U.S. patent application number 12/919770 was filed with the patent office on 2011-01-06 for expander.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. Invention is credited to Eiji Kumakura, Masakazu Okamoto, Katsumi Sakitani, Masanori Ukibune.
Application Number | 20110002803 12/919770 |
Document ID | / |
Family ID | 41064935 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110002803 |
Kind Code |
A1 |
Kumakura; Eiji ; et
al. |
January 6, 2011 |
EXPANDER
Abstract
An expander includes a cylinder at which an inflow port and an
outflow port are formed, a piston eccentrically disposed in the
cylinder relative to a rotational shaft to form a fluid chamber
between the piston and the cylinder, and a blade dividing the fluid
chamber into a high pressure side and a low pressure side. The
cylinder, the piston and the blade are arranged and configured such
that the expander recovers power of a fluid depressurized in the
fluid chamber. The cylinder has an inner diameter Dc, the inflow
port has a diameter Di, and the outflow port has a diameter Do. The
relationship 0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc and/or
0.065.times.Dc.ltoreq.Do.ltoreq.0.13.times.Dc is satisfied.
Inventors: |
Kumakura; Eiji; ( Osaka,
JP) ; Okamoto; Masakazu; (Osaka, JP) ;
Ukibune; Masanori; (Osaka, JP) ; Sakitani;
Katsumi; (Osaka, JP) |
Correspondence
Address: |
GLOBAL IP COUNSELORS, LLP
1233 20TH STREET, NW, SUITE 700
WASHINGTON
DC
20036-2680
US
|
Assignee: |
DAIKIN INDUSTRIES, LTD.
Osaka-shi, Osaka
JP
|
Family ID: |
41064935 |
Appl. No.: |
12/919770 |
Filed: |
February 26, 2009 |
PCT Filed: |
February 26, 2009 |
PCT NO: |
PCT/JP2009/000859 |
371 Date: |
August 27, 2010 |
Current U.S.
Class: |
418/60 |
Current CPC
Class: |
F01C 21/18 20130101;
F01C 1/0207 20130101; F01C 1/322 20130101; F01C 11/008 20130101;
F04C 2250/10 20130101 |
Class at
Publication: |
418/60 |
International
Class: |
F01C 1/02 20060101
F01C001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2008 |
JP |
2008-060726 |
Claims
1. An expander comprising: a cylinder at which an inflow port and
an outflow port are formed; a piston eccentrically disposed in the
cylinder relative to a rotational shaft to form a fluid chamber
between the piston and the cylinder; and a blade dividing the fluid
chamber into a high pressure side and a low pressure side, the
cylinder, the piston and the blade being arranged and configured
such that the expander recovers power of a fluid depressurized in
the fluid chamber, the cylinder having an inner diameter Dc, the
inflow port having a diameter Di, and
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc.
2. The expander of claim 1, wherein a density of a fluid in the
inflow port is .rho.i, a density of a fluid in the outflow port is
.rho.o, the outflow port has a diameter Do, and
Do=Di.times.(.rho.i/.rho.o).sup.2.
3. An expander comprising: a cylinder at which an inflow port and
an outflow port are formed; a piston eccentrically disposed in the
cylinder relative to a rotational shaft to form a fluid chamber
between the piston and the cylinder; and a blade dividing the fluid
chamber into a high pressure side and a low pressure side, the
cylinder, the piston and the blade being arranged and configured
such that the expander recovers power of a fluid depressurized in
the fluid chamber, wherein the cylinder having an inner diameter
Dc, the outflow port having a diameter Do, and
0.065.times.Dc.ltoreq.Do.ltoreq.0.13.times.Dc.
4. The expander of claim 3, wherein a density of a fluid in the
inflow port is .rho.i, a density of a fluid in the outflow port is
.rho.o, the inflow port has a diameter Di, and
Di=Do.times.(.rho.o/.rho.i).sup.2.
Description
TECHNICAL FIELD
[0001] The present invention relates to expanders which recover
power of a fluid depressurized in a cylinder.
BACKGROUND ART
[0002] Expanders which recover power of a fluid have been known,
and are applied in refrigeration devices such as air
conditioners.
[0003] Patent Document 1 discloses a positive displacement expander
of this type. The positive displacement expander is connected to a
refrigerant circuit in which a refrigerant circulates to implement
a refrigeration cycle, and is configured to perform an expansion
process of the refrigeration cycle. The expander forms a so-called
rotary fluid device, and includes a cylinder and a piston which
rotates along an inner periphery surface of the cylinder. In the
expander, a fluid chamber (expansion chamber) is formed between the
cylinder and the piston.
[0004] In the expander, a refrigerant flows into the expansion
chamber through an inflow port. When the refrigerant is
depressurized in the expansion chamber, the power of the
refrigerant is recovered as rotational power of the piston. The
refrigerant depressurized in the expansion chamber flows out into
the refrigerant circuit through an outflow port. As mentioned
above, in the positive displacement expander of this type, the
kinetic energy of the refrigerant is recovered as rotational power
of the piston and a rotational shaft. The rotational power is used
as power for driving a compressor, or a power source of a
generator.
CITATION LIST
Patent Document
[0005] PATENT DOCUMENT 1: Japanese Patent Publication No.
