U.S. patent application number 10/540111 was filed with the patent office on 2006-11-09 for air conditioning system for a vehicle and associated operating method.
This patent application is currently assigned to BEHR GmbH & CO. KG. Invention is credited to Roland Burk, Gunther Feuerecker, Andreas Kemle, Hans-Joachim Krauss, Ottokar Kunberger, Thomas Strauss, Hans-Martin Stuck.
Application Number | 20060248906 10/540111 |
Document ID | / |
Family ID | 32667544 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060248906 |
Kind Code |
A1 |
Burk; Roland ; et
al. |
November 9, 2006 |
Air conditioning system for a vehicle and associated operating
method
Abstract
The invention relates to a simplified air conditioning system
(1) for a motor vehicle, comprising a flow channel (4) for an air
stream (2) to be conditioned. According to the invention, said
system is provided with a circuit (8) which can be operated in a
cooling mode or in a heating mode and is used to circulate a fluid
(F) for conditioning the air stream (2). In the heating mode, the
circuit comprises an compressor (26), a heat exchanger (24), and an
intermediate reservoir (28), and is controlled in such a way that
the suction pressure of the compressor (26) at least partially
exceeds a saturated vapour pressure in the circuit, caused by the
ambient temperature.
Inventors: |
Burk; Roland; (Stuttgart,
DE) ; Feuerecker; Gunther; (Stuttgart, DE) ;
Kemle; Andreas; (Edmund, DE) ; Krauss;
Hans-Joachim; (Stuttgart, DE) ; Kunberger;
Ottokar; (Korntal-Munchingen, DE) ; Strauss;
Thomas; (Neuffen, DE) ; Stuck; Hans-Martin;
(Gerhard-Haupfmann, DE) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
BEHR GmbH & CO. KG
|
Family ID: |
32667544 |
Appl. No.: |
10/540111 |
Filed: |
October 31, 2003 |
PCT Filed: |
October 31, 2003 |
PCT NO: |
PCT/EP03/12139 |
371 Date: |
June 26, 2006 |
Current U.S.
Class: |
62/160 ;
62/324.4 |
Current CPC
Class: |
F25B 2309/061 20130101;
B60H 1/3213 20130101; F25B 2700/1933 20130101; F25B 30/02 20130101;
F25B 2600/17 20130101; B60H 1/00914 20130101; B60H 2001/325
20130101; F25B 9/008 20130101 |
Class at
Publication: |
062/160 ;
062/324.4 |
International
Class: |
F25B 13/00 20060101
F25B013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2002 |
DE |
102 60 933.0 |
Claims
1. A method for operating an air conditioning system (1) of a
vehicle, in which a fluid (F) for conditioning an air stream (2) is
circulated in a circuit (8) operable in the cooling or heating
mode, characterized in that, in the heating mode, the circuit
comprises a condenser (26), a heat exchanger (24) and an
intermediate store (28), the circuit being controlled in such a way
that the intake pressure of the condenser (26) at least partially
overshoots a saturation pressure in the circuit caused by the
ambient temperature.
2. The method as claimed in claim 1, characterized in that the
heating mode corresponds to an operation of the circuit in a
dextrorotary triangulation process, in which the exit of the
condenser is connected to an entry of a control valve (38a),
connected on the exit side to the heat exchanger (24) which is
followed on the exit side by the intermediate store (28) and the
entry of the condenser (26).
3. The method as claimed in claim 1, characterized in that the
intake pressure can be controlled in a range of 10 bar to 110
bar.
4. The method as claimed in claim 1, characterized in that, in the
heating mode, the fluid (F) in the circuit can be divided into at
least one active part (8B) and at least one passive part (8A).
5. The method as claimed in claim 1, characterized in that, with
the activation of the heating mode, the fluid (F) is routed out of
the passive part of the circuit (8A) into the active part of the
circuit (8B).
6. The method as claimed in claim 1, characterized in that, when a
predeterminable threshold value for the intake pressure in the
active part of the circuit (8B) is undershot, the fluid (F) is
routed out of the passive part of the circuit (8A) into the active
part of the circuit (8B).
7. The method as claimed in either claim 5, characterized in that,
to transfer the fluid out of the passive part of the circuit into
the active part of the circuit, the circuit operated in the heating
mode is changed over to the cooling mode.
