U.S. patent application number 12/921545 was filed with the patent office on 2011-02-03 for refrigeration apparatus.
Invention is credited to Kazuhiro Furusho, Kouki Morimoto, Masanori Yanagisawa.
Application Number | 20110023535 12/921545 |
Document ID | / |
Family ID | 41090652 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110023535 |
Kind Code |
A1 |
Morimoto; Kouki ; et
al. |
February 3, 2011 |
REFRIGERATION APPARATUS
Abstract
In a refrigeration apparatus (1) for which refrigerant
containing a compound represented by a molecular formula of
C.sub.3H.sub.mF.sub.n(note that m=1-5, n=1-5, and m+n=6) is used, a
compressor including a first compression mechanism (20A) and a
second compression mechanism (20B) inside a casing (11) is used in
order to reduce or prevent decomposition of refrigerant due to an
increase in discharge temperature of a compressor (10) performing a
compression phase of refrigerant in a refrigeration cycle.
Inventors: |
Morimoto; Kouki; (Osaka,
JP) ; Yanagisawa; Masanori; (Shiga, JP) ;
Furusho; Kazuhiro; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
41090652 |
Appl. No.: |
12/921545 |
Filed: |
March 4, 2009 |
PCT Filed: |
March 4, 2009 |
PCT NO: |
PCT/JP2009/000975 |
371 Date: |
September 8, 2010 |
Current U.S.
Class: |
62/510 |
Current CPC
Class: |
F04C 2210/26 20130101;
F25B 1/10 20130101; C09K 2205/22 20130101; F04C 2210/263 20130101;
C09K 2205/126 20130101; F04C 18/322 20130101; C09K 5/045 20130101;
F04C 23/001 20130101; F04C 23/008 20130101; F04C 2270/19 20130101;
F25B 2400/121 20130101; F04C 2210/10 20130101; F04C 2210/1022
20130101; F25B 9/002 20130101 |
Class at
Publication: |
62/510 |
International
Class: |
F25B 1/10 20060101
F25B001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 18, 2008 |
JP |
2008-069286 |
Claims
1. A refrigeration apparatus in which refrigerant of a refrigerant
circuit (2) is single component refrigerant containing refrigerant
represented by a molecular formula: C.sub.3H.sub.mF.sub.n where "m"
and "n" are integers equal to or greater than 1 and equal to or
less than 5, and a relationship represented by an expression m+n=6
is satisfied, and having a single double bond in a molecular
structure, or refrigerant mixture containing the refrigerant, the
refrigeration apparatus, comprising: a compressor (10) for
performing a compression phase of refrigerant, wherein the
compressor (10) includes a first compression mechanism (20A) and a
second compression mechanism (20B) inside a casing (11).
2. The refrigeration apparatus of claim 1, wherein the first
compression mechanism (20A) of the compressor (10) is a lower-stage
compression mechanism (20L), and the second compression mechanism
(20B) is a higher-stage compression mechanism (20H); and both of
the compression mechanisms (20A, 20B) serve as a two-stage
compression mechanism (20L, 20H) for compressing refrigerant at two
stages.
3. The refrigeration apparatus of claim 1, wherein the compression
mechanism (20A, 20B) is a swing piston type compression mechanism
which includes a cylinder (21L, 21H) having a cylinder chamber
(25), and a swing piston (28) orbiting along an inner
circumferential surface of the cylinder (21L, 21H); in which a
blade (28b) outwardly protruding in a radial direction is formed in
the swing piston (28); and in which support members (29) for
holding the blade (28b) so as to move the blade (28b) back and
forth are rotatably held by the cylinder (21L, 21H).
4. The refrigeration apparatus of claim 1, wherein the refrigerant
represented by the molecular formula: C.sub.3H.sub.mF.sub.n, where
"m" and "n" are the integers equal to or greater than 1 and equal
to or less than 5, and the relationship represented by the
expression m+n=6 is satisfied, and having the single double bond in
the molecular structure is 2,3,3,3-tetrafluoro-1-propene.
5. The refrigeration apparatus of claim 1, wherein the refrigerant
of the refrigerant circuit (2) is refrigerant mixture further
containing difluoromethane.
6. The refrigeration apparatus of claim 1, wherein the refrigerant
of the refrigerant circuit (2) is refrigerant mixture further
containing pentafluoroethane.
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigeration apparatus,
and particularly relates to a refrigeration apparatus for which
refrigerant containing a compound represented by a molecular
formula of C.sub.3H.sub.mF.sub.n is used.
BACKGROUND ART
[0002] Conventionally, a refrigeration apparatus including a
refrigerant circuit in which a refrigeration cycle is performed has
been broadly applied to an air conditioning system etc. Patent
Document 1 discloses that refrigerant containing a compound
represented by a molecular formula of C.sub.3H.sub.mF.sub.n is used
as refrigerant of a refrigerant circuit. Such refrigerant has
excellent properties as the refrigerant of the refrigerant circuit,
and attempts have been made to improve a coefficient of performance
(COP) of a refrigeration apparatus. In addition, it has been known
that such refrigerant does not contain chlorine and bromine atoms,
and has a small influence on destruction of the ozone layer.
