U.S. patent application number 13/362648 was filed with the patent office on 2012-09-13 for scroll compressor.
This patent application is currently assigned to Hitachi Appliances, Inc.. Invention is credited to Masatsugu CHIKANO, Mutsunori Matsunaga, Eiji Sato, Takeshi Tsuchiya, Yuichi Yanagase.
Application Number | 20120230854 13/362648 |
Document ID | / |
Family ID | 46795750 |
Filed Date | 2012-09-13 |
United States Patent
Application |
20120230854 |
Kind Code |
A1 |
CHIKANO; Masatsugu ; et
al. |
September 13, 2012 |
Scroll Compressor
Abstract
A scroll compressor with high efficiency is provided according
to the present invention. The scroll compressor compresses a
refrigerant by meshing of an orbiting scroll and a fixed scroll,
wherein the orbiting scroll includes a back pressure hole which
intermittently connects a compression chamber and a back pressure
chamber per one orbit of the orbiting scroll, and the back pressure
hole communicates with the compression chamber and also with the
back pressure chamber and shuts off the communication with the back
pressure chamber after the communication with the compression
chamber is shut off.
Inventors: |
CHIKANO; Masatsugu; (Mito,
JP) ; Matsunaga; Mutsunori; (Shizuoka, JP) ;
Tsuchiya; Takeshi; (Tsuchiura, JP) ; Sato; Eiji;
(Kasumigaura, JP) ; Yanagase; Yuichi; (Namegata,
JP) |
Assignee: |
Hitachi Appliances, Inc.
Tokyo
JP
|
Family ID: |
46795750 |
Appl. No.: |
13/362648 |
Filed: |
January 31, 2012 |
Current U.S.
Class: |
418/55.2 |
Current CPC
Class: |
F04C 18/0215 20130101;
F04C 18/0253 20130101 |
Class at
Publication: |
418/55.2 |
International
Class: |
F01C 1/063 20060101
F01C001/063 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 10, 2011 |
JP |
2011-052348 |
Claims
1. A scroll compressor, comprising: a fixed scroll in which a
spiral wrap is vertically provided on a base plate; an orbiting
scroll in which a spiral wrap is vertically provided on an end
plate, the orbiting scroll meshing with the fixed scroll to form a
compression chamber; a discharge space to which a working fluid
having been compressed in the compression chamber is discharged; a
back pressure chamber provided in a back surface of at least any
one of the orbiting scroll and the fixed scroll to press at least
one of both members of the orbiting scroll and the fixed scroll
against the other one of the members; and a back pressure hole
formed in an end plate of at least any one of the fixed scroll and
the orbiting scroll to provide communication between the
compression chamber and the back pressure chamber to keep a
pressure in the back pressure chamber at a pressure between a
suction pressure and a discharge pressure, wherein the compression
chamber and the back pressure chamber intermittently communicate
with each other through the back pressure hole per one orbit of the
orbiting scroll, and a communication port of the back pressure hole
on a back pressure chamber side is blocked later than a
communication port of the back pressure hole on a compression
chamber side.
2. A scroll compressor, comprising: a fixed scroll in which a
spiral wrap is vertically provided on a base plate; an orbiting
scroll in which a spiral wrap is vertically provided on an end
plate, the orbiting scroll meshing with the fixed scroll to form a
compression chamber; a discharge space to which a working fluid
having been compressed in the compression chamber is discharged; a
back pressure chamber provided in a back surface of the end plate
of the orbiting scroll to press the orbiting scroll against the
fixed scroll; and a back pressure hole formed in the end plate of
the orbiting scroll to provide communication between the
compression chamber and the back pressure chamber to keep a
pressure in the back pressure chamber at a pressure between a
suction pressure and a discharge pressure, wherein the compression
chamber and the back pressure chamber intermittently communicate
with each other through the back pressure hole per one orbit of the
orbiting scroll, and a communication port of the back pressure hole
on a back pressure chamber side is blocked later than a
communication port of the back pressure hole on a compression
chamber side.
