(19) |
|
|
(11) |
EP 2 417 405 B1 |
(12) |
EUROPEAN PATENT SPECIFICATION |
(45) |
Mention of the grant of the patent: |
|
18.03.2020 Bulletin 2020/12 |
(22) |
Date of filing: 06.04.2009 |
|
(51) |
International Patent Classification (IPC):
|
(86) |
International application number: |
|
PCT/EP2009/002529 |
(87) |
International publication number: |
|
WO 2010/115435 (14.10.2010 Gazette 2010/41) |
|
(54) |
REFRIGERATING CIRCUIT AND METHOD FOR CONTROLLING THE OIL DISTRIBUTION WITHIN THE SAME
KÄLTEKREISLAUF UND VERFAHREN ZUR STEUERUNG DER ÖLVERTEILUNG DARIN
CIRCUIT DE RÉFRIGÉRATION ET PROCÉDÉ DE COMMANDER DE LA DISTRIBUTION D'HUILE DANS CELUI-CI
|
(84) |
Designated Contracting States: |
|
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO
PL PT RO SE SI SK TR |
(43) |
Date of publication of application: |
|
15.02.2012 Bulletin 2012/07 |
(73) |
Proprietor: Carrier Corporation |
|
Farmington, CT 06034-4015 (US) |
|
(72) |
Inventors: |
|
- HAFKEMEYER, Markus
53225 Bonn (DE)
- SIEGERT, Jan
55118 Mainz (DE)
|
(74) |
Representative: Schmitt-Nilson Schraud Waibel Wohlfrom
Patentanwälte Partnerschaft mbB |
|
Pelkovenstraße 143 80992 München 80992 München (DE) |
(56) |
References cited: :
EP-A1- 1 120 611 EP-A2- 1 614 983 JP-A- 1 193 088 JP-A- 63 034 451 JP-U- 5 027 560 US-A- 5 634 345
|
EP-A2- 0 403 239 EP-A2- 1 677 057 JP-A- 4 080 555 JP-A- 2000 337 726 US-A- 3 633 377
|
|
|
|
|
|
|
|
|
Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
|
[0001] The invention relates to a refrigerating circuit as well as to a method for controlling
the oil distribution within a multi-compressor unit of a refrigerating circuit.
[0002] JP 2000 337 726 A discloses an air conditioning system with a plurality of outdoor machines respectively
including a compressor. The outdoor machines are connected in parallel with an indoor
machine. The compressors are fluidly connected with each other through uniform oil
pipes which can transport residual oil in each compressor. Discharge bypass valves
and a capillary tube are provided on a discharge of the compressor of each outdoor
machine. The bypass pipings are connected with a pressure container of each compressor,
respectively.
[0003] In a conventional multi-compressor unit of a refrigerating circuit that comprises
two or more oil lubricated compressors of the same or different size working in parallel
the oil level in the individual compressors cannot be kept constant. Once started
some compressors lose oil that others accumulate by numerous reasons. This effect
is even stronger if the rotational speed of one or more of these compressors changes.
[0004] If a compressor of the multi-compressor unit runs out of oil, this compressor is
likely to be damaged. The same happens, when the oil accumulated in one compressor
exceeds a certain level. One conventional approach to ensure the oil level in the
compressors being in an acceptable range is to apply an oil distribution program in
which the compressor of the multi-compressor unit having an unacceptable oil level
if switched out of operation and supplied with the necessary amount of oil or the
excess oil is sucked off. This approach however significantly reduces the efficiency
of the multi-compressor unit and the refrigerating circuit, since quite often one
compressor cannot be operated in the refrigeration mode for a certain time interval.
[0005] Accordingly it would be beneficial to provide a refrigerating circuit and a method
for controlling the oil distribution within a multi-compressor unit of a refrigerating
circuit that provide an improved efficiency and that avoid switching off compressors
from operation to ensure an acceptable oil level range.