[0003] The refrigerant (C.sub.3H.sub.mF.sub.n) disclosed in Patent
Document 1 has properties such as a relatively-high theoretical COP
and low global warming potential (GWP). Thus, use of the
refrigerant for the refrigeration cycle can provide an
environment-friendly refrigeration apparatus having high
operational efficiency.
Citation List
Patent Document
[0004] Patent Document 1: Japanese Patent Application No.
04-110388
SUMMARY OF THE INVENTION
Technical Problem
[0005] However, the refrigerant are likely to be decomposed at high
temperature, and therefore the refrigerant is desirably used under
a condition where an increase in temperature is not likely to be
caused. When using, e.g., a conventional single-stage
single-cylinder compressor, if a cylinder volume or a compression
ratio is increased, then a discharge flow rate is increased in
response to an increase in so-called "over-compression" of
refrigerant, and a refrigerant temperature tends to increase. Thus,
there is a possibility that, when using the refrigerant in
combination with the single-stage single-cylinder compressor,
refrigerant is decomposed depending on conditions.
[0006] The present invention has been made in view of the
foregoing, and it is an object of the present invention to reduce
or prevent decomposition of refrigerant due to an increase in
discharge temperature of a compressor in a refrigeration apparatus
for which refrigerant containing a compound represented by a
molecular formula of C.sub.3H.sub.mF.sub.n is used.
Solution to the Problem
[0007] A first aspect of the invention is intended for a
refrigeration apparatus in which refrigerant of a refrigerant
circuit (2) is single component refrigerant containing refrigerant
represented by a molecular formula: C.sub.3H.sub.mF.sub.n (note
that "m" and "n" are integers equal to or greater than 1 and equal
to or less than 5, and a relationship represented by an expression
m+n=6 is satisfied) and having a single double bond in a molecular
structure, or refrigerant mixture containing the refrigerant.
[0008] The refrigeration apparatus includes a compressor (10) for
performing a compression phase of refrigerant, and the compressor
(10) includes a first compression mechanism (20A) and a second
compression mechanism (20B) inside a casing (11).
[0009] In the first aspect of the invention, a so-called
"two-cylinder" or "two-stage" compressor (10) can be used. However,
if the two-cylinder compressor (10) is used, a discharge flow rate
of each cylinder can be decreased as compared to that of a
single-cylinder compressor (10), thereby reducing over-compression.
Thus, for refrigerant which is likely to be decomposed at high
temperature, an increase in refrigerant temperature can be
reduced.
[0010] A second aspect of the invention specifies the configuration
of the compressor (10) in the first aspect of the invention as a
two-stage compressor. Specifically, the second aspect of the
invention is intended for the refrigeration apparatus of the first
aspect of the invention, in which the first compression mechanism
(20A) of the compressor (10) is a lower-stage compression mechanism
(20L), and the second compression mechanism (20B) is a higher-stage
compression mechanism (20H); and both of the compression mechanisms
(20A, 20B) serve as a two-stage compression mechanism (20L, 20H)
for compressing refrigerant at two stages.
[0011] In the second aspect of the invention, as will be seen from
a Mollier diagram of FIG. 4, refrigerant is compressed at two
stages to reduce the over-compression of refrigerant on a
higher-stage side as compared to a single-stage compression,
thereby decreasing a discharge temperature. Thus, an increase in
refrigerant temperature can be reduced.
[0012] A third aspect of the invention is intended for the
refrigeration apparatus of the first or second aspect of the
invention, in which the compression mechanism (20A, 20B) is a swing
piston type compression mechanism which includes a cylinder (21L,
21H) having a cylinder chamber (25), and a swing piston (28)
orbiting along an inner circumferential surface of the cylinder
(21L, 21H); in which a blade (28b) outwardly protruding in a radial
direction is formed in the swing piston (28); and in which support
members (29) for holding the blade (28b) so as to move the blade
(28b) back and forth are rotatably held by the cylinder (21L,
21H).
[0013] In the third aspect of the invention, the compression
mechanisms (20A, 20B) are the swing piston type compression
mechanisms. A rolling piston type compressor (10) includes a
cylinder having a cylinder chamber; and a rolling piston orbiting
along an inner circumferential surface of the cylinder. The
cylinder holds a blade, one end (tip end) of which is pressed
against, and is brought contact with, an outer circumferential
surface of the rolling piston. In such a rolling piston type
compressor, the outer circumferential surface of the rolling piston
and the tip end surface of the blade slide against each other to
generate heat, and therefore an inside of the compressor is likely
to have a high temperature. Thus, there is a possibility that, if
the refrigerant is used, the refrigerant is decomposed. However, in
the third aspect of the invention, since the swing piston type
compressor (10) is used considering refrigerant which is likely to
be decomposed at high temperature, the swing piston (28) and the
blade (28b) do not slide against each other, thereby not generating
heat in such a section. Thus, refrigerant is less susceptible to
heat.
[0014] A fourth aspect of the invention is intended for the
refrigeration apparatus of any one of the first to third aspects of
the invention, in which the refrigerant represented by the
molecular formula: C.sub.3H.sub.mF.sub.n (note that "m" and "n" are
the integers equal to or greater than 1 and equal to or less than
5, and the relationship represented by the expression m+n=6 is
satisfied) and having the single double bond in the molecular
structure is 2,3,3,3-tetrafluoro-1-propene.