3. The scroll compressor according to claim 1, wherein the
communication port of the back pressure hole on the back pressure
chamber side communicates with the back pressure chamber until the
communication port of the back pressure hole on the compression
chamber side is completely blocked.
4. The scroll compressor according to claim 1, wherein as a
structure for the intermittent communication between the
compression chamber and the back pressure chamber through the back
pressure hole, a cutout portion is provided in the end plate of the
fixed scroll to communicate with the back pressure chamber so that
the communication port of the back pressure hole on the back
pressure chamber side that is provided in the orbiting scroll is
caused to communicate with the cutout portion.
5. A refrigeration cycle apparatus for air-conditioning which is
constituted by using the scroll compressor according to claim
1.
6. A scroll compressor which compresses a refrigerant by meshing of
an orbiting scroll and a fixed scroll, wherein the orbiting scroll
comprises a back pressure hole which intermittently connects a
compression chamber and a back pressure chamber per one orbit of
the orbiting scroll, and the back pressure hole communicates with
the compression chamber and also with the back pressure chamber,
and shuts off the communication with the back pressure chamber
after the communication with the compression chamber is shut
off.
7. The scroll compressor according to claim 6, wherein timing of
the communication is regulated by using a cutout portion provided
in the fixed scroll.
8. A refrigeration cycle apparatus for air-conditioning which is
constituted by using the scroll compressor according to claim
2.
9. A refrigeration cycle apparatus for air-conditioning which is
constituted by using the scroll compressor according to claim
3.
10. A refrigeration cycle apparatus for air-conditioning which is
constituted by using the scroll compressor according to claim 4.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] The present invention relates to a scroll compressor which
is preferable as a refrigerant compressor used in a refrigeration
cycle for refrigeration, air-conditioning and the like, or a gas
compressor for compressing air and other gases.
[0003] (2) Description of Related Art
[0004] As a background art of the present technical field, there is
known a scroll compressor including a fixed scroll in which a
spiral wrap is vertically provided on a base plate, an orbiting
scroll in which a spiral wrap is vertically provided on an end
plate and which orbiting scroll meshes with the fixed scroll to
form a compression chamber, a discharge space to which a working
fluid having been compressed in the compression chamber is
discharged, a back pressure chamber which is provided at a back
surface of at least any one of the orbiting scroll and the fixed
scroll to press at least one of both members of the orbiting scroll
and the fixed scroll against the other one, and a back pressure
hole which is formed in an end plate of at least any one of the
fixed scroll and the orbiting scroll to provide communication
between the compression chamber and the back pressure chamber to
keep the pressure in the back pressure chamber at a pressure
between a suction pressure and a discharge pressure.
[0005] Further, JP-A-2010-106780 states that "A scroll compressor
includes a fixed scroll, an orbiting scroll which meshes with the
fixed scroll to form a compression chamber, a back pressure chamber
which is provided at a back surface of an end plate of the orbiting
scroll, a back pressure hole which is formed in the end plate of
the orbiting scroll to provide communication between the
compression chamber and the back pressure chamber, and a release
mechanism which is provided at an end plate of the fixed scroll and
discharges a working fluid in the compression chamber to a
discharge space when the pressure in the compression chamber
becomes higher than the pressure in the discharge space. A section
47 in which the compression chamber and the back pressure chamber
communicate with each other by the back pressure hole in accordance
with the orbiting movement of the orbiting scroll is configured so
as not to overlap sections 44 and 45 in which the compression
chamber and the discharge space communicate with each other by the
release mechanism." (see the Abstract).
BRIEF SUMMARY OF THE INVENTION
[0006] In the past, it has not been specifically taken into
consideration that when the back pressure hole which intermittently
provides communication between the compression chamber and the back
pressure chamber completes communication between a compression
chamber and a back pressure chamber and then communicates with the
next low-pressure compression chamber, the gas and oil which has
accumulated in the back pressure hole re-expand in the low-pressure
compression chamber to cause thermal fluid loss.
[0007] An object of the present invention is to provide a scroll
compressor with high efficiency.
