Fluid compressor

A fluid compressor includes a cylinder having first and second discharge ends, in which a rotating rod is rotatably arranged. First and second spiral grooves are formed on the outer circumference of the rod, and first and second spiral blades are fitted into the grooves. The first groove has a first starting end located in the middle portion of the rod, and extends from the starting end toward the first discharge end. The second groove has a second starting end located in the middle portion of the rod, and extends from the second starting end toward the second discharge end. The first and second starting ends are set apart from each other by a certain angle in the circumferential direction of the rod. Operating fluid is introduced into the middle portion in the cylinder, and fed to the first and second discharge ends of the cylinder through operating chambers defined by the first and second blades in the cylinder.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
The present invention relates to a fluid compressor and more particularly, 
to a compressor for compressing refrigerant gas in a refrigeration cycle, 
for example. 
2. Description of the Related Art 
A fluid compressor disclosed in U.S. Pat No. 4,871,304 (filed on July 11, 
1988 by the Applicant of the present invention), for example, is well 
known. The compressor of this type has a compression section driven by a 
motor and arranged in the closed case. The compression section is provided 
with a cylinder rotated together with a rotor in the motor. A piston 
having a center axis eccentric to the axis of the cylinder is rotatably 
15. housed in the cylinder. A spiral groove is formed on the outer 
circumference of the piston, extending from one end to the other end of 
the piston in the axial direction thereof, and pitches of this spiral 
groove are gradually narrowed with distance from one end to the other end 
of the piston. A blade having appropriate elasticity is fitted into the 
spiral groove. 
A space between the cylinder and the piston is partitioned into a plurality 
of operating chambers by the blade. The volumes of these operating 
chambers are gradually decreased with distance from the suction side to 
the discharge side of the cylinder. When the cylinder and the piston are 
rotated by the motor, synchronizing with each other, refrigerant gas in 
the refrigeration cycle is sucked into the operating chambers through the 
suction side of the cylinder. The gas thus sucked is successively fed to 
the operating chambers located on the discharge side of the cylinder while 
being compressed in these operating chambers, and then discharged into the 
closed case through the discharge end of the cylinder. 
In the above-described compressor, however, the pressure of the refrigerant 
gas in the operating chamber located on the discharge side of the cylinder 
is higher, as compared with that of the gas in the operating chamber 
located on the suction side of the cylinder. Therefore, thrust force acts 
on the piston, heading from the discharge side to the suction side of the 
cylinder, to thereby increase friction between the piston and bearings. A 
large drive force is thus needed to rotate the cylinder and piston. 
In order to solve this problem, applicants of the present invention propose 
another compressor in a Japanese Pat. application No 63-170693. 
According to this second compressor, the piston has two spiral grooves 
extending from the center to both ends thereof. A blade is fitted into 
each of the spiral grooves. Refrigerant gas is sucked into the cylinder 
through the center portion of the cylinder in the axial direction thereof, 
fed, while being compressed in two directions or toward both ends of the 
cylinder, and discharged into the closed case through these ends of the 
cylinder. 
This compressor has the following advantages. The refrigerant gas is 
transferred and compressed in two directions which are opposite to each 
other. Therefore, thrust forces which act on the piston from both ends to 
the center of the cylinder cancel each other out. In addition, this 
compressor enables stress, which acts on the blades, to be made smaller, 
as compared with those compressors which have a piston provided with a 
single spiral groove thereon and which has the same compression capacity 
as the above-described second compressor. 
The load torque of the compressor usually changes, drawing a sine curve, as 
the piston rotates. Its discharge pressure also pulsates, drawing a sine 
curve, as the piston rotates. In the case of the compressor in which the 
refrigerant gas is fed, while being compressed, in two directions, both 
the variation in the load torque and that in the discharge pressure are 
about two times greater than those in the compressor in which the 
refrigerant gas is fed, while being compressed, only in one direction. 
When the load torque and discharge pressure vary largely in this manner, 
vibration, noise, and the like of the compressor are increased. 
