having a low melting point and the relatively hard shaft are
combined and used to prevent occurrence of burning and the like
when the shaft and the bearing come in contact.
[0043] However, in a machine like the scroll compressor to which a
cantilever load is applied, the soft metal material cannot satisfy
the abrasion resistance and the burning resistance due to the
above-described partial contact problem, and thus, cannot be
employed.
[0044] Therefore, as a result of various examinations of the
combination of the shaft and the bearing in the machine like the
scroll compressor, to which a cantilever load is applied, it has
been found out that the following combination is favorable: a
unleaded resin impregnation material is used for the sliding
bearing, the crank shaft is made of a ferrous material, and a hard
carbon film including hydrogen is formed on a part of the crank
shaft sliding with the sliding bearing using the unleaded resin
impregnation material. With such combination, even in a case where
the compressor is used in an inclination contact state such as the
partial contact, or in a ultra-low speed operation of about less
than 20 Hz, for example, about 3 to 10 Hz, where the solid contact
may be caused between the shaft and the bearing, a low friction
loss can be realized and the burning can also be prevented.
Therefore, by applying the present embodiment, a refrigerant
compressor that is efficient in an ultra-low speed operation and
capable of wide range drive from a ultra-low speed to a ultra-high
speed can be realized.
[0045] To enhance the efficiency in an actual operation in the
scroll compressor, it is necessary to further enhance the operation
efficiency in the low load area. Therefore, it is necessary to make
the compression chamber volume smaller than a conventional one, to
make the operation frequency operable in a lower range, and to
enable a high speed operation so as to deal with an operation in
the high load area.
[0046] To respond to the demand, in the present embodiment, a hard
carbon film is provided in the crank shaft 101 as the slide member.
However, to enhance the efficiency in the low load operation, it is
necessary to decrease in friction coefficient of the sliding
portion in the low speed operation. Therefore, it has been found
out that consideration to the component configuration of the hard
carbon film formed on a part of the crank shaft sliding with the
sliding bearing is important.
[0047] That is, it has been found out that the bearing part is
subject to mixed lubrication and solid contact is caused especially
in an ultra-low speed operation. When the solid contact is caused,
the friction coefficient of the sliding portion is increased and
the efficiency in the low load operation is reduced. Therefore, the
power consumption in the low load area in the operation cannot be
sufficiently reduced. Therefore, for the improvement of efficiency
in the low load area in the operation, it is necessary that the
operation can be realized with a small friction coefficient even in
an ultra-low speed operation where the bearing part is operated the
mixed lubrication condition.
[0048] Then, as a result of various examinations, it has turned out
that the component configuration of the hard carbon film
substantially affects the frictional properties in the mixed
lubrication condition. That is, it has been found out that, when a
DLC film that belongs to the hard carbon film is used, the amount
of hydrogen contained in the film substantially affect the
frictional properties in the mixed lubrication condition.
[0049] FIG. 2 is an enlarged cross sectional view of the II portion
illustrated in FIG. 1. In the present embodiment, the crank shaft
101 uses a ferrous material as a base material, and a hard carbon
film (DLC film) made of DLC is formed on a surface of the eccentric
part 101a sliding with the orbiting bearing 103 and a surface of
the main shaft part 101b sliding with the main bearing 104.
Further, in the present embodiment, to enhance the adhesiveness of
the DLC film with respect to the base material of the ferrous
material, a chromium nitride (CrN) layer as the intermediate layer
is provided between the base material and the DLC film. That is,
the crank shaft 101 made of the ferrous material is used as the
base material, the intermediate layer of the chromium nitride (CrN)
is first formed on the base material, and the hard carbon film
layer (DLC layer) made of the DLC film is formed on the
intermediate layer.
[0050] Further, in the present embodiment, an intermediate layer
and a DLC layer similar to the above described layers are formed on
a surface of the sub shaft part 101c facing the sub bearing 105
using the unleaded resin impregnation material.
