COMPRESSOR UNIT FOR REFRIGERATION

MOTOCOMPRESSEUR POUR REFRIGERATION

English Abstract

A compressor for a refrigeration unit having a stator, a rotor orbiting in engagement with the stator to cyclically open, fill with refrigerant gas from at least one inlet port, compress and discharge compressed refrigerant gas through at least one discharge port, a rotary drive for orbiting the rotor, a driven element of a magnetic coupling in driving connection with the rotary drive, a casing sealed save for the ports and enclosing all of the foregoing components, a driving element of the magnetic coupling outside of the casing in close proximity to the driven element, and a motor to rotate the driving element. Preferably the rotor is a multilobed rotor orbiting within a trochoidal chamber defined by the stator. Most preferably, a three lobed rotor is journalled on an eccentric carried by a shaft of the rotary drive and has a ring gear driven by a gear of the rotary drive having the same eccentricity as the eccentric and rotated in synchronism therewith, the gear ratio of the ring gear to the eccentric being three to one.

French Abstract

Un compresseur pour une unité de réfrigération comportant un stator, un rotor en orbite en prise avec le stator pour ouvrir de manière cyclique, remplir de gaz réfrigérant à partir d'au moins un orifice d'entrée, comprimer et décharger le gaz réfrigérant comprimé à travers au moins un orifice d'évacuation, un entraînement rotatif pour graviter autour du rotor, un élément entraîné d'un couplage magnétique en liaison d'entraînement avec l'entraînement rotatif, une sauvegarde scellée encadrante pour les orifices et enfermant tous les composants suscités, un élément d'entraînement du couplage magnétique à l'extérieur du boîtier à proximité immédiate de l'élément entraîné, et un moteur pour faire tourner l'élément d'entraînement. De préférence, le rotor est un rotor polylobé en orbite dans une chambre trochoïdale définie par le stator. De manière préférée, un rotor à trois lobes est monté sur un excentrique porté par un arbre de l'entraînement rotatif et a une couronne entraînée par un engrenage de l'entraînement rotatif ayant la même excentricité que l'excentrique et mise en rotation en synchronisme avec celui-ci, le rapport d'engrenage de la couronne à l'excentrique étant de trois à un.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A compressor for a refrigeration unit comprising:
a sealed casing having at least one inlet port for
receiving refrigerant gas and at least one discharge port
for discharging compressed refrigerant gas, a stator
enclosed by the staled casing and defining a chamber in
communication with the at least one inlet port and in
communication with the at least one discharge port, a rotor
enclosed by the sealed casing, the rotor orbiting in said
chamber defined within the stator and being in engagement
with the at least one inlet port for receiving refrigerant
gas and at least one discharge port to cyclically receive
refrigerant gas through the at least one inlet port into
said chamber, compress the refrigerant gas within the
stator, and discharge the compressed refrigerant gas
through the at least one discharge port, a rotary drive
enclosed by the sealed casing and orbiting the rotor, a
driven element of a magnetic coupling in driving connection
with the rotary drive and orbiting the rotor, the driven
element enclosed by the sealed casing and including at
least one magnet, a driving element of the magnetic
coupling outside of the casing in close proximity to the

driven element, and an arrangement for rotating the driving
element.
2. A compressor according to claim 1, wherein the rotor
is a multilobed rotor and said chamber in which the rotor
is orbiting is a trochoidal chamber.
3. A compressor according to claim 2, wherein the rotor
is a three lobed rotor journalled on an eccentric carried
by a shaft of the rotary drive and has a ring gear driven
by an eccentric gear, the eccentric gear having the same
eccentricity as the eccentric and being constrained to
rotate in synchronism therewith, the gear ratio of the ring
gear to the eccentric gear being three to one.
4. A compressor according to claim 1, wherein the
arrangement for rotating the driving element includes an
electric motor.
5. A compressor according to claim 1, wherein the magnet
includes a plurality of permanent magnets.
6. A compressor according to claim 5, wherein the driving
element includes a plurality of permanent magnets.

Description

CA 02331589 2001-O1-22
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COMPRESSOR UNIT FOR REFRIGERATION
FIELD OF THE INVENTION
This invention relates to refrigeration compressor units especially but not
exclusively
units for small refrigeration units such are suitable for use in domestic ice
cream
makers, small refrigerators and similar appliances. 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
are
located within an enclosure which 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.
It is also known to use magnetic couplings in drives for pumps so as to avoid
the
necessity of sealing a drive shaft entering the pump chamber. Examples of such
arrangements are to be found in U.S. Patents Nos. 3,584,975 (Frohbieter);
3,680,984
(Young et al.); 4,065,234 (Yoshiyuki et al.); and 5,334,004 (Lefevre et al),
and in
ISOCHEM (Trademark) pumps from Pulsafeeder. Although the first of the patents
relates to a circulation pump for an absorption type air conditioning system,
the use of a
permanent magnet coupling in the drive to the compressor of a compressor type
refrigeration unit has not to the best of my knowledge previously been
proposed.