8. The method as claimed in either claim 5, characterized in that,
to transfer the fluid out of the passive part of the circuit into
the active part of the circuit, the circuit operated in the heating
mode is changed over to a laevorotatory triangulation process.
9. The method as claimed in either claim 7, characterized in that
the circuit can be operated in the cooling mode or in the
laevorotatory triangulation process up to the undershooting of a
settable threshold value, the circuit being capable of being
changed over to the heating mode again after the undershooting of
the threshold value.
10. The method as claimed in claim 9, characterized in that the
threshold value for an intake pressure and/or for a high pressure
and/or for a hot-gas temperature at the condenser can be
predetermined.
11. The method as claimed in claim 9, characterized in that the
threshold value of the intake pressure is set at least 3 bar,
preferably 5 bar, below the value of the saturation pressure caused
by the ambient temperature.
12. The method as claimed in claim 7, characterized in that the
circuit can be operated in the cooling mode or in the laevorotatory
triangulation process for a predeterminable period of time, the
circuit being capable of being changed over to the heating mode
again after the expiry of the period of time.
13. The method as claimed in claim 7, characterized in that an air
stream (2) through the evaporator can be reduced after the
changeover to the cooling mode or to the laevorotatory
triangulation process.
14. The method as claimed in claim 7, characterized in that an air
stream through a gas cooler can be reduced after the changeover to
the cooling mode or to the laevorotatory triangulation process.
15. The method as claimed in claim 10, characterized in that a
pressure equalization can be carried out in the circuit after the
return to the heating mode.
16. An air conditioning system (1) for a vehicle with a circuit
(8), operable in the cooling or heating mode, for the circulation
of a fluid (F) for conditioning an air stream (2), characterized in
that, in the heating mode, the circuit comprises a heat exchanger
(24), an intermediate store (28) and a condenser (26) for the
intermediate storage or for the condensation of the fluid (F), the
condenser being operated at an intake pressure which is higher than
the saturation pressure in the circuit (8) caused by the ambient
temperature.
17. The air conditioning system (1) as claimed in claim 16,
characterized in that the an evaporator (6) inserted in the flow
duct (4) of the air stream (2) on the secondary side and in the
circuit (8) on the primary side is provided, which is connected in
the circuit (8), on the exit side, to the intermediate store (28),
with a nonreturn valve (36) being interposed.
18. The air conditioning system (1) as claimed in claim 17,
characterized in that the volume of the evaporator (6) for fluid
reception is smaller than the storage volume of the intermediate
store (28).
19. The air conditioning system (1) as claimed in claim 18,
characterized in that the ratio of the storage volume of the
intermediate store to the volume of the evaporator lies in the
range of 2:1 to 20:1, preferably in the range of between 2:1 and
10:1.
20. The air conditioning system (1) as claimed in claim 16, in
which a control device (38B) is arranged between the heat exchanger
(24) and the intermediate store (28).
21. The air conditioning system (1) as claimed in claim 16, in
which a pressure sensor is assigned on the intake side to the
condenser (26).
22. The air conditioning system (1) as claimed in claim 16, in
which the circuit (8) is subdivided into at least one active and at
least one passive part.
23. The air conditioning system (1) as claimed in claim 22, in
which the active part is connected to the passive part by means of
a further control device (38C), the control device (38C) being
opened when the fluid quantity in the active part of the circuit
overshoots a predeterminable threshold value.
24. The air conditioning system (1) as claimed in claim 19, in
which the condenser (26) is connected to the evaporator (6) on the
exit side via a control means (42) and on the entry side via an
associated controllable connecting line (40), after the opening of
the control means gaseous fluid (F) passing into the evaporator and
forcing liquid fluid (F) out of the evaporator into the active part
(8B) of the circuit.
Description
[0001] The invention relates to an air conditioning system with a
flow duct for an air stream to be conditioned and with a heat
exchanger arranged in this flow duct and also with a circuit,
operable in the heating or cooling mode, for the circulation of a
fluid.
[0002] An air conditioning system of this type is used particularly
in a motor vehicle. The refrigerant flow is in this case
conventionally generated by a condenser or compressor which is
inserted into the refrigerant circuit and is driven directly by the
vehicle engine.
