U.S. patent application number 12/528873 was filed with the patent office on 2010-05-13 for rotary compressor.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. Invention is credited to Kazuhiro Furusho, Masanori Masuda, Yoshitaka Shibamoto, Takashi Shimizu, Takazou Sotojima, Akio Yamagiwa, Yoshiki Yasuda.
Application Number | 20100119378 12/528873 |
Document ID | / |
Family ID | 39720934 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100119378 |
Kind Code |
A1 |
Shibamoto; Yoshitaka ; et
al. |
May 13, 2010 |
ROTARY COMPRESSOR
Abstract
A rotary compressor includes a compression mechanism, an
electric motor and a controller. The compression mechanism includes
a piston and a cylinder having two cylinder chambers. The electric
motor is configured to change volumes of the cylinder chambers by
eccentrically moving the cylinder and the piston relative to each
other. The controller is configured to change an output torque of
the electric motor in accordance with a variation in a load torque
of the compression mechanism in one turn of rotation.
Inventors: |
Shibamoto; Yoshitaka;
(Osaka, JP) ; Shimizu; Takashi; (Osaka, JP)
; Masuda; Masanori; (Osaka, JP) ; Sotojima;
Takazou; (Osaka, JP) ; Furusho; Kazuhiro;
(Osaka, JP) ; Yamagiwa; Akio; (Shiga, JP) ;
Yasuda; Yoshiki; (Shiga, 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: |
39720934 |
Appl. No.: |
12/528873 |
Filed: |
February 28, 2007 |
PCT Filed: |
February 28, 2007 |
PCT NO: |
PCT/JP2007/053811 |
371 Date: |
August 27, 2009 |
Current U.S.
Class: |
417/44.1 ;
417/410.4; 417/44.2; 417/463; 417/467; 418/163 |
Current CPC
Class: |
F04C 28/16 20130101;
F04C 18/3562 20130101; F04C 2270/125 20130101; F04C 18/045
20130101; F04C 2270/035 20130101; F04C 23/008 20130101; F04C 23/001
20130101 |
Class at
Publication: |
417/44.1 ;
417/44.2; 417/410.4; 417/463; 417/467; 418/163 |
International
Class: |
F04C 28/00 20060101
F04C028/00; F04C 18/32 20060101 F04C018/32; F04C 23/00 20060101
F04C023/00; F04C 15/00 20060101 F04C015/00 |
Claims
1. A rotary compressor, comprising: a compression mechanism
including a piston and a cylinder having two cylinder chambers; an
electric motor configured to change volumes of the cylinder
chambers by eccentrically moving the cylinder and the piston
relative to each other; and a controller configured to change an
output torque of the electric motor in accordance with a variation
in a load torque of the compression mechanism in one turn of
rotation.
2. The rotary compressor of claim 1, wherein the cylinder includes
an annular cylinder chamber, and the piston is an annular piston
housed in the annular cylinder chamber to partition the annular
cylinder chamber into an outer cylinder chamber and an inner
cylinder chamber, which form the two cylinder chambers.
3. The rotary compressor of claim 2, wherein a volume ratio of the
inner cylinder chamber to the outer cylinder chamber is in a range
from 0.6 to 1.0.
4. The rotary compressor of claim 2, wherein the electric motor is
a brushless DC motor.
5. The rotary compressor of claim 2, wherein the controller is
further configured to change an output torque of the electric motor
by changing one of an input current, an input voltage, and an input
current phase of the electric motor.
6. The rotary compressor of claim 2, wherein the electric motor is
coupled to the cylinder in order to move the cylinder relative to
the annular piston, and the annular piston is stationary.
7. The rotary compressor of claim 2, wherein the electric motor is
coupled to the annular piston in order to move the annular piston
relative to the cylinder, and the cylinder is stationary.
8. The rotary compressor of claim 2, wherein the compression
mechanism is configured to perform two-stage compression on a
fluid, with one of the outer and inner cylinder chambers being a
low-stage side and the other one of the outer and inner cylinder
chambers being a high-stage side.
9. The rotary compressor of claim 8, wherein a volume ratio of the
inner cylinder chamber to the outer cylinder chamber is in a range
from 0.6 to 0.8.
10. The rotary compressor of claim 1, wherein the cylinder includes
a low-stage first cylinder and a high-stage second cylinder, with
each of the first and second cylinders having one of the two
cylinder chambers, the piston includes a first rotary piston housed
in the cylinder chamber of the first cylinder and a second rotary
piston housed in the cylinder chamber of the second cylinder, and
the compression mechanism is configured to perform two-stage
compression on a fluid in the first and second cylinders by
eccentrically moving the first and second rotary pistons with the
electric motor.
11. The rotary compressor of claim 10, wherein a volume ratio of
the cylinder chamber of the second cylinder to the cylinder chamber
of the first cylinder is in a range from 0.6 to 0.8.
12. The rotary compressor of claim 10, wherein the compression
mechanism is configured such that a rotational phase of the first
rotary piston in of the first cylinder is shifted 180.degree. from
a rotational phase of the second rotary piston in the second
cylinder.
13. The rotary compressor of claim 3, wherein the electric motor is
a brushless DC motor.
14. The rotary compressor of claim 3, wherein the controller is
further configured to change an output torque of the electric motor
by changing one of an input current, an input voltage, and an input
current phase of the electric motor.
15. The rotary compressor of claim 3, wherein the electric motor is
coupled to the cylinder in order to move the cylinder relative to
the annular piston, and the annular piston is stationary.
Description
TECHNICAL FIELD
[0001] The present invention relates to rotary compressors, and
particularly relates to measures against vibration caused by a
variation in load torque.
BACKGROUND ART
[0002] As a conventional rotary compressor including two cylinder
chambers, a compressor which compresses refrigerant by utilizing a
variation in the volume of a cylinder chamber caused by eccentric
rotation of an annular piston has been employed, as disclosed in,
for example, Patent Document 1.
[0003] The compressor of Patent Document 1 includes: a cylinder
having an annular cylinder chamber; and an annular piston placed in
the cylinder chamber. The cylinder is composed of concentrically
disposed outer and inner cylinders. Specifically, a cylinder
chamber is formed between the outer cylinder and the inner
cylinder, and this cylinder chamber is partitioned into an outer
cylinder chamber and an inner cylinder chamber with an annular
piston. The annular piston is configured to eccentrically rotate
about the cylinder center by driving an electric motor, with the
outer peripheral surface of the annular piston being in contact
with the inner peripheral surface of the outer cylinder at
substantially one point, and with the inner peripheral surface of
the annular piston being in contact with the outer peripheral
surface of the inner cylinder at substantially one point.
[0004] An outer blade is provided outside the annular piston. An
inner blade is provided inside the annular piston on an extension
of the outer blade. The outer blade is inserted in the outer
cylinder, is radially biased toward the inside of the annular
piston, and has its tip in pressure contact with the outer
peripheral surface of the annular piston. The inner blade is
inserted in the inner cylinder, is radially biased toward the
outside of the annular piston, and has its tip in pressure contact
with the inner peripheral surface of the annular piston. The outer
and inner blades respectively partition the outer and inner
cylinder chambers into high-pressure chambers and low-pressure
chambers. In this compressor, eccentric rotation of the annular
piston causes fluid to be sucked into the low-pressure chamber and
to be compressed in the high-pressure chamber in each of the
cylinder chambers.
Patent Document 1: Japanese Laid-Open Patent Publication No.
6-288358
DISCLOSURE OF INVENTION
Problems that the Invention is to Solve
[0005] However, disadvantageously, in the compressor of the Patent
Document 1, the load torque of a drive shaft varies in one turn of
rotation. This variation causes the rotation speeds of the drive
shaft and a rotor of the electric motor for driving the drive shaft
to vary, resulting in that vibration occurs in the tangential
direction of a casing in which a stator of the electric motor is
fixed. In a possible worst case, a pipe connected to the casing
might be broken.
[0006] It is therefore an object of the present invention to
suppress vibration caused by a load torque variation in one turn of
rotation in a rotary compressor in which relative eccentric
rotation is accomplished between a piston and a cylinder having two
cylinder chambers.
Means of Solving the Problems
[0007] A first aspect of the present invention is directed to a
rotary compressor including: a compression mechanism (20, 80)
including a piston (22, 87a, 87b) and a cylinder (21, 81a, 81b)
having two cylinder chambers (C1, C2, 82a, 82b); and an electric
motor (30, 65) configured to change volumes of the cylinder
chambers (C1, C2, 82a, 82b) by causing relative eccentric rotation
between the cylinder (21, 81a, 81b) and the piston (22, 87a, 87b).
The rotary compressor further includes a torque control means (50)
configured to change an output torque of the electric motor (30,
65) in accordance with a variation in a load torque of the
compression mechanism (20, 80) in one turn of rotation.
[0008] In this aspect, the relative eccentric rotation of the
cylinder (21, 81a, 81b) and the piston (22, 87a, 87b) caused by
driving the electric motor (30, 65) causes the volumes of the two
cylinder chambers (C1, C2, 82a, 82b) to vary. In each of the
cylinder chambers (C1, C2, 82a, 82b), fluid is sucked as the volume
of the low-pressure chamber (i.e., the suction chamber) increases,
whereas fluid in the high-pressure chamber (i.e., the compression
chamber) is compressed as the volume of the high-pressure chamber
decreases.
[0009] The load torque of the electric motor (30, 65) varies in
accordance with the rotation angle in one turn of rotation of the
compression mechanism (20, 80). Specifically, in each of the
cylinder chambers (C1, C2, 82a, 82b), the load torque is highest
substantially immediately before and after compressed fluid starts
to be discharged. Accordingly, in this state, the rotation speed of
the cylinder (21, 81a, 81b) or the piston (22, 87a, 87b) varies
because the output torque of the electric motor (30, 65) is fixed.
