U.S. patent application number 10/813779 was filed with the patent office on 2004-10-28 for refrigeration cycle apparatus and unit for refrigeration cycle apparatus.
Invention is credited to Iguchi, Masao, Iwasa, Jiro, Kawaguchi, Masahiro, Murase, Masakazu.
Application Number | 20040211203 10/813779 |
Document ID | / |
Family ID | 32844657 |
Filed Date | 2004-10-28 |
United States Patent
Application |
20040211203 |
Kind Code |
A1 |
Murase, Masakazu ; et
al. |
October 28, 2004 |
Refrigeration cycle apparatus and unit for refrigeration cycle
apparatus
Abstract
A refrigeration cycle apparatus has a compressor, a radiator, an
expansion device, an evaporator, and a variable-speed mechanism.
When a rotary shaft of the compressor is rotated, the compressor
increases the pressure of refrigerant. The radiator cools
refrigerant the pressure of which has been increased by the
compressor. The expansion device generates power using the
decompression and expansion and transmits the power to the rotary
shaft. The evaporator heats refrigerant that has been decompressed
and expanded by the expansion device. The variable-speed mechanism
is capable of changing the discharge rate of the expansion device
per rotation of the rotary shaft. This permits the expansion device
to increase the amount of recovered power.
Inventors: |
Murase, Masakazu;
(Kariya-shi, JP) ; Kawaguchi, Masahiro;
(Kariyaj-shi, JP) ; Iguchi, Masao; (Kariya-shi,
JP) ; Iwasa, Jiro; (Kariya-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
3 WORLD FINANCIAL CENTER
NEW YORK
NY
10281-2101
US
|
Family ID: |
32844657 |
Appl. No.: |
10/813779 |
Filed: |
March 31, 2004 |
Current U.S.
Class: |
62/226 ; 62/172;
62/228.4; 62/87 |
Current CPC
Class: |
F04B 35/002 20130101;
F25B 9/008 20130101; F04B 27/10 20130101; F25B 2309/061 20130101;
F25B 2600/0253 20130101; Y02B 30/741 20130101; Y02B 30/70 20130101;
F25B 9/06 20130101; F25B 1/04 20130101; F25B 2400/076 20130101 |
Class at
Publication: |
062/226 ;
062/087; 062/172; 062/228.4 |
International
Class: |
F25B 049/00; F28B
009/00; F25B 009/00; F25B 007/00; F25B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2003 |
JP |
2003-097047 |
Claims
1. A refrigeration cycle apparatus, comprising: a compressor having
a rotary shaft, wherein the rotary shaft is rotated by an external
drive source, wherein, when the rotary shaft is rotated, the
compressor increases the pressure of refrigerant; a radiator for
cooling refrigerant the pressure of which has been increased by the
compressor; an expansion device, wherein the expansion device
decompresses and expands refrigerant that has been cooled by the
radiator, and then discharges the refrigerant, and wherein the
expansion device generates power using the decompression and
expansion and transmits the power to the rotary shaft; an
evaporator, wherein the evaporator heats refrigerant that has been
decompressed and expanded by the expansion device; and a variable
discharge rate mechanism, which is capable of changing the
discharge rate of the expansion device per rotation of the rotary
shaft.
2. The refrigeration cycle apparatus according to claim 1, wherein
the expansion device has a rotary shaft, wherein the variable
discharge rate mechanism is a variable-speed mechanism located
between the rotary shaft of the compressor and the rotary shaft of
the expansion device, and wherein the variable-speed mechanism
changes the ratio of rotation speed between the rotary shaft of the
compressor and the rotary shaft of the expansion device.
3. The refrigeration cycle apparatus according to claim 2, wherein
the variable-speed mechanism is a planetary gear train.
4. The refrigeration cycle apparatus according to claim 1, wherein
the variable discharge rate mechanism is a variable displacement
mechanism, wherein the variable displacement mechanism is
incorporated in the expansion device and is capable of changing the
displacement of the expansion device.
5. The refrigeration cycle apparatus according to claim 4, wherein
the variable displacement mechanism includes a piston, a swash
plate that converts rotation of the rotary shaft into reciprocation
of the piston, and an actuator that changes the inclination angle
of the swash plate, and wherein the displacement of the expansion
device is changed according to the inclination angle of the swash
plate.
6. The refrigeration cycle apparatus according to claim 1, further
comprising: a refrigerant circulation passage that includes the
radiator, the evaporator, the compressor, and the expansion device;
a detection device that detects the pressure at an arbitrary
section in the refrigerant circulation passage; and a controller
that controls the variable discharge rate mechanism such that the
difference between a detection value of the detection device and a
predetermined target value is eliminated.
7. The refrigeration cycle apparatus according to claim 6, wherein
the detection device detects the pressure at a section of the
refrigerant circulation passage in the vicinity of an outlet of the
radiator.
8. The refrigeration cycle apparatus according to claim 6, wherein
the controller determines the target value based on the temperature
of the refrigerant at an outlet of the radiator.
9. The refrigeration cycle apparatus according to claim 1, wherein
the refrigerant is carbon dioxide.
10. The refrigeration cycle apparatus according to claim 1, wherein
the apparatus is mounted on a vehicle, and wherein the external
drive source is a drive source of the vehicle.