[0008] The above object of the present invention is achieved by a
scroll compressor including:
[0009] a fixed scroll in which a spiral wrap is vertically provided
on a base plate
[0010] an orbiting scroll in which a spiral wrap is vertically
provided on an end plate, which scroll meshes with the fixed scroll
to form a compression chamber,
[0011] a discharge space to which a working fluid having been
compressed in the compression chamber is discharged,
[0012] a back pressure chamber provided in a back surface of at
least any one of the orbiting scroll and the fixed scroll to press
at least one of both members of the orbiting scroll and the fixed
scroll against another one of both members, and
[0013] a back pressure hole formed in an end plate of at least any
one of the fixed scroll and the orbiting scroll, which hole
provides communication between the compression chamber and the back
pressure chamber to keep a pressure of the back pressure chamber at
a pressure between a suction pressure and a discharge pressure,
wherein
[0014] the compression chamber and the back pressure chamber
intermittently communicate with each other via the back pressure
hole during one orbit of the orbiting scroll, and
[0015] a communication port of the back pressure hole on a back
pressure chamber side is blocked later than a communication port of
the back pressure hole on a compression chamber side.
[0016] Further, the above described object of the present invention
is achieved by a scroll compressor, including
[0017] a fixed scroll in which a spiral wrap is vertically provided
on a base plate,
[0018] an orbiting scroll in which a spiral wrap is vertically
provided on an end plate, which scroll meshes with the fixed scroll
to form a compression chamber,
[0019] a discharge space to which a working fluid having been
compressed in the compression chamber is discharged,
[0020] a back pressure chamber provided in a back surface of the
end plate of the orbiting scroll to press the orbiting scroll
against the fixed scroll, and
[0021] a back pressure hole formed in the end plate of the orbiting
scroll, which hole provides communication between the compression
chamber and the back pressure chamber to keep a pressure of the
back pressure chamber at a pressure between a suction pressure and
a discharge pressure, wherein
[0022] the compression chamber and the back pressure chamber
intermittently communicate with each other via the back pressure
hole during one orbit of the orbiting scroll, and
[0023] a communication port of the back pressure hole on a back
pressure chamber side is blocked later than a communication port of
the back pressure hole on a compression chamber side.
[0024] Further, the above described object of the present invention
is achieved by a scroll compressor which compresses a refrigerant
by meshing of an orbiting scroll and a fixed scroll, wherein
[0025] the orbiting scroll has a back pressure hole which
intermittently connects a compression chamber and a back pressure
chamber during one orbit of the orbiting scroll, and
[0026] the back pressure hole communicates with the compression
chamber and also with the back pressure chamber, and shuts off the
communication with the back pressure chamber after the
communication with the compression chamber is shut off.
[0027] According to the present invention, a scroll compressor with
high efficiency can be obtained.
[0028] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0029] FIG. 1 is a plane view showing a meshed state of a fixed
scroll and an orbiting scroll which are one embodiment of the
present invention;
[0030] FIG. 2 is an example of a vertical sectional view of a
scroll compressor;
[0031] FIG. 3 is an example of an enlarged sectional view of a main
part showing a back pressure hole portion in FIG. 2 by enlarging
it;
[0032] FIG. 4 is a plane view showing a meshed state of a fixed
scroll and an orbiting scroll having a conventional structure;
[0033] FIG. 5 is an example of an adiabatic compression diagram
schematically showing a relationship between the crank angle and
the compression chamber pressure in the scroll compressor;
[0034] FIG. 6 is an example of a P-V diagram schematically showing
the relationship between the crank angle and the compression
chamber pressure in the scroll compressor;
[0035] FIG. 7 is a diagram schematically showing pressure changes
in the opening sections at both end portions of the back pressure
hole and pressure changes in the back pressure hole; and
[0036] FIG. 8 is a conceptual diagram of a refrigeration cycle
showing one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Hereinafter, an embodiment will be described by using the
drawings.