That is, when the load torque increases, the rotation speed
decreases, whereas when the load torque decreases, the rotation
speed increases. This variation in the rotation speed causes
vibration of the compressor in the tangential direction of the
casing.
[0010] On the other hand, in this aspect of the present invention,
the torque control means (50) adjusts the output torque of the
electric motor (30, 65) in accordance with a variation in the load
torque in one turn of rotation. Specifically, the output torque of
the electric motor (30, 65) decreases as the load torque decreases,
and increases as the load torque increases. That is, torque control
is performed such that the output torque of the electric motor (30,
65) is adjusted to a value commensurate with the load torque. This
control makes the rotation speed of the cylinder (21, 81a, 81b) or
the piston (22, 87a, 87b) substantially constant, thus suppressing
vibration of the compressor.
[0011] In a second aspect of the present invention, in the rotary
compressor of the first aspect, the cylinder (21) includes an
annular cylinder chamber (C1, C2), and the piston (22) is an
annular piston (22) housed in the annular cylinder chamber (C1, C2)
and partitioning the annular cylinder chamber (C1, C2) into two
cylinder chambers which are an outer cylinder chamber (C1) and an
inner cylinder chamber (C2).
[0012] In this aspect, relative eccentric rotation of the cylinder
(21) and the annular piston (22 (52)) caused by driving the
electric motor (30) causes the volumes of the outer cylinder
chamber (C1) and the inner cylinder chamber (C2) to vary. In each
of the cylinder chambers (C1, C2), fluid is sucked as the volume of
the low-pressure chamber (i.e., the suction chamber) increases,
whereas fluid in the high-pressure chamber (i.e., the compression
chamber) is compressed as the volume of the high-pressure chamber
decreases.
[0013] In this case, the load torque of the electric motor (30)
also varies in accordance with the rotation angle in one turn of
rotation of the compression mechanism (20), thereby causing the
rotation speed of the cylinder (21) or the annular piston (22) to
vary. This variation causes vibration of the compressor in the
tangential direction of the casing. On the other hand, in the
present invention, the torque control means (50) adjusts the output
torque of the electric motor (30) in accordance with a variation in
the load torque in one turn of rotation. Accordingly, the rotation
speed of the cylinder (21) or the annular piston (22) becomes
substantially constant, thus suppressing vibration of the
compressor.
[0014] In a third aspect of the present invention, in the rotary
compressor of the second aspect, a volume ratio of the inner
cylinder chamber (C2) to the outer cylinder chamber (C1) is in the
range from 0.6 to 1.0.
[0015] In this aspect, since the volume ratio of the inner cylinder
chamber (C2) to the outer cylinder chamber (C1) is set in the range
from 0.6 to 1.0, the variation range in the load torque in one turn
is small. Specifically, as shown in FIG. 5, as the volume ratio Vr
of the inner cylinder chamber (C2) to the outer cylinder chamber
(C1) decreases, the variation range (i.e., the amount of variation)
in the load torque increases. In particular, when the volume ratio
Vr is about 0.6 or less, the variation range in the load torque
becomes extremely large.
[0016] The torque control of the electric motor (30) changes the
output torque of the electric motor (30) by adjusting, for example,
an input current or an input voltage to the electric motor (30).
For example, when the load torque is high, the input current is
increased so as to increase the output torque of the electric motor
(30). On the other hand, when the load torque is low, the input
current is reduced so as to reduce the output torque of the
electric motor (30). In general, the electric motor (30) exhibits a
high operational efficiency when the electric motor (30) is driven
with a substantially constant input current or voltage.
Specifically, when the amount of variation (i.e., the degree of
control) in, for example, the input current becomes large, the
operational efficiency of the electric motor (30) greatly
decreases.
[0017] On the other hand, in the present invention, the volume
ratio Vr of the inner cylinder chamber (C2) to the outer cylinder
chamber (C1) is limited within a given range as described above,
thus reducing the amount of variation in the load torque in one
turn of rotation. Accordingly, the amount of variation in the input
current or the input voltage of the electric motor (30) is reduced
in one turn of rotation, resulting in suppressing a decrease in the
operational efficiency of the electric motor (30).
[0018] In a fourth aspect of the present invention, in the rotary
compressor of the second or third aspect, the electric motor (30)
is a brushless DC motor.
[0019] In this aspect, since a brushless direct-current (DC) motor
is used as the electric motor (30), the operational efficiency of
the electric motor (30) is higher than in the case of using an
alternating-current (AC) motor. In particular, in torque control
performed during low-speed rotation in which variation in the
rotation speed is likely to be large, the DC motor can maintain a
relatively high efficiently to a low speed, although the AC motor
greatly decreases in efficiency, and thus substantially is not
operable.
[0020] In a fifth aspect of the present invention, in the rotary
compressor of the second or third aspect, the torque control means
(50) is configured to change an output torque of the electric motor
(30) by changing one of an input current, an input voltage, and an
input current phase of the electric motor (30).
[0021] In this aspect, when the load torque decreases in one turn
of rotation, the input current or the input voltage is reduced,
thereby reducing the output torque of the electric motor (30). When
the load torque increases, the input current or the input voltage
is increased, thereby increasing the output torque of the electric
motor (30). In this manner, the output torque of the electric motor
(30) is adjusted to a value commensurate with the load torque. In
addition, by adjusting (i.e., moving forward or backward) the input
current phase, the output torque of the electric motor (30)
increases or decreases to a value commensurate with the load
torque. In particular, this adjustment of the input current phase
can allow the output torque of the electric motor (30) to more
closely follow a load torque which abruptly changes.
[0022] In a sixth aspect of the present invention, in the rotary
compressor of the second or third aspect, the electric motor (30)
is coupled to the cylinder (21) configured to rotate relative to
the annular piston (22) which is stationary.
[0023] In this aspect, the cylinder (21) is movable, and the
annular piston (22) is stationary. Specifically, the cylinder (21)
eccentrically rotates relative to the annular piston (22), and the
torque control means (50) suppresses a variation in the rotation
speed of the cylinder (21). As a result, vibration caused by the
variation in the rotation speed of the cylinder (21) can be
suppressed.
[0024] In a seventh aspect of the present invention, the rotary
compressor of the second or third aspect, the electric motor (30)
is coupled to the annular piston (22) configured to rotate relative
to the cylinder (21) which is stationary.
[0025] In this aspect, the cylinder (21) is stationary, and the
annular piston (52) is movable. Specifically, the annular piston
(22) eccentrically rotates relative to the cylinder (21), and the
torque control means (50) suppresses a variation in the rotation
speed of the annular piston (22). As a result, vibration caused by
the variation in the rotation speed of the annular piston (22) can
be suppressed.
[0026] In an eighth aspect of the present invention, the rotary
compressor of the second aspect, the compression mechanism (20) is
configured to perform two-stage compression on fluid, with one of
the outer and inner cylinder chambers (C1) and (C2) used at a
low-stage side and the other one of the outer and inner cylinder
chambers (C1) and (C2) used at a high-stage side.
[0027] In this aspect, first, low-pressure fluid sucked into the
outer cylinder chamber (C1) is compressed to be
intermediate-pressure fluid. This intermediate-pressure fluid is
sucked into the inner cylinder chamber (C2). This
intermediate-pressure fluid in the inner cylinder chamber (C2) is
further compressed to be high-pressure fluid. This series of
processes is performed in one turn of rotation of the compression
mechanism (20), thus changing the load torque of the electric motor
(30) in accordance with the rotation angle. In this case, the
torque control means (50) also makes the rotation speed of the
cylinder (21) or the annular piston (22) substantially constant,
resulting in suppressing vibration of the compressor.
[0028] In a ninth aspect of the present invention, the rotary
compressor of the eighth aspect, a volume ratio of the inner
cylinder chamber (C2) to the outer cylinder chamber (C1) is in the
range from 0.6 to 0.8.
[0029] In this aspect, the volume ratio of the inner cylinder
chamber (C2) to the outer cylinder chamber (C1) is set in the range
from 0.6 to 0.8, and thus the variation range in the load torque in
one turn of rotation is small. Specifically, as shown in FIG. 13,
the variation range (i.e., the amount of variation) in the load
torque is smaller in cases where the volume ratio Vr of the inner
cylinder chamber (C2) to the outer cylinder chamber (C1) is 0.6 and
0.8, than in a case where the volume ratio Vr is 0.5 (or 1.0). In
the case of the volume ratio Vr=1.0, the outer cylinder chamber
(C1) and the inner cylinder chamber (C2) have the same volume, and
thus this case corresponds to a one-cylinder compression mechanism
performing so-called single-stage compression. In this aspect, the
variation range in the load torque in one turn of rotation is
smaller than in the one-cylinder compression mechanism.
[0030] In a tenth aspect of the present invention, in the rotary
compressor of the first aspect, the cylinders (81a, 81b) are
respectively a low-stage first cylinder (81a) and a high-stage
second cylinder (81b) both including cylinder chambers (82a, 82b),
the pistons (87a, 87b) are respectively a first rotary piston (87a)
housed in the cylinder chamber (82a) of the first cylinder (81a)
and a second rotary piston (87b) housed in the cylinder chamber
(82b) of the second cylinder (81b), and the compression mechanism
(80) is configured to perform two-stage compression on fluid in the
cylinders (81a, 81b) by eccentric rotation of the rotary pistons
(87a, 87b) caused by the electric motor (65).