[0006] A refrigerating circuit according to exemplary embodiments of the invention comprises
- in flow direction - a multi-compressor unit, a condenser/gas cooler, a receiver,
at least one evaporator having a respective expansion device arranged before it, and
conduits circulating a refrigerant containing oil therethrough, wherein the multi-compressor
unit comprises a first compressor the rotational speed of which can be controlled
and at least one further compressor running at a constant rotational speed, wherein
the suction sides and the pressure sides of the compressors are connected in parallel,
wherein an oil balance line is provided between the oil sumps of the compressors,
said oil balance line connecting the oil sumps of the compressors at substantially
the same positions of height, and wherein a solenoid valve allowing oil flow in either
direction is arranged in the oil balance line between the first compressor and the
at least one further compressor for controlling the oil distribution between the oil
sumps of the compressors during operation of the compressors of the multi-compressor
unit. Means are provided for measuring a pressure difference between the first compressor
and one of the further compressors, and wherein the solenoid valve is controllable
so as to close if the pressure difference exceeds a predetermined threshold value,
thereby blocking an oil flow between the first compressor and the further compressors,
The solenoid valve is controllable so as to close if the rotational speed of the first
compressor exceeds a predetermined upper threshold value or falls below a predetermined
lower threshold value, thereby blocking an oil flow between the first compressor and
the further compressors.
[0007] A method for controlling the oil distribution within a multi-compressor unit of a
refrigerating circuit, the multi-compressor unit comprising a first compressor the
rotational speed of which is controllable and at least one further compressor running
at constant speed, wherein the suction sides and the pressure sides of the compressors
are connected in parallel, comprising the following steps carried out while all compressors
of the multi-compressor unit are running:
- (a) allowing an oil flow between the oil sumps of the compressors, and
- (b) blocking an oil flow between the first compressor and the further compressors,
if a sensed pressure difference between the first compressor and one of the further
compressors exceeds a predetermined threshold value, and/or if the rotational speed
of the compressor exceeds an upper threshold value or falls below a lower threshold
value, especially by closing a solenoid valve arranged in the oil balance line between
the first compressor and the at least one further compressor, said oil balance line
connecting the oil sumps of the compressors at substantially the same positions of
height.
[0008] Exemplary embodiments of the invention will be described in more detail with reference
to the enclosed figure, which shows a schematic diagram of a refrigeration circuit
applying a multi-compressor unit according to an embodiment of the invention.
[0009] The refrigeration circuit 2 comprises in flow direction a multi-compressor unit having
a speed controlled compressor 4, a first constant speed compressor 6 and a second
constant speed compressor 8, a condenser/gas cooler 12, a receiver/collecting container
14, three evaporators 18, 22 and 26 having a respective expansion valve 16, 20 and
24 arranged before it and conduits/piping circulating a refrigerant containing oil
therethrough. The operation of the refrigeration circuit 2 is known to a skilled person
and does not need to be explained further.
[0010] The conduit portion connecting the outputs of the evaporators 18, 22 and 26 to the
input sides of the compressors 4, 6 and 8 is called suction line 28 hereinafter. The
suction line 28 branches off into three separate parallel lines leading to the input
sides of the compressors 4, 6 and 8. The suction sides of the compressors 4, 6 and
8 are therefore connected in parallel.
[0011] The compressors 4, 6 and 8 can be reciprocating compressors. The speed controlled
compressor 4 can be a VSD-controlled compressor.
[0012] The conduit portion between the output sides of the compressors 4, 6 and 8 and the
entrance of the condenser/gas cooler 12 is called pressure line 10 hereinafter. The
pressure line portions from the output sides of the compressors 4, 6 and 8 join before
the condenser/gas cooler 12. Hence, the pressure side of the compressors 4, 6 and
8 are also connected in parallel. The refrigerant flow direction through these elements
of the refrigerating circuit 2 is schematically depicted by an arrow having the reference
numeral 38.
[0013] The condenser/gas cooler 12 works as a condenser liquefying the refrigerant, if the
refrigeration circuit 2 is operated in a sub-critical mode. The condenser/gas cooler
12 works as a gas cooler not liquefying but only cooling the gaseous refrigerant,
if the refrigeration circuit 2 is operated in a transcritical mode. The refrigerant
circulating in the refrigeration circuit can be of any conventional kind, however,
it is particularly suitable for transcritical operation. Thus, also CO2 can be used
as refrigerant.