[0038] FIGS. 2 and 3 are vertical sectional views of a scroll
compressor. As shown in the drawings, a fixed scroll (fixed scroll
member) 7 has a disk-shaped base plate 7a, a wrap 7b which is
vertically provided in a spiral shape on the base plate 7a, and a
cylindrical support portion 7d which is located on an outer
peripheral side of the base plate 7a and has an end plate surface
7e successively arranged with a tip end surface of the wrap 7b so
as to surround the wrap 7b. Since the wrap 7b is likened to
"tooth", the tip end surface of the wrap 7b is called a tooth tip,
and a surface of the base plate 7a on which the wrap 7b is
vertically provided is called a tooth bottom 7c since the surface
of the base plate 7a is located in a space formed by the wrap
7b.
[0039] Further, a surface on which the support portion 7d is in
contact with an end plate 8a of an orbiting scroll (orbiting scroll
member) 8 forms the end plate surface 7e of the fixed scroll 7. The
fixed scroll 7 has the support portion 7d fixed to a frame 17 by a
bolt or the like, and the frame 17 integrated with the fixed scroll
7 is fixed to a case (sealed container) 9 by a fixing means such as
welding.
[0040] The orbiting scroll 8 is disposed to be opposed to the fixed
scroll 7, and is provided in the frame 17 to be capable of
orbiting, with the wrap 7b of the fixed scroll and a wrap 8b of the
orbiting scroll meshing with each other. The orbiting scroll 8 has
a disk-shaped end plate 8a, the spiral wrap 8b which is vertically
provided from a tooth bottom 8c which is a surface of the end plate
8a, and a boss portion 8d which is provided at a center of a back
surface of the end plate 8a. Further, a surface of an outer
peripheral portion of the end plate 8a, that is in contact with the
fixed scroll 7, forms an end plate surface 8e of the orbiting
scroll 8.
[0041] The case 9 has a sealed container structure internally
accommodating a scroll portion consisting of the fixed scroll 7 and
the orbiting scroll 8, a motor portion 16 (16a: rotor, 16b:
stator), and a lubricant oil and the like. A shaft (rotary shaft)
10 which is fixed integrally with the rotor 16a of the motor
portion 16 is rotatably supported at the frame 17 via a main
bearing 5, and is coaxial with a center axis of the fixed scroll
7.
[0042] A crank portion 10a is provided at a tip end of the shaft
10, and is inserted in the boss portion 8d provided at the back
surface of the orbiting scroll 8, and the orbiting scroll 8 is
configured to be able to orbit with rotation of the shaft 10. An
orbiting bearing 11 is disposed between the crank portion 10a and
the boss portion 8d. A center axis of the orbiting scroll 8 is in a
state eccentric by a predetermined distance with respect to the
center axis of the fixed scroll 7. The wrap 8b of the orbiting
scroll 8 is superposed on the wrap 7b of the fixed scroll 7 while
being displaced by a predetermined angle in a circumferential
direction. Reference numeral 12 designates an Oldham ring for
making the orbiting scroll 8 perform orbiting movement relative to
the fixed scroll 7 while restraining the orbiting scroll 8 so as
not to rotate on its own axis.
[0043] FIG. 4 is a plane view showing a meshed state of a fixed
scroll and an orbiting scroll having a conventional structure. As
shown in the drawing, a plurality of crescent compression chambers
13 (13a, 13b) are formed between wraps 7b and 8b, and when the
orbiting scroll 8 performs orbiting movement, the volumetric
capacity of each of the compression chambers is continuously
reduced as each of the compression chambers moves to a central
portion. More specifically, the orbiting inner line side
compression chamber 13a and the orbiting outer line side
compression chamber 13b are formed on an inner line side and an
outer line side of the orbiting scroll wrap 8b, respectively.
Reference numeral 20 designates a suction chamber which is a space
located halfway for suction of fluid. The suction chamber 20
becomes the compression chamber 13 from the point of time at which
a phase of the orbiting movement of the orbiting scroll 8 advances
to complete containment of the fluid.
[0044] A suction port 14 is provided in the fixed scroll 7 as shown
in FIGS. 2 and 4. The suction port 14 is formed by being bored at
an outer peripheral side of the base plate 7a so as to communicate
with the suction chamber 20. Further, a discharge port 15 is bored
in the vicinity of a spiral center of the base plate 7a of the
fixed scroll 7 so as to communicate with the compression chamber 13
on the innermost peripheral side.
