U.S. patent application number 12/287301 was filed with the patent office on 2009-04-16 for suction structure in double-headed piston type compressor.
Invention is credited to Mitsuyo Ishikawa, Shinichi Sato, Manabu Sugiura.
Application Number | 20090097999 12/287301 |
Document ID | / |
Family ID | 40534402 |
Filed Date | 2009-04-16 |
United States Patent
Application |
20090097999 |
Kind Code |
A1 |
Ishikawa; Mitsuyo ; et
al. |
April 16, 2009 |
Suction structure in double-headed piston type compressor
Abstract
A suction structure is provided for allowing refrigerant into
first and second compression chambers from a suction pressure
region through first and second rotary valves and first and second
communication passages in a double-headed piston type compressor.
The first and the second rotary valves respectively have first and
second introduction passages. The distance to the first
communication passage from the suction pressure region through the
first introduction passage is greater than the distance to the
second communication passage from the suction pressure region
through the second introduction passage. The first communication
passage with a circular cross-section in the cylinder block
connects the first compression chamber to the first introduction
passage. The second communication passage with a circular
cross-section in the cylinder block connects the second compression
chamber to the second introduction passage. The diameter of the
first communication passage is greater than the diameter of the
second communication passage.
Inventors: |
Ishikawa; Mitsuyo;
(Kariya-shi, JP) ; Sato; Shinichi; (Kariya-shi,
JP) ; Sugiura; Manabu; (Kariya-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
3 WORLD FINANCIAL CENTER
NEW YORK
NY
10281-2101
US
|
Family ID: |
40534402 |
Appl. No.: |
12/287301 |
Filed: |
October 7, 2008 |
Current U.S.
Class: |
417/534 |
Current CPC
Class: |
F04B 27/1009 20130101;
F04B 39/10 20130101 |
Class at
Publication: |
417/534 |
International
Class: |
F04B 39/10 20060101
F04B039/10 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 15, 2007 |
JP |
2007-267973 |
Claims
1. A suction structure for allowing refrigerant from a suction
pressure region in a double-headed piston type compressor, the
compressor comprising: a cylinder block; a rotary shaft supported
by the cylinder block; a double-headed piston reciprocating with
rotation of the rotary shaft; a first cylinder bore and a second
cylinder bore formed in the cylinder block in a paired manner so as
to accommodate the double-headed piston; a first compression
chamber and a second compression chamber defined by the
double-headed piston in the first and the second cylinder bores,
respectively; the suction structure in the compressor comprising: a
first rotary valve introducing refrigerant from the suction
pressure region into the first compression chamber through a first
introduction passage; a second rotary valve introducing refrigerant
from the suction pressure region into the second compression
chamber through a second introduction passage, wherein each part of
the first and the second introduction passages is formed in the
rotary shaft; a first communication passage having a circular
cross-section and formed in the cylinder block so as to connect the
first compression chamber to the first introduction passage; and a
second communication passage having a circular cross-section and
formed in the cylinder block so as to connect the second
compression chamber to the second introduction passage, wherein the
distance to the first communication passage from the suction
pressure region through the first introduction passage is greater
than the distance to the second communication passage from the
suction pressure region through the second introduction passage,
wherein the diameter of the first communication passage is greater
than the diameter of the second communication passage.
2. The suction structure according to claim 1, wherein the diameter
of the first communication passage is less than or equal to 1.8
times of the diameter of the second communication passage.
3. The suction structure according to claim 2, wherein the diameter
of the first communication passage is less than or equal to 1.4
times of the diameter of the second communication passage.
4. The suction structure according to claim 1, wherein the second
introduction passage in the rotary shaft shares a part of the first
introduction passage.