[0031] In this aspect, the compression mechanism (80) is a
so-called two-cylinder rotary compression mechanism. In this
compression mechanism (80), the rotary pistons (87a, 87b)
eccentrically rotate by driving the electric motor (65). This
eccentric rotation of the rotary pistons (87a, 87b) causes the
volumes of the cylinder chambers (82a, 82b) to vary, thereby
achieving two-compression of fluid in the cylinders (81a, 81b).
Specifically, first, low-pressure fluid sucked into the cylinder
chamber (82a) of the first cylinder (81a) is compressed to be
intermediate-pressure fluid. This intermediate-pressure fluid is
sucked into the cylinder chamber (82b) of the second cylinder
chamber (82b). The intermediate-pressure fluid in the cylinder
chamber (82b) is further compressed to be high-pressure fluid. This
series of processes is performed in one turn of rotation of the
compression mechanism (20), thus changing the load torque of the
electric motor (30) in accordance with the rotation angle. In this
case, the torque control means (50) also makes the rotation speed
of the rotary pistons (87a, 87b) substantially constant, resulting
in suppressing vibration of the compressor.
[0032] In an eleventh aspect of the present invention, in the
rotary compressor of the tenth aspect, a volume ratio of the
cylinder chamber (82b) of the second cylinder (81b) to the cylinder
chamber (82a) of the first cylinder (81a) is in the range from 0.6
to 0.8.
[0033] In this aspect, the volume ratio of the cylinder chamber
(82b) of the second cylinder (81b) to the cylinder chamber (82a) of
the first cylinder (81a) is set in the range from 0.6 to 0.8, and
thus the variation range in the load torque in one turn of rotation
is small. Specifically, as shown in FIG. 13, the variation range
(i.e., the amount of variation) in the load torque is smaller in
cases where the volume ratio Vr of the inner cylinder chamber (C2)
to the outer cylinder chamber (C1) is 0.6 and 0.8, than in a case
where the volume ratio Vr is 0.5 (or 1.0).
[0034] In a twelfth aspect of the present invention, in the rotary
compressor of the tenth or eleventh aspect, the compression
mechanism (80) is configured such that a rotational phase of the
rotary piston (87a) of the first cylinder (81a) is shifted from a
rotational phase of the rotary piston (87b) of the second cylinder
(81b) by 180.degree..
[0035] In this aspect, when the volume of the cylinder chamber
(82a) decreases in the first cylinder (81a) with the rotation of
the rotary piston (87a), fluid compressed to an intermediate
pressure is discharged. At substantially the same time, the volume
of the cylinder chamber (82b) increases in the second cylinder
(81b) with the rotation of the rotary piston (87b), thereby sucking
the intermediate-pressure fluid discharged from the first cylinder
(81a). This sucked intermediate-pressure fluid is further
compressed with a decrease in the volume of the cylinder chamber
(82b) of the second cylinder (81b), and then is discharged.
EFFECTS OF THE INVENTION
[0036] Accordingly, in the present invention, the output torque of
the electric motor (30, 65) is adjusted according to a variation in
the load torque of the compression mechanism (20, 80) in one turn
of rotation. Thus, a variation in the rotation speed of the
cylinder (21, 81a, 81b) or the piston (22, 87a, 87b) can be
reduced. As a result, vibration of the compressor caused by a
variation in the rotation speed can be suppressed.
[0037] In the third aspect of the present invention, the volume
ratio of the inner cylinder chamber (C2) to the outer cylinder
chamber (C1) is limited within a given range (i.e., from 0.6 to
1.0), and thus the amount of variation in the load torque in one
turn of rotation can be reduced. Accordingly, the amount of
variation in the output torque of the electric motor (30) can be
reduced, thus suppressing a decrease in the operational efficiency
of the electric motor (30). As a result, energy saving in operating
the compressor can be achieved.
[0038] In the fourth aspect of the present invention, a brushless
direct-current motor is used as the electric motor (30). Thus, the
efficiency of the electric motor (30) can be enhanced, as compared
to the case of using an AC motor. As a result, further energy
saving in operating the compressor can be achieved.
[0039] In the ninth or eleventh aspect of the present invention,
the volume ratio of the high-stage cylinder chamber (C2, 82b) to
the low-stage cylinder chamber (C1, 82a) is also limited within a
given range (i.e., from 0.6 to 0.8) in a two-cylinder two-stage
compression mechanism. Accordingly, the amount of variation in the
load torque in one turn of rotation can be reduced, thus
suppressing a decrease in the operational efficiency of the
electric motor (30, 65).
BRIEF DESCRIPTION OF DRAWINGS
[0040] FIG. 1 is a longitudinal cross-sectional view illustrating a
compressor according to a first embodiment.
[0041] FIG. 2 is a transverse cross-sectional view illustrating a
compression mechanism of the first embodiment.
[0042] FIG. 3 shows transverse cross sections showing operation of
the compression mechanism of the first embodiment for every
90.degree. of rotation.
[0043] FIG. 4 is a graph showing variations in compression torques
in one turn of rotation.
[0044] FIG. 5 is a graph showing variations in compression torques
with respect to the volume ratios Vr.
[0045] FIG. 6 is a graph showing the amounts of decrease in a
torque variation ratio, a vibration ratio, and a motor efficiency
with respect to volume ratios Vr.
[0046] FIG. 7 is a longitudinal cross-sectional view illustrating a
compressor according to a second embodiment.
[0047] FIG. 8 is a transverse cross-sectional view illustrating a
compression mechanism of the second embodiment.
[0048] FIG. 9 shows transverse cross-sections showing operation of
the compression mechanism of the second embodiment for every
90.degree. of rotation.
[0049] FIG. 10 is a longitudinal cross-sectional view illustrating
a compressor according to a third embodiment.
[0050] FIG. 11 is a transverse cross-sectional view illustrating a
compression mechanism of the third embodiment.
[0051] FIG. 12 is a graph showing relationships between operating
pressure ratios and compression efficiencies based on volume ratios
Vr.
[0052] FIG. 13 is a graph showing variations in compression torque
with respect to volume ratios Vr.
[0053] FIG. 14 is a graph showing a torque variation ratio with
respect to the volume ratio Vr.
[0054] FIG. 15 is a longitudinal cross-sectional view illustrating
a compressor according to a fourth embodiment.
[0055] FIG. 16 is a transverse cross-sectional view illustrating a
compression mechanism of the fourth embodiment.
DESCRIPTION OF CHARACTERS
[0056] 1, 60 compressor [0057] 20 compression mechanism [0058] 21
cylinder [0059] 22 annular piston (piston) [0060] 30 electric motor
[0061] 50 controller (torque control means) [0062] C1 outer
cylinder chamber (cylinder chamber) [0063] C2 inner cylinder
chamber (cylinder chamber) [0064] 65 electric motor [0065] 80
compression mechanism [0066] 81a first cylinder (cylinder) [0067]
81b second cylinder (cylinder) [0068] 82a first cylinder chamber
(cylinder chamber) [0069] 82b second cylinder chamber (cylinder
chamber) [0070] 87a first rotary piston (piston) [0071] 87b second
rotary piston (piston)
BEST MODE FOR CARRYING OUT THE INVENTION
[0072] Hereinafter, embodiments of the present invention will be
specifically described with reference to the drawings. The
following embodiments are merely preferred examples in nature, and
are not intended to limit the scope, applications, and use of the
invention.
Embodiment 1
[0073] A first embodiment is directed to a rotary compressor as
illustrated in FIG. 1. This compressor (1) is of a fully-enclosed
type in which a compression mechanism (20) and an electric motor
(30) for driving the compression mechanism (20) are housed in a
casing (10), and are fully enclosed. The compressor (1) is used for
compressing refrigerant sucked from an evaporator and for
discharging the compressed refrigerant into a condenser in a
refrigerant circuit of an air conditioner, for example.
[0074] The casing (10) includes a cylindrical body (11) and upper
and lower heads (12) and (13) respectively fixed to the top and
bottom of the body (11). A suction pipe (14) penetrates the upper
head (12), and a discharge pipe (15) penetrates the body (11).
[0075] The compression mechanism (20) includes: upper and lower
housings (16) and (17) fixed to the casing (10); and a cylinder
(21). The cylinder (21) has an annular cylinder chamber (C1, C2),
and is located between the upper housing (16) and the lower housing
(17). The upper housing (16) includes an annular piston (22) which
is located in the cylinder chamber (C1, C2) and is continuous to
the upper housing (16). The cylinder (21) is configured to
eccentrically rotate relative to the annular piston (22).
Specifically, in this embodiment, the cylinder (21) and the annular
piston (22) provide relative eccentric rotation in which the
cylinder (21) is movable and the annular piston (22) is
stationary.
[0076] The electric motor (30) is a brushless direct-current (DC)
motor including a stator (31) and a rotor (32). The stator (31) is
located below the compression mechanism (20), and is fixed to the
body (11) of the casing (10). The rotor (32) is coupled to a drive
shaft (33) which rotates together with the rotor (32). The drive
shaft (33) longitudinally penetrates the compression mechanism
(20), and has an eccentric part (33a) located in the cylinder
chamber (C1, C2). This eccentric part (33a) has a diameter greater
than the other portion, and is eccentric from the axis of the drive
shaft (33) to a given extent.
[0077] An axially extending oil supply passageway (not shown) is
provided in the drive shaft (33). An oil supply pump (34) is
provided at the bottom of the drive shaft (33). This oil supply
pump (34) pumps lubricating oil accumulated in the bottom of the
casing (10), and supplies the oil to a sliding part of the
compression mechanism (20) through the oil supply passageway of the
drive shaft (33).
[0078] The cylinder (21) has an outer cylinder portion (24) and an
inner cylinder portion (25). The outer cylinder portion (24) and
the inner cylinder portion (25) are annular, and have the same
axis. These outer and inner cylinder portions (24) and (25) are
coupled to each other at an end by a head (26) to be continuous.