H08-338356
SUMMARY OF THE INVENTION
Technical Problem
[0006] However, the conventional rotary expander has a problem that
the inflow port and the outflow port temporarily communicate with
each other via the expansion chamber when the expansion chamber
starts to communicate with the inflow port, that is, a blow-by
phenomenon.
[0007] Specifically, as shown, for example, in FIG. 9, a piston
(102) of a conventional rotary expander (100) rotates in a cylinder
(101) as sequentially shown in FIG. 9(A), (B), (C), (D), (A), . . .
. Here, a fluid having flowed into an expansion chamber (105) in
the state of FIG. 9(A) through an inflow port (103) is
depressurized because the capacity of the expansion chamber (105)
is increased as the piston (102) rotates as sequentially shown in
FIGS. 9(B) and (C). The power of the refrigerant is recovered at
this time. The piston (102) further rotates, and when the piston
reaches the rotational position as shown in FIG. 9(D) (the location
of the top dead center of the cylinder that is closest to a bush
(106)), the inflow port (103) and the outflow port (104) may
communicate with each other via the expansion chamber (105). As a
result, the above-mentioned blow-by phenomenon may temporarily
occur in the state of FIG. 9(D), in which the power of refrigerant
having flowed through the inflow port (103) is not recovered and
the refrigerant flows out through the outflow port (104), thereby
decreasing the power recovery efficiency of the expander.
[0008] The present invention was made in view of the above
problems, and it is an objective of the invention to avoid a
blow-by phenomenon of an expander and thereby increase the
efficiency of the expander.
Solution to the Problem
[0009] The first aspect of the present invention is intended for an
expander having a cylinder (71) at which an inflow port (81) and an
outflow port (82) are formed, a piston (75) accommodated in the
cylinder (71) so as to be eccentric to a rotational shaft (40), and
a blade (76) which divides a fluid chamber (72) formed between the
piston (75) and the cylinder (71) into a high pressure side and a
low pressure side of a fluid, the expander recovering power of a
fluid depressurized in the fluid chamber (72). In this expander, an
inner diameter of the cylinder (71) is Dc [mm], and a diameter Di
[mm] of the inflow port (81) satisfies a relationship
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc.
[0010] According to the first aspect of the present invention, a
high pressure fluid flows into the fluid chamber (72) of the
cylinder (71) through the inflow port (81). This fluid is
depressurized in the fluid chamber (72) to a low pressure fluid.
Here, the piston (75) is rotated by power of the fluid, and the
power of the fluid is recovered as rotational power of the piston
(75) and the rotational shaft (40). The low pressure fluid
depressurized in the fluid chamber (72) flows out of the expander
through the outflow port (82).
[0011] Here, Di.ltoreq.0.13Dc stands in the present invention,
where the diameter of the inflow port (81) is Di, and the inner
diameter of the cylinder (71) is Dc. In other words, the inflow
port diameter Di of the present invention is set to 0.13Dc or less.
Thus, the inflow port diameter Di is not too large according to the
present invention, and it is thus possible to prevent the inflow
port (81) and the outflow port (82) from communicating with each
other via the fluid chamber (72) in the state of the conventional
case shown in FIG. 9(D). As a result, according to the expander of
the present invention, it is possible to avoid the occurrence of a
co-called blow-by phenomenon, and possible to avoid a reduction in
efficiency of the expander.
[0012] Further, 0.065Dc.ltoreq.Di stands in the present invention.
In other words, the inflow port diameter Di of the present
invention is set to 0.065Dc or more. Thus, the inflow port diameter
Di is not too small according to the present invention, and it is
thus possible to avoid an increase in pressure loss in the inflow
port (81). As a result, according to the expander of the present
invention, it is also possible to avoid a reduction in power
recovery efficiency of the expander with an increase in pressure
loss. That is, according to the expander of the present invention,
it is possible to increase the efficiency of the expander to a
maximum, because the blow-by phenomenon can be avoided and the
pressure loss in the inflow port (81) can be reduced.
[0013] The second aspect of the present invention is that, in the
expander of the first aspect of the present invention, a density of
a fluid in the inflow port (81) is .rho.i [kg/m.sup.3], and a
density of a fluid in the outflow port (82) is .rho.o [kg/m.sup.3];
and a diameter Do [mm] of the outflow port (82) satisfies a
relationship Do=Di.times.(.rho.i/.rho.o).sup.2
[0014] According to the second aspect of the present invention, a
density of a fluid in the inflow port (81) is .rho.i, and a density
of a fluid in the outflow port (82) is .rho.o; and the diameter Do
of the outflow port (82) satisfies
Do=Di.times.(.rho.i/.rho.o).sup.2. Here, if the inflow port
diameter Di and the outflow port diameter Do are set to have the
same diameter, the diameter of the outflow port (82) may be too
small and the pressure loss in the outflow port (82) may be
slightly increased, because a fluid whose density is lower than the
density of a fluid flowing in the inflow port (81) flows in the
outflow port (82). In view of this, according to the present
invention, a ratio of the density .rho.i of a fluid before
depressurization in the fluid chamber (72) to the density .rho.o of
the fluid after depressurization in the fluid chamber (72) (i.e.,
density ratio .rho.i/.rho.o) is considered, and the outflow port
diameter Do is decided by multiplying the inflow port diameter Di
by the square of the density ratio (.rho.i/.rho.o).