[0014] All of the compressors of the multi-compressor unit, namely the VSD-controlled compressor
4, the first constant speed compressor 6 and the second constant speed compressor
8 comprise an oil sump, and an oil balance line 30 attaches to the same positions
of height of the oil sump of the VSD-controlled compressor 4 and the constant speed
compressor 6 and connects the oil sumps of these compressors 4 and 6. This oil balance
line 30 also extends to the second constant speed compressor 8, and is connected to
the oil sump level of the second constant speed compressor 8 attaching to the same
position of height of its oil sump level. This oil balance line to the second constant
speed compressor 8 has the reference numeral 34. The oil sump levels are provided
with a sight glass for allowing monitoring of the oil sump levels within the oil sump
of the compressors 4, 6 and 8. In the oil balance line 30 between the VSD-controlled
compressor 4 and the first constant speed compressor 6 a solenoid valve 32 is provided
that allows oil flow in either direction and that is capable for controlling the oil
distribution between the oil sumps of the VSD-controlled compressor 4 on the one hand
and the constant speed compressor 6 and 8 on the other hand during operation of the
compressors 4, 6 and 8 of the multi-compressor unit. The oil flow direction within
the oil balance line 30 is depicted by an arrow having the reference numeral 36.
[0015] In one particular embodiment of operation, the oil sump levels of the compressors
4, 6 and 8 are monitored and the solenoid valve 32 is closed if the oil sump level
of one of the compressors 4, 6 and 8 exceeds a predetermined upper threshold value
or falls below a predetermined lower threshold value, thereby blocking an undesired
oil flow between the speed controlled compressor 4 and the constant speed compressors
6 and 8.
[0016] In another particular embodiment of operation, the oil sump levels of the compressors
4, 6 and 8 are monitored and the solenoid valve 32 is closed if the oil sump levels
difference between the speed controlled compressor 4 and one of the further constant
speed compressors 6 and 8 exceeds a predetermined upper threshold value, thereby blocking
an undesired oil flow between the speed controlled compressor 4 and the constant speed
compressors 6 and 8.
[0017] The pressure difference between the speed controlled compressor 4 and the constant
speed compressors 6 and 8 is monitored and the solenoid valve 32 is closed if this
pressure difference exceeds a predetermined threshold value, thereby blocking an undesired
oil flow between the speed controlled compressor 4 and the constant speed compressors
6 and 8.
[0018] Also, the rotational speed of the speed controlled compressor 4 is monitored and
the solenoid valve 32 is closed if the rotational speed of the speed controlled compressor
4 exceeds a predetermined upper threshold value or falls below a predetermined lower
threshold value, thereby blocking an undesired oil flow between the speed controlled
compressor 4 and the constant speed compressors 6 and 8.
[0019] These control features can employ means for sensing the required values (not shown
in the Figure), for example means for monitoring the oil sump levels, means for measuring
a pressure difference or means for measuring the rotational speed, and the solenoid
valve is controlled so as to close if the sensed values are no more in an acceptable
range and/or so as to close if the sensed values are in an acceptable range again.
[0020] When the rotational speed is used for as control feature, it is not necessary to
provide a certain device. It is possible to just refer to the known frequency controlled
by the VSD. Since every other compressor runs at the same, constant and of course
known frequency of the local power supply and the frequency of the VSD output is given
the difference can be used to calculate the difference of rotational speed.
[0021] These control features provide a reliable oil distribution between the oil sumps
of the compressors, and only require a minimum equipment of sensors and control.
[0022] The solenoid valve 32 can be closed and opened up at predetermined intervals for
blocking, and respectively, allowing oil flow between the speed controlled compressor
4 and the constant speed compressors 6 and 8.
[0023] By closing and opening up the solenoid valve 32 at predetermined intervals, the extent
of the oil distribution between the speed controlled compressor 4 and the constant
speed compressors 6 and 8 can be limited in terms of time, and the opening and closing
intervals can be selected according to the specification and the expected load or
performance of the refrigerating circuit. By this embodiment a reliable oil distribution
can be attained nearly without any sensor equipment.
[0024] As described above, the solenoid valve closes and avoids an oil distribution between
the speed controlled compressor and the other constant speed compressors.
[0025] It is possible to provide a unit controller (not shown in the Figure) that controls
the condenser/gas cooler 12, the compressors 4, 6 and 8 and the solenoid valve 32.
The control of this unit controller can be carried out by a control algorithm for
the solenoid valve 32 being integrated into the unit controller or by a separate impulse
generator.
[0026] As described above, the oil distribution between the compressors can be effected
during normal operation of the compressors of the multi-compressor unit. It is neither
necessary to switch off a compressor in order to run an oil distribution program nor
is it necessary to provide an additional oil separator. The oil distribution between
the oil sumps of the compressors can be controlled during operation of all the compressors
running which avoids switching off one or the other compressor for a certain time
interval and which significantly improves the efficiency of the refrigerating circuit.