11. The refrigeration cycle apparatus according to claim 1, wherein
the compressor, the expansion device, and the variable discharge
rate mechanism are integrated.
12. The refrigeration cycle apparatus according to claim 11,
wherein the expansion device and the variable discharge rate
mechanism are incorporated in a housing of the compressor.
13. A unit incorporated in a refrigeration cycle apparatus, wherein
the refrigeration cycle apparatus includes a radiator for cooling
introduced refrigerant, and an evaporator for heating introduced
refrigerant, the unit comprising: a compressor having a rotary
shaft, wherein the rotary shaft is rotated by an external drive
source, wherein, when the rotary shaft is rotated, the compressor
increases the pressure of refrigerant and sends the refrigerant to
the radiator; an expansion device, wherein the expansion device
decompresses and expands refrigerant sent from the radiator, and
discharges the refrigerant to the evaporator, and wherein the
expansion device generates power using the decompression and
expansion and transmits the power to the rotary shaft; and a
variable discharge rate mechanism, wherein the variable discharge
rate mechanism changes the discharge rate of the expansion device
per rotation of the rotary shaft, and wherein the compressor, the
expansion device, and the variable discharge rate mechanism are
integrated.
14. The unit according to claim 13, wherein the expansion device
and the variable discharge rate mechanism are incorporated in a
housing of the compressor.
15. The unit according to claim 13, wherein the expansion device
has a rotary shaft, wherein the variable discharge rate mechanism
is a variable-speed mechanism located between the rotary shaft of
the compressor and the rotary shaft of the expansion device, and
wherein the variable-speed mechanism changes the ratio of rotation
speed between the rotary shaft of the compressor and the rotary
shaft of the expansion device.
16. The unit according to claim 13, wherein the variable-speed
mechanism is a planetary gear train.
17. The unit according to claim 13, wherein the variable discharge
rate mechanism is a variable displacement mechanism, wherein the
variable displacement mechanism is incorporated in the expansion
device and is capable of changing the displacement of the expansion
device.
18. The unit according to claim 17, wherein the variable
displacement mechanism includes a piston, a swash plate that
converts rotation of the rotary shaft into reciprocation of the
piston, and an actuator that changes the inclination angle of the
swash plate, and wherein the displacement of the expansion device
is changed according to the inclination angle of the swash
plate.
19. The unit according to claim 13, wherein the refrigerant is
carbon dioxide.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a refrigeration cycle
apparatus having a refrigerant circulation passage including a
compressor that increases the pressure of refrigerant, a radiator
that cools refrigerant the pressure of which has been increased by
the compressor, an expansion device that decompresses and expands
the refrigerant cooled by the radiator to extract power to drive
the compressor, and an evaporator for heating the refrigerant that
has been decompressed and expanded by the expansion device. The
present invention also pertains to a unit for the refrigeration
cycle apparatus.
[0002] Japanese Laid-Open Patent Publication No. 2002-22298
discloses such a refrigeration cycle apparatus. The refrigeration
cycle apparatus includes a refrigerant circulation passage that
includes a compressor, a radiator, an expansion device, and an
evaporator. The expansion device and a decompression valve are
located between the outlet of the radiator and the inlet of the
evaporator. The expansion device is located upstream of the
decompression valve. The expansion device decompresses and expands
refrigerant that has been cooled by the radiator, thereby
generating power. The expansion device then transmits the power to
the compressor. That is, the expansion device recovers power.
[0003] To transmit power extracted by the expansion device to the
compressor, a structure may be employed in which a rotary shaft for
transmitting power generated by the expansion device is connected
to-a rotary shaft for driving the compressor, so that the shafts
rotate integrally. However, in this structure, the flow rate of
refrigerant discharged by the expansion device can fluctuate under
the influence of rotation speed of the rotary shaft of the
compressor. The fluctuation influences the cycle pressure of the
refrigerant circulation passage. The decompression valve, for
example, may be constructed to adjust the cycle pressure to cancel
the influence.
[0004] Line 101 in FIG. 3 represents the relationship between the
enthalpy and the pressure of the refrigerant in the above described
refrigeration cycle apparatus. In the line 101, a condition A
represents the enthalpy and the pressure of the refrigerant at the
suction inlet of the compressor (that is, at the outlet of the
evaporator). A condition B represents the enthalpy and the pressure
of the refrigerant at the discharge outlet of the compressor (that
is, at the inlet of the radiator). A condition C represents the
enthalpy and the pressure of the refrigerant at the inlet of the
expansion device (that is, at the outlet of the radiator). A
condition D represents the enthalpy and the pressure of the
refrigerant at the outlet of the expansion device (that is, at the
inlet of the decompression valve). A condition E represents the
enthalpy and the pressure of the refrigerant at the outlet of the
decompression valve (that is, at the inlet of the evaporator).
[0005] In the aforementioned refrigeration cycle apparatus, the
refrigerant shifts from the condition C to the condition D due to
decompression and expansion by the expansion device. The difference
of enthalpy between the condition C and the condition D represents
the magnitude of power generated by the expansion device. The
refrigerant is shifted from the condition D to the condition E of a
lower pressure by the decompression valve.