[0003] Modern low-consumption vehicles usually deliver too little
waste heat or heating energy to make it possible to heat up the
vehicle interior to comfortable temperatures in a time which, if
required, may even be short. Particularly windshield defrosting
lasts too long because of the low waste heat. In order to avoid
this, it is known, for example from EP 0 960 756, to connect what
may be referred to as a thermodynamic triangulation process in
which a separate heat exchanger is provided for the additional
heating of the air stream and therefore for conditioning. DE 3 907
201 also discloses an additional heat exchanger for heating the air
stream. In addition, the air conditioning system known from EP 0
733 504 makes it possible to control and regulate the fluid or
refrigerant circulating in the refrigerant circuit.
[0004] The air conditioning systems mentioned have the disadvantage
that either they are not suitable for a circuit with carbon dioxide
as fluid or refrigerant and consequently the heating capacity of
such air conditioning systems is limited or that they require
additional components, in particular complicated and cost-intensive
changeover or shutoff valves.
[0005] A carbon dioxide circuit, which is conventionally provided
with a header or intermediate store arranged on the suction side
and generally having the flow passing through it only in the
cooling mode, is limited in its heating capacity, the latter
moreover becoming lower with an increasing ambient temperature.
This results from the dependence of the density of the vapor sucked
in by the condenser on the ambient temperature. This leads to a
reduction in the conveyed mass fluid flow or mass refrigerant flow
and therefore also to a reduction in the heating capacity with a
decreasing ambient temperature. Furthermore, in the heating mode,
refrigerant and oil may accumulate in the intermediate store
through which the flow does not pass, and because of this too
little fluid or refrigerant flows through the circuit representing
the heating mode. In order to avoid this, therefore, even in a
carbon dioxide circuit, the circulating fluid stream is controlled
according to requirements. This leads, in turn, to the use of
complicated and cost-intensive regulating and control valves and
also of additional lines.
[0006] The object on which the invention is based is, therefore, to
specify a particularly simple air conditioning system for a motor
vehicle, which allows as good a conditioning of an air stream as
possible, along with a sufficiently good heating capacity. The
object on which the invention is based is, furthermore, to specify
a method for operating such an air conditioning system.
[0007] As regards a method for operating an air conditioning
system, this object is achieved, according to the invention, by
means of the features of patent claim 1.
[0008] As regards an air conditioning system, the object is
achieved, according to the invention, by means of the features of
claim 16.
[0009] The dependent claims relate to advantageous refinements
and/or developments of the invention.
[0010] The main idea of the invention is to control a circuit
having a fluid for conditioning an air stream in a heating mode in
such a way that the intake pressure of a condenser at least
partially overshoots a saturation pressure in the circuit caused by
the ambient temperature, in the heating mode, the circuit
preferably being operated in a dextrorotatory triangulation
process, a drive power of the condenser being converted completely
into heat by means of a heat exchanger, being transmitted to the
air stream routed to the vehicle interior and thus being used for
conditioning the air stream.
[0011] In a particularly advantageous development of the method, in
the heating mode, the fluid in the circuit can be divided into at
least one active part and at least one passive part.
[0012] Operating in a dextrorotatory triangulation process has the
advantage that there is a high intake pressure and therefore a high
mass flow in the circuit. In the method according to the invention,
an intermediate store is incorporated into the heating mode, the
fluid, for example a refrigerant, being supplied from the heat
exchanger, for example a heating element, to the intermediate
store, for example a low-pressure header, present in any case in
the circuit, in order to flow through said intermediate store
before being sucked in by the condenser.
[0013] By means of such a pressure-dependent control of the fluid
in individual regions of the circuit, in particular in a
refrigerant circuit, the fluid quantity in the active part of the
circuit is increased. In this case, depending on the type and
design of the air conditioning system, particularly by virtue of
appropriate methods of controlling and regulating the existing
components, accumulated refrigerant can be recovered, as required,
by being transferred into the as active part of the circuit. Such a
control and regulation of the air conditioning system makes it
possible to have a control and regulation of the heating capacity
which is largely independent of the ambient temperature.