The annular cylinder chamber (C1, C2) is formed between the inner
peripheral surface of the outer cylinder portion (24) and the outer
peripheral surface of the inner cylinder portion (25). The
eccentric part (33a) of the drive shaft (33) is slidably fit into
the inner cylinder portion (25). The cylinder (21) is made of cast
steel or an aluminum alloy, for example.
[0079] Each of the upper housing (16) and the lower housing (17)
has a bearing portion (16a, 17a) for rotatably supporting the drive
shaft (33). In this manner, the compressor (1) of this embodiment
has a penetration structure in which the drive shaft (33)
longitudinally penetrates the cylinder chamber (C1, C2) and both
axial ends of the eccentric part (33a) are held in the casing (10)
with the bearing portions (16a, 17a) interposed therebetween.
[0080] The outer peripheral surface of the annular piston (22) has
a diameter smaller than that of the inner peripheral surface of the
outer cylinder portion (24), and the inner peripheral surface of
the annular piston (22) has a diameter larger than that of the
outer peripheral surface of the inner cylinder portion (25). The
annular piston (22) is eccentrically placed in the annular cylinder
chamber (C1, C2) to partition the cylinder chamber (C1, C2) into an
outer cylinder chamber (C1) and an inner cylinder chamber (C2).
Specifically, the outer cylinder chamber (C1) is formed between the
inner peripheral surface of the outer cylinder portion (24) and the
outer peripheral surface of the annular piston (22). The inner
cylinder chamber (C2) is formed between the inner peripheral
surface of the annular piston (22) and the outer peripheral surface
of the inner cylinder portion (25). The head (26) of the cylinder
(21) serves as a first block member for blocking one end of the
cylinder chamber (C1, C2), and the upper housing (16) serves as a
second block member for blocking the other end of the cylinder
chamber (C1, C2).
[0081] The outer peripheral surface of the annular piston (22) is
in contact with the inner peripheral surface of the outer cylinder
portion (24) at substantially one point. At a position whose phase
is 180.degree. shifted from this contact point, the inner
peripheral surface of the annular piston (22) is in contact with
the outer peripheral surface of the inner cylinder portion (25) at
substantially one point.
[0082] As illustrated in FIG. 2, the compression mechanism (20) has
a blade (23) which partitions each of the outer cylinder chamber
(C1) and the inner cylinder chamber (C2) into a high-pressure
chamber (C1-Hp, C2-Hp) serving as a compression chamber and a
low-pressure chamber (C1-Lp, C2-Lp) serving as a suction chamber.
This blade (23) is in the shape of a rectangular plate which
penetrates the annular piston (22) and extends in the direction
along the diameter of the cylinder chamber (C1, C2). Both ends of
the blade (23) are respectively fixed to the inner peripheral
surface of the outer cylinder portion (24) and the outer peripheral
surface of the inner cylinder portion (25).
[0083] The annular piston (22) has a C-shape obtained by partially
cutting off the annular piston (22) so as to allow the blade (23)
to penetrate therethrough. The cut-off portion of the annular
piston (22) is provided with swing bushings (27). The swing
bushings (27) are constituted by a discharge-side bushing (27A) and
a suction-side bushing (27B). The discharge-side bushing (27A) and
the suction-side bushing (27B) are located toward the high-pressure
chamber (C1-Hp, C2-Hp) and the low-pressure chamber (C1-Lp, C2-Lp),
respectively, with the blade (23) sandwiched therebetween.
[0084] The discharge-side bushing (27A) and the suction-side
bushing (27B) are approximately semicircular in cross section, and
have their plane surfaces face each other. That is, a blade groove
(28) in which the blade (23) slides is formed between opposing
surfaces of the bushings (27A, 27B). The swing bushings (27) are
configured such that the blade (23) moves forward and backward in
the blade groove (28), with the blade (23) and the cylinder (21)
swinging in an integrated manner relative to the annular piston
(22). The bushings (27A, 27B) are not necessarily separated from
each other, and may be partially coupled to each other to be
continuous.
[0085] In the compression mechanism (20), with the rotation of the
drive shaft (33), the points of contact on the annular piston (22)
with the outer and inner cylinder portions (24) and (25)
sequentially move from the state shown in FIG. 3(A) to the state
shown in FIG. 3(D). Specifically, the rotation of the drive shaft
(33) causes the compression mechanism (20) to revolve about the
drive shaft (33), without causing the outer cylinder portion (24)
and the inner cylinder portion (25) to rotate.
[0086] The upper housing (16) has an inlet (41) in the shape of a
slot below the suction pipe (14). This inlet (41) penetrates the
upper housing (16) along the axis of the upper housing (16), and
allows the low-pressure chamber (C1-Lp, C2-Lp) of the cylinder
chamber (C1, C2) to communicate with the space (i.e., low-pressure
space (S1)) above the upper housing (16). The outer cylinder
portion (24) has a through hole (43) which allows suction space
(42) to communicate with the low-pressure chamber (C1-Lp) of the
outer cylinder chamber (C1). The annular piston (22) has a through
hole (44) which allows the low-pressure chamber (C1-Lp) of the
outer cylinder chamber (C1) to communicate with the low-pressure
chamber (C2-Lp) of the inner cylinder chamber (C2).
[0087] The annular piston (22) and the outer cylinder portion (24)
preferably have wedge shapes by chamfering top portions thereof
corresponding to the inlet (41) as indicated by broken lines in
FIG. 1. In this case, refrigerant can be efficiently sucked into
the low-pressure chambers (C1-Lp, C2-Lp).
[0088] The housing (16) has two outlets (45). These outlets (45)
penetrate the upper housing (16) along the axis of the upper
housing (16). The bottoms of the outlets (45) are respectively open
to the high-pressure chambers (C1-Hp, C2-Hp) of the cylinder
chambers (C1, C2). On the other hand, the tops of the outlets (45)
communicate with discharge space (47) through discharge valves (46)
for opening and closing the outlets (45).
[0089] This discharge space (47) is formed between the upper
housing (16) and a cover plate (18). The upper housing (16) and the
lower housing (17) are provided with a discharge passageway (47a)
which allows the discharge space (47) to communicate with space
(i.e., high-pressure space (S2)) below the lower housing (17).
[0090] The lower housing (17) is provided with a seal ring (29).
This seal ring (29) is placed in an annular groove (17b) of the
lower housing (17), and is in pressure contact with the bottom of
the head (26) of the cylinder (21). High-pressure lubricating oil
is introduced between the cylinder (21) and the lower housing (17)
at the inner side of the seal ring (29) in the radial direction of
the seal ring (29). In this manner, the seal ring (29) constitutes
a compliance mechanism in which an axial clearance between the
bottom surface of the annular piston (22) and the head (26) of the
cylinder (21) is reduced by utilizing the pressure of the
lubricating oil.
[0091] In this embodiment, the volume Vout of the outer cylinder
chamber (C1) is larger than the volume Vin of the inner cylinder
chamber (C2). Specifically, the volume ratio Vr (Vin/Vout) of the
inner cylinder chamber (C2) to the outer cylinder chamber (C1) is
set at about 0.7. This volume ratio Vr is preferably set in the
range from 0.6 to 1.0.
[0092] The compressor (21) includes a controller (50) which is a
torque control means for controlling the output torque of the
electric motor (30).
[0093] The controller (50) is configured to change the output
torque of the electric motor (30) in accordance with a variation in
the load torque of the compression mechanism (20) in one turn of
rotation. This controller (50) receives the rotation angle of the
rotor (32), and supplies, to the electric motor (30), current
having a value which has been previously set in accordance with the
rotation angle of the rotor (32). That is, the controller (50)
changes the output torque of the electric motor (30) by controlling
input current of the electric motor (30). The rotation angle of the
rotor (32) is equal to the rotation angle of the drive shaft (33).
As the rotation angle of the rotor (32), a value detected by a
rotation sensor or a value calculated from the induced voltage or
current of the electric motor (30) is used.
[0094] Specifically, input current is increased at a rotation angle
with a high load torque, whereas the input current is reduced at a
rotation angle with a low load torque. Since the output torque of
the electric motor (30) is proportional to the input current,
increase/decrease in the input current causes the output torque of
the electric motor (30) to increase/decrease accordingly. In this
manner, the output torque of the electric motor (30) becomes
commensurate with the load torque. Thus, a variation in the
rotation speed of the drive shaft (33) in one turn can be
suppressed, resulting in suppression of vibration.
[0095] In the present invention, instead of input current, an input
voltage or an input current phase may be controlled in accordance
with the rotation angle of the rotor (32) so as to change the
output torque of the electric motor (30). For example, the input
voltage is increased at a rotation angle with a high load torque,
whereas the input voltage is reduced at a rotation angle with a low
load torque. Accordingly, the output torque of the electric motor
(30) increases/decreases in proportion to the input voltage, and is
changed to a value commensurate with the load torque. A shift of
the input voltage phase causes the output torque of the electric
motor (30) to increase/decrease to a value commensurate with the
load torque. In particular, adjusting the input current phase
allows the output torque of the electric motor (30) to more closely
follow the load torque which abruptly changes.
--Operation--
[0096] Now, it is described how the compressor (1) operates with
reference to the drawings.
[0097] First, when the electric motor (30) is started, rotation of
the rotor (32) is conveyed to the outer cylinder portion (24) and
the inner cylinder portion (25) of the compression mechanism (20)
via the drive shaft (33). Accordingly, the blade (23) reciprocates
(i.e., moves forward and backward) between the swing bushings (27),
and the blade (23) and the swing bushings (27) swing in an
integrated manner with respect to the annular piston (22). The
outer cylinder portion (24) and the inner cylinder portion (25)
revolve about the annular piston (22) while swinging, thereby
causing the compression mechanism (20) to perform given compression
operation.