[0006] However, although the above configuration is capable of
recovering power with the expansion device while regulating the
cycle pressure, the decompression valve decreases the pressure of
refrigerant by an amount corresponding to the pressure difference
between the condition D and the condition E in order to adjust the
cycle pressure. Therefore, the amount of power that corresponds to
the decompression cannot be recovered
SUMMARY OF THE INVENTION
[0007] Accordingly, it is an objective of the present invention to
provide a refrigeration cycle apparatus and a unit for the
refrigeration cycle apparatus that permit an expansion device to
increase the amount of recovered power.
[0008] To achieve the foregoing objective, the present invention
provides a refrigeration cycle apparatus. The refrigeration cycle
apparatus has a compressor, a radiator, an expansion device, an
evaporator, and a variable discharge rate mechanism. The compressor
has a rotary shaft. The rotary shaft is rotated by an external
drive source. When the rotary shaft is rotated, the compressor
increases the pressure of refrigerant. The radiator cools
refrigerant the pressure of which has been increased by the
compressor. The expansion device decompresses and expands
refrigerant that has been cooled by the radiator, and then
discharges the refrigerant. The expansion device generates power
using the decompression and expansion and transmits the power to
the rotary shaft. The evaporator heats refrigerant that has been
decompressed and expanded by the expansion device. The variable
discharge rate mechanism is capable of changing the discharge rate
of the expansion device per rotation of the rotary shaft.
[0009] The present invention also provides a unit incorporated in a
refrigeration cycle apparatus. The refrigeration cycle apparatus
includes a radiator for cooling introduced refrigerant, and an
evaporator for heating introduced refrigerant. The unit has a
compressor, an expansion device and a variable discharge rate
mechanism. The compressor has a rotary shaft. The rotary shaft is
rotated by an external drive source. When the rotary shaft is
rotated, the compressor increases the pressure of refrigerant and
sends the refrigerant to the radiator. The expansion device
decompresses and expands refrigerant sent from the radiator, and
discharges the refrigerant to the evaporator. The expansion device
generates power using the decompression and expansion and transmits
the power to the rotary shaft. The variable discharge rate
mechanism changes the discharge rate of the expansion device per
rotation of the rotary shaft. The compressor, the expansion device,
and the variable discharge rate mechanism are integrated.
[0010] Other aspects and advantages of the invention will become
apparent from the following description, taken in conjunction with
the accompanying drawings, illustrating by way of example the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention, together with objects and advantages thereof,
may best be understood by reference to the following description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0012] FIG. 1 is a cross-sectional view illustrating a unit for a
refrigeration cycle apparatus according a first embodiment of the
present invention;
[0013] FIG. 2 is a cross-sectional view illustrating an expansion
device having a variable-speed mechanism included in the
refrigerant circulation passage shown in FIG. 1;
[0014] FIG. 3 is a graph showing the relationship between the
enthalpy and the pressure of refrigerant used in the refrigerant
circulation passage of FIG. 1; and
[0015] FIG. 4 is a partial cross-sectional view illustrating a unit
for a refrigeration cycle apparatus according to a second
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] A vehicular refrigeration cycle apparatus and a unit for the
refrigeration cycle apparatus according to first and second
embodiments of the present invention will be described in the
following. In the second embodiment, only the components different
from the first embodiment are explained. Like or similar components
are given the like numbers and detailed explanations are
omitted.
[0017] First, the refrigeration cycle apparatus will be
described.
[0018] As shown in FIG. 1, the refrigeration cycle apparatus has a
refrigerant circulation passage, which includes a compressor 11, a
radiator 12, an expansion device 13, and an evaporator 14. Carbon
dioxide is used as refrigerant (fluid) in the refrigerant
circulation passage.
[0019] The refrigerant circulation passage has refrigerant passages
20, 21. The refrigerant passage 20 includes a pipe connecting a
discharge port 11b of the compressor 11 with an inlet 12a of the
radiator 12. The refrigerant passage 21 connects an outlet 12b of
the radiator 12 with an inlet 13a of the expansion device 13. The
refrigerant circulation passage also has refrigerant passages 22,
23. The refrigerant passage 22 connects an outlet 13b of the
expansion device 13 with an inlet 14a of the evaporator 14. The
refrigerant passage 23 connects an outlet 14b of the evaporator 14
with a suction port 11a of the compressor 11. A pressure sensor
(detection device) 12c and a temperature sensor 12d are provided at
the outlet 12b of the radiator 12. The pressure sensor 12c detects
the pressure of refrigerant at the outlet 12b, which represents a
cycle pressure in this embodiment. The temperature sensor 12d
detects the temperature of the refrigerant. Detection values of the
sensors 12c, 12d are sent to an air conditioner ECU 15 (see FIG.
2). The air conditioner ECU 15 functions as a controller.