Particularly by means of the accurate removal and introduction of
refrigerant (=fluid) from the passive part and into the passive
part of the circuit, the refrigerant stream circulating in the
active part of the circuit can be set and optimized in terms of a
predetermined heating capacity. Such a simple control and
regulation of the refrigerant stream does not require any
additional components, apart from the shutoff devices, control
and/or regulating valves which are present in any case.
[0014] In one embodiment, the intake pressure can be controlled in
a range of 10 bar to 110 bar.
[0015] In a further version of the method, with the activation of
the heating mode, the fluid is routed out of the passive part of
the circuit into the active part of the circuit. Additionally or
alternatively, a threshold value for the intake pressure in the
active part of the circuit may be predetermined, and, when said
threshold value is undershot, the fluid is likewise routed out of
the passive part of the circuit into the active part of the
circuit.
[0016] To transfer the fluid out of the passive part of the circuit
into the active part of the circuit, the circuit operated in the
heating mode is at least briefly changed over to the cooling mode
or to a laevorotatory triangulation process. The changeover to the
laevorotatory triangulation process has the advantage, as compared
with the changeover to the cooling mode, that the laevorotatory
triangulation process is likewise a heating process which is
operated at a lower intake pressure than in the case of the
dextrorotatory triangulation process.
[0017] The circuit is operated in the cooling mode or in the
laevorotatory triangulation process up to the undershooting of a
settable threshold value, the circuit being changed over to the
heating mode again after the undershooting of the threshold value.
The threshold value can be predetermined, for example, for an
intake pressure and/or for a high pressure and/or for a hot-gas
temperature at the condenser.
[0018] In an advantageous embodiment, the threshold value of the
intake pressure is set at least 3 bar, preferably 5 bar, below the
value of the saturation pressure caused by the ambient
temperature.
[0019] Alternatively, the circuit can also be operated for a
predeterminable period of time in the cooling mode or in the
laevorotatory triangulation process, the circuit likewise being
changed over to the heating mode again after the expiry of the
period of time.
[0020] To increase the heating capacity, the air stream through the
evaporator and/or through a gas cooler can additionally be reduced
after the changeover to the cooling mode or to the laevorotatory
triangulation process.
[0021] Since, in the case of commercially available electrically
actuated 2/3-way valves, the magnetic force is not sufficient to
switch the valve when the differential pressure is too great, a
pressure equalization is carried out in the circuit before the
return to the heating mode.
[0022] In one embodiment, the circuit of the air conditioning
system for a vehicle, in the heating mode, comprises a heat
exchanger, an intermediate store and a condenser for the
intermediate storage or for the condensation of a fluid, the
condenser being operated at an intake pressure which is higher than
the saturation pressure in the circuit caused by the ambient
temperature.
[0023] In an advantageous refinement of the invention, an
evaporator inserted in the flow duct of the air stream on the
secondary side and in the circuit on the primary side is provided,
in which case the evaporator can be connected in the circuit, on
the exit side, to the intermediate store, with a nonreturn valve
being interposed.
[0024] In an advantageous version of the air conditioning system,
the volume of the evaporator for fluid reception is smaller than
the storage volume of the intermediate store, the ratio of the
storage volume of the intermediate store to the volume of the
evaporator lying, for example, in the range of 2:1 to 20:1,
preferably in the range of between 2:1 to 10:1.
[0025] To transfer the fluid out of the passive part into the
active part of the circuit, and vice versa, the two parts of the
circuit are connected to one another by means of at least one
control device, the control device being opened in order to
increase or reduce the fluid quantity in the active part of the
circuit.
[0026] In a further advantageous embodiment, the condenser is
connected to the evaporator on the exit side via a control means
and on the entry side via an associated controllable connecting
line, after the opening of the control means gaseous fluid passing
into the evaporator and forcing the liquid fluid located in the
evaporator out of the evaporator into the active part of the
circuit.
[0027] Exemplary embodiments of the invention are explained in more
detail below with reference to a drawing in which:
[0028] FIGS. 1 to 3 show, in a diagrammatic illustration,
alternative embodiments of an air conditioning system with a
circuit, operable in the cooling or heating mode, for the return of
a fluid flowing out from a condenser on the exit side and flowing
into the condenser on the intake side via an intermediate
store,
[0029] FIGS. 4 and 5 show thermodynamic graphs of the operation of
the air conditioning systems according to FIG. 3.