[0098] Specifically, in the outer cylinder chamber (C1), the volume
of the low-pressure chamber (C1-Lp) is approximately smallest in
the state shown in FIG. 3(D). While the drive shaft (33) rotates in
the clockwise direction in the drawings to shift from the state of
FIG. 3(D) to the states of FIGS. 3(A), 3(B), and 3(C) in this
order, the volume of the low-pressure chamber (C1-Lp) increases.
With this increase in the volume of the low-pressure chamber
(C1-Lp), refrigerant passes through the suction pipe (14), the
low-pressure space (S1), and the inlet (41) to be sucked into the
low-pressure chamber (C1-Lp). At this time, the refrigerant is not
only sucked directly into the low-pressure chamber (C1-Lp) from the
inlet (41), but also partially enters the suction space (42) from
the inlet (41), and then is sucked into the low-pressure chamber
(C1-Lp) through the through hole (43).
[0099] When the drive shaft (33) returns to the state of FIG. 3(D)
after one turn of rotation, the suction of refrigerant into the
low-pressure chamber (C1-Lp) is completed. This low-pressure
chamber (C1-Lp) is then changed to a high-pressure chamber (C1-Hp)
in which the refrigerant is compressed, and a new low-pressure
chamber (C1-Lp) is created with the blade (23) sandwiched between
the high-pressure chamber (C1-Hp) and the low-pressure chamber
(C1-Lp). Then, while the drive shaft (33) further rotates, suction
of refrigerant is repeated in the low-pressure chamber (C1-Lp),
whereas the volume of the high-pressure chamber (C1-Hp) decreases,
thereby compressing the refrigerant in the high-pressure chamber
(C1-Hp). The high-pressure refrigerant in the high-pressure chamber
(C1-Hp) flows from the outlets (45) into the discharge space (47),
and then flows into the high-pressure space (S2) through the
discharge passageway (47a).
[0100] In the inner cylinder chamber (C2), the volume of the
low-pressure chamber (C2-Lp) is approximately smallest in the state
shown in FIG. 3(B). While the drive shaft (33) rotates in the
clockwise direction in the drawings from the state of FIG. 3(B) to
the states of FIGS. 3(C), 3(D), and 3(A) in this order, the volume
of the low-pressure chamber (C2-Lp) increases. With this increase
in the volume of the low-pressure chamber (C2-Lp), refrigerant
passes through the suction pipe (14), the low-pressure space (S1),
and the inlet (41) to be sucked into the low-pressure chamber
(C2-Lp). At this time, the refrigerant is not only sucked directly
into the low-pressure chamber (C2-Lp) from the inlet (41), but also
partially enters the suction space (42) from the inlet (41), and
then passes through the through hole (43), the low-pressure chamber
(C1-Lp) of the outer cylinder chamber, and the through hole (44) to
be sucked into the low-pressure chamber (C2-Lp) of the inner
cylinder chamber (C2).
[0101] When the drive shaft (33) returns to the state of FIG. 3(B)
after one turn of rotation, the suction of refrigerant into the
low-pressure chamber (C2-Lp) is completed. This low-pressure
chamber (C2-Lp) is then changed to a high-pressure chamber (C2-Hp)
in which the refrigerant is compressed, and a new low-pressure
chamber (C2-Lp) is created with the blade (23) sandwiched between
the high-pressure chamber (C2-Hp) and the low-pressure chamber
(C2-Lp). Then, while the drive shaft (33) further rotates, suction
of refrigerant is repeated in the low-pressure chamber (C2-Lp),
whereas the volume of the high-pressure chamber (C2-Hp) decreases,
thereby compressing refrigerant in the high-pressure chamber
(C2-Hp). The high-pressure refrigerant in the high-pressure chamber
(C2-Hp) flows from the outlets (45) into the discharge space (47),
and then flows into the high-pressure space (S2) through the
discharge passageway (47a).
[0102] In this manner, high-pressure refrigerant which has been
compressed in the outer cylinder chamber (C1) and the inner
cylinder chamber (C2) and has flown into the high-pressure space
(S2) is discharged from the discharge pipe (15), is subjected to
condensation, expansion, and evaporation processes in the
refrigerant circuit, and then is sucked into the compressor (1)
again.
[0103] Now, it is described how the torque of the electric motor
(30) is controlled. In FIG. 3, it is assumed that FIG. 3(A)
corresponds to a rotation angle of 180.degree., FIG. 3(B)
corresponds to a rotation angle of 270.degree., FIG. 3(C)
corresponds to a rotation angle of)0.degree. (360.degree., and FIG.
3(D) corresponds to a rotation angle of 90.degree..
[0104] In the operation described above, the compression torque
(i.e., the load torque) of the drive shaft (33) in one turn of
rotation varies as indicated by the solid line in FIG. 4.
Specifically, in the compressor (1) of this embodiment, the
compression torque is highest around a rotation angle of
180.degree., and is lowest around rotation angles of 90.degree. and
270.degree.. On the other hand, as indicated by the broken line in
FIG. 4, in a general one-cylinder rotary compressor, the
compression torque is highest around a rotation angle of
180.degree., and is lowest around a rotation angle of 0.degree.
(360.degree.). Comparison of the torque variation ranges (i.e., a
difference between the maximum and minimum compression torques) in
one turn of rotation shows that the torque variation range (about
1.1 Nm) of the compressor (1) of the present invention is greatly
smaller than the torque variation range (about 2.3 Nm) of the
one-cylinder rotary compressor. The torque variations shown in FIG.
4 are obtained when the operation pressure ratio (i.e., the
condensation pressure/the evaporation pressure) occurring in an air
conditioner in an intermediate season is about 1.6.
[0105] Input current of the electric motor (30) is adjusted in
accordance with the variation of the compression torque described
above. Specifically, the input current value is largest when the
compression torque is highest, and the input current value is
smallest when the compression torque is lowest. In this manner, in
one turn of rotation of the drive shaft (33), the input current of
the electric motor (30) varies from the minimum value to the
maximum value. However, the amount of variation in this input
current (i.e., the degree of control) is smaller than that in the
one-cylinder rotary compressor. That is, the one-cylinder rotary
compressor exhibits a wide variation range of the compression
torque in one turn of rotation, and thus the amount of variation in
the input current is also large accordingly.
[0106] In general, as the amount of variation in the input current
of an electric motor decreases, the efficiency in the electric
motor increases (i.e., the amount of decrease in the efficiency
decreases). This shows that even with the same torque control, the
efficiency of the electric motor (30) less decreases in the
compressor (1) of the present invention than in the one-cylinder
rotary compressor. As a result, the compressor (1) can operate with
energy saving as a whole.
[0107] Now, a relationship among the volume ratio Vr between the
outer cylinder chamber (C1) and the inner cylinder chamber (C2),
the torque variation ratio, and the vibration ratio is
described.
[0108] First, FIG. 5 shows a relationship between the volume ratio
Vr (Vin/Vout) between the outer cylinder chamber (C1) and the inner
cylinder chamber (C2), and the torque variation range. In FIG. 5,
torque variation ranges are shown for five patterns of volume
ratios Vr (Vin/Vout): 50/50=1, 40/60=0.66, 25/75=0.33, 15/85=0.17,
and 0/100=0. The pattern of the volume ratio Vr (Vin/Vout)=0/100
corresponds to a one-cylinder rotary compressor. The torque
variations shown in FIG. 5 are obtained when the operating pressure
ratio (i.e., the condensation pressure/the evaporation pressure)
occurring in an air conditioner in rated operation is about 3.
[0109] Specifically, the case of the volume ratio Vr=0/100 exhibits
the largest torque variation range, and the case of the volume
ratio Vr=50/50 exhibits the smallest torque variation range. That
is, as the volume ratio Vr approaches 1 (one), the torque variation
range decreases. Accordingly, as the volume ratio Vr approaches 1
(one), vibration caused by a torque variation is more greatly
suppressed.
[0110] It is also shown that the period (i.e., an interval between
two valleys sandwiching one peak of a main torque variation) of a
main torque variation becomes shorter as the volume ratio Vr
approaches 1 (one). For example, the period ("c" in FIG. 5) of the
main torque variation in the case of the volume ratio Vr=50/50 is
shorter than the period ("b" in FIG. 5) of the main torque
variation in the case of the volume ratio Vr=25/75. This period
("b" in FIG. 5) of the main torque variation is shorter than the
period ("a" in FIG. 5) of the main torque variation in the case of
the volume ratio Vr=0/100. As the period of the main torque
variation increases, the motor vibrates more slowly, and thus the
amplitude of this vibration increases. In general, the amplitude
increases in proportion to the square of the period
(=1/frequency).
[0111] FIG. 6 shows how the amounts of decrease in a torque
variation ratio, a vibration ratio, and a motor efficiency (i.e.,
an electric-motor efficiency) are associated with the volume ratio
Vr. In FIG. 6, the torque variation ratio and the vibration ratio
are expressed as ratios of the torque variation range and vibration
to the volume ratio Vr, with the torque variation range and the
vibration in the case of the volume ratio Vr=0/100 being defined as
"1". The amount of decrease in the motor efficiency is obtained
when the rotation speed variation is suppressed to the lowest
degree with torque control. In FIG. 6, the amount of decrease in
the motor efficiency (i.e., the electric motor efficiency) is
indicated by a solid line, the torque variation ratio is indicated
by a broken line, and the vibration ratio is indicated by a
dash-dotted line.