[0020] The compressor 11 draws refrigerant from the evaporator 14
through the refrigerant passage 23 and the suction port 11a. The
compressor 11 compresses the drawn refrigerant, or increases the
pressure of the refrigerant. The compressor 11 then discharges the
compressed gas to the refrigerant passage 20 through the discharge
port 11b. The radiator 12 performs heat exchange between the
refrigerant from the refrigerant passage 20 and the outside air,
thereby cooling the refrigerant. The refrigerant in the radiator 12
is drawn to the expansion device 13 through the refrigerant passage
21. The expansion device 13 decompresses and expands the
refrigerant, thereby extracting power to be supplied to the
compressor 11. At the same time, the expansion device 13 discharges
the decompressed and expanded refrigerant to the refrigerant
passage 22 through the outlet 13b. The evaporator 14 performs heat
exchange between the refrigerant from the refrigerant passage 22
and the outside air, thereby heating the refrigerant.
[0021] The compressor 11 will now be described. The left end of the
compressor 11 in FIG. 1 is defined as the front of the compressor
11, and the right end is defined as the rear of the compressor
11.
[0022] The housing of the compressor 11 includes a cylinder block
31, a front housing member 32, a cylinder head 34, and a rear
housing member 35. The front housing member 32 is joined to the
front end of the cylinder block 31. The cylinder head 34 is joined
to the rear end of the cylinder block 31 with a valve assembly 33
in between. The rear housing member 35 is joined to the rear end of
the cylinder head 34.
[0023] A piston type compression mechanism 36 is accommodated in
the housing of the compressor 11. The compression mechanism 36
includes a compression mechanism rotary shaft 37 and a swash plate
38. The swash plate 38 rotates along rotation of the compression
mechanism rotary shaft 37. Pairs of shoes 39 are provided at the
peripheral portion of the swash plate 38. Rotation of the swash
plate 38 is converted into reciprocation of pistons 40 by the shoes
39. Refrigerant is compressed accordingly. A suction chamber 41 and
a discharge chamber 42 are defined in the cylinder head 34.
Refrigerant is drawn to the suction chamber 41 from the refrigerant
passage 23 through the suction port 11a. The refrigerant is then
drawn to compression chambers 43 and compressed in the compression
chambers 43. The compressed gas is discharged to the refrigerant
passage 20 through the discharge chamber 42 and the discharge port
11b.
[0024] A front portion of the compression mechanism rotary shaft 37
is rotatably supported by the front housing member 32 and protrudes
to the outside of the compressor housing. The front portion of the
compression mechanism rotary shaft 37, which extends to the outside
of the housing, is coupled to and driven by an engine Eg, which is
a drive source of the vehicle, by way of a power transmission
mechanism (not shown). The compression mechanism rotary shaft 37 is
rotated by power of the engine Eg. That is, the engine Eg functions
as a drive source of the compressor 11.
[0025] A rear portion of the compression mechanism rotary shaft 37
is rotatably supported by the cylinder block 31. The rear end of
the compression mechanism rotary shaft 37 extends through the valve
assembly 33 and projects rearward from the valve assembly 33 to be
located in a through hole 34a formed in the center of the cylinder
head 34.
[0026] The compression mechanism 36 is of a variable displacement
type. That is, the swash plate 38 is housed in a crank chamber 44
and can be inclined with respect to the compression mechanism
rotary shaft 37. The pressure in the crank chamber 44 is controlled
by adjusting the opening degree of a control valve 45. Accordingly,
the stroke of the pistons 40 is changed to vary the compressor
displacement.
[0027] The expansion device 13 will now be described.
[0028] The expansion device 13 is accommodated in the rear housing
member 35 of the compressor 11. The housing of the expansion device
13 is integrated with the housing of the compressor 11.
[0029] In this embodiment, the compressor 11 and the expansion
device 13 accommodated in the housing of the compressor 11 form a
unit for a refrigeration cycle apparatus.
[0030] A circulation hole 21b is formed in the rear housing member
35 to communicate with the inlet 13a of the expansion device 13. A
pipe 21a is attached to the rear housing member 35 to communicate
with the circulation hole 21b. The pipe 21a and the circulation
hole 21b form the refrigerant passage 21. A circulation hole 22b is
formed in the rear housing member 35 to communicate with the outlet
13b of the expansion device 13. A pipe 22a is attached to the rear
housing member 35 to communicate with the circulation hole 22b. The
pipe 22a and the circulation hole 22b form the refrigerant passage
22.
[0031] As shown in FIG. 2, the expansion device 13 includes a vane
type expansion mechanism 50, and a variable-speed mechanism 51
forming a variable discharge rate mechanism. The housing of the
expansion device 13 is formed of a front housing member 52 and a
rear housing member 54, which is joined to the rear end of the
front housing member 52 with a wall plate 53 in between. The front
housing member 52 and the wall plate 53 serve as the housing of the
variable-speed mechanism 51. That is, in this embodiment, the
housing of the variable-speed mechanism 51 forms part of the
housing of the expansion device 13.
[0032] The expansion mechanism 50 includes a substantially
cylindrical rotor 56. Vane grooves are formed in radial directions
on the outer circumferential surface of the rotor 56. The expansion
mechanism 50 also has vanes each of which received by one of the
vane grooves to reciprocate therein.