[0015] The third aspect of the present invention is intended for an
expander having a cylinder (71) at which an inflow port (81) and an
outflow port (82) are formed, a piston (75) accommodated in the
cylinder (71) so as to be eccentric to a rotational shaft (40), and
a blade (76) which divides a fluid chamber (72) formed between the
piston (75) and the cylinder (71) into a high pressure side and a
low pressure side of a fluid, the expander recovering power of a
fluid depressurized in the fluid chamber (72). In this expander, an
inner diameter of the cylinder (71) is Dc [mm], and a diameter Do
[mm] of the outflow port (82) satisfies a relationship
0.065.times.Dc.ltoreq.Do.ltoreq.0.13.times.Dc.
[0016] The third aspect of the present invention is intended for
the same expander as in the first aspect of the present invention.
Here, Do.ltoreq.0.13Dc stands in the present invention, where the
diameter of the outflow port (82) is Do, and the inner diameter of
the cylinder (71) is Dc. In other words, the outflow port diameter
of Do of the present invention is set to 0.13Dc or less. Thus, the
outflow port diameter Do is not too large according to the present
invention. Thus, it is possible to avoid the blow-by phenomenon
which occurs in the conventional case shown in FIG. 9(D), and
possible to avoid a reduction in efficiency of the expander.
[0017] Further, 0.065Dc.ltoreq.Do stands in the present invention.
In other words, the outflow port diameter Do of the present
invention is set to 0.065Dc or more. Thus, the outflow port
diameter Do is not too small according to the present invention,
and it is thus possible to avoid an increase in pressure loss in
the outflow port (82). As a result, according to the expander of
the present invention, it is also possible to avoid a reduction in
power recovery efficiency of the expander with an increase in
pressure loss. That is, according to the expander of the present
invention, it is possible to increase the efficiency of the
expander to a maximum as in the first aspect of the present
invention, because the blow-by phenomenon can be avoided and the
pressure loss in the outflow port (82) can be reduced.
[0018] The fourth aspect of the present invention is that, in the
expander of the third aspect of the present invention, a density of
a fluid in the inflow port (81) is .rho.i [kg/m.sup.3], and a
density of a fluid in the outflow port (82) is .rho.o[kg/m.sup.3];
and a diameter Di [mm] of the inflow port (81) satisfies a
relationship Di=Do.times.(.rho.o/.rho.i).sup.2.
[0019] According to the fourth aspect of the present invention, a
density of a fluid in the inflow port (81) is .rho.i, and a density
of a fluid in the outflow port (82) is .rho.o; and the diameter Di
of the inflow port (81) satisfies
Di=Do.times.(.rho.o/.rho.i).sup.2. Here, if the inflow port
diameter Di and the outflow port diameter Do are set to have the
same diameter, the diameter of the inflow port (81) may be larger
than desired, because a fluid whose density is higher than the
density of a fluid flowing in the outflow port (82) flows in the
inflow port (81). In view of this, according to the present
invention, a ratio of the density .rho.i of a fluid before
depressurization in the fluid chamber (72) to the density .rho.o of
a fluid after depressurization in the fluid chamber (72) (i.e.,
density ratio .rho.i/.rho.o) is considered, and the inflow port
diameter Di is decided by multiplying the outflow port diameter Do
by the square of the density ratio (.rho.o/.rho.i).
ADVANTAGES OF THE INVENTION
[0020] According to the first aspect of the present invention, the
inner diameter of the cylinder (71) is Dc [mm], and the diameter Di
[mm] of the inflow port (81) satisfies a relationship
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc. Therefore, according
to the present invention, the inflow port diameter Di is not too
large, and thus, a so-called blow-by phenomenon can be avoided.
Further, the inflow port diameter Di is not too small, and thus, an
increase in pressure loss in the inflow port (81) can be prevented.
As a result, desired efficiency can be obtained according to the
present invention, thereby making it possible to enhance the energy
saving characteristics of a refrigeration device or the like to
which the expander is applied.
[0021] Similarly, according to the third aspect of the present
invention, the diameter Do [mm] of the outflow port (82) satisfies
the relationship 0.065.times.Dc.ltoreq.Do.ltoreq.0.13.times.Dc.
Therefore, according to the present invention, the outflow port
diameter Do is not too large, and thus, a so-called blow-by
phenomenon can be avoided. Further, the outflow port diameter Do is
not too small, and thus, an increase in pressure loss in the
outflow port (82) can be prevented. As a result, desired efficiency
can be obtained according to the present invention, thereby making
it possible to enhance the energy saving characteristics of a
refrigeration device or the like to which the expander is
applied.
[0022] Further, according to the second and the fourth aspects of
the present invention, a ratio of the density of a fluid in the
inflow port (81) and the outflow port (82) is considered, thereby
making it possible to obtain optimum diameters of the inflow port
(81) and the outflow port (82) that can reduce pressure loss in the
inflow port (81) and the outflow port (82).
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 shows a piping diagram schematically illustrating a
structure of an air conditioner according to an embodiment.
[0024] FIG. 2 shows a vertical cross-sectional view of a
compressor-expander unit according to the embodiment.
[0025] FIG. 3 shows a horizontal cross-sectional view of an
expansion mechanism according to the embodiment.
[0026] FIG. 4 shows an example of each design point of the
expansion mechanism according to the embodiment.