[0015] A fifth aspect of the invention is intended for the
refrigeration apparatus of any one of the first to fourth aspects
of the invention, in which the refrigerant of the refrigerant
circuit (2) is refrigerant mixture further containing
difluoromethane.
[0016] A sixth aspect of the invention is intended for the
refrigeration apparatus of any one of the first to fifth aspects of
the invention, in which the refrigerant of the refrigerant circuit
(2) is refrigerant mixture further containing
pentafluoroethane.
[0017] In the fourth to sixth aspects of the invention, the
compressor (10) including the two compression mechanisms (20A, 20B)
is used considering refrigerant which is likely to be decomposed at
high temperature as in the first aspect of the invention, and
therefore refrigerant is less susceptible to heat.
ADVANTAGES OF THE INVENTION
[0018] According to the first aspect of the invention, the
so-called "two-cylinder" or "two-stage" compressor (10) can be
used. The two-cylinder compressor of such compressors, the
over-compression of refrigerant of each cylinder is reduced as
compared to the single-cylinder compressor (10), thereby decreasing
the discharge flow rate. Thus, the increase in refrigerant
temperature can be reduced, thereby reducing or preventing the
decomposition of refrigerant.
[0019] According to the second aspect of the invention, refrigerant
is compressed at the two stages, thereby decreasing the discharge
temperature as compared to that of the single-stage compression.
Thus, the decomposition of refrigerant can be reduced or prevented
as in the first aspect of the invention.
[0020] According to the third aspect of the invention, the
compression mechanisms (20A, 20B) are the swing piston type
compression mechanisms, thereby easily reducing the increase in
refrigerant temperature. Thus, combined with the use of the two
compression mechanisms (20A, 20B), the decomposition of refrigerant
can be more effectively reduced or prevented.
[0021] According to the fourth to sixth aspects of the invention,
the compressor (10) including the two compression mechanisms (20A,
20B) is used considering refrigerant which is likely to be
decomposed at high temperature, thereby reducing the increase in
refrigerant temperature. Thus, the decomposition of refrigerant can
be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] [FIG. 1] FIG. 1 is a refrigerant circuit diagram of a
refrigeration apparatus of a first embodiment of the present
invention.
[0023] [FIG. 2] FIG. 2 is a longitudinal sectional view of a
compressor.
[0024] [FIG. 3] FIG. 3 is a cross sectional view of a compression
mechanism.
[0025] [FIG. 4] FIG. 4 is a Mollier diagram showing a change in
refrigerant properties in the refrigerant circuit.
[0026] [FIG. 5] FIG. 5 is a longitudinal sectional view of a
compressor of a second embodiment.
DESCRIPTION OF REFERENCE CHARACTERS
[0027] 1 Refrigeration Apparatus [0028] 2 Refrigerant Circuit
[0029] 10 Compressor [0030] 11 Casing [0031] 20A First Compression
Mechanism [0032] 20B Second Compression Mechanism [0033] 21L
Cylinder [0034] 21H Cylinder [0035] 20L Lower-Stage Compression
Mechanism [0036] 20H Higher-Stage Compression Mechanism [0037] 25
Cylinder Chamber [0038] 28 Swing Piston [0039] 28b Blade [0040] 29
Swing Bush (Support Member)
DESCRIPTION OF EMBODIMENTS
[0041] Embodiments of the present invention will be described in
detail hereinafter with reference to the drawings.
First Embodiment of the Invention
[0042] A first embodiment of the present invention will be
described. The first embodiment relates to an air conditioning
system.
[0043] As illustrated in FIG. 1, an air conditioning system (1) is
a heat pump type air conditioning system, and is switchable between
a cooling operation and a heating operation.
[0044] A refrigerant circuit (2) of the air conditioning system (1)
includes a compressor (10) for performing a compression phase of
refrigerant in a refrigeration cycle; a four-way switching valve
(3) which is a flow direction switching mechanism for switching a
flow direction of refrigerant; an outdoor heat exchanger (4) which
is a heat-source-side heat exchanger; a first expansion valve (5A)
which is a first expansion mechanism; a gas-liquid separator (6); a
second expansion valve (5B) which is a second expansion mechanism;
an indoor heat exchanger (7) which is a utilization-side heat
exchanger; and an accumulator (8).
[0045] The refrigerant circuit (2) is formed as a closed circuit by
connecting such components with pipes.
[0046] The refrigerant circuit (2) of the present embodiment is
filled with single component refrigerant containing HFO-1234yf
(2,3,3,3-tetrafluoro-1-propene) as refrigerant. Note that a
chemical formula of the HFO-1234yf is represented by an expression
CF.sub.3--CF.dbd.CH.sub.2. That is, such refrigerant is a type of
single component refrigerant containing refrigerant represented by
a molecular formula of C.sub.3H.sub.mF.sub.n (note that "m" and "n"
are integers equal to or greater than 1 and equal to or less than
5, and a relationship represented by an expression m+n=6 is
satisfied) and having a single double bond in a molecular
structure.