[0033] A rotor chamber 57 is defined between the wall plate 53 and
the rear housing member 54. The rotor 56 is fixed to an expansion
mechanism rotary shaft 55 to rotate integrally with the expansion
mechanism rotary shaft 55. The expansion mechanism rotary shaft 55
extends through the rotor chamber 57 and rotatably supported by the
wall plate 53 and the rear housing member 54 with bearings. A space
defined by the inner circumferential surface of the rotor chamber
57, the outer circumferential surface of the rotor 56, and each
adjacent pair of the vanes consists a refrigerant chamber 57a to
decompress and expand refrigerant. Refrigerant is drawn into each
refrigerant chamber 57a through the inlet 13a. The refrigerant is
then decompressed and expanded, which generates rotational force of
the rotor 56. The rotational force is extracted as power by way of
the expansion mechanism rotary shaft 55. When the refrigerant
chamber 57a is moved to a downstream side, the decompressed and
expanded refrigerant is discharged to the refrigerant passage 22
from the refrigerant chamber 57a through the outlet 13b.
[0034] In the expansion device 13, a variable-speed mechanism
chamber 58 is defined between the front housing member 52 and the
wall plate 53 to accommodate the variable-speed mechanism 51. A
through hole 53a is formed in the wall plate 53. The expansion
mechanism rotary shaft 55 protrudes into the variable-speed
mechanism chamber 58 through the through hole 53a. The
variable-speed mechanism 51 is a planetary gear train. An internal
gear 60, which is part of the variable-speed mechanism 51, is fixed
to the front end portion of the expansion mechanism rotary shaft
55, which protrudes into the variable-speed mechanism chamber 58.
The internal gear 60 rotates integrally with the expansion
mechanism rotary shaft 55.
[0035] A variable-speed mechanism rotary shaft 61 is rotatably
supported by the front wall of the front housing member 52 with
bearings. A front end portion of the variable-speed mechanism
rotary shaft 61 protrudes frontward of the front housing member 52
through a through hole 52a formed in the front wall of the front
housing member 52. A sun gear 62 is fixed to the rear end of the
variable-speed mechanism rotary shaft 61 to rotate integrally with
the shaft 61.
[0036] Three planetary gears 63 (only two of which are shown in
FIG. 2) are located between and meshed with the internal gear 60
and the sun gear 62.
[0037] A gear carrier 64 is supported on the outer circumferential
surface of the variable-speed mechanism rotary shaft 61 to rotate
relative to the variable-speed mechanism rotary shaft 61. Three
support shafts 64b projects from the gear carrier 64. Each
planetary gear 63 is rotatably supported by the gear carrier 64
with one of the support shafts 64b. A main body 64a of the gear
carrier 64 is formed as a spur gear. A teeth portion 64c of the
main body 64a is meshed with a gear (not shown) fixed to an output
shaft of an electric motor 65. The rotation speed of the gear
carrier 64 about the axis of the variable-speed mechanism rotary
shaft 61 is adjusted by controlling the electric motor 65, that is
by controlling the rotation speed and the rotation direction of the
electric motor 65.
[0038] An engagement recess 61a is formed in the front end face of
the variable-speed mechanism rotary shaft 61. The engagement recess
61a is engaged with an engagement projection 37a formed on the rear
end face of the compression mechanism rotary shaft 37 (see FIG. 1).
The engagement permits power to be transmitted between the
compression mechanism rotary shaft 37 and the variable-speed
mechanism rotary shaft 61. That is, the variable-speed mechanism 51
is located in the power transmission path between the compression
mechanism rotary shaft 37 and the expansion mechanism rotary shaft
55.
[0039] Control of the electric motor 65 permits the variable-speed
mechanism 51 to continuously change the ratio of the rotation
speed, or the gear ratio, between the compression mechanism rotary
shaft 37 and the expansion mechanism rotary shaft 55. Adjusting the
rotation speed ratio between the compression mechanism rotary shaft
37 and the expansion mechanism rotary shaft 55 permits the
discharge rate of the expansion device 13 per rotation of the
compression mechanism rotary shaft 37 to be adjusted.
[0040] The air conditioner ECU 15 controls the electric motor 65
based on a detection value of the pressure sensor 12c and a
detection value of the temperature sensor 12d such that the
refrigerant pressure at the outlet 12b of the radiator 12
corresponds to the refrigerant temperature, thereby maintaining a
coefficient of performance (COP) at a high level. That is, based on
a detection value of the temperature sensor 12d, the air
conditioner ECU 15 computes a target value of the cycle pressure
that maintains the COP at a high level. The air conditioner ECU 15
controls the electric motor 65 to eliminate the difference between
the detection value of the pressure sensor 12c and the target
value.
[0041] When the detection value of the pressure sensor 12c is lower
than the target value, the air conditioner ECU 15 controls the
electric motor 65 to reduce the rotation speed of the expansion
mechanism rotary shaft 55. Reduction of the rotation speed of the
expansion mechanism rotary shaft 55 decreases the rate of
refrigerant discharged by the expansion device 13, which increases
the refrigerant pressure at the outlet 12b of the radiator 12. In
contrast, when the detection value of the pressure sensor 12c is
higher than the target value, the air conditioner ECU 15 controls
the electric motor 65 to increase the rotation speed of the
expansion mechanism rotary shaft 55. An increase of the rotation
speed of the expansion mechanism rotary shaft 55 increases the rate
of refrigerant discharged by the expansion device 13, which lowers
the refrigerant pressure at the outlet 12b of the radiator 12.
[0042] This embodiment provides the following advantages.