[0027] FIG. 5 shows an example of each design dimension of the
expansion mechanism according to the embodiment.
[0028] FIG. 6 shows horizontal cross-sectional views for explaining
the movement of the expansion mechanism according to the
embodiment. FIG. 6(A) shows the state when a rotational angle is
90'; FIG. 6(B) shows the state when the rotational angle is
180.degree.; FIG. 6(C) shows the state when the rotational angle is
270.degree.; and FIG. 6(D) shows the state when the rotational
angle is)360.degree. (0.degree..
[0029] FIG. 7 is a graph showing a relationship between a port
diameter and the efficiency of the expander, with respect to three
types of expansion mechanisms having a different cylinder's inner
diameter.
[0030] FIG. 8 is a graph showing a relationship between the
cylinder's inner diameter and a port diameter, for achieving high
efficiency of the expander.
[0031] FIG. 9 shows horizontal cross-sectional views for explaining
the movement of a conventional expansion mechanism. FIG. 6(A) shows
the state when a rotational angle is 90'; FIG. 6(B) shows the state
when the rotational angle is 180.degree.; FIG. 6(C) shows the state
when the rotational angle is 270.degree.; and FIG. 6(D) shows the
state when the rotational angle is)360.degree. (0.degree.).
DESCRIPTION OF REFERENCE CHARACTERS
[0032] 60 expansion mechanism (expander) [0033] 71 cylinder [0034]
72 fluid chamber [0035] 73 high pressure chamber [0036] 74 low
pressure chamber [0037] 75 piston [0038] 76 blade [0039] 81 inflow
port [0040] 82 outflow port [0041] Dc cylinder's inner diameter
[0042] Di inflow port diameter [0043] Do outflow port diameter
[0044] .rho.i refrigerant density of an inflow side (high pressure
side) [0045] .rho.o refrigerant density of an outflow side (low
pressure side)
DESCRIPTION OF EMBODIMENTS
[0046] An embodiment of the present invention will be described in
detail hereinafter, with reference to the drawings.
[0047] An expander according to the present invention is installed
in a compressor-expander unit (30). The compressor-expander unit
(30) is mounted in an air conditioner (10) which performs and
switches between a cooling operation and a heating operation for a
room air. The air conditioner (10) forms a refrigeration device
having a refrigerant circuit (20) in which a refrigerant circulates
to implement a refrigeration cycle.
[0048] As shown in FIG. 1, the air conditioner (10) includes an
outdoor unit (11) placed outdoors and an indoor unit (13) placed
indoors. An outdoor fan (12), an outdoor heat exchanger (23), a
first four-way switching valve (21), a second four-way switching
valve (22), and the compressor-expander unit (30) are accommodated
in the outdoor unit (11). An indoor fan (14) and an indoor heat
exchanger (24) are accommodated in the indoor unit (13). The
outdoor unit (11) and the indoor unit (13) are connected to each
other via a pair of connecting pipes (15, 16).
[0049] The air conditioner (10) includes a refrigerant circuit
(20). The refrigerant circuit (20) is a closed circuit in which a
refrigerant circulates to implement a refrigeration cycle. The
refrigerant circuit (20) is filled with carbon dioxide (CO.sub.2)
as a refrigerant.
[0050] The outdoor heat exchanger (23) and the indoor heat
exchanger (24) form an air heat exchanger which exchange heat
between the refrigerant and air. That is, in the outdoor heat
exchanger (23), heat is exchanged between an outdoor air blown by
the outdoor fan (12) and the refrigerant. In the indoor heat
exchanger (24), heat is exchanged between a room air blown by the
indoor fan (14) and the refrigerant.
[0051] The compressor-expander unit (30) is configured by a
compression mechanism (50), an expansion mechanism (60), a shaft
(40) and a motor (45) which are accommodated in the casing (31). A
suction pipe (32) and a discharge pipe (33) are connected to the
compression mechanism (50). An inflow pipe (34) and an outflow pipe
(35) are connected to the expansion mechanism (60). The
compressor-expander unit (30) will be described in detail
later.
[0052] Each of the first four-way switching valve (21) and the
second four-way switching valve (22) has four ports. In the first
four-way switching valve (21), the first port is connected to the
discharge pipe (33) of the compressor-expander unit (30); the
second port is connected to one end of the indoor heat exchanger
(24); the third port is connected to one end of the outdoor heat
exchanger (23); and the fourth port is connected to the suction
pipe (32) of the compressor-expander unit (30). In the second
four-way switching valve (22), the first port is connected to the
outflow pipe (35) of the compressor-expander unit (30); the second
port is connected to the other end of the outdoor heat exchanger
(23); the third port is connected to the other end of the indoor
heat exchanger (24); and the fourth port is connected to the inflow
pipe (34) of the compressor-expander unit (30).
[0053] Each of the first four-way switching valve (21) and the
second four-way switching valve (22) is configured to switch
between the state in which the first port and the second port are
connected to each other, and the third port and the fourth port are
connected to each other (the state shown in solid line in FIG. 1),
and the state in which the first port and the third port are
connected to each other, and the second port and the fourth port
are connected to each other (the state shown in broken line in FIG.
1).
