Refrigerant circulation pump for air-conditioner

A refrigerant circulation pump for circulating a liquid refrigerant through an air-conditioner has a small lubrication hole extending through a bearing by means of which a shaft for driving a compressor unit of the pump is rotatably supported. The lubrication hole communicates at one of its opposite ends with a compression chamber of the compressor unit, the other of the opposite ends communicating with a friction point between the shaft and the bearing. While the pump is operating, a part of the liquid refrigerant is fed under pressure from the compression chamber to the friction point between the shaft and the bearing, thereby lubricating the friction point. With this lubrication, the pump is able to operate reliably for a prolonged period of time without causing wear of the shaft and the bearing.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a pump used in an air-conditioner for 
circulating a liquid refrigerant through a refrigerating system of the 
air-conditioner. 
2. Description of the Prior Art 
In the refrigeration and air-conditioning industry, there has recently been 
proposed an air-conditioner equipped with a pump for circulating a liquid 
refrigerant through a refrigeration system of the air-conditioner. 
The refrigerant circulation pump of the proposed air-conditioner is 
designated by 1 such as shown here in FIGS. 4 through 7. The pump 1 
includes a closed container 2 which is composed of a tubular central shell 
body 3, a first end shell 5 closing one end 3a of the shell body 3 and 
provided with an electrode assembly 4 of the so-called "hermetic terminal" 
type, and a second end shell 8 closing an opposite end of the shell body 3 
and provided with a discharge pipe 6 (FIG. 7) and an intake pipe 7. The 
closed container 2 houses therein an electric motor unit 11 composed of a 
stator 9 and a rotor 10, a shaft 13 rotatably driven by the rotor 10 and 
having an eccentric portion 12, a cylinder 16 having defined therein a 
compression chamber 14 and an intake hole 15 and a discharge hole 19 that 
communicate with the compression chamber 14, and a roller 17 firmly fitted 
over the eccentric portion 12 for co-rotation therewith and slidably 
movable along an inside surface of the compression chamber 14 as the 
eccentric portion 12 of the shaft 13 rotates within the compression 
chamber 14. Numeral 18 (FIG. 5) is a vane reciprocally movable in a radial 
direction within a vane groove 20 extending between the intake hole 15 and 
the discharge hole 19. The vane 18 is normally urged against the roller 17 
by a spring 21. A bearing 22 is disposed adjacent to the cylinder 16 and 
rotatably supports an intermediate portion 13a of the shaft 13. The 
bearing 22 has an outer peripheral surface 22a firmly fitted with an 
inside surface of the closed container 2. The intake pipe 7 communicates 
with the inside of the closed container 2 and has an end 7a welded as at 
23 to the second end shell 8. The discharge pipe 6 extends through the 
second end shell 8 and has an end 6a press-fitted in the discharge hole 19 
in the cylinder 16. A liquid refrigerant 24 is filled in the closed 
container 2. The interior of the closed container 2 is communicated with 
the discharge pipe 6 through a pressure equalizing hole 25 (FIG. 7) formed 
in the discharge pipe 6. 
With the foregoing construction, when the motor unit 11 is energized via 
the electrode assembly 4 to rotate the shaft 3 and the rotor 10, a liquid 
refrigerant returning from an air-conditioning system (not shown) is 
introduce through the intake pipe 7 into the interior of the closed 
container 2 where the refrigerant is stirred and then drawn from the 
intake hole 15 into the compression chamber 14 in the cylinder 16. As the 
roller 17 rolls on and along the inside surface of the compression chamber 
14, the refrigerant is gradually compressed within the compression chamber 
14 and then discharged from the compression chamber 14 through the 
discharge hole 19. Thereafter, the compressed refrigerant is delivered to 
an air-conditioning system (not shown) via the discharge pipe 6. As the 
compressed refrigerant flows through the discharge pipe 6, a very small 
quantity of liquid refrigerant leaks out from the pressure equalizing hole 
26 into the enclosed container 2 so as to keep the interior of the 
enclosed container 2 at a high pressure. 
According to the known refrigerant circulation pump of the foregoing 
construction, the liquid refrigerant lubricates the shaft 13 and the 
bearing 22. However, as the level of the liquid refrigerant becomes low, 
lubrication of the shaft 13 and the bearing 22 is performed insufficiently 
with the result that the shaft 13 and the bearing 22 wear out severely. 