Moreover, the oil levels in the oil sumps of all the compressors can reliably be kept
in an acceptable range.
[0027] As described above, the oil balance line attaches to positions of height at the oil
sumps of the compressors that corresponds to the necessary oil level of the compressors
in operation. Alternatively, as an example not being part of the present invention,
the oil balance line can attach to other positions of height within an acceptable
oil level range between a position of minimum required oil level and a position of
maximum required oil level or even lower.
[0028] However, it is required that the oil balance line always attaches to substantially
the same positions of height of the oil sumps present in the multi-compressor unit,
wherein a variation of a few millimeters is acceptable.
[0029] According to exemplary embodiments, as described above, the suction pressure of the
compressors of the multi-compressor unit lies at substantially the same suction pressure
level for all compressors. The refrigerating circuit according to exemplary embodiments,
as described above, does not use a pressure difference for regulating the oil level,
and the equipment necessary for such oil regulation due to pressure differences can
be avoided, which saves further costs and effort.
[0030] While the invention has been described with reference to exemplary embodiments, it
will be understood by those skilled in the art that various changes may be made and
equivalents may be substituted for elements thereof without departing from the scope
of the invention. In addition many modifications may be made to adopt a particular
situation or material to the teachings of the invention without departing from the
essential scope thereof. Therefore, it is intended that the invention not be limited
to the particular embodiments disclosed, but that the invention include all embodiments
falling within the scope of the claims.
List of Reference Numerals
[0031]
- 2
- refrigeration circuit
- 4
- VSD controlled compressor
- 6
- constant speed compressor
- 8
- constant speed compressor
- 10
- pressure line
- 12
- condenser/gas cooler
- 14
- receiver
- 16
- first expansion device
- 18
- first evaporator
- 20
- second expansion device
- 22
- second evaporator
- 24
- third expansion device
- 26
- third evaporator
- 28
- suction line
- 30
- oil balance line
- 32
- solenoid valve
- 34
- oil balance line to additional compressor
- 36
- oil flow direction
- 38
- refrigerant flow direction
1. Refrigerating circuit, comprising - in flow direction - a multi-compressor unit (4,
6, 8), a condenser/gas cooler (12), a receiver (14), at least one evaporator (18,
22, 26) having a respective expansion device (16, 20, 24) arranged before it, and
conduits circulating a refrigerant containing oil therethrough,
wherein the multi-compressor unit (4, 6, 8) comprises a first compressor (4) the rotational
speed of which can be controlled and at least one further compressor (6, 8) running
at a constant rotational speed,
wherein the suction sides and the pressure sides of the compressors (4, 6, 8) are
connected in parallel,
wherein an oil balance line (30) is provided between the oil sumps of the compressors
(4, 6, 8), said oil balance line (30) connecting the oil sumps of the compressors
(4, 6, 8) at substantially the same positions of height,
wherein a solenoid valve (32) allowing oil flow in either direction is arranged in
the oil balance line (30) between the first compressor (4) and the at least one further
compressor (6, 8) for controlling the oil distribution between the oil sumps of the
compressors (4, 6, 8) during operation of the compressors (4, 6, 8) of the multi-compressor
unit (4, 6, 8), and
characterized in that means are provided for measuring a pressure difference between the first compressor
(4) and one of the further compressors (6, 8), and wherein the solenoid valve (32)
is controllable so as to close if the pressure difference exceeds a predetermined
threshold value, thereby blocking an oil flow between the first compressor (4) and
the further compressors (6, 8); or
in that the solenoid valve (32) is controllable so as to close if the rotational speed of
the first compressor (4) exceeds a predetermined upper threshold value or falls below
a predetermined lower threshold value, thereby blocking an oil flow between the first
compressor (4) and the further compressors (6, 8).
2. Refrigerating circuit according to claim 1, wherein the compressors (4, 6, 8) of the
multi-compressor unit operate substantially at the same suction pressure level.
3. Refrigerating circuit according to claim 1 or 2, wherein means to monitor the oil
sump levels are arranged in the oil sumps of the compressors (4, 6, 8), and wherein
the solenoid valve (32) is controllable so as to close if the oil sump level of one
of the compressors (4, 6, 8) exceeds a predetermined upper threshold value, thereby
blocking an oil flow between the first compressor (4) and the further compressors
(6, 8).