In order to increase the capacity of the compressor while making us of the 
merits available from the compressor of such type that feeds the 
refrigerant gas in two directions, it is therefore desired that the 
variation in the load torque and discharge pressure of the compressor can 
be reduced to a greater extent. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a compact fluid 
compressor capable of decreasing thrust force acting on a rotating body to 
reduce the variation in the load torque and discharge pressure of the 
compressor. 
In order to achieve the object, a fluid compressor according to the present 
invention comprises a cylinder having first and second discharge ends; a 
columnar rotating body arranged in the cylinder in the axial direction 
thereof and being eccentric to the center axis thereof, and rotatable 
while part of the rotating body is in contact with the inner 
circumferential surface of the cylinder, said rotating body having first 
and second spiral grooves on its outer circumference, said first spiral 
groove having a first starting end located substantially in the middle of 
the rotating body in the axial direction thereof, extending from the first 
starting end toward the first discharge end of the cylinder and having 
pitches gradually narrowed with distance from the first starting end to 
the first discharge end of the cylinder, while said second spiral groove 
having a second starting end located substantially in the middle of the 
rotating body in the axial direction thereof, extending from the second 
starting end toward the second discharge end of the cylinder and having 
pitches gradually narrowed with distance from the second starting end 
toward the second discharge end, said first and second spiral grooves 
being turned in directions opposite to each other, and said first and 
second starting ends being set apart from each other by a certain angle in 
the circumferential direction of the rotating body; first and second 
spiral blades fitted into the first and second grooves to be slidable in 
the radial direction of the rotating body, having outer circumferential 
surfaces closely in contact with the inner circumference of the cylinder, 
and 15. dividing the space between the inner circumference of the cylinder 
and the outer circumference of the rotating body into a plurality of 
operating chambers; means for guiding operating fluid into that area of 
the space which is adjacent to the first and second starting ends of the 
first and second spiral grooves; and means for rotating the rotating body 
synchronously with the cylinder so as to feed the operating fluid, 
introduced into said area through the guide means, to the first and second 
discharge ends of the cylinder through the operating chambers and to 
discharge the fluid outside through these discharge ends of the cylinder. 
According to the compressor having the above-described arrangement, the 
operating fluid introduced into the cylinder is fed, while being 
compressed, in two directions opposite to each other, and then discharged 
outside through the first and second discharge ends of the cylinder. 
Thrust forces, which act on the rotating body from both ends to the center 
of the body, are therefore balanced with each other. 
The load torque and discharge pressure, which are generated by the 
compressed fluid being discharged from the first discharge end of the 
cylinder, change periodically. The load torque and discharge pressure, 
which are generated by the compressed fluid being discharged from the 
second discharge end of the cylinder, change in the same way, but in 
different phase since the starting ends of the first and second spiral 
grooves are set apart from each other. Therefore, variations in the 
discharge pressure and the load torque of the compressor, which are the 
sum of the discharge pressures and the load torques at the first and 
second discharge ends, are smaller than in the case where discharge 
pressures and load torques change in the same phase, respectively. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention will now be described with reference 
to the accompanying drawings. 
FIG. 1 shows an embodiment to which the present invention is applied to a 
closed type compressor for compressing a refrigerant in a refrigerating 
cycle. 
The compressor includes a closed case 10, and motor and compression 
sections 12 and 14 arranged in the case 10. The motor section 12 includes 
a ring-shaped stator 16 fixed to the inner face of the case 10 and a 
ring-shaped rotor 18 located inside the stator 16. 
The compression section 14 has a cylinder 20, and the rotor 18 is coaxially 
fixed to the outer circumference of the cylinder 20. Both ends of the 
cylinder 20 are air tightly closed and rotatably supported by bearings 22a 
and 22b fixed to the inner face of the case 10. More specifically, the 
right end or first discharge end of the cylinder 20 is rotatably fitted 
onto the bearing 22a, while the left end or second discharge end thereof 
is rotatably fitted onto the bearing 22b. The cylinder 20 and the rotor 18 
fixed thereto are therefore supported, coaxial to the stator 16, by the 
bearings 22a and 22b. 
