Note: Descriptions are shown in the official language in which they were submitted.
CA 02636006 2008-07-23
ROTOR ASSEMBLY FOR ROTARY COMPRESSOR
FIELD OF THE INVENTION
This invention relates to rotor assemblies for rotary compressor units
especially
but not exclusively units for small refrigeration units such are suitable for
use in
small refrigerators and automotive air conditioners. Such units must be
compact,
quiet, reliable and economical to manufacture and operate.
BACKGROUND OF THE INVENTION
Compressor units for domestic refrigerators are commonly of the sealed unit
type
in which both the compressor and a motor permanently coupled to the
compressor is located within an enclosure that is completely and permanently
sealed except for refrigerant connections to the remainder of the
refrigeration
unit. Such a unit has the disadvantages that failure of either the motor or
the
compressor requires both to be discarded, different sealed units are required
for
electrical supplies requiring different motors, even though the compressor is
identical, and two devices, both of which generate unwanted heat, are
thermally
coupled within the same enclosure.
It is known in compressor units for automotive air conditioning systems, which
are engine driven, and thus require a clutch mechanism, to utilize an
electromagnetic clutch between a belt driven pulley and the compressor.
In the interests of smoother and more silent compressors, there has been some
adoption of scroll type compressors in compression type refrigeration units,
available for example from Lennox, Copeland and EDPAC International.
An alternative form of piston compressor which has been proposed, is the
rotary
piston compressor using a lobed rotor in a trochoidal chamber and having some
resemblance to rotary piston engines such as the Wankel engine although the
operating cycle is substantially different and the shaft is driven by an
external
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power source rather than being driven by the rotary piston. Such compressors
are exemplified in U.S. Patents Nos. 3,656,875 (Luck); 4,018,548 (Berkowitz);
and 4,487,561 (Eiermann).
U.S. Patent 5,310,325 (Gulyash) discloses a rotary engine using a symmetrical
lobed piston moving in a trochoidal chamber on an eccentric mounted on a
rotary
shaft and driven through a ring gear by a similarly eccentric planet gear
rotated at
the same rate as the eccentric, the gear ratio of the ring gear to the planet
gear
being equal to the number of lobes on the rotor, typically three. The apices
of the
lobes trace trochoidal paths tangent to the trochoidal chamber wall thus
simplifying sealing.
U.S. Patent 6,520,754 (Randolphi) discloses a compressor for a refrigeration
unit
having a three lobed rotor orbiting in a chamber defined within a sealed
casing
and using a magnetic coupling outside of the casing to rotate the rotor.
SUMMARY OF THE INVENTION
The present invention relates to a compressor having a rotor assembly within
which a rotor is rotated on an eccentric shaft in a sealed chamber. Two or
more
intake ports are provided that open into the sealed chamber and two or more
exhaust ports are provided with one way valves, to permit compressed gas to
exit the sealed chamber. The geometry of the rotor and sealed chamber and
eccentric drive are such that apices of the rotor remain in contact with a
peripheral wall of the sealed chamber as the rotor rotates and apex seals are
provided on the apices of the rotor to prevent leakage of the gas around the
apices of the rotor. In a preferred embodiment the rotor is a multi-lobed
rotor
orbiting within a trochoidal chamber.
The features of the present invention will be apparent from the following
description of a presently preferred embodiment thereof.
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SHORT DESCRIPTION OF THE DRAWINGS
Fig. 1 is a front schematic perspective view of a compressor having a rotor
assembly in accordance with the present invention and magnetic drive assembly
within a sealed outer casing;
Fig. 2 is a cross sectional schematic view of the compressor of Fig. 1 through
line
2-2 with an outer magnetic drive;
Fig. 3 is a perspective view of the rotor assembly for the compressor of Fig.
1;
Figs. 4 and 5 are cross-sections of the rotor assembly of Fig. 3 on the line 4-
4
showing different phases of its operation;
Fig.6. is a cross sectional schematic view of the rotor assembly of Fig. 4 on
the
line 6-6;
Fig.7. is a cross sectional schematic view of the rotor assembly of Fig. 4 on
the
line 7-7;
Fig.8. is a cross sectional schematic view of the rotor assembly of Fig. 4 on
the
line 8-8;
Fig. 9 is a schematic view of a flapper valve assembly contained within the
rotor
housing of Fig. 3;
Fig. 10 is a cross section of the flapper valve assembly on the line 9-9 in
Fig. 9.