[0045] When the shaft 10 is rotationally driven by the motor
portion 16, the rotational drive is transmitted from a crank
portion 10a of the shaft 10 to the orbiting scroll 8 through the
orbiting bearing 11, and the orbiting scroll 8 performs orbiting
movement with an orbiting radius of a predetermined distance around
the center axis of the fixed scroll 7. The orbiting scroll 8 is
restrained by the Oldham ring 12 so as not to rotate on its own
axis at the time of the orbiting movement.
[0046] By the orbiting movement of the orbiting scroll 8, the
compression chambers 13 formed between the respective wraps 7b and
8b continuously move to the center, and the volumetric capacities
of the compression chambers 13 are continuously reduced in
accordance with the movement. Thereby, the fluid (for example, a
refrigerant gas which circulates in the refrigeration cycle) sucked
from the suction port 14 is sequentially compressed in each of the
compression chambers 13, and the compressed fluid is discharged
from the discharge port 15 to a discharge space 54 at an upper
portion of the case. The discharged fluid enters a motor chamber 52
in the case 9 from the discharge space 54, and is supplied from a
discharge pipe 6 to the outside of the compressor, e.g., to a
refrigerant cycle.
[0047] The lubricant oil is stored at the bottom of the case 9, and
a positive displacement type or centrifugal type oil supply pump 21
is provided at a lower end of the shaft 10. The oil supply pump 21
is also rotated with rotation of the shaft, and the lubricant oil
is sucked from a lubricant oil suction port 25 which is provided in
an oil supply pump case 22, and is discharged from a discharge port
28 of the oil supply pump. The discharged lubricant oil is supplied
to an upper portion through a through-hole 3 which is provided in
the shaft. A part of the lubricant oil passes through a lateral
hole 24 which is provided in the shaft 10, lubricates an accessory
bearing 23, and returns to an oil reservoir 53 at the bottom
portion of the case. The other most part of the lubricant oil
passes through the through-hole 3 to reach an upper portion of the
crank 10a of the shaft 10, and passes through an oil groove 57
which is provided in the crank 10a to lubricate the orbiting
bearing 11. Subsequently, the lubricant oil lubricates the main
bearing 5 which is provided at a lower portion of the orbiting
bearing 11, and thereafter, passes through an oil drain hole 26a
and an oil drain pipe 26b to return to the oil reservoir 53 at the
bottom portion of the case.
[0048] Here, a space which is formed by the oil groove 57 and the
orbiting bearing 11, and a space which accommodates the main
bearing 5 (space which is formed by the frame 17, the shaft 10, a
frame seal 56, an orbiting boss member 34 in a collar shape which
is provided at the boss portion 8d of the orbiting scroll 8 and a
seal member 32) are collectively called a first space 33. The first
space 33 is a space having a pressure close to a discharge
pressure. Most of the lubricant oil which flows into the first
space 33 for lubrication of the main bearing 5 and the orbiting
bearing 11 passes through the oil drain hole 26a and the oil drain
pipe 26b to return to the bottom portion of the case. However, a
part of the lubricant oil that is the minimum necessary amount
required for lubrication of the Oldham ring 12, and lubrication and
sealing of slide portions between the fixed scroll 7 and the
orbiting scroll 8 enters a back pressure chamber 18 via an oil
leaking means which will be described later between an upper end
surface of the seal member 32 and an end surface of the orbiting
boss member 34. The back pressure chamber 18 will be called a
second space.