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Reasons may include the sharply fluctuating torque required by piston type
compressors normally used in such systems.
In the interests of smoother and more silent compression, 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, although not
to the
best of my knowledge for refrigeration applications, is the rotary piston
compressor
using a lobed rotor in a trochoidal chamber and having some superficial
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 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. There
is no
suggestion that similar principles of construction could be used in a
compressor.
SUMMARY OF THE INVENTION
In its broadest aspect, the invention provides a compressor for a
refrigeration unit
having a stator, a rotor orbiting in engagement with the stator to cyclically
open, fill with
refrigerant gas from at least one inlet port, compress and discharge
compressed
refrigerant gas through at least one discharge port, a rotary drive for
orbiting the rotor, a
driven element of a magnetic coupling in driving connection with the rotary
drive, a
casing sealed save for the ports and enclosing all of the foregoing
components, a

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driving element of the magnetic coupling outside of the casing in close
proximity to the
driven element, and means to rotate the driving element.
Preferably the rotor is a multilobed rotor orbiting within a trochoidal
chamber defined by
the stator, although a scroll type compressor with stationary and orbiting
scrolls may
also be utilized. Most preferably, a three lobed rotor is journalled on an
eccentric
carried by a shaft of the rotary drive and has a ring gear driven by a gear of
the rotary
drive having the same eccentricity as the eccentric and rotated in synchronism
therewith, the gear ratio of the ring gear to the eccentric being three to
one.
Further features of the invention will be apparent from the following
description of a
presently preferred embodiment thereof.
SHORT DESCRIPTION OF THE DRAWINGS
Figures 1 - 4 are cross-sectional views through a compressor in accordance
with the
invention, showing different phases of its operation, Figure 1 being a section
on the line
1 - 1 in Figure 5; and
Figure 5 is a longitudinal section of the unit on the line 5 - 5 in Figure 1,
with the
compressor and drive separated for clarity.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure 5, a compressor 2 comprises a casing 4 which is completely
sealed
apart from input and output pipes 6 and 8 which connect the compressor 2
respectively
to the evaporator and the condenser (not shown) of a refrigeration unit. A
third pipe 10
is used only to charge the unit with refrigerant and is then permanently
sealed.
Internally the pipes 6 and 8 are connected to chambers 12 and 14 respectively
(see
Figs. 1 - 4) formed between the casing 4 and a stator 16 of the compressor,
the
chambers being separated by walls 38. A compressor drive shaft 18 is
journalled in
bearings 20 in end walls 22, 24 of the stator, and carries at one end a driven
element
26 of a magnetic coupling which may for example consist of concentric rings of
ceramic

<IMG>

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S
equipped with spring valves such as reed valves 58 to prevent unwanted reverse
flow.
Figure 1 shows the position of the rotor 40 when the maximum eccentricities of
the
eccentric 40 and gear 46 are directed upwardly (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 and
stator and
of the drive are such that the apices remain in contact with the wall of
trochoidal
chamber 44. Apex B contacts the wall between the lower ports 54 and 56, while
the
surface of the rotor between apices A and C lies against the chamber wall,
obturating
the upper ports 54 and 56. As the rotor moves clockwise, gas is drawn through
the
lower port 56 into the chamber labeled D, while gas in chamber E is compressed
and
forced out of the chamber through lower port 54 past valve 58 if its pressure
exceeds
that in chamber 14.
As the rotor reaches the position shown in Figure 2, apex B moves past lower
port 56
cutting off the induction of gas into chamber D and then apex A moves past
upper port
54 so that gas compressed in chamber D on further motion of the rotor can pass
through that port once its pressure exceeds that in chamber 14. At the same
time, that
portion of the rotor between apices A and C moves away from the stator forming
chamber F into which gas is induced through upper port 56, and pressurized gas
continues to be expelled through lower port 54 from chamber E.
In Figure 3, the position is analogous to that in Figure 1, except that apex A
lies
between upper ports 54 and 56, and lower ports 54 and 56 are obturated by the
surface
of the rotor between apices B and C. In Figure 4 the position is analogous to
that in
Figure 2, with chamber F filled, chamber E refilling, and compressed gas being
expelled
from chamber D. When the eccentric again reaches the position shown in Figure
1, the
rotor has turned through 120 degrees and a similar sequence is then repeated.
After
three sequences, the rotor has turned through 360 degrees. In effect, three
compression cycles are occurring simultaneously, 120 degrees out of phase,
providing

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high volumetric efficiency and a very smooth action.
Particularly if at least one of the rotor and the stator is molded from
synthetic plastic, it
may be possible to dispense with apex seals, thus further simplifying
construction. The
use of an external motor means that the latter may also power other functions
of
S apparatus including a refrigeration unit incorporating the compressor, for
example
mixing paddles in an icecream maker. The compactness of the equipment suits it
for
use in portable applications such as refrigerated protective clothing.
Although a particularly preferred embodiment of compressor has been described,
other
forms of compressor using rotors orbiting in trochoidal chambers may be
utilized, as
may scroll compressors.

Representative Drawing