The service life of the known refrigerant circulation pump is, therefore, 
relatively short. 
SUMMARY OF THE INVENTION 
With the foregoing drawbacks of the prior art in view, it is an object of 
the present invention to provide a refrigerant circulation pump which is 
able to operate reliably for a prolonged period of time without causing 
wear of a shaft and a bearing of the pump. 
A refrigerant circulation pump of the present invention comprises a closed 
container in which an electric motor unit and a compressor unit that are 
disposed. The compressor unit has a cylinder. A shaft driven by the 
electric motor unit is rotatably supported by a bearing, The bearing and 
the cylinder jointly define therebetween a compression chamber in which a 
liquid refrigerant is compressed. The compression chamber is communicated 
with a friction point between the shaft and the bearing by a small 
lubrication hole extending through the bearing. With the lubrication hole 
thus provided, the friction point is lubricated with the liquid 
refrigerant supplied from the compression chamber under pressure. 
Preferably, the lubrication hole communicates at one end with a discharge 
hole of the compression chamber and, at an opposite end, with the friction 
point between the shaft and the bearing. 
With this construction, a part of the liquid refrigerant which is 
compressed within the compression chamber is supplied via the small hole 
to the friction point between the shaft and the bearing, thereby 
lubricating the friction point. With this lubrication, the refrigerant 
circulation pump is able to operate reliably for a long period of time 
without causing wear of the shaft and the bearing. 
The above and other objects, features and advantages of the present 
invention will become more apparent from the following description when 
making reference to the detailed description and the accompanying sheets 
of drawings in which preferred structural embodiments incorporating the 
principles of the present invention are shown by way of illustrative 
examples.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will be described below in greater detail with 
reference to certain preferred embodiments illustrated in the accompanying 
drawings. 
FIG. 1 shows, in cross section, a refrigerant circulation pump 30 according 
to a first embodiment of this invention. The pump 30 includes a closed 
container or shell 31 which is composed of a tubular central shell body 
32, a cup-shaped first end shell 33 closing one of opposite ends of the 
shell body 32, and a cup-shaped second end shell 34 closing the other end 
of the shell body 32. The first end shell 33 is provided with an electrode 
assembly 35 of the so-called "hermetic terminal" type to which electricity 
is applied to energize an electric motor unit 36 of the pump 30. The 
second end shell 34 is provided with an intake pipe 37 and a discharge 
pipe 38. 
The electric motor unit 36 is mounted in the closed container 32 and 
includes a stator 39 secured to the shell body 32, and a rotor 40 
rotatably disposed in the stator 39. A shaft 41 is rotatably supported by 
a pair of spaced bearings 42 and 43 and driven by the rotor 40 to operate 
a compressor unit 44 received within the closed container 31. The shaft 41 
has an eccentric portion 45 disposed between the bearings 42, 43. The 
bearing 42 rotatably support an intermediate portion 41a of the shaft 41 
and has an outer peripheral surface 42a firmly fitted with an inner 
peripheral surface of the closed container 31. The bearing 43 rotatably 
supports an end portion 41b of the shaft 41 projecting outwardly from the 
eccentric portion 45. 
The compressor unit 44 includes a cylinder 46 disposed between the bearings 
42 and 43 in concentrical relation to the shaft 41. The cylinder 46 is 
secured at one end with an end of the bearing 42, and the bearing 43 is 
secured to the opposite end of the cylinder 46. The cylinder 46 and the 
bearings 42, 43 jointly define therebetween a compression chamber 47 in 
which the eccentric portion 45 of the shaft 41 is received. A ring-shaped 
roller 48 is firmly fitted over the eccentric portion 45 so that the 
roller 48 rolls on and along the inside surface of the compression chamber 
47 as the eccentric portion 45 of the shaft 41 rotates. The compression 
chamber 47 communicates with an inlet hole 49 and a discharge hole 50 that 
are formed in the cylinder 46. The inlet hole 49 and the discharge hole 50 
are separated from one another by a vane 51 which is slidably received in 
a radial vane groove 52 and normally urged against an outer peripheral 
surface of the roller 48 by means of a spring 53. 