[0054] As shown in FIG. 2, the compressor-expander unit (30) has a
casing (31), which is a closed container having a circular
cylindrical shape. The compression mechanism (50), the motor (45),
and the expansion mechanism (60) are sequentially disposed in the
casing (31), from one end to the other end of the longitudinal
dimension of the casing (31).
[0055] The motor (45) includes a stator (46) and a rotor (47). The
stator (46) is fixed on the inner wall of the casing (31). The
rotor (47) is disposed at an inner side of the stator (46), and a
shaft (40) goes through the rotor (47).
[0056] The shaft (40) forms a rotational shaft, and includes a main
shaft portion (44), a small-diameter eccentric portion (43), and a
large-diameter eccentric portion (41). One end of the shaft (40) is
provided with the small-diameter eccentric portion (43), and the
other end of the shaft (40) is provided with the large-diameter
eccentric portion (41). The small-diameter eccentric portion (43)
has a diameter smaller than the diameter of the main shaft portion
(44), and is eccentric to the axis of the main shaft portion (44)
by a predetermined amount. The large-diameter eccentric portion
(41) has a diameter larger than the diameter of the main shaft
portion (44), and is eccentric to the axis of the main shaft
portion (44) by a predetermined amount.
[0057] The compression mechanism (50) forms a so-called scroll type
compressor. The compression mechanism (50) includes a fixed scroll
(51) and a movable scroll (54). The fixed scroll (51) is formed of
an end plate (52) on which a spiral-wall-like fixed side lap (53)
is vertically provided. The end plate (52) of the fixed scroll (51)
is fixed on the inner wall of the casing (31). On the other hand,
the movable scroll (54) is formed of a plate-like end plate (55) on
which a spiral-wall-like movable side lap (56) is vertically
provided. The fixed scroll (51) and the movable scroll (54) are
disposed face-to-face with each other. The fixed side lap (53) and
the movable side lap (56) engage with each other, thereby forming a
compression chamber (59). The movable scroll (54) includes a
protrusion portion formed at a central portion of the upper surface
of the end plate (55), and the small-diameter eccentric portion
(43) of the shaft (40) is rotatably fitted into the protrusion
portion. Further, the movable scroll (54) is supported by a frame
(57) via an Oldham ring (58). The Oldham ring (58) is for
controlling the rotation of the movable scroll (54) on its axis.
The movable scroll (54) is configured to revolve at a predetermined
turning radius, without rotating on its axis.
[0058] The suction pipe (32) is connected to an outer periphery
side of the fixed scroll (51). The outflow end of the suction pipe
(32) is open to the outermost periphery portion of the compression
chamber (59). The discharge pipe (33) is connected to the shaft
center of the fixed scroll (51). The inflow end of the discharge
pipe (33) is open to a central portion of the compression chamber
(59).
[0059] The expansion mechanism (60) is a so-called oscillating
piston type fluid device as shown in FIG. 2 and FIG. 3, and forms
an expander according to the present invention. The expansion
mechanism (60) includes a cylinder (71), a piston (75) accommodated
in the cylinder (71), a front head (61), and a rear head (62). In
the expansion mechanism (60), the front head (61), the cylinder
(71), and the rear head (62) are stacked in this order from one end
to the other end of the axis of the shaft (40). The cylinder (71)
has a circular cylindrical shape whose both ends are open. One end
of the cylinder (71) is closed by the front head (61), and the
other end is closed by the rear head (62). The main shaft portion
(44) of the shaft (40) passes through the front head (61), the
cylinder (71), and the rear head (62).
[0060] The piston (75) has a circular cylindrical shape whose outer
diameter is smaller than the inner diameter of the cylinder (71).
The outer periphery surface of the piston (75) is slidable on the
inner periphery surface of the cylinder (71); one end surface of
the piston (75) is slidable on the front head (61); and the other
end surface of the piston (75) is slidable on the rear head (62). A
fluid chamber (72) is formed between the inner periphery surface of
the cylinder (71) and the outer periphery surface of the piston
(75).
[0061] Further, the expansion mechanism (60) is provided with a
blade (76) and a pair of bushes (77). The blade (76) is integrally
formed with the piston (75). The blade (76) has a plate-like shape
which extends radially outward from the outer periphery surface of
the piston (75). The fluid chamber (72) in the cylinder (71) is
divided by the blade (76) into a high pressure chamber (73) in
which the pressure of the refrigerant is high, and a low pressure
chamber (74) in which the pressure of the refrigerant is low (see
FIG. 3).
[0062] The pair of bushes (77) are disposed so as to fit in a bush
groove in the cylinder (71). Each bush (77) has a flat surface and
an arc-shaped outer surface, thereby forming a generally half-moon
shape, and the flat surfaces face each other. The blade (76) is
held slidable between the bushes (77). In other words, in the
expansion mechanism (60), the bush (77) is rotatable with respect
to the cylinder (71), and the blade (76) is movable back and forth
with respect to the bush (77).
[0063] The cylinder (71) is provided with an inflow port (81) and
an outflow port (82). The inflow port (81) forms an inflow opening
for introducing a high pressure refrigerant into the fluid chamber
(72). The outflow port (82) forms an outflow opening for
discharging a low pressure refrigerant depressurized in the fluid
chamber (72) to the outside of the fluid chamber (72).