[0043] (1) The refrigeration cycle apparatus of this embodiment has
a variable discharge rate mechanism (the variable-speed mechanism
51), which is capable of changing the discharge rate of the
expansion device 13 per rotation of the compression mechanism
rotary shaft 37. Accordingly, even if the rotation speed of the
compression mechanism rotary shaft 37 fluctuates, the cycle
pressure is adjusted by changing the discharge rate of the
expansion device 13 per rotation of the compression mechanism
rotary shaft 37. Therefore, the configuration of this embodiment
permits the expansion device 13 to recover power while adjusting
the cycle pressure without a decompression valve for adjusting the
cycle pressure between the outlet 13b of the expansion device 13
and the inlet 14a of the evaporator 14 in the refrigerant
circulation passage.
[0044] Using the recovered power to drive the compressor 11
improves the COP of the refrigeration cycle apparatus.
[0045] Line 111 of FIG. 3 represents the relationship between the
enthalpy and the pressure of the refrigerant in the refrigeration
cycle apparatus according to this embodiment. In this embodiment,
the state of the relationship between the enthalpy and the pressure
shifts in the order of a state A, a state B, a state C, a state F,
and then the state A. The state F represents the state at the
outlet 13b of the expansion device, 13, that is, at the inlet 14a
of the evaporator 14. Unlike the prior art configuration with the
decompression valve described in the prior art section, the
expansion device 13 is capable of decompress refrigerant such that
the pressure of the refrigerant drops from the state C to the state
F without preserving the amount of pressure that corresponds to the
decompression by the decompression valve (the pressure difference
between the state D and the state E). In this embodiment, in
addition to the power generated by the expansion device 13 as the
state shifts from the state C to the state D, power generated by
the expansion device 13 as the state shifts from the state D to the
state F (power corresponding to the enthalpy difference between the
state D and the sate F) is recovered. Accordingly, the amount of
the recovered power is increased.
[0046] (2) The expansion device 13 is incorporated in the
compressor 11, and the housing of the compressor 11 and the housing
of the expansion device 13 are integrated. The housing of the
expansion device 13 forms part of the housing of the variable-speed
mechanism 51. Accordingly, compared to, for example, a case where
the housings are separately formed and not fixed to one another,
the piping between the compressor 11 and the expansion device 13 in
the refrigerant circulation passage is facilitated. Further,
compared to a case where the housing of the variable-speed
mechanism 51 is separate and spaced from the housing of the
expansion device 13 and the housing of the compressor 11, the
structure for transmitting power generated by the expansion device
13 to the compressor 11 is easily simplified and downsized.
[0047] (3) The variable-speed mechanism 51 is located in the power
transmission path between the compression mechanism rotary shaft 37
and the expansion mechanism rotary shaft 55, and the variable-speed
mechanism 51 is capable of changing the rotation speed ratio
between the compression mechanism rotary shaft 37 and the expansion
mechanism rotary shaft 55. Therefore, by adjusting the rotation
speed ratio between the compression mechanism rotary shaft 37 and
the expansion mechanism rotary shaft 55 in the variable-speed
mechanism 51, the discharge rate of the expansion device 13 per
rotation of the compression mechanism rotary shaft 37 is
controlled. Accordingly, the flow rate of refrigerant discharged by
the expansion device 13 is controlled.
[0048] (4) The variable-speed mechanism 51 is a planetary gear
train. Since the planetary gear train permits the rotation speed
ratio between the compression mechanism rotary shaft 37 and the
expansion mechanism rotary shaft 55 to be continuously changed, the
discharge rate of the expansion device 13 per rotation of the
compression mechanism rotary shaft 37 can be finely adjusted.
[0049] (5) The air conditioner ECU 15 drives the variable discharge
rate mechanism (the variable-speed mechanism 51) in a direction to
cancel the difference between the detection value of the pressure
sensor 12c and the target value, thereby adjusting the discharge
amount of the expansion device 13. This configuration permits the
COP of the refrigerant circulation passage to be accurately
maintained at a high level.
[0050] (6) The refrigerant is carbon dioxide. The COP of a
refrigeration cycle apparatus using carbon dioxide as refrigerant
is lower than that of a refrigeration cycle apparatus using
chlorofluorocarbon as refrigerant. Therefore, use of the power
generated by the expansion device 13 as drive force of the
compressor 11 is particularly effective for the refrigeration cycle
apparatus using carbon dioxide as refrigerant since the COP is
maintained at a high level.
[0051] (7) The engine Eg, which is the drive source of the vehicle,
is used as the drive source of the compressor 11. In such a
refrigeration cycle apparatus for a vehicle, the rotation speed of
the compression mechanism rotary shaft 37 is likely to be
influenced by the rotation speed of the engine Eg. Therefore, the
configuration for increasing the amount of recovered power by the
expansion device 13, which is capable of changing the discharge
rate per rotation of the compression mechanism rotary shaft 37,
while adjusting the cycle pressure is particularly effective for
improving the COP of the refrigeration cycle apparatus.
[0052] (8) The power generated by the expansion mechanism 50 of the
expansion device 13 is not converted into electricity, but is
transmitted to the compression mechanism rotary shaft 37 as
rotational force from the expansion mechanism rotary shaft 55 of
the expansion mechanism 50 through the variable-speed mechanism 51,
and is used as drive force of the compression mechanism 36.