[0030] Parts corresponding to one another are given the same
reference symbols in the figures.
[0031] The air conditioning system 1 illustrated diagrammatically
in FIG. 1 comprises a flow duct 4 through which an air stream 2
flows. In this case, the flow duct 4 has arranged in it an
evaporator 6, in particular a refrigerant evaporator, which fills
its cross section. In this case, for cooling the air stream 2
flowing into the flow duct 4 and flowing through the evaporator 6
on the secondary side, the evaporator 6 is connected to a circuit
8, forming a subcircuit 8A, for the circulation of the fluid F. The
fluid F is, for example, carbon dioxide or another refrigerant. The
circuit 8, by virtue of its functionality, is also designated as a
refrigerant circuit. The subcircuit 8A is designated further as a
passive subcircuit 8A because of its passive routing of the fluid F
for heating purposes.
[0032] The evaporator 6 is designed in the manner of a conventional
refrigerant evaporator used in vehicle air conditioning systems
(cf., for example, Kraftfahrtechnisches Taschenbuch/Bosch [Motor
Drive Manual/Bosch] [Chief Editor H. Bauer], 23rd edition,
Brunswick (Viebig), 1999, p. 777 ff.), in which heat is extracted
from the air stream 2 flowing through owing to the evaporation of
the refrigerant designated as the fluid F. To regulate the fluid F
flowing through the evaporator 6, the evaporator 6 is preceded on
the entry side by an expansion valve 12 which is arranged in the
refrigerant circuit 8 and which can close sealingly.
[0033] The evaporator 6 is followed by a heating body 14, as seen
in the flow direction of the air stream 2. The heating body 14
serves for the heating and therefore thermal control of the air
stream 2 by means of coolant M heated by the engine 16. For this
purpose, the heating body 14 is inserted on the secondary side into
a coolant circuit 18. A coolant pump 20 for controlling the coolant
stream is inserted in each case into the coolant circuit 18 on the
entry side and exit side of the engine 16. In addition to the
cooling of the coolant M, the latter is cooled by fresh air via a
radiator 22 arranged in the air stream 102.
[0034] Furthermore, for the further heating of the air stream 2,
the heating body 14 is followed in the flow duct 4 by a heat
exchanger 24. The heat exchanger 24 is designed as a heating
element and is inserted on the secondary side into a further
subcircuit 8B of the circuit 8. The subcircuit 8B in this case
causes an active control of the fluid F and is therefore designated
further as an active subcircuit 8B. To control the fluid stream, an
expansion valve 10 is expediently inserted into the active
subcircuit 8B between the condenser 26 and the heat exchanger
24.
[0035] In the cooling mode of the air conditioning system 1, a
refrigerant runs through the passive subcircuit 8A according to the
flow arrows P1 of the fluid F and therefore through the evaporator
6 and a condenser 26 driven by the engine 16. The fluid F is
delivered in liquid form to the evaporator 6 and introduced. When
it runs through the evaporator 6, the fluid F evaporates and at the
same time extracts heat from the air stream 2 flowing through the
evaporator 6 via corresponding heat exchange surfaces, not
illustrated in any more detail. The fluid F, for example, a gaseous
refrigerant, such as carbon dioxide, leaves the evaporator 6 and is
supplied to a gas cooler 32 for cooling in the passive subcircuit
8A, with an intermediate store 28 and a heat exchanger 30 being
interposed.
[0036] In the heating mode, the refrigerant runs through the active
subcircuit 8B according to the flow arrows P2 of the fluid F, the
fluid F being supplied on the exit side from the condenser 26 to
the heat exchanger 24 designed as a heating element and being
supplied to the condenser 26 again on the intake side via the
intermediate store 28 designed as a low-pressure header and via the
heat exchanger 30 which is deactivated in this mode. For changing
over the flow of the fluid F from the active subcircuit 8B to the
passive subcircuit 8A, or vice versa, shutoff devices 34 are
arranged in the respective subcircuits 8B and 8A.
[0037] According to the present invention, the subcircuit 8B which
is active in the heating mode makes it possible to convert the
drive power of the condenser 26 into heat for the additional
heating and thermal control of the air stream 2 by means of the
heat exchanger 24, in that the fluid F is supplied to the condenser
26 again on the intake side by the heat exchanger 24 via the
intermediate store 28.