[0051] Note that the intermediate layer may be made of metal such
as chrome (Cr) or titanium (Ti), titanium nitride (TiN), or
titanium carbide (TiC). In addition, if the hard carbon film layer
is formed of an inclination layer made of a mixture of carbon and
metal, in which the content of the metal such as chrome (Cr) or
titanium (Ti) is decreased from the base material toward an outside
and the content of carbon is increased from the base material
toward an outside, or of an inclination layer made of metal
carbide, the adhesiveness of the hard carbon film layer with
respect to the base material can be further enhanced.
[0052] Further, in the DLC layer, SP.sup.2 bond carbon and SP.sup.3
bond carbon are mixed. However, in the present embodiment, the DLC
layer is further formed of a hard carbon film including hydrogen. A
hard carbon film including the hydrogen content of 20 to 35 atom %
is used. The DLC film containing such hydrogen content can be
obtained by forming a film by a plasma CVD method (plasma-enhanced
chemical vapor deposition method), a UBMS method (unbalanced
magnetron sputtering method) in which hydrogen is introduced during
film formation, and the like.
[0053] FIG. 3 is a diagram illustrating comparison between the
frictional properties in the bearing sliding portion of the present
embodiment 1 and the frictional properties in a conventional
bearing sliding portion. In FIG. 3, the curved line A illustrates
the frictional properties in the bearing sliding portion of the
present embodiment, and the curved lines B and C illustrate the
frictional properties in the conventional bearing sliding
portion.
[0054] The configurations of the bearing sliding portions
corresponding to the curved lines A to C use the same PTFE based
unleaded resin impregnation material for the sliding bearing side.
Further, as for the shaft side sliding with the sliding bearing,
the curved line B illustrates a measured value in a case where the
ferrous base material is used as it is, and the curved line C
illustrates a measured value in a case where a DLC film having the
hydrogen content of 0 atom % is formed on the ferrous base material
is used. The case of the curved line C corresponds to the one
disclosed in Japanese Patent Application Laid-Open No. 2012-36878.
In contrast, the case of the present embodiment by the curved line
A illustrates a measured value when a DLC film having the hydrogen
content of 24 atom % is formed on the ferrous base material is
used. Note that, in measuring a friction coefficient, the friction
coefficient is measured where a shaft inclination angle is 1/1000
rad in all cases.
[0055] In FIG. 3, the horizontal axis represents a Sommerfeld
number that is a dimensionless number indicating the bearing
properties, and the Sommerfeld number is obtained by a definition
formula: "(c/D).sup.1.times..eta..times.N/P" ((bearing
clearance/shaft diameter).sup.2.times.oil viscosity.times.rotation
speed/bearing surface pressure). Further, the vertical axis
represents the friction coefficient ratio that is comparison of the
friction coefficients where the smallest value among the friction
coefficients measured in the case of the curved line B is 1.
[0056] As is clear from the definition formula of the Sommerfeld
number, under a low speed condition where the rotation speed is
small, the Sommerfeld number is small, and the compressor goes
under the mixed lubrication condition illustrated in FIG. 3. In
this mixed lubrication condition, the present embodiment
illustrated by the curved line A can substantially reduce the
friction coefficient than the conventional ones illustrated by the
curved lines B and C. Especially, it has turned out that, in the
area of the ultra-low speed operation corresponding to the rotation
speed of less than 20 Hz (see the area illustrated by "a" in FIG.
3), the friction coefficient can be decreased by half compared with
the conventional ones. In addition, even in the operation area of a
special ultra-low speed such as 3 to 10 Hz (see the area
illustrated by "b" in FIG. 3), substantial reduction of the
friction coefficient can be realized compared with the conventional
ones.
[0057] As is clear from the drawing, according to the present
embodiment, the friction coefficient in the bearing sliding portion
under a low load condition such as being operated at an ultra-low
speed can be substantially reduced. As a result, the friction loss
under the low load condition can be reduced by half, and the
compressor efficiency can be substantially improved.
[0058] FIG. 4 is a diagram describing a relationship between the
hydrogen content and the friction coefficient of the DLC film
formed at the shaft side in the bearing sliding portion, and
illustrates results obtained such that the friction coefficients
under the low load condition are measured and compared with respect
to the DLC films containing various amounts of the hydrogen
content. Note that the curved line illustrated in FIG. 4 indicates
data under the condition of a minimum friction coefficient. From
FIG. 4, it has been found out that the DLC films having the
hydrogen content in the range of 20 to 35 atom % can reduce the
friction coefficient about by half compared with the DLC films
having the hydrogen content of 0 atom %.