[0047] A discharge port of the compressor (10) is connected to a
first port (P1) of the four-way switching valve (3), and a second
port (P2) of the four-way switching valve (3) is connected to a
gas-side end of the outdoor heat exchanger (4). A liquid-side end
of the outdoor heat exchanger (4) is connected to a liquid-side end
of the indoor heat exchanger (7) through the first expansion valve
(5A), the gas-liquid separator (6), and the second expansion valve
(5B). A gas-side end of the indoor heat exchanger (7) is connected
to a third port (P3) of the four-way switching valve (3), and a
fourth port (P4) of the four-way switching valve (3) is connected
to a suction port of the compressor (10) through the accumulator
(8).
[0048] The four-way switching valve (3) is switchable between a
first state during the cooling operation, in which the first port
(P1) communicates with the second port (P2), and the third port
(P3) communicates with the fourth port (P4) (state indicated by a
solid line in FIG. 1); and a second state during the heating
operation, in which the first port (P1) communicates with the third
port (P3), and the second port (P2) communicates with the fourth
port (P4) (state indicated by a dashed line in FIG. 1).
[0049] An injection pipe (2A) is provided in the refrigerant
circuit (2). The injection pipe (2A) is an injection pipe for
injecting intermediate-pressure gaseous refrigerant which is
intermediate-pressure fluid, to the compressor (10). One end of the
injection pipe (2A) communicates with the gas-liquid separator (6),
and the other end communicates with the compressor (10). In the
gas-liquid separator (6), intermediate-pressure refrigerant is
stored, which has intermediate pressure between condensing pressure
of refrigerant which is high-pressure fluid, and evaporating
pressure of refrigerant which is low-pressure fluid. The injection
pipe (2A) is used for injecting intermediate-pressure gas-phase
refrigerant of the intermediate-pressure refrigerant stored in the
gas-liquid separator (6), to the compressor (10).
[0050] The first expansion valve (5A) and the second expansion
valve (5B) are motorized valves with adjustable opening.
Intermediate-pressure refrigerant made by reducing its pressure by
the first expansion valve (5A) or the second expansion valve (5B)
is stored in the gas-liquid separator (6).
[0051] The compressor (10) controls an operational capacity in a
single-step or multiple-step manner. To this end, as illustrated in
FIG. 2, an electric motor (30) for driving a compression mechanism
(20) is accommodated in the compressor (10). The electric motor
(30) is connected to a power source (35) through an inverter
(rotational speed control mechanism) (34), and a drive frequency is
changed to adjust the rotational speed.
[0052] The compressor (10) is a two-stage compressor. As
illustrated in FIG. 2, a lower-stage compression mechanism (20L)
which is a first compression mechanism (20A); a higher-stage
compression mechanism (20H) which is a second compression mechanism
(20B); and the electric motor (30) for driving both of the
compression mechanisms (20L, 20H) are accommodated in a hermetic
casing (11). The casing (11) includes a cylindrical body section
(12) having upper and lower openings; and end plate sections (13,
14) fixed to upper and lower end sections of the body section (12)
by welding.
[0053] The electric motor (30) includes a stator (31) fixed to an
inner circumferential surface of the casing (11); and a rotor (32)
arranged in a center section of the stator (31). A drive shaft (33)
is connected to a center section of the rotor (32). The drive shaft
(33) downwardly extends from the rotor (32), and is connected to
the lower-stage compression mechanism (20L) and the higher-stage
compression mechanism (20H).
[0054] A bottom section inside the casing (11) serves as an oil
storage section (17) of lubricant, and a lower end section of the
drive shaft (33) is dipped in the lubricant of the oil storage
section (17). A centrifugal oil pump (36) is provided in the lower
end section of the drive shaft (33), and the lubricant is supplied
to sliding sections and bearing sections of the lower-stage
compression mechanism (20L) and the higher-stage compression
mechanism (20H) through an oil supply path (33c) inside the drive
shaft (33).
[0055] The lower-stage compression mechanism (20L) and the
higher-stage compression mechanism (20H) are positioned below the
electric motor (30), and are stacked in two tiers. Both of the
lower-stage compression mechanism (20L) and the higher-stage
compression mechanism (20H) are so-called "swing piston type"
compression mechanisms.
[0056] The lower-stage compression mechanism (20L) and the
higher-stage compression mechanism (20H) have approximately the
same configuration, and the higher-stage compression mechanism
(20H) is arranged above the lower-stage compression mechanism
(20L). As illustrated in FIG. 3, in the compression mechanism (20L,
20H), a swing piston (28) is accommodated in a cylinder chamber
(25) formed in a cylinder (21H, 21L). As illustrated in FIG. 2, a
middle plate (22) is provided between the cylinders (21H, 21L) of
the compression mechanisms (20L, 20H). A lower plate (rear head)
(24) is provided on a lower surface of the lower-stage cylinder
(21L) to close the lower-stage cylinder (21L), and an upper plate
(front head) (23) is provided on an upper surface of the
higher-stage cylinder (21H) to close the higher-stage cylinder
(21H).
[0057] The whole of the swing piston (28) of the compression
mechanism (20L, 20H) is formed in an annular form, and an eccentric
section (33a, 33b) of the drive shaft (33) is rotatably fitted into
the swing piston (28). The eccentric section (33a, 33b) is formed
so as to be eccentric to the center of rotation of the drive shaft
(33).