5. A double-headed piston type compressor comprising: a cylinder
block; a rotary shaft supported by the cylinder block; a cam body
formed with the rotary shaft; a double-headed piston engaged with
the cam body, wherein rotation of the rotary shaft is transmitted
to the piston through the cam body; a first cylinder bore and a
second cylinder bore formed in the cylinder block in a paired
manner so as to accommodate the double-headed piston; a first
compression chamber and a second compression chamber defined by the
double-headed piston in the first and the second cylinder bores,
respectively; a first rotary valve rotated integrally with the
rotary shaft, wherein the rotary valve has a first introduction
passage so as to introduce refrigerant from a suction pressure
region into the first compression chamber through the first
introduction passage; a second rotary valve rotated integrally with
the rotary shaft, wherein the second rotary valve has a second
introduction passage so as to introduce refrigerant from the
suction pressure region into the second compression chamber through
the second introduction passage, wherein each part of the first and
second introduction passages is formed in the rotary shaft; a first
communication passage having a circular cross-section and formed in
the cylinder block so as to connect the first compression chamber
to the first introduction passage; and a second communication
passage having a circular cross-section and formed in the cylinder
block so as to connect the second compression chamber to the second
introduction passage, wherein the distance to the first
communication passage from the suction pressure region through the
first introduction passage is greater than the distance to the
second communication passage from the suction pressure region
through the second introduction passage, wherein the diameter of
the first communication passage is greater than the diameter of the
second communication passage.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a suction structure for
allowing refrigerant from a suction pressure region into
compression chambers in a double-headed piston type compressor.
More specifically, the compressor has rotary valves rotated
integrally with a rotary shaft and having introduction passages for
introducing refrigerant from the suction pressure region into the
compression chambers defined in cylinder bores by the double-headed
pistons.
[0002] In double-headed piston type compressors, there are two
types of suction valves. One is a rotary valve as disclosed in
Unexamined Japanese Patent Publication No. 2007-032445. The other
is a reed type suction valve as disclosed in Unexamined Japanese
Patent Publication No. 2000-145629. The piston type compressor
including the rotary valves has lower suction resistance in
introducing refrigerant into cylinder bores, and has superior
energy efficiency, compared to the piston type compressor including
the reed type suction valves.
[0003] In the compressor disclosed in the above reference No.
2007-032445, pairs of a front cylinder bore and a rear cylinder
bore accommodate double-headed pistons therein, and the pistons are
reciprocated in accordance with the rotation of a rotary shaft.
Each double-headed piston defines a front compression chamber in
the front cylinder bore and a rear compression chamber in the rear
cylinder bore. The rotary shaft has a front rotary valve and a rear
rotary valve which are formed integrally therewith. A supply
passage is formed in the rotary shaft, and outlets of the supply
passage are formed in the front and the rear rotary valves.
Communication passages are formed in cylinder blocks so as to
communicate with the compression chambers. The outlets of the
supply passage intermittently communicate with the communication
passages in accordance with the rotation of the rotary shaft, or,
the rotation of the rotary valves. When the outlets of the supply
passage communicate with the communication passages, the
refrigerant in the supply passage is introduced into the
compression chambers.
[0004] Generally, the communication passages have elongated
cross-sections, as disclosed in Unexamined Japanese Patent
Publication No. 6-129350. The elongated holes are formed such that
the dimensions of elongated holes in the axial direction of the
rotary shaft are larger than the dimensions thereof in the
circumferential direction. The elongated holes are applied in order
to collect the residual gas in the compression chambers thereby
improving the volume efficiency.
[0005] The supply passage communicates with the suction chamber
formed in the rear housing so as to supply refrigerant in the
suction chamber to the front and rear compression chambers
therethrough. The refrigerant in the front compression chamber is
discharged to the front discharge chamber formed in the front
housing, by pushing open the respective discharge valve. The
refrigerant in the rear compression chamber is discharged to the
rear discharge chamber formed in the rear housing, by pushing open
the respective discharge valve.
[0006] The pressure in the front discharge chamber is equal to the
pressure in the rear discharge chamber. The refrigerant in the
compression chambers is compressed up to the pressure level in the
discharge chambers. Therefore, as the amount of the refrigerant
introduced into the compression chambers is decreased, the
compression rate is increased. When the compression rate is
increased, the temperature of the compressed refrigerant rises,
accordingly.
[0007] The distance to the front compression chamber from the
suction chamber through the supply passage is greater than the
distance to the rear compression chamber from the suction chamber
through the supply passage. Therefore, the refrigerant amount into
the front compression chamber is smaller than that into the rear
compression chamber during the time when the communication passages
communicate with the outlets of the rotary valves, respectively.
The temperature of the refrigerant compressed in the front
compression chamber becomes higher than the temperature of the
refrigerant compressed in the rear compression chamber,
accordingly.