4. Refrigerating circuit according to any of the preceding claims, wherein means to monitor
the oil sump levels are arranged in the oil sumps of the compressors (4, 6, 8), and
wherein the solenoid valve (32) is controllable so as to close if the oil sump level
of one of the compressors (4, 6, 8) falls below a predetermined lower threshold value,
thereby blocking an oil flow between the first compressor (4) and the further compressors
(6, 8).
5. Refrigerating circuit according to any of the preceding claims, wherein means to monitor
the oil sump levels are arranged in the oil sumps of the compressors (4, 6, 8), and
wherein the solenoid valve (32) is controllable so as to close if the oil sump level
difference between the first compressor (4) and one of the further compressors (6,
8) exceeds a predetermined upper threshold value, thereby blocking an oil flow between
the first compressor (4) and the further compressors (6, 8).
6. Refrigerating circuit according to claim 1 or 2, wherein the solenoid valve (32) is
controllable so as to close and open up at predetermined intervals for blocking and,
respectively, allowing oil flow between the first compressor (4) and the further compressors
(6, 8).
7. Refrigerating circuit according to any of the preceding claims, further comprising
a unit controller for controlling the condenser/gas cooler (12), the compressors (4,
6, 8) and the solenoid valve (32).
8. Refrigerating circuit according to claim 7, wherein the control algorithm for the
solenoid valve (32) is integrated into the unit controller.
9. Refrigerating circuit according to any of claims 1 to 7, wherein the control of the
solenoid valve (32) is carried out by a separate impulse generator.
10. Method for controlling the oil distribution within a multi-compressor unit of a refrigerating
circuit, the multi-compressor unit (4, 6, 8) comprising a first compressor (4) the
rotational speed of which is controllable and at least one further compressor (6,
8) running at constant speed, wherein the suction sides and the pressure sides of
the compressors (4, 6, 8) are connected in parallel, the multi-compressor unit (4,
6, 8) further comprising an oil balance line (30) extending between the first compressor
(4) and the at least one further compressor (6, 8), and allowing an oil flow between
the oil sumps of the compressors (4, 6, 8);
characterized in that, while all compressors (4, 6, 8) of the multi-compressor unit are running,
the oil flow between the first compressor (4) and the further compressors (6, 8) is
blocked, when a sensed pressure difference between the first compressor (4) and one
of the further compressors (6, 8) exceeds a predetermined threshold value, and/or
when the rotational speed of the compressor (4) exceeds an upper threshold value or
falls below a lower threshold value, especially by closing a solenoid valve (32) arranged
in the oil balance line (30), said oil balance line (30) connecting the oil sumps
of the compressors (4, 6, 8) at substantially the same positions of height.
1. Kühlkreislauf, umfassend - in Strömungsrichtung - eine Mehrfachverdichtereinheit (4,
6, 8), einen Kondensator/Gaskühler (12), einen Sammelbehälter (14), mindestens einen
Verdampfer (18, 22, 26), der eine entsprechende Expansionsvorrichtung (16, 20, 24)
aufweist, die vor diesem angeordnet ist, und Leitungen, die ein Kältemittel, das Öl
enthält, dadurch zirkulieren lassen,
wobei die Mehrfachverdichtereinheit (4, 6, 8) einen ersten Verdichter (4), dessen
Drehzahl gesteuert werden kann, und mindestens einen weiteren Verdichter (6, 8), der
mit einer konstanten Drehzahl läuft, aufweist,
wobei die Saugseiten und die Druckseiten der Verdichter (4, 6, 8) parallel geschaltet
sind,
wobei eine Ölausgleichsleitung (30) zwischen den Ölwannen der Verdichter (4, 6, 8)
vorgesehen ist, wobei die Ölausgleichsleitung (30) die Ölwannen der Verdichter (4,
6, 8) an im Wesentlichen gleichen Höhenpositionen verbindet,
wobei ein Magnetventil (32), das einen Ölstrom in jede Richtung ermöglicht, in der
Ölausgleichsleitung (30) zwischen dem ersten Verdichter (4) und dem mindestens einen
weiteren Verdichter (6, 8) angeordnet ist, um die Ölverteilung zwischen den Ölwannen
der Verdichter (4, 6, 8) während des Betriebs der Verdichter (4, 6, 8) der Mehrfachverdichtereinheit
(4, 6, 8) zu steuern, und
gekennzeichnet
dadurch, dass Einrichtungen bereitgestellt werden, um eine Druckdifferenz zwischen dem ersten Verdichter
(4) und einem aus den weiteren Verdichtern (6, 8) zu messen, und wobei das Magnetventil
(32) so ansteuerbar ist, dass es sich schließt, wenn die Druckdifferenz einen vorbestimmten
Schwellenwert überschreitet, wodurch ein Ölstrom zwischen dem ersten Verdichter (4)
und den weiteren Verdichtern (6, 8) blockiert wird; oder
dadurch, dass das Magnetventil (32) so ansteuerbar ist, dass es sich schließt, wenn
die Drehzahl des ersten Verdichters (4) einen vorbestimmten oberen Schwellenwert überschreitet
oder einen vorbestimmten unteren Schwellenwert unterschreitet, wodurch ein Ölstrom
zwischen dem ersten Verdichter (4) und den weiteren Verdichtern (6, 8) blockiert wird.