[0058] A suction path (21a, 21b) is formed in the cylinder (21H,
21L), and one end of the suction path (21a, 21b) opens to the
cylinder chamber (25) to serve as a suction port. A discharge path
(24a) of the lower-stage compression mechanism (20L) is formed in
the lower plate (24), whereas a discharge path (23a) of the
higher-stage compression mechanism (20H) is formed in the upper
plate (23). One end of the discharge path (23a, 24a) opens to the
cylinder chamber (25) to serve as a discharge port. Although not
shown in the figure, a discharge valve for opening the discharge
port when reaching a predetermined discharge pressure is provided
in the discharge path (23a, 24a).
[0059] In the cylinder (21H, 21L), a cylindrical bush hole (21c)
which extends in an axial direction, and which is positioned
between the suction port and the discharge port is formed so as to
open to the cylinder chamber (25). In the swing piston (28), an
annular body section (28a) is integrally formed with a blade (28b)
protruding from the body section (28a) in a radial direction. A tip
end side of the blade (28b) is inserted into the bush hole (21c)
through swing bushes (29) which is a pair of support members.
[0060] The blade (28b) divides the cylinder chamber (25) into a
low-pressure chamber (25a) communicating with the suction path
(21a, 21b), and a high-pressure chamber (25b) communicating with
the discharge path (23a, 24a). The swing piston (28) compresses
refrigerant by orbiting the body section (28a) along an inner
circumferential surface of the cylinder chamber (25) while swinging
the blade (28b) about the swing bushes (29) as a pivot point.
[0061] A suction pipe (15) for supplying low-pressure gaseous
refrigerant to the lower-stage compression mechanism (20L) is
connected to the suction path (21a) of the lower-stage compression
mechanism (20L). A suction-side refrigerant pipe (2B) (see FIG. 1)
of the refrigerant circuit (2) is connected to the suction pipe
(15).
[0062] A lower muffler (26) is provided in the lower plate (24). A
middle path (20M) is formed in the compression mechanism (20). The
middle path (20M) penetrates the middle plate (22) through the
lower plate (24) and the lower-stage cylinder (21L), and
communicates with the suction path (21b) of the higher-stage
compression mechanism (20H).
[0063] The injection pipe (2A) is connected to the middle plate
(22) to communicate with the middle path (20M). That is, the middle
path (20M) is configured to be in an intermediate-pressure
atmosphere by supplying intermediate-pressure gaseous refrigerant
thereto. Such configuration supplies intermediate-pressure
refrigerant to the higher-stage compression mechanism (20H).
[0064] An upper muffler (27) covering the discharge path (23a) of
the higher-stage compression mechanism (20H) is provided in the
upper plate (23). The discharge path (23a) of the higher-stage
compression mechanism (20H) opens to the casing (11) through the
upper muffler (27), and is configured such that an inside of the
casing (11) is in a high-pressure atmosphere.
[0065] A discharge pipe (16) for discharging high-pressure gaseous
refrigerant to the refrigerant circuit (2) is fixed to an upper
section of the casing (11). A discharge-side refrigerant pipe (2C)
of the refrigerant circuit (2) is connected to the discharge pipe
(16) (see FIG. 1).
[0066] Operation
[0067] Next, an air conditioning operation of the air conditioning
system (1) will be described.
[0068] First, in the room cooling operation, the four-way switching
valve (3) is switched to the state indicated by the solid line in
FIG. 1. Refrigerant discharged from the compressor (10) is
condensed by exchanging heat with outdoor air in the outdoor heat
exchanger (4). The pressure of the liquid refrigerant is reduced by
the first expansion valve (5A), and then such refrigerant is stored
in the gas-liquid separator (6) as intermediate-pressure
refrigerant having intermediate pressure between the condensing
pressure and the evaporating pressure.
[0069] The pressure of intermediate-pressure liquid refrigerant of
the intermediate-pressure refrigerant in the gas-liquid separator
(6) is reduced by the second expansion valve (5B). Subsequently,
such refrigerant is evaporated by exchanging heat with room air in
the indoor heat exchanger (7), thereby cooling the room air. Then,
the gaseous refrigerant returns to the compressor (10) through the
accumulator (8), thereby performing a refrigeration circulating
operation.
[0070] On the other hand, in the heating operation, the four-way
switching valve (3) is switched to the state indicated by the
dashed line in FIG. 1. Refrigerant discharged from the compressor
(10) exchanges heat with room air in the indoor heat exchanger (7),
and then is condensed while heating the room air. Subsequently, the
pressure of the liquid refrigerant is reduced by the second
expansion valve (5B), and such refrigerant is stored in the
gas-liquid separator (6) as intermediate-pressure refrigerant.
[0071] The pressure of intermediate-pressure liquid refrigerant of
the intermediate-pressure refrigerant in the gas-liquid separator
(6) is reduced by the first expansion valve (5A), and then such
refrigerant is evaporated by exchanging heat with outdoor air in
the outdoor heat exchanger (4). Subsequently, the gaseous
refrigerant returns to the compressor (10) through the accumulator
(8), thereby performing the refrigerant circulating operation.
[0072] Since the injection pipe (2A) is provided,
intermediate-pressure gaseous refrigerant in the gas-liquid
separator (6) is injected to the compressor (10) in the air
conditioning operation.