Therefore, when compared to, for example, a configuration in which
power generated by an expansion device is converted into
electricity and a compression mechanism is driven by power of an
electric motor using the electricity, recovered power is
effectively used as drive force of the compression mechanism
without being wasted.
[0053] A second embodiment of the present invention will now be
described. In the first embodiment, the discharge rate of the
expansion device 13 per rotation of the compression mechanism
rotary shaft 37 is adjusted by adjusting the rotation speed ratio
between the compression mechanism rotary shaft 37 and the expansion
mechanism rotary shaft 55 with the variable-speed mechanism 51
provided on the power transmission path between the compression
mechanism rotary shaft 37 and the expansion mechanism rotary shaft
55. In contrast to this, in the second embodiment, the
variable-speed mechanism 51 is omitted, and the expansion device 13
is capable of changing the displacement. The displacement of the
expansion device 13 is adjusted to adjust the discharge rate of the
expansion device 13 per rotation of the compression mechanism
rotary shaft 37.
[0054] As shown in FIG. 4, an expansion device chamber 71 is
defined in the rear housing member 35 joined to the rear end of the
cylinder head 34 of the compressor 11. An expansion mechanism 70 of
the expansion device 13 of this embodiment is accommodated in the
expansion device chamber 71. The rear housing member 35 is used as
the housing of the expansion device 13. In this embodiment, the
compressor 11 and the expansion device 13 provided at the rear of
the compressor 11 form a unit for a refrigeration cycle
apparatus.
[0055] In the rear housing member 35, the expansion mechanism
rotary shaft 55 is rotatably supported with a bearing and extends
through the expansion device chamber 71. A front end portion of the
expansion mechanism rotary shaft 55 is inserted in the through hole
34a of the cylinder head 34. An engagement recess 55a is formed in
the front end face of the expansion mechanism rotary shaft 55.
Engagement of the recess 55a and the projection 37a on the
compression mechanism rotary shaft 37 permits power transmission
between the compression mechanism rotary shaft 37 and the expansion
mechanism rotary shaft 55.
[0056] The expansion mechanism 70 accommodated in the expansion
device chamber 71 is of an axial piston type. In the expansion
device chamber 71, a swash plate 72 having a cam surface 72a is
supported by the circumferential wall of the rear housing 35. The
swash plate 72 can be inclined with respect to the axis of the
expansion mechanism rotary shaft 55. A shaft hole 72b is formed in
the center of the swash plate 72 to receive the expansion mechanism
rotary shaft 55. The inclination angle the swash plate 72 (the cam
surface 72a) with respect to the axis of the expansion mechanism
rotary shaft 55 is changed by an actuator 79. The actuator 79
changes the inclination angle in response to a control signal from
the air conditioner ECU 15 (not illustrated in FIG. 4). The swash
plate 72 and the actuator 79 form a variable displacement mechanism
that is capable of changing the discharge amount of the expansion
mechanism 13.
[0057] The expansion mechanism 70 includes a cylinder block 73
located in the expansion device chamber 71. The cylinder block 73
is fitted about the expansion mechanism rotary shaft 55 to rotate
integrally with the shaft 55. Cylinder bores 74 are formed in the
cylinder block 73 about the expansion mechanism rotary shaft 55.
Although only two of them are shown in FIG. 4, the number of the
cylinder bores 74 is not limited to two. A piston 75 is
accommodated in each cylinder bore 74. Each piston 75 reciprocates
in the associated cylinder bore 74.
[0058] A shoe 76 is connected to each piston 75 with a spherical
joint 77. Each shoe 76 slides on the cam surface 72a of the swash
plate 72.
[0059] A valve plate 78 is fixed to a front surface 35a of the rear
wall of the rear housing member 35. The front surface of the valve
plate 78 and the rear surface of the cylinder 73 closely contact
each other and slide on each other.
[0060] An inlet port 78a and an outlet port 78b are formed in the
valve plate 78. The ports 78a, 78b extend between the front and
rear surfaces the valve plate 78. The inlet port 78a is connected
to the refrigerant passage 21 (the pipe 21a) through an inlet
passage 35b formed in the rear wall of the rear housing member 35.
That is, an opening of the inlet passage 35b that is connected to
the refrigerant passage 21 is the inlet 13a. Likewise, the outlet
port 78b is connected to the refrigerant passage 22 (the pipe 22a)
through an outlet passage 35c formed in the rear wall of the rear
housing member 35. That is, an opening of the outlet passage 35c
that is connected to the refrigerant passage 22 is the outlet
13b.
[0061] In a state where the inlet port 78a of the valve plate 78
communicates with one of the cylinder bores 74, refrigerant is
drawn to the cylinder bore 74 from the radiator 12 through the
inlet passage 35b. The refrigerant expands in the cylinder bore 74
and generates frontward thrust applied to the corresponding piston
75. The thrust presses the corresponding shoe 76 against the cam
surface 72a of the swash plate 72 with the corresponding spherical
joint 77. This generates a rotational force in the cylinder block
73 about the expansion mechanism rotary shaft 55. The expansion
device 13 extracts the rotational force as power and transmits the
power to the compression mechanism rotary shaft 37.