Fig. 11 is a top plan view of another embodiment of a compressor having a
rotor
assembly in accordance with the present invention without the magnetic drive
assembly and sealed outer casing as shown in Fig. 1 and showing major internal
components in dotted lines;
Fig. 12 is a cross sectional schematic view of the compressor of Fig. 9
through
the line 12-12;
Fig 13 is a cross sectional schematic view of the compressor of Fig. 9 through
the line 13-13.
Fig. 14 is a perspective view of another embodiment of a compressor having a
rotor assembly in accordance with the present invention;
Fig. 15 is a top schematic view of the compressor of Fig. 14 showing the
assembly transparently;
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Fig. 16 is a rear perspective view of the compressor of Fig. 14 showing the
assembly transparently.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the Figures 1-8, a compressor, generally indicated at 1 in Figs.
1 &
2, comprises a sealed outer casing generally indicated at 2 retains a rotor
assembly in accordance with one embodiment of the present invention, generally
indicated at 3 and an inner magnetic drive assembly generally indicated at 5.
The
compressor 1 in one application may be connected (as shown in Fig 2) by an
intake 90 and outlet 91 such as to an evaporator and a condenser of a
refrigeration unit. In the embodiment illustrated the sealed outer casing 2
has a
canister section 6 which holds the rotor assembly 3 and inner magnetic drive
assembly 5 and a lid section 7 which fits over the inner magnetic drive
assembly
5 and onto the canister section 6 with a pair of O-rings 8,9 to seal the outer
casing. In the embodiment illustrated the canister section 6 has a cylindrical
outer
wall 10 closed at one end by plate section 11. A peripheral flange 12 extends
outwardly from the top 13 of the cylindrical outer wall 10. The thickness of
cylindrical outer wall 10 in a first section 14 adjacent the plate section 11
is
greater than the thickness of a second section 15 which in turn is thicker
than a
third section extending 16 from the top 13 of the cylindrical outer wall 10.
The
reduction in thickness in the outer cylindrical wall 10 forms a pair of lips
17, 18 on
its inner surface 4.
The rotor assembly 3, in the embodiment illustrated in Figs. 2-8, is comprised
of
a back plate 19, rotor housing 20 and front plate 21. The inner peripheral
wall 22
of the rotor housing 20 together with the inner surfaces 25, 26 of back plate
19
and front plate 21 define a sealed chamber 23 within which a rotor 24 is
rotated.
One end 27 of an eccentric shaft 28 on which the rotor 24 is mounted, is
journal
led in bearings 29 housed within the back plate 19. A timing pinion 30 is
attached
to the inner surface 25 of back disk 19 and mates with a ring gear 31 attached
to
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rotor 24. In the embodiment illustrated the timing pinion 30 is % the diameter
of
the ring gear 31. A pair of intake ports 32, 32A (see Figs 4, 5 & 7) are
provided in
back plate 19 that open into the sealed chamber 23. A pair of exhaust ports
34,
35 are provided in the rotor housing 20 (see Fig. 6). One way valves generally
5 indicated at 38 (see Fig.9), shown as flapper valves in the drawings, permit
compressed gas to exit the sealed chamber 23 but do not allow any return flow
back through the exhaust ports 34,35 into the chamber 23.
in the embodiment illustrated, the rotor 24 is mounted on an eccentric shaft
28
for orbital movement along a path within chamber 23. The profile of chamber 23
is an outline of the path that the tips of the lobes A, B, C of the rotor 24
follows.
The ratio of the ring gear 31 to the eccentric gear 30 (or timing pinion) is
equal to
the number of lobes, in this case three, of the rotor 24. In the embodiment
illustrated in Figs. I to 8, the end 32 of the eccentric shaft 28 remote from
the
rotor 24 is attached to an inner magnetic drive assembly generally indicated
at 5.
The inner magnetic drive assembly 5 has an inner magnetic drive element 33
attached to the eccentric shaft 28 where the shaft 28 extends from the front
plate
21 of the rotor assembly 3. A cap portion 37 of lid section 7 of the sealed
outer
casing 2 encloses the inner magnetic drive assembly 5. An outer magnetic drive
38 is attached to a source of rotation (not shown) and rotates about the cap
portion 37 of lid section 7 providing a mating magnetic force to turn the
inner
magnetic drive element 33.