The intake pipe 37 has one end welded to the second end shell 34 and 
communicates with the interior of the closed container 31 in the same 
manner as the intake pipe 7 of the conventional pump shown in FIG. 4. The 
discharge pipe 38 extends through the second end shell 34 and has an end 
38a press-fitted in the discharge hole 50 in the cylinder 46. The 
discharge pipe 38 has a pressure equalizing hole 54 of a small diameter 
interconnecting the interior of the closed container 31 and the inside of 
the discharge pipe 38 so as to keep the interior of the closed container 
31 at a high pressure. A liquid refrigerant 55 is filled in the closed 
container 31. 
The bearing 42 has a first lubrication hole 56 which communicates, at one 
of its opposite ends, with the compression chamber 47 and, at the other 
end, with a friction point between the intermediate portion 41a of the 
shaft 41 and the bearing 42 for a purpose described below. More 
specifically, the one end of the first lubrication hole 56 opens to the 
compression chamber 47 while the other end of the first lubrication hole 
56 faces to a sliding surface of the intermediate portion 41a of the shaft 
41. Similarly, the bearing 43 has a second lubrication hole 57 which 
communicate at one of its opposite ends with the compression chamber 47 
and, at the other end, with a friction point between the end portion 41b 
of the shaft 41 and the bearing 43 for a purpose described below. More 
specifically, the one end of the second lubrication hole 57 opens to the 
compression chamber 47 while the other end of the second lubrication hole 
57 faces to a sliding surface of the end portion 41b of the shaft 41. 
The refrigerant circulating pump 30 of the foregoing construction operates 
as follows. When the electric motor unit 36 is energized via the electrode 
assembly 35, the rotor 40 and the shaft 41 rotate clockwise in FIG. 2. The 
liquid refrigerant 55 returning from the air-conditioning system (not 
shown) is discharged from the intake pipe 37 into the closed container 31 
in which the liquid refrigerant 55 is stirred and then drawn from the 
intake hole 49 into the compression chamber 47. The liquid refrigerant 55 
trapped between the cylinder 46, the roller 48 and the vane 51 is 
progressively compressed within the compression chamber 47 as the roller 
48 rolls on and along the inside surface of the compression chamber 47. 
When a peak of the eccentric portion 45 moves past the vane 55, the 
compressed liquid refrigerant 55 is discharged from the compression 
chamber 47 through the discharge hole 50 and thereafter fed through the 
discharge pipe 38 to the air-conditioning system. During that time, a very 
small quantity of liquid refrigerant bleeds out from the pressure 
equalizing hole 54 into the interior of the closed container 31 so as to 
maintain the interior of the closed container 31 at a high pressure. 
Since the first and second small lubrication holes 56, 57 communicate at 
one end with the compression chamber 47, the liquid refrigerant 55 is fed 
under pressure through the lubrication holes 56, 57 to the friction points 
between the shaft 41 and the respective bearings 42, 43. Thus, the 
friction points are lubricated with the liquid refrigerant 55. With this 
lubrication, the refrigerant circulation pump is able to operate reliably 
for a long period of time without causing were of the shaft 41 and the 
bearings 42, 43. 
FIG. 3 shows a refrigerant circulation pump 60 according to another 
embodiment of this invention. The pump 60 differs from the pump 30 of the 
foregoing embodiment shown in FIGS. 1 and 2 in that first and second small 
lubrication holes 56a and 57a communicate at one end with the discharge 
hole 50 of the compression chamber 47 instead of the compression chamber 
47. 
During the operation of the refrigerant circulation pump 60, the compressed 
liquid refrigerant 55 is discharged from the compression chamber 47 into 
the discharge hole 50 and thence to the discharge pipe 38. In this 
instance, a portion of the compressed liquid refrigerant 55 is fed from 
the discharge hole 50 to friction points between the shaft 47 and the 
bearings 42, 43 via the lubrication holes 56a, 57a. The friction points 
(namely, sliding surfaces between the shaft 41 and the bearings 42, 43) 
are lubricated with the liquid refrigerant 55. With this lubrication of 
the sliding surfaces, the shaft 41 and the bearings 42, 43 are protected 
from wearing out and, hence, the refrigerant circulation pump 60 has a 
long service life. 
Obviously, various minor changes and modifications of the present invention 
are possible in the light of the above teaching. It is therefore to be 
understood that within the scope of the appended claims the invention may 
be practiced otherwise than as specifically described.