[0059] Under the low load condition, the ratio of the friction loss
to the power consumption of the compressor is small. Therefore, to
obtain an effect of substantial enhancement of the efficiency,
reduction of the friction coefficient about by half is necessary.
Therefore, in the present embodiment, the hydrogen content in the
DLC film is 20 to 35 atom %, whereby the effect of substantial
enhancement of the efficiency can be obtained.
[0060] As described above, the present embodiment employs the
scroll compressor in which the DLC film having the hydrogen content
of 20 to 35 atom % is formed on each bearing sliding portion of the
crank shaft 101 and the sliding bearing uses the unleaded resin
impregnation material. Therefore, in the low load condition where
the compressor is operated at a low speed, especially at a
ultra-low speed less than 20 Hz, the friction can be reduced about
by half compared with a case where the surface of the crank shaft
is the same as a conventional surface made of a ferrous material,
or the surface is made by forming a DLC film not containing
hydrogen. In addition, because of the effect of the DLC as a hard
film, the adhesion abrasion between the slide members can be
prevented, and the burning resistance and the abrasion resistance
can be enhanced, whereby a highly reliable scroll compressor
(refrigerant compressor) can be obtained even in a middle speed
operation or a high speed operation.
[0061] As a result, a wide range operation (in a driving signal to
the motor, the frequency is about 10 to 150 Hz) becomes possible,
where the compressor is downsized to deal with a low load, the
operation frequency is operable in the ultra-low speed, and the
ultra-high speed operation is also available to deal with a high
load. Further, since the efficiency in the low load operation can
be substantially improved, highly efficient compressor performance
can be especially obtained in an actual operation where the
compressor is often operated in the low load operation.
[0062] According to the refrigerant compressor of the
above-described present embodiment, in the refrigerant compressor
capable of wide range drive where the compressor is operated from a
low speed to a high speed, the friction loss in the low speed
operation which may be a mixed lubrication area can be
substantially reduced, whereby a highly efficient refrigerant
compressor in the low speed operation can be obtained.
[0063] That is, according to the present embodiment, even in a case
where the compressor is operated under the mixed lubrication
condition where partial contact (solid contact) of the shaft and
the bearing occurs in the low speed operation, the friction
coefficient can be reduced by about half compared with conventional
ones, whereby a substantial increase in efficiency in the low speed
operation can be realized.
[0064] In addition, according to the present embodiment, even in a
compressor in which the partial contact easily occurs in the
bearing, occurrence of the burning and the abrasion can be
suppressed. Therefore, a highly reliable refrigerant compressor can
be obtained not only in the low speed operation, but also even in
the high speed operation, or in the ultra-high speed operation of
about 150 Hz.
[0065] Especially, according to the present embodiment, even in the
ultra-low speed operation where the rotation speed is less than 20
Hz, for example, 3 to 10 Hz, the high efficiency can be obtained,
and a refrigerant compressor having an excellent reduction effect
of the power consumption in the ultra-low speed operation can be
obtained. Further, since the reliability can be secured even in the
high speed operation, a refrigerant compressor operated in a wide
range from the ultra-low speed operation to the high speed
operation can be realized.
[0066] Note that the present invention is not limited to the
above-described embodiments and includes various modifications.
[0067] For example, in the above-described embodiment, the scroll
compressor has been described as the refrigerant compressor.
However, the refrigerant compressor is not limited to the scroll
compressor. That is, the present invention is applicable to a
compressor, in which a load acts on a crank shaft in a partially
contact state like the present embodiment and the shaft easily
comes in contact in a partially contact state in the bearing, for
example, to a reciprocating compressor used in a refrigerator for
household use, and the like, and similar effect can be
obtained.
[0068] Further, even a rotary compressor easily gets partial
contact in the bearing and has a similar problem to the scroll
compressor as long as one having a rotor being supported in a
cantilever state. Therefore, similar effect can be obtained by
applying the present invention.
[0069] Further, the description of embodiments have been given for
easy understanding of the present invention, and the present
invention is not necessarily limited to one including all described
configurations.
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