[0064] Specifically, the inflow port (81) and the outflow port (82)
pass through the cylinder (71) in a radial direction. The inflow
port (81) and the outflow port (82) are formed in the cylinder (71)
such that they are located close to the bush (77) and that they
have the bush (77) interposed therebetween. The inside of each of
the inflow port (81) and the outflow port (82) forms a channel
having a circular cross section. Here, diameters of the inflow port
(81) and the outflow port (82) are uniform from the inflow end to
the outflow end.
[0065] The inflow port (81) is formed at a location in the cylinder
(71) that is slightly shifted from the bush (77) in a clockwise
direction. The outflow end of the inflow pipe (34) is connected to
the inflow end of the inflow port (81). The outflow end of the
inflow port (81) is open in the high pressure chamber (73) of the
fluid chamber (72). The outflow port (82) is formed at a location
in the cylinder (71) that is slightly shifted from the bush (77) in
a counterclockwise direction. The inflow end of the outflow port
(82) is open in the low pressure chamber (74) of the fluid chamber
(72). The inflow end of the outflow pipe (35) is connected to the
outflow end of the outflow port (82).
[0066] <Design Values of Expander>
[0067] Next, design values of an expansion mechanism (60) according
to the present embodiment will be described. Here, FIG. 4 shows an
example of each design point of the expansion mechanism (60) based
on operational conditions of the air conditioner (10). FIG. 5 shows
an example of each design dimension of the expansion mechanism
(60).
[0068] As shown in FIG. 4, when a normal refrigeration cycle is
performed in the refrigerant circuit (20) of the air conditioner
(10), the pressure Pi of the refrigerant of the high pressure side
(inflow side) of the expansion mechanism (60) is 11.5 [MPa], and
the temperature Ti of the refrigerant of the high pressure side is
10.degree. C. Further, the pressure Po of the refrigerant of the
low pressure side (outflow side) of the expansion mechanism (60) is
3.5 [Mpa], and the temperature To of the refrigerant of the high
pressure side is 0.degree. C. Moreover, the density .rho.i of the
refrigerant of the inflow side (i.e., in the inflow port (81)) of
the expansion mechanism (60) is 931.7 [kg/m.sup.3], and the density
.rho.o of the refrigerant of the outflow side (i.e., in the outflow
port (82)) of the expansion mechanism (60) is 713.3
[kg/m.sup.3].
[0069] FIG. 5 shows example design dimensions for each of three
types (A, B, and C) of the expansion mechanism (60) having a
different cylinder capacity Vcc. Here, in these expansion
mechanisms (60), the diameter Di of the inflow port (81) is set
based on the inner diameter Dc of the cylinder (71). Specifically,
in the respective expansion mechanisms (60), the relationship
between the inner diameter Dc [mm] of the cylinder and the diameter
Di [mm] of the inflow port is set to satisfy
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc. Further, the inflow
port (81) of each expansion mechanism (60) has a diameter Di which
satisfies Di=0.085.times.Dc. On the other hand, in each expansion
mechanism (60), the diameter of the outflow port (82) is set based
on the diameter Di of the inflow port (81) and the density .rho.i
and the density .rho.o of the above-described refrigerant.
Specifically, the outflow port (82) of each expansion mechanism
(60) has a diameter Do [mm] which satisfies
Do=Di.times.(.rho.i/.rho.o).sup.2.
[0070] In the present embodiment, the diameters of the inflow port
(81) and the outflow port (82) are set as described above, thereby
avoiding the blow-by phenomenon of the refrigerant from the inflow
port (81) to the outflow port (82), and reducing the pressure loss
of the refrigerant in the inflow port (81) and the outflow port
(82). This will be described in detail later.
[0071] --Operational Behavior--
[0072] Next, a general operational behavior of the air conditioner
(10) will be described with reference to FIG. 1. In the air
conditioner (10), the operation is switched between a cooling
operation and a heating operation.
[0073] During a cooling operation, the first four-way switching
valve (21) and the second four-way switching valve (22) are
switched into the state as shown in broken line in FIG. 1. If the
motor (45) of the compressor-expander unit (30) is energized in
this state, the refrigerant circulates in the refrigerant circuit
(20) to perform a vapor compression refrigerating cycle.
[0074] The high pressure refrigerant compressed in the compression
mechanism (50) is discharged from the compressor-expander unit (30)
through the discharge pipe (33). The high pressure refrigerant is
transferred to the outdoor heat exchanger (23), and heat is
dissipated to the outdoor air. The high pressure refrigerant whose
heat is dissipated in the outdoor heat exchanger (23) flows into
the expansion mechanism (60) of the compressor-expander unit (30)
through the inflow pipe (34). The high pressure refrigerant is
depressurized in the fluid chamber (72) of the expansion mechanism
(60). Here, the internal energy of the refrigerant is converted to
the rotational power of the shaft (40). The low pressure
refrigerant depressurized in the fluid chamber (72) flows out of
the compressor-expander unit (30) through the outflow pipe
(35).
[0075] The low pressure refrigerant is transferred to the indoor
heat exchanger (24). In the indoor heat exchanger (24), the low
pressure refrigerant absorbs heat from a room air and evaporates,
thereby cooling the room air. The low pressure refrigerant which
flows out from the indoor heat exchanger (24) is sucked into the
compression mechanism (50) of the compressor-expander unit (30)
through the suction pipe (32), and is compressed again by the
compression mechanism (50).