A columnar rotating rod 24 having a diameter smaller than that of the 
cylinder 20 is arranged in the cylinder and extends between the bearings 
22a and 22b. The rotating rod 24 has a center axis A made eccentric to 
that B of the cylinder 20 by a distance e. Part of the outer circumference 
of the rod 24 is in contact with the inner circumference of the cylinder 
20. Smaller-diameter portions 26a and 26b at both ends of the rotating rod 
24 are rotatably supported by the bearings 22a and 22b. 
The cylinder 20 and the rotating rod 24 are connected to each other through 
an Oldham's mechanism 50 which serves as rotational force transmitting 
means as will be described later. When the motor section 12 is energized 
to rotate the cylinder 20 together with the rotor 18, therefore, the 
rotational force of the cylinder 20 is transmitted to the rod 24 by means 
of the Oldham's mechanism 50. As a result, the rod 24 is rotated in the 
cylinder 20 while the outer circumference thereof is partially in contact 
with the inner circumference of the cylinder 20. 
As shown in FIGS. 2 and 3, a first groove 30a is formed on the outer 
circumference of the rotating rod 24, extending from the middle portion of 
the rod to the right end thereof, while a second groove 30b is also formed 
on the rod 24, extending from the middle portion of the rod to the left 
end thereof. The pitches of the first groove 30a gradually become narrower 
at a certain rate with distance from the middle portion of the rod 24 to 
the right end thereof or to the first discharge end of the cylinder 20. 
The pitches of the second groove 30b gradually become narrower at the 
certain rate with distance from the middle portion of the rod 24 to the 
left end thereof or to the second discharge end of the cylinder 20. The 
first groove 30a has same turns as that of the second groove 30b, but the 
first groove 30a is turned in a direction opposite to that direction in 
which the second groove 30b is turned. FIG. 3 schematically shows the rod 
24 rotated about its center axis by 180.degree. from the state shown in 
FIG. 2. 
The first and second grooves 30a and 30b have starting ends 32a and 32b 
positioned near the middle of the rod 24. The starting ends 32a and 32b 
are set apart from each other by 180.degree. in the circumferential 
direction of the rod 24. Further, the starting end 32a is set apart from 
the starting end 32b in the axial direction of the rod 24 and particularly 
the starting end of one of the groove 30a and 30b is positioned so 
adjacent to the other groove as not to cross the latter. Either groove has 
width and depth which are uniform all over its length, and the side faces 
of the groove are perpendicular to the longitudinal axis of the rod 24. 
The rotating rod 24 has a suction passage 28 therein, which extends from 
the right end of the smaller-diameter portion 26a to the middle of the rod 
24. The right end of the suction passage 28 communicates with a suction 
tube 36 of the refrigerating cycle through a suction hole 34 bored in the 
bearing 22a. The left end of the suction passage 28 communicates with 
first and second suction ports 38a and 38b which are opened at the outer 
circumference of the middle portion of the rotating rod 24. The first 
suction port 38a is positioned between the starting end 32a of the first 
groove 30a and the terminal end of the first turn thereof. Similarly, the 
second suction port 38b is positioned between the starting end 32b of the 
second groove 30b and the terminal end of the first turn thereof. The 
suction ports 38a and 38b may be formed in a hatched area on the outer 
circumference of the rod 24 or in the area thereon which is enclosed by 
the first turns of the first and second grooves 30a and 30b. One of the 
suction ports may be omitted. 
First and second spiral blades 40a and 40b shown in FIG. 1 are fitted into 
the grooves 30a and 30b, respectively. The blades 40a and 40b are formed 
of elastic material, and can be fitted into their corresponding grooves by 
ulilizing their elasticity. The thickness of each blade is substantially 
equal to the width of the corresponding groove. Each portion of each blade 
is movable in the radial direction of the rod 24 along the corresponding 
groove. The outer circumference of each of the blades 40a and 40b is 
closely in contact with the inner circumference of the cylinder 20. 