[0049] The seal member 32 is inserted in a circular groove 31
provided in the frame 17, together with a wave-shaped spring (not
illustrated), and provides partition between the first space 33
which has the discharge pressure, and the back pressure chamber 18
which has a pressure between the suction pressure and the discharge
pressure. The aforementioned oil leaking means includes, for
example, a plurality of holes 30 which are provided in the orbiting
boss member 34, and the aforementioned seal member 32. The
aforementioned plurality of holes 30 perform circular motion across
the seal member 32 in accordance with the orbiting movement of the
orbiting scroll 8, and move between the first space 33 and the back
pressure chamber 18. Thereby, the minimum necessary oil can be
guided to the back pressure chamber 18 by storing the lubricant oil
in the first space 33 in the holes 30, and intermittently
transferring the lubricant oil to the back pressure chamber 18.
Instead of the plurality of holes 30, a slit or the like may be
provided to form the oil leaking means to the back pressure
chamber.
[0050] When the back pressure becomes high, the lubricant oil which
enters the back pressure chamber 18 passes through a back pressure
hole 35 which provides communication between the back pressure
chamber 18 and the compression chamber 13 to enter the compression
chamber, after which, the lubricant oil is discharged from the
discharge port 15, a part of it is discharged to the refrigeration
cycle from the discharge pipe 6 together with the refrigerant gas,
for example, and the remaining part is separated from the
refrigerant gas in the case 9 and is stored in the oil reservoir 53
at the bottom of the case.
[0051] Since the oil supply amount which is necessary for the
respective bearing portions and the oil supply amount which is
necessary for the compression chamber can be independently
controlled by providing the aforementioned first space 33, the back
pressure chamber 18 and the oil leaking means as described above,
it becomes possible to optimize the compression chamber oil supply
amount to obtain the compressor with high efficiency.
[0052] Next, for the scroll compressor described above, details of
the back pressure will be described. In the scroll compressor, the
force in the axial direction occurs so as to separate the fixed
scroll 7 and the orbiting scroll 8 from each other due to the
compression action thereof. When a so-called breakaway phenomenon
of the orbiting scroll 8 occurs, in which both the scrolls are
separated from each other by the force in the axial direction,
hermeticity of the compression chamber is worsened, and the
efficiency of the compressor is reduced. Thus, the back pressure
chamber 18 of which the pressure is between the discharge pressure
and the suction pressure is provided at the back surface side of
the end plate of the orbiting scroll 8, and the separating force is
cancelled out by the back pressure while the orbiting scroll 8 is
pressed against the fixed scroll 7. At this time, if the pressing
force is too large, the slide loss of the end plate surface 8e of
the orbiting scroll 8 and the end plate surface 7e of the fixed
scroll 7 increases, and the compressor efficiency is reduced. That
is, there is an optimal value for the back pressure, and if the
back pressure is too small, the hermeticity of the compression
chamber is worsened to increase thermal fluid loss, whereas if the
back pressure is too large, the slide loss is increased.
Accordingly, keeping the back pressure at the optimal value is
important for enhancement of performance and enhancement of
reliability of the compressor. In the present embodiment, the back
pressure hole 35 is included to keep the back pressure in an
optimal range.
[0053] The configuration of the back pressure hole 35 will be
described using FIGS. 3 and 4. In the end plate of the orbiting
scroll 8, the back pressure hole 35 (35a, 35b, 35c) is provided in
a U-shape. The back pressure hole 35 intermittently connects the
compression chamber 13 and the back pressure chamber 18 while the
orbiting scroll 8 orbits one time. A plug 35d is provided for
closing an end portion of a passage 35a to form the U-shaped back
pressure hole 35.
[0054] A cutout portion 36a which communicates with the back
pressure chamber 18 is provided at the end plate surface 7e on the
outer peripheral side of the fixed scroll 7. A back pressure
chamber side communication port (end portion 35c) which is one
communication port of the U-shaped back pressure hole 35
communicates with the back pressure chamber 18 by intermittently
communicating with the aforementioned cutout portion 36a by
orbiting movement shown in revolution loci 60 of FIG. 4, and the
communication port is blocked by the end plate surface 7e of the
fixed scroll 7 when the communication port does not communicate
with the cutout portion 36a. A compression chamber side
communication port (end portion 35b) which is the other
communication port of the back pressure hole 35 intermittently
communicates with the compression chamber 13 by orbiting movement,
and when the communication port does not communicate with it, the
communication port is blocked by the wrap 7b of the fixed scroll
7.