Fig. 4 shows the position of the rotor 24 when the eccentric shaft 28, timing
pinion 30 and ring gear 31 are as seen in the drawing. The direction of
rotation
in this example is clockwise, and the apices of the lobes of the rotor are
labeled
A, B and C for convenient reference. The geometry of the rotor 24 and chamber
23 and of the drive are such that the apices remain in contact with the inner
wall.
25 of the sealed chamber 23. Apices A, B and C of rotor 24 divide the sealed
chamber 23 into three parts labeled D, E and F. Gas is introduced into the
sealed
chamber 23 through intake ports 32,32A. As the rotor 24 rotates the gas in the
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parts D, E and F of the chamber 23 is compressed as the rotation of the rotor
24
reduces the size of part D, E and F of the chamber. Fig. 5 shows the position
of
the rotor 24 rotated from the position in Fig. 4 with the eccentric shaft 28,
timing
pinion 30 and ring gear 31 positioned as seen in the drawing. The part F of
the
sealed chamber 23 has been reduced, compressing the gas in that section. The
compressed gas is exhausted through exhaust port 34. As the rotor moves
clockwise, gas is drawn through the intake port 32,32A into the parts D, E and
F
of chamber 23, the gas is compressed and forced out of the chamber 23 through
exhaust ports 34, 35 past flapper valves 38.
In order to prevent compressed gas leaking from part D, E or F of chamber 23
into one of the other parts D, E or F of chamber 23 as the rotor 24 is
rotated,
apex seals 36 are provided in a slot 36A in the apex A, B and C of rotor 24.
In the
embodiment illustrated in figs. 1-8, the back side of the rotor 24 fits tight
against
the inner surface 25 of back plate 19 and together with a lubricant provides a
seal. Similarly the front side of the rotor 24 fits tight against the inner
surface 26
of front plate 21 and together with a lubricant provides a seal. As an
alternative to
relying on the tight fit and lubricant to form a seal, side seals may be
inserted to
prevent gas from leaking around the front and back sides of the rotor.
Fig. 6 illustrates a cross section of the rotor assembly 3 of Fig. 4 on line 6-
6. The
exhaust ports 34, 35 are shown in the rotor housing 20. Fig. 7 illustrates a
cross
section of the rotor assembly 3 of Fig. 4 on line 7-7. In this view the intake
ports
32, 32A are shown in the back plate 19 although they could be located in the
front plate 21 if desired. Fig. 8 illustrates a cross section of the rotor
assembly 3
of Fig. 4 on line 8-8. In this view the apex seals 36 on apex B of rotor 24
are
shown. The apex seals 36 are preferably compression seals retained within
slots
37 on rotor 24. The apex seals 36 run on the peripheral wall 22 of the chamber
23 defined by rotor housing 20 and as noted previously prevent leakage across
the tips of the rotor 24. An apex seal spring (not shown) provides the force
to
keep the apex seals 36 in contact with the profile of the chamber 23. In the
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embodiment illustrated the apex seal springs are coil springs but a leaf
spring or
other suitable design can be used.
Figs. 9 and 10 illustrate schematically the one way flapper valves 38 in the
exhaust ports 34,35 which allow the compressed gas to exit the compressor yet
allow no return flow back. The flapper valves 38 have a disk 39 connected to
one end of a spring 40 attached to a plug 42. The spring 40 keeps disk 39 in
sealing engagement with the inlet 43 of exhaust port 34 or 35 until the
pressure
of the compressed gas is sufficient to push the disk 39 to open the inlet 43
and
permit the compressed gas to exit through outlet 44. Alternatively the flapper
valve design can be different. For example the valve may be secured on one end
and flexes to allow gas to exit the compressor.
Figs. 11 -13 illustrate another embodiment of a compressor (suitable for use
as
in refrigerators although many other applications are possible) having a rotor
assembly in accordance with the present invention with a direct shaft drive.
The
compressor, generally indicated at 51 in Figs. 11-13, comprises a rotor
assembly, generally indicated at 53 and a vector plate assembly generally
indicated at 55. In the embodiment illustrated the vector plate assembly 55
comprises a rear vector plate 56 and a seal retention plate 57 which are
attached
to the rotor assembly 53. Pressure and suction lines are attached to the rear
vector plate 56 which is in turned bolted to the back plate 59 of the rotor
assembly 53. A refrigerant gas coming into the compressor by the suction line
is
collected in the internal cavity 58 formed by the mating of the rear vector
plate 56
and back plate 59 of the rotor assembly 53.