[0038] In order, as illustrated in FIG. 1, to avoid additional
components for the air conditioning system 1, a suction pressure of
the condenser 26 is in this case is set in such as way that the
suction pressure at least partially overshoots a saturation
pressure caused by the ambient temperature. The setting of the
suction pressure is in this case brought about in a particularly
simple way by means of structural features of the components of the
air conditioning system 1. For example, for this purpose, a storage
or evaporator volume representing the evaporator 6 is designed to
be so small that the fluid quantity or refrigerant quantity
collected or stored in the intermediate store 28 (=header) cannot
condense completely in the cold evaporator 6, the shutoff device
12, for example an expansion valve, preventing a further outflow
into the likewise cold gas cooler 32. Alternatively, the
intermediate store 28 may have a correspondingly large storage
volume which is substantially larger than the evaporator volume,
the volume of the evaporator lying, for example, in the range of 50
to 500 ccm and the volume of the header lying in the range of 200
to 2000 ccm, so that a ratio of the volume of the header to the
volume of the evaporator in the range of 2:1 to 20:1, preferably
2:1 to 10:1, can be selected.
[0039] Alternatively or additionally, as illustrated in FIG. 2, the
air conditioning system 1 may be supplemented by a nonreturn valve
36 arranged in the passive subcircuit 8A on the exit side of the
evaporator 6. The nonreturn valve 36 in this case prevents the
fluid F or the refrigerant from being capable of flowing out of the
active subcircuit 8B into the circuit components, namely the
evaporator 6 and the gas cooler 32, of the passive subcircuit 8A,
said circuit components being substantially colder and therefore
being under lower pressure in the heating mode. Since the condenser
power is utilized for heating the air stream 2 purely due to the
structural features of the components, an exact control of the
fluid stream in the active subcircuit 8B is not possible.
[0040] However, for example, after the vehicle has been stopped
several times or stopped for too long, an exact control and setting
of the circulation of the fluid F in the heating mode is desirable,
if not absolutely necessary, since, in this case, too much fluid F
collects in components, namely the evaporator 6 or the gas cooler
32, of the passive subcircuit 8A and therefore the performance of
the circuit 8 is markedly limited. In the other situation where too
much fluid F flows in the active subcircuit 8B, the suction
pressure may, under certain circumstances, rise to too high a
value, with the result that the condenser 26 may be damaged.
[0041] For this purpose, as illustrated in FIG. 3, two control
devices 38A and 38B are arranged in the active subcircuit 8B. The
control devices 38A and 38B are designed, for example, as
regulating valves or expansion valves. Depending on the type and
activation of the control devices 38A and 38B, various operating
processes of the air conditioning system 1 in the heating mode can
be set, which are explained in more detail by means of the
thermodynamic graphs according to FIGS. 4 and 5.
[0042] FIG. 4 in this case shows a pressure/enthalpy graph for what
is known as a laevorotatory triangulation process, and FIG. 5 shows
a pressure/enthalpy graph for what is known as a dextrorotatory
triangulation process. According to the method for operating the
air conditioning system 1, as shown in FIG. 4, the fluid F flowing
out of the condenser 26 at high pressure is supplied, throttled
only insignificantly, directly to the heat exchanger 24 by means of
the control device 38A according to the curve K1, according to
curve K2 the fluid F discharging its heat to the air stream 2
flowing through the heat exchanger 24 on the primary side. The
fluid F is supplied to the intermediate store 28 and the condenser
26 again from the heat exchanger 24 via the control device 38B
which, according to the curve K3, throttles the fluid F to the
intake pressure. For this purpose, the control device 38A, designed
as an expansion valve, is opened as completely as possible, so that
the pressure loss is low, and the predominant pressure reduction is
executed at the control device 38B, likewise designed as an
expansion valve. The curve K4 illustrates the pressure increase of
the fluid stream brought about by means of the condenser 26.