[0008] When the temperature of the refrigerant compressed in the
front compression chamber becomes excessively high, the temperature
of the front housing rises. The sealing function may be
deteriorated in seal members interposed between the front housing
and the cylinder block, accordingly.
[0009] The present invention is directed to suppress increase in
temperature of refrigerant compressed in compression chambers in a
double-headed piston type compressor.
SUMMARY OF THE INVENTION
[0010] In accordance with the present invention, a suction
structure is provided for allowing refrigerant from a suction
pressure region in a double-headed piston type compressor. The
compressor has a cylinder block, a rotary shaft, a double-headed
piston, first and second cylinder bores, and first and second
compression chambers. The rotary shaft is supported by the cylinder
block. The double-headed piston reciprocates with rotation of the
rotary shaft. The first and the second cylinder bores are formed in
the cylinder block in a paired manner so as to accommodate the
double-headed piston. The first and the second compression chambers
are defined by the double-headed piston in the first and the second
cylinder bores, respectively. The suction structure in the
compressor includes first and second rotary valves, and first and
second communication passages. The first rotary valve introduces
refrigerant from a suction pressure region into the first
compression chamber through a first introduction passage. The
second rotary valve introduces refrigerant from the suction
pressure region into the second compression chamber through a
second introduction passage. Each part of the first and the second
introduction passages is formed in the rotary shaft. The first
communication passage has a circular cross-section and is formed in
the cylinder block so as to connect the first compression chamber
to the first introduction passage. The second communication passage
has a circular cross-section and is formed in the cylinder block so
as to connect the second compression chamber to the second
introduction passage. The distance to the first communication
passage from the suction pressure region through the first
introduction passage is greater than the distance to the second
communication passage from the suction pressure region through the
second introduction passage. The diameter of the first
communication passage is greater than the diameter of the second
communication passage.
[0011] 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
[0012] The features of the present invention that are believed to
be novel are set forth with particularity in the appended claims.
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:
[0013] FIG. 1 is a longitudinal cross-sectional view of a
compressor according to a preferred embodiment of the present
invention;
[0014] FIG. 2A is a partially enlarged cross-sectional view of the
compressor according to the preferred embodiment;
[0015] FIG. 2B is a cross-sectional view which is taken along the
line III-III in FIG. 2A;
[0016] FIG. 2C is a cross-sectional view which is taken along the
line IV-IV in FIG. 2A;
[0017] FIG. 2D is a graph showing relation between temperature in
front discharge chamber and cross-section ratio with regard to area
of first communication passage to that of second communication
passage according to the preferred embodiment;
[0018] FIG. 3A is a cross-sectional view which is taken along the
line I-I in FIG. 1; and
[0019] FIG. 3B is a cross-sectional view which is taken along the
line II-II in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] A preferred embodiment of a double-headed piston type
compressor 10 according to the present invention will be described
with reference to FIGS. 1 through 3. It is noted that the front
side and the rear side of the double-headed piston type compressor
10 respectively correspond to the left side and the right side in
the drawings. In addition, the front side and the rear side of the
compressor 10 respectively serve as a first side and a second side.
Referring to FIG. 1, a front cylinder block 11 is joined to a rear
cylinder block 12. A front housing 13 is joined to the front
cylinder block 11. A rear housing 14 is joined to the rear cylinder
block 12. The front and rear cylinder blocks 11, 12 and the front
and rear housings 13, 14 constitute a whole compressor housing
assembly of the double-headed piston type compressor 10. A front
discharge chamber 131 as a discharge pressure region in the
compressor 10 is defined in the front housing 13. A rear discharge
chamber 141 as a discharge pressure region in the compressor 10 is
defined in the rear housing 14. A suction chamber 142 as a suction
pressure region is defined in the rear housing 14. It is noted that
"in the compressor" corresponds to the inside of the whole
compressor housing assembly of the compressor 10, and that "out of
the compressor" corresponds to the outside of the whole compressor
housing assembly.