The rotor assembly 53 is similar to the rotor assembly 3 shown in Figs, 3, 4
and
5. It comprises a back plate 59, rotor housing 60 and front plate 61. The
inner
peripheral wall 62 of the rotor housing 60 together with the inner surfaces
65, 66
of back plate 59 and front plate 61 define a sealed chamber 63 within which a
rotor 64 is rotated. One end 67 of an eccentric shaft 68 on which the rotor 64
is
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mounted, is journalled in bearings 69 housed within the back plate 59. A
timing
pinion is attached to the inner surface 65 of back plate 59 and mates with a
ring
gear 71 attached to rotor 64. In the embodiment illustrated the timing pinion
is z/3
the diameter of the ring gear 71. Intake ports are provided in back plate 59
from
cavity 58 and open into the sealed chamber 63. In large models the refrigerant
may also pass from cavity 58 through internal passages to the front of the
compressor and then through intake ports in the front plate 61 into chamber
63.
In situations where intake ports are provided in the front plate 61 the seal
retention plate 57 is replaced with a front vector plate. A pair of exhaust
ports
74,75 are provided in the rotor housing 60 (see Fig. 13). One way valves
generally indicated at 78 (see Fig.13), shown as flapper valves in the
drawings,
permit compressed gas to exit the sealed chamber 63 but do not allow any
return
flow back through the exhaust ports 74,75 into the chamber 63.
In the embodiment illustrated, the rotor 64 is mounted on an eccentric shaft
68
for orbital movement along a path within chamber 63. The profile of chamber 63
is an outline of the path that the tips of the lobes of the rotor 64 follows.
The ratio
of the ring gear 71 to the eccentric gear or timing pinion is equal to the
number of
lobes, in this case three, of the rotor 64. In the embodiment illustrated in
Figs. 11
to 13; the end 82 of the eccentric shaft 68 remote from the rotor 64 may be
attached to direct drive assembly (not shown). The seal retention plate 57
retains
a shaft seal 81 around the shaft 68 as it passes through the seal retention
plate
57.
The operation of the rotor 64 in Figs 11-13 is the same as in Figs 3-5. With
the
eccentric shaft 68, timing pinion and ring gear 71 as described, rotation of
the
rotor 64 is such that the apices of the rotor 64 remain in contact with the
inner
wall 62 of the sealed chamber 63. The apices of rotor 64 divide the sealed
chamber 63 into three parts. Gas is introduced into the sealed chamber 63
through the intake ports. As the rotor 64 rotates the volume of each part of
chamber 63 between the lobes of the rotor is continuously varied. As the
volume
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of the chambers increases refrigerant is drawn into the compressor, inversely
as
the volume decreases the now compressed gas is exhausted out of the
compressor. The three parts of chamber 63 are never compressing at once, each
is in a different phase of what could be considered a 2 phase cycle - intake
and
exhaust. As the size of a part of the sealed chamber 63 is reduced, the gas in
that section is compressed. The compressed gas is exhausted through exhaust
port 74. As the rotor moves clockwise, the part of the chamber from which the
compressed gas has been exhausted, increases in size and gas is drawn
through the intake port into that part of chamber 63. As the rotor 64
continues to
rotate, the gas is again compressed and forced out of the chamber 63 through
the other exhaust port 75 past flapper valves.
In order to prevent compressed gas leaking from one part of chamber 63 into
another one of the other parts of chamber 63 as the rotor 24 is rotated, apex
seals 76 are provided on the apices of rotor 64 as shown in Fig 12.
Fig. 12 illustrates a cross section of the compressor 51 of Fig. 11 on line 12-
12.
Fig. 13 illustrates a cross section of the compressor 51 of Fig. 11 on line 13-
13.
In this view the exhaust ports 74, 75 are shown in the rotor housing 60.
Figs. 14 -16 illustrate another embodiment of a compressor (suitable for use
as
in automotive air conditioners although many other applications are possible)
having a rotor assembly in accordance with the present invention with a direct
shaft drive. The compressor, generally indicated at 101 in Figs. 14-16,
comprises
a rotor assembly and a vector plate assembly. In the embodiment illustrated
the
vector plate assembly comprises a rear vector plate 106 and a front vector
plate
107 which are attached to the rotor assembly 103. Pressure and suction lines
are
attached to the rear vector plate 106 at suction inlet 104A and pressure
outlet
1048 respectively which is in turned bolted to the back plate 109 of the rotor
assembly 103. A refrigerant gas coming into the compressor by the suction line
is
collected in the internal cavity 108 formed by the mating of the rear vector
plate
106 and back plate 109 of the rotor assembly 103. In this embodiment one or
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more internal passages 108A connects the internal cavity 108 formed by the
mating of the rear vector plate 106 and back plate 109, with a similar
internal
cavity 108B formed by the mating of the front vector plate 107 and front plate
111
of the rotor assembly 103.