[0112] Specifically, as the volume ratio Vr approaches 1 (one), the
torque variation ratio and the vibration ratio decrease. The amount
of decrease in the motor efficiency is approximately 0%, i.e., is
smallest, when the volume ratio Vr is 1 (one), and increases as the
volume ratio Vr decreases. In addition, it is shown that the motor
efficiency gradually decreases while the volume ratio Vr is in the
range from 1.0 to 0.6, and steeply decreases when the volume ratio
Vr is less than 0.6. In this manner, while the volume ratio Vr is
in the range from 0.6 to 1.0, torque control can be performed with
a small amount of decrease in the motor efficiency, and thus
vibration can be suppressed as compared to the one-cylinder rotary
compressor.
[0113] As described above, in the compressor (1) of this
embodiment, torque control of the electric motor (30) enables
suppression of a decrease in the efficiency of the electric motor
(30) more greatly than torque control of a one-cylinder rotary
compressor. In addition, despite performing torque control with a
small amount of decrease in the efficiency of the electric motor
(30), vibration can be further suppressed by setting the volume
ratio Vr between the outer cylinder chamber (C1) and the inner
cylinder chamber (C2) at about 0.7. As a result, vibration of the
compressor (1) can be suppressed, and operation with energy saving
can be achieved.
[0114] In this embodiment, a brushless direct-current (DC) motor
having a higher efficiency than an alternating-current (AC) motor
is employed as the electric motor (30), and thus high efficiency
can be maintained even during low-speed operation necessary for an
air conditioner incorporating the compressor (1) of the present
invention in intermediate seasons, thus further saving energy.
[0115] In a conventional two-cylinder rotary compressor, two
cylinders having a volume ratio Vr of 1:1 are disposed
longitudinally, and thus a crank mechanism such as a rotary piston
and an eccentric shaft is needed for each cylinder. On the other
hand, in the compressor (1) of the present invention, one cylinder
is partitioned into the outer cylinder chamber (C1) and the inner
cylinder chamber (C2), and these cylinder chambers share the
annular piston (22). As a result, only one crank mechanism is
sufficient for the compressor (1), thus achieving cost
reduction.
[0116] In addition, if the cylinder (21) is made of an aluminum
alloy, centrifugal force during rotation is reduced. In this case,
vibration in high-speed operation can be suppressed, and warping of
the drive shaft (33) is also suppressed. Accordingly, highly
efficient operation with small vibration can be achieved in a wide
range.
Embodiment 2
[0117] As illustrated in FIGS. 7 and 8, a second embodiment is
obtained by modifying the configuration of the compression
mechanism (20) of the first embodiment. Specifically, in this
embodiment, an annular piston (52) is movable, a cylinder (21) is
stationary, and the annular piston (52) eccentrically rotates
relative to the cylinder (21).
[0118] A compression mechanism (20) of the second embodiment
includes an upper housing (16) and a piston assembly (55). The
upper housing (16) is continuous to the cylinder (21). The piston
assembly (55) is configured to eccentrically rotate relative to the
cylinder (21). In this embodiment, the lower housing (17) is
omitted.
[0119] The cylinder (21) includes outer cylinder portion (24) and
an inner cylinder portion (25). The outer cylinder portion (24) and
the inner cylinder portion (25) are annular, and have the same
axis. These outer and inner cylinder portions (24) and (25) are
provided on the lower surface of a head (26) of the upper housing
(16). An annular cylinder chamber (C1, C2) is formed between the
inner peripheral surface of the outer cylinder portion (24) and the
outer peripheral surface of the inner cylinder portion (25).
[0120] The piston assembly (55) includes: a head (51); the annular
piston (52) positioned upright on, and continuous to, the upper
surface of the head (51); and a cylindrical piston (53). The piston
assembly (55) is made of cast steel or an aluminum alloy. The
annular piston (52) has an inner diameter greater than the outer
diameter of the cylindrical piston (53), and has the same axis as
the cylindrical piston (53). The piston assembly (55) is configured
such that the annular piston (52) is placed in the annular cylinder
chamber (C1, C2) to partition the cylinder chamber (C1, C2) into an
outer cylinder chamber (C1) and an inner cylinder chamber (C2).
Specifically, the head (26) of the upper housing (16) serves as a
first block member for blocking an end of the cylinder chamber (C1,
C2). The head (51) of the piston assembly (55) serves as a second
block member for blocking the other end of the cylinder chamber
(C1, C2). The cylindrical piston (53) is located in the inner
cylinder portion (25).
[0121] In this embodiment, the volume Vout of the outer cylinder
chamber (C1) is also larger than the volume Vin of the inner
cylinder chamber (C2), and the volume ratio Vr (Vin/Vout) of the
inner cylinder chamber (C2) to the outer cylinder chamber (C1) is
also set at about 0.7.
[0122] An eccentric part (33a) is formed at the top of a drive
shaft (33) of an electric motor (30), and is coupled to the piston
assembly (55). Specifically, this eccentric part (33a) of the drive
shaft (33) is rotatably fitted in a fitting part (54) which has a
cylindrical shape and is continuous to the lower surface of the
piston assembly (55). In this manner, the piston assembly (55) is
caused to eccentrically rotate relative to the cylinder (21) by the
rotation of the drive shaft (33).
[0123] Next, it is described how this compressor (1) operates with
reference to FIG. 9. Advantages of the cylinder chamber (C1, C2) in
this operation are substantially the same as those in the first
embodiment.
[0124] Specifically, in the outer cylinder chamber (C1), the volume
of a low-pressure chamber (C1-Lp) is approximately smallest in the
state shown in FIG. 9(D). While the drive shaft (33) rotates to
shift from this state to the states of FIGS. 9(A), 9(B), and 9(C)
in this order, the volume of the low-pressure chamber (C1-Lp)
increases, and refrigerant is sucked into the low-pressure chamber
(C1-Lp). When the drive shaft (33) takes one turn, the low-pressure
chamber (C1-Lp) changes to a high-pressure chamber (C1-Hp). Then,
while the drive shaft (33) further rotates, the volume of the
high-pressure chamber (C1-Hp) decreases, thereby compressing
refrigerant.
[0125] On the other hand, in the inner cylinder chamber (C2), the
volume of the low-pressure chamber (C2-Lp) is approximately
smallest in the state shown in FIG. 9(B). While the drive shaft
(33) rotates to shift from this state to the states of FIGS. 9(C),
9(D), and 9(A) in this order, the volume of the low-pressure
chamber (C2-Lp) increases, and thus refrigerant is sucked into the
low-pressure chamber (C2-Lp). When drive shaft (33) takes one turn,
the low-pressure chamber (C2-Lp) changes to a high-pressure chamber
(C2-Hp). Then, while the drive shaft (33) further rotates, the
volume of the high-pressure chamber (C2-Hp) decreases, thereby
compressing refrigerant.
[0126] As in the first embodiment, torque control of the electric
motor (30) is performed by a controller (50) in this embodiment.
Accordingly, as compared to a case where torque control is
performed on a one-cylinder compressor, decrease in the efficiency
of the electric motor (30) is greatly suppressed, thus achieving
energy saving of the compressor (1).
[0127] As in the first embodiment, if the piston assembly (55) is
made of an aluminum alloy, vibration and warping of the drive shaft
(33) are suppressed during high-speed operation, thus performing
highly efficient operation with small vibration in a wide range.
Other configurations, operation, and advantages are similar to
those in the first embodiment.
Embodiment 3
[0128] As illustrated in FIGS. 10 and 11, a third embodiment is
obtained by modifying the compression mechanism (20) of the first
embodiment such that the compression mechanism (20) performs
two-stage compression on refrigerant. Specifically, in a
compression mechanism (20) of the third embodiment, an outer
cylinder chamber (C1) serves as a low-stage compression chamber,
and an inner cylinder chamber (C2) serves as a high-stage
compression chamber.
[0129] A compressor (1) is used for, for example, a refrigerant
circuit using carbon dioxide (CO.sub.2) as refrigerant and
operating in a two-stage compression one-stage expansion cycle.
Although not shown, in this refrigerant circuit, the compressor
(1), a heat dissipater (a gas cooler), a receiver, an intermediate
cooler, an expansion valve, and an evaporator are sequentially
connected to each other by refrigerant pipes. In this refrigerant
circuit, high-pressure refrigerant discharged from the inner
cylinder chamber (C2) of the compressor (1) sequentially flows in
the heat dissipater, the receiver, the expansion valve, and the
evaporator, and flows into the outer cylinder chamber (C1) of the
compressor (1). On the other hand, intermediate-pressure
refrigerant compressed in the outer cylinder chamber (C1) flows
into the intermediate cooler, and part of liquid refrigerant from
the receiver subjected to pressure reduction also flows into the
intermediate cooler. In this intermediate cooler, the
intermediate-pressure refrigerant from the outer cylinder chamber
(C1) is cooled. This cooled intermediate-pressure refrigerant
returns to the inner cylinder chamber (C2), and is compressed
again. This circulation is repeated, thereby cooling the inside air
in the evaporator, for example.
[0130] A body (11) of a casing (10) of the compressor (1) is
provided with a suction pipe (14), an inflow pipe (1a), and an
outflow pipe (1b). These pipes penetrate the body (11). The suction
pipe (14) is connected to the evaporator, and the inflow pipe (1a)
and the outflow pipe (1b) are connected to the intermediate cooler.
A discharge pipe (15) is provided through an upper head (12) of the
casing (10). This discharge pipe (15) is connected to the heat
dissipater.
[0131] An upper housing (16) of the compression mechanism (20) is
provided with a cover plate (18). In the casing (10), space above
the cover plate (18) is defined as high-pressure space (4a), and
space below a lower housing (17) is defined as
intermediate-pressure space (4b). An end of the discharge pipe (15)
is open to the high-pressure space (4a), and an end of the outflow
pipe (1b) is open to the intermediate-pressure space (4b).