[0021] A valve port plate 15, a valve plate 16, and a retainer
plate 17 are interposed between the front cylinder block 11 and the
front housing 13. A valve port plate 18, a valve plate 19, and a
retainer plate 20 are interposed between the rear cylinder block 12
and the rear housing 14. Discharge ports 151, 181 are respectively
formed in the valve port plates 15, 18. Discharge valves 161, 191
are respectively formed in the valve plates 16, 19 to open and
close the respective discharge ports 151, 181. Retainers 171, 201
are respectively formed in the retainer plates 17, 20 to regulate
the respective opening degrees of the discharge valves 161,
191.
[0022] Gaskets which are not shown in the drawings are respectively
interposed between the front and rear cylinder blocks 11, 12,
between the front cylinder block 11 and the front housing 13, and
between the rear cylinder block 12 and the rear housing 14. The
gaskets are made of metal plates whose both side surfaces are
covered by rubber sealing layers. The gaskets serve to prevent
leakage of refrigerant gas through the clearances between the
cylinder blocks 11, 12, between the cylinder block 11 and the front
housing 13, and between the cylinder block 12 and the rear housing
14.
[0023] A rotary shaft 21 is rotatably supported by the front and
rear cylinder blocks 11, 12 and is inserted into shaft holes 111,
121 which extend through the front and rear cylinder blocks 11, 12.
The outer periphery of the rotary shaft 21 is in contact with the
inner peripheries of the shaft holes 111, 121. The rotary shaft 21
is directly supported by the front and rear cylinder blocks 11, 12
through the inner peripheries of the respective shaft holes 111,
121. A contacting portion of the outer periphery of the rotary
shaft 21 with the shaft hole 111 forms a sealing circumferential
surface 211. A contacting portion of the outer periphery of the
rotary shaft 21 with the shaft hole 121 forms a sealing
circumferential surface 212.
[0024] A swash plate 23 as a cam body is secured to the rotary
shaft 21. The swash plate 23 is accommodated in a crank chamber 24
which is defined between the front and rear cylinder blocks 11, 12.
A lip-seal type shaft seal member 22 is interposed between the
front housing 13 and the rotary shaft 21. The shaft seal member 22
prevents leakage of the refrigerant gas through the clearance
between the front housing 13 and the rotary shaft 21. The front end
of the rotary shaft 21 protruding externally from the front housing
13 is connected to a vehicle engine 26 as an external drive source
through an electromagnetic clutch 25. The rotary shaft 21 receives
driving force for rotation from the vehicle engine 26 through the
electromagnetic clutch 25.
[0025] As shown in FIG. 3A, a plurality of first cylinder bores 27
is formed in the front cylinder block 11, and is arranged around
the rotary shaft 21. As shown in FIG. 3B, a plurality of second
cylinder bores 28 is formed in the rear cylinder block 12, and is
arranged around the rotary shaft 21. A double-headed piston 29 is
accommodated in each pair of the cylinder bores 27, 28.
[0026] As shown in FIG. 1, the double-headed pistons 29 are engaged
with the swash plate 23 through a pair of shoes 30. The swash plate
23 integrally rotates with the rotary shaft 21. The rotary motion
of the swash plate 23 is transmitted to the double-headed pistons
29 through the shoes 30 so that each double-headed piston 29
reciprocates in the respective pair of the cylinder bores 27, 28.
Each double-headed piston 29 has a first cylindrical head 291 which
defines a first compression chamber 271 in the respective first
cylinder bore 27. Each double-headed piston 29 has a second
cylindrical head 292 at the opposite end to the first head 291, and
the second head 292 defines a second compression chamber 281 in the
respective second cylinder bore 28.
[0027] An in-shaft passage 31 is formed in the rotary shaft 21. The
in-shaft passage 31 extends along the rotary axis 210 of the rotary
shaft 21. An inlet 311 of the in-shaft passage 31 is open to the
suction chamber 142 in the rear housing 14. A first outlet 312 of
the in-shaft passage 31 is open at the front sealing
circumferential surface 211 of the rotary shaft 21 in the shaft
hole 111. A second outlet 313 of the in-shaft passage 31 is open at
the rear sealing circumferential surface 212 of the rotary shaft 21
in the shaft hole 121.
[0028] As shown in FIGS. 2A and 3A, a first communication passage
32 is formed in the front cylinder block 11 so as to communicate
with the first cylinder bores 27 and the shaft hole 111. As shown
in FIGS. 2B and 3B, a second communication passage 33 is formed in
the rear cylinder block 12 so as to communicate with the second
cylinder bores 28 and the shaft hole 121. As the rotary shaft 21
rotates, the first and second outlets 312, 313 of the in-shaft
passage 31 intermittently communicate with the first and second
communication passages 32, 33, respectively.