[0076] During a heating operation, the first four-way switching
valve (21) and the second four-way switching valve (22) are
switched into the state as shown in solid line in FIG. 1. If the
motor (45) of the compressor-expander unit (30) is energized in
this state, the refrigerant circulates in the refrigerant circuit
(20) to perform a vapor compression refrigerating cycle.
[0077] The high pressure refrigerant compressed in the compression
mechanism (50) is discharged from the compressor-expander unit (30)
through the discharge pipe (33). The high pressure refrigerant is
transferred to the indoor heat exchanger (24). In the indoor heat
exchanger (24), heat of the high pressure refrigerant is dissipated
into the room air, thereby heating the room air. The high pressure
refrigerant whose heat is dissipated in the indoor heat exchanger
(24) flows into the expansion mechanism (60) of the
compressor-expander unit (30) through the inflow pipe (34). The
high pressure refrigerant is depressurized in the fluid chamber
(72) of the expansion mechanism (60). Here, the internal energy of
the refrigerant is converted to the rotational power of the shaft
(40). The low pressure refrigerant depressurized in the fluid
chamber (72) flows out of the compressor-expander unit (30) through
the outflow pipe (35).
[0078] The low pressure refrigerant is transferred to the outdoor
heat exchanger (23), where the low pressure refrigerant absorbs
heat from the outdoor air and evaporates. The low pressure
refrigerant which flows out from the outdoor heat exchanger (23) is
sucked into the compression mechanism (50) of the
compressor-expander unit (30) through the suction pipe (32), and is
compressed again by the compression mechanism (50).
[0079] Next, a behavior of the expansion mechanism (60) will be
described with reference to FIG. 6. In FIG. 6, drawings of the
piston (75) whose rotational angle is different by 90.degree. in a
clockwise direction are sequentially shown in FIG. 6(A), (B), (C),
and (D). In the expansion mechanism (60), a process in which a
capacity of the high pressure chamber (73) increases (inflow
process) and a process in which a capacity of the low pressure
chamber (74) decreases (outflow process) are simultaneously
performed as the shaft (40) rotates.
[0080] First, the inflow process in which the high pressure
refrigerant flows into the fluid chamber (72) of the expansion
mechanism (60) will be described. When the shaft (40) slightly
rotates from the position shown in FIG. 6(D), and the contact point
between the piston (75) and the cylinder (71) passes by the inflow
port (81), the high pressure refrigerant starts to flow into the
fluid chamber (72) through the inflow port (81). After that, as the
shaft (40) rotates as sequentially shown in FIG. 6(A), (B) and (C),
thereby increasing the capacity of the high pressure chamber (73),
the refrigerant is sequentially taken into the fluid chamber (72)
through the inflow port (81). Here, the high pressure refrigerant
is depressurized, and at the same time, the piston (75) is rotated
by the internal energy of the refrigerant. The inflow of the high
pressure refrigerant into the high pressure chamber (73) continues
until the rotational angle of the piston (75) reaches
360.degree..
[0081] Here, in the present embodiment, the inflow port (81) and
the outflow port (82) in the state of FIG. 6(D) are separated by
the piston (75). In other words, the diameter Di of the inflow port
(81) according to the present embodiment is set to satisfy
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc. Therefore,
communication between the inflow port (81) and the outflow port
(82) via the fluid chamber (72) is avoided in the state of FIG.
6(D). With this structure, the refrigerant having flowed into the
fluid chamber (72) through the inflow port (81) is prevented from
flowing to the outside through the outflow port (82) without giving
the internal energy to the piston (75) and the shaft (40).
[0082] Next, the outflow process in which the low pressure
refrigerant flows out of the low pressure chamber (74) of the
expansion mechanism (60) will be described. When the shaft (40)
slightly rotates from the position shown in FIG. 6(D), and the
contact point between the piston (75) and the cylinder (71) reaches
the outflow port (82), the low pressure chamber (74) and the
outflow port (82) communicate with each other. As a result, the low
pressure refrigerant in the low pressure chamber (74) starts to
flow out of the fluid chamber (72) through the outflow port (82).
After that, as the shaft (40) rotates as sequentially shown in FIG.
6(A), (B) and (C), thereby reducing the capacity of the low
pressure chamber (74), the refrigerant is sequentially discharged
from the fluid chamber (72) to the outside through the outflow port
(82). The outflow of the low pressure refrigerant from the low
pressure chamber (74) continues until the rotational angle of the
piston (75) reaches 360.degree..
Effects of Embodiment
[0083] In the above embodiment, the diameter Di of the inflow port
(81) satisfies the relationship
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc. With this structure,
it is possible to increase the efficiency of the expansion
mechanism (60) (power recovery efficiency) to a maximum in the
present embodiment. This will be described with reference to FIG. 7
and FIG. 8.
[0084] First, FIG. 7 shows a relationship between an inflow port
diameter Di and the theoretical efficiency of an expander, with
respect to three types of expansion mechanisms (A, B, C) having a
different cylinder capacity (i.e., cylinder's inner diameter Dc).