[0073] A change in refrigerant properties in the refrigerant
circuit (2) will be described with reference to FIG. 4.
[0074] First, refrigerant in the compressor (10) is compressed so
as to transition from a low-pressure state at a point A to a
high-condensing-pressure state at a point B through the injection
of intermediate-pressure refrigerant. The high-pressure gaseous
refrigerant is condensed in the outdoor heat exchanger (4) or the
indoor heat exchanger (7), and then changes into high-pressure
liquid refrigerant at a point C. The pressure of the high-pressure
liquid refrigerant is reduced to a point D by the first expansion
valve (5A) or the second expansion valve (5B), thereby changing
into intermediate-pressure refrigerant. The intermediate-pressure
refrigerant is stored in the gas-liquid separator (6), and is
separated into intermediate-pressure liquid refrigerant and
intermediate-pressure gaseous refrigerant in the gas-liquid
separator (6).
[0075] The separated intermediate-pressure gaseous refrigerant is
injected into the compressor (10) through the injection pipe (2A)
at a point E (refrigerant at the point D has a lower temperature
than that of gaseous refrigerant discharged from the lower-stage
compression mechanism (20L), and both of them are mixed together to
start a second stage of the compression at the point E). Meanwhile,
the pressure of the intermediate-pressure liquid refrigerant is
reduced from a point F to a point G by the second expansion valve
(5B) or the first expansion valve (5A), and thus, the refrigerant
becomes low-pressure two-phase refrigerant. The low-pressure
two-phase refrigerant is evaporated in the indoor heat exchanger
(7) or the outdoor heat exchanger (4). Subsequently, such
refrigerant transitions to the state at the point A, and then
returns to the compressor (10).
[0076] Consequently, in the heating operation,
intermediate-pressure gaseous refrigerant is added to refrigerant
flowing in the indoor heat exchanger (7) serving as a condenser,
thereby increasing an amount of circulating refrigerant. Thus,
heating capability is improved.
[0077] On the other hand, in the cooling operation, the
low-pressure two-phase refrigerant at the point G has an enthalpy
difference increasing from the point D to the point F, thereby
increasing a heat amount of refrigerant to be evaporated in the
indoor heat exchanger (7). Thus, cooling capability is
improved.
[0078] As will be seen from a Mollier diagram of FIG. 4, the
two-stage compression is employed in the present embodiment, and
therefore a discharge temperature of refrigerant is lower than that
in a single-stage compression refrigeration cycle shown by a
virtual line.
[0079] Next, a compression operation of the compressor (10) will be
described.
[0080] When rotating the drive shaft (33) by driving the electric
motor (30), the swing pistons (28) of the lower-stage compression
mechanism (20L) and the higher-stage compression mechanism (20H)
swing and orbit about the center of the bush hole (21c) as the
pivot point. Low-pressure gaseous refrigerant returning from the
accumulator (8) in the refrigerant circuit (2) flows into the
cylinder chamber (25) through the suction path (21a) of the
lower-stage compression mechanism (20L), and is compressed by the
swing of the swing piston (28).
[0081] Meanwhile, intermediate-pressure refrigerant is supplied
from the gas-liquid separator (6) to the middle path (20M), and
therefore the discharge valve of the lower-stage compression
mechanism (20L) is opened when the pressure of refrigerant in the
cylinder chamber (25) reaches an intermediate pressure level.
Refrigerant discharged from the lower-stage compression mechanism
(20L) passes from the discharge path (24a) through the lower
muffler (26), and flows into the suction path (21b) of the
higher-stage compression mechanism (20H) through the middle path
(20M). Such refrigerant joins intermediate-pressure refrigerant of
the injection pipe (2A) at the middle path (20M), and flows into
the cylinder chamber (25) of the higher-stage compression mechanism
(20H).
[0082] In the higher-stage compression mechanism (20H),
intermediate-pressure refrigerant is compressed, and high-pressure
refrigerant is discharged into the casing (11). The high-pressure
refrigerant passes between the stator (31) and the rotor (32) of
the electric motor (30), and is discharged to the refrigerant
circuit (2). The high-pressure refrigerant circulates in the
refrigerant circuit (2) as described above.
[0083] In such a state, if a rolling piston type compressor is used
as the compressor, an outer circumferential surface of a rolling
piston and a tip end surface of a blade slide against each other to
generate heat, and therefore an inside of a compressor is likely to
have a high temperature. Thus, there is a possibility that, when
using the refrigerant containing the compound represented by the
molecular formula of C.sub.3H.sub.mF.sub.n, such as the HFO-1234yf
refrigerant, the refrigerant is decomposed. However, in the present
embodiment, the swing piston type compressor is used considering
refrigerant which are likely to be decomposed at high temperature.
Thus, the piston and the blade do not slide against each other,
thereby not generating heat in such a section. Consequently,
refrigerant is less susceptible to heat.
[0084] Advantages of First Embodiment
[0085] In the present embodiment, as the refrigerant of the
refrigerant circuit (2), the single component refrigerant
containing the HFO-1234yf (2,3,3,3-tetrafluoro-1-propene) is used.