2. Kühlkreislauf nach Anspruch 1, wobei die Verdichter (4, 6, 8) der Mehrfachverdichtereinheit
im Wesentlichen mit demselben Saugdruckpegel betrieben werden.
3. Kühlkreislauf nach Anspruch 1 oder 2, wobei in den Ölwannen der Verdichter (4, 6,
8) Einrichtungen zum Überwachen der Ölwannenpegel angeordnet sind und wobei das Magnetventil
(32) so ansteuerbar ist, dass es sich schließt, wenn der Ölwannenpegel eines der Verdichter
(4, 6, 8) einen vorbestimmten oberen Schwellenwert überschreitet, wodurch ein Ölstrom
zwischen dem ersten Verdichter (4) und den weiteren Verdichtern (6, 8) blockiert wird.
4. Kühlkreislauf nach einem der vorstehenden Ansprüche, wobei Einrichtungen zum Überwachen
der Ölwannenpegel in den Ölwannen der Verdichter (4, 6, 8) angeordnet sind und wobei
das Magnetventil (32) so ansteuerbar ist, dass es sich schließt, wenn der Ölwannenpegel
eines der Verdichter (4, 6, 8) einen vorbestimmten unteren Schwellenwert unterschreitet,
wodurch ein Ölstrom zwischen dem ersten Verdichter (4) und den weiteren Verdichtern
(6, 8) blockiert wird.
5. Kühlkreislauf nach einem der vorstehenden Ansprüche, wobei Einrichtungen zum Überwachen
der Ölwannenpegel in den Ölwannen der Verdichter (4, 6, 8) angeordnet sind und wobei
das Magnetventil (32) so ansteuerbar ist, dass es sich schließt, wenn die Ölwannenpegeldifferenz
zwischen dem ersten Verdichter (4) und einem der weiteren Verdichter (6, 8) einen
vorbestimmten oberen Schwellenwert überschreitet, wodurch ein Ölstrom zwischen dem
ersten Verdichter (4) und den weiteren Verdichtern (6, 8) blockiert wird.
6. Kühlkreislauf nach Anspruch 1 oder 2, wobei das Magnetventil (32) so ansteuerbar ist,
dass es sich in vorbestimmten Intervallen schließt und öffnet, um einen Ölstrom zwischen
dem ersten Verdichter (4) und den weiteren Verdichtern (6, 8) zu blockieren beziehungsweise
zuzulassen.
7. Kühlkreislauf nach einem der vorstehenden Ansprüche, ferner umfassend eine Anlagensteuerung
zum Steuern des Kondensators/Gaskühlers (12), der Verdichter (4, 6, 8) und des Magnetventils
(32).
8. Kühlkreislauf nach Anspruch 7, wobei der Steueralgorithmus für das Magnetventil (32)
in die Anlagensteuerung integriert ist.
9. Kühlkreislauf nach einem der Ansprüche 1 bis 7, wobei die Steuerung des Magnetventils
(32) von einem gesonderten Impulsgenerator ausgeführt wird.