[0055] A section in which the back pressure chamber side
communication port (end portion 35c) communicates with the back
pressure chamber 18, and a section in which the compression chamber
side communication port (end portion 35b) communicates with the
compression chamber are generally different from each other, and
only when both of them communicate with each other, the compression
chamber 13 and the back pressure chamber 18 communicate with each
other.
[0056] When the shape of the aforementioned cutout portion 36a, and
the positions of both the end portions 35b and 35c of the back
pressure hole 35 are determined, the section (communication section
of the back pressure hole) in which the back pressure hole 35
provides communication between the compression chamber 13 and the
back pressure chamber 18 is determined, and the pressure of the
back pressure chamber 18 becomes the value corresponding to the
compression chamber pressure in the communication section. More
specifically, the timing of communication is regulated by using the
cutout portion 36a.
[0057] This will be further described in detail by FIGS. 5 and 6.
First, the pressure change of the compression chamber of the scroll
compressor will be described by FIG. 5. In the diagram of FIG. 5,
the axis of abscissa represents a crank angle (phase of the
orbiting movement of the orbiting scroll), whereas the axis of
ordinates represents the pressure of the compression chamber at the
time of adiabatic compression, and the diagram schematically shows
the relationship therebetween. The diagram of FIG. 5 shows the
compression chamber pressure of any one of the orbiting outer line
side compression chamber 13b and the orbiting inner line side
compression chamber 13a. When attention is paid to the compression
chamber shown by a solid line 49 in the drawing, a section 70 is a
suction section, a section 71 is a compression section, and a
section 72 is a discharge section. Reference numerals 73 and 74
represent changes of the pressures of the compression chambers in
the compression chambers which are formed before and after the
compression chamber shown by reference numeral 49.
[0058] Next, by using FIG. 6, description is made by paying
attention to only the compression chamber shown by reference
numeral 49. Reference numeral 49 designates an adiabatic
compression line, and the actual indication diagram expands upward
as reference numeral 51 with respect to the adiabatic compression
line 49 due to thermal fluid loss.
[0059] When explaining the conventional configuration as an
example, the end portion 35b communicates with the compression
chamber 13 in the section 46 from reference numerals 44 to 45, and
the end portion 35c communicates with the back pressure chamber 18
in a section 61 from reference numerals 48 to 45. Consequently, the
compression chamber 13 and the back pressure chamber 18 communicate
with each other in the section 61 in which both the end portions
provide communication. In the section 61, the compression chamber
pressure varies from reference numerals 48 to 45, and the back
pressure is set at a pressure 47 which is the average of the
compression chamber pressures in this section while involving a
little variation.
[0060] The above is the mechanism of generation of the back
pressure, and the problem in the conventional configuration will be
described hereinafter. In the conventional configuration, the back
pressure can be kept to be optimal as described above, but much
consideration has not been given to the fact that the U-shaped back
pressure hole 35 has a so-called dead volume. More specifically,
when consideration is given to the instant at which both of the end
portion 35b and the end portion 35c are blocked after the back
pressure hole 35 finishes providing communication between the
compression chamber 13 and the back pressure chamber 18, the fluid
flows from the end portion 35b side having the pressure 45 to the
end portion 35c having the back pressure (pressure 47), and the
inside of the back pressure hole 35 is filled with the pressure
close to the pressure 45. Subsequently, when the end portion 35b
communicates with the next compression chamber in accordance with
the orbiting movement, the compression chamber pressure is 44, and
therefore, the fluid in the back pressure hole 35 expands again
from the pressure close to the pressure 45 to the pressure 44, so
that thermal fluid loss occurs.