The HFO-1234yf has properties such as a relatively-high theoretical
COP. Thus, the single component refrigerant of such refrigerant is
used, thereby performing a refrigerant cycle with excellent
operational efficiency. Consequently, operational efficiency of the
refrigeration apparatus (1) can be improved.
[0086] In addition, the HFO-1234yf has properties such as
relatively-low global warming potential (GWP). Thus, the single
component refrigerant of such refrigerant is used as the
refrigerant, thereby providing the environment-friendly
refrigeration apparatus (1).
[0087] In the present embodiment, the two-stage compressor
including the lower-stage compression mechanism (20L) and the
higher-stage compression mechanism (20H) is used, resulting in the
lower discharge temperature of refrigerant than that of a
single-stage single-cylinder compressor. Thus, even in the
HFO-1234yf refrigerant which is likely to be decomposed at high
temperature, the decomposition of refrigerant is not caused.
[0088] In the present embodiment, the swing piston type compressor
(10) is used, thereby not causing the sliding of the outer
circumferential surface of the piston and the tip end surface of
the blade, which is caused in the rolling piston type compressor.
Thus, heat due to the sliding of such members is not generated,
thereby not causing the decomposition of refrigerant even in the
HFO-1234yf refrigerant which is likely to be decomposed at high
temperature.
[0089] The HFO-1234yf is refrigerant suitable for using under
low-pressure condition, and a sufficient circulating amount thereof
is hard to be ensured. Thus, considering sufficient refrigeration
capability which is hard to be ensured, intermediate-pressure
gaseous refrigerant is injected into the compressor (10) in the
present embodiment. Consequently, an apparent operational capacity
increases to increase the refrigerant circulating amount, thereby
enhancing the refrigeration capability even with the HFO-1234yf
with which the sufficient refrigeration capability is hard to be
ensured.
[0090] In the present embodiment, the inverter control is
performed, and therefore an increase in rotational speed results in
an increase in suction amount. Thus, such configuration also
increases the operational capacity to increase the refrigerant
circulating amount, thereby enhancing the refrigeration capability
even with the HFO-1234yf with which the sufficient refrigeration
capability is hard to be ensured.
[0091] Variation of First Embodiment
[0092] In the first embodiment, a system is employed, in which
intermediate-pressure gaseous refrigerant is injected to the
compressor (10) in the two-stage compression refrigeration
cycle.
[0093] As is apparent from the Mollier diagram of FIG. 4, the
two-compression refrigeration cycle is the system in which, after
low-pressure refrigerant gas is compressed to an intermediate
pressure level in the lower-stage compression mechanism (20L), the
intermediate-pressure gaseous refrigerant is cooled to a
temperature near a saturated vapor temperature, and then such
refrigerant is further compressed in the higher-stage compression
mechanism (20H). In the first embodiment, the gas injection system
is employed, in which the gas-liquid separator (6) is used as an
intermediate cooler (intermediate cooling unit) for cooling
intermediate-pressure gaseous refrigerant. However, as the
intermediate cooler, other systems including units such as a
refrigerant heat exchanger for exchanging heat between
high-pressure liquid refrigerant and two-phase refrigerant made by
reducing the pressure of the high-pressure liquid refrigerant to an
intermediate pressure level may be used.
Second Embodiment of the Invention
[0094] Next, a second embodiment of the present invention will be
described.
[0095] In the second embodiment, not a two-stage compressor but a
two-cylinder compressor (10) is used as a compressor for performing
a compression phase of a refrigeration cycle.
[0096] As illustrated in FIG. 5, in the compressor of the second
embodiment, a first compression mechanism (20A) and a second
compression mechanism (20B) are two compression mechanisms which
are not on lower and higher stages, but are in a parallel
relationship. A suction path (21a, 21b) is provided in each of the
compression mechanisms (20A, 20B), and the suction paths (21a, 21b)
are connected to a suction-side refrigerant pipe (2B) of a
refrigerant circuit (2) in parallel. In the first embodiment, the
first compression mechanism (20A) and the second compression
mechanism (20B) are on the lower and higher stages, and both of the
compression mechanisms (20A, 20B) are connected together by the
middle path (20M). However, such configuration is not employed in
the second embodiment.
[0097] A lower muffler (26) fixed to a lower plate (24) opens to an
internal space of a casing (11), and refrigerant discharged from
the first compression mechanism (20A) and the second compression
mechanism (20B) is separately discharged into the casing (11).
[0098] In the present embodiment, the configuration is not
employed, in which intermediate-pressure gaseous refrigerant is
injected to the compression mechanisms.
[0099] As for other configurations, the second embodiment has the
same configurations as those of the first embodiment. An operation
is the same as that of the first embodiment, except that the
two-stage compression is not performed.
[0100] Advantages of Second Embodiment
[0101] In the second embodiment, the single-stage two-cylinder
compressor (10) is used. In the single-stage two-cylinder
compressor, the volume of each cylinder can be reduced as compared
to that of the single-stage single-cylinder compressor. Thus,
over-compression in each cylinder can be reduced, thereby
decreasing a discharge flow rate. This reduces an increase in
refrigerant temperature, thereby reducing or preventing
decomposition of refrigerant.
[0102] As for other advantages, the second embodiment has the same
advantages as those of the first embodiment.