The space defined between the inner circumference of the cylinder 20 and 
the outer circumference of the rod 24, extending from the middle of the 
cylinder 20 to the first discharge side thereof, is partitioned into a 
plurality of operating chambers 42 by the first blade 40a, as shown in 
FIG. 1. Each of the operating chambers 42 is defined by two adjacent turns 
of the blade 40a and substantially in the form of a crescent, extending 
along the blade 40a from the contact portion between the rod 24 and the 
inner circumference of the cylinder 20 to the next contact portion. The 
volumes of these operating chambers 42 are reduced gradually with distance 
from the middle of the cylinder 20 toward the first discharge side 
thereof. 
Similarly the space defined between the inner circumference of the cylinder 
20 and the outer circumference of the rod 24, extending from the middle of 
the cylinder 20 to the second discharge side thereof, is partitioned into 
a plurality of operating chambers 44 by the second blade 40b. Each of the 
operating chambers 44 is defined by two adjacent turns of the blade 40b 
and substantially in the form of a crescent, extending along the blade 40b 
from a contact portion between the rod 24 and the inner circumference of 
the cylinder 20 to the next contact portion. The volumes of these 
operating chambers 44 are reduced gradually with distance from the middle 
of the cylinder 20 toward the second discharge end thereof. 
shown in FIG. 1, discharge holes 45a and 45b are formed in the bearings 22a 
and 22b, respectively. One end of the discharge hole 45a is opened into 
the first discharge end of the cylinder 20 while the other end thereof is 
opened into the case 10. One end of the discharge hole 45b is opened into 
the second discharge end of the cylinder 20 while the other end thereof is 
opened into the case 10. These discharge holes 45a and 45b may be formed 
in the cylinder 20. 
Reference numeral 46 in FIG. 1 represents a discharge tube communicating 
with the interior of the case 10. 
As shown in FIGS. 1, 4 and 5, the Oldham's mechanism 50 includes an 
Oldham's pin 52 which serves as a first pin member and an Oldham's slider 
54 which serves as a second pin member. 
The Oldham's pin 52 is columnar, having the same diameter over its entire 
length. This pin 52 is arranged in the cylinder 20 in the radial direction 
thereof and both ends of the pin 52 are fixed to the cylinder 20. The pin 
52 can rotate therefore together with the cylinder 20 around the center 
axis B thereof which is perpendicular to the pin 52. Further, the pin 52 
passes loosely through a through-hole 56 which extends through the 
rotating rod 24 in the radial direction thereof. The diameter of the 
through-hole 56 is larger by 2e than that of the Oldham's pin 52, where e 
represents the distance by which the center axis A of the rotating rod 24 
is made eccentric to the center axis B of the cylinder 20. 
The Oldham's slider 54 is columnar, having a same diameter over the whole 
length of it, which diameter is larger than that of the Oldham's pin 52. 
The slider 54 is slidably inserted into a slide hole 58 which extends 
through the rotating rod 24 in the radial direction thereof. The slide 
hole 58 extends perpendicular to the through-hole 56. Further, a 
through-hole 60 is formed in the slider 54 at the intermediate portion 
thereof, extending perpendicular to the axis of the slider 54. The 
Oldham's pin 52 is slidable inserted into the through-hole 60 and extends 
perpendicular to the slider 54. The Oldham's slider 54 is slidably 
therefore in the slide hole 58 in its axial direction and movable relative 
to the Oldham's pin 52 in the axial direction of the pin 52. 
The following is a description of the operation of the compressor 
constructed in this manner. 