10. Verfahren zum Steuern der Ölverteilung innerhalb einer Mehrfachverdichtereinheit eines
Kühlkreislaufs, wobei die Mehrfachverdichtereinheit (4, 6, 8) einen ersten Verdichter
(4), dessen Drehzahl gesteuert werden kann, und mindestens einen weiteren Verdichter
(6, 8), der mit einer konstanten Drehzahl läuft, aufweist, wobei die Saugseiten und
die Druckseiten der Verdichter (4, 6, 8) parallel geschaltet sind, wobei die Mehrfachverdichtereinheit
(4, 6, 8) ferner eine Ölausgleichsleitung (30) umfasst, die sich zwischen dem ersten
Verdichter (4) und dem mindestens einen weiteren Verdichter (6, 8) erstreckt und einen
Ölstrom zwischen den Ölwannen der Verdichter (4, 6, 8) ermöglicht;
dadurch gekennzeichnet, dass, wenn alle Verdichter (4, 6, 8) der Mehrfachverdichtereinheit laufen,
der Ölstrom zwischen dem ersten Verdichter (4) und den weiteren Verdichtern (6, 8),
insbesondere durch Schließen eines Magnetventils (32), das in der Ölausgleichsleitung
(30) angeordnet ist, blockiert wird, wenn eine erfasste Druckdifferenz zwischen dem
ersten Verdichter (4) und einem der weiteren Verdichter (6, 8) einen vorbestimmten
Schwellenwert überschreitet und/oder wenn die Drehzahl des Verdichters (4) einen oberen
Schwellenwert überschreitet oder einen unteren Schwellenwert unterschreitet, wobei
die Ölausgleichsleitung (30) die Ölwannen der Verdichter (4, 6, 8) an im Wesentlichen
gleichen Höhenpositionen verbindet.
1. Circuit de réfrigération, comprenant - dans la direction d'écoulement - une unité
multi-compresseur (4, 6, 8), un condenseur/refroidisseur de gaz (12), un récepteur
(14), au moins un évaporateur (18, 22, 26) ayant un dispositif de détente (16, 20,
24) respectif agencé au devant, et des conduits faisant circuler au travers une huile
contenant du fluide frigorigène,
dans lequel l'unité multi-compresseur (4, 6, 8) comprend un premier compresseur (4)
dont la vitesse de rotation peut être commandée et au moins un compresseur supplémentaire
(6, 8) fonctionnant à une vitesse de rotation constante,
dans lequel les côtés aspiration et les côtés pression des compresseurs (4, 6, 8)
sont raccordés en parallèle,
dans lequel une ligne d'équilibrage d'huile (30) est ménagée entre les carters d'huile
des compresseurs (4, 6, 8), ladite ligne d'équilibrage d'huile (30) raccordant les
carters d'huile des compresseurs (4, 6, 8) sensiblement aux mêmes positions de hauteur,
dans lequel une électrovanne (32) permettant un écoulement d'huile dans une direction
ou une autre est agencée dans la ligne d'équilibrage d'huile (30) entre le premier
compresseur (4) et l'au moins un compresseur supplémentaire (6, 8) pour commander
la distribution d'huile entre les carters d'huile des compresseurs (4, 6, 8) pendant
un fonctionnement des compresseurs (4, 6, 8) de l'unité multi-compresseur (4, 6, 8),
et
caractérisé en ce que
des moyens sont prévus pour mesurer une différence de pression entre le premier compresseur
(4) et l'un des compresseurs supplémentaires (6, 8), et dans lequel l'électrovanne
(32) peut être commandée de manière à se fermer si la différence de pression dépasse
une valeur seuil prédéterminée, bloquant ainsi un écoulement d'huile entre le premier
compresseur (4) et les compresseurs supplémentaires (6, 8) ; ou
en ce que l'électrovanne (32) peut être commandée de manière à se fermer si la vitesse de rotation
du premier compresseur (4) dépasse une valeur seuil supérieure prédéterminée ou tombe
en dessous d'une valeur seuil inférieure prédéterminée, bloquant ainsi un écoulement
d'huile entre le premier compresseur (4) et les compresseurs supplémentaires (6, 8).
2. Circuit de réfrigération selon la revendication 1, dans lequel les compresseurs (4,
6, 8) de l'unité multi-compresseur fonctionnent sensiblement au même niveau de pression
d'aspiration.