[0029] When one of the first cylinder bores 27 is in a suction
process, that is, in a process of the double-headed piston 29
moving from the left side to the right side in FIG. 1, the first
outlet 312 communicates with the first communication passage 32. As
a result, refrigerant in the suction chamber 142 is introduced into
the first compression chamber 271 in the first cylinder bore 27
through the in-shaft passage 31, the first outlet 312, and the
first communication passage 32.
[0030] When the first cylinder bore 27 is in a discharge process,
that is, in a process of the double-headed piston 29 moving from
the right side to the left side in FIG. 1, the communication
between the first outlet 312 and the first communication passage 32
is shut off. As a result, refrigerant in the first compression
chamber 271 is discharged to the front discharge chamber 131
through the discharge port 151 by pushing open the discharge valve
161. The refrigerant discharged to the discharge chamber 131 flows
out to an external refrigerant circuit 34 through a passage
341.
[0031] When one of the second cylinder bores 28 is in a suction
process, that is, in a process of the double-headed piston 29
moving from the right side to the left side in FIG. 1, the second
outlet 313 communicates with the second communication passage 33.
As a result, refrigerant in the suction chamber 142 is introduced
into the second compression chamber 281 of the second cylinder bore
28 through the in-shaft passage 31, the second outlet 313, and the
second communication passage 33.
[0032] When the second cylinder bore 28 is in a discharge process,
that is, in a process of the double-headed piston 29 moving from
the left side to the right side in FIG. 1, the communication
between the second outlet 313 and the second communication passage
33 is shut off. As a result, refrigerant in the second compression
chamber 281 is discharged to the rear discharge chamber 141 through
the discharge port 181 by pushing open the discharge valve 191. The
refrigerant discharged to the discharge chamber 141 flows out to
the external refrigerant circuit 34 through a passage 342.
[0033] The external refrigerant circuit 34 is provided with a heat
exchanger 37 for removing heat from refrigerant, an expansion valve
38, and a heat exchanger 39 for evaporating the refrigerant with
heat. The expansion valve 38 controls the flow rate of the
refrigerant in accordance with the fluctuation in temperature of
the refrigerant gas at the outlet of the heat exchanger 39. The
refrigerant flowing out to the external refrigerant circuit 34
returns to the suction chamber 142.
[0034] The part of the rotary shaft 21 corresponding to the sealing
circumferential surface 211 forms a first rotary valve 35. The part
of the rotary shaft 21 corresponding to the sealing circumferential
surface 212 forms a second rotary valve 36. The rotary valves 35,
36 are formed integrally with the rotary shaft 21. The in-shaft
passage 31 and the first outlet 312 form a first introduction
passage 40 for the rotary valve 35. The in-shaft passage 31 and the
second outlet 313 form a second introduction passage 41 for the
rotary valves 36. Part of the second introduction passage 41 in the
rotary shaft 21 shares part of the first introduction passage 40.
The length of the first introduction passage 40 is greater than the
length of the second introduction passage 41. That is, the distance
to the first communication passage 32 from the suction chamber 142
through the first introduction passage 40 is greater than the
distance to the second communication passage 33 from the suction
chamber 142 through the second introduction passage 41.
[0035] As shown in FIG. 1, the activation of the electromagnetic
clutch 25 is controlled by a computer C. The computer C is
connected to a switch W for operating an air conditioner, a setting
device S for setting a target room temperature, and a detecting
device F for detecting a room temperature. When the switch W is
turned on, the computer C controls the electric current for
activation and deactivation to the electromagnetic clutch 25 in
accordance with the temperature difference between the target room
temperature and the detected room temperature.
[0036] The computer C turns off the electric current to the
electromagnetic clutch 25, when the detected temperature is lower
than the target temperature, or, when the detected temperature is
higher than the target temperature and the temperature difference
is within an allowable range. In this case, the electromagnetic
clutch 25 is in a disengaged state, and the driving force of the
vehicle engine 26 is not transmitted to the rotary shaft 21. The
computer C supplies electric current to the electromagnetic clutch
25, when the detected temperature is higher than the target
temperature and the temperature difference between the detected
temperature and the target temperature is beyond the allowable
level. In this case, the electromagnetic clutch 25 is in an engaged
state, and the driving force of the vehicle engine 26 is
transmitted to the rotary shaft 21.