When the motor section 12 is switched on, the rotor 18 rotates together 
with the cylinder 20. The rotational force of the cylinder 20 is 
transmitted to the rotating rod 24 through the Oldham's mechanism 50, 
rotating the rod 24 synchronizing with the cylinder 20. More specifically, 
Oldham's pin 52 is rotated integral with the cylinder 20, and the Oldham's 
slider 54 is also rotated together with the pin 52 while being kept 
perpendicular to the pin 52. As shown in FIGS. 4 and 5, the Oldham's pin 
52 and slider 54 slide relative to each other while being kept 
perpendicular to each other. The slider 54 slides in the slide hole 58 in 
its axial direction while the pin 52 moves in the through-hole 56 in the 
radial direction thereof. The rotational force of the cylinder 20 is thus 
transmitted to the rotating rod 24 by means of the Oldham's pin 52 and 
slider 54, and the rod 24 is rotated about the center axis A thereof. The 
rotating rod 24 is rotated in this manner, synchronizing with the cylinder 
20 while its outer circumference is partially in contact with the inner 
circumference of the cylinder 20. The first and second blades 40a and 40b 
are also rotated together with the rod 24. 
The blades 40a and 40b rotate while keeping their outer circumferences in 
contact with the inner circumference of the cylinder 20. Therefore, they 
are pushed into the corresponding grooves 30a and 30b as they approach 
each contact portion between the outer circumference of the rod 24 and the 
inner circumference of the cylinder 20, and emerge from the grooves as 
they go away from the contact portion. When the compression section 14 is 
made operative, refrigerant gas is sucked into the cylinder 20, passing 
through the suction tube 36, suction hole 34, suction passage 28, and 
first and second suction ports 38a and 38b. This gas is confined in the 
operating chamber 42 defined between the first and second turns of the 
first blade 40a and in the operating chamber 44 defined between the first 
and second turns of the second blade 40b. As the rod 24 rotates, the gas 
in the operating chamber 42 is successively fed into the next operating 
chamber 42 while being confined between the two adjacent turns of the 
blade 40a. Similarly, the gas in the operating chamber 44 is successively 
fed into the next operating chamber 44 while being confined between the 
two adjacent turns of the blade 40b. The volumes of the operating chambers 
42 are gradually reduced with distance from the middle of the cylinder 20 
to the first discharge end thereof, while the volumes of the operating 
chambers 44 are gradually reduced with distance from the middle of the 
cylinder 20 to the second discharge end. Therefore, the gas confined in 
the operating chamber 42 is gradually compressed as it is delivered to the 
first discharge end of the cylinder 20, while the gas confined in the 
rotating chamber 44 is gradually compressed as it is delivered to the 
second discharge end of the cylinder 20. The gas thus compressed is 
discharged into the case 10 through the discharge holes 45a and 45b in the 
bearings 22a and 22b, and then returned to the refrigerating cycle through 
discharge tube 46. 
FIG. 6 shows the relationship between the rotational angle of the rotating 
rod 24 and load torque and discharge pressure of the compressor. A dot and 
dash line C represents the discharge pressure and load torque generated by 
the compressed gas discharged through the discharge hole 45a, which 
change, drawing a sine curve, in accordance with the rotation of the rod 
24. A broken line D denotes the discharge pressure and load torque 
generated by the compressed gas discharged via the discharge hole 45b, 
which change, drawing a sine curve, as the rod 24 rotates. As described 
above, the starting ends 38a and 38b of the first and second spiral 
grooves 30a and 30b on the rotating rod 24 are set apart from each other 
by 180.degree. in the circumferential direction of the rod 24. The gases 
compressed in the operating chambers 42 and 44 are alternately discharged 
from the discharge holes 45a and 45b every time the rod 24 rotates 
180.degree. degrees. The curve C has the same amplitude and cycle as those 
of the curve D, but is different in phase by 180.degree. from the curve D. 
Therefore, variations in the discharge pressure and the load torque of the 
compressor, which are the sum of the discharge pressures and the load 
torques represented by the curves C and D, can be reduced as shown by a 
solid line E in FIG. 6. 