[0062] When the cylinder bore 74 communicates with the outlet port
78b as the cylinder block 73 rotates, the expanded refrigerant in
the cylinder bore 74 is discharged to the refrigerant passage 22
through the outlet port 78b and the outlet passage 35c.
[0063] In the expansion device 13 of this embodiment, the stroke of
the pistons 75 is changed according to the inclination angle of the
swash plate 72. The displacement is changed accordingly. As the
displacement is changed, the discharge rate of the expansion device
13 per rotation of the compression mechanism rotary shaft 37 is
adjusted. In other words, the variable displacement mechanism of
the expansion device 13 forms a variable discharge rate
mechanism.
[0064] The air conditioner ECU 15 controls the inclination angle of
the swash plate 72 (the cam surface 72a) with the actuator 79 based
on a detection value of the pressure sensor 12c and a detection
value of the temperature sensor 12d. To decrease the displacement
of the expansion device 13, the air conditioner ECU 15 inclines the
swash plate 72 in a direction decreasing the stroke of the pistons
75. Conversely, to increase the displacement, the air conditioner
ECU 15 inclines the swash plate 72 in a direction increasing the
stroke of the pistons 75.
[0065] The air conditioner ECU 15 controls the inclination angle of
the swash plate 72 such that the refrigerant pressure at the outlet
12b of the radiator 12 corresponds to the refrigerant temperature,
thereby maintaining the COP at a high level. That is, the air
conditioner ECU 15 computes a target value of the cycle pressure
suitable for maintaining the COP at a high level based on a
detection value of the temperature sensor 12d, then controls the
inclination angle such that the difference between the detection
value of the pressure sensor 12c and the target value is
eliminated.
[0066] When the detection value of the pressure sensor 12c is lower
than the target value, the air conditioner ECU 15 reduces the
inclination angle of the swash plate 72 such that the refrigerant
discharge amount of the expansion device 13 is reduced. In
contrast, when the detection value of the pressure sensor 12c is
higher than the target value, the air conditioner ECU 15 increases
the inclination angle of the swash plate 72 so that the refrigerant
discharge amount is increased.
[0067] In addition to the advantages (1), (2) and (5) to (8), the
second embodiment has the following advantage.
[0068] (9) The expansion device 13 of this embodiment is capable of
changing the displacement. This configuration permits the
displacement of the expansion device 13 per rotation of the
compression mechanism rotary shaft 37 to be adjusted by adjusting
the displacement of the expansion device 13. Accordingly, the
discharge rate of refrigerant discharged by the expansion device 13
is adjusted.
[0069] The invention may be embodied in the following forms.
[0070] In the first embodiment, the housing of the compressor 11
and the housing of the expansion device 13 are separate. However,
the housing of the expansion device 13 may be omitted, and the rear
housing member 35 of the compressor 11 may be used as the housing
of the expansion device 13.
[0071] In the illustrated embodiments, the expansion mechanism 50,
the variable-speed mechanism 51, and the compressor 11 are
integrated. However, at least one of the expansion mechanism 50 and
the variable-speed mechanism 51 may be separate and spaced from the
compressor 11.
[0072] In the first embodiment, the variable-speed mechanism 51 is
capable of continuously varying the rotation speed ratio between
the compression mechanism rotary shaft 37 and the expansion
mechanism rotary shaft 55. However, the variable-speed mechanism 51
need not be capable of continuously varying the rotation speed
ratio as long as the variable-speed mechanism 51 is capable of
varying the rotation speed ratio in multiple stages.
[0073] In the first embodiment, a scroll type expansion device may
be employed.
[0074] In the first embodiment, the variable-speed mechanism 51 has
the three planetary gears 63. However, this configuration may be
modified.
[0075] In the illustrated embodiments, the piston type compression
mechanism 36 that is capable of changing the displacement is used.
However, other types of compression mechanism may be used. A piston
type compression mechanism of fixed displacement may be employed.
Compression mechanisms other than piston type, for example, a
scroll type compression mechanism or a vane type compression
mechanism may be employed.
[0076] The present invention may be applied to a refrigeration
cycle apparatus that is not used in vehicles.
[0077] Refrigerant other than carbon dioxide may be used. For
example, chlorofluorocarbon may be used. When chlorofluorocarbon is
used as the refrigerant, for example, the pressure sensor 12c and
the temperature sensor 12d provided at the outlet of the radiator
12 are omitted. Instead, a pressure sensor (detection means) and a
temperature sensor are provided at the outlet 14b of the evaporator
14 to detect the refrigerant pressure (the cycle pressure) and the
refrigerant temperature at the outlet 14b. In this case, the air
conditioner ECU computes a target value of the cycle pressure
suitable for maintaining the COP at a high level based, for
example, on a detection value of the temperature sensor. Then, the
air conditioner ECU adjusts the discharge rate of the expansion
device 13 by driving the variable discharge rate mechanism in a
direction minimizing the difference between the detection value of
the pressure sensor and the target value.
[0078] The present examples and embodiments are to be considered as
illustrative and not restrictive and the invention is not to be
limited to the details given herein, but may be modified within the
scope and equivalence of the appended claims.
* * * * *