Other Embodiments
[0103] The foregoing embodiments may have the following
configurations.
[0104] In the foregoing embodiments, e.g., the compressor including
the swing piston type compression mechanisms (20A, 20B) is used.
However, it is not limited to the swing piston type compression
mechanism, and a rolling piston type or scroll type compression
mechanism may be used. In such a case, a two-cylinder or two-stage
compression mechanism (20A, 20B) is employed, thereby reducing or
preventing an increase in discharge temperature of refrigerant.
Consequently, decomposition of HFO-1234yf which is refrigerant can
be reduced or prevented.
[0105] In the foregoing embodiment, as the refrigerant of the
refrigerant circuit (10), single component refrigerant of the
refrigerant represented by the molecular formula:
C.sub.3H.sub.mF.sub.n (note that m=1-5, n=1-5, and m+n=6) and
having the single double bond in the molecular structure, other
than the HFO-1234yf may be used. Specifically, the single component
refrigerant includes, e.g., 1,2,3,3,3-pentafluoro-1-propene
(referred to as "HFO-1225ye," and a chemical formula thereof is
represented by an expression CF.sub.3--CF.dbd.CHF);
1,3,3,3-tetrafluoro-1-propene (referred to as "HFO-1234ze," and a
chemical formula thereof is represented by an expression
CF.sub.3--CH.dbd.CHF); 1,2,3,3-tetrafluoro-1-propene (referred to
as "HFO-1234ye," and a chemical formula thereof is represented by
an expression CHF.sub.2--CF.dbd.CHF); 3,3,3-trifluoro-1-propene
(referred to as "HFO-1243zf," and a chemical formula thereof is
represented by an expression CF.sub.3--CH.dbd.CH.sub.2);
1,2,2-trifluoro-1-propene (a chemical formula thereof is
represented by an expression CH.sub.3--CF.dbd.CF.sub.2); and
2-fluoro-1-propene (a chemical formula thereof is represented by an
expression CH.sub.3--CF.dbd.CH.sub.2).
[0106] In the foregoing embodiments, refrigerant mixture may be
used, which is made by adding at least one of HFC-32
(difluoromethane), HFC-125 (pentafluoroethane), HFC-134
(1,1,2,2-tetrafluoroethane), HFC-134a (1,1,1,2-tetrafluoroethane),
HFC-143a (1,1,1-trifluoroethane), HFC-152a (1,1-difluoroethane),
HFC-161, HFC-227ea, HFC-236ea, HFC-236fa, HFC-365mfc, methane,
ethane, propane, propene, butane, isobutane, pentane,
2-methylbutane, cyclopentane, dimethyl ether,
bis-trifluoromethyl-sulfide, carbon dioxide, and helium; to the
refrigerant represented by the molecular formula and having the
single double bond in the molecular structure
(1,2,3,3,3-pentafluoro-1-propene; 2,3,3,3-tetrafluoro-1-propene;
1,3,3,3-tetrafluoro-1-propene; 1,2,3,3-tetrafluoro-1-propene;
3,3,3-trifluoro-1-propene; 1,2,2-trifluoro-1-propene; and
2-fluoro-1-propene).
[0107] Refrigerant mixture of, e.g., the HFO-1234yf and the HFC-32
may be used. In such a case, the refrigerant mixture may be used,
in which the proportion of the HFO-1234yf is 78.2% by mass, and the
proportion of the HFC-32 is 21.8% by mass. In addition, the
refrigerant mixture may be used, in which the proportion of the
HFO-1234yf is 77.6% by mass, and the proportion of the HFC-32 is
22.4% by mass. In the refrigerant mixture of the HFO-1234yf and the
HFC-32, the proportion of the HFO-1234yf may be equal to or greater
than 70% by mass and equal to or less than 94% by mass, and the
proportion of the HFC-32 may be equal to or greater than 6% by mass
and equal to or less than 30% by mass. The proportion of the
HFO-1234yf is preferably equal to or greater than 77% by mass and
equal to or less than 87% by mass, and the proportion of the HFC-32
may be equal to or greater than 13% by mass and equal to or less
than 23% by mass. More preferably, the proportion of the HFO-1234yf
is equal to or greater than 77% by mass and equal to or less than
79% by mass, and the proportion of the HFC-32 is equal to or
greater than 21% by mass and equal to or less than 23% by mass.
[0108] Refrigerant mixture of the HFO-1234yf and the HFC-125 may be
used. In such a case, the proportion of the HFC-125 is preferably
equal to or greater than 10% by mass, and more preferably equal to
or greater than 10% by mass and equal to or less than 20% by
mass.
[0109] Refrigerant mixture of the HFO-1234yf, the HFC-32, and the
HFC-125 may be used. In such a case, refrigerant mixture may be
used, which contains the HFO-1234yf of 52% by mass, the HFC-32 of
23% by mass, and the HFC-125 of 25% by mass.
[0110] The foregoing embodiments have been set forth merely for
purposes of preferred examples in nature, and are not intended to
limit the scope, applications, and use of the invention.
INDUSTRIAL APPLICABILITY
[0111] As described above, the present invention is useful for the
refrigeration apparatus for which the refrigerant containing the
compound represented by the molecular formula of
C.sub.3H.sub.mF.sub.n is used.
* * * * *