[0037] As shown in FIG. 2B, the first communication passage 32 has
a circular cross-section. As shown in FIG. 2C, the second
communication passage 33 has a circular cross-section. The diameter
D of the first communication passage 32 is set larger than the
diameter d of the second communication passage 33. The in-shaft
passage 31 has a circular cross-section, and the diameter of the
in-shaft passage 31 is set larger than the diameter D of the first
communication passage 32.
[0038] In FIG. 2D, a curve E indicates change in temperature of the
front discharge chamber 131 under such a condition that the
diameter D of the first communication passage 32 is varied while
the diameter d of the second communication passage 33 is held
constant. Points on the curve E indicate actually measured values.
The horizontal axis indicates a cross section ratio of a
cross-sectional area of first communication passage to a
cross-sectional area of second communication passage. A
cross-sectional ratio of this embodiment is expressed by
(.pi.D.sup.2/4)/(.pi.d.sup.2/4), whose (.pi.D.sup.2/4) means a
cross-sectional area of the first communication passage 32, and
(.pi.d.sup.2/4) means a cross-sectional area of the second
communication passage 33. The vertical axis indicates temperature
in the front discharge chamber 131.
[0039] A curve G in the graph of FIG. 2D is under a condition
having communication passages with respective elongated
cross-sections (for example, as shown in the reference No. 6-129350
as a background art). The dimension of the respective elongated
cross-section in the axial direction of the rotary shaft 21 is
larger than the dimension in the circumferential direction. The
curve G indicates change in temperature in the discharge chamber
131 against the cross section ratio as the elongated
cross-sectional area is varied.
[0040] In the both curves E and G, the total volumes of the first
and second compression chambers 271, 281 are 200 cc, and the
rotational speed of the double-headed piston type compressor 10 is
4500 rpm, and the ratio of the discharge pressure Pd to the suction
pressure Ps is 12.
[0041] As shown in the graph of FIG. 2D, the temperature in the
discharge chamber 131 indicated by the curve E is lower than the
lowest temperature indicated by the curve G in the range where the
cross section ratio is less than or equal to 1.8. That is the case
in that the diameter D of the first communication passage 32 is
larger than the diameter d of the second communication passage 33,
and additionally less than or equal to 1.8 times of the diameter d.
Especially, the temperature at the cross section ratio of 1.4
becomes equal to the temperature at the cross section ratio of 1.
That means, if the diameter D of the first communication passage 32
is larger than the diameter d of the second communication passage
33 and less than or equal to 1.4 times of the diameter d, the
temperature in the discharge chamber 131 becomes lower than that in
case where the diameters D, d equal. When the diameter D of the
first communication passage 32 is 1.2 times of the diameter d of
the second communication passage 33, the temperature in the
discharge chamber 131 is the lowest.
[0042] According to the preferred embodiment, the following
advantageous effects are obtained.
[0043] (1) The distance to the first compression chamber 271 from
the suction chamber 142 through the first introduction passage 40
is greater than the distance to the second compression chamber 281
from the suction chamber 142 through the second introduction
passage 41. In this case, the refrigerant amount into the first
compression chamber 271 through the first communication passage 32
may be smaller than that into the second compression chamber 28i
through the second communication passage 33, supposing that the
cross-sectional areas of the communication passages 32, 33 equal.
The compression ratio in the first compression chamber 271 may
become higher than the compression ratio in the second compression
chamber 281, accordingly. Thereby the temperature in the front
discharge chamber 131 may become higher than the temperature in the
rear discharge chamber 141.
[0044] In this embodiment, the diameter D of the first
communication passage 32 is set larger than the diameter d of the
second communication passage 33 so that the cross-sectional area of
the first communication passage 32 is set larger than that of the
second communication passage 33. Such a structure reduces the
difference between the refrigerant amount into the first
compression chamber 271 through the first communication passage 32
and the refrigerant amount into the second compression chamber 281
through the second communication passage 33. By decreasing the
difference in refrigerant amount, the temperature increase of the
refrigerant compressed in the first compression chamber 271 is
effectively suppressed.