As shown in the drawing, in the case of the expansion mechanism A
whose cylinder's inner diameter Dc is about 22 [mm], the efficiency
of the expander is increased to its maximum when the inflow port
diameter Di is set to about 1.9 mm (the point "a" in FIG. 7). On
the other hand, in the case where the inflow port diameter Di of
the expansion mechanism A is too large (e.g., about 2.9 [mm] or
so), the efficiency of the expander of the expansion mechanism A
decreases. This is because if the inflow port diameter Di is too
large, the inflow port (103) and the outflow port (104) communicate
with each other as shown, for example, in FIG. 9(D), and a
so-called blow-by phenomenon occurs. Also, in the case where the
inflow port diameter Di of the expansion mechanism A is too small
(e.g., about 1.2 [mm] or so), the efficiency of the expander of the
expansion mechanism A decreases. This is because if the inflow port
diameter Di is too small, the pressure loss of the refrigerant
cannel in the inflow port (81) increases, and so-called indicated
efficiency decreases.
[0085] Similarly, in the case of the expansion mechanism B whose
cylinder's inner diameter Dc is about 30 [mm], the efficiency of
the expander is increased to its maximum when the inflow port
diameter Di is set to about 2.6 mm (the point "b" in FIG. 7). In
the case of the expansion mechanism C whose cylinder's inner
diameter Dc is about 38 [mm], the efficiency of the expander is
increased to its maximum when the inflow port diameter Di is set to
about 3.2 [mm] (the point "c" in FIG. 7).
[0086] FIG. 8 is a graph showing a relationship between the
cylinder's inner diameter Dc and the inflow port diameter Di
obtained by approximation, for achieving high efficiency of each of
the above expansion mechanisms A, B and C. That is, high efficiency
can be achieved by setting the inflow port diameter Di to satisfy
0.085.times.Dc in relation to the cylinder's inner diameter Dc, as
the relations in FIG. 8 indicate. Further, the hatched area in FIG.
8 indicates a range in which the theoretical efficiency of the
expander shown in FIG. 7 is about 90% or more (the line L or above
in FIG. 7). In other words, relatively high efficiency of the
expander can be achieved by setting the inflow port diameter Di to
satisfy the relationship
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc in relation to the
cylinder's inner diameter Dc.
[0087] In other words, according to the present embodiment, the
diameter Di [mm] of the inflow port (81) satisfies the relationship
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc. Therefore, the
inflow port diameter Di is not too large, and thus, a so-called
blow-by phenomenon can be prevented; and the inflow port diameter
Di is not too small, and thus, an increase in pressure loss in the
inflow port (81) can be prevented. As a result, desired efficiency
can be obtained in the expansion mechanism (60) according to the
present embodiment, thereby making it possible to enhance the
energy saving characteristics of the air conditioner (10) to which
the expander is applied.
[0088] On the other hand, according to the present embodiment, the
diameter Do [mm] of the outflow port (82) is set to satisfy
Do=Di.times.(.rho.i/.rho.o).sup.2. Here, if the inflow port
diameter Di and the outflow port diameter Do are set to have the
same diameter, the outflow port diameter Do may be too small and
the pressure loss in the outflow port (82) may be slightly
increased, because a fluid whose density is lower than the density
of a fluid flowing in the inflow port (81) flows in the outflow
port (82). In view of this, according to the present embodiment, a
ratio of the density .rho.i of the refrigerant of the inflow side
(high pressure side) to the density .rho.o of the refrigerant of
the outflow side (low pressure side) (i.e., density ratio
.rho.i/.rho.o) is considered, and the outflow port diameter Do is
decided by multiplying the inflow port diameter Di by the square of
the density ratio (.rho.i/.rho.o). With this structure, it is
possible to avoid an increase in pressure loss in the outflow port
(82), and possible to further enhance the efficiency of the
expansion mechanism (60).
Other Embodiments
[0089] The following structures may be used in the above
embodiment.
[0090] In the above embodiment, the diameter Di [mm] of the inflow
port (81) is set to satisfy the relationship
0.065.times.Dc.ltoreq.Di.ltoreq.0.13.times.Dc. However, instead of
this relationship, the diameter Do of the outflow port (82) may be
set to satisfy the relationship
0.065.times.Dc.ltoreq.Do.ltoreq.0.13.times.Dc. In this case as
well, it is possible to prevent the occurrence of a blow-by
phenomenon because of the too large Do, and possible to avoid an
increase in pressure loss because of too small Do. As a result, in
this case as well, it is possible to achieve high efficiency of the
expansion mechanism (60). Further, in this case, the diameter Di of
the inflow port (81) is set to satisfy the relationship
Di=Do.times.(.rho.o/.rho.i).sup.2. Here, if the inflow port
diameter Di and the outflow port diameter Do are set to have the
same diameter, the diameter of the inflow port (81) may be larger
than desired, because a fluid whose density is higher than the
density of a fluid flowing in the inflow port (81) flows in the
outflow port (82). In view of this, a ratio of the density .rho.i
of the refrigerant of the inflow side (high pressure side) to the
density .rho.o of the refrigerant of the outflow side (low pressure
side) (i.e., density ratio .rho.i/.rho.o) may be considered, and
the inflow port diameter Di may be decided by multiplying the
outflow port diameter Do by the square of the density ratio
(.rho.o/.rho.i).
[0091] The foregoing embodiments are merely preferred examples in
nature, and are not intended to limit the scope, applications, and
use of the invention.
INDUSTRIAL APPLICABILITY
[0092] As described above, the present invention is useful for an
expander which recovers power of a fluid depressurized in a
cylinder.
* * * * *