3. Circuit de réfrigération selon la revendication 1 ou 2, dans lequel des moyens pour
surveiller les niveaux de carter d'huile sont agencés dans les carters d'huile des
compresseurs (4, 6, 8), et dans lequel l'électrovanne (32) peut être commandée de
manière à se fermer si le niveau de carter d'huile de l'un des compresseurs (4, 6,
8) dépasse une valeur seuil supérieure prédéterminée, bloquant ainsi un écoulement
d'huile entre le premier compresseur (4) et les compresseurs supplémentaires (6, 8).
4. Circuit de réfrigération selon l'une quelconque des revendications précédentes, dans
lequel les moyens pour surveiller les niveaux de carter d'huile sont agencés dans
les carters d'huile des compresseurs (4, 6, 8), et dans lequel l'électrovanne (32)
peut être commandée de manière à se fermer si le niveau de carter d'huile de l'un
des compresseurs (4, 6, 8) chute en dessous d'une valeur seuil inférieure prédéterminée,
bloquant ainsi un écoulement d'huile entre le premier compresseur (4) et les compresseurs
supplémentaires (6, 8).
5. Circuit de réfrigération selon l'une quelconque des revendications précédentes, dans
lequel les moyens pour surveiller les niveaux de carter d'huile sont agencés dans
les carters d'huile des compresseurs (4, 6, 8), et dans lequel l'électrovanne (32)
peut être commandée de manière à se fermer si la différence de niveau de carter d'huile
entre le premier compresseur (4) et l'un des compresseurs supplémentaires (6, 8) dépasse
une valeur seuil supérieure prédéterminée, bloquant ainsi un écoulement d'huile entre
le premier compresseur (4) et les compresseurs supplémentaires (6, 8).
6. Circuit de réfrigération selon la revendication 1 ou 2, dans lequel l'électrovanne
(32) peut être commandée de manière à se fermer et à s'ouvrir à des intervalles prédéterminés
pour bloquer et, respectivement, permettre un écoulement d'huile entre le premier
compresseur (4) et les compresseurs supplémentaires (6, 8).
7. Circuit de réfrigération selon l'une quelconque des revendications précédentes, comprenant
en outre un organe de commande d'unité destiné à commander le condenseur/refroidisseur
de gaz (12), les compresseurs (4, 6, 8) et l'électrovanne (32).
8. Circuit de réfrigération selon la revendication 7, dans lequel l'algorithme de commande
pour l'électrovanne (32) est intégré dans l'organe de commande de l'unité.
9. Circuit de réfrigération selon l'une quelconque des revendications 1 à 7, dans lequel
la commande de l'électrovanne (32) est réalisée par un générateur d'impulsions séparé.
10. Procédé de commande de la distribution d'huile au sein d'une unité multi-compresseur
d'un circuit de réfrigération, l'unité multi-compresseur (4, 6, 8) comprenant un premier
compresseur (4) dont la vitesse de rotation peut être commandée et au moins un compresseur
supplémentaire (6, 8) fonctionnant à une vitesse constante, dans lequel les côtés
aspiration et les côtés pression des compresseurs (4, 6, 8) sont raccordés en parallèle,
l'unité multi-compresseur (4, 6, 8) comprenant en outre une ligne d'équilibrage d'huile
(30) s'étendant entre le premier compresseur (4) et l'au moins un compresseur supplémentaires
(6, 8), et permettant un écoulement d'huile entre les carters d'huile des compresseurs
(4, 6, 8) ;
caractérisé en ce que, pendant que tous les compresseurs (4, 6, 8) de l'unité multi-compresseur fonctionnent,
l'écoulement d'huile entre le premier compresseur (4) et les compresseurs supplémentaires
(6, 8) est bloqué, lorsqu'une différence de pression captée entre le premier compresseur
(4) et l'un des compresseurs supplémentaires (6, 8) dépasse une valeur seuil prédéterminée,
et/ou lorsque la vitesse de rotation du compresseur (4) dépasse une valeur seuil supérieure
ou chute en dessous d'une valeur seuil inférieure, notamment en fermant une électrovanne
(32) agencée dans la ligne d'équilibrage d'huile (30), ladite ligne d'équilibrage
d'huile (30) raccordant les carters d'huile des compresseurs (4, 6, 8) sensiblement
aux mêmes positions de hauteur.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only.
It does not form part of the European patent document. Even though great care has
been taken in compiling the references, errors or omissions cannot be excluded and
the EPO disclaims all liability in this regard.
Patent documents cited in the description