[0132] An intermediate-pressure chamber (4c) and a high-pressure
chamber (4d) are formed between the upper housing (16) and the
cover plate (18). The upper housing (16) has an
intermediate-pressure passageway (4e). A pocket (4f) is formed on
the outer periphery of an outer cylinder (24) between the upper
housing (16) and the lower housing (17). The inflow pipe (1a) is
connected to an end of the intermediate-pressure passageway (4e).
The suction pipe (14) is connected to the pocket (4f) such that the
pocket (4f) is in a low-pressure atmosphere at a suction
pressure.
[0133] The outer cylinder (24) has a first inlet (41a) radially
penetrating the outer cylinder (24). The first inlet (41a) is
located at the right of a blade (23) in FIG. 11. That is, the first
inlet (41a) establishes communication among the outer cylinder
chamber (C1), the pocket (4f), and the suction pipe (14).
[0134] The other end of the intermediate-pressure passageway (4e)
is configured as a second inlet (41b). This second inlet (41b) is
located at the right of the blade (23), is open to the inner
cylinder chamber (C2), and establishes communication between the
inner cylinder chamber (C2) and the intermediate-pressure space
(4b).
[0135] The upper housing (16) has a first discharge port (45a) and
a second discharge port (45b). These discharge ports (45a, 45b)
axially penetrate the upper housing (16). An end of the first
discharge port (45a) is open to the high-pressure side of the outer
cylinder chamber (C1), and the other end of the first discharge
port (45a) is open to the intermediate-pressure chamber (4c). An
end of the second discharge port (45b) is open to the high-pressure
side of the inner cylinder chamber (C2), and the other end of the
second discharge port (45b) is open to the high-pressure chamber
(4d). Outer ends of the first discharge port (45a) and the second
discharge port (45b) are provided with valves (46) which are reed
valves.
[0136] The intermediate-pressure chamber (4c) and the
intermediate-pressure space (4b) communicate with each other with a
communication passageway (4g) formed in the upper housing (16) and
the lower housing (17). Although not shown, the high-pressure
chamber (4d) communicates with the high-pressure space (4a) via a
high-pressure passageway formed in the cover plate (18).
[0137] In this embodiment, the volume Vout of the outer cylinder
chamber (C1) is also larger than the volume Vin of the inner
cylinder chamber (C2), and the volume ratio Vr (Vin/Vout) of the
inner cylinder chamber (C2) to the outer cylinder chamber (C1) is
also set at about 0.7.
[0138] In this compressor (1), when the electric motor (30) is
started, the outer cylinder (24) and the inner cylinder (25)
revolve, while swinging relative to the annular piston (22), as in
the first embodiment. Then, the compression mechanism (20) performs
given compression operation.
[0139] When the volume of the outer cylinder chamber (C1) increases
with rotation of a drive shaft (33), low-pressure refrigerant is
sucked into the outer cylinder chamber (C1) from the suction pipe
(14) through the pocket (4f) and the first inlet (41a). Then, the
drive shaft (33) further rotates to cause the volume of the outer
cylinder chamber (C1) to decrease, thereby compressing refrigerant.
When the pressure of this outer cylinder chamber (C1) reaches a
given intermediate pressure, and the differential pressure between
the outer cylinder chamber (C1) and the intermediate-pressure
chamber (4c) reaches a set value, the valves (46) are opened.
Accordingly, intermediate-pressure refrigerant is discharged from
the outer cylinder chamber (C1) into the intermediate-pressure
chamber (4c), and flows from the outflow pipe (1b) through the
intermediate-pressure space (4b).
[0140] On the other hand, when the volume of the inner cylinder
chamber (C2) is caused to increase by the rotation of the drive
shaft (33), intermediate-pressure refrigerant is sucked into the
inner cylinder chamber (C2) from the inflow pipe (1a) through the
intermediate-pressure passageway (4e) and the second inlet (41b).
Then, the drive shaft (33) further rotates to cause the volume of
the inner cylinder chamber (C2) to decrease, thereby compressing
refrigerant. When the pressure of this inner cylinder chamber (C2)
reaches a given high pressure, and the differential pressure
between the inner cylinder chamber (C2) and the high-pressure
chamber (4d) reaches a set value, the valves (46) are opened.
Accordingly, high-pressure refrigerant is discharged from the inner
cylinder chamber (C2) into the high-pressure chamber (4d), and
flows from the discharge pipe (15) through the high-pressure space
(4a). In this manner, in the compressor (1) of this embodiment,
refrigerant compressed in the outer cylinder chamber (C1) is
further compressed in the inner cylinder chamber (C2), thereby
performing two-stage compression.
[0141] In general, an air conditioner (which is herein an inverter
air conditioner) is most frequently operated in a range of low
pressure ratios where the operating pressure ratio is in the range
from about 1.6 to about 2.0. The operating pressure ratio herein is
a ratio of a condensation pressure to an evaporation pressure in a
refrigerant circuit.
[0142] As shown in FIG. 12, in a low operating pressure ratio range
with a high operating frequency, as the volume ratio Vr of the
inner cylinder chamber (C2) to the outer cylinder chamber (C1)
increases, the compression efficiency increases. For example, in
the case of the volume ratio Vr=0.8, the compression efficiency is
highest around an operating pressure ratio of 1.5, and in the case
of the volume ratio Vr=0.6, the compression efficiency is highest
around an operating pressure ratio of 1.9. On the other hand, in
the case of the volume ratio Vr=0.5, the compression efficiency is
highest around an operating pressure ratio of 2.5, and while the
operating pressure ratio decreases to about 2.0 or less, the
compression efficiency greatly decreases. That is, in the two-stage
compression using the outer cylinder chamber (C1) and the inner
cylinder chamber (C2), as the volume ratio Vr decreases, the
compression ratio of the entire compression mechanism (20)
increases. Then, under operating conditions with a low operating
pressure ratio, overcompression losses are likely to occur, and
thus the compression efficiency is also likely to decrease.
[0143] FIG. 13 shows a relationship between the volume ratio Vr
(Vin/Vout) and the torque variation range. FIG. 14 shows a
relationship between the volume ratio Vr (Vin/Vout) and the torque
variation ratio. These graphs show that the torque variation range
and the torque variation ratio in the cases of the volume ratio
Vr=0.6 and 0.8 are smaller than those in the case of the volume
ratio Vr=0.5 and 1. Accordingly, such small torque variations
enable suppression of vibration. The torque variation ratio is the
torque variation range expressed in terms of ratio for each volume
ratio Vr, with the torque variation range in the case of the volume
ratio Vr=1 set at "1". FIGS. 13 and 14 are obtained by measurement
at an operating pressure ratio of about 2.
[0144] In the case of the volume ratio Vr=1, the outer cylinder
chamber (C1) and the inner cylinder chamber (C2) have the same
volume. In this case, refrigerant is not compressed in the outer
cylinder chamber (C1), but is compressed only in the inner cylinder
chamber (C2), i.e., is subjected to not two-stage compression but
single-stage compression. That is, the case of the volume ratio
Vr=1 substantially corresponds to the case where single-stage
compression is performed by a conventional one-cylinder rotary
compressor. Here, in the case of the volume ratio Vr=0.5, the
torque variation range and the torque variation ratio are greater
than those in the case of Vr=1. Specifically, large vibration
requires suppression of the vibration by means of torque control,
resulting in that the torque control might cause the operational
efficiency to be lower than that in the conventional one-cylinder
rotary compressor.
[0145] As described above, in the two-stage compression
configuration of this embodiment, the volume ratio Vr between the
inner and outer cylinder chambers (C1, C2) are set in the range
from about 0.6 to about 0.8. Accordingly, the compression
efficiency can be enhanced and vibration can be suppressed, as
compared to a conventional one-cylinder compressor.
Embodiment 4
[0146] As illustrated in FIGS. 15 and 16, a fourth embodiment is
obtained by modifying the two-stage compression configuration of
the compression mechanism (20) of the third embodiment.
Specifically, in the compression mechanism (20) of the third
embodiment, two cylinder chambers (C1, C2) are formed in the same
plane. On the other hand, in the fourth embodiment, a compression
mechanism (80) is formed by longitudinally stacking two cylinder
chambers (82a, 82b), and constitutes a so-called two-stage rotary
compressor.
[0147] More specifically, a compressor (60) of the fourth
embodiment is configured such that the compression mechanism (80)
having a low-stage compression mechanism (80a) and a high-stage
compression mechanism (80b) and an electric motor (65) are housed
in a casing (61) which is a sealed vessel in an elongated
cylindrical shape. In the casing (61), the electric motor (65) is
located above the compression mechanism (80).
[0148] A suction pipe (62) penetrates the body of the casing (61),
and a discharge pipe (63) penetrates the body at a position above
the suction pipe (62). The discharge pipe (63) is bent at the inlet
side thereof in the casing (61), then extends horizontally, and is
open at the end.
[0149] The electric motor (65) includes a stator (66) and a rotor
(67). The stator (66) is fixed to the inner peripheral surface of
the casing (61). The rotor (67) is located at the inner side of the
stator (66). A center portion of the rotor (67) is coupled to a
main shaft portion (71) of a drive shaft (70) which longitudinally
extends.
[0150] The drive shaft (70) constitutes a drive shaft. The drive
shaft (70) has a first eccentric part (72) and a second eccentric
part (73) which are located in this order from the bottom. Each of
the first eccentric part (72) and the second eccentric part (73)
has a diameter greater than that of the main shaft portion (71),
and is eccentric to the axis of the main shaft portion (71). The
first eccentric part (72) and the second eccentric part (73) are
respectively eccentric to the axis of the main shaft portion (71)
in opposite directions. The height of the first eccentric part (72)
is greater than that of the second eccentric part (73).