[0061] In contrast with this, the present embodiment expands the
section 61 in the conventional configuration of FIG. 6 to a section
62 by changing the shape of the cutout portion 36a which is
provided at the fixed scroll 7 as shown in FIG. 1. More
specifically, the back pressure hole 35 communicates with the
compression chamber 13 and also communicates with the back pressure
chamber 18, and shuts off the communication with the back pressure
chamber 18 after the communication with the compression chamber 13
is shut off. More specifically, even after the end portion 35b ends
communication with the compression chamber 13, the end portion 35c
communicates with the back pressure chamber 18. In other words, the
end portions 35b and 35c of the back pressure hole 35 are provided
to be in such a positional relationship that while the orbiting
scroll 8 orbits one time, the back pressure hole 35 intermittently
provides communication between the compression chamber 13 and the
back pressure chamber 18, and the communication port of the back
pressure hole 35 on the back pressure chamber 18 side is closed at
a timing later than the communication port of the back pressure
hole 35 on the compression chamber 13 side.
[0062] Thereby, the high pressure in the U-shaped back pressure
hole 35 reduces to the back pressure 47 after both end portions are
blocked, and re-expansion at the time when the end portion 35b
communicates with the next chamber in accordance with the orbiting
movement provides variation from the pressure 47 to the pressure
44, so that re-expansion loss can be reduced as compared with the
conventional configuration.
[0063] The above content will be described again by FIG. 7. The
upper portion of FIG. 7 shows the opening sections and the closed
sections of the end portions 35b and 35c of the back pressure hole,
and the lower portion of FIG. 7 shows the pressure in the back
pressure hole. The solid line shows the opening section and the
pressure change in the structure of the present embodiment (FIG.
1), and the broken line shows the opening section and the pressure
change in the conventional structure (FIG. 4). In the conventional
structure (FIG. 4), the pressure becomes 44 at the instant when the
end portion 35b opens to the compression chamber (the starting
point of the section 46), and the pressure in the back pressure
hole also becomes high with increase in the pressure of the
compression chamber. Even after the end portion 35c opens to the
back pressure chamber 18 (the starting point of the section 61),
the pressure increases, and the pressure becomes a pressure 45'
which is a little lower than the pressure 45 at the end point of
the sections 46 and the section 61. When the end portion 35b opens
to the next compression chamber which has the pressure 44, the
fluid in the back pressure hole expands again from the pressure 45'
to the pressure 44.
[0064] In contrast with this, in the structure (FIG. 1) of the
present embodiment, a section 62 is set so that the end portion 35c
opens to the back pressure chamber 18 even after the section 46
ends, and therefore, the pressure in the back pressure hole
temporarily rises to 45', and thereafter lowers to the back
pressure 47. When the end portion 35c opens to the next compression
chamber, the fluid in the back pressure hole expands again from the
pressure 47 to the pressure 44, but as compared with the
conventional structure (FIG. 4), the pressure can be reduced by the
re-expansion amount from the pressure 45' to the pressure 47.
[0065] The effect of reduction by the re-expansion amount becomes
larger when the volume of the back pressure hole 35 is larger. This
is because when a volume of the back pressure hole 35 is set as V,
and a swept volume (suction volume) of the compressor is set as
Vth, the re-expansion loss is substantially proportional to
V/Vth.
[0066] Further, the effect of reduction of the re-expansion amount
becomes larger when the pressure in the back pressure hole 35
reduces more significantly. The estimation is as follows in a
larger sense, though the estimation is rough. When the discharge
pressure is set as Pd, the suction pressure is set as Ps, and the
pressure in the back pressure hole 35 is assumed to re-expand by
.DELTA.P (45' to 44, or 47 to 44), the re-expansion loss is
substantially proportional to .DELTA.P/(Pd-Ps).
[0067] More specifically, the re-expansion loss is considered as
the following expression.
Re-expansion loss.varies.(V/Vth).times.(AP/(Pd-Ps))
[0068] Accordingly, when the pressure in the back pressure hole 35
is decreased from 45' to 47, the re-expansion loss can be made
smaller.
[0069] Further, by configuring a refrigeration cycle for
air-conditioning as shown in FIG. 8 by using the compressor 1 as
described above, a condenser 40, an expansion vale 41, an
evaporator 42, and a four-way valve 43, it is possible to provide
an air-conditioner which requires a small power consumption amount
throughout a year and is easy to use with a wide operation
range.
[0070] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
* * * * *