According to the compressor having the abovedescribed arrangement, the 
refrigerant gas sucked into the middle portion of the cylinder 20 is 
compressed while being fed in two opposite directions, that is, to the 
first and second discharge ends of the cylinder. When the gas is being 
compressed, therefore, thrust forces heading from the first discharge end 
of the cylinder to the middle thereof and from the second discharge end of 
the cylinder to the middle thereof act on the rotating rod 24, and they 
are balanced with each other because they are equal to each other. This 
can prevent the rod 24 from being displaced to push its end faces against 
the bearings. Therefore, during the operation of the compressor, friction 
between the rotating rod 24 and the bearings 22a and 22b can be reduced, 
thereby improving the operating efficiency of the compressor. 
If the compression capacity of the compressor is fixed, the pitches of each 
of the spiral grooves and the blades of the compressor, according to this 
embodiment, can be made smaller than those of a compressor which has a 
single spiral groove extending from one end to the other end of the 
rotating rod and a blade fitted into the groove. Therefore, with this 
embodiment, stress acting on each of the blades 40a and 40b can be 
reduced, so that abrasion of the blades ca be reduced and each blade 
smoothly moves in the corresponding groove. 
The starting ends 32a and 32b of the first and second spiral grooves 30a 
and 30b are set apart from each other in the rotating direction of the rod 
24. Therefore, the variation in the load torque and discharge pressure of 
the compressor can be greatly reduced, thereby decreasing the vibration 
and noise of the compressor to a greater extent. In addition, the starting 
ends 32a and 32b of the spiral grooves are set apart from each other in 
the axial direction of the rotating rod 24, particularly in the direction 
in which both of the spiral grooves come nearer to each other. As compared 
with the conventional compressor having a single spiral groove, therefore, 
the rotating rod can be made shorter to thereby make the compressor 
smaller in size. 
The Oldham's mechanism 50 for transmitting the rotational force of the 
cylinder 20 to the rod 24 comprises two through-holes bored in the rod 24, 
and the Oldham's pin and slider inserted through these through-holes. As 
compared with the conventional Oldham's ring, therefore, the Oldham's 
mechanism 50 needs a smaller space and this helps the compressor be made 
compact. Further, the Oldham's mechanism 50 needs no Oldham's ring. Thus, 
even when the smaller-diameter portions of the rotating rod 24 are made 
larger in diameter to make smaller those spaces which are defined between 
the inner circumference of the cylinder and the outer circumferences of 
the smaller-diameter portions of the rod 24, the mechanism 50 can be 
easily arranged in the cylinder. Even in the above case, the mechanism 50 
enables the Oldham's pin and slider to be sufficiently displaced in 
accordance with the eccentricity e of the rotating rod 24. 
The Oldham's mechanism 50 is simple in construction wherein the Oldham's 
pin and slider are inserted through the through-holes in the rotating rod. 
This simple construction enables the compressor to be more easily 
manufactured, particularly allowing the Oldham's mechanism to be more 
easily incorporated into the compressor. 
It should be understood that the present invention is not limited to the 
above-described embodiment but that various changes and modifications can 
be made without departing from the spirit and scope of the present 
invention. 
It is most preferable that the starting ends 32a and 32b of the first and 
second spiral grooves 30a and 30b are set apart from each other by 
180.degree. in the rotating direction of the rod 24. However, even when 
they are set apart by a value smaller than 180.degree., the variations in 
the load torque and discharge pressure of the compressor change can be 
smaller than those in the case where the starting ends are not set apart 
from each other. Further, turns and pitches of the first spiral groove may 
be different from those of the second spiral groove. Even in this case, 
the thrust forces acting on the rotating rod, as well as the load torque 
and discharge pressure of the compressor, can be reduced. 
The compressor of the present invention can be applied to other systems as 
well a the refrigerating cycle. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and representative devices, shown and described 
herein. Accordingly, various modifications may by without departing from 
the spirit or scope of the general inventive concept as defined by the 
appended claims and their equivalents.