[0151] The compression mechanism (80) is configured such that a
rear head (84), a first cylinder (81a), a middle plate (86), a
second cylinder (81b), and a front head (83) are stacked in this
order. The first cylinder (81a) houses a first rotary piston (87a).
The second cylinder (81b) houses a second rotary piston (87b).
[0152] The first cylinder (81a), the first rotary piston (87a), the
rear head (84), and the middle plate (86) constitute the low-stage
compression mechanism (80a). The second cylinder (81b), the second
rotary piston (87b), the front head (83), and the middle plate (86)
constitute the high-stage compression mechanism (80b). Each of the
low-stage compression mechanism (80a) and the high-stage
compression mechanism (80b) is configured by a rotary fluid machine
of a swinging piston type, which is a type of a
positive-displacement fluid machine.
[0153] As illustrated in FIG. 16, the first rotary piston (87a) of
the low-stage compression mechanism (80a) has an annular shape. The
first eccentric part (72) is rotatably fitted in this first rotary
piston (87a) of the low-stage compression mechanism (80a). The
second rotary piston (87b) of the high-stage compression mechanism
(80b) also has an annular shape. The second eccentric part (73) is
rotatably fitted in this second rotary piston (87b) of the
high-stage compression mechanism (80b).
[0154] The inner peripheral surfaces of the rotary pistons (87a,
87b) are respectively in slidable contact with the outer peripheral
surfaces of the eccentric parts (72, 73), and the outer peripheral
surfaces of the rotary pistons (87a, 87b) are respectively in
slidable contact with the inner peripheral surfaces of the
cylinders (81a, 81b). A cylinder chamber (82a, 82b) is formed
between the outer peripheral surface of the rotary piston (87a,
87b) and the inner peripheral surface of the cylinder (81a, 81b). A
blade (74) in the shape of a flat plate projects from a side
surface of each of the rotary pistons (87a, 87b). The blade (74) is
supported by the cylinder (81a, 81b) with a swing bushing (75)
interposed therebetween. The swing bushing (75) is provided between
a discharge port (89a, 89b) and a suction port (88a, 88b) which
will be described later. The blade (74) partitions the cylinder
chamber (82a, 82b) into a high-pressure side and a low-pressure
side.
[0155] In this manner, the compression mechanism (80) is configured
such that rotation of the eccentric part (72, 73) causes the rotary
piston (87a, 87b) to revolve and swing in the cylinder chamber
(82a, 82b). The rotational phases of the rotary pistons (87a, 87b)
shift from each other by 180.degree..
[0156] The first cylinder (81a) of the low-stage compression
mechanism (80a) and the second cylinder (81b) of the high-stage
compression mechanism (80b) have the same inner diameter. The first
rotary piston (87a) of the low-stage compression mechanism (80a)
and the second rotary piston (87b) of the high-stage compression
mechanism (80b) have the same outer diameter. The height of the
first cylinder (81a) of the low-stage compression mechanism (80a)
is greater than that of the second cylinder (81b) of the high-stage
compression mechanism (80b).
[0157] The middle plate (86) has an annular intermediate passageway
(90). A discharge port (89a) of the low-stage compression mechanism
(80a) is formed in the middle plate (86). This discharge port (89a)
allows the high-pressure side of the first cylinder chamber (82a)
of the low-stage compression mechanism (80a) to communicate with
the intermediate passageway (90). On the other hand, a discharge
port (89b) of the high-stage compression mechanism (80b) is formed
in the front head (83). This discharge port (89b) allows the
high-pressure side of the second cylinder chamber (82b) of the
high-stage compression mechanism (80b) to communicate with the
space in the casing (61). These discharge ports (89a, 89b) have
discharge valves (not shown) for opening and closing the respective
outlets of the discharge ports (89a, 89b).
[0158] The first cylinder (81a) of the low-stage compression
mechanism (80a) has a suction port (88a). This suction port (88a)
radially penetrates the first cylinder (81a). The terminal end of
the suction port (88a) is open to the first cylinder chamber (82a).
This suction port (88a) is connected to the suction pipe (62). The
second cylinder (81b) of the high-stage compression mechanism (80b)
has a suction port (88b) extending from the middle plate (86). The
starting end of the suction port (88b) is open to the intermediate
passageway (90), and the terminal end of the suction port (88b) is
open to the second cylinder chamber (82b).
[0159] An oil sump for storing lubricating oil is formed at the
bottom of the casing (61). A centrifugal oil supply pump (92)
immersed in the oil sump is provided at the bottom of the drive
shaft (70). This oil supply pump (92) longitudinally extends in the
drive shaft (70), and is connected to an oil supply passageway (91)
which communicates with the low-stage compression mechanism (80a)
and the high-stage compression mechanism (80b). The oil supply pump
(92) is configured to supply lubricating oil in the oil sump to a
sliding portion of the low-stage compression mechanism (80a) and to
a sliding portion of the high-stage compression mechanism (80b)
through the oil supply passageway (91).
[0160] In this embodiment, the volume V1 of the first cylinder
chamber (82a) is also larger than the volume V2 of the second
cylinder chamber (82b), and the volume ratio Vr (V2/V1) of the
second cylinder chamber (82b) to the first cylinder chamber (82a)
is also set at about 0.7.
[0161] In this compressor (60), when the electric motor (65) is
started, the rotary pistons (87a, 87b) revolve, while swinging in
the cylinder chambers (81a, 81b). Then, the compression mechanism
(80) performs given compression operation.
[0162] This compression operation is described with reference to
FIG. 16. In FIG. 16, the rotary piston (87a, 87b) swings, while
rotating in the clockwise direction. The position in which the
rotary piston (87a, 87b) is in contact with the top dead center is
defined as a rotation angle of 0.degree., and the position in which
the rotary piston (87a, 87b) is in contact with the bottom dead
center is defined as a rotation angle of 180.degree.. First, when
the drive shaft (70) slightly rotates from the state of a rotation
angle of 0.degree. so that the contact point between the first
rotary piston (87a) and the first cylinder (81a) passes by the
opening of the suction port (88a), refrigerant starts to flow from
the suction port (88a) to the first cylinder chamber (82a). The
refrigerant continues to flow into the first cylinder chamber (82a)
until the rotation angle of the drive shaft (70) reaches
360.degree..
[0163] Subsequently, in a state where the flow of refrigerant into
the first cylinder chamber (82a) is finished (i.e., the rotation
angle of the drive shaft (70) is 360.degree., when the drive shaft
(70) slightly rotates so that the contact point between the first
rotary piston (87a) and the first cylinder (81a) passes by the
opening of the suction port (88a), confinement of refrigerant in
the first cylinder chamber (82a) is completed. Then, from this
state, the drive shaft (70) further rotates, thereby starting
compression of refrigerant. When the pressure of refrigerant in the
first cylinder chamber (82a) exceeds the pressure of refrigerant in
the intermediate passageway (90), the discharge valve is opened,
thereby discharging intermediate-pressure refrigerant from the
discharge port (89a) into the intermediate passageway (90). The
discharge of refrigerant continues until the rotation angle of the
drive shaft (70) reaches 360.degree..
[0164] On the other hand, in the high-stage compression mechanism
(80b), the rotation of the drive shaft (70) causes
intermediate-pressure refrigerant in the intermediate passageway
(90) to flow from the suction port (88b) into the second cylinder
chamber (82b). Specifically, when the contact point between the
second rotary piston (87b) and the second cylinder (81b) passes by
the opening of the suction port (88b), refrigerant starts to flow
from the intermediate passageway (90) into the second cylinder
chamber (82b). The flow of intermediate-pressure refrigerant
continues until the rotation angle of the drive shaft (70) reaches
360.degree..
[0165] Thereafter, when the contact point between the second rotary
piston (87b) and the second cylinder (81b) passes by the opening of
the suction port (88b) so that confinement of refrigerant in the
second cylinder chamber (82b) is completed, compression of
refrigerant starts. Then, when the pressure of refrigerant in the
second cylinder chamber (82b) exceeds the pressure of refrigerant
in the space in the casing (61), the discharge valve is opened,
thereby discharging the high-pressure refrigerant from the
discharge port (89b) into the space in the casing (61). The
discharge of refrigerant continues until the rotation angle of the
drive shaft (70) reaches 360.degree.. The refrigerant discharged
into the space in the casing (61) is discharged from the discharge
pipe (63) to the refrigerant circuit. In this manner, in the
compressor (60) of this embodiment, refrigerant compressed in the
low-stage first cylinder chamber (82a) is further compressed in the
high-stage second cylinder chamber (82b), thereby performing
two-stage compression.
[0166] As in the third embodiment, the relationship between the
volume ratio Vr (V2n/V1) and the torque variation range and the
relationship between the volume ratio Vr (V2n/V1) and the torque
variation ratio also apply to the relationships shown in FIGS. 13
and 14. That is, the torque variation range and the torque
variation ratio in the case of the volume ratio Vr=0.6 and 0.8 are
smaller than those in the case of the volume ratio Vr=0.5 and 1.
Accordingly, such small torque variations enable suppression of
vibration. Thus, in the two-stage compression configuration in
which the low-stage and high-stage cylinder chambers (82a, 82b) are
longitudinally stacked, as long as the volume ratio Vr between
these cylinder chambers (82a, 82b) are set in the range from about
0.6 to about 0.8, the compression efficiency can be enhanced and
vibration can be suppressed, as compared to a conventional
one-cylinder compressor.
INDUSTRIAL APPLICABILITY
[0167] As described above, the present invention is useful for
rotary compressors each including two cylinder chambers whose
volume varies with eccentric rotation of a piston.
* * * * *