5
The rotor assembly 103 is similar to the rotor assembly 3 shown in Figs, 3, 4
and
5. It comprises a back plate, rotor housing and front plate similar to the
embodiments shown in the other figures although relative dimensions are
different. The inner peripheral wall of the rotor housing together with the
inner
10 surfaces of back plate 109 and front plate 111 define a sealed chamber
within
which a rotor is rotated. One end of an eccentric shaft 118 on which the rotor
is
mounted, is journalled in bearings housed within the back plate 109. A timing
pinion is attached to the inner surface of back plate 109 and mates with a
ring
gear attached to rotor. In the embodiment illustrated the timing pinion is 2/3
the
diameter of the ring gear. Intake ports are provided in back plate 109 from
cavity
108 and front plate 111 from cavity 108B and open into the sealed chamber. A
pair of exhaust ports are provided in the rotor housing. One way valves
preferably flapper valves, permit compressed gas to exit the sealed chamber at
pressure outlets 104B but do not allow any return flow back through the
exhaust
ports into the chamber.
In the embodiment illustrated, the rotor is mounted on an eccentric shaft 118
for
orbital movement along a path within chamber. The profile of the chamber is an
outline of the path that the tips of the lobes of the rotor follow. The ratio
of the
ring gear to the eccentric gear or timing pinion is equal to the number of
lobes, in
this case three, of the rotor. In the embodiment illustrated in Figs. 14 to
16; the
end 132 of the eccentric shaft 118 remote from the rotor may be attached to
direct drive assembly (not shown). The front vector plate 107 retains a shaft
seal
around the shaft 118 as it passes through the front vector plate 107.
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The operation of the rotor in Figs 14-16 is the same as in Figs 3-5. Rotation
of
the rotor is such that the apices of the rotor remain in contact with the
inner wall
of the sealed chamber. The apices of rotor divide the sealed chamber into
three
parts. Gas is introduced into the sealed chamber through the intake ports. In
the
embodiment illustrated there are intake ports provided in the back plate 109
and
additional intake ports in the front plate 111. As the rotor rotates the
volume of
each part of the chamber between the lobes of the rotor is continuously
varied.
As the volume of a part of the chamber increases refrigerant is drawn into the
compressor, inversely as the volume decreases the now compressed gas is
exhausted out of the compressor. The three parts of chamber are never all
compressing at the same time, each is in a different phase of what could be
considered a 2 phase cycle - intake and exhaust. As the size of a part of the
sealed chamber is reduced, the gas in that section is compressed. The
compressed gas is exhausted through exhaust port which is connected to
pressure outlet 104B. As the rotor moves clockwise, the part of the chamber
from
which the compressed gas has been exhausted, increases in size and gas is
drawn through the intake port into that part of chamber. As the rotor
continues to
rotate, the gas is again compressed and forced out of the chamber through the
other exhaust port past flapper valves to pressure outlet 104B.
In order to prevent compressed gas leaking from one part of chamber into
another one of the other parts of chamber as the rotor is rotated, apex seals
are
provided on the apices of rotor.
The rotor assembly of the present invention is particularly useful in
compressors
in various applications including (but not limited to) consumer household,
automotive air conditioners, industrial, portable, transportable, commercial,
scientific, medical, environmental and military disciplines. If required,
multiple
rotors or multiple rotor assemblies can be provided in a compressor in
accordance with present invention. A number of the advantages of the present
invention over conventional compressor designs are as follows:
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(a) only two major moving parts in the compressor
(b) light weight
(c) shaft driven rotor in combination with a simplified gear reduction drive
(d) apex seals on the rotor prevent loss of compression
(e) can utilize a variable speed drive
(f) can obtain variable output
It is to be understood by one of ordinary skill in the art that the present
discussion
is a description of exemplary embodiments only, and is not intended to limit
the
broader aspects of the present invention.
Although various preferred embodiments of the present invention have been
described herein in detail, it will be appreciated by those skilled in the
art, which
variations may be made thereto without departing from the spirit of the
invention
or the scope of the appended claims.