[0043] By a change in the width or degrees of opening of the
control devices 38A and 38B, the laevorotatory triangulation
process according to FIG. 4 can be changed over to a dextrorotatory
triangulation process according to FIG. 5. For example, a
changeover from the dextrorotatory triangulation process to the
laevorotatory triangulation process takes place in the situation
where too little fluid F or refrigerant, for example what is known
as R744 refrigerant, flows in the active subcircuit 8B. In the
dextrorotatory triangulation process, the substantial pressure
reduction takes place at the control device 38A according to FIG.
5, curve K1, while the control device 38B is completely open and
therefore brings about only a low pressure reduction to the value
of the intake pressure, according to curve K3. The result of this,
in a comparison of the laevorotatory with the dextrorotatory
triangulation process, is that the values of the intake pressures
in the dextrorotatory triangulation process according to FIG. 5 are
higher than in the laevorotatory triangulation process according to
FIG. 4. On account of this, the condenser 26 can convey a greater
mass flow of the fluid F, with the result that additional heating
capacity is generated by means of the heat exchanger 24. If the
switch to the laevorotatory triangulation process is made, the
intake pressure falls considerably, as compared with the
dextrorotatory triangulation process. If this intake pressure in
the laevorotatory triangulation process falls below the pressure in
the passive system part caused by the ambient temperature, a
displacement of refrigerant from the passive part into the active
part occurs.
[0044] In the event that too much fluid F flows through the active
subcircuit 8B, a further control device 38C between the two
subcircuits 8A and 8B is switched. By the control device 38C being
opened, the fluid F can then be routed, metered correspondingly,
into the passive subcircuit 8A to the gas cooler 32 or to the
evaporator 6.
[0045] In a further instance of use, to eliminate an accumulation
of fluid F or refrigerant, for example after a lengthy standstill,
at the start of travel the vehicle is operated, during the run-up
of the condenser 26, in the cooling mode and therefore in the
passive subcircuit 8A within a predetermined time range, with the
shutoff device 12 open at maximum, in order to bring about a
sufficiently good throughflow of the gas cooler 32, of the
evaporator 6 and of the intermediate store 28. As a result, an
accumulation of fluid F in the evaporator 6 or else in the gas
cooler 32 is at least partially eliminated, in that a sufficient
quantity of the fluid F, in particular of liquid refrigerant, is
routed into the intermediate store 28 or header and stored.
Subsequently, the air conditioning system 1 is operated according
to one of the above-described triangulation processes, as shown in
FIGS. 4 or 5. If, in this case, an accumulation of fluid F in the
passive subcircuit 8A occurs again, the heating mode (also called
additional heating operation) of the active subcircuit 8B is
interrupted by means of a brief changeover to the cooling mode of
the passive subcircuit 8A which routes the fluid F into the
intermediate store 28 again.
[0046] In addition to the control of the air conditioning system 1
according to the triangulation processes, as shown in FIGS. 4 and
5, by means of the above-explained design of the components and/or
arrangement of the control devices 38A to 38C, the condenser 26 may
be provided on the intake side with a pressure sensor, not
illustrated in any more detail. The pressure sensor in this case
serves for the essentially exact determination of the fluid
quantity in the active subcircuit 8B, thus making possible an
accurate and therefore settable introduction or removal of the
fluid F between the two subcircuits 8A and 8B. In another
alternative, the condenser 26 is connected on the exit side to the
evaporator 6 on the entry side via a controllable connecting line
40.
LIST OF REFERENCE SYMBOLS
[0047] 1 Air conditioning system [0048] 2 Air stream [0049] 4 Flow
duct [0050] 6 Evaporator [0051] 8 Refrigerant circuit [0052] 8A
Passive subcircuit [0053] 8B Active subcircuit [0054] 10 Expansion
valve [0055] 12 Sealingly closing expansion valve [0056] 14 Heating
body [0057] 16 Engine [0058] 18 Refrigerant circuit [0059] 20
Coolant pump [0060] 22 Radiator [0061] 24 Heat exchanger [0062] 26
Condenser [0063] 28 Intermediate store [0064] 30 Heat exchanger
[0065] 32 Gas cooler [0066] 34 Shutoff devices [0067] 36 Nonreturn
valve [0068] 38A,38B,38C Control device [0069] 40 Connecting line
[0070] 42 Control device [0071] 102 Air stream [0072] F Fluid
[0073] M Coolant [0074] K2,K3 Curve [0075] P1,P1 Flow arrow
* * * * *