[0045] (2) The first and second communication passages 32, 33 with
the circular cross-sections are easily manufactured.
[0046] (3) When the diameter D of the first communication passage
32 is larger than the diameter d of the second communication
passage 33 and less than or equal to 1.8 times of the diameter d,
the temperature increase in the refrigerant compressed in the first
compression chamber 271 is effectively suppressed.
[0047] (4) When the diameter D is larger than the diameter d and
less than or equal to 1.4 times of the diameter d, the temperature
of the refrigerant compressed in the first compression chamber 271
is effectively decreased, compared to a case where the diameters D,
d equal.
[0048] (5) When the diameter D is 1.2 times larger than the
diameter d, the temperature increase of the refrigerant compressed
in the first compression chamber 271 is further effectively
suppressed.
[0049] (6) Communication passages as a comparative conventional art
have elongated cross-sections. The dimension of each elongated
cross-section in the axial direction is set larger than the
dimension in the circumferential direction. Supposing the
cross-sectional areas of the comparative communication passages are
equal to those of the communication passages 32, 33, the diameters
of the communication passages 32, 33 are larger than the widths of
the elongated cross-sections of the comparative communication
passages (in the circumferential direction of the rotary valves 35,
36). Therefore, in accordance with a rotation of the rotary valves
35, 36, the timing of opening the communication passages 32, 33 is
earlier than the timing of opening the elongated cross-sectional
communication passages. It is noted that "the time of opening"
represents the time when the outlets 312, 313 of the in-shaft
passage 31 start to communicate with the communication passages 32,
33. Similarly, in accordance with a rotation of the rotary valves
35, 36, the timing of closing the communication passages 32, 33 is
later than the timing of closing the elongated cross-sectional
communication passages. It is also noted that "the timing of
closing" represents the time when the state of the outlets 312, 313
of the in-shaft passage 31 is changed from the connecting state to
the disconnecting state. Therefore, with the structure having the
circular cross-sectional communication passages 32, 33, the supply
of the refrigerant into the compression chambers 271, 281 is
appropriately increased, compared to the elongated cross-sectional
communication passages.
[0050] (7) As dimensions Z1, Z2 (as shown in FIG. 1) of the
communication passages 32, 33 measured in the axial direction are
set longer, lengths X, Y (as shown in FIG. 1) of the heads 291, 292
of the double-headed pistons 29 in the axial direction are required
to be set longer. As the lengths X, Y of the heads 291, 292 are set
longer, the weight of the double-headed pistons 29 may
increase.
[0051] The diameters of the circular cross-sectional communication
passages 32, 33 are smaller than the dimensions in the axial
direction of the elongated cross-sections of the comparative
communication passages, which respectively have the same
cross-sectional areas as the communication passages 32, 33.
Therefore, with the structure having the circular cross-sectional
communication passages 32, 33, the lengths X, Y of the heads 291,
292 are appropriately shortened, compared to the communication
passages having the elongated cross-sections.
[0052] (8) The circular cross-sections of the communication
passages 32, 33 shorten the dimensions Z1, Z2 of the communication
passages 32, 33 in the axial direction, compared to the case having
the elongated cross-sectional communication passages. In the
suction process, a timing when the end faces of the double-headed
pistons 29 complete to pass by the communication passages 32, 33
becomes earlier than the case having the elongated cross-sectional
communication passages, accordingly. That is, the timing when the
double-headed pistons 29 fully open the communication passages 32,
33 is set earlier than the case with the elongated cross-sectional
communication passages, thereby increasing the supply of the amount
of the refrigerant.
[0053] The present invention is not limited to the above-described
embodiment, but may be modified into the following alternative
embodiments.
[0054] The suction chamber may be formed in the front housing 13 so
as to introduce the refrigerant into the compression chambers 271,
281 through the in-shaft passage 31.
[0055] The suction pressure region may be provided outside of the
compressor so as to introduce the refrigerant into the first and
second introduction passages. The first and second rotary valves
35, 36 may be formed independently of the rotary shaft 21.
[0056] Therefore, 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 of the appended claims.
* * * * *